# Parameters for Properly Designed and Operated Flares

Report for Flare Review Panel April 2012

Prepared by U.S. EPA Office of Air Quality Planning and Standards (OAQP S)

This information is distributed solely for the purpose of pre -dissemination peer review under applicable information quality guidelines. It has not been formally dissemi nated by EPA. It does not represent

and should not be construed to represent any Agency determinati on or policy.This information is distributed solely for the purp ose of pre-dissemination peer review under applicab le information quality guidelines. It has not been formally disseminated by EPA. It does not repr esent and should not be construed to represent any Agency determination or policy.

Acronyms Page i 

## ACRONYMS

Acronym Definition
AFTIR Active Fourier Transform Infrared
API American Petroleum Institute ARI Aerodyne Research, Inc.
BTU British Thermal Units
CZ Combustion Zone Gas
C CZ 

## Fraction of Combustibles in the Combustion Zone Gas CFR Code of Federal Regulations DCS Distributed Control System EPA U.S. Environmental Protection Agency
FHR Flint Hills Resources
FHR AU Flint Hills Resources - Aromatics Unit FHR LOU Flint Hills Resources - Light Olefins Unit FLIR Forward Looking Infrared FTIR Fourier Transform Infrared Technology IMACC Industrial Monitor and Control Corporation INEOS INEOS ABS (USA) Corporation ISO International Standards Organization LFL Lower Flammability Limit
LFL CZ 

## Lower Flammability Limit of the Combustion Zone Gas

LFL VG 

## Lower Flammability Limit of the Flare Vent Gas LHV Lower Heating Value

LFL VG, C 

## Lower Flammability Limit of the Combustible Portion of the

Flare Vent Gas
MFR Momentum Flux Ratio MPC Marathon Petroleum Company, LP MPC Detroit Marathon Petroleum Company, LP Detroit Re finery MPC TX Marathon Petroleum Company, LP Texas City Refi nery NESHAP National Emission Standards for Hazardous Air P ollutants NHV Net Heating Value
NHV CZ 

## Net Heating Value of the Combustion Zone Gas
NHV LFL 

## Net Heating Value of the Flare Vent Gas if Diluted to the Lower

Flammability Limit
NHV VG 

## Net Heating Value of the Flare Vent Gas
NHV VG-LFL 

## Net Heating Value of the Flare Vent Gas if Diluted to the Lower

Flammability Limit
NSPS New Source Performance Standards OAQPS Office of Air Quality Planning and Standards PFTIR Passive Fourier Transform Infrared Technology
SCF Standard Cubic Feet SDP Shell Deer Park Refinery SDP GF Shell Deer Park Refinery Ground Flare SDP EPF Shell Deer Park Refinery East Property Flare
SR Stoichiometric Air Ratio TCEQ Texas Commission on Environmental QualityThis information is distributed solely for the purp ose of pre-dissemination peer review under applicab le information quality guidelines. It has not been formally disseminated by EPA. It does not repr esent and should not be construed to represent any Agency determination or policy.

Acronyms Page ii 

## Acronym Definition UFL Upper Flammability Limit
V max 

## Maximum Flare Tip Velocity Including, if Applicable, Cent er

Steam at Which Flame Lift Off is Not Expected to OccurThis information is distributed solely for the purp ose of pre-dissemination peer review under applicab le information quality guidelines. It has not been formally disseminated by EPA. It does not repr esent and should not be construed to represent any Agency determination or policy.

Table of Contents Page i 

## TABLE OF CONTENTS

1.0 INTRODUCTION ......................................

................................................... .............. 1-1

2.0 AVAILABLE FLARE TEST DATA .............................................. .............................. 2-1

2.1 Flare Performance Studies and Test Reports ............. ............................ 2-1
2.2 Flare Vent Gas Constituents ........................ ......................................... 2-3
2.3 Steam Injection Rates and Tip Design for Available Flar e Test Data .... 2-5
2.4 Air Injection Rates and Tip Design for Available Flare Test Data ......... 2-6
2.5 Flare Test Methods ................................. .............................................. 2-7
2.6 Combining All Available Test Run Data .................. ............................. 2-9
2.7 Data Removed After Being Considered ................... ........................... 2-10
2.8 Determination of Combustion Efficiency Representing Good Fl are Performance ....................................... ................................................ 2-11

3.0 STEAM AND FLARE PERFORMANCE ....................................... ............................. 3-1

3.1 Lower Flammability Limit of Combustion Zone Gas for S team-Assisted
Flares ............................................

................................................... .... 3-1
3.1.1 Flare Test Data and LFL CZ



## .................................................. ...... 3-5
3.1.2 The Le Chatelier Principle ........................ ................................ 3-7
3.1.3 Specific Test Data Not Fitting the Trend .............. ................... 3-11
3.1.4 Data Points with Good Combustion and High LFL CZ 

## .............. 3-20
3.1.5 Excluding Pilot Gas ................................. ............................... 3-26
3.2 Combustible Gas Concentration in the Combustion Zone ................... 3-27
3.3 Heat Content Based Limit for Steam-Assisted Flares .. ........................ 3-28
3.4 Other Operating Parameters Considered for Steam-Assiste d Flares..... 3-31
3.4.1 Net Heating Value ................................... ............................... 3-31
3.4.2 Steam Ratios ...................................... ..................................... 3-34

4.0 AIR AND FLARE PERFORMANCE ....................................... ................................... 4-1

4.1 Stoichiometric Air Ratio ........................... ............................................ 4-1
4.2 TCEQ Test Data .................................... ............................................... 4-3
4.3 Other Test Data ................................... ................................................. 4- 4
4.4 Analysis of Stoichiometric Air Ratio ............... ..................................... 4-4
4.5 Considering LFL VG 

## for Air-Assisted Flares ........................... ............... 4-7

5.0 WIND AND FLARE PERFORMANCE ....................................... ............................... 5-1

5.1 Introduction ......................................... ................................................. 5- 2
5.2 Flare Flow Mixing Regimes ........................... ...................................... 5-2
5.3 Efficiency Studies................................... .............................................. 5-4
5.4 Test Data Analysis ................................ .............................................. 5-10

6.0 FLARE FLAME LIFT OFF ............................................... .......................................... 6-1

6.1 Literature Review and V
max 

## Calculation ....................................... ......... 6-1
6.2 Test Data Analysis ................................ ................................................ 6-2
6.3 Other Operating Parameters Considered for Flame Lift Of f .................. 6-6This information is distributed solely for the purp ose of pre-dissemination peer review under applicab le information quality guidelines. It has not been formally disseminated by EPA. It does not repr esent and should not be construed to represent any Agency determination or policy.

Table of Contents Page ii 

## 7.0 OTHER FLARE TYPE DESIGNS TO CONSIDER .......................................... ........... 7-1

7.1 Non-Assisted Flares................................. ............................................. 7-1
7.2 Pressure-Assisted Flares and Other Flare Designs ...... ........................... 7-2

8.0 MONITORING CONSIDERATIONS .................................... ..................................... 8-1

8.1 LFL CZ 

## , LFL VG 

## , and LFL VG,C



## .................................................. ............... 8-1
8.2 Ratio of NHV CZ 

## to NHV VG-LFL



## .................................................. ........... 8-2
8.3 C CZ



## .................................................. ................................................... .. 8-2
8.4 SR ................................................

................................................... ..... 8-3
8.5 MFR ...............................................

................................................... ... 8-3
8.6 V max 

## .................................................. ................................................... . 8-4

9.0 REFERENCES ........................................

................................................... ................. 9-1

TECHNICAL APPENDICES

Appendix A. Brief Review Summary of Each Flare Perform ance Study and Test Report. Appendix B. Excel Workbook That Combines All Data Sets. Appendix C. Test Report Nomenclature Matrix. Appendix D. Detailed Calculation Methodologies For The Specific Parameters. Appendix E. Type and Amount of Components in Each Test R un by Test Report. Appendix F. Charts of Calculated and Measured LFL for Vari ous Combustible Gases in

Nitrogen and Carbon Dioxide. Appendix G. Details About Inerts and Further Explanation for Including an Equivalency Adjustment to Correct For Different Inert B ehavior. Appendix H. Effect of Nitrogen and Carbon Dioxide on the LFL of Various

Components: A Comparison of Le Chatelier Equation to Expe rimental
LFL Values. Appendix I. Methodology for Calculating Unobstructed Cros s Sectional Area of

Several Flare Tip Designs.This information is distributed solely for the purp ose of pre-dissemination peer review under applicab le information quality guidelines. It has not been formally disseminated by EPA. It does not repr esent and should not be construed to represent any Agency determination or policy.

Table of Contents Page iii 

## LIST OF TABLES

Tables Page

Table 2-1. Flare Performance Test Reports ............

................................................... ............... 2-2

Table 2-2. Flare Vent Gas Constituents by Test Report ...

................................................... ..... 2-3

Table 2-3. Minimum, Maximum, and Average Volume Percents o f Primary Constituents in Flare

Vent Gas ..........................................

................................................... ............. 2-4

Table 2-4. Steam-Assisted Flare Tip Design Detail ......

................................................... ........ 2-5

Table 2-5. Air-Assisted Flare Tip Design Detail ........

................................................... ........... 2-7

Table 2-6. Criteria To Exclude Data Points ..............

................................................... ...........2-12

Table 3-1. Recommended Values of Coefficient of Nitrogen Equivalency for Water and Carbon

Dioxide Relative to Nitrogen .......................... .................................................3-10

Table 3-2. Test Run Detail for 11 Data Points with LFL CZ 

## < 15.3% but Combustion Efficiency <

96.5% ................................................

................................................... ..........3-12

Table 3-3. Olefin and Hydrogen Approximately Equal ........... ................................................3-15

Table 3-4. High Hydrogen and Low Olefin .................

................................................... ........3-16

Table 3-5. Higher Olefin and Low Hydrogen ................

................................................... ......3-18

Table 3-6. Breakdown Of Steam Use For The 66 Test Runs a



## .................................................. 3-21

Table 3-7. Potential LFL
cz 

## Thresholds based on LFL VG,C



## ................................................... .....3-23This information is distributed solely for the purp ose of pre-dissemination peer review under applicab le information quality guidelines. It has not been formally disseminated by EPA. It does not repr esent and should not be construed to represent any Agency determination or policy.

Table of Contents Page iv 

## LIST OF FIGURES

Figures Page

Figure 3-1. Zabetakis Nose Plot For Methane And Inert In A ir ................................................ 3-3

Figure 3-2. Time Sequence of Flare Vent Gas Volume Moving Th rough Flammability Region Source: (Adapted from Evans and Roesler, 2011) ............. ............................... 3-4

Figure 3-3. Combustion Efficiency vs. LFL CZ



## .................................................. ....................... 3-7

Figure 3-4. Combustion Efficiency vs. LFL CZ 

## Adjusted for Nitrogen Equivalency .................3-11

Figure 3-5. Combustion Efficiency vs. LFL CZ 

## for Category A Test Runs (see Table 3-7) ........3-23

Figure 3-6. Combustion Efficiency vs. LFL CZ 

## for Category B Test Runs (see Table 3-7)........3-24

Figure 3-7. Combustion Efficiency vs. LFL CZ 

## for Category C Test Runs (see Table 3-7)........3-24

Figure 3-8. Combustion Efficiency vs. LFL CZ 

## for Category D Test Runs (see Table 3-7) ........3-25

Figure 3-9. Combustion Efficiency vs. C CZ



## .................................................. ..........................3-28

Figure 3-10. Combustion Efficiency vs. Ratio of NHV CZ 

## to NHV VG-LFL 

## .................................3-29

Figure 3-11. LFL CZ 

## vs. Ratio of NHV CZ 

## to NHV VG-LFL



## .................................................. .........3-30

Figure 3-12. Combustion Efficiency vs. NHV VG



## .................................................. ..................3-32

Figure 3-13. Combustion Efficiency vs. NHV CZ



## .................................................. ...................3-33

Figure 3-14. NHV VG 

## vs. LFL VG



## .................................................. ............................................3-34

Figure 3-15. Combustion Efficiency vs. S/VG by weight ...... .................................................3-35

Figure 3-16. Combustion Efficiency vs. S/VG by volume ....... ...............................................3-36

Figure 3-17. Combustion Efficiency vs. S/HC by volume........ ...............................................3-37

Figure 4-1. Combustion Efficiency vs. SR (using TCEQ data) .. .............................................. 4-3

Figure 4-2. Combustion Efficiency vs. SR (using EPA-600/2-85-106 data) ............................. 4-4

Figure 4-3. Combustion Efficiency vs. SR (combined TCEQ and E PA-600/2-85-106 data) ..... 4-5

Figure 4-4. Combustion Efficiency vs. SR, zoomed (using TCEQ da ta) .................................. 4-6

Figure 5-1. Air Egression Into Flare Stack Source: (Smoot et al., 2009) .................................. 5-2

Figure 5-2. Images of Flow Mixing Regimes Source: (Seebold et al., 2004) ............................ 5-3This information is distributed solely for the purp ose of pre-dissemination peer review under applicab le information quality guidelines. It has not been formally disseminated by EPA. It does not repr esent and should not be construed to represent any Agency determination or policy.

Table of Contents Page v 

## Figure 5-3. Fuel Detection Downwind of Wake-Dominated Flare S ource: (Johnston et. al, 2001)5-4

Figure 5-4. Flame Images Relating to Momentum Flux Ratio a nd Combustion Efficiency Source:

(Johnson and Kostiuk, 2000) ............................... ............................................. 5-6

Figure 5-5. Combustion Efficiency vs. Momentum Flux Ratio, Seebold Data Source: (Seebold et

al., 2004) ............................................

................................................... ........... 5-7

Figure 5-6. Combustion Efficiency vs. Momentum Flux Ratio ...............................................5-12

Figure 5-7. Combustion Efficiency vs. Momentum Flux Ratio, zoomed (MFR < 3.0; wakedominated mixing regime) ............................... ...............................................5-13

Figure 5-8. Combustion Efficiency vs. Momentum Flux Ratio, further zoomed (MFR < 0.1) .5-14

Figure 5-9. Combustion Efficiency vs. Power Factor .......

................................................... ....5-16

Figure 6-1. Conditions for Stable Flare Flame ..........

................................................... ............ 6-4This information is distributed solely for the purp ose of pre-dissemination peer review under applicab le information quality guidelines. It has not been formally disseminated by EPA. It does not repr esent and should not be construed to represent any Agency determination or policy.

Section 1.0: Introduction Page 1-1 

## 1.0 INTRODUCTION

Based on a series of flare performance studies conducted i n the early 1980s, the EPA

concluded that properly designed and operated flares achieve goo d combustion efficiency (e.g.,

greater than 98 percent conversion of organic compounds to ca rbon dioxide). It was observed,

however, that flares operating outside “their stable fla me envelope” produced flames that were

not stable or would rapidly destabilize, causing a decrease in both combustion and destruction

efficiency (Pohl and Soelberg, 1985). To define the stable flam e envelope of operating

conditions, the resulting regulations for flares (i.e ., 40 CFR 60.18 and 40 CFR 63.11(b)),

promulgated in their current form in 1998, included both minim um flare vent gas net heating

value requirements and a limit on velocity as a funct ion of net heating value.

Flares are often used at chemical plants and petroleum refineries as a control device for

regulated vent streams as well as to handle non-routine emissions (e.g., leaks, purges, emergency

releases); and since the development of the current fla re regulations, industry has significantly

reduced the amount of waste gas being routed to flares. Gen erally this reduction has affected the

base load to flares and many are now receiving a small fra ction of what the flare was originally

designed to receive with only periodic releases of epis odic or emergency waste gas that may use

up to the full capacity of the flare. Many flare vent ga s streams that are regulated by NESHAP

and NSPS are often continuous streams that contribute t o the base load of a flare; therefore, it is

critical for flares to achieve good combustion efficiency at all levels of utilization.

Available data suggest that there are numerous factors th at should be considered in order

to be confident that a flare is operated properly to achieve good combustion efficiency. Factors

that can reduce the destruction efficiency capabilities o f the flare include:

Over Steaming . Using too much steam in a flare can reduce flare perform ance. Given that many steam-assisted flares are designed to have a m inimum steam flow rate in order to protect the flare tip, over steaming has resulted, especially during base load conditions. In addition, operators acting cautiously to a void non-compliance with the visible emissions standards for flares have liberally u sed steaming to control any potential visible emissions, also resulting in over ste aming in some cases.This information is distributed solely for the purp ose of pre-dissemination peer review under applicab le information quality guidelines. It has not been formally disseminated by EPA. It does not repr esent and should not be construed to represent any Agency determination or policy.

Section 1.0: Introduction Page 1-2 

## Excess Aeration . Using too much air in a flare can reduce flare performan ce. Airassisted flares operate similarly to steam-assisted fl ares; however, air is used as the
assist-media instead of steam.

High Winds . A high crosswind velocity can have a strong effect on the flare flame dimensions and shape, causing the flame to be wake-dominated ( i.e., the flame is bent
over on the downwind side of a flare and imbedded in the w ake of the flare tip). This type of flame can reduce flare performance; and potentiall y damage the flare tip.

Flame Lift Off

. A condition in which a flame separates from the tip of the flare and there is space between the flare tip and the bottom of the flame due to excessive air induction as a result of the flare gas and center steam exit velocities. This type of flame can reduce flare performance; and can progress to a condition where the flame becomes completely extinguished.

The observations presented in this report are a result of the analysis of several

experimental flare efficiency studies and flare perform ance test reports. Section 2.0 summarizes

these data and reports. In addition, scientific inform ation from peer-reviewed studies and other

technical assessments about flammability, wind, and flame lift off were used in this report.

Sections 3.0 through 8.0 describe the development of our obs ervations. Section 9.0 provides a

list of documents referenced in this report. The primary o bservations are as follows:

• To identify over steaming situations that may occur on st eam-assisted flares, the data suggest that the lower flammability limit of combustion zone gas (LFL CZ 

## ) is the most appropriate operating parameter. Specifically, the data sugge st that, in order to maintain good combustion efficiency, the LFL CZ 

## must be 15.3 percent by volume or less for a
steam-assisted flare. As an alternative to LFL CZ 

## , the data suggest that the ratio of the net heating value of the combustion zone gas (NHV CZ 

## ) to the net heating value of the flare vent gas if diluted to the lower flammability limit (NHV LFL 

## ) must be greater than 6.54. Section 3.0 documents the analysis supporting these obser vations.

• To identify excess aeration situations that may occur o n air-assisted flares, the data suggest that the stoichiometric air ratio (SR) (the act ual mass flow of assist air to the
theoretical stoichiometric mass flow of air needed to c ombust the flare vent gas) is the most appropriate operating parameter. Specifically, the dat a suggest that, in order to maintain good combustion efficiency, the SR must be 7 or l ess for an air-assisted flare. Furthermore, the data suggest that the lower flammability limit of the flare vent gas (LFL VG 

## ) should be 15.3 percent by volume or less to ensure the fl are vent gas being sent to the air-assisted flare is capable of adequately burning wh en introduced to enough air. Section 4.0 documents the analysis supporting these obser vations.This information is distributed solely for the purp ose of pre-dissemination peer review under applicab le information quality guidelines. It has not been formally disseminated by EPA. It does not repr esent and should not be construed to represent any Agency determination or policy.

Section 1.0: Introduction Page 1-3 

## • The data suggest that flare performance is not significan tly affected by crosswind velocities up to 22 miles per hour (mph). There are limited data for flares in winds greater than 22 mph. However, a wake-dominated flame in winds gre ater than 22 mph may affect flare performance. The data available indicate that th e wake-dominated region begins at a momentum flux ratio (MFR) of 3 or greater. The MFR c onsiders whether there is enough flare vent gas and center steam (if applicable) exit vel ocity (momentum) to offset crosswind velocity. Because wake-dominated flames can be identified visually, observations could be conducted to identify wake-dominated fla mes during crosswind velocities greater than 22 mph at the flare tip. Sectio n 5.0 documents the analysis supporting these observations.

• To avoid flame lift off, the data suggest that the actual flare tip velocity (i.e., actual flare vent gas velocity plus center steam velocity, if appl icable) should be less than an established maximum allowable flare tip velocity calculat ed using an equation that is dependent on combustion zone gas composition, the flare tip diameter, density of the flare vent gas, and density of air. Section 6.0 documents the analysis supporting this
observation.

• LFL CZ 

## could apply to non-assisted flares (i.e., the LFL CZ 

## must be 15.3 percent by volume or less in order to maintain good combustion efficiency ). Also, the same operating conditions that were observed to reduce poor flare perfor mance associated with high crosswind velocity and flame lift off could apply to non- assisted flares. Finally, because of lack of performance test data on pressure-assisted fla re designs and other flare design technologies, it seems likely that the parameters im portant for good flare performance for non-assisted, steam-assisted, and air-assisted flares c annot be applied to pressure-assisted, or other flare designs without further information. Sect ion 7.0 documents the analysis supporting these observations.

For purposes of this report, flare vent gas shall mean al l gas found in the flare just prior to the

gas reaching the flare tip. This gas includes all flare waste gas, flare sweep gas, flare purge gas,

and flare supplemental gas, but does not include pilot gas, a ssist steam, or assist air. Also,

combustion zone gas, a term only used for steam-assist ed flares, shall mean all gases and vapors

found just after a flare tip. Combustion zone gas includes all flare vent gas and total steam.This information is distributed solely for the purp ose of pre-dissemination peer review under applicab le information quality guidelines. It has not been formally disseminated by EPA. It does not repr esent and should not be construed to represent any Agency determination or policy.

Section 2.0: Available Flare Test Data Page 2-1 

## 2.0 AVAILABLE FLARE TEST DATA

This section identifies the data and reports that were us ed to support our investigation on

the effects of flare performance with varying levels of steam (for steam-assisted flares); or air

(for air-assisted flares); and high wind and flame lift o ff (for both types of flares).

2.1 Flare Performance Studies and Test Reports

Specific test run data were extracted from the experime ntal flare efficiency studies and

flare performance test reports identified in Table 2-1. A brief summary of each study or report is

provided in Appendix A.

Data sets A through C in Table 2-1 are based on experimenta l data conducted on pilotscale test flares with tip sizes ranging from 3 to 12 inc hes (for steam-assisted flare designs); and

1.5 inches (for the air-assisted flare design tested in data set C). Although data set A includes

experimental data for an air-assisted flare, air flow rates and tip design were held confidential so

it was not considered in our analysis (see Section 2.7); efforts to acquire this information from

the authors were not successful.

Data sets D through I in Table 2-1 are from steam-assist ed flares located at various

chemical and refinery facilities for which EPA Office of Enforcement and Compliance

Assurance either requested studies pursuant to section 114 of th e Clean Air Act, or required the

study pursuant to a consent decree. With the exception of data set I (and the exception of data

sets A through C), flare tip sizes (in terms of the ef fective diameter of the flare tip) for these data

sets range from 16 to 54 inches (for steam-assisted flar e designs). Data set I includes test data for

a unique flare design and was not considered in our analysis (see Section 2.7). Data set J is based

on experimental data from a 36-inch steam-assisted flare tip; and a 24-inch air-assisted flare tip.

In general, the flare test runs were conducted at a high turndown ratio, which means the

actual flare vent gas flow rate is much lower than wha t the flare is designed to handle. Data sets

D through J focus completely on high turndown operating co nditions. Data sets A through C

offer some test data at low turndown ratios, while also offering test data at high turndown ratios.This information is distributed solely for the purp ose of pre-dissemination peer review under applicab le information quality guidelines. It has not been formally disseminated by EPA. It does not repr esent and should not be construed to represent any Agency determination or policy.

Section 2.0: Available Flare Test Data Page 2-2 

## Table 2-1. Flare Performance Test Reports

Data
Set
ID Test Study

(or Test Report)
ID Title Author Date
Published Test

Method(s)
Used
A EPA

- 600/2

- 83

- 052 Flare Efficiency Study

. McDaniel, M. July 1983 Extractive

B EPA-600/2-84-095 Evaluation of the Efficiency
of Industrial Flares: Test
Results. Pohl, J., et al. May 1984 Extractive

C EPA-600/2-85-106 Evaluation of the Efficiency
of Industrial Flares: Flare Head Design and Gas Composition. Pohl, J. and N. Soelberg. September

1985 Extractive

D MPC TX Performance Test of a
Steam-Assisted Elevated
Flare With Passive FTIR. (Conducted in Texas City, TX) Clean Air Engineering,
Inc. May 2010 PFTIR

E INEOS Passive Fourier Transform Infrared Technology (FTIR)
Evaluation of P001 Process
Control Device at the INEOS ABS (USA) Corporation Addyston, Ohio Facility. INEOS ABS (USA) Corporation July 2010 PFTIR

F MPC Detroit Performance Test of a
Steam-Assisted Elevated
Flare With Passive FTIR. (Conducted in Detroit, MI) Clean Air Engineering,
Inc. November

2010 PFTIR

G FHR AU

FHR LOU Flint Hills Resources Clean Air Engineering,
Inc. June 2011 PFTIR

H SDP EPF Shell Deer Park Refining LP Deer Park Refinery East Property Flare Test Report. Shell Global Solutions (US)
Inc. April 2011 PFTIR

I SDP GF Shell Deer Park Site Deer
Park Chemical Plant OP-3
Ground Flare Performance Test Report. Shell Global Solutions (US)
Inc. May 2011 AFTIR

J TCEQ TCEQ 2010 Flare Study Final Report. Allen, David
T. and Vincent
M. Torres. August

2011 Extractive,

AFTIR, and
PFTIRThis information is distributed solely for the purp ose of pre-dissemination peer review under applicab le information quality guidelines. It has not been formally disseminated by EPA. It does not repr esent and should not be construed to represent any Agency determination or policy.

Section 2.0: Available Flare Test Data Page 2-3 

## 2.2 Flare Vent Gas Constituents

Table 2-2 identifies the components that were quantified i n each experimental flare

efficiency study and flare performance test report. With the exception of data set E, all test runs

were based on flares burning propane, propylene, or a mixtur e of other refinery/petrochemical

type gases (with some olefins and aromatics). In general , test runs containing only propane or

propylene (with mixtures of inert) were from data sets A through C, and J; and test runs

containing a mixture of combustible refinery gases and iner ts were from data sets D, and F

through I. Test runs associated with data set E were con ducted while flaring 1,3-butadiene, in

various mixtures of natural gas and nitrogen at a chemical plant.

Table 2-2. Flare Vent Gas Constituents by Test Report

Flare Vent Gas ConstituentA:EPA 2-83-052B:EPA 2-84-095C:EPA 2-85-106D:MPC TXE:INEOSF:MPC DetroitG1:FHR AUG2:FHR LOUH:SDP EPFI:SDP GFJ:TCEQ



## ----- Combustibles

----- 1-Butene Υ Υ Υ Υ Υ 

### 1,3-Butadiene Υ Υ Υ Υ Υ Υ 

### Acetylene Υ Υ Υ Υ



### Benzene Υ Υ Υ



### Carbon Monoxide Υ Υ Υ Υ Υ



### Cis-2-Butene Υ Υ Υ Υ Υ Υ



### Ethane Υ Υ Υ Υ Υ Υ 

### Ethyl Benzene Υ Υ Υ 

### Ethylene Υ Υ Υ Υ Υ Υ 

### Hydrogen Υ Υ Υ Υ Υ Υ 

### Hydrogen Sulfide Υ Υ



### Iso-Butane Υ Υ Υ Υ Υ Υ 

### Iso-Butylene Υ Υ



### Methane Υ Υ Υ Υ Υ Υ Υ Υ 

### Methyl Acetylene Υ



### n-Butane Υ Υ Υ Υ Υ Υ



### Pentane and Heavier Alkanes Υ Υ Υ Υ Υ Υ 

### Propane Υ Υ Υ Υ Υ Υ Υ Υ Υ 

### Propylene Υ Υ Υ Υ Υ Υ Υ Υ



### Toluene Υ Υ



### Trans-2-Butene Υ Υ Υ Υ Υ 

### Xylenes Υ

Total Combustibles In Flare Vent Gas 

### 1 1 1 14 2 15 17 16 16 20 3 ( 1)This information is distributed solely for the purp ose of pre-dissemination peer review under applicab le information quality guidelines. It has not been formally disseminated by EPA. It does not repr esent and should not be construed to represent any Agency determination or policy.

Section 2.0: Available Flare Test Data Page 2-4



## Table 2-2. Flare Vent Gas Constituents by Test Report (Cont inued)

Flare Vent Gas ConstituentA:EPA 2-83-052B:EPA 2-84-095C:EPA 2-85-106D:MPC TXE:INEOSF:MPC DetroitG1:FHR AUG2:FHR LOUH:SDP EPFI:SDP GFJ:TCEQ



## ----- Other

----- Nitrogen Υ Υ Υ Υ Υ Υ Υ Υ Υ Υ Υ 

### Oxygen Υ Υ Υ Υ Υ



### Carbon Dioxide Υ Υ Υ Υ Υ Υ



### Water Y Y Y

Total Other Constituents

In Flare Vent



### Gas 1 1 1 4 1 3 2 3 4 4 1
1 – For data set J, tests were not performed with all th ree combustibles; tests were either performed with propane and methane, or propylene and methane.



## Data sets D, and F through I, used flare vent gas with me thane and hydrogen as the

primary combustibles, and data sets D and F also had signif icant amounts of olefins in the flare

vent gas. Table 2-3 shows the range and average of methane , hydrogen, olefins, and nitrogen in

the flare vent gas for each data set. More specific det ails regarding flare vent gas constituents are

discussed in Appendix A. Also, chemical composition for each test run (by test report) used in

the steam data analysis is discussed in section 3.0 of this report.

Table 2-3. Minimum, Maximum, and Average Volume Percents of

Primary Constituents in Flare Vent Gas

Test Report %

Hydrogen (Average) %

Methane (Average) % Total

Olefins (Average) % Total Other

Combustibles (Average) %

Nitrogen (Average)

EPA-2-83-052 8.8

– 100 (46) 0

– 9 (54)

EPA-2-85-106 12

– 18 (15) 82

– 88

(85)

MPC TX 3.1

– 24

(14) 3.8

– 41

(28) 11

– 44

(19) 7.6

– 43

(17) 8.2

– 35

(21)

INEOS 0

– 61 (20) 2.4

– 33

(18) 36

– 78 (61)

MPC Detroit 7.0

– 55

(23) 16

– 46

(30) 4.5

– 65

(20) 4.2

– 24

(13) 5.7

– 70

(16)

FHR AU 13

– 47

(30) 29

– 75

(55) 0.01 8

– 0.47

(0.13) 3.7

– 12

(6.5) 3.5

– 16

(7.2)

FHR LOU 20

– 30

(27) 55

– 69

(63) 1.2

– 7.7

(3.1) 3.2

– 4.2

(3.7) 0.90

– 9.0

(2.9)

SDP EPF 37

– 62

(52) 8.5

– 31

(18) 0.010

– 0.49

(0.14) 11

– 20

(13.8) 10

– 27

(16)

TCEQ 0

– 6.9 (4.0) 0

– 100

(24) 0

– 14.8

(2.2) 0

– 83

(70)This information is distributed solely for the purp ose of pre-dissemination peer review under applicab le information quality guidelines. It has not been formally disseminated by EPA. It does not repr esent and should not be construed to represent any Agency determination or policy.

Section 2.0: Available Flare Test Data Page 2-5 

## 2.3 Steam Injection Rates and Tip Design for Available Flare Test Data

A steam-assisted flare uses steam at the flare stack o r flare tip for purposes including, but

not limited to, protecting the design of the flare tip, pr omoting turbulence for mixing or inducing

air into the flame. Test data are available for nine di fferent steam-assisted flares when

considering the data sets listed in Table 2-1.

There are several different ways steam can be injecte d into the flare waste stream. The

location of steam injection on each of nine steam-ass isted flares varied between the data sets.

The steam-assisted flares had steam injected through ei ther: nozzles located above the main flare

tip opening (upper steam), nozzles on an external ring around the top of the flare tip (ring steam),

a single nozzle located inside the flare prior to the f lare tip (center steam), or internal tubes

interspersed throughout the flare tip (lower steam). The location of steam injection can change

the nominal flare tip diameter. An effective diameter of the flare tip considers the location of

steam injection by subtracting the obstructed exit area o f the flare tip (i.e., area of any stability

tabs, stability rings, and steam tubes) from the total exit area of the flare tip.

Table 2-4 summarizes the design detail (including steam injec tion location and effective

flare tip diameter) of each steam-assisted flare tip us ed for each data set. For most performance

tests, not only were the steam injection locations dif ferent, but also the steam rate varied between

test runs. For certain data sets and steam injection loc ations, the steam rate was held constant

over all test runs. Owners and operators are limited r egarding how much they can reduce steam

flow to the flare tip because steam-assisted flares oft en have a manufacturer’s minimum steam

requirement in order to protect the integrity and life o f the flare tip.

Table 2-4. Steam-Assisted Flare Tip Design Detail

Data
Set ID Flare Tip

Manufacturer and
Model Number Effective
Diameter 1 

### (inch) Tip Design and St eam Injection Test Rates
At or Above Tip Inside Tip Upper (lb/hr) Ring

(lb/hr) Lower

(lb/hr) Center

(lb/hr)



### A John Zink
STF-S-8 5.86 Varied None None NoneThis information is distributed solely for the purp ose of pre-dissemination peer review under applicab le information quality guidelines. It has not been formally disseminated by EPA. It does not repr esent and should not be construed to represent any Agency determination or policy.

Section 2.0: Available Flare Test Data Page 2-6



## Table 2-4. Steam-Assisted Flare Tip Design Detail (Continu ed)

Data
Set ID Flare Tip

Manufacturer and
Model Number Effective
Diameter 1 

### (inch) Tip Design and Steam Injection Test Rates
At or Above Tip Inside Tip Upper (lb/hr) Ring

(lb/hr) Lower

(lb/hr) Center

(lb/hr)



### B Energy and Environmental Research Corporation; and other manufacturer designs 2 

### 3, 6, and 12 Varied None None None

C Unknown Commercial Coanda (tulip) Flare Tip 12 140 None None None

D Callidus Technologies
BTZ-IS3/US-24-C 23.25 None 3 

### None Varied 500

E John Zink EEF-QS-16 16 Varied None None None

F NAO Inc.
20” NFF-RC 16 None Varied None 300

G Callidus Technologies
BTZ-US-16/20-C 20 None Varied None 500

G Callidus Technologies
BTZ-1S3-54C 54 None None Varied 2,890

H John Zink EEF-QA-36-C 36 Varied None None Varied

J John Zink EE-QSC-36” 36 Varied None None Varied

1 – The effective diameter of each flare tip was either d irectly extracted from the test report or calculated from effective area reported in the test report. The effective diameter (or area) considers the portion of the area that is occupied by obstructions and not available for flare vent gas to flow through; it is determined by subtracting the obstructed exit area of the flar e tip (i.e., area of any stability tabs, stability rings, and steam tubes) fro m the total exit area of the flare tip. 2 – Three simple pipe flare heads were designed and built by Energy and Environmental Research Corporation for testing. A retention ring was used on the 3-inch flare head during some t esting, so the effective diameter would be less than 3 inches during those specific tests. In addition to these simple pipe fl are heads, three commercial 12-inch diameter pipe flares were also tested; these flares were supplied by various flare manufacturers, but the specific design of the flare heads was held confident ial. 3 – The flare tip is equipped with upper steam; however, i t was not used during any test runs. (Dickens 2011)



## 2.4 Air Injection Rates and Tip Design for Available Flare T est Data

An air-assisted flare uses assist air at the flare ti p for purposes including, but not limited

to, protecting the design of the flare tip, promoting turbu lence for mixing, and inducing air into

the flame. Test data are available for three different air-assisted flares when considering the data

sets listed in Table 2-1. However, the experimental data for the air-assisted flare associated with

data set A were not considered in our analysis (see Sect ion 2.7) because air flow rates and tip

design were held confidential. Table 2-5 summarizes the des ign detail of each air-assisted flare

tip used for each data set.This information is distributed solely for the purp ose of pre-dissemination peer review under applicab le information quality guidelines. It has not been formally disseminated by EPA. It does not repr esent and should not be construed to represent any Agency determination or policy.

Section 2.0: Available Flare Test Data Page 2-7 

## Air is injected into the flare waste stream through no zzles located above the main flare tip

opening. Air injection rates were varied during each test r un; ranges of injection rates for each

air-assisted flare tip tested are provided in Table 2-5.

Table 2-5. Air-Assisted Flare Tip Design Detail

Data Set ID Flare Tip

Manufacturer and
Model Number Effective
Diameter 1 

### (inch) Range of Tested Air Injection Rates (lb/hr)

A John Zink
STF-LH-457-5 Unknown Unknown

C Unknown 1.5 8

, 100 to 150 ,000

J John Zink
LHTS-24/60 24 250 to 4,700

1 – The effective diameter of each flare tip was either d irectly extracted from the test report or calculated from effective area reported in the test report. The effective diameter (or area) considers the portion of the area that is occupied by obstructions and not available for flare vent gas to flow through; it is determined by subtracting the obstructed exit area of the flar e tip (i.e., area of any stability tabs, stability rings, and steam tubes) fro m the total exit area of the flare tip.



## 2.5 Flare Test Methods

Measuring emissions from a flare can be difficult and dan gerous because flares lack an

enclosed combustion chamber, may be elevated, and come i n many different designs and sizes.

With combustion taking place at and above the tip of the flare, the combusted gases are released

into the atmosphere in any direction given the meteor ological conditions and flare vent gas

velocity that exist at that moment. Although extractiv e techniques have been used to measure

emissions from flares, they require placement of a h ood-like structure, sampling rake with

multiple sample ports, or other scheme to ensure represe ntative collection of the flare plume.

This renders the use of extraction methods for testing i ndustrial flares impractical and relegated

to research studies, usually on smaller flares.

Recent technological advances have produced remote sensing i nstruments capable of

indicating the presence of combustion products (e.g., carbon dioxide, carbon monoxide, and

select hydrocarbons) without the safety hazards introduce d by physically extracting a sample of a

flare plume. The remote sensing techniques that have bee n used on flares discussed in this report

include: active Fourier transform infrared (AFTIR) and pas sive Fourier transform infrared

(PFTIR). The main difference between AFTIR and PFTI R is that AFTIR requires the remoteThis information is distributed solely for the purp ose of pre-dissemination peer review under applicab le information quality guidelines. It has not been formally disseminated by EPA. It does not repr esent and should not be construed to represent any Agency determination or policy.

Section 2.0: Available Flare Test Data Page 2-8 

## sensor be aligned to an artificial light source; wher eas PFTIR simply detects infrared radiation

emitted as heat (i.e., PFTIR uses thermal imaging). Tabl e 2-1 identifies whether each test report

used extractive, AFTIR, or PFTIR test methods to determi ne the combustion efficiency of a

flare. The majority of these reports used PFTIR, which i nvolves using a spectrometer positioned

on the ground to view hot gases from the flare which rad iate spectra that are unique to each

compound. The PFTIR tests were performed and analyzed by one company, and we are unaware

of other companies currently using this technique on flares.

Although AFTIR and PFTIR remote sensing offers an attrac tive alternative to

characterize emissions from flares, AFTIR and PFTIR are relatively expensive, new tools that

currently have no approved methods for universal use on flar es. Furthermore, for these remote

sensing techniques, accurate fitting of measurement and refere nce spectra for chemical species of

interest at representative flare temperatures are pivotal in accurately characterizing industrial

flares. Currently, high temperature spectra are not avail able for all chemical species that may be

found in flare vent gas.

The test report for data set J evaluated the performanc e of remote sensing technologies

against extractive techniques. The test report for data s et J concluded that the mean difference

and standard deviation of the reported AFTIR and PFTIR combus tion efficiency values increase

as the reported extractive combustion efficiency values decreases; however, both the AFTIR and

PFTIR methods actually compare very well to the extrac tive test results for combustion

efficiencies reported as 90 percent or greater. For combusti on efficiencies reported as 90 percent

or greater, the test report for data set J states tha t the mean difference of combustion efficiency

values averaged 2.5 percentage points different between ext ractive and AFTIR, and

2.2 percentage points different between extractive and P FTIR. Based on these conclusions, the

data collected from all the reports in Table 2-1 were com bined and used to support our

investigation on the effects of flare performance.This information is distributed solely for the purp ose of pre-dissemination peer review under applicab le information quality guidelines. It has not been formally disseminated by EPA. It does not repr esent and should not be construed to represent any Agency determination or policy.

Section 2.0: Available Flare Test Data Page 2-9 

## 2.6 Combining All Available Test Run Data

All data sets identified in Table 2-1 were combined into an Excel workbook (see

Appendix B) and the data were separated by flare type (i.e., steam-assisted versus air-assisted).

The Excel workbook identifies each specific test run by th e exact test condition and run

identification used in each individual report. For data s ets A through C, test run data from tables

provided within the reports had to be extracted and manually en tered into the Excel workbook.

Raw test data in the form of Excel worksheets were av ailable for data sets D through J, which

eliminated the need to manually enter data into the Excel workbook for these sets. Each

individual test run is identified in the “All Run Data” t ab of the Excel workbook.

The amount of detail provided per test run varies between ea ch data set. Also, the

nomenclature used to describe a variable is different betw een each data set. For example, data

set A uses the term “Lower Heating Value (Btu/scf)” whe n identifying the net heating value of

the flare vent gas, and data set D uses the term “Vent Gas HV” to describe the same variable.

Appendix C shows the nomenclature that each data set uses and how it is mapped to one

common term used in the Excel workbook.

In some cases, a data set did not explicitly provide a va riable, but it could be calculated

using details from the test reports. For example, for so me data sets, in order to calculate a

volumetric flow rate of the flare vent gas for a speci fic test run, known values for the mass flow

rate, molecular weight of the flare vent gas, and a c onversion factor for molar volume of an ideal

gas (379.48 scf/mol) were used. These cases are identified w ith the words “Calc Eq. D.##” in

Appendix C; where “##” is the specific calculation methodol ogy number. Each calculation

methodology is described in Appendix D.This information is distributed solely for the purp ose of pre-dissemination peer review under applicab le information quality guidelines. It has not been formally disseminated by EPA. It does not repr esent and should not be construed to represent any Agency determination or policy.

Section 2.0: Available Flare Test Data Page 2-10 

## 2.7 Data Removed After Being Considered

A total of 582 steam-assisted test runs (118 of these runs ca me from tests performed on a

steam-assisted flare, but no steam was used during the tes t) and 111 air-assisted test runs were

considered in our analysis. However, 270 of the steam-ass isted test runs (no steam was used

during the test for 109 of these runs) and 67 of the air-assi sted test runs were removed prior to

any final analysis.

Data sets B and I were not used in any of our analysis. Da ta set B does not provide

enough data to determine a flare vent gas flow rate, which is critical to calculating the various

operating limits and parameters we examined. Data set I pr ovides performance testing data for a

unique flare design that did not operate in the same way as the other flares and the test data did

not appear consistent. The design is a multistage steam -assisted enclosed ground flare with three

different stages, which become active at successively hi gher flows. The flare has 92 horizontallymounted burners (basically a refractory lined steel shell into which 92 raw flare vent gas burners

discharge). Because the flare tested in data set I is s o different from the flare designs in other

data sets, it is not appropriate to combine and compare its results with the others.

In addition to excluding data sets B and I in their entir ety, Table 2-6 identifies various

reasons why an individual test run was removed prior to any final analyses described in this

Report. Each individual test run removed from the analysi s is identified in the “Removed Data”

tab of the Excel workbook (see Appendix B). Each individua l air-assisted or steam-assisted test

run remaining (after removing data due to the reasons describe d in Table 2-6) is identified in

either the “Air Data Used All Analysis” or “Steam Da ta Used All Analysis” tabs of the Excel

workbook depending on flare tip type.This information is distributed solely for the purp ose of pre-dissemination peer review under applicab le information quality guidelines. It has not been formally disseminated by EPA. It does not repr esent and should not be construed to represent any Agency determination or policy.

Section 2.0: Available Flare Test Data Page 2-11 

## 2.8 Determination of Combustion Efficiency Representing Good Flare Performance

The PFTIR testing measures carbon dioxide, carbon mono xide, and hydrocarbons in the

plume of the flare in order to calculate combustion ef ficiency. Several current regulations,

including NSPS and NESHAP, require non-flare control devices to be installed and operated to

achieve 98 percent destruction efficiency. Therefore, it se emed reasonable to assume that a 98

percent destruction efficiency represents good performance for flares as well. However, most of

the flare data was reported in terms of combustion eff iciency, making it necessary to estimate a

combustion efficiency equivalent to 98 percent destruction e fficiency as a means for determining

which test runs (in reviewing the flare test data) demonst rated good performance.

According to the John Zink Combustion Handbook (Baukal, 2001), destruction efficiency

is a measure of how much of the hydrocarbon is destroyed ; and combustion efficiency is a

measure of how much the hydrocarbon burns completely to yield carbon dioxide and water

vapor. Baukal states that combustion efficiency will alw ays be less than or equal to the

destruction efficiency; and a flare operating with a com bustion efficiency of 98 percent can

achieve a destruction efficiency in excess of 99.5 percent. The relationship between destruction

and combustion efficiency is not constant and changes with different compounds; however, we

believe Baukal’s estimation of 1.5% difference is a rea sonable assumption. Extrapolating this to

98 percent destruction efficiency, and also considering the variability in results from the different

test methods used in this analysis (e.g., PFTIR vs. AFTI R, vs. extractive sampling methods), it

was determined that a combustion efficiency of 96.5 percent in the flare test data demonstrates

good flare performance.This information is distributed solely for the purpose of pre-dissemination peer review under applicable information quality guidelines. It has not beenformally disseminated by EPA. It does notrepresent and should not be construed to representany Agency determination or policy.Section 2.0: Available Flare Test DataPage 2-12Table 2-6. Criteria To Exclude Data PointsCriteriaExplanationTest report did not record combustion efficiency for aspecific test run.It was determined there was not enough information to be able to use the data point.Test report recorded combustion efficiency as 0% for aspecific test run.The flare flame was completely snuffed out and the datapoint was not useful in determiningtrends. However, the data point was reviewed to determineconditions that do not provide goodcombustion (all data points in this category had a LFLCZgreater than 15.3%; see Section 3.0 ofthis report for an explanation on LFLCZ).Test report recorded that the extraction probe positioningfora specific test run was located in the flame.Thespecific test runwas consideredinvalid because the extraction technique did not obtain agood sample of the flare plume.Test report recorded that the extraction probe positioningfora specific test run was uncertain.The specific test runwas consideredinvalid because the extraction technique may not haveobtained a good sample of the flare plume.Test report recorded a specific test run time as less than5 minutes.The specific test runhastoo much uncertainty and variability in the reported values. Note,there were four data points in data set D (i.e., runs6-1, 8-1, 10-1, and 10-2 from condition D)that were reported as having a run time greater than 5minutes; however, these points areincluded in this removal category because several of theminutes in the average of the test runeither showed zero entries for the PFTIR data. These4 runs had less than 5 minutes of datathat were not zero or not affected by wind.Test report recorded single test runs and an average of thespecific single test runs; the single test runs were removed,but the average was kept.The single test runswere consideredduplicative because each run was performed at the exactsame conditions.Test report recorded a specific test run as smoking.The specific test runwas consideredout of compliance because visible emissions are aviolation with the current regulation, and determined thattest runs that were considered out ofcompliance should not be used to establish operating parameters for good combustion.Test report did not record enough information to determinethe flare vent gas flow for a specific test run.It was determined there was not enough information to be ableto use the data point.Test report recorded that theflarevent gas flow rate of aspecific test run was less than 10 pounds per hour.The specific testresults for these runs are based on an extractive test method.The resultsshowed very different CE values than other similar runsexcept that these runs had flare ventgas flow rates less than 10 pounds per hour. The extractivetest method may not have correctlydetected the waste gas compositions because flow was too low.Specific to only data set H, the test report concluded that the"GE Panametric flow readings must be in error whennitrogen concentrations in the SDP EPF line were greaterthan 30v%".Theflarevent gas flowrates (above 30% N2)for data set Harereported asnot accurate. Thisobservation is limited to ten specific test runs.Specific to only data set C, two specific test runs werereported as achieving greater than 99% combustionefficiency, yet the fraction of combustible in the stream wasless than 2%.The specific testresults for these two test runs are based on an extractive test method whichmay not have correctly detected the waste gas compositions. Given the flammability of thestream, it is not possible for these two test runs to have achieved greater than 99% combustionefficiency (the combustibility of the stream is too low).This information is distributed solely for the purp ose of pre-dissemination peer review under applicab le information quality guidelines. It has not been formally disseminated by EPA. It does not repr esent and should not be construed to represent any Agency determination or policy.

Section 3.0: Steam and Flare Performance Page 3-1 

## 3.0 STEAM AND FLARE PERFORMANCE

Steam is used in some flares as a design feature to prote ct the flare tip. Steam injection

also promotes smokeless burning in a flare. A key factor to smokeless burning is having enough

waste gas momentum as it exits the flare burner so tha t sufficient amounts of air can mix with the

waste gas and achieve complete combustion. Steam injec tion is the most common technique for

adding momentum to low-pressure gases. In addition to adding m omentum, steam also provides

smoke suppression benefits of gas dilution and participates in the chemistry of the combustion

process (Baukal, 2001). Steam will react with hot carbon pa rticles in soot, removing the carbon

before it can cool and form smoke. Steam will also rea ct with intermediate combustion products

to form compounds that readily burn at lower temperatures (Castiñeira, 2006). Using too much

steam in a flare (over steaming) can result in a flar e operating outside its stable flame envelope,

reducing the destruction efficiency capabilities of the fl are. Moreover, the cooling effect from

use of excessive steam may actually inhibit dispersion of flared gases. In extreme cases, over

steaming can actually snuff out a flame and allow waste gases to go into the atmosphere

unburned (Peterson, 2007).

To identify over steaming situations that may occur on st eam-assisted flares, the data

suggest that the lower flammability limit of combustion zone gas (LFL CZ 

## ) is the most appropriate

operating parameter. Specifically, the data suggest that, i n order to maintain good combustion

efficiency, the LFL CZ 

## must be 15.3 percent by volume or less for a steam-assi sted flare. As an

alternative to LFL CZ 

## , the data suggest that the ratio of the net heating valu e of the combustion

zone gas (NHV CZ 

## ) to the net heating value of the flare vent gas if dil uted to the lower

flammability limit (NHV LFL 

## ) must be greater than 6.54. Section 3.1 documents the anal ysis

supporting this observation. Sections 3.2 through 3.4 explain ot her operating conditions that we

investigated for good combustion efficiency for steam-as sisted flares.

3.1 Lower Flammability Limit of Combustion Zone Gas for Steam-A ssisted Flares

The lower flammability limit (LFL) is an important ch emical property when considering

combustibility of a gas mixture. The LFL of any mixture is the lowest concentration of that

mixture in air at which the mixture will burn. Mixtures with a relatively high LFL are lessThis information is distributed solely for the purp ose of pre-dissemination peer review under applicab le information quality guidelines. It has not been formally disseminated by EPA. It does not repr esent and should not be construed to represent any Agency determination or policy.

Section 3.0: Steam and Flare Performance Page 3-2 

## flammable when released to the air than mixtures with a relatively low LFL. A gas mixture with

a relatively high LFL requires a larger volume of the m ixture to burn in a specific volume of air,

than would a mixture of gases with a relatively low LFL being combusted in that same volume

of air. The LFL of a mixture is therefore influenced by both the type and amount of chemical

components (including inerts) present in the gas being burne d and is a significant parameter

when assessing whether a mixture being combusted with an o pen flame will adequately combust.

The combustion zone of a steam-assisted flare includes the gas mixture that is created by

the flare vent gas and the steam that is supplied to the flare. The flare vent gas includes all waste

gas, sweep gas, purge gas, and supplemental gas, but does not inc lude pilot gas, or assist media.

Therefore, the combustion zone gas includes all the gase s injected into the combustion zone of

the flare except the pilot gas. See Section 3.1.5 for a discussion of why pilot gas is not included

in the combustion zone gas. The chemical components and their relative amounts in the

combustion zone for each test run used in the data anal ysis for this section can be seen in

Appendix E by test report. The LFL CZ 

## is the resulting LFL of the mixture that is created b y
combining both the flare vent gas and steam. This parameter was considered as a means to take

into account the effect of steam on the capability of the flare vent gas to burn.

Figure 3-1 shows the boundaries of flammability for severa l different inerts in methane

and air mixtures (Zabetakis, 1965). The plot is referred t o as a Zabetakis plot, or “nose plot”,

because of its shape and represents the concentrations of fuel (methane in this case), inert and air,

and the conditions in which combustion will occur. Note that the air concentration is determined

by subtracting the methane and inert concentrations fro m 100 percent. The line hitting the y-axis

near the bottom of the figure is the LFL with no inert added (5% for methane). The upper

flammability limit (UFL) is the line hitting the y-axis at a higher level (about 15%). The x-axis

shows the quantity of inert added to the methane and air mi xture. The curves show that the UFL

falls rapidly for mixtures with increasing amounts of i nert and the lowest UFL value occurs at

the maximum amount of inert at which combustion can st ill be supported. At this amount of

inert, the UFL has been reduced to be equal to the LFL and c ombustion can only occur at this

concentration. An amount of inert above this maximum would render the mixture nonflammable, because there would not be enough air to susta in combustion.This information is distributed solely for the purp ose of pre-dissemination peer review under applicab le information quality guidelines. It has not been formally disseminated by EPA. It does not repr esent and should not be construed to represent any Agency determination or policy.

Section 3.0: Steam and Flare Performance Page 3-3



## Figure 3-1. Zabetakis Nose Plot For Methane And Inert In Ai r

At the UFL, at any inert concentration, the combustible -inert-air mixture is oxygen

limited; there is enough fuel to burn but just enough oxygen to sustain combustion. Any less

oxygen, the mixture is not flammable. At the LFL, at any inert concentration, there is plenty of

oxygen with respect to the amount of fuel available. At any combustible concentration less than

the LFL, the fuel is too lean and the mixture is not fla mmable.

Adapted from Evans and Roesler (2011), Figure 3-2 uses a Zabetakis plot for methane in

air with water as the inert in order to illustrate h ow a ‘pocket’ of flare vent gas and steam mixture

interacts with the atmosphere as it travels from the flare tip through the combustion zone. For

simplicity, Figure 3-2 assumes that the flare vent gas i s methane and center steam has been

added, so the flare vent gas and steam mixture is 25 volume percent methane and 75 volume

percent water. Just prior to the flare vent gas and steam mixture being released from the flare tip

into the combustion zone, it contains no oxygen and is th erefore above the UFL (this point is notThis information is distributed solely for the purp ose of pre-dissemination peer review under applicab le information quality guidelines. It has not been formally disseminated by EPA. It does not repr esent and should not be construed to represent any Agency determination or policy.

Section 3.0: Steam and Flare Performance Page 3-4 

## represented on Figure 3-2 because this condition would exist off the graph). However, from the

point of release at the flare tip, the flare vent gas and steam mixture is quickly diluted by the

ambient air. At point A on Figure 3-2, the flare vent gas and steam mixture has mixed with air to

about 15 percent methane, 45 percent water, and 40 percent ai r; and the gas mixture is still too

rich to burn. As the gas mixture continues mixing with ai r it approaches the UFL (point B on

Figure 3-2). For this example, the UFL of the gas mixture is 8.3 percent methane, 25 percent

water, and 66.7 percent air. Just beyond point B, the gas mi xture is within the UFL and LFL and

will burn. While the gas mixture is burning it also contin ues to be diluted until the concentration

of the gas mixture is just at the LFL (point C on Figure 3-2) of 5.8 percent methane, 17.5 percent

water, and 76.7 percent air. Using this thought process for oth er mixtures, it becomes clearer that

if the flare vent gas and steam mixture are already ne ar the LFL when the gas mixture is released

into air, the concentration could quickly fall below t he mixture’s LFL (point D on Figure 3-2)

before having a chance to ignite and burn completely; and t herefore, it is possible to dilute the

flammable gas mixture to a mixture with no combustible ch aracteristics.

Figure 3-2. Time Sequence of Flare Vent Gas Volume Moving Through Flammability Region Source: (Adapted from Evans and Roesler, 2011) Blue: No combustion, above UFL (fuel rich) Red: Combustion, within flammability region Yellow: No combustion, below LFL (fuel lean)

Flare Tip 

### A B D

C

55Methane, Percent 15

14

13

5 6 7

0 5
Water, Percent 50 8 9 10 11 12

10 15 20 25 30 35 40 45 

### Just After Flare Tip (A)

UFL (B)

LFL (C)

Post Combustion (D) Zabetakis Plot:
Methane in air with water as the inert.

WaterThis information is distributed solely for the purp ose of pre-dissemination peer review under applicab le information quality guidelines. It has not been formally disseminated by EPA. It does not repr esent and should not be construed to represent any Agency determination or policy.

Section 3.0: Steam and Flare Performance Page 3-5 

## In addition, the inerts (e.g., nitrogen, carbon dioxide, steam, etc.) of the combustion zone

gas, which are either included in the flare vent gas or a re added as assist steam, compete for

space with the air and combustible components. The inert gases reduce the flammable range of

the gas-air mixtures (increase the LFL and decrease the UFL). Some of the heat from the

combustion reaction is absorbed by the inert gases (Mol narne et. al., 2005), which cools the

flame and slows the propagation of combustion. This is e specially a concern for mixtures with

higher LFL values. The higher the inert concentration pr esent in the combustion zone gas, the

higher the LFL CZ 

## . When the higher LFL combustion zone gas mixes with ai r, it takes less air to

dilute the gas mixture below the LFL and therefore this diluting effect can happen much more

quickly. Also, because there are fewer combustible gas molecules in the combustion zone gas,

more mixing is required to get the combustible components n ear oxygen molecules. Therefore,

the higher the LFL of the combustion zone gas, the more difficult it is to achieve and maintain

good combustion.

Section 3.1.1 discusses the flare test data and how these data suggest that 15.3 percent

LFL CZ 

## may be an appropriate threshold (an operating condition representing good combustion).

Section 3.1.2 describes the method for calculating LFL CZ 

## for mixtures using Le Chatelier’s

principle and the level of accuracy expected given differ ent flare vent gas compositions. Section

3.1.3 analyzes data points that had a LFL CZ 

## less than 15.3 percent but a combustion efficiency

less than 96.5 percent. Section 3.1.4 analyzes the 66 data po ints with good combustion efficiency

and a LFL CZ 

## greater than 15.3 percent, and provides possible further cat egorizing of the LFL CZ 

## to

provide more chemical component specificity to the LFL CZ 

## limit. Section 3.1.5 provides an

explanation for excluding pilot gas in these analyses.

3.1.1 Flare Test Data and LFL CZ



## The LFL CZ 

## was examined for 312 steam-assisted flare test runs to dete rmine if there is a

LFL CZ 

## threshold that would indicate whether good combustion w ould occur. Figure 3-3 shows

that as the LFL CZ 

## increases, the combustion efficiency of a flare dete riorates. The vertical dotted

line in Figure 3-3 marks the threshold where all test runs (47) at a LFL CZ 

## of less than or equal to

10.0 percent achieved a combustion efficiency of 96.5 percen t or greater. However, there are

several test runs with gas mixtures that have a LFL CZ 

## greater than 10.0 percent that had goodThis information is distributed solely for the purp ose of pre-dissemination peer review under applicab le information quality guidelines. It has not been formally disseminated by EPA. It does not repr esent and should not be construed to represent any Agency determination or policy.

Section 3.0: Steam and Flare Performance Page 3-6 

## combustion efficiencies. Looking at the extent of test points both above and below 96.5 percent

combustion efficiency reveals that test runs with a L FL CZ 

## of 15.3 percent or less resulted in good

combustion efficiency for all runs except eleven. At a LFL CZ 

## greater than 15.3 percent, there are

several test runs with good combustion efficiency, but for every run with good combustion, there

is at least one run with bad combustion. For example, using test runs with a LFL CZ 

## of 20.0

percent or less, there are 30 test runs with good combustion and 33 test runs with combustion

efficiency less than 96.5 percent.

The vertical solid line in Figure 3-3 shows a threshold wher e most test runs at a LFL CZ 

## of

less than or equal to 15.3 percent achieved a combustion effic iency of 96.5 percent or greater.

This level maximizes the number of test runs (105) with a c ombustion efficiency of 96.5 percent

or greater that are below 15.3 percent LFL CZ 

## while minimizing the number of test runs (11) that

have a combustion efficiency less than 96.5 percent. Ther e are 11 test runs (highlighted in red on

Figure 3-3) with a LFL CZ 

## between 10.0 and 15.3 percent that did not achieve a combustio n
efficiency of 96.5 percent or greater; further detail about the 11 test runs is provided in Section

3.1.3. Also evident from Figure 3-3 are several test runs th at achieved good combustion but all

had a LFL CZ 

## greater than 15.3 percent. There are 197 data points with a LFL CZ 

## greater than 15.3

percent and 61 of these points have a combustion efficie ncy of greater than 96.5 percent. These

data points are discussed further in Section 3.1.4.This information is distributed solely for the purp ose of pre-dissemination peer review under applicab le information quality guidelines. It has not been formally disseminated by EPA. It does not repr esent and should not be construed to represent any Agency determination or policy.

Section 3.0: Steam and Flare Performance Page 3-7



## Figure 3-3. Combustion Efficiency vs. LFL CZ



## 3.1.2 The Le Chatelier Principle

Le Chatelier’s principle was used to estimate lower fl ammability limits of the flare

combustion zone gas for each test run. Le Chatelier’s principle for determining flammability

limits for mixtures uses the reciprocal of the volume weighted average over the LFL of the

individual compounds for estimating the gas mixture’s LFL (Equation 3-1).



# ∑

= 

# 

       =

n

j j a



# LFL LFL

j

1 

# 100



# χ ( Eq. 3-1 )

Where:

LFL a 

## = Lower flammability limit of any gas mixture ‘a’, volume %.

a = Placeholder for any gas mixture.

n = Number of components in gas mixture ‘a’.

j = Individual pure component in gas mixture ‘a’.

40% 50% 60% 70% 80% 90% 100%

5% 10% 15% 20% 25% 30% 35% 40% 45% 50%Combustion Efficiency (%)

LFL CZ (%)10.0%15.3%This information is distributed solely for the purp ose of pre-dissemination peer review under applicab le information quality guidelines. It has not been formally disseminated by EPA. It does not repr esent and should not be construed to represent any Agency determination or policy.

Section 3.0: Steam and Flare Performance Page 3-8 

## x j 

## = Concentration of individual pure component j in gas mi xture ‘a’, volume %.

LFL j 

## = Lower flammability limit of individual pure componen t j, volume %.

Le Chatelier’s equation was originally limited to binary mixtures of combustible gases

(Coward et al., 1919). Coward et al. (1919) generalized the equa tion for mixtures containing

more than two combustible gases. Coward and Jones (1952) pres ented a method for using Le

Chatelier’s equation when inert gases are included in the mixture. This method entails assigning

amounts of inert gas to the combustible gases, identifying a LFL for each combustible–inert

combination from previous experimental data, and then using Le Chatelier’s equation to

calculate the LFL for the full mixture. For example, a mixture of 50:20:30 percent

nitrogen/hydrogen/methane could be broken up into two mixtures, one with 60:40 percent

nitrogen/hydrogen (30% nitrogen and 20% hydrogen from original mixt ure, or total of 50% of

the original mixture) and one with 40:60 nitrogen/methane (20% nitrogen and 30% methane

from original mixture, or total of 50% of the original mi xture). Experimental data of nitrogen and

hydrogen, and nitrogen and methane mixtures, such as the data graphed in Appendix F, can then

be used to determine each partial mixture’s LFL. Looking at A ppendix F, the LFL of a

60:40 percent nitrogen/hydrogen mixture is 6.5 percent; and 12.5 perce nt for a 40:60 percent

nitrogen/methane mixture. Then using Le Chatelier’s equatio n, a LFL of 8.6 percent is

determined for the full mixture:



# 8.6%

12.5 50

6.5 50 100

=

+ ( Eq. 3-2 )

This method is not practical for determining the LFL of f lare vent gas and steam mixtures

because flare vent gases can change at any moment and co nsist of a wide variety of chemicals.

The LFL data for mixtures with nitrogen (or carbon dioxide) and a combustible is limited; and

this type of information is essentially unavailable for steam. The results of the method also vary

significantly depending on how the combustibles and inerts are paired together.

Karim et al. (1985) describes another way to address mixtur es with inerts, which is to

include the inert in Le Chatelier’s equation and assume a LFL for the inert gas of infinity. This

zeros out the term for the inert in the equation since one divided by infinity is zero. The LFL CZ 

## in

Figure 3-3 assumes inerts have an infinite LFL (or a rec iprocal of the LFL equal to zero).This information is distributed solely for the purp ose of pre-dissemination peer review under applicab le information quality guidelines. It has not been formally disseminated by EPA. It does not repr esent and should not be construed to represent any Agency determination or policy.

Section 3.0: Steam and Flare Performance Page 3-9 

## However, assuming infinity for all inerts as Karim et a l. (1985) suggests does not address

the difference in behavior for the different inerts. Molnarne et al. (2005) describes a method for

taking into account non-nitrogen inerts. This method is use d in the International Standards

Organization (ISO) Standard 10156 and was originally presente d by Besnard (1996). In this

method, a nitrogen equivalency factor is used that varies depending on both the type of inert(s)

and combustible compound(s) in the mixture. Molnarne, et a l. describes the possible values for

nitrogen equivalency for the specific combustion gas and i nert combinations. Equation 3-3

incorporates this method into Le Chatelier’s equation. More details about inerts and further

explanation for including an equivalency adjustment to cor rect for different inert behavior are

provided in Appendix G. Appendix G also provides a more detail ed discussion about LFL and

the accuracy of calculated LFL values with respect to varying amounts of inerts and specific

combustible gases that can be contained in a mixture. Appendix G does not specifically discuss

the flare test data, but includes important concepts and c onsiderations helpful in understanding

the discussions contained in Sections 3.1.3 and 3.1.4.



# ( )( ) ( )( )

2 2 2 2 

# 1 1 100

, , 1 CO CO e O H O H e n

j j a



# x N x N LFL LFL

j



# − − − −         = 

# ∑

= 

# χ ( Eq. 3-3 )

Where:

LFL a 

## = Lower flammability limit of any gas mixture ‘a’, volume %.

a = Placeholder for any gas mixture (e.g., flare combus tion zone gas, ‘cz’; flare vent

gas with center steam, ‘vgcs’; or flare vent gas ‘vg’ ).

n = Number of components in gas mixture ‘a’.

j = Individual pure component in gas mixture ‘a’.

x j 

## = Concentration of individual pure component j in gas mi xture ‘a’, volume %.

LFL j 

## = Lower flammability limit of individual pure componen t j, volume %. The LFL of

individual compounds are based on experimental data and are provided in a Bureau of Mines Bulletin entitled: “Flammability Characte ristics of Combustible Gases and Vapors” (Zabetakis 1965). All inerts, including nitro gen, are assumed to have an infinite lower flammability limit (e.g., LFL N2 

## = ∞ ).

N e,H2O 

## = Coefficient of nitrogen equivalency for water rela tive to nitrogen, unitless. See

Table 3-1.This information is distributed solely for the purp ose of pre-dissemination peer review under applicab le information quality guidelines. It has not been formally disseminated by EPA. It does not repr esent and should not be construed to represent any Agency determination or policy.

Section 3.0: Steam and Flare Performance Page 3-10 

## x H2O 

## = Concentration of water in gas mixture ‘a’, volume fraction.

N e,CO2 

## = Coefficient of nitrogen equivalency for carbon dio xide relative to nitrogen,

unitless. See Table 3-1.

x CO2 

## = Concentration of carbon dioxide in gas mixture ‘a’, volume fraction.

Table 3-1. Recommended Values of Coefficient of Nitrogen Equi valency for Water and Carbon Dioxide Relative to Nitrogen

Combustible Component i in Flare Vent Gas N e,H2O 

## N e,CO2



## Methane 1.87 2.23

Ethane 1.40 1.87 Propane 1.51 1.93 Ethylene 1.68 1.84 Propylene 1.36 1.92 Hydrogen 1.35 1.51
All Other Combustibles 1.50 1.87 Source: Molnarne et al. (2005)

Figure 3-4 is the same plot as Figure 3-3, except the LFL CZ 

## has been adjusted for nitrogen

equivalency. All data points have essentially shifted to the right; and the amount each test run

shifted is dependent on the amount of water and carbon dio xide in the combustion zone gas. By

applying this adjustment, one of the 11 test runs highlighted ( in red) in Figure 3-3, is no longer

between the 10.0 and 15.3 percent LFL CZ 

## region. (See Section 3.1.3 about these test runs.) The

differences between Figures 3-3 and 3-4 do not appear signifi cant; however, from the perspective

of assuring that a LFL CZ 

## of 15.3 percent or less specifies a flare with good combu stion, it is

important as will become more evident throughout this sec tion and Appendix G.This information is distributed solely for the purp ose of pre-dissemination peer review under applicab le information quality guidelines. It has not been formally disseminated by EPA. It does not repr esent and should not be construed to represent any Agency determination or policy.

Section 3.0: Steam and Flare Performance Page 3-11 

## Figure 3-4. Combustion Efficiency vs. LFL CZ 

## Adjusted for Nitrogen Equivalency

3.1.3 Specific Test Data Not Fitting the Trend

The test runs highlighted red in Figures 3-3 through 3-8 (Figures 3-5 through 3-8 are

shown in Section 3.1.4) do not seem to fit the trend found f or the other test runs that good

combustion efficiency is achieved with a LFL CZ 

## less than 15.3 percent depicted by the vertical

blue line in each figure. These test runs have a LFL CZ 

## of less than 15.3 percent but they did not

have a combustion efficiency of greater than 96.5 percent . The specific test reports associated

with these test runs were examined. These test runs coul d be in error or have a higher variability

than other test runs, the estimate of the LFL could be incorrect, or the LFL may not be an

appropriate indicator of combustion efficiency. Given the previous discussion in Sections 3.1.1

and 3.1.2, the LFL appears to be a good indicator of combusti on efficiency (assuming wind and

velocity of the flare vent gas are within reasonable l imits as discussed in Sections 5 and 6 of this

report). Therefore, this section investigates the possibili ty of inaccuracies in testing or calculating

the LFL (the appropriateness of using Le Chatelier’s equati on for the mixture). Note that four of

40% 50% 60% 70% 80% 90% 100%

5% 10% 15% 20% 25% 30% 35% 40% 45% 50%Combustion Efficiency (%)

LFL CZ (%)10.0%15.3%This information is distributed solely for the purp ose of pre-dissemination peer review under applicab le information quality guidelines. It has not been formally disseminated by EPA. It does not repr esent and should not be construed to represent any Agency determination or policy.

Section 3.0: Steam and Flare Performance Page 3-12 

## the test runs are within the statistical uncertainty for the test method. As determined by Clean Air

Engineering (2010a), the measured combustion is ±1.5% at a con fidence level of 99%.

These data points (Table 3-2) were scrutinized against all o f the other test runs to see if

they were unique results that indicated an issue with th e accuracy in the test results, or whether

they are indicating a previously unseen trend. Figure 3-3 presents 11 data points in red; however,

Figures 3-4 though 3-8 only indicate 10 data points that do not f it the trend. The eleventh data

point (Flint Hills Resources LOU-C) shown in Figure 3-3 has a LFL CZ 

## greater than 15.3 percent

after the nitrogen equivalency adjustment was made. The refore, the data point follows the trend

of the majority of the data and is not discussed further i n this section. Section 3.1.3.1 describes

any test run specific information revealed by the review of the test reports. Section 3.1.3.2

includes observations from examining these test runs and co mparing them to other test runs.

Section 3.1.3.3 provides conclusions regarding these test r uns.

Table 3-2. Test Run Detail for 11 Data Points with

LFL CZ 

## < 15.3% but Combustion Efficiency < 96.5%

Test Site Condition

ID Run ID Combustion

Efficiency (%) %Combustible

In CZ (%) %Inert

In CZ (%) %Olefin
In CZ (%) a 

### %H2

In CZ (%)
MPC TX B 8

- 2 b 

### 95.8 28.0 72.0 5.06 5.72
MPC TX B 9

- 2 89.1 27.0 73.0 4.89 5.56
MPC TX D 7

- 2 b 

### 96.0 20.5 79.5 8.89 1.36
MPC Detroit B 8

- 1 94.6 28.0 72.0 4.20 10.5
MPC Detroit C 4

- 1 92.7 21.9 78.1 14.8 1.67
MPC Detroit C 4

- 2 93.7 22.3 77.7 14.5 1.83
MPC Detroit C 5

- 1 93.1 19.8 80.2 13.2 1.74
MPC Detroit C 5

- 2 91.6 19.4 80.6 12.3 1.70
MPC Detroit D 8

- 1 b 

### 96.2 24.8 75.2 2.75 11.6

FHR LOU LOU

- A 2.0(1) b 

### 95.9 35.0 65.0 2.83 10.6

FHR LOU LOU

- C 3 .0( 2 ) b, c 

### 95.8 30.8 69.2 0.50 9.03

a 

### Olefins include: 1-Butene, 1,2-Butadiene, 1,3-Butadiene, Cis -2-Butene, Ethylene, Iso-Butylene, Propadiene, Propylene, and Trans-2-Butene.

b 

### These test runs are within the testing uncertainty of 96.5%; they each had combustion efficiencies less than 1 .5%
below 96.5%.

c 

### After making the nitrogen equivalency adjustment for this run, the LFL CZ 

### is greater than 15.3% and therefore follows the trend for the majority of the data points (s ee Figures 3-3 and 3-4).This information is distributed solely for the purp ose of pre-dissemination peer review under applicab le information quality guidelines. It has not been formally disseminated by EPA. It does not repr esent and should not be construed to represent any Agency determination or policy.

Section 3.0: Steam and Flare Performance Page 3-13 

## 3.1.3.1 Review of Test Reports



## The MPC TX test report (Clean Air Engineering, Inc., 2010a) discusses a potential

problem with some reported data. The report says that whe n the wind came from a certain

direction steam may have interfered with the pilot due to a “shaping steam ring failure.” The

report states that “the shaping steam ring failure caused t he shaping pressure to be unbalanced,

with one side of the concentric ring starved for stea m. As the wind blew towards the area of

unbalance, the flame sheared off of the flare tip and was extinguished.” For all of the test runs

where this was noted in the raw data, the efficiency wa s more variable on a minute-by-minute

basis during the testing than for the other runs. This coul d mean that the efficiencies for test runs

affected by the flare steam ring failure and wind could be biased low. All of the MPC TX data

points included in Table 3-2 (i.e., B 8-2, B 9-2, and D 7-2) w ere affected by this issue. The raw

data showed that for test run B 8-2, there were 9 out of 12 minutes tested affected by this issue;

for test run B 9-2, there were 10 out of 10 minutes affected ; and for test run D 7-2, there were 4

out of 10 minutes affected.

The MPC Detroit test report (Clean Air Engineering, In c., 2010b) stated that if the wind

was “blowing directly away from the PFTIR at more than 5 mph,” the PFTIR view of the flare

plume could be obscured causing inaccuracies in the testing. The wind was blowing in the

“wrong” direction (for the PFTIR analysis) for all o f the MPC Detroit Condition C runs and for

the B 8-1 test run. However, the wind speeds were not ex cessive during these runs (average wind

speed for these test runs was less than 3.6 miles per hour ). The test run data revealed no issues

with the MPC Detroit test run D 8-1 and the Flint Hill s Resources (LOU) test run LOU-A 2.0(1).

3.1.3.2 Comparison of Data Runs



## The data points listed in Table 3-2 can be divided, general ly, into three groups when

considering the combustion zone gas: one with olefin a nd hydrogen both approximately equal to

5 percent; one with high hydrogen content (9 to 11.6%) and low olefin content (0.5 to 2.8%); and

the third group with relatively high olefin content (8.9 to 14. 8%) and low hydrogen content (less

than 2%). All of the available test data were reviewed t o determine if there were any similar test

runs to those in Table 3-2. The information found for each group is discussed below.This information is distributed solely for the purp ose of pre-dissemination peer review under applicab le information quality guidelines. It has not been formally disseminated by EPA. It does not repr esent and should not be construed to represent any Agency determination or policy.

Section 3.0: Steam and Flare Performance Page 3-14 

## Olefin and Hydrogen Approximately Equal

The test runs at MPC TX numbered B 8-2 and B 9-2 did not fit t he trend, and both had

olefin and hydrogen content at about 5 percent. Looking at the full set of test data, there were

several other test runs with a similar composition yet had combustion efficiencies greater than

96.5 percent and a LFL CZ 

## greater than 15.3 percent. Table 3-3 shows all the test run s where

olefin and hydrogen concentrations were approximately equal; data with an olefin to hydrogen

ratio from 0.81 to 1.23 were reviewed. As evident by Table 3-3, t here were several data points

with very similar concentrations of olefin, hydrogen, oth er combustibles and inerts. “Other

combustibles” include primarily methane and other alkanes.

High Hydrogen and Low Olefin

The test runs MPC Detroit B 8-1 and D 8-1, and Flint Hil ls test LOU-A 2.0(1) had a

higher concentration of hydrogen than olefin by about 2.5 t o 4 times. Table 3-4 provides the

information for all test runs with relatively high hydroge n and low olefin concentrations (ratio of

olefin to hydrogen of 0.12 to 0.55). All the test runs in Table 3-4 have less olefin than hydrogen

by a factor of between 2 and 8 and there is inert content of between 49 and 88 percent. Test runs

MPC Detroit D 8-1 and Flint Hills LOU-A 2.0(1) have meas ured combustion efficiencies that

are within the statistical uncertainty of 96.5%. Also, T able 3-4 shows several other test runs that

have similar conditions and all had combustion efficien cies of 96.5% or greater. These test runs

do not appear to indicate a unique trend.

The MPC Detroit test run B 8-1 is similar to several t est runs in Table 3-4 but it does

have a relatively high inert concentration (72%) for t he group. The MPC Detroit test runs A 4-2

and A 3-1 both have similar amounts of inert at 74 and 72 per cent respectively. However, there

is more hydrogen and olefin in the B 8-1 run than these runs

.This information is distributed solely for the purpose of pre-dissemination peer review under applicable information quality guidelines. It has not beenformally disseminated by EPA. It does not representandshould not be construed to represent any Agency determination or policy.Section 3.0: Steam and Flare PerformancePage 3-15Table 3-3. Olefin and Hydrogen Approximately EqualTest Site Condition Run CE%OlefinCZ(%)%H2-CZ(%)Ratio%Olefin-CZ/%H2-CZOtherCombustiblesin CZ(%)Inertin CZ(%)FractionCombustiblein CZSteamFractionof CZLFLCZAdjusted forNitrogen EquivalencyMPC TXA114-195.5%2.843.530.819.7883.860.160.7725.33%MPC TX C 3-2 99.2% 6.34 7.82 0.81 24.33 61.51 0.38 0.55 9.93%MPC TXA1112-161.6%1.381.690.824.3592.570.070.8962.75%MPC TX LTS 2-5 99.4% 6.91 8.41 0.82 23.94 60.75 0.39 0.53 9.50%MPC TX LTS 2-6 97.2% 7.40 8.89 0.83 19.20 64.51 0.35 0.54 9.79%MPC TXA116-192.5%2.262.710.838.6486.390.140.8131.88%MPC TX B 4-2 99.3% 6.89 8.09 0.85 23.59 61.44 0.39 0.54 9.66%MPC TX LTS 2-2 99.3% 6.88 8.07 0.85 23.56 61.49 0.39 0.54 9.68%MPC TXA112-195.6%3.624.250.8511.8280.310.200.7019.58%MPC TX LTS 2-3 99.0% 6.96 8.01 0.87 23.60 61.42 0.39 0.54 9.64%MPC TX B 5-2 99.0% 6.16 7.09 0.87 20.88 65.86 0.34 0.59 10.98%MPC TX B 10-2 96.7% 4.69 5.39 0.87 15.94 73.99 0.26 0.69 14.76%MPC TX B 6-1 98.4% 5.54 6.31 0.88 18.54 69.61 0.30 0.64 12.43%MPC TX B 6-2 98.5% 5.53 6.29 0.88 18.63 69.56 0.30 0.64 12.42%MPC TXB9-289.1%4.895.560.8816.5872.970.270.6814.16%MPC TX B 7-2 97.9% 5.27 5.98 0.88 17.87 70.88 0.29 0.65 13.06%MPC TX B 7-1 97.8% 5.32 6.03 0.88 17.77 70.88 0.29 0.65 13.01%MPC TXB8-295.8%5.065.720.8817.1872.050.280.6713.65%MPC TX B 9-1 97.6% 4.89 5.53 0.89 16.39 73.20 0.27 0.68 14.24%MPC TX B 8-1 97.6% 5.14 5.80 0.89 17.15 71.92 0.28 0.66 13.53%MPC TX B 5-1 98.7% 6.21 7.01 0.89 20.86 65.92 0.34 0.59 10.94%MPC Detroit LTS 8 98.7% 7.12 6.78 1.05 25.83 60.28 0.40 0.56 8.72%MPC Detroit LTS 7 99.3% 10.77 10.20 1.06 21.65 57.38 0.43 0.53 7.62%MPC Detroit LTS 5 99.1% 8.76 7.92 1.11 23.56 59.76 0.40 0.55 8.14%MPC Detroit LTS 4 98.9% 8.03 7.24 1.11 22.86 61.87 0.38 0.57 8.64%MPC Detroit LTS 1 98.9% 8.70 7.39 1.18 23.64 60.27 0.40 0.55 8.33%MPC TX C 3-1 98.9% 3.94 3.20 1.23 20.84 72.02 0.28 0.66 9.73%Pink = CE less than 96.5%, and LFLCZless than 15.3% (Test Runs from Table 3-2).Gray = LFLCZgreater than 15.3%.This information is distributed solely for the purpose of pre-dissemination peer review under applicable information quality guidelines. It has not beenformally disseminated by EPA. It does not representandshould not be construed to represent any Agency determination or policy.Section 3.0: Steam and Flare PerformancePage 3-16Table 3-4. High Hydrogen and Low OlefinTest Site Condition Run CE%OlefinCZ(%)%H2-CZ(%)Ratio%Olefin-CZ/%H2-CZOtherCombustiblesin CZ(%)Inertin CZ(%)FractionCombustiblein CZSteamFractionof CZLFLCZAdjusted forNitrogen EquivalencyFHR LOU LOU-B 1.0 (2) 99.4% 1.49 12.38 0.12 36.84 49.29 0.51 0.48 9.01%MPC Detroit D 3-1 97.5% 2.04 16.49 0.12 11.07 70.39 0.30 0.68 12.50%FHR LOU LOU-A MIN (3) 98.8% 1.59 11.47 0.14 22.98 63.96 0.36 0.60 12.59%FHR LOULOU-A8.5 (1)78.8%0.623.860.167.8987.630.120.8743.54%FHR LOULOU-A3.0 (2)99.1%1.308.010.1618.1872.500.270.7117.05%FHR LOULOU-A4.0 (2)98.6%1.066.410.1714.5777.950.220.7721.87%FHR LOULOU-A5.0 (2)96.5%0.895.300.1711.9281.900.180.8127.35%MPC DetroitD5-191.6%1.8511.050.177.4979.610.200.7818.43%FHR LOULOU-A6.0 (1)88.6%0.865.110.1710.4183.610.160.8330.63%MPC Detroit D 6-1 98.4% 3.43 20.30 0.17 13.17 63.10 0.37 0.60 9.73%FHR LOULOU-A6.0 (2)95.1%0.794.670.1710.2984.250.160.8332.34%FHR LOULOU-A5.0 (1)95.5%1.015.930.1712.1380.940.190.8025.53%FHR LOU LOU-A 2.0 (3) 98.6% 1.66 9.53 0.17 22.45 66.36 0.34 0.63 13.59%MPC DetroitD4-188.6%1.8410.310.187.2580.600.190.7919.44%FHR LOULOU-A4.0 (1)96.5%1.256.910.1814.1977.640.220.7721.08%FHR LOULOU-A3.0 (1)97.2%1.598.090.2016.8973.430.270.7217.37%FHR LOU LOU-A MIN (2) 99.2% 2.10 10.05 0.21 26.28 61.57 0.38 0.59 11.76%MPC Detroit D 9-1 98.6% 3.84 16.98 0.23 14.80 64.37 0.36 0.61 10.05%FHR LOU LOU-A 2.0 (2) 98.6% 1.65 7.29 0.23 25.65 65.41 0.35 0.64 13.42%MPC DetroitD8-196.2%2.7511.610.2410.4375.220.250.7314.78%FHR LOU LOU-A MIN (1) 97.5% 3.01 12.04 0.25 24.27 60.67 0.39 0.59 11.10%FHR LOULOU-A2.0 (1)95.9%2.8310.570.2721.5665.040.350.6312.55%MPC DetroitD7-183.5%2.198.060.278.2881.470.190.8020.28%MPC Detroit A 3-2 98.6% 2.69 8.77 0.31 18.26 70.28 0.30 0.65 13.08%MPC Detroit A 2-2 98.5% 3.23 9.73 0.33 19.84 67.20 0.33 0.62 11.60%MPC DetroitD10-181.8%2.125.400.397.2785.210.150.8425.71%MPC DetroitB8-194.6%4.2010.460.4013.3072.040.280.6912.19%MPC TX LTS 2-4 98.7% 5.10 11.02 0.46 16.24 67.64 0.32 0.54 11.64%MPC Detroit A 1-1 99.0% 4.51 9.00 0.50 23.26 63.23 0.37 0.56 10.23%MPC DetroitA7-195.2%2.845.620.5013.8777.670.220.7317.83%MPC DetroitA8-192.0%2.314.530.5112.0981.070.190.7721.00%MPC Detroit A 4-2 97.7% 3.18 6.18 0.51 16.46 74.18 0.26 0.69 15.12%MPC Detroit B 1-1 98.9% 9.07 17.61 0.52 27.10 46.21 0.54 0.41 6.19%MPC Detroit A 3-1 98.0% 3.48 6.65 0.52 18.13 71.74 0.28 0.66 13.47%MPC DetroitA9-181.3%1.933.660.539.9084.510.150.8226.94%MPC DetroitA6-296.7%2.885.380.5414.7476.990.230.7317.22%MPC Detroit A 2-1 97.7% 3.98 7.25 0.55 19.91 68.86 0.31 0.63 11.96%Pink = CE less than 96.5%, and LFLCZless than 15.3% (Test Runs from Table 3-2). Gray = LFLCZgreater than 15.3%.This information is distributed solely for the purp ose of pre-dissemination peer review under applicab le information quality guidelines. It has not been formally disseminated by EPA. It does not repr esent and should not be construed to represent any Agency determination or policy.

Section 3.0: Steam and Flare Performance Page 3-17 

## Higher Olefin and Low Hydrogen

There are five test runs from Table 3-2 that are in this category and they are shown in

Table 3-5 in the pink rows along with all other test runs where the olefin concentration was

greater than the hydrogen concentration (except for thos e runs where the olefin concentration

was just above hydrogen which are shown in Table 3-4). Only one of the five test runs is within

the statistical uncertainty of 96.5% combustion effici ency (MPC TX D 7-2). Table 3-5 shows

several test runs with good combustion efficiencies th at match the conditions of the five test

runs. However, none of the data points had the same or higher amounts of inerts than these five

test runs had. These five runs have the highest amounts of inerts (between 78 to 81%) of any of

the test runs with similar compositions in Table 3-5.

3.1.3.3 Conclusions on Ten Data Points



## The data points in Table 3-2 were expected to achieve good combustion efficiency

because their LFL CZ 

## were determined to be less than 15.3 percent using Le Chatel ier’s equation

and adjusting for nitrogen equivalency. However, these test runs achieved combustion

efficiencies between 89.1 and 96.2 percent. These data points were reviewed to determine if

these anomalies were an indication that the 15.3 percen t LFL CZ 

## was incorrect and should be

adjusted to better fit the data or if the points were j ust a few inaccurate test results in a group of

over 300 test points. By comparing the compositions and res ults of other test runs with the tests

in Table 3-2 it can be speculated whether the tests are inaccurate or a clue to something else.

For the two test runs where the olefin and hydrogen concen tration are approximately

equal (MPC TX B 9-2 and B 8-2), there are several example s of test runs of almost identical

conditions where a combustion efficiency of greater t han 96.5 percent was achieved. Also, both

of these test runs had the majority of the testing tim e affected by the steam ring failure. It appears

likely that these two test runs had inaccurate results a nd that their results should not impact the

15.3 percent LFL CZ 

## value.This information is distributed solely for the purpose of pre-dissemination peer review under applicable information quality guidelines. It has not beenformally disseminated by EPA. It does notrepresent and should not be construed to representany Agency determination or policy.Section 3.0: Steam and Flare PerformancePage 3-18Table 3-5. Higher Olefin and Low HydrogenTest Site Condition Run CE%OlefinCZ(%)%H2-CZ(%)Ratio%Olefin-CZ/%H2-CZOtherCombustiblesin CZ(%)Inertin CZ(%)FractionCombustiblein CZSteamFractionof CZLFLCZAdjusted forNitrogenEquivalencyMPC TX D 4-1 98.4% 11.03 1.83 6.03 12.63 74.51 0.25 0.69 8.75%MPC TXD7-296.0%8.891.366.5410.2379.510.200.7610.77%MPC TX D 4-2 98.2% 11.01 1.68 6.56 12.20 75.11 0.25 0.70 8.86%MPC Detroit C 3-1 96.8% 16.62 2.50 6.64 6.95 73.93 0.26 0.72 10.89%MPC Detroit C 2-1 98.4% 18.59 2.61 7.12 8.72 70.07 0.30 0.68 9.48%MPC Detroit C 2-2 99.1% 20.97 2.93 7.16 9.46 66.63 0.33 0.64 8.45%MPC DetroitC5-291.6%12.331.707.265.3780.600.190.7914.98%MPC Detroit C 1-2 99.4% 26.15 3.47 7.54 12.70 57.67 0.42 0.55 6.40%MPC DetroitC5-193.1%13.181.747.584.9380.150.200.7914.39%MPC DetroitC4-293.7%14.541.837.935.8977.740.220.7612.79%MPC Detroit C 3-2 97.4% 17.53 2.15 8.17 7.11 73.22 0.27 0.71 10.49%MPC DetroitC4-192.7%14.781.678.835.4878.060.220.7712.90%MPC TXE3-398.3%12.321.1011.2013.6972.890.270.707.62%MPC TXE5-297.5%10.680.9411.3311.9176.460.240.748.81%MPC TXE4-397.7%11.521.0111.3812.8674.600.250.728.13%MPC TXE5-196.8%11.440.8613.3711.5076.210.240.748.89%MPC TXE3-198.6%12.840.9313.7412.7673.470.270.717.97%MPC TXE4-198.1%12.120.8514.3111.8075.230.250.738.59%Pink = CE less than 96.5%, and LFLCZless than 15.3% (Test Runs from Table 3-2).Gray = LFLCZgreater than 15.3%.This information is distributed solely for the purp ose of pre-dissemination peer review under applicab le information quality guidelines. It has not been formally disseminated by EPA. It does not repr esent and should not be construed to represent any Agency determination or policy.

Section 3.0: Steam and Flare Performance Page 3-19 

## The three test runs that had relatively high hydrogen con tent, all about 10.5 percent, and

lower olefin content [FHR LOU-A 2.0(1), MPC Detroit B 8-1 and D 8-1] were compared with

other test runs. The FHR LOU-A 2.0(1) and MPC Detroit D 8 -1 were both very similar test runs,

and they both had combustion efficiencies within the s tatistical uncertainty of the method. There

were also several test runs that were very close mat ches to these runs that all achieved good

combustion. These test runs do not appear to signify a sepa rate trend or raise doubt regarding the

15.3 percent LFL CZ 

## threshold. The MPC Detroit test run B 8-1 can be nearl y matched to a few

test runs, including some with more inert that still ac hieved greater than 96.5 percent combustion

efficiency; indicating that these test runs are likely due to inaccurate test results.

The remaining test runs in Table 3-3 (MPC TX D 7-7 and MPC D etroit C 4-1, 4-2, 5-1,

and 5-2) are all very similar to each other, except that the MPC TX run has a much lower olefin

content and a higher amount of other combustibles (and it is the only run in this group with a

combustion efficiency within the statistical uncertai nty of 96.5%). There are several similar runs

with good combustion efficiency shown in Table 3-5, but th ey all have lower amounts of inert

than those runs shown in Table 3-2 — 78 to 81 percent inert fo r the test runs with a combustion

efficiency less than 96.5 percent compared to 58 to 76 percent inert for runs achieving greater

than 96.5 percent combustion efficiency. Because there ar e five test runs all similar in

composition and results, it seems that there could be is sues with one or more components acting

to inhibit the combustion to some degree; thereby interfer ing with the accuracy of the Le

Chatelier’s equation. Azatyan et al. (2005a, 2005b, and 2007) showe d that small amounts of

propylene can react with hydrogen and form chain terminatin g products that inhibit some of the

combustion reactions (see Appendix G for further discus sion). However, these test runs have

larger amounts of olefins and a small amount of hydrogen; it is unknown whether inhibition is

possible with this situation. Also, the test runs contai n other combustibles, such as methane and

propane. Therefore, it is difficult to make any conclusio n. The flare steam analysis was

performed on 312 data points; all but 17 had some amount of o lefin in the gas mixture, 203 test

runs with at least 1 percent olefin, and 198 test runs with both hydrogen and olefin. If there are

chain terminating reactions from olefins or another compo und, the inhibition affected very few

data points with respect to a LFL CZ 

## of 15.3 percent.This information is distributed solely for the purp ose of pre-dissemination peer review under applicab le information quality guidelines. It has not been formally disseminated by EPA. It does not repr esent and should not be construed to represent any Agency determination or policy.

Section 3.0: Steam and Flare Performance Page 3-20 

## 3.1.4 Data Points with Good Combustion and High LFL CZ



## Out of the 312 data points available for this analysis, 164 te st runs achieved a combustion

efficiency of 96.5 percent or greater; Figure 3-4 shows 66 of th ese runs (or 40%) have a LFL CZ 

## greater than 15.3 percent and achieve greater than 96.5 percent combustion efficiency. This

means that for approximately 40 percent of the test runs th at achieved a combustion efficiency of

96.5 percent or greater, and if LFL CZ 

## were being used to monitor flare performance, owners

would need to reduce the amount of inert in the combustion zon e (i.e., reduce the amount of

assist steam being used), or add additional combustible gas in order to lower the LFL CZ 

## below

the threshold of less than 15.3 percent. The test data we re scrutinized to see if there were any

commonalities or trends that could explain why the 66 test points still achieved good combustion

efficiency with a higher than expected LFL CZ 

## . Approximately half (36) of the 66 test points are

from INEOS, EPA, and TCEQ data sets and have only one or two flammable gases. Gas

compositions for these tests included nitrogen, propane, propyl ene, 1,3-butadiene, and natural

gas. The other 30 test points are from Shell, Marathon, and Flint Hill Resources data sets and

have 10 or more combustible constituents in the flare ve nt gas. The primary gas components for

these tests were hydrogen and methane.

Similar to the data points discussed in Section 3.1.3, the 66 data points do not fit the

overall trend because the calculation of the LFL CZ 

## is inaccurate, the combustion efficiency

measurements are inaccurate, or the flammability is no t an appropriate parameter to represent

flare performance or it does not completely explain th e performance of a flare. This section

explores two explanations for the 66 data points: (1) T he potential that some of the steam may

not enter the combustion zone due to wind effects, and ( 2) The LFL CZ 

## representing good

combustion may vary with the composition of the flare vent gas.

3.1.4.1 Partial Steam Contribution



## One factor that may contribute to overestimated LFL CZ 

## values is that the calculation

methodology for LFL CZ 

## that was used in this analysis assumes all assist stea m is incorporated

into the combustion zone gas. However, it is possible t hat some of the steam delivered from the

upper and/or lower ring steam nozzles may actually not par ticipate in mixing with theThis information is distributed solely for the purp ose of pre-dissemination peer review under applicab le information quality guidelines. It has not been formally disseminated by EPA. It does not repr esent and should not be construed to represent any Agency determination or policy.

Section 3.0: Steam and Flare Performance Page 3-21 

## combustion zone because wind can blow the flame away from a portion of the nozzles causing

steam to be shot directly into the atmosphere without ev er hitting the combustion zone. With this

in mind, the LFL CZ 

## values could be overestimated for some test runs depending on the steam

injection configuration and the wind direction and veloci ty.

The location of steam injection on each of the stea m-assisted flares varied between test

data sets (see Table 2-4 in Section 2.0). Table 3-6 shows th e breakdown of steam use for the

66 test runs that have a LFL CZ 

## greater than 15.3 percent and achieve greater than 96.5 percent

combustion efficiency when the LFL CZ 

## is adjusted for nitrogen equivalency. Sixty-one out of the

66 test runs that have a LFL CZ 

## greater than 15.3 percent (and achieve greater than 96.5%

combustion efficiency), were using steam that potential ly did not mix completely with the other

combustion zone gases. This means that for these test runs, the LFL CZ 

## that was calculated in this

analysis may actually be too high, which would explain why these test runs achieved greater than

96.5 percent combustion efficiency but the calculation sh ows a LFL CZ 

## greater than 15.3 percent.

Table 3-6. Breakdown Of Steam Use For The 66 Test Runs a



## Steam Configuration Test Run Count Test Reports

Upper 18 EPA-600/2-83-052; EPA-600/2-85-106; TCEQ; and INEOS Upper and Center 26 TCEQ and SDP EPF
Lower and Center 12 FHR LOU and MPC TX Ring b 

## and Center 5 MPC Detroit and FHR AU
No Steam 5 EPA-600/2-83-052

a 

### Those test runs that have a LFL CZ 

### greater than 15.3% and achieve greater than 96.5% combustion ef ficiency when
the LFL CZ 

### is adjusted for nitrogen equivalency.

b 

### The specific test reports do not clarify whether the r ing steam is located in an upper or lower position at the f lare tip.



## In a recent report, Marathon Petroleum Company reviewe d their performance testing

results against wind conditions and flare plume position to characterize how wind speed affects

the amount of steam mixing with the combustion zone gas (Cade et al., 2010). The report derived

a “Steam Contribution Factor” calculation methodology to predict conditions when non-mixing

steam is occurring; however, the methodology is not pract ical to apply to all flares because it

relies heavily on flare design, specific test data and f lame images.This information is distributed solely for the purp ose of pre-dissemination peer review under applicab le information quality guidelines. It has not been formally disseminated by EPA. It does not repr esent and should not be construed to represent any Agency determination or policy.

Section 3.0: Steam and Flare Performance Page 3-22 

## The amount of steam that mixes in the combustion zone at a given moment would depend

on the wind speed and direction and would vary moment-by-mo ment. Because of the difficulties

in determining how much upper, lower, and ring steam mixes w ith the combustion zone, and

since the upper, lower, and ring steam is designed to be inje cted into the combustion zone gas; it

is logical to assume that in the majority of situati ons complete mixing occurs and includes all the

steam, regardless of where it is injected, when calcula ting the LFL CZ 

## . However, to estimate the

possible effect of this assumption, a worst case analys is was conducted assuming no upper,

lower, and ring steam participated in mixing with the com bustion zone (i.e., only center steam

was used in the LFL CZ 

## calculation). The LFL CZ 

## for 37 of the 66 test runs, with only center steam

considered, computed to less than 15.3 percent. Therefore, e ven if it were known that the wind

was great enough on the day of testing to remove all upper, lower, and ring steam from the

combustion zone, this would only resolve just over hal f (56%) of the test runs with good

combustion efficiency but high LFL CZ 

## (greater than 15.3%).

3.1.4.2 More Specific LFL CZ 

## Thresholds



## Another detail that could be considered when establishing a L FL CZ 

## threshold on the entire

312 test runs is the commonalities in composition of flar e vent gas. Figures 3-5 through 3-8 are

plots of the same 312 test runs shown in Figures 3-3 and 3-4; however, the test runs are divided

into one of the four figures depending on the test run compo sition. The lower flammability limit

of the combustible portion of the flare vent gas (LFL VG,C 

## ) was used to define the composition

categories. This scheme was developed based on the obser vation that the smaller the LFL of a

pure component, the greater the amount of inert that chem ical can withstand and still propagate a

flame (Kondo, 2006a). Therefore, to allow the greatest amo unt of inert (or highest LFL CZ 

## ), the

data were divided into categories associated with their LFL without inert.

Four categories were developed and are shown in Table 3-7. For example, if the

combustible portion of the flare vent gas for a test r un consisted of 30 percent propane (and the

other 70% was nitrogen), the test run would fall into catego ry A because the LFL VG,C 

## is equal to

that of propane, or 2.1 percent. Table 3-7 also shows the pot ential LFL CZ 

## threshold for each

category based on Figures 3-5 through 3-8. The test runs tha t do not fit the trends in these

figures, as having not achieved a combustion efficiency of 96.5 percent or greater (but areThis information is distributed solely for the purp ose of pre-dissemination peer review under applicab le information quality guidelines. It has not been formally disseminated by EPA. It does not repr esent and should not be construed to represent any Agency determination or policy.

Section 3.0: Steam and Flare Performance Page 3-23 

## meeting the potential LFL CZ 

## threshold), are highlighted in red and have been discuss ed in

Section 3.1.3.

Table 3-7. Potential LFL cz 

## Thresholds based on LFL VG,C



## Category ID LFL VG,C 

## (%) Potential Threshold

for LFL CZ 

## (%)
A ≤ 2.4 ≤ 24.0
B >2.4 and ≤ 2.8 ≤ 18.5
C >2.8 and ≤ 3.8 ≤ 16.0
D >3.8 ≤ 14.5

Figure 3-5. Combustion Efficiency vs. LFL CZ 

## for Category A Test Runs (see Table 3-7)

30% 40% 50% 60% 70% 80% 90% 100%

0% 10% 20% 30% 40% 50% 60% 70%Combustion Efficiency (%)

LFLcz (%)0.24This information is distributed solely for the purp ose of pre-dissemination peer review under applicab le information quality guidelines. It has not been formally disseminated by EPA. It does not repr esent and should not be construed to represent any Agency determination or policy.

Section 3.0: Steam and Flare Performance Page 3-24 

## Figure 3-6. Combustion Efficiency vs. LFL CZ 

## for Category B Test Runs (see Table 3-7)

Figure 3-7. Combustion Efficiency vs. LFL CZ 

## for Category C Test Runs (see Table 3-7)

30% 40% 50% 60% 70% 80% 90% 100%

0% 10% 20% 30% 40% 50% 60% 70%Combustion Efficiency (%)

LFLcz (%)0.185

30% 40% 50% 60% 70% 80% 90% 100%

0% 10% 20% 30% 40% 50% 60% 70%Combustion Efficiency (%)

LFLcz (%)0.16This information is distributed solely for the purp ose of pre-dissemination peer review under applicab le information quality guidelines. It has not been formally disseminated by EPA. It does not repr esent and should not be construed to represent any Agency determination or policy.

Section 3.0: Steam and Flare Performance Page 3-25 

## Figure 3-8. Combustion Efficiency vs. LFL CZ 

## for Category D Test Runs (see Table 3-7)

By categorizing the data into these four categories, one test run (in Category D) no longer

meets the LFL CZ 

## threshold ( ≤ 14.5%) and has a combustion efficiency of 96.5 percent or bette r.

However, 22 test runs now meet the LFL CZ 

## threshold (in Table 3-7), and have an efficiency of

96.5 percent or greater. This reduces the number of test runs that have good combustion

efficiency, yet do not meet the LFL CZ 

## threshold, from 66 to 45 test runs. All but two of the 22

test runs that meet the thresholds in Table 3-7 and have good combustion efficiency are in

Category A. Generally, Category A includes test runs with only 1 or 2 combustible components

and Categories C and D have several constituents and most include hydrogen and methane.

Categorizing did not improve the results for Categories C and D. The test runs that make up a

given category generally are from specific test reports. For example, SDP EPF test runs are all in

Category C, while Category D is almost entirely FHR AU or FHR LOU test runs. The SDP EPF,

FHR AU and FHR LOU test runs are for mixtures with high er amounts of hydrogen.

Combustible mixtures that have components that enhance the combustion of other constituents

would also be a reason that a mixture with a higher cal culated LFL CZ 

## could have a combustion

efficiency of greater than 96.5 percent. As discussed in Appe ndix G, hydrogen can enhance the

30% 40% 50% 60% 70% 80% 90% 100%

0% 10% 20% 30% 40% 50% 60% 70%Combustion Efficiency (%)

LFLcz (%)0.145This information is distributed solely for the purp ose of pre-dissemination peer review under applicab le information quality guidelines. It has not been formally disseminated by EPA. It does not repr esent and should not be construed to represent any Agency determination or policy.

Section 3.0: Steam and Flare Performance Page 3-26 

## combustion of methane and this enhancement is not refle cted in the calculated LFL. However, an

understanding of the role that other constituents play in the combustion efficiency (such as

amounts of olefin, propane, etc., and better quantificati on of this hydrogen-methane effect) are

needed before this could be considered.

Also, there could be issues with the testing of the comb ustion efficiencies for these runs.

Information was not available to judge the accuracy for the FHR test runs. The SDP EPF test

report cited the possibility of inaccurately high combustion efficiency measurements during

times of unstable combustion conditions. However, th e test runs were not identified in the report

where this may have occurred. Without further testing it is difficult to determine why these

45 test runs had good combustion efficiencies with LFL CZ 

## greater than 15.3 percent.

3.1.5 Excluding Pilot Gas

Our analyses have not included the heat value or flamma bility properties of the pilot gas.

The pilot gas serves as a source of ignition for the c ombustion zone gas. The pilot gas does not

significantly contribute to the combustion zone gas mix ture, or the final output or operating limit

value of the LFL CZ 

## . In theory, the pilot gas is already fully combusted at the combustion zone,

and therefore would contribute a small amount of inert (i.e., carbon dioxide and water vapor) to

the combustion zone gas mixture. However, the amount o f inert that could be attributed to the

pilot gas is expected to be negligible — relative to th e volume of flare vent gas that would

actually participate in the combustion zone gas mixture (e.g. for 304 of the 312 test runs, the

pilot gas contributed less than 3% of the volumetric fl ow rate of the flare vent gas; and the pilot

gas contributed to less than 1% for 224 of these test runs ).

In addition, pilot gas is needed to maintain the pilot flame which is a requirement of

current flare regulations. Including the pilot gas in the calculation of the combustion zone

parameters, does not add any accuracy in identifying flares with (or without) good combustion.

Also, by leaving pilot gas out of the calculations, the e quations are simplified.This information is distributed solely for the purp ose of pre-dissemination peer review under applicab le information quality guidelines. It has not been formally disseminated by EPA. It does not repr esent and should not be construed to represent any Agency determination or policy.

Section 3.0: Steam and Flare Performance Page 3-27 

## 3.2 Combustible Gas Concentration in the Combustion Zone

If there are not enough combustible components in the com bustion zone, then the flare

vent gas will not burn, or will burn inadequately, resulti ng in lower combustion efficiency. The

addition of assist steam dilutes the combustible compone nts of the flare vent gas, which can

make it more difficult for the flare vent gas to burn. To simplify consideration of the operating

conditions for good combustion, we looked at the minimu m quantity of combustibles present in

the combustion zone that would maintain good combustion for the chemical compositions tested.

Figure 3-9 shows the combustion efficiency versus the frac tion of combustibles in the

combustion zone gas (C CZ 

## ). The vertical dotted line in Figure 3-9 identifies the th reshold where

all, but one test run with a fraction of combustibles in the combustion zone gas of 0.32 or greater

achieved a combustion efficiency of 96.5 percent or greater. All data sets had test runs with a

fraction of combustibles in the combustion zone gas a t greater and less than 0.32, except TCEQ.

Therefore, this trend was observable for a variety of f lare vent gas compositions and constituents.

All TCEQ test runs had enough inert (either nitrogen or s team) to cause the fraction of

combustibles in the combustion zone gas to be less tha n 0.32. Although Figure 3-9 illustrates a

strong trend (because all test runs except for FHR LOU-A 2.0(1) performed with at least

32 percent combustibles in the combustion zone gas achieve d greater than 96.5 percent

combustion efficiency – see Section 3.1.3 for a discussion about test run FHR LOU-A 2.0(1)),

there are a significant number of test runs that achie ved good combustion efficiency that did not

have at least 32 percent combustibles in the combustion zone gas. For these situations, a more

detailed review of the operating conditions would have to be considered, such as consideration of

the LFL CZ



## .This information is distributed solely for the purp ose of pre-dissemination peer review under applicab le information quality guidelines. It has not been formally disseminated by EPA. It does not repr esent and should not be construed to represent any Agency determination or policy.

Section 3.0: Steam and Flare Performance Page 3-28 

## Figure 3-9. Combustion Efficiency vs. C CZ



## 3.3 Heat Content Based Limit for Steam-Assisted Flares

A white paper (Evans and Roesler, 2011) was reviewed that descr ibes a method to define

flare operating conditions using the net heating value and the lower flammability limit. The

method is nearly identical mathematically (observatio ns with test data reveal some differences

that are discussed later in this section) to the recipro cal of the LFL CZ 

## parameter discussed in

Section 3.1 (provided you apply “combustion factors” as descri bed in the white paper); however,

it may be easier for flare owners and operators to unde rstand and implement because it uses a

familiar parameter (net heating value). The white paper uses Le Chatelier’s principle and

provides a methodology for determining the ratio of the net heating value of the combustion zone

gas (NHV CZ 

## ) to the net heating value of the flare vent gas if dilut ed to the lower flammability

limit (NHV VG-LFL 

## ).

Figure 3-10 shows that as the ratio of NHV CZ 

## to NHV VG-LFL 

## decreases, the combustion

efficiency of a flare deteriorates. The vertical dotte d line in Figure 3-10 marks the threshold 0% 20% 40% 60% 80% 100%

0.000 0.100 0.200 0.300 0.400 0.500 0.600Combustion Efficiency (%)

C CZ (volume fraction)0.32This information is distributed solely for the purp ose of pre-dissemination peer review under applicab le information quality guidelines. It has not been formally disseminated by EPA. It does not repr esent and should not be construed to represent any Agency determination or policy.

Section 3.0: Steam and Flare Performance Page 3-29 

## where all test runs with a ratio of NHV CZ 

## to NHV VG-LFL 

## greater than or equal to 10 achieved a

combustion efficiency of 96.5 percent or greater. The vert ical solid line in Figure 3-10 shows

another threshold where most test runs with a ratio of NHV CZ 

## to NHV VG-LFL 

## greater than or equal

to 6.5 achieved a combustion efficiency of 96.5 percent or g reater. There are 12 test runs with a

ratio of NHV CZ 

## to NHV VG-LFL 

## between 6.54 and 10.0 that did not achieve a combustion

efficiency of 96.5 percent or greater. Eleven of these 12 r uns are those listed in Table 3-2. This

observation was to be expected since this ratio is math ematically equal to the inverse of the

LFL CZ 

## ; however, this method has two more test runs (having a NHV CZ 

## to NHV VG-LFL 

## ratio

greater than 6.54) that do not achieve a combustion efficie ncy of 96.5 percent or greater. Out of

the 312 data points available for this analysis, 164 test run s achieved a combustion efficiency of

96.5 percent or greater; Figure 3-10 shows 61 of these runs (or 37%) have a NHV CZ 

## to NHV VGLFL 

## ratio less than 6.54 and achieve greater than 96.5 percent combustion efficiency.

Figure 3-10. Combustion Efficiency vs. Ratio of NHV CZ 

## to NHV VG-LFL 0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%

2.00 4.00 6.00 8.00 10.00 12.00 14.00 16.00 18.00Combustion Efficiency (%)

Ratio of NHV CZ to NHV VG-LFL6.5410.0This information is distributed solely for the purp ose of pre-dissemination peer review under applicab le information quality guidelines. It has not been formally disseminated by EPA. It does not repr esent and should not be construed to represent any Agency determination or policy.

Section 3.0: Steam and Flare Performance Page 3-30 

## Although the ratio of NHV CZ 

## to NHV VG-LFL 

## is mathematically equivalent to the inverse of

the LFL CZ 

## , there are several test runs where differences are observed between the two

parameters. Figure 3-11 is a log-log plot of LFL CZ 

## versus the ratio of NHV CZ 

## to NHV VG-LFL 

## for

each of the 312 test runs. The data points marked in red ha ve the greatest difference between the

two parameters.

Figure 3-11. LFL CZ 

## vs. Ratio of NHV CZ 

## to NHV VG-LFL



## One possible explanation for the observed differences bet ween the two methods is the

y-axis is a LFL CZ 

## value adjusted for nitrogen equivalency. A “nitrogen equivale ncy” adjustment

was incorporated for determining the ratio of NHV CZ 

## to NHV VG-LFL 

## . However, because the

procedure considers the LFL of the flare vent gas (as wel l as the NHV CZ 

## ) and not the actual LFL

of the combustion zone gas, the adjustment is hardly n oticeable. The adjustment applies to any

water and carbon dioxide that is found in the flare ven t gas (so it excludes the steam in the

combustion zone). The data points marked in red have som e of the greatest differences between

the LFL not adjusted for nitrogen equivalency and the adjust ed LFL. This means that these data y = 1.2432x -1.08
R2 = 0.9952

0.010 0.100 1.000

1.00 10.00 100.00LFLCZ

NHV CZ / NHV VG-LFLThis information is distributed solely for the purp ose of pre-dissemination peer review under applicab le information quality guidelines. It has not been formally disseminated by EPA. It does not repr esent and should not be construed to represent any Agency determination or policy.

Section 3.0: Steam and Flare Performance Page 3-31 

## points had significant amounts of water and/or carbon di oxide in the combustion zone relative to

nitrogen.

3.4 Other Operating Parameters Considered for Steam-Assi sted Flares

Numerous other operating parameters were examined to study t he effects of steam on

flare combustion efficiency; however, these did not pro ve as promising as the LFL CZ 

## operating

parameter or ratio of NHV CZ 

## to NHV VG-LFL 

## when compared to the test data. A brief review of

each of these parameters or concepts is provided in Secti ons 3.4.1 and 3.4.2.

3.4.1 Net Heating Value

The general provisions of 40 CFR 60.18(b) and 40 CFR 63.11(b) limit the net heating

value of the gas being combusted in a steam-assisted flar e (or air-assisted flare) to 300 Btu/scf or

greater. Figure 3-12 graphs combustion efficiency versus net heating value of the flare vent gas

(NHV VG 

## ) for the steam-assisted flares tested; it shows that poor combustion efficiency can occur

with flare vent gases that have high heat content (great er than 300 Btu/scf — depicted by the

vertical blue line) and good combustion may occur in flar e vent gas with lower heat content.This information is distributed solely for the purp ose of pre-dissemination peer review under applicab le information quality guidelines. It has not been formally disseminated by EPA. It does not repr esent and should not be construed to represent any Agency determination or policy.

Section 3.0: Steam and Flare Performance Page 3-32



## Figure 3-12. Combustion Efficiency vs. NHV VG



## The figure shows a general trend, as the heat content i ncreases, the combustion efficiency

increases. However, there are a significant number of test runs with flare vent gas heat content

much higher than 300 Btu/hr that do not achieve good combustion efficiency. Using the NHV VG 

## as an indicator of good combustion ignores any effect of steaming. Therefore, to incorporate

steaming, a net heating value of the combustion zone gas was calculated to include the assist

steam.

Figure 3-13 presents the combustion efficiency versus NHV CZ 

## . A much clearer trend

forms when the steam is factored into the operating para meter; as the NHV CZ 

## increases, the

combustion efficiency increases. For each test run, th e NHV CZ 

## is a lower value than the NHV VG 

## shown in Figure 3-12 because the steam dilutes the gas mix ture; each cubic foot of combustion

zone gas has less heating value than a cubic foot of th e flare vent gas.

0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%

0 500 1000 1500 2000 2500Combustion Efficiency (%)

NHV vg (Btu/scf)300 Btu/scfThis information is distributed solely for the purp ose of pre-dissemination peer review under applicab le information quality guidelines. It has not been formally disseminated by EPA. It does not repr esent and should not be construed to represent any Agency determination or policy.

Section 3.0: Steam and Flare Performance Page 3-33



## Figure 3-13. Combustion Efficiency vs. NHV CZ



## If Figure 3-13 were used to determine appropriate operating condit ions for flares,

operators would need to maintain a NHV CZ 

## between approximately 300 and 350 Btu/scf to

ensure good combustion. However, evident from Figure 3-13, ther e are a significant number of

test runs that are showing good combustion, but have a NHV CZ 

## less than 300 Btu/scf. Out of the

312 data points available for this analysis, 164 test runs a chieved a combustion efficiency of

96.5 percent or greater; 80 of these runs (or 49%) have a NHV CZ 

## less than 300 Btu/scf and

achieve greater than 96.5 percent combustion efficiency.

In addition, NHV may not be the best operating paramete r for determining flare

performance because the net heating value of a mixture ca n vary significantly at certain constant

lower flammability limits (and vice versa); Figure 3-14 sho ws this phenomenon. Figure 3-14

shows the NHV CZ 

## versus the LFL VG 

## of each test run. Based on Figure 3-14, for example, fla re
vent gas with a LFL of 0.04, may actually have a net heat ing value of anywhere between

500 Btu/scf and 2,000 Btu/scf; flare vent gas with a net heati ng value of 400 Btu/scf, may

actually have a LFL of anywhere between 0.06 and 0.25. In fa ct, Azatyan, et al (2002) observes

0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%

0 100 200 300 400 500 600 700 800 900Combustion Efficiency (%)

NHV CZ (Btu/scf)This information is distributed solely for the purp ose of pre-dissemination peer review under applicab le information quality guidelines. It has not been formally disseminated by EPA. It does not repr esent and should not be construed to represent any Agency determination or policy.

Section 3.0: Steam and Flare Performance Page 3-34 

## the same relationship stating that “...in many cases, dif ferent gases, even with identical

combustion heats and amounts of oxygen consumed per mole of fuel, differ essentially in

concentration limits of flame propagation.” Azatyan suppo rts this statement by providing an

example of how ethylene and ethanol have similar heat s of combustion (~1400 kJ/mol), but also

have very different upper and lower flammability limits (ethylene: 32.0 to 3.1%; and ethanol:

19.0 to 4.3%).

Figure 3-14. NHV VG 

## vs. LFL VG



## 3.4.2 Steam Ratios

The amount of steam added to flares with respect to the am ount of flare vent gas was

considered as a possible flare operating condition. Figure 3-15 shows the relationship between

combustion efficiency and actual steam-to-vent gas ratio (S/VG) by weight as it varied across the

different data sets. In general, as the S/VG increase s, the combustion efficiency deteriorates.

However, there appears to be multiple trends that are de fined by the different data sets and test

run series within a data set. The MPC TX data show severa l data points above 90 percent

0 500 1000 1500 2000 2500

0% 5% 10% 15% 20% 25% 30%NHVVG(Btu/scf)

LFL VG (%)This information is distributed solely for the purp ose of pre-dissemination peer review under applicab le information quality guidelines. It has not been formally disseminated by EPA. It does not repr esent and should not be construed to represent any Agency determination or policy.

Section 3.0: Steam and Flare Performance Page 3-35 

## combustion efficiency until a S/VG of about 3 and then the combustion efficiency begins to

decline more quickly with increasing S/VG. Many of the MPC -Detroit and FHR AU data points

seem to follow this trend. The FHR LOU test runs seem to show an ability to accept more steam

without adversely affecting the combustion efficiency, since a S/VG of 4 yields a 90 percent

combustion efficiency for most test runs. The Shell, EPA, and some TCEQ data appear to follow

the FHR LOU trend. Much of the TCEQ data; however, sho w a rapid degradation of combustion

efficiency, dropping below 90 percent with S/VG greater than 0.5.

Figure 3-15. Combustion Efficiency vs. S/VG by weight

Figure 3-16 is a similar plot to Figure 3-15, except that it s hows the S/VG by volume

instead of by mass. Putting the steam ratio in units of volume consolidates the perceived trends.

The MPC TX, MPC Detroit, FHR AU and FHR LOU test data seem to all follow the same

general trend. The TCEQ, EPA, and some of the Shell an d INEOS data points seem to define

two additional trends; one of rapid decline in combustion ef ficiency with increasing S/VG by

volume and one that is much slower.

0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%

0.00 1.00 2.00 3.00 4.00 5.00 6.00 7.00 8.00 9.00Combustion Efficiency (%)

Steam-to-vent-gas ratio by weight (S/VG wt ) [lb steam/lb vent gas] TCEQ

INEOS

MPC TX

MPC Detroit

FHR (AU)

FHR (LOU)

Shell (EPF)

EPA 2-83-052

EPA 2-85-106This information is distributed solely for the purp ose of pre-dissemination peer review under applicab le information quality guidelines. It has not been formally disseminated by EPA. It does not repr esent and should not be construed to represent any Agency determination or policy.

Section 3.0: Steam and Flare Performance Page 3-36



## Figure 3-16. Combustion Efficiency vs. S/VG by volume

Figure 3-17 presents the steam-to-hydrocarbon ratio (S/HC) by volume. This figure does

seem to show further improvement in the variation betw een different data sets and test run series

within a data set. However, this parameter does not take into account the amount of inert

components in the flare vent gas.

0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%

0.00 2.00 4.00 6.00 8.00 10.00 12.00 14.00Combustion Efficiency (%)

Steam-to-vent-gas ratio by volume (S/VG vol ) [scf steam/scf vent gas] TCEQ

INEOS

MPC TX

MPC Detroit

FHR (AU)

FHR (LOU)

Shell (EPF)

EPA 2-83-052

EPA 2-85-106This information is distributed solely for the purp ose of pre-dissemination peer review under applicab le information quality guidelines. It has not been formally disseminated by EPA. It does not repr esent and should not be construed to represent any Agency determination or policy.

Section 3.0: Steam and Flare Performance Page 3-37



## Figure 3-17. Combustion Efficiency vs. S/HC by volume

The variation in trends in Figures 3-15 through 3-17 is likely due to the variation in flare

vent gas components and compositions between each data s et. For example, the TCEQ test data

consists of flare vent gas streams of propylene or pro pane with nitrogen (and some natural gas

used as a supplemental gas), while the INEOS tests were c onducted with flare vent gas

containing various mixtures of 1,3-butadiene, natural gas, an d nitrogen. It appears that S/VG or

S/HC alone cannot fully address over steaming because neit her considers the variability of

chemical properties within the flare vent gas. As discuss ed in Section 3.1, unlike S/VG or S/HC,

the LFL CZ 

## is a good candidate for evaluating flare performance be cause it actually considers the

variability of chemical properties.

Another parameter investigated was the ratio of actual t otal mass flow rate of steam to a

recommended total mass flow rate of steam for a steam- assisted flare. This steam ratio parameter

was based on Table 11 of the American Petroleum Institut e (API) Standard 521 for pressurerelieving and depressuring systems. Table 11 of the API document suggests amounts of steam

that should be injected into certain gases being flared i n order to promote smokeless burning.

0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%

0.00 5.00 10.00 15.00 20.00 25.00Combustion Efficiency (%)

Steam-to-hydrocarbon ratio by volume (S/HC vol ) [scf steam/scf HC]

TCEQ

INEOS

MPC TX

MPC Detroit

FHR (AU)

FHR (LOU)

Shell (EPF)

EPA 2-83-052

EPA 2-85-106This information is distributed solely for the purp ose of pre-dissemination peer review under applicab le information quality guidelines. It has not been formally disseminated by EPA. It does not repr esent and should not be construed to represent any Agency determination or policy.

Section 3.0: Steam and Flare Performance Page 3-38 

## Because these steam recommendations in API 521 are inten ded for only smoke suppression, and

not meant to be correlated to combustion efficiency pe rformance, this steam ratio parameter was

not investigated any further. In addition, the suggested inject ion steam rates are provided for only

certain flared gases that are most common to petroleum and natural gas industries (they do not

cover a complete list of the chemicals that may be flared).This information is distributed solely for the purp ose of pre-dissemination peer review under applicab le information quality guidelines. It has not been formally disseminated by EPA. It does not repr esent and should not be construed to represent any Agency determination or policy.

Section 4.0: Air and Flare Performance Page 4-1 

## 4.0 AIR AND FLARE PERFORMANCE

Similar to how steam is used (See Section 3.0 for steam discussion), air injection can

promote smokeless burning in a flare. Air adds momentum and turbulence to the combustion

zone, which improves mixing and reduces the possibility of smoke formation. Because the

additional air is induced into the waste gas, it also pr ovides oxygen necessary to augment

smokeless capacity (Castiñeira and Edgar, 2006). However, jus t as in the use of steam, using too

much air in a flare (excess aeration) can actually re sult in a flare operating outside its stable

flame envelope, decreasing the combustion efficiency (Zee co Company, 2003). Assist air can

dilute the flare vent gas, making the flare vent gas too l ean to burn in the combustion zone.

To identify excess aeration situations that may occur o n air-assisted flares, the data

suggest that the stoichiometric air ratio (SR) (the act ual mass flow of assist air to the theoretical

stoichiometric mass flow of air needed to combust the fl are vent gas) is the most appropriate

operating parameter. Specifically, the data suggest that, i n order to maintain good combustion

efficiency, the SR must be 7 or less for an air-assist ed flare. Furthermore, the data suggest that

the lower flammability limit of the flare vent gas (LF L VG 

## ) should be 15.3 percent by volume or

less to ensure the flare vent gas being sent to the air- assisted flare is capable of adequately

burning when introduced to enough air. This section documents t he analysis supporting these

observations. Note: the LFL VG 

## is different from the LFL CZ 

## described in Section 3.1.2 of this

report because the LFL VG 

## does not consider any assist media; however, in general, the

methodology described in Section 3.1.2 for determining LFL st ill applies.

4.1 Stoichiometric Air Ratio

The stoichiometric air ratio (SR) is the ratio of ac tual mass flow of total assist air to the

theoretical stoichiometric mass of air needed to combust t he flare vent gas (this relationship is

shown in Equation 4-1). The SR increases as more assist air is added to the flare vent gas.

  

 	
 

## (Eq. 4-1)This information is distributed solely for the purp ose of pre-dissemination peer review under applicab le information quality guidelines. It has not been formally disseminated by EPA. It does not repr esent and should not be construed to represent any Agency determination or policy.

Section 4.0: Air and Flare Performance Page 4-2 

## Where:

SR = Ratio of actual mass flow of total assist air to the theoretical stoichiometric mass

of air needed to combust the flare vent gas, unitless.

m Air 

## = Actual mass flow of total assist air, pounds per hour, lb/hr.

m Stoic 

## = Theoretical stoichiometric mass of air needed to combus t the flare vent gas, lb/hr.

For flares that utilize air as an assist medium, th e stoichiometric amount of assist air

(m Stoic 

## ) represents the theoretical amount of air needed to obt ain complete combustion of a fuel

gas comprised of combustible compounds. This stoichiometric amount is based on the specific

chemical composition and quantity of the combustible co mpounds combusted in the flare. The

stoichiometric amount of assist air needed is determined from only the combustible portion of

the flare vent gas. While some flare vent gas streams may include non-combustible compounds,

such as carbon dioxide or nitrogen, the determination of t he stoichiometric air amount ignores

the contributions of these compounds to the total flow and composition of the fuel gas stream.

The theoretical stoichiometric molar amount of air re quired for combustion varies

between different combustible hydrocarbons, and can be det ermined by a balanced combustion

reaction equation. Equations 4-2 and 4-3 below are balanced co mbustion reaction equations for

methane and propane, respectively.

 

##  2  

##    

##  2  

##  (Eq. 4-2)

  

##  5  

##  3  

##  4  

##  (Eq. 4-3)

As seen in Equation 4-2, two moles of oxygen are required f or the complete combustion

of one mole of methane. Similarly, Equation 4-3 shows th at five moles of oxygen are required to

completely combust one mole of propane. Assuming ambient air contains approximately

21 percent oxygen, and using the molecular weight for methane , propane, and air, the

stoichiometric ratio of air to fuel can be calculated as shown in Equation 4-4 for methane and

Equation 4-5 for propane. For methane, the stoichiometric r atio of air to fuel is 17.1 pounds of

air per pound of methane; and for propane, it is 15.6 pounds of air per pound of propane. These

values are used with the actual amount of assist air an d fuel to calculate the SR. All data sets andThis information is distributed solely for the purp ose of pre-dissemination peer review under applicab le information quality guidelines. It has not been formally disseminated by EPA. It does not repr esent and should not be construed to represent any Agency determination or policy.

Section 4.0: Air and Flare Performance Page 4-3 

## the methodologies used in calculating the SR are outlined in Section 2.0, and Appendices C and

D of this report.

   
   ! 

## "   #$%

&.    

## " . ( #$%

  #$% 

## "    !

) (  ! 

##  *. ( #$%

 (  ! 

## (Eq. 4-4)

+   
   , - 

## "   #$%

&.    

## " . ( #$%

  #$% 

## "    , -

 (  , - 

##  +.) ( #$%

 (  , - 

## (Eq. 4-5)

4.2 TCEQ Test Data

The Texas Commission on Environmental Quality (TCEQ) 2010 flare study final report

(Allen and Torres, 2010) examined the effects of SR on an air-assisted flare’s combustion

efficiency. The results of the TCEQ study show that, in general, as more assist air is added to the

flare vent gas and the SR increases, the flare combusti on efficiency deteriorates. Figure 4-1 plots

35 test runs from the TCEQ study that clearly shows this t rend.

Figure 4-1. Combustion Efficiency vs. SR (using TCEQ data) 0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%

0 10 20 30 40 50 60 70 80 90 100Combustion Efficiency, %

Stoichiometric Ratio (SR)This information is distributed solely for the purp ose of pre-dissemination peer review under applicab le information quality guidelines. It has not been formally disseminated by EPA. It does not repr esent and should not be construed to represent any Agency determination or policy.

Section 4.0: Air and Flare Performance Page 4-4 

## 4.3 Other Test Data

The trend displayed in Figure 4-1 (as more assist air is a dded to the flare vent gas and the

SR increases, the flare combustion efficiency deterio rates) also exists with the nine specific airassist test runs extracted from the EPA-600/2-85-106 study (Pohl and Soelberg, 1985).

Figure 4-2 shows this trend. It was not possible to include, in Figure 4-2, the 13 air-assisted test

runs extracted from the EPA-600/2-83-052 study (McDaniel, 1983) beca use the air flow and air

flow velocity were considered proprietary information an d not included in the test report.

Figure 4-2. Combustion Efficiency vs. SR (using EPA-600/2-85-106 da ta)

4.4 Analysis of Stoichiometric Air Ratio

Figure 4-3 overlays Figures 4-1 and 4-2. It shows that although the trend exists for both

data sets, the threshold (or cliff) where combustion ef ficiency begins to deteriorate is much

different between the two data sets. The two studies we re reviewed carefully in an attempt to

identify differences between the EPA-600/2-85-106 and TCEQ te st runs. The test data from the

EPA-600/2-85-106 study used mixtures of propane and nitrogen, while TCE Q used propylene or

0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%

0 1 2 3 4 5 6Combustion Efficiency, %

Stoichiometric Ratio (SR)This information is distributed solely for the purp ose of pre-dissemination peer review under applicab le information quality guidelines. It has not been formally disseminated by EPA. It does not repr esent and should not be construed to represent any Agency determination or policy.

Section 4.0: Air and Flare Performance Page 4-5 

## propane with natural gas as a supplemental gas. The air-as sisted flare from the EPA-600/2-85-

106 study had a 1.5 inch diameter and the air-assisted flare f rom the TCEQ tests had a diameter

of 24 inches. Most of the test runs from the EPA-600/2-85-106 s tudy did not use a pilot during

testing but the TCEQ testing did include pilots. In additio n, the flare vent gas volumetric or mass

flow rates for the EPA-600/2-85-106 test runs were not repor ted, so assumptions were made

using the reported flare vent gas velocity to determine fl ow rates.

Figure 4-3. Combustion Efficiency vs. SR (combined TCEQ and EPA-600/2-85-106 data)

The EPA-600/2-85-106 test report noted that smaller flares did not produce data that

were comparable to larger flares (greater than 3 inches). Gogolek et al. (2010b) supports this

finding by concluding that results from pipe flares smalle r than 3 inches are not scalable to larger

diameter pipe flares (i.e., 6 to 12 inch diameter pipe flar es). This conclusion seems logical with

respect to all of the available air assist data, especia lly if the various sized flares are operated

with similar SR values. There is less distance acros s the volumetric flare vent gas flow of a small

flare at the tip exit than the distance across the vo lumetric flare vent gas flow of a larger flare at

the tip exit; therefore, more assist air would penetrate and mix with the flare vent gas if a smaller

0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%

0 10 20 30 40 50 60 70 80 90 100Combustion Efficiency, %

Stoichiometric Ratio (SR) TCEQ

EPA-600/2-85-106This information is distributed solely for the purp ose of pre-dissemination peer review under applicab le information quality guidelines. It has not been formally disseminated by EPA. It does not repr esent and should not be construed to represent any Agency determination or policy.

Section 4.0: Air and Flare Performance Page 4-6 

## flare were used. Because of these differences between the EPA-600/2-85-106 and TCEQ test

runs, the EPA-600/2-85-106 data were removed and only the TCEQ dat a were analyzed.

Figure 4-4 is the same as Figure 4-1, but with the axes nar rowed to a shorter range. The

vertical green line identifies the SR threshold where a ll test runs achieve a combustion efficiency

of 96.5 percent or greater. (See Section 2.8 of this report fo r a discussion of why 96.5 percent

was selected as a measure of good combustion efficienc y for reviewing the flare test data.) This

line shows a transition between good and poor combustion som ewhere between a SR of 7.0 and

9.

Figure 4-4. Combustion Efficiency vs. SR, zoomed (using TCEQ data)

Given the differences shown between the TCEQ and EPA- 600/2-85-106 data sets (see

Figure 4-3), we have concerns about the possible differenc es in SR threshold (transition between

good and poor combustion) between typical commercial fla re sizes. For example, is an SR value

of 7.0 appropriate for a 54 inch flare? Although Gogolek et al. (2010b) concluded that results

from flares smaller than 3 inches are not scalable to 6 to 12 inch diameter sized flares; the report

does not determine whether 6 to 12 inch diameter sized flare s are scalable to full-scale industrial

84% 86% 88% 90% 92% 94% 96% 98% 100%

3 5 7 9 11 13 15Combustion Efficiency, %

SR TCEQ

SR = 7.0

96.5% CEThis information is distributed solely for the purp ose of pre-dissemination peer review under applicab le information quality guidelines. It has not been formally disseminated by EPA. It does not repr esent and should not be construed to represent any Agency determination or policy.

Section 4.0: Air and Flare Performance Page 4-7 

## sized flares. The observed variation in SR thresholds b etween a 1.5 inch and 24 inch flare is not

expected to be as exaggerated for typical commercial fla re sizes. Given the steam-assisted flare

data encompass flare tip sizes (in terms of the effect ive diameter of the flare tip) from 5.86 inch

to 54 inches, and the apparent comparability of those resul ts (see Section 3.0 of this report), it is

likely that this issue is simply inherent with the much smaller flares (i.e., less than 3 inches).

For these reasons, the data suggest that a SR of 7.0 is the transition between good and

poor combustion for air-assisted flares.

4.5 Considering LFL VG 

## for Air-Assisted Flares

Operating a flare with a SR of 7.0 or less does not tell an owner or operator if there are

enough combustible components in the combustion zone to b urn adequately. If there are not

enough combustible components in the combustion zone, the n the flare vent gas will not burn, or

will burn inadequately, resulting in lower combustion eff iciency. Therefore, it is logical that an

owner or operator should be conscious of whether the fla re vent gas being sent through the

air-assisted flare is capable of burning.

It seems reasonable to assume that the LFL CZ 

## analysis in Section 3.0 of this report could

apply to an air-assisted flare. However, for an air-a ssisted flare, the “combustion zone gas”

would simply reduce to the “flare vent gas” because air i s the only assist media being added to

the combustion zone of an air-assisted flare. As disc ussed in Section 3.0 of this report, for steamassisted flares, the LFL is an indicator of how well a mixture can burn. For steam-assisted flares,

the LFL in the combustion zone was used to incorporate t he effect of the steam in the

determination of the LFL; however for air-assisted flar es, the mixture being introduced with air

is contained in the flare vent gas. Although, there is air being added as an assist media, it is no

different than the air in the atmosphere that the fla re vent gas would be mixed with, except that

the mixing is occurring much faster with air-assist. Th erefore, for air-assisted flares, instead of

using the term LFL CZ 

## as an indicator of how well a mixture can burn, we use the lower

flammability limit of the flare vent gas (LFL VG 

## ).This information is distributed solely for the purp ose of pre-dissemination peer review under applicab le information quality guidelines. It has not been formally disseminated by EPA. It does not repr esent and should not be construed to represent any Agency determination or policy.

Section 4.0: Air and Flare Performance Page 4-8 

## An observation made regarding the EPA-600/2-85-106 and TCEQ ai r-assist data is that

the LFL VG 

## for each of the 44 test runs (i.e., 35 TCEQ test runs an d 9 EPA-600/2-85-106 test

runs) is 15.0 percent by volume or less (when adjusted for nitrogen equivalency as described in

Section 3.1.2 of this report), but only nine test runs achieve d greater than 96.5 percent

combustion efficiency. This means that each test run (us ing the 15.3% LFL CZ 

## threshold analysis

provided in Section 3.0 of this report) had the capability of burning at high combustion

efficiency, provided the mixture was not diluted with too muc h assist air (i.e., the SR was 7.0 or

less). More details regarding the LFL are presented in S ection 3.0 of this report; however, there

is simply not enough air-assisted test data to determine w hether a new LFL CZ 

## threshold would be

warranted for air-assisted flares (i.e., a LFL VG 

## threshold different than 15.3 percent).

For these reasons, the data seem to suggest that, for an air-assisted flare, a LFL VG 

## (adjusted for nitrogen equivalency as described in Section 3.1.2 of this report) of 15.3 percent by

volume or less also indicates that a mixture can combus t and maintain a good combustion

efficiency, assuming that the air-assist flow is not t oo high to deteriorate efficiency.This information is distributed solely for the purp ose of pre-dissemination peer review under applicab le information quality guidelines. It has not been formally disseminated by EPA. It does not repr esent and should not be construed to represent any Agency determination or policy.

Section 5.0: Wind and Flare Performance Page 5-1 

## 5.0 WIND AND FLARE PERFORMANCE

The EPA Air Pollution Control Cost Manual - Sixth Edi tion (U.S. EPA, 2002) states that

in most flares, combustion occurs by means of a diffu sion flame. A diffusion flame is one in

which air diffuses across the boundary of the fuel/com bustion product stream toward the center

of the fuel flow, forming an envelope of combustible gas m ixture around a core of fuel gas. On

ignition, this combustible gas mixture establishes a stabl e flame zone around the gas core above

the flare tip. The inner gas core is heated by diffusion fr om the hot combustion products

produced in the flame zone. Leahey et al. (2001) suggest that predicting the size (length,

diameter, area, and volume) of a diffusion flame could be useful in estimating its combustion

efficiency because as a flame size is reduced, less oxygen entrains into the flame. Leahey et al.

(2001) also point out that if a flame’s dimensions are depe ndent on meteorological variables

(e.g., wind), a flame’s combustion efficiency would als o be dependent on meteorological

variables (e.g., wind).

A high crosswind velocity can have a strong effect on t he flare flame dimensions and

shape. When the flame is bent over on the downwind side of a flare and is imbedded in the wake

of the flare tip, it is said to be in a wake-dominated regi me. Many experts believe a wakedominated flame can lead to poor flare performance. The dat a suggest that flare performance is

not significantly affected by crosswind velocities up to 22 miles per hour (mph). There are

limited data for flares in winds greater than 22 mph. Howe ver, a wake-dominated flame in winds

greater than 22 mph may affect flare performance. The da ta available indicate that the wakedominated region begins at a momentum flux ratio (MFR) o f 3 or greater. The MFR considers

whether there is enough flare vent gas and center steam (if applicable) exit velocity (momentum)

to offset crosswind velocity. Because wake-dominated flam es can be identified visually,

observations could be conducted to identify wake-dominated fla mes during crosswind velocities

greater than 22 mph at the flare tip. This section documen ts the analysis supporting these

observations.This information is distributed solely for the purp ose of pre-dissemination peer review under applicab le information quality guidelines. It has not been formally disseminated by EPA. It does not repr esent and should not be construed to represent any Agency determination or policy.

Section 5.0: Wind and Flare Performance Page 5-2 

## 5.1 Introduction

Smoot et al. (2009), who examined operating and design issues f or pipe flares, provide an

illustration on how flare performance is affected by cro sswinds that shear the combustion zone.

These researchers state that wind shortens the flame, causing soot formation on the downwind

side of the flame. They also warn that high crosswin ds can result in air egress into the flare tip,

which creates internal burning and potential explosive cond itions (Figure 5-1).

Figure 5-1. Air Egression Into Flare Stack Source: (Smoot et al., 2009)

5.2 Flare Flow Mixing Regimes

Depending on crosswind and flare tip velocity, the appearanc e of a flare flame can be

quite different. In a report from a Joint Internationa l Combustion Symposium (Seebold et al.,

2004), the authors summarize and provide images (Figure 5-2) of t hree flare flow mixing

regimes: “wake-dominated”, “buoyancy-dominated”, or “inertia -dominated”. At low crosswind

velocity and high flare tip velocity, the flare flame is generally inertia-dominated, with the flameThis information is distributed solely for the purp ose of pre-dissemination peer review under applicab le information quality guidelines. It has not been formally disseminated by EPA. It does not repr esent and should not be construed to represent any Agency determination or policy.

Section 5.0: Wind and Flare Performance Page 5-3 

## positioned directly above the jet stack and the flame c urling straight upwards. In this case, the

strength of the jet momentum flux in relation to the strength of the wind ensures a stable

combustion zone and combustion efficiencies are invar iably higher (Seebold et al., 2004).

Figure 5-2. Images of Flow Mixing Regimes Source: (Seebold et al., 2004)

As crosswind velocities increase, “downwash” occurs as the flame lengthens horizontally

and a portion of the combustion gases are drawn into the low pressure region on the downwind

side of the stack (Johnson and Kostiuk, 2000). The flame zon e diminishes into detached pockets

of combustion interspersed beneath a non-reacting mixi ng layer containing unburned fuel

(Johnson and Kostiuk, 2000; Johnson et al., 2001). In these high crosswind (and low flare vent

gas velocity) situations, the flare flame is referred to as wake-dominated, which means the flame

is bent over on the downwind side of a flare pipe and is imbedded in the wake of the flare tip

(Figure 5-2), protected from the crosswind (Johnson et al., 2001). Under these conditions, the

main tail of the flame may be extinguished, and the prima ry combustion zone occurs as a

standing vortex on the downwind side of the stack (Johnso n et al., 2001; Johnson and Kostiuk,

1999, 2000).This information is distributed solely for the purp ose of pre-dissemination peer review under applicab le information quality guidelines. It has not been formally disseminated by EPA. It does not repr esent and should not be construed to represent any Agency determination or policy.

Section 5.0: Wind and Flare Performance Page 5-4 

## 5.3 Efficiency Studies

Seebold et al. (2004) state that the wake-dominated mixing regime may lead to low

combustion efficiency eddies. Several efficiency st udies conducted at high crosswind velocities

suggest that poor combustion efficiencies in wake-d ominated flare flames result from fuel

stripping where a portion of unburned fuel is strip ped from the flame stream prior to reaching a

flame zone (Johnson et al., 1999; Johnson and Kosti uk, 2000; Johnson et al., 2001; and

Castiñeira and Edgar, 2006). The unburned fuel is p rimarily ejected into the underside of the

flame. Johnston et al. (2001) provide a sketch of t he unburned hydrocarbons detected downwind

in a wake-dominated flare with a crosswind velocity of 8 meters/second (m/s) or about 18 mph

(Figure 5-3).

Figure 5-3. Fuel Detection Downwind of Wake-Dominat ed Flare Source: (Johnston et. al, 2001)This information is distributed solely for the purp ose of pre-dissemination peer review under applicab le information quality guidelines. It has not been formally disseminated by EPA. It does not repr esent and should not be construed to represent any Agency determination or policy.

Section 5.0: Wind and Flare Performance Page 5-5 

## Researchers from the University of Alberta have published a series of studies that

describe their investigations on the significance of win d on the fluid mechanics of a flare flame

at low MFR (Bourguignon et al., 1999; Johnson et al., 1998, 1999a, 1999b, 2001; and Johnson

and Kostiuk, 1999, 2000). The MFR is a measure of momentum stre ngth of the flare vent gas

relative to the crosswind (the product of flare vent gas density and velocity squared divided by

the product of air density and crosswind velocity squared). T he MFR at the flare tip can be

calculated using Equation 5-1.

./ 01 234 506 7 5 

8 1 9 :8 6 ;<= :  

## ( Eq. 5-1 )

Where:

MFR = Momentum flux ratio, unitless.

ρ vgcs 

## = Density of flare vent gas including center steam if a pplicable, lb/scf.

V tip 

## = Actual flare tip velocity (i.e., actual flare vent gas velocity plus center steam

velocity, if applicable), ft/s. The flare tip velocity is dependent on how the unobstructed cross sectional area of the flare tip is c alculated. John Zink provided details for determining the unobstructed cross sectional are a of several flare tip designs (see Appendix I).

ρ air 

## = Density of ambient air, lb/scf.

V wind 

## = Crosswind velocity, ft/s.

The experiments in these studies were conducted on about a one-inch diameter simple

pipe flare using a wind tunnel. The maximum crosswind veloci ty during these experiments was

31 mph. These studies concluded that increased crosswind velo city can adversely affect the

combustion efficiency of a flare; while increased flare tip velocity makes the flame less

susceptible to the effects of crosswind. One report (Johns on and Kostiuk, 2000) provides images

(Figure 5-4) of the flame, showing that as MFR decreases, the combustion efficiency of the

flame also decreases. Mathematical models presented by Ca stiñeira and Edgar (2006) determined

similar results for about 0.5-inch diameter simple p ipe flares. Further modeling (Castiñeira and

Edgar, 2008) showed a simulated flame almost completely exti nguished at crosswind velocities

of 22 mph.This information is distributed solely for the purp ose of pre-dissemination peer review under applicab le information quality guidelines. It has not been formally disseminated by EPA. It does not repr esent and should not be construed to represent any Agency determination or policy.

Section 5.0: Wind and Flare Performance Page 5-6 

## Figure 5-4. Flame Images Relating to Momentum Flux Ratio and Comb ustion Efficiency Source: (Johnson and Kostiuk, 2000) 1

1 Images from a one-inch diameter simple pipe flare using a wind tunnel. The “R” term is MFR, the “ η c” term is the combustion efficiency of the flame, the “U” term is crosswind velocity, and the “Vj” term is flare tip velocity.This information is distributed solely for the purp ose of pre-dissemination peer review under applicab le information quality guidelines. It has not been formally disseminated by EPA. It does not repr esent and should not be construed to represent any Agency determination or policy.

Section 5.0: Wind and Flare Performance Page 5-7 

## Seebold et al. (2004) present a graph (Figure 5-5) that shows a potentially strong

correlation between combustion efficiency and MFR, re vealing that as the MFR falls below 0.1,

the combustion efficiency decreases significantly (for some data). However, we are not able to

confirm the source of this data or anything about these test runs. Because the reference that

Seebold et al. (2004) provide (shown in the reproduced Figure 5-5 as “Reaction Efficiency of

Industrial Flares – The Perspective of the Past.” Septem ber 2003) does not contain details about

how Figure 5-5 was created, we have not used Figure 5-5 in o ur analysis.

Figure 5-5. Combustion Efficiency vs. Momentum Flux Ratio, Se ebold Data

Source: (Seebold et al., 2004)

Gogolek et al. (2010b) investigated the transition from a vertical jet flame to a

wake-dominated flame by performing tests on a 2 inch and 3 in ch flare tip (and also on a 3 inch

flare tip that had a flame retention ring). Gogolek et al. (2010b) determined visually that the

transition to a wake-dominated flame occurred at a MFR o f around 3 for all three pipes tested.

However, the study also revealed that there is no shar p change in flare performance with the

establishment of the wake-dominated flame. Additionally, Gogolek et al. (2010b) found that two

sets of operating conditions with the same MFR produce dr astically different flare performance

(one with high crosswind and moderate flare tip velocity , and another with moderate crosswindThis information is distributed solely for the purp ose of pre-dissemination peer review under applicab le information quality guidelines. It has not been formally disseminated by EPA. It does not repr esent and should not be construed to represent any Agency determination or policy.

Section 5.0: Wind and Flare Performance Page 5-8 

## and low flare tip velocity), indicating that MFR may hav e limitations for correlating the

performance of flares. The study concluded that a decreas e in combustion efficiency is more

likely to occur when the transition to a wake-dominated flame is caused by an increase in

crosswind velocity rather than by a reduction in flare tip velocity.

In lieu of the MFR, other parameters such as a plume buo yancy factor or a power factor

may be considered. It was through the research performed by the University of Alberta

(Bourguignon et al., 1999; Johnson et al., 1998, 1999a, 1999b, 2001; and J ohnson and Kostiuk,

1999, 2000) that these parameters were developed. Gogolek et al. (2010a) summarize the

methodologies for determining a plume buoyancy factor or power factor. The plume buoyancy

factor is calculated using Equation 5-2; and it considers cr osswind velocity and actual flare vent

gas velocity plus center steam velocity. The power fac tor is calculated using Equation 5-3; it is

the ratio of the power of the crosswind to the power o f combustion of the flare vent gas. (See

Gogolek et al. (2010a) for further detail on these two para meters.) Center steam should be

incorporated into the flare vent gas properties because cent er steam adds momentum (i.e., center

steam exits the flare tip in the same direction as th e flare vent gas).

>?  6 ;<= 0@AB 7 A6 7 5 C ,

D 

## (Eq. 5-2)

Where:

BP = Plume buoyancy factor, unitless.

V wind 

## = Average cross-sectional wind velocity, ft/s.

g = Acceleration due to gravity, ft/s 2



## .
D p 

## = Effective diameter of flare pipe, ft.

V tip 

## = Actual flare tip velocity (i.e., actual flare vent gas velocity plus center steam

velocity, if applicable), ft/s. The flare tip velocity is dependent on how the unobstructed cross sectional area of the flare tip is c alculated. John Zink provided details for determining the unobstructed cross sectional are a of several flare tip designs (see Appendix I).

?/  E 1 9 A6 ;<= AB 7 

1 F AG 7 A6 7 AH 6

I 

## J   D 

## (Eq. 5-3)This information is distributed solely for the purp ose of pre-dissemination peer review under applicab le information quality guidelines. It has not been formally disseminated by EPA. It does not repr esent and should not be construed to represent any Agency determination or policy.

Section 5.0: Wind and Flare Performance Page 5-9 

## Where:

PF = Power factor, unitless.

ρ a 

## = Density of air, lb/scf.

V wind 

## = Average cross-sectional wind velocity, ft/s.

D p 

## = Effective diameter of flare pipe, ft.

ρ f 

## = Density of flare vent gas including center steam, lb/s cf.

A p 

## = Unobstructed cross sectional area of the flare tip, ft 2 

## . John Zink provided details

for determining the unobstructed cross sectional area of so me of several flare tip designs (see Appendix I).

V tip 

## = Actual flare tip velocity (i.e., actual flare vent gas velocity plus center steam

velocity, if applicable), ft/s. The flare tip velocity is dependent on how the unobstructed cross sectional area of the flare tip is c alculated (See Appendix I).

LHV m 

## = Lower heating value (mass basis) of flare vent gas i ncluding center steam,

Btu/scf.

Gogolek et al. (2010b) tested the power factor using natural gas on 3, 4, and 6 inch flare

tips, and concluded that the power factor appears to be a use ful dimensionless parameter for

correlating flare performance data. However, Gogolek et al. (2010b) conclude that the power

factor would have to be augmented to correlate performanc e of different flare vent gas mixtures.

Gogolek et al. (2010b) also indicates that crosswind veloc ity thresholds for indicating good

combustion efficiency may differ depending on the compos ition of the flare vent gas. The study

concluded (based on tests using 3” flare retention ring flar e tips) that destruction efficiency

remains better than 98 percent for ethylene at crosswind velocities tested up to 24.6 mph; but fall

below 98 percent at crosswind velocities of 17.9 mph for pro pylene. The study also reports that

destruction efficiency remained above 97 percent for all c rosswind velocities tested for

propylene. These tests using 3” flare retention ring fla re tips produced results similar to the 2”

pipe flare, which are not scalable to industrial sized f lares. All tests conducted by Gogolek et al.

(2010b) on the flares found to be scalable to industrial siz ed flares (i.e., 3”, 4”, and 6” pipe flares,

and 6” with flame retention rings) showed combustion eff iciencies greater than 96.5 percent for

all fuels tested for winds of 22 mph and less.

Gogolek et al. (2010b) incorporate a “fuel factor” into thei r analysis as an attempt to

incorporate the effects of flare gas combustion properties, wind speed, and flare vent gas flowThis information is distributed solely for the purp ose of pre-dissemination peer review under applicab le information quality guidelines. It has not been formally disseminated by EPA. It does not repr esent and should not be construed to represent any Agency determination or policy.

Section 5.0: Wind and Flare Performance Page 5-10 

## rate; however, the “fuel factor” uses the upper flammabil ity limit (UFL), which is difficult to

calculate for mixtures, especially ones with inert. Al so, Gogolek et al. (2010b) report that the

"fuel factor" did not correlate well when flaring natural gas; and provide an explanation that the

"fuel factor" does not consider the reaction kinetics of combustible mixtures.

Excluding the data shown in Figure 5-5 (because flare size is unknown for this data) as

well as Gogolek’s et al. (2010b) power factor analysis, a ll of the studies mentioned in this section

(i.e., Section 5.3 of this report) were conducted on 3 inch flare tips and smaller, which are not of

typical size for an industrial flare. Gogolek et al. (2010b) states that results of pipes smaller than

3 inch do not scale-up to larger pipes; and it has not been de termined whether results for 3 inch

to 6 inch pipes can successfully be applied to full-scal e industrial flares. However, it does appear

crosswind velocity influences the size of a diffusion f lame (e.g., length, diameter, area, and

volume) and should be considered in flare performance no matter the size of a flare tip. It seems

reasonable to assume that combustion efficiency of an industrial sized flare will also likely be

sensitive to crosswind velocity.

5.4 Test Data Analysis

Although Gogolek et al. (2010b) indicates that MFR may have limitations for correlating

the performance of flares, we reviewed available MFR dat a as provided in raw test data

spreadsheets for 245 steam-assisted flare test runs from five of the eight studies discussed in

Section 2 of this report (i.e., TCEQ, MPC TX City, MPC Detroit, FHR AU, and FHR LOU).

Unfortunately, the data provided in these reports were not used consistently to calculate MFR

(i.e., some reports incorporated total assist steam, whil e others only center steam when using an

actual flare tip velocity in their MFR methodology). T herefore, we recalculated MFR for all

available test runs to incorporate only the center steam volume into the flare vent gas exit

velocity because it exits the flare tip in the same d irection as the flare vent gas. Steam and/or air

nozzles associated with the upper and lower ring locations were not incorporated into the flare

vent gas exit velocity when calculating MFR because it i s less clear whether steam contribution

from these nozzles should be included. Steam velocity and nozzle angle for upper and lower ring

locations was not available for all of the test repo rts. Upper and lower ring nozzles are generallyThis information is distributed solely for the purp ose of pre-dissemination peer review under applicab le information quality guidelines. It has not been formally disseminated by EPA. It does not repr esent and should not be construed to represent any Agency determination or policy.

Section 5.0: Wind and Flare Performance Page 5-11 

## directed up at about 30 to 45 degrees from horizontal (jettin g into but also in the direction of the

flare vent gas momentum), so only a portion of steam fr om upper and lower ring nozzles could

enhance the momentum of the flare vent gas flow.

These test data represent 245 test runs with flare tip vel ocities (including center steam

velocity) of less than 9 feet per second (ft/s) and wind speeds typically below 12 mph

(approximately 20% of the test runs were performed in wind spe eds above 12 mph; and no test

runs were performed in winds any higher than 22 mph). Most of these test runs inevitably have

low MFR values because the runs were performed at relat ively low flare tip velocities.

Nevertheless, the MFR from these test runs was plotte d against the combustion efficiency to

investigate whether a trend was discernable (Figures 5-6 and 5-7).

In general, Figure 5-6 shows that all runs were tested at a MFR less than about 7.0.

However, it is assumed that most of these data (149 ste am-assisted test runs) had poor

flammability characteristics because the LFL CZ 

## for these test runs was greater than 15.3 percent

by volume (see Section 3.0 of this report for an explanat ion of this LFL CZ 

## level). Also, there are

10 test runs highlighted in red in Figure 5-6 that had a LFL CZ 

## less than 15.3 percent by volume

and did not achieve a combustion efficiency of 96.5 percent or greater. The poor combustion

efficiency reported for these 10 test runs are discussed in Section 3.1.3 of this report.This information is distributed solely for the purp ose of pre-dissemination peer review under applicab le information quality guidelines. It has not been formally disseminated by EPA. It does not repr esent and should not be construed to represent any Agency determination or policy.

Section 5.0: Wind and Flare Performance Page 5-12



## Figure 5-6. Combustion Efficiency vs. Momentum Flux Ratio

Figure 5-7 presents a subset of the data in Figure 5-6—those w ith MFR values less than

3.0—because Gogolek et al. (2010b) suggests that a MFR of 3.0 is the observed boundary for the

transition to the wake-dominated mixing regime.

0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%

0 1 2 3 4 5 6 7 8Combustion Efficiency (%)

MFR LFL<15.3%, CE >96.5%

LFL<15.3%, CE < 96.5%

LFL>15.3%This information is distributed solely for the purp ose of pre-dissemination peer review under applicab le information quality guidelines. It has not been formally disseminated by EPA. It does not repr esent and should not be construed to represent any Agency determination or policy.

Section 5.0: Wind and Flare Performance Page 5-13



## Figure 5-7. Combustion Efficiency vs. Momentum Flux Ratio, zoom ed

(MFR < 3.0; wake-dominated mixing regime)

These plots indicate that good flare performance can exist in a wake-dominated mixing

regime. However, it is difficult to establish a MFR l imit to define a wake-dominated regime with

good combustion efficiency because it is not clear fro m these plots whether low MFR, high

LFL CZ 

## , or some combination of both contribute to poor flare per formance. Also, the available

test data represent only a narrow range of wind and flare v ent gas velocities (primarily <12 mph

and <8 ft/s, respectively). For example, although the te st data show that good flare performance

can occur at a MFR as low as 0.003 (identified on Figure 5-8 with solid blue vertical line), this

conclusion is based on only a single data point.

0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%

0.0 0.5 1.0 1.5 2.0 2.5 3.0Combustion Efficiency (%)

MFR LFL<15.3%, CE >96.5%

LFL<15.3%, CE < 96.5%

LFL>15.3%This information is distributed solely for the purp ose of pre-dissemination peer review under applicab le information quality guidelines. It has not been formally disseminated by EPA. It does not repr esent and should not be construed to represent any Agency determination or policy.

Section 5.0: Wind and Flare Performance Page 5-14 

## Figure 5-8. Combustion Efficiency vs. Momentum Flux Ratio, fu rther zoomed (MFR < 0.1)

The test runs shown in Figures 5-6 through 5-8 are of moderat e crosswind and low flare

tip velocity. It appears that the data confirms what Gog olek et al. (2010b) observed which was

that low MFRs created because of the low flare tip ve locity (and less so because of higher

crosswind) do not have the degraded combustion efficiency tha t low MFRs created by high

crosswind (and less so because of low flare tip velocit y) show. In other words, in the absence of

higher crosswind velocities, a lower MFR does not necess arily indicate poor flare performance.

Because we do not have test data of crosswind speeds greater than 22 mph, we are unable to

investigate this hypothesis further using the industrial flare test data. It should be noted that

Gogolek et al. (2010b) performed tests as high as about 27 mph; no test runs from that study that

were performed below 22 mph reflected poor flare performanc e.

0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%

0.00 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09 0.10Combustion Efficiency (%)

MFR LFL<15.3%, CE >96.5%

LFL<15.3%, CE < 96.5%

LFL>15.3%This information is distributed solely for the purp ose of pre-dissemination peer review under applicab le information quality guidelines. It has not been formally disseminated by EPA. It does not repr esent and should not be construed to represent any Agency determination or policy.

Section 5.0: Wind and Flare Performance Page 5-15 

## For these reasons, it seems reasonable to conclude tha t the momentum flux ratio (MFR)

should be 3 or greater in crosswinds that are greater tha n 22 miles per hour (mph) at the flare tip.

As an alternative to monitoring the MFR, flare operator s could perform observations to identify

wake-dominated flames during crosswind velocities greater th an 22 mph at the flare tip and flare

vent gas velocity could be increased if a wake-dominated fl ame is observed. Observation

monitoring for wake-dominated flames could be established sim ilarly to the current visible

emissions monitoring requirements for flares. For exam ple, the length of the observation period

as well as the frequency could be triggered by different wi nd speed thresholds or categories.

There are two main concerns with relying on observations : (1) that some flames may simply be

too difficult to see, and (2) it may be difficult to recogniz e when a flame is wake-dominated.

We also reviewed the power factor for the same 245 steam-a ssisted flare test runs that

were analyzed for MFR. Figure 5-9 is a plot of combustion e fficiency versus power factor. The

same could be said about power factor as was said about M FR; it is assumed that most of these

data (149 steam-assisted test runs) had poor flammability char acteristics because the LFL CZ 

## for

these test runs was greater than 15.3 percent by volume (s ee Section 3.0 of this report for an

explanation of this LFL CZ 

## threshold). Also, there are 10 test runs highlighted in r ed in Figure 5-9

that had a LFL CZ 

## less than 15.3 percent by volume and did not achieve a com bustion efficiency

of 96.5 percent or greater. The poor combustion efficiency re ported for these 10 test runs are

discussed in Section 3.1.3 of this report. Although it appears that a power factor of 0.15 or less

could be used as a level for indicating good combustion eff iciency, it is less clear whether this

level (i.e., 0.15 or less) would be appropriate for all f lare vent gas mixtures. In addition, we did

not attempt to incorporate a “fuel factor” as Gogolek et al. (2010b) did with their data, because

the UFL is difficult to calculate for mixtures, especi ally ones with inert.This information is distributed solely for the purp ose of pre-dissemination peer review under applicab le information quality guidelines. It has not been formally disseminated by EPA. It does not repr esent and should not be construed to represent any Agency determination or policy.

Section 5.0: Wind and Flare Performance Page 5-16



## Figure 5-9. Combustion Efficiency vs. Power Factor 0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%

0.05 0.15 0.25 0.35 0.45 0.55Combustion Efficiency (%)

Power Factor LFL<15.3%, CE >96.5%

LFL<15.3%, CE < 96.5%

LFL>15.3%This information is distributed solely for the purp ose of pre-dissemination peer review under applicab le information quality guidelines. It has not been formally disseminated by EPA. It does not repr esent and should not be construed to represent any Agency determination or policy.

Section 6.0: Flare Flame Lift Off Page 6-1 

## 6.0 FLARE FLAME LIFT OFF

Flare flame lift off can cause a flame to become uns table, which can negatively affect the

combustion efficiency of a flare. To avoid flame lift off, the data suggest that the actual flare tip

velocity (i.e., actual flare vent gas velocity plus c enter steam velocity, if applicable) should be

less than an established maximum allowable flare tip veloc ity calculated using an equation that is

dependent on combustion zone gas composition, the flare tip diameter, density of the flare vent

gas, and density of air. This section documents the analy sis supporting this observation.

6.1 Literature Review and V max 

## Calculation

Flare flame lift off is a condition where a flame s eparates from the tip of the flare and

there is space between the flare tip and the bottom of the flame due to excessive air induction as

a result of the flare gas and center steam exit veloci ties (Gogolek et al., 2010a describes this

situation as flame “blow-off”). Flame stability can exi st when flame lift off occurs; however, as

flame stability decreases (which can be caused by a vari ety of reasons, such as changes in flare

tip velocity, combustion zone gas composition, or wind direction and speed), a flare operating at

flame lift off can progress to a condition where the f lame is extinguished; at a minimum, the

flame will be inconsistent (Kalghatgi, 1981a; and Shore, 2007) . Therefore, flame lift off should

be monitored and avoided. A primary contributor to flame l ift off is flare tip velocity, especially

its relationship to the flame speed of the constituents in the flare vent gas (Shore, 2007).

Gogolek et al., 2010a provide three different equations that correlate flame lift off and

flare tip velocity. Each of the equations presented by Gogo lek et al. use a different combination

of variables. However, this section primarily focuses o n an equation presented by Shore (2007).

Shore’s equation was one of the equations presented by Gogo lek et al. (2010a). This equation

was selected because it considers lower flammability l imit, which would already be known by a

source if the recommendation of Section 3.0 of this report were followed. Also, other equations

presented by Gogolek et al. (2010a) use parameters that are not readily available for mixtures

(i.e., flame speed and upper flammability limit).This information is distributed solely for the purp ose of pre-dissemination peer review under applicab le information quality guidelines. It has not been formally disseminated by EPA. It does not repr esent and should not be construed to represent any Agency determination or policy.

Section 6.0: Flare Flame Lift Off Page 6-2 

## In order to calculate the boundary velocity between an unstable and stable discharge

velocity (or maximum velocity) for any gas or mixture e xiting the flare tip, Shore’s equation

(Equation 6-1) considers the flare tip diameter, lower fla mmability limit and density of the flare

vent gas, and density of air. Center steam should be inco rporated into the flare vent gas

properties because center steam exits the flare tip in th e same direction as the flare vent gas.

Shore developed the equation using published experimental result s on lift off using various

mixtures from several researchers.

K #L



## 2M N O P


## M  Q R E 100 U V/V W@XY 

## V/V W@XY 

## J Z [ W@XY



## [ #$% 

## \

6.85 _

` +



## (Eq. 6-1)

Where:

V max = Maximum flare tip velocity including, if applicable, c enter steam at which

flame lift off is not expected to occur, ft/sec.

π = 3.14, constant.

A u = Unobstructed cross sectional area of the flare tip, f t 2 

## . John Zink provided details for determining the unobstructed cross sectional are a of several flare tip designs (see Appendix I).

LFL vgcs = The lower flammability limit of flare vent gas inc luding, if applicable, center

steam, volume %. A methodology for calculating lower flammability limits is included in Section 3.0 of this report.

ρ vgcs = Density of flare vent gas including center steam if app licable, lb/scf.

ρ air = Density of ambient air, lb/scf.

6.2 Test Data Analysis

Test run data were evaluated against Equation 6-1 to see how well they would correspond

to the equation’s ability to predict a maximum flare tip velo city for flame lift off. Shore explains

that at the equation’s predicted maximum flare tip velocity, stream eddies from the flare tip have

reached a critical vertical shedding frequency and flame l ift off may occur (Shore, 2007).This information is distributed solely for the purp ose of pre-dissemination peer review under applicab le information quality guidelines. It has not been formally disseminated by EPA. It does not repr esent and should not be construed to represent any Agency determination or policy.

Section 6.0: Flare Flame Lift Off Page 6-3 

## Three hundred thirty (330) of the 356 steam-assisted and air-a ssisted flare test runs were

considered for this analysis. Twenty-six (26) test runs fr om the Shell Deer Park East Property

Flare study (Shell Global Solutions (US) Inc., 2011a) we re not included in the analysis because

there were limited steam information for these data po ints and a center steam rate could not be

determined (which is necessary to calculate the “LFL vgcs 

## ” term in Equation 6-1). It was assumed

that most of these data (183 steam-assisted test runs) h ad poor flammability characteristics

because the LFL CZ 

## for these test runs was greater than 15.3 percent by volu me (see Section 3.0

of this report for an explanation of this LFL CZ 

## threshold). It was also assumed that 30 air-assisted

test runs had too much assist air because the SR was grea ter than 7 (see Section 4.0 of this report

for an explanation of this SR threshold). Therefore, 213 of the 330 test runs were disregarded

because they were expected to have poor combustion effici ency regardless of the flare tip

velocity. Finally, all nine air-assist data points from the EPA-600/2-85-106 test report (Pohl and

Soelberg, 1985) were removed from the Equation 6-1 evaluation because these tests were

performed on a flare with a 1.5 inch diameter, which is not expected to be scalable to larger

industrial type flares (see Section 4.0 of this report for more details).

The analysis was performed on the remaining 108 test runs. Fi gure 6-1 is a plot of

Equation 6-1 against the 108 test runs that have either a LFL CZ 

## of less than or equal to

15.3 percent by volume (for steam-assist data), or a SR o f less than or equal to 7 (for air-assist

data). Ten (10) steam-assist test runs with a LFL CZ 

## less than 15.3 percent by volume that did not

achieve a combustion efficiency of 96.5 percent or greater, are highlighted in red in Figure 6-1.

The poor combustion efficiency reported for these 10 test runs is discussed in Section 3.1.3 of

this report.

The left side of the green line in Figure 6-1 marks the reg ion where vertical stability of

the flame may be compromised (the green line is the linea r relationship of Equation 6-1 and

represents the maximum flare tip velocity including, if a pplicable, center steam at which flame

lift off is not expected to occur). Although actual flame lift off data were available for only two

of these 108 test runs (lift off information is only provi ded in the EPA-600/2-85-106 study (Pohl

and Soelberg, 1985)), it is reasonable to assume that all o f the 108 test runs did not exhibit flame

lift off because the tests were done at high turndown ratios, which means the actual flare vent gasThis information is distributed solely for the purp ose of pre-dissemination peer review under applicab le information quality guidelines. It has not been formally disseminated by EPA. It does not repr esent and should not be construed to represent any Agency determination or policy.

Section 6.0: Flare Flame Lift Off Page 6-4 

## flow rate was much lower than what the flare is designe d to handle (even when center steam is

incorporated into the calculation). Therefore, all 108 tes t runs should fall on the right side of the

green line in Figure 6-1 because one would expect all 108 test runs to not have flame lift off.

It is difficult to draw any conclusions on whether th e three data points on the left side of

the Equation 6-1 threshold (see Figure 6-1) should be considere d outliers. Using Equation 6-1 as

the indicator, it is expected that these three data poin ts would have exhibited flame lift off during

their test run. However, one of these data points cam e from the EPA-600/2-85-106 study (Pohl

and Soelberg, 1985), which noted that no lift off occurred duri ng this particular test run (i.e., test

run 206). The other two test runs came from the EPA-600/2-83-052 s tudy (McDaniel 1983),

which does not provide any information on lift off.

Figure 6-1. Conditions for Stable Flare Flame Equation 6-1

0.010 0.100 1.000 10.000 100.000

1.000 10.000 100.000

>96.5% CE

>96.5% CE (Air Assist)

<96.5% CE

Note:

V VG-S is the actual flare vent gas velocity including cen ter steamThis information is distributed solely for the purp ose of pre-dissemination peer review under applicab le information quality guidelines. It has not been formally disseminated by EPA. It does not repr esent and should not be construed to represent any Agency determination or policy.

Section 6.0: Flare Flame Lift Off Page 6-5 

## Even though these three test runs fall on the left side of the Equation 6-1 threshold, they

each achieved a combustion efficiency of 96.5 percent or grea ter. This observation is not

surprising because good flare performance can still exist when flame lift off occurs. There are

four other data points in Figure 6-1 that are from the 1980s E PA studies, but these test runs fall

on the right side of the Equation 6-1 threshold and achieve a combustion efficiency of

96.5 percent or greater (one of these runs is from the EPA -600/2-85-106 study, which noted that

no lift off occurred during the test run; and the other thr ee runs came from the EPA-600/2-83-

052 study).

The two test runs from the EPA-600/2-85-106 study did not use a pilot during testing but

all other data points in Figure 6-1 had pilot operations. Also, the flare vent gas volumetric or

mass flow rates for the EPA-600/2-85-106 test runs were not re ported so assumptions were made

using the reported steam-to-fuel ratio and fuel composition to determine flow rates. The data

from the EPA-600/2-83-052 study came from tests using a steam-as sisted flare that was the

smallest sized flare of all test data included in Figure 6-1 (i.e., the flare tip diameter was

8.625 inches, and the effective diameter was less than 6 inches).

It appears nearly all the available test data fits Equati on 6-1; all but three test runs

evaluated had velocities less than the maximum velocity allowed by Equation 6-1. However, this

analysis does not test Equation 6-1 over a very large ran ge of possible flare tip velocities. All of

the recent flare test data were collected during high turn down ratios and consequently have

relatively low flare tip velocities. For the steam-a ssisted flares that were tested, the turndown

ratio ranged from 504.1 to 13.8 (or 0.20 to 7.24 percent utiliza tion); and tip velocities were less

than 10 feet per second with center steam excluded. For th e air-assisted flare (from the TCEQ

data set), the turndown ratio ranged from 410.2 to 155.3 (or 0.24 to 0.64 percent utilization); and

tip velocities were less than 2 feet per second. Maximum flare capacity design is unknown for

the flares used in this analysis that are from the EPA -600/2-83-052 and EPA-600/2-85-106

studies; therefore, the turndown ratios are unknown. Flar e tip velocities for these studies ranged

from approximately 2 to 50 feet per second (for those test runs included in Figure 6-1).This information is distributed solely for the purp ose of pre-dissemination peer review under applicab le information quality guidelines. It has not been formally disseminated by EPA. It does not repr esent and should not be construed to represent any Agency determination or policy.

Section 6.0: Flare Flame Lift Off Page 6-6 

## 6.3 Other Operating Parameters Considered for Flame Lift Off

There are other methods studied by researchers. For examp le, Gogolek et al. (2010a)

discuss two additional equations (other than Equation 6-1) tha t were developed by Nobel et al.

(1984) and Kalghatgi (1981a and b); however, these two equations w ere not analyzed against the

available flare test data. One of these equations that G ogolek et al. (2010a) discuss uses the upper

flammability limit (UFL), which is difficult to calc ulate for mixtures, especially ones with inerts.

Le Chatelier’s equation could be used to determine UFLs, but it is much less accurate than

calculating a LFL. The other equation Gogolek et al. (2010a) mention uses flame velocity, which

is a difficult parameter to acquire, because there are relatively few flame velocities that have

been tabulated and no accepted method is known for estima ting flame velocities for mixtures.This information is distributed solely for the purp ose of pre-dissemination peer review under applicab le information quality guidelines. It has not been formally disseminated by EPA. It does not repr esent and should not be construed to represent any Agency determination or policy.

Section 7.0: Other Flare Type Designs to Consider Page 7-1 

## 7.0 OTHER FLARE TYPE DESIGNS TO CONSIDER

7.1 Non-Assisted Flares

A non-assisted flare does not use any auxiliary steam, ai r, or vent stream pressure to

promote mixing at the flare tip. We are unable to verify w hether any of the analyses presented in

this technical report could apply to non-assisted flares bec ause there are minimal test data

available for non-assisted flares. It seems reasonable to assume that the LFL CZ 

## analysis in

Section 3.0 of this report could apply to a non-assisted fl are. For a non-assisted flare, the

“combustion zone gas” would simply become the “flare v ent gas” because no assist media is

added to the combustion zone of a non-assisted flare. The refore, a determination that LFL CZ 

## is

the most appropriate operating parameter to monitor for ste am-assisted flares, could also apply to

non-assisted flares (i.e., the LFL CZ 

## must be 15.3 percent by volume or less when regulated

material is being routed to a non-assisted flare in order to maintain good combustion efficiency).

Nine of the 312 test runs that were performed on a steam- assisted flare did not use any steam

during testing and could be considered a ‘non-assisted’ flar e test run. Of these nine test runs,

eight achieved greater than 96.5 percent combustion effici ency, but only three had a LFL CZ 

## less

than 15.3 percent. The remaining test run did not achieve grea ter than 96.5 percent combustion

efficiency and the LFL CZ 

## was greater than 15.3 percent. There is simply not enough non-assisted

test data to determine whether a new LFL CZ 

## threshold would be warranted (i.e., a LFL CZ 

## threshold different than 15.3 percent); however, a LFL CZ 

## level of 15.3 percent and less appears to

adequately predict good combustion for the nine non-assisted f lare test runs.

It is assumed that the wind analysis in Section 5.0 of this report and the flame lift off

analysis in Section 6.0 of this report apply to a non-assi sted flare because these factors (wind and

flame lift off) affect a diffusion flame from a non-a ssisted flare in the same way they would

affect a diffusion flame created by a steam-assisted or air-assisted flare. The MFR and V
max 

## methodologies in this report apply to non-assisted, steam -assisted, and air-assisted flares; assist

media is only included in these methodologies if applicable

.This information is distributed solely for the purp ose of pre-dissemination peer review under applicab le information quality guidelines. It has not been formally disseminated by EPA. It does not repr esent and should not be construed to represent any Agency determination or policy.

Section 7.0: Other Flare Type Designs to Consider Page 7-2 

## 7.2 Pressure-Assisted Flares and Other Flare Designs

The EPA Air Pollution Control Cost Manual - Sixth Edi tion (U.S. EPA, 2002) states that

pressure-assisted flares use the vent stream pressure to pro mote mixing at the burner tip. Several

vendors now market proprietary, high pressure drop burner tip de signs. If sufficient vent stream

pressure is available, these flares can be applied to st reams previously requiring steam or air

assist for smokeless operation. Pressure-assisted flare s generally (but not necessarily) have the

burner arrangement at ground level, and consequently, must be located in a remote area of the

plant where there is plenty of space available. They have multiple burner heads that are staged to

operate based on the quantity of gas being released. The s ize, design, number, and group

arrangement of the burner heads depend on the flare vent gas characteristics.

The amount of data available for pressure-assisted flares is small, especially considering

the wide range in pressure-assisted flare designs. In addition, we have no data to analyze other

new technologies, such as a hybrid steam-and-air-assist f lare. We are aware of the Pohl and

Soelberg (1985) flare study performed on pressure-assisted flar es. The 1985 flare study

published two curves for pressure-assisted flares illustratin g a relationship between a given exit

velocity and the minimum gas heat content that maintai ns the flame stability. We are also aware

of pressure-assisted flare testing that was conducted at t he John Zink test facility located in

Tulsa, Oklahoma; this test program was coordinated with TC EQ and the Dow Chemical

Company (Varner et al., 2007, see Docket ID No. EPA-HQ-OAR- 2010-0868). The test report

concluded that pressure-assisted flares can achieve performa nce levels at least as good as steamassisted and air-assisted flares; however, the test pro gram only tested two flare burner designs.

Because of lack of performance test data on pressure-assi sted flare designs and other flare

design technologies, and given the uniqueness in design of pressure-assisted flare designs from

non-assisted, steam-assisted, and air-assisted flares ( and across the population of pressureassisted flares), it seems likely that the observati ons made in this report for non-assisted, steamassisted, and air-assisted flares, cannot be applied to pre ssure-assisted flare designs or other flare

design technologies. Also, test data are not available to form general conclusions on operating

parameters that represent good combustion for these oth er flare designs.This information is distributed solely for the purp ose of pre-dissemination peer review under applicab le information quality guidelines. It has not been formally disseminated by EPA. It does not repr esent and should not be construed to represent any Agency determination or policy.

Section 8.0: Monitoring Considerations Page 8-1 

## 8.0 MONITORING CONSIDERATIONS

In order to determine if a flare is operated within the o perating parameter values

described in the previous sections, monitoring equipment will be needed. This section describes

the types of monitoring equipment and methodologies that could be used to determine LFL CZ 

## ,
LFL VG 

## , LFL VG,C 

## , the ratio of NHV CZ 

## to NHV VG-LFL 

## , C CZ 

## , SR, MFR, and V
max 

## on an ongoing

basis.

8.1 LFL CZ 

## , LFL VG 

## , and LFL VG,C



## We are only aware of one viable monitoring method that co uld be used to continuously

determine the LFL CZ 

## , LFL VG 

## , and/or LFL VG,C 

## . These parameters (i.e., LFL CZ 

## , LFL VG 

## , and/or

LFL VG,C 

## ) require a gas chromatograph to determine the individual co mponent concentrations

present in the flare vent gas, and flow meters to determ ine the volumetric flow rates of flare vent

gas and total steam (if applicable). The individual compone nt concentrations present in the flare

vent gas, the pure component LFL values, and volumetric f low rates of flare vent gas and total

steam (if applicable) are applied to the equations and met hods described in Section 3.1.2 of this

report to determine LFL CZ 

## , LFL VG 

## , and/or LFL VG,C



## .

There are several types of LFL monitors used for safety purposes, but we are not aware

of any that provide a direct measure of the LFL of a gas mixture. Instead, these types of LFL

monitors react to specific gas concentrations in air. Th ere are personal monitoring devices

available on the market that are used to detect explosive environments based on the LFL (for

safety purposes); however, these devices are not meant f or a continuous flow gases, can become

saturated quickly if they are in continuous contact with a gas mixture, and may need a specific

amount of oxygen to work properly. Other types of LFL monit oring devices that are used for

safety are generally calibrated for only one type of gas, yet flare vent gas can consist of any

variety of gas mixtures. The EPA is aware of one compa ny 2 

## that makes a LFL monitor that could

potentially be modified to continuously determine the LFL CZ 

## , LFL VG 

## , and/or LFL VG,C 

## ; however,

the monitor has never been used for this specific purpose. The device uses a continuous

2 

### Control Instruments Corporation – PrexEx Flammability AnalyzerThis information is distributed solely for the purp ose of pre-dissemination peer review under applicab le information quality guidelines. It has not been formally disseminated by EPA. It does not repr esent and should not be construed to represent any Agency determination or policy.

Section 8.0: Monitoring Considerations Page 8-2 

## hydrogen flame inside a small chamber. Flammable vapors are drawn from the sample point into

the chamber, where they are incinerated by the flame. A temperature detector measures the

resulting change in flame temperature and provides an output reading in percent of the LFL of

the gas mixture (not actual LFL). This LFL monitor provides a response time of less than

1 second, and can be accessed remotely. By combining this LF L monitor with metered air

injection and a feedback control signal to adjust the a ir until the meter reads a preset percent of

LFL, it seems possible that the meter could be used to me asure the LFL. Some integrated

programming to calculate the LFL from the flow rates an d percent of LFL reading would also be

needed, but this type of set up could potentially provide a LFL monitor without the expense of a

gas chromatograph.

8.2 Ratio of NHV CZ 

## to NHV VG-LFL



## Because the ratio of NHV CZ 

## to NHV VG-LFL 

## requires the LFL VG 

## to be known as part of the

calculation (see Equation D.22 of Appendix D of this report) , this parameter (i.e., the ratio of

NHV CZ 

## to NHV VG-LFL 

## ) requires a gas chromatograph. The gas chromatograph is us ed to

determine the individual component concentrations present in the flare vent gas. Flow meters are

also required to determine the volumetric flow rates of f lare vent gas and total steam (if

applicable). If there were a LFL monitor that could dete rmine LFL VG 

## as discussed in Section 8.1

of this report, a calorimeter (or BTU analyzer) could be used in lieu of a gas chromatograph to

determine the ratio of NHV CZ 

## to NHV VG-LFL



## .

8.3 C CZ



## Flares being used to control vent streams that have a c onsistently high combustible

concentration can benefit from monitoring C CZ 

## in lieu of either LFL CZ 

## , or the ratio of NHV CZ 

## to

NHV VG-LFL 

## (see Sections 3.2 and 3.3 of this report). The C CZ 

## parameter requires either a gas

chromatograph or hydrocarbon analyzer to determine the total combustible constituents in the

flare vent gas, and flow meters to determine the volumet ric flow rates of flare vent gas and total

steam (if applicable). The total combustible constituent s in the flare vent gas, and volumetricThis information is distributed solely for the purp ose of pre-dissemination peer review under applicab le information quality guidelines. It has not been formally disseminated by EPA. It does not repr esent and should not be construed to represent any Agency determination or policy.

Section 8.0: Monitoring Considerations Page 8-3 

## flow rates of flare vent gas and total steam (if applic able) are applied to Equation D.26 of

Appendix D of this report to determine C CZ



## .

8.4 SR

Flow meters measuring mass flow rates of flare vent gas and assist air (includes air

controls for manifold and valve instrumentation) would be r equired to determine the SR

parameter using the equation and methods described in Section 4.1 and Appendix D of this

report. For purposes of calculating the denominator of the SR parameter, a gas chromatograph

would also be needed so as to determine the individual compon ent concentrations present in the

flare vent gas.

8.5 MFR

A meteorological station or anemometer (to measure cr oss-sectional wind velocity at the

flare tip and the density of the ambient air) and flow m eters (to determine the volumetric flow

rates, velocity, and density of flare vent gas and total steam (if applicable)) would be required to

determine the MFR parameter using Equation D.41 of Appendix D of this report.This information is distributed solely for the purp ose of pre-dissemination peer review under applicab le information quality guidelines. It has not been formally disseminated by EPA. It does not repr esent and should not be construed to represent any Agency determination or policy.

Section 8.0: Monitoring Considerations Page 8-4 

## 8.6 V max



## The LFL vgcs 

## parameter that is used in the Shore equation methodolog y discussed in

Section 6.0 of this report requires a gas chromatograph to determine the individual component

concentrations present in the flare vent gas, and flow meters to determine the volumetric flow

rates of flare vent gas and total steam (if applicable). The individual component concentrations

present in the flare vent gas, the pure component LFL va lues, and volumetric flow rates of flare

vent gas and total steam (if applicable) are applied to Equat ion D.43 of Appendix D of this report

to determine LFL vgcs 

## . The LFL vgcs 

## and Equation D.45 of Appendix D are then used to determine

V max 

## . The flow meters would also be required to determine the velocity and density of flare vent

gas and total steam (if applicable).This information is distributed solely for the purp ose of pre-dissemination peer review under applicab le information quality guidelines. It has not been formally disseminated by EPA. It does not repr esent and should not be construed to represent any Agency determination or policy.

Section 9.0: References Page 9-1 

## 9.0 REFERENCES

Allen, D. T., and V. M. Torres. 2011. 2010 Flare study final report. Prepared for the Texas Commission on Environmental Quality, Tracking No. 2008-81.

< http://www.tceq.texas.gov/assets/public/implementation/ai r/rules/Flare/2010flarestudy/2010- flare-study-final-report.pdf > . September 20.

API 521. 2007. Pressure-relieving and depressuring systems. 5th Editio n. American Petroleum
Institute.

Avetisyan, A.A., V.V. Azatyan, V. I. Kalachev, V.V. Masalova, and A. A. Piloyan. 2007. Effect
of the molecular structure of olefin admixtures on the combustion and explosion of hydrogen-air mixtures. Kinetics and Catalysis. 48:1, 8-16.

Azatyan, V. V, A.A. Borisov, A.G. Merzhanov, V.I. Ka lachev, V.V Masalova, A.E. Mailkov, and K.Y Troshin. 2005. Inhibition of various hydrogen combustio n regimes in air by Propylene and Isopropanol. Combustion, Explosion, and Shock Waves. 41:1, 1-11.

Azatyan, V., and I.A. Bolodyan. 2002. The predominant role of competition between the chainbranching and chain-terminating reactions in the formulati on of concentration limits of flame propagation. Russian Journal of Physical Chemistry. 76:5, 775-784.

Azatyan, V. V., V.A. Pavlov, and O.P. Shatalov. 2005. Inhi bition of the combustion and detonation of hydrogen-air mixtures behind the shock front. K inetics and Catalysis. 46:6, 789-
799.

Baukal, C. E. 2001. The John Zink Combustion Handbook. Boca R aton, Florida. CRC Press.

Besnard, S. 1996. Fuel flammability test of gases and gas m ixtures in air. Centre European
Recherche Nucleaire.

Bourguignon, E., M.R. Johnson, and L.W. Kostiuk. 1999. The use of a closed-loop wind tunnel for measuring the combustion efficiency of flames in a cross flow. Combustion and Flame.
119:319-334.

Castiñeira, D., and T. F. Edgar. 2006. CFD for simulation of steam assisted and air assisted flare combustion systems. Energy and Fuels. 20:1044-1056.

Castiñeira, D., and T. F. Edgar. 2008. CFD for simulation of crosswind on the efficiency of high momentum jet turbulent combustion flames. Journal of Environmental Engineering. 134:7:561-
571.

Choudhuri, Ahsan R. and Mahesh Subramanya 2006. Investigation of H 2 

## Concentration and Combustion Instability Effects on the Kinetics of Strained Syngas Flame s . Final Technical Report for Department of Energy Grant DE-FG26-05NT42495.This information is distributed solely for the purp ose of pre-dissemination peer review under applicab le information quality guidelines. It has not been formally disseminated by EPA. It does not repr esent and should not be construed to represent any Agency determination or policy.

Section 9.0: References Page 9-2 

## Choudhuri, A. R. 2005. Investigation on the flame extincti on limit of fuel blends. Final Technical Report. U.S. Department of Energy Grant DE-FG 26-03NT41917.

Clean Air Engineering, Inc. 2010a. Performance test of a s team-assisted elevated flare with passive FTIR. Prepared by Marathon Petroleum Company, LLC, Findlay, OH and Clean Air Engineering, Inc., Palatine, IL.

Clean Air Engineering, Inc. 2010b. Performance test of a st eam-assisted elevated flare with passive FTIR - Detroit. Prepared by Marathon Petroleum Company, LLC Findlay, OH and Clean Air Engineering, Inc., Palatine, IL.

Clean Air Engineering, Inc. 2010c. Steam contribution to c ombustion zone gas in variable wind conditions. Prepared by Marathon Petroleum Company, LLC, Findlay, OH and Clean Air Engineering, Inc., Palatine, IL.

Clean Air Engineering, Inc. 2011. PFTIR test of steam-assi sted elevated flares – Port Arthur. Prepared for Flint Hills Resources Port Arthur, LLC.

Coward, H. F., and G. W Jones 1952. Limits of flammability of gases and vapors. Bureau of Mines, Bulletin 503.

Coward, H. F., C. W. Carpenter, and W. Payman. 1919. The di lution limits of inflammability of gaseous mixtures. Air. J. Chem. Soc. 115:119, 27–36.

Degges, M. J., J.E. Boyer, K.K. Kuo, and L. Basini. 2010. Inf luence of steam on the flammability limits of premixed natural gas/oxygen/steam mixtures. Chemical Engineering Journal. 165:2, 633-638.

Dickens, B. 2011. Personal communication from B. Dickens at U.S. EPA to J. Renzaglia, Eastern Research Group, Inc. (November).

Evans, S., and D. Roseler. 2011. Establishing a dynamic indic ator of flare performance using lower flammability limits. Prepared for Marathon Petro leum Company, LLC (March).

Gogolek, P., A. Caverly, R. Schwartz, J. Seebold, and J. Pohl. 2010a. Emissions from elevated flares - A survey of the literature. Prepared for the I nternational Flaring Consortium, CanmetENERGY (April).

Gogolek, P., A. Caverly, C. Balderson, R. Schwartz, J . Seebold, and J. Pohl. 2010b. Flare Test Facility - Results. Prepared for the International Fla ring Consortium, CanmetENERGY (October).

Heffington, W. M., and W. R. Gaines. 1981. Flammability cal culations for gas mixtures. Oil &
Gas Journal.This information is distributed solely for the purp ose of pre-dissemination peer review under applicab le information quality guidelines. It has not been formally disseminated by EPA. It does not repr esent and should not be construed to represent any Agency determination or policy.

Section 9.0: References Page 9-3 

## Hu, E., Z. Huang, J. He, C. Jin, and J. Zheng. 2009. Experime ntal and numerical study on laminar burning characteristics of premixed methane–hydrogen–air flames. International Journal of Hydrogen Energy. 34:11, 4876-4888.

INEOS ABS (USA) Corporation. 2010. Passive Fourier transf orm infrared technology (FTIR) evaluation of P001 process control device at the INEOS ABS (USA) Corporation. Addyston,
OH.

Johnson, M., A. Majeski, D. Wilson, and L.W. Kostiuk. 1998. The combustion efficiency of a propane jet diffusion flame in cross flow. Presented at The Combustion Institute, Western States Section, Seattle, WA (October).

Johnson, M., O. Zastavniuk, J. Dale, and L.W. Kostiuk. 1999a. The combustion efficiency of jet
diffusion flames in cross-flow. Presented at The Com bustion Institute, Joint Meeting of the United States Sections, Washington, D.C. (March).

Johnson, M., O.Zastavniuk, D.Wilson, and L.W. Kostiuk. 1999b. E fficiency measurements of
flares in a cross flow. Presented at Combustion Cana da, Calgary, Alberta (May).

Johnson, M., and L.W. Kostiuk. 1999. Effects of a fuel diluen t on the efficiencies of jet
diffusions flames in a crosswind. Presented at The Co mbustion Institute, Canadian Section, Edmonton, Alberta (May).

Johnson, M., and L.W. Kostiuk. 2000. Efficiencies of low-mo mentum jet diffusion flames in
crosswinds. Combustion and Flame. 23:189-200

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## Johnson, M., D. Wilson, and L.W. Kostiuk. 2001. A fuel stripp ing mechanism for wakestabilized jet diffusion flames in crossflow. Combustio n Science and Technology. 169:155-174.

Jones, G. W. 1929. Inflammability of mixed gases. U.S. Depar tment of the Interior, Bureau of Mines. Technical Paper 450.

Jones, G. W., and R. E. Kennedy. 1932. Inflammability of mi xed gases: mixtures of methane, ethane, hydrogen, and nitrogen. U.S. Department of the Inte rior, Bureau of Mines, Report of Investigations 3172.

Jones, G. W., and R. Kennedy. 1933. Limits of inflammabilit y of natural gases containing high percentages of carbon dioxide and nitrogen. U.S. Department of the Interior, Bureau of Mines. Report of Investigation 3216.

Jones, G. W., and R. E. Kennedy. 1938. Extinction of propyle ne flames by diluting with nitrogen and carbon dioxide and some observations of the explosi ve properties of propylene. U.S. Department of the Interior, Bureau of Mines. Report of I nvestigation 3395.This information is distributed solely for the purp ose of pre-dissemination peer review under applicab le information quality guidelines. It has not been formally disseminated by EPA. It does not repr esent and should not be construed to represent any Agency determination or policy.

Section 9.0: References Page 9-4 

## Jones, G. W., and R. E. Kennedy. 1943. Prevention of butad iene-air explosions by addition of nitrogen and carbon dioxide. U.S. Department of the Inter ior, Bureau of Mines. Report of Investigation 3691.

Kalghatgi, G.T. 1981a. Blow-out stability of gaseous jet di ffusion flames, Part I: In still air. Combustion Science and Technology. 26:233-239.

Kalghatgi, G.T. 1981b. Blow-out stability of gaseous jet di ffusion flames, Part II: Effect of cross wind. Combustion Science and Technology. 26:241-244.

Karim, G, Wierzba, I., & Boon, S. 1985. Some considerat ions of the lean flammability limits of mixtures involving hydrogen. International Journal of Hydrogen Energy, 10(2), 117-123.

Karim, G. A., I. Wierzba, and Y. Al-Alousi. 1996. Methane -- Hydrogen mixtures as fuels. International Journal of Hydrogen Energy. 21:7, 625-631.

Kondo, S., K. Takizawa, A. Takahashi, and K. Tokuhashi. 2006a. E xtended Le Chatelier’s formula and nitrogen dilution effect on the flammability limits. Fire Safety Journal. 41:5, 406-
417.

Kondo, S., K. Takizawa, A. Takahashi, and K. Tokuhashi. 2006b. E xtended Le Chatelier’s
formula for carbon dioxide dilution effect on flammabil ity limits. Journal of Hazardous Materials. 138:1, 1-8.

Kondo, Shigeo, Takizawa, Kenji, Takahashi, A., Tokuhashi, Ka zuaki, & Sekiya, A. 2008. A study on flammability limits of fuel mixtures. Journal of hazardous materials, 155(3), 440-8.

Laskin, A., H. Wang, and C.K. Law. 2000. Detailed kinetic mode ling of 1,3-butadiene oxidation at high temperatures. International Journal of Chemical Kinetics. 32:10, 589-614.

Leahey, D., and K. Preston. 2001. Theoretical and observa tional assessments of flare efficiencies. Journal of the Air & Waste Management A ssociation. 51:1610-1616.

Loehr, C., Djordjevic, S., & Liekhus, K. 1997. Flammabili ty assessment methodology program phase I: final report. http://scholar.google.com/scholar?hl=en&btnG=Search&q=intit le:FLAMMABILITY+ASSESS
MENT+METHODOLOGY+PROGRAM+PHASE+I+:+FINAL+REPORT#1

Mashuga, C. V., and D.A. Crowl. 1999. Flammability zone predi ction using calculated adiabatic flame temperatures. Process Safety Progress. 18:3, 127–134.

McDaniel, M. 1983. Flare efficiency study. Prepared for U.S . EPA Office of Research and Development EPA-600/2-83-052 by Engineering Science, Inc. (July ).

Molnarne, M., P. Mizsey, and V. Schröder. 2005. Flammabilit y of gas mixtures. Part 2: influence of inert gases. Journal of Hazardous Materials. 121:1-3, 45-9.This information is distributed solely for the purp ose of pre-dissemination peer review under applicab le information quality guidelines. It has not been formally disseminated by EPA. It does not repr esent and should not be construed to represent any Agency determination or policy.

Section 9.0: References Page 9-5 

## Noble, R.K., M.R. Keller, and R.E. Schwartz. 1984. An ex perimental analysis of flame stability of open air diffusion flames. American Flame Researc h Committee International Symposium on Alternate Fuels and Hazardous Wastes. Tulsa, OK.

Peterson, J., N. Tuttle, H. Cooper, and C. Baukal. 2007. Mini mize facility flaring. Hydrocarbon Processing. pp. 111–115.

Pohl, J., R. Payne, and J. Lee. 1984. Evaluation of the ef ficiency of industrial flares: Test Results. EPA-600/2-84-095. Prepared for U.S. EPA Office of Res earch and Development by Energy and Environmental Research Corporation (May).

Pohl, J. and N. Soelberg. 1985. Evaluation of the efficiency of industrial flares: Flare head design and gas composition. EPA-600/2-85-106. Prepared for U.S. EP A Office of Air Quality Planning and Standards. (September).

Schröder, V., and M. Molnarne. 2005. Flammability of gas mix tures. Part 1: Fire potential. Journal of Hazardous Materials. 121:1-3, 37-44.

Seebold, J., B. Davis, P. Gogolek, L.W. Kostiuk, J. Pohl, R. Schwartz, N. Soelberg, M. Strosher, and P. Walsh. 2003. Reaction efficiency of industrial flare s: The perspective of the past. American Flame Research Committee Symposium.

Seebold, J., P. Gogolek, J. Pohl, and R. Schwartz. 2004. Pr actical implications of prior research on today's outstanding flare emissions questions and a rese arch program to answer them,
Environmental Control of Combustion Processes: Innovati ve Technology For the 21st Century. Presented at the Joint International Combustion Sympos ium, Maui, HI (October).

Shell Global Solutions (US) Inc. 2011a. Shell Deer Park Refining LP Deer Park Refinery East Property Flare Test Report. Prepared by Shell Global Sol utions (US) Inc., Houston, TX (April).

Shell Global Solutions (US) Inc. 2011b. Shell Deer Park S ite Deer Park Chemical Plant OP-3 Ground Flare Performance Test Report. Prepared by Shell Global Solutions (US) Inc., Houston, TX (May).

Shore, D. 2007. Improving flare design, a transition from a rt-form to engineering science. Presented at AFRC-JFRC 2007 Joint Meeting, Waikoloa, HI (O ctober).

Smith, S. 2003. Flare system emissions control. Present ed at the Texas Technology Conference by the Zeeco Company (March).

Smoot, D. L., J.D. Smith, and R.E. Jackson. 2009. Technical foundations to establish new criteria for efficient operation of industrial steam- assisted gas flares. Presented at the
International Flame Research Foundation 16 th 

## International Members Conference, Boston, MA (June).

U.S. EPA. 2002. Air pollution control cost manual, 6 th 

## ed. EPA/452/B-02-001.This information is distributed solely for the purp ose of pre-dissemination peer review under applicab le information quality guidelines. It has not been formally disseminated by EPA. It does not repr esent and should not be construed to represent any Agency determination or policy.

Section 9.0: References Page 9-6 

## Van den Schoor, F., R.T.E. Hermanns, J.A. van Oijen, F. Verplaetsen, and L.P.H. de Goey. 2008. Comparison and evaluation of methods for the determinat ion of flammability limits, applied to methane/hydrogen/air mixtures. Journal of Hazardo us Materials. 150:3, 573-81.

Vidal, M., W. Wong, W.J. Rogers, M.S. Mannan. 2006. Evaluati on of lower flammability limits of fuel-air-diluent mixtures using calculated adiabatic fl ame temperatures. Journal of Hazardous Materials. 130:1-2, 21-7.

Wang, J., Z. Huang, C. Tang, H. Miao, and X. Wang. 2009. Numer ical study of the effect of hydrogen addition on methane–air mixtures combustion. In ternational Journal of Hydrogen Energy. 34:2, 1084-1096.

Wang, T., Chen, C., & Chen, H. 2010. Nitrogen and carbon d ioxide dilution effect on upper flammability limits for organic compound containing carbon , hydrogen and oxygen atoms. Journal of the Taiwan Institute of Chemical Engineers , 41(4), 453-464. Taiwan Institute of Chemical Engineers.

White, A. G. 1925. Limits for the propagation of flame in i nflammable gas/air mixtures, Part II: Mixtures of more than one gas and air. Journal of the C hemical Society, Transactions. 127:48,
48.

Wierzba, I., and V. Kilchyk. 2001. Flammability limits of hy drogen–carbon monoxide mixtures at moderately elevated temperatures. International Journa l of Hydrogen Energy. 26:6, 639-643.

Zabetakis, M.G. 1965. Flammability Characteristics of Co mbustible Gases and Vapors. U.S. Bureau of Mines, Bulletin 627.This information is distributed solely for the purp ose of pre-dissemination peer review under applicab le information quality guidelines. It has not been formally disseminated by EPA. It does not repr esent and should not be construed to represent any Agency determination or policy.



## APPENDIX A

Appendix A. Brief Review Summary of Each Flare Performance Study and Test ReportThis information is distributed solely for the purp ose of pre-dissemination peer review under applicab le information quality guidelines. It has not been formally disseminated by EPA. It does not repr esent and should not be construed to represent any Agency determination or policy.



## A-1 A.1 Data Set A: EPA-600/2-83-052 (McDaniel, 1983)

Tests from data set A were conducted on pilot-scale test flares in June 1982 at the John

Zink Company flare demonstration facility in Tulsa, Oklah oma. The gases used in this study

included mixtures of propylene diluted with nitrogen (chemical composition for each test run, by

test report, used in the steam data analysis described in this section 3.0 of this report is provided

in Appendix E). The primary objectives for these tests were to determine the combustion

efficiency and hydrocarbon destruction efficiency for both air- and steam-assisted flares under a

wide range of operating conditions. The test methodology involved a special 27-foot sample

probe suspended by a crane over the flare flame. The sam ple extracted by the probe was

analyzed by continuous emission monitors to determine conce ntrations of carbon dioxide, carbon

monoxide, total hydrocarbon, sulfur dioxide, nitrogen oxides, an d oxygen.

The report generally concluded that when flares operate under conditions representing

good industrial operating practice, combustion efficienci es at the sampling probe were greater

than 98 percent. Combustion efficiencies declined under con ditions of excessive steam and high

exit velocities of low heat content gases.

There are 14 non-assisted, 15 steam-assisted, and 13 air-ass isted test runs from this test

report. The 14 non-assisted data points came from tests pe rformed on the steam-assisted flare,

but no steam was used during the test. The steam-assisted flare was a John Zink Standard STF-S8 flare tip (effective flare tip diameter of 5.86 inches). The recommended steam flow for this

flare is approximately 0.4 pounds of steam per pound of propylene . The air-assisted flare was a

John Zink STF-LH-457-5 flare (flare tip diameter unknown). The mass or volumetric flow rate

of assist air as well as the assist air velocity we re considered proprietary information and not

included in the test report; therefore, the test data as sociated with this particular air-assisted flare

were not used in any analysis that is discussed in this re port. Both flares had two constant

ignition pilots designed to burn a total of 300 standard cubic feet per hour of natural gas.This information is distributed solely for the purp ose of pre-dissemination peer review under applicab le information quality guidelines. It has not been formally disseminated by EPA. It does not repr esent and should not be construed to represent any Agency determination or policy.



## A-2 A.2 Data Set B: EPA-600/2-84-095 (Pohl et al., 1984)

Tests from data set B were conducted at the Energy and Envi ronmental Research

Corporation’s El Toro, California test site. This study was limited to measuring the combustion

efficiencies of 3-, 6-, and 12-inch pipe flares burning mixtur es of propane diluted with nitrogen

at steady operating conditions with and without steam inj ection, in the absence of wind. All

steam injection was introduced as upper steam.

A.3 Data Set C: EPA-600/2-85-106 (Pohl and Soelberg, 1985)

Tests from data set C were conducted at the Energy and Envi ronmental Research

Corporation’s El Toro, California test site as a cont inuation of the tests conducted under

EPA-600/2-84-095. The gases used in this study included mixtures of pro pane diluted with

nitrogen (chemical composition for each test run, by te st report, used in the steam data analysis

described in this section 3.0 of this report is provided in Appe ndix E). The primary objective of

these tests was to determine the influence of flare head design on flare combustion efficiency.

The study held proprietary the design of the different f lare heads; however, some information

was provided. A “coanda” steam-injected flare head was tes ted at gas exit velocities ranging

from 0.2 to 9.9 feet per second based on a 12 inch diameter opening. Steam was injected into the

flare waste stream through nozzles located above the m ain flare tip opening (upper steam). All

measurements on this flare were made with a constant upper steam flow rate of 140 pounds per

hour. All steam-assisted test runs were performed without pilots. Also, an air-assisted flare head

was tested at gas exit velocities ranging from 8.5 to 428 fee t per second based on a 1.5 inch

diameter opening. The assist air flow rate was varied. Some air-assisted test runs were performed

with pilots, but the majority were not.

There are six steam-assisted and nine air-assisted test runs from this test report. This

report also includes 16 pressure-assisted test runs (nine runs ca me from a 1.5 inch diameter

pressure-assisted flare head and the other seven from a 3. 8 inch diameter pressure-assisted flare

head).This information is distributed solely for the purp ose of pre-dissemination peer review under applicab le information quality guidelines. It has not been formally disseminated by EPA. It does not repr esent and should not be construed to represent any Agency determination or policy.



## A-3 A.4 Data Set D: MPC TX (Clean Air Engineering, Inc., 2010a)

PFTIR performance testing was conducted from September 15, 2009 to September 24,

2009 on Marathon’s Texas City (MPC TX) refinery’s main flare in response to an EPA Office of

Enforcement request pursuant to section 114 of the Clean Ai r Act. Industrial Monitor and

Control Corporation (IMACC) performed the testing, and Clean Engineering, Inc. wrote the test

report. Tests were conducted while flare vent gas containe d saturates, olefins, nitrogen, and

hydrogen mixtures (chemical composition for each test run, by test report, used in the steam data

analysis described in this section 3.0 of this report is pro vided in Appendix E). For each test

series, steam was increased from the manufacturer’s r ecommended minimum cooling steam rate

to the point of snuffing the flare. For the majority of tests conducted, combustion efficiency

declined with increasing steam at constant flare vent gas mass loading and constant composition.

The Marathon Texas City main flare is an elevated st eam-assisted flare. The flare has an

effective tip diameter of 23.25 inches, was manufactured by Callidus Technologies (model BTZIS3/US-24-C), and was installed in December 2000. The tip has t hree points of steam addition:

center steam, a lower steam ring, and an upper steam ring . Although the flare tip is equipped

with upper steam, it was not used during any test runs; and al l measurements on this flare were

made with a constant center steam flow rate of 500 pounds per hour (Dickens 2011) and variable

lower ring steam addition. The lower steam ring manifol d piping has a connection to a small

sweep gas ring used for shaping the flare at the tip. The f lare has a manufacturer minimum total

steam requirement of 1,250 pounds per hour in order to protec t the flare tip. The flare operated

with approximately 100 standard cubic feet per hour of pilot gas during the test runs. The typical

base load for flare operation is approximately 1,100 to 2,0 00 pounds per hour of waste gas flow,

or less than 0.25 percent of the hydraulic capacity of the flare (approximately a 250:1 turndown

factor).

Raw test data (in the form of an Excel worksheet) was a vailable for this data set. There

are 138 steam-assisted test runs from the raw test data. However, 56 of these test runs were noted

in the test report as having a relatively low video score indicating that the PFTIR camera was

lacking aiming accuracy during the test run (see Table A.1).This information is distributed solely for the purp ose of pre-dissemination peer review under applicab le information quality guidelines. It has not been formally disseminated by EPA. It does not repr esent and should not be construed to represent any Agency determination or policy.



## A-4 Table A.1 Test Runs Explicitly Removed From Consideration

Condition Run

Number Reason for Omission

Data Set D

A19 1-2

Relatively low “video score” indicating that the PFTIR camera was lacking aiming accuracy during the test run. 1-3
3-2
4-2
5-1
6-1
7-2

A8 1-1

Relatively low “video score” indicating that the PFTIR camera was lacking aiming accuracy during the test run. 2-1
2-2
2-3
3-1
3-2
4-1
5-1
5-2
6-1
7-1
7-2
8-1
8-2
9-1
10-1

B 1-3

Relatively low “video score” indicating that the PFTIR camera was lacking aiming accuracy during the test run. 2-3
3-3
4-3
6-3
7-3
10-1

C 1-3

Relatively low “video score” indicating that the PFTIR camera was lacking aiming accuracy during the test run. 2-3
3-3
4-1
5-1

D 7-1 Relatively low “video score” indicating that the PFTIR camera was lacking aiming accuracy during the test run. 9-1This information is distributed solely for the purp ose of pre-dissemination peer review under applicab le information quality guidelines. It has not been formally disseminated by EPA. It does not repr esent and should not be construed to represent any Agency determination or policy.



## A-5 Table A.1 (Continued)

Condition Run

Number Reason for Omission

Data Set D

E 1-2

Relatively low “video score” indicating that the PFTIR camera was lacking aiming accuracy during the test run. 2-2
3-2
4-2
6-1

F 1-1

Relatively low “video score” indicating that the PFTIR camera was lacking aiming accuracy during the test run. 2-1
3-1
4-1
5-1
6-1

G 1-1

Relatively low “video score” indicating that the PFTIR camera was lacking aiming accuracy during the test run. 2-1
3-1
4-1
5-1
6-1

LTS 2-7 Relatively low “video score” indicating that the PFTIR camera was lacking aiming accuracy during the test run. 2-8

A.5 Data Set E: INEOS (INEOS ABS (USA) Corporation, 2010)

Pursuant to the consent decree (Civil Action No. 1:09-CV-545) , PFTIR performance

testing was conducted from November 3, 2009 to November 5, 2009 on INEOS ABS (USA)

Corporation’s flare controlling their P001 process in Addy ston, Ohio. IMACC performed the

testing. The purpose of the evaluation was to determine the appropriate net heating value of flare

vent gas necessary to assure the flare achieves 99 percent control efficiency. Tests were

conducted while flaring gases containing various mixtures of 1,3 -butadiene, natural gas, and

nitrogen (chemical composition for each test run, by te st report, used in the steam data analysis

described in this section 3.0 of this report is provided in Appe ndix E).

The flare tested is an elevated steam-assisted flare. The flare tip has an effective diameter

of 16 inches and is manufactured by John Zink (model no. EEF- QS-16). Steam is injected intoThis information is distributed solely for the purp ose of pre-dissemination peer review under applicab le information quality guidelines. It has not been formally disseminated by EPA. It does not repr esent and should not be construed to represent any Agency determination or policy.



## A-6 the flare waste stream through nozzles located above th e main flare tip opening (upper steam).

The manufacturer minimum total steam requirement to th e flare tip was not provided in the test

report. The flare operated with ~150 standard cubic feet per h our of pilot gas during the test runs.

There are 21 steam-assisted test runs from this test repor t.

A.6 Data Set F: MPC Detroit (Clean Air Engineering, Inc., 2010b)

PFTIR performance testing was conducted from July 8, 2010 to J uly 20, 2010 on

Marathon’s Detroit (MPC Detroit) refinery’s Complex 3 and 4 flare in response to an EPA

Office of Enforcement request pursuant to section 114 of th e Clean Air Act. IMACC performed

the testing. The main objective of the test was to bet ter understand the effects of steam on the

overall performance of the flare in terms of combusti on efficiency. Tests were conducted while

flaring gases containing refinery fuel gas, propylene, hydrogen, and nitrogen mixtures (chemical

composition for each test run, by test report, used in t he steam data analysis described in this

section 3.0 of this report is provided in Appendix E). For e ach test series, steam was increased

from the manufacturer’s recommended minimum cooling steam rate to the point of snuffing the

flare. For the majority of tests conducted, combustion efficiency declined with increasing steam

at constant flare vent gas mass loading and constant com position.

Marathon’s Detroit refinery’s Complex 3 and 4 flare is an elevated steam-assisted flare.

The flare tip has an effective diameter of 16 inches a nd is manufactured by NAO, Inc. (model no.

20” NFF-RC) and was constructed in 1961 to 1962. The flare tip w as replaced in October 2005.

The flare has two points of steam addition: center s team and ring steam. The center and ring

steam each have a manufacturer minimum steam requiremen t of 300 pounds per hour. All

measurements on this flare were made with a constant center steam flow rate of 300 pounds per

hour (and varying ring steam rates from 300 pounds per hour and up) . The ring steam has

alternating high and low points of injection around the fl are tip exit. The flare operated with

~135 standard cubic feet per hour of pilot gas during the test r uns. The typical base load for

typical flare operation is approximately 500 to 600 pounds per hour, or less than 0.25 percent of

the hydraulic capacity (approximately a 400:1 turndown factor).This information is distributed solely for the purp ose of pre-dissemination peer review under applicab le information quality guidelines. It has not been formally disseminated by EPA. It does not repr esent and should not be construed to represent any Agency determination or policy.



## A-7 Raw test data (in the form of an Excel worksheet) were available for this data set. There

are 62 steam-assisted test runs from the raw test data. However, six of these test runs were noted

in the test report as invalid runs (see Table A.2).

Table A.2 Test Runs Explicitly Removed From Consideration

Condition Run

Number Reason for Omission

Data Set F

A 6-1 Invalid run, secondary (road location) PFTIR only, no combustion efficiency data. 8-2 Invalid run, only 4 combustion efficiency readings. 9-2 Invalid run, only 1 combustion efficiency reading.

B 1-2 Invalid run, secondary (road location) PFTIR only, no combustion efficiency data. D 1-1 Invalid due to run instability.

E 4-1 Combustion efficiency for the E4-1 (N2 ≈ 66%) was measured with the secondary PFTIR at the road location

. Because of hardware issues with this instrument the data is not reported and the run was marked invalid.

A.7 Data Set G: Flint Hills Resources Aromatics Unit (F HR AU) and Light Olefins Unit

(FHR LOU) (Clean Air Engineering, Inc., 2011)

PFTIR performance testing was conducted in October and Nov ember of 2010 at Flint

Hills Resources, LLC in Port Arthur, TX on their Arom atics Unit and Light Olefins Unit flares in

response to an EPA Office of Enforcement request pursuant to section 114 of the Clean Air Act.

IMACC performed the testing. The main objective of the t ests was to better understand the

effects of steam on the overall performance of each flare in terms of combustion efficiency. Two

additional operating parameters were also examined during thi s test program. The effect of

hydrogen on combustion efficiency was studied on the FHR A U flare. The effect of flare vent

gas flow rate on combustion efficiency was studied on t he FHR LOU flare.

The FHR AU flare is an elevated steam-assisted flare. The current tip has an effective

diameter of 20 inches and was installed in 1996. This tip was manufactured by Callidus (modelThis information is distributed solely for the purp ose of pre-dissemination peer review under applicab le information quality guidelines. It has not been formally disseminated by EPA. It does not repr esent and should not be construed to represent any Agency determination or policy.



## A-8 no. BTZ-US-16/20-C) and has two points of steam addition : center steam and ring steam. The

center steam is injected in the flare vent gas stack pri or to reaching the flare tip, and the ring

steam is injected with nozzles around the flare tip rim . The center steam has a manufacturer

minimum steam requirement of 500 pounds per hour. All measurem ents on this flare were made

with a constant center steam flow rate of 500 pounds per h our (and varying ring steam rates).

The flare operated with approximately 100 standard cubic feet pe r hour of pilot gas during the

test runs. The typical FHR AU flare vent gas flow rat e during normal operation is approximately

800 pounds per hour, or less than 0.4 percent of the hydraulic capacity (approximately a 250:1

turndown factor).

The FHR LOU flare is an elevated steam-assisted flare . The current tip has an effective

diameter of 54 inches and was installed in June 2010. This tip was manufactured by Callidus

(model no. BTZ-1S3-54C) and has two points of steam additio n: center steam and lower steam.

The center steam is injected in the flare vent gas st ack prior to reaching the flare tip, and the

lower steam is injected through internal tubes interspers ed throughout the flare tip. The center

steam has a manufacturer minimum steam requirement of 2,890 pounds per hour; the lower

steam has a manufacturer minimum steam requirement of 500 pounds per hour. All

measurements on this flare were made with a constant center steam flow rate of 2,890 pounds

per hour (and varying lower steam rates from 500 pounds per hour and greater). The flare

operated with approximately 200 standard cubic feet per hour of pilot gas during the test runs.

The typical FHR LOU flare vent gas flow rate during nor mal operation is approximately

3,000 pounds per hour, or less than 0.3 percent of the hydraulic capacity (approximately a 333:1

turndown factor).

Raw test data (in the form of an Excel worksheet) were available for this data set. There

are 45 steam-assisted test runs from the FHR AU flare r aw test data. There are 46 steam-assisted

test runs from the FHR LOU flare raw test data. Chemi cal composition for each test run, by test

report, used in the steam data analysis described in this s ection 3.0 of this report is provided in

Appendix E.This information is distributed solely for the purp ose of pre-dissemination peer review under applicab le information quality guidelines. It has not been formally disseminated by EPA. It does not repr esent and should not be construed to represent any Agency determination or policy.



## A-9 A.8 Data Set H: Shell Deer Park East Property Flare (SDP EPF) (Shell Global Solutions

(US) Inc., 2011a)

PFTIR performance testing was conducted in March and April of 2010 on the Shell Deer

Park refinery’s East Property Flare in response to an EP A Office of Enforcement request

pursuant to section 114 of the Clean Air Act. IMACC perform ed the testing. The primary

objective of the SDP EPF testing was to obtain a bette r understanding of how the ratio of steam

to vent gas at the flare combustion zone and the hydrogen content of the flare vent gas affect the

combustion efficiency. The composition of the flare v ent gas during testing was consistent with

normal operation of the SDP EPF; flare vent gas const ituents consisted of hydrogen, nitrogen,

and methane, with minor contributions from other low-m olecular weight paraffinic, olefinic, and

aromatic hydrocarbons (chemical composition for each t est run, by test report, used in the steam

data analysis described in this section 3.0 of this report is provided in Appendix E).

The SDP EPF is an elevated steam-assisted flare. The current tip has an effective

diameter of 36 inches and was installed in May 1990. This tip was manufactured by John Zink

(model no. EEF-QA-36-C) and has two points of steam addi tion: center steam and upper steam.

The center steam has a manufacturer minimum steam requ irement of 1,500 pounds per hour; the

upper steam has a manufacturer minimum steam requirement of 500 pounds per hour. The flare

operated with 150 standard cubic feet per hour of pilot gas durin g the test runs. Typical flows at

the SDP EPF are approximately 4 percent of the smokeless capacity of the flare and 1 percent of

the maximum relief capacity.

Raw test data (in the form of an Excel worksheet) were available for this data set. There

are 53 steam-assisted test runs from the raw test data. However, 11 of these test runs were noted

in the test report as being part of an experiment for c omparing PFTIR detectors and were

removed from consideration (see Table A.3).This information is distributed solely for the purp ose of pre-dissemination peer review under applicab le information quality guidelines. It has not been formally disseminated by EPA. It does not repr esent and should not be construed to represent any Agency determination or policy.



## A-10 Table A.3 Test Runs Explicitly Removed From Consideration

Condition Run

Number Reason for Omission

Data Set H [EP-D-2.0(MCT1)] “Without a beam splitter IMACC could no t use a MCT
detector and an InSb detector at the same time. Since S DP has very limited means to control the composition of t he SDP EPF vent gas, it was also impractical to recreate test conditions identical to those that occurred when SDP
collected data with the InSb detector. Given these constraints, the only way to compare the MCT detector to the InSb detector was to gather as many data points as practical with the MCT detector at similar, but not identical, conditions as occurred when data were gathe red with the InSb detector, and then compare the two data
sets.” 1 

## [EP-D-3.0(MCT1)] [EP-D-4.0(MCT1)] [EP-D-5.0(MCT1)] [EP-D-4.0(MCT2)] [EP-D-5.0(MCT2)] [EP-D-2.0(MCT2)] [EP-D-3.0(MCT2)] [EP-D-4.0(MCT3)] [EP-D-5.0(MCT3)]

[EP-D-4.5(MCT)]

1 

### See page 19 of Section 2.1.4 of Shell Global Solutions ( US) Inc., 2011a.



## 2.9 Data Set I: Shell Deer Park Ground Flare (SDP GF) (Shell Global Solutions (US)

Inc., 2011b)

AFTIR performance testing was conducted in March and April of 2010 on the Shell Deer

Park refinery’s Olefin Plant 3 Ground Flare in response to an EPA Office of Enforcement

request pursuant to section 114 of the Clean Air Act. These tests were conducted with assistance

from both Shell Global Solutions (US) Inc. and IMACC pe rsonnel. The primary objective of the

SDP GF testing was to obtain a better understanding of h ow the ratio of steam to vent gas at the

flare combustion zone and the hydrogen content of the f lare vent gas affect combustion

efficiency. The primary components of the SDP GF flare vent gas are hydrogen, nitrogen,

methane, ethylene, propylene, and small quantities of higher molecular weight olefins, di-olefins,

and aromatics.

The SDP GF is a multistage steam-assisted enclosed groun d flare with three different

stages, which become active at successively higher flows. The SDP GF was installed in 1978 and

has 92 burners (basically a refractory lined steel shell into which 92 raw flare vent gas burners

discharge). The flare has three stages. The first stage has eight, horizontally-mounted burners and

eight pilots. The second stage has 24 horizontally-mount ed burners and 24 pilots, while the lastThis information is distributed solely for the purp ose of pre-dissemination peer review under applicab le information quality guidelines. It has not been formally disseminated by EPA. It does not repr esent and should not be construed to represent any Agency determination or policy.



## A-11 stage has 60, horizontally-mounted burners and 30 pilots. The enclosed ground flare has eight

faces. The horizontally-mounted burners are arranged in identical vertical drops, with four

burners to a drop. The flare operated with a total of 150 st andard cubic feet per hour pilot gas

during the test runs.

Each of the 92 burners is manufactured by John Zink (model n o. ZTOF SM-10 burners)

and equipped with a steam injection system to inject high- pressure steam for cooling, to aid

combustion, and to reduce smoke formation. A small amoun t of cooling steam is always routed

to each of the SDP GF’s 92 burners whether each burner h as flare vent gas going to it or not.

Steam enters the center of each burner via a “1” steam tip. The cooling steam is controlled by a

restriction orifice in a by-pass line around the steam va lve to each stage. This results in

approximately 870 pounds per hour of cooling steam to the 92 burners , or approximately

9.46 pounds per hour per burner. At the time of testing, typi cal flow at the SDP GF was

approximately 5,000 pounds per hour, or 5 percent of the maximum s mokeless capacity. The

flare vent gas flows used for the test runs required only the eight first stage burners.

Raw test data (in the form of an Excel worksheet) were available for this data set. There

are 21 steam-assisted test runs from the raw test data.

2.10 Data Set J: TCEQ (Allen and Torres, 2011)

In May 2009, the TCEQ contracted with The University of T exas at Austin to conduct a

comprehensive flare study project on full-scale steam- a nd air-assist flares at the John Zink

Company flare demonstration facility in Tulsa, Oklahoma . The gas used in this study included

mixtures of propylene or propane supplemented with natural ga s and diluted with nitrogen

(chemical composition for each test run, by test report , used in the steam data analysis described

in this section 3.0 of this report is provided in Appendix E). The purpose of the project was to

conduct field tests to measure flare emissions and collec t process and operational data in a semicontrolled environment to determine the relationship between flare design, operation, flare vent

gas lower heating value and flow rate, destruction effici ency, and combustion efficiency.This information is distributed solely for the purp ose of pre-dissemination peer review under applicab le information quality guidelines. It has not been formally disseminated by EPA. It does not repr esent and should not be construed to represent any Agency determination or policy.



## A-12 Aerodyne Research, Inc., (ARI) was contracted to dire ctly measure flare emissions at the

end of the flare plume using extractive techniques, and cal culate destruction and combustion

efficiency based on those measurements. The study also e valuated the performance of remote

sensing technologies against the extractive technique. Thes e remote sensing technologies

included Infrared Hyper-Spectral Imaging Technology (Contractor : Telops Inc.), PFTIR and

AFTIR (Contractor: IMACC), and Forward Looking Infrared (FL IR) GasFindIR Passive

Infrared (IR) Cameras (Contractor: Leak Surveys Inc.). The test report for data set J concludes

that the mean difference and standard deviation of the r eported AFTIR and PFTIR combustion

efficiency values increase as the reported extractive com bustion efficiency values decreases;

however, both the AFTIR and PFTIR methods actually com pare very well to the extractive test

results for combustion efficiencies reported as 90 perc ent or greater. For combustion efficiencies

reported as 90 percent or greater, the test report for data set J states that the mean difference of

combustion efficiency values is less than 3.2 percent be tween extractive and AFTIR, and less

than 3.5 percent between extractive and PFTIR.

The steam-assisted flare used in this study was a John Z ink model EE-QSC-36” flare tip

(flare tip effective diameter of 36 inches) with three EEP-503 pilots, and a maximum capacity of

937,000 pounds per hour. The center steam has a manufacturer m inimum steam requirement of

300 pounds per hour; the upper steam has a manufacturer minimu m steam requirement of

525 pounds per hour. The air-assisted flare was a John Zink m odel LHTS-24/60 flare tip (flare

tip effective diameter of 24 inches) with three pilots, and a maximum capacity of 144,000

pounds of propylene per hour. Both flares operated with 225 sta ndard cubic feet per hour of pilot

gas during the test runs.

Raw test data (in the form of an Excel worksheet) were available for this data set. There

are 131 steam-assisted test runs and 89 air-assisted test r uns from the raw test data.This information is distributed solely for the purp ose of pre-dissemination peer review under applicab le information quality guidelines. It has not been formally disseminated by EPA. It does not repr esent and should not be construed to represent any Agency determination or policy.



## APPENDIX B

Appendix B is an Excel workbook that combines all data se ts. The Excel workbook identifies each specific test run by the exact test con dition and run identification used in each individual report. Appendices C and D provide explanati on and methodologies for
how certain data fields in the workbook were determined.This information is distributed solely for the purp ose of pre-dissemination peer review under applicab le information quality guidelines. It has not been formally disseminated b y EPA. It does not represent and should not be cons trued to represent any Agency determination or policy.



## APPENDIX C

Test Report Nomenclature MatrixThis information is distributed solely for the purpose of pre-dissemination peer review under applicable information quality guidelines. It has not beenformally disseminated by EPA. It does notrepresent and should not be construed to representany Agency determination or policy.C-1Table C-1. Test Report Nomenclature MatrixKEY:“N/A” – not applicable. The specific parameter was not considered in the data set; or the specific parameter was not calculated.“Unknown” –unable to calculate the specific parameter becausethere was not enough information provided in the test reportand associateddata set.“Eq. D.##” –details from the test report and associated dataset used to calculate the specific parameter. See Appendix D for detailedmethodology; refer to the specific Equation identified in the matrix.Data Set IDA:EPA 2-83-052B:EPA 2-84-095C:EPA 2-85-106D:MPC TXE:INEOSF:MPC DetroitG1:FHR AUG2:FHR LOUH:SDP EPFI:SDP GFJ:TCEQ

Basic Run InfoReportedCombustionEfficiency(CE)[%]"CombustionEfficiency(%)""CombustionEfficiency(Percent)""CombEff. (%)""CE"Run Avg.RelativeEfficiency usingCarbon Count"CE(weighted)%""CE (weighted)%""CE(weighted) %""CE""Comb. Eff.CalculatedND@0 %""IMACC -PFTIR Avg.CE (%)"

General Flare Vent Gas DataFlare Vent GasNet HeatingValue (NHVVG)[Btu/scf]"LowerHeatingValue(Btu/SCF)""LowHeatingValue(Btu/ft3)""Low HtgVal(Btu/ft3)""Vent GasHV"Eq. D.1"Flare GasNHVBTU/scf""VG NHV (calc)BTU/scf""VG NHV(calc)BTU/scf""East Property FlareGas Net HeatingValue(BTU/SCF)""OP3 GroundFlare Gas NetHeating ValueBTU/SCF""Actual VentGas LHVBtu/scf"Flare Vent GasFlow Rate(mvg)[lb/hr]Eq. D.2N/AEq. D.3"Vent GasFlow Rate(lb/h)""TotalPanametricsFlow in lbs/hr""Flare GasFlow lb/hr""Flare GasFlow (DCS)lb/hr""Flare GasFlow (DCS)lb/hr"”East PropertyFlare- CalculatedMass Flow (lb/hr)"Mass FlowOP3 GroundFlare InstLB/HR""Actual VentGas (VG) FlowRates--Totallb/hr"Flare Vent GasFlow Rate(Qvg)[scf/hr]Eq. D.4N/AEq. D.5"Vent GasFlow Rate(scfh)"Eq. D.6"Std FlareGas Flowscf/hr"Eq. D.7"Std VG Flow(calc) scf/hr"Eq. D.6"OP3 GroundFlare FlowSCF/HR"Eq. D.6Flare Vent GasVelocity(Vvg)[ft/s]Eq. D.8A"Actual ExitVelocity(ft/sec)""ActualExitVelocity(ft/sec)""Flare TipVelocity"Eq. D.8A"Flare TipVelocity ft/s""VG ExitVelocity (calc)ft/s""Tip Velocity(no steam)(calc) ft/s"Vent gas velocityreport in test report"OP3 GroundFlare ExitVelocityFT/SEC"Eq. D.8BThis information is distributed solely for the purpose of pre-dissemination peer review under applicable information quality guidelines. It has not beenformally disseminated by EPA. It does notrepresent and should not be construed to representany Agency determination or policy.C-2Table C-1. Test Report Nomenclature Matrix (Continued)Data Set IDA:EPA 2-83-052B:EPA 2-84-095C:EPA 2-85-106D:MPC TXE:INEOSF:MPC DetroitG1:FHR AUG2:FHR LOUH:SDP EPFI:SDP GFJ:TCEQ

General Flare Vent Gas DataFlare Vent GasVelocity w/Center Steam(Vvg-s)[ft/s]Eq. D.8CEq. D.8CEq. D.8CEq. D.8CEq. D.8CEq. D.8CEq. D.8CEq. D.8CEq. D.8CEq. D.8C"Actual VentGas ExitVelocity fps"Flare Vent GasMolecularWeight(MWvg)[lb/lb-mol]Eq. D.9N/AEq. D.9"MWvg""PanametricsMeasured MW""MWvg (GCcalc)lb/lbmol""MWvg (calc)lb/lb-mol""MWvg (calc)lb/lb-mol""Vent Gas MW(lb/lb-mole)""OP3 GroundFlare MWLB/LB-MOL""Actual VentGas Mol Wtlb/lb-mole"Reported PilotGas Flow Rate(Qpg)[scf/hr]Reported as26.3 lb/hr inTest ReportNo pilot gasReportedas 2.1scf/min forsome runsin TestReportReported as100 scf/hr inTest ReportReported as150 scf/hr inTest ReportReported as135 scf/hr inTest Report"Pilot Gas FlowRate (scf/hr)""Pilot GasFlow Rate(scf/hr)"No pilot gasNo pilot gasReported as225 scf/hr inTest Report

Molar Percentage of Components in Flare Vent Gas [m ol %]1-Butene[mol %]N/AN/AN/A"Butenesmol%"N/A"i-Butene,Butene-1 mol%""Butene-1(bag)"N/A"HRVOC EPFLARE_Butene1&Isobutane""OP3 GNDFlare_Butene1&Isobutane"N/A1,2-Butadiene[mol %]N/AN/AN/AN/AN/AN/A"1,2-Butadiene(bag)"N/AN/AN/AN/A1,3-Butadiene(%1,3-B)[mol %]N/AN/AN/A"Butadienemol%"Eq. D.10"1,3-Butadienemol %""1,3-Butadiene(bag)""Butadiene(GC) mol%""HRVOC EPFLARE_13BD""OP3 GNDFlare_13BD"N/AAcetylene[mol %]N/AN/AN/A"Acetylenemol%"N/A"Acetylenemol %""Acetylene(bag)"N/A"HRVOC EPFLARE_Acetylene""OP3 GNDFlare_Acetylene"N/ABenzene[mol %]N/AN/AN/AN/AN/AN/A"Benzene (bag)""Benzene(GC) mol%"N/A"Benzene"N/ACarbonDioxide[mol %]N/AN/AN/A"CO2 mol%"N/A"CarbonDioxide mol%""CarbonDioxide (bag)""CarbonDioxide (GC)mol%""HRVOC EPFLARE_CarbonDioxide""OP3 GNDFlare_CarbonDioxide"N/ACarbonMonoxide[mol %]N/AN/AN/A"CO mol%"N/A"CarbonMonoxidemol %"N/A"CarbonMonoxide(GC) mol%""HRVOC EPFLARE_CarbonMonoxide""OP3 GNDFlare_CarbonMonoxide"N/AThis information is distributed solely for the purpose of pre-dissemination peer review under applicable information quality guidelines. It has not beenformally disseminated by EPA. It does notrepresent and should not be construed to representany Agency determination or policy.C-3Table C-1. Test Report Nomenclature Matrix (Continued)Data Set IDA:EPA 2-83-052B:EPA 2-84-095C:EPA 2-85-106D:MPC TXE:INEOSF:MPC DetroitG1:FHR AUG2:FHR LOUH:SDP EPFI:SDP GFJ:TCEQ

Molar Percentage of Components in Flare Vent Gas [m ol %]Cis-2-Butene[mol %]N/AN/AN/A"Cis-2-Butenemol%"N/A"Cis-Butene-2 mol %""Cis-Butene-2(bag)""2-Butene(GC) mol%""HRVOC EPFLARE_Cis2Butene""OP3 GNDFlare_Cis2Butene"N/ACyclopropane[mol %]N/AN/AN/AN/AN/AN/A"Cyclopropane(bag)"N/AN/AN/AN/AEthane[mol %]N/AN/AN/A"Ethanemol%"N/A"Ethane mol%""Ethane (bag)""Ethane (GC)mol%""HRVOC EPFLARE_Ethane""OP3 GNDFlare_Ethane"N/AEthyl Benzene[mol %]N/AN/AN/AN/AN/AN/AN/A"Ethylbenzene (GC)mol%"N/A"Ethylbenzene"N/AEthylene[mol %]N/AN/AN/A"Ethylenemol%"N/A"Ethylenemol %""Ethylene(bag)""Ethylene(GC) mol%""HRVOC EPFLARE_Ethylene""OP3 GNDFlare_Ethylene"N/AHydrogen[mol %]N/AN/AN/A"H2 mol%"N/A"Hydrogenmol %""Hydrogen(bag)""Hydrogen(GC) mol%""HRVOC EPFLARE_Hydrogen""OP3 GNDFlare_Hydrogen"N/AHydrogenSulfide[mol %]N/AN/AN/AN/AN/AN/AN/AN/A"HRVOC EPFLARE_HydrogenSulfide""OP3 GNDFlare_Hydrogen Sulfide"N/AIso-Butane[mol %]N/AN/AN/A"Iso-Butanemol%"N/A"Iso-Butanemol %""Isobutane(bag)""i-Butane(GC) mol%""HRVOC EPFLARE_IsoButane""OP3 GNDFlare_IsoButane"N/AIso-Butylene[mol %]N/AN/AN/AN/AN/AN/A"Isobutylene(bag)""iso-butylene(GC) mol%"N/AN/AN/AMethane[mol %]N/AN/AN/A"CH4 mol%"Eq. D.11"Methanemol %""Methane(bag)""Methane(GC) mol%""HRVOC EPFLARE_Methane""OP3 GNDFlare_Methane""Methane[mol %]"MethylAcetylene[mol %]N/AN/AN/AN/AN/AN/A"MethylAcetylene (bag)"N/AN/AN/AN/An-Butane[mol %]N/AN/AN/A"N-Butanemol%"N/A"NormalButane mol%""N-Butane(bag)""n-Butane(GC) mol%""HRVOC EPFLARE_Butane""OP3 GNDFlare_Butane"N/AThis information is distributed solely for the purpose of pre-dissemination peer review under applicable information quality guidelines. It has not beenformally disseminated by EPA. It does notrepresent and should not be construed to representany Agency determination or policy.C-4Table C-1. Test Report Nomenclature Matrix (Continued)Data Set IDA:EPA 2-83-052B:EPA 2-84-095C:EPA 2-85-106D:MPC TXE:INEOSF:MPC DetroitG1:FHR AUG2:FHR LOUH:SDP EPFI:SDP GFJ:TCEQ

Molar Percentage of Components in Flare Vent Gas [m ol %]Nitrogen(%N)[mol %]Eq. D.14N/AEq. D.13"N2 mol%"Eq. D.12"Nitrogenmol %""Nitrogen(bag)""Nitrogen(GC) mol%""HRVOC EPFLARE_Nitogen""OP3 GNDFlare_Nitogen""Nitrogen[mol %]"Oxygen[mol %]N/AN/AN/A"O2 mol%"N/A"Oxygen mol%""Oxygen (bag)""Oxygen (GC)mol%""HRVOC EPFLARE_Oxygen""OP3 GNDFlare_Oxygen"N/APentane Plus(C5+)[mol %]N/AN/AN/A"C5+ mol%"N/A"PentanePlus (C5+)mol %""C5& HeavierHydrocarbons(bag)""Pentane 5+(GC) mol%""HRVOC EPFLARE_C5+""OP3 GNDFlare_C5+"N/APropadiene[mol %]N/AN/AN/AN/AN/AN/A"Propadiene(bag)"N/AN/AN/AN/APropane(%p)[mol %]N/AN/A“%PropaneinNitrogen”"Propanemol%"N/A"Propanemol %""Propane (bag)""Propane(GC) mol%""HRVOC EPFLARE_Propane""OP3 GNDFlare_Propane""Propane[mol %]"Propylene[mol %]Eq. D.14N/AN/A"Propylenemol%"N/A"Propylenemol %""Propylene(bag)""Propylene(GC) mol%""HRVOC EPFLARE_Propylene""OP3 GNDFlare_Propylene""Propylene[mol %]"Toluene[mol %]N/AN/AN/AN/AN/AN/AN/A"Toluene (GC)mol%"N/A"Toluene"N/ATrans-2-Butene[mol %]N/AN/AN/A"Trans-2-Butenemol%"N/A"TransButene-2 mol%""Trans-Butene-2(bag)"N/A"HRVOC EPFLARE_Trans2Butene""OP3 GNDFlare_Trans2Butene"N/AWater[mol %]N/AN/AN/A"Watermol%"N/AN/AN/AN/A"HRVOC EPFLARE_Water""OP3 GNDFlare_Water"N/AXylenes[mol %]N/AN/AN/AN/AN/AN/AN/AN/AN/A"Xylene's"N/AThis information is distributed solely for the purpose of pre-dissemination peer review under applicable information quality guidelines. It has not beenformally disseminated by EPA. It does notrepresent and should not be construed to representany Agency determination or policy.C-5Table C-1. Test Report Nomenclature Matrix (Continued)Data Set IDA:EPA 2-83-052B:EPA 2-84-095C:EPA 2-85-106D:MPC TXE:INEOSF:MPC DetroitG1:FHR AUG2:FHR LOUH:SDP EPFI:SDP GFJ:TCEQ

Steam DataTOTALVolumetricSteam Rate(Qs)[scf/hr]Eq. D.18N/AEq. D.18Eq. D.18Eq. D.18Eq. D.18"Std Steam Flow(calc) scf/hr""Std SteamFlow (calc)scf/hr"Eq. D.18N/AEq. D.18TOTALMass SteamRate(ms)[lb/hr]“Steam Flow(lbs/hr)”N/A140 lb/hrConstant"Steam Flow(lb/h)"Eq. D.19"Steam Flowlb/hr""Steam Flow(DCS) lb/hr"Eq. D.17Eq. D.17N/A"Actual SteamFlow Rates--Total lb/hr"LowerVolumetricSteam Rate(Ql)[scf/hr]N/AN/AN/AUnknownN/AN/AN/AEq. D.20N/AN/AN/ALower MassSteam Rate(ml)[lb/hr]N/AN/AN/AUnknownN/AN/AN/AEq. D.19N/AN/AN/ACenterVolumetricSteam Rate(Qc)[scf/hr]N/AN/AN/AUnknownN/AEq. D.18Eq. D.18Eq. D.18UnknownUnknownEq. D.18Center MassSteam Rate(mc)[lb/hr]N/AN/AN/AUnknownN/A300 lb/hrConstant500 lb/hrConstant2,890 lb/hrConstantUnknownUnknown"Actual SteamFlow Rates--Center lb/hr"Ring VolumetricSteam Rate(Qr)[scf/hr]N/AN/AN/AN/AN/AEq. D.20Eq. D.20N/AN/AN/AN/ARing MassSteam Rate(mr)[lb/hr]N/AN/AN/AN/AN/AEq. D.19Eq. D.19N/AN/AN/AN/AUpperVolumetricSteam Rate(Qu)[scf/hr]Eq. D.20N/AEq. D.18N/AEq. D.18N/AN/AN/AUnknownN/AEq. D.18This information is distributed solely for the purpose of pre-dissemination peer review under applicable information quality guidelines. It has not beenformally disseminated by EPA. It does notrepresent and should not be construed to representany Agency determination or policy.C-6Table C-1. Test Report Nomenclature Matrix (Continued)Data Set IDA:EPA 2-83-052B:EPA 2-84-095C:EPA 2-85-106D:MPC TXE:INEOSF:MPC DetroitG1:FHR AUG2:FHR LOUH:SDP EPFI:SDP GFJ:TCEQ

Steam DataUpper MassSteam Rate(mu)[lb/hr]“Steam Flow(lbs/hr)”N/A140 lb/hrConstantN/A"Steam flow inlbs/hr primeter"N/AN/AN/AUnknownN/A"Actual SteamFlow Rates--Upper lb/hr"Steam-to-ventgas ratio byweight(S/VGwt)[lb steam/lb vent gas]Eq. D.21AN/AEq. D.21AEq. D.21AEq. D.21AEq. D.21AEq. D.21AEq. D.21AEq. D.21AN/A"Assist RatioSteam / VGFlow Rate"Steam-to-ventgas ratio byvolume(S/VGvol)[scf steam/scf vent gas]Eq. D.21BN/AEq. D.21BEq. D.21BEq. D.21BEq. D.21BEq. D.21BEq. D.21BEq. D.21BEq. D.21BEq. D.21BSteam-tohydrocarbonratio byvolume(S/HCvol)[scf steam/scf HC]Eq. D.21CN/AEq. D.21CEq. D.21CEq. D.21CEq. D.21CEq. D.21CEq. D.21CEq. D.21CEq. D.21CEq. D.21C

Air DataAir Assist FlowRate(mAir)[lb/hr]N/AN/AN/AN/AN/AN/AN/AN/AN/AN/A"Air AssistFlow Ratelb/hr"Air Assist FlowRate(QAir)[scf/hr]N/AN/A"Air AssistFlow RateSCFH"N/AN/AN/AN/AN/AN/AN/A"Air AssistFlow RateSCFH"Volumetric FlowRates For EachFlare Vent GasComponent In TheCombustion Zone(QCZ,i)[scf/hr]Eq. D.15BN/AEq. D.15AEq. D.15AEq. D.15C andEq. D.15DEq. D.15AEq. D.15AEq. D.15AEq. D.15AN/AEq. D.15AConcentration OfEach Flare VentGas Component InThe CombustionZone(XCZ,i)[volume fraction]Eq. D.16AN/AEq. D.16AEq. D.16AEq. D.16AEq. D.16AEq. D.16AEq. D.16AEq. D.16AN/AEq. D.16AThis information is distributed solely for the purpose of pre-dissemination peer review under applicable information quality guidelines. It has not beenformally disseminated by EPA. It does notrepresent and should not be construed to representany Agency determination or policy.C-7Table C-1. Test Report Nomenclature Matrix (Continued)Data Set IDA:EPA 2-83-052B:EPA 2-84-095C:EPA 2-85-106D:MPC TXE:INEOSF:MPC DetroitG1:FHR AUG2:FHR LOUH:SDP EPFI:SDP GFJ:TCEQConcentration ofEach Flare VentGas CombustibleComponent(VGc)[volume fraction]Eq. 16BEq. 16BEq. 16BEq. 16BEq. 16BEq. 16BEq. 16BEq. 16BEq. 16BEq. 16BEq. 16BConcentration ofEach Flare VentGas and CenterSteam OnlyComponent(Xvgcs)[volume fraction]Eq.16CEq.16CEq.16CEq.16CEq.16CEq.16CEq.16CEq.16CEq.16CEq.16CEq.16C

Dynamic NHV CZ CalculationRatio ofNHVcz toNHVLFL-VG(NHVratio)[unitless]Eq. D.22N/AEq. D.22Eq. D.22Eq. D.22Eq. D.22Eq. D.22Eq. D.22Eq. D.22N/AEq. D.22Net HeatingValue ofCombustionZone Gas(NHVCZ)[BTU/scf]Eq. D.23N/AEq. D.23Eq. D.23Eq. D.23Eq. D.23Eq. D.23Eq. D.23Eq. D.23N/AEq. D.23Net HeatingValue of VentGas if Dilutedto LowerFlammabilityLimit(NHVVG--LFL)[BTU/scf]Eq. D.24N/AEq. D.24Eq. D.24Eq. D.24Eq. D.24Eq. D.24Eq. D.24Eq. D.24N/AEq. D.24LowerFlammabilityLimit of VentGas AdjustedforNitrogenEquivalency(LFLVG)[vol frac]]Eq. D.25N/AEq. D.25Eq. D.25Eq. D.25Eq. D.25Eq. D.25Eq. D.25Eq. D.25N/AEq. D.25This information is distributed solely for the purpose of pre-dissemination peer review under applicable information quality guidelines. It has not beenformally disseminated by EPA. It does notrepresent and should not be construed to representany Agency determination or policy.C-8Table C-1. Test Report Nomenclature Matrix (Continued)Data Set IDA:EPA 2-83-052B:EPA 2-84-095C:EPA 2-85-106D:MPC TXE:INEOSF:MPC DetroitG1:FHR AUG2:FHR LOUH:SDP EPFI:SDP GFJ:TCEQ

LFL CZG calculationCombustibleComponents intheCombustionZone(CCZ)[vol frac]Eq. D.26N/AEq. D.26Eq. D.26Eq. D.26Eq. D.26Eq. D.26Eq. D.26Eq. D.26N/AEq. D.26Coefficient ofNitrogenEquivalency ofWater Relativeto Nitrogen(Ne,H2O)Eq. D.29N/AEq. D.29Eq. D.29Eq. D.29Eq. D.29Eq. D.29Eq. D.29Eq. D.29N/AEq. D.29Coefficient ofNitrogenEquivalency ofCarbonDioxideRelative toNitrogen(Ne,CO2)Eq. D.29N/AEq. D.29Eq. D.29Eq. D.29Eq. D.29Eq. D.29Eq. D.29Eq. D.29N/AEq. D.29LowerFlammabilityLimit ofCombustionZone GasAdjusted forNitrogenEquivalency(LFLCZ)[vol frac]Eq. D.27N/AEq. D.27Eq. D.27Eq. D.27Eq. D.27Eq. D.27Eq. D.27Eq. D.27N/AEq. D.27This information is distributed solely for the purpose of pre-dissemination peer review under applicable information quality guidelines. It has not beenformally disseminated by EPA. It does notrepresent and should not be construed to representany Agency determination or policy.C-9Table C-1. Test Report Nomenclature Matrix (Continued)Data Set IDA:EPA 2-83-052B:EPA 2-84-095C:EPA 2-85-106D:MPC TXE:INEOSF:MPC DetroitG1:FHR AUG2:FHR LOUH:SDP EPFI:SDP GFJ:TCEQ

Stoichiometric Air Ratio CalculationTheoreticalStoichiometricMass of AirNeeded toCombust theFlare Vent Gas(mStoic)[lb/hr]N/AN/AEq. D.31throughEq. 37N/AN/AN/AN/AN/AN/AN/AEq. D.31through Eq. 33CalculatedRatio of ActualMass Flow ofTotal AssistAir to theTheoreticalStoichiometricMass of AirNeeded toCombust theFlare Vent Gas(mAir/ mStoic)(SR)N/AN/AEq. D.30N/AN/AN/AN/AN/AN/AN/AEq. D.30Reported(mAir/ mStoic)(SR)N/AN/A"Air-Assist SR"N/AN/AN/AN/AN/AN/AN/A"Excess AirSR"This information is distributed solely for the purpose of pre-dissemination peer review under applicable information quality guidelines. It has not beenformally disseminated by EPA. It does notrepresent and should not be construed to representany Agency determination or policy.C-10Table C-1. Test Report Nomenclature Matrix (Continued)Data Set IDA:EPA 2-83-052B:EPA 2-84-095C:EPA 2-85-106D:MPC TXE:INEOSF:MPC DetroitG1:FHR AUG2:FHR LOUH:SDP EPFI:SDP GFJ:TCEQ

MFR CalculationReported MFR[unitless]N/AN/AN/A"MFR"N/A"MomentumFlux Ratio""MomentumFlux Ratio(calc)""MomentumFlux Ratio(calc)"N/AN/A“MomentumFlux Ratio”Flare Vent GasFlow RateIncludingCenter Steam(mvg-s)[lb/hr]Eq. D.38N/AN/AEq. D.38Eq. D.38Eq. D.38Eq. D.38Eq. D.38N/AN/AEq. D.38Density ofFlare Vent GasIncludingCenter Steam(pvg-s)[lb/scf]Eq. D.39N/AN/AEq. D.39Eq. D.39Eq. D.39Eq. D.39Eq. D.39N/AN/AEq. D.39Wind Velocity(Vwind)[ft/s]N/AN/AN/AEq. D.40N/AEq. D.40Eq. D.40Eq. D.40N/AN/AEq. D.40CalculatedMFR[unitless]N/AN/AN/AEq. D.41N/AEq. D.41Eq. D.41Eq. D.41N/AN/AEq. D.41This information is distributed solely for the purpose of pre-dissemination peer review under applicable information quality guidelines. It has not beenformally disseminated by EPA. It does notrepresent and should not be construed to representany Agency determination or policy.C-11Table C-1. Test Report Nomenclature Matrix (Continued)Data Set IDA:EPA 2-83-052B:EPA 2-84-095C:EPA 2-85-106D:MPC TXE:INEOSF:MPC DetroitG1:FHR AUG2:FHR LOUH:SDP EPFI:SDP GFJ:TCEQ

Shore Equation AnalysisShoreEquationVelocity-JetPeriphery(UO/**∏**/DO)[sec-1]Eq. D.42N/AEq. D.42Eq. D.42Eq. D.42Eq. D.42Eq. D.42Eq. D.42N/AN/AEq. D.42LowerFlammabilityLimit of FlareVent GasIncludingCenter SteamAdjusted forNitrogenEquivalency(LFLvgcs)[vol frac]Eq. D.43N/AEq. D.43Eq. D.43Eq. D.43Eq. D.43Eq. D.43Eq. D.43N/AN/AEq. D.43ShoreEquation(RAM)[lb flare ventgas includingcenter steam /lb of air]Eq. D.44N/AEq. D.44Eq. D.44Eq. D.44Eq. D.44Eq. D.44Eq. D.44N/AN/AEq. D.44MaximumAllowableFlare Vent GasVelocityIncludingCenter Steam(Vmax)[ft/s]Eq. D.45N/AEq. D.45Eq. D.45Eq. D.45Eq. D.45Eq. D.45Eq. D.45N/AN/AEq. D.45This information is distributed solely for the purp ose of pre-dissemination peer review under applicab le information quality guidelines. It has not been formally disseminated by EPA. It does not repr esent and should not be construed to represent any Agency determination or policy.



## APPENDIX D

Appendix D is a detailed list of all equations used in th e Excel file.This information is distributed solely for the purp ose of pre-dissemination peer review under applicab le information quality guidelines. It has not been formally disseminated by EPA. It does not repr esent and should not be construed to represent any Agency determination or policy.



## D-1 APPENDIX D – CALCULATIONS

INTRODUCTION

Appendix D provides detailed calculation methodologies for t he specific parameters identified in the Appendix C matrix. If a cell is labeled as “Eq. D.##” in the Appendix C matrix, the specific calculation methodology can be found here in Appendix D. As such, the equations presented in Appendix D were used only for the indicated data sets. See Table 1 in Section 2.0 of the memo to identify the test report associated with each data se t. If a particular data set is not identified in the equation in this appendix, it means that the correspon ding parameter was included in the test report (and no calculation was necessary).This information is distributed solely for the purp ose of pre-dissemination peer review under applicab le information quality guidelines. It has not been formally disseminated by EPA. It does not repr esent and should not be construed to represent any Agency determination or policy.



## D-2 a
K 6b 

##  c E % W@,$



## 100 J a
K

$ f

$g 

## Equation D.1

The flare vent gas net heating value (NHV VG 

## ), in Btu/scf, was calculated using Equation
D.1.

This equation was only used for data set E. The reported NHV VG 

## from the associated test report was used for all other data sets. It was assumed that the reported values used this equation as a basis. The net heating value of the flare vent gas is the sum of the net heat of combustion of each individual combustible component.

Where:
NHV VG 

## = Flare vent gas net heating value, BTU/scf.

i = Individual combustible component in flare vent gas.

n = Number of individual combustible components in flare vent gas. % vg,i 

## = Percentage of combustible component i in flare vent gas (i.e., 1,3-Butadiene and

Natural Gas), volumetric percentage. (See Equations D.10 t hrough D.12).
100 = Constant, percentage.
NHV i 

## = Reported net heating value of combustible component i , BTU/ scf.This information is distributed solely for the purp ose of pre-dissemination peer review under applicab le information quality guidelines. It has not been formally disseminated by EPA. It does not repr esent and should not be construed to represent any Agency determination or policy.



## D-3 h W@ 

##  h i 

##  h j



## h W@ 

##  .k

W@ 

## A E l W@ 

## 379.48 J Equations D.2 and D.3

If not reported, the flare vent gas flow rate ( m vg 

## ), in lb/hr, was calculated using either Equation D.2 or D.3.

Equation D.2: This equation was used for data set A.

Where:

m vg 

## = Flare vent gas flow rate, lb/hr.

m p 

## = Reported mass flow rate of combustible components (i.e ., Propylene Flow) in

flare vent gas, lb/hr.

m N2 

## = Reported mass flow rate of nitrogen (i.e., Nitrogen F low) in flare vent gas, lb/hr.

Equation D.3: This equation was used for data set C.

Where:

m vg 

## = Flare vent gas flow rate, lb/hr.
MW vg 

## = Molecular weight of flare vent gas, lb/lb-mole. ( See Equation D.9). Q vg 

## = Flare vent gas flow rate, scf/hr. (See Equation D.4)

. 379.48 = Constant, lb-mole/scf at dry standard conditions.This information is distributed solely for the purp ose of pre-dissemination peer review under applicab le information quality guidelines. It has not been formally disseminated by EPA. It does not repr esent and should not be construed to represent any Agency determination or policy.



## D-4 l W@ 

##  60 A 0 l i 

##  l j 

## 5

l W@ 

##  379.48 A o Z h Y



## / \ E % i 

## 100 J  Z % j 

## 100 \ p Equations D.4 through D.7

If not reported, the flare vent gas flow rate ( Q vg 

## ), in scf/hr, was calculated using one of the Equations D.4 through D.7.

Equation D.4: This equation was used for data set A.

Where: Q vg 

## = Flare vent gas flow rate, scf/hr.
60 = Constant, min/hr. Q p 

## = Reported volumetric flow rate of propylene (i.e., Pr opylene Flow), scf/min. Q N2 

## = Reported volumetric flow rate of nitrogen (i.e., Nit rogen Flow), scf/min.

Equation D.5: This equation was used for data set C.

Where: Q vg 

## = Flare vent gas flowrate, scf/hr.
379.48 = Constant, lb-mole/scf at dry standard conditions.

m s 

## = Reported total steam rate (i.e., Steam Flowrate), l b/hr. SF = Reported steam ratio (i.e., Steam Ratio), lb ste am / lb fuel.
% p 

## = Reported percentage of propane in flare vent gas (i.e., %Propane in Nitrogen),

molar percentage.
% N 

## = Percentage of nitrogen in flare vent gas, molar percent age. (See Equation D.13).
100 = Constant, molar percentage.This information is distributed solely for the purp ose of pre-dissemination peer review under applicab le information quality guidelines. It has not been formally disseminated by EPA. It does not repr esent and should not be construed to represent any Agency determination or policy.



## D-5 l W@ 

##  379.48 A q h W@



## .k W@ 

## r

l W@ 

##  l W@,%si%tsu 

## A 1,000

Equations D.4 through D.7 (Continued)

Equation D.6: This equation was used for data sets E, H, and J.

Where: Q vg 

## = Flare vent gas flow rate, scf/hr.
379.48 = Constant, lb-mole/scf at dry standard conditions.

m vg 

## = Reported flare vent gas flow rate, lb/hr. Reported for data set E as “Total Panametrics Flow in lbs/hr.” Reported for data set H as “East Property Flare – Calculated Mass Flow

(lb/hr).” Reported for data set J as “Actual Vent Gas (VG) Flow Rates, Total (lb/hr).”
MW vg 

## = Reported molecular weight of flare vent gas, lb/lb- mole. Reported for data set E as “Panametrics Measured MW.” Reported for data set H as” East Property Flare Gas Molecular We ight

(lb/lbmole).” Reported for data set J as “Actual Vent Gas Mol Wt (lb/lb-mole). ”

Equation D.7: This equation was used for data set G1.

Where: Q vg 

## = Flare vent gas flow rate, scf/hr. Q vg.reported 

## = Reported flare vent gas flow rate (i.e., Vol Flare G as Flow (DCS)), kscf/hr. 1,000 = Constant, scf/kscf.This information is distributed solely for the purp ose of pre-dissemination peer review under applicab le information quality guidelines. It has not been formally disseminated by EPA. It does not repr esent and should not be construed to represent any Agency determination or policy.



## D-6 K W@ 

##  K W@,%si%tsu 

## 60

K W@ 

##  K W@vY 

## U Q w R

l X 

## Z M 4 \ A E x

yt 

## 12 J  

## A 60 A 60 _

z ` Equation D.8A and D.8B

If not reported, the flare vent gas velocity ( V vg 

## ), in ft/s, was calculated using Equation D.8A or Equation D.8B.

Equation D.8A: This equation was used for data sets A and E.

Where:

V vg 

## = Flare vent gas velocity, ft/s.
V vg,reported 

## = Reported flare vent gas velocity, ft/min. Reported for data set A as “Relief Gas Flow (SCFM).” Reported for data set E as “Exit Velocity in ft/min.”
60 = Constant, s/min.

Equation D.8B: This equation was used for data set J.

Where:

V vg 

## = Flare vent gas velocity, ft/s.
V vg-s 

## = Reported flare vent gas velocity with center steam (i.e., Actual Vent Gas Exit

Velocity (fps), Includes Center Steam), ft/s. Q
c 

## = Center steam rate, scf/hr. (See Equation D.18 for da ta sets F, G1 and G2).

π /4 = Constant, used to calculate area of flare tip.
d ft 

## = Reported effective diameter of flare tip, in. (See t ip sizes identified in Section 2.0

of report). 12 = Constant, in/ft. 60 = Constant, s/min.
60 = Constant, min/hr.This information is distributed solely for the purp ose of pre-dissemination peer review under applicab le information quality guidelines. It has not been formally disseminated by EPA. It does not repr esent and should not be construed to represent any Agency determination or policy.



## D-7 K W@vY 

##  K

W@ 

##  Q w R

l X 

## Z M 4 \ A E x

yt 

## 12 J  

## A 60 A 60 _

z ` Equation D.8C

If not reported, the flare vent gas velocity with center st eam ( V vg-s 

## ), in ft/s, was calculated using Equation D.8C. For data sets A, B, C, E, and I that are without a center steam rate (Q c 

## ) or for data set H that has an unknown center steam rate ( Q c 

## ), the flare vent gas velocity with center steam ( V vg-s 

## ) is equal to flare vent gas velocity ( V vg 

## ).

Equation D.8C: This equation was used for data sets A, B, C, D, E, F, G1, G2, H and I.

Where:
V vg-s 

## = Flare vent gas velocity with center steam, ft/s.

V vg 

## = Flare vent gas velocity, ft/s. (See Equation D.8A fo r data sets A and E). Q
c 

## = Center steam rate, scf/hr. (See Equation D.18 for da ta sets F, G1 and G2).

π /4 = Constant, used to calculate area of flare tip.
d ft 

## = Reported effective diameter of flare tip, in. (See t ip sizes identified in Section 2.0

of report). 12 = Constant, in/ft. 60 = Constant, s/min.
60 = Constant, min/hr.This information is distributed solely for the purp ose of pre-dissemination peer review under applicab le information quality guidelines. It has not been formally disseminated by EPA. It does not repr esent and should not be construed to represent any Agency determination or policy.



## D-8 .k W@ 

##  c E % W@,{



## 100 J .k

{ f

{g 

## Equation D.9

If not reported, the flare vent gas molecular weight (MW vg 

## ), in lb/lb-mol, was calculated using Equation D.9.

This equation was used for data sets A and C.

Where:
MW vg 

## = Flare vent gas molecular weight, lb/lb-mole. j = Individual combustible or inert component in flare v ent gas.

n = Number of individual components in flare vent gas.
% vg,i 

## = Percentage of component j in flare vent gas, molar percentage.

(See Equation D.14 for data set A and Equation D.13 for data s et C).
100 = Constant, percentage.
MW j 

## = Molecular weight of component j , lb/lb-mole.This information is distributed solely for the purp ose of pre-dissemination peer review under applicab le information quality guidelines. It has not been formally disseminated by EPA. It does not repr esent and should not be construed to represent any Agency determination or policy.



## D-9 % ,v| 

##  100 q l ,v|



## l ,v| 

##  l j 

##  l jb 

## r

% jb 

##  100 q l jb



## l ,v| 

##  l j 

##  l jb 

## r

% j 

##  100 q l j



## l ,v| 

##  l j 

##  l jb 

## r

Equations D.10 through D.12

For data set E, the percentages of 1,3-butadiene (% 1,3-B 

## ), natural gas (% NG 

## ), and nitrogen (% N 

## ) in the flare vent gas, in volumetric percentage, were cal culated using Equations D.10 through D.12, respectively.

Equation D.10:

Where:
% 1,3-B 

## = Percentage of 1,3-Butadiene in flare vent gas, volume tric percentage.
100 = Constant, percentage. Q 1,3-B 

## = Volumetric flow rate of 1,3-Butadiene, scf/hr. (See E quation D.15C). Q N 

## = Volumetric flow rate of nitrogen, scf/hr. (See Equat ion D.15D). Q NG 

## = Reported volumetric flow rate of supplemental natural gas (i.e., Nat Gas flow in SCFH), scf/hr.

Equation D.11:

Where:
% NG 

## = Percentage of natural gas in flare vent gas, volumet ric percentage.
100 = Constant, percentage. Q 1,3-B 

## = Volumetric flow rate of 1,3-Butadiene, scf/hr. (See E quation D.15C). Q N 

## = Volumetric flow rate of nitrogen, scf/hr. (See Equat ion D.15D). Q NG 

## = Reported volumetric flow rate of supplemental natural gas (i.e., Nat Gas flow in SCFH), scf/hr.

Equation D.12:

Where:
% N 

## = Percentage of nitrogen in flare vent gas, volumetric percentage. 100 = Constant, percentage. Q 1,3-B 

## = Volumetric flow rate of 1,3-Butadiene, scf/hr. (See E quation D.15C). Q N 

## = Volumetric flow rate of nitrogen, scf/hr. (See Equat ion D.15D). Q NG 

## = Reported volumetric flow rate of supplemental natural gas (i.e., Nat Gas flow in SCFH), scf/hr.This information is distributed solely for the purp ose of pre-dissemination peer review under applicab le information quality guidelines. It has not been formally disseminated by EPA. It does not repr esent and should not be construed to represent any Agency determination or policy.



## D-10 % j 

##  100 U % } 

## Equation D.13

For data set C, the percentage of nitrogen in the flare ven t gas (% N 

## ), in molar percentage, was calculated using Equation D.13.

Where:
% N 

## = Percentage of nitrogen in flare vent gas, molar percen tage. 100 = Constant, percentage.
% P 

## = Reported percentage of propane in flare vent gas (i.e., %Propane in Nitrogen),

molar percentage.This information is distributed solely for the purp ose of pre-dissemination peer review under applicab le information quality guidelines. It has not been formally disseminated by EPA. It does not repr esent and should not be construed to represent any Agency determination or policy.



## D-11 % { 

##  100 q h {



## h { 

##  h { 

## r Equation D.14

For data set A, the percentage of component (propylene or ni trogen) in the flare vent gas (% j 

## ), in molar percentage, was calculated using Equation D.14.

Where:
% j 

## = Percentage of component in flare vent gas, molar per centage. j = Individual component in flare vent gas (i.e., propylen e or nitrogen).
100 = Constant, percentage.

m j1 

## = Reported mass flow rate of component 1 (i.e., Proplyl ene Flow or Nitrogen Flow),

lb/hr.

m j2 

## = Reported mass flow rate of component 2 (i.e., Proplyl ene Flow or Nitrogen Flow),

lb/hr.This information is distributed solely for the purp ose of pre-dissemination peer review under applicab le information quality guidelines. It has not been formally disseminated by EPA. It does not repr esent and should not be construed to represent any Agency determination or policy.



## D-12 l ~,$ 

##  l W@ 

## E % W@,$



## 100 J

l ~,$ 

##  l ~,$ %si%tsu 

## A 60 Equation D.15A and D.15B

The volumetric flow rate for each flare vent gas component in the combustion zone (Q CZ,i 

## ), in scf/hr, was calculated using Equation D.15A and Equation D .15B.

Equation D.15A: This equation was used for data sets C, D, F, G1, G2, H, and J.

Where: Q CZ,i 

## = Volumetric flow rate of each flare vent gas compon ent i in combustion zone,

scf/hr.

i = Individual flare vent gas component in combustion zone

. Q vg 

## = Flare vent gas flow rate, scf/hr. (If not reporte d, see Equations D.4 through D.7).
% vg,i 

## = Percentage of component i in flare vent gas, molar percentage.
100 = Constant, percentage.

Equation D.15B: This equation was used for data set A.

Where: Q CZ,i 

## = Volumetric flow rate of each flare vent gas compon ent i in combustion

zone, scf/hr.
i = Individual flare vent gas component in combustion zon e. Q CZ,i ,reported



## = Reported volumetric flow rate of each flare vent g as component i in

combustion zone (i.e., Propylene Flow or Nitrogen Flo w), scf/min.
60 = Constant, s/min.This information is distributed solely for the purp ose of pre-dissemination peer review under applicab le information quality guidelines. It has not been formally disseminated by EPA. It does not repr esent and should not be construed to represent any Agency determination or policy.



## D-13 l ,v| 

##  Z h ,v|,%si%tsu



## 0.159 \

l j 

##  l W@ 

## U l ,v| 

## U l jb 

## Equation D.15C and D.15D

For data set E, the volumetric flow rates of 1,3-butadiene (Q 1,3-B 

## ) and nitrogen (Q N 

## ) in the flare vent gas, in scf/hr, were calculated using Equations D.15C and D.15D, respectively.

Equation D.15C:

Where: Q 1,3-B 

## = Volumetric flow rate of 1,3-Butadiene, scf/hr.

m 1,3-B,reported



## = Reported mass flow rate of 1,3-Butadiene (i.e., BD fl ow in lb/hr), lb/hr.
0.159 = Constant, density of 1,3-Butadiene, lb/scf.

Equation D.15D:

Where: Q N 

## = Volumetric flow rate of nitrogen, scf/hr. Q vg 

## = Flare vent gas flow rate, scf/hr. (See Equations D. 6). Q 1,3-B 

## = Volumetric flow rate of 1,3-Butadiene, scf/hr. (See E quation D.15C). Q NG 

## = Reported volumetric flow rate of supplemental natural gas (i.e., Nat Gas flow in SCFH), scf/hr.This information is distributed solely for the purp ose of pre-dissemination peer review under applicab le information quality guidelines. It has not been formally disseminated by EPA. It does not repr esent and should not be construed to represent any Agency determination or policy.



## D-14  ~,$ 

##  l ~,$ 

## ∑ l ~,$ 

## Equation D.16A

The concentration of each flare vent gas component in the com bustion zone (X CZ,i 

## ) was calculated using Equation D.16.

This equation was used for data sets A, C, D, E, F, G1, G2, H, and J.

Where:

X CZ,i 

## = Concentration of component i in combustion zone gas, volume fraction.
i = Individual flare vent gas component in combustion zone

. Q CZ,i 

## = Volumetric flow rate of component i in combustion zone gas, scf/hr. (See

Equation D.15A or D.15B).This information is distributed solely for the purp ose of pre-dissemination peer review under applicab le information quality guidelines. It has not been formally disseminated by EPA. It does not repr esent and should not be construed to represent any Agency determination or policy.



## D-15 K X 

##  l ~,X 

## ∑ l ~,X 

## Equation D.16B

The concentration of each flare vent gas combustible component (VG C 

## ) was calculated using Equation D.16B.

This equation was used for all data sets.

Where:
VG
c 

## = Concentration of combustible component c in the flare vent gas, volume fraction.

c = Individual combustible component in the flare vent gas. Q CZ,c 

## = Volumetric flow rate of combustible component c in the flare vent gas, scf/hr.This information is distributed solely for the purp ose of pre-dissemination peer review under applicab le information quality guidelines. It has not been formally disseminated by EPA. It does not repr esent and should not be construed to represent any Agency determination or policy.



## D-16  W@XY 

##  l ~,X 

## ∑ l ~,X 

## Equation D.16C

The concentration of each flare vent gas and center steam only component (X vgcs 

## ) was calculated using Equation D.16C.

This equation was used for all data sets.

Where:

X vgcs 

## = Concentration of combustible component c in the flare vent gas and center steam

mixture, volume fraction.

c = Individual combustible component in the flare vent gas and center steam mixture. Q CZ,c 

## = Volumetric flow rate of combustible component c in the flare vent gas and center

steam mixture, scf/hr.This information is distributed solely for the purp ose of pre-dissemination peer review under applicab le information quality guidelines. It has not been formally disseminated by EPA. It does not repr esent and should not be construed to represent any Agency determination or policy.



## D-17 h Y 

##  h Y,%si%tsu 

## A 1,000 Equation D.17

If not reported, the total mass steam rate (m s 

## ), in lb/hr, was calculated using Equation D.17.

This equation was used for data sets G2 and H.

Where:

m s 

## = Total steam rate, lb/hr.

m s,reported 

## = Reported total steam rate, klb/hr. Reported for data set G2 as “Steam Flow (DCS).” Reported for data set H as “EPF Steam.” 1,000 = Constant, lb/klb.This information is distributed solely for the purp ose of pre-dissemination peer review under applicab le information quality guidelines. It has not been formally disseminated by EPA. It does not repr esent and should not be construed to represent any Agency determination or policy.



## D-18 l L 

##  379.48 E h L



## .k Y 

## J Equation D.18

The volumetric steam rate (Q
x 

## ), in scf/hr, was calculated using Equation D.18.

This equation was used for data sets A, C, D, E, F, G1, G2, H, and J.

Where: Q
x 

## = Type x steam rate, scf/hr. x = Type of steam rate (i.e., Total, Lower, Center, Ri ng, or Upper).
379.48 = Constant, lb-mole/scf at dry standard conditions.

m x 

## = Type x steam rate, lb/hr. (See Equation D.19).

MW
s 

## = Molecular weight of steam, 18 lb/lb-mole.This information is distributed solely for the purp ose of pre-dissemination peer review under applicab le information quality guidelines. It has not been formally disseminated by EPA. It does not repr esent and should not be construed to represent any Agency determination or policy.



## D-19 h Y 

##  h  

##  h X 

##  h % 

##  h P 

## Equation D.19

The total mass steam rate (m s 

## ), lower mass steam rate (m l 

## ), and ring mass steam rate (m
r 

## ), in lb/hr, were calculated using Equation D.19.

This equation was used for data sets E, F, G1, and G2.

Where:

m s 

## = Total steam rate, lb/hr. (See Equation D.17 for data s ets G2 and H). Total steam rate was a reported value for data sets R and G1.

m l 

## = Lower steam rate, lb/hr.

m c 

## = Center steam rate, lb/hr. Center steam rate was a reported constant value for data sets F, G 1 and G2.

m r 

## = Ring steam rate, lb/hr.

m u 

## = Upper steam rate, lb/hr. Upper steam rate was a reported value for data set E.This information is distributed solely for the purp ose of pre-dissemination peer review under applicab le information quality guidelines. It has not been formally disseminated by EPA. It does not repr esent and should not be construed to represent any Agency determination or policy.



## D-20 l Y 

##  l  

##  l X 

##  l % 

##  l P 

## Equation D.20

The ring volumetric steam rate (Q
r 

## ) and lower volumetric steam rate (Q l 

## ), in scf/hr, were calculated using Equation D.20.

This equation was used for data sets F, G1, and G2.

Where: Q
s 

## = Total steam rate, scf/hr. Q l 

## = Lower steam rate, scf/hr. Q
c 

## = Center steam rate, scf/hr. (See Equation D.18 for da ta sets F, G1 and G2). Q
r 

## = Ring steam rate, scf/hr. Q
u 

## = Upper steam rate, scf/hr.This information is distributed solely for the purp ose of pre-dissemination peer review under applicab le information quality guidelines. It has not been formally disseminated by EPA. It does not repr esent and should not be construed to represent any Agency determination or policy.



## D-21 /K t 

##  h Y



## h W@ 

## Equation D.21A

The steam-to-vent-gas ratio by weight (S/VG wt 

## ), in lb steam/lb vent gas, was calculated using Equation D.21A.

This equation was used for data sets A, C, D, E, F, G1, G2, and H.

Where:
S/VG wt 

## = The steam-to-vent-gas ratio by weight, lb steam/lb vent gas.

m s 

## = Total steam rate, lb/hr. (See Equation D.17 for data sets G2 and H. See

Equation D.19 for data set E).

m vg 

## = Flare vent gas flow rate, lb/hr. (See Equation D.2 for data set A. See

Equation D.3 for data set C).This information is distributed solely for the purp ose of pre-dissemination peer review under applicab le information quality guidelines. It has not been formally disseminated by EPA. It does not repr esent and should not be construed to represent any Agency determination or policy.



## D-22 /K W 

##  l Y



## l W@ 

## Equation D.21B

The steam-to-vent-gas ratio by volume (S/VG vol 

## ), in scf steam/scf vent gas, was calculated using Equation D.21B.

This equation was used for data sets A, C, D, E, F, G1, G2, H, I and J.

Where:
S/VG vol 

## = The steam-to-vent-gas ratio by volume, scf steam/s cf vent gas. Q
s 

## = Total steam rate, scf/hr. (See Equation D.18 for data sets A, C, D, E, F, and H). Q vg 

## = Flare vent gas flow rate, scf/hr. (See Equation D. 8A for data sets A and E.

See Equation D.8B for data set J).This information is distributed solely for the purp ose of pre-dissemination peer review under applicab le information quality guidelines. It has not been formally disseminated by EPA. It does not repr esent and should not be construed to represent any Agency determination or policy.



## D-23 / W 

##  l Y 

## ∑ l ~, $ 

## Equation D.21C

The steam-to-vent-hydrocarbon ratio by volume (S/HC vol 

## ), in scf steam/scf hydrocarbon, was calculated using Equation D.21C.

This equation was used for data sets A, C, D, E, F, G1, G2, H, I and J.

Where:
S/HC vol 

## = The steam-to-vent-gas ratio by weight, lb steam/lb vent gas. Q
s 

## = Total steam rate, scf/hr. (See Equation D.18 for data sets A, C, D, E, F, and H). Q CZ,HCi 

## = Volumetric flow rate of component i in combustion zone gas that is a

hydrocarbon, scf/hr. (See Equation D.15A or D.15B).This information is distributed solely for the purp ose of pre-dissemination peer review under applicab le information quality guidelines. It has not been formally disseminated by EPA. It does not repr esent and should not be construed to represent any Agency determination or policy.



## D-24 a
K %#t$ 

##  a
K

~ 

## a
K HHv6b



## a
K ~ 

##  l W@ 

## a
K

6b 

## 0 l W@ 

##  l Y 

## 5 Equations D.22 through D.25

The ratio of the net heating value of the combustion zone gas t o the net heating value of the flare vent gas if diluted to the lower flammability limit ( NHV ratio 

## ), was calculated using Equations D.22 through D.25.

Equations D.22 through D.25 were used for data sets A, C, D, E, F, G 1, G2, H and J.

Equation D.22:

Where:
NHV ratio 

## = The ratio of the net heating value of the combusti on zone gas to the net

heating value of the flare vent gas if diluted to the lo wer flammability
limit.

NHV CZ 

## = The net heating value of the combustion zone gas, BTU /scf (See Equation

D.23).
NHV LFL-VG 

## = The net heating value of the flare vent gas if dilute d to the lower

flammability limit, BTU/scf (See Equation D.24).

Equation D.23: The net heating value of the combustion zone gas is calculated by correcting the net heating value of the vent gas for the inclusion of steam in the combustion zone gas, as shown below.

Where:

NHV CZ 

## = The net heating value of the combustion zone gas, BTU /scf. Q vg 

## = Flare vent gas flow rate, scf/hr. (See Equation D.4 for data set A. See Equation

D.5 for data set C. See Equation D.6 for data sets E, H a nd J. See Equation D.7 for data set G1).

NHV VG 

## = Flare vent gas net heating value, BTU/scf (See Equati on D.1 for data set E). Q
s 

## = Total steam rate, scf/hr. (See Equation D.18 for data sets A, C, D, E, F, H and J).This information is distributed solely for the purp ose of pre-dissemination peer review under applicab le information quality guidelines. It has not been formally disseminated by EPA. It does not repr esent and should not be construed to represent any Agency determination or policy.



## D-25 a
K HHv6b 

##  a
K

W@ 

## A V/V W@ 

## Equations D.22 through D.25 (Continued)

Equations D.22 through D.25 were used for data sets A, C, D, E, F, G 1, G2, H and J.

Equation D.24: The net heating value of the flare vent gas if diluted to its lower flammability limit is calculated by multiplying the actual net heating value of the flare vent gas by its lower flammability limit, as
shown below.

Where:

NHV LFL-VG 

## = The net heating value of the flare vent gas if dilute d to the lower

flammability limit, BTU/scf.

NHV VG 

## = Flare vent gas net heating value, BTU/scf. (See Equa tion D. 1 for data set

E).

LFL vg 

## = Lower flammability limit of the flare vent gas adju sted for nitrogen

equivalency, volume fraction (See Equation D.25).

Equation D.25: This equation uses the Le Chatelier Principle with a nitrogen equivalency adjustment; it allows you to estimate the lower flammability limit of any mixture. For this particular analysis, the lower flammability limit of the flare vent gas is of interes t. The calculation uses the weighted average of the LFLs of the individual compounds (combustible and inert) weight ed by their volume percent of the flare vent gas. All inerts, including nitrogen, ar e assumed to have an infinite lower flammability limit (e.g., LFL N2 

## = ∞ ).



# ( )( ) ( )( )

2 2 2 2 

## 1 1 % 1

,

, 1 CO CO e O H O H e n

i i

i vg



## x N x N LFL LFL

− − − −         = 

# ∑

=



## Where:

LFL vg 

## = Lower flammability limit of the flare vent gas adju sted for nitrogen equivalency,

volume fraction

n = Number of individual combustible components in flare vent gas.
i = Individual combustible component in flare vent gas.
% i 

## = Percentage of combustible component i in flare vent gas, molar percent. (See

Table C-1 in Appendix C, most values are reported.)

LFL i 

## = Lower flammability limit of combustible component i in flare vent gas, volume

percent. Zabetakis M.G. “Flammability Characteristics of Combustible Gases and Vapors”, U.S. Bureau of Mines, Bulletin 627, 1965 was used to det ermine the lower flammability limit for each component in each t est run. Table D.1 lists these
values.
N e,H2O 

## = Coefficient of nitrogen equivalency for water relat ive to nitrogen, unitless (See

Equation D.29).

x H2O 

## = Reported concentration of water in flare vent gas, v olume fraction.
N e,CO2 

## = Coefficient of nitrogen equivalency for carbon dioxi de relative to nitrogen,

unitless (See Equation D.29).

x CO2 

## = Reported concentration of carbon dioxide in flare ve nt gas, volume fraction.This information is distributed solely for the purp ose of pre-dissemination peer review under applicab le information quality guidelines. It has not been formally disseminated by EPA. It does not repr esent and should not be construed to represent any Agency determination or policy.



## D-26 Table D.1 – Lower Flammability Limit of Select Compounds ( LFL i 

## ) – Flare Vent Gas

Compound LFL i 

## (vol %) Compound LFL i 

## (vol %) 1-Butene 1.8 Iso-Butylene 1.8 1,2-Butadiene 2 Methane 5 1,3-Butadiene 2 Methyl Acetylene 1.7 Acetylene 2.5 n-Butane 1.8 Benzene 1.3 Nitrogen ∞ Carbon Dioxide ∞ Oxygen ∞ Carbon Monoxide 12.5 Pentane Plus (C 5 

## +) 1.4 Cis-2-Butene 1.7 Propadiene 2.16 Cyclopropane 2.4 Propane 2.1 Ethane 3 Propylene 2.4 Ethyl Benzene 1 Toluene 1.2 Ethylene 2.7 Trans-2-Butene 1.7 Hydrogen 4 Water ∞ Hydrogen Sulfide 4 Xylenes 1.1

Iso-Butane 1.8This information is distributed solely for the purp ose of pre-dissemination peer review under applicab le information quality guidelines. It has not been formally disseminated by EPA. It does not repr esent and should not be construed to represent any Agency determination or policy.



## D-27 Equation D.26

The combustible components in the combustion zone (C CZ 

## ), in volume fraction, was calculated using Equation D.26.

This equation was used for data sets A, C, D, E, F, G1, G2, H and J

.



## ) ( 1

s vg vg

h n

i vg i

cz 

## Q

Q Q Q

C
+ +

     

= 

# ∑

= 

## χ χ



## Where:
C CZ 

## = Combustible components in the combustion zone ga s, volume fraction.

n = Number of individual combustible organic compone nts in flare vent gas.
i = Individual combustible organic component in flar e vent gas.

x i 

## = Concentration of combustible organic component i in flare vent gas, volume

fraction.

x h 

## = Concentration of hydrogen in flare vent gas, vol ume fraction. Q vg 

## = Flare vent gas flow rate, scf/hr. (See Equation D.4 for data set A. See Equation

D.5 for data set C. See Equation D.6 for data sets E, H and J. See Equation D.7 for data set G1.). Q
s 

## = Total steam flow, scf/hr. (See Equation D.18 for data sets A, C, D, E, F, H and J.).This information is distributed solely for the purp ose of pre-dissemination peer review under applicab le information quality guidelines. It has not been formally disseminated by EPA. It does not repr esent and should not be construed to represent any Agency determination or policy.



## D-28 Equations D.27 through D.29

The lower flammability limit of combustion zone gas adjusted for nitrogen equivalency ( LFL CZ 

## ), in volume fraction, was calculated using Equations D.27 thr ough D.29.



## Equations D.27 through D.29 were used for data sets A, C, D, E, F, G1, G2, H and J.

Equation D.27: This equation uses the Le Chatelier Principle with a nitrogen equivalency adjustment; it allows you to estimate the lower flammability limit of any mixture. For this particular analysis, the lower flammability limit of the combustion zone gas is of interest. The calculation uses the weighted average of the LFLs of the individual comp ounds (combustible and inert) weighted by their volume percent of the combustion zone gas. Al l inerts, including nitrogen, are assumed to have an infinite lower flammability limit (e.g., LF L N2 

## = ∞ 

## ).



# ( )( ) ( )( )

2 2 2 2 

## 1 1 % 1

,

, 1 CO CO e O H O H e n

i i

i cz



## x N x N LFL LFL

− − − −         = 

# ∑

=



## Where:
LFL CZ 

## = Lower flammability limit of combustion zone gas adjusted for nitrogen equivalency, volume fraction.

n = Number of components in combustion zone gas.
i = Individual component in combustion zone gas.
% i 

## = Percentage of component j in combustion zone gas, volume percentage. (See

Equation D.28).
LFL i 

## = Lower flammability limit of component j , volume percent. Zabetakis M.G.

“Flammability Characteristics of Combustible Gases and Vapors”, U.S. Bureau of Mines, Bulletin 627, 1965 was used to determine the lower flammability limit for each component in each test run. Table D.2 lists th ese values.
N e,H2O 

## = Coefficient of nitrogen equivalency for water re lative to nitrogen, unitless (See

Equation D.29).

x H2O 

## = Concentration of water in combustion zone gas, v olume fraction.
N e,CO2 

## = Coefficient of nitrogen equivalency for carbon d ioxide relative to nitrogen,

unitless (See Equation D.29).

x CO2 

## = Concentration of carbon dioxide in combustion zo ne gas, volume fraction.This information is distributed solely for the purp ose of pre-dissemination peer review under applicab le information quality guidelines. It has not been formally disseminated by EPA. It does not repr esent and should not be construed to represent any Agency determination or policy.



## D-29 % $ 

##  q l ~,$ 

## 0 l W@ 

##  l Y 

## 5 r A 100

Equations D.27 through D.29 (Continued)

The coefficients of nitrogen equivalency of water and carbon di oxide relative to nitrogen,
N e,H2O 

## and N e,CO2 

## , was calculated using Equation D.29.



## Equations D.27 through D.29 were used for data sets A, C, D, E, F, G1, G2, H and J.

Equation D.28:

Where:
% i 

## = Percentage of component i in combustion zone gas, volume percentage. Q CZ,i 

## = Volumetric flow rate of each flare vent gas comp onent i in combustion zone,

scf/hr. (See Equation D.15A for data sets C, D, E, F, GI, G2,H and J. See Equation D.15B for data set A). Q vg 

## = Flare vent gas flow rate, scf/hr. (See Equation D.4 for data set A. See Equation

D.5 for data set C. See Equation D.6 for data sets E, H and J. See Equation D.7 for data set G1.). Q
s 

## = Total steam rate, scf/hr. (See Equation D.18 for data sets A, C, D, E, F, H and J.).

Equation D.29:



# ∑ ∑

= 

## 

      

= n

i i

CZ i CZ

i k k e 

## Q

Q K N

1

, ,

, ,



## Where:
N e,k 

## = Coefficient of nitrogen equivalency for water o r carbon dioxide relative to

nitrogen, unitless. k = Individual inert component (i.e. water and carb on dioxide). n = Number of individual combustible components in flare vent gas. i = Individual combustible component in flare vent gas. K k,i 

## = Values for inert component k (i.e. water or carb on dioxide) for each combustible

component i in flare vent gas. Table D.3 lists thes e values. Q CZ,i 

## = Volumetric flow rate of each flare vent gas comp onent i in combustion zone,

scf/hr. (See Equation D.15A or D.15B).This information is distributed solely for the purp ose of pre-dissemination peer review under applicab le information quality guidelines. It has not been formally disseminated by EPA. It does not repr esent and should not be construed to represent any Agency determination or policy.



## D-30 Table D.2 – Lower Flammability Limit of Select Compounds (LF L i 

## ) –
Combustion Zone Gas

Compound LFL i 

## (vol %) Compound LFL i 

## (vol %)


## 1-Butene 1.8 Methane 5 1,2-Butadiene 2 Methyl Acetylene 1.7 1,3-Butadiene 2 n-Butane 1.8 Acetylene 2.5 Nitrogen ∞ 

## Benzene 1.3 Oxygen ∞ 

## Carbon Dioxide ∞ 

## Pentane Plus (C 5 

## +) 1.4 Carbon Monoxide 12.5 Propadiene 2.16 Cis-2-Butene 1.7 Propane 2.1 Cyclopropane 2.4 Propylene 2.4
Ethane 3 Toluene 1.2 Ethyl Benzene 1 Trans-2-Butene 1.7 Ethylene 2.7 Water ∞ 

## Hydrogen 4 Xylenes 1.1 Hydrogen Sulfide 4 Steam ∞ 

## Iso-Butane 1.8 Pilot Gas 5 Iso-Butylene 1.8

Table D.3 – Values for inert component k (i.e. water or ca rbon dioxide) for each combustible component i in flare vent gas

Combustible Component i in
Flare Vent Gas K Water 

## K Carbon

Dioxide 

## Methane 1.87 2.23
Ethane 1.40 1.87 Propane 1.51 1.93 Ethylene 1.68 1.84 Propylene 1.36 1.92 Hydrogen 1.35 1.51
All Other Combustibles 1.50 1.87This information is distributed solely for the purp ose of pre-dissemination peer review under applicab le information quality guidelines. It has not been formally disseminated by EPA. It does not repr esent and should not be construed to represent any Agency determination or policy.



## D-31 h

G$%



## h t$X



## h t$X 

##  c 8 h $ 

## :

f

$g 

## 8 O/

$ 

## :

O/ $ 

##  28.84 E a ,$



## 0.21 J

.k $ 

## Equations D.30 through D.37

For air-assisted flares, the stoichiometric ratio (SR) was calculated using Equations D.30 through D.37.



## Equations D.30 through D.32 were used for data sets C and J.

Equation D.30:

Where:
SR = Ratio of actual mass flow of total assist air to the theoretical stoichiometric mass

of air needed to combust the flare vent gas, unitle ss.

m Air 

## = Actual total assist air mass flow rate, lb/hr. ( See Equation D.34 for data set C).

m Stoic 

## = Theoretical stoichiometric mass of air needed to combust the flare vent gas, lb/hr

(See Equation D.31).

Equation D.31:

Where:

m Stoic 

## = Theoretical stoichiometric mass of air needed to combust the flare vent gas, lb/hr.

n = Number of individual combustible components in f lare vent gas.
i = Individual combustible component in flare vent g as.

m i 

## = Reported mass flow rate of combustible component i in the flare vent gas, lb/hr.

(See Equation D.35 for data set C).
AF i 

## = Stoichiometric air to fuel ratio of combustible com ponent i , lb of air/lb of combustible component i (See Equation D.32).

Equation D.32:

Where:
AF i 

## = Stoichiometric air to fuel ratio of combustible component i, lb of air/lb of

combustible component i.
N O2,i 

## = Stoichiometric amount of oxygen needed for one m ole of combustible component
i , moles (See Equation D.33).
i = Individual combustible component in flare vent g as. MWi = Molecular weight of combustible component i in the flare vent gas, lb/lb-mole.
28.84 = Constant, molecular weight of ambient air, lb/lb -mole.
0.21 = Constant, fraction of ambient air comprised of o xygen.This information is distributed solely for the purp ose of pre-dissemination peer review under applicab le information quality guidelines. It has not been formally disseminated by EPA. It does not repr esent and should not be construed to represent any Agency determination or policy.



## D-32 h #$% 

##  l #$% %si%tsu 

## A 60 A 0.07517

h $ 

##  .k

$ 

## A E l $ 

## 379.48 J Equations D.30 through D.37 (Continued)



## Equation D.33: This equation was used for data sets C and J.



## 4 ,

, ,2 i

H

i C i O 

## N N N + =

Where:
N O2,i 

## = Stoichiometric amount of oxygen needed for one m ole of combustible component i, moles. i = Individual combustible component in flare vent gas. N C,i 

## = Number of carbon atoms per molecule of combustib le hydrocarbon i.
N H,i 

## = Number of hydrogen atoms per molecule of combust ible hydrocarbon i.
4 = Constant.

Equation D.34: This equation was used for data set C.

Where:

m air 

## = Actual total assist air mass flow rate, lb/hr. Q air,reported 

## = Reported air assist flow rate, scf/min. 60 = Constant, min/hr.
0.07517 = Constant, assumed density of air, lb/scf.

Equation D.35: This equation was used for data set C.

Where:

m i 

## = Mass flow rate of combustible component i in the flare vent gas, lb/hr.
i = Individual flare vent gas component in combustio n zone. MW vg 

## = Molecular weight of combustible component (i.e., propane) in the flare vent gas,

lb/lb-mole. Q i 

## = Volumetric flow rate of each flare vent gas comp onent i , scf/hr. (See Equation

D.36).
379.48 = Constant, lb-mole/scf at dry standard conditions

.This information is distributed solely for the purp ose of pre-dissemination peer review under applicab le information quality guidelines. It has not been formally disseminated by EPA. It does not repr esent and should not be construed to represent any Agency determination or policy.



## D-33 l $ 

##  l W@ 

## E % W@,$



## 100 J

l W@ 

##  K

W@ 

## A 60 A 60 E 1.77

144 J Equations D.30 through D.37 (Continued)



## Equation D.36: This equation was used for data set C.

Where: Q i 

## = Volumetric flow rate of each flare vent gas comp onent i (i.e., propane or

nitrogen), scf/hr.
i = Individual component in flare vent gas (i.e., pr opane or nitrogen). Q vg 

## = Flare vent gas flow rate, scf/hr. (See Equation D.37).
% ,i 

## = Percentage of component i (i.e., propane or nitrogen) in flare vent gas, mol ar

percentage. % p 

## = Reported percentage of propane in flare vent gas (i.e., %Propane in Nitrogen),

molar percentage.
% N 

## = Percentage of nitrogen in flare vent gas, molar p ercentage. (See Equation D.13).
100 = Constant, percentage.

Equation D.37: This equation was used for data set C.

Where: Q vg 

## = Flare vent gas flow rate, scf/hr.
V vg 

## = Reported flare vent gas velocity, ft/s.
60 = Constant, s/min.
60 = Constant, min/hr.
1.77 = Constant, area of fuel exit port, in 2



## . 144 = Constant, ft 2 

## /in 2



## .This information is distributed solely for the purp ose of pre-dissemination peer review under applicab le information quality guidelines. It has not been formally disseminated by EPA. It does not repr esent and should not be construed to represent any Agency determination or policy.



## D-34 h W@,Y 

##  h W@ 

##  h X



## [ W@vY 

##  q h W@vY



## l W@ 

##  l X 

## r Equations D.38 through D.41

The calculated momentum flux ratio (MFR) was calculated usi ng Equations D.38 through
D.41.



## Equation D.38: This equation was used for data sets A, D, E, F, G1 , G2, and J.

Where:

m vg,s 

## = Flare vent gas flow rate including center steam, lb/hr.

m vg 

## = Flare vent gas flow rate, lb/hr. (See Equation D .2 for data set A. See Equation D.3

for data set C).

m c 

## = Center steam rate, lb/hr. Center steam rate was a reported constant value f or data sets F, G1 and G2.

Equation D.39: This equation was used for data sets A, D, E, F, G1 , G2, and J.

Where:

[ vg-s 

## = Density of flare vent gas including center steam , lb/scf.

m vg,s 

## = Flare vent gas flow rate including center steam, lb/hr. Q vg 

## = Flare vent gas flow rate, scf/hr. Q
c 

## = Center steam rate, scf/hr. (See Equation D.18 fo r data sets F, G1 and G2).This information is distributed solely for the purp ose of pre-dissemination peer review under applicab le information quality guidelines. It has not been formally disseminated by EPA. It does not repr esent and should not be construed to represent any Agency determination or policy.



## D-35 K $fu 

##  K

$f@,%si%tsu 

## A 5280

60 A 60

./ q [ W@vY 

## A K W@vY 



## 0.07492 A 8 K

$fu 

## :  

## r Equations D.38 through D.41 (Continued)



## Equation D.40: This equation was used for data sets D, F, G1, G2, and J.

Where:
V wind 

## = Wind velocity, ft/s.
V wind, reported 

## = Reported wind velocity, mph. 5280 = Constant, ft/mile. 60 = Constant, s/min. 60 = Constant, min/hr.

Equation D.41: This equation was used for data sets A, D, E, F, G1 , G2, and J.

Where: MRF = Calculated momentum flux ratio, unitless.

[ vg-s 

## = Density of flare vent gas including center stea m, lb/scf. (See Equation

D.39).
V vg-s 

## = Flare vent gas velocity with center steam, ft/s. (If not reported, see

Equation D.8C).
V wind 

## = Wind velocity, ft/s. (See Equation D.40). 0.07492 = Constant, assumed density of air, lb/scf.This information is distributed solely for the purp ose of pre-dissemination peer review under applicab le information quality guidelines. It has not been formally disseminated by EPA. It does not repr esent and should not be construed to represent any Agency determination or policy.



## D-36   

## /M/  

##  K

W@vY 

## M A Z x
12 \ Equations D.42 through D.45

The shore equation analysis was performed using Equations D.42 through D.45.



## These equations were used for data sets A, C, D, E, F, G1, G2, and J.

Equation D.42:

Where:
  

## /M/  

## = Shore Equation Velocity-Jet Periphery, sec -1



## . V vg-s 

## = Flare vent gas velocity with center steam, ft/s. (If not reported, see

Equation D.8C).

M 

## = Constant pi used to calculate area of flare ti p. d = Reported effective diameter of flare tip, in. ( See tip sizes identified in

Section 2.0 of report).
12 = Constant, in/ft.This information is distributed solely for the purp ose of pre-dissemination peer review under applicab le information quality guidelines. It has not been formally disseminated by EPA. It does not repr esent and should not be construed to represent any Agency determination or policy.



## D-37 Equations D.42 through D.45 (Continued)



## Equation D.43: This equation uses the Le Chatelier Principle with a nitrogen equivalency adjustment; it allows you to estimate the lower flammability limit of any mixture. For this particular analysis, the lower flammability limit of the flare vent gas incl uding center steam is of interest. The calculation uses the weighted average of the LFLs o f the individual compounds (combustible and inert) weighted by their volume percent of the flar e vent gas plus center steam. All inerts, including nitrogen, are assumed to have an infinite lower flammability limit (e.g., LFL N2 

## = ∞ 

## ).



# ( )( ) ( )( )

2 2 2 2 

## 1 1 1

, , 1 , CO CO e O H O H e n

i i i

vgcs vgcs



## x N x N LFL X LFL

− − − −         = 

# ∑

=



## Where:

LFL vgcs 

## = Lower flammability limit of the flare vent gas i ncluding center steam adjusted for nitrogen equivalency, volume fraction.

n = Number of individual combustible components in f lare vent gas.
i = Individual combustible component in flare vent g as. X vgcs,i 

## = Concentration of combustible component i in the flare vent gas and center steam mixture, volume fraction. (See Equation D.16C).

LFL i 

## = Lower flammability limit of combustible componen t i in flare vent gas, volume

percent. Zabetakis M.G. “Flammability Characteristi cs of Combustible Gases and Vapors”, U.S. Bureau of Mines, Bulletin 627, 1965 w as used to determine the lower flammability limit for each component in each test run. Table D.4 lists these
values.
N e,H2O 

## = Coefficient of nitrogen equivalency for water re lative to nitrogen, unitless. (See

Equation D.29).

x H2O 

## = Reported concentration of water in flare vent ga s, volume fraction.
N e,CO2 

## = Coefficient of nitrogen equivalency for carbon d ioxide relative to nitrogen,

unitless. (See Equation D.29).

x CO2 

## = Reported concentration of carbon dioxide in flar e vent gas, volume fraction.This information is distributed solely for the purp ose of pre-dissemination peer review under applicab le information quality guidelines. It has not been formally disseminated by EPA. It does not repr esent and should not be construed to represent any Agency determination or policy.



## D-38 Table D.4 – Lower Flammability Limit of Select Compounds ( LFL i 

## ) – Flare Vent Gas

Compound LFL i 

## (vol %) Compound LFL i 

## (vol %) 

## 1-Butene 1.8 Iso-Butylene 1.8 1,2-Butadiene 2 Methane 5 1,3-Butadiene 2 Methyl Acetylene 1.7 Acetylene 2.5 n-Butane 1.8 Benzene 1.3 Nitrogen ∞ 

## Carbon Dioxide ∞ 

## Oxygen ∞ 

## Carbon Monoxide 12.5 Pentane Plus (C 5 

## +) 1.4 Cis-2-Butene 1.7 Propadiene 2.16 Cyclopropane 2.4 Propane 2.1 Ethane 3 Propylene 2.4 Ethyl Benzene 1 Toluene 1.2 Ethylene 2.7 Trans-2-Butene 1.7 Hydrogen 4 Water ∞ 

## Hydrogen Sulfide 4 Xylenes 1.1

Iso-Butane 1.8This information is distributed solely for the purp ose of pre-dissemination peer review under applicab le information quality guidelines. It has not been formally disseminated by EPA. It does not repr esent and should not be construed to represent any Agency determination or policy.



## D-39G 

##  q 100 U 0 V/V W@XY 

## A 100 5

V/V W@XY 

## A 100 r Z [ W@XY



## 0.07492 \

K G 

##  Q w R

2M A 

M 4 A Z x
12 \ 



## M _ z ` A E G 

## 6.85 J + 

## Equations D.42 through D.45 (Continued)

The shore equation analysis was performed using Equations D.42 through D.45.



## These equations were used for data sets A, C, D, E, F, G1, G2, and J.

Equation D.44:

Where:

G 

## = Shore Equation, lb flare vent gas including cent er steam / lb of air.

LFL vgcs 

## = Lower flammability limit of the flare vent gas in cluding center steam

adjusted for nitrogen equivalency, volume fraction. (See Equation D.43). 100 = Constant, percentage.

[ vgcs 

## = Density of flare vent gas including center stea m, lb/scf. (See Equation

D.39). 0.07492 = Constant, assumed density of air, lb/scf.

Equation D.45:

Where:
K G 

## = Maximum allowable flare vent gas velocity inclu ding center steam, ft/s.

G 

## = Shore Equation, lb flare vent gas including cen ter steam / lb of air. (See

Equation D.44).

M 

## = Constant pi used to calculate area of flare ti p. d = Reported effective diameter of flare tip, in ( See tip sizes identified in

Section 2.0 of report). 12 = Constant, in/ft. 6.85 = Empirical constant, may contain elements of viscosity and other transport

properties of the gas and air.This information is distributed solely for the purp ose of pre-dissemination peer review under applicab le information quality guidelines. It has not been formally disseminated by EPA. It does not repr esent and should not be construed to represent any Agency determination or policy.



# Appendix E

Type And Amount Of Components In Each Test Run By Test Re port.This information is distributed solely for the purpose of pre-dissemination peer review under applicable information quality guidelines. It has not beenformally disseminated by EPA. It does notrepresent and should not be construed to representany Agency determination or policy.E-1

100.0% 99.9% 99.5% 99.9% 99.8% 99.7% 99.8% 99.8% 95.1% 99.3% 99.5% 98.7% 99.7% 99.9% 99.9% 82.2% 99.4% 97.9% 99.7% 99.6%0%10%20%30%40%50%60%70%80%90%100%1 5 11a 11b 11c 16a 16b 17 59a 59b 50 51 56 57 60 61 202 203 205 206EPA-600 2-83-052 and EPA-600 2-85-106PropanePropyleneSteamNitrogenThis information is distributed solely for the purpose of pre-dissemination peer review under applicable information quality guidelines. It has not beenformally disseminated by EPA. It does notrepresent and should not be construed to representany Agency determination or policy.E-2

99.5% 99.5% 97.5% 96.3% 94.8% 89.7% 92.6% 85.9% 82.8% 98.4% 99.0% 97.7% 97.4% 92.7% 93.9% 97.1% 89.2% 99.1% 99.0% 99.4% 99.7% 99.1% 97.8% 95.8% 92.5% 88.2% 91.7% 97.7% 98.9% 96.6% 98.3% 91.3% 84.5% 92.7% 87.9%0%10%20%30%40%50%60%70%80%90%100% A 2.0 (1) A 2.0 (2) A 3.0 (1) A 3.0 (2) A 4.0 (1) A 4.0 (2) A 4.0 (3) A 5.0 (1) A 5.0 (2) B 1.0 (1) B 1.0 (2) B 2.0 (1) B 2.0 (2) B 2.5 (1) B 2.5 (2) B 2.5 (3) B 3.5 (1) C 1.0 (1) C 1.0 (2) C 1.0 (3) C 1.0 (4) C 2.0 (1) C 2.0 (2) C 3.0 (1) C 3.0 (2) C 3.7 (1) C 3.7 (2) D 2.0 (1) D 2.0 (2) D 3.0 (1) D 3.0 (2) D 4.0 (1) D 4.0 (2) D 4.0 (3) D 4.3 (1)Flint Hills Resources (AU)1,3-ButadieneEthanePentane Plus (C5+)EthylenePropaneHydrogenPropyleneMethaneOtherIso-ButaneSteamNitrogenThis information is distributed solely for the purpose of pre-dissemination peer review under applicable information quality guidelines. It has not beenformally disseminated by EPA. It does notrepresent and should not be construed to representany Agency determination or policy.E-3

95.9% 98.6% 98.6% 97.2% 99.1% 96.5% 98.6% 95.5% 96.5% 88.6% 95.1% 78.7% 97.5% 99.2% 98.8% 98.4% 99.4% 98.7% 99.3% 98.3% 98.7% 96.8% 97.5% 92.0% 95.0% 89.0% 92.8% 88.4% 99.3% 98.8% 98.7% 98.9% 97.8% 95.8% 94.7% 89.8% 89.8% 89.3% 86.8% 85.0%0%10%20%30%40%50%60%70%80%90%100% A 2.0 (1) A 2.0 (2) A 2.0 (3) A 3.0 (1) A 3.0 (2) A 4.0 (1) A 4.0 (2) A 5.0 (1) A 5.0 (2) A 6.0 (1) A 6.0 (2) A 8.5 (1) A MIN (1) A MIN (2) A MIN (3) B 1.0 (1) B 1.0 (2) B 2.0 (1) B 2.0 (2) B 3.0 (1) B 3.0 (2) B 4.0 (1) B 4.0 (2) B 5.0 (1) B 5.0 (2) B 5.7 (1) B 5.7 (2) B 6.4 (2) C 1.0 (1) C 1.0 (2) C 2.0 (1) C 2.0 (2) C 3.0 (1) C 3.0 (2) C 4.0 (1) C 4.0 (2) C 5.0 (1) C 5.0 (2) C 5.5 (1) C 5.5 (2)Flint Hills Resources (LOU)1,3-ButadieneEthanePentane Plus (C5+)EthylenePropaneHydrogenPropyleneMethaneOtherIso-ButaneSteamNitrogenThis information is distributed solely for the purpose of pre-dissemination peer review under applicable information quality guidelines. It has not beenformally disseminated by EPA. It does notrepresent and should not be construed to representany Agency determination or policy.E-4

86.2% 31.8% 75.5% 97.8% 84.9% 97.0% 99.0% 95.9% 99.3% 99.1% 99.5% 95.8% 97.2% 88.3% 93.6% 94.5% 93.2% 99.3% 93.8% 98.9% 99.2%0%10%20%30%40%50%60%70%80%90%100%1 1A 1B 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 17A 18INEOS1,3-ButadieneMethaneSteamNitrogenThis information is distributed solely for the purpose of pre-dissemination peer review under applicable information quality guidelines. It has not beenformally disseminated by EPA. It does notrepresent and should not be construed to representany Agency determination or policy.E-5

99.0% 98.8% 97.7% 98.5% 98.0% 98.6% 96.9% 97.7% 95.2% 96.7% 95.2% 92.0% 95.2% 81.3% 88.7% 98.9% 98.4% 99.1% 98.3% 99.3% 98.2% 99.2% 96.7% 98.6% 94.6% 96.9% 99.4% 98.4% 99.1% 96.8% 97.4% 92.7% 93.7% 93.1% 91.5% 94.6% 97.5% 88.6% 91.6% 98.4% 83.5% 96.2% 98.6% 81.8% 91.6% 88.3% 93.5% 97.2% 89.7% 96.2% 98.9% 98.9% 99.1% 99.3% 98.7%0%10%20%30%40%50%60%70%80%90%100% A 1

- 1 A 1

- 2 A 2

- 1 A 2

- 2 A 3

- 1 A 3

- 2 A 4

- 1 A 4

- 2 A 5

- 1 A 6

- 2 A 7

- 1 A 8

- 1 A 8

- 3 A 9

- 1 A 9

- 3 B 1

- 1 B 2

- 1 B 2

- 2 B 3

- 1 B 3

- 2 B 4

- 1 B 4

- 2 B 6

- 1 B 6

- 2 B 8

- 1 B 8

- 2 C 1

- 2 C 2

- 1 C 2

- 2 C 3

- 1 C 3

- 2 C 4

- 1 C 4

- 2 C 5

- 1 C 5

- 2 D 2

- 1 D 3

- 1 D 4

- 1 D 5

- 1 D 6

- 1 D 7

- 1 D 8

- 1 D 9

- 1 D 10

- 1 E 1

- 1 E 2

- 1 E 3

- 1 E 5

- 1 E 6

- 1 E 7

- 1 LTS 1 LTS 4 LTS 5 LTS 7 LTS 8MPC Detroit1,3-ButadieneEthanePentane Plus (C5+)EthylenePropaneHydrogenPropyleneMethaneOtherIso-ButaneSteamNitrogenThis information is distributed solely for the purpose of pre-dissemination peer review under applicable information quality guidelines. It has not beenformally disseminated by EPA. It does notrepresent and should not be construed to representany Agency determination or policy.E-6

95.6% 97.4% 96.7% 97.8% 95.5% 93.8% 92.5% 87.0% 81.2% 74.4% 76.6% 67.9% 61.6% 61.9% 93.7% 89.6% 99.3% 98.7% 99.0% 98.4% 98.5% 97.8% 97.9% 97.6% 95.8% 97.6% 89.1% 96.7% 98.9% 99.2% 98.4% 98.2% 96.0% 98.6% 98.3% 98.1% 97.7% 96.8% 97.5% 99.3% 99.0% 98.7% 97.2% 99.4%0%10%20%30%40%50%60%70%80%90%100% A11 2

- 1 A11 2

- 2 A113

- 1 A113

- 2 A114

- 1 A115

- 1 A116

- 1 A117

- 1 A118

- 1 A119

- 1 A1110

- 1 A1111

- 1 A1112

- 1 A1113

- 1 A19 4

- 1 A19 7

- 1 B 4-2 B 5

- 1 B 5

- 2 B 6

- 1 B 6

- 2 B 7

- 1 B 7

- 2 B 8

- 1 B 8

- 2 B 9

- 1 B 9

- 2 B 10

- 2 C 3

- 1 C 3

- 2 D4

- 1 D4

- 2 D7

- 2 E 3

- 1 E 3-3 E 4

- 1 E 4-3 E 5

- 1 E 5

- 2 LTS 2

- 2 LTS 2

- 3 LTS 2

- 4 LTS 2

- 6 LTS 2

- 5MPC TX1,3-ButadieneEthanePentane Plus (C5+)EthylenePropaneHydrogenPropyleneMethaneOtherIso-ButaneSteamNitrogenThis information is distributed solely for the purpose of pre-dissemination peer review under applicable information quality guidelines. It has not beenformally disseminated by EPA. It does notrepresent and should not be construed to representany Agency determination or policy.E-7

96.9% 97.5% 97.3% 98.6% 99.0% 97.3% 79.8% 98.7% 98.9% 97.5% 57.1% 98.8% 98.0% 90.4% 95.7% 99.7% 99.3% 94.1% 90.9% 99.3% 98.0% 98.0% 87.9% 95.9% 98.8% 99.2%0%10%20%30%40%50%60%70%80%90%100% 4

- 13, 12:51

- 13:11 3

- 30, 10:40

- 11:30 3

- 30, 9:55

- 10:38 4/1 08:48

- 09:16 4/1 09:17

- 09:46 4

- 6, 10:00

- 10:16 4

- 6, 10:43

- 10:53 4

- 6, 11:16

- 11:24 4

- 6, 11:32

- 11:49 4

- 6, 11:50

- 11:58 4

- 6,10:17

- 10:42 3

- 22, 17:14

- 17:38 3

- 22, 17:39

- 19:16 3

- 22, 19:17

- 20:08 3

- 22, 20:09

- 20:39 3

- 24, 14:08

- 14:18 3

- 24, 14:26

- 14:35 3

- 24, 16:20

- 16:31 3

- 24, 16:41

- 16:52 3

- 24, 16:56

- 17:07 3

- 24.15:47

- 15:58 3

- 24.16:01

- 16:11 3

- 25, 10:02

- 10:16 3

- 25, 10:20

- 10:32 3

- 25, 11:28

- 11:37 3

- 25, 15:55

- 16:16ABBBBBBBBBBCCCCCCCCCCCCCCCShell Deer Park (EPF)EthanePentane Plus (C5+)EthylenePropaneHydrogenPropyleneMethaneOtherIso-ButaneSteamNitrogenThis information is distributed solely for the purpose of pre-dissemination peer review under applicable information quality guidelines. It has not beenformally disseminated by EPA. It does notrepresent and should not be construed to representany Agency determination or policy.E-8

99.9% 99.9% 99.8% 98.5% 94.7% 94.7% 94.9% 92.9% 84.7% 95.4% 93.9% 91.7% 82.7% 98.5% 96.6% 88.3% 48.4% 98.4% 97.8% 93.9% 71.3% 90.9% 99.1% 94.0% 99.4% 45.8% 83.5% 23.5% 88.0% 96.7% 99.1% 98.5% 94.4% 65.3% 48.6% 97.7% 11.6% 97.2% 92.6% 96.1% 86.5% 78.4% 70.0% 95.8% 48.1% 85.2% 66.8% 90.2% 92.9% 98.9% 64.3% 96.4% 83.1% 98.7% 90.3% 93.9% 86.7% 75.7% 38.6% 66.5% 95.5% 95.1% 93.3% 86.5% 90.6% 86.5% 92.2% 89.5% 84.9% 76.6% 70.8%0%10%20%30%40%50%60%70%80%90%100% S1.5 ,1 S1.6 ,1 S1.7 ,1 S1.8 ,1 S1.9 ,1 S10.1 ,1 S10.2 ,1 S10.3 ,1 S10.4,1 S11.1,1 S11.2,1 S11.3,1 S11.4,1 S12.1,Averages S12.2,Averages S12.3,Averages S12.4,1 S13.1,1 S13.2,1 S13.3,1 S13.4,Averages S13.5,1 S14.1,1 S14.4,1 S2.1,Averages S2.2,Averages S2.3,Averages S3.1,1 S3.2,2 S3.5,Averages S3.6,1 S3.7,1 S4.1,Averages S4.10,1 S4.11,1 S4.2,Averages S4.3,Averages S4.4,1 S4.5,1 S4.6,1 S4.7,1 S4.8,1 S4.9,1 S5.1,Averages S5.2,1 S5.3,Averages S5.4,Averages S5.5,1 S5.6,Averages S6.1,Averages S6.2,Averages S6.3,Averages S6.4,Averages S6.5,1 S6.6,1 S7.1,Averages S7.2,Averages S7.3,Averages S7.4,1 S7.5,1 S7.6,1 S8.1,1 S8.2,1 S8.3,1 S8.4,1 S8.5,1 S9.1,1 S9.2,1 S9.3,1 S9.4,1 S9.5,1TCEQPropanePropyleneMethaneSteamNitrogenThis information is distributed solely for the purp ose of pre-dissemination peer review under applicab le information quality guidelines. It has not been formally disseminated by EPA. It does not represent and should not be construed to represent any Agenc y determination or policy.



# Appendix F

Charts Of Calculated And Measured LFL For Various Combusti ble Gases

In Nitrogen And Carbon DioxideThis information is distributed solely for the purp ose of pre-dissemination peer review under applicab le information quality guidelines. It has not been formally disseminated by EPA. It does not repr esent and should not be construed to represent any Agency determination or policy.



## F-1 0% 10% 20% 30% 40% 50% 60% 70% 80%

0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%Lower Flammability Limit of the Mixture (%)

Inert in the Mixture (%) 

### Hydrogen and Nitrogen

Calculated using Le Chatelier Equation assuming an LFL for Nitrogen of Infinity

Experimental Data (Jones and Kennedy, 1932)

0% 10% 20% 30% 40% 50% 60% 70% 80%

0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%Lower Flammability Limit of the Mixture (%)

Inert in the Mixture (%) 

### Hydrogen and Carbon Dioxide

Calculated using Le Chatelier Equation with no equi valency adjustment and assuming an LFL for Inert of Infinit y

Calculated using Le Chatelier Equation adjusting CO 2 for Nitrogen equivalency and assuming and LFL for Nitrogen of In finity

Experimental Data (Jones, 1929)This information is distributed solely for the purp ose of pre-dissemination peer review under applicab le information quality guidelines. It has not been formally disseminated by EPA. It does not repr esent and should not be construed to represent any Agency determination or policy.



## F-2 0% 5% 10% 15% 20% 25% 30% 35% 40% 45% 50%

0% 10% 20% 30% 40% 50% 60% 70% 80% 90%Lower Flammability Limit of the Mixture (%)

Inert in the Mixture (%) 

### Methane and Nitrogen

Calculated using Le Chatelier Equation assuming an LFL for Nitrogen of Infinity

Experimental Data (Jones and Kennedy, 1933)

Experimental Data (Kondo et al., 2006a)

Experimental Data - (Vidal et al., 2006)

Pure component LFL at 5.0 for Jones and Kennedy (193 3) and Vidal et al. (2006) experiments, but 4.9 for Kondo et al. (2006a) experiments.

0% 5% 10% 15% 20% 25% 30% 35% 40% 45% 50%

0% 10% 20% 30% 40% 50% 60% 70% 80% 90%Lower Flammability Limit of the Mixture (%)

Inert in the Mixture (%) 

### Methane and Carbon Dioxide

Calculated using Le Chatelier Equation with no equi valency adjustment and assuming an LFL for Inert of Infinit y

Calculated using Le Chatelier Equation adjusting CO 2 for Nitrogen equivalency and assuming and LFL for Nitrogen of In finity

Experimental Data (Jones and Kennedy, 1933)

Experimental Data (Kondo et al., 2006b)

Experimental Data (Vidal et al., 2006)

Pure component LFL at 5.0 for Jones and Kennedy (193 3) and Vidal et al. (2006) experiments, but 4.9 for Kondo et al. (2006b) experiments.This information is distributed solely for the purp ose of pre-dissemination peer review under applicab le information quality guidelines. It has not been formally disseminated by EPA. It does not repr esent and should not be construed to represent any Agency determination or policy.



## F-3 0% 5% 10% 15% 20% 25% 30% 35% 40% 45% 50%

0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%Lower Flammability Limit of the Mixture (%)

Inert in the Mixture (%) 

### Ethane and Nitrogen

Calculated using Le Chatelier Equation assuming an LFL for Nitrogen of Infinity

Experimental Data (Jones and Kennedy, 1933)

0% 5% 10% 15% 20% 25% 30% 35% 40% 45% 50%

0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%Lower Flammability Limit of the Mixture (%)

Inert in the Mixture (%) 

### Ethane and Carbon Dioxide

Calculated using Le Chatelier Equation with no equi valency adjustment and assuming an LFL for Inert of Infinit y

Calculated using Le Chatelier Equation adjusting CO 2 for Nitrogen equivalency and assuming and LFL for Nitrogen of In finity

Experimental Data (Jones and Kennedy, 1933)This information is distributed solely for the purp ose of pre-dissemination peer review under applicab le information quality guidelines. It has not been formally disseminated by EPA. It does not repr esent and should not be construed to represent any Agency determination or policy.



## F-4 0% 10% 20% 30% 40% 50% 60%

0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%Lower Flammability Limit of the Mixture (%)

Inert in the Mixture (%) 

### Ethylene and Nitrogen

Calculated using Le Chatelier Equation assuming an LFL for Nitrogen of Infinity

Experimental Data (Kondo et al., 2006a)

0% 10% 20% 30% 40% 50% 60%

0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%Lower Flammability Limit of the Mixture (%)

Inert in the Mixture (%) 

### Ethylene and Carbon Dioxide

Calculated using Le Chatelier Equation with no equi valency adjustment and assuming an LFL for Inert of Infinit y
Calculated using Le Chatelier Equation adjusting CO 2 for Nitrogen equivalency and assuming and LFL for Nitrogen of In finity

Experimental Data (Kondo et al., 2006b)

Experimental Data (Vidal et al., 2006)

Pure component LFL at 2.74 for Kondo et al. (2006b) experiments, but 2.70 for Vidal et al. (2006) experiments.This information is distributed solely for the purp ose of pre-dissemination peer review under applicab le information quality guidelines. It has not been formally disseminated by EPA. It does not repr esent and should not be construed to represent any Agency determination or policy.



## F-5 0% 5% 10% 15% 20% 25% 30% 35% 40% 45% 50%

0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%Lower Flammability Limit of the Mixture (%)

Inert in the Mixture (%) 

### Propane and Nitrogen

Calculation using Le Chatelier Equation assuming an LFL for Nitrogen of Infinity

Experimental Data (Jones and Kennedy, 1933)

Experimental Data (Kondo et al., 2006a)

Pure component LFL at 2.3 for Jones and Kennedy (193 3) experiments, but 2.03 for Kondo et al. (2006a) expe riments.

0% 5% 10% 15% 20% 25% 30% 35% 40% 45% 50%

0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%Lower Flammability Limit of the Mixture (%)

Inert in the Mixture (%) 

### Propane and Carbon Dioxide

Calculated using Le Chatelier Equation with no equi valency adjustment and assuming an LFL for Inert of Infinit y

Calculated using Le Chatelier Equation adjusting CO 2 for Nitrogen equivalency and assuming and LFL for Nitrogen of In finity

Experimental Data (Jones and Kennedy, 1933)

Experimental Data (Kondo et al., 2006b)

Pure component LFL at 2.3 for Jones and Kennedy (193 3) experiments, but 2.03 for Kondo et al. (2006b) expe riments.This information is distributed solely for the purp ose of pre-dissemination peer review under applicab le information quality guidelines. It has not been formally disseminated by EPA. It does not repr esent and should not be construed to represent any Agency determination or policy.



## F-6 0% 5% 10% 15% 20% 25% 30% 35% 40% 45% 50%

0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%Lower Flammability Limit of the Mixture (%)

Inert in the Mixture (%) 

### Propylene and Nitrogen

Calculated using Le Chatelier Equation assuming an LFL for Nitrogen of Infinity

Experimental Data (Jones and Kennedy, 1938)

Experimental Data (Kondo et al., 200ba)

Pure component LFL at 2.4 for Jones and Kennedy (193 8) experiments, but 2.16 for Kondo et al. (2006a) expe riments.

0% 5% 10% 15% 20% 25% 30% 35% 40% 45% 50%

0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%Lower Flammability Limit of the Mixture (%)

Inert in the Mixture (%) 

### Propylene and Carbon Dioxide

Calculated using Le Chatelier Equation with no equi valency adjustment and assuming an LFL for Inert of Infinit y

Calculated using Le Chatelier Equation adjusting CO 2 for Nitrogen equivalency and assuming and LFL for Nitrogen of In finity

Experimental Data (Jones and Kennedy, 1938)

Experimental Data (Kondo et al., 2006b)

Pure component LFL at 2.4 for Jones and Kennedy (193 8) experiments, but 2.16 for Kondo et al. (2006b) expe riments.This information is distributed solely for the purp ose of pre-dissemination peer review under applicab le information quality guidelines. It has not been formally disseminated by EPA. It does not repr esent and should not be construed to represent any Agency determination or policy.



## F-7 0% 5% 10% 15% 20% 25% 30% 35% 40% 45%

0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%Lower Flammability Limit of the Mixture (%)

Inert in the Mixture (%) 

### Butane and Nitrogen

Calculated using Le Chatelier Equation assuming an LFL for Nitrogen of Infinity

Experimental Data (Jones and Kennedy, 1933)

0% 5% 10% 15% 20% 25% 30% 35% 40% 45%

0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%Lower Flammability Limit of the Mixture (%)

Inert in the Mixture (%) 

### Butane and Carbon Dioxide

Calculated using Le Chatelier Equation with no equi valency adjustment and assuming an LFL for Inert of Infinit y

Calculated using Le Chatelier Equation adjusting CO 2 for Nitrogen equivalency and assuming and LFL for Nitrogen of In finity

Experimental Data (Jones and Kennedy, 1933)This information is distributed solely for the purp ose of pre-dissemination peer review under applicab le information quality guidelines. It has not been formally disseminated by EPA. It does not repr esent and should not be construed to represent any Agency determination or policy.



## F-8 0% 5% 10% 15% 20% 25% 30% 35% 40% 45% 50%

0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%Lower Flammability Limit of the Mixture (%)

Inert in the Mixture (%) 

### 1,3 Butadiene and Nitrogen

Calculated using Le Chatelier Equation assuming an LFL for Nitrogen of Infinity

Experimental Data (Jones and Kennedy, 1943)

0% 5% 10% 15% 20% 25% 30% 35% 40% 45% 50%

0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%Lower Flammability Limit of the Mixture (%)

Inert in the Mixture (%) 

### 1, 3 Butadiene and Carbon Dioxide

Calculated using Le Chatelier Equation with no equi valency adjustment and assuming an LFL for Inert of Infinit y

Calculated using Le Chatelier Equation adjusting CO 2 for Nitrogen equivalency and assuming and LFL for Nitrogen of In finity

Experimental Data (Jones and Kennedy, 1943)This information is distributed solely for the purp ose of pre-dissemination peer review under applicab le information quality guidelines. It has not been formally disseminated by EPA. It does not repr esent and should not be construed to represent any Agency determination or policy.



## F-9 0% 10% 20% 30% 40% 50% 60% 70% 80%

0% 10% 20% 30% 40% 50% 60% 70% 80% 90%Lower Flammability Limit of the Mixture (%)

Inert in the Mixture (%) 

### Carbon Monoxide and Nitrogen

Calculated using Le Chatelier Equation assuming an LFL for Nitrogen of Infinity

Experimental Data (Jones, 1929)

0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%

0% 10% 20% 30% 40% 50% 60% 70% 80% 90%Lower Flammability Limit of the Mixture (%)

Inert in the Mixture (%) 

### Carbon Monoxide and Carbon Dioxide

Calculated using Le Chatelier Equation with no equi valency adjustment and assuming an LFL for Inert of Infinit y

Calculated using Le Chatelier Equation adjusting CO 2 for Nitrogen equivalency and assuming and LFL for Nitrogen of In finity

Experimental Data (Jones, 1929)This information is distributed solely for the purp ose of pre-dissemination peer review under applicab le information quality guidelines. It has not been formally disseminated by EPA. It does not repr esent and should not be construed to represent any Agency determination or policy.



## F-10 0% 10% 20% 30% 40% 50% 60%

0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%Lower Flammability Limit of the Mixture (%)

Inert in the Mixture (%) 

### Dimethyl Ether and Nitrogen

Calculated using Le Chatelier Equation assuming an LFL for Nitrogen of Infinity

Experimental Data (Kondo et al., 2006a)

0% 5% 10% 15% 20% 25% 30% 35% 40% 45%

0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%Lower Flammability Limit of the Mixture (%)

Inert in the Mixture (%) 

### Dimethyl Ether and Carbon Dioxide

Calculated using Le Chatelier Equation with no equi valency adjustment and assuming an LFL for Inert of Infinit y

Calculated using Le Chatelier Equation adjusting CO 2 for Nitrogen equivalency and assuming and LFL for Nitrogen of In finity

Experimental Data (Kondo et al., 2006b)This information is distributed solely for the purp ose of pre-dissemination peer review under applicab le information quality guidelines. It has not been formally disseminated by EPA. It does not repr esent and should not be construed to represent any Agency determination or policy.



## F-11 0% 10% 20% 30% 40% 50% 60%

0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%Lower Flammability Limit of the Mixture (%)

Inert in the Mixture (%) 

### Methyl Formate and Nitrogen

Calculated using Le Chatelier Equation assuming an LFL for Nitrogen of Infinity

Experimental Data (Kondo et al., 2006a)

0% 10% 20% 30% 40% 50% 60%

0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%Lower Flammability Limit of the Mixture (%)

Inert in the Mixture (%) 

### Methyl Formate and Carbon Dioxide

Calculated using Le Chatelier Equation with no equi valency adjustment and assuming an LFL for Inert of Infinit y

Calculated using Le Chatelier Equation adjusting CO 2 for Nitrogen equivalency and assuming and LFL for Nitrogen of In finity

Experimental Data (Kondo et al., 2006b)This information is distributed solely for the purp ose of pre-dissemination peer review under applicab le information quality guidelines. It has not been formally disseminated by EPA. It does not repr esent and should not be construed to represent any Agency determination or policy.



## F-12 0% 5% 10% 15% 20% 25% 30% 35% 40% 45% 50%

0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%Lower Flammability Limit of the Mixture (%)

Inert in the Mixture (%) 

### 1,1-Difluoroethane and Nitrogen

Calculated using Le Chatelier Equation assuming an LFL for Nitrogen of Infinity

Experimental Data (Kondo et al., 2006a)

0% 5% 10% 15% 20% 25% 30% 35% 40% 45% 50%

0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%Lower Flammability Limit of the Mixture (%)

Inert in the Mixture (%)



### 1,1-Difluoroethane and Carbon Dioxide

Calculated using Le Chatelier Equation with no equi valency adjustment and assuming an LFL for Inert of Infinit y

Calculated using Le Chatelier Equation adjusting CO 2 for Nitrogen equivalency and assuming and LFL for Nitrogen of In finity

Experimental Data (Kondo et al., 2006b)This information is distributed solely for the purp ose of pre-dissemination peer review under applicab le information quality guidelines. It has not been formally disseminated by EPA. It does not repr esent and should not be construed to represent any Agency determination or policy.



## F-13 0% 5% 10% 15% 20% 25% 30% 35% 40% 45% 50%

0% 10% 20% 30% 40% 50% 60%Lower Flammability Limit of the Mixture (%)

Inert in the Mixture (%) 

### Ammonia and Nitrogen

Calculated using Le Chatelier Equation assuming an LFL for Nitrogen of Infinity

Experimental Data (Kondo et al., 2006a)

0% 5% 10% 15% 20% 25% 30% 35% 40% 45% 50%

0% 10% 20% 30% 40% 50% 60%Lower Flammability Limit of the Mixture (%)

Inert in the Mixture (%) 

### Ammonia and Carbon Dioxide

Calculated using Le Chatelier Equation with no equi valency adjustment and assuming an LFL for Inert of Infinit y

Calculated using Le Chatelier Equation adjusting CO 2 for Nitrogen equivalency and assuming and LFL for Nitrogen of In finity

Experimental Data (Kondo et al., 2006b)This information is distributed solely for the purp ose of pre-dissemination peer review under applicab le information quality guidelines. It has not been formally disseminated by EPA. It does not repr esent and should not be construed to represent any Agency determination or policy.



# Appendix G

The following Appendix contains details about inerts and fur ther explanation for including an equivalency adjustment to correct for differe nt inert behavior. Section G.1 explores the accuracy of Le Chatelier with varying chemical composition in the mixture. Section G.2 presents research on nitrogen composition and it s effect on calculated LFL with respect to measured LFL; and Section G.3 discusses the effect of other types of inerts.
There are additional uncertainties associated with the calcu lation of UFL; however, these are not discussed in this report because UFL is not pres ented as an operating parameter to indicate adequate combustion in flares.This information is distributed solely for the purp ose of pre-dissemination peer review under applicab le information quality guidelines. It has not been formally disseminated by EPA. It does not repr esent and should not be construed to represent any Agency determination or policy.



## G-1 G.1 LFL Calculation Accuracy Associated with No-inert in Gas Mixture



## Researcher’s Observations of Measured and Calculate d LFL

Some researchers have observed that certain mixture s do not obey the Le Chatelier

principle and Le Chatelier’s equation does not accu rately predict the LFL for these mixtures.

Heffington and Gaines (1981) noted that large amoun ts of hydrogen sulfide can cause deviations

between calculated and experimental LFLs, and White (1925) specifically identified hydrogen

sulfide and methane mixtures as not following the r ule. White (1925) also found that hydrogen

and ethylene, acetylene and hydrogen, and mixtures containing carbon disulfide do not follow Le

Chatelier. Coward and Jones (1952) specifically not ed that the LFL calculated using Le

Chatelier’s equation for mixtures containing at lea st 2 of the compounds methane, hydrogen, or

carbon monoxide are “approximately accurate”. Choud huri (2005) described variations in the

measured and calculated LFLs (using Le Chatelier’s equation) for methane and propane, and

methane and ethane mixtures; and for hydrogen and c arbon monoxide mixtures (Choudhuri and

Subramanya, 2006).

Coward and Jones (1952) provided a qualitative disc ussion of the variation in accuracy of

the LFL calculated for mixtures using Le Chatelier’ s equation with different chemical

composition of the combustible gases. Table G.1 pro vides a summary of the researcher’s

observations and of other researchers’ findings on the differences in LFLs determined through

measurement and calculations using Le Chatelier’s e quation. Although it is difficult to judge the

extent of deviations shown in Table G.1 from the re searcher’s qualitative remarks (e.g., “Agreed

Closely” versus “Deviated Somewhat”) between measur ed and calculated LFLs, it would appear

that mixtures containing carbon disulfide, acetylen e, and paraffin-hydrocarbon halides give the

largest deviations. Carbon disulfide and paraffin-h ydrocarbon halides seem to effect a broader

group of mixtures, while it is less clear whether a cetylene mixed with non-hydrogen

combustibles will cause calculated LFL values to va ry significantly from the measured values.

Some variation was seen with methane and acetylene mixtures, but only slight; and carbon

monoxide and acetylene mixtures had measured and ca lculated LFLs that were in close

agreement.

Coward and Jones (1952) provide graphs (Figures 56 and 57 of Coward and Jones) for

the LFL of different mixtures of hydrogen sulfide a nd methane, and hydrogen sulfide andThis information is distributed solely for the purp ose of pre-dissemination peer review under applicab le information quality guidelines. It has not been formally disseminated by EPA. It does not repr esent and should not be construed to represent any Agency determination or policy.



## G-2 hydrogen. Both figures indicate a variation of the calculated LFL up to 1 percentage point below

the measured value for these mixtures. For hydrogen sulfide and hydrogen mixtures the variation

does not occur until there is about 22 percent H 2 

## S in the mixture. For hydrogen sulfide and

methane the variation occurs in almost all mixtures , but is less significant for mixtures with

2 percent or less H 2 

## S.

Paraffin-hydrocarbon halides cause variations of th e measured LFL from the calculated

value; however, current regulations do not allow fl aring of fuel gases with significant amounts of

halides, so these compounds should not affect the c alculation of LFL CZ 

## or its effectiveness as a

parameter to indicate flare combustion performance. It is assumed that the amount of hydrogen

sulfide and carbon disulfide that is burned in regu lated flares is also small because of the

emission limits of previous rules, such as the NSPS for petroleum refineries (40 CFR 60,

subparts J and Ja), Onshore Natural Gas Processing (40 CFR 60, subpart LLL), and New Source

Review permit limits, although this may require fur ther investigation. Therefore, hydrogen

sulfide and carbon disulfide are also not expected to be present in large enough quantities to

affect the accuracy of the calculated LFL CZ



## .This information is distributed solely for the purp ose of pre-dissemination peer review under applicab le information quality guidelines. It has not been formally disseminated by EPA. It does not repr esent and should not be construed to represent any Agency determination or policy.



## G-3 Table G.1. Le Chatelier Accuracy Observations by Coward and Jone s (1952)

Mixture Constituents Differences Between Measu red LFL and Values Calculated Using Le Chatelier’s Equation 1 

### Hydrogen and carbon monoxide Just exceeded experimental error Hydrogen and hydrogen sulfide Diverged widely; calculated LFL lower than measured Hydrogen, carbon monoxide, and methane Approxi mately accurate Hydrogen, methane, and ethane Approximately accurate Hydrogen and ethylene Calculated LFL slightly lower than measured Hydrogen and acetylene Calculated LFL lower than measured by a significant
amount for some mixtures. 2 

### Hydrogen sul fide and methane Calculated LFL lower than measured Hydrogen sulfide and acetylene Deviated by maximum of 0.3% Carbon disulfide and ether, benzene, acetone, or acetaldehyde No agreement

Carbon monoxide and methane Fair agreement
Carbon monoxide and ac etylene Close agreement Any two of: methane, ethane, propane, and butane Close agreement
Methane and pentane in air Close agreement Natural gas Fair agreement Methane and ethylene Calculated LFL slightly lower than measured Methane and acetylene Cal culated LFL slightly lower than measured Two or more of: cyclohexane, benzene, ethanol Fair agreement at temperatures of 100 to 250 ° C Two or more of: toluene, ethanol, ethyl acetate Fair agreement Two or more of: methyl cyclohexane, alcohol,
ether Fair agreement

Ethanol and gasoline; ethanol, gasoline and ether Fair agreement Isopropanol and gasoline Nearly agreed
Benzene and toluene Close agreement
Benzene and ethanol Deviated somewhat 3


### Benzole, methanol, ethanol Agreed within 11% at temperatures of 100 to 250 ° C
Methanol and ethanol Agreed (at 75 ° C) Methanol and ether; methanol and acetone; ethyl acetate and benzene; acetaldehyde and toluene; ethyl nitrite and ether Close agreement

Ethanol and ether; acetone and ether Good agreement
Ethanol and furfural Deviated somewhat
Ethanol and acetone Nearly agreed Ether and acetaldehyde Good agreement Acetone and methyl ethyl ketone Close agreement 4



### Paraffin

- hydrocarbon halides: methyl chloride and ethyl chloride; methyl chloride and methyl bromide; methyl bromide and ethyl chloride Differed appreciably

1 

### As observed by Coward and Jones (1952)

2 

### For mixtures up to 43% acetylene calculated values signi ficantly lower than measured values. Between 43 to 50% acetylene, the difference between calculated and measure d LFL decreased and greater than 50% acetylene the mixtures follow Le Chatelier’s equations.

3 

### However, at temperatures from 100 to 250 ° C the values agreed fairly well.

4 

### However, the LFL measured using an upward propagation method were slightly higher than calculated.This information is distributed solely for the purp ose of pre-dissemination peer review under applicab le information quality guidelines. It has not been formally disseminated by EPA. It does not repr esent and should not be construed to represent any Agency determination or policy.



## G-4 Table G.1 also indicates that several of the alcoho l mixtures had some deviation between

calculated and measured LFLs, indicating that mixtu res of benzene and ethanol, and furfural and

ethanol deviated “somewhat;” and measured LFL value s for ethanol and acetone, and

isopropanol and gasoline mixtures “nearly agreed” w ith the calculated values.

The researchers (Coward and Jones 1952) also noted small differences in calculated and

measured LFL values of various mixtures of hydrogen , carbon monoxide, methane, ethane, and

ethylene. The qualitative observations in Table G.1 do not provide enough specific information

to judge the accuracy of using Le Chatelier’s equat ion for these mixtures, but they do raise some

questions regarding how effective the LFL CZ 

## can be as an indicator of good combustion for a

wide variety of flare gas compositions.

Research on Reaction Kinetics and the Effect in LFL

Several other researchers (Azatyan et al., 2002, 20 05a, 2005b, and 2007; Degges et al.

2010; Laskin et al., 2000; Wang et al., 2009) have investigated the reaction kinetics of burning

gases, which is a possible explanation for these ob servations. In the flame of a flare, numerous

chemical reactions are taking place with the reacti on priority dependent on the temperature and

chemical composition in the burning mixture. Change s in composition can shift the reaction

kinetics to other primary pathways that can have co nsequences on the ability to achieve good

combustion. The LFL does a reasonable job of “summa rizing” (in one number) the reactions

going on during combustion of a specific chemical o r mixture. However, LFL of mixtures

calculated using Le Chatelier’s equation is only as accurate as how closely the individual

component’s LFL represent the combustion pathways t he chemical follows when it is part of a

mixture. This is because pure component LFLs used i n the Le Chatelier’s equation to estimate

LFL for the mixture are based on the combustion pat hways when the chemical is burned alone. If

mixture components follow reaction pathways that ar e different from their pure components, the

calculated LFL CZ 

## will vary from the actual. However, if the mixture ’s reaction pathways result in

similar heats of combustion, the variation in the c alculated LFL and the actual may not be

meaningful with respect to the LFL CZ 

## of 15.3 percent. Also, other factors may effect th e
accuracy of the calculated LFL which could mitigate or exacerbate the error, either making the

deviation between calculated and actual LFL more, o r less, of a concern.This information is distributed solely for the purp ose of pre-dissemination peer review under applicab le information quality guidelines. It has not been formally disseminated by EPA. It does not repr esent and should not be construed to represent any Agency determination or policy.



## G-5 The reaction kinetic researchers describe reactions that are considered “chain branching”

and “chain terminating.” The chain terminating reac tions are ones that lead to products that are

less active or that participate in reaction chains that recreate the original chemical and may not

result in complete combustion. Degges et al. (2010) describes the addition of steam and its

chemical influence on the kinetics of a flame inclu ding the effect of the steam cooling the flame.

Azatyan et al. (2002) provides an analysis on the r eactions taking place with hydrogen and

methane combustion (pure gases not a mixture). Wang et al., (2009) analyzes the combustion

reactions when hydrogen is added to methane in smal l amounts. The researcher shows an

enhancement of combustion with the addition of hydr ogen to methane and found that in mixtures

with hydrogen concentrations lower than 20 percent, hydrogen participates predominately in

intermediate reactions. Azatyan et al. (2005a, 2005 b, and 2007) describes the reaction kinetics of

hydrogen combustion with the addition of small amou nts of propylene or isopropanol and shows

that these compounds can inhibit the combustion rea ctions of hydrogen to some degree. Laskin

et al. (2000) investigates the reaction kinetics of 1,3-butadiene combustion.

Compiled Measured and Calculated LFL

To judge whether the differences between measured a nd calculated LFLs are significant,

experimental LFL values for mixtures were collected and compared to calculated LFL values.

Experimental LFL values were collected from eight p revious studies. These studies were

identified from the numerous research papers collec ted for the investigation of flare operating

parameters that indicate performance level. An exha ustive search for every measured mixture

LFL was not conducted, but using a targeted search of papers describing calculational or

modeled methods of determining LFL, a large group o f measured values was collected. (Papers

presenting analytical methods for determining LFL o ften have experimental values of LFL to

compare against the computational method.)

From the eight studies, 221 measured LFL values for mixtures were identified. The

values were limited to mixtures that had at least t wo combustible compounds. (Mixtures with

one combustible and an inert are discussed in Secti ons G.2 and G.3). Values were found for

mixtures containing two or more of 16 combustible c onstituents (hydrogen, methane, ethane,

ethylene, propane, propylene, butane, methyl ethyl ketone, toluene, dimethyl ether, methylThis information is distributed solely for the purp ose of pre-dissemination peer review under applicab le information quality guidelines. It has not been formally disseminated by EPA. It does not repr esent and should not be construed to represent any Agency determination or policy.



## G-6 formate, 1,1-difluoroethane, 1,2-dichloroethane, hy drogen sulfide, ammonia, and carbon

monoxide). Some mixtures also had inert compounds i ncluding nitrogen, carbon dioxide and

carbon tetrachloride.

Of the 221 measured values, 146 did not have inert compounds and 65 were mixtures

with inert compounds (mixtures with inerts are disc ussed in Section G.3). In calculating the LFL

for the mixture, the pure component LFL values used in Le Chatelier’s equation were taken from

the research paper that presented the measured valu es. This was done so the pure component

LFL was consistent with the same measurement method , technique, apparatus, and environment

that the mixture LFL was measured. Therefore, any s ignificant variation in measured and

calculated LFL that was identified was more likely due to the chemical constituents not

following Le Chatelier’s equation and not a variati on due to the test method. LFL was also

calculated using pure component LFLs from Zabetakis (1965) for comparison.

Appendix H provides the list of pure component LFL values used in the LFL calculations

for each research report and the measured LFLs coll ected, the mixture composition, the

calculated LFL using Zabetakis referenced pure comp onent LFLs, the calculated LFL using the

specific researcher’s pure component LFLs, the sour ce of each measured value, and the

difference between the measured and calculated valu es. The mixtures with and without inerts are

presented in two different tables in Appendix H.

The variation between measured and calculated LFL v alues is small for those mixtures

without inert components. The difference between me asured and calculated values was between

-0.30 and 0.88 percentage points and the average de viation for the 146 measured and calculated

pairs was 0.04 percentage points. Averaging the abs olute value of the difference gave an average

deviation just above this of 0.08 percentage points . There were only six measured LFL values

that varied from the calculated LFL by ±0.3 percent age points or greater. These are shown in

Table G.2.

Table G.2 does not reveal an obvious trend for the six measured LFL values with the

largest deviation from the Le Chatelier calculated values. One could speculate on what these six

points imply; however, the overall trend is that fo r most of the data for mixtures without inerts,This information is distributed solely for the purp ose of pre-dissemination peer review under applicab le information quality guidelines. It has not been formally disseminated by EPA. It does not repr esent and should not be construed to represent any Agency determination or policy.



## G-7 the Le Chatelier’s equation does a good job of pred icting the LFL. With all but six data points

showing agreement within a third of a percentage po int of the measured value, it would be

difficult to parse out experimental error from any situations where the components do not obey

Le Chatelier’s principal. Even the mixtures with hi gher deviations (Table G.2) are very close, all

but one having a deviation less than 10 percent of the experimental value.

Furthermore, very few, and possibly none, of the va riations between measured and

experimental LFL values that could occur in gas mix tures containing only combustion gases

(with no steam or air added) are important from the perspective of flare vent gas. In using the

LeChatelier equation to estimate the LFL CZ 

## , all mixtures will have a LFL CZ 

## of less than the

maximum pure component LFL of any component in the mixture. For example, ammonia has the

highest LFL (15%) of any compound in the Zabetakis (1965) LFL reference list; any mixture of

a combustible gas with ammonia (and no inert added) will have a LFL CZ 

## less than 15 percent.

This is dictated by the use of Le Chatelier’s equat ion. A value greater than 15 percent is not

mathematically possible. Consequently all mixtures of 100 percent combustible gases, including

mixtures with ammonia, will have a LFL CZ 

## less than 15.3 percent. Therefore, any flare vent

stream with no added assist air or steam containing no inerts will have a LFL that meets

15.3 percent and any variations between calculated and measured are likely unimportant unless

there are specific chemical interactions that can c ause a mixture of only combustibles to have a

much higher LFL than calculated. The comparison of the Le Chatelier equation to experimental

LFL values shown in the Appendix H data does not in dicate large variations for 100 percent

combustible mixtures. However, it should be noted t hat none of these mixtures with measured

LFLs contained acetylene, carbon disulfide, hydroge n sulfide, or alcohol, which were the

chemicals specifically cited as not following Le Ch atelier’s rule as closely as most chemicals.

Table G.2. Largest Deviations Found Between Measured and Calcu lated LFLs
for Mixtures with No InertsHydrogen (H2)(Volume %)Dimethyl ether(C2H6O)(Volume %)Ammonia (NH3)(Volume %)Other(Volume %) Experimental
LFL (Volume %) Researcher Pure Component
LFLs Zabetakis Pure Component
LFLs

Source Calculated
LFL (Volume %) Difference

Between Experimental
and
Calculated Calculated

LFL (Volume %) Difference

Between Experimental
and
Calculated

50 50% methyl ethyl ketone (C 4 H 8 O) 3.15 2.75 0.40 2.58 0.57 Loehr et al. (1997)This information is distributed solely for the purp ose of pre-dissemination peer review under applicab le information quality guidelines. It has not been formally disseminated by EPA. It does not repr esent and should not be construed to represent any Agency determination or policy.



## G-8 Table G.2. Largest Deviations Found Between Measured and Calcu lated LFLs

for Mixtures with No Inerts (Continued)Hydrogen (H2)(Volume %)Dimethyl ether(C2H6O)(Volume %)Ammonia (NH3)(Volume %)Other(Volume %) Experimental

LFL (Volume %) Researcher Pure Component
LFLs Zabetakis Pure Component
LFLs

Source Calculated
LFL (Volume %) Difference

Between Experimental
and
Calculated Calculated

LFL (Volume %) Difference

Between Experimental
and
Calculated

50 50% 1,2
Dichloroethane (C 2 H 4 C 12 ) 5.35 4.92 0.43 4.38 0.97 Loehr et al. (1997)

75 25% methyl formate (C 2 H 4 O 2 ) 10.94 10.31 0.63 10.00 0.94 Kondo et al. (2008)

75 25% Carbon Monoxide (CO) 15.2 14.32 0.88 14.29 0.91 Kondo et al. (2008)

75 25 3.8 4.10 -0.30 4.21 -0.41 Kondo et al. (2008)

50 50% Methane (CH 4 ) 4.25 3.94 0.31 4.05 0.20 Kondo et al. (2008)



## G.2 Accuracy of Le Chatelier Principle for Mixtures with Nitrogen



## As stated in Section 3.1.2, the calculation of LFL CZ 

## shown in Figure 3-3 of this report

includes an assumption that inerts have an infinite LFL. This can be understood for nitrogen by

reviewing the same Zabetakis nose plot that is show n in Figure 3-1 of this report (for ease, refer

to Figure G.1 as it is the same as Figure 3-1 of th is report). The plot shows several different

inerts in methane and air mixtures. Looking specifi cally at the LFL portion of the nitrogen curve

in Figure G.1, the methane concentration stays rela tively constant as nitrogen is added (moving

along the line at the underside of the nose). The L FL boundary is relatively horizontal as

nitrogen is added and the concentration of the comb ustible stays constant in the combustiblenitrogen-air mixture. Additional combustion gas (me thane in Figure G.1) is not needed to offset

the addition of nitrogen. The addition of nitrogen displaces air in the methane-nitrogen-air

mixture. Because the chemical properties of nitroge n and air are very similar and the amount of

oxygen in air displaced by the nitrogen is not sign ificant (since oxygen is not a limiting factor at

the LFL), the addition of nitrogen does not affect the measured methane concentration at the

LFL.This information is distributed solely for the purp ose of pre-dissemination peer review under applicab le information quality guidelines. It has not been formally disseminated by EPA. It does not repr esent and should not be construed to represent any Agency determination or policy.



## G-9 Figure G.1. Zabetakis nose plot for methane and inert in air



## In the research conducted on calculating the LFL, m ixtures with inert gases have

specifically been investigated. In general, the mor e inert (for flares, these are generally nitrogen,

carbon dioxide, and steam) added to a combustible g as, the higher the LFL will be for the

mixture. Le Chatelier’s principle was investigated regarding its accuracy to estimate LFL values

for combustion gases and nitrogen. It was found tha t the LFL calculated using Le Chatelier’s

principle deviates somewhat from experimental value s with higher concentrations of nitrogen in

the fuel mixture (and as the fuel mixture’s LFL app roaches the UFL at the point of maximum

inert – at the tip of the nose on a Zabetakis plot) . In addition, the amount the calculated value

deviates from the experimental value is dependent o n the type of combustible compound in the

fuel mixture.

Experimental LFL data for individual combustible co mpounds (i.e. hydrogen, methane,

ethane, ethylene, propane, propylene, butane, butad iene, carbon monoxide, dimethyl ether,

methyl formate, 1,1-difluoroethane, and ammonia) in nitrogen were graphed against the nitrogen

volume percent used in the experiments. The experim ental data were extracted from a series ofThis information is distributed solely for the purp ose of pre-dissemination peer review under applicab le information quality guidelines. It has not been formally disseminated by EPA. It does not repr esent and should not be construed to represent any Agency determination or policy.



## G-10 tests conducted by Jones and Kennedy (1932, 1938, a nd 1943), Kondo et al. (2006a and 2006b),

and Vidal et al (2006). Figure G.2 shows the effect of increasing nitrogen on the LFL of

methane-nitrogen mixtures. Appendix F provides thes e graphs for all 13 combustible gases in

nitrogen.

Figure G.2 illustrates the variation that can be fo und between the calculated LFL and the

measured LFL for methane and nitrogen mixtures. For most compounds considered (see

Appendix F for graphs showing other combustible com pounds with nitrogen) there is little to no

variation identified between the calculated and exp erimental LFL values. The deviations that

were found generally occur at greater than a LFL of 15.3 percent. Other than ammonia, methane

showed the greatest deviation at the lowest concent ration for the compounds examined. Looking

at a nitrogen concentration of 66 percent on Figure G.2, which crosses the LFL lines near the

LFL value of 15.3 percent shown in Figure 3-4 of th is report (where combustion efficiency

begins to degrade), the LFL is 15.5 percent for the experimental methane data and 14.8 percent

for the calculated results.

Figure G.2. Effect of Nitrogen on LFL of Methane 0% 5% 10% 15% 20% 25% 30% 35% 40% 45% 50%

0% 10% 20% 30% 40% 50% 60% 70% 80% 90%Lower Flammability Limit of the Mixture (%)

Inert in the Mixture (%) 

### Methane and Nitrogen

Calculated using Le Chatelier Equation assuming an LFL for Nitrogen of Infinity

Experimental Data (Jones and Kennedy, 1933)

Experimental Data (Kondo et al., 2006a)

Experimental Data - (Vidal et al., 2006)

Pure component LFL at 5.0 for Jones and Kennedy (193 3) and Vidal et al. (2006) experiments, but 4.9 for Kondo et al. (2006a) experiments.This information is distributed solely for the purp ose of pre-dissemination peer review under applicab le information quality guidelines. It has not been formally disseminated by EPA. It does not repr esent and should not be construed to represent any Agency determination or policy.



## G-11 This example illustrates that there could be situat ions where a source would be in

compliance with the proposed 15.3 percent LFL CZ 

## threshold for a given gas composition in the

combustion zone based on the calculated value, but a measured LFL for the mixture would not

support this conclusion. However, most combustion g ases showed a smaller deviation near

15.3 percent LFL (see Appendix F) between the calcu lated and measured LFL and the deviation

for methane is relatively small and would not affec t a wide range of flare gas compositions. Also

the uncertainties in using Le Chatelier’s equation are built into the analysis that resulted in the

proposed 15.3 percent maximum LFL. The limit was es tablished using the Le Chatelier equation

and pure component LFLs from Zabetakis (1965). Ther efore, the determination of compliance

should occur using Le Chatelier’s equation and Zabe takis pure component LFLs.

In reviewing the information in Figures G.1 and G.2 it is important to consider the

differences in these graphs. Figure G.1 shows the p ercent of methane in a mixture of air and

added nitrogen (the LFL of the methane in a “nitrog en-enriched” atmosphere); from the

perspective of a flare, Figure G.1 represents the g as mixture immediately above the flare. The

x-axis of Figure G.1 shows the composition of added nitrogen in the “nitrogen-enriched”

atmosphere. Therefore, the quantity of air can be c alculated from the figure by adding the LFL of

methane and the amount of added nitrogen, and subtr acting from 100 percent; or for example, for

Figure G.1, added nitrogen of 20 percent shows a 5 percent concentration of methane, which

means there is 75 percent air in the mixture at the LFL (100-20-5=75). Figure G.2 shows the

same data but gives the LFL of a mixture containing methane and nitrogen (instead of the LFL

for methane in nitrogen-enriched air). The LFL valu e still reflects the percent of “combustible”

in air (“combustible” for Figure G.2 represents the mixture of methane and added nitrogen);

however, the x-axis of Figure G.2 is the compositio n of the nitrogen in the methane-nitrogen

mixture, prior to mixing with air. Using the same e xample for illustration, the mixture of

5 percent methane, 20 percent added nitrogen and 75 percent air on Figure G.2 would be shown

with a nitrogen content of 80 percent because the r atio of methane to added nitrogen in the air

would be the same as in the mixture without air (5% methane to 20% nitrogen would be

20/(5+20) or 80% nitrogen). From Figure G.2, 80 per cent nitrogen in the mixture shows about a

25 percent LFL which means 25 percent of the methan e-nitrogen mixture in air is the LFL for

that mixture. This Figure G.2 example also indicate s that there would be 75 percent air at this

LFL which is consistent with the Figure G.1 Zabetak is plot.This information is distributed solely for the purp ose of pre-dissemination peer review under applicab le information quality guidelines. It has not been formally disseminated by EPA. It does not repr esent and should not be construed to represent any Agency determination or policy.



## G-12 G.3 Using Le Chatelier’s Equation for Non-Nitrogen Inerts



## The amount of deviation between a calculated LFL (u sing the Le Chatelier equation and

assuming infinity as the LFL for inerts) from exper imental LFL values is also dependent on the

type of inert in the gas mixture. For example, Figu re G.1 shows the variation of the LFL for

methane in different inert-air mixtures. As can be seen, it takes a concentration lower than

nitrogen for some non-nitrogen inerts to render the mixture non-flammable. Also the bottom of

the nose is less horizontal. For carbon dioxide, wa ter, carbon tetrachloride, and methylene

bromide, Figure G.1 shows that more methane must be added as the inert is increased to maintain

a combustible gas mixture. The carbon dioxide curve has the least horizontal nose underside of

the three inerts that are most often found in flare gas (steam, nitrogen, and carbon dioxide). For

example, at a carbon dioxide concentration in the m ethane, air, and carbon dioxide mixture of

20 percent, the methane concentration (LFL) would h ave to increase an additional percent, up to

about 6 percent, in order to maintain a flammable m ixture. Based on Figure G.1, the effect of

water in a mixture is greater than nitrogen, but no t as great as carbon dioxide. Because of this,

we have included a ‘nitrogen equivalency’ adjustmen t in the Le Chatelier’s equation (see

Equation 3-3 in Section 3.1.2 of this report).

Figure G.3 provides the same data for methane and c arbon dioxide mixtures in

Figure G.1 but in the same format as Figure G.2. Th e figure shows three sets of experimental

data for methane and carbon dioxide mixtures and tw o sets of calculated values. One set of

calculated LFLs (outline of red squares) is based o n using Le Chatelier’s equation assuming a

LFL of infinity for the carbon dioxide (no adjustme nt) and the other set of calculated LFL values

(outlines of blue circles) is the Le Chatelier’s eq uation with values adjusted for nitrogen

equivalency. The nitrogen adjusted calculated LFL v alues are very close to the experimental data

from all three sources. Comparing the two calculate d sets of values shows the effect of the

nitrogen adjustment. Left unadjusted, the calculate d LFL for methane in CO 2 

## would deviate a

significant amount even for mixtures with a LFL les s than 15 percent. Appendix F provides

similar graphs to Figures G.2 and G.3 (with nitroge n and carbon dioxide) for 13 combustible

gases.This information is distributed solely for the purp ose of pre-dissemination peer review under applicab le information quality guidelines. It has not been formally disseminated by EPA. It does not repr esent and should not be construed to represent any Agency determination or policy.



## G-13 Figure G.3. Effect of Carbon Dioxide on LFL of Methane



## As mentioned in Section 3.1.2 of this report, the n itrogen equivalency methodology is

based on a method investigated by Molnarne et al. ( 2005) for taking into account non-nitrogen

inerts which is used in ISO 10156 and described by Besnard (1996). This nitrogen equivalency

adjustment is also described by Shore (2007) and Go golek et al. (2010a). The Molnarne et al.

(2005) recommended values of “nitrogen equivalency” are tabulated in Table G.3 for water (or

steam) and carbon dioxide, the inerts that are like ly to be included in the flare combustion zone

(other than nitrogen).

Table G.3. Recommended Values of Nitrogen Equivalency for Water and Carbon
Dioxide

Combustible Component i in Flare Vent Gas K Water 

### K Carbon Dioxide



### Methane 1.87 2.23

Ethane 1.40 1.87 Propane 1.51 1.93 Ethylene 1.68 1.84 Propylene 1.36 1.92 Hydrogen 1.35 1.51

All Other Combustibles 1.50 1.87

Source: Molnarne et al. (2005)

0% 5% 10% 15% 20% 25% 30% 35% 40% 45% 50%

0% 10% 20% 30% 40% 50% 60% 70% 80% 90%Lower Flammability Limit of the Mixture (%)

Inert in the Mixture (%) 

### Methane and Carbon Dioxide

Calculated using Le Chatelier Equation with no equi valency adjustment and assuming an LFL for Inert of Infinit y

Calculated using Le Chatelier Equation adjusting CO 2 for Nitrogen equivalency and assuming and LFL for Nitrogen of In finity

Experimental Data (Jones and Kennedy, 1933)

Experimental Data (Kondo et al., 2006b)

Experimental Data (Vidal et al., 2006)

Pure component LFL at 5.0 for Jones and Kennedy (193 3) and Vidal et al. (2006) experiments, but 4.9 for Kondo et al. (2006b) experiments.This information is distributed solely for the purp ose of pre-dissemination peer review under applicab le information quality guidelines. It has not been formally disseminated by EPA. It does not repr esent and should not be construed to represent any Agency determination or policy.



## G-14 As can be seen in Figure G.2 and in Appendix F for other combustibles, the assumption

that the LFL is equal to infinity works well for ni trogen, but not as well for other inerts (see

Figure G.3 and Appendix F for carbon dioxide). The intent of the adjustment is to normalize the

effect of non-nitrogen inerts in the gas mixture an d to adjust the LFL to be on the same basis

with respect to inerts. After making the adjustment , all inerts are assumed to have an infinite LFL

and the Le Chatelier equation can be used. The flar e data sets used in the final analysis have gas

mixtures that contain various amounts of nitrogen, carbon dioxide, and water.

Compiled Measured and Calculated LFL for Mixtures w ith Inerts

As previously described, Appendix H provides measur ed LFLs for 65 mixtures that

contain inert components. The variation between the measured and the calculated value

(calculated using the specific researcher’s pure co mponent LFL values and adjusting for nitrogen

equivalency) ranged from -1.56 and 4.88 percentage points, and an average of 0.73 percentage

points. The information for these mixtures is shown in Table H.3 of Appendix H. The mixtures

in Table H.3 include the inerts carbon tetrachlorid e, nitrogen, carbon dioxide, or both nitrogen

and carbon dioxide; combustibles include hydrogen, methane, ethane, methyl ethyl ketone,

toluene, 1,2-dichlorethane, and carbon monoxide. Ta ble G.4 summarizes the variation between

measured and calculated LFLs for the different iner ts and shows a summary for the mixtures

with no inerts. Clearly the addition of inert compo unds has increased the variation between

calculated and measured LFLs for mixtures. The aver age of the absolute value of the differences

between calculated and measured LFLs for mixtures w ith inerts is roughly ten times that seen

with mixtures with no inerts.

Table G.4. Summary of Differences Between Calculated and Me asured LFLs for Mixtures

Type of Inert Average
Difference Average of the

Absolute
Value of
Difference Maximum Minimum Number
of
Mixtures

No Inert 0.04 0.08 0.88 -0.30 145

All Inerts 0.73 0.94 4.88 -1.56 65

Carbon Tetrachloride 0.74 0.74 2.52 0.08 18

Carbon Dioxide -0.78 0.78 -0.19 -1.56 5
Nitrogen 0.71 0.91 4.88 -0.70 24
Carbon Dioxide and Nitrogen 1.16 1.21 2.97 -0.21 18
Carbon Dioxide and/or Nitrogen 0.72 1.01 4.88 -1.56 47This information is distributed solely for the purp ose of pre-dissemination peer review under applicab le information quality guidelines. It has not been formally disseminated by EPA. It does not repr esent and should not be construed to represent any Agency determination or policy.



## G-15 The differences summarized in Table G.4, as well as shown in Appendix H, are

calculated as the measured minus the calculated val ues. Therefore, a negative value indicates that

the calculated value is higher than the measured va lue. In less than 25% of the mixtures with

inerts (15 out of 65) the difference was negative. Generally for mixtures with inert

concentrations close to the maximum amount of inert possible, while still flammable, the

deviation between measured and calculated LFL is at its greatest, with the measured LFL being

greater than the calculated value. This can be quic kly seen for mixtures with only one

combustible and one inert in Figures G.2 and G.3 an d in Appendix F; note the difference in

acceleration of the increase in slope between the m easured and calculated values as inert

increases. Look at the termination of the calculate d data in Figure G.2. The calculated data ends

at a nitrogen content of about 86 percent and a LFL of 35 percent; the measured data from Jones

and Kennedy (1933) ends at a LFL of about 39.5 perc ent, giving a maximum difference between

measured and calculated data of 4.5 percentage poin ts near the point of maximum inert

concentration. 5 

## As previously discussed regarding Figure G.2, the difference in measured and

calculated LFL at 66 percent nitrogen concentration is about 1 percentage point. Comparing this

to the 4.5 percentage point difference shows that t he greater difference between measured and

calculated LFLs are at maximum inert concentrations . Looking at Figure G.2 also shows why the

difference is expected to be a positive difference; Le Chatelier’s equation does not account for

the same level of increasing slope that appears to happen as mixtures approach their lower limit.

Except for two data points with carbon tetrachlorid e as the inert and one negative difference, the

difference between measured and calculated LFL is l ess than 1 percentage point for LFLs

measured less than 25%. Therefore, the larger posit ive differences seen in Appendix H and

Table G.4 are at least partly due to the mixture be ing closer to the maximum inert concentration.

Most of the experimental data found were for mixtur es of hydrogen, methane, carbon

monoxide, nitrogen, and/or carbon dioxide, except f or mixtures with carbon tetrachloride as the

inert. The calculated LFL for the carbon tetrachlor ide mixtures were adjusted for nitrogen

equivalency, but because a k value was not availabl e for carbon tetrachloride, the k values for

carbon dioxide were used. All of the measured and c alculated differences for these mixtures

were less than 1 except for two mixtures that were two of the highest LFLs (9.7 and 10.1%).

5 

### The Kondo, 2006a, data point in Figure G.2 at about 88 percen t nitrogen and a LFL of 44.5 percent is an inconsistency between the measurement methods used by K ondo and Jones and Kennedy in determining the maximum concentration of nitrogen that will still all ow flame propagation.This information is distributed solely for the purp ose of pre-dissemination peer review under applicab le information quality guidelines. It has not been formally disseminated by EPA. It does not repr esent and should not be construed to represent any Agency determination or policy.



## G-16 Although these are not high values with respect to the 15.3% that appears to be important for

good flare combustion, these could be high values f or carbon tetrachloride. Carbon tetrachloride

is a stronger inert than either carbon dioxide or n itrogen.

The mixtures with inert other than carbon tetrachlo ride all have hydrogen in them except

for eight with methane and ethane. The methane and ethane mixtures all have LFLs of 21% or

less, and the range of differences between measured and calculated is -0.15 to 0.43 with an

average of 0.14 percentage points. These appear ver y close differences. The second highest

difference is 0.33 percentage points, so most of th e differences are less than what it may appear

from the range.

There are six additional mixtures containing ethane . Three of these also include

hydrogen, methane, and nitrogen. All of these have high differences between measured and

calculated LFL ranging from 2.47 to 4.88 percentage points. They also have very high LFLs of

37 to 42%. Therefore, the mixtures are likely close to their maximum inert concentration and any

additional cause for the high differences cannot be determined given only 3 data points.

The other three mixtures containing ethane also inc lude hydrogen and nitrogen. The

range of differences between measured and calculate d values is 0.15 to 2.74 percentage points.

The higher difference (2.74) is for a mixture with a high LFL or 25.8, but it is difficult to form

any conclusions with these three points. However, b ecause of ethane’s similarity to methane,

these points could be compared to the results for h ydrogen and methane.

The remainder of the mixtures (33) with inert other than carbon tetrachloride, contain

methane, hydrogen and nitrogen and/or carbon dioxid e, with seventeen of the mixtures also

containing carbon monoxide.

Numerous researchers (for example Karim et al., 199 6, Wang et al. 2009 and 2010, Hu et

al. 2009, and White, 1925) have shown that hydrogen enhances the combustion of methane. For

mixtures that are not premixed, this effect levels off somewhat at about 32 or 40 percent

hydrogen in the fuel mixture (Wang et al., 2010). F rom the perspective of LFL values for

mixtures of hydrogen and methane, one would expect that the LFL values would be lower thanThis information is distributed solely for the purp ose of pre-dissemination peer review under applicab le information quality guidelines. It has not been formally disseminated by EPA. It does not repr esent and should not be construed to represent any Agency determination or policy.



## G-17 what would be calculated using Le Chatelier’s equat ion, because the equation does not take into

account the enhancement behavior. However, for mixt ures where there is more hydrogen than

methane, hydrogen still enhances the methane combus tion, but the primary combustible is

hydrogen; and from the perspective of hydrogen, met hane is inhibiting hydrogen combustion.

Because, methane has a higher LFL than hydrogen, th e use of Le Chatelier’s equation results in a

“dilution” of the hydrogen LFL by an amount proport ional to methane’s LFL and the

concentration of methane in the mixture. This calcu lation may be enough to represent the

inhibition of hydrogen combustion by methane or the re would be positive differences between

the measured and calculated LFL values.

Table G.5 shows all the mixtures with hydrogen, met hane, and an inert. The values in

Table G.5 are shown in order of the relative amount of hydrogen in total combustibles [hydrogen

concentration/(hydrogen plus methane concentrations )]. As expected the difference between the

measured and calculated LFL values is negative for mixtures where hydrogen is 33% or less

showing the enhancement in combustion is likely due to the presences of hydrogen. For mixtures

with a relative amount of hydrogen of 66% or greate r, the difference between the measured and

calculated LFLs is between -0.66 and 0.55 percent. There are four of these mixtures and two

have negative difference and two with positive diff erences. These correspond with the inert in

the mixture; carbon dioxide is part of the mixtures with negative differences, and nitrogen is the

inert in the mixtures with positive differences. Go golek et al. (2010a) recommended different kvalues from those provided in Molnarne et al. (2005 ) and shown in Table G.3. The Gogolek et al.

recommended values are shown in Table G.6. Using th e Gogolek et al. recommended k values,

the differences between the measured and calculated LFLs is between -0.07 to 0.55. This is

closer to what one would expect for hydrogen and me thane mixtures when hydrogen makes up

66 percent or more of the combustibles.This information is distributed solely for the purpose of pre-dissemination peer review under applicable information quality guidelines. It has not beenformally disseminated by EPA. It does not representandshould not be construed to represent any Agency determination or policy.G-18Table G.5: Hydrogen, Methane Mixtures With Either Only Nitrogen or Carbon Dioxide as the InertHydrogen(H2)(Volume %)Methane (CH4)(Volume %)Nitrogen (N2)(Volume %)CarbonDioxide(CO2)(Volume %)ExperimentalLFL(Volume %)CalculatedLFL(Volume %)DifferenceBetweenCalculatedExperimentalLFL Values% ErrorFraction ofHydrogen inTotalCombustibles(volumefraction)Source3.620.675.820.8521.55-0.70 -3.23 0.15 Karim et al., 19855.629.764.714.3714.75-0.38 -2.57 0.16 Karim et al., 19856.926.566.71515.38-0.38 -2.48 0.21 Karim et al., 19855.118.776.321.1721.58-0.41 -1.88 0.21 Karim et al., 19857.323.669.116.0716.43-0.36 -2.20 0.24 Karim et al., 198510.429.060.613.213.91a-0.71a-5.13 0.26 Karim et al., 198510.521.168.415.9317.49b-1.56b-8.94 0.33 Karim et al., 198516.6 16.7 66.714 13.58 0.42 3.06 0.50 Jones, 192910.9 10.9 78.221.5 20.74 0.76 3.65 0.50 Jones, 192915.115.169.816.4117.20c-0.79c-4.57 0.50 Karim et al., 198512.812.874.518.5518.460.09 0.51 0.50 Karim et al., 198525.3 25.2 49.59.5 8.95 0.55 6.13 0.50 Jones, 192914.77.677.620.3520.150.20 0.98 0.66 Karim et al., 198516.54.479.122.7523.41d-0.66d-2.83 0.79 Karim et al., 198513.52.883.72726.450.55 2.09 0.83 Karim et al., 198518.33.678.121.5921.78e-0.19e-0.87 0.84 Karim et al., 1985aUsing k values recommended by Gogolek et al. (2010a), the calculated LFL would be 13.39 % with a difference of -0.19 % from the experimental value.bUsing k values recommended by Gogolek et al. (2010a), the calculated LFL would be 16.65 % with a difference of -0.72 % from the experimental value.cUsing k values recommended by Gogolek et al. (2010a), the calculated LFL would be 16.56 % with a difference of -0.15 % fromthe experimental value.dUsing k values recommended by Gogolek et al. (2010a), the calculated LFL would be 22.82 % with a difference of -0.07 % from the experimental value.eUsing k values recommended by Gogolek et al. (2010a), the calculated LFL would be 21.37 % with a difference of +0.22 % fromthe experimental value.This information is distributed solely for the purp ose of pre-dissemination peer review under applicab le information quality guidelines. It has not been formally disseminated by EPA. It does not repr esent and should not be construed to represent any Agency determination or policy.



## G-19 Table G.6. Nitrogen Equivalency Values from Molnarne et al. (2005) and Gogolek et al. (2010a)

Species Molnarne et al.

Nitrogen Equivalency
Values for CO 2 

## Gogolek et al

Nitrogen Equivalency
Values for CO 2 

## Methane 2.23 1.6 Propane 1.93 2.5 Ethylene 1.84 1.8

Ethane 1.92 2.4 Hydrogen 1.51 1.5

There are five mixtures that have 50 percent of the combustibles as hydrogen. The

differences between the measured and calculated val ues are 0.09 to 0.76% for the mixtures with

nitrogen, and -0.79% for the mixture with carbon di oxide. Using the Gogolek et al. (2010a)

recommended k values, the difference for the mixtur e with carbon dioxide between the measured

and calculated LFL is -0.15 percent. The Jones (192 9) values have a much higher level of

uncertainly than the newer Karim et al. (1985) data has. For the higher inert mixtures, the

uncertainty is at least ±0.5 percent for the Jones data. Also, the highest difference for hydrogen

of 66% or greater for the Karim et al data set (0.5 5%) is for the highest inert concentration,

which one would expect to result in a higher positi ve difference. Taking the high uncertainty in

the Jones data and the high inert concentration mix ture into account and using Gogolek et al.

recommended k values, the mixtures with hydrogen of 66 percent and greater have close

calculated and measured LFLs; the range of differen ces is from -0.15 and 0.20 percent.

There are 17 mixtures with hydrogen, methane, and c arbon monoxide. Small amounts of

hydrogen in carbon monoxide mixtures have also been found to enhance combustion (Wierzba

and Kilchyk, 2001). Wierzba and Kilchyk showed that 20 percent or less hydrogen with carbon

monoxide, will result in the calculated LFL values to be greater than the measured values. This

behavior is not identifiable by the measured LFL fo und for the 17 mixtures of hydrogen,

methane, and carbon monoxide. These data all came f rom Jones (1929) and have a large

variability. Eleven of the mixtures have an inert c oncentration of 79 percent or greater; therefore,

the mixtures are close to its LFL where the variati on between measured and calculated are at

their greatest. The difference between measured and calculated LFL from the 17 mixtures isThis information is distributed solely for the purp ose of pre-dissemination peer review under applicab le information quality guidelines. It has not been formally disseminated by EPA. It does not repr esent and should not be construed to represent any Agency determination or policy.



## G-20 between -0.21 and 2.97 percent. Just looking at tho se mixtures with an inert concentration less

than 79 percent the variation is -0.21 and 0.71 per cent. All but two of the mixtures had carbon

dioxide and nitrogen as inert; therefore, these wou ld be affected by using the Gogolek et al.

(2010a) k values. Using these k values, the range in differences for the 17 mixtures is -0.21 to

3.48 and looking only at the mixtures with inert co ncentration less than 79 percent, the variation

would be -0.21 to 0.85 percent. In both cases the r ange widens between the calculated and

measured differences.

The differences in the measured and calculated LFLs are relatively close when looking at

mixtures that are not as close to the maximum inert concentration. For hydrogen concentrations

of 33% or less of the total combustible, the data a ppears to show some combustion enhancement

by hydrogen (although the dataset is small so this can only be considered a preliminary

observation). Additional observations are less clea r or not possible with the data collected. Also,

it should be noted that no data was found to invest igate other chemical interactions reported in

literature (e.g., propylene inhibition of hydrogen combustion).This information is distributed solely for the purp ose of pre-dissemination peer review under applicab le information quality guidelines. It has not been formally disseminated by EPA. It does not repr esent and should not be construed to represent any Agency determination or policy.



# Appendix H

Effect Of Nitrogen And Carbon Dioxide On The LFL Of Various Components. [comparison of Le Chatelier equation to experimental LFL val ues]This information is distributed solely for the purpose of pre-dissemination peer review under applicable information quality guidelines. It has not beenformally disseminated by EPA. It does notrepresent and should not be construed to representany Agency determination or policy.H-1Table H.1. List of pure component LFL values used in the LFL calculations for each research report.Component iLFLiZabetakis(1965)Van denSchoor(2008)Kondoet al.(2008)Vidal etal.(2005)Mashuga(1999)Loehr etal.(1997)Karim(1985)Jones(1929)Jones &Kennedy(1932)and(1933)Hydrogen (H2)4----54.1344Methane (CH4)54.44.954.85-5.475.25Ethane (C2H6)3-------3.1Ethylene (C2H4)2.7-2.742.72.62-3.22--Propylene (C3H6)2.4-2.16------Propane (C3H8)2.1-2.03---2.4-2.3Butane (C4H10)1.8-------1.8Methyl ethyl ketone (C4H8O)1.9----1.95---Toluene (C7H8)1.2----1.2---Dimethyl ether (C2H6O)3.4-3.3------Methyl formate (C2H4O2)5-5.25------1,1 Difluoroethane (C2H4F2)4.32a-4.32------1,2 Dichloroethane (C2H4Cl2)4.85b----4.85---Hydrogen Sulfide (H2S)4--------Carbon Monoxide (CO)12.5-12.2---13.7613.3-Ammonia (NH3)15-15.2------aZabetakis (1965) does not include a LFL for 1,1 Difluoroethane. This value is from Kondo et al. (2008).bZabetakis (1965) does not include a LFL for 1,2 Difluoroethane. This value is from Loehr et al. (1997).This information is distributed solely for the purpose of pre-dissemination peer review under applicable information quality guidelines. It has not beenformally disseminated by EPA. It does not representand should not be construed to represent any Agency determination or policy.H-2Table H.2. Collected measured LFLs, the mixture composition, the calculated LFL using Zabetakis referenced purecomponent LFLs, the calculated LFL using the specificresearcher’s pure component LFLs, the source of each measured value, and the difference between the measured andcalculated values. WITHOUT INERT.

Hydrogen (H2) Methane (CH4) Ethane (C2H6) Ethylene (C2H4) Propylene (C3H6) Propane (C3H8) Butane (C4H10) Methyl ethyl ketone (C4H8O) Toluene (C7H8) Dimethyl ether (C2H6O) Methyl formate (C2H4O2) 1,1 Difluoroethane (C2H4F2) 1,2 Dichloroethane (C2H4Cl2) Ammonia (NH3) Carbon Monoxide (CO)ExperimentalLFLUsing Zabetakis PureComponent LFL ValuesUsing Experimental Pure Component LFLValuesSourceCalculatedLeChatelierLFLDifferenceBetweenCalculatedandExperimentalDifferenceOn aPercentBasis(%)CalculatedLeChatelierLFLDifferenceBetweenCalculatedandExperimentalDifference On aPercent Basis(%)75 25 3.8 4.21 -0.41 -10.92 4.10 -0.30-7.98 Kondo et al., 200840 60 4 4.55 -0.55 -13.64 4.23 -0.23 -5.77 Van den Schoor et al., 200850 50 5.2 5.54 -0.34 -6.61 5.42 -0.22-4.28 Kondo et al., 200825 75 8.71 9.09 -0.38 -4.37 8.89 -0.18-2.06 Kondo et al., 200833.333.333.43.913.660.256.514.08-0.17-4.29Karim et al., 198560 40 4 4.35 -0.35 -8.70 4.15 -0.15 -3.77 Van den Schoor et al., 200850 50 2.65 2.73 -0.08 -3.03 2.78 -0.13-4.97 Loehr et al, 199720 80 4.2 4.76 -0.56 -13.38 4.31 -0.11-2.71 Van den Schoor et al., 200825 75 6.44 6.55 -0.11 -1.76 6.55 -0.11-1.68 Kondo et al., 200875 25 3.35 3.40 -0.05 -1.38 3.45 -0.10-2.87 Kondo et al., 200823.176.954.730.275.465.09-0.09-1.78Karim et al., 198550 50 2.7 2.73 -0.03 -1.12 2.78 -0.08-3.02 Loehr et al, 199750504.634.440.194.014.71-0.08-1.65Karim et al., 19853.133.1393.712.2111.230.988.0612.28-0.07-0.58Karim et al., 19854040204.253.940.317.394.31-0.06-1.38Karim et al., 19853040304.133.760.379.014.19-0.06-1.34Karim et al., 198550 50 4.42 4.44 -0.02 -0.47 4.47 -0.05-1.24 Kondo et al., 200833 33 33 3.41 3.56 -0.15 -4.51 3.45 -0.04-1.26 Kondo et al., 200850 50 3.54 3.68 -0.14 -4.07 3.58 -0.04-1.18 Kondo et al., 200850 50 1.45 1.47 -0.02 -1.45 1.49 -0.04-2.46 Loehr et al, 19974030304.053.690.368.934.08-0.03-0.84Karim et al., 198550 50 3.75 4.14 -0.39 -10.34 3.78 -0.03-0.87 Kondo et al., 200833.333.333.34.053.660.399.714.08-0.03-0.71Karim et al., 198533 33 33 3.2 3.27 -0.07 -2.20 3.23 -0.03-0.79 Kondo et al., 200833 33 33 3.4 3.57 -0.17 -5.08 3.42 -0.02-0.72 Kondo et al., 200833 33 33 3.29 3.34 -0.05 -1.48 3.31 -0.02-0.71 Kondo et al., 200850 50 4.62 4.58 0.04 0.95 4.64 -0.02 -0.50 Kondo et al., 200883.38.348.334.464.320.143.224.48-0.02-0.51Karim et al., 198533 33 33 2.53 2.70 -0.17 -6.53 2.55 -0.02-0.90 Kondo et al., 20087.1585.77.155.565.130.437.765.58-0.02-0.38Karim et al., 198533 33 33 4.02 4.07 -0.05 -1.25 4.04 -0.02-0.51 Kondo et al., 200825 75 3.74 3.72 0.02 0.62 3.76 -0.02 -0.51 Kondo et al., 200850 50 2.91 2.96 -0.05 -1.64 2.93 -0.02-0.61 Kondo et al., 2008This information is distributed solely for the purpose of pre-dissemination peer review under applicable information quality guidelines. It has not beenformally disseminated by EPA. It does not representand should not be construed to represent any Agency determination or policy.H-3Table H.2. Collected measured LFLs, the mixture composition, the calculated LFL using Zabetakis referenced purecomponent LFLs, the calculated LFL using the specificresearcher’s pure component LFLs, the source of each measured value, and the difference between the measured andcalculated values. WITHOUT INERT.

Hydrogen (H2) Methane (CH4) Ethane (C2H6) Ethylene (C2H4) Propylene (C3H6) Propane (C3H8) Butane (C4H10) Methyl ethyl ketone (C4H8O) Toluene (C7H8) Dimethyl ether (C2H6O) Methyl formate (C2H4O2) 1,1 Difluoroethane (C2H4F2) 1,2 Dichloroethane (C2H4Cl2) Ammonia (NH3) Carbon Monoxide (CO)ExperimentalLFLUsing Zabetakis PureComponent LFL ValuesUsing Experimental Pure Component LFLValuesSourceCalculatedLeChatelierLFLDifferenceBetweenCalculatedandExperimentalDifferenceOn aPercentBasis(%)CalculatedLeChatelierLFLDifferenceBetweenCalculatedandExperimentalDifference On aPercent Basis(%)50 50 2.4 2.54 -0.14 -5.88 2.42 -0.02-0.65 Kondo et al., 200833 33 33 2.63 2.77 -0.14 -5.43 2.64 -0.01-0.54 Kondo et al., 200850 50 2.08 2.24 -0.16 -7.69 2.09 -0.01-0.62 Kondo et al., 20083050204.033.700.338.184.04-0.01-0.31Karim et al., 198550 50 3.66 4.03 -0.37 -10.02 3.67 -0.01-0.28 Kondo et al., 200875 25 5.89 6.00 -0.11 -1.87 5.90 -0.01-0.16 Kondo et al., 200825 75 3.07 3.05 0.02 0.62 3.08 -0.01 -0.30 Kondo et al., 200825758.698.170.526.028.70-0.01-0.08Karim et al., 198533 33 33 3.26 3.34 -0.08 -2.41 3.26 0.00 -0.15 Kondo et al., 200875 25 2.56 2.65 -0.09 -3.57 2.56 0.00 -0.17 Kondo et al., 200850 50 2.51 2.60 -0.09 -3.44 2.51 0.00 -0.15 Kondo et al., 200850 50 4.05 4.05 0.00 0.06 4.05 0.00 -0.06Kondo et al., 200833 33 33 3.37 3.57 -0.20 -6.02 3.37 0.00 -0.07 Kondo et al., 200850 50 2.33 2.36 -0.03 -1.39 2.33 0.00 -0.09 Kondo et al., 200833 33 33 1.95 1.94 0.01 0.76 1.95 0.00 -0.11Loehr et al, 199750 50 2.76 2.83 -0.07 -2.40 2.76 0.00 -0.08 Kondo et al., 200850 50 3.74 3.81 -0.07 -1.74 3.74 0.00 -0.05 Kondo et al., 200833 33 33 2.61 2.66 -0.05 -1.78 2.61 0.00 -0.04 Kondo et al., 200850 50 3.48 3.60 -0.12 -3.33 3.48 0.00 -0.02 Kondo et al., 200850 50 3.06 3.24 -0.18 -5.99 3.06 0.00 -0.02 Kondo et al., 200850 50 2.88 3.09 -0.21 -7.14 2.88 0.00 0.00 Kondo et al., 200850 50 4.74 4.64 0.10 2.21 4.74 0.00 0.00 Kondo et al., 200875 25 2.72 3.01 -0.29 -10.57 2.72 0.00 0.02 Kondo et al., 200875 25 2.47 2.70 -0.23 -9.31 2.47 0.00 0.06 Kondo et al., 200875 25 2.57 2.62 -0.05 -1.87 2.57 0.00 0.09 Kondo et al., 200825 75 3.87 3.93 -0.06 -1.66 3.87 0.00 0.08 Kondo et al., 200875 25 2.25 2.32 -0.07 -3.20 2.25 0.00 0.17 Kondo et al., 200850 50 3 3.01 -0.01 -0.33 2.99 0.01 0.20Kondo et al., 200850 50 7 7.14 -0.14 -2.04 6.99 0.01 0.12Kondo et al., 200825 75 2.18 2.22 -0.04 -2.00 2.17 0.01 0.43 Kondo et al., 200825 75 4.02 4.05 -0.03 -0.65 4.01 0.01 0.25 Kondo et al., 200875 25 3.65 3.70 -0.05 -1.25 3.64 0.01 0.33 Kondo et al., 200875 25 2.14 2.32 -0.18 -8.28 2.13 0.01 0.66 Kondo et al., 200833 33 33 3.43 3.46 -0.03 -0.83 3.42 0.01 0.42 Kondo et al., 2008This information is distributed solely for the purpose of pre-dissemination peer review under applicable information quality guidelines. It has not beenformally disseminated by EPA. It does not representand should not be construed to represent any Agency determination or policy.H-4Table H.2. Collected measured LFLs, the mixture composition, the calculated LFL using Zabetakis referenced purecomponent LFLs, the calculated LFL using the specificresearcher’s pure component LFLs, the source of each measured value, and the difference between the measured andcalculated values. WITHOUT INERT.

Hydrogen (H2) Methane (CH4) Ethane (C2H6) Ethylene (C2H4) Propylene (C3H6) Propane (C3H8) Butane (C4H10) Methyl ethyl ketone (C4H8O) Toluene (C7H8) Dimethyl ether (C2H6O) Methyl formate (C2H4O2) 1,1 Difluoroethane (C2H4F2) 1,2 Dichloroethane (C2H4Cl2) Ammonia (NH3) Carbon Monoxide (CO)ExperimentalLFLUsing Zabetakis PureComponent LFL ValuesUsing Experimental Pure Component LFLValuesSourceCalculatedLeChatelierLFLDifferenceBetweenCalculatedandExperimentalDifferenceOn aPercentBasis(%)CalculatedLeChatelierLFLDifferenceBetweenCalculatedandExperimentalDifference On aPercent Basis(%)50 50 3.37 3.32 0.05 1.39 3.35 0.02 0.50Kondo et al., 200833 33 33 2.63 2.77 -0.14 -5.43 2.61 0.02 0.64 Kondo et al., 20086.2493.812.0311.040.998.2612.010.020.15Karim et al., 198575 25 3.13 3.05 0.08 2.53 3.11 0.02 0.58Kondo et al., 200875 25 5 4.81 0.19 3.79 4.98 0.02 0.36 Kondo et al., 200850 50 2.63 2.81 -0.18 -6.99 2.61 0.02 0.72 Kondo et al., 200875 25 2.36 2.41 -0.05 -2.10 2.34 0.02 0.84 Kondo et al., 200825 75 3.16 3.19 -0.03 -1.05 3.14 0.02 0.65 Kondo et al., 200883.316.74.74.510.194.014.680.020.52Karim et al., 198575 25 2.39 2.59 -0.20 -8.39 2.36 0.03 1.08 Kondo et al., 200833 33 33 3.56 3.71 -0.15 -4.23 3.53 0.03 0.74 Kondo et al., 20088010103.973.740.235.883.940.030.70Karim et al., 198525 75 4.48 4.47 0.01 0.18 4.45 0.03 0.63Kondo et al., 200875 25 5.29 5.26 0.03 0.65 5.26 0.03 0.54Kondo et al., 200850 50 2.9 2.96 -0.06 -1.99 2.87 0.03 1.01 Kondo et al., 20084040203.983.630.358.713.950.030.81Karim et al., 198525 75 3.81 3.76 0.05 1.40 3.78 0.03 0.90Kondo et al., 200850 50 3.55 3.51 0.04 1.23 3.51 0.04 1.00Kondo et al., 20088010104.153.890.266.254.110.040.86Karim et al., 198525 75 3.63 3.70 -0.07 -1.81 3.59 0.04 1.01 Kondo et al., 200814.314.371.42.832.470.3612.622.790.041.38Karim et al., 198550 50 3.64 3.51 0.13 3.67 3.60 0.04 1.08Kondo et al., 200833 33 33 4.88 4.80 0.08 1.67 4.84 0.04 0.81Kondo et al., 200833 33 33 2 1.88 0.12 5.87 1.96 0.04 2.01 Loehr et al, 199733.333.333.36.075.660.416.746.030.040.67Karim et al., 198525 75 7.33 7.49 -0.16 -2.17 7.29 0.04 0.59 Kondo et al., 200864.335.75.555.280.274.845.500.050.82Karim et al., 198550506.46.060.345.306.350.050.73Karim et al., 19857.784.67.75.124.610.519.985.070.050.97Karim et al., 198516.783.39.969.230.737.339.910.050.52Karim et al., 19858.3383.38.334.884.400.489.804.830.051.12Karim et al., 198550 50 3.06 3.24 -0.18 -5.99 3.00 0.06 2.02 Kondo et al., 200850503.12.750.3511.163.040.062.07Karim et al., 198550 50 13.6 13.64 -0.04 -0.27 13.54 0.060.47 Kondo et al., 2008This information is distributed solely for the purpose of pre-dissemination peer review under applicable information quality guidelines. It has not beenformally disseminated by EPA. It does not representand should not be construed to represent any Agency determination or policy.H-5Table H.2. Collected measured LFLs, the mixture composition, the calculated LFL using Zabetakis referenced purecomponent LFLs, the calculated LFL using the specificresearcher’s pure component LFLs, the source of each measured value, and the difference between the measured andcalculated values. WITHOUT INERT.

Hydrogen (H2) Methane (CH4) Ethane (C2H6) Ethylene (C2H4) Propylene (C3H6) Propane (C3H8) Butane (C4H10) Methyl ethyl ketone (C4H8O) Toluene (C7H8) Dimethyl ether (C2H6O) Methyl formate (C2H4O2) 1,1 Difluoroethane (C2H4F2) 1,2 Dichloroethane (C2H4Cl2) Ammonia (NH3) Carbon Monoxide (CO)ExperimentalLFLUsing Zabetakis PureComponent LFL ValuesUsing Experimental Pure Component LFLValuesSourceCalculatedLeChatelierLFLDifferenceBetweenCalculatedandExperimentalDifferenceOn aPercentBasis(%)CalculatedLeChatelierLFLDifferenceBetweenCalculatedandExperimentalDifference On aPercent Basis(%)50 50 5.26 5.35 -0.09 -1.63 5.19 0.07 1.24 Kondo et al., 200850 50 4.66 4.64 0.02 0.53 4.59 0.07 1.46Kondo et al., 200850 50 6.45 6.42 0.03 0.45 6.38 0.07 1.08Kondo et al., 200828.671.42.82.430.3713.222.730.072.63Karim et al., 198512.512.5753.572.990.5816.143.500.072.07Karim et al., 198562.537.53.332.990.3410.313.250.082.37Karim et al., 198575 25 3.7 3.72 -0.02 -0.45 3.62 0.08 2.15 Kondo et al., 200837.262.83.7 3.52 0.18 4.74 3.61 0.09 2.42 Jones & Kennedy, 193375 25 6.22 5.88 0.34 5.43 6.12 0.10 1.58Kondo et al., 200850 50 7.44 7.14 0.30 3.99 7.34 0.10 1.33Kondo et al., 200875 25 3.82 3.93 -0.11 -3.00 3.72 0.10 2.61 Kondo et al., 200825 75 8.48 8.48 0.00 -0.05 8.38 0.10 1.19Kondo et al., 200833 33 33 3.4 3.08 0.32 9.29 3.30 0.10 3.02Loehr et al, 19975129.419.63.973.580.399.923.860.112.71Karim et al., 198577.822.23.673.330.349.253.560.113.00Karim et al., 198550 50 2.05 1.85 0.20 9.94 1.94 0.11 5.59Loehr et al, 199750 50 2.05 1.85 0.20 9.94 1.94 0.11 5.59Loehr et al, 199742.957.23.042.640.4013.272.930.113.78Karim et al., 198525 25 25 25 2.4 2.20 0.20 8.21 2.28 0.12 4.89Loehr et al, 199725 25 25 25 2.4 2.20 0.20 8.21 2.28 0.12 4.89Loehr et al, 199750 50 7.53 7.50 0.03 0.40 7.41 0.12 1.58Kondo et al., 200862.837.23.6 3.30 0.30 8.25 3.48 0.12 3.33 Jones & Kennedy, 193350 50 2.05 1.92 0.13 6.15 1.92 0.13 6.15Loehr et al, 199750 50 6.86 6.71 0.15 2.21 6.73 0.13 1.93Kondo et al., 200850 50 7.94 7.50 0.44 5.54 7.80 0.14 1.71Kondo et al., 200882.817.22.9 2.69 0.21 7.19 2.76 0.14 4.92 Jones & Kennedy, 193350 50 5.22 5.00 0.22 4.21 5.07 0.15 2.89Kondo et al., 200890.57.11.60.84.8 4.61 0.19 3.87 4.64 0.16 3.24 Jones & Kennedy, 193375 25 5.15 5.00 0.15 2.91 4.98 0.17 3.24Kondo et al., 200890.79.34.9 4.71 0.19 3.92 4.73 0.17 3.46 Jones & Kennedy, 19333040303.893.360.5313.693.690.205.06Karim et al., 198525 75 6 5.92 0.08 1.41 5.80 0.20 3.38 Kondo et al., 200833 33 33 2.65 2.35 0.30 11.32 2.44 0.21 7.75Loehr et al, 199783.516.54.75 4.50 0.25 5.17 4.54 0.21 4.40 Jones & Kennedy, 1933This information is distributed solely for the purpose of pre-dissemination peer review under applicable information quality guidelines. It has not beenformally disseminated by EPA. It does not representand should not be construed to represent any Agency determination or policy.H-6Table H.2. Collected measured LFLs, the mixture composition, the calculated LFL using Zabetakis referenced purecomponent LFLs, the calculated LFL using the specificresearcher’s pure component LFLs, the source of each measured value, and the difference between the measured andcalculated values. WITHOUT INERT.

Hydrogen (H2) Methane (CH4) Ethane (C2H6) Ethylene (C2H4) Propylene (C3H6) Propane (C3H8) Butane (C4H10) Methyl ethyl ketone (C4H8O) Toluene (C7H8) Dimethyl ether (C2H6O) Methyl formate (C2H4O2) 1,1 Difluoroethane (C2H4F2) 1,2 Dichloroethane (C2H4Cl2) Ammonia (NH3) Carbon Monoxide (CO)ExperimentalLFLUsing Zabetakis PureComponent LFL ValuesUsing Experimental Pure Component LFLValuesSourceCalculatedLeChatelierLFLDifferenceBetweenCalculatedandExperimentalDifferenceOn aPercentBasis(%)CalculatedLeChatelierLFLDifferenceBetweenCalculatedandExperimentalDifference On aPercent Basis(%)74.425.63.65 3.44 0.21 5.86 3.44 0.21 5.86 Jones & Kennedy, 193391.28.84.75 4.46 0.29 6.14 4.53 0.22 4.59 Jones & Kennedy, 193350 50 3.65 3.51 0.14 3.93 3.40 0.25 6.79Mashuga, 199925 75 6.31 6.49 -0.18 -2.80 6.06 0.25 4.00 Kondo et al., 200833.433.333.33.833.240.5915.413.570.266.92Karim et al., 198589.510.54.5 4.21 0.29 6.37 4.21 0.29 6.37 Jones & Kennedy, 193350 50 4.25 4.05 0.20 4.76 3.94 0.31 7.20Kondo et al., 200850 50 3.15 2.58 0.57 18.21 2.81 0.34 10.93 Loehr et al, 199750 50 5.35 4.38 0.97 18.05 4.92 0.43 7.97Loehr et al, 199725 75 10.94 10.00 0.94 8.59 10.31 0.635.73 Kondo et al., 200875 25 15.2 14.29 0.91 6.02 14.32 0.88 5.79 Kondo et al., 2008This information is distributed solely for the purpose of pre-dissemination peer review under applicable information quality guidelines. It has not beenformally disseminated by EPA. It does not representand should not be construed to represent any Agency determination or policy.H-7Table H.3. Collected measured LFLs, the mixture composition, the calculated LFL using Zabetakis referenced purecomponent LFLs, the calculated LFL using the specificresearcher’s pure component LFLs, the source of each measured value, and the difference between the measured andcalculated values. WITH INERT.

Hydrogen (H2) Methane (CH4) Ethane (C2H6) Methyl ethyl ketone (C4H8O) Toluene (C7H8) 1,2 Dichloroethane (C2H4Cl2) Carbon Monoxide (CO) Nitrogen (N2) Carbon Dioxide (CO2) Carbon Tetrachloride (CCl3)TotalInertExperimentalLFLUsing Zabetakis PureComponent LFL ValuesUsing Experimental Pure Component LFLValuesUsing Experimental PureComponent LFL ValuesSourceCalculatedLeChatelierLFLDifferenceBetweenCalculated andExperimentalDifferenceOn aPercentBasis(%)CalculatedLeChatelierLFLDifferenceBetweenCalculated andExperimentalLFL ValuesDifferenceOn aPercentBasis(%)CalculatedLFLDifferenceBetweenCalculatedExperimentalLFL ValuesDifferenceOn aPercentBasis(%)5.2 4.95 4.6 61.623.6585.2542.5 37.62 4.88 11.48 38.49 4.01 9.43 41.78 0.72 1.72 Jones, 192910.4821.0968.4268.4215.9314.621.318.2115.640.291.8317.49-1.56-9.82Karim et al., 198510.9 10.9 78.278.2021.5 20.39 1.11 5.18 20.74 0.76 3.53 20.74 0.76 3.65 Jones, 19296.3 6 5.25 72.451082.4534 31.30 2.70 7.94 32.01 1.99 5.84 32.93 1.07 3.26Jones, 19299.3 10.3 9.5 70.970.9020.5 19.44 1.06 5.19 19.92 0.58 2.83 19.92 0.58 2.91 Jones, 192915.1115.1169.7769.7716.4114.701.7110.3915.570.845.1117.20-0.79-4.79Karim et al., 198510.3829.0260.6160.6113.211.911.299.7912.790.413.0913.91-0.71-5.41Karim et al., 19853.6020.6275.7875.7820.8519.900.954.5321.55-0.70-3.3421.55-0.70-3.34Karim et al., 198516.484.4079.1279.1222.7520.002.7512.0920.861.898.3223.41-0.66-2.91Karim et al., 19855.0518.6676.2976.2921.1720.021.155.4421.58-0.41-1.9221.58-0.41-1.92Karim et al., 19856.8726.4766.6766.671514.270.734.9015.38-0.38-2.5515.38-0.38-2.55Karim et al., 19855.5729.7164.7264.7214.3713.630.745.1214.75-0.38-2.6414.75-0.38-2.64Karim et al., 19857.2823.6569.0769.0716.0715.270.804.9916.43-0.36-2.2516.43-0.36-2.25Karim et al., 19854.1 1.35 7.6 79.27.7586.9558 52.55 5.45 9.40 53.88 4.12 7.11 55.73 2.27 4.08Jones, 192918.303.5778.1478.1421.5918.912.6812.4019.681.918.8621.78-0.19-0.87Karim et al., 19854.3 0.2 23.7 55.915.971.8036 33.21 2.79 7.75 34.54 1.46 4.06 36.16 -0.16 -0.45 Jones, 192914.55.779.879.8020.95 20.83 0.12 0.56 21.10 -0.15 -0.73 21.10 -0.15-0.72 Jones & Kennedy, 19336.3 6.7 6.1 80.980.9031.5 29.39 2.11 6.71 30.10 1.40 4.44 30.10 1.40 4.65 Jones, 19295.4 0.4 8.5 73.7511.9585.7052.5 47.39 5.11 9.73 48.40 4.10 7.81 50.58 1.92 3.80 Jones, 192952.6180.329.129.406.2 6.05 0.15 2.37 6.13 0.07 1.21 6.25 -0.05 -0.83Jones & Kennedy, 193352.31928.728.706 5.95 0.05 0.75 6.03 -0.03 -0.47 6.03 -0.03 -0.47Jones & Kennedy, 19336915.80.414.815.205.4 5.24 0.16 2.87 5.29 0.11 2.00 5.34 0.06 1.11 Jones & Kennedy, 193333 33 33 33.00 2.35 2.23 0.12 5.16 2.25 0.10 4.21 2.27 0.08 3.74 Loehr et al, 199712.7512.7574.5074.5018.5517.431.126.0418.460.090.5018.460.090.50Karim et al., 198520.84.974.374.3014.9 14.63 0.27 1.78 14.75 0.15 1.02 14.75 0.15 1.03 Jones & Kennedy, 193233 33 33 33.00 2.45 2.23 0.22 9.03 2.25 0.20 8.12 2.27 0.18 8.16 Loehr et al, 19979 9.7 11.3 521870.0021.5 19.63 1.87 8.69 20.14 1.36 6.32 20.80 0.70 3.35 Jones, 192914.747.6277.6477.6420.3519.201.155.6620.150.200.9720.150.200.97Karim et al., 198525 25 25 25 25.00 2.8 2.55 0.25 8.77 2.58 0.22 7.97 2.59 0.21 8.05 Loehr et al, 199727.58.464.164.1012.4 12.05 0.35 2.84 12.18 0.22 1.77 12.18 0.22 1.80 Jones & Kennedy, 193325.3 25.2 49.549.509.2 8.80 0.40 4.36 8.95 0.25 2.70 8.95 0.25 2.77 Jones, 192925 25 25 25 25.00 2.9 2.49 0.41 14.31 2.59 0.31 10.79 2.60 0.30 11.55 Loehr et al, 199773.112.114.814.805.7 5.36 0.34 5.95 5.40 0.30 5.29 5.40 0.30 5.58 Jones & Kennedy, 193340.67.627.624.251.8010.05 9.39 0.66 6.60 9.46 0.59 5.88 9.72 0.33 3.39Jones & Kennedy, 1933This information is distributed solely for the purpose of pre-dissemination peer review under applicable information quality guidelines. It has not beenformally disseminated by EPA. It does not representand should not be construed to represent any Agency determination or policy.H-8Table H.3. Collected measured LFLs, the mixture composition, the calculated LFL using Zabetakis referenced purecomponent LFLs, the calculated LFL using the specificresearcher’s pure component LFLs, the source of each measured value, and the difference between the measured andcalculated values. WITH INERT.

Hydrogen (H2) Methane (CH4) Ethane (C2H6) Methyl ethyl ketone (C4H8O) Toluene (C7H8) 1,2 Dichloroethane (C2H4Cl2) Carbon Monoxide (CO) Nitrogen (N2) Carbon Dioxide (CO2) Carbon Tetrachloride (CCl3)TotalInertExperimentalLFLUsing Zabetakis PureComponent LFL ValuesUsing Experimental Pure Component LFLValuesUsing Experimental PureComponent LFL ValuesSourceCalculatedLeChatelierLFLDifferenceBetweenCalculated andExperimentalDifferenceOn aPercentBasis(%)CalculatedLeChatelierLFLDifferenceBetweenCalculated andExperimentalLFL ValuesDifferenceOn aPercentBasis(%)CalculatedLFLDifferenceBetweenCalculatedExperimentalLFL ValuesDifferenceOn aPercentBasis(%)16.6 16.7 66.766.7014 13.35 0.65 4.63 13.58 0.42 2.97 13.58 0.42 3.06Jones, 192926.323.650.150.108.2 7.62 0.58 7.10 7.77 0.43 5.27 7.77 0.43 5.56 Jones & Kennedy, 193350 50 50.00 2.9 2.40 0.50 17.24 2.40 0.50 17.24 2.43 0.47 19.57 Loehr et al, 199733 33 33 33.00 3.45 2.92 0.53 15.50 2.92 0.53 15.50 2.94 0.51 17.39 Loehr et al, 199720 20 20 20 20 20.00 3.4 2.75 0.65 19.012.85 0.55 16.08 2.87 0.53 18.63 Loehr et al, 199750 50 50.00 10.8 8.00 2.80 25.93 10.00 0.80 7.41 10.26 0.54 5.25 Loehr et al, 19977.25 7.8 9.95 601575.0026 23.99 2.01 7.73 24.63 1.37 5.28 25.45 0.55 2.15Jones, 192913.522.7883.7083.702725.411.595.8826.450.552.0526.450.552.05Karim et al., 198533 33 33 33.00 3.5 2.92 0.58 16.71 2.92 0.58 16.71 2.94 0.56 19.09 Loehr et al, 199733 33 33 33.00 4.85 4.14 0.71 14.70 4.21 0.64 13.10 4.26 0.59 13.73 Loehr et al, 199725.223.651.251.207.8 7.06 0.74 9.50 7.19 0.61 7.85 7.19 0.61 8.52 Jones & Kennedy, 19327.55 3.55 2.4 81.64.986.5039.5 35.85 3.65 9.24 36.36 3.14 7.96 36.86 2.64 7.17 Jones, 192950 50 50.00 4.65 3.80 0.85 18.28 3.90 0.75 16.13 3.97 0.68 17.21 Loehr et al, 199733 33 33 33.00 3.65 2.80 0.85 23.36 2.93 0.72 19.66 2.95 0.70 23.66 Loehr et al, 199725 25 25 25 25.00 3.95 3.10 0.85 21.473.23 0.72 18.30 3.25 0.70 21.66 Loehr et al, 199725 25 25 25 25.00 5.15 4.07 1.08 20.954.35 0.80 15.48 4.39 0.76 17.36 Loehr et al, 19970.95 36.7 3.7 58.20.4558.6513 12.70 1.30 9.28 13.20 0.80 5.68 13.21 0.79 5.95Jones, 192933 33 33 33.00 5.2 3.90 1.30 24.93 4.25 0.95 18.25 4.29 0.91 21.18 Loehr et al, 199733 33 33 33.00 5.2 3.90 1.30 24.93 4.25 0.95 18.25 4.29 0.91 21.18 Loehr et al, 19973.65 3.55 9.5 67.2516.0583.3048.5 41.97 6.53 13.46 43.30 5.20 10.72 46.08 2.42 5.25 Jones, 19293.55 1.95 13.8 78.52.280.7046 41.99 4.01 8.72 43.48 2.52 5.49 43.83 2.17 4.95Jones, 19292.1 13.75 4 73.46.7580.1530.5 27.82 2.68 8.80 28.82 1.68 5.51 29.44 1.06 3.61 Jones, 19293 0.1 30.65 57.958.366.2534 31.04 2.96 8.72 32.53 1.47 4.31 33.29 0.71 2.14Jones, 19296.25 2.4 12.05 736.379.3036.5 33.26 3.24 8.87 34.13 2.37 6.50 34.73 1.77 5.10 Jones, 192933 33 33 33.00 9.7 6.64 3.06 31.52 7.46 2.24 23.09 7.58 2.12 27.89 Loehr et al, 19972.39.41.586.886.8036.5 33.84 2.66 7.29 34.03 2.47 6.78 34.03 2.47 7.27 Jones & Kennedy, 193233 33 33 33.00 10.1 6.64 3.46 34.23 7.46 2.64 26.13 7.58 2.52 33.17 Loehr et al, 19974.79.885.585.5025.8 22.51 3.29 12.74 23.06 2.74 10.62 23.06 2.74 11.88 Jones & Kennedy, 19322.38.32.187.387.3037.7 34.07 3.63 9.62 34.34 3.36 8.92 34.34 3.36 9.80 Jones & Kennedy, 19322.4 8.95 6.65 69.9512.0582.0040 34.22 5.78 14.44 35.45 4.55 11.38 37.03 2.97 8.02 Jones, 19292.191.187.887.8042.2 37.15 5.05 11.96 37.32 4.88 11.57 37.32 4.88 13.09 Jones & Kennedy, 1932This information is distributed solely for the purp ose of pre-dissemination peer review under applicab le information quality guidelines. It has not been formally disseminated by EPA. It does not repr esent and should not be construed to represent any Agency determination or policy.



## I-1 APPENDIX I

Appendix I provides methodology for calculating unobstructed cross sectional area of several flare tip de signs.This information is distributed solely for the purp ose of pre-dissemination peer review under applicab le information quality guidelines. It has not been formally disseminated by EPA. It does not repr esent and should not be construed to represent any Agency determination or policy.



## I-2This information is distributed solely for the purp ose of pre-dissemination peer review under applicab le information quality guidelines. It has not been formally disseminated by EPA. It does not repr esent and should not be construed to represent any Agency determination or policy.



## I-3