EPA 600/ 2- 86/(80

... ¥> 

# .. UnitedStates Erwironmemal**Pro~ectrC>n** Agency 

## ... 

# Researchand Development

EVALUATIONOFTHE EFFICIENCYOFINDUSTRIAL**FLA~ES:** H2SGAS MIXTURES AND PILOTASSISTEDFLARES


# Preparedfor EPA-600/2-86-080 September1986

Office.ofAirQualityPlanning and Standards



# Prepared

# by Airand Energy Engineering Research Laboratory ResearchTrianglePark NC 27711r .

RESEARCH REPORTING SERIES
Research reportsoftheOfficeofResearchandDevelopment.U.S.Environmental ProtectionAgency. have been grouped into nineseries.These ninebroadcategories were establishedto facilitatefurther development and applicationofenvironmental technology. Elimination of traditional grouping was consciously plannedtofost8ftechnologytransferandamaximuminterfaceinrelatedfields. Thenineseriesare: 1. EnvironmentalHealthEHeets Research 2. Environmental ProtectionTechnology 3. Ecological Research 4. EnvironmentalMonitoring 5. SocioeconomicEnvironmentalStudies 6. ScientificandTechnicalAssessment Reports (STAR) 7. InteragencyEnergy-EnvironmentResearchand Development 8

... Special"Reports 9. MiscellaneousReports Thisreport has been assignedtothe ENVIRONMENTAL PROTECTION TECHNOLOGYseries.This series describesresearchperformedtodevelopanddem· onstrate instrumentation, equipment, and methodologyto repairorprevent en· vironmentaldegradationfrompointandnon-pointsourcesofpollution.Thiswork providestheneworimprovedtechnology requiredforthecontrolandtreatment ofpollutionsourcestomeetenvironmentalqualitystandards.

U.;:>. Environnl:'.rt'il Prnt,.ct1oo Agi..l::l01**:cn-··~·-y, R"~**  ·**~-~n ~**  F'M<Hl-A 10: MStreet, S.W. \>i;,:.'das\•n. DC 20460

..·.:.:;1 EPAREVIEW NOTICE
Thisreporthasbeen reviewedbytheU.S. EnvironmentalProtectionAgency,and approvedforpublication.Approvaldoesnotsignifythatthecontentsnecessarily reflect theviews and policyoftheAgency, nordoes mentionoftradenamesor commercialproductsconstituteendorsementorrecommendationforuse. ThisdocumentisavailabletothepublicthroughtheNationalTechnicalInformationService, Springfield,Virginia22161.

### t> \/ \

• ' i ') : \ ',. ) ••. ·J 

## v' EPA-600/2-86-080 September1986


### EVALUATION OF THE EFFICIENCY OF INDUSTRIAL FLARES: H2S GAS MIXTURES AND PILOT ASSISTED FLARES
Prepared by: J. H. Pohl and N. R. Soelberg

• 

### ENERGY AND ENVIRONMENTAL RESEARCH CORPORATION 18 MASON IRVINE, CALIFORNIA 92718

EPA Contract No. 68-02-3661

EPA Project Officer: Bruce A. Tichenor Air and Energy Engineering Research Laboratory Hazardous Air Technology Branch Research Triangle Park. North Carolina 27711
Prepared for: U.S. Environmental Protection Agency

Office of Research and Development Washington, D.C. 20460

U.S EPAHeadquartersLibrary Mailcode3404T 1200PennsylvaniaAvenueNW Washington, DC 20460 282-566-0556ABSTRACT The U.S. EPAhas contractedwith Energy and EnvironmentalResearch Corporationtoconduct a researchprogramwhichwill resultinquantification ofemissionsfrom, and efficienciesof, industrialflares. Theprogramis dividedintofourphases: PhasesI andII (ExperimentalDesign and Designof TestFacilities, respectively) havebeenreported inreportEPA-600/2-83-070; andPhasesIll andIV (DevelopmentofTestFacilities and DataCollection) have beenreportedinreport EPA-600/2-84-095. Further datacollection (partof PhaseIV) isreportedinreport EPA-600/2-85-106. Initialresults (EPA-600/2·84-095) werelimited to tests conductedburning propane/N2 mixturesinpipeflares withoutpilotflare stabilization. Further results (EPA-600/2-85-106) reportedthew.fluence oftheflaredgas andflare headdesignondestructionandcombustionefficiencywithout stabilizationby pilotflares. Thecurrentreportisthefourthinthe series andgives testdata onthe combustionefficiencyanddestructionefficiencyof(1) gas mixtures containingH2S, and {2) flareflames with pilotflare stabilization. Thetestswere conductedon3- and6-in. openpipeflareswithout aerodynamicflame stabilization devices. Thefollowing results were obtainedfrom this work: o Gasmixturesof•H2S/N2 canbe stablyflared atmuchlowervolumetric gasheatingvalues thancan propane/N2 mixtures. o Destructionandcombustionefficienciesgreater than98% areobtained forgasmixturesofH2S/N2 andH2S/propane/N2 when thegasheating valueis atleast1.2 timesthelevelrequired to produce a stableflame. 0

0

0

0 FormixturescontainingbothH2S and propane, H2S destructionefficiencywas consistentlyhigher thanpropanecombustionefficiency. Thegasheatingvaluerequiredto maintaina stableflame, including theheatingvaluecontributionofthe pilotgas, is3 timeslowerwith pilot assistthanwithoutpilot assiston3- and6-in. open pipeflares withoutaerodynamicflame stabilizationdevices. Combustionefficienciesgreaterthan98% for pilot assistedflares are achievedwhentheheatingvalueisgreaterthan 1.2 timesthatrequiredto stabilizetheflame. Increasingthepilotflowfrom 2 to5 scfm, orthenumberofpilotflames from 1to3 (on3- and 6-in. openpipeflares withoutotherflame stabilization) coulddecreasetheheatingvalueofthe gas requiredfor stability byabout 10-20%. 

### •

ii



## ----·---·------------------------------------------

### TABLE OF CONTENTS Section 

### LIST OF FIGURES • • • 

# .

# ..

# . .. .

# . . • • • • • v 

### LIST OF TABLES 

# ..

# . .. . .

# . . ..

# .

# .. . .. . .

# . . • • vi 1.0

2.0

3.0

4.0 

### INTRODUCTION • 1.1 

### Previous Flare Results 1.2 

### Objectives •••• 1.3 Approach •••••• 1.4 References •.•• 

### SUMMARY AND CONCLUSIONS 2.1 

### Summary ••••••• 2.2 Conclusions

. • • • 2.3 References••••• 

### GAS MIXTURE TEST OF H2S 

# . . ...

# .. . . .

# . .. .

• I •


# . . .

# . ...


# . . . . . .

# . .. . . . .

# .
. . . .

# . ..



# . . . . .
. .. . 

# . . . .

. . . . . .. • • 1-1
• • 1-2 • • 1-7 • • 1-7 • • 1-10
• 2-1
• • 2-1 • 2-25 • • 2-26 

### 3-1

. 3-2 3.1 Measurement Techniques 

### 3.2 Laboratory Scale Tests • • • • • • 3-3 

### 3.3 Pilot Scale Tests ••••• 3.4 References••••••• 

### PILOT ASSISTED TEST RESULTS 

## .

# . . 4.1 Flame Stability •••••••

# . .. 4.2 Combustion Efficiency • 4.3 References•.•••••••••• • • • • 3-8 • 3-19 

### •• 4-1



# .

# . . . • 4-3 • 4-12



# . . . • 4-14 

### APPENDICES A

B 

### EPA FLARE TEST FACILITY AND PROCEDURES A.l 

### Flare Test Facility •.••••• A.2 FTF Procedures .•••••••• A.3 References • • • • • • • • • • •

# . .

# .. FLARE SCREENING FACILITY AND TEST PROCEDURES B.l Flare Screening Facility ••• 8.2 FSF Test Procedures •••••••••• B.3 Reference • • • • • • • • • •

Hi • A-1
• •• A-1 

### • • • A-6 • A-7



# .

# .. • • • • B-1
• • • B-1 

### • B-3 • • • B-3

### Section


## c

D

E

F 

### TABLE OF CONTENTS (CONTINUED)

FLAME STABILITY LIMIT•• C.1 Stability Limits C.2 References •.•

# . . .

# .

# .. . DATA ANALYSIS••••• D.1 FTF Data Analysis •• D.2 FSF Data Analysis 0.3 References•••.•• 

### QUALITY ASSURANCE•••. E.1 Flowrate Measurement. E.2 Sample Analysis E.3 References••. 

### CONVERSION FACTORS • 

# .

# . .

.

# . . . ..



# ..

•

1v • •



# . .

# . .

. .

..

# . .
.

# . ..


# . . • C-1 • • • • C-1



# . . ..

# .• • C-1



# ..

# .• • • D-1 •• D-1

.. • • • • • • D-4 •••••• D-8 

### • E-1



# . . . . . . • • • E-1

. E-2 

### •E-4 

# . . .
. . . .

.

# . . • F-1

•LIST OF FIGURES**~igure** 2-1 Flare Screening Faci1ity (FSF) • • • • • • • • • • • • • • 2-3 2-2 Flame stabilfty curves for propane/N2 and HzS/propane/Nz gas mixtures flared using a 0.042 inch ID nozzle • • • • • • • 2-5 2-3 EPA Flare Test Facility (FTF) at EER • • • • • • • • • • • 2-6 2-4 Flame stability limits for H2S gas mixtures flared using a 3-inch diameter open pipe flare. • • • • • • • • • • • • 2-8 2-5 Propane combustion efficiency of H2S/propane/N2 gas mixtures flared from an unassisted 3-inch open pipe flare • • • • • 2-10 2-6 Destruction efficiency of H2S gas mixtures flared from an unassisted 3-inch open pipe flare • • • • • • • • • • • 2-11 2-7 Correlation between H2S destruction efficiency and propane combustion efficiency for H2S/propane/N2 mixtures fiared from an unassisted 3-inch open pipe flare. • • . . • • • 2-12 2-8 Flame stability curves for 3-inch pipe flare with a single pilot at a pilot gas flowrate of 2.1-2.2 scfm natural gas. 2-17 2-9 Flame stability curves for 6-inch open pipe flare with a single pilot at a pilot gas flowrate of 1.0-1.1 scfm natural gas • • • • • • • • • . • • . • • • • • • • • • • • • 2-18 2-10 Flame stability curves for 6-inch open pipe flare with a single pilot at a pilot gas flowrate of 2.1-2.4 scfm natural gas •.•....•...... - • . • • • . • • • • 2-19 2-11 Flame stability curves for 6-inch open pipe flare with a single pilot at a pilot gas flowrate of 3.9-5.4 scfm natural gas . . . . . . . . . . . . . . . . . . . . . . . . . 2-20 2-12 Flame stability curves for 6-inch open pipe flare with multiple pilots at a total pilot gas flowrate of 2.0-2.3 scfm natural gas • • • . • • • • • • • • • • 2-21 2-13 Calculated adiabatic flame temperature vs. limiting stable gas exit velocity for propane/Nz gas mixtures flared using pilot-assisted 3-inch and 6-inch open pipe flares. • 2-23 2-14 Combustion efficiency of pilot assisted flares • • • • • • 2-24 3-1 Flame stability curves for**propane/N~** and H2S/propane/N2 gas mixtures flared using a 0.042 1nch ID nozzle • • • • • • • 3-6 3-2 Flame stability curves for H2S gas mixtures flared using a 3-inch diameter open pipe flare • • • • • • • • • • • • • • 3-9 3-3 Flame stability curves using heating value per mass relationship • • • • • • • • . . • • • • • . • • • • • • 3-10 3-4 Calculated adiabatic flame temperature versus limiting stable gas velocity from an unassisted 3-inch open pipe flare • • • • 3-13 3-5 Propane combustion efficiency of HzS/propane/N2 gas mixtures flared from an unassisted 3-inch open pipe f1are . . . . . . .. . . . . . . . . . . . . . . . . 3-16 3-6 Destruction efficiency of HzS gas mixtures flared from an unassisted 3-inch open pipe flare • • • • • • • • 3-17 3-7 Correlation between HzS destruction efficiency and propane combustion efficiency for H2S/propane/N2 mixtures flared from an unassisted 3-inch open pipe flare. • • • • • • 3-18 4-1 Schematics of single, double, and triple pilots • • • • • • 4-2

v

### Figure 4-2 

### 4-3 4-4 4-5 

### 4-6 4-7 4-8 

### A-1 A-2 

### A-3 8-1 D-1



### Table 1-1 2-1 2-2 

### 2-3 3-1 3-2 3-3 E-1 FIGURES (CONTINUED)
Flame stability curve for 3-inch pipe flare with a single

pilot at a 

### pilot gas flowrate of 2.1-2.2 scfm natural gas••• Flame stability curves for 

### 6-inch open pipe flare with a single pilot at a pilot gas flowrate of 1.0-1.1 scfm natura1 gas . . . • • . . . . . • . . . . • . .. . . • . . . . 

### Flame stability curves for 6-inch open pipe flare with a single pilot at apilot gas flowrate of 2.1-2.4 scfm natura1 gas . . . . . . • . . . . . . . . . . . . . . . . . . 

### Flame stability curves for 6-inch open pipe flare with a single pilot at a pilot gas flowrate of 3.9-5.4 

### scfm natural gas . . . . . . • . • .. . . . . . . . • . . . . . • . 

### Flame stability curve for 6-inch open pipe flare with multiple pilots at a total pilot gas flowrate of 2.

### 0-2.3scfm natura1 gas • • o• • o o o o o• • • • Calculated adiabatic flame temperature vso limiting stable 4-4 4-6 4-7 4-8 4-9 

### gas exit velocity for propane/Nz gas mixtures flared using pilot-assisted l-inch and 6-inch open pipe flares•• Combustion efficiency of pilot assisted flares •• • • 4-11 

### EPA Flare Test Facility (FTF) at EER • o •••• o Fuel flow control and metering system schematic•• • 0 

### 4-13 •• A-2 

### • • A-3 Flare Test Facility sample system. • • • •• o • A-5 

### Flare Screening Facility (FSF) ••••••••• Schematic of integration geometry••••••••• 0 • • • 8·2

• 0 • • 

### D·S

LIST OF TABLES Summary of Previous Flare Combustion Efficiency Studies •• Flare Screening Facility HzS Gas Mixture Test Results. Nozzle ID • Oo042 Inches • o •••••••••••••• H2S Gas Mixture Combustion and Destruction Efficiency Test Results

........................ . 

### Pilot Assisted Flare Head Test Results•••••••••• Measurement Techniques for H2S and SOz •••••••••••• Flare Screening Facility HzS Gas Mixture Test Results. Nozzle ID • 0.042 Inches •••••••••••••• Physical Properties of HzS and Propane at 60F, 1 Atlnosphere• •••••••••••••••••••••.•• 

### Flare Facility Analytical Methods ••••••••••• • •



### vi Page 1-3 2-4 2-7 2-13 3-4 3-7 3-14 E-3 •1.0 INTRODUCTION Large amounts ofwaste and purge gases are flared annually in the United States and worldwide. Exact figures are uncertain because of the limited measurement and control of flare gas flow. An estimate ofthe amount of gas flared in the United States in 1974 was 12 million tons1 {1.1); this estimate was extrapolated to 16 million tons of gas flared in 1980 (1.2). Sources of flared gases include oil refineries, oil and gas production, blast furnaces, coke ovens, and chemical plants. By volume, the largest contributor is from blast furnaces which were estimated to release 9.6 million tons {69 x 1012 Btu) in 1980•.By energy released however, the major contributors are oil refineries and oil and gas production wells which were estimated to release 5.0 million tons (219 x 1012 Btu) in 1980. Commonly flared gases include a wide variety of compounds, such as aliphatic hydrocarbons, aromatic hydrocarbons, and chlorinated, oxygenated, nitrogen-bearing, or sulfurbearing compounds. Industrial f'Jare operating conditions and emissions are frequently very difficult to measure. Flow control and measurement is often limited or nonexistent. Many flares burn mixtures of leaked or purged gases where the gas composition is largely unknown. Generally, flares are elevated to decrease ground level noise and radiation and to enhance dissipation of heat and combustion products. For this reason collection of plume samples from commerci61 flares is difficult. Various methods to determine plume composition and flare emissions by remote means are still being developed and are not yet available. The most flexible, economical and accurate method of determining flare emission and combustion efficiency is to use a pilot-scale facility dedicated to accurate flare gas flowrate measurement and control with reliable plume sampling to determine flare emissions. Scaling is then required to apply

1 English units are generally used throughout this report. Appendix F provides conversion factors from English to Metric units.



# ,_, •

### pilot-scale results to full-scale flare operations. Several studies have been conducted in which scaling criteria have been evaluated (1.2- 1.7). Flare research has been conducted at Energy and Environmental Research Corporation (EER) since 1980 (1.2, 1.4). Apilot-scale flare test facility was constructed for the 

## u.s. EPA in 1982. This research has been sponsored by the 

## u.s. EPA as part of an effort to provide data upon which to base regulations for industrial flaring practices. 1.1 Previous Flare Results In the past 15 years there has been increased interest in research on flare combustion efficiency, due largely to increased governmental and industrial environmental awareness. Since flare research using full-scale industrial flares is difficult and expensive, most recent research has been conducted on pilot-scale flares 12 inches in diameter or less. Industrial flares are as large as 60 inches in diameter, so application of pilot-scale test results to these large flares requires scaling, using fundamental energy and mass transfer principles. Scaling is difficult, however, because of {1) basic aerodynamic differences, such as incompatible Reynolds number and Richardson number relationships, between small and large flames, (2) nonlinear flame envelope and combustion zone characteristics, (3) the effects of the wide variety of industrial flare types and designs on flare performance, and (4) differences in wind and weather conditions. Scaling criteria have been investigated at EER by testing different sized flares (0.042-inch to 12- inch diameter) for comparison of fundamental differences (1.2, 1.3, 1.4, 1.6 1.7). Noble, et al (1.5) have also studied scaling criterial. Flare combustion efffciency research up to 1983 has been reviewed by Dubnowski and Davis (1.8). Since 1972, flares and nozzles with 0.042-inch to 47-inch diameters have been tested. As Table 1-1 shows, flare combustion efficiency testing after 1983 has been conducted by Pohl, et al. (1.3) and Pohl and Soelberg {1.6). Awide variety of commercial heads have been evaluated, and a data base of results from open pipe flares and nozzles has been accumulated. Gas exit velocities have ranged between 0.15 to 891 ft/

1-2**~** I w STUDY PAIAIIr (1.9) Herget (1.10) StrAitz (1.11) Siegel (1.12} Lee & Whipple (1.13)**HDN~s,** ettl. (1.14)

McDilllei (1.15, 1.16}

Pohl, etAI (1.2) 

### TABlE 1-1. SUMMARY OF PREVIOUS FLARE COMBUSTION EFFICIENCY STUDIES1

fLAil£ GAS EXIT GAS**MEASUR~g,.** COfiiUSTJ**~12E ~[LOCITY**  HEATIMG EffltlENtY YEAR (In} Dt:SIGH (fls} VALUf**(Btu/ft~** GAS FLARED 

# ' COfKNTS 1972 0.5 SteUIAssis ted 50

- 250 1448 Ethylene >97.8 Hellu.tracer for full**e~per1-.ntA1** nozzle stze flare evtluatlon
1971 47 full she IIA IIA CArbon blAck 2500:1 EPA ROSE reaote sensing viByl •onomer reduction systetR


## . InCO 1978 2-6 SteuAnd pilot 1000

- 2350 H1t11rAl 1145, 75

- 99 Results oflimited validity propene due to Instrument rAnge sensitivity Refinery gas2 

## . 1980 17. CoamercItI fl.regu 0.7

- 16 1500 97

- 99 Multtposltton plume extrtcthe sampling 1981 2 Holes**1~** 2• CIP 1.8 2190

- 2385 Propllle 96

- 100 (1.1 In open aret} 1981 ,13) to.erct&l Air 40

- 60 2385 PropAne 92

- 100 8othextrtcttve and EPA assist. Zlnk STF-LH ROSE pluae sampling 1981 3at4(4) eo.-rdAI lt.P. NeAr Sontc 1000 NaturAl gas >99 (estl••te) 1983 8 Cclaerci&J Ztnk 0.03

- 62 209

- 2183 Propylene/112 67

- 100 BothextrActive And EPA STF-S-8 ROSE plume S.lmpllng 1983 6(3) eo..erctll •lr J.4

- 218 83

- 218l Propylene/112 55

- 100 us1st Ztnk STF-LH-457-5 1984 3-12 Open pipe And 0.2

- 420 291

- 2350 Propane/112 90

- 99.9Multlprobe plume extrac- cllllllll!rclal tive s.ampltng

-**~** 

## •**~** 

### ·TABlE 1·1. 

### SUMMARY OF PREVIOUS FlARE COMBUSTION EFFICIENCY STUOIES1 

### (CONTINUED)

fLAil£ SIZE STUDY YlAR (tn) Polll and Soelberg.(1.6)

# ·- 0.042

--- 1!185 1.5-12

1985 0.042- 2.5 1985 3

--- --·---- MA •lotAvailable 1M • Not Measured I:ESUil Nozzle

Co..erc:lal coanda ste•lnjectton, pressure assisted, air assisted, open pipe, pilot assisted
louie Open pipe

-
1. In pert froa Oubnowskl and Davis (1.8) GASEUT VELOCITY (ft/HC) 31

- 854

0.2 • 5!11

5.6

- 891 0.15- ll!l

-··· MEASUIIEO GAS CCMWSTIOH HEATING EFFICIENCY VALUE (Btu/scf) GAS FLARED ( I)

i23

- 3320 2i differentgas >98 •btures (80

- 99.9!1 destruction effie:Ieney) 122

- 2350 Propane/N2 l6- !I!U

588- 2350 Propane/12 Ill 145

- 877 HzS/propane/112 92 • !1!1.7 Nlllpropane/12 (92

- 99.9 1,3-butedlene/12 destruction Ethylene Oxtde/112 efficiency)

- -·-

2. 501 hydrogen plus light hydrocarbons 3. Supplied through spiders; high 8tu gas through 1rea Is 5.30 ln2**~low** Btu gas through 11.24 tn2 4. Three spiders, each with an open area of 1.3 In COitlENTS co.paratlve screening tests

COAiparat1ve connercttll flare type evaluation

fl..eaerodynaatc tests &is alxture testing

--sec. Gases and gas mixtures flared in pilot-scale tests include natural gas, ethylene, propane, propylene, refinery gas (50 percent hydrogen plus light hydrocarbons), hydrogen sulfide, ammonia, 1,3-butadiene, and ethylene oxide. Results of these studies are being used as a data base for the promulgation of industrial flare practices and regulations. The key findings are:

• Flares can be operated with combustion and destruction efficiencies exceeding 98-99 percent.

• Flare efficiency depends on flame stability. Aflare operated within the envelope of stable operating conditions will exhibit high efficiency unless too much steam or air assist is used.

• A flare operated outside its stable flame envelope becomes unstable; this can result in combustion and destruction efficiency below 98 percent.

• The stable flame operating envelope is specific to flare head design and gas composition.

• Operating conditions that have the largest influence on flame stability for a given flare head are'the gas exit velocity and heating value. Depending on flare type, levels of steam, air, or pilot assist can also affect flame stability and destruction and combustion efficiency. Results also show that flare gases of equivalent heating value but different composition can have different stable flame operating envelopes when flared from the same flar·e. Flare efficiency depends on flame stability, which in turn depends on flare head design and flare gas exit velocity, heating value, and composition. There are practically as many different combinations of these variables as there are industrial flares. Therefore further research is

1-5

### needed on flare flames to improve and extend scaling factors, and to develop methods correlating the influences of gas mixture, flare head**~pe,** 

### and operating conditions on the combustion and destruction efficiency for commercial flares. EER was commissioned by the EPA in 1980 to conduct flare research. For this research, a pilot-scale Flare Test Facility was designed and constructed at EER's test site in El Toro, California (1.2) Flare research at EER is briefly summarized in Table 1-1. Adata base has been developed which includes flare performance and efficiency measurements for (1) open pipe nozzles and flares ranging in size from 0.042 to 12 inches in diameter, with and without flame retention rings, (2) seven commercial flare heads ranging in size (based on open area for gas flow) from 1.5 to 12 inches in diameter

-- representative ofcoanda steam injection, pressure, and air assist flare heads, and (3) limited steam and natural gas pilot assisted tests on both open pipe and commercial flare heads. Propane, blended with nitrogen diluent to alter gas heating value, was used as the flare gas for these tests. Scaling parameters investigated include exit velocity, residence time, Reynolds number, and Richardson number. Flare flame aerodynamics, including lift-off and flame length, were also studied. Additional tests have been conducted to generate a data base for flaring different gases and gas mixtures. Combustion and destruction efficiencies of 25 different gases and gas mixtures representing aliphatic, aromatic, chlorinated, oxygenated, sulfur-bearing, nitrogen bearing and low heating value compounds have been tested for comparative performance using a 0.042-inch nozzle. Pilot-scale flare performance of four gases, ammonia, 1,3-butadiene, ethylene oxide, and hydrogen sulfide, has been measured using an unassisted 3-inch open pipe flare. Throughout the EER flare research program, advice and consultation has been provided by a Technical Advisory Committee. Serving on this committee are representatives from EER, EPA, California Air Resources Board, flare manufacturers {Peabody Engineering, McGill, Inc., John Zink, and Flaregas Corporation) and industrial flare users (Exxon Chemical Company, Exxon R&E, Union Carbide, Getty Refining and Marketing Co., Chevron USA, and Dow

1-6Chemical Company}. Among the industrial user representatives are members of the Chemical Manufacturers Association {CMA) and the American Petroleum Institute (API). This committee has provided a review and critique of test plans and results, has ensured relevance of the ongoing study to current regulatory and industrial concerns, and has facilitated efficient information transfer. 1.2 Objectives Objectives for the research reported herein were: 1) Additional HzS gas mixture testing to evaluate flame stability and combustion and destruction efficiencies. 2) More extensive pilot assisted flare testing to measure the effects of single and multiple pilots at high and low flowrates on flare performance. 1.3 Approach Accurate measurement of flare emissions and combustion efficiency is difficult. Experimental difficulties encountered by previous researchers include:

1 Inability to close mass balances due to large amounts of plume materia1 lost.

1 Inability to measure soot emissions, which may be significant in smoking flare situations.

1 Sampling only on the plume centerline, not obtaining measurements representative of the entire plume.



# ,

...]

### • Flare flame fluctuations due to turbulence and/or wind, causing erroneous data by destabilizing or blowing out the flame, or consistently blowing the plume away from the sample probe. The Flare Test Facility at EER has been designed and built in order to minimize such problems. The following procedures have been developed to verify the accuracy of combustion efficiency measurements (1.3):

• Material balance closure was verified using a hood to capture the entire flare plume for**s~ll** 

### flames, and by using S02 as a tracer for large flames.

• Soot concentration was measured for all tests.

• The average concentration of completely and incompletely burned combustion species from the flare flame was determined for the entire plume by (1) using a hood to completely capture small flames, and (2) simultaneous sampling using separate probes at five radial positions in the plume for large flames.· These local measurements, combined with velocities calculated fromjettheory, were integrated to calculate overall combustion efficiency.

• The effects of flare flame fluctuations were limited by using five radially located sample probes and by collecting time-integrated samples over a 20 minute time period. This time span was experimentally determined to be sufficient to time-average flame f1

### uctuations. Previous EER studies have established accurate flame combustion efficiency test methodology, developed a pilot-scale test facility, and established a data base of combustion efficiency test results for 0.042 through 12 inch diameter flare heads and nozzles burning a variety of gas mixtures. This work has provided the experience necessary to qualitatively estimate flare flame combustion and destruction efficiency and has provided

1-8data for selection of scaling criteria to extrapolate the pilot-scale test results to full-scale operations. This report is the fourth in a series describing the EPA/EER flare research program, and provides results from the following tasks:

• Task 1. Determine flame stability limits for gas m.ixtures of increasing H2S concentration.

• Task 2. Develop an accurate technique for measuring H2S concentrations in plume samples containing relatively high SOz levels.

• Task 3. Measure overall combustion efficiency and H2S destruction efficiency measurements at and above the limit of flame stability as a function of gas mi_xture strengths and gas exit velocities.

• Task 4. Determine the flame stability limitsfor a flare assisted by single, double, and triple pilots at constant pilot gas flowrate, and by a single pilot at different pilot gas flowrates.

• Task 5. Measure overall combustion efficiency at and above the flame stability limits for the flare with each of the pilot assist conditions identified in Task 4.

• Task 6. Reduce, analyze, and report the data. Open pipe flares were used for these tests, to eliminate any complicating effects from flame holding or stabilization devices and for**~omparison** with the majority of previous EER data. Aerodynamic flame stabilization devices are commonly used industrially, and depending upon design, may be expected to affect the relationship between exit velocity, 1eat content, and flame stability. Anominal 3-inch (ID 

## =3.125 inches) head**~tas** be used for the H2S gas mixture tests and for the tests with a single

1-9

### pilot at a single pilot gas flowrate. For multiple pilot and pilot gas flowrate tests, a nominal 6-inch 

### (ID 

## =6.065 inches) head was used. Commercial gases are mixed at the Flare Test Facility prior to delivery to the flare. Holding tanks are available at the facility for commercial liquified propane and nitrogen. Liquified hydrogen sulfide and sulfur dioxide {used as a tracer) are provided in portable cylinders. Natural gas is· provided by the local utility company. Aflow regulating and measuring system is provided for each gas. The pure flare gas constituents are supplied to 

### a header where they are mixed, and then delivered through a series of baffles for blending, before entering the flare head. Mixtures of various amounts of hydrogen sulfide, propane, and nitrogen were used for the H2S gas mixture tests. Propane and nitrogen mixtures were used for the pilot assisted tests. Natural gas was used for the pilot flames. 1.4 References 1.1 Klett, M. G., and J. 

### B. Galeski, Flare Systems Study, EPA Report No. 600/2-76-079, (NTIS Report No. PB-251664), March 1976. 1.2 Joseph. 

### o., J. 

### Lee, C. McKinnon, R. Payne, and J. 

### Pohl, 11

### Evaluation of the Efficiency of Industrial Flares: Background-Experimental DesignFacilityN, EPA Report No. 600/2-83-070, NTIS No. PB83-263723, August 1983. 1.3 Pohl, J. 

### H., R. Payne, and J. 

### Lee, "Evaluation of the Efficiency of Industrial Flares: Test Results

.., EPA Report No. 600/2-84-095, NTIS 

### No. P884-199371, May 

### 1984. 1.4 Pohl, J. 

### H., N. R. Soelberg, and E. Poncelet. "The Structure of Large Buoyant Flames

.., American Flame Research Committee Fall Meeting, Livermore, CA, 16-18 October 1985.

1-101.5 Noble, R. K., M. R. Keller, and R. E. Schwartz, '1An Experimental Analysis of Flame Stability of Open Air Diffusion Flames 11

, presented at American Flame Research Committee, 1984 International Symposium on Alternative Fuels and Hazardous Wastes, Tulsa, Oklahoma, October, 1984. 1.6 Pohl, J. H. and N. R. Soelberg, 11Evaluation of the Efficiency of Industrial Flares: Flare Head Design and Gas Composition11

, EPA Report No. 600/2-85-106, NTIS No. PB86-100559/AS, 1985. 1.7 Pohl, J. H., J. Lee, R. Payne and B. Tichenor, 11The Combustion Efficiency of Flare Flames 11

, 77th Annual Meeting and Exhibition of the Air Pollution Control Association, San Francisco, CA., June 1984. 1.8 Dubnowski, J. J. and B. 

## c. Davis, '1Flaring Combustion Efficiency: A Review of the State of Current Knowledge, 11The 76th Annual Air Pollution Control Association Meeting, Atlanta, GA, 1983. 1.9 Palmer, P. A., ''A Tracer Technique for Determining Efficiency of an Elevated Flare," E. I. duPont de Nemours and Co., Wilmington, DE, 1972. 1.10 Herget, 

### w. F., "An Overview of the EPA Programs for Groundbased Remote Sensing of Air Pollution 1', 23rd SPIE Symposium, San Diego, CA, August 27-30, 1979. 1.11 Straitz, J. F., 11Flaring for Gaseous Control in the Petroleum Industry

.., 1978 Annual APCA Meeting, June 19, 1978. 1.12 Siegel, K. 

## o., "Degree of Conversion of Flare Gas in Refinery High Flares, "Ph.D. Oissertation, University of Karlsruhe (Federal Republic of Germany), February, 1980. 1.13 Lee, K. 

## c. and G. M. Whipple, "Waste Gas Hydrocarbon Combustion in a Flare," Union Carbide Corporation, South Charleston, WV, 1981.

1-111.14 Howes, J. E., T. E. Hill, R.N. Smith, G. R. Ward, and W. F. Herget, "Development of Flare Emission Measurement Methodology, Draft Report," EPA Contract No. 68-02-2686, Task 118, U.S. Environmental Protection Angency, 1981 (Oraft Report)•
1.15 McDaniel, M., "Flare Efficiency Study," EPA Report No. 600/2-B3-052, NTIS 

### No. PB83-261644, August 1983.
1.16 Keller, N. and R. Noble, "Ract for VOC- ABurning Issue", Pollution Engineering, July 1983.

1-122.0 SUt-f.1ARY ,,NO CONCLUSIONS The test program "Evaluation of the Efficiency of Industrial Flares" has been funded by the U.S. EPA and conducted at the Energy and Environmental Research Corporation (EER) El Tore Test Site. This program has been conducted in phases. The first phase involved construction of a pilot-scale



# . flare test facility. During the second phase, combustion efficiency tests were conducted on eight different commercial and EER prototype flare heads ranging in size between three and twelve inches in diameter. During the third phase, effects of flare head design and gas composition on flare combustion and destruction efficiencies were studied. Commercial coanda steam assisted heads, pressure heads, and an air-assisted flare head were tested. Also, different gas mixtures containing ammonia, 1,3-butadiene, ethylene oxide, and hydrogen sulfide were tested. Throughout this test program a Technical Advisory Committee has provided consultation. Committe-e members included representatives from EER, EPA, California Air Resources Board, flare manufacturers, and industrial flare users. Each phase of this test program has been designed to provide test data relevant to current regulatory and industrial concerns as defined by this co11111ittee. 2.1 Summary This phase of the work had two objectives:

• Evaluation of H2S destruction efficiency for H2S-containing flare gases

• Evaluation of the effects of pilot assist on flare combustion efficiency In order to determine the limits of stable flare operation for these gas 1uixtures and pilot assisted flares, and key operating conditions that affect flame stability and efficiency, some conditions with poor stability and low

2-1

### combustion efficiencies were measured. Such results merely indicated flare operating performance at or beyond the edge of the operating envelope, and are not indicative of normal commercial flare operation. 2.1.1 Destruction Efficiency of H2S Before HzS destruction efficiency could be evaluated, itwas necessary to develop techniques to accurately and reliably measure HzS at plume concentration levels of 0-1000 ppm, without interference from S02, present in levels between 0-10,000 ppm. Methods successfully adapted for this measurement were the methylene blue method and Draeger tubes. For higher HzS gas concentrations (25 ppm or greater}. gas chromatography was also used. Tests were conducted with H2S gas mixtures on the Flare Screening Facility CFSF) shown in Figure 2-1. These tests verified the applicability of HzS and SOz measurement methods and safely and inexpensively determined H2S destruction efficiency for HzS gas mixtures flared from a nozzle 0.042 inches fn diameter. Results of these tests are shown in Table 2-1. Very high H2S destruction efficiency (99.7 to >99.99 percent) and propane combustion efficiency {98.6 ·to 99.99 percent) were measured for tests conducted with gas heating values at and above the flame stability limits as shown in Figure 2-2. This stability limitcurve defines the minimum heating value for a given gas exit velocity which will maintain a flame. At heating values below this limit, flame blowout may 

### occur. Destruction efficiency tests of H2S were also conducted using a 3-inch diameter open pipe flare at the Flare Test Facility (FTF) shown in Figure 2-3. These tests aerodynamically approximate full-scale industrial operations while those of the laboratory-scale Flare Screening Facility tests do not. Test results are tabulated in Table 2-2. Flame stability limit curves for these tests are shown in Figure 2-4, where gas heating value on a volumetric basis is related to gas exit velocity. Gas heating value on a mass**bas~s** 

### may also be correlated to gas exit velocity, but is less effective in correlating flame stability for different gas mixtures. There is good agreement in Figure 2-4 between the current 1985, ·5

### percent H2S gas mixture

2-2

# MIXING CHAMBER

1116-1/8 

# IN I 

## NOZZLE

GLASS BEADS 

## HEATED 

# LINE


# SYRINGEDRIVE**~==GAS** 8

# AIRFAN

Figure 2-1. Flare Screening Facility (FSF).

2-3N I 

## .,.. -- 

### Test No•.

1 2 3 4 5 

### TABlE 2-1. 

### FlARE SCREENING FACILITY H 2

SGAS MIXTURE TEST RESULTS. NOZZLE ID 

### =0.042 

### INCHES

Gas C011pos1t1on Gas Nozzle 

### A1r H2S Propane (Remauder 

### N2l Heaung Exft Stofchfo Destruct1on CORibust1

### on 

### H

2

S Propane Value Veloc1ty metrfc Eff1c1ency Eff1clency (Btu/scf) (f/s) Ratfo (I)
. (I) 

### (%) (%)
4.31 45.2 1086 27.5 3.15 >99.99 99.9 34.8 52.0 1427 17.4 2.90 >99.99 99.99 31.9 55.0 1480 16.5 2.90 >99.99 99.9

4.28 45.5 1093 27.0 3.17 >99.7 99.9 69.5 30.5 1125 8.52 4.02 >99.99 98.6

--- --- ' 

### Mass Balance Closure Mass In/Mass Out 

## c 0 

## s 0.567 0.944 0.446 0.706 0.939 1.12 0.878 0.852 0.794 0.952 0.918 0.715 0.729 0.891 

## o.774

## ....**~** u**~ ~** **~ ~**  CQ**~ ~**  ...**~** 

### =-**~** 

# =

...**~ ~**  Q :c**~ ~**  U)**2400~--------------~------------~------------~**

1200

1000

800

600

400 1984 Tests, Propane/N2Mixtures (2.1 1985 Tests,**Propane/~** Mixtures Tests, 4-5% H 2S 1Mixtures Tests, 30-41% H 2

### s 1 Mixtures Tests, 50-70% H 2

SMixtures I 

# '**~** I I I I I I I 

# , I I 

## e'



# ' I I I 

# p '**200~**______________._ ____________**~~------------~** 1.0



### Figure 2-2. 10.0 100.0 Exit Velocity (f/s) 

### Flame stabilitycurves for propane/N and H

2

### S/propane/N2 

### gas mixtures flared

### u~ing 

### a 0.042 

### inch 

### rD nozzle. 1. 

### Remainder is 

### propane and N 2

2-5 1000.0N I 01 Adjustable Rake for Sa.ple Probes, Filters, Driers, Tenax Traps, and Bubblers for HzS, S02 & NHJ

Flare Gu Line Support Structure**S~le** Collect1on &

Analys1s for Oz co C02 Hydrocarbon SOz 112$ 110-IICJ,, NHJ



### Figure**2~3.** 

### EPA Flare Test Fac11tty (FTF) at EER.N I

....... TEST NO. 2" 2n 278 2, ]00 101 102 ]0] 

### TABLE 2-2. H 2

SGAS MIXTURE COMBUSTION AND DESTRUCTION EFFICIENCY TEST RESULTS1

GAS GAS COMPOSITJON2IIJ HEATING 

## UlJ VELOC lY rALIE

(f/s)



# .,,,s

8.88 0.48 O.S4 l2.S ,,46 

# '·" 0., PROPANE 

### u 2

### s ca u/scn 1S.1 

### }." 117 20.1 S.11 S02 14.4 4.81 

# "' 4.11 

### ,,,s S10 0 42.0 247 0 u.s 2U 0 s,.• }]1 0 28., 170

1. l-INCKPIP£ flARE, NO PILOT 2. REMAINDER IS NITROGEN l. HEIGHT ABOVE FLARE TIP 4. NOT APPLICABLE**.~~~~}** WIND SPEED (f) (ltPfl) 11 

### s 12 

# " l 

# " 4 4 15 4 8 4 8 4 J l OBSERVATIONS**Cl~Vfuc,t~ f~AME**  

## hiP LNCTH EFFICIENCY

(f) UnJ COLOR SNOICE SOUND (I) 

# ' } llcttTlltAHGE NONE NONE 

# '"·' 1' 2-S YELLOW ORANGE SLIGHT NONE 

# ''·" 1.5 o.s DIM YEllOW HillE NONE 77.7 2.S 0-2 liGHT PIJIPlE NONE ,,] 10 6-24 liGHT PlRPLE PROFUSE GREY BLUE HISS 

# ..

# , .. s· 0 BUf YELUIII GREY BLUE HONE NA 1 0 PIIIPLE YELLOW GREEN GREY BLUE NONE NA 1 0 INVISIBLE I 

# IGREY BlUE MilNE NA**~fS~iUcHON** I FFICJEIICY

(I) 

### "·2 ,,8 ,,2 100 78.] 

# "·' ,8.1 

# "·'N I oa 

# -

til 

### :J**~** 1984 -51

### u 2

### s 1n Propane/N2 Mixtures (2.1) 17 1985 

## -ss H 2S 1n Propane/N2 Mixtures 

### C> H 2StN2Mixtures**~-** v ____ .......,.'"'V 

### •

### 100~----------------------------------------------~----------------~ 0.1 1.0 ; 10.0 100.0 1000.0 Exit Velocity (f/s) 

### figure 2-4. Flame stabilitycurves for H 2

Sgas mixtures flared using a 3-inch diameter open pipe flare.tests and the 1984, -5 percent gas mixture tests. The stability limit curve for the H2S/N2 ga.s mixture tests is much lower than that for**t~e** tests for the 

### -5 percent H2S in propane/N2 mixture. This shows that gas heating value is not the only contributing factor to flame stability. Other factors may be (1) higher volumetric H2S concentration in an H2S/N2 mixture than propane in a propane/N2 mixture of equivalent heating value, {2) wider flammable range in air for H2S than for propane, (3) lower adiabatic flame temperature of H2S burned in a stoichiometric air mixture, and (4) lower ignition temperature of H2S. The combination of these factors apparently enhances flame stability of H2S gas mixtures. Propane combustion efficiency and H2S destruction efficiency were correlated to flame stability as shown in Figures 2-5 and 2-6. Destruction efficiencies greater than 98 percentwere attained when the gas heating value was at least 1.2 times the minimum gas heating value required for stability. Both propane combustion efficiency and H2S destruction efficiency can rapidly decrease below 98 percent when the gas heating value ratio decreases below 1.2. Destruction efficiency of H2S is compared_to**pro~ane** destruction efficiency in Figure 2-7 for tests of gas mixtures containing both H2S and propane. H2S destruction efficiency was consistently higher than propane combustion efficiency. 2.1.2 Influence of Pilot Flares Tests were also conducted using a pilot assisted 3-inch open pipe flare at the Flare Test Facility. These tests were conducted to measure the effects of pilot assist on combustion efficiency. The flare gas for these tests was propane diluted with nitrogen to reduce the heating value. The pilot gas was utility-supplied natural gas. Test results are shown in Table 2-3. Parameters tested were {1} flare size (3-inch and 6-inch), {2) pilot number from one to three, and (3} pilot gas flowrate, from one to five scfm. For these tests, the flare gas heating value includes the contribution of the pilot gas.

2-999.99 Reg1on for hydrocarbon cCII'Ibustfoa 0.01 

### effiei.enc:yforprev;ousTy testect propa.ne/NI'mixturesflared,frca3**,~** 

# - c: through 1**·~·**fnclt beads,.; and·for-'·**t~,.;;** . 0 .,Q butad'fenellt 2• ethylene**oxide/~. ~**  s.. 

## ,., propane/It¥'" and**~~ropane/ffi:** 

### gas · u flf,xtures 1 

### arect , .m unass :sted .• ·.·· 

# -**.~fncla''**ope&'fpfpe:fhrt·

### (Z'.t

### l 

## ,., 

# -**~** 99.9**~** 

# -0.1

# - i" r.:: 

# - 

# - -**~** Itc: 0 4J y**~** s.. c: cu ca. • 4J 

# -**~** 

# -"**~** y s..**~** 

### . QJ (J Q. c:

### ~ 

# - QJ [.7


# - c: y ' Q


# - 99.0 I"'" 

# - 1.0 .,Q It- s.. It- 

## ,., "" (.,) c: 

# t.**~** 0 4J 

# - c: ...., s.. II' :::s ::I

### ~ 

# = j 1984 

### 5% HS in >. u 7 

### Propane/N22 Mixtures (2.1) QJ ...., 

### 17 1985 

### 5% HSin 4J 

# f Propane/N22 Mixtures ..- 90.0**~** 

# -10.0 ca. 

### 5 c:::='

- 

### 70%**~S** 

### in Propane/ (J c: 

### N

2Mixt res 

# -**o~----------~·~----------~·~--------~100.0** 0 

### 1.0 2.0



### Heating Value/Minimum Heating Value

### for Stability Figure 2-5. Propane combustion efficiency of

### H,SI propane/N'- gas mixtures flared

### from an**uriassiste~** 

### 3-inch open pipe flare.

1. Scale is log (100

- Combustion Efficiency)

2·10..- 

# - ..., c Q,l u '- Q,l Q.. >, u c Q,l 

# - u 

## ....**~ ~**  LU c 0 

# - ..., u :::1" '- 

## ..., Ill 41 Q 

### 99.99

99.9

99.0

90.0 

# I Region ofdestruction 

### efffc..ienc:y foranaonia, 1

### .3•butacUene., ethylene oxide,. and propane.(2.1)



### 17 1985

- 5% H 

### 2S in 

### Propane/N2Mixtures(2.1) c:::'**-70~** 

### H 2

S in 

### Propane/N2Mixtures 

## C> H 2

S!N2Mixtures 0.01

0.1

1.0

10.0

0

# '-------......a.

______ _,_____ __. 100.0 0 1.0 2.0



### Heating Value/Minimum Heating Value for Stability Figure 2-6. 

### Destruction efficiency of H 2

### Sgas mixtures flared from an unassisted 3·fnch open pipe flare. 1. Scale is log (1Qo.·oestruction Efficiency)

2·11 

# - IG 

## .... ..., 

# - c 

# -

# ....**~** c**~ ~** **~ ~** **~ ~** **~** c**~** 

# ...**~** 

# ...**~ ~** **~** c 0**~ ~** **~ ~** **~ ~** **~ ~** **~ ~**  :c 100



## C? 51 H 2

Sin 

### Propane/N2Mixtures**~701** H 2S in 

### Propane/N2

### Mixtures 90._

____._ ____**~----~----_.----~** 94 96 98 100 

### Propane Combustion Efficiency (Percent)
Figure 2-7. Correlation between HS

### destruction efficiency and propane

### combustio~ efficiency

### for H 2

### Stpropane/ 

### N

1 

### mixtures flared from 

### an unassisted 3-inch open plpe flare.

2-12N I

...... w TEST NO. 304 305 306 307 308 309 310 311 312 313 114 115 316 111 318 319 320 321 322 323 124 325 326 FLARE NlltBER SIZE OF CJO) PILOTS 3.125 1 3.125 1 3.125 1 3.125 1 3.125 1 3.125 1 3.125 1 3.125 1 3.125 1 J.125 1 1.125 1 3.125 1 J.125 1 3.125 1 3.125 1 3.125 1 3.125 l 6.065 1 6.065 1 6.065 1 6.065 1 6.065 1 6.065 1 

### --

fLARE PilOT GAS GAS EXIT FLOWRATE VElOCITY

(scfa) (f/s) 2.1 19.5 2.1 78.5 2.1 116. 2.1 )4.2 2.1 JJ.O 2.1 17.2 2.1 18.5 2.1 &1.8 8.16 0.9 2.2 

### no. 2.2 121. 2.1 142. 2.1 148. 2.1 JJ.O 2.1 U.J 2.1 58.9 2.1 17.0 2.1 19.7 2.1 19.4 2.1 19.1 2.1 5.61 2.1 6.7J 2.1 7.}]**T~BLE** 

### 2-3. PILOT ASSISTED HEAD TEST RESULTS (PAGE 1OF 3)

GAS OBSERVATIONS liFT**HEATI~G** PROBE} IllNO FLAME I VALU£ tiEIGHl SPEED ENGTH4OFF PROPANE1(8tu/scf) (f) (lllph) (f) (Jn) COLOR 

# "' 11.0 28) ORANGE FLICKERS 15.8 377 ORANGE FLICKERS 8.60 206 I TRANSPARENT 13.4 326**~** STABILITY TESTS ORANGE fliCKERS 10.1 257 ORANGE FLICKERS 10.5 275 ORANGE FLICKERS 9.53 251 IJ ORANGE FLICKERS 6.93 174 15 4 385 3 TRANSPARENT 4.77 146 15 6 385 1 TRANSPARENT 8,88 211 25 4 405 0 TRANSPARENT 8.47 204 

## ' TRANSPARENT 6.99 168 TRANSPARENT 6.56 158**TRA~SPARENT** 9.08 229 ORANGE FLICKERS 6.61 168 TRANSPARENT 5.10 110 TRANSPARENT 3.89 

# '' STABIllJY JESTS TRANSPARENT 9.25 224 ORANGE FLICKERS 7.12 1" ORANGE FliCKERS 7.16 l76 TRACE ORANGE 10.24 264 ORANGE FLICKERS 8.44 219 FAINT ORANGE 7.76 201 ) TRANSPARENT CliiBUSTION EFFICIENCY SMOKE SOUND (I)

I

NONE lOll ROAR 99.2 NONE HISS 75.0 NONE ROAR 99.3N I


### .....**~** TEST NO. )27 328 329 )]0 331 312 331 334 }}5 }}6 3J7 338 }39 340 341 342 343 344 345 346 347 348 FlARE SIZE Un> 6.065 6.065 6.065 6.065 6.065 6.065 6.065 6.065 6.065 6.065 6.065 6.065 6.065 6.065 6.065 6.065 6.065 6.065 6.065 6.065 6.065 6.065 PILOT tatER L£4.\n PILOTS Cscf•> 1 2.2 1 2.4 t 2.1 1 2.1 1 1.1 1 1.1 1 1.1 1 1.1 1 S.J 1 5.4 1 5.3 1 5,} 1 1.1 1 1.1 1 1.1 1 1.1 t 1.1 1 1.1 1 1.1 1 1.1 1 5.1 1 3.9 

### TABlE 2-3. PILOT ASSISTED HEAD TEST RESUlTS (PAGE 2OF 3)
FlARE OBSERVATIONS

GAS GAf 

# vEfftHn**HEAT~** 

### PRDBf**WI~** 

## (LAME 

# IJP I VALUE HUCit 3SPED NGTH4 Cfls) PRDPANE1 (Btu/sen (f) C•ph) (f) 

### c Jnl COLOR 19.6 7.01 172 28 l 15 15 ORANGE FliCkERS 44.7 5.67 117 TRANSPARENT 34.8 6.49 1S1 18 3 17 2 TRANSPARENT 11.8 4.22 112 ' 7 4 5 12 TRANSPARENT 36.} 6.97 

# 1" TRACE ORANGE 

### n.t 7.96 187 ORANGE FLICKERS 36.9 5.12 121 TRANSPARENT 36.7 4.58 110 TRANSPARENT }6.7 4.58 118 FAINT ORANGE 16.9 5.23 1}} ORANGE FLICkERS 36.3 3.28 88.} TRANSPARENT 36.5 },67 97.1 TRANSPARENT 10.3 6.28 155 STABILITY**TEST~** TRANSPARENT 10.1 4.52 114 TRANSPARENT 10.1 3.72 95.8 TRANSPARENT 10.5 7.57 185 ORANGE FLICKERS 10.5 5." 141 TRANSPARENT 14.0 4.22 105 TRANSPARENT 1l.9 3.19 40.8 TRANSPARENT 9.61 6.16 lo;l TRANSPARENT 33.1 1.21 40.8 TRANSPARENT 34.8 1.72 48.9 I) TRANSPARENT SMOKE SOUND CCJ48USTIOH EffiCIENCY (I) NONE RIJIBLE/HISS 99.3 NONE ROAR 98.2 NOHE RIJIBLE/HISS 81.3N I

...... U1 

### TABLE 2-3. PILOT ASSISTED HEAD TEST RESULTS (PAGE 3OF 3) 

# r FLARE 

# I R GAS GAS · OBSE VATIONS FLARE NUMBER

### P~kRT EXIT 

# I**HEATI~G** PROBE WIND flAME liFT TEST SIZE OF FLOWRATE VELOCITY I · VALUE HEI&HT1SPEED LENCTH4Off NO. <lnl PilOTS <scf•l U/sl PROPANE1 lBtu/scf) (f) (llph) (f) (fl I COLOR 349 6.0&5 350 6.0&5 351 6.065 352 6.065 353 6.065 354 6.065 155 6.065 356 6.065 351 6.065 358 6.065 359 6.065 360 6.065 361 6.065 362 6.065 363 6,065 364 6.065 365 6.065 366 6.065 1 1 1 1 2 2 2 2 2 2 2 3 3 3 3 3 J ] 4.1 1.0 1.1 4.0 2.0 2.0 2.0 2.0 2.0 2.1 2.3 2.0 2.0 2.1 2.0 2.0 2.0 2.2 20.4 20.4 20.5 20.1 20.2 10.2 28.3 35.0 37.4 47.6 20.1 13.3 12.9 30.3 34.9 48.3 49.6 20.2 1.63 5.15 6.96 5.21 2.44 4.91 6.81 4.98 6.84 .5.31 5.22 6.34 2.85 6.39 3.88 6.07 4.81 5.21 100 125 167 138 65.1 130 165 121 164 128 U1 160 79 155 95 146 116 130 1. REMAINDER OF flARE GAS IS N 2AND S02(TRACER> 9 n 17 14

II 15



### >

15 3 4 ) 4 ) 17 4 14**~lABILITY** TESTS

3 I 13
lsTABILHV TESTS

3 I 13
2. INCLUDING THE HEATING VALUE CONTRIBUTION OF THE PILOT GAS 3. ABOVE flARE TIP 18 TRANSPARENT 18 TRANSPARENT 12 ORANGE FliCKERS

1 TRANSPARENT TRANSPARENT TRANSPARENT TRANSPARENT TRANSPAREMT TRANSPARENT TRANSPARENT 0 !TRANSPARENT FAINT ORANGE TRANSPARENT TRANSPARENT TRANSPARENT TRANSPARENT TRANSPARENT 12 !TRANSPARENT SNOKE! ·sooND NONE ROAR NONE LIN RUMBLE NONE RUMBLE NONE RUMBLE

NONEI LOWROAR

NONE ILOW ROAR

4. flAME LENGTH DETERMINEDBY LENGTH OF VISIBLE FLAME COLORING AND TRANSPARENT HEAT WAVES (liGHT DIFFRACTION) 5. INCLUDES HEAT WAVES ABOVE FlAME ENVELOPE 6. USEDWRONG ORIFICE METER COMBUSTIOH EFFICIENCY (I) 92.0 94.3 98.5 97.2

95.7

96.6The flame stability limit for the pilot assisted tests was difficult to determine, because the presence of a pilot effectively prevented flame blowout, even at very low flare gas heating values. Consequently, the definition and determination of the flame stability limit became more subjective. The gas heating value required for 98 percent combustion efficiency at a given flare gas exit velocity was found to be the operating point where the last faint flickers of orange color disappeared and the flame envelope became transparent. Such flare flames usually had blue-orange cones near the pilot and flare tips. In order to maintain consistency with previous results reported under this program, this operating point was defined as the J•stability limit". This stability limit is specific to these tests burning propane/nitrogen mixtures. Stability curves for the pilot assisted flares are shown in Figures 2-8 through 2-12. Use of pilot assist greatly enhances flame stability. For 3 and 6-inch unassisted open pipe flares, operated with a propane-nitrogen gas exit velocity of 40 f/s, the minimum gas heating value to maintain a flame is about 540 Btu/scf. If a 2 scfm natural gas pilot is used, the total heating value (including pilot contribution) can be reduced to 150 Btu/scf, when the flame envelope becomes transparent and, by definition, the stability limit is reached. For the 6-inch flare, the same heating value reduction can be attained with the pilot at only 1 scfm. Additional pilot assist, however, only marginally increases flame stability. Increasing the pilot gas to 5 scfm only·reduces the heating value to 120 Btu/scf for the 6-inch flare. Increasing the number of pilots to two or three while keeping the total pilot gas rate constant at 2 scfm decreases the limiting heating value to 130 Btu/ scf for a 6-inch pipe flare. The quantitative results of these stability tests are limited to open pipe flares in the 3 - 6inch diameter size range. By scaling the relative number of pilots, the pilot and flare gas flowrates and velocities, Richardson numbers, and Reynolds numbers, these results could also be applied to 12-inch or larger open pipe flares (4.1). The results of improved stability with pilot-assisted flares can be only qualitatively applied to flares that also have aerodynamic or other stability enhancing devices.

2-16 •N I ...&

....... 

# - .... 0 

### "'

....... :::11 

# ... al

......

01 :::11

..... tel > Dl c**~** 't 01 :::1: 

### "' c1 300
200
100 Visual Observations



### --- o Faint orange flicker in flame envelope (stable)

---- Q Disappearance of faint orange flicker (stabtlity limit) •••••••• Unstable**~** 3-inch open pipe flare with stn9le pilot at 2.1 scfm pilot gas rate (1984 tests)(2.1)

# ~ Fatnt orange

## flicker~ $) 1n fla!De envelope (stable)**~** 

### $lat' Disappearance of fatnt orange 

# r-- ..tfi,>-- •• ._.. flicker (stability ltmtt)**~ ~** **~-~······ ~**  

### 7 • 1. Includes pilot gas contribution**Unstable~**

### 0~---------------L----------------L---------------~----------------L---J 0.1 1.0 10.0 100 1000 Flare Ex1t ·velocity (f/s) Figure 2-8. Flame stability curve for 3-fnch pipe flare with a single pilot at a pilot gas flowrate of 2.1

- 2.2 scfm natural gas.

# -

..... u Ill 

# - :I**~** Gel 

# - .-

# ..

:I .- 

# .. > N ICft I IC
...... .,... co**~** 

# .. .. :z:: 

# = (D

### 120**~--------------~--------------~--------------y---------------~---**



# - 0



# ......

# -**~** Visual Observations Faint orange flicker 1n flame envelope (staple) Disappearance of faint orange flicker (stabtltty ltmtt)**uvv~-** ••-••

# • Unstable

200.-
100 1. Includes ptlot gas contribution Faint orange flicker (stable) 

### -o I 

## <>**·-~-·-Q-.~-** Stability 11mtt

### ······•··•·····~·-unstable

## 0~------------~~------------~~------------~~------------~~~ 0.1 1.0 10.0 100 Exit Velocity (f/s) 

### Figure 2-9. Flame stabilitycurves for 6-inch open pipe flare with a single pilot at a pilot gas flowrate of 1.0- 1.1 scfm natural gas.1

......... 

## .... u Ill

....... ::I**~** to 

# -

.....

Ql :I



### ..... 

## .., > g) c**·~** N "g I 

## .., ..... GJ 10 ::z:: Ill 

## .., (JI 

# a

·-·-·- Q



# --------

# .

---- Visual Observations

Stability curve for 3-inch

()**~nt ~e**  flicker (stable)



# -<Q ,. . 

# J·-·-·-·- •..Q-
- ••

# ~' Estimated stability limit ••••••1............... Stab111ty curve for l-inch f pilot assisted open pipe Unstable nozzle 1. 0.1 10.0 100 1000 Flare Gas Exit Velocity (f/s) Figure 2-10. Flame stability curves for 6-inch open pipe flare with a single pilot at a pilot gas flowrate of 2.1

- 2.4 scfm natural gas.

# - .... u lA

......**~** .,a CD 

# -

.....**~** ,... 

## • > 1\) CJ) I c: N**~** 0 .,a 

## • 

## • :z: lA 

## • (Jt V1sua1 Observations 

### D

·-·- •**~** 01sappearance of faint orange flicker
••••••••• • Unstable

100 

## .

Ol 1. Includes p11ot gas . . 

## ._JL.

# ~ Stabilitylf•tt .1 I cootrtbutton

..........

# ·~... 

## 'jo•• 1.0 1 Unstilble · 10.0 I

• octty (f/s) I 1 100 1000 Exit

### v1 

### Figure 2-11. Flame stabilitycurves for 6-inch open pipe flare with a single pilot at a pilot gas flowrate of 3.9

- 5.4 scfm natural gas.

# - .... u en

....... :J


### .... QO 

# - r-.,

:J .- 

### _, > N ltJ' c I ..... N 

## .... ..... 

### _, 4U ::c en 

### _, (D 

# -.-**~·-· ~**  •••••••

# • 0 

# --·-·**~** •••••••

# • Visual Observations Double pilot. disappearance of orange flicker (stability limit) Double pilot. unstable Triple pilot. faint orange flicker in flame envelope (stable Triple pilot. disappearance oforange flicker (stability Triple pilot. unstable limit)**'--ll-·~-·** •• Stability 11mit .........__ 

### 0**~r.l:** 1. Includes pilot gas contribution

## ~··1···· 01 1**Un~table**

0.1 1.0 10.0 100 Exit Velocity (f/s) 1000
Figure 2-12. flame stability curve for 6-fnch open pipe flare wfth multiple pilots at a total pilot gas flowrate of 2.0

- 2.3 scfm natural gas.

### Adiabatic flame temperature can be used as an indicator of flame stability for specific gases. The flame stability limit is approached when the flame speed approaches the relief gas velocity. Flame speed depends on mixing and flame reaction rates. Flame reaction rates are functions of flame temperature, frequency factors, and activation energies for flame reactions. Figure 2-13 shows that the limiting stable gas exit velocity can be correlated with an estimated adiabatic flame temperature of the gas mixture burned in a stoichiometric air mixture. However, the curves for different gas mixtures and for the pilot assisted flares are different. This indicates that differences in activation energies, frequency factors, mixture strengths, and mixing rates for different compounds may affect flame · stability differently for different flare gas mixtures and pilot assisted flares. Combustion efficiency for the pilot assisted flares is correlated to flame stability in Figure 2-14. Combustion efficiency is greater than 98 percent for heating value stability ratios greater than about 1.2. Combustion efficiency can rapidly decrease when the heating value ratio decreases below about 1.2. There are some subtle differences in combustion efficiency performance of the pilot assisted flames:

• Combustion efficiency greater than 98 percent is maintained forthe 3-fnch head down to a heating value stability ratio of 1.0. This could be because the impact of the piloton the flame for the 3- inch flare is greater than on the flame from the 6-inch flare. Also, tests for the 3-inch head were conducted at slightly higher gas heating values than for the 6-inch head, because the stability limit curve for the 3-inch head requires higher heating value than the curves for the 6-inch head.

• Below a heating value stability ratio of 1.0, however, the decrease in combustion efficiency for the 6-inch head at the high pilot gas rate and for the double and triple pilot is less rapid than for the

2-22

...

## -------------------------------'"""

# - lit

....... 

### .... 

# - ,.,
.... 

# - 

# - 

# -**~** oa


### .... V) I. 0


### .... 

## ,.,
.... 

# - u o- ,... cu :> Ql s:: 

# - .... 

# - E .,..

..... 1000 () l-inch flare with single pilot at 2 scfm pilot gas rate '84 

### o 3-inch flare with single pilot at Zscfm pil·ot gas rate () 6-inch flare with single pilot at 1 scfm pilot gas rate 

### CJ 6-inch flare with single pilot at 2 scfm pilot gas rate () 6-inch flare with single pilot at 4-5 scfm pilot gas rate () 6-inch flare with double pilot at 2 scfm pilot gas rate Cj 6-inch flare with triple pilot at 2 scfm pilot gas rate

100

10

1.0 Ethylene oxide/N2 gas mixtures flared from

unassisted l-inch

open pipe flares

H

2

S/N2gas mixtures flared from unassisted 3-inch open

pipe flares
Propane/N dominated gas mixtures flared from

3-inch**a~d** 6-inch open pipe flames (unassisted)

Figure 2-13. Calculated adiabatic flame temperature vs. limiting stable gas exit velocity for propane/N2 gas mixtures flared using pilot-assisted 3-inch and 6-inch open pipe flares. 2-23

### 0 0 

# ---{ () 

### CJ 

# ······{ D D 

### 0

100



# -
.... c: Qa 1:.1 

### '" 90 Qa 0.. 

# - ::00. 1:.1 c: u 

# - u 

# -**~**

.**~** IA.I c: Q 

# - ....**~ ~**  

# 1 80 y 3-fnch flare with single pilot at 2 scfm pilot gas rate (1984) (2.1) 3-fnch flare with single pilot at 2scfm pilot gas rate 6-inch flare with single pilot at 1 scfm pilot gas rate 6-inch flare with singlepilot at 2 scfm pilot gas rate 6-inch flare with single pilot at 4-5 scfm pilot gas rate 6-inch flare with double pilot at 2scfm pilot gas rate 6-inch flare with triplepilot at 2scfm pilot gas rate

' 

### ..: .. :: ...;

### ...

Region ofcombustion efffciency • measurements for previously tested 

# - propane/N mixtures flaredfrom 

# .. • 3, 6, and212-fnch open pipe flares(2. ) 

# .. 

# - .. • • • • • • • • 

### CJ**70~--------------._**______________._ ____________ __. 0 1.0 2.0 Heating Value/Minimum Heating Value Requiredfor Stability Figure 2-14. Combustion efficiency of pilot-assisted flares.

2-246-inch head with the single pilot medium and low pilot gas rates, and the 3-inch pilot assisted head. This may be because, even at or below the stability conditions, high relative pilot gas rates or multiple pilots can improve combustion efficiency. 2.2 Conclusions The following conclusions were made based on the results of this report:

• There are viable**met~ods** for accurate and reliable measurement of H2S and S02 in flare plume samples.

• Flame stability depends not only on flare head design and flare gas volumetric heating value, but also on compounds present in the flare gas. Gas mixtures of H2S/N2 can be stably flared at much lower volumetric gas heating values than can propane/N2 or -5 pePCent H2S in propane/N2 gas mixtures.

• High H2S**destr~ction** efficiency is achieved for H2S/N2 and -5

- 70 percent H2S in propane/N2 gas mixtures when the gas heating value is at least 1.2 times the level required for flame stability.

• For gas**~ixtures** containing both H2S and propane, H2S destruction efficiency was consistently higher than propane combustion efficiency.

• The total gas heating value required for a stable flame, including pilot contribution, is much lower for pilot assisted 3and 6-inch open pipe flares than for the same unassisted flares.

• High combustion efficiency is achieved for the pilot assisted tests when the gas heating value is at least 1.2 times the level required for flame stability. 

### •

2-25

### • There are subtle differences f

### n the flare combustion efficiency performance of the different pilot assist configurations tested in this program. Combustion efficiency greater than 98 percent is maintained for the 3-inch head even down to a heating value stability ratio of 1.00. Below a heating value stability ratio of 1.00, however, combustion efficiency decreases more rapidly for the 3-inch and 6-inch head with the single pilot at medium and low pilot gas rates, than for the 6-inch head with the single pilot at the high pilot gas rates and with the double and triple pilots. 2.3 References 2.1 Pohl, J. 

### H. and N. R. Soelberg, 11

### Evaluation of the Efficiency of Industrial Flares: Flare Head Design and Gas Composition,'' EPA Report No. 600/2-85-106, NTIS No. PB86-100559/AS, 1985.

2-263.0 GAS MIXTURE TESTS OF HzS Unburned hydrogen sulfide emissions from industrial flares are of great concern because of the large amounts of highly poisonous and noxious hydrogen sulfide gases flared in the petroleum industry. Work was conducted during the test program to evaluate the overall combustion efficiency and destruction efficiency of H2S in gas mixtures. This work repeats limited testing conducted at EER in 1984 (3.1) on gas mixtures containing propane, nitrogen, and 5percent H2S. Measurement errors for H2S prevented evaluation of HzS destruction efficiency for those tests. Testing of H2S gas mixtures proceeded in phases. First, HzS and SOz measurement techniques were evaluated for accuracy and adaptability to measurements of plume samples containing both H2S and S02 at high and low concentrations. After verifying the accuracy of measurement techniques using gas standards, tests were conducted using the laboratory-scale Flare Screening Facility. These tests were conducted to determine at what concentrations H2S could be burned efficiently. These tests were also used to verify the usefulness of H2S and SOz sampling and analysis. Although the flames produced on the 0.042 inch ID nozzle of the Flare Screening Facility are not similar to pilot scale and full sized flares, use of this facility has several advantages. Its low capital and operating costs provided an economical way to quickly evaluate if HzS could be burned efficiently. The nozzle is enclosed in a reactor shell, isolated from the environment which allowed**undiluted.~lume** samples to be collected. The small size and reactor shell enclosure increase safety for flaring toxic gases. The isolating enclosure also gives the ability to close inlet and exitmass balances, for verification of sampling techniques. After the review of measurement techniques and laboratory scale tests were completed, pilot scale H2S gas tests were conducted using the Flare Test • Facility. These tests repeated the incomplete and partially uncertain HzS gas mixture tests in EER's 1984 test program, and extended those results to

3-1

### include efficiency measurements for flare gases with higher H2S concentrations. 3.1 Measurement Techniques Accurate measurement of 

### HzS and S02 levels in plume samples is essential



# . to estimating H2S destruction efficiencies. It is important that measurements are made before 

### HzS and 

### SOz levels in the samples can significantly change due to reaction with other sampled species orwith the sample apparatus or

### containers. It is also important that either the H2S or S02 species be physically separated (such as by gas chromatography) before analysis, or 

### that the presence of 

### SOz in the sample does not interferewith H2S measurement, and vice versa. The H2S destruction efficiency measurements conducted at EER in 1984 were inconclusive because 

## so2 in the samples interfered with H2S measurements. Prior to 

### HzS gas mixture testing in this test program, a thorough investigation of 

### H2S and S02 sample techniques was conducted. Analysis methods for 

### H2S included:

• Concentration of gaseous 

### HzS gas scrubber bottles containing aqueous cadmium sulfate solution, followed by iodometric titration

• Concentration of gaseous H2S gas scrubber bottles containing aqueous zinc acetate solution, followed by colorimetric analysis using the methylene blue method

• Reaction of gaseous 

### HzS with lead acetate, causing darkening of lead acetate impregnated paper tape

• Gas chromatography

• Reaction with color indicators in Draeger tubes

3-2Methods for S02 sample analysis that were investigated were:

• Concentration of gaseous S02 gas scrubber bottles containing aqueous hydrogen peroxide solutions followed by barium perchlorate titration

• Gas chromatography

• Reaction with color indicators in Draeger tubes Tests were conducted using standardized gases and gas mixtures. These tests were conducted to verify app1icability of the techniques to measure plume gas concentration of H2S and 502 by evaluating accuracy, repeatability, reliability, and measurable ranges. Results of these tests are shown in Table 3-1. The fodometric titration and lead acetate methods for H2S measurement gave very inaccurate and unreliable results and were not used for further analyses. The methylene blue and Draeger**tub~** methods proved to be most accurate and reliable in the required sample range of 0-100 ppm. Where possible, both methods were used for H2S sample analysis. Gas chromatography was also used when the H2S concentration was within the GC detection range of 25

- 1000 ppm. For 502 measurement, the barium perchlorate titration method was most accurate. Occasionally, however, low measurements were obtained, possibly due to sample system leaks or analytical errors. Draeger tubes and gas chromatography were used to verify results from the titration measurements. 3.2 Laboratory Scale Tests Laboratory scale tests were conducted to determine concentrations at which H2S could be burned efficiently and to verify the usefulness of H2S and S02 sample procedures. The Flare Screening Facility, equipped with a 0.042 inch 10 nozzle, was used for these safer to operate than the larger FTF. 

### • tests, because it is less expensive and

Complete inlet and outlet mass balance

3-3c...l I**~** 

### TABLE 3-1. MEASUREMENT TECHNIQUES FOR H 2

SAND 

### so2

I£ASUREO IWtGE HOLDINGTIME I£TifOD SPECIES REf 

# ,.,., ACCURACY SENSITIVITY COffQTS lodoletrtc Titration H 2

S EPAMethod 11 1 6

- 520 !.1001 NM1 Large errors due to presence of 40 CFR Ch. 1 oxtdtzlng or redutlng agents. (7-1-85 Ed.) leaks. orH 2

### sloS$ 'ethylene BlueMethod**~s** MSI/ASlM 0.5-20 .!.501 0-301 No measurable Interference from D2725-70 Increase In other species**(Rea~proved** 111easured I eveIs 1975 In 24 hours lead Acetate Method HzS MSI/ASTM 100-2000 +lOOS NM Considerable Interference fro. (Tracor-Atlas**~S** D2420-66 

### - so2, reducing H2S aeasure.ents Mter) (Rearroved 1976 Dr1eger Tubes HzS Detector Tube 0.5-2000+**+2~** Gradual color Some Interference fro. SO HindbOOE, Uli boundary blurring presence. but thts 1s the2 best and ta. AUg. 1979 after5•lnutes to easiest

.. thod for H 2

s .. asurements 1llour so2 Detector Tube 0.5-8000+ !.201 Good holding ttme HiS also detected tn 50108 tube Rana60oE• :Uii exceeding 48hours r nges Ea•.AUg. 1979 &as Chra.atography H 2S Supelco 25-1000+ !.201 Sll

.. t .,.,..,. } (Perktn-El

.. r SigMa 2 Chromatography after24 hours &as Chra.atography Suppltes No H2S-S0f cross-senstttvtty. but not usefu atlow concentrations so2 Supelco 10-5000 !.201 Slight decrease**Chro~~~tography** after 24 hours Supplies

·Bart1111Perchlorate 

### SOz EPAMethod 6 1-2000+ +151 Good holdtng tt• Occastona1 low values from 1eats

Titration 40 CFR Ch.l 

# - exceeding48 hours tn systeMor analytical errors, but (7•1w85 Ed.) th1S ts the bestMethod for**S~ •asure~~ents.** **~-** --·-----**--~** 1. NM • NotMeasure4closure could also be determined with this facility to provide verification of sample procedures. Figure 3-1 compares flame stability limit results for the H2S gas mixtures to those for propane/N2 mixtures flared using the 0.042-inch nozzle and 3, 6, and 12-inch flare heads. The flame stability limit is defined as the operating condition where an increase in gas exit velocity or decrease in gas heating value results in flame blowout. The curves in Figure 3-1 were generated by determining the minimum gas heating value attainable before flame blowout for different gas exit velocities. Much higher gas heating values are required to maintain a flame on the 0.042 inch nozzle than for the 3, 6, and 12-inch heads. This is because of the aerodynamic differences between small and large diameterjets. Reynolds number (Re) indicates the degree of turbulence in a fluid stream. For jets from the 0.042 inch nozzle, Re ranged between 102 to 104, indicating that the flow was in the laminar to turbulent transition regime. Re for jets from the larger flare heads ranged from 103 to 106, denoting transition to turbulent flow. Richardson number (Ri) indicates relative influence of buoyant forces on aerodynamic flow. Richardson numbers greater than one indicate dominance by buoyant forces. The jets from the 0.042-inch nozzle had Ri ranging from to-6 to 10-J, signifying inertial force dominance over buoyant forces. For the 3through 12-inch heads, Ri was between l0-4 and 103. Some of these flames were dominated by inertial forces and some by buoyant forces. Most commercial flare flames are dominated by buoyant forces. The destruction efficiency of H2S and mass balances for these tests are shown in Table 3-2. The H2S gas content was 4.31 to 69.5 percent for these tests and the nozzle exit velocities ranged from 8.52 to 27.5 f/s. Greater than 99 percent H2S destruction efficiency was measured for all test conditions. Mass balance closure for carbon, oxygen, and sulfurwas less than 1.00 for all but one case. The best closure was with oxygen. Carbon and sulfur closure ratios were generally less than the corresponding oxygen closure ratios, but satisfactory for measurement of flare combustion and destruction efficiency.

3·5

# ....**~** u**~** 

## "**~ ~**  GQ 

# ....**~ ~**  ... 4 

### =-**~ ~**  ..-**~** 4**~** :c**~** 

## • «D**2400~------------~------------------------------**

1400

1200

1000**~0**

600 1984 Tests, Propane/N2Mixtures (3.1 1985 Tests,**Propane/~** Mixtures Tests, 4-5% H 2S1Mixtures Tests, 30-41% H 2



### s 1 Mixture Tests, 50-701 H 2

SMixtures

0 I 

# ' 

# ? ' I I I I I I I I I**~** l I I I 

# p '**roo~~--------------------------~--------------~** 1.0 10.0 100.0 1000.0 Exft Velocity (1/s) 

### Figure 3-1. Flame stabilitycurves for propane/N2 and H 2

### S/propane/ N

2gas mixtures flared using a 0.042 inch ID nozzle. 1. Remainder is propane and N 2
3-6w I

...... Test No.

1 2 3 4 5 

### TABLE 3-2. FLARE SCREENING FACILITY H 2SGAS MIXTURE TEST**RESULTS~** 

### NOZZLE ID 

### =0.042 INCHES

Gas Compos1t1on Gas Nozzle A1r H2S Propane (Remcunder N2) Heaung Exit Stofchfo Oestrucuon C011bust1on H

2

S Propane Value Velocity metric Efhc1ency _Eff1c1ency (Btu/scf) (f/s} Ratio (I) (S) 

### (') (') 4.31 45.2 1086 27.5 3.15 >99.99 99.9 34.8 52.0 1427 17.4 2.90 >99.99 99.99 31.9 55.0 1480 16.5 2.90 >99.99 99.9

4.28 45.5 1093 27.0 3.17 >99.7 99.9 69.5 30.5 1125 8.52 4.02 >99.99 98.6 Mass Balance Closure Mass In/Mass Out 

### c 0 

### s

I 0.567 0.944 0.446 ' 0.706 0.939 1.12 0.878 0.852 0.794 0.952 0.918 0.115 0.729 0.891 0.774

### 3.3 Pilot Scale Tests Pilot scale tests of H2S gas mixtures were conducted using a nonassisted 3-inch open pipe flare head at the Flare Test Facility. These tests were conducted to measure flame stability, combustion efficiency, and destruction efficiency for H2S gas mixtures. Results were used to verify incomplete results of the EER 1984 test program and to extend the"test data to include gas mixtures with higher H2S concentrations. Flame stability limit measurements are shown in Figure 3-2. These curves were generated by determining the minimum gas heating value attainable before flame blowout for a range of different gas exit velocities. Good reproducibility was attained between the 1984 and 1985 tests with -5 percent H2S in prop«ne/N2 mixtures. Since the dominant combustible gas in these mixtures is propane (14.4

- 20.1 percent), it is not surprising that the stability curve for these mixtures is**withi~** 

### boundaries previously determined for propane/Nz mixtures flared on the 3, 6, and 12-inch heads.**On~** 

### other method of.depicting the flame stability limit is to correlate the minimum gas heating value on a mass basis to the gas exit velocity. The difference between volumetric heating value and mass heating value for gaseous compounds depends on the compound molecular weight. Compounds with high volumetric heating values (1,3-butadiene, for example, having 2,730 Btu/ scf) may have low mass heating values (19,500 Btu/lb for 1,3-butadiene) compared to the heating values of other compounds (hydrogen, for example, having only 275 Btu/scf, but 51,000 Btu/lb). In Figure 3-3, the stability curve shown in Figure 3-2 is presented showing heating value on a mass basis. The correlation with exit velocity for different gases is no better than in Figure 3-2. Since the majority of the flare gas in all these mixtures is nitrogen (50

- 95 percent), the overall molecular weight and density of these gas mixtures only changes slightly from mixture to mixture. The flame stability limit curve for H2S/N2 gas mixtures in either Figure 3-2 or Figure 3-3 is much lower than for the H2S/propane/N2 or propane/N2 mixtures, but the volumetric heating value for H2S gas (588 Btu/

3-8w I 10 

# -

...... u Ul ';;' 800**~** CD



### .... ld >

"r'"**~** ld 

# .. ::z: Ill ld tD '\) 1984 -s% H 2

s in Propane/N2 Mixtures (3.1) [7 1985 -5% H 2S in Propane/N2 Mixtures 

### C> H 2StN2 Mixtures



## -""""-d>- 'f**-------------------.--------~---------------------------------------------- 100~--------------~~------------~~------------~~~----------------~**  0.1 1.0 10.0 100.0 1000.0 Exit Velocity (f/s) Figure 3-2. Flame stability curves for H 2

Sgas mixtures flared using a 3-inch diameter open pipe flare.

# - .0 

## .... ..... :;, +' II) 

# - .. :;, 

# .. =- en c 

# - w +' 

## • Ill 

## .... 

# .. 0**~** 

## .,. Ill cD 8000• Flared Using 3-Inch

### Op~n Pipe Without PilotAssist

100 () 1,3-butadtene/N2Mixtures (J Ethylene Oxtde/N2Mixtures 

# ,, ...**~e.,** 

# ,.,, "'

..1-

...

### ~'\o""

### \~· [> Hydrogen Sulf1de/N2Mixtures 

# ._,**~'**

### ~~e\~',Jt.o~'<..**~'(Q~b,**... ,o'(**~eti**

() 

### '\

.......... ,,....**t~o"** 

# "'"""'

...

# ~~ ...**~** ... b,'l.'

, fi.t'

,...."- b•**~ A~·**  a**,~.., ~0~** **~, ~e~~eb**  

# , ....**~** Ethylene Ox1de/N2 [> 

# _l

__**~()-** 

# J 1.3-butadiene H 2

SJN2**~o.-1--------------~1~.o--------------~1o--------------~1o~o----------~** Extt Velocity (f/s) 

### Figure 3-3. Flame stability curves using heating value per mass relationship.scf) is much lower than that of propane (2350 Btu/scf). There is actually a higher concentration of H2S (28.9

- 49.5 percent) in the H2S/N2 mixtures at the stability limit than the combined propane and H2S in the 5percent H2S mixtures {18.8

- 25.2 percent). The presence of higher H2S concentrations, and/or better combustion kinetics for H2S than for propane, may help to maintain a stable flame at lower heat input. The flame stability limit is approached when the flame propagation speed in the gas approaches the relief gas velocity. The determination of flame speed is very complex, involving reaction kinetics and mixing patterns. The inherent complexities discourage a direct evaluation of flare flame kinetic and mixing rates. However, the higher levels of H2S concentration in a mixture near the stability limit could increase the flame speed (unless the flame reactions are kinetically limited) by providing a greater number of H2S

- 02 molecular interactions relative to the total number of molecular interactions. However, the flame speed may be limited by reaction kinetics, and not affected by mixing. Kinetic rates of flame reactions are dependent on flame temperature and other parameters according to the exponential Arrhenius equation: -E/RT k

## =Ae (3-1) where k is the rate constant for a given reaction, Ais the frequency factor, E is the activation energy, R is the ideal gas constant, and T is temperature. If all parameters except temperature in Equation 3-1 are maintained constant as the temperature is increased, the reaction rate constant exponentially increases. If the flame speed is limited by reaction rates, the flame speed (and limiting maximum gas exit velocity) should increase exponentially as the flame temperature increases. The actual flare flame temperature is however difficult to determine accurately. Since the flame is in the open air, subject to wind and eddy conditions, both in-flame and optical temperature measurement methods are

3-11

### subject to errors. Also, within the flame envelope, thereis a wide temperature range due to varying degrees of air dilution and reaction completion. As a basis for comparison, apseudo flame temperature can be used for showing the dependence of flame stability on temperature for different flare gases. This pseudo flame temperature may be calculated assuming (1) adiabatic, complete combustion of the flare gas with a stoichiometric amount of air, or (2) adiabatic, complete combustion of a flare gas-air mixture with stoichiometry between the upper and lower flammability limits of the mixture, or (3) non-adiabatic, complete combustion of a flare gas-air mixture, assuming a certain amount of heat loss. In previous studies (3.1 and 3.2), pseudo adiabatic flame temperatures based on stoichiometric combustion of flare gas with a1

### r were..compared to flame stability. This pseudo adiabatic flame temperature was also combined with both upper and lower flammability limits and rel6ted to flame stability. Within the scope of this report, and fn order to make comparisons with previous EER research (3.1), p_seudo adiabatic flame temperatures based on stoichiometric combustion were related to flame stability in Figure 3-4. The limiting maximum stable gas exit velocity is shown to correlatewell with adiabatic flame temperature for individual gas mixtures. However, there is poor agreement between the correlations for the different gas mixtures. A much higher flame temperature is required to burn propane mixtures at a given velocity than other gas mixtures. Gas mixtures of H2S exhibit the lowest flame temperature for 

### a given gas exit velocity. Therefore factors other than flame temperature also affect the flame stability of different gases. Such differences in flame stability ofdifferent gas mixtures shown in Figure 3-4 is expected, considering the structural, physical, and chemical differences of the different compounds. Each of the compounds shown in Figure 3-4 has a different structure and properties distinctive of different classes ofmaterials -alkanes (propane), conjugated dienes (1,3-butadiene), oxygenated compounds (ethylene oxide), and sulfur compounds {hydrogen sulfide). Some comparative physical properties for HzS and propane are shown in Table 3-3. H2S has a wider flammable range, a lower adiabatic flame temperature, and a lower minimum ignition temperature than does propane.

3-12rn

.......

### 1000 Flare Gas Composition 

### o Propane N 2 

## a Ammonia/Propane/N

### 2 0 

### 1,3 Butadiene/N2 

### D Ethylene Oxide/A2**~** 

### 100**~** 

### Hydrogen Sulf1de7Propane/N2 

### (1984)**~** 

### Hydrogen Sulffde/Propane/N2 

### (1985)**~** 

### Hydrogen Sulfide/N2**~ ~**  

### ..... 

# - ·- .c IU**~** V') s.. Q



### ....**~ ~**  

### ..... u Q 

# - :: 01 c



### .....**~** 

### ..... e



### ..... ...J 

### 1,3-Butadiene

# ~~-

# ~ 10

Propane-Dominated Gas Mixtur

# ---- 1.0 Ethylene Oxide
0**0.1----~----~--------------~----------~-----** 

### 2.4 2.6 

### 2.8 3.0 3.2 

### 3.4 3.6 

### 3.8 4.0 Adiabatic Flame Temperature (1/R) 

### x 104 Figure 3-4. Calculated adiabatic flame temperature versus limiting stable gas exitvelocityfrom an unassisted 3-fnch open pipe flare.

3-13

### TABLE 3-3. PHYSICAL PROPERTIES1OF H 2

SAND PROPANE AT 60°F, 1ATMOSPHERE
Property ijzS 

### Propane Molecular Weight 34.076 44.097 Gas Density, (scf/lb) 11.4 8.77 Lower Heating Value**~Btu/sc~)** 

### 588 2350 Btu/lb 6700 20600 Flammability Limits fn Air (') Lower 4.3 2.1 

### Upper 45.5 10.1 

### Adiabatic Flame Temperature for Stofchiometfc Combustfon'Wfth Air (R) 

### Calculated2 3338 3838 Literature NA3 4055 Ignition Temperature (F) 558 871-898 Flame Velocity (f/s) NA3 0.95-1.3
1. Data From: Balzhiser, 

### R. E., M. 

### R. Samuels, and J.D. Eliassen, Chemical Engineering Thermodynamics. 1972 CRC 

### Handbook of Tables for Applied Engineering Science, 2nd Ed., 1976 CRC Handbook of Chemistry and Physics, 53rd Ed., 1972-73 Howard, H. F. and G. 

## w. Jones, 11

### Lim1ts of Flannability of Gases and Vapors•, USBM 8ullet1n 503, 1952 

### GPSA Engineering Data Book, 1972 Gas Engineers Handbook, lst Ed., 1965 North American Combustion Handbook, 1stEd., 1952 2. Calculated by integration of heat capacity data 3. 

### Not Ava1lable

3-14These differences indicate differences in other factors in Equation 3-1 which could influence kinetic rates for reactions in H2S and propane flames. The relationship between flame stability and flare combustion efficiency (see Appendix 0 for efficiency definitions) has been developed in previous studies. Figure 3-5 relates propane combustion efficiency for the H2S/ propane/N2 gas mixtures to the ratio of actual gas heating value and the minimum heating value required to produce a stable flame at that velocity. This correlation is within the range previously developed for a variety of gas mixtures and flare head types and designs. Combustion efficiency is high, exceeding 98 percent, for stability conditions greater than about 1.2. When stability conditions decrease below 1.2, combustion efficiency can rapidly decrease below 98 percent. A similar correlation for H2S destruction efficiency is seen in Figure 3-6. All data points except one fall within or above the previously determined destruction efficiency region for ammonia,**1,3-butadiene~** ethylene oxide, and propane. High destruction efficiency, greater than 99 percent, is attained for stability conditions greater than about 1.2. Destruction efficiency rapidly drops below 98 percent when the stability criteria decreases below 1.2. The presence of the single low efficiency point outside the shaded area is from a test that may have been influenced by ambient conditions or an upset or discontinuity in flow control or sample procedures. Since these tests were predominantly conducted very near the limit of flame stability, any slight change radically affected flare performance and efficiency. Destruction efficiency of H2S is compared to destruction efficiency of propane in Figure 3-7. For the H2S/propane/N2 mixtures and operating conditions of these tests, 

### HzS destruction efficiency was consistently higher than propane combustion efficiency. This indicates that H2S flames may be more stable and react more quickly than propane flames. Figure 3-2 shows that H2S flames are more stable than propane flames.

3-15"'"" 

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### S/ propane/N?. gas mixtures flared from an uriassistea 3-inch open pipe flare.

1. 

### Scale is log (100- 

### Combustion Efficiency)

3-16 

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### HSgas mixtures flared from an

### una~sisted 3-inch open pipe flare. 1. 

### Scale is log {100-0estruction Efficiency)

3-17 

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### destruction efficiency and propane

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2

### mixtures flared from an unassisted 3-inch 

### open pTpe flare.

3-183.4 References
1. Pohl, J. H. and N. R. Soelbel"'g, 11Evaluation of the Efficiency of Industria1 Flares: Flare Head Design and Gas Composition, 11 EPA Report 

### No. 600/2-85-106, NTIS No. PB86-100559/AS, 1985.
2. Noble, R. K., M. R. Keller. and R. E. Schwartz. 11An Experimental Analysis of Flame Stability of Open Air Diffusion Flames 11

, AFRC International Symposium on Alternative Fuels and Hazardous Wastes, Tulsa, OK, 1984.

3-194.0 PILOT ASSISTED TEST RESULTS Very little testing of pilot assisted flares has previously been conducted at EER or reported in the literature. Most previous work at EER has been on unassisted flares, in order to simplify the test programs and to evaluate operating parameters independent of pilot assist. Industrially, however, continuous gas pilots are commonly used to ensure safe, continuous and emergency flaring. Upon recommendation of the flare Technical Advisory Committee, more extensive pilot assisted testing has been conducted at EER. For these tests, the flare gas was a mixture of propane blended with nitrogen to vary the gas heating value. Utility-supplied natural gas was used for the pilot gas. Open pipes of 3 and 6-inch diameter were used as the flare heads. Single, double, and triple pilots were tested. The single pilot was a John Zink Co. 2-inch gas pilot equipped with a flame front generator. The double and triple pilots were manufactured by EER and are similar to the Zink pilot. Orientation of the pHots to the flare as suggested bythe Advisory Panel is shown in Figure 4-l. Operating parameters evaluated were the number of pilots and the pilot gas flowrate. Tests were conducted on the 3-inch and 6-inch flares with a single pilot and a nominal pilot gas flowrate of 2 scfm. Using the 6-inch flare, tests were also conducted with the single pilot at pilot gas flowrates ranging from 1-5 scfm. Tests were also conducted on the 6-inch flare with single, double, and triple pilots, maintaining the total pilot gas rate at 2 scfm. The flare gas exit velocity range for all these tests was limited to the range between 8-150 f/s for the 3-inch head and 5-50 f/s for the 6-inch head. Lower velocities were not used because of the high pilot gas rate relative to propane flowrate in the flare gas. Higher velocities were limited by the maximum nitrogen flowrate capacity of the Flare Test Facility.

4-1A. Single pilot



### B. Double pilot • Radial angle between pilots 1s 180 degrees.

C. Triple pflot. Radial angle between pilots 120 degrees. 

# ,,.\ I I \ I 

# '*' I I , I I I



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. I \ Dimensions: A. 30 degrees B. 2.5 inches C. 1 inch



### Figure 4-1. Schematics of single, double, and 

### triple pilots.

----------**----------~**4.1 Flame Stability For all combinations of pilot assist. flame stability limit curves were de.termined. The flame stability limit is defined in Appendix Cas the condition where a decrease in flare gas heating value or an increase in flare gas exit velocity results in flame blow-out. The previously used flame stability limit determination procedure was to incrementally decrease the flare gas heating value at constant gas exit velocity until flame destabilization and blowout occurs. This definition and procedure could not be applied in the p;lot assisted tests because the presence of a pilot prevented flame blowout, even at very low flare gas heating values. Consequently, the definition and determination of the flame stability limit were more subjective. The gas heating value required for 98 percent combustion efficiency at a given flare gas velocity was observed to be the operating condition where the last faint flickers of orange color completely disappeare and the flame envelope becomes completely transparent, except for blue-orange cones near the pilot and flare tips. This limit is determined by gradually decreasing the flare gas heating value, maintaining constant gas exit velocity and pilot gas flowrate and observing the flame, as orange and yellow color in the flame decreases and eventually disappears. This definition applies to specific pilot assisted tests of this**stu~** burning propane/nitrogen mixtures. Flame stability for the 3-inch pilot assisted head is shown in Figure 4-2. Curves defining stable, stability limit, and unstable flames are shown. The gas heating value includes the added heating value contribution of the pilot gas. Some scatter in the data points is due to the subjectivity of the visual measurements and to slight fluctuations in the ambient conditions, such as lighting and wind variations. For a given gas exit velocity, the stability curves occur at significantly lower gas heating values than the region of stability limit curves for unassisted 3through 12-inch flares. Clearly, this pilot-assisted open pipe flare can be operated stably at.much lower total heating values (pilot gas included) than the same flare without pilot assist. Again, it should be noted that these data are for very simple open pipe flares. In commercial practice a variety of aerodynamic

4-3

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100 Visual Observations**~** Faint orange flicker tn flame envelope (stable)**~---.** Disappearance of faint orange flicker (stability ltiDit) •••••••' Unstable**~** 3-tnch open pipe flare with single pilot at 2.1 scfm pilot gas rate (1984 tests)(4.1)

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# r---fl>--

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# Unstable~ • 0**~o-.,~----------~1~.o~-------------1~o-.o-------------1-0 0---------------1·ooo~-J**  Flare Extt·velocity (f/s) 

### Ffgure 4-2. Flame stabilitycurve for 3-1nch p1pe flare w1th a single pilot at a pilot gas flowrate of 2.1

- 2.2 scfm natural gas.stabilization devices are commonly used. Flares with such features may exhibit differences between piloted and non-piloted performance which are smaller than for the simple system studied here. Flame stability curves for the 6-inch flare with a single pilot at low, medium, and high pilot gas rates are shown in Figure 4-3 through 4-5. For each pilot gas flowrate series, the curves of total gas heating value (including pilot) vs flare gas exit velocity for the stability limit, as defined by the disappearance of orange coloring in the flame envelope. are shown. These stability limit curves depend only slightly on velocity in the range tested. For low and medium pilot gas flowrate, the limiting total gas heating value is about 150 Btu/scf for flare gas exit velocities between 5.6-45 f/s. For comparison, Figure 4-4 shows that this limiting heating value is the same as that for the 3-inch pilot assisted flare with a medium pilot gas rate, at a flare gas exit velocity of 35 f/s. The limiting heating value for the tests with high pJlot gas rate is also constant, but slightly lower at about 120 Btu/scf. Tests conducted below this level were in the unstable regime. Flame stability curves for the 6-inch flare with multiple pilots are shown in Figure 4-6. The stability limit for the double and triple pilot tests is flat at a constant heating value of about 130 Btu/scf, for gas exit velocities between 10-30 f/s. This is slightly lower than for the single pilot assisted tests at equal or lower pilot gas rates, but slightly higher than for the single pilot tests at higher pilot gas rates. At gas exit velocities above 40 f/s, the stability limit for the multiple pilot tests gradually increases as it does for the 3-inch pilot assisted flare tests. Use of pilot assist greatly enhanced flame stability during these tests. For 3 and 6-inch unassisted open pipe flares, operated with propane-nitrogen gas exit velocity of 40 f/s, the minimum gas heating value required to maintain a flame is about 540 Btu/scf. If a 2scfm natural gas pilot used, the total heating.value (including pilot contribution) required for a stable flame can be reduced to 150 Btu/scf. At this condition. the flame envelope becomes transparent and by definition. the stability limit is reached. For

4-5

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### Figure 4-3. Flame stability curves for 6-1nch open p1pe flare with a single pilot at a pilot gas flowrate of 1.0- 1.1 scfm natural gas.10



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### ti•••••J•••········~··stab111ty curve for 3-1nch f pilot assisted open pipe Unstable nozzle 1. at contribution 0.1 1.0 10.0 100 1000 Flare Gas Exit Velocity (f/s) Figure 4-4. Flame stabilitycurves for 6-inch open pipe flare with a single pilot at a pilot gas flowrate of 2.1

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- 5.4 scfm natural gas.

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## IQJ**~ ~ol>-·--0>-·~**  

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## 1 Ol 1 Unstable• 1 1 ·o.1 1.0 10.0 100 1000 Exit Velocity (f/s) Figure 4-6. Flame stability curve for 6-inch open pipe flare with multiple pilots at a total pilot gas flowrate of 2.0

- 2.3 scfm natural gas. 

## I• 

### the 6-inch flare, the same heating value reduction can be attained with the pilot at only 1 scfm. Added pilot assist, however, only marginally increases flame stability. Increasing the pilot gas rate to 5 

### scfm only reduces the limiting heating value to 120 Btu/scf for the 6-inch flare. Increasing the number of pilots to two or three while keeping the total pilot gas rate constant at 

### 2scfm decreases the limiting heating value to 130 Btu/scf. Another indicator of improved flame stability with pilot assist is the calculated adiabatic flame temperature of the gas mixtures flared at or near the stabi1

### ity limit. In Figure 4-7, 

### the maximum stable exit velocity is compared to the adiabatic flame temperature for pilot assisted and non assisted flares tested at 

### EER. The pilot assisted flares could stably burn propane/N2 gas mixtures with much lower adiabatic flame temperatures than non assisted flares could burn HzS/Nz, ethylene oxide/N2, and especially propane/ N2 gas mixtures. The scatter in the data for the pilot assisted tests fs apparently due to the increased difficulty in determining the flame stabiHty limit due to fluctuations in 

### ambient conditions and because the flame cannot be extinguished with pilot assist. 4.1.1 The quantitative flame stability results discussed above are applicable to flares of similar size and geometry (open-pipe, no aerodynamic or other stabilization devices). There is however a question with regard to the extent that these data are scalable to flares of a larger size. In an earlier study, Pohl and Soelberg (4.1) have reported aerodynamic and flame stability similarities for flare heads sized from 2-1/2 to 12 inches in diameter. Extrapolation of the pilot-assisted results for the 3and 6-inch heads. with one to three pilots at a pilot gas flowrate range between 1-5 scfm, may be used to predict flame stability for pilot-assisted open pipe flares up to 12 inches in diameter. Aconservative prediction would be further l.imited by (1) 

### using the minimum pilot gas to flare gas volumetric flowrate ratio of these tests (0.002) as the minimum allowable ratio for operation, {2) using three pilots on a 12-inch flare (even though little dependence of stability on number of pilots was observed on the 6-inch head)

4-10

# - ..Q 

### ..,

.... V1I1000

100 • () 3-inch flare with single pilot at 2 scfm pilot gas rate '84 () 3-inch flare with single pilot at 2 scfm pilot gas rate () 6-inch flare with single pilot at 1 scfm pilot gas rate 

### CJ 6-inch flare with single pilot at 2 scfm pilot gas rate C> 6-inch flare with single pilot at 4-5 scfm pilot gas rate C) 6-inch flare with double pilot at 2scfm pilot gas rate CJ 6-fnch flare with triple pilot at 2 scfm pilot gas rate



## .e 10 >, Ethylene oxide/N2gas mixtures flared from

unassisted 3-fnch

open pipe flares 

### .... 

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S/N2gas mixtures flared from unassisted 3-fnch open

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Propane/N dominated gas mixtures flared from

3-fnch**a~d** 6-inch open pipe flames (unassisted)



### Figure 4-7. Calculated adiabatic flame temperature vs. limiting stable gas exit velocity for propane/N2 gas mixtures flared using pilot-assisted 3-inch and 6-inch open pipe flares.

4-11for improved mixing, and (3) limiting the maximum exit velocities to ranges tested. With these limitations, a conservative prediction of minimum heating value is 150 Btu/scf for a stable flame on a 12-inch open pipe flare with three natural gas pilots. The maximum flare gas exit velocity for stability would be about 35 f/s. For velocities above 35 f/s, results from the 3-inch pilot-assisted head tests show increasing heating value limits with increasing velocity, up to a minimum heating value of 240 Btu/scf at 200 f/s. Maintaining the minimum experimental pilot gas/flare gas ratio of 0.002, the minimum total pilot gas rate would be about 20 scfm when the flare gas exit velocity is 200 f/s. Predictions such as these, although conservative, are based on extrapolations of the pilot scale data. Verification of these predictions by further, larger scale pilot-assisted stability testing is however required before these predictions can be considered valid. Only qualitative results of the test data reported herein can be applied to flares that have aerodynamic or other stability enhancing devices. 4.2 Combustion Efficiency Previous EER studies have shown that flare combustion efficiency can be related to flame stability. This correlation also holds for the pilot assisted flares with the flame stability limits defined as above, as shown in Figure 4-8. Measured combustion efficiencies for the pilot assisted flares are within approximately the same region of efficiency vs stability ratio already developed for unassisted 3, 6, and 12-inch flares. Combustion efficiency is greater than 98 percent for stability ratio conditions greater than about 1.2. Combustion efficiency rapidly decreases when the ratio of (heating 1alue)/(minimum heating value required for stability) decreases below about 1.2. The major difference between the pilot assisted and unassisted flares efficiency results is that measurements for the assisted flares were made at very low gas heating values, ranging from

4-12

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•

•

### -~ Region ofcombustion efficiency


# .. measurements for previously tested • propane/N mixtures flared from 

# - • 3, 6, and212-1nch open pipe flares(4-1 ) & • 

### •
• • • • • • • • 

## a**70~--------------~--------------~--------------~** 0 1.0 2.0 Heating Value/Minfmge Heating Value Required for Stability 

### Figure 4-8. Combustion efficiencyof pilot-assisted flares.

4-13100·211 Btu/scf while measurements for the unassisted flares made at higher gas heating values of 273-2350 Btu/scf. The stability limits for the pilot assisted flares are much lower than the stability limits at the same gas exit velocities compared to the unassisted flares. However, high combustion efficiency is maintained for the pilot assisted flares until the gas heating value, including the pilot contribution, decreases to within 1.2 times the stability limit heating value. There are some subtle differences**betw~en** combustion efficiency performance of the pilot assisted heads. Combustion efficiency greater than 98 percent for the 3-inch pilot assisted flare is maintained even down to a stability ratio of 1.0, demonstrating higher combustion efficiency between 1.0 and 1.2 stabi1ity ratio than for the 6-inch pi1ot assisted head. This could be due to the fact that, for the 3-inch head, the differences between the pilot (and pilot gas flow} are less than for the 6-inch head. Therefore, the impact of the pilot flame .is greater on the flame from the 3-inch head**~** than on the flame from the 6-inch head. Also, tests for the 3-fnch head were conducted at slightly higher gas heating values than for the 6-inch head, because the stability limit curve for the**~-inch** head was not as low as the curves for the 6-inch head. Below a stability ratio of 1.0, however, the decrease in combustion efficiency for the 6-inch head at the high pilot gas rate and for the double and triple pilot is less rapid than for the 6-inch head with the single pilot at medium and low pilot gas rates, and the 3-inch pilot assisted head. This is because, even at conditions near and below the stability limit, high relative pilot gas rates or multiple pilots can improve otherwise very low combustion efficiency. 4.3 References
4.1 Pohl, J. H. and N. R. Soelberg, "EvaluatioJ1 of the Efficiency of Industrial Flares: Flare Head Design and Gas Composition,•• EPA Report No. 600/2-85-106, NTIS No. PB86-100559/AS, 1985.

4·14

### APPENDIX A EPA FLARE TEST FACILITY AND PROCEDURES

A.l Flare Test Facility The EPA Flare Test Facility (FTF), shown in Figure A-1, was designed and built by EER at their El Toro Test Site for the U.S. Environmental Protection Agency, under EPA Contract No. 68-02-3661. The facility was completed in 1982. 

### The facility is reviewed briefly below, and is described in more detail by Joseph, et al. (A.l) and Pohl, et al. (A.2). For wind protection, the FTF is located in a box canyon surrounded by 70-foot cliffs. The facility includes gas delivery systems, a flare head mount enclosed in a framework structure supporting (1) screens for additional wind protection, and (2} plume sample probes, and a building containing delivery system controls and analytical instruments. The facility is designed for relief gas flows ranging from 10 to over 40,000 scfh. The maximum flow depends on gas composition. Gases are delivered to the flare and auxiliary equipment through parallel manifolds shown in Figure A-2. Propane, natural gas, and nitrogen manifolds each have three orifice meters and one small rotameter, each with its own control valve. These manifolds were designed to accurately measure and control a wide range of flowrates. One additional manifold of two parallel orifice meters (not shown) is used to measure the flow of one additional flare gas. The propane, natural gas, and nitrogen manifolds and flow lines are constructed of carbon steel. The flow line and manifold system for the additional flare gas is constructed of stainless steel, for compatability with corrosive gases such as ammonia and hydrogen sulfide. There are also similar supply systems for steam, sulfur dioxide (tracer) and air. Steam is used (1) for steam-assisted flare tests, (2) in steam heat exchangers for**~aporizing** 

### sulfur dioxide and flare test gases. and (3) for



### A-1

### f N AdjustAble like for Sa.ple Probes, Filters, Driers, Ten•x Trips, •nd Bubblers for H 2

S, S02I NH3 

# ............

# _.

Figure**A~l.** 

### EPA Flare Test Facility (FTF) atEER

.


### •.lquld llltrGIJMI 1--t:Xl-<...,.---n•rw Stack



### Figure A-2. Fuel flow control and metering system schematic.



### A-3 •

### sample probe heating. Sulfur dioxide is used as a tracer for flare testmass balances. Air is used during air-assisted flare tests. Flare and tracer gases (except natural gas) are supplied from cylinders 

### or tanks. Propane is stored as a liquid in a 2,100 gallon tank. At low flowrates, natural vaporization is sufficient to supply propane gas for flaring; at higher flowrates, propane-fired vaporizers are used to increase the propane flowrate up to 15,000 scfh. Natural gas is supplied by the local utility at a maximum flowrate of 7,000 scfh. Nitrogen is delivered from either a liquid nitrogen tank or liquid nitrogen cylinders to banks of finned-tube atmospheric vaporizers capable of providing amaximum nitrogen flowrate exceeding 24,000 scfh. Other liquified flare gases such as hydrogen sulfide are delivered from cylinders and vaporized in a steam heat exchanger. This system can deliver over 4,000 scfh of gas, depending upon the compound. Steam is produced using a 

### lS hp**~as-fired** 

### boiler. The boiler can supply up to 400 lbs/hr of 100 psig saturated steam. Sulfur dioxide, used as

## an inert tracer, is fed from liquid S02 cylinders and vaporized through a steamheated vaporizer at a flowrate of up to 7 

### scfh. Air is supplied by a forceddraft fan at a maximum flowrate of 60,000 

### scfh, at a static pressure of 17.6 

### inches H2o. The sample collection and analysis system is shown fn Figure A-3. 

### Plume samples are**collected--usin~ fl~st~inless-steel,**  

### steam-heated probes mounted on a movable rake. Samples are collected concurrently from five different radial locations in the plume. Pumps draw the soot- and moisture-laden samples into the probes, where filters collect the soot for subsequent weight measurement. Membrane tube bundles in Permapure dryers are used to selectively remove water vapor from the sample stream. The dried gas samples are collected in Tedlar bags for analysis of 02, CO, 

### C02, total hydrocarbons, H2S, S02, and NO/NOx content. Other species such as S02, H2S or NHJ are concentrated into aqueous solutions in absorption bubblers.

A-4

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figure A-3. Flare Test Facility sample system.A.2 FTF Procedures The Flare Test Facility {FTF) test procedure includes measuring background conditions, igniting the flame, establishing test conditions, sampling, and analysis. Tests are not conducted in rainy weather 

### or when the wind speed is greater than 5mph. Most testing is done in the morning, when the weather is calm. Atypical test requires about 4hours, although the actual sample period is only 20 minutes. Before each test, the ambient air is sampled and analyzed for background levels of 02. 

## co, C02, hydrocarbons, S02, NO/NOx. soot, and for H2S or NHJ, if applicable. The flame is then ignited using a hand-held spark igniter or a Zink flame front propagating igniter, and the test conditions are set by adjusting the gas flowrates. Most of the tests were conducted near the stability limit of the flame. The flame stability limit is determined by adjusting the flowrates until the flame becomes unstable and is eventually extinguished. After test conditions are set, plume samples are collected for 20 minutes in order to time-average perturbations and collect sufficient amounts of sample for analysis. Samples are collected from five different radial locations, at a height above the flame experimentally determined to be beyond the flame envelope. If the probes are too high, air dilution of the samples reduces combustion product measurement accuracy. If the probes are located too low, inside the flame envelope, incompletely burned samples may be collected, which would result in artificially low combustion efficiency measurements. While the plume is being sampled, the flame structure and other characteristics such as color are recorded visually and photographically. After sample collection and flame observations are complete, the flame is**shu~** down. Sample analysis is then conducted to measure levels of 02, CO, C02, HC, NO/NOx, soot, and other species in the plume samples.

A·6A.3 References
A.l Joseph, 0., J. Lee, 

## c. McKinnon, R. Payne, and J. Pohl, "evaluation of the Efficiency of Industrial Flares: Background-Experimental DesignFacility", EPA Report No. 600/2-83-070, NTIS No. PB8J

..263723, August 1983.
A.2 Pohl, J. H., R. Payne, and J. Lee, "Evaluation of the Efficiency of Industrial Flares: Test Results", EPA Report No. 600/2-84-095, NTIS No. PB84-199371, May 1984.



### A

..7

### APPENDIX 8 FLARE SCREENING FACILITY AND TEST PROCEDURES

8.1 Flare Screening Facility The laboratory-scale Flare Screening Facility (FSF) is used to inexpensively, quickly, and easily identify potential difficulties in flaring a wide variety of compounds. Advantages of the FSF over the Flare Test Facility are its small size, low operating cost for gases and materials, the ability to obtain complete, undiluted samples of flare combustion products, the ability to close mass balances, and the increased safety for flaring toxic gases. This facility is reviewed briefly below, and is described in more detail by Pohl and Soelberg (8.1). Figure B-1 shows the FSF schematic. The facility was adapted to burn either liquid or gaseous compounds supplied from pressure cylinders and metered through calibrated rotameters. Combustion air is injected to the reactor co-axially with the fuel stream, through a flow straightening screen. By maintaining a very low air velocity relative to the fuel velocity, effects of the co-current air stream on the fuel stream are minimized. Test results verify that the flame behavior is similar to that of ajet in a quiescent atmosphere. The flame is completely enclosed in a water-cooled reactor shell, with sample probes located at the reactor outlet. The shell isolates the flame from the environment and prevents air dilution of the flare products. This allows complete mass balance closure over the system. Asingle sample probe is located at the reactor shell outlet to enable sampling of a well-mixed plume sample.



### B-1

# 1116-1/8 IN. NOZZLE

GLASS BEADS 

# HEATED LINE**~==GAS** 

# SYRINGEDRIVE AIRFAN

Figure B-1. Flare Screening Facility (FSF).

B-28.2 FSF Test Procedures The FSF test procedures are simpler than the FTF test procedures. Since the facility is enclosed, it is not subject to environmental conditions such as wind or rain. The system is smaller and hence, more easily monitored. ·Probe positioning is unnecessary, since the sample probes are located

permanently at the reactor outlet. For each test, all the instruments are zeroed and calibrated. The flame is ignited by hand, and flow conditions are set. There is some time lapse, depending on the gas flowrates, for flare steady state to be achieved after gas flowrate or mixture changes because of gas residence time in the flowlines. After steady state is reached, sample collection is initiated and visual and photographic flame observations are recorded. Plume samples collected in Tedlar bags are analyzed for Oz, CO, COz, total hydrocarbons, HzS, S02, NO/NOx content, and other species using the instruments shown in Figure A-3. Plume samples are also bubbled through gas scrubber bottles for concentration and subsequent analysis of such species as HzS, S02, and NH3. 8.3 Reference 8.1 Pohl, J. H. and N. R. Soelberg, "Evaluation of the Efficiency of Industrial Flares: Flare Head Design and Gas Composition'', EPA Report No. EPA-600/2-85-106, NTIS No. PB86-100559/AS, September 1985.



### B-3APPENDIX C
FLARE FLAME STABILITY LIMIT C.l Stability Limits Previous work 

### (C.l through 

### C.4) has related flare combustion and destruction efficiency to flame stability. A stable flame exhibits high efficiency. However, as flame conditions approach the stability limit, efficiency can rapidly decrease. The flame stability limit is defined as the operating condition where an increase in flare gas exit velocity or a decrease in flare gas heating value results in flame blowout. Theoretically, this occurs when the gas velocity is not reduced to the flame velocity before the gas becomes diluted {by air !ntrainment and mixing) below its lower flammability limit or when the flame speed is less than the imposed velocity. Acharacteristic exit velocity vs heating value curve, maintaining all ather conditions constant, can be generated for each flare head and gas mixture combination. This curve is generated by determining the minimum gas heating value attainable before flame blowout, for a range of different gas**·~xit** velocities. At exit velocity and heating value combinations above this c:urve, a flame will be present; at conditions below the curve, there will be no flame. C:.2 References
C:.l Pohl, J. H., R. Payne, and J. Lee, ••Evaluation of the Efficiency of Industrial Flares: Test Results", EPA Report 

### No. 600/2-84-095, NTIS No. PB84-199371, May 1984. C.2 Pohl, J. H., J. Lee, R. Payne and B. Tichenor, "The Combustion Efficiency of Flares", 77th Annual Meeting and Exhibition of the Air Pollution Control Association, San Francisco, CA, June 1984.

C-1

### C.3 Pohl, J. 

### H. and N. R. Soelberg, "Evaulation of the Efficiency of Industrial Flares: Flare Head Design and Gas Composition••; EPA Report No. EPA-600/2-85-106, NTIS No. PB86-100559/AS, September 1985. C.4 Pohl, 

### J. H., N. R. Soelberg and E. Poncelet, "The Structure of Large Buoyant Flames", American Flame Research Committee Fall Meeting, Livermore, CA, 16-18 October 1985.

C·2APPENDIX D DATA ANALYSIS

0.1 FTF Data Analysis Data reduction and analysis must be conducted on the flare test results to determine flare combustion efficiency. Results of FTF tests must be :orrected for background levels of sampled species and air dilution of the Jlume. Also, numerical integration must be conducted using the local probe 1neasurements and velocities calculated from jet theory. The development and 1etails of the Flare Test Facility data analysis procedures are already**~eported** (D.l. 0.2) so only a summary is provided here. Data**reductio~** is conducted on the FTF plume sample results to determine local air dilution of the combustion products. local combustion and**~testruction** efficiencies, and integrated overall average combustion and ·riestruction efficiencies. The 1 oca1 di1 ution factor is:
Ym

- Yaf OF=--- D-1

where OF

## =dilution factor

## =volume of air in the local sample divided by the volume of stoichiometric combustion products. Y

## =local concentration of 02, C02, or S02 (tracer} m

### =measured in plume af

## =air-diluent-free, stoichiometric basis

b

## =background Combustion efficiency is defined as the degree to which all fuel naterials have been completely oxidized. The local combustion efficiency is based upon local probe measurements of plume constituents, whereas the

D-1integrated average combustion efficiency is calculated by integrating the local plume fluxes to obtain average compositions of plume species. Since local plume measurements are diluted by ambient air, they must be corrected for the background levels of plume species in the ambient air. These corrections are made using equation D-2:

0-3: where h

## =plume species c

## =corrected 0-2

Local combustion efficiency (CE) can then be calculated using equation

x; v; Y;,c CE • 1 - 

### D-3 Xj llj Y j ,c
where v·= stoichiometric coefffcfent i 

## =incompletely burned species j 

## =completely and incompletely burned species Local destruction efficiency is similar to local combustion efficiency, but is a measure of the degree of destruction of the particular fuel material. It is equal to the combustion efficiency for that species only when there are no incompletely burned intermediates, such as CO or soot for hydrocarbon species. Local destruction efficiency (DE) for a fuel species is calculated usfng equation D-4:

0-2DE = 1 

### D-4

where k

## =fuel species 1

## =completely and incompletely burned species fr.om the fuel species. Integrated average combustion and destruction efficiencies are computed by ·firstcombining the local corrected plume composition with the local plume velocity to obtain a local corrected mass flux for each plume constituent. The local corrected plume species concentrations are found using equation D-2, and the local plume velocity is calculated from jet theory using**equatio~s** D-5 and D-6:

Vr,x 

## =Ymax exp

where V

## =velocity 

# [ Rr2] -5- 

## x

R

## =radial distance from plume centerline X

## =probe axial distance above flare head r • radial pos1tion max 

## =maximum o

## =flare head outlet 

### D-5

D-6

llumerical integration of the local fluxes is used to calculate average c:ombustion and destruction efficiencies using equations D-7, D-8, and D-9:

D-3Xr

### x; v; Y;,c 

### Yr Ar CE a 1 • -------- Xr Xj Vj 

### Yj,c Yr Ar 

### D·7

D-8

D·9
where Ar 

## =radial area sampled by probe r (Figure D-1). D.2 FSF Data Analysis Data analysis for the Flare Screening Facility (FSF) test results is much simpler than for the Flare Test Facility (FTF) test results. The FSF flare flame is completely enclosed within a steel reactor shell. The inlet fuel and combustion air flowrates are metered, so the plume flowrates of excess air and air-free combustion products can be directly calculated based upon the combustion stoichiometry of

### the gas:

Ye.a. 

## =(SR-1) Vr.a.
where 

# v=volumetric flowrate, scfh e.a. • excess air S.R. a 

### stoichiometric ratio r.a.

## =required air for**100~** 

### combustion

D-4 D-10

D-11**~** 

# T , I I I I \ A4 X \

### ''' '

### ... 

# .......



### Figure 0-1. Schematic of integration geometry.



### D-5

### where p

## =stoichiometric products of combustion with air (air-free basis, 0percent 02) g

## =inlet gas 

### v

## =stoichiometric coefficient i =

### combustion product species ''i"

where t 

## =total plume This approach assumes 100 percent combustion, in order to determine the excess air, combustion product, and total plume flowrates. The same assumption was used in data reduction of the pilot-scale**tests~** 

### Where combustion is only slightly le.ss than 100 percent, flowrate errors due to**th~s** 

### assumption are small. Even where combustion is significantly less than 100 percent, the error 

### in total plume flowrate fs small, because a majority of the plume gas is nitrogen, unaffected by combustion efficiency (discounting N2

- NOx 

### reactions and combustion of nitrogen-containing fuel species, 0.2). The plume is sampled at the reactor exit, where the plume is well mixed. This eliminates the need for collection of multiple local plume samples across the plume radius, assumptions of local velocities at radial locations in the plume, and the integration of local species fluxes to calculate total plume species flowrates, because species concentrations in the plume sample are representative of average plume concentrations. Species flowrates in the plume are calculated using the measured concentrations and the plume flowrate found from equation D-13:

D-13

0-6where Y

## =mole fraction
In cases of high combustion efficiency, the plume concentration levels of incompletely combusted species such as CO and hydrocarbons are near background levels. The plume species flowrates must then be corrected by subtracting the background contribution:

where c

## =corrected b

## =background D-14

Combustion and destruction efficiencies are calculated using equations D-15 and D-16.



# . CE 

## = X; 

### v; V;

### ,c 1-**--~-** Z:j Vj 

### V;.c D-15

where i = incompletely burned species j = incompletely and completely burned species

DE 1 vk,c D-16 

### = 

## x, 111

# v,,c
where k

## =fuel species 1

## =incompletely and completely burned species that came from the fuel species

0-70.3 References
0.1 Pohl. J. H., R. Payne. and J. Lee, ••Evaluation of the Efficiency of Industrial Flares: Test Results 11

, EPA Report No. 600/2-84-095, NTIS No. PB84-199371, 

### May 1984.
0.2 Pohl, J. H. and N. R. Soelberg, 11Evaluation of the Efficiency of Industrial Flares: Flare Head Oesign and Gas Composition", EPA Report No. EPA-600/2-85-106, NTIS No. PB86-100559/AS, September 1985• •

D-8

### APPENDIX E QUALITY ASSURANCE
E.1 Flowrate Measurement The flare gases used at both the Flare Test Facility and the Flare Screening Facility were prepared by mixing the pure components. Accurate measurement and flow control of the pure gases was required to prepare the des1red flare gas composition and operate the flare at the**desire~·**gas exit velocity. Accurate flowrate measurement and control over a very wide range was achieved by using banks ofcalibrated parallel-flow square-edged orifice plates at the Flare Test Facility. For the smaller-scale Flare Screening Facility. banks of parallel-flow rotameters were used for accurate flowtate :neasurements• Each of the orifice plates used at the Fare Test Facility was calibrated Jsing the working gas for that orifice and a standard pre-calibrated laminar flowmeter. dry gas meter, or wet testmeter to obtain the flow coefficient for that particular orifice and gas. This orifice coefficient was used in ,:!quation E-1 for flowrate measurement:

• (P.4P ) 1/2 V = K

### MWT uhere 

### V = flowrate, scfm K 

## = orifice coefficient P 

## = static orifice pressure, psia**~P** 

## = orifice differential pressure, feet H20 column MW • gas molecular weight

T 

## = orifice temperature, R.



### E-1 E-1

### The standard deviation of Kfor 13 different orifices used in this test program was less than 5.4 percent. and less than 3.0 percent for the majority. Asimilar procedure was used to calibrate the rotameters used for flowrate measurement in the Flare Screening Facility. Each rotameter was calibrated using the working gas and pre-calibrated dry gas meters, wet test meters, or water displacement columns. Variations in pressure and temperature between the calibrated and actual operating values were corrected for using equation E-2: •



### E-2
where subscript 1 is for conditions during the calibration, and subscript 2 is for operating conditions. E.Z Sample Analysis Accurate sample analysis is critical for determining reliable combustion and destruction efficiency results. Table E-1 shows the analytical methods, instruments, and accuracies used in this test program. The listed accuracies are for the concentration ranges most tYPically encountered at the Flare Test Facility. Accuracy for a specific method may change if concentration levels for the sampled species are outside the ranges listed in Table E-1. Many of the analytical methods ofTable E-1 were developed in previous EER flare studies (E.l. E.Z). but methods for HzS and S02 measurement were evaluated in this study. Results of these evaluations are reported in Section 3 of this report. Only the most reliable of these methods were used for HzS and SOz measurements in the typical ranges observed at the Flare test Facility shown in Table E-1.



### E-2

# f I

1"11 I w SPECIES jlr*a:s::::aa•••=-=

02 ' 

### co C02 Total Hydrocarbons HzS

so2

NH3 NO/NOx Part1culate TABLE E-1. FLARE FACILITY ANALYilt;AL Mt::IHODS

II&STRUMENT PRINCIPLE RANGE ACCURACY 

## ·····--···======···==···===·=·8···===**~·=-=:;;:••.;a:::a:::z:a:s**

### P.•=====·=·===·

Taylor 570A Paramagnetism 0-1001 ;t0.2S of Measured Beck•an 315A NOIR 0-21 ;tD.1 ppm Beckman 3158 NOIR 0-20S :tD.021 of ·Measured Beckman 400 flO 0-5000 ppm ±0.5 PPII Draeger Tubes Color-lnd1cat1ng 

### o.5-2000 ppm ±20'1. of Chemtcal Reactfon Measured Color1111eter Methylene blue 0.5-20ppm ±.501 of Reactton Measured Draeger Tubes Color-lndtcatfng 

### o.5-5000 ppll ±20'1. of Chemtcal Reactfon Measured Bartu11 Perchlor- Bartu• Perchlor- 1-2000 PP• ±151 of ate T1tratton ate Reaction Measured Ion-Spec1f1c lon1c Potential 0.1-10 ppll ±151 of Electrode**~asured** Teco 14B-E Chemtlumtnescence 0.05-10 ppm ±51 of Measured ftlter Timed o-to-6 lb/cf ±lOS of Collection Measured MEASURED I CONCENTRATIONS**=======·=·==2=~=·•** 18-211 ' 3-500 ppm 0.05-21 3-1300 ppm

0-1000 ppll

0-1000 ppm
0.1-0.6 PPII· 0.02-10 ppm 10-8-to-6lb/cf

.. ·-E.3 References E.l Joseph, D., J. Lee, 

## c. McKinnon, R. Payne, and J. Pohl, "Evaluation of the Efficiency of Industrial Flares: Background-Experimental DesignFacility", EPA Report No. 600/2-83-070, NTIS No. PB83-263723, August 1983. E.2 Pohl, J. H., R. Payne, and J. Lee, 11Evaluation of the Efficiency of Industrial Flares: Test Results 11

, EPA Report No. 600/2-84-095, NTIS No. PB84-199371, May 1984. •

E-4

### APPENDIX F CONVERSION FACTORS To Convert From To l·1ultiply English Metric 

### By Btu B ritish Therma1 Unit kJ Kilojoule 1.055 c:fm Cubic Feet per Minute 

### m3;h Cubic Meters per Hour 1.700 ·in Inch m Meter 0.0254 ·in H 2



## o Inches Water Column Pa Pascal 249 psi Pounds per Square Inch Pa Pascal 6893 .:t Foot m Meter 0.3048 <:f Cubic Foot 

### m3 Cubic Meter 0.02832 ·:b Pound k.g Kilogram 0.4536 nph Miles per Hour km/h Kilometers per Hour 1.609
Degrees Rankine {R) is converted to degrees Celsius {C) via the following formula: C 

## = 5/9 (R

- 492) Degrees Fanrenheit (F) is converted to degrees Celsius (C) via: 

### C 

## = 5/9 (F

- 32)

F-1TECHNICALREPORTDATA**(Pleut~l'tltld l•~~n~ctiont** ontheTevenlbefoncomplttittl} 1. REPORT NO. ,2. 3. RECIPIENT'SACCESSIO

..NO. EPA-600/2-86-080 4. TITLiANOSUBTITLE 5, REPORTDATE EvaluationoftheEfficiencyofIndustrialFlares: H2S**S~tember** 1986

Gas Mixtures andPilotAssistedFlares 6.PERFORMINGORGANIZATIONCODE

7.AUTHOAISI 8. PERFORMING ORGANIZATION REPORTNO. J.H. PohlandN.R. Soelberg

9. PERFORMING OAOANIZATION NAMEANOADDRESS 10.I"ROGAAMELEMENTNO. EnergyandEnvironmentalResearch Corporation 18 Mason 11.**~!WIN** It1ACT/GAANT NO. Irvine. California 92718 68-02-3661 12.SPONSORINGAGENCY NAMEANOAOORESS 13.TYPEOF REI"ORTAN,pPERIODCOVERED EPA, Office ofResearchandDevelopment Final;4/85

- 7/86 14.SPONSORINGAGENCYCODE Air andEnerg:yEzu;(ineeringResearchLaboratory ResearchTrianglePark, NC 27711 EPA/600/13 15•suPPLEMENTARY NOTes AEERLprojectofficeris Bruce A. Tichenor. MailDrop 54. 919/ 541-2991.Earlierreports inthis series are EPA-600/2-85-106

.. -84-095. and 

### -83-oio 16. ABsTRACT Thereportisthefourthina serieson a researchprogramwhichwillresultinquantificationofemissionsfrom. and efficienciesof. industrialflares. The reportgives testdataonthe combustionefficiencyanddestructionefficiencyof (1) gasmixtures containingH2S. and (2) flareflames withpilotflame stabilization. (NOTE: Previousreports werelimitedtotestsburningpropane/N2mixtures onpipe flares withoutpilotflare stabilization. anddiscussed theinfluenceoftheflaredgas andflareheaddesignondestructionandcombustionefficiencywithout stabilization bypilotflares.) Thelatest tests,. conductedon3- and6-in. openpipeflareswithout aerodynamicflame stabilizationdevices, ledto conclusionsincluding: (1) gasmixtures ofH2S/N2 canbe stablyflared atmuch lowervolumetricgasheatingvalues thancanpropane/N2 mixtures; (2) destructionand combustion efficienciesgreater than98% are obtainedforgasmixtures ofH2S/N2 andH2S/propane/N2whenthegas heatingvalueis at least1.2 times thelevelrequired to produce a stableflame; (3) for mixturescontainingbothH2S andpropane. H2S destructionefficiencywas consistenUyhigherthanpropane combustionefficiency; and (4) combustionefficiencies greater than98%forpilotassistedflares are achievedwhentheheatingvalueis greaterthan1.2 times that requiredto stabilizetheflame.
17. KEY WORDSAND DOCUMENTANALYSIS a. DESCRIPTORS b.IDENTIFIERS/OPEN ENDEDTERMS c. COSATl Field/Group Pollution Pollution Control 13B Flames StationarySources 21B HydrogenSulfide IndustrialFlares 07B Nitrogen Flame Stabilization Propane 07C

HI. OISTRIEIUTIONSTATEMENT 19.SECURITY CLASS(ThisReport) 21. NO.OF PAGES Unclassified 103 Releaseto PubUc 20.SECURITY CLASS(Thispep) 22. PRICE Unclassified
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