PDH-1 Flare System – Pressure Assist

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FLARE SYSTEMS

Multipoint Ground Flares

PDH-1 Flare Emissions Test Results

TCEQ / EPA

February 2014

The Dow Chemical Company

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Agenda

• Introductions

• Meeting Purpose

• Permit Background

• Burner Testing

– Protocol

– Results

• Path Forward

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Dow Participants

• Jarod Davis, Regulatory Services Manager

• Cindy Rodriguez, Project Environmental Manager

• Cheryl Steves, Environmental Manager

• Vance Varner, Dow Flare Subject Matter Expert

• Russell Wozniak, Operations Regulatory Services

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Meeting Purpose

• Purpose: 

– To review previous meeting on the operation of 

pressure assist flare technology

– To present the results of emissions testing on the 

flare burners. 

• Outcome: Agreed path forward for approved 

operation of Multi Point Ground Flares at the Dow 

Chemical Company in Freeport, TX

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• Initial Permit Application for Propane 

Dehydrogenation Plant (PDH-1) was submitted to 

TCEQ on 1/24/12.

• Agreement to initially permit routine (non-pressureassisted) emissions, and to seek an AMOC 

authorization for the MSS (pressure-assisted) 

emissions

• PDH-1 Permit issued 1/11/13

Permit Background/Status

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• Initial Permit Application for Light Hydrocarbon 9 

Plant (LHC-9) was submitted to TCEQ on 

11/29/12.

• Propose similar permitting strategy as PDH-1; i.e., 

initially permit only routine emissions, and seek an 

AMOC

Permit Background/Status

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• Pressure assisted burners

• Header operates at a minimum of 15 psig

• Gas exits at sonic velocity

– Sonic velocity ranges from 700 to 1,400 ft/sec for common parafins and olefins

• High number of burners

– Number of burners based on required capacity

– Imagine a football field of burners

MPGF Burner Operation – Key Concepts

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Overall View

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Burners

Fence

Main gas manifold

Stage 1

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Pressure Assisted Burner

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• Multiple arms

• Holes for gas

• Cast construction

• Each supplier has a 

unique design

• Burner shape

• Number of holes

• Size of holes

• Orientation of holes

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Staging Concept

25-June-13

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Stage 3

Stage 2

Stage 1

Stages ... 

DCS

3 transmitters

From

KO Drum

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• Purpose: Show properly designed and operated PA 

burners will meet or exceed performance of other flare 

burners, even though the exit velocity will exceed the 

limits outlined in 40CFR 60.18 and 63.11.

• Facility: John Zink R&D test facility, Oklahoma.

– Facility is set up for appropriate data collection.

– Multiple other testing projects performed on site.

• Measurements: Emissions determined utilizing gas 

collection system and analytical equipment (TRC).

– Utilized PFTIR for comparison (Clean Air).

Emissions Testing Summary

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• One LRGO burner / pressure assist

• One SKEC burner / steam assist (1st stage)

• Pilot used for ignition, then turned off for testing

• Gas collection with scoop – same as used for 

TCEQ testing in 2010

• Testing performed in mid-November (2013)

Test Set Up

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Test Set Up

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• P1: 100% propylene

• P2: Mixture of propylene and nitrogen

• P3: Mixture of 50% propylene, 50% natural gas, then 

diluted with nitrogen

• P4: 90% hydrogen / 10% natural gas

• P1-P3: At high pressure (sonic velocity) and low pressure 

(de-staging).

– 3 tests each point, 20 minutes each

• P2-P3: Check for minimum heating value that has flame 

stability, then do emissions test there.

• P4: Test for flame stability only, 5 minutes.

Test Gas Mixtures / Testing Parameters

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• S1: Mixture of propylene and nitrogen, steam on

• S2: Mixture of propylene and nitrogen, steam off

• S3 – S4: Mixture of propylene and nitrogen, steam at minimum

• S5: Mixture of propylene and nitrogen, high steam flow

• S6: 100% propylene, steam at design rate

• S1 & S2: At high pressure / sonic velocity.

– 3 tests each point, 20 minutes each

• S3 – S6: At normal / expected operating pressure. Minimum 

heating value to maintain stable flame.

– 3 tests each point / 20 minutes each

Test Gas Mixtures / Testing Parameters

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Test Burners

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SKEC Burner

LRGO Burner

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Burner Test

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LRGO – Test P2

Propylene and Nitrogen

LRGO – Test P4

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Burner Testing

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LRGO – P1

Propylene

Video Monitor in Control Room

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Results – LRGO Burner

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Parameter 

Test ID P1H P1L P2H P2L P3H P3L 

Combustion Efficiency (%) 99.98 99.98 99.96 99.89 99.92 99.95 

THC DE (%) (Based on O2 F-Factor) 99.98 99.99 99.98 99.95 99.96 99.98 

Propylene DE Direct (%) (Based on O2 F-Factor) 99.91 99.95 99.93 99.96 99.95 99.98 

Propylene DE Bag (%) (Based on O2 F-Factor) 99.92 99.98 99.98 99.95 99.93 99.98 

Pressure at Flare Tip (psig) 13.5 5.2 13.4 5.0 14.0 4.9 

Exit Velocity at Flare Tip (ft/s) 880 597 1,017 669 1,101 706 

Fuel Gas LHV (BTU/SCF) (GC Analysis) 2,145 2,133 776 711 698 690 

Fuel Gas Flow Rate (lb/hr) 8,307 5,422 7,914 4,898 7,512 4,592 

Pressure Assisted Tests 

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Report Table JZ-2

Report Table JZ-4

Combustion Efficiency (%) - PFTIR 99.8 99.7 99.8 99.8 99.7 99.3 
PDH-1 Flare System – Pressure Assist

Results – SKEC Burner

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Parameter 

Test ID S1 S2 S3 S4 S5 S6 

Combustion Efficiency (%) 99.90 99.98 99.59 99.91 99.08 99.92 

THC DE (%) (Based on O2 F-Factor) 99.94 99.99 99.39 99.92 98.97 99.97 

Propylene DE Direct (%) (Based on O2 F-Factor) 99.94 99.94 99.50 99.80 99.32 99.97 

Propylene DE Bag (%) (Based on O2 F-Factor) 99.86 99.99 98.58 99.86 98.44 99.83 

Pressure at Flare Tip (psig) 12.0 12.0 0.38 2.15 0.47 0.45 

Exit Velocity at Flare Tip (ft/s) 993 997 161 413 181 152 

Fuel Gas LHV (BTU/SCF) (GC Analysis) 1,015 1,020 564 700 631 2,136 

Fuel Gas Flow Rate (lb/hr) 10,758 10,711 1,597 4,169 1,836 1,970 

Steam Flow Rate (lb/hr) 580 0 124 130 304 643 

Net Heating Value in Combustion Zone (BTU/SCF) 913 1011 499 685 530 1222 

Steam Assisted Tests 

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Report Table JZ-1

Report Table JZ-4

Combustion Efficiency (%) PFTIR 99.2 98.9 98.1 99.1 96.4 99.8 
PDH-1 Flare System – Pressure Assist

• Measurement of combustion efficiency is needed in addition to propylene 

DRE. 

– CO2, CO, and THC were measured during each test and combustion 

efficiency was calculated. 

– PFTIR was also used to measure combustion efficiency and to compare 

against the other measurements. 

• Characterization of vent streams

– 1

st stage (SKEC Burner): Nitrogen, methane, hydrogen, ethane, 

propane with larger amounts of propane and propylene during purges 

and maintenance flows

– 2

nd stage and above (Pressure Assisted LRGO Burners): Propane and 

Propylene are the main hydrocarbons flared. Nitrogen, methane, 

hydrogen, ethane, ethylene may also be present based on the venting 

scenario 

EPA Pre-testing Questions

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• 2

nd stage and above Realistic Maximum Flow Case

– PA Flare tip test cases cover a heating value range from 690 to 2,145 Btu/scf. Tests P1H, 

P2H, P3H cover the highest inlet pressures, thus the highest flows to an individual tip. 

EPA Pre-testing Questions

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Compound Composition

Hydrogen 4 wt% (45 mol %)

Methane 3 wt% (4 mol %)

Ethane 3 wt% (3 mol %)

Propylene 27 wt% (15 mol %)

Propane 62 wt% (33 mol %)

Nitrogen < 1 wt% (< 0.1 mol %)

Flow ~ 880,000 lbs/hr

Net Heating Value 1,283 Btu/scf
PDH-1 Flare System – Pressure Assist

• 2

nd stage and above Hydrogen content

– Hydrogen content expected to be less than 4 wt% under 

most scenarios with propylene and propane present.

– One scenario that is not expected to occur often includes a 

flare header purge and flaring net gas from the process: 

• Hydrogen 60 wt% (93 mol %)

• Methane 32 wt% (6 mol %)

• Ethane 4 wt% (< 0.1 mol %)

• Flow ~ 20,000 lbs/hr

– Test P4 showed a stable flame with mixture of 90% 

hydrogen and 10% methane. 

EPA Pre-testing Questions

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• Instrumentation 

– Both flare systems will be equipped with a vent gas flow 

meter and an on-line GC to comply with the Texas 

HRVOC regulations in the Houston, Galveston, Brazoria 

area

– GC will be capable of at least one measurement in a 15 

minute period for all C1 – C4 compounds, which 

constitute the vast majority of the hydrocarbons. Any 

C5+ compounds will be grouped together for inlet gas 

MW and heating value calculations.

– Instrument calibration and maintenance requirements 

are detailed in HRVOC regulations to ensure high 

quality measurements

EPA Pre-testing Questions

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• Potential Operating Parameter Limits 

– Stage 1 (SKEC tip) – Plans are to operate these flare tips in accordance with 

the regulations in 40 CFR 60.18 and 63.11. 

– Stage 2 and above (LRGO pressure assisted tips) –

• Results indicate that a high combustion efficiency and destruction 

efficiency can be maintained as long as the inlet gas net heating value is 

> 690 Btu/scf

• Note: LRGO flare tip testing by Marathon indicates that a net heating 

value of 550 Btu/scf is necessary for mixtures of natural gas and 

nitrogen. 

• Results indicate that high efficiencies can be obtained when hydrogen is 

flared. Since pure component net heating value for hydrogen is only 266 

Btu/scf, will need different limit for the case where high hydrogen content 

may be encountered. 

EPA Pre-testing Questions

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Compliance with 40 CFR 60.18 

Heating Value & Exit Velocity Requirements

• Routine vents will be routed to the first stage of the MPGF, which will 

operate similar to a steam assisted flare. This section of the MPGF will 

comply with 40 CFR 60.18 and 63.11. 

• MSS vents will increase the flare header pressure and the remaining 

stages will become operational. Since these stages operate at sonic exit 

velocity, the limits on maximum allowable exit velocity in 40 CFR 60.18 

and 63.11 cannot be met.

– Similar pressure assisted flares in our pipeline organization have 

been recognized as approved alternative flares for the TX HRVOC 

rules through the Alternative Means of Control (AMOC) process with 

alternate minimum net heating values. Dow has successfully worked 

with John Zink / TCEQ / EPA in the past to set AMOC limits.

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Known Pressure Assisted Flare Testing

• 1982 – Zink testing immediately after EPA-CMA flare testing

– Same instruments and techniques

• 1985 – Pohl & Soelberg

– EPA 600/2-85-106

• 2006 – Dow pipeline burners

• 2006 – BP

• 2012 – Marathon

• 2013 – Dow PDH-1

• Other testing by suppliers part of burner design / technology development

– Flame length / shape

– Flame stability

– Smokeless operation

– Noise / radiant heat

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• Pressure-assisted flares perform equivalent to or better than a 

conventional steam or air-assisted flare that meets the current 

regulations in 40 CFR 60.18 and 63.11. 

• Test results show both combustion and destruction efficiency > 

99%.

• The exit velocity limits for pressure-assisted flares should not 

apply.

• An inlet gas net heating value greater than 300 Btu/scf may be 

appropriate to ensure operations with a stable flame

– Dow Testing in 2013 indicates that > 690 Btu/scf may be 

appropriate 

– Marathon Testing reported in 1Q 2013 indicates that > 550 

Btu/scf may be appropriate.

• Additional provisions are needed to address high hydrogen flaring 

cases since the net heating value is only 266 Btu/scf. 

Conclusions – Dow Perspective

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• Submittal of Test Report – February 2014

• Technical Review of Test Report- ?

• Approval of Alternative Non-Opacity Emission 

Standard ?

• Public Comment Period on Approval ? 

• Federal Register Notice permitting the use of the 

alternative- October 2014

• Review and approval of TCEQ AMOC- October 

2014

Proposed Timeline

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Path Forward

• Present the test results to TCEQ on February 25th

• Address any remaining questions and/or provide 

additional information to assist with the technical 

review of the test report or the flare system in 

general 

• Engage both regulatory agencies to achieve 

agreement on future Operating Parameters

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Questions/Discussion

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Staging Curve

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Staging pressure set points:

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