August 5, 2014 

Certified Mail 7013 3020 0001 6360 6130 

Ms. Brenda Shine 

Sector Policies and Programs Division (E143-01)

Office of Air Quality Planning and Standards 

United States Environmental Protection Agency

Research Triangle Park, North Carolina 27711 

Approval Request for the Operation of the Pressure-Assisted Multi Point Ground Flare 

Technology for a Propane Dehydrogenation Plant and a 

Light Hydrocarbons Plant

The Dow Chemical Company, Texas Operations – Freeport, TX 

Dear Ms. Shine: 

The purpose of this letter is to further formalize our request to obtain an Alternative Means of 

Emission Limitation in order to operate two different pressure-assisted multi point ground 

flares at our Texas Operations site located in Freeport, Texas. An original request was filed 

with Mr. Steve Thompson at EPA Region 6 on August 20, 2013, and is included as an 

attachment to this letter. 

As communicated in the August 20, 2013 request, The Dow Chemical Company (Dow) has 

plans to construct and operate a pressure-assisted multi point ground flare for use with our 

planned propane dehydrogenation (PDH) plant. Dow also plans to install a second pressureassisted multi point ground flare for use with our planned Light Hydrocarbons Plant (LHC9). Both plants and flare systems will be constructed and operated at our Freeport, Texas 

location. 

Based on our review of this flare technology, we believe that these flare systems will operate 

with a VOC destruction and combustion efficiency greater than or equal to a flare that meets 

all of the requirements in 40 CFR 60.18 and 40 CFR 63.11 for traditional steam or airassisted flares. Dow believes that this technology is the best option for controlling VOC 

emissions for these plants. 

This flare technology operates by using the pressure upstream of each individual flare tip 

burner to enhance mixing with air due to high exit velocity, which in turn ensures a high 

VOC destruction and combustion efficiency. Due to the design of the flare tips, the flares

will meet or exceed the requirements in 40 CFR 60.18 and 40 CFR 63.11 with the exception 

of the exit velocity restrictions contained in 40 CFR 60.18(c)(3) – (c)(5) and 40 CFR 

63.11(b)(6) –(b)(8). The waste gas will exit the flare tip near or at sonic velocity, which can 

be in excess of 1,000 feet per second.
Ms. Brenda Shine, USEPA

August 5, 2014 

Page 2 

The PDH and LHC-9 processes will be subject to a number of TCEQ air pollution 

regulations that reference the flare requirements in 40 CFR 60.18 and 63.11. In order to 

address the exit velocity requirements, Dow has requested approval of the technology by 

submitting an Alternate Means of Control (AMOC) request to the TCEQ on August 20, 

2013. 

In addition to TCEQ rules, the PDH and LHC-9 processes will also be subject to a number of 

EPA air pollution control regulations under various subparts of 40 CFR 60, 61, and 63 that 

also reference the flare regulatory requirements in 40 CFR 60.18 and 63.11. The 

attachments provide information on the specific regulations that apply. In order to address 

the exit velocity requirements, Dow is proposing the following provisions and is requesting 

approval from EPA under the Alternative Means of Emission Limitation provisions: 

1. The maximum exit velocity requirements contained in 40 CFR 60.18(c)(3),(c)(4) and

(c)(5); should not be applied to these flares. Also, the maximum exit velocity 

requirements contained in 40 CFR 63.11(b)(6),(b)(7) and (b)(8) should not be applied to 

these flares. 

2. In order to ensure flame stability and a high destruction and combustion efficiency, the 

waste gas flowing to the flare tips should be maintained with a net heating value that is 

equal to or greater than values that were determined during a detailed flare emission 

testing program in November, 2013. The attachments provide details on the proposed 

operating limits for these flares. 

Therefore, for any applicable New Source Performance Standard (NSPS) in 40 CFR 60, we 

respectfully request that EPA approve our request for an Alternative Means of Emission 

Limitation under Section 111(h)(3) of the Clean Air Act. For any applicable National 

Emission Standard for Hazardous Air Pollutant Standard (NESHAP) in 40 CFR 61, and any 

applicable 40 CFR 63 MACT Standards, we respectfully request that EPA approve our 

request for an Alternative Means of Emission Limitation under EPA’s provisions in those 

respective rules and the “Use of an alternative nonopacity emission standard” in 40 CFR 

63.6(g).

If you have questions or concerns regarding this request or the attachments, please contact me at 

(361) 553-2920. 

 Sincerely,

Russell A. Wozniak 

Russell A. Wozniak 

EH&S Operations Regulatory Service

The Dow Chemical Company
cc: 

Andrew Bouchard, Sector Policies and Programs Division, OAQPS, USEPA, Raleigh, North 

Carolina 27711

Penny Lassiter, Group Leader, Sector Policies and Programs Division, OAQPS, USEPA, 

Raleigh, North Carolina 27711

Attachments:
1

Table of Contents

Item Page

Demonstration of Equivalency –

General Information on Rule

2

Regulatory Requirements for 

Propane Dehydrogenation Plant 

Flare

4

Regulatory Requirements for Light 

Hydrocarbons Plant Flare

7

Demonstration of Equivalency –

Pressure-Assisted Flares

11

Alternative Means of Emission 

Limitation Operating Conditions

14

August 20, 2013 – Original Request 17
2

Demonstration of Equivalency – General Information 

The two flare systems included in this request will receive different vent gas streams that are 

regulated by different subparts of the Part 60, 61, and 63 air pollution regulations. In all cases, 

these rules reference the flare requirements located in 40 CFR 60.18 and 40 CFR 63.11. All 

three regulatory programs contain provisions in the rules and/or the Clean Air Act that allow 

EPA to approve an alternative means of emission limitation if the alternative will achieve a 

reduction in emissions at least equivalent to the reduction in emissions achieved under the 

existing regulations. The provisions for Part 60 NSPS, Part 61 NESHAP, and Part 63 MACT 

rules are provided below: 

40 CFR 60 - NSPS Rules and Section 111(h)(3) of the Clean Air Act 

If after notice and opportunity for public hearing, any person establishes to the satisfaction of the 

Administrator that an alternative means of emission limitation will achieve a reduction in 

emissions of any air pollutant at least equivalent to the reduction in emissions of such air 

pollutant achieved under the requirements of paragraph (1), the Administrator shall permit the 

use of such alternative by the source for purposes of compliance with this section with respect to 

such pollutant. 

40 CFR 61 Subpart FF – NESHAP Rules, Section 61.353

(a) If, in the Administrator's judgment, an alternative means of emission limitation will achieve a 

reduction in benzene emissions at least equivalent to the reduction in benzene emissions from 

the source achieved by the applicable design, equipment, work practice, or operational 

requirements in §§61.342 through 61.349, the Administrator will publish in the FEDERAL 

REGISTER a notice permitting the use of the alternative means for purposes of compliance with 

that requirement. The notice may condition the permission on requirements related to the 

operation and maintenance of the alternative means. 

(b) Any notice under paragraph (a) of this section shall be published only after public notice and 

an opportunity for a hearing. 

(c) Any person seeking permission under this section shall collect, verify, and submit to the 

Administrator information showing that the alternative means achieves equivalent emission 

reductions. 

40 CFR 63.6(g) – MACT Rules 

(g) Use of an alternative nonopacity emission standard. (1) If, in the Administrator's 

judgment, an owner or operator of an affected source has established that an alternative means of 

emission limitation will achieve a reduction in emissions of a hazardous air pollutant from an 

affected source at least equivalent to the reduction in emissions of that pollutant from that 

source achieved under any design, equipment, work practice, or operational emission standard, 

or combination thereof, established under this part pursuant to section 112(h) of the Act, the 
3

Administrator will publish in the FEDERAL REGISTER a notice permitting the use of the 

alternative emission standard for purposes of compliance with the promulgated standard. Any 

FEDERAL REGISTER notice under this paragraph shall be published only after the public is 

notified and given the opportunity to comment. Such notice will restrict the permission to the 

stationary source(s) or category(ies) of sources from which the alternative emission standard will 

achieve equivalent emission reductions. The Administrator will condition permission in such 

notice on requirements to assure the proper operation and maintenance of equipment and 

practices required for compliance with the alternative emission standard and other requirements, 

including appropriate quality assurance and quality control requirements that are deemed 

necessary. 

The following pages contain additional details on the specific portions of the subparts that apply 

to these two flare system and show how these rules contain provisions for an Alternative Means 

of Emissions Limitation. 
4

Regulatory Requirements for Propane Dehydrogenation Plant Flare System

The following EPA air regulations will apply to various streams that are collected and routed to 

this flare and this section discusses how each rule allows for an Alternative Means of Emission 

Limitation. 

Regulation

40 CFR Subpart 60 Subpart VVa

Please note that this rule applies, but the plant is opting to comply with 40 CFR 63 Subpart H, as 

referenced by the MON Rule 40 CFR 63 Subpart FFFF, so this requirement will likely be 

satisfied by following the 40 CFR 63 Subpart H regulations. To avoid any confusion with the 

overlap provisions in these rules, information on how an AMEL may be used to satisfy the 

requirements in Subpart VVa is provided below. 

Citation in rule that requires gas streams to be controlled by a flare meeting 40 CFR 60.18. 

Several portions of Subpart VVa point to 40 CFR 60.482-10a. Section 60.482-10a(d) requires 

that flares used to comply with Subpart VVa shall comply with the requirements of §60.18. 

Citation in the rule or Statutory Provision that allows EPA to approve an alternative 

means of emission limitation. 

40 CFR 60.484a(a) and (b) allow EPA to permit the use of an alternative means of emission 

limitation if the owner/operator establishes to the satisfaction of the EPA that an alternative 

means of emission limitation will achieve a reduction in emissions of any air pollutant at least 

equivalent to the reduction in emissions of such air pollutant achieved under the requirements of 

the NSPS regulation. 

Regulation

40 CFR Subpart 60 Subpart NNN (Distillation Operations) 

Citation in rule that requires gas streams to be controlled by a flare meeting 40 CFR 60.18. 

40 CFR 60.662(b) contains an option for control to combust the emissions in a flare that meets 

the requirements of §60.18. 

Citation in the rule or Statutory Provision that allows EPA to approve an alternative 

means of emission limitation. 

Section 111(h)(3) allows EPA to permit the use of an alternative means of emission limitation if 

the owner/operator establishes to the satisfaction of the EPA that an alternative means of 
5

emission limitation will achieve a reduction in emissions of any air pollutant at least equivalent 

to the reduction in emissions of such air pollutant achieved under the requirements of the NSPS 

regulation. 

Regulation

40 CFR Subpart 60 Subpart RRR (SOCMI Reactor Processes) 

Citation in rule that requires gas streams to be controlled by a flare meeting 40 CFR 60.18. 

40 CFR 60.702(b) contains an option for control to combust the emissions in a flare that meets 

the requirements of §60.18. 

Citation in the rule or Statutory Provision that allows EPA to approve an alternative 

means of emission limitation. 

Section 111(h)(3) allows EPA to permit the use of an alternative means of emission limitation if 

the owner/operator establishes to the satisfaction of the EPA that an alternative means of 

emission limitation will achieve a reduction in emissions of any air pollutant at least equivalent 

to the reduction in emissions of such air pollutant achieved under the requirements of the NSPS 

regulation. 

Regulation

40 CFR Subpart 61 Subpart FF 

Citation in rule that requires gas streams to be controlled by a flare meeting 40 CFR 60.18. 

40 CFR 61.349(a)(2)(iii) contains an option for control to combust the emissions in a flare that 

meets the requirements of §60.18. 

Citation in the rule or Statutory Provision that allows EPA to approve an alternative 

means of emission limitation. 

40 CFR 61.353 (a) allows EPA to permit the use of an alternative means of emission limitation if 

the owner/operator establishes to the satisfaction of the EPA that an alternative means of 

emission limitation will achieve a reduction in emissions of any air pollutant at least equivalent 

to the reduction in emissions of such air pollutant achieved under the requirements of the 

regulation.
6

Regulation

40 CFR Subpart 63 Subpart H (Equipment Leaks)

Citation in rule that requires gas streams to be controlled by a flare meeting 40 CFR 

63.11(b). 

40 CFR 63.172(d) requires that flares used to comply with Subpart H shall comply with the 

requirements of §63.11(b) of Subpart A. §63.180)(e) reiterates which portions of §63.11(b) 

apply when a flare is used comply with §63.172(d). 

Citation in the rule that allows EPA to approve an alternative means of emission limitation 

or approve an alternative non opacity emission standard. 

40 CFR 63.177(b)(1) allows an owner/operator to apply for permission to use an alternative 

means of emission limitation under §63.6(g) of 40 CFR 63 Subpart A. 

Regulation

40 CFR Subpart 63 Subpart FFFF (Miscellaneous Organic NESHAP) 

Citation in rule that requires gas streams to be controlled by a flare meeting 40 CFR 

63.11(b). 

40 CFR 63.2450(a) requires the owner/operator to be in compliance with the emission limits and 

work practice standards in Table 1 through 7. Table 1 and Table 2 of Subpart F provide a control 

option for reducing the emissions using a flare. 

40 CFR 63.2450(e)(2) requires that vent gas streams that are routed through a closed-vent system 

to a flare meet the requirements of §63.982(b), which then requires one to meet §63.987 for 

flares, which requires a flare to meet the requirements in §63.11(b). 

Citation in the rule that allows EPA to approve an alternative means of emission limitation 

or approve an alternative non opacity emission standard. 

40 CFR 63.2545(b)(1) allows EPA to approve alternatives to the non-opacity emission limits and 

work practice standards in §63.2450(a) under §63.6(g).
7

Regulatory Requirements for Light Hydrocarbons Plant Flare System 

The following EPA air regulations will apply to various streams that are collected and routed to 

this flare and discusses how each rule allows for an Alternative Means of Emission Limitation. 

Regulation

40 CFR Subpart 60 Subpart Kb (Storage Tanks) 

Citation in rule that requires gas streams to be controlled by a flare meeting 40 CFR 60.18. 

40 CFR 60.112b(a)(3)(ii) contains an option for control to combust the emissions in a flare that 

meets the requirements of §60.18. 

Citation in the rule or Statutory Provision that allows EPA to approve an alternative 

means of emission limitation. 

40 CFR 60.114b allows EPA to permit the use of an alternative means of emission limitation if 

the owner/operator establishes to the satisfaction of the EPA that an alternative means of 

emission limitation will achieve a reduction in emissions of any air pollutant at least equivalent 

to the reduction in emissions of such air pollutant achieved under the requirements of the NSPS 

regulation. 

Regulation

40 CFR Subpart 60 Subpart VVa 

Citation in rule that requires gas streams to be controlled by a flare meeting 40 CFR 60.18. 

Several portions of Subpart VVa point to 40 CFR 60.482-10a. Section 60.482-10a(d) requires 

that flares used to comply with Subpart VVa shall comply with the requirements of §60.18. 

Citation in the rule or Statutory Provision that allows EPA to approve an alternative 

means of emission limitation. 

40 CFR 60.484a(a) and (b) allow EPA to permit the use of an alternative means of emission 

limitation if the owner/operator establishes to the satisfaction of the EPA that an alternative 

means of emission limitation will achieve a reduction in emissions of any air pollutant at least 

equivalent to the reduction in emissions of such air pollutant achieved under the requirements of 

the NSPS regulation. 
8

Regulation

40 CFR Subpart 60 Subpart NNN (Distillation Operations) 

Citation in rule that requires gas streams to be controlled by a flare meeting 40 CFR 60.18. 

40 CFR 60.662(b) contains an option for control to combust the emissions in a flare that meets 

the requirements of §60.18. 

Citation in the rule or Statutory Provision that allows EPA to approve an alternative 

means of emission limitation. 

Section 111(h)(3) allows EPA to permit the use of an alternative means of emission limitation if 

the owner/operator establishes to the satisfaction of the EPA that an alternative means of 

emission limitation will achieve a reduction in emissions of any air pollutant at least equivalent 

to the reduction in emissions of such air pollutant achieved under the requirements of the NSPS 

regulation. 

Regulation

40 CFR Subpart 60 Subpart RRR (SOCMI Reactor Processes) 

Citation in rule that requires gas streams to be controlled by a flare meeting 40 CFR 60.18. 

40 CFR 60.702(b) contains an option for control to combust the emissions in a flare that meets 

the requirements of §60.18. 

Citation in the rule or Statutory Provision that allows EPA to approve an alternative 

means of emission limitation. 

Section 111(h)(3) allows EPA to permit the use of an alternative means of emission limitation if 

the owner/operator establishes to the satisfaction of the EPA that an alternative means of 

emission limitation will achieve a reduction in emissions of any air pollutant at least equivalent 

to the reduction in emissions of such air pollutant achieved under the requirements of the NSPS 

regulation. 
9

Regulation

40 CFR Subpart 61 Subpart FF 

Citation in rule that requires gas streams to be controlled by a flare meeting 40 CFR 60.18. 

40 CFR 61.349(a)(2)(iii) contains an option for control to combust the emissions in a flare that 

meets the requirements of §60.18. 

Citation in the rule or Statutory Provision that allows EPA to approve an alternative 

means of emission limitation. 

40 CFR 61.353 (a) allows EPA to permit the use of an alternative means of emission limitation if 

the owner/operator establishes to the satisfaction of the EPA that an alternative means of 

emission limitation will achieve a reduction in emissions of any air pollutant at least equivalent 

to the reduction in emissions of such air pollutant achieved under the requirements of the 

regulation.

Regulation

40 CFR Subpart 63 Subpart UU (Equipment Leaks)

Citation in rule that requires gas streams to be controlled by a flare meeting 40 CFR 

63.11(b). 

Several portions of Subpart UU point to 40 CFR 63.1034. 40 CFR 63.1034(b)(2)(iii) requires 

that flares used to comply with Subpart UU shall comply with the requirements of 40 CFR 63 

Subpart SS. 40 CFR 63 Subpart SS (specifically §63.982(b) and §63.987) require a flare to meet 

the requirements §63.11(b). 

Citation in the rule that allows EPA to approve an alternative means of emission limitation 

or approve an alternative non opacity emission standard. 

40 CFR 63.1021 (a) – (d) allow EPA to issue an alternative means of emission limitation. 
10

Regulation

40 CFR Subpart 63 Subpart XX (Heat Exchange Systems and Waste Operations) 

Citation in rule that requires gas streams to be controlled by a flare meeting 40 CFR 

63.11(b). 

This rule references portions of the 40 CFR 61 Subpart FF requirements, which in turn require a 

flare to meet the 40 CFR 60.18 requirements. 

Citation in the rule that allows EPA to approve an alternative means of emission limitation 

or approve an alternative non opacity emission standard. 

40 CFR 63.1097 (b)(1) allows EPA to approve alternatives to the nonopacity emission standards. 

Regulation

40 CFR Subpart 63 Subpart YY (Generic Maximum Achievable Control Technology – Ethylene 

Production) 

Citation in rule that requires gas streams to be controlled by a flare meeting 40 CFR 

63.11(b). 

Table 7 of this rule requires storage vessels, ethylene process vents, and transfer racks to comply 

with various portions of 40 CFR 63 Subpart SS. Subpart SS (specifically§63.982(b) and 

§63.987(a)) require that a flare meets the requirements of §63.11(b). 

Citation in the rule that allows EPA to approve an alternative means of emission limitation 

or approve an alternative non opacity emission standard. 

40 CFR 63.1113 (a) allows EPA to approve an alternative means of emission limitation. If, in the 

judgment of the Administrator, an alternative means of emission limitation will achieve a 

reduction in HAP emissions at least equivalent to the reduction in emissions from that source 

achieved under any design, equipment, work practice, or operational standards (but not 

performance standards) in this subpart, the Administrator will publish in the FEDERAL REGISTER

a notice permitting the use of the alternative means for purposes of compliance with that 

requirement.
11

Demonstration of Equivalency – Pressure-Assisted Flares 

In order to demonstrate that the proposed pressure-assisted flare systems will achieve a reduction 

in emissions at least equivalent to the level of reduction in emissions from a flare meeting the 

exit velocity provisions outlined in 40 CFR 60.18(c)(3) - (c)(5) and 40 CFR 63.11(b)(6) – (b)(8), 

the owner or operator must demonstrate that the flare achieves a 96.5 combustion efficiency (or 

98 percent destruction efficiency). 

The Dow Chemical Company opted to conduct a series of emission tests at a flare vendor’s flare 

testing facility in order to make this demonstration. In order to capture the range of expected 

flow rates and gas compositions, the testing program consisted of multiple test runs where the 

following gas mixtures were flared: 

1. Propylene;

2. Mixtures of propylene and nitrogen; and 

3. Mixtures of propylene, nitrogen, and natural gas (Tulsa, Oklahoma natural gas). 

The purpose of the testing was to confirm a high destruction efficiency for propylene and a high 

combustion efficiency over a broad range of operating conditions. The test program involved 

both extractive sampling and analysis along with measurements made by PFTIR (Passive Fourier 

Transform Infrared) analysis. 

A complete copy of the emission testing report was provided to EPA on February 18, 2014. The 

test results are provided in the following tables from the test report. 

Table JZ-2 from Test Report

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 
12

Table JZ-4 from Test Report

Test Runs and Notes: 

P1H and P1L: 100% propylene

P2H and P2L: Mixture of propylene and nitrogen

P3H and P2L: Mixture of 50% propylene, 50% natural gas, then diluted with nitrogen

P4: 90% hydrogen / 10% natural gas

P1-P3: At high pressure (Tests P1H, P2H, and P3H = highest gas flows with an exit velocity at 

or near sonic velocity) and low pressure (Tests P1L, P2L, and P3L lower gas flows representing 

de-staging). 3 tests were conducted under each condition for a duration of 20 minutes.

P2-P3: The flare was operated at the minimum heating value that had flame stability, then the 

emission test was conducted at this point. .

P4: Test for flame stability only, 5 minutes. Detailed emission measurements were not 

conducted for this test. 

The test results show that the destruction efficiency of propylene was well above 98% and the 

overall combustion efficiency was well above 96.5%. Thus, the test results demonstrate that the 

pressure-assisted flare will achieve a destruction efficiency and combustion efficiency that is 

equivalent to and actually better than a flare meeting the exit velocity restrictions in 40 CFR 

60.18 and 40 CFR 63.11. 

Furthermore, Dow believes that the gas mixtures will be representative of the types of 

hydrocarbons combusted in each flare system as discussed below. Dow further proposes to 

operate each of the flare systems in accordance with the parameters included later in this 

document to ensure combustion with a stable flame, thus resulting in very high destruction and 

combustion efficiencies. 

PDH-1 Flare System 

The PDH-1 flare system will consist of 8 stages of flare tips. The first stage of flare tips will be 

operated in accordance with existing flare regulations in 40 CFR 60.18 and 40 CFR 63.11. 

Stages 2 through 8 will consist of pressure-assisted flare tips. Stages 2 through 8 will handle 

vent gas flows during a variety of start-up, shutdown, maintenance, and process upset conditions. 

The system is controlled by a process control system that monitors the main header pressure. As 

the pressure rises (indicating more flow), the next stage is opened. Should the pressure continue 

to rise, the next stage opens. If the pressure falls, the staging valves close in reverse sequence. 

During plant start-ups, common hydrocarbons including, but not limited to: ethane, propane, and 

propylene will be vented to the flare system. During plant shutdowns, common materials 

including, but not limited to: hydrogen, methane, ethylene, ethane, propylene, and propane will 
13

be vented to the flare system. In general, a pressure-assisted flare burning a gas that has a wide 

flammability limit range is easier to stabilize than one with a narrow flammability limit range.

Due to its relatively narrow flammability limit range, and the expected venting rates, propylene 

was used during the testing. The table below shows the various LFL% and UFL% values. Thus, 

it is reasonable to expect that if mixtures of propylene, natural gas, and nitrogen burn well, that 

the other common hydrocarbons should be destroyed/combusted at very similar levels. 

 

Compound LFL % by Volume in Air UFL % by Volume in Air

Propylene 2.4 11.0

Ethane 3.0 12.4

Ethylene 2.7 36.0

Hydrogen 4.0 75.0

Methane 5.0 15.0

Propane 2.1 9.5

 

LHC-9 Flare System 

The LHC-9 flare system will consist of 13 stages of flare tips. The first stage of flare tips will be 

operated in accordance with existing flare regulations in 40 CFR 60.18 and 40 CFR 63.11. 

Stages 2 through 13 will consist of pressure-assisted flare tips. Stages 2 through 13 will handle 

vent gas flows during a variety of start-up, shutdown, maintenance, and process upset conditions. 

The system is controlled by a process control system that monitors the main header pressure. As 

the pressure rises (indicating more flow), the next stage is opened. Should the pressure continue 

to rise, the next stage opens. If the pressure falls, the staging valves close in reverse sequence. 

Based on preliminary design information, common materials including, but not limited to: 

hydrogen, methane, ethane, ethylene, propane, and propylene will constitute the majority of the 

hydrocarbons vented to this flare system during plant start-ups, shutdowns, maintenance venting, 

and process upset conditions. 

Similar to the discussion above for the PDH-1 flare, it is reasonable to expect that if mixtures of 

propylene, natural gas, and nitrogen burn well, that other common hydrocarbons should be 

destroyed/combusted at very similar levels. 

In order to ensure that both flare systems operate with a stable flame and operate with a 

destruction efficiency that is equal to or greater than 98% and a combustion efficiency that is 

equal to or greater than 96.5%, the operating conditions on the following pages are suggested for 

inclusion into the Alternative Means of Emission Limitation. 
14

Alternate Means of Emission Limitation 

Operating Conditions

The Dow Chemical Company, Texas Operations

(RN 100225945)

1. This AMEL plan authorization shall apply at the Dow Chemical Company, Texas 

Operations. The facilities are covered by TCEQ Regulated Entity Number: RN

100225945.

2. A copy of the application and the AMEL Plan Authorization conditions must be kept 

on-site or at a centralized location and made available at the request of personnel 

from the TCEQ or any pollution control agency with appropriate jurisdiction. The 

application is defined by the AMEL application dated August 20, 2013, and 

subsequent supporting documents dated February 18, 2014, and August 5, 2014.

3. This authorization is granted under Title 30 Texas Administrative Code §115.910 (30 

TAC §115.910) and addresses issues associated with the use of these flare systems 

for emission sources regulated by 30 TAC 115 Subchapters B through H, as 

applicable, including 30 TAC §115.722(d) and §115.722(d)(2), and shall apply in lieu 

thereof. This authorization is also granted for the use of these flare systems for 

emission sources regulated by applicable subparts of 40 CFR §§ 60, 61, and 63, as 

approved by the United States Environmental Protection Agency. Compliance with 

this AMEL is independent of Dow Chemical’s obligation to comply with all other 

TCEQ permits and all other applicable EPA Regulations and TCEQ Regulations.

4. The following stationary pressure-assisted flares are covered under this AMEL plan: 

PDH-1 Flare (EPN OC4F9552) and LHC-9 flare (EPN OC2F9562). All flare tips covered 

under the AMEL plan shall be as specified in the AMEL application. 

5. Flares shall be designed and operated in accordance with the following 

requirements: 

A. The flare systems shall be designed and operated such that the waste gas stream 

flowing to each pressure-assisted flare system meets the following minimum net 

heating value in terms of British thermal units/standard cubic foot of the gas 

(Btu/scf) on an hourly average basis under normal, upset, maintenance, start-up, 

and shutdown flow conditions when the flare system is operated with the 

pressure-assisted flare burners in service. The net heating value shall be 

satisfied at all times during the operations authorized by this AMOC unless the 

flare systems meet the 40 CFR §60.18 specifications of minimum heating value 

and maximum tip velocity. Flare testing per 40 CFR §60.18(f) may be requested 
15

by the appropriate regional office to demonstrate compliance with these 

requirements.

 

Flare Name EPN Waste Gas Minimum Net 

Heating Value (Btu/scf)

PDH-1 Pressure Assisted 

Flare

OC4F9552 800

PDH-1 Pressure Assisted 

Flare (Shutdown Steps (1)) 

OC4F9552 690

PDH-1 Pressure Assisted 

Flare Hydrogen Case (2)

OC4F9552 270

LHC-9 Pressure Assisted 

Flare (3)

OC2F9562 690

LHC-9 Pressure Assisted 

Flare Hydrogen Case (2)

OC2F5962 270

1) The shutdown case covers certain phases of the planned shutdown where the 

systems are being purged with nitrogen and methane. 

2) The hydrogen case is one where the mole fraction of hydrogen in the waste gas 

stream is greater than 75%. The net heating value of pure hydrogen is 

approximately 270 Btu/scf, thus 270 Btu/scf is used in this case. 

3) A net heating value of 690 Btu/scf is suggested for this case since the volumetric 

net heating value of Ethylene is 1,477 Btu/scf vs. the volumetric net heating 

value of Propylene which is 2,150 Btu/scf. This value is more conservative for 

ethylene gas since a net heating value of 690 Btu/scf represents a mole fraction 

of ethylene in nitrogen of 0.467, and a net heating value of 800 Btu/scf 

represents a mole fraction of propylene in nitrogen of 0.372. 

B. Each flare system shall be operated with a flame present at all times when in 

use. Each row of flare tips shall have at least one pilot with a constant pilot 

flame. The pilot flame(s) shall be continuously monitored by a thermocouple. 

The time, date, and duration of any loss of pilot flame shall be recorded. Each 

monitoring device shall be maintained or replaced at a frequency in accordance 

with the manufacturer’s specifications. 

C. Each flare system shall be operated with no visible emissions except for periods 

not to exceed a total of five minutes during any two consecutive hours. A video 

camera can be used in order to conduct visible emission observations since 

operating personnel cannot enter the fenced area while the MPFG flare is 

operating. 
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D. Natural gas or off-gas combusted at the flares shall be sweet natural gas or offgas containing no more than five grains of total sulfur per 100 dry standard cubic 

feet. 

6. The AMEL plan authorization holder shall install and operate an on-line vent gas flow 

meter and an on-line gas chromatograph to measure the flow and composition of 

the vent gas to each flare. The holder shall comply with all applicable Monitoring 

and Testing Requirements and Recordkeeping and Reporting Requirements for these 

monitoring systems as specified in 30 TAC §§ 115.725 and 115.726, effective 

December 23, 2004. 
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August 20, 2013 – Original Request 
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