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Air Emissions Factors and Quantification

New Emissions Factors for Enclosed Ground Flares

Background

On February 5, 2018, EPA completed its review of the emissions factor for volatile organic compounds (VOC) for flares at natural gas production sites pursuant to section 130 of the Clean Air Act.

EPA evaluated test data available to the Agency for elevated and enclosed ground flares from natural gas production sites.  The agency’s review of available flare data did not result in a revision to this VOC factor, which remains available for estimating VOC emissions from elevated flares at natural gas production sites. 

EPA has developed two new THC emissions factors for enclosed ground flares at natural gas production sites.  The EPA recommends the use of the new THC emissions factors to estimate VOC emissions for enclosed ground flares with the SCCs specified in Table 1, as this new emissions factor is based on field data from similar units.  Additionally, EPA has developed four new THC emissions factor for enclosed ground flares at certain chemical manufacturing processes.

Additional information about the review of the factor is below.

Final Emissions Factors

The final emissions factors are presented in Table 1.  A description of the relevant source classification codes (SCCs) that describe the processes covered by these emissions factors is presented in Table 2. 

Table 1. Final Emissions Factors

Emissions Source

SCC

Pollutant

Emissions Factor 

Representativeness

Enclosed Ground Flares at Natural Gas Production Sites

31000205

31000212

31000227

THC

332 lb THC/MMscf gas burned

or

0.335 lb THC/MMBtu heat input

Poorly

Enclosed Ground Flares for Certain Chemical Manufacturing Processes

(low percent load)

30119701

30119705

30119709

30119741

30190099

THC

8.37 lb THC/MMscf gas burned

or

3.88e-3 lb THC/MMBtu heat input

Moderately

Enclosed Ground Flares for Certain Chemical Manufacturing Processes

(normal to high percent load)

30119701

30119705

30119709

30119741

30190099

THC

2.56 lb THC/MMscf gas burned

or

1.20e-3 lb THC/MMBtu heat input

Moderately


 

Table 2. SCC Descriptions

SCC

Level 1

Description

Level 2

Description

Level 3

Description

Level 4 Description

31000205

Industrial Processes

Oil and Gas Production

Natural Gas Production

Flares

31000212

Industrial Processes

Oil and Gas Production

Natural Gas Production

Condensate Storage Tank

31000227

Industrial Processes

Oil and Gas Production

Natural Gas Production

Glycol Dehydrator Reboiler Still Stack

30119701

Industrial Processes

Chemical Manufacturing

Butylene, Ethylene, Propylene, Olefin Production

Ethylene: General

30119705

Industrial Processes

Chemical Manufacturing

Butylene, Ethylene, Propylene, Olefin Production

Propylene: General

30119709

Industrial Processes

Chemical Manufacturing

Butylene, Ethylene, Propylene, Olefin Production

Propylene: Fugitive Emissions

30119741

Industrial Processes

Chemical Manufacturing

Butylene, Ethylene, Propylene, Olefin Production

Ethylene: Flue Gas Vent

30190099

Industrial Processes

Chemical Manufacturing

Butylene, Ethylene, Propylene, Olefin Production

Other Not Classified

Additional Documents

Review and Analysis of Emissions Test Reports for Purposes of Reviewing the Natural Gas Production Flares Volatile Organic Compounds Emissions Factor Under Clean Air Act Section 130 - February 2018 (PDF 622K).

We have finalized AP-42 Section 13.5 to incorporate the new factors. Section 13.5 can be accessed at the following link:

AP-42 Chapter 13: Miscellaneous Sources Section 13.5 Industrial Flares

Fact Sheet Summarizing the February 5, 2018 Action (PDF 365K)

Response to Comments

EPA received three comments on its June 2017 proposal.  Below is a link to the comments received and the agency’s responses:

Comments as of August 21, 2017 (PDF 1,327K)

Response to Comments Document   (PDF 84K)