[Federal Register Volume 80, Number 30 (Friday, February 13, 2015)]
[Proposed Rules]
[Pages 8023-8030]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2015-03064]


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ENVIRONMENTAL PROTECTION AGENCY

40 CFR Parts 60, 61, and 63

[EPA-HQ-OAR-2014-0738; FRL 9922-91-OAR]


Receipt of Approval Requests for the Operation of Pressure-
Assisted Multi-Point Ground Flare Technology

AGENCY: Environmental Protection Agency.

ACTION: Request for comments.

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[[Page 8024]]

SUMMARY: On August 5, 2014, The Dow Chemical Company (Dow) requested an 
Alternative Means of Emission Limitation (AMEL) under the Clean Air Act 
(CAA) in order to operate pressure-assisted multi-point ground flares 
at its Propane Dehydrogenation Plant and its Light Hydrocarbons Plant 
at its Texas Operations site located in Freeport, Texas. On October 21, 
2014, ExxonMobil Chemical Company (ExxonMobil) requested an AMEL under 
the CAA for its pressure-assisted multi-point ground flares at its' 
Olefins Plant in Baytown, Texas, and its' Plastics Plant in Mont 
Belvieu, Texas. In this document, the Environmental Protection Agency 
(EPA) is soliciting comment on all aspects of the AMEL requests and the 
resulting alternative operating conditions that are necessary to 
achieve a reduction in emissions of volatile organic compounds (VOC) 
and hazardous air pollutants (HAPs) at least equivalent to the 
reduction in emissions required by various standards in 40 CFR parts 
60, 61 and 63 that apply to emission sources controlled by these 
pressure-assisted multi-point ground flares. These standards point to 
the operating requirements for flares in the General Provisions to 
parts 60 and 63, respectively, to comply with the emission reduction 
requirements. Because pressure-assisted multi-point ground flares 
cannot meet the velocity requirements in these General Provisions, Dow 
and ExxonMobil are seeking an AMEL.

DATES: Comments. Written comments must be received on or before March 
30, 2015.
    Public Hearing. If requested by February 18, 2015, we will hold a 
public hearing on March 2, 2015, from 1:00 p.m. [Eastern Standard Time] 
to 5:00 p.m. [Eastern Standard Time] at EPA's Campus located in 
Research Triangle Park, NC. We will provide details on the public 
hearing on our Web site at: http://www.epa.gov/ttn/atw/groundflares/groundflarespg.html. To be clear, a public hearing will not be held 
unless someone specifically requests that the EPA hold a public hearing 
regarding these requests. Please contact Ms. Virginia Hunt of the 
Sector Policies and Programs Division (E143-01), Office of Air Quality 
Planning and Standards, Environmental Protection Agency, Research 
Triangle Park, NC 27711; telephone number: (919) 541-0832; email 
address: [email protected]; to request a public hearing, to 
register to speak at the public hearing or to inquire as to whether or 
not a public hearing will be held. The last day to pre-register in 
advance to speak at the public hearing will be February 25, 2015.

ADDRESSES: Submit your comments, identified by Docket ID No. EPA OAR- 
2014-0738, by one of the following methods:
     http://www.regulations.gov. Follow the on-line 
instructions for submitting comments.
     Email: [email protected]. Attention Docket ID Number 
EPA-HQ-OAR-2014-0738.
     Fax: (202) 566-9744. Attention Docket ID Number EPA-HQ-
OAR-2014-0738.
     Mail: U.S. Postal Service, send comments to: EPA Docket 
Center (EPA/DC), Attention Docket ID Number EPA-HQ-OAR-2014-0738, U.S. 
Environmental Protection Agency, Mailcode: 28221T, 1200 Pennsylvania 
Ave. NW., Washington, DC 20460.
     Hand Delivery: U.S. Environmental Protection Agency, EPA 
WJC West Building, Room 3334, 1301 Constitution Ave. NW., Washington, 
DC 20004. Attention Docket ID Number EPA-HQ-OAR-2014-0738. Such 
deliveries are only accepted during the Docket's normal hours of 
operation, and special arrangements should be made for deliveries of 
boxed information.
    Instructions. Direct your comments to Docket ID Number EPA-HQ-OAR-
2014-0738. The EPA's policy is that all comments received will be 
included in the public docket without change and may be made available 
online at http://www.regulations.gov, including any personal 
information provided, unless the comment includes information claimed 
to be confidential business information (CBI) or other information 
whose disclosure is restricted by statute. Do not submit information 
that you consider to be CBI or otherwise protected through http://www.regulations.gov or email. The http://www.regulations.gov Web site 
is an ``anonymous access'' system, which means the EPA will not know 
your identity or contact information unless you provide it in the body 
of your comment. If you send an email comment directly to the EPA 
without going through http://www.regulations.gov, your email address 
will be automatically captured and included as part of the comment that 
is placed in the public docket and made available on the Internet. If 
you submit an electronic comment, the EPA recommends that you include 
your name and other contact information in the body of your comment and 
with any disk or CD-ROM you submit. If the EPA cannot read your comment 
due to technical difficulties and cannot contact you for clarification, 
the EPA may not be able to consider your comment. Electronic files 
should not include special characters or any form of encryption and be 
free of any defects or viruses. For additional information about the 
EPA's public docket, visit the EPA Docket Center homepage at: http://www.epa.gov/dockets.
    Docket. The EPA has established a docket for this rulemaking under 
Docket ID Number EPA-HQ-OAR-2014-0738. All documents in the docket are 
listed in the regulations.gov index. Although listed in the index, some 
information is not publicly available, e.g., CBI or other information 
whose disclosure is restricted by statute. Certain other material, such 
as copyrighted material, is not placed on the Internet and will be 
publicly available only in hard copy. Publicly available docket 
materials are available either electronically in regulations.gov or in 
hard copy at the EPA Docket Center (EPA/DC), EPA WJC West Building, 
Room 3334, 1301 Constitution Ave. NW., Washington, DC. The Public 
Reading Room is open from 8:30 a.m. to 4:30 p.m., Monday through 
Friday, excluding legal holidays. The telephone number for the Public 
Reading Room is (202) 566-1744, and the telephone number for the EPA 
Docket Center is (202) 566-1742.

FOR FURTHER INFORMATION CONTACT: For questions about this proposed 
action, contact Ms. Brenda Shine, Sector Policies and Programs Division 
(E143-01), Office of Air Quality Planning and Standards (OAQPS), U.S. 
Environmental Protection Agency, Research Triangle Park, North Carolina 
27711; telephone number: (919) 541-3608; fax number: (919) 541-0246; 
and email address: [email protected].

SUPPLEMENTARY INFORMATION: 

Acronyms and Abbreviations

    We use multiple acronyms and terms in this document. While this 
list may not be exhaustive, to ease the reading of this document and 
for reference purposes, the EPA defines the following terms and 
acronyms here:

AMEL alternative means of emission limitation
BOP Baytown Olefins Plant
Btu/scf British thermal units per standard cubic feet
LFL lower flammability limit
LFLcz combustion zone lower flammability limit
LHC Light Hydrocarbons Unit
LRGO Linear relief gas oxidizer
MACT maximum achievable control technology
MBPP Mont Belvieu Plastics Plant
MPGF multi-point ground flare
NESHAP national emission standard for hazardous air pollutants

[[Page 8025]]

NHV net heating value
NHVcz combustion zone net heating value
NSPS new source performance standards
OAQPS Office of Air Quality Planning and Standards
PDH Propylene Dehydrogenation Unit
PFTIR passive fourier transform infrared
SKEC steam-assisted kinetic energy combustor

    Organization of This Document. The information in this document is 
organized as follows:

I. Statutory and Regulatory Background
    A. Flare Operating Requirements
    B. Alternative Means of Emission Limitation
II. Requests for Alternative Means of Emission Limitation
    A. Dow AMEL
    B. ExxonMobil AMEL
    C. EPA's Analysis of MPGF Burner Emission Tests
III. AMEL for Pressure-Assisted MPGF
IV. Request for Comments

I. Statutory and Regulatory Background

A. Flare Operating Requirements

    In their requests, Dow and ExxonMobil cite various regulatory 
requirements in 40 CFR parts 60, 61 and 63 that will apply to the 
different vent gas streams that will be collected and routed to their 
pressure-assisted multi-point ground flares (MPGF) at each plant. These 
requirements are included in Table 1.\1\ In all cases, these rules 
reference the flare operating requirements located in 40 CFR 60.18 and 
40 CFR 63.11.
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    \1\ EPA prepared Table 1 using the information provided in the 
requests, corrected as appropriate based on its own review of the 
regulations. However, the EPA has not independently verified whether 
Table 1 includes all of the regulatory requirements with which these 
plants must comply.

             Table 1--Summary of Applicable Rules That May Apply to Vents Streams Controlled by Pressure-Assisted Multi-Point Ground Flares
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                                                                                                                                        Provisions for
   Applicable rules with vent         Dow propane      Dow light hydro-       Exxon-Mobil      Exxon-Mobil Mont   Emission reduction   alternative means
    streams going to  control       dehydrogenation      carbons (LHC)      Baytown Olefins    Belvieu plastics       required and        of emission
             device                   (PDH) plant            plant               plant               plant           rule citation        limitation
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NSPS Subpart Kb.................  ..................                  X                   X   ..................  60.112b(a)(3)(ii)-  60.114b allows for
                                                                                                                   -Reduce VOC inlet   AMEL.
                                                                                                                   emissions by 95%;
                                                                                                                   If a flare is
                                                                                                                   used as a control
                                                                                                                   device, flare
                                                                                                                   must meet
                                                                                                                   requirements of
                                                                                                                   60.18.
NSPS Subparts VV/Vva............                  X                   X                   X   ..................  60.482-10a--Reduce  60.484(a) allows
                                                                                                                   VOC emissions by    for AMEL
                                                                                                                   95% or greater;
                                                                                                                   flare used to
                                                                                                                   comply with
                                                                                                                   subpart must meet
                                                                                                                   requirements of
                                                                                                                   60.18.
                                                                                                                  *Note--Under Dow
                                                                                                                   PDH Plant column,
                                                                                                                   NSPS subpart VVa
                                                                                                                   applies, but DOW
                                                                                                                   is opting to
                                                                                                                   comply with 40
                                                                                                                   CFR part 63,
                                                                                                                   subpart H (as
                                                                                                                   referenced by
                                                                                                                   Miscellaneous
                                                                                                                   Organic
                                                                                                                   NESHAP(MON) which
                                                                                                                   should satisfy
                                                                                                                   requirements in
                                                                                                                   subpart VVa.
NSPS Subpart DDD................  ..................  ..................  ..................                  X   60.562-1--Reduce    CAA section
                                                                                                                   emissions of        111(h)(3) allows
                                                                                                                   Total Organic       for AMEL.
                                                                                                                   Carbon (TOC) by
                                                                                                                   98%, or combust
                                                                                                                   in a flare that
                                                                                                                   meets the
                                                                                                                   requirements of
                                                                                                                   60.18.
NSPS Subpart NNN................                  X                   X                   X                   X   60.662- Reduce      CAA section
                                                                                                                   emissions of TOC    111(h)(3) allows
                                                                                                                   by 98%, or          for AMEL.
                                                                                                                   combust in a
                                                                                                                   flare that meets
                                                                                                                   the requirements
                                                                                                                   of 60.18.
NSPS Subpart RRR................                  X                   X                   X                   X   60.702--Reduce      CAA section
                                                                                                                   emissions of TOC    111(h)(3) allows
                                                                                                                   by 98%, or          for AMEL.
                                                                                                                   combust in a
                                                                                                                   flare that meets
                                                                                                                   the requirements
                                                                                                                   of 60.18.

[[Page 8026]]

 
NESHAP Subpart V................  ..................  ..................                  X   ..................  61.242-11(d)--flar  61.244 allows for
                                                                                                                   es used to comply   AMEL; also see
                                                                                                                   with subpart V      61.12(d).
                                                                                                                   must comply with
                                                                                                                   60.18.
NESHAP Subpart FF...............  ..................                  X                   X   ..................  61.349(a)--reduce   61.353 allows for
                                                                                                                   organic emissions   AMEL; also see
                                                                                                                   vented to control   61.12(d).
                                                                                                                   device by 95%; a
                                                                                                                   flare shall
                                                                                                                   comply with the
                                                                                                                   requirements of
                                                                                                                   60.18.
NESHAP Subparts F, G............  ..................  ..................                  X   ..................  63.102, 63.113,     63.102(b) allows
                                                                                                                   63.126--Reduce      for AMEL.
                                                                                                                   emissions of
                                                                                                                   Total Organic HAP
                                                                                                                   (TOHAP) by 98%,
                                                                                                                   or combust in a
                                                                                                                   flare that meets
                                                                                                                   the requirements
                                                                                                                   of 63.11(b).
                                                                                                                  63.120--Combust in
                                                                                                                   flare meeting
                                                                                                                   63.11. 63.139--
                                                                                                                   Reduce emissions
                                                                                                                   of TOHAP by 95%,
                                                                                                                   or combust in a
                                                                                                                   flare that meets
                                                                                                                   the requirements
                                                                                                                   of 63.11(b).
                                                                                                                   63.145(j)--Points
                                                                                                                   to sections of
                                                                                                                   63.11(b) for
                                                                                                                   flare control.
NESHAP Subpart H................                  X   ..................                  X   ..................  63.172--Reduce      63.177 allows for
                                                                                                                   organic HAP or      AMEL.
                                                                                                                   VOC by 95%;
                                                                                                                   flares used to
                                                                                                                   comply must meet
                                                                                                                   requirements of
                                                                                                                   63.11(b).
NESHAP Subpart SS...............                  X                   X                   X                   X   63.982(b) and       CAA section
                                                                                                                   63.987(a) require   112(h)(3) allows
                                                                                                                   that a flare        for AMEL.
                                                                                                                   meets the
                                                                                                                   requirements in
                                                                                                                   63.11(b).
NESHAP Subpart UU...............  ..................                  X   ..................  ..................  63.1034--Nonflare   63.1021 allows for
                                                                                                                   control devices     AMEL.
                                                                                                                   shall reduce
                                                                                                                   emissions by 95%;
                                                                                                                   flares shall
                                                                                                                   comply with
                                                                                                                   subpart SS.
NESHAP Subpart XX...............  ..................                  X   ..................  ..................  63.1091 requires    61.353 allows for
                                                                                                                   compliance with     AMEL; also see
                                                                                                                   subpart FF, which   61.12(d).
                                                                                                                   requires
                                                                                                                   compliance with
                                                                                                                   60.18.
NESHAP Subpart YY...............  ..................                  X                   X   ..................  Table 7 references  63.1113 allows for
                                                                                                                   subpart SS, which   AMEL.
                                                                                                                   requires
                                                                                                                   compliance with
                                                                                                                   60.18.
NESHAP Subpart EEEE.............  ..................  ..................                  X                   X   63.2378(a)          63.2346(g) allows
                                                                                                                   references          for AMEL; also
                                                                                                                   subpart SS, which   see Table 12
                                                                                                                   requires            which makes
                                                                                                                   compliance with     63.6(g)
                                                                                                                   60.18.              applicable to
                                                                                                                                       this subpart.

[[Page 8027]]

 
NESHAP Subpart FFFF.............                  X   ..................  ..................                  X   63.2450 requires    63.2540 and Table
                                                                                                                   compliance with     12 allow for AMEL
                                                                                                                   limits in Tables    by making 63.6(g)
                                                                                                                   1-7, which          applicable to
                                                                                                                   include reducing    this subpart.
                                                                                                                   total organic HAP
                                                                                                                   in vent streams
                                                                                                                   by either 95% or
                                                                                                                   98%, and provide
                                                                                                                   an option for
                                                                                                                   control using a
                                                                                                                   flare meeting
                                                                                                                   requirements of
                                                                                                                   63.982(b) which
                                                                                                                   requires meeting
                                                                                                                   63.987, which
                                                                                                                   requires a flare
                                                                                                                   to meet the
                                                                                                                   requirements of
                                                                                                                   63.11(b).
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    As shown in Table 1, the applicable rules require that control 
devices achieve destruction efficiencies of either 95 percent or 98 
percent either directly, or by reference, or allow control by flares 
meeting the flare operating requirements in 40 CFR 60.18 or 63.11. The 
flare operating requirements in 40 CFR 60.18 and 63.11 specify that 
flares shall be: (1) Steam-assisted air-assisted, or non-assisted; \2\ 
(2) operated at all times when emissions may be vented to them; (3) 
designed for and operated with no visible emissions (except for periods 
not to exceed a total of 5 minutes during any 2 consecutive hours); and 
(4) operated with the presence of a pilot flame at all times. The flare 
operating requirements in 40 CFR 60.18 and 63.11 also specify 
requirements for both the minimum heat content of gas combusted in the 
flare and the maximum exit velocity at the flare tip.\3\ These 
provisions specify maximum flare tip velocities based on flare type 
(non-assisted, steam-assisted or air-assisted) and the net heating 
value of the flare vent gas (see 40 CFR 60.18(c)(3), 63.11(b)(6)). 
These maximum flare tip velocities are required to ensure that the 
flame does not ``lift off'' or separate from the flare tip, which could 
cause flame instability and/or potentially result in a portion of the 
flare gas being released without proper combustion. Proper combustion 
for flares is considered to be 98 percent destruction efficiency or 
greater for HAPs and VOCs, as discussed in our recent proposal titled 
''Petroleum Refinery Sector Risk and Technology Review and New Source 
Performance Standards,'' 79 FR 36,880, 36,904-36,912 (June 30, 2014).
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    \2\ While Dow and ExxonMobil describe their flares as 
``pressure-assisted,'' these flares qualify as ``non-assisted'' 
flares under 40 CFR 60.18(b) or 63.11(b) because they do not employ 
assist gas.
    \3\ These requirements are not all inclusive. There are other 
requirements in 40 CFR 60.18 and 63.11 relating to monitoring and 
testing that are not described here.
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    The MPGF proposed by both Dow and ExxonMobil are conceptually 
similar yet inherently different in both flare head design and 
operation than the more traditional steam-assisted, air-assisted and 
non-assisted flare types currently able to comply with the flare 
operating requirements in 40 CFR 60.18 or 63.11. The MPGF technology 
operates by using the pressure upstream of each individual flare tip 
burner to enhance mixing with air at the flare tip due to high exit 
velocity, which allows the MPGF to operate with smokeless burning. The 
MPGF are constructed differently than normal elevated flares in that 
they consist of many rows of individual flare tips which are 
approximately 8 feet above ground level. The ground flare staging 
system opens and closes staging valves according to gas pressure such 
that stages containing multiple burners are activated as the flow and 
pressure increase or decrease in the header. While information supplied 
by Dow, and relied on by both Dow and ExxonMobil, indicates that the 
flare tips operate smokelessly and achieve high destruction 
efficiencies, the MPGF cannot meet the exit velocity requirements in 40 
CFR 60.18 and 40 CFR 63.11, which limit the exit velocity at the flare 
tip to a maximum of 400 feet per second. The exit velocities from MPGF 
typically range from 600 feet per second up to sonic velocity (which 
ranges from 700 to 1,400 feet per second for common hydrocarbon gases), 
or Mach =1 conditions. As a result, Dow and ExxonMobil are seeking an 
alternative means of complying with the flare operating requirements in 
40 CFR 60.18 and 63.11; specifically, the exit velocity requirements in 
40 CFR 60.18(c)(3), (c)(4), and (c)(5) and in 40 CFR 63.11(b)(6),(b)(7) 
and (b)(8).

B. Alternative Means of Emission Limitation

    As noted in Table 1, the specific rules in 40 CFR parts 60, 61 and 
63, or the General Provisions for parts 60, 61 and 63 of the CAA \4\ 
allow a facility to request an AMEL. These provisions allow the 
Administrator to permit the use of an alternative means of complying 
with an applicable standard, if the requestor demonstrates that the 
alternative achieves at least an equivalent reduction in emissions. The 
EPA must provide notice of the request and an opportunity for a public 
hearing on the request. After considering comments received, the EPA 
will issue a notice permitting the use of an

[[Page 8028]]

alternative means of emission limitation, if the Administrator 
determines that the alternative will achieve an equivalent reduction in 
emissions.
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    \4\ CAA section 111(h)(3) states: ``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.'' Section 112(h)(3) contains almost identical language.
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II. Requests for Alternative Means of Emission Limitation

A. Dow AMEL

    In its August 5, 2014, request, Dow indicates that it plans to 
construct and operate two new MPGFs at its Texas Operations site in 
Freeport, TX. One MPGF would be located at Dow's Propane 
Dehydrogenation Plant (PDH-1), scheduled to start-up in early 2015 and 
whose primary product is propylene. The other MPGF would be located at 
Dow's Light Hydrocarbons Plant (LHC-9), scheduled to start-up in early 
2017 and whose primary product is ethylene.
    The flare systems proposed for use by Dow at both plants consist of 
a staged design concept. The first stage, which is not at issue nor 
specifically part of the notice requesting an AMEL because it can meet 
the flare operating requirements of 40 CFR of 60.18 and 63.11, is a 
steam-assisted ground flare which has the primary function of 
controlling waste gases during periods of normal operation. The 
remaining stages consist of arrays of pressure-assisted flare tips (the 
MPGFs) and will control waste gases during periods of upset, 
maintenance, startup and shutdown (high-pressure, high flow periods). 
Pressure-assisted flares are also known as sonic flares because the 
exit velocity during periods of high-pressure feeds is at sonic 
velocities.
    At Dow, Stage 1 is the low pressure stage in which the flare acts 
as a steam-assisted flare. Stages 2 and beyond are activated for high-
pressure/high exit velocity flows. The flare system is surrounded by a 
panel type fence to protect nearby workers from the radiant heat from 
the flare system. At various times ranging from 2 hours for startup of 
processing equipment to 160 hours for a complete plant shutdown, Dow 
will have emissions from the MPGF for the following maintenance, start-
up and shutdown (MSS) activities: Perform plant start-up and shutdown, 
process equipment startup and shutdown, off-spec flaring, non-routine 
clearing and commissioning of process equipment and piping, fuel 
purging and flaring to maintain pressure of the net-gas system.
    Dow conducted testing on the two types of individual flare tips in 
its MPGF design to demonstrate that the MPGF can achieve good 
combustion efficiency under certain conditions and has proposed 
operating requirements for these MPGF that can achieve the emissions 
standards in the applicable NSPS and NESHAP. These proposed operating 
requirements are contained in Dow's request dated August 5, 2014, 
located in the docket for this document. A summary of test data and a 
complete copy of the emission testing report and appendices are 
available in the docket. The tests were conducted on individual flare 
tips because it is not possible to test the full field of MPGF because 
of the size and configuration of the full-scale MPGF installation 
(there are approximately 300 flare tips in the proposed array pattern 
that cover the size approximately equivalent to that of a football 
field in the actual installations). Although two flare tip types were 
tested during the effort, the results of one burner type, a steam-
assisted flare burner, John Zink model SKEC, are not discussed further 
as Dow is not seeking an AMEL for this burner because it operates at 
lower velocity and, thus, can meet the existing flare operating 
requirements.

B. ExxonMobil AMEL

    In its October 21, 2014, request, ExxonMobil indicates it plans to 
construct and operate two MPGFs, one at its Baytown Olefins Plant (BOP) 
in Baytown, TX, and the other at its Mont Belvieu Plastics Plant (MBPP) 
in Mont Belview, TX. Both of the proposed control strategies will be 
designed such that vent gases are routed to either a low pressure 
system, or in infrequent cases where high-pressure/high flow events 
occur, the high pressure MPGF. Both low pressure control systems at the 
BOP and MBPP consist of an elevated flare, but the MBPP low pressure 
control system also consists of three flameless thermal oxidizers. The 
elevated flares at both the BOP and MBPP will comply with 40 CFR 60.18 
and/or 40 CFR 63.11, as applicable.
    ExxonMobil did not supply any additional test data, but rather is 
relying on a series of publically available MPGF emissions tests, among 
them the 2013 test submitted by Dow, a 2012 test done by Marathon 
Petroleum Corporation, LP, a 2006 pipeline burner test done by Dow, and 
two earlier tests conducted by the EPA in the 1980s. ExxonMobil 
indicates that the BOP and MBPP burner tip designs will have comparable 
performance to the burners recently tested and submitted December 14, 
2014, supplemental application containing additional information on 
plans to use the John Zink LRGO burners for the MPGF installation at 
the MBPP, and ZEECO burners at the BOP. ExxonMobil asserts that the 
ZEECO burner design provides equivalent combustion efficiency and flame 
stability as that of the John Zink burners tested, although ExxonMobil 
has not supplied any data or information that could confirm this 
assertion of equivalency. We are requesting comment on this assertion 
as well as specifically soliciting data and comments from the public on 
burner design and performance of these MPGF burners.

C. EPA's Analysis of MPGF Burner Emission Tests

    Dow and ExxonMobil are proposing to follow all of the flare 
operating requirements contained in either 40 CFR 60.18 or 63.11, 
except for the exit velocity requirements. They are proposing to 
operate their high pressure MPGFs at higher velocity than the current 
requirements because their data indicate that these burners can operate 
with a stable flame at higher velocities and still achieve good 
combustion and destruction efficiencies. Instead of complying with the 
exit velocity requirements in 40 CFR 60.18 and 63.11, Dow and 
ExxonMobil are requesting that EPA grant their AMEL requests to allow 
them to operate the high pressure sections of their MPGFs such that the 
vent gas flowing to the flare tips is maintained with a net heating 
value that has been demonstrated to be equal to or greater than the 
values that were determined to achieve a reduction in emissions of 
pollutants being controlled by a steam-assisted, air-assisted or non-
assisted flare complying with the requirements of either 40 CFR 
63.11(b) or 40 CFR 60.18(b) during the burner emission tests.
    In the emission tests, the high pressure burners were subjected to 
a number of different operating conditions, and each set of conditions 
represented a separate test series. For purposes of this discussion, 
the relevant test results are those from Dow's 2013 test report, which 
are comprised of runs from test series P1 through P4 and were tested on 
John Zink's pressure assisted flare burner model LRGO-HC, as well as 
emissions data reported in Marathon's 2012 test report, which are from 
test series PA1 and PA2 and were tested on John Zink's pressure 
assisted flare burner model LRGO-D. These tests used the analytical 
technique of passive fourier transform infrared (PFTIR) spectroscopy to 
assess combustion efficiency. Dow's 2013 test report also presents data 
collected using an extractive method where flue gas was extracted from 
a collection hood that was suspended above the burner tip and analyzed 
using standard EPA methods.

[[Page 8029]]

The Marathon 2012 test report (see ``Performance Test of Steam-Assisted 
and Pressure-Assisted Ground Flare Burners with Passive FTIR--
Garyville'') and the Dow 2013 test report (see ``Report on Emissions 
Testing of Pressure Assisted LRGO-HC and Steam Assisted SKEC Burners'') 
are provided in the docket.
    The results of the PFTIR testing indicated that when a flame was 
present on the pressure-assisted flare burners tested that an average 
combustion efficiency of 99 percent or greater was always achieved. 
Each set of operating conditions tested by both Dow and Marathon for 
both combustion efficiency and flame stability generally consisted of a 
series of triplicate runs. In all, a total of 34 test runs were 
analyzed from these two tests (21 from Dow's P1 through P3 test series 
and 13 from Marathon's PA1 and PA2 test series). For test series P4, 
which was conducted as part of Dow's 2013 test using a 90 volume 
percent hydrogen/10 volume percent natural gas mixture, no combustion 
efficiency test was conducted; instead, a qualitative indication that 
the flame was stable at the conditions tested was made. We note that in 
Dow's 2013 test report that three of the 21 test runs were aborted 
because of loss of flame (which we refer to as flameout); only two of 
the three test runs (one in the P2H series and one in the P2L series) 
produced enough information before flameout to be analyzed in more 
detail. We requested more detailed information from Dow on the 
conditions that resulted in this loss of flame as it informs us of the 
conditions that would create a failure of the burners to sustain a 
stable flame and achieve good combustion. This document is included in 
the docket titled ``Supplement 1 to Dow report.'' Additionally, we also 
note that in Marathon's 2012 test report that two of the 13 test runs 
also experienced loss of flame (test PA1 Runs 4(2) and 4(4)). The 
results of all of these test runs are discussed in the memorandum 
titled ``Review of Available Test Data on Multipoint Ground Flares,'' 
located in the docket.
    There are two general conclusions from these test reports that are 
consistent with the earlier EPA 1985 study done on pressure-assisted 
flares (see conclusions on pages 2-19 and 2-22 in September 1985 EPA 
report titled ``Evaluation of the efficiency of industrial flares: 
Flare head design and gas composition''). The first is that ``flare 
head design can influence the flame stability curve.'' This is evident 
in Figures 2-3 and 2-5 of the 1985 EPA report where different stability 
curves were generated for the different flare heads (burners) tested 
over a range of differing exit velocities and flare gas net heating 
values. When comparing the current maximum flare tip velocity 
requirements in the general provisions with those tested on pressure-
assisted flare burners, this conclusion still holds true. The agency's 
current requirements would require that flares meet an increasing 
minimum net heating value with increasing velocity, all the way up to a 
minimum waste gas net heating value of 1,000 BTU/scf and maximum 
velocity of 400 feet per second. However, the recent test reports on 
pressure-assisted burners show that flame stability can be achieved at 
significantly higher velocities (i.e., sonic velocity) with waste gas 
net heating values below 1,000 BTU/scf. The second general conclusion 
made from EPA's 1985 study is that ``stable flare flames and high (>98-
99) combustion and destruction efficiencies are attained when flares 
are operated within operating envelopes specific to each flare burner 
and gas mixture tested. Operation beyond the edge of the operating 
envelope can result in rapid flame de-stabilization and a decrease in 
combustion and destruction efficiencies.'' The data where flameout of 
the burners occurred from test runs in both the Marathon 2012 test 
report and the Dow 2013 test report showed that the flare operating 
envelope was different for the different gas mixtures tested. 
Additionally, it was observed that combustion degradation beyond the 
edge of the operating envelope for pressure-assisted MPGF burners was 
so rapid that when a flame was present, the flare would still achieve a 
high level of combustion efficiency right up until the point of 
flameout.
    In order to assess the proper operating envelope for these flare 
types, the EPA evaluated both the net heating value (in BTU/scf), which 
is how the 40 CFR part 60 and 63 General Provisions currently address 
combustion zone properties, as well as the lower flammability limit 
(LFL) because the LFL may be a better indicator of performance than net 
heating value for some flare vent gas streams, notably those with the 
potential for high hydrogen content. Hydrogen is relatively flammable, 
but its net heating value is low on a BTU/scf basis when compared to 
other hydrocarbons. By using LFL, we eliminate the need to correct the 
hydrogen heat content or to select a lower BTU/scf limit for high 
hydrogen cases. Although Dow has requested operating limits in the form 
of BTU/scf and has presented the test data in BTU/scf, we believe it is 
important to consider both types of operating limits.
    Our review indicates that the LRGO burners tested achieve a high 
level of combustion efficiency when the lower flammability limit of 
waste gases burned in the flare is less than 6.5 volume percent (vol%) 
LFL or above 800 BTU/scf. We suggest the 6.5 vol% LFL based on the 
flammability of the stream during the flame out conditions experienced 
during the high pressure test run P2H1 (at 6.6 vol% LFL). The 
corresponding BTU content of the waste gas at this value was 789 BTU/
scf (according to Dow, the gas chromatograph analysis indicated this 
value was 746 BTU/scf, although the John Zink report based on measured 
flow rates indicated it was 789 BTU/scf). Dow's proposed operating 
conditions included startup/shutdown cases where the waste gas heat 
content could be as low as 690 BTU/scf and as high as 6.9 vol% LFL, and 
data from these tests indicate that good combustion can occur at these 
conditions. However, to establish the alternative operating 
requirements at a level that ensures good combustion and flame 
stability at all times under all operating conditions, we believe it is 
reasonable to establish the heat content requirements for BTU/scf above 
which there were no flame out observations. For LFL, that level would 
be set below which there are no flame out observations. This is because 
gas mixtures with a relatively high LFL are less flammable when 
released to the air than mixtures with a relatively low LFL. A gas 
mixture with a relatively high LFL requires a larger volume of the 
mixture to burn in a specific volume of air, than would a mixture of 
gases with a relatively low LFL being combusted in that same volume of 
air. We believe the flame out observations establish the limiting case 
because a flameout is a complete failure of the burner, indicating 
zero-percent combustion. Because of the quantity of waste gases 
potentially flared in the high-pressure zones of these MPGF, we believe 
it would be prudent to establish limits on the conservative side to 
prevent air emissions of unburned waste gas.
    We also reviewed whether we should consider velocity or burner 
operating pressure in describing conditions that should be met during 
the MPGF operation and whether we should require some testing to ensure 
that the individual burners will ignite properly when a new stage goes 
into service. Dow provided information on its process control system 
and indicated that cross-light testing (testing of burner ignition from 
pilots) of individual burners at its off-site test facility has been 
conducted

[[Page 8030]]

and the burners performed as expected. This discussion, titled 
``Process control system overview-multipoint ground flare system,'' is 
in the docket for this action. At this time, we are not considering any 
requirements for additional process control or ignition testing. 
However, we believe it would be important to require that cameras are 
installed and operated such that operators have a visual indication of 
flames from the flare at all times that the MPGF is operating and that 
this footage be available for inspection by the permitting agency, 
along with operational records of the waste gas flowrate, pressure in 
header and stages, pilot and waste gas composition.
    Because these flares are located at ground level, it is possible 
that ambient concentrations of pollutants could be higher than they 
would be under an alternative scenario where waste gases would be 
flared in an elevated flare, enabling greater dispersion and 
potentially lessening the impact to neighboring communities. To that 
end, we are soliciting comment on whether additional ambient monitoring 
is warranted to provide for immediate notification to emergency 
planning officials and the community during significant events and 
malfunctions of the system.

III. AMEL for Pressure-Assisted MPGF

    Considering the above requests from both Dow and ExxonMobil, we are 
seeking the public's input on the operating requirements for the 
proposed pressure-assisted MPGFs that would be used by both companies 
which would establish an AMEL that will achieve a reduction in 
emissions at least equivalent to the reduction in emissions being 
controlled by a steam-assisted, air-assisted or non-assisted flare 
complying with the requirements of either 40 CFR 63.11(b) or 40 CFR 
60.18(b). Information provided in the AMEL requests and the available 
emissions test data from the test reports described above indicate that 
the following list of operating requirements for pressure-assisted MPGF 
result in destruction efficiencies at least equivalent to destruction 
efficiencies expected from complying with the requirements of 40 CFR 
63.11(b) and 40 CFR 60.18(b) for the pressure-assisted MPGF being 
proposed for use by both Dow and ExxonMobil:
    1. The flare system must be designed and operated such that the net 
heating value of the combustion zone gas (NHVcz) for the 
pressure assisted flare burners meets a minimum heating value of 800 
BTU/scf or a lower flammability limit of the combustion zone gas 
(LFLcz) of less than or equal to 6.5 percent by volume under 
all conditions. We would expect owners or operators to calculate 
NHVcz and LFLcz in a manner similar to those in 
the currently proposed requirements of 79 FR 36980-40 CFR 63.670(l)-
(m).
    2. The flare system must be operated with a flame present at all 
times when in use. Each row of flare burners must have at least one 
pilot with a constant pilot flame. The pilot flame(s) must be 
continuously monitored by a thermocouple. The time, date and duration 
of any loss of pilot flame must be recorded. Each monitoring device 
must be maintained or replaced at a frequency in accordance with the 
manufacturer's specifications.
    3. The flare system must be operated with no visible emissions 
except for periods not to exceed a total of 5 minutes during any 2 
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 MPGF is operating.
    4. The operator must 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. We would expect the operator 
to comply with similar monitoring and testing requirements and 
recordkeeping and reporting requirements for these monitoring systems 
as currently proposed in 79 FR 36980-40 CFR 63.670(i)-(j) and (l)-(m).
    5. The operator should install and operate pressure and/or flow 
monitors on each stage of the flare. We would expect the operator to 
comply with similar applicable monitoring and testing requirements and 
recordkeeping and reporting requirements for these monitoring systems 
as currently proposed in 79 FR 36980-40 CFR 63.670(i).

IV. Request for Comments

    We solicit comments on all aspects of these requests for an AMEL. 
We specifically seek comment regarding whether or not the potential 
alternative operating requirements listed in section III above would be 
adequate for ensuring that the MPGF will achieve good combustion at all 
times and enable the facilities to meet their applicable emission 
standards. Additionally, several other entities have indicated to us 
that they intend to make similar requests for the ability to operate 
pressure-assisted MPGFs. We are also soliciting comment on whether the 
requirements listed above, if followed by these other entities, could 
enable these other facilities to receive approval of their own AMELs. 
As noted in section II.B above, we also solicit comment and data on 
other pressure-assisted flare burner types. Commenters should include 
data or specific examples in support of their comments.

    Dated: February 3, 2015.
Janet G. McCabe,
Acting Assistant Administrator.
[FR Doc. 2015-03064 Filed 2-12-15; 8:45 am]
BILLING CODE 6560-50-P