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 UNITED STATES ENVIRONMENTAL PROTECTION AGENCY
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REGION 8
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1595 Wynkoop Street
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Denver, CO   80202-1129
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Phone 800-227-8917
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www.epa.gov/region8


Ref: 8ARD-PM

Steven Branoff
Principal
Ramboll, Environmental and Health
2200 Powell Street, Suite 700
Emeryville, California  94608
Sbranoff@ramboll.com  

Dear Steven Branoff:

On July 12, 2023, you transmitted two letters on behalf of Chemtrade Refinery Services, Inc. (Chemtrade) to the U.S. Environmental Protection Agency, Region 8, requesting written confirmation that the Federal Minor New Source Review (MNSR) Permit Program for Indian country at 40 CFR part 49 does not apply to two proposed projects at Chemtrade's Riverton sulfuric acid manufacturing facility located on the Wind River Indian Reservation in Fremont County, Wyoming. As described in the letters the two projects consist of the addition of a scrubber that would result in a decrease of actual sulfuric acid (H2SO4) and sulfur dioxide (SO2) emissions, and the addition of a small boiler that would result in increases in allowable emissions of regulated pollutants that are all below the thresholds for review under the MNSR Permit Program. Therefore, Chemtrade concludes that neither project is subject to review under the MNSR Permit Program.

BACKGROUND

The Riverton facility uses two primary processes to manufacture sulfuric acid. The first process (Plant #1) uses a traditional contact process in which elemental sulfur is oxidized to form sulfur dioxide (SO2), which is then reacted in the presence of a catalyst to form sulfur trioxide (SO3). The SO3 is then reacted with sulfuric acid to form concentrated sulfuric acid of varying strengths. The sulfuric acid is then used to form ultra-pure acid (UPA) that is used in the electronics industry. The second process (Plant #2) involves the regeneration of spent sulfuric acid. The plant receives bulk shipments of spent acid and stores it onsite in a large aboveground storage tank. The spent acid is processed in a combustion chamber and the resulting SO2 is then reacted in the presence of a catalyst to form SO3, which is circulated through sulfuric acid to form new acid of varying strengths. 

The facility is subject to a synthetic minor permit that the EPA issued pursuant to the MNSR Permit Program on August 27, 2015 (Permit #SMNSR-WR-000003-2015.001). The permit contains SO2 and sulfuric acid mist emissions limitations and associated monitoring, performance testing, recordkeeping and reporting requirements, requiring use of a sodium-based scrubbing system and two absorbing towers. 

The steam load for each of the plant's processes is currently shared, making it necessary to run both plants continuously. Chemtrade is proposing to install a new auxiliary boiler to provide an independent source of steam to allow for more operational flexibility at the facility. According to information provided by Chemtrade, the new boiler would not be considered a modification to the production processes and would not allow for increased production from the facility that might further increase potential process emissions. Using manufacturer emission factors for the proposed new boiler, and conservatively assuming the boiler will operate full time at maximum load (100%), Chemtrade estimated the potential emissions new project would be below the minor source thresholds of the MNSR Permit Program at 40 CFR 49.153, Table 1. As such, Chemtrade concluded that the proposed project is not subject to review as a modification under the MNSR Permit Program.

During normal operations, spent acid vapors (consisting of H2SO4, SO2 and volatile organic compounds [VOC]) associated with Plant #2 are routed to the spent acid furnace for destruction. However, according to information provided by Chemtrade, during rare Plant #2 shutdowns when the combustion chamber is not operating, spent acid vapor from the Plant #2 tanks are instead routed to the atmosphere. The total emissions from these rare shutdown events are such that the facility to continues to meet permitted emissions limitations, but the spent acid vapors are a potential health and safety hazard for plant staff. To address these health and safety concerns, Chemtrade is proposing to add new blowers and piping to route the spent acid gas stream to a new scrubbing system during Plant #2 shutdowns. The proposed new scrubbing system would reduce actual H2SO4 and SO2 emissions from spent acid vapor during shutdowns and would not require a change to the facility's existing permitted allowable emissions. As such, Chemtrade concluded that the proposed new scrubber project is not subject to review as a modification under the MNSR Permit Program.

DISCUSSION

The MNSR Permit Program at 40 CFR 49.152 defines a minor source as a source "that has the potential to emit regulated NSR pollutants in amounts that are less than the major source thresholds in § 49.167 or § 52.21 of this chapter, as applicable, but equal to or greater than the minor NSR thresholds in                § 49.153", specifically Table 1 of § 49.153. Section 49.152 defines a modification as "any physical or operational change at a source that would cause an increase in the allowable emissions of a minor source or an increase in the actual emissions (based on the applicable test under the major NSR program) of a major source for any regulated NSR pollutant or that would cause the emission of any regulated NSR pollutant not previously emitted." The MNSR Permit Program at 49.153(a)(1)(i)(B) specifies that applicability to the program for a modification at an existing minor source is based on determining "whether the increase in allowable emissions from the proposed modification (calculated using the procedures in paragraph (b) of this section) would be equal to or greater than the minor NSR threshold in Table 1 of this section for the pollutant that you are evaluating." If not, the proposed modification is not subject to the MNSR Permit Program. 

Paragraph (b) of § 49.153 specifies that to determine the resulting increase in allowable emissions, "for each new emissions unit that is to be added, the emissions increase would be the potential to emit of the emissions unit." It also says that "for each emissions unit with an allowable emissions limit that is to be changed or replaced, the emissions increase would be the allowable emissions of the emissions unit after the change or replacement minus the allowable emissions prior to the change or replacement. However, this may not be a negative value. If the allowable emissions of an emissions unit would be reduced as a result of the change or replacement, use zero in the calculation." 

After reviewing the information provided by Chemtrade in its July 13, 2023 requests for formal MNSR Permit Program applicability determinations for the proposed new small boiler and new scrubbing system, we have concluded  the facts support  the proposed changes, and both considered individually and together, would not result in an increase in allowable emissions (in tons per year (tpy)) of any regulated NSR pollutant that exceeds the minor source thresholds in Table 1 of § 49.153. The potential to emit for all regulated NSR pollutants for the proposed new small boiler are below the minor source thresholds in Table 1 of § 49.153, with the highest emissions estimated for nitrogen oxides (NOX) at less than 1 tpy (the minor source threshold for NOX in the project area is 10 tpy). Additionally, the proposed addition of the new scrubbing system to the facility would reduce the actual emissions of H2SO4 and SO2 emissions from spent acid vapor during shutdowns and would not require a change to the facility's existing permitted allowable emissions of those pollutants. Therefore, the EPA concurs with Chemtrade's analysis that proposed projects are not subject to review under the MNSR Permit Program. 

If you have any questions concerning this matter, please contact Claudia Smith at (303) 312-6520 or at smith.claudia@epa.gov.   



                                          Sincerely, 
                                           
                                    Adrienne Sandoval 
                                    Director  
                                    Air and Radiation Division 
                                     
cc:	Honorable Lloyd Goggles, Chairperson, Northern Arapaho Tribe, lloyd.goggles@northernarapaho.com 
      Lee Spoonhunter, Council Member, Northern Arapaho Tribe, lee.spoonhunter@northernarapaho.com 
      Dean Goggles, Environmental Director, Northern Arapaho Tribe, dean.goggles@northernarapaho.com 
      Crystal C'Bearing, Deputy Director, Northern Arapaho Tribal Historic Preservation Office, crystal.cbearing@northernarapaho.com 
      Patrick Ramsey, Chemtrade, pramsey@chemtradelogistics.com
      Jenar Jasso, Chemtrade, jjasso@chemtradelogistics.com
      Kevin Ross, Senior Managing Consultant  -  Air Sciences, Ramboll, kross@ramboll.com
      Craig Harne, Ramboll, charne@ramboll.com   

