1 MEMORANDUM

DATE: March 24, 2011

SUBJECT: Revised Regulatory Alternative Imp acts for ExxonMobil Group 1 Polymers and Resins Facilities

FROM: Bradley Nelson, EC/R Incorporated

TO: Nick Parsons, EPA/OAQPS/SPPD/RCG Paula Hirtz, EP A/OAQPS/SPPD/RCG

The purpose of this memorandum is to pres ent revised estimated impacts of regulatory
alternatives identified to re duce hazardous air pollut ant (HAP) emissions from The ExxonMobil facilities that are subject to the Group 1 Poly mers and Resins National Emission Standards for HAP (NESHAP) – 40 CFR 63, subpart U. The revisions are a result of comments received from ExxonMobil on the proposed changes to the NE SHAP after the Risk and Technology Review (RTR) evaluation under section 112( d)(2), 112(d)(6) and 112(f)(3) of the Clean Air Act. The facilities include a Butyl Rubber Production fac ility in Baytown, TX and a Halobutyl Rubber Production/ Ethylene Propylene Ru bber Production facility in Baton Rouge, LA. Section 1 provides background information, followed by an identi fication of the regulatory alternatives in
Section 2. Section 3 summarizes the estimat ed costs and HAP emission reductions of the alternatives, and Section 4 summa rizes the secondary impacts.

1.0 BACKGROUND

Regulatory alternatives were developed a nd evaluated for the process “front-end” for Butyl Rubber Production, Halobutyl Rubber Production, and Ethylene Propylene Rubber Production at Baytown and Baton Rouge to redu ce hydrochloric acid (HCl) emissions. The front-end butyl rubber and halobut yl rubber processes are included in the same subcategory and regulatory alternatives were developed for this subgroup. Regulatory alternatives were also developed and evaluated for the process “back -end” for Butyl Rubber Production and Halobutyl Rubber Production at the Baytown and Baton Rouge facilities to reduce hazardous air pollutant (HAP) emissions. Again, these back end processe s are included in the same subcategory and regulatory alternatives were developed fo r this subgroup. During the comment period,2 ExxonMobil provided design flow rates, HCl and HAP emissions, and control equipment costs for the controlling the emission sources at these f acilities. EPA used these design flow rates and
HCl and HAP emissions to re-eva luate the regulatory alternatives for these sources and develop revised control equipment costs and cost per ton values for these sources.

2.0 REGULATORY ALTERNATIVES

Regulatory alternatives were evaluated fo r the process “front-e nd” for butyl rubber process at the Baytown facility, and halobutyl rubber and ethylene propylene rubber processes at the Baton Rouge facility. Each of the “front-end” processes wa s evaluated for the reduction of HCl emissions. Two “front-end” process regula tory alternatives were identified. The first
alternative was to establish an emissions limit ba sed on the current level of HCl emissions. This option did not require the installation of any additional controls, only that HCl emissions be
maintained at the curren t level. The second alternative was to require a 99 percent reduction of
the HCl created from the combustion of chlorinate d organic compounds. In each case, the HCl is generated by the combustion of chlorinated orga nic compounds in a flare. Since it is not possible to install an add-on device to redu ce these HCl emissions following the flare, the impacts are based on the replacement of the flares currently in use with incinerators followed by scrubbers that will achieve 99 per cent reduction in the HCl emissions.

Regulatory alternatives were also identif ied for the process “back-end” for the Butyl Rubber Production at the Baytown facility, and the Halobutyl Rubber Pr oduction at the Baton Rouge facility. Each of the “back-end” pro cesses were evaluated fo r the reduction of HAP
emissions. Two alternatives were considered for each source category/subcategory. The
alternative was to establish an emission limit based on the current HAP emissions levels considering existing levels of HAP stripping and recovery plus any existing controls. This option did not require the installation of any additional controls, only that HAP emissions be
maintained at the curren t level. The second regulatory alte rnative identified was to reduce the organic HAP emissions by requiri ng a 98 percent reduction in or ganic HAP emissions by using
an incinerator.3 3.0 RELEVANT EMISSION POINTS AND BASELINE EMISSIONS

Information about emission points and em issions were provided by the industry in response to a questionnaire distri buted by the EPA using their aut hority under section 114 of the CAA for the proposed rule. During the comm ent period, ExxonMobil provided additional information for the emission points for their Bayt own and Baton Rouge facilities. The sections below summarize the new information and compares it to the emission point information used for the proposed rule.

3.1 Front-End Emissions

ExxonMobil had two facilities that reported emissions of HCl from the flaring of chlorinated organic compounds present in front-end process vent emissions, one producing Butyl Rubber and one producing Halobutyl Rubber and Ethylene Propylene Rubber. In the proposal, HCl controls were estimated using the emissions and flow rates obtained from the section 114 letter. During the comment period, ExxonMob il provided design flow rates and revised emissions for the front-end processes. A summary of the changes in flow rate and reported HAP emissions are presented in Table 1. The two fac ilities are in compliance with the current MACT standard, which requires that organic HAP emissions from con tinuous group 1 front-end process vents be reduced by 98 percent, or by using a flare.4 Table 1. Comparison of the Proposal and Revised Inputs for the “Front-End” Process Vent Cost Estimate and Baseline Emissions

Source Category Pollutant Proposal Estimate Emissions (Tons/yr) Revised Estimate Emissions (Tons/yr) Proposal Flow Rate

(ft

3 /sec) Revised Flow Rate

(ft

3 /sec)

Butyl Rubber Hydrochloric Acid 30.1 24.7

205.98 5,700 Methyl Chloride 0.779 0.779

Hexane 6.53 6.53
1,3 Butadiene 0.001 0.001 Xylenes 0.0002 0.0002 Ethylene Propylene Rubber Hydrochloric Acid 19.8 24.1 459.4 1,325 Hexane 0.188 0.188

Halobutyl Rubber Hydrochloric Acid 76.8 76.9
459.43 1,325 Methyl Chloride 0.53 0.53

Hexane 0.06 0.06

3.2 Back-End Process Emissions

Following are HAP emission summaries of the back-end process emissions for the butyl and halobutyl source subcategory. The HAP emi ssions from the back-end process operations at the butyl rubber facility are approximately 54 TPY. There are two separate dryer vent streams at the butyl rubber facility, with one stream cont rolled. The controlled stream emits around 28 TPY of hexane, while the uncontro lled stream emits around 26 TPY of hexane. The regenerative
thermal oxidizer used to control emissions ach ieves approximately 98 percent control. The comments from ExxonMobil listed the design flow rate for the thermal oxidizer to be 15,000 cubic feet per minute, which is much greater than the 213 cubic feet per minute flow rate used in the proposal cost estimates. A summary of the proposal and revised estimate emissions and flow
rate used to cost the thermal oxi dizer are presented in Table 2.

The emissions from the back-end process operati ons at the halobutyl rubber facility are approximately 53 TPY. There are four separate dr yer vents at the halobutyl facility and only one5 vent is controlled. The controlled vent emits around 18 TPY of hexane and 0.04 TPY of hydrochloric acid. The regenerative thermal oxi dizer used to control emissions achieves approximately 97 percent control of the hexa ne emissions. The three uncontrolled vents collectively emit around 42 TPY of hexane. A su mmary of the HAP emissions used for the proposal and the revised emission are shown in Ta ble 2. Both the HAP emission rate and flow rate provided in the comments from ExxonMobil were greater than the values that were used for the proposal costs and were used to develop th e control costs for the re-evaluation of the regulatory alternatives.

Table 2. Comparison of the Proposal and Revi sed Inputs for the “Back-End” Process Vent Cost Estimate and Baseline Emissions

Source Category Pollutant Proposal Estimate Emissions (Tons/yr) Revised Estimate Emissions (Tons/yr) Proposal Flow Rate

(ft

3 /sec) Revised Flow Rate

(ft

3 /sec)
Butyl Rubber Hexane 26.19 25.8 213 15,000 Halobutyl Rubber Hexane 34.7 41.7 454 80,000

4.0 COSTS AND EMISSION REDUCTI ONS OF REGULATORY ALTERNATIVES

4.1 Front-End Process Vents

As noted in Section 2, there we re two regulatory alternatives identified to address HCl emissions from front-end process vents from the Butyl Rubber/Halobutyl Rubber and Ethylene Propylene Rubber source categories. The first altern ative would ensure that the current levels of HCl emissions are maintained. The only impact of this alternative woul d be costs due to the labor costs associated with the calculations, r ecords, and reports to demonstrate compliance.
These costs are summarized in Table 3.6 Table 3. Estimated Impacts for Front-End Regulatory Alternative 1

Source Category Baseline Organic HAP Emissions (tpy) Emission Reduction (tpy) Capital Costs ($) Annual Costs ($/yr) Cost Effectivenes

s ($/ton) Butyl Rubber 7.31 0 $0 $1,000 N/A Ethylene Propylene Rubber 0.188 0 $0 $1,000 N/A Halobutyl Rubber 0.59 0 $0 $1,000 N/A

As noted in section 2, the organic HAP emi ssions from these front-end vents are already controlled by a flare. The costs estimated are to replace the flare with an incinerator followed by a scrubber. The costs were estimated using cost spreadsheets developed to estimate control costs using the EPA control cost algorithms 1 for thermal incinerators, ducting, and acid-gas absorbers (scrubbers). The uncontrolled HAP emissions from the streams that are currently controlled were calculated by assuming the flare achieves 98 percent reduction in or ganic HAP emissions.
Flow rates from ExxonMobil’s comments were used to estimate the size and cost of the thermal
oxidizers. In addition to the costs included in the EPA Air Pollution Co sts Manual, auxiliary
costs submitted in the comments from ExxonM obil were also include d. This auxiliary equipment include: piperacks and piperack modifi cations, utility piping, and a new motor control

center.

Table 4 presents the costs based on the sec ond regulatory alternativ e requiring 99 percent reduction in HCl emissions. The Ethylene Pr opylene Rubber and Halobutyl Rubber processes are located at the same facility. The control costs were estimated by splitting the total flow rate from the combined stream using the HCl and organic HAP emissions rates. The control costs for the Baytown and Baton Rouge Butyl Rubber sources were totaled to develop an average cost of controlling HCl emissions from the butyl rubber process. This is shown in the Baytown/Baton Rouge Butyl Total column of Table 4. Detail s of these costs estimates are provided in
Attachment 1.

1 EPA Air Pollution Control Cost Manual, Sixth Edition, January 2002, EPA/452/B-02-0017 Table 4. Estimated Impacts for Front-End Regulatory Alternative 2

Parameter Baytown Butyl Rubber Baton Rouge Butyl Rubber Baytown/Baton Rouge Butyl Total Baton Rouge Ethylene Propylene

Rubber HCl Emissions at Baseline (tpy) 24.7 76.9 101.6 24.1

Incinerator Capital $399,696 $308,373 $708,069 $231,440 Annual $246,036 $174,376 $420,412 $116,645

Scrubber Capital $529,852 $110,558 $640,410 $55,327 Annual $188,508 $106,431 $294,939 $82,726 Auxiliary Equipment Capital $1,541,367 $1,657,628 $3,198,995 $1,657,628 Annual $266,629 $257,498 $524,127 $257,498

Total Capital $2,470,915 $2,076,560 $4,547,475 $1,944,396 Annual $701,174 $538,306 $1,239,480 $456,868 HCl Emission Reduction (tpy) 24.5 76.1 100.5 23.8 HCl Cost Effectiveness $28,674 $6,694 $12,329 $19,188 HCl after control (tpy) 0.2 0.8 1.0 0.2

4.2 Back-End Process Operations

As noted in Section 2, there were two regulatory alternatives identified to address backend emissions from the Butyl Rubber/ Halobuty l Rubber category. The fi rst alternative would
ensure that the current levels of emissions are maintained. The only impact of this alternative
would be costs due to the labor costs associated with the calcul ations, records, and reports to demonstrate compliance. These costs are summarized in Table 5.8 Table 5. Estimated Impacts for Back-End Regulatory Alternative 1

Source Category Baseline Emissions (tpy) Emission Reduction (tpy) Capital Costs ($) Annual Costs ($/yr) Cost Effectivenes

s ($/ton) Butyl Rubber 54 0 $0 $981.84 N/A Halobutyl Rubber 53 0 $0 $981.84 N/A

The Table 6 costs were estimated using th e EPA control cost algorithms for thermal
incinerators. Flow rates from ExxonMobil’s comments were used to estimate the size and cost
of the thermal oxidizers. Some of the back-end streams are already controlled. Further emission
reductions for the controlled streams were not considered. Instead, the cost impacts were
calculated based on the control of the uncontrolled streams. Detail s of these costs estimates are provided in Attachment 2.

Table 6. Estimated Cost and Emission Reduc tions for Back-End Regulatory Alternative 2

Parameter Butyl Rubber Halobutyl Rubber Butyl/Halobutyl Total HAP Emissions at Baseline (tpy) 25.8 41.7 67.5

Incinerator Capital $848,334 $2,470,051 $3,318,385 Annual $325,558 $1,151,729 $1,477,287 Auxiliary Equipment Capital $62,691 $71,123 $133,814 Annual $14,793 $16,977 $31,770

Total Capital $911,025 $2,541,175 $3,452,200 Annual $340,351 $1,168,706 $1,509,057 HAP Emission Reduction (tpy) 25.3 40.9 66.2 HAP Cost Effectiveness $13,461 $28,598 $22,795 HAP after control (tpy) 0.5 0.8 1.39 5.0 SECONDARY ENVIRONMENTAL IMPACTS

While the primary impact of the regulatory alternatives is to address HCl emissions on the front-end and organic HAP emissions on th e back-end, the applicat ion of the control technologies that would be requi red under the second regulatory alte rnatives can also have other environmental effects. These impacts can be positive, such as a reduction in non-HAP volatile organic compound air emissions; or negative, such as the generation of additional wastewater or energy consumption. In this se ction the secondary impacts on ai r pollution, water pollution, and energy are discussed. The methodologies used to calculate secondary im pacts can be found in
documentation for the MACT standard. 2

Air Pollution

For the sources included in this project, the secondary air pollution impacts are the increased criteria pollutant emissions caused by the on-site combustion of organic HAPs and
fuels. This combustion results in the emission of nitrogenous oxides (NO x ), carbon monoxide (CO), particulate matter (PM) , and sulfur dioxide (SO 2 ). In addition to these five criteria pollutants, emissions of carbon dioxide (CO 2 ) are also expected. Table 7 presents the estimated secondary air impacts for regulat ory alternative 2 for the front-e nd process vents, and Table 8 presents those for back-end process vents. The to tal criteria pollutant em issions for the front-end are estimated to be around 7 tpy, with NO x emissions from incinerato rs accounting for 6 tpy. The total criteria pollutant em issions for the back-end are estimated to be around 267 tpy, with
NO x emissions from incinerators accounting for 225 tpy. The CO 2 emissions are estimated to be around 2,607 tpy and 131,086 tpy for front-e nd and back-end, respectively.

2 Memorandum. Estimated Regulatory Alternative Imp acts for Elastomer Production Facilities (Polymers and Resins I). Norwood, P., EC/R, to Ev ans, L., EPA/OAQPS/ESD/OCG. May 10 , 1995. Contained in Hazardous Air Pollutant Emissions from Process Units in the Elasto mer Manufacturing Industry--Supplementary Information Document for Proposed Standards. EPA-453/R-95-005a. May 1995.10 Table 7. Secondary Air Impacts for Front-End Regulatory Alternative 2

Source Category Emissions (tpy) PM SO 2 NO X CO CO 2 Butyl Rubber 0.004 0.001 2 0.05 162
Halobutyl Rubber 0.03 0.006 2 0.40 1,233
Ethylene Propylene Rubber 0.03 0.006 2 0.40 1,219

Combined HBR AND EPR 0.06 0.012 4 0.70 2,445

Table 8. Secondary Air Impacts for Ba ck-End Regulatory Alternative 2

Source Category Emissions (tpy) PM SO 2 NO X CO CO 2 Butyl 0.01 0.003 8 0.2 593 Halobutyl 0.25 0.05 17 3 10,160

Water Pollution

The only impact on water pollution for the seco nd regulatory alternatives identified in
Section 2.0 is associated with th e incinerator/scrubber system for control of HCl from the frontend process vents. Control of organic HAP em issions using combustion only does not result in any significant increase in wast ewater discharge, since no wate r effluents are generated by the
thermal incinerator.

In the scrubber control system, water is us ed to remove the acid gas contained in the
thermal oxidizer outlet stream. The amount of wa stewater generated is equal to the amount of water needed by the scrubber to absorb the acid gas leaving the incinerator. It is estimated that about 90 million gallons of wastewat er will be generated annually from acid scrubbers at Butyl Rubber, Halobutyl Rubber, and Ethylene Propylene Rubber facilities. Almost 60 million of this total is from the Halobutyl and Ethylene Propylen e Rubber facility. The same assumptions were11 used for this analysis as those used in the MACT. 3 Table 9 presents the water pollution impacts from front-end regulatory alternative 2.

Table 9. Water Pollution Impacts from Front-End Regulatory Alternative 2

Source Category Flow Rate to Scrubber

(scfm) Operating Hours (hr/yr) Wastewater Treatment Flow Rate (1000 gal/yr) Butyl Rubber 7,000 8,760 75.8

Halobutyl Rubber 3,045 8,760 236

Ethylene Propylene Rubber 955 8,760 73.9

Energy Impacts

The energy demands associated with the c ontrol technologies for the second regulatory
alternatives include the need fo r additional electricity and natural gas. The total nationwide energy demands that would result from implemen ting regulatory alternative 2 for front-end and back-end process vents are presented in Tables 10 and 11, respectively. Overall, the controls would require approximately 1.0 x 10 9 Btu electricity and 4.4 x 10 10 Btu natural gas annually for front-end process vent control. Back-end pro cess vents would require approximately 3.7 x 10 10 Btu electricity and 2.2 x 10 12 Btu natural gas annually. More details about the methodologies
used can be found in the MACT documentation. 4

3 See footnote 1 4 See footnote 112 Table 10. Energy Requirements for Front-End Regulatory Alternative 2

Source Category Incinerator Scrubber Annual Electricity Cost ($/yr) Electricity (Kw-hr) Natural Gas Cost

($/yr) Natural Gas (Mscf/yr) Annual Electricity Cost ($/yr) Electricity (Kw-hr) Natural Gas Cost

($/yr) Natural Gas (Mscf/yr)

Butyl Rubber $13,444 196,257 $104,110 19,906 $33,608 490,628 0 0
Halobutyl

Rubber $4,763 69,536 $54,810 10,480 $4,150 60,584 0 0
Ethylene Propylene

Rubber $1,511 22,063 $11,854 2,266 $1,302 19,007 0 0

Table 11. Energy Requirements for Ba ck-End Regulatory Alternative 2

Source Category Annual Electricity Cost ($/yr) Electricity (Kwhr) Natural Gas Cost ($/yr) Natural Gas (Mscf/yr)

Butyl $35,185 513,650 $94,686 18,104 Halobutyl $187,668 2,739,675 $525,450 100,46813 Attachment 1
Capital and Annual Cost Summary Sheets