Document ID: EPA-R09-OAR-2020-0109-0022
Agency: epa
Document Type: Supporting & Related Material
Title: 
Posted Date: 2020-05-22T04:00Z

UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

                                     Technical Support Document for
                                       the EPA's Rulemaking for the
                            Arizona State Implementation Plan

                          Arizona Administrative Code Title 18, Chapter 2, Article 13
                        Part B  -  Hayden, Arizona, Planning Area
             R18-2-B1302  -  Limits on SO2 Emissions from the Hayden Smelter

                                            Prepared by Kevin Gong
                          Rules Office, Air Division Region 9 (Pacific Southwest)

                                       April 2020

RULE IDENTIFICATION
 Agency
Arizona Department of Environmental Quality
 SIP Approved Rules
    R-18-2-715 (sections F, G, and H)  -  Standards of Performance for Existing Primary Copper Smelters: Site-Specific Requirements
Amended  -  March 7, 2009
Submitted  -  July 28, 2011
Supplemented  -  May 16, 2014
EPA Approved  -  September 23, 2014 (79 FR 56655)
 
    R18-2-715.01  -  Standards of Performance for Existing Primary Copper Smelters, Compliance and Monitoring
Amended  -  July 18, 2009
Submitted  -  September 12, 2003
EPA Approved  -  November 1, 2004 (69 FR 63321)
 Rule that is the Subject of this TSD
    Arizona Administrative Code (A.A.C.) R18-2-B1302  -  Limits on SO2 Emissions from the Hayden Smelter 
Effective  -  July 1, 2018 or 180 calendar days after completion of all Converter Retrofit Project improvements authorized by Significant Permit Revision No. 60647
Submitted  -  April 6, 2017
 Completeness Finding
Determination of Completeness letter: July 17, 2017
BACKGROUND 
On June 22, 2010, the EPA promulgated a new 1-hour primary sulfur dioxide (SO2) National Ambient Air Quality Standard (NAAQS) of 75 parts per billion (ppb). On August 5, 2013, the EPA designated a first set of 29 areas of the country as nonattainment for the 2010 SO2 NAAQS, including the Hayden SO2 nonattainment area (NAA) within Arizona. These area designations became effective on October 4, 2013. Section 191(a) of the Clean Air Act (CAA) directs states to submit state implementation plans (SIPs) for areas designated as nonattainment for the SO2 NAAQS to the EPA within 18 months of the effective date of the designation, i.e., by no later than April 4, 2015, in this case. Under CAA section 192(a), these plans are required to include measures that will provide for the attainment of the NAAQS as expeditiously as practicable, but no later than 5 years from the effective date of designation, which for the Hayden SO2 NAA was October 4, 2018.

The Hayden NAA in Central Eastern Arizona is home to one of three operating copper smelters in the United States. The process of extracting copper from mined ore generates various process by-products, including SO2. The Hayden Smelter is owned and operated by ASARCO LLC ("Asarco"), a subsidiary of international minerals conglomerate Grupo México S.A., and accounts for over 99 percent of SO2 Emissions in the Hayden NAA. 

Asarco, as the current owner of the Hayden Smelter, is the subject of a 2015 consent decree with the EPA regarding allegations that the facility had violated the National Emission Standards for Hazardous Air Pollutants (NESHAP) for Primary Copper Smelting, 40 CFR part 63, subpart QQQ. Asarco's actions to comply with the consent decree are also a part of its control strategy to address the SO2 NAAQS, primarily through a major retrofit project focusing on the converters, and on improvements to the control equipment capturing and controlling process emissions. The converter retrofit project (CRP) involved installation of new process and control equipment that is intended to reduce fugitive lead and other hazardous air pollutant emissions, as well as emissions of SO2 from the smelting process. This project included the replacement of the existing five converter units with three larger ones, installation of extensive, more efficient and more effective fugitive gas control ducting around the converters, and the installation of additional process gas controls before venting to the main stack.

The Arizona Department of Environmental Quality (ADEQ) regulates the Hayden SO2 nonattainment area. ADEQ submitted an attainment plan for the Hayden SO2 nonattainment area on March 9, 2017, and submitted associated final rules, including Rule R18-2-B1302, on April 6, 2017. 

SO2 in the primary copper smelting process
Primary copper smelting at the Hayden Smelter can generate SO2 emissions during multiple steps of the refining process.

Copper ore concentrate (crushed metal-bearing rock) is first shipped from copper mines to a smelter for additional processing in a bedding plant. The concentrate is mixed with flux, and then dried before being fed into a primary smelting furnace. The Hayden Smelter uses an INCO Flash Furnace for primary smelting, which consists of a large rectangular refractory-lined chamber which has an off-gas flue rising from the center and burners in the end-walls. The concentrate mixture is introduced into the INCO flash furnace with oxygen-enriched air and a fuel (usually natural gas) which then reacts (with oxygen, sulfur and iron in the copper concentrate) and separates into a copper-rich matte, and a layer of slag consisting of byproduct minerals and metals, and in the process emits SO2. The slag is skimmed or tapped off for potential reprocessing or disposal. Pollutants can escape during skimming, tapping or charging of the furnace. The remaining matte is tapped into large ladles for the next step in processing in the converters.

Converters are large horizontal cylindrical chambers which further refine copper. Hayden's converters are of the Peirce-Smith type, which charge, tap, and vent through the same portal (or "mouth") by rotating the cylinder to change the position of the opening. Matte copper has a higher copper content than the copper ore concentrate in the INCO flash furnace, but still contains substantial impurities, including copper sulfides and lead. The molten matte is poured by ladles into the converters with additional silica flux, and air is blown into the converters through tubes (called tuyeres) which are submerged in the matte. The oxygen in the air reacts with the sulfides, generating SO2 process gas while further purifying the copper. This blowing can generate substantial SO2-bearing emissions, all of which is vented through the opening in the side of the Peirce-Smith converter. The blowing can go on for several hours without any additional external heating to maintain the matte's molten state, as this reaction is exothermic. Converter temperatures can be controlled by adding in cold materials, such as scrap copper. Additional slag is generated during the blowing process and can be returned to the flash furnace for reprocessing. The resulting blister copper contains few impurities at this stage, but still has substantial amounts of copper oxides that formed during converter processing.

The final primary smelter process occurs at the anode furnace, where the blister copper is blown over with natural gas, that will react with any remaining oxygen. The resultant anode copper is cast into anode sheets (at about 99% purity) for final treatment with electrowinning, an electrolytic plating process which can further purify the copper for industrial processes. The Hayden Smelter ships its copper anodes to other facilities for electrowinning. The blowing and casting processes can also generate SO2 emissions.

Process gas capture and control system and the retrofit project
The Hayden Smelter's existing capture system consists of the INCO flash furnace main flue, ventilation hoods installed at the charging and tapping points for the flash furnace, and ventilation hoods over each converter mouth. Process gas in the flash furnace main flue is sent to a venturi scrubber to capture and reduce particulate matter emissions, while the high sulfur content gas is further cleaned and processed at the acid plant.

Gases from the furnace tap points and the converters during operations are captured by the hooding system. The hoods over the tap points in the flash furnace capture SO2 gases, which are routed to an electrostatic precipitator (this device also captures particulates from hood and ventilation systems in the dryers that prepare the concentrate). The converter hoods cover the mouth during blowing operations, but the existing primary capture hoods do not operate effectively during charging or tapping operations when the converter is rotated away from the ventilation hood. This results in fugitive emissions that are vented from the smelting process and eventually emitted into the atmosphere through the converter aisle roofline. Asarco has installed covers for the converter mouths that would be in a closed position during blowing operations, to further minimize fugitive emissions, but do not seal the opening. Ventilation gas captured by the primary hooding system is routed for process gas cleaning and SO2 recovery at the acid plant. An emergency bypass stack is available for venting the entire system during malfunction or unexpected shutdowns, but is sealed during normal operations by two dampers.

Asarco's SO2 control strategy at the Hayden Smelter has included several equipment and process upgrades. The electrostatic precipitator controlling ventilation gas from the drying facility and the flash furnace has been replaced with a new vent gas baghouse system, which includes high surface area lime injection for SO2 control. The five old 13-foot diameter converters have been replaced with three new 15-foot diameter units. The new units operate more efficiently so that only one converter needs to operate at any one time (current operations may see two units operating to handle the flash furnace's output) and the capture system design will be simplified by reducing the number of converters that need to be hooded. Asarco has also installed extended secondary and tertiary hooding in the converter aisle to maximize ventilation gas capture during charging, transfer, and tapping operations. The Hayden Smelter's acid plant has also been improved with an upgraded pre-heater system, which is meant to reduce the length of start-up periods at the plant by bringing the SO2 catalyst beds up to temperature in a shorter amount of time.

ADEQ has estimated that SO2 emissions from the smelter would be reduced by 90 percent between 2011 and 2019 as a result of the CRP. 

History of sulfur dioxide nonattainment in the Hayden area and existing regulations
The Hayden area has been designated as nonattainment for the 1971 SO2 NAAQS since 1978. The State of Arizona submitted regulations to the EPA in 1979 and 1980 to reduce emissions from criteria pollutant sources in Hayden and across the state. The EPA approved these measures on January 14, 1983, but found that further analysis and control of smelter fugitive emissions was needed. The smelter operators submitted fugitive emissions studies in the 1990s to better estimate fugitive emissions during typical operation to eventually determine maximum emissions. This analysis resulted in the implementation of further control measures and emission limits at the Hayden Smelter. 

The current SIP-approved rules governing SO2 emissions from the Hayden Smelter include rules R18-2-715 (Rule 715) and R18-2-715.01 (Rule 715.01). Rule 715 subsection (F)(1) includes annual SO2 limits for the Hayden smelter, as well as a table outlining the number of acceptable cumulative occurrence exceedances for each of a series of specific 3-hour limits. Subsection (G) establishes an annual average fugitive emissions limit of 295 pounds per hour. 

Rule 715.01 was previously revised on July 18, 2002 and approved by the EPA on November 1, 2004 (69 FR 63321). Rule 715.01 addresses compliance and monitoring requirements at the Hayden Smelter (in addition to similar requirements for the Miami Smelter), including: specific requirements for compliance determination, compliance dates for limits, averaging methods, violation provisions, emissions monitoring requirements, measurement system requirements, maintenance requirements for monitoring systems, and other related provisions.

RULE SUMMARY
Rule R18-2-B1302  -  Limits on SO2 Emissions from the Hayden Smelter
R18-2-B1302 (Rule B1302) is a source-specific regulation in the AAC that limits SO2 Emissions from processes at the Hayden Smelter. This rule has an effective date of the earlier of July 1, 2018 or 180 days after the completion of the retrofit project.

This rule includes relevant definitions, an hourly SO2 emission limit for the main stack, operational standards for process equipment and control devices, baseline requirements for the process gas capture system and control devices operations and maintenance plan (O&M plan), performance testing and compliance demonstration requirements, and recordkeeping and reporting requirements.

Rule B1302 also requires the owner or operator of the smelter to conduct a fugitive emissions study following the completion of the CRP, in accordance with Appendix 14 of Title 18, Chapter 2. The EPA approved Appendix 14 into the SIP on November 14, 2018.

EVALUATION CRITERIA
The following criteria were used to evaluate the submitted rule.

 Enforceability - CAA section 110(a)(2)(A) requires SIPs to "include enforceable emission limitations and other control measures, means, or techniques . . . as may be necessary or appropriate to meet the applicable requirements of [the CAA]." Similarly, CAA section 172(c)(6) requires that attainment SIPs "include enforceable emission limitations, and such other control measures means or techniques . . . as well as schedules and timetables for compliance, as may be necessary or appropriate to provide for attainment of such standard in such area by the applicable attainment date . . ." The Bluebook (Issues Relating to VOC Regulation Cutpoints, Deficiencies, and Deviations, EPA, May 25, 1988) and the Little Bluebook (Guidance Document for Correcting Common VOC & Other Rule Deficiencies, EPA Region 9, August 21, 2001) were used to help evaluate compliance with the CAA requirements for enforceability.

 Stringency  -  CAA section 172(c)(1) requires that SIPS for nonattainment areas provide for the implementation of all reasonably available control measures (RACM), including any reasonably available control technology (RACT), in order to provide for attainment of the NAAQS. 

 SIP Revisions  -  CAA section 110(l) prohibits the EPA from approving any SIP revision that would interfere with any applicable requirement concerning attainment and reasonable further progress (RFP) or any other applicable requirement of the CAA. In addition, CAA section 193 prohibits the modification of any SIP-approved control requirement in effect before November 15, 1990, in a nonattainment area, unless the modification insures equivalent or greater emission reductions of the relevant pollutant(s).

EPA EVALUATION
 Enforceability of Rule B1302 
Rule B1302 sections (E), (F), (G), and (H) contain detailed monitoring, recordkeeping, and reporting requirements, which support the enforceability of the main stack emission limit. However, the EPA has identified several issues with the enforceability of Rule B1302:

 Lack of a numerical emission limit for fugitives 
The attainment demonstration modeling in the Hayden SO2 Plan includes emissions emanating from five locations around the facility: the main smelter stack, the anode furnace roofline, the converter aisle roofline, the flash furnace building roofline, and the outdoor slag pouring area. Of these, only the main stack is subject to a numeric emission limit and ongoing monitoring under Rule B1302. The EPA believes that the emissions from outdoor slag pouring are not susceptible to monitoring and therefore it is not reasonable to require a numeric emission limit for these emissions. Conversely, we find that emissions from the anode furnace roofline, the converter aisle roofline, and the flash furnace building roofline (collectively "building fugitive emissions"), are susceptible to monitoring, as further detailed below, and therefore must be subject to a numeric limit. Instead of such a limit, Rule B1302 relies on requirements in an operations and maintenance plan and two fugitive emissions studies lasting one year each to evaluate whether actual emissions correspond with the modeled levels of building fugitive emissions. While the fugitive emissions studies will provide useful information to verify the nature and extent of building fugitive emissions from the facility, this approach does not satisfy the requirements for enforceable limits that provide for attainment of the SO2 NAAQS under CAA section 172(c)(6). 

In particular, we note that updated modeling performed subsequent to the submittal of the Hayden SO2 plan indicates that these emissions have the potential to cause or contribute to violations of the 2010 SO2 NAAQS. We also note that the SO2 rule controlling emissions from the Miami Smelter (A.A.C. R18-2- C1302) includes fugitive emissions in the facility-wide emissions limit and establishes permanent continuous monitoring requirements for fugitives at that facility. Furthermore, the fact that Asarco is able to monitor these emissions on a temporary basis through the fugitive emissions studies suggests that it would be feasible to monitor them on an ongoing basis. Such ongoing monitoring would allow for the establishment of an enforceable numeric limit that would ensure that fugitive emissions remain at a level consistent with attainment of the SO2 NAAQS. 

 Option for alternative sampling points
Rule B1302 subsection (E)(4) provides that:

      If the owner or operator can demonstrate to the Director that measurement of stack gas volumetric flow rate in the outlet of any particular piece of SO2 control equipment would yield inaccurate results or would be technologically infeasible, then the Director may allow measurement of the flow rate at an alternative sampling point.

This provision could undermine the enforceability of the stack emission limit by providing undue flexibility to change sampling points without undergoing a SIP revision. While such flexibility might have been necessary at the time of rule development, as capture and control upgrades were still being installed, it appears that this flexibility is no longer necessary. We note that the Miami SO2 Rule, also contained a similar provision, but ADEQ withdrew this provision from EPA's consideration.  The EPA approved the Miami SO2 Rule (excluding this provision) on November 14, 2018 and we approved the related attainment plan for the Miami SO2 nonattainment area on March 12, 2019. 

 Option for removal of the CEMS requirement
Rule B1302 subsection (E)(6) provides that:

      The owner or operator of the Hayden Smelter may petition the Department to substitute annual stack testing for the tertiary ventilation or the anode furnace baghouse stack CEMS if the owner or operator demonstrates, for a period of two years, that either CEMS contribute(s) less than five percent individually of the total sulfur dioxide emissions. The Department must determine the demonstration adequate to approve the petition. 

These captured emissions from the tertiary ventilation and anode furnace bag house are then ducted to the main stack. The main stack does not have its own CEMS: rather, the monitoring strategy relies on multiple CEMS that are upstream of the stack that are then summed up to generate a main stack emission value. As a result, this provision would allow just under 10% of total facility SO2 emissions annually to be exempt from CEMS, which could compromise the enforceability of the main stack emission limit. 

 Lack of method for measuring or calculating emissions from shutdown ventilation flue 
Rule B1302 subsection (F)(1) requires Asarco to include emissions vented to "each uncontrolled shutdown ventilation flue" in determining compliance with the main stack emission limit, but the rule does not specify how these emissions are to be measured or estimated. Although subsection (G)(2)(e) requires Asarco to maintain "records of planned and unplanned shutdown ventilation flue utilization events and calculations used to determine emissions from shutdown ventilation flue utilization events if the owner or operator chooses to use the alternative compliance determination method," it does not specify how these calculations are to be performed. Because emissions from the shutdown ventilation flue are subject to the main stack emission limit, the lack of a calculation methodology could compromise the enforceability of this limit. 

 Lack of a method for calculating hourly SO2 emissions 
Rule B1302, section (F)(2) contains a procedure for substituting emissions data for compliance demonstration purposes, "when no valid hour or hours of data have been recorded by a continuous monitoring system." However, Rule B1302 lacks a requirement similar to subsection (F)(2) of the Miami SO2 rule, R18-2-C1302. Therefore, it is unclear what constitutes a "valid hour" for purposes of allowing data substitution under subsection (F)(2). This omission could compromise the enforceability of the main stack emission limit. 

 Stringency of SO2 Controls at the Hayden Smelter in Rule B1302
Rule B1302 subsection (C)(1) establishes a main stack emission limit of 1069.1 pounds per hour (lb/hr) on a 14-operating day average (unless 1,518 pounds or less is emitted during each hour of the 14-operating day period). This limit is more stringent than the annual-average limit of 6,882 lb/hr and three-hour limits of 8,556 -24,641 lb/hr in SIP-approved Rule 715 subsection (F)(1). Therefore, approval of Rule B1302 would increase the stringency of the SIP.

In a separate action on the Hayden SO2 plan, we are proposing to find that ADEQ has not satisfied the requirement in section 172(c)(1) to adopt and submit all RACM/RACT as needed to attain the standards as expeditiously as practicable in the Hayden SO2 area. Therefore, in this action we are not further evaluating whether Rule B1302 implements RACM/RACT for this facility.

 SIP Revisions
ADEQ submitted revisions to SIP-approved Rules R18-2-715 (Rule 715), R18-2-715.01 (Rule 715.01) and R18-2-715.02 (Rule 715.02) concurrently with Rule B1302. These revisions in the 715 series clarify references to other sections within each of these rules and add new language that provide for the 715 series to sunset upon the effective date of the new regulations. In 2018 we approved the revisions to 715.02, which allowed for the existing provisions of that rule to sunset. We have not yet acted on the revisions to 715 and 715.01 because we need to evaluate the effect of sunsetting the existing SIP-approved requirements of those rules in conjunction with the new requirements for the Hayden smelter established in Rule B1302.

As described above, Rule B1302's numeric limit for main stack emissions is more stringent than those found in the SIP-approved existing regulations.  However, Rule B1302 does not include a numeric fugitive emission limit, whereas Rule 715 subsection (G) includes an annual average fugitive limit of 295 lb/hr. 

In order to ensure that the existing fugitive limit of 295 lb/hr remains in the SIP, we are not acting on the revisions to Rule 715 at this time. Similarly, we are not acting on Rule 715.01, which includes requirements for SO2 compliance determination and monitoring that support the enforceability of the emission limits and requirements in Rule 715. 

Approval of Rule B1302 by itself would not result in removal of any control requirements from the SIP and would therefore comply with CAA section 110(l) and 193.

ADDITIONAL RECOMMENDATIONS 
 In subsection D(1) revise the reference to " emission control and/or control equipment" to "emission capture and/or control equipment" 
 In section (H), add a requirement for reporting of any control equipment malfunctions. 

THE EPA'S PROPOSED ACTION
Rule B1302 strengthens the SIP by establishing a more stringent SO2 emission limit for the main stack at the Hayden smelter, as well as operational standards for process equipment and control devices, baseline requirements for the process gas capture system and control devices O&M plan, performance testing and compliance demonstration requirements, and recordkeeping and reporting requirements. However, the rule does not fully meet CAA requirements for enforceability for the reasons described above. Therefore, EPA staff recommends a limited approval and limited disapproval of B1302 pursuant to CAA section 110(k)(3) and section 301(a). 

REFERENCES
 "Issues Relating to VOC Regulation Cutpoints, Deficiencies, and Deviations," (a.k.a., Bluebook) EPA OAQPS (May 25, 1988).
 "Guidance Document for Correcting Common VOC & Other Rule Deficiencies," (a.k.a., Little Bluebook), EPA Region 9 (August 21, 2001).
        Arizona State Implementation Plan Revision: Hayden Sulfur Dioxide Nonattainment Area for the 2010 SO2 NAAQS  ("Hayden SO2 Plan") (March 9, 2017).
        National Emission Standard for Hazardous Air Pollutants for Primary Copper Smelting (40 CFR part 63, subpart QQQ).
        Notice of Final Rulemaking, Title 18. Environmental Quality, Chapter 2. Department of Environmental Quality Air Pollution Control, Arizona Administrative Register, Vol. 23, Issue 14 (April 7, 2017).
        Letter dated April 29, 2019 from Elizabeth Adams, Air Division Director, to Timothy Franquist, Air Director, ADEQ, "Re: Comments on draft letter regarding R18-2-B1302."
        "Processing of State Implementation Plan (SIP) Submittals," Memorandum from John Calcagni, Director Air Quality Management Division, to EPA Regional Air Directors, Regions I-X, dated July 21, 1992.
        Consent Decree No. CV-15-02206-PHX-DLR (D. Ariz).