December 2020
MEMORANDUM
TO:		Docket ID: EPA-HQ-OAR-2020-0532
FROM:	Nathan Topham, Environmental Engineer, U.S. EPA
--------------------------------------------------------------------------------
SUBJECT:	Technical Support Document for the Cyanide Chemicals Manufacturing NESHAP Residual Risk and Technology Review Proposal
	This memo describes the cyanide chemicals manufacturing source category. The following sections cover the manufacturing process, emission points, uses of the end product, the data used to develop the modeling file, and the results of the technology review. 
       
1.0 Cyanide Chemicals Manufacturing Industry

1.1 Product and Manufacturing Overview 
	
	Cyanide chemicals are largely produced as intermediate chemicals used in the manufacturing of other chemicals (hydrogen cyanide) or for use in gold mining (sodium cyanide). The category includes, but is not limited to, production of hydrogen cyanide using any of the following methods: reaction of methane and ammonia over a platinum catalyst, reaction of methane and ammonia over a platinum-rhodium catalyst, co-production with acrylonitrile (via Sohio process), and pyrolysis of formaldehyde. In the 1992 initial listing document, sodium cyanide production includes any facility engaged in the production of sodium cyanide, a white crystalline solid commonly called white cyanide. The category includes, but is not limited to, production of sodium cyanide via the neutralization process, or so-called wet process, in which hydrogen cyanide reactions with sodium hydroxide solution usually in a unit system that involves evaporation of water and crystallization of the product.

1.2 Characterization of the Cyanide Chemicals Manufacturing Industry

   The cyanide chemicals manufacturing source category includes 13 facilities, a small decline since the 2002 final rule was promulgated. At that time, we identified 16 facilities in the source category. The EPA collected facility and emissions data for this rulemaking from EPA databases such as the 2017 National Emissions Inventory (NEI), Enforcement and Compliance History Online (ECHO), and state title V permit databases. 
   
Table 1: Cyanide Chemicals Manufacturing Facility List
                                 Facility Name
                                    FRS ID
                                    Address
                                     City
                                     State
ASCEND PERFORMANCE MATERIALS CHOCOLATE BAYOU PLANT
                                                                   110000503722
LOCATED ON FM 2917 APPROX 8 MI S OF INTX OF HWY 35
ALVIN
TX
CHEMOURS BEAUMONT ANILINE FACILITY
                                                                   110034393378
5470 N TWIN CITY HWY
NEDERLAND
TX
EVONIK CORPORATION
                                                                   110017408296
4201 EVONIK ROAD
THEODORE
AL
SYNGENTA CROP PROTECTION LLC - ST GABRIEL PLANT                                 
                                                                   110000597426
3905 HWY 75                                       
ST. GABRIEL
LA
INEOS NITRILES USA LLC
                                                                   110057376398
1900 FORT AMANDA RD.
LIMA
OH
INVISTA SARL
                                                                   110000464391
2695 OLD BLOOMINGTON RD N
VICTORIA
TX
ROHM AND HAAS TEXAS DEER PARK PLANT
                                                                   110069500864
1900 TIDAL RD
DEER PARK
TX
DOW TEXAS OPERATIONS FREEPORT
                                                                   110008170237
2301 N BRAZOSPORT BLVD
FREEPORT
TX
INVISTA SARL SABINE RIVER SITE
                                                                   110022523982
3055A FM 1006
ORANGE
TX
LUCITE BEAUMONT SITE
                                                                   110000463917
6350 N TWIN CITY HWY
NEDERLAND
TX
MHBA CHOCOLATE BAYOU PLANT
                                                                   110061084829
FROM STATE RD 35 HEAD SE ON FM ROAD FOR 7.0 MI TAK
ALVIN
TX
INEOS GREEN LAKE PLANT
                                                                   110000502867
13050 STATE HIGHWAY 185 N
PORT LAVACA
TX
CHEMOURS MEMPHIS PLANT
                                                                   110000374443
2571 FITE RD.
MEMPHIS
TN


2.0 Cyanide Chemicals Manufacturing Process

2.1 Overview of Process

	The cyanide chemicals manufacturing source category includes facilities that are engaged in the manufacture of HCN or sodium cyanide: (1) By reaction of methane and ammonia over a catalyst (the Blausaure Methane Anlage (BMA) process), (2) by reaction of methane and ammonia in the presence of oxygen over a catalyst (the Andrussow process), or (3) as a byproduct of the acrylonitrile production process (the Sohio production process). The source category also includes facilities that manufacture sodium cyanide via the neutralization process, sometimes referred to as the "wet process," in which HCN reacts with sodium hydroxide solution, usually in a system that includes the evaporation of water and crystallization of the product. 

2.2 Process Description

      We identified four distinct processes used to produce cyanide chemicals. Therefore, the definition of affected source for cyanide chemicals manufacturing specifies that a cyanide chemicals manufacturing process unit may be any one of the following: an Andrussow process unit, a BMA process unit, a sodium cyanide process unit, or a Sohio HCN process unit. The definitions of each of these types of process units describes the process and delineates where the process unit begins and ends. 

      The Andrussow and BMA process units begin with (and include) the raw material storage tanks and end at the point at which refined HCN enters a reactor in a downstream process or is shipped offsite.
      
      A Sohio HCN process unit, in which HCN is produced as a byproduct of acrylonitrile, begins at the point where the HCN leaves the unit operation where the HCN is separated from acrylonitrile. This unit operation is often referred to as the "light ends column." As with all the other HCN process units, the Sohio HCN process unit ends at the point at which refined HCN enters a reactor in a downstream process or is shipped offsite. 
      
      The sodium cyanide process unit begins just prior to the unit operation where refined HCN is reacted with sodium hydroxide and ends at the point just prior to where the solid sodium cyanide product is shipped offsite or enters a reactor in a downstream process.
      
3.0 Data Sources Used to Generate List of Facilities and Emissions Data to be Modeled
	The list of facilities subject to the NESHAP was created through searching the EPA's ECHO database, the 2017 National Emissions Inventory (NEI), and state databases of title V permits. Once the facility list was finalized, available emissions data were pulled from the NEI. Title V permits were used to determine which emission points at each facility are subject to the cyanide chemicals manufacturing NESHAP. 
	We compared the NEI data to title V permits to confirm that the NEI included all emission points listed as subject to the NESHAP according to the permit. We evaluated latitudes and longitudes listed in the NEI to ensure their accuracy using satellite imagery. All of the latitudes and longitudes used in our dispersion modeling are in the modeling file used for the proposed rule, which is available in docket ID: EPA-HQ-OAR-2020-0532. Corrections were made to emission point characteristics for one non-category emission point that appeared to have erroneous stack velocity entered into the NEI. This emission point's stack velocity was corrected to a default maximum value. All corrections made to emission point parameters are documented in the modeling file, available in docket ID: EPA-HQ-OAR-2020-0532. 	
3.1 Facility-wide, Acute and Allowable Emissions
      As discussed in section 4.0, we determined that actual emission rates are a reasonable estimate for allowable emission rates and we estimated facility-wide emission rates using data pulled from the 2017 NEI. As discussed in section 5.0, we used a factor of 2 times actual emissions to estimate short-term emissions from process vents and equipment leaks for the acute assessment. We used factors of 4 and 10 times actual emissions to estimate short-term emissions from storage tanks and transfer racks, respectively. We estimated facility-wide emission rates using data pulled from the 2017 NEI.

4.0 MACT-Allowable Emissions Estimates

      Generally speaking, available emissions data that form the basis of the inputs to the risk modeling file dataset are estimates of the mass of hazardous air pollutants (HAP) emitted during a specified annual time period. These emissions are commonly referred to as actual emissions, and in some cases these actual emissions levels can be less than the emissions limitations in a maximum achievable control technology (MACT) standard. The emissions level allowed to be emitted by a MACT standard (e.g., the MACT "floor") is more commonly referred to as the MACT-allowable emissions level for purposes of residual risk review.
      
      The basic approach used to estimate MACT-allowable emissions for the cyanide source category was to, first, start with the available emissions data estimates representing actual emissions and assess whether these data were reasonable estimates of the levels allowed by the MACT standards for emissions sources regulated by the national emission standards for hazardous for air pollutants (NESHAP) for cyanide chemicals manufacturing (i.e., 40 CFR part 63, subpart YY). Table 2 summarizes the formats of the various MACT standards for the emissions sources addressed in the NESHAP for cyanide. 

Table 2: Formats of MACT Standards for the Cyanide NESHAP
Emissions Source
Form of Primary Standard
Storage Vessels
Equipment Standards, Performance Standards
Process Vents (all types)
Equipment Standards, Performance Standards, or Concentration Limit
Transfer Racks
Equipment Standards, Performance Standards, or Concentration Limit
Equipment Leaks
Work Practice Standards
      
      The ability to estimate MACT-allowable emissions from the actual emissions dataset is
largely dependent on the format of the standard for a given emissions source as well as types of
controls employed by the source. With respect to the various types of controls used within the
cyanide source category, none is more prevalent than the use of a flare as a combustion
control device; and a flare can be used to control emissions for a single emissions source, or as is
generally the case, to control emissions from multiple emission sources/emission source types.
Flares are designed to handle a large range of variable flowrates and compositions of
combustible waste gases and, within the cyanide source category, generally control
emissions from multiple emission source types. Consideration of this, along with not having a
specific limit on how much gas can be combusted in a flare (given that in many cases multiple
emissions sources are being controlled by this control device), makes it extremely difficult to
determine an allowable emission rate for flares. However, flares in the cyanide source
category are currently complying with certain design and operational requirements that are
generally expected to achieve 98 percent control. HAP emissions inventories for flares in the
cyanide source category are developed using engineering knowledge and in many
instances presume this 98 percent level of control (e.g., see as an example Technical Supplement
4: Flares in "2019 Emissions Inventory Guidelines," (TCEQ. 2020)), and the agency is unaware
of any data that suggests that flares in the cyanide source category are consistently
over-controlling HAP emissions beyond 98 percent. Thus, weighing all of these factors for flares, we believe that the actual emission levels are a reasonable estimation of the MACT-allowable emissions levels where the performance standards allow the use of a flare as a control device (e.g., storage vessels, process vents, and transfer racks).

      For storage vessels in the cyanide source category, sources may either choose
to comply with a 98 weight-percent reduction of hydrogen cyanide performance standard, a 20 ppmv hydrogen cyanide exit outlet concentration limit, or to comply with equipment standards (e.g., use a flare). For those storage vessels meeting the equipment standards, assuming the equipment is maintained properly, in good working condition, and in compliance with the NESHAP, there would be no difference in the actual emissions level and the MACT-allowable emissions level. For those storage vessels complying with the performance standard, actual emissions reductions could be greater than the MACT-allowable emissions reductions if facilities are using control devices that consistently achieve greater than the 98 weight-percent reduction. Based upon our review of title V permits, storage vessels that are complying with the performance standard are all using a flare as a combustion control device. As discussed previously, we believe that the actual emission levels for flares are a reasonable estimation of the MACT-allowable emissions levels. Therefore, for storage vessels in the cyanide source category, we believe that the actual emission levels are a reasonable estimation of the MACT-allowable emissions levels.

      For cyanide process vents, which are subject to a 98 weight-percent reduction of total
HAP performance standard or 20 ppmv total HAP outlet exit concentration limit, actual emissions reductions could be greater than the MACT-allowable emissions reductions if facilities are using control devices that consistently achieve greater than the 98 weight-percent reduction or 20 ppmv outlet exit concentration limit. Based upon our review of title V permits, we are unaware of any cyanide process vents that are not already being controlled by use of combustion controls, and almost all cyanide process vents that are being controlled are routed to a flare combustion control device. Thus, given our previous discussion about flares, for cyanide process vents in the cyanide production source category, we believe that the actual emission levels are a reasonable estimation of the MACT-allowable emissions levels.

      For transfer racks, which are subject to equipment standards or the same performance
standard or concentration limit as cyanide process vents, there would be no difference between
actual and MACT-allowable emissions for facilities in the cyanide source category
complying with the equipment standards (e.g., collecting HAP-containing vapors displaced from
tank trucks or railcars during loading and routing them to a process, fuel gas system, or vapor
balance system) given that these emissions are collected and further reprocessed elsewhere. For
those transfer racks complying with the performance standard, we reviewed title V permits and determined that facilities that are employing this option are using a flare as a
combustion control device. Thus, given our previous discussion about flares, for transfer racks in
the cyanide source category, we believe that the actual emission levels are a reasonable estimation of the MACT-allowable emissions levels.

      For equipment leaks, which are subject to work practice standards, there would be no
difference between actual and MACT-allowable emissions for facilities in the cyanide source category, provided the facilities are in compliance with the NESHAP as well as not conducting additional work practices proven to reduce emissions beyond those required in the rule. We are aware of only one rule in the state of Texas, The Texas Commission on Environmental Quality (TCEQ) Highly-Reactive Volatile Organic Compounds (HRVOC) Rule (i.e., 30 TAC Chapter 115, Subchapter H, Division 3), which may contain more stringent leak definitions and/or monitoring frequencies for certain pieces of equipment for the 3 facilities impacted by this rule. However, we note based on our review of this Texas rule that the specific facilities impacted in the Houston-Galveston-Brazoria area are still conducting a leak detection and repair (LDAR) program using EPA Method 21, that the vast majority of equipment, including almost all pieces of equipment in gas and vapor service that would tend to highly contribute to the overall equipment leak air emissions are complying with the same leak definition as in the cyanide NESHAP, and that the TCEQ HRVOC Rule generally requires quarterly monitoring whereas the cyanide rule has varying degrees of monitoring frequencies depending on the percentage of leaking equipment that could lead to either more stringent, the same, or less stringent amount of times for which an EPA Method 21 measurement and repair of a leaking component (if measured) must occur. Therefore, weighing all of these factors for equipment leaks, we believe that the actual emission levels are a reasonable estimation of the MACT-allowable emissions levels allowed by the standard for the source category.

5.0 Acute Risk Emissions Estimates

      To develop estimates of acute exposures in risk and technology review (RTR) rulemakings, the agency generally assumes the 1-hr emissions rate for any emission point could be 10 times higher than its average hourly emissions (calculated by dividing the actual emissions by 8760 hours per year) in situations where the EPA lacks sufficient information on hourly emissions for given emissions sources. The basis for this assumption was derived from an analysis of short term release information collected from a Texas study of facilities in a four-county area (Harris, Galveston, Chambers, and Brazoria Counties, Texas) which were then compared against routine emissions rates for an entire facility. The conclusions for this analysis were that hourly emissions from any single release event to the average annual volatile organic compound (VOC) release rate for an entire facility were seldom greater than a factor of 10. 

5.1 Approach to Derivation of Hourly Emissions Rates
      
For the cyanide source category, a number of specific factors can be considered with respect to certain emissions sources in the source category to help fine tune and derive a conservative hourly emissions rate multiplier to assess acute risk rather than use a default factor of 10. These specific factors include, but are not limited to: process knowledge, the modes of operation (e.g., continuous, batch, intermittent, etc.) of certain unit operations and their connection to emissions, and other specific factors that would affect variability in hourly emissions from a given emissions source (e.g., meteorological conditions for storage vessels). Thus, in some cases, a factor of 10 may overestimate emissions while in others it may underestimate emissions for the upper range of expected variability for certain emissions sources. As such, consideration of these relevant factors, if known, should be applied to more accurately assess acute risk. 

5.2 Acute Risk Factors for the Cyanide Source Category

Based on the approach described in this section, we determined that the acute risk multipliers identified in Table 3 should be used in lieu of assigning a default factor of 10 to estimate hourly emissions and assess acute risks for each emissions source in the cyanide source category. The reasoning for changing the acute multiplier from the default (if it was changed) is also described in Table 3.

Table 3: Summary of Acute Risk Multipliers Developed to Assess Acute Risks for the Cyanide Source Category
Emissions Source
Acute Multiplier
Reasoning for Acute Multiplier
Storage Vessels
4
For storage vessels, the primary factors that would lead to higher hourly rates of emissions (e.g., higher hourly breathing losses and working losses) include: high hourly loading operations of tanks, high wind speeds driving losses from fitting controls on tanks, and temperature (seasonal variability). It is expected that loading rates would vary by a factor of 2 during normal operations and that seasonal/meteorological variations would also vary by factor of 2, leading to an hourly multiplier of 4 for storage vessels.
Process Vents
2
For process vents, these vent streams would be associated with continuous operations and essentially be steady state. Typical source variability would be minimal given their continuous nature. Thus, an hourly multiplier of 2 is applied for this emissions source.
Transfer Racks
10
This factor is very site specific and depends on a number of factors including type of loading operation (e.g., submerged fill, splash loading, etc.), maximum hourly pumping rates, hours of operation for loading operations, and actual conditions (e.g., temperature and pressure) of loading operation. Thus, the default was applied.
Equipment Leaks
2
For fugitives from equipment leaks, we note that the current methods of estimating emissions make use of correlation equations in conjunction with EPA Method 21 readings that ultimately provide an hourly emission rate for the monitoring period in question. The actual emission rates estimated based on the direct EPA Method 21 readings are commonly divided by two to estimate the average emission rate between monitoring intervals (i.e., assuming the leak started mid-way between monitoring intervals as described in the emissions protocol). We expect the emission estimates from the direct EPA Method 21 readings to provide a direct measure of the maximum hourly emissions (as leak repair will be applied to reduce hourly emissions immediately after a monitoring cycle). Therefore, we applied an hourly multiplier of 2 to estimate maximum hourly rates from the annual average emission rates for this emissions source.

6.0 Uncertainties in Emissions Estimates
	We recognize that there are uncertainties associated with the emissions estimates developed for this proposed rule. Some possible areas of uncertainty include the following:
 Accuracy of the emission point parameters entered into the NEI.
 Possible overestimation of source category emissions if emissions subject to the cyanide chemicals manufacturing NESHAP are combined with non-category emissions in NEI entries.
 Uncertainty associated with estimating facility boundaries using satellite imagery.  
      While these uncertainties may have a small effect on dispersion modeling results, we expect that it would likely bias the results towards a more conservative estimate of risk. We included a review tool to allow stakeholders to provide corrections to the parameters used in our dispersion modeling to support the proposed rule in docket ID: EPA-HQ-OAR-2020-0532.
7.0	Technology Review 
 7.1 Requirements of Section 112(d)(6) of the CAA
Section 112 of the Clean Air Act (CAA) requires the EPA to establish technology-based standards for sources of HAP. These technology-based standards are often referred to as maximum achievable control technology, or MACT, standards. Section 112 also contains provisions requiring the EPA to periodically review these standards. Specifically, paragraph 112(d)(6) states:
      (6) REVIEW AND REVISION.  -  The Administrator shall review, and revise as necessary (taking into account developments in practices, processes, and control technologies), emissions standards promulgated under this section no less often than every 8 years.
      
 Description of the Cyanide Chemicals Manufacturing Source Category and Requirements of the Current NESHAP
The current National Emissions Standards for Hazardous Air Pollutants (NESHAP) for the cyanide chemicals manufacturing source category were promulgated on July 12, 2002 (67 FR 46258) as 40 CFR part 63, subpart YY. The NESHAP applies to affected sources of HAP at cyanide chemicals manufacturing facilities that are major sources of HAP. The affected source covered by this subpart is each new, reconstructed, or existing facility that manufactures cyanide chemicals using an Andrussow process unit, a BMA process unit, a sodium cyanide process unit, or a Sohio hydrogen cyanide process unit. We identified 13 cyanide chemicals manufacturing facilities that are subject to the NESHAP. 

7.3 Developments in Practices, Processes, and Control Technologies
For the purposes of this technology review, a "development" was considered to be a(n): 
 Any add-on control technology or other equipment that was not identified and considered during development of the original MACT standards;
 Any improvements in practices, processes, or add-on control technology (that were identified and considered during development of the original MACT standards) that could result in significant additional emissions reduction;
 Any work practice or operational procedure that was not identified or considered during development of the original MACT standards;
 Any process change or pollution prevention alternative that could be broadly applied to the industry and that was not identified or considered during development of the original MACT standards;
 Any significant changes in the cost (including cost-effectiveness) of applying controls (including controls the EPA considered during the development of the original MACT standards).

We reviewed the original NESHAP and supporting documents and our conclusions reached in those analysis regarding technologies reviewed have not changed. We are unaware of any information to indicate that the effectiveness or costs of the technologies evaluated at that time have changed in a way that would be considered a "development". We also conducted a review of EPA's Technology Transfer Network (TTN) Clean Air Technology Center  -  RACT/BACT/LAER Clearinghouse (RBLC) database. The results of this analysis are presented in the following section.
 7.4	RACT/BACT/LAER Clearinghouse Search
Under EPA's "New Source Review" (NSR) program, if a company is planning to build a new plant or modify an existing plant such that air pollution emissions will increase by a large amount, then the company must obtain an NSR permit. The NSR permit is a construction permit which requires the company to minimize air pollution emissions by changing the process to prevent air pollution and/or installing air pollution control equipment.
The terms "RACT," "BACT," and "LAER" are acronyms for different program requirements under the NSR program. RACT, or Reasonably Available Control Technology, is required on existing sources in areas that are not meeting national ambient air quality standards (i.e., non-attainment areas). BACT, or Best Available Control Technology, is required on major new or modified sources in clean areas (i.e., attainment areas). LAER, or Lowest Achievable Emission Rate, is required on major new or modified sources in non-attainment areas. BACT and LAER (and sometimes RACT) are determined on a case-by-case basis, usually by State or local permitting agencies
The EPA established the RACT/BACT/LAER Clearinghouse, or RBLC, to provide a central data base of air pollution technology information (including past RACT, BACT, and LAER decisions contained in NSR permits) to promote the sharing of information among permitting agencies and to aid in future case-by-case determinations. However, data in the RBLC are not limited to sources subject to RACT, BACT, and LAER requirements. Noteworthy prevention and control technology decisions and information are included even if they are not related to past RACT, BACT, or LAER decisions.
The RBLC permit data base contains over 5,000 determinations that can help you identify appropriate technologies to mitigate most air pollutant emission streams. The RBLC permit data base was designed to help permit applicants and reviewers make pollution prevention and control technology decisions for stationary air pollution sources, and includes data submitted by several U.S. territories and all 50 States on over 200 different air pollutants and 1,000 industrial processes.
The RBLC provides several options for searching the permit database on-line to locate applicable control technologies. Searches of the RBLC database were conducted in October 2020. The permit dates for the searches used the NESHAP part 63 subpart YY promulgation date (July 12, 2002) through October 22, 2020. 
To search the database for applicable sources we used the pollutant search feature for all of the primary HAP emitted by cyanide chemicals manufacturing facilities. The result yielded 5-10 entries per pollutant. Of these entries, one was potentially applicable to the cyanide chemicals manufacturing source category but the emissions limits in the determination reflected performance already required by the NESHAP (98% destruction efficiency using a flare). Upon review, there is no new information from the RBLC search for the technology review.
8.0 References

 EPA's Enforcement and Compliance History Online (ECHO) database. Accessed at: 
https://echo.epa.gov/
 Various state environmental air agency websites for Title V permit.
 EPA's Multisystem Search System. Accessed at: https://www3.epa.gov/enviro/facts/multisystem.html
 Original NESHAP Support Documents, available at docket ID: EPA-HQ-OAR-2004-0041.
 U.S. EPA. RACT/BACT/LAER Clearinghouse. Available at: https://www3.epa.gov/ttn/catc/rblc/htm/welcome_eg.html
