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tkelley on DSKBCP9HB2PROD with PROPOSALS

Federal Register / Vol. 86, No. 5 / Friday, January 8, 2021 / Proposed Rules Section 112 of the CAA generally directs that standards be specified as numerical emission standards, if possible. However, if it is determined that it is not feasible to prescribe or enforce a numerical emission standard, CAA section 112h indicates that a design, equipment, work practice, or operational standard may be specified, provided the criteria of CAA section 112h2 are met. Those criteria define not feasible to prescribe or enforce an emission standard to mean any situation in which the EPA determines that: 1 A HAP or pollutants cannot be emitted through a conveyance designed and constructed to emit or capture such pollutant, or that any requirement for, or use of, such a conveyance would be inconsistent with any federal, state, or local law, or 2 the application of measurement methodology to a particular class of sources is not practicable due to technological and economic reasons. Most fugitive chlorine emission sources at mercury cell chlor-alkali plants are associated with cell rooms. Potential fugitive chlorine emissions are also located in the chlorine processing area. For both the cell room and the chlorine processing area, the fugitive chlorine emissions are primarily due to equipment leaks. Due to the nature of equipment leaks i.e., low flow rate, occurring from individual pieces of equipment, high variability in time, and location of occurrence it is technologically and economically impractical to collect the emissions and route them to a control device. As such, we believe that it is not feasible to either prescribe or enforce numerical emission limits for fugitive chlorine emissions from cell rooms or any other location at the facility, under both of the criteria set forth in CAA section 112h2A and B. Consequently, these proposed standards address fugitive chlorine emission sources at existing mercury cell chlor-alkali production facility affected sources through the establishment of work practice standards. As the NESHAP already effectively prohibits the construction or reconstruction of a mercury cell chloralkali production facility, there is no need to establish a new source MACT
floor for fugitive chlorine emissions.
There are many incentives for the identification and correction of chlorine leaks and to reduce fugitive chlorine emissions throughout the mecury cell chlor-alkali plant. First, chlorine is a primary product of the process, so lost chlorine equals lost product and lost profit. Second, chlorine, particularly wet chlorine, is very corrosive to
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process equipment. Therefore, prompt repair of chlorine leaks reduces damange to process equipment. These corrosive properties also mean that small leaks can quickly become large leaks, which could result in chlorine releases that are dangerous to plant workers and the surrounding community. For these reasons, the Westlake, West Virginia, facility has a program in place to identify and repair fugitive chlorine leaks across the plant.
Specifically, Westlake operators perform inspections during each shift to identify leaks of chlorine. Therefore, leaks are detected and corrective actions implemented to minimize and reduce any fugitive chlorine emissions. Based on available information, we understand that the method Westlake uses to identify leaks of chlorine from each piece of equipment is olfactory observations of chlorine gas. If leaks are detected using the olfactory method, the facility takes immediate actions to fix the identified leaks. Furthermore, Westlake has chlorine sensors installed and operated throughout the relevant process units. If one of these sensors measures a chlorine concentration of 2
parts per million by volume ppmv or greater, the facility takes action to identify and fix leaks. Since there is only one currently operating mercury cell chlor-alkali plant in the country, the MACT floor for existing sources is represented by the practices in place at the Westlake facility to reduce chlorine fugitive emissions.
As noted above, it is technologically and economically impractical to collect the emissions from every potential leak source at a facility and route them to a control device. The cell room building is generally under negative pressure and the air is routed through the roof vents.
As a beyond-the-floor option for fugitive chlorine emissions, we considered requiring the air from the roof vents to be routed to a scrubber or other control device. However, the volume of the air flow from the Westlake cell room is over 700 million cubic feet per day, or almost 500,000 cubic feet per minute. It would be technically infeasible for any control device to handle this volume of gas throughput. Therefore, we rejected this beyond-the-floor option.
Therefore, we are proposing the MACT floor level of control which represents the procedures in place at the Westlake, West Virginia, site. We developed the work practices in the proposed amendments to reflect these procedures, along with associated recordkeeping and reporting requirements to demonstrate compliance. Specifically, we are proposing that facilities must identify
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and inspect each piece of equipment that contains chlorine gas with a concentration of at least 5 percent chlorine by volume throughout the mercury cell chlor-alkali production facility affected source for leaks at least once each 12 hours. We are requesting comment on whether the 5 percent by volume threshold for defining equipment that must be inspected for chlorine leaks is the appropriate threshold for identifying equipment with the potential to generate fugitive emissions of chlorine gas. Equipment that is under negative pressure would be excluded from this requirement. The method that we are proposing to identify leaks of chlorine from each piece of equipment is olfactory observations of chlorine gas. However, we solicit comments regarding other methods e.g., auditory or visual that should also be allowed as a method to identify leaks.
When a leak is detected, we are proposing that a first attempt at repair be conducted within 1 hour of detection and that the leak be repaired within 1
day of detection. We are proposing that a leak is repaired when the evidence of the olfactory observation is eliminated.
Additionally, we are proposing that chlorine sensors be installed and operated continuously at least one measure every 15 minutes throughout the affected source. Each time one of these sensors measures a chlorine concentration of 2 ppmv or greater, the proposed rule would require a complete inspection for leaks of all equipment containing 5 percent chlorine by volume within 1 hour of detection. The chlorine sensors that the facility uses must have a detection limit of 2 ppm or less.
Furthermore, we propose the sensor must be calibrated and maintained following the manufacturers recommendations.
We are requesting comment on several aspects of the proposed requirements related to the use of chlorine sensors to identify leaks that may occur between the 12-hour regular inspections. First, we are requesting comment on where these ambient sensors should be located to ensure that chlorine emissions are detected by the ambient monitors. The proposed rule requires that they be placed throughout the mercury cell chlor-alkali manufacturing facility affected source, which includes all cell rooms and ancillary operations used in the manufacture of product chlorine, product caustic, and by-product hydrogen. We are requesting comment whether the rule should specify areas of the facility where sensors should be located and whether it should specify a
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