Advanced Silicon Materials Inc. - Executive Summary |
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Facility Information Advanced Silicon Materials Inc.'s (ASiMI) Butte, Montana facility is a manufacturer of silane and polycrystalline silicon for the electronics industry. The facility is new, having operated for approximately 1 year at the time of this plan submittal. ASiMI occupies an 250-acre plot, which is located aproximately 7 miles southwest of Butte, Montana on Rick Jones Way. The neighborhood is predominantly uncultivated land. Process Overview The ASiMI facility in Butte, MT is comprised of three different production units: 1) Silane, 2) Poly Reaction, and 3) Product Finishing. The Silane Unit, through a series of chemical reactions and separation steps, converts metallurgical silicon and hydrogen to a high purity silane gas. Ammonia refrigeration is used in the separation steps and for silane refrigeration. Intermediates produced in the silane unit are trichlorosilane and dichlorosilane. Some of the silane will packaged in tube trailers and modules once a loa ding facility is constructed and temporarily stored prior to sale. The Poly Reaction Unit uses the majority of the silane and converts it into hydrogen and polycrystalline silicon. The hydrogen is recycled back to the Silane Unit and the polycrystalline silicon is forwarded to the Product Finishing unit for mechanical processing and packaging. There is one covered "process" as defined by the RMP regulations at the Butte facility. This process includes the Silane and Poly Reaction production areas which are interconnected, a refrigeration unit contained within the Silane production area, and the future silane module storage area which will be adjacent to the Silane production area. Together these areas are identified as the Polysilicon Manufacturing process. This risk management plan uses "predictive filing" to account for variables in the total quantities of chemicals at the facility, and for planned changes to the facility. With predictive filing, the maximum quantity of chem icals that would be in the process at any one time is specified in this plan. Chemicals: Advanced Silicon has identified the following chemicals and maximum on-site quantities, which trigger compliance with the Risk Management Program (RMP) standards, 40 CFR Part 68: Trichlorosilane 340,000 pounds Silane 330,000 pounds Dichlorosilane 83,000 pounds Hydrogen 9,600 pounds Ammonia 12,000 pounds Hydrogen is also included in the plan, though the maximum quantity on site is less that the regulated threshold of 10,000 pounds. All RMP applicable chemicals at the source except ammonia are classified as flammables. Ammonia is classified as a toxic. In addition to the above RMP-covered chemicals, Advanced Silicon has identified other potentially hazardous chemicals which could have either onsite or offsite impacts. Risks from both these non RMP-covered chemicals as well as the RMP-covered chemicals are minimized using similar design standards, procedures, controls, mitigation measu res, and emergency response procedures. Advanced Silicon is also working with the local Department of Emergency Services and the Local Emergency Planning Committee (LEPC) to coordinate emergency planning and emergency response for all potentially hazardous chemicals. Worst-Case Scenarios: Four hypothetical worst-case flammable scenarios and one hypothetical worst-case toxic scenarios were identified and developed for the facility in accordance with RMP standards: The full hydrogen storage tank releases its entire contents, 8,500 pounds of hydrogen, which explodes with 10% explosion efficiency and no mitigation. The calculated distance to 1-psi overpressure is 0.23 miles. Public receptors within that radius are uncultivated fields, with no population. A full liquid silane storage tank releases its entire contents, 23,000 pounds of silane, which explodes with 10% explosion efficiency and no mitigation. The calculated distance to 1-psi overpressure is 0.23 miles. Public receptor s within that radius are uncultivated fields, with no population. A silane tube trailer releases its entire contents, 13000 pounds of silane, which explodes with 10% explosion efficiency and no mitigation. The calculated distance to 1-psi overpressure is 0.19 miles. Public receptors within that radius are uncultivated fields, with no population. A polycrystalline silicon furnace releases its entire contents of hydrogen and silane, totaling 36 pounds, which explodes with 10% explosion efficiency and no mitigation. The calculated distance to 1-psi overpressure is 0.03 miles. Public receptors within that radius are the facility employee parking lot,with no population. The ammonia high pressure receiver fails releasing its entire contents, 5000 pounds of ammonia, which vaporizes and disperses in the environment, with no mitigation. Modeling is performed with the parameters of 1.5 meters/second wind speed, rural topography and class F atmospheric stability. The modeled distance to the EPA-defined concentration endpoint of 0.14 milligrams per liter is 0.50 miles. Public receptors within that radius are uncultivated fields, with no population. Alternative Scenarios Three hypothetical alternative flammable scenarios and one hypothetical alternative toxic scenario were identified and developed for the facility in accordance with RMP standards: A silane tube trailer safety device fails and releases the entire tube contents, 1700 pounds of silane, the contents of the gas jet (71 pounds) explodes with 100% efficiency and no mitigation. The calculated distance to 1-psi overpressure is 0.07 miles. Public receptors within that radius are uncultivated fields with no population. A hydrogen superheater vessel fails and releases the entire vessel contents, 5 pounds of hydrogen, which explodes with 3% efficiency and no mitigation. The distance to 1-psi overpressure is 0.01 miles. There are no public receptors within that radius, only on-site impact. The conservat ive efficiency selection of 3% was based on published literature indicating an efficiency of 2% is typical for vapor cloud explosions. During a dichlorosilane reactor bed change out, the bed is drained but not properly purged and releases the entire remaining contents of 2300 pounds of dichlorosilane which evaporates and explodes with 3% explosion efficiency, with no mitigation. The distance to 1-psi overpressure is 0.04 miles. Public receptors within that radius are uncultivated fields with no population. The conservative efficiency selection of 3% was based on published literature indicating an efficiency of 2% is typical for vapor cloud explosions. The piping fails on the discharge of the lube oil separator on the refrigeration, releasing anhydrous ammonia vapor to the atmosphere where it disperses into the environment, with no mitigation. The entire system quantity, 9800 pounds of ammonia, is released at a rate of 1500 pounds per minute for 6.4 minutes. Modeling is pe rformed with the parameters of 3 meters/second wind speed, rural topography and class D atmospheric stability. The modeled distance to the EPA-defined concentration endpoint of 0.14 milligrams per liter is 0.27 miles. Public receptors within that radius are uncultivated fields, with no population. Accident History In the past five years Advanced Silicon has experienced 1alleged accidental release as defined by the RMP standards. This release consisted of less than 1 ounce of trichlorosilane. There were no known on-site or off-site impacts, although two contractor employees working in the facility at the time alleged irritation from the release and much later sought medical treatment. Accidental Release Prevention Program Advanced Silicon's accidental release prevention program is based on the following essential elements: hazard reviews of equipment and processes, preventative and predictive maintenance programs, a management of change program, operator job certification and performance testing, accurate operating procedures, internal and external auditing and inspection programs, accident and near-miss investigations, etc. Advanced process monitoring and control systems are in use at the facility, and critical parameters are monitored with duplicate instrumentation. Loss of utilities is protected against through the use of installed and routinely tested back-up systems. Engineering and design standards ensure materials and equipment meet industry specifications. Advanced Silicon is known as an industry leader in silane handling safety. Emergency Response Program Advanced Silicon's emergency response program has been coordinated with the local Department of Emergency Services and LEPC. The program includes information on locations, quantities, and associated hazards of materials at the facility, as well as fixed and portable methods for containment and/or suppression of spills and releases, internal and external notification and communications proc edures, alarm systems and evacuation plans. The facility itself is designed with numerous mitigating features, including containment and diking, deluge systems for fire and vapor suppression, strategically-placed fire hydrants and fire monitors, and emergency scrubber systems. Automatic and manual shutdown systems as well as automatic isolation valves are in place. Back-up firewater pumps are installed. Emergency equipment is routinely maintained and tested. In addition, Advanced Silicon maintains a highly skilled emergency response team on-site 24-hours a day. The team performs realistic monthly drills and exercises, covering a variety of response scenarios such as spill containment and cleanup, vapor suppression, fire fighting, and response to injuries. The team routinely attends professional fire-fighting training to stay current with fire-fighting techniques. Planned Changes to Improve Safety Advanced Silicon continues to seek and identify opportunities to improve safety t hrough process hazard analyses, safety reviews and inspections, internal and external audits, incident and near-miss investigations, employee and safety committee suggestions, etc. For example, an internal audit is scheduled for September, 1999 to evaluate the PSM and RMP programs and identify opportunities to improve safety. |