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Ammonia Storage Issues
THE ISSUE
As a result of the Clean Air Act, many power
generation plants have installed various types of emissions control technologies. One of these technologies is the
use of anhydrous ammonia in selective catalytic reduction units, which combine ammonia and a catalyst to convert the nitrogen oxides into nitrogen gas and water vapor.
However, there are a number of regulations governing the use and storage of anhydrous ammonia.
Anhydrous Ammonia is toxic to humans. Effects of inhalation of anhydrous ammonia
range from lung irritation to severe respiratory injuries, with possible fatality at higher concentrations.
Anhydrous ammonia also is corrosive and can burn the skin and eyes. Liquefied anhydrous ammonia is stored
as a liquid and has a boiling point of minus 28 degrees Fahrenheit. At this temperature it can cause
freezing burns. Liquid anhydrous ammonia expands 850 times when released to ambient air and can form large
vapor clouds. Also, liquid anhydrous ammonia if accidentally released, may aerosolize (i.e., small liquid
droplets may be released along with ammonia gas) and behave as a dense gas, even though it is normally
lighter than air.
Anhydrous ammonia may also cause water vapor to condense in the air forming a visible white cloud. Therefore,
when anhydrous ammonia is released to the air, it may travel along the ground in a cloud instead of
immediately rising into the air and dispersing. This dense gas behavior may increase the potential for
exposure of workers and the public.
Anhydrous ammonia storage containers have particular specifications as required by the Department of
Transportation (DOT). Storage tank specifications for anhydrous ammonia ensure that it is stored properly
as a pressurized liquid and a corrosive chemical. For example, some storage containers for anhydrous
ammonia must have rated pressure relief devices to reduce the likelihood of over pressurization of the
container. Because anhydrous ammonia is corrosive, specific valves and hoses that do not readily corrode
have to be used.
Pure anhydrous ammonia vapors can become an explosion hazard when in a confined space at concentrations
between 16 and 25% by volume. Anhydrous ammonia can be recognized by its pungent odor. Odor threshold
varies with the individual but ammonia can usually be detected at concentrations above 5 ppm.
Concentrations above 100 ppm are uncomfortable to most people; concentrations in the range of 300 to 500
ppm will cause people to leave the area and are immediately dangerous to life and health.
OSHA requirement for storage and handling of anhydrous ammonia under § 1910.111 (c)(6) state that "valves,
regulating, gauging, and other appurtenances shall be protected against tampering and physical damage.
STATUES AND REGULATIONS
The following is a list of federal statutes and regulations related to process safety, accident prevention, emergency planning, and release reporting of anhydrous ammonia.
Clean Air Act (CAA)
General Duty Clause [Section 112(r)(1) of the Act]- Facilities handling extremely hazardous chemicals (including anhydrous ammonia) have a general duty to assess hazards, design and maintain a safe facility, and minimize the consequences of accidental releases.
Risk Management Program (RMP) Rule [40 CFR 68] - Facilities that have anhydrous ammonia in quantities greater than 10,000 pounds are required to develop a hazard assessment, a prevention program, an emergency response program, and submit a risk management plan to EPA.
Emergency Planning and Community Right-To-Know Act (EPCRA)
Emergency Planning [40 CFR Part 355] - Facilities that have 500 pounds or more of ammonia must report to their LEPC and SERC and comply with certain requirements for emergency planning.
Emergency Release Notification [40 CFR Part 355] - Facilities that release 100 pounds or more of ammonia must immediately report the release to the LEPC and to the SERC.
Hazardous Chemical Reporting [40 CFR Part 370] - Facilities that have ammonia at or above 500 pounds must submit an MSDS to their LEPC, SERC, and local fire department and comply with the Tier I/Tier II inventory reporting requirements.
Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA)
Hazardous Substance Release Reporting [40 CRF 302] - Facilities that release 100 pounds or more of ammonia (other than the normal application of a fertilizer) must immediately report the release to the National Response Center (NRC) 1-800-424-8802.
DOT
The Department of Transportation (DOT) [49 CFR 100-180] - Research and Special Projects Administration has requirements covering the transportation of anhydrous ammonia containers.
OSHA
Process Safety Management (PSM) Standard [29 CFR 1910.119] Anhydrous ammonia is listed as a highly hazardous substance. Facilities that have ammonia in quantities at or above the threshold quantity of 10,000 pounds are subject to a number of requirements for management of hazards, including performing a process hazards analysis and maintaining mechanical integrity of equipment. The PSM requirements do not apply to retail facilities per 1910.119(a)(2).
Hazard Communication [29 CFR 1920.120] - Requires that the potential hazards of toxic and hazardous chemicals can be evaluated and that employers transmit this information to their employees.
Storage and Handling of Anhydrous Ammonia [29 CFR 1910.111] - Requires standards for design, construction, location, installation, and operation of anhydrous ammonia systems.
MODEL REGULATORY LANGUAGE
American National Standard Safety Requirements for the Storage and Handling of Anhydrous Ammonia (ANSI K61.1) - Sponsored by CGA, this standard includes standards for the location, design, construction, and operation of
anhydrous ammonia systems. Sections on refrigerated storage systems, systems mounted on farm vehicles, tank
motor vehicles, and tank railcars for transportation purposes are included. This standard does not apply
to ammonia manufacturing plants, or refrigerating or air conditioning systems.
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