Safety hazards associated with air-emission controls



Air-emission controls have been installed in refineries since 1990 to comply with environmental regulations such as Benzene NESHAP and the Clean Air Act. Companies have experienced incidents associated with these air-emission controls, but the extent of the problem could not be quantified. In this paper, we present the results of a survey of the member companies of API's Safety and Fire Protection Subcommittee (SFPS) to determine the number and type of air-emission controls which have been installed, and the types of incidents which they have experienced. The survey was completed in February 1998.

We obtained responses from eight SFPS member companies, including 16 refineries, 1 gas plant, 2 chemical plants and 1 marketing terminal.

A total of 2,110 air-emission controls have been installed at these facilities and 70 incidents associated with these controls have been reported. Of the 70 incidents a number involved recurring events associated with the same air-emission control, so when these events are deleted, only 32 unique incidents remain. 15 of these unique incidents resulted in injury or significant property damage.

Carbon canisters are the most common air-emission control installed (769) and there have been 10 unique incidents associated with carbon canisters/beds, of which 5 resulted in injury or significant property damage. Given the prevalence of carbon canister installations and the associated incidents, the SFPS Emission Control Safety Work groups decided to focus mitigation/prevention efforts on carbon canisters.

If carbon beds are overloaded with volatile organic compounds (VOCs) or highly reactive materials, they can overheat and catch fire, which can then provide an ignition source for VOC vapors.

The industry however does not appear to be fully aware of the hazards associated with the use of carbon canisters and the limitations on their use. In many installations safeguards to prevent fires or explosions may be necessary. Typical safeguards include:

  • pre-wet new canisters to prevent excessive heat buildup.

  • avoid applications where adsorption of highly reactive chemicals such as ketones, aldehydes and organic acids may occur.

  • avoid VOC concentrations in excess of 10,000 ppmv.

  • provide flame arrestors to pre vent flashback to VOC sources.

  • provide vacuum breakers directly on process equipment to prevent air ingress into hot carbon canisters.

We believe that the widespread use of carbon canisters presents the need to develop appropriate guidelines to prevent further incidents.

The objective of this project was to research and evaluate the safety hazards associated with certain air-emission control systems used in the petroleum industry and to develop recommendations to address these hazards.