Design of mitigation systems for indoor and outdoor ammonia releases

The paper describes the design of two mitigation systems adopted by an important food company, which uses ammonia for its refrigeration plant. The results of an accurate risk analysis identified the critical risk areas and the alternative mitigation systems. Two different approaches were used for indoor and outdoor accidents. A specific model was developed to estimate the time concentration of ammonia profile after a release inside an enclosure. It was used to minimise the amount of releasable ammonia by the insertion of automatic valve devices along the pipe containing pressurized ammonia. The approach for outdoor accidents led to the design of a fluid curtain capable of intercepting and absorbing the released ammonia cloud. Another specific model, which takes into account the two-phase character of an ammonia cloud, was devised in order to calculate the water flow rate needed to ensure adequate absorption efficiency. © 2003 Elsevier Science Ltd. All rights reserved.