Automatic Synthesis of Robust Accident Scenarios for Chemical Processes

Abstract

A new strategy for producing robust accident scenarios in quantitative risk assessment, which is performed in the process design or operation steps, is proposed. Worldwide chemical processes are in need of off-site risk assessment as well as the on-site risk management. Most governments over the world require industrial companies to submit proper emergency plans through the off-site risk assessment. However, there have been no systematic approaches or criteria for generating virtual accident scenarios reasonably, and it is very difficult to get the unified or coherent assessment results. To get over these shortcomings, this study proposes a strategy for analyzing process elements and then selecting and generating an accident scenario that simulates the worst accident most likely to happen, which should be given foremost consideration. The proposed scenario reasoning scheme consists of three types of knowledge base and four reasoning algorithms. The scenario reasoning structure consists of the following steps: macro decomposition, micro decomposition, equipment analysis, scenario selection, and the consequence analysis. In the macro decomposition, a process unit is selected through its function and the meteorological condition around the area. In the second step, the equipment behavior which consists of its property, flow rate, operating condition, safety devices, age, accident history and repaired history is analyzed using an equipment-screening algorithm, which is a sequential reasoning method. The analyzed process elements are ranked and risk grades are determined. According to the grades, risk assessment is performed. The result of the analysis enhances the reliability of the generated risk scenario and prevents the risks from being overestimated. The obtained result should be more helpful in the proper process design and emergency planning.