Quantitative Risk Analysis and Consequence Modeling the Explosion of Methane Storage Tanks in a Gas Refinery

Introduction: The major and high quality fossil fuels (oil and gas) have been widely used in various industries such as refineries. It is even though there are very high potentials for hazards in refineries and in the methane gas process, in particular, causing human and financial losses as a result of hazards leading to accidents. This study was aimed to quantitatively analyze the explosion risk of methane gas tanks in a refinery by analyzing the risk, and modeling and evaluating the related consequences. Materials and Methods: Hazard analysis by PHA (Primarily Hazard analysis) was used to choose the worst-case scenario. Then, the causes of the scenario and its probability were determined by FTA (fault tree analysis) Finally, PHAST (Process Hazard Analysis Software Tool) software package was employed to model and analyze the consequences. Results: Based on the results concluded by the preliminary hazard analysis, the explosion of methane gas tank (V-100) was selected as the worst-case scenario at the refinery. The qualitative fault tree showed three factors including mechanical, process, and human failures contribute to gas leakage. The leakage size and weather conditions were effective on the distance of explosion overpressure. Using the consequence modeling, including the discharge, dispersion, and scenario consequence modeling, vapor cloud explosion (VCE) was considered as the major consequence of the accident. Finally, to evaluate the consequence, probit equations were used to quantify losses and the percentage of fatalities due to the methane gas leakage and explosion occurrence. The maximum number of fatalities caused by explosion was 16 persons. Conclusions: In conclusion, the methane gas vessel in the refinery can be considered as the main source of hazard, therefore elimination of the mechanical failures, blast proofing against the explosions, implementation of the safety rules and procedures and personal protection equipment are proposed for decreasing the probable losses and fatalities.