Selection And Simulation Study To The Worst Credible Accident Secenarios Of Refinery Enterprise

Fires, explosions and other accidents in refinery enterpise often are devastating and catastrophic, a serious threat to the safety of people’s lives and property. At present, many countries have to strengthen safety management and risk assessment of refinery enterprises, in order to prevent the occurrence of accidents. The choice of the accident scenarios has an important influence on the layout of the plant, the safety design, the calculation of the safety protection distance. It is also the key to t he risk assessment, which directly determines whether the evaluation results are credible or not. Therefore, the urgent need to further develop the research of accident scenarios selection and simulation to refinery enterpise, provide important theoretical guidance and practical basis for the promotion of enterprise safety.This paper is based on the analysis of the existing accident scenarios（the worst accident scenarios, the maximum credible accident scenarios and reference accident scenarios）, put forward the concept of the worst credible accident scenarios, and establishes the principle and procedure of the worst credible accident scenarios selection. The process first determines plant important dangerous equipment, through the bow-tie analyse the accidents of important dangerous equipment that might occur, to guarantee the serious consequences of the accident scenarios; Secondly, using the improved method of identifying crediblity factor in maximum accident scenarios, to calculate the credibility of the accident scenarios, guaranting the credibility. Finally, through compare the credibility of various accident scenarios to determine the worst credible accident scenarios.The selection procedure of the worst credible accident scenarios will be applied to pulverized coal gasification device of refinery enterprises in this paper. The equipment with high risk level was selected by the reference of hazardous substances, which were the methanol storage tank V6501, the CO₂ absorption tower C-2202, the washing tower C-1301 A and the gasification furnace R-1301 A. According to the bow-tie structure and the calculation of the credible factor, the worst credible accident scenarios are the fire of the methanol storage tank, the vapor cloud explosion of the absorption tower, the steam cloud explosion of the washing tower and the mechanical explosion of the gasification furnace. An example shows that the result obtained by the worst credible accident scenario s is reliable and credible.Finally, this paper chooses the leakage accidents oftypical equipment as the research object. Simulation and analysis of leakage and diffusion process of methanol storage tank and CO₂ absorption tower by accident simulation software Fluidyn-PANACHE, getting the distribution of the concentration of toxic gases and influence area around, also found that, if the equipment leaks and promptly cut off the connection with other devices, the gas in the air does not reach the explosion limit, to prevent explosion.