Dynamic Risk Assessment Of Coal Water Slurry Gasification Unit Based On DBN

As one of the main ways of clean and efficient utilization of coal in China,coal gasification technology is currently in the transformation stage of industrial high-quality development.Coal-water slurry gasifier has compact space layout and rigorous operating conditions,which is easy to cause dangerous accidents such as explosion,leakage and poisoning.It will not only cause certain economic losses,but also seriously threaten personal safety.In order to strengthen the safety risk management of coal gasification production,a dynamic risk assessment method based on dynamic Bayesian network（DBN）is proposed to quantitatively analyze the accident risk of coal-water slurry gasification.Firstly,according to the hazard analysis of the coal gasification unit,two dangerous accident scenarios,gasifier overtemperature and syngas leakage,were determined as the research objects.Considering the timing relationship of risk factors,the dynamic bow-tie model（DBT）is used to establish the causal evolution model of accident scenarios.Then,the DBT model is transformed into DBN which introduces time series to establish dynamic risk evolution model.The parameter information of DBN was determined according to the fuzzy evaluation method as well as the probability time distribution of failure factors,thus the risk impact of accident scenario is inferred bidirectional.Finally,the dynamic probability change trend of accident and consequence for gasifier over-temperature and syngas leakage is predicted,and the critical events affecting the accident in different periods are determined.The results show the influence of gasifier over-temperature is mainly manifested in the abnormal fluctuation of the oxygen-carbon ratio and pulping section,the leakage of syngas is mainly caused by scouring and wear along the pipeline.At the same time,the accident risk has been significantly reduced under the influence of equipment maintenance factors.Therefore,this paper optimizes the periodic maintenance cycle of key equipment and gives risk response measures from both equipment and human factors based on the results of posterior reasoning.Dynamic risk assessment method based on DBN can intuitively describe the dynamic impact of risk factors,deduce the weaknesses of the system and avoid analysis errors caused by ignoring the impact of time factors.The research results are helpful for the production enterprises to make maintenance plans and or prevention decision,and provide theoretical basis for the safety risk management of coal gasification units.