Quantitative Risk Assessment For Domino Effect Of Dust Explosion

With the rapid development of modern industry,the level of mechanization and scale of enterprises had been increasing.The risks involved in production were becoming more and more frequent,and the domino effect caused disastrous consequences.The realistic accident situations were complex.Safe disposal measures may become a source of risk and lead to environmental accidents.Environmental pollution control facilities may also become dangerous sources and lead to safety accidents.Safety accidents and environmental accidents transfer each other,leaded to a double upgrade of regional safety risks and environmental risks.However,in our country,due to the lack of understanding of the domino effect,risk accidents were regarded as single events.The possibility of occurrence of a chain accident was ignored and the hazard was underestimated.The environmental and security risk prevention and control systems were artificially fragmented,which further exacerbated the difficulty of risk management.Especially in the powder industry,dust collectors were connected to production equipment through pipelines.Major domino accidents were happened from time to time.The risk situation was severe,but the corresponding risk assessment system was not perfect.Based on international research achievements in domino effect risk assessment and dust explosion,this study introduced the concept of domino effect,pointed out the mechanism of propagation of dust explosion with domino effect,and comprehensively considered environmental risks and safety risks,and established a set of dust explosion risk assessment method.The identification process of domino accident chain with dust explosion as the initial accident was discussed.Environmental protection equipment and production equipment were fully considered.Based on production process flow,and dust explosion formation conditions,and unit characteristics,a domino accident chain was established(i.e.,Bayesian network structure).The probability of domino accident based on Bayesian network was calculated.After effectively representing the possible propagation path of the domino effect of dust explosion accidents,the conditional probability table was calculated by the initial accident probability and escalation probability,and was assigned to each node.After that,the probability of occurrence of each unit's accidents and domino effects at all levels were calculated;Analysis of the accident consequences of different types of accidents from the two major aspects of the environment and safety.Fire and explosion models and human vulnerability models were used to analysis the hazard of safety accidents such as fire and explosion.The SLAB atmospheric diffusion model was used in the atmospheric environmental impact prediction.The environmental impact of each accident was simulated by combining pollutant attributes,pollution source information,and meteorological data,and the air pollution consequences were estimated based on the population exposure response.In the water environment impact prediction,the EFDC hydrodynamic-WASP water quality coupled model was used to simulate the diffusion of pollutants in the water body and the losses was calculated based on the method of econometrics;The personal safety risk and the environmental risk was calculated according to the above steps.The value of safety risk and the environmental risk was overlaid in the same space system to obtain comprehensive risk values.The comprehensive risk curve was drawn by MatlabR2017a,and the risk level was judged after that.The unit with higher risk was identified according to the probability value and risk value.And then the management means to control the dust explosion domino accident risk was changed from the aspects of intrinsic safety principle,engineering design safety,program protection.The above method was applied to ZhongRong Metal Products Limited Company in Kunshan.The dust removal system of the enterprise hub grinding and polishing workshop was the place for collection,treatment,discharge and accumulation of combustible aluminum dust,and it was connected to numerous production devices through the dust removal pipe network.Because of No.1 dust collector dust collector barrel was corrosion damaged,and aluminum powder was damped in it,oxidation exothermic reaction occurred,and the ignition temperature of the dust explosion was reached,explosion was occurred.Explosion shock wave pressure was not be relieved timely,and it spread along the pipeline to workshop,raised the dust accumulated in other units and created a domino effect.It caused the accident of the environmental protection equipment to be transformed into a major safety accident,and caused subsequent environmental impacts.Case calculations showed that the probability of dust explosion in the high-level units increased significantly due to the domino effect,which was 29%-79%more than the inherent probability;Dust explosions with domino effect formed multiple dust clouds,which increased the environmental risk in the central area of the accident and increased the impact;The overpressure effect of multiple explosion shock waves superimposed,resulting in an increase in the scope of safety risks and a significant risk upgrade;The highest comprehensive risk of the accident was 67.39 times of the initial accident;Under the influence of environmental risks and security risks,the comprehensive risk in the central region had been rapidly upgraded.Based on this study,the domino effect risk assessment method for dust explosions was constructed,which can more realistically reflect actual accident scenarios,calculate the probability of risk accidents in complex situations efficiently and reliably,and systematically assess the consequences of accidents,thereby providing a more reasonable and more targeted risk Management measures.The research results show that when conducting quantitative risk assessment,comprehensive consideration should be given to environmental risks and safety risks,and the characteristics of environmental protection and treatment facilities should be fully considered.Especially in industrial enterprises involving powder,the dust removal system should be an important target for environmental protection and safety management.In addition,the domino effect leads to increased consequences and risk escalation.It is also a factor that cannot be ignored in risk management.The domino effect must be taken into full consideration when formulating dust explosion prevention measures and emergency plans.