Simulation Study On Leakage And Deflagration Of Vinyl Chloride Gas

Vinyl chloride is an important raw material for the plastics industry.With the development of the chemical industry,the use of vinyl chloride gas continues to increase.Although the management technology and rules and regulations of storage,transportation and use of vinyl chloride at home and abroad are constantly improved,and the total number of accidents in vinyl chloride tank farm is on the decline in recent years,major accidents still occur from time to time.Therefore,the numerical simulation of the leakage and deflagration of vinyl chloride gas in the tank farm of chemical enterprises is carried out to study the temporal and spatial distribution law of the concentration in the leakage and diffusion process of vinyl chloride gas,and the change law of the shock wave overpressure and combustion temperature in the combustion and explosion process,so as to provide support for the accident prevention and emergency rescue of vinyl chloride tank farm of chemical enterprises,It has important practical significance to ensure the safe operation and social stability of vinyl chloride gas holder.Taking the leaking gas tank of a vinyl chloride tank farm in Zhangjiakou,Hebei Province as the research object,the Fluent series software was used to simplify the actual working conditions and the surrounding buildings of the tank farm.Based on the Realizable k-εmodel and the vortex dissipation model,the calculation model of the vinyl chloride gas diffusion deflagration flow field was established.The variation law of the flammable concentration range during the diffusion process of vinyl chloride gas in the tank area of chemical enterprises was studied,and the different effects of surrounding buildings,gradient environmental wind and leakage rate on the flammable range in the horizontal and height directions of the tank area of chemical enterprises were discussed respectively.On this basis,the irregular vinyl chloride gas cloud in the tank area is ignited,and the variation law of deflagration overpressure in the tank area in different building groups in the open space and the variation law of combustion temperature near the ground and height are studied.The simulation results show that the direction of the ambient wind determines the main direction of gas diffusion in the atmosphere.As the wind speed increases,the distance of the combustible concentration range in the wind direction of the vinyl chloride gas cloud spreads farther;when the ambient wind is small,the wind field disturbance affects the vertical wind direction.The influence of gas concentration diffusion distance is small.The influence of the leakage volume on the distance of the downwind direction of the gas cloud is far greater than the influence of the environmental wind on it.The buildings on the upwind side indirectly affect the diffusion process of the leaked gas by influencing the environmental wind flow field;the vertical wind direction buildings will accelerate the wind speed around the leaking gas tank;the buildings on the downwind side directly hinder the leaking gas diffusion process and have the greatest impact.During the deflagration of the vinyl chloride gas cloud in the tank area,due to the large number of upwind building groups,the large blockage rate and the close distance,the shock wave overpressure attenuation here is small and far greater than the maximum overpressure of the downwind building group.In the early stage of the combustion of the leaked gas vinyl chloride,the high temperature area is small,the peak temperature is high,and the flame front moves quickly;in the later stage of the combustion,the vinyl chloride gas basically completes the combustion reaction and the temperature drops.