Study On Vapor Diffusion And Explosion Hazard Of LNG Storage Tanks

Due to the low temperature flammability and explosive nature of liquefied natural gas,natural gas storage tanks are prone to leakage and diffusion during storage.During the leakage process,liquefied natural gas absorbs the rapid change of ambient temperature and evaporates,causing a sharp decrease in temperature in a local range and an increase in air density.The diffusion of heavy gas generated by LNG is not conducive to the diffusion of natural gas,thereby affecting the surrounding environment and personal property.Safety causes great damage.Based on the theory of fluid mechanics,heat transfer and engineering thermodynamics,this paper analyzes the leakage mode and diffusion mode of LNG,and proposes the calculation method of leakage rate,liquid pool radius and evaporation rate of LNG storage tank,which provides theoretical basis for establishing numerical model in this paper.Because the wind field has a great influence on the leakage and diffusion of LNG storage tanks,this paper firstly establishes the model for wind field simulation.Analysis of the atmospheric boundary layer near Surface features,determining the near-surface boundary layer calculation function of wind speed in the atmosphere,the write function to load UDF in Fluent numerical simulation.According to the principle of blocking rate and the principle of obstruction placement,the LNG storage tank leakage diffusion calculation basin is determined and a geometric model is established.The wind farm simulation analysis of LNG storage tanks is carried out to verify the rationality of the calculation of watershed modeling.In this paper,based on mass conservation equation,momentum conservation equation,energy conservation equation and composition equation,the numerical model of LNG leakage diffusion is established.The turbulence model and component transport model can be realized to simulate the leakage and diffusion behavior of liquefied natural gas.Through simulation,the effects of different influencing factors such as different leakage source locations,different leakage amounts,different wind speeds,different wind directions and different cofferdams on leakage diffusion are analyzed.Through the comparative analysis of the factors affecting different leakage spreads,the main conclusions are drawn.:LNG leakage spread range with different leakage source locations change significantly,the higher the leakage source location,the larger the gas cloud lower diffusion range of the wind,and the larger the dangerous area.The more the leakage,the greater the diffusion width of LNG in the downwind direction,the greater the concentration of gas cloud around the tank,the less likely the gas cloud will spread around the tank,and the greater the risk;the wind speed mainly affects the gas cloud diffusion speed and the farthest Diffusion distance,the greater the wind speed,the greater the gas cloud diffusion rate,the greater the farthest diffusion distance;the wind direction mainly affects the gas cloud transport direction and the diffusion width,and the gas cloud diffuses farthest distance under the wind direction,under the wind direction The diffusion width of the gas cloud is wide,and it is easy to form a pile around the storage tank;the cofferdam has a certain blocking effect on the diffusion of LNG.The higher the cofferdam,the smaller the farthest diffusion distance that the lower limit of the gas cloud can reach.