In view of the characteristics of LNG(Liquefied Natural Gas) leakage and dispersion of large LNG tank leakage, including pool evaporation (phase transition) and gas cloud dispersion, combined with the phase equilibrium principle and the continuous diffusion Gauss model, the leakage and dispersion process of LNG tank was simulated by using Eulerian multiphase flow numerical model in Fluent software. The effects of wind speed, spill rate and surface roughness on the leakage and diffusion of large LNG tanks are analyzed. The results show that the diffusion process of continuous leaking gas cloud in large LNG tank can be divided into three stages based on the form of leakage and diffusion, that is heavy gas diffusion (heating of gas cloud), passive diffusion and dilution dissipation. As the wind speed increases, when the volume fraction of methane reaches 0.5%, its maximum concentration shows a trend of first decreasing, then increasing, and then decreasing again. The spill time is 200 s. The maximum methane concentration is smaller at a distance of 0.5 LFL in the downwind direction. As the leakage rate increases, the length from the outer wall of the storage tank to the center of the pool, the diameter of the pool, the length of the pool and the maximum 0.5LFL downwind distance of methane concentration showed an increasing trend. With the increase of surface roughness, the length of the pool and the maximum 0.5LFL downwind distance of methane concentration shows a decreasing trend, while the accumulation height of combustible gas clouds is increasing. Wind speed and leakage rate mainly affect the horizontal diffusion distance of LNG gas cloud, while ground roughness affects the accumulation height of combustible gas clouds. The research results expand our understanding of the leakage and diffusion law of large LNG tank. Increased leakage rates significantly expand the dispersion area of flammable and explosive gas clouds. In contrast, greater ground roughness can help contain their horizontal spread to some degree, though it also leads to a greater accumulation height. When the wind speed is greater than 6 m/s, the continuous increase wind speed will be beneficial to the dissipation of gas clouds and reduce the aggregation range of flammable and explosive gas clouds, it can also reduce the probability of secondary disasters. This research can provide scientific basis and theoretical support for the safety design of LNG storage tanks at natural gas receiving stations and the safety management system within the stations, which helps to reduce the risk of explosion caused by LNG leakage and enhances the scientificity and handling efficiency of accident emergency response in LNG receiving stations.
Yuchen et al. (Thu,) studied this question.