The Numerical Simulation Research Of LNG Diffusion In Gasification Station

In recent years,the LNG industry has developed rapidly,with the growing number of LNG gasification station,the probability of LNG leakage risk is increasing.LNG leakage will cause serious personal property loss and environmental pollution,so using the reasonable method to research the leakage and diffusion law of small and medium tanks in LNG gasification station is meaningful for the optimization of LNG station construction,the formulation of emergency measures and some standards.In this paper,the 150 m~3 vertical LNG tank is used as the research object,the software called FLIUENT is used to simulate the phenomenon of LNG leakage and diffusion.With the secondary development port of FLUENT,the User defined function(UDF)is write to realize the temperature of ground changing when LNG touches ground.The density of methane will change with temperature changing to make the simulation more realistic.On the basis of the above,the influence of wind speed,temperature and the number of LNG tanks on LNG leakage and diffusion is studied.Results of simulation indicate:(1)The cryogenicl methane which comes from the gasification of LNG has significant characteristics of heavy gas diffusion in the air,and the fire dike can control the diffusion of methane on ground layer.(2)After the ground boundary loading UDF,the temperature gradient is formed in fire dike when LNG touches ground,and the lowest temperature can reach 150 K.At the same leakage time,the vertical diffusion distance of methane is smaller under the condition which loads UDF compared with the condition of constant ground temperature.(3)As the wind speed increases,the coverage area in fire dike of methane of high concentration on the ground increases,and the downwind diffusion distance of methane of low concentration increases.After 15 seconds,when wind speed respectively are 0 m/s,2 m/s,5 m/s and 10 m/s,the downwind diffusion distance on the ground of methane with the volume concentration of0.01 respectively are 19 m,19 m,64 m and 90 m.(4)The main effects of environmental temperature are heating LNG and gas clouds,and strengthen the atmospheric turbulence intensity.The higher the temperature,the higher the diffusion rate of methane gas cloud in the vertical and horizontal direction.(5)The effect of tanks for controlling the diffusion of methane gas cloud is not obvious.As the number of tanks increase,the area of fire dike and the distance between fire dike and leakage source increase,which led the diffusion distance along the horizontal direction of methane gas cloud to increase,but the diffusion distance along the vertical direction to decrease.