Numerical Simulation And Countermeasure Studies On Leakage Diffusion Of LNG Storage Tank In Coastal Receiving Station

As clean energy,Liquefied Natural Gas is widely used in various fields of life and production.LNG has small size,high purity and high calorific value.The amount of imported LNG is increasing day by day at present,and the number of coastal receiving terminals of China is also increasing.Large amount of LNG was stored in storage tanks.LNG has low-temperature and it's flammable and explosive,which can cause extremely serious fire accidents and endanger incalculable damage to life and property once LNG leakages.Using appropriate methods to study the law of leakage and diffusion of LNG storage tanks and the measures of combustion and explosion can reduce the hazards of accidents and provide guidance,which has practical significance for the safe operation and management of storage tanks at receiving terminals.Based on the research results of the relevant literature,the leakage diffusion mechanism of LNG was summarized.The reliability of FLUENT simulation was analyzed by using the data of LNG dispersion experiments abroad.In accordance with the simulation calculation process,the geometric model of the LNG storage tank was established,the size of the basin was determined,the calculate basin was meshed to hexahedral grids and the quality of the grid is verified.FLUENT is used to simulate the calculation of the leakage of the wind field and LNG storage tank in the calculate basin.The basic characteristics of the leakage diffusion of LNG are analyzed.The influence of leakage aperture,wind speed and obstacles on the diffusion of LNG leakage was studied,and the layout of storage tank monitoring points was optimized.The results show that:1.Compared with other simulation tools,The MG-VG value of the FLUENT simulation result is closest to the point(1,1),which reveals FLUENT has high reliability of simulating LNG leakage diffusion.2.The calculate basin and the placed position of storage tank is reasonable.Because of the obstruction,air around the tank has complex flow conditions such as stagnation,diversion,bypass,and backflow.3.LNG initially leaking out of the storage tank settles downward due to gravity.And the vapor cloud is short,wide and in high concentration near the ground.With the progress of leakage,the influence of wind is growing.The gas cloud tail bifurcates,and the width of the gas cloud expands slowly.When the density is lower than air,the gas cloud will enter the state of passive diffusion.4.The danger diffusion range of gas cloud,blasting range and downwind diffusion distance increase with the increasing of leakage aperture,and increase firstly and then decrease with the increasing of wind speed.While the width of gas cloud increases with the increasing of leakage aperture and wind speed.The growth rate is high in the first 10 s,while the increase range reduces in the latter 90 s.5.The smaller the aperture and wind speed,the shorter the time required for the diffusion to stabilize.6.Using the origin software to obtain the formula for the relationship of the downwind difffusion distance,the leakage time,and the leakage aperture.7.Due to the obstructing effect of the storage tank,the gas cloud is long and thin.And a large amount of gas gatheres between the two tanks,which is in high concentration.The danger range,the explosion range,the downwind diffusion distance and the width of gas cloud all increase firstly and then decrease with the increasing leakage time.