Numerical Simulation Of LNG Vapor Diffusion After Storage Tank Leakage

In recent years, the natural gas industry develops rapidly. Thus, as an importantcomponent of the natural gas industry, the liquefied natural gas (LNG) industry alsoentered into the golden age of its development. As the numbers of the LNG gasificationstation, filling stations and LNG liquefaction factories and other stations grows quickly,the possibility of LNG storage tank leakage is also increasing simultaneously. LNG is acryogenic liquid, its temperature is only-162. After evaporation of the LNG, the vaporis also a kind of flammable and explosive gas. Once the leakage happen, the accident willcause a lot of damage to the people, construction equipment, and the environment aroundthe storage tank. Therefore, to study and analyze the vapor’s diffusion and the keyparameters’ impact to the diffusion is very necessary and meaningful, which will providereference to the selection of LNG station’s site location, establishment of emergency plans,as well as the divided of the security zones and the assessment of accident hazards.According to the theory of gas jet, heat transfer, mass transfer and fluid dynamics,through the numerical simulation method, using Gambit, Fluent and Tecplot to buildthree-dimensional geometric model, simulation and post-processing. In that way, thediffusion of LNG vapor after a storage tank leakage can be simulated accurately. Theauthor simulated the diffusion with different wind velocity and directions. Besides, on thisbasis, the author set a barrier in the direction of wind to simulate its influence on thediffusion. According to the data of these numerical simulations, the author studied the lawof the vapor diffusion, the range of the lower explosive limit and the warningconcentration to analyze some key factors’ influence on the LNG vapor diffusioncomparatively.Through comparative analysis of these simulation results, we can draw severalconclusions that the value of the wind velocity have a significant impact on the rate of diffusion and diffusion range, the greater the wind speed is, the faster the vapor diffusesand the wider the diffusion range is; the wind direction mainly impact the vapor cloud’swidth, the width of the vapor cloud is relatively wider than other situation when theLNG pool is in the cross wind direction of the storage tank; the rectangular wall canrestrain the diffusion of the LNG vapor, which is connected to its width, its height and itsdistance from the storage tank; the wall’s width and distance from the storage tank mainlyinfluence the rate of the vapor diffusion, within a certain range, the wider or the closerfrom the tank the wall is, the slower the LNG vapor diffuses; the higher the barrier wall is,the shorter the maximum distance that the vapor’s lower explosive limit can achieve is,while the vapor cloud will be wider. These conclusions are very valuable for the layout forLNG station, the design of LNG storage tanks’ building envelope, the division of thesecurity zones and the assessment of accident hazards.