Research On Leakage And Diffusion And Consequences Of Fire And Explosion Of The Large LNG Storage Tank

In recent years,in order to meet the domestic demand for natural gas,many large LNG storage tanks have been built in coastal areas of China.Although LNG is clean and efficient energy,it is flammable and explosive.Once LNG leaks into the atmosphere,the surrounding persons,equipment and buildings will be harmed.Therefore,it is necessary to study the consequences of leakage of the large LNG tank.In view of the evolution of gas cloud after the leakage of the large LNG storage tank,a three-dimensional model of 16×10~4 m~3 large LNG storage tank is established by using ICEM modeling software.The multiphase flow model is selected to describe the diffusion of LNG vapor cloud in the atmosphere.The mass and heat transfer process of LNG vaporization is compiled with UDF.When simulating the leakage and diffusion of LNG,the influence of wind speed,wind direction,obstacles and tank area distribution on gas cloud diffusion is studied.The wind has strong effect on the mixing and dilution of high concentration gas cloud and strong effect on the advection transportation of low concentration gas cloud.Larger wind speed is more conducive to promote the diffusion of gas cloud.From downwind leakage to upwind leakage,the blocking effect of the tank on the diffusion of gas cloud gradually increases.And the diffusion speed of gas cloud gradually slows down.The upwind leakage is the most unfavorable to the diffusion of gas cloud,which may form very large dangerous cloud.The obstacles lead to the short-term accumulation of heavy gas cloud,which makes the gas cloud diffusion present two modes.The two modes are climbing and diverging.The simpler the downwind distribution of the tank farm is,the more conducive the LNG diffusion will be.Comparing the leakage and diffusion of single tank and tank farm under the same environmental conditions,it is found that the volume of dangerous gas cloud in the tank farm is much larger than that of single tank.Because other large tanks in the tank farm block the diffusion of gas cloud while changing the distribution of wind field.And they prolong the retention time of high concentration gas cloud in the air.In order to determine the severity of the accident after the leakage of large LNG storage tank,a prediction method for the consequences of fire and explosion was established.The consequences of fire and explosion of large LNG storage tank are simulated and calculated.The impact of environmental conditions on the consequences of the accident was studied.The results show that the distribution of fire and explosion risk areas is greatly affected by wind speed and atmospheric stability.The distribution is relatively less affected by environmental temperature,and basically not affected by air relative humidity.The results of the study have certain guiding significance for LNG terminal location,tank farm layout and prediction of leakage and diffusion.They also provide scientific basis for emergency protection strategy.