LNG Storage Tank Leakage Diffusion Analysis And Explosion Suppression Research

The security problem has become the greatest challenge faced with the LNG industry during the development while the demand for Liquefied Natural Gas is increasing with the development of Chinese economy.As a storage container for Liquefied Natural Gas,the tank stores up a lot of LNG in low temperature.Once the tank leaks,liquefied natural gas will evaporate immediately,turning into a large number of vapor clouds,and diffuse outwards when they are exposed to the outside environment.According to its characteristic that is inflammable and explosive,it's extremely possible to burn and explode massively when there are open fires,bringing great risks to people,equipments,buildings and environment around.Therefore,it is urgent to study on the leakage of LNG storage tank,the explosion of natural gas and the situation of explosion suppression.Based on Fluent,a simulative software,and a bunch of research results both domestic and abroad,the leakage model of natural gas plant and explosion model of natural gas were established respectively to analyze the leakage law of the LNG diffusion and the flame propagation during the explosion.As for the improvement of explosion suppressant in the tank's interlayers and pipelines of cluster tanks,it studies the suppression effect of inert gas on natural gas explosion in two aspects,simulation and experiment.The main contributions of the paper are as follow:(1)According to combine the research status of scholars at home and abroad with relevant theoretical knowledge of hydrodynamics and detonation,the key factor that influenced the leakage mode of the LNG tank and the diffusion behavior of vapor was analyzed.It also introduced the form of flame propagation and explained the chain reaction mechanism during the gas explosion.These characteristic parameters which are critical in the simulation process provide an important theoretical basis for the simulation in this paper.(2)Based on a certain two-dimensional plane model of a liquefied natural gas plant,the diffusion law of the LNG tank's leakage and the influence of wind speed,leakage aperture and temperature on gas cloud diffusion were analyzed.The research shows that after LNG leaks,it achieves dynamic equilibrium in 50s-60s.Meanwhile,as LNG reaches stable leakage and diffusion,the higher the wind speed,the more favorable to diffusion and the less dangerous;the larger the leakage aperture is,the longer the diffusion distance is,and the greater the hazard is;the higher the temperature,the more conducive to diffusion and the higher the risk.Based on this,the measures of safety management and safety technology are worked out to prevent leakage of tanks.(3)The natural gas that was diffusing after leakage together was gathered to be concentrated into a two-dimensional confined space to simulate explosion and explosion suppression.Through Fluent software,it analyzed the change of parameters and explosion pressure under different inert gas combinations during the explosion.The study shows that the natural gas explosion flame changes from laminar combustion to turbulent combustion within 0.1 s,and the explosion pressure reaches its maximum at 0.02 s.The explosion temperature and velocity increase with the propagation of the flame.N2,CO2 and the mixed gases have inhibitory effects on natural gas explosion when the greater the concentration,the smaller the maximum explosion pressure and the better the suppression effect.With the same concentration of inert gas,CO2 has the best suppression effect.(4)Through the explosive limit tester,the explosion limit of methane was measured with different inert gases.The experimental results show that the explosion limit of methane is 4.3%to 15.8%.After adding the explosive,the critical concentration of methane measured is 6.1%.The explosion suppression effects of the five explosion-inhibiting combination gases are:CO2>N2:CO2(1:2)>N2:CO2(1:1)>N2:CO2(2:1)>N2,and the CO2 suppression effect with the concentration of 28%is the best,which can be applied in gas replacement of the inner tank and injection of anti-explosion agent in the sandwich to prevent the LNG tank from burning and exploding.