Study On Using Cone Water Spray To Disperse LNG Vapor Clouds In Tank Farm

LNG(Liquefied Natural gas)tank farm is the key place of LNG receiving station and gasification station.So the safety of tank farm is very important to the normal running of the whole station.LNG leakage accidents and the fire explosion accidents lead by leakage can be the most serious safety accidents in tank farm.Water spray curtain method is considered to be a effective way to disperse LNG vapor clouds.Especially,it's ability of air entrainment,momentum exchange and thermal transfer,can reduce the concentration of LNG vapor.Thus reduce the possibility of fire and explosion accidents caused by LNG leakage.In this paper,the LNG vapor clouds diffusion and cone water spray dilution effect are simulated by using CFD software FLUENT.LNG diffusion simulation used the Species Transport model and the cone water spray simulation used the DPM(discrete phase model).Meanwhile,used the UDF programming to optimize the wind inlet boundary and ground heat transfer boundary.Also,chose the large foreign leak experiment Burro test and Mary Kay O'Connor Process Safety Center(MKOPSC)water spray dispersing test to verify the model used in the paper.On these basis,this paper study the water spray dispersing effect with considering the environment wind speed,the distance between water spray and the source,the water spray arrangement mode and the angle of water nozzles.The results showed that the greater the wind speed the farther LNG vapor clouds would diffuse.And the size of clouds will be longer and lighter.Moreover,the water spray diluting efficiency will reduce as the wind speed go greater,and the main influence of high speed wind is the level of water spray diluting efficiency from downwind direction.Secondly,the different distance between water spray and the source lead a similar water spray diluting efficiency line.But lines skew due to the different distance.In addition,the water spray diluting efficiency will reduce in both downwind and crosswind direction with the distance between water spray and the source increasing.Thirdly,in a certain number of water spray nozzles,the single row water spray perform better than the double rows,and with the distance between the rows get farther,the dispersion effect reduce.The inclined installation of the water curtain will decrease the suppression effect of the water curtain,and the larger the installation angle,the worse the suppression effect.Based on the study above and Literature reference,this paper continue to study on application of water spray in tank farm.Analyzed the law of the LNG collecting reservoir evaporation diffusion range and water curtain droplet splash range,through the experiment and numerical simulation.And determined water curtain set range of the LNG gasification station tank farm.Finally,air curtain is presented according to the shortage of the water spray method in dispersing LNG vapor clouds,and this paper carried on a preliminary study.The results showed that the primary mechanism of air curtain in dispersing LNG vapor clouds are air curtain's outstanding dilution ability and a lot of momentum exchange.Furthermore,the area that Air curtain take effect is just limited to the width of the air curtain set range.