Pre-cooling Simulation Analysis Of 160,000 Cubic LNG Storage Tank

Large-scale full-capacity LNG storage tanks need to be pre-cooled before being put into use to prevent the stress caused by the huge temperature difference from damaging the structure of the storage tank.This is the most critical and difficult part of the commissioning work before commissioning.Because the changes inside the storage tank are not steady state during the precooling process,experimental research is difficult.This article takes 160,000 cubic meters of full-capacity LNG storage tanks as the research object,analyzes the medium flow,pre-cooling time,and pre-cooling amount required for the pre-cooling of LNG storage tanks,combined with FLUENT numerical simulation,by observing the temperature and gas changes in the tank Provide feasibility suggestions for actual projects.The main research contents are as follows:(1)Taking into account the two factors of thermal conductivity and specific heat capacity of the material,a mathematical model for precooling the LNG storage tank was established using the energy balance method,and the entire precooling process was calculated in two stages with seven precooling rates.It is concluded that the largest proportion of cooling consumption is the thermal insulation layer.Optimizing the thickness of the thermal insulation layer is of great significance,which can save material costs and pre-cooling consumption.Increasing the cooling rate will reduce the amount of pre-cooling medium.It is recommended that when controlling the cooling rate,Adjust within 4K / h-5K / h to improve pre-cooling efficiency and save costs.(2)The ICEM software was used to 3D model the LNG storage tank,and then perform simulation calculations using FLUENT software.The entire pre-cooling process is divided into six parts.The BOG gas with different temperatures is used to cool the storage tank.The changes in the temperature field,velocity field,and pressure field of the storage tank during the precooling process are studied.It is concluded from the simulation results that the temperature change of the internal gas is affected by three factors: air velocity,gas density,and the boundary of the storage tank.The center of the tank,the bottom of the tank,and the center of the inner tank wall cool the fastest,and should be used as a key monitoring area.The junction between the tank wall and the top and bottom of the storage tank is a dead angle during the entire precooling process,especially the junction between the tank wall and the bottom of the tank.The temperature drops slowly;during the pre-cooling process,it is affected by the unstable air flow in the tank.The pre-cooling area of each inlet is not completely symmetrical.The direction of the low-temperature gas will be affected by the nozzle position and the inlet flow rate.Through trial calculation of different medium flow rates,the optimal medium flow range at different precooling stages is obtained.3h adjusts the inlet flow of the storage tank to improve the precooling efficiency under the premise of meeting the requirements.