Research On Insulation Structure And Performance Of The Large Scale LNG Tank

With the popularization of low temperature technology wider and wider are the applications of low temperature liquids,such as liquid nitrogen,oxygen,hydrogen and LNG,and the demands on storage and delivery of low temperature liquids in all industries are continually going up.Due to the low boiling point and small latent heat of low temperature liquids,in order to guarantee the safety;economic;and purity when using,for these precious,high purity and flammable and explosive liquid gases,should reduce the heat leakage in uttermost during the process of storage and transportation.Therefore,it has a very practical value to study the insulation performance of low temperature vessel.To explore the insulation performance and insulation system of LNG tank,consulted the relevant literature at home and abroad up,and fully understand the basis of heat transfer.Taking 160 thousand cubic meters full capacity LNG cryogenic tank as a research object,it respectively makes heat leak calculation on tank top,wall and bottom and reckons the tank daily evaporation rate,makes an analysis on the insulation performance of the LNG tank.It does some temperature numerical simulation on tank top,wall and bottom with ANSYS software,more accurate analysis is made through the simulation results,also the correctness of the conclusions proved by heat leakage.By setting different temperature,the distribution of temperature field in key parts of LNG storage tank(including top,wall and bottom)along the thickness direction is presented.Besides,the position where temperature gradient is the highest is analyzed for LNG storage tanks,by which basic numerical value and bases are available to analyzing insulation performance of LNG storage tanks.Taking 80 thousand cubic meters LNG tanks with single containment of some enterprise as a research object,study the distribution of temperature field of the wall of LNG storage tank,compared with the realistic data decected in the position of temperature monitor distributed in the enpanded perlite,through the results to prove the correctness of the insulation performance of LNG tank is analyzed by this simulation method.Relationship between the layer thickness of foam glass cold insulation and cold loss,evaporation capacity of the tank bottom were obtained by comparing the theoretical analysis and engineering examples calculation.The result shows that the cold insulation layer thickness exhibit hyperbolic function relationship with the cold loss,evaporation capacity in a certain range,the thickness of the insulation layer(mainly foam glass)is inversely proportional to the cold loss.At first,cold performance of foam glass cold insulation decreases rapidly with the layer thickness;and then tends to be stable.When the foam glass reaches a certain thickness,the cold loss decrease slowly with the thicknesses increase,so at this point to increase the thickness of the foam glass,is not much sense from the insulation and waste the cost.There is great space in optimizing the bottom insulation thickness for the large LNG in actual project.The research has some reference value to the design and optimization in insulation system of the large-scale LNG tank.