Thermal Insulation System Failure Modes And Settlement Deformation Analysis Of Large-scale LNG Storage Tank

The settlement will happen to the expanded perlite within the LNG storage tank insulation system with the passage of time, top connected space will form, resulting in the increasement of thermal conductivity which will greatly reduce the cooling effect and directly affect the safe operation of the storage tank. Based on the theoretical analysis and numerical simulation method, the insulation performance of large capacity LNG storage tanks insulation layer and settlement of the expanded perlite are calculated. The main research contents are as follows:(1) Considering the influence of thermal conductivity and the daily evaporation rate,the heat loss of the expanded perlite in the side wall of the storage tank is analyzed theoretically and numerically. It turns out that the results of theoretical analysis and numerical simulation are basically identical; results of normal thermal conductivity and two times the thermal conductivity of expanded perlite of storage tank cooling system meet the cold insulation standards, results of three times the thermal conductivity do not meet the cold insulation standards.(2) Based on the settlement of expanded perlite of the existing LNG storage tank insulation system, taking into account the influence of its conductivity and the daily evaporation rate, theoretical and numerical analysis on the leakage of the local actual settlement of the expansion perlite of the side wall of the storage tank is carried out. The results show that the influence of the settlement deformation on the leakage of LNG tank is very large, which can lead to a significant decrease on the cooling effect.(3) Based on theoretical analysis and numerical simulation of ANSYS, the settlement of expanded perlite is calculated and analyzed, results show that the settlement of the expanded perlite belongs to the plastic deformation behavior which is affected seriously by its own density and poisson's ratio. The elastic modulus and coefficient of friction also affect the settlement to a certain extent,among all the cohesion does the least influence to the settlement; Lateral compressive stress does not increase with the increase of depth of perlite, and after reaching a certain depth, it will tend to be stable; The expanded perlite of the bottom may be damaged due to plastic deformation, and the density of the perlite of the top will decrease due to the settlemen.