Large Lng Storage Tank Leakage Thermal Analysis And Simulation Study

Liquefied natural gas storage (LNG) tank is essential for transportation and storage of LNG. In recent years, LNG storage tanks are developing towards larger-capacity. Large storage tanks store natural gas at atmosphere pressure and low temperature(-162℃). As the storage temperature is particularly low, requirements for thermal insulation are particularly high. When the tank insulation performance fails to meet the standards, heat leakage may occur. It will cause a great waste of LNG in the tank and may even cause security incidents. Therefore, it is especially important to study the insulation properties, find out the main sources of heat leakage and provide operational advice for the safe storage of LNG.This article describes the structure of common types of LNG storage tanks and its way of heat leakage. Theoretical analysis was done starting from the theory of heat transfer. By studying the way of heat leakage and heat transfer mechanism of LNG storage tank, the heat leakage calculation model has been developed for common types of tank top, tank wall and tank bottom. According to the calculation model, the heat leakage of LNG storage tank whose actual capacity is16×104m3,can be calculated. By analyzing the calculation result, it can be known that heat leakage at tank bottom accounts for50%of the total heat leakage.Do numerical analysis of temperature and pressure field of LNG storage tank by using ANSYS and FLUNET. In order to show the conclusion of the numerical simulation more intuitive, numerical analysis of temperature and pressure field has been done, which described the heat leakage model of the top. wall and bottom of a real tank in Zhuhai, Guangdong. The temperature field simulated by ANSYS shows, different degrees of heat leakage will occur in the top. wall and bottom of tank, however, the bottom is the main leakage source. It also verified the conclusion that heat leakage at tank bottom accounts for50%of the total heat leakage, which was obtain by the calculation model of tank heat leakage. The pressure field simulated by FLUENT shows, pressure in tank is constantly changing in accordance with heat leakage rate, amount of LNG and initial LNG amount in tank. Analysis of simulation result shows, while LNG accounts for90%of the total volume of the tank, tank pressure will grow fastest, while LNG accounts for60%, tank pressure will grow slowest. Tank pressure will reduce as the amount of LNG increases. When initial amount of LNG accounts for92%of tank volume, there will be negative pressure in tank. As a result, it’s extremely important to reduce heat leakage rate, keep reasonable LNG volume and initial amount. This article will give some suggestions on insulation and operation of large LNG storage tanks.