The Thermal Stress Analysis Of A Large-scale LNG Storage Tank

With constant increase of world energy, environmental protection is continuouslyenhanced and the demand for liquefied natural gas (LNG) becomes increasingly higher. LNGstorage tanks have many advantages such as high capacity and excellent safety performance,so they have drawn world-wide concerns. At present, key technologies on LNG are primarilymastered by Western developed countries, whereas core technologies on LNG storage tankshaven’t been possessed by China.Adapting to the development of Chinese LNG industry and aiming at160,000cubicmeters of LNG storage tanks, temperature field and thermal stress field are analyzed in detailby theoretical analysis and numerical simulation with ANSYS. Based on domestic and foreignstudies, tasks are primarily fulfilled as follows:(1) According to basic theories on thermal stress, the temperature field of planethree-layer ring in a LNG storage tank is examined by theoretical calculation and finiteelement numerical simulation. On the premise that the temperature field is given, the thermalstress field of three-layer ring is investigated by finite element simulation and theoreticalanalysis, through which the relationships between temperature field and thermal stress fieldare obtained.(2) Pursuant to structural parameters of LNG storage tanks, a finite element model isestablished based on a given mechanical model for large LNG storage tanks with160,000cubic meters in volume. By setting different parameters such as ambient temperature andliquid level height, the distribution of temperature field in key parts of LNG storage tank(including top, wall and bottom) along the thickness direction is presented. Besides, theposition where temperature gradient is the highest is analyzed for storage tanks, by whichbasic numerical value and bases are available to analyzing temperature stress of storage tanks.(3) Based on above research, finite element analysis is conducted for thermal stress ofthe storage tank to study the thermal stress field and displacement field in key parts of a LNGstorage tank (top, wall and bottom) under different working conditions. Furthermore, therelationships and interactions between temperature field distribution and thermal stress aredetermined. Key parts where thermal stress is highly distributed are confirmed and certainbases are provided for guaranteeing the design safety of storage tanks.The present research has certain referential value for relevant studies on development of LNG storage tanks in China, their temperature field and thermal stress field.