A large LNG tank technology system “CGTank®” of CNOOC and its engineering application

AbstractLNG tanks are complex in design and building process and high in costs, so LNG tank technology is one of the most advanced ones in the field of energy, which has been monopolized by foreign companies for a long time. In order to work out LNG tank technology domestically, China National Offshore Oil Corporation (CNOOC for short), the largest LNG importer in China, develops a LNG tank technology system “CGTank®” successfully in reference to the design and construction experience of domestic and foreign companies, after years of scientific research in tackling difficult problems. This system presents four traits as follows. First, a set of calculation software is developed independently by CNOOC, and the tanks in all operating conditions are calculated after 3D hologram and multi-point contact model of fluid-solid coupling effect is built up. Second, earthquake effect research and inner tank check research are improved innovatively by means of response spectrum analysis after European standards are introduced. Third, it is put forward for the first time that the stress strength discrimination standard is based on the principal stress which is obtained by means of the maximum shearing failure theory. And fourth, a large LNG full-capacity tank technology package with completely independent intellectual property right is established. The “CGTank®” system was first applied in the Tianjin LNG demonstration project, which has passed all indicator tests and is now in operation smoothly. The project is provided with the core tank design technology by CNOOC Gas and Power Group and with the EPC by CNOOC Engineering Co., Ltd. The independent LNG tank technology can be applied in a wide scope and it is favorable for impelling domestic production of LNG industry completely

Optimal design for safety of LNG full-capacity storage tank under explosion load

In order to ensure the safety of LNG storage tank during operation, the optimization method of structural safety of LNG full-capacity storage tank under explosion load was studied. The finite element model for tank explosion analysis, which had taken into account the liquid sloshing in the tank, was established and the sloshing state of LNG was simulated by the impact and convection spring-mass model. The time-history analysis of the storage tank was conducted to determine the dynamic response of the storage tank structure. The M-N curve was used to analyze the safety of the storage tank, the solutions were proposed for the situations that did not meet the safety requirements, and the anti-explosion capability of LNG full-capacity tank was optimized. The results show that the structural response of LNG full-capacity tank appears as a periodic attenuation under the explosion load. The main impact area of explosion is located at the joining between the tank dome and the outer wall, and the impact on circumferential safety is greater than that on radial safety. Both reducing the peak pressure of explosion load and increasing the reinforcement of components can effectively improve the safety of full-capacity storage tank