Research On Temperature Monitoring And Fault Diagnosis Technique Of Large LNG Storage Tank

With rapid development of world economy and sharply increased population, the world's demand of energy is growing. Energy structure changes gradually because the use of coal causes a lot environmental problems and the oil reserve is declining. With efficient and environmental quality, LNG(Liquefied Natural Gas) is widely used in the field of manufacturing, petrochemical engineering and so on. LNG storage tank is the most important equipment at receiving terminal and its steady operation is crucial to the LNG industrial chain. In this dissertation temperature fields for the tank under normal and fault working condition were analyzed and temperature monitoring and fault diagnosis system were established. The main contents are listed below.The structure and the low temperature performance of LNG storage tank were studied and energy transfer model for the tank was analyzed. Energy transfer characteristics under different working states were made explicit, and the ways of boundary loading and the method of temperature field solving were studied.Simulation for the temperature field of LNG storage tank was conducted. Temperature field of the tank was studied under different liquid level, environment temperature and insulation thickness. Regularities of temperature distribution of LNG storage tank under working state were analyzed. Combined with the tank's structure and the characteristics of the temperature field, optical fiber was distributed reasonably and temperature monitoring system for internal structure of LNG storage tank was established, then real-time temperature monitoring was realized.Leakage temperature field of LNG storage tank was studied. Through establishing finite element model for the tank and conducting solid-liquid coupling, regularities of temperature distribution under fault state were analyzed. Sensitivity of external structure of LNG storage tank to the leakage temperature field was analyzed and typical malfunction feature library was established. Thermal infrared imagers were used to monitor the temperature of the outside wall of the LNG storage tank and fault diagnosis system was put forward. By extracting the feature information of the fault temperature field and matching it to the models in the typical malfunction feature library, intelligent judgment for the LNG storage tank's failure was made.Temperature monitoring and fault diagnosis system can guarantee stable work for the tank and provide technical support for the safe operation of LNG industry. Research on temperature monitoring and fault diagnosis technique of large LNG storage tank has important engineering significance to promote energy development in China.