Optimization Of The BOG Recondensation Process During The Vessel Transportation And Storage Of LNG

As a high quality and clean energy source, nature gas will be widely used in the future.When natural gas is existed as the form of liquid natural gas, the physical volume is onlyl/625 of its normal volume, which is very convenient for transportation and storage. With therapid development of the economy at home and abroad, the requirement of nature gas isincreasing day by day and LNG is favored all over the world for its high efficiency andflexibility during transportation and storage. But BOG is brought out for the special storagecondition of LNG, so it is necessary to deal with BOG—recondensation of BOG. Therecondensation process for BOG directly affects the safety and economic benefits, so it isstudied in this article.Firstly, the development of the BOG recondensation process, LNG ship and receivingterminal are introduced, and then universal process simulation software is taken as theresearch tool according to characteristics of the study object. After that, the recondensationprocesses on ship and in the receiving terminal are studied respectively.In this article, one typical recondensation process for BOG on ship is taken as studyobject. Because of its complexity, the recondensation process is studied from the perspectiveof its process flow and available energy. On this basis, a BOG precool process is raised andsome key parameters are optimized. After calculation, the result shows that the optimizedprocess can save 30% refrigerant and 22% work of compressors compared with the presentprocess.For BOG recondensation process of the LNG receiving terminal, one existing receivingterminal is taken as a study object. At first, the recondenser control system is optimized, thecontrol logic is changed from liquid control to pressure control, which makes the controlsystem work smoothly and creates conditions for the further optimization of therecondensation process. Then, the key parameters which affected BOG recondensationprocess are analysed and some improvemental measures are proposed. Based on this, anoptimized process named BOG precooling process using high pressure LNG is put forward.The optimized process can save 163kW work of BOG compressor, about 32.5% work of theoriginal process, and it can improve the operation flexibility to the gas transportation loadbetween the peak and volley. So the new process has better performance during peakadjustment.