The BOG dynamic generation model of LNG storage tank considering the SEMP operation

The BOG prediction is the key to designing Liquefied Natural Gas(LNG) storage tanks and Boil-off gas (BOG) recycling. The study on the dynamic law of BOG generation caused by the submerged electric motor pumps(SEMPs) operation is rare. Thus, a dynamic heat transfer model is established based on outer wall heat transfer and submerged pump heat dissipation. We used the fluid volume method (VOF) model to simulate the unloading conditions of cryogenic liquid two-phase flow, and the phase change under static pressure was analyzed. Then, the dynamic heat transfer simulation utilizing the finite element method combined with the steady-state evaporation model was established. The model error is about 1 %, based on testing the actual value of the tank's average temperature and average pressure. Finally, the dynamic BOG generation model is constructed based on the three different filling rates of 10,000 m³storage tanks, namely 80 %, 55 %, and 30 %. The dynamic BOG generation will increase by about 50 % compared with the existing steady-state BOG generation results, and the model has a margin of 10 % errors. The BOG dynamic generation model is more in line with the actual working conditions and is of great significance to energy-saving optimization and reduction of economic losses.