Study On BOG Recondensation Process At LNG Receiving Station

As China's primary energy consumption has increased year by year,problems such as uneven energy use and environmental pollution have become increasingly prominent.LNG is an inevitable choice for China to solve energy problems due to its cleanliness,high fuel value,and suitability for large-scale transportation.The LNG receiving station has developed rapidly.At present,the BOG recondensation process at the receiving station still has large energy consumption and low recovery rate.Poor stability and other issues,it is necessary to optimize the existing re-condensation process.Based on the actual equipment and operating parameters of the lowest domestic LNG receiving station,Aspen HYSYS is used to simulate the existing re-condensation process,A single factor method was used to analyze the influence of storage tank pressure,BOG output,compressor outlet pressure,and high-pressure pump outlet pressure on the energy consumption and material ratio of the recondensation process.The two control systems widely used in the existing recondensation process analyze the control logic corresponding to different operating conditions of the receiving station,compare the advantages and problems of the response measures,and point out the applicable receiving station type.Analyze the thermodynamic process of the existing re-condensation process to find the reason for the high process energy consumption and material ratio,and propose a precooling two stage compression BOG re-condensation process,using the high-pressure pump outlet LNG to pre-cool the first-stage compressor outlet BOG to reduce materials In contrast,the two-stage compression reduces the difference in BOG specific enthalpy of compressor imports and exports and reduces compressor energy consumption.Under normal export conditions,the new process saves energy by 6.21%,and under unloading conditions,the new process saves energy by 13.26%.Compared with the existing re-condensation process,the new process has higher stability.By effectively reducing the operating pressure of the two-stage re-condenser,the liquid level fluctuation of the re-condenser is reduced;the new process has good adaptability.The LNG stream at the inlet of the condenser is adapted to different types of receiving stations;the new process has adjustability to the minimum external volume,and the minimum external volume can be reduced by adjusting the equipment operating parameters.The new process improves the economy and stability of the receiving station and provides a reference for the choice of re-condensation process.