LNG-FSRU Regasification System And Cold Energy Utilization Research

LNG-FSRU is a new offshore LNG receiving terminal with highlighting advantages.In recent years, it has developed rapidly.Regasification system is a key part.Limited installation space, changing work environment at put higher demands on compactness and stability, reliability of the regasification system.LNG regasification process consumes a lot of power(LNG high-pressure pump, sea water pump, refrigerant pump power consumption),while releases huge amounts of cold energy(Typically, LNG releases cold energy about 830kJ/kg in gasification process).If this part of cold energy is used for power generation rationally and effectively, the LNG-FSRU can become a set of offshore energy station with the function of natural gas transmission and power supply.Learned the current situation and trend of the technology of LNG-FSRU regasification system,by reading, analyzing and summarizing a large number of domestic and foreign literature.Analyzed the characteristics of typical LNG vapourizer.A intermediate medium regasification system was the main object of study.The research and analysis of the operation characteristics of the system have be done, the study of the low-temperature Rankine cycle as a means of cold energy utilization of regasification system also has be done.The results show:For intermediate medium regasification system,With respect to R600 a, R717, R12, R290 has good overall performance.it's the preferred working fluid.During the operation, LNG vapour pressure, the higher the quality of the water consumed.There is a linear relationship between LNG vapour pressure and mass flow of seawater and R290, the higher vapour pressure the smaller mass flow of seawater and R290.The power consumption of LNG high-pressure pump is large,its power consumption accounted for 45.9% and 53% of the total system consumption at the vapour pressure of 8MPa and 10 MPa.The outlet natural gas temperature of LNG vaporizer determines the thermal load.Taking the economic and operational reliability of the system into account, that the LNG vaporizer heat load accounted 70%-80% of the total system heat load is appropriate.At the vapour pressure of 8MPa and the outlet natural gas temperature of LNG vaporizer was seted as-40?,the mass flow of seawater is 33.69 times the amount of LNG,while the mass flow of R290 is 1.21 times the amount of LNG,to reduce the working fluid loop pressure appropriatly, this value can be reduced to 0.98.For single stage low temperature Rankine cycle cold energy utilization regasification system,with respect to R143a?R152a?R290?R717?R134a?R1270, taking the mass flow of working fluid, the net power output, system exergy efficiency, environmental protection into account,R290 has good overall performance.it's the preferred working fluid.At the LNG vapour pressure of 8MPa and working fluid vapour temperature 15?,the exergy efficiency of the system is 8.1%, exergy loss mainly occurs in the working fluid condenser(LNG vaporizer), accounting for 67.3% of the total exergy loss.For two stage low temperature Rankine cycle cold energy utilization regasification system,selected R290 as the working fluid of the lower temperature stage cycle,with respect to R23?R116, R170 is the preferred working fluid.With respect to the single-stage system, under the same vapour pressure of LNG and vapour temperature of working fluid conditions,the exergy efficiency of system increased to 15.6%. Seawater temperature has greater impact on the net work output of system, the water temperature rises from 20?to 30 ?, the net work outputr increases 10.53%.