Optimization Simulation Of Co-production Of LHG And NGL Technological Process

As a green energy,liquefied natural gas(LNG)has the characteristics of high calorific value,convenient transportation and strong environmental protection.In the process of producing liquefied natural gas,the C2+ component in the feedstock gas can be recovered into natural gas liquid(NGL),which also has high industrial utilization value.Since the co-production of LNG and NGL processes share a refrigeration system,it has the outstanding advantage of saving up-front investment and operating costs.In order to further reduce the unit energy consumption of the process system and improve the efficiency of liquefaction exergy,it is necessary to carry out the optimization research of LNG and NGL co-production process.This paper combed the domestic and international relevant research results,determine propane precooling mixed refrigerant liquid(C3MR)process,dual mixed refrigerant liquid(DMR)process,mixed refrigerant cascade(MFC)liquefaction process as a liquid cooling system,and uses the gas subcooled process(GPS)of NGL recovery process,based on ASPEN HYSYS simulation software was set up three kinds of LNG and NGL co-production process model;According to the refrigeration temperature range of each refrigeration cycle,the refrigerant components suitable for refrigeration cycle were analyzed and determined.A component splitter is used to divide the mixed refrigerant into individual components in the multiphase logistics,and the process flow is optimized by the process parameter optimizer built into HYSYS,which takes the minimum energy consumption as the objective function.The minimum unit energy consumption and liquefaction exergy efficiency of each process were compared and analyzed.The results show that the exergy loss of compressor,expander and heat exchanger accounts for more than half of the total loss of the process due to the irreversibility of compression and expansion and the necessary temperature difference of heat transfer in the heat exchanger.By comparing the three types of LNG and NGL co-production processes identified in this paper,it is found that with the increase of mixed refrigerant components and refrigeration cycle stages,the heat transfer temperature difference in the heat exchanger decreases,the unit energy consumption of the co-production process decreases,and the efficiency of exergy increases.By comparing the co-production process in this study with other co-production processes,it can be seen that the three co-production processes provided in this paper are all superior to other co-production processes(under the premise that the ethane recovery rate is above 90%).The MFC and NGL co-production process has the lowest unit energy consumption and the highest exergy efficiency,followed by the DMR and NGL co-production process,while the C3MR and NGL co-production process has higher unit energy consumption and lower efficiency.For the C3MR and NGL co-production process,the unit energy consumption is higher,but the cycle process and refrigerant ratio process of the process are relatively simple.