Modeling And Optimization Of Low Carbon Power Systems With LNG Cold Energy Utilization

In order to make full use of the cold energy carried by imported liquefied natural gas?LNG?and reduce CO₂emissions during power generation,this paper studies the modeling and optimization of low-carbon power systems using LNG cold energy,which mainly includes three technical routes,namely,directly power generation that use LNG cold energy,oxy-fuel combustion power systems and post-combustion CO₂capture power systems which all based on LNG cold energy utilization.The specific research results are as follows:?1?A cryogenic cascade power system integrated by multi-stage Rankine cycle and a cryogenic combined power system integrated with the Kaline cycle and Rankine cycle have been established.Under the same external conditions.The cryogenic combined power system is about10%more efficient than the low-temperature cascade power system cryogenic cascade power system,and the net power generation using unit LNG cold energy has increased by 33.3%to166.2 k J/kg _LNG.?2?An integration of LNG regasification process in gas-fired power system for post-combustion CO₂capture?referred to as novel post-combustion capture system?has been established.Compared with the conventional post-combustion capture system,the net power efficiency and the exergy efficiency of the novel post-combustion capture system is respectively increased by 3.79%and 1.4%at the same CO₂capture rate;due to the utilization of LNG cold energy,the primary energy consumption?SPECCA?and exergy consumption?SECCA?for CO₂avoided are 1.38 GJ/t _CO2and 2.39 GJ/t _CO2,which are 54.5%lower and 21.6%lower than the conventional system respectively.?3?An integration of LNG regasification process in gas-fired power system with oxy-fuel combustion?referred to as novel oxy-fuel combustion system?has been established.Its net power efficiency and SPECCA are comparable to chemical chain combustion system,much higher than conventional oxy-fuel combustion system.Compared with the existing oxy-fuel combustion power systems using LNG cold energy,the exergy efficiency of the novel oxy-fuel combustion power system is basically equivalent,but the LNG cold energy consumption captured per unit of CO₂?SLNCC?decreased by 68.2-96.2%.At the same time,when the purity of O₂is 97.0%and the CO₂capture rate is 97.0%,the energy consumption of CO₂capture is the lowest,and SPECCA,SECCA,and SLNCC all reach the minimum values,which are 1.87GJ_LHV/t _CO2and 2.60 GJ/t _CO2and 1.88 t _LNG/t _CO2.?4?The three low-carbon power systems that use LNG cold energy are compared and analyzed in terms of energy utilization efficiency,energy-saving benefits from LNG cold energy and CO₂emission reduction effects,and the advantages and disadvantages of different technical routes are found.