The Study Of LNG And Liquid Oxygen Direct Combustion Power Cycle System

In order to solve the problems of environmental pollution and clean energy combustion,a novel of LNG/liquid O₂ direct combustion cycle generating electricity is proposed.The combustion of LNG and liquid oxygen produces ultra-high temperature and ultra-high pressure gas,which expands and works in the turbine and drives the generator to generate electricity.ASU consumes surplus valley electricity to produce liquid oxygen.The peak load regulation pressure of power grid is alleviated,and"peak load shifting and valley filling"and cross-time utilization of power are realized.CO₂ is liquefied by LNG and liquid oxygen.Based on thermodynamics and heat transfer theory,the cycle is constructed and utilized by Aspen Plus.Based on the simulation results,the relationship between the evaluation criteria of the cycle and the changes of turbine inlet pressure and inlet temperature is analyzed and summarized.Optimize the liquid oxygen direct combustion power cycle system step by step.The relationship between the cold energy of LNG and liquid oxygen and pressure is analyzed by the method of exergy analysis.The result shows that the cold energy decreases gradually with the increase of working medium pressure.In this paper,a liquid oxygen direct combustion power cycle system is proposed,in which CO₂ is injected into the combustor as cooling medium to protect the shell of combustor.Aspen Plus is used to simulate the liquid-oxygen direct-fired power cycle system with CO₂ as cooling medium.The results show that the thermal efficiency of power generation increases gradually with the increase of turbine inlet temperature when the turbine inlet pressure is constant,and increases gradually with the increase of turbine inlet pressure when the turbine inlet temperature is constant.Compressor in the circulating system consumes a large amount of energy,and the share of auxiliary power reaches 24%.When the inlet temperature is 1200?,the inlet pressure increases from 40MPa to 70MPa,and the thermal efficiency of power generation increases from 48.5%to 51.2%.When the inlet temperature of the turbine is 1500?and the inlet pressure is 70MPa,the thermal efficiency of power generation reaches64.9%,and the net output efficiency is 61.6%except for the oxygen consumption of ASU.Aiming at the problem of high energy consumption of compressors,an optimized liquid oxygen direct combustion power cycle system is proposed.The compressor with high energy consumption in the system is removed.The calculation shows that when the turbine inlet pressure is 40MPa,the share of auxiliary power is less than 4%.When the inlet temperature of the turbine is 1200?,the inlet pressure increases from 40MPa to 70MPa,and the thermal efficiency of the system increases from 51.4%to 54.2%.When the inlet temperature of the turbine is 1500?and the inlet pressure is 70MPa,the thermal efficiency of the power generation reaches 66.3%.The thermal efficiency of the power generation reaches 62.9%after removing the oxygen consumption of ASU.At the same time,the exhaust gas passes through the condenser and the multi-stage heat exchangers in the system to realize the separation of CO₂ and water,and the liquefaction and capture of CO₂.At last,comparing the difference between water and CO₂ as cooling medium,it is found that the mass flow rate of CO₂ is about three times of that of circulating water under the same working condition.Because CO₂ is in supercritical state and has high density in the process of circulating,when it expands to the last stage of turbine,the volume is 1/10 of that when water is used as circulating working medium under the same working condition.