Research On Structural Optimization Of Thermal System Of Coal-fired Unit Based On Post-combustion Carbon Capture

At present,global climate anomalies caused by excessive greenhouse gas emissions have become an urgent environmental problem.Among them,carbon dioxide?CO₂?emissions contribute more than 60%to global temperature rise,while coal-fired power generation industry CO₂ emissions account for 50%of China's total emissions.Aiming at the characteristics of stable,large-volume and easy centralized treatment of CO₂ emissions from coal-fired power plants,centralized capture of the emitted carbon dioxide can effectively reduce carbon emissions.Post-combustion carbon capture is highly applicable to existing coal-fired power plants,but there is a large energy loss,resulting in a decrease in unit efficiency.In this paper,the double reheat unit is taken as the reference object to study the characteristics of the unit's extraction and reboiler coupling thermal system.Firstly,the simulation of the traditional medium-low pressure cylinder connecting pipe extraction scheme is performed.When the desorption heat source is provided by the unit extraction steam,the cycle thermal efficiency of the unit is reduced by 7.9%,and the carbon emission intensity is 17.8%of the reference unit.Then,combined with the unit optimization theory and technical route,the problem of excessive superheat of extraction steam temperature is studied.The carbon extraction turbine is assisted to extract steam and establish the mathematical model of cycle thermal efficiency.The adaptive particle swarm optimization algorithm?DAPSO_ex?is used to determine four improved integrations.The optimal extraction parameters for the program.Through the above work,the integrated schemes are simulated by EBSILON after the structure and parameters are optimal.Finally,the performance of the unit after simulation is compared and analyzed,and the detailed distribution of unit consumption is listed,and the sensitivity of the unit when the parameters of the carbon capture system are changed are analyzed.The results show that the cycle thermal efficiency of the unit optimized by DAPSO_ex algorithm is 0.24%higher than that of the equal lift method,and the coal consumption is reduced by 1.78g/kW·h.It shows that the carbon capture power plant system is more complicated.The advanced and intelligent optimization algorithm can improve the overall performance of the unit;analyze the four improved integration schemes.When the carbon capture turbine steam source is in the first reheat hot section,the return water point selects the heater.The performance index is optimal between#5-#6.Compared with the traditional carbon-removing transformation scheme,the cycle thermal efficiency is increased by 1.47%,the standard coal consumption rate is reduced by 8.53g/kW·h,and the carbon capture effect is more excellent,resulting in CO₂ emission intensity.decrease by 3.43 g/kW·h.For this integration method,when the carbon capture rate or unit energy consumption changes within a certain range,the standard coal consumption rate shows a high linear trend:when the CO₂ capture rate increases by 1%,the standard coal consumption rate increases by 0.57 g/kW·h;while the unit energy consumption is reduced by 0.1GJ/t,the standard coal consumption rate is reduced by 1.29 g/kW·h.