Design And Analysis Of Integrated Power Generation And Carbon Capture System Based On SCO₂-Steam Combined Cycle

In recent years,a large number of greenhouse gases,such as CO₂,emitted by human life and industrial production,have entered the atmosphere.The greenhouse effect has led to the rising temperature,which has caused irreversible damage to the natural ecology.The concept of"Lucid waters and lush mountains are invaluable assets"has gradually been deeply rooted in people’s hearts.Energy conservation and carbon reduction have been incorporated into the development of national economy and society.China’s coal consumption ranks first in the world,of which about 54%is used for coal-fired power generation,and a large amount of CO₂ produced by combustion is discharged into the atmosphere.How to effectively reduce CO₂ emission from coal-fired power plants is of great significance for improving ecological environment and realizing"double carbon target".In this paper,660 MW ultra-supercritical coal-fired power units in China are taken as the research object,and the CO₂ in boiler flue gas is captured by cyclic calcination/carbonation reaction of Ca-based absorbent.The model of Ca-based carbon capture system is established based on Aspen Plus,and the thermodynamic performance and key parameters of the system are analyzed.According to the energy released by Ca-based carbon capture system,this paper puts forward two waste heat recovery schemes:additional Rankine cycle waste heat recovery scheme;Integrated system waste heat recovery scheme.Based on EBSILON,an integrated system model of power generation and carbon capture based on SCO₂-Steam combined cycle and an additional Rankine cycle model are established.The thermodynamic performance,waste heat recovery efficiency and heat exchange area of the system are analyzed.The sensitivity of key parameters of the integrated system is analyzed.The results show that 90%CO₂ in flue gas can be captured by Ca-based carbon capture system,and finally 775.7 t/h CO₂ can be compressed and sealed.The energy consumption of calcination process in CO₂ capture system is 714.1 MW,and the air separation unit and CO₂ compression system need to consume 136.7 MW electric energy.In the process of carbon capture,the system will release about 762.4 MW of high-grade energy and 107.2 MW of low-grade energy.The waste heat recovery efficiency of integrated system is 93.13%,which is 2.86%higher than that of additional Rankine cycle.The net power generation efficiency of integrated SCO₂ cycle is 49.87%,which is 8.53%higher than that of additional Rankine cycle.The total net power of the system is 856.215 MW,which is 39.83 MW higher than that of the additional Rankine cycle scheme.The total net power generation efficiency is 39.8%,and the efficiency loss is reduced by 1.9%to 3.96%compared with the additional Rankine cycle scheme.In the integrated system,the total heat exchange area of boiler heat exchanger increased by about 25.5%,and the total heat exchange area of waste heat recovery heat exchanger increased by 51.46%.When the inlet pressure of the main compressor increases by 0.1MPa,the inlet pressure of the high-pressure turbine increases by 1 MPa,and the compressor compression efficiency in the integrated system increases from 90%to 94%,the total net power generation efficiency of the integrated system is 40.64%,and the efficiency loss is 3.12%.