Objective Coal-fired power plants are one of the main sources of flue gas carbon dioxide emissions. This paper proposes a compression heat pump system scheme for flue gas carbon dioxide capture, based on compression heat pump technology, to address the energy consumption issues associated with carbon capture in coal-fired power plants. The aim is to reduce energy consumption and promote the utilization of low-grade waste heat energy.

Method Thermodynamic calculations and pinch analysis were conducted for the heat pump unit based on the thermophysical parameters of the circulating working fluid at each node. By varying different parameters, a variable condition analysis of the system was performed. The influences of refrigerant type, condensation temperature, evaporation temperature, subcooling degree, superheat degree, compressor efficiency, and outlet temperature of lean/rich amine liquids on COP and the energy consumption of the carbon capture system were studied.

Result The data indicates that COP increases from 2.79 to 4.46 when evaporation temperature increases from 35 ℃ to 50 ℃. With the condensation temperature increasing from 95 ℃ to 110 ℃, COP decreases from 3.21 to 2.40. Correspondingly, when the outlet temperature of the lean amine solution is increased and the outlet temperature of the rich amine solution is decreased, the energy saving of the carbon dioxide capture system gradually increases. When the outlet temperature of the rich amine solution is set to 92 ℃, the energy saving of the carbon dioxide capture system can reach 2.7539 MW. When the superheat degree increases from 2 ℃ to 8 ℃, the COP decreases from 2.89 to 2.67 and the energy saving of CO₂ capture system decreases from 2.6159 MW to 2.503 MW. The trend of the variation of subcooling degree is just opposite to that of superheat degree. When the subcooling degree increases from 2 ℃ to 8 ℃, the COP increases from 2.73 to 3.05 and the energy saving of the carbon dioxide capture system increases from 2.5375 MW to 2.6885 MW. With the increase of compressor efficiency, the COP of the compression heat pump increases gradually. When the compressor efficiency is 1, the COP can reach 3.49, which can save energy consumption of 2.8539 MW.

Conclusion The introduction of compression heat pump system is of great significance in reducing the energy consumption of carbon dioxide capture systems.