System integration for combined heat and power (CHP) plants with post-combustion CO2 capture

Based on a typical 1000 MWe coal-fired power plant with ultra-supercritical parameters, this study proposes a new integration scheme for the combined heat and power (CHP) plant with post-combustion CO2 capture. By introducing a back-pressure heat supply (BPHS) turbine and a back-pressure CO2 capture (BPCC) turbine, the superheated degree of the extraction steam is effectively retrieved for parameter matching of CO2 capture and heat supply. With 90% CO2 capture efficiency and 785.06 MWth heat supply, the total efficiency penalty for the CHP plants with solid amine-based CO2 capture reaches 19.32%. To optimize the proposed integration scheme, over 90% of the waste heat in the CO2 capture is recovered by applying the absorption heat exchanger (AHE) to increase the heating capacity of the integrated system. Energy analysis results show that the heating capacity of the integrated system is increased by 64.18%. Exergy analysis results reveal that the exergy destruction of the CO2 capture process and the heat exchange between the primary and secondary heating networks is reduced by 40.27 MWex and 10.33 MWex. Economic analysis results show that the cost of electricity (COE) and the cost of CO2 avoided (COA) are reduced by 2.59 $/MWh and 4.19 $/t CO2.