Investigation on thermal system performance of solar-double reheat coal-fired units based on carbon capture

Three coupled scenarios of solar power-double reheat coal-fired units based on carbon capture are proposed. The matrix models of thermodynamic analysis, exergy analysis and contribution analysis of fuel exergy are established, and the important indicators including the thermal economy index, exergy analysis index, average carbon capture cost and external fuel exergy contribution of each system, are evaluated. The results indicate that all three scenarios can improve the thermal performance of the system, by comparing each performance index, the second scenario that the solar collector system replaces the first high-pressure heater and the heat source of reboiler extracts from the intermediate pressure cylinder, is the best integration scheme. Under this scenario, the increase of carbon capture rate or renewable energy consumption results in the raising of coal consumption and the reduction of cycle thermal efficiency and power generation efficiency. In addition, for 1% increase in the carbon capture rate, the turbine exergy losses are reduced by 4.424 kJ/kg and the exergy efficiency is increased by 0.1%. With the increase of solar radiation intensity, both the average carbon capture cost of the system and contribution of solar exergy diminish gradually, whereas the contributions of coal exergy in boiler, primary reheat and double reheat systems promote gradually. © 2020, Solar Energy Periodical Office Co., Ltd. All right reserved.