A new proposed approach for future large-scale de-carbonization coal-fired power plants

•Problems caused by CO2 capture in the power plant are deeply analyzed.•An improved design idea for coal-fired power plants with CO2 capture is proposed.•Thermodynamic, exergy and techno-economic analyses are quantitatively conducted.•Energy-saving effects are found in the proposed coal-fired power plant design idea.

The post-combustion CO2 capture technology provides a feasible and promising method for large-scale CO2 capture in coal-fired power plants. However, the large-scale CO2 capture in conventionally designed coal-fired power plants is confronted with various problems, such as the selection of the steam extraction point and steam parameter mismatch. To resolve these problems, an improved design idea for the future coal-fired power plant with large-scale de-carbonization is proposed. A main characteristic of the proposed design is the adoption of a back-pressure steam turbine, which extracts the suitable steam for CO2 capture and ensures the stability of the integrated system. A new let-down steam turbine generator is introduced to retrieve the surplus energy from the exhaust steam of the back-pressure steam turbine when CO2 capture is cut off. Results show that the net plant efficiency of the improved design is 2.56% points higher than that of the conventional one when CO2 capture ratio reaches 80%. Meanwhile, the net plant efficiency of the improved design maintains the same level to that of the conventional design when CO2 capture is cut off. Finally, the match between the extracted steam and the heat demand of the reboiler is significantly increased, which solves the steam parameter mismatch problem. The techno-economic analysis indicates that the proposed design is a cost-effective approach for the large-scale CO2 capture in coal-fired power plants.