Optimal design for double reheat coal-fired power plants with post-combustion CO2 capture: A novel thermal system integration with a carbon capture turbine

The development of post-combustion capture is greatly restricted by its high energy consumption and the thermal efficiency penalty resulting from absorbent regeneration. This study provides novel insights into the design of a thermal system for double reheat coal-fired power plants integrated with full-scale post-combustion CO2 capture. To this end, this study proposed a modified thermal system integration scheme that included an extraction backpressure turbine called carbon capture turbine (CCT) to provide thermal energy for the regenerative heaters and CO2 capture system. A generalized thermal economy calculating framework and a thermal system parameter optimization model was also established to maximize the cycle thermal efficiency for the proposed scheme. A new unit was designed based on the modified scheme, and its parameters were determined by taking a 1000 MW double reheat coal-fired unit as a reference. These parameters were then optimized via dynamic adaptive particle swarm optimization. Compared with a conventional retrofitted unit, the coal consumption and CO2 emission rates of this newly designed unit were reduced by 0.01264 kg/(kW·h) and 0.00423 kg/(kW·h) after the parameter optimization, respectively. An exergy analysis for the proposed system shows that using CCT can efficiently prevent the extraction of steam superheat and the mismatch between the intermediate pressure cylinder exhaust and the reboiler from generating excessive exergy losses.