Energy-Saving Optimization Study on 700°C Double Reheat Advanced Ultra-Supercritical Coal-Fired Power Generation System

700 degrees C double reheat advanced ultra-supercritical power generation technology is one of the most important development directions for the efficient and clean utilization of coal. To solve the great exergy loss problem caused by the high superheat degrees of regenerative steam extractions in 700 degrees C double reheat advanced ultra-supercritical power generation system, two optimization systems are proposed in this paper. System 1 is integrated with the back pressure extraction steam turbine, and system 2 is simultaneously integrated with both the outside steam cooler and back pressure extraction steam turbine. The system performance models are built by the Ebsilon Professional software. The performances of optimized systems are analyzed by the unit consumption method. The off-design performances of optimization systems are analyzed. The results show that: the standard power generation coal consumption rates of optimization systems 1 and 2 are decreased by 1.88 g(kW center dot h)(-1), 2.97 g(kW center dot h)(-1) compared with that of the 700 degrees C reference system; the average superheat degrees of regenerative steam extractions of optimized systems 1 and 2 are decreased by 122.2 degrees C, 140.7 degrees C (100% turbine heat acceptance condition), respectively. The comparison results also show that the performance of the optimized system 2 is better than those of the optimized system 1 and the 700 degrees C reference system. The power generation standard coal consumption rate and the power generation efficiency of the optimized system 2 are about 232.08 g(kW center dot h)(-1) and 52.96% (100% turbine heat acceptance condition), respectively.