Investigation on the allowable load ramping-up rate and wet-to-dry conversion time of a 660 MW supercritical coal-fired power plant with deep peak-shaving work conditions

Shortening the state conversion time can improve the flexibility and safety of coal-fired power plants operating under peak-shaving conditions. This study analyzes various approaches to accelerate the wet-to-dry state conversion process, focusing on the recirculation system and the corresponding safety operation boundaries. The revised control schemes are proposed to maximize the utilization of energy storage in the recirculation system. The set value of the recirculation water flow rate is optimized to minimize the water wall inlet subcooling degree under safety operating boundaries, assisted by the revised feedforward value of the fuel supply rate to increase the separator superheat steadily. The performances of the proposed control schemes are evaluated based on the established model. The results reveal that the allowable load ramping-up rate during the wet-to-dry state conversion process can be increased from 0.5 % Pe min⁻¹ to 2.0 % Pe min⁻¹ by adopting the revised control schemes. The duration of state conversion can be shortened by 35 % at most. The minimum dry-state load can be reduced from 25.5 % Pe to 23.8 % Pe without frequent state conversion. The proposed control schemes enable rapid, smooth, and safe state conversion, thereby being significant in guiding the control optimization of deep peak-shaving power plants.