Regulation of reheating temperatures for sCO2 coal-fired power plant to improve the peak regulation depth

Abstract

Unstable renewable energies can be stabilized by the partial-load-operation (PLO) of supercritical carbon dioxide (sCO₂) coal-fired power plant, under which the reheating temperature deviates from the rated value to deteriorate the efficiency and safety. Challenge exists on the varied heat absorption ratio of the reheater under PLO conditions. We break through the limitation of the reheater arranged in the convection region only for water-steam boiler, but propose a hybrid radiation-convection-reheater (RCRH) for sCO₂ boiler to stabilize the reheating temperature. Three methods including RCRH, flue gas recirculation (FGR) and burner angle adjustment (BAA) are compared, by establishing a partial load model. Our results show that without regulation, the reheating temperature decreases by 32 K at 20 % load, which is not acceptable. FGR and BAA mitigate the reheating temperature deviation to 23 K and 22 K respectively at 20 % load. To satisfy the criterion of 10 K temperature deviation, both FGR and BAA cover the load ratio range of (45–100) %, indicating not effectiveness of these methods. RCRH mitigates the reheating temperature deviation to (1∼2.5) K covering a wide load ratio range of (20–100) %, indicating a large peak regulation depth of 80 % rated power. The proposed RCRH ensures the sCO₂ power plant to operate at an ultra-low load ratio, which is beneficial to balance unstable renewable energies.