Tube-Wall Temperature Prediction ofa 660-MW Ultra-Supercritical Double-Reheat Boiler under Flexible Peak Shaving

Ultra-supercritical double-reheat boilers employ multiple temperature-regulating methods during flexible peak shaving.This exposes the boiler to significant tube-wall temperature deviations and overtemperatures.In this study,a compartment model was developed to subdivide the overlapping high-temperature heating surfaces of a 660-MW double-reheat boiler into smaller compartments.The model was verified using field experimental data and was applied to calculate the enthalpy and tube-wall temperature distributions under different loads.In addition,the effects of three temperature-regulating methods(swinging burners,regulating dampers,and flue gas recirculation)on the variation tendency and deviations of the tube-wall temperature were analysed.The results indicated that overtemperatures occurred in the high-temperature superheater under a low load.The regulating damper method caused the high-temperature secondary reheater to exceed the permissible temperature by 21.4℃.The tube-wall temperature exhibited a bimodal distribution along the width.At 0%flue gas recirculation,the maximum tube-wall temperature deviation attained 13.39℃,exceeding a reasonable value by 3.39℃.The swinging burner method was the least likely to cause tube-wall temperature deviations and overtemperatures.The reasonable regulation ranges for swinging burners,regulating dampers,and flue gas recirculation were-20°to 7°,45%to 60%,and 8%to 24%,respectively.Based on different flexible peak shaving constraints,an appropriate temperature-regulating method was selected,and the regulation rangewas specified.