660 MW 燃煤机组变负荷过程 SCR 脱硝性能研究

Coal-fired power generation produces nitrogen oxides (NO_x) that are extremely harmful to the environment. Selective catalytic reduction (SCR) denitrification technology effectively reduces NO_x emissions of coal-fired units. However, in the frequent load-cycling processes, it is difficult to accurately control the NH₃ injection rate of SCR system, resulting in large fluctuation of NO_x emission. In this paper, the dynamic simulation model of thermal system and SCR system model of coal-fired units are developed, and the denitrification performance in load-cycling processes are analyzed. It is found that the NO_x emission in the load-lifting process of coal-fired units is lower than the set value of 45 mg·m⁻³, and the average NO_x emission concentration is 42.124 mg·m⁻³. While in the load-shedding process, NO_x emission is higher than the set value, which is 52.536 mg·m⁻³, but NH₃ escape is significantly lower than that in the load-lifting process. The study shows that in the transient process, the NH₃ storage effect of SCR catalyst layer leads to the difference between the NO_x reduction reaction rate and the transfer rates of heat and mass of fluegas, which results in the instability of denitrification performance in load-cycling processes. The research results provide a theoretical basis for the optimization of NH₃ injection control logic of SCR system.