An improved control strategy for a denitrification system using cooperative control of NH3 injection and flue gas temperature for coal-fired power plants

Selective catalytic reduction (SCR) technology is widely applied for flue gas denitrification in coal-fired power plants. Given the high penetration of renewable power, coal-fired power plants should operate flexibly to support power grid peak regulation. However, the flexible operation of coal-fired power plants often causes transient overshoot of the NOx outlet concentration and NH3 slip, and restricting the clean and reliable operation of coal-fired power plants is a difficult issue. In this study, a dynamic model of the coal-fired power plant is developed, and the characteristics of a denitrification system during load cycling transient processes were evaluated. Then, an improved control strategy for the denitrification system using cooperative control of NH3 injection and flue gas temperature is proposed. Moreover, the control targets of NH3 injection and flue gas temperature are analytically derived. The NOx outlet concentration exceeds the standard value by 14.22 and 6.80 mg m−3, respectively, during the loading down processes and loading up processes with the original control strategy. When the improved control strategy is adopted, the NOx outlet concentration can be controlled to be smaller than the standard value, and the NH3 slip can be controlled well.