Enhancement of SCR denitrification control strategy considering fluegas temperature fluctuation: Fundamental principle and performance evaluation

Abstract

Nitrogen oxides (NOx) constitute a primary pollutant in coal-fired power plants, and are mitigated through the application of selective catalytic reduction (SCR). Coal-fired power plants should frequently change their output power to help the power grid to accommodate high penetration of intermittent renewable power. However, NOx emission transient overshoot often occurs in coal-fired power plants when coal-fired power plants dynamically change their output power. To address this issue, dynamic models for both coal-fired power plants and SCR denitrification were established. The study identifies fluctuations in fluegas temperature as a critical factor contributing to transient NOx overshoots. The change law of SCR reaction temperature during load cycling processes is obtained, and its prediction model based on neural network algorithm is developed. An enhanced control strategy, accounting for the temperature variations at the SCR inlet, was subsequently introduced. Performance comparisons indicate that the enhanced control strategy effectively eliminates transient NOx overshoots during load cycling processes. Specifically, the maximum NOx emissions during loading down and loading up processes under the enhanced control strategy are 48.62 and 49.44 mg m−3, representing reductions of 7.36 and 4.63 mg m−3 compared to the original control strategy. Additionally, when the enhanced control strategy is adopted, the cumulative ammonia (NH3) consumption decreases by 0.48 and 11.84 g m−3 during loading down and loading up processes, respectively.