In this paper, a model predictive control (MPC) case study is presented on the selective catalytic reduction (SCR) in a coal-fired power plant. The MPC is used for optimizing the volume of ammonia injection in order to meet the emission standard of nitrogen oxides (NOx) as well as to prevent ammonia slip. A gain scheduling model is applied to deal with the nonlinearity of the SCR unit. The model gain is developed by kernel density estimation and the dynamic model is estimated by the asymptotic method of identification. The MPC control result shows that the standard deviation of outlet NOx concentration can be reduced by two-thirds, which leads to about 25% reduction of reagent consumption and the prevention of ammonia slip. (C) 2017 Elsevier Ltd. All rights reserved.