Application of Fuzzy Smith Control in SCR De-NOx System

Based on the selective catalytic reduction (SCR) reaction method, the fuzzy Smith control method is used to study the outlet nitrogen oxides concentration control of SCR de-NOx system. The prediction model of ammonia nitrogen mass ratio and the prediction model of inlet nitrogen oxides concentration are established by using linear regression prediction theory, which makes the theoretical ammonia injection quantity more accurate and more real-time. Fuzzy control and Smith prediction can, to a large extent, achieve precise control to the entire ammonia flow system, which improves the quality of ammonia flow control and effectively reduces the emission of nitrogen oxides. And the delay for the measurement of ammonia is solved by taking Smith predictive control. The simulation result shows that the fuzzy Smith control, compared with the traditional PID control scheme, can effectively solve the problems of large lag, nonlinearity and multiple delays, which cannot be solved by the traditional control scheme.