For such characteristics as large time delay and nonlinear of ammonia spraying control in selective catalytic reduction(SCR) denitrification system

a control method based on Smith predictor and conditional integral sliding mode control was proposed. In this method

the Smith predictor was used to compensate the system delay and shorten the adjustment time

the robustness of the sliding mode control(SMC) was applied to overcome the influence of controlled object environment changes and external disturbance on the system

and the conditional integral sliding surface was used in the SMC to eliminate the steady-state error and to restrain chattering in the system. Moreover

the SCR flue gas denitrification system with general PID control

sliding mode control based on the Smith predictor

conventional integral sliding mode control based on the Smith predictor and conventional integral sliding mode control based on the Smith predictor was simulated at 100%

80% and 60% of the actual load. The simulation results show that

for the general PID control

the regulation speed is slow

the overshoot is large and the anti-disturbance ability is poor. All the three kinds of sliding mode control have stronger robustness to the disturbance

the system has strong stability after the disturbance

the adjustment time is short and the fluctuation range is very small. For the conventional integral SMC based on the Smith predictor

the regulation speed is fast and the overshoot is small

the system has strong stability after the disturbance and the change range is small

so the control effect is better than the other three control modes.