The large delay during control of the spraying ammonia system of SCR denitration system leads to unsatisfactory automatic control effect.To solve this problem

the SCR inlet NO_xconcentration prediction model was established by adopting the nonlinear fitting method.Using the prediction value of this model as the feed forward signal

a modified cascade Smith control strategy was put forward and realized configuration optimization control in the DCS system.The actual operation results show that

this Smith strategy can predict the change of NO_xconcentration at the SCR denitration system inlet effectively

which overcomes the delay property of the system to some extent.The modified strategy improves the control effect and considerably deceases the quantity of the sprayed ammonia by about 15%to 20%.