In order to improve the control quality and economy of selective catalytic reduction(SCR) denitration system

it is necessary to establish an accurate dynamic model of NO_x production at inlet of the SCR denitrification reactor. On the basis of fuzzy tree model

this paper builds up a dynamic model for NO_x production at the SCR reactor inlet

and proposes using a joint time-delay estimation method based on multiple correlation coefficients to estimate the time-delay of the input variables which affect the NO_x production. The method was applied to the operation data of a 600 MW coal-fired unit

and the time-delay of input variables were estimated by correlation coefficient method and multiple correlation coefficient method. The experimental results show that

the fuzzy-tree model has high accuracy and generalization ability

the time-delay estimation of input variables based on multiple correlation coefficient method improves more accurate and generalization ability for the model than the correlation coefficient method.