A dynamic model of five-stage (C+D)EDED bleach plant was developed usi
ng SIMNON, a dynamic simulation language developed at Lund Institute o
f Technology, as a platform. The model is composed of individual modul
es that represent each bleaching stage. Each module includes chemical
addition and mixing, diffusion and reaction in a retention tower, and
washing. These unit operations are coupled with chemical kinetics for
each bleaching stage using appropriate models. A relationship between
the (C+D)E Kappa number and the input absorption coefficient to the D-
1 stage was used to link the delignification and brightening partial s
equences of the bleach plant. The model, verified using steady-state d
ata, was used to model the dynamic response of the plant to step chang
es in production rate, (C+D) chemical addition, and incoming Kappa num
ber, as well as the open-loop response of the plant to a simulated var
iation in incoming Kappa number. The modular structure of the program
allows a variety of bleach plants to be assessed once flow parameters
and chemical kinetics are known. The dynamic model can also be used to
develop and compare control strategies before being implemented at th
e mill.