MODELING AND DYNAMIC SIMULATION OF A BLEACH PLANT

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.