Virtual bleach plants. Part 3: Caustic extraction and peroxide bleaching models

This paper presents a kinetic model for caustic extraction and peroxide bleaching. A reaction network has been proposed for chemical reactions among pulp components and bleaching chemicals. We use a set of kinetic equations to describe the reaction rate for each reaction in the network. Laboratory data serve to identify model parameters. Combining this model with other models in this series of papers, a virtual bleach plant (VBP) can be built in simulation. This virtual bleach plant can serve as an engineering tool to test various process options and to optimize bleach plants, e.g., evaluating COD carryover impacts on bleaching chemical consumption. It can also be used as a full bleach plant software sensor for advanced process control. Application: The modeling approach described here can help address complicated mill operation and process improvement issues.