Multiscale modeling and model-based feedback control of pulp digester

In addition to the Kappa number, which indicates the residual lignin content in the wood pulp, microscopic properties of wood chips such as porosity are also very important as it determines the paper quality as well as the rate of delignification. However, there are very few models that are able to describe the evolution of porosity of wood chips during delignification processes like pulp digester. Motivated by this consideration, in this work, a multiscale model for a batch-type digester is developed. Specifically, the Purdue model is used to describe the interactions among the free liquor, entrapped liquor and solid phases, and the kinetic Monte Carlo model is employed to show the evolution of wood chip porosity. Then, a model-based feedback control system is developed to regulate the porosity and Kappa number to desired values.