Multiscale modeling and control of fiber length in pulp digester

Abstract

During the Kraft pulping process, the fiber morphology such as fiber length and cell wall thickness changes due to degradation reactions. In this work, a multiscale model that integrates a widely employed mathematical model (i.e., extended Purdue model) and a microscopic model (i.e., kinetic Monte Carlo algorithm) is proposed to capture the dynamic evolution of the fiber morphology while cooking, as well as conventionally measured pulp quality index (i.e., Kappa number). To deal with the computational requirement of this multiscale model, a reduced-order model is identified and implemented to a model-based controller to regulate the fiber length and Kappa number to desired values.