Multi scale modeling of the delignification kinetics during kraft cooking

The kraft process is today the dominant industrial technology for the production of pulp from wood. In this process, wood chips are boiled with chemicals in order to dissolve lignin, hemicellulose and extractives. The process itself contains several complex mass transport mechanisms, where the chemicals are to be transported into the wood chip and then further into the fiber wall to react with, among other things, the lignin. The reaction products are then transported out into solution in the subsequent steps. Even if the process works, there is a need for better understanding of its governing physical and chemical mechanisms. To that end, this project aims to develop a multi-scale model, based on atomistic models of solution and fiber wall components. Solubility, structure and adhesion are examined with molecular dynamic (MD) simulations, after which the various mass transport steps are systematically examined with suitable continuum models for diffusion. With such a complete model, both troubleshooting and optimization of the process will be easier to implement.