The kinetics of lignin extraction in oxygen delignification
A better, fundamental understanding of the behavior of oxygen bleaching systems, including the kinetics and mass transport resistance is needed. This knowledge is expected to result in further improvements in the technology and will enable the development of resource efficiency in the process of the bio-based industry.
This project is part of the Industrial Graduate School Resource Smart Processes ( www.resurssmarta.se ).
Project description
An additional step using oxygen is widely used for lignin removal before the bleaching sequence during the production of semi- and fully-bleached kraft pulps. A low lignin content in the pulp after oxygen delignification, entering the bleach plant enables a substantial reduction in the consumption of bleaching chemicals. Other objectives of extending the oxygen delignification are to reach a higher brightness of bleached pulp and facilitate bleach plant closure. A higher yield of bleached pulp is obtained if an extended delignification by oxygen replaces a part of the residual delignification by kraft cooking.
Mass transfer of reactants is important to consider because oxygen bleaching systems have all three phases present. Oxygen must cross the gas-liquid interface, diffuse through the liquid film surrounding the fiber, and finally diffuse into the fiber wall before reacting. Then, the reaction products need to be extracted from the fiber wall.
This project aims to provide a fundamental understanding of the behavior of oxygen delignification systems, in more detail about kinetics and mass transport. For an adequate prediction of the delignification rate and carbohydrate degradation, both reaction kinetics and mass transport resistance must be considered. Currently, this field is largely unexplored. With new knowledge, it will be possible to further optimize the efficiency of oxygen delignification when producing kraft pulp.
Financing
Vinnova
Pulp and paper companies
Collaborators
Olena Sevastyanova, KTH
Gunnar Henriksson, KTH
Merima Hasani, Chalmers University of Technology
Hans Theliander, Chalmers University of Technology
Malin Wohlert, Uppsala University
Tomas Vikström, Valmet
Stora Enso
SCA
Södra skogsägarna ekonomiska förening
BillerudKorsnäs
Holmen