Engineering reaction kinetics in sulfite and sulfite-anthraquinone pulping

In this study, engineering reaction kinetics of sulfite and sulfite-anthraquinone pulping of black spruce wood are investigated. The considered sulfite processes are neutral-sulfite (NS), neutral sulfite-anthraquinone (NS-AQ), neutral sulfite semichemical (NSSC) and neutral sulfite semichemical anthraquinone (NSSC-AQ).;Delignification and carbohydrate degradation rate expressions for both NS and NS-AQ pulping were developed. Research was extended to develop delignification rate expressions for NSSC and NSSC-AQ pulping. The degree of delignification was measured by determining the lignin content of the pulp. Carbohydrate content in the pulp was estimated from the difference between the pulp yield and the residual lignin in the pulp. Reaction temperature and pulping chemical concentrations were held essentially constant in all kinetic experiments. Isothermal experiments were conducted in the temperature range between 165 and 180;The effect of sulfite concentration on the delignification rate expressions for NS and NS-AQ pulping was also investigated. The rates of delignification were determined at 175;The applicability of the H-factor for predicting pulping characteristics during NS-AQ and NSSC-AQ pulping was confirmed.;In preliminary studies, an experimental design was tested and optimum kinetic conditions were found so that penetration and diffusion would not be the rate-controlling steps and the amount of anthraquinone would not be reaction limiting.;The role of anthraquinone as a redox catalyst in NS-AQ was investigated. It was observed that anthraquinone is reduced in NS liquor, and that the redox cycle is involved in NS-AQ pulping.