High sulphidity kraft pulping

The object of this project wits to evaluate the effect of high sulphidity oil the performance of the kraft cooking process Softwood (SW) mix (50150 of spruce. Picea abies, and pine, Pinus sylvestris) and a hardwood (HW birch. Betula pendula) have been explored as wood rave material The reference kraft cook was carried out at 35% sulphidity The laboratory kraft cooking trials showed that the rate of delignification in kraft cooking increases with Increasing sulphidity for both these raw materials An increase in sulphidity from 35% to 80% increases the apparent delignification rate by a factor of almost two. The faster delignification rate could be exploited as an Increase in production and/or as a reduction in EA charge (2%-units for both raw materials) and, or lis a decrease in cooking temperature (5 C for SW) at the sane production The yield of softwood kraft pulp at it given kappa number was not affected by the increase in sulphidity For hardwood, the combination of high sulphidity and reduced effective alkali charge gave sin increase In pulp yield of one %--unit The pulp viscosity at a given kappa number was increased The high sulphidity in SW kraft cooking (at it given EA-charge) led to a slightly better bleachability in sin OD(I-IT)DD bleaching sequence. The fully bleached SW kraft pulp at 80% sulphidity had;I Slightly higher tear index and higher fibre strength than the corresponding reference kraft pulp at 35% sulphidity. The other strength properties were virtually unchanged The fully bleached HW kraft pulp at 80% sulphidity showed better optical properties, light scattering and opacity, which are. In fact, the critical properties for fully bleached hardwood pulps.