Washing of Sulphite Spruce Pulp

Abstract

The displacement washing of spruce sulphite and kraft pulps was simulated using a laboratory washing cell. Geometrical properties of pulp fibres, as well as intrinsic properties of spent red and black liquors were determined. The sulphite spruce pulp beds showed the greater intrinsic permeability and lower specific resistance in comparison with the kraft spruce pulp. The displacement washing process was described by the washing curves measured for lignosulphonates and/or alkali lignin. The wash yield determined for sulphite spruce pulp was found to be greater than that for kraft spruce pulp. The relationships between the wash yield, on the one hand, and the Péclet number for each pulp sort and/or two independent dimensionless criteria for all data obtained for both pulp sorts, on the other hand, were expressed by the correlation equations.