Displacement Washing of Kraft Spruce Pulp with Low and High Kappa Number

Abstract

The paper deals with the displacement washing of kraft spruce pulp delignified to two kappa number levels. Using the step function input change method, the washing breakthrough curves measured for alkali lignin as a tracer were described by the dispersed plug flow model. Besides the traditional wash yield, the relationships between the axial dispersion coefficient and Reynolds number, as well as between the mean residence time and space time were investigated as well. The results obtained showed that remarkable differences in the wash yield, dispersion coefficient, as well as mean residence time were found for both kappa numbers of kraft spruce pulp.