Displacement of black liquor from pulp fibre bed

Using distilled water and/or aqueous polyacrylamide solutions, the mechanis m of the displacement washing of unbleached kraft pulp was investigated. Th e step change technique has been employed in the investigation of displacem ent of black liquor. To characterize the displacement of black liquor, the washing curves as well as wash yield at the wash liquor ratio equal to unit y were determined. The results obtained for pure wash water were compared w ith those for polyacrylamide solutions.