Polymer enhanced brownstock washing: Mill trial

Cationic polymer was applied onto fiber pads supported on brownstock vacuum drum washers in an effort to increase displacement washing efficiency. Sodium concentration, liquor conductivity, and lignin (VIS absorbance) at the feed and for pulp samples taken off the washer drum were measured as a function of polymer treatment concentration. Washing was characterized by the relative displacement ratio, RDR, defined as the displacement ratio of the treated portion of the drum divided by the displacement ratio of the control section. Displacement ratios are defined as the mass of material (sodium or lignin) removed from the pad divided by the total initial amount in the pad that is removable. In all cases, the RDA increased with the addition of polymer, thus indicating that cationic polymers improved the displacement washing efficiency. The most dramatic changes were observed with the first washer where the RDR for sodium improved from 0.815 to 0.957 by the addition of 6 g/L of cationic polymer (13 kg polymer per o.d. metric ton of pulp).