Video observation of pulp pad formation and properties in brownstock washing

Ten years of brownstock washing research results from McMaster University are overviewed with emphasis on polymer enhanced brownstock washing. Reported for the first time are the direct measurements of the effects of dispersed air and defoamer addition on the flow rate of black liquor pulp through pulp pads on the a laboratory brownstock washer screen. The presence of air bubbles in the vat can lower the liquor flow rate by a factor of ten. Defoamer addition gave larger air bubbles that passed through the pulp pad giving nearly the same liquor flow rates observed in the absence of air bubbles.