Effect of Flocculation on Pulp Drainage Characteristics, 1996 Engineering Conference Proceedings

Flocculation induced by polymeric agents or by ionic species is an important phenomenon in the processing of pulps. The effect of polymeric flocculation on the drainability of pulps has been investigated in the prior literature by characterizing the drainage property of pulps through well known but empirical measures such as the freeness or drainage times and rates. In this work, we study the effects of flocculation by following more fundamental properties. The permeability and compressibility properties of a pulp are evaluated through its specific surface area, specific volume and its compressibility parameters (indexes) as measured by the Pulmac permeability tester instrument. Bleached kraft softwood pulps in ionic forms were investigated in the flocculated and unflocculated states by the use of a dual polymeric flocculation agent (poly DADMAC in conjunction with Anionic PAM) and also by the use of sodium chloride. The specific surface areas and the specific volumes (as measured by the Pulmac tester ) showed significant reductions contributing to the increased drainabilities of the pulp. Interestingly, it was found that the compressibility parameters were not affected to a great extent.