Water Release from Fractionated Stock Suspensions. 2. Effects of Consistency, Flocculants, Shear, and Order of Mixing

摘要

The rate of gravity drainage from a papermaking stock suspension was found to be highly dependent on the initial consistency, as well as on the presence of cellulosic fines. The results of testing were fitted to a model based on different linear contributions to drainage resistance due to the fibers and due to each type of fines. Deviations from the model at relatively high consistency were tentatively attributed to flocculation phenomena. By selectively treating either the fines, the fibers, or the combined furnish with cationic polyelectrolytes it was possible to achieve substantially higher rates of dewatering. Results were consistent with several mechanisms, which may possibly act in parallel during ordinary papermaking. Attachment of cellulosic fines to fiber surfaces can prevent those fines from migrating to choke points within a wet web. Agglomeration of fines to each other can reduce their effective surface area. Flocculation of the fibers can make the fiber mat less uniform, thus providing larger channels for water to flow from the mat.