Investigation of Green Liquor Clarifier Design Features, 1998 International Chemical Recovery Conference Proceedings

As pulp mills attempt to incrementally increase production, the green liquor clarifier is forced to handle more liquor, often exceeding its design optimum. The goal of this research is to determine the effect of higher liquor feed rates on clarifier performance and the effect of certain design features in aiding performance.

Dye tracer studies recorded on videotape show a radical change in the fluid flow patterns as the feed rate is increased beyond the optimum design rate for a model clarifier. These changes involve increased turbulence and a large backmixing pattern in the clarifier. Experiments using a slurry of calcium carbonate showed a corresponding decrease in the solids removal efficiency for the clarifier. This decreasing trend was not changed with different feedwell designs or with polymer addition, although there was an increase in solids removal at each feed rate with polymer addition. The placement of a bed of metal dendrite fibers between the feedwell and the clarifier wall also increased the solids removal efficiency and did not significantly decrease as the clarifier feed rate was changed. The increased solids removal at the optimum feed rate was the same as with polymer. These results show promise for using dendrite fibers as a possible method to incrementally increase clarifier capacity.