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US 5,310,460 AGranted
Clotting washing
OwnerRobert H. Pelton, Pei Liinventors
Life of this patent
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Abstract
Brown stock washing of wood pulp is improved by adding a water-soluble cationic polymer to the wash water. The cationic polymer reacts with lignin solution present in the larger channels in the pulp mat to give a precipitate which lowers the flow rate of wash water through the larger channels. A more efficient wash water usage is obtained.
Claims9
An improved process for the displacement washing of fibrous material, which comprises:
- applying a wash water to a mat of said fibrous material to effect displacement washing of said mat,
- sensing zones of higher flow rate of wash water through said mat, and
- precipitating solid clots formed by ionic interaction between oppositely-charged species in said mat and in said wash water in said zones so as to inhibit wash water flow in said zones and to achieve a greater uniformity of displacement washing.
A process of washing wood pulp free from spent pulping chemicals by displacement washing of a mat of said wood pulp, the improvement which comprises:
- applying a wash water to a mat of said wood pulp to effect displacement washing of said mat,
- sensing zones of higher flow rate of wash water through said mat, and
- adding to said pulp mat at least one water-soluble cationically-charged species to effect reaction with lignin solution present in a plurality of channels tending to form through the mat during said displacement washing to form a solid precipitate in said channels, so that such solid precipitate tends to lower the flow rate of wash water through said channels and provide a more uniform washing of the pulp mat by wash water.
Dependencies are inferred from the claim text.