US 3,938,206 AGranted

Method for continuous displacement washing of liquid-containing pulp materials

OwnerPer Stranger-Johannesseninventor

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Abstract

Liquid-containing pulp material, especially sulphate pulp containing black liquor, is deposited as a mat on a moving filter and subjected to displacement washing with a liquid such as clean water supplied to one side of the pulp mat and displacing the black liquor, which emerges in substantially undiluted form from the opposite side of the mat. The filter is a screen moving over a supporting floor, said floor and screen together forming a "resistance floor" providing a substantial flow resistance to the liquid. A layer of displacement or washing liquid (e.g., water) is maintained over the pulp mat covering the surface thereof. This layer may have a depth or height of e.g. 10 to 100 cm, thus protecting the surface of the mat against the effect of supply means for displacement liquid and providing a pressure on the upper side of the pulp mat assisting in overcoming the flow resistance of the pulp and the floor.

Claims8

Dependent claims

A method for the continuous washing of liquid-containing pulp material with a displacement liquid, comprising traversing a filter along a predetermined path, supporting said filter throughout a substantial portion of said path upon a support floor, continuously depositing a mat of liquid-containing pulp material upon said filter for movement therewith, separately supplying displacement liquid to the upper surface of said mat of pulp material and maintaining a predetermined head of said displacement liquid thereon, said head of displacement liquid being sufficient to overcome the resistance to the flow of liquids through said mat offered by the average flow resistance of the mat and the additional resistance to flow offered by a resistance floor which includes at least one of said filter and support floor, whereby the liquids in said pulp material are continuously displaced by said displacement liquid, and recovering the displaced pulp liquids substantially undiluted by said displacement liquid.

Dependencies are inferred from the claim text.