Apparatus for treating pulp produced by solvent pulping

Abstract

An apparatus and process for the solvent pulping and washing of pulp using vessels purged of oxygen free gas when the process is arrested or terminated. The washing is accomplished by first continuously passing the pulp to a pressure diffuser, then to a first multi-stage drum displacer washer, and then to a second multi-stage drum displacer. In the pressure diffuser the lignin is washed out of the pulp, utilizing as wash liquid a mixture of solvent and water having a solvent concentration equal to or higher than that required by the extraction process within the digester, and at a pressure at least about 350 psi. The pressure in the second and third stages is lower, and water is the wash liquid in the third stage. Alcohol can be recovered from the spent wash liquid of the first wash stage, so that all but about ten gallons or less of alcohol per ton of pulp is recovered.

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