PROCESS FOR THE RECOVERY OF PROCESSING CHEMICALS FROM THE BLACK LIQUOR IN THE PRODUCTION OF CELLULOSE BY ORGANO-SOLVENT PROCESSES

摘要

In order to recover inorganic chemicals from waste liquors in cellulose manufacturing processes it is proposed to separate the alkali or alkaline earth from the organic components by partial or complete oxidation in the aqueous phase with air and/or oxygen. Before this oxidation process, it is possible to separate the lignin in the black liquor by acidification and precipitation with a mineral acid, the resins by extraction and the demi-celluloses by ultra-filtration, whereupon the residual organic substances still remaining in solution are oxidised. Wet oxidation is possible such that the carboxylic acids, especially the acetic acid, is not burned as well and can be separated by crystallisation after caustification. The chemical solution thus freed of organic substances can be returned to the liquor by caustification and made available in the cellulose production cycle.