Method of increasing cellulosic pulp yields in an alkaline digestion process
AssigneeSvenska Traforskningsinstitutet
InventorsInga L. Backstrom, Nils J. C. Hartler, Knut P. Kringstad
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Abstract
Increased pulp yields are obtained by alkaline digestion of cellulosic material until a pulp yield of not above 65% is obtained, lowering the pH of the digestion liquid is lowered to allow 11 causing organic substances to precipitate from the digestion liquor and then continuing digestion in the presence of the pulp until at least 5% of the organic substances which have been precipitated out are absorbed by the pulp.
Claims6
In a method of preparing pulp by alkaline digestion of cellulosic material, the improvement which comprises digesting said cellulosic material containing organic substances in an alkaline digestion liquid at a temperature of from 50.degree.C to 200.degree.C to give a pulp yield of not above 65 percent, lowering the pH of the digestion liquid to below 11 in the presence of the pulp to precipitate out at least 5 percent, based on said cellulosic material, of organic substances dissolved in the digestion liquid, and then continuing said digestion at a temperature of 50.degree.C to 200.degree.C until a large percentage of said precipitated organic substances have been absorbed by the pulp during an absorption period.
Dependencies are inferred from the claim text.