Abstract: A process is provided for preparing groundwood pulp from debarked pulpwood logs, which comprises grinding the logs under a superatmospheric pressure of a gas selected from the group consisting of steam, air, and steam and air, while continuously supplying thereto water comprising spent bleaching liquor at a temperature of at least 70.degree. C. and forming a pulp suspension in the resulting aqueous liquor; centrifugally separating steam from the pulp suspension and using the separated hot steam to heat spent bleaching liquor supplied for the grinding; thickening the pulp suspension to a concentration within the range from about 5 to about 40% and supplying water separated therefrom to the grinding; diluting the pulp suspension to a concentration within the range from about 0.5 to about 4.

Abstract: A process is provided for preparing groundwood pulp from debarked pulpwood logs which comprises grinding the logs under a superatmospheric pressure of a gas selected from the group consisting of steam, air and steam and air, while continuously supplying thereto process white water and water separated in thickening groundwood pulp suspension at a temperature within the range from about 75.degree. to about 100.degree. C.

Abstract: Wood chips are digested at a temperature above 100.degree. C in contact with a solution of a hydroxide or salt of an alkali metal or alkaline earth metal or ammonium in a solvent which boils above 100.degree. C at atmospheric pressure, such as ethylene glycol. The cellulose pulp is then separated from the dissolved lignin. The dissolved lignin may be precipitated and removed from the solvent and the solvent may then be recycled, so that there is no waste spent liquor. Examples of salts which may be used are sodium phenoxide and a combination of sodium bisulfite and an aldehyde or a ketone.

Abstract: An apparatus and method for the treatment of cellulosic fiber material with maximum efficiency while minimizing capital costs. Fiber material entrained in digesting liquid is impregnated with the liquid in an impregnation vessel, sluiced to a separate digesting vessel, and from the digesting vessel sluiced to one or more separate washing vessels without a significant reduction in pressure. Countercurrent washing is effected in the washing vessel(s). Digesting liquid withdrawn from the digesting vessel is heated in a transfer line back to the impregnation vessel.

Abstract: The invention relates to a continuous method of making cellulosic pulp from wood chips within a range of yield from 65 to 90 per cent by digestion with a digestion liquor containing Na.sub.2 S and Na.sub.2 CO.sub.3. The digestion is effected at temperatures between 150.degree. and 190.degree.C and malodorous sulfur compounds are removed from the pulp, the liquor and the vapors prior to their withdrawal from the digesting process. In order to eliminate their capacity of emitting obnoxious odors, the sulfur compounds are oxidized by addition of molecular oxygen to the digester prior to discharge of pulp and spent liquor from the digester after which the spent liquor is removed from the digested pulp, concentrated and burned for renewed use in preparation of fresh digesting liquor.