Abstract: A method for producing bleached sulfate pulp comprising the steps of:(1) conducting an initial bleaching of a sulfate pulp, wherein the pulp is manufactured by a sulfate process from softwood, with at least one non-chlorine-containing bleaching agent, the initial bleaching comprising one or more consecutive stages,(2) during step (1), lowering the kappa number of the pulp to below 12, while permitting the limit viscosity to fall below 900 cm.sup.3 /g,(3) fractionating the pulp prior to or at a time subsequent to step (1) to obtain:(a) a long fiber fraction comprising fibers, wherein less than 10% by weight of the fibers pass through 200 mesh and greater than 60% by weight of the fibers are retained on 30 mesh, wherein the long fiber fraction has a shive content of less than 0.

Abstract: Coarse wood residues, slivers and shives present in groundwood pulp as obtained in grinders are removed by passing a uniform flow of the pulp suspension containing coarse wood residues and shives from the grinder to a conical crushing and beating refiner having two treatment zones with a stationary part and a rotary part for reducing all wood material present in the suspension to free fibers, while measuring and controlling the freeness of the pulp within selected limits by controlling both the power input to the grinder and the power input to the conical crushing and beating refiner, and the degree of beating of the pulp, obtaining groundwood pulp having a low shives content and superior strength properties, at a low energy consumption.

Abstract: A process is provided for pretreating particulate lignocellulosic material to remove heavy metals and resin without any delignification or defibration, which comprises washing particulate lignocellulosic material; compressing the washed material to a solids content of at least 40% to remove absorbed and excess liquid; impregnating the compressed material with an alkaline aqueous solution comprising alkali and at least one of a heavy metal ion complexing agent and a heavy metal ion reducing agent; heating the impregnated material at a temperature within the range from abut 50.degree. to 100.degree. C. for up to approximately 0.75 hour; compressing the pretreated material to a solids content of at least 40%; and separating undiluted liquor squeezed out during the compression, while maintaining conditions during the pretreating such that the pH of the squeezed-out liquor is within the range from about 4 to about 9.

Abstract: A process for manufacturing bleached groundwood pulp of improved and uniform quality, in which debarked wood logs or wood chips are ground in a closed pocket grinder at atmospheric or super-atmospheric pressure, while applying shower water to the free surfaces of the grindstone, and shower water containing bleaching chemicals to the grinding zone where the wood is in contact with the grindstone, i.e.

Abstract: A process is provided for manufacturing groundwood pulp of uniform quality by maintaining a high and uniform moisture content in the wood in the grinding zone which comprises grinding debarked wood logs or wood chips in a closed pocket grinder under atmospheric or superatmospheric pressure while applying shower water both to the free surfaces of the grindstone and to the grinding zone where the logs or chips are in contact with the grindstone, such as by spraying the water at the end portions of the logs or chip mass, optionally together with applying shower water via the ram plates and a water trap arranged around the lower part of the log pockets, and preferably retaining shower water within the grinding zone by filling with shower water the hollows between the logs or chips located nearest the surface of the grindstone.

Abstract: A process is provided which comprises the steps of:(1) grinding lignocellulosic material to form an aqueous groundwood pulp fiber suspension;(2) screening the groundwood pulp fiber suspension through a coarse screen having screen openings not less that about 5 mm;(3) defibrating lignocellulosic material separated out on the coarse screen;(4) recycling the defibrated lignocellulosic material to the groundwood pulp fiber suspension from the grinding step (1);(5) separating the groundwood pulp fiber suspension from step (2) into (a) an accepts fraction and (b) a rejects fraction, the latter comprising from about 30% up to about 85% by weight of the fiber suspension;(6) screening the rejects fraction 5 (b) of the groundwood pulp fiber suspension through a screen having screen openings of less than about 5 mm;(7) separating the fiber suspension from step (6) into (a) an accepts fraction and (b) a rejects fraction;(8) recycling the rejects fraction 7(b) to the defibrating step (3) and then to the groundwood pulp fi

Abstract: A method for delignifying and/or bleaching cellulose pulp adds to the cellulose pulp a liquid which contains chlorine dioxide, causes the pulp to react with the chlorine dioxide over a selected period of time, and then reduces the amount of available active chlorine, optionally to a negligible amount, either by reducing the amount of liquid accompanying the cellulose pulp and/or by displacing such liquid with a newly supplied liquid containing no active chlorine or at most only a small amount of active chlorine; the displaced liquor can be replenished with chlorine and optionally with chlorine dioxide, and then added mainly to fresh cellulose pulp in the same bleaching stage, and/or to cellulose pulp in another bleaching stage.

Abstract: A process and apparatus are provided for the deresination and brightness improvement of cellulose pulp, by adjusting the pulp concentration to within the range from about 15 to about 35%; adding sufficient alkali to the pulp to bring the amount of alkali, calculated as NaOH, within the range from about 0.5 to about 17 g/kg of water accompanying the pulp; adding sufficient oxidizing bleaching agent to the pulp to bring the amount of oxidizing bleaching agent to within the range from about 0.2 to about 22 g/kg of water; subjecting the pulp to a mild, mechanical working in the bite of twin interdigitated rotating screws at an energy input of from 8 to 100 kWh per ton of pulp; removing and reacting the pulp with the added alkali and bleaching agent for from about 0.1 to about 5 hours; and then washing out dissolved resin from the pulp.

Abstract: A process is provided for preparing groundwood pulp from debarked pulpwood logs, which comprises grinding the logs in the presence of water under a superatmospheric pressure of a gas selected from the group consisting of steam, air, and steam and air, and forming and discharging a pulp suspension in the resulting aqueous liquor, while continuously supplying water during the grinding in a volume of less than 35 parts per part of bone dry pulp at a rate of addition such that the temperature of the discharged pulp suspension is below 200.degree. C. and preferably below 180.degree. C. and within the range from about 1.5 to about 50, preferably from 2 to 8, times the temperature in .degree.C. of the added water at a pressure within the range from about 8 to about 40 kiloponds/cm.sup.2, preferably from 10 to 30 kiloponds/cm.sup.2, higher than the superatmospheric pressure and at a temperature within the range from about 2 to about 63.degree. C.

Abstract: A process is provided for the manufacture of bleached chemimechanical cellulose pulp in high yield of between 65 and 95% from particulate and preferably washed lignocellulosic material, such as wood chips, featuring the use of spent or waste bleaching liquid, preferably from a lignin-preserving bleaching process, in at least one stage of the process where a cooling and diluting liquid is required, such as during mechanical defibration of the material.

Abstract: A process is provided for the chemical refining of cellulose pulp which comprises, in sequence, the steps of:(1) impregnating the cellulose pulp with refining chemicals in an amount selected to effect chemical modification of the pulp;(2) adjusting the pulp consistency to within the range from about 30 to about 70%; and(3) passing the pulp in turbulent flow through an elongated reaction zone from one end to another end thereof in a gaseous atmosphere consisting essentially of steam and preferably containing less than 1% by volume of oxygen at a superatmospheric pressure within the range from about 5 to about 400 kPa and a temperature within the range from about 100 to about 150.degree. C. at which the chemical modification proceeds without a mechanical working sufficient to change the degree of beating of the pulp by more than about 2.degree.

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: 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 the bleaching of cellulose pulp, particularly for the peroxide bleaching of high yield pulp, which comprises forming a suspension of lignocellulosic pulp material; mixing the suspension in a mixing zone with a bleaching agent while adjusting the temperature of the pulp suspension to within the range from about +10.degree. C. to about -10.degree. C. of a temperature within the range from about 40.degree. to about 95.degree. C. at which bleaching is to be carried out; quickly dewatering the pulp suspension to a pulp consistency within the range from about 18 to about 50%, equal to or at most 5% less than the pulp consistency of the pulp suspension charged to the mixing zone; passing the dewatered pulp suspension to the bleaching zone before its temperature can change substantially from the adjusted temperature; carrying out the bleaching with a bleaching agent at the selected bleaching temperature within the range from about 40 to about 95.degree. C.

Abstract: Process and apparatus are provided for the preparation of improved high-yield cellulose pulps, such as semichemical, chemimechanical, thermomechanical, and mechanical pulps, which comprises mechanically defibrating a mixture of particulate lignocellulosic materials which have been partially pulped and softened to different extents. Part of the raw lignocellulosic material is particulate form is washed, moistened with steam, impregnated with pulping chemicals and pulped to a yield of from about 65 to about 92%. Another part is treated in similar manner but either not pulped at all or, if pulped, pulped to a lesser extent. The two parts are mixed without intermediate washing, after which the mixture is subjected to a vapor phase pulping by heating to a temperature within the range from about 90 to about 200.degree. C. under pressure to obtain softening of the lignin, and delignification, after which the resulting product is mechanically defibrated to form cellulose pulp.