Mo Och Domsjo Aktiebolag

Mooch Domsjo Ab

Modo-chemetics Ab

Jonas A Lindahl

Lars G Rudstrom

Pekka O Haikkala

Claes G Svensson

John R Bergstrom

Sten L Haggstrom

Ernst B Tiberg

Gustaf E Johnsson

Method for producing bleached sulfate pulp having a long fiber fraction

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.

Method and apparatus for the processing of groundwood pulp to remove

A process is provided for producing high yield bleached cellulose pulp, such as groundwood pulp, thermomechanical pulp, chemimechanical pulp and waste paper pulp, having a broad field of use, which comprises bleaching cellulose pulp, thinning the pulp to a low pulp consistency; mechanically working the pulp; and fractionating the cellulose pulp into a long-fiber fraction and a fine-fiber fraction, the freeness of the long-fiber fraction exceeding the freeness of the fine-fiber fraction by from about 150 to about 600 ml C.S.F. and the fine-fiber fraction constituting from about 35 to about 70% by weight of the bleached pulp.

Process for producing high yield bleached cellulose pulp

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 9.5; thereby separating heavy metal ions, resins and alkali-extracted substances in solution in the expressed liquor, but not any lignin.

Process for pretreating particulate lignocellulosic material to remove

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., such as by spraying such shower water upon the end portions of the logs or chip mass, optionally combined with a supply of shower water delivered via the ram plates and a water trap arranged around the lower part of the log pockets facing the grindstone, so as to maintain a high uniform level of moisture content in the grinding zone, and to retain the shower water within said zone to an extent such that hollows between the logs or chips located nearest the surface of the stone are also filled with shower water; the wood can thus be brought into effective contact with bleaching chemicals at an early stage, resulting in a pulp of high brightness.

Process for manufacturing bright and strong bleached groundwood pulp of

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.

Process for manufacturing groundwood pulp while maintaining a high and

A process is provided which comprises the steps of:

Process for preparing groundwood pulp as short fiber and long fiber

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.

Method for delignifying or bleaching cellulose pulp wherein chlorine is

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.

Process and apparatus for the deresination and brightness improvement of

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.; then, optionally, any one or more of the steps of centrifugally separating steam from the pulp suspension and using the separated hot steam for heating purposes; thickening the pulp suspension within the range from about 5 to about 50% and supplying water separated therefrom to the grinding; and adding bleaching chemicals to the pulp and bleaching the pulp; the groundwood pulp is obtained in a higher pulp concentration and at considerable saving in energy, can be used with our without bleaching, and has a high content of long flexible fibers.

Process for the preparation of groundwood pulp

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.

Process for manufacturing chemimechanical cellulose pulp in a high yield

A process is provided for the chemical refining of cellulose pulp which comprises, in sequence, the steps of:

Process for the chemical refining of cellulose pulp

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., and forming a pulp suspension in the resulting aqueous liquor; centrifugally separating steam from the pulp suspension, and using the separated steam to heat the water supplied to the grinding; thickening the pulp suspension to a pulp concentration within the range from about 5 to about 40%, and supplying water separated therefrom to the grinding; diluting the thickened pulp, and screening the diluted pulp suspension; after thickening the screened rejects suspension to a pulp concentration of at least 10% and defibrating the screened rejects suspension in a refiner, recycling the defibrated screened rejects to the from-steam-separated pulp suspension; and mixing the thickened and refined rejects suspension, having a pulp concentration of at least 8%, with the pulp suspension, thereby increasing the pulp concentration of the from-steam-separated pulp suspension, and thus facilitating its thickening.

Method for producing groundwood pulp

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 4.0%; screening the pulp suspension; thickening the pulp suspension to a concentration within the range from about 10 to about 50% and supplying water separated therefrom to the screening; adding bleaching chemicals to the pulp and bleaching the pulp; diluting the bleached pulp with spent bleaching liquor to a concentration within the range from about 1 to about 6%; thickening the bleached pulp suspension to a concentration within the range from about 10 to about 50%; and separating, heating and recycling to the grinding spent bleaching liquor containing residual bleaching chemicals.

Method of producing groundwood pulp

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.; and recycling the bleaching liquor recovered from the dewatering to the mixing zone while maintaining a temperature in the recycled liquor to bring the pulp suspension to within said range of the bleaching temperature during the mixing with bleaching agent.

Growing community of inventors

Domsjo, Sweden

Jonas A Lindahl