Abstract: A process is provided for the treatment of an acidic aqueous effluent derived from a chlorine or chlorine compound bleaching process. The acidic effluent is reacted with a neutralizing base selected from carbonates, hydroxides and oxides of Al, Cr, Co, Fe, Mg, Mn, and Ni. The neutralized effluent is concentrated and residual base and HCl are subsequently recovered. The concentration of neutralized effluent may be accomplished by passing the neutralized effluent through the cooling tower of the pulp mill.

Abstract: Sodium sulfide or hydrosulfide is oxidized to produce sodium polysulfide and sodium hydroxide. Under appropriate conditions, the oxidation may be pursued further to convert all the sodium sulfide into sodium thiosulfate. The oxidation is carried out at or above atmospheric pressure in a mixed reactor or in a pipeline reactor, by sparging oxygen or air, in a mixture of white liquor and lime mud particles produced in the recausticizing plant of a kraft mill.

Abstract: A process for increasing the pulp producing capacity of a kraft mill including the steps of removing at least a portion of the lignin from kraft black liquor and separating the lignin from the aqueous phase. The next step is treating the aqueous phase to separate the inorganics and organics with the organics preferably being recycled to the process loop to be burned in the recovery furnace. The inorganics are converted into pulping chemicals which bypass the recovery furnace and are transported to white liquor preparation.

Abstract: A method of removing dissolved and colloidal macro-molecular organic substances from effluents from processes used in the manufacture of pulp and paper, wherein an acid sludge containing cellulose fibres and being acidified to a pH value of 1.6-2.5, is added to an effluent containing said organic substances, and the pH value is adjusted to 4.5-6.0 before the mixture is subjected to sedimentation to achieve precipitation of the fibres with said organic substances adhered thereto. According to the invention the fibres used as precipitant are subjected to mechanical treatment prior to said acidification, so that the fibres are broken and split open, increasing their specific fibre surface and thereby their ability to catch the organic substances in the effluent.

Abstract: An elongated, imperforate housing (2) has a slurry inlet port (5) at one end and a pulp discharge port (6) at the other end. A pressing section (2b) within the housing is in direct fluid communication with the inlet port, and extracts liquid from the slurry by passing the slurry through a first compression restriction (108) to produce a pressed pulp. An annular washing section (2c) within the housing is positioned immediately downstream of, and in direct fluid communication with, the first compression restriction. The washing section has radially inner (109) and outer (14) cylindrical walls defining an annular washing chamber (110) for decompressing, diluting, and washing the pressed pulp. The washing is accomplished by injecting a washing liquid into the washing chamber through the inner wall, and simultaneously through the outer wall while the mixture is agitated. A repressing section (2d) within the housing is in direct fluid communication with the washing section, for receiving the conveyed mixture.

Abstract: A process is provided for the activation and delignification of cellulose pulp, which comprises:(1) subjecting chemical cellulose pulp to activation by reaction with nitrogen dioxide in the presence of water at a temperature within the range from about 20.degree. to 120.degree. C., while(a) separating gas containing at least 1.2 mml nitrogen oxides, including NO, per liter of gas determined at 25.degree. C. and calculated as nitrogen, reacting nitrogen oxides in said withdrawn gas with oxygen gas in an amount within the range from about 10 to about 200 mole percent, calculated on the amount of NO present, and recycling the reacted gas to the activation; and(b) separating gas containing less than 0.4 mml nitrogen oxides, including NO, per liter of gas determined at 25.degree. C. and calculated as nitrogen from the cellulose pulp and removing said gas from the process; and(2) delignifying the activated cellulose pulp.

Abstract: A method of removing macromolecular organic dissolved and colloidal compounds from the effluents of a paper and cellulose mill by using waste sludge containing fibers and chemicals. The sludge is acidified to a pH of approx. 2 by a mineral acid prior to adding into the effluent. Organic material is precipitated with fibers in a sedimentation vessel at a pH of 4.5-6.

Abstract: A method of removing lignin from bleach plant effluents by using cellulose fibres. The method comprises an acidous phase during which sludge containing cellulose fibres is added to the acidous effluent, and an alkaline phase during which alkaline waste water is added to the effluent-sludge solution. A portion of the produced fraction containing fibres is recirculated to the acidous phase for reuse of the fibres.

Abstract: A process is provided for producing nitrogen oxides from aqueous waste cellulose pulp liquors containing nitrogen compounds including oxygen linked to nitrogen in the molecule, which includes initiating an autocatalytic reaction generating nitrogen oxide in a liquid phase comprising aqueous waste cellulose pulp liquor containing nitrogen compounds including oxygen linked to nitrogen in the molecule at a temperature within the range from about 40.degree. to about 180.degree. C. and at an acid pH within the range from about 0 to about 5 in the presence of nitrate ion NO.sub.3.sup.- in a concentration calculated as nitrogen within the range from about 0.2 to about 5 grams moles per kilogram of water and of lignin in a weight ratio lignin:water within the range from about 0.001:1 to about 1:1; and then continuing the autocatalytic reaction while maintaining a gas phase in contact with the liquid phase having a partial pressure of nitrogen oxide within the range from about 0.

Abstract: A method for batch pulp digestion with hydroxide-bearing cooking liquors in combination with continuous alkaline oxygen delignification is described. The brown stock washing plant and the connected oxygen stage are freed from oxygen-consuming black liquid by withdrawing black liquor from a pre-cook wherein cooking liquor is reacted with a surplus of hydroxide-consuming chips. Moreover, spent cooking liquor in the brown stock washing plant is displaced with spent liquor from the oxygen delignification stage (oxy-liquor) and/or alkalization spent liquor (bleaching spent liquor worth recovering because of its sodium content). A mixture of said liquors is prepared in a pressurized cooking liquor accumulator and charged to the digestion plant liquor circulation system.

Abstract: A method of introducing anthraquinone into the kraft pulping process for the delignification of lignocellulosic material by dissolving or homogeneously dispersing the anthraquinone in a mixture of from about 10% to about 50% white kraft pulping liquor and, correspondingly, from about 90% to about 50% black kraft pulping liquor and then blending this solution with the white liquor feed into the pulping digesters.

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 is provided for the recovery of sulfur dioxide liberated in the chemical pulping of lignocellulosic material, which comprises(1) collecting sulfur dioxide-containing gas emitted during the pulping and separating it into at least two portions;(2) contacting at least one portion with chlorine gas, thereby forming a gaseous mixture comprising sulfur dioxide and chlorine;(3) effecting reaction of sulfur dioxide, chlorine and water to form hydrochloric acid and sulfuric acid while forming an intimate dispersion in said gaseous mixture of an aqueous solution of hydrochloric acid and sulfuric acid;(4) dissolving said hydrochloric acid and sulfuric acid in said solution;(5) recovering said solution and separating it from substantially sulfur dioxide-free residual gas.

Abstract: A process of producing cooking liquor for addition to a digester for enhancement of the yield derived from kraft pulping of wood chips in which a portion of the black liquor is treated with lime under certain conditions and then reused as cooking liquor. The causticizing of the black liquor results in the generation of polysulfide ions and allows, through the formation of calcium-organo complexes, for the carryover of soluble calcium with the black liquor. The presence of calcium ions synergistically enhances the effectiveness of polysulfide such that the use of the new cooking liquor results in pulp yield increases of several percentage points for the same lignin content when compared to conventional kraft pulping.

Abstract: A method for recovery of wastewater residues containing the activated sludge biomass, fibre and bark comprising the steps of treating these with alkali solution having a concentration of 5-80 g/l on the Na.sub.2 O basis at a temperature of 20.degree.-70.degree. C. and dewatering the reaction mixture obtained, the alkali filtrate decanted containing the activated sludge alkali hydrolysis products being used to dissolve the melt in the course of preparing the alkali pulping liquor, and the dewatered alkali mass being added, in an amount of up to 40 percent by mass, to the fibred mass composition for the manufacture of cardboard and wood-fibre board.

Abstract: A process is provided for inhibiting the formation of deposits in the course of pulping lignocellulosic material and in the treating of cellulose pulp, by addition to the cellulose pulping or treating process of compounds of polyvalent metals other than aluminum and manganese capable of complexing deposit-forming anions, thereby maintaining the deposit-forming anions in solution in the form of a liquor-soluble complex.

Abstract: An apparatus and process for the oxygen delignification of pulp is provided in which the pulp is transported by means of timing screws in essentially plug flow through one or more substantially horizontal reactor tubes. Oxygen gas is injected into the system at a point adjacent to the pulp inlet and travels concurrently in substantially plug flow with the pulp through the system. In this manner, the pulp is initially exposed to gas of a high oxygen partial pressure while gas vented from the system adjacent the pulp outlet is of low oxygen partial pressure and has a high content of diluent gases. The process and apparatus avoid the formation of gas pockets and hot spots which may adversely affect the pulp. In an alternate embodiment, a countercurrent gas flow process is disclosed. Also provided is a catalytic treatment and recirculation system for the vented gas which permits efficient use of oxygen within the system.

Abstract: A process is provided for the alkaline oxygen delignification and bleaching of chemical cellulose pulp while inhibiting degradation of carbohydrates in the pulp, due to the presence of one or more aromatic diamines, preferably having the diamine groups directly linked to an aromatic ring.

Abstract: A method of utilizing kraft black liquor by converting the black liquor to "green liquor" and then oxidizing the green liquor with air in the presence of a quinone compound or spent liquor from the kraft process, the soda semi-chemical process or the neutral sulfite semi-chemical process as a catalyst. A marked improvement in the rate of oxidation is obtained. The thus oxidized green liquor is then able to be used as part at least of the digestion liquor in the NSSC process.

Abstract: A process for making a refiner mechanical pulp from wood chips which comprises:(a) Comminuting the wood chips largely by splitting along the wood grain;(b) Wetting said particles with a solution of a sulphite salt of an alkali metal to add an amount of said alkali metal salt within the range of 1% to 10% of the oven dry weight of said particles, said solution having a pH within the range of 7 to 12.5;(c) Steam heating the sulphite salt solution bearing particles to a temperature within the range between 80.degree. C. and 165.degree. C. and holding them within that temperature range for a period of 0.5 to 80 minutes;(d) Passing the particles, after said period of heating, through a disc refiner to produce refiner mechanical pulp.

Abstract: Fibrous material is pre-steamed, impregnated with alkali liquor, refined, and then oxygen pulped at a low consistency (about 3 to 8 percent solids) using an alkali liquor which contains boron compounds. The pulping step of the process is carried out in stages with recycle of liquor to preceding stages after it has been reoxygenated. By recycling a major portion of the pulping liquor, the actual liquor to fibrous material ratio at each stage of the pulping step is maintained at a relatively high level (12/1 to 30/1) while the effective liquor to fibrous material ratio for the overall process is much lower (4/1 to 8/1). This results in a bright pulp of acceptable strength as well as a high solids content spent liquor which is economically recoverable.

Abstract: Water used in the treatment of waste paper is now commonly re-cycled. Hard water is required for such processes. For maintaining the hardness of the water, the re-cycled water is hardened by dissolving calcium carbonate and carbon dioxide in it, thereby forming calcium bicarbonate. An apparatus for hardening the water comprises a mixing container with inlets for waste water, carbon dioxide, and calcium carbonate, and with outlets for foam, hardened water and undissolved calcium carbonate.

Abstract: A process is provided for inhibiting the formation of deposits in the course of pulping lignocellulosic material and in the treating of cellulose pulp, by addition to the cellulose pulping or treating process of compounds of polyvalent metals capable of complexing deposit-forming anions, thereby maintaining the deposit-forming anions in the form of a liquor-soluble complex.

Abstract: A mixture of wood chips and impregnation liquor is continuously passed through an impregnation zone, the mixture is agitated throughout said impregnation zone to maintain the consistency of the mixture constant and the residence time of the chips uniform throughout said impregnation zone, the mixture is withdrawn from said impregnation zone, excess liquor is removed from the chips and said chips are then digested in a cooking zone.

Abstract: An improvement in the delignification (pulping) of raw cellulose by treatment with oxygen and an alkaline buffer solution at elevated temperature and pressure, which comprises carrying out the process in an unflooded condition, that is, where contact between the raw cellulose and buffer solution is intermittent, both gaseous and liquid phases being present at all times. Optionally, cupric ion may be present as a catalyst.

Abstract: By pretreating lignocellulose with an alkaline pretreatment liquor containing anthraquinone or a related compound, prior to alkaline digestion, a higher yield of pulp having a lower lignin content can be produced using less alkali. The pretreatment step is carried out under conditions that ensure survival of at least 50% of the anthraquinone or related compound in the pretreatment liquor, which is separated from the pretreated lignocellulose and reused to pretreat other lignocellulose.

Abstract: A process for producing high yield chemimechanical pulps from woody lignocellulosic material, such as wood chips, whereby the material is treated with an aqueous solution of a mixture of sulfite and bisulfite, said solution being of sufficient strength to sulfonate said material to at least about 85% of the maximum level of sulfonation that can be achieved on said material without reducing the pulp yield to below 90% and subjecting the resulting sulfonated material to mechanical defibration.

Abstract: A process for bleaching cellulose pulp with molecular oxygen under alkaline conditions and at an elevated temperature in a bleaching zone is disclosed in which oxygen gas is dispersed into an alkaline bleaching solution under an increased pressure, the oxygen-containing, alkaline bleaching solution is heated to at least the elevated bleaching temperature, the pressure of the hot, oxygen-containing, alkaline bleaching solution is lowered to the pressure prevailing in the bleaching zone, and the hot, oxygen-containing, alkaline bleaching solution is brought, in the bleaching zone, into contact with the cellulose pulp to bleach the latter with the oxygen gas released from the bleaching solution.

Abstract: A process for pulping hardwood to produce cellulose pulp in good yield and of high quality, with a low requirement for causticized pulping liquor, which comprises in a first pulping stage pulping the hardwood in an alkaline pulping liquor containing sodium sulfide at a pH of about 10.5 to about 13 and at a temperature within the range from about 110.degree. to about 170.degree. C while generating hydrogen sulfide in situ by reaction of sodium sulfide with organic acids liberated in the pulping; and then in a second pulping stage, following directly after the first pulping stage, continuing the pulping at a pH higher than said first stage pH, within the range of about 12.5 to about 14 and at a temperature higher than said first stage temperature within the range from about 145.degree. to about 190.degree. C, in the presence of added alkaline pulping liquor comprising sodium hydroxide and sodium sulfide until cellulose pulp is produced.

Abstract: A process is provided for reducing the requirement of fresh chemicals without increasing emissions in the pulping of cellulosic material with alkaline sodium- and sulfur-containing-sulfate pulping liquor, which comprises evaporating and burning spent sulfate pulping liquor to obtain a smelt; dissolving the resulting smelt in water to form a sodium-sulfide-sodium carbonate-containing solution green liquor; regenerating pulping white liquor containing sodium sulfide and sodium hydroxide from said green liquor; and recirculating said regenerated white liquor to the pulping stage; oxidizing at least one of the resulting green and white liquors to form sodium thiosulfate therein; reacting the oxidized liquor with residual acid liquor, from the manufacture of chlorine dioxide by reduction of an alkali metal chlorate solution, to convert thiosulfate to sulfur dioxide and sulfur; removing and recovering formed sulfur dioxide; and returning the residual liquor, freed from sulfur dioxide, to the pulping.

Abstract: Cellulosic material is delignified with oxygen previously dissolved into a fresh alkaline aqueous medium, all of the oxygen contacting said cellulosic material being introduced into said cellulosic material by said alkaline aqueous medium containing oxygen dissolved therein and the cellulosic material consistency during delignification being such as to form an agglomeration of said cellulosic material and alkaline aqueous medium in the form of a layer without any gaseous space therein.

Abstract: The pulping of lignocellulosic material in the presence of oxygen gas and an alkaline liquid is improved by carrying out the process in two stages. In the first stage, the alkaline liquid is trickled over the material as the oxygen is passed up through the material. In the second stage, the material is submerged in oxygenated alkaline liquid which flows through the material.

Abstract: A slurry of cellulosic material is diluted to a flowable consistency and subjected to a pressure differential on a permeable surface to increase the slurry consistency to a value between the consistency of the diluted slurry and the consistency of th slurry prior to dilution thereby forming a mat of cellulosic material on the permeable surface. The liquid and solids which pass through the permeable surface as a result of the pressure differential are recycled for use as slurry diluent, and to the mat of cellulosic material is applied a treating liquid, such as a washing liquid.

Abstract: A method for treating cooked fiber pulp as it comes from a continuous digester. The cooked pulp is bleached by intensively mixing the pulp with an oxygen containing gas and reacting the mixture while moving the mixed mass upwardly through a funnel shaped body within a pessurized reactor. The funnel shaped body is open at the upper end whereat the pulp mixture cascades over the side and flows downwardly into a ring chamber area between the reactor shell and funnel body, the pulp thereby forming a pressure barrier to any surplus gas within the reactor. The surplus unreacted gas is removed from the upper portion of the chamber for recycle with fresh pulp from the digestor and added gas. The treated pulp is removed from the lower portion of the ring chamber after passing downward therein.