Abstract: A process for the delignification and bleaching of chemical and semi-chemical cellulosic pulps in which the pulp is subjected to a treatment with oxygen and a subsequent treatment with peroxide. The effluent from the treatment with peroxide is at least partially recycled to the treatment with oxygen.

Abstract: A method is disclosed for delignification of ligno-cellulose containing fiber material comprising mixing an oxygen-containing gas with the cellulose fiber material so as to atomize the gas and form a foam of the gas and the cellulose fiber material, and without an intervening oxidation step, subjecting the foam to upwardly flowing, substantially non-pressurized, alkali extraction. The alkali extraction step is conducted at a temperature of from about 40.degree. to about 80.degree. C. and at a pH, ligno cellulose containing fiber concentration and oxygen containing gas concentration sufficient to provide a bleached, delignified cellulose fiber without bleaching the lignin substance extracted from the material and to suppress lignin condensation reaction during the extraction.

Abstract: The disclosure is concerned with a pretreatment process for removing lignin from lignocellulosic material so as to enhance enzymatic or microbial decomposability of cellulose. The pretreatment process comprises wetting lignocellulosic material with an alkaline aqueous solution in a manner that interstices between the cellulosic material remain, and exposing the wetted cellulosic material to an ozone-containing gas so as to decompose lignin in the lignocellulosic material with a very small energy consumption.

Abstract: In a method for bleaching oxygen delignified cellulose-containing pulp such as sulphate, sodium and sulphite pulps with ozone and peroxide, the ozone treatment takes place at two stages, the alkaline solution which is added subsequent to the ozone treatment includes peroxide and complex formers, and 55 to 85% of the total amount of chemicals is added at the first stage.

Abstract: A process for delignifying bleaching cellulose pulp in three stages, an activating stage, and first and second alkaline stages, NO and/or NO.sub.2 and O.sub.2, and optionally HNO.sub.3, being supplied to the water-containing pulp in the activating stage; in the first alkaline stage, alkali being supplied as carbonate, primarily HCO.sub.3.sup.-, with oxygen gas having a partial pressure, on average, of from 0 to 0.2 MPa, the lignin content of the pulp being lowered in this stage so that the Kappa number of the pulp after the stage is from 10 to 60% of the Kappa number of the pulp entering the activating stage; in the second alkaline stage, alkali being supplied as carbonate, primarily CO.sub.3.sup.=, with oxygen gas at a partial pressure, on average, of from 0.1 to 3 MPa.

Abstract: A two-stage oxygen bleaching of chemical cellulose pulp is provided, in which an alkaline oxygen bleaching stage is preceded by a nitrogen dioxide activating stage in which oxygen is added to the activating stage in an amount such that nitrogen monoxide formed as an intermediate during the activation process is consumed, so regulating the amount of oxygen added that when the activation reaction is practically complete, substantially all of the nitrogen dioxide and nitrogen monoxide has been consumed.

Abstract: A method for produce both kraft pulp and alcohol from hardwood chips or the like. The chips are subjected to mild acid prehydrolysis following by mild caustic pre-extraction. The withdrawn hydrolysate has insufficient furfural to inhibit microorganism growth, and both the hexose and pentose sugars in the hydrolysate are fermented to ultimately produce ethanol, butanol, or the like. The chips - after caustic pre-extraction - are subjected to a sulphate cook, and wash, and the resultant pulp is kraft pulp and even has viscosity and tear strength characteristics more desirable than that of conventional kraft pulp. The pulp can be subjected to oxygen delignification, and achieve a higher K number in fewer subsequent bleaching stages than conventional kraft pulp.

Abstract: Rejects such as knots, shives, slivers, chops, and uncooked and partially cooked wood chips are separated from a pulp slurry and treated to produce a bleachable grade pulp. The rejects are dewatered to a 10-15% consistency, mechanically fiberized, and then delignified at the same 10-15% consistency in the presence of oxygen and alkaline pulping chemicals. The delignification is carried out at 80.degree.-140.degree. C. for 5-120 minutes. The process has low external power requirements, requires no expensive dewatering machinery, and proceeds at a rapid rate to yield a bleachable grade pulp which can be used alone or mixed with other pulp.

Abstract: Good temperature and pH control as well as uniform mixing of pulp or other fibrous materials is achieved in a medium consistency oxygen delignification method and system. Alkaline chemicals are sprayed, optionally using oxygen gas as the atomizing agent, into the gas space above the level of pulp maintained in one or more substantially horizontal tubular reaction vessels. At least a part of the steam requirement of the reaction is added only after the major portion of alkaline chemicals has been added to the system. In other embodiments of the invention, alkaline chemicals may be injected into the substantially vertical conduit connecting two reaction vessels or two different alkaline chemicals may be injected at different points in the system.

Abstract: An apparatus and method for mixing a fluid, such as chlorine or oxygen gas, into a suspension, such as comminuted cellulosic material. A circular cross-section conduit defines a flow path for a suspension, and a circular smooth-faced disc is mounted in the conduit for rotation, covering substantially the entire interior of the conduit. A relatively small opening extends through the disc, and that disc is rotated in the conduit with small portions of suspension flowing in the conduit progressively passing through the opening and being fluidized when passing through the opening. The fluid is introduced into the suspension as the suspension flows through the opening, and in this way an even distribution of fluid in the suspension, with minimum power consumption, is provided.

Abstract: A method and apparatus provide for the continuous treatment of a porous, fibrous material such as paper pulp, with a gas, such as ozone. The material is entrained with gas and passed in a first path. The material and gas move in a path defined by a downwardly curved upper wall and an open bottom, with a baffle disposed adjacent the bottom termination of the downwardly curved wall, so that the material is separated from the gas, the material flowing in a second path and the gas in a third path, distinct from the second path. The material in the second path is moved so that it intersects the flow of gas in the third path at least once, with the gas passing through the material while remaining in the third path, until the desired treatment of the material has been achieved. Preferably the second path is a serpentine path including horizontal portions, and the third path is a substantially straight downward path. After treatment, the material is discharged in a fourth path, and the gas passes along a fifth path.

Abstract: A method of treating medium consistency paper pulp or the like with a treament gas, such as oxygen, is provided to achieve uniform treatment results. The treatment gas is added to the pulp in finely distributed small bubbles, and the density of the suspension is measured at at least one moment, or the average density is measured during at least one time period. The temperature and the pressure of the suspension corresponding to the density measurements are determined, and the rest gas content of the substance is calculated at the actual moments or time periods based upon the measurements in the preceding steps. The gas consumption is then calculated as the difference between the quantity of gas added, and the residual gas quantity, or between two residual gas quantities. The gas addition step is controlled based upon the calculated consumption to obtain substantially uniform treatment results.

Abstract: A process is set forth for the recovery of fiber from paper waste and paper broke which paper has been treated with wet-strength resins. The process involves shredding the paper to be recovered and then subjecting the shredded paper to an alkaline solution and an oxygen containing atmosphere to liberate the paper fiber from the resin with retention of the paper fiber brightness. The liberated fiber can then be recycled through the paper web forming process. The process is particularly appropriate to the removal of thermoplastic resins from paper.

Abstract: A process is provided for the bleaching delignification of cellulose pulp with oxygen gas in the presence of alkali, wherein the pulp is first activated with nitrogen dioxide and then washed, preferably with water. The invention is characterized in that the acid solution obtained is used to pretreat the digested pulp subsequent to washing the pulp with waste liquor obtained from the oxygen gas bleaching delignification stage.

Abstract: Press dried paper sheets from certain ozonated high yield pulps are disclosed. Such sheets show substantially improved strength over comparable sheets prepared from non-ozonated pulps and over non-press dried sheets from ozonated pulps.

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 chlorine-free bleaching process for lignocellulosic pulp characterized by a series of bleaching stages comprising in sequence a peroxide bleaching stage, the peroxide being selected from the group consisting of alkaline hydrogen peroxide, acidic hydrogen peroxide, and peroxy acid and at least one ozone bleaching stage and in one embodiment the sequence including an initial oxygen bleaching stage before the peroxide bleaching stage. In continuous operation the effluent from each of these sequential stages provides the preferred wash for the preceding washing step and the diluent for the preceding bleaching stage, the final effluent being recyclable for effective closed cycle operation.

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: Medium consistency oxygen delignification of pulp is carried out in a series of tubular reaction zones. Rapid delignification is achieved by agitating the pulp by rotating a timing screw in the first reaction zone at a speed in excess of 10 rpm, modifying the flights on the timing screw to increase the amount of agitation, or a combination of the two. Primary oxygenation is carried out in the first reaction zone while subsequent zones provide the retention time needed for the delignification reaction to go to completion. A thick stock pump is used to introduce the pulp into the first reaction zone.

Abstract: In a two-stage cellulosic pulping and bleaching system having first-stage pulping using standard pulping chemicals and second-stage bleaching using an alkaline oxygen system, the addition of a protector occurs only in the first stage pulping instead of between the first and second stages or in the second stage bleach. A magnesium compound is normally used as the protector.

Abstract: A method and apparatus for reducing or eliminating the transfer of chemicals across a washer when reusing washer filtrate as a washing medium in a counterflow system. The flow of washing fluid on the washers before and after a treatment stage is split and the liquid in the pulp mat leaving the washer is principally the type used to treat the pulp after the washer, and the filtrate from the washer is principally the type used to treat the pulp before the washer.

Abstract: A wood pulp slurry is treated with oxygen in a mill with little change to the process or structure of the mill. No special pressure tanks are required. The consistency of the pulp need not be altered for the treatment step. It may be treated at the usual process consistency of the pulp; e.g., it may be treated at the usual consistency of the pulp leaving a washer or subsequent steam mixer without additional dewatering or additional dilution.The oxygen is added into a closed section of the system so that it cannot immediately vent to the atmosphere. Alkali should also be present when the oxygen is mixed with the slurry. The mixing should occur near to the point of oxygen addition.The mixing occurs in a relatively small mixer that intensively mixes the slurry and gas. The mixer has a mixing zone with a swept area of 10,000 to 1,000,000 square meters per metric ton of oven-dry pulp.

Abstract: A wood pulp slurry is treated with oxygen in a mill with little change to the process or structure of the mill. No special pressure tanks are rquired. The consistency of the pulp need not be altered for the treatment step. It may be treated at the usual process consistency of the pulp; e.g., it may be treated at the usual consistency of the pulp leaving a washer or subsequent steam mixer without additional dewatering or additional dilution.The oxygen is added into a closed section of the system so that it cannot immediately vent to the atmosphere. Alkali should also be present when the oxygen is mixed with the slurry. The mixing should occur near to the point of oxygen addition.An existing extraction stage within the system may be used as a source of alkali. In an existing extraction stage, the mixer and upstream oxygen line would be placed in the line between the steam mixer and the extraction tower.The mixing occurs in a relatively small mixer that intensively mixes the slurry and the gas.

Abstract: A wood pump slurry is treated with oxygen in a mill with little change to the process or structure of the mill. No special pressure tanks are required. The consistency of the pulp need not be altered for the treatment step. It may be treated at the usual process consistency of the pulp; e.g., it may be treated at the usual consistency of the pulp leaving a washer or subsequent steam mixer without additional dewatering or additional dilution.The oxygen is added into a closed section of the system so that it cannot immediately vent to the atmosphere. Alkali should also be present when the oxygen is mixed with the slurry. The mixing should occur near to the point of oxygen addition.The oxygen is inserted into the pulp slurry and mixed with the pulp slurry between a washer and the subsequent storage tank.The mixing occurs in a relatively small mixter that intensively mixes the slurry and gas. The mixer has a mixing zone with a swept area of 10,000 to 1,000,000 square meters per metric ton of oven-dry pulp.

Abstract: Washed wood pulp from a continuous digester is treated with oxygen in the blow line from the digester. Most of the treatment occurs within the mixer. The mixer has a mixing zone with a swept area of 10,000 to 1,000,000 square meters per metric ton of oven-dry pulp. A preferred range is 25,000 to 150,000 square meters per ton of oven-dry pulp and an optimum range is around 65,400 square meters per metric ton of oven-dry pulp. Following mixing, the pulp may be taken to a subsequent process, a diffusion washer, or to a storage tank.

Abstract: A wood pulp slurry is treated with oxygen in a mill with little change to the process or structure of the mill. No special pressure tanks are required. The consistency of the pulp need not be altered for the treatment step. It may be treated at the usual process consistency of the pulp; e.g., it may be treated at the usual consistency of the pulp leaving a washer or the subsequent steam mixer without additional dewatering or additional dilution.The oxygen is added into a closed section of the system so that it cannot immediately vent to the atmosphere. Alkali should also be present when the oxygen is mixed with the slurry. The mixing should occur near to the point of oxygen addition.The oxygen is inserted into the pulp slurry and mixed with the pulp slurry between a pair of washers. The second washer may be a vacuum, pressure or diffusion washer.The mixing occurs in a relatively small mixer that intensively mixes the slurry and gas.

Abstract: A process for the delignification and bleaching of lignocellulosic pulp employing electronically excited oxygen generated in situ which comprises subjecting an aqueous slurry of said lignocellulosic pulp having a consistency of from about 0.01% to about 10.0%, by weight of oven-dried pulp, and whose slurry pH is between about 8 and about 13 to irradiation with ultraviolet light while admitting oxygen into said slurry.

Abstract: The bleaching of fluff cellulosic pulp with a gaseous ozone bleaching agent at an acidic pH is often followed by an alkaline treatment, usually an alkaline extraction or an alkaline hydrogen peroxide bleaching treatment, at a much higher water content than the gaseous ozone treatment of the fluff pulp. Such a bleaching sequence of gaseous ozone bleaching followed by an alkaline treatment is improved by the present invention based upon two discoveries, first, the discovery of peroxygen bleaching values in the water associated with the fluff pulp leaving the ozone bleaching treatment, and second, the peroxygen values are destroyed at the alkaline pH used for the alkaline treatment that follows the gaseous ozone bleaching treatment. In accordance with the discoveries, a Low Consistency Acidic Retention Treatment is interposed between the gaseous ozone bleaching treatment and the alkaline treatment.

Abstract: When treating refined mechanical pulp and thermo mechanical pulp with ozone, it is of great importance that the process be carried out at the most favorable conditions and with a minimum consumption of energy. According to the present invention the pulp is refined to a freeness value of at least 200 csf in a first stage refiner from which the pulp is passed to a high consistency ozonizer and maturation reactor for a time limited to maximum 30 minutes. From the reactor the pulp is passed direct to a second stage refiner, the pulp then having a solids content of approximately 8-10% and an alkaline value in the range of 7-10.

Abstract: In a reactor plant for treating finely divided bulk material an acid bulk material or pulp having a solids content of approximately 35-50% is conveyed to a combined high-consistency ozonizer and maturation reactor as a substantially vertical pulp column forming a gas blocking means. In the transition area between the ozonizer and the maturation reactor the finely divided and ozonized pulp which has a very acid pH-value is mixed with chemicals to a pH-value of approximately 8-11 and to a solids content of approximately 15-20%, at which solids content the alkaline pulp in the form of a continuously advancing column is subjected to a maturation process which terminates at a pH-value of the pulp of 6-7.

Abstract: The invention relates to a process for bleaching preoxidized paper pulp enabling a pulp having a very high degree of whiteness to be obtained with a limited number of treatment steps and enabling pollution to be reduced without degrading the qualities of the pulp; such a process essentially comprises the combination of the three successive treatment steps, namely:(a) a first step of hot chlorination with gaseous chlorine at a temperature of between about 30.degree. and 80.degree. C., and preferably between 35.degree. and 50.degree. C., in the presence of urea used at a rate of 0.5 to 5% by weight of the chlorine used, and preferably from 1 to 3%, with a concentration of pulp of between 3 and 30%, and a duration of retention of the chlorine of 30 seconds to 45 minutes;(b) a second step of alkaline extraction in the presence of an oxidizing agent of the hypochlorite or peroxide type, at a temperature of between about 30.degree. and 70.degree. C., and at a pH of between about 8 and 12, and preferably between 10.

Abstract: A process for producing alkali pulp by using a single, cylindrical pressurized reaction vessel having therein a liquor-inpregnating zone, a cooking zone, a washing zone, and a diluting zone in that order, and having a motor-driven scraping or agitating device and a pulp discharging outlet in the end portion of the diluting zone. Alkaline aqueous medium containing dissolved oxygen therein is introduced into the diluting zone. A part of the introduced alkaline aqueous medium countercurrently contacts cooked cellulosic materials transferred from the washing zone to the diluting zone to proceed with oxygen-alkali delignification, and is finally discharged out of the vessel from the end portion of the cooking zone.

Abstract: A method and apparatus for the treatment of fiber material by oxygen bleaching. Digested cellulosic fiber material is treated with oxygen to reduce the Kappa number thereof further to about 15 or below. The reaction products are removed immediately after formation, and during the oxygen bleaching process. The fiber material is at a first consistency of about 8 to 15% consistency, and treatment with oxygen is accomplished by mixing the pulp with O.sub.2, NaOH solution, and water to thereby form an integral mixture of pulp with oxygen at a second consistency, thickening the integral mixture to return it to generally its first consistency, and repeating the mixing and thickening until pulp of a desired Kappa number (15 or below) is reached. The pulp is then washed and may be subsequently treated to reduce the Kappa number thereof to any desired value. A thickener is used which can thicken pulp at superatomspheric pressures and at a temperature greater than 100.degree. C.

Abstract: A method is provided for reducing waste stream pollutants by the control and separation of color bodies, COD, BOD and other organics from inorganic chloride pollutants in the aqueous waste effluent of a cellulosic pulp bleaching process containing a sequential chlorination stage (D.sub.c) or mixture (D/C) stage followed by an extraction (E) or oxygen (O) stage, comprising, maintaining the conditions of the D.sub.

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: Knots separated from sulphite cellulose produced by a sulphite cellulose cooking process are converted to unbleached sulphite cellulose by first separating and defibrating the sulphite knots and then treating the defibrated sulphite knots with oxygen under pressure in an alkaline milieu at an elevated temperature. The resultant cellulose may be bleached by itself, or mixed with sulphite cellulose produced from knot-free cellulose pulp for bleaching therewith.

Abstract: In bleaching wood pulp with ozone a small amount of alcohol enhances the bleaching. The effect appears to be most pronounced with aliphatic alcohols having the hydroxyl group on an end carbon. The concentration of alcohol is in the range of 0.0000001 to 0.03 moles per liter of the liquid phase.

Abstract: A method for oxygen delignifying magnesium sulfite pulp is disclosed. More particularly, a method is disclosed by which the spent liquors from digestion of magnesium sulfite pulp and from alkaline oxygen bleaching of the pulp can be combined and combusted without a smelt of sodium compounds being formed during the combustion.

Abstract: A method and apparatus for the delignification of cellulosic fiber material to minimize the amount of reject material in the final pulp produced. The fiber material is digested, washed, oxygen delignified, and passed through a screening stage to provide a main pulp stream, and a reject stream from the separation stage. The flow and consistency of the separated reject material is determined, the reject material is refined, and sufficient chemical is added to the separated reject material, based upon the flow and consistency thereof, so that subsequent delignification of the reject material may be effected. This may be accomplished either by passing the reject material through a separate oxygen delignification stage and then returning it to the main pulp stream, or adding caustic to it and soaking it in a soak tank for predetermined period of time, and then returning it to the main pulp stream before the oxygen delignification stage therein.

Abstract: A slurry of cellulosic fiber and water having a consistency in the range of 0.017-4.9% of the total ungassed weight of fiber and water is bleached with ozone. This is done without the usual addition of organic additives. The water can include impurities created by the bleaching process. Rapid reaction times under 8 minutes and preferably under 5 minutes are achieved.The reaction is enhanced in the consistency range of about 0.017-0.7%.The slurry is mixed using a mixing energy of 0.002-1.0 horsepower per cubic foot of gassed slurry. The mixing energy will determine whether the gas-liquid or liquid-solid interface will limit the speed of the reactions. The passage of ozone from the gas to a liquid phase will be the limiting factor below about 0.2 horsepower per cubic foot of gassed slurry. The increasing presence of ozone in the liquid as the horsepower increases from about 0.2 to about 0.

Abstract: In a process for delignifying wood pulp with oxygen, a pulp slurry and oxygen are introduced into an elongated reactor having a plurality of gravitational fall zones at which oxygen is dissolved in the liquid phase of the slurry. The length of the reactor is sufficient to provide the residence time required for delignification reactions. Alkali is added in controlled quantities along the reactor length in response to sensed slurry pH to maintain a predetermined slurry pH throughout the reactor. The oxygen treated slurry discharged from the reactor is separated into pulp and hot recycle liquor, the latter being utilized to effect thermal, chemical and water economies.

Abstract: A Kraft pulp bleaching process comprising from one to about three treatments with ozone and a final treatment with an alkaline peroxide solution, the treatments being separated by an alkaline extraction, wherein effluent from the bleach treatments is utilized in subsequent bleaching operations or in the chemical recovery system of a Kraft pulping process.

Abstract: Method of producing mechanical pulp of improved brightness and light-scattering properties in a defibration apparatus in which wood chips are ground between a pair of discs which rotate relative to one another in a pressurized grinding zone. Prior to the defibrating process, the chips are impregnated with a solution of alkali, selected from the group consisting of sodium hydroxide, alkali silicate, alkali carbonate and alkali bicarbonate, and peroxide, surplus impregnating solution is removed from the chips by compression of the chips, the chips are introduced into a pressure vessel which is in communication with the grinding zone and compressed air is introduced into the pressure vessel in an amount sufficient to maintain the chips in the pressure vessel at a temperature below 90.degree. C. and to maintain superatmospheric pressure within the defibrating 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: In an apparatus for treating cellulose pulp with oxygen gas by passing the pulp and oxygen gas through a reaction vessel at elevated temperature and pressure, the improvement whereby the exothermic heat of reaction is controlled and the temperature of the pulp being treated is maintained below the point where the pulp would be degraded, the improvement comprising means for withdrawing oxygen gas from the vessel after the gas has been in contact with the pulp, dividing the withdrawn gas into two portions, cooling one of the portions to remove water vapor therefrom, recombining the gas portions whereby the resulting gas has a lower temperature than the gas withdrawn from the vessel and returning the resulting gas to the vessel for further contact with pulp therein, the amount of gas withdrawn from the vessel and the degree of cooling of the cooled portion of withdrawn gas being regulated to maintain the temperature within the vessel below the point where the pulp is degraded.

Abstract: A one-stage oxygen delignification system in which wood chips are first pressurized with oxygen and the oxygen allowed to reach equilibrium within the chips before the addition of cooking liquor. Cooking liquor is added to the chips while they are maintained under the pressurized oxygen. After the addition of cooking liquor under pressure, the oxygen pressure may be further raised. The cooking liquor may be at cooking temperature when added, or the slurry may be raised to cooking temperature after the liquor is added or after the additional pressure has been applied. The pressure may be pulsed by lowering and raising it during cooking.

Abstract: A method and apparatus for continuous oxygen bleaching of cellulosic pulp is provided utilizing first and second pressurized chambers with a number of tubes in fluid communication with both of first and second chambers. Oxygen bearing fluid is intimately mixed with digested cellulosic pulp and is continuously fed under pressure to the first chamber. Communication is selectively provided between the first and second chambers through at least one of the tubular members to allow passage of pulp from the member to the second chamber. The tubular member through which pulp flows to the second chamber is progressively changed as are the members through which passage is blocked, so that the pulp remains within each tubular member sufficient time to allow oxygen-bleaching thereof without degradation, and passes through the members without channelling. The oxygen bleached pulp is continuously discharged from the second chamber. The passage of pulp through the tubular members may either be downwardly or upwardly.

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: This invention relates to a process for multi-stage alkaline pulping of ligno-cellulosic raw materials and recovery of delignification spent liquors, i.e. black liquor from digestion with white liquor and oxy-liquor comprising bleach plant effluent extracted from alkaline oxygen delignification of brown stock.According to the invention, oxy-liquor and intermediate black liquor in the digester are passed through that part of the material column to which the cellulosic raw material, e.g. wood chips, enters. There, hydroxide deriving from two sources, white liquor and oxy-liquor, is exhausted prior to its discharge as terminal black liquor. White liquor is consequently injected to the level of the pre-digested material in the column. This injection is controlled by continuous measurement, e.g. by automated titration analysis, of the hydroxide concentration in the joint volume of oxy-liquor and white liquor in the main cooking liquor circulation system.

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.