Abstract: A process for bleaching a lignocellulosic matter in the form of a mechanical, thermomechanical, chemicomechanical or chemicothermomechanical papermaking pulp, or of wood chips while being converted into one of these pulp types by processing in a machine consisting essentially of two interpenetrating spiral surfaces wound around parallel shafts driven in synchronous rotation in the same direction inside a barrel which encloses them, and determining between upstream and downstream in the direction of forward travel of the matter a series of zones for drawing and braking the matter, which comprises combining a bleaching treatment using a reducing agent and a bleaching treatment using an oxidizing agent, characterized in that, after pretreatment using at least one metal-complexing or sequestering agent, the lignocellulosic matter undergoes a washing operation with an efficiency greater than 96% before undergoing in succession a bleaching treatment using a reducing agent at a pH of between about 8 and 12, a washin

Abstract: An improved method of brown stock washing is disclosed. A nonionic surfactant in combination with a polyelectrolyte dispersant, and preferably a solvent, are utilized in the washing step in the pulping of virgin cellulosic fiber. The methods of the invention provide for the enhanced removal and recovery of cooking chemicals and organics from the pulp.

Abstract: A pulp mat is formed on the outside of a permeable, rotatable drum by feeding a pulp slurry through a mat forming and pressing zone, followed by a mat washing zone. In the mat washing zone, the mat is washed with liquid from a first source and then washed with liquid from a second source.A washing baffle has a first portion extending from its upstream end partially along the outside surface of the drum and slightly spaced from the outside surface of the drum. This first portion is followed by a second portion extending partially along the outside surface of the drum and spaced further from the outside surface of the drum than the first portion.

Abstract: An apparatus having a liquid-permeable belt for receiving cellulose pulp, a liquid supply device for discharging treatment liquid on the cellulose pulp, and a container extending across the entire width of the belt for collecting treatment liquid penetrating the belt. The container is adapted to maintain a treatment liquid level at such a distance from the belt so that the formation of foam from treatment liquid is reduced. The container includes a liquid outlet for discharging the treatment liquid and a vapour outlet for discharging vapours and gases from the bottom of the container. The vapour outlet communicates with a passageway within the container, which passageway is formed as a pipe or is partially defined by a container wall. A deflector can be provided on the container for operatively deflecting treatment liquid away from the passageway.

Abstract: A process is disclosed for the pretreatment of lignocellulosic fibrous materials prior to delingification. The process in one of its embodiments is comprised of the following steps:1. Contacting the pulp material with treated filtrate and alkali for a short reaction period of about 1 to 2 minutes at 40.degree. C.,2. Withdrawing part of the liquid phase by filtration,3. Displacing substantially all of the remaining liquid phase with treated filtrate, and4. Allowing the pulp to react under conditions normally used for alkaline extraction or oxygen delignification.The treated filtrate is obtained by subjecting the liquor removed from the pulp at steps 2 and 3 to temperature of 5.degree. to 60.degree. C. for periods of about 5 to 10 minutes. Alternatively, step 3 can be eleminated.

Abstract: Apparatus is disclosed for continuously measuring the conductivity of the liquor in a pulp mat on a pulp washer. The apparatus comprises a probe which rests on and squeezes washing liquor from the pulp mat. Two modifications of the probe are disclosed, one fixed and one rotatable. In each case, the probe comprises a pair of electrodes separated from one another by non-conducting material. The electrodes are arranged on the probes to be submerged within the washing liquor squeezed from the mat. The electrodes are connected to an energy source, and when current is applied to one electrode, the current flows through the liquor to the other electrode to complete an electrical circuit. The measurement of the current flow or the resistance to current flow is directly related to the conductivity of the liquor and can be correlated with the soda loss in the pulp washing step.

Abstract: A process for peroxide bleaching of mechanical pulps by washing the pulp to remove substantially all of the heavy metal ions from the pulp, mixing hydrogen peroxide in an amount of at least about 11/2% based on the dry weight of the pulp with the washed pulp to uniformly disperse the hydrogen peroxide throughout the pulp followed by mixing an aqueous solution of sodium hydroxide with the pulp containing hydrogen peroxide to uniformly distribute the sodium hydroxide throughout the pulp and to react the sodium hydroxide with the peroxide to produce perhydroxyl ions in situ in the pulp and then reacting the perhydroxyl ions with the pulp to increase the brightness of the pulp and provide a residual peroxide of at least 35% of the peroxide added. This system provides a significant increase in residual brightening chemical in the residual liquor separated from the brightened pulp.

Abstract: The screens of a pulp treating vessel, such as a paper pulp thickener, or diffuser, are back flushed in a simple yet effective manner. The screens are mounted to a supporting conduit within a vertical vessel, and a cylinder is connected at one open end to the conduit, and the other open end is disposed within the pulp inside the vessel. A piston is mounted within the cylinder and relative movement between the piston and cylinder is effected periodically in order to force liquid from within the cylinder into the conduit and out the screens, backflushing the screens and preventing clogging. Since no additional volume of liquid is added to the vessel during backflushing, no surge occurs in the vessel. Conventional accumulators, on/off valves, and the like can be eliminated while--in the case of diffusion washing--efficiency can be increased as much as 20-30%, and capacity increased as much as about 15%.

Abstract: A method in connection with continuous pulp cooking to wash the delignified pulp in a vertical, elongated pressure vessel comprising a cooking zone (1), a main washing zone (3) and a conditioning zone (4) at the bottom of the vessel, where the pulp is further washed and optionally diluted and cooled, said cooking zone being separated from said main washing zone by an interruption zone (2), where diluting/washing liquid displaces the cooking liquor, which is drained via one or several interruption circulation screen girdles (5), while contaminated washing liquid in the conditioning zone is displaced by cleaner washing liquid and is drained via one or several bottom screen girdles (10). At least part of that washing liquid which has been drained through the bottom screen girdle/s/ (10) is passed in counter-current to, but not through, the pulp, i.e.

Abstract: An apparatus for washing cellulose, wherein the cellulose is conducted through between a rotary drum and a stationary shell encircling it, in the form of a layer supported by the permeable mantle surface of the drum. The principle of operation of the apparatus is: conducting washing liquid through the shell, through compartments located under the mantle surface of the drum and serving as washing liquid collectors, and through a valve system composed of a rotary part associated with the drum and a stationary part placed thereagainst, several times through the cellulose layer so that when the apparatus is operating the washing liquid at the same time moves in the direction opposite to the direction of rotation of the drum, stepwise, through the apparatus.

Abstract: A method for the production of cellulose by the batch cooking process, wherein the digester is filled with chips and cooking liquor, and the batch is cooked at elevated temperature and pressure in order to obtain a delignified cellulose pulp in the digester. For the impregnation stage a cooking liquor is used which contains a substantially higher amount of active chemicals than is required for the cooking of the batch, and before the actual delignification stage the active-chemical batch for the cooking is adjusted and the excess amount of active chemicals is removed by replacing it by part of the hot spent cooking liquor recovered from a previous cooking.

Abstract: An apparatus for treating a fiber suspension, comprises a drum rotatably journalled to a stand and having an envelope surface to support a fiber web formed from the fiber suspension. A curved wall plate which is concave in the direction to the envelope surface of the drum is spaced from the envelope surface (and generally parallel thereto) to define a material space therebetween for said fiber web. The space includes an axial inlet gap and an axial outlet gap. The wall is continuous and encloses a major portion of the envelope surface of the drum and is arranged to move freely in the circumferential direction of the drum to compensate for radial alterations during adjustment of the distance of the wall from the envelope surface at one or more positions between the inlet gap and outlet gap. Adjustment devices cooperate with the wall for adjusting the distance of the wall from the envelope surface of the drum.

Abstract: Control of pulp and water flow rates out of a bleaching tower in a multistage pulp bleaching process wherein each stage comprises a bleaching tower and a washing drum, comprises the steps of (a) measuring total weight of pulp composition per square meter on at least one washing drum and from such measurement and the speed of rotation and area of the washing drum surface and the consistency of pulp composition, determining the total weight per unit time of pulp and of water coming out of the bleaching tower previous to said washing drum, and (b) controlling the rate of pulp and water flow out of said previous tower based on the determination of the total weight per unit time of pulp and of water as determined in step (a), and (c) controlling the amount of bleaching chemical flow to the pulp going to any following stage to match the pulp flow rate as determined from the measurement of step (a) and the percentage of bleaching chemicals to be applied.

Abstract: A method and apparatus for monitoring and controlling the operation of a counter-current pulp washing system. The dilution factor, soda loss, wash liquor ratio and displacement ratio of the washing system are determined on-line. The value of either the soda loss or of dilution factor is continuously maintained within a preselected range and changes in the value of the other variable are monitored to provide an indication of whether the washing system is operating optimally. Based on the on-line determination of displacement ratio and wash liquor ratio, the efficiency of the washers is monitored, the cause of any decrease in efficiency is identified and the appropriate control action is applied to adjust the operating parameters of the washers to compensate for changed washing conditions or changed processing conditions.

Abstract: A process for the decolorization of alkaline pulp such as that derived from paper waste water wherein the waste water is contacted with a strong mineral acid, contacted with a coagulated agent and then the solid coagulum is separated and neutralized to liquify the color bodies in concentrated form.

Abstract: A method for the treatment of a suspension, such as pulp, with one or more treatment liquids in a manner that maximizes treatment efficiency and minimizes heat loss. The pulp flows in a flow path confined to a given web thickness, and has first and second opposite sides. Treatment liquid is added to the first side of the flow path at spaced predetermined points along its length. Liquid displaced by the treatment liquid is withdrawn from the second side of the flow path at substantially the predetermined points. The displaced liquid at the first predetermined point along the flow path consists essentially of original suspension liquid, while the liquid fraction of the pulp past the last predetermined point of the flow path is composed mainly of treatment liquid added at the last predetermined point. Treatment can be accomplished at super-atmospheric pressure and at a temperature above 100.degree. C. The web thickness is between about 50-500 mm.

Abstract: A modified batch cooking technique for making sulfate pulp with a high degree of delignification or with a normal degree of delignification but with increased pulp viscosity. This is effected by one or several displacements of the liquor in the digester with liquor of the same temperature as the cooking liquor but with a lower lignin content.

Abstract: A method of, and washing machine or washer for, washing stock suspensions, wherein a rotatable cylinder having a solid smooth surface is encircled along a portion of its circumference by a movable endless wire or filter band. The stock suspension to be dewatered and washed is infed by a flat jet nozzle between the rotatable solid cylinder and the movable endless wire. The fiber web formed between the rotatable solid cylinder and the movable endless wire has a weight of less than 100 grams per square meter, preferably 30 to 70 grams per square meter. The wire speed and the circumferential speed of the rotatable solid cylinder is in the order of about 400 to 1,200 meters per minute. After through-flow of the stock suspension between the rotatable solid cylinder and the movable endless wire, the dewatered and washed fiber material is removed from the movable endless wire and the rotatable solid cylinder, respectively, collected in a collecting container and delivered for further processing.

Abstract: A process and apparatus for removing ink particles from an inked paper product which includes a conveyor for conveying the paper product along a path, the conveyor being constructed of a semi-permeable material that passes the ink particles while retaining the paper product. Vacuum boxes are positioned proximate to a first side of the conveyor for establishing a pressure differential across the conveyor and across a first segment of the path to draw the ink particles from the paper product through the conveyor. Shower heads on a second side of the conveyor directed a liquid toward the conveyor and on to the paper product as the paper product is advanced along the second segment of the path.

Abstract: A shower pipe for a rotary drum filter has a square cross-sectional shape defined by top, bottom and side walls. The sidewalls and a pair of lengthwise-extending continuous diffusion flanges depending from the bottom wall of the pipe stiffen the pipe against sag for placement at a 12 o'clock position spanning the filter drum. The pipe is formed of fiberglass reinforced plastic in two longitudinally-divided hollow sections in a pair of mirror image, trough-like molds. Each section has a pair of interconnection flanges for mating the sections together. The interconnection flanges extend normally to the sidewalls to stiffen the pipe when the bottom wall of the pipe is vertically-oriented for placing the pipe at a 9 o'clock position along one side of the filter durm. Glass rods are secured in the interior corners of the pipe to provide diagonal rigidity, for placing the pipe at, e.g., 10-11 o'clock position between the top and side of the filter drum.

Abstract: Method for the washing of chemical pulp (1) by means of a fourdrinier wire machine in two or more stages (6,10; 6',10'; 6", 10"; 6'", 10'") while the pulp web runs on the wire (3). The liquid contained in the pulp web is displaced by a washing liquid. The pulp web and the wire (3) run, during the washing, as submerged in the washing liquid while the washing liquid flows through the pulp web and the wire. One embodiment comprises passing the washing liquid upwardly through the pulp and then downwardly through the pulp.

Abstract: A method and apparatus are provided for effecting presteaming and deaeration of wood chips, or like comminuted cellulosic fibrous material. Presteaming takes place in a vertical presteaming vessel, utilizing a plurality of uniformly radially spaced nozzles adjacent the bottom of the vessel, a plurality of generally uniformly radially spaced steam introduction pipes in a central portion of the vessel, and a pair of synchronized rotating valves for feeding steam to the introduction nozzles and pipes in a coordinated manner. After presteaming, the chips pass through a chips meter to a vertical chute in which they are entrained in liquid, and then pass to a horizontal deaerating vessel. In the deaerating vessel, deaerated liquid is passed in a path generally perpendicular to the path of the material flowing through the deaeration vessel.

Abstract: A method and apparatus is provided for measuring the present and ongoing performance of paper pulp brown stock washers. Black liquor carryover within a washer mat past wash liquor application showers is quantified by determination of and correlation with the mat liquor specific conductivity.

Abstract: A cellulose pulp fiber sampling and cleaning device for preparing clean pulp fiber samples for automatic analysis of cellulose pulp fiber properties, comprising a pulp sample receptacle having a housing; an elongated pulp fiber sample chamber therein, with fluid passage openings at each end; liquid-permeable and pulp fiber-impermeable material covering each end opening; ports in the housing communicating with the lowest portion of the chamber intermediate the two ends and with each end of the chamber on the outside of the liquid-permeable pulp fiber-impermeable material; and valves controlling flow through the ports; means for introducing and withdrawing washing liquor through the ports at each end of the chamber; and means for introducing and withdrawing pulp fiber suspension and withdrawing cleaned pulp fibers through the port intermediate the two ends.

Abstract: The washing efficiency of removal of cooking and bleaching chemicals from cellulose paper pulp on horizontal belt washing filters is improved by disrupting the filter mat adjacent the belt intermediately of soft, displacement wash liquor applications to the filter mat topside. The objective may be achieved by directing a line of low volume, high pressure jets of filtrate or wash liquor against the belt underside. Alternatively, sonicly vibrated foils extended transversely of and adjacent to the belt are effective to disrupt the filler mat pursuant to the invention objective.

Abstract: The invention relates to a process for the washing of pulp with a maximum recovery of energy, the pulp after digestion being washed in a plurality of successive washing steps at a pressure above atmospheric in at least one of the steps and washing filtrate from a following step or fresh water being used as diluting and washing liquid in a given step. The outgoing washing filtrate from a washing step should be heat exchanged against incoming diluting and washing liquid to the subsequent step and a part of the filtrate (21) from the second step should be heat exchanged against washing filtrate (10) from the first step and then be combined with cooking liquor (23) for the digestion of the pulp. As diluting and washing liquids in the last two steps (4, 5), fresh water is used, which has also been heat exchanged against outgoing washing filtrate (54, 10) from the last and the first washing step.

Abstract: Comminuted cellulosic fibrous material, such as wood chips, are treated in a continuous digester to produce paper pulp or the like in a manner providing completely uniform treatment of the chips. The chips are introduced in a feed liquid slurry into the top of the digester, with a swirling action, and establish a vertical column in the digester having a substantially horizontal top, with some liquid between the top of the digester and the top of the chips. Below the top of the chips the feed liquor is withdrawn through a first set of withdrawal screens, and recirculated to entrain other chips to feed them to the top of the vessel. At other vertically spaced areas of the digester other screens are provided for withdrawing, cooking, quench, washing, and like liquors, and effecting recirculation thereof. At each screen set a plurality of nozzles are provided circumferentially spaced around the digester, each nozzle cooperating with only a particular radial segment of the screens.

Abstract: The present invention seeks to provide a method for treating the cellulose obtained from the cellulose cooking process for paper-making purposes. According to this method, the cellulose is separated from black liquor or other similar waste slurry produced in the cooking process by means of compression and washed, bleached and dried, and an essential feature of the present invention is that all the phases of treatment are carried out in a pressure filter (4). The treatment is performed so that black liquor or similar waste slurry is first compressed from the cellulose pulp slurry, whereafter the resulting cellulose cake is washed by conducting washing liquid into the filter, after which the cellulose is bleached by treating the cake with one or several bleaching chemicals led into the filter and by re-washing, if necessary, the cake between the various bleaching phases, and finally, the cellulose cake is dried and removed from the filter.

Abstract: A method and apparatus is provided for measuring the present and ongoing performance of paper pulp brown stock washers. Black liquor carryover within a washer mat past wash liquor application showers is quantified by determination of and correlation with the mat liquor specific conductivity.

Abstract: A method for diffusion washing and/or thickening paper pulp having a consistency of 6 to 15%. A number of withdrawal screens and fluid introducing structures are provided supported by spider arms which comprise conduits for introduction of liquid into and withdrawal of liquid from an elongated upright hollow vessel in which the assembly is disposed. The conduit means, with attached screen structures, is reciprocated up and down by a single linear actuator located preferably above the vessel and within the cross-sectional area thereof so that the wall of the vessel need not be penetrated by the conduits. The screens and fluid introducing structures remain stationary with respect to each other during reciprocation. A number of wiper blades, which may be operated by a single linear actuator, are provided at the top of the vessel for moving upwardly flowing pulp into withdrawal conduits surrounding the vessel periphery.

Abstract: A mechanism and method for continuously washing wood pulp fibers including a looped traveling foraminous wire, a plurality of stock chambers above the wire arranged sequentially in the direction of wire travel to provide a sequence of baths submerging the wire, pumps beneath each of the baths removing water drained through the wire and pumping the water back into the next upstream bath, means feeding stock into the first bath, and means measuring the level of stock in the first bath and supplying fresh water to the last bath as a function of the level, and pressing the stock between a roll and the looped wire in the last bath and removing the stock from the roll as it is carried upwardly out of the bath.

Abstract: Wood pulp is bleached in a process which includes passing pulp slurry from a chlorine tower through a washer to a downflow extraction tower which is open to the ambient atmosphere. Caustic and steam are supplied to the extraction tower as is dilution water which is introduced into the lower portion thereof. Oxygen is dissolved in the dilution water which may be at least partially comprised of recycled washer filtrate. This addition of oxygen to the dilution zone of an extraction stage enables the consumption of chemicals such as hypochlorite and/or chlorine dioxide to be reduced while still meeting required levels of pulp brightness and strength. Oxygen may be added to the extraction or other alkaline stages of a bleaching process.

Abstract: The washing efficiency of removal of cooking and bleaching chemicals from cellulose paper pulp on horizontal belt washing filters is improved by disrupting the filter mat adjacent the belt intermediately of soft, displacement wash liquor applications to the filter mat topside. The objective may be achieved by directing a line of low volume, high pressure jets of filtrate or wash liquor against the belt underside. Alternatively, sonicly vibrated foils extended transversely of and adjacent to the belt are effective to disrupt the filler mat pursuant to the invention objective.

Abstract: An apparatus and method are provided for treating flowing suspensions, extracting liquid from the suspensions and, if desired, introducing a treatment liquid into the flowing suspensions. Suspension flows in an elongated container from an inlet to an outlet in a first direction, and a screen surface is mounted within the container for screening a portion of the liquid from the suspension. The screen body is elongated in the direction of elongation of the container and defines a screen cavity volume within it, the volume tapering inwardly in the first direction. A baffle is disposed within the screen cavity volume. During movement of the screen in a second direction, opposite the first direction, at a higher speed, backflushing of the screen takes place, substantially evenly over the whole of the screen surface.

Abstract: Method and apparatus for pulp bleaching at several bleaching stages by utilizing two or more different bleach chemicals. Bleach chemical (E) is in turn led to the pulp so that it displaces of pulp the chemical used at the preceding stage (C/D, D). Displacing chemical (E) is led to the pulp sheet when on the filtering area of a multi-stage drum washer (1, 2).

Abstract: A liquid distribution device comprising a tubular horizontal reservoir for holding liquid to be distributed, a plurality of passageways through the upper wall of the reservoir and communicating with an elongated space substantially enclosed by an elongated arcuate cap member extending lengthwise along the outside of the tubular reservoir, the cap member having an outlet edge which is adjustable with respect to the outside surface of the reservoir to produce an elongated narrow slit outlet through which the liquid can flow in the form of a thin sheet. This device finds its principal use in delivering wash liquid to a wet sheet of paper pulp.

Abstract: In a procedure for washing cellulose in a drum a continuous web is conducted through a plurality of mutually separated washing zones and in the procedure the pure washing liquid is introduced at the washing step which is last in the direction of travel of the web. This liquid displaces suspension fluid contained in the web and the latter is urged with the aid of a drained fluid pipe system to a washing step located upstream in the web's direction of travel and the displaced suspension fluid repeats the displacement washing process performed by the pure washing liquid in the last washing step. This procedure is repeated until each washing step has received a flow of washing liquid. To utilize the concentration raising capacity of the washing procedure and apparatus, before discharging the pulp, part of the drained fluid pipe system is emptied and the drained fluid therefrom obtained is returned to an earlier washing step.

Abstract: A method of, and wire machine for, washing stock suspensions is disclosed wherein a cylinder having a solid smooth surface is encircled along a portion of its circumference by an endless wire or filter band. The stock suspension which is to be dewatered is infed between the solid cylinder and the wire by means of a flat jet nozzle. After throughflow of the stock suspension between the cylinder and the wire the dewatered fiber material is removed from the wire and the cylinder, respectively, collected in a collecting container and delivered for further processing.

Abstract: A method of improving the washing efficiency for removal of cooking and bleaching chemicals from cellulose paper pulp on rotary vacuum filters by disrupting the filter mat with a low volume, directly impinged flow of wash liquor applied intermediately of soft, displacement wash liquor applications. No additional wash liquor is allocated for respective wash stages but the mat disturbing flow volume is deducted from the predetermined requirement with the remainder divided in substantially equal proportions applied before and after the mat disturbing application.

Abstract: A method of pipe line washing is described, in which raw pulp liquid is washed by clean water or washing liquid having a lower concentration than liquid chemicals in the raw pulp liquid by making use of all or a part of a pipe line.

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 and apparatus for effecting washing, bleaching, or thickening, etcetera of paper pulp of the like utilizes stationary screens, yet provides efficient treatment without significant screen clogging. Pulp introduced into the bottom of a cylindrical upright vessel is caused to flow in particular radial segments and channels. Introduction of pulp into all channels of a particular radial segment, extraction of withdrawn liquid from the radial segments, removal of treated pulp from the top of the vessel, and the introduction of treating liquid between the stationary screens, are coordinated so that uniform treatment of the upwardly flowing pulp results.

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 treatment for wood chips in the manufacture of pulp is described. Prior to chip washing, the chips are placed in contact with an impregnation liquid such that all readily fillable cavities in the chips become filled with the liquid. The chips can be steamed prior to the impregnation process to increase the liquid absorption. After the impregnated chips are drained of the excess liquid, no appreciable amount of washing liquid is absorbed by them during a subsequent washing cycle used to remove included gravel and sand.

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: An improved displacement washing process for recovering processing chemicals from a porous medium, particularly wood pulp, is described. The effective mobility of a displacing solution, typically a more dilute solution of the chemical sought to be recovered, is reduced such that it is less than the mobility of the solution to be recovered. In a pulp mill washing system, consumption of wash water may be reduced 0.6 tons of water per ton of pulp produced without reducing chemical recovery. Conversely, chemical effluent from the washer could be reduced by 50% without increasing wash water requirement. Mobility is proportional to the permeability of the porous medium with respect to the solution of interest and inversely proportional to the viscosity of that solution. Mobility of the wash solution relative to the solution to be displaced is preferrably reduced by the addition of a soluble, high molecular weight polymer, greater than 10.sup.

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: Procedure and apparatus for the washing of cellulose in the form of a continuous web. The continuous web produced in a concentrating zone is washed in a washing zone comprising between 2 and 6 washing steps, so that into the web pressurized washing liquid is introduced according to the counter-current principle to the purpose of displacing the suspension liquid contained in the web, using one pumping operation for transporting the washing liquid through a plurality of washing steps.

Abstract: PCT No. PCT/SE78/00092 Sec. 371 Date Aug. 10, 1979 Sec. 102(e) Date Aug. 10, 1979 PCT Filed Dec. 11, 1978 PCT Pub. No. WO79/00375 PCT Pub. Date June 28, 1979A bulk material is treated in a drum rotating in a bulk of the bulk material to be treated. The drum (16, 68) is provided with feeding-in openings (28, 70) in the cylindrical face of the drum. The bulk material tumbles around in the drum and is conveyed towards a discharge part in one end of the drum by means of a worm conveyor in the drum rotating in opposite direction to the drum. A treatment fluid is introduced into the drum through apertures (11a, 85) in the shaft of the worm conveyor. After the fluid has treated the bulk material in the drum it is led away through the same openings (28, 70) as those through which the bulk material is continuously being fed into the drum. Further the fluid advances up into the bulk of bulk material which therethrough also is treated before the material is fed into the drum.

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.