Abstract: A process for making bleached pulp comprises contacting an unbleached pulp mixture with a first recycled filtrate obtained from a first location (3) of a first recycled filtrate loop, to obtain a first pulp mixture having a first consistency; bleaching the first pulp mixture, to obtain a first bleached pulp mixture; pressing or dewatering the first bleached pulp mixture, to obtain a first pressed bleached pulp mixture and a second filtrate; sending at least a portion of the second filtrate to a second location (5) of the first recycled filtrate loop, wherein the second location (5) is downstream of and in fluid communication with the first location (3); contacting the first pressed bleached pulp mixture with a second recycled filtrate obtained from a third location (6) of the first recycled filtrate loop, to obtain a second pulp mixture having a second consistency, wherein the second consistency is greater than the first consistency, and wherein the third location (6) is downstream of and in fluid communicati

Abstract: A biomass hydrothermal decomposition apparatus includes, a biomass feeder (31) that feeds biomass material (11) under normal pressure to under increased pressure, a hydrothermal decomposition device (42A) that allows the fed biomass material (11) to be gradually moved inside a device main body (42A) from either end thereof in a consolidated condition, and also allows hot compressed water (15) to be fed from an other end of a feed section for the biomass material into the main body (42A), so as to cause the biomass material (11) and the hot compressed water (15) to countercurrently contact with each other and undergo hydrothermal decomposition, and that elutes a lignin component and a hemicellulose component into the hot compressed water, so as to separate the lignin component and the hemicellulose component from the biomass material (11); and a biomass discharger (51) that discharges, from the side where the hot compressed water is fed into the device main body, a biomass solid residue (17) under increased pr

Abstract: An inventive method includes the steps of: loading a fiber product in an appropriate form into a treatment vessel; wetting the fiber product; forcibly circulating an ozone-containing liquid in contact with the wetted fiber product to thereby bleach the fiber product; and forcibly circulating an ozone decomposing chemical agent liquid in contact with the ozone-treated fiber product to decompose ozone. This method ensures efficient bleaching of the fiber product with the ozone. Further, the method is advantageous in that the resulting bleached fiber product is less liable to be yellowed over time.

Abstract: The system and method reduce the liquid/wood ratio at the top of a vapor phase digester in a continuous digester plant. Chips that are to be cooked in the vapor phase digester are fed as a mixture of chips and liquid at a liquid/wood ratio that exceeds 8:1 in a transfer line to an inverted top separator arranged at the top of the vapor phase digester. The top separator feeds the chips upwardly. More than 50% of the liquid content of the mixture of chips and liquid is withdrawn in the top separator and the remaining liquid is fed out from the top separator to the top of the vapor phase digester. A pile of chips and a liquid volume are established at the top, wherein the pile of chips is disposed above the liquid surface of the liquid volume.

Abstract: The invention proposes an installation (10) in which the impregnation and fractionation of the raw material (MP) are conducted at atmospheric pressure, characterized in that it comprises means (18, 20) for transferring the raw material (MP) successively to a first treatment station (PT1) and a second treatment station (PT2), each comprising means (G1, G2) for temporarily combining, at the first station (PT1), the raw material (MP) with a quantity of a first mixture of organic acids and, at the second station (PT2), for temporarily combining the raw material (MP) with a quantity of a second mixture; and means, after impregnation, for at least partially recovering the quantity of second mixture after impregnation and for recycling at least a portion of the second recovered mixture to form at least partially said first impregnation mixture used at the first station (PT1).

Abstract: The invention relates to an apparatus for continuous digestion of wood chip comprising an upright generally cylindrical vessel having a top end and a bottom end. The top end of the cylindrical vessel is adapted to receive wood chips mixed with a cooking liquor to be treated therein. A first conduit is integrally attached at a first location positioned between the top and bottom ends of the vessel for selectively extracting a first quantity of cooking liquor from the vessel. The first location is positioned upstream of a second location within the vessel where the cooking liquor being at substantially full cooking temperature. A second conduit is integrally attached at a third location positioned downstream from the first and second locations of the vessel.

Abstract: A pulp digester includes a vessel having an inlet, an outlet and a wall extending between the inlet and the outlet, the wall of the vessel having a curved interior surface. The digester includes a screen assembly positioned inside the vessel adjacent to the curved interior surface of the wall for removing liquid from pulp material. The screen assembly is movable relative to the curved interior surface of the vessel wall. The digester includes at least one support element permanently attached to the vessel wall for limiting movement of the screen assembly relative to the curved interior surface of the vessel wall. In certain embodiments, the at least one support, such as a ledge permanently attached to the vessel wall, supports a portion of the screen assembly. The screen assembly may have an inner face that is concave in a horizontal direction and convex in a vertical direction.

Abstract: A method for feeding a cellulosic fibrous material to a high pressure processing vessel including: pressurizing a low pressure flow of the fibrous material in a high pressure transfer device; discharging a high pressure flow of the fibrous material from the transfer device to a conduit in fluid communication with the processing vessel; discharging a low pressure flow of fluid and fibrous material from the transfer device; downstream of the transfer device, pressurizing the discharged low pressure flow; merging the pressurized low pressure discharge flow with the discharged high pressure flow, and transferring the merged flow to the processing vessel.

Abstract: A method and apparatus for treating pulp in connection with a blow tank or a storage tank. The pulp is discharged from a batch digester and fed either to the upper or the lower part of a blow tank, depending on the consistency of the pulp being discharged from the digester.

Abstract: A top separator assembly for a digester is disclosed comprising: a rotatable shaft for the top separator; a packing for the shaft; and a sealing ring operatively mounted to the shaft and having a nominal clearance with the pack box, said sealing ring mounted so that up lifting of said shaft provides a substantially fluid tight seal between said pack box and a side of said ring (in the digester) opposite the pack box.

Abstract: A top separator assembly for a digester is disclosed comprising: a rotatable shaft for the top separator; a packing for the shaft; and a sealing ring operatively mounted to the shaft and having a nominal clearance with the pack box, said sealing ring mounted so that up lifting of said shaft provides a substantially fluid tight seal between said pack box and a side of said ring (in the digester) opposite the pack box.

Abstract: A system and method for feeding comminuted cellulosic fibrous material such as wood chips to the top of a treatment vessel such as a continuous digester provide enhanced simplicity, operability, and maintainability by eliminating the high pressure transfer device conventionally used in the prior art. Instead of a high pressure transfer device the steamed and slurried chips are pressurized using one or more slurry pumps located at least thirty feet below the top of the treatment vessel and for pressurizing the slurry to a pressure of at least about 10 bar gauge. A return line from the top of the digester may, but need not necessarily, be operatively connected to the one or more pumps and if connected to the pumps, the liquid in the return line may be cooled to a temperature at which it will not flash during handling. Recirculation loops may be established associated with one or all of the slurry pumps to facilitate startup.

Abstract: The release of malodorous TRS-containing gases from a comminuted cellulosic fibrous material feed system for a digester is minimized utilizing a particular arrangement associated with a pressure isolation device. Material is fed through the pressure isolation device and the pressure of the material increases from the inlet to the outlet, and the material is discharged from the pressure isolation device into a treatment vessel, such as a horizontal steaming vessel. Malodorous gases from the pressure isolation device are discharged substantially independently of the material discharged from the isolation device, and at least some of the malodorous gases discharged from the pressure isolation device are pressurized (e.g. in an eductor or thermocompressor) and reintroduced into the flow of cellulosic material downstream of the pressure isolation device (for example into the horizontal steaming vessel or a vessel downstream of it).

Abstract: A comminuted cellulosic fibrous material treatment vessel assembly includes a substantially vertical vessel having a top, bottom, and outlet, and through which the material flows in a flow direction. The vessel preferably has a substantially cylindrical wall with at least one diameter-changing transition between the inlet and the outlet. A screen assembly is preferably provided at or just past the transition. The screen assembly comprises one or more annular screen surfaces diverging in the flow direction of the material, the angle of divergence being between about 0.5-10° to the vertical, and preferably substantially continuous. Providing such a screen assembly reduces the radial compression of material thereon, and increases the volume and rate of liquid that can flow through the material and be removed through the screen surface compared to a non-diverging screen surface (that is a right-cylindrical surface).

Abstract: A method in connection with continuous cooking of chips, comprising impregnation of the chips with impregnation liquid in an impregnation vessel (3) and cooking of the impregnated chips in a digester (4), the impregnation vessel and the digester being connected to each other by means of a transfer circulation, which partly, via a feed line (25), feeds the chips from an outlet end (27) of the impregnation vessel to the top of the digester for separation of free liquid in a separator (28), and partly, via a return line (26), feeds separated liquid from the top of the digester to the outlet end of the impregnation vessel for use as transfer liquid for the impregnated chips, besides which cooking liquid is added to the chips in the top of the digester. According to the invention, as a first part, less than 100%, preferably less than 95% and more preferred less than 90% of the liquid which is separated from the chips in the transfer circulation, is recirculated to be used as transfer liquid.

Abstract: In the production of chemical pulp, such as kraft pulp, it is possible to reduce the amount of ancillary equipment, and/or the size of the continuous digester vessel, while achieving enhanced uniformity of treatment by avoiding “hang ups”. Instead of providing vertical counter-current flow of liquid and comminuted cellulosic fibrous material being treated in the lower half of the digester, the counter-current flow may be a cross flow, that is substantially horizontal (e.g. radial) while the flow of the chip column is vertical. Regardless of the configuration of the digester vessel, a single pump may be utilized for all of the recirculations, or only a few pumps for all of the recirculations.

Abstract: Kraft pulp of increased strength and bleachability may be produced with decreased consumption of effective alkali, and at a lower H factor, by keeping the dissolved organic material (DOM) concentration low substantially through the entire kraft cook, including by extracting high DOM liquid from at least one part of a continuous digester and replacing it with much lower level DOM liquid. Existing pulp mills having two-vessel hydraulic, one-vessel hydraulic, or other systems may be retrofit to provide for extractions and additions of low DOM dilution liquor (including substantially DOM-free white liquor). Also, commercial size batch digesters (8 tons per day of pulp or more) can be operated with low DOM liquor to produce increased strength pulp. Using dilution with low DOM liquor also results in reduced H factor and effective alkali consumption, and increased bleachability.

Abstract: The invention relates to a process system and a method for preliminary treatment of disintegrated cellulose-containing material, preferably wood chips, prior to pulp digestion. The process system and the method according to the invention make use of a process vessel intended to function both as a so-called chip bin and as a pre-impregnation vessel. The characteristics of the invention are that a sloping steaming vessel is arranged downstream of the process vessel for the purpose of separating an excess of pre-impregnation liquid from the pre-impregnated cellulose-containing material, that the sloping steaming vessel is arranged for supplying steaming vapor which preferably has been generated by flashing of extraction liquor from a pulp digester, and that the sloping steaming vessel is connected to a chip chute communicating with a condenser for connection to a system for managing foul-smelling process gases.

Abstract: In a single-vessel system for continuous cooking of kraft pulp, chips and liquor are conveyed from a high pressure feeder in a transfer line to a first end of a digester. A part of the liquor is separated from the chips that are withdrawn from an outlet defined in an upper part of the digester and conveyed in a return line to the high pressure feeder. A constituent flow of liquor is led from the return line and heated and fed via one or more inlets into the digester at a location that is downstream of the outlet for the return line.

Abstract: An apparatus and method for use in a displacement batch digesting process is provided which reduces the amount of equipment required to carry out an efficient displacement batch digestion process. Specifically, an apparatus and method are disclosed which eliminates the need for separate warm fill pumps, hot fill pumps and further which consolidates the cool pad pump, displacement pump and dilution pump functions into a single booster pump. Still further, the recirculation pump and discharge pump functions are consolidated into a single pump.

Abstract: A comminuted cellulosic fibrous material treatment vessel assembly includes a substantially vertical vessel having a top, bottom, and outlet, and through which the material flows in a flow direction. The vessel preferably has a substantially cylindrical wall with at least one diameter-changing transition between the inlet and the outlet. A screen assembly is preferably provided at or just past the transition. The screen assembly comprises one or more annular screen surfaces diverging in the flow direction of the material, the angle of divergence being between about 0.5-10.degree. to the vertical, and preferably substantially continuous. Providing such a screen assembly reduces the radial compression of material thereon, and increases the volume and rate of liquid that can flow through the material and be removed through the screen surface compared to a non-diverging screen surface (that is a right-cylindrical surface).

Abstract: A vertical pulp treatment vessel having a top and bottom, such as a continuous or batch digester, has at least a first substantially annular screen assembly disposed within the vessel between the top and bottom. A first substantially annular header is associated with the first screen assembly and first and second withdrawal conduits extend outwardly from the header and are in fluid communication with it. A barrier, such as a radially extending plate, is disposed in the header between the withdrawal conduits, the withdrawal conduits being adjacent each other (typically spaced from each other between about 2-30.degree., e.g. between about 10-20.degree.). A small, compared to the prior art, platform is provided for allowing access to the withdrawal conduits, and automatically controlled valves or like structures in or associated with the conduits, the platform having an arcuate extent of less than 180.degree., typically less than about 110.degree. (e.g. about 90.degree. or less).

Abstract: The present invention relates to a digester for continuous cooking under raised pressure and temperature of fibre material in a vertical digester (1), where input of fibre material and cooking liquid takes place at the top of the digester, withdrawal of spent cooking liquor is carried out from at least one digester screening arrangement (1D) between the top and the bottom of the digester, and fibre material is fed out from the bottom (1C) of the digester, wherein the digester (1) is fitted with an additional digester screening arrangement (2) above the lowest screening arrangement (1B) of the digester so that the temperature in all the participatory cooking zones in the digester can be kept at essentially the same temperature level.

Abstract: Kraft pulp of increased strength and bleachability may be produced with decreased consumption of effective alkali, and at a lower H factor, by keeping the dissolved organic material (DOM) concentration low substantially through the entire kraft cook, including by extracting high DOM liquid from at least one part of a continuous digester and replacing it with much lower level DOM liquid. Existing pulp mills having two-vessel hydraulic, one-vessel hydraulic, or other systems may be retrofit to provide for extractions and additions of low DOM dilution liquor (including substantially DOM-free white liquor). Also, commercial size batch digesters (8 tons per day of pulp or more) can be operated with low DOM liquor to produce increased strength pulp. Using dilution with low DOM liquor also results in reduced H factor and effective alkali consumption, and increased bleachability.

Abstract: A chip feeding system for a continuous digester provides for a greater rate of delivery of chip slurry to the digester, and is much less expensive than conventional chip feeding systems, typically being only 40-50% of the height of the conventional system. An atmospheric vessel may be connected at the bottom thereof to a slurry pump which pumps the chip slurry to a conventional high pressure feeder. A recirculation loop for returning liquid from the feeder to the vessel may include an atmospheric level tank, and a liquid cooler. The vessel may have one dimensional convergence and side relief, and instead of a conventional cylindrical chip bin, the chip bin may have a hopper having two transitions with one dimensional convergence and side relief. The chip bin also may be at atmospheric pressure so that no low pressure feeder between the bin and vessel is necessary.

Abstract: Kraft pulp of increased strength and bleachability may be produced with decreased consumption of effective alkali, and at a lower H factor, by keeping the dissolved organic material (DOM) concentration low substantially through the entire kraft cook, including by extracting high DOM liquid from at least one part of a continuous digester and replacing it with much lower level DOM liquid. Existing pulp mills having two-vessel hydraulic, one-vessel hydraulic, or other systems may be retrofit to provide for extractions and additions of low DOM dilution liquor (including substantially DOM-free white liquor). Also, commercial size batch digesters (8 tons per day of pulp or more) can be operated with low DOM liquor to produce increased strength pulp. Using dilution with low DOM liquor also results in reduced H factor and effective alkali consumption, and increased bleachability.

Abstract: Digester systems for producing paper pulp from comminuted cellulosic fibrous material take into account the level of dissolved organic materials (DOM), such as lignin, hemi-cellulose, and cellulose, maintaining the DOM level at about 100 g/l throughout the cook (particularly kraft cook). In order to make sure there is sufficient liquid to slurry the material in the feed system of a two vessel system, some liquid is withdrawn from the circulation conduits between the digester and impregnation vessel, cooled, and fed to the feed system. In a vapor phase digester, the level of liquid at the top of the digester is more precisely controlled by circulating some of the withdrawn liquid from a circulatory loop of the digester to the level tank associated with the feed system. An in-line drainer may be provided in the feed system between a make-up liquor pump and a liquid inlet conduit leading to the top of an impregnation vessel.

Abstract: A screen system for a digester for continuous cooking under raised pressure and temperature of fiber material in a vertical vessel, where input of fiber material and cooking liquid takes place at the top of the digester, withdrawal of spent cooking liquor is carried out from at least one digester screening arrangement (1D) between the top and the bottom of the digester, and fiber material is fed out from the bottom (1C) of the digester, wherein at least one of said screening arrangements (1, 2) has at least one screen element (2A) of which the main configuration is circular and which is assembled by means of welding, and which is fitted into the digester shell by means of welding.

Abstract: Mixing devices for mixing a processing agent with a pulp suspension are disclosed including a mixing vessel, an agitator mounted on the surface of the mixing vessel to create a flow of the pulp suspension across the mixing vessel, a processing agent supply for supplying processing agent to the flow of pulp suspension, and a flow divider mounted on the inner surface of the mixing vessel opposite the agitator, in which the flow divider includes a substantially vertical front distribution edge and a pair of arcuate front surfaces extending from that edge to the inner surface of the mixing vessel on opposite sides thereof.

Abstract: Digester systems for producing paper pulp from comminuted cellulosic fibrous material take into account the level of dissolved organic materials (DOM), such as lignin, hemi-cellulose, and cellulose, maintaining the DOM level at about 100 g/l throughout the cook (particularly kraft cook). In order to make sure there is sufficient liquid to slurry the material in the feed system of a two vessel system, some liquid is withdrawn from the circulation conduits between the digester and impregnation vessel, cooled, and fed to the feed system. In a vapor phase digester, the level of liquid at the top of the digester is more precisely controlled by circulating some of the withdrawn liquid from a circulatory loop of the digester to the level tank associated with the feed system. An in-line drainer may be provided in the feed system between a make-up liquor pump and a liquid inlet conduit leading to the top of an impregnation vessel.

Abstract: A method and continuous digester system provide for a high Na.sub.2 S concentration in the beginning of the cook of comminuted cellulosic fibrous material to produce cellulose pulp, providing a more selective cook and potential to lower cooking kappa. Two different streams of spent (e.g. "sulphurous" and "black") liquor are removed from different screens associated with continuous digesters. The spent liquor removed from the uppermost screen has a relatively high effective alkali and Na.sub.2 S concentration. The second spent liquor, removed from the second screen, has effective alkali and Na.sub.2 S concentrations which are at least 25% less than for the first spent liquor. The first spent liquor is circulated to an impregnation vessel, or other part of a chip feed system, to enhance the amount of sulphur present at the beginning of the cooking stage in the digester.

Abstract: A system for feeding wood chips entrained in cooking liquor to a high pressure feeder connected to a continuous digester includes a vertical treatment (e.g. steaming) vessel, a metering device connected to the discharge from the steaming vessel, a generally vertical chip chute extending downwardly from the metering device, and a slurry pump having an inlet. The slurry pump pumps the slurry from an outlet thereof to a high pressure feeder low pressure inlet. In order to minimize the effect of changes in liquid volume upon the operation of the system, and to provide separate control of liquor volume and chip volume, a substantially vertical liquor tank having a top and bottom the bottom including a discharge opening above the slurry pump inlet is provided. A conduit directly connects the liquor tank discharge opening with the slurry pump inlet. A pressure isolating device may be used in the system if it is to operate at superatmospheric pressure rather than atmospheric pressure.

Abstract: Kraft pulp of increased strength and bleachability may be produced with decreased consumption of effective alkali, and at a lower H factor, by keeping the dissolved organic material (DOM) concentration low substantially through the entire kraft cook, including by extracting high DOM liquid from at least one part of a continuous digester and replacing it with much lower level DOM liquid. Existing pulp mills having two-vessel hydraulic, one-vessel hydraulic, or other systems may be retrofit to provide for extractions and additions of low DOM dilution liquor (including substantially DOM-free white liquor). Also, commercial size batch digesters (8 tons per day of pulp or more) can be operated with low DOM liquor to produce increased strength pulp. Using dilution with low DOM liquor also results in reduced H factor and effective alkali consumption, and increased bleachability.

Abstract: A screen system for a digester for continuous cooking under raised pressure and temperature of fibre material in a vertical vessel, where input of fibre material and cooking liquid takes place at the top of the digester, withdrawal of spent cooking liquor is carried out from at least one digester screening arrangement (1D) between the top and the bottom of the digester, and fibre material is fed out from the bottom (1C) of the digester, wherein at least one of said screening arrangements (1, 2) has at least one screen element (2A) of which the main configuration is circular and which is assembled by means of welding, and which is fitted into the digester shell by means of welding.

Abstract: Digester systems for producing paper pulp from comminuted cellulosic fibrous material take into account the level of dissolved organic materials (DOM), such as lignin, hemi-cellulose, and cellulose, maintaining the DOM level at about 100 g/l throughout the cook (particularly kraft cook). In order to make sure there is sufficient liquid to slurry the material in the feed system of a two vessel system, some liquid is withdrawn from the circulation conduits between the digester and impregnation vessel, cooled, and fed to the feed system. In a vapor phase digester, the level of liquid at the top of the digester is more precisely controlled by circulating some of the withdrawn liquid from a circulatory loop of the digester to the level tank associated with the feed system. An in-line drainer may be provided in the feed system between a make-up liquor pump and a liquid inlet conduit leading to the top of an impregnation vessel.

Abstract: A pulp digester having a number of screening/cleaning units mounted within the digester. Each unit has a screen member and a cleaning propeller which is mounted adjacent the inner surface of the screen member. There is for each unit a hydraulic motor which is positioned entirely within the digester housing, and which rotates the propeller. Hydraulic lines extends through sealed openings in the digester wall and power is supplied from an exterior hydraulic pump which is controlled by a valve.

Abstract: A process for the continuous digestion of cellulosic fiber material, comprising impregnation with impregnating liquid consisting of at least one fresh digesting liquor, in a closed impregnating system and subsequent digestion with digesting liquid in a closed digester system, said impregnating liquid being supplied through a supply system, together with steamed fibre material, to an inlet end of the impregnating system, liquid being withdrawn from the impregnating system at a point (46) located at a predetermined distance from said inlet end.

Abstract: A method and apparatus for reclaiming cellulosic fibers from a bale containing waste papers, in which the bale is positioned in a treatment enclosure, and the enclosure is placed under a vacuum. A treating fluid is drawn into the enclosure, which penetrates the bale interior spaces, and produces a preferential swelling-of uncontaminated cellulosic fibers. After the treating fluid is withdrawn from the enclosure, a slurrying fluid is passed through the bale contents, to form a fiber-fluid suspension slurry.

Abstract: A chip feeding system for a continuous digester provides for a greater rate of delivery of chip slurry to the digester, and is much less expensive than conventional chip feeding systems, typically being only 40-50% of the height of the conventional system. An atmospheric vessel may be connected at the bottom thereof to a slurry pump which pumps the chip slurry to a conventional high pressure feeder. A recirculation loop for returning liquid from the feeder to the vessel may include an atmospheric level tank, and a liquid cooler. The vessel may have one dimensional convergence and side relief, and instead of a conventional cylindrical chip bin, the chip bin may have a hopper having two transitions with one dimensional convergence and side relief. The chip bin also may be at atmospheric pressure so that no low pressure feeder between the bin and vessel is necessary.

Abstract: Enhanced uniformity of treatment of the material with a treatment liquid in a continuous treatment vessel, is provided. The invention is particularly applicable to the treatment of comminuted cellulosic fibrous material to produce paper pulp, specifically for the digesting (kraft or sulfite, or solvent pulp processing) of wood chips to produce paper pulp. The vessel has at least one annular screen divided into at least four arcuate screen segments disposed around the internal periphery of the vessel, and a first liquid having treatment properties, and a second, spent liquid, are utilized in the treatment. A second liquid is withdrawn through at least a first of the arcuate screen segments while simultaneously the first liquid through or adjacent at least a second of the arcuate screen segments opposite the first screen segment. The various screen segments are operated, and at rest, in sequence to provide the uniformity of treatment.

Abstract: In a method of producing high-yield pulp from pulp chip material containing lignocellulose the material is treated with steam in a steam treating station (1) for driving air out of the material and heating the latter. Heat treated material is mixed in a mixing station (8) with a liquid containing chemicals. The mixture of steam treated material and said liquid is transferred from the mixing station to an impregnation station (25) for impregnating the material by means of said chemicals. Impregnated material is supplied to a refining station (36) for refining the material. According to the invention the steam treated material is mixed with said liquid in proportions, such that the created mixture of material and liquid leaving the mixing station (8) assumes a flowing pumpable consistency. Further, said flowing mixture is pumped from the mixing station (8) to the impregnation station (25).

Abstract: An apparatus and method for use in a batch digesting process to quantitatively displace fluids in the digester by pumping into the digester under pressure a first volume of displacing fluid at the upper end and a second volume of displacing fluid at the lower end of the digester. Displaced fluids are collected and removed from the digester near the midline between the top and the bottom of the digester.

Abstract: A method and apparatus provide for the continuous digestion of comminuted cellulosic fibrous material (e.g. wood chips) to produce paper pulp, with increased sulfidity. When black liquor is withdrawn from the continuous digester, instead of merely passing it to a pair of flash tanks and then to recovery, the concentrated liquor from a first flash tank is fed to a vessel in which the comminuted material is slurried with a liquid. Since the black liquor remains in intimate contact with the chips for a significant period of time, the lignin in the chips is partly sulfonized. Ultimately the black liquor is replaced with white liquor or the like, and the separated out black liquor is circulated to recovery or disposal. A high pressure feeder and a solids/liquid separator are utilized.

Abstract: Extended delignification of kraft pulp in a pressure diffuser allows a pulp mill with a digester (e.g. continuous digester) to increase its production capacity without building a new line, or to decrease its demand in its bleach plant, or to increase the strength of softwood pulp it produces. Comminuted cellulosic fibrous material is kraft cooked to produce kraft pulp having a blow temperature over about 300.degree. F. The pulp is diffusion treated in the first stage of a pressure diffuser to replace the water around the pulp with delignifying liquor. The liquor has a dissolved lignin concentration of less than 12% (optimally less than about 4%), has an effective alkali concentration of at least 2 gm/l (preferably 8-55 gm/l), and a temperature of at least about 300.degree. F. Treating the pulp with the delignifying liquor significantly reduces the K-number (e.g. on the order of about 5). After extended delignification, the pulp is washed in subsequent stages of the pressure diffuser.

Abstract: For bleaching cellulose pulp or a fraction thereof, e.g. reject pulp, the cellulose pulp or fraction, having a concentration of 0.5-10%, preferably 3-6%, is introduced into a screw press comprising at least a first (47) and a second (48) dewatering zone, is dewatered in the first zone to a concentration of 20-40%, whereupon a liquor of bleach chemicals is introduced centrally into the pulp which, during continued treatment, is dewatered in the second zone to a discharge pulp concentration of 15-50, preferably 15-30%, the liquid pressed out of the second zone, together with fresh bleach chemicals, being returned to the pulp in the screw press as liquor of bleach chemicals.

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 having a plurality of annular screen systems each set vertically spaced from the other sets. 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. Withdrawal of liquid through the nozzles is practiced so that liquid is being withdrawn substantially through only one nozzle at a time, and it is being withdrawn at the same radial segment of the digester at each screen set at any particular point in time, with progressive switching in a circumferential sequence of the nozzles through which liquor is being withdrawn.

Abstract: A method and apparatus in defibration of wood chips or similar vegetable material for conveying in steam pulp produced in a refiner (2) to a separator (7) for separating steam and pulp. The separator is bounded against the atmosphere and is kept pressurized by steam, while a limited amount of excess steam is led off. A flow of steam liberated from the pulp is taken from the separator and given an increased pressure for utilization in extracting pulp from the refiner. The steam flow is hereby led through the refiner and further to the separator, whereby the pulp is transferred to the separator by the steam which thus circulates to a considerable extent, said steam having been given the higher pressure either in the refiner itself, by means of pressure increasing means (19) therein, or upstream of the refiner in a separate pressure increasing means (11).

Abstract: A versatile process and apparatus is presented for producing, in high yields, many different grades of pulp from a single wood specie or for pulping any specie or type of woody material, and for storage and recycling of the by-product liquid and gaseous materials. The process of this invention is virtually pollution free, and the reactant chemicals are recoverable from the by-products. In the alternative, the by-products themselves have a commercial value which may forestall recovery of the reactants. The lignin constituent extracted from the pulp is usable as a resin binder, a wood rehardening agent, or a glue.

Abstract: A method and apparatus for screenless treatment of cellulose fiber material without channeling of treatment liquid through a fiber material column being treated. An inner vertical vessel extends into an outer vertical vessel which has a larger diameter than the inner vessel, and an annular space in the outer vessel is defined by a portion of the inner vessel extending into the outer vessel. At least three baffles extend through the annular space into the area of the outer vessel below the inner vessel to define at least three distinct flow areas, and an outlet nozzle is provided in each of the flow areas. Liquid is withdrawn from the annular space through at least two of the flow areas, while liquid is backflushed into one of the flow areas.

Abstract: A comminuted cellulosic fibrous material treatment vessel assembly includes a substantially vertical vessel having a top, bottom, and outlet, and through which the material flows in a flow direction. The vessel preferably has a substantially cylindrical wall with at least one diameter-changing transition between the inlet and the outlet. A screen assembly is preferably provided at or just past the transition. The screen assembly comprises one or more annular screen surfaces diverging in the flow direction of the material, the angle of divergence being between about 0.5-10° to the vertical, and preferably substantially continuous. Providing such a screen assembly reduces the radial compression of material thereon, and increases the volume and rate of liquid that can flow through the material and be removed through the screen surface compared to a non-diverging screen surface (that is a right-cylindrical surface).