Abstract: Method and apparatus for producing thermo-mechanical pulp from wood chips and the like in which the chips are first heated in a steaming chamber or preheater to a fiber temperature below the softening point of the lignin of middle lamella section of the wood fibers. The thus heated chips are conveyed in a sealed system to the inlet of a difibrating zone enclosed within a housing in a gaseous atmosphere of superatmospheric pressure, where it is compressed by a screw conveyor into a plug which seals the defibrator housing against blow-back of the pressurized gaseous medium.

Abstract: A method and apparatus is provided for controlling the effect of centrifugal force on pulp stock while being ground in the grinding space of a defibrating apparatus. The grinding space includes a central portion, a first grinding zone defined between first and second rotatable grinding discs and extending outwards from the central portion, and a second grinding zone extending angularly from the outer end of the first grinding zone and being defined between one of the rotatable grinding discs and a stationary grinding surface. Pulp stock to be ground is introduced into the central portion and accelerated through the first and second grinding zones by centrifugal force generated by the rotating discs. The angular second grinding zone serves to retard centrifugal force acting on the pulp in the second grinding zone to increase the dwell time of the pulp in the grinding space for achieving optimum refining efficiency.

Abstract: An installation for processing waste paper containing a stock pulper or slusher equipped with a rotor and two sieves or screens having different size holes or openings. By means of the sieve having the larger size openings there is conducted the obtained stock suspension through a primary line system which, for instance, leads to a papermaking machine. Cooperating with the sieve having the larger size openings or holes is an auxiliary circulation circuit containing a device for the removal of contaminants or rejects. There is preferably arranged at the auxiliary circulation circuit or system a separator for heavy contaminants or rejects, a pump, a secondary stock pulper or fiberizer and a sieve or filtering device.

Abstract: A method and apparatus for use in making refiner pulp by refining lignocellulose-containing materials in a disc refiner. In accordance with the method and apparatus, the retention time of the material in a gap between a pair of refining discs is increased by diluting the refined material exiting from the gap so as to form a fiber suspension having an easily pumpable concentration and maintaining a predetermined amount of the fiber suspension adjacent to the outlet of the gap.

Abstract: A method of grinding wood under pressurized conditions in a grinder according to which wood is fed in batches into a pressurized gas-filled grinding chamber provided with a rotary grinding means. The wood batches are fed through a feeding chamber provided with means for sequentially opening and pressure-tightly closing said feeding chamber from two sides in and respectively out of communication with the atmosphere and said grinding chamber respectively. The groundwood stock is discharged from the grinding chamber through a pressure lock formed by the groundwood stock. In this way feeding of the wood batches into the grinding chamber and the discharging of the groundwood stock out from said grinding chamber are carried out as sluicing steps, whereby a continuous pressure can be maintained in the grinding chamber in spite of feeding of new wood batches and discharging of groundwood stock.

Abstract: Waste paper containing materials, e.g. commercial "waste paper", are treated for recovery of reusable paper therefrom by slushing in a pulper from which two fractions are continuously extracted--a first fraction through small holes, e.g. 3/16 inch in diameter, and a second fraction through substantially larger holes, e.g. 1 inch in diameter. The second fraction is screened, preferably after a centrifugal cleaning operation, in a screen having small perforations sized to accept only substantially defibered paper, and the accepts flow is mixed directly with the first extracted fraction. The reject flow from this screen is conducted, with or without an intermediate deflaking operation, to a tailing screen from which the accepts are recycled to the pulper and the rejects are eliminated from the system.

Abstract: A method of discharging groundwood stock when grinding wood under pressurized conditions in a grinding chamber, according to which the groundwood is suspended into stock and collected in a tank provided with an outflow for groundwood stock to atmospheric pressure. The surface of the stock in said tank is maintained at such a level above said outflow, that the stock in said tank forms a pressure lock in the communication between the grinding chamber and said outflow. In this way the discharging of the groundwood stock out from said grinding chamber is carried out as a sluicing step, whereby a continuous pressure can be maintained in the grinding chamber in spite of discharging of groundwood stock.

Abstract: A method of beating fibre slurries, such as paper pulp, and lump-goods, such as wood-chips and shavings. The good are subjected to repeated, rapid pressure pulsations and working moments of short duration. This is obtained by causing the hydraulic pressure to increase during a compression phase with increasing internal frictional co-action between individual fibres, whereafter said hydraulic pressure is caused to fall momentarily during a following expansion phase.

Abstract: Chips of scrap wood having a length at least twice the desired length of shavings for the making of particle board panels, as considered in the direction of grain, are fed into a rotor having an annulus of blades which split the chips in the direction of grain and feed the comminuted chips into the range of stationary comb-like knives serving to subdivide the split chips into shavings of ultimate length.

Abstract: A novel coating agent for solid medicaments containing a hydrogel-like substance of a water-insoluble hydroxypropyl cellulose having 5-16% by weight of a hydroxypropoxy group or the dry powder of a hydrogel-like substance. By coating solid medicaments with the coating agent, solid medicaments having high impact resistance and showing very less aging can be provided advantageously in industry.

Abstract: The disclosure concerns both a process and an apparatus for producing wood pulp. Wood to be pulped is fed into a housing where the wood is ground. The housing is pressurized above atmospheric pressure. Water at a temperature over 100.degree. C. is fed to the pressurized housing in the grinding zone. The wood pulp produced by grinding is collected and is conveyed through a worm conveyor which causes the water in the pulp to be removed therefrom, while the pulp and the water removed therefrom are maintained at elevated pressure. The water under pressure is returned to the grinding zone in the housing. The wood pulp is thereafter returned to atmospheric pressure. Various pressure lock devices for transmitting the wood pulp from being under pressure to atmospheric pressure are disclosed including a nozzle, a pressure lock device, a hydrocyclone and/or a disc refiner.

Abstract: A method and apparatus is provided for controlling the effect of centrifugal force on pulp stock while being ground in the grinding space of a defibrating apparatus defined between a pair of grinding discs which rotate relative to one another in a fluid environment under superatmospheric pressure and corresponding elevated temperature. The grinding space includes a central portion, a first outwardly extending grinding space and a second outer grinding zone extending at an inclined angle from the first grinding zone. Pulp stock to be ground is introduced into the central portion and accelerated through the first and second grinding zones by centrifugal force generated by the rotating discs. The inclined grinding zone serves to split the centrifugal force into a vector perpendicular to the direction of flow of the pulp material and a vector aligned with the axial flow to reduce the accelerating force on the pulp grist in the direction of outward flow.

Abstract: There is disclosed an improved process for preparing cellulose ether derivatives which in pertinent part accomplishes this by providing for the uniform distribution of caustic and etherifying reagents over the exposed area of fiberized, never-dried, non-purified natural polysaccharide materials by fluidizing said materials while simultaneously contacting the material with said reagents.

Abstract: An improved method and means for dry defibrating fiber material in the form of chemical, chemi-mechanical or mechanical fiber pulp or mixtures thereof by means of known defibration devices, so-called shredders, mills or similar devices, to obtain fluff, i.e. exposed, unbonded fibers and fiber flocks used in a manner known per se to make paper, paper-like and absorbent products, by which method said fiber material is fed to the defibration device in the form of a continuous web from a bale being said means and consisting of a pressed or non-pressed zig-zag-shaped, repeatedly folded continuous web.

Abstract: Disclosed is a process for producing stone groundwood pump from wood chips, by compressing a wood chip mass into an apparent volume corresponding to 70% or less, preferably, from 40 to 60%, of the original apparent volume of the wood chip mass and by grinding the compressed wood chip mass, under pressure, with a stone grinder. The wood chips may be treated, before the grinding step, with both or either one of steam and a treating agent, such as sodium monosulfite, sodium disulfite and sodium bicarbonate.

Abstract: A method for separating fibers from a stack of pulp sheets. The stack of pulp sheets is fed slowly and continuously to the fiberizing means of fiberizing apparatus and in shingled relation so that the tails of individual sheets are presented singly to the fiberizing means. The fiberizing apparatus may be conventional hammermill or pulp picking equipment and suitably includes an output screen to limit the size of unfiberized particles which may pass from the fiberizer.

Abstract: The invention relates to a method in or relating to grinding of vegetable material in a grinding apparatus equipped with discs mounted rotatably relatively one another in a casing, within which a superatmospheric pressure is maintained by steam. This steam is introduced into the casing together with the vegetable material to be ground through a central inlet into an interspace defined by the discs. The material and the steam pass radially outward through said interspace. Immediately on departure from the interspace the ground pulp is received by an atmosphere of a non-condensable gas, the action of which gives the final product desired properties.

Abstract: Method and apparatus for producing pulp from moisture-containing lignocellulosic material, such as wood chips, which is ground in a grinding space defined between a pair of grinding discs which rotate relative to one another in an environment of pressurized steam generated during the grinding process, in a closed housing. The ground fiber or pulp discharged from the grinding housing is propelled by the accompanying steam into a cyclone, where the ground pulp is separated from the steam for further treatment, while the steam is recycled for further use in the pulping process. The pressure in the cyclone is so controlled that a pressure is maintained therein which is substantially equal to a pressure drop which is sufficient merely to maintain the propellant force of the steam to convey the ground pulp from the grinding housing to the cyclone while discharging the separated steam and recycling it for further use in the pulping process.

Abstract: A wood chip rechipping method and apparatus are provided wherein a slotted, cylindrical drum rotates about a concentrically mounted rotatable anvil rotor having a plurality of arms, each of which has a blade at its outer extremity. The drum and anvil rotor arms rotate in the same direction, but at different speeds. The rotating apparatus induces centrifugal force on the wood chips to position them against the inner periphery of the drum where the blades on the relatively faster rotating anvil arms shear off a chip slice having a predetermined thickness. This shearing action continues until each chip has been rechipped into slices capable of passing through one of the drum knife slots and into the discharge outlet.

Abstract: A process and plant for treating waste paper in which a beater is employed for rough-pulping the waste paper followed by a first sorting stage from which the separated-out foreign matter is processed further in a subsidiary circuit which includes a vibratory sorter for lightweight foreign matter and a hydrocyclone for heavy foreign matter, the fibers separated out during this further processing being returned again to the treatment process. In the first sorting stage, a sufficiently rigorous separation process is carried out to remove the greater part of the foreign matter, together with unpulped lumps of fibers, which is then passed to the subsidiary circuit in which it and half-stuffs still containing foreign matter, which have been sorted in the hydro-cyclone and in the vibratory sorter, are subjected together to a multi-stage further sorting and speck-removing process.

Abstract: Method and apparatus for refining fiberous material in a disc refiner for withdrawing steam developed during refining of such fiberous material. The disc refinger comprises a pair of refining discs each of which includes a inner refining surface. The refining discs are mounted for rotation relative to one another in a housing with the refining surfaces opposing one another during the relative rotation and defining a refining space therebetween. Each of the refining surfaces of the refining discs is provided with a passageway for withdrawing steam developed in the refining space. The passageways extend from the respective refining surfaces in a direction away from the refining space and radially inward relative to the direction that the fiberous material moves through the refining space.

Abstract: A method and apparatus for treating waste paper by pulping or defibering the paper in a stock pulper or slusher while infeeding water, wherein there are removed in succession, externally of the stock pulper, heavy weight particles, floatable substances and plastic foils. Thereafter, paper constituents which have incompletely defiberized are removed and further defibered in a special apparatus. The already defibered fibers are directly infed for further processing. The removal of the contaminants can be accomplished at a suspension density in the order of 1%, whereas the defibering or pulping of the waste paper in the stock pulper occurs at about 4%. The employed sorting apparatus is connected with the stock pulper, while dispensing with the use of a sieve or screen.

Abstract: Components of pulped scrap material containing paper, metal and plastic materials are separated by subjecting the pulped material to sorting in cyclone separators, the discharge from the top part thereof being led to a screen sorter where the material is divided into two parts, one part containing in its major part paper stuff, the other part containing plastic material, the discharge from the bottom part of the cyclone separators containing metal components.

Abstract: A process and apparatus is disclosed for dry refining cellulosic pulp wherein the liberated fibers are structurally deformed and twisted without producing unwanted knots or fiber bundles. For the purposes of the invention, a disk refiner is used which is modified to include one or more air jets located at the periphery of the refiner housing. During refining, the refiner is provided with a cooling means, while air is introduced into the housing through the air jets to prevent fibers from becoming trapped between the ends of the refiner disks and the housing walls, thus preventing the formation of knots and fiber bundles.

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: Method and apparatus for separating fibers from agglomerated masses thereof is disclosed, and achieved by paired rolls having roll surfaces with randomly disposed protuberances thereon, such protuberances being initially deformed randomly as the roll surfaces approach complete conjugacy and being further deformed as the roll surfaces move into complete conjugacy to induce shearing and tearing action on the agglomerated fiber masses therebetween to separate discrete fibers therefrom. The roll surfaces are characterized by each having the elastomeric roll surface thereof with a Poisson ratio different from the Poisson ratio of the other.

Abstract: Method and apparatus for coordinating the rate of feed and the moisture content of the pulp material to the heat quotients of the mechanical energy input in a refiner system in which the moisture-containing pulp material is introduced at an adjustable rate of feed into the central portion of an axially adjustable grinding space defined between a pair of grinding discs which rotate relative to one another within a closed housing and in which grinding space the material is propelled by centrifugal force created by the rotation of the discs in an annular radial path toward the periphery of the discs while being subjected to a grinding operation in an environment of steam generated by the heat produced by friction in the grinding space.

Abstract: In a timbering operation wherein the felled trees are fed into a chipper for conversion to chips at the timbering site the chips are fed into a trailer-mounted rotary cylindrical screen which separates the chips from dirt and fine bark particles. Preferably the chips entering the cylindrical screen are blown into engagement with an impact plate to aid in disloading particles of dirt and bark from the chips. The chipper may be mounted on the same trailer or may be a separate trailer-mounted unit.

Abstract: Method and apparatus for minimizing steam consumption in the production of pulp used for the manufacture of fiberboard and the like, in which chips of cellulosic material are ground in a defibrator or refiner in an environment of saturated steam above 100.degree. C and corresponding steam pressures. The chips are normally presteamed with atmospheric steam separated from the pulp at the discharge end of the defibrating process to a temperature between 90.degree. C and 100.degree. C and compressed and dewatered to a dryness of at least 50% and then passed into a preheater which forms part of the defibrating or refining apparatus, where the compressed and dewatered chips are heated to the desired defibrating or refining temperature, usually ranging between 130.degree. C and 200.degree.

Abstract: An apparatus for reducing fiber material to chip form including an anvil assembly defining an anvil bearing surface of generally U-shaped configuration having leg portions joined by a connecting portion, at least one knife blade and carrier means for moving the knife blade in surface-to-surface bearing engagement with the anvil bearing surface in a direction extending from adjacent the ends of the leg portions towards the connecting portion to effect cutting or severing of the material into chip form.

Abstract: Solid trash is comminuted and classified into an organic fraction and a metals-inorganic fraction. The organic fraction is processed for recovery of paper pulp and the residue pyrolysed. The metals-inorganic fraction is processed for recovery of each major metal and inorganic constituent.

Abstract: Disclosed are method and apparatus for applying forces to a waste paper mixture programmed to procure progressive fragmentation of the respective components of the mixture; the method including the step of harvesting the resulting paper fragments at intervals when fragmentation of one component is virtually completed and fragmentation of the next commences.

Abstract: In the continuous production of paper pulp from ligno-cellulose raw material, the raw material is subjected to grinding and/or delignification by passing it in the form of small pieces between interpenetrating helicoidal surfaces driven synchronously in rotation inside a casing. The pitch of the helicoidal surfaces is arranged to provide at least one supply zone in which the material is driven downstream by rotation of the surfaces and at least one braking zone in which the material is braked.

Abstract: Improved fluffed pulp consisting of 95 to 25 percent by weight groundwood and 5 to 75 percent by weight chemical pulp, with a liquid retention capacity of at least 6.5 gram liquid per gram pulp, a liquid dispersing capacity of at least 2.5 gram liquid per gram pulp per minute, a bulk of at least 18 cm.sup.3 /gram and a web strength of at least 0.2 Newton, and a method of producing said pulp by mixing 95 to 25 percent by weight groundwood and 5 to 75 percent by weight chemical pulp beaten in a wet state with each other, dewatering mechanically to a dry solids content of 40 to 50 percent by weight, coarse-defibrating, drying in a flash drying step to 60 to 85 percent by weight, finish-defibrating and finish-drying to 80 to 95 percent by weight dry solids content.

Abstract: A method of reducing the particle size of cellulose compounds selected from the group consisting of cellulose and ether derivatives thereof which comprises grinding said compounds in a vibration mill in the presence of air and in the presence of sufficient water to yield a product having a water content of from 2 to 10% by weight, wherein at least 50% of the particles in the product have a particle size of 100 .mu. or less, a product obtained by said method and a binder composition containing said product.

Abstract: Procedure for preparing hot groundwood from wood chips, wherein a chip stream is conducted into a pressurized steaming chamber, where the chips stay a few minutes and are heated to a temperature higher than 100.degree. C., and from the steaming chamber through a sluice feeder into a hot grinder of enclosed construction, i.e. the stage I grinder, when the pre-ground groundwood is conducted through a separating cyclone into a stage II grinder, the groundwood derived herefrom being conducted towards further treatment steps. The pre-ground groundwood is conducted from the steam separating cyclone through a sluice feeder into the stage II grinder. The stage II grinding is carried out in a hot grinder of enclosed construction.

Abstract: The present invention relates to fluffed pulp comprising unwashed mechanical pulp with a liquid-diffusing capacity of at least 3.5 grams liquid per gram pulp per minute, a bulk of at least 18 cm.sup.3 /gram and a volume weight in blocks or bales of at most 0.8 grams/cm.sup.3. The invention also comprises a method of producing such a fluffed pulp by means of defibrating the wood and thereafter drying the same with warm air to a dry content of 80-95% by weight without subjecting the pulp to any mechanical compression.

Abstract: A wood chip stream capable of being selectively delaminated is produced by separating a mill-wood chip stream into respective first and second fractions on the basis of wood chip thickness. The first fraction consisting of wood chips having a predetermined thickness, is then pulped by conventional techniques. The wood chips in the second fraction are reduced to said predetermined thickness and are then selectively delaminated by compression means. After being subjected to selective delamination, the delaminated chips are pulped by conventional techniques. Accordingly, a high yield, uniform wood pulp having reduced pulp screen rejects is produced.

Abstract: Raw fibrous material is preheated in a preheater in the presence of steam under a pressure greater than atmospheric pressure and then continuously introduced into a disc refiner, without prior defibration, whereby steam is generated in said disc refiner. The generated steam is continuously conducted away from said disc refiner as subsequent fibrous material is continuously being introduced into the disc refiner in order to obtain a pressure in the disc refiner which is greater than atmospheric pressure but less than the pressure in said preheater.

Abstract: Waste wood, such as stumps and snag, is treated to make it suitable for the production of paper pulp, whereby the raw waste wood is initially crushed so that part of the bark, sand and stones attached to the wood is detached at this stage already, the obtained crushed material is fed into a washer tank for further washing away bark, sand, stone and peat material from the wood, high-pressure water nozzles being provided at an inlet end of said washer to impinge strong water jets on the crushed wood material, and flow creating means being provided at the lower part of the washer tank to produce a water flow directed slantedly upwards towards an outlet end of the washer tank in order to entrain heavy wood fragments, which may tend to sink into the material leaving the washer tank at said outlet end thereof, said material being further after-crushed and sieved to separate an accept fraction thereof for feeding to a pulp production process.

Abstract: A process is provided for producing novel convoluted, fiberized substantially nonfibrillated, cellulose fibers and novel sheet products from low moisture-content cellulose pulp, at a high through-put rate, which includes the application of contortive forces to a pulp mass under controlled operating conditions, wherein the feed rate, work space gap, and relative rate of movement of the working elements applying the contortive forces are correlated to maintain the work space filled with fibers under sufficient compression. Sheets made from these fibers exhibit excellent bulk, softness and absorbency properties, even when the formation process is conducted in an aqueous system, and even when substantial compacting forces are applied to the wet web processing.

Abstract: A stream of disintegrated fibrous cellulosic pulp material and steam under pressure is subjected to an instantaneous pressure reduction as said stream and steam pass through a throttling nozzle, in a throttling zone, wherein a liquid solution of a bleaching agent is admixed with said stream and which stream, admixed with bleaching agent, is then passed into an expansion zone ahead of the throttling nozzle resulting in a uniform dispersion of the bleaching agent into the fibers in the stream of fibrous cellulosic pulp material.

Abstract: A process for defibrating cellulosic materials into fluffed materials wherein blocks and at least one strip of cellulosic fibrous materials are continuously fed into a defibration unit where they are simultaneously disintegrated in a dry state upon contact with impact elements which are pivotably mounted on a rotor, fluffed and mixed by the impact elements so as to form a homogeneous mixture of fluffed materials.An apparatus for performing the process which comprises a defibration unit provided with separate feed units for blocks and strips of cellulosic fibrous materials and a rotor having pivotably mounted impact elements which disintegrate, fluff and mix the entering feed materials. The mixture is discharged through a sieve located in the bottom of the defibrating unit.The position of the entering feed blocks on a feed plate is maintained within angle limits to prevent blocks from being uncontrollably pulled into the defibration unit.

Abstract: A process for the preparation of a cellulose pulp by mechanically freeing wood fibers in a grinder to form a fibrous pulp and bleaching the fibrous pulp with a peroxide-containing bleaching agent, as the only bleaching agent, in a peroxide bleaching stage, the mechanical freeing of the fibers being carried out in the presence of a spent liquor from the peroxide bleaching stage have a pH of 7 to 9.

Abstract: The present invention concerns a novel method of making short inorganic glass fibers and mineral wool fibers with a very low shot content and the fibers thus produced.

Abstract: A novel process for producing reactive, homogeneous, self-bondable lignocellulose fibers is provided in which individual, separate, lignocellulose fibers are oxidatively modified, employing oxidative reagent system. Pursuant to the teachings of the present invention, the oxidative modification step is conducted in a controlled manner, for example, employing a confrication step, using a liquid-phase reagent system, the subject product fibers, prior to sheet formation, being substantially free of residual oxidative reagent. Sheets are formed from the product fibers on subsequent bonding, employing mild formation conditions, the sheets having improved dry- and wet-strength properties.

Abstract: Disclosure is made of improved apparatus for continuously processing waste papers, contaminated with inks, adhesives, resins, groundwood, foreign objects, paper fasteners and the like, into usable grades of cellulosic fiber pulps. The disclosure is also of a method for the continuous processing of contaminated waste papers into nearly quantitative yields of usable cellulosic fiber pulps.

Abstract: An improved apparatus and method for manufacturing ground wood pulp from ligno-cellulose containing wood block material by forcing the block material to be ground against the end surface of a rotatably mounted grinding disc which has projecting grinding means in the shape of elevations or ridges located on the disc end surface which define grooves directed towards the end surface circumference. The apparatus includes a pressure plate for pressing the block material along a longitudinal side against the disc end surface with the fibers directed outwardly from the center of the grinding disc and toward the periphery of circumference of the disc while the fibers are separated. In this manner the fibers are oriented in the same direction as the edges of the elevations or ridges which carry the fibers radially outward and the elevation edges engage the block fibers under a movement component which is transverse to the longitudinal direction of the fibers.

Abstract: Lignocellulose fiber containing chips, preheated with steam liberated from a previous chip defibration, are dewatered and then defibrated in an atmosphere of saturated steam and in the presence of backwater and suspended in backwater to form a pulp suspension whereafter wet sheets are formed from the pulp suspension, water is mechanically removed from the wet sheets and recycled as backwater to be supplied simultaneously, with dewatered chips, to the defibration step and to form a new pulp suspension and said wet sheets are dried.

Abstract: Continuously operating procedure for preparing hot groundwood from wood chips, wherein the chip flow is conducted into a pressurized steaming chamber, where the chips reside a few minutes and are heated to a temperature in excess of 100.degree. C, and from the steaming chamber to a sealing feeder, the rotor of which is circumferentially divided into mutually adjacent compartments, each of which in its turn fills through a feeding aperture with chips and empties in another angular position of the rotor through a discharge opening into a feeding conveyor, which carries the chips to a hot grinder, the groundwood derived from the latter being carried to further treatments, whereat the steam generated by the hot grinder and discharging from its throat in the direction against the chip flow is conducted away from the grinder. The steam is conducted through the feeding conveyor to the sealing feeder, where each compartment, as it is emptied of chips in its turn, fills with steam.