FI62150C - ANORDING VIDEO MALAPPARAT FOER FIBROEST LIGNOCELLULOSAHALTIGT MATERIAL - Google Patents

Description

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Patent- och refisterstyrelsen '' AnsMan uttafd och uti.tkr (ft «n pubticarad (32) (33) (31) Pyri · ** ataolkau * —Bagtrd prtarltat 05.09.75

Sweden-Sweden (SE) 750990i * -U

(71) (72) Arne Asplund, Tykövägen 20, 188 6l Lidingo 3, Sweden-Sverige (SE) (7 * 0 Oy Kolster Ab (5 * 0 Fiber lignocellulosic material grinding device arrangement -

Anordning vid en malapparat föröst lignocellulosahaltigt material

The invention relates to an arrangement of a grinding device for a fibrous lignocellulosic substance, provided with rotating grinding plates having mutually rotating grinding surfaces formed by mutually parallel or nearly parallel radially extending rods made as separate units and having radially extending peripherals and connecting them. arranged in both refining plates in rows of separate pockets separated by transverse booms, the pockets of which in radial section are curved in each refining plate and wherein the pockets in one plate are displaced radially relative to the pockets in the other plate.

2 62150

The pulp produced is intended for use in the manufacture of newsprint, paperboard, tissue paper and the like, and fibrous lignocellulosic materials derived from wood or other plants, e.g. ba-gass, can be used as raw material. The process used can be classified as a mechanical process that can be performed under normal atmospheric conditions or at temperatures above 100 ° C and up to 140 ° C, in which case it is generally classified as "thermomechanical".

The object of the invention is to provide an improvement in pulping in which the fibers are separated from each other and released by means of an abrasive effect obtained by means of mechanically acting friction surfaces fitted to a plant material moistened with water. During the process, the plant material acquires an almost dough-like plastic state, whereby the elasticity of the material is low. Due to the fact that discrete wood fibers have considerable elastic properties, the material can become elastic, which affects its ability to bind capillary moisture. In the following, the material treated in the process will be referred to as "grinding material".

During the defibering and grinding process (milling process), the grinding material is a moist accumulation of the raw material to be treated, which - if it is of coniferous origin, e.g. spruce - consists mainly of 2-3 mm long tracheids with a length-to-width ratio of approximately 100: 1 . The tracheids, in turn, consist of three concentric lamellar layers with a thickness of about 0.001 mm and a layer of fibrils helically arranged around a fourth lamella surrounding the inner cavity, the lumen. The thickness of the fibres is in the order of ten-thousandths of a millimeter, but as a whole they are estimated to make up about 70-80% of the trachid matter. It is an object of the invention to effectively separate the fibers from one another and to act on the lamellae to such an extent that the fibrils are partially released. This improves the invalidity properties of the pulp paper produced.

The invention is characterized in that the rods are arranged so that the pockets of the two plates radially overlapping each other are of the same width in the area of the refining surface, and that the free edges of the rods in both plates are arranged in planes defining the refining gap and a substantially harder material than the plate in general so as to maintain a high defibrating and fibrating power when the grinding material, after dividing and compressing the second plate into separate small pieces into compact small pieces, passes in this form under abrasive action between the free edges of the rotating rods .

The invention will be explained with reference to the accompanying drawings, which illustrate various embodiments of the device according to the invention, Fig. 1 is a side view of the refiner according to the invention, Fig. 2 shows a part of Fig. 1 on a larger scale, Fig. 3 is a perspective view of the center of the refiner. Fig. 4 shows an axial section of the refiner plates, Figs. 5A-5C show a section on the line VV in Fig. 3, and Fig. 6 shows a vertical section of the refiner plates according to a modified embodiment of the invention.

In the drawings, the number 10 denotes a refiner body 10 on which a fixed refiner plate 12 rests. This refiner plate cooperates with a refiner plate 16 attached to a rotating shaft 14. The shaft 14 of the refiner plate 16 is supported in bearings on either side, which are not shown in the drawing as well as non-käyttömootto riakaan. Three refining elements 18, 20 and 50 are arranged concentrically in the fixed grinding plate 12. The grinding plate 16 also has three concentrically arranged elements 22, 24 and 30. Thus, three grinding zones are formed, namely one between the elements 18 and 22 where the ignited raw material takes place. e.g., preliminary crushing of chips. Further coarse defining takes place in the second zone formed by the grinding elements 20 and 24 before the grinding medium enters the third grinding zone consisting of the grinding elements 30 and 50. The two inner grinding zones can be provided with elements and fins of a previously known structure.

The raw material, e.g. wood chips formed from wood or other fibrous lignocellulosic material, is fed through an opening 4 62150 32 in the body 10 and is conveyed therefrom by a helical 36 feed screw 34 through openings in the central portions of the fixed and rotating grinder plate. A central ring 38 provided with vanes 39 is attached to the rotating plate 16 for further conveying the chips towards the first grinding zone.

According to the invention, the refining elements 30 and 50 in the third zone, which are preferably made in circular rings with the refining surfaces facing each other, are provided with rods (blades) forming radially arranged pockets, 41-46 in the ring 30 and 61-66 in the ring 50.

A small deviation from the radius of these pockets is acceptable. The pockets of the rotating grinder plate should be shaped to help change the direction of travel of the grinding material moving in the pockets from radial to axial. The curved bottom of the pockets of the fixed refining plate should preferably have the shape of a circular segment.

Radial or nearly radial slits have been machined into these two circular rings 30 and 50 of the grinding plates. These slits should preferably have vertical radial sides to form a rectangular cross section. The ring 30 of the rotating grinding disc has six pockets numbered 41-46. The rods 47 and the grooves turned on the front surface of the ring 30 form these pockets. Pocket 41 then acts as an entry pocket. The number of subsequent pockets can be varied within wide limits if desired. The pockets of the fixed plate are indicated by the numbers 61-66 and the separating bars by the number 67. These flat bars 67 form the side walls of the pockets, as can be seen in Fig. 3. The bottom of the fixed pockets 61-66 must have the shape of a circular segment. The geometric center of these segments should be located slightly outside the edges of the bars forming the radial side walls of the pockets.

Otherwise the movement of the grinding agent seam will be prevented. The rotating pockets 41-46 may have the same shape, but as shown in section, these pockets are somewhat expanded to increase their cross-section, which gives them a larger volume than the fixed plate pockets. This can be seen in Figure 4. The pocket sets of the two refiner plates are radially displaced relative to each other, e.g., half the length of the pocket. The grinding medium is introduced through an opening 40 which forms the inlet of the innermost pocket 41. The outermost pocket 66 of the fixed grinder plate is open 5,62150 to form an outlet for the finished pulp (i.e., the friction exiting between the grinder plates).

The radial bars 47, 67 between the pockets, which act as their side walls, must be made of a material which has a considerably higher wear resistance than the material of the rings 30, 50. The circumferential bases 51, 52 between the pocket grooves (Fig. 4) extend to the front edge surfaces of the faces 47, 67. The axial clearance of the refining surfaces of the rings 30 and 50 is adjusted by axially displacing the refining shaft. This is often done with a hydraulic servomotor, which in some cases can be adjusted to generate an axial load of 30 tons to keep the grinding clearance constant. The clearance can be changed from 0.5 millimeters to 0.05 millimeters or less to obtain the desired grinding effect. A clearance of 0.8 mm has been used for special masses. The servo motor should be able to keep this grinding clearance constant with a tolerance of 0.01 mm.

As an example of the actual structure of a refiner according to the invention, it can be mentioned that the outer diameter of the circular rings 30, 50 can be 1270 mm and the inner diameter 1016 mm. The "rotor" 16 rotating grinder plate is built to operate at a speed of 1500 to 1800 rpm. The width 2 of the individual pockets 41-46 can be 0.38 cm and the cross section 1.5 cm, whereby the volume becomes 0.57 cm 2. The thickness of the bars can be 3 mm. width 15 mm and length 127 mm. The circumference of such a plate may have 504 rods arranged in groups of 72, each with 7 parallel rods, the rods making scissor-like cuts instead of the long parallel cuts obtained when all the rods are arranged radially. The pockets and rods of the fixed refining element 50 can be arranged substantially in the same way as in the rotating element 30. Grouping into parallel rods helps to provide a more even distribution of angular torque during use. This alignment of the different groups of rods also simplifies the machining (machining) of the refining elements 30, 50, allowing the milling of several slits in one operation.

The grinder works as follows. The raw material, for example wood chips, is comminuted in the first zone formed by the elements 18 and 22 with a reasonable energy consumption. The reduction of the substance is continued in the second grinding zone between the elements 20 and 24. The grinding medium can then have 800 ml of "freeness" as determined according to Canadian Standard Freeness Method 6 62150 (CSF). The grinding medium then passes through the opening 40 into the pocket 41 in the rotating grinding ring JO. · The outlet portion 48 of the pocket 41 directs the grinding medium laterally towards the innermost pocket 61 of the fixed grinding ring 50. Thereafter, the grinding medium passes alternately between the rotating and fixed grinding plate until it finally exits the grinding zone through the pocket 66. This is indicated by arrow A in Figure 4.

Figure 4 shows how the pockets of both grinding plates are open against each other in the position shown in Figure 5A. When the rotary powder;-hinlevy travels in the direction indicated by arrow 31, the rods 47 move from the position shown in Figure 5A, wherein the pockets are completely transparent to each other. In the figure, the opening between the pockets is closing and in Fig. 5C the opening is completely closed except for the narrow gap between the grinding plates, which is controlled by a hydraulic servomotor controlling the axial position of the rotating shaft. In this way, each special pocket of the fixed refining plate bypasses the 10800 pockets of the rotating refining plate every second, which corresponds to the mutual bypass of the pockets every 0.1 milliseconds. However, the flow of grinding medium from the pockets of the rotating plate to the pockets of the fixed plate is not obstructed despite this very short time. This can be detected if the chip flow fed to the refiner is interrupted and the rotating plate of the refiner is made to stop. When the grinder is opened for inspection, the pockets of the rotating plate are found to be completely empty. When the effect of the rotating plate on the ground support material has ceased, the mass remains in the fixed pockets.

The grinding material leaving the pocket 41 moves at a very high speed, approximately 82 m / s, and has thus acquired a considerable amount of kinetic energy.

When the grinding medium is ejected into a fixed pocket, it applies considerable mechanical pressure to the grinding medium already in it, compacting it n.

To a density of 0.79 g / cm 2. Internal friction occurs when the edge of the next rod is cut into the grinding material seam, resulting in the desired grinding illumination. This effect can be converted by adjusting the distance between the grinding plates, the clearance. For example, when making pulp for newsprint, a clearance of 0.1 to 0.2 mm can be used. When making tissue paper, a clearance of 0.5 to 0.5 mm can be used. When making pulp for egg cells, a clearance of up to 0.7 mm can be used.

When the grinding material leaving the rotating pocket 41 compresses the grinding material seam already in the fixed pocket 61, the wedge-shaped top of this pile "wraps" into the pocket 42. This part is then "scraped" by the rod 67 and then centrifuged and finally guided into the pocket 62.

Each time the grinding aid is stopped, the kinetic energy of the rotational motion is converted into heat, which raises the temperature of the grinding medium. Since the temperature of the grinding medium affects the quality of the pulp, it is somewhat important for 7,621,150 to resist these fluctuations. In general, the grinding process is carried out at a temperature very close to the boiling point of water, whether under atmospheric conditions or under steam pressure in a pressure mill, this heat also causes the water to evaporate to such an extent that the moisture of the grinding medium may decrease. With respect to the friction surfaces developed by the shear forces in the aggregate accumulation, the effect of these forces is largely dependent on the amount of moisture present, so the evaporated water must be compensated. This is done by spraying a suitable amount of water, e.g. from line 55 · The velocity of the grinding material turned from the pocket 41 is about 80 m / s, which gives it a centrifugal acceleration of 1530 g, whereupon it presses against the grinding medium in the pocket 61 and stops abruptly. The fixed pocket 61 must be provided with crosslinked grinding material as the fibers are oriented perpendicular to the rods. The kinetic energy of the grinding medium is converted into heat, which evaporates the moisture. The transition to the grinding medium is repeated each time the pockets of the two grinding plates open to each other. As the rods 47 cut the condensed grinding medium, friction surfaces develop between which the fibers separate and fibrillate. The power of the drive motor is thus transferred to the grinding medium by means of the rods 47, and the kinetic energy of the rotational movement is converted into a ketch-escape acceleration of the grinding medium of 1000 to 1300 g. By controlling the flow of grinding agent, it is possible to develop the internal frictional forces necessary for the desired fiber separation support and fibrillation.

It is mentioned that each time the pockets 41 and 6l of the rotating and fixed grinding plates merge, as shown in Fig. 5Δ, a new amount of grinding material is transferred to the pocket 61. It is also mentioned that the grinding material entangled in the fixed pocket turns in the pocket due to this geometric circle shape around its center, as indicated by line 69 in Figure 4. This means that the flow of grinding material through the grinder is maintained as long as new material is fed through the opening 40 into the pocket 41. This in turn means that when the grinding medium is continuously fed into the inlet of the fixed pocket 61 and sealed in this pocket, a corresponding amount of grinding material is squeezed out and cut off. from the outlet portion of the pocket 6l to the pocket 42 of the rotating plate grinding element 30 · By the grinding material in this pocket new friction surfaces develop into the grinding medium in the pocket 61 as the fast moving rod 47 cuts the compacted grinding medium collection which cannot remain out of the pocket 61. In this way, the grinding medium moves alternately between the movable and fixed pockets until it finally leaves the fixed element 50 through one of its outer circumferential outlets 66.

Depending on the distance between the grinding plates, i.e. the clearance, and also the relative amount of grinding material in the fixed pockets, some of the grinding material may leave the pocket 41 directly radially past the friction surfaces provided by the base 51 in Fig. 4.

Figures 5A-5C show that when the rods 47 pass the rods 67, the connection between the pockets of the rotating and fixed element of the refiner is opened and closed alternately. In the 1270 mm refiner used as an example here, this is repeated for each rod at a frequency of almost 10,000 times / s. The grinding material accumulations leaving the fixed pockets have been affected by forces ranging from a few kilograms / cm to zero, which causes the grinding material to pass through the pockets. This vibration effect also helps in the compaction of the grinding medium, enabling the development of very high frictional forces as the grinding medium moves from a fixed pocket to a rotating pocket.

The distance between the opposite edges of the rods 47 and 67 of the fixed and rotating refining element, Fig. 5 · ^, corresponds to the clearance of the grinding discs (so-called blade clearance), which is an important factor for refiner operation and depends on operating conditions, raw material type and desired pulp type. . In some cases, when a very finely ground mass is desired, the clearance can be reduced to as much as 0.05 mm, but this reduces the capacity of the grinder. A pulp with a CSF permeability of 2 milliliters can then be prepared.

In most cases, the grinding plate clearance is a multiple of the fiber diameter of several plant raw materials, which is, for example, approx. 0.02 and 0.03 mm for spruce tracheids. · It is therefore not possible to cut the fibers directly between the leading edges of the refining rods. The grinding material is ground by the combined action of the edge or edge of the rod and the compacted grinding material collection. The mechanical effect on the fiber is therefore dependent on the state of the frictional forces developed in the grinding material. This in turn depends on the mechanical severity of the refiner. The grinder must be rigid enough to prevent direct metal contact between the surfaces of the grinder plates.

In order to separate the fibers and, for example, to separate the anatomical parts of the coniferous tracheids and to apply the desired grinding effect to the pulp, the grinding material must be compressed to such an extent that sufficiently high stresses develop inside it.

The first condition for this condition is provided in particular by the compressive stress ranges which develop at the transition points between the rotating pockets 41-46. Depending on the diameter of the grinding plates, the moving grinding medium can be compressed by a centrifugal force of about 500 g or even 1500 g when it abruptly stops in one of the fixed pockets 61-66.

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The frictional force fields developed for the transitions from the fixed refining element to the 5 ° rotating refining element 30, on the other hand, have a different character, more like "slapping on the ear". When the rod 47 drives the grinding material at an accelerating speed into the pocket 42, the effect is different. The tensions are then rather reminiscent of the effect of a dull knife as it cuts a piece of cheese. In the compacted grinding material driven away from the fixed grinding plate, the rotating rods thus also provide friction surfaces. In the rotating pocket 42, the grinding medium is then sliced and detached and the rods 47 accelerate them to a considerable speed and the removed material is directed from the edge 49 to the pocket 42. From here the grinding medium is transferred to a fixed pocket 62 where its angular velocity drops back to zero.

The lignocellulosic material is hydrophilic and thermoplastic when moist.

As its temperature rises to the boiling point of water (100 ° C), it begins to soften, and when the temperature reaches 140 to 150 ° C with various lignocellulosic materials, the strength of the bond between the fibers is very poor.

The grinding process according to the invention (so-called grinding process) is preferably carried out in closed grinders, generally called pressure grinders, in which the grinding process can be carried out under the pressure of steam. The desired temperature can then be maintained during the grinding process. The energy required to raise the temperature to the desired level is obtained from the heat released in the grinding process. The amount of mechanical energy used in the grinding process, usually about Θ00 to 2000 kWh / ton of pulp, releases more heat than is needed to keep the grinding medium at a suitable temperature, e.g. 130 ° C. This heat then evaporates some of the moisture contained in the grinding medium. Thus, if the mechanical work required to carry out the grinding or milling process according to the invention corresponds to Θ00 kWh / ton of dry wood, the heat used corresponds to 688,000 koal / ton of dry matter. If the process is carried out at a temperature of 120 ° C (and the corresponding steam pressure) in order to take advantage of the thermoplastic softening of the wood, at this temperature I309 kg of water per tonne of treated wood evaporates.

Assuming that in the example shown the moisture ratio of the chips fed to the refiner was 2 * 1, evaporation would reduce the moisture ratio to 0.7 * 1. If the 2 * 1 moisture ratio of the grinding medium during the process is necessary to achieve an acceptable grinding result, the corresponding amount of water should be added to the grinding zone. The wires required for this addition are shown at 55 in Figures 1-5. · In the process according to the invention, the amount of water added can be automatically adjusted.

The addition water is rapidly distributed on the surfaces of the fibers of the grinding medium and therefore affects the friction between the fibers and thus the grinding process.

10 _ 62150

As the moisture ratio of the grinding fluid increases, the liquid film thickens. The thick film of purple acts as a lubricant and reduces the efficiency of the grinding process.

When the moisture ratio decreases to 1: 1 or less, there is a considerable risk of the formation of microscopic lumps or fiber bundles which are difficult to decompose by post-grinding. The higher amount of water also increases the energy consumed to increase the speed of the grinding medium in the pockets of the rotating grinder plate.

When looking at micrographs of cross-sections of spruce fibers (tracheids) magnified 50 times, it is easy to observe the cross-sections of private fibers and how their size varies in annual rings. Statistical research shows that the cross-sectional area of tracheids is generally 0.03 x 0.03 mm, which corresponds to about 100,000 fibers / cm. The fiber length is about 2.5 mm, which means about 400,000 tracheids per cm 2. The dry weight of spruce is about 0.42 g / cm 2, which indicates that 1 g (-2.4 cm 2) of spruce contains about 1,000,000 fibers 2 and that the total surface area of the separated whole fibers is about 3 m / g of wood. The ground mass (grind) can - depending on its CSF value - be 10 times the total or total surface area. The thickness of the liquid film distributed to the particles is calculated to be less than 0.001 mm. Although the ground pulp has a large surface area and a thin water film in addition to the hydrophilic properties of the wood material, a limited excess of water can still be allowed without greatly reducing the frictional forces desired for the ground material.

A grinder equipped with grinding discs or discs according to the present invention provides more efficient friction surfaces for the grinding medium than has been possible with any prior art type of grinding. In the refiner applying the invention, it is also possible to use rods (blades) with higher wear resistance than before. This is also possible due to the new way in which the rods are embedded in the plate body.

The friction surfaces that develop into the grinding material can also be "adapted" by changing the distance between the surfaces of the rotating rods and the fixed rods. An effective grinding effect can therefore be obtained when a greater distance, i.e. clearance, is used than has been possible with previously known structures. This means less wear on opposite surfaces of the bars. This extended distance also resists excessive shortening of the fibers by shear.

The bars used in the grinding plates according to the invention gradually begin to wear from their opposite surfaces, which may lead to dulling of the leading edge. Worn rods can be easily replaced with new ones.

With the axially adjustable ring 56 outside the circumference of the fixed grinding element 50, it is possible to adjust the area of the outlets of the outer fixed pockets 11 62150 to slow down the outflow of grinding material between the grinding elements 30 and 30, if desired.

The bars 47 and 67 can be made of hard wear-resistant materials such as carborundum, silicon carbide or other ceramic materials. Circular or circular rings 30 and 50 can be made of a softer, easier to process material and can therefore be made into full circular rings depending on the type of refiner. The rods are attached to the machined radial slits, preferably with high-strength synthetic organic adhesives, according to known methods. The bars can also be cast into these components. Thanks to the contours of the curves of the grooves 41 to 46 and 61 to 66, the bars remain very stable in place.

Alternatively, the Grinder elements shown in Figures 1 and 20 in the secondary grinding zone may be made similar to elements 30 and 50 in the same figure. * After assembly, the work surfaces of the grinder plates must be finished with the highest possible accuracy for best performance when the grinder is running.

The inner radius of the first pocket 41 of the grinding plate 30 is 526 mm. When the grinding material with a moisture ratio of 3: 1 is accelerated to a speed of 83 m / s, the required kinetic input power is 14 * 5 kVh / l ton of pulp, calculated as oven dry. When the grinding medium enters the pocket 61 of the fixed grinding plate 50, it decelerates to a speed of zero, but upon leaving this pocket its speed is again accelerated in the pocket 42. The grinding medium passing through the refiner is thus accelerated and decelerated six times in succession, once for each pocket row. This would correspond to a power consumption of about 95 kWh / l tonne of pulp produced. As described above, the edges or edges of the rods create friction surfaces as the grinding medium as it leaves the compressed form from the fixed pockets * The intensity of this friction can be varied by changing the distance between the grinding plates as described above. The power used for the grinding process can thus be changed from a few hundred to thousands of kWh per 1 ton of common pulp species. When particularly low permeability values for pulp are desired, powers up to 2000 kWh per tonne of pulp can be used. When the grinder plate clearance is increased, a short cut can be made, which allows a part of the grinding medium to pass directly over the bases 51 from the pocket to the next radial pocket. In this case, quite a bit is lost in grinding efficiency, but power consumption / ton is reduced.

In the embodiment disclosed in Figure 6, the pockets 61 to 66 and 71 of the fixed refining element 50 are circular in axial section as in the previous embodiment, but the radius of said segment corresponding to the full depth of the pocket is somewhat larger. The individual pockets of the refining element 30 are also curved in the axial section of the element. Unlike 12 621 50 in the embodiment of Figure 4, a single pocket has an inclined wall portion 72 radially on its outer surface, this wall portion being flat or approximately flat and tangentially at the bottom of the pocket becoming a wall portion 73 »perpendicularly or almost perpendicular to against. The arcuate portion 73 may have a radius of curvature approximately corresponding to the full depth of the pocket. The rotating pockets thus form a contour in the section with a relatively long and flat part deflecting the grinding medium. On the radially inner side of the grinder element 50, the grinding medium is fed through the opening 41 and thrown at high speed into the innermost fixed pocket 61, as indicated by arrow 40, where the grinding medium abruptly stops and fills the pocket as a tight plug or pile. This is then introduced into the innermost rotating pocket 42 as it passes both between the rods 47 and between the cutting or friction surfaces, where the separate fibers or fibrils of the grinding medium are separated from each other. Due to the circular segment section of the pockets, the grinding material accumulation accumulating in them rotates around the center 49, as indicated by the line 69, by the action of the new grinding material ejected through the opening 41. Said pile then comes into contact with rotating rods 47 which grind the grinding medium as it is removed. In the rotating pocket, the grinding material is suddenly accelerated to a high speed of the grinding element, whereby it constricts and is ejected due to the inclined, long plane 72 and favorable radial and axial distribution of force components to the next pocket 62, where it again forms a circular segment. The cycle is repeated with every second outward movement of the grinding material between the fixed and rotating pockets and the final product obtained leaves the last fixed groove 71 *

Claims (5)

13,621 50 An arrangement of a refining device for a fibrous lignocellulosic material, provided with rotating grinding plates (12, 16) rotating relative to each other, the radially extending rods (47, 67) of parallel or nearly parallel discrete units being formed into mutually facing grinding surfaces. transversely oriented booms (51, 52) wherein rows of separate pockets (41-46, 61-66) separated by transverse booms are arranged parallel to and spaced between the rods, the shape of the pockets in radial section being curved in each grinding plate and wherein the pockets are displaced radially relative to the pockets in the second plate, characterized in that the rods are arranged so that the pockets of the two plates radially overlapping each other are of the same width in the area of the grinding surface, and that the free edges of the rods are n in both plates adapted to the planes which determine the size of the grinding gap (h) and that the rods are also of a substantially harder material than the plate in general so as to maintain a high defibrating and fibrinating efficiency when grinding material into compact small pieces in separate pockets; after compression, in this form passes under the abrasive effect between the free edges of the rods rotating relative to each other into the pockets of the second plate. An arrangement according to claim 1, characterized in that the radial rods (47, 67) are made of a very hard material, such as carborundum or silicon carbide. An arrangement according to claim 1 or 2, characterized in that the width of the rods (47, 67) in the second plate relative to the pockets of the second plate is such that the different pockets close momentarily almost completely or completely and which pockets are thus separated from adjacent pockets by the plates. during the relative rotation between. An arrangement according to claim 1, 2 or 3, wherein the second plate (12) is stationary, characterized in that the pockets (61-65) in the stationary plate are in the shape of a circular segment and the pockets 14 in the rotating plate (16) are in the shape of 621 5 0 in radial section is such that the angle of inclination of its radial inner wall surface is greater than the angle of inclination of its radial outer wall surface. Arrangement according to one of the preceding claims, characterized in that the bars in each plate and the opposite pockets have the same width or almost the same width. is 62150