Method and device for producing a dry-laid fibrous web, in particular a paper, cardboard, or tissue web, from cellulose bales

Abstract

The invention relates to a method for producing a dry-laid fibrous web (36), in particular a paper, cardboard, or tissue web, from cellulose bales, comprising a plurality of cellulose sheets stacked one over the other. The method has the following steps: supplying the cellulose bales to a shredder (16) in order to produce chips (20) from the supplied cellulose bales; supplying the chips (20) to a defibration device (32) in order to defiber the chips (20) in a dry process; and supplying the fibers to an air-laying unit (34) in order to form a dry-laid fibrous web (36) from the fibers, wherein the shredder (16) is designed and operated such that at least 50% of the chips (20) produced there substantially have the shape of an irregular polygon with a weight-to-perimeter ratio between 5.0 g / m and 10 g / m. The invention additionally relates to a device for carrying out the method according to the invention.

Description

[0001] Method and device for producing a dry-laid fibrous web, in particular paper, board or tissue web, from bale pulp

[0002] The invention relates to a method for producing a dry-laid fibrous web, in particular a paper, board, or tissue web, from bale pulp, which comprises a plurality of stacked pulp plates, comprising the following steps: feeding the bale pulp into a shredder to produce chips from the supplied bale pulp; feeding the chips to a defibration device to defiberize the chips in a dry process; and feeding the fibers into an air-laying unit to form a dry-laid fibrous web from the fibers. Furthermore, the invention relates to a corresponding device for producing a dry-laid fibrous web, in particular a tissue web, from bale pulp.

[0003] Many fibrous webs, and in particular paper, board, and tissue webs, were and still are produced almost exclusively using the wet process on an industrial scale in the past. Unless waste paper is used, baled pulp is usually dissolved in large quantities of water in a vat to produce a fiber suspension consisting of approximately 99% water by weight and only approximately 1% fiber by weight. The fiber suspension is then applied to a forming fabric via a headbox to form a sheet. The fibrous web is then dewatered or dried using pressure and heat until it can be wound up or processed in another way. The wet process has the advantage that hydrogen bonds form between the individual fibers during dewatering or drying, giving the fibrous web the necessary strength.The disadvantage of this process, however, is that large amounts of energy are required to dry the fibrous web. Therefore, especially in light of current climate change, alternatives to this traditional wet process are being intensively sought.

[0004] One alternative to the wet process is the dry air-laying process, in which fibers are laid down in a largely dry state to form a fibrous web. In order to give the fibrous web the necessary strength, only relatively small amounts of water (to form hydrogen bonds) and / or other binding agents are added. This means that significantly less energy is required for drying. One challenge with this process is to achieve good and even fiber distribution (also called formation). Unlike in suspension, the dry fibers tend to form undesirable flakes. Good fiber separation is therefore extremely important. For this reason, so-called "fluff pulp" is generally used for the dry air-laying process.This is pulp that has been pretreated so that the individual fibers already have fewer and / or weaker bonds to one another. This makes the pulp more voluminous, more absorbent, and better suited for the dry air-laying process. However, fluff pulp, which is usually produced in rolls, is much more expensive than conventional baled pulp, as is typically used in the paper industry. For this reason, the dry air-laying process is currently primarily used to manufacture sanitary products such as diapers, and not to produce paper, cardboard, or tissue webs, at least not on an industrial scale. On such an industrial scale, the use of fluff pulp would be uneconomical, despite currently high energy costs.

[0005] It would therefore be advantageous if a way could be found to produce a fibrous web, in particular a paper, cardboard, or tissue web, on an industrial scale with sufficiently good formation using the dry air-laying process from the relatively inexpensive conventional bale pulp. The production of a fibrous web from bale pulp using the dry air-laying process, according to the preamble of claim 1, is already described in US Pat. No. 4,167,378. The dry-laid fibrous web from bale pulp is produced in three stages: First, the bale pulp is shredded into chips in a shredder. Then, the chips are shredded in a fiberizing device before they are finally deposited in an air-laying device to form a fibrous web.The intermediate step of shredding makes it possible, in principle, to produce a fibrous web from conventional bale pulp using the dry air-laying process, as the individual chips can be better processed by the defibration device, such as a hammer mill, so that the fibers can be separated more reliably. However, the quality of the fibrous web produced in this way using the dry air-laying process is still not always satisfactory. It is therefore the object of the present invention to solve or at least minimize the aforementioned problems of the prior art. In particular, a method and an apparatus are to be provided with which a high-quality fibrous web, in particular paper, board, or tissue web, can be produced from conventional bale pulp using the dry air-laying process. This should be possible on an industrial scale, i.e.with production quantities of several tonnes by weight per day, preferably of at least one tonne by weight per hour, wherein the produced fibrous web is wound up as a roll at the end of the production machine.

[0006] This object is achieved by the independent claims. The dependent claims relate to advantageous developments of the invention. Specifically, this object is achieved according to a first aspect of the present invention by the generic method described at the outset, which is particularly characterized in that the shredder is designed and operated in such a way that at least 50%, preferably at least 70%, more preferably at least 80%, of the chips produced therein essentially have the shape of an irregular polygon, with a weight-to-circumference ratio between 5.0 g / m and 10 g / m, preferably between 5.5 g / m and 8.7 g / m.

[0007] The inventors have discovered that the design of the individual chips influences the quality of the resulting fibrous web. Firstly, the chips should be as similar to one another as possible in terms of size, shape and weight in order to achieve good defibration results. The more homogeneous the chips are in this respect, the better the defibration device can be adjusted to break the chips down into their individual fibers as completely as possible. Furthermore, the inventors have surprisingly discovered that it has a beneficial effect on the quality of the resulting fibrous web if the chips have a relatively long peripheral edge in relation to their area or weight. The sweep angle, i.e. the weight-to-circumference ratio, is correspondingly small.The exact reason for this is not yet conclusively known, but experiments with shredders that produced almost rectangular chips led to poorer results. One possible explanation could be that such chips are created in a shredder when the pulp sheets are smashed rather than cut. The chips then essentially have the shape of an irregular polygon, similar to the shards of a broken glass plate. It could also be that the "smashing" causes the fibers at the edges of the chips to be plucked from the pulp sheet rather than cut. As a result, they usually retain their original length, which has a beneficial effect on the formation of the fibrous web in the further process.

[0008] Furthermore, chips formed according to the present application have also proven particularly easy to further process, in particular to transport and / or clean in an air stream between the shredder and the air-laying unit. This applies in particular if the shredder is further designed and operated in such a way that at least 50%, preferably at least 70%, more preferably at least 80%, of the chips produced therein have a first dimension L1 in a first direction which lies between 10 mm and 50 mm, in particular between 25 mm and 50 mm, preferably between 30 mm and 45 mm, and have a second dimension L2 in a second direction which is orthogonal to the first direction and which lies between 10 mm and 50 mm, in particular between 10 mm and 30 mm, preferably between 15 mm and 25 mm.Furthermore, the shredder should preferably be designed and operated in such a way that at least 50%, preferably at least 70%, and more preferably at least 80%, of the chips produced therein weigh between 0.5 g and 1.0 g, preferably between 0.6 g and 0.9 g. The weight of the chips depends significantly on the thickness of the pulp boards, the density of the pulp in the boards, and the surface area.

[0009] As is usual for commercially available bale pulp for paper production, the individual pulp sheets of the bale pulp can have a thickness between 1 mm and 3 mm and / or the bale pulp can have a density between 800 kg / m 3 and 1,000 kg / m 3 This clearly distinguishes this type of pulp from the much more expensive fluff pulp. Thus, with a weight of 0.6 g and 0.9 g per chip, there is a certain range for the size and surface area of ​​the chips.

[0010] An advantageous development of the present invention provides for a collection container for the chips to be provided between the shredder and the defibration device. The collection container serves as a kind of intermediate buffer, ensuring that a continuous flow of chips can always be fed to the defibration device.

[0011] In the collection container, the chips should be as loose and uncompressed as possible in order to facilitate further processing, particularly to feed them into the defibration device in a continuous stream. It has proven advantageous if the density of the pulp in the collection container, where the pulp is in chips, is no more than a quarter of the density of the pulp before shredding, where the pulp is in the form of baled pulp. The density of the pulp in the collection container can be easily determined by dividing the total weight of all chips in the collection container by the internal volume of the collection container, at least up to its fill level if it is not completely full. When using a typical baled pulp with a density between 800 kg / m 3 and 1,000 kg / m 3 As a starting material, this results in a maximum density of the pulp in the collection container between 200 kg / m3 and 250 kg / m 3 .

[0012] As already mentioned, in practice, the chips produced according to the present invention can be transported between the shredder and the defibration device, at least partially, preferably completely, by air flow. The use of an air flow has the advantage that the chips are already well separated and loosened, resulting in a lower density in any collection container.

[0013] The inexpensive baled pulp typically used for wet-process fibrous web production often contains impurities such as sand, depending on the type and length of storage. Therefore, it is preferred that the chips be cleaned between the shredder and the defibration device in a cleaning device, particularly an air separator. In an air separator, for example, heavier particles such as sand or the like can be separated downwards in a downpipe, while the chips rise upwards in the riser pipe due to an air flow directed from the bottom to the top. To separate the air used for cleaning and the chips again, it is proposed that a cyclone air separator be provided downstream of the cleaning device.Chips with the characteristics according to the invention, which are as similar as possible to each other in terms of size, shape, and weight, can be produced effectively and reliably in a shredder, especially if only 1-50, preferably 2-25, and more preferably 3-10, cellulose sheets of the bale pulp are fed into the shredder at a time. It is advantageous for the process if the bale height or stack height is limited.

[0014] In particular, the speed of the shredder is such that the speed of the radially outer tips of the projections is more than 2 m / s, preferably more than 5 m / s, more preferably more than 10 m / s. At the same time, the speed at which the baled pulp is fed to the shredder is controlled via the torque of the at least one rotor of the shredder. In particular, the feed speed can be reduced as soon as the torque of the at least one rotor of the shredder exceeds a predetermined threshold. This, in turn, relieves the load on the rotor and prevents the torque from increasing excessively. This has a positive effect on achieving the desired chip dimensions and parameters.

[0015] Both measures combined resulted in no longer any noticeable plasticization of the fibers in the edge area of ​​the chips. Due to the increased rotor speed on the one hand and the torque limitation by controlling the feed speed on the other, the pulp was surprisingly torn or chipped into individual chips rather than cut or crushed. This led to noticeably less change in the individual fibers in the edge area of ​​the chips and to an irregular, frayed contour of the chips.

[0016] According to an advantageous development of the present invention, however, the speed of the rotor should not be too high either, since in this case it has been observed that well-defined chips are no longer produced, but rather an undefined wad, which is more difficult to process in the subsequent process steps, in particular to shred and / or transport, store and / or dose. Thus, it is specifically proposed that the at least one rotor of the shredder be operated at a speed so low that the speed of the radially outer tips of the projections is less than 80 m / s, preferably less than 40 m / s, more preferably less than 20 m / s.

[0017] Further advantageously, the original average fiber lengths of the supplied bale pulp can be maintained or only insignificantly shortened if the speed of the radially outer tips of the projections is in the range between more than 2 m / s and less than 80 m / s.

[0018] As already mentioned above, it is particularly preferred if the speed at which the bale pulp is fed to the shredder is reduced as soon as the torque of at least one rotor of the shredder exceeds a predetermined threshold value.

[0019] Pulp boards typically have two base surfaces and four side surfaces, with the base surfaces being essentially the same size and having several times more surface area than the side surfaces. In a substantially square base, the four side surfaces are approximately the same size. A rectangular base has two short side surfaces and two long side surfaces with different surface areas.

[0020] Baled pulp consists of pulp boards stacked vertically on top of each other on the base. The baled pulp also has four sides, formed by the sides of the stacked boards.

[0021] The baled pulp, or the pulp boards, can be fed into the shredder in a substantially horizontal direction. Experiments in which the pulp boards were fed into the shredder in a substantially vertical direction from above, namely via a hopper into which the pulp boards were repeatedly pushed by a reciprocating pressure ram, resulted in noticeable load fluctuations on the shredder and, consequently, in poorer shred quality.

[0022] Furthermore, a “substantially horizontal feeding” of the baled pulp or the pulp boards is understood to mean that the baled pulp and / or the pulp boards are fed to the shredder in such a way that the pulp boards or the stacked pulp boards are fed to the rotor of the shredder essentially horizontally with their base surface lying horizontally, preferably with one or two side surfaces pointing in the direction of the rotor, in particular laterally.

[0023] In other words, the at least one, in particular two, surface normals of the base area of ​​a pulp plate are spatially oriented substantially orthogonal to the horizontal and also substantially orthogonal to the rotation axis of the rotor, wherein at the same time the pulp plates move or are fed laterally towards the rotor.

[0024] This feed allows the rotor to first interact with one or two side surfaces of the pulp board(s) or bale pulp, whereby the rotor, starting from the side surfaces, "tears off" or "knocks off" the pulp boards or bale pulp.

[0025] This feeding of the pulp boards to the shredder can be very well controlled and regulated, so that the average fiber lengths of the pulp are largely maintained and not shortened.

[0026] Furthermore, it can be advantageous that by "pulling off" or "knocking off" the baled pulp or the pulp boards, the resulting chips are smashed, knocked off, or torn from the pulp boards in a shredder rather than cut. The chips then essentially have the shape of an irregular polygon, similar to the shards of a broken glass plate. It could also be the case that by "gnawing off" or "knocking off," the fibers at the chip edges are plucked from the pulp board rather than cut. As a result, the fibers usually retain their original, particularly average, length, which has a beneficial effect on the formation of the fibrous web in the further process.

[0027] For example, the bale pulp can be fed to the shredder at least partially via two driven feed rollers located upstream of at least one rotor of the shredder, wherein the speed at which the bale pulp is fed to the shredder can be influenced by adjusting the drive power of the two feed rollers. The two feed rollers can be driven, for example, by electric motors that can be switched on and off, wherein the drive power of the motors can preferably be adjusted in several stages or, more preferably, even continuously. One or more pulp sheets can be fed to at least one rotor of the shredder through a preferably substantially horizontally aligned gap between the two feed rollers.

[0028] Alternatively or in addition to the two feed rollers, the bale pulp can be fed to the shredder at least partially via a driven conveyor belt and / or a driven vibrating chute, whereby the speed at which the bale pulp is fed to the shredder can be influenced by adjusting the drive power of the conveyor belt or the vibrating chute. The conveyor belt and / or the vibrating chute can, for example, simply be switched on and off, although it is also preferred here if the drive power of the conveyor belt or the vibrating chute can be adjusted in several stages or, more preferably, even continuously.

[0029] The baled pulp or the pulp boards can be fed to the shredder in a substantially horizontal direction. For example, a conveyor belt and / or a vibrating device can be used for this. Tests in which the pulp boards were fed to the shredder in a substantially vertical direction from above, namely via a hopper into which the pulp boards were repeatedly pushed by means of a back and forth moving pressure stamp, have led to noticeable load fluctuations on the shredder and consequently to poorer quality of the chips. The feed can be via a driven conveyor belt and / or a driven vibrating chute, and / or via two driven feed rollers that are arranged upstream of at least one rotor of the shredder. Preferably, the feed initially takes place via the conveyor belt orthe vibrating chute and then over the two feed rollers, whereby the pulp boards are fed through a gap between the two feed rollers to at least one rotor of the shredder.

[0030] A further aspect of the present invention relates to a use of pulp chips, preferably produced from bale pulp by a shredder, for producing a dry-laid fibrous web, in particular a paper, cardboard or tissue web, in that the chips are first defibrated in a defibration device in a dry process and then the fibers are dried in an air-laying unit to form a fibrous web, wherein at least 50%, preferably at least 70%, more preferably at least 80%, of the chips used essentially have the shape of an irregular polygon, with a weight-to-circumference ratio between 5.0 g / m and 10 g / m, preferably between 5.5 g / m and 8.7 g / m.

[0031] Yet another aspect of the present invention relates to a device for producing a dry-laid fibrous web, in particular a paper, board or tissue web, from baled pulp, which comprises a plurality of stacked pulp plates, comprising a shredder designed to produce chips from the baled pulp; a defibration device designed to defiber the chips in a dry process; and an air-laying unit designed to form a dry-laid fibrous web from the fibers; wherein the shredder is designed such that at least 50%, preferably at least 70%, more preferably at least 80%, of the chips produced therein have a substantially irregular shape, with a weight-to-perimeter ratio between 5.0 g / m and 10 g / m, preferably between 5.5 g / m and 8.7 g / m.The device according to the invention should therefore preferably be able to carry out the method according to the invention. The advantageous developments described with regard to the method according to the invention also apply mutatis mutandis to the device according to the invention, and vice versa.

[0032] Thus, the device can comprise a cleaning device, in particular an air separator, between the shredder and the defibration device to clean the chips. Furthermore, the device can comprise a cyclone air separator, which is provided downstream of the cleaning device to separate the chips from an air flow. The device can also comprise a collecting container for the chips between the shredder and the defibration device.

[0033] The shredder can thus comprise at least one rotor for shredding the baled pulp or the pulp sheets, with projections arranged around its circumference. It is advantageous if the rotor has distributed projections that interact with the baled pulp or the pulp sheets. The projections can be distributed in the same circumferential position with intervals, or they can be staggered around the circumference and in the axial direction of the rotor.

[0034] Preferably, a projection at the same circumferential position in the axial direction is followed by a free distance with at least, in particular twice, the extension in the axial direction as the previous projection.

[0035] Further preferably, a projection in the circumferential direction is followed by a free distance with at least, in particular twice or three times, the extent of the previous projection in the circumferential direction.

[0036] It is advantageous for the process if the projections are arranged in this way.

[0037] Thus, the projections of the at least one rotor can have a maximum extension in the axial direction of the rotor which is less than or equal to a first or second dimension of the chips to be produced by the rotor. This has an effect

[0038] Thus, the projections of the at least one rotor can have an extension in the radial direction which is greater than or equal to a first or second dimension of the chips to be produced by the rotor.

[0039] It is advantageous for the process if the projections have this dimension.

[0040] Furthermore, the projections may have an extension in the axial direction of the rotor which is smaller than an extension in the radial direction.

[0041] It is advantageous for the process if the projections have this dimension.

[0042] Thus, the projections which are arranged at the same circumferential position of the rotor can have a gap in the axial direction and the projection following in the circumferential direction of the rotor can be arranged offset from a previous projection in the axial direction of the rotor, such that the projections at the same circumferential position form a broken line in the axial direction.

[0043] It is advantageous for the process if the projections are arranged in this way.

[0044] An embodiment of the present invention is illustrated below with reference to purely schematic drawings. In the drawings: Fig. 1 shows an apparatus according to the invention for producing a dry-laid fibrous web from baled pulp; and

[0045] Fig. 2 shows a single chip of pulp produced as an intermediate product according to the present invention; and

[0046] Fig. 3 shows a detail of the device according to the invention from Fig. 1, which shows the bale pulp or pulp board feed to the shredder;

[0047] Fig. 4 is a perspective view of a single pulp plate of a bale pulp in relation to a rotor of the shredder.

[0048] Figure 1 shows a schematic representation of an apparatus for producing a dry-laid fibrous web, in particular a paper, board, or tissue web, from bale pulp according to the present invention. A bale 10 consisting of a plurality of stacked pulp boards, for example from the manufacturer "Mercer Stendal GmbH," serves as the starting material. This pulp can be NBSK pulp, as is commonly used for producing a paper, board, or tissue web using the wet process. The bale pulp can have a density between 800 kg / m 3 and 1,000 kg / m€, in particular around 920 kg / m 3 , wherein the individual cellulose plates can have a thickness between 1.0 mm and 2.0 mm, in particular of approximately 1.5 mm.

[0049] The bales 10 first enter a chute 12, beneath which a conveyor belt 14 circulates. The chute 12 is designed such that only 1 to 50, preferably 2 to 25, more preferably 3 to 10, of the pulp boards are fed simultaneously in a substantially horizontal direction to a shredder 16. The shredder 16 comprises at least one rotor 18 provided with projections, upstream of which are two driven feed rollers. The rotor 18 can, for example, have a diameter of approximately 368 mm and can be operated, for example, at a substantially constant speed of around 620 revolutions per minute. The torque of the rotor 18 can also be measured during operation, and the measured value can be used to control the speed at which the baled pulp is fed to the shredder 18. The feed speed can be reduced as soon as a predetermined torque threshold is exceeded.This can be achieved by reducing the drive power or the speed of the conveyor belt 14 and / or the two feed rollers. The shredder 18 produces a plurality of chips 20 from the baled pulp fed to it.

[0050] According to the invention, the shredder 16 is designed and operated in such a way that at least 50%, preferably at least 70%, more preferably at least 80%, of the chips 20 produced therein have substantially the shape of an irregular polygon, with a weight-to-circumference ratio between 5 g / m and 10 g / m, preferably between 5.5 g / m and 8.7 g / m. A single one of these chips 20 is shown schematically in an enlarged view in Figure 2. As can be seen, the chip 20 resembles the shard of a broken glass pane in terms of its shape. It has a plurality of substantially rectilinear edges, which together form the shape of an irregular polygon. Adding the length of the individual edges yields the circumference of the chip 20. If the weight of the chip 20 is also measured, the aforementioned weight-to-circumference ratio can be easily calculated.In the present embodiment, at least 50%, preferably at least 70%, more preferably at least 80%, of the chips 20 can weigh between 0.5 g and 1.0 g, preferably between 0.6 g and 0.9 g.

[0051] Furthermore, in this exemplary embodiment, at least 50%, preferably at least 70%, more preferably at least 80%, of the chips 20 can have a first dimension L1 in a first direction, which lies between 15 mm and 50 mm, in particular between 25 mm and 50 mm, preferably between 30 mm and 45 mm, and a second dimension L2 in a second direction, which is orthogonal to the first direction, which lies between 10 mm and 50 mm, in particular between 10 mm and 30 mm, preferably between 15 mm and 25 mm. Preferably, the chips should have an irregular outer contour, wherein the maximum extension of a base area of ​​the individual chip, when laid flat, occupies a rectangular base area, for example 50 mm in a first dimension L1 and approximately 15 mm in a second dimension L2.The chips should particularly preferably have an irregular outer contour, wherein the maximum extent of a base area of ​​the individual chip when laid flat occupies a substantially square base area, for example, it would be ideal if the chip were substantially identical in a first dimension L1 and a second dimension L2. The chips 20 produced in this way, having the properties according to the invention, can be further processed very well and lead to a high-quality fibrous web. As shown in Figure 1, the chips 20 produced in the shredder 16 are next fed, preferably by air flow, to a cleaning device 22. This cleaning device 22 can be a so-called air sifter, for example. In this, the chips 20 are guided into a riser pipe through which air is blown from below by means of a blower 24.The chips 20 are washed around and swirled by the air stream, dislodging impurities 26, such as sand or the like. These impurities 26 fall downwards in the riser pipe due to gravity against the air flow, where they can exit the riser pipe. The chips 20, however, are carried upwards by the air flow and then enter a cyclone air separator device 28, where the air is separated from the chips. The separated air can, for example, be returned to the chips 20 before the cleaning device 22, as indicated by an arrow in Figure 1. The cleaned chips 20 fall downwards from the cyclone air separator device 28 into a collecting container 30. The density of the pulp in the collecting container 30, where the pulp is present in chips 20, is preferably at most one quarter of the density of the pulp before shredding 16, where the pulp is in the form of baled pulp.In other words, the pulp in the form of chips 20 is preferably present relatively loosely in the collecting container 30.

[0052] From the collection container 30, a continuous stream of chips 20 can then be fed, preferably also by air flow, for which a further blower 24 can be used, to a fiberizing device 32, where the chips 20 are fiberized into individual fibers in a dry process. The individual fibers then enter an air-laying unit 34 to form a dry-laid fibrous web 36 from the fibers. The fibrous web 36 is formed on a rotating, air-permeable forming fabric 38, over which the fibrous web 36 is simultaneously transported away.

[0053] Not shown in Figure 1 are a consolidation device following the forming fabric 38, in which the dried fibrous web 38 is consolidated, and a reel where the consolidated fibrous web 38 is then wound up. Figure 3 shows a detail of the device according to the invention from Figure 1, which shows the bale pulp 10 with a substantially horizontal feed to the shredder 16 with at least one rotor 18 for shredding the bale pulp 10. The bale pulp 10 is transported horizontally on a conveyor belt 14 and / or a vibrating chute 14.2 in the direction of the shredder 16 or in the direction of the arrow shown. Furthermore, the bale pulp 10 is shown in its stack structure with individual pulp plates 11 stacked one above the other and aligned substantially horizontally.The pulp boards 11 are stacked vertically with their base surface, in particular their largest surface, one above the other, such that the substantially horizontally aligned pulp boards 11 are fed substantially horizontally to the at least one rotor 18 of the shredder 16. Furthermore, such an embodiment also makes it possible to transport only a portion of the pulp boards 11 from a bale of pulp 10 to the shredder 16. In the illustrated embodiment in Figure 3, the shaft 12 (from Figure 1) is shown as a means 12.2, for example a partially open shaft wall or a push rod, which is suitable for breaking up the stack of the bale of pulp 10, such that only 1-50, preferably 2-25, more preferably 3-10, pulp boards 11 of the bale of pulp 10 are fed to the shredder 16 at the same time.Furthermore, an optional embodiment of the feed of the baled pulp to the shredder 16 is shown, wherein the baled pulp 10 or the pulp boards 11 are fed at least partially via two driven feed rollers 15, which are arranged upstream of at least one rotor 18 of the shredder 16. The speed at which the baled pulp 10 or the pulp boards 11 are fed to the shredder 16 can be influenced by adjusting the drive power of the two feed rollers 15. The two feed rollers 15 can be driven, for example, by electric motors that can be switched on and off, wherein the drive power of the motors can preferably be adjusted in several stages or, more preferably, even continuously.One or more pulp boards can be fed to at least one rotor 18 of the shredder 16 through a gap, preferably substantially horizontally aligned, between the two feed rollers 15.

[0054] Alternatively or in addition to the two feed rollers 15, the bale pulp 10 can be fed to the shredder 16 at least partially via a driven conveyor belt 14 and / or a driven vibrating chute 14.2, wherein the speed at which the bale pulp 10 is fed to the shredder 16 can be influenced by adjusting the drive power of the conveyor belt 14 and / or the vibrating chute 14.2. The conveyor belt 14 and / or the vibrating chute 14.2 can, for example, simply be switched on and off, although it is also preferred here if the drive power of the conveyor belt 14 and / or the vibrating chute 14.2 can be adjusted in several stages or, more preferably, even continuously.

[0055] A preferred embodiment of the present invention provides that the bale pulp 10 or the pulp boards 11 are fed to the shredder 16 both at least partially via two driven feed rollers 15 and at least partially via a driven conveyor belt 14 and / or a driven vibrating chute 14.2. Pulp boards 11 of the bale pulp can be transported to the feed rollers 15 by means of the conveyor belt 14 and / or the vibrating chute 14.2. In this case, it is further preferred if the drive power of the two feed rollers 15 is reduced as soon as the torque of the at least one rotor 18 of the shredder 16 exceeds a predetermined first threshold value, and if the drive power of the conveyor belt 14 and / or the vibrating trough 14.2 is reduced as soon as the torque of the at least one rotor 18 of the shredder 16 exceeds a predetermined second threshold value.During operation, the at least one rotor 18 of the shredder 16 draws the pulp boards 11 into the shredder, so that simply shutting down the feed rollers 15 is sometimes insufficient to reduce the feed speed of the pulp boards 11 to such an extent that the torque of the at least one rotor 18 decreases. Therefore, it may be advisable to also reduce the drive power of the conveyor belt 14 or the vibrating chute 14.2, or even to switch them off completely.

[0056] The shredder 16 comprises at least one rotor 18, which has a plurality of projections 19 distributed around its circumference. The projections 19 extend over the entire length in the axial direction of the rotor 18 and extend radially outwards, distributed at three, four, or five points around the circumference. At the radially outward-pointing tips of the projection, these tips form a point or edge which interacts with the bale pulp 10 or the pulp boards 11 and shreds them. Furthermore, the projections, which are arranged at the same circumferential position in the axial direction, are arranged such that the projections are interrupted in the axial direction and have a space between them. In other words, the projection 19 shown in the transverse view of Figure 3 is divided at the same circumferential position in the axial direction, or is not continuous.

[0057] Figure 4 shows a perspective view of the at least one rotor 18 with a possible embodiment of the projections 19. Figure 4 also shows an exemplary pulp board 11 in its spatial orientation relative to the at least one rotor 18.

[0058] The at least one rotor 18 in Figures 3 and 4 comprises projections 19 at four circumferential positions. However, projections can also be provided at only two or three circumferential positions, or at five, six, or more circumferential positions. As further shown in Figure 4, the projections 19 are interrupted or provided with a gap at the same circumferential position in the axial direction R18 of the at least one rotor 18. The projections 19.2 of the subsequent circumferential position are arranged offset such that they cover the gaps of the previous projections of the previous circumferential position 19.1. This results in a projection 19 that is continuous in the axial direction for the incoming pulp board.

[0059] The projections must be selected in their dimension or extension such that the achievable first dimension L1 of the chips and / or the second dimension L2 of the chips 20 is less than or equal to the axial extension V2 of each projection 19. In other words, the axial extension of an individual projection 19 in the axial direction should be selected to be greater than or equal to the first dimension L1 and / or the second dimension L2 of the chips 20.

[0060] Furthermore, it is advantageous if the projections 19 are selected to be larger in their radial extent than the first dimension L1 and / or the second dimension L2 of the chips 20.

[0061] Figure 4 further shows a single pulp board 11 of a bale of pulp 10, wherein this pulp board 11 has two base surfaces 11 A and four side surfaces 11 B, 11 C. Typically, the surface area of ​​a base surface 11 A is several times larger than that of the side surfaces 11 B, 11 C. If a pulp board has a substantially square base shape, the side surfaces 11 B, 11 C are substantially the same size. If the pulp board 11, as shown, is of a rectangular basic shape, there are two long side surfaces 11B and two short side surfaces 11C. Regardless of the basic shape, the pulp boards 11 are stacked one above the other on their base surfaces 11A to form a bale 10. The bale 10 can be placed on a conveyor belt 14 and / or vibrating trough 14 in a substantially horizontal orientation of the base surface 11A.2 are transported in such a way that the pulp boards 11 conveyed into the at least one rotor 18 interact in a substantially horizontal orientation with one or two side surfaces 11 B or 11 C with the at least one rotor 18 or the projections 19.

[0062] This makes it possible to chip, tear out or gnaw off the chips 20 from the cellulose plates 11 through the projections 19 rather than cutting them off.

[0063] List of reference symbols:

[0064] 10 bales of pulp

[0065] 11 Pulp board

[0066] 11A Floor area

[0067] 11 B long side surface

[0068] 11 C short side surface

[0069] 12 shafts

[0070] 12.2 Means for dividing the bale pulp into 1-50 pulp plates

[0071] 14 Conveyor belt

[0072] 14.2 Vibrating trough

[0073] 15 feed roller(s)

[0074] 16 shredders

[0075] 18 Rotor

[0076] 19 projections

[0077] 19.1 previous lead

[0078] 19.2 following lead 20 schnitzel

[0079] 22 Cleaning device

[0080] 24 fans

[0081] 26 contaminants

[0082] 28 Cyclone air separator device

[0083] 30 collection containers

[0084] 32 defibration device

[0085] 34 Air laying unit

[0086] 36 Fibre web

[0087] 38 forming screen

[0088] NA Surface normal base area

[0089] NB Surface normal long side surface

[0090] NC surface normal short side surface

[0091] L1 first dimension

[0092] L2 second dimension

[0093] R18 Rotation axis of the rotor, axial direction

[0094] V1 Extension of a projection in the radial direction of the rotor

[0095] V2 Extension of a projection in the axial direction of the rotor

Claims

1. A method for producing a dry-laid fibrous web (36), in particular a paper, cardboard or tissue web, from bale pulp, which comprises a plurality of pulp plates stacked one above the other, comprising the following steps: Feeding the bale pulp into a shredder (16) to produce chips (20) from the fed bale pulp; Feeding the chips (20) to a defibrating device (32) to defibrate the chips (20) in a dry process; and Feeding the fibers into an air-laying unit (34) to form a dry-laid fibrous web (36) from the fibers; characterized in that the shredder (16) is designed and operated such that at least 50%, preferably at least 70%, more preferably at least 80%, of the chips (20) produced therein have substantially the shape of an irregular polygon, with a weight-to-perimeter ratio between 5.0 g / m and 10 g / m, preferably between 5.5 g / m and 8.7 g / m.

2. Method according to claim 1, characterized in that the shredder (16) is further designed and operated in such a way that at least 50%, preferably at least 70%, more preferably at least 80%, of the chips (20) produced therein have a first dimension (L1) in a first direction which lies between 15 mm and 50 mm, in particular between 25 mm and 50 mm, preferably between 30 mm and 45 mm, and a second dimension (L2) in a second direction which is orthogonal to the first direction (L1), which lies between 10 mm and 50 mm, in particular between 10 mm and 30 mm, preferably between 15 mm and 25 mm.

3. Method according to claim 1 or 2, characterized in that the shredder (16) is further designed and operated in such a way that at least 50%, preferably at least 70%, more preferably at least 80%, of the chips (20) produced therein weigh between 0.5 g and 1.0 g, preferably between 0.6 g and 0.9 g.

4. Method according to one of the preceding claims, characterized in that a collecting container (30) for the chips (20) is provided between the shredder (16) and the defibration device (32).

5. Method according to one of the preceding claims, characterized in that the chips (20) are transported between the shredder (16) and the defibration device (32) at least in sections, preferably completely, by air flow.

6. Method according to one of the preceding claims, characterized in that the chips (20) are cleaned between the shredder (16) and the defibration device (32) in a cleaning device (22), in particular an air classifier.

7. Method according to one of the preceding claims, characterized in that only 1-50, preferably 2-25, more preferably 3-10, pulp plates of the bale pulp are fed to the shredder (16) at a time.

8. Method according to one of the preceding claims, characterized in that the bale pulp is fed to the shredder (16) in a substantially horizontal direction.

9. Method according to one of the preceding claims, characterized in that the shredder (16) comprises at least one rotor (18) with projections (19) arranged on its circumference, and in that the at least one rotor (18) is operated at a speed which is so high that the speed of the radially outer tips of the projections (19) is more than 2 m / s, preferably more than 5 m / s, more preferably more than 10 m / s, in particular less than 80 m / s, preferably less than 40 m / s, more preferably less than 20 m / s.

10. Use of pulp chips (20), preferably produced from baled pulp by a shredder, for producing a dry-laid fibrous web (36), in particular a paper, cardboard or tissue web, by first defibrating the chips (20) in a defibration device (32) in a dry process and then dry-laying the fibers in an air-laying unit (34) to form a fibrous web (36), characterized in that at least 50%, preferably at least 70%, more preferably at least 80%, of the chips (20) used have substantially the shape of an irregular polygon, with a weight-to-circumference ratio between 5.0 g / m and 10 g / m, preferably between 5.5 g / m and 8.7 g / m. 11 . Device for producing a dry-laid fibrous web (36), in particular a paper, cardboard or tissue web, from baled pulp, which comprises a plurality of stacked pulp plates, comprising: a shredder (16) designed to produce chips (20) from the baled pulp; a defibration device (32) designed to defiber the chips (20) in a dry process; and an air-laying unit (34) designed to form a dry-laid fibrous web (36) from the fibers; characterized in that the shredder (16) is designed such that at least 50%, preferably at least 70%, more preferably at least 80%, of the chips (20) produced therein have substantially the shape of an irregular polygon, with a weight-to-circumference ratio between 5.0 g / m and 10 g / m, preferably between 5.5 g / m and 8.7 g / m.

12. Device according to claim 11, characterized in that the device comprises a cleaning device (22), in particular an air sifter, between the shredder (16) and the defibration device (32) in order to clean the chips (20).

13. Device according to one of claims 11 to 12, characterized in that the shredder (16) comprises at least one rotor (18) with projections (19) arranged on its circumference, and that the Projections (19) have an extension (V2) in the axial direction (R18) of the rotor (18) which is less than or equal to a first (L1) or second dimension (L2) of the chips (20) to be produced by the rotor (18).

14. Device according to one of claims 11 to 13, characterized in that the shredder (16) comprises at least one rotor (18) with projections (19) arranged on its circumference, and in that the projections (19) have an extension (V1) in the radial direction of the rotor (18) which is greater than or equal to a first (L1) or second dimension (L2) of the chips (20) to be produced by the rotor (18).

15. Device according to one of claims 11 to 14, characterized in that the shredder (16) comprises at least one rotor (18) with projections (19) arranged on its circumference, and in that the projections (19), which are arranged at the same circumferential position of the at least one rotor (18), have a gap in the axial direction and, wherein the projection (19.2) following in the circumferential direction of the rotor (18) is arranged offset from a previous projection (19.1) in the axial direction of the rotor (18), such that the projections at the same circumferential position form a broken line in the axial direction.

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