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, in particular a paper, cardboard, or tissue web, from cellulose bales (10), comprising a plurality of cellulose sheets stacked one over the other. The method has the following steps: supplying the cellulose bales (10) to a shredder (16), which has at least one rotor (18) with a plurality of protrusions, in order to produce chips from the supplied cellulose bales; supplying the chips (20) to a defibration device (32) in order to defiber the chips in a dry process; and supplying the fibers to an air-laying unit (34) in order to form a dry-laid fibrous web from the fibers, wherein the at least one rotor (18) of the shredder (16) is operated at a rotational speed which is so high that the speed of the radially outer tips of the protrusions is more than 2 m / s, preferably more than 5 m / s, more preferably more than 10 m / s, wherein the speed at which the cellulose bales are supplied to the shredder is regulated via the torque of the at least one rotor of the shredder. The invention additionally relates to a device which is designed to carry out the production method according to the invention.

Description

[0001] Method and device for producing a dry-elected 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 having at least one rotor with a plurality of projections to produce shreds from the supplied bale pulp; feeding the shreds to a defibration device to defiber the shreds 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 finally 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 shredding step makes it possible, in principle, to produce a fibrous web from conventional baled pulp using the dry air-laying process, as the individual chips are easier to process with fiberizing equipment such as a hammer mill, allowing the fibers to be separated more reliably. However, tests with a conventional shredder have shown that the results, particularly the formation of the fibrous web, are still unsatisfactory even with this process.

[0006] It is therefore an object of the present invention to solve or at least minimize the aforementioned problems of the prior art. In particular, a method and a device are to be provided with which a high-quality fibrous web, in particular a paper, board, or tissue web, can be produced from conventional baled pulp using the dry air-laying process. This should be possible on an industrial scale, i.e., with production quantities of several tons per day, preferably of at least one ton per hour, with the produced fibrous web being wound up as a roll at the end of the production machine.

[0007] 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 at least one rotor of the shredder is operated at a speed which is so high 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, wherein the speed at which the bale pulp is fed to the shredder is regulated via the torque of the at least one rotor of the shredder.

[0008] The inventors discovered through experiments that when using a conventional shredder, the pulp fibers are damaged more severely than expected, especially in the edge area of ​​the individual chips. Not only are the fibers severed there more often, thereby disadvantageously reducing their length, but the pulp is also compressed and heated in this area. This leads to a type of plasticization of the material at the chip edges. Closer examination under a microscope revealed that the individual fibers there literally fuse together. In some cases, the fibers also exhibited yellowish discoloration in the area of ​​the chip edges. As a result, the defibration device has difficulty achieving even remotely complete separation of the fibers, which then leads to a poor quality formation of the fibrous web.

[0009] Furthermore, the inventors have discovered that there are two key influencing parameters in the shredder which, when applied cumulatively, can noticeably improve the result. Firstly, it was recognized that the speed at which the at least one rotor of the shredder is operated should be selected to be higher than in the conventional shredder with which experiments were initially carried out. In particular, according to the invention, the speed is so high 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, according to the invention, the speed at which the bale 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 value.This in turn relieves the load on the rotor and prevents the torque from increasing too much.

[0010] 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.

[0011] 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 wadding, which is more difficult to further process in the subsequent process steps, in particular to shred, 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.

[0012] 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.

[0013] 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.

[0014] Contrary to what is shown in the above-mentioned publication US 4,167,378, it has also proven advantageous if not all pulp sheets from a commercially available bale of baled pulp are fed to the shredder at once. Instead, only 1-50, preferably 2-25, and more preferably 3-10, pulp sheets from the baled pulp should be fed to the shredder at a time. The inventors suspect that this also contributes to maintaining a relatively low torque and preventing excessive pressure on the fibers in the edge area of ​​the chips, thus counteracting plasticization there. It is advantageous for the process if the bale height or stack height is limited.

[0015] Furthermore, chips produced according to the present application are particularly easy to process further in the downstream defibration device. These chips can also be transported and / or cleaned particularly efficiently and controllably in an air stream between the shredder and the air-laying unit. This is particularly true 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 there have a first dimension L1 in a first direction that lies between 15 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 that is orthogonal to the first direction and also 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.

[0016] 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.

[0017] 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.

[0018] 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.

[0019] 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.

[0020] 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.

[0021] 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.

[0022] 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.

[0023] 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.

[0024] 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.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.

[0025] A preferred embodiment of the present invention provides that the bale pulp is fed to the shredder both at least partially via two driven feed rollers and at least partially via a driven conveyor belt and / or a driven vibrating chute. Plates of the bale pulp can be transported to the feed rollers by means of the conveyor belt or the vibrating chute. In this case, it is further preferred if the drive power of the two feed rollers is reduced as soon as the torque of the at least one rotor of the shredder exceeds a predetermined first threshold value, and if the drive power of the conveyor belt or the vibrating chute is reduced as soon as the torque of the at least one rotor of the shredder exceeds a predetermined second threshold value.During operation, the shredder's at least one rotor draws the pulp boards into the shredder, so simply shutting down the feed rollers is sometimes insufficient to reduce the feed speed of the pulp boards to such an extent that the torque of the at least one rotor decreases. Therefore, it may be advisable to also reduce the drive power of the conveyor belt or vibrating chute, or even switch them off completely.

[0026] It should be noted that the torque of the at least one rotor of the shredder does not depend solely on the amount of pulp being fed into the shredder on the inlet side, but also on the amount of pulp circulating on the rear side of the at least one rotor, facing away from the inlet side. Behind the at least one rotor there is a screen which prevents overly large chips from leaving the shredder. Thus, the chips are often shredded several times by the rotor of the at least one shredder until they are small enough to pass through the screen. If the space between the rotor and the screen fills up, the torque of the at least one rotor can increase even if no new pulp is being fed into the shredder.

[0027] In principle, the predefined second threshold value can be equal to the predefined first threshold value, so that the drive power of the conveyor belt or vibrating chute is always reduced at the same time as the drive power of the two feed rollers. However, tests have shown it to be advantageous if the predefined second threshold value is greater than the predefined first threshold value. In other words, it has proven advantageous to initially reduce only the drive power of the two feed rollers and only later, if the torque of at least one rotor of the shredder continues to increase, to also reduce the drive power of the conveyor belt or vibrating chute.

[0028] It should be noted that the term “drive power” in the context of the present invention can also be understood to mean the term “speed”.

[0029] 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.

[0030] A further aspect of the present invention relates to a device for producing a dry-laid fibrous web, in particular a paper, cardboard or tissue web, from baled pulp, which comprises a plurality of pulp plates stacked one above the other, comprising a shredder with at least one rotor having a plurality of projections, wherein the shredder is designed to produce chips from the baled pulp; a defibration device which is designed to defiber the chips in a dry process; and an air-laying unit which is designed to form a dry-laid fibrous web from the fibers;According to the invention, the shredder further comprises: a drive control for the at least one rotor, which is designed to operate the rotor at a speed 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; sensor means designed to determine the torque of the at least one rotor; and a control unit designed to control the speed at which the bale pulp is fed to the shredder based on the torque of the rotor determined by the sensor means.

[0031] The device may further comprise two driven feed rollers which are arranged 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.

[0032] Alternatively or preferably additionally, the device may further comprise a driven conveyor belt and / or a driven vibrating chute, wherein 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.

[0033] A preferred embodiment of the present invention provides that the control unit is designed to reduce the drive power of the two feed rollers as soon as the torque of the at least one rotor of the shredder exceeds a predetermined first threshold value, and that the control unit is further designed to reduce the drive power of the conveyor belt or the vibrating chute as soon as the torque of the at least one rotor of the shredder exceeds a predetermined second threshold value, wherein the second threshold value is preferably greater than the first threshold value.

[0034] The present invention is explained in more detail below using an embodiment.

[0035] A bale consisting of a multitude of stacked pulp boards from the manufacturer "Mercer Stendal GmbH" was chosen as the starting material for the production of a fibrous web using the dry air-laid process. This pulp was NBSK pulp, which is commonly used to produce paper, board, or tissue webs using the wet process. The starting material had a density of approximately 920 kg / m³. 3, whereby the individual pulp boards had a thickness of approximately 1.5 mm. 1 to 5 of these pulp boards were always fed simultaneously in a substantially horizontal direction to a shredder whose rotor provided with projections had a diameter of approximately 368 mm and which was operated at an essentially constant speed of around 620 revolutions per minute. The tips of the projections on the rotor therefore had a speed of around 12 m / s. The torque of the rotor was measured during operation and the measured value was used to monitor the speed at which the baled pulp was fed to the shredder. The feeding took place via a driven vibrating chute as well as two motor-driven feed rollers which were arranged directly in front of at least one rotor of the shredder.Both the drive power of the vibrating chute and the drive power of the two feed rollers influenced the feed speed. The feed speed was reduced as soon as a predefined torque threshold was exceeded. Specifically, the drive power of the two feed rollers was reduced as soon as a predefined first torque threshold of the at least one rotor was exceeded, and the drive power of the vibrating chute was reduced as soon as a predefined second torque threshold of the at least one rotor was exceeded, with the second threshold being greater than the first threshold. The chips produced by the shredder had a weight between 0.6 and 0.9 g per chip in over 90% of cases.

[0036] The chips were characterized by their edges being free of plasticization. No discoloration of the fibers or increased compaction of the material was detected in this area. Furthermore, it was determined that the average fiber length in the chips corresponded to more than 95% of the average fiber length in the original baled pulp.

[0037] The chips were then fed by air flow to a fiberizing device, where they were fiberized in a dry process. The fibers were then fed to an air-laying unit, where the fibers were formed into a dry-laid fiber web. At the end of the production device, the fiber web was wound into a roll. Thus, the shredder can 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.

[0038] In this case, a distribution of the projections in a same circumferential position with intervals, or a staggered arrangement of the projections over the circumference and in the axial direction of the rotor can be provided.

[0039] 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.

[0040] 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.

[0041] It is advantageous for the process if the projections are arranged in this way.

[0042] 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

[0043] 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.

[0044] It is advantageous for the process if the projections have this dimension.

[0045] Furthermore, the projections may have an extension in the axial direction of the rotor which is smaller than an extension in the radial direction.

[0046] It is advantageous for the process if the projections have this dimension.

[0047] Thus, the projections 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 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. It is advantageous for the method if the projections are arranged in this way.

[0048] An exemplary embodiment of the present invention is illustrated below using purely schematic drawings. In the drawings:

[0049] Fig. 1 shows an apparatus according to the invention for producing a dry-laid fibrous web from bale pulp; and

[0050] Fig. 2 shows a single chip of pulp produced as an intermediate product according to the present invention; and

[0051] 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;

[0052] Fig. 4 is a perspective view of a single pulp plate of a bale pulp in relation to a rotor of the shredder.

[0053] 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 3and 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.

[0054] 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.

[0055] 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-perimeter 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 rectilinearly extending edges which together result in the shape of an irregular polygon.

[0056] By summing the length of the individual edges, one obtains the circumference of the schnitzel 20. If one also measures the weight of the schnitzel 20, 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 schnitzel 20 can weigh between 0.5 g and 1.0 g, preferably between 0.6 g and 0.9 g.

[0057] Furthermore, in this embodiment, at least 50%, preferably at least 70%, more preferably at least 80%, of the chips 20 may 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 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.

[0058] Preferably, the schnitzels should have an irregular outer contour, wherein the maximum extent of a base area of ​​the individual schnitzel 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. Particularly preferably, the schnitzels should have an irregular outer contour, wherein the maximum extent of a base area of ​​the individual schnitzel when laid flat occupies a substantially square base area, for example, it would be ideal if the schnitzel were substantially the same in a first dimension L1 and a second dimension L2.

[0059] The chips 20 thus produced, having the properties according to the invention, are very easy to further process and result in 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, for example, a so-called air classifier. In this device, the chips 20 are guided into a riser pipe through which air is blown from below by a blower 24. The chips 20 are washed around and swirled by the air flow, 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 upward by the air flow and next 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 downward from the cyclone air separator device 28 into a collection container 30. The density of the pulp in the collection container 30, where the pulp is present in chips 20, is preferably a maximum of 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 relatively loose in the collection container 30.

[0060] A continuous stream of chips 20 can then be fed from the collection container 30, preferably also by air flow, for which a further blower 24 can be used, to a defibration device 32, where the chips 20 are defibrated into individual fibers in a dry process. The individual fibers then reach an air-laying unit 34 in order 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. Not shown in Figure 1 are a consolidation device following the forming fabric 38, in which the dry-laid fibrous web 38 is consolidated, and a reel where the consolidated fibrous web 38 is then wound up.

[0061] Figure 3 shows a detail of the device according to the invention from Figure 1, which shows the baled pulp 10 with a substantially horizontal feed to the shredder 16 with at least one rotor 18 for shredding the baled pulp 10. The baled 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 baled pulp 10 is shown in its stack structure with individual pulp plates 11 stacked one above the other and aligned essentially horizontally. The pulp plates 11 are stacked with their base surface, in particular their largest surface, one above the other in the vertical direction, such that the essentially horizontally aligned pulp plates 11 are fed essentially 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 pulp boards 11 from a bale of pulp 10 to the shredder 16. In the illustrated embodiment from Figure 3, the shaft 12 (from Figure 1) is shown as a means 12.2, for example a partially opened 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 feeding of the bale pulp to the shredder 16 is shown, wherein the bale pulp 10 or the pulp plates 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, wherein the speed at which the bale pulp 10 orThe speed at which 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, whereby 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 preferably substantially horizontally aligned gap between the two feed rollers 15.

[0062] 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.

[0063] 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 stopping the feed rollers 15 is sometimes not enough 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 expedient to also reduce the drive power of the conveyor belt 14 or the vibrating chute 14.2, or even to switch them off completely. 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 outward, 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 an edge which interacts with the bale pulp 10 or the pulp plates 11 and shreds them.

[0064] 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 gap 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.

[0065] 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.

[0066] 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.

[0067] The projections must be selected in their dimension or extent 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 extent V2 of each projection 19. In other words, the axial extent 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. Furthermore, it is advantageous if the projections 19 are selected to be greater than the first dimension L1 and / or the second dimension L2 of the chips 20 in their radial extent.

[0068] 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.

[0069] 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.

[0070] 10 bales of pulp

[0071] 11 Pulp board

[0072] 11A Floor area

[0073] 11 B long side surface

[0074] 11 C short side surface

[0075] 12 shafts

[0076] 12.2 Means for dividing the bale pulp into 1-50 pulp plates

[0077] 14 Conveyor belt

[0078] 14.2 Vibrating trough

[0079] 15 feed roller(s)

[0080] 16 shredders

[0081] 18 Rotor

[0082] 19 projections

[0083] 19.1 previous lead

[0084] 19.2 subsequent lead

[0085] 20 schnitzels

[0086] 22 Cleaning device

[0087] 24 fans

[0088] 26 contaminants

[0089] 28 Cyclone air separator device

[0090] 30 collection containers

[0091] 32 defibration device

[0092] 34 Air laying unit

[0093] 36 Fibre web

[0094] 38 forming screen

[0095] NA Surface normal base area

[0096] NB Surface normal long side surface

[0097] NC surface normal short side surface

[0098] L1 first dimension

[0099] L2 second dimension

[0100] R18 Rotation axis of the rotor, axial direction

[0101] V1 Extension of a projection in the radial direction of the rotor

[0102] V2 Extension of a projection in the axial direction of the rotor

Claims

1. A method for producing a dry-laid fibrous web, in particular a paper, cardboard or tissue web, from bale pulp (10) comprising a plurality of pulp plates stacked one above the other, comprising the following steps: Feeding the bale pulp into a shredder having at least one rotor with a plurality of projections (19) to produce chips (20) from the fed bale pulp (10); feeding the chips to a defibrating device (32) to defibrate the chips in a dry process; and Feeding the fibers into an air-laying unit (34) in order to form a dry-laid fibrous web from the fibers; characterized in that the at least one rotor (18) of the shredder (16) 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, wherein the speed at which the bale pulp (10) is fed to the shredder is regulated via the torque of the at least one rotor of the shredder.

2. Method according to claim 1, characterized in that the at least one rotor (18) of the shredder (16) is operated at a speed which is so low that the speed of the radially outer tips of the projections (19) is less than 80 m / s, preferably less than 40 m / s, more preferably less than 20 m / s.

3. Method according to claim 1 or 2, characterized in that the speed at which the bale pulp is fed to the shredder is reduced as soon as the torque of the at least one rotor (18) of the shredder exceeds a predetermined threshold value.

4. Method according to one of the preceding claims, characterized in that only 1-50, preferably 2-25, more preferably 3-10, pulp plates (11) of the baled pulp (10) are fed to the shredder at a time.

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

6. Method according to one of the preceding claims, characterized in that the feeding of the bale pulp to the shredder takes place at least partially via two driven feed rollers which are arranged 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.

7. Method according to one of the preceding claims, characterized in that the supply of the bale pulp to the shredder takes place 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 supplied to the shredder (16) can be influenced by adjusting the drive power of the conveyor belt or the vibrating chute.

8. Method according to claim 6 and 7, characterized in that 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 exceeds a predetermined first threshold value, and in that the drive power of the conveyor belt (14) and / or the vibrating chute (14.2) is reduced as soon as the torque of the at least one rotor (18) of the shredder exceeds a predetermined second threshold value.

9. Device for producing a dry-laid fibrous web, in particular a paper, cardboard or tissue web, from bale pulp (10), which comprises a plurality of pulp plates (11) stacked one above the other, comprising: a shredder (16) with at least one rotor (18) having a plurality of projections (19), the shredder being designed to produce chips (20) from the baled pulp (10); a defibration device (32) designed to defiber the chips in a dry process; and an air-laying unit (34) designed to form a dry-laid fibrous web from the fibers; characterized in that the shredder (16) further comprises: a drive control for the at least one rotor (18), which is designed to operate the rotor at a speed such 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; Sensor means configured to determine the torque of the at least one rotor; and a control unit configured to control the speed at which the bale pulp is fed to the shredder based on the rotor torque determined by the sensor means.

10. Device according to claim 9, characterized in that the device further comprises two driven feed rollers (15) which are arranged upstream of the at least one rotor (18) of the shredder (16), 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.

11. Device according to claim 9 or 10, characterized in that the device further comprises a driven conveyor belt (14) and / or a driven vibrating chute (14.2), wherein 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.

12. Device according to claim 10 and 11, characterized in that the control unit is designed to reduce the drive power of the two feed rollers (15) as soon as the torque of the at least one rotor of the shredder exceeds a predetermined first threshold value, and in that the control unit is further designed to reduce the drive power of the conveyor belt (14) and / or the vibrating trough (14.2) as soon as the torque of the at least one rotor of the shredder exceeds a predetermined second threshold value, wherein the second threshold value is preferably greater than the first threshold value.

13. Device according to one of claims 9 to 12, characterized in that the projections (19) of the at least one rotor (18) have a maximum extension (V2) in the axial direction 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 9 to 13, characterized in that the projections (19) have an extension (V1) in the radial direction 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 9 to 14, characterized in that the projections (19) which are arranged at the same circumferential position of the rotor (18) have a gap in the axial direction and that the projection (19.2) following in the circumferential direction of the rotor is arranged offset from a previous projection (19.1) in the axial direction of the rotor (18), so that the projections at the same circumferential position form a broken line in the axial direction.

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