Compressing device, and plant and method for producing kraft paper

Abstract

The invention relates to a compressing device (21), in particular a Clupak device, and to a method for compressing a fibrous web in a plant for producing Kraft paper, - wherein the compressing device (21) has an endless blanket (26), a blanket drive (27) that drives the blanket (26), a counter-roller (28), a counter-roller drive (29) that drives the counter-roller (28), and a compression nip (30) formed between the blanket (26) and the counter-roller (28), - wherein the compressing device (21) has a compression mode in which it is operated in such a way that the fibrous web passes through the compression nip (30) at production speed, and is conveyed therein between the moving blanket (26) and the moving counter-roller (28), and is thereby compressed in the machine running direction (1), and wherein the blanket (26) is driven by the blanket drive (27) in the compression mode.

Description

[0001] Upsetting device and plant and process for the production of kraft paper

[0002] The invention relates to a compression device, a system, a method and a kraft paper according to the features of the independent patent claims.

[0003] Various processes for producing kraft paper are known in the art. Kraft paper is a special type of paper characterized, among other things, by its particularly high strength. Due to this property, it is used for various packaging applications, such as the production of paper bags. In addition to strength, other parameters are also important, depending on the specific application of the kraft paper, such as stretchability or air permeability.

[0004] When it comes to the extensibility of kraft paper, a distinction is generally made between extensibility in the machine direction and extensibility across the machine direction, i.e., in the cross direction. To influence extensibility in the machine direction, it is known to use a compression device that compresses the fibrous web running through the production line in the machine direction. A widely used device for continuously compressing a fibrous web in the machine direction is a so-called "Clupak device." In this type of compression device, the fibrous web is conveyed through a compression gap. This compression gap is defined on one side by a compression belt called a "cloth" and on the other side by a drive roller. The cloth is usually an endlessly rotating belt made of an elastic material, which is pressed against the drive roller by a pressure bar in the area of ​​the compression gap.The pressure bar compresses the elastic fabric between the counterroller and the pressure bar, locally reducing its thickness. After passing the pressure bar, the fabric expands again, which, due to a transverse contraction effect, leads to a local slowing of the fabric. The fibrous web rests against the fabric in this area, causing it to be compressed in the machine direction during the described slowing of the fabric. The effect and structure of such compression devices are described in detail in the prior art. This effect is also utilized in the present invention.

[0005] A disadvantage of known upsetting devices of the above-mentioned type is their relatively high maintenance requirements. For example, slippage in the area of ​​the pressure beam and also in the area of ​​the counter roller exerts high frictional forces on the fabric. These frictional forces and the relative movement cause significant wear. In practice, this leads to the fabric requiring frequent maintenance or replacement.

[0006] During maintenance of the compression device, the system cannot produce paper with the desired properties because the compression device cannot be used to process the fibrous web. Even after maintenance, restarting the compression device involves a great deal of effort. In conventional devices, the cloth is driven by contact with the drive roller located on the other side of the compression gap. The stationary cloth is pressed against the drive roller by the pressure beam and thus carried along. This start-up process therefore takes some time. Since paper with the desired parameters cannot be produced during maintenance, maintenance of the compression device reduces the efficiency of the system. For this reason, attempts are being made to make the components of the compression device more robust in order to extend maintenance intervals and thus improve the efficiency of the system.One object of the present invention is to improve the efficiency of a plant for producing kraft paper. However, in contrast to the prior art, this object is achieved using a fundamentally different approach.

[0007] The problem is solved in particular by the features of the independent patent claims.

[0008] In this edging device, instead of the usual configuration of a drive roller and a non-driven fabric, the fabric is also driven at production speed. Auxiliary drives for the fabric are known in the prior art, which reduce the slippage between the fabric and the drive roller when the edging device is raised. However, these only drive the fabric up to a low speed of up to 100 m / min during the edging device's rise, not at production speed.

[0009] However, the present design does not feature a drive roller in the traditional sense. Instead, there is a blanket with a blanket drive and a counter roller with a counter roller drive. The two drives are dimensioned and designed in such a way that they can drive the blanket and counter roller at production speed, preferably even when the pressure bar is not pressing the blanket against the counter roller, for example, even when the blanket and counter roller are not in direct contact or operative contact with each other. The counter roller can also be referred to or act as a Clupak cylinder or heating cylinder.

[0010] With this compression device, a fundamental distinction can be made between two operating modes: In compression mode, the fibrous web is conveyed at production speed through the compression gap, i.e., between the moving fabric and the moving counter roll, and is thereby compressed in the machine direction. In this compression mode, the fabric is driven by a fabric drive. The fabric drive is preferably a drive that acts directly on the fabric via a fabric drive roll. In this compression mode, the counter roll is preferably also driven by its own counter roll drive. In this configuration, there are therefore two drives and two driven rolls.

[0011] In freewheel mode, the pressure bar is in the retracted position, meaning the fabric is not pressed against the counter roller, or at least less firmly. Preferably, even in freewheel mode, the fabric is driven by the fabric drive and the counter roller by the counter roller drive.

[0012] These individual drives make it possible to drive the fabric at production speed even when the pressure bar is in its retracted position and the fabric is not pressing against the counter roller.

[0013] If necessary, the fibrous web can also be conveyed in free-running mode between the moving fabric and the moving counter roll. Preferably, the fabric is driven by the fabric drive and the counter roll by the counter roll drive. Preferably, the fabric, the counter roll, and the fibrous web are driven at production speed.

[0014] Surprisingly, it has now been found that this configuration leads to a significant improvement in the efficiency of the plant, the process and the upsetting device.

[0015] This allows the speeds of the fabric and counter roll to be brought up to production speed without the need to rest or press the fabric against the counter roll. This reduces wear when starting up the edging device and extends the maintenance interval. If necessary, the fiber web can be conveyed through the edging device at production speed, even if it is in free-running mode. In this case, the fabric and counter roll can be driven at production speed. When the edging device switches from free-running mode to edging mode, efficiency is improved by the components, i.e. the fabric and counter roll, being driven at production speed.

[0016] In addition, if a paper tear occurs in the system, the pressure bar can be immediately returned to its retracted position, e.g., in less than 2 seconds or, preferably, in less than one second, thus switching the compression device from compression mode to free-running mode. This also allows the fabric and counter roll to continue moving at production speed without slippage between the counter roll and fabric, which would lead to significant wear on the fabric. This also extends the maintenance interval and improves the efficiency of the system.

[0017] In particular, the invention relates to a compression device, in particular a Clupak device, for compressing a fibrous web of a plant for producing kraft paper.

[0018] Preferably, the upsetting device comprises a rotating cloth, a cloth drive driving the cloth, a counter roll, a counter roll drive driving the counter roll and an upsetting gap formed between the cloth and the counter roll.

[0019] Preferably, the compression device has a compression mode in which it is operated such that the fibrous web runs through the compression gap at production speed and is conveyed there between the moving cloth and the moving counter roll and is thereby compressed in the machine running direction.

[0020] Preferably, the fabric is driven by the fabric drive in compression mode. Preferably, the counter roller is driven by the counter roller drive in compression mode, whereby both the fabric and the counter roller are each driven by their own drive in compression mode.

[0021] If necessary, it is provided that the drive speed of the cloth drive and the counter-roller drive can be controlled or regulated independently of each other.

[0022] Where appropriate, it is provided that the rotational speed of the cloth and the rotational speed of the counter-roller in the compression mode are greater than 400 m / min, in particular greater than 600 m / min, and essentially correspond to the production speed.

[0023] Optionally, it is provided that a cloth drive roller is provided which transmits the drive torque of the cloth drive to the cloth, wherein the cloth drive roller is in particular in direct contact with the cloth, and wherein the cloth drive roller is provided in addition to the counter roller.

[0024] In particular, the two drives each provide more than 25% of the required drive power. Preferably, the two drives provide approximately 50% of the required drive power. For example, the counter-roller drive provides approximately 50% to 75% of the required drive power.

[0025] Preferably, a tensioning roller is provided to tension the fabric in compression mode.

[0026] Preferably, an adjustable pressure bar is provided within the fabric, which is displaced toward the counter roll in the compression mode and presses the fabric toward the counter roll in the area of ​​the compression gap. In particular, the fabric is compressed between the pressure bar and the counter roll in the compression mode.

[0027] Optionally, the upsetting device has a free-running mode as an alternative to the upsetting mode. In this mode, the pressure bar is in a retracted position compared to the upsetting mode, and the fabric therefore exerts no pressure on the counter roller or a reduced pressure compared to the upsetting mode. In the free-running mode, both the fabric and the counter roller are driven by the fabric drive, and the counter roller is driven by the counter roller drive.

[0028] If necessary, the fibrous web can also be conveyed in free-running mode between the moving fabric and the moving counter roll. Preferably, the fabric is driven by the fabric drive and the counter roll by the counter roll drive. Preferably, the fabric, the counter roll, and the fibrous web are driven at production speed.

[0029] The rotational speed of the cloth and the rotational speed of the counter roller in free-running mode are preferably greater than 400 m / min, in particular greater than 600 m / min.

[0030] If appropriate, it is provided that the pressure bar is pressed in the compression mode with a force of at least 5 kN / m, in particular of at least 10 kN / m, in particular of at least 45 kN / m, preferably of 5 kN / m or 10 kN / m or 40 kN / m to 70 kN / m towards the counter roll.

[0031] If appropriate, it is provided that the cloth has a cloth thickness of more than 15 mm, in particular more than 20 mm and preferably from 20 mm to 30 mm.

[0032] Where appropriate, the fabric shall have a width measured transversely to the machine direction of more than 3.5 m, in particular greater than 5.5 m.

[0033] Where appropriate, the cloth shall have a Shore A hardness between 40 and 70, in particular between 50 and 60.

[0034] If necessary, the counter roll is heated in compression mode.

[0035] If necessary, the counter roll is heated with a steam pressure of 2 bar to 15 bar and / or with a temperature of 70°C to 180°C.

[0036] In particular, the invention relates to a plant for producing kraft paper, comprising the following plant parts: - a wire section for forming a fibrous web by continuously applying a fibrous suspension along the machine direction through a headbox,

[0037] - a shaking device for shaking the fibrous web transversely to the machine direction, i.e. in the transverse direction,

[0038] - a press section for pressing the fibrous web partially dewatered in the wire section,

[0039] - a drying section for drying the fibrous web,

[0040] - a winding station for winding the paper web formed from the fibrous web,

[0041] - and a compression device.

[0042] Preferably, the drying section comprises a pre-drying section and a post-drying section.

[0043] If necessary, the compression device is arranged between the pre-dryer section and the after-dryer section and compresses the fibrous web between the pre-dryer section and the after-dryer section in the machine direction.

[0044] If necessary, the compression device is designed to compress the fibrous web at a dry content of the fibrous web of 55% to 70%.

[0045] In particular, the invention relates to a method for producing kraft paper, in which the fibrous web of a plant for producing kraft paper is compressed in a compression device, wherein the compression device is designed in particular as a Clupak device.

[0046] Procedural steps can be:

[0047] - that a rotating cloth is driven by a cloth drive,

[0048] - that a counter roll is driven by a counter roll drive,

[0049] - that in a compression mode of the compression device, the fibrous web runs at production speed through a compression gap provided between the cloth and the counter roll and is conveyed there between the moving cloth and the moving counter roll and is compressed in the machine direction, and that the cloth is driven by the cloth drive in compression mode. If necessary, the fibrous web can be conveyed through the compression device at production speed, even if the device is in free-running mode. In this case, the cloth and the counter roll can be driven at production speed. If the compression device changes from free-running mode to compression mode, the cloth driven at production speed is pressed against or towards the counter roll, with the fibrous web conveyed at production speed running between the cloth and the counter roll.

[0050] Similarly, the compression device can switch from compression mode to free-running mode. Here, too, the fabric, the counter roll, and especially the fiber web can be driven at production speed.

[0051] This means that the compression of the fibrous web by the compression device can be flexibly switched on and off as needed without the system having to stop or slow down production.

[0052] According to a preferred embodiment, the cloth should have a distance from the counter roller in free-running mode.

[0053] According to a preferred embodiment, the fibrous web should rest against the counter roll when it is guided through the compression device in free-running mode.

[0054] Further procedural steps may include:

[0055] - in a wire section, a fibrous web is formed by continuously applying a fibrous suspension along the machine direction through a headbox,

[0056] - the fibrous web is shaken transversely to the machine direction, i.e. in the transverse direction, by a shaker,

[0057] - in a press section the fibrous web partially dewatered in the wire section is pressed,

[0058] - the fibrous web is dried in a drying section,

[0059] - the paper web formed from the fiber web is wound up in a winding station. It may be advantageous if the drying section comprises a pre-drying section and a post-drying section.

[0060] It can be advantageous if the compression device compresses the fibrous web between the pre-drying section and the after-drying section in the machine direction.

[0061] It may be advantageous if the compression device compresses the fibrous web at a dry content of the fibrous web of 55% to 70%.

[0062] In particular, the invention relates to a kraft paper produced on a described plant and / or produced by a described method.

[0063] The invention relates, among other things, to a process for producing kraft paper, in particular sack kraft paper, in which, in a first step, a fibrous web running in the machine direction is formed. This is achieved, in particular, by applying a fibrous suspension to a wire section by means of a headbox.

[0064] In particular, after the suspension is applied to the wire section, the fiber material is shaken or jolted with a high-frequency shaking device on the breast roll. This contributes to reducing fiber alignment in the machine direction and increasing it in the cross direction.

[0065] In the wire section, a fibrous band or sheet is formed by a filtration process, in particular using dewatering devices.

[0066] Following the wire section, a press section is arranged, in particular, in which mechanical dewatering with simultaneous compaction of the fibrous web can take place. This can typically be achieved using several press nips, the first of which is usually designed as a suction press with double felt guides, and the others as roller presses or shoe presses with either double or single felt guides. The mechanically pressed fibrous web can be subjected to one or more drying processes to achieve the desired dry content. Further production and / or processing steps can be provided before, between, or after one or more drying processes, for example, upsetting the fibrous web or calendering the fibrous web.

[0067] The compression of the fibrous web can be performed particularly between two drying steps, i.e., after a pre-drying step in a pre-drying section and before a post-drying step in a post-drying section. This can increase the paper's extensibility in the machine direction. This step takes place in the compression device.

[0068] Calendering or embossing of the fiber web can, for example, take place after the final drying step. Calendering can be performed using either thermal rolls or embossing rolls. Thermal rolls are used to provide the smoothest possible paper surface, while embossing rolls are used to give the paper surface a different appearance.

[0069] After the final processing step, the finished paper web can be wound up on the reel and then further processed to the desired finished roll width.

[0070] This system and / or the compression device preferably have a production speed of greater than 400 m / min. The width of the fibrous web or the produced paper web is preferably greater than 3.5 m, in particular greater than 5.5 m, typically greater than 6.0 m.

[0071] Optionally, the cloth and the counter-roller have a width of at least 4.0 m, in particular of at least 7.0 m, typically of at least 8.0 m.

[0072] Optionally, the production speed is at least 600 m / min, in particular at least 1000 m / min or at least 1100 m / min. In particular, the fiber used to produce the kraft paper is pulp made from softwood or coniferous long fibers. The kappa number of the pulp can be at least 30. The kraft paper produced can, in particular, be unbleached, brown kraft paper.

[0073] Preferably, the extensibility of the kraft paper, in particular according to ISO 1924-3:2005, is greater than 5% in the transverse direction, preferably greater than 7.5%. These values ​​are preferably also met in the machine direction.

[0074] Preferably, the width of a paper web of the kraft paper is greater than 3.5 m and in particular greater than 5.5 m, for example greater than 6.0 m. In connection with the present invention, the width refers in particular to the dimension of a paper web in the transverse direction of the paper.

[0075] Preferably, the difference in the extensibility of the paper in the transverse direction between the edge region and the center region of the paper web is a maximum of 1.5%. In absolute terms, the extensibility of the paper web can be between 5% and 8% in the center and between 7.5% and 12% at the edges, depending on the manufacturing process. The edge region refers in particular to an area 50 cm wide, starting from each outer edge of the paper web. The center region refers in particular to an area 50 cm wide, extending 25 cm on either side of the geometric center of a paper web, determined in the width direction.

[0076] An example of a possible measurement of extensibility is between 0.75 and 1.5 hours, typically 1.0 hours, after the production of the kraft paper, i.e., after completion of the final manufacturing step. However, the measurement can also be performed at a later or earlier time if necessary.

[0077] Where applicable, the Ambertec formation of the paper is not more than 0.7 (g / m 2 ).

[0078] Where appropriate, the Gurley drag of the paper, in particular according to ISO 5636-5:2013, is at most 15 s, preferably at most 10 s. Where appropriate, the tensile energy absorption index of the paper in the machine direction, in particular according to ISO 1924-3:2005, is at least 2.5 J / g, preferably at least 3.0 J / g. Where appropriate, these values ​​also apply to the machine direction of the paper.

[0079] The fiber contained in the paper may be unbleached pulp. Bleached pulp may also be used if necessary.

[0080] Where appropriate, the fiber contained in the paper consists of softwood long fibers with an average fiber length of at least 2 mm. Fiber analysis can be performed, in particular, according to ISO 16065-2:2014, for example, optically using the Fiber Tester L&W.

[0081] Where appropriate, the fibre contained in the paper has a kappa number of at least 30, in particular of at least 50.

[0082] The cloth is preferably made of an elastic elastomer material, which may optionally have a reinforcing structure. The cloth can, in particular, be designed as a conventional Clupak cloth.

[0083] In all embodiments, the production speed is preferably the inlet speed of the fibrous web into the compression device.

[0084] Further features of the invention emerge from the patent claims, the figures and the description of the embodiment.

[0085] The present invention is explained in detail below using an exemplary embodiment.

[0086] They show:

[0087] Fig. 1a-c is a schematic overall view of a kraft paper manufacturing plant according to a first embodiment of the invention; and

[0088] Fig. 2 is a schematic detailed view of an upsetting device. Unless otherwise indicated, the following features are shown in the figures: Machine direction 1, wire section 2, headbox 3, jogging device 4, press section 5, dryer section 6, reeling station 7, dewatering wire 8, outer side 9, breast roll 10, first dewatering section 11, inner side 12, second dewatering section 13, first dewatering device 14, second dewatering device 15, forming bar 16, suction zone 17, top former dewatering wire 18, pre-dryer section 19, after-dryer section 20, edging device 21, calendering device 22, running direction of the fibrous web 23, suction box 24, paper roll 25, fabric 26, fabric drive 27, counter roll 28, counter roll drive 29, edging gap 30, fabric drive roll 31, tension roll 32, pressure bar 33, wrap roller 34, wrap angle 35, release agent dispensing arrangement or silicone spray device 36, scraper 37, coolant nozzle 38.

[0089] Fig. 1a-c show a schematic overall view of a kraft paper production plant according to a first embodiment of the invention. The plant comprises, in the machine direction 1, a headbox 3, a wire section 2, a press section 5, a pre-dryer section 19, an upsetting device 21, an after-dryer section 20, a calendering device 22, and a winding station 7. The calendering device 22 can alternatively be designed as an embossing device.

[0090] The headbox 3 serves, in a known manner, to apply a fiber suspension to the continuously rotating dewatering wire 8 of the wire section 2, thereby forming a fiber web. As the system progresses, the fiber web is continuously dewatered or dried, passing successively through the aforementioned system components. Finally, paper rolls 25 are formed, which can be transported away and / or fed to further processing steps.

[0091] The production speed of the system in this exemplary embodiment is approximately 1100 m / min. The produced paper web has a paper width of approximately 6.4 m. The function of the individual system components is well known to a person skilled in the field of paper production and will not be explained in detail here. The following description refers in particular to wire section 2.

[0092] The fiber suspension from the headbox 3 is preferably applied to the outer side 9 of the dewatering wire 8 of the wire section 2, forming a fiber web. The machine direction 1 of the system or of the paper produced coincides with the machine direction 23 of the fiber web.

[0093] The dewatering screen 8 is guided in continuous rotation over an arrangement of several rollers, with the fiber suspension being applied in the area of ​​the breast roll 10 of the screen section 2. The dewatering screen 8 has, for example, a width of approximately 7.2 m.

[0094] In this embodiment, the fiber is cellulose, for example, from softwood with an average fiber length of approximately 2.2 mm. These are so-called long fibers. The pulp is unbleached and has a kappa number of approximately 60. The consistency of the fiber suspension when applied to the dewatering screen 8 is approximately 0.22%. However, bleached pulp can also be used.

[0095] The speed of the fiber suspension emerging from the headbox 3 is preferably about 2% higher than the running speed of the dewatering screen 8. The dewatering screen 8 can have a speed of about 1100 m / min.

[0096] A high-frequency shaking device 4 can be configured to oscillate the breast roll 10 and thereby also the dewatering screen 8 in the region of the breast roll 10. This reduces the longitudinal alignment of the fibers in the machine direction 1, which contributes to improving the properties of the paper produced in the transverse direction, i.e., transverse to the machine direction 1. In this exemplary embodiment, the oscillation occurs at a frequency of approximately 7 Hz and an amplitude of approximately 35 mm. Viewed in the running direction 23, after the suspension has been applied to the dewatering screen 8, the fiber sliver enters a first dewatering section 11. Here, the fiber sliver is dewatered downwards, i.e., from the inside 12 of the dewatering screen 8.In the first dewatering section 11, a first dewatering device 14 is arranged, which first enables a primarily gravity-driven dewatering of the fibrous web, followed by a downward suction treatment. The suction treatment is carried out by means of suction boxes 24.

[0097] In the first dewatering section 11, the fibrous web is dewatered exclusively downwards.

[0098] The first dewatering section 11 is followed by a second dewatering section 13, in which the fibrous web is dewatered upwards, i.e., toward the top side of the fibrous web. For this purpose, a second dewatering device 15 is provided in the area of ​​the outer side 9 of the dewatering screen 8. This second dewatering device is designed as a suction dewatering device with four consecutive suction zones 17. A continuously circulating top-forming dewatering screen 18 is guided between the second dewatering device 15 and the fibrous web and moves at the same speed as the main dewatering screen 8.

[0099] Furthermore, four formation bars 16 are preferably provided, arranged one after the other in the running direction 23 of the dewatering screen 8, which exert pressure on the inner side 12 of the dewatering screen 8 and thereby press the fibrous web toward the top former dewatering screen 18 or the second dewatering device 15. The contact pressure exerted by the formation bars 16 is adjustable between 5 and 25 kPa.

[0100] The fibrous web then exits wire section 2 and is further processed in the other plant sections, as shown in Fig. 1, to be further dewatered or dried, and finally to form a paper web. Due to the treatment in wire section 2, the resulting kraft paper exhibits a variety of advantageous properties, particularly relating to transverse stretchability and paper formation.

[0101] The kraft paper produced according to the described embodiment has the following exemplary property profile:

[0102] Fig. 2 shows a schematic view of a swaging device 21. The swaging device 21 comprises a cloth 26. The cloth 26 is an endless belt that is guided around several deflection rollers or guide rollers. In particular, the swaging device 21 comprises a cloth drive roller 31 with a cloth drive 27. The cloth drive 27 drives the cloth drive roller 31, wherein the cloth drive roller 31 is preferably in direct operative contact with the cloth 26 in order to drive it continuously.

[0103] The upsetting device 21 comprises a pressure bar 33. The pressure bar 33 is designed to be displaceable and, as in the present position, can press the fabric 26 toward or against a counterroller 28. In the present embodiment, the counterroller 28 has a counterroller drive 29. The counterroller drive 29 and the fabric drive 27 are preferably independently controllable or adjustable drives and are preferably rotary drives. A compression gap 30 is formed between the fabric 26 and the counterroller 28. The compression gap 30 is bounded on one side by the counterroller 28 and on the other side by the fabric 26.

[0104] The illustrated position of the compression device 21 essentially corresponds to the compression mode, in which the fibrous web is compressed. In the compression mode, the fibrous web runs at production speed through the compression gap 30 and is conveyed there between the moving fabric 26 and the counter roll 28, thereby being compressed in the machine direction 1.

[0105] In compression mode, the cloth 26 is driven by the cloth drive 27.

[0106] In the compression mode, the counter roller 28 is driven by the counter roller drive 29, whereby in the compression mode both the cloth 26 and the counter roller 28 are each driven by their own drive.

[0107] The rotational speed of the cloth 26 and the rotational speed of the counter roll 28 in the compression mode are preferably greater than 400 m / min, in particular greater than 600 m / min, and essentially correspond to the production speed.

[0108] The cloth drive roller 31 transmits the drive torque of the cloth drive 27 to the cloth 26. The rollers 31, 34 and 39 preferably act as cloth guide rollers.

[0109] Because the cloth 26 is pressed in the area of ​​the compression gap 30 by the pressure bar 33 towards the counter roll 28 and is thereby compressed between the pressure bar 33 towards the counter roll 28, the thickness of the cloth 26 is reduced in this area. Along the running direction 23 of the fibrous web after the pressure bar 33, the thickness of the elastically deformed cloth 26 increases again to its original thickness. Via a transverse contraction effect, the cloth 26 contracts by a certain amount along its direction of movement, whereby the speed of the cloth 26 is locally reduced. Because the fibrous web rests against the cloth 26 in this area, the fibrous web is compressed by this effect. This compression takes place in the machine running direction 1.The process can preferably be adjusted by adjusting the wrap-around roller 34 so that the contact time of the fibrous web between the cloth 26 and the counter roller 28 can be adjusted at an angle of approximately 15°-90°, preferably between 20°-45°.

[0110] By displacing the pressure bar 33, as shown in dashed lines, the pressure or force acting on the fabric 26 in front of the pressure bar 33 toward the counter roll 28 can be reduced or completely eliminated. By relieving the pressure bar 33 in this way, the upsetting device 21 can be put into a free-running mode. In both operating modes, i.e., upsetting mode and free-running mode, the two drives can preferably drive the fabric 26 and the counter roll 28. Preferably, the drive takes place at a speed that essentially corresponds to the production speed.

[0111] Preferably, the fibrous web can also be conveyed in free-running mode between the moving fabric 26 and the moving counter roller 28. Preferably, the fabric 26 is also driven by the fabric drive 27, and the counter roller 28 is driven by the counter roller drive 29. Preferably, the fabric 26, the counter roller 28, and also the fibrous web are driven at production speed.

[0112] In the present embodiment, the compression device 21 comprises a tensioning roller 32. The tensioning roller 32 serves to maintain the tension of the fabric 26. The tensioning roller 32 is preferably designed to be displaceable and maintains the tension of the fabric 26, for example, when it stretches due to wear.

[0113] In addition, the tension roller 32 can also keep the cloth 26 taut if necessary when the pressure bar 33 is retracted.

[0114] In the present embodiment, the compression device 21 comprises a wrap-around roller 34. The wrap-around roller 34 is arranged such that the path of the cloth 26 runs, at least in one section, along the outer contour of the counter-roller 28. The position of the wrap-around roller 34 thus determines the wrap angle 35 of the cloth 26 on the counter-roller 28. The larger the wrap angle 35, the longer the contact distance of the cloth 26 and thus also of the fibrous web on the counter-roller 28.

[0115] In the present embodiment, the wrap roller 34 is designed to be movable in order to adjust or change the wrap angle 35. When the wrap roller 34 is displaced, it is preferably provided that the tension roller 32 is displaceable in such a way that it can compensate for the shift in the path of the cloth 26 caused by the displacement of the wrap roller 34. An adjusted position of the wrap roller 34 and the tension roller 32 is shown in dashed lines. For example, the wrap angle can be adjusted or changed within a range of 15° to 90°, preferably from 20° to 45°.

[0116] The compression device 21 according to Fig. 2 comprises a release agent dispensing arrangement, in particular a silicone spray device 36 and preferably also a scraper 37. The silicone spray device 36 applies release agent to the surface of the counter roll 28. This reduces the tendency of the fibrous web to adhere to the counter roll 28. Excess release agent can be scraped off and collected via the scraper 37. In particular, several silicone spray devices 36 can be provided to distribute the release agent across the entire width of the counter roll 28.

[0117] A coolant nozzle 38 may also be provided, which can be used to apply a coolant to the surface of the compression belt 26. In particular, several coolant nozzles 38 are provided to distribute the coolant across the entire width of the fabric 26.

Claims

1. A compacting apparatus (21), in particular a Clupak device, for compacting a fibrous web in a kraft paper production system,- wherein the compacting device (21) has a circulating belt (26), a belt drive (27) driving the belt (26), a counter roll (28), a counter roll drive (29) driving the counter roll (28) and a compaction nip (30) formed between the belt (26) and the counter roll (28),- wherein the compacting apparatus (21) has a compacting mode, in which it is operated in such a way that the fibrous web passes through the compaction nip (30) at production speed, and is advanced between the moving belt (26) and moving counter roll (28), being thereby compacted in the machine flow direction (1),characterised in that in the compacting mode the belt (26) is driven by the belt drive (27).

2. The compacting apparatus (21) according to claim 1, characterised in that in the compacting mode the counter roll (28) is driven by the counter roll drive (29), whereby in the compacting mode, the belt (26) and counter roll (28) are each driven by a dedicated drive.

3. The compacting apparatus (21) according to any one of claim 1 or 2, characterised in that the drive speeds of the belt drive (27) and the counter roll drive (29) are independently controllable.

4. The compacting apparatus (21) according to any one of claims 1 to 3, characterised in that in the compacting mode the circulation speed of the belt (26) and the circulation speed of the counter roll (28) exceed 400 m / min, in particular exceed 600 m / min, and substantially equal production speed.

5. The compacting apparatus (21) according to any one of claims 1 to 4, characterised in that a belt drive roll (31) is provided which transmits the drive torque of the belt drive (27) to the belt (26), wherein the belt drive roll (31) is in particular in directcontact with the belt (26), and wherein the belt drive roll (31) is provided in addition to the counter roll (28).

6. The compacting apparatus (21) according to any one of claims 1 to 5, characterised in that in the compacting mode a tensioning roll (32) for tensioning the belt (26) is provided.

7. The compacting apparatus (21) according to any one of claims 1 to 6, characterised in that, in particular inside the belt (26), an adjustable nip bar (33) is provided, which, in the compacting mode, is shifted towards the counter roll (28) and presses the belt (26) towards the counter roll (28) in the region of the compaction nip (30).

8. The compacting apparatus (21) according to claim 7, characterised in that- the compacting apparatus (21) has a free-running mode as an alternative to the compacting mode,- in the free-running mode, compared to the compacting mode, the nip bar (33) is in a retracted position, as a result of which the belt (26) exerts no pressure or reduced pressure on the counter roll (28) compared to the compacting mode,- and in the free-running mode the belt (26) is driven by the belt drive (27) and the counter roll (28) is driven by the counter roll drive (29).

9. The compacting apparatus (21) according to any one of claim 7 or 8, characterised in that in the free-running mode, the running speed of the belt (26) and the running speed of the counter roll (28) exceed 400 m / min, in particular exceed 600 m / min.

10. The compacting apparatus (21) according to any one of claims 7 to 9, characterised in that in the compacting mode the nip bar (33) is pressed towards the counter roll (28) with a force of at least 5 kN / m, in particular at least 10 kN / m, in particular at least 40 kN / m, preferably of 10 kN / m or 40 kN / m to 70 kN / m.

11. The compacting apparatus (21) according to any one of claims 1 to 10, characterised in that- the belt (26) has a belt thickness of more than 15 mm, in particular more than 20 mm and preferably 20 mm to 30 mm,- and / or the belt (26) has a belt width measured transversely to the machine flow direction (1) of more than 3.5 m, in particular more than 5.5 m,- and / or the belt (26) has a Shore A hardness between 40 and 60, in particular between 50 and 60.

12. The compacting apparatus (21) according to any one of claims 1 to 11, characterised in that- the counter roll (28) is heated in the compacting mode,- in particular, the counter roll (28) is heated at a vapour pressure of 2 bar to 15 bar, and / or at a temperature of 70 °C up to 180 °C.

13. A system for producing kraft paper, comprising the following system components:- a wire section (2) for forming a fibrous web by continuously applying a fibrous suspension along the machine flow direction (1) by a headbox (3),- a shaking apparatus (4) for shaking the fibrous web transversely to the machine flow direction (1), i.e. in the cross direction,- a press section (5) for pressing the fibrous web that has been partially dewatered in the wire section (2),- a dryer section (6) for drying the fibrous web,- a reeling station (7) for reeling the paper web formed from the fibrous web,- and a compacting apparatus (21) according to any one of the preceding claims.

14. The system according to claim 13, characterised in that- the drying section (6) comprises a pre-dryer section (19) and an after-dryer section (20),- the compacting apparatus (21) is arranged between the pre-dryer section (19) and the after-dryer section (20) and compacts the fibrous web between the pre-dryer section (19) and the after-dryer section (20) in the machine flow direction (1).

15. The system according to claim 13 or 14, characterised in that the compacting apparatus (21) compacts the fibrous web at a dry content of 55 % to 70 %.

16. A method for producing kraft paper, in which a fibrous web in a kraft paper production system is compacted in a compacting apparatus (21), wherein the compacting apparatus (21) is designed in particular as a Clupak device,- wherein a circulating belt (26) is driven by a belt drive (27),- wherein a counter roll (28) is driven by a counter roll drive (29),- wherein in a compacting mode of the compacting apparatus (21) the fibrous web passes through a compaction nip (30) provided between the belt (26) and the counter roll (28) at production speed and is advanced between the moving belt (26) and the moving counter roll (28), thereby being compacted in the machine flow direction (1),characterised in that in the compacting mode the belt (26) is driven by the belt drive (27).

17. The method according to claim 16, characterised in that in the compacting mode the counter roll (28) is driven by the counter roll drive (29), whereby in the compacting mode the belt (26) and the counter roll (28) are each driven by a dedicated drive.

18. The method according to any one of claims 16 or 17, characterised in that the drive speeds of the belt drive (27) and the counter roll drive (29) are independently controllable.

19. The method according to any one of claims 16 to 18, characterised in that in the compacting mode the circulation speed of the belt (26) and the circulation speed of the counter roll (28) exceed 400 m / min, in particular exceed 600 m / min, and substantially equal production speed.

20. The method according to any one of claims 16 to 19, characterised in that inside the belt (26) an adjustable nip bar (33) is provided, which is shifted towards the counter roll (28) in the compacting mode and presses the belt (26) towards the counter roll (28) in the region of the compaction nip (30).

21. The method according to claim 20, characterised in that- the compacting apparatus (21) has a free-running mode as an alternative to the compacting mode,- the nip bar (33) is retracted in the free-running mode compared to the compacting mode, as a result of which the belt (26) exerts no pressure or reduced pressure on the counter roll (28) compared to the compacting mode,- and in the free-running mode the belt (26) is driven by the belt drive (27) and the counter roll (28) is driven by the counter roll drive (29).

22. The method according to any one of claims 20 or 21, characterised in that in the free-running mode the circulation speed of the belt (26) and the circulation speed of the counter roll (28) exceed 400 m / min, in particular exceed 600 m / min.

23. The method according to any one of claims 20 to 22, characterised in that in the compacting mode the nip bar (33) is pressed towards the counter roll (28) with a force of at least 5 kN / m, in particular at least 10 kN / m, in particular at least 40 kN / m, and preferably between 40 kN / m and 50 kN / m.

24. The method according to any one of claims 16 to 23, characterised in that - the counter roll (28) is heated in the compacting mode,- in particular, in that the counter roll (28) is heated at a vapour pressure of 2 bar to 15 bar, and / or at a temperature of 70 °C up to 180 °C.

25. The method according to any one of claims 16 to 24, characterised in that- in a wire section (2), a fibrous web is formed by continuously applying a fibrous suspension along the machine flow direction (1) by a headbox (3),- a shaking apparatus shakes the fibrous web transversely to the machine flow direction (1), i.e. in the cross direction,- in a press section (5), the fibrous web that has been partially dewatered in the wire section (2) is pressed,- in a drying section (6), the fibrous web is dried,- in a reeling station (7), the paper web formed from the fibrous web is wound.

26. The method according to claim 25, characterised in that- the drying section (6) comprises a pre-dryer section (19) and an after-dryer section (20),- and the compacting apparatus (21) compacts the fibrous web in the machine flow direction (1) between the pre-dryer section (19) and the after-dryer section (20).

27. The method according to any one of claims 17 to 26, characterised in that the compacting apparatus (21) compacts the fibrous web at a dry content of 60 % to 70 %.

28. Kraft paper, produced by a system according to any one of claims 13 to 15, and / or produced by a method according to any one of claims 16 to 27.

Images