Installation and method for producing kraft paper, said installation having a bypass assembly

Abstract

The invention relates to a method and an installation for producing kraft paper, said installation comprising the following installation parts: - a wire section (2) for forming a fibrous web by continuously applying a fibrous suspension along the machine running direction (1) by means of a headbox (3); - a shaking device (4) for shaking the fibrous web transversely to the machine running direction (1), i.e. in the transverse direction; - a pressing section (5) for pressing the fibrous web partially dewatered in the wire section (2); - a drying section (6) for drying the fibrous web; - a compacting device (21), in particular a Clupak device, for compacting the fibrous web in the machine running direction (1), - and a winding station (7) for winding up the paper web formed from the fibrous web, wherein a bypass assembly (46) is provided for conveying the fibrous web along a bypass path (47) so as to bypass the compacting device (21).

Description

[0001] Plant and method for producing kraft paper with a bypass arrangement

[0002] The invention relates to a plant and a method according to the features of the independent patent claims. In particular, the invention relates to a method and a plant for producing kraft paper, wherein the plant comprises an upsetting device and a bypass arrangement for bypassing the upsetting device.

[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 stretchability of kraft paper, a distinction is generally made between stretchability in the machine direction and stretchability across the machine direction, i.e., in the cross direction. To influence stretchability in the machine direction, it is known to use a compression device that compresses the fiber web in the machine direction as it passes through the production line.

[0005] A widely used device for continuously compressing a fibrous web in the machine direction is a so-called "Clupak" device. In this type of compressing device, the fibrous web is conveyed through a compression gap. This compression gap is defined on one side by a compression belt known as the "cloth" and on the other side by a drive roller. The cloth is usually a continuously 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 cloth between the counter roller and the pressure bar, thereby locally reducing its thickness. After passing the pressure bar, the cloth expands again, which leads to a local deceleration of the cloth due to a transverse contraction effect.In this area, the fibrous web rests against the fabric, causing it to be compressed in the machine direction during the described deceleration 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.

[0006] 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.

[0007] During maintenance of the compression device, the system cannot produce paper with the desired properties, as the compression device cannot be used to process the fibrous web. Even after maintenance, restarting the compression device involves considerable 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 driven along. This start-up process therefore takes some time.

[0008] Since paper cannot be produced with the desired parameters during maintenance and adjustment, servicing the compression device reduces the efficiency of the system. For this reason, efforts are being made to make the compression device components more robust in order to extend maintenance intervals and thus improve the efficiency of the system.

[0009] 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.

[0010] The problem is solved in particular by the features of the independent patent claims.

[0011] The invention particularly relates to a plant for producing kraft paper, comprising one, several or all of the following plant components:

[0012] - a wire section for forming a fibrous web by continuously applying a fibrous suspension along the machine direction through a headbox,

[0013] - a shaking device for shaking the fibrous web transversely to the machine direction, i.e. in the transverse direction,

[0014] - a press section for pressing the fibrous web partially dewatered in the wire section,

[0015] - a drying section for drying the fibrous web,

[0016] - a compression device, in particular a Clupak device, for compressing the fibrous web in the machine direction,

[0017] - and a winding station for winding the paper web formed from the fibrous web. Preferably, a bypass arrangement is provided for conveying the fibrous web along a bypass path, bypassing the compression device.

[0018] If the fibrous web cannot be guided through the compression device due to a fault or due to maintenance work, the present design allows it to be guided past the compression device using a bypass arrangement, but can continue to pass through other sections of the system, in particular all other sections of the system.

[0019] This special design allows the fibrous web to continue being conveyed even when the compression device is not functioning. This allows the system, with the exception of the compression device, to continue operating, and production does not have to be stopped. This eliminates the time-consuming system start-up process. Furthermore, by passing the fibrous web through the bypass arrangement past the compression device, kraft paper can be produced that has different product properties than in an operating mode in which the fibrous web passes through the compression device. For example, there are certainly paper types that do not require longitudinal compression in a compression device. These advantages can increase the efficiency of the system.

[0020] Preferably, the bypass arrangement is provided exclusively in the area of ​​the compression device and is designed to transport the fibrous web bypassing the compression device but not bypassing other parts of the system.

[0021] Preferably, the upsetting device is arranged along the machine direction between a system component upstream of the upsetting device and a system component downstream of the upsetting device. The bypass path of the bypass arrangement preferably extends from the outlet of the upstream system component to the inlet of the downstream system component.

[0022] If appropriate, the drying section may comprise a pre-drying section and an after-drying section arranged downstream of the pre-drying section along the machine direction. If appropriate, the edging device may be arranged along the machine direction between the pre-drying section and the after-drying section, and the bypass arrangement may transport or be capable of transporting the fibrous web from the pre-drying section to the after-drying section, bypassing the edging device.

[0023] If necessary, the bypass arrangement is provided to comprise an adjustable switch for selectively conveying the fibrous web or a strip of the fibrous web through the compression device or through the bypass path.

[0024] In all embodiments, the strip can be, for example, approximately 10 cm to 25 cm wide. In all embodiments, the strip should be narrower than the width of the produced paper web.

[0025] If necessary, the switch may be designed as an adjustable suction belt or vacuum belt, for example.

[0026] If necessary, a cable guide is provided for selectively guiding a strip of the fibrous web through the bypass arrangement or through the compression device.

[0027] If necessary, the cable guide comprises a bypass cable guide for guiding the strip of the fibrous web through or into the bypass arrangement and a compression cable guide for guiding the strip of the fibrous web through or into the compression device.

[0028] Where appropriate, the bypass rope guide and the compression rope guide are provided permanently and / or simultaneously next to each other.

[0029] Optionally, the bypass cable guide comprises a first pair of cables, in particular a first cable and a second cable, for guiding the strip through or into the bypass arrangement. Optionally, the compression cable guide comprises a second pair of cables, in particular a third cable and a fourth cable, for guiding the strip through or into the compression device.

[0030] If necessary, it is provided that the rope guide, for guiding the strip into the downstream component of the system, has a section with a further pair of ropes following the bypass rope guide and following the compression rope guide.

[0031] If appropriate, it is provided that the further rope pair is preferably formed by a rope of the first rope pair and a rope of the second rope pair, in particular by the first rope and the fourth rope.

[0032] If necessary, one or more rope drives are provided to drive the ropes, and in particular a first rope drive and a second rope drive.

[0033] If necessary, the first rope drive is intended to drive one rope of the first rope pair and one rope of the second rope pair.

[0034] If necessary, the second rope drive is intended to drive the other rope of the first rope pair and the other rope of the second rope pair.

[0035] Where appropriate, the first rope drive is intended to drive the second rope and the third rope and the second rope drive is intended to drive the first rope and the fourth rope.

[0036] If necessary, a movable adjusting roller is provided in the section where the bypass cable guide and the compression cable guide are brought together.

[0037] If necessary, the adjusting pulley is provided to change the path of at least one of the ropes during its displacement such that the strip of fibrous web, depending on whether it comes from the bypass rope guide or the compression rope guide, is guided further along the rope guide to the downstream system component. If necessary, a deflection pulley is provided in the section where the bypass rope guide and the compression rope guide converge.

[0038] If necessary, it is provided that when the strip of the fibrous web is guided along the bypass rope guide, the third rope is looped around the deflection pulley by the adjusting pulley in such a way that it is further guided between the first rope and the fourth rope.

[0039] If necessary, it is provided that when the strip of the fibrous web is guided along the compression rope guide, the third rope is displaced by the adjusting roller in such a way that the strip runs unhindered from the compression rope guide into the further rope guide.

[0040] If appropriate, it is provided that the bypass arrangement is set up to convey the fibrous web at production speed, wherein the production speed is preferably greater than 400 m / min, in particular greater than 600 m / min.

[0041] Optionally, the invention relates to a method for operating a plant for producing kraft paper,

[0042] - wherein in a wire section a fibrous web is formed by continuously applying a fibrous suspension along the machine direction through a headbox,

[0043] - whereby the fibrous web is shaken by a shaker transversely to the machine direction, i.e. in the transverse direction,

[0044] - whereby the fibrous web partially dewatered in the wire section is pressed in a press section,

[0045] - the fibrous web is dried in a drying section,

[0046] - whereby the paper web formed from the fibrous web is wound up in a winding station.

[0047] Preferably, the fibrous web is optionally:

[0048] - in an upsetting device, in particular a Clupak device, runs through an upsetting gap provided between a cloth and a counter-roller and is conveyed there between the moving cloth and the moving counter-roller and is thereby upset in the machine direction,

[0049] - or is transported via a bypass arrangement along a bypass path, bypassing the upsetting device.

[0050] If appropriate, the method comprises the step of conveying the fibrous web by the bypass arrangement bypassing the compression device but not bypassing other parts of the system.

[0051] Optionally, the method comprises the step of arranging the upsetting device along the machine direction between a plant part upstream of the upsetting device and a plant part downstream of the upsetting device, and conveying the fibrous web along the bypass path of the bypass arrangement from the outlet of the upstream plant part to the inlet of the downstream plant part.

[0052] Optionally, the method comprises the step of drying the fibrous web in a pre-drying section of the drying section and in a post-drying section of the drying section arranged downstream of the pre-drying section along the machine direction.

[0053] Optionally, the method comprises the step of arranging the compression device along the machine direction between the pre-drying section and the after-drying section.

[0054] Optionally, the method comprises the step that the bypass arrangement conveys or can convey the fibrous web from the pre-drying section to the after-drying section, bypassing the compression device.

[0055] Optionally, the method comprises the step of guiding a strip of the fibrous web with a cable guide either through the bypass arrangement or through the compression device. Optionally, the method comprises the step of a bypass cable guide of the cable guide guiding the strip of the fibrous web through or into the bypass arrangement, and a compression cable guide of the cable guide guiding the strip of the fibrous web through or into the compression device.

[0056] If necessary, the method comprises the step of providing the bypass cable guide and the compression cable guide permanently or simultaneously next to each other, but only selectively guiding the strip of the fibrous web.

[0057] Optionally, the method comprises the step of the bypass cable guide guiding the strip through or into the bypass arrangement with a first pair of cables, in particular with a first cable and a second cable.

[0058] Optionally, the method comprises the step of the compression cable guide guiding the strip through or into the compression device with a second pair of cables, in particular with a third cable and a fourth cable.

[0059] Where appropriate, the method comprises the step of the rope guide guiding the strip into the downstream component of the system, following the bypass rope guide and following the compression rope guide, in a section with another pair of ropes.

[0060] Optionally, the method comprises the step of driving the ropes by one or more rope drives, and in particular by a first rope drive and a second rope drive.

[0061] Optionally, the method comprises the step of the first rope drive driving one rope of the first rope pair and one rope of the second rope pair.

[0062] Optionally, the method comprises the step of the second rope drive driving the other rope of the first rope pair and the other rope of the second rope pair. Optionally, the method comprises the step of the first rope drive driving the second rope and the third rope, and the second rope drive driving the first rope and the fourth rope.

[0063] Optionally, the method comprises the step of the bypass arrangement conveying the fibrous web at production speed, wherein the production speed is greater than 400 m / min, in particular greater than 600 m / min.

[0064] Optionally, the method comprises the steps of producing a first type of kraft paper when the fibrous web passes through the upsetting device,

[0065] - and that a second type of kraft paper is produced when the fibrous web passes through the bypass arrangement, bypassing the upsetting device, and the upsetting device is serviced if necessary.

[0066] The system can include a conventional upsetting device, and the bypass arrangement can, in principle, be operated with any type of upsetting device. However, the upsetting device may have modifications necessary for diversion along the bypass path. The same applies to the process.

[0067] The compression device can be operated in compression mode. 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 compressed in the machine direction.

[0068] The fibrous web guided through the nip forms a separation layer between the heated counter roll and the rotating cloth of the nip. This separation layer is formed on the one hand by the fiber material itself. In addition, the separation layer is also formed by the water content of the fibrous web. The partially evaporating water content of the fibrous web in the nip creates a type of vapor cushion layer that improves the effect of the separation layer. In the event of disruptions in production, a (partial) web break of the fibrous web can occur, meaning that the fibrous web does not pass through the nip or does not pass through its entire width. This means that the cloth of the nip is in direct contact with the heated counter roll. The resulting increased thermal and mechanical stress on the cloth leads to increased wear on the cloth.If the cloth wear becomes excessive, and especially if the cloth falls below a certain minimum thickness, the cloth must be replaced. This can lead to a deterioration in the efficiency of the entire system.

[0069] In addition to improving efficiency through the bypass arrangement, an emergency mode can be activated in which the cloth is quickly lifted from the counter roller.

[0070] The invention relates in particular to a method for operating a plant for producing kraft paper comprising a compression device for compressing a fibrous web, in particular comprising a Clupak device.

[0071] The compression device preferably comprises a rotating cloth, a pressure bar, a wrap-around roller, a tensioning roller, a counter roller and preferably a cloth drive roller.

[0072] The compression device can be operated in a compression mode in which the rotating cloth is pressed by the pressure bar towards the counter roll and wraps around the counter roll by a wrap angle, whereby in the compression mode a compression gap is formed between the cloth and the counter roll, which is designed to convey the fibrous web through at production speed and thereby compress it in the machine direction.

[0073] The upsetting device can optionally be operated in an emergency mode, in which the pressure bar is retracted relative to the upsetting mode, creating a gap between the fabric and the counter roll. Optionally, the separation time in the emergency mode—that is, the time required to create a gap between the fabric and the counter roll from the upsetting mode—is less than 2 seconds, preferably less than 1 second. Optionally, the position of the wrap-around roll is changed in the emergency mode such that the fabric is lifted from the counter roll.

[0074] If necessary, the tensioning roller is designed to re-tension the fabric in emergency mode and thereby lift it off the counter roller.

[0075] If necessary, it is provided that a belt break signal from a sensor for detecting a fault, such as an at least partial belt break of the fibrous web, is processed and directly or indirectly activates the emergency mode.

[0076] If necessary, it is provided that the fibrous web is cut off before or during the emergency running mode by a cutting device in an area along the machine direction in front of the compression device.

[0077] If necessary, the belt break signal is processed and directly or indirectly activates the cutting device.

[0078] If necessary, a cloth drive is provided to drive the cloth drive roller and thus the cloth in emergency mode, even if a gap has already been formed between the cloth and the counter roller.

[0079] Where appropriate, it is provided that the cloth drive can or does drive the cloth preferably at a rotational speed that essentially corresponds to the production speed.

[0080] The production speed is preferably greater than 400 m / min and in particular greater than 600 m / min. If necessary, a counter-roller drive is provided to drive the counter-roller in emergency mode, even if a gap has already formed between the fabric and the counter-roller.

[0081] If necessary, it is provided that the counter-roller drive can drive or drives the counter-roller preferably at a rotational speed that essentially corresponds to the production speed.

[0082] If necessary, the pressure bar is retracted pneumatically or hydraulically in emergency mode, in particular by means of a bellows cylinder.

[0083] If necessary, 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 45 kN / m, preferably of 5 kN / m or 45 kN / m to 70 kN / m towards the counter roll.

[0084] In particular, the invention relates to a plant for producing kraft paper comprising a compression device for compressing a fibrous web, in particular comprising a Clupak device which carries out the described method.

[0085] With the present edging device, instead of the usual configuration of a drive roller and a non-driven fabric, the fabric can also be driven at production speed. Auxiliary drives for the fabric are known in the prior art, which reduce the slip between the fabric and 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 rise, and not at production speed. This design preferably does not have a drive roller in the conventional sense. Instead, there is a fabric with a fabric drive and a counter roller with a counter roller drive.The two drives are dimensioned and designed to drive the blanket and counter roll at production speed, preferably even when the pressure bar is not pressing the blanket against the counter roll, for example, even when the blanket and counter roll are not in direct contact or operative contact with each other. The counter roll may also be referred to as a Clupak cylinder or heating cylinder.

[0086] With this upsetting device, a distinction can basically be made between different operating modes:

[0087] 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 if necessary. 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.

[0088] In emergency mode, the pressure bar is retracted compared to the compression mode, creating a gap between the fabric and the counter roller. Preferably, even in emergency mode, the fabric is driven by the fabric drive and the counter roller by the counter roller drive.

[0089] 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.

[0090] If necessary, the speeds of the blanket and counter roll can be brought up to production speed without the need for the blanket to be placed on or pressed against the counter roll. This can reduce wear when the compression device is started up and extend the maintenance interval. Furthermore, if a paper tear occurs in the system, the pressure bar can be moved immediately, for example in less than 2 seconds or preferably in less than one second, into its retracted position, which switches the compression device from its compression mode to emergency mode. Here, too, the blanket and counter roll can continue to move preferably at production speed without slippage occurring between the counter roll and blanket, which would lead to severe wear on the blanket. This also extends the maintenance interval and improves the efficiency of the system.

[0091] 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.

[0092] 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.

[0093] 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.

[0094] Preferably, a tensioning roller is provided to tension the fabric in compression mode.

[0095] 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.

[0096] If necessary, the upsetting device has an emergency mode as an alternative to the upsetting mode. In this mode, the pressure bar is in a retracted position relative to the upsetting mode, and the fabric therefore exerts no pressure on the counter roller. In the emergency mode, both the fabric and the counter roller are driven by the fabric drive, as well as the counter roller by the counter roller drive.

[0097] Preferably, an adjusting device is provided for displacing the wrap roller and thereby for adjusting the wrap angle.

[0098] By changing the wrap angle, the compression of the fibrous web can be flexibly and precisely adjusted, in particular controlled and / or regulated. Optionally, the adjustment device is designed such that the wrap angle can be adjusted by at least 10°, in particular by at least 20°, in particular by at least 25°, in particular by at least 40°, or in particular by at least 60°.

[0099] If necessary, the adjustment device is designed such that the wrap angle of the cloth can be adjusted between 15° and 90°, preferably between 20°-60°.

[0100] If necessary, a compensating roller which can be displaced along a compensating path is provided to compensate for the displacement of the wrap-around roller while maintaining an essentially constant cloth length.

[0101] If necessary, the compensating roller has a freedom of movement or a stroke of more than 10 cm along the compensating path, in particular more than 45 cm and preferably between 5 cm or 10 cm and 55 cm.

[0102] If necessary, the compensating roller acts as a tensioning roller to tension the fabric.

[0103] If necessary, the compensating roller is the tensioning roller, in particular the only tensioning roller, for tensioning the fabric.

[0104] If necessary, a guide roller arranged downstream of the counter roller along the machine direction is provided for guiding or deflecting the fibrous web emerging from the compression gap or leaving the counter roller.

[0105] If necessary, the guide roller can be moved to change the angle of wrap of the fiber web around the counter roller.

[0106] This allows the application time and thus the heat input of the heated counter roll to the fiber web to be adjusted.

[0107] If necessary, the wrap-around roller is mounted on pivot bearings on both sides. If necessary, the adjustment device includes means for changing and fixing the position of the pivot bearings relative to the counter roller.

[0108] If necessary, the adjustment device comprises a guide arrangement for guiding the pivot bearings or their bearing blocks and a drive for changing the position of the pivot bearings relative to the counter roller.

[0109] If necessary, the drive is a hydraulic or an electric drive.

[0110] If necessary, the wrapping roller and the pressure bar are arranged one after the other on the inside of the cloth along the course of the cloth.

[0111] If necessary, the counter roller is arranged in the area between the wrap roller and the pressure bar on the outside of the cloth.

[0112] If necessary, the cloth is guided in compression mode by the wrap roller and the pressure bar around the counter roller at a wrap angle.

[0113] If necessary, the cloth is an endless belt, along the course of which the cloth drive roller, the pressure bar, the counter roller, the wrap-around roller and the compensating roller, preferably designed as a tensioning roller, are arranged one after the other.

[0114] If necessary, it is provided that the adjustment device is designed to displace the wrap roller and thereby to adjust the wrap angle in the compression mode, wherein the displacement can preferably take place at production speed.

[0115] Optionally, it is provided that the adjusting device is designed to displace the wrap roller and thereby to adjust the wrap angle at a rotational speed of the cloth and the counter roll in compression mode of more than 400 m / min, in particular more than 600 m / min, and essentially at production speed. In all embodiments, the axes of rotation of the counter roll and the wrap roller preferably run parallel to one another. In all embodiments, the axes of rotation of the counter roll and the wrap roller preferably run parallel to one another, even if the wrap angle is or is changed. In all embodiments, the axes of rotation of the counter roll and the guide roller preferably run parallel to one another, in particular even if the paper web wrap angle is or is changed.

[0116] 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.

[0117] 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.

[0118] 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.

[0119] Where appropriate, the cloth shall have a Shore A hardness between 40 and 70, in particular between 50 and 60.

[0120] If necessary, the counter roll is heated in compression mode.

[0121] If necessary, the counter roller is heated at least temporarily in emergency mode.

[0122] If necessary, the counter roll is not heated, at least temporarily, in emergency mode. Heating can be stopped or reduced, for example, to ensure safety for operators, for example, during a cloth change.

[0123] 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. In particular, the kraft paper production plant comprises the following components:

[0124] - a wire section for forming a fibrous web by continuously applying a fibrous suspension along the machine direction through a headbox,

[0125] - a shaking device for shaking the fibrous web transversely to the machine direction, i.e. in the transverse direction,

[0126] - a press section for pressing the fibrous web partially dewatered in the wire section,

[0127] - a drying section for drying the fibrous web,

[0128] - a winding station for winding the paper web formed from the fibrous web,

[0129] - and a compression device.

[0130] Preferably, the drying section comprises a pre-drying section and a post-drying section.

[0131] 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.

[0132] If necessary, the compression device is designed to compress the fibrous web at a dry content of the fibrous web of 55% to 70%.

[0133] Also disclosed is 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.

[0134] Procedural steps can be:

[0135] - that a rotating cloth is driven by a cloth drive,

[0136] - that a counter roll is driven by a counter roll drive,

[0137] - 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 thereby compressed in the machine direction, and that the cloth is driven by the cloth drive in the compression mode.

[0138] Further procedural steps may include:

[0139] - in a wire section, a fibrous web is formed by continuously applying a fibrous suspension along the machine direction through a headbox,

[0140] - the fibrous web is shaken transversely to the machine direction, i.e. in the transverse direction, by a shaker,

[0141] - in a press section the fibrous web partially dewatered in the wire section is pressed,

[0142] - the fibrous web is dried in a drying section,

[0143] - the paper web formed from the fibrous web is wound up in a winding station.

[0144] Disclosed is 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.

[0145] 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.

[0146] In the wire section, a fibrous band or sheet is formed by a filtration process, in particular using dewatering devices.

[0147] Following the wire section, a press section is typically arranged, where mechanical dewatering with simultaneous compaction of the fibrous web can take place. This can typically be achieved with 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.

[0148] The mechanically extruded fibrous web can be subjected to one or more drying processes to achieve the desired dry content. Further manufacturing and / or processing steps, such as compressing or calendering the fibrous web, can be performed before, between, or after one or more drying processes.

[0149] 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.

[0150] 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.

[0151] 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.

[0152] 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.

[0153] Optionally, the fabric and the counter roll have a width of at least 4.0 m, in particular of at least 7.0 m, typically of at least 8.0 m. Optionally, the production speed is at least 600 m / min, in particular at least 1100 m / min.

[0154] In particular, the fiber used to produce 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.

[0155] 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.

[0156] 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.

[0157] The difference in extensibility of the paper in the transverse direction between the edge region and the middle region of the paper web is preferably a maximum of 1.5%. In absolute terms, the extensibility of the paper web can be between 5% and 8% in the middle 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 an outer edge of the paper web. The middle region refers in particular to an area with a width of 50 cm that extends 25 cm on either side of the geometric center of a paper web determined in the width direction. An example possible way of measuring extensibility is between 0.75 h and 1.5 h, typically 1.0 h, after the production of the kraft paper, i.e. after completion of the last manufacturing step. If necessary, the measurement can also be carried out at a later or earlier time.

[0158] Where applicable, the Ambertec formation of the paper is not more than 0.7 (g / m 2 ). Where appropriate, the Gurley drag of the paper, in particular according to ISO 5636-5:2013, shall be no more than 15 s, preferably no more than 10 s.

[0159] 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.

[0160] The fiber contained in the paper may be unbleached pulp. Bleached pulp may also be used if necessary.

[0161] 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.

[0162] Where appropriate, the fibre contained in the paper has a kappa number of at least 30, in particular of at least 50.

[0163] 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.

[0164] In all embodiments, the production speed is preferably the inlet speed of the fibrous web into the compression device.

[0165] The invention will be further described below using exemplary embodiments.

[0166] Fig. 1a-c show a schematic overall view of a kraft paper production plant.

[0167] Fig. 2 shows a schematic view of a section of the system in which the upsetting device and the bypass arrangement are provided. Unless otherwise indicated, the following features are shown in Figures 1 and / or 2: 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 roller 32, pressure bar 33, wrap roller 34, guide roller 42, knock-off device 45,Bypass arrangement 46, bypass path 47, switch 48, rope guide 49, bypass rope guide 51, compression rope guide 52, first rope 53, second rope 54, third rope 55, fourth rope 56, first rope drive 57, second rope drive 58, deflection pulley 59, adjusting pulley 60. In Fig. 3, the first rope 53 is shown schematically with the line type "long dashes", the second rope 54 with the line type "dash-dot", the third rope 55 with the line type "dash-dot-dot" and the fourth rope 56 with the line type "short dashes".

[0168] Fig. 1a-c show a schematic overall view of a kraft paper production plant according to a first embodiment. 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.

[0169] The headbox 3 serves, in a known manner, to apply a fiber suspension to the continuously circulating 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. The system preferably includes a sensor for detecting a fault. In particular, such a sensor can detect a sliver break or a partial sliver break in the fibrous web. This sensor can generate a sliver break signal, which, for example, activates the emergency mode.

[0170] The system preferably comprises a cutting device 45. The cutting device 45 enables the fibrous web to be cut off, i.e., completely severed. This cutting device 45 is activated, for example, when the web break signal detects at least a partial web break. In this case, an emergency mode can be activated. Depending on the malfunction, the subsequent fibrous web can then be guided further through the system, in particular also further through the compression device 21, or the subsequent fibrous web can be redirected. In emergency mode, the compression device 21 is preferably operated in emergency mode.

[0171] The production speed of the system in this exemplary embodiment is approximately 1100 m / min. The resulting paper web has a paper width of approximately 6.4 m.

[0172] The compression device 21 comprises a cloth 26. The cloth 26 is an endless belt that is guided around several deflection rollers 59 or deflection rollers. In particular, the compression device 21 preferably 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.

[0173] The compression 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 towards or against a counter-roller 28. In the present embodiment, the counter-roller 28 has a counter-roller drive 29. The counter-roller 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 counter-roller 28. The compression gap 30 is delimited on one side by the counter-roller 28 and on the other side by the fabric 26. 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 cloth 26 and the counter roll 28 and is thereby compressed in the machine direction 1.

[0174] In compression mode, the cloth 26 is driven by the cloth drive 27.

[0175] 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.

[0176] 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.

[0177] 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 fabric 26 and the counter-roller 28 can be adjusted at an angle of approximately 15°-90°, preferably between 20°-45°. By displacing the pressure bar 33, the pressure or force acting on the fabric 26 in front of the pressure bar 33 in the direction of the counter-roller 28 can be reduced or completely eliminated. By thus relieving the pressure bar 33, the compression device 21 can be put into a free-running mode. In both operating modes, i.e., in compression mode and in free-running mode, the two drives can preferably drive the fabric 26 and the counter-roller 28. The drive preferably takes place at a speed that essentially corresponds to the production speed.

[0178] 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.

[0179] In addition, the tension roller 32 can also keep the cloth 26 taut if necessary when the pressure bar 33 is retracted.

[0180] In the present embodiment, the upsetting device 21 comprises a wrap-around roller 34. The wrap-around roller 34 is preferably 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 of the cloth 26 on the counter-roller 28. The greater the wrap angle, the longer the contact distance of the cloth 26 and thus also of the fibrous web on the counter-roller 28. In the upsetting mode, the cloth 26 is therefore guided by the wrap-around roller 34 and the pressure bar 33 by a wrap angle around the counter-roller 28.

[0181] In the present embodiment, the wrap roller 34 is designed to be displaceable in order to be able to adjust or change the wrap angle.

[0182] The system comprises in the area of ​​the compression device 21 a bypass arrangement 46 for conveying the fibrous web bypassing the compression device 21 along a bypass path 47. The bypass arrangement 46 is preferably exclusively in the area of ​​the compression device

[0183] 21 and is designed to transport the fibrous web bypassing the compression device 21 but not bypassing other parts of the system.

[0184] In particular, the upsetting device 21 is arranged along the machine direction 1 between a system part upstream of the upsetting device 21 and a system part downstream of the upsetting device 21. The bypass path 47 of the bypass arrangement 46 extends from the outlet of the upstream system part to the inlet of the downstream system part.

[0185] The drying section 6 comprises a pre-drying section 19 and an after-drying section 20 arranged downstream of the pre-drying section 19 along the machine direction 1. The compression device 21 is preferably arranged between the pre-drying section 19 and the after-drying section 20 along the machine direction 1. The bypass arrangement 46 can transport the fibrous web from the pre-drying section 19 to the after-drying section 20, bypassing the compression device 21.

[0186] The bypass arrangement 46 comprises an adjustable switch 48 for selectively conveying the fibrous web or a strip of the fibrous web through the compression device 21 or through the bypass path 47. The switch 48 is designed, for example, as an adjustable suction belt or vacuum belt.

[0187] In addition, a cable guide 49 is provided for selectively guiding a strip of the fibrous web through the bypass arrangement 46 or through the compression device 21.

[0188] Fig. 2 shows a schematic side view of components of the system, and in particular the bypass arrangement 46 and the cable guide 49. The bypass arrangement 46 enables the fibrous web produced on the system to be guided either through the compression device 21 or through the bypass arrangement 46. In the bypass arrangement 46, the fibrous web is guided along a bypass path 47 past the compression device 21. Preferably, the fibrous web runs through all parts of the system with the exception of the compression device 21.

[0189] If, for example, the compression device 21 requires maintenance, the fibrous web cannot be conveyed through the compression device 21 for safety reasons, but usually also for technical reasons. In this case, the fibrous web is guided past the compression device 21 by the bypass arrangement 46. While the compression device 21 is being serviced, the present design can produce paper that has not been compressed in the longitudinal direction by the compression device 21. This paper generally has different properties than paper compressed in the compression device 21. However, the paper produced without the compression device 21 can still be used as a product.

[0190] If the fibrous web is to be guided through the bypass arrangement 46 instead of through the compression device 21, the following procedure can be followed: The fibrous web is preferably cut off by a cutting device 45 (see Fig. 1b). Subsequently, not the entire fibrous web is guided across its entire width, but only a narrow strip of the fibrous web is guided towards the compression device 21 and bypass arrangement 46. In all embodiments, the narrow strip can be, for example, approximately 10 cm to 25 cm wide. Subsequently, a switch 48 is actuated. This switch 48 can, for example, be designed as a suction belt or a vacuum belt and can be adjusted so that the course or direction of the strip of fibrous web can be changed. The switch 48 directs the strip into a cable guide 49.

[0191] The cable guide 49 includes a bypass cable guide 51 that can guide the strip along the bypass path 47. Furthermore, the cable guide 49 includes a compression cable guide 52 that guides the strip into or through the compression device 21. The strip can then be inserted through the switch 48 either into the bypass cable guide 51 or the compression cable guide 52.

[0192] The cable guide can be designed, for example, as follows: A first cable 53 and a second cable 54 run along the compression cable guide 52, starting from the switch 48. The first cable 53 and the second cable 54 run directly adjacent to one another in the direction of the compression device 21 and form the compression cable guide 52 in this area. However, the first cable 53 and the second cable 54 do not run through the compression gap 30 of the compression device 21, but rather laterally past the compression device 21. At the exit of the compression gap 30, the strip is in turn conveyed further by the compression cable guide 52 in the direction of the downstream machine component.

[0193] In this downstream area, the strip is guided by the first cable 53 and a fourth cable 56, which run directly adjacent there.

[0194] The bypass cable guide 51 comprises, in the area after the switch 48, a third cable 55 and the fourth cable 56. The third cable 55 and the fourth cable 56 run directly adjacent to one another in this area and guide the strip along the bypass path 47 through the bypass arrangement 46. In the area in which the strip is transferred to the components of the system downstream of the bypass arrangement 46, the cable guide 49 is formed by the first cable 53 and the fourth cable 56 in the present embodiment.

[0195] In all embodiments, the bypass cable guide 51 can comprise a first pair of cables, in particular the first cable 53 and the second cable 54. This first pair guides the strip of fibrous web along the bypass path 47.

[0196] In all embodiments, the compression cable guide 52 can comprise a second pair of cables, in particular the third cable 55 and the fourth cable 56. This second pair guides the strip of fibrous web through or into the compression device 21.

[0197] In all embodiments, it can be provided that the cable guide 49 has a section adjacent to the bypass cable guide 51 and adjacent to the compression cable guide 52 running parallel thereto, in which the strip of the fibrous web is guided by a cable of the first cable pair and a cable of the second cable pair. In particular, in the present embodiment, the strip is guided in this area by the first cable 53 and the fourth cable 56.

[0198] The cables 53, 54, 55, 56 are preferably all designed as endless, circular cables in all embodiments. In particular, one or more cable drives 57, 58 are provided to drive the cables 53, 54, 55, 56. In the present embodiment, a first cable drive 57 and a second cable drive 58 are provided. In the present embodiment, the first cable drive 57 drives the second cable 54 and the third cable 55. In the present embodiment, the second cable drive 58 drives the first cable 53 and the fourth cable 56.

[0199] In particular, it can be provided that one drive drives one rope of the first rope pair and one rope of the second rope pair. In particular, it can be provided that another drive drives the second rope of the first rope pair and the second rope of the second rope pair.

[0200] An adjusting roller 60 can be provided in the section where the bypass cable guide 51 and the compression cable guide 52 converge. As shown in the enlarged detail, the adjusting roller 60, when actuated, shifts the position of at least one of the cables 53, 54, 55, 56 such that the strip of fibrous web, depending on whether it comes from the bypass cable guide 51 or the compression cable guide 52, can be guided further along the cable guide 49 to the downstream system component.

[0201] In the present embodiment, a deflection pulley 59 is provided in this area. If the strip of fibrous web is guided along the bypass cable guide 51, the third cable 55 is looped around the deflection pulley 59 by the adjusting pulley 60 such that it is guided further between the first cable 53 and the fourth cable 56. If, however, the strip of fibrous web emerges from the compression cable guide 52, the adjusting pulley 60 can displace a portion of the third cable 55 such that the strip can run unhindered from the compression cable guide 52 into the further cable guide 49. In particular, a loop of the third cable 55 is retracted by the adjusting pulley 60.

Claims

Patent claims 1. Plant for the production of kraft paper, comprising the following plant components: - a wire section (2) for forming a fibrous web by continuously applying a fibrous suspension along the machine direction (1) through a headbox (3), - a shaking device (4) for shaking the fibrous web transversely to the machine running direction (1 ), i.e. in the transverse direction, - a press section (5) for pressing the fibrous web partially dewatered in the wire section (2), - a drying section (6) for drying the fibrous web, - a compression device (21), in particular a Clupak device, for compressing the fibrous web in the machine direction (1), - and a winding station (7) for winding the paper web formed from the fibrous web, characterized in that - that a bypass arrangement (46) is provided for conveying the fibrous web along a bypass path (47) bypassing the compression device (21), - that a cable guide (49) is provided for selectively guiding a strip of the fibrous web through the bypass arrangement (46) or through the compression device (21), - that the cable guide (49) comprises a bypass cable guide (51) for guiding the strip of the fibrous web through or into the bypass arrangement (46) and a compression cable guide (52) for guiding the strip of the fibrous web through or into the compression device (21), - and that the bypass cable guide (51) and the compression cable guide (52) are provided permanently and / or simultaneously next to each other.

2. Plant according to claim 1, characterized in that - that the bypass arrangement (46) is provided exclusively in the area of the compression device (21) and is designed to transport the fibrous web bypassing the compression device (21) but not bypassing other parts of the system, - in particular that the upsetting device (21) is arranged along the machine direction (1 ) is arranged between a system part upstream of the upsetting device (21 ) and a system part downstream of the upsetting device (21 ), and the bypass path (47) of the bypass arrangement (46) extends from the outlet of the upstream system part to the inlet of the downstream system part, 3. Installation according to one of claims 1 or 2, characterized in that - that the drying section (6) comprises a pre-drying section (19) and a post-drying section (20) arranged downstream of the pre-drying section (19) along the machine running direction (1 ), - that the compression device (21) is arranged along the machine direction (1) between the pre-drying section (19) and the after-drying section (20), - and that the bypass arrangement (46) conveys or can convey the fibrous web from the pre-drying section (19) to the after-drying section (20), bypassing the upsetting device (21).

4. Plant according to one of claims 1 to 3, characterized in that - that the bypass arrangement (46) comprises an adjustable switch (48) for selectively conveying the fibrous web or a strip of the fibrous web through the compression device (21) or through the bypass path (47), - wherein the switch (48) is designed, for example, as an adjustable suction belt or vacuum belt.

5. Plant according to claim 1 to 4, characterized in that - that the bypass cable guide 51 comprises a first pair of cables for guiding the strip through or into the bypass arrangement (46), - and that the compression cable guide (52) comprises a second pair of cables for guiding the strip through or into the compression device (21).

6. Plant according to one of claims 1 to 5, characterized in that - that the cable guide (49), for guiding the strip into the downstream component of the system, has a section with a further pair of cables following the bypass cable guide (51) and following the compression cable guide (52).

7. Plant according to one of claims 1 to 6, characterized in that - that one or more cable drives (57, 58) are provided for driving the cables of the cable guide (49), and in particular a first cable drive (57) and a second cable drive (58).

8. Plant according to one of claims 1 to 7, characterized in that the bypass arrangement (46) is designed to convey the fibrous web at production speed, wherein the production speed is greater than 400 m / min, in particular greater than 600 m / min.

9. Plant according to one of claims 1 to 8, characterized in that the width of the fibrous web is greater than 3.5 m, in particular greater than 6 m.

10. Plant according to one of claims 1 to 9, characterized in that - that in the compression device (21), a circulating cloth (26), a pressure bar (33), a wrap-around roller (34) and a counter-roller (28) are provided, - that the compression device (21) has a compression mode in which the rotating cloth (26) is pressed by the pressure bar (33) towards the counter-roller (28) and in which the cloth (26) wraps around the counter-roller (28) by a wrap angle, - that in the compression mode, a compression gap (30) is formed between the cloth (26) and the counter-roller (28), which is designed to convey the fibrous web through at production speed and thereby compress it in the machine direction (1). 11 . Method for operating a plant for the production of kraft paper, - wherein in a wire section (2) a fibrous web is formed by continuously applying a fibrous suspension along the machine direction (1) through a headbox (3), - wherein the fibrous web is shaken by a shaker transversely to the machine running direction (1 ), i.e. in the transverse direction, - wherein the fibrous web partially dewatered in the wire section (2) is pressed in a press section (5), - wherein the fibrous web is dried in a drying section (6), - wherein the paper web formed from the fibrous web is wound up in a winding station (7), characterized in that - that the fibrous web optionally runs in an upsetting device (21), in particular a Clupak device, through an upsetting gap (30) provided between a cloth (26) and a counter-roller (28) and is conveyed there between the moving cloth (26) and the moving counter-roller (28) and is thereby compressed in the machine direction (1 ) or is conveyed via a bypass arrangement (46) bypassing the upsetting device (21) along a bypass path (47), - that a strip of the fibrous web is guided by a cable guide (49) either through the bypass arrangement (46) or through the compression device (21) - that a bypass cable guide (51) of the cable guide guides the strip of the fibrous web through or into the bypass arrangement (46) and a compression cable guide (52) of the cable guide guides the strip of the fibrous web through or into the compression device (21), - and that the bypass cable guide (51) and the compression cable guide (52) are permanently or simultaneously provided next to each other, but only selectively guide the strip of the fibrous web.

12. Method according to claim 11, characterized in that - that the fibrous web is conveyed by the bypass arrangement (46) bypassing the compression device (21) but not bypassing other parts of the system, - in particular that the compression device (21) is arranged along the machine direction (1) between a system part upstream of the compression device (21) and a system part downstream of the compression device (21), and the fibrous web is conveyed along the bypass path (47) of the bypass arrangement (46) from the outlet of the upstream system part to the inlet of the downstream system part.

13. Method according to one of claims 11 or 12, characterized in that - that the fibrous web is dried in a pre-drying section (19) of the drying section (6) and in one of the pre-drying sections (19) along the machine direction (1 ) downstream after-drying section (20) of the drying section (6), - that the compression device (21) is arranged along the machine direction (1) between the pre-drying section (19) and the after-drying section (20), - and that the bypass arrangement (46) conveys or can convey the fibrous web from the pre-drying section (19) to the after-drying section (20), bypassing the upsetting device (21).

14. Method according to one of claims 11 to 13, characterized in that - that the bypass arrangement (46) comprises an adjustable switch (48) which conveys the fibrous web or a strip of the fibrous web selectively through the compression device (21) or through the bypass path (47), - wherein the switch (48) is designed, for example, as an adjustable suction belt or vacuum belt.

15. Method according to claim 11 to 14, characterized in that the bypass cable guide (51) guides the strip through or into the bypass arrangement (46) with a first pair of cables - and that the compression cable guide (52) guides the strip through or into the compression device (21) with a second pair of cables.

16. Method according to one of claims 11 to 15, characterized in that - that the cable guide (49) guides the strip into the downstream component of the system, following the bypass cable guide (51) and following the compression cable guide (52), in a section with another pair of cables.

17. Method according to one of claims 11 to 16, characterized in that - that the ropes of the rope guide (49) are driven by one or more rope drives (57, 58) and in particular by a first rope drive (57) and a second rope drive (58).

18. Method according to one of claims 11 to 17, characterized in that the bypass arrangement (46) conveys the fibrous web at production speed, wherein the production speed is greater than 400 m / min, in particular greater than 600 m / min.

19. Method according to one of claims 11 to 18, characterized in that the width of the fibrous web is greater than 3.5 m, in particular greater than 6 m.

20. Method according to one of claims 11 to 19, characterized in that - that in the compression device (21), a circulating cloth (26), a pressure bar (33), a wrap-around roller (34) and a counter-roller (28) are provided, - that the compression device (21) has a compression mode in which the rotating cloth (26) is pressed by the pressure bar (33) towards the counter-roller (28) and in which the cloth (26) wraps around the counter-roller (28) by a wrap angle, - that in the compression mode, a compression gap (30) is formed between the cloth (26) and the counter roller (28), in which the fibrous web is conveyed through at production speed and is thereby compressed in the machine running direction (1 ).

21. Method according to one of claims 11 to 20, characterized in that - that a first type of kraft paper is produced when the fibrous web passes through the compression device (21), - and that a second type of kraft paper is produced when the fibrous web passes through the bypass arrangement (46), bypassing the upsetting device (21), and the upsetting device (21) is serviced if necessary.

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