Method for operating an installation for producing kraft paper

Abstract

The invention relates to a method for operating an installation for producing kraft paper, said installation comprising a compacting device (21) for compacting a fibrous web, in particular a Clupak device, wherein - the compacting device (21) has a circulating cloth (26), a pressing bar (33), a wrap-around roller (34), a tensioning roller (32), a counter roller (28) and preferably a cloth drive roller (31), - the compacting device (21) can be operated in a compacting mode in which the circulating cloth (26) is pressed by the pressing bar (33) in the direction of the counter roller (28) and wraps around the counter roller (28) by a wrap-around angle (35), - in the compacting mode, a compacting gap (30) is formed between the cloth (26) and the counter roller (28), said compacting gap being designed such that the fibrous web is conveyed through the compacting gap at a production speed and is thereby compacted in the machine running direction (1), and - the compacting device (21) can be operated in an emergency running mode in which the pressing bar (33) is retracted in comparison to the compacting mode such that a distance is formed between the cloth (26) and the counter roller (28).

Description

[0001] Method for operating a plant for the production of kraft paper

[0002] The invention relates to a method, a compression device, and a system according to the features of the independent patent claims. In particular, the invention relates to a method for operating a system for producing kraft paper, wherein the system comprises a compression device or a Clupak device that can optionally be operated in an emergency mode.

[0003] Various processes for producing kraft paper are known in the prior 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 extensibility or air permeability. When it comes to the extensibility of kraft paper, a distinction is generally made between extensibility in the machine direction and extensibility transverse to the machine direction, i.e. in the transverse 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.

[0004] 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.

[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, 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.

[0007] 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.

[0008] 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.

[0009] The problem is solved in particular by the features of the independent patent claims.

[0010] 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.

[0011] 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 leads to a deterioration in the efficiency of the entire system.

[0012] To prevent this, an emergency mode can be activated in the present method, in which the cloth is quickly lifted from the counter roller.

[0013] 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.

[0014] 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.

[0015] 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.

[0016] The upsetting device can 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 roller. This gap can be, for example, more than 3 mm or more than 5 mm. Preferably, the wrap-around roller can also be displaced, if necessary, to enable or accelerate the lifting of the fabric from the counter roller.

[0017] If necessary, the separation time in the emergency mode, i.e., the time required to create a gap between the fabric and the counter roll from the compression mode, is less than 2 seconds, preferably less than 1 second. If necessary, the position of the wrap-around roll is changed in the emergency mode such that the fabric is lifted from the counter roll.

[0018] If necessary, the tensioning roller is designed to re-tension the fabric in emergency mode and thereby lift it off the counter roller.

[0019] 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 operation mode.

[0020] If necessary, it is provided that the fibrous web is cut off by a cutting device in an area along the machine direction in front of the compression device before or during the emergency running mode.

[0021] If necessary, the belt break signal is processed and directly or indirectly activates the cutting device.

[0022] 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.

[0023] If appropriate, the fabric drive can or does drive the fabric at a rotational speed that essentially corresponds to the production speed. The production speed is preferably greater than 400 m / min and in particular greater than 600 m / min.

[0024] If necessary, a counter roller drive is provided to drive the counter roller in emergency mode, even if a gap has already been formed between the cloth and the counter roller.

[0025] 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.

[0026] If necessary, the pressure bar is retracted pneumatically or hydraulically in emergency mode, in particular by means of a bellows cylinder.

[0027] 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.

[0028] 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.

[0029] In particular, the invention relates to an upsetting device of a plant for producing kraft paper, wherein the upsetting device is designed for upsetting a fibrous web and in particular as a Clupak device, wherein the upsetting device has an emergency running mode in which the pressure bar is retracted relative to the upsetting mode, so that a distance is formed between the cloth and the counter roll.

[0030] With the present edging device, the fabric can also be driven at production speed, if necessary, instead of the usual configuration of a drive roller and a non-driven fabric. 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 process, not at production speed.

[0031] In the present design, however, a drive roller in the traditional sense is preferably not present. 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 such that they can drive the blanket and the 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 the 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.

[0032] With this upsetting device, a distinction can basically be made between different operating modes:

[0033] 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. 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.

[0034] 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.

[0035] These individual drives make it possible to drive the blanket at production speed even when the pressure bar is in its retracted position and the blanket is not pressing against the counter roll. If necessary, the speeds of the blanket and counter roll can be brought up to production speed without the need to contact or press the blanket against the counter roll. This can reduce wear when starting up the swaging device and extend the maintenance interval. Furthermore, in the event of a paper break 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 swaging device from its swaging mode to emergency mode.Here, too, the fabric and counter roll can continue to move at production speed without slippage between the counter roll and fabric, which would lead to excessive wear on the fabric. This also extends maintenance intervals and improves the efficiency of the system.

[0036] 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.

[0037] 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.

[0038] 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.

[0039] Preferably, a tensioning roller is provided to tension the fabric in compression mode.

[0040] Preferably, an adjustable pressure bar is provided within the fabric, which is displaced toward the counterroller in the compression mode and presses the fabric toward the counterroller in the area of ​​the compression gap. In particular, the fabric is compressed between the pressure bar and the counterroller in the compression mode. Optionally, the compression device has an emergency mode as an alternative to the compression mode, in which the pressure bar is in a retracted position compared to the compression mode, and the fabric therefore exerts no pressure on the counterroller. In the emergency mode, both the fabric and the counterroller are driven by the fabric drive, as appropriate.

[0041] Preferably, an adjusting device is provided for displacing the wrap roller and thereby for adjusting the wrap angle.

[0042] By changing the wrap angle, the compression of the fibrous web can be adjusted flexibly and precisely, in particular controlled and / or regulated.

[0043] If necessary, the adjustment device is designed in such a way

[0044] - 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°.

[0045] 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° and 60°.

[0046] 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.

[0047] 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.

[0048] If necessary, the compensating roller acts as a tensioning roller to tension the cloth.

[0049] If necessary, the compensating roll is the tensioning roll, in particular the only tensioning roll, for tensioning the fabric. If necessary, a guide roller arranged downstream of the counter roll along the machine direction is provided for guiding or deflecting the fibrous web emerging from the compression gap or leaving the counter roll.

[0050] If necessary, the guide roller can be moved to change the angle of wrap of the fiber web around the counter roller.

[0051] This allows the application time and thus the heat input of the heated counter roll to the fiber web to be adjusted.

[0052] If necessary, the wrap roller is mounted on pivot bearings on both sides.

[0053] If necessary, the adjusting device comprises means for changing and fixing the position of the pivot bearings relative to the counter roller.

[0054] If necessary, the adjusting 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.

[0055] If necessary, the drive is a hydraulic or an electric drive.

[0056] 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.

[0057] If necessary, the counter roller is arranged in the area between the wrap roller and the pressure bar on the outside of the cloth.

[0058] 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.

[0059] 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, which is preferably designed as a tensioning roller, are arranged one after the other.

[0060] 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.

[0061] Where appropriate, 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 roller in the compression mode of more than 400 m / min, in particular of more than 600 m / min, and essentially at production speed.

[0062] In all embodiments, the axes of rotation of the counter roll and the wrap-around roll preferably run parallel to each other. In all embodiments, the axes of rotation of the counter roll and the wrap-around roll preferably run parallel to each other, even if the wrap angle is or is changed.

[0063] In all embodiments, the axes of rotation of the counter roller and the guide roller preferably run parallel to each other, and this is particularly the case when the paper web wrap angle is or is changed.

[0064] 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.

[0065] 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.

[0066] 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.

[0067] Where appropriate, the cloth shall have a Shore A hardness between 40 and 70, in particular between 50 and 60.

[0068] If necessary, the counter roll is heated in compression mode. If necessary, the counter roll is heated at least temporarily in emergency mode.

[0069] 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.

[0070] 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.

[0071] In particular, the plant for the production of kraft paper comprises the following plant components:

[0072] - a wire section for forming a fibrous web by continuously applying a fibrous suspension along the machine direction through a headbox,

[0073] - a shaking device for shaking the fibrous web transversely to the machine direction, i.e. in the transverse direction,

[0074] - a press section for pressing the fibrous web partially dewatered in the wire section,

[0075] - a drying section for drying the fibrous web,

[0076] - a winding station for winding the paper web formed from the fibrous web,

[0077] - and a compression device.

[0078] Preferably, the drying section comprises a pre-drying section and a post-drying section.

[0079] 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.

[0080] Optionally, the compression device compresses the fibrous web at a dry content of the fibrous web of 55% to 70%. 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.

[0081] Procedural steps can be:

[0082] - that a rotating cloth is driven by a cloth drive,

[0083] - that a counter roll is driven by a counter roll drive,

[0084] - 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.

[0085] Further procedural steps may include:

[0086] - in a wire section, a fibrous web is formed by continuously applying a fibrous suspension along the machine direction through a headbox,

[0087] - the fibrous web is shaken transversely to the machine direction, i.e. in the transverse direction, by a shaker,

[0088] - in a press section the fibrous web partially dewatered in the wire section is pressed,

[0089] - the fibrous web is dried in a drying section,

[0090] - the paper web formed from the fibrous web is wound up in a winding station.

[0091] It may be advantageous if the drying section comprises a pre-drying section and a post-drying section.

[0092] 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.

[0093] It may be advantageous if the compression device compresses the fibrous web at a dry content of the fibrous web of 55% to 70%. A kraft paper produced on a described system and / or by a described method is disclosed.

[0094] 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 carried out, in particular, by applying a fibrous suspension to a wire section by means of a headbox.

[0095] 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.

[0096] In the wire section, a fibrous band or sheet is formed by a filtration process, in particular using dewatering devices.

[0097] 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.

[0098] 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.

[0099] The compression of the fibrous web can occur particularly between two

[0100] Drying steps can be carried out 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 stretchability in the machine direction. This step takes place in the compression device.

[0101] 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.

[0102] 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.

[0103] 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.

[0104] 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.

[0105] Where appropriate, the production speed is at least 600 m / min, in particular at least 1100 m / min.

[0106] 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.

[0107] 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. The width of a paper web of the kraft paper is preferably greater than 3.5 m and in particular greater than 5.5 m, for example greater than 6.0 m. In the context of the present invention, the width refers in particular to the dimension of a paper web in the transverse direction of the paper.

[0108] 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.

[0109] Where applicable, the Ambertec formation of the paper is not more than 0.7 (g / m 2 ).

[0110] Where appropriate, the Gurley drag of the paper, in particular according to ISO 5636-5:2013, is not more than 15 s, preferably not more than 10 s.

[0111] 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.

[0112] The fiber contained in the paper may be unbleached pulp. Bleached pulp may also be used if necessary.

[0113] 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.

[0114] Where appropriate, the fibre contained in the paper has a kappa number of at least 30, in particular of at least 50.

[0115] 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.

[0116] In all embodiments, the production speed is preferably the inlet speed of the fibrous web into the compression device.

[0117] Further features of the invention emerge from the patent claims, the figures and the description of the embodiment.

[0118] The present invention is explained in detail below using an exemplary embodiment.

[0119] They show:

[0120] Fig. 1a-c a schematic overall view of a kraft paper manufacturing plant;

[0121] Fig. 2 is a schematic detailed view of an upsetting device; and Fig. 3 is a schematic detailed view of an upsetting device.

[0122] 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 orSilicone spray device 36, scraper 37, coolant nozzle 38, adjustment device 39, compensation path 40, compensation roller 41, guide roller 42, paper web wrap angle 43, pivot bearing 44, knock-off device 45.

[0123] 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.

[0124] 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.

[0125] The system preferably includes a sensor for detecting a malfunction. In particular, such a sensor can detect a sliver break or a partial sliver break of the fibrous web. This sensor can generate a sliver break signal, which, for example, activates the emergency mode.

[0126] The system preferably comprises a cutting device 45. The cutting device 45 makes it possible to cut off the fibrous web, i.e. to completely separate it. This cutting device 45 is activated, for example, when the sliver break signal detects at least a partial sliver 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 is diverted. In emergency mode, the compression device 21 is preferably operated in emergency mode. The production speed of the system in this exemplary embodiment is, for example, approximately 1100 m / min. The produced paper web has a paper width of approximately 6.4 m.

[0127] The function of the individual plant components is well known to a specialist in the field of paper production and will not be explained in detail here. The following description refers specifically to wire section 2.

[0128] 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.

[0129] 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.

[0130] 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.

[0131] 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.

[0132] A high-frequency shaking device 4 can be configured to oscillate the breast roll 10 and thus 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 produced paper in the transverse direction, i.e., transverse to the machine direction 1. In this embodiment, the oscillation occurs at a frequency of approximately 7 Hz and an amplitude of approximately 35 mm.

[0133] Viewed in the running direction 23, after the suspension has been applied to the dewatering screen 8, the fiber web enters a first dewatering section 11. Here, the fiber web is dewatered downwards, i.e., from the inner side 12 of the dewatering screen 8. A first dewatering device 14 is arranged in the first dewatering section 11, which initially enables a primarily gravity-driven dewatering of the fiber web, followed by a downward suction treatment. The suction treatment is carried out by means of suction boxes 24.

[0134] In the first dewatering section 11, the fibrous web is dewatered exclusively downwards.

[0135] 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.

[0136] Furthermore, four formation bars 16 are preferably provided, arranged one after the other in the running direction 23 of the dewatering screen 8. These formation bars 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. The fibrous web then exits the screen section 2 and is further processed in the other system components, as shown in Fig. 1, to be further dewatered or dried and finally to form a paper web.

[0137] Due to the treatment in wire section 2, the resulting kraft paper has a number of advantageous properties, particularly relating to the extensibility in the transverse direction and the formation of the paper.

[0138] The kraft paper produced according to the described embodiment has the following exemplary property profile:

[0139] Fig. 2 shows a schematic view of a compression device 21. The compression device 21 comprises a cloth 26. The cloth 26 is an endless belt that is guided around a plurality of deflection pulleys or guide rollers. In particular, the compression 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. The compression device 21 comprises a pressure bar 33. The pressure bar 33 is designed to be displaceable and can, as in the present position, press the cloth 26 towards or against a counter-roller 28. The pressure bar 33 can be displaced via a drive (not shown), for example via a pneumatic or hydraulic drive. In the present embodiment, the counter-roller 28 has a counter-roller drive 29.Preferably, the counter-roller drive 29 and the fabric drive 27 are independently controllable or adjustable drives, and preferably rotary drives. A compression gap 30 is formed between the fabric 26 and the counter-roller 28. The compression gap 30 is bounded on one side by the counter-roller 28 and on the other side by the fabric 26.

[0140] 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. In the compression mode, the fabric 26 is preferably driven by the fabric drive 27.

[0141] In the compression mode, the counter roller 28 is driven by the counter roller drive 29, whereby in the compression mode, preferably both the cloth 26 and the counter roller 28 are each driven by their own drive.

[0142] 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.

[0143] 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.

[0144] Because the cloth 26 in the area of ​​the compression gap 30 is held by the pressure bar 33

[0145] towards the counter-roller 28 and thereby compressed between the pressure bar 33 towards the counter-roller 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°.

[0146] 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 roller 28 can be reduced or completely eliminated. By thus relieving the pressure bar 33, the compression device 21 can be placed into a free-running mode, in which the pressure of the pressure bar 33 is at least reduced. In both operating modes, i.e., compression mode and free-running mode, the two drives can preferably drive the fabric 26 and the counter roller 28. The drive preferably occurs at a speed that essentially corresponds to the production speed.

[0147] 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.

[0148] In addition, the tensioning roller 32 can also tension the cloth 26 when the pressure bar 33 is retracted.

[0149] 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.

[0150] 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 35 can be adjusted or changed within a range of 15° to 90°, preferably from 20° to 45°.

[0151] The adjustment is carried out via a schematically illustrated adjustment device 39, with which the wrap angle 35 can be changed and adjusted by moving the wrap roller 34.

[0152] In the present embodiment, the adjustment device 39 comprises guides or guide arms arranged on both sides of the wrap-around roller 34 and a drive. By actuating the drive, the pivot bearings for supporting the wrap-around roller 34 can be moved in a targeted manner.

[0153] Preferably, the wrap angle 35 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°. The displacement is preferably carried out using an electromechanical adjusting device 39, although the movement can also be carried out hydraulically. The displacement movement is carried out, for example, linearly by means of a spindle lifting element, wherein the wrap roller 34 is mounted via a pivot point so that the wrap angle 35 of the cloth 26 on the counter roller 28 can be adjusted (min. / max. movement). The maximum stroke of the adjusting device 39 essentially corresponds to the maximum wrap of the cloth 26 on the counter roller 28. If the adjusting device 39 is fully retracted, there may be no cloth contact with the counter roller 28. The cloth 26 can be operated in freewheel mode. All movement sequences should or must be synchronous.The movement sequences include, in particular, the adjustment of the cloth 26 on the counter rollers 28 and the tensioning of the cloth 26 to compensate for the change in length. When relieving the pressure rod or pressure beam 33, the movements should also be synchronized with the cloth movement, particularly within a period of less than 2 seconds, preferably less than 1 second.

[0154] In all embodiments, all three movements preferably run synchronously: adjusting the wrap roller 34, tensioning the fabric 26 with the tension roller 32 and relieving the pressure bar 33. This ensures that the fabric 26 can continue to be operated at full operating speed.

[0155] If necessary, the wrap angle 35 can be adjusted between 15° and 90°, preferably between 20° and 60°.

[0156] In the present design, the displacement of the wrap roller 34 can be compensated for while maintaining a substantially constant cloth length by displacing a compensating roller 41 that is displaceable along a compensation path 40. If the wrap roller 34 is displaced to change the wrap angle 35, this change in the position of the wrap roller 34 must be compensated for by changing the bearings of the compensating roller 41. Finally, the cloth 26 has a substantially constant length and should stretch only slightly along its longitudinal extent.

[0157] The compensating roller 41 can be moved along the compensating path 40, for example, by more than 10 cm, in particular by more than 45 cm, and preferably between 5 cm or 10 cm and 55 cm. In the present embodiment, the compensating roller 41 simultaneously acts as a tensioning roller 32 for tensioning the fabric 26. In particular, the compensating roller 41 is the only tensioning roller 32 for tensioning the fabric 26.

[0158] The fibrous web is wrapped around the counter roller 28 at a paper web wrap angle 43. After leaving the counter roller 28, the fibrous web is guided or deflected around a guide roller 42. The paper web wrap angle 43 of the fibrous web around the counter roller 28 can be changed by changing the position of the guide roller 42.

[0159] The compression device 21 according to Fig. 2 comprises 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.

[0160] A coolant nozzle 38 may also be provided, which can be used to apply a coolant to the surface of the cloth 26. In particular, several coolant nozzles 38 are provided to distribute the coolant across the entire width of the cloth 26.

[0161] Fig. 3 shows a compression device 21, in particular the compression device 21 from Fig. 2, in the emergency running mode and in particular in a position in which a distance is formed between the cloth 26 and the counter roller 28.

[0162] During the emergency mode, starting from the compression mode, as shown, for example, in Fig. 2, the pressure bar 33 is rapidly retracted. The pressure bar 33, which presses the fabric 26 toward the counter roller 28 in the compression mode, enables the fabric 26 to be lifted from the counter roller 28 by its retraction. The pressure bar 33 can be retracted, for example, pneumatically or hydraulically in the emergency mode. Preferably, a bellows cylinder can be provided as the actuator, which acts on the pressure bar 33, for example, via a pivoting lever and / or a guide.

[0163] In addition, if necessary, the wrap roller 34 can also be displaced to enable or accelerate the lifting of the fabric 26 from the counter roller 28. The adjustment can be carried out using the schematically illustrated adjustment device 39, with which the wrap angle 35 can also be changed and adjusted by displacing the wrap roller 34. In the illustration in Fig. 3, the wrap roller 34 is displaced compared to the operating mode in Fig. 2. In an alternative embodiment, the distance between the fabric 26 and the counter roller 28 can also be adjusted exclusively by displacing the pressure bar 33. This is particularly advantageous for upsetting devices that have a rigid wrap roller 34 with a non-displaceable axis.

[0164] In order to achieve rapid and targeted lifting of the fabric 26 from the counter roller 28, the tensioning roller 32 of the upsetting device is preferably also displaced in emergency mode. The tensioning roller 32 is the roller that holds the fabric 26 at the desired tension in upsetting mode. With a displaceable wrap-around roller 34, this tensioning roller 32 can simultaneously serve as a compensating roller 41. The tensioning roller 32 is also preferably displaced quickly in emergency mode, so that the fabric 26 is lifted from the counter roller 28 through the interaction of the retraction of the pressure bar 33 and the displacement of the tensioning roller 32. If there is a displaceable wrap-around roller 34, this can also occur in conjunction with the displacement of the wrap-around roller 34.

[0165] 3, the cloth 26 can, if necessary, be driven further in rotation. For this purpose, a cloth drive 27 and a cloth drive roller 31 are provided. The cloth 26 can thus be driven in rotation, even though there is a distance between the counter roller 28 and the cloth 26 and even though the counter roller 28 can no longer drive the cloth 26. Preferably, the counter roller 28 is also driven in rotation by a counter roller drive 29. The cloth 26 and the counter roller 28 therefore preferably each have a drive, wherein the two drives can drive the cloth 26 and the counter roller 28 independently of one another. The rotational speed of the cloth 26 and the rotational speed of the counter roller 28 can thus be maintained or adjusted, even if there is a distance between the cloth 26 and the counter roller 28.In particular, the rotational speeds of the cloth 26 and the counter-roller 28 can essentially correspond to the production speed. The production speed is preferably greater than 400 m / min and in particular greater than 600 m / min.

[0166] If the upsetting device 21 is to be returned to upsetting mode, the fabric 26 is pressed back against the counter roller 28 by the pressure bar 33. During the transition from the emergency mode to the upsetting mode, the specially driven elements of the counter roller 28 and fabric 26 prevent detrimental slippage between these elements, thereby further reducing wear.

[0167] The emergency mode is preferably triggered by a signal. This signal can be a signal triggered by a person or another signal, such as a belt break signal from a sensor for detecting a malfunction. For example, the system includes a sensor that can detect a belt break or a partial belt break of the fibrous web. This sensor is preferably located upstream of the compression device 21 in the machine direction 1.

Claims

1. A method for operating a system for producing kraft paper, comprising a compacting apparatus (21) for compacting a fibrous web, in particular comprising a Clupak device,- wherein the compacting apparatus (21) comprises a circulating belt (26), a nip bar (33), a wrap roll (34), a tension roll (32), a counter roll (28) and preferably a belt drive roll (31),- wherein the compacting apparatus (21) may be operated in a compacting mode in which the circulating belt (26) is pressed towards the counter roll (28) by the nip bar (33) and wraps around the counter roll (28) over a wrap angle (35),- wherein, in the compacting mode, a compaction nip (30) is formed between the belt (26) and the counter roll (28), which is designed to convey the fibrous web at production speed, thereby compacting it in the machine flow direction (1),- wherein the compacting apparatus (21) can be operated in an emergency operation mode, in which the nip bar (33) is retracted compared to the compacting mode, so that a gap is formed between the belt (26) and the counter roll (28), wherein the gap is preferably larger than 5 mm,- wherein additionally, if required, the wrap roll (34) can also be displaced in order to enable or accelerate the lifting of the belt (26) from the counter roll (28).

2. The method according to claim 1, characterised in that the separation time of the emergency operation mode, i.e. the time required to form a gap between the belt (26) and the counter roll (28) starting from the compacting mode, is less than 2 s, preferably less than 1 s.

3. The method according to claim 1 or 2, characterised in that the position of the wrap roll (34) is changed in emergency operation mode in such a way that the belt (26) is lifted off the counter roll (28).

4. The method according to any one of claims 1 to 3, characterised in that the tension roll (32) retensions the belt (26) in emergency operation mode and thus lifts it off the counter roll (28).

5. The method according to any one of claims 1 to 4, characterised in that a web break signal from a sensor for detecting a malfunction, such as, for example, an at least partial web break in the fibrous web, is processed and directly or indirectly activates the emergency operation mode.

6. The method according to any one of claims 1 to 5, characterised- in that the fibrous web is cut off by a web cutting device (45) in an area upstream of the compacting apparatus (21) along the machine flow direction (1) before or during the emergency operation mode,- in particular in that the web break signal is processed and directly or indirectly activates the web cutting device (45).

7. The method according to any one of claims 1 to 6, characterised- in that a belt drive (27) drives the belt drive roll (31) and thus the belt (26) in emergency operation mode, even if a gap has already formed between the belt (26) and the counter roll (28),- wherein the belt drive (27) can or does preferably drive the belt (26) at a circulation speed that substantially corresponds to the production speed,- wherein the production speed preferably exceeds 400 m / min, and in particular exceeds 600 m / min.

8. The method according to any one of claims 1 to 7, characterised- in that a counter roll drive (29) drives the counter roll (28) in emergency operation mode, even if a gap has already formed between the belt (26) and the counter roll (28),- wherein the counter roll drive (29) can or does drive the counter roll (28) preferably at a circulation speed that substantially corresponds to the production speed,- wherein the production speed preferably exceeds 400 m / min, and in particular exceeds 600 m / min.

9. The method according to any one of claims 1 to 8, characterised in that the nip bar (33) is retracted pneumatically or hydraulically in emergency operation mode, in particular by a bellows cylinder.

10. The method according to any one of claims 1 to 9, characterised in that in the compacting mode, the nip bar (33) is pressed toward the counter roll (28) with a force of at least 5 kN / m, in particular at least 45 kN / m, preferably of 5 kN / m or 45 kN / m to 70 kN / m.

11. The method 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 in that 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 in that the belt (26) has a Shore A hardness between 40 and 60, in particular between 50 and 60.

12. The method according to any one of claims 1 to 11, characterised - in that, in the compacting mode, the counter roll (28) is heated, - in particular, in that the counter roll (28) is heated with a steam pressure of2 bar to 15 bar, and / or at a temperature of 70°C up to 180°C.

13. The method according to any one of claims 1 to 12, 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),- the fibrous web is shaken transversely to the machine flow direction (1), i.e. in the cross direction, by a shaking apparatus (4),- 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,- in that the drying section (6) comprises a pre-dryer section (19) and an afterdryer section (20),- and in that the compacting apparatus (21) compacts the fibrous web in the machine flow direction (1) between the pre-dryer section (19) and the afterdryer section (20).

14. A system for producing kraft paper, comprising a compacting apparatus (21) for compacting a fibrous web, in particular comprising a Clupak device, characterised in that the method according to any one of claims 1 to 13 is performed.

15. A compacting apparatus (21) of a system for producing kraft paper, wherein the compacting apparatus is configured for compacting a fibrous web and, in particular, as a Clupak device,- wherein the compacting apparatus (21) comprises a circulating belt (26), a nip bar (33), a wrap roll (34), a tension roll (32), a counter roll (28) and preferably a belt drive roll (31),- wherein the compacting apparatus (21) can be operated in a compacting mode in which the circulating belt (26) is pressed towards the counter roll (28) by the nip bar (33) and wraps around the counter roll (28) over a wrap angle (35),- wherein, in the compacting mode, a compaction nip (30) is formed between the belt (26) and the counter roll (28), which is designed to convey the fibrous web at production speed, thereby compacting it in the machine flow direction (1),- wherein the compacting apparatus (21) can be operated in an emergency operation mode, in which the nip bar (33) is retracted compared to the compacting mode, so that a gap is formed between the belt (26) and the counter roll (28),- and wherein the wrap roll (34) is configured to be displaceable in order to enable or accelerate the lifting of the belt (26) off the counter roll (28).

Images