System for producing a width-controlled, wet-laid fibrous web, method for producing a width-controlled, wet-laid fibrous web

Abstract

The invention relates to a system (100) for producing a fibrous web (1), comprising a distributor (2) and a head box (3) for wet-laying fibres to form the fibrous web (1), wherein a tube bundle (4) for introducing a fibrous material suspension from the distributor (2) into the head box (3) is provided between the distributor (2) and the head box (3), wherein a valve (5) is arranged on each of a plurality of tubes (41) at the lateral edges of the tube bundle (4) for selectively conveying the fibrous material suspension from the distributor (2) into the head box (3) or conveying a replacement liquid from a liquid feed (6) into the head box (3). The invention further relates to a method for producing a fibrous web (1).

Description

[0001] Plant for producing a width-controlled, wet-laid fiber web, method for producing a width-controlled, wet-laid fiber web

[0002] The invention relates to a system for producing a width-controlled, wet-laid fiber web. Furthermore, the invention relates to a method for producing a width-controlled, wet-laid fiber web.

[0003] Systems for producing wet-laid fiber webs are known. Depending on the requirements, there are different demands on the width of the wet-laid web. One way to reduce the width of the wet-laid fiber web is to trim the edges. If the material from the trimmed edges is not to be discarded but reused, this results in a considerable increase in workload. The fibers from the trimmed edges must be separated and fed back into the headbox.

[0004] If this is to be avoided, the width of the fiber web can be reduced by not introducing the fiber suspension into the headbox across its entire width. However, this results in significant disadvantages with regard to the fluid dynamic properties and the fluid dynamic operation of the headbox.

[0005] It is therefore an object of the present invention to provide a system for producing a width-controlled, wet-laid fiber web and a method for producing a width-controlled, wet-laid fiber web, which prevent the described disadvantages and which offer a simple, cost-effective and sustainable way to regulate the width of the fiber web without causing deviations in the fluid dynamics of the headbox.

[0006] This problem is solved by the subject matter of claim 1 and claim 9.

[0007] The system according to the invention is a system for producing a fiber web. For this purpose, the system comprises a distributor and a headbox, which is designed for wetting fibers to form the fiber web. The distributor can be a transverse distributor. It is also conceivable that the distributor can be a circular distributor. A tube bundle is provided between the distributor and the headbox, through which a fiber suspension is introduced from the distributor into the headbox. According to the invention, a valve is arranged on a plurality of tubes at the lateral edges of the tube bundle, allowing either the passage of the fiber suspension from the distributor into the headbox or the passage of a substitute liquid from a liquid supply into the headbox. In other words, it can be determined for each of the plurality of tubes whether the fiber suspension or the substitute liquid is introduced into the headbox through it.This makes it advantageous to adjust the width of the fiber web without having to accept any fluid dynamic disadvantages.

[0008] It is conceivable that the fibrous suspension is a fibrous foam.

[0009] Pipes within the meaning of the present invention are not limited to rigid pipes. Pipes within the meaning of the present invention can also be hoses. Hoses have the advantage of flexibility over rigid pipes and are potentially easier to connect. Thus, the pipe bundle within the meaning of the present invention is also not limited to consisting solely of rigid pipes. It is conceivable that the pipe bundle comprises one or more hoses or is a bundle of hoses. It is conceivable that the valve is a three-way valve. However, "valve" within the meaning of the present invention can also be understood functionally. For example, it is conceivable that the pipes of the majority of the pipes have a connection for introducing the replacement fluid. The connection could, for example, be a T-piece. A check valve could be installed upstream of the connection in the pipes of the majority of the pipes.If the substitute fluid is fed into the pipes of the majority of the pipes, and the pressure of the substitute fluid is higher than that of the fiber suspension, such an arrangement functions like a three-way valve. It is also conceivable that a two-way valve is provided in the pipes of the majority of the pipes before the connection and / or in the fluid supply. Any other type of valve-like control for selecting between the fiber suspension and the substitute fluid is also conceivable, such as pinch valves on the pipes of the majority of the pipes before the connection and / or pinch valves at the fluid supply.

[0010] The replacement fluid is intended to contain essentially no fibers. However, it is acceptable if the replacement fluid contains a negligible amount of fibers. The replacement fluid can be, for example, fresh water. It is also conceivable that the replacement fluid consists of water discharged from the system, such as from a system drainage system. This discharged water could be, for example, so-called white water, i.e., water containing a negligible amount of fibers. Alternatively, the replacement fluid could consist of other process water from the system's operation and / or clear water, i.e., filtered process water.

[0011] It is conceivable that the replacement fluid is a replacement foam. For example, the replacement fluid could be a replacement fiber foam. In this case, it is conceivable that the fiber concentration, i.e., the number of fibers per unit volume, is lower in the replacement fiber foam than in the fiber suspension.

[0012] If the width of the fiber web is to be reduced, the substitute fluid is introduced into a corresponding number of tubes at the lateral edges of the tube bundle instead of the fiber suspension. The substitute fluid replaces the fiber suspension in the areas where no fibers are to be laid, i.e., in the regions where no fiber web is to be formed. The substitute fluid maintains the carefully controlled fluid dynamics in the headbox. In particular, this eliminates the need to introduce the fiber suspension at the lateral edges without causing significant changes in the pressure distribution and flow conditions in the headbox, and especially directly at the headbox outlet during the fiber laying process.

[0013] It is particularly preferred that a valve is arranged on the lateral edges of the tube bundle on the majority of the tubes, allowing either the passage of the fiber suspension from the distributor into the headbox or the passage of a substitute liquid from a liquid supply into the headbox. In other words, such a valve is not provided on every tube of the tube bundle. This enables particularly cost-effective manufacturing of the system by concentrating on the essential components.

[0014] Preferably, the fiber suspension is provided to contain natural fibers and / or artificial fibers and / or regenerated fibers.

[0015] Advantageous embodiments and further developments of the invention can be found in the dependent claims and in the description with reference to the drawings.

[0016] According to a preferred embodiment of the present invention, the liquid supply comprises a water line. This advantageously makes it possible to introduce water into the headbox as a substitute liquid or to mix it with the substitute liquid before introducing it into the headbox. Water is neutral with respect to the production of the fiber web and does not alter the chemical properties of the fiber web.

[0017] According to a further preferred embodiment of the present invention, the system includes a device for supplying an additional fiber web. The headbox is arranged for wetting the fiber web onto the additional fiber web. It is also conceivable that the system includes a transfer device for laying the additional fiber web onto the existing fiber web. The device for supplying the additional fiber web can, for example, include another headbox for wetting fibers, a device for aerodynamically laying the additional fiber web, a carding unit, or an unwinding device for unwinding the additional fiber web, in particular a carded web, a spunbond layer, or a spunbond layer.The combination of wetting the fiber web with regulating the web width and merging the fiber web with the next fiber web makes it possible to produce a layered structure of a fabric in which the widths of the layers are very precisely matched, excessive trimming is avoided, and by maintaining the desired fluid dynamic properties of the headbox, an excellent quality of the fiber web and thus of the layered structure is ensured.

[0018] It is particularly preferred that the system be configured to adjust the width of the fiber web to the width of the subsequent fiber web by passing the substitute fluid through a corresponding number of pipes on the sides of the tube bundle. It is conceivable that the system includes a process control system for this purpose, which is designed to regulate the valves according to the intended width of the fiber web or the width of the subsequent fiber web.

[0019] According to a further preferred embodiment of the present invention, the system includes a dewatering device for draining the fiber web after wetting, with a liquid supply for feeding water from the dewatering device to the valves. This advantageously makes it possible to reuse water from the system's dewatering device, so-called white water, for use in the liquid supply, thereby reducing the system's operating costs and enabling more sustainable production. For example, the dewatering device could include a suction port located below a screen belt of the system. It is also conceivable that the white water is filtered before being fed to the valves.

[0020] A particularly preferred embodiment of the present invention is one in which means for measuring the pressure and / or volume flow rate of the fiber suspension are provided in the headbox and / or the distributor. The valves are control valves. Alternatively or additionally to the control valves, the system includes a speed-controlled pump for introducing the substitute fluid into the pipes. The system preferably includes a process control system configured to automatically control the control valves and / or the pump depending on the measured pressure and / or volume flow rate of the fiber suspension. This enables very precise and demand-based control of the fluid dynamics in the headbox. Changes in the fluid dynamics in the headbox, particularly changes in the width of the wet web, can affect the pressure and / or volume flow rate.The flow rate is adjusted to ensure optimal wet laying results at all times. The pressure and flow rate are regulated to minimize lateral turbulence between the substitute fluid and the fiber suspension within the headbox. This minimizes mixing of the substitute fluid and fiber suspension, which facilitates precise width control of the wet-laid fiber web. In other words, adjusting the pressure and flow rate prevents the fibers of the fiber suspension from entering the headbox at the lateral edges where the substitute fluid is introduced.

[0021] The pressure or flow rate can be measured on one or both sides of the headbox. Measuring the pressure or flow rate on both sides improves accuracy compared to measuring on only one side. Alternatively or additionally, the pressure or flow rate can be measured in the manifold. The pressure or flow rate of the substitute fluid is set so that, downstream of the valve or the speed-controlled pump, it corresponds to the measured pressure or flow rate plus or minus an offset. This offset is then set so that the pressure or flow rate of the substitute fluid in the headbox essentially matches that of the fiber suspension in the headbox. In practice, a mathematically precise adjustment of the pressure or flow rate is not necessary. Rather, a visual inspection of the edges of the wetted fiber web or...The pressure and / or flow rate of the substitute fluid in the areas adjacent to the edges must be checked to ensure that it is within a range that ensures satisfactory results, i.e., that the width of the fiber web is set within the desired limits. It is particularly conceivable that the pressure and / or flow rate in the distributor could be measured at two spaced-apart positions. This would also provide information about the pressure profile perpendicular to the production direction.

[0022] To adjust the pressure or flow rate of the substitute fluid, one or more additional means for measuring the pressure and / or flow rate of the substitute fluid are preferably provided. Preferably, the one or more additional means for measuring the pressure and / or flow rate of the substitute fluid are provided at the fluid supply, particularly preferably at a central line from which the substitute fluid is distributed to the pipes of the plurality of pipes.

[0023] Preferably, the system includes a speed-controlled pump. The speed-controlled pump is preferably arranged on a central line from which the substitute fluid is distributed to the pipes of the plurality of pipes. Alternatively, the system can also include multiple speed-controlled pumps, with each pipe of the plurality of pipes having its own dedicated pump. This advantageously allows for even finer control of the fluid dynamics within the headbox. Instead of just one speed-controlled pump for the plurality of pipes, or a few speed-controlled pumps for the plurality of pipes, the flow of the substitute fluid through each pipe of the plurality of pipes can thus be individually and precisely controlled.

[0024] According to a further preferred embodiment of the present invention, the system comprises a vortex chamber. The vortex chamber is part of a headbox, specifically the headbox, of the system. A homogenizing device of the system ensures a uniform introduction of the fiber suspension and the substitute liquid into the vortex chamber. The homogenizing device is, in particular, the distributor. The fiber suspension and the substitute liquid are introduced into the vortex chamber in a stream with the tube bundle through inlets on a feed side of the vortex chamber. Each tube of the tube bundle is preferably connected to an inlet. The use of the homogenizing device in conjunction with the tube bundle ensures a homogeneous introduction of the fiber suspension and the substitute liquid into the vortex chamber, although the introduction may be disjoint across multiple sections, but on average over a considerable distance transverse to the direction of the stream.Opposite the feed side, a guide side of the vortex chamber is arranged. The inlets on the feed side are positioned so that the flow is directed towards the guide side. This creates a stagnation point flow, causing the flow to be split into two partial flows. In fact, the flow is divided in a mushroom shape. For simplicity, however, this will be described below using the terms "partial flow" and "partial flow." The transition into the vortex chamber and from the flow to the partial flows introduces a high degree of kinetic energy into the fiber suspension, enabling the fibers to be separated by sufficiently high shear forces and turbulence, thus breaking up the geometric pattern initially introduced by the inlets.In particular, the movement of the fiber suspension appears mushroom-shaped in the stagnation point flow region, resulting in thorough mixing and further homogenization of the fiber suspension. Typically, one or more laminar and non-laminar vortices form, which may extend predominantly across the width or length of the vortex chamber or be locally confined. The interaction of these vortices with one another and the associated mixing of the fibers in the fiber suspension leads to a uniform distribution of the fibers. In particular, large-area transverse vortices occur, which ensure a homogenization of the fiber concentration in the transverse direction and thus prevent longitudinal striation. The energy introduced into the fiber suspension corresponds at most to the Carnot impact loss during an abrupt 90° transition.In addition to the aforementioned advantages regarding stripe formation, this embodiment is particularly advantageous because it requires significantly fewer components than a conventional system for producing a fiber web, making it more cost-effective and requiring less installation space. In particular, no diffusers or moving internal components are required to break up fiber flakes. Despite the turbulence, the introduction of the substitute fluid effectively limits the width of the fiber web.

[0025] Preferably, the fiber suspension and the substitute fluid are introduced into the vortex chamber along an inflow direction. Preferably, the feed side is arranged at an angle of 45° to 135° to the inflow direction.

[0026] It is conceivable that the inlets have cross-sectional enlargements or reductions. It is also conceivable that the inlets are chamfered. This makes it possible to adapt the flow velocity to the conditions in the vortex chamber and the physical parameters of the fiber suspension.

[0027] It is also conceivable that the headbox, in particular the inlets, could have feed lines for diluting the fiber suspension. This would advantageously allow the fiber content of the fiber suspension, and thus the basis weight, to be adjusted locally.

[0028] Preferably, the fiber suspension comprises fibers made of viscose and / or lyocell and / or natural fibers and / or recycled fibers and / or synthetic fibers and / or inorganic fibers such as glass fibers and / or man-made fibers and / or fiber from pulp, northern (bleached) softwood pulp and / or southern (bleached) softwood pulp. It is conceivable that the fiber suspension contains 10–100% man-made fibers.

[0029] According to a preferred embodiment of the present invention, a termination side is arranged between the feed side and the guide side. Opposite the termination side, an outlet side is arranged for directing the fibers out of the vortex chamber. This allows for the advantageous routing of the partial flows through the vortex chamber to the outlet side.

[0030] Preferably, the guiding side has a curved impact area for redirecting the current and / or the termination side is at least partially curved for redirecting the fiber suspension. The curvature forces movement of the fiber suspension in all directions. This generates high shear rates, resulting in excellent fiber separation and mixing. In the context of the present invention, "curved" means that the surface is curved. The surface is, in particular, the surface of the guiding side or termination side facing the interior of the vortex chamber. It is especially preferred that the current impacts the guiding side or termination side at a transition from a non-curved area to a curved area. This is particularly effective, increases the shear rates in the vortex chamber, and prevents dead spaces.

[0031] In particular, it is provided that a portion of the current is directed along the feed side to the outlet side. By splitting the flow of the fiber suspension from the feed side and diverting it along the feed side to the outlet side, dead zones in the vortex chamber and thus the formation of fiber flakes in the vortex chamber are avoided.

[0032] According to a further preferred embodiment of the present invention, a shear rate of at least 10 1 / sec, and preferably at least 50 1 / sec, and particularly at least 100 1 / sec, is generated in the vortex chamber. This ensures optimal separation and mixing of the fibers upon exiting the vortex chamber. Furthermore, the distribution of the exit velocity of the fiber suspension in the MD direction along the CD direction is very uniform and exhibits deviations of preferably less than 5% and particularly preferably less than 2.5%. A deviation of the velocity within the meaning of the present invention is calculated as: (Maximum velocity - Minimum velocity) / Average velocity. A further particular advantage is an isotropic fiber orientation upon exiting the vortex chamber.The aforementioned advantages make it particularly easy to precisely adjust different fiber web strengths in the MD and CD directions. In particular, it is possible to achieve very high strengths in the CD direction. Despite the turbulence, the introduction of the substitute fluid effectively limits the width of the fiber web.

[0033] MD direction, as used in the present invention, is the direction in the machine direction. CD direction, as used in the present invention, is the direction horizontally perpendicular to the machine direction.

[0034] According to a preferred embodiment of the present invention, the end face is at least partially curved. This allows the partial flow to be advantageously directed towards the feed-in side. Sedimentation at the sides is thus prevented.

[0035] According to a further preferred embodiment of the present invention, the distance between the feed side and the guide side decreases towards the outlet side, or the feed side is at least partially arranged such that the distance between the feed side and the guide side decreases towards the outlet side. Reducing this distance accelerates the fiber suspension towards the outlet side, which particularly facilitates the exit of the fiber suspension from the vortex chamber. Furthermore, the turbulence in the fiber suspension is dampened before deposition, resulting in a smoother structure in the final product.

[0036] It is particularly preferred that the feed side and the guide side enclose a first chamber angle. The first chamber angle is between 10° and 45° and preferably between 15° and 25°. This results in optimal outflow of the fiber suspension from the fluidized chamber.

[0037] Furthermore, it is preferably provided that the inlet side and the outlet side enclose a second chamber angle. The second chamber angle is between 90° and 150° and preferably between 100° and 120°. This advantageously ensures high shear rates in the area of ​​the outlet side.

[0038] It is conceivable that the headbox has a back wall, with a discharge gap formed between the underside of the headbox and the back wall. The underside preferably adjoins the guide side of the vortex chamber and is particularly arranged parallel to the guide side of the vortex chamber. However, it is also conceivable that the underside and the guide side are arranged at an angle to each other. The back wall is arranged directly adjacent to the feed side. Preferably, the discharge gap angle between the back wall and the underside is adjustable. For this purpose, the back wall can be adjusted in its distance and / or angle to the underside, in particular by being rotatable about a pivot joint. Furthermore, it is preferably provided that the fiber suspension exits the discharge gap along a discharge direction and that the angle between the discharge direction and a belt on which the fiber suspension is deposited is adjustable.For this purpose, it is particularly provided that the vortex chamber is rotatable with the underside or that the underside is rotatable about an axis which is arranged orthogonally to the outlet direction.

[0039] According to a further preferred embodiment of the present invention, several inlets arranged in a row are provided on the feed side. Preferably, several inlets arranged in two rows are provided on the feed side. The fiber suspension is thus fed to the fluidized bed chamber through several individual sections. It is conceivable that the inlets are connected via the tube bundle to a circular distributor, central distributor, or cross-flow distributor.

[0040] Preferably, the inlet has a diameter of 5 mm to 100 mm, preferably 10 mm to 60 mm, and particularly 15 mm to 25 mm. It is conceivable that each of the inlets has a diameter of 5 mm to 100 mm, preferably 10 mm to 60 mm, and particularly 15 mm to 25 mm.

[0041] According to a further preferred embodiment of the present invention, the headbox has no open edges, in particular no inlet openings for diffusers, perforated rollers and / or lamellae. This ensures that the device is very cost-effective, requires little maintenance and saves installation space.

[0042] Alternatively, it is preferably provided that the headbox has a diffuser. This advantageously makes it possible to swirl the fiber suspension in multiple stages.

[0043] A further object of the present invention for solving the aforementioned problem is a method for producing a fiber web. A fiber suspension is fed from a distributor through a tube bundle to a headbox and from the headbox to the fiber web, where it is wetted. By controlling valves on a plurality of tubes of the tube bundle at the sides of the tube bundle of the headbox, either the fiber suspension or a substitute fluid is selectively supplied. The width of the fiber web is adjusted by feeding the substitute fluid into the headbox through more or fewer tubes of the tube bundle instead of the fiber suspension. The inventive method for producing the fiber web advantageously enables flexible adjustment of the width of the produced fiber web while maintaining the desired fluid dynamic properties of the headbox.In particular, it is intended that the process will be carried out using a system according to the invention.

[0044] According to a further preferred embodiment of the present invention, the fiber web is laid on top of another fiber web, or another fiber web is laid on top of the fiber web, whereby the width of the fiber web is adapted to the width of the other fiber web. Adjusting the width of the fiber web by introducing the substitute fluid into a corresponding number of tubes of the plurality of tubes makes it possible to avoid at least significant trimming of the fiber web and to ensure high fiber web quality by maintaining the desired fluid dynamic properties in the headbox.

[0045] A particularly preferred embodiment of the present invention is one in which the fiber web is dewatered by a dewatering device after wetting. In this embodiment, water from the dewatering device is supplied as a replacement fluid through the valves of the headbox. This preferred embodiment advantageously allows water to be reused, thereby reducing process costs and making the operation of the system more sustainable.

[0046] According to a further preferred embodiment of the present invention, the pressure and / or volume flow rate of the fiber suspension in the headbox and / or distributor is measured. The substitute fluid is introduced into the plurality of pipes by means of control valves and / or at least one speed-controlled pump. The control valves and / or the pump are controlled based on the measured pressure and / or the measured volume flow rate. This advantageously adapts the fluid dynamics in the headbox to the required conditions, thus ensuring the production of a wide variety of fiber web widths while maintaining consistently high quality.

[0047] According to a further preferred embodiment of the present invention, the fiber suspension and the substitute fluid are introduced into a vortex chamber of a system according to the invention. The flow of the fiber suspension and the substitute fluid is divided in the vortex chamber into a partial flow and a further partial flow. The fiber suspension is then discharged at the outlet side of the vortex chamber.

[0048] In particular, it is provided that a shear rate of at least 10 1 / sec, preferably at least 50 1 / sec, and especially at least 100 1 / sec, is generated throughout the entire vortex chamber. This ensures optimal separation and mixing of the fibers of the fiber suspension upon exiting the vortex chamber.

[0049] Preferably, the fiber suspension is introduced into the vortex chamber in a continuous flow, and the flow is split and redirected at the conducting side into two partial flows. The latter flows along the conducting side towards the outlet, and the former flows along the terminal side to the inlet side and then along the inlet side towards the outlet. This eliminates dead spaces. High shear rates prevail throughout the vortex chamber.

[0050] In particular, it is intended that the fiber suspension, after leaving the vortex chamber, is deposited on an inclined screen or a long screen and / or on the further fiber layer.

[0051] All details, features, and advantages previously disclosed in connection with the first described system according to the invention also apply to the method according to the invention, and vice versa. Further details, features, and advantages of the invention will become apparent from the drawings and from the following description of preferred embodiments with reference to the drawings. The drawings merely illustrate exemplary embodiments of the invention, which do not limit the inventive concept.

[0052] They show:

[0053] Fig. 1: a schematic view of part of a system according to an exemplary embodiment of the present invention,

[0054] Fig. 2: a schematic view of a plant according to an exemplary

[0055] embodiment of the present invention,

[0056] Fig. 3: a schematic view of a detail of a system according to an exemplary embodiment of the present invention,

[0057] Fig. 3: a schematic view of a detail of a system according to an exemplary embodiment of the present invention and

[0058] Fig. 4: a schematic view of a detail of a system according to an exemplary embodiment of the present invention.

[0059] Figures 1 and 2 show a system 100 according to an exemplary embodiment of the present invention. The system 100 is designed for producing a fiber web 1.

[0060] For this purpose, the system 100 includes a headbox 3. A fiber suspension is fed to the headbox 3 from a distributor 2, which acts as a leveling device, via a tube bundle 4. In the embodiment shown here, the distributor 2 is designed as a transverse distributor. Alternatively, however, the distributor 2 can also be a circular distributor. The fiber suspension comprises a fiber-water mixture. To produce the fiber web 1, the fibers are wet-laid, that is, the fiber suspension (shown as arrows in Fig. 1) is laid from the headbox 3 onto a belt 12, which moves in the material transport direction W.

[0061] A further fiber web 8 is arranged between fiber web 1 and tape 12. Fiber web 1 is therefore not laid directly onto tape 12, but rather onto the further fiber web 8. In the illustrated embodiment, the further fiber web 8 is a carded fiber web. A carding unit 11 is provided for producing the further fiber web 8. However, it is also conceivable that the further fiber web 8 is laid wet, for example, analogous to fiber web 1, that the further fiber web is fed from a winding device of the system 100, or that the further fiber web 8 is laid aerodynamically.

[0062] Although this illustration shows that fiber web 1 is laid onto the further fiber web 8, it is also conceivable that the further fiber web 8 is laid onto fiber web 1. It is also conceivable that (not shown) additional fiber webs are arranged above and / or below fiber web 1 and / or the further fiber web 8. In the embodiment shown here, fiber web 1 is a P-layer. The further fiber web 8 is a C-layer. After fiber web 1 is laid onto the further fiber web 8, both form a PC web. However, as previously described, CP, PP, CCP, CPC, PCC, PPC, CCP, and CPP webs, as well as other combinations of different layers, are also conceivable, as long as they include a P-layer.

[0063] Especially with multi-layered webs, such as the PC web shown here, consisting of fiber web 1 and another fiber web 8, a difficulty arises in adjusting the width of fiber web 1 to that of the other fiber web 8. Fiber web 1 can be cut to size at the edges if it is wider than the other fiber web 8. However, this approach is material-intensive and therefore expensive to operate.

[0064] Another way to adjust the width of the fiber web 1 is to introduce fiber suspension only partially across the entire width of the headbox 3. The disadvantage here is that the fluid dynamic conditions in the headbox 3 change if the fiber suspension is no longer introduced across the entire width. The illustrated system overcomes this problem by providing valves 5 on a majority of the tubes 4.1 at the sides of the tube bundle 4. The valves 5 allow either fiber suspension from the distributor 2 or a substitute fluid to be supplied to the headbox 3. Thus, the width of the fiber web 1 can be adjusted by allowing the substitute fluid, instead of the fiber suspension, to flow into the headbox 3 through more or fewer of the majority of the tubes 4.1 at the sides of the tube bundle 4.By introducing the substitute fluid, the fluid dynamics remain essentially unchanged, just as they would be if fiber suspension were introduced across the entire width. This allows for significant trimming to be avoided with highly flexible width adjustments, and ensures consistently high quality through reliably controlled fluid dynamics in the Headbox 3.

[0065] The headbox 3 and the distributor 2 are equipped with means for measuring pressure and / or volume flow 14. A process control system 10 uses the measurement data from these means to monitor the production of the fiber web 1 and, in particular, the situation in the headbox 3. Depending on the measurement data, the process control system 10 controls the injection of the substitute fluid into the headbox 3. This is made possible by the fact that the valves 5 are designed as control valves and / or that the system includes a speed-controlled pump 9 for introducing the substitute fluid into the headbox 3. In the illustrated embodiment, the system has 100 control valves and, additionally, a speed-controlled pump 9 on a central line, from which the substitute fluid is distributed to the pipes of the majority of pipes 4.1.

[0066] The pressure of the substitute fluid is controlled so that the substitute fluid in headbox 3 has essentially the same pressure as the fiber suspension in headbox 3. This reduces mixing of the substitute fluid and fiber suspension in the headbox. To improve the control of the substitute fluid pressure, an additional means for measuring the pressure 15 of the substitute fluid is provided at a central line that supplies the fluid feed.

[0067] In the present embodiment, the belt 12 is designed as a screen belt. A dewatering device 13 is arranged below the belt 12, which drains water from the laid fiber web 1, here through the further fiber web 8. The dewatering device 13 could, for example, have a suction box. The drainage of the water results in the formation of a stable fiber web 1. It is conceivable that the fiber web 1 and / or the further fiber web 8 are compacted and / or consolidated in the following process steps (not shown). All common compaction and consolidation methods, such as pressure rolling or water jet forming, are conceivable.

[0068] A central line, in this case a water line 7, leads from the drainage device 13 to the liquid supply 6. Water from the drainage device 13 flows through the water line 7 to the liquid supply 6. The water from the drainage device 13 serves as a replacement liquid. This reuse of the water extracted from the fiber web 1 makes the described process even more economical and sustainable.

[0069] The fiber suspension is a mixture of water and fibers, for example, natural or synthetic fibers. Lying on belt 12, the fiber suspension is dewatered by the dewatering device 13, for example, with suction boxes. The fibers can consist of viscose and / or lyocell. It is conceivable that the fibers are natural fibers and / or recycled fibers and / or synthetic fibers and / or inorganic fibers such as glass fibers and / or man-made fibers and / or fiber from pulp, northern (bleached) softwood pulp and / or southern (bleached) softwood pulp. It is conceivable that the fiber suspension contains 10–100% man-made fibers.

[0070] The system 100 includes the distributor 2, from which the fiber suspension is fed to a vortex chamber 16 of the headbox 3 via the tube bundle 4. The tube bundle 4 is connected to the vortex chamber 16 via inlets 22 such that the fiber suspension flows into the vortex chamber 16 in a stream A at a feed side 17 of the vortex chamber 16. The inlets 22 are preferably connected in one or more (not shown) rows, which here extend orthogonally to the plane of the sheet. The inlet 22, and preferably all inlets, have a diameter of 10 mm to 100 mm. A guide side 18 of the vortex chamber 16 is arranged opposite the feed side 17. The stream A is directed towards the guide side 18, resulting in a stagnation point flow and thus a division of the stream A into a partial stream B and a further partial stream C.

[0071] Upon entry of the fiber suspension into the vortex chamber 16 and during the division of the flow A, high shear forces and turbulence occur, which separate and mix the fibers of the fiber suspension. This breaks up fiber clumps, leading to a more uniform basis weight of the fiber web. Furthermore, transverse turbulence occurs in the vortex chamber 16. This transverse turbulence mixes the fibers, particularly in the CD direction, thus preventing longitudinal striations that would otherwise have resulted from the arrangement of the disjoint inlets 22.

[0072] To maintain high shear forces in the vortex chamber 3, the incoming flow A of the fiber suspension first encounters an impact zone 19 on a guide side 18 opposite the feed side 17. At the impact zone 19, the flow A is split into partial flow B and partial flow C and redirected. A termination side 20 connects the guide side 18 and the feed side 17. The guide side 18 and / or the termination side 20, preferably both, have a curvature. Partial flow B flows from the impact zone 19 along the curvature past the termination side 20. Subsequently, partial flow B is directed along the feed side 17 to an outlet side 21. The outlet side 21 is located opposite the termination side 20. High shear forces are maintained throughout the entire vortex chamber 16, preventing the individual fibers from clumping together again.For this purpose, the device 1 is designed to generate a shear rate of at least 10 1 / sec, preferably at least 50 1 / sec, and particularly at least 100 1 / sec, throughout the entire vortex chamber 16. A discharge gap 25 adjoins the outlet side 21 and is formed by a rear wall 23 and a bottom surface 24 of the headbox 3. The fiber suspension is deposited onto the belt 12 through the discharge gap 25.

[0073] The end face 20 is partially curved and connects with a smooth contour to the curved impact area 19 of the guide face 18. The feed face 17 and the guide face 18 are not parallel to each other. Rather, the distance between the feed face 17 and the guide face 18 decreases towards the outlet face 21. Here, the feed face 17 and the guide face 18 form a first chamber angle β of 15° to 25°. The reduction in the distance between the guide face 18 and the feed face 17 towards the outlet face 21 causes the fiber suspension to accelerate on its way to the outlet gap 25. To increase the shear rates, the feed face 4 and the end face 20 form a second chamber angle β of 100° to 120°.

[0074] The discharge gap 25, in particular a discharge gap angle y between the back wall 23 and the underside 24, is adjustable by rotatably connecting the back wall 23 to a pivot joint 26. By means of a rocker arm 27, the back wall 23 can be rotated on the pivot joint 26 about an axis of rotation, which here is arranged orthogonally to the plane of the paper. This allows the discharge gap angle y, and thus the discharge gap 25, to be increased or decreased as required.

[0075] In its described configuration, the outlet gap 25 serves to dampen the turbulence generated in the vortex chamber 16. This makes it possible to obtain a very uniform fiber distribution in the manufactured fiber web.

[0076] List of reference signs:

[0077] 1 fiber web

[0078] 2 distributors

[0079] 3 Headbox

[0080] 4 tube bundles

[0081] 4.1 Plurality of pipes

[0082] 5 valve

[0083] 6. Liquid supply

[0084] 7 Water pipe

[0085] 8 more fiber webs

[0086] 9 pump

[0087] 10 Process control system

[0088] 11 carding units

[0089] Volume 12

[0090] 13 Drainage device

[0091] 14 Means for measuring pressure and / or volume flow

[0092] 15 other means for measuring pressure and / or volume flow

[0093] 16th cervical chamber

[0094] 17 Feed-in side

[0095] 18 Main page

[0096] 19 Impact area

[0097] 20 Final page

[0098] 21 Outlet side

[0099] 22 Admission

[0100] 23 Back panel

[0101] 24 Underside

[0102] 25 outlet gap

[0103] 26 Swivel joint

[0104] 27 Swingarm

[0105] 100 plant

[0106] A current

[0107] B Partial current

[0108] C further partial flow

[0109] W Goods transport direction Y Outlet gap angle

Claims

Patent claims:

1. Plant (100) for manufacturing a fiber web (1) comprising a distributor (2) and a headbox (3) for wetting fibers to form the fiber web (1), wherein a tube bundle (4) for introducing a fiber suspension from the distributor (2) into the headbox (3) is provided between the distributor (2) and the headbox (3), wherein a valve (5) for selectively passing the fiber suspension from the distributor (2) into the headbox (3) or passing a substitute liquid from a liquid supply (6) into the headbox (3) is arranged on a plurality of tubes (4.1) at the lateral edges of the tube bundle (4).

2. System (100) according to claim 1, characterized in that the liquid supply (6) comprises a water line (7).

3. System (100) according to one of the preceding claims, characterized in that the system (100) comprises a device for providing a further fiber web (8), wherein the headbox (3) for wetting the fiber web (1) is arranged on the further fiber web (2) or wherein the system (100) has a transfer device for depositing the further fiber web (8) onto the fiber web (1).

4. System (100) according to claim 3, characterized in that the system (100) is configured to adapt the width of the fiber web (1) to the width of the further fiber web (8) by passing the substitute fluid through a corresponding number of tubes on the sides of the tube bundle (4).

5. Plant (100) according to claim 3 or 4, characterized in that the device for providing the further fiber web (8) comprises a carding unit (11) or an unwinding device for unwinding a carded fiber web or a spunbond layer, preferably a spunbond layer.

6. Plant (100) according to one of the preceding claims, characterized in that the plant (100) has a drainage device (10) for draining the fiber web (1) after wetting, wherein the liquid supply (6) is provided for supplying water from the drainage device (10) to the valves (5).

7. System (100) according to one of the preceding claims, characterized in that means for measuring a pressure and / or a volume flow rate (14) of the fiber suspension are provided in the headbox (3) and / or in the distributor (2), wherein the valves (5) are control valves and / or the system (100) has a speed-controlled pump (9) for introducing the substitute fluid into the pipes, wherein the system (100) preferably has a process control system (10), wherein the process control system (10) is configured to automatically control the control valves and / or the pump (9) depending on the measured pressure and / or the volume flow rate of the fiber suspension.

8. System (100) according to claim 7, characterized in that the system (100) has a speed-controlled pump (9) or a plurality of speed-controlled pumps (9), wherein each pipe of the plurality of pipes is assigned its own pump (9) of the plurality of speed-controlled pumps (9).

9. Plant (100) according to one of the preceding claims, characterized in that the headbox (3) has a vortex chamber (16), wherein the tube bundle (4) is provided for introducing the fiber suspension in a stream through inlets (22) on a feed side (17) of the vortex chamber (16), wherein a guide side (18) is arranged opposite the feed side (17) such that a stagnation point flow of the stream (A) is created, wherein the stream (A) is divided into a partial stream (B) and a further partial stream (C).

10. System (100) according to claim 9, characterized in that a termination side (20) is arranged between the feed side (17) and the guide side (18), wherein an outlet side (21) for discharge of the fiber suspension from the vortex chamber (16) is arranged opposite the termination side (20), wherein it is preferably provided that the The guide side (18) has a curved impact area (19) for diverting the current (A) and / or the end side (20) is at least partially curved and in particular at least partially arc-shaped for diverting the fibrous suspension.

11. Method for producing a fiber web (1), wherein a fiber suspension is conveyed from a distributor (2) through a tube bundle (4) to a headbox (3) and wetted from the headbox (3) to the fiber web (1), wherein by controlling valves (5) on a plurality of tubes of the tube bundle (4) on the sides of the tube bundle (4) to the headbox (3) selectively the fiber suspension or a substitute liquid is supplied, wherein the width of the fiber web (1) is adjusted by conveying the substitute liquid instead of the fiber suspension into the headbox (3) through more or fewer tubes of the tube bundle (4).

12. Method according to claim 11, characterized in that the fiber web (1) is placed on a further fiber web (8) or that a further fiber web (8) is placed on the fiber web (1), wherein the width of the fiber web (1) is thereby adapted to the width of the further fiber web (8).

13. Method according to one of claims 11 to 12, characterized in that the fiber web (1) is dewatered after wetting by a dewatering device (13), wherein water from the dewatering device (13) is supplied as a substitute liquid through the valves (5) of the headbox (3).

14. Method according to one of claims 11 to 13, characterized in that a pressure and / or a volume flow rate of the fiber suspension is measured in the headbox (3) and / or in the distributor (2), wherein the substitute fluid is introduced into the plurality of pipes by means of control valves and / or by at least one speed-controlled pump (9), wherein the control valves and / or the pump (9) are controlled on the basis of the measured pressure and / or the measured volume flow rate.

15. Method according to one of claims 11 to 14, characterized in that fibrous suspension is introduced into a vortex chamber (16) of a system (100) according to one of claims 9 to 10, wherein the flow (A) of the fibrous suspension in the vortex chamber (16) is divided into a partial flow (B) and a further partial flow (C) and wherein the fibrous suspension is discharged at the outlet side (21) of the vortex chamber (16), wherein preferably a shear rate of at least 10 1 / sec, preferably at least 50 1 / sec and in particular at least 100 1 / sec is generated in the entire vortex chamber (16).

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