Method and machine for producing a dry-laid fibrous web

Abstract

The invention relates to a method for producing a fibrous web (309), preferably a tissue, paper or cardboard web or a nonwoven web, in particular a tissue web having a weight per unit area of 28g / m² to 42g / m², comprising the following steps: a) processing raw material of cellulose-containing fibres (200) to form individual fibres and / or fibre bundles (209); b) forming the individual fibres and / or fibre bundles (209) in an air flow to form a flat laid scrim (300) on a forming belt (40) by means of a dry forming method; c) applying a fluid, preferably water and / or a water-additive mixture, to the laid scrim (300); d) solidifying the flat laid scrim (300) by applying pressure in at least one press gap (80, 83, 84); wherein the laid scrim (305) is received by a transfer belt (103) in a transfer region after solidification and is pre-dried in the transfer region by means of at least one pre-drying device (11) before the pre-dried laid scrim (305) is dried in a drying device (10).

Description

[0001] Method and machine for producing a dry-elasticated fiber web

[0002] The invention relates to a method for producing a fibrous web, preferably a tissue, paper or cardboard web or a nonwoven web, in particular a tissue web with a basis weight of 28g / m². 2 up to 42g / m² 2 , comprising the following steps: a) low-water raw material preparation of cellulose-containing fibers into individual fibers and / or fiber bundles; b) forming the individual fibers and / or fiber bundles in an air stream into a flat fiber fabric on a forming belt by a dry forming process, preferably by means of at least one application device; c) application of a fluid, preferably water and / or a water-additive mixture, onto the fiber fabric; d) solidifying the flat fiber fabric by applying pressure and / or, in particular, temperature in at least one pressing gap.

[0003] Many fibrous webs, especially paper, cardboard, or tissue, were and still are produced almost exclusively using the wet process on an industrial scale. For this process, unless recycled paper is used, baled pulp is typically dissolved in large quantities of water in a vat, resulting in a fiber suspension consisting of approximately 99% water by weight and only about 1% fiber by weight. This fiber suspension is then applied to a forming wire via a headbox to form sheets. The resulting fibrous web is subsequently dewatered or dried by pressure and heat until it can be wound up or otherwise processed. The wet process has the advantage that hydrogen bonds form between the individual fibers during dewatering or drying, giving the fibrous web the necessary strength.However, a disadvantage of this process is that large amounts of energy are required to dry the fiber web. Especially in light of current climate change, there is therefore an intensive search for alternatives to this traditional wet process.

[0004] As an alternative to the wet process, the dry air-laying process is already known, in which fibers are laid down to form a fiber web in a largely dry state. To give the fiber web a certain degree of strength, small amounts of water (to form hydrogen bonds) and / or other binders are added. This results in significantly less energy being required for drying.

[0005] The embodiment shown in Figure 3 in publication WO 2019 / 137667 A1 already discloses a generic method, described above, for producing a dry-formed fiber web. In this process, fibers are first laid onto a forming belt to form a flat fiber mat using a dry forming process. The fiber mat is then transferred from the forming belt to a press belt. The press belt transports the fiber mat to a press gap formed by two rollers, through which the press belt and the fiber mat pass. The fiber mat is compressed in the press gap, thereby increasing its strength.

[0006] In the prior art manufacturing process, the energy savings required for producing fiber webs have not yet been satisfactorily resolved. Further energy savings or improvements in drying efficiency are particularly desirable with regard to drying performance. It would be advantageous if these energy savings did not adversely affect the strength of the fiber web. In particular, it is desirable that improvements in energy savings for drying performance are not achieved primarily by reducing the amount of applied fluid, as this can affect the strength of the fiber web. Therefore, the object of the present invention is to provide a method and a machine for producing a dried fiber web, especially a tissue web, which solves or at least reduces the problems described above.In particular, the aim is to enable the production of fiber webs with increased drying energy efficiency compared to known manufacturing methods, ideally without reducing the strength of the fiber webs. Furthermore, the present invention aims to improve the control and regulation of the drying process. In this respect, achieving a more homogeneous drying result would be desirable.

[0007] The problem described above is solved by the features of the independent claims. The dependent claims relate to advantageous embodiments of the present invention.

[0008] In particular, the problem is solved by a generic manufacturing process described above, which is characterized in that the fiber fabric, after consolidation, preferably in a final press gap in the machine direction (MD), is picked up by a transfer belt in a transfer area and is pre-dried in the transfer area by means of at least one pre-drying device before the pre-dried fiber fabric is dried in a drying device.

[0009] This method offers the particular advantage that pre-drying the fiber fabric before drying it in the dryer unit results in increased drying energy efficiency. During pre-drying in the transfer area, a large portion of the moisture can be removed from the fiber fabric, meaning that less residual moisture needs to be removed in the dryer unit. This leads to increased efficiency, especially in the subsequent dryer unit, as it can dry the fiber fabric with its lower moisture content more efficiently.

[0010] A further advantage of this process is that pre-drying allows for a more uniform distribution of residual moisture within the fiber fabric. This prevents particularly dry areas in the final product. In this context, pre-drying also enables better adjustment and adaptation of the overall drying process, as the fiber fabric can be prepared for passage through the dryer during the pre-drying stage. This also helps to avoid over-drying.

[0011] Furthermore, this method offers the advantage that different temperature profiles can be set or applied during pre-drying and drying in the dryer, if required. This allows for different temperatures to be used at different drying stages, for example, to protect sensitive materials and, in particular, to operate more energy-efficiently.

[0012] The fiber fabric is picked up by the transfer belt in the transfer section, which then transports the already compacted fiber fabric to a further processing unit, preferably a drying screen. Therefore, after passing through the press gap, the fiber fabric is transported, for example, hanging upside down, on the conveying section of the transfer belt. The fiber fabric is also referred to as compacted fiber fabric because it has already passed through at least one press gap before entering the transfer section. Vacuum devices can be provided in the screen loop or belt loop of the transfer belt to facilitate the upside-down transport of the fiber fabric. These vacuum devices, for example, so-called vacuum boxes, serve, among other things, to hold the fiber fabric against gravity on the transfer belt.Furthermore, vacuum media in the sieve loop of the transfer belt are advantageous when a fluid is applied to the side of the further consolidated fiber fabric facing away from the transfer belt. The transfer area can therefore be understood as at least the area in which the fiber fabric is held by the transfer belt.

[0013] It should be noted here that in mechanical engineering, the term "Trum" regularly refers to a part or branch of a rotating component. In particular, the terms "loaded run" and "slack run" for belts that transmit tensile forces are common in mechanical engineering. For the purposes of the present invention, the term "Trum" is used specifically to describe the section of a covering or belt that transports the fiber fabric.

[0014] Preferably, the transfer conveyor can pick up the compacted fiber fabric shortly behind the press gap and, in particular, transfer it to a drying screen on which the compacted fiber fabric is dried or fed into the drying unit. For this purpose, the transfer conveyor and the drying screen are preferably both guided substantially parallel to the displacement direction of the fiber fabric over a certain length. By guiding the two parallel components over the corresponding length, the fiber fabric is given sufficient time, even at high production speeds, to detach from the transfer conveyor and adhere to the drying screen. "Substantially parallel" here means that any angular deviation, if measurable at all, should be very small, in particular less than 5°, preferably less than 3°, and even more preferably less than 1°.

[0015] A press gap is preferably formed by two rollers. The surface materials of the two rollers should be designed to withstand sufficiently high compressive forces on the fiber fabric. In particular, the material for this purpose can be a metallic material, such as steel, and / or a ceramic material. A pre-drying device is a component designed for pre-drying the fiber fabric. For example, a pre-drying device can generate heat and introduce it into the fiber fabric or direct a heat flow, such as an airflow, to the fiber fabric. This allows the fiber fabric to be pre-dried before entering the drying device. A pre-drying device can be designed, for example, as an electric fan, an infrared heater, or a heated electric fan.

[0016] For example, several pre-drying devices can be arranged along the transfer conveyor. In particular, one or more pre-drying devices can be arranged in such a way as to enable homogeneous and uniform pre-drying of the fiber layup. For example, one or more pre-drying devices can be arranged on the side of the fiber layup opposite the strand. However, it is also possible for one or more pre-drying devices to be arranged on the same side of the fiber layup as the strand. In the case of an overhead suspended fiber layup, the pre-drying device would, for example, be arranged in the conveyor loop.

[0017] The fiber layup can be moistened in the transfer area. The transfer belt or transfer area can thus be advantageously used, for example, to apply a fluid to the side of the further consolidated fiber layup facing away from the transfer belt while the fiber layup is being transferred. Furthermore, it can be advantageous to apply wet-strength agents to the fiber layup after the press gap. Wet-strength agents serve to impart a degree of mechanical strength—albeit limited—to the fiber web, particularly tissue webs, even when wet. Without wet-strength agents, the fiber web would lose its internal cohesion due to the breaking of hydrogen bonds upon exposure to water. In their processed state, wet-strength agents are generally water-soluble polymers, primarily made from polyamides and epichlorohydrin derivatives, which react with the fibers.This process creates water-insoluble cross-links between the fibers, which stabilize the fiber web. Dry-strength agents, on the other hand, primarily serve to further increase the strength of the fiber web, especially tissue webs, in its dry state. A well-known and relatively inexpensive dry-strength agent is starch, particularly cationic starch. However, there are also chemical dry-strength agents, such as sodium carboxymethylcellulose (CMC). For this reason, application devices can be provided in the transfer area, which can be designed, for example, as nozzle applicators. Such application devices can spray a fluid onto the fiber web in the form of a spray jet consisting of individual small fluid droplets. Alternatively, the application devices can also be designed so that the fluid is applied in the form of foam, mist, or vapor.Application devices can, for example, be arranged on the core side of the fiber fabric or, in particular, on the side of the fiber fabric facing away from the core.

[0018] The transfer belt can be cleaned. Wet-strength agents that have not yet dried, and to some extent also dry-strength agents, typically tend to contaminate or adhere to the surfaces of machine parts with which they come into contact. For this reason, wet-strength agents should preferably be applied to the fiber web only after the last press gap of the manufacturing process or machine, in order to protect the elements, especially rollers that form a press gap, from contamination. To ensure that the fiber layup is picked up and released from the transfer belt, the transfer belt can therefore be cleaned, preferably in the transfer area and / or in a deflected section. For this purpose, application devices and / or compressed air cleaners can be provided, for example. The at least one pre-drying device can direct an airflow to the fiber layup in the transfer area to pre-dry it.For example, a pre-drying device designed as an electric fan can be configured to direct an airflow to the fiber fabric. This airflow can then be used to pre-dry the fabric. For instance, the airflow can pre-dry the fabric by means of convection drying. Advantageously, the air in the airflow can already have a certain level of moisture content when the pre-drying device draws it in or exhausts it.

[0019] The airflow can be humidified and / or heated before being directed to the fiber mat. Therefore, the efficiency of pre-drying can be improved by both humidifying and heating the airflow. Warm air can thus absorb more moisture convectively from the fiber mat. Furthermore, warm air introduces more energy into the fiber mat, leading to improved evaporation. Due to the high specific heat capacity of water, humid air can also introduce more energy into the fiber mat, further enhancing evaporation. It can therefore be advantageous to both heat and humidify the airflow. Additionally, it can be beneficial to draw in or exhaust already warm and / or humid air for the airflow.For this purpose, heating coils, humidifiers and / or burners can be arranged in one or more pre-drying devices.

[0020] The airflow can be discharged from the dryer. Discharge is particularly advantageous because it warms the airflow and humidifies it upon intake. As previously described, this leads to improved pre-drying efficiency. Furthermore, pre-drying using an airflow discharged from the dryer can improve the overall energy efficiency of the system. For example, waste heat from the dryer can also be used to heat the airflow.

[0021] It may be possible to divert up to 100%, in particular up to 50%, preferably up to 25%, of the airflow from the dryer device into the pre-drying stage.

[0022] Furthermore, a dynamic control system can be provided that adjusts the proportion of the redirected airflow to the requirements of the pre-drying process. For example, a measuring device can be provided after and / or before the pre-drying process, based on which the relevant parameters of the fiber web or fiber fabric are recorded and the control system is adjusted accordingly.

[0023] The airflow can be directed to the side of the fiber mat facing away from the conveyor belt. Advantageously, this allows the heat transported by the airflow to be directed directly onto the fiber mat, thus contributing entirely to its pre-drying. If the heat flow is directed to the side of the conveyor belt, heat from the airflow is also, or even more so, transferred into the conveyor belt itself, resulting in less heat being available for evaporating moisture and thus for pre-drying.

[0024] The fiber fabric can be pre-dried by infrared radiation using at least one pre-drying device designed as an infrared emitter. Designing at least one pre-drying device as an infrared emitter can be advantageous because infrared emitters can be controlled or switched on at short notice. This allows the pre-drying capacity to be adjusted to the respective process parameters during the process. Furthermore, infrared emitters can be precisely aligned, thus ensuring homogeneous pre-drying. Infrared emitters are also energy-efficient. It is also advantageous to combine infrared radiation with an airflow for pre-drying. Immediately before being picked up by the transfer conveyor, the fiber fabric can be passed unsupported through a press gap for consolidation by pressure and / or temperature.In an alternative embodiment, the press gap is a final press gap through which the fiber fabric is consolidated before it is picked up by the conveying belt. Higher pressure during the consolidation of the fiber fabric can tend to lead to greater strength in the final product. When the fiber fabric is guided through a press gap with support, the conveying belt, which is usually made of plastic threads, can only withstand limited pressure without deforming. Therefore, higher pressure can be applied when the fiber fabric is guided through the press gap unsupported, i.e., without a tensioning device such as the conveying belt.

[0025] The fiber fabric can be transferred from the conveyor belt to a drying screen, where it is dried. A drying screen can also provide additional mechanical drying of the fiber fabric before it enters the drying unit. In this way, moisture can be removed from the fiber fabric by gravity alone. Furthermore, a drying screen ensures optimal drying of the fiber fabric within the drying unit.

[0026] After consolidation in a transfer area, the fiber fabric can be picked up by a pre-positioned, preferably inverted, second transfer belt and pre-dried in the transfer area by means of a second pre-drying device before the pre-dried fiber fabric is picked up by the transfer belt and pre-dried by the at least one pre-drying device, and then dried in the dryer device.

[0027] In an alternative design, the transfer belt is mirrored on an MD-CD plane as an inverted transfer belt with a pre-drying device, so that the fiber web or fiber fabric is supported on the transfer belt and experiences a force towards the transfer belt due to its gravity.

[0028] In this design, a transfer to the dryer device with drying screen can take place in a single, free pass without any additional components.

[0029] Alternatively, in this design, a transfer to the dryer unit with a drying screen can be provided using an additional transfer belt, analogous to the old design of the transfer belt without a pre-dryer. This additional transfer belt, following the inverted transfer belt with pre-dryer, picks up the suspended fiber web by vacuum and transfers it to the dryer unit.

[0030] In the alternative embodiment with three transfer belts, wherein one transfer belt is equipped with a pre-drying device and is inverted, it can also be provided that the transfer belts are only provided at the edge, so that only the edge area is transferred instead of the entire fiber web width.

[0031] The transfer belt can be guided over at least three, in particular four, in particular five or more, deflection rollers. This allows the length of the transfer belt, including the section transporting the fiber fabric, as well as a space arranged within the transfer belt, to be geometrically defined in such a way that devices can be arranged therein or along the section of the transfer belt transporting the fiber fabric, which serve to treat the fiber fabric during its transfer or interact with it.

[0032] One of the deflection rollers regulates the web path, and with at least three deflection rollers, sufficient installation space can be created for additional devices.

[0033] Possible additional devices include, for example, devices for dry and / or wet cleaning of the screen or mesh. Alternatively or additionally, the additional devices can be further drying devices or pre-drying devices and / or extraction devices.

[0034] Advantageously, this allows for stabilization of the web guidance and / or rapid cleaning in case of contamination by additives during an application, and / or, when a pre-drying stage is integrated, the additives are not transferred into the drying unit and / or the contamination is prevented from drying onto the drying screens of the drying unit. This is particularly crucial for a consistently high production rate at machine speeds of 400 m / min or higher.

[0035] In the alternative embodiment, water is applied to one side of the fiber lay-up in the machine direction before a final press gap by means of a first application device.

[0036] In the alternative embodiment, in the machine direction, after a final press gap and before the pre-drying device, an application of a water-additive mixture is carried out on a first side of the fiber layup by means of a second application device; and in particular, the application is carried out by means of the second application device in the transfer area on the transfer belt.

[0037] In the alternative embodiment, after a final press gap, the application of the water-additive mixture is carried out against gravity in the machine direction using the second application device.

[0038] In the alternative embodiment, a dryer with a drying screen is arranged in the machine direction after a final press gap and after the transfer area, and the fiber fabric is laid down onto the drying screen from the transfer belt with its first side facing down. In the alternative embodiment, after application by the second application device, a water-additive mixture is applied to the second side of the fiber fabric opposite the first side by means of a third application device in the machine direction.

[0039] In the alternative embodiment, after the last press gap, the second application device applies in a first application direction in the machine direction, and the third application device applies in a second application direction opposite to the first application direction.

[0040] The application of a water-additive mixture after the last press gap and before the pre-drying device is advantageous with regard to the contamination of the last press gap and also of the subsequent connecting belt as well as the drying screen of the dryer device.

[0041] A particular advantage of the inventive method and machine is to enable the application of a water-additive mixture to both sides of the fiber fabric with reduced contamination of components such as the support elements over which the fiber fabric applied with a water-additive mixture is guided.

[0042] The application of a water-additive mixture, where, for example, the additive is a wet-strength agent, means that the water-additive mixture has a sticky consistency until it has completely dried or hardened, which tends to leave a contamination on surfaces with which it comes into contact, which can negatively affect the operation of the system.

[0043] The arrangement of the second application device after a final press gap on a subsequent transfer belt in combination with the pre-drying device enables an initial "drying" of the water-additive mixture applied to a first side, before the fiber fabric is transferred with the opposite second side to a subsequent connecting belt or drying screen and laid down.

[0044] "Pre-drying" refers to the process by which sufficient drying power is applied by the pre-dryer to the fiber fabric, which has been treated with a water-additive mixture. This results in the formation of an initial "surface skin" or "surface film" on the upper side of the fiber fabric facing the pre-dryer. This surface film exhibits no or significantly reduced adhesion, stickiness, and / or susceptibility to soiling on the support elements. This leads to no or significantly reduced soiling, improved transfer properties, and improved system operation, such as more stable web flow, particularly when the fiber fabric is laid down with this initial side onto the subsequent transfer belt or drying screen.

[0045] Furthermore, the present invention relates to a machine for producing a fibrous web, preferably a tissue, paper or cardboard web or a nonwoven web, in particular a tissue web with a basis weight of 28g / m². 2 up to 42g / m² 2, comprising: a) a raw material processing plant for the low-water processing of cellulose-containing fibers into individual fibers and / or fiber bundles; b) a dry forming device for the dry forming of the individual fibers and / or fiber bundles in an air stream into a planar fiber layup on a forming belt; c) an application device for applying a fluid, preferably water and / or a water-additive mixture, to the fiber layup; d) a consolidation device for consolidating the planar fiber layup by applying pressure in a press gap; wherein the machine is particularly designed for carrying out the method according to one of the examples described above, and wherein the machine has a transfer section arranged between a final press gap and a dryer device, with a transfer belt and at least one pre-dryer device.

[0046] The advantageous further developments previously described for the method according to the invention also apply analogously to the machine according to the invention.

[0047] The conveying belt can be designed as a spiral screen. A spiral screen can consist of a carrier belt with numerous spirally arranged threads or wires. These spirally arranged threads can be made of plastic, such as polyester. The individual threads, which can also be described as spirals, interlock to form the carrier belt. They are arranged essentially parallel to one another. This arrangement of the individual threads or spirals results in high air and moisture permeability for the entire spiral screen, which is particularly advantageous for pre-drying. Furthermore, spiral screens are mechanically robust and can be closed at their seams within the machine that guides them. They are also easy to maintain and clean.

[0048] Furthermore, a sieve with a pin seam or a spiral sieve that can be closed with a seam allows the machine to be designed without cantilever beams in the area of ​​the transfer belt ("non-cantilevered"), as the spiral sieve can be threaded in very easily, for example, for replacement. A design without cantilever beams allows for a simpler and less bulky foundation or support structure for the machine components in this area. This also makes it possible to dimension the cavity formed within the rotating transfer belt in a cost- and space-optimized manner, so that the pre-dryer can be positioned in the necessary drying section within this area. Compared to other variants, the spiral sieve offers the advantage that it has no transition at the seam, unlike, for example, a variant with a so-called "pin seam" for rapid feeding.

[0049] The spiral screen can be designed with a specific air permeability for use in air-through drying (TAD). A minimum value of 200 cfm, in particular more than 300 cfm, and preferably more than 450 cfm, is desirable, since a denser screen requires more force to direct the drying air to the fiber web.

[0050] The sieve can also be made of metal wires, making it easier and more efficient to clean.

[0051] At least one pre-drying device can be designed as an electric fan and / or at least one pre-drying device can be designed as an electric fan with a heating device and / or at least one

[0052] A pre-dryer device can be an electric fan with a

[0053] be equipped with a humidification device and / or at least one

[0054] The pre-drying device can be designed as an electric fan with a heating device and a humidifying device and / or at least one

[0055] The pre-drying device can be designed as an infrared emitter.

[0056] The machine for guiding the transfer belt can have at least three, in particular four, and in particular five or more, deflection rollers. This allows the length of the transfer belt, including the fiber mat transporting section, as well as a space arranged within the transfer belt, to be geometrically defined in such a way that devices can be arranged within or along the fiber mat transporting section of the transfer belt. These devices serve to treat the fiber mat during its transfer or interact with it. Likewise, a design with multiple deflection rollers allows for a particularly cost- and space-optimized design of the cavity formed within the circulating transfer belt. This cavity is provided for the pre-drying device and / or complex cleaning equipment for dry and wet cleaning.

[0057] Several deflection rollers are provided, one of which is a regulating roller for good straight running of the transfer belt.

[0058] Furthermore, the deflection roller can be designed as a tensioning roller and contribute to optimal tension of the transfer belt.

[0059] At least one deflection roller of the transfer belt can be relocatable, in particular pivotable. To ensure the most reliable transfer from the press gap, even at industrial production speeds, it is advantageous if at least one deflection roller of the transfer belt can be adjusted in its position, for example, so that the angle at which the fiber fabric leaves the press gap can be precisely controlled. This allows for advantageous control of the fiber fabric's release behavior from the surfaces of the two rollers forming the press gap. Therefore, it is advantageous if at least one deflection roller is relocatable, for example, relocatable parallel to the rollers of the press gap or pivotable.

[0060] The term "industrial level" refers to a high, continuous production speed of 150 m / min or greater, in particular 250 m / min or greater, and preferably 400 m / min or greater. Furthermore, at an industrial level, the width of the continuously produced fiber web is preferably 0.5 m or greater, more preferably 1 m or greater, in particular 2.3 m or greater, but generally 10 m or less. At least one deflection roller may have a diameter of no more than 0.5 m, in particular no more than 0.4 m, and in particular no more than 0.3 m. For example, if the first deflection roller of the transfer belt, which is located at the beginning of the conveying section of the transfer belt and therefore closest to the press gap, has only the aforementioned relatively small diameter, this deflection roller can be positioned correspondingly close to the press gap.The diameter of this deflection roller should preferably be less than half the diameter of at least one of the two rollers that together form the press gap. Furthermore, the transfer belt can have a small thickness and / or low flexural stiffness, in particular a smaller thickness and / or lower flexural stiffness than the drying screen, in order to be guided or deflected over this deflection roller, provided the latter has a correspondingly small diameter.

[0061] In an alternative embodiment, the final press gap is unsupported. This means that the press gap is free of any covering or press belt, and the fiber fabric can advantageously be subjected to higher pressing pressures; see also the corresponding sections in the description of the process.

[0062] This allows the existing installation space to be used to advantage, thus eliminating the need for additional covering.

[0063] In an alternative embodiment, the machine comprises a second application device and a third application device after the last press gap, wherein the second and third application devices are arranged such that they have a substantially opposite application direction, in particular in the form of a spray jet, and are each arranged on the opposite side of the solidified fiber fabric.

[0064] In an alternative embodiment, the machine comprises a second application device in the transfer area with a transfer belt. In an alternative embodiment, the second application device has an application direction against gravity. See also the corresponding sections in the description of the method.

[0065] In an alternative embodiment, the machine comprises a second application device and a third application device after the last press gap, wherein the second and third application devices are arranged such that they have a substantially uniform application direction, in particular in the form of a spray jet. See also the corresponding sections in the description of the method.

[0066] For the purposes of the present invention, the term "low-water" raw material processing also includes the processing of the raw material entirely without the targeted addition of water and / or other liquids.

[0067] "Low-water" raw material processing means that the amount of water already contained in the provided, air-dried raw material is sufficient for the processing, and the processing can be carried out without adding any further water or moisture. The water content of the air-dried raw material is typically between 1% and 30%, particularly between 1% and 20%, and preferably between 1% and 10%, based on the mass of the raw material.

[0068] Alternatively, in a "low-water" raw material processing method, a small amount of water or moisture can be added to the raw material during the processing, ensuring that the water content of the raw material, chips, and / or individual fibers does not exceed a maximum of 30%, particularly 20%, preferably 10%, based on the mass of the raw material, chips, or individual fibers in any of the processing steps. It is important to note that the raw material can absorb water or moisture from its environment during storage for at least several hours, with this maximum amount depending on the raw material, the storage conditions, and the environmental conditions.

[0069] The invention expressly extends to embodiments which are not given by combinations of features from explicit cross-references of the claims, whereby the disclosed features of the invention can be combined arbitrarily with one another - insofar as this is technically sensible.

[0070] To differentiate between the manufactured fiber webs, for example a tissue, paper or cardboard web on the one hand and a nonwoven web (in English "non-woven") on the other, the following distinction is made, which is based on fiber length, density and fiber bonding type:

[0071] A fibrous web with predominantly medium fiber lengths, shorter than the fiber lengths of nonwoven webs, of less than or equal to 5 mm, in particular less than or equal to 4 mm, preferably less than or equal to 3 mm, predominantly bonded by hydrogen bonds and with a bulk density of greater than or equal to 0.4 g / cm³, is placed beneath a tissue, paper or cardboard web. 3 Understood. The fibers used in a tissue, paper or cardboard web are additionally characterized by having a slenderness ratio of fiber length to fiber diameter of less than or equal to 200, in particular less than or equal to 150, preferably less than or equal to 100.

[0072] A nonwoven web, which also consists primarily of fibers, is defined—as a key distinction from tissue, paper, or cardboard webs—by having a fiber content of at least 30% consisting of very long fibers with an average fiber length of more than 5 mm, or continuous fibers, which determine the nonwoven characteristics. Furthermore, a fiber-to-diameter ratio of greater than or equal to 300 is targeted for a nonwoven web. The remaining fiber content of a nonwoven web can be of a different composition, and the bulk density should be below 0.40 g / cm³. 3 to classify a fibrous web as a nonwoven fabric.

[0073] Further features and advantages of the invention will become apparent from the following description of a preferred embodiment with reference to the drawing.

[0074] The invention will be explained below with reference to the following figures.

[0075] Fig. 1 shows a schematic representation of a raw material processing plant 2 for the low-water processing of cellulose-containing fibers 200;

[0076] Fig. 2 shows a schematic representation of a fiber web plant 3 for the production of a dry-formed fiber web 309.

[0077] Fig. 3 shows a schematic representation of a section of a fiber web plant 3 for the production of a dry-formed fiber web 309.

[0078] Fig. 4 shows an alternative embodiment of Figure 3.

[0079] Fig. 5 shows another alternative embodiment of Figure 3.

[0080] To clarify the individual directions, a higher-level Cartesian coordinate system is shown in the figures. The x-direction corresponds to a longitudinal extension, also referred to as the machine direction MD (Machine-Direction). The y-direction corresponds to a direction orthogonal to the machine direction MD. It is also referred to as the machine cross-direction CD (Cross-Direction). The z-direction, on the other hand, corresponds to the vertical direction. Figures 1 and 2 each show a schematic representation of a possible embodiment of the method or machine 1 according to the invention. Figure 3 also shows a schematic representation of a partial area of ​​a possible embodiment of the method or machine according to the invention, in particular the partial area of ​​the transfer belt 103 or the transfer area.

[0081] Figure 1 schematically depicts a possible embodiment of a low-water processing plant, or a low-water raw material processing plant 2, in which the individual fibers and / or fiber bundles 209 are produced, for example, from fiber-containing recycled material and / or from virgin fiber pulp as bales 200, by comminution devices 221, 222, 223 and / or fiberizing devices 222, 223. After successful comminution or fiberizing, the individual fibers and / or fiber bundles 209 are transported in an airflow. Specifically, the air / fiber mixture is fed via a distribution channel or several distribution channels to at least one of the dry forming devices 4A, 4B, 4C shown in Figure 2 of a fiber web plant 3 for the production of a dry-formed fiber web 309.

[0082] A coupling of the two manufacturing processes of the low-water raw material preparation 2 and the fiber web plant 3 is an important component for the production of high-quality fiber webs 309, both of which can be coordinated, controlled and / or regulated via a higher-level control and / or regulation device 60.

[0083] The low-water raw material preparation process or raw material preparation plant 2 is characterized by a multi-stage comminution of the discontinuously fed raw material, whereby at the end of the low-water raw material preparation process 2, an airflow containing dissolved individual fibers and / or fiber bundles 209, tailored to the subsequent fiber web plant 3, can be continuously provided. The low-water raw material preparation process or raw material preparation plant 2 and the subsequent fiber web plant 3 are preferably free of an intermediate storage of the individual fibers 209 between plants 2 and 3 and are thus provided to the fiber web plant 3 "on demand".

[0084] The general term "raw material" is used for cellulose-containing fibers 200, preferably virgin fiber pulp in bales 200 and / or recycled fibers. The recycled fibers can originate from the fiber web plant 3 itself as high-quality recycled virgin fiber pulp and / or it can be provided that recycled material from waste paper is used to further improve the overall efficiency of the manufacturing process.

[0085] The discontinuously supplied raw material is usually fed as bales 200 via a conveyor belt 220 to a first shredding device 221. The first shredding device 221, preferably a first shredder 221, is designed such that it can perform a first shredding of the bales 200 into coarse chips, shreds or chips 201.

[0086] For example, a bale of 200 mm virgin fiber pulp can consist of numerous stacked 200 mm pulp sheets. This pulp is NBSK pulp, typically used for wet-process paper, board, or tissue production. The starting material can have a density of approximately 920 kg / m³. 3The chips 201 consist of individual cellulose sheets with a thickness of approximately 1.5 mm. One to five of these cellulose sheets can be fed simultaneously in a substantially horizontal direction to a first comminution device 221, preferably a shredder 221. The chips 201 are then fed to a cleaning device 230, where any undesirable components, so-called "rejects," such as metals, contaminants, and / or packaging residues, that may still be contained in the chips 201 can be filtered out. After passing through the cleaning device 230, which can be, for example, a cyclone separator, the chips 201 are present as cleaned chips 202.

[0087] These cleaned chips 202 are ideally temporarily stored in a larger storage unit 240, which can be designed as a silo. Advantageously, this is the only large storage unit 240 in the entire raw material processing plant 2. Advantageously, the storage unit 240 is located immediately after the cleaning of the chips 201, thus minimizing the increase in volume.

[0088] Optionally, a conditioning device 260 or a conditioning process can be provided for the cleaned chips 202 after the cleaning of the chips 201 and before the memory 240. During this conditioning process, a small amount of moisture can be supplied to the cleaned chips 202, for example, to minimize or prevent dust formation and / or electrostatic charging.

[0089] The storage unit 240 is preferably designed as a vertical storage silo 240, wherein the cleaned chips 202 can be easily compressed by their own weight. Furthermore, at least one discharge device 241 is provided in the storage unit 240, which enables continuous discharge of the cleaned chips 202.

[0090] To facilitate the discharge of the cleaned chips 202 from the storage unit 240, a first airflow 90 is introduced directly at the outlet of the storage unit 240. This allows the cleaned chips 202 to disperse and mix within the first airflow 90, thus facilitating their transport to the second comminution device 222. The second comminution device 222, or first fiberizing device 222, is preferably designed as a first hammer mill 222. In this mill, the cleaned chips 202 are comminuted or fiberized until individual fibers with isolated nodes 205 are formed. These fibers can then pass through a filter device included in the second comminution device 222. The introduction of an airflow 90 downstream of the second comminution device 222 assists the discharge of the individual fibers 205 from the second comminution device 222 and facilitates their transport to the next processing station.The individual fibers with isolated nodes 205B are highly resolved in the supplied airflow 90.

[0091] The individual fibers with isolated nodes 205B can be further processed in a fiber processing device 250 to form a continuous mass flow of fibers 206, to which a further air flow 90 is subsequently added and the continuous mass flow of fibers 206 becomes a high-resolution, continuous mass flow of a fiber-air mixture 207.

[0092] The high-resolution, continuous mass flow of a fiber-air mixture 207 is fed directly to the third comminution device 223 or second fiberizing device 223, which is preferably designed as a second hammer mill 223. The third comminution device 223 comminsues or fiberizes the high-resolution, continuous mass flow of a fiber-air mixture 207 until essentially only individual fibers 208 remain, preferably free of knots or with only a small proportion of knots, which can then pass through a filter device arranged in the third comminution device 223.

[0093] To further reduce the single-fiber concentration, another airflow 90 can then be added. Alternatively or additionally, for example, exhaust air from the vacuum boxes 32 included in the fiber web system 3 can be added for web stabilization (see also Fig. 2) before the high-resolution single fibers 209, essentially free of knots, are precisely metered and continuously fed to the fiber web system 3 via a distribution system or distribution channels.

[0094] In the embodiment shown in Figure 2, three dry forming devices 4A, 4B, 4C are arranged one behind the other to produce three superimposed layers of the finished fiber web 309. However, this is not mandatory. The fiber web system 3 could also include fewer than three dry forming devices, in particular only a single dry forming device, or it could include more than three dry forming devices.

[0095] The individual fibers and / or fiber bundles 209 transported by the airflow are guided to at least one of the dry forming devices 4A, 4B, 4C of the fiber web system 3 and distributed as evenly as possible transversely to the machine direction MD or in the transverse direction CD of the fiber web system 3. Provided that the capacity of the raw material preparation system 2 is sufficiently large and all three layers of the finished fiber web 309 are to consist of the same fiber material, the raw material preparation system 2 feeds all three dry forming devices 4A, 4B, 4C. For example, at least one of the dry forming devices 4A, 4B, 4C can be fed by another method. This can be done, in particular, by a further raw material preparation system, not shown here, which can be similar to or essentially identical to the raw material preparation system 2 described above.The provision of at least three dry forming devices 4A, 4B, 4C has the advantage that the two outer cover layers of the finished fiber web 309 can be formed from a different, in particular higher quality, fiber material than the at least one layer in between.

[0096] Following the dry forming devices 4A, 4B, 4C, preferably at least one application device 7, 71, 72, 73 is provided, which applies or deposits a fluid, preferably water or a water-additive mixture, onto the fiber fabric 300 or the solidified fiber fabric 305.

[0097] Following the dry forming devices 4A, 4B, 4C, at least one consolidation device 8 is provided which can consolidate the fiber fabric 300. In the embodiment shown in Fig. 2, three consolidation devices 8 are arranged. Preferably, at least one consolidation device 8 is designed such that, in addition to consolidating the fiber fabric, it can also structure and / or heat it. Structuring by the consolidation device 8 is particularly useful for producing a tissue web with low- and high-pressure zones, preferably a tissue web with a basis weight of 28 g / m². 2 up to 42g / m² 2 significant.

[0098] To complete the continuously produced fiber web 309, a web-width winding unit 12 is arranged at the end of the fiber web system 3.

[0099] Furthermore, a dryer 10 is arranged in the fiber web system 3. It is advantageous if the at least one dryer 10 is arranged downstream of the application devices 7, 71, 72, 73 in order to dry the fiber web 309 onto which the fluid has been applied. Preferably, the at least one dryer 10 is arranged upstream of the winding unit 12 of the finished fiber web 309, which is also arranged in the fiber web system 3.

[0100] The dry forming step in at least one of the dry forming devices 4A, 4B, 4C can be controlled and / or regulated by at least one control and / or regulating means, wherein the individual fibers and / or fiber bundles 209 in the dry forming devices 4A, 4B, 4C are deposited, in particular partially, by weight onto a circulating, preferably permeable, forming belt 40 and form a fiber fabric 300, which is in particular still substantially unconsolidated. Furthermore, the dry forming devices 4A, 4B, 4C can each have a suction device 30 which supports the depositing of the individual fibers 209 onto the permeable forming belt 40 and can influencing this process, in particular also as a control and / or regulating means.

[0101] Preferably, the fiber layup 300 is measured with respect to its mass distribution by at least one enclosed measuring device 61, preferably a mass measuring device extending in the machine transverse direction CD, wherein the measuring signal can act as a control variable, in particular via the higher-level control and / or regulating device 60, on the supply of the individual fibers without knots 209 from the raw material preparation plant 2 and / or on the suction device 30.

[0102] As shown in Fig. 2, the fiber fabric 300 deposited in the at least one dry forming device 4A, 4B, 4C can pass through a first press gap 83 before the first application device 71, in which the still unconsolidated fiber fabric 300 receives a first, full-surface pre-consolidation or pre-compacting over the entire transverse direction CD.

[0103] The application devices 7, 71, 72, 73 are preferably designed as nozzle applicators which can spray a fluid in the form of a spray jet consisting of individual small fluid droplets onto the fiber fabric 300, 305. Alternatively, the application devices 7, 71, 72, 73 can also be designed such that the fluid is applied in the form of foam, mist, or vapor.

[0104] Immediately before being wound 12, the fibrous web 309 is guided through a dryer 10, preferably electrically operated. The properties of the fibrous web 309 with regard to its thickness, feel, and absorption capacity can be advantageously maintained by means of a non-contact dryer 10. The non-contact dryer 10 can, for example, be designed as a hot air dryer, a flow-through drying hood, or a TAD dryer. Alternatively or additionally, the dryer 10 can also be designed with infrared elements.

[0105] Due to the small amounts of moisture used in the manufacturing process, the length of the dryer unit 10 can be kept very compact compared to the usual drying sections from wet lay-up processes. This allows the overall length of the fiber web plant 3 and infrastructure costs to be kept low.

[0106] The application devices 7, 71, 72, 73 are designed such that the fiber fabric 300 can be wetted over its entire surface with the fluid. "Over its entire surface" means that the fluid is applied essentially uniformly over the entire width or over the entire transverse direction CD of the fiber fabric. In the application devices 7, 71, 72, 73, a vacuum box 31 can be arranged on the side of the fiber fabric 300 opposite the side to be wetted. This vacuum box draws ambient air through the fiber fabric 300 and through a permeable support element that supports the fiber fabric 300, preferably a pressure belt 41 and / or a transfer belt 103 and / or a drying screen 42, by means of a vacuum applied preferably during application.This advantageously allows, for example, influencing the penetration depth of the applied fluid into the fiber fabric 300 and / or the quantity distribution in the machine direction MD or machine transverse direction CD during the application of a fluid. It should be noted that the reference numeral 22 indicates the respective running direction of the press belt 41 and other coverings in Fig. 2.

[0107] Optionally, at least one moisture measuring device 63 and / or a measuring device for monitoring the fluid application may be provided. Preferably, the at least one moisture measuring device 63 is arranged such that it can measure the moisture before and / or after the dryer device 10. It is also conceivable to provide a moisture measuring device 63 directly after each application device 7, 71, 72, 73. The moisture measuring device 63 can be stationary or traversing in the machine transverse direction CD. Furthermore, the moisture measuring device 63 can also be suitable for measuring other fiber web properties, such as mass, thickness, formation, opacity, or the like.

[0108] After passing through the first press gap 83, the fiber fabric 300 is transported on the conveying section of the forming belt 40 to a transfer area 100. The transfer area 100 serves to transfer the fiber fabric 300 from the forming belt 40 to the press belt 41. Preferably, this transfer is particularly gentle, so that even at high production speeds and with low moisture content of the fiber fabric 300, no qualitative impairment of the fiber fabric 300 occurs.

[0109] The first press belt deflection roller is preferably vacuum-operated to enable the "gentle" transfer of the fiber fabric 300 to begin immediately at the start of the transfer section 100. Several vacuum boxes 32 or other vacuum devices can be arranged in the screen loop of the press belt 41 behind the first press belt deflection roller to continue the transfer of the fiber fabric 300 over the entire length of the transfer section 100 and to hold the fiber fabric upside down on the conveying section of the press belt 41 even after the transfer section 100.

[0110] At the end of the conveying section of the press belt 41, the fiber fabric 300, which has meanwhile been consolidated by the second press gap 80, is transferred from the press belt 41 to a connecting belt 102 in a further transfer section. The second transfer section is designed analogously to transfer section 100. Although the fiber fabric 300 exhibits a significantly greater strength after the second press gap 80 than before the second press gap 80, the principle of "gentle transfer" has also proven advantageous for the quality of the final fiber web 309 at this point.

[0111] After passing through the second press gap 80, the fiber fabric 300 is transported overhead on the conveying section of the press belt 41 to the further transfer area. The further transfer area serves to transfer the fiber fabric 300 from the press belt 41 to the connecting belt 102. For this purpose, the press belt 41 and the connecting belt 102 are preferably both guided substantially parallel to a further transfer direction.

[0112] The connecting belt 102 serves to guide the fiber fabric 300 from the press belt 41 to just before the third press gap 84, through which the fiber fabric 300 is then guided unsupported. In the third press gap 84, the fiber fabric 300 is further consolidated by pressure before being guided as a consolidated fiber fabric 305 to the dryer 10. The third press gap 84, like the second press gap 80, can be provided by the nip between two rollers. However, because the fiber fabric 300 is guided unsupported through the third press gap 84, unlike in the previous second press gap 80, no consideration needs to be given to the stability of a supporting fabric for the fiber fabric 300 at this point. Thus, it is possible to apply significantly higher pressures to the fiber fabric 300 in the third press gap 84 than in the second press gap 80.The higher pressures allow for significantly greater strength in the finished 309 fiber web. The rollers should therefore be designed to be correspondingly robust. For example, the rollers can be made primarily of steel.

[0113] The connecting belt 102 is specifically designed to guide the fiber fabric 300 as close as possible to the third press gap 84, in order to keep the free pull, i.e., the distance that the fiber fabric 300 must travel unsupported between the connecting belt 102 and the third press gap 84, as short as possible. For this purpose, a final connecting belt deflection roller, i.e., the deflection roller at the end of the conveying section of the connecting belt 102, can have a relatively small diameter, and the connecting belt 102 itself can be sufficiently flexible to follow the correspondingly strong surface curvature of the final connecting belt deflection roller.

[0114] After leaving the third press gap 84, the consolidated fiber fabric 305 is picked up in a transfer area by a transfer belt 103, which transfers the consolidated fiber fabric 305 to the drying screen 42. For similar reasons as before, the transfer belt 103 can be designed similarly to or identically with the connecting belt 102. In particular, the transfer belt 103 can be designed to pick up the fiber fabric 305 as close as possible to the third press gap 84 in order to keep the free pull, i.e., the distance that the further consolidated fiber fabric 305 has to travel unsupported between the third press gap 84 and the transfer belt 103, as short as possible. For this purpose, the first deflection roller 104 of the transfer belt 103, i.e.,The deflection roller 104 at the beginning of the conveying section of the transfer belt 103 has a relatively small diameter, and the transfer belt 103 itself can be sufficiently flexible to follow the correspondingly strong surface curvature of this deflection roller 104. It should be noted that the press gap 80, 83, or 84, after which the transfer belt 103 receives the fiber fabric 300, does not necessarily have to be a press gap 84 with free tension. It is also generally possible for the fiber fabric 300 to be guided through the press gap 80 or 83 with support.

[0115] To ensure the fiber fabric 300 can be guided as smoothly as possible, even at industrial production speeds, it is advantageous if at least one of the two rollers forming the third press gap 84 and / or the transfer belt 103 is / are adjustable in position so that the angle at which the compacted fiber fabric 305 exits the third press gap 84 can be precisely adjusted. For example, the two rollers forming the third press gap 84 can be designed to be adjustable in the z-direction. Alternatively or additionally, this roller arrangement could also be designed to be tiltable about an axis running in the machine transverse direction CD. In particular, it may also be possible to design the first deflection roller 104 of the transfer belt 103 to be displaceable and / or pivotable in the z-direction and / or in the MD-direction.

[0116] In the sieve loop of the transfer belt 103, a second application device 72 and a vacuum means 31 arranged opposite it within the sieve loop can be provided in Fig. 2. Preferably, an application of a water-additive mixture is carried out on one side of the solidified fiber fabric 305 by means of the second application device 72.

[0117] Vacuum devices, not shown in Fig. 2, may be provided in the sieve loop of the connecting belt 102 and / or in the sieve loop of the transfer belt 103. This applies particularly to the transfer belt 103, on which the further consolidated fiber fabric 305 is transported hanging upside down. Here, the vacuum devices can help to hold the consolidated fiber fabric 305 against gravity on the transfer belt 103. Furthermore, vacuum devices in the sieve loop of the transfer belt 103 are advantageous if a fluid is to be applied to the side of the further consolidated fiber fabric 103 facing away from the transfer belt 103.

[0118] To protect the rollers forming the third press gap 84 from contamination and to minimize the effort required for their cleaning, it is advantageous to apply only water and / or dry-strength agents to the fiber fabric 300 before the third press gap 84. These result in no or only minimal contamination of the rollers. After the third press gap 84, however, a wet-strength agent can be applied to the compacted fiber fabric 305 to impart a certain degree of wet strength to the finished fiber web 309. Common wet-strength agents, in particular, tend to contaminate surfaces, at least until they have dried.

[0119] Furthermore, a cleaning device (not shown) may be provided which cleans the conveyor belt 103, in particular from contamination by applied liquids. A cleaning device may, for example, operate without contact using a medium such as compressed air or another gaseous or liquid cleaning medium. Such a cleaning device may, for example, be arranged within the screen loop of the conveyor belt 103.

[0120] In Fig. 2, a pre-drying device 11, designed as an electric fan, is also arranged in the transfer area, namely below the conveying section of the transfer belt 103. The pre-drying device 11 is designed for pre-drying the fiber fabric 305. The pre-drying device 11 shown in Fig. 2 is specifically designed to direct an airflow to the fiber fabric 305. For this purpose, the pre-drying device 11 can draw in air through its intake opening 110 and direct it towards the fiber fabric 305. For example, the pre-drying device 11 can also be configured to humidify and / or heat the air drawn in through the intake opening 110. Therefore, the pre-drying device 11 can, for example, include a heating coil, a humidifier, and / or a burner.Advantageously, the intake opening 110 can also be connected to the dryer unit 10, allowing air to be directly discharged from or drawn into the dryer unit 10. This can particularly improve the overall energy efficiency of the machine 1 or the fiber web system 3. Furthermore, it is possible for several pre-drying units 11 to be arranged in the transfer area below or above the fiber layup 305. These pre-drying units can, for example, all be identical or different from one another.

[0121] Fig. 3 shows a schematic representation of a section of a fiber web system 3 for producing a dry-formed fiber web 309. In particular, the section shown begins with the third press gap 84, through which the fiber fabric 305 is guided without support in the exemplary embodiment, and ends with the dryer device 10, which is only partially shown. For the components of the fiber web system 3 not shown, please refer to the descriptions in Figs. 1 and 2.

[0122] The transfer conveyor 103 shown in Fig. 3 differs from the transfer conveyor 103 shown in Fig. 2, in particular, in that the transfer conveyor 103 is deflected by five deflection rollers 105 or 104. The first deflection roller 104 has a small diameter, for example, no more than 0.5 m. The first deflection roller 104 of the transfer conveyor 103 is located at the beginning of the conveying section of the transfer conveyor 103 and is therefore closest to the press gap 84. Because the first deflection roller 104 has only a comparatively small diameter, it can be positioned correspondingly close to the press gap 84. The diameter of this first deflection roller 104 should, in particular, be less than half the diameter of at least one of the two rollers that together form the press gap 84.In addition, the transfer belt 103 can have a small thickness and / or a low bending stiffness in order to be guided or deflected over this first deflection roller 104.

[0123] Furthermore, the first deflection roller 104 of the transfer belt is designed to be displaceable. It is attached to a horizontal mounting beam 310 of a base frame (not shown). Along this mounting beam 310, the first deflection roller 104 can be displaced, for example, horizontally, i.e., in the MD direction. It is advantageous if the first deflection roller 104 can also be displaced, and in particular pivoted, in the z direction. This allows, in particular, control of the release behavior of the fiber layup 305 from the surfaces of the two rollers that form the press gap 84. In addition, a deflection roller 105 is pivotably mounted on a pivot beam 311, which is pivotably mounted on the base frame (not shown). The two arrows associated with the pivot beam 311 schematically symbolize that the pivot beam 311 can be pivoted about its pivot axis.

[0124] Furthermore, an application device 7, 72 is arranged below the conveyor belt 103. The application device 7, 72 is designed such that the fiber fabric 305 can be wetted with a fluid over its entire surface. "Overall" means that the fluid is applied essentially uniformly over the entire width or the entire transverse direction CD of the fiber fabric 305. In the application device 7, 72, a vacuum box 31 is arranged on the side of the fiber fabric 305 opposite the side to be wetted. This vacuum box draws ambient air through the fiber fabric 305 and through the permeable conveyor belt 103, which supports the fiber fabric 305, by means of a vacuum applied, preferably during application.This advantageously allows, for example, influencing the penetration depth of the applied fluid into the fiber fabric 305 and / or the quantity distribution in the machine direction MD or machine transverse direction CD during the application of a fluid. Furthermore, the vacuum boxes 31 arranged in the transfer belt loop support a secure hold of the overhead guided fiber fabric 305 on the transfer belt 103.

[0125] Below the transfer conveyor 305, several pre-drying devices 11 are arranged, which direct an airflow to the fiber fabric and thus pre-dry it in the transfer area before it is transferred to the drying screen 42. The intake openings, although not shown in Fig. 3, are connected to the dryer 10 and thus draw air from the dryer 10. Such an arrangement has the particular advantage that pre-drying the fiber fabric 305 before drying in the dryer 10 increases the efficiency, and especially the energy efficiency, of the drying process. In this way, a large proportion of the moisture can already be removed from the fiber fabric 305 during pre-drying in the transfer area, so that only a smaller amount of residual moisture needs to be removed from the fiber fabric 305 in the dryer 10.In particular, increased efficiency is achieved in the dryer device 10, since it dries less efficiently at a higher moisture content of the fiber fabric 305.

[0126] Figure 4 shows an alternative embodiment of the design shown in Figure 3, in which the transfer conveyor 103 can be mirrored or inverted at the machine plane MD-CD compared to the embodiment shown in Figure 3. The further transfer from the transfer conveyor 103 to the dryer unit 10 and the drying screen 42 can be carried out in a single, uninterrupted pass. Alternatively and optionally, a further, more compact transfer conveyor 108 can be provided, thus enabling a transfer in a closed pass. Within the inverted transfer conveyor 103, at least one pre-dryer unit 11 is provided, which is arranged downstream of an application unit 72.

[0127] Figure 5 shows an alternative embodiment of the design shown in Figure 3. In this embodiment, a second transfer conveyor 106 can be positioned upstream of the transfer conveyor 103, which is mirrored or inverted at the machine plane MDCD. The further transfer from the second transfer conveyor 106 to the transfer conveyor 103 takes place in a closed loop. A second pre-drying device 13 is provided within the second transfer conveyor 106, which is arranged downstream of an application device 72. In Figures 3, 4, and 5, a cleaning device 107 can be arranged, which enables cleaning of the transfer conveyor.

[0128] List of reference signs

[0129] 1 machine

[0130] 2 Raw material processing plant

[0131] 3 Fiber web plant

[0132] 4A, 4B, 4C dry forming device

[0133] 7 Application device

[0134] 8 Solidification device

[0135] 10 T dryer device

[0136] 11 Pre-dryer

[0137] 12 Roll-up

[0138] 13 second pre-dryer

[0139] 22 Direction of travel

[0140] 30 Suction device of the dry forming device

[0141] 31 Vacuum box - Application device

[0142] 32 vacuum boxes

[0143] 39A, 39B, 39C extracted air

[0144] 40 support element, forming belt

[0145] 41 Support element, press band

[0146] 42 Support element, drying sieve

[0147] 60 Control and / or regulating device

[0148] 61 Measuring device

[0149] 63 Moisture measuring device

[0150] 71 first application device

[0151] 72 second application device

[0152] 73 third application device

[0153] 80 second press gap

[0154] 81 Press roller

[0155] 82 Press element

[0156] 83 first press gap

[0157] 84 third press gap airflow

[0158] Transfer area

[0159] Connection strap

[0160] Transfer belt, first deflection roller (of the transfer belt)

[0161] Deflection roller (of the transfer belt) second, preferably inverted, transfer belt

[0162] Cleaning device for the conveyor belts

[0163] Compact conveyor belt

[0164] Intake opening (of the pre-dryer) first connecting belt deflection roller last press belt deflection roller cellulose-containing fibers (bales) shredded bales, chips cleaned chips

[0165] Single fibers with isolated nodes or fiberized chips; Single fibers with isolated nodes or fiberized chips, high-resolution in a fiber-air mixture; continuous mass flow of fibers; continuous mass flow of fibers, high-resolution in a fiber-air mixture

[0166] Individual fibers essentially free of knots

[0167] single fibers and / or fiber bundles

[0168] Conveyor belt first shredding device second shredding device, preferably

[0169] Fibre-shredding device, in particular first hammer mill; third comminution device, preferably fibre-shredding device, in particular second hammer mill

[0170] Cleaning device

[0171] Storage 241 discharge device

[0172] 250 fiber processing device

[0173] 260 Conditioning device

[0174] 300 fiber layups after dry forming device

[0175] 305 reinforced fiber fabric

[0176] 309 Fibre web

[0177] 310 fastening beams

[0178] 311 Swivel beam

[0179] MD Machine direction

[0180] CD machine transverse direction z vertical direction

Claims

- 42 - 1. Method for producing a fibrous web (309), preferably a tissue, paper or cardboard web or a nonwoven web, in particular a tissue web with a basis weight of 28g / m² 2 up to 42g / m² 2, comprising the following steps: a) low-water raw material preparation of cellulose-containing fibers (200) into individual fibers and / or fiber bundles (209); b) forming the individual fibers and / or fiber bundles (209) in an air stream into a planar fiber fabric (300) on a forming belt (40) by a dry forming process; c) application of a fluid, preferably water and / or a water-additive mixture, to the fiber fabric (300), preferably by means of at least one application device (71, 72, 73); d) consolidation of the planar fiber fabric (300) by applying pressure in at least one pressing gap (80, 83, 84);characterized in that the fiber fabric (305) is picked up in a transfer area by a transfer belt (103) after consolidation, preferably in a final press gap (84) in the machine direction (MD), and is pre-dried in the transfer area by means of at least one pre-drying device (11) before the pre-dried fiber fabric (305) is dried in a drying device (10).

2. Method for producing a fibrous web (309) according to claim 1, characterized in that the fiber fabric (305) is moistened in the transfer area.

3. Method for producing a fibrous web (309) according to at least one of the preceding claims, characterized in that the transfer belt (103) is cleaned. - 43 - 4. Method for producing a fibrous web (309) according to at least one of the preceding claims, characterized in that the at least one pre-drying device (11 ) for pre-drying the fiber fabric (305) in the transfer area directs an airflow to the fiber fabric (305).

5. Method for producing a fibrous web (309) according to claim 4, characterized in that the airflow is moistened and / or heated before being directed to the fiber fabric (305).

6. Method for producing a fibrous web (309) according to at least one of claims 4 or 5, characterized in that the airflow is discharged from the dryer device (10).

7. Method for producing a fibrous web (309) according to at least one of claims 4 to 6, characterized in that the airflow is directed to the side of the fiber layup (305) facing away from the transfer belt (103).

8. Method for producing a fibrous web (309) according to at least one of the preceding claims, characterized in that the fiber fabric (305) is pre-dried by infrared radiation using at least one pre-drying device (11) designed as an infrared emitter.

9. Method for producing a fibrous web (309) according to at least one of the preceding claims, characterized in that the fiber fabric (305) is guided unsupported through a final press gap (84) immediately before it is picked up by the transfer belt (103) for consolidation by means of pressure and / or temperature. - 44 - 10. Method for producing a fibrous web (309) according to at least one of the preceding claims, characterized in that the fiber fabric (305) is transferred from the transfer belt (103) to a drying screen (42) on which the fiber fabric (305) is dried.

11. Method for producing a fibrous web (309) according to at least one of the preceding claims, characterized in that the fiber fabric (305) is picked up after consolidation in a transfer area by a pre-positioned, preferably inverted, second transfer belt (106) and is pre-dried in the transfer area by means of a second pre-drying device (13) before the pre-dried fiber fabric (305) is picked up by the transfer belt (103) and is pre-dried by the at least one pre-drying device (11) and is then dried in the dryer device (10).

12. Method for producing a fibrous web (309) according to at least one of the preceding claims, characterized in that, in the machine direction (MD) before a last press gap (84), water is applied to one side of the fiber layup (300) by means of a first application device (71).

13. Method for producing a fibrous web (309) according to at least one of the preceding claims, characterized in that, in the machine direction (MD) after a last press gap (84) and before the pre-drying device (11), an application of a water-additive mixture is carried out on a first side of the fiber lay-up (305) by means of a second application device (72); and wherein, in particular, the application by means of the second application device (72) is carried out in the transfer area on the transfer belt (103).

14. Method for producing a fibrous web (309) according to claim 13, characterized in that, in the machine direction (MD) after a final press gap (84), the application of the water-additive mixture is carried out against gravity by means of the second application device (72).

15. Method for producing a fibrous web (309) according to at least one of the preceding claims, characterized in that a dryer device (10) with a drying screen (42) is arranged in the machine direction (MD) after a last press gap (84) in the machine direction (MD) after the transfer area and the fiber layup (305) is laid down from the transfer belt (103) with its first side onto the drying screen (42).

16. Method for producing a fiber web (309) according to claim 13, characterized in that, in the machine direction (MD), after application by means of the second application device (72), an application of a water-additive mixture is carried out by means of a third application device (73) on a second side of the fiber fabric (305) opposite the first side.

17. Method for producing a fibrous web (309) according to claim 16, characterized in that, in the machine direction (MD) after the last press gap (84), an application direction of the second application device (72) is carried out in a first application direction and the application by means of the third application device (73) is carried out in a second application direction opposite to the first application direction.

18. Method for producing a fibrous web (309) according to claim 17, characterized in that the first application direction is against gravity.

19. Method for producing a fibrous web (309) according to claim 17 or 18, characterized in that the second application direction is in the direction of gravity.

20. Machine (1) for producing a fibrous web (309), preferably a tissue, paper or cardboard web or a nonwoven web, in particular a tissue web with a basis weight of 28g / m² 2 up to 42g / m² 2, comprising: a) a raw material preparation plant (2) for the low-water processing of cellulose-containing fibers (200) into individual fibers and / or fiber bundles (209); b) a dry forming device (4) for the dry forming of the individual fibers and / or fiber bundles (209) in an air stream into a planar fiber fabric (300) on a forming belt (40); c) an application device (7), in particular a first (71), second (72) and third (73) application device, for applying a fluid, preferably water and / or a water-additive mixture, to the fiber fabric (300); d) a consolidation device (8) for consolidating the planar fiber fabric (300) by applying pressure in a press gap (80, 83, 84);wherein the machine (1 ) is designed in particular for carrying out the method according to one of the preceding claims, characterized in that the machine (1 ) has a transfer area arranged between a last press gap (84) and a dryer device (10) with a transfer belt (103) and at least one pre-dryer device (11 ). - 47 - 21. Machine (1 ) for producing a fibrous web (309) according to claim 20, characterized in that the transfer belt (103) is designed as a spiral sieve.

22. Machine (1) for producing a fibrous web (309) according to at least one of claims 20 or 21, characterized in that at least one pre-drying device (11) is designed as an electric fan and / or at least one pre-drying device (11) is designed as an electric fan with a heating device and / or at least one pre-drying device (11) is designed as an electric fan with a humidifying device and / or at least one pre-drying device (11) is designed as an electric fan with a heating device and a humidifying device and / or at least one pre-drying device (11) is designed as an infrared emitter.

23. Machine (1) for producing a fibrous web (309) according to at least one of claims 20 to 22, characterized in that the machine (1) has at least three, in particular four, in particular five or more deflection rollers (104, 105) for guiding the transfer belt (103).

24. Machine (1 ) for producing a fibrous web (309) according to claim 23, characterized in that at least one deflection roller (104, 105) of the transfer belt (103) is designed to be displaceable, in particular pivotable.

25. Machine (1 ) for producing a fibrous web (309) according to claim 24, characterized in that at least one deflecting roller (104, 105) has a diameter of no more than 0.5 m, in particular no more than 0.4 m, in particular no more than 0.3 m. - 48 - 26. Machine (1) for producing a fibrous web (309) according to at least one of claims 20 to 25, characterized in that the last press gap (84) is an unsupported last press gap (84), which is in particular free of a covering or a press belt.

27. Machine (1) for producing a fibrous web (309) according to at least one of claims 20 to 26, characterized in that the machine (1) comprises a second application device (72) in the transfer area with a transfer belt (103).

28. Machine (1) for producing a fibrous web (309) according to at least one of claims 20 to 27, characterized in that the machine (1) comprises a second application device (72) and a third application device (73) after the last press gap (84), wherein the second (72) and third (73) application devices are arranged such that they have a substantially opposite application direction, in particular in the form of a spray jet, and are each arranged on the opposite side of the consolidated fiber layup (305).

29. Machine (1) for producing a fibrous web (309) according to at least one of claims 20 to 28, characterized in that the second application device (72) has an application direction against gravity.

30. Machine (1) for producing a fibrous web (309) according to at least one of claims 20 to 27, characterized in that the machine (1) comprises a second application device (72) and a third application device (73) after the last press gap (84), wherein the second (72) and third (73) application device are arranged such that - 49 - so that they have an essentially uniform application direction, in particular in the form of a spray jet.

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