CN108291366B

CN108291366B - Device for producing a fibrous web

Info

Publication number: CN108291366B
Application number: CN201680068172.XA
Authority: CN
Inventors: T.吕尔; K-P.奥尔特罗格; M.哈姆斯
Original assignee: Voith Patent GmbH
Current assignee: Voith Patent GmbH
Priority date: 2015-11-30
Filing date: 2016-10-25
Publication date: 2020-10-20
Anticipated expiration: 2036-10-25
Also published as: WO2017092932A1; EP3384083A1; DE102015223663A1; CN108291366A; EP3384083B1

Abstract

An apparatus for producing a fibrous web, in particular a packaging paper web, has a headbox, a screen section for dewatering a fibrous suspension introduced by the headbox and for forming the fibrous web from the fibrous suspension, a press section for further dewatering the fibrous web, and a drying section for drying the fibrous web. The headbox is designed with three layers and is equipped with a partition foil protruding beyond the headbox nozzle of the headbox. Furthermore, a starch size is provided, by means of which starch can be inserted into at least one layer. The screen section comprises a single layer of a gap former. The press section has at least one nip, in particular at least one shoe nip, which extends in the direction of travel of the web.

Description

Device for producing a fibrous web

Technical Field

The invention relates to a device for producing a fibrous web, in particular a packaging paper web, having a headbox, a screen section for dewatering a fibrous suspension introduced by the headbox and for forming the fibrous web from the fibrous suspension, a press section for further dewatering the fibrous web, and a drying section for drying the fibrous web.

Background

Like paperboard, wrapping paper constitutes in practice the vast majority of the packaging material. The wrapping paper is widely applicable, clean and flexible. All types of corrugated paper, kraft paper for paper bags, traditional brown wrapping paper and even facing layers of plasterboards belong to the wrapping paper. Which generally have a higher proportion of waste paper. Corrugated material is embedded in corrugated paper manufacture as a middle layer between two facing layers, i.e. two layers applied on the inside and outside of a corrugated paper package or board. It is typically made from 100% waste paper. The required strength is achieved by coating with starch.

Apparatuses of the aforementioned type are known, the screen section of which has a multi-layer former and in the drying section of which steel cylinders are used in order to guide the drying wire with a somewhat elevated wire tension.

Disclosure of Invention

The object of the invention is to provide a device of the type mentioned above, which is particularly suitable for producing wrapping paper, and which ensures a high degree of strength in the end product, while ensuring a high dry matter content, a high web guidance and a high quality of the end product, with minimal investment and operating costs.

The above technical problem is solved according to the invention by a process for the production of less than 100g/m²The object of the invention is achieved by an apparatus for a fiber web of grammage having a headbox, a screen section for dewatering a fiber suspension introduced by the headbox and for forming the fiber web from the fiber suspension, a press section for further dewatering the fiber web, and a drying section for drying the fiber web, wherein the headbox is designed with three layers and is provided with a separating sheet protruding beyond the headbox nozzle of the headbox, and a starch sizing element is provided, by means of which starch can be introduced into at least one layer, the screen section comprises a single-layer web former, and the press section has a single-layer web formerAt least one nip, in particular at least one shoe nip, which extends in the direction of travel of the web of material, and which is designed as a slatted wire former and comprises an at least substantially horizontal dewatering section.

The device according to the invention for producing a fibrous web, in particular a packaging paper web, has a headbox, a screen section for dewatering a fibrous suspension introduced by the headbox and for forming the fibrous web from the fibrous suspension, a press section for further dewatering the fibrous web, and a drying section for drying the fibrous web. The headbox is designed with three layers and is equipped with a partition foil protruding beyond the headbox nozzle of the headbox. Furthermore, a starch size is provided, by means of which starch can be inserted into at least one layer. The screen section comprises a single layer of a gap former. The press section has at least one nip, in particular at least one shoe nip, which extends in the direction of travel of the web.

Due to this design, a higher quality and in particular also a higher strength of the end product is achieved with a high dry matter content, good web guidance, with minimal investment and operating costs, wherein the device according to the invention is suitable in a particular manner for producing wrapping paper.

A headbox or a three-layer headbox with three layers is designed with three, in particular overlapping, suspension flow channels, through which a partial pulp flow or medium is fed to the headbox, from which a fibre suspension jet issuing from the headbox is formed. The projecting separating webs in particular achieve a better delamination and thus a better covering quality, that is to say a reduced transmission of the uncolored opposite side of, for example, a carton paperboard. The strength of the end product can be increased in particular accordingly by adding starch. In this case, the crack resistance of the respective end product can be increased accordingly, and the surface strength of the respective end product can be increased accordingly, by means of a corresponding starch addition. A gap former is a twin-wire former in which the fibre suspension is laid directly between two wires and dewatered on both sides. The use of a single layer gap former helps to minimise investment costs. With at least one nip or at least one shoe nip extending in the direction of travel of the web, a correspondingly higher dry matter content after the press is obtained on the basis of a higher linear load.

In particular, starch is advantageously inserted at least into the intermediate layer by means of the starch size. The internal strength of the respective end product can be increased in particular by this addition of starch to the intermediate layer.

By means of the starch sizing element, starch can be introduced into the fiber suspension or into the pulp jet produced by the headbox or applied to the fiber web before the headbox, in the headbox and/or at the latest in the screen section after the headbox.

The sheet fed into the headbox nozzle allows a better formation and a uniform starch penetration in the case of at least a portion of the starch being added by the starch sizing element already before or in the headbox. If the starch is at least partially inserted before the headbox, the starch addition can take place, for example, in a mixing tub or the like. However, as already mentioned above, the starch can also be introduced at least partially in the headbox or after the headbox and/or at the latest in the screen section or the forming section.

As mentioned above, a headbox designed with three layers can be fed through three inflow openings or media.

The clip former can be designed in particular as a slat clip former. Such a slat gap former is a gap former or a gap former with a stationary initial dewatering element, through which the fibrous web is formed. Thus, for example, a more compact or shorter slat-net former may be used.

It is also advantageous, in particular, that the gap former design does not have a suction roll, whereby its construction is further simplified and correspondingly less expensive.

Suitably, the gap former comprises an at least substantially horizontal dewatering section. In this horizontal dewatering section of the gap former dewatering takes place at least substantially downwards and upwards.

The press section advantageously comprises two nips extending in the direction of travel of the web of material, in particular two shoe nips. The press section here comprises in particular a double-shoe press or an inline Nipcoflex press.

Shoe presses for dewatering a fibrous web do not generate a pressing force with a rotating roll and counter roll, but a stationary shoe presses against a rolling counter roll. For this purpose, a flexible plastic sleeve is guided around the boot. An oil film is formed between the boot and the plastic sleeve for lubrication. The water emerging from the fibrous web is fed to at least one circulating felt, as in the case of conventional extruders. By virtue of the design of the shoe, the so-called nip is made considerably longer than in conventional presses, with a corresponding increase in the residence time of the fibrous web in the nip. The need for thermal drying is correspondingly reduced. Finally, the logs are obtained by a relatively gentle dehydration.

The press section may in particular comprise only the two nips extending in the direction of travel of the web or only the two shoe nips or only the double shoe press.

It is also advantageous, in particular, if the respective shoe nip is formed between a shoe press roll and a counter roll provided with a polyurethane coating. Here, the polyurethane coating of the respective roll of each shoe extruder preferably has an open face in the range of 10% to 40%. It is also advantageous, in particular, if the polyurethane coating of the counter roller of each shoe extruder has a thickness of 500 to 1500ml/m²A storage volume within the range. Whereby the dry matter content after the press section can be correspondingly further increased.

Preferably, an impermeable lower transfer belt is guided through the second or last nip of the press section, seen in the direction of web travel. By using such a belt or belt in the lower part of the last nip of the press, the moisture regain can be reduced, especially in the case of a low mass per unit area range, and in this way, especially below 100g/m²The lighter grammage of the pellets increases the dry matter content.

The fibrous web is preferably guided continuously in a supported manner up to the first drying cylinder of the drying section, so that a better web guidance is achieved and the risk of web tearing is minimized.

According to a further advantageous embodiment of the apparatus according to the present invention, the drying section is designed at least partially with steel cylinders. It is particularly advantageous if the dryer section is designed for a dryer wire tension of more than 5 kN/m.

The steel cylinder block has a higher thermal conductivity than the cast iron cylinder block due to the material. A further increase in the heat transfer is thus achieved, in particular in combination with a higher drying wire stress. By designing the dryer section for dryer wire tensions of more than 5kN/m, the dryer wire can be guided around the cylinder with a correspondingly higher tension.

In order to further increase the drying efficiency, the dryer section advantageously comprises at least one high-performance dryer, in particular at least one impingement dryer and/or at least one infrared dryer. The impingement dryer is a high-performance dryer which applies a jet of hot air and/or a jet of hot steam at least on one side to the fibrous web. Here, for example, at least one high-performance dryer can be arranged in the starting region of the pre-drying section of the drying section. The total length of the apparatus or the paper machine can be further shortened by an additional high-performance dryer in the beginning area of the drying section. Furthermore, the strength of the end product is increased after, for example, the starch introduced has coagulated more early.

The machine solution according to the invention is adjusted according to the preferred specific investment costs. In particular, the resource potential in the case of wrappers with a high proportion of recycled fibre material, in part or up to 100%, is also taken into account. Here, in order to form the recycled fiber material as a raw material into a wrapping paper, the ideal running speed also depends mainly on the strength properties of the raw material. The strength properties of the feedstock determine the speed range within which it can operate with reasonable machine efficiency. Thereby primarily keeping the number of tears within an economically reasonable range and minimizing the necessary standstill of the machine. Since asia is the major growing market for wrapping paper, raw materials that are applied in this location and are economically available should be considered. For this purpose, the speed range suitable for the operation of the apparatus is between 1100 and 1500 m/min. The trend towards lighter grammage in white cardboard and corrugated materials should therefore also be considered.

In terms of an ideal machine solution for special boundary conditions, it is particularly advantageous to produce a two-layer product, for example a white cardboard, using a single-layer former solution with the use of a two-layer headbox. The projecting separating webs in this case achieve good delamination and thus good covering quality, i.e. a reduction in the transparency of the undyed counter side of the ivory board. It has been shown that by combining a suitable speed with a lighter grammage, the use of a rotary knife gap former is no longer necessary and the required production rate can also be achieved with a knife gap former having a lower dewatering capacity or yield. Such a blade gap former can be implemented in particular in a horizontal configuration, so that the use of the material pulling device is facilitated by the frame. The higher machine direction orientation according to the solution facilitates sheet forming compared to hybrid formers, so that maximum speed performance can be utilized. The strength in the transverse direction, which is adversely affected thereby, can be compensated for by additives, such as starch or special or high-value fiber materials. Reinforcing additives, such as starch, can be added to the raw materials. The addition is either into the pulp jet before the headbox, in the headbox or into the forming section in the form of a starch injection pipe. This can be achieved by means of a multi-layer headbox in the headbox or in the pulp jet.

In the further operation of the plant or paper machine, a press section with a high press impact is advantageous in order to achieve a high dry matter content on the one hand and a high sheet compaction on the other hand. Both of which improve the sheet strength or wet strength and thus the runnability or runnability of the machine. For this purpose, the at least one nip is advantageously designed as a shoe press. A double shoe press may suitably be used. Such a double shoe press has the further advantage of continuously supporting the guidance of the web through the press in addition to the high pressure impact and thus the high dry matter content.

A suitable variant in the lighter grammage range consists in using a transport belt in the second position below the press section, whereby the moisture regain is reduced andthereby especially aiming at 100g/m²The lower lighter grammage increases the dry matter content.

Furthermore, simple felting nips are advantageous in terms of cross-directional moisture distribution. A good cross-directional moisture distribution at the end of the press section achieves a web tension characteristic that is uniform in the cross direction of the machine, thereby improving runnability or runnability in the critical output area of the dryer section. Humidity differences and the resulting web stress differences and traction wrinkles are avoided.

In the further operation of the fiber web through the drying section, a high heat flow is advantageous in principle, so that the drying efficiency is increased and at the same time the length required for drying is reduced and thus also the length of the entire machine and of the machine hall. It should be noted here, however, that an excessively high heat flow at the beginning of the drying section can lead to a blocking of the web surface and thus be disadvantageous for the drying efficiency and even damage to the page. The corresponding possible and reasonable heating power depends on the raw materials and the grammage. The special wrapping paper is less sensitive here and can be loaded with a relatively steep heating curve.

For this reason, it is also possible to use steel cartridges which have a higher heat conduction by the material than cast iron cartridges. This may furthermore be combined with higher dry web stresses. Here, a higher web stress achieves a further increase in the heat transfer. The apparatus is advantageously operated so that the drying wire stress is in the range of 5 to 8 kN/m. The effect here also does not have a negative effect on the quality of the paper, in particular the wrapping paper. Furthermore, a typical dryer web with seams can still withstand the stresses. Finally, the increase in costs for dimensioning other components, such as the wire puller, the adjusting member and the roller, is still relatively gentle and economically justifiable compared to using a faster, more efficient drying section.

Furthermore, vigorous drying at the beginning of the pre-drying section is advantageous for the effect of starch or other enhancing additives added to the constant part of the machine and the wet section. This effect can be purposefully further enhanced by the use of high-efficiency dryers, for example impingement flow drying hoods, at the beginning of the pre-dryer section. Here, for example, two to six drying hoods are economically and technically justifiable in order to achieve the effect of increasing the strength with suitable investment and operating costs.

Drawings

The invention will be explained in more detail below on the basis of an embodiment with reference to the drawings, in which:

fig. 1 shows a schematic view of an exemplary embodiment of an apparatus according to the invention for producing a fibrous web, in particular for producing a packaging paper web, and

figure 2 shows a schematic view of a screen section of another exemplary embodiment of an apparatus according to the present invention.

Detailed Description

Fig. 1 shows a schematic view of an exemplary embodiment of an apparatus 10 according to the present invention for producing a fibrous web, in particular for producing a packaging paper web.

The apparatus 10 comprises a headbox 12, a screen section 14 for dewatering a fibre suspension introduced through the headbox 12 and for forming a fibre web from the fibre suspension, a press section 16 for further dewatering of the fibre web and a drying section 18 for drying the fibre web. Furthermore, a winding machine 20 can be connected downstream of the drying section 18 for winding up the dried, ready-prepared fibrous web.

The headbox 12 is designed with three layers and with a separating sheet protruding beyond the headbox nozzle of the headbox. Starch sizing elements are also provided, by means of which starch can be introduced into at least one of the layers.

The screen section includes a single layer of gap former 22. Here, for example, a hob-type gap former is provided in this case, which has a rear dewatering section 24 extending at least substantially horizontally.

The press section 16 comprises at least one nip 26, in particular at least one shoe nip, extending in the direction of web travel 11.

The starch sizing element can be designed in particular such that starch can be inserted at least into the intermediate layer.

Starch can be added to the fiber suspension or to the pulp jet produced by the headbox 12 or applied to the fiber web by means of the starch sizing element before the headbox 12, in the headbox 12 and/or at the latest in the screen section 14 after the headbox 12. The strength of the end product is increased in particular accordingly by the addition of starch.

A headbox 12 designed with three layers can be fed through three inflow ports or media.

The clip former 22 can be designed in particular as a slat clip former. Such a slat gap former is a gap former or a gap former with a stationary initial dewatering element, by means of which the fibrous web is structured or dewatered.

Furthermore, the gap former 22 may in particular be designed without suction rollers, whereby a simpler and correspondingly less costly construction results.

The gap former 22 may comprise an at least substantially horizontal dewatering section. The dewatering of the fibrous web takes place in this horizontal dewatering section at least substantially upwards and downwards through the screen section of the gap former 22.

In this example, the press section 16 comprises, for example, two nips 26 or shoe nips extending in the web running direction L. The press 16 may in this case comprise, in particular, a double-shoe press or a tandem double nip press.

Shoe presses for dewatering a fibrous web do not utilize a rotating roll and counter roll to generate a pressing force, but rather a stationary shoe presses against a rolling counter roll. In this case, a flexible roller sleeve is guided around the press shoe. An oil film for lubrication is formed between the shoe and the flexible roller sleeve. The water pressed out of the fibrous web is conveyed like a conventional press onto at least one surrounding felt. By virtue of the design of the shoe, the so-called nip is made considerably longer than in conventional presses, with a corresponding increase in the residence time of the fibrous web in the nip. By means of the higher press impact, a correspondingly higher dry matter content is obtained after the press section.

As can be seen from fig. 1, the press section 16 in this example comprises only two nips 26 or only two shoe nips or only two shoe presses, which extend in the web travel direction L.

Each shoe nip 26 may be constructed between a shoe press roll and a corresponding roll provided with a polyurethane coating. The polyurethane coating of the counter roll of each shoe nip 26 here has in particular an open face in the range from 10% to 40%. In addition, the polyurethane coating of the counter roll of each shoe nip 26 has, in particular, a coating of 500 to 1500ml/m²A storage volume within the range. Whereby the dry matter content after the press section 16 can be correspondingly further increased.

The impermeable lower transfer belt 30 can be guided through the second or last press nip 26 of the press section 16, viewed in the web running direction L. By using such a transport belt or belt 30 in the lower position of the last press nip 26 of the press section, the moisture regain can be reduced, in particular in the lighter grammage range, and thus in particular for 100g/m²The lower lighter grammage increases the dry matter content.

The fibrous web can be guided continuously in a supported manner as far as the first drying cylinder 28 of the drying section 18, so that a safe web run is achieved and the risk of web breaks is minimized.

The dryer section 18 may be designed to have at least partially steel cylinders. Furthermore, the dryer section 18 is designed for a dryer wire tension of in particular more than 5 kN/m. The drying wire can thus be guided around the drying cylinder or the steel cylinder with a correspondingly higher tension.

By designing the drying section 18 at least partially with a steel cylinder and for a higher drying wire tension, the heat conduction to the fibrous web is improved and the energy efficiency of the drying can be increased, whereby the length of the drying section is correspondingly reduced. The steel cylinder block has a higher thermal conductivity than the cast iron cylinder block due to the material. In addition, the heat transfer is further increased by the higher drying wire tension.

To further increase the drying efficiency, the drying section 18 may be equipped with a high-performance dryer, such as, inter alia, an impingement dryer and/or an infrared dryer. The impingement dryer is a high-performance dryer which applies a jet of hot air and/or a jet of hot steam at least on one side to the fibrous web. In this case, at least one such high-performance dryer can be arranged in particular in the initial region of the pre-drying section of the drying section 18, as a result of which the overall length of the plant can be further reduced. Furthermore, the strength of the end product is increased after the starch introduced has coagulated earlier.

Fig. 2 shows a schematic view of a screen section 14 of a further exemplary embodiment of the apparatus 10 according to the invention, which differs at least substantially from the apparatus according to fig. 1 only in the absence of forming rolls 25 in the screen section 14 and in that the entire dewatering section is guided substantially horizontally in the twin screen section.

List of reference numerals

10 device

12 headbox

14 screen section

16 press section

18 drying section

20 winding machine

22 net clamping former

Dewatering section at the rear of 24

25 forming roller

26 nip, shoe nip

28 first drying cylinder

30 lower conveyor belt

Claims

1. Is used for manufacturing a product of less than 100g/m²Has a headbox (12), a screen section (14) for dewatering a fibre suspension introduced by the headbox (12) and for forming the fibre web from the fibre suspension, a press section (16) for further dewatering the fibre web, and a drying section (18) for drying the fibre web, wherein the headbox (12) is designed with three layers and is provided with a separating sheet projecting beyond a headbox nozzle of the headbox (12), and a starch sizing element is provided, by means of which starch can be introduced into at least one layer, the screen section (14) comprises a single-layer wire former (22), and the press section (16) has at least one press nip (26) extending in the web travel direction (L)The gap former (22) is designed as a slatted gap former and comprises at least one horizontal dewatering section, wherein the slatted gap former is a gap former with a stationary initial dewatering element, by means of which the fibrous web is formed or dewatered.

2. An arrangement according to claim 1, characterized in that the at least one nip (26) extending in the web running direction (L) is at least one shoe nip.

3. An apparatus according to claim 1, characterized in that starch is inserted at least in the intermediate layer by means of said starch sizing element.

4. An apparatus according to any one of claims 1 to 3, characterized in that starch can be introduced into the fibre suspension before the headbox (12) by means of the starch sizing element.

5. An apparatus according to any one of claims 1 to 3, characterized in that starch can be introduced into the pulp jet produced by the headbox (12) by means of the starch sizing element in the headbox (12).

6. An arrangement according to any one of claims 1 to 3, characterized in that starch can be applied to the fibrous web by means of the starch sizing element at the latest in the screen section (14) after the headbox (12).

7. The apparatus according to claim 1, characterized in that the headbox (12) designed with three layers is fed through three inflow openings.

8. An apparatus according to claim 1, characterized in that the gap former (22) is designed without a suction roll.

9. An arrangement according to claim 1, characterized in that the press section (16) comprises two press nips (26) extending in the direction of travel of the web.

10. An arrangement according to claim 9, characterized in that the press section (16) comprises only the two press nips (26) extending in the web travelling direction (L).

11. An arrangement according to claim 9, characterized in that the two nips (26) extending in the direction of travel of the web are two shoe nips.

12. An apparatus according to claim 11, characterized in that the press section (16) comprises only two shoe nips.

13. An apparatus according to claim 2 or 11, characterized in that each shoe nip (26) is constructed between a shoe press roll and a counter roll provided with a polyurethane coating.

14. An apparatus according to claim 13, wherein the polyurethane coating of the respective roll of each shoe extruder has an open face in the range of 10% to 40%.

15. An apparatus according to claim 13, wherein the polyurethane coating of the corresponding roll of each shoe extruder has a thickness of 500 to 1500ml/m²A storage volume within the range.

16. An arrangement according to claim 9, characterized in that an impermeable lower transfer belt (30) is guided through the second or last press nip (26) of the press section (16) seen in the web travel direction (L).

17. An apparatus according to claim 1, characterized in that the dryer section (18) is designed at least partly with steel cylinders.

18. An apparatus according to claim 1, characterized in that the dryer section comprises at least one impingement dryer and/or at least one infrared dryer.

19. The apparatus of claim 1, wherein the fibrous web is a packaging paper web.