EP2432932A2

EP2432932A2 - Apparatus and method for treating a fibrous material web in a long nip press unit

Info

Publication number: EP2432932A2
Application number: EP10717020A
Authority: EP
Inventors: Wilhelm Mausser; Andreas Anzel
Original assignee: Andritz AG
Current assignee: Andritz AG
Priority date: 2009-05-19
Filing date: 2010-04-09
Publication date: 2012-03-28
Also published as: AT508305A3; CN101892605B; EP2264243A1; EP2264243B1; AT508305A2; PL2264243T3; WO2010132903A3; CA2703265A1; US20120055644A1; US20100300635A1; WO2010132903A2; US8349138B2; ATE549456T1; AT508331B1; CN101892605A; CN102428230A; ES2384090T3; AT508331A1; CA2703265C

Abstract

The invention relates to an apparatus and a method for treating a fibrous material web (9) in a paper or cardboard machine in a long nip press unit (29) comprising a press roll (24), which has a rotating press jacket (25) and a mating roll (23), wherein the fibrous material web (9) is dewatered in an extended press nip (26) between the mating roll (23) and the press jacket (25) of the press roll (24). According to the invention, the fibrous material web (9) is guided after the extended press nip (26) on a special rotating press jacket (25) of the press roll (24) to a transfer region (30), in which the fibrous material web (9) is transferred from the press jacket (25) to a transfer element (31, 27).

Description

Apparatus and method for treating a fibrous web in a long-nip press unit

The invention relates to a device for treating a fibrous web in a paper or board machine in a long-nip press unit with a

Press roll having a rotating or rotating press cover and a counter roll, wherein the fibrous web is dewatered in an extended press nip between the counter roll and the press cover of the press roll. The invention also relates to a method for treating a fibrous web which is carried out with the device according to the invention.

In conventional processes for paper and tissue production, the mechanical dewatering of a fibrous web before the thermal drying by a direct contact pressure of the fibrous web against a drying cylinder (Yankee cylinder). Such a production process is described in DE 102 33 920 A1. In these paper or tissue machines, however, the mechanical pressure or the achievable line load is limited because it is pressed against the Yankee drying cylinder. By an upstream pressing step, as described for example in EP 1 075 567 B1, the mechanical dewatering takes place in a pressing unit independent of the Yankee cylinder. Optimum pressing conditions can be set here, because you no longer press against the drying cylinder and thus are not limited by the load limits of the drying cylinder. The mechanical dewatering can be significantly improved by this upstream pressing step, which is preferably carried out with a long-nip press unit, in particular a shoe press. The expense for the thermal drying is reduced, which leads to energy savings.

EP 1 397 553 B1 describes a method for producing a fibrous web in which the fibrous web is dewatered by a shoe press before it is transferred to a through-flow drum (TAD) for thermal drying. In conventional paperboard manufacturing processes, one or more separate pressing steps for mechanical dewatering prior to thermal drying are prior art. Such a press arrangement is described, for example, in EP 0 954 634 B1. Again, the pressing steps are often performed with one or more Langnip press units, such as shoe presses.

For dewatering in a long-nip press unit, such as a shoe press, the fibrous web is passed on a felt through an extended press nip formed by a shoe press roll having a rotating press shell and a counter roll. After the extended press nip, the felt is separated as quickly as possible from the fibrous web. The fibrous web is then carried on either a string, which was also passed through the extended press nip, or by the backing roll.

The press cover of Langnip press units has contact with a covering in conventional systems in the extended press nip and serves only for mechanical dewatering. Therefore, the press jackets are optimized in conventional systems only for the pressing of the fibrous web but not for a further transport of the fibrous web. Conventional shoe presscoats are poorly suited for a reliable further transport of the fibrous web.

The further transport of the fibrous web is always realized by other components.

The aim of the present invention is to disclose a device for treating a fibrous web, in which the dewatering and the further transport of the fibrous web is to be realized without an intervening web transfer.

In the press arrangement according to the invention, the fibrous web is guided through an extended press nip of a Langnip press unit, wherein the Langnip- Pressing unit has a press roll with rotating press cover and a counter roll. The fibrous web is, following the extended press nip on the press cover of the shoe press roll to a transfer element, which takes over the fibrous web, out. Advantageously, the press roll is a shoe press roll.

Thus, the rotating press cover not only fulfills its function as a pressing element, but also serves as a means for further transport of the fibrous web after mechanical dewatering. A transfer fabric, which is performed in some embodiments in addition to the felt through the extended press nip, is therefore superfluous.

The aim of the invention is also to disclose a rotating press cover, with which a reliable further transport of the fibrous web can be carried out after the press nip.

The rotating press cover according to the invention consists of a carrier and an elastic compressible polymer layer. The compressible polymer layer is located on the side of the press jacket that touches the fibrous web. The polymer layer has a hardness between 50 and 97 Shore-A. The surface of the polymer layer which contacts the fibrous web has a reversible pressure-dependent roughness, this roughness in an unloaded state having a value of R _z = 2-80 μm and in a state loaded with a line load of 20-600 kN / m has a roughness of R _z = 0 to 20 microns. The roughness is measured according to ISO 4287, Part 1. The R _z value is the height of ten points, defined in the ISO standard as the average distance between the five highest peaks and the five lowest low points of the reference length measured from a line parallel to the center line and the surface profile not severed.

The fibrous web adheres very well to the disclosed flexible press cover by the pressing. In the state of the art currently only conveyor belts with the mentioned properties are known, as for example from EP 1 088 131 A1, but no press jackets.

Preferably, the circulating press cover is substantially impermeable, ie it has an air permeability of less than 6 m ³ / m ² / min, the air permeability being according to the Standard Test Method for Air Permeability of Textile Fabrics, ASTM D 737-75, American Society of Testing and Materials ".

The polymer layer may advantageously be a polymer composition such as acrylic polymer resin, polyurethane polymer resin or polyurethane / polycarbonate polymer resin composition.

The polymer layer may also comprise a particulate filler having a different hardness than the polymer layer, such as kaolin clay, a polymer material or metal, preferably stainless steel.

The invention also relates to a method for treating a fibrous web in a paper or board machine in a long-nip press unit with a

Press roll having a rotating press cover and a counter roll, wherein the fibrous web in an extended press nip between the

Counter roll and the press cover of the press roll is dewatered. The

Method according to the invention is characterized in that the fibrous web after the extended press nip on the rotating

Press jacket of the press roll to a transfer area in which the

Fiber web is passed from the press cover to a transfer element, is guided, wherein a press cover with the properties according to the

Claims 1 to 5 is used.

In the following the invention will be described with reference to drawings. It shows: Fig. 1 shows a paper machine with shoe press technology for the production of tissue paper according to the prior art

Fig. 2 shows a press section of a board machine according to the prior art

3 a tissue machine with the pressing arrangement according to the invention

4 shows a detailed view of the press arrangement according to the invention

Fig. 5 shows a board machine with the pressing arrangement according to the invention

Fig. 6 shows the course of a conventional and a long-nip press profile

The same reference numerals in the individual figures designate the same components.

In Fig. 1, a conventional tissue machine is shown with shoe press technology. About a headbox 1, the pulp suspension is fed to the forming unit, it occurs between a breast roll 4 and a forming roller 5 from the headbox 1 from. The breast roll 4 is wrapped by an outer fabric 2. In the forming unit, the pulp suspension is dewatered so far that forms a fibrous web 9 on the fabric 3. The fabric 3 is preferably a felt which conveys the fibrous web 9 to a shoe press roll 6. Between the shoe press roll 6 and the Yankee cylinder 7, an extended press nip is formed in which the fibrous web is mechanically dewatered and transferred to the Yankee cylinder 7. At the Yankee cylinder 7, the thermal drying of the fibrous web 9 takes place. A scraper 8 releases the dry fibrous web 9 from the Yankee cylinder 7. Due to the direct contact pressure of the fibrous web 9 to the Yankee cylinder 7, the mechanical drainage is limited, since the shoe press roll 6 can not press any strength on the Yankee cylinder 7 for stability reasons. Most of the maximum line load is limited to 170 kN / m. As a result of the press arrangement according to the invention, the mechanical dewatering of the fibrous web 9 relative to the press arrangement in FIG. 1 can be considerably increased.

Fig. 2 shows schematically a press section 11 of a board machine according to the prior art. The press section 11 is arranged after a wet end 10 and before a drying section 12. The fibrous web 9 is passed through the wire 13 of the wet end 10 to the press section 11. The web transfer to the press felt 14a is supported by the evacuated takeover roll 15. In the press section 11, the fibrous web 9 is mechanically dewatered by the two shoe presses 16a and 16b. The shoe presses 16a, 16b each consist of a shoe press roll 18a, 18b and a counter roll 17a, 17b. Between the shoe press rollers 18a, 18b and the counter rollers 17a, 17b, an extended press nip is formed, in which the fibrous web 9 is mechanically dewatered. The moisture from the fibrous web 9 is thereby received by the press felts 14a, 14b, 14c and 14d, which are also performed together with the fibrous web 9 through the extended press nips.

After the mechanical dewatering, the fibrous web 9 is transferred by means of the transfer roller 22 to the dryer wire 21 of the dryer section 12. In the drying section 12, the fibrous web 9 is guided through the drying wire 21 meandering over the drying cylinder 19 and the suction rolls 20 and thereby thermally dried.

FIG. 3 now shows a tissue machine with the pressing arrangement according to the invention. It consists of a long-nip press unit 29, which has a press roll 24 with rotating press cover 25 and a counter-roller 23. Between the press roll 24 and the counter roll 23, an extended press nip 26 is formed.

The press arrangement according to the invention now works in the following way: The fibrous web 9 is guided on the felt 33 through the extended press nip 26. In the extended press nip 26, the felt 33 takes moisture from the Fiber web 9 on. The felt 33 has a three-dimensional structure in the present example. The fibrous web 9 can thereby escape during the pressing process in the three-dimensional structure of the felt 33. The pressure is thus punctiform and not flat. The felt 33 is separated from the fibrous web 9 immediately after the extended press nip 26 in order to avoid rewetting.

After the extended press nip 26, the fibrous web no longer runs on the felt 33 but on the press cover 25 on. The press cover 25 consists of a carrier and an elastic compressible polymer layer. The compressible polymer layer is located on the side of the press jacket that touches the fibrous web. The polymer layer has a hardness between 50 and 97 Shore-A. The surface of the polymer layer which contacts the fibrous web has a reversible pressure-dependent roughness, this roughness in an unloaded state having a value of R _z = 2-80 μm and in a state loaded with a line load of 20-600 kN / m has a roughness of R _z = 0 to 20 μm. The press cover 25 is substantially impermeable, ie it has an air permeability of less than 6 m ³ / m ² / min.

The carrier may e.g. consist of a multi-layered woven structure made of a polymer monofilament yarn such as polyester, polyamide and the like.

In a transfer region 30, the press cover 25 transfers the fibrous web 9 to a transfer element 31. In the present example, the transfer element 31 is a transfer cover 27. However, the transfer element can also be a roller which takes over the fibrous web 9 from the press cover 25. This roller can also be drained.

The fibrous web transfer to the transfer fabric 27 is supported by the drawn roll 28. Between the evacuated roller 28 and the

Press roll 24 is an extended transfer nip 32 is formed. The transfer fabric 27 is permeable in the present example, of course, the use of a non-permeable transfer fabric 27 is conceivable. The transfer fabric 27 may have a smooth or a textured surface.

In the transfer region 30, a further web treatment step of the fibrous web 9 can be carried out, namely a creping or stretching of the fibrous web 9. For a crepe, the surface of the transfer fabric 27 moves slightly slower (lower relative speed) through the extended transfer nip 32 than the press cover 25, thus the fibrous web 9 is slightly compressed or creped during the transfer to the transfer fabric. Conversely, it is also possible to apply tensile forces to the fibrous web 9, which lead to an expansion of the fibrous web 9. For this purpose, the transfer cover 27 moves slightly faster (higher relative speed) than the press cover. A faster-moving transfer cover 27 can also have a positive effect on the fibrous web transfer.

The conditioning of the transfer fabric 27 should be such that there is no or only a very small moistening of the transfer fabric

27 comes through the conditioning process. Therefore, the conditioning can be carried out for example with compressed air or a compressed air sword.

When conditioning with water, it must be ensured that the

Transfer fabric 27 is dried or sucked dry before it takes over the fibrous web 9 again.

To stabilize the fibrous web 9 on the transfer fabric 27, it may be advantageous if the region in which the transfer fabric 27, the

Fiber web transported 9, is continuously sucked.

Following the mechanical dewatering in the long-nip press unit 29, the thermal drying takes place on a Yankee cylinder 7, from which the dry fibrous web 9 is scraped off with the aid of a scraper 8. In Fig. 3, an adjustable felt guide 40 is shown. By this adjustable Filzleitwalze 40, the exit angle of the felt 33 can be adjusted from the Langnip- pressing unit 29, for example by +/- 15 °. Thereby, the contact surface or the contact length of the felt 33 with the fibrous web 9 after the extended press nip 26 is adjustable. The adjustability of the felt guide roll 40 is represented by a double arrow.

By enlarging this contact surface or contact length, it is possible to ensure that the felt 33 runs along the press cover 25 for a little longer, the fibrous web 9 being clamped between the felt 33 and the press cover 25. A reduction of this contact surface between felt 33 and fibrous web 9 causes a particularly rapid separation of the felt 33 from the fibrous web 9 after the extended press nip 26. To transfer a Einfädelstreifens first as large a contact surface is realized are, so that the threading securely runs along the press cover 25. After threading and spreading the fibrous web 9, this contact surface can be reduced so that the rewet of the fibrous web 9 is minimized.

Through the steam blower box 36, the fibrous web can be heated.

In Fig. 4, the long-nip press unit 29 according to the invention is shown in more detail. It can clearly be seen the extended press nip 26 between the press cover 25 of the press roll 24 and the backing roll 23. Also recognizes the extended transfer nip 32 between the press cover 25 of the press roll 24 and the transfer fabric 27. The press roll 24 is designed as a shoe press roll.

The extended transfer nip 32 is formed by the transfer fabric 27 being pressed against the press cover 25 by a roller, in the present case by a drawn roll 28, the press cover 25 in the transfer region 30 substantially following the surface contour of the roller 28. The support and guide surface of the press roll 24 for the press cover 25 is formed in the transfer region 30 so that the press cover 25 in this area to the center axis 39 of the press roll 24th is pressed in, similar to that in the region of the extended press nip 26 of the case. By changing the immersion depth of the press jacket 25, the length of the extended transfer nip 32 can be changed.

In the interior of the press roll 24, an overpressure is applied, by means of which the circulating press jacket 25 is stabilized. The end faces of the press roll 24 have corresponding sealing cover.

The backing roll 23 of the long-nip press unit 29 may have grooves in the cross-machine direction to improve the drainage. The

Grooves should be as narrow as possible and as close together as possible, this can significantly improve the drainage. A

Groove width smaller than 0.5 mm, especially smaller than 0.4 mm, and a groove number of 5 or more grooves per cm in the circumferential direction of the backing roll 23 is desirable. The surface of the mantle roll 23 may for example be made of a hard elastomer or of metal, in these materials, the grooves can be incorporated well.

FIG. 4 shows cleaning devices 34 for cleaning the press jacket 25 after the transfer area 30. The cleaning devices 34 may be one or more scrapers, or else they may be

Spray nozzles for a cleaning fluid such as water or air. The

Cleaning device 34 may also for the web removal during transfer of the

Fiber web 9 can be used. The fibrous web 9 can be removed from the press cover 25, for example, be scraped, and a

Pulper are supplied until the web has stabilized and the

Fiber web 9 of the dryer section can be supplied.

In addition, an interface regulation mixture can be applied to the surface of the press jacket 25 before the press cover 25 passes through the extended press nip 26. The application can be carried out for example by a spray bar 35 with spray nozzles which spray the Grenzflächenregulierungsgemisch on the press cover 25. By This process step, the surface adhesion of the fibrous web 9 can be influenced on the press cover 25.

Interfacial control mixtures include, but are not limited to, all fluids used to surface finish Yankee cylinders 7, as well as TAD chemicals.

The dewatering of the fibrous web 9 in the extended press nip 26 can also be improved by heating the fibrous web 9, for example by means of a steam blower box 36, which is arranged in front of the extended press nip 26. The adjustable felt guide roll 40 is also shown.

2, but this time with the long-nip press unit 29 according to the invention. The transfer of the fibrous web 9 from the press cover 25 is effected directly onto the dryer wire 21 of the dryer section 12. The fibrous web transfer in the extended transfer nip 32 is through the suctioned Roller 28 supports. The length of the extended transfer nip 32 can be controlled by the immersion depth of the evacuated roll 28 into the nip roll 24.

A comparison with FIG. 2 shows that the press felt 14c is no longer needed in the board machine according to the invention.

In the extended press nip 26, a precisely defined press profile can act on the fibrous web 9. Such a press profile of a long-nip press unit 29 is shown in FIG. 6 as a curve 37. Curve 38 shows a press profile of a press unit with standard rollers without extended press nip 26. The adjustable felt guide 40 also allows adjustment of the contact surface or the contact length between felt 33 and fibrous web 9 after the extended press nip 26. Again, a steam blower box (not shown) be provided to heat the fibrous web 9 before the extended press nip 26. In the long-nip press unit 29, the smallest possible pressing pressure on the fibrous web 9 should preferably act on entry of the fibrous web 9 into the extended press nip 26. This pressing pressure then rises slowly, as can be clearly seen from the curve 37 in FIG. 6. By this gentle increase of the pressing pressure, the specific volume (BuIk) of the fibrous web 9 is maintained. With increasing dry content of the fibrous web 9 and the pressing pressure for further drainage can be increased, without thereby the BuIk is significantly affected. At a dry content of 40 to 50%, the pressing pressure reaches a maximum. At the end of the extended press nip 26, the pressing pressure should drop as quickly as possible, since this largely prevents or minimizes rewetting of the fibrous web 9 by the felt 33.

The embodiments shown in the drawings represent only a preferred embodiment of the invention. The invention also includes other embodiments in which, for example, the press cover 25 is partially wrapped in the transfer region 30 by the transfer fabric 27. This also forms an extended transfer nip 32 for the transfer of the fibrous web 9.

Claims

claims

1. Press arrangement of a paper or board machine for treating a fibrous web (9), wherein the fibrous web (9) by an extended press nip (26) of a Langnip-pressing unit (29) is guided, wherein the Langnip- pressing unit (29) a press roll (24) with a rotating press cover (25) and a counter roll (23), characterized in that the fibrous web (9) following the extended press nip (26) on the press cover (25) of the press roll (24) to a transfer element (31, 27), which takes over the fibrous web (9), is guided, wherein the rotating press jacket (25) consists of a support and an elastic compressible polymer layer, wherein the polymer layer facing the fibrous web and a hardness between 50 and 97 Shore A and wherein the fibrous web contacting surface of the polymer layer has a reversible pressure-dependent roughness, the roughness of R _z = 2-8 in an unloaded state 0 μm, measured in accordance with ISO 4287, and has a roughness of R _z = 0 to 20 μm in a state loaded with a line load of 20 - 600 kN / m.

2. Press arrangement according to claim 1, characterized in that the peripheral press cover (25) is substantially impermeable.

3. Press assembly according to claim 1 or 2, characterized in that the polymer layer comprises a polymer composition such as acrylic polymer resin, polyurethane polymer resin or a polyurethane / polycarbonate polymer resin composition.

4. Press arrangement according to one of claims 1 to 3, characterized in that the polymer layer comprises a particulate filler, such as kaolin clay, a polymer material or metal, preferably stainless steel.

5. Press arrangement according to one of claims 1 to 4, characterized in that the polymer layer completely surrounds the carrier.

6. A method for treating a fibrous web (9) in a paper or board machine in a long-nip press unit (29) with a press roll (24) having a rotating press cover (25) and a counter-roller (23), wherein the fibrous web ( 9) in an extended press nip (26) between the backing roll (23) and the press shell (25) of the press roll (24), characterized in that the fibrous web (9) after the extended press nip (26) on the rotating press shell ( 25) of the press roll (24) to a transfer region (30), in which the fibrous web (9) from the press cover (25) is transferred to a transfer element (31, 27) is guided, wherein a rotating press cover (25) according to one of Claims 1 to 5 is used.