AU1249600A

AU1249600A - Process and device for producing a fibrous material web

Info

Publication number: AU1249600A
Application number: AU12496/00A
Authority: AU
Inventors: Josef Bachler; Gunter Halmschlager; Christoph Merckens
Original assignee: Voith Sulzer Papiertechnik Patent GmbH
Current assignee: Voith Patent GmbH
Priority date: 1999-01-28
Filing date: 2000-01-19
Publication date: 2000-08-03
Also published as: EP1075568B1; AU3276400A; DE19903943A1; ATE335101T1; ATE325232T1; EP1024224A2; EP1024224A3; EP1024224B1; EP1075568A1; NZ502443A; DE59913733D1; WO2000044980A1; DE50012677D1

Abstract

The additive supply unit (21) has a controller varying the volumetric flow and pressure of the additive. Preferred features: The supply unit has a connection for admixture of e.g. compressed air or steam. It is located near the start or the central region of the dewatering zone. Following the supply unit there is a balanced pressure, reduced-intensity dewatering section, e.g. its plate is non-perforated. The supply unit extends over the band width, divided into several sections, each individually controlled to discharge a fraction of the additive. They have moving cleansing units. Spacing between successive dewatering sections (16A, 16B) is variable. In the double band zone, against one porous band, there is a porous plate dewatering section, opposed to strip formations on the opposite side of the double band. Strip widths and/or their spacing vary. Plate and/or strips are pressed flexibly against the double band.

Description

AUSTRALIA

Patents Act 1990 COMPLETE SPECIFICATION FOR A STANDARD PATENT 0 t 0L** 4 *4* Name of Applicant: Actual Inventors: Address for Service: VOITH SULZER PAPIERTECHNIK PATENT

GMBH

GOnter HALMSCHLAGER, Josef BACHLER, Christoph MERCKENS CULLEN CO., Patent Trade Mark Attorneys, 240 Queen Street, Brisbane, QId. 4000, Australia.

Invention Title: PROCESS AND DEVICE FOR PRODUCING A FIBROUS MATERIAL WEB The following statement is a full description of this invention, including the best method of performing it known to us Process and Device for Producing a Fibrous Material Web The invention relates to a process for producing a fibrous material web, in particular a paper or cardboard web, from a fibrous material suspension. The invention also relates to a device for carrying out this process.

The starting point for the invention is the Patent Application EP0894894 (file PA10569 EP which has not yet been published. According to this Patent Application, the formation of a fibrous material web occurs between two endless, water-permeable belts, preferably wire belts. This takes place in a known manner by virtue of the fact that a part of the suspension fluid is removed through the belts. In a part of this web-forming zone, the 10 belts, together with the fibrous material web forming between them, is guided between socalled uniform pressure drainage elements in the form of perforated plates). A particular embodiment provides for an additive to be supplied to the fibrous material web being formed by virtue of the fact that this additive flows through one of the uniform pressure drainage elements and through the porous belt traveling on top of it. For example, an ink, filler, adhesive, or draining agent is provided as the additive.

The object of the present invention is to improve the web forming process and the device affiliated therewith to the extent that certain properties of the finished fibrous material web are improved.

In the course of this, as many of the following requirements as possible should be fulfilled.

1) It should be possible to deliberately influence the so-called two-sidedness of the fibrous material web; the intent is either to achieve as little two-sidedness as possible (the most uniform properties possible on both sides of the web) or to produce -laan "intentional two-sidedness" so that the two sides of the fibrous material web have different properties.

2) An additive supplied to the fibrous material web should be employed in the best possible manner, a rinsing-out of the additive should be prevented to the greatest extent possible during the further drainage of the fibrous material web.

3) If the fibrous material web produced is united with another fibrous material web for the purpose of producing a multi-ply product, then the so-called ply bond between the two webs should be as high as possible.

It should be possible to influence the cross profile of particular web properties.

.oo The intent is to be able to influence the intensity of the drainage, for example, in particular partial regions of the web-forming zone.

This object is attained with the process according to the invention in that the supply ••of the additive is controlled or regulated in such a way that the fibrous material web formed has the respectively deliberate (slight or clearly perceptible) two-sidedness. In other words, the supply of the additive is controlled or regulated in such a way that, with regard to a particular surface quality (or with regard to a particular quality level that can be measured on the surfaces of the web), a particular ratio is produced between the properties or quality levels of the two sides of the web.

In a particular embodiment of the process according to the invention, during the continuous manufacturing process, a particular property is continuously measured on both sides of the traveling fibrous material web paper web). Thus, a continuous determination is made as to whether the intended degree oftwo-sidedness is being achieved.

If the degree of two-sidedness deviates from the intended value of two-sidedness (set point), then the volume flow and/or the pressure of the additive being supplied, for example, is varied in such a way that the two-sidedness approaches the set point in the fibrous material web being produced, preferably with the aid of a closed control loop. By varying the pressure, the penetration depth of the additive, among other things, can be controlled in a deliberate manner. This leads to an optimization of the distribution of additive in the Z-direction.

Other embodiments of the process according to the invention are disclosed in the claims that are dependent on claim 1. A particularly important further concept of the invention is that a fine fibrous material suspension is used as an additive. This can preferably obtained from the suspension fluid removed in the beginning region of the twin wire zone, the so-called white water. In this instance, a definite, particularly high, fines content can be produced on one of the two web sides of the fibrous material web or on both of the web sides. The level of the fines content is important, for example, for the printability of the finished fibrous material web. In a similar manner, it is important in the production of a multioo ply product that, before the uniting of two fibrous material webs, the fines content of the web sides coming into contact with one another has been increased to the greatest extent possible.

Other possible additives include filler suspension, polymer solution, adhesive solution, or starch solution, or an ink that is supplied, for example, at a particular location.

The following applies to all embodiments or intended uses of the process according to the invention.

In all cases, the location of the supply of the additive is the region of the so-called uniform pressure drainage. This is the region of the web formation in which the drainage takes place through the use of an essentially pulsation-free drainage pressure. This means that, in the relevant part of the web-forming zone, the drainage pressure either remains essentially the same or changes almost continuously, increases. Consequently, a drainage of this type differs from the drainage method normally used in the beginning region of the web formation in which, with the aid of so-called forming strips, pressure pulsations are produced in the suspension still present between the belts. This results in the fibrous material remaining as uniformly distributed as possible during the web formation process.

A particular advantage of the supply location (for the additive) in the vicinity of the uniform pressure drainage is then comprised in that after the supply of the additive, the subsequent drainage can be controlled in such a way that as little as possible of the supplied additive is lost. This is achieved, for example, by virtue of the fact that the additive is supplied at the beginning region or in the middle region of the uniform pressure drainage zone and that, downstream of the supply point, the intensity of the subsequent drainage is reduced o• on the relevant side of the web. For example, the drainage can be completely suppressed in a particular section. At the same time, the intensity of the drainage on the opposite web side can be increased, for example, through the use of a vacuum and/or by virtue of the fact that increased perforation cross sections are provided in a particular region.

The prevention of the drainage on the side of the web on which the additive has been supplied is possible, for example, by virtue of the fact that a closed, non-perforated, plate element is provided in a particular partial region of the uniform pressure drainage zone or by -virtue of the fact that a part of the perforation is closed, for example, with the aid of a compressed air buffer. In any case, it is assured that a very high retention of the supplied additives can be expected. Otherwise, the invention also assures that the fines and/or fillers contained in the fibrous material suspension from the beginning are retained to a higher percentage than previously in the fibrous material web being formed.

As an alternative to the embodiment concept defined in claim 1, the stated object can also be attained according to claim 14 by virtue of the fact that, with the aid of uniform pressure drainage elements of different permeabilities, it is possible to assure that drainage through the one belt is more intense than the drainage through the other belt. In the extreme case, in a particular region of the uniform pressure drainage zone, the removal of suspension fluid through one of the two belts can be suppressed at least to a large extent, namely with the aid of a water-impermeable uniform pressure drainage element. The latter assures that, on this side of the fibrous material web being formed, the fines and/or fillers that are supplied with the fibrous material suspension cannot escape. As a result, a fibrous material web is obtained which has a considerably higher proportion of fines and/or fillers on one side of the web.

The stated object, based on a device according to the Patent Application mentioned at the beginning, is also attained by means of the characterizing features of claim 16. Other o. embodiments of the invention are disclosed in the claims that are dependent on claim 16.

•Claims 23 to 26 pertain to possibly advantageous measures for the additional control of the drainage intensity and for the most uniform possible distribution of the fibrous material; these measures can also be used independently of those in claim 1.

Numerous other possibilities for embodying the process according to the invention and the device according to the invention are contained in the Patent Application EP0894894 mentioned at the beginning. It is expressly emphasized that all features described in this as yet unpublished application can be combined with the features of the current application.

Exemplary embodiments of the invention will be explained below in conjunction with the accompanying drawings.

Fig. 1 is a schematic side view of a twin-wire former with an additive supply.

Fig. 1A shows a detail from Fig. 1, Fig. 2 is an oblique view of a possible modification of the additive supply device from Fig. 1, Fig. 3 shows a former for producing a two-ply fibrous material web, and Fig. 4 shows a modified detail from Fig. 3.

In Fig. 1, a headbox 1 can be seen (shown only by way of example as a multi-layer headbox), which "shoots" a fibrous material suspension flow into a nip that is formed by two wire belts S1 and S2 at the beginning of the twin wire zone. At this point, the two wire belts SI and S2 travel over a forming suction roll 10 which is disposed inside the loop of the lower S.wire S1. The upper wire S2 travels from a wire guide roll 9 onto the forming roll and winds around this in the vicinity of a forming zone FZ. Forming strips can be provided there inside the loop of the upper wire S2, but have been omitted in the drawing. In the forming zone FZ, the formation of a fibrous material web begins by means of the removal of suspension fluid ""through the wires.

o: The removed suspension fluid flows in a known manner, partly through the forming roll 10 and partly through a catch container 27 disposed inside the loop of the upper wire.

In the web travel direction downstream of the forming zone FZ, a uniform pressure drainage zone GE is provided in which a number of uniform pressure drainage elements 16 are disposed. For example, these are plate segments that are disposed one after the other in the web travel direction and are connected to one another in an articulated fashion. They are perforated in order to permit the removal of further suspension fluid. According to Fig.

1, the perforation is embodied as essentially the same in all of the plate segments. In contrast to this, however, the perforation diameter and/or the number of perforations can be selected as different from segment to segment. Instead of cylindrical bores, conically widening bores can be provided. Instead of bores disposed perpendicular to the wire plane, oblique bores can also be provided. A part of the suspension fluid can also be removed through the gap between two adjacent plate segments; see the gap between the plate segments 16A and 16B. In order to control the drainage intensity, the internal width of the above-mentioned gap can be changed by shifting the plate segment 16B in the direction of the double arrow shown.

The upper plate segments 15 and 15A are fastened to a support structure 8 by means of their articulations. The lower plate segments 16, 16A, and 16B in turn rest against pneumatic hoses 4. The internal pressure in each of the pneumatic hoses 4 can be individually controlled so that each of the plate segments can be pressed flexibly against the inside of the lower wire S 1 with a force that can be freely selected. If necessary, the plate segments 15, 16 can be heated electrically, for example, as schematically indicated by the reference character 20. In addition, if necessary, an oscillation producer or oscillator (not shown in the drawing) can be .oo• connected to the plate segments. A suction separator 13 is disposed at the end of the twin wire zone in a known manner. This assures that the fibrous material web produced separates from the upper wire S2 and continues to travel with the lower wire S 1, from which the web is removed in a known manner and is supplied to other treatment stations.

!According to the invention, one of the central upper plate segments 15 is provided with a supply device for the additive, which is indicated as a whole with the reference character 21. This supply device includes a storage tank 22, a pump 23 if necessary, a control valve 24, and a distribution chamber 25 disposed on the plate segment 15A, as well as associated tube lines.

If necessary, a propellant from a reservoir 26, compressed air (preferably heated) or steam, can be supplied to the additive between the control valve 24 and the distribution chamber 25, among other things, for the purpose of controlling the penetration depth. In contrast to Fig. 1, the plate segment 15A that.immediately follows the supply device 21 can be embodied as closed (without perforation). Fig. 1A shows a cleaning device in the form of a shower pipe 19, which can be moved back and forth along the support device 8.

Fig. 2 shows a modified embodiment of the supply device, labeled as a whole with the reference character 21A. The distribution chamber 25A is subdivided into numerous sections over the web width. A supply line with an individually controllable control valve 24A feeds into each section. If the addition of a propellant from a reservoir 26A is provided in turn, then this propellant is likewise supplied to each section by way of an individually controllable line, either directly into the relevant section of the distribution chamber 25A or into the section line downstream of the control valve 24A. By means of this, influence can be exerted on the cross profile of one web property or another, the cross profile of the basis weight, the dry matter content, or the ash content.

S.I :The basic design of the multi-ply former shown in Fig. 3 corresponds to that in Fig.

ofEP0851058 (file PA10449). A fourdrinier wire unit 31 is shown, with an approximately horizontally guided wire belt 32 that has a travel direction according to the arrow 33. A first :o fibrous material ply is formed on the wire belt 32 by means ofa headbox 34 and with the aid of a number of drainage elements 35. In order to form a second fibrous material ply, a twinwire former, labeled as a whole with the reference character 40, is disposed above the unit 31 oooo and has two wire belts 41 and 42, which form a twin wire zone with each other. This zone in turn begins at a forming roll 43. In the upper region of this forming roll, a fibrous suspension flow is "shot" between the wires 41 and 42 by means ofa headbox 44. The two wires, along with the fibrous material web forming between them, travel top to bottom from the forming roll 43; they then wind around a drainage box 45, whose curvature runs opposite the curvature of the forming roll casing. A water catch container is labeled with the reference character 46.

The two wires then travel between two plate-shaped uniform pressure drainage elements 47 and 48, whereupon the two wire belts separate. A suction separator 49 is provided downstream of the drainage element 47 disposed inside the loop of the one wire belt 41, so that the second fibrous material ply produced travels along with the wire belt 41 to the couch roll 50. This couch roll brings the two fibrous material plies in contact with each other so that they are united to form a two-ply fibrous material web. This two-ply fibrous material web is separated from the wire belt 41 by means of another suction separator 36 and continues to travel together with the wire belt 32, for example, by way of a suction box 37 and a wire suction roll 38.

The fibrous material web is then removed from the wire belt 32 in a known manner by means of a felt band and a pickup roll 39 and is supplied to a subsequent unit a press section).

:The plate-shaped drainage element 47 is attached, for example, to a water catch container 47a; it has partly cylindrical, partly conically extending perforations. The plate- 15 shaped drainage element 48, which is disposed inside the loop of the other wire belt 42, *g underneath the forming roll 43, rests on a water catch container 48a with the interposition of pneumatic hoses and, as a result, can be flexibly pressed with an adjustable force against the inside of the wire belt 42.

0**0 *ga.

o0oo Similar to Fig. 1, a supply device 51 for an additive is once again provided, including a storage tank 52, a pump 53, a control valve 54, and a distribution chamber 55. The latter is disposed in the beginning region of the uniform pressure drainage zone, at the upper end of the plate-shaped drainage element 48. According to Fig. 3, this plate-shaped drainage element 48 is perforated over its entire length. However, is also possible that, underneath the distribution chamber 55, the plate 48 is closed, at least in certain areas. As a result, it can be assured that the supplied additive penetrates as far as possible into the fibrous material web being formed and remains therein. Preferably, a fine fibrous material is supplied as the additive. As a result, the underside of the second fibrous material ply formed in the twin-wire former is enriched with fines. In the first fibrous material ply formed on the fourdrinier wire unit 31, the top side has a relatively high fines content because the drainage only occurs toward the bottom. Consequently, the sides of the two fibrous material plies which have an increased fines content come into contact with each other on the couch roll 50. As a result, this produces an increased ply adhesion of the finished multi-ply product.

Fig. 4 shows a possible modification of the structure according to Fig. 3. In contrast to Fig. 3, in Fig. 4, the plate-shaped uniform pressure drainage element 48', which is disposed inside the loop of the wire belt 42, beneath the forming roll 43, is embodied as a closed plate, in which a supply device for an additive has been eliminated. In this case, an enrichment of fines takes place in turn in the uniform pressure drainage zone, on the underside of the second fibrous material ply being produced because, in this instance, the drainage only takes place SS through the perforation of the other plate-shaped drainage element 47. The result is the same S° or similar to the one achieved in the embodiment according to Fig. 3.

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