EP1024224B1 - Process and apparatus for making a fibrous web - Google Patents

Process and apparatus for making a fibrous web Download PDF

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Publication number
EP1024224B1
EP1024224B1 EP99125356A EP99125356A EP1024224B1 EP 1024224 B1 EP1024224 B1 EP 1024224B1 EP 99125356 A EP99125356 A EP 99125356A EP 99125356 A EP99125356 A EP 99125356A EP 1024224 B1 EP1024224 B1 EP 1024224B1
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EP
European Patent Office
Prior art keywords
dewatering
additive
web
process according
fibrous web
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EP99125356A
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German (de)
French (fr)
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EP1024224A2 (en
EP1024224A3 (en
Inventor
Günter Dr. Halmschlager
Josef Bachler
Christoph Merckens
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Voith Patent GmbH
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Voith Paper Patent GmbH
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Publication of EP1024224A3 publication Critical patent/EP1024224A3/en
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    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21F—PAPER-MAKING MACHINES; METHODS OF PRODUCING PAPER THEREON
    • D21F9/00—Complete machines for making continuous webs of paper
    • D21F9/003—Complete machines for making continuous webs of paper of the twin-wire type
    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
    • D21H23/00—Processes or apparatus for adding material to the pulp or to the paper
    • D21H23/02—Processes or apparatus for adding material to the pulp or to the paper characterised by the manner in which substances are added
    • D21H23/22—Addition to the formed paper
    • D21H23/24—Addition to the formed paper during paper manufacture
    • D21H23/26—Addition to the formed paper during paper manufacture by selecting point of addition or moisture content of the paper
    • D21H23/28—Addition before the dryer section, e.g. at the wet end or press section

Definitions

  • the invention relates to a method for forming a fibrous web, in particular a paper or board web, from a pulp suspension.
  • the invention also relates to an apparatus for carrying out this method.
  • a dye for example, a dye, a filler, glue or a drainage aid is provided.
  • the present invention has for its object to further develop the web forming process and the associated device in that certain properties of the finished fibrous web are improved.
  • This object is achieved in the inventive method in that the addition of the additive is controlled or regulated so that in the formed fibrous web a certain ratio between a grade, e.g. Fines content, the top of the track and this grade of the track bottom is achieved.
  • a grade e.g. Fines content
  • a specific property is continuously measured on both sides of the continuous fibrous web (eg paper web) during the continuous production process. This will continuously determine if the desired degree of two-sidedness is achieved.
  • the volume flow and / or the pressure of the additive to be added is varied, preferably by means of a closed control loop, such that the two-sidedness occurs in the resulting fibrous web approaches the target value.
  • the penetration depth of the additive can be selectively controlled. This leads to an optimization of the distribution of the additive in the Z direction.
  • a particularly important further concept of the invention consists in using as additive a fine pulp suspension. This can preferably be obtained from the suspension liquid removed in the initial region of the double-belt zone, the so-called white water.
  • the amount of fines content is important, for example, for the printability of the finished fibrous web.
  • Other possible additives are: filler suspension, polymer solution, glue or starch solution or a locally added dye.
  • the obstruction of the drainage on the web side to which the additive has been added is possible by providing a closed, ie non-perforated plate member in a certain portion of the DC pressure dewatering zone or by blocking off a portion of the perforation, for example with Help of a compressed air cushion.
  • the removal of suspension fluid through one of the two belts can at least largely be prevented in a certain region of the constant-pressure dewatering zone, namely with the aid of a water-impermeable constant-pressure dewatering element.
  • the latter ensures that can not escape on this side of the forming fibrous web zoom brought up with the pulp suspension fine and / or fillers.
  • the result is a fibrous web which has on one side of the web a significantly higher proportion of fillers and / or fillers.
  • Claims 23 to 26 may relate to advantageous measures for additionally controlling the dewatering intensity and distributing the fiber material as evenly as possible; These measures are also applicable independently of those of claim 1.
  • a headbox 1 (shown only by way of example as a multi-layer headbox), which injects a pulp suspension flow into a gusset formed at the beginning of a twin-wire zone by two sieve belts S1 and S2
  • the two sieve belts S1 and S2 run at this point via a Formiersaugwalze 10, which lies in the loop of the lower wire S1.
  • the upper wire S2 runs from a Seibleitwalze 9 on the forming and wraps around this in the region of a forming zone FZ
  • the removed suspension liquid flows in a known manner partly through the forming roller 10, partly through a collecting container 27 located in the loop of the top wire.
  • an equal-pressure dewatering zone GE in which a plurality of equal-pressure dewatering elements 15,16 are arranged. These are, for example, arranged in the web running direction one behind the other and hinged together plate segments. These are perforated, thereby allowing the removal of further suspension liquid. According to Figure 1, the perforation in all plate segments is formed substantially the same. Deviating from this, however, one can choose the perforation diameter and / or the number of perforations from segment to segment differently. Instead of cylindrical holes can be provided conically widening holes. Instead of arranged perpendicular to the plane of the drill holes and oblique holes can be provided.
  • a part of the suspension liquid can also be removed by the gap existing between two adjacent plate segments; see, e.g. the gap between the plate segments 16A and 16B.
  • the upper plate segments 15 and 15A are attached to a support structure 8 by means of their joints.
  • the lower Plattensegemente 16, 16A and 16B rest dagen on pneumatic tubes 4.
  • the internal pressure in each of the pneumatic tubes 4 is individually adjustable, so that each of the plate segments with a freely selectable force to the inner side of the lower wire S1 is pressed pressed. If necessary, one can electrically heat the plate segments 15, 16, for example, as indicated schematically at 20.
  • a vibrator or oscillator (not shown in the drawing).
  • a separating sucker 13 This ensures that the fibrous web formed separates from the upper wire S2 and continues with the lower wire S1, from which the web is removed in a known manner and fed to other treatment stations.
  • one of the middle, upper plate segments 15 is provided with an additive feeder, generally designated 21.
  • This feeder comprises a reservoir 22, if necessary a pump 23, a control valve 24 and a distribution chamber 25 arranged on the plate segment 15A and associated piping.
  • the additive between the control valve 24 and the distribution chamber 25 may be supplied from a reservoir 26 with a propellant, e.g. Compressed air (preferably heated) or add steam, u. a. for the purpose of controlling the penetration depth.
  • a propellant e.g. Compressed air (preferably heated) or add steam, u. a. for the purpose of controlling the penetration depth.
  • FIG. 1A shows a cleaning device in the form of a spray tube 19, which can be displaced back and forth along the carrier device 8.
  • FIG. 2 shows a modified embodiment of the feed device, designated overall by 21A.
  • the distribution chamber 25A is divided across the web width into numerous sections. In each section opens a supply line with an individually controllable control valve 24A. In turn, if adding a propellant from a reservoir 26A is provided, it is also supplied to each section via an individually controllable conduit, either directly into the respective section of the manifold chamber 25A or into the section conduit downstream of the control valve 24A.
  • FIG. 3 The basic construction of the multilayer former shown in FIG. 3 corresponds to that of FIG. 1 of European patent application EP0851058 A2.
  • a Fourdrinier-Langsieb aggregate 31 with an approximately horizontally guided screen belt 32 in the direction of arrow 33.
  • On the screen belt 32 is formed by means of a headbox 34 and with the aid of several dewatering elements 35, a first pulp layer.
  • a double-wire former designated as a whole by 40, is arranged above the unit 31, with two screen belts 41 and 42 which together form a double-layer zone. This in turn begins at a forming roller 43.
  • a fiber suspension flow is injected between the screens 41 and 42 by means of a headbox 44.
  • the two screens, together with the fibrous web therebetween run down from the forming roller 43 from top to bottom; They then wrap around a dewatering box 45, the curvature of which is opposite to the curvature of the forming roll mantle.
  • a separating sucker 49 is provided behind the arranged in the loop of a sieve belt 41 dewatering element 47 so that the formed second pulp layer runs with the wire 41 to the couch roll 50. This brings the two pulp layers in contact with each other, so that they are joined together to form a two-ply fibrous web.
  • This two-ply fibrous web is separated from the screen belt 41 by means of a further separating sucker 36 and continues to run together with the screen belt 32, e.g. via a suction box 37 and a suction sieve 38.
  • the plate-shaped dewatering element 47 is attached, for example, to a water collecting container 47a; it has partly cylindrical and partly conical widening perforations.
  • the arranged in the loop of the other screen belt 42 below the forming roller 43 plate-shaped drainage element 48 rests - with the interposition of pneumatic hoses - on a water collecting container 48a and can be pressed with an adjustable force yielding to the inside of the wire 42.
  • a feed device 51 is again provided for an additive, comprising a reservoir 52, a pump 53, a control valve 54 and a distribution chamber 55.
  • the latter is in the initial region of the constant-pressure dewatering zone, ie at the upper end of the plate-shaped dewatering element 48 arranged. This is perforated according to Figure 3 over its entire length.
  • the plate 48 is at least partially closed. This can ensure that the additive added penetrates as much as possible in the forming fibrous web and remains in this.
  • a fine fiber is added as an additive.
  • the underside of the second pulp layer formed in the twin-wire former is enriched with fines.
  • the upper side has a relatively high fines content because the dehydration takes place only downwards.
  • those sides of the two pulp layers come into contact with each other, which has an increased fines content. As a result, this results in an increased gap strength of the finished multilayer product.
  • a feed device for an additive has been dispensed with.
  • an enrichment of fines takes place once again on the underside of the forming second fibrous layer, because here the dewatering takes place only through the perforation of the other plate-shaped dewatering element 47.
  • the result is the same as or similar to the embodiment according to FIG. 3.

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

Die Erfindung betrifft ein Verfahren zum Bilden einer Faserstoffbahn, insbesondere einer Papier- oder Kartonbahn, aus einer Faserstoffsuspension. Die Erfindung betrifft außerdem eine Vorrichtung zum Durchführen dieses Verfahrens.The invention relates to a method for forming a fibrous web, in particular a paper or board web, from a pulp suspension. The invention also relates to an apparatus for carrying out this method.

Ausgangspunkt der Erfindung ist die nicht vorveröffentlichte europäische Patentanmeldung EP 0 894 894 A2, die ein Verfahren und eine Vorrichtung zum Bilden einer Faserstoffbahn, insbesondere einer Papier- oder Kartonbahn, aus einer Faserstoffsuspension offenbart. Das offenbarte Verfahren umfasst dabei die folgenden Verfahrensschritte:

  • man führt die Faserstoffsuspension zwischen zwei endlose, kontinuierlich umlaufende poröse Bänder, z.B. Siebbänder, die miteinander eine Doppelbandzone bilden, worin ein Teil der Suspensionsflüssigkeit durch die porösen Bänder hindurch entfernt wird, so daß sich zwischen den Bändern die Faserstoffbahn bildet;
  • das Entfernen der Suspensionsflüssigkeit erfolgt wenigstens teilweise dadurch, daß man die sich bildende Faserstoffbahn, eingehüllt zwischen den Bändern, zwischen sogenannten Gleichdruck-Entwässerungselementen hindurchführt; und
  • im Bereich der Gleichdruck-Entwässerung wird der entstehenden Faserstoffbahn durch wenigstens eines der Bänder hindurch ein Zusatzstoff zugegeben.
The starting point of the invention is the non-prepublished European patent application EP 0 894 894 A2, which discloses a method and an apparatus for forming a fibrous web, in particular a paper or board web, from a pulp suspension. The disclosed method comprises the following method steps:
  • passing the pulp suspension between two endless, continuously circulating porous bands, eg sieve bands, which together form a double band zone, wherein a portion of the suspension liquid is removed through the porous bands, so that forms between the bands, the fibrous web;
  • the removal of the suspension liquid takes place at least partially by passing the fibrous web which forms itself, enveloped between the bands, between so-called equal-pressure dewatering elements; and
  • In the area of equal pressure dewatering, an additive is added to the resulting fibrous web through at least one of the belts.

Als Zusatzstoff ist beispielsweise ein Farbstoff, ein Füllstoff, Leim oder ein Entwässerungshilfsmittel vorgesehen.As an additive, for example, a dye, a filler, glue or a drainage aid is provided.

Der vorliegenden Erfindung liegt die Aufgabe zugrunde, das Bahnbildungsverfahren und die dazugehörende Vorrichtung dahingehend weiter zu entwickeln, daß gewisse Eigenschaften der fertigen Faserstoffbahn verbessert werden.The present invention has for its object to further develop the web forming process and the associated device in that certain properties of the finished fibrous web are improved.

Dabei sollen möglichst viele der nachfolgenden Forderungen erfüllt werden können:

  1. 1) Die sogenannte Zweiseitigkeit der Faserstoffbahn soll gezielt beeinflußt werden können; d.h. man will entweder eine möglichst geringe Zweiseitigkeit (möglichst gleiche Eigenschaften auf beiden Bahnseiten) erreichen; oder man will eine "gewollte Zweiseitigkeit" herbeiführen, so daß die beiden Seiten der Faserstoffbahn unterschiedliche Eigenschaften aufweisen.
  2. 2) Ein der Faserstoffbahn zugegebener Zusatzstoff soll in bestmöglicher Weise ausgenutzt werden, d.h., beim weiteren Entwässern der Faserstoffbahn soll ein Wieder- Auswaschen des Zusatzstoffes möglichst weitgehend verhindert werden.
  3. 3) Wenn die gebildete Faserstoffbahn mit einer anderen Faserstoffbahn zusammengeführt wird, zwecks Herstellung eines mehrlagigen Produkts, so soll die sogenannte Spaltfestigkeit zwischen den beiden Bahnen möglichst hoch sein.
  4. 4) Das Querprofil bestimmter Bahn-Eigenschaften soll beeinflußt werden können.
  5. 5) Die Intensität der Entwässerung soll beeinflußbar sein, beispielsweise in gewissen Teilbereichen der Bahnbildungszone.
As many of the following requirements should be fulfilled:
  1. 1) The so-called two-sidedness of the fibrous web should be able to be influenced in a targeted manner; ie you want to either achieve the lowest possible two-sidedness (preferably the same properties on both sides of the web); or one wants to bring about a "wanted two-sidedness", so that the two sides of the fibrous web have different properties.
  2. 2) An added to the fibrous web additive should be exploited in the best possible way, ie, during further dewatering of the fibrous web rewashing the additive should be prevented as much as possible.
  3. 3) If the formed fibrous web is combined with another fibrous web, in order to produce a multi-layer product, the so-called gap strength between the two webs should be as high as possible.
  4. 4) The cross-section of certain web properties should be able to be influenced.
  5. 5) The intensity of the dewatering should be influenced, for example in certain subregions of the formation zone.

Diese Aufgabe wird bei dem erfindungsgemäßen Verfahren dadurch gelöst, dass die Zugabe des Zusatzstoffes derart steuert oder regelt wird, daß in der gebildeten Faserstoffbahn ein bestimmtes Verhältnis zwischen einem Gütegrad, z.B. Feinstoffgehalt, der Bahnoberseite und diesem Gütegrad der Bahnunterseite erzielt wird.This object is achieved in the inventive method in that the addition of the additive is controlled or regulated so that in the formed fibrous web a certain ratio between a grade, e.g. Fines content, the top of the track and this grade of the track bottom is achieved.

In einer besonderen Ausgestaltung des erfindungsgemäßen Verfahrens wird während des kontinuierlichen Herstellungsprozesses auf beiden Seiten der laufenden Faserstoffbahn (z.B. Papierbahn) eine bestimmte Eigenschaft kontinuierlich gemessen. Dadurch wird kontinuierlich ermittelt, ob der gewünschte Grad der Zweiseitigkeit erzielt wird.In a particular embodiment of the method according to the invention, a specific property is continuously measured on both sides of the continuous fibrous web (eg paper web) during the continuous production process. This will continuously determine if the desired degree of two-sidedness is achieved.

Wenn der Grad der Zweiseitigkeit von dem gewünschten Wert der Zweiseitigkeit (Soll-Wert) abweicht, dann wird - vorzugsweise mit Hilfe eines geschlossenen Regelkreises - beispielsweise der Volumenstrom und/oder der Druck des zuzugebenden Zusatzstoffes derart variiert, daß in der entstehenden Faserstoffbahn die Zweiseitigkeit sich dem Soll-Wert annähert. Durch Variieren des Druckes ist u.a. auch die Penetrationstiefe des Zusatzstoffes gezielt steuerbar. Das führt zu einer Optimierung der Verteilung des Zusatzstoffes in der Z-Richtung.
Weitere Ausgestaltungen des erfindungsgemäßen Verfahrens sind in den vom Anspruch 1 abhängigen Ansprüchen angegeben. Ein besonders wichtiger weiterführender Gedanke der Erfindung besteht darin, daß man als Zusatzstoff eine Fein-Faserstoff-Suspension verwendet. Diese kann vorzugsweise aus der im Anfangsbereich der Doppelbandzone entfernten Suspensionflüssigkeit, dem sogenannten Siebwasser, gewonnen werden. In diesem Falle kann man auf einer der beiden Bahnseiten oder auf beiden Bahnseiten der Faserstoffbahn einen bestimmten, z.B. besonders hohen Feinstoffgehalt herbeiführen. Die Höhe des Feinstoffgehaltes ist beispielsweise wichtig für die Bedruckbarkeit der fertigen Faserstoffbahn.
In ähnlicher Weise ist es beim Herstellen eines mehrlagigen Produktes wichtig, daß vor dem Zusammenführen zweier Faserstoffbahnen der Feinstoffgehalt der miteinander in Kontakt kommenden Bahnseiten möglichst weitgehend erhöht worden ist. Andere mögliche Zusatzstoffe sind: Füllstoffsuspension, Polymerlösung, Leim- oder Stärkelösung oder ein z.B. örtlich zugegebener Farbstoff.If the degree of the two-sidedness deviates from the desired value of the two-sidedness (nominal value), then the volume flow and / or the pressure of the additive to be added is varied, preferably by means of a closed control loop, such that the two-sidedness occurs in the resulting fibrous web approaches the target value. By varying the pressure, among other things, the penetration depth of the additive can be selectively controlled. This leads to an optimization of the distribution of the additive in the Z direction.
Further embodiments of the method according to the invention are specified in the dependent claims of claim 1. A particularly important further concept of the invention consists in using as additive a fine pulp suspension. This can preferably be obtained from the suspension liquid removed in the initial region of the double-belt zone, the so-called white water. In this case, one can bring about a particular, for example, particularly high fines content on one of the two web sides or on both sides of the fibrous web. The amount of fines content is important, for example, for the printability of the finished fibrous web.
Similarly, when producing a multi-ply product, it is important that the fines content of the contacting web sides be increased as much as possible prior to merging of two pulp webs. Other possible additives are: filler suspension, polymer solution, glue or starch solution or a locally added dye.

Für alle Ausführungsformen oder Anwendungsfälle des erfindungsgemäßen Verfahrens gilt folgendes:

  • Der Ort der Zugabe des Zusatzstoffes ist in allen Fällen der Bereich der sogenannten Gleichdruck-Entwässerung. Dies ist derjenige Bereich der Bahnbildung, in dem die Entwässerung unter Anwendung eines im wesentlichen pulsationsfreien Entwässerungsdrukkes stattfindet. Das bedeutet, daß in dem betreffenden Teil der Bahnbildungszone der Entwässerungsdruck entweder im wesentlichen gleich bleibt oder sich wenigstens annähernd kontinuierlich verändert, z.B. ansteigt. Eine solche Art der Entwässerung unterscheidet sich somit von der meistens im Anfangsbereich der Bahnbildung angewandten Entwässerungsmethode, bei der mit Hilfe sogenannter Formierleisten in der zwischen den Bändern noch vorhandenen Suspension Druckpulsationen erzeugt werden. Dadurch will man erreichen, daß das Fasermaterial während des Bahnbildungsvorganges möglichst gleichmäßig verteilt bleibt.
  • Ein besonderer Vorteil des Zugabeortes (für den Zusatzstoff) im Bereich der Gleichdruck-Entwässerung besteht nun darin, daß man nach dem Zugeben des Zusatzstoffes die weitere Entwässerung derart steuern kann, daß von dem zugegebenen Zusatzstoff möglichst wenig verlorengeht. Dies gelingt beispielsweise dadurch, daß man den Zusatzstoff im Anfangsbereich oder im mittleren Bereich der Gleichdruck-Entwässerungszone zugibt, und daß man hinter der Zugabestelle die Intensität der weiteren Entwässerung auf der betreffenden Bahnseite reduziert. Beispielsweise kann man die Entwässerung auf einer bestimmten Strecke ganz unterbinden. Gleichzeitig kann man die Intensität der Entwässerung auf der gegenüberliegenden Bahnseite erhöhen, beispielsweise durch Anwenden von Unterdruck und/oder dadurch, daß man in einem bestimmten Bereich erhöhte Perforations-Querschnitte vorsieht.
For all embodiments or applications of the method according to the invention, the following applies:
  • The place of addition of the additive is in all cases the area of so-called equal pressure drainage. This is the area of web formation in which dewatering takes place using a substantially pulsation-free dewatering pressure. This means that in the relevant part of the forming zone, the dewatering pressure either remains essentially the same or changes at least approximately continuously, for example increases. Such a type of drainage thus differs from the most commonly used in the initial area of the formation of web dewatering method in which are generated by means of so-called Formierleisten in the remaining between the bands suspension pressure pulsations. As a result, it is desirable to ensure that the fiber material remains as evenly distributed as possible during the formation process.
  • A particular advantage of the addition site (for the additive) in the field of equal-pressure dewatering consists in the fact that you can control the further dehydration after adding the additive so that as little as possible is lost from the added additive. This is achieved, for example, by adding the additive in the initial region or in the middle region of the constant-pressure dewatering zone, and reducing the intensity of the further dewatering on the relevant web side behind the addition point. For example, you can completely prevent the drainage on a particular route. At the same time, one can increase the intensity of the drainage on the opposite side of the web, for example by applying negative pressure and / or by providing increased perforation cross-sections in a certain area.

Das Behindern der Entwässerung auf derjenigen Bahnseite, welcher der Zusatzstoff zugegeben wurde, ist beispielsweise dadurch möglich, daß man in einem bestimmten Teilbereich der Gleichdruck-Entwässerungszone ein geschlossenes, also nicht perforiertes Plattenelement vorsieht oder dadurch, daß man einen Teil der Perforation absperrt, beispielsweise mit Hilfe eines Druckluftpolsters. In jedem Fall wird erreicht, daß man mit einer sehr hohen Retention der zugegebenen Zusatzstoffe rechnen kann. Im übrigen wird dank der Erfindung auch erreicht, daß die von Anfang an in der Faserstoffsuspension vorhandenen Fein- und/oder Füllstoffe zu einem höheren Prozentsatz als bisher in der sich bildenen Faserstoffbahn zurückgehalten werden.
In einer weiteren bevorzugten Ausführungsform ist vorgesehen,
daß man mit Hilfe von Gleichdruck-Entwässerungselementen unterschiedlicher Permeabilität dafür sorgt, daß die Entwässerung durch das eine Band intensiver ist als diejenige durch das andere Band. Im Extremfall kann man in einem bestimmten Bereich der Gleichdruck-Entwässerungszone das Entfernen von Suspensionsflüssigkeit durch eines der beiden Bänder zumindest weitgehend unterbinden, nämlich mit Hilfe eines wasserundurchlässigen Gleichdruck-Entwässerungselementes. Das letztere sorgt dafür, daß auf dieser Seite der sich bildenden Faserstoffbahn die mit der Faserstoff-Suspension herangeführten Fein- und/oder Füllstoffe nicht entweichen können. Im Ergebnis erhält man eine Faserstoffbahn, die auf einer Bahnseite einen erheblich höheren Anteil von Fein- und/oder Füllstoffen aufweist.The obstruction of the drainage on the web side to which the additive has been added, for example, is possible by providing a closed, ie non-perforated plate member in a certain portion of the DC pressure dewatering zone or by blocking off a portion of the perforation, for example with Help of a compressed air cushion. In any case, it is achieved that one can count on a very high retention of the added additives. Moreover, thanks to the invention it is also achieved that the fine and / or fillers present in the pulp suspension from the beginning are retained to a higher percentage than previously in the fibrous web which is formed.
In a further preferred embodiment, it is provided
that it is ensured by means of equal pressure dewatering elements of different permeability that the drainage through the one band is more intense than that by the other band. In extreme cases, the removal of suspension fluid through one of the two belts can at least largely be prevented in a certain region of the constant-pressure dewatering zone, namely with the aid of a water-impermeable constant-pressure dewatering element. The latter ensures that can not escape on this side of the forming fibrous web zoom brought up with the pulp suspension fine and / or fillers. The result is a fibrous web which has on one side of the web a significantly higher proportion of fillers and / or fillers.

Die gestellte Aufgabe wird, ausgehend von einer Vorrichtung gemäß der eingangs erwähnten Patentanmeldung, auch durch die kennzeichnenden Merkmale des Anspruches 16 gelöst. Weitere Ausgestaltungen der Vorrichtung sind in den vom Anspruch 16 abhängigen Unteransprüchen angegeben. Die Ansprüche 23 bis 26 betreffen eventuell vorteilhafte Maßnahmen zum zusätzlichen Steuern der Entwässerungsintensität und zum möglichst gleichmäßigen Verteilen des Fasermaterials; diese Maßnahmen sind auch unabhängig von denen des Anspruchs 1 anwendbar.The object is achieved, starting from a device according to the aforementioned patent application, also by the characterizing features of claim 16. Further embodiments of the device are specified in the dependent of claim 16 subclaims. Claims 23 to 26 may relate to advantageous measures for additionally controlling the dewatering intensity and distributing the fiber material as evenly as possible; These measures are also applicable independently of those of claim 1.

Zahlreiche weitere Möglichkeiten zur Ausgestaltung des erfindungsgemäßen Verfahrens und der erfindungsgemäßen Vorrichtung sind in der eingangs erwähnten Patentanmeldung EP0894894 enthalten. Es wird deshalb ausdrücklich darauf hingewiesen, daß alle in dieser noch nicht veröffentlichten Anmeldung beschriebenen Merkmale mit den Merkmalen der hier vorliegenden Anmeldung kombinierbar sind.Numerous other possibilities for the embodiment of the method according to the invention and the device according to the invention are contained in the aforementioned patent application EP0894894. It is therefore expressly pointed out that all features described in this not yet published application with the features of the present application can be combined.

Nachfolgend werden Ausführungsbeispiele der Erfindung anhand der beigefügten Zeichnung erläutert.Hereinafter, embodiments of the invention will be explained with reference to the accompanying drawings.

Die Figur 1 zeigt einen Doppelsiebformer mit einer Zusatzstoff-Zuführung in einer schematischen Seitenansicht. Die Figur 1 A zeigt ein Detail aus Figur 1.

  • Die Figur 2 zeigt eine mögliche Abwandlung der Zusatzstoff-Zuführeinrichtung der Figur 1 in einer Schrägansicht.
  • Die Figur 3 zeigt einen Former zur Herstellung einer zwei-lagigen Faserstoffbahn.
  • Die Figur 4 zeigt eine abgewandelte Einzelheit aus Figur 3.
FIG. 1 shows a twin-wire former with an additive feed in a schematic side view. FIG. 1 A shows a detail from FIG. 1.
  • FIG. 2 shows a possible modification of the additive supply device of FIG. 1 in an oblique view.
  • FIG. 3 shows a former for producing a two-ply fibrous web.
  • FIG. 4 shows a modified detail from FIG. 3.

In Figur 1 erkennt man einen Stoffauflauf 1 (nur beispielhaft dargestellt als ein Mehrschichten-Stoffauflauf), der einen Faserstoff-Suspensionsstrom in einen Zwickel einschießt", der am Anfang einer Doppelsiebzone von zwei Siebbändern S1 und S2 gebildet ist. Die beiden Siebbänder S1 und S2 laufen an dieser Stelle über eine Formiersaugwalze 10, die in der Schlaufe des Untersiebes S1 liegt. Das Obersieb S2 läuft von einer Seibleitwalze 9 auf die Formierwalze und umschlingt diese im Bereich einer Formierzone FZ. Dort können in der Schlaufe des Obersiebes S2 Formierleisten vorgesehen sein, die jedoch in der Zeichnung weggelassen sind. In der Formierzone FZ beginnt das Bilden einer Faserstoffbahn durch Entfernen von Suspensionsflüssigkeit durch die Siebe hindurch.1 shows a headbox 1 (shown only by way of example as a multi-layer headbox), which injects a pulp suspension flow into a gusset formed at the beginning of a twin-wire zone by two sieve belts S1 and S2 The two sieve belts S1 and S2 run at this point via a Formiersaugwalze 10, which lies in the loop of the lower wire S1.The upper wire S2 runs from a Seibleitwalze 9 on the forming and wraps around this in the region of a forming zone FZ There may be provided in the loop of the upper wire S2 forming strips, however, which are omitted in the drawing, forming a fibrous web begins in the forming zone FZ by removing suspension liquid through the sieves.

Die entfernte Suspensionsflüssigkeit strömt in bekannter Weise teils durch die Formierwalze 10, teils durch einen in der Schlaufe des Obersiebes befindlichen Auffangbehälter 27.The removed suspension liquid flows in a known manner partly through the forming roller 10, partly through a collecting container 27 located in the loop of the top wire.

In Bahnlaufrichtung hinter der Formierzone FZ ist eine Gleichdruck-Entwässerungszone GE vorgesehen, in der mehrere Gleichdruck-Entwässerungselemente 15,16 angeordnet sind. Dies sind beispielsweise in Bahnlaufrichtung hintereinander angeordnete und miteinander gelenkig verbundene Plattensegmente. Diese sind perforiert, um hierdurch das Abführen weiterer Suspensionsflüssigkeit zu ermöglichen. Gemäß Figur 1 ist die Perforation in allen Plattensegmenten im wesentlichen gleich ausgebildet. Abweichend hiervon kann man jedoch die Perforationsdurchmesser und/oder die Anzahl der Perforationen von Segment zu Segment unterschiedlich wählen. Anstelle von zylindrischen Bohrungen können konisch sich erweiternde Bohrungen vorgesehen sein. Anstelle von senkrecht zur Siebebene angeordneten Bohrungen können auch schräge Bohrungen vorgesehen werden. Ein Teil der Suspensionsflüssigkeit kann auch durch den zwischen zwei benachbarten Plattensegmenten vorhandenen Spalt abgeführt werden; siehe z.B. den Spalt zwischen den Plattensegmenten 16A und 16B. Zur Steuerung der Entwässerungsintensität kann man die lichte Weite des genannten Spaltes verändern durch Verschieben des Plattensegmentes 16B in Richtung des dargestellten Doppelpfeiles. Die oberen Plattensegmente 15 und 15A sind mittels ihrer Gelenke an einer Tragkonstruktion 8 befestigt. Die unteren Plattensegemente 16, 16A und 16B ruhen dagen auf Pneumatikschläuchen 4. Der Innendruck in jedem der Pneumatikschläuche 4 ist individuell einstellbar, so daß jedes der Plattensegmente mit einer frei wählbaren Kraft nachgiebig an die Innenseite des Untersiebes S1 andrückbar ist. Falls erforderlich, kann man die Plattensegmente 15, 16 beispielsweise elektrisch beheizen, wie bei 20 schematisch angedeutet ist. Außerdem kann man, falls erforderlich, an die Plattensegmente einen Schwingungserzeuger oder Oszillator anschließen (in der Zeichnung nicht dargestellt). Am Ende der Doppelsiebzone befindet sich in bekannter Weise ein Trennsauger 13. Dieser sorgt dafür, daß die gebildete Faserstoffbahn sich vom Obersieb S2 trennt und mit dem Untersieb S1 weiterläuft, von dem die Bahn in bekannter Weise abgenommen und weiteren Behandlungsstationen zugeführt wird.In the web running direction behind the forming zone FZ an equal-pressure dewatering zone GE is provided, in which a plurality of equal-pressure dewatering elements 15,16 are arranged. These are, for example, arranged in the web running direction one behind the other and hinged together plate segments. These are perforated, thereby allowing the removal of further suspension liquid. According to Figure 1, the perforation in all plate segments is formed substantially the same. Deviating from this, however, one can choose the perforation diameter and / or the number of perforations from segment to segment differently. Instead of cylindrical holes can be provided conically widening holes. Instead of arranged perpendicular to the plane of the drill holes and oblique holes can be provided. A part of the suspension liquid can also be removed by the gap existing between two adjacent plate segments; see, e.g. the gap between the plate segments 16A and 16B. To control the dewatering intensity, you can change the inside width of said gap by moving the plate segment 16 B in the direction of the double arrow shown. The upper plate segments 15 and 15A are attached to a support structure 8 by means of their joints. The lower Plattensegemente 16, 16A and 16B rest dagen on pneumatic tubes 4. The internal pressure in each of the pneumatic tubes 4 is individually adjustable, so that each of the plate segments with a freely selectable force to the inner side of the lower wire S1 is pressed pressed. If necessary, one can electrically heat the plate segments 15, 16, for example, as indicated schematically at 20. In addition, if necessary, connect to the plate segments a vibrator or oscillator (not shown in the drawing). At the end of the twin-wire zone is located in a known manner a separating sucker 13. This ensures that the fibrous web formed separates from the upper wire S2 and continues with the lower wire S1, from which the web is removed in a known manner and fed to other treatment stations.

Gemäß der Erfindung ist einem der mittleren, oberen Plattensegmente 15 ein insgesamt mit 21 bezeichnete Zuführeinrichtung für einen Zusatzstoff vorgesehen. Diese Zuführeinrichtung umfaßt einen Vorratsbehälter 22, falls erforderlich eine Pumpe 23, ein Steuerventil 24 und eine auf dem Plattensegment 15A angeordnete Verteilkammer 25 sowie dazugehörende Rohrleitungen.According to the invention, one of the middle, upper plate segments 15 is provided with an additive feeder, generally designated 21. This feeder comprises a reservoir 22, if necessary a pump 23, a control valve 24 and a distribution chamber 25 arranged on the plate segment 15A and associated piping.

Falls erforderlich kann man dem Zusatzstoff zwischen dem Steuerventil 24 und der Verteilkammer 25 aus einem Speicher 26 ein Treibmittel, z.B. Preßluft (vorzugsweise erhitzt) oder Dampf zugeben, u. a. zwecks Steuerung der Penetrationstiefe. Abweichend von Figur 1 kann das Plattensegment 15A, das unmittelbar auf die Zuführeinrichtung 21 folgt, geschlossen (ohne Perforation) ausgeführt werden. Die Figur 1A zeigt eine Reinigungsvorrichtung in Form eines Spritzrohres 19, das entlang der Tragvorrichtung 8 hin und her verschiebbar ist.If necessary, the additive between the control valve 24 and the distribution chamber 25 may be supplied from a reservoir 26 with a propellant, e.g. Compressed air (preferably heated) or add steam, u. a. for the purpose of controlling the penetration depth. Notwithstanding Figure 1, the plate segment 15A, which follows directly on the feeder 21, closed (without perforation) are performed. FIG. 1A shows a cleaning device in the form of a spray tube 19, which can be displaced back and forth along the carrier device 8.

Die Figur 2 zeigt eine abgewandelte Ausführungsform der Zuführeinrichtung, insgesamt mit 21A bezeichnet. Die Verteilkammer 25A ist über die Bahnbreite in zahlreiche Sektionen unterteilt. In jede Sektion mündet eine Zuführleitung mit einem individuell steuerbaren Steuerventil 24A. Falls wiederum das Zugeben eines Treibmittels aus einem Speicher 26A vorgesehen ist, wird dieses ebenfalls jeder Sektion über eine individuell steuerbare Leitung zugeführt, entweder direkt in die betreffende Sektion der Verteilkammer 25A oder in die Sektionsleitung stromabwärts von dem Steuerventil 24A. Man kann hierdurch das Querprofil der einen oder anderen Bahneigenschaft beeinflussen, z.B. das Flächengewichts- oder das Trockengehalts- oder das Aschegehalts-Querprofil.FIG. 2 shows a modified embodiment of the feed device, designated overall by 21A. The distribution chamber 25A is divided across the web width into numerous sections. In each section opens a supply line with an individually controllable control valve 24A. In turn, if adding a propellant from a reservoir 26A is provided, it is also supplied to each section via an individually controllable conduit, either directly into the respective section of the manifold chamber 25A or into the section conduit downstream of the control valve 24A. One can thereby influence the transverse profile of one or the other web property, e.g. the basis weight or dry content or ash content cross profile.

Der Grundaufbau des in Figur 3 dargestellten Mehrlagen-Formers entspricht demjenigen der Figur 1 der europaischen Patentanmeldung EP0851058 A2. Man erkennt ein Fourdrinier-Langsieb-Aggregat 31 mit einem etwa horizontal geführten Siebband 32 mit Laufrichtung gemäß Pfeil 33. Auf dem Siebband 32 wird mittels eines Stoffauflaufes 34 und mit Hilfe mehrerer Entwässerungselemente 35 eine erste Faserstofflage gebildet. Zum Formen einer zweiten Faserstofflage ist oberhalb des Aggregates 31 ein insgesamt mit 40 bezeichneter Doppelsiebformer angeordnet, mit zwei Siebbändern 41 und 42, die miteinander eine Doppeisiebzone bilden. Diese beginnt wiederum an einer Formierwalze 43. Im oberen Bereich dieser Formierwalze wird mittels eines Stoffauflaufes 44 ein Fasersuspensionsstrom zwischen die Siebe 41 und 42 eingeschossen". Die beiden Siebe laufen zusammen mit der sich dazwischen bildenden Faserstoffbahn von oben nach unten von der Formierwalze 43 ab; sie umschlingen danach einen Entwässerungskasten 45, dessen Krümmung der Krümmung des Formierwalzenmantels entgegengesetzt ist. Ein Wasserauffangbehälter ist mit 46 bezeichnet.The basic construction of the multilayer former shown in FIG. 3 corresponds to that of FIG. 1 of European patent application EP0851058 A2. One recognizes a Fourdrinier-Langsieb aggregate 31 with an approximately horizontally guided screen belt 32 in the direction of arrow 33. On the screen belt 32 is formed by means of a headbox 34 and with the aid of several dewatering elements 35, a first pulp layer. For forming a second pulp layer, a double-wire former, designated as a whole by 40, is arranged above the unit 31, with two screen belts 41 and 42 which together form a double-layer zone. This in turn begins at a forming roller 43. In the upper region of this forming roller, a fiber suspension flow is injected between the screens 41 and 42 by means of a headbox 44. The two screens, together with the fibrous web therebetween, run down from the forming roller 43 from top to bottom; They then wrap around a dewatering box 45, the curvature of which is opposite to the curvature of the forming roll mantle.

Danach laufen die beiden Siebe zwischen zwei plattenförmigen Gleichdruck-Entwässerungselementen 47 und 48 hindurch, wonach sich die beiden Siebbänder trennen. Hinter dem in der Schlaufe des einen Siebbandes 41 angeordneten Entwässerungselement 47 ist ein Trennsauger 49 vorgesehen, so daß die gebildete zweite Faserstofflage mit dem Siebband 41 zur Gautschwalze 50 läuft. Diese bringt die beiden Faserstofflagen miteinander in Kontakt, so daß sie zu einer zweilagigen Faserstoffbahn zusammengefügt werden. Diese zweilagige Faserstoffbahn wird mittels eines weiteren Trennsaugers 36 vom Siebband 41 getrennt und läuft zusammen mit dem Siebband 32 weiter, z.B. über einen Saugkasten 37 und eine Siebsaugwalze 38.Thereafter, the two screens run between two plate-shaped equal-pressure dewatering elements 47 and 48 therethrough, after which separate the two screen belts. Behind the arranged in the loop of a sieve belt 41 dewatering element 47, a separating sucker 49 is provided so that the formed second pulp layer runs with the wire 41 to the couch roll 50. This brings the two pulp layers in contact with each other, so that they are joined together to form a two-ply fibrous web. This two-ply fibrous web is separated from the screen belt 41 by means of a further separating sucker 36 and continues to run together with the screen belt 32, e.g. via a suction box 37 and a suction sieve 38.

Danach wird die Faserstoffbahn in bekannter Weise mittels eines Filzbandes und einer Abnahmewalze 39 vom Siebband 32 entfernt und einem nachfolgenden Aggregat (z.B. Pressenpartie zugeführt).
Das plattenförmige Entwässerungselement 47 ist beispielsweise an einem Wasserauffangbehälter 47a befestigt; es hat teils zylindrische teils konisch sich erweiternde Perforationen. Das in der Schlaufe des anderen Siebbandes 42 unterhalb der Formierwalze 43 angeordnete plattenförmige Entwässerungselement 48 ruht - unter Zwischenschalten von Pneumatikschläuchen - auf einem Wasserauffangbehälter 48a und kann dadurch mit einer einstellbaren Kraft nachgiebig an die Innenseite des Siebbandes 42 angedrückt werden.Thereafter, the fibrous web is removed in a known manner by means of a felt belt and a take-off roller 39 from the wire belt 32 and a subsequent unit (eg press section supplied).
The plate-shaped dewatering element 47 is attached, for example, to a water collecting container 47a; it has partly cylindrical and partly conical widening perforations. The arranged in the loop of the other screen belt 42 below the forming roller 43 plate-shaped drainage element 48 rests - with the interposition of pneumatic hoses - on a water collecting container 48a and can be pressed with an adjustable force yielding to the inside of the wire 42.

Ähnlich wie in Figur 1 ist wiederum eine Zuführeinrichtung 51 für einen Zusatztstoff vorgesehen, umfassend einen Vorratsbehälter 52, eine Pumpe 53, ein Steuerventil 54 und eine Verteilkammer 55. Die letztere ist im Anfangsbereich der Gleichdruck-Entwässerungszone, also am oberen Ende des plattenförmigen Entwässerungselementes 48 angeordnet. Dieses ist gemäß Figur 3 auf seiner ganzen Länge perforiert. Es ist jedoch auch möglich, daß unterhalb der Verteilkammer 55 die Platte 48 zumindest bereichsweise geschlossen ist. Dadurch kann sichergestellt werden, daß der zugegebene Zusatzstoff möglichst weitgehend in die sich bildende Faserstoffbahn eindringt und in dieser verbleibt. Vorzugsweise wird als Zusatzstoff ein Fein-Faserstoff zugegeben. Dadurch wird die Unterseite der im Doppelsiebformer gebildeten zweiten Faserstofflage mit Feinstoff angereichert. Bei der auf dem Langsieb-Aggregat 31 gebildeten ersten Faserstofflage hat die Oberseite einen relativen hohen Feinstoffgehalt, weil die Entwässerung nur nach unten stattfindet.
Somit kommen an der Gautschwalze 50 diejenigen Seiten der beiden Faserstofflagen miteinander in Kontakt, welche einen erhöhten Feinstoff-Gehalt aufweist. Im Ergebnis wird hierdurch eine erhöhte Spaltfestigkeit des fertigen Mehrlagen-Produktes erzielt.Similar to FIG. 1, a feed device 51 is again provided for an additive, comprising a reservoir 52, a pump 53, a control valve 54 and a distribution chamber 55. The latter is in the initial region of the constant-pressure dewatering zone, ie at the upper end of the plate-shaped dewatering element 48 arranged. This is perforated according to Figure 3 over its entire length. However, it is also possible that below the distribution chamber 55, the plate 48 is at least partially closed. This can ensure that the additive added penetrates as much as possible in the forming fibrous web and remains in this. Preferably, a fine fiber is added as an additive. As a result, the underside of the second pulp layer formed in the twin-wire former is enriched with fines. In the first pulp layer formed on the four-wire unit 31, the upper side has a relatively high fines content because the dehydration takes place only downwards.
Thus, on the couch roll 50 those sides of the two pulp layers come into contact with each other, which has an increased fines content. As a result, this results in an increased gap strength of the finished multilayer product.

Eine mögliche Abwandlung der Bauweise gemäß Figur 3 ist in Figur 4 dargestellet. Abweichend von Figur 3 ist in Figur 4 das in der Schlaufe des Siebbandes 42 unterhalb der Formierwalze 43 angeordnete plattenförmige Gleichdruck-Entwässerungselement 48' als geschlosse Platte ausgebildet, wobei auf eine Zuführeinrichtung für einen Zusatzstoff verzichtet worden ist. Hier findet in der Gleichdruck-Entwässerungszone wiederum auf der Unterseite der sich bildenden zweiten Faserstofflage eine Anreicherung von Feinstoff statt, weil hier die Entwässerung nur durch die Perforation des anderen plattenförmigen Entwässerungselementes 47 hindurch erfolgt. Das Ergebnis ist gleich oder ähnlich wie bei der Ausführungsform gemäß Figur 3.A possible modification of the construction according to FIG. 3 is shown in FIG. Notwithstanding FIG. 3, in FIG. 4, the plate-shaped equal-pressure dewatering element 48 'arranged in the loop of the screen belt 42 below the forming roller 43 is designed as a closed plate, wherein a feed device for an additive has been dispensed with. Here, in the constant-pressure dewatering zone, an enrichment of fines takes place once again on the underside of the forming second fibrous layer, because here the dewatering takes place only through the perforation of the other plate-shaped dewatering element 47. The result is the same as or similar to the embodiment according to FIG. 3.

Claims (26)

  1. Process for making a fibrous web, in particular a paper or board web, from a fibrous suspension, having the following process steps:
    a) the fibrous suspension is led between two endless, continuously circulating porous belts, for example wires (S1, S2), which form a twin-belt zone with each other, in which part of the suspension liquid is removed through the porous belts, so that the fibrous web is made between the belts,
    b) the removal of the suspension liquid is carried out at least to some extent by the fibrous web being made, enclosed between the belts, being led through between what are known as equal pressure dewatering elements (15, 16; 15A, 16A; 47, 48; 47, 48');
    c) in the region of the equal pressure dewatering (GE), an additive is added through at least one of the belts to the fibrous web being made;
    d) the addition of the additive is controlled or regulated in such a way that, in the fibrous web made, a specific ratio is achieved between a quality level, for example fines content, of the top side of the web and this quality level of the underside of the web.
  2. Process according to Claim 1, characterized in that the addition of the additive is controlled or regulated in such a way that the aforementioned quality level is at least approximately the same on both sides of the web.
  3. Process according to Claim 1, characterized in that the addition of the additive is controlled or regulated in such a way that the aforementioned quality level is unequal on the two sides of the web.
  4. Process according to one of Claims 1 to 3, characterized in that the volume flow of the additive to be added is controlled or regulated.
  5. Process according to one of Claims 1 to 4, characterized in that, during the addition of the additive, the pressure of the same is controlled or regulated.
  6. Process according to Claim 5, characterized in that the pressure of the additive is controlled or regulated by admixing a propellant, for example compressed air, steam or the like.
  7. Process according to one of the preceding claims, characterized in that the addition of the additive is carried out in the initial region or in the central region of the equal pressure dewatering zone (GE).
  8. Process according to Claim 7, characterized in that, on the side of the addition of the additive, the intensity of the dewatering is reduced after the addition point.
  9. Process according to one of the preceding claims, characterized in that the additive used is a fine fibrous material.
  10. Process according to Claim 9, characterized in that the fine fibrous material is obtained from the suspension liquid, for example white water, removed in the initial region of the twin-belt zone.
  11. Process according to Claim 9 or 10, characterized in that the still moist fibrous web made, is combined with another fibrous web for the purpose of making a multi-layer fibrous web.
  12. Process according to Claim 11, characterized in that the fibrous webs are combined in such a way that web sides with an increased fines content are brought into contact with each other.
  13. Process according to one of the preceding claims, characterized in that the additive is supplied to the region of the equal pressure dewatering (GE) through a plurality of section lines that are distributed over the web width and can be controlled individually.
  14. Process according to one of the preceding claims, characterized in that, in the region of the equal pressure dewatering (GE), the dewatering taking place through one of the two belts is carried out more intensively than the dewatering taking place through the other belt, namely with the aid of equal pressure dewatering elements (15, 16; 15A, 16A; 47, 48; 47, 48') with a different permeability, so that different quality levels, for example fines contents, are achieved on the two sides of the fibrous web made.
  15. Process according to Claim 14, characterized in that, at least in a subregion of the equal pressure dewatering, the removal of suspension liquid through one of the two belts is suppressed, namely with the aid of an equal pressure dewatering element that is impermeable to water.
  16. Apparatus for making a fibrous web, in particular a paper or board web, from a fibrous suspension, having the following features:
    a) two continuously circulating endless porous belts, for example wires (S1, S2) form a twin-belt zone with each other to accommodate a suspension stream and to make the fibrous web by means of removal of suspension liquid through the two belts;
    b) provided in the twin-belt zone are what are known as equal pressure dewatering elements (15, 16; 15A, 16A; 47, 48; 47, 48'), between which the belts run through with the fibrous web being made between them in contact with the dewatering elements (15, 16; 15A, 16A; 47, 48; 47, 48');
    c) at least some of the dewatering elements (15, 16; 15A, 16A; 47, 48; 47, 48') supporting the belts are perforated or, on the surface which contacts the belt, have recesses to accommodate suspension liquid, so that the dewatering is carried out while applying a substantially pulsation-free dewatering pressure;
    d) a feed device (21; 21A) for an additive is provided on at least one of the dewatering elements (15); and
    e) the feed device (21; 21A) has a control or regulating device (24; 24A) for varying the volume flow and/or the pressure of the additive to be added.
  17. Apparatus according to Claim 16, characterized in that the feed device (21; 21A) has a connection for admixing a propellant, for example compressed air, steam or the like.
  18. Apparatus according to Claim 16 or 17, characterized in that the feed device (21; 21A) for the additive is arranged in the initial region or in the central region of the equal pressure dewatering zone (GE).
  19. Apparatus according to Claim 18, characterized in that, with respect to the belt running direction, after the feed device (21; 21A) there is arranged at least one equal pressure dewatering element (15; 15A) which is suitable for reducing the dewatering intensity, for example by being formed as an unperforated plate.
  20. Apparatus according to one of Claims 16 to 19, characterized in that the feed device (21A) is subdivided over the web width into numerous sections, and in that an individually controllable section line for the supply of a partial amount of the additive opens into each section.
  21. Apparatus according to one of Claims 16 to 20, characterized in that at least one of the equal pressure dewatering elements (15) is assigned a cleaning device (19) which can preferably be moved, in particular displaced.
  22. Apparatus according to Claim 16, characterized in that the distance between two dewatering elements (16B) following each other in the web running direction can be varied, in particular by displacing one of these dewatering elements (16B).
  23. Apparatus, in particular according to Claim 16, characterized in that, in the twin-belt zone, a plate-like, preferably perforated dewatering element rests on the one porous belt, and in that, opposite the latter, a plurality of formation strips rest on the other porous belt.
  24. Apparatus according to Claim 23, characterized in that the width of the formation strips, measured in the web running direction, is different.
  25. Apparatus according to Claim 23 or 24, characterized in that the distances between the formation strips are different.
  26. Apparatus according to one of Claims 23 to 25, characterized in that either the plate-like dewatering element or the formation strips can be pressed compliantly onto the relevant belt.
EP99125356A 1999-01-28 1999-12-20 Process and apparatus for making a fibrous web Expired - Lifetime EP1024224B1 (en)

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DE19903943A DE19903943A1 (en) 1999-01-28 1999-01-28 Method and device for forming a fibrous web
DE19903943 1999-01-28

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EP1024224A2 EP1024224A2 (en) 2000-08-02
EP1024224A3 EP1024224A3 (en) 2003-07-16
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ATE335101T1 (en) 2006-08-15
DE19903943A1 (en) 2000-08-03
ATE325232T1 (en) 2006-06-15
NZ502443A (en) 2000-09-29
DE50012677D1 (en) 2006-06-08
EP1024224A2 (en) 2000-08-02
WO2000044980A1 (en) 2000-08-03
DE59913733D1 (en) 2006-09-14
AU1249600A (en) 2000-08-03
EP1075568B1 (en) 2006-05-03
AU3276400A (en) 2000-08-18
EP1024224A3 (en) 2003-07-16
EP1075568A1 (en) 2001-02-14

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