EP1895050B1 - Process for moistening a fibrous web - Google Patents

Process for moistening a fibrous web Download PDF

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Publication number
EP1895050B1
EP1895050B1 EP07108110A EP07108110A EP1895050B1 EP 1895050 B1 EP1895050 B1 EP 1895050B1 EP 07108110 A EP07108110 A EP 07108110A EP 07108110 A EP07108110 A EP 07108110A EP 1895050 B1 EP1895050 B1 EP 1895050B1
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EP
European Patent Office
Prior art keywords
fibrous web
web
water
smoothing
wet steam
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EP07108110A
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German (de)
French (fr)
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EP1895050A1 (en
Inventor
Fabian Döling
Joachim Hinz
Ulrich Rothfuss
Josef Kohnen
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Voith Patent GmbH
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Voith Patent GmbH
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    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21G—CALENDERS; ACCESSORIES FOR PAPER-MAKING MACHINES
    • D21G1/00—Calenders; Smoothing apparatus
    • D21G1/0073—Accessories for calenders
    • D21G1/0093—Web conditioning devices

Definitions

  • the invention relates to a method for moistening a paper, cardboard or another fibrous web in front of a calendering slit, through which the fibrous web is guided for smoothing, wherein the fibrous web is subjected to wet steam by means of a moistening device.
  • Such moistening devices have been known for a long time and on the one hand serve to reduce the tendency of the fibrous web to curl and, on the other hand, also to influence the smoothing process.
  • the moistening device is preferably close to a Glättspalt.
  • the GB862115A , the US2004 / 074981A1 and the WO00 / 03087A already disclose the common application of water and water vapor (ie, for example in the form of wet steam) on the paper web.
  • water and water vapor ie, for example in the form of wet steam
  • US2004 / 074981A1 It is described how changes in the paper quality can be achieved at a preset mixing ratio by changing the total mass flow impinging on the paper web.
  • the object of the invention is to allow a uniform and sufficient moistening of the fibrous web and thereby to influence the smoothing process.
  • the object with regard to the method has been achieved by reacting to variations in the orbital parameters, such as gloss or smoothness, by adjusting the mass ratio between liquid and gaseous water in a mixing chamber of the moistening device.
  • Wet steam consists of a mixture of gaseous and liquid water whose conditions of origin can be read from the known entropy-temperature diagram of water.
  • the mass ratio between liquid and gaseous water should be adjustable.
  • the moistening device has a nozzle arrangement which applies wet steam to the fibrous web.
  • the nozzle arrangement should be formed by a plurality of nozzles arranged in and / or at right angles to the web running direction and arranged on the fibrous web.
  • the nozzle assembly should preferably extend across the web direction across the entire width of the fibrous web.
  • One or more mixing chambers are suitable for forming the wet steam, wherein the nozzles of the nozzle arrangement are each connected to a mixing chamber and the mixing chambers saturated or superheated steam and boiling water or water condensate is supplied.
  • the mass ratio between liquid and gaseous water is adjustable separately in zones transverse to the web running direction.
  • each zone of nozzles being connected to a certain mixing chamber.
  • a controllable valve should be located in the steam and / or water condensate supply line, preferably each mixing chamber.
  • the mass ratio can also be adjusted depending on the type of fibrous web and / or depending on the basis weight of the fibrous web and / or the operating speed.
  • the mass fraction of the liquid water in the wet steam and / or the amount of wet steam applied to the fibrous web per unit time must be changed accordingly.
  • the mass fraction of the gaseous water in the wet steam and / or the amount of wet steam applied to the fibrous web per unit time is to be changed.
  • the total mass flow of liquid and gaseous water is adjusted depending on the type of fibrous web and / or the basis weight and / or the operating speed.
  • the fibrous web can be passed through one or more smoothing gaps.
  • the fibrous web passes through a plurality of smoothing gaps, it is advantageous if the fibrous web is subjected to wet steam at least between two calendering nips.
  • the wet steam loading of the fibrous web should be done with a distance between 10 and 100 cm before the first or single nip.
  • wet steam is applied to the fibrous web between two calendering nips, then this should be done with a distance between 10 and 100 cm before the calendering nip.
  • the distance is considered to be the length of the fibrous web between the end of the wet steam application and the following nip.
  • the distance between the nozzles and the fibrous web is between 10 and 100 cm.
  • the diagram according to FIG. 1 shows the dependence of entropy s, temperature t and ambient pressure p.
  • the specially marked curve shows the phase transitions of water at an ambient pressure p of 2.5 bar.
  • A denotes a point in the condensate phase
  • a * stands for boiling water
  • B * for saturated steam
  • Wet steam is a mixture of boiling water and saturated steam, where C shows a possible mixing ratio.
  • This wet steam will, as in FIG. 2 shown produced in a mixing chamber 6 by mixing saturated or superheated steam and condensate.
  • the steam is fed via a feed line 7 and the water condensate via a feed line 8 to the mixing chamber 6.
  • a controllable valve 9,10 is ever a controllable valve 9,10, about which the mass ratio between liquid and gaseous water in the mixing chamber 6 can be adjusted.
  • the mixing chamber 6 is connected to the nozzles 5 of a nozzle arrangement which direct the wet steam onto the fibrous web 1.
  • the nozzle arrangement is formed by a number of nozzles 5 arranged side by side transversely to the web running direction 4.
  • the nozzles 5 extend over the entire width of the fibrous web 1.
  • the distance between the nozzles 5 and the fibrous web 1 is between 10 and 100 cm.
  • each mixing chamber 6 is connected to a group of nozzles 5, for example the nozzles 5 at the web edge or in the middle of the web.
  • wet steam to moisten the fibrous web 1 allows due to the components of liquid water, a relatively large, but still uniform moisture application.
  • the gaseous portion of the wet steam allows an increase in the temperature of the fibrous web 1, which may be advantageous for influencing gloss and smoothness in subsequent smoothing nips.
  • the smoothing arrangement is here, as in FIG. 2 to see, for example, formed by a calender, which consists of several superposed and pressed against each other smoothing rollers 2.
  • the fibrous web 1 passes through all calendering slits of the calender from top to bottom.
  • the upper side of the fibrous web 1 with a nozzle arrangement and after the second smoothing nip the opposite side of the fibrous web 1 is moistened with a different nozzle arrangement before the first smoothing nip.
  • the fibrous web 1 Due to the two-sided moistening the fibrous web 1 can be completely rewetted, but also a curl of the fibrous web 1 can be effectively countered.
  • the invention is not limited to this arrangement of humidifying devices.
  • the moistening is to be intensified or reduced, the mass fraction of liquid water in the mixing chamber 6 and / or the amount of wet steam applied to the fibrous web 1 per unit of time is increased or decreased.
  • the temperature of the fibrous web 1 is to be increased or decreased, then the mass fraction of gaseous water in the mixing chamber 6 and / or the increased or reduced applied to the fibrous web 1 per unit time wet steam amount.

Abstract

The fibrous web (1) is subjected to treatment with wet steam from a nozzle (5) arrangement. This is carried out between two or more smoothing nips through which the web passes. The moistening device is located 10-100 cm before the nip. The mass ratio: liquid water/vaporized water, is adjustable. Separate adjustment is provided in zones across the direction of web travel (4). Ratio adjustment is a function of the type of web, its weight and/or the operating speed. The nozzles are at right angles to the web, over its entire width. They are connected to a mixing chamber (6) supplied with saturated or superheated steam and boiling water or condensate. There are a number of mixing chambers. A control valve is included in each steam (7) and/or water condensate (8) supply line. A spacing of 10-100 cm intervenes in each case, between nozzles and web and between nozzles and smoothing nip.

Description

Die Erfindung betrifft ein Verfahren zur Befeuchtung einer Papier-, Karton- oder einer anderen Faserstoffbahn vor einem Glättspalt, durch den die Faserstoffbahn zur Glättung geführt wird, wobei die Faserstoffbahn mittels einer Befeuchtungsvorrichtung mit Nassdampf beaufschlagt wird.The invention relates to a method for moistening a paper, cardboard or another fibrous web in front of a calendering slit, through which the fibrous web is guided for smoothing, wherein the fibrous web is subjected to wet steam by means of a moistening device.

Derartige Befeuchtungseinrichtungen sind seit längerem bekannt und dienen einerseits dazu die Rollneigung der Faserstoffbahn zu vermindern und andererseits aber auch dazu den Glättprozess zu beeinflussen.Such moistening devices have been known for a long time and on the one hand serve to reduce the tendency of the fibrous web to curl and, on the other hand, also to influence the smoothing process.

Wie beispielsweise in der EP-A-1674615 offenbart, befindet sich die Befeuchtungseinrichtung gerne nahe vor einem Glättspalt.Such as in the EP-A-1674615 discloses the moistening device is preferably close to a Glättspalt.

Während das Aufsprühen von Flüssigkeit wegen der Wassertröpfchen keinen gleichmäßigen Wasserauftrag ermöglicht, führt das Aufbringen von Wasserdampf nur zu einem geringen Flüssigkeitsauftrag.While the spraying of liquid due to the water droplets does not allow a uniform application of water, the application of water vapor only leads to a low liquid application.

Deshalb war man in der folgenden Entwicklung - wie insbesondere auch in der DE29813663U1 - bestrebt, sowohl Wasser als auch Dampf an unterschiedlichen Stellen auf die Papierbahn aufzutragen.Therefore one was in the following development - as in particular in the DE29813663U1 - strives to apply both water and steam at different locations on the paper web.

In der DE19829131A1 wird Wasserdampf gemeinsam mit beispielsweise Heißluft auf die Papierbahn geblasen. Durch Variation des Wasserdampfanteils lässt sich Einfluss auf das Glättergebnis nehmen.In the DE19829131A1 steam is blown onto the paper web together with hot air, for example. By varying the water vapor content can influence the smoldering result.

Die GB862115A , die US2004/074981A1 und die WO00/03087A offenbaren bereits den gemeinsamen Auftrag von Wasser und Wasserdampf (also beispielweise in Form von Nassdampf) auf die Papierbahn. Insbesondere in der US2004/074981A1 ist beschrieben, wie bei voreingestelltem Mischungsverhältnis durch Veränderung des Gesamtmassenstroms, der auf die Papierbahn trifft, Veränderungen in der Papierqualität erreicht werden können.The GB862115A , the US2004 / 074981A1 and the WO00 / 03087A already disclose the common application of water and water vapor (ie, for example in the form of wet steam) on the paper web. Especially in the US2004 / 074981A1 It is described how changes in the paper quality can be achieved at a preset mixing ratio by changing the total mass flow impinging on the paper web.

Die Aufgabe der Erfindung ist es, eine gleichmäßige und ausreichende Befeuchtung der Faserstoffbahn zu ermöglichen und dabei den Glättprozess zu beeinflussen.The object of the invention is to allow a uniform and sufficient moistening of the fibrous web and thereby to influence the smoothing process.

Erfindungsgemäß wurde die Aufgabe hinsichtlich des Verfahrens dadurch gelöst, auf Schwankungen der Bahnparameter, wie Glanz oder Glätte durch Einstellung des Massenverhältnisses zwischen flüssigem und gasförmigem Wasser in einer Mischkammer der Befeuchtungsvorrichtung zu reagieren.According to the invention, the object with regard to the method has been achieved by reacting to variations in the orbital parameters, such as gloss or smoothness, by adjusting the mass ratio between liquid and gaseous water in a mixing chamber of the moistening device.

Nassdampf besteht aus einer Mischung aus gasförmigem und flüssigem Wasser, dessen Entstehungsbedingungen aus dem bekannten Entropie-Temperatur-Diagramm von Wasser ablesbar sind.Wet steam consists of a mixture of gaseous and liquid water whose conditions of origin can be read from the known entropy-temperature diagram of water.

Um den Nassdampf zu erhalten, wird hier gesättigter oder überhitzter Wasserdampf und kondensiertes oder siedendes Wasser gemischt.
Während der Anteil des flüssigen Wassers dabei für den Umfang der Befeuchtung wesentlich ist, beeinflusst der Anteil des gasförmigen Wassers die Temperatur der Faserstoffbahn entscheidend.To obtain the wet steam, saturated or superheated steam and condensed or boiling water are mixed here.
While the proportion of liquid water is essential for the extent of humidification, the proportion of gaseous water decisively influences the temperature of the fibrous web.

Daher sollte das Massenverhältnis zwischen flüssigem und gasförmigem Wasser einstellbar sein.Therefore, the mass ratio between liquid and gaseous water should be adjustable.

Die Befeuchtungsvorrichtung weist eine Düsenanordnung auf, die die Faserstoffbahn mit Nassdampf beaufschlagt. Dabei sollte die Düsenanordnung von mehreren in und/oder quer zur Bahnlaufrichtung nebeneinander angeordneten und auf die Faserstoffbahn gerichteten Düsen gebildet werden.The moistening device has a nozzle arrangement which applies wet steam to the fibrous web. In this case, the nozzle arrangement should be formed by a plurality of nozzles arranged in and / or at right angles to the web running direction and arranged on the fibrous web.

Außerdem sollte sich die Düsenanordnung vorzugsweise quer zur Bahnlaufrichtung über die gesamte Breite der Faserstoffbahn erstrecken.In addition, the nozzle assembly should preferably extend across the web direction across the entire width of the fibrous web.

Zur Bildung des Nassdampfes eignen sich eine oder mehrere Mischkammern, wobei die Düsen der Düsenanordnung mit jeweils einer Mischkammer verbunden sind und den Mischkammern gesättigter oder überhitzter Wasserdampf und siedendes Wasser oder Wasserkondensat zugeführt wird.One or more mixing chambers are suitable for forming the wet steam, wherein the nozzles of the nozzle arrangement are each connected to a mixing chamber and the mixing chambers saturated or superheated steam and boiling water or water condensate is supplied.

Falls die gesamte Faserstoffbahn mit dem gleichen Mischungsverhältnis hinsichtlich des Massenanteils von gasförmigem und flüssigem Wasser beaufschlagt werden sollen, so genügt eine Mischkammer.If the entire fibrous web to be applied with the same mixing ratio in terms of mass fraction of gaseous and liquid water, so a mixing chamber is sufficient.

Im Interesse einer Prozessoptimierung, insbesondere auch um auf zonale Abweichungen der Bahnparameter reagieren zu können, ist es jedoch von Vorteil, wenn das Massenverhältnis zwischen flüssigem und gasförmigem Wasser in Zonen quer zur Bahnlaufrichtung separat einstellbar ist.In the interest of process optimization, in particular also in order to be able to respond to zonal deviations of the web parameters, it is advantageous if the mass ratio between liquid and gaseous water is adjustable separately in zones transverse to the web running direction.

In diesem Fall sollten mehrere Mischkammern vorhanden sein, wobei jede Zone von Düsen mit einer bestimmten Mischkammer verbunden ist.In this case, there should be several mixing chambers, each zone of nozzles being connected to a certain mixing chamber.

Zur Einstellung des Massenverhältnisses sollte sich in der Wasserdampf- und/oder der Wasserkondensat-Zuleitung, vorzugsweise jeder Mischkammer ein steuerbares Ventil befinden.To set the mass ratio, a controllable valve should be located in the steam and / or water condensate supply line, preferably each mixing chamber.

Das Massenverhältnis kann aber auch in Abhängigkeit von der Art der Faserstoffbahn und/oder in Abhängigkeit vom Flächengewicht der Faserstoffbahn und/oder der Betriebsgeschwindigkeit eingestellt werden.However, the mass ratio can also be adjusted depending on the type of fibrous web and / or depending on the basis weight of the fibrous web and / or the operating speed.

Soll dabei der Umfang der Befeuchtung der Faserstoffbahn verändert werden, so muss der Massenanteil des flüssigen Wassers im Nassdampf und/oder die auf die Faserstoffbahn pro Zeiteinheit aufgebrachte Menge an Nassdampf entsprechend verändert werden.If the amount of moistening of the fibrous web is to be changed, the mass fraction of the liquid water in the wet steam and / or the amount of wet steam applied to the fibrous web per unit time must be changed accordingly.

Zur Veränderung der Bahntemperatur ist der Massenanteil des gasförmigen Wassers im Nassdampf und/oder die auf die Faserstoffbahn pro Zeiteinheit aufgebrachte Menge an Nassdampf zu verändern.To change the web temperature, the mass fraction of the gaseous water in the wet steam and / or the amount of wet steam applied to the fibrous web per unit time is to be changed.

Dementsprechend kann es auch von Vorteil sein, wenn der Gesamtmassenstrom von flüssigem und gasförmigem Wasser in Abhängigkeit von der Art der Faserstoffbahn und/oder dem Flächengewicht und/oder der Betriebsgeschwindigkeit eingestellt wird.Accordingly, it may also be advantageous if the total mass flow of liquid and gaseous water is adjusted depending on the type of fibrous web and / or the basis weight and / or the operating speed.

Je nach Art der Faserstoffbahn und den Anforderungen hinsichtlich Glanz und Glätte kann die Faserstoffbahn durch einen oder mehrere Glättspalte geführt werden.Depending on the type of fibrous web and the requirements in terms of gloss and smoothness, the fibrous web can be passed through one or more smoothing gaps.

Falls die Faserstoffbahn durch mehrere Glättspalte läuft, so ist es von Vorteil, wenn die Faserstoffbahn zumindest zwischen zwei Glättspalten mit Nassdampf beaufschlagt wird.If the fibrous web passes through a plurality of smoothing gaps, it is advantageous if the fibrous web is subjected to wet steam at least between two calendering nips.

Um einerseits ein ausreichendes Eindringen der Feuchtigkeit in die Faserstoffbahn zu ermöglichen und andererseits eine gewünschte Bahntemperatur sowie eine kompakte Anordnung zu ermöglichen, sollte die Nassdampf-Beaufschlagung der Faserstoffbahn mit einem Abstand zwischen 10 und 100 cm vor dem ersten oder einzigen Glättspalt erfolgen.On the one hand to allow a sufficient penetration of moisture into the fibrous web and on the other hand to allow a desired web temperature and a compact arrangement, the wet steam loading of the fibrous web should be done with a distance between 10 and 100 cm before the first or single nip.

Erfolgt die Nassdampf-Beaufschlagung der Faserstoffbahn zwischen zwei Glättspalten, so sollte dies mit einem Abstand zwischen 10 und 100 cm vor dem Glättspalt erfolgen.If the wet steam is applied to the fibrous web between two calendering nips, then this should be done with a distance between 10 and 100 cm before the calendering nip.

Allgemein hängt der Abstand natürlich von der Bahngeschwindigkeit ab, wobei eine höhere Geschwindigkeit oft auch einen längeren Abstand erfordert.Of course, the distance of course depends on the web speed, with a higher speed often requires a longer distance.

Als Abstand wird dabei die Länge der Faserstoffbahn zwischen dem Ende der Nassdampf-Beaufschlagung und dem folgenden Glättspalt angesehen.The distance is considered to be the length of the fibrous web between the end of the wet steam application and the following nip.

Von Vorteil ist es außerdem, wenn der Abstand zwischen den Düsen und der Faserstoffbahn zwischen 10 und 100 cm liegt.It is also advantageous if the distance between the nozzles and the fibrous web is between 10 and 100 cm.

Nachfolgend soll die Erfindung an einem Ausführungsbeispiel näher erläutert werden. In der beigefügten Zeichnung zeigt:

Figur 1:
eine Entropie-Temperatur-Diagramm von Wasser und
Figur 2:
eine schematische Darstellung eines Teils eines Kalanders mit Düsenanordnung.
The invention will be explained in more detail with reference to an exemplary embodiment. In the attached drawing shows:
FIG. 1:
an entropy-temperature diagram of water and
FIG. 2:
a schematic representation of a portion of a calender with nozzle assembly.

Das Diagramm gemäß Figur 1 zeigt die Abhängigkeit von Entropie s, Temperatur t und Umgebungsdruck p. Die besonders gekennzeichnete Kurve zeigt die Phasenübergänge von Wasser bei einem Umgebungsdruck p von 2,5 bar.The diagram according to FIG. 1 shows the dependence of entropy s, temperature t and ambient pressure p. The specially marked curve shows the phase transitions of water at an ambient pressure p of 2.5 bar.

Dabei kennzeichnet A einen Punkt in der Kondensat-Phase, A* steht für siedendes Wasser, B* für gesättigten Dampf und B für überhitzten Dampf.A denotes a point in the condensate phase, A * stands for boiling water, B * for saturated steam and B for superheated steam.

Nassdampf stellt eine Mischung aus siedendem Wasser und gesättigtem Dampf dar, wobei C ein mögliches Mischungsverhältnis zeigt.Wet steam is a mixture of boiling water and saturated steam, where C shows a possible mixing ratio.

Dieser Nassdampf wird, wie in Figur 2 gezeigt, in einer Mischkammer 6 durch Mischung von gesättigtem oder überhitzten Wasserdampf und Kondensat erzeugt.This wet steam will, as in FIG. 2 shown produced in a mixing chamber 6 by mixing saturated or superheated steam and condensate.

Hierzu wird der Wasserdampf über eine Zuleitung 7 und das Wasserkondensat über eine Zuleitung 8 zur Mischkammer 6 geführt. In beiden Zuleitungen 7,8 befindet sich je ein steuerbares Ventil 9,10, worüber das Massenverhältnis zwischen flüssigem und gasförmigem Wasser in der Mischkammer 6 eingestellt werden kann.For this purpose, the steam is fed via a feed line 7 and the water condensate via a feed line 8 to the mixing chamber 6. In both supply lines 7,8 is ever a controllable valve 9,10, about which the mass ratio between liquid and gaseous water in the mixing chamber 6 can be adjusted.

Die Mischkammer 6 ist mit den Düsen 5 einer Düsenanordnung verbunden, welche den Nassdampf auf die Faserstoffbahn 1 richten.The mixing chamber 6 is connected to the nozzles 5 of a nozzle arrangement which direct the wet steam onto the fibrous web 1.

Hierzu wird die Düsenanordnung von einer Reihe quer zur Bahnlaufrichtung 4 nebeneinander angeordneten Düsen 5 gebildet. Um die Faserstoffbahn 1 gänzlich befeuchten zu können erstrecken sich die Düsen 5 über die gesamte Breite der Faserstoffbahn 1. Der Abstand zwischen den Düsen 5 und der Faserstoffbahn 1 liegt zwischen 10 und 100 cm.For this purpose, the nozzle arrangement is formed by a number of nozzles 5 arranged side by side transversely to the web running direction 4. In order to be able to moisten the fibrous web 1 completely, the nozzles 5 extend over the entire width of the fibrous web 1. The distance between the nozzles 5 and the fibrous web 1 is between 10 and 100 cm.

Falls die Befeuchtung in Zonen quer zur Bahnlaufrichtung 4 separat steuerbar sein soll, so sind hierfür mehrere, hinsichtlich des Massenverhältnisses separat steuerbare Mischkammern 6 vorzusehen. Dabei ist jede Mischkammer 6 mit einer Gruppe von Düsen 5, beispielsweise den Düsen 5 am Bahnrand oder in der Bahnmitte verbunden.If the humidification in zones transversely to the web running direction 4 should be controllable separately, then several, with regard to the mass ratio separately controllable mixing chambers 6 are provided. Each mixing chamber 6 is connected to a group of nozzles 5, for example the nozzles 5 at the web edge or in the middle of the web.

Damit kann beispielsweise einer Übertrocknung der Bahnränder in einer vorhergehenden Trockenpartie begegnet werden.This can be countered, for example, over-drying of the web edges in a preceding drying section.

Die Verwendung von Nassdampf zur Befeuchtung der Faserstoffbahn 1 ermöglicht wegen den Bestandteilen an flüssigem Wasser einen relativ großen, aber dennoch gleichmäßigen Feuchteauftrag.The use of wet steam to moisten the fibrous web 1 allows due to the components of liquid water, a relatively large, but still uniform moisture application.

Der gasförmige Anteil des Nassdampfs erlaubt eine Erhöhung der Temperatur der Faserstoffbahn 1, was zur Beeinflussung von Glanz und Glätte in nachfolgenden Glättspalten von Vorteil sein kann.The gaseous portion of the wet steam allows an increase in the temperature of the fibrous web 1, which may be advantageous for influencing gloss and smoothness in subsequent smoothing nips.

Die Glättanordnung wird hier, wie in Figur 2 zu sehen, beispielsweise von einem Kalander gebildet, der aus mehreren übereinander angeordneten und gegeneinander gedrückten Glättwalzen 2 besteht.The smoothing arrangement is here, as in FIG. 2 to see, for example, formed by a calender, which consists of several superposed and pressed against each other smoothing rollers 2.

Die Faserstoffbahn 1 durchläuft alle Glättspalte des Kalanders von oben nach unten.The fibrous web 1 passes through all calendering slits of the calender from top to bottom.

Zwischen den Glättspalten wird die Faserstoffbahn 1 über Leitwalzen 3 geführt.Between the Glättspalten the fibrous web 1 is guided over guide rollers 3.

Dabei wird hier vor dem ersten Glättspalt die Oberseite der Faserstoffbahn 1 mit einer Düsenanordnung und nach dem zweiten Glättspalt die gegenüberliegende Seite der Faserstoffbahn 1 mit einer anderen Düsenanordnung befeuchtet.In this case, the upper side of the fibrous web 1 with a nozzle arrangement and after the second smoothing nip the opposite side of the fibrous web 1 is moistened with a different nozzle arrangement before the first smoothing nip.

Durch die beidseitige Befeuchtung kann die Faserstoffbahn 1 umfassend rückbefeuchtet, aber auch einer Rollneigung der Faserstoffbahn 1 wirkungsvoll begegnet werden.Due to the two-sided moistening the fibrous web 1 can be completely rewetted, but also a curl of the fibrous web 1 can be effectively countered.

Die Erfindung ist jedoch nicht auf diese Anordnung von Befeuchtungsvorrichtungen beschränkt.However, the invention is not limited to this arrangement of humidifying devices.

Soll dabei die Befeuchtung intensiviert bzw. vermindert werden, so wird der Masseanteil von flüssigem Wasser in der Mischkammer 6 und/oder die auf die Faserstoffbahn 1 pro Zeiteinheit aufgebrachte Nassdampfmenge erhöht bzw. verringert.If the moistening is to be intensified or reduced, the mass fraction of liquid water in the mixing chamber 6 and / or the amount of wet steam applied to the fibrous web 1 per unit of time is increased or decreased.

Soll dagegen die Temperatur der Faserstoffbahn 1 erhöht bzw. vermindert werden, so wird der Masseanteil von gasförmigem Wasser in der Mischkammer 6 und/oder die auf die Faserstoffbahn 1 pro Zeiteinheit aufgebrachte Nassdampfmenge erhöht bzw. verringert.If, on the other hand, the temperature of the fibrous web 1 is to be increased or decreased, then the mass fraction of gaseous water in the mixing chamber 6 and / or the increased or reduced applied to the fibrous web 1 per unit time wet steam amount.

Claims (6)

  1. Process for moistening a paper, board or other fibrous web (1) before a smoothing nip, through which the fibrous web (1) is led in order to smooth it, the fibrous web (1) having wet steam applied to it by means of a moistening device, characterized in that fluctuations in the web parameters, such as gloss or smoothness, are reacted to by adjusting the mass ratio between liquid and gaseous water in a mixing chamber (6) of the moistening device.
  2. Process according to Claim 1, characterized in that the fibrous web (1) is led through a plurality of smoothing nips and the fibrous web (1) has wet steam applied to it, at least between two smoothing nips.
  3. Process according to Claim 1 or 2, characterized in that the application of wet steam to the fibrous web (1) is carried out at a distance between 10 and 100 cm before the first smoothing nip.
  4. Process according to Claim 3, characterized in that the mass ratio between liquid and gaseous water can be adjusted separately in zones transversely with respect to the web running direction (4).
  5. Process according to Claims 1 to 4, characterized in that the mass ratio between liquid and gaseous water is adjusted as a function of the type of fibrous web and/or the grammage and/or the operating speed.
  6. Process according to one of the preceding claims, characterized in that the total mass flow of liquid and gaseous water is adjusted as a function of the type of fibrous web and/or the grammage and/or the operating speed.
EP07108110A 2006-08-30 2007-05-14 Process for moistening a fibrous web Expired - Fee Related EP1895050B1 (en)

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Publication number Priority date Publication date Assignee Title
DE102012212111A1 (en) 2012-07-11 2014-01-30 Metso Paper, Inc. Device for moistening moving fiber web, has roller provided with recesses suitable for receiving liquid, where roller is brought in contact indirectly with fiber web, and roller is arranged before treatment gap

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2950989A (en) 1958-03-17 1960-08-30 Warren S D Co Method of producing drum-finished coated paper
DE19826899B4 (en) 1998-05-08 2005-05-19 V.I.B. Systems Gmbh Method and apparatus for on-line calendering of SC-A paper
DE19829131A1 (en) 1998-06-30 2000-01-13 Wilhelm Wanke Process for smoothing fibrous webs, preferably paper or cardboard webs, including exposure to medium, and devices therefor
US6569288B1 (en) 1998-07-10 2003-05-27 Metso Paper, Inc. Method for manufacturing surface-treated printing paper
US6962296B2 (en) 2002-10-16 2005-11-08 Abb Ltd. Steam water spray systems
DE102004062618A1 (en) 2004-12-24 2006-07-06 Voith Paper Patent Gmbh screed assembly

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DE502007000662D1 (en) 2009-06-10
ATE430216T1 (en) 2009-05-15
EP1895050A1 (en) 2008-03-05

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