EP0854228B9 - Press section - Google Patents

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Publication number
EP0854228B9
EP0854228B9 EP97119262A EP97119262A EP0854228B9 EP 0854228 B9 EP0854228 B9 EP 0854228B9 EP 97119262 A EP97119262 A EP 97119262A EP 97119262 A EP97119262 A EP 97119262A EP 0854228 B9 EP0854228 B9 EP 0854228B9
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EP
European Patent Office
Prior art keywords
pressure
press
fibrous web
web running
zone
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EP97119262A
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German (de)
French (fr)
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EP0854228B1 (en
EP0854228A3 (en
EP0854228A2 (en
Inventor
Hans Loser
Joachim Henssler
Karl Dr. Steiner
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Voith Patent GmbH
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Voith Paper Patent GmbH
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    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21F—PAPER-MAKING MACHINES; METHODS OF PRODUCING PAPER THEREON
    • D21F3/00—Press section of machines for making continuous webs of paper
    • D21F3/02—Wet presses
    • D21F3/0209—Wet presses with extended press nip
    • D21F3/0218—Shoe presses
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10S162/00—Paper making and fiber liberation
    • Y10S162/06—Moisture and basic weight

Definitions

  • the invention relates to a press section of a machine for Production of a fibrous web, in particular paper and / or Board web, according to the preamble of claim 1.
  • the fibrous web to be treated has a low strength. This has to be one too high pressure increase in the web running direction unwanted displacement the train in the press nip result. The danger of a such suppression exists especially with large basis weights the fibrous web.
  • the aim of the invention is a press section of the above to create said type, in the best possible Drainage performance and the highest possible quality of produced fibrous web are guaranteed.
  • At a low dry content of the incoming fibrous web is the maximum pressure gradient occurring in the web running direction dp dl Max of the pressure generated in the inlet zone and / or the Hauptpreßzone of the press nip p selected so that it at least substantially the relationship is satisfied, in which p is the pressure of the main press zone and FG is the basis weight of the incoming fibrous web.
  • the low dry content of the fibrous web is at a dry content of about 8 to 25%.
  • the pressure gradient dp / dl of the pressure p generated in the inlet zone of the press nip in the web running direction is advantageously selected such that it at least substantially satisfies the relationship satisfies, in the p 1, the predetermined pressure at the beginning of the Hauptpreßzone or the predetermined pressure at the end of the inlet zone and FG is the basis weight of the incoming fibrous web.
  • the predetermined pressure p 1 at the beginning of the Hauptpreßzone is chosen so that it at least substantially the relationship p 1 ( bar ) ⁇ T % 3.5 to 4 is satisfied, where T is the dry content of the incoming fibrous web.
  • the particular desired pressure pressure curve is by a corresponding shoe design (e.g., length, shape) predetermined.
  • the extended in the running direction press nip is between a circumferential, at least one press shoe guided flexible press belt and a counter-roller formed.
  • the extended press nip can thus in particular be formed by a shoe press.
  • the counter-roller is preferably perforated, grooved and / or suctioned.
  • the lubricant in question can thus additionally in a perforated and / or grooved counter roll drain or even be sucked off.
  • the by the rotating flexible press belt formed band loop is open at both ends.
  • FIG. 1 shows purely schematically the course of the pressure p over the gap length 1. Thereafter included the relevant, extended in the running direction press nip an inlet zone a, a Hauptpreßzone b and an outlet zone c. While the pressure p in the inlet zone a and in the Hauptpreßzone b rises continuously, he falls in the Exit zone c again.
  • the predefinable pressure at the beginning of the Hauptpreßzone b is designated by p 1 .
  • p max The predefinable pressure at the end of the Hauptpreßzone b.
  • the pressure gradient dp / dl of the pressure p produced in the main press zone a of the press nip in the web running direction and thus in the direction of the nip length 1 is now in the range of about 0.01 ⁇ p at a medium or high dry content of the fibrous web entering the press nip max / cm to about 0.08 x p max / cm , preferably having a value of about 0.04 x p max / cm .
  • the maximum pressure gradient occurring in the web running direction is reached dp dl Max of the pressure generated in the inlet zone a and / or the Hauptpreßzone b of the press nip p selected so that it at least substantially the relationship satisfies, in the p again the pressure of Hauptpreßzone and FG is the basis weight of the incoming fibrous web.
  • a low dry content of the fibrous web is at one Dry content of about 8 to about 25%.
  • the pressure gradient dp / dl occurring in the running running direction of the pressure p produced in the inlet zone a of the press nip is selected at a medium or high dry content of the incoming fibrous web such that it at least substantially satisfies the relationship fulfilled, in the p 1 again the predetermined pressure at the beginning of Hauptpreßzone b or the predetermined pressure at the end of the inlet zone a and FG is the basis weight of the incoming fibrous web.
  • the occurring in the web running direction pressure gradient dp / dl of the generated in the outlet zone c of the press nip sloping pressure p is selected at a medium or high dry content of the incoming fibrous web so that at least substantially the relationship is met, in the p max again the predetermined maximum pressure at the end of Hauptpreßzone b and FG is the basis weight of the incoming fibrous web.
  • the predeterminable pressure p 1 at the beginning of the Hauptpreßzone b is preferably chosen so that it at least substantially the relationship p 1 ( bar ) ⁇ T % 3.5 to 4 fulfilled, in which T is again the dry content of the incoming fibrous web.
  • Figure 2 shows a rough approximation purely by way of example the pressure curve over at least two in the web running direction successively lying Preß réelle I and II, wherein in particular the first Preßschuh I is designed to treat the fibrous web with a mean or higher inlet dryness in the range of for example 25% to 30%.
  • the pressure gradient dp / dl of the pressure p generated in the main press zone b (see also FIG. 1) of the press nip has a value of about 0.04 ⁇ p max / cm in the present case.
  • the pressure curve in the inlet region a is indicated purely schematically in the diagram.
  • Figure 3 shows a rough approximation purely by way of example the pressure curve over three successively in the web running direction Preß réelle I, II and III, wherein in particular the first Preßschuh I is designed to treat a fibrous web with a low inlet dryness, for example, less than 20%.
  • the pressure gradient dp / dl of the pressure p generated in the main press zone b (see also FIGURE 1) of the press nip may be the maximum pressure gradient previously specified, depending on the maximum pressure p max at the end of the main press zone and the basis weight FG of the incoming fibrous web dp dl Max do not exceed.
  • the value of the pressure gradient dp / dl at 0.08 ⁇ p max / cm, eluting with p max back to the predetermined pressure is indicated at the end of the main pressing zone b (see also FIG. 1).
  • the pressure curve in the inlet region a see also FIG.
  • the particular desired pressure pressure curve is by a corresponding shoe design (e.g., length, shape) predetermined.

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Description

Die Erfindung betrifft eine Pressenpartie einer Maschine zur Herstellung einer Faserstoffbahn, insbesondere Papier- und/oder Kartonbahn, nach dem Oberbegriff des Anspruchs 1.The invention relates to a press section of a machine for Production of a fibrous web, in particular paper and / or Board web, according to the preamble of claim 1.

In Pressenpartien der eingangs genannten Art kommt es insbesondere bei mittleren und höheren Eingangstrockengehalten der zu behandelnden Faserstoffbahn häufig zu einer Verdichtung der Bahnoberfläche durch zu hohe Drücke. Steile Druckanstiege sind hierbei besonders schädlich. Die Folge ist unter anderem eine geringere Druckleistung in der Trockenpartie und eine relativ geringe Spaltfestigkeit. Zudem ergibt sich eine geringere Wirksamkeit der nachfolgenden Pressen.In press sections of the type mentioned in particular at medium and higher input dry levels, the to be treated fibrous web often to a compaction the web surface by too high pressures. Steep pressure increases are particularly harmful here. The episode is among others a lower pressure in the dryer section and a relatively low gap strength. In addition, there is a lower Effectiveness of the following presses.

Bei niedrigen Trockengehalten besitzt die zu behandelnde Faserstoffbahn eine geringe Festigkeit. Dies hat bei einem zu hohen Druckanstieg in Bahnlaufrichtung ein unerwünschtes Verdrücken der Bahn im Preßspalt zur Folge. Die Gefahr eines solchen Verdrückens besteht insbesondere bei großen Flächengewichten der Faserstoffbahn.At low dry contents, the fibrous web to be treated has a low strength. This has to be one too high pressure increase in the web running direction unwanted displacement the train in the press nip result. The danger of a such suppression exists especially with large basis weights the fibrous web.

Aus DE-A-3410172 ist eine Pressenpartie gemäß dem Oberbegriff des Anspruchs 1 bekannt.From DE-A-3410172 is a press section according to the preamble of claim 1.

Ziel der Erfindung ist es, eine Pressenpartie der eingangs genannten Art zu schaffen, bei der eine möglichst optimale Entwässerungsleistung und eine möglichst hohe Qualität der erzeugten Faserstoffbahn gewährleistet sind.The aim of the invention is a press section of the above to create said type, in the best possible Drainage performance and the highest possible quality of produced fibrous web are guaranteed.

Die Aufgabe wird nach der Erfindung gemäß den Merkmalen des Anspruchs 1 gelöst. The object is according to the invention solved according to the features of claim 1.

Bei einem niedrigen Trockengehalt der einlaufenden Faserstoffbahn ist der in Bahnlaufrichtung auftretende maximale Druckgradient dp dl max des in der Einlaufzone und/oder der Hauptpreßzone des Preßspaltes erzeugten Druckes p so gewählt, daß er zumindest im wesentlichen die Beziehung

Figure 00020001
erfüllt, in der p der Druck der Hauptpreßzone und FG das Flächengewicht der einlaufenden Faserstoffbahn ist.At a low dry content of the incoming fibrous web is the maximum pressure gradient occurring in the web running direction dp dl Max of the pressure generated in the inlet zone and / or the Hauptpreßzone of the press nip p selected so that it at least substantially the relationship
Figure 00020001
is satisfied, in which p is the pressure of the main press zone and FG is the basis weight of the incoming fibrous web.

Bei niedrigen Trockengehalten der einlaufenden Faserstoffbahn wird der maximale Druckgradient somit auch in Abhängigkeit vom jeweiligen Flächengewicht der einlaufenden Faserstoffbahn gewählt. Im Ergebnis ist der maximal zulässige Druckgradient somit eine Funktion sowohl des Trockengehaltes der einlaufenden Faserstoffbahn als auch des Flächengewichts der Bahn.At low dry levels of incoming Fibrous web becomes the maximum pressure gradient thus also depending on the respective basis weight the incoming fibrous web selected. In the result the maximum permissible pressure gradient is thus a function both the dry content of the incoming fibrous web as well as the basis weight of the web.

Es ist somit auch möglich, Entwässerungsbereiche, die bisher der Siebpartie vorbehalten waren, abzudecken. It is therefore also possible to use drainage areas, previously reserved for the wire section to cover.

Der niedrige Trockengehalt der Faserstoffbahn ist bei einem Trockengehalt von etwa 8 bis 25 % gegeben.The low dry content of the fibrous web is at a dry content of about 8 to 25%.

Bei einem mittleren oder hohen Trockengehalt der einlaufenden Faserstoffbahn ist der in Bahnlaufrichtung auftretende Druckgradient dp / dl des in der Einlaufzone des Preßspaltes erzeugten Druckes p vorteilhafterweise so gewählt, daß er zumindest im wesentlichen die Beziehung

Figure 00030001
erfüllt, in der p1 der vorgebbare Druck am Anfang der Hauptpreßzone bzw. der vorgebbare Druck am Ende der Einlaufzone und FG das Flächengewicht der einlaufenden Faserstoffbahn ist.In the case of a medium or high dry content of the incoming fibrous web, the pressure gradient dp / dl of the pressure p generated in the inlet zone of the press nip in the web running direction is advantageously selected such that it at least substantially satisfies the relationship
Figure 00030001
satisfies, in the p 1, the predetermined pressure at the beginning of the Hauptpreßzone or the predetermined pressure at the end of the inlet zone and FG is the basis weight of the incoming fibrous web.

Von besonderem Vorteil ist, wenn bei einem mittleren oder hohen Trockengehalt der einlaufenden Faserstoffbahn der in Bahnlaufrichtung auftretende Druckgradient dp / dl des in der Auslaufzone des Preßspaltes erzeugten abfallenden Druckes p so gewählt ist, daß für seinen Betrag zumindest im wesentlichen die Beziehung

Figure 00030002
erfüllt ist, in der pmax der vorgebbare maximale Druck am Ende der Hauptpreßzone und FG das Flächengewicht der einlaufenden Faserstoffbahn ist.It is particularly advantageous if at a medium or high dry content of the incoming fibrous web of the occurring in web running direction pressure gradient dp / dl of the generated in the outlet zone of the nip falling pressure p is chosen so that at least substantially the relationship
Figure 00030002
is met, in the p max, the predetermined maximum pressure at the end of the Hauptpreßzone and FG is the basis weight of the incoming fibrous web.

Bei der in der Praxis bevorzugten Ausführungsform der erfindungsgemäßen Pressenpartie ist der vorgebbare Druck p1 am Anfang der Hauptpreßzone so gewählt, daß er zumindest im wesentlichen die Beziehung p 1 (bar) ≈ T % 3,5 bis 4 erfüllt, in der T der Trockengehalt der einlaufenden Faserstoffbahn ist.In the practice preferred embodiment of the press section according to the invention, the predetermined pressure p 1 at the beginning of the Hauptpreßzone is chosen so that it at least substantially the relationship p 1 ( bar ) ≈ T % 3.5 to 4 is satisfied, where T is the dry content of the incoming fibrous web.

Zusammen mit einem in der zuvor genannten Weise gewählten Druckgradienten führt ein solcher Druck p1 am Anfang der Hauptpreßzone zu einem insgesamt optimalen Druckverlauf, wobei berücksichtigt ist, daß mit einem entsprechenden Druckegradienten auch der Trockengehalt der Faserstoffbahn entlang der Spaltlänge durch Entwässerung entsprechend zunimmt und durch den Druckgradienten auch der zeitliche Verlauf des Druckes bestimmt ist.Together with a pressure gradient selected in the aforementioned manner, such a pressure p 1 at the beginning of the main pressing zone leads to an overall optimum pressure profile, taking into account that with a corresponding pressure gradient the solids content of the fibrous web also increases along the gap length by dewatering and through the Pressure gradient and the time course of the pressure is determined.

Der jeweils gewünschte Preßdruckverlauf ist durch eine entsprechende Schuhgestaltung (z.B. Länge, Form) vorgebbar.The particular desired pressure pressure curve is by a corresponding shoe design (e.g., length, shape) predetermined.

Der in Bahnlaufrichtung verlängerte Preßspalt ist zwischen einem umlaufenden, über wenigstens einen Preßschuh geführten flexiblen Preßband und einer Gegenwalze gebildet. Der verlängerte Preßspalt kann somit insbesondere durch eine Schuhpresse gebildet sein.The extended in the running direction press nip is between a circumferential, at least one press shoe guided flexible press belt and a counter-roller formed. The extended press nip can thus in particular be formed by a shoe press.

Die Gegenwalze ist vorzugsweise gelocht, gerillt und/oder besaugt.The counter-roller is preferably perforated, grooved and / or suctioned.

Das betreffende Schmiermittel kann somit zusätzlich in einer gelochten und/oder gerillten Gegenwalze abfließen oder auch abgesaugt werden. The lubricant in question can thus additionally in a perforated and / or grooved counter roll drain or even be sucked off.

Insbesondere bei niedrigen Linienkräften der betreffenden Langspaltpresse, die beispielsweise im Bereich von 10 kN/m liegen können und bei denen die Schmierfilmdicke relativ groß ist, ist der Bereich zwischen Preßschuh und flexiblem Preßband zweckmäßigerweise mit Wasser geschmiert. Damit besteht insbesondere auch die Möglichkeit, den betreffenden Preßschuh in eine stirnseitig offene Bandschleife einzusetzen und entsprechend ein offenes System zu verwenden, bei dem die Schuhlänge relativ groß und beispielsweise deutlich größer als 350 mm sein kann.Especially at low line forces of the concerned Extended nip press, for example, in the range of 10 kN / m can lie and where the lubricant film thickness is relatively large is the area between press shoe and flexible press belt suitably lubricated with water. That exists in particular, the possibility of the respective press shoe insert into a frontally open belt loop and accordingly to use an open system where the shoe length relatively large and, for example, significantly larger than 350 mm can be.

Bei einer in der Praxis bevorzugten Ausführungsform ist somit vorgesehen, daß die durch das umlaufende flexible Preßband gebildete Bandschleife an ihren beiden Stirnseiten offen ist.In a preferred embodiment in practice is thus provided that the by the rotating flexible press belt formed band loop is open at both ends.

Die Erfindung wird im folgenden rein beispielhaft unter Bezugnahme auf die Zeichnung nochmals näher erläutert; in dieser zeigen:

Figur 1
eine rein schematische Darstellung des Druckverlaufs in einem in Bahnlaufrichtung verlängerten Preßspalt zur Erläuterung der Spaltaufteilung in eine Einlaufzone, Hauptpreßzone und Auslaufzone,
Figur 2
ein Diagramm, in dem rein schematisch der Druckverlauf über zwei aufeinander folgende Preßschuhe dargestellt ist und
Figur 3
ein Diagramm, in dem rein schematisch der Druckverlauf über drei aufeinander folgende Preßschuhe dargestellt ist.
The invention will be explained in more detail below purely by way of example with reference to the drawing; in this show:
FIG. 1
a purely schematic representation of the pressure curve in an extended web direction in the press nip to explain the splitting into an inlet zone, Hauptpreßzone and outlet zone,
FIG. 2
a diagram in which purely schematically the pressure curve over two successive Preßschuhe is shown and
FIG. 3
a diagram in which purely schematically the pressure curve over three successive Preßschuhe is shown.

Das in Figur 1 dargestellte Diagramm zeigt rein schematisch den Verlauf des Druckes p über der Spaltlänge 1. Danach umfaßt der betreffende, in Bahnlaufrichtung verlängerte Preßspalt eine Einlaufzone a, eine Hauptpreßzone b und eine Auslaufzone c. Während der Druck p in der Einlaufzone a und in der Hauptpreßzone b kontinuierlich ansteigt, fällt er in der Auslaufzone c wieder ab.The diagram shown in Figure 1 shows purely schematically the course of the pressure p over the gap length 1. Thereafter included the relevant, extended in the running direction press nip an inlet zone a, a Hauptpreßzone b and an outlet zone c. While the pressure p in the inlet zone a and in the Hauptpreßzone b rises continuously, he falls in the Exit zone c again.

Der vorgebbare Druck am Anfang der Hauptpreßzone b ist mit p1 bezeichnet. Am Ende der Hauptpreßzone b wird der vorgebbare maximale Druck pmax erreicht.The predefinable pressure at the beginning of the Hauptpreßzone b is designated by p 1 . At the end of the Hauptpreßzone b the predetermined maximum pressure p max is reached.

Der in Bahnlaufrichtung und damit in Richtung der Spaltlänge 1 auftretende Druckgradient dp / dl des in der Hauptpreßzone a des Preßspaltes erzeugten Druckes p liegt nun erfindungsgemäß bei einem mittleren oder hohen Trockengehalt der in den Preßspalt einlaufenden Faserstoffbahn in einem Bereich von etwa 0,01· p max / cm bis etwa 0,08· p max / cm, wobei er vorzugsweise einen Wert von etwa 0,04· p max / cm besitzt.The pressure gradient dp / dl of the pressure p produced in the main press zone a of the press nip in the web running direction and thus in the direction of the nip length 1 is now in the range of about 0.01 × p at a medium or high dry content of the fibrous web entering the press nip max / cm to about 0.08 x p max / cm , preferably having a value of about 0.04 x p max / cm .

Dagegen ist bei einem niedrigen Trockengehalt der einlaufenden Faserstoffbahn der in Bahnlaufrichtung auftretende maximale Druckgradient dp dl max des in der Einlaufzone a und/oder der Hauptpreßzone b des Preßspaltes erzeugten Druckes p so gewählt, daß er zumindest im wesentlichen die Beziehung

Figure 00060001
erfüllt, in der p wieder der Druck der Hauptpreßzone und FG das Flächengewicht der einlaufenden Faserstoffbahn ist.By contrast, with a low dry content of the incoming fibrous web, the maximum pressure gradient occurring in the web running direction is reached dp dl Max of the pressure generated in the inlet zone a and / or the Hauptpreßzone b of the press nip p selected so that it at least substantially the relationship
Figure 00060001
satisfies, in the p again the pressure of Hauptpreßzone and FG is the basis weight of the incoming fibrous web.

Ein niedriger Trockengehalt der Faserstoffbahn ist bei einem Trockengehalt von etwa 8 bis etwa 25 % gegeben. A low dry content of the fibrous web is at one Dry content of about 8 to about 25%.

Der in Bahnlaufrichtung auftretende Druckgradient dp / dl des in der Einlaufzone a des Preßspaltes erzeugten Druckes p ist bei einem mittleren oder hohen Trockengehalt der einlaufenden Faserstoffbahn so gewählt, daß er zumindest im wesentlichen die Beziehung

Figure 00070001
erfüllt, in der p1 wieder der vorgebbare Druck am Anfang der Hauptpreßzone b bzw. der vorgebbare Druck am Ende der Einlaufzone a und FG das Flächengewicht der einlaufenden Faserstoffbahn ist.The pressure gradient dp / dl occurring in the running running direction of the pressure p produced in the inlet zone a of the press nip is selected at a medium or high dry content of the incoming fibrous web such that it at least substantially satisfies the relationship
Figure 00070001
fulfilled, in the p 1 again the predetermined pressure at the beginning of Hauptpreßzone b or the predetermined pressure at the end of the inlet zone a and FG is the basis weight of the incoming fibrous web.

Der in Bahnlaufrichtung auftretende Druckgradient dp / dl des in der Auslaufzone c des Preßspaltes erzeugten abfallenden Drukkes p ist bei einem mittleren oder hohen Trockengehalt der einlaufenden Faserstoffbahn so gewählt, daß für seinen Betrag zumindest im wesentlichen die Beziehung

Figure 00070002
erfüllt ist, in der pmax wieder der vorgebbare maximale Druck am Ende der Hauptpreßzone b und FG das Flächengewicht der einlaufenden Faserstoffbahn ist.The occurring in the web running direction pressure gradient dp / dl of the generated in the outlet zone c of the press nip sloping pressure p is selected at a medium or high dry content of the incoming fibrous web so that at least substantially the relationship
Figure 00070002
is met, in the p max again the predetermined maximum pressure at the end of Hauptpreßzone b and FG is the basis weight of the incoming fibrous web.

Zudem ist der vorgebbare Druck p1 am Anfang der Hauptpreßzone b vorzugsweise so gewählt, daß er zumindest im wesentlichen die Beziehung p 1 (bar) ≈ T % 3.5 bis 4 erfüllt, in der T wieder der Trockengehalt der einlaufenden Faserstoffbahn ist. In addition, the predeterminable pressure p 1 at the beginning of the Hauptpreßzone b is preferably chosen so that it at least substantially the relationship p 1 ( bar ) ≈ T % 3.5 to 4 fulfilled, in which T is again the dry content of the incoming fibrous web.

Figur 2 zeigt in grober Annäherung rein beispielhaft den Druckverlauf über wenigstens zwei in Bahnlaufrichtung hintereinander liegende Preßschuhe I und II, wobei insbesondere der erste Preßschuh I zur Behandlung der Faserstoffbahn mit einem mittleren oder höheren Einlauftrockengehalt im Bereich von beispielsweise 25 % bis 30 % ausgelegt ist. Dabei besitzt der Druckgradient dp / dl des in der Hauptpreßzone b (vgl. auch Figur 1) des Preßspaltes erzeugten Druckes p im vorliegenden Fall einen Wert von etwa 0,04· p max / cm. In dem Diagramm ist zudem rein schematisch der Druckverlauf im Einlaufbereich a (vgl. auch Figur 1) angedeutet.Figure 2 shows a rough approximation purely by way of example the pressure curve over at least two in the web running direction successively lying Preßschuhe I and II, wherein in particular the first Preßschuh I is designed to treat the fibrous web with a mean or higher inlet dryness in the range of for example 25% to 30%. In this case, the pressure gradient dp / dl of the pressure p generated in the main press zone b (see also FIG. 1) of the press nip has a value of about 0.04 · p max / cm in the present case. In addition, the pressure curve in the inlet region a (see also FIG. 1) is indicated purely schematically in the diagram.

Im übrigen sind die betreffenden Preßspalte in der zuvor angegebenen Weise ausgelegt.Moreover, the press gaps concerned in the above Way designed.

Figur 3 zeigt in grober Annäherung rein beispielhaft den Druckverlauf über drei in Bahnlaufrichtung hintereinander liegende Preßschuhe I, II und III, wobei insbesondere der erste Preßschuh I zur Behandlung einer Faserstoffbahn mit einem niedrigen Einlauftrockengehalt von beispielsweise weniger als 20% ausgelegt ist. Dabei darf der Druckgradient dp / dl des in der Hauptpreßzone b (vgl. auch Figur 1) des Preßspaltes erzeugten Druckes p den zuvor angegebenen, in Abhängigkeit von dem maximalen Druck pmax am Ende der Hauptpreßzone und dem Flächengewicht FG der einlaufenden Faserstoffbahn gewählten maximalen Druckgradienten dp dl max nicht überschreiten. Im vorliegenden speziellen Fall liegt der Wert des Druckgradienten dp / dl bei 0,08· p max / cm, wobei mit pmax wieder der vorgebbare Druck am Ende der Hauptpreßzone b (vgl. auch Figur 1) angegeben ist. In dem Diagramm ist zudem rein schematisch wieder der Druckverlauf im Einlaufbereich a (vgl. auch Figur 1) angedeutet.Figure 3 shows a rough approximation purely by way of example the pressure curve over three successively in the web running direction Preßschuhe I, II and III, wherein in particular the first Preßschuh I is designed to treat a fibrous web with a low inlet dryness, for example, less than 20%. The pressure gradient dp / dl of the pressure p generated in the main press zone b (see also FIGURE 1) of the press nip may be the maximum pressure gradient previously specified, depending on the maximum pressure p max at the end of the main press zone and the basis weight FG of the incoming fibrous web dp dl Max do not exceed. In this particular case, the value of the pressure gradient dp / dl at 0.08 · p max / cm, eluting with p max back to the predetermined pressure is indicated at the end of the main pressing zone b (see also FIG. 1). In addition, the pressure curve in the inlet region a (see also FIG.

Im übrigen sind die betreffenden Preßspalte in der zuvor angegebenen Weise ausgeführt.Moreover, the press gaps concerned in the above Way executed.

In den beiden Diagrammen der Figuren 2 und 3 ist die auf der Abszisse aufgetragene Spaltlänge 1 in cm und der auf der Ordinate aufgetragene Druck p in bar angegeben.In the two diagrams of Figures 2 and 3, the on the Abscissa applied gap length 1 in cm and that on the ordinate applied pressure p indicated in bar.

Der jeweils gewünschte Preßdruckverlauf ist durch eine entsprechende Schuhgestaltung (z.B. Länge, Form) vorgebbar. The particular desired pressure pressure curve is by a corresponding shoe design (e.g., length, shape) predetermined.

BezugszeichenlisteLIST OF REFERENCE NUMBERS

aa
Einlaufzoneinlet zone
bb
Hauptpreßzonemain press
cc
Auslaufzonerun-off area
ll
Spaltlängegap length
pp
Druckprint
p1 p 1
vorgebbarer Druck am Anfang der Hauptpreßzonepredefinable pressure at the beginning of the main pressing zone
pmax p max
vorgebbarer maximaler Druck am Ende der Hauptpreßzonepredefinable maximum pressure at the end of the Hauptpreßzone
II
Preßschuhpress shoe
IIII
Preßschuhpress shoe
IIIIII
Preßschuhpress shoe

Claims (7)

  1. Press section for a machine for producing a fibrous web, in particular a paper and/or board web, having at least one press nip which is extended in the web running direction, comprises an inlet zone (a), a main pressing zone (b) and an outlet zone (c), and through which the fibrous web is led, the press nip extended in the web running direction being formed between a circulating flexible press belt guided over at least one press shoe and an opposing roll, and it being possible for the pressure profile to be predefined by means of an appropriate shoe configuration, for example by length or shape,
    characterized in that in the web running direction and therefore in the direction of the nip length 1, the pressure gradient dp / dl that occurs of the pressure p produced in the main pressing zone (b) of the press nip is selected on the basis of whether the fibrous web running into the press nip has, on the one hand, a medium or high dryness content or, on the other hand, a low dryness content,
    and in that at a medium or high dryness content of the fibrous web running in, for example 25% to 30%, this pressure gradient dp / dl lies in a range from about 0.01 • p max cm to about 0.08 • p max cm and preferably has a value of about 0.04 • p max cm where pmax is the predefinable maximum pressure at the end of the main pressing zone (b),
    and in that at a low dryness content of the fibrous web running in of about 8% to about 25%, the maximum pressure gradient ( dp / dl)max occurring in the web running direction of the pressure p produced in the inlet zone (a) and/or the main pressing zone (b) of the press nip is selected such that it at least substantially satisfies the relationship
    Figure 00150001
    in which pmax is the predeterminable maximum pressure at the end of the main pressing zone (b) and FG is the grammage of the fibrous web running in.
  2. Press section according to Claim 1, characterized in that at a medium or high dryness content of the fibrous web running in, the pressure gradient dp / dl occurring in the web running direction of the pressure p produced in the inlet zone (a) of the press nip is selected such that it at least substantially satisfies the relationship
    Figure 00160001
    in which p1 is the predefinable pressure at the start of the main pressing zone (b) or the predefinable pressure at the end of the inlet zone (a), and FG is the grammage of the fibrous web running in.
  3. Press section according to Claim 1 or 2, characterized in that at a medium or high dryness content of the fibrous web running in, the pressure gradient dp / dl occurring in the web running direction of the falling pressure p produced in the outlet zone (c) of the press nip is selected such that its magnitude at least substantially satisfies the relationship
    Figure 00160002
    in which pmax is the predefinable maximum pressure at the end of the main pressing zone (b) and FG is the grammage of the fibrous web running in.
  4. Press section according to one of the preceding claims, characterized in that the predefinable pressure p1 at the start of the main pressing zone (b) is selected such that it at least substantially satisfies the relationship p 1 (bar) ≈ T % 3,5 to 4 in which T is the dryness content of the fibrous web running in.
  5. Press section according to one of the preceding claims, characterized in that the opposing roll is perforated, grooved and/or evacuated.
  6. Press section according to one of the preceding claims, characterized in that the region between the press shoe and flexible press belt is lubricated with water.
  7. Press section according to Claim 5, characterized in that the belt loop formed by the circulating flexible press belt is open on both its sides.
EP97119262A 1996-12-20 1997-11-04 Press section Revoked EP0854228B9 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE19653505A DE19653505A1 (en) 1996-12-20 1996-12-20 Press section
DE19653505 1996-12-20

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EP0854228A2 EP0854228A2 (en) 1998-07-22
EP0854228A3 EP0854228A3 (en) 1999-05-26
EP0854228B1 EP0854228B1 (en) 2003-03-19
EP0854228B9 true EP0854228B9 (en) 2005-04-06

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US11401659B2 (en) 2018-08-23 2022-08-02 Eastman Chemical Company Process to produce a paper article comprising cellulose fibers and a staple fiber
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Also Published As

Publication number Publication date
EP0854228B1 (en) 2003-03-19
EP0854228A3 (en) 1999-05-26
EP0854228A2 (en) 1998-07-22
US6120645A (en) 2000-09-19
DE59709565D1 (en) 2003-04-24
DE19653505A1 (en) 1998-06-25

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