WO2006051005A1

WO2006051005A1 - Drier section

Info

Publication number: WO2006051005A1
Application number: PCT/EP2005/053783
Authority: WO
Inventors: Wolfgang Mayer; Peter Kahl; Torben Schlieckau; Roland Mayer; Roland Kurz
Original assignee: Voith Patent Gmbh
Priority date: 2004-11-12
Filing date: 2005-08-03
Publication date: 2006-05-18
Also published as: ATE506485T1; DE102004054886A1; DE502005011290D1; EP1819872B1; CN101057030A; EP1819872A1

Abstract

In a drier section (10) of a machine for producing a fibrous web, in particular, a paper, cardboard or tissue web, this fibrous web, starting from the last nip (12) of a press part (14), is guided over a straight or slightly curved transfer section (16) to an, in particular, larger backup roll (18) with an assigned impingement flow drier (20) by means of which the fibrous web guided around the backup roll (18) can be subjected to the action of an impingement flow consisting of hot air and/or hot steam. The transfer section (16) is formed by a screen (28) guided around two suction rolls (24, 26), and one or more film and/or vacuum cases (30) are assigned to said screen in order to hold the fibrous web on the screen (28). The first suction roll (24) removes the fibrous web from a press belt or press felt (32) exiting the nip (12) or removes it from a transfer belt, whereas the second suction roll (26) holds the fibrous web only when redirected around this roll.

Description

drying section

The invention relates to a dryer section of a machine for producing a fibrous web, in particular paper, board or tissue web, and a machine for producing a fibrous web with such a drying section.

In most of the hitherto customary multi-cylinder drying sections, the paper web is guided for drying over a plurality of steam-heated cylinders or via an arrangement of the plurality of steam-heated cylinders and suction suction rolls. In particular at the beginning of the drying, where the paper web still does not have sufficient strength, however, problems often occur with respect to the web guide, which are in particular due to the fact that the still wet web sticks to the smooth contact surfaces which are sufficient for heat transfer are absolutely necessary. Correspondingly, relatively high trains are required, which now frequently lead to railway declines and overstretching of the web edges. As a result, it is usually necessary to ensure that the drying takes place more slowly, ie. For example, at the beginning, a lower vapor pressure prevails, which means that the required dryer section becomes longer overall. The above-mentioned problems increasingly occur at higher web speeds.

In DE 199 35 138 A, it has already been proposed to use at the beginning of the drying section one or more, in particular larger, back-up rolls, each with an associated impingement-flow dryer.

The invention has for its object to provide an improved dryer section and an improved machine of the type mentioned, in which at the same time both at high machine speed the best possible drying rate at the beginning of drying and a secure web guide is guaranteed. In addition, a problem-free removal of rejects should be possible in particular. The railway transfer from the press should be improved. In particular, a sufficient distance from the first support roller with associated impingement flow dryer should be ensured in order to gain space for any hood movement and the sieve guide.

According to the invention, this object is achieved by a dryer section of a machine for producing a fibrous web, in particular paper, board or tissue web, in which the fibrous web, starting from the last press nip of a press section via a straight or slightly curved transfer line to a particular larger support roller with associated impingement through which the guided around the support roller fibrous web with a hot air and / or hot steam impact flow is acted upon, wherein the transfer path is formed by a guided around two suction rolls sieve, the one for holding the Faserstoffahn on the screen one or more Foil- / / or vacuum boxes are assigned, and wherein the first suction roll, the fibrous web decreases from a expiring from the press nip press belt or - felt or from a transfer belt and the second suction roll holds the fibrous web only at the deflection around this roller. The fibrous web is preferably guided around at least two, in particular larger Stützwal¬ zen each associated impingement dryer, wherein the fibrous web advantageously without Abnahmesaugwalze directly from the first support roller looping sieve on the second support roller um¬ looping sieve or the sieve entwined second support roller is passed. The fibrous web can therefore be transferred, for example, shortly before the second support roller onto the sieve thereof or directly onto the sieve wrap around the second support roller. In the transfer section, the moisture transverse profile of the fibrous web can be detected via a corresponding measuring device on the free side of the fibrous web.

Furthermore, it may also be advantageous to arrange separating devices for separating an edge strip or a transfer strip of the fibrous web in the area of the transfer line.

Thus, with a high drying performance, a good reject distance can be achieved by, for example, only one hood located below. In addition, an optimal transfer of the fibrous web from the press section to the first impingement or impingement dryer with sufficient space for the wire guide is ensured. Compared to a conventional multi-cylinder dryer section, there is a higher speed potential due to the increased dry content in the impingement dryer and the concomitant increase in strength of the still wet fibrous web. Finally, there are also corresponding quality improvements of the fibrous web in terms of volume, porosity and gap strength.

It is expedient for the fibrous web to have no contact with a smooth press roll in the press section and to come into contact with a smooth drying cylinder only in the dryer section after reaching a relatively high moisture content and thus sufficient strength, ie after the impingement flow dryers , This excludes the possibility of stretching the fibrous web when it comes off a smooth lateral surface. In a preferred practical embodiment of the dryer section according to the invention, the region in which the second suction roll of the transfer web is looped except for the transfer felt and the fibrous web is also surrounded by the wire guided around the first, in particular larger, support roll with associated impingement dryer. In this case, the wrap-around region in question is preferably variably adjustable via an adjustable roller arranged within the loop of the support roller screen.

A respective support roller with associated impingement dryer is expediently acted upon by vacuum.

A respective impingement flow dryer may comprise at least one hot air and / or superheated steam hood. Preferably, each larger support roller is associated with only one hood.

Preferably, the or the particular larger back-up rolls, each with an associated impingement flow dryer, are arranged in the web running direction directly after the press section and before a cylinder drying section.

Advantageously, an impingement dryer is at least provided, the blowing speed to about 550 ⁰ C and / or with a Aus¬ to about 130 m / s operable at a temperature of about 300 from about the 70th

The hood of a respective impingement flow dryer can be provided, for example, with a perforated plate and / or slots as nozzles for the hot air or steam. The diameter of the perforated nozzles advantageously lies in a range from about 4 to about 12 mm, and preferably in one Range from about 6 to about 9 mm. The proportion of the nozzles in the total area is advantageously about 2 to about 4%.

The hood of a respective impingement flow dryer preferably has a plurality of return air openings, via which the hot air can be sucked out together with the steam of the drying. These Rückluftöffnun¬ gene are preferably covered with a perforated plate or grid, which is insbe¬ special prevents that shreds enter these openings.

It is also particularly advantageous if a respective hood wraps around the respective support roller in accordance with an angle of at least 80 ° and at most 180 °, wherein this wrap angle is preferably in a range of about 90 to about 130 °.

The hood of a respective impingement flow dryer preferably consists of a plurality of modules, each with a separate hot air or hot steam cycle over the width of the fibrous web, wherein the width of each module is preferably in a range of about 2 to about 4 m.

In a preferred practical embodiment of the drying section according to the invention, two impingement flow dryers are provided which are designed for a dry content increase of about 2 to about 10%, the corresponding dry content increase for papers having a surface weight of more than 60 g / m ² in a range of from about 2 to about 5% and in the range of about 4 to about 10% for papers having a basis weight of less than 60 g / m ² . Advantageously, the hood of a respective impingement flow dryer is movably mounted and can be lifted, for example, for transfer, for cleaning and maintenance or for changing the screen of the respective support roller.

In particular, a respective back-up roll may have a special pattern of dripping with stripes having a larger open area than the remaining areas. In this case, the strips can be provided in particular in the region of the lateral web edges. Alternatively or additionally, a plurality of strips across the width may also be provided in the central region of the web.

A respective support roller is preferably not sucked over the relevant bearing, but by an outer box over the lateral surface.

Preferably, a respective backup roll has a diameter of at least about 3 m.

As can already be seen from the above, a respective Transfer¬ suction box between the two suction rolls after the press section in particular special vacuum generation by suction or via a Foileffekt include.

Advantageously, the vacuum of a respective Foil- and / or Vakuum¬ box control and / or regulated, so that for transferring a sufficient vacuum generated or a high amount of air can be sucked, in operation in coverage by the fibrous web but no to high vacuum occurs with a strong Siebauslenkung, ie it is sucked in operation only a smaller amount of air. A respective foil and / or vacuum box is expediently adjustable in its position in order, for example, to compensate for a sieve deflection after the fibrous web has been completely transferred.

A respective foil and / or vacuum box is advantageously designed so that a short-term contact between the sieve and the box after the transfer and before the time at which the vacuum is reduced to the operating value, to no damage to the wire or box and also can not lead to the collapse of the vacuum. For this purpose, a respective foil and / or vacuum box on the side facing the screen is preferably provided with rounded contact surfaces, Teflon strips and / or surfaces serving as spacers.

A respective foil and / or vacuum box is expediently provided with a lateral seal against the transfer screen. In this case, this lateral seal may comprise, for example, an air knife and / or a side plate preferably made of Teflon.

At the inlet or outlet, a respective foil and / or vacuum box can be sealed, for example, by a Teflon plate and / or a scraper blade against the adjacent suction roll.

Preferably, a respective foil and / or vacuum box is operated in operation with a vacuum in the range of about 50 to 1000 Pa, and preferably in the range of about 100 to about 600 Pa.

The transfer distance between the two suction rolls is expediently shorter than about 4 m and preferably shorter than about 3 m. The transfer section can be horizontal or slightly inclined to the horizontal.

The machine according to the invention comprising a press section and a dryer section for producing a fibrous web, in particular a paper, board or tissue web, is characterized in that it is provided with a dryer section according to the invention.

The press section preferably comprises at least one shoe press.

The press section is preferably designed so that the fibrous web does not come into contact with any smooth roller in this press section.

In a preferred embodiment of the machine according to the invention, the press section consists only of one or more shoe presses.

The press section may comprise a tilted tandem or single shoe press.

It is also particularly advantageous if the press section comprises a press arrangement with a roll press nip and a press nip.

In an expedient practical embodiment of the machine according to the invention, the press section comprises a press arrangement with at least one suction press roll.

At least one transfer belt may be provided in the press section. Preferably, the dry content after the press section in wood-free or specialty papers at least 40%, preferably at least 43%, and at holz¬ containing papers (such as newspaper printing, SC, LWC, ....) at least 46%, preferably at least 49%.

The machine speed may be greater than about 800 m / min, preferably greater than about 1000 m / min for wood-free paper types, and in particular greater than about 1200 m / min, preferably greater than 1500 m / min for wood-containing papers.

As already mentioned, the fibrous web in the press section should preferably not be in contact with a smooth press roll and only in the dry section after reaching a relatively high moisture content and correspondingly sufficient strength, i. After the impingement blower (s) come into contact with a smooth drying cylinder. It is thus ruled out that, when detaching from a smooth lateral surface, undesired stretching of the fibrous web can occur.

The invention will be explained in more detail below with reference to an embodiment with reference to the drawing.

The sole figure of the drawing shows a schematic partial representation of a drying section 10 of a machine for producing a fibrous web, which may be in particular a paper, board or tissue web.

In this dryer section 10, the fibrous web, starting from the last press nip 12 of a press section 14 via a straight transfer section 16, for example, which may also be slightly curved, leads to a first, in particular larger, support roller 18 with associated impingement dryer 20. By a larger back-up roll is meant, for example, a back-up roll whose diameter is greater than the diameter of a conventional drying cylinder. Preferably, such a larger support roller has a diameter of at least 3 m.

The support roller 18 is looped by a sieve 22. The fibrous web guided around the sieve-like support roll 18 is subjected to a hot-air and / or superheated steam flow by the impingement-flow dryer 20.

The first back-up roll 18 is an upper back-up roll, i. the fibrous web is supplied to this roller from bottom to top and removed from top to bottom of this roller again. The impingement flow dryer 20 is e.g. arranged in the upper region of this first support roller 18.

The transfer section 16 is formed by a screen 28 guided around two suction rollers 24, 26, to which one or more foil and / or vacuum boxes 30 are assigned to hold the fibrous web on the wire 28.

The first suction roll 24 removes the fibrous web from a press belt or felt running out of the press nip 12, while the second suction roll 26 holds the fibrous web only during the deflection around this roll. In the area of the first suction roll 24, the fibrous web can also be removed, for example, from a transfer belt.

In the present case, a second, in particular larger support roller 34 is provided with associated impingement dryer 36. The Faser¬ is fabric without pick-up suction directly from the first support roller 18 to ^¬ twining wire 22 to which the second support roller 34 wrapping around screen 38 or transferred directly to the sieve wrap around second support roller 34. In the present case, the transfer takes place immediately before the second support roller 34.

As can be seen from the figure, the area in which the second suction roll 26 of the transfer line 16 is surrounded except by the transfer felt 28 and the fibrous web and by the guided around the first particular larger support roller 18 sieve 22, variably adjustable. This results in a variable "sandwich" wrap. In this case, the surrounding looping region can be variably adjustable via an adjustable roller 40 arranged within the loop of the supporting roller screen 22.

The two support rollers 18, 34 are as well as the two boxes 30 each acted upon by vacuum.

The second back-up roll 34 is a lower roll, i. the fibrous web is supplied to this roll from top to bottom and removed from bottom to top of this roll. The impingement-flow dryer 36 is here arranged in the region of the lower right quadrant of the support roller 34.

The two support rollers 18, 34, each with associated impingement flow dryers 20, 36, can thus be arranged directly downstream of the press section 14 and upstream of a cylinder drying section 42, viewed in the web running direction.

The two impingement-type dryers 20, 36 may each comprise a hot-air and / or superheated steam hood 44, 46. In the present case, the transfer line 16 is horizontal. In principle, however, it may also be slightly inclined to the horizontal.

LIST OF REFERENCE NUMBERS

10 drying section

12 press nip

14 press section

16 transfer distance

18 first backup roll

20 impingement dryer

22 sieve

24 suction roll

26 suction roll

28 sieve

30 Foil or vacuum box

32 press belt or felt

34 second backup roller

36 impingement dryer

38 sieve

40 adjustable roller

42 cylinder drying section

44 hood

46 hood

Claims

claims

1. drying section (lθ) of a machine for producing a fibrous web, in particular a paper, board or tissue web, in which the fibrous web starting from the last press nip (12) of a press section (14) via a straight or slightly curved transfer path ( 16) is guided to a particularly larger support roller (18) with associated impingement-flow dryer (20) through which the fibrous web guided around the support (18) can be acted upon by a hot-air and / or superheated steam impingement, wherein the transfer section (FIG. 16) is formed by a sieve (28) guided around two suction rolls (24, 26), the first suction roll (24) decreases the fibrous web from a press belt or felt (32) leaving the press nip (12) or from a transfer belt and the second suction roll (26) holds the fibrous web only at the deflection around this roller.

2. Drying section according to claim 1, characterized in that one or more foil and / or vacuum boxes (30) are assigned to the screen (28) of the transfer section (16) for holding the fibrous web on the screen (28).

3. Drying section according to claim 1 or 2, characterized in that the fibrous web is guided around at least two, in particular larger support rollers (18, 34) each with associated impingement dryer (20, 36) and the fibrous web without Abnahmesaugwalze di directly from the first support roller (18) looping sieve (22) onto which the second support roller (34) looping sieve (38) or the sieve ^¬ looped second support roller (34) is passed.

4. Drying section according to one of the preceding claims, characterized in that the region in which the second suction roll (26) of the transfer line (16) except from the transfer felt (28) and the fibrous web also from the first in particular larger support roller (18 ) with associated impingement-flow dryer (20) guided sieve (22) is looped, is variably adjustable.

5. Drying section according to claim 4, characterized in that it e e n e c i n e t that the wrapping area in question about a within the

Loop of the Stützwalzensiebes (22) arranged adjustable roller (40) is variably adjustable.

6. Drying section according to one of the preceding claims, characterized in that a respective larger support roller (18, 34) with associated ^¬ impingement impingement dryer (20, 36) can be acted upon with vacuum.

7. Drying section according to one of the preceding claims, characterized in that a respective impingement flow dryer (20, 36) comprises a hot air and / or hot steam hood (44, 46).

8. Drying section according to one of the preceding claims, characterized in that each larger support roller (18, 34) is associated with only one hot air and / or hot ^¬ steam hood.

9. Drying section according to one of the preceding claims, characterized in that the or in particular larger back-up rolls (18, 34) each with associated impingement dryer (20, 36) in the web running direction considered directly after the press section (14) and in front of a cylinder -

Drying section (42) are arranged.

10. Drying section according to one of the preceding claims, characterized in that at least one impingement flow dryer (20, 36) is provided, which at a temperature of about 300 to about 550 ⁰ C and / or with a blow-out speed of about 70 to about 130 m / s is operable.

11. Drying section according to one of the preceding claims, characterized in that the hood (44, 46) of a respective impingement flow dryer (20, 36) is provided with a perforated plate and / or slots as nozzles for the hot air or steam.

12. Drying section according to claim 11, characterized in that the diameter of the hole nozzles in a range of about 4 to about 12 mm, and preferably in a range of about 6 to about 9 mm.

13. Drying section as claimed in claim 11 or 12, characterized in that the proportion of nozzles in the total area is about 2 to about 4%.

14. Drying section according to one of the preceding claims, characterized in that the hood (44, 46) of a respective impingement flow dryer has a plurality of return air openings into which the hot air together with the

Steam of the drying is sucked, said Rückluftöffnun¬ conditions are preferably covered with a perforated plate or grid.

15. Drying section according to one of the preceding claims, characterized in that a respective hood (44, 46), the support roller in question entspre ^¬ accordingly an angle of at least 80 ° and wraps around more than 180 °, this wrap angle preferably in a range of about 90 to about 130 °.

16. Drying section according to one of the preceding claims, characterized in that the hood (44, 46) of a respective impingement flow dryer (20, 36) consists of several modules, each with separate hot air or hot steam cycle over the width of the fibrous web, wherein the

Width of a respective module is preferably in a range of about 2 to about 4 m.

17. Drying section according to one of the preceding claims, characterized in that two impingement flow dryers (20, 36) are provided, which are designed for a dry content increase of about 2 to about 10%, wherein the corresponding dry content increase in papers with a

Basis weight of more than 60 g / m ² in a range of about 2 to about 5% and in papers with a basis weight less than 60 g / m ² in a range of about 4 to about 10%.

18. Drying section according to one of the preceding claims, characterized in that the hood (44, 46) of a respective impingement flow dryer (20, 36) movably mounted and from the respective support roller (18, 34) from ^¬ liftable.

19. Drying section according to one of the preceding claims, characterized in that a respective support roller (18, 34) has a special drill pattern with strips having a larger open area than the remaining areas.

20. Drying section according to claim 19, characterized in that the strips are provided in the region of the lateral web edges.

21. Drying section according to claim 19 or 20, characterized in that a plurality of strips are seen vorge¬ across the width in the central region of the web.

22. Drying section according to one of the preceding claims, characterized in that a respective support roller (18, 34) is sucked not over the relevant bearing, but by an outer box over the lateral surface suction.

23. Drying section according to one of the preceding claims, characterized in that a respective support roller (18, 34) has a diameter of at least ^¬ least about 3 m.

24. Drying section according to one of the preceding claims, characterized in that there is a vacuum, that the vacuum of a respective foil and / or vacuum box (30)

Can be controlled and / or regulated.

25. Drying section according to one of the preceding claims, characterized in that a respective foil and / or vacuum box (30) is adjustable in its position.

26. Drying section according to one of the preceding claims, characterized in that a respective foil and / or vacuum box (30) is rounded off

Contact surfaces, Teflon strips and / or serving as spacers surfaces is provided.

27. Drying section according to one of the preceding claims, characterized in that a respective foil and / or vacuum box (30) is provided with a seitli¬ Chen seal against the transfer screen (28).

28. Drying section according to claim 27, characterized in that the lateral seal comprises an air knife and / or a side plate preferably consisting of Teflon.

29. Drying section according to one of the preceding claims, characterized in that a respective foil and / or vacuum box (30) at the inlet or outlet against the adjacent suction roll (24, 26) is sealed.

30. Drying section according to claim 29, characterized in that the seal in question comprises a teflon plate and / or a Scha ^¬ berblinge.

31. Drying section according to one of the preceding claims, characterized in that a respective foil and / or vacuum box (30) in operation with a vacuum in the range of about 50 to about 1000 Pa and preferably in the range of about 100 to about 600 Pa is operable.

32. Drying section according to one of the preceding claims, characterized the transfer distance (16) between the two suction rolls (24, 26) is shorter than about 4 m and preferably shorter than about 3 m.

33. Drying section according to one of the preceding claims, characterized in that it e e n e c e s e s that the transfer section (16) extends horizontally or slightly horizontally to the horizontal.

34. Machine for producing a fibrous web, in particular paper, board or tissue web, with a press section (14) and a drying section (lθ) according to one of the preceding claims.

35. The machine according to claim 34, characterized in that the press section (14) comprises at least one shoe press.

36. Machine according to claim 35, characterized in that the fibrous web in the press section (14) does not come into contact with any smooth roller.

37. The machine according to claim 35 or 36, characterized in that it e e n e c e s e s that the press section (14) consists only of one or more shoe presses.

38. Machine according to one of the preceding claims, characterized that the press section (14) has a tilted arranged tandem or Sin gle ^¬ includes shoe press.

39. Machine according to one of the preceding claims, characterized in that the press section (14) comprises a press arrangement with a roll nip and a nip press nip.

40. Machine according to one of the preceding claims, characterized in that the press section (14) comprises a press arrangement with at least one suction press roll.

41. Machine according to one of the preceding claims, characterized in that at least one transfer belt is provided in the press section (14).

42. Machine according to one of the preceding claims, characterized in that the dry content after the press section (14) is at least 40%, preferably at least 43%, for wood-free or specialty papers, and at least 46%, preferably at least 49%, for wood-containing papers.

43. Method for operating a machine according to one of the vorhergehen¬ claims, characterized in that the machine speed for wood-free paper types greater than about 800 m / min, preferably greater than about 1000 m / min, and wood-containing papers greater than about 1200 m / min, preferably greater than 1500 m / min is selected.