EP1738023A1

EP1738023A1 - Drying system

Info

Publication number: EP1738023A1
Application number: EP05731760A
Authority: EP
Inventors: Thomas Gruber-Nadlinger; Dominik Mai; Manfred Gloser; Antony Morton; Erich Brunnauer; Manfred Feichtinger
Original assignee: Voith Patent GmbH
Current assignee: Voith Patent GmbH
Priority date: 2004-04-13
Filing date: 2005-03-21
Publication date: 2007-01-03
Also published as: DE102004017809A1; WO2005100684A1

Abstract

Disclosed is a system (1) in a machine for producing a paper web, cardboard web, tissue web, or another fiber web (2) with a predrying zone and/or at least one drying zone. According to the invention, at least one heated drying cylinder (3, 10) over which the fiber web (2) is guided along with at least one wire (5) and an impermeable covering (14), is disposed upstream of, within, or downstream of the predrying zone, or upstream of, within, or downstream of the drying zone. Said at least one drying cylinder (3, 10) is covered, across a section of the outer circumference thereof, by at least one pressing hood (4, 11) which applies a certain contact pressure to the drying cylinder (3, 10).

Description

dry arrangement

The invention relates to an arrangement in a machine for producing a paper, cardboard, tissue or other fibrous web with a pre-dryer section and / or at least one dryer section.

A drying arrangement for the continuous drying of a porous web is known from EP 0 949 377 A2. The drying arrangement comprises a drying cylinder which is wrapped by the web over at least two thirds of its outer surface. On the top of the cylinder, in addition to nozzles for applying a coolant, a plurality of rotating rollers are arranged, each of which has a hydraulic unit in its interior for applying a contact pressure against the drying cylinder.

DE 35 32 853 C2 describes a method and a device for drying a web of paper, cardboard or the like. Before it reaches a drying area, the web is subjected to a venting treatment while it lies against an intermediate belt which absorbs water and water vapor. The intermediate belt is guided around the cylinder in a drying area. The fibrous web is covered by a metal band as it rotates around the cylinder. The metal strip is returned to the drying area in a return loop after leaving the cylinder. The intermediate belt is freed of condensed water after leaving the cylinder. The fibrous web is passed between the intermediate belt and the metal belt around the cylinder while it is being cooled. The metal strip is heated in the return loop, and the heated metal strip heats the outside of the fibrous web surrounding the cylinder in direct contact.

In known processes for producing a fibrous web, the desired smoothness of the surface is achieved by smoothing rolls or by using belt systems within the press section and by a Yankee cylinder or by calenders reached the dryer section.

It is the object of the invention to provide an aggregate with which good drying of the fibrous web can be achieved. At the same time, the paper properties are also to be improved.

According to the invention, this object is achieved in that at least one heated drying cylinder is arranged in front of the pre-dryer section, within the pre-dryer section, after the pre-dryer section, before the dryer section, within the dryer section or after the dryer section, via which the fibrous web together with at least one screen and with one impermeable covering is performed, the at least one drying cylinder being covered over part of its outer circumference by at least one pressure hood exerting a contact pressure against the drying cylinder.

Due to the invention, the desired surface smoothness of the fibrous web is achieved during drying itself due to the use of at least one drying cylinder covered by a pressure hood or by a plurality of drying cylinders with pressure hoods preferably arranged one behind the other.

The use of the invention also saves the use of calenders and other additional smoothing devices to achieve a smooth surface of the fibrous web. As far as it is important to achieve the largest possible volume in the production of the fibrous web, the invention achieves a very high volume in relation to the smoothness achieved. Excellent smoothness results are achieved due to the relatively high pressure prevailing in the pressure hood and a relatively long residence time of the fibrous web between the drying cylinder and the pressure hood. In connection with a press section in which only a single felt belt is used, the construction of the machine according to the invention can preferably be used Manufacture wrapping paper, testliner, corrugated cardboard, cardboard, especially folding boxboard, and graphic papers. Cardboard and graphic papers are produced using coating equipment; in these two cases, a calender is also used at the output end of the machine, for example a calender as is known from EP 0 732444 B1

While, according to the prior art, packaging paper types in particular are produced by the addition of strength-increasing additives, such as starch, for example, the additives either being added in the wet phase or via a coating unit, for example using a film press or a size press, according to the invention Strength of packaging materials increased by the type of drying. The higher strength of the packaging paper is an inherent property of the drying process using at least one drying cylinder with a pressure hood. Here, the addition of additives is no longer necessary or only to a considerably reduced extent. The combined use of the drying process and the use of a high contact pressure, in particular even when the dry content is still low, results in a strong compression of the fibrous material, as a result of which a high degree of flexural strength and a high bond strength between the fibers are achieved.

According to the invention, no additives are preferably added to the wet fibrous material. Likewise, no size press or other devices for applying an additive, in particular glue or starch, to the surface of the fibrous web to increase the strength, in particular after the dryer section, are preferably also required. Due to the increased strength, cardboard and packaging paper (B&P materials) can be produced with the same strength with a reduced number of layers compared to conventional B&P materials. According to the invention, it is thus possible to improve the strength of cardboard, paperboard and graphic papers, in which those are usually arranged in the wet phase and or by one arranged in or after the dryer section Application device starch is added, which is saved entirely or at least partially according to the invention. The amount of additives applied superficially, which are used for coating cardboard papers or for the production of coated graphic papers, can also be reduced, or the additives can be saved entirely.

According to the invention, it is possible to use both a drying cylinder heated as a whole, for example with steam, and a drying cylinder which is only heated locally, in particular with respect to the at least one pressure hood. This has the advantage of a particularly targeted energy supply.

Advantageous developments of the invention result from the subclaims, the description and the drawings.

In one embodiment of the invention it is provided that the fibrous web is transferred between the drying cylinders in a free draw. Alternatively, the fibrous web is transferred between the drying cylinders by changing from the at least one first screen to the at least one second screen. To support this transfer process, the fibrous web is removed from the at least one first screen by means of a screen suction roll and drawn onto the second screen.

According to the invention, at least two drying cylinders each equipped with at least one pressure hood are preferably arranged one behind the other, for example behind the press section or within the predrying section or at the beginning or within a two-row dryer section.

In a further embodiment of the invention, the drying cylinders are arranged alternately with a pressure hood attached to the top of the drying cylinder and a pressure hood attached to the bottom of the drying cylinder. It can also be advantageously provided that a nozzle humidifier for moistening the fibrous web or a device for applying starch or an odorous substance or another liquid is provided in front of the first drying cylinder or between the first and second drying cylinders or that a means for densifying the fibrous web is provided , in particular water, is arranged in the area in front of one of the drying cylinders or on one of the drying cylinders themselves and / or in the area of the screens.

The invention also relates to a method for drying a paper, cardboard, tissue or other fibrous web in a machine comprising a predrying section and / or at least one drying section for producing the fibrous web.

According to the invention, the method is characterized in that the fibrous web is arranged together with at least one sieve and with an impervious covering over at least one, before the pre-dryer section, within the pre-dryer section, after the pre-dryer section, before the dryer section, within the dryer section or after the dryer section , heated and is guided over part of its outer circumference by at least one drying cylinder which exerts a contact pressure against the drying cylinder.

In the process, the pressure hood advantageously exerts a pressure of between 0.5 and 5 bar on the drying cylinder.

The process preferably uses a steam pressure inside the drying cylinder, which is preferably between 1.5 and 12 bar. If a fibrous web with a very smooth surface is to be produced, the vapor pressure is between 1.5 bar and 5 bar. The temperature in the pressure hood is, for example, between 60 and 90 ° C. If a fibrous web of high strength is to be produced, vapor pressures between 6 and 12 bar are preferably used within the drying cylinder. The temperature of the steam inside the drying cylinder is, for example, between 150 and 190 ° C.

To produce a fibrous web with a smooth surface, the speed is set such that the fibrous web runs between the at least one drying cylinder and the printing hood in a time period between 0.1 and 6 s.

In order to produce a surface that is as smooth as possible, the fibrous web is pre-dried before it passes between the at least one drying cylinder and the printing hood to such an extent that it has a dry content between 35 and 95%, preferably between 40 and 70%. After it has passed between the drying cylinder and the pressure hood, it has a dry content of between 50 and 98%, especially if the fibrous web is to be of high strength; this applies in particular if a fibrous web with high strength is to be produced. In this case, 10 to 50% of the additives used according to the prior art can be saved. As a rule, the use of a size press or a coating machine can also be dispensed with.

In this case, the drying cylinder with the printing hood or a plurality of drying cylinders each having a printing hood is arranged either within the track section or immediately after the press section. Conventional drying cylinders arranged in one or two rows can then be connected behind this drying cylinder.

In the drying arrangement according to the invention, drying cylinders provided with at least one pressure hood can be used, for example one

Have diameters between 1 and 7 m. A nozzle humidifier can be use especially when producing cardboard.

With the aid of the drying cylinders equipped according to the invention with a pressure hood, a higher drying rate can be achieved compared to a conventional drying cylinder. Conventional drying cylinders can thus be replaced by drying cylinders according to the invention in already existing paper machines if the production speed is to be increased without the length of the paper machine having to be increased. New paper machines can be made shorter.

The invention is explained in more detail in exemplary embodiments with reference to the drawings. Show it:

1 shows a cross section through a drying arrangement with two drying cylinders 3, 10 between which the fibrous web 2 is transported in free train,

2 shows a cross section through a drying arrangement with two drying cylinders 23, 30 between which the fibrous web 18 is supported, FIG. 3 shows a series of drying cylinders arranged one behind the other, each of which is equipped with a pressure hood, and FIG. 4 shows two drying cylinders 53 arranged next to one another, 62 according to FIG. 3 in detail.

A drying arrangement 1 (FIG. 1) in a machine for producing a fibrous web 2 comprises a first heatable drying cylinder 3, which is surrounded on its upper side by a pressure hood 4 or alternatively by a plurality of rollers which press against its outer surface, in or in which a cooling medium flows in each case to absorb the heat given off by the drying cylinder 3, which heats the fibrous web 2, while at the same time removing moisture from it. The moisture given off by the fibrous web 2 is caused by a fine-meshed sieve 5, which is moved around the drying cylinder 3 together with the fibrous web 2, and by a sieve lying above it coarse-mesh sieve 6 added. Above the screen 6, a fabric 7 impermeable to moisture and other media is guided between the drying cylinder 3 and the pressure hood 4 or the rollers.

The fibrous web 2, together with the screens 5, 6 and the covering 7, is first of all via a deflection or guide roller 8 attached below the cylinder 3 around the jacket of the cylinder 3 between the latter and the rollers 4 and then by a second one also below the cylinder 3 arranged guide roller 9 discharged from this.

The fibrous web 2 is now passed on to a second drying cylinder 10. Sieves 12, 13 and a covering 14 together with the fibrous web 2 are also guided over guide rollers 15, 16 between it and a pressure hood 11 applied to it. Instead of the pressure hood 11, rollers or press shoes can also be present.

Another drying arrangement 17 (FIG. 2) according to the invention provides that a fibrous web 18 is first passed together with screens 19, 20 and a covering 21 via a guide roller 22 and between a drying cylinder 23 and a pressure hood 24 or alternatively rollers or press shoes becomes. At least the screen 19 continues to run together with the fibrous web 18 via an output-side guide roller 25, while the clothing 21 and, if a second screen 20 is present, are guided away via the guide roller 25.

Opposite an area between the guide roller 25 and a further guide roller 26, the screen 19 or the screens 19 and 20 and the fibrous web 18 is opposite a screen suction roller 27, over which a screen 28 is guided. The screen suction roller 27 is equipped with a suction zone 29 through which the fibrous web 18 is sucked off the screen 19 or 20 and sucked onto the screen 28. Together with the screen 28, the fibrous web 18 is then transferred to a further drying cylinder 30. In addition to the fibrous web 18 and the fine A further coarse screen 32 and an impervious covering 33 are passed between a drying cylinder 30 and a pressure hood 34 or an element pressing the fibrous web 18 against the drying cylinder 30 via a guide roller 31 via a guide roller 31. The fibrous web 18 is guided away from the drying cylinder 30 together with the screens 28 and 32 and the fabric 33 via a guide roller 35.

Instead of merely passing the wire 28 over the wire suction roll 27, the wire 32 can alternatively be guided together with the wire 28 over the wire suction roller 27, so that the fibrous web 18 together with the fine wire 28 on which it rests and from a coarser fabric existing screen 32 is transferred to the drying cylinder 30.

In all the cases described above, instead of two screens, only one can be present. To produce markings or a desired structure, the screen 12 or 28 lying next to the fibrous web 2, 18 can also be provided with a superficial structure.

In another embodiment of the invention, a plurality of drying cylinders 36, 37, 38, 39, 40, 41, 42, 43 (FIG. 3) are designed in a row one behind the other. The drying cylinders 36 to 43 each have a pressure hood 44, 45, 46, 47, 48, 49, 50, 51. The printing hoods 44 to 50 are alternately arranged on the top and on the bottom of the drying cylinders 36 to 42, while the printing hoods 50, 51 are both arranged on the top of the drying cylinders 50, 51. A fibrous web 52 to be dried is passed between the drying cylinders 36 to 51.

In detail, the drying cylinders 36 to 42 shown in FIG. 3 are constructed one behind the other as will be explained in more detail with reference to FIG. 4. A drying cylinder 53 has a pressure hood 54 on its upper side. Between the drying cylinder

53 and the pressure hood 54, at least one screen 55 is passed through. to Return of the screen 55 serves a plurality of deflecting rollers 56. In order that the hot fluid flowing in the pressure hood 54 cannot escape, an impermeable band 57 is additionally passed between the screen 55 and the pressure hood 54. The belt 57 is in turn fed back over deflection rollers 58.

A fibrous web 59 is passed together with the screen 55 and the belt 57 over a guide roller 60 between the drying cylinder 53 and the printing hood 54 and then out again together with the screen 55 and the belt 57 via a further guide roller 61.

During the transfer to an adjacent drying cylinder 62, the fibrous web 59 initially traveling with the screen 55 is sucked through a screen suction roller 63 onto a screen 64 which runs around the drying cylinder 62.

Then, like in the drying cylinder 53, the fibrous web 59 runs between the drying cylinder 62 and a pressure hood 65 on the underside of the drying cylinder 62. This ensures that the fibrous web 59 does not have to be transported between the drying cylinders 53 and 62 in a free pull; this eliminates web breaks.

Claims

claims

1. Arrangement (1, 17) in a machine for producing a paper, cardboard, tissue or other fibrous web (2, 18, 52, 59) with a pre-dryer section and / or at least one dryer section, characterized in that before the pre-dryer section, within the pre-dryer section, after the pre-dryer section, before the dryer section, within the dryer section or after the dryer section, at least one heated drying cylinder (3, 10, 23, 30, 53, 62) is arranged over which the fibrous web (2, 18 , 52, 59) together with at least one sieve (5, 19, 55, 64) and with an impermeable covering (14, 33, 57), the at least one drying cylinder (3, 10, 23, 30, 53, 62) is covered over part of its outer circumference by at least one pressure hood (4, 11, 24, 34, 54) exerting a contact pressure against the drying cylinder (3, 10, 23, 30, 53, 62).

2. Arrangement (1, 17) according to claim 1, characterized in that the fibrous web (2) from a first, with a pressure hood (4, 24, 54) equipped drying cylinder (3, 23, 53) to an adjacent, second drying cylinder (10, 30, 62) either in free pull or by means of a screen suction roller (27, 63) from a screen (55) guided over the first drying cylinder (3, 23, 53) to a second screen, over the second drying cylinder (3, 23 , 53) guided sieve (64) can be transferred.

3. Arrangement according to claim 1 or 2, characterized in that at least two drying cylinders (36, 37, 38, 39, 40, each equipped with at least one pressure hood (44, 45, 46, 47, 48, 49, 50, 51), 41, 42, 43) are arranged one behind the other.

4. Drying arrangement according to claim 3, characterized in that the drying cylinders (36, 37, 38, 39, 40, 41, 42) alternately with one on the top of the drying cylinder (36, 37, 38, 39, 40, 41 , 42) and a pressure hood (44, 45, 46, 47, 48, 49, 50, 51) attached to the underside of the drying cylinder (36, 37, 38, 39, 40, 41, 42).

5. Drying arrangement according to one of claims 1 to 4, characterized in that in front of the first drying cylinder (3, 23) or between the first (3, 23) and the second drying cylinder (10, 30) a nozzle humidifier for moistening the fibrous web (2 , 18, 52, 59) or a device for applying starch or an odorous substance or another liquid is provided or that a means for compacting the fibrous web (2, 18, 52, 59), in particular water, in the area in front of one of the drying cylinders (3, 10; 23, 30) or on one of the drying cylinders (3, 10; 23, 30) itself and / or in the area of the screens (5, 6, 12, 13; 19, 20, 28, 32, 55, 64) is arranged.

6. A method for drying a paper, cardboard, tissue or other fibrous web (2, 18, 52, 59) in a machine comprising a pre-dryer section and / or at least one drying section for producing the fibrous web (2, 18, 52, 59), characterized in that the fibrous web (2, 18, 52, 59) together with at least one sieve (5, 19, 55, 64) and with an impermeable covering (14, 33, 57) over at least one in front of the Predrying section, inside the predrying section, after the predrying section, before the drying section, within the drying section or after the drying section, heated and over part of its outer circumference by at least one contact pressure against the drying cylinder (3, 10; 23, 30, 53, 62) exerting pressure hood (4, 11, 24, 34, 54) covered drying cylinder (10, 30, 23, 30, 53, 62) becomes.

7. The method according to claim 6, characterized in that the pressure hood (4, 11, 24, 34, 54) with a pressure between 0.5 and 5 bar against the drying cylinder (10, 30, 23, 30, 53, 62 ) presses.

8. The method according to claim 6 or 7, characterized in that the vapor pressure of the steam in the drying cylinder (10, 30, 23, 30, 53, 62) is between 1, 5 and 12 bar.

9. The method according to any one of claims 6 to 8, characterized in that the fibrous web (2, 18, 52, 59) between the at least one drying cylinder (10, 30, 23, 30, 53, 62) and the pressure hood (4, 11 , 24, 34, 54) runs in a time period between 0.1 and 6 s.

10. The method according to any one of claims 6 to 9, characterized in that the fibrous web (2, 18, 52, 59) before passing between the at least one drying cylinder (10, 30, 23, 30, 53, 62) and the pressure hood ( 4, 11, 24, 34, 54) has a dry matter content between 35 and 95%, preferably between 40 and 70%, and then a dry matter content between 50 and 98%.