FI122111B - Method and apparatus for a drying portion of a paper machine - Google Patents

Description

Method and apparatus in the drying section of a papermaking machine

The invention relates to a method according to the preamble of claim 1.

The invention also relates to a paper machine drying section according to the preamble of claim 11.

10 Increasing the speed of paper machines brings with it new problems, most often related to machine runnability. Today, paper machines use speeds up to about 1800 m / min. Raising paper machine speeds also exacerbates paper machine runnability issues because the web is too aqueous and weak when it comes to the first drying cylinder of the en-15 dryer dryer that applies cylinder drying, causing web breaks and other malfunctions that cause downtime. With a modern paper machine, the break time cost is now about 10,000 € / h.

Recently, speeds as high as about 40 m / s = 2400 m / min have been planned for paper machine speeds. Implementing such high speeds, especially on wide machines, presents more difficult problems to solve, one of the most important of which is the high-speed runnability of the machine.

cm In the prior art, two-wire and / or single-wire runs are used in the drying groups of the dry and dry portions of the papermaking machine.

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> - Two wires for export The drying cylinder groups have two wires which press the sheet one above and the other below the heated cylinder surfaces. Between the rows of drying cylinders, generally horizontal rows, the web has free and unpowered strokes which are prone to fluttering, which may cause a web roof 30, especially since the web is still relatively damp and consequently weak. Therefore, recently, the use of said 2 single-wire threads, with only one dryer wire in each drying cylinder group, is supported, the web remains on the outer side 5 of the curve. Thus, in a single-wire delivery, the drying cylinders are outside the wire loop and the turning cylinders or rollers are inside it.

As paper machine speeds increase, runner problems have also begun to occur in the single-wire delivery region, particularly in the first cylinder drying groups of the dryer section, particularly the first dryer cylinder of the first cylinder dryer group. As has been known in the past, these problems have been reduced by using various runnability components such as the applicant's trade names UnoRun, blow boxes marketed by HiRun, and replacing the lower roll with a suction roll, such as 15 by VacRoll. However, it is still unclear at what speeds these known solutions are sufficient to support the wet path at the beginning of the drying section as the speeds continue to increase.

Thus, as the speeds of the papermaking machines increase, the runnability of the papermaking machine is affected by 20 drying portions, which, in addition to the previously known multicylinder dryers, would also be unacceptably long at high speeds. If the current multi-cylinder dryer is to be operated at a web speed of 40 m / s, it would have about 70 drying cylinders and its machine-length would be ~ 180 m.

In this case, the dryer would have about 15 different wire groups and an equal number of cp 25 leads. It is expected that the speed range of 30-40 m / s will be normal in the past

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> - the runnability of the known multi-cylinder dryers would no longer be close to satisfactory, but a large number of web breaks would occur, especially at the beginning of the drying section, which σ> reduces the efficiency of the paper machine.

o o o o 30 The wet strength and Kimmo properties of the paper web are dependent on the dry solids content of the web, and it has been problematic to achieve sufficient tension in the web immediately after the press section due to the web being not dry enough. As a result, the single wire export groups at the beginning of the drying section, the so-called slalom export groups, have often encountered problems with runnability, especially on high speed paper machines. One solution is to use short groups of only a few cylinders 5 at the beginning of the drying section so that the line tension can be maintained with a positive speed difference between the groups. However, the solution will increase investment and operating costs due to increased wire circulation.

In addition, when paper is tensioned through successive support web speeds 10, the paper web may have been unevenly tapered and large draw differences on the web may have caused problems to achieve a sufficiently uniform quality, particularly with respect to the transverse profile of the paper.

It is, therefore, an object of the present invention to provide new solutions to the problems discussed above, so that the aforementioned and subsequent disadvantages are substantially avoided in the prior art.

It is known in the art to use various overhead and wire / blast drying units for the evaporation drying of the paper web.

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With reference to the prior art relating to the invention, reference is made to Applicant's European Patent Publication No. 102623 which discloses an i-process for blow-drying in a papermaking machine or the like, wherein the paper web or the like is dewatered, wherein the paper web or? -

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after crossing, the paper web or the like is dried in at least one drying group based on a blow drying or the like, wherein the paper σ> web is guided substantially linearly or using a large radius of curvature,

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and wherein in the drying step, after the blow-drying, the paper web or counter is dried in at least one drying group employing standard single-wire threading, wherein the paper web is passed from the press step to the drying step in a closed export. In the method, the paper web is guided from the compression step to the single-wire threading area of the drying step so that the paper web is continuously supported against at least one support surface.

Reference is also made to the Applicant's FI patent application 20002429, which describes so-called vertical blow-drying groups for use in blow-drying, also referred to herein as the "vertical set". This publication discloses an inflatable drying unit for a drying section of a fiber web machine, preferably a paper or board machine, having at least one drying group and an inflatable drying unit extending above and / or below a row of drying cylinders and wherein the inflatable i. The blowing surface or tangent to the blowing surface or the line through or extending from the upstream and downstream ends of the blowing surface or the center or symmetry line of the blast drying unit forms an angle between 120 ° and 60 °, preferably 120 ° to 60 °, or the blow-drying unit is in a substantially upright position. The at least one over-blow drying device acts on at least one over-blow surface defined by the outer surface of the drying fabric passing through the over-blow drying unit, wherein

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cp 25 blasting directly affects the web. The blow-drying unit is arranged co as part of the drying group or between two drying groups or between the drying groups.

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£ pounds. In this specification, the term Vertical Blow Drying Group, abbrev.

σ> vertical group, refers to the spray drying groups containing blowing units o ° of the type described above.

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It is an object of the present invention to provide a method and apparatus in a drying section of a papermaking machine which provides good runnability and essentially closed export of the web.

In order to achieve the foregoing and further objects, the method according to the invention is essentially characterized by what is stated in the characterizing part of claim 1.

The drying section of the paper machine according to the invention is essentially characterized by what is set forth in the characterizing section of claim 11.

According to the invention, in the drying section of a papermaking machine, the dry solids content of the web is raised to a sufficient value, typically between 50 and 65% solids, up to 70% solids, before drying cylinders are used. Thus, according to the invention, the paper web is then dried after the press section by blow-drying in a vertical blow-drying group prior to cylinder drying. According to the invention, in the method, the paper web is led from the press section to a vertical blow blast drying group from at least one transfer wire from the last fabric of the press section, i.e. transbelt or felt.

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In connection with the invention, at least one transfer wire used for guiding the web from the press section to the first vertical blow dryer drying group of the dryer section is provided with a movable roll or the like, for example cm which is moved to the threading position during tapping.

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25 after threading to a position where it does not affect web travel. The proportion of web to be controlled from the movable co> roll to the pulper can be selected, for example, by moistening the £ roll at that desired width, whereupon the forward band σ> tan would be dry and similarly moistening the roll over the entire width. Preferably, the transfer wire is provided with blowing boxes 30, which provide a vacuum effect through which the web remains in transport of the transfer wire. According to a further advantageous feature of the invention 6, after the first transfer wire, there follows a second transfer wire, which is below the web and through which the web is fed to a drying wire of a vertical blow-drying group.

According to a preferred embodiment of the invention, the web is guided from the last press nip of the press member on the surface of the last fabric, preferably transbelt or felt from which the web is transferred to the first transfer wire. Thereafter, as the web passes, there is followed by a bevel or other similar means for cutting the headband. This is followed by a movable roll, preferably smooth, with a scraper in position. The web is driven from the pick-up roll of the first transfer wire loop, i.e., the roll which picks from the previous fabric, full width to this displaceable roll, which is displaced to the tapping position, the upper position when the pick-up roll descends and the web press portion. Since the transfer wire covers a portion of the roll to be moved, the web follows the roll and becomes the roll color of the roll, from where it flows into the pulper. Thereafter, the concept includes a second transfer wire for transferring the web to the drying wire of a vertical blow drying group. The vertical blow blast drying group has a drying effect such that the dry solids of the web can be raised to 50-65% solids, preferably 55-63% solids, before being fed to the cylinder for drying. The pose-20 movable roll is in the upper position when the web end export strip is passed over the vertical blowing unit and once the web has been laid, the movable roll roll is lowered into the unaffected position of the web, lower so that it does not pose a problem kilometers, which otherwise would cause adversely affecting the running of the web

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cp 25 effective vacuum is not formed. Inside the first transfer wire loop

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side boxes are provided with blow boxes, preferably boxes of the type marketed by the applicant under the trade name g PressRun to ensure the flow of the web.

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According to another preferred embodiment of the invention, which otherwise corresponds to the above-described embodiment, the second wire is constructed in a manner other than the first embodiment such that the web runs in a straight line with the movable roll position in the unaffected position. The advantage of this application is that there is no suction roll between the transfers of the web, which ensures a successful transfer.

According to a third advantageous embodiment of the invention, the positioning roll is placed inside the transfer wire loop, preferably between the blowing boxes, whereby during threading it is moved to a lower position, whereby the web is guided to pass through a rolled-up roll. The web is then transferred to a second transfer wire and thence to a vertical blow dry dryer group.

According to a fourth advantageous embodiment of the invention, the paper web is also guided from the last fabric of the press section by a transfer wire, also in a vertical blow-drying group, whereby the number of transfer points and thus the need for transfer suction rolls 15 is reduced.

In the context of the invention, the transfer suction rolls are also movable to the threading position during the threading of the web. For transfer suction rollers, this position is also a constant driving position, whereby the headlift and normal driving are different for the suction roll roller under-20 pressure levels so that the vacuum generally used during headlifting is higher.

The solution according to the invention eliminates the runnability problems of high speed paper and cm board machines at the opening of the cylinder, whereby the efficiency of the i cp 25 machine is improved and speeds can be further increased.

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g In the following, the invention will be described in more detail with reference to the drawings in the accompanying drawing, the details of which, however, are not to be construed as being:

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Figure 1 schematically illustrates an embodiment of the invention.

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Figure 2 schematically illustrates another embodiment of the invention.

Figure 3 schematically shows a third embodiment of the invention.

Figure 4 schematically shows a fourth embodiment of the invention.

In the following Figures 1-4, the same reference numerals are used for like parts, unless otherwise stated.

In the embodiment of Figure 1, web W from its last press nip N formed between rolls 12, 13 is pressed from the press section 10 to a first transfer web 20 to which web W is transferred to a pick-up roll. 21. With the transfer wire 20, the passage of the web is supported by blowing boxes 25, preferably blowing boxes of the type marketed by the Applicant's commercial press 15. This is followed by an inclined whip 26 or the like for cutting the threading strip, followed by a displaceable roll 30, preferably smooth and provided with a pattern 31. During threading, the displaceable roll 30 is raised to the upper position as indicated by dotted lines in the figure. From the smooth roller 30, the web 20 is scraped with the formulas 31 during threading to the pulper 41. The passage of the web to the pulper is secured by the baffle 42 and the guide 43 guides the advanced web in the event of failure / pulper 41, if necessary. to the pulper 41. ° From the first transfer wire 20, the web is led to the second transfer wire 36, to which the web 10 is passed through the transfer suction roll 35. You can then follow the

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an overflow drying unit 40 with transfer wire 36. The first transfer wire loop control and guide rolls are designated by reference numeral 22. The control and guide rollers of one transfer wire are denoted by reference numerals 37 and 38. On the other, the transfer fabric 36 web is led to vertical blow-drying on its drying web 30 to roll 59 through. Firstly, the web W passes 9 substantially vertically downwards, whereupon it is dried by the blowing unit 51, after which the web direction is rotated by a roller 53, after which the web W passes substantially vertically upwards, during which it is dried on top. through the blows provided by the blowing unit 52. Thereafter, the web 5 is led by a drying wire 59 to a cylinder drying where the drying web W is sandwiched between the drying wire 59 and the heated cylinder surface 56 and the web W has a normal single wire passage, whereby its direction on the knees is rotated For transfer suction rollers, this position is also a constant driving position, 10 whereby head and normal driving differ from the vacuum suction roll levels of the transfer suction rolls, so that the vacuum generally used during head roll is higher.

The embodiments of the invention shown in Figures 2-4 below are similar to the embodiment shown in Fig. 15 unless otherwise stated.

In the embodiment shown in Fig. 2, the web passage is substantially linear and this is arranged such that the second transfer wire 36 extends over the entire web passage area 20 of the first transfer wire loop, whereby the web passage can be arranged substantially linearly. In this embodiment, the web is conveyed by a transfer suction roll 37 to a transfer fabric 36 and a transfer suction roll 55 further to the blow drying group drying fabric 59. In this embodiment, the first transfer fabric loop 20 is provided with three blowing boxes 25 to control the web flow.

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cp 25 In the embodiment shown in Fig. 3, the movable roller is positioned in a pre-

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> - inside the first transfer wire loop 20 and is designated 22B, £ because it simultaneously forms one of the control and guide rolls of the transfer wire loop during the export of the head σ>. Since this roll is movable, the transfer wire loop is also provided with a second position adjustable roll 22a to maintain the tension of the transfer wire loop 20.

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In the embodiment shown in Figure 3, the second transfer wire loop 36 carries the web W only a short distance closest to the transfer suction roll 37 and a small portion before the web W encounters the blow drying group 59 at the transfer suction roll 55. The second roll 34 of the transfer wire loop 36 is movable in position, as indicated by an arrow and a dotted transfer station in the figure. In this way, the transfer wire loop 36 can be moved out of contact with the transfer suction roll 55 of the blow-drying group, whereby, in the event of a malfunction / need, the web W can be led through the mouth 43 to the pulper.

In the embodiment shown in Figure 4, the transfer wire 20 is at the same time a vertical group drying wire, whereby the number of transfer points and thus the need for transfer suction rolls is reduced. The roller 33 is preferably a blow roller and the suction box 58 can also be secured by a wire run down the wire 20 of the web W. At the same time, the length of the blow-drying section can be increased. Track 33 is preferably a blow roll 15 but by enhancing the vacuum means 58 may be placed in a position even if the cylinder, which has a threading situation may be slightly less advantageous alternative, since it is then able to use the roll in a controlled manner on the opposite side of the roll across the width of a progressive band. If the roll 33 is a blow roll, it can be, for example, a warm blow roll, about 140 ° C inside the roll, or the roll may be a grooved roll having a groove size of 1 x 1 mm, whereby its effect is enhanced by the vacuum means 58.

The invention has been described above only with reference to a few preferred embodiments thereof, the details of which, however, are not intended to be construed in any way,

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Claims (19)

11 A method in a drying section of a papermaking machine, wherein the papermaking web (W) is dried after dewatering by pressing 5 on a papermaking press (10), and wherein the papermaking web (W) is dried at least by blow drying and cylinder drying, characterized in that ) is led via at least one transfer fabric (20; 36) from a press machine portion (10) of the papermaking machine to a 10 vertical blowing drying group (50) located in the first drying section of the papermaking dryer, wherein the paper web (W) is ) is provided with a movable positioning smooth roll (30) which is movable to the main export position during the threading of the web (W) and that during the threading, the web (W) 15 is scraped from the positioning smooth roll la (31) to pulpper (41). Method according to Claim 1, characterized in that the paper web (W) is dried by vertical blow-drying 20 to a dry substance content of 50-65% before being fed to a cylinder-drying dryer (56). i- Method according to Claim 1 or 2, characterized in that in the method the paper web (W) is guided by a transfer wire (20) in a vertical o 25 in the blow-drying group (50). c/o A method according to claim 1 or 2, characterized in that in the method the paper web (W) is conducted from the first transfer from the wire (20) to the drying wire (59) of the overblow drying group (50). o o 30 cm 12 5. A method according to claim 1 or 2, characterized in that the paper web (W) is passed through two transfer wires (20, 36) to a drying fabric (59) of a vertical blow drying group (50), the first fabric (11) following the last fabric (11). after the transfer wire (20), the web (W) is conducted to a second transfer wire (36), whereby the web (W) is fed to a drying wire (59) of a vertical blow-drying group (50). Method according to one of Claims 1 to 5, characterized in that in method 10 the web (W) is guided from the last press nip (N) of the press section (10) on the surface of the last fabric (11) of the press section (10) to the first transfer fabric (20). followed by the passage of the web (W) is followed by a means (26) for cutting the main strip of the web (W). Method according to one of Claims 1 to 6, characterized in that the web (W) is guided from a transfer wire (20) to a pulper (41) via a displaceable, preferably smooth roll (30) and a scraper (31). Method according to one of Claims 5 to 7, characterized in that in the method 20 the web (W) is guided from the last fabric (11) of the press section (10) to the first transfer fabric (20) and further to the second transfer fabric (36). passing in a straight line with the movable f— roll (30) in an unaffected position with respect to the web (W). δ CM o 25 Method according to one of Claims 1 to 8, characterized in that, in the CO <method, the movable roll (22B) is disposed inside the transfer wire (20), whereby during the main export of the web (W) the roll is moved to a lower position, wherein the web (W) is guided to pass through an external roll (30) of a transfer wire loop (20) provided with a scraper (31). 1 30 13 Method according to one of Claims 1 to 9, characterized in that in the method the passage of the web (W) is supported by at least one blow box (25) located in connection with the first transfer wire loop (20). Apparatus in a papermaking dryer section located after the papermaking press section (10) of a papermaking dryer and comprising at least one blow-drying group and a cylinder drying, characterized in that the paper web (W) is led from the papermaking press section (10) to at least one transfer wire (20, 36) is disposed within the vertical overflow drying group (50) so that at least one transfer wire (20) is provided with a position-displaceable, smooth roll (30) movable to a main transfer position during web tapping (W) , a scraper (31) is provided in connection with the smooth roll (30) for scraping the web 15 (W) during threading to the pulper (41). Apparatus according to Claim 11, characterized in that the vertical overrun drying group (50) is arranged to dry the web (W) to a dry matter content of 50-65% before passing the web to the drying of cylinders by drying cylinders (56). Device according to Claim 11 or 12, characterized in that the transfer fabric (20) is also a drying δ (M wire, c c cp 25) of a vertical blow-drying group (50). Apparatus according to claim 11 or 12, characterized in that the transfer fabric (20) is disposed as a fabric immediately preceding the drying fabric (59) of the blow drying group (50). • 't o o o 30 Apparatus according to claim 11 or 12, characterized in that a second transfer wire (36) is disposed after the transfer fabric (20) 14 next to the last fabric (11) of the press section (10) for guiding the web (W) in the vertical blow-drying group (10). 50) for a drying wire (59). Device according to one of Claims 11 to 15, characterized in that a means (26) for cutting the main strip of the web (W) is disposed over the first transfer wire (20), and preferably a smooth roll (30) with which a scraper (31) is impressed. ), and pulper (41). Apparatus according to claim 15 or 16, characterized in that the first transfer wire (20) and the second transfer wire (36) are arranged such that the web (W) passes in a straight line with the web (W) being displaceable in position. ) in an unaffected position. Device according to one of Claims 11 to 17, characterized in that the positioning roll (22B) is disposed inside the transfer wire loop (20). Device according to one of Claims 11 to 18, characterized in that at least one blowing box (25) is arranged in connection with the first transfer wire loop (20) to support the passage of the web (W). δ <M ώ o co X cc CL σ> o o o o CM 15