FI89614C - FRAMEWORK FOR THE PURPOSE OF UPDATING AV EN PAPPERS- ELLER KARTONGBANA - Google Patents

Description

8961 4

Method and apparatus for heating a paper or board web Förfarande och anordning för upphettning av en pappers-eller kartonbana 5

The invention relates to a method for heating a paper or board web on a press section of a paper or board machine, said track being conveyed through press nips formed by press rolls to remove water from the web, and a transfer belt formed by tension and guide rollers being passed around the center roll of the press section. are formed between the center roll and the other two press rolls, and extend beyond the area of the press rolls to which the web of paper or board is transferred to pass, whereby the web is heated from the region of said loop 15 outside the press rolls by heating devices.

The invention also relates to a device for heating a paper or board web on a press section of a paper or board machine 20, which press section comprises a plurality of press rolls forming press nips for removing water from the web and in which a transfer belt is formed around the center roll of the press section. extend beyond the region of the press rolls into an endless loop passing through the press nips formed by the center roll .. 25 and the other two press rolls so that the web is moved to pass along said transfer belt, the transfer belt loop being arranged outside the press rolls to heat the track, heat directly to the track.

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For example, in a paper machine, a paper web is formed from pulp: in a paper web forming section, after which the formed web is supported and supported by paper machine felts into a paper machine press section, where the web and supporting felts are passed through nips formed by press rolls. From the press section, the web is further fed to the drying section of the paper machine. The conventional solution in the press section comprises a large and massive central roll and a series of wire or felt silicas grouped around it, the rollers inside which, either together or together with the central roll, form press nips through which water is removed from the web by compression.

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The general aim is to improve the dewatering efficiency of the presses in the press section of the paper machine. Getting the moisture of the paper web already as low as possible in the press section means considerable cost savings for paper production, because the drier the paper web can be taken from the press section 10 to the drying section, the lower the steam consumption in the drying section. As a kind of rule of thumb, if the moisture in the track is reduced by one percentage point with the press section, the steam consumption in the drying section is five percent lower, which means considerable cost savings. The dewatering efficiency is generally improved by raising the temperature of the paper web. If the track is heated with steam or otherwise from above the track, there is a risk of condensation and dirt accumulating on the track. However, water or dirt dripping onto the track substantially inhibits paper production and in some extreme cases may even prevent production altogether.

20 In addition, the center roll of the press is a rather difficult disadvantage in the structures used today. The disadvantage is due to the material of the center roll, in which some suitable stone, for example granite, is commonly used. It is known, however, that the fittings are quite sensitive to large and sudden changes in temperature, the effects of which can be quite fatal. Efforts have been made to develop suitable substitutes for granite rolls. However, making a suitable surface for the center roll is difficult and also limits the choice of other material in the roll. In addition, different paper grades may require a different coating and perhaps also a different coating manufacturing method. If the central roll 30 is coated, for example welded, or if the coating is elastic, for example rubber-like, the device for heating the paper web must necessarily be above the web if such a heating device is to be arranged in the structure before the third press nip. However, there is very little space in the press before the third press nip 35 to provide an efficient device for raising the temperature of the track and adjusting the temperature profile. However, the disadvantage of the heating device located at said location is that it causes dirt to accumulate and drip onto the paper web.

With regard to the state of the art, reference is also made to DE 236 021 and 5 EN 75 382.

It is an object of the present invention to provide a solution which brings about a significant improvement over the prior art and which avoids the disadvantages described above. More particularly, it is an object of the invention to provide a method and apparatus for raising the temperature of a paper or board web substantially by the press section and for changing the material of the press center roll from a problematic granite to a lighter material, for example cast iron. To achieve this, the method is mainly characterized in that the transfer strip is a metal strip and that the paper web is further heated by heating the transfer strip from inside the loop.

The device according to the invention, in turn, is mainly characterized in that the transfer belt is a metal strip and in that a heater is additionally mounted inside the transfer belt loop 20, which is adapted to heat the transfer belt directly.

Among the advantages achieved by the invention, e.g. follow-ous. In the solution according to the invention, the paper web can be efficiently heated by the press section 25 without the disadvantages associated with conventional heating methods. If necessary, the heating distance of the paper web can be made very long, which means that the heating efficiency is correspondingly very good. The center roll of the press can be manufactured simply and pre-. . for example, of the 30 materials best suited for the purpose in terms of strength and corrosion properties. For example, cast iron can be used as the material. In addition, the heating devices can be placed completely freely in connection with the press. Since a metal strip is used as the transfer belt according to the invention, it can be scraped with e.g. a steel-blade scraper and a proper blade pressure can be used in the scraper.

35 S 9 61 4 4

The invention will now be explained in detail with reference to the figures of the accompanying drawing.

Figure 1 schematically shows a part of the press-5 part of a paper or board machine in which the solution according to the invention has been applied.

Figure 2 shows an alternative embodiment of the solution according to Figure 1.

The press section shown in a schematic side view of Figure 1 of the drawing comprises a closed press structure comprising three successive nips N1fN2 and N3. Said nips are formed between the first, second and third press rolls 11,21,31 of the press section and the central roller 1. The press section comprises a first fabric 10 and a second fabric 20, 15 which are generally blankets and both of which pass through the first nip Nx and of which the first fabric 10 generally acts as a pick-up fabric for moving the paper web U from the web forming section to the press section and further as a press fabric at the second nip N2. The third press fabric 30 passes through the third nip N3. In the embodiment of the figure, the fourth fabric 40 shown in Fig. 12 of the drawing functions as a single export fabric of the drying section, to which the paper web W is transferred from the center roll 1 under the control of the transfer roll 41. Said fourth fabric 40 thus transfers the paper web W from the press section as a single fabric outlet to the drying section (not shown). After the closed press structure shown in the figure, the press part 25 may further comprise a fourth separate nip, whereby the fourth fabric 40 shown in Fig. 1 would thus transfer the paper web W to said fourth nip N 1.

For the first fabric 10, the paper web W is transferred from the forming section 30 to a pickup roll (not shown). The first fabric 10 is guided by guide wires 13, one of which is used to keep the tension of the first fabric 10 appropriate. Similarly, the second fabric 20 is guided by the guide rollers 22 and the third fabric 30 is guided by the guide rollers 32.

The first press roll 11 is a suction roll and is thus provided with a suction zone 12. The second press roll 21 is, for example, a conventional groove roll. Said suction roll 11 and the groove roll 21 thus together form a first nip Nj of the press part, through which the paper web W passes between the first fabric 10 and the second fabric 20.

After the first nip Nx, the paper web W is sucked by the suction zone 12 of the first press roll 11 from the second press fabric 20 onto the surface of the first press fabric 10 and under the guidance of the first press roll 11 into the second nip N2 of the press. For this purpose, a so-called pick-up felt 10 is used as said first press fabric 10, and a suction roll 11 acting as a first press roll is provided with a suction zone 12 of suitable length which ensures that the paper web W detaches from the second press fabric 20 on the first press fabric 10. The suction roll 11 may further be provided with its own steam box, which is indicated by the reference number 15 in Fig. 1. A second nip N2 is formed between the first press roll 11 and the central roll 1 of the press part.

After the second nip N2, said first press fabric 10 is guided away from the central roll 1.

In conventional press constructions, the paper web W would move after the second nip 20 N2 to the surface of the press roll 1, along which the web W would pass to the third nip N3 of the press. In the solution according to the invention, instead, a transfer belt 2 formed as an endless loop or loop is passed around the central roll 1, which in the embodiment of Fig. 1 is guided far outside the central roll 1 under the guidance of the guide roll 3 acting as a tension roll and the guide roll 4. After the second nip N2, the paper web W is thus transferred to the surface of said transfer belt 2, supported by which the paper web W is transferred to the third nip N3 of the press. The material of the transfer belt 2 is selected according to the desired properties and these properties are e.g. heat duration, wear duration, patternability 30, and adhesion between the transfer belt and the paper web W. According to the desired properties, the material of the transfer belt 2 is most preferably metal, for example steel.

According to FIG. 1, a plurality of units are arranged around the transfer belt loop 2 and on the other hand on the inside, with which the paper web W is heated. Of the heating units shown in Fig. 1, reference numeral 5 6 H 9 614 denotes a steam box with which the paper web W is heated by means of steam. As can be seen from Fig. 1, the steam box can be formed very long in the direction of travel of the paper web, if necessary, whereby the steam box provides a very effective heating effect. In the embodiment of Fig. 1, after the steam box 5, an exhaust suction device marked with reference numeral 7 in the direction of travel of the paper web W is provided, so-called "steam extractor", which sucks excess steam and thus reduces the risk of water and dirt dripping onto the paper web W. over. the paper web W is subjected to a centrifugal force which tends to detach the paper web W from the transfer belt 2. Therefore, according to Fig. 1, it is appropriate to provide a blow device 8 outside the guide roll 3 after the extractor 7 to provide a support blow to ensure the paper web W remains on the transfer belt 2. Some type of suction roller can also be used as the roller 3 15.

In the embodiment of Figure 1, a second heating unit, indicated by reference numeral 9, is arranged outside the paper web W after the blowing device 8. Said second heating unit may be, for example, an infrared heater to supplement the heating provided by the steam box 5. In Fig. 1 a third heater, denoted by reference numeral 6, is further arranged inside the transfer belt loop 2 according to the invention. Since the transfer belt 2 is made of metal, an induction heating device can be used as the third heating device, with which the transfer belt 2 is inductively heated.

In this connection, it should be emphasized that almost all the heating devices and methods shown in Fig. 1 30 can be complementary and / or substitutable, in which case not all heating devices shown in Fig. 1 need to be used in connection with the press section, but it is preferred to use one or more of the heating devices shown in Fig. 1, in addition to the heating device 6 heating the transfer belt 2 from inside the loop 35. One advantageous alternative is that a steam box 5 is used as the so-called basic heater and the heating of the paper web W provided by it is supplemented by an induction heater 6.

After the heaters and the guide roll 4, the transfer belt 2 and the heated paper web W 5 thereon are guided to the third fabric 30 so that the paper web W passes to the third nip N3 between the transfer belt 2 and said third fabric 30. After the third nip N3, the paper web W follows a transfer belt 2 on the surface of the central roll 1 for some distance, after which the paper web W is transferred to the fourth fabric 40 under the direction of the transfer roll 41. Said fourth fabric 40 can transfer the paper web W to a fourth press nip or a paper machine. the dryer section. Reference numeral 42 denotes a scraper which removes the wreck W 'from the surface of the transfer belt 2 and guides it, for example, to a conventional wreck type. Also during the start-up of the machine-15 and a possible path break, the scraper 42 guides the paper path to the wreck type.

Figure 2 shows an alternative embodiment for the arrangements of the heaters of Figure 1. Fig. 2 shows the press part only in a sectional view, but it is to be understood that the parts omitted from Fig. 2 may be completely identical to those shown in Fig. 1. The structure shown in Fig. 2 essentially corresponds to the embodiment of Fig. 1, and thus in Fig. 2 reference numeral 10 denotes the first fabric and reference numeral 13 denotes the first fabric guide roll and ____ 25 reference numeral 30 denotes the third fabric and reference numeral 32 the guide roll as in Fig. 1. Reference numeral 103 denotes a guide roller acting as a tensioning roller for the transfer belt 2 and a guide roller 104 for the transfer belt. The steam box is denoted by reference numeral 105, the induction heater by reference numeral 106, the exhaust suction device by reference numeral 107, the blowing device 30 providing support support 30 and the infrared heating device by reference numeral 109. The solution shown in Figure 2 is thus substantially the same as in Figure 1. 2 is provided with an additional folding roller 110 by means of which the transfer belt 2 and the paper path W 35 thereon are guided in the area of the steam box 105 to run in a more horizontal direction than in the embodiment of Fig. 1. According to Fig. 2, the folding roll 110 8961 4 8 may be provided with a scraper 111. Such a solution ensures that the steam box 105 will be located entirely below the paper path W, whereby the embodiment of Fig. 2 completely avoids the problems of water and / or dirt dripping onto the paper path. W from the steam box 105.

In summary of the invention, in the method according to the invention and in the device applying the method, the paper web W is transferred to the transfer belt 2 from the outer region of the press rolls 1,11,21,31, whereby the paper web can be efficiently heated by several different methods. High-power heaters and / or paper web profilers can then be placed completely freely. With further reference to the above description of the invention, it should be noted that the invention has been described above only by way of example with reference to the embodiments shown in the figures of the drawing. However, the invention is not intended to be limited solely to the examples shown in the figures, but many modifications are possible within the scope of the inventive idea defined by the appended claims.

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Claims (6)

9 8961 4 A method for heating a paper or board web with a press section of a paper or board machine, wherein said web (W) is conveyed through press nips (N 1 N 2, 3) formed by press rolls (1,11,21,31) to remove water from the web ( W), and in which a transfer belt (2) formed as an endless loop is passed around the central roll (1) of the press section by means of tensioning and guide rollers (3,4; 103,104,110) and passes through press nips (N2, N3) formed by the central roller (1) and two between the other 10 press rolls (11,31) and extends beyond the area of the press rolls (1,11,21,31) to which the web or paperboard web (W) is transferred to the transfer belt (2), whereby the web (W) is heated from the region of said loop (1,11,21,31) by heating devices (5,9; 105,109) which supply heat directly to the web (W), characterized in that the transfer strip (2) is a metal strip and that the paper web (W) ) further heats the transfer belt (2) inside the loop by heating. Method according to Claim 1, characterized in that the transfer belt (2) is heated inductively by means of an induction heater (6; 106) arranged inside the transfer belt loop. Apparatus for carrying out the method according to claim 1 for heating a web of paper or board with a press section of a paper or board machine, the press section comprising a plurality of press rolls (1,11,21, 31) forming a press for removing water from the track (W) nips (N1f N2, N3), and in which a transfer belt (2) is formed around the central roll (1) of the press section, which is formed by means of tensioning and guide rollers (3,4; 103,104,110) to extend the press rolls 30 (1,11,21,31 ) as an endless loop passing through the press nips (N2, N3) formed by the central roll (1) and the other two press rolls (11,31) so that the track (W) is moved to pass said transfer belt (2). ), where heating means (5,9; 105,109) are provided for heating the track (W) in the region of the loop of the transfer belt (2) outside the press rolls (1,11,21,31), which bring heat directly to the track (W), characterized in that that 8961 4 10 the transfer strip (2) is a metal strip and that a heater (6; 106) is further mounted inside the loop of the strip strip (2), which is adapted to heat the transfer strip (2) directly. Device according to claim 3, characterized in that the heater (6; 106) mounted inside the transfer belt loop is an induction heater arranged to inductively heat the metal transfer belt (2). Device according to Claim 3 or 4, characterized in that the transfer belt (2) is made of steel. Device according to one of Claims 3 to 5, characterized in that the transfer belt (2) is turned by means of a folding roller (110) into a substantially horizontal direction so that a heating device (105) directly heating the track (W) is mounted on the track (W). below. i n 89614