FI103423B - A method for increasing the drying capacity of a paper machine - Google Patents

Description

103423

Method for Increasing the Drying Capacity of a Paper Machine 1 i Förfarande för ekning av torkningskapaciteten i en pappersmaskin 5 i

The invention relates to methods according to the preamble of claim 1, 2 or 5.

10

As is known in the prior art, multi-cylinder dryers of a papermaking machine utilize a double wire feeder and / or a single wire feeder. In a two-wire feeder, the drying cylinder groups have two wires that press one of the web against the top and the other against the heated cylinder surfaces. Between the rows of drying cylinders, generally horizontal rows, the web has free and unsupported strokes that are prone to flutter, which can cause web breaks, especially when the web is still relatively damp and consequently weak. Because of this, there has recently been an increasing use of said single-wire thread, with 20 drying roller groups having only one drying wire, the support of which passes through the entire group so that the drying wire presses the web against the the rolls remain on the outer side of the curve.

25

In prior art conventional single-wire export groups, heated drying cylinders are in the top row and drying cylinders or swivel cylinders or rollers are in the bottom row, which rows are generally horizontal and parallel to each other. Also known as so-called. inverted 30 single-wire sets with heated drying cylinders in the bottom row and drying cylinders or roll-up cylinders or rolls in the top row ·· for the main purpose of drying the web on one side relative to the normal single-wire belt group.

35 In the following, the terms "normal (drier) group" and "inverted (dehydrated) group" are used to refer to monofilament groups of the kind mentioned above.

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It is also known in the art to use various blowing / blowing units for the evaporation-drying of the paper web, wherein the paper web is dried by blowing dry air or superheated steam approximately perpendicularly to the paper 5 at relatively high speeds.

One problem with the single-wire export groups at the beginning of the drying section has been the need to use very low vapor pressures on the upstream drying cylinders to prevent the fibers from burning, whereby efficient evaporation at the beginning of the drying section using drying cylinders has not been achieved.

The maximum web speeds for paper machines are already in the order of 25 m / s, but before long the speed range of 25-40 m / s will be introduced. Thus the bottleneck for the runnability of the paper machine will become more and more a drying section which, in addition, will be quite long using the known drying section concepts. In addition, efforts are being made to increase the speed and capacity of existing paper machines by means of retrofitting operations, which makes it important to simplify and simplify the process of retrofitting existing paper machines.

It is an object of the invention to provide a method by which the drying capacity of an existing paper machine can be increased and the speed of the paper machine can be increased by simple and easy measures.

In particular, it is an object of the present invention to provide a method whereby the operations required to increase the capacity and speed of an existing paper machine can be mainly performed at a paper mill.

. In order to achieve the foregoing and further objects, the methods of the invention are essentially characterized by what is set forth in the characterizing parts of claim 1, 2 or 5.

Thus, by the method of the invention, the capacity and speed of an existing paper machine can be increased and the necessary operations can be performed mainly at the paper mill. According to the invention, the existing single-wire or double-wire feed group can be converted by simple steps into an inverted single-wire feed group, in which the top row cylinders or rollers are provided with overflow devices.

The method of the invention is suitable for use with a papermaking machine rebuilding a drying group applying twin-wire threading to an inverted single-wire threading group, wherein the top row cylinders are converted to swivel cylinders or rolls while removing the top drying wire and top roller. The method according to the invention is also suitable for use in the renewal of a papermaking machine in which the drying group applying the standard single-wire export is converted to the inverted single-wire export group by moving the lower row turning cylinders / rolls to the upper row Further, the method of the invention is particularly advantageous for use in the renewal of a paper machine having a single wire thread drying group having drying rows in both rows such that the top row drying cylinders are turned into swivel cylinders / rolls and the fan roll is moved. The method of the invention thus provides an increase in the evaporation efficiency of the drying section of the paper machine.

According to a most preferred embodiment of the invention, the invention is applied to an existing paper machine for which additional drying capacity is desired and wherein at least the first group is a so-called single wire export group, thereby converting the first drive group into a reversed group. 30 cylinder groups. At the same time, the said code is changed. · drying cylinder tops · drying cylinders into turning cylinders / rolls and inserting overflow hoods above the top cylinders, as well as the necessary circulation air equipment. The lower row drying cylinders are kept intact. With such an arrangement, there is a considerable increase in drying capacity 35, e.g. 25 ... 30%, without the need to extend the drying section, and this * · 103423 4 arrangement loses any efficient drying cylinder. Furthermore, in the process of the invention, the frame structures and actuators of the drying groups can be utilized at least in part. Also, there is no need to make major changes to the dryer section hood, since in many applications 5 overflow hoods fit inside an old hood. Of the old drying cylinders, rotary cylinders / rollers, preferably rolls marketed by the applicant under the trademark VAC ROLL (VAC rolls), are preferably manufactured by grooving and drilling, which in itself is less expensive than positioning entirely new VAC rolls 10 in a paper machine. and the switches must be replaced. In addition, the use of VAC rollers improves group runnability and facilitates head tapping. Further advantageous in the arrangement according to the invention is that the overflow boxes are located above the cylinders or rolls and remain self-clean, without the need for separate cleaning arrangements. If necessary, the blowing devices can be equipped with e.g. pneumatic cylinders or other similar lifting devices so that they can be lifted up during breaks.

Blowing is also very advantageous when placed at the beginning of the dryer section, because the cylinders are less efficient at the beginning of the dryer section because very low vapor pressures are used in the upstream cylinders to prevent the fibers from burning. By blowing up, the track is quickly warmed, allowing the cylinder temperatures to rise faster.

“25 In addition, it is advantageous to place the blowing on top for the curvature of the web, since the curvature is not significantly affected by the unilateral drying in this area. At the end of the drying section, the paper is much more sensitive to the asymmetry of the drying. This avoids the use of the downward blowing hoods, which is a great advantage for the clean-button 30 of the drying section.

β *

In the following, the method according to the invention will be described in more detail with reference to the figures in the accompanying drawings.

Figures IA and IB schematically illustrate a preferred embodiment of the invention.

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Figures 2A and 2B schematically illustrate another embodiment of the invention.

Figures 3A and 3B schematically illustrate an additional embodiment of the invention.

In the drying group shown in Fig. 1A, the drying fabric 15 is guided by guide rolls 18 in a normal single-wire threading group R. The drying fabric 15 presses the upper row RY of the web W The bottom row RA drying cylinders may have steam on or off steam supply. The dryer section hood is designated 20.

15

Fig. 1B shows a group modified from the drying group of Fig. 1A by the method of the invention, which is the inverted single-wire export group RN, in which the loop of the drying wire 15 passes below the R group. The drying rows 10 of the top row RY according to Fig. 1 are converted into 20 turning cylinders / rolls, preferably VAC rolls 25, and above them are added blowing devices 26. If necessary, the blowing devices 26 may be provided with lifting means (not shown) up times when needed. The top row RY drying cylinders 10 • 25 are converted into VAC rolls, for example, by being grooved and making the necessary drilling. The ends and couplings of the drying cylinders are exchanged for VAC rolls. The lower row RA drying cylinders 11 are retained and, if necessary, the steam supply is switched on. Thus, the rotary actuator cylinders / rolls 25 are provided, preferably 30, by the applicant under the trademark VAC ROLL, without an inner suction box, the details of which are referred to in Applicant's FI Patent No. 83680 (U.S. Pat. No. 5,022,163).

2A-2B, when applying the invention to a standard single-wire export group having upper row RY having 103423 6 drying cylinders 10 and lower row RA turning cylinders or rollers 25 (Fig. 2A), changing the upper row RY drying cylinders 10 to lower rows RA into the upper row RY and are provided with blowing devices 26. The drying wire cycle 5 is displaced such that the wire cycle passes below the group R „. Thus, an inverted drying group R 'according to Fig. 2B is obtained.

The method according to the invention is also suitable for use in drying groups R2 which have previously had a two-wire outlet as shown in Figures 3A-3B. Hereby, the upper drying wire 33 and its guide rolls 18 are removed and the drying rollers 31 of the upper row RY are converted to VAC rolls 25. The drying cylinders 32 of the lower row RA are still considered as drying cylinders 32. Otherwise, the required steps are similar to those described in the embodiment of FIG.

15

The invention has been described above only with reference to a preferred embodiment thereof, the details of which, however, are not to be construed in any way narrowly limited. Many modifications and variations are possible within the scope of the inventive idea defined in the following claims.

Claims (8)

A method of increasing the drying capacity of a paper machine, wherein a method of existing paper machine is renewed and wherein a paper machine is used in at least one drying group (R) normal envirus lining, wherein the web (W) runs supported by a drying wire through the drying group (R ), which drying wire (15) presses the web (W) at the drying cylinders (10) in an upper row (RY) towards the heated cylinder surfaces and at the drying cylinders (11) in a lower row (RA), the web (W) on the outer swivel side, k characterized in that, in the process, a normal enviro-feeding group (R) is converted to an inverse enviro-feeding group (R ") in such a way that the circulation course of the dryer wire (15) is transferred to the lower side of the group (R) and the drying cylinders (10) ) in the upper row (RY) of the group is converted into break cylinders or rollers (25) and inflating devices (26) are added on the upper side of these (25). A method of increasing the drying capacity of a paper machine, wherein a method of existing paper machine is renewed and in which the paper machine is provided with at least one group (Rz) having a wire feeder having two wires (33,34) pressing the web (W). one on the upper side and the other on the lower side against heated cylinder surfaces of drying cylinders, characterized in that, in the process, a cross-winding group (R2) is converted to an inverted winding group (R ") in such a way that and the drying cylinders (31) in the upper row (RY) are converted into break cylinders / rollers (25) and provided with blowing means (26). Method according to claim 1 or 2, characterized in that the drying cylinders (10, 31) in the upper row (RY) are converted into 30 suction cylinders / rollers (25) without internal suction. 4. A method according to claim 3, characterized in that the male ends of the drying cylinders (10, 31) in the upper row (RY) are provided with rafters and bores and that the ends and couplings of said cylinders (10, 31) are replaced. wherein the drying cylinders (10, 31) have been changed to suction cylinders / rollers (25). 103423 A method of increasing the drying capacity of a paper machine, wherein a method of existing paper machine is renewed and wherein the paper machine is used in at least one drying group (R) normal envirus lining, wherein the web (W) runs supported by a drying wire (15) through a drying group. - the pen (R), which drying wire (15) presses the web (W) at the drying cylinders (10) in an upper row (RY) towards the heated cylinder surfaces and at the breaking cylinders or rollers (25) between the drying cylinders (10), the web (W) on the outer pivot side, characterized in that a normal one-wire guide group (R) in the method is converted to a reverse one-wire guide group (RN) in such a way that the circulation course of the drying wire (15) is transferred to the lower side of the the group and drying cylinders (10) in the upper row (RY) of the group (R) are moved to the lower row (RA) and the breaking cylinders or rollers (25) in the lower row (RA) are moved to the upper row (RY) and that inflating means (26) 1 5 is added to the upper side of the break cylinders or rollers (25) in the upper row (RY). Method according to any of the preceding claims, characterized in that the blowing devices (26) are provided with lifting means for lifting the blowing devices (26) for service and / or repair measures. Method according to any of the preceding claims, characterized in that the blowing means (26) are provided with circulating air devices. 8. A method according to any of the preceding claims, characterized in that the first drying group in the drying portion of the papermaking machine is renewed during the process. 30