JPH038882A - Press roll part for sheet, board, or pulp drier - Google Patents

Abstract

PURPOSE: To carry a specific carrying felt provided in a press roll section between a second press felt and a winding paper through a press nip and pulls the winding paper in a closed drawing to draw the paper at a higher speed. CONSTITUTION: A transfer felt 1 is arranged so as to pass a press nip formed with surface release rolls between second press felts 30, 50 and 70 of the nips N1 , N2 and N3 and a winding paper W, and the winding paper W running between the nips is supported in a closed drawing state. The transfer felt 1 is made to water permeable and water re-absorption of the winding paper just after passing through the nips is inhibited not so as to absorb considerable amount of water into itself.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a press roll section of a paper, cardboard or bulb dryer.

[Conventional technology]

Dewatering paper, cardboard or pulp webs by evaporation requires a lot of energy and is therefore expensive and uneconomical. Therefore, before reaching the web or drying section,
It is usually attempted to remove as much water as possible from the web by mechanical means. The most important step in this process is the press roll section, where moisture is removed from the web by pressing it between rolls. It is well known that water removal from the web becomes easier when the temperature is increased by 1 degree; this is because under pressure the viscosity of water and the elastic modulus of the web are This is because it decreases as the temperature rises. In this way, the drying area of the paper web that has passed through the press roll section is considerably enlarged, so that the energy consumption required for drying can be significantly reduced.

(Problem to be solved by the invention!&i) As the production speed of dryers for paper, cardboard, etc. increases, a new problem arises: loose pulling of the paper web in the press roll section. , and also the free pulling of the web after passing through the press roll section, for example from the press roll section to the drying section. Additionally, in conventional press roll sections, the web is pulled through a press nip so that there is a press felt on at least one side of the web that absorbs moisture from the web. The problem of re-absorption of the web after the nip also arises since the web tends to re-absorb moisture into itself after passing through the press nip. Therefore, attempts have been made to prevent re-absorption of moisture by making the web more dense. However, this introduced a new drawback, which was that the risk of tearing the web was considerably increased. As mentioned above, it is economical from an energy consumption point of view if as much moisture as possible can be removed from the web in advance in the press roll section before the web reaches the drying section. . For example, in a paper dryer, roughly speaking, if the moisture content of the web in the press roll section can be reduced by 1%, the water vapor consumption in the drying section can be reduced by 5%.

Further, as mentioned above, increasing the temperature of the paper web is one means for enlarging the dry area in the press roll section.

However, in conventional press roll sections, loose pulling of the web, which is the pulling of the web running without any support, often occurs, so heating the web using, for example, a steam box is not practical. It was extremely difficult. Thus, in the press roll section of the prior art, increasing the temperature has been a problem. Accordingly, in conventional press roll sections, it has been necessary to use expensive press suction rolls, but the use of such rolls is fraught with a number of deficiencies, briefly discussed below.

Perforation by press suction rolls leaves marks in the paper web, which not only detracts from the appearance of the paper but can also affect the surface properties of the paper.Furthermore, perforation by press suction rolls is a difficult and costly process. be. The strength of the shell of the roll is also reduced by the perforation, which requires the use of a special alloy as the material for the roll and an increase in the thickness of the shell, which ultimately leads to an increase in material costs. Furthermore, press suction rolls consume large amounts of air.

Next, U.S. Patent Nos. 3,268,390 and 421,938
No. 3 discloses an oven press roll section with several separate nips formed by a pair of press rolls. The press roll section has the disadvantage, for example, that the web tends to become damp again after passing through the press nip. This reabsorption is the second
This is particularly noticeable between the third nip and the third nip, and is a problem especially when the paper being produced is thin.

Generally, in the above-mentioned conventional press roll section, the degree of dryness of the paper web after passing through the second nip is relatively high, and when the paper web is conveyed to the third nip by the paper web or the press felt, the paper web is dried. reabsorb moisture. In the conventional press roll section mentioned above, an attempt has been made to separate the paper web from the press felt immediately after passing through the third nip, which makes it necessary to convey the paper web to the drying section as an open bow. I also did it raw. In the case of thinning and stretching, the strength of the rolled paper immediately after passing through the press roll section is also relatively low due to the moisture contained therein, so there is a high risk of damage to the rolled paper.

Furthermore, with respect to the press roll section disclosed in U.S. Pat. No. 3,268,390, the conveyance of the paper web onto the second upper press felt after passing through the second nip is carried out via a suction pick-up roll, Again, the re-absorption of moisture in the paper web occurs during the running of the paper web after passing through the suction pickup roll. Furthermore, in the above-mentioned US patent, after passing through the third press nip, the web is stretched open in a drying section. US Patent No. 42
In No. 19383, the paper web is conveyed through all three consecutive press nips by a lower felt which also serves as a press felt. In this case, reabsorption of the web occurs between the nips by reabsorption of moisture from the lower felt into the web after passing through the nip. In Finnish patent application no. 833132, a press roll section of a paper dryer is disclosed which consists of a separate press roll. There, the moisture-absorbing press felt is arranged only on one side of the paper web, so that dehydration takes place only on one surface of one paper web. Furthermore, at least one of the press roll parts
In most press nips, expensive press suction rolls are used. As disclosed in the above-mentioned patent application, the purpose is to achieve a closed tension of the web between the press nips, by arranging the conveying felt on the opposite side of the web with respect to the felt. It supports the paper and transports it from one nip to the other. However, in the Finnish Patent Application No. 833,132 mentioned above, the conveying felt has a smooth surface or is not permeable to water. Finnish patent application no. A water-impermeable conveying felt is provided on the opposite side to achieve closing tension of the web.

Thus, the solution according to this patent application also does not realize dewatering from both sides of the web.

It is an object of the present invention to provide a press roll section that eliminates or at least substantially reduces the defects in conventional press roll sections.

[Means to solve the problem]

To achieve this objective, the main feature of the invention is that through said press nip formed by a surface release roll between the second press felt of the nip and the web,
One or more felts are arranged to provide sufficient support to the web running between the nips, thereby effecting the closing of the web.

While the conveying felt is water permeable, it does not absorb significant amounts of water into itself.

In the press roll section of the present invention, several separate press nips are formed in the direction of travel of the web, thereby removing a significant amount of water from the web. Each press nip is formed between two press rolls, and in the first two of these nips the web runs between two water-permeable press felts, so that the winding does not occur in said nip. Dewatering takes place on both sides of the paper, and at least the first two nips are formed between two surface release rolls.

(Example) Next, a detailed description of the invention will be given with reference to the accompanying drawings.

According to FIGS. 1, 2 and 3, the paper web W is formed on a paper screen 10, which may be a wire-forming screen or a two-wire forming section. It is either a support net.

During the downward travel of the paper screen 1O, between the suction air roll 11 and the paper screen drive roll 12, the web W passes through the first upper felt at the separation point P1 of the suction portion 23 of the pick-up roll 22. 20, said upper felt 20 thus also functioning as a pick-up felt. The first upper fel 1 20 conveys the web W on its bottom side to a first nip press N1, which is between two press rolls, namely a first upper roll 21 and a first lower roll 31. It is formed of. The first upper felt 20 forms an endless loop through a felt roll and a guide roll 24, and the felt roll and guide roll apply appropriate tension to the felt 20. The first nip Nl has two pressed felts, namely the first upper felt 20 and the first lower felt 30, and the first lower felt is also formed into an endless loop through a felt roll and a guide roll 32. are doing. The felt roll and guide roll also provide appropriate tension to the lower felt 30. The press rolls 21 and 31 of the first press nip Nl are surface release rolls shown in broken lines in FIGS. 1-3. In FIG. 4, the release surfaces are identified by reference numerals 21a and 3.
1a.

According to FIGS. 1, 2, and 3, the first press nip N1 is followed by a second press nip N2 at a distance in the direction of the web W, and the second press nip N2 has two press nip N1. It is formed between a press roll, that is, a second upper roll 41 and a second bottom roll 51. 2nd press nip N
2 also two press felts, namely the second upper felt 4
0 and a second lower felt 50. Similar to the first press nip N1, the second upper felt 40 forms an endless loop via a felt roll and a guide roll 42 - the felt roll and guide roll also
Appropriate tension is applied to the upper felt 40. Similarly, the second lower felt 50 forms an entrestrial loop through a felt roll and a guide roll 52, which apply appropriate tension to the second lower felt 50. The press rolls 41 and 51 of the second press nip N2 are also surface open press rolls.

The second press nip N2 is followed by a third press nip N3 at a distance in the direction of the web W. The third press nip N3, shown in the embodiment of FIGS. 1 and 2, is formed between two press rolls, namely the fJIJ3 upper roll 61 and the third lower roll 71.

Press rolls 61 and 71 are of open surface type. As shown in FIGS. 1 and 2, the third breath nip N3 is
Similar to the press nips Nl and N2 described above, it includes two press felts, namely a third upper felt 60 and a third lower felt 70. The press felts 60 and 70 of the third breath nip N3 shown in the embodiments of FIGS.
and 72 to form an endless loop, and the felt roll and guide roll also connect to the felts 60 and 7.
Appropriate tension is applied to 0. As seen in the embodiments of FIGS. 1 and 2, dewatering is performed on both sides of the web W in all press nips N1, N2, and N3.

The embodiment of FIG. 3 differs from FIGS. 1 and 2 in that it includes only a third breath nip N3 or only one press felt, the third lower felt 70. The third
The lower felt forms an entrestrial loop via felt rolls and guide rolls 72, as in FIGS. 1 and 2. Also in the third embodiment, the third lower roll 71 is a surface open press roll as in the previous embodiment. However, in the embodiment of FIG. 3, the third upper roll 61a is a smooth press roll. In the embodiment of FIG. 1, in the press roll section there is a conveying felt 1 which is formed into an entrenched loop via felt, guide and tension rolls 2. In the embodiment shown in FIG. The conveying felt l runs through all press nips N1, N2 and N3 of the press roll section. The conveying felt is made of a material that is permeable to water but does not itself absorb significant amounts of water. As the conveying felt 1, for example, a single-layer thin paper mesh felt can be used, but other materials may also be used. In the embodiment of FIG. 1, the web W is thus supported by the transport felt l throughout its run through the press roll section. In the embodiment shown in FIG. 1, the conveying felt l is arranged to run between the lower felts 30, 50 and 70 and the web W, but it runs between the upper felts 20, 40 and 60 and the web W. It may be arranged so as to run between the paper W and the paper W.

The paper roll W is transported by a conveying felt l in the press roll section.
, it is easy to install a steam box on top of the web W, thereby heating the web W and promoting dehydration. In FIG. 1 the steam box is designated by reference numbers 3, 4 and 5. Among the above steam boxes, the first
The steam box 3 is located inside the first upper felt loop 20, the second steam box 4 is located on the track between the first breath nip N1 and the second breath nip N2, and the third steam box 5 is located on the second Press nip N2
and the third press nip N3. Felt 30 behind the nip as shown in Figure 4
The gap G between the carrier felt 1 and the carrier felt 1 is in a vacuum state due to the air vortex. This vacuum promotes dehydration from the web W through the conveying felt 1, and can reduce reabsorption of moisture into the web W. The above effect can be further increased by installing, for example, a blow suction box in the gap G behind the nip. 1st
In the figure, said blow suction box is schematically shown arranged in the gap G between the conveying felt l and the corresponding felt 30, 50 and 70, behind each nip N1, N2 and N3. In FIG. 1 the blow suction box is indicated by reference numbers 6.7 and 8.

In the embodiment of FIG. 1, after the web W has run through the entire press roll section, the web W is transferred to
1 onto a drying sand screen 80 at a separation point P2. Dry sand! 180 transfers the web W onto the drying cylinder 82.

The embodiment of FIG. 2 differs from the embodiment of FIG. 1 in that each press nip has its own conveying felt. Thus, in this embodiment, the first transport felt 101 runs through the first breather unit Nl.

The first conveying felt 101 forms an endless loop via the felt, the guide, and the stretching roll 102. Similar to FIG. 1, in this embodiment also a steam box 3 is installed inside the upper felt loop 20 to heat the web W. Furthermore, as in Figure 'S1, the first lower felt 30 behind the first nip Nl
A blow suction box 6 is provided in the gap G between the first conveying felt 101 and the first conveying felt 101 .

Similarly, in the second press nip, a second conveying felt 201 runs between the web W and the second lower felt 50. The second conveying felt 201 forms an entrestrial loop via the felt, the guide, and the stretching roll 202. A blow suction box 7 is also installed in the gap between the second conveying felt 201 and the second lower felt 50 behind the second nip N2. Similarly, in the third press nip, the third conveying felt 30
An entresive loop is formed through felt, a guide, and a stretching roll 302. A blow suction box 8 is also provided in the gap between the third conveying felt 301 and the lower felt 7° behind the third nip N3.

In addition, a steam box 9 is provided below the conveying felt 301 in the third breath nip. The steam box 9 sprays steam onto the web W through the conveying felt 301, thereby heating the web.

Similarly to the embodiment shown in FIG. 1, in the embodiment shown in FIG. The paper roll W is transferred onto the first drying cylinder 82 of the drying section.

In the embodiment shown in FIG. 2, the web W is pulled from the conveying felt of the previous press by the upper felt of the subsequent press to close and pull the web. Thus, in FIG.
1 reaches the region of the second upper felt 40, and correspondingly the second conveying felt 201 reaches the third L portion felt 60.
has reached the area of The advantage of the embodiment of FIG. 2 compared to FIG.
01, it is possible to avoid various problems caused by differences in speed between presses. The embodiment of FIG. 2 also includes the conveying felt lots, 201 and 301, in a different correspondence than in FIG. 2, namely the web W and the top felt 20.
40 and 60. Transport felt 1
Other properties and materials of 01, 201 and 301 are the same as those of the conveying felt 1 described in FIG.

As far as the first two presses of the press roll section are concerned, the embodiment of FIG. 3 is completely similar to the embodiment of FIG. 2. Please refer to the above explanation regarding this part. The embodiment of FIG. 3 instead does not use a conveying felt in the third press nip as in the first and second presses. As mentioned above, in this embodiment, the third nip N3 is formed between the open surface lower roll 71 and the smooth press roll 61a. The press felt 70 rotates only around the surface release roll 71, and the L foot lower felt 70 rotates around the felt roll and guide roll 72.
It forms an endless loop. In the embodiment of FIG. 3, the web tension is thus not closed in all press roll sections, but instead the web W is transferred from the second transport felt 201 to the third lower felt 70. When the press nip is opened, an open pull is being performed at a point P3 between the second and third press nips.

From the upper roll 61a of the third press nip, the web is transferred via transport rolls 85 and 81 onto a drying screen 80. Furthermore, the drying grate 80 transports the web W onto a first drying cylinder 82 of the drying section.

In the above description, conveyance felt l, toi.

Requirements are stated for the materials 201 and 301, and it is particularly important that the conveying felt, while having water permeability, does not absorb a large amount of water into itself. Particularly in the press roll section of paper and cardboard dryers, the material of the conveying felt must not be harsh, leaving marks on the web W.

The present invention has been described in detail using the reference numerals in the drawings. Therefore, it will be fully understood that the present invention is not limited to the description shown in the drawings, but that modifications can be made within the scope of the invention as set forth in the claims.

(Effects of the Invention) Compared to the prior art, the present invention has several advantages, such as those described below. The most important advantage of the present invention when compared to the prior art is that the tensioning of the web is carried out as a closed tension, such that the web is supported by a conveying felt. As a result, the press roll section of the present invention can run at a higher speed than the conventional press roll section. Another advantage of the invention is that dewatering takes place on both sides of the web in every press nip, and that the web can be separated from the press felt by a conveying felt immediately after passing through the nip. It is possible to almost completely prevent the web from re-absorbing moisture, and there is no need to use an expensive suction roll as a press roll, and a normal surface release roll can be used. In addition, in the press roll section of the present invention, since the conveying felt supports the web between the nips, it is not necessary to install a steam blower in front of each nip to raise the temperature of the web. It is easy and thus the content of dry parts can be improved.

[Brief explanation of drawings]

FIG. 1 is a schematic side elevational view of a first embodiment of a press roll section according to the present invention. FIG. 2 is an elevational view corresponding to FIG. 1, and shows a second embodiment of the press roll section according to the final stage 11. FIG. 3 is an elevational view corresponding to FIGS. 1 and 2,
A third embodiment of the press roll section according to the present invention is shown. FIG. 4 is a detailed elevational view of the first press nip of the press roll section. [Explanation of symbols of main parts] W... Self... Rolled paper

Claims (1)

[Claims] 1. Several press nips (N1, N2, N3) are separately provided in the direction of travel of the web (W) to remove a considerable amount of moisture from the web (W). and each of the above nips is 2
The paper web (W) is Running between two water permeable felts (20, 30; 40, 50; 60, 70), dewatering is performed on both sides of the winding (W) in the nip (N1, N2), Furthermore, said at least two first nips (N1, N2) are formed between two surface release rolls (21a, 31a) of paper;
In the press roll section of a cardboard or pulp dryer, one or more conveying felts (1; 101, 201,
301) is disposed in the press roll section, the conveying felt has water permeability and has the property of not absorbing a considerable amount of water into itself, and furthermore, the conveying felt is placed in the press to perform closing tension. Nip (N1, N2, N3
) between the second press felt (30, 50, 70) of the nip and the web (W) to provide sufficient support for the web (W) running between 21a, 31a), characterized in that it is arranged to run through a press nip (N1, N2, N3) formed by a press roll (21a, 31a). 2. The conveying felt (1) is formed on an endless loop and press nip (N1,
N2, N3) so that the web (W) is sufficiently supported by the conveying felt (1) throughout the entire process of the press roll section. The press roll part according to claim 1. 3. At least two continuous conveyor felts (101,
201, 301) in the press roll section, the surface release rolls (21, 31; 41, 51; 6
a specific conveying felt (101, 201) arranged to run through at least one press nip (N1, N2, N3) formed by
, 301).The press roll section according to claim 1, characterized in that it comprises: , 301). 4. The unique conveying felt (101, 201, 301) is attached to the surface release roll (21, 31; 41) of the press roll section.
, 51; 61, 71), and is arranged to run through each press nip (N1, N2, N3) formed by a press roll (N1, N2, N3). 5. Separate conveying felts (101, 201, 301) are passed through the previous press nip (N1 or N2) to perform a closing pull from the conveying felt of the previous press nip to the press felt of the next press nip. The running conveyor felt (101 or 201) reaches the area of the press felt (40 or 60) of the next press nip (N2 or N3) and the press felt is located on the opposite side of the web (W). 5. The press roll section according to claim 3, wherein the press roll section is continuously disposed in the press roll section. 6. The blow suction box (6, 7, 8) is made of conveyor felt (1; 101, 201, 301) and press felt (
30, 50, 70) and the surface release rolls (21, 3).
1; 41, 51; 61, 71), and is installed in the gap (G) behind the press nip (N1, N2, N3) formed by Felt (1;
101, 201, 301) to promote dehydration. 7. At least one heating device (3, 4, 5, 9),
One or more conveying felts (1; 1
01, 201, 301), which increases the temperature of the web (W) and improves the dry matter content of the web (W). ,
Press roll part according to 2, 3, 4, 5 or 6. 8. The heating device (3, 4, 5, 9) has a surface release roll (
21, 31; 41, 51; 61, 71) in the press roll section in front of one or more nips (N1, N2, N3) formed by press roll section. 9. Press roll according to claim 7 or 8, characterized in that the heating device comprises a steam box (3, 4, 5, 9) or an equivalent for blowing steam onto the web (W). Department. 10. The steam box (3, 4, 5, 9) has one or more conveyor felts (1:101, 201, 301)
10. Press roll section according to claim 9, characterized in that it is located on the opposite side of the web (W) with respect to the paper web (W).