WO2013026597A1

WO2013026597A1 - Twin-wire former for a machine for producing a fibrous web from at least one fibrous-material suspension

Info

Publication number: WO2013026597A1
Application number: PCT/EP2012/062434
Authority: WO
Inventors: Bernd Güldenberg; Wolfgang Schwarz; Thomas RÜHL; Volker Schmidt-Rohr
Original assignee: Voith Patent Gmbh
Priority date: 2011-08-22
Filing date: 2012-06-27
Publication date: 2013-02-28
Also published as: DE102011081312A1

Abstract

The invention relates to a twin-wire former (1) for a machine (100) for producing a fibrous web (2) from a fibrous-material suspension (3), comprising two wires (4, 5), of which the first wire (4) runs over a forming element (6) and the second wire (5) runs over a guide element (8) and thereafter runs to the first wire (4) in the region of the forming element (6) such as to form a wedge-shaped stock inlet gap (10), which receives the fibrous-material suspension (3) directly from a headbox (11), the two wires (4, 5) having the fibrous-material suspension (3) located therebetween then forming a twin-wire zone (12) in the wire running direction (S), wherein a forming suction box (13) is arranged in the region of the twin-wire zone (12) on the side opposite the forming element (6), over which forming suction box the two wires (4, 5) having the fibrous-material suspension (3) located therebetween are guided, and the two wires (4, 5) having the fibrous-material suspension (3) located therebetween then run over a separating device (17) in the wire running direction (S), wherein the second wire (5) is separated from the fibrous web (2) located on the first wire (4). The twin-wire former (1) according to the invention is characterized in that the first wire (4) having the fibrous web (2) located thereon is then guided over a guide roller (18), which preferably is not suctioned directly through the roller cylinder (18.M), at a roller wrap (18. U) of at least 25°, and that a suction element (20) is arranged between a pick-up roller (19) for picking up the fibrous web (2), which pick-up roller follows the guide roller (18) in the wire running direction (S) on the side opposite the first wire (4), and the guide roller (18).

Description

Twin-wire former for a machine for producing a fibrous web from at least one pulp suspension

The invention relates to a twin-wire former for a machine for producing a fibrous web from at least one pulp suspension, with two circumferential endless screens, of which the first sieve over a peripheral region of at least one forming element, in particular a forming roll or both a guide element, in particular a breast roll and a rigid , curved and suctioned impingement shoe runs and the second wire over a peripheral region of a guide element, in particular a breast roll runs and then in the region of the forming element on the first sieve to form a wedge-shaped material inlet gap, which immediately from a headbox receives the at least one pulp suspension accumulates, the two sieves with the at least one fibrous suspension between them in the direction of wire stretching then at least partially form a double-wire zone, wherein in the region of the twin-wire zone and each other of the Fo a Formiersaugkasten with a preferably curved Formierfläche is arranged, which consists of a plurality of spaced apart and rigid strips, over which the two wires are guided with the at least one located between them pulp suspension, and in the direction of wire direction at least one with a preferably controllable / Forming zone acted upon underpressure forms, and the two sieves with the at least one fibrous suspension between them in the direction of wire winding then via a separating device, preferably a curved and evacuated separating element, in particular a Roller or a stationary Trennsauger, run while the second sieve is separated from the at least one located on the first wire to be produced fibrous web. Such a twin-wire former is known, for example, from the document DE 198 03 591 A1.

The twin-wire former disclosed in each case in FIGS. 1 to 3 and 6 has a screen suction roller after screen separation, ie after the separation of one screen, in particular of the second screen, from the fibrous web to be produced on the other screen. The use of such a suction sieve causes high acquisition and operating costs. An acquisition cost of considerable height has to be applied for the suction sieve roll (operating roll and a reserve roll). Moreover, the extraction of the suction sieve designed consuming and therefore high operating costs due to increased energy and maintenance costs. In addition, the gutter leads to Siebsaugwalze double doubling not inconsiderable high costs. It is therefore an object of the invention to develop a twin-wire former of the type mentioned in such a way that an energy-efficient drainage without Siebsaugwalze is made possible with sufficient sieve or process stability. It should also be the production of a fibrous web with a production rate of about 1 .800 m / min, preferably of more than 1, 500 m / min, ie the highest speed potential, but no disadvantages in terms of achievable product quality and runnability, possible.

This object is achieved in a twin-wire former of the type mentioned according to the invention that the first sieve with the fibrous web thereon thereon then preferably not directly through the roll jacket sucked guide roll at a roll wrap of at least 25 °, preferably of at least 35 °, in particular of at least 45 °, is guided and that between one of the guide roll of each other of the first sieve in the direction of wire sieve subsequent pickup roller for the decrease of the fibrous web to be produced and the Guide roller at least one preferably controllable / controllable suction element, in particular a suction box is arranged.

The object of the invention is completely solved in this way. The inventive provision of a preferably not directly sucked through the roll shell, so no holding forces generating guide roll with sufficient Walzenumschlingung and downstream in Sieblaufrichtung suction, in particular suction box ensures energy-efficient drainage with adequate sieve or process stability. From the use of a hitherto used and the disadvantages described sieve suction can therefore be dispensed with altogether. In addition, the production of a fibrous web with a production rate of more than 1, 800 m / min, preferably of more than 1 500 m / min, ie with the highest speed potential possible, and this without any disadvantages in terms of achievable product quality and runnability.

The preferably not directly drawn through the roll shell guide roll preferably has a grooved, blind drilled, drilled or otherwise structured surface structure. Such a surface structure of the guide roller effectively prevents floating due to a possible fluid absorption and thus a bleeding of the first sieve with overlying fibrous web to be produced in this former region. The first sieve is thus reliably stabilized in its barrel. For this purpose, the guide roller, in particular the surface structure of the guide roller also preferably an open area of> 20%, preferably of> 30%, in particular of> 40%, on. In a preferred embodiment, the forming element is a forming roll having a roll diameter in the range of 1, 000 to 2,500 mm, preferably 1, 500 to 2,000, in particular 1, 700 to 1, 900 mm. In this case, the two wires extend with the at least one fibrous suspension between them in one of the forming roller downstream in the wire direction of the double-wire zone at an angle of 10 to 50 °, preferably from 20 to 40 °, in particular from 25 to 35 °, to an imaginary vertical plane downward. The forming roller ensures a fast and efficient initial drainage of the introduced pulp suspension and the course down brings, inter alia, the advantage of a shortened, but still efficient drainage of the introduced pulp suspension. The twin-wire zone may extend down to an imaginary vertical plane immediately after the end of the first wire from the forming roller in a limited range at an angle of> 0 to 45 °, preferably from> 0 to 30 °, in particular from> 5 to 15 ° ,

Furthermore, between the arranged in the wire loop of the second screen Formiersaugkasten and disposed in the wire loop of the first screen separator, preferably the curved and evacuated separating element, in particular the roller or the stationary separating sucker, preferably a deflection device, preferably a deflecting element, in particular a guide roller, arranged in the wire loop of the second screen. After this deflection, the two wires extend with the at least one fibrous suspension between them at an angle, preferably at an angle of> 0 to 45 °, in particular at an angle of 5 to 25 °, to an imaginary horizontal plane upwards. Among other things, the deflection device and the subsequent upward course provide the advantage of a markedly shortened, but still efficient, dewatering of the incorporated pulp suspension. And in a preferred alternative embodiment, the forming element is a rigid, curved and suctioned impingement shoe having a shoe length of 200 to 2,000 mm, preferably 300 to 1,500 mm, more preferably 400 to 1,200 mm. In this case, the two wires extend with the at least one fibrous suspension between them in an impingement shoe in the direction of wire downstream of the double-wire zone at an angle of> 0 to 45 °, preferably from 5 to 25 °, to an imaginary horizontal plane upwards. This impingement shoe also ensures fast and efficient initial drainage of the introduced pulp suspension and the course upwards provides, inter alia, the course of a shortened, but still efficient drainage of the introduced pulp suspension.

In both preferred embodiments, in the at least one forming zone, opposite the forming suction box and in the wire direction at a distance from the leading edge of the first rigid strip of Formiersaugkastens at least two arranged between each two adjacent and rigid strips of Formiersaugkastens formation strips are provided, which are supported by means of resilient elements and which are pressed with a selectable force against the touching first sieve. This embodiment has a positive effect on improving the formation in the fibrous web to be produced, in particular due to the introduction of shear forces.

Alternatively and / or additionally, preferably at least one deflector is provided in the at least one forming zone, opposite the forming suction box and in the direction of wire run at a distance from the leading edge of the first rigid strip of the forming suction box. This embodiment also has a positive effect on improving the formation in the fibrous web to be produced, in particular due to the introduction of shear forces. Furthermore, the rolls of the twin-wire former according to the invention are preferably designed such that the sum of all roll deflections in the web or machine center of the rolls, resulting from a total load, in particular a total operating load, including, inter alia, the wire tension and the dead weight, <10 mm, preferably < 7 mm, in particular <5 mm. The inventive and not sucked through the roll shell guide roller provides the disadvantage of a Haftkraftverl usts against the screen, so a reduction in the screen stability. In order for this disadvantage to be made up for the most part again, the sieve must be stabilized otherwise. One way of stabilizing the screen is in the mentioned type of allowable sum of the roll deflections.

Also, the ratio of the difference of the length of a respective wire loop from edge to center based on the entire length of this wire loop is preferably <5%, preferably <4%, in particular <3%.

Of course, a machine for producing a fibrous web, in particular a paper, cardboard or packaging paper web of at least one pulp suspension may be provided with at least one twin-wire former according to the invention.

Here, the twin-wire former is preferably arranged downstream of a press section with at least one press unit, in particular a shoe press, preferably directly in the machine or wire feed direction. Such a press section leads to a further and marked increase in the dry content of the fibrous web to be produced at a reasonable cost and acceptable quality disadvantages.

Further features and advantages of the invention will become apparent from the following description of several preferred embodiments with reference to the drawings. Show it

Figures 1 to 3 are schematic side views of preferred

Embodiments of a respective Doppelsiebfornners invention for a machine for producing a fibrous web; and

Figure 4 is a schematic representation of the forces acting on its rollers during operation of the twin-wire former according to the invention.

Figures 1 to 3 show schematic side views of preferred embodiments of a respective Doppelsiebformers 1 for a machine not shown 100 for producing a fibrous web 2 (dashed line) of at least one pulp suspension 3. The produced fibrous web 2 is in particular an at least single-layered Paper, cardboard or packaging paper web.

The respective twin-wire former 1 comprises two continuous endless sieves 4, 5, of which the first sieve 4 runs over a peripheral region 7 of both a known guide element, in particular a breast roll, and a forming element 6. The second wire 5, however, runs over a peripheral region 9 of a guide element 8, in particular a breast roll 8.1 and then in the region of the forming element 6 on the first wire 4 to form a wedge-shaped material inlet gap 10, the directly from a headbox 1 1, the at least one pulp suspension third picks up.

The two screens 4, 5 with the at least one fibrous suspension 3 between them form in Sieblaufrichtung S (arrow) then at least partially a twin-wire zone 12. In the area of this Doppelsiebzone 12 and each other of the forming element 6 is a known Formiersaugkasten 13, in the art as well Upper sieve suction box, arranged with a preferably curved forming surface 13.F. It consists of a plurality of mutually spaced and rigid strips 14, via which the two wires 4, 5 are guided with the at least one fibrous suspension 3 located between them. Moreover, it forms in Sieblaufrichtung S (arrow) at least one with a preferably controllable / regulate ble vacuum pu acted upon forming zone 15 from. The preferably controllable negative pressure pu in the forming zone 15 is generated by means of a known to those skilled and only schematically indicated negative pressure source 16. Subsequently, the two wires 4, 5 run with the at least one between them pulp suspension 3 in wire direction S (arrow) via a separator 17, preferably a curved and evacuated separating element 17.1, in particular a roller, not shown, or a stationary vacuum cleaner shown. In this case, the second sieve 5 is separated from the at least one fibrous web 2 located and to be produced on the first sieve 4.

Now, the first wire 4 with the thereon and to be produced fibrous web 3 via a preferably not directly through the roll shell 18.M suctioned guide roller 18 at a roll turn 18.U of at least 25 °, preferably at least 35 °, in particular at least 45 ° , guided. And between one of the guide roller 18 of each other of the first sieve 4 in wire direction S (arrow) subsequent pickup roller 19 for the decrease of the produced fibrous web 3 and the guide roller 18 is a preferably tax- / rule Bares suction member 20, in particular a suction box 20.1 arranged. Of course, it is also possible to provide a plurality of preferably controllable suction elements, in particular suction boxes, in this region of the twin-wire former 1. The preferably not directly sucked through the roll shell 18.M guide roller 18 has on the one hand a grooved, blind drilled, drilled or otherwise structured Surface structure 18.S, on the other hand, an open area 18.F of> 20%, preferably of> 30%, in particular of> 40%, on.

In the two embodiments of FIGS. 1 and 2, the forming element 6 is a forming roller 6.1 which has a roller diameter 6.1 D in the range from 1 .000 to 2,500 mm, preferably from 1 .500 to 2,000 mm, in particular from 1 .700 to 1,900 mm, has.

Furthermore, the two wires 4, 5 extend with the at least one fibrous suspension 3 located between them in a region of the twin-wire zone 12 arranged downstream of the forming roller 6.1 in the wire direction S (arrow) at an angle A of 10 to 50 °, preferably 20 to 40 °, in particular from 25 to 35 °, to an imaginary vertical plane V down.

The twin-wire zone 12 moreover passes immediately after the passage of the first wire 4 from the forming roller 6.1 in a limited range at an angle of> 0 to 45 °, preferably from> 0 to 30 °, in particular from> 5 to 15 °, to an imaginary Vertical plane down.

Between the forming suction box 13 arranged in the wire loop of the second wire 5 and the separating device 17 arranged in the wire loop of the first wire 1, a deflection device 21, preferably a deflection element 21 .1, in particular a deflection roller, is arranged in the wire loop of the second wire 5. Furthermore, the two wires 4, 5 extend with the at least one fiber suspension 3 located between them after the deflection device 21, preferably the deflection element 21 .1, in particular the guide roller, at an angle B, preferably at an angle B of> 0 to 45 °, in particular at an angle B of 5 to 25 °, to an imaginary horizontal plane H upwards. Also, in the embodiment of FIG. 1, in the forming zone 15, opposite the forming suction box 13 and in the wire-running direction S (arrow) in FIG a distance C to the leading edge of the first rigid bar 14 of Formiersaugkastens 13 at least two arranged between each two adjacent and rigid bars 14 of Formiersaugkastens 13 formation strips 22 which are supported by resilient elements 23 and with a selectable force 23. K (arrow ) are pressed against the contacting first sieve 4. Of course, instead of the formation strip 22, a deflector known to the person skilled in the art (see FIG.

On the other hand, in the embodiment of FIG. 2, at least one deflector 24 is provided in the forming zone 15, opposite the forming suction box 13 and in the wire running direction S (arrow) at a distance C from the leading edge of the first rigid bar 14 of the forming suction box 13. Of course, instead of the deflector 24, a flexible and compressible formation strip known to those skilled in the art (see FIG.

In the embodiment of FIG. 3, the forming element 6 is a rigid, curved and suctioned impingement shoe 6.2 with a shoe length 6.2L of 200 to 2,000 mm, preferably of 300 to 1,500 mm, in particular of 400 to 1,200 mm.

Furthermore, the two wires 4, 5 extend with the at least one fibrous suspension 3 located between them in a region of the twin-wire zone 12 downstream of the impingement shoe 6.2 in the wire-winding direction S (arrow) at an angle D of> 0 to 45 °, preferably of 5 to 25 ° , to an imaginary horizontal plane H upwards.

Also, in the embodiment of FIG. 3, in the forming zone 15, opposite the forming suction box 13 and in the wire direction S (arrow) at a distance C from the leading edge of the first rigid bar 14 of the forming suction box 13, at least two between each two adjacent and rigid bars 14 of the Formiersaugkastens 13 arranged formation strips 22nd provided, which are supported by means of resilient elements 23 and which are pressed with a selectable force 23 K against the first sieve 4 touching them. FIG. 4 shows a schematic and exemplary representation of the forces acting on its rollers during the operation of a twin-wire former 1. The individual rolls are independent of their roll type (forming roll, guide roll, guide roll, guide roll, etc.) consistently provided with the letter W and the individual acting forces are represented as a function of their effective size and effective direction by a bar and consistently provided with the letter K. ,

The rolls W of the twin-wire former 1 according to the invention are now designed such that the sum of all roll deflections in the web or machine center of the rolls W, resulting from a total load, in particular a total operating load, including, inter alia, the wire tension and the own weight, <10 mm, preferably <7 mm, in particular <5 mm. Furthermore, the ratio of the difference of the length of a respective wire loop formed from the respective wire 4, 5, from edge to center based on the entire length of this wire loop <5%, preferably <4%, in particular <3%. The double-wire former 1 according to the invention, which is shown schematically and at least partially in each case in FIGS. 1 to 4, is particularly suitable for use in a machine 100 for producing a fibrous web 2, in particular a paper, board or packaging paper web from at least one fibrous stock suspension. In this case, the twin-wire former 1 is preferably followed by a press section known to the person skilled in the art with at least one press unit, in particular a shoe press, directly in the machine or wire direction. In summary, it should be noted that a twin-wire former of the type mentioned above is further developed by the invention so that an energy-efficient drainage without Siebsaugwalze is made possible with sufficient Sieb- or process stability. Also, the production of a fibrous web with a production rate of about 1 .800 m / min, preferably of over 1, 500 m / min, ie with the highest speed potential, but no disadvantages in terms of achievable product quality and runnability possible.

LIST OF REFERENCE NUMBERS

1 twin wire former

2 fibrous web

3 pulp suspension

4 First sieve

5 second sieve

6 forming element

6.1 Forming roller

6.1 D roller diameter

6.2 Impingement shoe

6.2L shoe length

7 peripheral area

8 guide element

8.1 breast roll

9 peripheral area

10 fabric inlet gap

1 1 headbox

12 twin-wire zone

13 forming suction box; Upper sieve suction box 13.F Forming surface

14 bar

15 forming zone

16 negative pressure source

17 separating device

17.1 separating element; suction separator

18 guide roller

18.F Open area

18.M roll jacket

8.S surface structure

18.U roll wrap 19 pickup roller

20 suction element

20.1 Suction box

21 redirecting

21 .1 Umlenkelennent; deflecting

22 formation bar

23 Resilient element

23.K Selectable force

24 deflector

100 Machine for producing a fibrous web

A angle

B angle

C distance

D angle

H horizontal plane

K force (bar)

pu negative pressure

S wire direction (arrow)

V vertical plane

W roller

Claims

claims

Double-wire former (1) for a machine (100) for producing a fibrous web (2), in particular a paper, board or packaging paper web from at least one pulp suspension (3), with two continuous endless screens (4, 5), of which the first Sieve (4) over a peripheral region (7) of at least one forming element (6), in particular a forming roller (6.1) or both a guide element, in particular a breast roll and a rigid, curved and suctioned Impingementschuhs (6.2) runs and the second sieve (5 ) over a peripheral region (9) of a guide element (8), in particular a breast roll (8.1) and then in the region of the forming element (6) on the first sieve (4) to form a wedge-shaped Stoffeinlaufspalts (10), directly from a Headbox (1 1) receives at least one pulp suspension (3) accumulates, the two sieves (4, 5) with the at least one between them fibrous suspension (3) in Siebl erection (S) then at least in sections form a double-wire zone (12), wherein in the region of the twin-wire zone (12) and each other of the forming element (6) a Formiersaugkasten (13) having a preferably curved forming surface (13 a plurality of mutually spaced and rigid strips (14) over which the two wires (4, 5) are guided with the at least one fibrous suspension (3) between them, and in the direction of the wire (S) at least one with a preferably control / controllable negative pressure (pu) acted upon forming zone (15), and the two sieves (4, 5) with the at least one between them pulp suspension (3) in the wire direction (S) then via a separating device (17), preferably a curved and suctioned separating element (17.1), in particular a roller or a stationary separating suction, run, wherein the second sieve (5) of the at least one located on the first sieve (4) and to be produced fibrous web (2) is separated,

characterized,

in that the first sieve (4) with the fibrous web (2) thereon and to be produced subsequently has a guide roll (18) preferably not directly drawn through the roll shell (18.M) at a roll turn (18.U) of at least 25 °, preferably is guided by at least 35 °, in particular by at least 45 °, and that between one of the guide roller (18) of each other of the first sieve (4) in the wire direction (S) subsequent pickup roller (19) for the decrease of the fibrous web to be produced (2) and the guide roller (18) at least one preferably controllable / rule Bares suction element (20), in particular a suction box (20.1) is arranged.

2. twin wire former (1) according to claim 1,

characterized,

the guide roll (18), which is preferably not directly drawn through the roll shell (18.M), has a grooved, blind drilled, drilled or otherwise structured surface structure (18.S).

3. twin-wire former (1) according to claim 2,

characterized,

the guide roller (18), in particular the surface structure (18.S) of the guide roller (18), has an open area (18.F) of> 20%, preferably of> 30%, in particular of> 40%.

Twin-wire former (1) according to claim 1, 2 or 3,

characterized,

that the forming element (6) is a forming roller (6.1) having a roller diameter (6.1 D) in the range of 1 .000 to 2,500 mm, preferably 1 .500 to 2,000 mm, in particular 1 .700 to 1,900 mm, and in that the two screens (4, 5) with the at least one fibrous suspension (3) located in one of the forming rollers (6.1) downstream in the screen direction (S) of the twin-wire zone (12) at an angle (A) of 10 to 50 ° , Preferably from 20 to 40 °, in particular from 25 to 35 °, to an imaginary vertical plane (V) run down.

Twin-wire former (1) according to one of the preceding claims,

characterized,

in that the forming suction box (13) arranged in the wire loop of the second wire (5) and the separating device (17) arranged in the wire loop of the first wire (4), preferably the curved and vacuumed separating element (17.1), in particular the roller or the stationary one Separating suction, a deflection device (21), preferably a deflection element (21 .1), in particular a guide roller, in the wire loop of the second wire (5) is arranged, wherein the two wires (4, 5) with the at least one fibrous suspension between them (3) after the deflection device (21), preferably the deflection element (21 .1), in particular the guide roller, at an angle, preferably at an angle (B) of> 0 to 45 °, in particular at an angle of 5 to 25 ° , up to an imaginary horizontal plane (H).

Twin-wire former (1) according to claim 1,

characterized, in that the forming element (6) is a rigid, curved and suctioned impingement shoe (6.2) with a shoe length (6.2L) of 200 to 2,000 mm, preferably of 300 to 1,500 mm, in particular of 400 to 1,200 mm; the two sieves (4, 5) with the at least one fiber suspension (3) located between them in a region of the twin-wire zone (12) arranged downstream of the impingement shoe in the wire-winding direction (S) at an angle (D) of> 0 to 45 °, preferably of 5 to 25 °, to an imaginary horizontal plane (H) upwards.

7. twin-wire former (1) according to one of the preceding claims,

characterized,

in that in the at least one forming zone (15), opposite the Formiersaugkasten (13) and in wire direction (S) at a distance (C) to the leading edge of the first rigid strip (14) of Formiersaugkastens (13) at least two between each two adjacent and formation strips (22) are provided, which are supported by means of resilient elements (23) and which are pressed with a selectable force (23. K) against the first sieve (4) contacting them.

8. twin-wire former (1) according to one of the preceding claims,

characterized,

in that at least one deflector (24) is provided in the at least one forming zone (15), opposite the forming suction box (13) and in the wire running direction (S) at a distance (C) from the leading edge of the first rigid strip (14) of the forming suction box (13) is.

9. twin wire former (1) according to one of the preceding claims,

characterized,

the rolls (W) are designed such that the sum of all roll deflections in the web or machine center of the rolls (W), resulting from a total load, in particular a total operating load, including, inter alia, the wire tension and its own weight, <10 mm, preferably <7 mm, in particular <5 mm.

10. twin-wire former (1) according to one of the preceding claims,

characterized,

the ratio of the difference of the length of a respective wire loop from edge to center, based on the total length of this wire loop, is <5%, preferably <4%, in particular <3%.

1 1. Machine (100) for producing a fibrous web (2), in particular a paper, board or packaging paper web from at least one pulp suspension (3),

characterized,

in that it comprises at least one twin-wire former (1) according to one of the preceding claims.

12. Machine (100) according to claim 1 1,

characterized,

that the twin-wire former (1) preferably directly in Maschinenbzw. Sieblaufrichtung (S) downstream of a press section with at least one press unit, in particular a shoe press.