Device and method for producing a fibrous web

Abstract

A device and a method for producing a pulp web in which the first clothing and the second clothing are wrapped partly round the forming roll and another roll. The pulp web formed is guided between the forming roll and the other roll on the first clothing and the second clothing is guided separately from the first clothing, at least in one section. This enables the pulp web to be produced with low energy consumption and operating costs.

Claims

1. A device for producing a pulp web (9), comprising: a headbox (1), a first clothing run comprising a continuously revolving clothing (4) and first clothing guides, and defining an inside and an outside, a second clothing run comprising a second continuously revolving clothing (3) and second clothing guides, and defining an inside and an outside, a forming roll (2) disposed on the inside of the first continuously revolving clothing (4), at least one other roll (11) disposed on the inside of the first continuously revolving clothing (4), an external clothing guide (13), and a means for reducing a water load in the second revolving clothing (3) provided between the forming roll (2) and the other roll (11), wherein the first continuously revolving clothing (4) is wrapped partly around the forming roll (2) and the other roll (11) with the forming roll (2) and the other roll (11) disposed on the outside of the second continuously revolving clothing (3), the second continuously revolving clothing (3) is wrapped partly around the forming roll (2) and the other roll (11), the first continuously revolving clothing (4) is disposed between the second continuously revolving clothing (3) and the forming roll (2), the first continuously revolving clothing (4) is disposed between the second continuously revolving clothing (3) and the other roll (11) and between the forming roll (2) and the headbox (1) for placing a pulp suspension between the first continuously revolving clothing (4) and the second continuously revolving clothing (3), the second clothing run has the external clothing guide (13) positioned between the forming roll (2) and the other roll (11) to guide the second continuously revolving clothing (3) separately from the first continuously revolving clothing (4) in a section between the forming roll (2) and the other roll (11), the external clothing guide (13) is disposed on the outside of the second continuously revolving clothing (3), the external clothing guide (13) is disposed between the first continuously revolving clothing (4) and the second continuously revolving clothing (3), and the water load is reduced in the section of the second continuously revolving clothing (3) that is separately guided between the forming roll (2) and the other roll (11) by the means for reducing a water load.

2. The device according to claim 1, wherein the first continuously revolving clothing (4) is a felt and the second continuously revolving clothing (3) is a forming fabric.

3. The device according to claim 1, wherein the other roll (11) is a suction roll.

4. The device according to claim 3, comprising a steam blow box or a dryer hood provided in an area of the other roll (11) configured to apply one or both of hot air and steam in a direction toward the other roll (11), wherein the steam blow box or dryer hood is disposed on the inside of the second clothing run.

5. The device according to claim 1, wherein the means for reducing a water load is configured as one or more of suction strips, suction boxes, air nozzles, slotted nozzles and air blades provided between the forming roll (2) and the other roll (11) and configured to reduce the water load in the section of the second continuously revolving clothing (3) that is separately guided.

6. The device according to claim 5, wherein the means for reducing water load comprises one or more of suction strips, suction boxes, air nozzles, slotted nozzles and air blades disposed for dispersion on the outside of the second clothing run.

7. The device according to claim 6, wherein the means for reducing a water load comprises one or more of suction strips, suction boxes, air nozzles, slotted nozzles and air blades disposed in an inlet area between the external clothing guide (13) and the second continuously revolving clothing (3).

8. The device according to claim 5, wherein the means for reducing a water load comprises one or both of suction strips and suction boxes provided between the forming roll (2) and the other roll (11) and configured for applying suction to the second continuously revolving clothing (3) in the section of the second continuously revolving clothing (3) that is separately guided.

9. The device according to claim 1, comprising a press roll (10) disposed on the inside of the second clothing run in an area of the other roll (11), thereby forming a pressing area with the other roll (11).

10. The device according to claim 1, wherein the means for reducing a water load comprises one or both of suction strips and suction boxes provided between the forming roll (2) and the other roll (11) and configured for applying suction to the second continuously revolving clothing (3) in the section of the second continuously revolving clothing (3) that is separately guided.

11. The device according to claim 6, wherein the means for reducing a water load additionally comprises one or both of suction strips and suction boxes provided between the forming roll (2) and the other roll (11) and configured for applying suction to the second continuously revolving clothing (3) in the section of the second continuously revolving clothing (3) that is separately guided.

12. The device according to claim 7, wherein the means for reducing a water load additionally comprises one or both of suction strips and suction boxes provided between the forming roll (2) and the other roll (11) and configured for applying suction to the second continuously revolving clothing (3) in the section of the second continuously revolving clothing (3) that is separately guided.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The invention will now be described using the examples in the drawings.

(2) FIG. 1 shows a device for producing a pulp web according to the state of the art.

(3) FIG. 2 shows another device for producing a pulp web according to the state of the art.

(4) FIG. 3 shows a first device for producing a pulp web.

(5) FIG. 4 shows a second device for producing a pulp web.

(6) FIG. 5 shows a third device for producing a pulp web.

DETAILED DESCRIPTION

(7) FIG. 1 shows a device for producing a pulp web 9 according to the state of the art shown in WO 2017/060053 A1. Here, a pulp suspension is fed through a headbox 1 and placed on a first revolving clothing 4 that is a felt and a second revolving clothing 3 that is a forming fabric and dewatered by centrifugal force in the area of a forming roll 2, the felt and the forming fabric being wrapped partly round the forming roll 2 and the felt being guided between the forming roll 2 and the forming fabric. The felt and the forming fabric are guided over another roll 11 directly after the forming roll 2, the other roll 1 being a suction roll and the felt and the forming fabric being wrapped partly round the other roll 11. Here, the felt is guided between the other roll 11 and the forming fabric. In order to aid dewatering at the other roll 11, a means 12 of applying hot air and/or steam can be provided, the other roll 11 then advantageously being a suction roll. The pulp web 9 is carried on the first clothing 4 after the other roll and is further dewatered. As an option, an impingement dryer 8 can be provided for thermal drying of the pulp web 9. The pulp web is transferred in a press nip from the felt to a Yankee 6, further mechanical dewatering being obtainable in the press nip. The web undergoes further thermal drying on the Yankee 6, an optional Yankee hood 7 permitting improved thermal drying. Hence, Yankee hoods 7 are typically impingement dryers. The pulp web 9 is typically removed from the Yankee 6 by creping.

(8) FIG. 2 shows another state-of-the-art device for producing a pulp web 9. Here, a pulp suspension is fed through a headbox 1 and placed on a first revolving clothing 4 that is a felt and a second revolving clothing 3 that is a forming fabric and dewatered by centrifugal force in the area of a forming roll 2, the felts and the forming fabric being wrapped partly round the forming roll 2 and the felt being guided between the forming roll 2 and the forming fabric. The forming fabric is lifted off the felt on the forming roll 2 or immediately after it, the pulp web 9 being carried onwards on the felt and further dewatered. As an option, an impingement dryer 8 can be provided for thermal drying of the pulp web 9. In a press nip, the pulp web is transferred from the felt to a Yankee 6, further mechanical dewatering being feasible in the press nip. The web undergoes further thermal drying on the Yankee 6, an optional Yankee hood 7 permitting improved thermal drying. Hence, Yankee hoods 7 are typically impingement dryers. The pulp web 9 is typically removed from the Yankee 6 by creping.

(9) FIG. 3 shows a first device according to the disclosure for producing a pulp web, the pulp web 9 being, in particular, a tissue or a sanitary paper web. In order to form the pulp web 9, a pulp suspension is fed through a headbox 1 and placed between a first revolving clothing 4 that is a felt and a second revolving clothing 3 that is a forming fabric, and then dewatered by centrifugal force in the area of a forming roll 2. Here, the first clothing 4 and the second clothing 3 are wrapped partly round the forming roll 2, the first clothing 4 being guided between the forming roll 2 and the second clothing 3. The first clothing 4 and the second clothing 3 are wrapped round part of another roll 11, the first clothing 4 being guided between the other roll 11 and the second clothing 3. In particular, the pulp web 9 formed is guided between the forming roll 2 and the other roll 11 on the first clothing 4, the second clothing 3 being guided separately from the first clothing 4 between the forming roll 2 and the other roll 11, at least in one section 5. As shown in FIG. 3, the second clothing 3 is lifted off the first clothing 4 while still on the forming roll 2 and guided over the external web guide 13 of the second clothing run, the pulp web 9 being carried onward on the first clothing 4. The second clothing 3 is then placed on the first clothing 4 again on the other roll 11, the section 5 being defined as the area between the forming roll 2 and the other roll 11 where the second clothing 3 is guided separately from the first clothing 4. In this section 5, the water load in the second clothing 3 guided separately is reduced by various means of reducing the water load, the means of reducing the water load comprising means 14 of dispersing a fluid and/or means 15 of applying suction to the second continuously revolving clothing 3. The means 14 of dispersing a fluid is disposed advantageously outside the second clothing run, where it makes sense to use air, compressed air, hot air, process air, etc., as fluid, and a specialist would consider compressed air nozzles, slotted nozzles and air blades as obvious such devices 14 for dispersing a fluid. Similarly, it is an advantage to dispose the means 14 of dispersing a fluid in the inlet area between the external clothing guide 13 and the second continuously revolving clothing 3. The means 15 of applying suction to the second continuously revolving clothing comprise suction strips, suction boxes, or similar. Advantageously, the other roll 11 is a suction roll, hot air and/or steam being applied optionally to the forming fabric through a means of applying hot air and/air steam and the suction roll drawing the hot air and/or steam by suction through the forming fabric in the direction of the pulp web 9. According to the invention, the pulp web 9 is carried on the first clothing 4 after the other roll 11 and further dewatered mechanically and/or thermally.

(10) FIG. 4 shows a second device according to the invention for producing a pulp web. Compared to the illustration of the first device according to the invention in FIG. 3, the illustration of the second device according to the invention in FIG. 4 differs particularly in that a press roll 10 is disposed in the area of the other roll 11 inside the second clothing run, a pressing area being able to be formed by the other roll 11 and the press roll 10, and the first revolving clothing, the pulp web 9 and the second revolving clothing 3 being guided through the pressing area. The other explanations relating to the first device according to the invention in FIG. 3 also apply to the second device according to the invention in FIG. 4.

(11) FIG. 5 shows a third device according to the invention for producing a pulp web. Compared to the illustration of the first device according to the invention in FIG. 3, the illustration of the third device according to the invention in FIG. 5 differs particularly in that the second clothing 3 is not lifted off the first clothing 4 until after the forming roll 2 and is guided over the external web guide 13 of the second clothing run, the pulp web 9 being guided onward on the first clothing 4. The second clothing 3 is then placed on the first clothing 4 again before the other roll 11, the section 5 being defined as the area between the forming roll 2 and the other roll 1 in which the second clothing 3 is guided separately from the first clothing 4. The other explanations relating to the first device according to the invention in FIG. 3 also apply to the third device according to the invention in FIG. 5.

(12) The inventive embodiments thus offer numerous advantages. They provide optimized production of a pulp web with significantly improved dewatering of the pulp web in the area between the forming roll and the other roll. In particular, this significant improvement in dewatering of the pulp web can be achieved by simple means, such as means of dispersing a fluid, the fluid enabling a reduction in the water load of the second revolving clothing and, in consequence, a significant improvement in dewatering of the pulp web at the other roll. In this way, overall energy consumption compared to state-of-the-art solutions can be reduced. In addition, the solution according to the invention enables these benefits to be achieved with low investment costs, two revolving clothings, i.e. a first and a second, being sufficient to achieve this. Furthermore, the invention provides an improvement in the quality characteristics of the pulp web, such as its bulk or caliper, because the improvement in dewatering of the pulp web enables improved ability to achieve these quality characteristics in subsequent drying of the pulp web, particularly in subsequent mechanical pressing.

REFERENCE NUMERALS

(13) (1) Headbox (2) Forming roll (3) Second revolving clothing, forming fabric (4) First revolving clothing, felt (5) Section (6) Yankee (7) Yankee hood (8) Impingement dryer (9) Pulp web (10) Press roll (11) Other roll (12) Means of applying hot air and/or steam (13) External clothing guide (14) Means of dispersing a fluid (15) Means of applying suction