Method for producing a fibrous material web

Abstract

A method for producing a fibrous material web, particularly for producing a tissue or hygienic paper web, in which a fibrous suspension is dewatered in a crescent former to obtain a fibrous material web, and dried on a Yankee. After the crescent former, the fibrous material web is guided along with the forming screen and felt over a suction roller downstream of the forming roller. A device for carrying out the method for producing a fibrous material web.

Claims

1. A method for production of a fibrous pulp web (9), comprising: in a Crescent former (10), feeding a fibrous pulp suspension through a headbox (1) between a forming wire (3) and a felt (4) to dewater the fibrous pulp suspension by centrifugal force in the area of a forming roll (2) to form a fibrous pulp web (9), guiding the fibrous pulp web (9) over a suction roll (11) together with the forming wire (3) and the felt (4) directly after the forming roll (2) to dry the fibrous pulp web (9) with the aid of a Yankee (6), wherein the felt (4) is between the suction roll (11) and the fibrous pulp web (9) and the forming wire (3) is wrapped around the fibrous pulp web (9) on the outside.

2. The method of claim 1, wherein the fibrous pulp web (9) is wrapped round the suction roll (11) in places and a hot fluid flows through the fibrous pulp web (9) on the suction roll (11).

3. The method of claim 2, wherein the hot fluid is air at a temperature of more than 150 C.

4. The method of claim 3, wherein the air flowing through the fibrous pulp web (9) has a moisture content of more than 150 g H.sub.2O/kg air.

5. The method of claim 3, wherein the air is exhaust air from a Yankee hood (7).

6. The method of claim 5, wherein the felt has multiple layers, including a first layer defining a first surface facing the fibrous pulp web having a first average fineness that is less than 6.7 dtex, a second layer directly beneath the first layer having a second average fineness that is less than 17 dtex, and a third layer defining a third surface facing the suction roll having a third average fineness that is greater than 17 dtex.

7. The method of claim 3, wherein the felt has multiple layers, including a first layer defining a first surface facing the fibrous pulp web having a first average fineness that is less than 6.7 dtex, a second layer directly beneath the first layer having a second average fineness that is less than 17 dtex, and a third layer defining a third surface facing the suction roll having a third average fineness that is greater than 17 dtex.

8. The method of claim 2, wherein steam flows through the fibrous pulp web (9) in an initial section of the suction roll (11).

9. The method of claim 1, wherein the fibrous pulp web (9) is conveyed to the Yankee (6) on the felt (4).

10. The method of claim 9, wherein the fibrous pulp web (9) is transferred to the Yankee (6) with the aid of a shoe press roll (5), and the felt is wrapped around the shoe press roll (5) at an angle of more than 60.

11. The method of claim 10, wherein the felt is wrapped around the shoe press roll (5) at an angle of more than 90.

12. The method of claim 1, wherein the felt has multiple layers, including a first layer defining a first surface facing the fibrous pulp web having a first average fineness, a second layer directly beneath the first layer having a second average fineness that is greater than the first average fineness, and a third layer defining a third surface facing the suction roll having a third average fineness that is greater than the second average fineness.

13. The method of claim 1, wherein the felt has multiple layers, including a first layer defining a first surface facing the fibrous pulp web having a first average fineness that is less than 6.7 dtex, a second layer directly beneath the first layer having a second average fineness that is less than 17 dtex, and a third layer defining a third surface facing the suction roll having a third average fineness that is greater than 17 dtex.

14. The method of claim 1, wherein the fibrous pulp web (9) is pre-dried by an impingement dryer (8) before the Yankee (6) and after the suction roll (11).

15. A method for production of a fibrous pulp web (9), comprising: feeding a fibrous pulp suspension through a headbox (1) between a forming wire (3) and a felt (4) to dewater the fibrous pulp suspension by centrifugal force in the area of a forming roll (2) to form a fibrous pulp web (9), guiding the fibrous pulp web (9) over a suction roll (11) together with the forming wire (3) and the felt (4) directly after the forming roll (2) to dry the fibrous pulp web (9), wherein the felt (4) is between the suction roll (11) and the fibrous pulp web (9) and the forming wire (3) is wrapped around the fibrous pulp web (9) on the outside, the fibrous pulp web (9) is wrapped round the suction roll (11) in places and a moist air having a temperature greater than 150 C. and moisture content of more than 150 g H.sub.2O/kg air flows through the fibrous pulp web (9) on the suction roll (11).

16. The method of claim 15, comprising a Yankee (6) aids the step of guiding the fibrous pulp web (9) and the moist air is exhaust from a Yankee hood (7).

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 shows a representation of the disclosed method and device.

DETAILED DESCRIPTION

(2) In the following, an embodiment of the invention is described on the basis of FIG. 1.

(3) In FIG. 1, the fibrous pulp suspension is fed through a headbox 1 in between a felt 4 and a forming wire 3 at a forming roll 2 in a Crescent former 10.

(4) The felt 4 and the forming wire 3 are wrapped round a part of the outer circumference of the forming roll 2, so that the water in the fibrous pulp suspension is thrown outwards through the forming wire by the centrifugal forces. Here, the felt is on the inside. After the forming roll 2, the dryness of the fibrous pulp web 9 is approximately 10%.

(5) Following this centrifugal dewatering, the felt 4, the fibrous pulp web 9 and the forming wire 3 are guided over a suction roll 11 around which they are wrapped in places. The suction roll 2 draws the moisture out of the fibrous pulp web 9 and through the felt 4 by suction in a vacuum dewatering process.

(6) In order to improve dewatering, a steam blow box 12 is mounted in the first wrapped area of the suction roll 11. Hot steam flows through this steam blow box onto the fibrous pulp web 9 and heats it in this way. After the suction roll 11, the fibrous pulp web 9 has approximately 25% to 30% dryness. As the fibrous pulp web 9 is still very damp in the area of the suction roll 11, there is very little evaporation here. On the contrary, the heat supply reduces the viscosity of the water in the fibrous pulp web 9, which causes the water to be sucked out of the fibrous pulp web 9 through the suction roll 11. The fine-pored felt 4 enhances the dewatering process through capillary dewatering.

(7) After the suction roll 11, the forming wire 3 is lifted off the fibrous pulp web 9. In the present example, this is followed by impingement drying 8. Radiation drying (e.g. infra-red radiation) would also be feasible. Here, the impingement dryer 8 is arranged on the side of the fibrous pulp web 9. The fibrous pulp web has approximately 30% to 35% dryness. Finally, the fibrous pulp web 9 is transferred from the felt 4 to a Yankee 6 by means of a shoe press roll 5. In the present embodiment, the felt 4 is wrapped round the shoe press roll 5 with an angle of wrap () of 175. At the Yankee 6, the fibrous pulp web 9 is dried by the hot air applied through the Yankee hood 7 in a way that is known and then scraped off. The dryness of the fibrous pulp web 9 when transferred to the Yankee 6 is approximately 50%.