Process for production of a fibrous pulp web

Patent metadata

Field	Value
Publication number	US-9856603-B2
Application number	US-201615283636-A
Country	US
Kind code	B2
Filing date	Oct 3, 2016
Priority date	Oct 5, 2015
Publication date	Jan 2, 2018
Grant date	Jan 2, 2018

Abstract

A method for producing a fibrous pulp web, in which a fibrous pulp suspension is dewatered in a Twin Wire Former to form a fibrous pulp web which is dried with a TAD dryer. A pre-dewatering device with a hood and suction roll is provided after the Twin Wire Former and before the TAD dryer. The fibrous pulp web is guided through the pre-dewatering device between exactly two machine cloths. The machine cloth between suction roll and the web is a porous felt, and the machine cloth between web and hood is a structured wire. A volume flux of hot drying fluid greater than 100 m 3 /(m 2 ·min), preferably greater than 250 m 3 /(m 2 ·min,) is drawn through the fibrous pulp web into the suction roll.

First claim

The invention claimed is:

1. The method for producing a fibrous pulp web, comprising:
dewatering a fibrous pulp suspension between forming wires in a Twin Wire Former to form a fibrous pulp web;
conveying the fibrous pulp web from the Twin Wire Former to a pre-dewatering device including a hood and suction roll where the fibrous pulp web is carried through the pre-dewatering device between the hood and the suction roll via guiding only between a felt on the suction roll and a wire between the fibrous web and the hood;
in the pre-dewatering device, drawing a volume flux of hot drying fluid greater than 100 m 3 /(m 2 ·min) through the fibrous pulp web into the suction roll; and
following the pre-dewatering device, drying the fibrous pulp web in a hot-air dryer on a structured wire and through air dryer (TAD) drum.

2. The method according to claim 1 , wherein the fibrous pulp web is guided through the pre-dewatering device with a structured wire.

3. The method according to claim 2 , wherein
the drying fluid includes hot air at a temperature greater than 150° C.;
a differential pressure in the pre-dewatering device between the hood and the suction roll is greater than 0.25 bar; and
the flux of drying fluid through the fibrous pulp web is greater than 100 m 3 /(m 2 ·min).

4. The method according to claim 2 , wherein
the fibrous pulp web passes through first and second zones in succession in the pre-dewatering device, where the drying fluid is at a temperature greater than 200° C. and includes steam and hot air flowing through the fibrous pulp web in the first zone and only hot air flowing through the fibrous pulp web in the second zone; and
a differential pressure in the pre-dewatering device between the hood and the suction roll is greater than 0.45 bar.

5. The method according to claim 1 wherein the fibrous pulp web formed on a forming wire of the Twin Wire Former is guided through the pre-dewatering device on said forming wire.

6. The method according to claim 5 , wherein said forming wire that guides the fibrous pulp web is unstructured.

7. The method according to claim 1 wherein the drying fluid is hot air at a temperature greater than 150° C.

8. The method according to claim 7 , wherein the drying fluid is moist hot air, with a moisture content greater than 150 g H2O /kg air .

9. The method according to claim 1 , wherein the drying fluid is hot steam.

10. The method according to claim 1 , wherein the fibrous pulp web passes through first and second zones in succession in the pre-dewatering device, where steam and hot air flow through the fibrous pulp web in the first zone and hot air flows through the fibrous pulp web in the second zone.

11. The method according to claim 1 , wherein a differential pressure in the pre-dewatering device between the hood and the suction roll is greater than 0.25 bar.

12. The method according to claim 1 , wherein the felt is a fine-pored material having through-pores between opposite exterior surfaces, with an average pore size of the felt surface facing the fibrous pulp web smaller than the average pore size of the felt surface facing the suction roll.

13. The method according to claim 1 , wherein the fibrous pulp web is guided through the pre-dewatering device on the structured wire of the TAD drum.

14. The method according to claim 1 , wherein the fibrous pulp web is fed to a Yankee after the TAD drum.

15. The method according to claim 1 , wherein a contact roll confronts the suction roll to press the fibrous pulp web against the felt before the fibrous pulp web is guided between said felt and said wire.

16. The method according to claim 1 , wherein the flux of drying fluid is greater than 200 m 3 /(m 2 ·min).

17. The method according to claim 1 , wherein the drying fluid is at a temperature greater than 200° C.

18. The method according to claim 1 , wherein the drying fluid includes moist hot air, with a moisture content greater than 150 g H2O /kg air .

19. The method according to claim 18 , wherein the moist hot air has a moisture content greater than 300 g H2O /kg air .

20. The method according to claim 1 , wherein a differential pressure in the pre-dewatering device between the hood and the suction roll is greater than 0.45 bar.

Assignees

• Andritz Ag Maschf

Inventors

• Anzel Andreas
• Gissing Klaus
• Scherb Thomas
• Mausser Wilhelm

Classifications

• D21F11/145

  including a through-drying process · CPC title

• D21F5/02

  Drying on cylinders · CPC title

• D21F5/18

  Drying webs by hot air · CPC title

• D21F1/48

  Suction apparatus (suction rolls D21F3/10) · CPC title

• D21F11/006 Primary

  Making patterned paper · CPC title