Machine for dewatering and drying a fibrous web

Patent metadata

Field	Value
Publication number	US-11286617-B2
Application number	US-201816207902-A
Country	US
Kind code	B2
Filing date	Dec 3, 2018
Priority date	Jun 3, 2016
Publication date	Mar 29, 2022
Grant date	Mar 29, 2022

Abstract

A machine for dewatering and drying a paper, cardboard or other fibrous web, to which machine a fibrous stock suspension is fed which is formed at least partially from waste paper. The machine includes at least two press nips which are formed in each case by two press rolls, wherein a fibrous web runs through first press nip with a water absorbing dewatering belt on both sides. The fibrous web then runs through a second press nip with at least one other dewatering belt and a smooth impermeable transfer belt on both sides. A transfer belt transfers the fibrous web after second press nip to a belt in a downstream machine unit, e.g. dryer group. The dryer group allows the fibrous web to be guided in a serpentine manner alternatively over heated dryer cylinders and vacuum equipped guide rolls.

First claim

What is claimed is:

1. A machine for dewatering and drying a fibrous web formed at least partially from waste paper, the machine comprising:
a press section including a plurality of press rolls forming at least two press nips therebetween, the at least two press nips including a first press nip and a second press nip;
the first press nip being configured to allow two water absorbing dewatering belts and the fibrous web contained therebetween to run through;
the second press nip being configured to allow at least one other dewatering belt and a smooth impermeable transfer belt with the fibrous web contained therebetween to run through, the smooth impermeable transfer belt running under and transferring the fibrous web after the second press nip to a receiving belt in a downstream machine unit, the receiving belt being a dryer fabric and the downstream machine unit being a dryer group in which the fibrous web is guided in a serpentine manner alternatively over at least one heated dryer cylinder and at least one vacuum equipped guide roll, the at least one heated dryer cylinder including a first heated dryer cylinder and a second heated dryer cylinder downstream of the first heated dryer cylinder;
at least one removal receiving doctor being assigned to the first heated dryer cylinder of the downstream dryer group; and
a pulper located under the removal receiving doctor, wherein an axis of the first heated dryer cylinder and an axis of the at least one vacuum equipped guide roll are offset vertically relative to one another and located at a horizontal distance from one another, the horizontal distance being 85-95% of the sum of a radius of the first heated dryer cylinder and a radius of the at least one vacuum equipped guide roll such that web travel is stable and a web-wide transfer of the fibrous web through the press section occurs at the first heated dryer cylinder of the downstream dryer group, two of the plurality of press rolls forming at least one of the two press nips are a cylindrical press roll that are extended and a shoe press roll equipped with a flexible roll cover that is pressed by a pressure shoe having a concave contact surface against the cylindrical press roll, the shoe press roll being above the cylindrical roll.

2. The machine according to claim 1 , wherein the horizontal distance is greater than 90% of the sum of the radii of the first heated dryer cylinder and the at least one vacuum equipped guide roll.

3. The machine according to claim 1 , wherein the smooth impermeable transfer belt after the second press nip and delivery of the fibrous web is cleaned by a cleaning device which directs a cleaning fluid at a pressure of at least 50 bar onto a side of the smooth impermeable transfer belt that carries the fibrous web, the cleaning device further includes at least one doctor.

4. The machine according to claim 3 , wherein the smooth impermeable transfer belt is supported on at least one guide roll in a region of the cleaning device.

5. The machine according to claim 1 , wherein a distance between the second press nip and a transfer of the fibrous web to the receiving belt is shorter than 2.5 m.

6. The machine according to claim 1 , wherein the at least one press nip at least one of extends over 250 mm in a machine direction and has a linear force of at least 800 kN/m.

7. The machine according to claim 1 , wherein the smooth impermeable transfer belt on a side supporting the fibrous web has a roughness Rz of less than 12 μm in a machine direction.

8. The machine according to claim 1 , wherein the fibrous web is carried prior to the first press nip by the two water absorbing dewatering belts over an as long as possible travel section.

9. The machine according to claim 1 , wherein the two water absorbing dewatering belts include an upper dewatering belt and a lower dewatering belt, the upper dewatering belt of the first press nip is redirected away from the fibrous web during a suction application upon the lower dewatering belt.

10. The machine according to claim 1 , wherein the at least one other dewatering belt is redirected away from the fibrous web a maximum of 200 mm after the second press nip.

11. The machine according to claim 1 , wherein the fibrous web produced on the machine has a base weight between 50 and 180 g/m2.

Assignees

• Voith Patent Gmbh

Inventors

• Gronych Daniel
• RüHL THOMAS

Classifications

• D21F1/32

  Washing wire-cloths or felts · CPC title

• D21F5/042

  in combination with suction or blowing devices · CPC title

• D21F3/045 Primary

  including at least one extended press nip · CPC title

• D21F1/76

  with suction · CPC title

• D21F7/04

  Paper-break control devices · CPC title