Twin wire press and method for dewatering a fibre suspension

Abstract

The invention relates to a twin wire press (2) for dewatering a fibre suspension, comprising a lower wire (8) and an upper wire (10) between which a fibre web (F) is formed. An arrangement of rolls (4) comprises a first dewatering control means (22) having a dewatering element (24) forming a press nip (25) with a first roll (26) (or a second dewatering control means), where the element and the first roll, (or alternative second control means), along a section of the press nip where they bear on each other, are adapted to each other to provide a thickness profile designed to provide a dewatering profile, and where the element presses the formed web (F) against the first roll, or the alternative second control means, via the wires, whereby water pressed from the web is drained through the element. The invention also concerns a method for dewatering a fibre suspension.

Description

technical field [0001] The invention relates to a twin wire press and to a method for dewatering a fiber suspension in a twin wire press. Background technique [0002] Twin wire presses for dewatering a fibrous suspension and forming a continuous fibrous web are known. The pulp is typically dewatered from an inlet consistency of 3-8% by weight to an outlet consistency of 30-50% by weight. Such a twin wire press known in the prior art comprises a lower roll, a continuous lower wire running as a web around said lower roll, an upper roll, and a continuous wire running as a web around said upper roll. The two wires interact along the dewatering section of the web where they form wedge-shaped spaces for the fiber suspension. As the two wires move along said dewatering section, the two wires thus continuously press the fiber suspension in the wedge-shaped dewatering space, whereby the fiber suspension is initially pressed and dewatered and a cohesive fibrous web is formed betwee...

AI Technical Summary

Problems solved by technology

Too high a load on the dewatering table directly leads to high friction and very high energy consumption

Going from relatively slow dewatering in the dewatering table to very fast dewatering in the roller unit is a non-negligible step which sometimes causes problems in the first nip of the roller unit

When the fibrous web leaves the dewatering table with too low a pulp consistency, it enters and deforms in the first nip of the roll arrangement at too high a speed, thus damaging the fibrous web

[0005] The first nip immediately after the dewatering table has an additional disadvantage: a relatively high flow of white water is generated, which cannot be completely removed from the fibrous web

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