Forming section

Abstract

A forming section comprises a lower wire loop (11) which constitutes a first single- wire section (Tl) following a breast roll (12). The beginning of the first single- wire section comprises a first dewatering zone (Zl) which consists of at least one stationary, first forming shoe (40) and a pulsating strip cover (50) following it. In the first forming shoe, there are a leading edge and a trailing edge as well as a cover provided with through holes and underpressure affecting through the holes of the cover. The holes are constituted of openings or slots substantially in the longitudinal direction of the machine, whereby non-pulsating dewatering is applied on the stock travelling on top of the lower wire. The forming section further comprises a multi-layer headbox (30) by means of which a pulp suspension jet is fed at an impact point after the leading edge of the first forming shoe. The cover of the first forming shoe is straight at least on the section between the impact point of the pulp suspension jet and the trailing edge of the first forming shoe.

Description

technical field [0001] The invention relates to a method according to the preamble of claim 1 . [0002] The invention also relates to a forming section according to the preamble of claim 11 . Background technique [0003] The task of the forming section is to remove water from the fiber suspension supplied by the headbox. The concentration of the fiber suspension fed onto the forming section is typically 1%, and after the forming section, the web formed on the forming section is again of 18-20% consistency. [0004] When the web is made from a moisture-rich lignocellulosic feedstock, the moisture in the pulp is removed on the forming section by passing one or more forming wires to initiate web forming. The wood pulp fibers are distributed randomly on the forming wire, or between multiple forming wires moving together. [0005] Different types of raw materials are used depending on the grade of web to be manufactured. The amount of water that can be removed from differen...

AI Technical Summary

Problems solved by technology

[0010] The problem associated with hybrid formers is that the residual variation of the formed web depends on the speed of the machine

[0015] A problem associated with devices according to the prior art is that the formation and tension ratio of the web is largely dependent on the jet-wire ratio

The problem with the first combination is that the investment is high

Since the first partial web formed on the Fourdrinier wire section must have time to dry sufficiently when the second partial web is brought onto the first partial web at the beginning of the twin-wire section, the latter combination Able to have good layer purity, but the production speed of the hybrid former is still low due to the above reasons

If a hybrid former according to the prior art uses a multi-layer headbox again at the beginning of the fourdrinier wire section, the layer purity is compromised during the pulse dewatering of the fourdrinier wire section

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