WO1998033594A1

WO1998033594A1 - Refining element

Info

Publication number: WO1998033594A1
Application number: PCT/SE1998/000109
Authority: WO
Inventors: Nils Virving
Original assignee: Sunds Defibrator Industries Ab
Priority date: 1997-01-31
Filing date: 1998-01-27
Publication date: 1998-08-06
Also published as: SE9700304D0; SE508286C2; SE9700304L; AU5888698A

Abstract

A refining element for disintegrating and refining fiber material in a disc refiner. The refining element is formed with a base surface (1, 11), on which a pattern of bars (2, 12) is arranged. The bars (2, 12) extend over the surface of the refining element and are separated by intermediate grooves (6, 13), and flow restrictions (14) can be located in the grooves (6, 13) between the bars (2, 12). Channels (7, 15) are arranged at the same level as the base surface (1, 11) of the refining element for a free passage of steam outward and inward without obstruction by bars (2, 12) of the refining element, or fiber material in the grooves (6, 13) or flow restrictions (14) in the grooves (6, 13). The upper edges of the bars can thereby remain unbroken.

Description

Refining element

This invention relates to the disintegration and refining of lignocellulosic material in a disc refiner. The invention, more precisely, relates to a refining element in a refiner of the said type.

A disc refiner comprises two opposed refining discs rotating relatively to each other, one or both of which are rotary. On the refining discs a plurality of refining elements are attached. These refining elements are formed with a base surface, on which a pattern of bars and intermediate grooves is provided. The refining discs are so arranged that the refining elements form a refining gap, through which the fiber material is intended to be passed from the inside outward and the disintegration and refining are carried out by the bars of the refining elements.

In the inner part of the refining gap, the refining elements are formed with coarser bars for an initial disintegration and for feeding the material outward to the outer part of the refining gap, where the proper disintegration and refining take place.

The refining of the material requires a high energy input, which is supplied by the rotation of the rotating refining disc or discs. The greatest part of the energy is transformed to heat, which results in the generation of large amounts of steam, because the material contains water. The steam^', which substantially is formed in the refining gap, has high pressure and flows both outward and inward in the refining gap.

In order to cause the fiber material to be disintegrated and refined by the bars of the refining elements, it is in most cases necessary to arrange flow restrictions, so-called dams, in the grooves between the bars. The material is thereby forced upward out of the grooves to be worked between the bars in the refining gap whereby unworked material is prevented from passing out through the refining gap. These dams, however, form at the same time an obstacle for the generated steam, which thereby disturbs the material flow and affects negatively the capacity and operational stability of the refiner. The fiber material in the grooves also impedes the steam flow.

According to the European patent 179 041, the refining element is formed with wide channels without bars. The channels extend outward through the outer portion of the refining element and are bent in the intended rotation direction of the refining element. The steam can thereby flow outward through the channels, and at the same time, due to the rotation of the refining element, the fiber material is prevented from following along. These channels, however, reduce the size of the working surface of the refining element and thereby its efficiency.

The present invention implies, that the aforesaid problems can be reduced and at the same time additional advantages concerning the quality of the refined material be obtained. According to the invention, the refining element is formed with channels for the steam which are arranged at the same level as the base surface of the refining element, so that the upper edges of the bars remain unbroken.

By this design of the refining element the fiber material will be worked effectively by unbroken bars in the refining gap between refining elements on the two opposed refining discs. The generated steam is at the same time directed away through the channels without obstructing or disturbing the material flow through the refining gap. In this way the capacity of the refiner is increased, at the same time as the quality of the pulp can be improved.

The characterizing features of the invention are apparent from the attached claims.

The invention is described in greater detail in the following, with reference ttrthe accompanying drawing illustrating two embodiments of the invention. Fig. 1 shows a refining element intended for a plane portion of a refining disc in a disc refiner;

Fig. 2 is a section according to II-II in Fig. 1;

Fig. 3 shows a refining element for a conical portion of a refining disc in a disc refiner;

Fig. 4 is a section according to IV-IN in Fig. 3.

The refining element according to Fig. 1 is plane and intended to be placed on a plane portion of a refining disc in a disc refiner. On the base surface 1 of the refining element substantially radial bars 2 are arranged in an outer portion 3 and substantially radial coarser bars 4 are arranged in an inner portion 5. The bars 2 are placed so that intermediate grooves 6 are formed. In the grooves flow restrictions, so-called dams, can also be provided.

At the same level as the base surface 1 , channels 7 extend beneath the bars 2 obliquely in relation to the direction of the bars. The upper edges of the bars 2 thereby remain unbroken. The channels 7 permit free passage of steam outward and inward without obstruction by the bars 2 and the material or flow restrictions in the grooves 6 between the bars 2.

The refining element according to Fig. 3 is curved to be placed on a conical portion of a refining disc in a disc refiner. It can be an outer conical portion of a refining disc located outside an inner plane portion in a disc refiner or an entirely conical refining disc.

On the base surface 11 of the refining element bars 12 are located, which are- separated by intermediate grooves 13. In the grooves flow restrictions 14, so-called dams, are arranged to force the material upward out of the grooves to be worked between the upper edges of the bars 12 on refining elements of opposed refining discs. According to this embodiment, channels 15 are arranged at the same level as the base surface 11 beneath the flow restrictions 14. The steam can thereby pass beneath the flow restrictions 14 without being obstructed or disturbed by the material flow.

Claims

1. A refining element for disintegrating and refining fiber material in a disc refiner, where the refining element is formed with a base surface (1,11), on which a pattern of bars (2,12) is arranged, which bars (2,12) extend over the surface of the refimng element and are separated by intermediate grooves (6,13), and flow restrictions (14) can be provided in the grooves (6,13) between the bars (2,12), characterized in that channels (7,15) are arranged at the same level as the base surface (1,11) of the refining element for a free passage of steam outward and inward without obstruction by bars (2,12) of the refining element, fiber material in the grooves (6,13) and flow restrictions (14) in the grooves (6,13), and that the upper edges of the bars are unbroken.

2. A refining element as defined in claim 1, characterized in that the channels (7) extend obliquely in relation to the bars (2).

3. A refining element as defined in claim 2, characterized in that the channels (7) are formed in the base surface (1) of the refining element beneath the bars (2).

4. A refining element as defined in claim 1, characterized in that flow restrictions (14) are arranged in the grooves (13), and that the channels (15) are formed beneath the flow restrictions (14).