Paper making and fiber liberation – Processes of chemical liberation – recovery or purification... – With washing
Patent
1994-09-30
1996-09-17
Czaja, Donald E.
Paper making and fiber liberation
Processes of chemical liberation, recovery or purification...
With washing
162 52, 8156, D21C 902, D06B 102
Patent
active
055565085
DESCRIPTION:
BRIEF SUMMARY
The following invention relates to a method and a device for treating fibre suspensions, in particular for washing a fibre suspension in the form of cellulose pulp.
It is well known that fibre suspensions exhibit very special properties which demand special measures in connection with treating such suspensions. Washing a fibre suspension is an example of a treatment of this nature which requires special measures because of the special behaviour of a fibre suspension. More or less complicated apparatus for this purpose is already known. A feature possessed in common by these known processes and devices is, however, that, in connection with the actual liquid penetration phase, there is physical contact between a significant part of the fibre suspension and some form of sieving device. In connection with pulp production, in particular, such physical contact is undesirable since it gives rise to friction between the pulp bed and the sieving device, which in turn can cause disturbances in the feed-through of the pulp bed.
An object of the present invention is to present a method and a device which make it possible to change the liquid content of a fibre suspension in an effective manner without exposing the pulp bed to undesirable physical stresses.
The above mentioned object is achieved with the aid of a method and device according to the present invention, as described below.
From EP 0337 432 there is known a method of treating a fibre suspension to alter its liquid content, whereby the suspension is fed into a displacement space (12) whose outer limiting surface (2B) rotates around the axis of symmetry, which surface (2B) is permeable to fluid and is affected by a fluid under pressure acting from the outside. In this known method for washing a fibre suspension there is physical contact between a significant part of the fibre suspension and the sieving device of the washing apparatus. Further the displacement space is divided into several compartments, which increases the total area of pulpcontacting surfaces of the washing apparatus and which also eliminates the possibility of layering of the suspension as a result of the centripetal acceleration. Accordingly there are essential differences between a method known from EP 0337 432 and our invention which is characterised in that the displacement space is rotationally symmetrical and by a high rotation speed whereby as a result of the centripetal acceleration a rapid layering between the fibre and the liquid is established and that said from the outside acting fluid balances the pressure with which the fibre layer as a result of the centripetal acceleration is acting in the direction of said outer limiting surface (2B).
The invention will be explained in more detail below with the aid of the attached drawings, in which:
FIG. 1 shows a preferred embodiment of a device according to the invention, and
FIG. 2 shows an alternative embodiment of a device according to the invention.
The device consists of an axle 1 which extends along a line of symmetry C. The axle 1 is arranged to be rotatable in a support 10 with the aid of bearing 7 and to be driven with the aid of a drive 8 in the form of a V-belt system. An arrangement 2, which is Y-shaped in longitudinal section, is connected to the axle 1 so that it turns with it. This Y-shaped arrangement 2 consists of a circular part 2A, 2B, which is liquid-permeable and which extends in an axial direction, a connecting part 2C, which extends essentially radially, and an inner base part 2D which at its inner periphery is connected to the said axle 1, in the preferred case by means of splines. The liquid-permeable part 2A, 2B possesses suitable perforations, for example in the form of circular holes or slits.
A space 3 encloses the circular part 2A, 2B, which space will hereinafter be termed the fluid space 3. The fluid space 3 is delimited outwards by a housing wall 4 which is essentially Y-shaped and which is suspended in bearing 7 by means of its base part 4B. A conical housing part 4C extends between the outermost cylindr
REFERENCES:
patent: 5013460 (1991-05-01), Meredith
patent: 5204009 (1993-04-01), Rowland
patent: 5221434 (1993-06-01), Henricson
Ekholm Rolf
Jansson Ulf
Czaja Donald E.
Kananen Ronald P.
Kvaerner Pulping Technologies Aktiebolag
Padgett Calvin
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