Solid material comminution or disintegration – Apparatus – Cooperating comminuting surfaces
Patent
1985-10-09
1987-08-04
Bashore, S. Leon
Solid material comminution or disintegration
Apparatus
Cooperating comminuting surfaces
162261, 2412612, D21D 130, B02C 700
Patent
active
046840737
DESCRIPTION:
BRIEF SUMMARY
FIELD OF INVENTION
The present invention relates to apparatus for thickening, i.e. de-watering, and refining fibre-pulp suspensions, comprising a screw-press thickener or dewaterer and a refiner.
BACKGROUND ART
In present day fibre-pulp processing techniques, the pulp is thickened in a separate unit, for example a screw-press thickener, while refinement of the pulp is effected in a unit separate from the thickener, for example a disc refiner. Consequently, a screw feeder is required for transporting pulp from the pulp-thickening unit to the pulp-refining unit, this screw-feeder also serving as a refiner-infeed screw. In an arrangement such as this, the pulp is liable to absorb air during its passage from the outlet of the thickener to the inlet of the refiner, among other things due to the fact that the pressure created within the pulp in the screw-press thickening unit and the extent to which the pulp has been compressed therein cannot be maintained during transfer of the pulp by the feed screw. All air introduced into the pulp subsequent to it thickening has a deleterious effect on the subsequent treatment stages, however, and consequently the aforedescribed method of transferring pulp to the feed screw is encumbered with serious disadvantages.
Another disadvantage with present day apparatus arrangements of this kind, is that they require the provision of an additional unit, namely the combined conveying and infeed screw, which increases costs relating to initial investment, operation and maintenance.
In addition, each additional unit presents a stoppage hazard, and makes it difficult to sustain or reach a uniform pulp flow to the refiner. Another obvious disadvantage is that each additional unit requires a corresponding amount of space to be made available.
The prime object of the present invention is to provide an apparatus of the aforementioned kind intended for thickening, i.e. de-watering, and refining fibre-pulp suspensions, in which the aforementioned disadvantages are eliminated.
The general solution to the problem upon which the invention is based resides in the understanding that all the aforementioned disadvantages can be eliminated by connecting the screw-press thickener directly to the refiner, in the absence of an interconnecting combined pulp-conveying and infeed screw. In this way there is provided a fully closed system in which the pressure created in the pulp in the screw-press thickener and the extent to which the pulp is compressed therein can be maintained right up to the point at which the pulp is fed into the refiner. In this way problems related to the introduction of air into the pulp and the necessity of using a separate unit are eliminated.
DISCLOSURE OF THE INVENTION
A particular characteristic of an apparatus of the kind described in the introduction and based on this understanding is that the outfeed end of the screw-press thickener is connected directly to the infeed end of the refiner so as to function also as a screw infeed to the refiner, and in that the screw of the screw-press thickener is encased in a screening jacket of which at least a part thereof converges in the feed direction of the pulp, to achieve the requisite press effect for de-watering the pulp in the screw press while obtaining, at the same time, a reduction in the diameter of the screening jacket to enable the thickener to be connected to the refiner.
In a preferred embodiment there is used a screw-press thickener of the kind described, for example, in U.S. Pat. No. 4,286,512, because the drainage of free water resulting from the centrifugal forces generated by a rotating screening drum can be effected in said thickener with a high degree of efficiency. This means that the thickener can be made short in length and thus the screw and screening drum, for example, may be incorporated in a single free-bearing unit supported at its one end. In addition hereto, the requisite press effect in the thickener can be achieved by using a screening drum which converges over at least a part thereof in the direct
REFERENCES:
patent: 4082233 (1978-04-01), Reinhall
patent: 4163525 (1979-08-01), Reinhall
patent: 4202505 (1980-05-01), Ruuskanen
patent: 4220290 (1980-09-01), Johansson
patent: 4269365 (1981-05-01), Berggren
patent: 4283252 (1981-08-01), Reinhall
patent: 4286512 (1981-09-01), Berggren
Bashore S. Leon
Hastings K. M.
Thune-Eureka A/S
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