Liquid purification or separation – Plural distinct separators – Filters
Patent
1985-08-12
1987-01-06
Sever, Frank
Liquid purification or separation
Plural distinct separators
Filters
210346, 210486, B01D 3326
Patent
active
046345299
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to a disc filter of the kind which includes a plurality of rotatable, axially spaced, annular discs, which are adapted to be partly submerged in a liquid or a suspension to be filtered, each disc consisting of a plurality of hollow filter elements, the interiors of which communicate with axial suction channels for withdrawal of filtrate, a collecting funnel being introduced through all the annular discs to receive particles or parts of a filter cake falling therefrom.
BACKGROUND OF THE INVENTION
In a previously known disc filter of this kind (SE-C-7406315-7) the axial suction channels are connected with the radially inner portions of the filter elements. Particularly when filtering pulp suspensions, the suction channels axially extending between the discs constitute an obstacle for falling lumps of the filter cakes deposited on the filter elements, so that such lumps can even end up hanging over the suction channels.
This problem was addressed in Swiss Patent No. 162,137 by providing peripheral suction and a central discharge funnel for filter cake. However, this construction gave rise to the further problem of backflow of the liquid radially inwardly when the filter elements rise above the liquid surface.
SUMMARY OF THE INVENTION
The object of the invention is to solve this problem by the provision of backflow barriers projecting into the suction conduits.
According to another feature of the invention, the suction channels are given a wedge or shovel shape, so that particles deposited at the bottom of the vessel, or thickened suspension, can be lifted from the bottom and remixed into the remaining liquid or suspension.
BRIEF DESCRIPTION OF THE DRAWINGS
In order that the invention may be more clearly understood, it will now be described with reference to the accompanying drawing, which shows a schematical cross-section through a filter according to the invention.
DETAILED DESCRIPTION
On a base structure 1 rests a machine stand 2 which in turn supports a vessel 3 having a semi-cylindrical envelope surface 4, which at its long sides is tangentially extended upwards by vertical portions 5 and 6, the upper edge 7 of the latter forming an overflow inlet, over which liquid or suspension is supplied from an inlet casing 8. In practice, the top of vessel 3 is covered by a casing (non-shown).
In the stand 2 is rotatably journalled an aggregate of a plurality of axially spaced, annular filter discs 9, one of which is shown in the drawing. Each such disc 9 consists of a plurality of substantially triangular, hollow filter elements 10 arranged adjacent each other and having their apex portions 11 directed inwardly and their base portions 12 located at the disc circumference. The base portions 12 are arcuate and mounted in a manner such that the interior of each filter element is in communication with an axially oriented suction conduit 13. All the suction conduits 13 are mutually connected in a suitable way such that they jointly form a "hollow axle" common to all filter discs 9, said axle being driveable for rotating the filter discs in a counter-clockwise direction as seen in the drawing).
In a manner known to those skilled in the art, the suction conduits 13 are connected to an outlet conduit for filtrate such that an under-pressure is established in those suction conduits whose associated filter elements are located partly or entirely under the liquid surface, and is maintained at least until the filter elements have been entirely raised above the liquid surface.
Extending through all the annular filter discs 9 is a collecting funnel 14, which may be provided with a discharge screw (not shown).
Now, if the arrangement is such that the under-pressure ceases as a suction conduit 13' is in the illustrated one o'clock position, particles, or, e.g., a filter cake of pulp fibers sucked onto the filter element 10', can be made to drop into the collecting funnel 14. As is quite obvious, by means of the invention, this can happen without any hindrance during
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