Liquid purification or separation – With repair or assembling means
Patent
1997-10-23
1999-09-14
Lithgow, Thomas M.
Liquid purification or separation
With repair or assembling means
210239, 210327, 210331, 210334, 210402, 210542, 210784, 210780, B01D 3321, B01D 3376
Patent
active
059518618
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION AND PRIOR ART
This invention is related to a device for filtering a liquid substance according to the pre-characterizing part of enclosed claim 1. Furthermore, the invention is related to a method for converting a drum filter into a disc filter according to the pre-characterizing part of enclosed claim 16.
The expression "liquid substance" occurring hereinafter is intended to comprise various liquids, suspensions et cetera containing constituents desired to be filtered away. Even if the invention in no way is restricted thereto, a preferred application of the invention is in connection with dewatering of fibre suspensions. As fibres, cellulose fibres are primarily in view. In disc filters of the nature in question there are two main types relevant in this connection, namely a first according to the pre-characterizing part of claim 1, in which the means for removal of the released material and being present between two adjacent filter discs has the character of a chute, an upper end of which is designed to receive the material released and which is arranged to deliver, at its lower end, this material to a receiver, which as a rule is formed by a conveyor, for instance a screw conveyor, extending with its longitudinal direction substantially parallel to the axis of the rotor. The conveyor is in practise located under the container. In the other main type, which does not correspond to the pre-characterizing part of claim 1, there is instead arranged, within the inner rotor part, a conveyor extending along the axis of rotation of the inner rotor part, said conveyor being arranged to intercept material released from the filter discs and remove the same at one end of the rotor and the container.
These known techniques involve several disadvantages. Without being in any way exhausting, some of these disadvantages will be pointed out: In the first main type of disc filter, a disadvantage is that the chutes occurring between the filter discs require a rather large space, which means that the filter discs must be located at a rather large axial distance from each other. Furthermore, it is a problem that the material which has been filtered away and released tends to adhere to the chute walls since they are stationary. This problem is of such a serious nature that it has been found to be necessary to arrange specific liquid spraying members to establish, along at least parts of the chute walls, a liquid flow tending to deliberate the chute walls from material filtered away and possibly deposited thereon. This liquid spraying involves, however, necessarily an increased liquid content in the material filtered away, this being as a rule a considerable disadvantage. The requirement for designing the upper portion of the chute so as to be able to intercept material filtered away and released means in practice that the substance level in the container must be set to be relatively low, which involves a relatively low capacity, in particular in connection with the need for a relatively large axial distance between the filter discs. Furthermore, the arrangement of the chutes between the filter discs means that a particular inlet box must be arranged along the longitudinal extent of the container. The purpose of this inlet box is to distribute the arriving substance to be filtered in a uniform manner along the filter discs of the rotor. The inlet box may, to achieve uniform distribution of the substance, comprise inlet sections opening between adjacent pairs of filter discs. Such inlet box structures increase considerably the cost for the device in its entirety.
The second main type of disc filter suffers from the disadvantage that it is a rather costly construction to arrange the longitudinal conveyor within the inner rotor part. Furthermore, this longitudinal conveyor tends to necessitate a relatively bulky design of the inner rotor part. In addition, the location of the conveyor in the inner rotor part complicates the formation of conduits for conveying the filtrate from the filter discs and makes th
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Kvaerner Pulping AS
Lithgow Thomas M.
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