AU614289B2 - Improvements in dewatering and compacting equipment - Google Patents

Description

COMMONWEALTH OF AUSTRALIA g f Patents Act 1952-1969 2 COMPLETE SPECIFICATION

(ORIGINAL)

FOR OFFICE USE: Class Int. Class Application Number Lodged Complete Application No.

Specification Lodged Published T PFiojity: I. 9 SRotated art: a 0a o «a e o Q 9 9 99 9 Name of Applicant: 9 99 9 9 9 oAiodress of Applicant: AlztUal Inventor: TO BE COMPLETED BY APPLICANT MACRAE ENGINEERING PTY. LIMITED 1 Evergood Close, Weston, A.C.T.

Conrnonwealth of Australia DENNIS MACRAE ddress for Service: COLLISON CO., Patent Attorneys, 117 King William Street, Adelaide, South Australia, 5000.

Comnplete Specification for the invention entitled: IMPROVEMENTS IN DEWATERING AND COMPACTING EQUIPMENT The following statement is a full description of this invention, including the best method of performing it known to me: 10/06/88 P/'TEN TRADE MARKS DESIGNS SUB-OFFICE 10 JUN 1988 SOUTH AUSTRALIA Bl-OFFICE N 1987 To: de THE COMMISSIONER OF PATENTS This form must be accompanied by either a provisional specification (Form 9 and true copy) or by a complete specification (Form 10 and true copy), s 56o 2 This invention relates to improvements in dewatering and compacting equipment and more particularly to equipment for the dewatering of particulate or fibrous slurries to produce a solid waste product and a relatively clean or clean filtrate.

Various forms of filtration and compaction equipment have been devised and patented but in general these have included either many moving parts or a fixed system both of which have worked in a batch compaction mode. That is, a batch of slurry to be dewatered is fed into a chamber and then a piston may compact the slurry with water escaping through a screen to produce a wad or block of dewatered waste which is then removed. The limitation on this process is that it is non continuous and hence not applicable for industrial application. There is a high wear because of the piston I travel past an inlet port and also wear within the chamber and ,o hence particularly abrasive slurries can wear such a chamber out S: in very short time. There may also be a slow compaction rate which will again reduce the usefulness of such a process.

It is the object of this present invention to provide a more a a' continuous process for the compaction of slurries and the like.

To look at one example in the asbestos removal industry for instance, considerable amounts of liquids contaminated with fibrous asbestos are produced and these wastes are difficult to dispose of unless the fibrous material can be extracted from the liquid. The fibres may be a very low concentration in the liquid but still all of the liquid must be filtered. Similarly in the paper making industry, paper fibres remain in the waste waters and these should be removed before the waste waters are disposed of.

The invention however is not restricted to the removal of fibrous materials from slurries but may also be used for the removal of particulate materials such as clays, diatomaceous earths and the like from water.

in) insrt UAlt La u L' of signing (ti Sign .turc(s) of dcclarnftl(s) No kaih/atlon or olhcr wilncis required TO: The Commissioner.of Patents 3 It is the object of this invention therefore to provide a continuous compaction arrangement to separate liquids from solids when these are slurries.

It is also to be realised that this invention is directed towards systems in which it is desirable to remove waste water from a wanted solid as much as it is for the removal of unwanted solid from a desirable liquid. An example of the former may be the removal of a desired precipitate from a chemical solution where a continuous process is desirable and an example of the latter may be the extraction of fruit juice from fruit juice pulp.

1 5 In one form therefore the invention may be said to reside in a dewatering apparatus to dewater a slurry and produce a liquid product and a substantially solid dewatered product in a continuous process, the apparatus comprising an elongate screen chamber defined by fixed parallel side walls, the side walls comprising a screen arrangement, slurry inlet means at one end of the chamber and the other end of the chamber defining an exit means for solid product, and a high pressure pump arrangement to pump slurry to the chamber through the inlet means and to exert pressure directly C• o onto the slurry to achieve the dewatering, wherein the exit means is an opening in the end of the screen chamber and said high pressure pump arrangement applies pressure to said slurry within said chamber to continuously extrude said solid product through the opening.

It will be seen that by this invention there is provided a dewatering device which in continuous operation will pump slurry at high pressure into a chamber and with the water or liquid product being expelled through the sides of the chamber the solid product will be compacted in the end of the chamber and in continuous process extruded from the chamber by the pressure of slurry in the chamber and be extruded through the exit means.

4 It will be realised that if the mesh size in the chamber is selected to a particular size then the apparatus can be said to remove some material from the slurry but to allow other material -o pass through the mesh. Hence the device could be used to remove material only above a certain size.

In one preferred embodiment the walls of the screen chamber may be comprised of a plurality of wedge bars arranged longitudinally and spaced apart to provide filtering spaces therebetween. With such wedge bars it will be realised that the gap between the bars will widen and this widening may be directed towards the outside or the exterior of the screen to prevent the screen from clogging.

The wedge bars will also provide a smooth internal surface along which the compacted wad of solid product may be extruded without catching on the bars.

S Alternatively the chamber walls may be provided with a suitable mesh.

9 0 The screen chamber may be cylindrical or square or any other desired shape depending upon whether a solid product of a particular extruded shape is required.

At leasK part of the chamber may be enclosed by a vacuum housing to assist with dewatering of the wad of solid material being produced in the chamber.

The pump to supply slurry at high pressure into the chamber may be any suitable form of positive displacement pump to provide such a high pressure such as a diaphragm pump or a piston pump. The pump arrangement may also include an auxiliary pump to supply extra pressure to the slurry in the chamber. Such an auxiliary pump may comprise a periodically acting piston pump and the slurry inlet means upstream from the auxiliary pump may include a one-way -7 -7* 4a flow valve. By this means the main pump can supply fluid into the screen chamber and the auxiliary pump used at intervals to provide extra pressure to compact the wad as it is being formed and to extrude the wad without the extra pressure being directed back down the inlet pipe.

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C II I I I I t (1 In one preferred embodiment the pump arrangement may supply slurry at a pressure of up to 3,000 pounds per square inch and the auxiliary pump may be adapted to supply pressure up to 6,000 pounds per square inch. More than one pump acting in series or in parallel may be provided to give the required pressure or a single pump may be used to supply slurry to a number of dewatering devices in parallel with facilities provided to close off one or more devices at a time for cleaning and servicing.

The exit means may be a opening in the end of the screen chamber of the same size and continuous cross sectional area as the screen chamber so that in use solid product can continuously extrude through the opening. It will be realised that some form of plug S means may be necessary when starting up the apparatus so that a wad of compacted material can build up before commencing 6% extruding.

Alternatively the exit means may include a gate which can be S opened at intervals to enable the extrusion of a plug of solidified product.

00 0 Hence the exit means may merely be a gate which may be closed i until a sufficient wad of compacted material has been produced i which then may be opened to allow the continuous extrusion of a 02t5 wad of compacted material. There may be provided suitable knife ii means for instance or some other cut off arrangement to cut the Scompacted material off at intervals as it is extruded.

In the case of removal of paper fibres from slurries from the paper making industry for instance the extruded wad of material may be cut off in suitable lengths to be dried and used for burning in domestic fires or industrial incinerators.

In a further form the exit means may comprise a multi-chambered revolving extractor such that in one position a chamber of the extractor is in a plug of solid product receiving position and in a further position the chamber is in a plug of solid product removal position. There may be for instance an hydraulic ram provided to push out the compacted wad from the revolving extracted chamber in the removal position.

The rotary extractor may be provided with further dewatering means such as a vacuum dewatering system for each of the chambers so that between the receiving position and the removal position further dewatering can be achieved by application of for instance a vacuum so that a very dry product may be produced.

In an alternative form the invention may then be said to reside in a a method of dewatering a slurry on a continuous basis comprising pumping the slurry under high pressure into an elongate parallel walled filter chamber, the filter chamber having side walls comprising a screen arrangement and an open exit end, causing a wad of dewatered material to build up in the chamber towards the open exit end and continuously extruding the wad from the open end by means of the high pressure of pumped slurry exerted on the wad within the chamber.

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With this form of the invention the extraction rate obtained will be dependant upon the rate of build up of the wad, that is upon the solids content of the slurry and also upon the pressure used to pump slurry into the chamber including any auxiliary pressure used.

This then generally describes the invention the subject of the present application but to assist with understanding of the invention reference will now be made to the accompanying drawings which show preferred embodiments of the invention.

Now looking generally at the drawings:- FIG. 1 shows a first embodiment of a dewatering apparatus according to this invention.

FIG. 2 shows a portion of a screen wall comprised of wedge bars.

FIG. 3 shows an alternative form of compaction equipment with wad removal apparatus.

FIG. 4 shows an alternative embodiment of screen chamber.

Now looking more closely at the drawings and in particular at FIG.

1, it will be seen that the dewatering apparatus of the present invention essentially comprises a screen chamber 1, in this case a cylindrical screen chamber surrounded by a housing 2. This housing may have vacuum applied to it to assist with extraction of water from the chamber. A slurry containing solid waste is fed through inlet pipe 3 past non-return valve 4 so that it enters the chamber through inlet means 5. A high pressure pump 6 is used to provide slurry at high pressure to the inlet pipe 3.

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0e Op 00 0 00 0 '1 O 0 0 o 0 0OC A wad 7 of compacted material will build up in the chamber as liquid in the slurry is forced out through the walls of the screen chamber 1 into the housing 2 and out through the drain 8.

20 An auxiliary piston pump 9 includes a ram 10 which at intervals may be activated by means not shown to provide extra pressure to go of the wad within the chamber so that at intervals the wad 7 to be forced out from the screen chamber through the exit means 11. A Srotating knife 12 rotating on axis 13 may be provided to cut off the wad at regular intervals. As discussed earlier some form of gate means, not shown, may be provided to allow an initial build up of wad in the screen chamber before being opened to allow continuous extrusion. The pressures used will of course depend upon the amount cf particulate or fibrous material in the slurry and the rate of extrusion required.

It is to be realised that for some slurries the auxiliary pump 9 will not be necessary.

FIG. 2 shows an embodiment of a screen chamber wall which includes wedge bars as the screen arrangement. The screen chamber wall includes a circumferential support bar 20 to which are fastened by welding or other suitable method a plurality of 8 wedge bars 21 which have spaces 22 between them. These spaces 22 provide the filtering spaces and as will be particularly noted the space 23 behind the filtering spaces 22 enlarges beyond the width of the filterings gap so that clogging of the filter bars will not occur.

It will be noted also that the considerable depth of the wedge bars compared with their frontal surface area onto the screen chamber will provide considerable strength so such wedge bars may take a very high pressure within the screen chamber. Also by having the wedge bars extending longitudinally along the length of the screen chamber there may only be a small resistance to longitudinal movement of the wad in the chambers. Spacing and size of the wedge bars or wedge wires will of course be selected for the type and composition of the slurry to be dewatered or deliquified, I however spacings may be in range of 0.25 millimetres down to 0.05 4 millimetres. As discussed as an alternative a perforated mesh S screen may be used for the walls of the screen chamber.

In the embodiment shown in FIG. 3, a similar form of screen S chamber 30 is used with a housing 31 around the screen chamber but a rotary extractor 33 is used instead of the earlier arrangement.

o In this embodiment slurry is provided through inlet means 34 into the screen chamber 30 so that liquid will extrude out through the walls 35 of the screen chamber but the solid wad of product 36 will S be extruded into the rotating extractor 33. The rotating extractor 33 includes a number of chambers 37 rotating on an co-parallel axis 38. When a chamber is suitably full of wad the extractor 33 is rotated with the edge of the chamber cutting off the wad at that position so that a further chamber presents itself to receive a further wad and the compacted wad proceeds to a wad removal position. In this position a hydraulic ram 39 pushes an extractor plate 40 into the chamber 41 thereby pushing the wad 42 out, the extractor is then withdrawn ready for the next wad to be removed.

By this means the embodiment shown in FIG. 3 can be used as a continuous apparatus but with discreet wads of a known size being produ .ed.

7 FIG. 4 shows a further embodiment dewatering apparatus according to this invention. In this embodiment a square cross-sectional area screen chamber is provided. The screen chamber comprises 3 fixed walls 50, 51 and 52 and a movable wall 53. The movable wall 53 is pivoted on axis 54 so that it can be reciprocated by means of hydraulic ram 55 acting through arm 56 to connector 57 on the screen wall 53.

The outer housing of the screen chamber in this embodiment has been omitted for clarity. In use slurry is pumped through inlet pipe 58 to enter the screen chamber and liquid is allowed to escape S through the walls 50, 51, 52 and 53. In the initial stage the 0 reciprocating wall 53 is fully depressed so that it meets the wall 51 1-5- at one end thereby preventing the extrusion of any wad.

0 0 Once a reasonable quantity of wad has built up, the reciprocating wall may be lifted to allow an extrusion of wad and then reciprocated at regular intervals to allow extra compression of the wad as it is extruded so that the end 60 of the reciprocating wall 53 provides extra compaction of the product.

a 99 Suitable cut off means, not shown, may be provided to remove the wad at intervals.

In one preferred embodiment of this form of the invention the screen chamber may be two metres long with cross-sectional dimensions of 200 millimetres. The aperture in the screen chamber may range from 50 microns to 4 millimetres depending upon the type of product to be dewatered and the pressure in the chamber may range of 10 pounds per square inch to 6,000 pounds per square inch depending upon the product to be dewatered.

It will be seen that by this invention there is provided a continuously operating screen chamber with no moving parts in the screen thereby eliminating considerable wear problems.

Claims (9)

1. A dewatering apparatus to dewater a slurry and produce a liquid product and a substantially solid dewatered product in a continuous process, the apparatus comprising an elongate screen chamber defined by fixed parallel side walls, the side walls comprising a screen arrangement, slurry inlet means at one end of the chamber and the other end of the chambered defining an exit means for solid product, and a high pressure pump arrangement to pump slurry to the chamber through the inlet means and to exert pressure directly onto the slurry to achieve the dewatering, wherein the exit means is an opening in the end of the screen chamber and said high pressure pump arrangement applies pressure to said slurry within said chamber to continuously extrude said solid product through the opening.

The dewatering apparatus of claim 1 wherein the walls of the o 20 screen chamber are comprised of a plurality of wedge bars arranged longitudinally and spaced apart to provide filtering spaces therebetween. 4

3. The dewatering apparatus of claim 1 wherein the pump arrangement includes an auxiliary pump to apply extra pressure to the slurry in the chamber.

4. The dewatering apparatus of claim 1 wherein the auxiliary pump comprises a periodically acting piston pump and the slurry inlet means upstream from the auxiliary pump includes a one-way flow valve.

The dewatering apparatus of claim 3 wherein the pump arrangement supplies slurry at a pressure of up to 3,000 pounds per square inch and the auxiliary pump is adapted to supply pressures of up to 6,000 pounds per square inch. ty 4 ri 11

6. The dewatering apparatus as in claim 1 wherein the exit means includes a gate which may be opened at intervals to enable the extrusion of a plug of solid product.

7. The dewatering apparatus of claim 1 wherein the exit means includes a multi-chambered revolving extractor such that in one position a chamber of the extractor is in a plug of solid product receiving position and in a further position the chamber is in a plug of solid product removal position.

8. A dewatering apparatus as in any one preceding claim wherein a housing around the chamber has vacuum applied thereto to assist with dewatering of the slurry.

9. A method of dewatering a slurry on a continuous basis i comprising pumping the slurry under high pressure into an elongate ,parallel walled filter chamber, the filter chamber having side t T 20 walls comprising a screen arrangement and an open exit end, I, causing a wad of dewatered material to build up in the chamber Ki towards the open exit end and continuously extruding the wad from i the open end by means of the high pressure of pumped slurry exerted on the wad within the chamber. A dewatering apparatus substantially as hereinbefore described with reference to and as illustrated by the accompanying drawings. ii 30 Dated this 4th day of June 1991 MACRAE ENGINEERING PTY. LIMITED. By their Patent Attorneys COLLISON CO.