CA1056734A

CA1056734A - Oil-water separator with enveloped coalescer regenerated by compression

Info

Publication number: CA1056734A
Application number: CA226,330A
Authority: CA
Inventors: Daniel H. Fruman
Original assignee: Hydronautics Inc
Current assignee: Hydronautics Inc
Priority date: 1974-05-06
Filing date: 1975-05-06
Publication date: 1979-06-19
Also published as: JPS5817643B2; JPS5123864A; DE2519959A1; DE2519959C2; IT1037882B; FR2269992A1; FR2269992B1; GB1495314A

Abstract

INVENTOR
DANIEL H. FRUMAN

TITLE
OIL-WATER SEPARATOR WITH
ENVELOPED COALESCER
REGENERATED BY COMPRESSION

ABSTRACT OF THE DISCLOSURE

Oil-water separation apparatus having a flow-through chamber containing a block foam filter material regenerable by squeezing, a pair of perforated end plates located on either side of the foam block within the chamber at least one of which responds to applied pressure to squeeze the foam, and a flexible envelope of impervious material sur-rounding the foam block between the block and the inside walls of the chamber and connected at each end to the plates to avoid channeling and friction between the foam block and the walls of the chamber.

Description

~0~6734 This invention relates to oil-water separation apparatus. More particularly, this invention relates to an improved, cartridge-type filtering apparat~ls contalning a block of squeezable foam that is encased in an envelope of flexible, impervious material to avoid channeling and provide a more efflcient and effective oil-water separation process.
In U. S. Patent No. 3,617,551 to Johnston, there is generally disclosed oil-water separation apparatus having a flow-through chamber containing a block of regenerable, porous filter material, such as polyurethane foam. The block of material is located between a pair of spaced, perforated plates and at least one of the plates is movable in response to an applied pressure to periodically squeeze absorbedoil from the filter material and regenerate it for further use.
To minimize the tendency to channel or short-circuit the feed water along the walls of the chamber, the foam block is oversized with respect to the chamber to produce precompression of the foam against the inside walls of the chamber. The oversizing of the foam, however, necessarily creates friction between the foam and the stationary walls of the chamber during regeneration, preventing it from recovering its initial shape following regeneration. Mini-mization of the channeling, therefore, is limited by the elastic capacity of the foam to overcome this friction generated by the lateral precompression. Moreover, the shape of the foam resulting from its incomplete recovery because of wall friction results in a deterioration of its filtration characteristics and may affect its integrity after repeated squeezing.
Accordingly, it is an object of the present invention to provide a cartridge-type, filtering apparatus that success-

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fully avoids channeling in the flow o~ -feed water through the apparatus but that perlnits the foam block to readily compress and expand within the chamber during regeneration without interfeTing with the side walls of the chamber.
In accordance with the present invention, SUC]l objectives are achieved in oil-water separation apparatus having a flow-through separation chamber containing a block of porous material regenerable by compression and a pair of perforated plates located on either side of the block at least one of whicll responds to applied pressure to compress the material, by providing an envelope of flexible, impervious material completely surrounding the outer surface of the foam block between the block and the inside walls of the chamber. The envelope is connected at either end to the plates and prefer-ably in a releasable manner so that the foam material and envelope can be readily replaced when necessary.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory but are not restrictive of the inventicn.
The accompanying drawings constitute a part of the speci~ication and illustrate a p-feferred embodiment of the invention and together with the description serve to explain the principles of the invention.
Of the drawings:
FIG. 1 is a schematic, cross-sectional view of a cartridge-type oil-water separation apparatus embodying the improvement of the prqsent invention;
1 ~7. ~ is an cxploded, fragmentary view showing a clamp^
in~ of the flexible envelope to the perforated plates; and l:IG. 3 is a fragmentary view similar to FIG. 1, but s}lowing tne foam block during regencration.

_ 3 ~

~0567~

With reference to FIG. 1, the oil-water separation appara-tus includes a housing 10 having an oil-contaminated water inlet 12 and outlets 14 and 16 for the separated oil and water, respectively. ~lousing 10 is divided into three interconnected chambers, preferably arranged horizontally as shown in the drawings. These chambers consist of a separation chamber 20 essentially in the middle of the housing, a feed chamber 22 communicating with the influent side of separation chamber 20 for distributing the flow of feed uniformly through that chamber, and a floatation chamber 24 on the effluent side of the separation chamber for receiving the effluent from the separation chamber and permitting gravity separation of the effluent.
Separation chamber 20 is filled with a cartridge or block of porous material 26, having filtering characteristics Wit]l respect to the contaminated feed and, more particularly, oil-absorbing and oil-coalescing characteristics, that is regenerable by compression to remove absorbed contaminant from the material. Block 26 is held in position in housing 10 between two perforated plates 28 and 30; the rear perforated plate 28 being fixed in the housillg ancl the front plate 30 being mounted for axial movement in response to applied pressure with respect to fixed plate 28. As shown, the means for applying pressure to plate 30 to compress porous block 26 and regenerate it for furthe:r use comprises a hydraulic cylinder 32 mounted on the front wall 3~ of housing 10 and having a piston 36 that extends through feed chamber 22 and is connected to movable perforated plate 30. Thus, it can be seen that, as hydraulic cylinder 32 is actuated, perforated plate 30 pushes towards fixed rear plate 2~
compressing material block 26 and expelling absorbed contamin-ant out of thc block and into chambers 22 and 24.

1~56734 Alternatively, if it is desired to express the absorbed contaminant during compression in only one direction, for example, only into floatation chamber 24, suitable one-way valves would be incorporated in plate 30 that would be open during the flow of feed through the system, but that would close during compression and regeneration.
Feed chamber 22 of housing 10 is defined by the space between the inside of front wall 34 and the front face of perforated plate 30 in its retracted position. ~Vhile the provision of a feed chamber is not essential, it is desirable to permit the feed to be uniformly distributed over perforated plate 30 for uniform flow through porous block 26.
In accordance with the present invention, a flexible envelope 40 of impervious material completely surrounds the outer surface of foam block 26 and is located between the block and the inner wall surface 42 of separation chamber 20. Envelope 40 is of less diameter than wall surface 42 and is connected at either end to perforated plates 28 and 30, thus essentially providing a cartridge of filter material between the end plates that is separated from the inner wall of the housing.
The selection of the material comprising porous block 26 is not critical provided the material has an open, reticulated structure and when used as an oil-water separator desirably have both oil-absorbing and oil-coalescing proper~ies.
A material found to be ideally suited for such use is a block of polyurethane foam having a pore size of between 30 and 100 pores per linear inch (ppi) and preferably a pore size of around 60 ppi. As more f--lly described below in connection with the operation of ths system, it has been found that such polyurethane foams demonstrate excellent oil-scavenging propertics wit?l good flow characteristics over a large range of oil properties ~nd concentrations.

Material 26 may consist of a pluraliky of discrete chips OT a plurality of se-gmented pads lined up in series within the envelope, but preferably is a single, integral block of the porous foam. The block, in general, is found to be more eficient than filling up the envelope with a plurality of small chips of a compressible material.
Envelope 40 is preferably a sheet of impervious fabric having a rubberized coating, such as a hy~alon coated sheet of a polyester fabric.
In accordance with the invention, clamping means are provided for releasably clamping the ends of the envelope to the plates so that the envelope and foam block can be removed and replaced when necessary. As embodied and as best shown in FIG. 2, this means comprises an annular bracket 44 located on the inner surfaces of each plate that forms a channel 46 opening outwardly with respect to separation chamber 20.
The ends of envelope 40 are draped into channels 46 and then clamped in place by a cable 48. The ends of cables 48 can be simply crimped together and then cut apart when it is necessary to replace the envelope or preferably they can be provided with a quick releasable clamp so they can be reused following replacement of the envelope. In any event, the clamping means should be tight enough to provide a sealed connection between the envelope and the plate and in particular between the envelope and the downstream plate.
Preferably, housing 10 and foam block 26 are circular and the block is oversized with respect to envelope 40 to precompress the foam against the envelope and avoid channeling between the envelope and the foam and the envelope is of less diameter than the chamber to prevent the envelope from contacting with the walls of the separation cllamber.
Preferably, floatation chamber 24 is contiguous with separation chamber 20, forming an integral part of housing 10 and detined by the section between fixed rear perEorated plate 2g and the rear w~ll of the hous;ng. This provides a more COJIlpaCt and efficient separator, but it will readily be apparent to those skilled in the art that chamber 2~ could be remote from the housing with suitable piping to transfer the effluent to the chamber.
Chamber 24 is preferably divided into two parts, as more clearly sho~n in Fig. 1, by a baffle 39 to avoid contamination of the clean water outlet 16 and to increase gravity separation by creating an upward flow of the ef-fluent in the chamber. When the oil is a light oil, the coalesced droplets accumulate at the top of chamber 24 and the upward flow of effluent along the baffle 39 assi,sts in purgi,ng the ' droplets in this direction and out through oil outlet 14.
To control the level of accumulated oil in chamber 24, a plurality of oil-water interface detectors 41,- 43, and 45 schematically il'lustrated in Fig. 1 are provided in rear wall 38 of housing 10. These detectors are conventional and operate on the differences in electrical conductivity of water and oil. Thus, for example, when the oil level in chamber 24 falls below middle dectector 43, thus changing the conductivity between detectors 43 and 45, an oil pump (not shown~ would be activated to pull the oil out of outlet 14 and thereby prevent the oil from falling to a level where it could contaminate the clean water outlet. Oil withdrawal is contînued until the oil-water interface reaches detector 41 and then the pump is de-activated. This, of course, would be the arrangement for light oil-contaminated water, suitable modifications being made when heavy oil-contaminated water was being passed through the system.
In operation and with reference to Figc 1, the con-taminated feed is fed through inlet 12 into feed chamber 22 of separator 10 wherc it is evenl~ distributed throughout ~056734 the cross-sec~ional dimensions o ~he hous~ng. The porous regenerable material 26 meetîng the abo~e-de:Eined criterion is typicall~ a piece of polyurethane foa~ su~stantially filling up the space in separation cham~er 20 bounded by e-nvelope 40 aild plates 2~ and 3a and having 60 pores per linear inch, a thickness of approximatel~ 16 inches, and a cross-sectional area of approximately 4 square feet. rhe conta2,l-nated feed flows through foam block 26 where the oil is absorbed and/or coalesced depending upon the degree of saturation of the foam.
In the beginning, practically all of the oil is absorbed by the foam, but after the foam begins to become saturated~
large droplets of coalesced oil start to appear in the effluent as a result of the oily water passing through the foam. Discharging this effluent in chamber 24, however, permits the large coalesced droplets of the oil to be readily separated by gravity, so that it is not necessary to shut off the feed at this point and regenerate the foam just because oil appears in the effluent. The separated droplets are then withdrawn through oil outlet 14 and the heavier, clean water through outlet 16.
The separation step cannot be sustained indefinitely.
At a certain level of oil saturation of foam pad 26, the pressure drop across the foam increases to such an extent that it tends to block the flow of contaminated water. The flow of water is then stopped and regeneration of foam block 26 is accomplished by moving perforated plate 30 toward fixed plate 28 by hydraulic cylinder 32 to compress the foam and expel the absorbed oil. The oil expelled from the foam

3~ flows into both feed chamber 22 and ~loatation chamber 24 where it rises to the top of the chambers and ~s dra~n off through oil outlets 14 and 14'.
To assist in purging th.e e~pelled oi;l, clean water can be pumped back into cham~crs 2Z and 2~ during regeneration by pump 59, as shown in Fig. 1, to push.accumulated oil toi~.ards oil outlets 14 and 14'. Following regeneratiorl, hydraul~c cylinder 32 is retracted, water inlet 16' and oil outlet 14' to feed chamber 22 are closed, and the oily water is again fed to the separator.
By permitting gravity floatation of the effluent from th.e polyurethane foam, both the abso.rbing and coalescing properties of the foam can be utilized resulting primarily in longer periods of operation between regeneration without sacrificing the quality of the effluent or the flow rate th.rough the separator.
During operation the feed will slip past plate 30 and form a stagnant pool of feed water around the envelope in the annular space 50 between the envelope and the chamber of equal or greater pressure than that of the flow of fluid th.rough the foam block. While this feed is still contamin-ated, it can be seen that it cannot short-circuit the block and pass unfiltered to chamber 24 because the downstream end of the envelope is sealably clamped to fixed plate 28. The presence of this pressurized pool o-f feed water keeps the envelope out of contact with the walls of the housing and helps to compress the envelope against foam block 26, thus avoiding collapse of the foam and preventing channeling between the foam block and the envelope.
D.lri.ng regenerati.on, as discussed above and as shown in Fi~. 3, the flexible envelope folds up with the foam and 3~ keeps it out.of contact with the walls of the chamber, thercb~ a~oid.ing friction during compression and conse~uent wear on the su-rface of the foain and pelmitting e~pansion of 1~56734 the foam ~ack to its intial shaRe following regeneratian for more effective filtration.
In additi.on and to Rrevent slid~ng of the foam with respect to the envelope during compression and expansion, the flexible envelope can be glued to the outer surface of the foam block with a suitable polyurethane compatible glue, such as silicon rubber, with.out departing from the scope of th.e present invention.
The invention thus provides an improved foam block oil-water separator that more e-ffectivel~ avoi.ds channeli.ng wh.ile eliminating friction between the foam and the chamber walls during regeneration.
The invention ir its broader aspects is not limited to the specific details shown and described`and departures may be made from such details without departing from the principles of the invention and without sacrificing its chief advantages.

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Claims

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. Oil-water separation apparatus for separating an oil-water fluid comprising a housing having an inlet end and an outlet end; a pair of perforated plates axially spaced within the housing intermediate its ends, said plates forming between them and with the inner wall surface of the housing a flow-through separation chamber; porous filter material that is regenerable by compression located within the chamber; an envelope of flexible, impervious material surrounding the outer surface of the porous material adjacent the inner wall surface of the separation chamber, said envelope having an outer dimension less than the dimension of the inner wall surface of the chamber and being connected at each end to said plates to form an annular chamber spaced around the enveloped porous filter material between the enveloped and the inner wall surface of the chamber that can be pressurized with fluid in opposition to the pressure of flow of oil-water fluid through the separation chamber; said porous filter material being oversized in an uncompressed state with respect to said dimension of the envelope so that it is compressed into the envelope; and means for moving under pressure at least one of the plates with respect to the other plate so that the porous filter material and its surrounding envelope can be axially compressed within the chamber.

2. Apparatus of claim 1, wherein said outer surface of the, porous material is bonded to the envelope.

3. Apparatus of claim 1, wherein the perforated plate adjacent the outlet end is fixedly connected and sealed to the housing and the plate adjacent the inlet end is moveable within the housing, said envelope being sealably connected to the fixed plate to prevent the flow of oil and water being fed to the separation chamber from bypassing the porous material as it flows through the chamber and to form a stagnant pool of fluid around the envelope having a pressure equal to that of the flow of fluid being fed to the separation chamber.

4. Apparatus of claim 1, wherein the porous filter material comprises a block of polyurethane foam.

5. Apparatus of claim 1, wherein the housing, chamber, and plates have a circular cross section.

6. Apparatus of claim 1, including releasable clamping means clamping the ends of the envelope to the plates.

7. Apparatus of claim 6, wherein the clamping means comprises an annular bracket around the periphery of the perforated plates on the side adjacent the separation chamber and forming an annular and radially outwardly opening channel for receipt of the ends of the envelope; and a cable stretched around the channel to hold the ends of the envelope in place.

8. Apparatus of claim 1, wherein the envelope is a rubber coated sheet of fabric.