IMPROVEMENTS IN OR RELATING TO SEPARATORS

Abstract: This invention relates to a method of, and apparatus for, separating contaminates from a base liquid and whereby the contaminated base liquid is passed through a pretreatment vessel before being passed to a conventional separator. In one described embodiment, the pretreatment vessel (11) is of generally cylindrical form arranged with its axis substantially vertical, base liquid to be de-contaminated is supplied into the mid-height regions of the vessel through a tangential device (16) to cause circulating flows within the vessel (11), and the vessel (11) includes an outlet (13a) in its top regions (13) for the release of light contaminates, an outlet (12a) in its lower regions for the release of heavy contaminates, and an outlet duct (30) in its mid-region, spaced from the inlet for releasing partially contaminated liquid from the vessel (11), for release into a conventional separator (26). Preferably the method includes the steps of introducing a first treatment material to the base liquid before, or as, the base liquid enters the vessel (11) and adding a second treatment material into the partially decontaminated base liquid to be directed to the conventional separator (26).

Description: " -PROVE-.ENTS IN OR RELATING TO SEPARATORS" This invention relates to separators and, more particularly, to separators for separating particulate solids and semi-solids contaminates from a base liquid. Separators for separating particulate solids and semi-solids contaminates from a base liquid are well known in the art and in one form comprises a generally cylindrical vessel, arranged with its axis substantially vertical, a conical bottom closing the lower regions of the vessel and a top or roof closing the upper regions of the vessel. The vessel includes an outlet for "heavy" contaminates, that is to say contaminates having a specific gravity greater than the specific gravity of the base liquid, in the lower regions of said bottom and from which the heavy contaminates are continuously extracted, an outlet for "light" contaminates, that is to say contaminates having a specific gravity less than the specific gravity of the base liquid, in the upper regions of the vessel and from which light contaminates are continuously extracted and an outlet for de-contaminated liquid in the upper regions of the vessel from which de-contairiinated liquid is continuously extracted. The contaminated liquid is supplied into the vessel tangentially through a side opening and the tangential entry of the contaminated base liquid generates circulating flows within the vessel, which induce laminar flows to assist in the vertical displacement of the contaminates within the vessel. This form of separator, hereinafter referred to as a separator of the type defined, is well known in the art and the construction and method of operation are known in such detail, as for example from British Patent Publication No.2205512 and British Patent Publication No. 2158741, that no further description of the separator, or its mode of operation, is required herein. Separators of the type defined work efficiently only within relatively close limits, wherein the rates of flow of C-Ontaπ nated base liquid into the vessel and through the outlets from the vessel are substantially constant and the residence time of the contaminates in the separator is sufficient for said contaiiiinates to fall or rise towards their respective outlets and thereby out of the flows to the de¬ contaminated liquid outlet. A serious problem with separators of the type defined arises when the contaminated base liquid is very heavily contaminated with light or heavy contaminates, when the relevant ccmtarninate outlet(s) may be inadequate for dealing with the excessive volume of contaminates to be removed and become choked with contaminates. If, because of a complete or partial blockage, the rate of flow through a conl-aininates outlet should be reduced, the flow system throughout the separator will change and contaminates will be carried up the spiralling flows in the upper central regions of the vessel and will be carried over with the de-contairtinated liquid. This problem is particularly acute when the contaminate contents of the ccntaininated base liquid is variable. It has been proposed that this problem may be overcome by arranging two separators of the type defined in series, whereby the partially de-contaminated liquid from the first separator is supplied to the second separator, but this solution simply means that the first separator is subjected to the overload conditions defined above and, even if the first separator is able to cope with the contaminates, the varying volume of contaminates removed in the first separator can vary the rate of flow of the partially de-contaminated liquid flowing to the second separator and will thereby adversely affect the efficiency of that separator. It is well known in the art to add treatment materials to a contaminated base liquid, to chemically change one or more of said contaminates or to cause flocculation of contaminates, to facilitate remove of the treated contaminates but, to be effective, such treatment materials must be intimately mixed throughout the base liquid and the flows within a separator of the type defined are too slow to effect the required distribution of a treatment material injected into the vessel. A further problem is that the treatment materials often require a time period in order to effectively react with the contaminates and, as in separators of the type defined the greater part of the contaminates are removed, or are committed to removal, in the early part of the entry of the cont_aminated liquid into the separator, the residence time of the base liquid in a separator of the type defined is inadequate for most treatment materials to be effective on the contaminates and for the separator to effectively separate the treated contaminates from the base liquid. The present invention seeks to provide a method for separating contaminates from a base liquid and which is more efficacious than the known methods of separating. According to the present invention there is provided a method for separating contaminates from a base liquid comprising the steps of supplying contaminated base liquid at a substantially uniform rate to a pre-treatment vessel in a manner to cause circulating flows within said vessel, treating said contaminated liquid in said vessel, allowing contaminated base liquid to flow from the vessel through an outlet so spaced from the inlet for the contaminated liquid, in the direction of said circulating flows, that the liquid flowing through said outlet has spent at least a predeteππined time in said vessel and passing the treated contaminated base liquid to a separator of the type defined. Preferably the method includes the steps of introducing the contaminated liquid tangentially into the said pre-treatment vessel. In one embodiirtent the method is characterised by the steps of treating the contaminated base liquid in said vessel by inducing flows in said vessel to concentrate at least part of the contaminates in one part of the vessel, continuously extracting the concentration of contaminates from said vessel, allowing partially de-contaminated base liquid to flow from the vessel through an outlet spaced from that part of the vessel in which contaitiinates are concentrated and passing the partially de-contaminated base liquid to the separator of the type defined. In one enibodiment the method is characterised by the steps of arranging an outlet through which heavy contaminates can be extracted in the lower regions of the vessel and arranging the outlet for the partially de¬ contaminated liquid in the upper regions of said vessel. In another embodiment the method is characterised by the steps of arranging an outlet through which light contaminates ca be extracted in the upper regions of the vessel and arranging the outlet for the partially de- contaminated liquid in the lower regions of said vessel. Preferably the method is characterised by the steps of arranging an outlet through which light contaminates can be extracted in the upper regions of the vessel, arranging an outlet through which heavy contaminates can be extracted in the lower regions of the vessel and arranging the outlet for the partially de-containinated liquid to open into the mid-height region of the vessel. In such an embodiment the method preferably includes the steps of arranging the outlet for the partially de¬ contaminated liquid to open adjacent the central axis of the said vessel Preferably the method is characterised by the steps of introducing a treatment material into the contaminated base liquid. Preferably the method includes the steps of introducing the treatment material into the contaminated base liquid before said contaminated base liquid is passed into said vessel. Preferably the method includes the steps of selecting said treatment material from the group comprising ferric salts, (sulphate or chloride), aluminium sulphates, lime, lime carbonate, caustic soda or any other of the materials for chemically changing or flocculating contaminates well known in the art. In a prefered embodiment the method is characterised by the steps of introducing a second treatment material into the partially de-contaminated base liquid being supplied to the separator of the type defined. In such an embodiment the method includes the steps of selecting the second treatment material to comprise a polymer material intended to cause a reaction of the contaπiinates in the base liquid, after intimate mixing with the first treatment material. The invention also envisages apparatus, comprising a separator of the type defined in combination with a pre- treatment vessel, characterised by means for generating circulating flows in the contaminated liquid in said pre¬ treatment vessel and means for supplying treated contaminated liquid to the separator of the type defined. Preferably the apparatus is characterised in that the pre-treatment vessel comprises a substantially cylindrical vessel arranged with its axis substantially vertical. In one embodiment the apparatus is characterised by means for removing heavy contaminates from the lower regions of the vessel and means for extracting partially de-contaminated liquid from the upper regions of the vessel. In another embodiment the apparatus is characterised by means for extracting light contaminates from an upper region of the vessel and means for extracting partially de-cont3minated liquid from the lower regions of the vessel. In a further embodiment the apparatus is characterised by means for extracting light contaminates from the upper regions of the vessel, means for removing heavy contaminates from the lower regions of the vessel and means for removing treated contaminated liquid from a mid-height region of the pre-treatment vessel. Preferably the apparatus is characterised by means for introducing a treatment material into the contaminated base liquid being supplied to said pre-treatment vessel. Preferably the apparatus includes means for mixing the said treatment material into said contaminated base liquid. Preferably the apparatus includes means for mixing a second treatment material into the base liquid being supplied from said pre-treatment vessel to said separator. In a preferred eπi-x>d-urιent the said means for mixing comprise a hydro-brake mixing device. The invention will now be described further by way of example with reference to the acccjmpanying drawings in which the single figure shows, diag ammatically and partially in cross-section, a separator arrangement in accordance with the invention. In the illustrated embodiment a pre-treatment vessel 11, of generally cylindrical form, is arranged with its central axis substantially vertically, the lower regions of the vessel are defined by a conical bottom 12 and the upper regions of the vessel are defined by a conical top 13. A central aperture 12a_ in the bottom 12 defines an outlet for heavy contaminates and a central outlet 13a_, in the top 13, defines an outlet for light contaminates. The vessel 11 is supplied with contaminated base liquid from a header tank 14 which discharges via a duct 15. The duct 15 opens into the mid-height region of the vessel 11 and, via a tangential flow device 16, the liquid from duct 15 is discharged tangentially into the vessel 11 to generate circulating flow therein. Tangential devices 16 are well known in the art and are described in detail in, for example, the British Patent Publications referred to hereinbefore and, accordingly, no further description thereof is necessary. With the tangential device 16 generating circulating flows about the central axis of the vessel 11, and which circulating flows essentially develop liminar flows in the liquid, heavy contaminates in the liquid are allowed to fall tinder gravity to the bottom 12 and light contaminates flow upwardly within the vessel to the top 13. The aperture 12a_ in the bottom 12 of the vessel 11 opens to a flow passage 17, which connects with a valve 18. The valve 18, when in one position, ducts liquid from the flow passage 17 to a duct 19, which leads to an exhaust. In its other position the valve 18 ducts liquid from the flow passage 17 to a duct 20. In like manner the aperture 13a_ in the top 13 is open to a flow passage 21 which extends to a valve 22. The valve 22, in one position, ducts the liquid from flow passage 21 to a duct 23, extending to an exhaust, and in another position a valve 22 ducts liquid from flow passage 21 to a duct 24. The ducts 20 and 24 extend to, and open into, a common duct 25, which constitutes the inlet duct to a separator of the type defined 26. In one mode for operating the apparatus described thus far, and when a contaminated base liquid to be processed include a large volume of heavy contaminates, the valve 18 is set to duct all the flows from flow passage 17 through to duct 19. At the same time the valve 22 is so positioned that flows from flow passage 21 to duct 23 are closed and all the flows from flow passage 21 are directed through the valve 22 to duct 24. With the valves 18 and 22 so set, and with the vessel 11 charged with contaminated liquid, and heavily C-ontaminated liquid entering the vessel 11 via the duct 15 and tangential device 16, the greater part of the heavy contaminates entering the vessel 11 fall rapidly down the vessel 11 to the conical bottom 12, down the sloping wall of conical bottom 12 into the fiow passage 17 and to exhaust, via the duct 19. The partially de-contaminated liquid, perhaps with some small part of the heavy contaminates as may be carried upwardly in the vessel 11 and with the light contaminates, flows through the flow passage 21 to the duct 24 and, therefrom, via duct 25 into the separator 26. Thus, by this mode of operating the pre-treatment vessel 11, the greater part of the heavy contaminates are removed from the contaminated liquid before said liquid is passed into the conventional separator 26. In another mode of operation, when the contaminated liquid includes a large volume of light contaminates, the valve 22 is positioned to duct liquid from the flow passage 21 to the exhaust duct 23, and the valve 18 is set to open the flow passage 17 to the duct 20. Thus, in this mode of operation, the light contaminates entering the vessel 11 are allowed to flow upwardly witnin the vessel 11 and therefrom through the aperture 13 to flow passage . 21 and through the valve 22 to the exhaust duct 23. At the same time partially de-contaminated liquid, with the heavy contaminates and perhaps some part of the light contaminates, flows through aperture 12a_, through flow passage 17, through the valve 18, and along the duct 20 to the duct 25. In another mode of operation, intended for use when the contaminated liquid contains large volumes of both heavy and light contaminates, the vessel is modified to include a duct 30, which extends from the duct 25, through the wall of the vessel 11 and terminates in a vertical duct 31, open at both ends and having its axis concentric with the axis of the vessel 11. the upper open end of the duct 31 lies above the horizontal plane passing through tangential device 16 and the lower open end of the duct 31 lies below said plane. The duct 30 conveniently includes a valve 32. In operating the apparatus in this mode, the valve 18 is positioned to discharge all the heavy contaminates falling through the aperture 12a. to the exhaust 19, the valve 22 is positioned to discharge all the light contaiτiinates rising through the aperture 13a_ to exhaust 23 and the partially de¬ contaminated liquid is taken off through the duct 31, the duct 30, and through the valve 32 to the duct 25 supplying the separator 26. It will be appreciated that when the liquid has a large volume of light or heavy contaminates the flow rates through the relevant contaminates flow passage 17 or 21 will be controlled so that the maxiπum volume of contaminates with the minimum volume of liquid is passed to exhaust It will be observed that in all the above described embodiments the contaminated liquid is supplied to the vessel under a substantially constant hydraulic head and with the cross sectional area of the duct 15 greater than the sum of the cross-sectional areas of all the outlets 12a, 13a_ and 31, a substantially uniform supply of partially contaminated liquid to the separator is obtained. The separator apparatus as illustrated also includes a mixing device 33, for example a hydro-brake device, in the supply conduit 15 and by way of which a treatment material may be added to the contaminated liquid via a duct 34. Thus, the treatment material can be continuously added to the contaminated liquid and intimately mixed therewith in the device 33. The mixing and distribution of the treatment material through the contaminated liquid will continue as the liquid passes into and through the vessel 11 and the residence time of the treated liquid in the vessel 11 will allow the treatment material to be effective on the liquid and/or the contaminates in the liquid, before the treated liquid is passed to the separator 26. Treatment materials which may advantageously be used as flocculation/collection agents conveniently comprises ferric salts, (sulphate or chloride), aluminium sulphates, lime, lime carbonate, caustic soda, or any other of the materials for chemically changing or flocculating contaminates well known in the art. The apparatus preferably also includes a further hydro-brake 35, in the duct 20, and via which a second treatment material such as a "fixing" material, i.e. a polymer, may be added to the partially contaminated liquid via a duct 36. It will now be apparent that the apparatus illustrated allows a pre-treatment material to be added to the -tntaminated liquid, intimately mixed throughout said material, and afforded a time interval within which to react with the liquid or contaminates in the liquid before the treated liquid is passed to the separator 26 of the type defined, and the apparatus also allows a second treatment material to be introduced into the pre-treatment material to be introduced into, and intimately mixed with, the pre-treated liquid before said liquid is passed to the separator 26. It will also be apparent that the treatment material aspects of the invention can be practised with or without use of the vessel 11 as a means for removing excessive heavy or light contaminates from the contaminated liquid. Whilst in the embodiment described above a single multi-purpose, pre-treatment vessel has been described it will be appreciated that the apparatus may include more than one pre-treatment vessel and thus, for certain applications, the apparatus may comprise a first pre-treatment vessel for removing excess heavy contaminates from the liquid, a second pre-treatment vessel for removing excess light contaminates from the partially decontaminated liquid, and a third pre¬ treatment vessel for chemically treating the liquid before said liquid is passed to the separator 26.

Claims: CLAIMS 1. A method for separating contaminates from a base liquid comprising the steps of supplying contaminated base liquid at a substantially uniform rate to a pre-treatment vessel in a manner to cause circulating flows within said vessel, treating said contaminated liquid in said vessel, allowing contaminated base liquid to flow from the vessel through an outlet so spaced f om the inlet for the contaminated liquid, in the direction of said circulating flows, that the liquid flowing through said outlet has spent at least a predetermined time in said vessel and passing the treated contaminated base liquid to a separator of the type defined. 2. A method according to claim 1, characterised by the steps of introducing the contaminated liquid tangentially into the said pre-treatment vessel. 3. A method according to claim 1 or 2, characterised by the steps of treating the contaminated base liquid in said vessel by inducing flows in said vessel to concentrate at least part of the contaminates in one part of the vessel, continuously extracting the concentration of contaminates from said vessel, allowing partially de-contaminated base liquid to flow from the vessel through an outlet spaced from that part of the vessel in which contaminates are concentrated and passing the partially de-contaminated base liquid to the separator of the type defined. 4. A method according to claim 3, characterised by the steps of arranging an outlet through which heavy contaminates can be extracted in the lower regions of the vessel and arranging the outlet for the partially de-contaminated liquid in the upper regions of said vessel. 5. A method according to claim 3, characterised by the steps of arranging an outlet through which light contaminates can be extracted in the upper regions of the vessel and arranging the outlet for the partially de-contaminated liquid in the lower regions of said vessel. 6. A method according to any one of claims 1,2,3,4 or 5, characterised by the step of arranging an outlet through which light contaminates can be extracted in the upper regions of the vessel, arranging an outlet through which heavy contaminates can be extracted in the lower regions of the vessel and arranging the outlet for the partially de¬ contaminated liquid to open into the mid-height region of the vessel. 7. A method according to claim 6, characterised by the steps of arranging the outlet for the partially de-contaminated liquid to open adjacent the central axis of the said vessel 8. A method according to any one of claim 1 to 7 inclusive characterised by the steps of introducing a treatment material into the contaminated base liquid. 9. A method according to claim 8, characterised by the steps of introducing the treatment material into the contairiinated base liquid before said contaminated base liquid is passed into said vessel. 10. A method according to claims 8 or 9, characterised by the steps of selecting said treatment material from the group comprising ferric salts, (sulphate or chloride), aluminium sulphates, lime, lime carbonate, caustic soda or any other of the materials for chemically changing or flocculating contaminates well known in the art. 11. A method according to claim 8,9 or 10, characterised by the steps of introducing a second treatment material into the partially de-contaminated base liquid being supplied to the separator of the type defined. 12. A method according to claim 11, characterised by the steps of selecting the second treatment material to comprise a polymer material intended to cause a reaction of the contaminates in the base liquid, after intimate mixing with the first treatment material. 13. Apparatus comprising a separator of the type defined in combination with a pre-treatment vessel, characterised by means for generating circulating flows in the contaminated liquid in said pre-treatment vessel and means for supplying treated contaminated liquid to the separator of the type defined. 14. Apparatus according to claim 13, characterised in that the pre-treatment vessel comprises a substantially cylindrical vessel arranged with its axis substantially vertical.. 15. Apparatus according to claims 13 or 14, characterised by means for removing heavy ccrntaminates from the lower regions of the vessel and means for extracting partially de-contaminated liquid from the upper regions of the vessel. 16. Apparatus according to claims 8,13 or 14, characterised by means for extracting light contaminates from an upper region of the vessel and means for extracting partially de-contaminated liquid from the lower regions of the vessel. 17. Apparatus according to claims 13,14,15 or 16, characterised by means for extracting light contaminates from the upper regions of the vessel, means for removing heavy contaminates from the lower regions of the vessel and means for removing treated contaminated liquid from a mid-height region of the pre-treatment vessel. 18. Apparatus according to claims 13,14,15,16 or 17, characterised by means for introducing a treatment material into the contaminated base liquid being supplied to said pre¬ treatment vessel. 19. Apparatus according to claim 18 characterised by means for mixing the said treatment material into said contaminated base liquid. 20. Apparatus according to claims 18 or 19 characterised by means for mixing a second treatment material into the base liquid being supplied from said pre-treatment vessel to said separator. 21. Apparatus according to claims 19 or 20 characterised in that said means for mixing comprise a hydro- brake -nixing device. 22. Apparatus for separating contaminates from a base liquid substantially as herein before described with reference to and as illustrated in the accompanying drawings.

Inventors: TIMMONS ALBAN, TIMMONS, ALBAN
Applicants: CLEAN WATER CO LTD, THE CLEAN WATER COMPANY LIMITED
Application year: 1992
Main classification: B01D21
IPC codes: B01D17, B01D21, B03D3, C02F1