Liquid purification or separation – Processes – Making an insoluble substance or accreting suspended...
Patent
1994-04-26
1996-06-25
McCarthy, Neil
Liquid purification or separation
Processes
Making an insoluble substance or accreting suspended...
2105121, 210787, 210788, C02F 152, C02F 138
Patent
active
055296980
DESCRIPTION:
BRIEF SUMMARY
This invention relates to separators and, more particularly, to separates for separating particulate solids and semi-solids contaminants from a base liquid.
Separators for separating particulate solids and semi-solids contaminants 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" contaminants, that is to say contaminants 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 contaminants are continuously extracted, an outlet for "light" contaminants, that is to say contaminants having a specific gravity less than the specific gravity of the base liquid, in the upper regions of the vessel and from which light contaminants are continuously extracted and an outlet for de-contaminated liquid in the upper regions of the vessel from which de-contaminated 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 contaminants 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 contaminated base liquid into the vessel and through the outlets from the vessel are substantially constant and the residence time of the contaminants in the separator is sufficient for said contaminants to fall or rise towards their respective outlets and thereby out of the flows to the decontaminated 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 contaminants, when the relevant contaminants outlet(s) may be inadequate for dealing with the excessive volume of contaminants to be removed and become choked with contaminants. If, because of a complete or partial blockage, the rate of flow through a contaminants outlet should be reduced, the flow system throughout the separator will change and contaminants will be carried up the spiralling flows in the upper central regions of the vessel and will be carried over with the de-contaminated liquid.
This problem is particularly acute when the contaminant contents of the contaminated 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 contaminants, the varying volume of contaminants 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 contaminants or to cause flocculation of contaminants, to facilitate removal 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 m
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patent: 3788469 (1974-01-01), Hirsch et al.
patent: 3989628 (1976-11-01), Bier
patent: 4146468 (1979-03-01), Wilson
patent: 4278550 (1981-07-01), Watts
patent: 4855065 (1989-08-01), Keeter et al.
patent: 4863617 (1989-09-01), Katoh et al.
patent: 5082560 (1992-01-01), Eli et al.
patent: 5368747 (1994-11-01), Rymal, Jr. et al.
Drucker William A.
McCarthy Neil
The Clean Water Company Limited
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