Liquid purification or separation – Processes – Separating
Reexamination Certificate
1997-01-28
2001-03-13
Upton, Christopher (Department: 1724)
Liquid purification or separation
Processes
Separating
C210S800000, C210S307000, C210S416100, C210S499000, C210SDIG005, C210S540000
Reexamination Certificate
active
06200489
ABSTRACT:
BACKGROUND OF THE INVENTION
There are many industrial applications where it is necessary to separate first and second liquids. One application is in separating a small quantity of oil that is intimately mixed with water, so the oil can be recovered for use and the water can be disposed of without violating environmental regulations. A corresponding use is in separating a small amount of water contained in a larger quantity of oil, so the water does not harm machinery that uses the oil. Still another widespread use is in removing light organic components (e.g. kerosene) from an aqueous stream (e.g. water, or electrolyte, or raffinate) as described in U.S. Pat. No. 5,273,654. Larger droplets of the second liquid can be removed by known coalescing devices such as a plate coalescer. However, a high proportion of microscopic droplets, left after coalescing, cannot be removed by such devices.
A high proportion of microscopic droplets of one liquid, such as water mixed into oil, usually can be removed by pumping the mixture through a disposable filter such as an automobile oil filter. However, it is expensive to use such disposable filter where a large quantity of the second liquid must be removed. Perhaps 90% of microscopic droplets would eventually coalesce and rise to the surface of a settling tank, after a period of time of a few days to a few months (assuming the mixture was not disturbed), but this period is too long for most applications. It is noted that automobile filters, fine steel wool, and sintered metal can serve as filters, but they have long passages that clog and that are not readily cleaned by reverse flow. Such devices can be cleaned of oil and a small amount of solid particles by flowing a light hydrocarbon such as kerosene that dissolve them, but this results in the problem of how to environmentally dispose of the kerosene. A system for use in removing a high percentage of microscopic droplets of a second liquid contained in an intimate mixture with a first liquid, such as oil from water, water from oil, or organics from an aqueous stream, which was of moderate cost to construct and operate, would be of value.
SUMMARY OF THE INVENTION
In accordance with one embodiment of the present invention, a system is provided for use with an intimate mixture of first and second liquids, which coalesces microscopic droplets of the second liquid by passing the mixture through a screen, so the coalesced drops of the second liquid can be readily removed by conventional devices, which is highly of moderate cost and which is effective. The screen is formed of woven threads of a material that is wetted by the second liquid. The screen has very closely spaced threads so the screen retains fine particles such as those having a diameter no more than 25 microns. The mixture is pumped through the screen at a very low velocity such as no more than thirty centimeters per minute (twelve inches per minute). Applicant finds that by thus slowly moving the liquid through the very fine screen, that the microscopic droplets of the second liquid are coalesced by the screen into larger droplets that can be readily separated as by a conventional plate coalescer.
Flow through the woven screen is reversed at intervals, with the liquids passing through the screen being delivered to a coalescer for either direction of movement through the screen. Thus, the reversal is not a backwash. The fine screen can be wrapped around a rigid tube that has numerous holes, with a resilient holder wrapped around the screen to hold it in intimate contact with the outside of the tube.
The novel features of the invention are set forth with particularity in the appended claims. The invention will be best understood from the following description when read in conjunction with the accompanying drawings.
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Dzhragatspanyan Misak
Greene William A.
Rosen Leon D.
Spintek Systems, Inc.
Upton Christopher
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