Liquid purification or separation – Processes – Liquid/liquid solvent or colloidal extraction or diffusing...
Reexamination Certificate
1997-12-01
2002-06-11
Drodge, Joseph W. (Department: 1723)
Liquid purification or separation
Processes
Liquid/liquid solvent or colloidal extraction or diffusing...
C210S087000, C210S093000, C210S108000, C210S139000, C210S321690, C210S739000, C096S422000
Reexamination Certificate
active
06402954
ABSTRACT:
TECHNICAL FIELD
The invention herein resides in the art of fluid filtration systems and, more particularly, to a liquid filtration system which accommodates the periodic cleaning of the filter with a cleaning solution. Specifically, the invention relates to a liquid filtration system in which the efficiency of the system is continually optimized by periodically cleaning the filter to its maximum filtration capability and subsequently entering the filtration process until such time that the permeate flow rate of the liquid through the filter membrane indicates that cleansing of the filter is again required.
BACKGROUND ART
It has previously been known to filter liquids which comprise a process fluid having both low molecular weight organics such as water, dissolved salts, solvents, and high molecular weight organics such as emulsified oils, suspended solids, colloids, and polymers therein. Particularly, it has been known to provide a means for separating the low molecular weight liquid from the high molecular weight organic material entrained therein by passing the process fluid through a membrane filter. Such systems employ reverse osmosis filters or what are generally termed “ultra filters” in a two tank system in order to achieve the necessary filtering. Typically, a working tank contains the process fluid to be filtered and a cleaning solution tank contains a cleaning fluid such as an appropriate detergent to clean the filter itself. The systems typically contain valves that switch the filter from a working tank to a cleaning tank and back again. Such valves may be either manual or automated.
Ultra filters need to be cleaned or regenerated after they have been used for a period of time. One of the ways of determining that cleaning of the filter is required is to monitor the flow of liquid (permeate) from the filter membrane itself. As the flow decreases due to fouling or blinding of the filter, the efficiency of the system decreases. Accordingly, periodic cleaning of the filter itself is required by passing a cleaning fluid or detergent therethrough.
It is particularly important to terminate the filtering process and clean the filter prior to any point in time that the filter itself has become totally clogged or damaged. Such membrane filters are extremely expensive and, accordingly, in order to protect the filter and assure optimum operation of the filtering system, such periodic monitoring and cleansing of the filter is required. In the past, a variable area inline flow meter was monitored to manually determine the permeate flow rate through the filter membrane and to determine when cleaning of the filter was required. Such a technique is, of course, extremely inaccurate and given to costly error.
The prior art has generally taught numerous types of filtration systems for filtering the process fluid. Specifically, the prior art has taught a broad range of filtering systems in which periodic cleansing of the filter medium is undertaken. However, none of the prior art systems are given to an optimized automated approach to such filtration and maintenance of system integrity. There is a need in the art for an automated fluid filtration system which achieves optimization of the filtering process by monitoring the flow rate of permeate through the filter membrane and periodic cleaning of the filter as a function of such flow rate.
DISCLOSURE OF INVENTION
In light of the foregoing, it is a first aspect of the invention to provide a fluid filtration system which is substantially automatic in nature. Another aspect of the invention is the provision of a fluid filtration system which maximizes operation by periodically cleaning the filter medium when the permeate rate of flow drops below a determined level.
Still a further aspect of the invention is the provision of a fluid filtration system which substantially eliminates the possibility of human error in monitoring and determining the efficiency of the system.
Yet another aspect of the invention is the provision of a fluid filtration system which is highly efficient, reliable and durable in operation, and easy to implement with state of the art components and techniques.
The foregoing and other aspects of the invention which will become apparent as the detailed description proceeds are achieved by a fluid filtration system, comprising: a first supply of process fluid to be filtered; a second supply of filter cleaning fluid; a filter interposed between said first and second supplies; a pump interposed among said filter and said first and second supplies; an array of valves interconnected to said pump, filter, and first and second supplies, said valves allowing selective interconnection and circulatory intercommunication of said filter with said first and second supplies; and a flow meter connected to said filter, said flow meter providing output signals determinative of said selective interconnection.
Other aspects of the invention which will become apparent herein are attained by a method for filtering the process fluid, comprising: passing the process fluid through the filter until the flow rate of the permeate through the filter membrane drops below a first threshold; passing a cleaning solution through said filter to clean said filter to accommodate an increased flow rate of permeate through the filter membrane; reestablishing said first threshold; and passing process fluid through said filter until the flow rate of the permeate through the filter membrane drops below said first threshold.
REFERENCES:
patent: 3992301 (1976-11-01), Shippey et al.
patent: 4708790 (1987-11-01), Bray
patent: 4918426 (1990-04-01), Butts et al.
patent: 4921610 (1990-05-01), Ford et al.
patent: 4935143 (1990-06-01), Kopp et al.
patent: 5147552 (1992-09-01), Hlavacek et al.
patent: 5647988 (1997-07-01), Kawanishi et al.
Drodge Joseph W.
Renner Kenner Greive Bobak Taylor & Weber
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