Liquid purification or separation – Casing divided by membrane into sections having inlet – Each section having inlet
Reexamination Certificate
1999-03-31
2001-07-03
Barry, Chester T. (Department: 1724)
Liquid purification or separation
Casing divided by membrane into sections having inlet
Each section having inlet
C210S321890
Reexamination Certificate
active
06254773
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to filtration processes and apparatus of the kind using microporous membranes, wherein feed containing contaminant matter is applied under pressure to a feed receiving surface of the membrane for passage therethrough and wherein filtrate is withdrawn from the permeate side of the membranes.
More particularly, the invention relates to systems using microporous filters comprising elongate bundles of microporous polymeric fibres, wherein feed to be filtered is fed to the outside of the bundles of fibres and permeate is extracted from the ends of the fibre lumens. The systems also preferably incorporate a backwashing facility for periodic cleansing of the feed surfaces of the fibres.
BACKGROUND OF THE INVENTION
Typical prior art filter systems of the type described above generally include elongate tubular cartridges enclosing a bundle of the microporous hollow fibres. Manifold or header arrangements are then used to connect the cartridges, usually at one or both ends, these manifolds acting to separate and divert the respective flows of contaminated feed and permeate through the system. In this regard, cross-flow systems typically have two feed manifolds (inlet and re-circulation outlet) and one or two permeate manifolds. In cross-flow filtration systems of the prior art the stream to be filtered, flows tangential to or across the surface of the membrane. This generates a sweeping action at the membrane surface, keeping the surface cleaner. Conversely, systems configured for dead end operations have only one feed inlet manifold and one permeate outlet manifold. Further, these prior art manifolds or header arrangements are often configured to facilitate the construction of modular two or three dimensional cartridge arrays.
It should be noted that these systems operate under significant internal pressures. Accordingly, the cartridge casings and header manifold structures need to be made from high strength, and thereby correspondingly high cost, materials such as stainless steel and higher grade reinforced plastic materials specifically designed to withstand these pressures.
Most of the prior art designs available to date have proved satisfactory for small to medium scale applications. However, as there is now an increasing demand for larger scale systems, the current structures are proving to be prohibitively expensive due, for example, to the additional amount of connecting pipe work required and the costs of the componentary associated with each individual cartridge.
When attempting to design larger systems, it is not simply a matter of scaling up all the individual components. This is due, in part, because it is preferred that the individual constituents of the system remain sized so as to be readily man handlable for the purpose of assembly and maintenance. Further, as the structures themselves and associated flow paths get larger, the problems with pressure drops through the system become more significant.
It is an object of the present invention to provide a modified filtration assembly of the kind herein before described which overcomes or substantially ameliorates at least some of the disadvantages of the prior art or at least offers a useful alternative thereto.
DISCLOSURE OF THE INVENTION
According to a first aspect of the invention there is provided a filter assembly comprising:
an elongate housing having two or more discrete filter bundle lengths disposed end to end in a series configuration, each filter bundle comprising a multitude of parallel microporous polymeric hollow fibres, wherein feed to be filtered is fed to the outside of the bundle of fibres and permeate is extracted from one or both discharge ends of the fibre lumens;
one or more feed passages extending longitudinally along said housing to direct feed to said filter bundle lengths in a direction generally parallel thereto;
one or more longitudinally extending permeate return passages extending generally parallel to said filter bundle length, said permeate return passages being sealed from contact with said feed and adapted to be in free fluid flow communication with each of said permeate discharge ends of said fibre lumens in said filter bundle lengths; and
one or more manifold arrangements, each having a feed inlet port connecting with said one or more longitudinally extending feed passages and a separate permeate outlet port connected with said one or more permeate return-passages.
In a preferred form, the manifold arrangements are disposed at one or both longitudinal ends of said housing and are configured to connect a plurality of the filter assemblies into banks.
Advantageously, the housing can include two, three or four filter bundle lengths disposed end to end in a series configuration. More preferably, each longitudinal length of the housing also has therein two or more co-extending filter bundle lengths that are each similarly connected in series to adjacent filter bundle lengths. In this manner, large systems can be constructed using filter bundle lengths or sub-modules that are of a size that are readily manhandable.
In one form co-extensive filter bundle lengths are interconnected as a subassembly of multiple filter bundle lengths. Preferably, each bundle length is separately potted in the conventional manner described in more detail hereafter.
In yet other forms, the invention provides an elongate housing containing at any one point four co-extensive filter bundles with three or four such filter bundle lengths connected in series. In a preferred form a peripheral feed passage is provided that is generally parallel to the external walls of the housing that is desirably no more than about 15 mm in radial depth at any point, together with a central feed passage that passes through the centre of the four co-extensive filter bundle lengths. In one form, the peripheral feed passage and/or central feed passage may be configured, by the use of packing material for example, to assist in directing the flow of feed both around and into the filter bundles.
It is further preferred that four separate permeate return tubes are provided that are equally spaced within the housing intermediate the central and peripheral feed passages.
Manifold arrangements in the form of headers are preferably provided at both longitudinal ends of the housing to facilitate cross-flow filtration, wherein a portion of the feed can be discharged from the other end for recirculation. The feed outlet port can also be used as a flushing fluid inlet port for operation during the backwashing process, wherein fluid under pressure is applied to the inner surface of the fibre lumens via the filtrate or permeate outlet ports and a backwashing fluid is subsequently applied to the external surfaces of the fibres to flush out any accumulated contaminants that may have been dislodged from the fibres.
It is also preferred, particularly in systems utilising large diameter filter bundles, to provide feed passages through the centre of each individual filter bundle.
Finally, other preferred forms of the invention could also include means to isolate individual filter assemblies or banks of assemblies in the event of failure of a filter bundle. This is achieved in one embodiment by means of individual valves associated with each filter bundle length, filter assembly housing, or manifold arrangement, as required.
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patent: 5282964 (1994-02-01), Young
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patent: 5906739 (1999-05-01), Osterland et al.
Barry Chester T.
Knobbe Martens Olson & Bear LLP
USF Filtration and Separations Group Inc.
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