Simplified filtration system

Details Simplified filtration system Simplified filtration system

1999-04-09

2002-07-09

Fortuna, Ana (Department: 1723)

Liquid purification or separation

Casing divided by membrane into sections having inlet

Each section having inlet

C210S321840, C210S321670, C210S321630, C210S331000, C210S332000, C210S486000, C210S367000

Reexamination Certificate

active

06416666

ABSTRACT:

BACKGROUND OF THE INVENTION
A feed fluid such as waste water, can be separated into permeate, such as pure water which passes through a membrane, and concentrate which includes water with a high concentration of particles. Such separation can be accomplished by the use of one or more membrane packs lying within a container. Fouling of the membrane packs, by the buildup of particles at the surface which block pores of the membranes, can be reduced by rapidly rotating the membrane packs, as described in U.S. Pat. No. 4,025,425, by Croopnick. Fouling can be further reduced by placing stationary turbulators close to the membrane pack faces to create turbulence in the gap between them. It is noted that when a membrane pack has large pores (many microns wide) it may be referred to as a filter pack, but applicant uses the term membrane pack herein for both.
A common filtration construction directs the feed fluid in series through the gaps. Such serial flow has the advantage that the feed fluid moves along a long path in contact with the surfaces of the membrane packs, to remove a considerable portion of the filtrate. However, such serial flow has a disadvantage that feed fluid is not homogeneous, in that the concentration of particles in the feed fluid may increase between the upstream and downstream ends of the feed fluid path. Also, there can be a large pressure drop along the long path. The flow of the feed fluid in parallel through all of the gaps is seldom used, because the short path length requires repeated return of the fluid for reflow, resulting in large pressure losses during flow near the center of the rotor. A filtration system which allowed the feed fluid to flow along a long path in contact with the membrane surfaces while maintaining the feed fluid largely homogeneous in pressure and particle concentration, would be of value in the filtration of a wide variety of fluids.
SUMMARY OF THE INVENTION
In accordance with one embodiment of the present invention, a filtration system is provided, of the type wherein at least one rotatable membrane pack has surfaces slightly spaced from substantially stationary turbulators to leave gaps through which feed fluid moves, which produces enhanced filtration. The system is operated so the feed fluid is flowed into a conduit that connects the radially outer edges of the gaps that separate the rotating membrane pack(s) from the stationary turbulators. Portions of the feed fluid flow largely radially inwardly along inward paths that lie adjacent to the stationary turbulators, and flow largely radially outwardly along outward paths that lie adjacent to the rotating membrane pack(s), to produce a largely circulating flow along each gap. Portions of the fluid that have moved radially inwardly and outwardly along a path, pass into the feed conduit to move to another gap, while other portions move back into the same gap along the inward paths. The feed fluid moves along a long path in moving into and out of each of the gaps and flowing radially inwardly and outwardly along each gap, and yet a substantially homogeneous feed fluid is maintained because fluid in each gap is constantly mixed with fluid from other gap(s) by way of the feed conduit.
The centrifugal force and large shear (difference in fluid velocity near the pack surfaces) minimizes the buildup of particles at the membrane surface which would clog its pores. The stationary turbulators have apertures or recesses to leave spokes, which helps create shear.
A low cost system with one or a limited number of membrane packs, can be made at lower cost by better utilizing the motor. The motor is made with a long protruding shaft portion that extends into the filtration container and that directly supports the membrane pack(s). The container is fixed to the motor housing. This allows use of the motor shaft bearings instead of additional container bearings. A pump which uses a rotating pump member that creates centrifugal force can be constructed with the rotating pump member also on the motor shaft.
The motor shaft has a passage with one end connected to the membrane pack(s) to receive permeate, and with the other end discharging the filtrate.
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.


REFERENCES:
patent: 4025425 (1977-05-01), Croopnick et al.
patent: 4936990 (1990-06-01), Brunsell et al.
patent: 5130585 (1992-07-01), Iwamatsu et al.
patent: 5275725 (1994-01-01), Ishii et al.
patent: 5679249 (1997-10-01), Fendya et al.
patent: 5939807 (1999-08-01), Patyk et al.

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