Liquid purification or separation – Filter – Supported – shaped or superimposed formed mediums
Reexamination Certificate
2001-05-23
2004-11-30
Kim, John (Department: 1723)
Liquid purification or separation
Filter
Supported, shaped or superimposed formed mediums
C210S321830, C210S500230, C156S169000, C156S173000
Reexamination Certificate
active
06824679
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to filtration modules or elements, and in particular to a new and useful method of producing multi-layer hollow fiber filtration modules. Moreover, the present invention provides a method of producing a variety of multi-layer hollow fiber filtration modules that have performance results that have a predictable performance such that the modules are directly scalable. Specifically, the present invention is directed to an improvement of the invention described in U.S. Pat. No. 5,626,758 hereinafter “the Belfort patent”), incorporated herein by reference in its entirety.
Vortices are well known in the art. Both Taylor and Dean vortices have been harnessed to improve the performance of pressure driven membrane processes. See Winzeler, H. and Belfort, G., “Enhanced performance for pressure-driven membrane processes: the argument for fluid instabilities”, J. Membrane Sci., 80. 35-47 (1993). Moreover, such vortices have been harnessed with curved tubular membranes. See Srinivasan, S. and Tien, C. “Reverse osmosis in a curved tubular membrane duct”, Third International Symposium on Fresh Water from the Sea, Vol. 2, pp. 587-600 (1970). The Belfort patent is directed to harnessing Dean vortices in curved hollow fiber membranes to reduce polarization and fouling at the membrane surface, thereby increasing the efficiency of the membrane module.
Dean vortices are formed in curved conduits under laminar flow conditions when the Dean number of the fluid is above a critical Dean number. Vortices exist in turbulent flow, but such vortices are chaotic and excessive pumping energy and/or large diameter tubes are required to generate them. The physical cause behind the formation of the vortices is the centrifugal force exerted on the fluid elements as the liquid flows around the curved surface. This results in the radial motion of the fluid elements in the plane transverse to the principal direction of the flow and the final formation of vortices in that plane.
FIG. 1
provides an illustration of Dean vortices in a curved fluid tube, such being known to the prior art.
The Belfort patent is directed to the use of Dean vortices in curved hollow fibers to obtain filter modules with unique performance attributes. The Belfort patent discloses the use of a curved fluid tube constructed to form Dean vortices to improve filtration. The Belfort patent improved upon other prior art modular designs for pressure-driven membrane processes, such as reverse osmosis, and ultrafiltration that were based on maximizing membrane area per unit volume and on the handling convenience of the module.
Indeed, the Belfort patent adds to the many pre-existing methods for reducing concentration polarization (“CP”) and fouling, including chemical modification of the membrane surface and physical methods such as scouring. Hydrodynamic methods are also known which rely on eddies during turbulent flow, or induced flow instabilities. Introducing inserts into the flow path can create such induced flow instabilities.
Many of these methods were discussed in the paper by George Belfort entitled, “Fluid mechanics in membrane filtration: recent developments”, J. Membrane Sci., 40, 123-147 (1989). However, these prior art methods, as well as the Belfort patent, fail to provide guidance on producing Dean vortices-producing filtration modules that are directly scalable.
The Belfort patent teaches multi-layered modules. See
FIG. 14
of the. Belfort patent. However, it fails to provide any teaching on manufacturing Dean vortices-producing filtration modules that are directly scalable.
In view of the teachings of the Belfort patent, one of ordinary skill in the art would recognize that a pilot or process module, as opposed to a lab scale module, would either require multiple layers of hollow fibers to handle the increased fluid flow, an implausibly long cartridge with fibers wrapped around a single mandrel or a very wide cartridge that has a low packing density with multiple single-layered fiber wrapped mandrels sealed into a tube-sheet. However, as with other prior art uses of flow instabilities, the Belfort patent fails to teach those of skill in the art the ability to directly scale up a lab module to a multi-layered pilot or process (manufacturing) module without requiring significant trial and error. The Belfort patent merely suggests that the invention is amenable to such scaling.
The present invention provides Dean vortices-producing multi-layer filtration modules that are directly scalable. Specifically, the present invention provides methods that use a performance characteristic to develop substantially directly scalable multi-layer filtration modules for filtering solutions that benefit from the de-fouling properties of Dean vortices. More specifically, the present invention includes using a mathematical relationship of Dean number and shear rate to predict the performance of individual layers within a multi-layered module of curved hollow fibers. The present invention allows for performance of each layer within a multi-layered module to be designed to be substantially equivalent (defined below). The present invention describes the means of producing such multi-layered modules.
SUMMARY OF THE INVENTION
The present invention is directed to Dean vortices-producing multi-layered filtration modules and methods of designing such modules. Such modules are characterized by each layer having a substantially equivalent performance characteristic. This characteristic allows for the construction of filtration modules that are directly scalable. This is a substantial improvement over the prior art as it allows one to predict the performance of an eleven-layer module, for example, based upon the performance characteristics of a one-layer module.
As provided above, the present invention is also directed to methods of producing the multi-layered filtration modules using a performance characteristic. This performance characteristic is computed via a mathematical function including the Dean number and shear of a liquid. In determining this performance characteristic, the inventors have discovered a means for accurately and precisely estimating the performance of one or more layers of hollow fiber tubing in a filter module designed to use Dean vortices to de-foul the inner surface of the membrane. The inventors can then create subsequent layers having substantially equivalent performance by manipulating one or more of the characteristics of the hollow fiber to be used in such a module. Such hollow fiber characteristics that are contemplated for manipulation include the inner diameter, outer diameter, wall thickness, length, pore size and symmetry of the membrane. Of course, the composition of the hollow fiber can also be adjusted, that is the polymer or polymers used to create the hollow fiber.
For purposes of this invention, the phrase “de-foul” or “de-fouling” means the removal of species retained on the surface of a hollow fiber including, but not limited to solutes, particulate matter and gels. Inherent with such “de-fouling” is that solutions which tend to polarize become less polarized.
While it is within the present invention to produce a multi-layered filtration module with layers of hollow fibers comprised of different materials, this is not preferred. Moreover, it is even less expensive to produce a module of the present invention with fibers of the same material and having the same internal diameter and external diameter. Shortening the fiber length of the hollow fibers used in the subsequent fiber layer of the filter module to produce layers having substantially equivalent performance is the preferred means of producing the filtration modules of the present invention.
The present invention is particularly adapted for use with polarized solutions, preferably polarized aqueous solutions, and therefore includes methods of producing multi-layer filtration modules that use Dean vortices to remove deposits, remove suspended dissolved matter near the membrane and/or direct solutes away
Dzengeleski Stephen
Kuriyel Ralf
Pearl Steven R.
Hubbard John Dana
Kim John
Millipore Corporation
LandOfFree
Hollow fiber separation module and methods for manufacturing... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Hollow fiber separation module and methods for manufacturing..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Hollow fiber separation module and methods for manufacturing... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3283675