Liquid purification or separation – Filter – Supported – shaped or superimposed formed mediums
Patent
1995-11-15
1997-09-09
Walker, W. L.
Liquid purification or separation
Filter
Supported, shaped or superimposed formed mediums
21050025, 21050026, 210501, 210503, 2105101, B01D 2708
Patent
active
056652348
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention at hand relates to a micro-filter disc, particularly for the sterilization of water, and a method for its production.
During the mechanical sterilization of water by means of a microfilter, it is essential that the pore size of the filter device be small enough and be of a typical size of 0.4 to 0.5.mu. so that bacteria are safely re-trained. Ceramics or other materials having suitable pore sizes, up to now, could not be produced in just any desirable form so that filters with large surfaces and having good filtering effectiveness could only be produced under large expenditures and poor serviceability. The until now used large surface area filter columns and having been made of ceramics are difficult to clean, whereby known filter installations, commonly, have to be opened frequently and have to be cleaned by hand.
Reference is particularly made to the European patent application 92 810 843, wherein a self-cleaning filter installation is being described having been provided with a cleaning unit being moveable relative to the filter surfaces and being movable thereagainst for the scraping off of filter material. Such filters can be regularly cleaned in an assembled state by cleaning brushes being driven from the outside to thereby substantially simplify the maintenance.
An object of the invention at hand is the provision of a flat micro-filter disc having a large surface area which, for example, can be installed in a self-cleaning filtering installation. Furthermore, a suitable method for the production of such a micro-filter disc is indicated.
To attain this object, a micro-filter disc is provided which is produced on a kieselguhr (diatomaceous earth) basis and contains at least two silicately bonded kinds of kieselguhr of which at least one is pre-calcined and later being sintered, and whereby the micro-filter disc exhibits of pore size in the magnitude of 0.05 to 0.5.mu., preferably 0.1 to 0.3.mu.. It has been discovered that the presence of a kind of a pre-calcined kieselguhr assures the stability of the micro-filter disc during its production and forms a framework for the provision of at least a further kind of kieselguhr of a different kind, whereby a stable form is obtained having the desired pore sizes. Particularly, a monolithical round microfilter disc can be produced having a diameter of at least 25 cm, preferably at least 35 cm. Such a disc can have a thickness of 0.5 to 2 cm, preferably about 1 to 1.5 cm. A good filtering effect is obtained with a simultaneous good breaking strength of the disc having a thickness of about 0.5 cm. A typical permeability of the disc, according to the invention, stands at 0.5 to 0.7 liter (midm.sup.2), preferably at 0.6.
It is preferred that the micro-filter disc has a central round opening having a diameter of 3 to 15 cm, preferably 6 to 10 cm. Because of the presence of this opening, several micro-filter discs can be superimposed upon each other on a central column, wherein the column can rotate or have a rotatable shaft to facilitate a relative movement between the micro-filter discs.
In order to be able to tightly install such micro-filter discs in a filtering installation, the outer and inner margins of the micro-filter disc have to be cut to exact tolerances which can be obtained by high pressure water-jet cutters. The margins are preferably provided with a sealing layer which also overlaps around the disc on at least one side by about 1 to 8 mm, preferably by 3 to 5 mm. In this manner, the disc can be mounted sealingly with its margins as well as with an underlayer. The seals should have a thickness of 1 to 3 mm in order to accommodate any size changes of the disc.
It is preferred that the filter disc exhibit open pores on its upper surface to enhance an automatic cleaning of the upper surface from time to time, which surface should be soft enough to obtain an abrading by means of a cleaning brush. Such cleaning brush can have man-made bristles, for example, particularly nylon or precious metal bristles, whereby th
REFERENCES:
patent: 583698 (1897-06-01), Bennett
patent: 4968487 (1990-11-01), Yamamoto et al.
patent: 4980334 (1990-12-01), Brennan
Dilenge Angelo
Gruter Peter
Lukopat AG
Walker W. L.
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