Liquid purification or separation – Processes – Liquid/liquid solvent or colloidal extraction or diffusing...
Reexamination Certificate
1998-07-07
2001-03-20
Drodge, Joseph W. (Department: 1723)
Liquid purification or separation
Processes
Liquid/liquid solvent or colloidal extraction or diffusing...
C210S321830, C210S321850, C210S321890, C096S008000
Reexamination Certificate
active
06203707
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to a membrane module of an installation for membrane separation of material mixtures comprising one or more tube membranes, a process for their manufacture by extrusion of synthetic material as well as applications of the membrane module.
Such membrane modules are known as structural elements in cross current filtration plants. They comprise mostly a plurality of tube membranes acting as filters. The tube membranes are designed as porous tubes either themselves designed as membrane filters or carrying filtration membranes of organic or inorganic materials on their surface. Tube membranes comprising interior or exterior membranes, are known. Their inside diameters range from some decimillimeters to about 100 millimeters.
In order to attain acceptable construction lengths of the membrane modules, combined with a useful filtration output, a small or larger number of straight tube membranes are installed in a straight jacket tube. This module tube has a combined entry and exit for all tube membranes for the medium to be filtered as a retentate and one or two exits for a filtrate as a permeate.
Membrane modules designed as so-called coil modules are also known. In this context cloth-like filter membranes are wound into an elongate roll in which the flow-through of the retentate and the drainage of the permeate is made possible by co-wound thin elastic spacers or nets. Coil modules of this design are very reasonably priced having regard to their filtration performance. However, because of their tendency to clog they are unsuitable for the separation of material mixtures having a high solids content. In contrast to this, with tube membranes having an inside diameter of some millimeters (a plurality of millimeters) even material mixtures having a high solids content such as pressed fruit juices, for example, can be processed without risk of clogging.
As the specific filtration output, in relation to the surface area, of known tube membranes of polysulphone or PDVF is relatively low, a number of modules, each comprising e.g. 19 tube membranes of 3 m length each, are interconnected in one installation in series and also in parallel in order to attain higher, economically acceptable filtration outputs.
If the number of the modules connected in series is high, up to 16 modules per series are known, the latter are interconnected by way of 180 degree pipe bends. If the group comprises as few as 5 series or passes switched simultaneously in parallel, 80 modules have to be provided in as compact a single unit as possible in order to attain a membrane filter surface area of about 180 m
2
. The individual modules are for this purpose mounted on support arms on racks and the numerous connections on the retentate side and the permeate side are brought about. This entails the following problems:
4 tube connections and two to three supports on support arms are required per membrane module. In an installation having 80 modules, these connections and supports result in 80 connecting bends, 85 hose connections and 320 connecting points, they further result in high installation costs thus reducing the cost efficiency of the plant.
Separating membranes have only a limited useful life. The membrane modules are thus parts subjected to wear and tear, having to be replaced at certain time intervals.
The efforts for assembly and disassembly as well as for the complex construction are thus enormous for this design.
SUMMARY OF THE INVENTION
It is therefore the object of the invention to eliminate the stated problems to a large extent.
According to the invention this object is attained by a membrane module of the type as set out in the opening paragraph in that the tube membranes are provided in the membrane module in a curved configuration. An advantageous modification of this membrane module is characterized in that the tube membranes are provided in the membrane module in a coiled configuration.
This may lead to the feature that the tube membranes in the form of at least one bundle of a plurality of tube membranes are coiled in the membrane module in rope-like twisted form (lay).
Further modifications of the membrane module, a process for the manufacture of tube membranes suited therefor by way of extrusion of synthetic resin as well as the use of the membrane module, are set out in the patent claims.
It has been found that a lay-out according to the invention may be attained with conventional tube membranes which can be bent at bending radii less than 20 times the inner diameter of the tube without damaging the membrane layer. For this purpose tube membranes of organic materials in the required lengths are commercially available. Known tube membranes of an inorganic material, such as sintered metal, can be produced in the required lengths from commercially available tube pieces of up to 1 m length by bending, welding together and application of the membrane by coating.
Compared with conventional membrane modules, membrane modules according to the invention offer the advantage of a high packing density and a simpler design. Compared with the abovementioned group of 80 conventional membrane modules, such a group may be replaced by a membrane module according to the invention having an outer diameter of about 1.40 m and a structural height of 1.40 m having the same membrane filter surface area of about 180 m
2
. Instead of the aforesaid 320 connections only about 3 connections will still be necessary, depending on the design. For this purpose, the membrane filter surface in the membrane module is formed by 150 parallel membrane tubes having an inner diameter of about 7 mm and a length of 55 m each.
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patent: 3784470 (1974-01-01), Richardson et al.
patent: 3880755 (1975-04-01), Thomas et al.
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patent: 3963622 (1976-06-01), Baudet et al.
patent: 4036760 (1977-07-01), Bardonnet et al.
patent: 4242459 (1980-12-01), Chick et al.
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patent: 4789480 (1988-12-01), Bruschke
patent: 4925555 (1990-05-01), Spielberg
patent: 5202023 (1993-04-01), Trimmer et al.
patent: 97/05946 (1997-02-01), None
patent: 97/30779 (1997-08-01), None
Bucher-Guyer AG
Burns Doane Swecker & Mathis
Drodge Joseph W.
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