Liquid purification or separation – Casing divided by membrane into sections having inlet – Planar membrane
Patent
1996-04-10
1997-10-28
Fortuna, Ana
Liquid purification or separation
Casing divided by membrane into sections having inlet
Planar membrane
210231, 210232, 210456, 210486, B01D 6300
Patent
active
056814640
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to a filter intended for cross-flow filtration of a fluid containing suspensed or emulsified substances, which filter is constructed of equally dimensioned plates between which there are formed passages for retentate and permeate flow. The passages are sealed by way of edge packings and the plates have in- and outlet openings to form collection channels, through which unfiltered fluid is led to and retentate och permeate are led away from the passages.
BACKGROUND OF THE INVENTION
The technology for cross-flow filtration started to grow in connection with the development regarding reverse osmosis in the beginning of the sixties. Since then this technique has been used both for reverse osmosis as ultra filtration and microfiltration. The pore size of the membranes which are used for these purposes varies with the smallest pore size being used in membranes for reverse osmosis and the largest being used in microfiltration membranes. In cross-flow filtration the entering stream is divided into two flows usually called permeate and concentrate or retentate. The permeate is the fraction which has passed the membrane while the retentate is the fraction which has been enriched with the emulsified or suspensed substance which has not passed the membrane.
Micro- and particle filtration are the newest of these filtration techniques. This type of membrane filtration is used today in many purposes within the food industry, both for purification of products as well as for regeneration of waste and by-products. Microfiltration is also used to produce pure water.
Cross-flow filters for microfiltration are today usually formed as tubes, "plate and frame" and spirals.
Within the brewery industry one has for a long time looked for a substitute for the kieselguhr filters which have been used for the final purification of beer, since kieselguhr is considered to bring about both contaminations of the environment and damages for the brewery personnel working with the filters.
A microfilter which has been used for beer filtration is described in GB 2 176 715. This filter consists of ceramic membranes in the shape of channels in a body of a more coarse ceramic material.
One problem with filtration of beer is that the filters easily get clogged and only may be used during short operation times. One way of preventing clogging of the microfilter is to use permeate for cleaning of the same. The permeate is then pressurized during short periods in such a way that it is forced to pass the membrane from the permeate side to the concentrate side. In this way the operation times may be extended.
In order to increase the capacity of the microfilters the liquid which is to be treated in the filter is brought to circulate in a circulation path over the filter. The disadvantage with this is that the energy consumption is high, since large flows are pumped around in the network. The liquid may also be subjected to a non-desired heating. Liquid which is not yet treated is added to the circulation path and brings about a dilution of the retentate.
SUMMARY OF THE INVENTION
According to the present invention there is now suggested a new design of a filter for cross-flow filtration intended especially for micro- or particle filtration. The filter according to the invention has a large membrane area but a small need for space and is mainly characterized in that there are plates (membrane plates) comprising a membrane of material which is chemically and physically inert to the fluid. This membrane has a pore size of 0.1-50 .mu.m and the permeate passes this membrane. There are also plates which are impervious to the fluid. Retentate and permeate passages are formed between the plates, which plates all have three openings. The retentate passages are connected to the channels for unfiltered fluid and to the channel for retentate and sealed against the channel for permeate. The permeate passages are connected to the channel for permeate and sealed against the channels for unfiltered fluid and for
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Alfa Laval Brewery Systems AB
Fortuna Ana
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