Filtration medium

Details Filtration medium Filtration medium

1995-05-08

1997-11-25

Fortuna, Ana

Liquid purification or separation

Casing divided by membrane into sections having inlet

Cylindrical membrane

21032179, 2105001, 210505, 55527, 55528, 264DIG48, B01D 6300

Patent

active

056908237

DESCRIPTION:

BRIEF SUMMARY
The present invention relates to a filtration medium for use in filtering a fluid, and a method for making a filtration medium.
Filtration is one of the most widely used separation techniques. The process of filtration can be subdivided in a number of ways, for instance according to the filtration mechanism or the size of the particles which are to be separated, i.e. filtered, from the fluid. In the case of filtration for the separation of particles of size in the microscopic range, the following terms are widely used to specify the size of the particles which are to be separated: Macrofiltration (retention of particles having a size of at least 5 .mu.m), microfiltration (retention of particles having a size in the range of 0.05 .mu.m-5 .mu.m) and ultrafiltration (retention of particles having a size below approximately 0.05 .mu.m). Most bacteria fall within the microfiltration range, whereas viruses clearly fall within the ultrafiltration range.
At present, one of the most widely used types of filter for filtration in the microfiltration and ultrafiltration ranges is a filter membrane. Such membranes are relatively thin (approximately 150 .mu.m) and have a well-defined and stable pore structure. Despite the great advantages of membrane filters, it is highly disadvantageous that the flow rate (and, thus, the filtration capacity) through the filter must normally be kept low due to the low mechanical strength of such membranes. Furthermore, membrane filters are very expensive.
Today, there is much focus on the quality of water for use domestically as well as for industrial purposes, partly due to the increasing pollution of the environment in general and partly due to increasing public awareness with regard to the quality of food and beverages, which in turn results from the enormous interest in physical well-being, fitness and health which is shown by a large proportion of the population in industrialised and urbanised countries throughout the world. In turn, this has led to an increasing demand for means for providing, for instance, household tap water of satisfactory quality. A variety of filtration means are marketed for this purpose, charcoal type filters being among the most widely used types. However, the known filtration means all have the disadvantages that they are rather expensive, rather voluminous and, most important, they are often incapable of discharging the particles filtered from the fluid. Accordingly, the filtration means must be renewed rather frequently in order to maintain the quality of the filtered water, since the accumulation of microbiological material in the filter in the long run will eventually turn the filter into a site of harmful microbiological growth.
Thus, there is a pressing need for a filtration medium which is simple and inexpensive, so that the filtration medium can be renewed as frequently as necessary, and which at the same time is of considerable mechanical strength so as to permit high flow rates. Furthermore, it would be even more advantageous if the filtration medium could be regenerated in situ from time to time in order to prevent clogging and minimize microbiological growth therein.
Therefore, it is an object of the present invention to provide a filtration medium which is capable of removing by filtration particles of a given size from a fluid flowing through the filtration medium without causing an unacceptably large pressure drop and which at the same time is relatively inexpensive and simple to manufacture.
It is essential that the fluid-flow passages in the filtration medium can be dimensioned sufficiently accurately so that the resulting filtration medium is capable of retaining particles of a predetermined size, i.e. that a filtration medium of a well-defined specification can be produced.
It has now been found surprisingly that a simple and novel type of filtration medium can fulfil the above-mentioned requirements.
The present invention relates to a filtration medium for use in filtering a fluid, the filtration medium comprising a plurality of fibers

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