Arrangement in membrane filter

Details Arrangement in membrane filter Arrangement in membrane filter

1989-04-14

1990-03-06

Spear, Frank

Liquid purification or separation

Recirculation

Of filtrate

210247, 2103218, 21032189, B01D 1300

Patent

active

049063626

DESCRIPTION:

BRIEF SUMMARY
The present invention relates to an arrangement in membrane filter with one or several tubular flow channels for liquid which is to be treated in the filter. The walls of the flow channels consist on the inner side of membranes and on the outer side of a supporting structure, through which the filtered liquid (permeate) shall pass. The flow channels are surrounded by an outer casing, which limits a collection space for permeate between itself and the flow channels.
Membrane filters may e.g. be used for food applications of different kind as protein separation of beer, wine and different fruit juices, as e.g. apple juice. Dairy products, including milk and whey, may be purified from bacteria in membrane filters with a suitable pore size, milk fat may also be removed.
When micro-filtering milk, which is a complex and hard-treated medium, the filter may rapidly get blocked. This depends on the fact that small particles in the milk enter into the filter and rapidly block the pores. By means of so called cross-flow filtration the blocking rate may be diminished, but large flow rates in the filter channels bring about large pressure fall and consequently different pressures along the filter channels. If the pressure difference between the two sides of the membrane (the driving pressure) is increased, the capacity increases but the blocking rate increases even more rapidly and a large part of the available filter area is rapidly blocked. The result is consequently an insufficient flow. A high driving pressure may in a first period also press through unwanted particles to the permeate. If the pore size is increased a larger amount of liquid passes through the membrane but the retention, i.e. the separation of particles, is worse.
One way of equalizing the pressure difference between the two sides of the membrane along the filter channels is described in SE 396 017. In this publication there is described a filtering method where a medium is forced to flow through a filter channel, which extends along one side of a membrane. In order to achieve the same driving pressure over the whole area of the membrane the pressure in the permeate channel, which extends along the other side of the membrane, is adapted to the pressure in the filter channel, e.g. by recirculation of the permeate. In order to achieve a high pressure in the recirculated permeate a large pumping capaity is needed, especially if the amount of permeate which is to circulate in the circuit is large. For these reasons one has not used a recirculation of permeate in membrane filters of the kind described above due to the high cost for this procedure.
According to the invention it is now proposed a new arrangement in membrane filters of the described kind. This arrangement is characterized by connecting the flow channels and the said collection space to separate outer circuits comprising pumps in order to bring as well the liquid which is to be filtered (retentate) as permeate to circulate concurrently pass the membrane filter, and that the collection space is filled by filling bodies which constitute an essential mechanical hinder for the flow of circulating permeate. Means are arranged at least at the inlet to the flow channels, which means has the shape of a disk provided with holes which abuts against the outer casing and keeps the filling bodies in the collection space and distributes the permeate flow over the same.
By such an arrangement the pressure on the permeate side may be adapted to the pressure on the retentate side in such a way that the driving pressure is kept constant over the whole membrane area from inlet to outlet with a limited consumption of pumping energy. According to earlier technique the same counter pressure of permeate was obtained over the whole filter area and the driving pressure therefore varied with the pressure in the circulation circuit for retentate. When membrane filtering with circulating flows the amount of permeate increases during the filtration while the flow of retentate diminishes. In order to obtain good operati

REFERENCES:
patent: 4565626 (1986-01-01), Azuma et al.

Affiliated with

Also associated with

Rating

Arrangement in membrane filter does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Arrangement in membrane filter, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Arrangement in membrane filter will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-45770