GB2343853A

GB2343853A - Fluid distributor plate for filter cassettes

Info

Publication number: GB2343853A
Application number: GB9925085A
Authority: GB
Inventors: Mohammad-Saeed Ajam; Matthias Grabosch; Knut Kuss; Karl-Heinz Pischke
Original assignee: Sartorius AG
Current assignee: Sartorius AG
Priority date: 1998-11-04
Filing date: 1999-10-22
Publication date: 2000-05-24
Anticipated expiration: 2019-10-22
Also published as: FR2785197A1; GB2343853B; JP2000157842A; GB9925085D0; DE19850707C1

Abstract

A mono- or bi-directional distributor plate for filter cassettes has, in one or both of its major surfaces, four kinds of openings 12-15 which communicate with feed/filtrate ports 8-11 in its side edges. First and second openings 12,13 are arranged in a line parallel to and adjacent one side 6. Each opening 12 connects with an obliquely angled passage leading to a fluid port, the passages being of different lengths and the longer the passage the larger its diameter. Openings 13 communicate with passages parallel to the side 6 and open into a duct 16 leading to a fluid port 10. Openings 14,15 are arranged likewise, adjacent the other side 7, and are connected similarly with ports 9,11. In a modification (Figs 4,5) the oblique passages 12,15 are of equal length and open into a duct (20,21) closed at both ends and having a central outlet (22,23) to the port 8,9. A pressure monitor (24,25) may be connected to the ducts (20,21).

Description

2343853 DISTRIBUTOR PLATE FOR CROSSFLOW CASSETTE FILTRATION APPARATUS The

present invention relates to a distributor plate for crossflow cassette filtration apparatus, for example as used in ultrafiltration and in microfiltration of liquids.

Crossflow cassette filtration apparatus usually consist, according to the state of the art, of a holder, filter cassettes and end plates. The holder receives the end plates and at least one filter cassette, which is sealingly pressed between the end plates. For that purpose the end plates are arranged on the holder to be movable on one another. At least one end plate is constructed as a distributor plate with connections for the feed of liquid, which is to be filtered, into the filter cassettes and for the discharge of concentrate and filtrate from the filter cassettes. If the feed and/or discharge of the fluids takes place merely at one surface of the distributor plate, the plate is termed a monodirectional distributor plate and if the feed and/or discharge of the fluids takes place at the front and back surface of the distributor plate, it is termed a bidirectional distributor plate. In the latter case, the filter cassettes are arranged at both ends at the front and back surface of the distributor plate.

In DE-OS 34 41 249 there is described a crossflow cassette filtration device in which the filter cassettes are clamped between two end plates respectively constructed as distributor plates. It is disadvantageous that the connections at the two distributor plates cannot be fixedly piped in, because the distributor plates have to be moved on one another for the clamping of the filter cassettes in place. Fixed piping would, however, significantly increase the filtration reliability, inclusive of the capability of the device to be sterilised, which is particularly important in sensitive areas of filtration, for example the pharmaceutical or biotech nolog ica I field. US-PS 47 15 955 describes a crossflow cassette filtration apparatus consisting of holder, filter cassette and end plates, wherein one of the end plates is constructed as a monodirectional distributor plate at which are arranged all the connections for the feed and discharge of the fluids. A design of this distdbutor plate as a bidirectional distributor plate is discussed in EP 0 345 209 B1. In both cases the distributor plates have opposite planar front and back surfaces, opposite narrow first and second side walls, opposite narrow first and second edge walls, a respective connection for the feed of liquid to be filtered and for the discharge of concentrate and two connections for the discharge of filtrate. The front surface or the front and back surfaces have mutually spaced openings which agree with corresponding openings of the filter cassettes to be connected to the distributor plate. The openings for the feed of liquid to be

2 filtered and a first number of openings for the discharge of filtrate lie on a straight line parallel to the first narrow edge wall, and the openings for the discharge of concentrate and a second number of openings for the discharge of filtrate lie on a straight line parallel to the second narrow edge wall. The first number of openings for the discharge of filtrate open at an acute angle with respect to the front surface or the front and back surfaces into a first channel, which extends parallelly to the first narrow edge wall and to the front and back surfaces. It exits from the distributor plate at at least one of the side walls. The second number of openings for the discharge of filtrate open at an acute angle with respect to the front surface or front and back surfaces into a second channel, which extends parallelly to the second narrow edge wall and to the front and back surfaces. it exits from the distributor plate at at least one of the side walls.

It is disadvantageous that the connection for the feed of liquid to be filtered and the connection for the discharge of concentrate are effected at, respectively, the end of the first channel and the end of the second channel from one of the side walls. That leads to an undesired pressure decay in the direction of the end, which is opposite to the connection, of the channels, which continues on over the membrane surfaces. This pressure gradient leads to a non-uniform flowing over and through the membrane surfaces and thus to a non-uniform utilisation of the membrane surfaces of the filter cassette, which has as a consequence a reduction in the filtration performance and a premature blocking of the membranes in the more strongly loaded regions.

There is thus a need for a distributor plate for cassette filtration apparatus which may enable an improved filtration performance and a longer service life of the cassette filtration apparatus.

According to the present invention there is provided a distributor plate for crossflow cassette filtration apparatus, with oppositely disposed planar front and back surfaces, oppositely disposed narrow first and second side walls, oppositely disposed narrow first and second edge walls, a respective connection for the feed of liquid to be filtered and for the discharge of concentrate and two connections for the discharge of filtrate, wherein the front and/or back surfaces have mutually spaced openings of four kinds which agree with corresponding channel openings of the filter cassettes to be connected to the distributor plate and wherein the openings of the first kind and the second kind lie on a straight line extending parallelly and adjacently to the first narrow edge wall and those of the third kind 3 and the fourth kind lie on a straight line extending parallelly and adjacently to the second narrow edge wall, the openings of the second kind on the straight line extending parallelly and adjacently to the first narrow edge wall open at a right angle with respect to the front and/or back surface into a first channel, which extends parallelly to the first narrow edge wall as well as to the front and back surfaces and exits from the distributor plate on at least one of the side walls as at least one first connection, and the openings of the fourth kind on the straight line extending parallelly and adjacently to the second narrow edge wall open at an acute angle with respect to the front and/or back surface into a second channel, which extends parallelly to the second narrow edge wall as well as to the front and back surfaces and exits from the distributor plate on at least one of the side walls as at least one second connection.

In one aspect of the invention, in a monodirectional or bidirectional distributor plate, the openings of the first kind, which lie on th& straight line extending adjacently and parallelly to the first edge wall, extend at an acute angle to the front and back surfaces and parallelly to the side walls and pass over into auxiliary channels which are of different lengths and open rectilinearly into a third connection in the first edge wall, preferably in the centre point thereof, and the openings of the third kind, which lie on the straight line extending adjacently and parallelly to the second narrow edge wall, extend at right angles to the front and back surfaces and parallelly to the side walls and are similarly connected with auxiliary channels, which open rectilinearly into a fourth connection in the second narrow edge wall, preferably in the centre point thereof.

An optimisation of such a distributor plate ran be effected if the longer auxiliary channels in the direction of the openings closer to the side walls have greater diameters than the shorter auxiliary channels.

In another aspect of the invention, in a monodirectional or bidirectional distributor plate, the openings of the first kind, which lie on the straight line extending adjacently and parallelly to the first edge wall, extend at right angles to the front and back surfaces and parallelly to the side walls and intersect a third channel which is closed at the ends and is connected at a spacing from its ends with a connecting channel opening into a third connection in the first edge wall, and the openings of the third kind, which lie on the straight line extending adjacently and parallelly to the second narrow edge wall, extend at right angles to the front and back surfaces and parallelly to the side walls and open into a fourth channel which is 4 closed at its ends and is connected at a spacing from its ends with a connecting channel opening into a fourth connection in the second edge wall.

In both aspects of the invention it is possible to feed the liquid, which is to be filtered, either by way of the third or by way of the first connection of the distributor plate and to discharge the concentrate either by way of the fourth or by way of the second connection. The connections which in that case are not loaded are then available for the discharge of filtrate. Of the four connection possibilities, the feed of liquid, which is to be filtered, by the way of the third connection and the discharge of concentrate by way of the second connection are preferred.

Due to the manner of flow to and/or from associated filter cassettes by way of a distributor plate embodying the invention it may be possible to achieve approximately the same pressure at all channels, which communicate with the said openings, of the filter cassettes. Thus, an equal flowing over the membrane surfaces in terms of area and an equal flowing through the membranes in the filter cassettes may be ensured, which may produce an increase in the filtration performance by up to 15 % and an approximately equivalent extension of the service life of cassette filtration apparatus equipped with such a distributor plate.

The high variability of the connection possibilities moreover offers particular advantages in the installation of crossflow cassette filtration apparatus, especially when several apparatus of that kind are to be combined into larger filtration batteries and it is important to obtain easily accessible ducts and to keep dead spaces to a minimum.

In an advantageous embodiment, the third and/or the fourth channel opens by one end into one of the side walls and this channel end is closed by a pressure indicating device. In a further embodiment of the invention one of two outlet openings of the first and/or second channel at one of the side walls is closed by a pressure indicating device. Through pressure detection directly at the channels, an optimum manner of operating the cassette filtration apparatus can be achieved.

In yet another embodiment, the first and the second channel end at one and the same side wall, where they communicate with the connections. This on the one hand simplifies installation and cleaning of the filtration apparatus and on the other hand requires little space. Moreover, the distributor plate can be equipped as a monodirectional plate, wherein only the front surface of the plate has the mutually spaced openings which agree with corresponding openings of a filter cassette.

Embodiments of the present invention will now be more particularly described by way of example with reference to the accompanying drawings, in which:

Fig. 1 is a schematic perspective view of a first embodiment of a distributor plate according to the invention; Fig. 2 is a front view of the distributor plate of Fig. 1; Fig. 3 is a side view of the distributor plate of Fig. 1; Fig. 4 is a front view of a second embodiment of a distributor plate according to the invention; and Fig. 5 is a side view of the distributor plate of Fig. 4.

Referring now to the drawings there is shown in Figs. 1 to 3 a bidirectional distributor plate I for crossflow cassette filtration apparatus, with oppositely disposed planar front surface 2 and back surface 3, oppositely disposed narrow first and second side walls 4 and 5, oppositely disposed narrow first and second edge or end walls 6 and 7, a third connection 8 for the feed of liquid to be filtered or in an alternative embodiment for the discharge of filtrate, a fourth connection 9 for the discharge of concentrate or in an alternative embodiment for the discharge of filtrate, a first connection 10 for the discharge of filtrate or in an alternative embodiment for the feed of liquid to be filtered and a second connection 11 for the discharge of filtrate or in an alternative embodiment for the discharge of concentrate. The front and back surfaces 2 and 3 have mutually spaced openings 12, 13, 14 and 15 of different kinds, which agree with corresponding channel openings of the filter cassettes to be connected to the distributor plate 1. The openings 12 of a first kind, which are for the feed of liquid to be filtered or in an alternative embodiment for the discharge of filtrate, and the openings 13 of a second kind, which are for the discharge of filtrate or in an alternative embodiment for the feed of liquid to be filtered, lie on a straight line extending parallelly to and at a spacing from the first edge wall 6. The openings 14 of a 6 third kind, which are for the discharge of concentrate or in an alternative embodiment for the discharge of filtrate, and the openings 15 of a fourth kind, which are for the discharge of filtrate or in an alternative embodiment for the discharge of concentrate lie on a straight line extending parallelly to and at a spacing from the second edge wall 7. Passages extending from the openings 13 open at right angles with respect to the front and the back surface 2 and 3 into a first channel 16, which extends parallelly to the first edge wall 6 and to the front and back surfaces 2 and 3 and which exits from the distributor plate 1 at the side wall 4. Passages extending from the openings 15 open at an acute angle with respect to the front and back surfaces 2 and 3 into a second channel 17, which extends parallelly to the second edge wall 7 and to the front and back surfaces and which similarly exits from the distributor plate 1 at the side wall 4. Passages extending from the openings 12 extend at an acute angle to the front and back surfaces 2 and 3 and parallelly to the side walls 4 and 5 and pass over into auxiliary channels 18 of different lengths. The auxiliary channels 18 open rectilinearly into the third connection 8, which is provided at the first edge wall 6. Passages extending from the openings 14 extend at right angles to the front and back surfaces 2 and 3 and parallelly to the side walls 4 and 5 and communicate with auxiliary channels 19 of different lengths. The auxiliary channels 19 open rectilinearly into the fourth connection 9, which is provided in the second side wall 7. For clarity, not all openings and auxiliary channels are shown in Figs. 1 to 3. Their exact number depends on the configuration of the filter cassettes.

The bidirectional distributor plate 1 illustrated in Figs. 4 and 5 differs in the following manner from the embodiment of Figs. 1 to 3. Passages extending from the openings 12 of the first kind for the feed of liquid to be filtered or in an alternative embodiment for the discharge of filtrate extend at an acute angle with respect to the front and back surfaces 2 and 3 and open into a third channel 20. The third channel 20 is connected at a spacing from its ends with a connecting channel 22, which opens into the third connection 8, which is provided in the first edge wall 6. Passages extending from openings 14 of the third kind extend at right angles to the front and back surfaces 2 and 3 and parallelly to the side walls 4 and 5 and intersect a fourth channel 21 closed at its ends. The fourth channel 21 is connected at a spacing from its ends with a connecting channel 23, which opens into the fourth connection 9, which is provided in the second edge wall 7. In the illustrated embodiment, the channels 20 and 21 each open at one end at the second side wall 5, where the two channel ends are closed by removable pressure indicating devices, for example, monometers; 24 and 25.

7 In filtration operation the bidirectional distributor plate I is in one embodiment supplied under pressure by way of the third connection 8 with the liquid to be filtered, which is fed through the auxiliary channels 18 (or through the connecting channel 22 and the third channel 20) by way of the openings 12 into the corresponding channels of the respective filter cassettes, which are disposed at the front and the back surfaces 2 and 3 of the distributor plates 1 and in turn stand in connection with alternating filter cells. The liquid flows over the filter membranes of these alternatingly arranged filter cells and collects as concentrate in corresponding channels, which are congruent with the openings 14 for the discharge of concentrate on the front and back surfaces 2 and 3 of the distributor plate 1. From there, the concentrate passes by way of the auxiliary channels 19 (or by way of the fourth channel 21 and the connecting channel 23) into the fourth connection 9 and is discharged from the crossflow filtration apparatus or fed again to the connection 8. The filtrate, which passes through the membranes during flowing of the liquid away through the membrane surfaces, is collected in further filtrate chambers arranged in alternation to the first filter cells and is conducted by way of corresponding channels of the filter cassettes into the openings 13 and 15 for filtrate on the front and back surfaces 2 and 3 of the distributor plate 1, with which they are congruent. The filtrate is discharged from the filtration apparatus first and by way of the second channels 16 and 17 and the connections 10 and 11.

8

Claims

1 A distributor plate for connection to filter cassettes in crossfiow filtration apparatus, the plate having two opposite major front and back walls, two opposite minor side walls and two opposite minor end walls and being provided at the walls with ports for the feed of liquid to be filtered and the discharge of filtrate and concentrate and with first and second spaced-apart passages, which open at at least one of the front and back walls along a line substantially parallel to one end wall and closer thereto than to the other end wall and which in use communicate with corresponding channels in such a cassette, and third and fourth spacedapart passages, which open at at least one of the front and back side walls along a line substantially parallel to said other end wall and closer thereto than to said one end wall and which in use communicate with corresponding channels in the or another such cassette, wherein the first passages extend at an oblique angle to the front and back walls and substantially parallelly to the side walls and are respectively connected by connecting channels of different lengths with a port at said one end wall, the second passages extend at a right angle to the front and/or back wall and are connected with a duct which extends substantially parallelly to the front and back walls and said one end wall and which communicates with a respective port at at least one of the side walls, the third passages extend at a right angle to the front and back walls and substantially parallelly to the side walls and are connected by connecting channels with a port at said other end wall and the fourth passages extend at an oblique angle to the front and/or back wall and are connected with a further duct which extends substantially parallelly to the front and back walls and said other end wall and which communicates with a respective port at at least one of the side walls.

2. A distributor plate as claimed in claim 1, wherein the port at at least one of the end walls is disposed substantially in the centre thereof.

3. A distributor plate as claimed in claim 1 or claim 2, wherein the flow cross-sections of the connecting channels with different lengths increase with increasing length of these channels.

4. A distributor plate for connection to filter cassettes in crossflow filtration apparatus, the plate having two opposite major front and back walls, two opposite minor side walls and two opposite minor end wails and being provided at the walls with ports for the feed of 9 liquid to be filtered and the discharge of filtrate and concentrate and with first and second spaced-apart passages, which open at at least one of the front and back walls along a line substantially parallel to one end wall and closer thereto than to the other end wall and which in use communicate with corresponding channels in such a cassette, and third and fourth spaced-apart passages, which open at at least one of the front and back side walls along a line substantially parallel to said other end wall and closer thereto than to said one end wall and which in use communicate with corresponding channels in the or another such cassette, wherein the first passages extend at an oblique angle to the front and back walls and substantially parallelly to the side walls and are connected with a first duct which is closed at its ends and connected intermediate its ends with a channel communicating with a port at said one end wall, the second passages extend at a right angle to the front and/or back wall and are connected with a second duct which extends substantially parallelly to the front and back walls and said one end wall and which communicates with a respective port at at least one of the side walls, the third passages extend at a right angle to the front and back walls and substantially parallelly to the side walls and are connected with a third duct which is closed at its ends and connected intermediate its ends with a channel communicating with a port at said other end wall and the fourth passages extend at an oblique angle to the front and/or back wall and are connected with a fourth duct which extends substantially parallelly to the front and back walls and said other end wall and which communicates with a respective port at at least one of the side walls.

5. A distributor plate as claimed in any one of claims 1 to 4, wherein the port connected with the first passages is arranged to receive the liquid to be filtered and the port connected with the third passages is arranged for the discharge of concentrate.

6. A distributor plate as claimed in any one of claims 1 to 4, wherein the port connected with the first passages is arranged to receive the liquid to be filtered and the port connected with the fourth passages is arranged for the discharge of concentrate.

7. A distributor plate as claimed in any one of claims 1 to 4, wherein the ports connected with the first and third passages are arranged for the discharge of filtrate.

8. A distributor plate as claimed in claim 4, wherein each of the first and third ducts is connected substantially centrally thereof with the respective channel.

9. A distributor plate as claimed in claim 4 or claim 8, wherein at least one of the channels communicates at one end thereof with one of the side walls and is closed at that end by a pressure-indicating device.

10. A distributor plate as claimed in claim 1 or claim 2, wherein at least one of the ducts communicates with the respective port at one of the side walls and additionally communicates at one end with the other side wall and is closed at that end by a pressureindicating device.

11. A distributor plate as claimed in claim 1 or claim 2, wherein the ducts communicate with the respective ports at one and the same side wall.

12. A distributor plate as claimed in any one of the preceding claims, wherein the first, second, third and fourth passages open at only one of the front and back walls.

13. A distributor plate substantially as hereinbefore described with reference to Figs. I to 3 of the accompanying drawings.

14. A distributor plate substantially as hereinbefore described with reference to Figs. 4 and 5 of the accompanying drawings.

15, Crossfiow filtration apparatus comprising a distributor plate as claimed in any one of the preceding claims and a respective filter cassette connected to the plate at at least one of the front and back walls thereof.