SE526154C2 - Filter for system for preparing liquid solution for e.g. hemodialysis treatment, includes slit-shaped opening(s) having two extensions perpendicular to filter direction, where second extension is shorter than the first extension - Google Patents

Abstract

A filter (23, 24) comprises a slit-shaped opening(s) having a first extension, and a second extension being perpendicular to a filter direction and to the first extension, where the second extension is shorter than the first extension. An independent claim is also included for a system for preparing a liquid solution for a medical procedure, including: (1) a cartridge (9); (2) a first liquid conduit having a first end communicating with a source of liquid to withdraw the liquid into the first liquid conduit and a second end; (3) a second liquid conduit having a first end communicating with a source of liquid and a second end communicating with the inlet of the cartridge for introducing the liquid into an inner space (10) to produce a concentrate liquid solution containing part of a particulate material (20) dissolved in the liquid; (4) a third liquid conduit communicating with the outlet of the cartridge and with a mixing point in the first liquid conduit intermediate the first and second ends for conducting the concentrate liquid solution from the cartridge into the first liquid conduit to be mixed with the liquid being conducted through the first liquid conduit to produce the liquid solution in the first liquid conduit for delivery to the second end of the first liquid conduit;and (5) a filter(s) arranged at the outlet and to permit passage of the liquid through the filter.

Description

In a dialysis kit it is known to use such a cartridge for supplying various substances to the dialysis fluid, see EP-B-278 100. The particulate material contained in the cartridge may comprise various substances to be supplied to the dialysis fluid, such as sodium bicarbonate, sodium chloride and other salts. In use, the dialysis fluid flows through the cartridge, whereby the particulate substance is gradually dissolved and thus the dialysis fluid is added. Accordingly, the general purpose of the filter is to allow the passage of the dialysis fluid together with a dissolved quantity of the substance but to prevent the passage of any particles of the particulate material. If such particles of the substance are found in the dialysis fluid, sensitive parts of the dialysis equipment, such as the pumps, can be damaged.

The filter currently used in such a cartridge is made of a fibrous material, such as polypropylene, in the form of a woven mesh. Such a filter is fl visible and thus not self-supporting. The filter must therefore be supported by a support component, for example in the form of a support plate. The filter is mounted to the support plate in a position adjacent to the support plate, the filter and the support plate forming a common unit which is capable of being mounted in the cartridge. Manufacturing such a filter unit is relatively complicated and expensive because the manufacturing involves the separate steps of manufacturing the woven filter, manufacturing the backing plate and joining the filter and the plate together. Furthermore, it is difficult to obtain exactly the desired permeability for such a filter. In particular, the permeability is often too high, which entails a risk of channels forming in the particulate material contained in the cartridge.

Another problem that can arise with the cartridges used today is that the particulate material leaks out of the cartridge through the inlet and outlet before the cartridge is actually used, especially through the inlet during the initial fl desolation. To reduce this risk of leakage, an ñlt plate or other similar porous element is incorporated in the inlet and outlet. In particular, the oil plate at the inlet is important during de-icing from below, via the outlet. The porous plate is usually made of a material other than the rest of the cartridge, which is disadvantageous in terms of recycling. SUMMARY OF THE INVENTION The object of the present invention is to provide an improved filter for a cartridge containing a particulate material. In particular, it is aimed at a filter which is inexpensive to manufacture and which exhibits a uniform and reliable permeability.

This object is achieved by means of the initially defined filter, which is characterized in that the filter comprises at least one slit-shaped opening, which has a first extent and a second extent which is substantially perpendicular to the filter direction and to the first extent, the second extent being considerably shorter than to the first extent.

By means of such a filter, a uniform fate zone is ensured for the slit-shaped opening or the slit-shaped openings. Any particles in the particulate material having a minimum size greater than the second extent will be effectively prevented from passing through the filter and thus from causing damage to components located downstream of the filter. Such an filter also allows a desired pressure drop across the filter to be achieved. With a suitable pressure drop, a channel formation in the particulate material can be avoided. It should also be pointed out that such a filter can be manufactured inexpensively by means of an injection molding process.

According to an embodiment of the invention, the second extent is also considerably shorter than the length of the slit-shaped opening in the filter direction. This feature allows a certain thickness for the filter, which ensures a sufficient strength of the filter. Consequently, the filter is self-supporting and does not need to have a support plate arranged next to the filter, which also helps to reduce manufacturing costs.

According to a further embodiment of the invention, the second extent is equal to or less than 0.1 mm, preferably equal to or less than 0.08 mm. Furthermore, the second extent may be equal to or greater than 0.02 mm, preferably equal to or greater than 0.04 mm.

According to an advantageous embodiment, the second extent is approximately 0.06 mm.

According to a further embodiment of the invention, the filter is made of a polymeric material, comprising one of polypropylene and polycarbonate.

According to a further embodiment of the invention, the filter comprises a disc, the slit-shaped opening extending through the disc.

Preferably, the filter comprises a number of such slit-shaped openings, which extend through the disc. Such a disc can easily be formed in a single piece. The first extent of each slot-shaped opening can extend in a radial which is directed towards a center point of the disc, which gives a number of slot-shaped openings in a star-like configuration.

According to a further embodiment of the invention, the slit-shaped opening has an upstream end and a downstream end in relation to the filter direction, the second extent of the slit-shaped opening increasing in the filter direction from a minimum value at the upstream end of the slit-shaped opening to a maximum value at the downstream end of the opening. Such a shape of the slit-shaped opening or the slit-shaped openings is advantageous in terms of manufacture.

According to another embodiment of the invention, the filter comprises a first disc and a second disc, which are arranged parallel to each other and separated from each other by a space which forms the slit-shaped opening. Preferably, the gap is formed by spacer elements arranged in the space between the discs, each of these spacer elements having a predetermined height corresponding to the second extent. Furthermore, each of these spacer elements may comprise a protrusion extending from either of the first disc and the second disc. In order to provide the liquid passage through the filter, the first disc may be provided with at least one opening, which constitutes an inlet passage to the gap, and the second disc with at least one opening, which constitutes an outlet passage from the gap. According to a further embodiment of the invention, the disc is manufactured by means of an injection molding process. The object is also achieved by means of the cartridge to which they are initially initiated, which is characterized in that the filter comprises at least one slit-shaped opening, which has a first extent and a second extent which is substantially perpendicular to the direction and to the first extent, the second extent, the second extent is considerably shorter than the first extent.

Advantageous embodiments of the cartridge are specified in subclaims 20 to 37.

Furthermore, the object is achieved by using such a filter in such a cartridge, the use comprising the step of supplying the liquid to the cartridge in such a way that the liquid passes through particulate material and thereby dissolves at least a part of the particulate material to form a liquid solution. The fluid may be a dialysis fluid. The particulate material may include bicarbonate and / or sodium chloride.

Furthermore, the object is achieved by means of the system initially defined, which is characterized in that the filter comprises at least one slit-shaped opening, which has a first extent which is substantially perpendicular to the direction and a second extent which is substantially perpendicular to the direction and to the first direction. the extent, the second extent being substantially shorter than the first extent.

Advantageous embodiments are defined in claims 42 to 44.

BRIEF DESCRIPTION OF THE DRAWINGS The present invention will now be described in more detail by the following description of various embodiments and with reference to the accompanying drawings.

Fig. 1 schematically shows a system for preparing a surface solution for a medical procedure. Fig. 2 schematically shows a cartridge according to the present invention.

Fig. 3 schematically shows a plan view of a first embodiment of a filter to be arranged in the cartridge according to Fig. G. 2.

Fig. 4 schematically shows a sectional view of the filter along line IV-IV in fi g. 3.

Fig. 5 schematically shows a sectional view of the filter along line V-V in fi g. 3.

Fig. 6 schematically shows a plan view of a second embodiment of a filter to be arranged in the cartridge according to Fig. G. 2.

Fig. 7 schematically shows a sectional view of the filter along line VII-VII in fi g. 6.

DETAILED DESCRIPTION OF VARIOUS EMBODIMENTS OF THE INVENTION In ñg. 1 schematically shows a system for producing a surface solution for a medical procedure. More specifically, the system is designed for the production of a surface dialysis solution for carrying out a hemodialysis treatment. The system can also be used for hemodialysis and hemoliteration. The system shown in fi g. 1 can thus form part of a dialysis equipment.

The system comprises a source 1 which contains a liquid, and in particular a dialysis liquid. The source 1 can be supplied with the liquid via an inlet line 2.

A first liquid line 3 has a first end 4 which communicates with the source 1 for drawing the dialysis liquid into the first liquid line 3. The first liquid line 3 also has a second end 5 for delivering a surface dialysis solution to a receiver (not shown). ) such as dialysis equipment. A second liquid line 6 has a first end 7 which communicates with the source 1 and a second end 8 which communicates with the inlet of a cartridge 9 for introducing the liquid from the source 1 into an inner space 10 in the cartridge 9 for producing a concentrated liquid solution. A third liquid line 11 has a first end 12 which communicates with the outlet of the cartridge 9 and a second end 12 which communicates with the first liquid line 3 at a mixing point 13 between the first end 4 and the second end 5.

The third liquid line 11 is thus arranged to draw the concentrated, liquid solution from the cartridge 9 into the first liquid line 3 to be mixed with the liquid passed through the first liquid line 3 from the source. 1, in order to produce a superficial solution for delivery to the recipient. The concentrated surface solution is transported through the third liquid line 1 by means of a pump 15.

The liquid is transported from the source 1 to the receiver through the first liquid line 3 by means of a pump 16. A control loop 17 comprising a valve 19 can be arranged to control the quantity of concentrated liquid solution to be delivered to the liquid in the first liquid line. 3.

The cartridge 9 is explained below with reference to fi g. 2. In the embodiment shown, reference is made to the preparation of a surface dialysis solution, to which sodium bicarbonate has been added. It should be noted that substances other than sodium bicarbonate can also be added to the dialysis fluid in a similar manner, for example sodium chloride and other salts. It should also be noted that the system, the cartridge and the components contained therein can also be used for the production of surface solutions other than a dialysis fluid.

The cartridge 9 is arranged to contain a particulate material 20 in the inner space 10. In the embodiment shown, the particulate material 20 is a sodium bicarbonate powder. The cartridge 9 has an inlet 21 which is arranged to allow the introduction of a liquid into the inner space 10. In the embodiment shown, the inlet 21 is connected to and communicates with the second liquid line 6. The cartridge 9 also has an outlet 22 which is arranged to allow discharge of liquid from the inner space 10. In the embodiment shown, the outlet 22 is connected to and communicates with the third liquid line 11 for discharge of the concentrated, surface solution.

A first filter 23 is provided at the outlet 22 to allow passage of the liquid through the filter 23 but prevent passage of the particulate material 20 through the filter 23. The filter 23 denies an filter direction x and thus allows the liquid to pass through the filter 23 in the filter direction x.

The cartridge 9 also includes a second filter 24 which is provided at the inlet 21 to allow passage of the liquid through the filter 24 but to prevent the passage of the particulate material 20 through the filter 24. Also the second filter 24 defines a The direction x and allows the liquid to pass through the filter 24 in the direction x. It should be noted that according to this invention there is such a filter 23 arranged at the outlet 22.

The arrangement of the second filter 24 at the inlet 21 is preferred but not mandatory.

The filters 23 and 24 rest on separate support elements in the form of a lug 25, 26 which extends around the inner circumference of the inner space 10 adjacent the inlet 21 and 21, respectively. the outlet 22. Furthermore, each extends a smaller heel 27 resp. 28 around the inner circumference of the inner space 10 above the filter 24 resp. 23 in order to enable fixing of the filters 23, 24 in their respective positions on the lugs 25, 26.

Preferably, the filters 23 and 24 are identical to each other. Two different embodiments of the filters 23, 24 will be explained below with reference to Figs. 3-7.

I ñg. 3-5 show a first embodiment of the filter 23, 24. The filter 23, 24 has the shape of a substantially circular and substantially flat disc 29 which has a substantially extension plane. It should be noted that the thickness of the disc 29 has been exaggerated in the drawings in order to simplify the explanation of the construction of the filter. The filter 23, 24 comprises a number of slit-shaped openings 30.

Each such opening 30 has a first extent shown by the line 31 in fi g. 3 for one of the apertures 30. Each aperture 30 also has a second extent shown by line 32 in fi g. 3 and 5. The second extent 32 is substantially perpendicular to the first extent 31.

Both the second extent 32 and the first extent 31 are substantially perpendicular to the direction of fate x.

According to the present invention, the second extension 32 is considerably shorter than the first extension 31. Furthermore, the second extension 32 is considerably shorter than the length 33 of the slit-shaped opening 30 in the direction x. For example, the length 33 may be 10-100 times the second extension 32. In particular, the second extent 32 is equal to or less than 0.1 mm, preferably equal to or less than 0.08 mm. Furthermore, the second extent 32 is equal to or greater than 0.02 mm, preferably equal to or greater than 0.04 mm. In a preferred embodiment, the second extent 32 is approximately 0.06 mm.

The slit-shaped openings 30, which extend through the disc 29, are in the embodiment shown arranged so as to extend in a radial direction with respect to the first extension 31 and a center point of the disc 29. However, the slit-shaped openings 30 may also be so arranged to extend in other directions; for example, the disc 29 may comprise a number of slit-shaped openings 30 extending parallel to each other. The sheet 29 is made of a polymeric material, for example polycarbonate or polypropylene. The disc 29 can be manufactured by an injection molding process by injecting the polymeric material into a mold space having the shape of the disc 29. Each slit-shaped opening 30 has an upstream end and a downstream end in relation to the xlter direction x. As shown in fi g. 5, the second extent 32 of the slit-shaped opening 32 in the direction x increases from a minimum value at the upstream end of the slit-shaped opening 30 to a largest value at the downstream end of the slit-shaped opening 30. Such a shape on the slit-shaped opening facilitates the injection molding of the disc 29.

The filter 23, 24 comprises an circumferential edge portion 36 extending around the circumference which is formed as part of the disc 29. The edge portion 36 is visible in a direction radially inwards and formed by arranging a groove 37 extending around the circumference which extends radially inside consequently, the flexible edge portion 36 may bend radially inwardly when the filter 23, 24 is inserted into place on the lug 25, 26 to pass the lug 27, 28. After passing the lug 27, 28, the flexible edge portion 36 may spring return to the external position shown in fi g. 4.

I fi g. 6 and 7 show a second embodiment of the filter 23, 24. The filter 23, 24 according to this embodiment comprises two discs, a first disc 41 and a second disc 42. The discs 41 and 42 are both substantially circular and substantially planar and each have a substantially extension plane. .

The discs 41, 42 are arranged substantially parallel to each other and separated from each other by means of a number of spacer elements 43. The spacer elements 43 form part of and extend from one of the discs 41, 42. In the described embodiment, the spacer elements are formed on the second disc 42. Thanks to the spacer elements 43, a gap 44 is formed between the discs 41 and 42. The spacer elements 43 have a predetermined height which defines the thickness of the gap 44.

In the second embodiment, unlike in the first embodiment, the direction x extends parallel to the discs 41 and 42. The slit-shaped opening 30 is formed by the gap 44. Consequently, the second extension 32 corresponds to the height of each spacer element 43.

The first disc 41 comprises a number of openings 46 which extend through the first disc 41 and form outlet passages from the gap 44. The second disc 44 also comprises a number of openings 47 which form an inlet passage to the gap 44. The openings 46 of the first disc 41 are arranged in such a way that they are not located in the middle of any of the openings 47 of the second disc 42. More specifically, the openings 47 are arranged along a radially inner ring and a radially outer ring, while the openings 46 are arranged along a ring in an intermediate position between the inner ring and the outer ring. It should be noted that the openings 46, 47 can also be arranged in other positions than those shown.

The liquid passing through the filter 23, 24 will thus enter the gap 44 via one of the openings 47 and flow through the gap 44 in the direction x to one of the openings 46 of the first disc 41 to be emptied from the filter 23, 24. Since the liquid can flow from an opening at the outer ring or from an opening along the inner ring towards an opening along the intermediate ring, the direction of fate in the second embodiment comprises all directions in a plane parallel to the main extension plane of the discs 41, 42. This is indicated by the double arrow x i ñg. 7.

The spacer elements 43 are located between the openings 47 along the inner ring and between the openings 47 along the outer ring. More specifically, a spacer element 43 is arranged between each pair of adjacent openings along the inner and outer rings.

The first disc 41 also comprises a central cavity 48 which is arranged to receive a central projection 49 on the second disc 42.

By means of the cavity 48 and the projection 49, the second disc 42 can be firmly placed in the first disc 41. In the present invention it is not limited to the described embodiments but can be varied and modified within the scope of the appended claims. In the i ñg. 3-5, the first extent 31 is substantially straight. It should be noted, however, that the first extent 31 as an alternative may be curved.

Claims (43)

526 154 a PATENTKRAV A filter (23, 24) for a cartridge (9) containing a particulate material (20), the filter being intended to allow the passage of a liquid through the filter and thus the cartridge but to prevent the passage of the particulate material, the filter allowing the liquid to pass through the filter in a direction (x), characterized in that the filter comprises at least one slit-shaped opening (30), which has a first extension (31) and a second extension (32) which is substantially perpendicular to the direction (x) and to the first extent (31), the second extent (32) being considerably shorter than the first extent and equal to or less than 0.1 mm. Filter according to Claim 1, characterized in that the second extension (32) is considerably shorter than the length (33) of the slit-shaped opening in the filter direction (x). Filter according to one of Claims 1 and 2, characterized in that the second extent (32) is equal to or less than 0.08 mm. Filter according to one of the preceding claims, characterized in that the second extent (32) is equal to or greater than 0.02 mm. Filter according to one of the preceding claims, characterized in that the second extent (32) is equal to or greater than 0.04 mm. Filter according to one of the preceding claims, characterized in that the second extension (32) is approximately 0.06 mm. Filter according to one of the preceding claims, characterized in that the filter (23, 24) is made of a polymeric material, comprising one of polypropylene and polycarbonate. Filter according to one of the preceding claims, characterized in that the first extension (31) is substantially perpendicular to the terlter direction (x). 526 154/3. ... . .. ... Filter according to one of the preceding claims, characterized in that the filter (23, 24) comprises a disc (29), the slit-shaped opening (30) extending through the disc. Filter according to claim 9, characterized in that the filter (23, 24) comprises a plurality of slit-shaped openings (30) extending through the disc. Filter according to claim 10, characterized in that the first extent of each slit-shaped opening (30) extends in a radial direction towards a center point of the disc (29). Filter according to one of Claims 9 to 11, characterized in that the slit-shaped opening (30) has an upstream end and a downstream end in relation to the direction (x), the second extent (32) of the slit-shaped opening (30) increasing in The direction (x) from a minimum value at the upstream end of the slit-shaped opening to a maximum value at the downstream end of the opening. Filter according to one of Claims 1 to 8, characterized in that the filter (23, 24) comprises a first disc (41) and a second disc (42), which are arranged substantially parallel to one another and separated from one another by a space ( 44) forming the slit-shaped opening (30). Filter according to claim 13, characterized in that the gap (44) is formed by spacer elements (43) arranged in the gap (44) between the discs (41, 42), each of these spacer elements (43) having a predetermined determined height corresponding to the second extent (32). Filter according to claim 14, characterized in that each of the spacer elements (43) comprises a projection extending from either of the first disc (41) and the second disc (42). Filter according to one of Claims 13 to 15, characterized in that the first disc (41) is provided with at least one opening (46) which constitutes an outlet passage to the gap and in that the second disc (42) is provided with at least an opening (47) which forms an inlet passage from the gap. 526 154 17. W. ... . . . . Filter according to one of Claims 9 to 16, characterized in that the disc (29, 41, 42) is manufactured by means of an injection molding process. A cartridge containing a particulate material (20), the cartridge comprising: an interior space (10) adapted to accommodate the particulate material; an inlet (21) arranged to allow the introduction of a liquid into the inner space (10); an outlet (22) arranged to allow discharge of liquid from the inner space (10); and at least a first filter (23) arranged at the outlet (22) and for allowing passage of the liquid through the filter but preventing passage of the particulate material (20) through the filter, the filter allowing the liquid to pass through the filter in a filter direction ( x), characterized in that the filter (23) comprises at least one slit-shaped opening (30), which has a first extension (31) and a second extension (32) which is substantially perpendicular to the filter direction (x) and to the first extension, wherein the second extent (32) is considerably shorter than the first extent (31). A cartridge according to claim 18, wherein the cartridge comprises a second filter (24) arranged at the inlet (21) and for allowing passage of the liquid through the filter (24) but preventing passage of the particulate material (20) through the filter (24), the second filter allowing the liquid to pass through the filter (24) in an filter direction (x), characterized in that the second filter comprises at least one slit-shaped opening, which has a first extension (31) and a second extension (32) which is substantially at right angles to the direction (x) and to the first extent (31), the second extent (32) being considerably shorter than the first extent (31). Cartridge according to one of Claims 19 and 19, characterized in that the second extension (32) is considerably shorter than the length of the slot-shaped opening in the direction (x). Cartridge according to one of Claims 18 to 20, characterized in that the second extent (32) is equal to or less than 0.1 mm. 5 2 6 1 5 4 §II = gïï: '/ Ü Cartridge according to one of Claims 18 to 20, characterized in that the second extent (32) is equal to or less than 0.08 mm. Cartridge according to one of Claims 18 to 22, characterized in that the second extent (32) is equal to or greater than 0.02 mm. Cartridge according to one of Claims 18 to 23, characterized in that the second extent (32) is equal to or greater than 0.04 mm. Cartridge according to one of Claims 18 to 24, characterized in that the second extent (32) is approximately 0.06 mm. Cartridge according to one of Claims 18 to 25, characterized in that the filter (23, 24) is made of a polymeric material, comprising one of polypropylene and polycarbonate. Filter according to one of Claims 18 to 26, characterized in that the first extent (31) is substantially perpendicular to the direction (x). Cartridge according to one of Claims 18 to 27, characterized in that the filter (23, 24) comprises a disc (29), the slot-shaped opening (30) extending through the disc. Cartridge according to claim 28, characterized in that the filter (23, 24) comprises a plurality of slit-shaped openings (30), which extend through the disc (29). Cartridge according to claim 29, characterized in that the first extension (31) of each slot-shaped opening (30) extends in radial direction towards a center point of the disc (29). Cartridge according to one of Claims 28 to 30, characterized in that the slit-shaped opening (30) has an upstream end and a downstream end in relation to the filter direction, the second extent (32) of the slit-shaped opening increasing in the direction from a minimum value at the slit-shaped the upstream end of the opening to a maximum value at the downstream end of the opening (30). 526 154 ¿; - / 4 ' Cartridge according to one of Claims 18 to 29, characterized in that the filter (23, 24) comprises a first disc (41) and a second disc (42), which are arranged parallel to one another and separated from one another by a space (44). ) forming the slit-shaped opening (30). Cartridge according to claim 32, characterized in that the gap (44) is formed by spacer elements (43) arranged in the gap (44) between the discs (41, 42), each of these spacer elements (43) having a pre-spaced determined height corresponding to the second extent (32). Cartridge according to claim 33, characterized in that each of the spacer elements (43) comprises a projection extending from either of the first disc (41) and the second disc (42). Cartridge according to one of Claims 32 to 34, characterized in that the first disc (41) is provided with at least one opening (46) which forms an outlet passage to the gap (44) and in that the second disc (42) is provided with at least one opening (47) which constitutes an inlet passage from the space (44). Cartridge according to one of Claims 28 to 35, characterized in that the disc (29, 41, 42) is manufactured by means of an injection molding process. Use of a filter (23, 24) in a cartridge (9) containing a particulate material, the cartridge comprising: an inner space (10) intended to accommodate the particulate material (20); an inlet (21) arranged to allow introduction of a liquid into the inner space (10); an outlet (22) arranged to allow discharge of liquid from the interior space (10); and at least one filter (23) arranged at the outlet (22) and for allowing passage of the liquid through the filter but preventing passage of the particulate material through the filter, the filter allowing the liquid to pass through the filter in a filter direction (x), wherein the filter (23) comprises at least one slit-shaped opening (30), which has a first extent (31) and a second extent (32) which is substantially perpendicular to the direction (x) and to the first extent (31), the second extent (32) is considerably shorter than the first extent (31), which use comprises the step of supplying the liquid to the cartridge (9) in such a way that the liquid passes through the particulate material (20) and thereby dissolves at least a part of the particulate material. (20) to form a surface solution. Use according to claim 37, wherein the fluid is a dialysis fluid. Use according to any one of claims 37 and 38, wherein the particulate material comprises bicarbonate and / or sodium chloride. A system for preparing a surface solution for a medical procedure, the system comprising: a cartridge containing in an interior space thereof a particulate material and comprising an inlet (21) and an outlet (22); a first liquid line (3) having a first end (4), which communicates with a source (1) of liquid for drawing the liquid into the first liquid line (3), and a second end; a second liquid line (6) having a first end (7), which communicates with a source (1) of liquid, and a second end (8), which communicates with the inlet of the cartridge (9) for insertion of the liquid in the inner space (10) to form a concentrated, surface solution containing at least a part of the particulate material dissolved in the liquid; a third liquid line (11) communicating with the outlet of the cartridge and with a mixing point (13) in the first liquid line (3) between the first and second ends (4, 5) for guiding the concentrated, surface solution from the cartridge (9 ) into the first liquid line to be mixed with the liquid passed through the first liquid line to thereby form the fl liquid solution in the first liquid line for delivery to the second end of the first liquid line; and at least one filter (23) arranged at the outlet (22) and for allowing passage of the liquid through the filter but preventing passage of the particulate material through the filter, the filter (23) allowing the liquid to pass through the filter in a filter direction (x), characterized in that the filter comprises at least one slit-shaped opening (30), which has a first extension (31) and a second extension (32) which is substantially perpendicular to the direction (x) and to the first 526 154;:; ¿_ W. the extent (31), the second extent (32) being considerably shorter than the first extent (31). A system according to claim 40, characterized in that the filter comprises the wound features of any of claims 2 to 14. A system according to any one of claims 40 and 41, wherein the fluid is a dialysis fluid. A system according to any one of claims 40 to 42, wherein the particulate material comprises bicarbonate and / or sodium chloride.