WO1995022397A1

WO1995022397A1 - Assembly for processing an aqueous fluid by reverse osmosis

Info

Publication number: WO1995022397A1
Application number: PCT/DK1995/000077
Authority: WO
Inventors: Peter Stubtoft
Original assignee: Peter Stubtoft
Priority date: 1994-02-21
Filing date: 1995-02-21
Publication date: 1995-08-24
Also published as: AU1806695A

Abstract

An assembly for treating an aqueous fluid by reverse osmosis comprises a housing (1), which comprises a plurality of tubular filter units (10, 11), each filter unit being made of a fluid-permeable porous material (26, 27). On the outer side, the fluid-permeable porous material is covered by a fluid-impermeable material (28, 29), and on the inner side it is covered by a semipermeable membrane (30, 31) allowing passage of purified water from the porous material (26, 27) to the through central passageway. The assembly comprises channels (15, 40; 18, 19; 21, 14) carrying pressurized untreated fluid to the filter units (10, 11) as well as purified water away from the central passageway of the filter units (10, 11) again. The filter units (10, 11) are mounted on their respective perforated core pipe (18, 19) closed at one end and connected at the opposite end to a common separate base member (9) forming a wall in the housing (1). The resulting assembly is relatively simple, easy to operate and maintain because the filter units are all secured to the same base member, and accordingly they can be mounted and removed as a unit together with said base member.

Description

Title: Assembly for processing an aqueous fluid by reverse osmosis.

Technical Field.

The invention relates to an assembly for treatment of an aqueous fluid by reverse osmosis, said assembly comprising a housing with a plurality of tubular filter units, where each filter unit is made of a liquid-permeable porous material covered on the outer side by a liquid-impermeable material and on the inner side by a semipermeable membrane which by reverse osmosis allows purified water to pass from the porous material to the through central passageway, where said assembly comprises channels carrying untreated, pressurized water to the filter units and purified water away from the central passageway of the filter units as well as draining off the fluid having passed axially through the porous material of the filter units.

Background Art.

Various assemblies are known for treating an aqueous fluid, such as pol¬ luted water by reverse osmosis. These assemblies often comprise a num¬ ber of various interconnected chambers, in which the filter units are mounted and which are interconnected by means of channel systems at each end of said filter units. Generally speaking, these assemblies are of a rather complicated structure and difficult to maintain.

Brief Description of the Invention.

The object of the invention is to provide an assembly, which is of a rather simple structure, inexpensive to manufacture, and easy to handle and maintain.

The assembly according to the invention is characterised in that the filter units are mounted on their respective perforated core pipe, which is closed at one end and which at the opposite end is connected to a common, separate base member forming a wall in the housing, said filter units at the end adjacent said base member sealingly abutting the circumference of their respective opening in an inner wall in said base member, whereas the core pipes extend freely through said openings and are connected to an outer wall in the base member, the inner and the outer wall of said base member together with a circumferential connecting wall defining a space, which sealingly surrounds the core pipes and receives untreated concen- trated fluid from the filter units, that the core pipes are sealingly closed towards the inner circumference of the filter units adjacent both ends of the filter units, and that the openings in the core pipes forming the perforations are only open for passage of treated water within an area between the sealing closings of the core pipes towards the filter units.

The resulting assembly is relatively simple, easy to operate and maintain because the filter units are all secured to the same base member, and accordingly they can be mounted and removed as a unit together with said base member. The core pipes ensure a reliable securing of the filter units, which besides are of a conventionally known type. The relatively few parts imply that the assembly can be reliably structured. The treated water is drained off through drain pipes connected to the outer wall of the base member in connection with the interior of the core pipes. The untreated fluid entering the space in the interior of the base member is also drained off through a drain pipe connected to the base member. As the filter units are only connected to the inner wall of the base member, only said inner wall need be dimensioned to the filter units in question. In this manner the use of other types of filter units requires nothing but a replacement of the inner wall.

The base member may according to the invention comprise a plate-shaped inner wall and an also plate-shaped outer wall formed integral with the circumferential connecting wall, which extends parallel to the core pipes, whereby the base member is particularly simple.

Furthermore, the base member may according to the invention comprise a circumferential outer flange which is to be mounted against a correspond- ing, circumferential flange on the remaining portion of the housing, where¬ by the mounting of the base member on the housing is particularly simple.

The core pipes may according to the invention be shaped with an external thread engaging an inner thread extending in openings shaped in the outer wall of the base member. In this manner the mounting of the core pipes in the base member is also particularly simple.

According to the invention the filter units may be sealingly tightened against the inner wall of the base member by means of tightening nuts, which are screwed onto outer threads on the ends of the core pipe posi¬ tioned opposite the base member. In this manner the filter units can be mounted on the core pipes without the use of special tools, and accord¬ ingly a replacement, if any, of the filter units can be easily performed in situ.

Furthermore, the tightening nuts may be fixedly tightened to the free ends of the filter units through intermediary, annular flow-adjusting members, through which the fluid in question reaches the porous material of the filter units. As a result, it is possible in a simple manner to adjust, if desired, the pressure of the entering fluid in such a manner that the pressure thereof has been adjusted to the filter units. Such an adjustment is of particular interest in case the necessary pump is too strong. The flow-adjusting members must only be disks with axial, through openings of a diameter suited for the pressure conditions. They can also be used as inlet filters for the filter units. The sealing closing of the core pipes towards the inner circumference of the filter units is according to the invention preferably provided by means of sleeve-shaped adjustment members inserted over the pipes. Such adjustment members are structured so as to match the type of filter unit in question.

Furthermore, according to the invention the core pipes may be shaped such that they are only perforated within a restricted area adjacent the base member. In this manner the core pipes can be used relatively easily for various lengths of filter units, the varying dimensions thereof being compensated for by a suitable choice of the adjustment members.

According to a particularly preferred embodiment of the invention, the housing may comprise a detachable cover in such a manner that access can be provided in a relatively easy manner to the free ends of the filter units without necessitating a removal of the base member with filter units. According to the invention, this cover may advantageously be connected to a pump unit, through which the fluid to be treated is pumped into the housing, whereby the assembly is particularly compact and can be used while moving.

Finally according to the invention, a closing member may be mounted around a core pipe at the corresponding opening through the inner wall of the base member, and a flow-adjusting member may be coupled between said closing member and the corresponding filter unit, said flow-adjusting member being adapted to allow flow of pressurized fluid from the sur¬ roundings and into the porous portion of the filter unit, and at the same time a fluid-guiding length of pipe may be mounted between the free end of the filter unit in question and the free end of another filter unit, whereby two filter units are connected in series in a simple manner.

Brief Description of the Invention. The invention is explained in greater detail below with reference to the accompanying drawing, in which

Fig. 1 is an axial sectional view through a preferred embodiment of an assembly according to the invention,

Fig. 2 is an axial sectional view through a second embodiment of the invention, and

Fig. 3 illustrates two filter units mounted so as to co-operate in series,

Best Mode for Carrying Out the Invention

The assembly shown in Fig. 1 according to the invention for treating an aqueous fluid comprises a housing designated the general reference numeral 1 . In the shown preferred embodiment, this housing is shaped with a circular cross section of a plastic pipe 2. One end of the plastic pipe is closed by means of a top wall 3 welded or glued thereon, and at the opposite end said plastic pipe comprises a bottom wall 4. The bottom wall 4 is secured to the pipe 2 by means of a circumferential flange 5 and a strap 6, and for this purpose the pipe is provided with a circumferential flange 7 secured to said pipe 2 by way of welding or gluing. A sealing ring 8 is mounted between the two flanges 5 and 7.

The bottom wall 4 of the housing forms part of a base member designated the general reference numeral 9 and provided for the mounting of a plural¬ ity of tubular filter units 10 and 1 1 . The bottom wall 4 is formed by a circular disk or plate of a relatively large thickness. This plate comprises an axially extending upward skirt 12, which at the free end comprises a circumferential inward collar 13. As illustrated in Fig. 1 , a plurality of axially extending openings are shaped in the bottom wall 4. One opening 14 opens on to the inner side of the bottom wall 4 within the skirt 1 2, whereas a second opening 1 5 continues through a defined thickening on the skirt 12 upwards so as to open on to the top side of the collar 1 3 of the skirt 12.

In addition, the bottom wall 4 comprises a number of openings 1 6, 1 7 corresponding to the number of filter units 10, 1 1 , said openings extending axially through said bottom wall 4. These openings 1 6 and 1 7 are provided with an inner thread for the mounting of core pipes 18, 1 9, cf. the following description.

The base member 9 comprises furthermore a circular disk 20, which is adapted to sealingly abut the top side of the collar 1 3 on the skirt 12 of the bottom wall 4 in such a manner that said disk 20 forms an inner wall defining a space 21 inside the base member 9. The disk 20 comprises a plurality of openings 22 and 23 extending coaxially with the openings 1 6 and 17 for receiving the above core pipes 18, 1 9 in the bottom wall 4. At the end facing the space 21 , the openings 22 and 23 are provided with an inward flange 24, 26 serving as contact face for the lower ends of the filter units 10, 1 1 , while the inner dimensions of said openings 22 and 23 correspond to the outer dimensions of the filter units 10 and 1 1 .

The filter units 10 and 1 1 are of a conventionally known type made of a tubular porous material 26, 27, which on the outer side is covered by a liquid-impermeable layer 28 and 29, respectively, and on the inner side provided with a water-permeable membrane 30 and 31 , respectively. The water-permeable membrane 30, 31 has in the drawing been indicated by means of dotted lines. The filter units 10, 1 1 are adapted to allow passage of water by reverse osmosis from the porous material 26, 27 into the interior of the filter units 10, 1 1 .

The filter units 10, 1 1 are accommodated on the above core pipes 18, 1 9, which extend from the bottom wall 4 of the base member 9 and centrally upwards through the openings 22 and 23 of the inner wall 20 and into the interior of the housing 1. Thus the core pipes 18, 19 extend coaxially through the filter units 10 and 1 1. At the lower end, the core pipes 18, 19 are provided with external threads 32 and 33, respectively, for the secur- ing in the openings 16 and 17 in the bottom wall 4 of the base member 9. At the upper ends, the core pipes are also provided with external threads 34 and 35, respectively, sealingly co-operating with their respective tightening nut 36, 37. Through intermediary rings or disks 38 and 39, respectively, these tightening nuts 36, 37 serve to tighten the filter units 10, 1 1 sealingly against the flanges 24 and 25 in the respective openings 22, 23 in the inner wall 20 of the base member 9 and consequently also to tighten the inner wall 20 sealingly against the skirt 12 of the bottom wall 4. In this manner an opening 40 extending through the inner wall 20 is placed in continuation of the opening 15 through the bottom wall 4 and up to the collar 13 of the skirt 12 with the result that a direct connection is established between the outer side of the housing 1 and the inner side thereof.

The intermediary rings 38, 39 are provided with openings (not shown), said openings allowing passage of fluid from the surrounding space in the housing 1 to the porous material 26 and 27, respectively, of the filter units 10, 1 1.

At the upper ends in the interior of the housing 1 , the core pipes 18, 19 are sealingly closed in any suitable manner, such as by insertion of a metal plug. In the portion of the core pipes 18, 19 accommodated in the interior of the filter units 10 and 19, said core pipes 18, 19 are perforated, cf . the indicated openings 41 and 42, respectively, at the portion of said core pipes 18, 19 which has been partially cut through.

These openings 41 and 42 allow the water passing through the mem¬ branes 30 and 31 to pass into the interior of the core pipes 18 and 19, respectively, and out through said core pipes.

At the ends of the filter units 10, 1 1 , the interior of the filter units is sealingly closed towards the area outside said filter units by means of sleeve-shaped adjustment members 42, 43, and 44, respectively. These sleeve-shaped adjustment members 42, 43, and 44 are adapted to the filter unit in question and the core pipes in question, and for this purpose said adjustment members are provided with a flange 46, 47, 48, and 49, respectively, abutting the inner side of the filter units. The flange can be provided with sealing rings (not shown). The perforations of the core pipes 18, 19 are suitably only accommodated between the respective adjustment members 42-45, but when they are accommodated outside this area as well, the adjustment members must ensure that they are covered. The perforations in the core pipes 18, 19 are suitably only accommodated inside the area adjacent the base member 9, whereby various lengths of filter units can be used without causing problems of ensuring a closing of openings placed outside the area of the filter units. As further illustrated in Fig. 1 , the lower adjustment members 43 and 44, respectively, rest on the bottom wall 4, and the upper adjustment members 42 and 44, respectively, rest on the intermediary rings or disks 38 and 39, respectively.

When the assembly of Fig. 1 is used, the opening 15 is connected in a manner not shown with a source for feeding an aqueous pressurized fluid. This fluid can in a conventionally known manner be carried through a number of coarse filters before it is fed through the opening 15 and into the interior of the housing 1. In addition, the opening 14 in the bottom wall is in a manner not shown either connected to a discharge of concentrate, i.e. fluid not having passed through the water-permeable membrane 30 and 31. Finally, the outward ends of the core pipes 16 and 17 are connected to pipes for draining off treated water through for instance their respective tap allowing a closing for fluid from one or more of the filter units.

The pressurized fluid is carried through the opening 1 5 in the bottom wall 4 and the opening 48 in the inner wall 20, said fluid flowing as indicated by means of an arrow 50 upwards into the upper end of the interior of the housing 1 . From this upper end, the fluid flows through the intermediary rings or disks 38 and 39 and into the porous material 26 and 27, respect¬ ively, of the filter units 10, 1 1 . Subsequently, the fluid flows downwards as indicated by means of arrows 51 and down into the inner space 21 in the base member. From this space 21 , the fluid flows out through the opening 14. While passing the filter units 10, 1 1 , the purified water passes by reverse osmosis through the water-permeable membranes 30 and 31 . Then the purified water flows into the interior of the core pipes 18 and 1 9 through the perforations whereafter the water is drained off as indicated by means of arrows 52.

As illustrated, the filter units 10 and 1 1 are mounted together with the base member 9 as a unit through the core pipes 1 8 and 1 9. This unit can be removed from and mounted on the housing 1 in order to be cleaned or so as to allow a replacement of the filter units 10 and 1 1 , which requires no special tools.

The fed pressurized fluid is provided by means of a suitable pump and is adjusted by means of a manometer to the osmotic pressure of the fluid in question. The dimensions of the openings through the intermediary rings or disk 39 can, if desired, be adjusted to the pressure conditions in such a manner that said intermediary rings or disks can have a pressure-re- ducing and filtrating effect on the fluid. The dimensions of the housing and the walls are adjusted to the pressure conditions applying to the treatment of the fluid in question.

The assembly is suited for treatment of various types of fluid. In connection with conversion of salt water into drinking water, a pressure of approximately 25 bar must be set for the operation. The treatment of conventional water to be purified of heavy metals, chlorine, bacteria etc. requires no more than approximately 8 bar. The assembly can be made of relatively simple materials. The housing 1 can for instance be made of a conventional length of pipe for the transport of water or natural gas. Then the treatment of salt water requires a wall thickness of approximately 25 mm and a top wall of approximately 50 mm. Several types of filter units can be used as filter units. It is, for instance, possible to use so-called Desal-membranes sold by the company Desalination Systems Inc., USA.

The described embodiment of the housing and the base member 1 is, as mentioned, of a circular cross section. The number of filter units 10, 1 1 in such a housing 1 is preferably four. In other words, the base member is shaped such that it can receive maximum four filter units, but one or more of the filter units can, if desired, be omitted by the openings 22, 23 in the inner wall 20 of the base member 9 being closed or by taps being closed which communicate with the core pipes 1 8 and 1 9. The assembly can, however, also be structured so as to comprise more filter units than four and be of other sectional shapes than the circular cross section.

As mentioned, the fluid in question to be treated is carried from a pump to the assembly shown in Fig. 1 . According to a second embodiment of the invention it is possible instead of using a through opening 1 5 and 40 for the pressurized fluid in question to use a pump 53 which is mounted as an integrated unit with a top cover 54, cf. Fig. 2., whereby the assembly with the pump 53 is particularly compact. This top cover 54 is secured to the housing 1 in the same manner as the base member 9 in Fig. 1 by means of co-operating flanges and a circumferential strap not shown. As shown by means of arrows, the fluid is carried into the interior of the assembly through the pump 53. A removal of a detachable top cover with or without a pump allows an easy access to the filter units in such a man- ner that said filter units can be replaced, if desired, without necessitating a removal of the entire unit with filter units and base member. As an alternative possibility, it is also possible to mount a separate unit with filter units and base member 9 in each end of an extended housing 1 instead of using a top cover 54 with or without pump 53.

If desired, two filter units can be reset such that they operate in series, cf . Fig. 3. The latter is performed by a closing ring 55 being mounted around one core pipe 18 in one opening 22 in the inner wall 20 of the base mem¬ ber 9. The closing ring prevents fluid from flowing into the space 21 through the opening 22 in question in the inner wall 20. An intermediary ring or disk 56 corresponding to the above intermediary rings or disks 38 and 39 is arranged on top of this closing ring 25, said ring or disk 56 allowing passage of fluid from the surroundings into the filter unit 10 arranged thereon. Like above, this filter unit 10 is secured to the base member 9 by means of tightening nuts. A U-shaped length of pipe 57 is mounted on top of the filter unit 10, the opposite end of said length of pipe being secured to the upper end of a filter unit 1 1 adjacent the filter unit 10. As a result, a free passage exists for the flow of concentrate from the filter unit 10 into the filter unit 1 1 through the length of pipe 57, whereby the two filters 10 and 1 1 operate in series.

The invention has been described with reference to a preferred embodi¬ ment. Many modifications can be carried out without thereby deviating from the scope of the invention. The base member with filter units secured thereto can for instance be mounted on the housing in many other ways beyond the one illustrated.

Claims

Claims.

1. An assembly for treatment of an aqueous fluid by reverse osmosis, said assembly comprising a housing with a plurality of tubular filter units, where each filter unit is made of a liquid-permeable porous material covered on the outer side by a liquid-impermeable material and on the inner side by a semipermeable membrane which by reverse osmosis allows purified water to pass from the porous material to the through central passageway, where said assembly comprises channels carrying untreated, pressurized water to the filter units and purified water away from the central passageway of the filter units as well as draining off the fluid having passed axially through the porous material of the filter units, c h a r a c - t e r i s e d in that the filter units (10, 1 1 ) are mounted on their respective perforated core pipe (18, 19), which are closed at one end and which at the opposite end are connected to a common separate base member (9) forming a wall in the housing (1 ), said filter units (10, 1 1 ) at the end adjacent said base member (9) sealingly abutting the circumference of their respective opening (22, 23) in an inner wall (20) in said base member (9), whereas the core pipes (18, 19) extend freely through said openings (22, 23) and are connected to an outer wall (4)in the base member (9), the inner and the outer wall (20, 4) of said base member (9) together with a circumferential connecting wall (12) defining a space (21 ), which sealingly surrounds the core pipes (18, 19) and receives untreated concentrated fluid from the filter units (10, 1 1 ), that the core pipes (18, 19) are sealingly closed towards the inner circumference of the filter units (10, 1 1 ) adjacent both ends of the filter units (10, 1 1 ), and that the openings (41 , 42) in the core pipes (18, 19) forming the perforations are only open for passage of treated water within an area between the sealing closings of the core pipes (18, 19) towards the filter units (10, 1 1 ).

2. An assembly as claimed in claim 1 , c h a r a c t e r i s e d in that the base member (9) comprises a plate-shaped inner wall (20) and an outer wall (4) which is also plate-shaped and formed integral with the circumfer¬ ential connecting wall (12) which extends parallel to the core pipes (18, 19).

3. An assembly as claimed in claim 1 or2, characterised in that the base member (9) comprises a circumferential outer flange (5) for mounting against a corresponding circumferential flange (7) on the remain¬ ing portion of the housing (1).

4. An assembly as claimed in claim 1, 2 or 3, ch aracteri sed in that the core pipes (18, 19) are provided with an external thread (32, 33) engaging an internal thread in openings (16, 17) shaped in the outer wall (4) of the base member (9).

5. An assembly as claimed in claim 1, 2, 3 or 4, c h a racte rised in that the filter units (10, 11) are sealingly tightened against the inner wall (20) of the base member (9) by means of tightening nuts (36, 37) to be screwed on external threads (34, 35) on the ends of the core pipes (18, 19) opposite the base member (9).

6. An assembly as claimed in the claims 1 to 5, c h a racte ri sed in that the tightening nuts (36, 37) are fixedly tightened to the free ends of the filter units (10, 11) through intermediary annular flow-adjusting members (38, 39), through which the fluid in question reaches the porous material (26, 27) of the filter units (10, 11).

7. An assembly as claimed in one or more of the claims 1 to 6, ch a r¬ a c t e r i s e d in that the sealing closing of the core pipes (18, 19) towards the inner circumference of the filter units (10, 11) is provided by means of sleeve-shaped adjustment members (42, 43, 44, 45) inserted over the core pipes (18, 19).

8. An assembly as claimed in one or more of the claims 1 to 7, ch ar¬ a cte ri sed in that the core pipes (18, 19) are only perforated within a restricted area adjacent the base member (9).

9. An assembly as claimed in claim 1, characterised in that the housing comprises a detachable cover (54).

10. An assembly as claimed in claim 9, characterised in that the detachable cover (54) is connected to a pump unit (53), through which the fluid to be treated is pumped into the housing (1).

11. An assembly as claimed in claim 1, c h ara cte r i sed in that a closing member (55) is mounted around a core pipe (18, 19) at the corre¬ sponding opening (22, 23) through the inner wall (20)of the base member (9), and that a flow-adjusting member (56) is coupled between said closing member (55) and the corresponding filter unit (10, 11), said flow-adjusting member (55) being adapted to allow flow of pressurized fluid from the surroundings and into the porous portion (26, 27)of the filter unit (10, 11), and that a fluid-guiding length of pipe (57)is mounted between the free end of the filter unit (10, 11) in question and the free end of another filter unit (10, 11).