EP0041506A1

EP0041506A1 - Water desalting and purification device by reverse osmosis and ultrafiltration

Info

Publication number: EP0041506A1
Application number: EP80902055A
Authority: EP
Inventors: Hans Timm; Jürgen MOHN
Original assignee: GKSS Forshungszentrum Geesthacht GmbH
Current assignee: GKSS Forshungszentrum Geesthacht GmbH
Priority date: 1979-11-09
Filing date: 1980-10-28
Publication date: 1981-12-16
Also published as: DE2945317A1; DE2945317C2; WO1981001371A1

Abstract

Le dispositif comprend des empilements d'ensembles de membranes planes et superposees (19) composes d'une couche de drainage (23) disposee entre des membranes superieure et inferieure (21, 22) jointes de facon etanche par leur peripherie. Du cote des membranes, ces empilements sont exposes a l'eau brute et le permeat s'ecoule par des canaux (34) traversant les empilements. Afin d'augmenter le rendement de ces empilements de membranes, c'est-a-dire pour augmenter le rendement par surface et par volume, pour permettre une extensibilite accrue des empilements sans creer des tensions mecaniques, pour faciliter l'echange des empilements et pour obtenir d'autres avantages du point de vue de la fabrication, de l'entretien et du cout, les empilements de membranes superposes alternant avec des couches d'espacement (20) nopees en (51) et munies d'ouvertures (52) sont disposes dans un bati interieur supplementaire (8) a extremites ouvertes dont le couvercle (14) ne s'appuie que sur la partie interieure (13) du bati. L'empilement de membranes (19) est traverse par un boulon central (25) pourvu d'un canal axial (34) et de canaux radiaux (26) conduisant vers l'interieur de l'empilement (19). Plusieurs batis interieurs (8) sont disposes les uns apres les autres a l'interieur d'une enveloppe tubulaire exterieure (1), dans laquelle l'une des extremites comprend les raccords appropries pour l'alimentation (10) en eau brute, l'evacuation (11) du permeat et l'evacuation (9) de la saumure.The device comprises stacks of sets of flat and superimposed membranes (19) composed of a drainage layer (23) arranged between upper and lower membranes (21, 22) tightly joined by their periphery. On the side of the membranes, these stacks are exposed to raw water and the permeate flows through channels (34) passing through the stacks. In order to increase the yield of these stacks of membranes, that is to say to increase the yield by surface and by volume, to allow increased extensibility of the stacks without creating mechanical tensions, to facilitate the exchange of the stacks and to obtain other advantages from the point of view of manufacture, maintenance and cost, the stacks of superposed membranes alternating with spacing layers (20) nopees in (51) and provided with openings (52) are arranged in an additional internal frame (8) with open ends, the cover (14) of which rests only on the internal part (13) of the frame. The stack of membranes (19) is crossed by a central bolt (25) provided with an axial channel (34) and radial channels (26) leading towards the interior of the stack (19). Several internal frames (8) are arranged one after the other inside an external tubular casing (1), in which one of the ends comprises the appropriate connections for the supply (10) of raw water, l evacuation (11) of the permeat and evacuation (9) of the brine.

Description

Device for water desalination and purification by reverse osmosis and ultrafiltration

The invention relates to a device for water de-salting and water purification by reverse osmosis and ultrafiltration with a plurality of membrane cushions stacked flat in an outer housing, which consist of a drainage layer between the upper and lower membrane layers which are sealingly connected to one another and are flowed over by raw water on the membrane side and discharge the permeate through channels passing through the stack of pillows on the filter side.

Attempts made to date with such stacked membrane cushions have not yet led to any practical results, since it has so far not been possible to overcome a multitude of difficulties that have arisen. The main difficulties were as follows: 1. The membrane surfaces were underused because they are very close to each other in the stack and a uniform, parallel flow of raw water over all membrane surfaces could not be ensured, resulting in poor efficiency. 2. The membranes were quickly damaged due to strong mechanical stress due to pressure and axial forces and - especially in view of their relatively high manufacturing costs - had a short lifespan.

3. Holding a stack of membrane cushions together was extremely difficult, since when the tension is too low there is a poor degree of filling and because if the tension is too high, the membrane surfaces are damaged by spacers placed between them.

4. In an attempt to hold the membrane cushion stack together with a plurality of clamping bolts, the freedom of movement of the individual membrane cushions in the direction of their surface area was very badly affected, so that after switching the system on and off several times and the associated pressure change the membranes on the spacers in between have been damaged.

5. The replacement of the membrane cushions, which were designed to be very large because of their efficiency, required a great deal of work and expense.

The object of the present invention is to eliminate the aforementioned difficulties and to provide a device of the type mentioned in the introduction, which requires comparatively low costs in the manufacture, maintenance and operation and, despite a very compact construction, a high degree of efficiency (membrane pressure resistance and effective membrane area per device volume). The above object is achieved according to the invention by the Merkipale specified in the characterizing part of the main claim.

Further details of the invention emerge from the subclaims.

A preferred exemplary embodiment of the invention is explained in more detail below with reference to the drawings.

The drawings show:

1 shows an axial section through a device for water desalination and water purification according to the invention,

1a, the section designated by A in FIG. 1 on an enlarged scale,

2 shows a cross section along the section line. II-II of Fig. 1a,

3 is a front view of the device in viewing direction III-III of FIG. 1,

4 shows a detail of FIG. 2 on an enlarged scale, FIG. 5 shows a top view of the support ring shown in FIG. 4, FIG. 6 shows a section along the section line VT-VI of FIG. 5,

7 is a plan view of a spacer for the stacked membrane cushions, 8 is a plan view of a membrane cushion, partially broken away,

9 shows an enlarged section through the edge of a membrane cushion according to FIG. 8 and

10 shows a broken top view of the clamping of adjacent inner housings of the device.

The device according to the invention shown in FIG. 1 in an axial section consists of a tubular outer housing 1, which is closed at one end with a dome-shaped bottom 2 formed in one piece. At the free end of the outer housing 1 there is an annular flange 3 which contains screw bolts 4 for the cover 5 to be fitted, the design of which is shown in FIG. 3. This cover 5 engages with a shoulder 6 of reduced diameter in a corresponding inner annular recess in the outer housing 1 in order to achieve a sealing closure there. On the inside of the cover 5 there is an approximately square-shaped step-shaped recess 7 (FIG. 1) into which an inner housing 8 containing a membrane cushion 19 to be described in detail below can engage in a liquid-tight manner. The inner surface of the cover 5 opens into a central brine outlet connection 9 via a conical intermediate section within the recess 7. Furthermore, the cover contains one or more raw water inlet connections 10 outside the recess 7. Finally, the cover 5 also contains three outlet connections below the brine outlet connection 9 11 for the permeate obtained. The lid 5 is held on the outer housing 1 with nuts 12, which can be screwed onto the bolts 4. As already mentioned, there are one or more inner housings 8 arranged one behind the other in the axial direction, the design of which can best be seen from FIGS. 1a and 2. Each inner housing 8 consists of a trough-like lower part 13, which can be closed at the top with a flat cover 14 (FIG. 1a). The inner housing 8 is open at the end and thus forms a box-shaped flow cross section.

For stiffening, for axially connecting a plurality of inner housings 8 and for axially guiding inside the outer housing 1, there are ribs 15 on the outside of the side walls of the lower part 13 and the cover 14, which extend perpendicular to the corresponding surfaces. The front ends of the lower parts 13 and the cover 14 are stepped in opposite directions, so that, as shown in FIG. 1, they are well guided and - if desired - can also interlock with one another in a fluid-tight manner. At the ends of the ribs 15, as can be seen above all from FIG. 10, bores 16 and recesses 17 are provided. The angled free ends of essentially U-shaped clamp brackets 18 engage in the bores 16 of two adjacent ribs 15 and can be hooked into the recesses 17 of the ribs of an adjacent module. In the hooked-together state, a plurality of inner housings 8 can be inserted into the outer housing 1 correctly aligned axially with one another.

The interior of the lower part 13 delimited by the cover 14 is completely filled by the stack of membrane cushions 19 (FIG. 8) and the intermediate flat spacers 20 (FIGS. 4 and 7). Each membrane cushion 19 (FIGS. 8 and 9) consists of an upper membrane layer 21 and a lower membrane layer 22, which are sealingly connected to one another at the edge. At least one drainage layer 23 consisting of fine tissue is located between the layers 21 and 22. In order to distribute the liquid flows evenly, it can also be expedient to arrange a separating film 24 and two drainage layers 23a and 23b between the membrane layers 21 and 22. For permeate removal and storage in the inner housing 8, the membrane cushion 19 contains a central opening 35 (FIG. 8).

The spacer 20 in the form of a thin plate, preferably made of plastic, contains, as shown in FIG. 7, a multiplicity of through openings 52 and studs distributed in a web-like manner between these, with which the individual membrane cushions 19 are kept at a distance. The stand-off switch 20 contains a central opening 36 for proper storage in the inner housing.

The size and shape of the membrane cushions 19 and spacers 20 are adapted to the space present within the inner housing 8 in order to form a block-shaped stack which on the face side of the raw water flowing from the right to the linJ-s in FIG can be exposed. The raw water is guided between the membrane cushions 19 by the spacers 20, which, thanks to the knobs 51 and openings 52, ensure a calming of the water and constant mixing. The resulting pressure drop across the membrane section causes a lower pressure difference to the outer sides of the inner housing 8. The membrane stack 19 absorbs the resulting force due to its inherent stability in the transverse direction tion over the spacers 20 and in the vertical through the membrane stack 19 itself.

Raw water can also be fed in between the stacks 19 via bores in the inner housing 8. With this, it follows a favorable influence on the concentration, the flow rate and the pressure drop within the process line.

In a test installation, for example, fifty membrane pillows 19 and fifty spacers 20 were placed in an inner housing 8 of 500 x 100 x 100 mm, since the maximum thicknesses of the membrane pillows 19 and the spacers 20 are approximately 1 mm each. This results in an effective area of an individual membrane cushion of 0.1 m ² , ie the effective membrane area of a membrane stack 19 is 5 m ² . If, unlike in the drawing, which shows only two modules, four inner housings 8 are connected in series, a total membrane area of 20 m ² results for a total length of 2.3 m, which corresponds to a flow rate with a raw water throughput of 6 m ³ / h corresponds to the membranes of approx. 40 cm / s.

The inner structure of the inner housing 8 is then described with reference to FIGS. 1a and 2. The central pin 25 is used to connect the lower part 13 and cover 14 of the inner housing 8, to secure the position of the membrane stack 19 and to remove the permeate. The central pin 25 passes through a central opening 54 in the cover 14, the central opening

35 (FIG. 8) of the stacked membrane cushions 19, the central opening 36 (FIG. 7), the intermediate spacers 20 and the bore 53 in the bottom of the lower part 13. The central pin 25 has a longitudinal groove in the area of the membrane stack 19

26 on and is at its lower end with an external thread

27 and provided with an external thread 29 at the upper end. The undore thread 27 is screwed into a connector 28 arranged under the bottom of the lower part 13 and the upper thread 29 is used for screwing on a cap nut 30 which is supported on the outside of the cover 14. Ring seals 31 and 32, which are provided in corresponding ring grooves in the area of the screw connection on the cover 14 and on the bottom of the lower part 13, serve for the external sealing of the bolt 25 with respect to the inner housing 8. When the central bolt 25 is tightened with the nut 30, the cover 14 rests immovably on the lower part 13 in the longitudinal recess 33 and between axial projections (not shown).

The filling of the inner housing 8, which is still in the open state, takes place as shown in FIG. 4, ie a support ring 37 with a spacer 20 and a membrane cushion 19 are always threaded alternately onto the central bolt 25. The support ring 37, which surrounds the central pin 25 with its lower ring part 40 (FIG. 6), is provided on its circumference with an O-ring 38, which comes into sealing contact when stacked in the area of the central opening 35 of the membrane cushion 19, so that the raw water acting on the outside of the membrane has no access to the permeate discharge channels to be described below. The central opening 36 of the spacer 20 is dimensioned such that this central opening can enclose the O-ring 38 with little play. The upper ring part 39 of the support ring 37 has an inner diameter which is slightly larger than the outer diameter of the central bolt 25, so that an annular gap remains opposite the latter, which serves to remove the permeate. The outer diameter of the upper ring part 39 corresponds essentially to the diameter of the central opening 35 of the membrane cushion 19. The upper ring part 39 of the support ring 37 consists, as in FIG shows, from several segments 41, between which passages 42 are provided. In this way, the permeate emerging in the individual membrane cushions 19 in the region of the drainage layers 23a and 23b can reach the circumference of the central pin 25 via the passages 42. In order to pass the permeate from the circumference of the central bolt 25, the latter has a longitudinal groove 26 which is connected to the inner bore 34 (FIG. 2) of the hollow central bolt 25. In operation, the collected permeate can thus reach the connecting piece 28 via the inner bore 34 of the central bolt 25 in order to be passed on from there.

In addition to the threaded bore for the external thread 27 of the central bolt 25, the connecting piece 28 contains two mutually opposite sleeve-shaped ends 43 and 44, which extend in the longitudinal direction of the housing. These sleeve-shaped

Ends 43 and 44 are used to connect the permeate discharge pipes 45, which have 46 annular seals 47 in the form of an O-ring at their connecting ends. The permeate drain pipes 45 connect the individual inner housings 8 to one another and to the (permeate) outlet connections 11 provided in the cover 5. As shown in FIG. 1, the end of the inner housing 8 adjacent to the bottom 2 of the outer housing 1 is closed with a stopper 48 . Due to the pressure drop occurring in the outer housing - 1, the force acting on the individual inner housings 8 and on the stopper 48 ensures that the permeate drain pipes 45 provided with seals are held securely in the connecting pieces 28 even without any screw connection. The elimination of special screw connections facilitates the assembly and disassembly of the device during maintenance and when changing the membrane. If it is desired to separate the permeates of individual membrane stacks 19, further connecting pieces 49 and 50 can be provided on the connecting piece 28, as shown in FIG.

For example, the permeate of the inner housing 8 shown on the left in FIG. 1 could be conducted via one of the connecting pieces 49 or 50 to one of the three outlet connections 11 for permeate (FIG. 3), while another of the three outlet connections for permeate with the one shown in FIG 1 inner housing shown on the right is connected.

The membrane cushions used for the reverse osmosis preferably consist of vapor-coated polyamides, they can also have an acetate-cellulose coating.

A membrane cushion module designed according to the invention is distinguished by the following advantages:

a) By using small single membrane cushions, the rejects can be reduced considerably during manufacture.

b) Smaller units combined in an inner housing can be checked before installation.

c) The pressure resistance of the individual membrane cushions is considerably increased and can be up to 100 bar.

d) A membrane stack housed in an inner casing represents a practical shipping unit that can be quickly and easily removed and installed by the user. e) The permeate can be removed as a whole, but also individually from each membrane stack.

f) The device according to the invention can be started up and shut down without any problems since the strong pressure changes can no longer have a damaging effect on the membrane stack.

During operation of the device according to the invention, raw water is let into the outer housing through the raw water inlet connections 10, which flows through the individual membrane stacks 19 in the area of the spacers 20 from the bottom 2 in succession and leaves the device at the brine outlet connection 9 again as enriched brine. When the membranes overflow, the permeate reaches the drainage layers 23a and 23b and then flows through the central openings 35 of the membrane cushions and the passages 42 to the circumference of the central bolt 25 and then reaches the connecting piece 28 and thus the permeate drain pipe 45 and via the longitudinal groove 26 and the inner bore 34 one of the (permeate) outlet connections 11 in the cover 5 of the outer housing 1.

Claims

1.Device for water desalination and water purification by reverse osmosis and ultrafiltration with a plurality of membrane cushions stacked flat in an outer housing, which consist of a drainage layer between the upper and lower membrane layers sealingly connected to each other and overflowed with raw water on the membrane side and on the filter side Discharge the permeate through the channels traversing the cushion pad, characterized in that the membrane cushions (19) stacked on top of one another and plate-shaped spacers (20) lying between them are arranged in an additional inner housing (8) which is adapted to the stack cross section and consists of both ends open trough-shaped lower part (13) of rectangular

Cross section and a flat cover (14) which is supported solely on the lower part (13) is that the spacers (20) between adjacent membrane cushions (19) have the same area, are nubbed on both sides (51) and provided with openings (52), preferably made of plastic Films are that for each membrane stack (19) there is a single central bolt (25) which extends through the flat cover (14) and the stacked membrane cushions (19) and spacers (20) provided with the central opening (35) and on the floor the lower part (13) is fastened so that the central bolt (25) has a longitudinal groove (26) and is surrounded by a plurality of supporting rings (37) which keep the individual membrane cushions (19) at a distance and which have ring seals (38) on the membrane layers (21, 22) and a connection to the longitudinal groove (26) of the central bolt (25) is made via passages (42) arranged in them, so that the inner housing (8) is in a tubular outer housing use (1) is arranged, one end of which with a preferably dome-shaped bottom (2) is closed and at the opposite end has a removable cover (5), in which the raw water inlet connection (10), the brine outlet connection (9) and the outlet (11) for permeate are located so that the inner housing (8) are designed at their front ends so that they engage like a sleeve, and that under the bottom of the lower part (13) on the central bolt (25) with its longitudinal groove (26) there are L or T-shaped connecting pieces (28) for permeate discharge pipes ( 45) are provided.

2. Device according to claim 1, characterized in that in the outer housing (1) a plurality of consecutive, membrane cushions (19) containing inner housing (8) is arranged.

3. Device according to claim 1, characterized in that the stiffening and guide ribs (15) of the inner housing (8) are provided at their ends with recesses (17) or bores (16) in the two inner housing (8) in the axial direction connecting brackets (15) can be inserted.

4. The device according to claim 1, characterized in that the permeate drain pipes (45) with the interposition of sealing rings (47) are inserted axially movable in the connecting pieces (28).