Separation membrane module

A separation membrane module (1A) includes: a tubular pressure container (7); a plurality of separation membrane elements (2) inserted in the pressure container (7) and each having a first end member (3) and a second end member (4); and a sealing member (5A) mounted on one of or both the first end member (3) and the second end member (4) that are adjacent to each other. In a normal condition, the sealing member (5A) is located radially inward of a maximum diameter portion of the first end member (3) and/or the second end member (4) on which the sealing member (5A) is mounted. The sealing member (5A) is deformed due to contact between the adjacent separation membrane elements (2) or due to supply of a pressurized liquid into the pressure container (7), and comes into close contact with an inner circumferential face (7a) of the pressure container (7).

TECHNICAL FIELD

The present invention relates to a separation membrane module in which a plurality of separation membrane elements are inserted in a tubular pressure container.

BACKGROUND ART

For example, separation membrane modules used for seawater desalination, ultrapure water production etc., are conventionally known. For example, Patent Literature 1 discloses a separation membrane module10as shown inFIG. 12andFIG. 13. The separation membrane module10includes a tubular pressure container11and a plurality of separation membrane elements12inserted in the pressure container11in a line. As shown by an arrow inFIG. 12, when raw water is supplied into the pressure container11from one end of the separation membrane module10, the raw water is separated into permeated water and concentrated water by separation membranes of the separation membrane elements12, and the permeated water and the concentrated water are separately discharged from the other end of the separation membrane module10.

Each separation membrane element12has a layered body including a separation membrane and wound around a central pipe, and has a pair of end members13disposed in such a way as to sandwich the layered body. In the separation membrane module10shown inFIG. 12andFIG. 13, a packing15having an approximately U-shaped cross-section is mounted on the end member13located on the upstream side, and the packing15seals a gap between the separation membrane element12and the inner circumferential face of the pressure container11by means of a pressure of the raw water applied from the upstream side.

The packing15has an outer diameter which is nearly equal to the diameter of the inner circumferential face of the pressure container1, even in a natural posture where no pressure from the upstream side is exerted. Therefore, when the separation membrane element12is inserted into the pressure container11, the separation membrane element12is conventionally pushed into the pressure container11in such a manner that the packing15pressed by the weight of the separation membrane element12is rubbed against the inner circumferential face of the pressure container11.

CITATION LIST

Patent Literature

Patent Literature 1: JP 2009-220104 A

SUMMARY OF INVENTION

Technical Problem

Conventional separation membrane elements generally have an outer diameter of 8 inches. In the recent years, however, large-size separation membrane elements having an outer diameter of 16 to 24 inches have been developed. However, in such a large-size separation membrane element, the area of contact between the inner circumferential face of the pressure container and the packing is increased, and the weight of the separation membrane element is also increased. Therefore, with a conventional structure of a separation membrane module, it is difficult to insert a separation membrane element into a pressure container.

In view of such circumstances, the present invention aims to provide a separation membrane module that allows easy insertion of a separation membrane element into a pressure container.

Solution to Problem

In order to solve the above problem, the present invention provides a separation membrane module including: a tubular pressure container; a plurality of separation membrane elements each having a separation membrane, and a first end member and a second end member that are disposed so as to sandwich the separation membrane, the plurality of separation membrane elements being inserted in the pressure container in such a manner that the first end members and the second end members are alternately arranged in an axial direction of the pressure container; and a sealing member being annular and mounted on one of or both the first end member and the second end member that are adjacent to each other, the sealing member in a normal condition being located radially inward of a maximum diameter portion of the first end member and/or the second end member on which the sealing member is mounted. The sealing member is deformed due to contact between the separation membrane elements adjacent to each other or due to supply of a pressurized liquid into the pressure container, and comes into close contact with an inner circumferential face of the pressure container.

The “normal condition” means a state where the sealing member is merely mounted on the first end member and/or the second end member (hereinafter, may be simply referred to as “the end member”), and maintains a natural shape free from any external force, that is, a state where the sealing member mounted on the end member has no deformation caused by an external force.

Advantageous Effects of Invention

With the above configuration, the sealing member in the normal condition is located radially inward of the maximum diameter portion of the end member, and therefore, each separation membrane element can easily be inserted into the pressure container by sliding the end member on the inner circumferential face of the pressure container. The sealing member is deformed to seal a gap between the separation membrane element and the inner circumferential face of the pressure container when another separation membrane element is subsequently placed at a proper position or when raw water is supplied into the pressure container after all of the separation membrane elements are placed at proper positions.

DESCRIPTION OF EMBODIMENTS

Hereinafter, embodiments of the present invention will be described with reference to the drawings. The following description relates to some examples of the present invention, and the present invention is not limited by these examples.

First Embodiment

A separation membrane module1A according to a first embodiment of the present invention is shown inFIG. 1. The separation membrane module1A includes a tubular pressure container7called a vessel, and a plurality of separation membrane elements2inserted in the pressure container7.

Disc-shaped caps8and9are attached to both ends of the pressure container7. In the cap8on one side (left side inFIG. 1), a supply pipe81for supplying raw water into the pressure container7is provided at a position apart from the center. In the cap9on the other side (right side inFIG. 1), a first discharge pipe91for drawing permeated water is provided at the center, and a second discharge pipe92for drawing concentrated water is provided at a position apart from the center. That is, a flow of raw water from the cap8on the one side to the cap9on the other side is formed in the pressure container7. The supply pipe81and the second discharge pipe92may be provided in the pressure container7.

In the present embodiment, a spiral reverse osmosis membrane element is used as the separation membrane element2. However, the separation membrane element2may be, for example, a spiral ultrafiltration membrane element or a cylindrical element of another type.

Each separation membrane element2includes: a central pipe21functioning as a water collecting pipe; a layered body22wound around the central pipe21; a first end member3and a second end member4that are disposed so as to sandwich the layered body22; and an outer covering material28enclosing the layered body22. The first end member3and the second end member4also function to prevent the layered body22from extending telescopically.

In the present embodiment, each separation membrane element2is inserted in the pressure container7in such an orientation that the first end member3is located on the upstream side, and the second end member4is located on the downstream side. In other words, the first end members3and the second end members4are alternately arranged in the axial direction of the pressure container7.

In addition, in the present embodiment, any two adjacent separation membrane elements2are coupled by a coupler61fitted in the central pipes21of both of the separation membrane elements2, in such a manner that the first end member3of one separation membrane element2and the second end member4of the other separation membrane element2are in close contact with each other, in other words, in such a manner that the adjacent separation membrane elements2are in direct contact with each other. In addition, in the separation membrane element2located on the most upstream side, a plug62is attached to one end of the central pipe21that is opposite from the coupler61. A low of raw water into the central pipe21is thus blocked. Furthermore, the central pipe21of the separation membrane element2located on the most downstream side is coupled to the first discharge pipe91by a second coupler63.

As shown inFIG. 2, the central pipe21of each separation membrane element2is provided with a plurality of introduction holes for flowing permeated water into the central pipe21.

The layered body22has a rectangular shape, and is wound in a direction from one side of the rectangle to the opposite side. The layered body22includes: a membrane member composed of a permeated water flow path material24and separation membranes23placed over both faces of the permeated water flow path material24; and a raw water flow path material25. The separation membranes23are joined to each other at their three sides so that the membrane member has the shape of a sack that is open in one direction. The opening communicates with the introduction holes of the central pipe21. The permeated water flow path material24is, for example, a net made of a resin, and forms a flow path for flowing permeated water between the separation membranes joined to each other. The raw water flow path material25is, for example, a net made of a resin (a net that has larger meshes than the permeated water flow path material24), and forms a flow path for flowing raw water between wound layers of the membrane member.

Examples of the material of the separation membranes23include aromatic polyamide-based materials excellent in pressure reducing performance, polyvinyl alcohol-based materials excellent in permeability, and sulfonated polyethersulfone-based materials suitable for nanofiltration membranes.

Referring back toFIG. 1, the first end member3has an inner tubular portion31externally fitted to one end of the central pipe21, and has an outer tubular portion32being concentric with the inner tubular portion31and surrounding the inner tubular portion31at a distance from the inner tubular portion31. The inner tubular portion31and the outer tubular portion32are coupled by an annular plate in which a plurality of ribs or through holes are formed (not shown in the drawings). Thus, flow-through openings which penetrate the first end member3and through which raw water flows are formed between the inner tubular portion31and the outer tubular portion32.

Similar to the first end member3, the second end member4has an inner tubular portion41externally fitted to the other end of the central pipe21, and has an outer tubular portion42being concentric with the inner tubular portion41and surrounding the inner tubular portion41at a distance from the inner tubular portion41. The inner tubular portion41and the outer tubular portion42are coupled by an annular plate in which a plurality of ribs or through holes are formed (not shown in the drawings.) Thus, flow-through openings which penetrate the second end member4and through which raw water flows are formed between the inner tubular portion41and the outer tubular portion42.

An annular sealing member5A is mounted on any of the first end members3that are adjacent to the second end members4(i.e., the first end members3of the separation membrane elements2other than the separation membrane element2that is located on the most upstream side). The conventional packing15having an approximately U-shaped cross-section is mounted on the first end member3of the separation membrane element2located on the most upstream side. In the present embodiment, the first end member3of the separation membrane element2located on the most upstream side is formed in the same shape as the other first end members3.

On the other hand, a pressing portion40(seeFIGS. 3A and 3B) that presses the sealing member5A is provided in any of the second end members4that are adjacent to the first end members3(i.e., the second end members4of the separation membrane elements2other than the separation membrane element2that is located on the most downstream side). In the present embodiment, the second end member4of the separation membrane element2located on the most downstream side is formed in the same shape as the other second end members4. However, the second end member4of the separation membrane element2located on the most downstream side may have a shape with no pressing portion40(e.g., the same shape as that of the first end member3).

Next, the configuration around the sealing member5A will be described in detail with reference toFIGS. 3A and 3B.

The outer tubular portion32of the first end member3has a guide portion33fitted to the inside of the outer covering material28, and a flange portion34that blocks the movement of the outer covering material28in the axial direction. The flange portion34extends radially outward beyond the outer covering material28, and the maximum diameter of the first end member3is defined by the outer circumferential face of the flange portion34. In addition, the flange portion34has an outer end face that faces the opposite side to the outer covering material28(i.e., an outer end face perpendicular to the axial direction of the pressure container7), and the sealing member5A is supported by the outer end face from the opposite side to the second end member4.

In addition, the outer tubular portion32has a reduced diameter portion35that supports the sealing member5A from inside, and a projecting portion36that projects radially outward from an edge of the reduced diameter portion35and that prevents the sealing member5A from being disengaged from the reduced diameter portion35. In other words, the flange portion34, the reduced diameter portion35, and the projecting portion36form a groove extending in the circumferential direction and intended for mounting of the sealing member5A.

In a state (normal condition) where the sealing member5A is merely mounted on the first end member3, and maintains a natural shape free from any external force, the sealing member5A has such an outer diameter that the sealing member5A is located radially inward of the maximum diameter portion of the first end member3. That is, the outer diameter of the sealing member5A in the natural posture is slightly smaller than the maximum diameter of the first end member3. The sealing member5A is deformed due to contact between the adjacent separation membrane elements2, and comes into close contact with the inner circumferential face7aof the pressure container7.

A hollow elastic body is shown as an example of the sealing member5A used in the present embodiment. However, the sealing member5A does not need to be hollow. The cross-sectional shape of the sealing member5A is preferably circular, but may be polygonal. Examples of materials usable for forming the sealing member5A include: synthetic rubbers such as nitrile rubbers (NBR), ethylene propylene rubbers (EPDM), silicone rubbers, fluorine rubbers, and butyl rubbers (IIR); and natural rubbers. In addition, the hardness of the sealing member5A is preferably in the range of 30 to 80, and is more preferably in the range of 40 to 60, in terms of shore hardness. If the hardness is too high, the sealing member5A is likely to be broken by pressing. If the hardness is too low, the sealing member5A cannot withstand the pressure of a fluid, and cannot perform sufficient sealing function.

On the other hand, the outer tubular portion42of the second end member4has a guide portion43fitted to the inside of the outer covering material28, and a flange portion44that blocks the movement of the outer covering material28in the axial direction. The flange portion44extends radially outward beyond the outer covering material28, and the maximum diameter of the second end member4is defined by the outer circumferential face of the flange44. The maximum diameter of the second end member4may be equal to or different from the maximum diameter of the first end member3.

A projecting portion that is tubular is formed integrally in the outer tubular portion42, and the projecting portion projects from an end face facing the first end member3at a position corresponding to the sealing member5A mounted on the first end member3. The above-described pressing portion40is the projecting portion. The pressing portion40has an front end face that is flat and parallel to the end face of the outer tubular portion42. That is, as shown inFIG. 3B, when the adjacent separation membrane elements2are coupled together and brought into contact with each other, the pressing portion40presses the sealing member5A in the axial direction of the pressure container7to deform the sealing member5A into a shape compressed in the axial direction, and thus to press the sealing member5A against the inner circumferential face7aof the pressure container7.

Furthermore, in the present embodiment, a flow path20for guiding raw water having passed through the separation membrane element2to a space around the separation membrane element2is formed between the first end member3and the second end member4. For example, the flow path20can be a groove formed in an end face of the outer tubular portion32of the first end member3that faces the second end member4.

In addition, a through hole penetrating the pressing portion40in the radial direction is formed in the pressing portion40, and the through hole forms a communication path40athat allows the flow path20to communicate with a space between the separation membrane element2and the inner circumferential face7aof the pressure container7. Therefore, as shown inFIG. 4A, the separation membrane module1A is configured as a downstream pressure application-type separation membrane module in which the pressure of raw water having passed through each separation membrane element2is exerted on the outer face of the outer covering material28of the separation membrane element2. Accordingly, for example, at the time of start of operation when the pressure of raw water is sharply increased, it is possible to prevent a large pressure difference between the inside and outside of the separation membrane element2, and thus to prevent breakage of the separation membrane element2. The pressing portion40may be divided into a plurality of arc-shaped pieces, and the communication path40amay be gaps formed between the pieces.

In the separation membrane module1A of the present embodiment described above, the sealing member5A in the normal condition is located radially inward of the maximum diameter portion of the first end member3. Therefore, each separation membrane element2can easily be inserted into the pressure container7by sliding the first end member3on the inner circumferential face7aof the pressure container7. The sealing member5A is deformed to seal the gap between the separation membrane element2and the inner circumferential face7aof the pressure container7when another separation membrane element2is subsequently placed at a proper position.

Modification Example

The separation membrane element2may be inserted in the pressure container7in the reverse manner of the above-described embodiment, i.e., in such an orientation that the first end member3is located on the downstream side, and the second end member4is located on the upstream side. In this case, as shown inFIG. 4B, it is possible to provide an upstream pressure application-type separation membrane module in which the pressure of raw water that has not passed through each separation membrane element2yet is exerted on the outer face of the outer covering material28of the separation membrane element2. In that case, as shown inFIG. 4B, it is sufficient that the conventional packing15should be mounted on the first end member3of the separation membrane element2that is located on the most downstream side.

In addition, in the case where the pressure of raw water is gradually increased or where an operation pressure applied to raw water is small, the flow path20does not need to be formed between the first end member3and the second end member4, and the communication path40adoes not need to be provided in the pressing portion40.

In the above embodiment, the adjacent separation membrane elements2are coupled in such a manner that the first end member3and the second end member4are in close contact with each other. However, similar to the case of the conventional separation membrane module10shown inFIG. 12, the adjacent separation membrane elements2may be coupled by a coupler externally fitted to the central pipe21in such a manner that the first end member3and the second end member4are spaced from each other. That is, the adjacent separation membrane elements2may not necessarily come into direct contact with each other, and may be connected by a coupler. In this case, the flow path20for guiding raw water having passed through the separation membrane element2to a space around the separation membrane element2is a gap formed between the first end member3and the second end member4.

Furthermore, although the pressing portion40is a projecting portion formed integrally in the second end member4in the above-described embodiment, the pressing portion40provided in the second end member4may be a discrete member supported by the second end member4as in a separation membrane module1B shown as a modification example inFIGS. 5A and 5B.

Specifically, in the separation membrane module1B, the outer tubular portion42of the second end member4includes a flange portion44, a reduced diameter portion45, and a projecting portion46which respectively have the same shapes as those of the flange portion34, the reduced diameter portion35, and the projecting portion36of the outer tubular portion32of the first end member3. The pressing portion40is a tubular member held by the projecting portion46from inside, and is supported by an outer end face of the flange portion44from the opposite side to the first end member3, the outer end face facing the opposite side to the outer covering material28(i.e., the outer end face being perpendicular to the axial direction of the pressure container7).

With such a configuration, the first end member3and the second end member4can be formed in symmetrical shapes, or can be formed as the same components. This allows reduction of production cost.

Second Embodiment

Next, a separation membrane module1C according to a second embodiment of the present invention will be described with reference toFIGS. 6A and 6B. In the present embodiment, the same components as those described above are denoted by the same reference numerals, and the description thereof is omitted. The same applies to the other embodiments described later.

A solid elastic body is shown as an example of a sealing member5B used in the present embodiment. However, a hollow elastic body may also be used. The cross-sectional shape of the sealing member5A is preferably circular, but may be polygonal. The usable materials and preferable hardness for the sealing member5B are the same as in the first embodiment.

Similar to the sealing member5A of the first embodiment, in a state (normal condition) where the sealing member5B is merely mounted on the first end member3, and maintains a natural shape free from any external force, the sealing member5B has such an outer diameter that the sealing member5B is located radially inward of the maximum diameter portion of the first end member3. That is, the outer diameter of the sealing member5B in the natural posture is slightly smaller than the maximum diameter of the first end member3. The sealing member5B is deformed due to contact between the adjacent separation membrane elements2, and comes into close contact with the inner circumferential face7aof the pressure container7.

As in the first embodiment, a tubular projecting portion is formed integrally in the outer tubular portion42of the second end member4, and the projecting portion projects from an end face facing the first end member3at a position corresponding to the sealing member5B mounted on the first end member3. The pressing portion40is the projecting portion. In the present embodiment, the outer circumferential face of the pressing portion40is such a tapered face that the diameter decreases with distance from the end face of the outer tubular portion42. That is, as show inFIG. 6B, when the adjacent separation membrane elements2are coupled together and brought into contact with each other, the pressing portion40presses the sealing member5B outward in the radial direction to deform the sealing member5B so that the sealing member5B is radially expanded, and thus to press the sealing member5B against the inner circumferential face7aof the pressure container7.

In addition, as in the first embodiment, the pressing portion40is provided with the communication path40athat allows the space between the separation membrane element and the inner circumferential face7aof the pressure container7to communicate with the flow path20formed between the first end member3and the second end member4to guide raw water having passed through the separation membrane element2to a space around the separation membrane element2.

Also with the separation membrane module1C of the present embodiment, the same effects as those of the separation membrane module1A of the first embodiment can be obtained.

Modification Example

Similar to the modification example of the first embodiment, the pressing portion40provided in the second end member4may be a discrete member supported by the second end member4as in a separation membrane module1D shown as a modification example inFIGS. 7A and 7B. It should be understood that the other modifications described in the first embodiment are applicable to the second embodiment.

Third Embodiment

Next, a separation membrane module1E according to a third embodiment of the present invention will be described with reference toFIGS. 8A and 8B.

In the present embodiment, the first end member3and the second end member4have approximately symmetrical shapes, and an annular sealing member5C is mounted in a straddling manner on the first end member3and the second end member4that are adjacent to each other. Specifically, a groove extending in the circumferential direction and intended for mounting of the sealing member5C is formed in the first end member3by the flange portion34, the reduced diameter portion35, and the projecting portion36, while a groove extending in the circumferential direction and intended for mounting of the sealing member5C is formed in the second end member4by the flange portion44, the reduced diameter portion45, and the projecting portion46.

In a state (normal condition) where the sealing member5C is merely mounted on the first end member3and the second end member4, and maintains a natural shape free from any external force, the sealing member5C has such an outer diameter that the sealing member5C is located radially inward of the maximum diameter portions of the first end member3and second end member4. That is, the outer diameter of the sealing member5C in the natural posture is slightly smaller than the maximum diameters of the first end member3and the second end member4. As shown inFIG. 8B, when the adjacent separation membrane elements2are coupled together and brought into contact with each other, the sealing member5C is pressed by the first end member3and the second end member4to be expanded radially outward, and is thus pressed against the inner circumferential face7aof the pressure container7. That is, as in the first embodiment and the second embodiment, the sealing member5C is deformed due to contact between the adjacent separation membrane elements2, and comes into close contact with the inner circumferential face7aof the pressure container7.

Specifically, the sealing member5C includes a first ring portion51having a rectangular cross-sectional shape, a second ring portion52having the same cross-sectional shape as that of the first ring portion51, and a bridge portion53bulging radially outward and bridging the first ring portion51and the second ring portion52.

The first ring portion51is inserted in the groove formed by the flange portion34, the reduced diameter portion35, and the projecting portion36, and is thus held by the first end member3. The second ring portion52is inserted in the groove formed by the flange portion44, the reduced diameter portion45, and the projecting portion46, and is thus held by the second end member4. When the adjacent separation membrane elements2are coupled together and brought into contact with each other, the first ring portion51is pressed toward one side (the upstream side) of the pressure container by the outer end face of the flange portion34of the first end member3that faces the opposite side to the outer covering material28, while the second ring portion52is pressed toward the other side (the downstream side) of the pressure container by the outer end face of the flange portion44of the second end member4that faces the opposite side to the outer covering material28.

In the axial direction of the sealing member5C, the bridge portion53has a length which is sufficiently larger than the sum of the thicknesses of the projecting portion36and the projecting portion46. When the adjacent separation membrane elements2are coupled together and brought into contact with each other, the bridge portion53is deformed to bulge radially outward, and the center of the bridge portion53is pressed against the inner circumferential face7aof the pressure container7.

A plurality of through holes53aare provided in the bridge portion53at positions upstream from the center of the bridge portion53, and allow the space between the separation membrane element2and the inner circumferential face7aof the pressure container7to communicate with the flow path20formed between the first end member3and the second end member4to guide raw water having passed through the separation membrane element2to a space around the separation membrane element2. Therefore, as in the first embodiment, the separation membrane module1E is configured as a downstream pressure application-type separation membrane module as shown inFIG. 4A. If the thorough holes53aare provided at positions downstream from the center of the bridge portion53, an upstream pressure application-type separation membrane module as shown inFIG. 4Bcan be realized. In addition, the through holes53aare preferably arranged on the same circumference at regular angular intervals as shown inFIG. 9.

In the case of the separation membrane module1E of the present embodiment described above, when the separation membrane elements2are inserted into the pressure container7, the insertion was carried out while the adjacent separation membrane elements2are kept spaced from each other at a certain distance. For example, the separation membrane element2on the upstream side is pushed while the separation membrane element2on the downstream side is concurrently pulled.

In the separation membrane module1E of the present embodiment described above, the sealing member5C in the normal condition is located radially inward of the maximum diameter portions of the first end member3and the second end member4. Therefore, each separation membrane element2can easily be inserted into the pressure container7by sliding the first end member3and the second end member4on the inner circumferential face7aof the pressure container7. The sealing member5C is deformed to seal the gap between the separation membrane element2and the inner circumferential face7aof the pressure container7when another separation membrane element2is subsequently placed at a proper position.

Modification Example

The bridge portion53of the sealing member5C may not necessarily have an arc-shaped cross-section as shown inFIGS. 8A and 8B, and may have a V-shaped cross-section as shown inFIG. 10, for example.

Fourth Embodiment

Next, a separation membrane module1F according to a fourth embodiment of the present invention will be described with reference toFIGS. 11A and 11B.

Except for the shape of a sealing member5D, the separation membrane module1F of the present embodiment has the same configuration as that of the separation membrane module1E of the third embodiment. The sealing member5D used in the present embodiment is configured to be hardly deformed merely by coupling the adjacent separation membrane elements2together after the sealing member5D is mounted on the first end member3and the second end member4.

In a state (normal condition) where the sealing member5D is merely mounted on the first end member3and the second end member4, and maintains a natural shape free from any external force, the sealing member5D has such an outer diameter that the sealing member5D is located radially inward of the maximum diameter portions of the first end member3and the second end member4. That is, the outer diameter of the sealing member5D in the natural posture is slightly smaller than the maximum diameters of the first end member3and the second end member4. As shown inFIG. 11B, when the adjacent separation membrane elements2are coupled together, and then a pressure applied from one side of the pressure container7in the axial direction (the upstream side in the present embodiment) becomes higher than a pressure applied from the other side of the pressure container7in the axial direction (the downstream side in the present embodiment), the sealing member5D is deformed to be expanded radially outward, and is thus pressed against the inner circumferential face7aof the pressure container7. That is, the sealing member5D is deformed due to supply of raw water (a pressurized liquid) into the pressure container7, and comes into close contact with the inner circumferential face7aof the pressure container7.

Specifically, the sealing member5D includes a first ring portion51having a trapezoidal cross-sectional shape, a second ring portion52having the same cross-sectional shape as that of the first ring portion51, and a bridge portion53bridging the first ring portion51and the second ring portion52. The cross-sectional shapes of the first ring portion51and the second ring portion52may be rectangular as in the third embodiment.

The first ring portion51is inserted in a groove formed by the flange portion34, the reduced diameter portion35, and the projecting portion36, and is thus held by the first end member3. The second ring portion52is inserted in a groove formed by the flange portion44, the reduced diameter portion45, and the projecting portion46, and is thus held by the second end member4.

In the axial direction of the sealing member5D, the bridge portion53has such a length that the natural length of the sealing member5D is approximately equal to a distance between the flange portion34of the first end member3of one of the adjacent separation membrane elements2coupled together and being in contact with each other, and the flange portion44of the second end member4of the other of the adjacent separation membrane elements2. That is, when the adjacent separation membrane elements2are coupled together and brought into contact with each other, the bridge portion53is hardly deformed. In the example shown in the drawings, the bridge portion53is curved in such a manner that its center bulges radially outward. However, the bridge portion53may have the shape of a tube extending parallel to the axial direction of the sealing member5D.

A diameter-expanding portion54is provided on the outer circumferential face of the bridge portion53, and extends toward one side (the upstream side in the present embodiment) of the pressure container7in the axial direction in such a manner as to gradually expand radially. In the present embodiment, a second diameter-expanding portion55having a shape symmetrical to that of the diameter-expanding portion54is provided on the outer circumferential face of the bridge portion53in continuity with the diameter-expanding portion54. However, the sealing member5D may have an approximately Y-shaped cross-section without having the second diameter-expanding portion55.

In addition, a plurality of through holes53aare provided in an area of the bridge portion53that is located on the opposite side to the direction in which the diameter-expanding portion54extends (the other side of the pressure container7in the axial direction), with respect to a position at which the diameter-expanding portion54connects with the bridge portion53. The thorough holes53aallow the space between the separation membrane element2and the inner circumferential face7aof the pressure container7to communicate with the flow path20formed between the first end member3and the second end member4to guide raw water having passed through the separation membrane element2to a space around the separation membrane element2. Therefore, in contrast to the first embodiment, the separation membrane module1F is configured as an upstream pressure application-type separation membrane module as shown inFIG. 4B.

The diameter-expanding portion54forms an opening which is open to the upstream side between the bridge portion53and the diameter-expanding portion54. As shown inFIG. 11B, when raw water flows into the opening from the upstream side, the diameter-expanding portion54is deformed to be expanded radially outward, and the edge of the diameter-expanding portion54is pressed against the inner circumferential face7aof the pressure container7. At the same moment when the diameter-expanding portion54is deformed, the second ring portion52is displaced to the downstream side by a pressure difference between the upstream side and the downstream side, and the bridge portion53is deformed to slightly bulge radially outward.

In the case of the separation membrane module1F of the present embodiment, when the separation membrane element2is inserted into the pressure container7, the separation membrane element2can be pushed into the pressure container7from one side (the upstream side or the downstream side) of the pressure container7in the axial direction.

In the separation membrane module1F of the present embodiment described above, the sealing member5D in the normal condition is located radially inward of the maximum diameter portions of the first end member3and the second end member4. Therefore, each separation membrane element2can easily be inserted into the pressure container7by sliding the first end member3and the second end member4on the inner circumferential face7aof the pressure container7. When all of the separation membrane elements2are placed at proper positions, and raw water is supplied into the pressure container7, the sealing members5D are deformed to seal the gaps between the separation membrane elements2and the inner circumferential face7aof the pressure container7.

Modification Example

In the case where the separation membrane element2is inserted in the pressure container7in such an orientation that the first end member3is located on the downstream side, and the second end member4is located on the upstream side, the diameter-expanding portion54forms an opening which is open to the downstream side between the bridge portion53and the diameter-expanding portion54, and the through holes53aare located on the opposite side to the opening. In this case, a downstream pressure application-type separation membrane module as shown inFIG. 4Acan be realized.

DESCRIPTION OF THE REFERENCE NUMERALS