JP5315728B2 - Membrane element - Google Patents

Description

  The present invention relates to a submerged membrane element used when purifying sewage or waste water generated from a production factory, a restaurant, a fish processing factory, or a food factory in a treatment tank.

  If domestic wastewater and industrial wastewater (hereinafter collectively referred to as “sewage wastewater”) are discharged into the environment as they are, they will lead to environmental pollution. Therefore, it is required to discharge after purifying to a certain level. Therefore, conventionally, sewage wastewater is put into a treatment tank (activated sludge tank), and pollutants in the sewage wastewater are decomposed by microorganisms while passing air to obtain activated sludge liquid, and then activated sludge liquid is separately provided. It has been widely practiced to discharge supernatant water after sedimentation and separation of pollutants on the ground. This is called the activated sludge method.

  In recent years, with the improvement of polymer membrane technology and membrane separation technology, a method called membrane separation activated sludge method has been used. In this method, the membrane separation device is submerged in the activated sludge liquid in the treatment tank (activated sludge tank), and decomposition by microorganisms and membrane filtration from the activated sludge liquid by the membrane are simultaneously performed, and purified water is taken out. Since the water taken out through membrane filtration is purified to such an extent that it can be discharged as it is, there is an advantage that it is not necessary to install a sedimentation basin for sedimentation separation.

  Here, in the treatment tank in which the membrane separation apparatus is immersed, together with the supplied wastewater, the microorganisms for microbial treatment of it and the activated sludge liquid generated by the microbial treatment are stored in a mixed state, Hereinafter, the liquid mixture present in the treatment tank is referred to as a liquid to be treated.

  As shown in FIG. 10, the membrane separation apparatus used here is mainly composed of an element block 3 in which a large number of membrane elements 10 each having a filtration membrane bonded to both the front and back surfaces of a support are arranged. An air diffuser 4 is disposed below the element block 3. The membrane element is provided with a nozzle pipe 32 for taking out the filtrate. The liquid collection pipe 8 is connected to the nozzle pipe 32 via the tube 5 and the suction pump 6 is connected to the downstream side thereof. Negative pressure is applied to the inside of the element 10 and the filtrate is taken out. The air diffuser 4 is connected to the blower 7. Air is ejected from the lower air diffuser 4 toward the membrane separation device 3 submerged in the liquid to be treated in the treatment tank (membrane immersion tank) 2, which is referred to as aeration. Aeration has the effect of accelerating the decomposition of sludge by supplying oxygen to microorganisms and activating them.

  Aeration from the air diffuser 4 also removes sludge to be attached to the outer surfaces of the separation membranes disposed on both surfaces of each membrane element 10 to suppress the adhesion and accumulation of sludge on the membrane, and also has an air lift effect. This also creates a flow for circulating the liquid to be treated in the tank between the membrane elements. Between the membrane elements, there is an upward flow of the liquid to be treated due to aeration, and this upward flow collides with the outer surface of the membrane, so that the surface is washed and clogging of the membrane is suppressed, and the solid-liquid separation performance Can be suppressed over time.

  In the process of cleaning the surface of the separation membrane of the membrane element by aeration described above, the membrane element vibrates not a little. Therefore, the support that supports the separation membrane is constantly subjected to vibration repeatedly in the liquid to be treated, which leads to a decrease in durability of the support, that is, the membrane element. In order to suppress the vibration of the membrane element, the membrane element is stored and fixed in a casing (not shown) at a predetermined interval, but still prevents vibration caused by the liquid to be treated and the flow of air. It is difficult to do.

  The stress due to the vibration of the membrane element tends to concentrate on the liquid collection part provided so as to penetrate the support body in the front and back direction. When the shape of the liquid collection part is a shape having a corner such as a rectangular hole, stress is particularly likely to concentrate at the corner.

  In addition, since the support for the membrane element is desired to be light and low-cost, it is usually formed by resin injection molding. In the case of a support of a resin molded product, there is a problem that cracks are generated from the corners of the liquid collection part where stress is concentrated during use, leading to damage of the support, that is, damage to the membrane element.

  When a support is manufactured by injection molding of resin, it is necessary that a mold pin that forms an inner diameter of a nozzle hole and a mold block that forms a liquid collection portion are in close contact with each other at high pressure. If even a small gap exists between the pin and the block, a resin burr is generated in that portion, and if the burr remains, the flow of the filtrate is hindered. Removal of burrs after injection molding increases the number of finishing steps, which increases the manufacturing cost.

In order to manufacture the liquid collection part in the membrane element in consideration of the constraints imposed by the mold during the injection molding, the following liquid collection part shapes have been proposed.
For example, a horizontally long liquid collection part extending in the width direction is provided on the upper part of the support of the membrane element, a nozzle hole is communicated with the liquid collection part, and a plurality of slit-like grooves communicating with the liquid collection part There is a method in which holes are provided long in the height direction of the support (Patent Document 1).

  When the length of the liquid collection part penetrating the support body in the thickness direction is long, the cross-sectional secondary moment of the support body becomes small, and it becomes easier to vibrate. Further, when a plurality of slits penetrating the support plate in the thickness direction are provided in the height direction of the support body, the support body exhibits different vibration modes on the outer side and the inner side of the liquid collection part, and Due to the vibration inside the liquid collecting part, there arises a problem that the separation membrane attached to the support is easily damaged from the back side. Therefore, in the form of the membrane element of Patent Document 1, it is difficult to eliminate the problem of poor durability due to vibration.

  Furthermore, in Patent Document 1, since the separation membrane is attracted to the support side by suction of the filtrate from the nozzle hole and easily falls into the liquid collection part, a spacer is interposed between the support plate and the separation membrane. However, providing a spacer on the membrane element has a problem that the manufacturing process becomes complicated and the cost increases.

Further, in Patent Document 2, a laterally long liquid collection part extending in the lateral direction is provided on the upper part of the support of the membrane element, and a plurality of slits extending in the vertical direction in communication therewith are arranged in parallel with a narrow slit interval. The arranged structure is described. However, in the case of this embodiment as well, as in the case of Patent Document 1, it is difficult to solve the problem of durability failure due to vibration.
Japanese Patent No. 3119773 Japanese Patent No. 3255521

As described above, the membrane element vibrates not a little by aeration in the membrane immersion tank. For this reason, the support is repeatedly deformed, and if there is a place where stress is likely to be concentrated on the structure, it is easily damaged.
In addition, since the membrane separation apparatus is submerged in an immersion tank and used continuously for a long period of time, it is not easy to maintain it by pulling it up from the tank. Therefore, it is desired that the membrane element is not damaged as much as possible.

  However, in the conventional membrane separation apparatus, there is a problem that cracks due to stress concentration are likely to occur due to the liquid collecting portion structure of the support plate of the membrane element, and the durability is not sufficient.

Therefore, in order to solve the above problems, the membrane element of the present invention, a separation membrane, a membrane element comprising a support having a nozzle hole supporting the separation membrane to derive the filtrate, the support There has liquid-collecting section penetrating in the front-back direction, shape viewed from the support front side of the liquid collecting portion is substantially T-shaped and chamfering the ends of each side, and the lateral sides of the substantially T-shaped The upper plane communicates with the nozzle hole.

Further, the length of the upper side of the horizontal side of the liquid collecting portion in the substantially T shape is longer than the inner diameter of the nozzle hole, and the end of the nozzle hole side of the vertical side of the substantially T shape is the nozzle hole. It is preferable that the opening part on the liquid collecting part side is located.
Furthermore, it is preferable that the width of the horizontal side and the width of the vertical side in the substantially T-shape of the liquid collecting part are each equal to or less than the support thickness.

  The support of the membrane element of the present invention has a substantially T-shaped shape in which the liquid collecting portion is chamfered at the end of each side. Damage to the support can be avoided. Furthermore, the restriction | limiting of the metal mold | die at the time of production by injection molding of resin can be solved by making it communicate with the said nozzle hole by the upper side plane of a substantially T-shaped side.

  In addition, by setting the width of each side of the substantially T-shaped portion of the liquid collecting portion to be equal to or less than the thickness of the support, it is possible to prevent the filtration membrane from dropping into the liquid collecting portion and the front and back filtration membranes from being closely adhered to each other Flow is not hindered.

  Furthermore, the length of the upper side of the horizontal side of the substantially T-shape of the liquid collection part is longer than the inner diameter of the nozzle hole, and the length direction of the vertical side of the membrane element and the length direction of the nozzle hole are substantially the same. When the support body is manufactured by injection molding by being positioned on the extension line, the mold pin that forms the inner diameter of the nozzle hole is pressed against the block of the mold that forms the liquid collection part at high pressure. Since the mold block is long in the direction in which the force of the pin acts, the rigidity can be maintained. As a result, the mold pin and the mold block can be brought into tight contact with each other, and the occurrence of burrs in the injection molded product can be avoided.

(Embodiment 1)
An embodiment of the present invention will be described with reference to the drawings.

  FIG. 1 is a partially broken perspective view showing a position embodiment of a membrane element 10 of the present invention. A part of the separation membrane 41 is cut away so that the water collecting part 33 can be seen. In the membrane element 10, separation membranes 41 are bonded to both the front and back surfaces of the support 31. FIG. 1 does not show the separation membrane on the back side.

  The filtrate that has passed through the separation membrane 41 disposed on the front and back of the support 31 flows through a liquid collection path (not shown) between the support and the separation membrane and travels toward the filtrate outlet (nozzle hole 33). . A nozzle tube 32 for taking out the filtrate is disposed so as to be connected to the nozzle hole 33 of the support 31. The filtrate collected in the liquid collection part 34 through the liquid collection path is taken out from the nozzle tube 32 through the nozzle hole 33. The taken out filtrate is sent out of the membrane separation device through the tube 5 and the liquid collection tube 8 as shown in FIG.

  The liquid collection part 34 is a hole provided on the inside of the support plate close to the nozzle tube 32, and the upper end of the support plate on which the nozzle tube 32 is disposed has the same diameter as the flow path in the nozzle tube 32. A nozzle hole 33 is provided.

  The liquid collection path between the support and the separation membrane may be a channel groove formed on the surface of the support, or a porous net (net, non-woven fabric, etc.) and the support. It is good also as a liquid collection path by interposing between separation membranes.

  As the separation membrane 41, a separation membrane capable of filtering the liquid to be treated (sewage wastewater or activated sludge liquid) existing in the treatment tank is used, and it is often a flat membrane made of a porous resin. As the material, a polyethylene terephthalate resin, a polyethylene resin, a polypropylene resin, a polyvinyl chloride resin, a polyvinylidene fluoride resin, a polysulfone resin, or the like can be used as a main component. However, it is not limited to these.

  FIG. 2 shows a partially broken perspective view of a conventional general membrane element. Also in this figure, a part of the separation membrane is cut out so that the water collecting portion can be seen. FIG. 3 is a partially enlarged view of the relationship between the nozzle tube 32, the nozzle hole 33, and the liquid collecting portion 34 in the support plate 31 of the membrane element of FIG. In the case of the membrane element 10, when the entire membrane element vibrates, stress is generated inside the support 31. In this case, since the liquid collection part 34 is rectangular and has corner portions C at the corners, the stress due to vibration tends to concentrate on the corner portions C, and cracks are likely to occur starting from the corner portions C.

  The crack generated from the corner C as a starting point gradually grows outward and becomes a crack connected to a support part that is not covered with the separation membrane (for example, the support outer surface in the vicinity of the nozzle hole). In this way, when the crack generated from the inner surface side of the support expands until it is connected to the outer surface side, the liquid to be processed enters the inside of the crack and enters the inside of the membrane element 10, and as a result, The treatment liquid is mixed with the filtrate side without being filtered by the separation membrane 41. And the filtrate which the to-be-processed liquid mixed without being filtered passes through the liquid collection part 34, and is collected from the nozzle hole 33 and the nozzle pipe | tube 32, and the cleanliness of the collected liquid falls. That is, the membrane element 10 in which the crack has occurred does not perform the filtration function.

  FIG. 4 is a partially enlarged view of the relationship between the nozzle tube 32, the nozzle hole 33, and the liquid collecting portion 34 in the support plate 31 of the membrane element of the present invention as viewed from the front of the support. In this case, the liquid collection part 34 is substantially T-shaped, and the end of each side is chamfered. Here, “cornering” is to make a corner portion inside the hole into a curved surface so that the hole has no corner. By eliminating the corners at the end of the hole in this way, stress concentration during vibration can be significantly suppressed, and cracking can be prevented. The nozzle tube 32 in the shape of FIG. 4 may be integrally formed with the support plate 31 by a mold arrangement as shown in FIG. 5, or the nozzle tube 32 is joined to the support plate 31 after forming. It may be a thing.

  Further, FIG. 5 is a schematic diagram showing a die pin 51a and a die block 52a for manufacturing the shapes of the nozzle tube 32, the nozzle hole 33, and the liquid collecting portion 34 shown in FIG. 4 by injection molding. . In this case, since the mold pin 51a and the mold block 52a are planarly aligned at the joint surface, both can be joined without a gap. Therefore, if injection molding is performed using the mold pin 51a and the mold block 52a of FIG. 4 joined without a gap, the mold pin 51a and the mold can be connected to each other at the time of injection molding without any particularly high-precision processing. Resin does not enter the joint with the mold block 52a. Therefore, unnecessary burrs are not generated in the liquid collection part / nozzle hole part of the obtained injection molded product.

  In addition to the above, the following matters can be mentioned as the advantage that the liquid collection part 34 is substantially T-shaped. In FIG. 5, since the vertical side of the mold block 52a is long in the direction in which the force of the mold pin 51a acts, it is difficult to be distorted, the shape of the liquid collecting portion 34 can be always stabilized and injection molding can be performed. It becomes hard to break. Therefore, it is important that the liquid collection part 34, which is a space formed by the mold block 52a, has a substantially T shape specified in the present invention.

  Further, the width of each side of the substantially T-shaped liquid collecting part 34 is preferably equal to or less than the thickness of the support 31. This is because when the width is wider than this, the separation membrane 41 is drawn into the liquid collection portion 34 by the suction force of the filtrate from the nozzle hole 33 and the flow of the filtrate is inhibited. By determining the width of the liquid collection part 34 as described above, it is not necessary to interpose a spacer between the support plate and the separation membrane. Moreover, even if the width | variety of these each side is narrow, it is preferable to make it wider than the diameter of the nozzle hole 33, in order to ensure the smooth flow of a filtrate. Here, the thickness T of the support is the thickness of the support in the portion where the liquid collection part 34 is provided. The diameter of the nozzle hole 33 may be the same as the inner diameter of the nozzle tube 32.

  Further, the substantially T-shape of the liquid collecting portion 34 in the present invention is a shape in which the vertical side V extends downward from the substantially central portion of the horizontal side H. The length of the upper plane of the horizontal side H is determined by the length of the nozzle. It is preferable that the inner diameter of the hole 33 is equal to or larger than the inner diameter of the hole 33, and the length direction of the vertical side V in the substantially T-shape and the length direction of the nozzle hole 33 are located on the substantially extended line. This is to ensure the rigidity of the mold block 52a against the pressing force of the mold pin 51a that forms the hollow portion of the nozzle hole 33, as shown in FIG.

  As shown in the figure, when the nozzle hole 33 is provided in the upper part of the membrane element, the substantially T-shaped lateral side H of the liquid collection part is the same horizontal side as the width direction of the support of the membrane element. Further, the vertical side V in the substantially T-shape is a side in the length direction (vertical direction) of the support of the membrane element. The length of the upper plane of the horizontal side H is the length of the plane portion on the upper side of the horizontal side H, and excludes the length of the curved portion for rounding off the end. The nozzle hole may be disposed on the side surface (lateral side) of the membrane element. In this case, the substantially T-shaped lateral side H is the vertical side, and the substantially T-shaped longitudinal side V is This is the horizontal side.

  FIG. 7 shows a case where the upper and lower end portions of the rectangular liquid collection portion 34 extending vertically as shown in FIG. 3 are simply chamfered and the corner portions are eliminated. FIG. 7 is a partially enlarged view of the nozzle tube 32, the nozzle hole 33, and the liquid collecting portion 34 as viewed from the front of the support. The liquid collecting part 34 having the shape shown in FIG. 7 has a hole shape in which the shape of the eaves extending vertically is connected from the front side to the back surface of the support, that is, a semicylindrical shape above and below the rectangular parallelepiped extending vertically. This is a hole having a shape (hereinafter referred to as a heel-cube) connected to (a bowl shape). When the hole-shaped liquid collecting part 34 is manufactured by injection molding, in order to form the hole shape, the upper side of the mold block 52b of the cuboid rectangular parallelepiped for forming the liquid collecting part 34 is formed. The cylindrical mold pin 51b for forming the hollow portion of the nozzle hole 33 must be connected and arranged as shown in the schematic diagram of FIG.

  However, in this case, it is necessary to make the mold pin 51b and the mold block 52b adhere to each other with the curved surfaces S. In the injection molding, in order to prevent the resin from entering the surface portion where the curved surfaces S are brought into close contact with each other, the curved surface S where the mold pin 51b and the mold block 52b are in contact with each other must be curved with a considerably high accuracy. Don't be. Therefore, the problem that the manufacturing cost of a metal mold | die becomes expensive arises. Furthermore, when the arrangement in which the mold pin 51b and the mold block 52b shown in FIG. 8 are connected is viewed from the A direction (side surface direction) shown in FIG. 8, the arrangement is as shown in FIG. When the cylindrical mold pins 51b are brought into close contact with the curved surface S on the bowl shape of the mold block 52b, the lower end side of the mold pin 51b is aligned with the bowl-shaped curved surface. The edge part 51c must be provided in the outer peripheral part side. Since the edge portion 51c is thin and has a sharp shape, it is easily deformed by receiving resin pressure and heat during injection molding, and does not adhere to the mold block 52b, and the resin intrudes during injection molding to form burrs. There is a problem that.

Therefore, as shown in FIG. 7, it is difficult to adopt the shape of the liquid collecting part 34 in the shape of a rectangular parallelepiped in order to industrially produce a support plate by resin injection molding.

It is a partially broken perspective view which shows the membrane element regarding this invention. It is a partially broken perspective view which shows the conventional membrane element. It is the elements on larger scale seen from the support body front which show the relationship between the nozzle tube in the conventional support plate, a nozzle hole, and a liquid collection part. It is the elements on larger scale seen from the support body front which show the relationship between the nozzle pipe | tube in the support body in this invention, a nozzle hole, and a liquid collection part. It is a schematic diagram which shows an example of the metal mold | die structure for manufacturing the nozzle hole and liquid collection part of the support body of FIG. 4 by injection molding. FIG. 6 is a left side view of the mold structure of FIG. 5. In FIG. 3, it is the elements on larger scale seen from the support body front, which shows the case where the corner | angular part of a liquid collection part is simply lose | eliminated. It is a schematic diagram which shows an example of the metal mold | die structure for manufacturing the nozzle hole and liquid collection part of the support body of FIG. 7 by injection molding. FIG. 9 is a left side view of the mold structure of FIG. 8. It is a figure which shows the apparatus structure which carries out the membrane separation which installed the membrane element in the processing tank.

Explanation of symbols

DESCRIPTION OF SYMBOLS 3 Element block 4 Air diffuser 5 Tube 6 Suction pump 7 Blower 8 Liquid collection pipe 10 Membrane element 31 Support body 32 Nozzle pipe 33 Nozzle hole 34 Liquid collection part H The side of the liquid collection part substantially T-shaped V The liquid collection part Side of substantially T-shaped C Corner portion of liquid collecting part T Thickness of support 51a, 51b Mold pin 52a, 52b Mold block S Curved surface where mold pin and mold block contact

Claims (3)

A membrane element comprising a separation membrane and a support having a nozzle hole for supporting the separation membrane and leading out the filtrate, the support having a liquid collection part penetrating in the front and back direction, The shape of the film as viewed from the front of the support is substantially T-shaped with the edges of each side chamfered, and communicates with the nozzle hole on the upper surface of the substantially T-shaped lateral side. element. The length of the upper side of the horizontal side of the liquid collecting part in the substantially T-shape is longer than the inner diameter of the nozzle hole, and the end of the nozzle hole on the nozzle hole side of the vertical side in the substantially T-shape. 2. The membrane element according to claim 1, wherein an opening on the liquid collection part side is located. 3. The membrane element according to claim 1, wherein a width of a horizontal side and a width of a vertical side in the substantially T-shape of the liquid collecting part are each equal to or less than a thickness of the support.

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