WO2012108008A1

WO2012108008A1 - Membrane air diffuser

Info

Publication number: WO2012108008A1
Application number: PCT/JP2011/052685
Authority: WO
Inventors: 久人辻川; 克行保科; 義雄北川
Original assignee: 株式会社クボタ
Priority date: 2011-02-09
Filing date: 2011-02-09
Publication date: 2012-08-16
Also published as: CN103118991B; CN103118991A

Abstract

A membrane air diffuser in which air hole parts are opened by the expansion of an air diffusion membrane (3) in a mountain shape when viewed in a longitudinal direction (A) by the pressure of air supplied to the air diffusion membrane (3) when air is diffused, wherein a plurality of first air hole parts (8) and a plurality of second air hole parts (9) are formed while being arranged in the longitudinal direction (A) and the lateral direction (B) of the air diffusion membrane (3), the first air hole parts (8) are each a hole that is longer in the longitudinal direction (A) of the air diffusion membrane (3), the second air hole parts (9) are each a hole that is longer in the direction inclined with respect to the longitudinal direction (A) of the air diffusion membrane (3), and the second air hole parts (9) are each located between the first air hole parts (8) adjacent to each other in the longitudinal direction (A) and/or the lateral direction (B).

Description

Membrane diffuser

The present invention relates to a membrane-type air diffuser installed in a tank of a sewage treatment facility or the like, and relates to a technique for performing air diffusion for biological treatment or stirring.

Conventionally, this type of membrane diffuser includes, for example, those shown in FIGS. In this example, a rectangular diffuser membrane 252 is mounted on the upper surface of a rectangular base plate 251, and an air supply port 253 is provided at a predetermined position. An air supply unit is provided between the base plate 251 and the diffuser membrane 252. 254 is formed. The air supply port 253 communicates with the air supply unit 254.

The diffuser film 252 is a synthetic resin film or synthetic rubber film provided with a large number of slits 255 (pores), and the periphery of the diffuser film 252 is fixed to the base plate 251 by a fixing part 256. Each slit 255 is a slit elongated in the longitudinal direction A of the diffuser membrane 252 and is parallel to the longitudinal direction A.

As shown in FIG. 34 (a), when the aeration is stopped, the aeration film 252 receives the water pressure in the tank and is pressed against the upper surface of the base plate 251. At this time, the diffuser membrane 252 does not expand and the slit 255 is closed.

Further, at the time of air diffusion, compressed air is supplied from the air supply port 253 to the air supply unit 254, and as shown in FIG. 34 (b), the air diffusion film 252 receives the pressure of the compressed air from the longitudinal direction A. It expands into a mountain shape. When the diffuser membrane 252 expands in this way, the slit 255 opens in the short direction B, and the air in the air supply unit 254 passes through the slit 255 and becomes a bubble 258, from the inner side to the outer side of the diffuser membrane 252. To erupt.

As described above, an air diffuser in which a large number of slits 255 are formed in the air diffuser membrane 252 is described in, for example, Japanese Patent Publication No.

JP2007-777

However, in the above-described conventional format, as shown in FIG. 35, when the interval D between the slits 255 in the longitudinal direction A is set short, the slit 255 is used when the air supply amount supplied to the air supply unit 254 is small and the air volume is small. There is a problem that the bubbles generated from the bubbles and bubbles generated from the adjacent slits 255 are combined and coarsened, and the oxygen transfer efficiency is lowered.

Note that when the bubbles become coarse, the ratio of the surface area to the volume of the bubbles decreases, so the gas-liquid contact area decreases and the buoyancy increases and the ascent time is shortened. Movement efficiency decreases.

As a countermeasure against this, it is conceivable to set the interval D between the slits 255 long to suppress the coupling between the bubbles. In this case, the number of slits 255 per unit area of the diffuser membrane 252 decreases. End up. Therefore, when the air volume is increased from the small air volume to the large air volume, there is a problem that the number of slits 255 is insufficient and the initial pressure loss and the increase in pressure loss are increased.

In addition, when air diffuses, as shown in FIG. 34 (b), when the air diffuser film 252 expands in a mountain shape when viewed from the longitudinal direction A, the tensile force F in the short direction B acts on the slit 255 and the slit. 255 opens in the short direction B, but as shown in FIG. 35, the tensile force F generates a crack 257 at the end of the slit 255, and this crack 257 propagates to the adjacent slit 255 in the longitudinal direction A. There is a problem that the adjacent slits 255 are connected via the crack 257.

The present invention can suppress an increase in the initial pressure loss and the pressure loss, and it is possible to prevent a decrease in oxygen transfer efficiency by dispersing bubbles uniformly when the air volume is small. An object of the present invention is to provide a membrane diffuser capable of preventing the propagation of cracks.

In order to achieve the above object, according to the first aspect of the present invention, a plurality of pores are formed in a diffuser membrane,
At the time of air diffusion, the air diffuser film expands in a mountain shape by the pressure of the air supplied to the air diffuser film, and the pores open.
A membrane-type air diffuser that closes the pores when the air diffuser is not expanded when the air diffuser stops,
The diffuser membrane is formed by arranging a plurality of first pores and second pores that are more difficult to open than the first pores,
A second pore portion is located between adjacent first pore portions.

According to this, during the aeration operation, the aeration membrane expands in a mountain shape due to the pressure of the air supplied to the aeration membrane, and a tensile force is generated in the aeration membrane. This tensile force serves as a force for opening the first pore portion and the second pore portion. At this time, since the second pore portion is harder to open than the first pore portion, air is diffused with a small air volume. In this case, the first pore portion is opened before the second pore portion, and most of the air supplied to the diffuser membrane passes through the opened first pore portion and becomes air bubbles from the inside of the diffuser membrane. While being ejected to the outside, there are hardly any bubbles ejected to the outside through the second pore part that is difficult to open.

Thereby, it is possible to prevent the bubbles ejected from the first pore portion from being combined with the bubbles from the adjacent second pore portion. Furthermore, since the 2nd pore part is located between the adjacent 1st pore parts, the space | interval of 1st pore parts is expanded, and it ejects from the bubble which ejected from the 1st pore part, and the 1st pore part of the vicinity. It is possible to prevent the bubbles from being combined. Thereby, at the time of a small air volume, bubbles can be dispersed and generated uniformly, and a decrease in oxygen transfer efficiency can be prevented.

In addition, when air is diffused by increasing the air volume from the small air volume to the large air volume, the larger the amount of air supplied, the easier the second pores open, and the number of second pores ejecting bubbles increases. For this reason, the air supplied to the diffuser membrane passes through the first pore portion and the second pore portion, and is blown out from the inside of the diffuser membrane to the outside. As described above, when the air volume is small, the bubbles are mainly ejected from the first pore portion. However, as the air volume increases, the number of the second pore portions that eject the air bubbles increases, so that the initial pressure loss and the pressure loss increase. Can be suppressed.

In the membrane-type air diffuser according to the second aspect of the present invention, the first air hole is a hole that is long in a predetermined direction of the air diffuser,
The direction in which the first pore part opens coincides with the direction of the tensile force generated in the diffuser film when the diffuser film expands in a mountain shape,
The second pore portion is a hole that is long in a direction inclined with respect to the first pore portion.

According to this, during the aeration operation, the aeration membrane expands in a mountain shape due to the pressure of the air supplied to the aeration membrane, and a tensile force is generated in the aeration membrane. This tensile force is a force for opening the first pore portion and the second pore portion. At this time, the opening direction of the first pore portion coincides with the direction of the tensile force, but the second pore portion is Since it inclines with respect to the 1st pore part, the direction which the 2nd pore part opens, and the direction of tensile force do not correspond. Thereby, it becomes difficult for the 2nd pore part to open compared with the 1st pore part.

In the third invention, a plurality of pores are formed in the diffuser membrane,
When diffused, the diffused film expands in a mountain shape when viewed from the longitudinal direction due to the pressure of the air supplied to the diffused film, and the pores open,
A membrane-type air diffuser that closes the pores when the air diffuser is not expanded when the air diffuser stops,
A plurality of first pore portions and second pore portions are respectively arranged in the longitudinal direction and the short direction of the diffuser membrane,
The first pore portion is a long hole in the longitudinal direction of the diffuser membrane,
The second pore portion is a long hole in a direction inclined with respect to the longitudinal direction of the diffuser membrane,
A second pore portion is located between adjacent first pore portions.

According to this, during the diffuse operation, the diffuser membrane expands in a mountain shape when viewed from the longitudinal direction due to the pressure of the air supplied to the diffuser membrane (that is, the cross-sectional shape orthogonal to the longitudinal direction of the diffuser membrane is a mountain shape) And a tensile force in the short direction is generated in the diffuser membrane. This tensile force is a force for opening the first pore portion and the second pore portion. At this time, the opening direction of the first pore portion coincides with the direction of the tensile force, but the second pore portion is Since it inclines with respect to the longitudinal direction, the direction in which the second pore portion opens and the direction of the tensile force do not match. Thereby, it becomes difficult for the 2nd pore part to open compared with the 1st pore part.

Therefore, when air is diffused with a small air volume, the first pore portion is opened before the second pore portion, and most of the air supplied to the diffuser membrane passes through the opened first pore portion, and bubbles The air bubbles are ejected from the inside to the outside of the diffuser membrane, whereas there are almost no air bubbles ejected to the outside through the second pore portion that is difficult to open.

In the fourth invention, a plurality of pores are formed in the diffuser membrane,
When air diffuses, the pores open when the air diffuser expands into a mountain shape due to the pressure of the air supplied to the air diffuser.
A membrane-type air diffuser that closes the pores when the air diffuser is not expanded when the air diffuser stops,
A plurality of first pore portions and second pore portions are arranged in concentric circles on the diffuser membrane,
The first pore portion is a hole long in the circumferential direction of the diffuser membrane,
The second pore portion is a hole long in a direction inclined with respect to the circumferential direction of the diffuser membrane,
A second pore portion is located between adjacent first pore portions.

In the membrane-type air diffuser according to the fifth aspect of the invention, the second pore portion is a long hole in a direction inclined at an angle of 5 ° to 25 ° with respect to the first pore portion.

In the sixth aspect of the present invention, the membrane type air diffuser has a third pore portion formed adjacent to at least one of the longitudinal direction of the first pore portion or the second pore portion,
The third pore portion is a hole that is long in a direction substantially perpendicular to the first pore portion.

According to this, at the time of air diffusion, when the air diffuser film expands in a mountain shape, a tensile force acts on the first pore portion to open the first pore portion. Even if a crack occurs at the end of the first pore due to this tensile force, the crack does not advance further from the end of the first pore to the third pore. Therefore, the crack can be prevented from propagating from the first pore portion to the adjacent first pore portion.

Further, the membrane-type air diffuser in the seventh invention is formed by arranging a plurality of first and third pore portions in the air diffuser film,
At the time of air diffusion, the first pore part is opened by the air diffusion film expanding in a mountain shape by the pressure of the air supplied to the air diffusion film,
When the aeration is stopped, the first pore portion is closed in a state where the aeration film is not expanded,
The third pore portion is formed at a position adjacent to at least one of the longitudinal directions of the first pore portion,
The third pore portion is a hole that is long in the direction intersecting the first pore portion.

According to this, at the time of air diffusion, the air diffusion film expands in a mountain shape by the pressure of the air supplied to the air diffusion film, and the first pore portion is opened by the tensile force generated in the air diffusion film. The supplied air passes through the first pore portion, becomes a bubble, and is ejected from the inside to the outside of the diffuser membrane.

At this time, since the third pore portion is a hole that is long in a direction intersecting the first pore portion, even if a crack occurs at the end portion of the first pore portion due to the tensile force, When reaching the third pore portion from the end portion of the pore portion, it does not proceed further from there. Therefore, the crack can be prevented from propagating from the first pore portion to the adjacent first pore portion.

Also, when the aeration is stopped, the supply of air to the aeration film is interrupted, the aeration film does not expand, and the first and second pores are closed.

In the membrane-type air diffuser according to the eighth aspect of the present invention, the third pore portion is a hole that is long in a direction substantially perpendicular to the first pore portion.

According to this, when the air is diffused, the first pore portion is opened, and the supplied air passes through the first pore portion and becomes a bubble to be ejected from the inside of the diffuser membrane to the outside.

At this time, since the third pore portion is a hole that is long in a direction substantially orthogonal to the first pore portion, even if a crack occurs at the end portion of the first pore portion, this crack is not generated in the first pore portion. When reaching the third pore portion from the end portion, there is no further progress from there.

In addition, at the time of air diffusion, the third pore portion is closed, and there are almost no bubbles ejected to the outside through the third pore portion.

The membrane diffuser in the ninth invention is formed by arranging a plurality of first and third pores on the diffuser membrane,
The first pore portion is a long hole in the longitudinal direction of the diffuser membrane,
The third pore portion is a hole that is long in the short direction of the diffuser membrane, and is formed at a position adjacent to at least one of the first pore portions in the longitudinal direction of the diffuser membrane,
At the time of air diffusion, the air diffusion film expands in a mountain shape by the pressure of the air supplied to the air diffusion film, and the first pore portion opens in the short direction,
When the aeration is stopped, the first pore portion is closed in a state where the aeration film is not expanded.

According to this, at the time of air diffusion, the air diffuser film expands in a mountain shape due to the pressure of the air supplied to the air diffuser film, and the first pore portion is short in the short direction due to the short direction tensile force generated in the air diffuser film. Open to. The supplied air passes through the first pore portion, becomes a bubble, and is ejected from the inside to the outside of the diffuser membrane.

At this time, even if a crack occurs in the end portion of the first pore portion due to the tensile force, when the crack reaches the third pore portion from the end portion of the first pore portion, it does not proceed further from there. Absent. Therefore, it is possible to prevent the crack from propagating from the first pore portion to the adjacent first pore portion in the longitudinal direction of the diffuser membrane.

In addition, at the time of air diffusion, the second pore portion is closed, and there are almost no bubbles ejected to the outside through the second pore portion.

The membrane-type air diffuser in the tenth aspect of the present invention is formed by arranging a plurality of first and third pore portions concentrically on the air diffuser membrane,
The first pore portion is a hole long in the circumferential direction of the diffuser membrane,
The third pore portion is a hole that is long in the radial direction of the diffuser membrane, and is formed at a position adjacent to at least one of the first pore portions in the circumferential direction of the diffuser membrane,
At the time of air diffusion, the air diffusion film expands in a mountain shape by the pressure of the air supplied to the air diffusion film, and the first pore portion opens in the radial direction,
When the aeration is stopped, the first pore portion is closed in a state where the aeration film is not expanded.

According to this, at the time of air diffusion, the air diffusion film expands in a mountain shape by the pressure of the air supplied to the air diffusion film, and the first pore portion opens in the radial direction by the radial tensile force generated in the air diffusion film. . The supplied air passes through the first pore portion, becomes a bubble, and is ejected from the inside to the outside of the diffuser membrane.

At this time, even if a crack occurs in the end portion of the first pore portion due to the tensile force, when the crack reaches the third pore portion from the end portion of the first pore portion, it does not proceed further from there. Absent. Therefore, the crack can be prevented from propagating from the first pore portion to the adjacent first pore portion in the circumferential direction of the diffuser membrane.

Also, when the aeration is stopped, the supply of air to the aeration film is cut off, the aeration film does not expand, and the first and third pores are closed.

The membrane-type air diffuser according to the eleventh aspect of the present invention is such that a plurality of second pore portions that are long in the direction inclined at an angle of 5 ° to 25 ° with respect to the first pore portion are formed on the diffuser membrane.

According to this, when air is diffused with a small air volume, the air diffuser film expands in a mountain shape due to the pressure of the air supplied to the air diffuser film, and the tensile force generated in the air diffuser film leads to the second pore part. The first pore portion opens. The supplied air passes through the opened first pore portion and becomes a bubble and is ejected from the inside to the outside of the diffuser membrane, whereas the bubble that is ejected to the outside through the second pore portion that is difficult to open There is almost no.

In addition, when the air volume is increased from the small air volume to the large air volume, the second pore portion is easily opened as the air supply amount is increased, and the number of the second pore portions ejecting bubbles is increased. For this reason, the air supplied to the diffuser membrane passes through the first pore portion and the second pore portion, and is blown out from the inside of the diffuser membrane to the outside. As described above, when the air volume is small, the bubbles are mainly ejected from the first pore portion. However, as the air volume increases, the number of the second pore portions that eject the air bubbles increases, so that the initial pressure loss and the pressure loss increase. Can be suppressed.

As described above, according to the present invention, it is possible to suppress an increase in the initial pressure loss and the pressure loss, and it is possible to prevent a decrease in oxygen transfer efficiency by dispersing and generating bubbles uniformly when the air volume is small. Is possible. Moreover, propagation of cracks can be prevented.

It is a perspective view of the membrane type air diffuser in the 1st Embodiment of this invention. FIG. 2 is an SS arrow view in FIG. 1 and shows a state during an aeration operation. It is a top view which shows the arrangement pattern of the slit of a membrane type air diffuser. FIG. 4 is an enlarged plan view of the slit of the membrane-type air diffuser, where (a) shows a state in which the first to third slits are closed, and (b) shows a state in which the first and second slits are opened and the third slit is closed. It shows the state. FIG. 3 is an enlarged cross-sectional view of the first and second slits of the membrane-type air diffuser, in which (a) is a state where the first and second slits are closed, and (b) is a state where the first slit is opened and the second slit is opened. (C) shows a state in which the first and second slits are open. It is a figure for demonstrating the general relational expression of the maximum stress which generate | occur | produces at the front-end | tip of a notch, and the radius | R of the front-end | tip of a notch. The graph (a) shows the relationship between the membrane surface ventilation rate and the number of foam slits, and the graph (b) shows the membrane surface ventilation rate and the ratio of the first to third slits in all the foam slits. This shows the relationship. It is a graph which shows the relationship between the inclination-angle of a 2nd slit, and the ratio of the number of the 2nd slit to foam when the number of the 1st slit to foam is set to 100. FIG. FIG. 5 is a plan view showing an arrangement pattern in which slit directions are arranged at random, which is in proportion to the first embodiment. It is a top view which shows the arrangement pattern of the slit of the membrane type air diffuser in the 2nd Embodiment of this invention. It is a top view which shows the arrangement pattern of the slit of the membrane type air diffuser in the 3rd Embodiment of this invention. It is a top view which shows the arrangement pattern of the slit of the membrane type air diffuser in the 4th Embodiment of this invention. It is a perspective view of the membrane type air diffuser in the 5th Embodiment of this invention. FIG. 14 is an SS arrow view in FIG. 13. It is a top view which shows the arrangement pattern of the slit of a membrane type air diffuser. It is a top view of the membrane type air diffuser in the 6th Embodiment of this invention. FIG. 17 is an SS arrow view in FIG. 16. It is a perspective view of the membrane type air diffuser in the 7th Embodiment of this invention. FIG. 19 is a view taken along the line SS in FIG. 18 and shows a state during the aeration operation. It is a top view which shows the arrangement pattern of the slit of a membrane type air diffuser. FIG. 4 is an enlarged plan view of the slit of the membrane diffuser, where (a) shows a state where the first and third slits are closed, and (b) shows a state where the first slit is open and the third slit is closed. Indicates. It is an expanded sectional view of the 1st slit of a membrane type diffuser, (a) shows the state where the 1st slit is closed, and (b) shows the state where the 1st slit is opened. It is a figure for demonstrating the general relational expression of the maximum stress which generate | occur | produces at the front-end | tip of a notch, and the radius | R of the front-end | tip of a notch. It is a top view which shows the arrangement pattern of the slit of the membrane type air diffuser in the 8th Embodiment of this invention. FIG. 4 is an enlarged plan view of the slit of the membrane-type air diffuser, where (a) shows a state in which the first to third slits are closed, and (b) shows a state in which the first and second slits are opened and the third slit is closed. It shows the state. The graph (a) shows the relationship between the membrane surface ventilation rate and the number of foam slits, and the graph (b) shows the membrane surface ventilation rate and the ratio of the first to third slits in all the foam slits. This shows the relationship. It is a graph which shows the relationship between the inclination-angle of a 2nd slit, and the ratio of the number of the 2nd slit to foam when the number of the 1st slit to foam is set to 100. FIG. It is a perspective view of the membrane type air diffusion apparatus in the 9th Embodiment of this invention. FIG. 29 is an SS arrow view in FIG. 28. It is a top view which shows the arrangement pattern of the slit of a membrane type air diffuser. It is a top view of the membrane type air diffusion apparatus in the 10th Embodiment of this invention. FIG. 32 is an SS arrow view in FIG. 31. It is a perspective view of the conventional membrane type diffuser. It is an expanded sectional view of the slit of a membrane type air diffuser, (a) shows a state where the slit is closed, and (b) shows a state where the slit is open. It is a top view which shows the arrangement pattern of the slit of a membrane type air diffuser.

First, first to sixth embodiments of the invention described in claims 1 to 6 will be described with reference to the drawings.

(First embodiment)
In the first embodiment, as shown in FIGS. 1 and 2, reference numeral 1 denotes a membrane-type air diffuser installed in an aeration tank such as a sewage treatment facility. The membrane diffuser 1 includes a rectangular base plate 2 made of plastic or metal, and a rectangular (an example of a shape that is long in one direction) attached to the upper surface of the base plate 2. Have. The air diffusion membrane 3 has elasticity, and is made of, for example, rubber such as EPDM or silicon, or resin such as polyurethane.

The periphery of the diffuser membrane 3 is fixed to the base plate 2 by a fixing portion 6 (for example, a caulking member), and an air supply portion 4 is formed between the base plate 2 and the diffuser membrane 3. Further, a short cylindrical air supply port 5 is provided at one end portion in the longitudinal direction A (an example of a predetermined direction) of the diffuser membrane 3. The air supply port 5 communicates with the air supply unit 4 and is connected to an air supply source (not shown).

The diffuser membrane 3 may have, for example, the following properties (1) to (3).
* Properties (1)
Material: Rubber (EPDM), Hardness (A): 50-70, Thickness (mm): 1-3
* Properties (2)
Material: Rubber (silicon), Hardness (A): 35-55, Thickness (mm): 1-3
* Properties (3)
Material: Resin (Polyurethane), Hardness (A): 70-98, Thickness (mm): 0.3-1
The properties of the air diffusing membrane 3 are examples, and are not limited to these, and can be appropriately changed and optimized according to the conditions to be used.

At the time of air diffusion, as shown by the solid line in FIG. 2, the air diffusion film 3 expands in a mountain shape when viewed from the longitudinal direction A by the pressure of the air supplied to the air diffusion film 3. At this time, since both ends in the longitudinal direction A of the diffuser membrane 3 are fixed to the base plate 2, the diffuser membrane 3 does not have a mountain shape when viewed from the longitudinal direction A, but most regions excluding both ends of the diffuser membrane 3. Since the diffuser membrane 3 expands in a mountain shape when viewed from the longitudinal direction A, the two ends of the diffuser membrane 3 are excluded here.

A plurality of first to third slits 8 to 10 (an example of first to third pores) are formed in the diffuser membrane 3. As shown in FIGS. 3 and 4, the first slit 8 is an elongated hole (slit) in the longitudinal direction A, and is parallel to the longitudinal direction A. The second slit 9 is an elongated hole (slit) in a direction inclined at a predetermined inclination angle α with respect to the longitudinal direction A (that is, the first slit 8). In the present embodiment, the predetermined inclination angle α is set to 13 ° (acute angle). The third slit 10 is a hole (slit) elongated in the short direction B and is orthogonal to the longitudinal direction A (that is, the first slit 8).

The first to third slits 8 to 10 are arranged in a predetermined arrangement pattern in the longitudinal direction A and the short direction B. That is, a plurality of first slits 8 are formed at predetermined intervals in the longitudinal direction A, and the second slits 9 are located between the first slits 8 adjacent in the longitudinal direction A. Further, the third slit 10 is located between the first slit 8 and the second slit 9 adjacent in the longitudinal direction A, and is located between the first slits 8 adjacent in the longitudinal direction A, As a result, the first slit 8 and the second slit 9 are adjacent to each other. The second slit 9 is also located between the first slits 8 adjacent in the short direction B.

Hereinafter, the operation of the above configuration will be described.

At the time of air diffusion operation, air of a predetermined pressure is supplied from the air supply source (not shown) through the air supply port 5 to the membrane-type air diffuser 1, so that air is supplied from the air supply port 5 as shown by the solid line in FIG. The diffuser membrane 3 expands in a mountain shape when viewed from the longitudinal direction A by the pressure of air supplied to the supply unit 4, and a tensile force F in the short direction B is generated in the diffuser membrane 3.

As shown in FIG. 4, the tensile force F is a force for opening the first slit 8 and the second slit 9. At this time, the direction in which the first slit 8 opens and the direction of the tensile force F coincide with each other. However, since the second slit 9 is inclined at the inclination angle α, the direction in which the second slit 9 opens and the direction of the tensile force F do not match. That is, the first slit 8 is opened by the tensile force F, while the second slit 9 is opened by the Fcosα force F ′, which is smaller than the tensile force F. For this reason, the second slit 9 becomes harder to open than the first slit 8 as the inclination angle α increases.

Therefore, when aeration is performed with a small amount of air, as shown in FIG. 5 (b), the first slit 8 opens before the second slit 9, and most of the air supplied to the air supply unit 4 is While passing through the opened first slit 8 and forming bubbles 13 from the inside of the diffuser membrane 3 to the outside, almost no bubbles are ejected to the outside through the second slit 9 that is difficult to open.

Thereby, it is possible to prevent the bubbles ejected from the first slit 8 from being combined with the bubbles from the adjacent second slit 9. Further, as shown in FIG. 3, since the second slit 9 is located between the adjacent first slits 8, the interval D between the first slits 8 is enlarged, and the bubbles ejected from the first slit 8 and the bubbles It is possible to prevent the bubbles ejected from the neighboring first slits 8 from being combined. Thereby, at the time of a small air volume, bubbles can be dispersed and generated uniformly, and a decrease in oxygen transfer efficiency can be prevented.

In addition, when the air volume is increased from the small air volume to the large air volume, the air pressure of the air supply unit 4 increases as the amount of air supplied to the air supply unit 4 increases, and the second slit 9 It becomes easy to open, and the number of the second slits 9 for ejecting bubbles increases. For this reason, as shown in FIG.5 (c), the air of the air supply part 4 passes the 1st slit 8 and the 2nd slit 9, becomes the bubble 13, and is ejected from the inner side of the diffuser film 3 to the outer side. The Thus, with a small air volume, the bubbles 13 are mainly ejected from the first slit 8, but as the air volume increases, the number of the second slits 9 that eject the air bubbles 13 increases, so that the initial pressure loss and pressure loss are increased. Can be suppressed.

4B, when the air is diffused, the first slit 8 is opened by the tensile force F in the short direction B acting on the first slit 8, and the first slit 8 is opened by this tensile force F. Even if a crack 12 occurs at the end of the first slit, the crack 12 does not advance further from the end of the first slit 8 until it reaches the third slit 10. Therefore, the crack 12 can be prevented from propagating from the first slit 8 to the adjacent first slit 8 in the longitudinal direction A.

The reason why the propagation of the crack 12 is prevented as described above will be described below for reference. That is, as shown in FIG. 6, generally, when the average stress σ ₀ is applied to the member 16 in which the notch 15 is formed, the maximum stress σ _max generated at the tip of the notch 15 is expressed by the following equation.

According to the above equation, the maximum stress σ _max increases as the radius ρ at the tip of the notch 15 decreases. In the case of the crack 12, the radius ρ at the tip is very small, so that the crack 12 gradually grows due to the stress concentration. Here, as shown in FIG. 4, since the length direction of the third slit 10 and the direction of the tensile force F coincide with each other, the third slit 10 has a notch with a very large radius ρ at the tip. Can be considered. For this reason, the maximum stress σ _max obtained by the above formula becomes very small, and the stress concentration hardly occurs in the third slit 10, thereby preventing the propagation of the crack 12 in the third slit 10.

In addition, since the tensile force F in the short direction B is mainly generated in the diffuser film 3 expanded in a mountain shape at the time of air diffusion, and the force in the longitudinal direction A is hardly generated, the third slit 10 is closed. There is almost no air jetted from the air supply unit 4 through the third slit 10 to the outside.

Further, when the aeration is stopped, the supply of air to the aeration film 3 is interrupted, and the aeration film 3 receives water pressure as shown in the phantom line of FIG. 2 and FIG. It will be in the state pressed against. At this time, the diffuser membrane 3 does not expand, and the first to third slits 8 to 10 are closed.

Note that the graph of FIG. 7 is an example of measurement data of the number of foam slits by air volume, and among these, the graph of FIG. 7A shows the relationship between the membrane surface ventilation rate and the number of foam slits. The graph of FIG. 7B shows the relationship between the membrane surface air flow rate and the ratio of the first to third slits 8 to 10 occupying in all the foaming slits.

In the graph of FIG. 7 (a), the membrane surface air flow rate indicates the air flow rate of air passing through the diffuser membrane 3 per hour and per m ^2, and from the membrane surface air flow rate M1 to the membrane surface air flow rate M4. It has increased to become. It should be noted that the smaller the amount of air supplied to the membrane-type air diffuser 1, the smaller the air flow rate on the membrane surface, and the greater the air flow rate, the greater the air flow rate on the membrane surface.

The number of foam slits is the number of first slits 8 that ejected bubbles from among the 100 first slits 8 and the number of second slits 9 that ejected bubbles from among the 100 second slits 9. The number and the number of the third slits 10 from which the bubbles are jetted out of the 100 third slits 10 are shown.

In the graph of FIG. 7 (b), the ratio occupied in all the foam slits is the first to the second of the total number of foam slits for each membrane surface air flow rate M1 to M4 in the graph of FIG. 7 (a). The ratio of the three slits 8 to 10 is shown. The diffuser membrane 3 at this time is made of polyurethane resin (hardness 85A) and has a thickness of 0.6 mm, and the lengths of the first to third slits 8 to 10 are about 0.4 mm.

According to the graph of FIG. 7, when air is diffused with a small air volume (for example, membrane surface ventilation M1), most of the bubbles are generated from the first slit 8 and almost no bubbles are generated from the second slit 9. Further, there is no bubble generated from the third slit 10 in both cases of the small air volume and the large air volume. Moreover, the ratio of the 2nd slit 9 which occupies for all the foaming slits is increasing according to the air volume increasing.

FIG. 8 shows a case where the inclination angle α of the second slit 9 and the number of the foamed first slits 8 are 100 when the air volume supplied to the membrane-type air diffuser 1 is 2 liters / minute. It is a graph which shows the relationship with the ratio of the number of the 2nd slit 9 to foam. For example, when the inclination angle α is 13 °, the ratio of the foamed second slit 9 is about 58%. At this time, if the number of the first slits 8 ejecting (foaming) air is 24, the number of the second slits 9 ejecting (foaming) air is 14 (= 24 × 0.58). It becomes.

Although the inclination angle α of the second slit 9 is set to the optimum value of 13 ° based on the relationship shown in the graph of FIG. 8, it is not limited to 13 ° but is in the range of 5 ° to 25 °. An angle of 10 ° to 15 ° is more preferable.

For comparison, FIG. 9 shows an example of the diffuser membrane 3 in which the orientations of the slits 18 are randomly arranged. In this case, the smaller the inclination angle α with respect to the longitudinal direction A, the easier the slit 15 opens. However, since the ratio of the slits 15 having the small inclination angle α decreases, there is a problem that the pressure loss increases. In addition, when the sludge is clogged with the foamed sludge during air diffusion, the air is foamed from the slit 15 having a larger inclination angle α, which increases the pressure loss.

In the first embodiment, as shown in FIG. 4, the third slit 10 is formed at the most effective angle of 90 ° with respect to the longitudinal direction A, but it is about 70 ° to 110 °. You may form in the angle within the range.

(Second Embodiment)
In the said 1st Embodiment, although the 3rd slit 10 was formed in the diffuser film 3, as shown in FIG. 10, you may not form the 3rd slit 10 as 2nd Embodiment. .

(Third embodiment)
As a third embodiment, as shown in FIG. 11, two types of second slits 9 and 11 (an example of the second pore portion) having different inclination angles α between the first slits 8 adjacent in the longitudinal direction A. ) May be formed. Here, the inclination angle α of one second slit 9 is set to 13 °, and the inclination angle α of the other second slit 11 is set to 6 °.

According to this, one second slit 9 is harder to open than the other second slit 11, and the other second slit 11 is harder to open than the first slit 8. Therefore, when the air is diffused with a small air volume, the first slit 8 is opened before the

second slits

9 and 11, and most of the air supplied to the air supply unit 4 passes through the opened first slit 8. Erupted through. Further, when the air volume is increased from the small air volume to the large air volume, the other second slit 11 is easily opened after the first slit 8, and the number of the other second slits 11 ejecting bubbles is increased. Then, when the air volume further increases, one of the second slits 9 is easily opened, and the number of one of the second slits 9 for ejecting bubbles increases.

In the third embodiment, the inclination angle α of the other second slit 11 is set to 6 °, but is not limited to 6 ° and is set to an angle in the range of 5 ° to 20 °. May be.

(Fourth embodiment)
In the said 1st Embodiment, although the 2nd slit 9 was formed between the 1st slits 8 adjacent in the longitudinal direction A, as shown in FIG. The second slits 9 may be formed between the adjacent first slits 8, and all the slits arranged in the longitudinal direction A may be unified.

(Fifth embodiment)
In the first to fourth embodiments, as shown in FIG. 1, the shapes of the base plate 2 and the diffuser membrane 3 are rectangular. However, the shape is not limited to the rectangle, and the fifth embodiment. As shown in FIGS. 13 to 15, the shape of the base plate 2 and the diffuser membrane 3 may be circular.

That is, the short tubular air supply port 5 is provided at the center of the base plate 2, the upper end of the air supply port 5 communicates with the air supply unit 4, and the lower end of the air supply port 5 is connected to the air supply tube 21 and communicates therewith. ing. At the time of air diffusion, as shown by the solid line in FIG. 14, the air diffusion film 3 expands in a mountain shape when viewed from the radial direction R by the pressure of the air supplied to the air diffusion film 3.

A plurality of first to third slits 8 to 10 (an example of first to third pores) are formed in the diffuser membrane 3. As shown in FIG. 15, the first slit 8 is a hole (slit) elongated in the circumferential direction C of the diffuser membrane 3. The second slit 9 is a hole (slit) elongated in a direction inclined at a predetermined inclination angle α with respect to the circumferential direction C (that is, the first slit 8). The predetermined inclination angle α is set to 13 ° (acute angle). The third slit 10 is a hole (slit) elongated in the radial direction R of the diffuser membrane 3 and is orthogonal to the circumferential direction C.

The first to third slits 8 to 10 are arranged in a plurality of concentric circles in a predetermined arrangement pattern. That is, a plurality of first slits 8 are formed at predetermined intervals in the circumferential direction C, and the second slits 9 are located between the first slits 8 adjacent in the circumferential direction C. Further, the third slit 10 is located between the first slit 8 and the second slit 9 adjacent in the circumferential direction C, and is positioned between the first slits 8 adjacent in the circumferential direction C. Yes.

Hereinafter, the operation of the above configuration will be described.

At the time of air diffusion operation, air of a predetermined pressure is supplied from the air supply pipe 21 through the air supply port 5 to the membrane-type air diffuser 1, so that the air supply port 5 supplies the air supply unit 4 as shown by the solid line in FIG. 14. The diffuser membrane 3 expands in a mountain shape when viewed from the radial direction R by the pressure of the supplied air, and a tensile force F in the radial direction R is generated in the diffuser membrane 3.

The tensile force F is a force for opening the first slit 8 and the second slit 9. At this time, the direction in which the first slit 8 opens coincides with the direction of the tensile force F. Since the second slit 9 is inclined at an inclination angle α, the direction in which the second slit 9 opens and the direction of the tensile force F do not match. As a result, the second slit 9 becomes harder to open than the first slit 8 as the inclination angle α increases.

Therefore, when aeration is performed with a small amount of air, the first slit 8 is opened before the second slit 9, and most of the air supplied to the air supply unit 4 passes through the opened first slit 8, While it becomes a bubble and is ejected from the inside of the diffuser film 3 to the outside, there are almost no bubbles that are ejected to the outside through the second slit 9 that is difficult to open.

In addition, when the air volume is increased from the small air volume to the large air volume, the air pressure of the air supply unit 4 increases as the amount of air supplied to the air supply unit 4 increases, and the second slit 9 It becomes easy to open, and the number of the second slits 9 for ejecting bubbles increases. For this reason, the air of the air supply part 4 passes the 1st slit 8 and the 2nd slit 9, becomes a bubble, and is ejected from the inner side of the diffuser film 3 to the outer side.

Further, when air is diffused, the first slit 8 is opened by the tensile force F in the radial direction R acting on the first slit 8, but even if a crack 12 occurs at the end of the first slit 8 due to this tensile force F. When the crack 12 reaches the third slit 10 from the end of the first slit 8, the crack 12 does not advance further from there. Therefore, the crack 12 can be prevented from propagating from the first slit 8 to the adjacent first slit 8 in the circumferential direction C.

In addition, since the tensile force F of radial direction R mainly generate | occur | produces in the diffused film 3 expanded in the mountain shape at the time of air diffusion, and the force of the circumferential direction C hardly generate | occur | produces, the 3rd slit 10 was closed. There is almost no air jetted from the air supply unit 4 through the third slit 10 to the outside.

Further, when the aeration is stopped, as shown by the phantom line in FIG. 14, the aeration film 3 receives a water pressure and is pressed against the upper surface of the base plate 2. At this time, the diffuser membrane 3 does not expand, and the first to third slits 8 to 10 are closed.

In the fifth embodiment, the shape of the base plate 2 and the diffuser membrane 3 is circular, but it may be a regular polygon such as a square.

(Sixth embodiment)
In the first to fifth embodiments, the membrane diffuser 1 is provided with the diffuser film 3 on the upper surface of the base plate 2. As the sixth embodiment, FIG. 16 and FIG. As shown, a rectangular diffuser film 3 may be provided on the upper surface of the rectangular bag 25. The bag-like body 25 is made of an air-impermeable sheet-like member and has an air supply part 4 inside. An air supply port 5 is provided on one outer edge of the bag-like body 25. The air supply port 5 communicates with the air supply unit 4 and is connected to an air supply source (not shown).

The diffuser film 3 is attached to the diffuser opening 26 formed on the upper surface of the bag 25 and covers the diffuser opening 26. As in the first embodiment, a large number of first to third slits 8 to 10 are formed in the diffuser membrane 3. At the time of air diffusion, as shown by the solid line in FIG. 17, the air diffusion film 3 is mountain-shaped when viewed from the longitudinal direction A due to the pressure of air supplied from the air supply port 5 to the air supply unit 4 in the bag-like body 25. Inflates.

According to this, the same operation and effect as the first embodiment can be obtained.

In the sixth embodiment, the bag 25 and the diffuser membrane 3 are rectangular, but may be circular.

In the first to sixth embodiments, when the first slit 8 is abbreviated as X, one second slit 9 is abbreviated as Y, the other second slit 11 is abbreviated as Y ′, and the third slit 10 is abbreviated as Z, In the first embodiment, as shown in FIG. 3, the slit arrangement pattern in the longitudinal direction A is set to “X, Z, Y, Z, X, Z, Y, Z, X. In the fifth embodiment, as shown in FIG. 15, the arrangement pattern of the slits in the circumferential direction C is “X · Z · Y · Z · X · Z · Y · Z · X. However, the present invention is not limited to this arrangement pattern. For example, the following arrangement patterns (1) to (4) may be set.
Pattern (1): X, Y, X, Y, X, Y, X ...
Pattern (2): X, X, Y, X, X, Y, X, X, Y, X ...
Pattern (3): X, Y, Y ', X, Y, Y', X, Y, Y ', X ...
Pattern (4): X, Y, X, Y ', X, Y, X, Y', X ...
In FIG. 1 to FIG. 17, the slits 8 to 11 are exaggerated and enlarged as compared with actual ones for easy understanding, but in actuality, the slits 8 to 11 have a minute size. For example, the length of each of the slits 8 to 11 is preferably set in the range of 0.2 mm to 1 mm, more preferably in the range of 0.4 mm to 0.6 mm.

Also, the actual number of slits 8 to 11 is larger than the number depicted in FIGS. Furthermore, the first slit 8 and the second slit 9 may have the same length or different lengths.

In the first to sixth embodiments, the first slit 8 is parallel to the longitudinal direction A. However, the first slit 8 may be slightly inclined with respect to the longitudinal direction A. In this case, if the inclination angle of the second slit 9 is set larger than the inclination angle of the first slit 8, the second slit 9 can be set to be more difficult to open than the first slit 8. For example, an embodiment in which the first slit 8 is inclined by 3 ° with respect to the longitudinal direction A and the second slit 9 is inclined by 15 ° with respect to the longitudinal direction A can be considered. In addition, these can be suitably adjusted according to the material of the diffuser film 3, and the length of a slit.

In the first to sixth embodiments, the second slit 9 is more difficult to open than the first slit 8 by providing an angle between the first slit 8 and the second slit 9. By making the length of 9 shorter than the length of the first slit 8, the second slit 9 can be set to be more difficult to open than the first slit 8. For example, by setting the length of the first slit 8 to 0.6 mm and the length of the second slit 9 to 0.4 mm, the second slit 9 is set to be harder to open than the first slit 8.

In the first to sixth embodiments, the diffuser membrane 3 has a rectangular or circular shape. However, in addition to these, an elliptical shape, an elliptical shape in which both ends are formed in an arc shape, an L shape, A square shape, a rhombus shape, etc. may be sufficient.

Next, seventh to tenth embodiments of the invention described in claims 7 to 11 will be described with reference to the drawings.

(Seventh embodiment)
In the seventh embodiment, as shown in FIGS. 18 and 19, 101 is a membrane type air diffuser installed in an aeration tank such as a sewage treatment facility. This membrane-type air diffuser 101 includes a rectangular base plate 102 made of plastic, metal, or the like, and a rectangular air diffuser membrane 103 attached to the upper surface of the base plate 102. The air diffusion membrane 103 has elasticity, and is made of, for example, rubber such as EPDM or silicon, or resin such as polyurethane.

The periphery of the diffuser membrane 103 is fixed to the base plate 102 by a fixing unit 106 (for example, a caulking member), and an air supply unit 104 is formed between the base plate 102 and the diffuser membrane 103. Further, a short cylindrical air supply port 105 is provided at one end in the longitudinal direction A of the diffuser membrane 103. The air supply port 105 communicates with the air supply unit 104 and is connected to an air supply source (not shown).

As the diffuser membrane 103, for example, the following properties (1) to (3) can be used.
* Properties (1)
Material: Rubber (EPDM), Hardness (A): 50-70, Thickness (mm): 1-3
* Properties (2)
Material: Rubber (silicon), Hardness (A): 35-55, Thickness (mm): 1-3
* Properties (3)
Material: Resin (Polyurethane), Hardness (A): 70-98, Thickness (mm): 0.3-1
The properties of the air diffusing membrane 103 are examples, and are not limited to these, and can be appropriately changed and optimized according to the conditions to be used.

At the time of air diffusion, as shown by the solid line in FIG. 19, the air diffusion film 103 expands in a mountain shape when viewed from the longitudinal direction A due to the pressure of the air supplied to the air diffusion film 103. At this time, since both ends in the longitudinal direction A of the diffuser membrane 103 are fixed to the base plate 102, it does not have a mountain shape when viewed from the longitudinal direction A, but most regions excluding both ends of the diffuser membrane 103. Since the diffuser membrane 103 expands in a mountain shape when viewed from the longitudinal direction A, the two ends of the diffuser membrane 103 are excluded here.

A plurality of first and third slits 108 and 109 (an example of first and third pore portions) are formed in the diffuser membrane 103. As shown in FIGS. 20 and 21, the first slit 108 is an elongated hole (slit) in the longitudinal direction A, and is parallel to the longitudinal direction A. The third slit 109 is a hole (slit) that is elongated in the lateral direction B, and is orthogonal to the longitudinal direction A.

A plurality of first and

third slits

108 and 109 are arranged in a predetermined arrangement pattern in the longitudinal direction A and the transverse direction B. That is, a plurality of the first slits 108 are formed at predetermined intervals in the longitudinal direction A, and the third slits are disposed between the first slits 108 adjacent in the longitudinal direction A (an example of positions adjacent to at least one of the first slits 108). A slit 109 is located. In addition, a plurality of first slits 108 are formed at predetermined intervals also in the short direction B, and the third slits 109 are located between adjacent first slits 108 in the short direction B.

Hereinafter, the operation of the above configuration will be described.

At the time of the air diffusion operation, air of a predetermined pressure is supplied from the air supply source (not shown) through the air supply port 105 to the membrane type air diffuser 101 so that the air is supplied from the air supply port 105 as shown by the solid line in FIG. The diffuser membrane 103 expands in a mountain shape when viewed from the longitudinal direction A due to the pressure of the air supplied to the supply unit 104, and a tensile force F in the short direction B is generated in the diffuser membrane 103. FIG. 22, the first slit 108 is opened in the short direction B by the tensile force F. The air supplied to the air supply unit 104 passes through the first slit 108, becomes a bubble 113, and is ejected from the inside of the diffuser membrane 103 to the outside.

At this time, as shown in FIG. 21B, even if a crack 112 occurs at the end of the first slit 108 due to the tensile force F, the crack 112 extends from the end of the first slit 108 to the third slit. When reaching 109, there is no further progress. Therefore, the crack 112 can be prevented from propagating from the first slit 108 to the adjacent first slit 108 in the longitudinal direction A.

The reason why the propagation of the crack 112 is prevented as described above will be described below for reference. That is, as shown in FIG. 23, generally, when the average stress σ ₀ is applied to the member 116 in which the notch 115 is formed, the maximum stress σ _max generated at the tip of the notch 115 is expressed by the following equation.

According to the above equation, the maximum stress σ _max increases as the radius ρ at the tip of the notch 115 decreases. In the case of the crack 112, the radius ρ at the tip is very small, and the crack 112 gradually grows due to the stress concentration. Here, as shown in FIG. 20, since the length direction of the third slit 109 coincides with the direction of the tensile force F, the third slit 109 has a notch with a very large radius ρ at the tip. Can be considered. For this reason, the maximum stress σ _max obtained by the above formula becomes very small, and the stress concentration hardly occurs in the third slit 109, whereby the propagation of the crack 112 in the third slit 109 can be prevented.

Note that, when the air diffuses, the diffuser film 103 that expands in a mountain shape mainly generates a tensile force F in the short direction B and hardly generates a force in the longitudinal direction A. As shown, the third slit 109 remains closed, and almost no air is ejected from the air supply unit 104 through the third slit 109 to the outside.

Further, when the aeration is stopped, the supply of air to the aeration film 103 is interrupted, and as shown in FIG. 22 (a), the aeration film 103 receives water pressure and is pressed against the upper surface of the base plate 102. Become. At this time, the diffuser membrane 103 does not expand, and the first and

second slits

8 and 9 are closed.

(Eighth embodiment)
In the eighth embodiment, as shown in FIGS. 24 and 25, the diffuser membrane 103 has a predetermined inclination angle α with respect to the longitudinal direction A in addition to the first and

third slits

108 and 109. A plurality of second slits 110 (an example of a second pore portion) that are elongated holes are formed in the direction inclined at. The predetermined inclination angle α is set to 13 ° (acute angle). The second slit 110 is located between the first slits 108 adjacent in the longitudinal direction A. The third slit 109 is located between the first slit 108 and the second slit 110 adjacent in the longitudinal direction A, and is located between the first slits 108 adjacent in the longitudinal direction A.

Hereinafter, the operation of the above configuration will be described.

During the aeration operation, the tensile force F in the short direction B generated in the diffuser film 103 that has expanded in a mountain shape serves as a force for opening the first slit 108 and the second slit 110. The direction in which the first slit 108 opens coincides with the direction of the tensile force F. On the other hand, since the second slit 110 is inclined at the inclination angle α, the direction in which the second slit 110 opens and the tensile force F Does not match the direction. That is, the first slit 108 is opened with the tensile force F, while the second slit 110 is opened with the force F ′ of Fcosα, which is smaller than the tensile force F. For this reason, as the inclination angle α increases, the second slit 110 becomes harder to open than the first slit 108.

Therefore, when air is diffused with a small amount of air, most of the air supplied to the air supply unit 104 passes through the opened first slit 108 and is blown out from the inside of the air diffusion membrane 103 to the outside. On the other hand, almost no bubbles are ejected to the outside through the second slit 110 that is difficult to open.

Thereby, it is possible to prevent the bubbles ejected from the first slit 108 from being combined with the bubbles from the adjacent second slit 110. Further, since the second slit 110 is located between the adjacent first slits 108, the interval D between the first slits 108 is enlarged, and the bubbles ejected from the first slit 108 and the neighboring first slits 108 are increased. Bonding with the ejected bubbles can be prevented. Thereby, at the time of a small air volume, bubbles can be dispersed and generated uniformly, and a decrease in oxygen transfer efficiency can be prevented.

In addition, when the air volume is increased from the small air volume to the large air volume, the air supply of the air supply unit 104 increases as the amount of air supplied to the air supply unit 104 increases, and the second slit 110 It becomes easy to open, and the number of the second slits 110 for ejecting bubbles increases. For this reason, the air of the air supply part 104 passes through the 1st slit 108 and the 2nd slit 110, and is ejected from the inner side of the diffuser film 103 to the outer side as a bubble. As described above, the bubbles are mainly ejected from the first slit 108 at a small air volume. However, as the air volume increases, the number of the second slits 110 that eject the air bubbles increases. The rise can be suppressed.

Note that the graph of FIG. 26 is an example of measurement data of the number of foam slits by air volume, and among these, the graph of FIG. 26A shows the relationship between the membrane surface air flow rate and the number of foam slits. The graph of FIG. 26 (b) shows the relationship between the air flow rate on the membrane surface and the ratio of the first to third slits 108 to 110 in the total foaming slits.

In the graph of FIG. 26 (a), the membrane surface ventilation rate indicates the ventilation rate of air passing through the diffuser membrane 103 per hour and per 1 m ^2, and from the membrane surface ventilation rate M1 to the membrane surface ventilation rate M4. It has increased to become. It should be noted that the smaller the amount of air supplied to the membrane type air diffuser 101, the smaller the air flow rate on the membrane surface, and the greater the air volume, the greater the air flow rate on the membrane surface.

The number of foam slits is the number of first slits 108 that ejected bubbles from among the 100 first slits 108 and the number of third slits 109 that ejected bubbles from among the 100 third slits 109. The number and the number of second slits 110 from which bubbles are ejected out of 100 second slits 110 are shown.

In the graph of FIG. 26 (b), the ratio occupied in all the foaming slits is the first to the second of the total number of foaming slits for each membrane surface air flow rate M1 to M4 in the graph of FIG. The ratio occupied by the three slits 108 to 110 is shown. The diffuser membrane 103 at this time is made of polyurethane resin (hardness 85A) and has a thickness of 0.6 mm, and the lengths of the first to third slits 108 to 110 are about 0.4 mm.

According to the graph of FIG. 26, when the air is diffused with a small air volume (for example, the membrane surface ventilation rate M1), most of the bubbles are generated from the first slit 108 and almost no bubbles are generated from the second slit 110. Moreover, there is no bubble generated from the third slit 109 in both cases of the small air volume and the large air volume. Moreover, the ratio of the 2nd slit 110 which occupies for all the foaming slits is increasing according to the air volume increasing.

FIG. 27 shows a case where the inclination angle α of the second slit 110 and the number of foamed first slits 108 are 100 when the air volume supplied to the membrane-type air diffuser 101 is 2 liters / minute. It is a graph which shows the relationship with the ratio of the number of the 2nd slit 110 to foam. For example, when the inclination angle α is 13 °, the ratio of the foamed second slit 110 is about 58%. At this time, if the number of the first slits 108 ejecting (foaming) air is 24, the number of the second slits 110 ejecting (foaming) air is 14 (= 24 × 0.58). It becomes.

Note that the inclination angle α of the second slit 110 is set to the optimum value of 13 ° based on the relationship shown in the graph of FIG. 27, but is not limited to 13 ° and is in the range of 5 ° to 25 °. An angle of 10 ° to 15 ° is more preferable.

In the seventh and eighth embodiments, the third slit 109 is formed at the most effective angle of 90 ° with respect to the longitudinal direction A, but it is within the range of about 70 ° to 110 °. You may form at an angle.

In the seventh and eighth embodiments, the first slit 108 is parallel to the longitudinal direction A. However, the first slit 108 may be slightly inclined with respect to the longitudinal direction A.

(Ninth embodiment)
In the seventh and eighth embodiments, the shapes of the base plate 102 and the diffuser membrane 103 are rectangular. However, the shape is not limited to a rectangle, and FIGS. 28 to 30 show the ninth embodiment. As shown, the shape of the base plate 102 and the diffuser membrane 103 may be circular.

That is, the short tubular air supply port 105 is provided at the center of the base plate 102, the upper end of the air supply port 105 communicates with the air supply unit 104, and the lower end of the air supply port 105 communicates with the air supply tube 121. ing.

At the time of air diffusion, as shown by the solid line in FIG. A plurality of first and

third slits

108 and 109 are formed concentrically on the diffuser membrane 103. As shown in FIG. 30, the first slit 108 is a hole (slit) elongated in the circumferential direction C of the diffuser membrane 103. The third slit 109 is a hole (slit) elongated in the radial direction R of the diffuser membrane 103 and is orthogonal to the circumferential direction C.

A plurality of first and

third slits

108 and 109 are arranged in a predetermined arrangement pattern in the circumferential direction C and the radial direction R. In other words, a plurality of first slits 108 are formed at predetermined intervals in the circumferential direction C, and between the first slits 108 adjacent in the circumferential direction C (an example of a position adjacent to at least one of the first slits 108). A third slit 109 is located.

Hereinafter, the operation of the above configuration will be described.

At the time of air diffusion operation, as shown by the solid line in FIG. 29, the air diffusion film 103 is mountain-shaped when viewed from the radial direction R due to the pressure of air supplied from the air supply pipe 121 through the air supply port 105 to the air supply unit 104. The tensile force F in the radial direction R is generated in the diffuser membrane 103, and the first slit 108 is opened in the radial direction R by the tensile force F. The air supplied to the air supply unit 104 passes through the first slit 108 and becomes a bubble, and is ejected from the inside of the diffuser membrane 103 to the outside.

At this time, as shown in FIG. 30, even if the tensile force F causes a crack 112 at the end of the first slit 108, the crack 112 reaches the third slit 109 from the end of the first slit 108. Then there is no further progress. Therefore, the crack 112 can be prevented from propagating from the first slit 108 to the adjacent first slit 108 in the circumferential direction C.

In addition, since the tensile film F in the radial direction R is mainly generated in the diffuser film 103 expanded in a mountain shape at the time of air diffusion, and the force in the circumferential direction C is hardly generated, the third slit 109 is closed. There is almost no air jetted from the air supply unit 104 to the outside through the third slit 109.

In addition, when the aeration is stopped, the supply of air to the aeration film 103 is interrupted, and the aeration film 103 is pressed against the upper surface of the base plate 102 under water pressure. At this time, the diffuser membrane 103 does not expand, and the first and

third slits

108 and 109 are closed.

In the ninth embodiment, the first and

third slits

108 and 109 are formed in the diffuser membrane 103. However, in the circular diffuser membrane 103, the same as in the eighth embodiment. The first to third slits 108 to 110 may be formed. Also in this case, as in the case of the eighth embodiment, bubbles can be dispersed and uniformly generated when the air volume is small, and it is possible to prevent a decrease in oxygen transfer efficiency. An increase in pressure loss and initial pressure loss can be suppressed.

In the ninth embodiment, the shape of the base plate 102 and the diffuser membrane 103 is circular, but it may be a regular polygon such as a square.

(Tenth embodiment)
In the seventh to ninth embodiments, the membrane diffuser 101 is provided with the diffuser film 103 on the upper surface of the base plate 102. As the tenth embodiment, FIG. 31 and FIG. As shown, a rectangular diffuser film 103 may be provided on the upper surface of the rectangular bag-shaped body 125. The bag-like body 125 is made of an air-impermeable sheet-like member and has an air supply unit 104 inside. An air supply port 105 is provided on one outer edge of the bag-like body 125, and the air supply port 105 communicates with the air supply unit 104 and is connected to an air supply source (not shown).

The diffuser membrane 103 is attached to the diffuser opening 126 formed on the upper surface of the bag-like body 125 and covers the diffuser opening 126. As in the seventh embodiment, the diffuser membrane 103 is formed with first and

third slits

108 and 109. At the time of air diffusion, as shown by the solid line in FIG. 32, the air diffusion film 103 is mountain-shaped when viewed from the longitudinal direction A due to the pressure of the air supplied from the air supply port 105 to the air supply unit 104 in the bag-like body 125. Inflates.

According to this, the same operation and effect as the seventh embodiment can be obtained.

In the tenth embodiment, the bag-like body 125 and the diffuser membrane 103 are rectangular, but they may be circular. In addition, first to third slits 108 to 110 similar to those in the eighth embodiment may be formed in the diffuser membrane 103.

In FIG. 18 to FIG. 32, the slits 108 to 110 are exaggerated and enlarged as compared with actual ones for easy understanding, but in actuality, the slits 108 to 110 have a minute size. For example, the length of each of the slits 108 to 110 is preferably set in the range of 0.2 mm to 1 mm, more preferably in the range of 0.4 mm to 0.6 mm.

Further, the actual number of the slits 108 to 110 is larger than the number depicted in FIGS. Further, the first slit 108 and the third slit 109 may have the same length, or may have different lengths.

In the seventh to tenth embodiments, the shape of the diffuser membrane 103 is rectangular or circular. However, in addition to these, an elliptical shape, an oval shape in which both ends are formed in an arc shape, an L shape, A square shape, a rhombus shape, etc. may be sufficient.

Claims

A plurality of pores are formed in the diffuser membrane,
At the time of air diffusion, the air diffuser film expands in a mountain shape by the pressure of the air supplied to the air diffuser film, and the pores open.
A membrane-type air diffuser that closes the pores when the air diffuser is not expanded when the air diffuser stops,
The diffuser membrane is formed by arranging a plurality of first pores and second pores that are more difficult to open than the first pores,
A membrane-type air diffuser characterized in that a second pore portion is located between adjacent first pore portions.
The first pore portion is a hole long in a predetermined direction of the diffuser membrane,
The direction in which the first pore part opens coincides with the direction of the tensile force generated in the diffuser film when the diffuser film expands in a mountain shape,
The membrane-type air diffuser according to claim 1, wherein the second pore portion is a hole that is long in a direction inclined with respect to the first pore portion.
A plurality of pores are formed in the diffuser membrane,
When diffused, the diffused film expands in a mountain shape when viewed from the longitudinal direction due to the pressure of the air supplied to the diffused film, and the pores open,
A membrane-type air diffuser that closes the pores when the air diffuser is not expanded when the air diffuser stops,
A plurality of first pore portions and second pore portions are respectively arranged in the longitudinal direction and the short direction of the diffuser membrane,
The first pore portion is a long hole in the longitudinal direction of the diffuser membrane,
The second pore portion is a long hole in a direction inclined with respect to the longitudinal direction of the diffuser membrane,
A membrane-type air diffuser characterized in that a second pore portion is located between adjacent first pore portions.
A plurality of pores are formed in the diffuser membrane,
When air diffuses, the pores open when the air diffuser expands into a mountain shape due to the pressure of the air supplied to the air diffuser.
A membrane-type air diffuser that closes the pores when the air diffuser is not expanded when the air diffuser stops,
A plurality of first pore portions and second pore portions are arranged in concentric circles on the diffuser membrane,
The first pore portion is a hole long in the circumferential direction of the diffuser membrane,
The second pore portion is a hole long in a direction inclined with respect to the circumferential direction of the diffuser membrane,
A membrane-type air diffuser characterized in that a second pore portion is located between adjacent first pore portions.
The membrane type according to any one of claims 2 to 4, wherein the second pore portion is a long hole in a direction inclined at an angle of 5 ° to 25 ° with respect to the first pore portion. Air diffuser.
A third pore portion is formed adjacent to at least one of the longitudinal direction of the first pore portion or the second pore portion;
The membrane type air diffuser according to any one of claims 2 to 5, wherein the third pore portion is a hole that is long in a direction substantially orthogonal to the first pore portion.
A plurality of first and third pores are arranged in the diffuser membrane,
At the time of air diffusion, the first pore part is opened by the air diffusion film expanding in a mountain shape by the pressure of the air supplied to the air diffusion film,
When the aeration is stopped, the first pore portion is closed in a state where the aeration film is not expanded,
The third pore portion is formed at a position adjacent to at least one of the longitudinal directions of the first pore portion,
The membrane type air diffuser characterized in that the third pore portion is a hole that is long in a direction intersecting the first pore portion.
The membrane-type air diffuser according to claim 7, wherein the third pore portion is a hole that is long in a direction substantially perpendicular to the first pore portion.
A plurality of first and third pores are arranged in the diffuser membrane,
The first pore portion is a long hole in the longitudinal direction of the diffuser membrane,
The third pore portion is a hole that is long in the short direction of the diffuser membrane, and is formed at a position adjacent to at least one of the first pore portions in the longitudinal direction of the diffuser membrane,
At the time of air diffusion, the air diffusion film expands in a mountain shape by the pressure of the air supplied to the air diffusion film, and the first pore portion opens in the short direction,
A membrane type air diffuser characterized in that the first pore portion closes when the air diffuser is not expanded when the air diffuser is stopped.
A plurality of first and third pore portions are concentrically arranged on the diffuser membrane,
The first pore portion is a hole long in the circumferential direction of the diffuser membrane,
The third pore portion is a hole that is long in the radial direction of the diffuser membrane, and is formed at a position adjacent to at least one of the first pore portions in the circumferential direction of the diffuser membrane,
At the time of air diffusion, the air diffusion film expands in a mountain shape by the pressure of the air supplied to the air diffusion film, and the first pore portion opens in the radial direction,
A membrane type air diffuser characterized in that the first pore portion closes when the air diffuser is not expanded when the air diffuser is stopped.
11. The plurality of second pore portions that are long in a direction inclined at an angle of 5 ° to 25 ° with respect to the first pore portion are formed in the diffuser membrane. The membrane-type air diffuser according to Item.