JP5334741B2 - Membrane diffuser - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a membrane type air diffusion device capable of controlling the initial pressure loss, and preventing oxygen transfer efficiency from dropping by dispersing and generating bubbles evenly at the time of low air flow. <P>SOLUTION: In the membrane type air diffusion device, at the time of air diffusion, an air diffusion membrane 3 swells in a mountain shape as viewed from the longitudinal direction A by the pressure of the air supplied to the air diffusion membrane 3, and pore parts open. A plurality of the first pore parts 8 and the second pore parts 9 are arranged and formed in the longitudinal direction A and the short-side direction B of the air diffusion membrane 3 respectively. The first pore parts 8 are holes long in the longitudinal direction A of the air diffusion membrane 3, and the second pore parts 9 are holes long in the direction inclined against the longitudinal direction A of the air diffusion membrane 3. The second pore parts 9 are located between the first pore parts 8 that are at least next to each other either in the longitudinal direction A or in the short-side direction B. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  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. This is one in which a rectangular diffuser film 52 is mounted on the upper surface of a rectangular base plate 51 and an air supply port 53 is provided at a predetermined position. An air supply unit is provided between the base plate 51 and the diffuser film 52. 54 is formed. The air supply port 53 communicates with the air supply unit 54.

  The diffuser film 52 is a synthetic resin film or synthetic rubber film provided with a large number of slits 55 (pores), and the periphery of the diffuser film 52 is fixed to the base plate 51 by fixing portions 56. Each slit 55 is a slit elongated in the longitudinal direction A of the diffuser membrane 52, and is parallel to the longitudinal direction A.

  As shown in FIG. 19A, when the aeration is stopped, the aeration film 52 receives the water pressure in the tank and is pressed against the upper surface of the base plate 51. At this time, the diffuser membrane 52 does not expand and the slit 55 is closed.

  Further, at the time of air diffusion, compressed air is supplied from the air supply port 53 to the air supply unit 54, and as shown in FIG. 19 (b), the air diffusion film 52 receives the pressure of the compressed air and starts from the longitudinal direction A. It expands into a mountain shape. When the diffuser membrane 52 expands in this way, the slit 55 opens in the short direction B, and the air in the air supply unit 54 passes through the slit 55 and becomes a bubble 58, from the inner side to the outer side of the diffuser membrane 52. To erupt.

  An air diffuser in which a large number of slits 55 are formed in the air diffuser film 52 as described above is described in, for example, Patent Document 1 below.

JP2007-777

  However, in the above-described conventional format, as shown in FIG. 20, if the interval D between the slits 55 in the longitudinal direction A is set short, the slit 55 is used when the air supply amount supplied to the air supply unit 54 is small and the air volume is small. There is a problem that the bubbles generated from the gas bubbles and the bubbles generated from the adjacent slit 55 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, it is conceivable to set the interval D between the slits 55 long to suppress the coupling between the bubbles. In this case, however, the number of slits 55 per unit area of the diffuser membrane 52 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 55 is insufficient and the initial pressure loss and the increase in pressure loss increase.

  Further, as shown in FIG. 19 (b), when the air diffuser film 52 expands in a mountain shape when viewed from the longitudinal direction A, a tensile force F in the short direction B acts on the slit 55 as shown in FIG. 55 opens in the short direction B, but as shown in FIG. 20, a crack 57 is generated at the end of the slit 55 by this tensile force F, and this crack 57 propagates to the adjacent slit 55 in the longitudinal direction A. There's a problem.

  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,
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 second pore portion is a hole that is long in a direction inclined with respect to the first pore portion,
A second pore portion is located between adjacent first pore portions.

According to this, at the time of the air diffusion operation, the air diffusion film expands in a mountain shape by the pressure of the air supplied to the air diffusion film, and a tensile force is generated in the air diffusion film. 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.
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.

  Thereby, it is possible to prevent the bubbles ejected from the first pore part from being combined with the bubbles from the adjacent second pore part. 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.

  Further, when air is diffused by increasing the air volume from the small air volume to the large air volume, the second air holes are more easily opened as the amount of air supplied is increased, and the number of second air holes that eject 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.

In the second 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.

  Thereby, it is possible to prevent the bubbles ejected from the first pore part from being combined with the bubbles from the adjacent second pore part. 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.

  Further, when air is diffused by increasing the air volume from the small air volume to the large air volume, the second air holes are more easily opened as the amount of air supplied is increased, and the number of second air holes that eject 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.

In the third 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.

  According to this, at the time of the air diffusion operation, the air diffusion film expands in a mountain shape by the pressure of the air supplied to the air diffusion film, and a tensile force is generated in the air diffusion film. 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.

  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.

  Thereby, it is possible to prevent the bubbles ejected from the first pore part from being combined with the bubbles from the adjacent second pore part. 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.

  Further, when air is diffused by increasing the air volume from the small air volume to the large air volume, the second air holes are more easily opened as the amount of air supplied is increased, and the number of second air holes that eject 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.

In the membrane-type air diffuser according to the fourth aspect of the present 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.
The membrane-type air diffuser in the fifth aspect of the present invention 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 diffuser film expands in a mountain shape, a tensile force acts on the first pore portion, and the first pore portion opens. 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.

  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. It is a SS arrow line view in Drawing 1, and shows the state at the time of aeration operation. It is a top view which shows the arrangement pattern of the slit of a membrane type air diffuser. It is an enlarged plan view of the slit of the membrane-type diffuser, wherein (a) shows a state in which the first to third slits are closed, and (b) shows that the first and second slits are open 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 of (a) shows the relationship between the membrane surface air flow rate and the number of foam slits, and the graph of (b) shows the membrane surface air flow 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. It is a SS arrow line view in FIG. 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. It is SS arrow line view in FIG. 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.

A first embodiment of the present invention will be described below with reference to the drawings.
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).

In addition, the diffuser film | membrane 3 can use the thing of the following characteristics (1)-(3), for example.
* 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, 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 as shown by the solid line in FIG. 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 pore portions) 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).

  A plurality of first to third slits 8 to 10 are arranged in a predetermined arrangement pattern in the longitudinal direction A and the transverse 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.7 (b) shows the relationship between the membrane surface ventilation | gas_flowing amount and the ratio of the 1st-3rd slits 8-10 which occupy for 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.

  Moreover, in the graph of FIG.7 (b), the ratio which occupies in all the foaming slits is 1st-1st among the total numbers of the foaming slits for each membrane surface ventilation | gas_flowing amount M1-M4 in the graph of Fig.7 (a). The ratio which 3 slits 8-10 occupy 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, the membrane surface ventilation rate 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 °. Inside is preferable, and 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 an angle of 90 ° that is the most effective with respect to the longitudinal direction A, but is about 70 ° to 110 °. You may form in the angle within the range.

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. .
Further, as a third embodiment, as shown in FIG. 11, two types of second slits 9 and 11 (second pore portions) having different inclination angles α between the first slits 8 adjacent in the longitudinal direction A. Example) 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 within a range of 5 ° to 20 °. May be.
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.

  In the said 1st-4th embodiment, as shown in FIG. 1, although the shape of the baseplate 2 and the diffuser film 3 was made into the rectangle, it is not limited to a rectangle, 5th 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 pore portions) 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.

  A plurality of first to third slits 8 to 10 are arranged concentrically 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.
In each of the above embodiments, the membrane-type air diffuser 1 is provided with the air diffuser film 3 on the upper surface of the base plate 2, but as a sixth embodiment, as shown in FIGS. A rectangular diffuser film 3 may be provided on the upper surface of the bag-like body 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 membrane 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 effect as the first embodiment is obtained.
In the said 6th Embodiment, although the bag-like body 25 and the diffuser film 3 are made into the rectangular shape, circular shape may be sufficient.

In each of the above 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, the first embodiment In the 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 this embodiment, as shown in FIG. 15, the arrangement pattern of the slits in the circumferential direction C is set to “X, Z, Y, Z, X, Z, Y, Z, X. However, it is not limited to this arrangement pattern, and may be set to the following arrangement patterns (1) to (4), for example.
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 each drawing, the slits 8 to 11 are exaggerated and enlarged than the actual ones for easy understanding, but actually, the slits 8 to 11 have a very small size. 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.

  Moreover, the actual number of each slit 8-11 is larger than the number drawn by drawing. Furthermore, the first slit 8 and the second slit 9 may have the same length or different lengths.

  In each of the above 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 each of the above embodiments, the second slit 9 is made more difficult to open than the first slit 8 by providing an angle between the first slit 8 and the second slit 9, but the length of the second slit 9 is By making the length shorter than the length of the first slit 8, the second slit 9 can be set to be harder 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 each said embodiment, although the shape of the diffuser film | membrane 3 was made into rectangular shape or circular shape, in addition to these, elliptical shape, the ellipse shape by which both ends were formed in circular arc shape, L shape, square shape, rhombus shape Etc.

DESCRIPTION OF SYMBOLS 1 Membrane type diffuser 3 Diffuser 8 First slit (first pore part)
9,11 Second slit (second pore part)
10 3rd slit (3rd pore part)
A Longitudinal direction (predetermined direction)
B Short direction C Circumferential direction F Tensile force

Claims (5)

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,
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 second pore portion is a hole that is long in a direction inclined with respect to the first pore portion,
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 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 1 to 3, 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 1 to 4, wherein the third pore portion is a hole that is long in a direction substantially orthogonal to the first pore portion .

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