JP2011230068A - Air diffusing body - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an air diffusing body which can be easily produced, hardly causes distortion, has a light weight and can generate minute air bubbles.SOLUTION: A porous body is obtained by molding a mixture of mullite powder and phenol resin and baking the mixture at 300°C or less. Then, the hydrophilicity is imparted to the surface of the porous body by treating the surface of the porous body with at least one of an urethane based treating agent for imparting hydrophilicity and a siloxane based treating agent for imparting hydrophilicity. An air diffusing device 10 is produced by using such a porous body as the air diffusing body 1.

Description

  The present invention relates to a diffused gas that generates fine bubbles.

  The activated sludge method is a method for purifying sewage, sewage, drainage, etc. using microorganisms, and is widely used in sewage treatment facilities, sewage treatment facilities, human waste treatment facilities, septic tanks and the like. In the following, sewage, sewage, drainage, etc. will be referred to as “sewage, etc.”, and sewage treatment facilities, sewage treatment facilities, human waste treatment facilities, septic tanks, etc. will be referred to as “clean water treatment facilities”. In the activated sludge method, oxygen supply (aeration) to sewage is required, so an aeration tank is provided in the water purification facility, and air is supplied to the sewage or the like as fine bubbles in the aeration tank. A diffuser is provided.

  The air diffuser includes a diffused gas having small holes that generate fine bubbles, a holder that holds the diffused gas, and a packing that maintains airtightness between the diffused gas and the holder and prevents air leakage. I have. And the air supplied in the holder turns into a fine bubble through the small hole which a diffused gas has, and is supplied to the sewage etc. in an aeration tank. Since these fine bubbles activate microorganisms in the aeration tank, sewage and the like are purified.

Conventional general diffused gases include rubber or resin sheets in which a large number of through holes are formed, and porous bodies obtained by sintering ceramic powder.
Here, an example of a conventional method for producing a diffuse gas obtained by sintering ceramic powder will be described. A mixture of ceramic powder such as silica and mullite and a binder such as alumina is formed into a desired shape using a mold. Then, after demolding, drying is performed, and further, baking is performed at a high temperature of 1000 ° C. or higher to obtain a diffused gas composed of a porous body.

JP 2003-320388 A JP-A-8-155484 JP 2003-24974 A JP 2007-117871 A

However, since it is necessary to sinter at a high temperature of 1000 ° C. or higher in order to produce a diffused gas composed of a porous body, a large amount of energy is required for the production of the diffused gas, and a large amount of Carbon was generated. Further, since the firing is performed at a high temperature, it cannot be fired while being put in the mold, and is taken out from the mold and fired, so that the diffused gas is likely to be distorted by firing. Therefore, labor has been required to produce a diffused gas having excellent dimensional accuracy. Furthermore, it takes a long time for firing, and it also takes a long time for cooling after firing. Furthermore, in order to bake at a high temperature of 1000 ° C. or higher, a large-scale heating device is required.
Furthermore, the conventional gas diffused by sintering ceramic powder has a large mass because of its high specific gravity. Therefore, a cost is required for a support material for fixing the diffused gas.

In addition, rubber and resin diffused gas is hydrophobic, so when fine bubbles are released from the small holes of the diffused gas, the bubbles expand along the surface of the diffused gas due to surface tension, and adjacent bubbles In some cases, they merged to form large bubbles. Since large bubbles have a high ascent rate in water, the contact time with water is shortened, and the transfer efficiency of oxygen to water tends to decrease.
Accordingly, an object of the present invention is to solve the above-described problems of the prior art and to provide a light diffused gas that is easy to manufacture and has little distortion and is light. It is another object to provide a diffused gas capable of generating fine bubbles.

In order to solve the above problems, the present invention has the following configuration. That is, the diffused gas according to the present invention is characterized by being composed of a porous body formed by molding a mixture of ceramic powder and resin and firing at 300 ° C. or lower.
In such a diffused gas according to the present invention, the ceramic powder is preferably mullite powder. Further, the resin is preferably a thermosetting resin, and more preferably a phenol resin.

Furthermore, in the diffused gas according to the present invention, it is preferable that hydrophilicity is imparted to the surface. This hydrophilicity can be imparted by a hydrophilic treatment agent, and the hydrophilic treatment agent is preferably at least one of a urethane-based hydrophilic treatment agent and a siloxane-based hydrophilic treatment agent.
Further, the diffused gas according to the present invention, in the diffused gas composed of a porous body, has a bubble discharge surface that discharges bubbles, and a gas intake surface formed on the opposite side of the bubble discharge surface, The bubble discharge surface is a curved surface curved in a convex shape.

  Such a diffused gas according to the present invention preferably has a substantially rectangular shape, and has a cross-sectional shape that is thickest at the center in the width direction and gradually becomes thinner toward both ends in the width direction. The bubble discharge surface is a curved surface curved in a convex shape along the width direction, the gas intake surface is a curved surface curved in a concave shape along the width direction, and the radius of curvature of the gas intake surface is It is preferable that the radius of curvature of the bubble discharge surface is larger.

  Since the diffused gas according to the present invention can be manufactured at a low temperature of 300 ° C. or less, it is easy to manufacture and is light with little distortion. Moreover, since hydrophilicity is imparted to the surface, fine bubbles can be generated. Furthermore, since the bubble discharge surface is a curved surface that is curved in a convex shape, sludge is less likely to accumulate on the bubble discharge surface than in the case where the bubble discharge surface is formed flat.

It is a perspective view of the diffused gas which concerns on this invention. It is sectional drawing of the diffused gas of FIG. It is sectional drawing of the air diffusion apparatus of 1st embodiment. It is a front view of the aeration apparatus of a second embodiment. It is a top view of the diffuser of 2nd embodiment.

An embodiment of a diffused gas according to the present invention will be described in detail with reference to the drawings.
[First embodiment]
1 and 2 are a perspective view and a cross-sectional view of the diffused gas of the first embodiment. Moreover, FIG. 3 is sectional drawing of an air diffusion apparatus provided with the air diffusion of 1st embodiment.
The diffused gas 1 of this embodiment is comprised with the porous body. Since the porous body has a plurality of small holes, a gas such as air or oxygen passes through the small holes to form fine bubbles and is generated from the surface of the diffused gas 1. This porous body is made of a ceramic powder and a resin, and can be obtained by forming a mixture of both into a desired shape using a mold or the like and then firing the molded product at 300 ° C. or lower.

  Next, an air diffuser 10 including the above-described air diffuser 1 will be described with reference to FIG. The air diffuser 10 maintains the airtightness between the air diffuser 1 and the holder 3, and the air diffuser 1 having a small hole that generates fine bubbles, the holder 3 that holds the air diffuser 1, and prevents air leakage. Packing 5 to be provided. Such an air diffuser 10 is installed at the bottom of the aeration tank of the water treatment facility, and the air or oxygen supplied into the space formed between the holder 3 and the diffused gas 1 is diffused gas 1. Fine bubbles are formed through the small holes of the gas and are supplied from the bubble discharge surface 1a to sewage or the like in the aeration tank.

In addition, although such an aeration apparatus 10 is mainly used for the aeration tank of a water treatment facility for purification | cleaning of sewage etc., it can be used also for another use.
The method of fixing the diffused gas 1 and the holder 3 is not particularly limited, but can be easily fixed by a conventional method such as using a metal fitting. Further, the diffused gas 1 of the present embodiment is more flexible and less brittle than the conventional ceramic diffused gas, so that the diffused gas 1 and the holder 3 are sufficiently connected even with a moderate clamping force. Can be firmly fixed.

  The shape of the diffused gas 1 is not particularly limited, and may be a plate shape, a tubular shape, a semi-tubular shape, a spherical shape, an elliptical spherical shape, a rectangular parallelepiped shape, or the like. However, in order to increase the efficiency of oxygen transfer to water, it is preferable to increase the area of the surface (bubble releasing surface 1a) that generates fine bubbles. Therefore, the bubble discharge surface 1a is preferably a curved surface. For example, a bowl-shaped (dome-shaped) diffused gas 1 having a cylindrical surface as shown in FIGS.

  Moreover, when the bubble discharge | release surface 1a is a cylindrical surface like the diffused gas 1 shown in FIG.1, 2, since a bubble is discharge | released radially along a cylindrical surface, a bubble is easy to spread | diffuse widely. In addition, when the bubbles are discharged radially, the sewage and the like in the aeration tank are strongly stirred as compared with the case where the bubbles are discharged straight upward. Further, since the bubbles are discharged radially, turbulent flow is likely to occur in the vicinity of the diffused gas 1, and thus a swirling water flow is likely to be generated in the entire aeration tank. As a result, accumulation of sludge in sewage or the like on the diffused gas 1 is suppressed.

  In addition, it is preferable that bubbles are uniformly discharged from the bubble discharge surface 1a of the diffused gas 1. Therefore, a concave portion is formed on the opposite surface of the bubble discharge surface 1a (the surface facing the inside of the air diffuser 10) so that the bubbles are discharged uniformly from the entire bubble discharge surface 1a. And the inner surface (gas intake surface 1b) of this recessed part has comprised the cylindrical surface of a larger curvature radius than the curvature radius of the bubble discharge | release surface 1a. As a result, the thickness of the diffused gas 1 is not uniform, and as shown in the cross-sectional view of FIG. 2, the central portion in the width direction is the thickest and gradually decreases toward both ends in the width direction. Is the thinnest cross-sectional shape (substantially crescent moon shape).

  When the thickness of the diffused gas 1 is uniform over the entire width direction, bubbles are not evenly discharged from the entire bubble discharge surface 1a, and most bubbles are released from the central portion in the width direction. However, if the cross-sectional shape is as described above, bubbles are evenly discharged from the entire bubble discharge surface 1a. If the bubbles are evenly discharged from the entire bubble discharge surface 1a, the shape of the bubble discharge surface 1a may not be a cylindrical surface as shown in FIGS.

  The conventional gas diffused by firing ceramic powder had to be fired at a high temperature of 1000 ° C. or higher. However, since the gas diffused 1 of this embodiment contains a resin, it is at a low temperature of 300 ° C. or lower. Can be produced by firing. Therefore, in addition to less energy required for the production of the diffused gas 1, the amount of carbon dioxide generated during the production is also small. Further, since the firing is performed at a low temperature, a long time is not required for firing and cooling after firing. Furthermore, since the firing is performed at a low temperature, a large-scale heating device is not necessary, and the manufacturing can be performed with a simple heating device. Thus, since the diffused gas 1 of this embodiment can be manufactured at a low temperature of 300 ° C. or less, it is easy to manufacture and has high productivity.

Furthermore, since the firing is performed at a low temperature, the molded product can be fired while being placed in a molding die, and therefore, the diffused gas 1 is hardly distorted during firing. Therefore, the diffused gas 1 of this embodiment has high dimensional accuracy. In addition, since distortion is unlikely to occur, there is almost no need to perform post-processing to finish the original target dimensions after firing.
Although the diffused gas 1 of this embodiment can be manufactured even if it exceeds 300 degreeC, since each said merit becomes difficult to be acquired, so that baking temperature is high, it is preferable to set it as 300 degrees C or less. In order to make the above merits easier to obtain, baking at 240 ° C. or lower is more preferable. Moreover, in order to fully solidify the mixture of ceramic powder and resin, it is preferable to fire at 180 ° C. or higher.
The firing time is not particularly limited, but is usually from 8 minutes to 12 minutes.

Moreover, the mixing ratio of the ceramic powder and the resin is not particularly limited, but is preferably a ratio of 91: 9 to 99: 1 by mass ratio. When the ratio of the ceramic powder is more than 99% by mass, the strength of the diffused gas 1 is insufficient, and there is a possibility that the ceramic powder tends to crack. On the other hand, if the proportion of the ceramic powder is less than 91% by mass, that is, if the proportion of the resin is more than 9% by mass, the amount of gas generated from the resin during firing may increase, Small holes may be clogged with resin.
In order to make such inconvenience difficult to occur, the mixing ratio of the ceramic powder and the resin is more preferably a ratio of 94: 6 to 97: 3, and a ratio of 95: 5 to 96: 4. More preferably it is.

Furthermore, the kind of the ceramic powder is not particularly limited, and a general ceramic powder such as silica or alumina can be used without any problem as long as the porous shape can be obtained after maintaining the granular shape after firing. . Moreover, the kind of ceramic powder to be used is not limited to one kind, and two or more kinds can be mixed and used.
However, mullite powder is particularly preferable among various ceramic powders. When mullite powder is used, a light diffused gas 1 that is lighter than a conventional diffused gas obtained by firing ceramic powder can be produced. If the diffused gas 1 is lightweight, it is possible to reduce the cost for transportation and the like, and it is possible to reduce the amount of carbon dioxide generated along with the transportation. Incidentally, mullite, aluminosilicate mineral, i.e. a compound of aluminum oxide and silicon dioxide, the chemical formula and _{3Al 2 O 3 · 2SiO 2 ~2Al} 2 O 3 · SiO 2 or Al ₆ O ₁₃ Si ₂ .

Furthermore, the kind of resin is not particularly limited, and a general resin can be used without any problem as long as the ceramic powder can be hardened to form a porous body. However, among various resins, a thermosetting resin is preferable, and a phenol resin is more preferable.
Examples of the method of mixing the resin with the ceramic powder include a method of mechanically mixing the resin powder and the ceramic powder, and a method of coating the resin on the surface of each particle of the ceramic powder.

In such a diffused gas 1, it is preferable that the surface (bubble releasing surface 1a) has hydrophilicity. When the bubble releasing surface 1a has hydrophobicity, when a fine bubble is released from the small hole of the diffused gas 1, the bubble expands along the surface of the diffused gas 1 due to surface tension, and the adjacent bubble There is a case where the bubbles merge to form large bubbles. However, if the bubble discharge surface 1a has hydrophilicity, the bubbles are difficult to spread along the surface of the diffused gas 1 and adjacent bubbles are difficult to coalesce, so that fine bubbles having a diameter of about 1 mm are generated. Can do.
Large bubbles have a high ascent rate in water, so the contact time with water tends to be short and oxygen transfer efficiency to water tends to decrease, but fine bubbles have a slow rate of ascent in water, The contact time with water becomes longer, and the transfer efficiency of oxygen into water is improved. As a result, microorganisms in the aeration tank are more activated, so that sewage and the like are purified with high efficiency.

In addition, it is preferable that hydrophilicity is imparted to the bubble discharge surface 1 a of the diffused gas 1 because the ventilation resistance when fine bubbles are discharged from the small holes of the diffused gas 1 is reduced.
A method for imparting hydrophilicity to the surface of the diffused gas 1 is not particularly limited, but a method of treating the surface of the diffused gas 1 with a hydrophilizing agent is preferable. The type of the hydrophilic treatment agent is not particularly limited, but a urethane type or siloxane type hydrophilic treatment agent is preferable.

  When the surface of the diffused gas 1 is treated with a hydrophilic treatment agent, the hydrophilic treatment agent is applied to the surface of the diffused gas 1 and fixed by heat treatment. Since the diffused gas 1 is composed of a porous body, the hydrophilization treatment agent slightly permeates through the small holes from the surface of the diffused gas 1 and is subjected to a hydrophilic treatment together with the outermost surface. In addition, by processing with a hydrophilic treatment agent, hydrophilicity is imparted to the surface and charging is also suppressed.

  Here, a manufacturing example of the diffused gas 1 of the present embodiment will be shown. Mullite powder 91-99 mass% and phenol resin powder 9-1 mass% were mechanically mixed, and this mixed powder was loaded into a mold. And it baked at 180-240 degreeC for 8-12 minutes, pressing mixed powder. Then, the porous body which has many small pores with an average diameter of 100-260 micrometers was obtained. The average diameter of the small holes can be adjusted to a desired value by the bulk density (particle diameter) of the ceramic powder and the pressure applied to the mixed powder in the mold during molding. Moreover, you may manufacture the diffused gas 1 combining the some porous body from which the average diameter of a small hole differs.

When the firing was completed, the porous body was taken out of the mold and subjected to a treatment for imparting hydrophilicity to the surface using, for example, at least one of a urethane hydrophilizing agent and a siloxane hydrophilizing agent. That is, after applying a hydrophilizing agent to the surface of the porous body and allowing it to penetrate slightly into the inside, and removing the excess hydrophilizing agent by centrifugation, heat it at 80 to 120 ° C. for 40 to 60 minutes using a conveyor furnace. By doing so, the hydrophilizing agent was fixed on the surface. After cooling, for example, it was naturally dried for 7 days and cured to obtain a finished diffuser plate.
In addition, the diffuser plate 1 of this embodiment can recycle | recycle and use the ceramic powder which is a raw material. An example of the method is shown below.

  First, the used diffuser plate 1 is washed and then pulverized to form a powder. Next, it is heated to a high temperature to burn and completely remove organic materials such as phenol resin as a raw material. Then, ceramic powder can be obtained by removing impurities and sieving. Since the regenerated ceramic powder can be used in the same manner as the original ceramic powder, it can be used for the production of the diffused gas 1 or can be used for other purposes.

[Second Embodiment]
Next, the diffuser provided with the diffused gas according to the second embodiment will be described. 1 and 2 are a perspective view and a cross-sectional view of the diffused gas of the second embodiment. Moreover, FIG. 4 is a front view of an air diffuser provided with the air diffuser of the second embodiment, and FIG. 5 is a plan view of the air diffuser provided with the air diffuser of the second embodiment.
In the figure, reference numeral 10 denotes an air diffuser installed in an aeration tank such as a water purification treatment facility. The air diffuser 10 includes an air diffuser 12a, 12b, 12c, 12d, 12e, a holder 3, a packing 5 and a feeding device. A trachea 15 is provided.

  The diffused gas 12a to 12e is for generating fine bubbles in the sewage or the like stored in the aeration tank. For example, a mixed material of 91 to 99% by mass of mullite powder and 1 to 9% by mass of phenol resin is used. It is formed by firing at a temperature of 180 ° C to 240 ° C. The diffused gas 12a to 12e has a bubble discharge surface 1a that discharges bubbles to sewage or the like stored in the aeration tank. The bubble discharge surface 1a has a rectangular shape with dimensions of, for example, a width of 100 mm and a length of 300 mm. While being formed, it is surface-treated with at least one of a urethane hydrophilizing agent and a siloxane hydrophilizing agent.

Further, as shown in FIG. 2, the diffused gases 12a to 12e have a gas intake surface 1b on the opposite side of the bubble discharge surface 1a, and the gas intake surface 1b is rectangular with a dimension of, for example, a width of 65 mm and a length of 265 mm. It is formed in a shape. Furthermore, the diffused gases 12a to 12e have a packing contact surface that contacts the packing 5, and this packing contact surface is formed around the gas intake surface 1b with a width of 17.5 mm, for example.
Further, as shown in FIG. 2, the diffused gases 12a to 12e are made of a porous body, and the porous body is formed between the bubble discharge surface 1a and the gas intake surface 1b. The diffused gases 12a to 12e are pressed onto the upper surface of the holder 3 via the packing 5 by a pressing metal (not shown).

The holder 3 holds the diffused gases 12a to 12e in a row at the bottom of the aeration tank with the bubble discharge surfaces 1a of the diffused gases 12a to 12e facing upward. As shown in FIG. Has been. The holder 3 has a rectangular top plate on which the diffused gases 12 a to 12 e are placed via the packing 5, and a plurality of through holes 17 are formed at predetermined positions on the top plate. . Furthermore, the holder 3 is formed in a shape that does not hinder the flow of sewage or the like stored in the aeration tank.
The packing 5 seals between the diffused gases 12a to 12e and the holder 3 in a watertight manner.

  The air supply pipe 15 supplies pressurized air to a hollow portion formed inside the holder 3, and the pressurized air supplied from the air supply pipe 15 to the hollow portion of the holder 3 It circulates through the through-hole 17 drilled in the plate, and flows into a sealed space formed between the diffused gases 12 a to 12 e and the holder 3. And the air which flowed into the sealed space is taken into the diffused gas 12a to 12e from the gas intake surface 1b of the diffused gas 12a to 12e, and is released from the bubble discharge surface 1a as fine bubbles. Yes.

  As shown in FIG. 3, the bubble discharge surfaces 1a of the diffused gases 12a to 12e are curved surfaces that are convexly curved along the width direction of the diffused gases 12a to 12e, and the gas intake surfaces 1b are The curved surface is curved in a concave shape along the width direction of the gases 12a to 12e. The porous body is curved along the width direction, and the central portion in the width direction is thicker than both sides. Further, as shown in FIG. 3, the porous body is formed between the bubble discharge surface 1a and the gas intake surface 1b by making the curvature radius of the gas intake surface 1b larger than the curvature radius of the bubble discharge surface 1a. Has been. When the curvature radius of the bubble discharge surface 1a is 91 mm, for example, the gas intake surface 1b is formed on the opposite side of the bubble discharge surface 1a with a curvature radius of 122 mm, for example.

  As in the above-described embodiment of the present invention, the bubble discharge surface 1a of the diffused gas 12a to 12e is a curved surface that is convexly curved along the width direction of the diffused gas 12a to 12e. The area of the bubble discharge surface 1a is larger than that formed in a flat shape. Then, since more bubbles can be discharged with respect to sewage or the like, the transfer efficiency of oxygen to water is increased.

  Further, the porous body is formed between the bubble discharge surface 1a and the gas intake surface 1b by making the radius of curvature of the gas intake surface 1b larger than the radius of curvature of the bubble discharge surface 1a. The thickness of the part is thinner than the central part of the porous body. As a result, as in the case where the thickness of the porous body is constant in the width direction of the diffused gas 12a to 12e, fine bubbles are present in the central portion in the width direction of the bubble discharge surface in the sewage or the like stored in the aeration tank. Fine bubbles are discharged from the entire surface of the bubble discharge surface 1a without being discharged only from the bubbles. Therefore, it is possible to efficiently aerate the sewage stored in the aeration tank.

Furthermore, the mixture of mullite powder and phenol resin was baked to form the diffused gas 12a to 12e, so that the diffused gas was formed by adding a binder and a binder to the mullite powder. Since the gas becomes lighter and the ventilation resistance becomes smaller, it is possible to reduce the weight of the air diffuser and to release a large amount of bubbles into the aeration tank.
Moreover, since the hydrophilic property of the bubble discharge | release surface 1a becomes good by surface-treating the bubble discharge | release surface 1a of the diffused gas 12a-12e by at least one of a urethane type hydrophilic treatment agent and a siloxane type hydrophilic treatment agent, it is a diffuse gas. A large amount of fine bubbles can be discharged from the bubble discharge surface 1a of 12a to 12e.

  In the present embodiment, the diffused gases 12a to 12e are made of a porous body made of mullite powder and a phenol resin, but are made of other materials as long as they have the shape described above. You may be comprised with the porous body. For example, a porous body obtained by solidifying metal powder, resin powder, ceramic powder, or the like may be used.

DESCRIPTION OF SYMBOLS 1 Air diffuser 1a Bubble discharge | release surface 1b Gas intake surface 3 Holder 5 Packing 10 Air diffuser 12a, 12b, 12c, 12d, 12e Air diffuser 15 Air supply pipe 17 Through-hole

Claims (16)

  A diffused gas comprising a porous body formed by molding a mixture of ceramic powder and resin and firing at 300 ° C. or lower.   The diffused gas according to claim 1, wherein the ceramic powder is mullite powder.   The gas diffusion according to claim 1 or 2, wherein the resin is a thermosetting resin.   The gas diffusion according to claim 3, wherein the thermosetting resin is a phenol resin.   The air diffused according to any one of claims 1 to 4, wherein hydrophilicity is imparted to the surface.   The gas diffusion according to claim 5, wherein hydrophilicity is imparted by a hydrophilic treatment agent.   The diffused gas according to claim 6, wherein the hydrophilizing agent is at least one of a urethane hydrophilizing agent and a siloxane hydrophilizing agent.   2. A bubble discharge surface for discharging bubbles and a gas intake surface formed on the opposite side of the bubble discharge surface, wherein the bubble discharge surface is a curved surface that is convexly curved. The diffused gas according to any one of ˜7.   The diffused gas according to claim 8, which has a substantially rectangular shape and has a cross-sectional shape in which the central portion in the width direction is thickest and gradually becomes thinner toward both ends in the width direction.   The bubble discharge surface is a curved surface convexly curved along the width direction, the gas intake surface is a curved surface curved concavely along the width direction, and the curvature radius of the gas intake surface is the bubble. The diffused gas according to claim 9, wherein the diffused gas is larger than a radius of curvature of the discharge surface.   A diffused gas composed of a porous body has a bubble discharge surface for discharging bubbles and a gas intake surface formed on the opposite side of the bubble discharge surface, and the bubble discharge surface is curved in a convex shape. A diffuse gas characterized by a curved surface.   The diffused gas according to claim 11, wherein the diffused gas has a substantially rectangular shape, and has a cross-sectional shape that is thickest at a central portion in the width direction and gradually becomes thinner toward both ends in the width direction.   The bubble discharge surface is a curved surface convexly curved along the width direction, the gas intake surface is a curved surface curved concavely along the width direction, and the curvature radius of the gas intake surface is the bubble. The diffused gas according to claim 12, wherein the diffused gas is larger than a radius of curvature of the discharge surface.   14. The air diffusion according to any one of claims 11 to 13, wherein hydrophilicity is imparted to the bubble discharge surface.   The gas diffusion according to claim 14, wherein hydrophilicity is imparted by a hydrophilizing agent.   The diffused gas according to claim 15, wherein the hydrophilizing agent is at least one of a urethane hydrophilizing agent and a siloxane hydrophilizing agent.

Images