JP2003230824A - Apparatus and method for fine bubble generation - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fine bubble generation apparatus which suppresses the coalescence of a large number of fine bubbles generated in a fine bubble generating part. <P>SOLUTION: This fine bubble generation apparatus includes: a liquid introduction part for introducing a liquid; a gas introduction part for mixing a gas into the liquid to be introduced; a fine bubble generating part for generating a large number of fine bubbles from the mixed gas; and a release port for releasing the large number of generated fine bubbles. The liquid contains a surfactant, and the fine bubbles are released while suppressing the coalescence of the large number of fine bubbles generated in the fine bubble generating part through the action of the surfactant. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus and method for producing microbubbles, and more particularly to means for releasing microbubbles while preventing coalescence of the produced microbubbles.

[0002]

2. Description of the Related Art Microbubbles have a large specific surface area with respect to volume, a long residence time in water, and are electrically charged and adsorbable to suspended matter. For example, oxygen is introduced into water. It is used to increase the amount of dissolved oxygen in water and to adsorb and float on contaminants in water.
More specifically, it is used for purification of water in closed water areas such as rivers, lakes, inland bays, dam reservoirs, etc., and increase in dissolved oxygen content in farms.

Techniques for producing minute bubbles include a method of ejecting gas from minute holes and a method of utilizing shearing force. In the former method, gas is ejected from minute nozzles or gas is expelled from a porous plate. The latter method includes a method in which the gas on the liquid surface is entrained by a jet flow, a method in which the gas is blown into the high-speed liquid flow, and the like.

As described above, although various studies have been made on how to generate the micro bubbles, there have been few reports on the prevention of coalescence of the generated micro bubbles. If the micro bubbles generated at the corners are united again to be discharged as larger micro bubbles, the generation efficiency of the micro bubbles will be deteriorated. Therefore, in the generation of microbubbles, how to release the generated microbubbles without coalescing them is an important issue.

In addition, the conventional micro-bubble generating device naturally sucks the gas by the action of introducing the liquid, and since the introduction of the gas depends on the introduction of the liquid, the gas-liquid ratio is arbitrarily set. Could not be adjusted or adjusted. In addition, it was difficult to increase the ratio of gas in the liquid by natural suction of gas.

Further, the conventional micro-bubble generator has a relatively complicated structure and relies on the introduction of a liquid at a high pressure, which increases the manufacturing and operating costs of the device. ing.

[0007]

SUMMARY OF THE INVENTION It is an object of the present invention to suppress the coalescence of a large number of micro bubbles generated in a micro bubble generator. Another object of the present invention is to
It is an object of the present invention to provide a microbubble generating device capable of adjusting the amount of gas to be introduced. Another object of the present invention is to provide a micro-bubble generator having a simple structure and low operating cost.

[0008]

The technical means adopted by the present invention are a liquid introducing section for introducing a liquid, a gas introducing section for mixing a gas into the introduced liquid, and a large number of micro bubbles from the mixed gas. And a discharge port for a large number of generated microbubbles. The liquid contains a surfactant, and the liquid is generated in the microbubble generation unit by the action of the surfactant. It is characterized in that the microbubbles are discharged while suppressing the coalescence of a large number of microbubbles.

The kind of the surfactant used in the present invention is not limited, and the essential point is that it has a hydrophilic portion and a hydrophobic portion in the molecule, and it may be an anionic surfactant or a cationic surfactant. , Nonionic surfactants. Further, the present invention includes not only a liquid to which a surfactant has been added but also a liquid which already has a surfactant. As the liquid having a surfactant in advance, seawater, river water, lake water, dam water, sewage, sewage tank water, aquaculture tank water, aquarium water tank for aquatic organisms, bioreactor Examples include liquid and water for hydroponic cultivation. In the experiment, it was found that the diameter of the released microbubbles varies depending on the concentration of the surfactant, and it is also possible to control the diameter of the released microbubbles by controlling the concentration of the surfactant. .

Although the structure of the micro-bubble generator is not limited,
In a preferred mode, the microbubble generation part has a narrowed part that narrows the flow cross-sectional area and a divergent part where the flow cross-sectional area increases in the flow direction of the gas-liquid mixed fluid. A large number of micro bubbles are generated by generating a shock wave by generating a pressure difference in the flow direction of the gas-liquid mixed fluid. More preferably, the micro-bubble generating portion has a conical shape and expands in the flow direction of the gas-liquid mixed fluid. Furthermore, from the viewpoint of energy saving,
It is desirable that the opening angle of the micro-bubble generating portion is narrow (the pressure of the liquid to be introduced can be lowered), and the opening angle of the micro-bubble generating portion is less than 40 degrees, further 30 degrees or less, and further 20. The opening angle of the micro-bubble generating portion may be 10 degrees or less, specifically 6 degrees in the embodiment described later. If the opening angle of the micro-bubble generating portion is narrowed, the problem of coalescence of the generated micro-bubbles may occur, but in the present invention, the problem was cleared by using a liquid containing a surfactant.

In another preferred embodiment, the gas introduction section is for forcibly introducing gas. The forced introduction means that the gas is not naturally sucked, and includes, for example, introducing the gas pressurized by using a compressor. By forcibly introducing the gas, it is possible to arbitrarily set or adjust the gas-liquid ratio, or to increase the gas ratio in the liquid. It is considered that the flow ratio of the liquid and the gas to be introduced can be increased up to, for example, about 20%. In addition, it is possible to control the diameter of the generated microbubbles by controlling the flow rate ratio. In the present invention, the gas may be naturally aspirated.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described. FIG. 1 shows a micro-bubble generating device according to the present invention, which has a nozzle body 1 and a divergent nozzle portion 2 which is connected to the nozzle body 1 in fluid communication therewith. The nozzle body 1 has a substantially cylindrical outer shape, and the space surrounded by the inner wall of the nozzle body also has a cylindrical shape. The tip side of the nozzle body 1 has an opening shape and is connected to the divergent nozzle 2. The base end side of the nozzle body 1 has a large wall thickness, and a liquid introduction port 3 for introducing a liquid is formed on a side wall of the thick wall portion, and a liquid introduction pipe 4 is connected to the side wall. On the bottom wall of the thick wall portion, an insertion hole 6 for receiving and inserting a gas introduction pipe 5 for introducing gas is formed, and a support plate 7 is further fixed.

The divergent nozzle 2 is a nozzle whose cross-sectional area first decreases in the flow direction and then gradually increases, and has a shape similar to a Venturi tube. Suehiro nozzle 2
Has a base end portion 8 which is fluidly connected to an opening portion on the tip end side of the nozzle body 1, and a tip end portion 9 which constitutes a discharge port for discharging the gas-liquid mixed fluid. A squeezed portion having a narrowed flow cross-sectional area is formed at the base end portion 8 of the divergent nozzle 2.
When passing through the throat 10 formed by the throttle,
The inner wall continuously expands in diameter, and the space 11 surrounded by the inner wall after the throat 10 has a substantially conical shape. Space (substantially conical space) 11 surrounded by the inner wall of the divergent nozzle 2
Form a micro-bubble generation part. In the illustrated example, the narrowed portion of the base end portion 8 of the divergent nozzle 2 is formed in the R surface, but may be a linear inclined surface in a side view (cross-sectional view).

In the figure, the substantially conical space 11 has a divergence angle θ of 6 degrees in a side view. Spread angle θ
Is not limited to that shown in the figure, and for example, in a preferable range, the spread angle θ is less than 40 degrees. If the divergence angle θ is large, flow separation occurs near the discharge port, and resistance to the flow increases. Therefore, the pressure at the inlet of the nozzle needs to be increased by that much, and power is additionally used by that amount. By narrowing the divergence angle θ,
It is possible to provide a nozzle excellent in energy saving. In the illustrated embodiment, the inner wall of the space 11 surrounded by the inner wall of the divergent nozzle 2 has a linear shape in a side view (cross section) (the space has a conical shape), but is gentle in a side view (cross section), for example. You may form in a curved surface.

The liquid introduction pipe 4 connected to the liquid introduction port 3 of the nozzle body 1 is fluidly connected to a liquid supply source through a pump (not shown), and for example, pressurized water is introduced into the liquid introduction pipe 4 Is introduced from the liquid introduction port 3. The fluid introduced from the fluid introduction port contains a surfactant such as pentanol and ethanol. In one example, the tip side of the divergent nozzle 2 is fluidly connected to the water tank 12 and discharges a large number of micro bubbles to the water in the water tank 12. One end of the liquid introducing pipe 4 is in fluid communication with the water in the water tank 12 via a pump (not shown) at the other end, and the water in the water tank 12 serves as water introduced from the liquid introducing port 3. It is recycled.

The gas introducing pipe 5 for introducing gas is a 1/8 inch pipe as shown in the drawing, which penetrates the bottom wall of the nozzle body 1 and extends in the length direction of the nozzle body 1 (fluid flow direction). It extends in parallel. Further, the gas introduction pipe 5 is extended on the virtual axis 13 passing through the throat 10, and the gas introduction port 14 at the tip of the gas introduction pipe 5 is provided at the base end portion 8 of the divergent nozzle 2.
Facing the opening. The base end side of the gas introduction pipe 5 is connected to a gas supply unit (not shown) (may be via a compressor or the like), and releases the pressurized gas from the gas introduction pipe 5. The one shown in the figure does not naturally suck the gas by the action of the introduced liquid, but introduces the gas by the gas introduction part which is independent of the introduction of the liquid, and the gas-liquid ratio is higher than that of the natural suction. It can be increased, and the gas-liquid ratio can be set arbitrarily.

A plate-like base end side flange 15 and a plate-like end end side flange 16 are provided on the base end portion 8 and the tip end portion 9 of the divergent nozzle 2 respectively.
5 and 16 are integrated by a connecting rod 17 connecting both flanges. A receiving portion for receiving the tip portion of the nozzle body 1 is formed on the proximal side flange 15,
The tip portion of the nozzle body is received in the receiving portion, and both are welded and integrated. The front end side flange 16 is the base end side flange 1.
5 is further extended in the surface direction, and a screw hole is formed in the extended portion, and the tip side flange 16 is connected to the bottom wall of the water tank 12 by using a screw (not shown). ing.

In the microbubble generating device thus constructed, when water containing a surfactant is introduced from the liquid introduction port 3 and air is introduced from the gas introduction pipe 5, the throat 10 of the divergent nozzle 2 is introduced. A large number of micro bubbles are generated in the crossing space 11, and the generated micro bubbles are directly discharged from the discharge port of the base end 9 into the water tank 12 while suppressing coalescence. In the embodiment, there is a risk of coalescing of micro bubbles generated by narrowing the spread angle θ, but coalescing of micro bubbles is suppressed by using water to which a surfactant is added.

In the figure, the nozzle body 1 and the divergent nozzle 2 are shown as separate members, but they may be formed as a single member. In the illustrated example, the constituent members of the nozzle body 1 are made of metal (stainless steel) and the divergent nozzle 2 is made of plastic (acrylic resin), but the material of the nozzle body 1 and the divergent nozzle 2 is limited to these. However, it can be suitably adopted from a suitable metal or plastic. Although the spatial orientations of the nozzle body 1 and the divergent nozzle 2 are vertical in the illustrated example, these orientations are not limited to this.
For example, it may be extended in the horizontal direction.

[0020]

[Experimental example] An experiment was conducted using the micro-bubble generator shown in FIG. Water was introduced through the liquid introduction port 3 and oxygen was introduced through the gas introduction pipe 5. Water flow rate is 10 l / min,
The oxygen flow rate is 100 ml / min. First, when microbubbles were generated in a state where pentanol was not added, it was observed that the introduced oxygen was miniaturized at a site slightly above the throat 10 in the space 11. However, the generated micro-bubbles then coalesced and became larger and were emitted. Then, when pentanol was added to the water introduced in the state where the micro bubbles were generated, the micro bubbles generated in a portion slightly above the throat 10 were discharged as they were without being coalesced.

Further, an experiment was conducted on the relationship between the concentration of the surfactant and the size of the generated microbubbles by using the microbubble generator shown in FIG. Water flow rate is 8l / mi
n, the oxygen flow rate was 1 l / min, the pentanol concentration was changed, and the diameter of the generated microbubbles and VPDF (volume probability density function) were measured. The concentration of pentanol is 2
It was set to 0 ppm, 50 ppm, and 100 ppm. When the concentration of pentanol is 20 ppm, the diameter of microbubbles is 8
There is a VPDF peak at 01-850 μm,
When the concentration of pentanol is 50 ppm, there is a peak of VPDF at the microbubble diameter of 351 to 400 μm, and when the concentration of pentanol is 100 ppm, the microbubble diameter is at 201 to 250 μm. VP
There was a DF peak. From this, it was found that the size of the released microbubbles varies depending on the concentration of pentanol.

[0022]

As described above, according to the present invention, it is possible to provide a micro-bubble generating device and a method which, while having a simple structure, discharge a large number of micro-bubbles generated in the micro-bubble generating section without coalescing. it can.

[Brief description of drawings]

FIG. 1 is a schematic view of a micro-bubble generating device according to the present invention.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Yoichiro Matsumoto             1-42-20-302 Hayamiya, Nerima-ku, Tokyo F term (reference) 2B104 CA01 EB01 EB03 EF09                 4D029 AA01 AB06 AB07 BB11 BB13                 4G035 AB05 AC17

Claims (8)

[Claims] 1. A liquid introducing part for introducing a liquid;
(B) a gas introducing section for mixing gas into the introduced liquid,
(C) It has a micro-bubble generating part for generating a large number of micro-bubbles from the mixed gas, and (d) a discharge port for the large number of generated micro-bubbles, and (e) the liquid contains a surfactant. In addition, the microbubble generating device is characterized in that the microbubbles are released while suppressing the coalescence of a large number of microbubbles generated in the microbubble generating unit by the action of the surfactant. 2. The microbubble generating unit according to claim 1,
A micro-bubble generating device comprising: a narrowed portion that narrows the flow cross-sectional area, and a divergent portion that increases the flow cross-sectional area in the flow direction of the gas-liquid mixed fluid. 3. The microbubble generating device according to claim 1, wherein the microbubble generating portion has a conical shape and expands in a flow direction of a gas-liquid mixed fluid. 4. The microbubble generator according to claim 3, wherein the opening angle of the microbubble generator is less than 40 degrees. 5. The micro-bubble generating device according to claim 1, wherein the gas introducing part is for forcibly introducing gas. 6. The microbubble generating device according to claim 1, wherein the gas introducing section introduces gas in a flow direction of the gas-liquid mixed fluid in the microbubble generating section. . 7. The liquid according to claim 1, wherein the liquid containing a surfactant is seawater, river water, lake water, dam water,
A fine bubble generating apparatus comprising: sewage, sewage tank water, aquaculture tank water, aquarium water tank water, bioreactor liquid, and hydroponic water. 8. A method for producing microbubbles, which comprises introducing a liquid and a gas and producing microbubbles from the introduced gas, by suppressing the coalescence of the produced microbubbles by adding a surfactant to the liquid. A method for producing microbubbles, characterized in that the microbubbles are released.