JPH0459937A - Method for bubble refining by ultrasonic wave and apparatus therefor - Google Patents

Abstract

PURPOSE:To refine bubbles present in a liquid, to promote the reaction of the process and to improve its efficiency by blowing a gas into a liquid while ultrasonic waves are excited and passing the gas into an area where cavitation bubbles are densified. CONSTITUTION:One end of a ultrasonic horn 1 is fitted with a ultrasonic oscillator 2 as well as the other end is immersed into a vessel 3 filled with a liquid 4, and ultrasonic waves are excited thereto. Together with this, a gas 7 is blown into the vessel 3 from a nozzle 8 to form bubbles 5. At the time of the excitation of the ultrasonic waves in the liquid, the bubbles 5 are infiltrated into a cavitation area 6 formed at the tip of the ultrasonic horn 1. In this way, the refining of the bubbles can surely and easily be executed, and the effect of the treating process of executing the gas blowing into the liquid can remarkably be increased.

Description

Detailed Description of the Invention [Industrial Field of Application] The present invention is applicable to processes in which gas is blown into liquid for treatment, such as aeration treatment in water treatment, molten metal refining, bubble columns, etc. The present invention relates to a method and device for making bubbles finer using sound waves.

[Prior Art] There are several methods for making bubbles present in a liquid fine. For example, an aeration device for biologically treating wastewater is disclosed in Japanese Patent Application Laid-open No. 178899/1983. As shown in FIG. 10, this aeration device 11 is constructed by pasting a porous membrane 16 on the surface of a swirling vane 12 installed in a processing tank, blowing gas 7 through the membrane, and rotating the swirling vane 12. , a shearing force is applied when the bubbles leave the porous membrane to generate fine bubbles (hereinafter this method will be referred to as the first method).
.

Next, in the refining process of molten metal,
There is one shown in Japanese Patent No.-179079. In this method, as shown in Figure 11, the shape of the nozzle through which the gas is blown is modified so that a swirling flow is applied when the gas is discharged, and the liquid (molten metal) that is generated by the swirling of the gas is The bubbles are made finer by the shear force of the contact surface (hereinafter, this method will be referred to as the second method).

Furthermore, as a method for making bubbles in liquid finer using ultrasonic waves, there is a method disclosed in Japanese Patent Application Laid-Open No. 1-127624. As shown in Fig. 12, this ultrasonic bubble miniaturization device applies ultrasonic waves to a nozzle 8 into which gas 7 is blown to make the bubbles microscopic (hereinafter, this method will be referred to as the third method). ).

In FIG. 12, 2 indicates an ultrasonic vibrator, 4 indicates a liquid, and 20 indicates a refractory.

[Problems to be Solved by the Invention] However, these methods have several problems.

First, in the method of ¥S1, it is possible to achieve fine bubbles at the time of gas injection, but it is inevitable that the bubbles will aggregate and coalesce into coarse bubbles during the rising process.
In order to maintain the bubbles in a fine state even during the bubble rising process, it was necessary to separately use some kind of bubble refinement means.

Next, in the second method, in addition to the problems of the first method, in order to achieve bubble refinement during gas blowing,
It was necessary to maintain a certain constant gas blowing pressure.

Finally, in the third method, in addition to the problems of the first method, as shown in FIG. 13, the length of the continuous phase of the gas ( Hereinafter, this length will be referred to as the bubble reach distance 14) If the length exceeds a certain value, bubbles 5 that cannot be further refined will be generated, making it difficult to apply to industrial-scale processes.

The present invention improves the prior art as described above, and by making the bubbles present in the liquid finer, the aeration process and the molten metal 1+i! The purpose is to promote reactions and improve efficiency in metallization processes, etc.

[Means for Solving the Problems] In order to achieve the above objects, the present invention has the following objectives: (1) When performing treatment by blowing gas into a liquid while exciting ultrasonic waves, a region with dense cavitation bubbles (hereinafter referred to as (2) A method of bubble miniaturization using ultrasonic waves, which is characterized by passing a gas through a cavitation region (referred to as a cavitation region). An ultrasonic bubble miniaturization method characterized by covering the range through which existing bubbles pass with a cavitation region generated by ultrasonic excitation; An ultrasonic bubble miniaturization method characterized by covering the opening of a nozzle with a cavitation region generated by ultrasonic vibration during injection; In performing this, a gas flow path is provided inside the ultrasonic horn, and when gas is blown through this flow path, the length of the continuous phase of gas generated at the nozzle tip is the length reached by the cavitation region generated by ultrasonic excitation. (5) Items (1), (2), (3) or (4) above, characterized in that the frequency is 30 kHz or less; (6) The ultrasonic wave output is 100W or more, as described in (1), (2), (3), (4) or (5) above. The ultrasonic bubble miniaturization method described, (
7) An ultrasonic bubble atomization device characterized by being equipped with a u-sonic wave excitation device body and an ultrasonic horn or ultrasonic tip (hereinafter referred to as an ultrasonic horn) immersed in a liquid, (8) ) The ultrasonic horn is installed at an angle with respect to the rising direction of the bubbles. The ultrasonic bubble atomization device according to item (7) or (8), characterized in that the device is installed within 30 cm of the range through which existing air bubbles pass; (10) the ultrasonic horn is a nozzle for blowing gas; (a) above, characterized in that it is installed within 30 cm of the opening;
The ultrasonic bubble atomization device as described in item (7), (8), (9) or (1) above, characterized in that a plurality of ultrasonic horns are installed.
The ultrasonic bubble atomization device according to item 0), (12) a gas passage formed inside an ultrasonic horn, and a plurality of nozzles of the ultrasonic horn for blowing gas into the liquid. The ultrasonic bubble atomization device according to item (A) above as a special feature, (13) the ultrasonic horn having a tip diameter of 5 mm or more (7), (8), (9). ,
The gist of the present invention is the ultrasonic bubble micronization device described in (10), (++) or (12).

[Function] First, the present inventors investigated the mechanism of miniaturization of bubbles in liquid by ultrasonic waves using a water model experimental apparatus shown in FIG. To briefly explain the experimental equipment, the ultrasonic horn 1
The ultrasonic vibrator 2 is attached to one end (the material can be made of metal or ceramics), the other end is immersed in the container 3 filled with the liquid 4, and the gas 7 is excited by ultrasonic vibration. The purpose of this study is to investigate the influence of ultrasonic vibrations at the tip of the ultrasonic horn 1 on the bubbles 5 produced by blowing from the nozzle 8.

As a result, as shown in FIG.
It has been found that only the bubbles 5 that have entered the interior become finer. This is because, as a bubble refinement mechanism, the enormous impact pressure generated when the cavitation bubbles 9 existing in the cavitation region 6 collapse becomes a force greater than the bubble interfacial tension that forms the bubbles, and the bubble interface This is thought to be because it acts on

In other words, the bubbles 5 existing in the liquid form the cavitation region 6 both during gas blowing and during the bubble rising process.
It was found that if the particles were allowed to pass through the interior, they would become finer. As a result, by making the bubbles smaller during aeration and refining processes, it has become possible to accelerate reactions and improve efficiency, as well as reduce liquid surface fluctuations and splatter caused by bubble bursting. .

[Example] The embodiment shown in the figures will be described below.

First, using the experimental apparatus shown in Fig. 3, ultrasonic vibration is applied to water, and the ultrasonic frequency and output (ultrasonic horn tip amplitude ) was investigated. At this time, the material of the ultrasonic horn 1 is titanium, and the tip diameter of the ultrasonic horn is 40 mm.
It was mm. The results are shown in FIG. From Figure 4, if we compare the ultrasonic frequencies between 10k)lz and 20kHz, we can see that with the same ultrasonic horn tip amplitude, the lower frequency (10k)
) 12), it was found that the length of the cavitation region becomes larger, and that the length of the cavitation region becomes larger as the output (ultrasonic horn tip amplitude) becomes larger. In other words, in order to improve the efficiency of bubble miniaturization by ultrasonic waves, it is considered effective to use low frequency and high output.

Next, using the experimental apparatus shown in FIG. 3, ultrasonic waves were excited into water, and the influence of the diameter of the ultrasonic horn tip on the length 10 of the cavitation region 6 generated at the tip of the ultrasonic horn 1 was investigated. The results are shown in FIG. From Figure 5, when comparing the ultrasonic horn tip diameters of 20 mm and 40 mm, with the same ultrasonic horn tip amplitude, the ultrasonic horn tip diameter is larger (40 mm), but the cavitation region length becomes larger. I understand. In other words, in order to improve the efficiency of bubble miniaturization by ultrasonic waves, it is considered effective to increase the diameter of the tip of the ultrasonic horn.

Then, using the experimental apparatus shown in FIG. 1, air was blown into water to generate bubbles, and ultrasonic waves were applied to investigate the bubble refinement effect. According to the inventors' observations, regardless of the blown gas flow rate, the bubbles that entered the cavitation gradient region were all 1/10 of the initial bubble diameter (before being thinned).
It has been refined below.

In addition, using the experimental apparatus shown in Fig. 6, when ultrasonic waves were applied to a two-phase flow of water and air so that the entire cross section of the flow path through which air bubbles passed was covered with the cavitation region 6, the air bubbles rose up the flow path. It has been found that it is possible to make all the bubbles 5 fine. In the figure, 3 is a container and 4 is water.

Furthermore, using the experimental equipment shown in Section 7, when ultrasonic vibration was applied so that the entire cross section of the nozzle 8 that blows air 7 was covered with the cavitation region 6, it was found that in the gas flow rate range where the bubble reaching length was smaller than the cavitation region. It was found that it is possible to make all the bubbles fine.

Then, using the experimental apparatus shown in Fig. 8, a flow path for gas 7 was provided in the ultrasonic horn 1, air was blown into water through this gas flow path, and ultrasonic vibration was applied. It has been found that in a gas flow rate range smaller than the cavitation region 6, it is possible to make all the bubbles fine.

Finally, in order to increase the amount of blown gas that enables bubble refinement under the same ultrasonic excitation conditions in the experimental apparatus shown in Fig. 8, the nozzle shape of the ultrasonic horn shown in Fig. 6 was changed to that shown in Fig. 9 (A).
, CB) was changed as shown in (increasing the number of holes), air was blown into the water through the gas flow path, and ultrasonic vibration was applied. In the gas flow range where the bubble reaching length was smaller than the cavitation region, all It was found that it is possible to make the bubbles smaller. As a result, the efficiency of bubble miniaturization by ultrasonic waves is improved by the method shown in Figure 8 (
It was found that increasing the number of holes in the gas blowing nozzle and decreasing the bubble reach distance was effective for increasing the bubble refinement ratio under the same ultrasonic excitation conditions.

[Effects of the Invention] As described above, since the present invention guides the bubbles rising in the liquid into the cavitation region and makes them fine, the bubbles can be made fine easily and reliably. There is a significant effect that the effectiveness of the treatment process in which gas is blown into the liquid can be significantly increased.

[Brief explanation of the drawing]

FIG. 1 is a sectional view illustrating the experimental apparatus of the present invention, FIG. 2 is a schematic diagram illustrating the cavitation region according to the present invention,
FIG. 3 is a cross-sectional view illustrating the experimental apparatus, FIGS. 4 and 5 are diagrams showing the experimental results, and diagrams showing the relationship between the ultrasonic horn tip amplitude and the cavitation region length. FIGS. FIG. 8 is a sectional view showing an embodiment of the device of the present invention, and FIG. 9(A)
and (B) are side and front views illustrating the nozzle according to the present invention, FIGS. 10 and 11 (8), (B), M 12
The figure is an explanatory diagram of the prior art, and FIG. 13 is a cross-sectional diagram illustrating the length of the continuous phase of the blown gas. 1... Ultrasonic horn 2... Ultrasonic vibrator 3...
Container 4... Liquid 5... Bubbles 6... Cavitation area 7... Gas 8... Nozzle 9... Cavitation bubbles 10... Cavitation area length 11... Aeration device 12...・Swirl blade 13...
Membrane body 14... Bubble reach distance and 4 others Figure 1 Figure 3 IO: Cavitation area length Figure 4 Ultrasonic horn tip amplitude (μm) Figure 5 Ultrasonic horn tip amplitude (μm) Figure 3. Container diagram A (△)

Claims (1)

[Claims] 1. A method characterized in that when processing is performed by blowing gas into a liquid while applying ultrasonic waves, the gas is passed through a dense region of cavitation bubbles that are generated as a result of the ultrasonic vibrations. A method of bubble miniaturization using ultrasonic waves. 2. When processing is performed by blowing gas into the liquid while applying ultrasonic waves, the area through which the bubbles existing in the liquid pass is covered with a dense area of cavitation bubbles generated by the ultrasonic vibrations. This is a bubble miniaturization method using ultrasonic waves. 3 Ultrasonic bubbles characterized in that when gas is blown into a liquid through a nozzle or tuyere while applying ultrasonic waves, the opening of the nozzle is covered with a dense area of cavitation bubbles generated by the ultrasonic vibrations. Refinement method. 4. When processing by blowing gas into liquid while exciting ultrasonic waves, a gas flow path is provided inside the ultrasonic horn, and when gas is blown through this flow path, a continuous phase of gas is generated at the nozzle tip. A method for making bubbles finer using ultrasonic waves, characterized in that the length of the bubbles is made equal to or less than the length reached by a dense region of cavitation bubbles generated by ultrasonic excitation. 5. The method of ultrasonic bubble miniaturization according to claim 1, 2, 3, or 4, characterized in that the frequency is 30 kHz or less. 5. The ultrasonic bubble micronization method according to claim 1, 2, 3, 4, or 5, characterized in that the ultrasonic output is 100 W or more. 7. An ultrasonic bubble micronization device characterized by comprising an ultrasonic vibration device main body and an ultrasonic horn or ultrasonic tip immersed in a liquid. 8. The ultrasonic bubble atomization device according to claim 7, wherein the ultrasonic horn is installed at an angle to the upward direction of the bubbles. 9. Claim 7, characterized in that the ultrasonic horn is installed within 30 cm of the range through which air bubbles present in the liquid pass.
Or the bubble micronization device using ultrasonic waves according to 8. 10. The ultrasonic bubble atomization device according to claim 7 or 8, wherein the ultrasonic horn is installed within 30 cm of a nozzle opening for blowing gas. 11. The ultrasonic bubble atomization device according to claim 7, 8, 9 or 10, characterized in that a plurality of ultrasonic horns are installed. 12 A gas passage is formed inside the ultrasonic horn, and the number of holes of the nozzle of the ultrasonic horn that blows gas into the liquid is plural.
8. The ultrasonic bubble micronization device according to claim 7, further comprising: an ultrasonic bubble micronization device. 13. Claims 7, 8, 9, 10, 1, characterized in that the diameter of the side of the ultrasonic horn that is immersed in the liquid is 5 mm or more.
13. The ultrasonic bubble micronization device according to 1 or 12.