JP5190834B2 - Bubble generation method - Google Patents

Description

  The present invention relates to a bubble generating device and a bubble generating method, and more particularly to a bubble generating device and a bubble generating method for generating fine bubbles in a liquid.

  Fine bubbles dispersed in a liquid have characteristics such as a large specific surface area relative to volume and a long residence time in the liquid compared to normally observed bubbles having a diameter of several hundred μm or more. ing. Taking advantage of these features, microbubbles are used in various fields such as purification / sterilization / disinfection, liquid phase chemical reactor, removal of harmful substances in solution, drug delivery, blood contrast agent, reduction of frictional resistance, etc. Yes. For example, microbubbles with a diameter of 50 μm or less are called microbubbles, and the diameter decreases as the gas in the bubbles dissolves into the surrounding liquid phase, so the inside becomes high pressure and high temperature due to the effect of surface tension. It is known that pressure waves are generated with free radicals having high oxidizing power such as OH radicals when bubbles disappear (see, for example, Non-Patent Document 1). Furthermore, fine bubbles having a bubble diameter smaller than 1 μm and a size of several tens to several hundreds of nanometers are called nanobubbles.

  As a method for producing such fine bubbles, for example, in Patent Document 1, an ejector is provided on the suction side of the pressure pump of the treated water introduction pipe and ozone gas is sucked and mixed, and ozone mixed water is added. A pressurization type ozone treatment device comprising means for press-fitting with a pressure pump and spraying from an orifice atomizer to a dissolution tank to make ozone gas into fine bubbles and a dissolution tank having an inner tank in which the injected ozone mixed water stays is used. A method is disclosed.

  Further, in Patent Document 2, before the gas supplied into the liquid from the gas supply port of the fine tube having the gas supply port provided in the liquid generates complete bubbles, the gas and the gas-liquid of the liquid A method of generating a plurality of microbubbles continuously from the gas-liquid interface by applying ultrasonic waves to the interface is disclosed.

  Further, Patent Document 3 discloses a method of generating nanobubbles by applying a physical stimulus to the microbubbles generated by the microbubble generator to rapidly reduce the microbubbles.

Patent Document 4 discloses a generation method, mechanism, and physicochemical properties of fine bubbles that have a bubble diameter of about 30 μm or less when generated under normal pressure, and that gradually become finer after generation and disappear and dissolve. -Functions etc. are disclosed.
JP-A-10-225696 JP 2002-113340 A JP 2005-245817 A Japanese Patent Application Laid-Open No. 2003-143885 JP 2005-74369 A JP 2005-108600 A Republished 2004/094306 "Characteristics of water and new utilization technology", NTS Corporation, 2004

  However, the fine bubbles produced by the methods disclosed in the above-mentioned Patent Documents 1 to 4 have a problem that the bubble diameter varies and the size is distributed (see, for example, Patent Document 4). . In addition, there is a problem that the apparatus for generating fine bubbles is large or takes time to generate.

  In the method disclosed in Patent Document 5, a liquid having a viscosity of 10 times or more than that of water is used in order to make the diameters of the fine bubbles uniform. This method cannot be used for water that is particularly demanding as a liquid for dispersing fine bubbles.

  The present invention has been made in view of the above points, and an object of the present invention is to provide a bubble generating apparatus and a bubble generating method for easily generating fine bubbles having a uniform diameter in a liquid such as water. It is in.

  In order to solve the above problems, a bubble generating device of the present invention is a bubble generating device that generates fine bubbles in a liquid, the first and second electrodes being in contact with the liquid, the first and second electrodes And a power source for applying an AC voltage or a pulse voltage between the second electrodes. Here, the fine bubbles refer to microbubbles having a bubble diameter of 1 μm or more and 50 μm or less and nanobubbles having a bubble diameter of less than 1 μm. The AC voltage includes a voltage whose waveform is a triangular wave, sawtooth wave, or composite wave.

  With the above configuration, by applying an alternating voltage or pulse voltage between the two electrodes in contact with the liquid, bubbles are generated in the liquid from the electrode, and the bubble diameter corresponds to the frequency of the alternating voltage or the pulse width of the pulse voltage. It becomes.

  The first electrode has a portion covered with insulation and a portion where a conductor is exposed, and at least a portion where the conductor is exposed is in contact with the liquid. There may be. Further, the first electrode may be linear, and the first electrode may be covered with insulation except for the tip, and the conductor may be exposed at the tip.

  The second electrode may be a ground electrode.

  At least a portion of the second electrode that is in contact with the liquid may be covered with insulation.

  The frequency of the AC voltage is preferably 10 Hz to 500 kHz, or the pulse width of the pulse voltage is preferably 5 nsec to 50 msec.

  The liquid may contain a molecule having a polar group.

  The bubble diameter may be 100 nm or more and 50 μm or less.

  The bubble generation method of the present invention is a bubble generation method for generating fine bubbles in a liquid, the step of bringing a second electrode into contact with the liquid, and applying an AC voltage or a pulse voltage between the two electrodes. And a voltage applying step to be applied.

  The frequency of the AC voltage is preferably 10 Hz to 500 kHz, or the pulse width of the pulse voltage is preferably 5 nsec to 50 msec.

  The liquid may contain a molecule having a polar group.

  Fine bubbles may be ejected from at least one of the two electrodes into the liquid to generate a flow in the liquid.

  The bubble diameter may be 100 nm or more and 50 μm or less.

  The liquid is water, and water in which bubbles containing hydrogen gas are dispersed may be generated. At this time, it is preferable to apply a pulse voltage having a negative peak voltage in the voltage application step.

  The liquid is water, and water in which bubbles containing oxygen gas are dispersed may be generated. At this time, it is preferable to apply a pulse voltage having a positive peak voltage in the voltage application step.

  In the voltage application step, plasma may be generated from at least one of the electrodes.

  With a simple device configuration in which an alternating voltage or a pulse voltage is applied between two electrodes that are in contact with the liquid, it is possible to generate fine bubbles having a uniform diameter in the liquid.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the following drawings, components having substantially the same function are denoted by the same reference numerals for the sake of brevity.

(Embodiment 1)
As shown in FIG. 1, the bubble generating apparatus according to the first embodiment is obtained by inserting a first electrode 20 and a second electrode 30 into a liquid 80. Liquid 80 is contained in container 10.

  The bubble generating device 1 of this embodiment further includes a power source 40, which is connected to the first electrode 20 and grounded by a ground line 50. The second electrode 30 is also grounded by the ground line 50. When an AC voltage or a pulse voltage is applied between the first electrode 20 and the second electrode 30 from the power supply 40, it is visually observed that fine bubbles are generated from the first electrode 20.

  As shown in FIG. 2, the first electrode 20 and the second electrode 30 have a configuration in which a coating 22 made of an insulator or a dielectric is applied to the surface of a linear conductive member 21. The conductive member 21 may be any material as long as it has conductivity such as metal, carbon, and organic conductive material. In this embodiment, a copper wire is used. Further, the tip of the portion of the first electrode 20 that is immersed in the liquid 80 is not covered with the coating 22, and the conductive member 21 is exposed. With such a configuration, bubbles are generated from the tip of the first electrode 20 where the electric field concentrates.

  The insulator constituting the coating 22 is an electrically insulating polymer such as fluorine resin such as PFA, PTFE, FEP, polyurethane resin, polyimide resin, polyamide resin, or diamond-like carbon (DLC). And so on. Moreover, as a dielectric material which comprises the coating | cover 22, the substance with high dielectric constants, such as barium titanate, can be mentioned. The insulator / dielectric constituting the coating 22 is preferably a substance having high electrical insulation, heat resistance, and impact resistance. In this embodiment, the coating 22 is formed of a polyurethane resin.

  The power source 40 applies an AC voltage or a pulse voltage. The shape, material, and length of the first electrode 20, such as the distance between the first electrode 20 and the second electrode 30, the type of the liquid 80, Whether or not bubbles are generated depending on temperature or the like and the speed of bubble generation are greatly affected, and therefore the frequency and magnitude of the AC voltage or pulse voltage are not particularly limited. As shown in FIG. 3, the pulse voltage is preferably a pulse whose polarity changes (+ to-or-to +), or a pulse which rises from 0V to either the + side or the-side, and the pulse voltage is continuous in time. Is preferably supplied, since bubbles are continuously generated. The pulse voltage continuously changed in polarity in this way can be said to be a square-wave AC voltage.

Although the frequency and voltage of the power supply 40 are not particularly limited as described above, the bubble size generated varies depending on the frequency or pulse width. That is, when the frequency is high or the pulse width is small, the bubble diameter is small, and when the frequency is low or the pulse width is large, the bubble diameter is large. Therefore, in order to generate so-called microbubbles and nanobubbles, the frequency is preferably 10 Hz to 100 kHz. The voltage is preferably 1 V to 500 kV from the viewpoint of the amount of bubbles generated, and is preferably 1 V to 20 kV from the viewpoint of ease of handling of the apparatus. The electric field strength in the vicinity of the first electrode 20 when an AC voltage or a pulse voltage is applied to the first electrode 20 by the power source 40 is preferably 10 ⁴ V / m or more and 10 ¹⁰ V / m or less.

  The liquid 80 preferably contains a substance to be electrolyzed. When a substance to be electrolyzed is included, in the bubble generating device 1 of the present embodiment, electrolysis is performed by applying an alternating voltage or a pulse voltage between the two electrodes 20 and 30, and the electrolysis is caused by the electrolysis. The gas is dispersed in the liquid 80 as fine bubbles. In the present embodiment, since electrolysis is performed by applying an alternating voltage or a pulse voltage, gas is generated in a half period of alternating current or time of pulse width, and this becomes a bubble (in the next half period of alternating current, another kind of gas is generated. Gas may be generated). Since the bubbles are charged, they are separated from the first electrode 20 by the electric field around the first electrode 20. Or it separates from the 1st electrode 20 by the flow of water driven by the electric field. With such a mechanism, fine bubbles can be generated, and the bubble diameter can also be controlled by frequency or pulse width.

  The substance to be electrolyzed contained in the liquid 80 is a substance having a polar group, and examples thereof include water, alcohol, amine, and acid (inorganic acid, organic acid). Even if the liquid 80 does not contain an electrolyzed substance, if the plasma is generated around the first electrode 20 by dielectric barrier discharge or the like, the substance constituting the liquid 80 is caused by the plasma. It causes physical and chemical changes, and bubbles are generated. Even if the liquid 80 contains a substance to be electrolyzed, bubbles are generated by plasma. Therefore, if the bubble generating device of this embodiment is used, bubbles can be generated in the liquid 80 regardless of the polarity of the molecules constituting the liquid 80 and the viscosity of the liquid 80. When bubbles are generated by plasma, the bubble diameter is determined by the frequency of the AC voltage or the pulse width of the pulse voltage. That is, when the frequency is high or the pulse width is small, the bubble diameter is small, and when the frequency is low or the pulse width is large, the bubble diameter is large. Also, when the frequency is high or the pulse width is small, the variation in bubble diameter is small, and when the frequency is low or the pulse width is large, the variation in bubble diameter is large. This is a measure of whether the bubble diameter is uniform or not, but when the average bubble diameter is T, the bubble diameter of 80% or more in number is within the range of 0.1T to 10T. If there is, it can be considered to be almost uniform. If 90% or more is within the above range, the uniformity is high and preferable.

  The container 10 for storing the liquid 80 is preferably made of an electrically insulating substance.

  Next, a method for generating bubbles using the bubble generator 1 of this embodiment will be described.

  First, an insulating container 10 is prepared. A second electrode 30 is installed in the container 10. Then, the liquid 80 is put into the container 10. The second electrode 30 is grounded.

  Next, the first electrode 20 is placed in the liquid 80. At this time, the position of the first electrode 20 is adjusted so that the first electrode 20 does not contact the second electrode 30.

  Then, a power source 40 is connected to the first electrode 20 and an AC voltage or a pulse voltage is applied. When an AC voltage or a pulse voltage is applied, bubbles are generated in the liquid 80 from the tip of the first electrode 20. The bubbles are separated from the first electrode 20 at a high speed by receiving the force of the electric field, and generate a flow in the liquid 80. The frequency of the AC voltage or the pulse width of the pulse voltage is adjusted according to the desired bubble diameter. Further, plasma can be generated simultaneously from the first electrode 20 by adjusting the voltage condition. When plasma is generated, a pulsed current flows and light is emitted, so that the generation of plasma can be easily confirmed. Since the phenomenon described above is visually, there is a possibility that microscopic bubbles are generated microscopically from the portion covered by the coating 22 of the first electrode 20 or from the second electrode 30. There is also.

  When the voltage application is stopped, the generation of bubbles stops. In addition, since heat is applied to the liquid 80 by voltage application, it is preferable to cool the liquid 80.

  In the bubble generation method, the order in which the second electrode 30, the liquid 80, and the first electrode 20 are placed in the container 10 is not limited to the order described above. Further, the first electrode 20 may be connected to the power source 40 before being put into the liquid 80.

  Since the bubble generation device 1 and the bubble generation method of the present embodiment are a simple device and method in which two electrodes 20 and 30 are placed in the liquid 80 contained in the container 10 and an AC voltage or a pulse voltage is applied. The bubble generating device 1 can be manufactured at low cost, and the device configuration can be designed relatively freely depending on the location and size of the bubble to be generated. In addition, the bubble diameter in various liquids can be controlled by the frequency or pulse width of the power source, and the variation in diameter can be reduced, so that it can be applied to various applications. In particular, it has been difficult in the past to generate nanobubbles with a small bubble diameter with a simple method, but using the bubble generation device and the bubble generation method of this embodiment, it is easy to generate nanobubbles with a uniform diameter at low cost. Can be generated. Thereby, the application to medical fields, such as adsorption separation of a virus and bacteria, can be performed widely. Further, since the generated bubbles are ejected from the first electrode 20 into the liquid 80 and a flow is generated in the liquid 80, the bubbles rapidly expand into the liquid 80.

  Furthermore, it is considered that chemical species generated by plasma can be confined in bubbles by adjusting the power supply voltage and current. That is, if plasma is generated in the first electrode 20 and bubbles are generated at the same time, it is considered that the plasma can be confined in the bubbles. Patent Documents 6 and 7 disclose devices that generate plasma in bubbles in a liquid, but these generate bubbles using a conventional bubble generator using ultrasonic waves, and microwaves are generated there. Irradiation generates plasma, and it has not been realized at present to make the bubble diameters uniform and uniform. When plasma is generated in the bubbles, radicals and the like are confined in the bubbles, and a higher energy state is maintained. Furthermore, if a large energy is generated when the bubbles are crushed and a high-energy plasma is generated, this high-energy plasma can be used for various applications.

-Example-
<Example 1>
Using an apparatus similar to the apparatus shown in FIG. 1, fine bubbles were generated in water. Specifically, water was poured into a polystyrene cylindrical container (inner diameter 3.5 cm, height 6 cm) by a height of about 4 cm, and enameled wires were used as the first and second electrodes. . The enameled wire is obtained by coating a copper wire having a diameter of 0.6 mm with an electrically insulating polyurethane resin. The first electrode was straight and the coating was removed only at the tip (that is, the cut enameled wire was used as it was), and the second electrode was coiled (diameter of about 6 mm) and placed on the bottom of the container. Note that all the portions of the second electrode contained in the container are covered with insulation. The first electrode and the second electrode were installed so as not to contact each other.

  The second electrode was grounded and the first electrode was connected to a grounded power source. A pulse voltage (10 kHz, 20 kVpp, rectangular wave, duty ratio 50%) was applied from the power source to the first electrode. Note that since the second electrode and the power source are both grounded, the power source applies a voltage between the first electrode and the second electrode.

  Immediately after the voltage was applied, fine bubbles flowed from the tip of the first electrode into the liquid. After 1 to 2 seconds, the mixed flow of fine bubbles swirled and the container became cloudy. At this time, the tip of the first electrode emitted light, and it was confirmed that plasma was generated. The above situation was observed visually.

  Next, the voltage condition of the pulse voltage was changed from 10 kHz, 0 V to −10 kV, rectangular wave, duty ratio 99% (pulse width 1 μsec) and applied to the first electrode. The diameter appeared to be finer. Therefore, 11 minutes and 17 seconds after the application of the voltage was stopped, the bubble diameter in water was measured by a laser diffraction method using a device called a laser diffraction particle size distribution measuring device HELOS system manufactured by Sympatec GmbH. The measurement results are shown in FIG. About 90% of the bubbles had a diameter of 0.38 μm (380 nm) to 1.3 μm, resulting in a bubble size distribution having a peak at 780 nm. FIG. 5 shows the result of dividing the same sample into 10 and measuring them. Thus, nanobubbles having a substantially uniform cell diameter were obtained.

  In this embodiment, the voltage generated by the function generator is multiplied by 1000 using an amplifier. However, since the amplifier has only a rising performance of 0V → 500V in 1 μsec, the above voltage is actually Is likely to be about several hundred volts.

  Here, it is considered that fine bubbles containing hydrogen gas are dispersed in water. On the other hand, when the voltage is set from 0 V to a positive peak voltage, fine bubbles containing oxygen gas are dispersed in water, and when the peak voltage is set on both the positive side and the negative side, hydrogen gas is included. Water with mixed fine bubbles and fine bubbles containing oxygen gas is obtained.

  Further, when bubbles were generated under different conditions, fine bubbles having a bubble diameter distribution having a peak at about 400 nm or about 600 nm were generated.

<Example 2>
Example 2 is the same as Example 1 except that ethanol is used as a liquid instead of water.

  Even when ethanol was used as a liquid, a large amount of fine bubbles were generated as in the case of water, and plasma was also generated.

  In the present embodiment, the second electrode 30 may be an electrode having a structure different from that of the first electrode 20. The type and thickness of the coating and the constituent material of the conductive member may be different from those of the first electrode 20, and the overall shape may be, for example, a plate shape. Further, bubbles are generated even without the coating 22 in the second electrode 30, but without the coating 22, the conductive member 21 may be affected by a reaction product generated by electrolysis.

(Embodiment 2)
As shown in FIG. 4, the bubble generating apparatus according to the second embodiment is that the first electrode 20 is placed in the liquid 80 and the power source 40 is connected to the first electrode 20. However, since the second electrode 35 is different from that of the first embodiment, the difference from the first embodiment will be described below.

  In the present embodiment, the container 11 and the second electrode 35 are integrated. That is, the side wall surface and the bottom surface of the container 11 are configured by the second electrode 35, and the second electrode 35 is insulated and coated on the inner surface of the container 11 that is in contact with the liquid 80. The conductive member and the insulation coating of the second electrode 35 are the same as those in the first embodiment. The second electrode 35 is connected to a power source 40, and the line connecting them is grounded.

  In the bubble generating device 2 of the present embodiment, fine bubbles are generated in the liquid 80 in the container 11 as in the first embodiment. In this embodiment, the position adjustment of the first electrode 20 is easier than in the first embodiment as long as the container 11 integrated with the second electrode 35 is prepared. Other effects are the same as those of the first embodiment.

(Embodiment 3)
The bubble generating apparatus according to the third embodiment is different from the first embodiment because the second electrode is different from that of the first embodiment and other than that is the same as that of the first embodiment.

  In the present embodiment, the second electrode has the same shape as the first electrode. That is, the second electrode is linear and immersed in the liquid, and the conductive member is exposed at the tip. As in the first embodiment, in this embodiment, the second electrode is grounded.

  In the present embodiment, when an AC voltage or a pulse voltage is applied to the first electrode as in the first embodiment, unlike the first embodiment, bubbles are also generated from the tip of the second electrode. Note that the exposed portion of the conductive member of the second electrode is not limited to the tip, and the number of exposed portions may be plural.

(Other embodiments)
The above embodiments and examples are examples of the present invention, and the present invention is not limited to these examples. The shape of the first electrode may be a three-dimensional shape such as a plate shape or a spherical shape other than the linear shape. Further, the liquid is not limited to water and ethanol, and a liquid containing a substance to be electrolyzed, a liquid in which gas is generated by plasma, or the like can be used in the present invention.

  A plurality of exposed conductor portions may exist in the portion of the first electrode immersed in the liquid. Current concentration occurs in these conductor exposed portions, and bubbles are generated from these portions. Alternatively, the first electrode may be shaped like a sword mountain, and a plurality of needle-shaped tips may be used as the conductor exposed portion.

  The second electrode may be a part of the container, not the entire wall of the container. For example, an insulating coating electrode may be laid on the bottom surface of the container, or an electrode may be embedded in the side wall of the container so that the liquid is separated from the insulating film.

  As described above, the bubble generating device according to the present invention can easily generate fine bubbles having a uniform diameter in a liquid, purifying / sterilizing / disinfecting, a liquid phase chemical reactor, harmful in a solution. It is useful because it can generate fine bubbles that can be used for substance removal, drug delivery, blood contrast media, and the like.

Schematic diagram of the bubble generator according to Embodiment 1 Sectional drawing of the electrode which concerns on Embodiment 1. Diagram showing pulse voltage Schematic diagram of the bubble generator according to Embodiment 2 Distribution diagram of generated bubble diameter according to Example 1

Explanation of symbols

1, 2 Bubble generators 10, 11 Container 20 First electrode 21 Conductive member 22 Coating 30, 35 Second electrode 40 Power supply 50 Ground wire 80 Liquid

Claims (9)

A bubble generation method for generating fine bubbles in a liquid,
Contacting the liquid with two electrodes, a first electrode and a second electrode;
Applying a pulse voltage having a negative peak voltage between the two electrodes, and
The portion of the second electrode that is in contact with the liquid is covered with insulation;
Pulse width of the previous Symbol pulse voltage is equal to or less than 50msec more 5nsec,
Diameter of the bubbles state, and are more 50μm or less 100 nm,
The bubble generation method, wherein the bubbles are generated from the first electrode . The bubble generation method according to claim 1 , wherein the liquid contains molecules having a polar group. The fine bubbles from the first electrode to produce a flow in the ejected liquid into the liquid, bubble generating method as claimed in claim 1 or 2. The bubble generation method according to any one of claims 1 to 3 , wherein the liquid is water, and water in which bubbles containing hydrogen gas are dispersed is generated. A bubble generation method for generating fine bubbles in a liquid,
Contacting the liquid with two electrodes, a first electrode and a second electrode;
A voltage applying step of applying a pulse voltage having a positive peak voltage between the two electrodes,
The portion of the second electrode that is in contact with the liquid is covered with insulation;
Pulse width of the previous Symbol pulse voltage is equal to or less than 50msec more 5nsec,
Diameter of the bubbles state, and are more 50μm or less 100 nm,
The bubble generation method, wherein the bubbles are generated from the first electrode . The bubble generation method according to claim 5 , wherein the liquid contains molecules having a polar group. The bubble generating method according to claim 5 or 6 , wherein fine bubbles are ejected from the first electrode into the liquid to generate a flow in the liquid. It said liquid is water, thereby producing water bubbles containing oxygen gas are dispersed, the bubble generation method described in any one of claims 5-7. Wherein the voltage applying step, the plasma from at least one of the electrodes of the first electrode and the second electrode is generated, the bubble generation method described in any one of claims 1 to 8.