JP2015018654A - Plasma processing device and method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a plasma processing device and method capable of obtaining a high reaction speed by generating the plasma in the liquid having a high electron density and a large volume, in a device and method for performing plasma processing by generating plasma in the bubbles in a liquid.SOLUTION: A glass cylinder 1, an upper flange 2 and a lower flange 3 constitute a closed container. Furthermore, a gas exhaust piping 6, a liquid introduction piping 7, and a liquid discharge piping 8 are provided. A coil 9 is wound, in the shape of solenoid, around the glass cylinder 1. When the glass cylinder 1 is filled with water W, gas is supplied from gas introduction piping 5 to a bubble ring generator 4, and a bubble ring 10 arrives at a position close to the coil 9, a high frequency power is supplied from a high frequency power supply 12 to the coil 9, inductively-coupled thermal plasma is generated in the bubble ring 10, and the water W can be cleaned at high speed.

Description

  The present invention relates to an apparatus and a method for performing plasma processing by generating plasma in bubbles in a liquid.

  As conventional liquid purification methods, activated sludge treatment methods using microorganisms are used in sewerage treatment facilities, manure treatment facilities, factory wastewater treatment facilities, livestock wastewater treatment facilities, lake water purification facilities, and the like. In addition, because there are substances and microorganisms that cannot be removed by treatment with microorganisms, as a method to increase the efficiency of deodorization, decolorization, sterilization, etc., a high voltage is applied to domestic wastewater such as sewage and urine to generate an underwater discharge, A liquid purification method for killing E. coli is disclosed (see, for example, Patent Document 1).

  In-liquid plasma is used to purify gases as well as liquids. As a method for treating combustion exhaust gas containing harmful substances discharged from a waste incinerator, a method using in-liquid plasma is disclosed (for example, see Patent Document 2).

  There are other uses besides fluid purification. For example, a method of synthesizing carbon nanotubes by underwater plasma (for example, see Non-Patent Document 1), a method of synthesizing a phosphor crystal by in-liquid pulse plasma (for example, see Non-Patent Document 2), and the like are disclosed. .

  In addition, as a method of generating in-liquid plasma, a high-voltage electrode having a protrusion is immersed in a liquid, and a high-repetitive high-voltage pulse is applied between the electrode pair to joule-heat the liquid in the vicinity of the electrode and continuously. The vaporization bubble region that surrounds the tip of the protruding portion of the electrode is formed by the vaporization bubble. Next, a method for generating plasma in liquid is disclosed in which vaporized substances in vaporized bubbles are ionized (plasmaized) to form various ions, and ion species in the plasma are infiltrated and diffused in the liquid (for example, patent document). 3).

JP-A-61-136484 JP 2002-336650 A JP 2007-207540 A

K. Takekoshi et al. , Jpn. J. et al. Appl. Phys. 51 (2012) 125102 E. Omurzak et al. , Jpn. J. et al. Appl. Phys. 50 (2011) 01AB09

  However, the conventional submerged plasma technology has a problem that the plasma generation intensity (electron density × volume) is not sufficient, and the reaction rate of purification, synthesis, etc. is low.

  In the method described in Patent Document 1, since it is necessary to generate a very high potential difference between the planar electrodes, the energy efficiency is poor. In the methods described in Patent Documents 2 to 3 and Non-Patent Documents 1 and 2, plasma is generated only locally.

  The present invention has been made in view of the above problems, and in an apparatus and method for performing plasma processing by generating plasma in bubbles in a liquid, generating an in-liquid plasma having a high electron density and a large volume. Accordingly, an object of the present invention is to provide a plasma processing apparatus and method capable of obtaining a high reaction rate.

  A plasma processing apparatus according to a first invention of the present application includes a cylindrical insulating container, a bubble ring generator provided below the container, a gas inlet for supplying gas to the bubble ring generator, and a gas from the container. And a coil for generating a high-frequency electromagnetic field in the container, and a high-frequency power source for supplying high-frequency power to the coil.

  With such a configuration, a high reaction rate can be obtained by generating in-liquid plasma having a high electron density and a large volume.

  In the plasma processing apparatus of the first invention of the present application, it is preferable that a liquid introduction port for supplying a liquid into the container and a liquid discharge port for discharging the liquid in the container are preferably provided.

  With such a configuration, liquid purification can be performed effectively.

  Preferably, the container is provided with a refrigerant pipe, and the refrigerant pipe is provided near the central axis of the container.

  With such a configuration, it is possible to suppress liquid overheating and perform stable processing.

  Preferably, a timing control unit for controlling the bubble ring generation timing of the bubble ring generator and the high frequency power generation timing of the high frequency power source is preferably provided.

  With such a configuration, power efficiency can be improved.

  In the plasma processing method of the second invention of the present application, a liquid is introduced into a cylindrical insulating container, a gas is supplied to a bubble ring generator provided below the container to generate a bubble ring in the container, and a coil is formed. A high frequency electromagnetic field is generated in the container by supplying a high frequency power, and a liquid is processed by generating plasma in a bubble ring.

  With such a configuration, a high reaction rate can be obtained by generating in-liquid plasma having a high electron density and a large volume.

  According to the present invention, a high reaction rate can be obtained by generating in-liquid plasma having a high electron density and a large volume.

Sectional drawing which shows the structure of the plasma processing apparatus in Embodiment 1 of this invention Sectional drawing which shows the structure of the plasma processing apparatus in Embodiment 2 of this invention. Sectional drawing which shows the structure of the plasma processing apparatus in Embodiment 3 of this invention.

  Hereinafter, a plasma processing apparatus according to an embodiment of the present invention will be described with reference to the drawings.

(Embodiment 1)
Hereinafter, Embodiment 1 of the present invention will be described with reference to FIG.

  FIG. 1 is a cross-sectional view showing the configuration of the plasma processing apparatus according to Embodiment 1 of the present invention. In FIG. 1, a glass cylinder 1 as a cylindrical insulating container is sandwiched between an upper flange 2 and a lower flange 3, and these three constitute an airtight container. A bubble ring generator 4 is provided below the glass cylinder 1, and a gas introduction pipe 5 serving as a gas introduction port is connected to the bubble ring generator 4.

  The bubble ring is a donut-shaped (ring-shaped) bubble in water, and is also called a vortex ring or a vortex ring. Dolphins are known to play with a ring of bubbles that spits out of the mouth in the water, but this is also a type of bubble ring.

  A device that artificially generates a bubble ring is a bubble ring generator, and those disclosed in Japanese Patent Application Laid-Open No. 2003-39896, Japanese Patent Application Laid-Open No. 6-141733, Japanese Patent Application Laid-Open No. 2005-103456, and the like can be used. it can. The upper flange 2 is provided with a gas exhaust pipe 6 as a gas outlet, a liquid inlet pipe 7 as a liquid inlet, and a liquid outlet pipe 8 as a liquid outlet. It arrange | positions so that it may become lower than the lower end of the exhaust pipe 6. FIG.

  The coil 9 is wound around the glass tube 1 in a solenoid shape, and a high frequency electromagnetic field can be generated in the glass tube 1 by supplying high frequency power. The coil 9 is a hollow copper tube, and a coolant such as cooling water flows inside to prevent overheating. A bubble ring generator control unit 11 is connected to the bubble ring generator 4 so that the bubble ring generation timing can be controlled.

  A high frequency power source 12 is connected to the coil 9 via the matching unit 13. A timing control unit 14 is connected to both the bubble ring generator control unit 11 and the high frequency power source 12, and the bubble ring generation timing of the bubble ring generator and the high frequency power generation timing of the high frequency power source can be controlled.

  The glass tube 1 is filled with a liquid, for example, water W. Then, argon gas is supplied from the gas introduction pipe 5 to the bubble ring generator 4 to generate the bubble ring 10 filled with argon gas. When high frequency power is supplied to the coil 9 from the high frequency power supply 12 when the bubble ring 10 reaches a position close to the coil 9, inductively coupled thermal plasma is generated in the bubble ring 10.

  The inductively coupled thermal plasma generated at this time has a very high plasma density and is active at high temperatures. Further, since plasma is generated over the entire circumference of the bubble ring 10, the volume thereof is large. Therefore, it is possible to obtain a higher reaction rate than before.

  When the bubble ring 10 is no longer generated in the bubble ring 10 to maintain the plasma away from the coil 9, the plasma disappears. The bubble ring 10 ascends in the glass tube 1 and eventually joins the space between the upper flange and the water level of the water W beyond the level of the water W. Excess gas is discharged from the gas exhaust pipe 6 to the outside of the glass tube 1.

  By using such a series of cycles (generation of bubble ring 10, rise of bubble ring 10, plasma generation, plasma extinction, gas merging, gas discharge), a process using liquid plasma such as liquid purification and substance synthesis. Can be performed at high speed.

  The high-frequency power supplied to the coil 9 at the timing when plasma is not generated does not contribute to the progress of the in-liquid plasma process, and wastes power in the coil 9 and the matching unit 13. Therefore, the timing control unit 14 is operated, and the bubble ring generator control unit 11 and the high frequency power supply 12 are controlled so that the high frequency power is supplied to the coil 9 in accordance with the timing when the bubble ring 10 reaches a position close to the coil 9. As a result, the power efficiency can be increased.

  When purifying the liquid, the liquid may be continuously or intermittently discharged from the liquid discharge pipe 8 while supplying the liquid into the glass cylinder 1 continuously or intermittently from the liquid introduction pipe 7. Since there is a fast liquid flow around the bubble ring 10, liquid agitation occurs and high-speed processing can be realized. The reason why the liquid is purified is considered to be that the pollutants are decomposed by the strong oxidizing power of hydrogen peroxide generated by the plasma.

  In an inductively coupled thermal plasma generator, a phenomenon in which the plasma mode changes discontinuously between two modes, a capacitive coupling mode (low electron density, low temperature) and an inductive coupling mode (high electron density, high temperature) ( Mode jump).

  Since it is very difficult to generate inductively coupled mode high temperature plasma in the two bubble rings 10 at the same time, it is preferable to generate the bubble ring 10 at such a frequency that only one bubble ring 10 always passes through the inside of the coil 9. Alternatively, the bubble ring 10 may be generated at a higher frequency, and the bubble ring 10 where no plasma is generated may be used for stirring the liquid.

(Embodiment 2)
Hereinafter, a second embodiment of the present invention will be described with reference to FIG.

  FIG. 2 is a cross-sectional view showing the configuration of the plasma processing apparatus according to the second embodiment of the present invention.

  In FIG. 2, a refrigerant tube 15 formed in a U shape is provided near the central axis of a cylindrical glass tube 1. Other configurations are the same as those in the first embodiment. In the drawing, only the cross section on the refrigerant inflow side is shown, but an outlet is provided in the front and back direction of the drawing.

  Since the inductively coupled thermal plasma is extremely high in temperature, the liquid W becomes too hot when the high frequency power is increased to increase the processing speed or the rate of time during which the plasma is generated is increased. Sometimes. If the entire liquid W boils, the pressure in the glass tube 1 increases too much, which is dangerous. Therefore, the temperature of the liquid W should be kept low to some extent. Therefore, the present embodiment realizes a stable process by flowing a refrigerant (for example, cooling water) through the refrigerant pipe 15 so as to cool the liquid W and suppressing overheating of the liquid W. .

  Since the bubble ring 10 and the inductively coupled plasma always have a donut shape, even if the refrigerant tube 15 is inserted in the vicinity of the central axis of the cylindrical glass tube 1, the process is not hindered. On the contrary, there is an effect of suppressing and stabilizing the collapse of the shape of the bubble ring 10.

(Embodiment 3)
A third embodiment of the present invention will be described below with reference to FIG.

  FIG. 3 is a cross-sectional view showing the configuration of the plasma processing apparatus according to the third embodiment of the present invention. In FIG. 3, a refrigerant pipe composed of a double pipe composed of an outer pipe 16 and an inner pipe 17 arranged coaxially is provided in the vicinity of the central axis of the cylindrical glass tube 1. Other configurations are the same as those in the first embodiment.

  The bottom of the outer tube 16 is closed, and the bottom of the inner tube 17 is open. The refrigerant (for example, cooling water) is introduced from the outer flow path between the outer tube 16 and the inner tube 17, and the liquid W in the glass tube 1 is cooled by discharging the refrigerant from the inner flow channel inside the inner tube 17. To do. The direction of the flow of the refrigerant is arbitrary. The material of the outer tube 16 and the inner tube 17 is preferably a dielectric in order to prevent abnormal discharge such as an arc, and for example, glass or the like can be used. Even if it is a conductor, an arc does not occur depending on conditions, so the material may be selected as appropriate.

  The plasma processing apparatus and method described above merely exemplify typical examples of the scope of application of the present invention.

  For example, in order to speed up the process of synthesizing substances by conventional arc discharge in liquid, the contrivance such as attaching the raw material to the inner wall of the glass tube 1 or the outer walls of the refrigerant pipe 15 and the outer pipe 16 is used. May be added.

  Alternatively, a timing control unit, for example, a pulse transmitter is built in the high-frequency power source 12, and high-frequency power is supplied in synchronization with the pulse generated by the pulse transmitter, and the pulse is taken out of the high-frequency power source 12 to generate a bubble ring. You may use for the drive timing control of a device.

  As described above, the present invention can obtain a high reaction rate by generating submerged plasma having high electron density and large volume in plasma processing using submerged plasma such as liquid purification and substance synthesis. It is a useful invention that can be made.

DESCRIPTION OF SYMBOLS 1 Glass tube 2 Upper flange 3 Lower flange 4 Bubble ring generator 5 Gas introduction piping 6 Gas exhaust piping 7 Liquid introduction piping 8 Liquid discharge piping 9 Coil 10 Bubble ring 11 Bubble ring generator control unit 12 High frequency power supply 13 Matching device 14 Timing control unit

Claims (5)

A cylindrical insulating container; a bubble ring generator provided below the container; a gas inlet for supplying gas to the bubble ring generator; a gas outlet for discharging gas from the container; A coil that generates a high-frequency electromagnetic field therein, and a high-frequency power source that supplies high-frequency power to the coil;
A plasma processing apparatus. The plasma processing apparatus according to claim 1, further comprising: a liquid introduction port that supplies a liquid into the container; and a liquid discharge port that discharges the liquid inside the container. The plasma processing apparatus according to claim 1, wherein a refrigerant pipe is provided inside the container, and the refrigerant pipe is provided near a central axis of the container. The plasma processing apparatus according to claim 1, further comprising a timing control unit that controls a bubble ring generation timing of the bubble ring generator and a high frequency power generation timing of the high frequency power source. A liquid is introduced into a cylindrical insulating container, gas is supplied to a bubble ring generator provided below the container to generate a bubble ring inside the container, and high frequency power is supplied to the coil to supply the container. Processing liquid by generating a high-frequency electromagnetic field inside and generating plasma in the bubble ring,
A plasma processing method characterized by the above.

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