JP6653475B2 - Liquid treatment equipment - Google Patents

Description

  The present disclosure relates to a liquid processing apparatus using plasma.

  BACKGROUND ART Conventionally, a technique using plasma for purifying or sterilizing a liquid has been known. For example, Patent Literatures 1 and 2 disclose a liquid processing apparatus that supplies a gas into a liquid and generates plasma in the supplied gas.

JP-A-2015-33694 JP 2015-136644 A

  However, in the above-mentioned conventional liquid processing apparatus, there is a problem that the plasma becomes unstable.

  Therefore, the present disclosure provides a liquid processing apparatus capable of stably generating plasma.

  In order to solve the above problem, a liquid processing apparatus according to an embodiment of the present disclosure includes a first electrode and a second electrode at least partially disposed in a liquid to be processed, and a side surface of the first electrode. A first cylindrical insulator, which is disposed so as to surround through a space, and has an opening at an end surface in contact with the liquid to be treated, and a gas supplied to the first insulator, whereby the opening is formed. A gas supply device that discharges the gas into the liquid to be processed through a gas supply device, and a power supply that generates plasma by applying a voltage between the first electrode and the second electrode, A first distance, which is a distance between a side surface of the first electrode and an inner side surface of the first insulator, is 1 mm or more.

  According to the present disclosure, it is possible to provide a liquid processing apparatus capable of stably generating plasma.

FIG. 1 is a diagram showing a result of observing a deposit attached to an insulator from an opening side of the insulator. FIG. 2 is a diagram showing an analysis result of a deposit attached to the insulator shown in FIG. FIG. 3 is a diagram illustrating a configuration of the liquid processing apparatus according to the first embodiment. FIG. 4A is a cross-sectional view illustrating an example of the first electrode according to Embodiment 1. FIG. 4B is a cross-sectional view illustrating another example of the first electrode according to Embodiment 1. FIG. 5 is a cross-sectional view illustrating an example of the second electrode according to the first embodiment. FIG. 6 is a diagram showing a result of observing the first electrode and the insulator according to the first embodiment from the opening side. FIG. 7 is a diagram showing the stability of plasma with respect to the distance between the first electrode and the insulator and the amount of retreat of the end face of the first electrode according to the first embodiment. FIG. 8 is a diagram showing a result of observing the first electrode and the insulator from the opening side when the distance shown in FIG. 7 is 1.1 mm and the amount of retreat is 4 mm. FIG. 9 is a diagram showing the stability of plasma with respect to the amount of retreat of the end face of the first electrode and the air flow rate according to the first embodiment. FIG. 10A is a diagram showing a result of observing the first electrode and the insulator from the side when the retreat amount shown in FIG. 9 is 4 mm and the air flow rate is 0.3 L / min. FIG. 10B is a diagram showing a result of observing the first electrode and the insulator from the side when the retreat amount shown in FIG. 9 is 4 mm and the air flow rate is 1.0 L / min. FIG. 11 is a diagram illustrating a configuration of a liquid processing apparatus according to the second embodiment. FIG. 12 is a diagram illustrating a result of observing the second insulator of the liquid processing apparatus according to the second embodiment from the side. FIG. 13 is a diagram illustrating a result of observing the first insulator of the liquid processing apparatus according to Embodiment 2 from the side. FIG. 14 shows a result of simulating the relationship between the second distance between the first electrode and the second insulator according to the second embodiment and the electric field value generated on the inner surface of the second insulator. FIG. FIG. 15 is a diagram illustrating a configuration of a liquid processing apparatus according to the third embodiment. FIG. 16 is a cross-sectional view illustrating an example of a first electrode and an insulator according to Embodiment 3. FIG. 17 is a front view of the first electrode and the insulator according to the third embodiment when viewed from the distal end side. FIG. 18 is a diagram illustrating a result of simulating a position of a gas-liquid interface near an insulator according to a comparative example of the third embodiment. FIG. 19 is a diagram showing a gas flow velocity distribution in the same simulation as FIG. FIG. 20 is a diagram showing the result of simulating the position of the gas-liquid interface near the insulator according to the third embodiment. FIG. 21 is a diagram showing a gas flow velocity distribution in the same simulation as FIG. FIG. 22 is a cross-sectional view showing the vicinity of a first electrode and an insulator of a liquid processing apparatus according to a modification of the third embodiment.

(History leading to obtaining one embodiment according to the present disclosure)
The inventor of the present application has confirmed that when tap water is treated using the liquid treatment apparatus described in Patent Document 1, the discharge becomes unstable within about 3 minutes after the start of the discharge. Five minutes after the start of the discharge, it was visually confirmed that the deposit was attached near the opening of the insulator.

  FIG. 1 is a diagram illustrating a result of observing a precipitate 90x attached to the insulator 50x from the opening side of the insulator 50x. In FIG. 1, a white or gray substantially circular ring having a predetermined width indicates a schematic shape of the insulator 50x. Since the first electrode 30x is located behind the opening of the insulator 50x, it was not photographed in the image shown in FIG. For this reason, the schematic shape of the first electrode 30x when viewed from the opening side is indicated by a white broken circle. These are the same in FIGS. 6 and 8 described later.

  The inner diameter of the insulator 50x is 1 mm, and the outer diameter of the first electrode 30x is 0.8 mm. Therefore, the distance between the side surface of the first electrode 30x and the inner side surface of the insulator 50x, that is, the width d1 of the space 52x is 0.1 mm. In this case, as shown in FIG. 1, it can be seen that the precipitate 90x is attached to the inner surface near the opening of the insulator 50x.

  FIG. 2 is a diagram showing an analysis result of the precipitate 90x attached to the insulator 50x shown in FIG. Specifically, FIG. 2 shows the result of analyzing the precipitate 90x by EDX (Energy Dispersive X-ray) analysis using a scanning electron microscope (SEM). In FIG. 2, the horizontal axis is the energy of the characteristic X-ray, and the vertical axis is its intensity (count value).

As shown in FIG. 2, it can be seen that the precipitate 90x is a compound of silicon oxide (SiO _x ). The inventor of the present application has studied the factors that cause the deposit 90x to adhere to the inner surface of the insulator 50x as follows.

  In the first electrode 30x and the insulator 50x shown in FIG. 1, the width d1 of the space 52x is about 0.1 mm. That is, since the first electrode 30x and the insulator 50x are close to each other, a dielectric barrier discharge or a creeping discharge occurs between the first electrode 30x and the insulator 50x. It is considered that the silica included in the tap water was deposited on the inner surface of the insulator 50x by exposing the surface of the insulator 50x to the plasma generated by these discharges. That is, the precipitate 90x is considered to be a substance formed by precipitation of silica contained in tap water.

  When the deposit 90x is formed in the vicinity of the opening, discharge occurs between the deposit 90x and the first electrode 30x. Therefore, the voltage used for the discharge generated between the first electrode 30x and the second electrode (not shown) changes, and the plasma becomes unstable.

  Therefore, in order to solve the above problem, a liquid processing apparatus according to one embodiment of the present disclosure includes a first electrode and a second electrode at least partially disposed in a liquid to be processed, and the first electrode A first insulator having a cylindrical shape, which is disposed so as to surround the side surface of the first insulator via a space, and provided with an opening at an end face in contact with the liquid to be treated, and supplying gas into the first insulator. A gas supply device that releases the gas into the liquid to be processed through the opening, and a power supply that generates plasma by applying a voltage between the first electrode and the second electrode. The distance between the side surface of the first electrode and the inner surface of the first insulator is 1 mm or more.

  As a result, the distance between the side surface of the first electrode and the inner side surface of the first insulator is 1 mm or more, so that dielectric barrier discharge or creeping between the first electrode and the first insulator is possible. Discharge and the like hardly occur. For this reason, the surface of the first insulator is less exposed to the plasma generated when these discharges occur, so that deposits such as silica adhere to the inner surface of the first insulator. Is suppressed.

  Further, for example, the first distance may be 1 mm or more and 3 mm or less.

  Accordingly, since the distance between the side surface of the first electrode and the inner side surface of the first insulator is not more than 3 mm and is not too far, the supplied gas can easily cover the first electrode. Therefore, the liquid processing apparatus according to an aspect of the present disclosure can stably discharge and generate plasma stably.

  Further, for example, the end face of the first electrode may be recessed or protruded from the opening of the first insulator by 0 mm or more and 3 mm or less.

  Accordingly, a discharge is easily generated between the end surface of the first electrode and the gas-liquid interface, and the generation of a discharge between the first electrode and the first insulator can be suppressed. Therefore, since generation of a precipitate such as silica can be suppressed, the liquid processing apparatus according to one embodiment of the present disclosure can more stably discharge and generate plasma more stably.

  Further, the volume of discharge generated between the first electrode and the gas-liquid interface can be controlled by the flow rate of the supplied gas. Therefore, for example, in the liquid processing apparatus according to an aspect of the present disclosure, the flow rate of the gas supplied by the gas supply device may be 0.5 L / min or more.

  Thus, the larger the flow rate of the gas, the more the discharge can be suppressed from spreading toward the inner surface of the first insulator, so that the surface of the first insulator is less likely to be exposed to plasma. Therefore, since generation of a precipitate such as silica can be suppressed, the liquid processing apparatus according to one embodiment of the present disclosure can more stably discharge and generate plasma more stably.

  Further, for example, the first electrode has a long columnar electrode portion, and the first insulator is a long cylinder surrounding a side surface of the electrode portion, and The first insulator may be arranged coaxially.

  Thus, since a space having a uniform width is formed between the electrode portion and the first insulator, the surface of the first insulator is less likely to be exposed to plasma. Further, since the amount of gas flowing in the space can be equalized, the liquid processing apparatus according to one embodiment of the present disclosure can generate plasma more stably.

  By the way, in the case where the gas advances in the predetermined flow path, when the flow path width of the gas changes, the flow velocity of the gas locally changes, and the change causes a swirling flow. When a swirling flow is generated inside the first insulator, the liquid is drawn into the first insulator through the opening of the first insulator, and the insulating property of the first electrode can be secured. Disappears.

  On the other hand, in the liquid processing apparatus according to an aspect of the present disclosure, for example, the first electrode is provided on a long columnar electrode portion and a rear end side of the electrode portion, and the electrode portion A support portion having a columnar support thicker than the electrode portion, wherein the support portion is provided with a gas supply hole through which gas supplied by the gas supply device passes, and The opening width of the supply hole and the inner diameter of the first insulator may be substantially the same.

  Thereby, when the gas supplied by the gas supply device enters the inside of the first insulator through the gas supply hole, the gas flow width between the gas supply hole and the first insulator is substantially reduced. It can be uniform. For this reason, generation of a swirling flow of gas inside the first insulator can be suppressed, and plasma can be more stably generated.

  Further, for example, an inlet is provided on a rear end side of the first insulator for introducing a gas supplied by the gas supply device into the inside of the first insulator. The flow direction of the gas when passing the gas may intersect the axial direction of the first insulator.

  Thus, the gas introduced from the inlet proceeds in a direction intersecting with the axial direction and hits the inner surface of the first insulator, and then travels along the inside of the first insulator along the axial direction. I do. As described above, once the traveling direction is changed by the inner surface or the like, the gas can flow at a stable flow velocity along the axial direction near the opening of the first insulator. Therefore, the generation of the swirling flow of the gas inside the first insulator can be suppressed, and the plasma can be more stably generated.

  In addition, for example, an opening width is further provided with a bottomed cylindrical body part substantially the same as the first insulator, and the bottomed cylindrical body part is coaxial with the first insulator, The inlet is connected to a rear end side of the first insulator, the inlet is provided on a side wall of the bottomed cylindrical body, and a flowing direction of the gas when passing through the inlet is the first insulating. It may be substantially perpendicular to the axial direction of the body.

  Thereby, the gas introduced from the introduction port travels in a direction orthogonal to the axial direction and hits the side wall of the bottomed tubular body, and then travels inside the first insulator along the axial direction. . As described above, once the traveling direction is changed by the side wall or the like, the gas can flow at a stable flow rate along the axial direction in the first insulator. Therefore, the generation of the swirling flow of the gas inside the first insulator can be suppressed, and the plasma can be more stably generated.

  In addition, when a voltage is applied to the first electrode surrounded by the first cylindrical insulator via a space, a gas-liquid interface (a gas-liquid interface) near the opening of the first insulator is formed. A Maxwell stress is applied to the interface according to the intensity of the electric field generated at the interface. Therefore, the liquid to be treated permeates along the inner surface from the opening of the first insulator. As a result, when the liquid to be treated that has entered the inside of the first insulator reaches the base of the first electrode and comes into contact therewith, a short circuit between the electrodes or unstable discharge occurs.

  Therefore, in the liquid processing apparatus according to an aspect of the present disclosure, for example, the liquid processing apparatus further includes a cylindrical second insulator disposed so as to surround a side surface of the first electrode via a space. Is connected to the rear end of the first insulator so that the inside of each of the second insulator and the first insulator communicates with each other, and the side surface of the first electrode A second distance, which is a distance between the first insulator and the inner surface of the second insulator, may be greater than the first distance.

  Accordingly, the electric field generated between the inner surface of the second insulator and the first electrode is smaller than the electric field generated between the inner surface of the first insulator and the first electrode. The treatment liquid that has entered the inside of the insulator is less likely to enter the inside of the second insulator. Therefore, it is possible to suppress reaching to the root of the first electrode, and thus it is possible to suppress occurrence of a short circuit between the electrodes or instability of discharge. Therefore, according to the liquid processing apparatus according to an aspect of the present disclosure, plasma can be more stably generated.

  Further, for example, the second distance is a distance determined according to a value of a voltage applied by the power supply, and an electric field generated on an inner surface of the second insulator by the voltage is equal to or less than a predetermined value. The distance may be as follows.

  Accordingly, the second insulator can be designed to have an appropriate size according to the voltage applied between the first electrode and the second electrode. Therefore, for example, use of an unnecessarily large second insulator can be avoided, so that the liquid processing apparatus can be reduced in size, weight, and cost.

  Also, for example, the value of the voltage applied between the first electrode and the second electrode may be 5 kV or less, and the second distance may be 2.6 mm or more.

  Thereby, when the applied voltage is 5 kV or less, the intrusion of the liquid to be treated into the inside of the second insulator can be suppressed.

  Further, for example, the value of the voltage applied between the first electrode and the second electrode may be 5 kV or more, and the second distance may be 5 mm or more.

  Thus, when the applied voltage is 5 kV or more, it is possible to suppress the intrusion of the liquid to be processed into the inside of the second insulator.

  Further, for example, the first electrode has a long columnar electrode portion, the first insulator is a cylindrical body surrounding a tip side surface of the electrode portion, and The insulator may be a cylindrical body that surrounds a side surface on the rear end side of the electrode unit, and the electrode unit, the first insulator, and the second insulator may be coaxially arranged. Further, for example, the second insulator may be a cylindrical body or a rectangular cylindrical body.

  As a result, a space having a uniform width is formed between the electrode portion and the first insulator and between the electrode portion and the second insulator. The intensity of the generated electric field can be made uniform. Therefore, a portion where the electric field is locally strong is less likely to be generated, so that the liquid to be treated can be suppressed from entering the inside of the second insulator. Therefore, the liquid processing apparatus according to an aspect of the present disclosure can generate plasma more stably.

  Further, for example, the first insulator and the second insulator may be made of different materials.

  Thereby, the workability of each of the first insulator and the second insulator can be improved. Therefore, for example, since each of the first insulator and the second insulator can be formed precisely, the reliability of the liquid processing apparatus can be improved.

  Further, for example, the first insulator and the second insulator may be integrally formed of the same material.

  Thus, the number of parts can be reduced, and the weight of the liquid processing apparatus can be reduced. Further, in the manufacturing method of the liquid processing apparatus, the number of steps of assembling parts can be reduced, so that cost reduction can be realized.

  Hereinafter, embodiments will be specifically described with reference to the drawings.

  Each of the embodiments described below shows a comprehensive or specific example. Numerical values, shapes, materials, constituent elements, arrangement positions and connection forms of constituent elements, steps, order of steps, and the like shown in the following embodiments are merely examples, and do not limit the present disclosure. In addition, among the components in the following embodiments, components not described in the independent claims indicating the highest concept are described as arbitrary components.

  In addition, each drawing is a schematic diagram, and is not necessarily strictly illustrated. Therefore, for example, the scales and the like do not always match in each drawing. Further, in each of the drawings, substantially the same configuration is denoted by the same reference numeral, and redundant description will be omitted or simplified.

(Embodiment 1)
[1-1. Overview]
First, an outline of the liquid processing apparatus according to the embodiment will be described with reference to FIG. FIG. 3 is a diagram illustrating a configuration of the liquid processing apparatus 1 according to the present embodiment.

  As shown in FIG. 3, the liquid processing apparatus 1 generates a plasma 4 in a gas 3 supplied into a liquid 2. The gas 3 supplied into the liquid 2 exists in the liquid 2 as bubbles. The gas-liquid interface of the gas bubbles caused by the gas 3 may be closed in the liquid 2 or may be in communication with the external space.

The liquid 2 is a target liquid to be processed by the liquid processing apparatus 1. The liquid 2 is, for example, water such as tap water or pure water or an aqueous solution. The liquid processing apparatus 1 generates an active species (reactive species) in the liquid 2 by generating a plasma 4 in the liquid 2. The active species include, for example, hydroxyl radical (OH), hydrogen radical (H), oxygen radical (O), superoxide anion (O ₂ ⁻ ), monovalent oxygen ion (O ⁻ ), or hydrogen peroxide (H ₂ O). ₂ ) and the like.

  Since the generated active species decomposes substances to be decomposed included in the liquid 2, the liquid processing apparatus 1 can sterilize the liquid 2. Alternatively, the liquid 2 containing the active species (ie, the plasma-treated liquid 2) can be used to sterilize another liquid or gas. The plasma-treated liquid 2 can be used not only for sterilization but also for various other purposes.

[1-2. Constitution]
Next, the configuration of the liquid processing apparatus 1 according to the present embodiment will be described.

  As shown in FIG. 3, the liquid processing apparatus 1 includes a processing tank 10, a reaction tank 15, a pipe section 20, a first electrode 30, a first holding section 35, a second electrode 40, A second holding unit 45, an insulator 50, a gas supply pump 60, a liquid supply pump 70, and a power supply 80 are provided. Hereinafter, each component included in the liquid processing apparatus 1 will be described in detail.

[1-2-1. Processing tank]
The processing tank 10 is a container for storing the liquid 2. The outer shape of the processing tank 10 may be any shape such as a rectangular parallelepiped, a column, or a sphere. The processing tank 10 may be, for example, a liquid storage tank having an open portion, or a tray having an open upper portion.

  A piping section 20 is connected to the processing tank 10. Specifically, the processing tank 10 is connected to the reaction tank 15 via a piping section 20. A liquid supply pump 70 is connected to the pipe section 20, and the liquid 2 is circulated between the processing tank 10, the reaction tank 15 and the pipe section 20.

  The processing tank 10 is formed of, for example, an acid-resistant resin material. For example, the processing tank 10 is formed of a fluororesin such as polytetrafluoroethylene, silicon rubber, polyvinyl chloride, stainless steel, ceramic, or the like.

[1-2-2. Reaction tank]
The reaction tank 15 is a tank in which the first electrode 30 and the second electrode 40 are arranged. Specifically, the first electrode 30 and the second electrode 40 are arranged so as to penetrate the side wall of the reaction tank 15. The reaction tank 15 is filled with the liquid 2. In the reaction tank 15, the plasma 4 is generated by discharging between the first electrode 30 and the second electrode 40 in the gas 3 (bubbles) supplied by the gas supply pump 60.

  The external shape of the reaction tank 15 may be any shape such as a rectangular parallelepiped, a column, or a sphere. The reaction tank 15 may be, for example, a liquid storage tank having an opening, or a tray having an open top. Further, the reaction tank 15 may be a part of the piping section 20.

  The reaction tank 15 is formed of, for example, an acid-resistant resin material. For example, the reaction tank 15 is formed of a fluorine resin such as polytetrafluoroethylene, silicon rubber, polyvinyl chloride, stainless steel, ceramic, or the like.

[1-2-3. Piping section]
The pipe section 20 is a pipe for forming a flow path of the liquid 2. The piping unit 20 is formed from a tubular member such as a pipe, a tube, or a hose. The pipe section 20 is formed from an acid-resistant resin material or the like. For example, the pipe section 20 is formed of a fluororesin such as polytetrafluoroethylene, silicon rubber, polyvinyl chloride, stainless steel, ceramic, or the like.

  In the present embodiment, the pipe section 20 connects the processing tank 10 and the liquid supply pump 70, connects the liquid supply pump 70 and the reaction tank 15, and connects the reaction tank 15 and the processing tank 10. . As described above, the piping unit 20 connects the processing tank 10, the liquid supply pump 70, the reaction tank 15, and the processing tank 10 in this order, and forms a circulation path of the liquid 2. In FIG. 3, solid arrows drawn along the pipe section 20 indicate directions in which the liquid 2 flows (circulation directions).

[1-2-4. First electrode]
FIG. 4A is a cross-sectional view illustrating an example of the first electrode 30 according to the present embodiment. Specifically, FIG. 4A shows a cross section passing through the long axis of the first electrode 30. As shown in FIG. 4A, the first electrode 30 includes an electrode part 31 and a screw part 32.

  The first electrode 30 is one of a pair of electrodes for generating the plasma 4. The first electrode 30 is used as a reaction electrode, and a plasma 4 is generated around the first electrode 30.

  The electrode portion 31 is a long columnar electrode portion provided on the tip side of the first electrode 30. The diameter of the electrode portion 31 may be any as long as the plasma 4 can be generated, and is, for example, 2 mm or less. Here, as an example, the diameter of the electrode portion 31 is 0.8 mm.

  The electrode unit 31 is formed of, for example, tungsten, but is not limited to this. The electrode unit 31 may be formed from a metal material such as aluminum, iron, copper, or an alloy thereof.

  The first electrode 30 is at least partially disposed in the liquid 2. Specifically, the electrode portion 31 of the first electrode 30 is disposed in the reaction tank 15 and contacts the liquid 2. The electrode portion 31 is surrounded by an insulator 50 via a space 52 as shown in FIG. 4A. When the gas 3 is supplied by the gas supply pump 60, the supplied gas 3 fills the space 52, so that the electrode portion 31 is covered with the supplied gas 3 and does not contact the liquid 2.

  In the present embodiment, the electrode section 31 and the insulator 50 are coaxially arranged. A space 52 is provided between the electrode portion 31 and the insulator 50 over the entire circumference. That is, the space 52 is a cylindrical space having a substantially uniform width d1. The width d1 is a first distance that is a distance between the side surface of the first electrode 30 and the side surface of the insulator 50, and is 1 mm or more. The width d1 may be, for example, 1 mm or more and 3 mm or less.

  The screw part 32 is a metal member that supports the electrode part 31. Specifically, the electrode portion 31 is fixed by being pressed into the screw portion 32. The screw portion 32 is electrically connected to the electrode portion 31 and transmits power received from the power supply 80 to the electrode portion 31.

  The screw part 32 is a cylindrical support part provided on the rear end side of the electrode part 31. The diameter of the screw part 32 is larger than the diameter of the electrode part 31, for example, 3 mm. For example, the screw portion 32 is formed using a metal material that is easy to process, such as stainless steel or iron.

  The screw part 32 is held by the first holding part 35. Specifically, a male screw is provided on the outer surface of the screw portion 32. The screw portion 32 is held by the first holding portion 35 by screwing the male screw with a female screw provided on the first holding portion 35.

  The screw portion 32 is provided with a through hole 34 connected to the gas supply pump 60. The through hole 34 communicates with the space 52. Therefore, the gas 3 supplied from the gas supply pump 60 is discharged from the opening 51 of the insulator 50 into the liquid 2 stored in the reaction tank 15 through the through hole 34 and the space 52.

  In the present embodiment, as shown in FIG. 4A, the screw portion 32 is provided with two through holes 34. Thereby, the pressure loss of the gas 3 in the through hole 34 is suppressed. The number of the through holes 34 may be only one or three or more.

  As shown in FIG. 4A, the end face 33 of the first electrode 30 is recessed from the opening 51. At this time, the retreat amount d2 is a range in which the contact between the plasma 4 generated near the end face 33 of the first electrode 30 and the inner surface of the insulator 50 is suppressed. Specifically, the retreat amount d2 of the end face 33 of the first electrode 30 is 0 mm or more and 3 mm or less.

  The retreat amount d2 can be adjusted by rotating the screw portion 32 around the axis. The rotation of the screw portion 32 causes the electrode portion 31 and the screw portion 32 to move in the axial direction relative to the insulator 50 fixed to the first holding portion 35 in conjunction with each other. Thereby, the position of the end face 33 can be made variable. For example, as shown in FIG. 4B, the end face 33 of the first electrode 30 may protrude from the opening 51.

  FIG. 4B is a cross-sectional view illustrating another example of the first electrode 30 of the present embodiment. The projection amount d3 at this time is a range that can be accommodated in the gas 3 supplied by the gas supply pump 60. Specifically, the protrusion amount d3 of the end face 33 of the first electrode 30 is 0 mm or more and 3 mm or less.

[1-2-5. First holding unit]
The first holding unit 35 is a member for holding the first electrode 30. In the present embodiment, the first holding unit 35 holds the first electrode 30 and the insulator 50 and attaches the first electrode 30 and the insulator 50 to a predetermined position of the reaction tank 15.

  The first holding portion 35 is provided with a female screw. The female screw is screwed with the male screw of the screw portion 32 of the first electrode 30. Thus, by rotating the screw portion 32 around the axis, the position of the first electrode 30 in the axial direction with respect to the first holding portion 35 can be adjusted. Since the insulator 50 is fixed to the first holder 35 or the reaction tank 15, the position of the end face 33 of the first electrode 30 with respect to the opening 51 of the insulator 50 can be adjusted. That is, the retreat amount d2 or the protrusion amount d3 of the end face 33 of the first electrode 30 can be adjusted.

[1-2-6. Second electrode]
FIG. 5 is a sectional view showing the second electrode 40 according to the present embodiment. Specifically, FIG. 5 shows a cross section passing through the long axis of the second electrode 40. As shown in FIG. 5, the second electrode 40 includes an electrode part 41 and a screw part 42.

  The second electrode 40 is the other of the pair of electrodes for generating the plasma 4. The second electrode 40 is at least partially disposed in the liquid 2. Specifically, the electrode portion 41 of the second electrode 40 is arranged in the reaction tank 15 and contacts the liquid 2.

  The electrode portion 41 is a long cylindrical electrode portion provided on the tip side of the second electrode 40. The size and material of the electrode portion 41 are the same as those of the electrode portion 31 of the first electrode 30, but may be different.

  The screw part 42 is a metal member that supports the electrode part 41. Specifically, the electrode part 41 is fixed by being press-fitted into the screw part 42. The screw portion 42 is electrically connected to the electrode portion 41 and transmits the power received from the power supply 80 to the electrode portion 41.

  The screw portion 42 is a columnar support provided on the rear end side of the second electrode 40. The diameter of the screw portion 42 is larger than the diameter of the electrode portion 41, for example, 3 mm. For example, the screw portion 42 is formed using a metal material that is easy to process, such as stainless steel or iron.

  The screw part 42 is held by a second holding part 45. Specifically, a male screw is provided on the outer surface of the screw portion 42. The screw portion 42 is held by the second holding portion 45 by screwing the male screw with a female screw provided on the second holding portion 45.

[1-2-7. Second holding unit]
The second holding unit 45 is a member for holding the second electrode 40. In the present embodiment, the second holding unit 45 holds the second electrode 40 and attaches the second electrode 40 to a predetermined position of the reaction tank 15.

  The second holding portion 45 is provided with a female screw. The female screw is screwed with the male screw of the screw portion 42 of the second electrode 40. Thereby, the position of the electrode part 41 located in the reaction tank 15 can be adjusted.

[1-2-8. Insulator (first insulator)]
The insulator 50 is an example of a first insulator arranged so as to surround the side surface of the first electrode 30 via the space 52. The insulator 50 is a cylindrical insulator provided with an opening 51 at an end face 53 in contact with the liquid 2. In the present embodiment, the insulator 50 is a long cylinder surrounding the side surface of the electrode portion 31 of the first electrode 30.

  The inner diameter of the insulator 50 is larger than the outer diameter of the electrode part 31. Further, the electrode section 31 and the insulator 50 are coaxially arranged. Therefore, the space 52 is formed in a cylindrical shape over the entire circumference of the electrode unit 31. Due to the space 52, the electrode portion 31 does not contact the insulator 50. For example, the inner diameter of the insulator 50 is 3 mm, and the outer diameter of the electrode part 31 is 0.8 mm. Thereby, the width d1 of the space 52 becomes 1.1 mm.

  The gas 3 supplied to the space 52 is released into the liquid 2 in the reaction tank 15 through the opening 51. The released gas 3 is diffused into the liquid 2 as bubbles. At this time, the opening 51 has a function of determining the upper limit of the size of the bubble.

  The insulator 50 is made of, for example, alumina ceramic. Alternatively, the insulator 50 may be made of magnesia, zirconia, quartz, yttrium oxide, or the like.

  The insulator 50 is not limited to a cylindrical body, but may be a rectangular cylindrical body. Further, the insulator 50 is held by the first holding portion 35, but may be fixed to the wall surface of the reaction tank 15. Further, a gap between the insulator 50 and the first holding portion 35 or a gap between the insulator 50 and the wall surface of the reaction tank 15 may be filled with an adhesive such as an epoxy adhesive. Accordingly, it is possible to prevent the liquid 2 from penetrating into the insulator 50 from the gap and destabilizing the discharge.

[1-2-9. Gas supply pump]
The gas supply pump 60 is an example of a gas supply device that discharges the gas 3 into the liquid 2 through the opening 51 by supplying the gas 3 into the insulator 50. The gas supply pump 60 is connected to, for example, the screw portion 32 of the first electrode 30. The gas supply pump 60 takes in, for example, ambient air and supplies the gas 3 to the space 52 via the through hole 34 of the screw portion 32. The gas supply pump 60 may supply not only air but also argon, helium, nitrogen gas, oxygen gas, or the like.

  In the present embodiment, the flow rate of the gas 3 supplied by the gas supply pump 60 is 0.5 L / min or more. When the gas supply pump 60 supplies the gas 3, the gas 3 pushes out the liquid 2 stored in the space 52 from the opening 51, and the gas 3 covers the electrode unit 31. The gas 3 is released into the liquid 2 in the reaction tank 15 through the opening 51.

[1-2-10. Liquid supply pump]
The liquid supply pump 70 is an example of a liquid supply device that circulates the liquid 2 between the processing tank 10 and the reaction tank 15 via the piping unit 20. In the present embodiment, the liquid supply pump 70 is arranged in the middle of the piping section 20.

[1-2-11. Power supply]
The power supply 80 generates the plasma 4 by applying a voltage between the first electrode 30 and the second electrode 40. Specifically, the power supply 80 applies a pulse voltage or an AC voltage between the first electrode 30 and the second electrode 40.

  For example, the voltage to be applied is a positive high voltage pulse of 2 kV to 50 kV / cm, 1 Hz to 100 kHz. The voltage waveform may be, for example, any of a pulse shape, a half sine waveform, and a sine waveform. The value of the current flowing between the first electrode 30 and the second electrode 40 is, for example, 1 mA to 3 A. Here, as an example, the power supply 80 applies a positive pulse voltage having a frequency of 30 kHz and a peak voltage of 4 kV.

[1-3. motion]
Subsequently, an operation of the liquid processing apparatus 1 according to the present embodiment will be described.

  In the liquid processing apparatus 1 according to the present embodiment, the gas supply pump 60 supplies the gas 3 while the liquid supply pump 70 circulates the liquid 2. The gas 3 supplied by the gas supply pump 60 is supplied to the space 52 through the through hole 34 of the screw portion 32. The liquid 2 filling the space 52 before the supply of the gas 3 is discharged into the liquid 2 in the reaction tank 15 through the opening 51. For example, the flow rate of the gas 3 is 0.8 L / min. The gas 3 covers the electrode portion 31 of the first electrode 30 by filling the space 52.

  The power supply 80 applies a voltage between the first electrode 30 and the second electrode 40. For example, a positive pulse voltage having a frequency of 30 kHz and a peak voltage of 4 kV is applied. As a result, a discharge is generated in the gas 3 (bubble) covering the first electrode 30 from the end face 33 of the first electrode 30, and the plasma 4 is generated. Active species are generated by the plasma 4, and the generated active species is taken into the liquid 2. Since the liquid 2 is circulating, the active species can be distributed throughout the liquid 2.

[1-4. Effects etc.]
[1-4-1. Effect of distance (width d1) between first electrode and insulator on plasma]
In the liquid processing apparatus 1 according to the present embodiment, the distance between the side surface of the first electrode 30 and the inner side surface of the insulator 50 is 1 mm or more, for example, 3 mm or less.

  As described above, in the liquid processing apparatus 1, the distance between the outer surface of the first electrode 30 and the inner surface of the insulator 50 (that is, the width d1 of the space 52) is 1 mm or more and is distant. Therefore, a dielectric barrier discharge and a creeping discharge between the insulator 50 and the first electrode 30 are less likely to occur. Therefore, the surface of the insulator 50 is less likely to be exposed to the plasma generated by these discharges, so that the deposition of silica on the inner surface of the insulator 50 is suppressed.

  FIG. 6 is a diagram showing a result of observing the first electrode 30 and the insulator 50 according to the present embodiment from the opening 51 side. Specifically, FIG. 6 shows that after using 500 cc of water having a silica concentration of 72 ppm as the liquid 2, the power supply 80 applies a voltage between the first electrode 30 and the second electrode 40 for one hour. , An opening 51 is shown. In FIG. 6, the end face 33 of the first electrode 30 is partially photographed, and a white portion is shown near the center of the dashed circle.

  In the liquid processing apparatus 1 according to the present embodiment, as shown in FIG. 6, no precipitate is seen on the inner side surface near the opening 51 of the insulator 50. Even if a small amount of precipitate adheres to the inner surface of the insulator 50, the instability of discharge hardly occurs because the width d1 is 1 mm or more.

  In the liquid processing apparatus 1, the width d1 is 3 mm or less and is not too far. For this reason, the gas 3 supplied to the space 52 can easily cover the electrode portion 31, so that the shape of the gas-liquid interface is easily stabilized, and the discharge is stabilized.

  As described above, the liquid processing apparatus 1 according to the present embodiment can stably discharge and generate the plasma 4 stably.

[1-4-2. Influence of retreat d2 on plasma]
Next, the relationship between the distance (width d1) between the side surface of the first electrode 30 and the inner surface of the insulator 50 and the amount d2 of retreat from the opening 51 of the end surface 33 of the first electrode 30 will be described. .

  Here, 500 cc of water having a silica concentration of 88 ppm is used as the liquid 2, and after the power supply 80 applies a voltage between the first electrode 30 and the second electrode 40 for 1 hour, the discharge becomes unstable. It was observed whether to do. The flow rate of the gas 3 supplied by the gas supply pump 60 was set to 1.0 L / min, the inner diameter of the insulator 50 was set to 3 mm, and the diameter of the electrode portion 31 of the first electrode 30 and the position of the end face 33 were changed. Observation was made for each combination of the width d1 and the receding amount d2. The result of the observation is shown in FIG.

  FIG. 7 shows the stability of the plasma 4 with respect to the distance (width d1) between the first electrode 30 and the insulator 50 and the retreat amount d2 of the end face 33 of the first electrode 30 according to the present embodiment. FIG. In FIG. 7, the horizontal axis is the width d1, and the vertical axis is the retreat amount d2. Further, a circle (）) indicates that the amount of precipitated silica was extremely small and the discharge was stable. Crosses (x) indicate that silica was precipitated and the discharge was unstable. In addition, when the light due to the discharge is blinking visually, it is determined that the discharge is unstable, and when the light due to the discharge can be continuously confirmed at a predetermined luminance, it is determined that the discharge is stable. It was judged.

  As shown in FIG. 7, when the width d1 was smaller than 1 mm (specifically, about 0.1 mm and 0.3 mm), the discharge was not stable regardless of the receding amount d2. When the width d1 was 1.1 mm, when the receding amount d2 was 2 mm and 3 mm, no precipitation of silica was observed, and the discharge was stabilized.

  On the other hand, as shown in FIG. 8, even when the width d1 was 1.1 mm, when the receding amount d2 was 4 mm, a precipitate 90x of silica was observed, and the discharge was not stable. FIG. 8 is a diagram showing a result of observing the first electrode 30 and the insulator 50 from the opening 51 side when the width d1 shown in FIG. 7 is 1.1 mm and the retreat amount d2 is 4 mm. .

  As described above, in the liquid processing apparatus 1 according to the present embodiment, the end surface 33 of the first electrode 30 is recessed from the opening 51 of the insulator 50 by 0 mm or more and 3 mm or less.

  Accordingly, a discharge is easily generated between the end surface 33 of the first electrode 30 and the gas-liquid interface, and the generation of a discharge between the first electrode 30 and the insulator 50 can be suppressed. Therefore, since the generation of the precipitate 90x such as silica can be suppressed, the liquid processing apparatus 1 can more stably discharge and generate the plasma 4 more stably.

  As shown in FIG. 7, when the width d1 was 2.6 mm and the receding amount d2 was 3 mm, no precipitation of silica was observed and the discharge was stabilized. Therefore, as described above, if the width d1 is 3 mm or less, the plasma 4 can be generated stably. Although not shown, when the width d1 was larger than 3 mm, the shape of the gas-liquid interface was not stable, and the discharge was not stable.

  Further, although the retreat amount d2 is described here, the plasma 4 can be stably generated even when the end face 33 of the first electrode 30 projects from the opening 51. This is because most of the discharge occurs between the end surface 33 and the gas-liquid interface, and the discharge between the electrode portion 31 and the inner surface of the insulator 50 is suppressed.

  However, when the protrusion amount d3 of the end face 33 is 3 mm or more, it is difficult for the gas 3 to cover the entire electrode portion 31 including the end face 33, and the discharge becomes difficult to stabilize. Therefore, when the protrusion amount d3 is equal to or greater than 0 mm and equal to or less than 3 mm, the discharge is stable, and the plasma 4 can be stably generated. For example, if the gas 3 can be stably covered with the gas 3 by increasing the supply amount of the gas 3, the protrusion amount d3 may be larger than 3 mm.

[1-4-3. Effect of gas flow rate on plasma]
Next, the relationship between the retreat amount d2 and the flow rate (air flow rate) of the gas 3 supplied by the gas supply pump 60 will be described.

  Here, discharge was observed for each combination of the retreat amount d2 and the air flow rate under the same conditions as those shown in FIGS. 7 and 8 while changing the retreat amount d2 and the air flow rate. The result of the observation is shown in FIG.

  FIG. 9 is a diagram showing the stability of the plasma 4 with respect to the retreat amount d2 of the end face 33 of the first electrode 30 and the air flow rate according to the present embodiment. In FIG. 9, the horizontal axis is the retreat amount d2, and the vertical axis is the air flow rate. The meanings of the circles (○) and the crosses (X) are the same as those in FIG. Here, the distance (width d1) between the electrode portion 31 and the inner surface of the insulator 50 is 1.1 mm.

  As shown in FIG. 9, when the air flow rate was 0.5 L / min, when the retreat amount d2 was in the range of 1 mm to 3 mm, no precipitation of silica was observed, and the discharge was stabilized. When the retreat amount d2 was 4 mm and the air flow rate was 0.5 L / min, precipitation of silica was observed and the discharge became unstable. On the other hand, even when the retreat amount d2 was 4 mm, when the air flow rate was 1.0 L / min, no precipitation of silica was observed, and the discharge was stabilized.

  FIGS. 10A and 10B are diagrams showing the results of observing the first electrode 30 and the insulator 50 from the side when the retreat amount d2 shown in FIG. 9 is 4 mm. Specifically, FIG. 10A shows a case where the air flow rate is 0.3 L / min, and FIG. 10B shows a case where the air flow rate is 1.0 L / min.

  In FIGS. 10A and 10B, transparent quartz is used as a material of the insulator 50 to facilitate observation from the side. In addition, in order to make the positional relationship between the first electrode 30 and the space 52 easy to understand, the outline shapes of the first electrode 30 and the insulator 50 are shown by white solid lines.

  As can be seen by comparing FIGS. 10A and 10B, as the gas flow rate increases, the plasma 4 flows along the flow of the gas 3, and therefore, the amount of the plasma 4 spreading toward the insulator 50 (ie, in the lateral direction) increases. Less. As described above, by adjusting the flow rate of the gas 3, the generation region of the plasma 4 can be controlled. Specifically, the amount of exposure of the plasma 4 to the insulator 50 can be controlled by adjusting the flow rate of the gas 3.

  From the above, in the liquid processing apparatus 1 according to the present embodiment, the flow rate of the gas 3 supplied by the gas supply pump 60 is 0.5 L / min or more.

  With this, as the flow rate of the gas 3 increases, the spread of the plasma 4 in the direction of the insulator 50 can be suppressed, so that the surface of the insulator 50 is less likely to be exposed to the plasma 4. Therefore, since the generation of the precipitate 90x such as silica can be suppressed, the liquid processing apparatus 1 can more stably discharge and generate the plasma 4 more stably.

  In addition, as the flow rate of the gas 3 is smaller, the spread of the plasma 4 is larger. However, when the end face 33 of the electrode portion 31 protrudes from the opening 51, even if the plasma 4 spreads, the plasma 4 remains inside the insulator 50. Barely touches the sides. Therefore, for example, when the end face 33 protrudes from the opening 51 or when the retreat amount d2 is small, the flow rate of the gas 3 may be smaller than 0.5 L / min.

(Embodiment 2)
Next, a second embodiment will be described. Note that, in the following Embodiment 2, a description will be made focusing on portions different from Embodiment 1, and description of the same structure, operation, and effect as those in Embodiment 1 may be omitted.

[2-1. Constitution]
FIG. 11 is a diagram showing a configuration of the liquid processing apparatus 101 according to the present embodiment. As shown in FIG. 11, the liquid processing apparatus 101 includes a first insulator 150 and a second insulator 155 instead of the insulator 50 as compared with the liquid processing apparatus 1 according to the first embodiment. The points are different. Also, the difference is that the first electrode 30 is attached to the upper surface of the reaction tank 15 instead of the lower surface, but the present invention is not limited to this. The first electrode 30 may be attached to a lower surface or a side surface of the reaction tank 15.

[2-1-1. First insulator]
The first insulator 150 is substantially the same as the insulator 50 according to the first embodiment, except that a second insulator 155 is connected to the rear end side. Specifically, the first insulator 150 is a tubular insulator that surrounds not the entire electrode portion 31 of the first electrode 30 but only a part thereof. For example, the first insulator 150 is a cylindrical body having an opening 151, and surrounds the side surface on the tip (front end) side of the electrode portion 31 of the first electrode 30 via the space 152.

  The first insulator 150 is arranged coaxially with the electrode unit 31. The first distance D1, which is the distance between the inner side surface of the first insulator 150 and the side surface of the first electrode 30 (specifically, the electrode portion 31), is the distance D1 of the space 52 according to the first embodiment. It is the same as the width d1. The first distance D1 is 1 mm or more. The first distance D1 may be, for example, 1 mm or more and 3 mm or less.

  The first insulator 150 is fixed to, for example, a wall surface of the reaction tank 15. The gap between the first insulator 150 and the wall surface of the reaction tank 15 may be filled with an adhesive such as an epoxy adhesive. Alternatively, the first insulator 150 may be fixed and supported by the second insulator 155. In this embodiment, the rear end of the first insulator 150 is connected to the front end of the second insulator 155.

  The material, size, function, and the like of the first insulator 150 are the same as, for example, the insulator 50 according to the first embodiment.

[2-1-2. Second insulator]
The second insulator 155 is a cylindrical insulator arranged so as to surround the side surface of the first electrode 30 via the space 156. The second insulator 155 is connected to the end of the first insulator 150 opposite to the end face on the distal end side so that the insides of the second insulator 155 and the first insulator 150 communicate with each other. ing. Specifically, the space 152 of the first insulator 150 and the space 156 of the second insulator 155 communicate with each other.

  The second insulator 155 is a cylindrical body that surrounds a rear end side surface of the electrode portion 31 of the first electrode 30. Note that the rear end side (or the front end side) of the electrode unit 31 is the upstream side (or the downstream side) in the direction in which the gas supplied by the gas supply pump 60 flows. That is, in FIG. 11, the lower side is the front end side, and the upper side is the rear end side. The second insulator 155 surrounds a portion on the rear end side of the electrode portion 31 surrounded by the first insulator 150. That is, the second insulator 155 does not have to surround the end face on the rear end side of the electrode section 31, specifically, the screw section 32.

  A second distance D2, which is a distance between the side surface of the first electrode 30 and the inner side surface of the second insulator 155, is larger than the first distance D1. The second distance D2 is a distance determined according to a voltage applied between the first electrode 30 and the second electrode 40. That is, the second distance D2 is a distance determined according to the voltage applied by the power supply 80. Details will be described later.

  The second insulator 155 is, for example, a cylindrical body, but is not limited to this. For example, the second insulator 155 may be a rectangular cylinder. Specifically, as shown in FIG. 11, the second insulator 155 is a cylindrical body having both the front end and the rear end closed. A circular opening having a diameter substantially corresponding to the outer diameter of the first insulator 150 is provided at the tip end side of the second insulator 155, and the first insulator 150 is connected to the opening. . On the rear end side of the second insulator 155, a circular opening having a diameter substantially matching the outer diameter of the screw portion 32 is provided, and the screw portion 32 is fixed to the opening. Here, a female screw to be screwed with the male screw of the screw portion 32 may be provided in the opening on the rear end side.

  The second insulator 155 is, for example, a flat cylindrical body, but is not limited thereto. The second insulator 155 may be a cylindrical body that is long in the axial direction of the electrode unit 31. Further, the second insulator 155 may be, for example, a rectangular parallelepiped or a cube having a hollow inside.

  The member forming the second insulator 155 may be an insulator, for example, acrylic resin such as PMMA (Polymethyl methacrylate), PPS (Polyphenylenesulfide), PEEK (Polyetheretherketone), alumina ceramic, quartz, magnesia, zirconia, etc. May be configured.

  Note that the first insulator 150 and the second insulator 155 may be made of different materials. Alternatively, the first insulator 150 and the second insulator 155 may be integrally formed of the same material.

[2-2. Effects etc.]
Hereinafter, the effect of the present embodiment by providing the second insulator 155 on the rear end side of the first insulator 150 will be described, including the circumstances leading to the present embodiment.

[2-2-1. Process leading to the present embodiment and main features of the present embodiment]
As in the first electrode 30 of the present disclosure, when a high voltage is applied through a space to an electrode surrounded by a cylindrical insulator having an opening to generate plasma, the opening of the insulator is reduced. A Maxwell stress is applied to the gas-liquid interface of the liquid to be processed in the vicinity according to the electric field generated there. As a result, the liquid to be treated infiltrates the inside of the insulator along the inner surface from the opening of the insulator. As a result, the liquid to be treated that has entered the inside of the insulator reaches the base of the electrode, causing a phenomenon that a short circuit or discharge becomes unstable.

  On the other hand, in the liquid treatment apparatus 101 according to the present embodiment, the distal end side of the side surface of the first electrode 30 is surrounded by the cylindrical first insulator 150, and the base side of the first electrode 30 is located at the base side. It was surrounded by a cylindrical second insulator 155. Further, the rear end of the first insulator 150 and the front end of the second insulator 155 were connected.

  At this time, the second distance D2 between the side surface of the first electrode 30 and the inner side surface of the second insulator 155 is defined as the distance between the side surface of the first electrode 30 and the inner side surface of the first insulator 150. The distance is set to be larger than the first distance D1 between them. Thus, the electric field generated on the inner surface of the second insulator 155 is smaller than the electric field generated on the inner surface of the first insulator 150, and the Maxwell stress applied to the inner surface of the second insulator 155 is also reduced. Become smaller. Therefore, the liquid 2 that has entered through the opening 151 of the first insulator 150 is less likely to enter the inside of the second insulator 155, and the liquid 2 is prevented from reaching the root of the first electrode 30. Can be.

  At this time, the second distance D2 is, for example, a distance determined according to a value of a voltage applied between the first electrode 30 and the second electrode 40. From the experimental results and simulation results described later, for example, when the voltage value is 5 kV or less, the second distance D2 may be set to 2.6 mm or more. If the value of the voltage is 5 kV or more, the second distance D2 may be set to 5.0 mm or more. Thereby, the electric field is sufficiently relaxed on the inner surface of the second insulator 155. Thereby, a high suppression effect can be expected with respect to infiltration of the liquid 2 into the inner surface of the second insulator 155.

[2-2-2. Experimental result]
In this embodiment, a positive pulse voltage having a peak voltage of 5 kV is applied between the first electrode 30 and the second electrode 40 to generate plasma between the first electrode 30 and the liquid 2. In this case, it was observed whether or not the liquid 2 penetrated into the inside of the first insulator 150 and the inside of the second insulator 155. At this time, tap water was used as the liquid 2.

  Here, as a comparative example, the first distance D1 and the second distance D2 were both set to 1.1 mm, and discharge was performed continuously for 2 hours. In this case, it was confirmed that the liquid 2 had penetrated into the inner surfaces of the first insulator 150 and the second insulator 155 about 50 minutes after the start of the discharge.

  On the other hand, the same experiment was performed when the first distance D1 was 1.1 mm and the second distance D2 was 2.6 mm. The results of the experiment are shown in FIGS.

  FIG. 12 is a diagram illustrating a result of observing the second insulator 155 of the liquid processing apparatus 101 according to the present embodiment from the side. FIG. 13 is a diagram illustrating a result of observing the first insulator 150 of the liquid processing apparatus 101 according to the present embodiment from the side. Here, the first insulator 150 and the second insulator 155 are each formed using transparent quartz so that the inside can be visually recognized.

  12 is a region surrounded by the second insulator 155, that is, a region corresponding to the space 156. A black portion extending in the vertical direction substantially at the center of the space 156 indicates the electrode portion 31 of the first electrode 30. A substantially rectangular area (white two-dot chain line) surrounding the electrode portion 31 (not clearly shown in the figure) in the lower part of FIG. 12 is an area surrounded by the first insulator 150, that is, This is an area corresponding to the space 152. The portion surrounding the electrode portion 31 in the upper part of FIG.

  In FIG. 12, the liquid 2 has not penetrated into the space 156, as can be seen from the fact that the electrode portion 31 of the space 156 is clearly visible. On the other hand, the tip side of the electrode portion 31 surrounded by the first insulator 150 cannot be clearly seen, indicating that the liquid 2 has penetrated.

  A rectangular region (cylindrical portion, dashed white line) extending in the vertical direction at the center of FIG. 13 indicates the first insulator 150. The black portion extending vertically along the center of the first insulator 150 is the electrode portion 31 of the first electrode 30. The white area extending downward from the lower end of the electrode part 31 is the plasma 4 generated by the discharge. Note that the black ring-shaped portion extending in the left-right direction at the center of FIG. 13 is another member that supports the first insulator 150.

  As in FIG. 12, since it is difficult to clearly see the electrode portion 31 inside the first insulator 150, the liquid 2 is filled inside the first insulator 150 (space 152, white two-dot chain line). You can see that it is invading. Although it is difficult to confirm from FIG. 13, it was confirmed that water droplets adhered along the inner side surface of the first insulator 150.

  As described above, by making the second distance D2 larger than the first distance D1, the liquid 2 that has entered the first insulator 150 does not enter the second insulator 155. I understand. That is, it was confirmed that the provision of the second insulator 155 was able to suppress the infiltration of the liquid 2 into the root of the electrode portion 31.

  Further, a discharge experiment was performed for two hours continuously for each of three cases where the first distance D1 was 2.6 mm and the second distance D2 was 4.6 mm, 7.1 mm and 9.6 mm. At this time, in an environment where the second distance D2 is 2.6 mm or more, no infiltration of the liquid 2 into the inside of the second insulator 155 was observed. From this result, it is understood that the electric field is sufficiently reduced on the inner surface of the second insulator 155.

[2-2-3. simulation result]
Here, a simulation result regarding the relationship between the applied voltage and the second distance D2 will be described. Specifically, a voltage of 5 kV is applied between the first electrode 30 and the second electrode 40, and when the second distance D2 is 2.6 mm, the inner surface of the second insulator 155 Was calculated by simulation to find that it was 1.6 × 10 ⁶ V / m. Since the value of the Maxwell stress decreases as the value of the electric field decreases, at least in an environment where an electric field of 1.6 × 10 ⁶ V / m or less is generated, the infiltration of the liquid 2 into the inside of the second insulator 155 is observed. It is not considered.

  FIG. 14 shows the relationship between the second distance D2 between the first electrode 30 and the second insulator 155 according to the present embodiment and the electric field value generated on the inner side surface of the second insulator 155. It is a figure showing the result of simulation. Specifically, FIG. 14 shows the results of the electrostatic field simulation in the case where the applied voltage between the first electrode 30 and the second electrode 40 is 2.5 kV, 5 kV, and 10 kV. . Each plot shows the case where the second distance D2 is 1.1 mm, 2.6 mm, 4.9 mm, 7.1 mm, and 9.6 mm.

The simulation results shown in FIG. 14 show how the absolute value of the electric field generated on the inner surface of the second insulator 155 changes according to the second distance D2. The dashed line in FIG. 14 represents the threshold value (1.6 × 10 ⁶ V / m) of the electric field at which it is considered that the liquid 2 does not enter the inner surface of the second insulator 155 based on the above-described experimental results. I have. If it is below the broken line, it is possible to prevent the liquid 2 from entering the inside of the second insulator 155. If it is above the broken line, the liquid 2 may enter the second insulator 155.

From the simulation results shown in FIG. 14, by setting the second distance D2 to 5 mm or more, the magnitude of the electric field generated on the inner surface of the second insulator 155 can be reduced even when the applied voltage is 10 kV or less. It can be 1.6 × 10 ⁶ V / m or less. That is, infiltration of the liquid 2 into the second insulator 155 can be suppressed.

When the applied voltage is 5 kV or less and not large, the magnitude of the electric field generated on the inner surface of the second insulator 155 is set to 1.6 × by setting the second distance D2 to 2.6 mm or more. It can be 10 ⁶ V / m or less.

  As described above, according to the present embodiment, the second distance D2 is set according to the value of the voltage applied between first electrode 30 and second electrode 40, whereby the second distance D2 is set. The electric field generated on the inner surface of the insulator 155 can be sufficiently reduced. As a result, it is possible to suppress the liquid 2 from entering the inside of the second insulator 155 and to suppress a short circuit between the liquid 2 and the first electrode 30, so that stable plasma generation is possible.

(Embodiment 3)
Next, a third embodiment will be described. In the following, the third embodiment will be described focusing on portions different from the first embodiment, and the description of the same structure, operation, and effect as the first embodiment may be omitted.

[3-1. Constitution]
FIG. 15 is a diagram illustrating a configuration of a liquid processing apparatus 201 according to the present embodiment. As shown in FIG. 15, the liquid processing apparatus 201 is different from the liquid processing apparatus 1 according to Embodiment 1 in that the first electrode 230 and the first holding unit 35 are replaced with the first electrode 230 and The difference is that a first holding unit 235 is provided.

  FIG. 16 is a cross-sectional view illustrating the first electrode 230 and the insulator 50 according to the present embodiment. FIG. 17 is a front view of the first electrode 230 and the insulator 50 according to the present embodiment when viewed from the distal end side. Note that FIG. 17 does not show the first holding unit 235. In FIG. 17, the same hatching as that of each member in FIG. 16 is attached to each member in order to easily understand the schematic shape of each member.

[3-1-1. First electrode]
The first electrode 230 includes an electrode portion 231 and a screw portion 232, as shown in FIGS. The first electrode 230 is one of a pair of electrodes for generating the plasma 4. The first electrode 230 is used as a reaction electrode, and the plasma 4 is generated around the first electrode 230.

  The electrode part 231 is a long cylindrical electrode part provided on the tip side of the first electrode 230. The length (axial direction) of the electrode portion 231 is, for example, the same as the length (axial direction) of the insulator 50 or longer than the length of the insulator 50. When the electrode portion 231 is arranged so that the end surface 233 on the front end side is receded from the opening 51 of the insulator 50, the rear end protrudes from the opening 54 on the rear end side of the insulator 50. For example, the length of the electrode portion 231 is 15 mm or more and 30 mm or less, but is not limited thereto.

  The screw part 232 is an example of a support part provided on the rear end side of the electrode part 231 and supporting the electrode part 231. The screw portion 232 is a columnar portion that is thicker than the electrode portion 231. As shown in FIG. 17, a gas supply hole 234 is provided in the screw portion 232.

  The gas supply holes 234 are holes through which the gas 3 supplied by the gas supply pump 60 passes. The gas supply hole 234 is, for example, a through hole that passes through the screw portion 232 in the axial direction. In the present embodiment, the opening width of the gas supply hole 234 and the inner diameter of the insulator 50 are substantially the same.

  Specifically, as shown in FIG. 17, the gas supply hole 234 has a cross shape (cross shape) in a front view. The electrode portion 231 is press-fitted into the center of the cross-shaped gas supply hole 234. Thereby, the screw part 232 supports the electrode part 231. The gas supply holes 234 are formed radially around the electrode portion 231 in a front view. Specifically, the gas supply hole 234 has two through holes 234a and 234b. Each of the two through holes 234a and 234b has a long rectangular opening in the radial direction of the screw portion 232, and is orthogonal to the center of the screw portion 232 in a front view. The length of each of the rectangular openings of the through holes 234 a and 234 b matches the inner diameter of the insulator 50. The length of the rectangular opening is, for example, the length along the radial direction of the screw portion 232, and is the opening width of the gas supply hole 234. The width of the rectangular opening is, for example, shorter than the diameter of the electrode unit 231.

  The shape of the gas supply hole 234 is not limited to the illustrated example. For example, the gas supply hole 234 may be only one of the single through holes 234a and 234b, or may be a combination of three or more through holes.

[3-1-2. First holding unit]
The first holding unit 235 is a member for holding the first electrode 230. In the present embodiment, the first holding unit 235 holds the first electrode 230 and the insulator 50, and is attached to a predetermined position of the reaction tank 15.

  The first holding portion 235 holds the screw portion 232 as shown in FIG. Specifically, a female screw (not shown) is provided on the inner surface of the first holding portion 235, and is screwed to a male screw (not shown) provided on the outer surface of the screw portion 232.

  The first holding portion 235 is a cylindrical body having an inside diameter substantially the same as the inside diameter of the insulator 50. Specifically, as shown in FIG. 16, the first holding unit 235 has a space 236 that communicates with the gas supply hole 234 and the space 52 of the insulator 50. The inner diameter of the space 236 and the inner diameter of the space 52 substantially match. The space 236 is a part of a flow path through which the gas 3 supplied from the gas supply pump 60 flows. The space 236 stabilizes the flow of the gas 3 discharged from the gas supply hole 234 and introduces the gas 3 into the space 52 of the insulator 50. The length of the space 236 in the axial direction is not particularly limited, but the longer the space, the more the flow of the gas 3 can be stabilized.

[3-2. Effects etc.]
Hereinafter, the effect of the present embodiment by making the opening width of the gas supply hole 234 approximately equal to the inner diameter of the insulator 50 will be described, including the circumstances leading up to the present embodiment.

[3-2-1. Background to the present embodiment]
As described in the present disclosure, when the distance (the width d1 of the space 52) between the side surface of the electrode unit 31 and the inner side surface of the insulator 50 is increased, that is, when the inner diameter of the insulator 50 is increased, The size of the gas supply hole for introducing the airflow into the insulator 50 may be smaller than the inner diameter of the insulator 50. At this time, the flow width of the gas 3 supplied from the gas supply hole changes discontinuously at the connection portion between the gas supply hole and the insulator 50. Due to the discontinuous change in the flow width of the gas 3, a swirling flow of the gas 3 is generated near the inner surface of the insulator 50, and the liquid 2 entrained in the swirling flow travels along the inner surface of the insulator 50. And enters the inside of the insulator 50.

  For example, FIG. 18 is a diagram illustrating a result of simulating (numerical calculation) the position of the gas-liquid interface near the insulator 50 according to the comparative example of the present embodiment. FIG. 19 is a diagram showing the flow velocity distribution of the gas 3 in the same simulation as FIG. 18 and 19, the screw portion 232x and the insulator 50 are shown as having no thickness for easy understanding. The same applies to FIGS. 20 and 21 described later.

  Here, the opening width of the gas supply hole 234x is 0.8 mm, the inner diameter of the insulator 50 is 3.0 mm, the flow rate of the gas 3 supplied from the gas supply hole 234x is 1.5 L / min, and the liquid 2 (tap water). Are calculated assuming that the flow rate circulating in the reaction tank is 1.0 [L / min].

  As shown in FIGS. 18 and 19, it can be seen that a swirling flow occurs near the inner surface of the insulator 50. Further, it can be seen that the gas-liquid interface enters the inside of the insulator 50 through the opening 51 in response to the generation of the swirling flow.

  When the liquid 2 enters the inside of the insulator 50, the electrode portion 31 and the liquid 2 may come into contact with each other. For this reason, there is a problem that a short circuit occurs between the first electrode 30 and the liquid 2 (the second electrode 40), and that the discharge becomes unstable.

[3-2-2. Main features according to the present embodiment]
On the other hand, in the liquid processing apparatus 201 according to the present embodiment, as shown in FIGS. 16 and 17, since the opening width of the gas supply hole 234 and the inner diameter of the insulator 50 are substantially the same, The flow velocity distribution of the gas 3 supplied to the inside of the body 50 is stabilized, and the shape of the bubble formed at the opening 51 of the insulator 50 is stabilized.

  FIG. 20 is a diagram showing the result of simulating (numerical calculation) the position of the gas-liquid interface near the insulator 50 according to the present embodiment. FIG. 21 is a diagram showing the flow velocity distribution of the gas 3 in the same simulation as FIG.

  At this time, the opening width of the gas supply hole 234 is 3.0 mm, the inner diameter of the insulator 50 is 3.0 mm, the flow rate of the gas 3 supplied from the gas supply hole 234 is 1.5 L / min, and the liquid 2 is supplied to the reaction tank 15. Numerical calculations are performed assuming that the flow rate circulating in the inside is 1.0 L / min.

  As shown in FIGS. 20 and 21, it can be seen that the flow velocity distribution of the gas 3 generated inside the insulator 50 is uniform. As a result, as shown in FIG. 20, the gas-liquid interface is located in the vicinity of the opening 51 of the insulator 50 and hardly penetrates into the inside of the insulator 50.

  As described above, in the liquid processing apparatus 201 according to the present embodiment, since the uniform flow velocity distribution of the gas 3 is generated inside the insulator 50, the liquid 2 is not drawn into the insulator 50. Therefore, a short circuit between the liquid 2 and the vicinity of the root of the first electrode 30 can be suppressed, and stable plasma generation is possible.

  In the present embodiment, screw portion 232 may be inserted inside insulator 50. That is, the gas 3 that has passed through the gas supply holes 234 without providing the space 236 is directly introduced into the space 52 of the insulator 50 without passing through the space 236.

[3-3. Modification]
Subsequently, a modified example capable of suppressing the generation of the swirling flow inside the insulator 50 will be described with reference to FIG. FIG. 22 is a cross-sectional view showing the vicinity of the first electrode 230 and the insulator 50 of the liquid processing apparatus according to the present modification.

  As shown in FIG. 22, the liquid processing apparatus according to the present modification includes a bottomed cylindrical body 332 and an inlet 335 instead of the threaded part 232 of the first electrode 230.

  The bottomed tubular body 332 is a bottomed tubular member having substantially the same opening width as the insulator 50. For example, the bottomed cylinder 332 is a bottomed cylinder having a space 333 and a circular opening 334. The bottomed cylindrical body part 332 functions as a flow path changing part for changing the traveling direction of the gas 3 supplied by the gas supply pump 60 in the space 333 and stably supplying the inside of the insulator 50.

  The bottomed cylindrical body 332 is provided on the rear end side of the insulator 50. Specifically, the bottomed cylindrical body 332 is connected to the rear end of the insulator 50 so as to be located coaxially with the insulator 50. The space 333 of the bottomed cylindrical body 332 and the space 52 of the insulator 50 communicate with each other. The space 333 and the space 52 constitute a flow path of the gas 3.

  For example, as shown in FIG. 22, the opening 334 of the bottomed cylindrical body 332 is connected to the opening 54 on the rear end side of the insulator 50. The opening 54 and the opening 334 have the same shape and the same size. That is, the bottomed cylindrical body portion 332 and the insulator 50 are connected so that the flow path width is substantially uniform.

  The material forming the bottomed cylindrical body 332 is, for example, an insulator. Specifically, the bottomed cylindrical body portion 332 may be made of, for example, an acrylic resin such as PMMA (Polymethyl methacrylate), PPS (Polyphenylene sulfide), PEEK (Polyetheretherethertone), alumina ceramic, quartz, magnesia, zirconia, or the like. Good.

  The inlet 335 is an opening for introducing the gas 3 supplied by the gas supply pump 60 into the insulator 50. The inlet 335 is not orthogonal to the axial direction of the insulator 50. Specifically, the inlet 335 is provided on the side wall of the bottomed cylindrical body 332, and is substantially parallel to the axial direction of the insulator 50. In other words, the inflow direction of the gas 3 when passing through the inlet 335 (that is, the direction orthogonal to the inlet 335) is substantially orthogonal to the axial direction. Note that the inlet 335 may be inclined with respect to the axial direction of the insulator 50. That is, the inflow direction of the gas 3 when passing through the inlet 335 may intersect the axial direction of the insulator 50.

  The gas 3 supplied into the bottomed cylindrical body 332 via the inlet 335 changes its traveling direction in the space 333 of the bottomed cylindrical body 332 and proceeds toward the insulator 50. Since the opening 334 of the bottomed cylindrical body 332 and the opening 54 on the rear end side of the insulator 50 have the same shape and the same size, the gas 3 is insulated without a discontinuous change in the flow path width. It travels inside the body 50 (space 52) along the axial direction, and is discharged into the liquid 2 from the opening 51.

  As described above, since there is no discontinuous change in the flow width of the gas 3 inside the insulator 50, a uniform flow velocity distribution of the gas 3 can be generated inside the insulator 50. Therefore, the generation of the swirling flow inside the insulator 50 is suppressed, so that the inflow of the liquid 2 can be suppressed. Thereby, according to the liquid processing apparatus according to the present modification, a short circuit between the liquid 2 and the first electrode 30 is suppressed, and stable plasma can be generated.

  In the present modification, the example in which the inlet 335 is provided on the side wall of the bottomed cylindrical body 332 provided on the rear end side of the insulator 50 has been described, but the present invention is not limited to this. The inlet 335 may be provided to penetrate the side wall of the insulator 50. That is, the insulator 50 may have a bottomed cylindrical shape in which the opening 54 on the rear end side is closed, and the inlet 335 may be provided on a side wall near the opening 54. Thus, the number of parts can be reduced, and the weight and cost of the liquid processing apparatus can be reduced.

  Further, in this modification, the insulator 50 and the bottomed cylindrical body 332 are directly connected. However, similarly to the configuration shown in FIG. A first holding unit 235 having a space 236 may be provided. In this case, the space 333, the space 236, and the space 52 have substantially the same diameter, and the flow width of the gas 3 can be made substantially constant.

(Other embodiments)
As described above, the liquid processing apparatus according to one or more aspects has been described based on the embodiments. However, the present disclosure is not limited to these embodiments. Unless departing from the gist of the present disclosure, various modifications conceivable by those skilled in the art are applied to the present embodiment, and forms configured by combining components in different embodiments are also included in the scope of the present disclosure. It is.

  For example, in the above embodiment, the case where the position of the end face 33 of the electrode unit 31 is variable by rotating the screw unit 32 has been described, but the present invention is not limited to this. The positional relationship between the electrode unit 31 and the insulator 50 may be fixed. Specifically, the first holding portion 35 may not be provided with a female screw, and the screw portion 32 may not be provided with a male screw.

  In addition, for example, the example in which the first electrode 30 includes the electrode portion 31 and the screw portion 32 has been described, but the first electrode 30 may be a single rod-shaped electrode (cylindrical body). Alternatively, the first electrode 30 may be a prismatic or flat electrode. The same applies to the second electrode 40.

  Further, the liquid processing apparatus 1 does not include at least one of the first holding unit 35 and the second holding unit 45 and directly fixes at least one of the first electrode 30 and the second electrode 40 to the reaction tank 15. May be.

  Further, for example, in the above-described embodiment, the processing tank 10 and the reaction tank 15 are connected via the pipe unit 20 and the liquid 2 is circulated by the liquid supply pump 70, but the invention is not limited thereto. For example, the liquid processing apparatus 1 may generate the plasma 4 in a non-flowing liquid 2 (for example, still water) without including the processing tank 10 and the pipe unit 20.

  Further, for example, in the above-described embodiment, an example in which tap water containing silica is used as the liquid 2 has been described, but the present invention is not limited to this. The liquid 2 may be pure water or a liquid containing a mineral component such as calcium.

  In each of the above embodiments, various changes, replacements, additions, omissions, and the like can be made within the scope of the claims or the equivalents thereof.

  INDUSTRIAL APPLICATION This indication can be utilized as a liquid processing apparatus which can generate | occur | produce plasma stably, and can be utilized for a sterilization apparatus, a purification apparatus, etc., for example.

1, 101, 201 Liquid processing device 2 Liquid 3 Gas 4 Plasma 10 Processing tank 15 Reaction tank 20 Pipes 30, 30x, 230 First electrodes 31, 41, 231 Electrodes 32, 42, 232, 232x Screw 33, 53, 233 End surfaces 34, 234a, 234b Through holes 35, 235 First holding unit 40 Second electrode 45 Second holding unit 50, 50x Insulators 51, 54, 151, 334 Openings 52, 52x, 152, 156 236, 333 Space 60 Gas supply pump 70 Liquid supply pump 80 Power supply 90x Deposit 150 First insulator 155 Second insulator 234, 234x Gas supply hole 332 Bottomed cylindrical body 335 Inlet

Claims (16)

A first electrode and a second electrode at least partially disposed in the liquid to be treated;
A cylindrical first insulator disposed so as to surround a side surface of the first electrode via a space, and having an opening provided on an end surface in contact with the liquid to be treated;
A gas supply device that supplies the gas into the first insulator to release the gas into the liquid to be processed through the opening;
A power supply that generates plasma by applying a voltage between the first electrode and the second electrode,
A first distance that is a distance between a side surface of the first electrode and an inner side surface of the first insulator is 1 mm or more.
Liquid treatment equipment. The first distance is 1 mm or more and 3 mm or less;
The liquid processing apparatus according to claim 1. The end face of the first electrode is 0 mm or more and 3 mm or less, recedes or protrudes from the opening of the first insulator.
The liquid processing apparatus according to claim 1. A flow rate of the gas supplied by the gas supply device is 0.5 L / min or more;
The liquid processing apparatus according to claim 1. The first electrode has a long cylindrical electrode portion,
The first insulator is a long cylindrical body surrounding a side surface of the electrode unit,
The electrode portion and the first insulator are coaxially arranged,
The liquid processing apparatus according to claim 1. The first electrode is
A long cylindrical electrode part,
A support portion provided on the rear end side of the electrode portion and supporting the electrode portion, having a columnar support portion thicker than the electrode portion,
The support portion is provided with a gas supply hole through which gas supplied by the gas supply device passes,
The opening width of the gas supply hole and the inner diameter of the first insulator are substantially the same,
The liquid processing apparatus according to claim 1. An inlet provided on a rear end side of the first insulator, for introducing a gas supplied by the gas supply device into the inside of the first insulator;
The inflow direction of the gas when passing through the inlet intersects the axial direction of the first insulator,
The liquid processing apparatus according to claim 1. An opening width is further provided with a bottomed cylindrical body portion substantially the same as the first insulator,
The bottomed tubular body is connected to a rear end of the first insulator so as to be located coaxially with the first insulator,
The inlet is provided on a side wall of the bottomed cylindrical body,
An inflow direction of the gas when passing through the introduction port is substantially orthogonal to an axial direction of the first insulator.
The liquid processing apparatus according to claim 7. A cylindrical second insulator disposed so as to surround a side surface of the first electrode via a space,
The second insulator is connected to a rear end side of the first insulator so that the insides of the second insulator and the first insulator communicate with each other,
A second distance, which is a distance between a side surface of the first electrode and an inner side surface of the second insulator, is greater than the first distance.
The liquid processing apparatus according to claim 1. The second distance is a distance determined according to a value of a voltage applied by the power supply, and is a distance at which an electric field generated on the inner surface of the second insulator by the voltage is equal to or less than a predetermined value. is there,
The liquid processing apparatus according to claim 9. A value of the voltage applied between the first electrode and the second electrode is 5 kV or less;
The second distance is not less than 2.6 mm;
The liquid processing apparatus according to claim 9. A value of the voltage applied between the first electrode and the second electrode is 5 kV or more;
The second distance is 5 mm or more;
The liquid processing apparatus according to claim 9. The first electrode has a long cylindrical electrode portion,
The first insulator is a cylindrical body surrounding a side surface on a tip side of the electrode unit,
The second insulator is a cylindrical body surrounding a side surface on a rear end side of the electrode unit,
The electrode unit, the first insulator and the second insulator are coaxially arranged,
The liquid processing apparatus according to claim 9. The second insulator is a cylindrical body or a rectangular cylindrical body,
The liquid processing apparatus according to claim 13. The first insulator and the second insulator are made of different materials, respectively.
The liquid processing apparatus according to claim 9. The first insulator and the second insulator are integrally formed of the same material,
The liquid processing apparatus according to claim 9.