JP6949775B2 - Liquid plasma generator and liquid processing device - Google Patents

Description

The present invention relates to an in-liquid plasma generator in which an electric field is applied to a gas supplied in a liquid to generate plasma in the liquid, and a liquid processing apparatus using the same.

Many techniques for producing a liquid containing a chemically active active species have been proposed as a means for producing a reaction product and a means for detoxifying harmful substances and bacteria. For example, in the technique described in Patent Document 1, bubbles are generated in the water to be treated flowing through the dielectric tube, and a high voltage is applied between the electrodes arranged in the liquid to discharge the cells in the bubbles to generate plasma. Let me. Further, in the technique described in Patent Document 2, one electrode is provided outside the dielectric tube through which the liquid in which the gas is mixed flows, and the other electrode is provided inside the tube.

Japanese Unexamined Patent Publication No. 2015-116561 Japanese Unexamined Patent Publication No. 2013-206767

In the above-mentioned conventional technique, since at least one of the electrodes is in the liquid and an electric discharge is generated around the electrodes, the components of the electrodes exposed to the generated plasma may elute into the liquid. In addition, since the state of the liquid containing bubbles surrounding the electrode changes from moment to moment, the density and amount of generated plasma tend to become unstable. Therefore, there is room for improvement in the above-mentioned prior art in improving the plasma generation efficiency and the stability of plasma generation with respect to the input gas and energy.

The present invention has been made in view of the above problems, and provides a technique capable of generating highly efficient and stable plasma in a submerged plasma generator that generates plasma in a gas supplied in a liquid. The purpose.

One aspect of the submerged plasma generator according to the present invention is a housing that holds a liquid in an internal space, and a gas supply pipe that has an opening in the internal space and discharges gas into the liquid from the opening. The gas supply pipe protrudes into the internal space through the opening, and the protruding portion is provided so as to surround the first electrode having a structure in which the conductor portion is covered with a dielectric material and the protruding portion of the first electrode. A second electrode having a conductor portion separated from the liquid by a dielectric and a voltage applying portion for applying a voltage between the first electrode and the second electrode are provided, and the protruding portion and the first electrode are provided. The space between the two electrodes is a flow path through which the gas discharged from the opening flows.

In the invention configured in this way, since the protruding portion of the first electrode protrudes from the opening of the gas supply pipe that supplies gas into the liquid, the gas discharged from the opening surrounds the protruding portion. It is distributed to the liquid and introduced into the liquid. Then, the space between the protruding portion of the first electrode and the second electrode provided surrounding the protruding portion is a flow path of the gas discharged from the opening, and the plasma generating electric field is generated by applying a voltage between the electrodes. It is a plasma generation field that is formed. Therefore, the gas introduced into the liquid passes through the plasma generation field with an extremely high probability.

The conductor portions of the first electrode and the second electrode are both separated from the liquid by a dielectric material. In particular, around the protruding portion of the first electrode, the gas discharged from the opening forms a bubble that encloses the protruding portion, so that a dielectric material that covers the conductor portion between the conductor portion of the first electrode and the gas. The layer is interposed, and the discharge generated by applying the voltage becomes a dielectric barrier discharge. Therefore, it is possible to generate a stable discharge in a wider area than when the electrode is provided so as to be in contact with the liquid. Further, since the conductor portion is coated, it is possible to prevent the material (for example, metal) of the conductor portion from being eluted into the liquid due to exposure to plasma.

As described above, in the present invention, the gas discharged from the opening of the gas supply pipe that opens in the liquid flows so as to wrap around the protruding portion of the first electrode and is introduced into the liquid, and plasma is formed around the protruding portion. Since the generation field is formed, highly efficient and stable plasma can be generated in the gas. Further, by supplying the plasmalized gas into the liquid in this way, it becomes possible to efficiently generate a liquid containing abundant active species produced by the plasma formation.

It is a figure which shows the structural example of the liquid processing apparatus equipped with one Embodiment of the liquid plasma generating apparatus which concerns on this invention. It is a figure which shows the appearance of the plasma generation part. It is sectional drawing which shows the internal structure of the plasma generation part. It is an enlarged view which shows the structure around the protrusion part in more detail. It is a horizontal cross-sectional view of a plasma generating part. It is a figure explaining the principle of plasma generation in this embodiment. It is a figure which shows the photograph when the plasma is generated by the plasma generating part. It is a figure which shows an example of the experimental result for comparing the amount of plasma active species. It is a figure which shows the modification of the 2nd electrode.

FIG. 1 is a diagram showing a configuration example of a liquid processing apparatus equipped with an embodiment of the submerged plasma generator according to the present invention. This liquid treatment device 1 is a device that generates a treatment liquid in which an active species is dissolved in water stored in a storage tank 2, and an underwater plasma (in the present invention) is generated in a plasma generation unit 3 in order to generate the active species. It corresponds to an example of "submerged plasma"). Thus, in this embodiment, water corresponds to an example of the "liquid" of the present invention. In each of the following figures, the vertical upward direction is represented as the (+ Z) direction, and the downward direction is represented as the (−Z) direction.

The liquid processing apparatus 1 is a piping system 5 responsible for the flow of liquid in the apparatus including supply of liquid to storage tank 2 and delivery of liquid from storage tank 2, and a flow path of liquid formed by the piping system 5. It includes a plasma generating unit 3 and a pump 6 inserted therein. Specifically, one end of the pipe 51 included in the pipe system 5 is connected to a position below the liquid level of the liquid L inside on the side surface of the storage tank 2, and the other end of the pipe 51 is the plasma generating portion 3. It is connected to the liquid inlet, which will be described later, provided at the bottom of the. A pump 6 is inserted in the pipe 51, and when the pump 6 operates in response to an operation command from the control unit 7 that controls the entire device, the liquid stored in the storage tank 2 passes through the pipe 51. Is supplied to the plasma generation unit 3.

As will be described in detail later, the plasma generating unit 3 is a device that contains an active species in a liquid by a plasma treatment in the liquid. Specifically, the plasma generation unit 3 mixes the gas from the gas introduction unit 8 with the liquid sent through the pipe 51 by the pump 6, and generates plasma in the gas by a high voltage from the AC power supply 4. Therefore, it has the function of dissolving the generated active species in the liquid. In this way, the plasma generating unit 3 receives the liquid supplied from the outside as the liquid to be treated, and outputs the liquid in which the active species generated by the plasma generation is dissolved in the liquid to be treated as the treated liquid.

One end of the pipe 53 is connected to the upper part of the plasma generating unit 3, and the other end of the pipe 53 is connected to the storage tank 2. Therefore, the liquid output from the plasma generation unit 3, that is, the liquid that has undergone the submerged plasma treatment in the plasma generation unit 3 can be returned to the storage tank 2. In the liquid processing apparatus 1, as shown by the broken line arrow, the liquid stored in the storage tank 2 circulates through the pipes 51 and 53, and the plasma generating unit 3 generates the submerged plasma while performing the circulation. This makes it possible to increase the concentration of active species contained in the liquid.

When the liquid containing the active species, that is, the treatment liquid is generated in this way, it is necessary to send the treatment liquid from the storage tank 2 to the outside at an appropriate timing. For this purpose, the pipe 54 is connected to the lower side surface of the storage tank 2. An on-off valve 55 is inserted in the pipe 54, and when the on-off valve 55 is opened in response to an opening command from the control unit 7, the treatment liquid (= liquid + active species) stored in the storage tank 2 is opened. Can be taken out to the outside. Further, a pipe 56 is connected to the upper side surface of the storage tank 2, and the storage tank 2 is connected to a liquid supply source (not shown) by the pipe 56. An on-off valve 57 is inserted in the pipe 56, and when the on-off valve 57 is opened in response to an opening command from the control unit 7, the liquid before processing, that is, the liquid containing no active species is put into the storage tank 2. Will be replenished. Further, a pipe 58 is connected to the ceiling surface of the storage tank 2, and the internal space of the storage tank 2 is connected to the surrounding atmosphere of the liquid treatment device 1 by the pipe 58. An on-off valve 59 is inserted in the pipe 58, and when the on-off valve 59 is opened in response to an opening command from the control unit 7, the internal space of the storage tank 2 is communicated with the surrounding atmosphere of the liquid processing device 1. The inside of the storage tank 2 can be returned to atmospheric pressure, and the on-off valve 59 functions as a so-called leak valve.

The pipe 83 of the gas introduction unit 8 is connected to the plasma generation unit 3. The gas introduction unit 8 has a gas supply source 81 for supplying gas through the pipe 83, and an on-off valve 82 inserted in the pipe 83. The on-off valve 82 opens and closes in response to an on-off command from the control unit 7, thereby changing the amount of gas supplied to the plasma generating unit 3 over time. That is, when the on-off valve 82 is opened in response to the opening command from the control unit 7, gas is pumped from the gas supply source 81 through the on-off valve 82 and the pipe 83 while being opened, and is supplied to the plasma generating unit 3. Will be done.

FIG. 2 is a diagram showing the appearance of the plasma generating portion. Further, FIG. 3 is a cross-sectional view showing the internal structure of the plasma generating portion. As shown in FIG. 2, the plasma generating unit 3 mainly includes a cylindrical housing 31 extending in the vertical direction, and FIG. 3 shows a cross section of the housing 31 in a vertical plane including a tube axis AX. Shown.

The housing 31 is, for example, a tubular tube formed of quartz glass and having a hollow inside, and thick-walled portions 31a and 31c having a thicker tube wall at both ends of the thin-walled portion 31b having a relatively thin tube wall. Has a connected structure. For example, the housing 31 can be manufactured by joining thick-walled pipes having the same inner diameter to both ends of the thin-walled pipe by welding. Alternatively, a thick-walled pipe may be thinned by cutting, polishing, or stretching a part of the side wall surface.

Although not shown, the upper end of the thick portion 31a is connected to the pipe 53. A liquid introduction pipe 31d for receiving the liquid supplied from the storage tank 2 as a liquid to be treated is joined to the side surface of the lower thick portion 31c, and the pipe 51 is connected to the liquid introduction pipe 31d. Will be done. Therefore, in the internal space SP of the housing 31, the liquid introduced as the liquid to be treated flows upward from the lower part and is sent out as the treated liquid from the upper end part.

An inner pipe 32 extending in the vertical direction is inserted into the internal space SP of the housing 31. The inner tube 32 is, for example, a tube made of quartz glass having an outer diameter smaller than the inner diameter of the housing 31, and is connected to the tube shaft AX of the housing 31 by a seal stopper 33 made of an elastic material such as silicon rubber. It is supported almost coaxially. The seal stopper 33 also has a function as a seal that separates the internal space SP from the external space and prevents the outflow of liquid. In the internal space SP of the housing 31, the inner pipe 32 extends above the position where the liquid is introduced by the liquid introduction pipe 31d, and the upper end 32a thereof is, for example, substantially the center of the thin portion 31b of the housing 31 in the vertical direction. It is located in the department. The upper end 32a of the inner pipe 32 communicates with the internal space SP of the housing 31. That is, the upper end 32a of the inner pipe 32 has an upward opening 32b.

On the other hand, the lower end of the inner pipe 32 projects downward to the outside of the housing 31 via the seal plug 33, and the gas introduction pipe 32c is connected to the side surface thereof. Although not shown, the gas introduction pipe 32b is connected to the pipe 83 of the gas introduction unit 8. The gas supplied from the gas introduction unit 8 is introduced into the liquid flowing upward through the internal space SP of the housing 31 from the opening 32b via the inside of the gas introduction pipe 32c and the inner pipe 32. Therefore, the introduced gas becomes bubbles in the liquid and moves upward in the internal space SP.

A first electrode 34 extending in the vertical direction is inserted inside the inner pipe 32. The first electrode 34 has a structure in which the surface of a rod-shaped conductor portion 341 having a substantially circular cross section is covered with a surface layer 342 made of a dielectric, for example, quartz glass. The surface layer 342 may be a tube made of a dielectric material in which the surface of the conductor portion 341 is coated with a dielectric material, or the upper end portion is sealed and the conductor portion 341 is inserted therein. good. The first electrode 34 is supported substantially coaxially with the inner tube 32 by a seal stopper 35 made of an elastic material such as silicon rubber. At the lower end of the first electrode 34, the conductor portion 341 is not partially covered by the surface layer 342 and is exposed, and the AC power supply 4 is electrically connected to this portion.

The upper end 34a of the first electrode 34 extends above the upper end 32a of the inner tube 32. Therefore, the tip of the first electrode 34 is in a state of protruding upward from the opening 32b of the inner tube 32. Hereinafter, the portion of the first electrode 34 that protrudes above the upper end 32a of the inner tube 32 is referred to as a “protruding portion” and is designated by reference numeral 34b.

FIG. 4 is an enlarged view showing the structure around the protruding portion in more detail. As shown in FIGS. 3 and 4, the second electrode 36 is provided so as to surround the protruding portion 34b of the first electrode 34 from the side (horizontal direction). Specifically, the second electrode 36 made of an annular metal plate is arranged so as to surround the position corresponding to the protruding portion 34b in the vertical direction in the thin portion 31b of the housing 31. The vertical position of the second electrode 36 is set so that at least a part of the second electrode 36 overlaps the protruding portion 34b in the side view. The second electrode 36 is isolated from the liquid in the internal space SP by a layer of quartz glass which is a dielectric forming the tube wall of the thin portion 31b.

FIG. 5 is a diagram showing a horizontal cross section of the plasma generating portion, specifically, a cross section taken along the line AA of FIG. As shown in FIG. 5, in the vicinity of the protruding portion 34b, the conductor portion 341 of the first electrode 34, the surface layer 342, the inner pipe 32, the thin portion 31b of the housing 31, and the second electrode 36 are arranged substantially coaxially with each other. ing.

The outer diameter of the first electrode 34 is smaller than the inner diameter of the inner tube 32. Therefore, in a plan view, the first electrode 34 is included inside the opening 32b of the inner tube 32. Therefore, the space between the outer surface of the first electrode 34 and the inner surface of the inner tube 32 becomes a gas flow path. The gas flowing through this flow path passes around the first electrode 34 and flows into the internal space SP of the housing 31 through the opening 32b. Further, the outer diameter of the inner pipe 32 is smaller than the inner diameter of the housing 31. Therefore, the space between the outer surface of the inner tube 32 and the inner surface of the housing 31 becomes a liquid flow path.

By applying a high AC voltage from the AC power supply 4 between the first electrode 34 and the second electrode 36, a strong AC electric field is formed in the space around the first electrode 34. By arranging the annular second electrode 36 so as to surround the rod-shaped conductor portion 341 of the first electrode 34, the second electrode 36 is substantially uniform in the circumferential direction and particularly strong in the vicinity of the first electrode 34. An electric field will be formed. That is, in the plasma generation unit 3, the electric field can be concentrated around the protruding portion 34b of the first electrode 34 to form a locally strong plasma generation field.

Further, as shown in FIG. 3, the vertical length of the second electrode 36 is made larger than the length of the protruding portion 34b, and the upper end portion of the second electrode 36 extends to the upper side of the upper end portion of the protruding portion 34b. The lower end of the second electrode 36 is arranged so as to extend below the lower end of the protruding portion 34b. By doing so, a substantially uniform electric field can be formed around the protruding portion 34b even in the height direction.

FIG. 6 is a diagram illustrating the principle of plasma generation in this embodiment. The processing space SP inside the housing 31 is filled with the liquid L supplied from the storage tank 2. As shown by the broken line arrow, the liquid L circulates upward in the space between the inner wall of the housing 31 and the outer wall of the inner pipe 32. On the other hand, the gas G supplied from the gas introduction unit 8 and flowing inside the inner pipe 32 flows upward around the first electrode 34 as shown by the dotted arrow, and is introduced into the liquid as bubbles from the opening 32b. Will be done. At this time, if the flow rate of the gas G is appropriately set, it is possible to form a bubble B1 that encloses the protruding portion 34b of the first electrode 34 by the action of the surface tension of the liquid L.

As described above, since a particularly strong electric field is formed around the protruding portion 34b, plasma due to electric discharge is generated in the bubble B1. Since the conductor portion 341 of the first electrode 34 is covered with the dielectric surface layer 342, the discharge at this time is a dielectric barrier discharge. Further, a substantially uniform electric field is formed around the protruding portion 34b in the axial direction and the radial direction. From these facts, it is possible to stably generate a uniform plasma in a wide region in the bubble B1 surrounding the protruding portion 34b.

When the gas G is further supplied through the inner pipe 32, the bubble B1 is released from the protruding portion 34b into the liquid. The liberated bubble B2 contains a high-concentration active species generated by plasma, and when this is dissolved in the liquid, the liquid L contains the active species. When the liquid L containing the active species is refluxed to the storage tank 2 via the pipe 53, the concentration of the active species in the liquid in the storage tank 2 increases. By circulating the liquid through the piping system 5, the concentration of the active species in the liquid can be further increased.

Neither the conductor portion of the first electrode 34 nor the conductor portion of the second electrode 36 is in contact with the liquid L. As a result, the mode of the generated discharge can be set to the dielectric barrier discharge, and stable plasma can be generated in a wide range. Further, the conductor material is prevented from being eluted into the liquid by exposing the conductor portion to plasma. As described above, the liquid treatment apparatus 1 of the present embodiment can generate a liquid containing abundant active species and free of impurities as a treatment liquid.

FIG. 7 is a diagram showing a photograph when plasma is generated by the plasma generating unit. In the photograph, the bright portion extending in the vertical direction is the housing 31, and the dark portion appearing in the central portion thereof is the second electrode 36. The portion of the inside of the housing 31 surrounded by the second electrode 36 shines particularly brightly, and it can be seen that high-concentration plasma is generated in this portion.

Next, the reason why the housing 31 is configured by connecting the thick portions 31a and 31c and the thin portion 31b will be described. First, considering the strength of the entire housing 31 and the ease of manufacturing, it is desirable that the entire housing 31 is made of a thick tube. In particular, a sufficient thickness is required for the upper end portion where the external pipe 53 is connected and the portion where the liquid introduction pipe 31d is joined. On the other hand, from the viewpoint of obtaining a high electric field strength around the protruding portion 34b of the first electrode 34, the quartz glass of the tube wall, which is a dielectric, should be as thin as possible. Therefore, in the housing 31 of this embodiment, the above requirements are satisfied by using thick-walled portions 31a and 31c at both ends and thin-walled portions 31b at the central portion where the plasma generation field is generated.

The requirement for thinning the dielectric layer interposed between the electrodes is the same for the first electrode 34. That is, it is preferable that the dielectric surface layer 342 of the first electrode 34 is as thin as possible without impairing the mechanical strength.

This is especially important when the gas G is a gas species that is unlikely to generate plasma. The inventor of the present application conducted various experiments using water (pure water) as the liquid L and a quartz tube having an outer diameter of about 10 mm as the housing 31. According to the result, when the tube wall was 1 mm, plasma was generated relatively easily when the gas G was argon, but plasma was not generated when air was used as the gas G. When air was used, plasma was not generated unless the tube wall was 0.5 mm or less. The same applies to the surface layer 342 of the first electrode 34. Therefore, the thickness of the tube wall in the thin portion 31b of the housing 31 is set to 0.4 mm, and the thickness of the surface layer 342 of the first electrode 31 is set to 0.3 mm. By doing so, even when air was used as the gas G, high-concentration plasma could be stably generated.

In the form in which the treatment liquid containing active species is used in the atmosphere, such as sterilization and promotion of plant growth, it is a great merit that air (atmosphere) can be used as a gas for plasma generation. There is. That is, since the treatment liquid can be generated using the virtually inexhaustible atmosphere existing in the operating environment of the apparatus, no special gas supply source is required. As the gas supply source 81 of the liquid processing apparatus 1, for example, a compressor that takes in the surrounding atmosphere, pressurizes it, and sends it out may be sufficient. This is advantageous in simplifying the device configuration and reducing the size of the device, and of course, the processing cost can also be reduced.

Even when a gas type such as helium or argon, which is relatively easy to generate plasma, is used as the gas G, the effect of thinning the tube wall is large. That is, since the plasma density is increased by increasing the electric field strength due to the thinning of the tube wall, the utilization efficiency of the introduced gas is increased, and more active species can be generated if the same amount of gas is used. It is possible to generate a treatment liquid having a high effect such as sterilization. Further, since the amount of gas used to obtain the same plasma density can be suppressed, the processing cost can be reduced. In addition, it is possible to reduce the time and energy consumption required to generate a treatment liquid containing an active species having a required concentration.

FIG. 8 is a diagram showing an example of experimental results for comparing the amounts of plasma active species. The inventor of the present application injected water containing indigocarmine into the plasma generating unit 3 and conducted an experiment to investigate how the liquid color changes with the treatment time. Since indigocarmine decolorizes when it reacts with an active species, the liquid color was evaluated by absorbance. The curve A is the result when the thickness of the tube wall of the housing 31 is 1 mm and the thickness of the surface layer 342 of the first electrode 34 is 0.7 mm. On the other hand, the curve B is a result when the housing 31 is provided with a thin portion 31b having a tube wall of 0.4 mm and the thickness of the surface layer 342 of the first electrode 34 is 0.3 mm. As is clear from the figure, it can be seen that the decrease in absorbance progresses in a shorter time by thinning the tube wall, and more active species are produced in the treatment liquid.

As described above, in the above embodiment, the plasma generator 3 functions as the "submersible plasma generator" of the present invention, and the housing 31, the first electrode 34, and the second electrode 36 are the present inventions, respectively. It corresponds to the "housing", "first electrode" and "second electrode" of the present invention. The inner pipe 32 functions as the "gas supply pipe" of the present invention, and the AC power supply 4 functions as the "voltage application unit" of the present invention.

Further, in the housing 31, the opening of the liquid supply pipe 31 to which the pipe 51 is connected corresponds to the “introduction port” of the present invention, and the opening at the upper end of the housing 31 to which the pipe 53 is connected is the present. It corresponds to the "outlet" of the invention. Further, in the liquid processing apparatus 1 of the above embodiment, the storage tank 2 functions as the "storage unit" of the present invention, and the pump 6 functions as the "liquid supply unit" of the present invention.

The present invention is not limited to the above-described embodiment, and various modifications other than those described above can be made without departing from the spirit of the present invention. For example, in the description of the above embodiment, it is assumed that the protruding portion 34b of the first electrode 34 is completely surrounded by the bubble B1, but the present invention is not limited to this. For example, even under the condition that many fine bubbles are generated so as to surround the periphery of the protruding portion 34b, the presence of many bubbles around the protruding portion 34b where a high electric field is formed causes the presence of many bubbles in each bubble. It is possible to efficiently generate plasma by increasing the plasma generation probability of.

Further, in the above embodiment, the second electrode 36 that covers the outer peripheral surface of the thin portion 31b of the housing 31 in an annular shape is provided, but the second electrode has, for example, the following structure in addition to the above. Is also possible.

FIG. 9 is a diagram showing a modified example of the second electrode. The second electrode 37 shown in FIG. 9A is composed of a plurality of electrode pieces 371 divided in the circumferential direction. Even with such a structure, it is possible to generate a substantially uniform electric field in the circumferential direction around the protruding portion 34b of the first electrode 34.

Further, the second electrode 38 shown in FIG. 9B has a structure in which the conductor portion 381 is covered with the surface layer 382 of a dielectric (for example, quartz glass), and is arranged in the internal space SP in the housing 31. ing. Even with such a structure, it is possible to generate a substantially uniform electric field in the circumferential direction around the protruding portion 34b. Further, since the distance between the electrodes can be reduced as compared with the case where the second electrode is provided outside the housing, the electric field strength can be increased or the applied voltage can be decreased. In addition, for example, the structure may be such that the second electrode is embedded in the housing.

Further, the surface layer 342 of the housing 31 and the first electrode 34 in the above embodiment is made of quartz glass, which is used as an example of a dielectric, and has resistance to the liquid and plasma used. Further, any dielectric material other than this may be used as long as it does not elute impurities into the liquid. For example, in practice it is not essential that the tube wall be transparent, and opaque materials can be used.

Further, the thick portion and the thin portion of the housing 31 may be made of different materials, or the entire pipe may be made thin and reinforced by other mechanical means. Further, the entire tube wall may be thick as long as an electric field strength sufficient to generate plasma is obtained around the protruding portion of the first electrode.

Further, in the first electrode 34 of the above embodiment, the entire conductor portion 341 in the housing 31 is covered with the surface layer 342. However, the portion of the inner tube 32 that is so far from the second electrode 36 that no electric discharge is generated and that does not come into contact with the liquid does not necessarily need to be covered.

Further, in the above embodiment, the housing 31, the inner tube 32, and the first electrode 34 are arranged coaxially with each other, but these do not have to have a strictly coaxial structure. That is, it is sufficient that the gas flowing through the inner tube 32 is introduced into the liquid so as to wrap around the first electrode 34. For this purpose, for example, in a plan view, the protruding portion 34b of the first electrode 34 may be included inside the opening 32b of the inner tube 32. To this extent, the inner tube 32 and the first electrode 34 do not necessarily have to be coaxial. That is, the first electrode 34 does not have to be exactly centered on the inner tube 32. Further, the housing 31 and the inner pipe 32 do not necessarily have to be coaxial as long as the liquid smoothly flows through the space between them. Further, the cross-sectional shape of these pipes does not necessarily have to be circular or similar to each other, and can be appropriately modified.

Further, in the above embodiment, since a seal plug made of an elastic material is used for attaching the inner tube 32 to the housing 31 and attaching the first electrode 34 to the inner tube 32, the plasma generating portion 3 can be easily disassembled. Is. However, instead of this, the members may be permanently fixed, for example, by adhesion or welding.

Further, the plasma generating unit 3 of the above embodiment also has a function of the housing 31 as a part of a pipe for circulating a liquid. However, the "housing" in the present invention is not limited to such a configuration, and may have a function as, for example, a container for storing a liquid in an internal space.

Further, in the above embodiment, the plasma generating unit 3 has a tubular shape having a tube axis AX in a substantially vertical direction, but the present invention is not limited to this. For example, even when the plasma generating unit 3 having the structure of FIG. 2 is arranged so that the tube axis AX is horizontal, plasma can be generated satisfactorily. When the liquid and gas in the plasma generating portion are pumped, the bubbles formed by the gas discharged from the opening of the inner tube extend mainly in the discharge direction and the direction along the pumping direction of the surrounding liquid. Therefore, if the extending direction of the bubbles and the extending direction of the protruding portion of the first electrode are substantially the same, the same effect as described above can be obtained.

In the above embodiment, the extension direction of the inner pipe 32 is the vertical direction, gas is discharged from the upward opening 32b provided at the upper end 32a of the inner pipe 32, and the first electrode 34 is further projected upward from the opening 32b. .. Therefore, the extending direction of the protruding portion 34b coincides not only with the flow direction of the liquid L and the gas G but also with the direction of the buoyancy acting on the gas G in the liquid L, and the bubbles surround the protruding portion 34b. It is possible to increase the probability that it will occur. As a result, the plasma generation region in the liquid is widened, and more efficient plasma generation is possible.

Further, the above embodiment is a "liquid processing device" provided on a flow path of a liquid circulating in a plasma generating unit 3 which is a "liquid plasma generating device" according to the present invention, but the liquid plasma generating device of the present invention is provided. The apparatus itself has a function of dissolving an active species in a liquid to generate a treatment liquid, and the scope of its application is not limited to those having such a circulation route. For example, the processed liquid output from the upper part of the plasma generating unit 3 may be directly taken out to the outside and used as a processing liquid. Further, the liquid and gas used are not limited to the above and are arbitrary.

As described above, as described by exemplifying a specific embodiment, the submerged plasma generator according to the present invention has an opening that opens upward, a protruding portion that protrudes upward from the opening, and a conductor portion of the second electrode. May be configured to surround the protruding portion from the side. According to such a configuration, since the gas discharged from the opening flows upward in the liquid, it is possible to increase the probability of plasma generation by allowing a large amount of gas to pass around the projecting portion extending upward.

Further, for example, in a plan view, the protruding portion may be inside the opening, and the second electrode may surround the circumference of the opening. Further, in the side view, the protruding portion and the second electrode may be at least partially overlapped with each other. According to such a configuration, most of the gas discharged from the opening passes around the protruding portion where the plasma generation field is formed and is introduced into the liquid, so that the plasma generation efficiency can be improved. Can be enhanced.

Further, the first electrode is a rod-shaped body extending along the tube axis of the gas supply pipe, and the space between the side surface of the rod-shaped body and the inner side surface of the gas supply pipe serves as a gas flow path. It may be a configuration. According to such a configuration, the gas flows smoothly through the flow path having an annular cross section, and the first electrode has a structure surrounded by this flow path, so that bubbles are stably formed around the protruding portion. can do.

Further, the housing has a tubular body formed of a dielectric material, and a gas supply pipe is provided inside the tubular body coaxially with the tubular body so that the inner side surface of the tubular body and the gas supply pipe are connected to each other. The structure may be such that the liquid is held in the space between them. According to such a configuration, all the gas supplied from the gas supply pipe comes into contact with the surrounding liquid, so that the active species generated by the generation of plasma in the gas can be efficiently dissolved in the liquid. can.

Further, the housing may have a tubular body formed of a dielectric material, and the second electrode may be provided on the outer peripheral surface of the tubular body. According to such a configuration, the second electrode can be isolated from the liquid in the housing by the wall surface of the housing, and the second electrode can be prevented from coming into contact with the liquid.

Further, the conductor portion of the second electrode may be an annular conductor surrounding the outer peripheral surface of the tubular body. According to such a configuration, a substantially uniform electric field can be generated around the first electrode in the circumferential direction in a plan view, and a uniform plasma can be generated around the first electrode.

Further, the first electrode, the gas supply pipe, the tubular body, and the second electrode may be provided coaxially with respect to the vertical axis. According to such a configuration, the gas flow path between the first electrode and the gas supply pipe and the liquid flow path between the gas supply pipe and the tubular body have a constant cross-sectional shape in the vertical direction. Therefore, gas and liquid can be smoothly circulated in each flow path. As a result, the flow of liquid and gas around the protruding portion of the first electrode is stabilized, and plasma generation in this region can be stabilized. Further, by coaxially arranging the first electrode and the second electrode, the electric field formed around the first electrode can be made uniform.

Further, the housing may be provided with an introduction port for introducing the liquid into the internal space below the protruding portion and an outlet for discharging the liquid to the outside above the protruding portion. According to such a configuration, the liquid flows upward in the housing, and the bubbles containing the plasma active species and rising in the liquid are in contact with the liquid for a long time, so that the active species are efficiently taken into the liquid. be able to.

Further, in the liquid processing apparatus according to the present invention, for example, the liquid supply unit may be configured to supply the liquid stored in the storage unit to the introduction port. According to such a configuration, the concentration of the active species in the liquid can be increased by circulating the liquid passing through the plasma generator in the liquid.

The present invention can be applied to a technique for generating plasma in a liquid and a technique for producing a treatment liquid containing an active species by using the technique in general.

1 Liquid processing device 2 Storage tank (storage unit)
3 Plasma generator (submersible plasma generator)
4 AC power supply (voltage application part)
6 Pump (liquid supply unit)
31 Housing 32 Inner pipe (gas supply pipe)
32b Aperture 34 1st electrode 34b Protruding part 36 2nd electrode 341 Conductor part 342 Surface layer G Gas L Liquid

Claims (12)

A housing that holds liquid in the internal space and
A gas supply pipe having an opening in the internal space and discharging a gas into the liquid from the opening,
A first electrode having a structure in which a conductor portion is coated with a dielectric material is projected from the inside of the gas supply pipe into the internal space through the opening.
A second electrode provided so as to surround the protruding portion of the first electrode and having a conductor portion isolated from the liquid by a dielectric.
A voltage application unit for applying a voltage between the first electrode and the second electrode is provided.
A submerged plasma generator in which the space between the protruding portion and the second electrode is a flow path through which the gas discharged from the opening flows. The submerged plasma generator according to claim 1, wherein the opening opens upward, the protruding portion projects upward from the opening, and the conductor portion of the second electrode surrounds the protruding portion from the side. The submerged plasma generator according to claim 2, wherein the protruding portion is inside the opening and the second electrode surrounds the periphery of the opening in a plan view. The submerged plasma generator according to any one of claims 1 to 3, wherein the protruding portion and the second electrode overlap each other at least in a part thereof in a side view. The first electrode is a rod-shaped body extending along the pipe axis of the gas supply pipe, and the space between the side surface of the rod-shaped body and the inner side surface of the gas supply pipe is the flow path of the gas. The submerged plasma generator according to any one of claims 1 to 4. The housing has a tubular body formed of a dielectric material, and the gas supply pipe is provided coaxially with the tubular body inside the tubular body, and the inner side surface of the tubular body and the gas are provided. The submerged plasma generator according to any one of claims 1 to 5, wherein the liquid is held in a space between the supply pipe and the liquid. The submerged plasma generator according to any one of claims 1 to 5, wherein the housing has a tubular body formed of a dielectric material, and the second electrode is provided on an outer peripheral surface of the tubular body. The submerged plasma generator according to claim 6 or 7, wherein the conductor portion of the second electrode is an annular conductor surrounding the outer peripheral surface of the tubular body. The submerged plasma generator according to any one of claims 1 to 8, wherein the first electrode, the gas supply pipe, the cylindrical body, and the second electrode are provided coaxially with respect to the vertical axis. A claim that the housing is provided with an introduction port for introducing the liquid into the internal space below the protruding portion and a delivery port for delivering the liquid to the outside above the protruding portion. The submerged plasma generator according to any one of 1 to 9. A liquid treatment device that produces a treatment liquid containing an active species.
The submerged plasma generator according to claim 10 and
A liquid supply unit that supplies the liquid to the introduction port,
A liquid processing apparatus including a storage unit that stores the liquid delivered from the outlet as the processing liquid. The liquid processing apparatus according to claim 11, wherein the liquid supply unit supplies the liquid stored in the storage unit to the introduction port.

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