Plasma processing apparatus and plasma processing method

Abstract

Provided is a plasma treatment device capable of reliably generating plasma. This plasma treatment device is provided with a plasma generation means for generating plasma. The plasma treatment device is provided with an irradiation means for irradiating a first liquid with the generated plasma. The plasma treatment device is provided with a contact means for bringing the first liquid irradiated with the plasma into contact with a second liquid.

Description

Technical Field

[0004] ,

[0005] ,

[0001] This application claims priority based on Japanese Patent Application No. 2021-113787 filed on July 8, 2021. All the contents of that application are incorporated herein by reference. This specification discloses a technology related to a plasma processing apparatus and a plasma processing method for irradiating a liquid with plasma.

Background Art

[0002] For example, Japanese Unexamined Patent Application Publication No. 2019-57381 discloses a technology for irradiating a liquid to be processed with microwave plasma.

Summary of the Invention

Problems to be Solved by the Invention

[0003] Depending on the components contained in the liquid to be processed, the plasma generation unit may be affected, making it difficult to generate plasma.

Means for Solving the Problems

[0004] This specification discloses a plasma processing apparatus. The plasma processing apparatus includes plasma generation means for generating plasma. The plasma processing apparatus includes irradiation means for irradiating the generated plasma onto a first liquid. The plasma processing apparatus includes contact means for bringing the first liquid irradiated with plasma into contact with a second liquid.

[0005] There are various ways in which the first liquid is brought into contact with the second liquid. For example, the two liquids can be brought into contact by mixing them. In the plasma processing apparatus of this specification, a highly reactive first liquid containing chemically active species can be generated by irradiating the first liquid with plasma. Then, by bringing the first liquid into contact with the second liquid, it becomes possible to perform plasma treatment on the second liquid. Since it is not necessary to irradiate the second liquid with plasma, even if the second liquid contains components that adversely affect the plasma generating means, the plasma generating means will not be affected by those components.

[0006] The plasma generation means may include a plasma generation space for generating plasma. The plasma generation means may also include a depressurization means for reducing the pressure of the plasma generation space.

[0007] The depressurization means may include a first flow path having a narrowed cross-sectional area. The first flow path may carry a first liquid or a second liquid. The narrowed portion may be connected to the plasma generation space.

[0008] The plasma processing apparatus may include a second flow path that merges with the first flow path. The second flow path may be connected to the plasma generation space. The second liquid may flow through the first flow path. The first liquid may flow through the second flow path.

[0009] The plasma processing apparatus may include an inner tube and an outer tube that surrounds the outer circumference of the inner tube. The plasma generation space and the second flow path may be located within the inner tube. The inner tube and the outer tube may be arranged so that their central axes coincide. A first flow path may be formed between the inner tube and the outer tube, surrounding the outer circumference of the inner tube. The first flow path has a route from one end of the inner tube and the outer tube to the other, and may include a throttling section along the route. In the throttling section, the flow of the second liquid may have a velocity component that swirls around the central axis.

[0010] The plasma processing apparatus may further include at least one flow straightening section located on the first flow path leading to the throttling section. The flow straightening section may extend in the axial direction of the central axis and be inclined with respect to the axial direction of the central axis.

[0011] The flow straightening section may be formed on at least one of the outer wall surface of the inner tube or the inner wall surface of the outer tube. The flow straightening section may have a projection shape that protrudes from the wall surface or a groove shape that is recessed from the wall surface.

[0012] The plasma processing apparatus may further include a supply unit that discharges a second liquid into the first flow path. The discharge direction of the second liquid by the supply unit may be inclined with respect to the axial direction of the central axis.

[0013] The inner tube may comprise a first tube having a first electrode at its first end and a second tube having a second electrode at its second end. The first tube, the second tube, and the outer tube may be arranged so that their central axes coincide. The first end and the second end may face each other in a non-contact state. A first flow path may be formed between the outer circumferences of the first and second tubes and the inner circumference of the outer tube. A second flow path and a plasma generation space may be formed in the region where the first end and the second end face each other.

[0014] The plasma processing apparatus may further include a propagation space configured to enable the propagation of microwaves into the plasma generation space.

[0015] The first liquid may be a liquid in which no solid solute is dissolved. The second liquid may be a liquid in which a solid solute is dissolved.

[0016] One embodiment of a plasma processing method disclosed herein comprises an irradiation step of irradiating a first liquid with plasma. The plasma processing method comprises a contact step of bringing the first liquid into contact with a second liquid.

[0017] In the irradiation process, the plasma may be generated in a reduced-pressure environment.

[0018] In the contacting step, the first liquid may be brought into contact while flowing the second liquid. In the irradiation step, a decompressed environment may be generated by the Venturi effect obtained by the flow of the second liquid.

[0019] In the contacting step, microwaves may be incident on the space where plasma is generated.

Brief Description of the Drawings

[0020] [Figure 1] It is a schematic cross-sectional view of the plasma processing apparatus 100 of Example 1. [Figure 2] It is a schematic cross-sectional view of the plasma processing apparatus 200 of the comparative example. [Figure 3] It is a schematic cross-sectional view of the plasma processing apparatus 300 of Example 2. [Figure 4] It is a schematic perspective view of the plasma processing apparatus 400 of Example 3. [Figure 5] It is a schematic perspective view of the plasma processing apparatus 400a of the modified example.

Modes for Carrying Out the Invention

Examples

[0021] (Configuration of Plasma Processing Apparatus 100) FIG. 1 is a schematic cross-sectional view of the plasma processing apparatus 100 of Example 1. The z direction indicates vertically upward. The plasma processing apparatus 100 includes a first outer conductor 120, a second outer conductor 130, an external tube 140, and an insulating spacer 180.

[0022] The first outer conductor 120 and the second outer conductor 130 are cylindrical in shape and share a central axis CA. The materials of the first outer conductor 120 and the second outer conductor 130 are copper, brass, or other metals. The first outer conductor 120 includes a flow path space CH1, a plasma propagation space MP1, and a first electrode 121. The flow path space CH1 is a space through which a fluid can flow. The flow path space CH1 also has a function of cooling the first outer conductor 120 with a liquid. The plasma propagation space MP1 is a space for propagating microwaves generated by a microwave generation unit (not shown). The first electrode 121 is disposed at the first end E1 of the first outer conductor 120.

[0023] The second outer conductor 130 includes a flow path space CH2 and a second electrode 131. The flow path space CH2 is a space that forms a part of a second flow path LP2, as will be described later. A plurality of flow path spaces CH2 are arranged rotationally symmetric with respect to the central axis CA. The second electrode 131 is disposed at the second end E2 of the second outer conductor 130. The second electrode 131 protrudes from the second end E2. The shapes of the first electrode 121 and the second electrode 131 are annular with substantially the same diameter.

[0024] The first end E1 of the first outer conductor 120 and the second end E2 of the second outer conductor 130 are connected via a ring-shaped insulating spacer 180. The first outer conductor 120 and the second outer conductor 130 may be fixed by bolts (not shown).

[0025] A plasma generation space PG1 is formed in the region where the first end E1 and the second end E2 face each other. The plasma generation space PG1 is an annular space. In the plasma generation space PG1, the first electrode 121 and the second electrode 131 are disposed to face each other. A slit S1 is formed between the first electrode 121 and the second electrode 131. The width of the slit S1 is on the order of 0.05 mm or more and 1 mm or less.

[0026] Gaps G1 and G2 are formed between the first end E1 and the second end E2. Gap G1 is formed inside the insulating spacer 180 and functions as a flow channel connecting the flow channel spaces CH1 and CH2. Gap G2 is formed on the outer circumference of the first outer conductor 120 and the second outer conductor 130 and functions as a flow channel connecting the plasma generation space PG1 and the outer circumference space OS1. The flow channel space CH1, gap G1, flow channel space CH2, and gap G2 form a second flow channel LP2, as indicated by the dotted arrow. The second flow channel LP2 is a flow channel that merges with the first flow channel LP1 from the flow channel space CH1 via the plasma generation space PG1. Since the plasma generation space PG1 is not immersed by the liquid flowing through the second flow channel LP2, a stable plasma can be generated.

[0027] Furthermore, the gap G2 has a region that extends diagonally downward with respect to the horizontal direction (x direction). This allows gravity to suppress the fluid flowing through the first channel LP1 from flowing back into the plasma generation space PG1.

[0028] The outer tube 140 is positioned outside the first outer conductor 120 and the second outer conductor 130. The outer tube 140 has a cylindrical shape and shares a central axis CA with the first outer conductor 120 and the second outer conductor 130. The material of the outer tube 140 is, for example, glass.

[0029] An outer peripheral space OS1 is formed between the outer circumferences of the first outer conductor 120 and the second outer conductor 130 and the inner circumference of the outer tube 140. The outer peripheral space OS1 functions as a first flow path LP1, as indicated by the dotted arrow. The first outer conductor 120 has a first inclined surface 122 that protrudes toward the outer tube 140 as it approaches the first end E1. The second outer conductor 130 has a second inclined surface 132 that protrudes toward the outer tube 140 as it approaches the second end E2. As a result, a constricted section RP with a narrower cross-sectional area is formed near the confluence point JP of the first flow path LP1 and the second flow path LP2.

[0030] The flow velocity of the liquid flowing through the first channel LP1 becomes very high around the throttling section RP. Due to the Venturi effect, the liquid pressure can be reduced. For example, a liquid at 1 atmosphere can be reduced to about 0.1 atmospheres. Since the plasma generation space PG1 is connected to the throttling section RP via a gap G2, the plasma generation space PG1 can be depressurized. Because depressurization can be achieved without using a pump or the like, the plasma processing apparatus 100 can be simplified.

[0031] (Plasma treatment method) The plasma treatment method according to Example 1 will be explained using the production of metal nanoparticles as an example. First, a solution containing a metal or metal compound is prepared. In this example, an aqueous silver nitrate solution was used. The concentration of AgNO3 was 0.1 mol / L. Then, the aqueous silver nitrate solution was flowed through the first channel LP1. Due to the Venturi effect, the atmospheric pressure around the plasma generation space PG1 decreased. In this example, the flow rate was 55 L / min. The pressure in the plasma generation space PG1 was approximately 0.2 atmospheres. In addition, pure water was flowed through the second channel LP2. In this example, the flow rate was 250 mL / min.

[0032] Next, microwaves generated by a microwave generation unit (not shown) are radiated into the plasma propagation space MP1. The microwaves propagate through the plasma propagation space MP1 in the direction of arrow M1 and reach the plasma generation space PG1. In this embodiment, the microwave frequency was 2.45 GHz and the microwave power was 1 kW.

[0033] Then, surface currents are induced in the first outer conductor 120 and the second outer conductor 130. As a result, a relatively strong electric field is applied between the first electrode 121 and the second electrode 131. This causes a discharge to occur between the first electrode 121 and the second electrode 131, and plasma is generated in the plasma generation space PG1. The plasma generated in the plasma generation space PG1 irradiates the pure water flowing through the second channel LP2 with plasma products. Here, plasma products include electrons, cations, radicals, and ultraviolet light. As a result, the pure water flowing through the second channel LP2 is plasma-treated, and plasma-treated water containing chemically active species is generated.

[0034] The plasma-treated water is immediately introduced to the confluence point JP due to the pressure difference caused by the Venturi effect and mixed with the silver nitrate aqueous solution. In other words, the plasma-treated water comes into contact with the silver nitrate aqueous solution. This allows the chemically active species contained in the plasma-treated water to react with the silver nitrate aqueous solution before they become inactive. Thus, silver nanoparticles can be generated. These silver nanoparticles are aggregates of silver particles with a particle size of approximately 20 nm to 50 nm. Plasma treatment can be performed continuously in-line on the silver nitrate aqueous solution flowing through the first channel LP1. Compared to batch processing, it is possible to increase the efficiency of silver nanoparticle generation.

[0035] (Challenges and effects) First, the problem will be explained using the comparative example plasma processing apparatus 200 shown in Figure 2. The comparative example plasma processing apparatus 200 (Figure 2) differs from the plasma processing apparatus 100 (Figure 1) of Example 1 in that it does not have a second channel LP2. In other words, the comparative example plasma processing apparatus 200 is a device that directly irradiates the silver nitrate aqueous solution flowing through the first channel LP1 with plasma. Due to the depressurization of the plasma generation space PG1 by the Venturi effect, a backflow channel LPb may be formed from the confluence point JP toward the plasma generation space PG1. When the silver nitrate aqueous solution flows backward to the plasma generation space PG1, droplets DR of the silver nitrate aqueous solution adhere to the first electrode 121 and the second electrode 131. Since the silver nitrate aqueous solution is a liquid in which a solid solute is dissolved, the solid solute solidifies, and deposits DE accumulate on the first electrode 121 and the second electrode 131. The discharge stops, and plasma processing cannot be performed.

[0036] On the other hand, the plasma processing apparatus 100 of Example 1 is equipped with a second channel LP2 that merges with the first channel LP1 via the plasma generation space PG1. By irradiating pure water flowing through the second channel LP2 with plasma, highly reactive plasma-treated water containing chemically active species can be generated. Then, by mixing the plasma-treated water with the silver nitrate aqueous solution flowing through the first channel LP1, silver nanoparticles can be generated. In other words, plasma treatment can be performed on the silver nitrate aqueous solution via the plasma-treated water. It is possible to completely separate the plasma-treated water generation region and the plasma-treated silver nitrate aqueous solution region. Since it is not necessary to irradiate the silver nitrate aqueous solution with plasma, even if the silver nitrate aqueous solution contains components that form deposits DE, the first electrode 121 and the second electrode 131 are not affected by those components. Also, since pure water is a liquid in which no solid solutes are dissolved, deposits DE do not occur. Continuous plasma treatment for long periods of time becomes possible.

[0037] In the comparative example plasma processing apparatus 200 (Figure 2), it is conceivable to form an air curtain using gas, for example, to prevent the formation of a backflow channel LPb. However, since gas has a much lower density than liquid, an air curtain cannot adequately prevent backflow. In the plasma processing apparatus 100 of Example 1, the formation of a backflow channel LPb can be prevented by pure water flowing through the second channel LP2. By pushing back the backflow liquid with pure water, backflow can be reliably prevented. This makes it possible to prevent the generation of deposits DE. [Examples]

[0038] Figure 3 is a schematic cross-sectional view of the plasma processing apparatus 300 of Example 2. The plasma processing apparatus 300 comprises a plasma-treated water generation unit 301 and a tank 302. The plasma-treated water generation unit 301 comprises a flow channel space 310, a plasma generation space PG2, a first electrode 331, a second electrode 332, a microwave introduction unit 340, and a dielectric unit 350. The flow channel space 310 functions as a flow channel LP, as indicated by the dotted arrow. In this embodiment, pure water flows through the flow channel LP. The flow channel space 310 has a throttling section RP2 in the portion communicating with the plasma generation space PG2 and in its vicinity. The throttling section RP2 is a region with a reduced cross-sectional area, and the plasma generation space PG2 can be depressurized by the Venturi effect.

[0039] The plasma generation space PG2 is a space formed to extend outward in a direction perpendicular to the flow path LP. Within the plasma generation space PG2, annular first electrodes 331 and second electrodes 332 are arranged opposite each other with a gap between them. The microwave introduction section 340 is the part for propagating microwaves into the plasma generation space PG2. The dielectric section 350 covers the outer periphery of the plasma generation space PG2, thereby insulating the plasma generation space PG2 from the outside. The tank 302 is the part that holds the liquid 303 to be plasma-treated. In this embodiment, an aqueous silver nitrate solution was used as the liquid 303.

[0040] (Plasma treatment method) The plasma treatment method according to Example 2 will be explained using the case of producing metal nanoparticles as an example. First, an aqueous silver nitrate solution is held in tank 302. Then, pure water is flowed through the channel LP. Due to the Venturi effect, the air pressure in the plasma generation space PG2 decreases. Next, microwaves generated in a microwave generation unit (not shown) are radiated into the microwave introduction unit 340.

[0041] By applying an electric field between the first electrode 331 and the second electrode 332, plasma is generated in the plasma generation space PG2. The generated plasma irradiates the pure water flowing through the channel LP with plasma products. As a result, the pure water flowing through channel LP is plasma-treated, and plasma-treated water containing chemically active species is produced. The plasma-treated water is discharged downward from the channel space 310 and flows into the tank 302, where it is mixed with the silver nitrate aqueous solution. The chemically active species contained in the plasma-treated water react with the silver nitrate aqueous solution to produce silver nanoparticles.

[0042] (effect) Plasma treatment of a silver nitrate aqueous solution becomes possible via plasma-treated water. Since it is not necessary to irradiate the silver nitrate aqueous solution with plasma, the first electrode 331 and the second electrode 332 are not affected by components contained in the silver nitrate aqueous solution. This enables continuous plasma treatment for extended periods.

[0043] (Modified version of Example 2) The liquid 303 to be plasma-treated is not limited to being held in a tank 302. For example, a second channel for flowing the liquid 303 may be provided. The plasma-treated water flowing through channel LP may be merged with the liquid 303 flowing through the second channel. Because plasma treatment can be performed continuously in-line, it is possible to increase the processing efficiency compared to batch processing. [Examples]

[0044] (Configuration of the plasma processing apparatus 400) Figure 4 shows a schematic perspective view of the plasma processing apparatus 400 of Example 3. The plasma processing apparatus 400 of Example 3 differs from the plasma processing apparatus 100 of Example 1 (Figure 1) in that it is equipped with a rectifier 403, etc. The same reference numerals are used for parts that are the same as those in the plasma processing apparatus 100, and their explanations are omitted. In Figure 4, the outer pipe 140 is shown by a dashed line, and the supply channel LP0 and the first channel LP1 are shown by dotted lines.

[0045] The plasma processing apparatus 400 mainly comprises an outer tube 140, an inner tube 401, a pump 402, a plurality of rectifiers 403, a tank 404, a particle size distribution measuring device 405, and a control device 406. The inner tube 401 has a structure in which a first outer conductor 120 and a second outer conductor 130 are combined. As described in Embodiment 1, a plasma generation space PG1 and a second flow path LP2 are arranged in the region where the first outer conductor 120 and the second outer conductor 130 face each other. The inner tube 401 and the outer tube 140 are arranged so that their central axes CA coincide. Between the inner tube 401 and the outer tube 140, a ring-shaped first flow path LP1 is formed, surrounding the outer circumference of the inner tube 401. The first flow path LP1 has a path from the upper end UE to the lower end LE of the inner tube 401 and the outer tube 140. A throttling section RP is also provided along the path of the first flow path LP1.

[0046] A ring-shaped first flow channel inlet LP1E is formed at the upper end UE. Multiple flow straightening sections 403 are formed near the upper end UE. That is, the multiple flow straightening sections 403 are arranged on the path leading to the throttling section RP of the first flow channel LP1. Each of the multiple flow straightening sections 403 is a plate-shaped member that radially connects the outer circumference of the first outer conductor 120 and the inner circumference of the outer tube 140. Each of the flow straightening sections 403 extends in the axial direction (z direction) of the central axis CA and has an inclination A1 with respect to the axial direction (z direction). The magnitude of the inclination A1 is not particularly limited. Furthermore, the inclination A1 may be configured to be variable.

[0047] Pump 402 is a supply unit that discharges a silver nitrate aqueous solution into the first channel LP1. The silver nitrate aqueous solution discharged from pump 402 is supplied to the first channel inlet LP1E via supply channel LP0. As shown by the dotted line in Figure 4, supply channel LP0 has a ring-shaped branched channel so as to supply the entire ring-shaped first channel inlet LP1E. The flow rate of the silver nitrate aqueous solution supplied from pump 402 can be adjusted by the rotational speed of pump 402. The rotational speed of pump 402 can also be controlled by control device 406. The control device 406 is not particularly limited and may be, for example, a PC.

[0048] At the first channel inlet LP1E, an aqueous silver nitrate solution is introduced vertically downward (-z direction). The direction of the introduced aqueous silver nitrate flow is changed by the flow straightening section 403 by a slope A1. Therefore, the first channel LP1 output from the flow straightening section 403 becomes a swirling flow that rotates around the central axis. The first channel LP1 reaches the throttling section RP while maintaining its swirling state. Therefore, at the throttling section RP, the flow of the aqueous silver nitrate solution has a velocity component that rotates around the central axis CA. That is, the flow velocity of the aqueous silver nitrate solution at the throttling section RP has velocity components not only in the z direction but also in the x and y directions. The flow velocity of the aqueous silver nitrate solution at the throttling section RP is not particularly limited and may be, for example, 10 m / s or more.

[0049] A silver nitrate aqueous solution containing silver nanoparticles is discharged from the lower end LE. The discharged silver nitrate aqueous solution passes through the particle size distribution analyzer 405 and is stored in the tank 404. The particle size distribution analyzer 405 can measure the particle size distribution of silver nanoparticles in the discharged silver nitrate aqueous solution in real time. The type of particle size distribution analyzer 405 is not particularly limited. The measurement results of the particle size distribution are transmitted to the control device 406.

[0050] The control device 406 provides feedback control of the flow rate of the silver nitrate aqueous solution based on the measurement results of the particle size distribution. This will be explained in detail. By changing the flow rate of the silver nitrate aqueous solution, the concentration of plasma-treated water introduced into the silver nitrate aqueous solution from the second channel LP2 can be controlled. That is, since the flow rate per unit time of plasma-treated water supplied from the second channel LP2 and the concentration of chemically active species in the plasma-treated water are constant, the lower the flow rate per unit time of the silver nitrate aqueous solution, the higher the concentration of chemically active species in the silver nitrate aqueous solution can be. The higher the concentration of chemically active species, the greater the amount of chemical reaction, and therefore the larger the particle size distribution of silver nanoparticles can be shifted. As a result, by appropriately feedback controlling the rotation speed of the pump 402 based on the real-time measurement results of the particle size distribution, it becomes possible to control the particle size distribution of silver nanoparticles within a predetermined range.

[0051] (effect) As shown in Figure 1, a second flow channel LP2 is formed on the inner side (towards the central axis CA) near the throttling section RP. In the technique of Example 3, a velocity component that swirls around the central axis CA can be generated in the flow of the silver nitrate aqueous solution. This generates a centrifugal force in the throttling section RP that pushes the silver nitrate aqueous solution against the outer tube 140. Since the silver nitrate aqueous solution can be moved away from the second flow channel LP2, backflow can be reliably prevented. Furthermore, even when using a swirling flow, the Venturi effect can be generated in the throttling section RP, making it possible to reduce the pressure in the plasma generation space PG1. It is preferable that the centrifugal force acting on the silver nitrate aqueous solution in the throttling section RP be 1G or more.

[0052] (Modified version of Example 3) The structure of the rectifier is not limited to the example in Figure 4 and may have various structures. The rectifier can be formed on at least one of the outer circumferential wall surface of the inner tube 401 or the inner circumferential wall surface of the outer tube 140. The rectifier can also have a protruding shape from the wall surface or a groove shape recessed from the wall surface. For example, as shown in the modified plasma processing apparatus 400a, the rectifier 403a may be a wall-shaped protrusion formed on the outer circumferential wall surface of the first outer conductor 120. At least a portion of the rectifier 403a may be located within the range of the region R1 where the first inclined surface 122 is formed. Note that in Figure 5, the outer tube 140 is omitted for clarity.

[0053] There are various ways in which the silver nitrate aqueous solution is discharged from the pump. For example, as shown in Figure 5, the pump may be equipped with a nozzle 402n that is inclined with respect to the axial direction (z direction) of the central axis CA. This allows the silver nitrate aqueous solution, which is in a swirling flow state with an inclination A2 with respect to the axial direction, to be introduced into the first flow channel LP1. Alternatively, as shown in Figure 5, the silver nitrate aqueous solution may be introduced from one location of the ring-shaped first flow channel inlet LP1E.

[0054] Although embodiments of the present invention have been described in detail above, these are merely illustrative and do not limit the scope of the claims. The technologies described in the claims include various modifications and changes to the specific examples illustrated above.

[0055] (modified version) The technology described herein can be widely applied to various liquids and can stably form new chemical reaction fields using plasma. This opens up possibilities for its application as a new process reaction field for chemical reactions. The applications of the plasma treatment described herein are not limited to nanoparticle generation but are applicable to a variety of fields. For example, it can be used in organic matter decomposition and disinfectant water production.

[0056] This specification describes the production of silver nanoparticles, but is not limited to this form, and various types of nanoparticles can be produced. For example, gold nanoparticles can be produced using an aqueous solution of chloroauric acid.

[0057] The liquid to be plasma-treated is not limited to pure water; various liquids are acceptable. For example, liquids without dissolved solid solutes are also acceptable. Since no deposits (DE) are formed, continuous plasma generation is possible. Specific examples include alcohols, carboxylic acids, aldehydes, nitric acid, hydrochloric acid, carbonic acid, and aqueous ammonia.

[0058] The means for reducing the pressure in the plasma generation spaces PG1 and PG2 are not limited to methods using the Venturi effect, but various other methods can be used. For example, a pump may be used to reduce the pressure.

[0059] The plasma used in the technology described herein is not limited to reduced-pressure plasma. Atmospheric pressure plasma may also be used.

[0060] The plasma generation method used in the technology described herein may vary. For example, it may be a DC discharge, a DC pulsed discharge, a high-frequency discharge, or the like.

[0061] The technical elements described herein or in the drawings demonstrate technical usefulness individually or in various combinations, and are not limited to the combinations described in the claims at the time of filing. Furthermore, the technologies illustrated herein or in the drawings can achieve multiple objectives simultaneously, and achieving even one of these objectives constitutes technical usefulness in itself.

[0062] Pure water is an example of the first liquid. Silver nitrate aqueous solution is an example of the second liquid. The second flow path LP2 and flow path space 310 are examples of contact means. The first outer conductor 120 is an example of the first pipe. The second outer conductor 130 is an example of the second pipe. The pump 402 is an example of a supply unit.

[0063] The following are embodiments of this technology. [Aspect 1] A plasma generating means for generating plasma, An irradiation means for irradiating the first liquid with the generated plasma, A contact means for bringing the first liquid irradiated with the plasma into contact with the second liquid, A plasma processing apparatus equipped with the following features. [Aspect 2] The plasma generating means is A plasma generation space for generating the aforementioned plasma, Depressurization means for reducing the pressure in the plasma generation space, A plasma processing apparatus according to embodiment 1, comprising: [Aspect 3] The pressure reducing means includes a first flow path having a constricted portion with a narrowed cross-sectional area, and the first flow path through which the first liquid or the second liquid flows. The plasma processing apparatus according to embodiment 2, wherein the throttling portion is connected to the plasma generation space. [Aspect 4] It comprises a second flow path that merges with the first flow path, The second flow path is connected to the plasma generation space, The second liquid flows into the first channel, The plasma processing apparatus according to embodiment 3, wherein the first liquid flows through the second flow path. [Aspect 5] The inner tube and An outer tube covering the outer circumference of the inner tube, Equipped with, The plasma generation space and the second flow path are located in the internal tube. The inner tube and the outer tube are arranged so that their central axes coincide. Between the inner tube and the outer tube, the first flow path is formed, surrounding the outer circumference of the inner tube. The first flow path has a path from one end to the other of the inner tube and the outer tube, and the constricted portion is provided on the path. The plasma processing apparatus according to embodiment 4, wherein in the throttling portion, the flow of the second liquid has a velocity component that swirls around the central axis. [Aspect 6] The system further comprises at least one rectifier positioned on the first flow path leading to the diaphragm, The plasma processing apparatus according to embodiment 5, wherein the rectifying portion extends in the axial direction of the central axis and is inclined with respect to the axial direction of the central axis. [Aspect 7] The rectifier is formed on at least one of the outer wall surface of the inner tube or the inner wall surface of the outer tube. The rectifying section has a protruding shape that extends from the wall surface or a groove shape that is recessed from the wall surface. The plasma processing apparatus according to embodiment 6. [Aspect 8] The first flow path is further provided with a supply unit that discharges the second liquid, The plasma processing apparatus according to any one of embodiments 5 to 7, wherein the discharge direction of the second liquid by the supply unit is inclined with respect to the axial direction of the central axis. [Aspect 9] The aforementioned internal tube is A first tube having a first electrode at its first end, A second tube having a second electrode at its second end, It is equipped with, The first tube, the second tube, and the outer tube are arranged so that their central axes coincide with each other. The first end and the second end face each other in a non-contact state. The first flow path is formed between the outer circumference of the first and second pipes and the inner circumference of the outer pipe. A plasma processing apparatus according to any one of embodiments 5 to 8, wherein the second flow channel and the plasma generation space are formed in the region where the first end and the second end face each other. [Aspect 10] A plasma processing apparatus according to any one of embodiments 2 to 9, further comprising a propagation space configured to enable the propagation of microwaves into the plasma generation space. [Aspect 11] The first liquid is a liquid in which no solid solute is dissolved. The plasma processing apparatus according to any one of embodiments 1 to 10, wherein the second liquid is a liquid in which a solid solute is dissolved. [Aspect 12] The irradiation process involves irradiating the first liquid with plasma, A contact step of bringing the first liquid into contact with the second liquid, A plasma treatment method comprising the following features. [Aspect 13] The plasma treatment method according to embodiment 12, wherein the irradiation step generates the plasma in a reduced-pressure environment. [Aspect 14] In the contact step, the first liquid is brought into contact with the second liquid while the second liquid is flowing. The plasma treatment method according to embodiment 13, wherein the irradiation step generates the reduced pressure environment by the Venturi effect obtained by the flow of the second liquid. [Aspect 15] The plasma processing method according to any one of embodiments 12 to 14, wherein the contact step involves injecting microwaves into the space where the plasma is generated. [Explanation of symbols]

[0064] 100: Plasma processing device 120: First outer conductor 121: First electrode 130: Second outer conductor 131: Second electrode 140: Outer tube JP: Confluence point RP: Constriction LP1: First channel LP2: Second channel PG1: Plasma generation space

Claims

1. An internal tube, An outer tube covering the outer circumference of the inner tube, Plasma generating means comprising a plasma generation space arranged in the internal tube for generating plasma, and a depressurization means for reducing the pressure of the plasma generation space, An irradiation means for irradiating the first liquid with the generated plasma, A contact means for bringing the first liquid irradiated with the plasma into contact with the second liquid, Equipped with, The inner tube and the outer tube are arranged so that their central axes coincide. A first flow path is formed between the inner tube and the outer tube, surrounding the outer circumference of the inner tube. The first flow path has a path from one end to the other of the inner tube and the outer tube, and is provided with a constricted portion with a narrowed cross-sectional area along the path, and the constricted portion is connected to the plasma generation space. The internal tube is provided with a second flow path that merges with the first flow path. The second flow path is connected to the plasma generation space, The first liquid flows into the second flow path. The second liquid flows into the first channel, In the constricted portion, the flow of the second liquid has a velocity component that swirls around the central axis. Plasma processing equipment.

2. The system further comprises at least one rectifier positioned on the first flow path leading to the diaphragm, The plasma processing apparatus according to claim 1, wherein the rectifying portion extends in the axial direction of the central axis and is inclined with respect to the axial direction of the central axis.

3. The rectifier is formed on at least one of the outer wall surface of the inner tube or the inner wall surface of the outer tube. The rectifying section has a protruding shape that extends from the wall surface or a groove shape that is recessed from the wall surface. The plasma processing apparatus according to claim 2.

4. The first flow path is further provided with a supply unit that discharges the second liquid, The plasma processing apparatus according to claim 1, wherein the discharge direction of the second liquid by the supply unit is inclined with respect to the axial direction of the central axis.

5. The aforementioned internal tube is A first tube having a first electrode at its first end, A second tube having a second electrode at its second end, It is equipped with, The first tube, the second tube, and the outer tube are arranged so that their central axes coincide with each other. The first end and the second end are facing each other in a non-contact state. The first flow path is formed between the outer circumference of the first and second pipes and the inner circumference of the outer pipe. The plasma processing apparatus according to claim 1, wherein the second flow channel and the plasma generation space are formed in the region where the first end and the second end face each other.

6. The plasma processing apparatus according to claim 1, further comprising a propagation space configured to enable the propagation of microwaves into the plasma generation space.

7. The first liquid is a liquid in which no solid solute is dissolved. The plasma processing apparatus according to any one of claims 1 to 6, wherein the second liquid is a liquid in which a solid solute is dissolved.

8. An internal tube, An outer tube covering the outer circumference of the inner tube, Plasma generating means comprising a plasma generation space arranged in the internal tube for generating plasma, and a depressurization means for reducing the pressure of the plasma generation space, An irradiation means for irradiating the first liquid with the generated plasma, A contact means for bringing the first liquid irradiated with the plasma into contact with the second liquid, A plasma processing method using a plasma processing apparatus equipped with, In the aforementioned plasma processing apparatus, The inner tube and the outer tube are arranged so that their central axes coincide. A first flow path is formed between the inner tube and the outer tube, surrounding the outer circumference of the inner tube. The first flow path has a path from one end to the other of the inner tube and the outer tube, and is provided with a constricted portion with a narrowed cross-sectional area along the path, and the constricted portion is connected to the plasma generation space. The internal tube is provided with a second flow path that merges with the first flow path. The second flow path is connected to the plasma generation space, The first liquid flows into the second flow path. The second liquid flows into the first channel, In the aforementioned throttling section, the flow of the second liquid has a velocity component that swirls around the central axis. The aforementioned method, An irradiation step of irradiating the first liquid with the plasma generated in the plasma generation space, A contact step of bringing the first liquid irradiated with the plasma into contact with the second liquid, A plasma treatment method comprising the following features.

9. The plasma treatment method according to claim 8, wherein the irradiation step generates the plasma in a reduced-pressure environment.

10. In the contact step, the first liquid is brought into contact with the second liquid while the second liquid is flowing. The plasma treatment method according to claim 9, wherein in the irradiation step, the reduced pressure environment is generated by the Venturi effect obtained by the flow of the second liquid.

11. The plasma processing method according to any one of claims 8 to 10, wherein in the contact step, microwaves are incident on the space where the plasma is generated.

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