Nanoparticle manufacturing apparatus and nanoparticle manufacturing method

Abstract

To provide a nanoparticle manufacturing apparatus and a nanoparticle manufacturing method, having excellent recovery efficiency of nanoparticles.SOLUTION: A nanoparticle manufacturing apparatus 10 comprises: a plasma torch 11 for producing a plasma flame 16; a raw material supply part 12 for supplying a raw material 20 to the plasma flame 16, vaporizing the raw material 20 and generating raw material gas 21; a reaction vessel 13 in which a gas flow 23 including nanoparticles 22 generated by condensation of the raw material gas 21 is generated; a rectification / cooling part 14 into which the gas flow 23 including the nanoparticles 22 is introduced, and which rectifies a stream of the gas flow 23 and cools the gas flow 23; and a recovery part 15 into which the cooled gas flow 23 is introduced, and which recovers the nanoparticles 22.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an apparatus and a method for producing nanoparticles. [Background technology]

[0002] In recent years, nanoparticles with a diameter of less than 1000 nm have been used in a variety of fields, including electronic devices, sensors, biotechnology, medicine, and semiconductors. For example, carbon is commonly used as the anode material for lithium-ion secondary batteries, but silicon has become a promising candidate for further increasing capacity. When silicon is used as the anode material, cracking of the silicon during charging and discharging becomes an issue, and nanoparticle silicon has been proposed as an effective solution to this problem.

[0003] Although it has been demonstrated at the laboratory level that nanoparticleization of materials can produce a variety of beneficial effects, there are significant technical challenges to be overcome before high-quality nanoparticles can be produced on an industrial scale. Known nanoparticle production methods include mechanical ironing, the sol-gel method, and CVD, but these methods have issues such as being unsuitable for mass production. One nanoparticle production method that is expected to be used industrially is the high-frequency plasma spray method. In the high-frequency plasma spray method, nanoparticles are formed by supplying raw materials to high-temperature plasma, which completely evaporates the raw materials to generate raw material gas, which then rapidly condenses.

[0004] Patent Document 1 discloses a nanoparticle production device that uses high-temperature plasma to evaporate raw materials and recover them as nanoparticles. In Patent Document 1, high-temperature gas containing nanoparticles is passed between stacked cooling plates to increase the area where the evaporated gas comes into contact with the cooling plates, and turbulence is generated in the gas to efficiently cool it, actively capturing the generated nanoparticles. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-136200 Summary of the Invention [Problem to be solved by the invention]

[0006] However, the nanoparticle production apparatus described in Patent Document 1 requires the use of a brush or other tool to sweep away nanoparticles that have remained inside the apparatus and adhered to the inner walls of the apparatus before reaching the cooling plate, nanoparticles that have adhered to the cooling plate, and nanoparticles that have fallen to the bottom of the apparatus. This makes it difficult to operate the apparatus continuously for long periods of time, and also poses the problem of workers being exposed to the nanoparticles.

[0007] An object of the present invention is to provide a nanoparticle production apparatus and a nanoparticle production method that are excellent in nanoparticle recovery efficiency. [Means for solving the problem]

[0008] The nanoparticle production apparatus according to the present invention comprises a plasma torch that generates a plasma flame, a raw material supply unit that supplies raw material to the plasma flame and vaporizes the raw material to generate raw material gas, a reaction vessel in which a gas flow containing nanoparticles produced by condensation of the raw material gas is generated, a rectification / cooling unit into which the gas flow containing the nanoparticles is introduced and which rectifies the flow of the gas flow and cools the gas flow, and a recovery unit into which the cooled gas flow is introduced and which recovers the nanoparticles.

[0009] The method for producing nanoparticles according to the present invention includes supplying a raw material to a plasma flame, vaporizing the raw material to generate a raw material gas, condensing the raw material gas to generate nanoparticles, rectifying a gas flow containing the nanoparticles, cooling the gas flow, and recovering the nanoparticles contained in the cooled gas flow. [Effects of the Invention]

[0010] According to the present invention, it is possible to provide a nanoparticle production apparatus and a nanoparticle production method that are excellent in nanoparticle recovery efficiency. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a schematic diagram showing the configuration of a nanoparticle manufacturing apparatus according to a first embodiment. [Figure 2] FIG. 10 is a schematic diagram showing the configuration of a nanoparticle manufacturing apparatus according to a second embodiment. [Figure 3] FIG. 1 is a schematic diagram of an axial flow cyclone. DETAILED DESCRIPTION OF THE INVENTION

[0012] The present embodiment will be described in detail below with reference to the drawings. In the following description, the same components are denoted by the same reference numerals, and duplicated descriptions will be omitted.

[0013] First Embodiment 1. Overall structure 1, a nanoparticle production apparatus 10 according to this embodiment includes a plasma torch 11, a raw material supply unit 12, a reaction vessel 13, a rectification / cooling unit 14, and a recovery unit 15. In the nanoparticle production apparatus 10, the plasma torch 11 and the reaction vessel 13 are arranged in series, with the plasma torch 11 on the upper side and the reaction vessel 13 on the lower side.

[0014] The plasma torch 11 is installed in the reaction vessel 13. The plasma torch 11 generates a plasma flame 16. Examples of the plasma torch 11 include a DC plasma torch, a radio-frequency plasma torch, and a hybrid plasma torch that combines a DC plasma torch and a radio-frequency plasma torch. A DC plasma torch has a cathode and an anode connected to a DC power source and a flow path through which a working gas flows between the electrodes. A DC plasma torch generates DC plasma by supplying a working gas to the gas flow path and applying a DC voltage between the electrodes, which generates a discharge between the electrodes to convert the working gas into plasma. A radio-frequency plasma torch has an insulating tube through which the working gas flows and a radio-frequency induction coil wrapped around the insulating tube and connected to a radio-frequency power source. A radio-frequency plasma torch generates radio-frequency plasma by supplying a working gas to the insulating tube and applying a radio-frequency current to the radio-frequency induction coil to convert the working gas into plasma through electromagnetic induction. The hybrid plasma torch generates hybrid plasma by superimposing DC plasma and high frequency plasma. In this embodiment, the plasma torch 11 is a hybrid plasma torch.

[0015] The plasma torch 11 is connected to a power source, a working gas supply unit, a coolant supply unit, and a control unit (not shown). The power source applies current and voltage to the plasma torch 11. The working gas supply unit supplies working gas to the plasma torch 11. For example, a mixture of Ar gas and H2 gas is used as the working gas. The coolant supply unit cools the plasma torch 11 using a coolant (for example, water). The control unit is electrically connected to the power source, working gas supply unit, and coolant supply unit and controls and monitors the current, voltage, amount of working gas supplied, flow rate of working gas, pressure inside the reaction vessel 13, amount of coolant supplied, and coolant temperature. The plasma torch 11 receives working gas supplied from the working gas supply unit and receives current and voltage from the power source, converting the working gas into plasma and generating a high-temperature plasma flame 16. The average speed of the plasma flame 16 is several tens of meters per second. The plasma flame 16 is introduced into the reaction vessel 13.

[0016] The temperature of the plasma flame 16 decreases from the generation portion 17 of the plasma flame 16 toward the tail flame portion 18. The generation portion 17 of the plasma flame 16 has a temperature range above the boiling point of the powder raw material 20, which will be described later. The generation portion 17 is the highest temperature region of the plasma flame 16.

[0017] The raw material supply unit 12 is provided in the plasma torch 11. In this embodiment, the raw material supply unit 12 is provided above the plasma torch 11, but is not limited thereto and may be provided below the plasma torch 11, for example. The raw material supply unit 12 supplies a powder raw material 20 containing elements constituting nanoparticles to the plasma flame 16. In this embodiment, the raw material supply unit 12 supplies the powder raw material 20 to the generator 17 of the plasma flame 16 using a carrier gas. Examples of the carrier gas that can be used include Ar, H2, N2, O2, CH4, C2H2, and mixtures thereof. The raw material supply unit 12 may also be configured to supply a suspension of the powder raw material 20 in a solvent such as water or ethanol to the plasma flame 16. When the raw material 20 is supplied from the raw material supply unit 12 to the plasma flame 16, the raw material 20 is vaporized, generating a raw material gas 21.

[0018] The raw material 20 may be any material that melts and vaporizes in the plasma flame 16. Examples of such materials include metals such as Si, Cu, Al, Fe, and Ti, mixed powders or alloys of these metals, and ceramics such as oxides, nitrides, and carbides. Therefore, the nanoparticle production apparatus 10 produces metal nanoparticles, alloy nanoparticles, ceramic nanoparticles, and nanoparticles having a composite structure composed of multiple elements, depending on the selected raw material 20. When producing alloy nanoparticles or nanoparticles having a composite structure containing multiple elements, an alloy may be used as the raw material 20, or multiple metals that make up the alloy may be used as the raw material 20. In this embodiment, Si is used as the raw material 20. The diameter of the powder raw material 20 is preferably 0.1 μm or more and 100 μm or less, more preferably 0.1 μm or more and 20 μm or less, and particularly preferably 0.1 μm or more and 5 μm or less.

[0019] The reaction vessel 13 has an upper portion 13a, a lower portion 13b facing the upper portion 13a, and a side portion 13c connecting the upper portion 13a and the lower portion 13b. The shape of the reaction vessel 13 is cylindrical in this embodiment, but is not limited thereto and may be an elliptical cylinder, a rectangular column, an inverted cone, an inverted rectangular column, or the like. The upper portion 13a is a disk-shaped lid attached to the upper end of the side portion 13c. A plasma torch 11 is provided in the center of the upper portion 13a. The lower portion 13b is a cylindrical vessel with a bottom and an open top. The side portion 13c is composed of a cylindrical portion 30 connected to the upper portion 13a and a conical portion 31 connected to the lower portion 13b. The cylindrical portion 30 has an opening on its side to which the rectifying / cooling unit 14 is connected. The upper portion 13a of the reaction vessel 13 is connected to the plasma torch 11, and a plasma flame 16 is introduced from the plasma torch 11. The temperature of the plasma flame 16 introduced into the reaction vessel 13 decreases from the upper portion 13a to the lower portion 13b of the reaction vessel 13.

[0020] A plasma flame 16 is introduced into the reaction vessel 13, and a source gas 21 is generated in the plasma flame 16. The source gas 21 moves along the flow of the plasma flame 16 from the generation section 17 to the tail flame section 18, and is cooled as it moves. As the source gas 21 cools, it rapidly condenses to generate nanoparticles 22. Here, nanoparticles are particles with a diameter of less than 1000 nm. A gas flow 23 containing nanoparticles 22 is generated in the reaction vessel 13. Because the generated nanoparticles 22 are light, they float inside the reaction vessel 13 on the gas flow 23. If the nanoparticles 22 collide with the inner wall of the reaction vessel 13, they may adhere to the inner wall. In this embodiment, the gas flow 23 containing the nanoparticles 22 is rectified by the rectifying / cooling section 14, which will be described later. Collisions of the nanoparticles 22 with the inner wall of the reaction vessel 13 are suppressed, and the amount of nanoparticles 22 adhering to the inner wall of the reaction vessel 13 can be reduced. The rectifying effect of the rectifying / cooling section 14 can reduce the convection circulation of the nanoparticles 22 within the reaction vessel 13, suppressing the adhesion (probability) of the nanoparticles 22 to the inner wall of the reaction vessel 13 and reducing the amount of nanoparticles 22 adhering to the inner wall of the reaction vessel 13. In addition to the nanoparticles 22, coarse particles 24 are generated in the reaction vessel 13 as a result of the raw material 20 not completely evaporating and agglomerating. Here, coarse particles are particles with a particle size of 1 μm or more. The coarse particles 24 do not ride on the gas flow 23 and fall to the lower part 13b of the reaction vessel 13. The coarse particles 24 may be collected from the lower part 13b of the reaction vessel 13.

[0021] In this embodiment, the reaction vessel 13 has a cooling gas inlet 13d. In FIG. 1, the cooling gas inlet 13d is provided at the top 13a of the reaction vessel 13, but this is not limiting and it may be provided at the side 13c of the reaction vessel 13. The cooling gas inlet 13d is connected to a cooling gas supply unit (not shown) and introduces a cooling gas 25 supplied from the cooling gas supply unit into the reaction vessel 13. Examples of the cooling gas 25 include Ar, H2, N2, O2, CH4, C2H2, and mixtures thereof. The cooling gas 25 may be the same as the carrier gas used to supply the powdered raw material 20 to the plasma flame 16 in the raw material supply unit 12. The cooling gas 25 may be a gas different from the carrier gas. By introducing cooling gas 25 into reaction vessel 13, the flow rate of gas flow 23 flowing through rectification / cooling section 14, which will be described later, increases, the amount of nanoparticles 22 flowing into rectification / cooling section 14 increases, and adhesion of nanoparticles 22 to the inner wall of reaction vessel 13 is suppressed. As a result, the amount of nanoparticles 22 transported to collection section 15 increases, and the amount of nanoparticles 22 collected in collection section 15 can be increased. Note that reaction vessel 13 is not limited to one having cooling gas inlet section 13d.

[0022] The rectifying / cooling section 14 is provided between the reaction vessel 13 and the recovery section 15. The rectifying / cooling section 14 has an inlet 14a connected to the reaction vessel 13 and an outlet 14b connected to the recovery section 15. In the rectifying / cooling section 14, a gas flow 23 flows in through the inlet 14a and flows out through the outlet 14b. The inlet 14a of the rectifying / cooling section 14 is disposed in the side section 13c (cylindrical section 30) of the reaction vessel 13. The inlet 14a of the rectifying / cooling section 14 is desirably disposed in the side section 13c (cylindrical section 30) of the reaction vessel 13 between the generation section 17 and the tail flame section 18 of the plasma flame 16. The temperature of the inlet 14a of the rectifying / cooling section 14 is preferably 200°C or higher and 3000°C or lower, more preferably 400°C or higher and 2500°C or lower, and particularly preferably 600°C or higher and 2500°C or lower. In this embodiment, the inlet 14a of the rectifying / cooling section 14 is provided in the cylindrical section 30 near the tail flame section 18 of the plasma flame 16, and the temperature of the inlet 14a is 900° C. The temperature of the inlet 14a is detected by a temperature sensor (not shown).

[0023] A gas flow 23 containing nanoparticles 22 is introduced into the rectifying / cooling section 14 from the reaction vessel 13. At the inlet 14a of the rectifying / cooling section 14, the gas flow 23 is guided in a specific direction by suction from the exhaust section 29 and passed through the rectifying / cooling section 14, thereby rectifying and cooling the gas flow 23. The rectifying / cooling section 14 rectifies the flow of the gas flow 23 so that the nanoparticles 22 contained in the gas flow 23 do not collide with the inner wall of the reaction vessel 13. The rectifying / cooling section 14 cools the temperature of the gas flow 23 introduced from the reaction vessel 13 to a temperature below the heat-resistant temperature of the recovery section 15. The gas flow 23 cooled by the rectifying / cooling section 14 is led to the recovery section 15 from the outlet 14b. The temperature of the outlet 14b of the rectifying / cooling section 14 is preferably 180°C or less, more preferably 120°C or less, and particularly preferably 60°C or less. In this embodiment, the temperature of the outlet 14b is 27°C. The temperature of the outlet 14b is detected by a temperature sensor (not shown).

[0024] In this embodiment, the rectifying / cooling unit 14 is a straight-tube radiator having straight pipes 26 that rectify the flow of the gas flow 23 containing nanoparticles 22 in one direction and refrigerant pipes 27 through which refrigerant 28 flows. The straight-tube radiator referred to here has a structure similar to a double-pipe heat exchanger in which the gas flow 23 containing nanoparticles 22 inside the straight pipes 26 is cooled by the refrigerant 28 flowing through the refrigerant pipes 27, or a structure similar to a shell-and-tube heat exchanger consisting of multiple straight pipes 26 and refrigerant pipes 27 (also referred to as outer shells) surrounding them, in which the gas flow 23 containing nanoparticles 22 inside the straight pipes 26 is cooled by the refrigerant 28 flowing inside the outer shells. Because the gas flow path is a straight pipe, the gas flow 23 and the nanoparticles 22 contained in the gas flow 23 are cooled while moving linearly. The gas flow 23 is cooled by heat exchange with the pipe walls, and the nanoparticles 22 are effectively cooled by heat transfer cooling via the gas flow 23 as well as radiation to the walls of the straight pipes 26, which can promote particle cooling in a solid-gas mixed flow. To enhance the effect of heat transfer and radiation, the straight tube 26 may be provided with fins extending parallel to the axial direction of the straight tube 26 inside to increase the heat transfer surface.

[0025] The straight-tube radiator serving as the rectifying / cooling unit 14 has a double-pipe structure in which a refrigerant pipe 27 is provided outside a straight pipe 26. In FIG. 1, the rectifying / cooling unit 14 is configured so that a gas flow 23 flowing through the straight pipe 26 and a refrigerant 28 flowing through the refrigerant pipe 27 flow in opposite directions. The gas flow 23 is cooled by heat exchange between the gas flow 23 flowing through the straight pipe 26 and the refrigerant 28 flowing through the refrigerant pipe 27. The rectifying / cooling unit 14 causes the gas flow 23 introduced from the reaction vessel 13 to flow in one direction along the inner wall of the straight pipe 26 and guides it to the recovery unit 15. The nanoparticles 22 contained in the gas flow 23 have a reduced chance of colliding with the inner wall of the straight pipe 26, and when the flow velocity within the pipe is equal to or greater than the initial airflow velocity, the attached particles are detached. This reduces the number of nanoparticles 22 adhering to the inner wall of the straight pipe 26, and increases the number of nanoparticles 22 reaching the recovery unit 15.

[0026] The length of the straight pipe 26 is preferably 1250 mm or less, more preferably 750 mm or less, and particularly preferably 500 mm or less. 2 More than 180mm 2 Less than 5mm is preferable 2 More than 20mm 2 Less than 5mm is preferable 2 More than 10mm 2 The following is particularly preferable. In this case, when considering the length of the straight pipe 26, the heat transfer area per straight pipe is 5500 mm 2 Over 59,000mm 2 The flow velocity of the gas flow 23 flowing inside the straight pipe 26 is preferably 0.1 m / s or more and 120 m / s or less, and particularly preferably 25 m / s or more and 120 m / s or less, from the viewpoints of suppressing particle adhesion to the inner wall of the straight pipe 26 and peeling off adhered particles due to shear force.

[0027] In this embodiment, the rectifying / cooling section 14 has one straight pipe 26 and one refrigerant pipe 27, but is not limited thereto. The rectifying / cooling section 14 may be a shell-and-tube type having multiple straight pipes 26. When multiple straight pipes 26 are included, the multiple straight pipes 26 are preferably arranged in a honeycomb pattern when viewed axially of the straight pipes 26. The rectifying / cooling section 14 may also have multiple refrigerant pipes 27. When multiple refrigerant pipes 27 are included, the multiple refrigerant pipes 27 may be arranged to cover one straight pipe 26 or multiple bundled straight pipes 26. The multiple straight pipes 26 may be arranged at intervals from each other, and the refrigerant pipes 27 may be provided between the straight pipes 26. In this embodiment, the cross-sectional shape of the straight pipes 26 is circular, but is not limited thereto. The cross-sectional shape may be elliptical, polygonal, or an irregular shape (e.g., multi-lobed) that increases the contact area between the inner wall of the straight pipe 26 and the gas flow 23. In this embodiment, the cross-sectional shape of the refrigerant pipe 27 is circular, but is not limited to this and may be elliptical, polygonal, or have an uneven shape (for example, a multi-lobed shape) that increases the contact area between the inner wall of the refrigerant pipe 27 and the refrigerant 28.

[0028] The collection unit 15 receives the gas flow 23 cooled by the rectification / cooling unit 14 and collects the nanoparticles 22 contained in the gas flow 23. The collection unit 15 is connected to an exhaust unit 29 formed of a vacuum pump or the like, and is configured to exhaust the gas flow 23. The collection unit 15 may be configured to be detachable from the rectification / cooling unit 14 and the exhaust unit 29.

[0029] The collection unit 15 has a filter 15a and valves 15b and 15c. The filter 15a is for capturing nanoparticles 22 contained in the gas flow 23. The collection unit 15 preferably has a backwash filter as the filter 15a. Backwashing refers to the operation of generating an airflow (referred to as a backwash airflow) in the opposite direction to the airflow used to capture nanoparticles with the filter, thereby removing nanoparticles attached to the filter. The backwash airflow separates the nanoparticles captured by the filter from the filter surface and causes them to settle in the filter container. This backwashing operation not only unclogs the filter 15a and restores its nanoparticle capturing ability, but also eliminates the need for manual particle collection work, improving work efficiency and safety.

[0030] Valves 15b and 15c are used to seal filter 15a (backwash filter). Gate valves, for example, are used as valves 15b and 15c. Valve 15b is provided between rectifier / cooler 14 and filter 15a. Valve 15c is provided between filter 15a and exhaust unit 29. By opening valves 15b and 15c, gas flow 23 generated in reaction vessel 13 flows through rectifier / cooler 14, recovery unit 15, and exhaust unit 29 in this order. By closing valves 15b and 15c, nanoparticles 22 can be recovered by recovery unit 15 without exposure to the atmosphere. Therefore, in nanoparticle production apparatus 10, oxidation of nanoparticles 22 recovered by recovery unit 15 can be suppressed. Furthermore, in nanoparticle production apparatus 10, valves 15b and 15c can control the degree of oxidation of nanoparticles 22. For example, by increasing the opening of the valves 15b and 15c, the degree of oxidation of the nanoparticles 22 can be increased (oxidation can be advanced).

[0031] 2. Manufacturing method A nanoparticle production method for producing the nanoparticles 22 will be described below.

[0032] First, raw material 20 is supplied to plasma flame 16. The powder raw material 20 supplied to plasma flame 16 flies through the plasma flame 16, passing through a temperature range above the boiling point of the raw material 20, and is completely vaporized. In this example, raw material 20 is completely vaporized as it passes through generation section 17, which is the highest temperature range of plasma flame 16. In this way, raw material 20 is vaporized, and raw material gas 21 is generated.

[0033] The source gas 21 moves along the flow of the plasma flame 16 from the generation portion 17 of the plasma flame 16 toward the tail flame portion 18, and is cooled as it moves. In the cooling process of the source gas 21, nanoparticles 22 are generated by condensation of the source gas 21.

[0034] Next, the flow of the gas flow 23 containing the nanoparticles 22 is rectified, and the gas flow 23 is cooled. If the flow of the gas flow 23 containing the nanoparticles 22 is not rectified, the gas flow 23 becomes turbulent due to friction with the low-velocity gas in the reaction vessel 13, causing the nanoparticles 22 contained in the gas flow 23 to collide with the inner wall of the reaction vessel 13 and making the nanoparticles 22 more likely to adhere to the inner wall of the reaction vessel 13. In contrast, in this embodiment, the gas flow 23 is rectified so that the nanoparticles 22 contained in the gas flow 23 do not collide with the inner wall of the reaction vessel 13, thereby suppressing adhesion of the nanoparticles 22 to the inner wall of the reaction vessel 13. The gas flow 23 is cooled to a temperature equal to or lower than the heat-resistant temperature of the recovery unit 15. Then, the nanoparticles 22 contained in the cooled gas flow 23 are recovered.

[0035] 3. Action and Effects The nanoparticle production apparatus 10 described above includes a rectifying / cooling section 14 that rectifies the flow of a gas flow 23 containing nanoparticles 22 and cools the gas flow 23, and a recovery section 15 that recovers the nanoparticles 22 contained in the cooled gas flow 23. The amount of nanoparticles 22 adhering to the inner wall of the reaction vessel 13 decreases, and the amount of nanoparticles 22 that reaches the recovery section 15 increases. Therefore, the nanoparticle production apparatus 10 has excellent recovery efficiency of the nanoparticles 22.

[0036] The nanoparticle production apparatus 10 is equipped with a straight-tube radiator as the rectifying / cooling section 14, and the nanoparticles 22 contained in the gas flow 23 do not collide with the inner wall of the straight tube 26, thereby increasing the amount of nanoparticles 22 transported to the collection section 15. In addition, the straight-tube radiator enables rapid cooling of the gas flow 23, allowing the reaction vessel 13 to be made smaller. By making the reaction vessel 13 smaller, the area of ​​the inner wall of the reaction vessel 13 can be minimized, further increasing the amount of nanoparticles 22 transported to the collection section 15.

[0037] The collection unit 15 has a backwash filter as the filter 15a. The nanoparticle production apparatus 10 can recover the nanoparticle collection ability by clearing clogging of the filter 15a, and also eliminates the need for manual particle collection work, improving work efficiency and safety.

[0038] The collection unit 15 has valves 15b and 15c. By closing the valves 15b and 15c, the nanoparticle production apparatus 10 can collect the nanoparticles 22 without exposing them to the atmosphere, thereby achieving excellent collection efficiency of the nanoparticles 22 and suppressing oxidation of the nanoparticles 22. The nanoparticle production apparatus 10 can control the degree of oxidation of the nanoparticles 22 by adjusting the opening of the valves 15b and 15c.

[0039] The above-described nanoparticle production method rectifies the flow of gas flow 23 containing nanoparticles 22, cools gas flow 23, and recovers nanoparticles 22 contained in cooled gas flow 23. As described above, the amount of nanoparticles 22 adhering to the inner wall of reaction vessel 13 decreases, and the amount of nanoparticles 22 reaching recovery section 15 increases. Therefore, the nanoparticle production method has excellent nanoparticle 22 recovery efficiency.

[0040] Second Embodiment The first embodiment is provided with a straight pipe radiator as the rectifying / cooling section 14, whereas the second embodiment is provided with an axial flow cyclone as the rectifying / cooling section. The same reference numerals are used for the same members as in the first embodiment, and the description thereof will be omitted.

[0041] 2, the nanoparticle production apparatus 40 includes a plasma torch 11, a raw material supply unit 12, a reaction vessel 43, a rectifying / cooling unit 44, and a recovery unit 15. Descriptions of the plasma torch 11, the raw material supply unit 12, and the recovery unit 15 will be omitted.

[0042] The reaction vessel 43 has an upper portion 13a, a lower portion 13b disposed opposite the upper portion 13a, and a side portion 13c connecting the upper portion 13a and the lower portion 13b. The reaction vessel 43 has the same configuration as the reaction vessel 13 of the first embodiment, except that it does not have the cooling gas inlet portion 13d (see FIG. 1) of the first embodiment. A plasma flame 16 is introduced into the reaction vessel 43, and a source gas 21 is generated in the plasma flame 16. The source gas 21 is cooled as it moves along the flow of the plasma flame 16, and nanoparticles 22 are generated by rapid condensation of the source gas 21. A gas flow 23 containing nanoparticles 22 is generated in the reaction vessel 43. Note that the reaction vessel 43 may also have the cooling gas inlet portion 13d. If the reaction vessel 43 has the cooling gas inlet portion 13d, the flow rate of the gas flow 23 flowing through the rectifying / cooling portion 44 increases, the amount of nanoparticles 22 flowing into the rectifying / cooling portion 44 increases, and adhesion of the nanoparticles 22 to the inner wall of the reaction vessel 43 is suppressed. As a result, the amount of nanoparticles 22 transported to the collection section 15 increases, and the amount of nanoparticles 22 collected by the collection section 15 can be increased.

[0043] The rectifying / cooling section 44 is provided inside the reaction vessel 43. More specifically, the rectifying / cooling section 44 is provided near the tail flame section 18 of the plasma flame 16. The rectifying / cooling section 44 receives the gas flow 23 containing the nanoparticles 22 produced in the reaction vessel 43. The rectifying / cooling section 44 rectifies the flow of the gas flow 23 and cools the gas flow 23.

[0044] As shown in FIG. 3 , the rectifying / cooling section 44 is an axial-flow cyclone having vanes 45 that rectify the flow of the gas flow 23 to create a swirling flow, a cooling section 46 that cools the gas flow 23, and a flow path 47 that guides the cooled gas flow 23 to the recovery section 15. The axial-flow cyclone serving as the rectifying / cooling section 44 has multiple vanes 45 arranged at intervals in an annular shape, and is configured so that the gas flow 23 is drawn through gaps between adjacent vanes 45. The gaps between adjacent vanes 45 function as the inlet of the rectifying / cooling section 44. The temperature at the inlet of the rectifying / cooling section 44 is preferably 200°C or higher and 3000°C or lower, more preferably 400°C or higher and 2500°C or lower, and particularly preferably 600°C or higher and 2500°C or lower. The gas flow 23 is drawn through the gaps between the vanes 45 and flows along the vanes 45, thereby moving in a swirling manner from the upper portion 13a to the lower portion 13b of the reaction vessel 43. After moving to the lower portion 13b of the reaction vessel 43, the gas flow 23 reverses its flow direction and moves from the lower portion 13b to the upper portion 13a of the reaction vessel 43. The nanoparticles 22 move from the lower portion 13b to the upper portion 13a of the reaction vessel 43 on the gas flow 23 and are guided to the collection section 15 via the flow path 47. If the gas flow 23 contains coarse particles 24, the coarse particles 24 are pressed against the inner wall of the side portion 13c (cylindrical portion 30 and conical portion 31) of the reaction vessel 43 by centrifugal force due to the swirling flow of the gas flow 23 and fall into the lower portion 13b of the reaction vessel 43 by their own weight. The coarse particles 24 that have fallen into the lower portion 13b of the reaction vessel 43 may be collected. In this embodiment, the vane 45 is arranged with a gap between it and the side portion 13c of the reaction vessel 43 (see FIG. 2), but this is not limited thereto; the vane 45 may also be arranged without a gap between it and the side portion 13c of the reaction vessel 43. The cooling section 46 is connected to a refrigerant supply section (not shown) and cools the gas flow 23 with the refrigerant supplied from the refrigerant supply section. The flow path 47 is connected to the recovery section 15. The flow path 47 has an inlet 47a provided inside the reaction vessel 43 and an outlet 47b provided in the side section 13c of the reaction vessel 43. The gas flow 23 flows into the flow path 47 from the inlet 47a and flows out from the outlet 47b. The outlet 47b of the flow path 47 functions as the outlet of the rectification / cooling section 44. The temperature at the outlet of the rectification / cooling section 44 is preferably 180°C or less, more preferably 120°C or less, and particularly preferably 60°C or less.

[0045] The nanoparticle production apparatus 40 described above includes a rectifying / cooling section 44 that rectifies the flow of the gas flow 23 containing the nanoparticles 22 and cools the gas flow 23, and a recovery section 15 that recovers the nanoparticles 22 contained in the cooled gas flow 23. The amount of nanoparticles 22 adhering to the inner wall of the reaction vessel 43 decreases, and the amount of nanoparticles 22 that reaches the recovery section 15 increases. Therefore, the nanoparticle production apparatus 40 has excellent nanoparticle 22 recovery efficiency.

[0046] The nanoparticle production apparatus 40 is equipped with an axial flow cyclone as the rectification / cooling section 44, which rectifies the flow of the gas flow 23 to create a swirling flow, thereby separating and recovering the nanoparticles 22 and the coarse particles 24. As a result, the recovered nanoparticles 22 do not become mixed with the coarse particles 24, eliminating the need for classification after recovery. In addition, an axial flow cyclone can be made smaller than a tangential inflow cyclone, allowing for a smaller reaction vessel 43. By reducing the size of the reaction vessel 43, the area of ​​the inner wall of the reaction vessel 43 can be minimized, further increasing the amount of nanoparticles 22 transported to the recovery section 15.

[0047] 4. Working Example An experiment was conducted to investigate the amount of nanoparticles 22 recovered in the recovery section 15. Examples 1 and 2 were nanoparticle production apparatuses 10 that used a straight-tube radiator as the rectifying / cooling section 14. In Example 1, cooling gas 25 was not introduced into the reaction vessel 13. In Example 2, cooling gas 25 was introduced into the reaction vessel 13. That is, in Example 2, by introducing cooling gas 25 into the reaction vessel 13, the flow rate of the gas flow 23 flowing through the rectifying / cooling section 14 was increased compared to Example 1. The cooling gas inlet section 13d was provided on the side section 13c of the reaction vessel 13. A nanoparticle production apparatus that uses a cooling plate to cool the gas flow containing nanoparticles was used as a comparative example.

[0048] The nanoparticle production apparatus 10 of Examples 1 and 2 used a hybrid plasma torch as the plasma torch 11, with the power of the DC power supply being 3 kW and the power of the high frequency power supply being 55 kW. A mixed gas of Ar gas and H2 gas was used as the working gas. The flow rate of Ar gas was 140 slm. The flow rate of H2 gas was 20 slm. Water was used as the refrigerant to cool the plasma torch 11. The raw material supply unit 12 supplied Si powder with an average particle size of 16 μm at a supply rate of 5 g / min. The internal pressure of the reaction vessel 13 was 30 kPa. The rectifying / cooling unit 14 used 605 straight pipes 26, each with a length of 500 mm and a cross-sectional area of ​​9.6 mm 2 The flow rate of the carrier gas for supplying the Si powder was set to 10 slm. In Example 2, the flow rate of the cooling gas 25 was set to 300 slm. The nanoparticle production apparatus of the comparative example was configured in the same way as Example 1, except that a cooling plate was placed in the lower part of the reaction vessel so as to collide with the gas flow containing nanoparticles, instead of the rectifying / cooling section 14.

[0049] Table 1 compares the ratio (recovery ratio) of the amount of Si nanoparticles recovered in recovery section 15 to the total amount of Si nanoparticles recovered from the inner wall of reaction vessel 13 and recovery section 15.

[0050] [Table 1]

[0051] It was confirmed that in Examples 1 and 2, more Si nanoparticles were recovered in recovery section 15 than in the comparative example. It was found that in Examples 1 and 2, the flow of gas flow 23 was rectified by rectification / cooling section 14, and the Si nanoparticles could be efficiently transported to recovery section 15. Comparing Example 1 and Example 2, Example 2, in which cooling gas 25 was introduced, recovered a larger amount of Si nanoparticles than Example 1, in which cooling gas 25 was not introduced. This is thought to be because the flow rate of gas flow 23 flowing through straight pipe 26 of rectifying / cooling section 14 increased, suppressing adhesion of Si nanoparticles to the inner wall of straight pipe 26 and increasing the amount of Si nanoparticles transported to recovery section 15.

[0052] The nanoparticle production apparatus according to the present invention is equipped with a rectifying / cooling section and a recovery section, allowing for 24-hour operation, and has high marketability and industrial advantages. Furthermore, the highly efficient cooling mechanism enables the heat source to be increased in output, contributing to improved production speed and reducing manual labor required for recovering the produced nanoparticles, making it suitable for industrial use. Furthermore, by utilizing thermal fluid simulation to design the temperature history of the raw material particles, it is possible to optimize process conditions and improve the quality of the particles. Furthermore, since the nanoparticle recovery process reduces worker exposure to nanoparticles and their release into the surrounding environment, it is also useful in terms of safety and health. Therefore, the nanoparticle production apparatus and nanoparticle production method according to the present invention are suitable as industrial nanoparticle production apparatuses and methods.

[0053] Although the embodiments and examples of the present invention have been described above, the present invention is not limited to the above embodiments and examples and can be modified as appropriate within the scope of the present invention. For example, it is possible to configure an apparatus in which multiple mechanisms combining the rectification / cooling section 14 and the recovery section 15 are installed in parallel with one reaction vessel 13. By performing the process of collecting nanoparticles during normal operation and the process of backwashing the filter after collection and removing the nanoparticles in parallel, it is possible to produce nanoparticles in long-term continuous operation. [Explanation of symbols]

[0054] 10, 40 Nanoparticle manufacturing equipment 11 Plasma Torch 12 Raw material supply department 13, 43 Reaction vessel 14, 44 Rectification / cooling section 15 Collection Department 15a filter 15b, 15c valves 16 Plasma Flame 20 raw materials 21 Raw material gas 22 Nanoparticles 23 Gas flow 26 straight pipe 27 Refrigerant pipe 28 Refrigerant 45 vane 46 Cooling section 47 Flow path

Claims

1. a plasma torch that generates a plasma flame; a raw material supply unit that supplies a raw material to the plasma flame and vaporizes the raw material to generate a raw material gas; a reaction vessel in which a gas stream containing nanoparticles produced by condensation of the raw material gas is generated; a rectifying / cooling unit into which the gas flow containing the nanoparticles is introduced, which rectifies the flow of the gas flow and cools the gas flow; a collection section into which the cooled gas flow is introduced and which collects the nanoparticles; the flow rectifying / cooling unit includes a straight pipe that rectifies the flow of the gas in one direction and a refrigerant pipe through which a refrigerant flows, The rectifying / cooling section has an inlet connected to the reaction vessel and an outlet connected to the recovery section, and the inlet is disposed in the reaction vessel between the plasma flame generation section and the tail flame section. Nanoparticle manufacturing equipment.

2. A nanoparticle manufacturing apparatus as described in claim 1, wherein the temperature of the gas flow at the inlet is not less than 600°C and not more than 3000°C, and the temperature of the gas flow at the outlet is not more than 180°C.

3. A nanoparticle manufacturing apparatus as described in claim 1 or 2, wherein the flow rate of the gas flowing inside the straight pipe is 0.1 m / s or more and 120 m / s or less.

4. A plasma torch that generates a plasma flame; a raw material supply unit that supplies a raw material to the plasma flame and vaporizes the raw material to generate a raw material gas; a reaction vessel in which a gas stream containing nanoparticles produced by condensation of the raw material gas is generated; a rectifying / cooling unit into which the gas flow containing the nanoparticles is introduced, which rectifies the flow of the gas flow and cools the gas flow; a collection section into which the cooled gas flow is introduced and which collects the nanoparticles; the rectifying / cooling unit includes a vane that rectifies the flow of the gas flow to form a swirling flow, a cooling unit that cools the gas flow, and a flow path that guides the gas flow cooled by the cooling unit to the recovery unit, The flow path has an inlet provided inside the reaction vessel and an outlet provided on the side of the reaction vessel. Nanoparticle manufacturing equipment.

5. 5. The nanoparticle production apparatus according to claim 1, wherein the recovery section has a backwash filter.

6. The nanoparticle production apparatus according to claim 5 , wherein the recovery unit has a valve that seals the backwash filter.

7. supplying a raw material to a plasma flame and vaporizing the raw material to generate a raw material gas; generating nanoparticles by condensing the source gas in a reaction vessel; a flow straightening / cooling unit for straightening the flow of the gas flow containing the nanoparticles and cooling the gas flow; A method for producing nanoparticles, comprising recovering the nanoparticles contained in the cooled gas flow in a recovery unit, the flow rectifying / cooling unit includes a straight pipe that rectifies the flow of the gas in one direction and a refrigerant pipe through which a refrigerant flows, The rectifying / cooling section has an inlet connected to the reaction vessel and an outlet connected to the recovery section, and the inlet is disposed in the reaction vessel between the plasma flame generation section and the tail flame section. Nanoparticle manufacturing method.

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