Device and method for preparing nano silicon through cooperation of medium-frequency melting and plasma gasification

Abstract

The invention discloses a device and a method for preparing nano silicon through medium-frequency melting in cooperation with plasma gasification, and belongs to the field of nano powder production.The device comprises a medium-frequency melting system, a plasma gasification system and a nano silicon collecting system.The silicon material is heated to 1700 DEG C or above in a vacuum environment through a medium-frequency melting furnace; the method comprises the following steps: removing sulfur and oxygen impurities by combining bottom blowing gas (methane / hydrogen), purifying by a deacidification tower and an activated carbon adsorption tower, transferring high-purity silicon liquid to a plasma gasification furnace, and heating to 1800-2100 DEG C (the contact area reaches 3200-3600 DEG C) under the driving of inert gas by utilizing a transferred arc plasma torch, so that the silicon liquid is gasified into steam. The steam is nucleated by a primary cooler (1600-2100 DEG C) and quenched by a liquid nitrogen quench tower to be below room temperature, and finally, nano silicon with the particle size of 30-60 nm and the purity of more than or equal to 99.99% is collected by a bag collector, multi-furnace collaborative feeding, dynamic liquid level adjustment and inert gas protection are adopted, efficient and continuous production is realized, and the problems of low efficiency, poor purity, insufficient safety and the like of a traditional method are solved.

Description

Technical Field

[0001] The present invention relates to the field of nano powder production, in particular to a device and method for preparing nano silicon by medium frequency melting and transferred arc plasma in coordination with non-transferred arc plasma gasification. Background Art

[0002] Currently, new energy vehicles are the mainstream means of transportation for emission reduction. The main material for the negative electrode in lithium-ion batteries is graphite. Due to its inherent storage capacity limitations, graphite cannot meet the requirements of large-capacity energy storage devices and high energy density. Silicon has a theoretical capacity nearly 10 times higher than graphite (silicon's theoretical capacity is as high as 4200mA.h / g), a lower lithium insertion potential, and ranks second on Earth in reserves. It is also environmentally friendly. However, silicon expands nearly three times in volume when intercalated with lithium. This volume expansion pulverizes the silicon, hindering electrical connectivity, posing safety risks to the application of lithium batteries, and restricting the application of silicon in lithium batteries. Currently, there are two inherent challenges: first, the volume expansion of up to 300% during charging and discharging can easily lead to damage to the electrode structure, capacity decay, and reduced cycle efficiency; second, the poor conductivity of silicon itself affects the battery's rate performance.

[0003] To address these challenges, the industry has mainly started from material structure design and adopted a variety of strategies: including nano-sizing silicon-based materials, developing materials with special structures (such as porous, hollow, and core-shell structures) to solve the expansion problem, and coating silicon atoms with carbon or metal oxides to improve conductivity.

[0004] Controlling silicon particle size below 20nm is crucial. Silicon particles smaller than 20nm have significantly enhanced fracture toughness and are less prone to breakage. Nanosizing also shortens lithium-ion transport distances, reduces polarization, and improves material utilization.

[0005] Nano silicon preparation method has chemical etching method, laser ablation method, mechanical grinding method, aqueous phase synthesis method so far, and these methods all can not reach satisfied nano silicon quality, and although some methods can reach ideal quality but can not mass produce (i.e. industrial application).Wherein CN118595449A discloses a kind of ultrafine nano powder manufacturing device based on plasma and manufacture method thereof, although this method solves the problem that nano powder is deposited at vacuum tank inner wall bottom and is difficult to large-scale efficiency collection in subsequent powder collection process, but adopt laser to make plasma in method, laser self efficiency is low, and production is intermittent i.e. production cost height, is difficult to mass produce; And, laser is easily reflected at the specular surface of making material, very easily causes safety incident.

[0006] CN202420803503.1 discloses a nano-silicon powder plasma preparation system, which directly uses plasma to nano-spheroidize quartz sand below 200 meshes. Since the high temperature of the plasma is used to heat the quartz sand for gasification, the gas-solid heat transfer is poor, so the production cost is high. CN114031082B discloses a method for preparing nano-silicon by pyrolysis of silane using induction plasma. This method uses argon as the working gas of the plasma and silane as the raw material. The induction plasma efficiency is low, and the cost of argon and silane is high. In addition, the preparation of nano-silicon from silane will produce hydrogen as a by-product, which has the risk of explosion. CN106185947A and CN212864154U disclose a nano-silicon powder production device. Although this device can improve the purity, output and particle size distribution control effect of the silicon powder produced, it also uses the high temperature of the plasma to heat and gasify the silicon powder, which belongs to gas-solid heat transfer and has low energy utilization. Summary of the Invention

[0007] In order to overcome the above-mentioned defects of the prior art, the technical problem to be solved by the embodiments of the present invention is to provide a device and method for producing nano-silicon by medium-frequency melting and transferred arc coordinated with non-transferred arc plasma gasification, which can prepare nano-silicon materials with high energy utilization, large-scale production and stable quality.

[0008] The specific implementation scheme of the present invention is: a device and method for producing nano-silicon by medium frequency melting and transferred arc coordinated with non-transferred arc plasma gasification, including: medium frequency melting and transferred arc melting system, non-transferred arc plasma gasification system and nano-silicon nucleation, growth, crystallization and collection system.

[0009] Medium frequency melting and transferred arc melting system, including silicon material feeding sealing mechanism, vacuum pump, medium frequency melting furnace, medium frequency heating and transferred arc heating system, bottom blowing device, rotating system, deacidification tower, alkali liquid tank, activated carbon adsorption tower and fan;

[0010] Non-transferred arc plasma gasification system, including plasma gasification furnace, transferred arc plasma torch, refrigerator, deionized water circulation pump, silicon liquid connecting pipeline, and recycling chamber;

[0011] A nano-silicon nucleation, growth, crystallization and collection system comprising a primary cooler, a quenching tower, a bag dust collector (10) and a vacuum system;

[0012] The medium frequency melting furnace is connected to the plasma gasification furnace through a silicon liquid connecting pipe, and the outlet of the plasma gasification furnace is connected to a primary cooler, a quenching tower and a bag dust collector in sequence.

[0013] Furthermore, the heating method of the medium frequency melting furnace is medium frequency coil heating or transferred arc electrode heating, or a combination of the two.

[0014] Furthermore, the plasma torch of the plasma gasification furnace uses an inert working gas, including but not limited to nitrogen or argon.

[0015] Furthermore, the impurity removal gas introduced into the bottom blowing device is methane or hydrogen and other gases, which are used to remove impurities such as sulfur and oxygen in the silicon material.

[0016] Furthermore, the quenching tower uses liquid nitrogen countercurrent cooling to cool the nano-silicon-containing gas to below room temperature.

[0017] A process of producing nano-silicon by medium frequency melting and plasma gasification:

[0018] 1. Open the silicon material feeding sealing mechanism (19), and transport the silicon material (which can be silicon powder, silicon wafers, silicon ingots, etc.) into the medium frequency melting furnace (1). Start the B vacuum pump (20), which can be a roots pump, a screw pump or a vortex pump. After the vacuum is drawn to a vacuum degree of ≤0.5Pa, stop the vacuum pump. Start the medium frequency and transferred arc heating system (2) to heat the silicon material in the melting furnace. While heating, start the alkali liquid circulation pump (14) and the fan (18). When the temperature of the melting furnace (1) reaches 1700℃, start the rotating device of the medium frequency melting furnace, rotate the crucible in the melting furnace clockwise (or counterclockwise) or rotate the heating coil. The purpose of rotating the crucible is to keep the molten liquid in the pot heated evenly and the temperature field consistent, and to remove water vapor in the silicon material. Start the bottom blowing system while the crucible is rotating, and input the impurity removal gas (the impurity removal gas can be methane or hydrogen) into the bottom blowing system to remove impurities such as sulfur and oxygen in the silicon material. Impurity gases such as hydrogen sulfide, water, and hydrocarbons generated during the silicon material melting process are pumped to the deacidification tower (16) under the suction action of the fan (18). The alkali liquid in the alkali liquid tank (15) is pumped to the deacidification tower (16) by the alkali liquid circulation pump (14), and forms an atomized state through the atomizing nozzle in the deacidification tower (16). The atomized alkali liquid and the impurity gas undergo a rapid heat and mass transfer reaction to absorb the acidic gas in the impurity gas. The deacidified gas passes through the wire mesh demister of the deacidification tower to remove all the liquid in the gas. After removal, the gas enters the activated carbon adsorption tower (17) to adsorb the remaining harmful components in the impurity gas, and the adsorbed gas is discharged. In addition to using the crucible itself to rotate and bottom-blown stirring, the molten liquid in the medium frequency melting furnace (1) can also be stirred by a stirrer. The purpose is to remove impurities in the molten silicon liquid, heat it evenly, and facilitate the degassing and modification of the bottom-blown airflow.

[0019] 2. When the temperature of the melt in the intermediate frequency melting furnace (1) reaches 1700°C, start the deionized water circulation pump (13) and the refrigerator (12), open the nitrogen valve, start the plasma torch (4), heat the plasma gasification furnace (3), heat the crucible in the plasma gasification furnace (3) to 1800°C, and then keep it warm for standby use. At the same time, close the shut-off valve (5) of the pipeline connecting the plasma gasification furnace (3) and the casting mold chamber (7). Open the inlet and outlet valves on the water-cooled side of the primary cooler to put the primary cooler into the cold end state.

[0020] 3. When the temperature in the intermediate frequency melting furnace (1) is maintained at 1700°C for 10 to 45 minutes and the impurity gas is removed, open the furnace cover of the melting furnace and the feed cover of the plasma gasification furnace (3), start the lifting device of the crucible, and lift the liquid outlet of the crucible to a certain position (100 to 300 mm higher than the solution inlet of the plasma gasification furnace). Then, open the valve on the liquid outlet of the intermediate frequency melting furnace and start the pouring device of the melting furnace (1). Pour all the silicon liquid in the melting furnace into the plasma gasification system, open the feed cover of the plasma gasification furnace (3), close the valve on the discharge pipe of the intermediate frequency melting furnace (1), start the pouring device and the lifting device to restore the crucible in the intermediate frequency melting furnace, and close the furnace cover of the intermediate frequency melting furnace to add the next batch of materials for melting.

[0021] 4. In order to ensure the continuous production of the plasma gasification furnace, multiple plasma medium frequency melting furnaces can be used. The plasma gasification furnace is placed in the middle, and medium frequency melting furnaces are evenly distributed around it for batch production. The medium frequency melting furnace (1) can be heated by coil alone or by transfer arc or by a combination of the two. After closing the liquid inlet of the plasma gasification furnace, start the plasma torch (4) and open the liquid nitrogen valve at the same time. The silicon liquid in the plasma gasification furnace boils and vaporizes under the high temperature heating of the plasma. After the silicon liquid is vaporized, silicon gas is formed and the high temperature gas generated by the plasma is used to carry out the nano-silicon nucleation, growth, crystallization and collection system.

[0022] 5. The crucible temperature in the plasma gasification furnace is maintained at 1800-2100°C, while the temperature of the silicon liquid in contact with the plasma is maintained at 3200-3600°C. Under the high temperature of the plasma, the silicon liquid begins to boil and vaporize to form silicon vapor. As the silicon solution evaporates, the silicon liquid level begins to drop. To maintain the contact temperature between the plasma and the silicon liquid (the power of the plasma torch is constant, that is, the flame length of the plasma torch is constant), the crucible lifting device is activated according to the evaporation rate of the silicon liquid (that is, the rate of liquid level drop in the crucible). The lifting speed of the lifting device is consistent with the rate of liquid level drop.

[0023] 6. High-temperature nitrogen and silicon vapor enter the nano-silicon nucleation, growth, crystallization, and collection system. Silicon vapor nucleates and generates nano-silicon in the primary cooler. The temperature of the silicon vapor mixture in the primary cooler (8) is 1600-2100°C, ensuring that the silicon vapor nucleates, grows, spheroidizes, and forms. The nano-silicon formed in the primary cooler enters the quenching tower under the nitrogen flow. The quenching tower uses liquid nitrogen for cooling. The liquid nitrogen and the high-temperature nitrogen containing nano-silicon are in countercurrent contact to quench the nano-silicon to prevent the nano-silicon from agglomerating and affecting the quality of the nano-silicon. The liquid nitrogen in the quenching tower cools the nano-silicon and nitrogen to room temperature or very low temperature. The silicon-containing gas cooled to room temperature is sucked to the bag dust collector by the fan (11). The nano-silicon is filtered by the bag for gas-solid separation. The separated nano-silicon is packaged and sold. Since there are only nano-silicon and nitrogen in the gasification process, the nitrogen generated in the gasification process does not need to be treated and can be reused or bottled for sale.

[0024] 7. When the liquid level of the silicon solution in the plasma gasification furnace is less than 5 mm, or when the nano-silicon nucleation, growth, crystallization and collection system fails, the intermediate frequency power supply of the intermediate frequency system is started to heat the connecting pipe between the plasma gasification furnace and the recycling chamber (7). When the pipe is heated to 1600° C., the valve of the connecting pipe is opened to send the remaining silicon solution in the plasma gasification furnace to the recycling chamber for molding into silicon ingots so that it can be melted again to produce nano-silicon.

[0025] The shutdown sequence of the system is as follows: turn off the plasma power supply, turn off the heating power supply of the intermediate frequency melting furnace (1). When the temperature in the intermediate frequency melting furnace (1) drops to room temperature, turn off the alkali liquid circulation pump (14) and the fan (18); when the temperature of the plasma gasification furnace drops to room temperature, turn off the deionized water pump (13) and the refrigerator (12); and close the water valve and fan (11) of the primary cooler.

[0026] Beneficial effects: The process of the present invention is reasonably designed and highly practical, and has the following beneficial effects:

[0027] (1) The medium frequency melting furnace adopts bottom blowing technology, which facilitates the purification and modification of materials to improve the purity of nano-silicon, and its purity can reach more than 0.9999%;

[0028] (2) The medium frequency melting furnace adopts a variety of heating methods to speed up the melting speed of silicon materials and improve production efficiency;

[0029] (3) The combination of multiple medium frequency melting furnaces and a gasification furnace can achieve large-scale continuous production;

[0030] (4) The medium frequency melting furnace and plasma gasification furnace are used for coordinated production, saving energy and improving production efficiency;

[0031] (5) Using a plasma torch can increase the temperature of the silicon melt to a higher level, reducing the requirements for materials;

[0032] (6) The plasma torch can use a variety of inert working gases (such as nitrogen and argon), avoiding the risk of nano-silicon explosion and ensuring the safety of the entire system.

[0033] (7) A low temperature or ultra-low temperature environment and a rapid freezing rate are used, thereby achieving the best chemical uniformity and extremely fine granulation effect. At the same time, the prepared nanoparticles also have the advantages of less hard agglomeration and high chemical purity.

[0034] (8) The bag harvesting with inert gas atmosphere and inert blowing is adopted to completely eliminate the risk of nanoparticle dust explosion and achieve inherent safety.

[0035] (9) The purified inert gas re-enters the process and the plasma gas source, basically realizing the recycling of the inert gas. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 The present invention is a work flow chart for producing nano-silicon by medium frequency melting and transferred arc coordinated with non-transferred arc plasma gasification.

[0037] Figure 2 This is a system configuration diagram of a medium frequency melting furnace.

[0038] Figure 3 It is a schematic diagram of the planar structure of a medium frequency melting furnace.

[0039] Figure 4 This is a top view of a medium frequency melting furnace.

[0040] Figure 5 This is a scanning electron microscope image of nano-silicon SME prepared under working condition 1.

[0041] Figure 6 This is a scanning electron microscope image of nano-silicon SME prepared under working condition 2.

[0042] In the figure: 1 - medium frequency melting furnace; 2 - medium frequency and transferred arc heating system; 3 - ion gasification furnace; 4 - plasma torch; 5 - cut-off valve; 6 - medium frequency power supply; 7 - reflow chamber; 8 - primary cooler; 9 - quenching tower; 10 - bag filter; 11 - vacuum pump No. A; 12 - refrigerator; 13 - deionized water circulation pump; 14 - alkali solution circulation pump; 15 - alkali solution tank; 16 - deacidification tower; 17 - activated carbon adsorption tower; 18 - fan; 19 - silicon material feed sealing mechanism; 20 - vacuum pump No. B; 21 - vacuum feeding system; 22 - medium frequency melting and transferred arc melting system; 23 - transferred arc (electrode) flow channel system; 24 - plasma generation system; 25 - plasma vaporization system; 26 - aerosol powder making system; 27 - recycling casting system; 1-1 - feed vacuum valve;

[0043] 1-2—feed vacuum chamber; 1-3—discharge vacuum valve; 1-4—inert gas inlet; 2-1—lifting and turning device;

[0044] 2-2—Intermediate frequency heating tube; 2-3—Melted graphite pot; 2-4—Carbon-based mixer; 2-5—Inert bottom blowing chamber;

[0045] 2-6—Inert gas inlet flange; 2-7—Automatic balancing leg; 3-1—Cathode graphite flow channel; 3-2—Flow channel flipper; 3-3—Vacuum quick-break valve; 3-4—Anode generator; 4-1—Plasma torch-1; 4-2—Plasma torch-2; 4-3—Plasma torch-3; 4-4—Inert gas inlet hole; 5-1—Gasification pot; 5-2—Gasification chamber; 5-3—Gasification exhaust flange hole; 5-4—Pneumatic lifter; 5-5—Return pipe; 5-6—Rotator; 5-7—Inert gas bottom blowpipe; 6-1—Exhaust hole; 6-2—Explosion-proof disk; 6-3—Plasma torch-4; 6-4—Impact ball; 6-5—Waste liquid flange; 6-6—Atomizer; 7-1—Reuse three-way valve; DETAILED DESCRIPTION

[0046] The subject matter described herein will now be discussed with reference to exemplary embodiments. It should be understood that these embodiments are discussed solely to enable those skilled in the art to better understand and implement the subject matter described herein, and that the functions and arrangements of the elements discussed may be varied without departing from the scope of this specification. Various examples may omit, substitute, or add various processes or components as needed. In addition, features described with respect to some examples may also be combined in other examples.

[0047] like Figure 1-4As shown, a device for producing nano-silicon by medium-frequency melting and transferred arc coordinated with non-transferred arc plasma gasification realizes the continuous production of high-purity nano-silicon through the synergistic effect of three core links: medium-frequency melting purification, plasma high-temperature gasification, and rapid cooling crystallization collection. The specific working principle is as follows: 1. Medium-frequency melting purification: The silicon material is fed into the medium-frequency melting furnace through a vacuum feeding system. After being evacuated to ≤0.5Pa, it is heated to above 1700℃ using a medium-frequency coil or a transferred arc electrode to completely melt the silicon material. During the melting process, methane or hydrogen is introduced into the bottom blowing device, which reacts with impurities such as sulfur and oxygen in the silicon liquid to generate gas, which is then purified and removed through a deacidification tower and an activated carbon adsorption tower. At the same time, the rotation or stirring system of the melting furnace ensures that the silicon liquid is heated evenly and impurities are fully removed, providing high-purity silicon liquid for subsequent gasification. 2. Plasma High-Temperature Gasification: The purified molten silicon liquid is transferred to a plasma gasifier. High-temperature plasma generated by a transferred arc plasma torch (driven by an inert gas) heats the silicon liquid to 1800-2100°C, with temperatures in the contact zone reaching as high as 3200-3600°C. This rapidly vaporizes the silicon liquid into silicon vapor. The torch power and liquid level adjustment are dynamically adjusted to maintain a stable vaporization temperature. If the silicon liquid is depleted or a system failure occurs, the remaining silicon liquid can be transported to a recycling chamber for ingot casting and recovery, ensuring continuous production. 3. Rapid Cooling and Crystallization and Collection: The silicon vapor and high-temperature gas enter a primary cooler, where they are slowly cooled at 1600-2100°C to nucleate and form nanosilicon particles. They then enter a quench tower where they are instantly cooled to below room temperature in a countercurrent flow of liquid nitrogen to prevent particle agglomeration. Finally, the nanosilicon-containing gas is filtered and separated through a bag filter, yielding nanosilicon particles with a size of 30-60 nm and a purity of ≥99.99%. The system uses inert gas protection throughout the process, combined with waste heat recovery and explosion-proof design to achieve safe and efficient large-scale production.

[0048] Implementation method 1:

[0049] like Figure 5As shown, this embodiment uses silicon waste as raw material, and the specific process is as follows: 50kg of silicon waste is fed into the medium frequency melting furnace (1) through the vacuum feeding sealing mechanism (19). After evacuation to ≤0.5Pa, the 100KW medium frequency heating system (2-2) and the transferred arc electrode (3-1) are started, and the furnace temperature is raised to 1700℃ to melt the silicon material. Hydrogen is introduced into the bottom blowing device (2-5) to remove sulfur and oxygen impurities. The impurity gas is neutralized in the deacidification tower (16) and purified by the activated carbon adsorption tower (17). The molten silicon liquid is transferred to the plasma gasification furnace (5-1) and gasified into silicon vapor at a high temperature of 3400℃ by the 80KW plasma torch (4-1). The gasification process is dynamically adjusted by the liquid level lifting device (5-4) to maintain temperature stability. After the silicon vapor is nucleated at 1600°C in the primary cooler (8), it enters the quench tower (9) and is quenched to 25°C with liquid nitrogen. Finally, it is collected by the bag dust collector (10) to obtain nano-silicon with an average particle size of 56.5nm. This solution is suitable for the efficient recovery of silicon waste, and high-temperature gasification ensures the uniformity of large-particle nano-silicon. Implementation 2:

[0050] like Figure 6 As shown, this embodiment uses silicon powder as raw material, and the specific process is as follows: 30kg of silicon powder is fed into the medium frequency melting furnace (1) through the vacuum feeding system (19), and after vacuuming, it is heated to 1750℃ by the 80KW medium frequency coil (2-2) to melt. Methane is introduced into the bottom blowing device (2-5) to remove impurities, and the purification system simultaneously removes acidic gases. The molten silicon liquid is transferred to the plasma gasification furnace (5-1) and gasified at 3450℃ by the 60KW plasma torch (4-1). The gasification efficiency is maintained by adjusting the plasma power and the silicon liquid level (5-4). After the silicon vapor nucleates and grows in the 1600℃ environment of the primary cooler (8), it is quenched to 25℃ by the liquid nitrogen quenching tower (9), and finally separated by the bag dust collector (10) to obtain nano-silicon with an average particle size of 33.9nm. This solution achieves stable production of nano-silicon with smaller particle size by reducing heating power and precise temperature control, and is suitable for direct conversion of high-purity silicon powder.

[0051] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A device for producing nano-silicon by medium frequency melting and plasma gasification, characterized in that: include: A medium frequency melting and transferred arc melting system (22) comprises a silicon material feeding sealing mechanism (19), a vacuum pump (20), a medium frequency melting furnace (1), a medium frequency heating and transferred arc heating system (2-2), a bottom blowing device (2-5), a rotating system (2-6), a deacidification tower (16), an alkali liquid tank (15), an activated carbon adsorption tower (17) and a fan (18); A non-transferred arc plasma gasification system (25) comprises a plasma gasification furnace (5-1), a transferred arc plasma torch (4-1), a refrigerator (12), a deionized water circulation pump (13), a silicon liquid communication pipeline (5-5), and a mold chamber (7-3); A nano-silicon nucleation, growth, crystallization and collection system (26) comprising a primary cooler (8), a quenching tower (9), a bag dust collector (10) and a vacuum system (11); The medium frequency melting furnace (1) is connected to the plasma gasification furnace (5-1) through a silicon liquid connecting pipe (5-5), and the outlet of the plasma gasification furnace (5-1) is connected to a primary cooler (8), a quenching tower (9) and a bag dust collector (10) in sequence to achieve gasification, nucleation, quenching and collection of the molten silicon liquid.

2. A method for producing nano-silicon by medium frequency melting and plasma gasification, characterized in that: The following steps are involved: The silicon material is fed into the medium frequency melting furnace (1) through the silicon material feeding sealing mechanism (19), and after being evacuated to a vacuum degree of ≤0.5 Pa, the silicon material is heated to above 1700° C. and melted by the medium frequency heating and transferred arc heating system (2-2), and methane or hydrogen is introduced through the bottom blowing device (2-5) to remove impurities; The molten silicon liquid is transferred to a plasma gasification furnace (5-1), and is heated to 1800-2100°C by a transferred arc plasma torch (4-1) driven by an inert working gas to gasify the silicon liquid into silicon vapor, and the temperature of the plasma contact area is controlled at 3200-3600°C; Silicon vapor is sequentially passed through a primary cooler (8) to form nuclei and grow at 1600-2100°C, and then cooled to below room temperature by liquid nitrogen countercurrent in a quenching tower (9). Finally, nano-silicon with a particle size of 30-60nm and a purity of ≥99.99% is separated through a bag dust collector (10).

3. The device according to claim 1, characterized in that The heating method of the medium frequency melting furnace (1) is medium frequency coil heating, transferred arc electrode heating or a combination thereof, and a carbon-based stirrer (2-4) is configured to ensure the uniformity of the melt.

4. The device according to claim 1, characterized in that The impurity removal gas introduced into the inert bottom blowing chamber (2-5) is methane or hydrogen, which is used to remove sulfur and oxygen impurities in the silicon liquid, and multi-stage purification of the impurity gas is achieved through the deacidification tower (16) and the activated carbon adsorption tower (17).

5. The device according to claim 1, characterized in that The plasma torch of the vaporization pot (5-1) uses nitrogen or argon as the working gas, and the silicon liquid level is dynamically adjusted by a pneumatic lifter (5-4) to maintain a stable vaporization temperature.

6. The device according to claim 1, characterized in that The quenching tower (9) uses liquid nitrogen countercurrent cooling to instantly cool the gas containing nano-silicon to ≤25° C., thereby inhibiting particle agglomeration.

7. The device according to claim 1, characterized in that The device comprises a plurality of medium frequency melting furnaces (1) arranged around each other, and realizes continuous production through sequential batch feeding.

8. The method according to claim 2, characterized in that The vaporization temperature gradient of the molten silicon liquid in the vaporization pot (5-1) is: the furnace body temperature is 1800-2100°C, and the plasma contact area temperature is 3200-3600°C.

9. The method according to claim 2, characterized in that When the temperature of the precooler (8) is 1600°C, the average particle size of the prepared nano-silicon is 56.5nm; when the temperature is increased to 2100°C, the particle size is reduced to 33.9nm.

10. The method according to claim 2, characterized in that When the silicon liquid level in the vaporizer (5-1) is lower than 5 mm, the remaining silicon liquid is transferred to the recycling mold chamber (7-3) through a connecting pipe heated to 1600°C for ingot recovery.

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