An apparatus for producing nanosilicon

Abstract

The utility model discloses a device of making nanometer silicon belongs to nanometer powder production field, and this device includes intermediate frequency melting system, plasma gasification system and nanometer silicon collection system, and through intermediate frequency melting furnace heats silicon material to 1700 DEG C above under vacuum environment, combines bottom blowing gas (methane / hydrogen) and removes sulfur, oxygen impurity, and after the deacidification tower, activated carbon adsorption tower purification, will high purity silicon liquid shift to plasma gasification furnace, utilizes the heating of transfer arc plasma torch under the drive of inert gas to 1800~2100 DEG C (contact area reaches 3200~3600 DEG C), makes silicon liquid gasification for steam. Steam is nucleated (1600~2100 DEG C) through primary cooler, and the liquid nitrogen quenching tower is suddenly cooled to below room temperature, and finally the nanometer silicon with the particle size of 30~60nm and the purity of 99.99% is collected by bag dust collector, the utility model discloses adopt multiple furnace collaborative feeding, dynamic liquid level regulation and inert gas protection, realize efficient continuous production, solve the problem such as low efficiency, poor purity, insufficient safety of traditional method.

Description

Technical Field

[0001] This utility model relates to the field of nanopowder production, specifically to an apparatus for producing nano-silicon. Background Technology

[0002] Currently, the carbon reduction and carbon neutrality goals are driving the rapid development of new energy vehicles, which are becoming the mainstream mode of transportation for emission reduction. Graphite is the primary material for the negative electrode in lithium-ion batteries. However, due to its limited energy storage capacity, graphite cannot meet the requirements of large-capacity energy storage devices and high energy density. Silicon, on the other hand, has a theoretical capacity nearly 10 times higher than graphite (its theoretical capacity is as high as 4200 mA·h / g), a lower lithium intercalation potential, and is the second most abundant material on Earth, while also being environmentally friendly. However, silicon expands nearly three times in volume during lithium intercalation, which pulverizes the silicon, hindering electrical conductivity and posing safety risks to lithium battery applications, thus limiting the use of silicon in lithium batteries. Nanostructuring silicon is one of the effective measures to suppress the volume expansion of silicon-based negative electrodes.

[0003] To date, methods for preparing nano-silicon include chemical etching, laser ablation, mechanical grinding, and aqueous synthesis. None of these methods can achieve satisfactory nano-silicon quality. Some methods, while achieving ideal quality, are not suitable for mass production (i.e., industrial application). CN118595449A discloses a plasma-based ultrafine nanopowder manufacturing device and method. While this method solves the problems of nanopowder deposition at the bottom of the vacuum chamber wall and the difficulty in large-scale, efficient collection during subsequent powder collection, it uses a laser to generate plasma. Lasers themselves have low efficiency, and production is intermittent, resulting in high production costs and making mass production difficult. Furthermore, laser reflection on the mirror surface of the material being processed poses a significant safety hazard.

[0004] CN202420803503.1 discloses a plasma preparation system for nano-silicon powder. This method directly uses plasma to nano-spheroidize quartz sand smaller than 200 mesh. However, due to the high temperature of the plasma used to heat and vaporize the quartz sand, gas-solid heat transfer is poor, resulting in high production costs. CN114031082B discloses a method for producing nano-silicon through induction plasma pyrolysis of silane. This method uses argon as the working gas of the plasma and silane as the raw material. Induction plasma efficiency is low, and both argon and silane are expensive. Furthermore, the production of nano-silicon from silane produces hydrogen as a byproduct, posing an explosion risk. CN106185947A and CN212864154U disclose a nano-silicon powder production device. While this device can improve the purity, yield, and particle size distribution control of the produced silicon powder, it also utilizes the high temperature of the plasma to heat and vaporize the silicon powder, resulting in low energy utilization due to gas-solid heat transfer. Utility Model Content

[0005] In order to overcome the above-mentioned defects of the prior art, the technical problem to be solved by the present invention is to provide an apparatus for preparing nano-silicon, which can prepare nano-silicon materials with high energy utilization, large-scale production and stable quality.

[0006] The specific implementation scheme of this utility model is as follows: an apparatus for preparing nano-silicon includes: a medium-frequency melting and transfer arc melting system, a non-transfer arc plasma vaporization system, and a nano-silicon nucleation, growth, crystallization and collection system.

[0007] The medium-frequency melting and transfer arc melting system includes a silicon material feeding sealing mechanism, a vacuum pump, a medium-frequency melting furnace, a medium-frequency heating and transfer arc heating system, a bottom blowing device, a rotary system, a deacidification tower, an alkali tank, an activated carbon adsorption tower, and a blower;

[0008] The non-transfer arc plasma vaporization system includes a plasma vaporization furnace, a transfer arc plasma torch, a chiller, a deionized water circulation pump, a silicon liquid connecting pipe, and a casting chamber.

[0009] The nano-silicon nucleation, growth, crystallization and collection system includes a primary cooler, a quench tower, a bag filter (10) and a vacuum system;

[0010] The medium-frequency melting furnace and the plasma gasification furnace are connected by a silicon liquid connecting pipe, and the outlet of the plasma gasification furnace is sequentially connected to a primary cooler, a quench tower and a bag filter dust collector.

[0011] Furthermore, the heating method of the medium-frequency melting furnace is medium-frequency coil heating or transfer arc electrode heating, or a combination of both.

[0012] Furthermore, the plasma torch of the plasma gasification furnace uses an inert working gas, including nitrogen or argon.

[0013] Furthermore, the impurity removal gas introduced by the bottom blowing device is methane or hydrogen, used to remove sulfur and oxygen impurities from the silicon material.

[0014] Furthermore, the quench tower employs countercurrent liquid nitrogen cooling to cool the gas containing nano-silicon to below room temperature.

[0015] The working principle of nano-silicon preparation:

[0016] 1. Open the silicon material feeding sealing mechanism (19) and transport the silicon material (which can be silicon powder, silicon wafer, silicon ingot, etc.) to the medium-frequency melting furnace (1). Start vacuum pump B (20). The vacuum pump can be a Roots pump, screw pump, or vortex pump. After the vacuum is evacuated to a vacuum degree ≤0.5Pa, stop the vacuum pump. Start the medium-frequency and transfer arc heating system (2) to heat the silicon material in the melting furnace. At the same time as heating, start the alkaline solution circulation pump (14) and the blower (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 from the silicon material. At the same time as the crucible rotates, start the bottom blowing system and input the impurity removal gas (which can be methane or hydrogen) into the bottom blowing system to remove impurities such as sulfur and oxygen from the silicon material. Impurity gases such as hydrogen sulfide, water, and hydrocarbons generated during the silicon melting process are pumped to the deacidification tower (16) by the suction of the blower (18). The alkali solution in the alkali solution tank (15) is pumped to the deacidification tower (16) by the alkali solution circulation pump (14). The alkali solution in the deacidification tower (16) is atomized by the atomizing nozzle. The atomized alkali solution and the impurity gases undergo rapid heat and mass transfer reaction to absorb the acidic gases in the impurity gases. 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 gases. The adsorbed gas is discharged. In addition to the crucible rotation and bottom blowing 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, so that the heating is uniform and the bottom blowing gas flow can be used for impurity removal, degassing and modification.

[0017] 2. When the temperature of the molten liquid in the medium frequency melting furnace (1) reaches 1700℃, start the deionized water circulation pump (13), the chiller (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℃ and keep it warm for later use, and at the same time close the shut-off valve (5) of the connecting pipe between the plasma gasification furnace (3) and the mold chamber (7). Open the inlet and outlet valves of the water-cooled side of the primary cooler to put the primary cooler in the cold end state.

[0018] 3. When the temperature in the medium frequency melting furnace (1) is maintained at 1700℃ for 10~45min, after 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, raise the liquid outlet of the crucible to a certain position (100~300mm higher than the solution inlet of the plasma gasification furnace), open the valve on the liquid outlet of the medium frequency melting furnace and start the tilting 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 medium frequency melting furnace (1), start the tilting device and the lifting device to restore the crucible in the medium frequency melting furnace, close the furnace cover of the medium frequency melting furnace and start the next batch of feeding and melting.

[0019] 4. To ensure continuous production of the plasma gasification furnace, multiple plasma intermediate frequency melting furnaces can be used, with the plasma gasification furnace placed in the middle and intermediate frequency melting furnaces evenly distributed around it for sequential batch production. The intermediate frequency melting furnace (1) can be heated by coil alone, by a transfer arc, or by a combination of both. After the liquid inlet of the plasma gasification furnace is closed, the plasma torch (4) is started, and the liquid nitrogen valve is opened 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 vaporizes, it forms silicon gas, which, together with the high temperature gas generated by the plasma, forms a nano-silicon nucleation, growth, crystallization, and collection system.

[0020] 5. The temperature of the crucible in the plasma vaporization furnace is maintained at 1800~2100℃, while the temperature of the area where the molten silicon contacts the plasma is maintained at 3200~3600℃. The molten silicon begins to boil and vaporize at the high temperature of the plasma, forming silicon vapor. As the silicon solution evaporates, its level begins to drop. To maintain a constant temperature between the plasma and the molten silicon (assuming the plasma torch power is constant, i.e., the flame length of the plasma torch is constant), a crucible lifting device is activated based on the evaporation rate of the molten silicon (i.e., the rate at which the liquid level in the crucible drops). The lifting device's upward speed matches the rate at which the liquid level in the molten silicon drops.

[0021] 6. High-temperature nitrogen gas and silicon vapor enter the nano-silicon nucleation, growth, crystallization, and collection system. Silicon vapor undergoes nucleation in the primary cooler, generating nano-sized silicon. The temperature of the silicon vapor mixture in the primary cooler (8) is 1600~2100℃, ensuring that the silicon vapor undergoes nucleation, growth, spheroidization, and shaping. The nano-silicon formed in the primary cooler is carried by the nitrogen gas flow into the quench tower. The quench tower uses liquid nitrogen for cooling. The liquid nitrogen comes into countercurrent contact with the high-temperature nitrogen gas containing nano-silicon to quench the nano-silicon, preventing the nano-silicon from agglomerating and affecting its quality. The liquid nitrogen in the quench tower cools the nano-silicon and nitrogen gas to room temperature or extremely low temperature. The silicon-containing gas cooled to room temperature is drawn to the bag filter by the fan (11). The nano-silicon undergoes gas-solid separation through the filter bag. The separated nano-silicon is packaged and sold externally. Since only nano-silicon and nitrogen are present during the gasification process, the nitrogen gas generated during the gasification process does not need to be treated and can be reused or bottled and sold externally.

[0022] 7. When the level of silicon solution in the plasma gasification furnace is <5mm, or when the nano-silicon nucleation, growth, crystallization and collection system malfunctions, start the medium frequency power supply of the medium frequency system to heat the connecting pipe between the plasma gasification furnace and the casting chamber (7). When the pipe is heated to 1600℃, open the valve of the connecting pipe to send the remaining silicon solution in the plasma gasification furnace to the casting chamber for casting into silicon ingots, so that it can be melted again to make nano-silicon.

[0023] The system shutdown sequence is as follows: turn off the plasma power supply and turn off the heating power supply of the medium-frequency melting furnace (1). When the temperature in the medium-frequency melting furnace (1) drops to room temperature, turn off the alkali circulation pump (14) and the blower (18); when the temperature of the plasma gasification furnace drops to room temperature, turn off the deionized water pump (13) and the chiller (12); and turn off the water valve and the blower (11) of the primary cooler.

[0024] Beneficial effects: The process design of this utility model is reasonable and highly practical, and it has the following beneficial effects:

[0025] (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%;

[0026] (2) The medium-frequency melting furnace adopts multiple heating methods, which accelerates the melting speed of silicon material and improves production efficiency;

[0027] (3) By combining multiple medium-frequency melting furnaces with one gasification furnace, large-scale continuous production can be achieved;

[0028] (4) The use of a medium-frequency melting furnace and a plasma gasification furnace for co-production saves energy and improves production efficiency;

[0029] (5) Using a plasma torch can raise the temperature of the molten silicon to a higher level, reducing the requirements for materials;

[0030] (6) The plasma torch can use a variety of inert working gases (such as nitrogen and argon), which avoids the risk of nano-silicon explosion and ensures the safety of the entire system.

[0031] (7) Low temperature and extremely low temperature environment and rapid freezing rate are adopted, so as to have 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.

[0032] (8) The baghouse is equipped with an inert gas atmosphere and inert jetting, which completely eliminates the risk of nanoparticle dust explosion and achieves inherent safety.

[0033] (9) The purified inert gas re-enters the process and the plasma gas source, which basically realizes the recycling of inert gas. Attached Figure Description

[0034] Figure 1 This is a flowchart illustrating the process of preparing nano-silicon.

[0035] Figure 2 This is a system configuration diagram of a medium-frequency melting furnace.

[0036] Figure 3 This is a schematic diagram of the planar structure of a medium-frequency melting furnace.

[0037] Figure 4 This is a top view of a medium-frequency induction furnace.

[0038] Figure 5 This is a scanning electron microscope (SEM) image of nano-silicon prepared under operating condition 1.

[0039] Figure 6 This is a scanning electron microscope (SEM) image of nano-silicon prepared under operating condition 2.

[0040] In the diagram: 1—Medium-frequency melting furnace; 2—Medium-frequency and transfer arc heating system; 3—Ion gasification furnace; 4—Plasma torch; 5—Shut-off valve; 6—Medium-frequency power supply; 7—Casting chamber; 8—Primary cooler; 9—Quick cooling tower; 10—Bag filter; 11—Vacuum pump A; 12—Refrigeration unit; 13—Deionized water circulation pump; 14—Alkali circulation pump; 15—Alkali tank; 16—Deacidification tower; 17—Activated carbon adsorption tower; 18—Fan; 19— Silicon material feeding sealing mechanism; 20—Vacuum pump 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—Recycled casting system; 1-1—Feed vacuum valve; 1-2—Feed vacuum chamber; 1-3—Discharge vacuum valve; 1-4—Inert gas inlet; 2-1—Lifting and tilting mechanism 2-2—Medium frequency heating tube; 2-3—Fused graphite pot; 2-4—Carbon-based stirrer; 2-5—Inert bottom blowing device; 2-6—Inert gas inlet flange; 2-7—Automatic balancing support leg; 3-1—Cathode graphite flow channel; 3-2—Flow channel flipper; 3-3—Vacuum quick-closing 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; 5-1—Plasma gasification furnace; 5-2—Gasification chamber; 5-3—Gasification exhaust flange hole; 5-4—Pneumatic lifter; 5-5—Recirculation pipe; 5-6—Rotator; 5-7—Inert gas bottom blow pipe; 6-1—Exhaust port; 6-2—Explosion-proof plate; 6-3—Plasma torch-4; 6-4—Impact ball; 6-5—Waste liquid flange; 6-6—Atomizer; 7-1—Reuse three-way valve; 7-2—Reuse reflux pipe; 7-3—Reuse casting chamber. Detailed Implementation

[0041] The subject matter described herein will now be discussed with reference to exemplary embodiments. It should be understood that these embodiments are discussed only to enable those skilled in the art to better understand and implement the subject matter described herein, and changes may be made to the function and arrangement of the elements discussed without departing from the scope of this specification. Various processes or components may be omitted, substituted, or added as needed in the examples. Furthermore, features described in some examples may be combined in other examples.

[0042] like Figure 1-4As shown, a device for producing nano-silicon through a combination of medium-frequency melting and transfer arc synergistic non-transfer arc plasma gasification achieves continuous production of high-purity nano-silicon through the synergistic effect of three core processes: medium-frequency melting purification, high-temperature plasma gasification, and rapid cooling crystallization collection. The specific working principle is as follows: 1. Medium-frequency melting purification: Silicon material is fed into a 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 transfer arc electrode to completely melt the silicon material. During the melting process, methane or hydrogen is introduced through a bottom-blowing device, reacting with impurities such as sulfur and oxygen in the silicon melt to generate gases, which are then purified and removed through a deacidification tower and an activated carbon adsorption tower. Simultaneously, the rotation or stirring system of the melting furnace ensures uniform heating of the silicon melt and thorough removal of impurities, providing high-purity silicon melt for subsequent gasification. 2. High-Temperature Plasma Gasification: The purified molten silicon is transferred to a plasma gasification furnace. High-temperature plasma (driven by inert gas) generated by the transfer arc plasma torch heats the silicon to 1800-2100℃, with the contact area temperature reaching as high as 3200-3600℃, rapidly vaporizing the silicon into silicon vapor. The plasma torch power and liquid level adjustment device are dynamically adjusted to maintain a stable gasification temperature. If the silicon is depleted or the system malfunctions, the remaining silicon can be transported to the casting chamber for ingot casting and recovery, ensuring continuous production. 3. Rapid Cooling Crystallization and Collection: Silicon vapor and high-temperature gas enter the primary cooler, where they are slowly cooled at 1600-2100℃ to nucleate and generate nano-silicon particles. These particles then enter a rapid cooling tower, where they are instantly cooled to below room temperature by countercurrent contact with liquid nitrogen, preventing particle agglomeration. Finally, the gas containing nano-silicon is filtered and separated by a bag filter to obtain nano-silicon with a particle size of 30-60nm and a purity ≥99.99%. The system employs inert gas protection throughout the entire process, combined with waste heat recovery and explosion-proof design, to achieve safe and efficient large-scale production.

[0043] Implementation method 1:

[0044] 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 the vacuum is evacuated to ≤0.5Pa, the 100KW medium-frequency heating system (2-2) and the transfer arc electrode (3-1) are started to raise the furnace temperature to 1700℃ to melt the silicon material. The inert bottom blowing device (2-5) introduces hydrogen to remove sulfur and oxygen impurities. The impurity gas is neutralized by 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 is vaporized into silicon vapor by the 80KW plasma torch (4-1) at a high temperature of 3400℃. The vaporization process is dynamically adjusted by the liquid level lifting device (5-4) to maintain temperature stability. Silicon vapor nucleates at 1600°C in the primary cooler (8), then enters the quench tower (9) where it is rapidly cooled to 25°C with liquid nitrogen. Finally, it is collected by a bag filter (10) to obtain nano-silicon with an average particle size of 56.5 nm. This method is suitable for the efficient recycling of silicon waste, and the high-temperature gasification ensures the uniformity of large-particle nano-silicon.

[0045] Implementation Method 2:

[0046] like Figure 6 As shown, this embodiment uses silicon powder as raw material, and the specific process is as follows: 30 kg 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°C by an 80 KW medium-frequency coil (2-2) to melt. Methane is introduced through the inert bottom blowing device (2-5) to remove impurities, and the purification system removes acidic gases simultaneously. The molten silicon liquid is transferred to the plasma gasification furnace (5-1), and vaporized at 3450°C by a 60 KW 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 primary cooler (8) at 1600°C, it is quenched to 25°C by the liquid nitrogen quench tower (9), and finally separated into nano-silicon with an average particle size of 33.9 nm by the bag filter (10). This scheme achieves stable production of nano-silicon with smaller particle size by reducing heating power and precise temperature control, and is suitable for the direct conversion of high-purity silicon powder.

[0047] Although embodiments of the present invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the present invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. An apparatus for producing nano-silicon, characterized in that, include: The medium-frequency melting and transfer arc melting system (22) includes a silicon material feeding sealing mechanism (19), a vacuum pump (20), a medium-frequency melting furnace (1), a medium-frequency heating and transfer arc heating system (2-2), an inert bottom blowing device (2-5), a rotating system (2-6), a deacidification tower (16), an alkali tank (15), an activated carbon adsorption tower (17), and a blower (18). The non-transfer arc plasma vaporization system (25) includes a plasma vaporization furnace (5-1), a transfer arc plasma torch (4-1), a chiller (12), a deionized water circulation pump (13), a silicon liquid connecting pipe (5-5), and a casting chamber (7-3). The nano-silicon nucleation, growth, crystallization and collection system (26) includes a primary cooler (8), a quench tower (9), a bag filter (10) and a vacuum system (11). The medium-frequency melting furnace (1) is connected to the plasma gasification furnace (5-1) through the silicon liquid connecting pipe (5-5). The outlet of the plasma gasification furnace (5-1) is connected in sequence to the primary cooler (8), the quench tower (9) and the bag dust collector (10) to realize the gasification, nucleation, quenching and collection of molten silicon liquid.

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

3. The apparatus for preparing nano-silicon according to claim 1, characterized in that, The inert bottom blowing device (2-5) introduces methane or hydrogen as the impurity removal gas, which is used to remove sulfur and oxygen impurities from the silicon liquid, and achieves multi-stage purification of the impurity gas through the deacidification tower (16) and the activated carbon adsorption tower (17).

4. The apparatus for preparing nano-silicon according to claim 1, characterized in that, The plasma torch of the plasma gasification furnace (5-1) uses nitrogen or argon as the working gas, and the liquid level of the silicon liquid is dynamically adjusted by the liquid level lifting device (5-4) to maintain the stability of the gasification temperature.

5. The apparatus for preparing nano-silicon according to claim 1, characterized in that, The quench tower (9) uses liquid nitrogen countercurrent cooling to instantly cool the gas containing nano-silicon to ≤25℃, thus inhibiting particle agglomeration.

6. The apparatus for preparing nano-silicon according to claim 1, characterized in that, The device comprises multiple medium-frequency melting furnaces (1) arranged around the main body, enabling continuous production through sequential batch feeding.

7. The apparatus for preparing nano-silicon according to claim 2, characterized in that, When the silicon liquid level in the plasma gasification furnace (5-1) is lower than 5 mm, the remaining silicon liquid is transferred to the recycling mold chamber (7-3) for ingot recycling through a connecting pipe heated to 1600℃.

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