Method and apparatus for producing nanosized tin oxide powder using a liquid tin feed plasma

Abstract

This invention provides a method and apparatus for preparing nano-tin oxide powder using a liquid tin-feed plasma device. The method includes: S1: heating and melting tin raw material into liquid tin; S2: using a working gas excited by a high-frequency electromagnetic field of a plasma generator to form a high-temperature plasma torch, atomizing and breaking the liquid tin into micron-sized continuous fine streams through a nozzle, which are then injected at high speed into the plasma glow core region for further vaporization into tin vapor; S3: using the working gas to carry the tin vapor and reacting with simultaneously introduced oxygen to generate tin oxide aerosol; S4: the aerosol undergoing staged quenching to form nano-tin oxide powder. This invention utilizes high-frequency plasma equipment to directly vaporize and oxidize molten metallic tin to prepare nano-tin oxide (SnO2) powder. This method is simple, efficient, and has the potential for industrial-scale production, resulting in uniform particle dispersion and resistance to agglomeration.

Description

Technical Field

[0001] This invention relates to the field of nano-metal oxide powder preparation technology, specifically to a method and apparatus for preparing nano-tin oxide powder using a liquid tin-feed plasma device. Background Technology

[0002] Nano-sized tin oxide (SnO2), as an important n-type wide-bandgap semiconductor material, exhibits significant surface, volume, and quantum size effects when its size is reduced to the nanometer scale. This results in superior electrical, optical, and gas-sensitive properties that are distinctly different from those of ordinary micron-sized tin oxide.

[0003] There are various existing methods for preparing nano-tin oxide, but they all have some shortcomings, such as: cumbersome and wasteful raw material pretreatment: tin powder or tin oxide powder must be prepared in advance, and the powder preparation process involves approximately 5% to 8% metal loss and high energy consumption; uneven solid powder feeding: tin powder has poor flowability, especially micron-sized tin powder, which is prone to agglomeration and bridging, causing feeding fluctuations, resulting in unstable plasma region reactions and large product particle size dispersion; high risk of material blockage: tin powder is soft and easily adheres to the stainless steel inner wall in the conveying pipeline and feeder, gradually forming tin blocks that block the pipeline, requiring frequent shutdowns for cleaning, affecting continuous production; and a single cooling method: using only single-stage rapid cooling (compressed air) makes it difficult to accurately control the growth and crystal form of tin oxide nuclei, and the product uniformity needs to be improved.

[0004] Patent CN112125331B employs an arc plasma method using tin ingots as raw materials, but it fails to address the issues of liquid feeding and staged cooling. Patent CN102126746A uses micron-sized tin oxide or metallic tin powder as raw materials, which are fed into a high-frequency plasma torch via a disc feeder. The powder is vaporized at 5000-8000°C and then rapidly cooled to below 120°C with compressed air to obtain nano-tin oxide powder. However, this technology uses a rapid cooling method, resulting in insufficient particle dispersion uniformity in the final product.

[0005] Therefore, there is a need for a method and apparatus for preparing nano-tin oxide powder using liquid tin-feed plasma equipment to solve the problems existing in the prior art. Summary of the Invention

[0006] To address the problems mentioned in the background section, the main objective of this invention is to provide a method and apparatus for preparing nano-tin oxide powder using a liquid tin-feed plasma device. This invention utilizes high-frequency plasma equipment to directly vaporize and oxidize molten metallic tin to prepare nano-tin oxide (SnO2) powder. This method is simple, efficient, and has the potential for large-scale industrial production. Furthermore, the particles are uniformly dispersed and do not easily agglomerate.

[0007] In a first aspect, a method for preparing nano-tin oxide powder using a liquid tin-feed plasma device is provided, including: S1: Heat and melt the tin raw material into liquid tin; S2: The working gas is excited by the high-frequency electromagnetic field of the plasma generator to form a high-temperature plasma torch. Liquid tin is atomized and broken into micron-level continuous fine streams through the nozzle. The fine streams are injected at high speed into the plasma glow core region and further vaporized into tin vapor. S3: The working gas carrying tin vapor reacts with the oxygen introduced simultaneously to generate tin oxide aerosol; S4: Aerosol is quenched step by step to form nano-tin oxide powder.

[0008] In some embodiments, in S1, the tin raw material is selected from at least one of tin ingots (purity 99.992%), tin alloys (such as Sn-Bi, Sn-Ag), or tin-containing waste.

[0009] In some embodiments, in S1, the heating and melting temperature is 350~500℃, preferably any one of the following ranges: 350℃, 360℃, 370℃, 380℃, 390℃, 400℃, 410℃, 420℃, 430℃, 440℃, 450℃, 460℃, 470℃, 480℃, 490℃, 500℃, and any two of the above values.

[0010] In some embodiments, liquid tin in S1 is transported to the high-frequency plasma generator via a high-temperature pump and an insulated pipeline. In some embodiments, the rotational speed of the high-temperature pump is 0~200 mL / min, preferably any one of 0, 50 mL / min, 100 mL / min, 150 mL / min, 200 mL / min, or any two of the above values. In some embodiments, the rate at which the insulated pipeline transports the liquid tin is 10~100 g / min, preferably any one of 10 g / min, 20 g / min, 40 g / min, 50 g / min, 60 g / min, 80 g / min, 100 g / min, or any two of the above values.

[0011] In some embodiments, the working gas is at least one of argon and nitrogen. If it is a mixture of the two, the volume percentage of argon is 20% to 100%, preferably 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, 100%, or any two of the above values ​​forming a range.

[0012] In some embodiments, the flow rate of the working gas is 20~50L / min, preferably 20L / min, 25L / min, 30L / min, 35L / min, 40L / min, 45L / min, 50L / min, or any two of the above values ​​forming a range.

[0013] In some embodiments, the temperature of the plasma glow core region is 5000~10000℃, preferably 5000℃, 5500℃, 6000℃, 6500℃, 7000℃, 7500℃, 8000℃, 8500℃, 9000℃, 9500℃, 10000℃, etc., or any two of the above values ​​forming a range.

[0014] In some embodiments, the plasma generator is selected from a high-frequency plasma generator, a DC arc plasma generator, or a microwave plasma generator. As long as the temperature of the central region is higher than the boiling point of tin (2270°C) and a stable glow region can be formed, liquid tin vaporization and oxidation can be achieved. In some embodiments, the power of the high-frequency plasma generator is 50~150kW, preferably 50kW, 100kW, 150kW, or any two of the above values ​​forming a range.

[0015] In some embodiments, the nozzle is selected from a single-hole direct-fire nozzle, a multi-hole swirling nozzle, or an ultrasonic vibration atomizing nozzle. Different types of nozzles improve the uniformity of molten solder atomization, resulting in more complete vaporization and making them suitable for large-scale production.

[0016] In some embodiments, the oxygen flow rate is 5~20 L / min, preferably 5 L / min, 6 L / min, 7 L / min, 8 L / min, 9 L / min, 10 L / min, 11 L / min, 12 L / min, 13 L / min, 14 L / min, 15 L / min, 16 L / min, 17 L / min, 18 L / min, 19 L / min, 20 L / min, or any two of the above values ​​forming a range.

[0017] In some embodiments, the step-by-step quenching is selected from at least one of the first-stage rapid cooling region, the second-stage crystal transformation region, and the third-stage natural cooling region.

[0018] In some embodiments, the step-by-step quenching further includes a shell-and-tube heat exchanger combined with air cooling to achieve temperature reduction.

[0019] In some embodiments, the temperature of the first-stage rapid cooling zone is controlled at 800~1000℃, preferably any one of the ranges of 800℃, 850℃, 900℃, 950℃, 1000℃, etc., or any two of the above values.

[0020] In some embodiments, the cooling medium used in the first-stage rapid cooling zone is selected from at least one of liquid water, water vapor, and an inert gas (nitrogen or argon). In some embodiments, when the cooling medium is a mixture of water vapor and an inert gas, the volume percentage of the inert gas is 20-80%, preferably 20%, 50%, or 80%. In some embodiments, when the cooling medium is a mixture of nitrogen and argon, the volume percentage of nitrogen is 20-80%, preferably 20%, 50%, or 80%. In this application, using a mixture of water vapor and an inert gas enables ultra-high-speed quenching, resulting in products with smaller particle sizes, such as 5-15 nm.

[0021] In some embodiments, the temperature of the second-stage crystal transformation region is controlled at 200~300℃, preferably 200℃, 250℃, 300℃, or any two of the above values ​​forming a range. In some embodiments, the cooling medium used in the second-stage crystal transformation region is selected from liquid nitrogen, and liquid nitrogen-assisted cooling is suitable for ultrafine powders with special requirements.

[0022] In some embodiments, the temperature of the third-stage natural cooling zone is controlled between 20 and 50°C, preferably any one of the ranges of 20°C, 25°C, 30°C, 35°C, 40°C, 45°C, 50°C, or any two of the above values. In some embodiments, the cooling medium used in the third-stage natural cooling zone is air.

[0023] In a second aspect, an apparatus for implementing the method of the present invention is provided, comprising: Tin ingot melting system, high-temperature conveying system, high-frequency plasma generator, oxygen unit, oxidation unit, staged quenching unit, and collection system; The tin ingot melting system, high-temperature conveying system, and high-frequency plasma generator are connected in sequence. The outlets of the high-frequency plasma generator and the oxygen device are both connected to the inlet of the oxidation device. The outlet of the oxidation device is connected to the inlet of the staged quenching device. The step-by-step quenching device is connected to the collection system.

[0024] In some embodiments, the tin ingot melting system is a resistance-heated crucible furnace with temperature control.

[0025] In some embodiments, the high-temperature conveying system includes a high-temperature gear pump and an insulated heating tube, wherein the insulated heating tube includes a ceramic pipe, a heating wire covering the pipe, and an insulation layer covering the pipe.

[0026] In some embodiments, the high-frequency plasma generator is provided with a liquid tin nozzle outlet located above the high-frequency plasma glow region, and the liquid tin nozzle outlet is provided with a cooling jacket.

[0027] In some embodiments, the oxygen device provides high-purity oxygen.

[0028] In some embodiments, the molten tin and high-purity oxygen react in an oxidation device to produce tin oxide aerosol.

[0029] In some embodiments, the step-by-step quenching device has at least two cooling stages. In some embodiments, the step-by-step quenching device is selected from at least two of the following: a first-stage rapid cooling zone, a second-stage crystal transformation zone, a shell-and-tube heat exchanger combined with air cooling zone, and a third-stage natural cooling zone.

[0030] In some embodiments, the collection system is provided with a cyclone separator and a bag filter in sequence.

[0031] Compared with the prior art, one of the above technical solutions has the following advantages or beneficial effects: This invention provides a method and apparatus for preparing nano-tin oxide powder using a liquid tin-feed plasma device.

[0032] This invention employs a direct liquid tin feeding method, eliminating the need for traditional solid tin powder or tin oxide powder and completely preventing powder blockage in the equipment. Simultaneously, the liquid tin is transported to the high-temperature plasma zone via a high-temperature pump and insulated pipelines, achieving integrated "melting-transporting-vaporization" of tin and avoiding the powder preparation step. This invention, using direct liquid tin feeding, completely eliminates metal loss during tin powder preparation (saving approximately 5-8% in raw material costs); continuous and uninterrupted feeding improves production efficiency by over 30%; and the elimination of a powder feeder avoids dust pollution and explosion risks.

[0033] This invention completely solves the industry problem of tin powder forming tin blocks due to friction in stainless steel pipes, causing blockages; it achieves "uniform feeding", stabilizes the temperature field of the plasma reaction zone, and greatly improves the consistency of product batches; the equipment can operate continuously for more than 72 hours without cleaning.

[0034] This invention employs controlled oxygen oxidation and step-by-step quenching gradient temperature control technology. This is manifested in the independent introduction of oxygen after the tin raw material vaporizes, precisely controlling the oxygen partial pressure and oxidation reaction kinetics; and the use of multiple quenching zones with different cooling rates / temperatures to step-by-step control the nucleation, growth, and crystal form of nanoparticles. Compared to existing single-stage rapid quenching (such as CN102126746A), the nano-tin oxide prepared by this invention has a narrower particle size distribution (D98≤0.1μm), a single crystal form (pure tetragonal rutile phase), and no impurities; the specific surface area has a large controllable range (10~30 m²). 2 / g), meeting the application needs of high-end electronic pastes, gas sensors, etc.

[0035] The overall process of this invention is continuous, clean, and has a high yield. The entire process from tin ingot to nano-tin oxide is closed and continuous, with no intermediate transfer losses, and the exhaust gas is treated to meet emission standards. The overall yield of the process of this invention is ≥99.9%, which is much higher than that of the traditional powder method (90%~95%); energy consumption is reduced by about 15% (because no additional crushing, ball milling, or other processes are required).

[0036] The nano-tin oxide (SnO2) powder prepared by the method has a primary particle size of approximately 25 nm and a specific surface area of ​​10–30 m². 2 / g, no aggregated hard lumps.

[0037] The equipment operated continuously for 8 hours without any material blockage or fluctuations in material flow. The entire system operated under slight negative pressure, which effectively prevented dust leakage. Attached Figure Description

[0038] Figure 1 A schematic diagram of an apparatus for preparing nano-tin oxide powder using a liquid tin-feed plasma device.

[0039] Figure 2 Images of the nano-tin oxide powder prepared in Example 1. (a) 500 nm, (b) 5 μm, (c) 1 μm.

[0040] Figure 3 Images of the nano-tin oxide powder prepared in Comparative Example 1. (a) 500 nm, (b) 5 μm, (c) 1 μm.

[0041] Terminology Explanation Certain embodiments of the invention will now be described in detail, examples of which are illustrated by the accompanying structural and chemical formulas. The invention is intended to cover all alternatives, modifications, and equivalents, all of which are included within the scope of the invention as defined in the claims. Those skilled in the art will recognize that many similar or equivalent methods and materials can be used to practice the invention. The invention is by no means limited to the methods and materials described herein. In the event that one or more of the incorporated documents, patents, and similar materials differ from or contradict this application (including, but not limited to, defined terminology, application of terminology, described techniques, etc.), this application shall prevail.

[0042] It should be further appreciated that certain features of the invention, for clarity, have been described in multiple independent embodiments, but may also be provided in combination in a single embodiment. Conversely, various features of the invention, for brevity, have been described in a single embodiment, but may also be provided individually or in any suitable sub-combination.

[0043] Unless otherwise stated, all technical terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art. All patents and publications related to this invention are incorporated herein by reference in their entirety.

[0044] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0045] In the following content, all numbers disclosed herein, whether or not they use words such as "approximately" or "about," are approximate values. The value of each number may vary by 1%, 2%, 5%, 7%, 8%, 10%, 15%, or 20%. Whenever a number with a value of N is disclosed, any numbers with values ​​of N+ / -1%, N+ / -2%, N+ / -3%, N+ / -5%, N+ / -7%, N+ / -8%, N+ / -10%, N+ / -15%, or N+ / -20% will be explicitly disclosed, where "+ / -" indicates addition or subtraction.

[0046] High-frequency plasma: refers to a plasma torch generated by exciting working gas (such as argon, nitrogen, etc.) through high-frequency induction or radio frequency power supply, with a temperature that can reach 5000~10000℃.

[0047] Tin vaporization: Liquid tin metal instantly transforms from a liquid state to a gaseous tin vapor state in the high-temperature region of plasma.

[0048] Step-by-step quenching: Multiple cooling zones with different temperature gradients are used to gradually cool and condense tin oxide vapor, thereby controlling the particle size and distribution of nanoparticles.

[0049] High-temperature pump / heating tube: a specialized device used to transport and maintain the temperature of molten tin above its melting point (232°C) while maintaining good fluidity. Detailed Implementation

[0050] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. The specific embodiments described herein are for illustrative purposes only and are not intended to limit the invention in any way. Furthermore, descriptions of well-known structures and techniques are omitted in the following description to avoid unnecessarily obscuring the concepts of this disclosure. Such structures and techniques have also been described in many publications.

[0051] All reagents used in this invention can be purchased commercially or prepared by the methods described in this invention.

[0052] Example 1 like Figure 1 As shown, an apparatus for preparing nano-tin oxide powder using liquid tin-feed plasma technology is disclosed, enabling continuous preparation of nano-tin oxide powder. The apparatus includes: The system includes: 1. Tin ingot melting system; 2. High-temperature conveying system; 3. High-frequency plasma generator; 4. Oxygen unit; 5. Oxidation unit; 6. Step-by-step quenching unit; and 7. Collection system. The tin ingot melting system 1, the high-temperature conveying system, and the high-frequency plasma generator 3 are connected in sequence. The outlets of the high-frequency plasma generator 3 and the oxygen device 4 are both connected to the inlet of the oxidation device 5. The outlet of the oxidation device 5 is connected to the inlet of the staged quenching device 6. The step-by-step quenching device 6 is connected to the collection system.

[0053] The tin ingot melting system 1 is equipped with a resistance heating crucible furnace with temperature control function, which can achieve a temperature of 350~500℃ and melt the tin ingot into liquid tin.

[0054] The high-temperature conveying system includes a high-temperature gear pump 21 (temperature resistant 500℃) and an insulated heating tube 22. The insulated heating tube includes a ceramic pipe, a heating wire covering the pipe, and an insulation layer. The high-frequency plasma generator 3 operates at a frequency of 5MHz and uses argon as the working gas to generate a high-temperature plasma glow region (center temperature of 6000~7000℃). A liquid tin nozzle outlet is located above the high-frequency plasma glow region. The liquid tin nozzle outlet is equipped with a cooling jacket to prevent heat conduction to the outlet, which could lead to melting and blockage. The liquid tin nozzle outlet adopts a coaxial structure to disperse the molten tin into fine liquid lines.

[0055] The oxygen device 4 provides high-purity oxygen and can be used to control the partial pressure of oxygen. Tin molten metal reacts with high-purity oxygen in oxidation unit 5 to produce tin oxide aerosol. The step-by-step quenching device 6 is equipped with three cooling stages. The first stage uses a circulating water jacket, which can quickly cool down to 800~1000℃; the second stage uses a combination of air cooling and water cooling, which cools down to 200~300℃; and the third stage uses natural air cooling, which cools down to room temperature (20~30℃).

[0056] The collection system is equipped with a cyclone separator 7 and a bag filter 8 in sequence to collect nano tin oxide powder, and the exhaust gas is discharged after washing.

[0057] This invention provides a method for preparing nano-tin oxide powder using a liquid tin-feed plasma device, comprising: S1: Heat the tin ingot (99.992% purity) to 400℃ to completely melt it into liquid tin, keep it at the temperature and let it stand to remove the surface oxide residue.

[0058] S2: Start the high-temperature pump at a speed of 50 mL / min. The liquid tin is transported through the high-temperature pump and the heat-insulated pipeline (maintaining the temperature at 320~400℃) to the liquid feed nozzle at the top of the high-frequency plasma generator. The heat-insulated pipeline transports the liquid tin at a rate of 50 g / min. Argon gas at a flow rate of 35 L / min is excited by the high-frequency electromagnetic field of the high-frequency plasma generator (power supply of 50 kW) to form a continuous and stable high-temperature plasma torch. The liquid tin is atomized by the nozzle and broken into micron-sized continuous fine streams. The fine streams are injected at high speed into the plasma glow core region with a temperature of over 6000℃. In a very short time, sufficient heat energy is absorbed to complete the rapid phase change from liquid to gas, and finally it is completely vaporized to generate pure tin vapor. S3: The working gas carrying tin vapor (flow rate 35 L / min) reacts with the simultaneously introduced oxygen (flow rate 12 L / min) to generate tin oxide aerosol; S4: Aerosol enters the staged quenching zone: The first-stage rapid cooling zone uses liquid water as the cooling medium to rapidly cool the first stage to 900℃, inhibiting excessive grain growth; the cooling water jacket outlet temperature is 70℃. The second-stage crystal transformation zone uses liquid nitrogen as the cooling medium; the secondary cooling airflow is 10 m³ / s. 3 The second stage cools down to 220°C at a speed of 1 / min, completing the crystal transformation; the cooling medium used in the third stage natural cooling zone is air, and the third stage cools down to room temperature of 30°C, forming nano-tin oxide powder with uniform particle size (25nm, specific surface area 10-30 m² / g, no agglomerates or hard lumps).

[0059] The powder is recovered via a cyclone separator and bag filter, with a collection efficiency of ≥99.9%. The entire system operates under slight negative pressure to prevent dust leakage. After 8 hours of continuous operation, no material blockage or fluctuations in material flow were observed. Results are as follows... Figure 2 As shown, at 500 nm, 5 μm and 1 μm, the particles are distinct and there is no aggregation.

[0060] Example 2 Same as Example 1, except that the tin ingot is replaced with the tin alloy Sn-Bi.

[0061] Example 3 Same as Example 1, except that the tin ingot is replaced with the tin alloy Sn-Ag.

[0062] Example 4 Same as Example 1, except that the nozzle is set as a multi-hole swirling nozzle.

[0063] Example 5 Same as Example 1, except that the nozzle is set as an ultrasonic vibration atomizing nozzle.

[0064] Example 6 Similar to Example 1, except that the cooling medium used in the first-stage rapid cooling zone is a mixture of water vapor and argon, with argon accounting for 50% of the volume. The mixture is sprayed to achieve ultra-high-speed quenching and obtain tin oxide powder with a particle size of 5~15nm.

[0065] Example 7 Same as Example 1, except that the plasma power source is a DC arc plasma.

[0066] Example 8 Same as Example 1, except that the plasma power source is microwave plasma.

[0067] Example 9 The difference from Example 1 is that the step-by-step quenching is set to two stages, namely the first stage rapid cooling zone and the third stage natural cooling zone.

[0068] Example 10 The difference from Example 1 is that the quenching process is set to four stages, and a cooling device combining a shell-and-tube heat exchanger and air cooling is added before the third stage natural cooling zone.

[0069] Comparative Example 1 The difference from Example 1 is that the step-by-step quenching is set to only one stage, that is, rapid cooling is performed using high-speed compressed air with an air volume of 800m³. 3 / h, using high-speed compressed air at a rate 30 times that of tin oxide vapor, to achieve rapid cooling to 120~130℃, and collect the finished product. Results are as follows: Figure 3 As shown, the particles exhibit severe aggregation at 500 nm, 5 μm, and 1 μm.

[0070] The method of this invention has been described through preferred embodiments. Those skilled in the art will readily be able to modify or appropriately alter and combine the methods and applications described herein within the scope, spirit, and context of this invention to implement and apply the technology of this invention. Those skilled in the art can refer to the content herein to appropriately improve process parameters. It should be particularly noted that all similar substitutions and modifications are obvious to those skilled in the art and are considered to be included within the scope of this invention.

Claims

1. A method for preparing nano-tin oxide powder using a liquid tin-feed plasma device, characterized in that, include S1: Heat and melt the tin raw material into liquid tin; S2: The working gas is excited by the high-frequency electromagnetic field of the plasma generator to form a high-temperature plasma torch. Liquid tin is atomized and broken into micron-level continuous fine streams through the nozzle. The fine streams are injected at high speed into the plasma glow core region and further vaporized into tin vapor. S3: The working gas carrying tin vapor reacts with the oxygen introduced simultaneously to generate tin oxide aerosol; S4: Aerosol is quenched and cooled in stages to form nano-tin oxide powder; The step-by-step quenching includes a first-stage rapid cooling region, a second-stage crystal transformation region, and a third-stage natural cooling region. The temperature of the first-stage rapid cooling zone is controlled at 800~1000℃; the temperature of the second-stage crystal transformation zone is controlled at 200~300℃; and the temperature of the third-stage natural cooling zone is controlled at 20~50℃.

2. The method according to claim 1, characterized in that, In S1, the tin raw material is selected from at least one of tin ingots, Sn-Bi tin alloy, Sn-Ag tin alloy or tin-containing waste; Alternatively, in S1, the heating and melting temperature is 350~500℃; Alternatively, liquid tin in S1 is transported to the high-frequency plasma generator via a high-temperature pump and insulated pipeline; Alternatively, the speed of the high-temperature pump is 0~200 mL / min; Alternatively, the rate at which the insulated pipeline delivers molten tin is 10~100 g / min.

3. The method according to claim 1, characterized in that, The working gas is at least one of argon and nitrogen; Alternatively, the flow rate of the working gas is 20~50L / min; Alternatively, the temperature of the plasma glow core region is 5000~10000℃; Alternatively, the plasma generator may be selected from a high-frequency plasma generator, a DC arc plasma generator, or a microwave plasma generator; Alternatively, the power supply of the plasma generator is 50~150kw; Alternatively, the nozzle may be selected from a single-hole direct-fire nozzle, a multi-hole swirling nozzle, or an ultrasonic vibration atomizing nozzle; Alternatively, the oxygen flow rate is 5~20 L / min.

4. The method according to claim 1, characterized in that, The step-by-step quenching also includes a combination of shell-and-tube heat exchangers and air cooling.

5. The method according to claim 1, characterized in that, The cooling medium used in the first-stage rapid cooling zone is selected from at least one of liquid water, water vapor, nitrogen or argon.

6. The method according to claim 1, characterized in that, The cooling medium used in the second-stage crystal transformation region is liquid nitrogen.

7. The method according to claim 1, characterized in that, The cooling medium used in the third-level natural cooling zone is air.

8. An apparatus for implementing the method according to any one of claims 1 to 7, characterized in that, include: Tin ingot melting system, high-temperature conveying system, plasma generator, oxygen unit, oxidation unit, staged quenching unit, and collection system; The tin ingot melting system, the high-temperature conveying system, and the plasma generator are connected in sequence. The outlets of the plasma generator and the oxygen device are both connected to the inlet of the oxidation device. The outlet of the oxidation device is connected to the inlet of the staged quenching device. The step-by-step quenching device is connected to the collection system.

9. The apparatus according to claim 8, characterized in that, The tin ingot melting system is a resistance heating crucible furnace with temperature control function; Alternatively, the high-temperature conveying system may include a high-temperature gear pump and an insulated heating pipe; Alternatively, the plasma generator may have a liquid tin nozzle outlet located above the plasma glow region, and the liquid tin nozzle outlet may have a cooling jacket.

10. The apparatus according to claim 8, characterized in that, The step-by-step quenching device is provided with at least two cooling sections; or, the step-by-step quenching device is selected from at least two of the following: the first-stage rapid cooling zone, the second-stage crystal transformation zone, the shell-and-tube heat exchanger and air-cooled combination zone, and the third-stage natural cooling zone. Alternatively, the collection system may be equipped with a cyclone separator and a bag filter in sequence.

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