High-purity key material micro-nano scale precision grading method and device

Abstract

The invention relates to a high-purity key material micro-nano scale precision grading method and device, belongs to the technical field of high-purity key material grading, and solves the problems of low grading precision, poor grading effect and the like of a high-purity key material grading technology in the prior art when fine particles are treated. The invention provides a high-purity key material micro-nano scale precision grading method. The high-purity key material micro-nano scale precision grading method comprises the following steps that S1, a to-be-graded high-purity key material is prepared and pretreated; s2, initializing a system and purifying a grading environment; s3, quantitatively feeding and pre-dispersing the high-purity key material; s4, performing adjustment and charge treatment on the charge unit; s5, integrating a transition section and a flow field of the grading device; and S6, static grading chamber operation and grading control are carried out. By means of the method, the high grading precision and the good grading effect of the high-purity key materials can be obtained.

Description

Technical Field

[0001] This invention relates to the field of high-purity critical material classification technology, and in particular to a method and apparatus for precise classification of high-purity critical materials at the micro-nano scale. Background Technology

[0002] High-purity key materials refer to materials with extremely high purity levels (typically above 99.999%), where impurity content is controlled at extremely low levels. These are fundamental materials supporting the development of modern high-tech industries. In the semiconductor industry, materials used to manufacture high-performance chips mainly include high-purity antimony, high-purity phosphorus, and high-purity arsenic, requiring a purity of 6N or higher. In the field of infrared detection and imaging, materials such as high-purity tellurium, high-purity cadmium, and zinc cadmium telluride require a purity of 7N. In the photovoltaic power generation field, thin-film photovoltaics and crystalline silicon photovoltaics use materials such as high-purity cadmium telluride, high-purity phosphorus, and high-purity gallium, requiring a purity of 5N or higher. High-purity key materials have extremely strict requirements for particle size. Different application areas have specific requirements for parameters such as particle size distribution and particle size. Particle size distribution directly affects material performance. Particle size control of high-purity materials not only affects their specific surface area, bulk density, and reactivity, but also directly relates to the conductivity, mechanical properties, and process stability of the final product. The particle size requirements for high-purity quartz sand used in semiconductors are the most stringent. The particle size should be within the range of 70μm to 350μm, and the cumulative mass fraction within this range should be greater than or equal to 90%. The cumulative mass fraction of particles smaller than 100μm or larger than 300μm should be less than 1%. For high-purity quartz sand used in optical fiber manufacturing, the proportion of particles with a ratio of the longest to the shortest Freret diameter not exceeding 2:1 should be over 90% to ensure regular particle shape, which is beneficial for the preparation of optical fiber preforms. The particle size requirements for photovoltaic-grade high-purity quartz sand are relatively concentrated, typically requiring that the content of particles between 0.075mm and 0.25mm should not be less than 95.0% to ensure the density and thermal stability of the quartz crucible. With the development of semiconductor, optical fiber communication, and other technologies towards the nanoscale, the requirements for the particle size of high-purity materials are becoming increasingly stringent, moving towards finer particle sizes, narrower distributions, and higher uniformity. There is an urgent need to develop precise particle size control methods and technologies at the micro- and nano-scale.

[0003] Commonly used classification technologies include sieving, pneumatic classification, centrifugal classification, and sedimentation classification. However, these technologies reveal numerous drawbacks when faced with the need for fine classification of high-purity silicon powder. Sieving equipment such as vibrating screens and rotary screens, while simple to operate, suffers from severe clogging due to the strong interparticle forces and electrostatic adsorption of high-purity silicon powder, leading to a sharp decline in classification efficiency and making it difficult to accurately separate high-purity silicon powder with minute particle size differences. Pneumatic classification often employs turbine-type air classifiers and cyclone separators. Although pneumatic classification can handle finer materials to some extent, the small particle size, large specific surface area, and light weight of high-purity silicon powder mean that even small changes in airflow velocity and pressure can significantly affect its movement, causing it to easily agglomerate in high-speed airflow, greatly reducing classification accuracy. Furthermore, during the classification process, the high-speed airflow carries silicon particles that impact the inner wall of the equipment, easily generating debris and impurities that mix into the high-purity materials, affecting their high-purity properties. Centrifugal classification equipment, such as centrifugal classifiers, is suitable for continuous operation and separation of large particles. However, high-purity silicon powder has a small particle size and light weight, resulting in very similar characteristics and low classification accuracy. Furthermore, high-speed operation of the equipment can easily damage the particle structure. Sedimentation classification equipment, such as settling tanks and centrifugal settling machines, also suffers from this problem. High-purity silicon powder has small differences in particle size and density, leading to very similar settling velocities and difficulty in forming an effective separation interface. This results in low classification efficiency, a slow process, and susceptibility to environmental disturbances. In addition, settling media such as water pose a risk of secondary pollution, severely affecting the properties of key material particles, and increasing the workload of subsequent drying processes.

[0004] Electrostatic classification technology utilizes the difference in force experienced by particles in an electric field for separation, enabling dry classification of key materials. It offers advantages such as high classification accuracy and minimal impact on material purity. However, existing electrostatic classification devices suffer from the following problems when processing high-purity key materials: (1) uneven material transport and dispersion affect particle charging and classification effectiveness; (2) lack of a real-time monitoring and feedback system makes it difficult to control operating parameters in real time, thus affecting classification accuracy; (3) lack of flexible interfaces between modules, resulting in poor device structural adaptability. Therefore, there is an urgent need to develop a novel, high-purity key material fine classification device with a reasonable structure, adjustable parameters, high classification accuracy, and real-time monitoring and feedback control to solve the aforementioned problems and improve the accuracy and purity of high-purity key material classification. Summary of the Invention

[0005] Based on the above analysis, the present invention aims to provide a precision classification device and method for high-purity key materials at the micro-nano scale, in order to solve the problems of low classification accuracy and poor classification effect faced by existing high-purity key material classification technologies when processing fine particles.

[0006] On the one hand, the present invention provides a method for precise classification of high-purity key materials at the micro-nano scale, comprising the following steps:

[0007] Step S1: Preparation and pretreatment of high-purity key materials to be graded;

[0008] Step S2: System initialization and purification of the hierarchical environment;

[0009] Step S3: Quantitative feeding and pre-dispersion of high-purity key materials;

[0010] Step S4: Charged cell adjustment and charge processing;

[0011] Step S5: Integration of the transition section of the grading device with the flow field;

[0012] Step S6: Operation and classification control of the electrostatic classification chamber.

[0013] Further, step S1 includes the following steps:

[0014] Step S1.1: Preparation of high-purity key material raw materials: Select high-purity key materials with target particle size distribution;

[0015] Step S1.2: Drying of key materials: Spread the target key materials evenly and place them in a vacuum drying oven or a forced-air drying oven;

[0016] Step S1.3: Dispersion of key materials: Pass the target key materials through a 100-200 mesh sieve to remove hard agglomerates or foreign impurities.

[0017] Furthermore, in step S1.2, the drying temperature is set between 80°C and 150°C, and the drying is continued for 4 to 12 hours to ensure that the moisture content drops below 0.1%.

[0018] Further, step S2 includes the following steps:

[0019] Step S2.1: Check the airtightness of the connections between each unit of the grading device to ensure the insulation and airtightness of the system;

[0020] Step S2.2: Place the grading device in a clean environment, check the ambient humidity, start the negative pressure fan, and establish a stable airflow circulation loop.

[0021] Further, step S4 includes the following steps:

[0022] Step S4.1: Apply a high-voltage DC voltage to the discharge electrode to generate a stable corona discharge between the discharge electrode and the ground electrode;

[0023] Step S4.2: The key material particles pass through the electric field region of the charged chamber with the airflow, and gain charge under the corona discharge effect, forming a charged gas-solid two-phase flow.

[0024] Furthermore, step S4 also includes step S4.3: periodically measuring the average charge and charge distribution of the sample using a Faraday cup.

[0025] Furthermore, in step S5, the charged key material enters the make-up air chamber with the airflow for transition and make-up air is supplied.

[0026] Further, step S6 includes the following steps:

[0027] Step S6.1: Apply a high-voltage DC voltage to the parallel electrode plates of the electrostatic classification chamber to generate a stable electric field;

[0028] Step S6.2: The high-purity key material moves laterally under the drive of airflow, and is simultaneously deflected longitudinally by the action of electric field force. Particles with different trajectories enter the multiple adjustable classification plates, realizing multi-level precision classification.

[0029] Furthermore, it also includes step S7: graded product collection and testing evaluation.

[0030] Further, step S7 includes the following steps:

[0031] Step S7.1: System shutdown and cleaning: Shut down the feeding unit and stop feeding high-purity key materials; turn off the first high-voltage DC power supply and the second high-voltage DC power supply in sequence; after all the remaining key materials in the system have entered the collection or exhaust gas treatment, turn off the negative pressure fan to complete the system shutdown.

[0032] Step S7.2: Product collection: After grading, the key materials between the adjustable grading plates are collected through the switchable window on the side wall of the electrostatic grading chamber; the products are accurately numbered and their corresponding grading conditions are recorded.

[0033] Step S7.3: Detection and Evaluation: For micro-nano scale products, a high-precision particle size analyzer is used to detect the particle size of key materials at each level; a mass spectrometer is used to detect the content of impurity elements in key materials at each level.

[0034] Step S7.4: The real-time operating data recorded by the monitoring and control unit is correlated with the detection results of steps S7.2 and S7.3 to optimize the matching and adjustment of the charging voltage, make-up air flow rate and baffle position, so as to achieve the stability and high precision of the grading process.

[0035] On the other hand, the present invention provides a classification device for classifying high-purity key materials using the aforementioned micro-nano scale precision classification method.

[0036] Furthermore, the grading device includes a feeding unit, a charge enhancement unit, and an electrostatic grading unit connected sequentially along the material conveying direction; the feeding unit includes a screw feeding mechanism and a key material conveying mechanism, the screw feeding mechanism being connected to the key material conveying mechanism, and the key material conveying mechanism being connected to the charge enhancement unit.

[0037] Furthermore, the charge enhancement unit includes a charge chamber, a discharge electrode, and a ground electrode. The discharge electrode and the ground electrode are both disposed in the charge chamber. The discharge electrode is suspended in the middle of the charge chamber, and the ground electrode is a metal plate disposed at the bottom of the charge chamber.

[0038] Furthermore, the electrostatic classification unit includes a makeup air chamber, an electrostatic classification chamber, and two electrode plates. The makeup air chamber is located between the charging chamber and the electrostatic classification chamber, and the two electrode plates are arranged parallel to each other on the upper and lower sides of the electrostatic classification chamber. Each of the two opposite side walls of the makeup air chamber is provided with a makeup air inlet.

[0039] Furthermore, the electrostatic grading unit also includes multiple adjustable grading plates, which are disposed in the electrostatic grading chamber and located at the bottom of the electrostatic grading chamber.

[0040] Furthermore, the high-purity key material micro-nano scale precision classification device also includes a post-processing and air-expelling unit, which is located downstream of the electrostatic classification unit. The post-processing and air-expelling unit includes an exhaust gas treatment chamber, a negative pressure fan, and a multi-stage filtration assembly. The exhaust gas treatment chamber is located downstream of the electrostatic classification chamber. The negative pressure fan is connected to the lower end of the exhaust gas treatment chamber, and the upper end of the exhaust gas treatment chamber is connected to the electrostatic classification chamber. The multi-stage filtration assembly is located inside the exhaust gas treatment chamber.

[0041] Compared with the prior art, the present invention can achieve at least one of the following beneficial effects:

[0042] (1) The feeding unit of the present invention adopts a combination design of screw feeding device and air amplifier. First, the feeding amount is precisely controlled by mechanical means, and then the Venturi effect is used for pre-dispersion and acceleration to avoid problems such as key material particles clogging the feeding port and agglomeration, thereby improving the uniform dispersion of key materials before entering the charging chamber.

[0043] (2) This invention achieves independent control of the particle charging process and the classification process by connecting the charge enhancement unit and the electrostatic classification unit in series and introducing a make-up air chamber structure. The make-up air chamber structure can not only adjust the air volume required for the classification of key materials, but also ensure that the charged key material particles enter the classification zone in a stable state.

[0044] (3) By integrating multiple sensors such as wind speed, humidity, and mass flow rate, as well as system circuit controllers into the detection and control unit, this invention can achieve real-time monitoring of key system parameters and precise circuit control, thus ensuring the safety and stability of system operation.

[0045] (4) The present invention adopts a modular design, and each unit is connected by screws and glue, which can be disassembled and assembled independently. It is convenient to change the electrode type, adjust the size of the classification chamber or optimize the flow field structure according to experimental or production needs. The device is flexible and highly adaptable.

[0046] In this invention, the above-described technical solutions can be combined with each other to achieve more preferred combinations. Other features and advantages of this invention will be set forth in the following description, and some advantages may become apparent from the description or be learned by practicing the invention. The objects and other advantages of this invention can be realized and obtained from what is particularly pointed out in the description and drawings. Attached Figure Description

[0047] The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. Throughout the drawings, the same reference numerals denote the same parts.

[0048] Figure 1 This is a schematic diagram of the micro-nano-scale precision classification process for high-purity key materials in a specific embodiment.

[0049] Figure 2 This is a schematic diagram of the micro-nano scale precision classification device for high-purity key materials in a specific embodiment;

[0050] Figure 3 This is a schematic diagram of the feeding unit in a specific embodiment;

[0051] Figure 4 This is a schematic diagram of the charge enhancement unit in a specific embodiment;

[0052] Figure 5 This is a schematic diagram of the electrostatic classification unit in a specific embodiment;

[0053] Figure 6 This is a schematic diagram of the post-processing and air extraction unit in a specific embodiment.

[0054] Figure label:

[0055] 1-Feeding unit; 11-Screw feeding mechanism; 111-Hopper; 112-Screw conveyor; 1121-Rotating rod; 1122-Screw blade; 1123-Outer shell; 113-Stepper motor; 114-Reducer; 115-Support frame; 12-Conveying mechanism; 2-Charging enhancement unit; 21-Charging chamber; 22-Discharge electrode; 23-Grounding electrode; 24-Insulating bracket; 25-Connecting pipe; 3-Electrostatic classification unit; 31-Make-up air chamber; 311-Make-up air inlet; 312-Flow regulating valve; 32-Electrostatic classification chamber; 321-Window; 33-Electrode plate; 34-Adjustable classification plate; 4-Post-treatment and exhaust unit; 41-Tail gas treatment chamber; 42-Negative pressure fan; 43-Multi-stage filter assembly; 5-Support. Detailed Implementation

[0056] The preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings, which constitute a part of the present invention and are used together with the embodiments of the present invention to illustrate the principles of the present invention, but are not intended to limit the scope of the present invention.

[0057] Example 1

[0058] A specific embodiment of the present invention, such as Figure 1 As shown, a precise micro-nano scale classification method for high-purity key materials is disclosed, including the following steps:

[0059] Step S1: Preparation and pretreatment of high-purity key materials to be graded.

[0060] Step S1.1: Preparation of high-purity key material raw materials: Select high-purity key materials with target particle size distribution (such as high-purity alumina, silicon nitride, etc.) to ensure that their purity meets the requirements before classification.

[0061] Step S1.2: Drying of key materials: Spread the target key materials evenly and place them in a vacuum drying oven or a forced-air drying oven. Set the drying temperature between 80°C and 150°C and continue drying for 4 to 12 hours until the quality of the key materials is constant and the moisture content is reduced to below 0.1%.

[0062] Step S1.3: Dispersion of key materials: Pass the target key materials through a 100-200 mesh sieve to remove any large hard agglomerates or foreign impurities that may be present.

[0063] Step S2: System initialization and purification of the hierarchical environment.

[0064] Step S2.1: Check the airtightness of the screw bonding and locking connections between each unit of the grading device (feeding unit 1, charge enhancement unit 2, electrostatic grading unit 3, post-treatment and induced draft unit 4) to ensure the system's insulation and airtightness.

[0065] Step S2.2: Place the grading device in a clean environment (such as a local Class 100 or Class 1000 clean area) to ensure that the grading process is carried out in a highly clean environment and to prevent external contamination. Detect the ambient humidity, start the negative pressure fan 42, and control the operating frequency of the variable frequency fan and the air valves at each location through the circuit controller to precisely adjust the total air volume and negative pressure of the system, establishing a stable airflow circulation loop (reducing the concentration of suspended particulate matter inside the device to an extremely low level). Monitor the wind speed and pressure sensors at the outlet of the negative pressure fan 42, the inlet of the charged chamber 21, and the inlet and outlet of the electrostatic grading chamber 32, as well as the humidity sensors at the air inlet and the make-up air chamber 31 in real time to ensure that the airflow velocity, system pressure difference, and airflow humidity reach the preset stable state.

[0066] Step S3: Quantitative feeding and pre-dispersion of high-purity key materials.

[0067] The speed of the stepper motor 113 in the screw feeding mechanism 11 is controlled by the circuit controller in the monitoring and control unit, which drives the screw conveyor 112 to achieve precise quantitative feeding of high-purity key materials. The feeding rate is monitored in real time by the mass flow sensor (e.g., continuously adjustable within the range of 3-60 g / min).

[0068] The electric proportional valve of the air amplifier is controlled to adjust the conveying speed, so that the key material is fully dispersed and accelerated at the air amplifier by the Venturi effect of the high-speed airflow, and mixed with the supplementary airflow to form a stable gas-solid two-phase flow, which then enters the charge enhancement unit 2. At the same time, the wind speed sensor and humidity sensor in the monitoring control unit monitor the air amplifier in real time, and the data is transmitted to the computer.

[0069] Step S4: Charged unit adjustment and charge processing.

[0070] Step S4.1: Apply a set high voltage DC voltage (in the range of -100kV to +100kV) to the discharge electrode 22 of the charge enhancement unit 2, and adjust the electrode spacing, airflow speed and charging time, etc., to generate a stable corona discharge between the discharge electrode 22 and the ground electrode 23.

[0071] Step S4.2: The key material particles pass through the electric field region of the charged chamber 21 with the airflow, gaining charge under corona discharge, forming a charged gas-solid two-phase flow. The output terminal of the first high-voltage DC power supply is monitored in real time by a high-voltage / current sensor to prevent electric shock or abnormal discharge.

[0072] Step S4.3: The stability of airflow velocity and pressure difference is monitored in real time using pressure sensors and wind speed sensors at the inlet of charging chamber 21. The average charge and charge distribution of the sample are periodically measured using a Faraday cup. If the measured average charge is lower than the target value, the voltage is gradually increased or the charging time is extended; if the charge deviation is too large, the voltage is decreased.

[0073] Step S5: Integration of the transition section of the grading device with the flow field.

[0074] After being charged, the key materials enter the transition section (make-up air chamber 31) of the electrostatic classification unit 3 with the airflow. The two make-up air inlets 311 on both sides adjust the make-up air valves to provide make-up air according to the calculated airflow required for classification. The incoming air is rectified by the main air duct through the grille and needle-punched felt. Simultaneously, the charged particles undergo a transition within the make-up air chamber 31. Wind speed sensors and differential pressure sensors at the make-up air inlets 311 monitor and provide feedback on the airflow status in real time.

[0075] Step S6: Operation and classification control of electrostatic classification chamber 32.

[0076] Step S6.1: Apply a set high voltage DC voltage (in the range of -100kV to +100kV) to the parallel electrode plates 33 of the electrostatic grading chamber 32, and adjust the grading zone length, electrode spacing, etc. to generate a stable electric field between the upper and lower parallel electrode plates 33.

[0077] Step S6.2: Inside the electrostatic classification chamber 32, the high-purity key material moves laterally under the drive of airflow, while simultaneously being deflected longitudinally by an electric field. Particles with different trajectories enter the spaces between multiple adjustable classification plates 34, achieving multi-level precision classification. Spatial distribution based on particle size / charge classification is achieved by adjusting voltage, airflow speed, and feed rate.

[0078] Pressure and wind speed sensors at the inlet and outlet of electrostatic classification chamber 32 monitor the stability of airflow velocity and pressure difference in real time. High-voltage / current sensors monitor the output of the second high-voltage DC power supply in real time to prevent electric shock or abnormal discharge.

[0079] Step S7: Graded product collection and testing evaluation.

[0080] Step S7.1: System Shutdown and Cleanup: Shut down feeding unit 1 to stop feeding high-purity critical materials. Sequentially shut down the first and second high-voltage DC power supplies. After all remaining critical materials in the system have entered the collection or exhaust gas treatment process, shut down the negative pressure fan 42 to complete the system shutdown.

[0081] Step S7.2: Product Collection: After grading, the key materials in the adjustable grading plates 34 are collected through the openable window 321 (pressed by a quick-pressing plate) on the side wall of the electrostatic grading chamber 32. The products are accurately numbered, and their corresponding grading conditions are recorded.

[0082] Step S7.3: Testing and Evaluation: For micro-nano scale products, a high-precision particle size analyzer is used to detect the particle size of key materials at each level; a mass spectrometer (ICP-MS) and other precision analytical instruments are used to detect the content of impurity elements in key materials at each level.

[0083] Step S7.4: Perform correlation analysis between the real-time operating data (such as charged electrode voltage, grading electrode voltage, wind speed, humidity, mass flow rate, etc.) recorded by the monitoring and control unit and the detection results of steps S7.2 and S7.3, so as to optimize the matching and adjustment of parameters such as charged voltage, makeup air flow rate, and adjustable grading plate 34 position, so as to achieve the stability and high precision of the grading process.

[0084] Example 2

[0085] Another specific embodiment of the present invention, in conjunction with Figure 2 and Figure 3 As shown, a high-purity key material micro-nano scale precision classification device is disclosed for use in the method of Example 1. The classification device includes a feeding unit 1, a charge enhancement unit 2 and an electrostatic classification unit 3 connected in sequence along the material conveying direction. The feeding unit 1 includes a screw feeding mechanism 11 and a conveying mechanism 12. The screw feeding mechanism 11 is connected to the conveying mechanism 12, and the conveying mechanism 12 is connected to the charge enhancement unit 2.

[0086] Compared with the prior art, the high-purity key material micro-nano scale precision classification device provided in this embodiment is provided with a feeding unit 1, a charge enhancement unit 2 and an electrostatic classification unit 3 connected in sequence along the material conveying direction. The key material particles conveyed by the feeding unit 1 are first enhanced in the charge enhancement unit 2 and then enter the electrostatic classification unit 3 for classification, realizing independent control of the charging process and the classification process of the key material particles. Moreover, the screw feeding mechanism 11 is connected to the conveying mechanism 12. The key material particles are conveyed to the conveying mechanism 12 through the screw feeding mechanism 11. The feeding amount is first precisely controlled by mechanical means, and then the Venturi effect is used for pre-dispersion and acceleration, avoiding problems such as key material particles clogging the feeding port and agglomeration. This improves the uniform dispersion of high-purity key materials before entering the charging chamber 21, thereby improving the accuracy and purity of key material classification.

[0087] like Figure 3 As shown, the screw feeding mechanism 11 includes a hopper 111 and a screw conveyor 112. The hopper 111 is connected to the screw conveyor 112, and key material particles are conveyed from the hopper 111 to the screw conveyor 112. The screw conveyor 112 includes a rotating rod 1121, a helical blade 1122, and a housing 1123. The helical blade 1122 is spirally arranged along the outer circumference of the rotating rod 1121. Both the helical blade 1122 and the rotating rod 1121 are disposed inside the housing 1123. The hopper 111 is connected to the housing 1123, so that the key material particles in the hopper 111 are directly conveyed through the rotating rod 1121.

[0088] To achieve the rotation of the rotating rod 1121, as follows: Figure 3As shown, the screw feeding mechanism 11 also includes a stepper motor 113, a reducer 114, and a support frame 115. The stepper motor 113 is connected to the support frame 115, and the screw conveyor 112 is mounted on the support frame 115. One end of the rotating rod 1121 is connected to the stepper motor 113 through the reducer 114, and the other end of the rotating rod 1121 extends into the outer casing 1123. The stepper motor 113 drives the rotating rod 1121 to rotate, and the screw blades 1122 drive the key material particles forward. The outer casing 1123 extends to the conveying mechanism 12, and the key material particles conveyed from the rotating rod 1121 enter the conveying mechanism 12. By controlling the rotation speed of the stepper motor 113, precise quantitative feeding of the key material can be achieved, and the processing capacity can be continuously adjusted within the range of 3-60 g / min.

[0089] The conveying mechanism 12, also known as the air amplifier (preferably LT100A), is located at the outlet of the screw feeder 11. It utilizes a high-speed airflow to create a negative pressure zone through the Venturi effect, uniformly drawing in and accelerating the input key material. After thorough mixing with the supplementary airflow, a stable gas-solid two-phase flow is formed, which then enters the charge enhancement unit 2. This combined design of the screw feeder 11 and the air amplifier effectively prevents material blockage at the feed inlet and ensures uniform material dispersion before entering the main conveying pipeline.

[0090] It is worth noting that a mass flow sensor and a capacitive humidity sensor are installed at the inlet of the feeding unit 1, which can monitor the feeding rate and the humidity of the ambient airflow in real time.

[0091] In this embodiment, high-purity silicon powder enters the screw conveyor 112 through the hopper 111. After being fed at a given speed, it moves forward as the screw blades 1122 rotate. Subsequently, it is dispersed and conveyed at the air amplifier, and then enters the charge enhancement unit 2. Through the combined design of the screw feeding mechanism 11 and the air amplifier, key material conveying without mechanical impellers can be achieved, effectively preventing material blockage at the feed port. At the same time, it can also ensure the continuity and stability of the feeding and the uniformity of material dispersion before entering the main conveying pipeline.

[0092] The charge enhancement unit 2 is used to charge the passing key material particles, which then enter the electrostatic classification unit 3 with the airflow. Specifically, combined with... Figure 2 and Figure 4As shown, the charge enhancement unit 2 includes a charging chamber 21, a discharge electrode 22, and a grounding electrode 23. The charging chamber 21 is made of highly insulating transparent plexiglass, and its interior is kept sealed to prevent leakage and external interference. Both the discharge electrode 22 and the grounding electrode 23 are located inside the charging chamber 21. The discharge electrode 22 is suspended in the middle of the charging chamber 21, and the grounding electrode 23 is a metal plate located at the bottom of the charging chamber 21. The discharge electrode 22 can be selected from different forms, such as a barbed wire electrode, a two-tooth electrode, or a four-tooth electrode, as needed.

[0093] Combination Figure 2 and Figure 4 As shown, the charge enhancement unit 2 also includes an insulating support 24 and a first high-voltage DC power supply (not shown in the figure). One end of the insulating support 24 is located inside the charge chamber 21, and the other end is connected to the top of the charge chamber 21. The output terminal of the first high-voltage DC power supply is connected to one end of the discharge electrode 22. The voltage range of the first high-voltage DC power supply is -100kV to +100kV, used to generate stable corona discharge. The ground electrode 23 is connected to the ground electrode of the first high-voltage DC power supply, forming an electric field region with the discharge electrode 22.

[0094] Understandably, combined Figure 2 and Figure 4 As shown, the charge enhancement unit 2 also includes a connecting pipe 25, one end of which is connected to the conveying mechanism 12 and the other end is connected to the charge chamber 21.

[0095] In this embodiment, the high-purity key material enters the charging chamber 21 via the airflow from the feeding unit 1. When passing through the electric field region between the discharge electrode 22 and the ground electrode 23, it gains charge through corona discharge. The charging efficiency and charging stability of the particles can be optimized by adjusting parameters such as particle size, dielectric constant, electric field voltage, and electrode spacing. A high-voltage voltage / current sensor is connected to the output terminal of the first high-voltage DC power supply to monitor the discharge status in real time and prevent electric shock.

[0096] Combination Figure 2 and Figure 5As shown, the electrostatic classification unit 3 includes an air supply chamber 31, an electrostatic classification chamber 32, and electrode plates 33. The air supply chamber 31 is located between the charging chamber 21 and the electrostatic classification chamber 32. Two electrode plates 33 are provided, arranged parallel to each other on the upper and lower sides of the electrostatic classification chamber 32. One electrode plate 33 is connected to the top of the electrostatic classification chamber 32, and the other electrode plate 33 is connected to the bottom of the electrostatic classification chamber 32. Exemplarily, the two electrode plates 33 are threadedly fixed to the aluminum alloy fixing frame by pre-embedded countersunk screws protruding from the inside to the outside on the upper and lower sides of the electrostatic classification chamber 32. Each of the two opposite side walls of the air supply chamber 31 is provided with an air supply inlet 311, which is used to supplement the air volume required during electrostatic classification. Understandably, the air supply inlet 311 is connected to an independently controllable flow regulating valve 312. In order to rectify and uniformly distribute the airflow, the inner side of the air supply inlet 311 is provided with a grid and needle-punched felt to ensure that the charged key material particles enter the electrostatic classification chamber 32 in a stable state. The electrostatic grading chamber 32 is made of transparent plexiglass with high insulation properties.

[0097] It is worth noting that the opening of the make-up air chamber 31 from the charged chamber 21 to the electrostatic classification chamber 32 gradually increases, that is, the upper and lower side plates of the make-up air chamber 31 are set horizontally, the two side plates are set at an angle, and the make-up air inlet 311 is set on the two angled side plates.

[0098] Combination Figure 2 and Figure 5 As shown, the electrostatic classification unit 3 also includes adjustable classification plates 34 and a second high-voltage DC power supply (not shown in the figure). Two electrode plates 33 are respectively connected to the output terminal and ground terminal of the second high-voltage DC power supply. The voltage range of the second high-voltage DC power supply is -100kV to +100kV, used to generate a stable electric field. Multiple adjustable classification plates 34 are disposed within the electrostatic classification chamber 32 and located at the bottom of the chamber. Their position and angle can be precisely adjusted according to the target particle size. Charged particles move along different trajectories under the combined action of electric field force, airflow resistance, and gravity. By setting multiple adjustable classification plates 34, particle groups with different motion trajectories can be guided into the corresponding adjustable classification plates 34, achieving multi-level precision classification. For example, the two ends of the adjustable classification plates 34 are connected to the side wall of the electrostatic classification chamber 32 via slots. The spacing between adjacent adjustable classification plates 34 can be adjusted by sliding along the slots.

[0099] To facilitate the collection of critical materials after grading and the adjustment of the spacing of the adjustable grading plates 34, such as Figure 5 As shown, an openable window 321 is provided on the lower side wall of the electrostatic classification chamber 32. The window 321 is pressed shut by a quick-pressing plate, and the uncollected ultrafine particles enter the subsequent unit with the main airflow.

[0100] In this embodiment, the key material particles charged by the charge enhancement unit 2 enter the make-up air chamber 31 with the airflow. Two make-up air inlets 311 on both sides of the make-up air chamber 31 provide make-up air according to the required airflow for grading. The incoming air is rectified by the main air duct through the grille and needle-punched felt, while the charged particles undergo a transition within the make-up air chamber 31. The charged particles then enter the electric field formed by the parallel electrode plates 33 with the airflow. Under the combined action of the electric field and airflow, particles of different sizes enter their corresponding adjustable grading plates 34, achieving precise grading. By matching and adjusting the voltage, make-up airflow, and position of the adjustable grading plates 34, the efficiency of fine particle grading can be effectively improved.

[0101] It is worth noting that thermal wind speed sensors and micro differential pressure sensors are installed at the air supply inlet 311, the inlet of the electrostatic classification chamber 32, and the outlet to monitor the airflow status in real time.

[0102] like Figure 2 As shown, the high-purity key material micro-nano scale precision classification device also includes a post-processing and air-guiding unit 4, which is located downstream of the electrostatic classification unit 3. That is, the feeding unit 1, the charge enhancement unit 2, the electrostatic classification unit 3 and the post-processing and air-guiding unit 4 are connected in sequence along the material conveying direction.

[0103] Combination Figure 2 and Figure 6 As shown, the post-treatment and exhaust unit 4 includes an exhaust gas treatment chamber 41, a negative pressure fan 42, and a multi-stage filtration assembly 43. The exhaust gas treatment chamber 41 is located downstream of the electrostatic classification chamber 32. The negative pressure fan 42 is connected to the lower end of the exhaust gas treatment chamber 41, and the upper end of the exhaust gas treatment chamber 41 is connected to the electrostatic classification chamber 32. The multi-stage filtration assembly 43 is located inside the exhaust gas treatment chamber 41. The multi-stage filtration assembly 43 includes high-efficiency filter media such as needle-punched felt and filter screens, used to capture unsettled fine critical materials, preventing particles from being discharged with the exhaust gas and causing secondary pollution, thus ensuring the cleanliness of the laboratory or production environment. The negative pressure fan 42 is located at the end of the classification system. A three-way valve and a control valve are installed at the inlet of the negative pressure fan 42 to control the incoming air volume, thereby controlling the air volume and velocity in the loop, maintaining the airflow circulation of the entire device, ensuring that critical material particles smoothly complete the charging and classification process under the drive of airflow, and introducing the gas-solid mixture into the exhaust gas treatment chamber 41 after classification.

[0104] It is worth noting that a wind speed sensor and a pressure sensor are installed at the outlet of the negative pressure fan 42 to monitor the airflow speed and pressure difference in real time, so as to promptly determine whether there is a blockage or leak in the air path. A humidity sensor is also installed to monitor the air humidity.

[0105] The high-purity key material micro-nano scale precision classification device also includes a monitoring and control unit. This unit comprises a sensor network and a circuit controller. The sensor network includes wind speed sensors, humidity sensors, pressure sensors, mass flow sensors, voltage sensors, and current sensors. Wind speed and pressure sensors are located at the outlet of the negative pressure fan 42, the inlet of the charging chamber 21, and the inlet and outlet of the electrostatic classification chamber 32 to monitor airflow velocity and pressure difference in real time, promptly determining whether there is blockage or leakage in the air path. Humidity sensors are located at the air inlets (the air amplifier inlet and the negative pressure fan 42 inlet) and the make-up air chamber 31 to monitor air humidity and prevent excessive humidity from causing a decrease in the charging efficiency of key materials or exacerbating agglomeration. A mass flow sensor is located at the feed inlet to monitor the feeding rate of the screw feeder. Voltage and current sensors are respectively installed at the high-voltage power ports of the charging electrode and the classification electrode to detect the electric field strength and corona discharge state. The circuit controller controls the rotational speed of the stepper motor 113 of the screw feeder mechanism 11 to precisely adjust the feed rate.

[0106] In this embodiment, during the entire operation, the wind speed sensor, humidity sensor, and voltage / current sensor monitor the operating parameters of each module in real time. The control system adjusts the power of the negative pressure fan 42, the opening degree of the flow regulating valve 312 of the air supply chamber 31, and the high-voltage power output according to the monitoring results, so as to achieve precise control of the system operating parameters and ensure the stability and high precision of the grading process.

[0107] like Figure 2 As shown, the high-purity key material micro-nano scale precision classification device also includes a support 5. The feeding unit 1, charge enhancement unit 2, electrostatic classification unit 3, and post-processing and air extraction unit 4 are all connected to the support 5. The feeding unit 1, charge enhancement unit 2, electrostatic classification unit 3, and post-processing and air extraction unit 4 are connected by screws and glue. The monitoring and control units are distributed in the key parts of the classification device (i.e., the parts where sensors are set) formed by the series connection of the various units.

[0108] In this embodiment, the feeding unit 1 adopts a combination design of a screw feeding mechanism 11 and an air amplifier. First, the feeding amount is precisely controlled mechanically, and then the Venturi effect is used for pre-dispersion and acceleration, avoiding problems such as easy blockage of the feeding port and agglomeration of key material particles, thus improving the uniform dispersion of key materials before entering the charging chamber 21. Through the series design of the charging enhancement unit 2 and the electrostatic classification unit 3, and the introduction of the make-up air chamber 31 structure, independent control of the particle charging process and the classification process is realized. The make-up air chamber 31 structure can not only adjust the air volume required for the classification of key materials, but also ensure that the charged key material particles enter the classification zone in a stable state. By integrating multiple sensors such as wind speed, humidity, and mass flow rate, as well as the system circuit controller, the detection and control unit can realize real-time monitoring of key parameters of the system and precise circuit control, ensuring the safety and stability of system operation. Through the modular design, each unit is connected by screws and glue, which can be independently disassembled and assembled, making it easy to change the electrode type, adjust the size of the classification chamber, or optimize the flow field structure according to experimental or production needs, making the device flexible and adaptable.

[0109] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for precise micro-nano scale classification of high-purity key materials, characterized in that, Includes the following steps: Step S1: Preparation and pretreatment of high-purity key materials to be graded; Step S2: System initialization and purification of the hierarchical environment; Step S3: Quantitative feeding and pre-dispersion of high-purity key materials; Step S4: Charged cell adjustment and charge processing; Step S5: Integration of the transition section of the grading device with the flow field; Step S6: Operation and classification control of the electrostatic classification chamber.

2. The high-purity key material micro-nano scale precision classification method according to claim 1, characterized in that, Step S1 includes the following steps: Step S1.1: Preparation of high-purity key material raw materials: Select high-purity key materials with target particle size distribution; Step S1.2: Drying of key materials: Spread the target key materials evenly and place them in a vacuum drying oven or a forced-air drying oven; Step S1.3: Dispersion of key materials: Pass the target key materials through a 100-200 mesh sieve to remove hard agglomerates or foreign impurities.

3. The high-purity key material micro-nano scale precision classification method according to claim 2, characterized in that, In step S1.2, the drying temperature is set between 80°C and 150°C, and the drying is continued for 4 to 12 hours to ensure that the moisture content drops below 0.1%.

4. The method for precise micro-nano scale classification of high-purity key materials according to any one of claims 1-3, characterized in that, Step S2 includes the following steps: Step S2.1: Check the airtightness of the connections between each unit of the grading device to ensure the insulation and airtightness of the system; Step S2.2: Place the grading device in a clean environment, check the ambient humidity, start the negative pressure fan, and establish a stable airflow circulation loop.

5. The method for precise micro-nano scale classification of high-purity key materials according to any one of claims 1-3, characterized in that, Step S4 includes the following steps: Step S4.1: Apply a high-voltage DC voltage to the discharge electrode to generate a stable corona discharge between the discharge electrode and the ground electrode; Step S4.2: The key material particles pass through the electric field region of the charged chamber with the airflow, and gain charge under the corona discharge effect, forming a charged gas-solid two-phase flow.

6. The high-purity key material micro-nano scale precision classification method according to claim 5, characterized in that, Step S4 further includes step S4.3: periodically measuring the average charge and charge distribution of the sample using a Faraday cup.

7. The method for precise micro-nano scale classification of high-purity key materials according to any one of claims 1-3 and 6, characterized in that, In step S5, the charged key material enters the make-up air chamber with the airflow for transition and make-up air is supplied.

8. The method for precise micro-nano scale classification of high-purity key materials according to any one of claims 1-3 and 6, characterized in that, Step S6 includes the following steps: Step S6.1: Apply a high-voltage DC voltage to the parallel electrode plates of the electrostatic classification chamber to generate a stable electric field; Step S6.2: The high-purity key material moves laterally under the drive of airflow, and is simultaneously deflected longitudinally by the action of electric field force. Particles with different trajectories enter the multiple adjustable classification plates, realizing multi-level precision classification.

9. The high-purity key material micro-nano scale precision classification method according to claim 8, characterized in that, It also includes step S7: graded product collection and testing evaluation.

10. A grading device, characterized in that, The high-purity key material micro-nano scale precision classification method according to any one of claims 1-9 is used to classify high-purity key material substances.

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