A method and apparatus for removing granular silicon powder

Abstract

This invention discloses a method and apparatus for removing granular silicon powder. The method includes: continuously introducing granular silicon into a sealed powder removal chamber and introducing a pulsed airflow to form a microfluidic expanded bed of granular silicon within the sealed powder removal chamber; performing in-situ electrostatic neutralization treatment on the surface of the granular silicon within the sealed powder removal chamber to eliminate the electrostatic adsorption force between the granular silicon particles and the fine powder adhering to their surfaces, causing the fine powder to desorb and be discharged from the sealed powder removal chamber with the airflow; purifying the discharged airflow to separate the fine powder, and then returning the purified airflow to the sealed powder removal chamber as a pulsed airflow to form a closed-loop circulation. This invention can efficiently remove stubbornly adhered fine powder from the surface of granular silicon particles, enhance powder removal stability, ensure particle integrity and processing uniformity, prevent fine powder leakage, and inhibit particle oxidation and oxygenation.

Description

Technical Field

[0001] This invention belongs to the field of crystalline silicon material technology, specifically relating to a method and apparatus for removing granular silicon powder. Background Technology

[0002] Granular silicon is an important product form of photovoltaic and electronic-grade polycrystalline silicon, and its preparation typically employs fluidized bed chemical vapor deposition (FCVD). During the growth of granular silicon in fluidized bed FCVD, a large amount of micron-sized fine powder readily adsorbs onto the surface of the particles.

[0003] Currently, the main methods for removing fine powder from the surface of granular silicon are as follows: one is conventional physical removal methods, including traditional methods such as conventional pneumatic purging and vibrating sieving, which are currently the most widely used powder removal methods in industry; the other is a method proposed in recent years that combines electrostatic adsorption and airflow purging, using an external high-voltage electric field to adsorb fine powder while simultaneously using airflow purging to achieve powder removal from the surface of granular silicon. The above methods have at least the following shortcomings in practical applications:

[0004] 1) Incomplete removal of stubbornly adhering fine powder: Conventional methods such as pneumatic purging and vibrating sieving can only remove a small amount of loose floating powder from the particle surface. For these types of fine powders that are strongly adhered to the masterbatch (silicon particles) due to electrostatic adsorption and van der Waals forces, the removal effect is extremely limited. Although the combined electrostatic adsorption and airflow purging technology introduces a high-voltage electric field, it cannot fundamentally eliminate the intrinsic electrostatic adsorption potential between the fine powder and the masterbatch by relying solely on the external high-voltage electric field to forcibly adsorb and tear the fine powder. As a result, stubbornly adhering fine powder is still difficult to remove completely.

[0005] 2) Serious problem of secondary adhesion of fine powder: Under the action of high voltage electric field, fine powder is prone to polarization. After polarization, the fine powder is prone to fall back and re-adhere to the particle surface under the change of electric field or air flow disturbance, resulting in secondary adhesion, which leads to poor powder removal stability and large fluctuation in effect.

[0006] 3) Particle breakage and deterioration of sphericity: The existing process uses a conventional constant flow direct airflow method. The airflow is prone to forming eddies inside the equipment, which aggravates the collision and friction between particles. This not only causes particle breakage and generates new micro powder, but also damages the sphericity of the particles, affecting product quality.

[0007] 4) Uneven material processing: Existing processes generally lack an effective fluidized and loose structure, and materials tend to accumulate in the equipment, forming processing blind spots, resulting in low powder removal efficiency and poor consistency.

[0008] 5) Poor airtightness and micro-negative pressure control: The existing process has poor airtightness design and weak micro-negative pressure control, which makes fine powder easy to leak, causing not only material loss but also pollution of the working environment.

[0009] 6) Open-loop operation of gas path leads to easy oxidation and oxygenation of particles: The gas path system of the existing process is mostly open-loop operation, and nitrogen is not circulated in a closed loop. It is difficult to control the oxygen content in the equipment. Particles are easily oxidized during the process, resulting in an increase in the oxygen content of the product, which makes it difficult to meet the cleanliness and low oxygen requirements of high-end granular silicon. Summary of the Invention

[0010] The technical problem to be solved by the present invention is to address the above-mentioned deficiencies in the prior art by providing a method and apparatus for removing granular silicon powder, which can efficiently remove stubborn fine powder adhering to the surface of granular silicon particles, enhance the stability of powder removal, ensure the integrity of particles and uniformity of processing, prevent fine powder leakage, and inhibit particle oxidation and oxygenation.

[0011] The technical solution of the present invention to solve the above-mentioned technical problems is:

[0012] According to a first aspect of the present invention, a method for removing granular silicon powder is provided, comprising:

[0013] Granular silicon is continuously introduced into a closed dust removal chamber and a pulsed airflow is introduced to form a microfluidic expanded bed of granular silicon in the closed dust removal chamber.

[0014] The surface of granular silicon in the sealed dust removal chamber is subjected to in-situ electrostatic neutralization treatment to eliminate the electrostatic adsorption force between granular silicon particles and the fine powder adhering to their surface, so that the fine powder is desorbed and discharged from the sealed dust removal chamber with the airflow.

[0015] The exhaust airflow is purified to separate fine powder. The purified airflow is then pulsated and returned to the sealed dust removal chamber to form a closed-loop circulation.

[0016] Optionally, the working voltage of the in-situ electrostatic neutralization treatment is 6kV~12kV, and after the in-situ electrostatic neutralization treatment, the electrostatic potential on the surface of the granular silicon particles is within ±100V.

[0017] Optionally, the pulsating gas flow is formed by nitrogen with a purity of ≥99.999% and an inlet pressure of 0.02MPa~0.04MPa.

[0018] Optionally, the frequency of the pulsating airflow is 0.5Hz~3Hz, and the fluidized apparent gas velocity is 0.08m / s~0.25m / s.

[0019] Optionally, the particle size of the granular silicon is 1~3mm, and the residence time of the granular silicon is 6s~18s.

[0020] Optionally, the expansion ratio of the microfluidic expanded bed is 1.2 to 1.8.

[0021] Optionally, the purification process includes:

[0022] First, the exhaust airflow is subjected to cyclone separation for pre-dust removal, and then fine filtration is performed with a precision of 0.1μm~0.5μm.

[0023] Optionally, the sealed dust removal chamber is kept under a slight negative pressure, with a negative pressure value of -50Pa to -300Pa.

[0024] Optionally, the air volume of the air discharged from the sealed dust removal chamber is 5% to 10% higher than the air volume of the air introduced into it.

[0025] According to a second aspect of the present invention, a granular silicon descaling device is also provided, comprising a sealed descaling chamber, a pulsed fluidized bed air distribution system, an in-situ electrostatic neutralization electrode assembly, and a purification system, wherein:

[0026] The sealed dust removal chamber has a feed inlet at the top, a discharge outlet at the bottom, and an exhaust outlet at the top.

[0027] The pulsating fluidized air distribution system is connected to the lower part of the sealed dust removal chamber and is used to introduce pulsating airflow into the sealed dust removal chamber, so that the granular silicon in the sealed dust removal chamber forms a microfluidic expanded bed.

[0028] The in-situ electrostatic neutralization electrode group is located in the corresponding fluidization region of the closed powder removal cavity. It is used to perform in-situ electrostatic neutralization treatment on the surface of granular silicon in the closed powder removal cavity, eliminate the electrostatic adsorption force between granular silicon particles and the fine powder adhering to their surface, and desorb the fine powder.

[0029] The purification system is connected to the exhaust port and the pulsed fluidized air distribution system respectively. It is used to receive the airflow discharged from the sealed dust removal chamber and purify it to separate fine powder. The purified airflow is then introduced into the pulsed fluidized air distribution system to form a pulsed airflow before returning to the sealed dust removal chamber to form a closed loop.

[0030] Optionally, the in-situ electrostatic neutralization electrode group includes 4 to 6 electrostatic neutralization electrodes, each of which is evenly arranged around the circumference of the sealed dust removal cavity, with an operating voltage of 6kV to 12kV and an operating current of ≤50μA.

[0031] Optionally, the in-situ electrostatic neutralization electrode assembly is located on the inner wall of the sealed dust removal chamber; or, it is located on the outer wall of the sealed dust removal chamber to achieve non-contact electrostatic control.

[0032] Optionally, the pulsed fluidized air distribution system includes a pulsed air distribution plate, a pulsed airflow generator, and a pressure stabilizing tank; the pulsed airflow generator is used to generate pulsed airflow; the pulsed air distribution plate is located at the lower part of the sealed dust removal chamber and is connected to the pulsed airflow generator to evenly distribute the pulsed airflow into the sealed dust removal chamber; the pressure stabilizing tank is connected to the purification system and the pulsed airflow generator respectively, and is used to introduce the purified airflow into the pulsed airflow generator to form pulsed airflow and stabilize the inlet pressure of the pulsed airflow generator.

[0033] Optionally, the pulsating air distribution plate is a double-layer perforated plate structure with a hole diameter of Φ1.5mm~Φ2.5mm and an opening rate of 1.2%~2.5%.

[0034] Optionally, the operating frequency of the pulsed airflow generator is 0.5Hz~3Hz, and the fluidization apparent gas velocity is 0.08m / s~0.25m / s.

[0035] Optionally, the purification system includes a cyclone separator, a high-precision cartridge filter, and an induced draft fan. The cyclone separator is connected to the exhaust port and is used to perform cyclone separation and pre-dust removal on the discharged airflow. The high-precision cartridge filter is connected to the cyclone separator and has a filtration accuracy of 0.1μm to 0.5μm. It is used to filter the airflow after cyclone pre-dust removal. The induced draft fan is located downstream of the high-precision cartridge filter, and its outlet is connected to the pulsed fluidized air distribution system. It is used to transport the filtered airflow back to the closed dust removal chamber to form a closed-loop circulation.

[0036] Optionally, the device also includes a micro-negative pressure airflow balancing system, which includes a micro-pressure sensor and a controller. The micro-pressure sensor is used to detect the pressure value inside the sealed dust removal chamber. The controller is electrically connected to the micro-pressure sensor and the induced draft fan, and has a preset negative pressure threshold. It is used to acquire the pressure value detected by the micro-pressure sensor and compare it with the negative pressure threshold, and to perform linkage control on the induced draft fan according to the comparison result, so as to maintain the sealed dust removal chamber in a micro-negative pressure state.

[0037] Optionally, the inner wall of the sealed dust removal chamber is lined with a high-purity, high-temperature resistant non-metallic lining, which is either a polytetrafluoroethylene lining or a silicon nitride lining.

[0038] Optionally, the sealed dust removal chamber is a stainless steel vertical cylindrical structure with an inner diameter of Φ400mm~Φ1200mm and a straight section height of 1800mm~3000mm.

[0039] The granular silicon descaling method and apparatus of the present invention have the following advantages compared with the prior art:

[0040] (1) In-situ electrostatic neutralization and pulsating fluidization work together to achieve efficient removal of stubborn fine powder: In-situ electrostatic neutralization is carried out by setting up an in-situ electrostatic neutralization electrode group to eliminate the intrinsic electrostatic adsorption potential between granular silicon particles and fine powder from the root, so that the adhesion of fine powder is significantly reduced and it is naturally desorbed, rather than relying on external high voltage electric field to forcibly adsorb and tear it; At the same time, by setting up a pulsating fluidization air distribution system to introduce pulsating airflow to form a microfluidic expansion bed, the granular silicon particles are in a continuous microfluidic state. The pulsating fluidization airflow provides the kinetic conditions for the detachment of fine powder and carries away the desorbed fine powder in time, avoiding the fine powder from falling back and causing secondary adhesion, thereby achieving efficient removal of stubborn fine powder, more thorough powder removal, and the comprehensive fine powder removal rate can reach more than 85%.

[0041] (2) The pulsating fluidization is mild and controllable, and the integrity and sphericity of the particles are maintained: By setting up a pulsating fluidization air distribution system to introduce pulsating airflow to form a micro-fluidized expansion bed, compared with the conventional DC purging airflow which is prone to forming eddies and causing violent collisions of particles, the flow field is uniform and mild, and the granular silicon particles are in a low-shear, low-collision micro-expansion state without strong eddy impact, which can significantly reduce the particle breakage rate and protect the integrity and sphericity of the particles to the greatest extent.

[0042] (3) Microfluidic expanded bed eliminates processing blind spots and improves powder removal uniformity: By setting up a pulsed fluidized air distribution system to introduce pulsed airflow, granular silicon forms a microfluidic expanded bed. The material is in a uniformly dispersed and continuously tumbling fluidized state with no dead corners of accumulation. This state works in conjunction with in-situ electrostatic neutralization treatment to ensure that the surface of each granular silicon particle can be fully exposed to the electrostatic neutralization field, avoiding processing blind spots formed by material accumulation and bridging. The powder removal efficiency is higher and the batch consistency is better.

[0043] (4) Closed-loop operation, low oxygen increment and stable fluidization: The closed-loop design is adopted. By connecting the pressure stabilizing tank to the purification system and the pulsed airflow generator respectively, and connecting them in series between the exhaust fan outlet and the pulsed airflow generator, the purified airflow can be returned to the sealed dust removal chamber for recycling after being formed into a pulsed airflow. It can also effectively isolate air, significantly reduce the oxygen increment of the product, and meet the cleanliness requirements of post-processing of electronic grade granular silicon. At the same time, this design can also stabilize the inlet pressure of the pulsed airflow generator and replenish the lost nitrogen through the external nitrogen pipeline to ensure the stability of the pulsed fluidization gas source pressure and avoid fluidization instability caused by gas source fluctuations.

[0044] (5) Automatic control of micro negative pressure, no dust leakage: The fully enclosed structure is adopted, and the micro negative pressure air volume balance system can be automatically adjusted to maintain the micro negative pressure state in the enclosed dust removal chamber in real time, ensuring that there is no dust leakage during operation and avoiding material loss and pollution of the working environment.

[0045] (6) Two-stage combined dust removal, balancing filter element protection and operational reliability: By setting up a purification system to combine cyclone separation pre-dust removal and high-precision filtration, large dust particles are removed first, and then the airflow after pre-dust removal is finely filtered. This graded dust removal method, in conjunction with closed-loop circulation, can effectively protect the subsequent high-precision filter element, extend the service life of the filter element and the continuous operation time, and make the system operation more reliable.

[0046] (7) High-purity non-metallic lining improves system cleanliness: By lining the inner wall of the sealed dust removal chamber with a high-purity, high-temperature resistant non-metallic lining, fine powder can be reduced from adhering to the wall, particle friction damage can be reduced, metal precipitation pollution can be avoided, and the system cleanliness and operational stability can be further improved in conjunction with the mild fluidization state of the microfluidic expanded bed.

[0047] (8) Good adaptability and meets industrial needs: It is suitable for granular silicon with a particle size of 1~3mm, a residence time of 6s~18s, and a wide range of process parameters, which can be flexibly adjusted according to actual production needs. The synergistic effect of in-situ electrostatic neutralization and pulsed fluidization can achieve efficient powder removal in a short residence time and can achieve continuous and stable operation. It can better meet the industrial post-processing needs of photovoltaic and electronic grade granular silicon and can be widely used in the preparation and optimization of high-purity silicon materials. Attached Figure Description

[0048] Figure 1 This is a schematic diagram of the granular silicon descaling method and apparatus in an embodiment of the present invention.

[0049] In the diagram: 1-Inlet; 2-Sealed dust removal chamber; 3-High-purity, high-temperature resistant non-metallic liner; 4-In-situ electrostatic neutralization electrode assembly; 5-Pulsating air distribution plate; 6-Outlet; 7-Cyclone separator; 8-High-precision filter cartridge; 9-Exhaust fan; 10-Circulation pipeline; 11-Pulsating airflow generator; 12-Pressure stabilizing tank; 13-Micro pressure sensor. Detailed Implementation

[0050] To enable those skilled in the art to better understand the technical solutions of the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of the present invention.

[0051] In the description of this invention, it should be noted that the terms "above" and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience and simplification of the description and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0052] In the description of this invention, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the stated features. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0053] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "connection," "setting," "installation," "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a direct connection, an indirect connection through an intermediate medium, or a connection within two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0054] It is understood that, without conflict, the various embodiments and features in the embodiments of the present invention can be combined with each other.

[0055] It is understood that, for ease of description, only the parts related to the present invention are shown in the accompanying drawings, while the parts unrelated to the present invention are not shown in the drawings.

[0056] To address the significant shortcomings of existing granular silicon descaling technologies in terms of thoroughness, stability, particle integrity, processing uniformity, equipment airtightness, and low-oxygen protection, which make it difficult to meet the quality requirements of photovoltaic and electronic-grade high-end granular silicon for cleanliness, low oxygen content, and high sphericity, this invention provides a granular silicon descaling method, comprising:

[0057] Granular silicon is continuously introduced into a closed dust removal chamber and a pulsed airflow is introduced to form a microfluidic expanded bed of granular silicon in the closed dust removal chamber.

[0058] The surface of granular silicon in the sealed dust removal chamber is subjected to in-situ electrostatic neutralization treatment to eliminate the electrostatic adsorption force between the granular silicon particles and the fine powder adhering to their surface, so that the fine powder is desorbed and discharged from the sealed dust removal chamber with the airflow.

[0059] The exhaust airflow is purified to separate fine powder. The purified airflow is then pulsated and returned to the sealed powder removal chamber to form a closed-loop circulation.

[0060] Furthermore, the present invention also provides a granular silicon de-powdering device, comprising a sealed de-powdering chamber, a pulsed fluidized air distribution system, an in-situ electrostatic neutralization electrode assembly, and a purification system; the sealed de-powdering chamber has an inlet at the top, an outlet at the bottom, and an exhaust port at the top; the pulsed fluidized air distribution system is connected to the lower part of the sealed de-powdering chamber and is used to introduce pulsed airflow into the sealed de-powdering chamber, so that the granular silicon in the sealed de-powdering chamber forms a micro-fluidized expanded bed; the in-situ electrostatic neutralization electrode assembly is disposed in the corresponding flow of the sealed de-powdering chamber. The location of the purification zone is used to perform in-situ electrostatic neutralization treatment on the surface of granular silicon in the sealed dust removal chamber, eliminating the electrostatic adsorption force between the granular silicon particles and the fine powder adhering to their surface, thereby desorbing the fine powder; the purification system is connected to the exhaust port and the pulsed fluidized air distribution system respectively, and is used to receive the airflow discharged from the sealed dust removal chamber and purify it to separate the fine powder, and to flow the purified airflow into the pulsed fluidized air distribution system to form a pulsed airflow before returning to the sealed dust removal chamber to form a closed loop.

[0061] Example 1

[0062] like Figure 1 As shown, this embodiment discloses a method for removing granular silicon powder, including:

[0063] Granular silicon is continuously fed into the sealed dust removal chamber 2 through the feed inlet 1. Under the action of gravity, it slowly moves downward and a pulsating airflow is introduced to form a microfluidic expanded bed of granular silicon in the sealed dust removal chamber 2.

[0064] The in-situ electrostatic neutralization electrode group 4 is activated to perform in-situ electrostatic neutralization treatment on the surface of granular silicon in the sealed powder removal chamber 2, eliminating the electrostatic adsorption force between granular silicon particles and the fine powder adhering to their surface, causing the fine powder to desorb and be discharged from the sealed powder removal chamber 2 through the exhaust port with the airflow. The clean granular silicon after de-powdering is continuously discharged from the discharge port 6 at the bottom of the sealed powder removal chamber 2.

[0065] The exhaust airflow is purified to separate fine powder. The purified airflow is then pulsated and returned to the sealed powder removal chamber 2 to form a closed loop.

[0066] The in-situ electrostatic neutralization treatment operates at a voltage of 6kV~12kV. After in-situ electrostatic neutralization, the electrostatic potential on the surface of the granular silicon particles is within ±100V, significantly reducing the adhesion of fine powder and ensuring effective powder removal. Compared to the traditional combination of electrostatic adsorption and airflow purging technology, which uses an external high-voltage electric field to adsorb fine powder, this method uses in-situ electrostatic neutralization to eliminate the intrinsic electrostatic adsorption potential between the granular silicon particles and the fine powder, preventing the generation of a dust adsorption electric field. It also achieves gentle powder removal through negative pressure pulsed fluidization and incorporates a closed-loop circulation design, representing a substantial difference from traditional technologies and belonging to a different category of high-voltage electrostatic powder removal processes.

[0067] In some embodiments, the pulsating gas flow is formed by a gas that will not react with granular silicon under the conditions of this method via a pulsating gas flow generator 11. For example, nitrogen, which is high-purity nitrogen with a purity ≥99.999%, and has an inlet pressure of 0.02MPa~0.04MPa. The nitrogen is stably output from the pressure stabilizing tank 12 to the pulsating gas flow generator 11 to stabilize the inlet pressure fluctuations and make the fluidization state more stable.

[0068] In some implementations, the frequency of the pulsating airflow is 0.5 Hz to 3 Hz, and the fluidization apparent velocity is 0.08 m / s to 0.25 m / s.

[0069] In some embodiments, the particle size of the granular silicon is 1-3 mm, and the residence time of the granular silicon is 6-18 s.

[0070] By controlling the residence time of granular silicon to a minimum of 6 seconds (i.e., not less than 6 seconds): On the one hand, this ensures sufficient contact time for electrostatic neutralization, allowing for a dynamic process of neutralization of the native electrostatic charge on the surface of the granular silicon particles. Simultaneously, the release of reverse ions from the electrode requires a certain contact time to control the electrostatic potential on the surface of the granular silicon particles within ±100V. When the residence time is less than 6 seconds, charge neutralization is incomplete, the adhesion of fine powder is not fully released, and the removal rate of deeply stubborn powder drops significantly. On the other hand, this avoids insufficient pulsating fluidization stripping. Fine powder desorption relies on the synergy of "electrostatic de-adhesion + periodic airflow shearing," and the stripping ability of a single pulsating disturbance is limited. When the residence time is too short, the granular silicon particles do not undergo enough pulsating cycles, and stubborn fine powder in interlayers and concave surfaces cannot be completely removed, resulting in an overall powder removal rate of less than 80%.

[0071] By controlling the residence time of granular silicon to an upper limit of 18 seconds (i.e., no more than 18 seconds): First, it avoids prolonged frictional wear of the particles. When the residence time is greater than 18 seconds, it means that the granular silicon particles tumble back and forth in the bed for too long. Even with low expansion and gentle fluidization, prolonged and continuous slight friction will still slowly wear down the particle surface, generating trace amounts of newly formed fine powder and reducing the cleanliness of the finished product. Second, it can control production capacity and reduce the contact time with nitrogen oxidation. The longer the residence time, the lower the throughput for the same chamber volume, resulting in insufficient continuous industrial production capacity. Long-term contact between granular silicon particles and the circulating airflow leads to the slow adsorption of trace amounts of oxygen and water vapor, causing an increase in oxygen increment, which cannot meet the low oxygen requirements for electronic grade. Third, it can prevent the accumulation of fine powder in the bed. Excessive residence time will cause some fine powder to be repeatedly suspended and settled in the dense phase region, repeatedly contacting the parent particles and increasing the probability of secondary adhesion.

[0072] In some more specific implementations, for high-volume processing conditions (e.g., 300 kg / h ~ 350 kg / h), the fine powder load of granular silicon particles is relatively low, and the residence time of granular silicon is 6 s ~ 10 s. This allows for rapid neutralization and descaling, balancing production capacity and basic descaling efficiency. For low-volume processing conditions with high-stickiness materials (i.e., high content of virgin fine powder), the residence time of granular silicon is 10 s ~ 18 s. Extending the contact time ensures deep electrostatic neutralization and sufficient pulsation stripping, resulting in a stable descaling rate of over 88%.

[0073] In some implementations, the expansion ratio of the microfluidic expanded bed is 1.2 to 1.8.

[0074] Specifically, the expansion ratio = fluidized bed height / static bed height. By controlling the lower limit of the expansion ratio of the microfluidic expanded bed to 1.2 (i.e., not less than 1.2): First, it can eliminate dead beds and bridging blind zones. When the expansion ratio is <1.2, the airflow cannot completely penetrate the particle packing layer, and the material at the bottom and corners of the cavity wall remains stationary, easily forming processing dead zones. Adhering fine powder cannot come into contact with the pulsating airflow and neutralizing ions, resulting in a significant decrease in powder removal uniformity and large fluctuations in the cleanliness of batch materials. Second, it can ensure slight tumbling disturbance of particles. Slight expansion allows for a small gap between granular silicon particles, and the pulsating airflow can penetrate into the gaps between the granular silicon particles, peeling off the fine powder adhering to the interlayer on the contact surface of the granular silicon particles; in the static dense packing state, the interlayer powder cannot be removed at all.

[0075] By controlling the expansion ratio of the microfluidic expanded bed to an upper limit of 1.8 (i.e., not higher than 1.8): First, it can strictly control the collision intensity of granular silicon particles, protecting the integrity of spherical particles and preventing the formation of secondary microparticles. When the expansion ratio is >1.8, it belongs to high-expansion dilute phase fluidization, which significantly increases the suspension height of granular silicon particles, resulting in high-speed collisions and friction between granular silicon particles and between granular silicon particles and the cavity wall; the edges and corners of spherical granular silicon particles are worn and broken, generating a large number of newly formed submicron fine powders, which in turn increases the dust removal load and reduces the cleanliness of the finished product. Second, it can avoid excessive separation and secondary adhesion of fine powders. A high expansion ratio will carry a large amount of freshly separated fine powder upwards at high speed, resulting in violent airflow turbulence. Fine powders are very likely to settle in the low-speed zone at the top of the cavity and re-adhere to the surface of the descending granular silicon particles, resulting in secondary powder adhesion problems. Third, it can reduce the energy consumption of airflow circulation and stabilize the negative pressure system. The higher the expansion ratio, the greater the required apparent air velocity, and the higher the power consumption required for airflow circulation. In the low expansion range of 1.2~1.8, a low air velocity of 0.08m / s~0.25m / s can be used, resulting in lower energy consumption for closed-loop airflow circulation and easier stable control of the cavity's -50Pa~-300Pa micro-negative pressure. Fourth, to adapt to the pulsating low-frequency flow field characteristics of this method, pulsating airflow of 0.5Hz~3Hz only provides periodic slight loosening and does not possess the strong lift required for high-expansion fluidization. When the expansion ratio exceeds 1.8, periodic throttling and airflow deviation will occur, leading to unstable fluidization and fluctuating dust removal efficiency.

[0076] This method, by controlling the expansion ratio of the microfluidic expanded bed to 1.2~1.8, can form a low-disturbance dense-phase micro-expanded fluidized bed, causing the granular silicon particles to slowly move downwards as a whole, with only minor local tumbling. It achieves the following balances: the granular silicon is sufficiently loose with no dead corners, and electrostatic neutralization ions and pulsating airflow can contact the surface of all granular particles; the collision force of the granular silicon particles is extremely low, the sphericity is intact, and almost no secondary powder breakage is generated; the flow field is stable without strong eddies, and the detached fine powder enters the two-stage dust removal in an orderly manner with the gentle upward airflow, significantly reducing the probability of secondary adhesion.

[0077] In some embodiments, the purification process includes: first, performing cyclone separation pre-dust removal on the discharged airflow, followed by fine filtration, with a precision of 0.1μm to 0.5μm. The cyclone separation pre-dust removal process can remove large dust particles carried in the discharged airflow, protecting the high-precision filter element used in subsequent filtration processes and extending its service life.

[0078] In some embodiments, the dust removal process of this method maintains a slightly negative pressure state inside the sealed dust removal chamber 2, with a negative pressure value of -50Pa to -300Pa, to prevent dust from escaping.

[0079] Specifically, by controlling the airflow discharged from the sealed dust removal chamber 2 to be 5% to 10% higher than the airflow entering it, a slightly negative pressure state is maintained inside the sealed dust removal chamber 2.

[0080] Example 2

[0081] like Figure 1 As shown, this embodiment discloses a granular silicon descaling device, including a sealed descaling chamber 2, a pulsed fluidized bed air distribution system, an in-situ electrostatic neutralization electrode group 4, and a purification system, wherein:

[0082] The sealed de-powdering chamber 2 has a feed inlet 1 at the top, a discharge outlet 6 at the bottom, and an exhaust outlet at the top. The feed inlet 1 is used to introduce granular silicon to be de-powdered, the discharge outlet 6 is used to discharge the de-powdered granular silicon, and the exhaust outlet is used to discharge the airflow carrying the de-powdered fine powder.

[0083] The pulsating fluidized air distribution system is connected to the lower part of the sealed dust removal chamber 2 and is used to introduce pulsating airflow into the sealed dust removal chamber 2, so that the granular silicon in the sealed dust removal chamber 2 forms a microfluidic expanded bed.

[0084] The in-situ electrostatic neutralization electrode group 4 is located at the corresponding fluidization region of the sealed powder removal chamber 2, and is used to perform in-situ electrostatic neutralization treatment on the surface of granular silicon in the sealed powder removal chamber 2, eliminate the electrostatic adsorption force between granular silicon particles and the fine powder adhering to their surface, and desorb the fine powder.

[0085] The purification system is connected to the exhaust port at the top of the sealed dust removal chamber 2 and the pulsed fluidized air distribution system, respectively. It is used to receive the airflow discharged from the sealed dust removal chamber 2 and purify it to separate fine powder. The purified airflow is then introduced into the pulsed fluidized air distribution system to form a pulsed airflow before returning to the sealed dust removal chamber 2 to form a closed loop.

[0086] Specifically, the sealed dust removal chamber 2 is a vertical cylindrical structure made of stainless steel, such as an S30408 ​​stainless steel vertical cylindrical structure or an S31603 stainless steel vertical cylindrical structure. The inner diameter of the sealed dust removal chamber is Φ400mm~Φ1200mm, and the height of the straight section is 1800mm~3000mm.

[0087] In some embodiments, the inner wall of the sealed dust removal chamber 2 is lined with a high-purity, high-temperature resistant non-metallic liner 3, such as a polytetrafluoroethylene liner or a silicon nitride liner, to reduce fine powder adhering to the wall, reduce particle friction damage, avoid metal precipitation contamination, and improve cleanliness.

[0088] In some embodiments, the in-situ electrostatic neutralization electrode group 4 includes 4 to 6 electrostatic neutralization electrodes, each of which is uniformly arranged around the circumference of the sealed dust removal cavity 2, with an operating voltage of 6kV to 12kV and an operating current of ≤50μA.

[0089] In some embodiments, the in-situ electrostatic neutralization electrode group 4 is disposed on the inner wall of the sealed powder removal cavity 2, which results in higher neutralization efficiency.

[0090] In some implementations, the in-situ electrostatic neutralization electrode group 4 is located on the outer wall of the sealed dust removal chamber 2 to achieve non-contact electrostatic control, which is more suitable for ultra-high cleanliness conditions.

[0091] In some embodiments, the pulsating fluidized bed air distribution system includes a pulsating air distribution plate 5, a pulsating airflow generator 11, and a pressure stabilizing tank 12. The pulsating airflow generator 11 is used to generate pulsating airflow. The pulsating air distribution plate 5 is located at the lower part of the sealed dust removal chamber 2 and connected to the pulsating airflow generator 11, used to evenly distribute the pulsating airflow within the sealed dust removal chamber 2. The pressure stabilizing tank 12 is connected to the purification system and the pulsating airflow generator 11 respectively, used to introduce the purified airflow into the pulsating airflow generator 11 to form pulsating airflow, and to stabilize the inlet pressure of the pulsating airflow generator 11, avoiding fluidization instability caused by air source fluctuations, thus making the vulcanization state more stable.

[0092] Specifically, the pulsed gas flow is high-purity nitrogen with a purity ≥99.999% and an inlet pressure of 0.02MPa~0.04MPa. The pressure stabilizing tank 12 is a nitrogen pressure stabilizing tank equipped with a nitrogen replenishment line, through which nitrogen loss in the system is replenished. The operating frequency of the pulsed gas flow generator 11 is 0.5Hz~3Hz, and the fluidized apparent gas velocity is 0.08m / s~0.25m / s.

[0093] By controlling the lower limit of the inlet air pressure to be no less than 0.02 MPa: First, it ensures uniform air distribution through the pulsating air distribution plate, preventing flow deviation and dead bed. When the inlet air pressure is below 0.02 MPa, it not only leads to insufficient total kinetic energy of the airflow, uneven air pressure difference at each outlet of the pulsating air distribution plate, weak airflow on both sides of the cavity wall and strong airflow in the middle, resulting in local accumulation of granular silicon particles forming processing blind zones, but also makes it impossible to stably form a bed expansion ratio of more than 1.2, making it difficult for fine powder adhering to the interlayer to be penetrated and peeled off by the airflow, and significantly reducing the uniformity of powder removal. Second, it ensures the periodic disturbance effect of the pulsating airflow. The pulsating airflow generator relies on stable back pressure to form pulse impacts. Insufficient air source pressure will cause pulse attenuation, resulting in only weak airflow and no periodic loosening shear force, which can only remove surface floating powder, significantly reducing the removal efficiency of stubborn powder adhering to the gaps in granular silicon particles. Third, it can overcome the resistance loss of the cavity under slight negative pressure. The chamber maintains a slight negative pressure of -50 to -300 Pa. There is friction resistance along the pipeline, the pulsating air distribution plate, and the pressure stabilizing tank. If the inlet pressure is insufficient, the fluidizing gas at the bottom layer cannot overcome the negative pressure suction, causing the bed to collapse, material to settle and accumulate, bridging and blocking, and preventing continuous and stable discharge. Fourth, it matches the pressure loss of the closed-loop airflow circulation system. The purification system and closed-loop circulation pipeline experience continuous pressure loss. 0.02 MPa is the minimum threshold to offset the overall system resistance, ensuring stable flow in the airflow circulation loop and avoiding problems such as insufficient inlet and unbalanced suction.

[0094] By controlling the upper limit of the inlet air pressure to no more than 0.04 MPa: First, it avoids excessively high air velocity, preventing high expansion fluidization and breakage of granular silicon particles. When the inlet air pressure exceeds 0.04 MPa, the pulsating airflow rate and apparent air velocity increase synchronously, the bed expansion ratio exceeds 1.8, and it transforms into dilute phase suspension fluidization. Granular silicon particles rise violently, collide with the cavity wall at high speed, and rub against each other. Spherical granular silicon particles wear and break, generating a large amount of secondary fine powder, which increases the dust removal load and product impurities. Second, it can suppress strong fine powder separation and reduce secondary adhesion. High-pressure, high-speed airflow will quickly roll the newly separated submicron fine powder to the upper low-speed zone of the cavity to settle, falling back to the surface of the descending granular silicon particles, causing secondary powder adhesion, offsetting the powder removal gain brought by electrostatic neutralization. When the upper limit of the inlet air pressure is no more than 0.04 MPa, the low-pressure airflow rises slowly, and the fine powder enters the two-stage dust removal at a uniform speed with the airflow, greatly reducing the probability of settling back. Third, it can reduce the energy consumption of airflow circulation and reduce filter element scouring wear. Higher pressure results in a greater load on the purification system. Simultaneously, the high-speed airflow carrying hard silica powder rapidly washes over the high-precision filter element, accelerating filter wear and clogging, shortening continuous operation cycles, and increasing maintenance costs. Low-pressure ranges allow for long-term stable operation. Fourth, it adapts to low-oxygen, closed-loop conditions, reducing the risk of air infiltration. Under high-pressure conditions, the total airflow inside the cavity is large, and airflow disturbances are severe. Pressure fluctuations easily occur at equipment flanges and inlet / outlet seals, allowing trace amounts of air to infiltrate the cavity, leading to silica oxidation and oxygenation. Low-pressure micro-fluidization (0.02~0.04MPa) combined with a slight negative pressure in the cavity (inlet < extraction 5%~10%) ensures stable airflow pressure, with no positive pressure overflow or negative pressure backflow at the sealing interface. Fifth, it avoids severe pulsating airflow surges and fluidization instability. When the inlet pressure is greater than 0.04 MPa, the low-frequency pulsed airflow is prone to forming periodic large bubbles and swells in the cavity, causing the material to tumble violently up and down, resulting in uncontrolled fluidization. The residence time of granular silicon particles at different locations fluctuates greatly, and the uniformity of the de-powdering effect deteriorates.

[0095] By precisely controlling the inlet air pressure to 0.02 MPa~0.04 MPa, and matching it with an apparent gas velocity of 0.08 m / s~0.25 m / s, an expansion ratio of 1.2~1.8, and a residence time of 6s~18s, a mild and controllable micro-dense phase fluidization can be formed. It can also ensure stable gas source pressure, guaranteeing that the granular silicon particles are sufficiently loose when the electrostatic neutralization electrode is in operation, allowing ions to contact all particle surfaces and achieve uniform potential neutralization. It can also balance four indicators: continuous production capacity, fine powder removal rate, particle integrity, and low-oxygen cleanliness, while balancing nitrogen consumption and equipment operation stability.

[0096] In some embodiments, the pulsating air distribution plate 5 is a double-layer perforated plate structure with a hole diameter of Φ1.5mm~Φ2.5mm and an opening rate of 1.2%~2.5%.

[0097] In some embodiments, the purification system includes a cyclone separator 7, a high-precision cartridge filter 8, and an induced draft fan 9. The cyclone separator 7 is connected to the exhaust port at the top of the sealed dust removal chamber 2, and is used to perform cyclone separation pre-dust removal on the discharged airflow, removing large dust particles, protecting the subsequent high-precision cartridge filter 8, extending the filter's service life, and making the system more reliable. The high-precision cartridge filter 8 is connected to the cyclone separator 7, and its filtration accuracy is 0.1μm~0.5μm. It is used to filter the airflow after cyclone pre-dust removal, separating the remaining fine powder to obtain purified airflow. The induced draft fan 9 is located downstream of the high-precision cartridge filter 8, and its outlet is connected to the pressure stabilizing tank 12, the pulsating airflow generator 11, and the pulsating air distribution plate 5 in the pulsating fluidized air distribution system via a circulation pipeline 10. It is used to transport the filtered airflow to the pulsating airflow generator 11 to form a pulsating airflow, which then returns to the sealed dust removal chamber 2 to form a closed-loop circulation.

[0098] In some embodiments, the device further includes a micro-negative pressure airflow balancing system, which includes a micro-pressure sensor 13 and a controller. The micro-pressure sensor 13 is located outside the sealed dust removal chamber 2, for example, on the connecting pipeline between the exhaust port and the cyclone separator 7, and is used to detect the pressure value inside the sealed dust removal chamber 2. The controller is electrically connected to the micro-pressure sensor 13 and the induced draft fan 9, and has a preset negative pressure threshold. It is used to acquire the pressure value detected by the micro-pressure sensor 13 and compare it with the negative pressure threshold, and to perform linkage control on the induced draft fan 9 based on the comparison result, so as to maintain a micro-negative pressure state inside the sealed dust removal chamber 2.

[0099] Example 3

[0100] This embodiment discloses a method for removing granular silicon powder, which is carried out using the apparatus described in Embodiment 2, including:

[0101] Granular silicon is continuously fed into the S31603 stainless steel vertical sealed dust removal chamber 2 through the feed inlet 1. Under the action of gravity, it slowly moves downwards and is introduced by a pulsating airflow through the pulsating air distribution plate 5, forming a microfluidic expanded bed of granular silicon within the sealed dust removal chamber 2. The sealed dust removal chamber 2 has an inner diameter of Φ600mm, a straight section height of 2400mm, and an inner wall lined with high-purity polytetrafluoroethylene. The pulsating air distribution plate 5 has a pore size of Φ2.0mm and an opening ratio of 1.8%. The pulsating airflow is nitrogen with a purity ≥99.999%, a pulsating airflow frequency of 1.5Hz, and a fluidized apparent gas velocity of 0.15m / s. The particle size of the granular silicon is 1mm~3mm, the feed flow rate is 200kg / h, and the material residence time is 12s.

[0102] The in-situ electrostatic neutralization electrode group 4 is activated to perform in-situ electrostatic neutralization treatment on the surface of granular silicon within the sealed dust removal chamber 2. This eliminates the electrostatic adsorption force between the granular silicon particles and the fine powder adhering to their surfaces. In conjunction with pulsed fluidized stripping, the fine powder is desorbed and discharged from the sealed dust removal chamber 2 through the exhaust port with the upward airflow. The clean granular silicon after de-powdering is continuously discharged from the discharge port 6 at the bottom of the sealed dust removal chamber 2. The in-situ electrostatic neutralization electrode group 4 includes four electrostatic neutralization electrodes evenly arranged along the circumference of the sealed dust removal chamber 2, with an operating voltage set to 9kV. The pressure inside the sealed dust removal chamber 2 is controlled at -150Pa through a micro-pressure sensor 13 and a frequency converter linkage between the blower 9 and the pressure sensor 13.

[0103] The exhaust airflow is purified to separate fine powder. After being stabilized by a pressure stabilizing tank 12, the purified airflow enters a pulsating airflow generator 11 to form a pulsating airflow, which then returns to the sealed dust removal chamber 2 via a pulsating air distribution plate 5, forming a closed-loop circulation. The purification process includes cyclone separation pretreatment by a cyclone separator 7, followed by fine filtration by a high-precision cartridge filter 8 with a precision of 0.1μm to 0.5μm. The operating frequency of the pulsating airflow generator 11 is 1.5Hz.

[0104] After processing by the method of this embodiment, the removal rate of fine powder on the surface of granular silicon can reach about 91%, which can better maintain the integrity and sphericity of the particles, and the oxygen increment of the product can be controlled at about 1.6 ppmw.

[0105] Example 4

[0106] This embodiment discloses a method for removing granular silicon powder, which differs from Embodiment 3 only in that:

[0107] The inner diameter of the sealed dust removal chamber is Φ800mm, the straight section height is 2800mm, and the inner wall is lined with a high-temperature resistant silicon nitride liner; the pulsed airflow frequency is set to 2Hz, and the fluidized apparent gas velocity is set to 0.18m / s; the working voltage of the in-situ electrostatic neutralization electrode group 4 is set to 10kV; the pressure inside the sealed dust removal chamber 2 is controlled at -200Pa; the feed flow rate of granular silicon is 350kg / h, and the material residence time is 9s.

[0108] After processing by the method of this embodiment, the removal rate of fine powder on the surface of granular silicon can reach about 88%, with no obvious breakage, and the oxygen increment of the product can be controlled at about 1.8 ppmw, which can meet the requirements of continuous and stable industrial operation.

[0109] Example 5

[0110] This embodiment discloses a method for removing granular silicon powder, which differs from Embodiment 3 only in that:

[0111] The inner diameter of the sealed dust removal chamber 2 is Φ400mm, and the height of the straight section is 1800mm; the aperture of the pulsating air distribution plate 5 is Φ1.5mm, and the opening ratio is 1.2%; the frequency of the pulsating airflow is 0.5Hz, and the fluidization apparent air velocity is 0.08m / s; the material residence time is 6s; the working voltage of the in-situ electrostatic neutralization electrode group 4 is set to 6kV; and the pressure inside the sealed dust removal chamber 2 is controlled at -50Pa.

[0112] After processing by the method of this embodiment, the removal rate of fine powder on the surface of granular silicon can reach about 84%, with no obvious breakage, and the oxygen increment of the product can be controlled at about 2 ppmw, which can meet the requirements of continuous and stable industrial operation.

[0113] Example 6

[0114] This embodiment discloses a method for removing granular silicon powder, which differs from Embodiment 3 only in that:

[0115] The inner diameter of the sealed dust removal chamber 2 is Φ1200mm, and the height of the straight section is 3000mm; the aperture of the pulsating air distribution plate 5 is Φ2.5mm, and the opening ratio is 2.5%; the frequency of the pulsating airflow is 3Hz, and the fluidization apparent air velocity is 0.25m / s; the material residence time is 18s; the working voltage of the in-situ electrostatic neutralization electrode group 4 is set to 12kV; and the pressure inside the sealed dust removal chamber 2 is controlled at -300Pa.

[0116] After processing by the method of this embodiment, the removal rate of fine powder on the surface of granular silicon can reach about 95%, with no obvious breakage, and the oxygen increment of the product can be controlled at about 1 ppmw, which can meet the requirements of continuous and stable industrial operation.

[0117] In summary, the granular silicon descaling method and apparatus of the present invention have the following advantages compared with the prior art:

[0118] (1) In-situ electrostatic neutralization and pulsating fluidization work together to achieve efficient removal of stubborn fine powder: In-situ electrostatic neutralization is carried out by setting up an in-situ electrostatic neutralization electrode group to eliminate the intrinsic electrostatic adsorption potential between granular silicon particles and fine powder from the root, so that the adhesion of fine powder is significantly reduced and it is naturally desorbed, rather than relying on external high voltage electric field to forcibly adsorb and tear it; At the same time, by setting up a pulsating fluidization air distribution system to introduce pulsating airflow to form a microfluidic expansion bed, the granular silicon particles are in a continuous microfluidic state. The pulsating fluidization airflow provides the kinetic conditions for the detachment of fine powder and carries away the desorbed fine powder in time, avoiding the fine powder from falling back and causing secondary adhesion, thereby achieving efficient removal of stubborn fine powder, more thorough powder removal, and the comprehensive fine powder removal rate can reach more than 85%.

[0119] (2) The pulsating fluidization is mild and controllable, and the integrity and sphericity of the particles are maintained: By setting up a pulsating fluidization air distribution system to introduce pulsating airflow to form a micro-fluidized expansion bed, compared with the conventional DC purging airflow which is prone to forming eddies and causing violent collisions of particles, the flow field is uniform and mild, and the granular silicon particles are in a low-shear, low-collision micro-expansion state without strong eddy impact, which can significantly reduce the particle breakage rate and protect the integrity and sphericity of the particles to the greatest extent.

[0120] (3) Microfluidic expanded bed eliminates processing blind spots and improves powder removal uniformity: By setting up a pulsed fluidized air distribution system to introduce pulsed airflow, granular silicon forms a microfluidic expanded bed. The material is in a uniformly dispersed and continuously tumbling fluidized state with no dead corners of accumulation. This state works in conjunction with in-situ electrostatic neutralization treatment to ensure that the surface of each granular silicon particle can be fully exposed to the electrostatic neutralization field, avoiding processing blind spots formed by material accumulation and bridging. The powder removal efficiency is higher and the batch consistency is better.

[0121] (4) Closed-loop operation, low oxygen increment and stable fluidization: The closed-loop design is adopted. By connecting the pressure stabilizing tank to the purification system and the pulsed airflow generator respectively, and connecting them in series between the exhaust fan outlet and the pulsed airflow generator, the purified airflow can be returned to the sealed dust removal chamber for recycling after being formed into a pulsed airflow. It can also effectively isolate air, significantly reduce the oxygen increment of the product, and meet the cleanliness requirements of post-processing of electronic grade granular silicon. At the same time, this design can also stabilize the inlet pressure of the pulsed airflow generator and replenish the lost nitrogen through the external nitrogen pipeline to ensure the stability of the pulsed fluidization gas source pressure and avoid fluidization instability caused by gas source fluctuations.

[0122] (5) Automatic control of micro negative pressure, no dust leakage: The fully enclosed structure is adopted, and the micro negative pressure air volume balance system can be automatically adjusted to maintain the micro negative pressure state in the enclosed dust removal chamber in real time, ensuring that there is no dust leakage during operation and avoiding material loss and pollution of the working environment.

[0123] (6) Two-stage combined dust removal, balancing filter element protection and operational reliability: By setting up a purification system to combine cyclone separation pre-dust removal and high-precision filtration, large dust particles are removed first, and then the airflow after pre-dust removal is finely filtered. This graded dust removal method, in conjunction with closed-loop circulation, can effectively protect the subsequent high-precision filter element, extend the service life of the filter element and the continuous operation time, and make the system operation more reliable.

[0124] (7) High-purity non-metallic lining improves system cleanliness: By lining the inner wall of the sealed dust removal chamber with a high-purity, high-temperature resistant non-metallic lining, fine powder can be reduced from adhering to the wall, particle friction damage can be reduced, metal precipitation pollution can be avoided, and the system cleanliness and operational stability can be further improved in conjunction with the mild fluidization state of the microfluidic expanded bed.

[0125] (8) Good adaptability and meets industrial needs: It is suitable for granular silicon with a particle size of 1~3mm, a residence time of 6s~18s, and a wide range of process parameters, which can be flexibly adjusted according to actual production needs. The synergistic effect of in-situ electrostatic neutralization and pulsed fluidization can achieve efficient powder removal in a short residence time and can achieve continuous and stable operation. It can better meet the industrial post-processing needs of photovoltaic and electronic grade granular silicon and can be widely used in the preparation and optimization of high-purity silicon materials.

[0126] It is understood that the above embodiments are merely exemplary implementations used to illustrate the principles of the present invention, and the present invention is not limited thereto. For those skilled in the art, various modifications and improvements can be made without departing from the spirit and essence of the present invention, and these modifications and improvements are also considered to be within the scope of protection of the present invention.

Claims

1. A method for removing granular silicon powder, characterized in that, include: Granular silicon is continuously fed into a sealed dust removal chamber and a pulsating airflow is introduced to form a microfluidic expanded bed of granular silicon in the sealed dust removal chamber. The surface of the granular silicon in the sealed dust removal chamber is subjected to in-situ electrostatic neutralization treatment to eliminate the electrostatic adsorption force between the granular silicon particles and the fine powder adhering to their surface, so that the fine powder is desorbed and discharged from the sealed dust removal chamber with the airflow. The exhaust airflow is purified to separate fine powder. The purified airflow is then pulsated and returned to the sealed powder removal chamber to form a closed-loop circulation.

2. The method for removing granular silicon powder according to claim 1, characterized in that, The working voltage of the in-situ electrostatic neutralization treatment is 6kV~12kV, and after the in-situ electrostatic neutralization treatment, the electrostatic potential on the surface of the granular silicon particles is within ±100V.

3. The method for removing granular silicon powder according to claim 1, characterized in that, The pulsating airflow is formed from nitrogen gas with a purity ≥99.999% and an inlet pressure of 0.02MPa~0.04MPa.

4. The method for removing granular silicon powder according to claim 1, characterized in that, The frequency of the pulsating airflow is 0.5Hz~3Hz, and the fluidized apparent air velocity is 0.08m / s~0.25m / s.

5. The method for removing granular silicon powder according to claim 1, characterized in that, The particle size of the granular silicon is 1~3mm, and the residence time of the granular silicon is 6s~18s.

6. The method for removing granular silicon powder according to claim 1, characterized in that, The expansion ratio of the microfluidic expander bed is 1.2 to 1.

8.

7. The method for removing granular silicon powder according to claim 1, characterized in that, The purification process includes: The discharged airflow is first subjected to cyclone separation for pre-dust removal, and then subjected to fine filtration with a precision of 0.1μm~0.5μm.

8. The method for removing granular silicon powder according to any one of claims 1 to 7, characterized in that, Maintain a slight negative pressure state within the sealed dust removal chamber, with a negative pressure value of -50Pa to -300Pa.

9. The method for removing granular silicon powder according to claim 8, characterized in that, The airflow discharged from the sealed dust removal chamber is 5% to 10% higher than the airflow introduced into it.

10. A granular silicon descaling device, characterized in that, Includes a sealed dust removal chamber, a pulsed fluidized air distribution system, an in-situ electrostatic neutralization electrode assembly, and a purification system; The sealed dust removal chamber is provided with a feed inlet at the top, a discharge outlet at the bottom, and an exhaust outlet at the top. The pulsating fluidized air distribution system is connected to the lower part of the sealed dust removal cavity and is used to introduce pulsating airflow into the sealed dust removal cavity, so that the granular silicon in the sealed dust removal cavity forms a microfluidic expanded bed. The in-situ electrostatic neutralization electrode group is located at the corresponding fluidization region of the sealed powder removal cavity, and is used to perform in-situ electrostatic neutralization treatment on the surface of granular silicon in the sealed powder removal cavity, eliminate the electrostatic adsorption force between granular silicon particles and the fine powder adhering to their surface, and desorb the fine powder. The purification system is connected to the exhaust port and the pulsed fluidized air distribution system, respectively, and is used to receive the airflow discharged from the sealed dust removal chamber and purify it to separate fine powder. The purified airflow is then introduced into the pulsed fluidized air distribution system to form a pulsed airflow and then returned to the sealed dust removal chamber to form a closed loop.

11. The granular silicon descaling device according to claim 10, characterized in that, The in-situ electrostatic neutralization electrode group includes 4 to 6 electrostatic neutralization electrodes, each of which is uniformly arranged circumferentially along the sealed dust removal cavity. The working voltage is 6kV to 12kV and the working current is ≤50μA.

12. The granular silicon descaling device according to claim 10, characterized in that, The in-situ electrostatic neutralization electrode assembly is disposed on the inner wall of the sealed dust removal cavity; or, disposed on the outer wall of the sealed dust removal cavity, to achieve non-contact electrostatic control.

13. The granular silicon descaling device according to claim 10, characterized in that, The pulsed fluidized air distribution system includes a pulsed air distribution plate, a pulsed airflow generator, and a pressure stabilizing tank; The pulsed airflow generator is used to generate pulsed airflow; The pulsating air distribution plate is located at the lower part of the sealed dust removal cavity and is connected to the pulsating airflow generator to evenly distribute the pulsating airflow into the sealed dust removal cavity. The pressure stabilizing tank is connected to the purification system and the pulsating airflow generator respectively, and is used to introduce the purified airflow into the pulsating airflow generator to form a pulsating airflow and stabilize the intake pressure of the pulsating airflow generator.

14. The granular silicon descaling device according to claim 13, characterized in that, The pulsating air distribution plate is a double-layer perforated plate structure with a hole diameter of Φ1.5mm~Φ2.5mm and an opening rate of 1.2%~2.5%.

15. The granular silicon descaling apparatus according to any one of claims 10 to 14, characterized in that, The purification system includes a cyclone separator, a high-precision cartridge filter, and an exhaust fan; The cyclone separator is connected to the exhaust port and is used to perform cyclone separation and pre-dust removal on the discharged airflow. The high-precision filter cartridge is connected to the cyclone separator, and its filtration accuracy is 0.1μm to 0.5μm. It is used to filter the airflow after the cyclone pre-dust removal. The induced draft fan is located downstream of the high-precision filter cartridge, and its outlet is connected to the pulsed fluidized air distribution system to transport the filtered airflow back to the sealed dust removal chamber to form a closed loop.

16. The granular silicon descaling device according to claim 15, characterized in that, The device also includes a micro-negative pressure airflow balancing system, which includes a micro-pressure sensor and a controller; The micro-pressure sensor is used to detect the pressure value inside the sealed dust removal chamber; The controller is electrically connected to the micro-pressure sensor and the induced draft fan, respectively. It has a preset negative pressure threshold, which is used to obtain the pressure value detected by the micro-pressure sensor and compare it with the negative pressure threshold, and to perform linkage control on the induced draft fan according to the comparison result, so as to maintain the micro-negative pressure state in the sealed dust removal chamber.

17. The granular silicon descaling device according to claim 16, characterized in that, The inner wall of the sealed dust removal chamber is lined with a high-purity, high-temperature resistant non-metallic liner, which is a polytetrafluoroethylene liner or a silicon nitride liner.

18. The granular silicon descaling device according to claim 17, characterized in that, The sealed dust removal chamber is a stainless steel vertical cylindrical structure with an inner diameter of Φ400mm~Φ1200mm and a straight section height of 1800mm~3000mm.

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