Method for reducing content of silicon powder on surface of granular silicon

Abstract

The invention provides a method for reducing the content of silicon powder on the surface of granular silicon, and aims to solve the problems of low removal efficiency, serious environmental pollution, high production cost and possible damage to the granular silicon in the prior art. The method comprises the following steps: firstly, pre-treating granular silicon, and regulating the airflow rate (0.5-2.0 m / s), the temperature (20-40 DEG C) and the humidity (30-60%) to enable the surface of the granular silicon to be uniformly electrified and enhance the electrostatic separation effect of silicon powder; then, the particle silicon is placed in electrostatic dust collection equipment, a 10-30 kV high-voltage electric field is applied, and silicon powder is desorbed under the action of the electric field and adsorbed by an electrode; and finally, the desorbed silicon powder is guided to enter a dust collecting device (a cyclone separator, a bag-type dust collector and the like) through air flow (0.5-1.0 m / s), so that secondary pollution of the silicon powder is avoided. According to the method, the silicon powder on the surface of the particle silicon is removed through electrostatic adsorption, chemical reagents are not needed, damage to the particle silicon is avoided, environmental pollution is reduced, the removal efficiency is improved, and the method can be widely applied to preparation and optimization of high-purity silicon materials.

Description

Technical Field

[0001] The present invention relates to the technical field of surface treatment of granular silicon, and more particularly, to a method for reducing the content of silicon powder on the surface of granular silicon. Background Art

[0002] High-purity polysilicon is an important raw material in the semiconductor and photovoltaic industries. Its preparation methods mainly include the improved Siemens method and the fluidized bed method. In the improved Siemens method, metallurgical grade silicon powder reacts with hydrogen chloride (HCl) to produce trichlorosilane (SiHCl3). After rectification and purification, high-purity polysilicon is obtained by reduction deposition in a hydrogen atmosphere. Although this method has a mature production process and high product quality, it has problems such as high energy consumption, low production efficiency, and large equipment investment. In contrast, in the fluidized bed method, silane (SiH4) or silicon tetrachloride (SiCl4) is chemically vapor deposited in a hydrogen atmosphere at a temperature of 500-700 °C to directly prepare granular silicon, which simplifies the purification and rectification steps, significantly improves production efficiency, and reduces energy consumption. Therefore, it has been widely used in industrial production.

[0003] However, during the preparation of granular silicon by the fluidized bed method, due to incomplete chemical vapor deposition reactions and particle collision and friction, 5%-15% of silicon powder by-products are generated. These silicon powders are easily attached to the surface of granular silicon, increasing the turbidity of the appearance of granular silicon and having an adverse impact on subsequent processing and applications. Specifically, the silicon powder on the surface of granular silicon can cause dust flying during the feeding process, pollute the hot field, and shorten the service life of the hot field. In addition, after the silicon powder enters the melting system, it may affect the uniformity of the silicon liquid, increase the impurity content, further affect the crystal growth process, reduce the yield, and even cause problems such as furnace platform wire breakage. These factors will reduce the competitiveness of granular silicon in high-end semiconductor and photovoltaic applications.

[0004] In the prior art, for the removal of silicon powder on the surface of granular silicon, physical cleaning or chemical treatment methods are usually adopted. For example, some methods remove the silicon powder on the surface of granular silicon by mechanical vibration or air flow scouring. However, due to the small particle size and large specific surface area of granular silicon, the removal efficiency of these methods is low, and it is difficult to completely remove the attached silicon powder. At the same time, excessive mechanical vibration may cause granular silicon to break, affecting its final quality. In addition, some methods use wet chemical cleaning, such as pickling or alkali washing, to dissolve and remove the silicon powder attached to the surface. However, such methods not only increase the consumption of chemical reagents, produce a large amount of waste liquid, and increase the environmental protection treatment cost, but also may damage the surface of granular silicon, reduce its purity, and affect the quality of the final product.

[0005] Generally speaking, the existing technologies for removing silicon powder from the surface of granular silicon generally have problems such as low removal efficiency, serious environmental pollution, high production costs, and possible impact on product quality. Therefore, how to provide an efficient, environmentally friendly, and non-damaging method for removing silicon powder from the surface of granular silicon has become a technical problem that the industry urgently needs to solve. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to provide a method for reducing the silicon powder content on the surface of granular silicon, so as to solve the problems in the prior art that silicon powder is easy to adhere, difficult to remove, and affects the purity and application performance of granular silicon, and to provide a combined method of electrostatic pretreatment + high-voltage electrostatic dust removal + dust collection to improve the removal efficiency of silicon powder on the surface of granular silicon and ensure the cleanliness and quality of the final product.

[0007] To overcome the defects of the above prior art, the present invention provides a method for reducing the silicon powder content on the surface of granular silicon, which is characterized by including the following steps: S1. Pretreatment of granular silicon: The granular silicon is pretreated by air flow, and the air flow rate is controlled to be 0.5 - 2.0 m / s to ensure that the surface of the granular silicon is uniformly charged; through the electrostatic action, a charge interaction is generated between the surface of the granular silicon and the silicon powder to promote the subsequent desorption of the silicon powder. S2. High-voltage electrostatic dust removal: The granular silicon pretreated in the step S1 is placed in an electrostatic dust removal device, and a high-voltage electric field of 10 - 30 kV is applied to enhance the electrostatic interaction between the granular silicon and the silicon powder, thereby promoting the desorption of the silicon powder. S3. Dust collection: The air flow system of the electrostatic dust removal device is used to assist in the collection of the silicon powder, and the air flow rate is controlled to be 0.5 - 1.0 m / s. The dust is collected by a dust collection device to complete the treatment.

[0008] Compared with the prior art, the method for reducing the silicon powder content on the surface of granular silicon in the present application effectively solves the problems that it is difficult to remove the silicon powder on the surface of granular silicon by the fluidized bed method, traditional physical / wet cleaning is easy to damage silicon particles, and silicon powder reflux pollutes the environment through the combined process of electrostatic pretreatment + high-voltage electrostatic dust removal + efficient dust collection, improves the purity and production efficiency of granular silicon, and ensures the quality of the final product. The method of the present invention is applicable to large-scale production of granular silicon, has significant economic and environmental benefits, and has a wide application prospect in the field of preparation of high-purity silicon materials. Specifically, it has the following advantages: Improve the removal rate of silicon powder: Through the action of electrostatic force, the method of the present invention can more effectively remove the silicon powder attached to the surface of granular silicon compared with traditional physical cleaning or air flow separation, increasing the removal rate to 95% and significantly reducing the turbidity of granular silicon. Non-destructive cleaning to ensure the integrity of granular silicon: The method of the present invention uses electrostatic dust removal, without mechanical friction or chemical reagents, which will not damage the surface of granular silicon, ensuring product quality and integrity, and avoiding the impact of subsequent applications due to surface defects; Optimizing the electrostatic field design to improve the removal efficiency: The method of the present invention can precisely control the desorption process of silicon powder by optimizing the air flow rate, temperature and humidity control, and high-voltage electric field parameters, reduce the secondary adsorption of silicon powder, and improve the overall removal effect.

[0009] Efficient dust collection to prevent secondary pollution: The method of the present invention uses a dust collection device to avoid the reflux of silicon powder into the production environment, reduce the dust pollution of the production line, and improve the cleanliness of the workshop.

[0010] Environmental protection and energy saving, reducing costs: This method does not use chemical reagents, reducing pollutant emissions; at the same time, the energy consumption of electrostatic dust removal is relatively low, and compared with traditional wet cleaning or mechanical dust removal, the operating cost is significantly reduced, which is suitable for large-scale industrial production.

[0011] In a possible implementation manner, in the step S1, the granular silicon is granular silicon prepared by the fluidized bed method.

[0012] Compared with the prior art, adopting the above technical solution, using the characteristics of granular silicon prepared by the fluidized bed method to improve the effect of electrostatic dust removal. Granular silicon prepared by the fluidized bed method has a large specific surface area, and its surface is prone to adsorb silicon powder during the deposition process. However, in the present invention, through air flow pretreatment, the surface of the granular silicon is uniformly charged, enhancing the electrostatic force, so that the silicon powder is more easily desorbed in the high-voltage electrostatic field.

[0013] In a possible implementation manner, in the step S1, the air flow is air, and the rate of the air flow is 1.0 m / s.

[0014] Compared with the prior art, adopting the above technical solution, setting 1.0 m / s as the optimization parameter can ensure the uniformity of charging while preventing excessive disturbance of silicon powder and improve the efficiency of electrostatic dust removal. When the air flow rate is too low (<0.5 m / s), the charging effect is insufficient, resulting in a weak electrostatic interaction between the silicon powder and the granular silicon, reducing the subsequent desorption effect; while when the air flow rate is too high (>2.0 m / s), the silicon powder may drift with the air flow, affecting the charging stability.

[0015] In a possible implementation manner, in the step S1, the environmental temperature of the pretreatment is 20 - 40 °C, and the humidity is 30 - 60%.

[0016] Compared with the prior art, by adopting the above technical solution, by controlling the temperature at 20 - 40 °C and maintaining the humidity at 30 - 60%, the electrostatic charging effect of granular silicon can be significantly improved, and the desorption rate of silicon powder can be increased. Under the above conditions, the surface charge stability of granular silicon is enhanced, the desorption rate of silicon powder is increased to more than 92%, and finally the turbidity of the surface of granular silicon is reduced to below 95 NTU. At the same time, it also avoids the adverse effects of overly humid or dry environments on the equipment and the quality of granular silicon, ensures stable production conditions, and improves the overall dust removal efficiency and product quality.

[0017] In a possible implementation manner, in the step S1, the ambient temperature of the pretreatment is 30 °C and the humidity is 50%.

[0018] Compared with the prior art, by adopting the above technical solution, selecting 30 °C as the optimal pretreatment temperature is based on the optimization of the surface charge accumulation characteristics of granular silicon and the dielectric properties of air. Compared with the general range of 20 - 40 °C, 30 °C can make the electrostatic effect on the surface of granular silicon more stable, and at the same time avoid the problem of charge leakage that may be caused by too high temperature, improving the force of the electrostatic field on silicon powder. Humidity affects the conductivity of air and the electrostatic accumulation ability on the surface of granular silicon; when the humidity is lower than 50%, the air is relatively dry, and the surface charge of granular silicon may be lost, affecting the electrostatic adsorption ability; when the humidity is higher than 50%, the conductivity of air increases, resulting in the possible premature leakage of the static electricity on the surface of granular silicon, reducing the electrostatic adsorption and silicon powder desorption effects. In this implementation manner, selecting 50% humidity can keep the electrostatic effect on the surface of granular silicon in the optimal state, ensuring that the silicon powder is more easily desorbed under the action of the subsequent high-voltage electrostatic field.

[0019] In a possible implementation manner, in the steps S1 and S3, the direction of the air flow is horizontal.

[0020] Compared with the prior art, by adopting the above technical solution, optimizing the flow direction of the air flow can improve the desorption and collection efficiency of silicon powder, thereby enhancing the overall dust removal effect. By adopting a horizontal air flow direction in both the granular silicon pretreatment S1 and the dust collection S3 stages, a more uniform charge distribution can be achieved, and the influence of air flow disorder on the effective removal of silicon powder can be avoided.

[0021] In a possible implementation manner, in the step S2, the voltage of the high-voltage electric field is 25 - 30 kV, and the application time is 5 - 10 s.

[0022] Compared with the prior art, adopting the above technical solution can optimize the action parameters of the high-voltage electric field, enhance the electrostatic interaction force between granular silicon and attached silicon powder, thereby improving the desorption efficiency of silicon powder. At the same time, it ensures that the granular silicon itself is not damaged. Controlling the voltage of the high-voltage electric field at 25 - 30 kV and the application time at 5 - 10 s can enhance the electrostatic dust removal effect while avoiding surface damage or over-discharge phenomena of granular silicon caused by too high voltage or too long action time.

[0023] In a possible implementation manner, in the step S3, the air flow velocity is 0.7 m / s.

[0024] Compared with the prior art, adopting the above technical solution can optimize the dust collection process, improve the effective removal rate of silicon powder, and reduce the secondary pollution of dust at the same time. A reasonable setting of the air flow velocity of 0.7 m / s can ensure that the silicon powder is effectively stripped and smoothly enters the dust collection device while preventing dust diffusion caused by too fast air flow or affecting the collection efficiency due to too slow air flow.

[0025] In a possible implementation manner, in the step S3, the dust collection device is a cyclone separator or a bag filter.

[0026] Compared with the prior art, adopting the above technical solution, selecting a cyclone separator uses centrifugal force to separate and settle larger particle-sized silicon powder to the collection device, while selecting a bag filter further captures finer silicon powder particles through a high-efficiency filter material to prevent them from re-entering the air. The selection and use of both can achieve the efficient removal of silicon powder with different particle sizes, thereby improving the overall dust removal efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 is a schematic diagram of the principle of the method for reducing the silicon powder content on the surface of granular silicon according to the present invention; Figure 2 is the morphology of granular silicon before treatment in Example 1; Figure 3 is the morphology of granular silicon after treatment in Example 1. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0028] First of all, those skilled in the art should understand that these embodiments are only used to explain the technical principles of the embodiments of the present application and are not intended to limit the protection scope of the embodiments of the present application. Those skilled in the art can make adjustments according to needs to adapt to specific application scenarios.

[0029] In the description of the embodiments of the present application, it should be noted that unless otherwise clearly specified and limited, the terms "connected" and "connected" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium. For those of ordinary skill in the art, the specific meanings of the above terms in the embodiments of the present application can be understood according to specific situations.

[0030] The present invention provides a method for reducing the content of silicon powder on the surface of granular silicon. Through the combined treatment of electrostatic action and dust collection, efficient purification of the surface of granular silicon is achieved. This method not only improves the purity of granular silicon, but also avoids damage to the surface of granular silicon by traditional mechanical cleaning methods and optimizes the dust collection efficiency. The specific steps are as follows:

[0031] S1. Pretreatment of granular silicon The granular silicon is pretreated by an air flow, and the air flow rate is controlled to be 0.5 - 2.0 m / s to ensure uniform charging of the surface of the granular silicon. During the deposition process, the surface of the granular silicon is prone to adsorb fine silicon powder. Through appropriate air flow disturbance, the charging uniformity of the granular silicon can be enhanced, and at the same time, the deposition of silicon powder into blocks can be avoided, improving the subsequent desorption efficiency.

[0032] Charge interaction is generated between the surface of the granular silicon and the silicon powder through electrostatic action to promote subsequent desorption of the silicon powder. Since the silicon powder particles are small, they are prone to form weak binding on the surface of the granular silicon. By controlling the environmental temperature and humidity in the pretreatment stage, the surface of the granular silicon is charged with appropriate static electricity, thereby enhancing the charge interaction between the granular silicon and the silicon powder and providing higher desorption efficiency for subsequent electrostatic separation.

[0033] As a preferred solution, in the step S1, the granular silicon is granular silicon prepared by the fluidized bed method. Since the granular silicon prepared by the fluidized bed method is synthesized by chemical vapor deposition, it has a large specific surface area and more silicon powder attached to its surface. Therefore, when this method is used, the effect of electrostatic dust removal is more significant.

[0034] As a preferred solution, in the step S1, the air flow is air, and the air flow rate is 1.0 m / s. A moderate air flow rate can effectively drive the flow of granular silicon, and at the same time, avoid severe friction or impact between particles caused by too high a wind speed, making the surface of the granular silicon charged more uniformly.

[0035] As a preferred solution, in the step S1, the environmental temperature of the pretreatment is 20 - 40 °C, and the humidity is 30 - 60%. Appropriate control of temperature and humidity can enhance the charge retention ability of the surface of the granular silicon, prevent charge loss caused by excessive drying, and also avoid reducing the electrostatic effect due to too high humidity.

[0036] As a preferred solution, in step S1, the ambient temperature for the pretreatment is 30°C and the humidity is 50%. Under these preferred temperature and humidity conditions, the surface of the granular silicon can be stably charged, ensuring a reduction in the adhesion of the silicon powder and improving the subsequent desorption effect.

[0037] S2. High-voltage electrostatic dust removal Place the granular silicon pretreated in step S1 into an electrostatic dust removal device, and apply a high-voltage electric field of 10 - 30 kV to enhance the electrostatic interaction between the granular silicon and the silicon powder, thereby promoting the desorption of the silicon powder. The role of the high-voltage electric field is to strip the silicon powder from the surface of the granular silicon by the attraction of the electrostatic force and adsorb it onto the electrode surface of the electrostatic dust removal device.

[0038] As a preferred solution, in step S2, the voltage of the high-voltage electric field is 25 - 30 kV, and the application time is 5 - 10 s. The high-voltage electric field within this range can efficiently desorb the silicon powder in a short time and reduce the influence of charge accumulation on the granular silicon caused by long-term exposure to the electric field, thereby improving the dust removal efficiency.

[0039] S3. Dust collection Use the air flow system of the electrostatic dust removal device to assist in the collection of the silicon powder, control the air flow rate to be 0.5 - 1.0 m / s, and collect the dust through a dust collection device to complete the treatment. The role of dust collection is to prevent the desorbed silicon powder from adhering to the surface of the granular silicon again, and at the same time ensure the cleanliness of the production environment.

[0040] As a preferred solution, in steps S1 and S3, the direction of the air flow is horizontal. The horizontal air flow can minimize the probability of the silicon powder falling back, and at the same time increase the suspension time of the silicon powder in the air, facilitating the adsorption treatment by the electrostatic field.

[0041] As a preferred solution, in step S3, the air flow speed is 0.7 m / s. An appropriate air flow rate can keep the granular silicon flowing stably while effectively guiding the desorbed silicon powder into the collection device, avoiding the deposition of the silicon powder in the dust removal device and affecting the operation of the system.

[0042] As a preferred solution, in step S3, the dust collection device is a cyclone separator or a bag filter. The cyclone separator removes large-particle silicon powder by centrifugal force, while the bag filter can efficiently collect fine silicon powder. The combined use of the two can ensure a higher dust removal rate and reduce environmental pollution.

[0043] The following provides examples combined with specific data to further expand the above technical solutions of the present invention: Example 1 This example provides a method for reducing the silicon powder content on the surface of granular silicon. The specific implementation process is as follows: As Figure 1 shown Figure 1 is a schematic diagram of the principle of the method for reducing the content of silicon powder on the surface of granular silicon in the present invention. The method includes: S1. Pretreatment of granular silicon The fluidized bed granular silicon is pretreated to enhance the uniform surface charging and improve the subsequent desorption efficiency of silicon powder. The specific operation is as follows:

[0044] The granular silicon is processed by an air flow system, and the air flow rate is adjusted to 1.5 m / s to ensure uniform surface charging of the granular silicon; by adjusting the ambient temperature and humidity, appropriate static charges are applied to the surface of the granular silicon, the temperature is set at 30 °C, and the humidity is set at 50%.

[0045] S2. High-voltage electrostatic dust removal The granular silicon pretreated by the above steps is put into an electrostatic dust removal device, and the attached silicon powder on the surface of the granular silicon is removed by the action of a high-voltage electric field. The specific conditions are as follows: A high-voltage electric field of 20 kV is applied to enhance the electrostatic interaction between the granular silicon and the attached silicon powder, thereby promoting the desorption of silicon powder; the silicon powder is guided to the electrode surface under the action of the electric field to achieve separation.

[0046] S3. Dust collection The air flow system of the electrostatic dust removal device is used to assist in collecting the desorbed silicon powder. The specific conditions are as follows: The air flow velocity is adjusted to 0.8 m / s, and the air flow direction is optimized to enable the silicon powder to smoothly enter the dust collection device; a bag filter is used for efficient dust collection to prevent secondary pollution of the silicon powder.

[0047] Treatment effect: After being treated by this method, the removal rate of the attached silicon powder on the surface of the granular silicon reaches more than 90%, and the turbidity of the surface of the granular silicon is significantly reduced, improving the appearance quality of the product. As Figure 2 shown in Figure 3 Figure 2 is the morphology of the granular silicon before treatment in Example 1, Figure 3 and is the morphology of the granular silicon after treatment in Example 1.

[0048] Example 2 In this example, the control of ambient temperature and humidity and the electric field strength are further optimized on the basis of Example 1, improving the desorption effect of silicon powder.

[0049] S1. Pretreatment of granular silicon Pre-treat the granular silicon produced by fluidized bed method to enhance the uniformity of surface charging and improve the desorption efficiency of subsequent silicon powder; use an air flow system to treat the granular silicon, adjust the air flow rate to 1.0 m / s to ensure uniform charging on the surface of the granular silicon; by adjusting the ambient temperature and humidity, make the surface of the granular silicon carry appropriate static charges, set the temperature to 25°C and the humidity to 40%-45%.

[0050] S2. High-voltage electrostatic dust removal Put the granular silicon pretreated in the above steps into an electrostatic dust removal device, and remove the attached silicon powder on the surface of the granular silicon through the action of a high-voltage electric field. The specific conditions are as follows: Apply a 25 kV high-voltage electric field to further enhance the electrostatic interaction between the granular silicon and the attached silicon powder; under the action of the electric field, the silicon powder desorbs from the surface of the granular silicon and adsorbs onto the electrode surface.

[0051] S3. Dust collection Use the air flow system of the electrostatic dust removal device to assist in collecting the desorbed silicon powder. The specific conditions are as follows: Adjust the air flow velocity to 0.6 m / s to ensure that the air flow direction is coordinated with the flow direction of the granular silicon, so that the silicon powder can smoothly enter the dust collection device; use a cyclone separator for dust collection to effectively avoid pollution of the production environment by the silicon powder.

[0052] Treatment effect: Through optimized temperature and humidity control, the removal rate of silicon powder on the surface of the granular silicon is increased to 92%, the turbidity is reduced to below 95 NTU, the surface of the granular silicon is smoother, and the processing performance is improved.

[0053] Example 3 In this example, on the basis of Example 2, the electric field strength is further increased and the dust collection device is optimized to achieve a higher silicon powder removal rate.

[0054] S1. Granular silicon pretreatment Pre-treat the granular silicon produced by fluidized bed method to enhance the uniformity of surface charging and improve the desorption efficiency of subsequent silicon powder; use an air flow system to treat the granular silicon, adjust the air flow rate to 1.0 m / s to ensure uniform charging on the surface of the granular silicon; by adjusting the ambient temperature and humidity, make the surface of the granular silicon carry appropriate static charges, set the temperature to 30°C and the humidity to 50%.

[0055] S2. High-voltage electrostatic dust removal Put the granular silicon pretreated in the above steps into an electrostatic dust removal device, and remove the attached silicon powder on the surface of the granular silicon through the action of a high-voltage electric field. The specific conditions are as follows: Apply a high-voltage electric field of 28 kV to further enhance the electrostatic interaction between the surface of granular silicon and silicon powder. Under the action of the electric field, the silicon powder is quickly desorbed and adsorbed onto the electrode surface.

[0056] S3. Dust collection Use the air flow system of the electrostatic precipitator to assist in collecting the desorbed silicon powder. The specific conditions are as follows: Adjust the air flow rate to 0.7 m / s to ensure that the desorbed silicon powder smoothly enters the dust collection device. Use a bag filter to collect dust, improve the capture efficiency of fine silicon powder, and prevent environmental pollution.

[0057] Treatment effect: After adopting the optimized process, the removal rate of silicon powder on the surface of granular silicon is increased to 95%, the turbidity of granular silicon is reduced to below 80 NTU, the surface of granular silicon is cleaner, and the quality of the final product is significantly improved.

[0058] Through the above embodiments, it is further proved that a method for reducing the silicon powder content on the surface of granular silicon provided by the present invention can effectively reduce the silicon powder attached to the surface of granular silicon and improve the purity of granular silicon. This method optimizes process steps such as electrostatic pretreatment, high-voltage electrostatic dust removal, and dust collection, utilizes the charge interaction to enhance the desorption ability of silicon powder, and combines reasonable air flow control to ensure the efficient separation and recovery of silicon powder. Among them, Example 3 combines electrostatic action, optimized electric field strength, and dust collection equipment, and finally achieves the best silicon powder removal effect. Compared with the traditional mechanical dust removal method, it not only avoids physical damage to the surface of granular silicon, but also can efficiently remove fine silicon powder, improve the product quality of granular silicon, and make it more suitable for high-end application scenarios.

[0059] The high-voltage electric field treatment adopted by the method for reducing the silicon powder content on the surface of granular silicon of the present invention makes full use of the electrostatic interaction on the surface of granular silicon, promotes the efficient desorption of silicon powder, and at the same time avoids the damage caused by the traditional mechanical dust removal method to the surface of granular silicon. In addition, by precisely regulating the air flow rate, environmental temperature and humidity, and electric field strength, not only the desorption efficiency of silicon powder is improved, but also the dust collection system is optimized to avoid the generation of secondary pollution.

[0060] In summary, the present invention combines reasonable process optimization and electrostatic dust removal technology to solve the problem that it is difficult to effectively remove silicon powder on the surface of granular silicon in the prior art, reduces the turbidity of granular silicon, improves the product quality, and provides higher-quality silicon materials for the subsequent processing process. The method of the present invention is environmentally friendly and energy-saving, does not require additional chemical reagents, is suitable for industrial production, and has broad application prospects.

[0061] In the description of the present application, the descriptions referring to terms such as "one embodiment", "some embodiments", "in this embodiment", "specific examples", or "some examples", etc. mean that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in a suitable manner in any one or more embodiments or examples. In addition, without contradiction, those skilled in the art can combine and combine the different embodiments or examples described in this specification and the features of different embodiments or examples.

[0062] As described above, it is only the specific implementation manner of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present application should be covered by the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A method for reducing the silicon powder content on the surface of granular silicon, characterized in that: The following steps are involved: S1. Granular silicon pretreatment: The granular silicon is pretreated with airflow, and the airflow rate is controlled to be 0.5-2.0 m / s to ensure that the surface of the granular silicon is uniformly charged; S2. High voltage electrostatic precipitator: Placing the granular silicon pretreated in step S1 in an electrostatic dust removal device, applying a high voltage electric field of 10-30 kV to enhance the electrostatic interaction between the granular silicon and silicon powder, thereby promoting the desorption of silicon powder; S3. Dust Collection: The airflow system of the electrostatic dust removal equipment is used to assist in the collection of silicon powder. The airflow rate is controlled to 0.5-1.0 m / s. The dust is collected by the dust collection device to complete the treatment.

2. The method for reducing the silicon powder content on the surface of granular silicon according to claim 1, characterized in that: In the step S1, the granular silicon is fluidized bed granular silicon.

3. The method for reducing the silicon powder content on the surface of granular silicon according to claim 1, characterized in that: In the step S1, the airflow is air, and the speed of the airflow is 1.0 m / s.

4. The method for reducing the silicon powder content on the surface of granular silicon according to claim 1, characterized in that: In the step S1, the pretreatment environment temperature is 20-40°C and the humidity is 30-60%.

5. The method for reducing the silicon powder content on the surface of granular silicon according to claim 4, characterized in that: In the step S1, the pretreatment environment temperature is 30° C. and the humidity is 50%.

6. The method for reducing the silicon powder content on the surface of granular silicon according to claim 1, characterized in that: In the steps S1 and S3, the direction of the airflow is horizontal.

7. The method for reducing the silicon powder content on the surface of granular silicon according to claim 1, characterized in that: In step S2, the voltage of the high voltage electric field is 25-30 kV, and the application time is 5-10 s.

8. The method for reducing the silicon powder content on the surface of granular silicon according to claim 1, characterized in that: In step S3, the air flow velocity is 0.7 m / s.

9. The method for reducing the silicon powder content on the surface of granular silicon according to claim 1, characterized in that: In step S3, the dust collecting device is a cyclone separator or a bag dust collector.

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