Method and system for recycling waste silicon powder generated in cold hydrogenation process

Abstract

The invention discloses a method and system for recycling waste silicon powder generated in a cold hydrogenation process, and the method comprises the following steps: mixing cold hydrogenation external cyclone silicon powder and industrial silicon auxiliary powder according to a certain proportion, carrying out mechanical activation, and then separating out impurities to obtain activated silicon powder; and putting the activated silicon powder into a trichlorosilane synthesis furnace, and enabling the activated silicon powder to react with hydrogen chloride to generate trichlorosilane. According to the method, the waste silicon powder generated in the cold hydrogenation process can be recycled and converted into a material with a certain value and application, resource waste is avoided, the recycled silicon powder is used for trichlorosilane synthesis, the trichlorosilane synthesis efficiency can be greatly improved, the silicon unit consumption in polycrystalline silicon production is reduced, and the production cost is reduced. And cyclic utilization and sustainable development of resources are realized.

Description

Technical Field

[0001] The present invention relates to the technical field of polysilicon, and in particular to a method and system for recycling waste silicon powder generated in a cold hydrogenation process. Background Art

[0002] With the development of society and the acceleration of industrialization, waste issues have gradually attracted people's attention, one of which is the treatment and utilization of waste silicon powder. Cold hydrogenated external cyclone silicon powder and industrial silicon by-powder are both common waste silicon powders, among which: cold hydrogenated external cyclone silicon powder is a by-product produced in the cold hydrogenation process during the preparation and processing of polysilicon. Since the silicon powder will react with hydrogen chloride after entering the fluidized bed, the proportion of impurities after the reaction increases, and the silicon content decreases. In addition, the cold hydrogenated external cyclone silicon powder will be oxidized to form silicon dioxide when it comes into contact with air after being discharged from the external cyclone, further reducing its activity. It is usually regarded as waste and discarded; industrial silicon by-powder is a by-product produced during the grinding and screening of industrial silicon. In addition to its fine particle size, the industrial silicon by-powder meets the requirements of polysilicon production in other aspects. However, due to the excessive fineness of the industrial silicon by-powder (the proportion of particles finer than 160 mesh is relatively large), it is not effective to use it directly in polysilicon production, and it needs to be re-smelted and then ground and screened.

[0003] For the above-mentioned waste silicon powder, the existing solutions mainly include: 1) landfilling or solidifying the cold hydrogenated external cyclone silicon powder to fix it in a certain matrix to reduce its impact on the environment and prevent it from further diffusion and release. However, there is still a large amount of silicon powder with utilization value in the cold hydrogenated external cyclone silicon powder. Landfilling or solidification treatment will lead to waste of resources, fail to effectively realize the resource utilization of waste silicon powder and the concept of circular economy, and are not fully consistent with the requirements of sustainable development. Moreover, even if landfilling or solidification treatment is carried out, waste silicon powder may still leak or release in the landfill, posing a risk of pollution to the soil, groundwater and surrounding environment; 2) re-melting the external cyclone silicon powder and industrial silicon by-powder into industrial silicon. However, the re-melting process requires additional energy consumption, and the waste gas generated by smelting the cold hydrogenated external cyclone silicon powder is prone to cause secondary environmental pollution. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a method and system for recycling waste silicon powder generated in a cold hydrogenation process in view of the above-mentioned deficiencies in the prior art, which can regenerate the waste silicon powder generated in the cold hydrogenation process and convert it into materials with certain value and use, thereby avoiding waste of resources. The recycled silicon powder is used for trichlorosilane synthesis, which can greatly improve the efficiency of trichlorosilane synthesis, reduce the silicon consumption per unit in polysilicon production, and realize the recycling and sustainable development of resources.

[0005] The technical solution of the present invention to solve the above technical problems is:

[0006] According to one aspect of the present invention, a method for recycling waste silicon powder generated in a cold hydrogenation process is provided, comprising:

[0007] The cold hydrogenated external cyclone silicon powder and the industrial silicon by-powder are mixed in a certain proportion, and mechanically activated, and then the impurities are separated to obtain the activated silicon powder;

[0008] The activated silicon powder is put into a trichlorosilane synthesis furnace to react with hydrogen chloride to generate trichlorosilane.

[0009] Optionally, the mass ratio of the cold hydrogenated external cyclone silicon powder to the industrial silicon by-powder is 1:1 to 5:1.

[0010] Optionally, the mechanical activation is specifically as follows: cold hydrogenated external cyclone silicon powder and industrial silicon by-powder are introduced into the mechanical activation device evenly from the top in proportion, and gas is introduced in the horizontal direction, so that the cold hydrogenated external cyclone silicon powder and the industrial silicon by-powder are driven by the airflow to move in the opposite direction in the horizontal direction to collide and rub.

[0011] Optionally, the total feed amount of the cold hydrogenated external cyclone silicon powder and the industrial silicon by-powder is controlled to be 1 / 3 to 1 / 2 of the volume of the mechanical activation device.

[0012] Optionally, the gas flow velocity entering the mechanical activation device is controlled to be 50-100 m / s, the gas flow pressure is controlled to be 0.6-0.8 MPa, the temperature is controlled to be 30-280° C., and the mechanical activation device continues to operate for 5-10 min after the feeding is completed.

[0013] Optionally, the median particle size of the activated silicon powder is in the range of 80-120 μm.

[0014] According to another aspect of the present invention, a system for recycling waste silicon powder generated in a cold hydrogenation process is provided, comprising a mechanical activation device, wherein the mechanical activation device is respectively connected to a cold hydrogenation external cyclone device and an industrial silicon grinding and screening device in the cold hydrogenation process, and is used to introduce cold hydrogenation external cyclone silicon powder and industrial silicon by-powder and mechanically activate them and separate impurities from them to obtain activated silicon powder; the mechanical activation device is also connected to a trichlorosilane synthesis furnace, and is used to feed the activated silicon powder into the trichlorosilane synthesis furnace to react with hydrogen chloride to generate trichlorosilane.

[0015] Optionally, the mechanical activation device includes a tank body, which is provided with a first feed port, a second feed port and an air inlet, and the tank body is provided with a first cyclone device, a second cyclone device and a separation mechanism, the first feed port is provided with a first screw feeder, the first screw feeder is connected to the cold hydrogenated external cyclone device, the second feed port is provided with a second screw feeder, the second screw feeder is connected to the industrial silicon by-powder tank truck to control the cold hydrogenated external cyclone silicon powder and the industrial silicon by-powder to be uniformly introduced into the tank body of the mechanical activation device from the top in proportion, the air inlet is used to introduce gas, the air inlet is provided with an airflow accelerator to control the airflow speed and pressure, the first cyclone device and the second cyclone device operate in opposite directions, so that the cold hydrogenated external cyclone silicon powder and the industrial silicon by-powder in the tank body are driven by the airflow to move in the opposite direction horizontally to collide and rub to obtain mixed silicon powder; the separation mechanism is arranged below the first cyclone device and the second cyclone device, and is used to separate impurities in the mixed silicon powder obtained after collision and friction to obtain activated silicon powder.

[0016] Optionally, the separation mechanism includes a silicon powder grading component, a 10-micron aperture screen and a vibrating screening component, the vibrating screening component is arranged at the bottom of the tank body, the 10-micron aperture screen is arranged above the vibrating screening component, and the silicon powder grading component is arranged above the 10-micron aperture screen.

[0017] Optionally, the system also includes a control unit, which is electrically connected to one or more of the first screw feeder, the second screw feeder, and the airflow accelerator in the mechanical activation device, and is used to perform comprehensive real-time monitoring of the feed amount, airflow velocity, pressure, temperature, and particle size distribution parameters during the operation of the mechanical activation device, and automatically adjust in real time according to a preset computer program, and display the operating status in real time.

[0018] Optionally, the mechanical activation device also includes a temperature sensor and a cooling mechanism, and the temperature sensor and the cooling mechanism are electrically connected to the control unit to form a temperature detection and adjustment system for monitoring and adjusting the temperature inside the tank of the mechanical activation device to ensure that it is within the optimal operating temperature range.

[0019] Beneficial effects:

[0020] The method for recycling waste silicon powder generated in the cold hydrogenation process of the present invention can improve the particle size, shape and surface properties of waste silicon powder through mechanical activation treatment, improve product quality, and can recycle the waste silicon powder generated in the cold hydrogenation process and convert it into materials with certain value and use, thereby avoiding waste of resources; and, compared with the prior art that requires the purchased industrial silicon to be ground and screened first, the particle size of activated silicon powder in this method is relatively small and the activity is relatively high, which can greatly improve the efficiency of trichlorosilane synthesis, reduce the silicon consumption per unit in polysilicon production, and realize the recycling and sustainable development of resources. Compared with the prior art, it is specifically reflected in the following aspects:

[0021] 1. Through mechanical activation, the cold hydrogenated external cyclone silicon powder can be subjected to high-speed impact and friction, effectively removing the silicon dioxide and impurities on the surface of the external cyclone silicon powder, which can increase the surface area of ​​the silicon powder, enhance its activity and reactivity, and play a better role in the subsequent production process.

[0022] 2. By controlling the feed ratio, feed amount, air flow velocity and other parameters of the waste silicon powder, activated silicon powder with the highest particle size conversion rate for synthesizing trichlorosilane can be further obtained, and the improvement of the particle shape and physical properties of the treated silicon powder can reduce the generation of by-products and wastes during the reaction process, which helps to reduce environmental pollution and the cost of waste treatment.

[0023] 3. The use of airflow mechanical activation treatment can cause the surface of silicon powder particles to be broken and reconstructed, resulting in silicon lattice distortion, converting mechanical energy into chemical energy, thereby leading to changes in surface physical and chemical properties, improving the adsorption capacity, dispersibility and adhesion of silicon powder, making it more suitable for trichlorosilane synthesis.

[0024] 4. Through mechanical activation treatment, the quality and performance of cold hydrogenated external cyclone silicon powder can be improved, ensuring that the recycled silicon powder meets the requirements of reuse and ensuring the stability, consistency and reliability of the produced products. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 Schematic diagram of a method and system for recycling waste silicon powder generated in a cold hydrogenation process in an embodiment of the present invention;

[0026] Figure 2 for Figure 1 A top view of

[0027] Figure 3 This is a comparison chart of the activity of silicon powder before and after mechanical activation in an embodiment of the present invention;

[0028] Figure 4 This is a comparison diagram of the median diameter of silicon powder before and after mechanical activation in an embodiment of the present invention;

[0029] Figure 5 This is a comparison chart of the conversion rate changes of trichlorosilane synthesized from silicon powder before and after mechanical activation in the examples of the present invention.

[0030] In the figure: 1. Cold hydrogenation external cyclone device; 2. First screw feeder; 3. Control unit; 4. Second screw feeder 5. Cyclone device; 6. Silicon powder particles; 7. Silicon powder grading assembly; 8. Product outlet; 9. Industrial silicon by-powder tanker; 10. Vibrating screening assembly; 11. Cooling mechanism; 12. 10 micron aperture screen; 13. Impurity outlet; 14. Air inlet; 15. Air outlet; 16. First feed inlet; 17. Second feed inlet. DETAILED DESCRIPTION

[0031] In order to enable those skilled in the art to better understand the technical solution of the present invention, the technical solution of the present invention will be clearly and completely described below in conjunction with the drawings in the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work belong to the protection scope of the present invention.

[0032] In view of the problems that the treatment method of waste silicon powder generated in the cold hydrogenation process in the prior art has resource waste, additional energy consumption, pollution risks, etc., the present invention provides a method for recycling waste silicon powder generated in the cold hydrogenation process, comprising: mixing cold hydrogenation outer cyclone silicon powder and industrial silicon by-powder in a certain proportion, and mechanically activating them, and then separating impurities to obtain activated silicon powder; putting the activated silicon powder into a trichlorosilane synthesis furnace to react with hydrogen chloride to generate trichlorosilane.

[0033] Correspondingly, the present invention also provides a recycling system for waste silicon powder generated in a cold hydrogenation process, comprising a mechanical activation device, wherein: the mechanical activation device is respectively connected to a cold hydrogenation external cyclone device and an industrial silicon grinding and screening device in the cold hydrogenation process, and is used to introduce cold hydrogenation external cyclone silicon powder and industrial silicon by-powder and mechanically activate them and separate impurities to obtain activated silicon powder; the mechanical activation device is also connected to a trichlorosilane synthesis furnace, and is used to put the activated silicon powder into the trichlorosilane synthesis furnace to react with hydrogen chloride to generate trichlorosilane.

[0034] Example 1

[0035] like Figure 1 , Figure 2 As shown, this embodiment discloses a method for recycling waste silicon powder generated in a cold hydrogenation process, comprising:

[0036] Step 1: Mix the cold hydrogenated external cyclone silicon powder and fresh industrial silicon by-powder in a certain proportion, and perform mechanical activation, then separate the impurities to obtain activated silicon powder.

[0037] Mechanical activation can not only remove or reduce the oxide layer and impurities on the surface of silicon powder, thereby improving the purity and reactivity of silicon powder, but also distort and partially destroy the silicon lattice of the cold hydrogenated external cyclone silicon powder particles, thereby increasing the internal energy of the silicon powder particles and improving the reactivity. It can also make the shape of silicon powder particles more uniform and delicate, and the particle distribution more uniform, thereby improving the reactivity and utilization rate of silicon powder. In addition, the silicon powder after mechanical activation treatment also has higher reactivity and faster reaction rate due to the addition of fresh industrial silicon by-powder, and can more effectively participate in chemical reactions, thereby improving reaction efficiency and product quality.

[0038] Step 2: Put the activated silicon powder into a fluidized bed reactor to react with hydrogen chloride at 300-320°C and 0.1-0.2MPaG pressure to generate trichlorosilane. The main reaction is: Si+3HCl→SiHCl3+H2.

[0039] Improving the conversion rate of trichlorosilane by optimizing the activity of silicon powder is a complex and delicate task. Studies have found that increasing the exposure of the maximum crystal surface of silicon surface density can greatly improve the activity of silicon powder. The main factor that determines the reactivity of silicon is the atomic state. This method distorts and destroys the crystal lattice of silicon powder through mechanical activation, which increases the internal energy of silicon powder, increases the exposure of crystal surface, and increases the contact area with hydrogen chloride, thereby increasing the reaction area between silicon powder and hydrogen chloride and increasing the consumption of hydrogen chloride. Compared with non-mechanically activated silicon powder, activated silicon powder can produce more trichlorosilane, such as Figure 5 shown.

[0040] In addition, due to the small particle size of silicon powder, the gas flow rate required to achieve fluidization is small, and the gas flow rate required to achieve fluidization is large due to the large particle size, that is, small particles are easy to fluidize, and large particles are difficult to fluidize. However, if the particle size of silicon powder is too small, the gas flow rate to achieve the take-out speed is also small, that is, silicon powder particles are more likely to be taken out of the fluidized bed, resulting in waste. Therefore, in production, it is necessary to select appropriate silicon powder for production according to the characteristics of the process and specific conditions.

[0041] In some embodiments, the median diameter (median particle size) of the activated silicon powder is controlled at 80-120 μm, so that the conversion rate of synthesizing trichlorosilane in the above reaction is higher.

[0042] The method adjusts the ratio of cold hydrogenated external cyclone silicon powder and industrial silicon by-powder during the mechanical activation process, so that the silicon powder after mechanical activation reaches the optimal particle size range.

[0043] In some embodiments, the mass ratio of cold hydrogenated external cyclone silicon powder to industrial silicon by-powder is controlled to be 1:1 to 5:1, preferably 2:1.

[0044] Specifically, the feed amount of cold hydrogenated external cyclone silicon powder and industrial silicon by-powder will directly affect the load and treatment effect of mechanical activation. In this method, the supply amount of cold hydrogenated external cyclone silicon powder and industrial silicon by-powder is adjusted by the first screw feeder and the second screw feeder respectively to ensure uniform feeding and avoid affecting the activation effect by too much or too little proportion of the two types of waste silicon powder.

[0045] In this embodiment, the median diameter of the cold hydrogenated external cyclone silicon powder is about 50-100 μm, and the median diameter of the industrial silicon by-powder is about 50-90 μm. The median particle size after mechanical activation according to the above ratio is about 50-95 μm, which is within the most suitable silicon powder particle size range.

[0046] In some embodiments, the mechanical activation in the present method is specifically as follows: cold hydrogenated outer cyclone silicon powder and industrial silicon side powder are uniformly introduced into the mechanical activation device from the top according to the above ratio, and gas is introduced in the horizontal direction through an air pump or a compressed air system, so that the cold hydrogenated outer cyclone silicon powder and the industrial silicon side powder are driven by the airflow to move in the opposite direction in the horizontal direction (for example, move in the clockwise direction and move in the counterclockwise direction respectively) to collide and rub at high speed. Since the hardness of the industrial silicon side powder is slightly greater than the hardness of the cold hydrogenated outer cyclone silicon powder, this collision and friction can cause the silicon powder particles to rub against each other, remove the silicon dioxide on the surface of the cold hydrogenated outer cyclone silicon powder, and increase the silicon lattice internal energy of the industrial silicon side powder and the cold hydrogenated outer cyclone silicon powder, thereby achieving mechanical activation. After separating fine particles, activated silicon powder with a relatively uniform particle size can be obtained. In the process of mechanical activation, the particle size and morphology of the activated silicon powder particles are adjusted by controlling parameters such as airflow velocity and feed amount.

[0047] In some embodiments, the total feed amount of the cold hydrogenated external cyclone silicon powder and the industrial silicon by-powder is controlled to be 1 / 3 to 1 / 2 of the volume of the mechanical activation device. The feed time is controlled to be 3 to 5 minutes, which is specifically adjusted according to the powder characteristics and equipment load.

[0048] Specifically, intermittent feeding is generally adopted. After the activated silicon powder after mechanical activation is discharged, new waste silicon powder is fed in. Among them, the feed amount of cold hydrogenated external cyclone silicon powder generally accounts for 50-80%, and the feed amount of industrial silicon by-powder generally accounts for 20-50%.

[0049] In some embodiments, the gas flow velocity entering the mechanical activation device is controlled to be 50-100 m / s, the gas flow pressure is controlled to be 0.6-0.8 MPa, and the temperature is controlled to be 30-280°C. After the feeding is completed, the mechanical activation device continues to operate for 5-10 minutes to ensure thorough mixing of the two powders. At this time, the mechanical energy input during the mixing process will cause cracks, defects and activation on the surface of the powder, thereby enhancing the reaction activity.

[0050] Specifically, there is a certain relationship between the feed amount of waste silicon powder and the air flow velocity. Generally speaking, the larger the feed amount, the larger the required air flow velocity needs to be to keep the powder suspended and flowing stably and transported.

[0051] In this embodiment, when the total feed amount is small (about 1 / 3 of the equipment volume), a lower air flow velocity is suitable, which is usually controlled between 50-70m / s; when the total feed amount reaches a medium level (about 1 / 2 of the equipment volume), a higher air flow velocity is required, which is generally controlled to be 70-100m / s; when the total feed amount is large (exceeding 1 / 2 of the equipment volume), the air flow velocity needs to be further increased, usually to more than 100m / s, to ensure that the air flow can carry away all the powder.

[0052] During the mechanical activation process, the violent friction between the material particles will cause a certain amount of heat to be generated in the equipment. In order to avoid damage to the mechanical activation device due to excessive temperature, in some embodiments, the method also includes: equipping a temperature detection and adjustment system to monitor and adjust the temperature of the mechanical activation process to ensure that it is within the optimal operating temperature range.

[0053] In order to verify the activity of the silicon powder (activated silicon powder) after mechanical activation in this method, this example carried out the following activity verification tests on cold hydrogenated outer cyclone silicon powder of different particle size ranges, industrial silicon by-powder and the silicon powder after mechanical activation in this method:

[0054] (1) Turn on the water bath, turn on the switch, and set the temperature to 60°C;

[0055] (2) Mix the silicon powder and weigh 5 grams of silicon powder with weighing paper for later use;

[0056] (3) Use a measuring cylinder to measure 100 mL of 3% sodium hydroxide solution and pour it into a 500 mL beaker;

[0057] (4) When the water bath temperature reaches 60°C, place the beaker containing the sodium hydroxide solution in the water bath and preheat for 15 minutes;

[0058] (5) Pour the weighed silicon powder into a beaker, and the silicon powder and the sodium hydroxide solution begin to react and release gas. After the silicon powder and the sodium hydroxide react completely (no more bubbles are generated), filter, dry, and weigh the silicon powder after the reaction, and record it as mass m in grams;

[0059] (6) Silicon powder activity (%) = [(5-m) / 5]*100%.

[0060] The results are as follows Figure 3 As shown, when sodium hydroxide solution is used as the silicon powder activity test agent, the reaction ratio of the silicon powder after mechanical activation is the highest, which is above 90%, indicating that the activity of the silicon powder is greatly improved after mechanical activation.

[0061] The method for recycling waste silicon powder generated by the cold hydrogenation process of this embodiment can improve the particle size, shape and surface properties of waste silicon powder through mechanical activation treatment, improve product quality, and recycle the waste silicon powder generated by the cold hydrogenation process, converting it into materials with certain value and use, avoiding waste of resources; and, compared with the prior art that requires the purchased industrial silicon to be ground and screened first, the particle size of activated silicon powder in this method is relatively small and the activity is high, which can greatly improve the efficiency of trichlorosilane synthesis, reduce the silicon consumption per unit of polysilicon production, and realize the recycling and sustainable development of resources. Compared with the prior art, it is specifically reflected in the following aspects:

[0062] 1. Through mechanical activation, the cold hydrogenated external cyclone silicon powder can be subjected to high-speed impact and friction, effectively removing the silicon dioxide and impurities on the surface of the external cyclone silicon powder, which can increase the surface area of ​​the silicon powder, enhance its activity and reactivity, and play a better role in the subsequent production process.

[0063] 2. By controlling the feed ratio, feed amount, air flow velocity and other parameters of the waste silicon powder, activated silicon powder with the highest particle size conversion rate for synthesizing trichlorosilane can be further obtained, and the improvement of the particle shape and physical properties of the treated silicon powder can reduce the generation of by-products and wastes during the reaction process, which helps to reduce environmental pollution and the cost of waste treatment.

[0064] 3. The use of airflow mechanical activation treatment can cause the surface of silicon powder particles to be broken and reconstructed, resulting in silicon lattice distortion, converting mechanical energy into chemical energy, thereby leading to changes in surface physical and chemical properties, improving the adsorption capacity, dispersibility and adhesion of silicon powder, making it more suitable for trichlorosilane synthesis.

[0065] 4. Through mechanical activation treatment, the quality and performance of cold hydrogenated external cyclone silicon powder can be improved, ensuring that the recycled silicon powder meets the requirements of reuse and ensuring the stability, consistency and reliability of the produced products.

[0066] Example 2

[0067] like Figure 1 , Figure 2 As shown, this embodiment discloses a recycling system for waste silicon powder generated in a cold hydrogenation process, including a mechanical activation device, which is respectively connected to a cold hydrogenation external cyclone device 1 and an industrial silicon grinding and screening device in the cold hydrogenation process, and is used to introduce cold hydrogenation external cyclone silicon powder and industrial silicon by-powder and mechanically activate them and separate impurities to obtain activated silicon powder; the mechanical activation device is also connected to a trichlorosilane synthesis furnace, and is used to put the activated silicon powder into the trichlorosilane synthesis furnace to react with hydrogen chloride to generate trichlorosilane.

[0068] In some embodiments, the mechanical activation device comprises a tank body, on which a first feed port 16, a second feed port 17, an air inlet 14, and an air outlet 15 are provided, and a cyclone device 5 (specifically a first cyclone device, a second cyclone device) and a separation mechanism are provided in the tank body, wherein:

[0069] The first feed port 16 is provided with a first screw feeder 2, and the first screw feeder 2 is connected to the ash discharge port of the cold hydrogenated external cyclone device 1 through a pipeline. The second feed port 17 is provided with a second screw feeder 4, and the second screw feeder 4 is connected to the industrial silicon secondary powder tanker 9 to control the cold hydrogenated external cyclone silicon powder and the industrial silicon secondary powder to be uniformly introduced into the tank body of the mechanical activation device from the top in proportion. The air inlet 14 is used to introduce gas, and the air inlet 14 is provided with an airflow accelerator to control the airflow speed and pressure. The first cyclone device and the second cyclone device operate in opposite directions, so that the cold hydrogenated external cyclone silicon powder and the industrial silicon secondary powder in the tank body move in the opposite direction horizontally (for example, move in the clockwise direction and move in the counterclockwise direction respectively) driven by the airflow to collide and rub, so as to obtain mixed silicon powder;

[0070] The separation mechanism is arranged below the first cyclone device and the second cyclone device, and is used to separate impurities in the mixed silicon powder obtained after collision and friction to obtain activated silicon powder. The activated silicon powder is discharged from the product outlet 8 on the side of the tank body through the silicon powder discharge device, the separated impurities are discharged from the impurity outlet 13 at the bottom of the tank body, and the gas in the tank body is discharged from the gas outlet 15.

[0071] In this embodiment, the first feed port 16 and the second feed port 17 are respectively located on two sides of the top of the tank body, and the air outlet 15 is located on the opposite side of the air inlet 14 .

[0072] In some embodiments, the separation mechanism includes a silicon powder grading component 7, a 10-micron aperture screen 12 and a vibrating screening component 10. The vibrating screening component 10 is arranged at the bottom of the tank, the 10-micron aperture screen 12 is arranged above the vibrating screening component 10, and the silicon powder grading component 7 is arranged above the 10-micron aperture screen 12. The mixed silicon powder first passes through the silicon powder grading component 7. The silicon powder grading component 7 includes multiple stages, which can finely grade the silicon powder, and retain the silicon powder particles 6 with larger particle sizes in the upper silicon powder grading component 7 and continue to collide and rub through the airflow, while the silicon powder particles 6 with smaller particle sizes enter the silicon powder grading component 7 of the next layer, and so on. Finally, the particles passing through the silicon powder grading component 7 of the lowest layer are screened by the 10-micron aperture screen 12, and the silicon powder with a particle size below 10 μm falls on the vibrating screening component 10, and then is discharged from the impurity outlet 13. The particles left after screening by the 10-micron aperture screen 12 are activated silicon powder.

[0073] In some embodiments, the system also includes a control unit 3, which is electrically connected to one or more of the first screw feeder 2, the second screw feeder 4, the airflow accelerator and other equipment in the mechanical activation device, and is used to perform comprehensive real-time monitoring of parameters such as feed amount, airflow velocity, pressure, temperature, particle size distribution and other parameters during the operation of the mechanical activation device, and automatically adjust in real time according to a preset computer program, display the operating status in real time, optimize the particle size range, and ensure that the activated silicon powder has a uniform particle size.

[0074] In some embodiments, the mechanical activation device also includes a temperature sensor and a cooling mechanism 11. The temperature sensor and the cooling mechanism 11 are electrically connected to the control unit 3 to form a temperature detection and adjustment system for monitoring and adjusting the temperature in the tank of the mechanical activation device to ensure that it is within the optimal operating temperature range and to prevent safety hazards caused by overheating of silicon powder.

[0075] Specifically, the temperature sensor detects the temperature inside the tank and transmits it to the control unit; the control unit 3 presets a temperature threshold (specifically determined according to the optimal operating temperature range), the control unit 3 receives the temperature transmitted by the temperature sensor, compares it with the temperature threshold, and controls the cooling mechanism 11 to cool the tank according to the comparison result to maintain the temperature inside the tank stable within the preset temperature range. In this embodiment, the cooling mechanism 11 adopts a jacket water cooling device.

[0076] Example 3

[0077] This embodiment discloses a method for recycling waste silicon powder generated in a cold hydrogenation process, which uses the above-mentioned recycling system, and the steps are as follows:

[0078] The cold hydrogenated external cyclone silicon powder is conveyed to the first screw feeder 2, and the industrial silicon by-powder is conveyed to the second screw feeder 4. The feed mass ratio of the cold hydrogenated external cyclone silicon powder to the industrial silicon by-powder is set to 2:1, and the total feed flow rate is set to 50-100 kg / h. The total feed volume is about 1 / 2 of the tank volume, and the feed flow control device is checked to ensure that the raw materials are conveyed according to the set ratio; the gas flow rate is set to 85 m / s, and the air flow pressure is 1-3 bar to ensure sufficient air flow supply;

[0079] The cold hydrogenated external cyclone silicon powder and the industrial silicon by-powder are uniformly introduced into the tank of the mechanical activation device from the top according to the set ratio, and the air pump or the compressed air system is started to introduce gas in the horizontal direction, so that the cold hydrogenated external cyclone silicon powder and the industrial silicon by-powder are driven by the airflow to move in the clockwise direction and the counterclockwise direction respectively, so as to perform high-speed collision and friction for 10 minutes, and the silicon dioxide on the surface of the cold hydrogenated external cyclone silicon powder is removed to obtain mixed silicon powder; after the mixed silicon powder passes through the silicon powder grading component, the 10-micron aperture screen and the vibration screening component in sequence, the particle impurities below 10μm are separated to obtain activated silicon powder, the median particle size of the activated silicon powder is 98μm, and the surface characteristics of the activated silicon powder particles are: due to mechanical activation and collision, the surface energy of the particles is increased, the surface is rougher, and the cracks are increased, which helps to improve the chemical activity of the particles and the ability to combine with other substances;

[0080] Put the activated silicon powder into the fluidized bed reactor, control the bed height within 2.7 meters, the fluidized bed pressure difference at 30-40KpaG, the temperature at 345-355℃, the pressure at 0.3-0.4MPa, and the hydrogen chloride flow rate at 800Nm 3 / h, the purity of hydrogen chloride is greater than 90%, and the hydrogen flow rate is controlled at 80-200Nm 3 / h (which can inhibit side reactions, assist silicon powder fluidization, and control reaction temperature) to allow the activated silicon powder to react with hydrogen chloride to generate trichlorosilane.

[0081] Example 4

[0082] In order to further study the effect of the particle size and mass ratio of the cold hydrogenated outer cyclone silicon powder and the industrial silicon by-powder on the mixed silicon powder (i.e., activated silicon powder) after mechanical activation in this method, the method and steps described in Example 3 above were repeated by mixing the raw material combinations of the particle sizes shown in Table 1 at different mass ratios. The results are as follows: Figure 4 shown.

[0083] Table 1

[0084] Cold hydrogenated external cyclone silicon powder (μm) Industrial silicon by-product(μm) Sample 1 71.24 84.13 Sample 2 71.95 83.31 Sample 3 73.36 82.87 Sample 4 75.28 79.82 Sample 5 74.89 78.65 Sample 6 75.47 78.72 Sample 7 77.21 77.17 Sample 8 77.84 77.59 Sample 9 77.55 78.15 Sample 10 80.71 81.27

[0085] Depend on Figure 4 It can be seen that the median diameter of the mechanically activated mixed silicon powder and the cold hydrogenated external cyclone silicon powder is relatively high, both between 90-100 microns, and the median diameter of the industrial silicon by-powder is between 50-70 microns, both within the median diameter range of 80-120 microns required for trichlorosilane synthesis. Therefore, the mechanically activated mixed silicon powder meets the use requirements of silicon powder for trichlorosilane synthesis.

[0086] Example 5

[0087] As shown in Table 2, five groups of silicon powder after mechanical activation and silicon powder without mechanical activation in the method of the present invention were respectively taken and put into a trichlorosilane synthesis furnace for trichlorosilane synthesis reaction, wherein the silicon powder feed amount of each group of experiments was the same, which was 0.04 tons; the reaction conditions were the same, the bed height was controlled within 2.7 meters, the fluidized bed pressure difference was controlled at 30-40 KpaG, the temperature was controlled at 345-355°C, the pressure was controlled at 0.3-0.4 MPa, and the hydrogen chloride flow rate was controlled at 800 Nm 3 / h, the purity of hydrogen chloride is greater than 90%, and the hydrogen flow rate is controlled at 80-200Nm 3 / h, silicon powder reacts with hydrogen chloride to generate trichlorosilane. Figure 5 shown.

[0088] Table 2

[0089] Experimental data point number Median particle size (micrometers) Impurity content (%) 1 87.25 0.88 2 82.18 1.05 3 84.21 0.95 4 85.25 0.92 5 85.20 1.00 6 85.50 0.62 7 85.72 0.75 8 86.60 0.68 9 87.26 0.61 10 87.48 0.79

[0090] In this embodiment, there are five groups of mechanically activated silicon powder and five groups of non-mechanically activated silicon powder. The five groups are repeated experiments, which is equivalent to doing the same experiment five times, and the reaction conditions are the same.

[0091] Depend on Figure 5 It can be seen that the average conversion rate of silicon powder without mechanical activation is 87.06%, the highest is 89%, and the lowest is 85%. The average conversion rate of silicon powder with mechanical activation is 90.36%, the highest is 94.5%, and the lowest is 86.5%. Compared with silicon powder without mechanical activation, the trichlorosilane synthesis conversion rate of silicon powder after mechanical activation has been significantly improved.

[0092] It is to be understood that the above embodiments are merely exemplary embodiments used to illustrate the principles of the present invention, but the present invention is not limited thereto. For those of ordinary skill 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 recycling waste silicon powder produced in a cold hydrogenation process, characterized in that: include: The cold hydrogenated external cyclone silicon powder and the industrial silicon by-powder are mixed in a certain proportion, and mechanically activated, and then the impurities are separated to obtain the activated silicon powder; The activated silicon powder is put into a trichlorosilane synthesis furnace to react with hydrogen chloride to generate trichlorosilane.

2. The method for recycling waste silicon powder produced in the cold hydrogenation process according to claim 1, characterized in that: The mass ratio of the cold hydrogenated external cyclone silicon powder to the industrial silicon by-powder is 1:1 to 5:

1.

3. The method for recycling waste silicon powder produced in the cold hydrogenation process according to claim 1, characterized in that: The mechanical activation is specifically: The cold hydrogenated external cyclone silicon powder and the industrial silicon by-powder are introduced into the mechanical activation device evenly from the top in proportion, and the gas is introduced in the horizontal direction, so that the cold hydrogenated external cyclone silicon powder and the industrial silicon by-powder are driven by the airflow to move in the opposite direction in the horizontal direction to collide and rub.

4. The method for recycling waste silicon powder produced in the cold hydrogenation process according to claim 3, characterized in that: The total feed amount of the cold hydrogenated external cyclone silicon powder and the industrial silicon by-powder is controlled to be 1 / 3 to 1 / 2 of the volume of the mechanical activation device.

5. The method for recycling waste silicon powder produced in the cold hydrogenation process according to claim 3, characterized in that: The gas flow velocity entering the mechanical activation device is controlled to be 50-100 m / s, the gas flow pressure is controlled to be 0.6-0.8 MPa, and the temperature is controlled to be 30-280° C. After the feeding is completed, the mechanical activation device continues to operate for 5-10 minutes.

6. The method for recycling waste silicon powder produced in the cold hydrogenation process according to claim 1, characterized in that: The median particle size of the activated silicon powder is in the range of 80-120 μm.

7. A system for recycling waste silicon powder produced in a cold hydrogenation process, characterized in that: Including mechanical activation device, The mechanical activation device is connected to the cold hydrogenation external cyclone device and the industrial silicon grinding and screening device in the cold hydrogenation process, respectively, and is used to introduce the cold hydrogenation external cyclone silicon powder and the industrial silicon by-powder and mechanically activate them and separate impurities to obtain activated silicon powder; The mechanical activation device is also connected to the trichlorosilane synthesis furnace and is used to put the activated silicon powder into the trichlorosilane synthesis furnace to react with hydrogen chloride to generate trichlorosilane.

8. The system for recycling waste silicon powder produced in the cold hydrogenation process according to claim 7, characterized in that: The mechanical activation device comprises a tank body, on which a first feed inlet (16), a second feed inlet (17), and an air inlet (14) are arranged, and inside the tank body there are a first cyclone device, a second cyclone device, and a separation mechanism. The first feed port is provided with a first screw feeder (2), the first screw feeder is connected to the cold hydrogenation external cyclone device (1), the second feed port is provided with a second screw feeder (4), the second screw feeder is connected to the industrial silicon by-powder tanker (9), so as to control the cold hydrogenation external cyclone silicon powder and the industrial silicon by-powder to be uniformly introduced into the tank body of the mechanical activation device from the top in proportion, The air inlet is used to introduce gas, and an airflow accelerator is provided on the air inlet to control the airflow speed and pressure. The first cyclone device and the second cyclone device operate in opposite directions, so that the cold hydrogenated outer cyclone silicon powder and the industrial silicon secondary powder in the tank body move in the opposite direction in the horizontal direction driven by the airflow to collide and rub, thereby obtaining mixed silicon powder; The separation mechanism is arranged below the first cyclone device and the second cyclone device, and is used to separate impurities in the mixed silicon powder obtained after collision and friction to obtain activated silicon powder.

9. The system for recycling waste silicon powder produced in the cold hydrogenation process according to claim 8, characterized in that: The separation mechanism comprises a silicon powder classification component (7), a 10 micron aperture screen (12) and a vibration screening component (10). The vibration screening component is arranged at the bottom of the tank body, the 10-micron aperture screen is arranged above the vibration screening component, and the silicon powder classification component is arranged above the 10-micron aperture screen.

10. The system for recycling waste silicon powder produced in the cold hydrogenation process according to claim 8, characterized in that: The system further comprises a control unit (3), The control unit is electrically connected to one or more of the first screw feeder, the second screw feeder, and the airflow accelerator in the mechanical activation device, and is used to perform comprehensive real-time monitoring of the feed amount, airflow velocity, pressure, temperature, and particle size distribution parameters during the operation of the mechanical activation device, and automatically adjust in real time according to a preset computer program, and display the operating status in real time.

11. The system for recycling waste silicon powder produced in the cold hydrogenation process according to claim 10, characterized in that: The mechanical activation device also includes a temperature sensor and a cooling mechanism (11). The temperature sensor and the cooling mechanism are both electrically connected to the control unit to form a temperature detection and regulation system for monitoring and regulating the temperature in the tank of the mechanical activation device to ensure that it is within the optimal operating temperature range.

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