Application and device of recycled silicon powder in polycrystalline silicon production in ferrosilicon smelting

Abstract

The invention provides an application and a device of recycled silicon powder in polycrystalline silicon production in ferrosilicon smelting. High-purity fine silicon powder generated in the polycrystalline silicon production process is recycled and used for ferrosilicon smelting, resource utilization of industrial solid waste is achieved, and remarkable environmental protection and economic value is embodied. The high-purity silicon powder can be directly subjected to a solid-phase reduction reaction with iron oxide in furnace charge, so that the consumption of coke or other carbon sources is reduced, the emission of carbon dioxide is reduced, and the energy consumption required for reducing silica into silicon is also reduced. According to the scheme, complex impurity removal treatment is not needed, the silicon powder can participate in the reduction reaction through segmented blowing of the blast furnace tuyere, operation is easy and convenient, the source is stable, the quality uniformity of raw materials is guaranteed, and therefore the chemical component controllability and the smelting efficiency of silicon iron products are improved. The recycled silicon powder is small in particle size, large in specific surface area and high in reaction rate, the smelting time can be further shortened, and the overall production efficiency is improved.

Description

Technical Field

[0001] This invention relates to the field of metallurgy, and more particularly to the application and apparatus of recycled silicon powder in polycrystalline silicon production for ferrosilicon smelting. Background Technology

[0002] Polysilicon, as a fundamental core material in the semiconductor and photovoltaic industries, is directly related to the manufacturing of key products such as integrated circuits and solar cells. During the production of polysilicon using mainstream processes such as the Siemens process or fluidized bed process, a large amount of extremely fine silicon powder byproducts are inevitably generated by vapor deposition or reaction byproducts. With the continuous expansion of the global photovoltaic and semiconductor markets, polysilicon production is constantly increasing, and the total amount of fine silicon powder generated is also increasing daily. Effective treatment and resource utilization of this fine silicon powder has become an unavoidable issue for the industry.

[0003] The fine silicon powder generated during these production processes, typically in the micrometer range, is irregularly shaped, highly surface-active, and often contains trace impurities, making it unsuitable for direct return to the main process for polysilicon production. A more significant problem is its extremely high specific surface area and chemical activity, which makes it highly susceptible to oxidation and heat release in air. If mixed with air at specific concentrations, it poses a significant flammability and explosion risk, creating serious safety hazards in production, storage, and transportation. Therefore, this type of fine silicon powder is often treated as hazardous waste in industry. Currently, for technical and safety reasons, large quantities of fine silicon powder are passively disposed of through high-energy-consuming, low-value methods such as high-frequency furnace smelting for silicon recovery or special storage, further wasting silicon resources. As a high-purity strategic raw material, the preparation of fine silicon powder is energy-intensive and valuable; simply discarding it does not meet the requirements of a circular economy and sustainable development. The underutilization of its value leads to overall low resource efficiency in polysilicon production and increases raw material consumption and energy input in downstream smelting processes.

[0004] Therefore, there is an urgent need to find a safe, efficient and economical new way to utilize these fine silicon powders that have potential value but are difficult to reuse in polysilicon production, so as to reduce resource waste and environmental burden. Summary of the Invention

[0005] To address the aforementioned issues, this invention provides an application of recycled silicon powder from polysilicon production in ferrosilicon smelting. This application enables the recycled silicon powder to undergo a solid-phase reduction reaction with iron oxides, thereby utilizing the recycled silicon powder while reducing carbon dioxide emissions and silicon ore resource consumption.

[0006] The present invention also provides a ferrosilicon smelting apparatus. This apparatus uses recycled silicon powder as the main silicon source in ferrosilicon smelting, eliminating the need to use silicon ore resources such as silicon dioxide to generate silicon vapor through carbon reduction. This not only reduces carbon dioxide emissions and silicon ore resource consumption, but also shortens smelting time, reduces energy consumption, and improves production efficiency and product quality.

[0007] In a first aspect, the present invention provides an application of recycled silicon powder in polysilicon production in ferrosilicon smelting.

[0008] In one possible implementation, as described above, the ferrosilicon smelting comprises: subjecting a raw material system including the recycled silicon powder and iron oxide to a reduction reaction to obtain the ferrosilicon alloy.

[0009] In one possible implementation, as described above, the temperature of the reduction reaction is 1500-1600°C;

[0010] And / or, the reduction reaction is carried out using microwave heating;

[0011] And / or, the reduction reaction is carried out under the protection of an inert gas.

[0012] In one possible implementation, as described above, the recycled silicon powder has a purity greater than 99.9% and a Dv50 median particle size of 20-100 μm, more specifically 20-50 μm.

[0013] And / or, the raw material system may also include auxiliary materials containing rare earth elements.

[0014] In one possible implementation, as described above, the raw material system includes a core material comprising a core and a coating layer disposed on at least a portion of the surface of the core, the core comprising the iron oxide and the coating layer comprising the recycled silicon powder.

[0015] In one possible implementation, as described above, the product of the reduction reaction further includes silicon-containing slag, wherein the silicon-containing slag contains 40%-60% silicon dioxide by mass.

[0016] It also includes the step of returning the silicon-containing slag to participate in the reduction reaction; the mass ratio of the recovered silicon powder to the silicon-containing slag is (1:8)-(1:10).

[0017] In a second aspect, the present invention provides a ferrosilicon smelting apparatus, comprising a silicon powder storage tank and a reduction reactor, wherein the silicon powder storage tank is used to store the recovered silicon powder from the silicon powder collection device, and the reduction reactor is used to conduct the reduction reaction of the raw material system to obtain the ferrosilicon alloy.

[0018] The silicon powder collection outlet of the silicon powder collection device is connected to the silicon powder storage inlet of the silicon powder storage tank, and the silicon powder storage outlet of the silicon powder storage tank is connected to the silicon powder inlet of the reduction reactor.

[0019] In one possible implementation, the apparatus as described above further includes a slag recycling unit, wherein the slag recycling inlet of the slag recycling unit is connected to the slag outlet of the reduction reactor, and the slag recycling outlet of the slag recycling unit is connected to the slag outlet of the reduction reactor.

[0020] And / or, it also includes a reaction monitoring unit, the reaction monitoring unit including at least one temperature sensor disposed inside the reduction reactor, at least one pressure sensor disposed on the top of the reduction reactor, and a sampling analyzer connected to the slag outlet and molten iron outlet of the reduction reactor.

[0021] In one possible implementation, the apparatus as described above further includes a feed control unit, wherein the iron oxide outlet of the feed control unit is connected to the iron oxide inlet of the reduction reactor, the coke outlet of the feed control unit is connected to the coke inlet of the reduction reactor, the pulverized coal outlet of the feed control unit is connected to the pulverized coal inlet of the reduction reactor, and the flux outlet of the feed control unit is connected to the flux inlet of the reduction reactor.

[0022] In one possible implementation, the apparatus as described above further includes a blower unit, the gas inlet of which is connected to the gas outlet of the reduction reactor, and the hot air outlet of which is connected to the hot air inlet of the reduction reactor.

[0023] This invention achieves the resource utilization of industrial solid waste by recovering high-purity fine silicon powder generated during polysilicon production and using it in ferrosilicon smelting, demonstrating significant environmental and economic value. High-purity silicon powder can directly undergo a solid-phase reduction reaction with iron oxides in the furnace charge, thereby reducing carbon source consumption, lowering carbon dioxide emissions, and reducing the energy required to reduce silica to silicon. This method eliminates the need for complex impurity removal treatment; the silicon powder can participate in the reduction reaction through segmented injection at the blast furnace tuyeres. The operation is simple and the source is stable, ensuring uniform raw material quality and improving the controllability of the chemical composition of ferrosilicon products and smelting efficiency. The recovered silicon powder has a small particle size and large specific surface area, resulting in a fast reaction rate, which can further shorten smelting time and improve overall production efficiency. In summary, this invention not only achieves the resource utilization of recovered silicon powder, reducing mineral and energy consumption, but also reduces greenhouse gas emissions, demonstrating significant economic benefits and environmental advantages. Attached Figure Description

[0024] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with the invention and, together with the description, serve to explain the principles of the invention.

[0025] Figure 1 A schematic diagram of the ferrosilicon smelting apparatus provided by the present invention.

[0026] Explanation of reference numerals in the attached drawings: 1-Reduction reactor; 2-Silicon powder storage tank; 3-Silicon powder collection device; 4-Feed control unit; 5-Slag recycling unit; 6-Blower unit.

[0027] The accompanying drawings have illustrated specific embodiments of the invention, which will be described in more detail below. These drawings and descriptions are not intended to limit the scope of the invention in any way, but rather to illustrate the concept of the invention to those skilled in the art through reference to particular embodiments. Detailed Implementation

[0028] Exemplary embodiments will now be described in detail, examples of which are illustrated in the accompanying drawings. When the following description relates to the drawings, unless otherwise indicated, the same numerals in different drawings denote the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with the present invention. Rather, they are merely examples of apparatuses and methods consistent with some aspects of the invention as detailed in the appended claims.

[0029] The technical solution of the present invention and how the technical solution of the present invention solves the above-mentioned technical problems are described in detail below with specific embodiments. These specific embodiments can be combined with each other, and the same or similar concepts or processes may not be described again in some embodiments. The embodiments of the present invention will now be described with reference to the accompanying drawings.

[0030] High-purity silicon powder from existing polysilicon production is often discarded or used for low-value purposes after collection, such as in landfills or as building filler, leading to resource waste. On the other hand, existing ferrosilicon smelting technology mainly relies on the carbothermic reduction method, which uses coke or coal as a reducing agent to reduce silicon dioxide to silicon at high temperatures, and then reacts with iron oxides to form a ferrosilicon alloy. This process requires a large amount of carbon source, resulting in significant carbon dioxide emissions. Furthermore, the reduction of silicon dioxide to silicon consumes a large amount of electrical or thermal energy, requiring furnace temperatures to be maintained at 1500-2000℃, with smelting cycles lasting several hours, resulting in high overall energy consumption, long smelting time, and low efficiency. In addition, existing technologies have high requirements for raw materials, requiring pretreatment of silica to remove impurities, increasing process complexity and waste generation. Based on these problems, the inventors propose recovering the high-purity fine silicon powder generated during polysilicon production and using it for ferrosilicon smelting. The recovered high-purity silicon powder can directly undergo a solid-phase reduction reaction with iron oxides in the furnace charge, thereby reducing the consumption of carbon sources and silicon ore resources. Furthermore, high-purity fine silicon powder does not require impurity removal, which reduces the introduction of impurities. At the same time, due to its small particle size, large specific surface area, and fast reaction rate, it can further shorten the smelting time and improve the overall production efficiency.

[0031] To address the above problems, this invention provides an application and apparatus for recycled silicon powder in polysilicon production and ferrosilicon smelting, as detailed below:

[0032] In a first aspect, the present invention provides an application of recycled silicon powder in polysilicon production in ferrosilicon smelting.

[0033] In one possible embodiment, as described above, high-purity silicon powder can directly react with iron oxides in the furnace charge under high-temperature conditions in a blast furnace. Compared to the traditional method of reducing silicon dioxide to generate silicon vapor using a carbon source, this reduces the amount of carbon source added and carbon dioxide emissions. This reaction process does not require the energy consumed in reducing silicon dioxide to generate silicon vapor, resulting in a faster reaction rate, which helps shorten smelting time and reduce energy consumption per unit product. The small particle size and large specific surface area of ​​silicon powder give it higher reactivity in the high-temperature region of the hearth, enabling it to participate in the reduction reaction without significantly increasing the furnace temperature load. This provides a fundamental condition for its application in existing blast furnace systems.

[0034] In one possible embodiment, as described above, multiple steps in the polysilicon production process generate silicon powder byproducts in various forms, which are important sources of recycled silicon powder. For example, polysilicon produced by the modified Siemens process is mainly in rod-shaped polysilicon form. After being formed, the rod-shaped silicon needs to be water-quenched and then crushed, sieved, and packaged. A certain amount of fine silicon powder is also generated during jaw crushing and sieving. In the reduction process, high-temperature resistant and highly conductive graphite chucks are typically used in the reduction furnace to connect the silicon core, forming inverted "U"-shaped silicon rods and maintaining a high-temperature reaction environment. At a high temperature of approximately 1100°C, trichlorosilane reacts with hydrogen to generate crystalline silicon. The resulting polysilicon not only deposits on the surface of the silicon core to form silicon rods but also deposits on the surface of the graphite chucks. This portion of polysilicon deposited on the graphite chucks, along with the silicon material with graphite impurities adhering to its surface, is called carbon head material. The carbon head material is usually crushed and separated using tools or equipment. During this mechanical crushing and sorting process, fine silicon powder with small particle sizes is inevitably generated. The silicon powder produced by the above process has the characteristics of stable source and high purity, making it suitable for subsequent resource utilization.

[0035] In one possible embodiment, as described above, the silicon powder generated during the polysilicon crushing process can be centrally recovered using a closed collection hood, a negative pressure dust removal system, or a bag filter. To ensure the usability of the recovered silicon powder, a screening or grading unit can be installed after collection to control the particle size and meet the requirements for injection or feeding. The collected silicon powder can be stored in a sealed silo and then fed into the ferrosilicon smelting unit via a screw conveyor, pneumatic conveyor, or other means. Since the silicon powder originates from polysilicon production, its chemical composition is relatively stable, and it can usually be directly used in subsequent processes without complex impurity removal treatment, thereby reducing processing costs.

[0036] In one possible embodiment, as described above, recycled silicon powder can be introduced into the blast furnace through segmented injection at the tuyeres to directly react with iron oxides to obtain ferrosilicon alloy. This avoids the uneven distribution and reaction lag problems associated with traditional solid charge additions. The injection method allows the silicon powder to directly enter the hearth or lower reaction zone, ensuring sufficient contact with the iron oxides and melt, thus improving the efficiency of the solid-phase reduction reaction. Simultaneously, by coordinating the adjustment of the hot blast stove temperature, air volume, and injection rate, the reaction rhythm of the silicon powder can be effectively controlled, ensuring thermal balance and stable melt circulation within the furnace, thereby preserving the existing blast furnace operating system. This application, compatible with existing blast furnaces, significantly lowers the technological transformation threshold, demonstrating good engineering feasibility and economic efficiency.

[0037] In one possible embodiment, as described above, recycled silicon powder can be used as an auxiliary charge, mixed with a portion of recycled slag in a certain proportion and then reintroduced into the furnace to dynamically adjust the composition of the slag and ferrosilicon alloy. Silicon powder has a fine particle size and large specific surface area, allowing it to rapidly participate in the slag phase melting and composition homogenization process under high-temperature conditions, making the slag basicity and structure more stable, thereby maintaining a reasonable liquid slag layer thickness and fluidity. This method effectively avoids slagging, furnace sticking, or reaction imbalance problems caused by fluctuations in slag composition, while simultaneously enabling the reuse of recycled slag and reducing the consumption of fresh slag-forming raw materials. In the final reaction stage of the hearth, molten iron, slag, and coke come into full contact, completing the final formation and compositional balance of the ferrosilicon alloy. Recycled silicon powder can primarily serve as a highly reactive silicon source in this stage, allowing for precise control of the silicon content in the molten iron. By controlling the amount of silicon powder injected or its proportion added with the charge, compensation or adjustment of the silicon content can be achieved without significantly increasing the hearth temperature. Compared to directly adding bulk quartz or silica, silicon powder reacts faster and can be adjusted more precisely, which helps to improve the controllability of the smelting process and overall energy efficiency, while also ensuring process stability and product quality.

[0038] In one possible embodiment, as described above, a closed powder storage silo, screw feeder, or loss-in-weight metering feeder can be used to achieve moisture-proof storage and accurate metering of recovered silicon powder. For silicon powder with fine particle size and poor flowability, a vibration arch-breaking or pneumatic loosening device can be configured. Depending on the application, a pneumatic conveying system and a spray gun assembly can be selected to quantitatively spray silicon powder into a specific temperature zone inside the furnace, or it can be added after pre-mixing with lumpy furnace charge via belt conveyor and mixer. The spray system can be connected to the electric furnace through a reserved interface on the furnace side wall or furnace top, and with the high-temperature resistant spray gun and sealing structure, air leakage and dust escape can be reduced. The solid furnace charge feeding system can be directly connected to existing feeding chutes or furnace top feeding devices, with strong compatibility. The silicon powder feeding amount, feeding sequence, and spray carrier gas flow rate can also be linked and controlled by a PLC or DCS system, and dynamically adjusted in conjunction with online detection data of furnace temperature, electrode load, and slag composition. Through reasonable equipment and system integration, not only can the stable and safe resource utilization of recycled silicon powder in ferrosilicon smelting be guaranteed, but also the fine control of reaction efficiency, silicon recovery rate and furnace condition stability can be achieved.

[0039] In one possible embodiment, as described above, ferrosilicon smelting includes: subjecting a raw material system comprising recycled silicon powder and iron oxide to a reduction reaction to obtain a ferrosilicon alloy.

[0040] In this embodiment, the recycled silicon powder possesses high activity, high specific surface area, and low reaction diffusion resistance. Under high-temperature conditions, it can serve as an effective reduction participant or reaction promoter, undergoing direct or indirect reduction-alloying reaction pathways with iron oxides. On one hand, silicon powder readily forms localized silicon-rich reaction zones with iron oxides at high temperatures, lowering the reduction reaction barrier of iron oxides and accelerating the reaction kinetics. On the other hand, the generated liquid or semi-liquid ferrosilicon mesophase facilitates the dissolution and diffusion of silicon into iron, thereby improving the effective utilization rate of silicon. Compared to traditional smelting methods that primarily use blocky silicon raw materials or high-silicon furnace charges, this method reduces reaction scale mismatch and limited mass transfer problems, making the reduction reaction more uniform and controllable. The participation of silicon powder in the reaction can also balance the reaction heat distribution within the furnace to a certain extent, improving furnace stability and providing greater adjustment space for controlling the composition of ferrosilicon alloys, demonstrating significant technical feasibility and industrial application advantages.

[0041] In one possible embodiment, as described above, specifically, recycled silicon powder and iron oxide can be metered in a certain proportion to form a stable raw material system. A closed storage silo combined with a loss-in-weight metering feeder can be used to precisely control the silicon powder and iron oxide separately. A premixing method can be employed, for example, using a twin-shaft mixer or continuous mixing equipment, to uniformly disperse the recycled silicon powder on the surface of the iron oxide particles, and then feed it into the blast furnace via a screw conveyor or pneumatic conveyor. The mixed raw material can be fed into the ferrosilicon smelting electric furnace through an existing electric furnace charging system for co-smelting with conventional furnace materials. Alternatively, a jet-type charging method can be used, with injection ports installed near the blast furnace sidewall or top, continuously or intermittently feeding the recycled silicon powder into the high-temperature reaction zone via carrier gas. Furthermore, the silicon powder feeding amount, charging rhythm, and key furnace parameters can be linked and adjusted via PLC or DCS. Through linkage control with furnace temperature, electrode power, and furnace gas composition monitoring, it can flexibly adapt to different furnace conditions, achieving precise control of the ferrosilicon alloy composition and stable operation of the smelting process.

[0042] In one possible embodiment, as described above, the reduction reaction is carried out at a temperature of 1500-1600°C.

[0043] In this embodiment, due to the large specific surface area and high reactivity of silicon powder, silicon exhibits a sufficiently strong reducing ability towards iron oxides within this temperature range, resulting in a negative reaction free energy change and a spontaneous reaction. Simultaneously, the solubility of silicon in iron is significantly increased, which is beneficial for the formation of a stable ferrosilicon alloy phase. Secondly, this temperature range significantly enhances the diffusion rate at the solid-liquid or liquid-liquid interface, lowers the activation energy, and makes the reaction between silicon powder and iron oxides more rapid and complete, avoiding the problems of reaction stagnation or incomplete reduction at low temperatures. Compared with traditional higher-temperature smelting methods (e.g., 1800-1900℃), energy consumption is significantly reduced in this temperature range, decreasing electricity or coke consumption and helping to lower unit product energy consumption and production costs. Furthermore, the reduced heat load on high-temperature components such as furnace linings and electrodes helps extend equipment lifespan and improve operational stability. In addition, within the milder high-temperature range, the risk of silicon powder volatilization and secondary oxidation is reduced, contributing to increased silicon yield. In industrial practice, it takes into account reaction efficiency, energy consumption control and equipment reliability, demonstrating obvious technical characteristics linkage and comprehensive economic advantages.

[0044] In one possible embodiment, as described above, a submerged arc furnace or a closed electric furnace is specifically selected as the smelting equipment. The heat distribution within the furnace is precisely controlled by the electrode input power, ensuring the temperature of the main reaction zone is stably maintained within the target range. Simultaneously, a hot blast stove or preheating system is used to preheat the combustion gas or carrier gas entering the furnace, reducing the additional heating burden within the furnace. Real-time feedback adjustment of the furnace temperature is achieved through online temperature detection devices (such as infrared thermometers or thermocouples) linked to electrode power and injection volume control. Through the aforementioned equipment and process control, a reduction reaction at 1500–1600℃ can be reliably achieved under industrial conditions, ensuring the continuity and controllability of the ferrosilicon smelting process.

[0045] In one possible embodiment, as described above, the reduction reaction is carried out using microwave heating.

[0046] In this embodiment, the recovered silicon powder, iron oxides, and carbon-containing components typically possess certain dielectric loss characteristics. Especially in high-temperature or mixed systems, they can effectively absorb microwave energy and rapidly heat up, thereby forming an internal heat source within the reaction particles. This heating method helps to overcome the temperature gradient limitation of traditional outside-to-inside heat transfer, significantly improving the start-up speed and reaction uniformity of the reduction reaction. Compared with traditional high-temperature furnace heating methods, microwave heating also enables rapid start-up and shutdown and precise power adjustment, facilitating matching with segmented feeding and staged reactions. Simultaneously, the furnace wall and refractory materials experience lower heating levels, helping to extend equipment life and reduce maintenance costs. Furthermore, microwave heating is particularly beneficial for fine-particle silicon powder, reducing volatilization, oxidation, or burn-off problems caused by prolonged high-temperature exposure. In summary, using microwave heating for reduction reactions demonstrates significant advantages in energy efficiency, reaction controllability, and silicon resource utilization, exhibiting clear engineering application advantages.

[0047] In one possible embodiment, as described above, microwave heating can be used as an independent unit in the ferrosilicon smelting process or as a composite heating system with a traditional electric furnace. For example, recycled silicon powder and iron oxide are mixed or pre-formed according to a set ratio and then fed into a sealed reaction chamber equipped with an industrial-grade microwave source. The reaction chamber is lined with a microwave-transparent and high-temperature-resistant ceramic material to avoid energy shielding and structural overheating. By adjusting the microwave output power and duration, the reactant system is rapidly heated to the temperature range required for the reduction reaction, and the reduction of iron oxide by silicon is completed under the action of the microwave field. In addition, the microwave power module can be linked with temperature sensors, atmosphere monitoring, and the feeding system to achieve closed-loop control, ensuring reaction uniformity and safety.

[0048] In one possible embodiment, as described above, the reduction reaction is carried out under the protection of an inert gas.

[0049] In this embodiment, due to the small particle size, large specific surface area, and high surface activity of the recovered silicon powder, it is highly susceptible to side reactions with oxygen or water vapor at high temperatures, generating silicon dioxide, resulting in the loss of effective silicon and reducing reduction efficiency. By introducing an inert gas (e.g., nitrogen or argon) to create a low oxygen partial pressure environment, the high-temperature oxidation of silicon powder can be significantly suppressed, ensuring that silicon preferentially participates in the target reduction reaction, thereby improving silicon utilization and reaction selectivity. In an inert atmosphere, the oxygen partial pressure of the system is controlled at a low level, which is conducive to the reduction of iron oxides to lower valence states or even metallic iron, while reducing reverse oxidation reactions caused by the participation of ambient oxygen. Under these conditions, the reduction reaction between silicon and iron oxides is closer to the ideal reaction path, and the by-product silicon dioxide mainly comes from the reaction itself rather than from environmental introduction, which is beneficial to the stable control of slag composition. The inert gas also plays a role in isolating air, uniformly transferring heat and mass, and avoiding uneven reaction or sintering caused by local oxygen enrichment. For processes using jet blowing or fine powder feeding methods, inert gas protection can reduce premature oxidation and fly-through of silicon powder before it enters the high-temperature zone, and increase the proportion of powder that effectively enters the reaction zone.

[0050] In one possible embodiment, as described above, the reduction reactor can specifically employ a closed or semi-closed structure. An inert gas, such as argon or nitrogen, is introduced into the silicon powder blowing zone, pre-reaction zone, or microwave / electrically heated reaction chamber to replace air and maintain a low oxygen partial pressure environment. The inert gas can enter through an independent gas source pipeline, arranged coaxially or in parallel with the feeding system or blowing system to achieve continuous protection of the reaction area. In the blowing feeding process, the inert gas can be used as a carrier gas for recovering silicon powder or separated from the blower air, ensuring the silicon powder is coated with inert gas before entering the high-temperature zone, thereby reducing oxidation along the process. In the premixed feeding process, inert gas pre-purging can be performed before the reaction, and inert gas is continuously replenished during the reaction, with pressure balance controlled through the exhaust port. To ensure stable gas composition, an online oxygen content detector can be configured to form a closed-loop control with the inert gas flow regulating valve. When an abnormally high oxygen content is detected, the system automatically increases the inert gas supply or adjusts the exhaust volume to achieve stable and reliable inert gas protection, thereby improving silicon utilization and reaction stability.

[0051] In one possible embodiment, as described above, the purity of the recycled silicon powder is greater than 99.9%; the median Dv50 particle size is 20-100 μm, and more specifically 20-50 μm.

[0052] In this embodiment, since the silicon powder generated during the polysilicon production process is itself a high-purity silicon product, its impurity control system is mature, and the content of harmful elements such as metallic impurities, boron, and phosphorus is extremely low. High-purity silicon powder can be obtained through physical recovery and classification. High-purity silicon powder can effectively avoid the accumulation of impurity elements in ferrosilicon alloys, reducing the adverse effects on alloy composition, mechanical properties, and subsequent refining processes, which is especially beneficial for the stable production of high-quality ferrosilicon or specific grades of products. At the same time, low impurity content means fewer side reactions and more controllable slag composition, which helps to reduce flux consumption and process fluctuations. In addition, in terms of particle size, the specific surface area of ​​recycled silicon powder with a median particle size of 20–100 μm in Dv50 is significantly higher than that of block silicon or coarse-particle raw materials, which is conducive to sufficient contact with iron oxides at high temperatures, shortening the diffusion path and accelerating the solid-phase or liquid-phase reduction reaction kinetics. At the same time, it avoids the problems of severe scattering, large transportation losses, and increased safety risks caused by excessively fine particle size (e.g., median particle size of Dv50 less than 10 μm). Further optimizing the median particle size of Dv50 to 20-50μm can achieve a better balance between reaction rate, injection stability and material deposition behavior, taking into account both reactivity and process operability.

[0053] In one possible embodiment, as described above, the recovered silicon powder primarily originates from reduction deposition, crushing and sorting, and manual sorting processes, and is collected centrally by bag filters or cyclone dust collectors. To ensure purity, the equipment lining and conveying path can be specially designed before collection to avoid direct friction with metal parts and reduce secondary pollution. The collected silicon powder can be particle size controlled using physical sieving, airflow classification, or multi-stage cyclone separation. By adjusting the classification wind speed and the number of separation stages, the Dv50 can be stabilized within the range of 20–100 μm, and further fine classification can be used to obtain an optimal particle size of 20–50 μm. For any graphite or trace impurities that may be entrained, low-intensity magnetic separation, gravity separation, or surface cleaning processes can be used for removal without complex chemical purification. The final silicon powder, after being confirmed by an online particle size analyzer and chemical composition sampling, is stored in a sealed silo and then transported to the ferrosilicon smelting system. By combining the above processes, recycled silicon powder that meets the purity and particle size requirements can be stably obtained without significantly increasing costs, enabling large-scale and continuous application.

[0054] In one possible embodiment, as described above, the raw material system further includes auxiliary materials containing rare earth elements.

[0055] In this embodiment, the metallurgical role of rare earth elements in iron-based alloys has been widely verified. Their high chemical activity and strong deoxidizing, desulfurizing, and modifying capabilities enable them to preferentially react with impurity elements such as oxygen and sulfur in high-temperature smelting environments, thereby improving the thermodynamic conditions and reaction pathways of the system. Rare earth elements are used as reaction regulators and microstructure modifiers, synergistically recovering silicon powder to participate in the formation of ferrosilicon alloys. Rare earth elements have a strong affinity for oxygen, preferentially consuming residual oxygen in the system during the initial reduction phase, reducing local oxygen partial pressure, and thus creating a more favorable environment for the reduction reaction of silicon with iron oxides. This pre-purification effect helps improve the effective utilization rate of silicon and reduce losses due to non-target oxidation. Simultaneously, rare earth oxides, after formation, mostly enter the slag phase, optimizing the slag structure, improving slag fluidity and stability, and indirectly enhancing the controllability of the smelting process. From the perspective of product performance, the addition of appropriate amounts of rare earth elements to ferrosilicon alloys or molten iron can refine silicon grains, purify inclusions, and improve alloy uniformity. This is beneficial for improving the intrinsic quality and subsequent performance of ferrosilicon alloys, and further amplifies the comprehensive advantages of recycling silicon powder resources.

[0056] In one possible embodiment, as described above, the rare earth-containing auxiliary material can be selected in the form of rare earth metals, rare earth alloys, or rare earth oxides, such as lanthanum, cerium, or their oxides, with the addition method and amount determined based on the target product and process conditions. For the spray-feed process, the rare earth-containing material can be co-sprayed with silicon powder or sprayed in stages to ensure uniform dispersion in the reaction zone. Furthermore, the rare earth auxiliary material can also be in powder or fine particle form, premixed with recycled silicon powder and iron oxides, or added to the furnace in the early or middle stages of the reduction reaction via an independent feeding device. To avoid excessive oxidation or burn-off of rare earth elements, feeding can be carried out under inert gas protection, and its addition location should be controlled close to the high-temperature reduction zone to ensure rapid participation in the reaction. The addition amount can be controlled experimentally or empirically within the range of ppm to kilo-grade to leverage its metallurgical advantages without significantly increasing costs.

[0057] In one possible embodiment, as described above, the raw material system includes a core material comprising a core and a coating layer disposed on at least a portion of the surface of the core, the core comprising iron oxide and the coating layer comprising recycled silicon powder.

[0058] In this embodiment, the core-shell structure is essentially an interface engineering design for solid-phase or high-temperature reduction reactions. By pre-constructing the reactant contact interface at the microscale, the reaction conditions between silicon and iron oxide are significantly improved. Since the reduction reaction of silicon to iron oxide mainly occurs at the contact interface, in traditional processes, the silicon source and iron oxide often exist in a mixed state, with random and uneven contact, easily limited by factors such as long diffusion distances and insufficient local reactions. However, by directly coating the surface of iron oxide particles with recycled silicon powder, the diffusion path of silicon to iron oxide can be significantly shortened, allowing the reaction to occur synchronously at the particle scale in the early stages of heating, thereby accelerating the reduction rate and improving reaction completeness. This core-shell structure facilitates the formation of a high silicon activity environment locally, suppressing the consumption of silicon by external oxygen or oxidizing components in the slag, allowing silicon to preferentially participate in the target reduction reaction. Simultaneously, the silicon powder coating layer can rapidly soften or partially melt upon heating, forming a continuous reaction interface, which helps reduce the reaction initiation temperature and overall energy consumption.

[0059] In one possible embodiment, as described above, the core-shell structure can be prepared using mature powder composite and molding technologies. For example, iron oxide particles with a suitable particle size (e.g., a median Dv50 particle size of 200-400 μm) are selected as the core. Recycled silicon powder is mixed with the core in a set ratio, and under mechanical mixing, drum granulation, or high-speed stirring conditions, the silicon powder is uniformly adhered to the surface of the iron oxide particles by electrostatic action, mechanical embedding, or the action of a small amount of binder, forming a coating layer. To improve the coating stability, a small amount of organic binder that can decompose or burn out at high temperatures can be introduced, or inorganic salts can be used as a temporary binder phase, leaving no harmful impurities during subsequent heating. The obtained core-shell structure particles can be further dried and sieved to obtain a particle size range suitable for injection or in-furnace feeding. The raw material for this core-shell structure can be added to the ferrosilicon smelting furnace through a conventional feeding port, injection system, or pre-reaction unit, improving silicon utilization efficiency and reaction rate without significant modifications to the main furnace structure.

[0060] In one possible embodiment, as described above, the product of the reduction reaction further includes silicon-containing slag, wherein the silicon-containing slag contains 40%-60% silicon dioxide by mass; and further includes the step of returning the silicon-containing slag to participate in the reduction reaction; the mass ratio of the recovered silicon powder to the silicon-containing slag is (1:8)-(1:10).

[0061] In this embodiment, after the recovered silicon powder undergoes a reduction reaction with iron oxides, some silicon inevitably reacts with oxygen to transform into silicon dioxide, which enters the slag phase. Returning this silicon-containing slag to participate in the reduction reaction creates a stable silicon oxide chemical buffer environment within the system, helping to maintain the continuity of slag acidity and chemical composition and avoiding slag fluctuations caused by frequent additions of fresh flux. Especially when the silicon dioxide content is controlled at 40%-60%, the slag maintains good chemical activity and possesses adjustable melting point and viscosity, making it suitable for synergistic effects with newly added silicon powder in high-temperature zones. The recovered silicon powder and silicon-containing slag are mixed at a mass ratio of (1:8)-(1:10), with the silicon-containing slag acting as a stable phase to dilute locally highly active silicon powder, preventing severe oxidation or loss. Simultaneously, the reaction at the interface between silicon powder and slag at high temperatures helps promote the migration and redistribution of oxygen in the slag, providing favorable conditions for further reduction of iron oxides. This process ensures the reactivity of silicon powder without significantly increasing slag viscosity, which helps maintain good melt flowability and reduces the cost of frequent flux additions.

[0062] In one possible embodiment, as described above, a slag diversion and recycling unit can be set up in the ferrosilicon smelting system. After the high-temperature reaction, the discharged silicon-containing slag is cooled, crushed, and screened to select slag portions with the required composition and particle size as recycled slag. Through online or offline chemical composition analysis, the silica content is confirmed to be within the target range of 40%-60%. The recycled slag can be premixed with recycled silicon powder at a mass ratio of (1:8)-(1:10) in an independent mixing device to form a uniform composite charge, which is then fed into the reduction reaction zone through a conventional feeding port or a blowing system. For the blowing process, the slag can be pre-formed into particles of suitable size to improve conveying stability; for block or shaped material processes, the composite charge can be formed into lumps or core-shell structures before being added to the furnace. Furthermore, by monitoring slag composition, adjusting the feeding ratio, and linking it with furnace temperature and pressure parameters, the influence of recycled slag on the main reaction can be ensured to be within a controllable range, thereby improving silicon resource utilization and reaction stability.

[0063] Secondly, the present invention provides a ferrosilicon smelting apparatus, comprising a silicon powder storage tank and a reduction reactor. The silicon powder storage tank is used to store recycled silicon powder from a silicon powder collection device, and the reduction reactor is used for a reduction reaction of the raw material system to obtain a ferrosilicon alloy. The silicon powder collection outlet of the silicon powder collection device is connected to the silicon powder storage inlet of the silicon powder storage tank, and the silicon powder storage outlet of the silicon powder storage tank is connected to the silicon powder inlet of the reduction reactor.

[0064] In one possible embodiment, as described in the above-described apparatus, the recovered silicon powder from the polysilicon production process is characterized by small particle size, adjustable flowability, and high chemical activity, making it suitable for centralized collection, sealed storage, and quantitative transportation in powder form. The silicon powder collection device itself possesses stable gas-solid separation capabilities, and its silicon powder collection outlet is typically located under negative or slightly positive pressure, naturally suitable for sealed connection with downstream storage units. By connecting this outlet to the silicon powder storage inlet of the silicon powder storage tank, silicon powder can be directly transferred without exposure to air, avoiding secondary dust and oxidation risks. Simultaneously, the silicon powder storage tank plays a core role in the apparatus, acting as a buffer, metering unit, and stabilizing the supply. Since the reduction reaction in the ferrosilicon smelting process requires continuous and controllable silicon source supply, directly rigidly connecting the silicon powder collection device to the reduction reactor is not advisable. By setting up an independent silicon powder storage tank, the silicon powder generation process and the smelting process can be decoupled on a time scale, allowing the recovered silicon powder to accumulate stably and be continuously or intermittently output according to the smelting rhythm.

[0065] In this embodiment, the silicon powder storage outlet of the silicon powder storage tank is connected to the silicon powder inlet of the reduction reactor, allowing the recovered silicon powder to be directly used as a raw material in the reduction reaction to participate in the ferrosilicon alloy formation process. Since the silicon powder has undergone centralized collection and controlled storage before entering the reduction reactor, its physical state, particle size distribution, and supply rate can be precisely adjusted, thereby enabling the silicon powder to form a stable and predictable reaction behavior with iron oxides within the reaction zone. This three-stage "source-tank-furnace" structure is beneficial for maximizing silicon utilization under high-temperature smelting conditions.

[0066] In one possible embodiment, as described above, the silicon powder collection device can specifically employ a cyclone separator, a bag filter, an electrostatic precipitator, or a combination of multiple filtration systems. Preferably, a bag filter is used, with its inlet connected to the crushing, sorting, or pulverizing process in polysilicon production to collect the fine silicon powder generated during production. The silicon powder collection outlet of the bag filter is located at the bottom of its hopper and is equipped with a star-shaped discharge valve or a double-flap valve for airtight unloading.

[0067] In one possible embodiment, as described above, the silicon powder storage tank can specifically adopt a vertical, sealed silo structure with a silicon powder storage inlet at the top, connected to the silicon powder collection outlet of the silicon powder collection device via a flange or flexible connecting pipe. A flexible compensation structure can be installed at this connection to absorb equipment vibration and ensure sealing. An arch-breaking device or vibration device can be configured inside the silicon powder storage tank to prevent silicon powder bridging and arching. A conical discharge section is provided at the bottom of the tank as the silicon powder storage outlet. The silicon powder storage outlet and the silicon powder inlet of the reduction reactor can be connected via a screw conveyor, pneumatic conveying pipeline, or injection pipeline. For embodiments using an injection process, the silicon powder storage outlet is connected to the metering unit of the injection system, and the silicon powder, under the action of a carrier gas (air, inert gas, or a combination thereof), is fed into the high-temperature reaction zone of the reduction reactor via the injection pipeline. For non-injection processes, the silicon powder can be directly fed into the reactor's feed port via a sealed screw feeder.

[0068] In one possible embodiment, as described above, the reduction reactor can specifically be a blast furnace, electric furnace, or other reaction apparatus suitable for ferrosilicon smelting. Its silicon powder inlet can be located on the furnace side wall, in the tuyeres area, or in a dedicated feeding channel, and is sealed to the silicon powder conveying pipeline. To achieve precise control, a weighing and feeding device can be installed between the silicon powder storage tank and the reactor to achieve real-time adjustment of the silicon powder supply. Each unit can operate in conjunction with a centralized control system: the operating status of the silicon powder collection device determines the feeding rhythm of the silicon powder storage tank, and the material level signal of the silicon powder storage tank is fed back to the feeding system to adjust the rate at which silicon powder is supplied to the reduction reactor. Through the above equipment selection and connection methods, the device of this invention can operate stably under existing industrial conditions, achieving closed-loop transportation and efficient utilization of recovered silicon powder from generation to consumption.

[0069] In one possible embodiment, the apparatus as described above further includes a slag recycling unit, wherein the slag recycling inlet of the slag recycling unit is connected to the slag outlet of the reduction reactor, and the slag recycling outlet of the slag recycling unit is connected to the slag outlet of the reduction reactor.

[0070] In this embodiment, the slag recycling unit is located on the slag discharge path of the reduction reactor. Its slag recycling inlet is connected to the slag outlet of the reduction reactor via a high-temperature, abrasion-resistant connecting pipe, allowing the high-temperature slag generated during the reduction reaction to directly enter the slag recycling unit under gravity or auxiliary conveying. After processing by the slag recycling unit (e.g., crushing, screening, alkali adjustment), the slag is reconnected to the slag outlet or slag return interface of the reduction reactor via the slag recycling outlet, enabling at least a portion of the slag to re-enter the reduction reactor to participate in subsequent reduction reactions or serve as a molten medium in the reaction system. Through this closed-loop connection structure, the slag forms a controllable circulation path between the reduction reactor and the slag recycling unit, rather than being discharged all at once. This structure fully utilizes the sensible heat and chemical composition advantages carried by the slag. On the one hand, the direct recycling of high-temperature slag into the reduction reactor can reduce the energy consumption for heating newly added materials and lower the overall energy consumption level. On the other hand, the slag is rich in unreacted oxides or fluxing components, and its recycling is beneficial to stabilizing the composition of the molten pool in the furnace and improving mass and heat transfer conditions.

[0071] In one possible embodiment, as described above, the slag recycling unit is preferably arranged in a modular manner in the slag discharge area downstream of the reduction reactor. The slag outlet of the reduction reactor can be configured as a refractory-lined conical or trough-type slag discharge port, connected to the slag recycling inlet of the slag recycling unit via a short-distance high-temperature chute or heat-resistant steel pipe. This connection can employ a flange with a flexible compensation structure to accommodate thermal expansion and contraction and reduce stress concentration.

[0072] Furthermore, to ensure that the recycled slag does not adversely affect the structure and permeability of the furnace charge, the slag recycling unit preferably includes a crushing module and a screening module. By crushing and screening the slag, the particle size of the recycled slag is controlled within a certain range (e.g., a Dv50 median particle size of 5-20 mm), thus enabling it to form a stable particle size distribution with the solid charge in the furnace after recycling, avoiding problems such as material suspension, collapse, or increased aeration resistance caused by excessively large or small particle sizes. Simultaneously, the slag recycling unit can also be equipped with an analysis and testing module to detect the composition of the crushed and screened slag, including the content analysis of major components such as silica and calcium oxide, to assess the slag's alkalinity level. When the test results show that the slag alkalinity deviates from the target range, an alkalinity adjuster such as lime is added to correct the slag alkalinity, making it meet the process requirements for recycling and realizing the reuse of effective components in the slag.

[0073] In one possible embodiment, the apparatus as described above further includes a reaction monitoring unit, which includes at least one temperature sensor disposed inside the reduction reactor, at least one pressure sensor disposed at the top of the reduction reactor, and a sampling analyzer connected to the slag outlet and molten iron outlet of the reduction reactor.

[0074] In this embodiment, a temperature sensor can detect and reflect the furnace condition. When the recovered silicon powder and iron oxide undergo a reduction reaction, the local temperature inside the furnace will show a significant rise or a stable plateau, which can serve as a direct criterion for the start and continuation of the reaction. An abnormal drop in temperature usually indicates insufficient raw material supply, reaction obstruction, or insufficient heat input, while an abnormal rise in temperature may correspond to local over-reduction or reaction concentration. A pressure sensor can detect and reflect the gas generation, gas phase migration, and escape behavior accompanying the reduction of iron oxide. A sampling analyzer connected to the slag outlet and molten iron outlet of the reduction reactor can analyze the C, Si, Mn, S, and P content in the product (for example, Si content of 0.2%-0.6%; if the Si content is too low, the furnace hearth temperature is insufficient, and the reduction reaction is incomplete). Through the above connection methods and equipment combinations, the reaction monitoring unit can achieve visualized monitoring of the entire reduction reaction process, providing a reliable data foundation for subsequent process optimization, automatic control, or intelligent upgrades.

[0075] In one possible embodiment, as described above, the temperature sensor can be a high-temperature thermocouple or a fiber optic temperature measuring device, inserted into a designated position inside the reduction reactor via a pre-embedded protective sleeve. The outer wall of the sleeve is sealed with refractory material to prevent molten material erosion and gas leakage. Multiple temperature sensors can be arranged in layers along the height direction to monitor the temperature gradient inside the furnace. The pressure sensor is connected to the gas phase space inside the reduction reactor through a top pressure sampling port. A cooling section and anti-clogging structure can be installed in the pressure sampling channel to prevent high-temperature gas and dust from directly impacting the sensor. The pressure sensor is electrically connected to the control system for real-time feedback of pressure changes inside the furnace. Regarding the sampling analyzer, the slag sampling channel can be located to the side or downstream of the slag outlet, using a wear-resistant and heat-resistant sampling tube and a quick-switching valve to achieve small-flow sampling during slag discharge; the molten iron sampling channel can be located at the molten iron outlet or tundish, working in conjunction with an automatic sampling device to obtain representative samples. The sampling analyzer itself can be an online composition analyzer or a semi-online experimental analysis device.

[0076] In one possible embodiment, the apparatus as described above further includes a feed control unit, wherein the iron oxide outlet of the feed control unit is connected to the iron oxide inlet of the reduction reactor, and the coke outlet of the feed control unit is connected to the coke inlet of the reduction reactor. The pulverized coal outlet of the feed control unit is connected to the pulverized coal inlet of the reduction reactor, and the flux outlet of the feed control unit is connected to the flux inlet of the reduction reactor.

[0077] In this embodiment, the feed control unit, as the core regulating hub for the raw material system entering the reduction reactor, adopts a multi-channel, independently controlled structure for each material. This feed control unit is equipped with iron oxide outlets, coke outlets, pulverized coal outlets, and flux outlets. Each outlet is connected to the corresponding iron oxide inlet, coke inlet, pulverized coal inlet, and flux inlet of the reduction reactor via independent conveying channels, thereby achieving the separate delivery of different raw materials. Iron oxides, typically the main material to be reduced, are quantitatively fed into the main reaction zone of the reduction reactor after being controlled by the feed control unit. Coke, as a solid reducing agent and supporting material bed framework, is fed into the lower or middle region of the furnace via an independent channel. Pulverized coal, in powder or particulate form, enters the high-temperature zone through the pulverized coal inlet to supplement the reducing atmosphere and participate in the rapid reaction. Flux enters the furnace via a separate channel, contacting the slag system to adjust the slag basicity and fluidity. The feed control unit, on the one hand, prevents premature mixing, bridging, or stratification of different raw materials during the feeding stage, ensuring conveying stability. On the other hand, the corresponding furnace entry position and feeding rhythm can be selected according to the physical form and reaction role of different materials, thereby improving the overall controllability of the reduction reaction.

[0078] In one possible embodiment, as described above, the feed control unit can specifically adopt a modular assembly structure. The iron oxide feed section preferably uses a closed silo with a weighing feeder or belt scale, connected to the iron oxide inlet of the reduction reactor via a high-temperature resistant screw conveyor or elevator, achieving continuous and metered feeding. The coke feed section can use a large-capacity silo with gravity feeding or vibratory feeding, with a gate valve or rotary valve at the outlet to accommodate the stable feeding of lumpy or granular coke. The pulverized coal injection section preferably adopts a mature injection system structure, including a pulverized coal silo, a metering screw, pneumatic conveying pipelines, and a spray gun assembly. The pulverized coal outlet is directly and sealed to the pulverized coal inlet of the reduction reactor, using carrier gas to precisely deliver the pulverized coal into the designated high-temperature zone. The flux feed section can use a screw feeder or pneumatic conveying method depending on the flux form, and is equipped with a wear-resistant lining and anti-arching structure at the inlet. Flanges or quick-connect connections are preferably used between each material outlet and the inlet of the reduction reactor for easy maintenance and replacement. The feeding control unit is centrally managed by a PLC or DCS system and can also be linked with the reaction monitoring unit to adjust the feeding rate of each channel in real time according to the furnace condition.

[0079] In one possible embodiment, the apparatus as described above further includes a blower unit, the gas inlet of which is connected to the gas outlet of the reduction reactor, and the hot air outlet of which is connected to the hot air inlet of the reduction reactor.

[0080] In this embodiment, the gas inlet of the blast unit is connected to the gas outlet of the reduction reactor, and the hot air outlet is connected to the hot air inlet of the reduction reactor, forming a closed-loop circulation structure for furnace gas recovery, heating, and reuse. The gas produced in the reduction reactor during the high-temperature reduction process, containing combustible components such as carbon monoxide and hydrogen, is discharged through the gas outlet and enters the gas inlet of the blast unit. Within the blast unit, the gas undergoes heat recovery, purification, and heating, transforming into high-temperature hot air, which is then returned to the reduction reactor through the hot air outlet for blast heating and reaction enhancement. This connection structure achieves the cascaded utilization of furnace gas energy. The furnace gas itself carries a large amount of sensible heat and chemical energy; direct emission not only wastes energy but also increases the environmental burden. By connecting to the blast unit, the heat in the gas can be converted into stable and controllable hot air to maintain the high-temperature environment required for the reduction reaction. The blast unit also makes the gas conditions within the reduction reactor easier to control. By adjusting the blast pressure and hot air flow rate, the furnace pressure and material layer permeability can be affected, which helps improve melt fluidity and reduce the risk of localized slagging.

[0081] In one possible embodiment, as described above, the blower unit can specifically adopt an integrated structure consisting of a gas pretreatment module, a heat exchange module, and a blower module. The gas inlet is sealed to the gas outlet at the top or side of the reduction reactor via a high-temperature, corrosion-resistant pipe. Cyclone dust collectors or bag filters can be sequentially installed in the pipe to remove dust particles from the gas, preventing scaling or wear on subsequent equipment. The heat exchange module can be a regenerative or shell-and-tube heat exchange structure, utilizing the sensible heat of gas combustion to heat the blown air. The blower module preferably uses a high-temperature centrifugal fan or axial flow fan, coupled with a variable frequency speed control device, to achieve precise control of hot air flow and pressure. The hot air outlet is connected to the hot air inlet of the reduction reactor via an insulated pipe. The inlet location can be set at the furnace bottom, side wall, or tuyeres area depending on the furnace type to meet the actual needs of different smelting conditions. The blast unit can also be linked with the reaction monitoring unit to adjust the blast intensity and hot air temperature in real time according to the furnace temperature, pressure and gas composition. This not only reduces external fuel consumption, but also significantly improves the energy utilization efficiency and overall economy of the ferrosilicon smelting process.

[0082] To further illustrate the ferrosilicon smelting apparatus provided by the present invention, in one possible embodiment, such as Figure 1The diagram shows a schematic of a ferrosilicon smelting apparatus. The silicon powder collection device 3 and the silicon powder storage tank 2 are directly connected via a silicon powder collection outlet and a silicon powder storage inlet, enabling centralized storage of silicon powder generated or recovered during polysilicon production without intermediate transfer. The silicon powder storage outlet of the silicon powder storage tank 2 is further connected to the silicon powder inlet of the reduction reactor 1, ensuring that recovered silicon powder can be added to the reduction reaction system on demand and in a measured quantity. This avoids resource loss caused by powder discharge and improves silicon source utilization efficiency. The feed control unit 4 is connected to the iron oxide inlet, coke inlet, pulverized coal inlet, and flux inlet of the reduction reactor 1, respectively, allowing for independent metering and coordinated addition of various solid or powder raw materials, thereby achieving precise control of the reduction reaction conditions.

[0083] Based on this, the blast unit 6 is connected to the gas outlet of the reduction reactor 1 via the gas inlet and to the hot air inlet of the reduction reactor 1 via the hot air outlet, enabling the reaction-generated gas to be effectively recovered and converted into hot air for reintroduction into the furnace, forming an internal energy cycle. The slag recycling unit 5 forms a slag recycling inlet-slag outlet loop connection structure with the reduction reactor 1, allowing the slag generated during the reduction reaction to be extracted, processed, and then returned to participate in the reaction or to adjust the furnace composition, achieving controllable slag recycling, reducing new flux consumption, and stabilizing the slag system. The reaction monitoring unit, by installing temperature sensors inside the reduction reactor 1, pressure sensors at the top, and sampling analyzers at the slag outlet and molten iron outlet, achieves multi-dimensional monitoring of the furnace's thermal state, pressure state, and product flow composition, providing real-time data for feed adjustment and operating condition control. Through the rational connection of the above units, this invention improves resource utilization while achieving stable operation of the reaction process and reducing energy consumption.

[0084] Finally, it should be noted that other embodiments of the invention will readily occur to those skilled in the art upon consideration of the specification and practice of the invention disclosed herein. This invention is intended to cover any variations, uses, or adaptations of the invention that follow the general principles of the invention and include common knowledge or customary techniques in the art not disclosed herein. It is not limited to the precise structures described above and shown in the accompanying drawings, and various modifications and changes can be made without departing from its scope. The scope of the invention is limited only by the appended claims.

Claims

1. An application of recycled silicon powder in polysilicon production in ferrosilicon smelting.

2. The application according to claim 1, characterized in that, The ferrosilicon smelting process includes: subjecting a raw material system comprising the recovered silicon powder and iron oxide to a reduction reaction to obtain a ferrosilicon alloy.

3. The application according to claim 2, characterized in that, The temperature of the reduction reaction is 1500-1600℃; And / or, the reduction reaction is carried out using microwave heating; And / or, the reduction reaction is carried out under the protection of an inert gas.

4. The application according to claim 2 or 3, characterized in that, The purity of the recycled silicon powder is greater than 99.9%; the median particle size of Dv50 is 20-100μm, and more specifically 20-50μm; And / or, the raw material system may also include auxiliary materials containing rare earth elements.

5. The application according to any one of claims 2-4, characterized in that, The raw material system includes a core material, which includes a core and a coating layer disposed on at least a portion of the surface of the core. The core includes the iron oxide, and the coating layer includes the recycled silicon powder.

6. The application according to any one of claims 2-5, characterized in that, The products of the reduction reaction also include silicon-containing slag, wherein the silicon-containing slag contains 40%-60% silicon dioxide by mass. It also includes the step of returning the silicon-containing slag to participate in the reduction reaction; the mass ratio of the recovered silicon powder to the silicon-containing slag is (1:8)-(1:10).

7. A ferrosilicon smelting apparatus, characterized in that, It includes a silicon powder storage tank and a reduction reactor. The silicon powder storage tank is used to store recycled silicon powder from the silicon powder collection device, and the reduction reactor is used to carry out a reduction reaction in the raw material system to obtain ferrosilicon alloy. The silicon powder collection outlet of the silicon powder collection device is connected to the silicon powder storage inlet of the silicon powder storage tank, and the silicon powder storage outlet of the silicon powder storage tank is connected to the silicon powder inlet of the reduction reactor.

8. The apparatus according to claim 7, characterized in that, It also includes a slag recycling unit, wherein the slag recycling inlet of the slag recycling unit is connected to the slag outlet of the reduction reactor, and the slag recycling outlet of the slag recycling unit is connected to the slag outlet of the reduction reactor. And / or, it also includes a reaction monitoring unit, the reaction monitoring unit including at least one temperature sensor disposed inside the reduction reactor, at least one pressure sensor disposed on the top of the reduction reactor, and a sampling analyzer connected to the slag outlet and molten iron outlet of the reduction reactor.

9. The apparatus according to claim 7 or 8, characterized in that, It also includes a feed control unit, wherein the iron oxide outlet of the feed control unit is connected to the iron oxide inlet of the reduction reactor, the coke outlet of the feed control unit is connected to the coke inlet of the reduction reactor, the pulverized coal outlet of the feed control unit is connected to the pulverized coal inlet of the reduction reactor, and the flux outlet of the feed control unit is connected to the flux inlet of the reduction reactor.

10. The apparatus according to any one of claims 7-9, characterized in that, It also includes a blower unit, the gas inlet of which is connected to the gas outlet of the reduction reactor, and the hot air outlet of which is connected to the hot air inlet of the reduction reactor.

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