Direct-current three-electrode-based silicon series alloy smelting system and carbon monoxide recovery method

Abstract

The invention provides a direct-current three-electrode-based silicon series alloy smelting system and a carbon monoxide recovery method, and relates to the technical field of smelting, the system is characterized in that three cathode electrodes connected with the cathode of a short net are distributed and arranged at the top of the furnace, and three anode electrodes connected with the anode of the short net and the three cathode electrodes are arranged at the bottom of the furnace in an aligned manner; the discharging end of the feeding mechanism extends into the furnace body, protective gas is introduced into the feeding end of the feeding mechanism, and gas in the furnace is prevented from escaping from the feeding mechanism in the mode that pressure higher than the pressure in the furnace is generated at the feeding end; the gas inlet end of the exhaust-rate-adjustable carbon monoxide recovery mechanism is communicated with the interior of the submerged arc furnace body, and the gas outlet end is connected to a subsequent process; the micro-positive pressure adjusting mechanism is connected with the carbon monoxide recycling mechanism and the feeding mechanism, monitors the air pressure in the furnace body and adjusts the exhaust rate and the feeding amount according to the air pressure in the furnace, so that micro-positive pressure is kept in the furnace. According to the scheme, carbon monoxide generated in the silicon series alloy smelting process can be recycled.

Description

Technical Field

[0001] The present invention relates to the field of smelting technology, and in particular to a direct current three-electrode-based silicon series alloy smelting system and a carbon monoxide recovery method. Background Art

[0002] As a crucial piece of equipment in the smelting industry, submerged arc furnaces primarily consist of a furnace body, an electrode system, a charging system, a tapping system, and electrical equipment. The furnace body is typically constructed of steel plates, with a refractory interior built to withstand the high temperatures and erosion of the charge. The electrode system is the core component of the submerged arc furnace. Electric energy is introduced into the furnace through the electrodes, generating an arc between the electrode tips and the charge, releasing energy. During smelting, electrical energy is converted into thermal energy through resistance heating and arc heat, causing a chemical reaction within the furnace, including ore and reducing agents, at high temperatures, thereby reducing and purifying the metal. In industrial applications, submerged arc furnaces are particularly widely used in the smelting of silicon alloys. By reacting raw materials such as silica and coke at high temperatures, submerged arc furnaces produce silicon alloy products that meet diverse industrial needs. These silicon alloys are essential raw materials for industries such as steel and foundry.

[0003] During the smelting process of silicon-series alloys, large amounts of carbon monoxide (CO) are produced as a byproduct. Carbon monoxide is not only a toxic gas, but if released directly into the atmosphere without treatment, it can cause serious harm to the surrounding environment and human health. For example, it can cause poisoning and disrupt the atmospheric balance. Furthermore, carbon monoxide is a potential energy source with a high calorific value, and its direct emission represents a significant waste of energy. Therefore, collecting and recycling the carbon monoxide produced during the smelting of silicon-series alloys can not only reduce the risk of environmental pollution, but also achieve secondary energy utilization and improve resource utilization efficiency, which has significant economic and environmental benefits.

[0004] However, when using an AC submerged arc furnace to smelt silicon alloys, part of the carbon monoxide gas produced will burn in the furnace to form carbon dioxide and be discharged through the flue gas, while the other part of the unburned carbon monoxide will also be discharged out of the submerged arc furnace along with the flue gas. This not only causes a waste of carbon monoxide, but may also cause environmental pollution. Summary of the Invention

[0005] In view of this, in order to address the above shortcomings, it is necessary to propose a silicon series alloy smelting system and carbon monoxide recovery method based on DC three electrodes to recover the carbon monoxide generated during the silicon series alloy smelting process.

[0006] In a first aspect, the present invention provides a silicon series alloy smelting system based on DC three electrodes, comprising: a submerged arc furnace body, an electrode mechanism, a feeding mechanism, a carbon monoxide recovery mechanism, and a micro-positive pressure regulating mechanism; The electrode mechanism includes three cathode electrodes and three anode electrodes. The three cathode electrodes are distributed on the top of the submerged arc furnace body and are all connected to the negative electrode of the short network. The three anode electrodes are arranged at the bottom of the submerged arc furnace body in alignment with the three cathode electrodes and are all connected to the positive electrode of the short network, so as to form three groups of electric arcs in the submerged arc furnace body. The feeding mechanism is arranged on the top of the submerged arc furnace body, and the discharge end of the feeding mechanism extends into the interior of the submerged arc furnace body for feeding smelting raw materials; the feeding end of the feeding mechanism is fed with protective gas to limit the escape of the gas in the furnace from the feeding mechanism by generating a higher pressure than that in the furnace at the feeding end; The air inlet end of the carbon monoxide recovery mechanism is connected to the interior of the submerged arc furnace body, and the air outlet end is connected to the subsequent carbon monoxide treatment equipment or use equipment. The exhaust rate of the carbon monoxide recovery mechanism is adjustable; the micro-positive pressure adjustment mechanism is connected to the carbon monoxide recovery mechanism and the feeding mechanism, and is used to monitor the air pressure inside the submerged arc furnace body, and adjust the exhaust rate and feed amount according to the air pressure in the furnace, so as to maintain a micro-positive pressure inside the submerged arc furnace body and inhibit the entry of outside air.

[0007] Preferably, the main body of the ore-arc furnace includes a short smoke hood and a furnace body, and the short smoke hood and the furnace body are sealed by a sealing material; at least one observation window is provided on the side of the short smoke hood; at least one drain port is provided on the side of the furnace body, and the drain port is provided at a position higher than the upper surface of the anode electrode.

[0008] Preferably, a plurality of grid-like gaps are provided on the outer surface of the furnace body, and the gaps are filled with magnetic insulating materials to reduce the attraction of the magnetic field generated by the electrodes to the furnace shell by isolating the magnetic circuit, thereby reducing arc deflection.

[0009] Preferably, three protective screens connecting the inside and outside of the submerged arc furnace body are provided on the low smoke hood, and the lower ends of the three cathode electrodes respectively pass through a protective screen and extend into the interior of the submerged arc furnace body; the outer side of the protective screen is sealed and fixedly connected to the low smoke hood, and a sealing material is provided on the inner side to seal the gap formed between the protective screen and the electrode.

[0010] Preferably, a working platform is provided above the main body of the electric arc furnace, and three groups of the feeding mechanisms are provided, which are respectively arranged on the working platform near the three cathode electrodes; each feeding mechanism includes at least one feeding assembly arranged around the cathode electrode, and each feeding assembly includes a storage bin, a first feeding pipe and a discharge assembly; the storage bin is fixedly mounted on the working platform, one end of the first feeding pipe is connected to the lower end of the storage bin, and the other end passes through the working platform and the low smoke hood in sequence and extends into the interior of the electric arc furnace body, so as to feed the smelting raw materials toward the surrounded cathode electrodes; a discharge assembly is provided between the storage bin and the first feeding pipe, which is used to control the feeding of metallurgical raw materials; a gas inlet is provided on the storage bin, which is connected to the protective gas system, and is used to introduce protective gas into the storage bin, so as to limit the gas in the furnace from escaping from the feeding mechanism by generating a pressure higher than the pressure in the furnace in the storage bin.

[0011] Preferably, a second feed pipe is provided near the center of the working platform, and the storage bins of one group of feed assemblies near the center of the working platform among the three groups of feed mechanisms are connected to the upper end of the second feed pipe, and the lower end of the second feed pipe passes through the working platform and the low smoke hood in sequence and then extends into the body of the submerged arc furnace to feed the smelting raw materials into the center of the submerged arc furnace.

[0012] Preferably, the carbon monoxide recovery mechanism is a variable frequency fan, the air inlet end of the variable frequency fan is connected to the interior of the electric arc furnace body, and the air outlet end is connected to the subsequent carbon monoxide treatment equipment or use equipment; the micro-positive pressure regulating mechanism includes a gas monitoring component, a pressure monitoring component and a controller, the gas monitoring component and the pressure monitoring component are electrically connected to the controller, and the controller is electrically connected to the variable frequency fan and the feeding mechanism; the gas monitoring component is used to detect the concentrations of hydrogen, oxygen and carbon monoxide in the furnace, and upload the detection results to the controller, so that during the furnace startup stage, the controller determines whether the safety requirements for closing the furnace door are met based on the gas concentration detection results, and prompts the staff to perform the operation of closing the furnace door when the safety requirements are met; the pressure monitoring component is used to monitor the pressure in the furnace, and upload the monitoring results to the controller, so that the controller can adjust the operating power of the variable frequency fan and the feeding amount of the feeding mechanism based on the pressure monitoring results.

[0013] Preferably, the lining of the furnace body adopts a gradient material structure design, which is composed of high-purity graphite bricks, silicon carbide bricks, high-alumina bricks and insulation bricks from the inside to the outside; the bottom of the furnace body adopts a three-layer composite structure, which is composed of graphite bricks, microporous carbon blocks and clay bricks from top to bottom.

[0014] In a second aspect, the present invention provides a method for recovering carbon monoxide, which is implemented based on the DC three-electrode silicon alloy smelting system as described in any one of the first aspects, and the recovery method comprises: Step 101: With the furnace door open, metallurgical raw materials are fed into the submerged arc furnace body through a feeding mechanism for reaction; Step 102: Detecting the concentrations of hydrogen, oxygen, and carbon monoxide in the furnace using a gas monitoring component, and uploading the detection results to a controller; Step 103: When the controller determines that the safety requirement for closing the furnace door is met based on the uploaded gas concentration detection result, it prompts the staff to close the furnace door; Step 104: Metallurgical raw materials are continuously fed into the submerged arc furnace body for reaction, and the protective gas system is simultaneously activated to introduce protective gas into the storage bin, thereby generating a pressure in the storage bin higher than that in the furnace to prevent the gas in the furnace from escaping from the feeding mechanism. Step 105: Recovering the carbon monoxide gas in the furnace body by using a carbon monoxide recovery mechanism; Step 106: Detecting the gas pressure in the furnace using a micro-positive pressure regulating mechanism, and uploading the detection result to the controller; Step 107: Analyze the uploaded air pressure detection results using the controller; Step 108: If the gas pressure in the furnace exceeds the micro-positive pressure range, the exhaust rate of the carbon monoxide recovery mechanism is increased to reduce the pressure by quickly discharging the gas in the furnace; and / or, the feed amount is reduced by controlling the feeding mechanism to reduce the pressure by reducing the efficiency of carbon monoxide gas generation in the furnace; if the gas pressure in the furnace is lower than the micro-positive pressure range, the exhaust rate of the carbon monoxide recovery mechanism is reduced to increase the pressure in the furnace; and / or, the feed amount is increased by controlling the feeding mechanism to increase the pressure by increasing the efficiency of carbon monoxide gas generation in the furnace; and / or, protective gas is introduced into the furnace to increase the pressure in the furnace.

[0015] Preferably, the micro-positive pressure range is that the pressure inside the furnace is 80~120Pa higher than the pressure outside the furnace.

[0016] It can be seen from the above technical solution that this solution has at least the following beneficial effects compared with the existing solution: In the DC three-electrode silicon alloy smelting system provided by this solution, a feeding mechanism is installed on the top of the submerged arc furnace. The discharge end of the feeding mechanism extends into the interior of the submerged arc furnace for feeding smelting raw materials. A protective gas is introduced into the inlet end of the feeding mechanism, which can limit the escape of furnace gas from the feeding mechanism by generating a pressure higher than that inside the furnace at the inlet end. This ensures a sealing effect at the feeding mechanism, reduces carbon monoxide leakage and environmental pollution, and also helps to improve the carbon monoxide recovery rate. Furthermore, by sealing the feeding mechanism with protective gas, it also helps to reduce air ingress through the feeding mechanism, thereby reducing safety hazards. It also reduces the combustion of carbon monoxide in the furnace and helps to improve the carbon monoxide recovery efficiency.

[0017] The exhaust rate of the carbon monoxide recovery mechanism provided in this solution is adjustable. At the same time, this solution also provides a micro-positive pressure adjustment mechanism, which is connected to the carbon monoxide recovery mechanism and the feeding mechanism, and can monitor the air pressure inside the ore-fired furnace. In this way, the exhaust rate of the carbon monoxide recovery mechanism and the feed amount of the feeding mechanism can be adjusted by monitoring the air pressure. Therefore, the pressure inside the furnace can be adjusted by adjusting the exhaust rate or adjusting the reaction rate inside the furnace, so that the furnace maintains a micro-positive pressure state that is 80~120Pa higher than the air pressure outside the furnace. By maintaining a micro-positive pressure state inside the furnace, the entry of outside air can be greatly reduced, thereby reducing the risk of explosion caused by the entry of outside air. At the same time, it also reduces the combustion of carbon monoxide in the furnace, which helps to improve the carbon monoxide recovery rate.

[0018] This proposal also considers the use of a three-electrode DC solution, which can generate three sets of stable arcs in the furnace. These arcs generate high temperatures to heat the metallurgical raw materials in the furnace and melt them. Compared with AC electrodes, DC electrodes do not generate eddy current losses, which helps improve the heating efficiency in the furnace. Moreover, in the electrode structure, the current flows from the cathode electrode at the top to the shared anode pool at the bottom, forming a vertical current field from top to bottom. This configuration avoids the horizontal current and phase interference between electrodes in traditional AC furnaces, reducing energy losses caused by arc overburning and open arc operation. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 A schematic structural diagram of a silicon series alloy smelting system based on DC three electrodes provided in an embodiment of the present invention.

[0020] Figure 2 A schematic structural diagram of a submerged arc furnace body provided in an embodiment of the present invention.

[0021] Figure 3 This is a schematic diagram of the installation of a submerged arc furnace body and a feeding mechanism provided in an embodiment of the present invention.

[0022] Figure 4 A schematic diagram of a feeding assembly provided in an embodiment of the present invention.

[0023] Figure 5 A schematic diagram of an electrode mechanism provided in an embodiment of the present invention.

[0024] Figure 6 The present invention provides a flow chart of a carbon monoxide recovery method.

[0025] In the figure: the ore-fired furnace body 10, the low smoke hood 11, the furnace body 12, the first asbestos 13, the observation window 14, the drain port 15, the protective screen 16, the second asbestos 17, the electrode mechanism 20, the cathode electrode 21, the anode electrode 22, the feeding mechanism 30, the feeding assembly 31, the storage bin 311, the first feeding pipe 312, the discharge assembly 313, the vibration assembly 314, the upper level meter 315, the lower level meter 316, the gas outlet 317, the second feeding pipe 32, the carbon monoxide recovery mechanism 40, the micro-positive pressure adjustment mechanism 50, the explosion-proof valve 60, the working platform 70, and the protective gas system 80. DETAILED DESCRIPTION

[0026] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following is a brief introduction to the drawings required for use in the embodiments. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0027] See also Figure 1-5 The present invention provides a silicon series alloy smelting system based on DC three electrodes, which includes: a submerged arc furnace body 10, an electrode mechanism 20, a feeding mechanism 30, a carbon monoxide recovery mechanism 40 and a micro-positive pressure adjustment mechanism 50; The electrode mechanism 20 includes three cathode electrodes 21 and three anode electrodes 22. The three cathode electrodes 21 are distributed on the top of the submerged arc furnace body 10 and are all connected to the negative pole of the short circuit network. The three anode electrodes 22 are arranged at the bottom of the submerged arc furnace body 10 in alignment with the three cathode electrodes 21 and are all connected to the positive pole of the short circuit network, so as to form three groups of arcs in the submerged arc furnace body 10. The feeding mechanism 30 is disposed on the top of the submerged arc furnace body 10. The discharge end of the feeding mechanism 30 extends into the interior of the submerged arc furnace body 10 for feeding smelting raw materials. A protective gas is introduced into the inlet end of the feeding mechanism 30 to limit the escape of furnace gas from the feeding mechanism 30 by generating a higher pressure than the furnace pressure at the inlet end. The air inlet end of the carbon monoxide recovery mechanism 40 is connected to the interior of the submerged arc furnace body 10, and the air outlet end is connected to the subsequent carbon monoxide treatment equipment or use equipment. The exhaust rate of the carbon monoxide recovery mechanism 40 is adjustable; the micro-positive pressure adjustment mechanism 50 is connected to the carbon monoxide recovery mechanism 40 and the feeding mechanism 30, and is used to monitor the air pressure inside the submerged arc furnace body 10, and adjust the exhaust rate and feed amount according to the air pressure in the furnace to maintain a micro-positive pressure inside the submerged arc furnace body 10.

[0028] For the ore-heating furnace body 10, it is considered to make improvements based on the frame structure of the original three-phase AC ore-heating furnace. Specifically, in order to reduce the secondary combustion of CO and thereby improve the recovery rate of CO. In one embodiment, the ore-heating furnace body 10 may include a short smoke hood 11 and a furnace body 12, and the short smoke hood 11 and the furnace body 12 are sealed by a sealing material, for example, the short smoke hood 11 and the furnace body 12 can be sealed by a first asbestos 13. The height of the short smoke hood 11 can be set to 1 / 3 to 1 / 2 of the traditional high smoke hood, for example, it can be 1.2m, which can effectively reduce the dead zone volume in the furnace and shorten the residence time of the furnace gas in the smoke hood from the traditional 8 to 10 seconds to 2 to 3 seconds, thereby significantly reducing the secondary combustion loss of CO.

[0029] At least one observation window 14 is provided on the side of the low smoke hood 11 for observing the combustion conditions in the furnace. At least one drain port 15 is provided on the side of the furnace body 12, and the position of the drain port 15 should be higher than the upper surface of the anode electrode 22. In this way, when the molten charge flows into the furnace, a stagnant liquid layer will form between the drain port 15 and the molten charge at the furnace bottom. This stagnant liquid layer forms a conductive path with the three cathodes at the top of the furnace, and the current will continue to flow through the conductive path, rather than relying mainly on the three anodes at the bottom of the furnace for conduction. Since the stagnant liquid layer is conductive to the cathode, the current density of the three anodes at the bottom of the furnace will be significantly reduced, which reduces the electrochemical corrosion and thermal stress of the anode, significantly reduces the consumption of the anode, and thus extends the service life of the anode.

[0030] Furthermore, since the three cathode electrodes 21 need to extend from above the low chimney 11 into the interior of the submerged arc furnace body 10, to ensure a sealed furnace interior and maintain a slightly positive pressure, consideration is given to sealing the area where the low chimney 11 extends into the cathode electrodes 21. Specifically, the low chimney 11 is equipped with three protective screens 16 that connect the interior and exterior of the submerged arc furnace body 10. The lower ends of the three cathode electrodes 21 extend through a corresponding protective screen 16 into the interior of the submerged arc furnace body 10. The outer sides of the protective screens 16 are sealed and fixedly connected to the low chimney 11, and the inner sides are provided with sealing material to seal the gaps between the protective screens 16 and the electrodes. For example, a second asbestos layer 17 can be used for sealing.

[0031] In one embodiment, to reduce the risk of explosion and improve the safety of silicon alloy smelting, an explosion-proof valve 60 can be installed on the low smoke hood 11. When the pressure in the furnace exceeds a preset value, a spring expands to push the explosion-proof valve 60 open to release the pressure. When the pressure returns to a normal range, the spring contracts to close the explosion-proof valve 60. This prevents excessive pressure in the furnace and the possibility of explosion.

[0032] To improve the internal penetration resistance of furnace body 12, a gradient material design is being considered for the lining of furnace body 12. From the inside out, the lining consists of high-purity graphite bricks, silicon carbide bricks, high-alumina bricks, and insulation bricks. The purity of the high-purity graphite bricks should be greater than 99%, and the total thickness of the lining should reach 800-1000mm. Further consideration is being given to strengthening the furnace bottom by replacing the traditional single-layer carbon bricks with a three-layer composite structure consisting of graphite bricks, microporous carbon blocks, and clay bricks, from top to bottom. This will increase penetration resistance by more than three times, effectively preventing the penetration and erosion of molten silicon and slag.

[0033] Since the electrodes in the furnace body 12 generate a magnetic field, they will generate a magnetic force on the metal shell of the furnace body 12, thereby causing arc deflection. On the one hand, the generation of arc deflection will lead to uneven heating in the furnace and uneven melting speed of the charge on the molten pool surface; on the other hand, arc deflection will also significantly harm the substrate. The furnace wall close to the direction of arc deflection will receive stronger arc radiation, and the furnace lining here will be more easily damaged. In addition, arc deflection will also affect the normal operation of the smelting furnace, thereby reducing production. Therefore, in one embodiment, it is considered to provide a plurality of grid-like gaps on the outer surface of the furnace body 12, and the gaps are filled with magnetic insulating materials, such as stainless steel, so as to reduce the attraction of the magnetic field generated by the electrodes to the outer shell of the furnace body 12 by isolating the magnetic circuit, thereby reducing arc deflection.

[0034] Regarding the electrode mechanism 20, this solution considers three cathode electrodes 21 arranged equidistantly at 120° angles on the furnace roof. Through phase shift control, the electric field vectors between the top electrodes cancel each other out, achieving zero reactive power loss in the charge surface area. Each of these electrodes is connected to the negative pole of the short circuit network. Three anode electrodes 22 are located at the bottom of the submerged arc furnace body 10, facing each of the three cathode electrodes 21. The three anode electrodes 22 are connected to the positive pole of the short circuit network to form three stable arcs within the submerged arc furnace body 10. These arcs generate high temperatures, heating the charge within the furnace and causing it to melt. The diameter of the anode electrode 22 can be 20%-30% larger than the cathode diameter. This allows for a relatively large surface area, resulting in a more even distribution of the arc across the anode when current flows through it, reducing local overheating and arc concentration. The larger anode surface area also reduces current density, resulting in a more even current distribution, preventing arc bias and improving the stability and safety of the submerged arc furnace. Of course, the electrodes can also be powered by an adjustable DC voltage in the voltage range of 50V-480V to adjust the output voltage at different smelting stages, thereby improving the utilization rate of electrical energy.

[0035] In this DC three-electrode process, the dynamic changes in the material layer structure differ significantly from those of traditional processes. Because the top electrode of the DC electrode is unfinished, the material surface temperature is low, preventing premature crust formation. This allows the raw material to maintain good air permeability, typically achieving a material layer porosity of 35%-45%. The raw material slowly sinks under gravity, with an average residence time of 4-6 hours, which facilitates the full progress of the reduction reaction.

[0036] Specifically, the DC electrode solution provided by this solution allows the raw materials to undergo a series of complex physical changes and chemical reactions within the furnace. These transformation processes directly determine the quality and production efficiency of industrial silicon. Compared with traditional AC smelting, the unique current distribution and temperature gradient of the DC system make the raw material transformation exhibit distinct stage characteristics, from preheating and drying at the top to melting and reduction at the bottom, forming a clearer reaction hierarchy. Among them, the raw silicon undergoes the following physical transformation processes: 1. Initial stage of entering the furnace (the upper temperature of the furnace is about 100-300℃) Silica enters the upper region of the electric furnace through feeding mechanism 30. This region, away from the heat source at the furnace bottom, has a relatively low temperature of approximately 100-300°C. At this point, the silica exists primarily in a solid form, either in blocks or granules, with only a minimal amount of internal moisture evaporating. Its physical structure remains largely unchanged, with only a slightly roughened surface, providing a larger contact area for subsequent heat transfer. 2. Sinking preheating stage (temperature range 300-1000℃) As the silica sinks, it begins to be affected by heat conducted from the furnace bottom, gradually raising the ambient temperature to 300-1000°C. The bottom of the silica is the first to be exposed to the rising heat, creating a significant temperature difference between the bottom and the top, which in turn generates thermal stress. Under the influence of thermal stress, microcracks appear at the bottom of the silica, which extend toward the top as it sinks. When the temperature reaches 600-800°C, the evaporation of water within the silica accelerates, increasing the water vapor pressure within the pores and exacerbating the silica's fragmentation, breaking some into smaller pieces. Simultaneously, the alkali metal oxide impurities in the silica, which have lower melting points, begin to soften at 800-1000°C. These softened impurities gradually seep out of the silica surface, forming bonds between the silica fragments and altering the overall stacking structure, making it more loose and plastic. 3. Deep reaction stage (temperature range 1000-1500℃) As the silica continues to sink, approaching the melting pool at the bottom of the furnace, the temperature rises further to 1000-1500°C. At this point, the edges of most silica fragments begin to soften. Due to the continuous upward conduction of heat from the bottom, the silica becomes soft at the bottom and hard at the top. The softened edges fuse together, and the silica fragments gradually agglomerate into larger blocks. At 1200-1400°C, some of the silicate impurities in the silica begin to melt. These molten silicate impurities flow through the silica blocks, filling cracks and pores, increasing their density and altering their thermal conductivity, accelerating the transfer of heat into the silica. 4. Melting stage (temperature ≥ 1500°C, industrial silicon smelting is about 1800-2000°C) As the silica sinks to the surface of the melt pool at the bottom of the furnace, its temperature rises dramatically to over 1500°C, reaching 1800-2000°C under industrial silicon smelting conditions. Under these high temperatures, the silica rapidly transforms from a softened state to a fully molten state. Because the temperature is highest at the bottom, the silica melts completely first, forming a liquid silica melt. The liquid region then gradually expands upward. During the melting process, the silica undergoes significant volume changes due to thermal expansion and phase changes, causing residual gases and impurities to rise and be discharged from the liquid. Ultimately, the silica is completely melted into a uniform liquid silica melt, which mixes thoroughly with the other liquid materials in the melt pool, creating optimal conditions for the reduction reaction at the bottom. This differs significantly from the traditional process, where work is performed between electrodes and the silica reacts near the charge surface. Under this new process, the silica undergoes a more complete physical transformation, ensuring the efficiency of subsequent chemical reactions.

[0037] The DC three-electrode system employs a unique operating mode. Its DC arc is highly stable and does not exhibit the periodic zero-crossing arc extinction characteristic of an AC arc, allowing for continuous and stable energy release. Furthermore, the DC electric field intensity is highly concentrated, enabling the arc to precisely target the smelting area, resulting in more efficient energy transfer compared to AC smelting. This concentrated electric field and stable arc generate higher heat output, significantly improving heat utilization efficiency during the smelting process. During operation, the DC three-electrode system can achieve a 10-15% increase in operating voltage compared to AC smelting, while reducing current limiting by 20-25%. This reduces energy losses caused by the skin effect while effectively minimizing wear and tear on the electrodes and lining due to unstable arcing and uneven heat shock, significantly extending their service life.

[0038] In the DC three-electrode scheme, the reduction of SiO2 shows obvious stratification characteristics. The main reaction in the upper preheat zone is SiO2 + C → SiO + CO. This reaction stage absorbs heat and generates gaseous SiO; the main reaction in the medium temperature zone is SiO + 2C → SiC + CO. This stage forms a SiC transition layer; the main reaction in the crucible zone is SiO2 + 2SiC → 3Si + 2CO, which is the main smelting reaction in this process; the main reaction in the molten pool zone is SiO2 + 2C → Si + 2CO, which is the final reduction process. During the reaction process, the continuous action of DC makes Si 4+ The directional migration of O²⁻ promotes the interfacial reaction, and the reduction rate is increased by 20-30% compared with AC smelting.

[0039] In addition, DC smelting is more adaptable to raw materials and can adopt a high-coke, low-coal ratio scheme. For example, based on 200kg of silica, 55-75kg of oil coke, 30-55kg of clean coal, and 20-30kg of wood chips can be used. The reducing agent utilization rate is increased by 15-20%. It is particularly noteworthy that the DC scheme can better control the balance between the formation and decomposition of SiC. Due to the electrochemical corrosion of SiC by the DC electric field, that is, in the cathode region, SiC + 4e⁻ → Si + C 4 ⁻; Generated C 4 ⁻ The ions migrate to the anode and re-participate in the reaction in the molten pool, forming a dynamic balance of SiC, which avoids the problem of furnace bottom rising caused by SiC accumulation in traditional processes.

[0040] In order to ensure the heating and melting effect of the metallurgical raw materials and to prevent the furnace gas from escaping from the feeding port, it is considered to add materials in the direction of the electrode, and at the same time, use protective gas to seal the feeding port. Specifically, in one embodiment, a working platform 70 is provided above the main body 10 of the electric arc furnace, and three groups of feeding mechanisms 30 are provided, which are respectively arranged on the working platform 70 near the three cathode electrodes 21; each feeding mechanism 30 includes at least one feeding assembly 31 arranged around the cathode electrode 21, and each feeding assembly 31 includes a storage bin 311, a first feeding pipe 312 and a discharge assembly 313; the storage bin 311 is fixedly installed on the working platform 70, and one end of the first feeding pipe 312 is connected to the lower end of the storage bin 311. The other end passes through the working platform 70 and the low smoke hood 11 in sequence and then extends into the interior of the electric arc furnace body 10 to feed the smelting raw materials toward the surrounded cathode electrode 21; a discharge assembly 313 is provided between the storage bin 311 and the first feeding pipe 312 for controlling the input of metallurgical raw materials; a gas inlet is provided on the storage bin 311, which is connected to the protective gas system 80 for introducing protective gas into the storage bin 311, so as to limit the escape of the gas in the furnace from the feeding mechanism 30 by generating a pressure higher than the pressure in the furnace in the storage bin 311.

[0041] In this embodiment, each feeding mechanism 30 preferably has four feeding assemblies 31, i.e., four feeding assemblies 31 are evenly distributed around each electrode. These feeding assemblies 31 are positioned close to the electrode, or with the discharge port facing the electrode, to bring the metallurgical raw material closer to the electrode, thereby improving melting efficiency. The discharge assembly 313 can be a motor-driven gate. A controller controls the opening and closing of the gate, as well as the amount of opening and closing, by controlling the operation of the drive motor, thereby controlling the feed rate.

[0042] To further ensure uniform feeding, a second feeding pipe 32 can be installed near the center of the work platform 70. The storage bins 311 of the feeding assemblies 31 of the three feeding mechanisms 30 located near the center of the work platform 70 are all connected to the upper end of this second feeding pipe 32. The lower end of this second feeding pipe 32 passes through the work platform 70 and the low smoke hood 11, then extends into the submerged arc furnace body 10 to feed the smelting raw materials into the center of the submerged arc furnace. In this way, there is no need to install a separate feeding mechanism 30 at the center of the work platform 70. Instead, a discharge pipe can be separated from the storage bins 311 located near the center of the other three feeding mechanisms 30 to feed the material into the center of the submerged arc furnace body 10.

[0043] In addition, the storage bin 311 is provided with a gas outlet 317, and the gas inlet 317 is connected to the protective gas system 80, so that a protective gas can be introduced into the storage bin 311, such as nitrogen, argon, etc., into the storage bin 311, preferably nitrogen with lower cost is used as the protective gas. In this way, a greater pressure than that in the furnace can be generated in the storage bin 311, which avoids the outside air from entering the furnace body 12 during the feeding process, causing the furnace body 12 to have a hidden danger of explosion, and also reduces the combustion of carbon monoxide, which helps to improve the carbon monoxide recovery rate. In addition, by means of nitrogen sealing, it is also avoided that the furnace gas in the furnace escapes from the feeding mechanism 30 during the feeding process, causing environmental pollution and reducing the recovery rate of carbon monoxide.

[0044] In order to prevent the smelting raw materials in the storage bin 311 from being blocked, in one embodiment, a vibration component 314 can be installed on the storage bin 311 to make the smelting raw materials fall smoothly by vibration. Specifically, the vibration component 314 can be a 25kHz ultrasonic vibration device.

[0045] In addition, an upper level meter 315 and a lower level meter 316 are respectively provided on the upper and lower sides of the storage bin 311 to detect the amount of smelting raw materials in the storage bin 311. The level meter can be an infrared detector, an ultrasonic detector, a contact switch, etc.

[0046] Considering that a slightly positive pressure must be maintained inside the submerged arc furnace body 10 during normal smelting, the furnace pressure can be adjusted by adjusting the exhaust rate of the carbon monoxide recovery mechanism 40. Specifically, in one embodiment, the carbon monoxide recovery mechanism 40 can be a variable frequency fan, the air inlet of which is connected to the interior of the submerged arc furnace body 10, and the air outlet is connected to a subsequent carbon monoxide treatment device or device. In this way, by adjusting the operating power of the variable frequency fan, the rate of extraction of furnace gas from the furnace is adjusted, thereby achieving the purpose of regulating the furnace pressure. The air outlet of the variable frequency fan can be connected to a subsequent furnace gas purification system to improve the purity of the carbon monoxide.

[0047] The micro-positive pressure regulating mechanism 50 may include a gas monitoring component, a pressure monitoring component, and a controller. The gas monitoring component and the pressure monitoring component are both electrically connected to the controller, which is electrically connected to the variable frequency blower and the feeding mechanism 30. The gas monitoring component is used to detect the concentrations of hydrogen, oxygen, and carbon monoxide in the furnace and upload the detection results to the controller. During the furnace startup phase, the controller determines whether the safety requirements for closing the furnace door are met based on the gas concentration detection results, and prompts the staff to perform the operation of closing the furnace door when the safety requirements are met. For example, the gas monitoring component may be a hydrogen and oxygen analyzer and a carbon monoxide concentration detector. The hydrogen and oxygen analyzer can also be used to analyze whether the hydrogen content in the furnace exceeds the standard. If it exceeds the standard, it indicates that the moisture content of the raw materials is too high, and the moisture content of the smelting raw materials input needs to be adjusted by drying or other means.

[0048] The pressure monitoring component is used to monitor the pressure within the furnace and upload the monitoring results to the controller. The controller then adjusts the operating power of the variable frequency fan and the feeding amount of the feeding mechanism 30 based on the pressure monitoring results. The controller can be integrated into a PLC control cabinet, thereby adjusting the operating power of the variable frequency fan and the feeding amount of the feeding mechanism 30 based on the pressure monitoring results.

[0049] Of course, it should be pointed out that the smelting system, such as the batching system, brake system, motor lifting system, water supply system, and cooling system, continue to use the structural scheme of the existing AC submerged arc furnace, and this scheme will not be described in detail.

[0050] like Figure 6 As shown, the present invention also provides a carbon monoxide recovery method, which is implemented based on the DC three-electrode silicon series alloy smelting system of any of the above embodiments, and the method may include the following steps: Step 101: With the furnace door open, metallurgical raw materials are fed into the submerged arc furnace body 10 through the feeding mechanism 30 for reaction; Step 102: Detecting the concentrations of hydrogen, oxygen, and carbon monoxide in the furnace body 12 using a gas monitoring component, and uploading the detection results to the controller; Step 103: When the controller determines that the safety requirement for closing the furnace door is met based on the uploaded gas concentration detection result, it prompts the staff to close the furnace door; Step 104: Metallurgical raw materials are continuously fed into the submerged arc furnace body 10 for reaction, and the protective gas system 80 is simultaneously activated to introduce protective gas into the storage bin 311 , thereby generating a pressure higher than that in the furnace in the storage bin 311 to prevent the escape of furnace gas from the feeding mechanism 30 ; Step 105: Recover the carbon monoxide gas in the furnace body 12 using the carbon monoxide recovery mechanism 40; Step 106: Use the micro-positive pressure regulating mechanism 50 to detect the gas pressure in the furnace, and upload the detection result to the controller; Step 107: Analyze the uploaded air pressure detection results using the controller; Step 108: If the gas pressure in the furnace exceeds the micro-positive pressure range, the exhaust rate of the carbon monoxide recovery mechanism 40 is increased to reduce the pressure by quickly discharging the gas in the furnace; and / or, the feed amount is reduced by controlling the feeding mechanism 30 to reduce the pressure by reducing the efficiency of carbon monoxide gas generation in the furnace; if the gas pressure in the furnace is lower than the micro-positive pressure range, the exhaust rate of the carbon monoxide recovery mechanism 40 is reduced to increase the pressure in the furnace; and / or, the feed amount is increased by controlling the feeding mechanism 30 to increase the pressure by increasing the efficiency of carbon monoxide gas generation in the furnace; and / or, protective gas is introduced into the furnace to increase the pressure in the furnace.

[0051] In this embodiment, the slightly positive pressure range should be that the pressure inside the furnace is 80-120 Pa higher than the pressure outside the furnace.

[0052] In addition, when performing micro-positive furnace pressure regulation in step 108, in addition to adjusting the feed amount through the feeding mechanism 30 and adjusting the exhaust rate through the carbon monoxide recovery mechanism 40, the heating power can also be adjusted by adjusting the electrode current, thereby adjusting the concentration of carbon monoxide in the furnace, and then achieving adjustment of the pressure in the furnace.

[0053] Since the system embodiment provided by the present invention is based on the same inventive concept as the method embodiment of this specification, the specific content can be found in the description of the system embodiment of this specification and will not be repeated here.

[0054] The modules or units in the apparatus of the embodiments of the present invention may be combined, divided, or deleted as needed. The above disclosure is merely a preferred embodiment of the present invention and is not intended to limit the scope of the present invention. Persons skilled in the art will appreciate that any equivalent variations made by implementing all or part of the processes of the above embodiments in accordance with the claims of the present invention are still within the scope of the invention.

Claims

1. A silicon series alloy smelting system based on DC three electrodes, characterized in that: include: Submerged arc furnace body, electrode mechanism, feeding mechanism, carbon monoxide recovery mechanism and micro-positive pressure adjustment mechanism; The electrode mechanism includes three cathode electrodes and three anode electrodes. The three cathode electrodes are distributed on the top of the submerged arc furnace body and are all connected to the negative electrode of the short network. The three anode electrodes are arranged at the bottom of the submerged arc furnace body in alignment with the three cathode electrodes and are all connected to the positive electrode of the short network, so as to form three groups of electric arcs in the submerged arc furnace body. The feeding mechanism is arranged on the top of the submerged arc furnace body, and the discharge end of the feeding mechanism extends into the interior of the submerged arc furnace body for feeding smelting raw materials; the feeding end of the feeding mechanism is fed with protective gas to limit the escape of the gas in the furnace from the feeding mechanism by generating a higher pressure than that in the furnace at the feeding end; The air inlet end of the carbon monoxide recovery mechanism is connected to the interior of the submerged arc furnace body, and the air outlet end is connected to the subsequent carbon monoxide treatment equipment or use equipment. The exhaust rate of the carbon monoxide recovery mechanism is adjustable; the micro-positive pressure adjustment mechanism is connected to the carbon monoxide recovery mechanism and the feeding mechanism, and is used to monitor the air pressure inside the submerged arc furnace body, and adjust the exhaust rate and feed amount according to the air pressure in the furnace, so as to maintain a micro-positive pressure inside the submerged arc furnace body and inhibit the entry of outside air.

2. The silicon series alloy smelting system based on DC three electrodes according to claim 1 is characterized in that: The main body of the ore-fired furnace includes a short smoke hood and a furnace body, which are sealed by sealing material; at least one observation window is provided on the side of the short smoke hood; at least one drain port is provided on the side of the furnace body, and the drain port is provided at a position higher than the upper surface of the anode electrode.

3. The silicon series alloy smelting system based on DC three electrodes according to claim 2 is characterized in that: A plurality of grid-like gaps are provided on the outer surface of the furnace body, and the gaps are filled with magnetic insulating materials to reduce the attraction of the magnetic field generated by the electrodes to the furnace body shell by isolating the magnetic circuit, thereby reducing arc deflection.

4. The silicon alloy smelting system based on DC three electrodes according to claim 2 is characterized in that: The low smoke hood is provided with three protective screens connecting the inside and outside of the submerged arc furnace body, and the lower ends of the three cathode electrodes respectively pass through a protective screen and extend into the interior of the submerged arc furnace body; the outer side of the protective screen is sealed and fixedly connected to the low smoke hood, and a sealing material is provided on the inner side to seal the gap formed between the protective screen and the electrode.

5. The silicon series alloy smelting system based on DC three electrodes according to claim 1 is characterized in that: A working platform is provided above the main body of the submerged arc furnace, and three groups of feeding mechanisms are provided, which are respectively arranged on the working platform near the three cathode electrodes; each feeding mechanism includes at least one feeding assembly arranged around the cathode electrode, and each feeding assembly includes a storage bin, a first feeding pipe and a discharge assembly; the storage bin is fixedly installed on the working platform, one end of the first feeding pipe is connected to the lower end of the storage bin, and the other end passes through the working platform and the low smoke hood in sequence and extends into the interior of the submerged arc furnace body, so as to feed the smelting raw materials toward the surrounded cathode electrodes; a discharge assembly is provided between the storage bin and the first feeding pipe, which is used to control the feeding of metallurgical raw materials; a gas inlet is provided on the storage bin, which is connected to the protective gas system, and is used to introduce protective gas into the storage bin, so as to limit the escape of the gas in the furnace from the feeding mechanism by generating a pressure higher than the pressure in the furnace in the storage bin.

6. The silicon series alloy smelting system based on DC three electrodes according to claim 5 is characterized in that: A second feeding pipe is provided near the center of the working platform, and the storage bins of one group of feeding components near the center of the working platform among the three groups of feeding mechanisms are connected to the upper end of the second feeding pipe. The lower end of the second feeding pipe passes through the working platform and the low smoke hood in sequence and extends into the body of the submerged arc furnace to feed the smelting raw materials into the center of the submerged arc furnace.

7. The silicon alloy smelting system based on DC three electrodes according to claim 1 is characterized in that: The carbon monoxide recovery mechanism is a variable frequency fan, the air inlet end of which is connected to the interior of the ore-fired furnace body, and the air outlet end is connected to the subsequent carbon monoxide treatment equipment or use equipment; the micro-positive pressure adjustment mechanism includes a gas monitoring component, a pressure monitoring component and a controller, the gas monitoring component and the pressure monitoring component are both electrically connected to the controller, and the controller is electrically connected to the variable frequency fan and the feeding mechanism; the gas monitoring component is used to detect the concentrations of hydrogen, oxygen and carbon monoxide in the furnace, and upload the detection results to the controller, so that during the furnace startup stage, the controller can determine whether the safety requirements for closing the furnace door are met based on the gas concentration detection results, and prompt the staff to perform the operation of closing the furnace door when the safety requirements are met; The pressure monitoring component is used to monitor the pressure in the furnace and upload the monitoring results to the controller, so that the controller can adjust the operating power of the variable frequency fan and the feeding amount of the feeding mechanism according to the pressure monitoring results.

8. The silicon alloy smelting system based on DC three electrodes according to claim 2, characterized in that: The furnace lining adopts a gradient material structure design, which is composed of high-purity graphite bricks, silicon carbide bricks, high-alumina bricks and insulation bricks from the inside to the outside; the furnace bottom adopts a three-layer composite structure, which is composed of graphite bricks, microporous carbon blocks and clay bricks from top to bottom.

9. A method for recovering carbon monoxide, characterized in that: The recovery method is implemented based on the DC three-electrode silicon alloy smelting system according to any one of claims 1 to 8, and includes: Step 101: With the furnace door open, metallurgical raw materials are fed into the submerged arc furnace body through a feeding mechanism for reaction; Step 102: Detecting the concentrations of hydrogen, oxygen, and carbon monoxide in the furnace using a gas monitoring component, and uploading the detection results to a controller; Step 103: When the controller determines that the safety requirement for closing the furnace door is met based on the uploaded gas concentration detection result, it prompts the staff to close the furnace door; Step 104: Metallurgical raw materials are continuously fed into the submerged arc furnace body for reaction, and the protective gas system is simultaneously activated to introduce protective gas into the storage bin, thereby generating a pressure in the storage bin higher than that in the furnace to prevent the gas in the furnace from escaping from the feeding mechanism. Step 105: Recovering the carbon monoxide gas in the furnace body by using a carbon monoxide recovery mechanism; Step 106: Detecting the gas pressure in the furnace using a micro-positive pressure regulating mechanism, and uploading the detection result to the controller; Step 107: Analyze the uploaded air pressure detection results using the controller; Step 108: If the gas pressure in the furnace exceeds the micro-positive pressure range, the exhaust rate of the carbon monoxide recovery mechanism is increased to reduce the pressure by quickly discharging the gas in the furnace; and / or, the feed amount is reduced by controlling the feeding mechanism to reduce the pressure by reducing the efficiency of carbon monoxide gas generation in the furnace; if the gas pressure in the furnace is lower than the micro-positive pressure range, the exhaust rate of the carbon monoxide recovery mechanism is reduced to increase the pressure in the furnace; and / or, the feed amount is increased by controlling the feeding mechanism to increase the pressure by increasing the efficiency of carbon monoxide gas generation in the furnace; and / or, protective gas is introduced into the furnace to increase the pressure in the furnace.

10. The carbon monoxide recovery method according to claim 9, characterized in that: The micro-positive pressure range is that the pressure inside the furnace is 80~120Pa higher than the pressure outside the furnace.

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