Method for synergistically strengthening smelting of ferrosilicon ore-hearth furnace center iron and carbon enrichment

Abstract

This invention discloses a method for synergistic enhancement of ferrosilicon smelting through central iron addition and carbon enrichment in a submerged arc furnace, relating to the field of ferrosilicon smelting technology. The method includes preliminary preparation, central iron addition operation, carbon enrichment synergistic operation, and parameter monitoring and feedback mechanisms. Addressing the problems of poor crucible connectivity, low silicon recovery rate, and high power consumption in submerged arc furnace smelting, this method focuses on "phased progression and precise quantitative control." Through a synergistic operation of "central iron addition followed by targeted carbon enrichment," combined with dynamic matching parameters of furnace conditions, it achieves effective connectivity and expansion of the three-phase crucible. Specifically, it includes differentiated iron addition through the central feed pipe, directional carbon enrichment in the furnace shell area, and personalized handling of abnormal material surface conditions. Combined with precise raw material and fuel ratios and synergistic control of electrical parameters, this method solves the pain points of slow furnace charge circulation and low reduction efficiency in traditional processes, significantly improving the economy and stability of ferrosilicon smelting.

Description

Technical Field

[0001] This invention relates to the field of ferrosilicon smelting technology, specifically to a method for synergistic intensification of ferrosilicon smelting through central iron addition and carbon enrichment in a ferrosilicon submerged arc furnace. Background Technology

[0002] Ferrosilicon, as an important ferroalloy, is widely used in various industrial fields such as steel smelting and casting. Its production efficiency and quality have a significant impact on the development of downstream industries. Submerged arc furnace smelting is the mainstream method for ferrosilicon production, and the connectivity of the three-phase crucibles in the furnace and the reduction efficiency of the molten pool are the core factors determining the power consumption and output during the ferrosilicon smelting process.

[0003] In traditional ferrosilicon submerged arc furnace smelting processes, two major technical challenges severely restrict the improvement of production efficiency and the reduction of production costs. First, the furnace charge circulation control method has limitations. Traditional processes rely on overall charge adjustment to achieve furnace charge circulation, which is difficult to precisely meet the reaction needs of different areas within the furnace. During smelting, the central area often experiences insufficient iron, leading to slow molten pool formation. Delayed molten pool formation hinders the effective connection of the three-phase crucible, confining the reaction area to a small range, failing to fully utilize the furnace space and energy, ultimately resulting in low smelting efficiency and difficulty in increasing output. Second, carbon enrichment operations lack specificity and precision. Traditional carbon enrichment operations mostly involve overall carbon increase, and this extensive control method is prone to causing localized carbon imbalances. When there is an excess of carbon in a local area, it will lead to a decrease in the resistance of the furnace charge and deeper electrode insertion. This will not only increase energy consumption but may also affect the stability of the reaction in the furnace. When there is an insufficient amount of carbon in a local area, the silicon reduction reaction cannot proceed fully, and the silicon recovery rate is generally lower than 88% (usually around 83%). This not only wastes resources but also keeps the smelting power consumption high, usually exceeding 8350 kWh / t, which significantly increases production costs.

[0004] While existing technologies address the aforementioned issues by mentioning individual iron-addition or carbon enrichment measures, none of these solutions establish a synergistic control logic of "iron-addition and carbon enrichment." Furthermore, they lack precise, quantifiable control based on real-time furnace conditions, failing to fundamentally resolve the problems of weak reaction in the central region and excessive dead material in the furnace shell. Due to the lack of a systematic and precise process solution, existing technologies struggle to simultaneously optimize power consumption and output during ferrosilicon smelting, thus failing to meet current industrial demands for efficient, low-consumption, and high-quality ferrosilicon products. Summary of the Invention

[0005] This invention provides a method for synergistic enhancement of ferrosilicon smelting through central iron addition and carbon enrichment in a ferrosilicon submerged arc furnace. The aim is to break through the bottleneck of traditional smelting processes and meet the current industrial production demand for efficient, low-consumption, and high-quality ferrosilicon products by using a synergistic control approach of "directional iron addition, zoned carbon enrichment, and dynamic matching".

[0006] To achieve the above objectives, the present invention adopts the following technical solution: This invention relates to a method for smelting ferrosilicon submerged arc furnace by center-adding iron and carbon enrichment in a synergistic manner, comprising three stages: preliminary preparation, center-adding iron operation, and carbon enrichment synergistic operation. The preliminary preparation stage includes raw material pretreatment and electrical parameter calibration: (1) Raw material pretreatment: Select silica with SiO2 content ≥98.5%, Al2O3 content ≤1.5% and particle size of 60-150mm; Select semi-coke with fixed carbon content ≥82%, ash content ≤9%, volatile matter 6-10% and particle size of 6-18mm; Select iron oxide scale with iron content ≥70% as iron material, and mix all raw materials evenly; (2) Electrical parameter calibration: Stabilize the secondary voltage at 215V, adjust the load to 6±1 level, control the active power entering the furnace at ≥27000kW, set the natural power factor monitoring benchmark value to 0.7, and ensure that the 35kV primary side voltage of the power supply system is in the range of 37-38kV; The central iron-adding operation stage includes iron-adding timing control, iron-adding method control, and iron-adding amount control: (1) Iron-adding timing control: After the smelting stage indicators meet the standards, namely, daily output ≥75t, smelting power consumption ≤8350kWh / t, and the alloy composition is stable at 72.5-73.5% and shows an upward trend, the central iron-adding is started; (2) Iron-adding method control: Iron material is added separately through the central feed pipe of the electric arc furnace. Compared with other non-central feed pipes in the furnace, 15-30kg of iron material is added per batch, so that the material surface height in the central area is 50-80mm higher than other parts, forming a material surface gradient of "high in the center and low around the perimeter"; (3) Iron-adding amount control: Initially, 20kg of iron material is added per batch. The silicon element recovery rate is monitored daily. If the recovery rate increases by <2%, the iron-adding amount is increased by 5kg / batch every 3 days. The maximum amount added at one time does not exceed 30kg / batch, ensuring that the total amount of iron material and the carbon content match the requirements of the reduction reaction; The carbon enrichment synergistic operation stage includes carbon enrichment timing control, carbon enrichment zone operation, carbon enrichment adjustment and furnace condition personalized handling: (1) Carbon enrichment timing control: 48 hours after the central iron addition is started, when the iron material in the furnace has initially melted to form a local molten pool and the electrode work is stable, that is, when the three-phase current deviation is ≤5%, the carbon enrichment operation is started; (2) Carbon enrichment zone operation: ① Central area carbon enrichment: synchronous with the central feed pipe iron addition, the amount of semi-coke added in each batch is 10-15kg more than that in the non-central feed pipe, to ensure that the molar ratio of carbon to the newly added iron material is maintained at 1.2:1-1.5:1; ② Furnace shell area carbon enrichment: 150-200kg of carbon is evenly applied to one ring of the furnace shell each shift, and the amount of carbon applied is controlled within 3kg of the average carbon amount of the batch in that shift, and semi-coke with fixed carbon ≥85% is preferred; (3) Carbon enrichment adjustment: if the electrode is stuck in the lowering position If the furnace charge is difficult and sticky, the carbon enrichment amount per batch should be reduced by 3-5 kg; if the power consumption decreases and the silicon element recovery rate decreases, the carbon enrichment amount per batch should be increased by 2-3 kg, and the adjustment interval should be ≥24h; (4) Personalized handling of furnace conditions: ① Treatment of sticky material surface: When the material surface is locally sticky or caking, use a tie rod to poke holes in the furnace shell, the large triangular area and the small dead material area. After the tie rod is inserted 300-400mm deep into the furnace charge, it is lifted up and the sticky material is picked out. Then, 5-8 kg of carbon is attached to the poke area. The poke operation interval should be ≥8h; ② Furnace mouth temperature control: During the carbon enrichment period, the furnace mouth temperature should be controlled ≤460℃. If it exceeds the standard, the temperature should be reduced to the standard range within 20 minutes by increasing the feeding frequency of the central material pipe from once every 1h to once every 45min, and reducing the carbon enrichment amount per batch by 5kg.

[0007] Furthermore, the method also includes a parameter monitoring and feedback mechanism, specifically as follows: the amount of iron added to the central feed pipe, the amount of carbon enrichment, the secondary voltage, the current, and the furnace mouth temperature are recorded every 2 hours; the daily accounting target is a silicon element recovery rate of ≥88%; if the daily accounting does not reach this target, the amount of iron added to the central feed pipe or the amount of carbon enrichment is adjusted the following day, with an adjustment range of 5 kg / batch; the effect of semi-coke entering the furnace is evaluated weekly; if the carbon enrichment efficiency decreases due to excessive ash content in the semi-coke, the semi-coke supplier is changed, and priority is given to purchasing from suppliers with a fixed carbon content of ≥85%.

[0008] Furthermore, during the central iron feeding operation, the material level height difference between the central area and other parts is monitored in real time by a material level height monitoring device. If the material level height difference is less than 50mm, the feeding frequency of the central material pipe is increased.

[0009] Furthermore, in the carbon-rich zone operation, the preferred semi-coke for the furnace shell area with a fixed carbon content of ≥85% is Shaanxi Huineng semi-coke or Jinchuan Hongtai semi-coke.

[0010] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) Significant breakthroughs in production indicators and substantial improvement in economic benefits. This invention breaks through the bottleneck of traditional smelting processes through a synergistic control method of "targeted iron addition, zoned carbon enrichment, and dynamic matching," achieving improved ferrosilicon smelting efficiency, reduced power consumption, and increased silicon recovery rate, thus promoting the green and efficient development of the ferrosilicon industry. Compared with traditional processes, the improved silicon recovery rate means that for the same amount of raw materials, more qualified ferrosilicon products can be produced, greatly improving the utilization rate of raw materials. At the same time, smelting power consumption is reduced by 200 kWh / t. Given the current rising electricity costs, the economic benefits brought by this reduction are considerable. Based on 300 days of production per year, the daily output increases by 1.2 tons, resulting in an additional 360 tons of ferrosilicon produced annually. Based on the current market price of ferrosilicon, the additional output value is considerable; while the electricity savings exceed 500,000 yuan, further enhancing the company's competitiveness in the market.

[0011] (2) Significantly optimized furnace stability and more reliable equipment operation. In the traditional ferrosilicon submerged arc furnace smelting process, the three-phase crucible connectivity is low, resulting in uneven reaction inside the furnace, a large dead material zone in the furnace shell, slow material circulation speed, and large electrode fluctuations, which seriously affect the stability of the furnace conditions and the service life of the equipment. After the implementation of this invention, the three-phase crucible connectivity is improved, making the heat distribution inside the furnace more uniform, the reaction more complete, reducing the dead material zone in the furnace shell, accelerating the material circulation speed, effectively improving the flow of materials and the reaction environment inside the furnace, reducing electrode consumption, reducing the probability of equipment failure, extending the service life of the equipment, and also reducing the cost of equipment maintenance and repair.

[0012] (3) Standardized operating procedures and strong technical applicability. This invention clarifies quantitative parameters such as iron addition, carbon enrichment, and adjustment intervals, and combines them with monitoring indicators such as furnace mouth temperature and recovery rate to form a complete standardized operating procedure. In traditional processes, the operator's experience has a significant impact on furnace condition control and production indicators, and differences in the operating skills of different operators may lead to production instability. However, the standardized operating procedure of this invention reduces the dependence on operator experience. Even newly hired operators can quickly master the operating essentials after simple training, ensuring the stability and consistency of production. In addition, this process has strong versatility and can be quickly promoted to other furnaces, providing a feasible solution for the technological upgrading and efficiency improvement of the entire ferrosilicon smelting industry. Detailed Implementation

[0013] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0014] Taking the No. 3 submerged arc furnace of a certain ferroalloy company as an example, the method of ferrosilicon submerged arc furnace with center iron addition and carbon enrichment synergistic strengthening smelting provided by the present invention includes three stages: preliminary preparation, center iron addition operation, and carbon enrichment synergistic operation.

[0015] Before starting this method, ensure that the No. 3 electric arc furnace meets the following conditions: 1. Smelting stage: Daily output ≥75t, power consumption ≤8350kWh / t, furnace condition stable and without abnormalities (such as electrode breakage, iron leakage from the furnace bottom, etc.); 2. Equipment status: The central material pipe is unblocked, the material is fed evenly, the furnace shell temperature measuring points are intact, and the electrode pressure release system is normal (the daily pressure release can be stably ≥500mm). 3. Raw material reserves: The reserves of standard silica, semi-coke, and iron oxide scale are sufficient to meet the production needs for more than 7 days.

[0016] Example 1 The preliminary preparation phase includes raw material pretreatment and electrical parameter calibration: (1) Raw material pretreatment: Select silica with SiO2 content of 98.5%, Al2O3 content of 1.5% and particle size of 100mm; select semi-coke with fixed carbon content of 82%, ash content of 9%, volatile matter of 8% and particle size of 12mm; select iron oxide scale with iron content of 70% as iron material, and mix all raw materials evenly. (2) Electrical parameter calibration: Stabilize the secondary voltage at 215V, adjust the load to level 6, control the active power entering the furnace at 27000kW, set the natural power factor monitoring benchmark value to 0.7, and ensure that the 35kV primary side voltage of the power supply system is in the 37kV range. The central iron-addition operation phase includes iron-addition timing control, iron-addition method control, and iron-addition quantity regulation: (1) Timing control of iron addition: When the indicators in the smelting stage meet the standards, namely, daily output of 75t, smelting power consumption of 8350kWh / t, and alloy composition stabilizes at 72.5% and shows an upward trend, the central iron addition is started. (2) Iron addition method control: Iron is added separately through the central feed pipe of the electric arc furnace. Compared with other non-central feed pipes in the furnace, 15kg of iron is added per batch, so that the material level in the central area is 50mm higher than that in other parts, forming a material level gradient of "high in the center and low around the perimeter". (3) Iron addition control: Initially, add 20kg of iron per batch. Monitor the silicon recovery rate daily. If the recovery rate increases by <2%, add 5kg of iron per batch every 3 days. The maximum amount added at one time shall not exceed 30kg per batch to ensure that the total amount of iron and the carbon content are matched to meet the requirements of the reduction reaction. The carbon-enriched synergistic operation phase includes carbon enrichment timing control, carbon enrichment zone operation, carbon enrichment adjustment, and personalized furnace condition handling: (1) Control of carbon enrichment timing: After the central iron addition is started for 48 hours, wait for the iron material in the furnace to initially melt and form a local molten pool, and the electrode work to be stable, that is, when the three-phase current deviation is ≤5%, start the carbon enrichment operation. (2) Carbon enrichment zone operation: ① Central area carbon enrichment: When adding iron in the central feed pipe, the amount of semi-coke added in each batch is 10kg more than that in the non-central feed pipe, to ensure that the molar ratio of carbon to newly added iron is maintained at 1.2:1; ② Furnace shell area carbon enrichment: 150kg of carbon is evenly applied to one ring of the furnace shell in each shift. When applying carbon, the method of "even spreading + light pushing and compacting" is adopted to avoid semi-coke floating on the material surface. The amount of carbon applied is controlled within 3kg of the average amount of carbon in the batch of the shift. Shaanxi Huineng semi-coke with a fixed carbon content of 85% is preferred. (3) Carbon enrichment adjustment: If the electrode is difficult to lower or the furnace charge is sticky, the carbon enrichment amount of each batch should be reduced by 3 kg; if the power consumption decreases or the silicon element recovery rate decreases, the carbon enrichment amount of each batch should be increased by 2 kg, and the adjustment interval should be ≥24h. (4) Personalized handling of furnace conditions: ① Treatment of sticky material surface: When the material surface becomes sticky or caking, use a φ50mm binding rod to make holes around the furnace shell, the large triangular area and the small dead material area. After inserting the binding rod 300mm deep into the furnace material, lift it slightly to pick up the sticky material. Then apply 5kg of carbon to the hole area. The interval between hole-making operations is ≥8h. After re-inspection, the material surface circulation in this area is normal and there is no secondary crusting. ② Furnace mouth temperature control: During the carbon enrichment period, the furnace mouth temperature is controlled ≤460℃. If it exceeds the standard, the temperature is reduced to the standard range within 20 minutes by increasing the feeding frequency of the central material pipe from once every 1h to once every 45min and reducing the amount of carbon enriched at one time by 5kg.

[0017] During the smelting process, the daily output increased to 1.2t, the silicon recovery rate was 90%, the smelting power consumption was reduced by 200kWh / t, and the natural power factor was 0.72.

[0018] Example 2 The preliminary preparation phase includes raw material pretreatment and electrical parameter calibration: (1) Raw material pretreatment: Select silica with SiO2 content of 99%, Al2O3 content of 1% and particle size of 60mm; select semi-coke with fixed carbon content of 82%, ash content of 9%, volatile matter of 6% and particle size of 6mm; select iron oxide scale with iron content of 75% as iron material, and mix all raw materials evenly. (2) Electrical parameter calibration: Stabilize the secondary voltage at 215V, adjust the load to level 7, control the active power entering the furnace at 28000kW, set the natural power factor monitoring benchmark value to 0.7, and ensure that the 35kV primary side voltage of the power supply system is in the range of 37.5kV. The central iron-addition operation phase includes iron-addition timing control, iron-addition method control, and iron-addition quantity regulation: (1) Timing control of iron addition: When the indicators in the smelting stage meet the standards, namely, daily output of 75t, smelting power consumption of 8350kWh / t, and alloy composition stabilizes at 73% and shows an upward trend, the central iron addition is started. (2) Iron addition method control: Iron is added separately through the central feed pipe of the electric arc furnace. Compared with other non-central feed pipes in the furnace, 22kg of iron is added per batch, so that the material level in the central area is 65mm higher than that in other parts, forming a material level gradient of "high in the center and low around the perimeter". (3) Iron addition control: Initially, add 20kg of iron per batch. Monitor the silicon recovery rate daily. If the recovery rate increases by <2%, add 5kg of iron per batch every 3 days. The maximum amount added at one time shall not exceed 30kg per batch to ensure that the total amount of iron and the carbon content are matched to meet the requirements of the reduction reaction. The carbon-enriched synergistic operation phase includes carbon enrichment timing control, carbon enrichment zone operation, carbon enrichment adjustment, and personalized furnace condition handling: (1) Control of carbon enrichment timing: After the central iron addition is started for 48 hours, wait for the iron material in the furnace to initially melt and form a local molten pool, and the electrode work to be stable, that is, when the three-phase current deviation is ≤5%, start the carbon enrichment operation. (2) Carbon enrichment zone operation: ① Central area carbon enrichment: When adding iron in the central feed pipe, the amount of semi-coke added in each batch is 12kg more than that in the non-central feed pipe, to ensure that the molar ratio of carbon to newly added iron is maintained at 1.35:1; ② Furnace shell area carbon enrichment: 175kg of carbon is evenly applied to one ring of the furnace shell in each shift. When applying carbon, the method of "even spreading + light pushing and compacting" is adopted to avoid semi-coke floating on the material surface. The amount of carbon applied is controlled within 3kg of the average amount of carbon in the batch of the shift. Jinchuan Hongtai semi-coke with a fixed carbon content of 85% is preferred. (3) Carbon enrichment adjustment: If the electrode is difficult to lower or the furnace charge is sticky, the carbon enrichment amount per batch should be reduced by 4 kg; if the power consumption decreases or the silicon recovery rate decreases, the carbon enrichment amount per batch should be increased by 2.5 kg, with an adjustment interval of ≥24 h. (4) Personalized handling of furnace conditions: ① Treatment of sticky material surface: When the material surface becomes sticky or caking, use a φ50mm binding rod to make holes around the furnace shell, the large triangular area and the small dead material area. After inserting the binding rod 350mm into the furnace material, lift it slightly to pick up the sticky material. Then attach 6.5kg of carbon to the hole area. The interval between hole-making operations is ≥8h. After re-inspection, the material surface circulation in this area is normal and there is no secondary crusting. ② Furnace mouth temperature control: During the carbon enrichment period, the furnace mouth temperature is controlled ≤460℃. If it exceeds the standard, the temperature is reduced to the standard range within 20 minutes by increasing the feeding frequency of the central material pipe from once every 1h to once every 45min and reducing the amount of carbon enriched at one time by 5kg.

[0019] During the smelting process, the daily output increased to 1.2t, the silicon recovery rate was 88%, the smelting power consumption was reduced by 202kWh / t, and the natural power factor was 0.73.

[0020] Example 3 The preliminary preparation phase includes raw material pretreatment and electrical parameter calibration: (1) Raw material pretreatment: Select silica with SiO2 content of 99.5%, Al2O3 content of 0.5% and particle size of 150mm; select semi-coke with fixed carbon content of 82%, ash content of 9%, volatile matter of 10% and particle size of 18mm; select iron oxide scale with iron content of 80% as iron material, and mix all raw materials evenly. (2) Electrical parameter calibration: Stabilize the secondary voltage at 215V, adjust the load to level 5, control the active power entering the furnace at 28000kW, set the natural power factor monitoring benchmark value to 0.7, and ensure that the 35kV primary side voltage of the power supply system is in the 38kV range. The central iron-addition operation phase includes iron-addition timing control, iron-addition method control, and iron-addition quantity regulation: (1) Timing control of iron addition: When the indicators in the smelting stage meet the standards, namely, daily output of 75t, smelting power consumption of 8350kWh / t, and alloy composition stabilizes at 73.5% and shows an upward trend, the central iron addition is started. (2) Iron addition method control: Iron is added separately through the central feed pipe of the electric arc furnace. Compared with other non-central feed pipes in the furnace, 30kg of iron is added per batch, so that the material level in the central area is 80mm higher than that in other parts, forming a material level gradient of "high in the center and low around the perimeter". (3) Iron addition control: Initially, add 20kg of iron per batch. Monitor the silicon recovery rate daily. If the recovery rate increases by <2%, add 5kg of iron per batch every 3 days. The maximum amount added at one time shall not exceed 30kg per batch to ensure that the total amount of iron and the carbon content are matched to meet the requirements of the reduction reaction. The carbon-enriched synergistic operation phase includes carbon enrichment timing control, carbon enrichment zone operation, carbon enrichment adjustment, and personalized furnace condition handling: (1) Control of carbon enrichment timing: After the central iron addition is started for 48 hours, wait for the iron material in the furnace to initially melt and form a local molten pool, and the electrode work to be stable, that is, when the three-phase current deviation is ≤5%, start the carbon enrichment operation. (2) Carbon enrichment zone operation: ① Central area carbon enrichment: When adding iron in the central feed pipe, the amount of semi-coke added in each batch is 15kg more than that in the non-central feed pipe, to ensure that the molar ratio of carbon to newly added iron is maintained at 1.5:1; ② Furnace shell area carbon enrichment: 200kg of carbon is evenly applied to one ring of the furnace shell in each shift. When applying carbon, the method of "even spreading + light pushing and compacting" is adopted to avoid semi-coke floating on the material surface. The amount of carbon applied is controlled within 3kg of the average amount of carbon in the batch of materials in the shift. Jinchuan Hongtai semi-coke with a fixed carbon content of 85% is preferred. (3) Carbon enrichment adjustment: If the electrode is difficult to lower or the furnace charge is sticky, the carbon enrichment amount of each batch should be reduced by 5 kg; if the power consumption decreases or the silicon element recovery rate decreases, the carbon enrichment amount of each batch should be increased by 3 kg, and the adjustment interval should be ≥24h. (4) Personalized handling of furnace conditions: ① Treatment of sticky material surface: When the material surface becomes sticky or caking, use a φ50mm binding rod to make holes around the furnace shell, the large triangular area and the small dead material area. After inserting the binding rod 400mm into the furnace material, lift it slightly to pick up the sticky material. Then apply 8kg of carbon to the hole area. The interval between hole operations is ≥8h. After re-inspection, the material surface circulation in this area is normal and there is no secondary crusting. ② Furnace mouth temperature control: During the carbon enrichment period, the furnace mouth temperature is controlled ≤460℃. If it exceeds the standard, the temperature is reduced to the standard range within 20 minutes by increasing the feeding frequency of the central material pipe from once every 1h to once every 45min and reducing the amount of carbon enriched at one time by 5kg.

[0021] In addition, the method for synergistic enhancement of smelting by adding iron and enriching carbon in the center of the ferrosilicon submerged arc furnace also includes a parameter monitoring and feedback mechanism, specifically as follows: The amount of iron added to the central feed pipe, the amount of carbon enrichment, the secondary voltage, the current, and the furnace mouth temperature are recorded every 2 hours; a daily accounting target of silicon element recovery rate ≥88% is used. If this target is not achieved on a given day, the amount of iron added or the amount of carbon enrichment in the center is adjusted the following day, with an adjustment range of 5 kg / batch; the effect of semi-coke feeding into the furnace is evaluated weekly. If the carbon enrichment efficiency decreases due to excessive ash content in the semi-coke, the semi-coke supplier is changed, and priority is given to purchasing from Shaanxi Huineng Semi-coke or Jinchuan Hongtai Semi-coke manufacturers with a fixed carbon content ≥85%. The material level height difference between the central area and other parts is monitored in real time using a material level monitoring device. The central material level height is checked every 2 hours to ensure it is 50-80 mm higher than the surrounding area. If the material level height difference is <50 mm, the feeding frequency of the central feed pipe needs to be increased from once every 1 hour to once every 50 minutes.

[0022] During the smelting process, the daily output increased to 1.2t, the silicon recovery rate was 92%, the smelting power consumption was reduced by 198kWh / t, and the natural power factor was 0.72.

[0023] During the implementation of this method, the following parameters for the electric arc furnace are required: (1) Daily output: Daily output increased to 1.2t, meeting the requirement of ≥1t; (2) Smelting power consumption: The average smelting power consumption was reduced by 200 kWh / t, meeting the requirement of a reduction of 150 kWh / t; (3) Silicon recovery rate: increased from the current 83% to 92%, averaging 90%, meeting the requirement of ≥88%; (4) Natural power factor: stable at 0.72-0.73, higher than the stage target of 0.7.

[0024] This method is also applicable to the No. 1 and No. 2 submerged arc furnaces of the ferroalloy company. The adaptation and adjustment are as follows: the initial increase in iron addition at the center is 15kg / batch, which is dynamically adjusted according to the active power of the furnace (No. 1 and No. 2 furnaces ≥25000kW); the carbon enrichment in the furnace shell area is adjusted to 120-180kg per shift to match the differences in furnace volume and capacity of No. 1 and No. 2 furnaces.

Claims

1. A method for synergistic intensification of ferrosilicon submerged arc furnace smelting with central iron addition and carbon enrichment, characterized in that, It includes three stages: preliminary preparation, central iron addition operation, and carbon enrichment synergistic operation; The preliminary preparation stage includes raw material pretreatment and electrical parameter calibration: (1) Raw material pretreatment: Select silica with SiO2 content ≥98.5%, Al2O3 content ≤1.5% and particle size of 60-150mm; Select semi-coke with fixed carbon content ≥82%, ash content ≤9%, volatile matter 6-10% and particle size of 6-18mm; Select iron oxide scale with iron content ≥70% as iron material, and mix all raw materials evenly; (2) Electrical parameter calibration: Stabilize the secondary voltage at 215V, adjust the load to 6±1 level, control the active power entering the furnace at ≥27000kW, set the natural power factor monitoring benchmark value to 0.7, and ensure that the 35kV primary side voltage of the power supply system is in the range of 37-38kV; The central iron-adding operation stage includes iron-adding timing control, iron-adding method control, and iron-adding amount control: (1) Iron-adding timing control: After the smelting stage indicators meet the standards, namely, daily output ≥75t, smelting power consumption ≤8350kWh / t, and the alloy composition is stable at 72.5-73.5% and shows an upward trend, the central iron-adding is started; (2) Iron-adding method control: Iron material is added separately through the central feed pipe of the electric arc furnace. Compared with other non-central feed pipes in the furnace, 15-30kg of iron material is added per batch, so that the material surface height in the central area is 50-80mm higher than other parts, forming a material surface gradient of "high center - low periphery"; (3) Iron-adding amount control: Initially, 20kg of iron material is added per batch. The silicon element recovery rate is monitored daily. If the recovery rate increases by <2%, the iron-adding amount is increased by 5kg / batch every 3 days. The maximum amount added at one time does not exceed 30kg / batch, ensuring that the total amount of iron material and the carbon content match the requirements of the reduction reaction; The carbon enrichment synergistic operation stage includes carbon enrichment timing control, carbon enrichment zone operation, carbon enrichment adjustment and furnace condition personalized handling: (1) Carbon enrichment timing control: 48 hours after the central iron addition is started, when the iron material in the furnace has initially melted to form a local molten pool and the electrode work is stable, that is, when the three-phase current deviation is ≤5%, the carbon enrichment operation is started; (2) Carbon enrichment zone operation: ① Central area carbon enrichment: synchronous with the central feed pipe iron addition, the amount of semi-coke added in each batch is 10-15kg more than that in the non-central feed pipe, to ensure that the molar ratio of carbon to the newly added iron material is maintained at 1.2:1-1.5:1; ② Furnace shell area carbon enrichment: 150-200kg of carbon is evenly applied to one ring of the furnace shell each shift, and the amount of carbon applied is controlled within 3kg of the average carbon amount of the batch in that shift, and semi-coke with fixed carbon ≥85% is preferred; (3) Carbon enrichment adjustment: if the electrode is stuck in the lowering position If the furnace charge is difficult and sticky, the carbon enrichment amount per batch should be reduced by 3-5 kg; if the power consumption decreases and the silicon element recovery rate decreases, the carbon enrichment amount per batch should be increased by 2-3 kg, and the adjustment interval should be ≥24h; (4) Personalized handling of furnace conditions: ① Treatment of sticky material surface: When the material surface is locally sticky or caking, use a tie rod to poke holes in the furnace shell, the large triangular area and the small dead material area. After the tie rod is inserted 300-400mm deep into the furnace charge, it is lifted up and the sticky material is picked out. Then, 5-8 kg of carbon is attached to the poke area. The poke operation interval should be ≥8h; ② Furnace mouth temperature control: During the carbon enrichment period, the furnace mouth temperature should be controlled ≤460℃. If it exceeds the standard, the temperature should be reduced to the standard range within 20 minutes by increasing the feeding frequency of the central material pipe from once every 1h to once every 45min, and reducing the carbon enrichment amount per batch by 5kg.

2. The method for synergistic intensification of ferrosilicon submerged arc furnace smelting with central iron addition and carbon enrichment as described in claim 1, characterized in that: The method also includes a parameter monitoring and feedback mechanism, specifically as follows: the amount of iron added to the central feed pipe, the amount of carbon enrichment, the secondary voltage, the current, and the furnace mouth temperature are recorded every 2 hours; the daily accounting target is a silicon element recovery rate of ≥88%. If the daily accounting does not reach this target, the amount of iron added to the central feed pipe or the amount of carbon enrichment is adjusted the following day, with an adjustment range of 5 kg / batch; the effect of semi-coke entering the furnace is evaluated weekly. If the carbon enrichment efficiency decreases due to excessive ash content in the semi-coke, the semi-coke supplier is replaced, and priority is given to purchasing from suppliers with a fixed carbon content of ≥85%.

3. The method for synergistic intensification of ferrosilicon submerged arc furnace smelting with central iron addition and carbon enrichment as described in claim 2, characterized in that: During the central iron-adding operation phase, the material level height difference between the central area and other parts is monitored in real time by a material level height monitoring device. If the material level height difference is less than 50mm, the feeding frequency of the central material pipe is increased.

4. The method for synergistic intensification of ferrosilicon submerged arc furnace smelting with central iron addition and carbon enrichment as described in claim 3, characterized in that: In the carbon-enriched zoning operation, the preferred carbon-enriched semi-coke with a fixed carbon content of ≥85% in the furnace shell area is Shaanxi Huineng semi-coke or Jinchuan Hongtai semi-coke.