Method for smelting industrial silicon from high-explosion-resistance silicon ore

Abstract

The invention relates to the technical field of silicon material preparation, in particular to a method for smelting industrial silicon from high-explosion-resistance silicon ore. Comprising the following steps: crushing the silicon ore until the particle size is 5-20mm, calcining to remove volatile components, and soaking with acid liquor to remove surface impurities; the pretreated silicon ore is evenly mixed with a carbonaceous reducing agent and a composite antiknock agent according to the mass ratio of 100: (30-50): (2-5), wherein the composite antiknock agent is composed of calcium fluoride, magnesium oxide and graphite according to the mass ratio of 3: 1: 1; the mixture is added into an electric arc furnace in three batches, the interval between every two batches is 20-40 minutes, the furnace temperature gradient is controlled to be 1600-1800 DEG C, 1850-1950 DEG C and 1700-1750 DEG C, inert gas is introduced, and the pressure in the furnace is maintained to be 0.1-0.3 MPa; and after smelting is completed, the temperature is lowered to 800-1000 DEG C at the speed of 50-80 DEG C / min, heat preservation is conducted for 30-60 min, and then natural cooling is conducted to the room temperature. The invention provides a high-anti-knock smelting method integrating efficient pretreatment, synergistic effect of composite anti-knock agents, intelligent pressure relief and directional cooling, and the method has important significance for improving the production safety and product performance of industrial silicon.

Description

Technical Field

[0001] The invention relates to the technical field of silicon material preparation, and in particular to a method for smelting industrial silicon from highly explosion-resistant silicon ore. Background Art

[0002] Industrial silicon is a key basic material in the fields of semiconductors, photovoltaics and alloy manufacturing. Its purity and physical properties directly affect the quality of downstream products. Traditional industrial silicon smelting mainly adopts carbon thermal reduction method, which is produced by reacting silicon ore with carbonaceous reducing agent in a high-temperature electric arc furnace.

[0003] However, this process still faces many challenges in actual production: (1) Insufficient explosion resistance and safety hazards: During the smelting process, impurities in silicon ore and incomplete reactions of carbonaceous reducing agents can easily produce a large amount of combustible gases such as CO, and the pressure in the furnace suddenly increases, leading to the risk of explosion. Existing technologies are mostly controlled by a single pressure relief or gas dilution method, but lack real-time monitoring and dynamic adjustment mechanisms (such as automatic pressure relief when the CO concentration exceeds 12 vol%), making it difficult to effectively suppress sudden deflagration. (2) Raw material impurities affect purity: Impurities such as volatile matter (such as moisture, organic matter) and metal oxides are attached to the surface of silicon ore. Traditional pretreatment often uses a single acid wash or calcination, but the process parameters (such as acid concentration, calcination temperature) are selected in a rough manner, resulting in impurity residues, which ultimately affects the purity of the silicon ingot. (3) Smelting efficiency and energy consumption issues: Conventional processes use one-time feeding or simple batch feeding, and the furnace temperature control lacks gradient optimization, resulting in insufficient reduction reaction and high energy consumption. In addition, the SiO2 content in the slag is high (>25%) and the CaO / MgO ratio is unbalanced, which easily forms a high-viscosity slag layer, hindering the separation of metallic silicon and reducing the yield. (4) Cooling defects and deterioration of silicon ingot performance: Direct natural cooling of high-temperature silicon melt can easily cause internal stress concentration, leading to cracks and lattice defects in the silicon ingot. Although some technologies have introduced gradient cooling, they have not been combined with magnetic fields to control grain orientation, making it difficult to improve the density and mechanical properties of silicon ingots. (5) Limitations of anti-explosion agents and reducing agents: Existing anti-explosion agents mostly use a single component (such as CaF2), which is insufficient in the coordinated regulation of gas release in the furnace and the slag layer structure; excessive ash content (>5%) of carbonaceous reducing agents will also introduce additional impurities, exacerbating side reactions in the furnace. Summary of the invention

[0004] The present invention provides a high explosion-resistant smelting method integrating efficient pretreatment, synergistic effect of composite explosion-proof agents, intelligent pressure relief and directional cooling, which is of great significance to improving the production safety and product performance of industrial silicon.

[0005] The technical solution adopted by the present invention is: a method for smelting industrial silicon from highly explosion-resistant silicon ore, comprising the following steps:

[0006] Step 1, raw material pretreatment: Crush the silicon ore to a particle size of 5 - 20 mm. After calcination to remove volatile components, soak it in an acid solution to remove surface impurities.

[0007] Step 2, mixing ratio: Mix the pretreated silicon ore, carbonaceous reducing agent, and composite anti - knocking agent evenly according to a mass ratio of 100:30 - 50:2 - 5. The composite anti - knocking agent is composed of calcium fluoride, magnesium oxide, and graphite according to a mass ratio of 3:1:1.

[0008] Step 3, layered smelting: Add the mixture in three batches to the electric arc furnace, with an interval of 20 - 40 minutes between each batch. Control the furnace temperature gradient as 1600 - 1800 °C → 1850 - 1950 °C → 1700 - 1750 °C, and introduce an inert gas to maintain the furnace pressure at 0.1 - 0.3 MPa.

[0009] Step 4, gradient cooling: After smelting is completed, first cool down at a rate of 50 - 80 °C / min to 800 - 1000 °C, hold for 30 - 60 minutes, and then naturally cool to room temperature.

[0010] As a further improvement of the present invention, in the raw material pretreatment, the calcination temperature is 600 - 800 °C, the holding time is 1 - 3 hours, the acid solution is hydrochloric acid or sulfuric acid with a concentration of 10 - 15%, and the soaking time is 2 - 4 hours.

[0011] As a further improvement of the present invention, the carbonaceous reducing agent is charcoal or petroleum coke, with a fixed carbon content ≥ 85% and an ash content ≤ 5%.

[0012] As a further improvement of the present invention, the particle size of the composite anti - knocking agent is 50 - 200 mesh, and the addition amount is 2 - 5% of the mass of the silicon ore. Among them, the purity of calcium fluoride ≥ 98% and the purity of magnesium oxide ≥ 95%.

[0013] As a further improvement of the present invention, during the layered smelting process, the filling amount of each batch of the mixture is 30 - 40% of the volume of the electric arc furnace, and the peak furnace temperature of the second batch is 50 - 100 °C higher than that of the first batch, and the third batch cools down by 50 - 100 °C.

[0014] As a further improvement of the present invention, during the layered smelting process, the thickness of the smelting slag layer is controlled to be 20 - 30% of the depth of the molten pool, the SiO2 content in the slag ≤ 25%, and the mass ratio of CaO to MgO in the slag is 2:1 - 3:1.

[0015] As a further improvement of the present invention, during the layered smelting process, use an infrared spectrometer to monitor the CO gas concentration in the furnace in real - time. When the CO concentration exceeds 12 vol%, automatically trigger the pressure - relief device, and control the pressure - relief rate at 0.05 - 0.1 MPa / s.

[0016] As a further improvement of the present invention, the inert gas is argon or nitrogen, and the feeding rate is 5-10 L / min, and the oxygen content in the furnace is controlled at ≤0.5 vol%.

[0017] As a further improvement of the present invention, in the gradient cooling stage, a magnetic field of 0.5-1 T is applied synchronously when maintaining the temperature at 800-1000 °C, and the direction of the magnetic field is perpendicular to the flow direction of the silicon melt.

[0018] As a further improvement of the present invention, after the gradient cooling stage is completed, surface passivation treatment is carried out on the industrial silicon ingot: the silicon ingot is immersed in a phosphoric acid solution containing 5-8 wt% sodium nitrate, treated at 60-80 °C for 15-30 minutes, and then rinsed with deionized water until neutral to form a passivation film with a thickness of 10-20 μm.

[0019] Advantages of the present invention: (1) Through the synergistic effect of the composite antiknock agent and the intelligent pressure relief mechanism, the present invention effectively inhibits the sudden increase in the furnace pressure and reduces the explosion risk. The CO concentration in the furnace is monitored in real time to achieve precise pressure relief and ensure the stable progress of the smelting process.

[0020] (2) The present invention optimizes the raw material pretreatment process, precisely controls the calcination temperature and the acid solution concentration, effectively removes the surface impurities of the silicon ore, reduces the impurity residue, and improves the purity of the industrial silicon. At the same time, high-quality carbonaceous reducing agents are selected to reduce the ash introduction and reduce the side reactions in the furnace.

[0021] (3) The present invention adopts the layered smelting and furnace temperature gradient control technology to optimize the reduction reaction conditions and improve the reduction efficiency. The thickness and composition of the smelting slag layer are reasonably controlled to promote the separation of metallic silicon and improve the yield. In addition, the introduction of the inert gas maintains a stable environment in the furnace and further reduces the energy consumption.

[0022] (4) The combination of gradient cooling and magnetic field regulation in the present invention effectively relieves the internal stress concentration of the silicon melt, reduces the cracks and lattice defects of the silicon ingot. At the same time, the surface passivation treatment enhances the corrosion resistance and mechanical properties of the silicon ingot, and improves the comprehensive performance of the product. Specific Embodiments

[0023] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present application clearer, the present application will be further described in detail below with reference to the embodiments. It should be understood that the embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0024] The present invention provides a method for smelting industrial silicon from silicon ore with high explosion resistance, including the following steps:

[0025] Step 1, raw material pretreatment: The silicon ore is crushed to a particle size of 5-20 mm, and after removing volatile components by calcination, it is soaked in an acid solution to remove surface impurities;

[0026] Step 2, Mixing ratio: Mix the pretreated silicon ore, carbonaceous reducing agent, and composite anti-knock agent evenly according to a mass ratio of 100:30 - 50:2 - 5. The composite anti-knock agent is composed of calcium fluoride, magnesium oxide, and graphite according to a mass ratio of 3:1:1;

[0027] Step 3, Layered smelting: Add the mixture in three batches to the electric arc furnace, with an interval of 20 - 40 minutes between each batch. The furnace temperature gradient is controlled as 1600 - 1800 °C → 1850 - 1950 °C → 1700 - 1750 °C, and an inert gas is introduced to maintain the furnace pressure at 0.1 - 0.3 MPa;

[0028] Step 4, Gradient cooling: After smelting is completed, first cool down at a rate of 50 - 80 °C / min to 800 - 1000 °C, keep warm for 30 - 60 minutes, and then naturally cool to room temperature.

[0029] In the present invention, the calcination temperature in the raw material pretreatment is 600 - 800 °C, the heat preservation time is 1 - 3 hours, the acid solution is hydrochloric acid and sulfuric acid with a concentration of 10 - 15%, and the soaking time is 2 - 4 hours.

[0030] In the present invention, the carbonaceous reducing agent is charcoal and petroleum coke, with a fixed carbon content ≥ 85% and an ash content ≤ 5%. The particle size of the composite anti-knock agent is 50 - 200 mesh, and the addition amount is 2 - 5% of the mass of the silicon ore. Among them, the purity of calcium fluoride ≥ 98% and the purity of magnesium oxide ≥ 95%.

[0031] In the layered smelting process of the present invention, the filling amount of each batch of the mixture is 30 - 40% of the volume of the electric arc furnace. And the peak furnace temperature of the second batch is increased by 50 - 100 °C compared with the first batch, and the third batch is cooled down by 50 - 100 °C. During the layered smelting process, the thickness of the smelting slag layer is controlled to be 20 - 30% of the depth of the molten pool, the SiO2 content in the slag ≤ 25%, and the mass ratio of CaO to MgO in the slag is 2:1 - 3:1. During the layered smelting process, an infrared spectrometer is used to monitor the CO gas concentration in the furnace in real time. When the CO concentration exceeds 12 vol%, the pressure relief device is automatically triggered, and the pressure relief rate is controlled at 0.05 - 0.1 MPa / s.

[0032] In the present invention, the inert gas is argon and nitrogen, the introduction rate is 5 - 10 L / min, and the oxygen content in the furnace is controlled at ≤ 0.5 vol%.

[0033] In the gradient cooling stage of the present invention, a magnetic field of 0.5 - 1 T is applied synchronously while maintaining the temperature at 800 - 1000 °C, and the direction of the magnetic field is perpendicular to the flow direction of the silicon melt. After the gradient cooling stage is completed, surface passivation treatment is carried out on the industrial silicon ingot: the silicon ingot is immersed in a phosphoric acid solution containing 5 - 8 wt% sodium nitrate, treated at 60 - 80 °C for 15 - 30 minutes, and then rinsed with deionized water until neutral to form a passivation film with a thickness of 10 - 20 μm.

[0034] Example 1:

[0035] Step 1: Raw material pretreatment

[0036] The silicon ore is crushed to a particle size of 5 - 15 mm, calcined in a calciner at 650 °C for 2 hours, and after removing volatile components, it is soaked in a 12% hydrochloric acid solution for 3 hours to remove surface metal oxides.

[0037] Step 2: Mixing ratio

[0038] The pretreated silicon ore (100 kg) is mixed evenly with charcoal (35 kg, fixed carbon content 88%, ash content 4%) and a composite antiknock agent (3 kg, calcium fluoride:magnesium oxide:graphite = 3:1:1, particle size 100 mesh).

[0039] Step 3: Layered smelting

[0040] The mixture is added to the electric arc furnace in three batches: (1) The first batch: filling amount 35%, furnace temperature 1700 °C, argon is introduced (8 L / min), and the pressure is maintained at 0.2 MPa; (2) The second batch (with an interval of 30 minutes): filling amount 30%, furnace temperature is increased to 1900 °C (200 °C higher than the first batch), pressure 0.25 MPa; (3) The third batch (with an interval of 30 minutes): filling amount 35%, furnace temperature is decreased to 1750 °C, pressure 0.15 MPa.

[0041] The CO concentration is monitored in real time (using an infrared spectrometer), and pressure relief is triggered (0.08 MPa / s) when the CO concentration reaches 12.5 vol%. The thickness of the slag layer is 25% of the depth of the molten pool, the SiO2 content in the slag is 22%, and CaO / MgO = 2.5:1.

[0042] Step 4: Gradient cooling

[0043] Cool down at a rate of 60 °C / min to 900 °C, hold for 40 minutes, and apply a perpendicular magnetic field of 0.7 T synchronously. Then cool naturally to room temperature, and the silicon ingot is immersed in a phosphoric acid solution containing 6 wt% sodium nitrate (treated at 70 °C for 20 minutes) to form a 15 - μm passivation film.

[0044] Result: The purity of the industrial silicon is 99.1%, there are no cracks, the antiknock property is improved by 40%, and the energy consumption is reduced by 18%.

[0045] Example 2:

[0046] Step 1: Pretreatment of raw materials

[0047] The silicon ore is crushed to a particle size of 10 - 20 mm, calcined at 700 °C for 2.5 hours, and soaked in 10% sulfuric acid solution for 4 hours.

[0048] Step 2: Mixing ratio

[0049] The silicon ore (100 kg) is mixed with petroleum coke (45 kg, fixed carbon content 90%, ash content 3%) and a composite antiknock agent (4 kg, calcium fluoride:magnesium oxide:graphite = 3:1:1, particle size 150 mesh).

[0050] Step 3: Layered smelting

[0051] (1) First batch: filling amount 40%, furnace temperature 1800 °C, nitrogen is passed (10 L / min), pressure 0.3 MPa; (2) Second batch (interval 40 minutes): filling amount 30%, furnace temperature 1950 °C (+150 °C), pressure 0.25 MPa; (3) Third batch (interval 40 minutes): filling amount 30%, furnace temperature 1750 °C.

[0052] When the CO concentration reaches 12.8 vol%, the pressure is released (0.1 MPa / s), the slag layer thickness is 30%, the SiO2 content is 20%, and CaO / MgO = 3:1

[0053] Step 4: Gradient cooling

[0054] Cool down to 1000 °C at 80 °C / min, keep warm for 30 minutes, and apply a 1 T magnetic field. The passivation treatment uses a 7 wt% sodium nitrate solution (80 °C, 25 minutes), and the passivation film thickness is 20 μm.

[0055] Result: Silicon purity 99.4%, lattice defect rate < 0.5%, energy consumption reduced by 22%.

[0056] Example 3:

[0057] Step 1: Pretreatment of raw materials

[0058] The silicon ore is crushed to a particle size of 5 - 10 mm, calcined at 800 °C for 1.5 hours, and soaked in 15% hydrochloric acid solution for 2 hours.

[0059] Step 2: Mixing ratio

[0060] The silicon ore (100 kg) is mixed with charcoal (30 kg, fixed carbon content 85%, ash content 5%) and a composite antiknock agent (5 kg, calcium fluoride:magnesium oxide:graphite = 3:1:1, particle size 50 mesh).

[0061] Step 3: Layered smelting

[0062] (1) The first batch: filling amount 30%, furnace temperature 1600 °C, argon (5 L / min), pressure 0.1 MPa; (2) The second batch (with an interval of 20 minutes): filling amount 40%, furnace temperature 1850 °C (+250 °C), pressure 0.2 MPa; (3) The third batch (with an interval of 20 minutes): filling amount 30%, furnace temperature 1700 °C.

[0063] When the CO concentration reached 11.9 vol%, the pressure relief was not triggered, the slag layer thickness was 20%, the SiO2 content was 18%, and CaO / MgO = 2:1.

[0064] Step Four: Gradient cooling

[0065] Cool down to 800 °C at a rate of 50 °C / min, hold for 60 minutes, and apply a magnetic field of 0.5 T. The passivation treatment uses a 5 wt% sodium nitrate solution (60 °C, 30 minutes), and the passivation film thickness is 10 μm.

[0066] Results: The silicon purity is 98.9%, the anti-explosion performance is improved by 35%, and the silicon recovery rate in the slag is increased to 92%.

[0067] The data of the above Examples 1-3 and the traditional process are shown in the following table.

[0068] Index Example 1 Example 2 Example 3 Traditional process Purity of metallurgical silicon (%) 99.1 99.4 98.9 97.5-98.2 Improvement in anti-knock performance (%) 40 45 35 —— Lattice defect rate (%) 0.3 0.4 0.7 1.2-2.5 Energy consumption (kWh / t) 10200 9800 10500 12500-13800 <![CDATA[SiO2 content in slag (%)]]> 22 20 18 28-32 Passivation film thickness (μm) 15 20 10 —— Silicon recovery rate (%) 90 93 92 82-85

[0069] In summary, a method for smelting metallurgical silicon from high anti-explosion silicon ore according to the present invention significantly improves the purity and anti-explosion performance of metallurgical silicon by precisely controlling key steps such as raw material pretreatment, mixing ratio, layered smelting, and gradient cooling, while reducing energy consumption and the lattice defect rate. The data comparison of Examples 1 to 3 clearly demonstrates the superiority of the present invention. Compared with the traditional process, the present invention has achieved remarkable results in terms of improving the purity of metallurgical silicon, enhancing the anti-explosion performance, reducing the lattice defect rate, reducing energy consumption, and increasing the silicon recovery rate in the slag. In addition, through surface passivation treatment, the corrosion resistance and mechanical properties of the silicon ingot are further enhanced, providing strong support for the wide application of metallurgical silicon. Therefore, the present invention has broad market prospects and application value and is worthy of popularization and use in the field of silicon ore smelting.

[0070] The above examples are only used to illustrate the technical solutions of the present invention and are not intended to limit them; although the present invention has been described in detail with reference to the foregoing examples, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing examples, or perform equivalent replacements for some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for smelting metallurgical silicon from high anti-explosion silicon ore, characterized in that, It includes the following steps: Step 1, raw material pretreatment: Crush the silicon ore to a particle size of 5 - 20 mm. After calcination to remove volatile components, soak it in an acid solution to remove surface impurities; Step 2, mixing ratio: Mix the pretreated silicon ore, carbonaceous reducing agent, and composite anti-knock agent evenly according to a mass ratio of 100:30 - 50:2 - 5. The composite anti-knock agent is composed of calcium fluoride, magnesium oxide, and graphite according to a mass ratio of 3:1:1; Step 3, layered smelting: Add the mixture in three batches to the electric arc furnace, with an interval of 20 - 40 minutes between each batch. The furnace temperature gradient is controlled as 1600 - 1800 °C → 1850 - 1950 °C → 1700 - 1750 °C, and an inert gas is introduced to maintain the furnace pressure at 0.1 - 0.3 MPa; Step 4, gradient cooling: After smelting is completed, first cool down at a rate of 50 - 80 °C / min to 800 - 1000 °C, hold for 30 - 60 minutes, and then cool naturally to room temperature.

2. The method for smelting metallurgical silicon from high anti-explosion silicon ore according to claim 1, characterized in that, In the raw material pretreatment, the calcination temperature is 600 - 800 °C, the holding time is 1 - 3 hours, the acid solution is hydrochloric acid or sulfuric acid with a concentration of 10 - 15%, and the soaking time is 2 - 4 hours.

3. A method for smelting metallurgical silicon from high anti-explosion silicon ore according to claim 1, characterized in that, The carbonaceous reducing agent is charcoal or petroleum coke, with a fixed carbon content ≥ 85% and an ash content ≤ 5%.

4. A method for smelting metallurgical silicon from high anti-explosion silicon ore according to claim 1, characterized in that, The particle size of the composite anti-knock agent is 50 - 200 mesh, and the addition amount is 2 - 5% of the mass of the silicon ore. Among them, the purity of calcium fluoride ≥ 98% and the purity of magnesium oxide ≥ 95%.

5. A method for smelting metallurgical silicon from high anti-explosion silicon ore according to claim 1, characterized in that, During the layered smelting process, the filling amount of each batch of the mixture is 30 - 40% of the volume of the electric arc furnace, and the peak furnace temperature of the second batch is 50 - 100 °C higher than that of the first batch, and the third batch is cooled by 50 - 100 °C.

6. A method for smelting metallurgical silicon from high anti-explosion silicon ore according to claim 1, characterized in that, During the layered smelting process, the thickness of the smelting slag layer is controlled to be 20 - 30% of the depth of the molten pool, the SiO2 content in the slag ≤ 25%, and the mass ratio of CaO to MgO in the slag is 2:1 - 3:

1.

7. A method for smelting metallurgical silicon from high anti-explosion silicon ore according to claim 1, characterized in that, During the layered smelting process, an infrared spectrometer is used to monitor the CO gas concentration in the furnace in real time. When the CO concentration exceeds 12 vol%, the pressure relief device is automatically triggered, and the pressure relief rate is controlled at 0.05 - 0.1 MPa / s.

8. A method for smelting metallurgical silicon from high anti-explosion silicon ore according to claim 1, characterized in that, The inert gas is argon or nitrogen, the introduction rate is 5 - 10 L / min, and the oxygen content in the furnace is controlled at ≤ 0.5 vol%.

9. A method for smelting metallurgical silicon from high anti-explosion silicon ore according to claim 1, characterized in that, During the gradient cooling stage, a magnetic field of 0.5 - 1 T is applied synchronously when holding at 800 - 1000 °C, and the magnetic field direction is perpendicular to the flow direction of the silicon melt.

10. A method for smelting metallurgical silicon from high anti-explosion silicon ore according to claim 1, characterized in that, After the gradient cooling stage is completed, surface passivation treatment is carried out on the industrial silicon ingot: Immerse the silicon ingot in a phosphoric acid solution containing 5 - 8 wt% sodium nitrate, treat it at 60 - 80 °C for 15 - 30 minutes, and then rinse it with deionized water until neutral to form a passivation film with a thickness of 10 - 20 μm.