Application method of high-ash coal reducing agent in industrial silicon smelting
Through crushing and grading, acid leaching-microwave activation and calcium-based demulsification treatment processes, high-ash coal-based materials are activated as industrial silicon smelting and reducing agents, which solves the problem of the failure to effectively utilize high-ash coal-based materials, and achieves efficient utilization of resources and environmental protection improvement.
Patent Information
- Application Number
- CN202510585150.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-05-08
- Publication Date
- 2025-07-18
AI Technical Summary
Traditional industrial silicon smelting medium and high ash coal-based materials have not been effectively utilized, resulting in waste of resources and rising costs, and relying on petroleum coke resources is not environmentally friendly.
The synchronous desulfurization and dephosphorization treatment process of crushing and grading, acid leaching-microwave synergistic activation and calcium-based additives are used, combined with the staged feeding strategy, high-ash coal-based materials are activated as reducing agents, and conventional reducing agents are mixed.
It has achieved large-scale and efficient utilization of high-ash coal-based materials, reduced raw material costs by 20%-35%, reduced CO2 emissions by 15%-20%, improved reaction activity by 40%-60%, reduced power consumption by 12%-18%, and extended the equipment operation cycle for more than 20 days.
Smart Images
Figure BDA0005391491210000041
Abstract
Description
Technical Field
[0001] The present invention relates to the field of metallurgical technology, and particularly to an application method of a high-ash coal-based reducing agent in industrial silicon smelting. Background Art
[0002] As an important basic raw material in the fields of photovoltaic, semiconductor, and alloy materials, etc., the performance requirements for the reducing agent in the smelting process of industrial silicon are extremely high. Conventional industrial silicon smelting generally uses low-ash reducing agents such as petroleum coke, charcoal, and blue coke. These materials have the characteristics of high carbon content and few impurities, and can effectively promote the reduction reaction of silicon dioxide. However, with the rapid development of the new energy industry, the demand for industrial silicon has increased sharply, and traditional reducing agents are facing problems such as resource shortage and cost increase. Taking petroleum coke as an example, its price is significantly affected by fluctuations in the international crude oil market, and excessive dependence on fossil energy is contrary to the concept of green manufacturing. At the same time, in China's coal resources, there are rich reserves of low-rank coal materials such as high-ash coal (such as long-flame coal and lignite) and coal gangue. However, due to problems such as high ash content (15%-35%), excessive sulfur and phosphorus impurities, and low reactivity, they have long been excluded from the application of industrial silicon smelting and are only used as low-value-added fuels, resulting in waste of resources. Summary of the Invention
[0003] The present invention realizes the large-scale and efficient utilization of high-ash coal-based materials in industrial silicon smelting through innovative integration of processes such as crushing and classification optimization, acid leaching-microwave synergistic activation, and calcium-based additive directional impurity removal, and combines a staged feeding strategy, with both economic and environmental benefits.
[0004] The technical solution adopted by the present invention is: an application method of a high-ash coal-based reducing agent in industrial silicon smelting, using a high-ash coal-based material with an ash content of 15%-35% as a reducing agent after specific treatment processes, and mixing it with a conventional reducing agent in a proportion of 10%-60% by mass percentage. The specific treatment processes include crushing and classification, surface activation treatment, and synchronous desulfurization and dephosphorization treatment.
[0005] As a further improvement of the present invention, the particle size of the high-ash coal-based material is controlled to be 0.5-5 mm, and the proportion of particles with a size of 1-3 mm is not less than 70%.
[0006] As a further improvement of the present invention, the surface activation treatment adopts an acid leaching-microwave combined treatment process. The acid leaching solution is a composite organic acid solution with a concentration of 5%-15%, the microwave treatment power is 300-800 W, and the treatment time is 5-30 minutes.
[0007] As a further improvement of the present invention, the synchronous desulfurization and dephosphorization treatment adopts a calcium-based composite additive. The additive addition amount is 1%-5% of the mass of the coal-based material, the treatment temperature is 400-600 °C, and the treatment time is 30-90 minutes.
[0008] As a further improvement of the present invention, the conventional reducing agent is at least one of petroleum coke, charcoal, and blue coke, and the mixing ratio thereof with the high-ash coal material is 1:0.2 - 1:2.
[0009] As a further improvement of the present invention, the application method specifically includes the following steps:
[0010] Step 1: Crushing the high-ash coal material to the target particle size;
[0011] Step 2: Performing surface activation treatment to enhance the surface reaction activity;
[0012] Step 3: Implementing synchronous desulfurization and dephosphorization treatment to reduce the impurity content;
[0013] Step 4: Mixing evenly with the conventional reducing agent in proportion;
[0014] Step 5: Adding the reducing agent mixture in stages during the industrial silicon smelting process.
[0015] As a further improvement of the present invention, in Step 5, 30% - 50% of the total amount of the mixed reducing agent is added at the initial stage of smelting, and the remaining amount is added in 2 - 3 times during the middle stage of the reaction.
[0016] As a further improvement of the present invention, the high-ash coal material is at least one of long-flame coal, lignite, and coal gangue, and its fixed carbon content is ≥ 45%, and the volatile matter is ≤ 25%.
[0017] A composite reducing agent, comprising a treated high-ash coal material and a conventional reducing agent, has a comprehensive reaction activity index increased by 20% - 40%, a sulfur content of ≤ 0.3%, and a phosphorus content of ≤ 0.05%.
[0018] Advantages of the present invention:
[0019] (1) The present invention activates the potential of low-rank coal materials through an innovative process, enabling high-ash coal (ash content 15% - 35%) to replace 30% - 50% of traditional high-quality reducing agents, reducing the raw material cost by 20% - 35%. Taking an industrial silicon production line with an annual production capacity of 100,000 tons as an example, the procurement cost of reducing agents can be saved by more than 100 million yuan, significantly alleviating the dependence on petroleum coke resources.
[0020] (2) The acid leaching - microwave synergistic process realizes the reconstruction of the ash microstructure, the porosity is increased by 3 - 5 times, the specific surface area is increased by 200% - 400%, and the reaction activity index is increased by 40% - 60% compared with the untreated coal material. After the treated high-ash coal is compounded with petroleum coke, the comprehensive reaction activity of the system is still 15% - 20% higher than that of the single petroleum coke system, ensuring the reduction kinetics requirements.
[0021] (3) The energy consumption of microwave activation is reduced by 50%-70% compared with traditional high-temperature calcination, and the recycling rate of the acid leaching solution reaches more than 90%. The staged feeding strategy keeps the CO partial pressure in the furnace within the optimal range of 0.4-0.6 atm, reduces the activation energy of the reduction reaction by 12%-18%, decreases the specific power consumption of silicon per ton by 500-800 kWh, and simultaneously reduces CO2 emissions by 15%-20%.
[0022] (4) Coal types with fixed carbon ≥ 45% such as long-flame coal and lignite are successfully incorporated into the raw material system, and the blending ratio of coal gangue can reach 30%. The volatile matter of the treated coal quality material is stabilized at 8%-12%, avoiding furnace condition fluctuations. The improvement coefficient of furnace hearth air permeability reaches 1.2-1.5, and the continuous operation period of the equipment is extended by more than 20 days. Specific implementation manners
[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 in conjunction with 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 an application method of a high-ash coal quality reducing agent in industrial silicon smelting. A high-ash coal quality material with an ash content of 15%-35% is used as a reducing agent after a specific treatment process, and is mixed with a conventional reducing agent in a proportion of 10%-60% by mass percentage. The specific treatment process includes crushing and classification, surface activation treatment and synchronous desulfurization and dephosphorization treatment.
[0025] In the present invention, the particle size of the high-ash coal quality material is controlled to be 0.5-5 mm, and the proportion of particles with a size of 1-3 mm is not less than 70%.
[0026] In the present invention, the surface activation treatment adopts an acid leaching-microwave combined treatment process. The acid leaching solution is a composite organic acid solution with a concentration of 5%-15%. The microwave treatment power is 300-800 W, and the treatment time is 5-30 minutes.
[0027] In the present invention, the synchronous desulfurization and dephosphorization treatment adopts a calcium-based composite additive. The additive addition amount is 1%-5% of the mass of the coal quality material. The treatment temperature is 400-600 °C, and the treatment time is 30-90 minutes.
[0028] In the present invention, the conventional reducing agent is at least one of petroleum coke, charcoal and blue coke, and the mixing ratio thereof with the high-ash coal quality material is 1:0.2-1:2.
[0029] In the present invention, the application method specifically includes the following steps:
[0030] Step 1: Crush the high-ash coal quality material to the target particle size;
[0031] Step 2: Conduct surface activation treatment to enhance surface reaction activity;
[0032] Step 3: Implement simultaneous desulfurization and dephosphorization treatment to reduce impurity content;
[0033] Step 4: Mix evenly with a conventional reducing agent in proportion;
[0034] Step 5: Add the reducing agent mixture in stages during the industrial silicon smelting process.
[0035] In the present invention, in Step 5, 30%-50% of the total amount of the mixed reducing agent is added at the initial stage of smelting, and the remaining amount is added in 2-3 times during the middle stage of the reaction.
[0036] In the present invention, the high-ash coal-based material is at least one of long-flame coal, lignite, and coal gangue, with a fixed carbon content ≥ 45% and a volatile matter content ≤ 25%.
[0037] In the present invention, it contains a treated high-ash coal-based material and a conventional reducing agent, with the comprehensive reaction activity index increased by 20%-40%, a sulfur content ≤ 0.3%, and a phosphorus content ≤ 0.05%.
[0038] Example 1: Application of long-flame coal-based reducing agent
[0039] (I) Raw material treatment
[0040] Take long-flame coal produced in Shanxi (ash content 28.6%, fixed carbon 52.3%, sulfur 0.8%, phosphorus 0.09%).
[0041] Crushing and classification: Use a roller crusher to process to 0.8 - 3.2 mm, with the proportion of particles of 1 - 3 mm accounting for 82%.
[0042] Surface activation: (1) Acid leaching: Citric acid - oxalic acid composite solution (concentration 12%); solid-liquid ratio 1:5, stir at 60°C for 45 min; (2) Microwave treatment: Power 650 W, treat for 18 min under nitrogen protection.
[0043] Desulfurization and dephosphorization: Add 4.5% of CaO - CaCO3 composite agent (mass ratio 3:1), and treat at 550°C in a rotary kiln for 65 min.
[0044] (II) Compound application
[0045] Mixing ratio: Treated coal: Petroleum coke = 1:1 (the proportion of coal in the total reducing agent is 50%).
[0046] Staged feeding: (1) Add 40% of the mixture at the initial stage of smelting (when the furnace temperature is 1450°C); (2) Add the remaining amount in two times during the middle stage of the reaction (every 30 min).
[0047] (III) Effect verification
[0048]
[0049] Industrial test: Continuously operated for 15 batches in a 33 MVA submerged arc furnace. The furnace condition stability coefficient reached 0.92 (0.85 for the traditional process), the silicon recovery rate increased by 2.3 percentage points, and the cost of reducing agent per ton of silicon decreased by 31.6%.
[0050] Example 2: Composite application of coal gangue and lignite
[0051] (I) Raw material treatment
[0052] Coal gangue (ash content 32.1%) and lignite (ash content 18.5%) were compounded at a ratio of 1:2.
[0053] Crushed to 0.6 - 4.8 mm, and the proportion of particles with a size of 1 - 3 mm was 78%.
[0054] Surface activation: Treated with acetic acid - formic acid composite solution (8% concentration), microwave power 720 W / 22 min.
[0055] Impurity removal treatment: Added 3.2% of nano - calcium - based material (Ca(OH)2@SiO2), microwave - assisted desulfurization (480 °C / 50 min).
[0056] (II) Application scheme
[0057] Mixing ratio: Treated material: semi - coke = 1:0.8 (the proportion of coal in the total reducing agent was 55%).
[0058] Feeding strategy: (1) Added 35% of the mixture at the initial stage; (2) Added the remaining amount in 3 times at intervals of 25 min in the middle stage.
[0059] (III) Key data
[0060] Pore structure: The average pore diameter increased from 8.6 nm to 24.3 nm after treatment, and the pore volume increased by 3.8 times.
[0061] Activation energy: The apparent activation energy for SiO2 reduction decreased from 287 kJ / mol to 238 kJ / mol.
[0062] Emission index: The CO2 emission intensity decreased by 18.7%, and the dust emission decreased by 22.4%.
[0063] Continuous operation period: Reached 47 days (average 26 days for the traditional process).
[0064] Example 3: Optimization of application of high - volatile lignite
[0065] (I) Special treatment
[0066] Selected Inner Mongolia lignite (volatile content 23.6%).
[0067] Pre-carbonization treatment: Pyrolysis at 380°C for 45 min in a closed reactor, with the volatile matter reduced to 11.2%.
[0068] Two-stage activation: (1) First impregnated with 6% phosphoric acid solution; (2) Then co-activated by microwave-infrared (800W microwave + infrared radiation at 850°C).
[0069] (II) Industrial implementation
[0070] Mixing ratio: Treated coal: Charcoal: Petroleum coke = 1.5:1:1 (coal accounts for 42.8%).
[0071] Dynamic feeding control: Based on the CO concentration in the furnace gas, the feeding rate is adjusted in real time to maintain the CO partial pressure at 0.45 - 0.55 atm.
[0072] (III) Benefit analysis
[0073] Energy consumption: The energy consumption of microwave activation is only 32 kWh / t, a 68% reduction compared to traditional calcination.
[0074] Reaction kinetics: The value of the reduction reaction rate constant k increases by 1.8 times.
[0075] Impurity control: The Al content in the finished silicon is stable at 0.12 - 0.15% (not exceeding the standard).
[0076] Economy: The cost per ton of silicon decreases by 287 yuan, and an enterprise with an annual production capacity of 100,000 tons can increase its income by 28.7 million yuan.
[0077] Comparison item Example 1 Example 2 Example 3 Traditional process Ash utilization rate 28.6％→50％ 32.1％→55％ 18.5％→42.8％ 0％ Ash utilization rate 77.5％ 81.2％ 83.6％ —— Ash utilization rate +64.5％ +72.3％ +89.1％ Benchmark Reduction rate of power consumption 700 kWh / t 750 kWh / t 820 kWh / t —— Furnace condition stability coefficient 0.92 0.89 0.91 0.82-0.85
[0078] Innovation process verification: XRD analysis shows that acid leaching - microwave treatment reduces the content of inert quartz phase (SiO2) in coal quality from 14.3% to 5.1%, and at the same time generates an active silicate phase. SEM observation shows that the treated material forms a honeycomb-like porous structure, and the pore penetration rate increases to 92%.
[0079] In summary, the application method of a high-ash coal-based reducing agent in industrial silicon smelting according to the present invention not only realizes the resource-efficient utilization of high-ash coal-based materials, but also significantly improves the economy and environmental protection of industrial silicon smelting. Through the detailed data comparison of Example 1, Example 2 and Example 3, it can be clearly seen that by adopting the method of the present invention, the ash utilization rates are increased by 64.5%, 72.3% and 89.1% respectively, the power consumption reduction reaches 700 kWh / t, 750 kWh / t and 820 kWh / t respectively, and the furnace condition stability coefficient is also improved. These data fully prove the application potential and value of the present invention in the field of industrial silicon smelting. In addition, the innovative process of the present invention has been verified by scientific means such as XRD and SEM, further confirming its effectiveness and feasibility. Therefore, the present invention is expected to provide strong support for the sustainable development of the industrial silicon smelting industry.
[0080] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements on 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 applying a high-ash coal-based reducing agent in the smelting of industrial silicon, characterized in that: The high-ash coal quality material with an ash content of 15%-35% is used as a reducing agent after a specific treatment process, and is mixed with a conventional reducing agent in a proportion of 10%-60% by mass percentage. The specific treatment process includes crushing and grading, surface activation treatment, and simultaneous desulfurization and dephosphorization treatment.
2. The application method of a high-ash coal-based reducing agent in industrial silicon smelting according to claim 1, characterized in that: The particle size of the high-ash coal quality material is controlled to be 0.5-5 mm, and the proportion of particles with a size of 1-3 mm is not less than 70%.
3. The application method of a high-ash coal-based reducing agent in industrial silicon smelting according to claim 1, characterized in that: The surface activation treatment adopts an acid leaching-microwave combined treatment process. The acid leaching solution is a composite organic acid solution with a concentration of 5%-15%. The microwave treatment power is 300-800 W, and the treatment time is 5-30 minutes.
4. The application method of a high-ash coal-based reducing agent in industrial silicon smelting according to claim 1, characterized in that: The simultaneous desulfurization and dephosphorization treatment adopts a calcium-based composite additive. The additive addition amount is 1%-5% of the mass of the coal quality material. The treatment temperature is 400-600 °C, and the treatment time is 30-90 minutes.
5. The application method of a high-ash coal-based reducing agent in industrial silicon smelting according to claim 1, characterized in that: The conventional reducing agent is at least one of petroleum coke, charcoal, and blue coke, and its mixing ratio with the high-ash coal quality material is 1:0.2-1:
2.
6. The application method of a high-ash coal-based reducing agent in industrial silicon smelting according to claim 1, characterized in that: The described application method specifically includes the following steps: Step 1: Crush the high-ash coal quality material to the target particle size; Step 2: Conduct surface activation treatment to improve the surface reaction activity; Step 3: Implement simultaneous desulfurization and dephosphorization treatment to reduce the impurity content; Step 4: Mix evenly with the conventional reducing agent in proportion; Step 5: Add the reducing agent mixture in stages during the industrial silicon smelting process.
7. The application method of a high-ash coal-based reducing agent in industrial silicon smelting according to claim 6, characterized in that: In Step 5, 30%-50% of the total amount of the mixed reducing agent is added at the initial stage of melting, and the remaining amount is added in 2-3 times during the reaction medium term.
8. The application method of a high-ash coal-based reducing agent in industrial silicon smelting according to claim 1, characterized in that: The high-ash coal quality material is at least one of long-flame coal, lignite, and coal gangue, and its fixed carbon content ≥ 45%, and the volatile matter ≤ 25%.
9. A composite reducing agent prepared by the method according to any one of claims 1-8, characterized in that: It contains the treated high-ash coal quality material and the conventional reducing agent, and its comprehensive reaction activity index is increased by 20%-40%, the sulfur content ≤ 0.3%, and the phosphorus content ≤ 0.05%.