A method for preparing niobium carbide by fire reduction recovery from aluminum niobium slag

Abstract

The application discloses a method for preparing niobium carbide from aluminum niobium slag by fire reduction recovery. The method comprises the following steps: taking aluminum niobium slag, graphite powder and fluorite according to the mass ratio of 100:6-12:3-8, mixing them uniformly to obtain a mixture; loading the mixture into an electric arc furnace preheated to 700-900 DEG C and into which a protective gas is introduced, heating to 1750-2050 DEG C and keeping constant temperature for 2-4 hours, and then discharging aluminum slag mixture and niobium carbide alloy ingot after layering; crushing the niobium carbide alloy ingot, adding it into an alkaline solution according to the solid-liquid ratio of 1g:8-12ml, heating to 80-100 DEG C and stirring for 2-4 hours, filtering and washing with water until pH=7-8 while hot after the reaction, and then performing acid washing and drying. The application has wide raw material adaptation range, high niobium recovery rate and product purity, and obvious cost advantage.

Description

Technical Field

[0001] This invention relates to the field of aluminum-niobium slag resource utilization technology, and in particular to a method for pyrometallurgical reduction and recovery of niobium carbide from aluminum-niobium slag. Background Technology

[0002] Niobium, an important refractory metal, possesses excellent properties such as high melting point, high strength, good superconductivity, corrosion resistance, and biocompatibility, and is widely used in high-end fields such as aerospace, semiconductors, superconducting materials, medical implants, and the nuclear industry. With the increasing global demand for niobium resources and the gradual depletion of primary niobium ore resources, the technology of recovering niobium from industrial waste has become an important way to solve the resource shortage problem.

[0003] Aluminum-niobium slag is an industrial waste generated during the production of aluminum-niobium alloys, tantalum-niobium smelting, or the treatment of niobium-containing waste. Its niobium content typically ranges from 5% to 30%, and it also contains various impurities such as aluminum, silicon, and iron. Direct disposal not only wastes valuable niobium resources but also poses an environmental pollution risk due to the leakage of harmful substances from the waste. Currently known processes for recovering niobium from aluminum-niobium slag mainly include the following three categories: (1) Wet leaching-extraction purification process: Impurities are separated through acid leaching, alkali melting and extraction. Although the impurity removal rate is high, the process is complex, the consumption of acid and alkali reagents is large, the environmental treatment cost is high, and the treatment efficiency for low-grade aluminum niobium slag is low, and the adaptability to large-scale production is poor. (2) Chlorination volatilization-condensation process: Separation is achieved by utilizing the difference in boiling points between niobium and impurity chlorides. The product has high purity, but it is highly corrosive to equipment and has high investment costs (investment of RMB 250,000 to 350,000 per ton of processing equipment). It is only suitable for small-scale, refined production. (3) Traditional pyrometallurgical reduction process: Niobium is separated from impurities through high-temperature reduction, but it has problems such as narrow raw material compatibility (only applicable to high-grade slag with ≥10% niobium content), high energy consumption (power consumption per ton ≥10000kWh), low niobium recovery rate (usually less than 75%), and incomplete separation of impurities (residual Al content ≥0.1%), which makes it difficult to meet the needs of large-scale industrial production of aluminum-niobium slag of different grades.

[0004] Therefore, developing a pyrometallurgical niobium extraction technology from aluminum niobium slag that is widely adaptable to raw materials, has a short process, high efficiency, controllable cost, meets environmental standards, and can balance recovery rate and purity is of great practical significance and industrial application value. Summary of the Invention

[0005] To address the aforementioned shortcomings, the present invention aims to provide a method for the pyrochemical reduction and recovery of niobium carbide from aluminum niobium slag, thereby solving the problems of high cost and low efficiency in the current recovery of niobium from aluminum niobium slag.

[0006] The objective of this invention is achieved through the following technical solution: A method for preparing niobium carbide from aluminum niobium slag by pyrometallurgical reduction includes the following steps: (1) Raw material pretreatment: Weigh aluminum niobium slag, graphite powder and fluorite in a mass ratio of 100:6~12:3~8, mix them evenly to obtain a mixture; (2) Electric arc furnace reduction smelting: The mixture is loaded into an electric arc furnace preheated to 700~900℃ and a protective gas is introduced in batches. The temperature is raised to 1750~2050℃ and kept at a constant temperature for 2~4 hours. After standing, the aluminum slag mixture and niobium carbide alloy ingots are discharged in layers. In step (2), Al2O3 in the aluminum-niobium slag is reduced to metallic aluminum by graphite powder, and Nb2O5 reacts with graphite powder to generate niobium carbide (NbC). The core reaction equation is: 2Al2O3+6C=4Al+6CO, Nb2O5+7C=2NbC+5CO; After the reaction, an aluminum slag mixture and a niobium carbide alloy ingot are obtained. The main components of the aluminum slag mixture are metallic aluminum (approximately 35-40%), a small amount of unreacted fluorite, Al2O3, and other impurity oxides. The metallic aluminum can be extracted through further recycling. The main component of the niobium carbide alloy ingot is niobium carbide (NbC, purity ≥90%), and it also contains a small amount of metallic impurities such as Al, Si, and Fe.

[0007] Fluorite (CaF2) is added to this process as a flux, and is a key auxiliary agent in the pyrometallurgical reduction smelting stage. Its core functions are to lower the melting point of the reaction system, optimize slag fluidity, break the crystal structure of silicate impurities in aluminum-niobium slag, promote the full progress of the reduction reaction, and improve niobium recovery rate and product separation efficiency. The specific functions and related reactions are as follows: 1. Lower the melting point and viscosity of slag The oxides such as Al2O3 and SiO2 contained in aluminum niobium slag will form a high-melting-point silicate system. Fluorite can react with these high-melting-point oxides to generate low-melting-point fluorides and fluorosilicates, which will significantly reduce the melting point of the slag (reduce the melting temperature of the system by 200~400℃), while reducing the viscosity of the slag, improving the stratification effect between the slag and the niobium carbide alloy ingot, and avoiding the loss of recovery rate caused by the niobium carbide being covered by the slag.

[0008] 2. Break the silicate lattice to release the niobium component. In aluminum-niobium slag, some niobium exists in the form of niobium silicate, which has a stable crystal structure and is difficult to reduce. Fluorite can disrupt this crystal lattice, releasing the niobium component into Nb2O5, which readily reacts with graphite powder, thereby improving the reduction efficiency of niobium.

[0009] 3. Reduce slag buildup on the furnace walls and protect the furnace body. Low-viscosity slag is less likely to adhere to the surface of the high-alumina refractory brick lining of the electric arc furnace, reducing slagging on the furnace wall, reducing furnace erosion, and improving the temperature uniformity inside the furnace, ensuring the stable progress of the reduction reaction.

[0010] Core chemical reaction formula 1. Forms low-melting-point fluorides with alumina and silica (core fluxing reaction) 3CaF2+ Al2O3+ SiO2= Ca3Al2SiF6O5 CaF2 + Al2O3 = CaAl2F2O3 (calcium fluoroaluminate, melting point approximately 1050℃, significantly reducing the melting point of slag) CaF2 + SiO2 = CaSiF2O2 (Calcium fluorosilicate, melting point approximately 730℃, reduces slag viscosity) 2. Reaction with niobium oxide (releases niobium components, which are easily reduced) 5CaF2 + Nb2O5 = Ca5Nb2F 10 O5 (calcium fluoroniobate, an intermediate product, is easily reduced to NbC by graphite powder) Subsequent reduction: Ca5Nb2F 10 O5 + 7C = 2NbC + 5CaF2 + 5CO↑ (Fluorite can participate in the reaction repeatedly in this step, improving its utilization rate) O generated by the reaction of fluorite 2- (Divalent oxygen) will rapidly react with the large amount of Ca in the system. 2+ Al 3+ Si 4+ Metal cations combine to form stable oxides / composite oxides, O² - The CaO, aluminates, and silicates formed by the combination react with fluorite to form fluoroaluminates and fluorosilicates, which further form low-melting-point eutectic slag. This not only enhances the fluxing effect of fluorite but also allows it to separate from niobium carbide alloy ingots through density differences. Ultimately, it is discharged along with the aluminum slag mixture and can be recycled and processed with the aluminum slag in the future.

[0011] (3) Alkali dissolution-acid washing combined purification of niobium carbide: After crushing the niobium carbide alloy ingot, add it to an alkaline solution at a solid-liquid ratio of 1g: 8~12mL, heat to 80~100℃ and stir for 2~4h. After the reaction is completed, filter while hot and wash with water until pH=7~8. After acid washing and drying, high-purity niobium carbide is obtained.

[0012] In step (3), the niobium carbide alloy ingot is crushed, which increases the specific surface area and helps to improve the efficiency of subsequent impurity removal. The crushed niobium carbide alloy ingot is added to an alkaline solution. The residual metal Al in the alloy ingot reacts with the alkaline solution to generate soluble aluminates, thereby removing aluminum impurities. The reaction equation is (taking NaOH as an example): 2Al + 2NaOH + 2H2O = 2NaAlO2 + 3H2. After the alkaline dissolution reaction is completed, the filter is filtered while hot to remove the alkaline filtrate containing aluminum impurities. Then, the filter residue is washed with deionized water until the pH of the washing liquid is 7~8 to remove the residual alkaline solution.

[0013] Furthermore, the filter residue after water washing is acid-washed to remove residual metallic Fe. The corresponding reaction equation is (taking HCl as an example): Fe + 2HCl = FeCl2 + H2, where some Fe is oxidized to Fe2+. 3+ The chemical reaction is: Fe + 2FeCl3 = 3FeCl2, and ultimately all Fe reacts as Fe. 2+ / Fe 3+ The niobium carbide (NbC) is then introduced into the filtrate. It should be noted that niobium carbide (NbC) is chemically stable and does not react under the above-mentioned alkaline dissolution and acid washing conditions. Only residual impurities such as Al and Fe are selectively dissolved and removed. Si impurities can be discharged with the filtrate through the formation of a small amount of sodium silicate during the alkaline dissolution process, thus ultimately achieving the purification of niobium carbide.

[0014] Preferably, the aluminum niobium slag in step (1) has a Nb content of 8-30%, an Al2O3 content of ≤35%, a Si content of ≤6%, and an Fe content of ≤4%.

[0015] Preferably, the aluminum-niobium slag in step (1) is crushed to 80-120 mesh before mixing, and the graphite powder is dried to a moisture content of ≤0.8% before mixing.

[0016] Preferably, the mixture in step (1) is prepared by mixing the raw materials with a frequency converter for 20-40 minutes to achieve a mixing uniformity of ≥93%.

[0017] Preferably, the mixture in step (2) is pressed to a density of 2.6~3.2 g / cm³ before being loaded into the electric arc furnace. 3 The blank.

[0018] Preferably, the protective gas in step (2) is at least one of nitrogen and argon; the flow rate of the protective gas is 1.0~3.0 m³ / h. 3 / h.

[0019] Preferably, the oxygen content in the electric arc furnace in step (2) is ≤0.8%, and the electric arc furnace is heated to 1750~2050℃ at a rate of 8~15℃ / min.

[0020] Preferably, the niobium carbide alloy ingot in step (3) is crushed to 100-200 mesh and then added to an alkaline solution.

[0021] Preferably, the alkaline solution in step (3) is at least one of sodium hydroxide and potassium hydroxide.

[0022] Preferably, the concentration of the alkaline solution in step (3) is 8~12 mol / L.

[0023] Preferably, the specific steps of acid washing in step (3) are as follows: the water-washed filter residue is added to dilute hydrochloric acid with a concentration of 3-5 mol / L at a solid-liquid ratio of 1g:10-15mL, and the mixture is stirred at room temperature for 1-2 hours. After the reaction is completed, the filter residue is washed with water until no Cl is visible in the washing liquid. - .

[0024] Preferably, the specific steps of drying in step (3) are as follows: drying the acid-washed filter residue at 110~150℃ for 2~3 hours.

[0025] Compared with the prior art, the beneficial effects of the present invention include: (1) Wide range of raw material compatibility: This invention breaks through the limitation that traditional pyrometallurgical processes are only applicable to high-grade aluminum-niobium slag. It can process medium-low grade to medium-high grade aluminum-niobium slag containing 8~30% Nb, which greatly expands the application scenarios of raw materials and reduces the cost of raw material screening.

[0026] (2) High niobium recovery rate and high product purity: By optimizing the raw material ratio, inert protection smelting, precise temperature control and efficient refining, the present invention increases the niobium recovery rate to 76~87%, which is 3~13 percentage points higher than the traditional pyrometallurgical process. The residual Al content is ≤0.08%, and the impurity removal effect is significantly better than the traditional process.

[0027] (3) High resource utilization rate and obvious cost advantage: The aluminum slag mixture by-product of this invention can be further recycled into metallic aluminum, with a comprehensive resource utilization rate of ≥92%; the amount of graphite powder used as reducing agent can be flexibly adjusted according to the raw material grade, and industrial-grade waste graphite (purity ≥95%) can be selected, which can reduce the raw material cost by 30~40%; the overall single-ton processing cost is 20~25% lower than that of wet process and 50~60% lower than that of chlorination volatilization process, and has broad prospects for industrial application. Detailed Implementation

[0028] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0029] Example 1 A method for preparing niobium carbide from aluminum niobium slag by pyrometallurgical reduction includes the following steps: (1) Raw material pretreatment: Weigh 100kg of aluminum niobium slag (containing 8% Nb, 32% Al2O3, 5% Si, and 3% Fe), 6kg of industrial-grade waste graphite powder (purity of 95%), and 3kg of fluorite; crush the aluminum niobium slag to 120 mesh, dry the graphite powder to a moisture content of 0.6%, mix the aluminum niobium slag, fluorite, and graphite powder, and stir with a frequency converter for 20 minutes (mixing uniformity of 93%) to obtain a mixture. Press the mixture into blocks of φ40mm×20mm with a density of 2.6g / cm³. (2) Electric arc furnace reduction smelting: Preheat the 1000kVA electric arc furnace to 700℃, and introduce nitrogen gas (flow rate of 1.0m³). 3 The oxygen content in the furnace was 0.7%; then, the pressed block material was added to the electric arc furnace in two batches, heated to 1750℃ at a heating rate of 8℃ / min and held at that temperature for 4 hours; the power consumption for smelting was 8000kWh, and the waste heat recovery was 1200kWh; after the holding period, the mixture was left to stand for 20 minutes, and 28kg of aluminum slag mixture was discharged through a 15° tilting device, and 12.3kg of niobium carbide alloy ingots were collected; (3) Alloy refining (alkali dissolution-acid washing combination): The niobium carbide alloy ingot is crushed to 150 mesh, and then added to a sodium hydroxide solution with a concentration of 8 mol / L at a solid-liquid ratio of 1 g: 8 mL. The mixture is stirred at 90 °C for 3 h. After the reaction is completed, the mixture is filtered while hot, and the filter residue is washed with deionized water until the pH of the washing water is 7. Then, the filter residue is added to a dilute hydrochloric acid solution with a concentration of 3 mol / L at a solid-liquid ratio of 1 g: 10 mL. The mixture is stirred at room temperature for 1.5 h. After the reaction is completed, the filter residue is washed with water until no Cl is present in the washing liquid. - The acid-washed filter residue was dried at 120℃ for 2.5 hours to obtain 10.2 kg of high-purity niobium carbide powder.

[0030] According to the test and calculation, the niobium recovery rate of Example 1 was 76%, the purity of niobium carbide powder was 98.5%, and the residual Al content was 0.06%, Si content was 0.09%, and Fe content was 0.07%.

[0031] Example 2 A method for preparing niobium carbide from aluminum niobium slag by pyrometallurgical reduction includes the following steps: (1) Raw material pretreatment: Weigh 100kg of aluminum niobium slag (containing 15% Nb, 28% Al2O3, 4% Si, and 2% Fe), 9kg of industrial-grade graphite powder (purity of 98%), and 5kg of fluorite; crush the aluminum niobium slag to 100 mesh, dry the graphite powder to a moisture content of 0.4%, mix the aluminum niobium slag, fluorite, and graphite powder, and stir with a frequency converter for 30 minutes (mixing uniformity of 95%) to obtain a mixture. Press the mixture into blocks of φ50mm×30mm with a density of 2.9g / cm³. (2) Electric arc furnace reduction smelting: Preheat the 1000kVA electric arc furnace to 800℃, and introduce argon gas (flow rate of 2.0m³ / h). 3 / h), the oxygen content in the furnace is 0.5%; then the pressed block material is added to the electric arc furnace in 3 batches, heated to 1900℃ at a heating rate of 12℃ / min and held at that temperature for 3h; the power consumption of smelting is 8500kWh, and the waste heat recovery is 1500kWh; after the holding time is completed, after standing for 30min, 32kg of aluminum slag mixture is discharged through a 15° tilting device, and 23.5kg of niobium carbide alloy ingots are collected; (3) Alloy refining (alkali dissolution-acid washing combination): The niobium carbide alloy ingot is crushed to 120 mesh, and then added to a 10 mol / L sodium hydroxide solution at a solid-liquid ratio of 1 g: 10 mL. The mixture is stirred at 95 °C for 2.5 h. After the reaction, the mixture is filtered while hot, and the filter residue is washed with deionized water until the pH of the washing water is 7.5. Then, the filter residue is added to a 4 mol / L dilute hydrochloric acid solution at a solid-liquid ratio of 1 g: 12 mL. The mixture is stirred at room temperature for 1 h. After the reaction, the filter residue is washed with water until no Cl is present in the washing liquid. - The acid-washed filter residue was dried at 130℃ for 2 hours to obtain 20.8 kg of high-purity niobium carbide powder.

[0032] According to the test and calculation, the niobium recovery rate of Example 2 was 82%, the purity of niobium carbide powder was 99.0%, and the residual Al content was 0.04%, Si content was 0.06%, and Fe content was 0.05%.

[0033] Example 3 A method for preparing niobium carbide from aluminum niobium slag by pyrometallurgical reduction includes the following steps: (1) Raw material pretreatment: Weigh 100kg of aluminum niobium slag (containing 30% Nb, 25% Al2O3, 3% Si, 1% Fe), 12kg of industrial grade graphite powder (purity of 98%), and 8kg of fluorite; crush the aluminum niobium slag to 80 mesh, dry the graphite powder to a moisture content of 0.3%, mix the aluminum niobium slag, fluorite and graphite powder, and stir with a frequency converter for 40min (mixing uniformity of 96%) to obtain a mixture. Press the mixture into blocks of φ60mm×40mm with a density of 3.2g / cm³. (2) Electric arc furnace reduction smelting: Preheat the 1000kVA electric arc furnace to 900℃, and introduce a nitrogen-argon mixture (flow rate of 3.0m³). 3 The oxygen content in the furnace was 0.3%; then, the pressed block material was added to the electric arc furnace in 4 batches, heated to 2050℃ at a heating rate of 15℃ / min and held at that temperature for 2 hours; the power consumption for smelting was 9000kWh, and the waste heat recovery was 1800kWh; after the holding time was completed, the mixture was left to stand for 40 minutes, and 25kg of aluminum slag mixture was discharged through a 15° tilting device, and 45.2kg of niobium carbide alloy ingots were collected; (3) Alloy refining (alkali dissolution-acid washing combination): The niobium carbide alloy ingot is crushed to 180 mesh, and then added to a 12 mol / L sodium hydroxide solution at a solid-liquid ratio of 1 g: 12 mL. The mixture is stirred at 100 °C for 2 h. After the reaction, the mixture is filtered while hot, and the filter residue is washed with deionized water until the pH of the washing water is 8. Then, the filter residue is added to a 5 mol / L dilute hydrochloric acid solution at a solid-liquid ratio of 1 g: 15 mL. The mixture is stirred at room temperature for 0.8 h. After the reaction, the filter residue is washed with water until no Cl is present in the washing liquid. - The acid-washed filter residue was dried at 140℃ for 2 hours to obtain 41.5 kg of high-purity niobium carbide powder.

[0034] According to the test and calculation, the niobium recovery rate of Example 1 was 87%, the purity of niobium carbide powder was 99.3%, and the residual Al content was 0.02%, Si content was 0.04%, and Fe content was 0.03%.

[0035] Comparative Example 1 A traditional pyrometallurgical reduction method for preparing niobium carbide comprises the following steps: Weigh 100 kg of aluminum niobium slag (containing 15% Nb) and 10 kg of industrial-grade graphite powder (purity 98%). Crush the aluminum niobium slag to 80 mesh. Mix the aluminum niobium slag and graphite powder evenly and then directly load them into an electric arc furnace. Preheat the electric arc furnace to 800℃, then continue to raise the temperature to 1900℃ and hold it at that temperature for 3 hours. After holding, let it stand for 30 minutes and then discharge the alloy ingot. Crush the alloy ingot to 120 mesh and then dry it directly to obtain niobium carbide.

[0036] According to the test and calculation, the niobium recovery rate of Comparative Example 1 was 72%, the purity of niobium carbide powder was 97.2%, and the residual Al content was 0.15%, Si content was 0.20%, and Fe content was 0.23%.

[0037] Comparative Example 2 A method for recovering and preparing niobium carbide from aluminum niobium slag, comprising the following specific steps: (1) Raw material pretreatment: Weigh 100kg of aluminum niobium slag (containing 15% Nb, 28% Al2O3, 4% Si, and 2% Fe), 9kg of industrial-grade graphite powder (purity of 98%), and 5kg of fluorite; crush the aluminum niobium slag to 100 mesh, dry the graphite powder to a moisture content of 0.4%, mix the aluminum niobium slag, fluorite, and graphite powder, and stir with a frequency converter for 30 minutes (mixing uniformity of 95%) to obtain a mixture. Press the mixture into blocks of φ50mm×30mm with a density of 2.9g / cm³. (2) Electric arc furnace reduction smelting: Preheat the 1000kVA electric arc furnace to 800℃, and introduce argon gas (flow rate of 2.0m³ / h). 3 / h), the oxygen content in the furnace is 0.5%; then the pressed block material is added to the electric arc furnace in 3 batches, heated to 1900℃ at a heating rate of 12℃ / min and held at that temperature for 3h; the power consumption of smelting is 8500kWh, and the waste heat recovery is 1500kWh; after the holding time is completed, after standing for 30min, 32kg of aluminum slag mixture is discharged through a 15° tilting device, and 23.5kg of niobium carbide alloy ingots are collected; (3) The niobium carbide alloy ingot is placed at 1200°C and an oxygen-nitrogen mixture is introduced (the volume ratio of oxygen to nitrogen is 1:2, and the flow rate of the mixture is 1.5 m). 3 Selective oxidation to remove impurities was carried out for 1.5 hours to obtain high-purity niobium carbide powder.

[0038] According to the test and calculation, the niobium recovery rate of Comparative Example 2 was 83%, the purity of niobium carbide powder was 98.8%, and the residual Al content was 0.05%, Si content was 0.07%, and Fe content was 0.10%.

[0039] Comparative Example 3 A method for recovering and preparing niobium carbide from aluminum niobium slag, comprising the following specific steps: (1) Raw material pretreatment: Weigh 100kg of aluminum niobium slag (containing 15% Nb, 28% Al2O3, 4% Si, and 2% Fe), 9kg of industrial-grade graphite powder (purity of 98%), and 5kg of fluorite; crush the aluminum niobium slag to 100 mesh, dry the graphite powder to a moisture content of 0.4%, mix the aluminum niobium slag, fluorite, and graphite powder, and stir with a frequency converter for 30 minutes (mixing uniformity of 95%) to obtain a mixture. Press the mixture into blocks of φ50mm×30mm with a density of 2.9g / cm³. (2) Electric arc furnace reduction smelting: Preheat the 1000kVA electric arc furnace to 800℃, and introduce argon gas (flow rate of 2.0m³ / h). 3 / h), the oxygen content in the furnace is 0.5%; then the pressed block material is added to the electric arc furnace in 3 batches, heated to 1900℃ at a heating rate of 12℃ / min and held at that temperature for 3h; the power consumption of smelting is 8500kWh, and the waste heat recovery is 1500kWh; after the holding time is completed, after standing for 30min, 32kg of aluminum slag mixture is discharged through a 15° tilting device, and 23.5kg of niobium carbide alloy ingots are collected; (3) Alloy refining (alkali dissolution): The niobium carbide alloy ingot is crushed to 120 mesh, and then added to a sodium hydroxide solution with a concentration of 10 mol / L at a solid-liquid ratio of 1 g: 10 mL. The mixture is stirred and reacted at 95 °C for 2.5 h. After the reaction is completed, the mixture is filtered while hot and the filter residue is washed with deionized water until the pH of the washing water is 7.5. After drying, high-purity niobium carbide powder is obtained.

[0040] According to the test and calculation, the niobium recovery rate of Comparative Example 3 was 81%, the purity of niobium carbide powder was 98.0%, and the residual Al content was 0.05%, Si content was 0.08%, and Fe content was 0.18%.

[0041] The recovery rate, purity, residual impurity content, and various costs of niobium carbide recovered in Example 2 and Comparative Examples 1-3 were statistically analyzed, and the results are shown in Table 1.

[0042] Table 1 Statistical Results

[0043] As can be seen from Table 1, Example 2 of the present invention exhibits superior overall performance compared to Comparative Examples 1-3 in key indicators such as niobium carbide recovery rate, purity, and residual impurity content. Furthermore, the energy consumption per ton processed in Example 2 is significantly lower than that in Comparative Examples 1-2, and although slightly higher than that in Comparative Example 3, its environmentally friendly treatment cost is more advantageous.

[0044] The above embodiments merely illustrate implementation methods of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A method for pyrochemically reducing and preparing niobium carbide from aluminum niobium slag, characterized in that, Includes the following steps: (1) Weigh aluminum niobium slag, graphite powder and fluorite in a mass ratio of 100:6~12:3~8, mix them evenly to obtain a mixture; (2) The mixture is loaded into an electric arc furnace preheated to 700~900℃ and a protective gas is introduced in batches, heated to 1750~2050℃ and kept at a constant temperature for 2~4 hours, and then discharged in layers after standing. (3) After crushing the niobium carbide alloy ingot, add it to an alkaline solution at a solid-liquid ratio of 1g: 8~12mL, heat it to 80~100℃ and stir it for 2~4h. After the reaction is completed, filter it while it is hot and wash it with water until pH=7~8. After acid washing and drying, high-purity niobium carbide is obtained.

2. The method for preparing niobium carbide from aluminum niobium slag by pyrometallurgical reduction according to claim 1, characterized in that, The aluminum-niobium slag in step (1) has a Nb content of 8-30%, an Al2O3 content of ≤35%, a Si content of ≤6%, and an Fe content of ≤4%; and / or In step (1), the aluminum niobium slag is crushed to 80-120 mesh before mixing, and the graphite powder is dried to a moisture content of ≤0.8% before mixing.

3. The method for preparing niobium carbide from aluminum niobium slag by pyrometallurgical reduction according to claim 1, characterized in that, The mixture in step (1) is prepared by mixing the raw materials in a frequency converter for 20-40 minutes to achieve a mixing uniformity of ≥93%; and / or Before being loaded into the electric arc furnace, the mixture described in step (2) is pressed to a density of 2.6~3.2 g / cm³. 3 The blank.

4. The method for preparing niobium carbide from aluminum niobium slag by pyrometallurgical reduction according to claim 1, characterized in that, The protective gas in step (2) is at least one of nitrogen and argon; the flow rate of the protective gas is 1.0~3.0 m³ / h. 3 / h.

5. The method for preparing niobium carbide from aluminum niobium slag by pyrometallurgical reduction according to claim 4, characterized in that, In step (2), the oxygen content in the electric arc furnace is ≤0.8%, and the electric arc furnace is heated to 1750~2050℃ at a rate of 8~15℃ / min.

6. The method for preparing niobium carbide from aluminum niobium slag by pyrometallurgical reduction according to claim 1, characterized in that, In step (3), the niobium carbide alloy ingot is crushed to 100-200 mesh and then added to an alkaline solution.

7. The method for preparing niobium carbide from aluminum niobium slag by pyrometallurgical reduction according to claim 6, characterized in that, The alkaline solution in step (3) is at least one of sodium hydroxide and potassium hydroxide.

8. The method for preparing niobium carbide from aluminum niobium slag by pyrometallurgical reduction according to claim 7, characterized in that, The concentration of the alkaline solution in step (3) is 8~12 mol / L.

9. The method for preparing niobium carbide from aluminum niobium slag by pyrometallurgical reduction according to claim 1, characterized in that, The specific steps of acid washing in step (3) are as follows: Add the water-washed filter residue to dilute hydrochloric acid with a concentration of 3-5 mol / L at a solid-liquid ratio of 1g:10-15mL, stir the reaction at room temperature for 1-2 hours, and after the reaction is completed, wash the filter residue with water until no Cl is visible in the washing liquid. - .

10. The method for preparing niobium carbide from aluminum niobium slag by pyrometallurgical reduction according to claim 9, characterized in that, The specific steps of drying in step (3) are as follows: the acid-washed filter residue is dried at 110~150℃ for 2~3 hours.

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