A method for preparing metallic vanadium by magnesium thermal reduction in a KCl-CeCl3 molten salt system
Patent Information
- Application Number
- CN202611179603.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-08-05
- Publication Date
- 2026-10-13
AI Technical Summary
[0027]1、有效破除MgO氧化层阻碍：本发明利用CeCl3与MgO的原位化学反应（MgO+CeCl3→MgCl2+CeOCl），将传统镁热还原中难以克服的固相MgO氧化层持续转化为液相，解决MgO包裹效应导致的反应动力学受阻问题。
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Figure CN122898733A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of rare metal metallurgy, and in particular to a method for preparing metallic vanadium by magnesium thermal reduction in a KCl-CeCl3 molten salt system. Background Technology
[0002] Vanadium, a high-melting-point rare metal (melting point 1890℃), possesses properties such as corrosion resistance, high high-temperature creep strength, and a small fast neutron capture cross-section, making it a key strategic material in aerospace, nuclear industry, and new energy storage. Currently, approximately 85% of vanadium is used in the steel industry in the form of vanadium-containing steel, while high-purity vanadium is used in high-end fields such as vanadium-titanium alloys, all-vanadium redox flow batteries, and neutron detectors in nuclear reactor cores.
[0003] The current mainstream method for industrial vanadium preparation is the aluminothermic reduction process, which involves reacting V₂O₅ or V₂O₃ as the vanadium source with metallic aluminum powder at temperatures above 2000℃, utilizing the strong reducing properties of Al to reduce vanadium oxides to metallic vanadium. Although this process has been scaled up, it has significant limitations: First, aluminum is consumed in a single process, resulting in high costs; second, the ultra-high temperature of 2000℃ leads to huge energy consumption and stringent requirements for the heat resistance of equipment; third, residual aluminum and oxygen (oxygen content of 1%–2%) remain in the product, requiring further purification through vacuum refining, increasing the process chain length and overall cost; and fourth, the aluminothermic reduction slag (mainly containing Al₂O₃) is difficult to recover economically, resulting in a large environmental impact.
[0004] To overcome the aforementioned shortcomings, a magnesothermic reduction method using metallic magnesium as a reducing agent was explored. Thermodynamically, magnesium has a stronger reducing ability for vanadium oxides, which can reduce the oxygen content of the product to a lower level. However, in the actual reaction, the byproduct MgO continuously accumulates on the surface of unreacted vanadium oxide particles, forming a dense MgO / MgV₂O₄ composite oxide layer. This layer hinders the contact between molten magnesium and the internal vanadium oxides, leading to incomplete reaction. This is the core bottleneck limiting the large-scale application of the magnesothermic reduction method in the field of vanadium metallurgy.
[0005] To break the MgO coating, ZrCl appears. 4- In the KCl reactive molten salt system, solid MgO is converted into liquid phase through the reaction of ZrCl4 with MgO (ZrCl4 + 2MgO → ZrO2 + 2MgCl2). However, ZrCl4 sublimates at 331℃, which is far below the reaction temperature (750–950℃), resulting in a large amount of molten salt volatilization loss, severe compositional deviation, and ZrCl4 is extremely sensitive to moisture, requiring stringent storage and operating conditions.
[0006] Therefore, developing a novel molten salt system magnesium thermal reduction method that is stable at high temperatures, non-volatile, can effectively remove the MgO oxide layer barrier, and is easy to operate has significant technical value and application prospects. Summary of the Invention
[0007] This invention provides a method for preparing metallic vanadium by magnesothermic reduction using a KCl-CeCl3 molten salt system. It utilizes a KCl-CeCl3 mixed molten salt as the reaction medium to prepare high-purity metallic vanadium through magnesothermic reduction of vanadium oxide. This method solves the technical problems of existing magnesothermic reduction methods for preparing metallic vanadium, which suffer from reaction kinetics hindrance due to the encapsulation effect of the byproduct MgO oxide layer, and the large molten salt loss and poor process stability of the existing ZrCl4-KCl molten salt system due to severe high-temperature volatilization of ZrCl4 and its sensitivity to moisture.
[0008] This invention provides a method for preparing metallic vanadium by magnesium thermal reduction in a KCl-CeCl3 molten salt system, comprising:
[0009] (1) Vanadium oxide, magnesium granules and KCl-CeCl3 mixed molten salt are added to a mixing equipment and mixed evenly to obtain a composite material;
[0010] (2) The composite material is placed in a closed high-temperature furnace and heated to 750~950℃ under inert gas protection and kept at the temperature for 1~5 hours for reduction calcination to obtain the calcined product; during the calcination process, CeCl3 reacts with the magnesium thermal reduction byproduct MgO to generate MgCl2 and CeOCl to break the MgO coating on the reaction interface.
[0011] (3) After cooling the roasted product to room temperature, take it out to obtain a solid product with a layered structure. Separate the CeOCl-containing molten salt slag in the upper part and the vanadium-containing product in the lower part by mechanical separation.
[0012] (4) The vanadium-containing product in the lower part is acid-leached, filtered and dried to obtain the vanadium product and the cleaning filtrate, respectively.
[0013] (5) The CeOCl in the molten salt slag obtained in step (3) is regenerated into CeCl3 by carbothermic chlorination and recycled for step (1).
[0014] Further, in step (1), the vanadium oxide is one or more of VO, V2O3 or V2O5; the particle size of the magnesium metal particles is 1~5mm.
[0015] Further, in step (1), the molar ratio of KCl to CeCl3 in the KCl-CeCl3 mixed molten salt is 1:1 to 1:3.
[0016] Further, in step (1), the mass ratio of the vanadium oxide, magnesium metal particles and KCl-CeCl3 mixed molten salt in the composite material is 1:(0.4~1.0):(3~7).
[0017] Further, in step (2), the inert gas is argon or helium; the heating rate is 5~15℃ / min.
[0018] Further, in step (4), the specific operation of acid leaching and cleaning is as follows: the lower vanadium-containing product is placed in 3-5 wt% dilute hydrochloric acid and stirred and cleaned at 30-50°C for 2-4 hours.
[0019] The drying process involves drying in a forced-air drying oven at 80-110°C for 2-4 hours.
[0020] Furthermore, step (5) specifically includes:
[0021] The upper CeOCl-containing molten salt slag was subjected to water immersion treatment and filtration to obtain a filtrate containing KCl and MgCl2 and a CeOCl filter residue.
[0022] The CeOCl filter residue is regenerated into CeCl3 by carbothermic chlorination, and the regenerated CeCl3 is returned to step (1) for recycling.
[0023] Furthermore, the specific process of the carbothermic chlorination treatment is as follows: a carbonaceous reducing agent is added to the CeOCl filter residue, and chlorine gas is introduced and reacted for 2 to 4 hours under conditions of 700 to 950°C and normal pressure; wherein, the amount of carbonaceous reducing agent added is 10 to 20% of the mass of the CeOCl filter residue.
[0024] Furthermore, the flow rate of the chlorine gas introduced is 50~200 mL / min; the carbonaceous reducing agent is graphite or activated carbon.
[0025] Further, the cleaning filtrate obtained in step (4) is combined with the filtrate containing KCl and MgCl2 and then evaporated to dryness to recover KCl and return it to step (1) for recycling.
[0026] The beneficial effects of this invention are as follows:
[0027] 1. Effectively overcomes the MgO oxide layer barrier: This invention utilizes the in-situ chemical reaction between CeCl3 and MgO (MgO+CeCl3→MgCl2+CeOCl) to continuously transform the solid MgO oxide layer, which is difficult to overcome in traditional magnesothermic reduction, into a liquid phase, thus solving the problem of reaction kinetics obstruction caused by the MgO encapsulation effect.
[0028] 2. Molten salt systems exhibit excellent high-temperature stability and extremely low volatility: CeCl3 has a melting point of 807-848℃ and a boiling point as high as 1727℃; while ZrCl4 has a melting point of 437℃ (triple point) and a boiling / sublimation point of only 331℃. At reaction temperatures of 750-950℃, CeCl3 remains in a stable molten state with extremely low vapor pressure and almost no volatility; ZrCl4, on the other hand, sublimates almost completely at 331℃. This difference ensures the KCl-CeCl3 molten salt system maintains stable composition during high-temperature reactions, preserving its reactivity over a long period and avoiding component deviations and equipment contamination problems caused by molten salt volatilization in the ZrCl4-KCl system.
[0029] 3. Good chemical stability and convenient operation: Compared with ZrCl4, which is extremely sensitive to moisture and prone to deliquescence and hydrolysis, CeCl3 has better chemical stability, making it more convenient to store, transport and operate, reducing the difficulty of operation and the overall cost of use.
[0030] 4. Molten salt is recyclable with low environmental impact: In this invention, CeOCl, generated by the reaction of CeCl3 with the byproduct MgO, can be converted back into CeCl3 through carbothermic chlorination (using Cl2 + carbonaceous reducing agent, reacting at 700-950℃). Combined with the recovery of KCl, a closed-loop cycle of molten salt components is achieved, reducing raw material consumption and waste emissions.
[0031] 5. Moderate reaction temperature, easy to industrialize: The reaction temperature of this invention is 750~950℃, which is much lower than the 2000℃ or more of the aluminothermic reduction method. It has lower equipment requirements, simple operation process, and is easy to achieve large-scale production. Attached Figure Description
[0032] Figure 1 This is a schematic diagram of the process flow for preparing metallic vanadium according to the present invention.
[0033] Figure 2 The XRD pattern of the metallic vanadium obtained by this invention is shown.
[0034] The realization of the objective, functional features and advantages of the present invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation
[0035] It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
[0036] This invention provides a method for preparing metallic vanadium by magnesothermic reduction using a KCl-CeCl3 molten salt system. The method replaces the existing volatile ZrCl4-KCl system with a KCl-CeCl3 mixed molten salt. By utilizing the in-situ chemical reaction between CeCl3 and the magnesothermic reduction byproduct MgO, the solid MgO is continuously converted into a liquid phase, effectively breaking the obstruction of the reaction interface by the MgO oxide layer, ensuring that the reduction reaction proceeds fully, and simultaneously achieving closed-loop recycling of the molten salt.
[0037] Combination Figure 1 ( Figure 1 The process flow diagram of this invention shows the complete process flow from composite material preparation, reduction roasting, product separation and cleaning to molten salt recycling. The preparation method specifically includes the following steps:
[0038] (1) Vanadium oxide, magnesium granules, and KCl-CeCl3 mixed molten salt are added to a mixing device and mixed evenly to obtain a composite material. The vanadium oxide is one or more of VO, V2O3, or V2O5; the magnesium granules have a particle size of 1-5 mm; the molar ratio of KCl to CeCl3 in the KCl-CeCl3 mixed molten salt is 1:1 to 1:3; and the mass ratio of the vanadium oxide, magnesium granules, and KCl-CeCl3 mixed molten salt in the composite material is 1:(0.4-1.0):(3-7).
[0039] (2) The composite material is placed in a sealed high-temperature furnace and heated to 750~950℃ under the protection of an inert gas (argon or helium) and held for 1~5 hours for reduction roasting to obtain the roasted product; the heating rate is 5~15℃ / min. During this roasting process, metallic magnesium reduces vanadium oxide to generate metallic vanadium and byproduct MgO; at the same time, CeCl3 in the molten salt reacts with the solid byproduct MgO generated by the magnesium thermal reduction to generate liquid phase MgCl2 and CeOCl (chemical reaction principle: MgO(s) + CeCl3(l) = MgCl2(l) + CeOCl(s)), continuously converting solid phase MgO into liquid phase, thereby continuously exposing fresh vanadium oxide reaction interface, so that the reduction reaction can be carried out continuously and fully.
[0040] (3) After cooling the roasted product to room temperature, take it out to obtain a solid product with a layered structure. Separate the molten salt slag in the upper part and the vanadium-containing product in the lower part by mechanical separation.
[0041] (4) The lower vanadium-containing product is acid-leached, filtered, and dried to obtain the vanadium product and the cleaning filtrate. The specific acid-leaching operation is as follows: after removing the upper molten salt slag adhering to the surface, the lower vanadium-containing product is placed in 3-5 wt% dilute hydrochloric acid and stirred and washed at 30-50℃ for 2-4 hours to remove residual molten salt components (KCl, MgCl2, etc.) and soluble by-products;
[0042] The drying process involves placing the filtered residue in a forced-air drying oven at 80-110℃ for 2-4 hours to obtain the final product. Figure 2 ( Figure 2 The image shows the XRD pattern of the vanadium metal obtained in this embodiment.
[0043] (5) This embodiment also includes the steps of adjusting and recycling the molten salt composition: the upper molten salt slag is subjected to water leaching and filtration to obtain a filtrate containing KCl and MgCl2 and CeOCl filter residue. The CeOCl filter residue is regenerated into CeCl3 by carbothermic chlorination treatment, and the regenerated CeCl3 is recycled for mixing with vanadium oxide and magnesium granules.
[0044] The specific process of carbothermic chlorination is as follows: a carbonaceous reducing agent (graphite or activated carbon) is added to the CeOCl filter residue, and chlorine gas is introduced at a flow rate of 50-200 mL / min at 700-950℃ and normal pressure for 2-4 hours; wherein the amount of carbonaceous reducing agent added is 10-20% of the mass of the CeOCl filter residue. At the same time, the washing filtrate obtained in step (4) is combined with the filtrate containing KCl and MgCl2 and then evaporated to dryness. KCl is recovered and recycled for mixing with vanadium oxide and magnesium granules.
[0045] To further fully disclose and verify the technical effects of the parameter ranges in the above embodiments, within the framework of the overall technical solution described above, several specific experimental operations and comparative examples are described below as verification support for the above embodiments.
[0046] Example 1
[0047] Raw materials: VO powder (purity ≥99.5%); magnesium granules (purity ≥99.8%, particle size 2~4mm); KCl (analytical grade); CeCl3 (anhydrous, purity ≥99.5%).
[0048] step:
[0049] (1) Preparation of composite material: combining Figure 1As shown, KCl and CeCl3 were weighed at a molar ratio of 1:1, mixed and ground evenly, and then weighed with VO and magnesium granules at a mass ratio of 1:0.40:3.5. The mixture was placed in a planetary ball mill and dry-mixed at 200 rpm for 40 minutes to obtain a uniform composite material.
[0050] (2) Reduction roasting: combined with Figure 1 As shown, the composite material was loaded into an alumina crucible and placed in a tube furnace. High-purity argon gas (99.999%, flow rate 100 ml / min) was introduced, and the temperature was increased to 850°C at a rate of 8°C / min and held for 3 hours.
[0051] (3) Cooling and separation: combined Figure 1 As shown, after the heat treatment was completed, the crucible was cooled to room temperature with the furnace and then removed. The product exhibited a layered structure, with the upper layer being a molten salt slag containing CeOCl and the lower layer being a mixture of metallic vanadium and residual molten salt. The lower core material was taken and placed in 5wt% dilute hydrochloric acid, stirred at room temperature for 1 hour, and then filtered.
[0052] (4) Drying: Place the filter residue in a 90℃ forced-air drying oven and dry for 3 hours to obtain metallic vanadium product.
[0053] Result: Combination Figure 2 As shown, the oxygen content is 0.55 wt%, and the purity of the metallic vanadium is 98.83%.
[0054] Example 2
[0055] The molar ratio of KCl to CeCl3 is 1:1, and it is weighed together with VO and magnesium granules in a mass ratio of 1:0.47:5.0. The remaining steps are the same as in Example 1.
[0056] Result: Combination Figure 2 As shown, the oxygen content is 0.09 wt%, and the purity of the metallic vanadium is 99.87%.
[0057] Example 3
[0058] The molar ratio of KCl to CeCl3 is 1:1.5, and the KCl, VO, and magnesium granules are weighed out in a mass ratio of 1:0.69:6.0. Figure 1 As shown, the temperature was increased to 880°C at a rate of 10°C / min and held for 3 hours. The remaining steps were the same as in Example 1.
[0059] Result: Combination Figure 2 As shown, the oxygen content is 0.26 wt%, and the purity of the metallic vanadium is 99.46%.
[0060] Example 4
[0061] Raw materials: V2O3 powder (purity ≥99.5%); magnesium granules (particle size 2~4mm); KCl; CeCl3.
[0062] The molar ratio of KCl to CeCl3 is 1:1, and the KCl, CeCl3, V₂O₃, and magnesium granules are weighed out in a mass ratio of 1:0.5:1:4.5. Figure 1 As shown, the temperature was increased to 900°C at a rate of 8°C / min and held for 1 hour. The remaining operations were the same as in Example 1.
[0063] Result: Combination Figure 2 As shown, the oxygen content is 0.52 wt%, and the purity of the metallic vanadium is 98.90%.
[0064] Example 5
[0065] The molar ratio of KCl to CeCl3 is 1:1, and the KCl, CeCl3, V₂O₃, and magnesium granules are weighed out in a mass ratio of 1:0.63:6.5. Figure 1 As shown, the temperature was increased to 800°C at a rate of 8°C / min and held for 3 hours. The remaining operations were the same as in Example 1.
[0066] Result: Combination Figure 2 As shown, the oxygen content is 0.05 wt%, and the purity of the metallic vanadium is 99.90%.
[0067] Example 6
[0068] The molar ratio of KCl to CeCl3 is 1:2, and the KCl, CeCl3, V2O3, and magnesium granules are weighed out in a mass ratio of 1:0.97:7.0. Figure 1 As shown, the temperature was increased to 920°C at a rate of 10°C / min and held for 5 hours. The remaining operations were the same as in Example 1.
[0069] Result: Combination Figure 2 As shown, the oxygen content is 0.33 wt%, and the purity of the metallic vanadium is 99.37%.
[0070] Comparative Example
[0071] Using only KCl as the molten salt medium (without CeCl3), VO and magnesium granules were mixed at a mass ratio of 1:0.47:4.0 and reacted at 850℃ under argon protection for 3 hours. A large amount of VO remained unreduced in the product, which was mainly a mixture of VO and MgO, with a vanadium content of less than 5%.
[0072] By comparing the data from Examples 1-6 with those from the comparative examples, and in conjunction with the overall process flow, it can be fully demonstrated that the specific embodiments provided by the present invention can achieve the following significant beneficial effects:
[0073] 1. Effectively overcomes the MgO oxide layer barrier: As can be seen from the comparison of the results of the examples and the comparative examples, the purity of vanadium metal in the comparative example without CeCl3 is less than 5%. However, the present invention utilizes the in-situ chemical reaction between CeCl3 and MgO (MgO+CeCl3=MgCl2+CeOCl) to continuously transform the solid MgO oxide layer, which is difficult to overcome in the traditional magnesothermic reduction, into a liquid phase. This solves the problem of reaction kinetics obstruction caused by the MgO encapsulation effect, resulting in a final vanadium metal purity of up to 98.83%~99.90%.
[0074] 2. The molten salt system exhibits excellent high-temperature stability and extremely low volatility: CeCl3 has a melting point of 807~848℃ and a boiling point as high as 1727℃; while ZrCl4 in existing technologies has a melting point of 437℃ (triple point) and a boiling / sublimation point of only 331℃. At reaction temperatures of 750~950℃, CeCl3 remains in a stable molten state with extremely low vapor pressure and almost no volatility; whereas ZrCl4 has already sublimated completely at 331℃. This difference ensures that the KCl-CeCl3 molten salt system maintains stable composition during high-temperature reactions, preserving its reactivity over a long period, and avoiding the component deviation and equipment contamination problems caused by molten salt volatilization in the ZrCl4-KCl system.
[0075] 3. Good chemical stability and convenient operation: Compared with ZrCl4, which is extremely sensitive to moisture and prone to deliquescence and hydrolysis, CeCl3 has better chemical stability, making it more convenient to store, transport and operate, reducing the difficulty of operation and the overall cost of use.
[0076] 4. Molten salt is recyclable and has a low environmental impact: As shown in step (5) of the present invention, CeOCl generated by the reaction of CeCl3 with the byproduct MgO can be converted back into CeCl3 through carbothermic chlorination (using Cl2 + carbonaceous reducing agent, reacting at 700~950℃). Combined with the recovery of KCl, a closed-loop cycle of molten salt components is achieved, significantly reducing raw material consumption and waste emissions.
[0077] 5. Moderate reaction temperature, easy to industrialize: The reaction temperature of this invention is 750~950℃, which is much lower than the high temperature of over 2000℃ in the existing aluminothermic reduction method. It has lower equipment requirements, simple operation process, and is easy to achieve large-scale production.
[0078] It should be noted that, in this document, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, apparatus, article, or method that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, apparatus, article, or method. Unless otherwise specified, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, apparatus, article, or method that includes that element.
[0079] The above description is merely a preferred embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural or procedural transformations made based on the content of the present invention's specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.
Claims
1. A method for preparing metallic vanadium by magnesium thermal reduction in a KCl-CeCl3 molten salt system, characterized in that, include: (1) Vanadium oxide, magnesium granules and KCl-CeCl3 mixed molten salt are added to a mixing equipment and mixed evenly to obtain a composite material; (2) The composite material is placed in a closed high-temperature furnace and heated to 750~950℃ under inert gas protection and kept at the temperature for 1~5 hours for reduction calcination to obtain the calcined product; during the calcination process, CeCl3 reacts with the magnesium thermal reduction byproduct MgO to generate MgCl2 and CeOCl to break the MgO coating on the reaction interface. (3) After cooling the roasted product to room temperature, take it out to obtain a solid product with a layered structure. Separate the CeOCl-containing molten salt slag in the upper part and the vanadium-containing product in the lower part by mechanical separation. (4) The vanadium-containing product in the lower part is acid-leached, filtered and dried to obtain the vanadium product and the cleaning filtrate, respectively. (5) The CeOCl in the molten salt slag obtained in step (3) is regenerated into CeCl3 by carbothermic chlorination and recycled for step (1).
2. The method for preparing metallic vanadium by magnesium thermal reduction in the KCl-CeCl3 molten salt system according to claim 1, characterized in that, In step (1), the vanadium oxide is one or more of VO, V2O3 or V2O5; the particle size of the magnesium metal particles is 1~5mm.
3. The method for preparing metallic vanadium by magnesium thermal reduction in the KCl-CeCl3 molten salt system according to claim 1, characterized in that, In step (1), the molar ratio of KCl to CeCl3 in the KCl-CeCl3 mixed molten salt is 1:1 to 1:
3.
4. The method for preparing metallic vanadium by magnesium thermal reduction in the KCl-CeCl3 molten salt system according to claim 3, characterized in that, In step (1), the mass ratio of the vanadium oxide, magnesium granules and KCl-CeCl3 mixed molten salt in the composite material is 1:(0.4~1.0):(3~7).
5. The method for preparing metallic vanadium by magnesium thermal reduction in the KCl-CeCl3 molten salt system according to claim 1, characterized in that, In step (2), the inert gas is argon or helium; the heating rate is 5~15℃ / min.
6. The method for preparing metallic vanadium by magnesium thermal reduction in the KCl-CeCl3 molten salt system according to claim 1, characterized in that, In step (4), the specific operation of acid leaching and cleaning is as follows: the lower vanadium-containing product is placed in 3-5 wt% dilute hydrochloric acid and stirred and cleaned at 30-50°C for 2-4 hours. The drying process involves drying in a forced-air drying oven at 80-110°C for 2-4 hours.
7. The method for preparing metallic vanadium by magnesium thermal reduction in the KCl-CeCl3 molten salt system according to claim 1, characterized in that, Step (5) specifically includes: The upper CeOCl-containing molten salt slag was subjected to water immersion treatment and filtration to obtain a filtrate containing KCl and MgCl2 and a CeOCl filter residue. The CeOCl filter residue is regenerated into CeCl3 by carbothermic chlorination, and the regenerated CeCl3 is returned to step (1) for recycling.
8. The method for preparing metallic vanadium by magnesium thermal reduction in the KCl-CeCl3 molten salt system according to claim 7, characterized in that, The specific process of the carbothermic chlorination treatment is as follows: a carbonaceous reducing agent is added to the CeOCl filter residue, and chlorine gas is introduced and reacted for 2 to 4 hours under conditions of 700 to 950°C and normal pressure; wherein, the amount of carbonaceous reducing agent added is 10 to 20% of the mass of the CeOCl filter residue.
9. The method for preparing metallic vanadium by magnesium thermal reduction in the KCl-CeCl3 molten salt system according to claim 8, characterized in that, The flow rate of the chlorine gas introduced is 50~200 mL / min; the carbonaceous reducing agent is graphite or activated carbon.
10. The method for preparing metallic vanadium by magnesium thermal reduction in the KCl-CeCl3 molten salt system according to claim 7, characterized in that, The cleaning filtrate obtained in step (4) is combined with the filtrate containing KCl and MgCl2 and then evaporated to dryness to recover KCl and return to step (1) for recycling.