Method for preparing vanadium metal through thermal reduction of metal in molten salt medium

Abstract

The invention discloses a method for preparing metal vanadium through metal thermal reduction in a molten salt medium, which comprises the following steps: 1, pretreating high-valence vanadium oxide to obtain low-valence vanadium oxide; 2, low-valence vanadium oxide is mixed with a reducing agent and fused salt, and a mixture is obtained; 3, sequentially carrying out ball milling and high-temperature roasting on the mixture under the protection of inert gas to obtain a reactant; and 4, carrying out acid pickling and suction filtration on the reactant to obtain the elemental metal vanadium. V2O5 is reduced into low-valence vanadium oxide, the low-valence vanadium oxide reacts with the reducing agent and the molten salt mixture, high-temperature roasting is conducted in the closed container, acid pickling and suction filtration are conducted on the reaction product after heat preservation, and the simple substance metal vanadium is obtained. The preparation process is simple, the raw material obtaining difficulty is low, the cost is relatively low, and the whole reaction process is simple and free of pollution; the roasting temperature in the reaction process is low, the required heat is low, and the energy consumption can be effectively reduced, so that the production efficiency is improved, and the production cost is reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of metal smelting, and in particular relates to a method for preparing metallic vanadium by thermal reduction of metal in a molten salt medium. Background Art

[0002] Metal vanadium, due to its excellent physical and chemical properties, has shown wide application potential in many fields such as alloys, batteries, chemicals, aerospace and medicine. However, despite its broad application prospects, the preparation process of metal vanadium faces many obstacles and limitations. These challenges not only affect the production efficiency and cost of vanadium, but also restrict its large-scale application. First, the traditional production process of metal vanadium is complex and the process is long, which directly leads to an increase in production costs. In the production process, multiple steps and links need to be precisely controlled to ensure the quality and purity of the final product. However, this complexity not only increases the difficulty of operation, but also makes it difficult to improve production efficiency. In addition, traditional processes are often accompanied by large energy consumption, which not only increases production costs, but also imposes a heavy burden on the environment. Secondly, insufficient product purity is another key issue in the preparation of metal vanadium. Since vanadium exists in various forms in nature and often coexists with other elements, it is difficult to completely remove impurities during extraction and refining. The presence of these impurities not only affects the physical and chemical properties of vanadium, but also limits its application in some high-end fields. In order to improve purity, more complex and expensive purification processes are often required, which further increases production costs and time costs.

[0003] In the extraction technology of metallic vanadium, although the molten salt electrolysis method has great development potential, it also has some technical difficulties. In the process of vanadium molten salt electrolysis extraction, due to the multiple valence states of vanadium ions and the coordination behavior of electrolyte ions and vanadium ions, the existence form of vanadium ions becomes very complex. This complexity not only affects the composition and morphology of the electrolysis products, but also has a significant impact on the current efficiency. Therefore, how to optimize the electrolysis conditions, improve the current efficiency, and reduce energy consumption and costs have become key issues that need to be solved in the preparation of metallic vanadium by molten salt electrolysis. In addition to the molten salt electrolysis method, vacuum smelting and purification method and iodide thermal dissociation purification method are also commonly used methods for preparing high-purity vanadium. However, these methods also have some limitations and challenges. Although the vacuum smelting and purification method can improve the purity of the metal, the operation process is complicated and has high requirements for equipment. The preparation process of metallic vanadium faces multiple challenges such as complex processes, insufficient product purity, technical difficulties, and cost and environmental burdens. In order to overcome these limitations and promote the large-scale application of metallic vanadium, it is necessary to continuously develop new preparation technologies and process methods, optimize the operating parameters and conditions of existing technologies, and improve production efficiency and product quality. At the same time, it is also necessary to strengthen interdisciplinary cooperation and the integration of industry, academia and research to promote the innovation and upgrading of metallic vanadium preparation technology. At present, the industry often uses the aluminothermic method to reduce V2O5 and V2O3 to prepare metallic vanadium. This method is to crush and grind vanadium oxide, metallic aluminum and quicklime together into powder, heat them to 2000℃ in an electric furnace and keep them warm for a period of time, separate the slag and gold, and remove excess aluminum and other impurities by vacuum smelting. This method still has some shortcomings: 1) The smelting temperature is high and the energy consumption is large; 2) A large amount of lime is consumed, thereby generating a large amount of waste slag; 3) Most of the generated metals are vanadium-aluminum alloys, which require vacuum smelting to remove excess aluminum.

[0004] Therefore, in order to reduce the smelting temperature from the source, it is urgent and necessary to find a new method for preparing metallic vanadium. Summary of the invention

[0005] The technical problem to be solved by the present invention is to provide a method for preparing metallic vanadium by metal thermal reduction in a molten salt medium in view of the deficiencies of the above-mentioned prior art. The method reduces V2O5 to low-valent vanadium oxide, reacts it with a reducing agent and a molten salt mixture, performs high-temperature roasting in a closed container, and after heat preservation, acid washes and filters the reaction product to obtain elemental metallic vanadium. The entire reaction process is simple and pollution-free, reduces the energy consumption of metallic vanadium, improves production efficiency, and reduces production costs.

[0006] In order to solve the above technical problems, the technical solution adopted by the present invention is: a method for preparing metallic vanadium by metal thermal reduction in a molten salt medium, characterized in that the method comprises the following steps: Step 1, pretreating high-valent vanadium oxide to obtain low-valent vanadium oxide; the high-valent vanadium oxide is V2O5, and the low-valent vanadium oxide is V2O3 or VO; Step 2: Mix the low-valent vanadium oxide obtained in step 1 with a reducing agent and a molten salt to obtain a mixture; when the low-valent vanadium oxide is V2O3, the mass ratio of the low-valent vanadium oxide to the reducing agent and the molten salt in the mixture is 1:2.5-3.5:5; when the low-valent vanadium oxide is VO, the mass ratio of the low-valent vanadium oxide to the reducing agent and the molten salt in the mixture is 1:1.5-2:4; Step 3: ball-milling the mixture obtained in step 2 under the protection of inert gas, and then heating to 1000° C. to 1200° C. for 1 h to 2 h under the protection of inert gas to obtain a reactant; Step 4: acid-wash the reactant obtained in step 3, and then filter it to obtain elemental metallic vanadium.

[0007] The present invention pre-treats vanadium oxide, that is, reduces high-valent V2O5 to low-valent V2O3 or VO to prepare low-valent vanadium oxide. On the one hand, the amount of reducing agent used can be reduced to save production costs, and on the other hand, the accumulation of oxides in the metal thermal reduction process can be reduced to increase reaction efficiency.

[0008] The present invention mixes the reduced low-valent vanadium oxide with a reducing agent and a molten salt in proportion, wherein the ratio of V2O3, the reducing agent and the molten salt is 1:2.5-3.5:5, and the ratio of VO, the reducing agent and the molten salt is 1:1.5-2:4. Sufficient molten salt helps the reaction to proceed fully, ensures that V2O3 or VO is completely reacted to generate V, improves its yield, clarifies the amount of reactants added in the production process, and facilitates industrial adjustment in the later small-scale test and pilot stage. The molten salt is used to assist thermal reduction, which, on the one hand, improves the mass transfer effect of oxygen, and on the other hand, generates oxides that react with the molten salt to break the encapsulation and promote the generation of metallic vanadium.

[0009] The present invention ball-mills the mixture under the protection of inert gas, which helps to reduce the oxidative influence of the reducing agent on the subsequent reaction, so that V2O3 or VO is fully in contact with the reducing agent, and then calcined at high temperature. The molten salt serves as a reaction medium to dissolve the reaction by-products and increase the mass transfer of the reactants. By controlling the insulation time, the reaction is fully completed, the impurity residue of the metal vanadium is reduced, and the metal vanadium is obtained.

[0010] The present invention dissolves the unreacted reducing agent, molten salt and reaction slag after pickling, and then removes them by suction filtration to obtain elemental metal vanadium.

[0011] The above-mentioned method for preparing metallic vanadium by metal thermal reduction in a molten salt medium is characterized in that the pretreatment process described in step 1 is: hydrogen with a volume purity greater than 99.999% is introduced at a flow rate of 500mL / min~800mL / min, and then heated to 800°C~1600°C. The present invention allows V2O5 to be in full and continuous contact with hydrogen by introducing hydrogen and heat treatment, and controlling parameters, so as to react and obtain V2O3 or VO. The reaction process is simple and controllable, and no other waste is generated.

[0012] The above-mentioned method for preparing metallic vanadium by metal thermal reduction in a molten salt medium is characterized in that the reducing agent described in step 2 is calcium particles with a particle size of 2mm to 5mm. The present invention uses calcium as a reducing agent, and the main reaction that occurs is that Ca reduces V2O3 or VO to generate V and CaO, and the generated CaO reacts with the molten salt to form CaCl2 to promote the reaction. Compared with the traditional use of aluminum as a reducing agent, calcium is used as a reducing agent, and the calcium thermal reaction releases more heat and has stronger reducibility, so it not only ensures the sufficient supply of heat in the reduction process, but also deeply reduces low-valent vanadium oxide to obtain metallic vanadium with a lower oxygen content, and controls the particle size of calcium particles, reduces the specific surface area of ​​Ca, is conducive to the forward reaction, and is conducive to warehouse storage, reducing safety hazards.

[0013] The above-mentioned method for preparing metallic vanadium by metal thermal reduction in a molten salt medium is characterized in that the molten salt in step 2 is a mixture of CaCl2 and KCl in a mass ratio of 3.5-5:1-2. The present invention controls the composition and ratio of the molten salt, and uses CaCl2 and KCl as reaction media to accelerate the mass transfer of reactants on the one hand, and on the other hand, react with the product CaO to reduce the accumulation of CaO during the reaction process to hinder the reaction. The advantage is that it can be removed by rinsing with deionized water in the later stage, and the treatment and recycling are convenient.

[0014] The above-mentioned method for preparing metallic vanadium by metal thermal reduction in a molten salt medium is characterized in that the high-temperature roasting in step 3 is carried out in a pressure-bearing reactor, the high-temperature roasting is a sealed reaction, and the gas pressure of the pressure-bearing reactor is less than -1MPa. The present invention adopts a sealed pressure-bearing reactor for high-temperature roasting to reduce the volatilization of molten salt during the reaction process, so that the entire metal thermal reduction reaction is fully carried out, the reaction rate is increased, the safety is improved, the reaction environment is accurately controlled, and the purity of the reaction product is ensured.

[0015] The above-mentioned method for preparing metallic vanadium by thermal reduction of metal in a molten salt medium is characterized in that the temperature of the high-temperature roasting in step 3 is 1100°C and the time is 2 hours. The present invention improves the reaction speed through the parameters of high-temperature roasting, reduces energy consumption compared with the high-temperature 1600°C thermal reduction of metallic vanadium, increases the insulation time to fully complete the reaction, and reduces the impurity residue of metallic vanadium.

[0016] The above-mentioned method for preparing metallic vanadium by metal thermal reduction in a molten salt medium is characterized in that the pickling in step 4 adopts a dilute hydrochloric acid solution or a dilute nitric acid solution, and the pickling time is more than 1 hour. The present invention controls the pickling solution used for pickling and the pickling time, fully dissolves and removes the unreacted reducing agent, molten salt and reaction slag, so that they are more fully separated from the metallic vanadium element, and the purity of the metallic vanadium is ensured. The dilute hydrochloric acid solution is a dilute hydrochloric acid solution with a mass fraction of less than 20%, and the dilute nitric acid solution is a dilute nitric acid solution with a mass concentration of less than 6 mol / L.

[0017] The above-mentioned method for preparing metallic vanadium by metal thermal reduction in a molten salt medium is characterized in that the waste liquid obtained by filtration in step 4 is evaporated and condensed for recovery. The present invention can reuse the waste liquid for the reduction reaction involved in the present invention multiple times after evaporation and condensation recovery treatment, and can be extracted again for the next reduction process.

[0018] The above-mentioned method for preparing metallic vanadium by metal thermal reduction in a molten salt medium is characterized in that the mass purity of the elemental metallic vanadium described in step 4 is not less than 99.92%.

[0019] Compared with the prior art, the present invention has the following advantages: 1. The present invention reduces V2O5 to low-valent vanadium oxide, reacts it with a reducing agent and a molten salt mixture, and obtains elemental metallic vanadium through high-temperature roasting, pickling and filtration. The entire reaction process is simple and pollution-free, the preparation process is simple, the raw materials are easy to obtain, the cost is relatively low, the roasting temperature in the reaction process is low, the required heat is low, and the energy consumption can be effectively reduced, thereby improving production efficiency and reducing production costs. Compared with the Al thermal method, the present invention can directly obtain elemental metallic vanadium instead of vanadium-aluminum alloy, which can greatly reduce the energy consumption of metallic vanadium and reduce the electron beam melting process required for the aluminum-vanadium alloy in the later stage, thereby improving production efficiency and reducing production costs.

[0020] 2. The reaction temperature of the present invention is lower than that of traditional technologies. This feature not only reduces energy consumption, but also helps to extend the service life of equipment and reduce the potential safety hazards caused by high-temperature operations. At the same time, low-temperature reaction conditions are more conducive to the synthesis of fine chemicals and improve the purity and quality of products. Furthermore, the reduction in required heat means less impact on the environment during the production process, which is in line with the current concept of green, low-carbon and sustainable development, and helps to reduce carbon emissions and protect the ecological environment.

[0021] 3. The present invention uses metallic calcium as a reducing agent. Compared with metallic aluminum, the heat release of calcium thermal reaction is greater and its reducing property is stronger. Therefore, it not only ensures sufficient heat supply in the reduction process, but also can obtain metallic vanadium with a lower oxygen content. In addition, molten salt is used to assist calcium thermal reduction. On the one hand, it improves the mass transfer effect of oxygen, and on the other hand, it generates oxides that react with molten salt to break the encapsulation and promote the formation of metallic vanadium.

[0022] 4. The present invention has the outstanding advantage of low cost, which is mainly reflected in the more economical selection of raw materials, the simplification of the production process reduces the overall manufacturing cost, greatly improves the competitiveness of the product in the market, reduces the production cost of metallic vanadium, and can promote the industrial preparation of metallic vanadium.

[0023] 5. The present invention not only improves economic benefits, but also takes environmental protection into consideration, and has broad application prospects and market value.

[0024] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 The present invention provides a flow chart of reducing low-valent metal vanadium in a molten salt medium using the metallothermic reduction method. DETAILED DESCRIPTION

[0026] Figure 1 This is a flow chart of reducing low-valent metal vanadium in a molten salt medium by a metallothermic reduction method according to the present invention, from Figure 1 It can be seen that the high-valent V2O5 is pretreated to obtain low-valent V2O3 or VO, which is then mixed and ball-milled with a reducing agent and molten salt, calcined at high temperature, and finally pickled and filtered to obtain elemental metallic vanadium.

[0027] Example 1 This embodiment includes the following steps: Step 1: V2O5 is pretreated by introducing hydrogen with a volume purity greater than 99.999% at a flow rate of 500 mL / min and then heating to 800°C to obtain V2O3; Step 2: Mix the V2O3 obtained in step 1 with calcium particles with a particle size of 2 mm to 5 mm and molten salt to obtain a mixture; the mass ratio of V2O3 to calcium particles and molten salt in the mixture is 1:2.5:5; the molten salt is a mixture of CaCl2 and KCl in a mass ratio of 3.5:1; Step 3, ball-milling the mixture obtained in step 2 under the protection of inert gas, and then calcining at 1000° C. for 1 h in a sealed pressure-bearing reactor under the protection of inert gas and at a pressure of less than -1 MPa to obtain a reactant; Step 4: The reactant obtained in step 3 is pickled with a dilute hydrochloric acid solution or a dilute nitric acid solution for more than 1 hour, and then filtered to obtain elemental metallic vanadium, and the waste liquid obtained by filtration is evaporated, condensed and recovered.

[0028] The composition of the single metal vanadium prepared in this example was tested, and the results are shown in Table 1.

[0029] Table 1

[0030] It can be seen from Table 1 that the quality purity of the elemental metal vanadium prepared in this embodiment is relatively high.

[0031] Example 2 This embodiment includes the following steps: Step 1: V2O5 is pretreated by introducing hydrogen with a volume purity greater than 99.999% at a flow rate of 600 mL / min and then heating to 900°C to obtain V2O3; Step 2: Mix the V2O3 obtained in step 1 with calcium particles with a particle size of 2 mm to 5 mm and molten salt to obtain a mixture; the mass ratio of V2O3 to calcium particles and molten salt in the mixture is 1:3.0:5; the molten salt is a mixture of CaCl2 and KCl in a mass ratio of 4:1.5; Step 3: ball-milling the mixture obtained in step 2 under the protection of inert gas, and then calcining it at 1100° C. for 2 h in a sealed pressure-bearing reactor under the protection of inert gas and at a pressure of less than -1 MPa to obtain a reactant; Step 4: The reactant obtained in step 3 is pickled with a dilute hydrochloric acid solution or a dilute nitric acid solution for more than 1 hour, and then filtered to obtain elemental metallic vanadium, and the waste liquid obtained by filtration is evaporated, condensed and recovered.

[0032] The composition of the single metal vanadium prepared in this example was tested, and the results are shown in Table 2.

[0033] Table 2

[0034] It can be seen from Table 2 that the quality purity of the elemental metal vanadium prepared in this embodiment is relatively high.

[0035] Example 3 This embodiment includes the following steps: Step 1: V2O5 is pretreated by introducing hydrogen with a volume purity greater than 99.999% at a flow rate of 700 mL / min and then heating to 1000°C to obtain V2O3; Step 2: Mix the V2O3 obtained in step 1 with calcium particles with a particle size of 2 mm to 5 mm and molten salt to obtain a mixture; the mass ratio of V2O3 to calcium particles and molten salt in the mixture is 1:3.5:5; the molten salt is a mixture of CaCl2 and KCl in a mass ratio of 5:2; Step 3, ball-milling the mixture obtained in step 2 under the protection of inert gas, and then calcining at 1200° C. for 2 h in a sealed pressure-bearing reactor under the protection of inert gas and at a pressure of less than -1 MPa to obtain a reactant; Step 4: The reactant obtained in step 3 is pickled with a dilute hydrochloric acid solution or a dilute nitric acid solution for more than 1 hour, and then filtered to obtain elemental metallic vanadium, and the waste liquid obtained by filtration is evaporated, condensed and recovered.

[0036] The composition of the single metal vanadium prepared in this example was tested, and the results are shown in Table 3.

[0037] Table 3

[0038] It can be seen from Table 3 that the quality purity of the elemental metal vanadium prepared in this embodiment is relatively high.

[0039] Example 4 This embodiment includes the following steps: Step 1: V2O5 is pretreated by introducing hydrogen with a volume purity greater than 99.999% at a flow rate of 800 mL / min and then heated to 1600°C to obtain VO; Step 2: Mix the VO obtained in step 1 with calcium particles with a particle size of 2 mm to 5 mm and molten salt to obtain a mixture; the mass ratio of VO to calcium particles and molten salt in the mixture is 1:1.5:4; the molten salt is a mixture of CaCl2 and KCl in a mass ratio of 5:2; Step 3: ball-milling the mixture obtained in step 2 under the protection of inert gas, and then calcining at 1100° C. for 1 h in a sealed pressure-bearing reactor under the protection of inert gas and at a pressure of less than -1 MPa to obtain a reactant; Step 4: The reactant obtained in step 3 is pickled with a dilute hydrochloric acid solution or a dilute nitric acid solution for more than 1 hour, and then filtered to obtain elemental metallic vanadium, and the waste liquid obtained by filtration is evaporated, condensed and recovered.

[0040] The composition of the single metal vanadium prepared in this example was tested, and the results are shown in Table 4.

[0041] Table 4

[0042] It can be seen from Table 4 that the quality purity of the elemental metal vanadium prepared in this embodiment is relatively high.

[0043] Example 5 This embodiment includes the following steps: Step 1: V2O5 is pretreated by introducing hydrogen with a volume purity greater than 99.999% at a flow rate of 800 mL / min and then heated to 1300°C to obtain VO; Step 2: Mix the VO obtained in step 1 with calcium particles with a particle size of 2 mm to 5 mm and molten salt to obtain a mixture; the mass ratio of VO to calcium particles and molten salt in the mixture is 1:2:4; the molten salt is a mixture of CaCl2 and KCl in a mass ratio of 5:2; Step 3, ball-milling the mixture obtained in step 2 under the protection of inert gas, and then calcining at 1200° C. for 2 h in a sealed pressure-bearing reactor under the protection of inert gas and at a pressure of less than -1 MPa to obtain a reactant; Step 4: The reactant obtained in step 3 is pickled with a dilute hydrochloric acid solution or a dilute nitric acid solution for more than 1 hour, and then filtered to obtain elemental metallic vanadium, and the waste liquid obtained by filtration is evaporated, condensed and recovered.

[0044] The elemental metal vanadium prepared in this example was tested for composition, and the results are shown in Table 5.

[0045] Table 5

[0046] It can be seen from Table 5 that the quality purity of the elemental metal vanadium prepared in this embodiment is relatively high.

[0047] The above is only a preferred embodiment of the present invention and does not limit the present invention in any way. Any simple modification, change and equivalent change made to the above embodiment according to the technical essence of the present invention still falls within the protection scope of the technical solution of the present invention.

Claims

1. A method for preparing metallic vanadium by metal thermal reduction in a molten salt medium, characterized in that: The method comprises the following steps: Step 1, pretreating high-valent vanadium oxide to obtain low-valent vanadium oxide; the high-valent vanadium oxide is V2O5, and the low-valent vanadium oxide is V2O3 or VO; Step 2: Mix the low-valent vanadium oxide obtained in step 1 with a reducing agent and a molten salt to obtain a mixture; when the low-valent vanadium oxide is V2O3, the mass ratio of the low-valent vanadium oxide to the reducing agent and the molten salt in the mixture is 1:2.5-3.5:5; when the low-valent vanadium oxide is VO, the mass ratio of the low-valent vanadium oxide to the reducing agent and the molten salt in the mixture is 1:1.5-2:4; Step 3: ball-milling the mixture obtained in step 2 under the protection of inert gas, and then heating to 1000° C. to 1200° C. for 1 h to 2 h under the protection of inert gas to obtain a reactant; Step 4: acid-wash the reactant obtained in step 3, and then filter it to obtain elemental metallic vanadium.

2. The method for preparing metallic vanadium by metal thermal reduction in a molten salt medium according to claim 1, characterized in that: The pretreatment process in step 1 is: introducing hydrogen with a volume purity greater than 99.999% at a flow rate of 500 mL / min~800 mL / min, and then heating to 800°C~1600°C.

3. The method for preparing metallic vanadium by metal thermal reduction in a molten salt medium according to claim 1, characterized in that: The reducing agent in step 2 is calcium particles with a particle size of 2mm~5mm.

4. The method for preparing metallic vanadium by metal thermal reduction in a molten salt medium according to claim 1, characterized in that: The molten salt in step 2 is a mixture of CaCl2 and KCl in a mass ratio of 3.5~5:1~2.

5. The method for preparing metallic vanadium by metal thermal reduction in a molten salt medium according to claim 1, characterized in that: The high-temperature calcination in step three is carried out in a pressure-bearing reactor. The high-temperature calcination is a sealed reaction, and the gas pressure of the pressure-bearing reactor is less than -1 MPa.

6. The method for preparing metallic vanadium by metal thermal reduction in a molten salt medium according to claim 1, characterized in that: The high temperature calcination in step 3 is carried out at a temperature of 1100° C. and for a time of 2 h.

7. The method for preparing metallic vanadium by metal thermal reduction in a molten salt medium according to claim 1, characterized in that: The pickling in step 4 uses a dilute hydrochloric acid solution or a dilute nitric acid solution, and the pickling time is more than 1 hour.

8. The method for preparing metallic vanadium by metal thermal reduction in a molten salt medium according to claim 1, characterized in that: The waste liquid obtained by filtration in step 4 is evaporated, condensed and recovered.

9. The method for preparing metallic vanadium by metal thermal reduction in a molten salt medium according to claim 1, characterized in that: The mass purity of the elemental metallic vanadium described in step 4 is not less than 99.92%.

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