Method for cleanly extracting vanadium from vanadium slag based on dolomite
By co-roasting dolomite and vanadium slag and controlling the heating rate through segmented roasting, the problems of low vanadium yield and high production cost in vanadium slag extraction were solved, achieving efficient and low-cost vanadium extraction and wastewater recycling, and improving product quality.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-01-09
- Publication Date
- 2026-04-07
AI Technical Summary
Existing vanadium extraction processes from vanadium slag suffer from low vanadium yield, poor product quality stability, and high production costs. In particular, sodium roasting requires a large amount of soda ash, resulting in high energy consumption for wastewater treatment, while calcification roasting has a relatively low vanadium yield.
Dolomite is used to replace traditional calcification or sodium-based roasting aids and is co-roasted with vanadium slag. The heating rate is controlled by staged roasting. CaO and MgO in the dolomite are used to activate the vanadium slag, promoting the oxidation of vanadium and the formation of vanadates. Combined with ammonium sulfate precipitation and water washing, vanadium is extracted efficiently.
It improved the vanadium leaching rate, reduced production costs, and reduced energy consumption through wastewater recycling and reagent recovery, thereby increasing product purity and market competitiveness.
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Abstract
Description
TECHNICAL FIELD
[0001] The present application relates to the technical field of hydrometallurgy, in particular to a method for clean vanadium extraction from vanadium slag based on dolomite. BACKGROUND
[0002] In the production of vanadium extraction from vanadium slag, the existing mainstream process mainly includes two technical paths of sodium roasting water leaching vanadium extraction and calcium roasting acid leaching vanadium extraction. Specifically, the vanadium slag needs to be crushed and ground to a certain particle size, and then different roasting additives are added according to the process type, such as sodium roasting needs to add soda ash and industrial salt, and calcium roasting uses limestone or lime as an auxiliary material; after roasting, the separation of vanadium is realized through targeted leaching, that is, the sodium roasting product adopts water leaching, and the calcium roasting product adopts acid leaching; through repeated cycle leaching, vanadium liquid of different concentrations can be obtained; the vanadium liquid is purified by removing impurities and acid ammonium salt precipitation to obtain ammonium polyvanadate; finally, through drying, calcination and ammonia removal or melting and casting processes, vanadium pentoxide product is obtained. In terms of wastewater treatment, sodium roasting vanadium precipitation wastewater needs to be treated by vanadium and chromium precipitation, ammonia removal and evaporation before being reused, and calcium roasting vanadium precipitation wastewater needs to be treated by reducing agent reduction, lime neutralization and filtration to realize internal circulation of the system. However, the existing process has significant bottlenecks: sodium roasting needs to consume a large amount of expensive soda ash, and a large amount of liquid caustic and steam needs to be invested in the ammonia removal and evaporation process during wastewater treatment, resulting in high production cost, which seriously affects the market competitiveness of enterprises; calcium roasting has certain advantages in terms of additive cost, but has problems of low vanadium recovery rate and poor product quality stability, which limits the product added value and market competitiveness. Therefore, a clean vanadium extraction technology with high recovery rate needs to be proposed to break through the development limitations of the existing process. SUMMARY
[0003] The present application provides a method for clean vanadium extraction from vanadium slag based on dolomite, which solves the problem of low vanadium leaching rate in the related art.
[0004] The technical scheme of the present application is as follows: The present application provides a method for clean vanadium extraction from vanadium slag based on dolomite, which includes the following steps: S1, crushing, iron removal and grinding the vanadium slag to obtain refined vanadium slag, then mixing dolomite with the refined vanadium slag to obtain a mixture; the mass ratio of (CaO+MgO) / V2O5 in the mixture is 0.5-0.7; S2, roasting the mixture to obtain a clinker after cooling; S3, leaching the clinker to obtain a vanadium liquid; S4, adding ammonium sulfate I to the vanadium liquid to obtain a mixture; adjusting the pH of the mixture to be alkaline, then precipitating and filtering to obtain a vanadium liquid after impurity removal; S5. After adjusting the pH of the vanadium solution to acidic, add ammonium sulfate II and mix. Continue to adjust the pH to acidic, heat, and allow to stand and separate into layers to obtain the upper wastewater and the lower slurry. Wash and filter the lower slurry to obtain ammonium polyvanadate. S6. Dry and calcine ammonium polyvanadate to obtain powdered V2O5.
[0005] As a further technical solution, the powdered V2O5 can be further processed by melting and casting to obtain flake V2O. 5. .
[0006] As a further technical solution, the temperature during the melting and casting of the sheet is 700~900℃.
[0007] As a further technical solution, in step S1, the magnesium oxide content of the dolomite is 19%~25% by mass; the particle size distribution of the dolomite is as follows: the proportion of dolomite with a particle size of 50 mesh ≤ particle size < 80 mesh is 20% of the total mass of dolomite, and the proportion of dolomite with a particle size of 80 mesh ≤ particle size ≤ 100 mesh is 80% of the total mass of dolomite.
[0008] As a further technical solution, the Fe content in the refined vanadium slag is <1% by mass; the particle size distribution of the refined vanadium slag is as follows: the proportion of refined vanadium slag with a particle size of 100 mesh ≤ < 120 mesh is 20% of the total mass of refined vanadium slag, and the proportion of refined vanadium slag with a particle size of 120 mesh ≤ 150 mesh is 80% of the total mass of refined vanadium slag.
[0009] As a further technical solution, in step S2, the calcination is to first heat the temperature to 550~650℃ at a first heating rate and calcin for 1~3 hours, and then heat the temperature to 900~950℃ at a second heating rate and calcin for 1~3 hours; the first heating rate is less than the second heating rate.
[0010] This invention relates to a method for clean vanadium extraction from dolomite slag. By employing segmented roasting and limiting the first heating rate to be less than the second heating rate, the vanadium transfer leaching rate can be improved. In the low-temperature pre-roasting stage (550~650℃), slow heating ensures the full decomposition of MgCO3 in the dolomite and the gradual oxidation of low-valent vanadium in the vanadium slag, preventing material loss or agglomeration. In the high-temperature main roasting stage (900~950℃), rapid heating quickly crosses the CaCO3 decomposition range, reducing side reactions between CaO and impurities, promoting the stabilization of high-valent vanadium and the formation of calcium magnesium vanadate, ultimately achieving an improved vanadium transfer leaching rate.
[0011] As a further technical solution, the first heating rate is 8~12℃ / min; the second heating rate is 15~20℃ / min.
[0012] As a further technical solution, in step S2, the cooling is to cool to below 50°C.
[0013] As a further technical solution, in step S3, the leaching treatment includes primary leaching and secondary leaching; the pH of the leachate during primary leaching is 2-4, and the pH of the leachate during secondary leaching is 1-3.
[0014] As a further technical solution, in step S3, the concentration of the vanadium solution is 20~25g / L.
[0015] As a further technical solution, in step S4, the Mg in the mixture 2+ :PO4 3+ :NH4 + The molar ratio is 1~3:1~3:1~3.
[0016] As a further technical solution, in step S4, adjusting the pH to alkaline means adjusting the pH to 9-10.
[0017] As a further technical solution, step S5 involves adjusting the pH of the vanadium solution after impurity removal to 2-4, then adding ammonium sulfate II and mixing, further adjusting the pH to 1.9-2.1, heating to 95-100℃, allowing it to stand and separate into layers to obtain an upper layer of wastewater and a lower layer of slurry; washing and filtering the lower layer of slurry to obtain ammonium polyvanadate.
[0018] As a further technical solution, in step S5, the mass ratio of the added ammonium sulfate II to the mass of vanadium in the purified vanadium solution is 0.7~2.0, preferably 1.2.
[0019] As a further technical solution, in step S6, the drying temperature is 200~400℃.
[0020] As a further technical solution, in step S6, the calcination temperature is 450~550℃.
[0021] As a further technical solution, after adding a reducing agent to the upper wastewater obtained in step S5, lime is added to adjust the pH to 8-10, and then the filtrate is obtained by filtration. The filtrate can be used as a leachate for primary and secondary leaching in step S3.
[0022] This invention reuses the filtrate from the treated upper wastewater in the leaching process of step S3, achieving efficient reuse of water resources through wastewater recycling. This eliminates the high-energy-consuming steps of traditional deep wastewater treatment and reduces the cost of replenishing fresh water. At the same time, the residual ammonium salts in the filtrate can re-participate in the leaching and subsequent vanadium precipitation reaction, reducing production costs from multiple dimensions such as water resource recycling, reagent recovery, and energy consumption control.
[0023] As a further technical solution, the reducing agent includes one or both of ferrous sulfate and sodium thiosulfate.
[0024] As a further technical solution, the filtrate is used as the leachate for the primary and secondary leaching in step S3. Step S4 is as follows: ammonium sulfate I is added to the vanadium solution according to the amount of ammonium ions in the vanadium solution, and the mixture is mixed to obtain a mixture, so that the Mg in the mixture is... 2+ :PO4 3+ :NH4 + The molar ratio satisfies 1~3:1~3:1~3; after adjusting the pH of the mixture to alkaline, precipitation and filtration are performed to obtain the purified vanadium solution.
[0025] The working principle and beneficial effects of this invention are as follows: This invention improves the vanadium conversion leaching rate by replacing traditional calcification or sodium-based roasting aids with dolomite during the co-roasting of vanadium slag. The invention utilizes dolomite in the co-roasting of vanadium slag. The CaO contained in dolomite disrupts the stable structure of the vanadium slag, activates low-valent vanadium, and promotes its conversion into soluble vanadates. MgO acts as a co-active roasting component, enhancing the formation activity and acid leaching reactivity of vanadates. Compared to traditional roasting aids, MgO increases the conversion efficiency and leaching rate of vanadium from vanadium slag to the leachate, helping to improve the vanadium conversion leaching rate and laying a crucial foundation for subsequent efficient vanadium recovery. Detailed Implementation
[0026] 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.
[0027] Example 1 A method for clean vanadium extraction from dolomite slag includes the following steps: S1. After crushing, removing iron, and grinding the vanadium slag to obtain refined vanadium slag, the dolomite is mixed with the refined vanadium slag to obtain a mixture. The dolomite contains 20% magnesium oxide by mass; the dolomite particle size distribution is as follows: 20% of the total dolomite mass is 50 mesh ≤ particle size < 80 mesh, and 80% of the total dolomite mass is 80 mesh ≤ particle size ≤ 100 mesh. The Fe content in the refined vanadium slag is 0.5% by mass; the particle size distribution of the refined vanadium slag is as follows: 20% of the refined vanadium slag has a particle size of 100 mesh ≤ particle size < 120 mesh, and 80% of the refined vanadium slag has a particle size of 120 mesh ≤ particle size ≤ 150 mesh. The mass ratio of (CaO+MgO) / V2O5 in the mixture is 0.5; S2. The mixture is first heated to 550°C at a first heating rate of 8°C / min and calcined for 3 hours. Then, it is heated to 900°C at a second heating rate of 15°C / min and calcined for 3 hours. Finally, it is cooled to 40°C to obtain the clinker. S3. After leaching the clinker once with a sulfuric acid aqueous solution with a pH of 2, it is then leached a second time with a sulfuric acid aqueous solution with a pH of 1 to obtain a vanadium solution with a concentration of 20 g / L; calculate the vanadium transfer leaching rate. S4. The vanadium solution was analyzed by adding ammonium sulfate and mixing to obtain a mixture. The pH of the mixture was adjusted to 9, followed by precipitation and filtration to obtain a purified vanadium solution. The mixture contained Mg... 2+ :PO4 3+ :NH4 + The molar ratio is 3:1:3; S5. After adjusting the pH of the purified vanadium solution to 2 using a 20wt% sulfuric acid aqueous solution, ammonium sulfate is added and mixed. The pH is then adjusted to 1.9 using a 20wt% sulfuric acid aqueous solution. After heating to 95℃ and allowing to stand and separate into layers, an upper layer of wastewater and a lower layer of slurry are obtained. The lower layer of slurry is washed with water and filtered to obtain ammonium polyvanadate. The mass ratio of the added ammonium sulfate to the mass of vanadium in the purified vanadium solution is 1.2. S6. After drying ammonium polyvanadate at 300°C, it is calcined at 500°C to obtain powdered V2O5.
[0028] Example 2 A method for clean vanadium extraction from dolomite slag includes the following steps: S1. After crushing, removing iron, and grinding the vanadium slag to obtain refined vanadium slag, the dolomite is mixed with the refined vanadium slag to obtain a mixture. The dolomite contains 20% magnesium oxide by mass; the dolomite particle size distribution is as follows: 20% of the total dolomite mass is 50 mesh ≤ particle size < 80 mesh, and 80% of the total dolomite mass is 80 mesh ≤ particle size ≤ 100 mesh. The Fe content in the refined vanadium slag is 0.5% by mass; the particle size distribution of the refined vanadium slag is as follows: 20% of the refined vanadium slag has a particle size of 100 mesh ≤ particle size < 120 mesh, and 80% of the refined vanadium slag has a particle size of 120 mesh ≤ particle size ≤ 150 mesh. The mass ratio of (CaO+MgO) / V2O5 in the mixture is 0.5; S2. The mixture is first heated to 600°C at a first heating rate of 8°C / min and calcined for 2 hours. Then, it is heated to 930°C at a second heating rate of 15°C / min and calcined for 2 hours. After that, it is cooled to 40°C to obtain the clinker. S3. After leaching the clinker once with a sulfuric acid aqueous solution with pH 3, it is then leached a second time with a sulfuric acid aqueous solution with pH 2 to obtain a vanadium solution with a concentration of 21 g / L; calculate the vanadium transfer leaching rate. S4. The vanadium solution was analyzed by adding ammonium sulfate and mixing to obtain a mixture. The pH of the mixture was adjusted to 9.5, followed by precipitation and filtration to obtain a purified vanadium solution. The mixture contained Mg... 2+ :PO4 3+ :NH4 + The molar ratio is 3:1:3; S5. After adjusting the pH of the purified vanadium solution to 3 using a 20wt% sulfuric acid aqueous solution, ammonium sulfate is added and mixed. The pH is then adjusted to 2.0 using another 20wt% sulfuric acid aqueous solution. After heating to 98℃ and allowing to stand and separate into layers, an upper layer of wastewater and a lower layer of slurry are obtained. The lower layer of slurry is washed with water and filtered to obtain ammonium polyvanadate. The mass ratio of the added ammonium sulfate to the mass of vanadium in the purified vanadium solution is 1.2. S6. After drying ammonium polyvanadate at 300°C, it is calcined at 500°C to obtain powdered V2O5.
[0029] Example 3 A method for clean vanadium extraction from dolomite slag includes the following steps: S1. After crushing, removing iron, and grinding the vanadium slag to obtain refined vanadium slag, the dolomite is mixed with the refined vanadium slag to obtain a mixture. The dolomite contains 20% magnesium oxide by mass; the dolomite particle size distribution is as follows: 20% of the total dolomite mass is 50 mesh ≤ particle size < 80 mesh, and 80% of the total dolomite mass is 80 mesh ≤ particle size ≤ 100 mesh. The Fe content in the refined vanadium slag is 0.5% by mass; the particle size distribution of the refined vanadium slag is as follows: 20% of the refined vanadium slag has a particle size of 100 mesh ≤ particle size < 120 mesh, and 80% of the refined vanadium slag has a particle size of 120 mesh ≤ particle size ≤ 150 mesh. The mass ratio of (CaO+MgO) / V2O5 in the mixture is 0.5; S2. The mixture is first heated to 650°C at a first heating rate of 8°C / min and calcined for 1 hour. Then, it is heated to 950°C at a second heating rate of 15°C / min and calcined for 1 hour. After cooling to 40°C, the clinker is obtained. S3. After leaching the clinker once with a sulfuric acid aqueous solution with pH 4, it is then leached a second time with a sulfuric acid aqueous solution with pH 3 to obtain a vanadium solution with a concentration of 25 g / L; calculate the vanadium transfer leaching rate. S4. Analyze the composition of the vanadium solution. After adding ammonium sulfate and mixing, a mixture is obtained. Adjust the pH of the mixture to 10, precipitate, and filter to obtain the purified vanadium solution. The Mg content in the mixture... 2+ :PO4 3+ :NH4 + The molar ratio is 3:1:3; S5. After adjusting the pH of the purified vanadium solution to 2-4 using a 20wt% sulfuric acid aqueous solution, ammonium sulfate is added and mixed. The pH is then adjusted to 2.1 using another 20wt% sulfuric acid aqueous solution. After heating to 100℃ and allowing to stand and separate into layers, an upper layer of wastewater and a lower layer of slurry are obtained. The lower layer of slurry is washed with water and filtered to obtain ammonium polyvanadate. The mass ratio of ammonium sulfate added to vanadium in the purified vanadium solution is 1.2. S6. After drying ammonium polyvanadate at 300°C, it is calcined at 500°C to obtain powdered V2O5.
[0030] Example 4 Compared with Example 1, the only difference in this example is that the mass ratio of (CaO+MgO) / V2O5 in the mixture in step S1 of this example is 0.6.
[0031] Example 5 Compared with Example 1, the only difference in this example is that the mass ratio of (CaO+MgO) / V2O5 in the mixture in step S1 of this example is 0.7.
[0032] Example 6 Compared with Example 1, the only difference in this example is that step S2 in this example is: the mixture is first heated to 550°C at a first heating rate of 8°C / min, calcined for 3 hours, and then heated to 900°C at a second heating rate of 18°C / min, and calcined for 3 hours to obtain the clinker.
[0033] Example 7 Compared with Example 1, the only difference in this example is that step S2 in this example is: the mixture is first heated to 550°C at a first heating rate of 8°C / min, calcined for 3 hours, and then heated to 900°C at a second heating rate of 20°C / min, and calcined for 3 hours to obtain the clinker.
[0034] Example 8 Compared with Example 1, the only difference in this example is that step S2 in this example is: the mixture is first heated to 550°C at a first heating rate of 10°C / min, calcined for 3 hours, and then heated to 900°C at a second heating rate of 18°C / min, and calcined for 3 hours to obtain the clinker.
[0035] Example 9 Compared with Example 1, the only difference in this example is that step S2 in this example is: the mixture is first heated to 550°C at a first heating rate of 12°C / min, calcined for 3 hours, and then heated to 900°C at a second heating rate of 18°C / min, and calcined for 3 hours to obtain the clinker.
[0036] Example 10 Compared with Example 1, the only difference in this example is that step S2 in this example is: the mixture is first heated to 550°C at a first heating rate of 18°C / min, calcined for 3 hours, and then heated to 900°C at a second heating rate of 8°C / min, and calcined for 3 hours to obtain the clinker.
[0037] Example 11 Compared with Example 1, the only difference in this example is that step S2 in this example is: the mixture is heated to 900°C at 18°C / min and roasted for 3 hours to obtain the cooked material.
[0038] Example 12 A method for clean vanadium extraction from dolomite slag includes the following steps: S1. After crushing, removing iron, and grinding the vanadium slag to obtain refined vanadium slag, the dolomite is mixed with the refined vanadium slag to obtain a mixture. The dolomite contains 20% magnesium oxide by mass; the dolomite particle size distribution is as follows: 20% of the total dolomite mass is 50 mesh ≤ particle size < 80 mesh, and 80% of the total dolomite mass is 80 mesh ≤ particle size ≤ 100 mesh. The Fe content in the refined vanadium slag is 0.5% by mass; the particle size distribution of the refined vanadium slag is as follows: 20% of the refined vanadium slag has a particle size of 100 mesh ≤ particle size < 120 mesh, and 80% of the refined vanadium slag has a particle size of 120 mesh ≤ particle size ≤ 150 mesh. The mass ratio of (CaO+MgO) / V2O5 in the mixture is 0.5; S2. The mixture is first heated to 550°C at a first heating rate of 8°C / min and calcined for 3 hours. Then, it is heated to 900°C at a second heating rate of 18°C / min and calcined for 3 hours. Finally, it is cooled to 40°C to obtain the clinker. S3. After adding ferrous sulfate to the upper wastewater obtained in step S5 of Example 1, lime is added to adjust the pH to 8. After filtration, the filtrate is obtained. The filtrate is adjusted to pH 3 using a 20wt% sulfuric acid aqueous solution and used as a leachate to leach the clinker to obtain a vanadium solution with a concentration of 20g / L. The vanadium transfer leaching rate is calculated. S4. Based on the amount of ammonium ions in the vanadium solution, ammonium sulfate is added to the vanadium solution and mixed to obtain a mixture, so that the Mg in the mixture... 2+ :PO4 3+:NH4 + The molar ratio of the mixture satisfies 3:1:3; after adjusting the pH of the mixture to 9, precipitation and filtration are performed to obtain the purified vanadium solution. S5. After adjusting the pH of the purified vanadium solution to 2 using a 20wt% sulfuric acid aqueous solution, ammonium sulfate is added and mixed. The pH is then adjusted to 1.9 using a 20wt% sulfuric acid aqueous solution. After heating to 95℃ and allowing to stand and separate into layers, an upper layer of wastewater and a lower layer of slurry are obtained. The lower layer of slurry is washed with water and filtered to obtain ammonium polyvanadate. The mass ratio of the added ammonium sulfate to the mass of vanadium in the purified vanadium solution is 1.2. S6. After drying ammonium polyvanadate at 300°C, it is calcined at 500°C to obtain powdered V2O5; the powdered V2O5 is melted and cast at 850°C to obtain flake V2O5.
[0039] Comparative Example 1 Compared with Example 1, the only difference in this comparative example is that the mass ratio of (CaO+MgO) / V2O5 in the mixture in step S1 of this comparative example is 0.4.
[0040] Comparative Example 2 Compared with Example 1, the only difference in this comparative example is that the mass ratio of (CaO+MgO) / V2O5 in the mixture in step S1 of this comparative example is 0.8.
[0041] Vanadium transfer leaching rate = (total mass of V2O5 in vanadium solution / total mass of V2O5 in refined vanadium slag) × 100%.
[0042] The vanadium transfer leaching rates and the purity of the prepared powdered V₂O₅ in Examples 1-11 and Comparative Examples 1-2 are shown in Table 1 below: Table 1 Vanadium leaching rate and purity of the prepared powdered V₂O₅
[0043] Table 1 shows that limiting the mass ratio of (CaO+MgO) / V2O5 in the mixture to 0.5~0.7 can improve the vanadium transfer leaching rate. Furthermore, during calcination, first heating to 550~650℃ at a first heating rate of 8~12℃ / min and calcining for 1~3 hours, followed by heating to 900~950℃ at a second heating rate of 18~20℃ / min and calcining for 1~3 hours can further improve the vanadium transfer leaching rate.
[0044] The vanadium transfer leaching rate and the purity of the prepared flake V₂O₅ in Example 12 are shown in Table 2 below: Table 2 Vanadium leaching rate and purity of the prepared flake V₂O₅
[0045] The data in Table 2 show that by reusing the filtrate after treating the upper wastewater in the leaching process in step S3, the vanadium conversion leaching rate can reach 94.2%, and the purity of the prepared flake V2O5 can reach 99.28%.
[0046] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.
Claims
1. A method for clean vanadium extraction from dolomite slag, characterized in that, Includes the following steps: S1. After crushing, removing iron, and grinding the vanadium slag to obtain refined vanadium slag, dolomite is mixed with the refined vanadium slag to obtain a mixture; the mass ratio of (CaO+MgO) / V2O5 in the mixture is 0.5~0.
7. S2. The mixture is roasted and cooled to obtain a cooked product; S3. The clinker is leached to obtain vanadium solution; S4. After adding ammonium sulfate I to the vanadium solution and mixing, a mixture is obtained; after adjusting the pH of the mixture to alkaline, precipitation and filtration are performed to obtain the purified vanadium solution. S5. After adjusting the pH of the vanadium solution after impurity removal to acidic, add ammonium sulfate II and mix. Continue to adjust the pH to acidic, heat, and let it stand to separate into layers to obtain the upper wastewater and the lower slurry. The lower layer of slurry was washed and filtered to obtain ammonium polyvanadate; S6. Dry and calcine ammonium polyvanadate to obtain powdered V2O5.
2. The method for clean vanadium extraction from dolomite-based vanadium slag according to claim 1, characterized in that, In step S1, the magnesium oxide content of the dolomite is 19%~25% by mass; the particle size distribution of the dolomite is as follows: the proportion of dolomite with a particle size of 50 mesh ≤ particle size < 80 mesh is 20% of the total mass of dolomite, and the proportion of dolomite with a particle size of 80 mesh ≤ particle size ≤ 100 mesh is 80% of the total mass of dolomite.
3. The method for clean vanadium extraction from dolomite-based vanadium slag according to claim 1, characterized in that, The Fe content in the refined vanadium slag is <1% by mass; the particle size distribution of the refined vanadium slag is as follows: 20% of the refined vanadium slag has a particle size of 100 mesh ≤ particle size < 120 mesh, and 80% of the refined vanadium slag has a particle size of 120 mesh ≤ particle size ≤ 150 mesh.
4. The method for clean vanadium extraction from dolomite-based vanadium slag according to claim 1, characterized in that, In step S2, the calcination is performed by first heating to 550~650℃ at a first heating rate and calcining for 1~3 hours, and then heating to 900~950℃ at a second heating rate and calcining for 2~3 hours; the first heating rate is less than the second heating rate.
5. A method for clean vanadium extraction from dolomite-based vanadium slag according to claim 4, characterized in that, The first heating rate is 8~12℃ / min; the second heating rate is 15~20℃ / min.
6. The method for clean vanadium extraction from dolomite-based vanadium slag according to claim 1, characterized in that, In step S3, the leaching treatment includes primary leaching and secondary leaching; the pH of the leachate during primary leaching is 2-4, and the pH of the leachate during secondary leaching is 1-3.
7. The method for clean vanadium extraction from dolomite-based vanadium slag according to claim 1, characterized in that, In step S4, the Mg in the mixture 2+ :PO4 3+ :NH4 + The molar ratio is 1~3:1~3:1~3.
8. The method for clean vanadium extraction from dolomite-based vanadium slag according to claim 1, characterized in that, Step S5 involves adjusting the pH of the vanadium solution after impurity removal to 2-4, then adding ammonium sulfate II and mixing, further adjusting the pH to 1.9-2.1, heating to 95-100℃, and allowing it to stand and separate into layers to obtain the upper wastewater and the lower slurry. The lower layer of slurry was washed and filtered to obtain ammonium polyvanadate.
9. A method for clean vanadium extraction from dolomite-based vanadium slag according to claim 1, characterized in that, In step S6, the drying temperature is 200~400℃.
10. A method for clean vanadium extraction from dolomite-based vanadium slag according to claim 1, characterized in that, In step S6, the calcination temperature is 450~550℃.