Method for separating vanadium and chromium from high-chromium vanadium slag

Abstract

The invention belongs to the technical field of chemical engineering, and particularly relates to a method for separating vanadium and chromium from high-chromium vanadium slag, which comprises the following steps: obtaining the high-chromium vanadium slag, mixing the high-chromium vanadium slag with sodium salt, and carrying out oxidizing roasting to obtain roasted clinker; the roasted clinker is subjected to first chlorination under the inert gas condition, and vanadium oxytrichloride and first residues are obtained; the first residues are subjected to second-time chlorination under the inert gas condition, vanadium oxytrichloride and second residues are obtained, and the second residues contain the chromium element. According to the method, separation of vanadium and chromium in the high-chromium vanadium slag can be realized in a manner of combining oxidizing roasting and step-by-step temperature control chlorination; the use of a large amount of organic solvent or the generation of high-concentration acidic wastewater is avoided, the pollution to the environment is reduced, the purpose of green and clean separation of vanadium and chromium is achieved, and the sustainable development concept is met; the method is suitable for high-chromium vanadium slag with different components, efficient separation of vanadium and chromium can be achieved by adjusting technological parameters, and the method has good industrial application prospects.

Description

Technical Field

[0001] The present invention relates to the field of chemical technology, and in particular to a method for separating vanadium and chromium from high-chromium vanadium slag. Background Art

[0002] Due to their adjacent positions in the periodic table, vanadium and chromium exhibit extremely similar physical and chemical properties, leading to their common coexistence and enrichment in minerals such as vanadium-titanium magnetite and chromite. The smelting process of high-chromium vanadium-titanium magnetite typically forms a high-chromium vanadium slag rich in vanadium and chromium, with vanadium content ranging from 10% to 15% by weight as V2O5 and chromium content ranging from 5% to 10% by weight as Cr2O3. The complex symbiotic relationship between vanadium and chromium has made their effective separation a technical challenge within the industry. Currently, common separation methods include acid leaching and alkaline leaching. While acid leaching can dissolve vanadium and chromium, it can cause severe corrosion to equipment and generate large amounts of highly concentrated acidic wastewater, resulting in high treatment costs and environmental pollution. While alkaline leaching is less corrosive to equipment, it offers poor selective leaching of vanadium and chromium, making separation efficiency insufficient for industrial production. Furthermore, the large amount of waste slag generated during the leaching process hinders efficient resource utilization and environmental friendliness. Therefore, developing an efficient, environmentally friendly and industrially suitable method for separating vanadium and chromium from high-chromium vanadium slag has important practical significance and application value. Summary of the Invention

[0003] The present application provides a method for separating vanadium and chromium from high-chromium vanadium slag. By optimizing the process route and parameters, the problems of low efficiency and high pollution of existing separation technology are solved, and the efficient, green and simple separation of vanadium and chromium in high-chromium vanadium slag is achieved, thereby promoting the large-scale development and utilization of high-chromium vanadium titanium magnetite resources.

[0004] The method for separating vanadium and chromium from high-chromium vanadium slag of the present application comprises the following steps: S1. Obtain high-chromium vanadium slag, mix the high-chromium vanadium slag with sodium salt, and perform oxidative roasting to obtain roasted clinker; S2, performing a first chlorination on the roasted clinker under inert gas conditions to obtain vanadium oxychloride and a first residue; S3. Chlorinate the first residue for the second time under inert gas conditions to obtain vanadium oxychloride and a second residue, wherein the second residue contains chromium.

[0005] As a preferred embodiment of the method for separating vanadium and chromium from high-chromium vanadium slag of the present application, in step S2: mixing the roasted clinker with anhydrous aluminum chloride and sodium chloride, and performing a first chlorination at a first temperature under inert gas conditions; In step S3: the first residue is subjected to a second chlorination at a second temperature under an inert gas condition; The second temperature is greater than the first temperature.

[0006] In the above technical solution, when high-chromium vanadium slag is mixed with sodium salt for oxidation roasting, various types of chlorinated vanadates and water-soluble chromates are generated, including Na4V2O7, Na3VO4, NaVO3 and Na2CrO4. The ratio of different types of chlorinated vanadates and water-soluble chromates generated by roasting can be adjusted by adjusting the amount of sodium salt added. For example, when the amount of sodium salt added is reduced, the amount of water-soluble chromates generated will be reduced, thereby resulting in a decrease in the leaching rate of chromium, but it can promote the roasting to generate more NaVO3 that is easily converted in the first chlorination process, thereby improving the first chlorination process. Vanadium extraction rate; vanadate, AlCl3 and NaCl are mixed, and AlCl3 is used as the chlorinating agent. NaCl can form a liquid phase with AlCl3 at about 110°C, effectively reducing the volatilization of AlCl3; at a first temperature, NaVO3 will preferentially undergo chlorination to generate VOCl3 in gaseous form, which can be recovered by condensation, while Na4V2O7 and Na3VO4 will only be chlorinated at a second temperature higher than the first temperature. Therefore, the use of step-by-step temperature-controlled chlorination to chlorinate various vanadates into VOCl3 can not only achieve efficient vanadium recovery but also save energy.

[0007] As a preferred embodiment of the method for separating vanadium and chromium from high-chromium vanadium slag of the present application, after step S3, the method further includes: S4. Dissolving the second residue in water, filtering and collecting the filtrate, subjecting the filtrate to precipitation treatment, and recovering chromium in the precipitate.

[0008] As a preferred embodiment of the method for separating vanadium and chromium from high-chromium vanadium slag of the present application, the method further comprises, before step S1: The high chromium vanadium slag raw material is sieved and dried to obtain the high chromium vanadium slag.

[0009] As a preferred embodiment of the method for separating vanadium and chromium from high-chromium vanadium slag of the present invention, the vanadium element in the high-chromium vanadium slag is 10wt% to 15wt% in terms of V2O5, and the chromium element is 5wt% to 10wt% in terms of Cr2O3.

[0010] As a preferred embodiment of the method for separating vanadium and chromium from high-chromium vanadium slag of the present application, the sodium salt includes sodium carbonate, and the mass ratio of sodium carbonate to high-chromium vanadium slag is 0.2:1 to 0.6:1.

[0011] As a preferred embodiment of the method for separating vanadium and chromium from high-chromium vanadium slag of the present application, in step S1, the temperature of the oxidizing roasting is 700-1000° C., and the time is 1.5-2.5 h.

[0012] As a preferred embodiment of the method for separating vanadium and chromium from high-chromium vanadium slag of the present application, the mass ratio of the roasted clinker to anhydrous aluminum chloride is 1:2, and the mass ratio of anhydrous aluminum chloride to sodium chloride is 3:2.

[0013] As a preferred embodiment of the method for separating vanadium and chromium from high-chromium vanadium slag of the present application, in step S2, the first temperature is 150-170°C and the time is 1.5-2.5 hours; in step S3, the second temperature is 230-250°C and the time is 1.5-2.5 hours.

[0014] As a preferred embodiment of the method for separating vanadium and chromium from high-chromium vanadium slag of the present application, in step S4, the temperature when the second residue is dissolved in water is 80° C. and the time is 1.5 to 2.5 hours.

[0015] The present application proposes a method for separating vanadium and chromium from high-chromium vanadium slag, which has the following beneficial effects: vanadium and chromium can be separated from high-chromium vanadium slag by combining oxidative roasting and step-by-step temperature-controlled chlorination; the method avoids the use of large amounts of organic solvents or the generation of highly concentrated acidic wastewater, thereby reducing environmental pollution and achieving the goal of green and clean separation of vanadium and chromium, in line with the concept of sustainable development; the method is applicable to high-chromium vanadium slags with different compositions, and by adjusting process parameters, efficient separation of vanadium and chromium can be achieved, which has good prospects for industrial application. DETAILED DESCRIPTION

[0016] The following will be a clear and complete description of the technical solutions in the embodiments. Obviously, the embodiments described are only part of the embodiments of this application, not all of them. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0017] The technical solution proposed in this application includes the following steps: S1. Obtain high-chromium vanadium slag, mix the high-chromium vanadium slag with sodium salt, and perform oxidative roasting to obtain roasted clinker; Specifically, the high-chromium vanadium slag raw material is sieved through a 200-mesh sieve and dried at 100° C. for 4 hours to obtain high-chromium vanadium slag; Na2CO3 and the high-chromium vanadium slag are uniformly mixed in a mass ratio of 0.2:1 to 0.6:1, and oxidative roasting is performed at 700 to 1000° C. for 1.5 to 2.5 hours to obtain roasted clinker; specifically, the mass ratio of Na2CO3 to the high-chromium vanadium slag can be any one of 0.2:1, 0.3:1, 0.4:1, 0.5:1, and 0.6:1, or a range between any two of them, and the oxidative roasting temperature can be any one of 700° C., 750° C., 800° C., 850° C., 900° C., 950° C., and 1000° C., or a range between any two of them; S2, performing a first chlorination on the roasted clinker under inert gas conditions to obtain vanadium oxychloride and a first residue; Specifically, the roasted clinker is mixed with AlCl3 and NaCl, wherein the mass ratio of the roasted clinker to AlCl3 is 1:2, and the mass ratio of AlCl3 to NaCl is 3:2. Under inert gas conditions, the reaction temperature is controlled to be 150-170°C, and the first chlorination is performed for a reaction time of 1.5-2.5 hours to obtain VOCl3 and a first residue; VOCl3 is in a gaseous state and is partially extracted by condensation and collection. Specifically, the reaction temperature of the first chlorination can be any one of 150°C, 155°C, 160°C, 165°C, and 170°C, or a range between any two of them. S3, chlorinating the first residue for a second time under inert gas conditions to obtain vanadium oxychloride and a second residue, wherein the second residue contains chromium; Specifically, the first residue is subjected to a second chlorination under inert gas conditions with the reaction temperature controlled at 230-250°C for 1.5-2.5 hours to obtain VOCl3 and a second residue; VOCl3 is in a gaseous state and is collected by condensation to further extract vanadium; while the chromium element remains in the second residue; specifically, the reaction temperature of the second chlorination can be any one of 230°C, 235°C, 240°C, 245°C, and 250°C or a range between any two of them; the second residue is dissolved in water, leached at 80°C for 1.5-2.5 hours, filtered, and the filtrate is precipitated to recover the chromium in the precipitate.

[0018] By adopting the above technical solution to separate vanadium and chromium from high-chromium vanadium slag, the vanadium leaching rate is ≥75%, and the chromium recovery rate is ≥40%. Preferably, the vanadium leaching rate is ≥80%, and the chromium recovery rate is ≥85%.

[0019] The technical solution of this application is further described below with reference to specific embodiments.

[0020] Each embodiment and comparative example of the present application uses a high-chromium vanadium slag raw material produced by a domestic company, in which the vanadium content in terms of V2O5 is 11.5 wt%, and the chromium content in terms of Cr2O3 is 7.34 wt%.

[0021] Example 1 The high chromium vanadium slag raw material was passed through a 200-mesh sieve and dried at 100°C for 4 hours to obtain high chromium vanadium slag; Na2CO3 and high chromium vanadium slag were evenly mixed in a mass ratio of 0.6:1, placed in a corundum crucible, and placed in a muffle furnace for oxidation roasting at 800°C for 2 hours. During the roasting process, sufficient oxygen was ensured in the furnace to obtain roasted clinker; the roasted clinker was evenly mixed with AlCl3 and NaCl, wherein the mass ratio of roasted clinker: AlCl3: NaCl was 3:6:4, placed in a three-necked flask, and heated under inert gas. Under inert gas conditions, the reaction temperature was controlled at 160°C for a first chlorination reaction for 2 hours to obtain VOCl3 and a first residue, and the resulting gaseous VOCl3 was condensed and collected. The first residue was subjected to a second chlorination reaction at 240°C under inert gas conditions for a reaction time of 2 hours to obtain VOCl3 and a second residue, and the resulting gaseous VOCl3 was condensed and collected. The second residue was dissolved in water and leached at 80°C for 2 hours. The filtrate was filtered and precipitated to recover chromium. Testing showed that the vanadium extraction rate was 85% and the chromium recovery rate was 90%.

[0022] Example 2 The high chromium vanadium slag raw material was passed through a 200-mesh sieve and dried at 100°C for 4 hours to obtain high chromium vanadium slag; Na2CO3 and high chromium vanadium slag were evenly mixed in a mass ratio of 0.45:1, placed in a corundum crucible, and placed in a muffle furnace for oxidation roasting at 1000°C for 1.5 hours. During the roasting process, sufficient oxygen was ensured in the furnace to obtain roasted clinker; the roasted clinker was evenly mixed with AlCl3 and NaCl, wherein the mass ratio of roasted clinker: AlCl3: NaCl was 3:6:4, placed in a three-necked flask, and heated under inert gas. Under inert gas conditions, the reaction temperature was controlled at 170°C for a first chlorination reaction for 1.5 hours to obtain VOCl3 and a first residue, and the resulting gaseous VOCl3 was condensed and collected. The first residue was subjected to a second chlorination reaction at 250°C for 1.5 hours under inert gas conditions to obtain VOCl3 and a second residue, and the resulting gaseous VOCl3 was condensed and collected. The second residue was dissolved in water and leached at 80°C for 1.5 hours. The filtrate was filtered and precipitated to recover chromium. Testing showed a vanadium extraction rate of 83% and a chromium recovery rate of 86%.

[0023] Example 3 The high chromium vanadium slag raw material was passed through a 200-mesh sieve and dried at 100°C for 4 hours to obtain high chromium vanadium slag; Na2CO3 and high chromium vanadium slag were evenly mixed in a mass ratio of 0.2:1, placed in a corundum crucible, and placed in a muffle furnace for oxidation roasting at 800°C for 2 hours. During the roasting process, sufficient oxygen was ensured in the furnace to obtain roasted clinker; the roasted clinker was evenly mixed with AlCl3 and NaCl, wherein the mass ratio of roasted clinker: AlCl3: NaCl was 3:6:4, placed in a three-necked flask, and heated under inert gas. Under inert gas conditions, the reaction temperature was controlled at 160°C for a first chlorination reaction for 2 hours, yielding VOCl3 and a first residue. The resulting gaseous VOCl3 was condensed and collected. The first residue was subjected to a second chlorination reaction at 240°C under inert gas conditions for 2 hours, yielding VOCl3 and a second residue. The resulting gaseous VOCl3 was condensed and collected. The second residue was dissolved in water and leached at 80°C for 2 hours. The filtrate was filtered and precipitated to recover chromium. Testing showed a vanadium extraction rate of 76% and a chromium recovery rate of 41%. Reducing the amount of Na2CO3 added reduced the chlorinable vanadates and water-soluble chromates produced during roasting, resulting in lower vanadium extraction and chromium leaching rates.

[0024] Example 4 The high chromium vanadium slag raw material was passed through a 200-mesh sieve and dried at 100°C for 4 hours to obtain high chromium vanadium slag; Na2CO3 and high chromium vanadium slag were evenly mixed in a mass ratio of 0.6:1, placed in a corundum crucible, and placed in a muffle furnace for oxidation roasting at 700°C for 2.5 hours. During the roasting process, sufficient oxygen was ensured in the furnace to obtain roasted clinker; the roasted clinker was evenly mixed with AlCl3 and NaCl, wherein the mass ratio of roasted clinker: AlCl3: NaCl was 3:6:4, placed in a three-necked flask, and heated under inert gas conditions. Under inert gas conditions, the reaction temperature was controlled at 150°C for a first chlorination reaction for 2.5 hours to obtain VOCl3 and a first residue, and the resulting gaseous VOCl3 was condensed and collected. The first residue was subjected to a second chlorination reaction at 230°C for 2.5 hours under inert gas conditions to obtain VOCl3 and a second residue, and the resulting gaseous VOCl3 was condensed and collected. The second residue was dissolved in water and leached at 80°C for 2.5 hours. The filtrate was filtered and precipitated to recover chromium. Testing showed an extraction rate of 80% for vanadium and an 89% for chromium.

[0025] Comparative Example 1 The high-chromium vanadium slag raw material was passed through a 200-mesh sieve and dried at 100°C for 4 hours to obtain high-chromium vanadium slag. Na2CO3 and the high-chromium vanadium slag were mixed in a 0.6:1 mass ratio, placed in a corundum crucible, and oxidatively roasted in a muffle furnace at 800°C for 2 hours, ensuring sufficient oxygen in the furnace during the roasting process to obtain roasted clinker. The roasted clinker was then mixed with AlCl3 and NaCl in a mass ratio of 3:6:4 clinker:AlCl3:NaCl. The mixture was then placed in a three-necked flask and subjected to a chlorination reaction at 160°C under inert gas for 2 hours to obtain VOCl3 and a residue. The generated gaseous VOCl3 was condensed and collected. The residue was dissolved in water and leached at 80°C for 2 hours. The filtrate was filtered and precipitated to recover chromium. Testing showed a vanadium extraction rate of 43% and a chromium recovery rate of 94%.

[0026] This comparative example is consistent with Example 1 except that the second chlorination is not performed at the second temperature. The vanadium extraction rate is significantly lower than that of Example 1, indicating that the vanadium extraction is not thorough enough because only one chlorination reaction is performed at the lower first temperature. The chromium leaching rate is slightly higher than that of Example 1 because, in Example 1, the second chlorination causes the first residue to react more thoroughly, and the pH of the solution after the generated second residue is dissolved in water changes, thereby affecting the chromium leaching rate. By adjusting the pH of the solution during leaching, the chromium recovery rate in Example 1 can be made consistent with that in Comparative Example 1.

[0027] Comparative Example 2 The high-chromium vanadium slag raw material was passed through a 200-mesh sieve and dried at 100°C for 4 hours to obtain high-chromium vanadium slag. Na2CO3 and the high-chromium vanadium slag were mixed uniformly in a mass ratio of 0.45:1, placed in a corundum crucible, and oxidatively roasted in a muffle furnace at 1000°C for 1.5 hours, ensuring sufficient oxygen in the furnace. This produced a clinker. The clinker was then mixed uniformly with AlCl3 and NaCl in a mass ratio of 3:6:4. The mixture was placed in a three-necked flask and subjected to a chlorination reaction at 170°C under inert gas for 1.5 hours to produce VOCl3 and a residue. The resulting gaseous VOCl3 was condensed and collected. The residue was dissolved in water and leached at 80°C for 1.5 hours. The filtrate was filtered and precipitated to recover chromium. Testing showed a vanadium extraction rate of 50% and a chromium recovery rate of 86%.

[0028] Comparative Example 3 The high-chromium vanadium slag raw material was passed through a 200-mesh sieve and dried at 100°C for 4 hours to obtain high-chromium vanadium slag. Na2CO3 and the high-chromium vanadium slag were mixed uniformly in a mass ratio of 0.2:1, placed in a corundum crucible, and oxidatively roasted in a muffle furnace at 800°C for 2 hours, ensuring sufficient oxygen in the furnace during the roasting process to obtain roasted clinker. The roasted clinker was then mixed uniformly with AlCl3 and NaCl in a mass ratio of 3:6:4. The mixture was placed in a three-necked flask and subjected to a chlorination reaction at 160°C under inert gas for 2 hours to obtain VOCl3 and a residue. The generated gaseous VOCl3 was condensed and collected. The residue was dissolved in water and leached at 80°C for 2 hours. The filtrate was filtered and precipitated to recover chromium. Testing showed a vanadium extraction rate of 66% and a chromium recovery rate of 41%.

[0029] Comparative Example 4 The high-chromium vanadium slag raw material was passed through a 200-mesh sieve and dried at 100°C for 4 hours to obtain high-chromium vanadium slag. Na2CO3 and the high-chromium vanadium slag were mixed uniformly in a mass ratio of 0.6:1, placed in a corundum crucible, and oxidatively roasted in a muffle furnace at 800°C for 2 hours, ensuring sufficient oxygen in the furnace during the roasting process to obtain roasted clinker. The roasted clinker was then mixed uniformly with AlCl3 and NaCl in a mass ratio of 3:6:4. The mixture was placed in a three-necked flask and subjected to a chlorination reaction at 240°C under inert gas for 2 hours to obtain VOCl3 and a residue. The generated gaseous VOCl3 was condensed and collected. The residue was dissolved in water and leached at 80°C for 2 hours. The filtrate was filtered and precipitated to recover chromium. Testing showed a vanadium extraction rate of 74% and a chromium recovery rate of 89%.

[0030] This comparative example is consistent with Example 1 except that the chlorination reaction is not carried out at the first temperature. The vanadium extraction rate is lower than that of Example 1, indicating that the vanadium extraction is not thorough enough because only one chlorination reaction is carried out at the higher second temperature.

[0031] According to the above examples and comparative examples, it can be seen that when separating vanadium and chromium from high-chromium vanadium slag, the step-by-step temperature-controlled chlorination method can greatly improve the vanadium extraction rate and has little effect on the chromium recovery rate.

[0032] The present application proposes a method for separating vanadium and chromium from high-chromium vanadium slag, which has the following beneficial effects: vanadium and chromium can be separated from high-chromium vanadium slag by combining oxidative roasting and step-by-step temperature-controlled chlorination; the method avoids the use of large amounts of organic solvents or the generation of highly concentrated acidic wastewater, thereby reducing environmental pollution and achieving the goal of green and clean separation of vanadium and chromium, in line with the concept of sustainable development; the method is applicable to high-chromium vanadium slags with different compositions, and by adjusting process parameters, efficient separation of vanadium and chromium can be achieved, which has good prospects for industrial application.

[0033] The above description is only a preferred embodiment of the present application and does not limit the patent scope of the present application. All equivalent structural transformations made using the contents of the present application specification under the inventive concept of the present application, or direct / indirect application in other related technical fields are included in the patent protection scope of the present application.

Claims

1. A method for separating vanadium and chromium from high-chromium vanadium slag, characterized in that: The following steps are involved: S1. Obtain high-chromium vanadium slag, mix the high-chromium vanadium slag with sodium salt, and perform oxidative roasting to obtain roasted clinker; S2. chlorinating the calcined clinker for the first time under inert gas conditions to obtain vanadium oxychloride and a first residue; S3. Chlorinate the first residue for the second time under inert gas conditions to obtain vanadium oxychloride and a second residue, wherein the second residue contains chromium.

2. The method for separating vanadium and chromium from high-chromium vanadium slag according to claim 1, characterized in that: In the step S2: the roasted clinker is mixed with anhydrous aluminum chloride and sodium chloride, and a first chlorination is performed at a first temperature under an inert gas condition; In the step S3: the first residue is subjected to a second chlorination at a second temperature under an inert gas condition; The second temperature is greater than the first temperature.

3. A method for separating vanadium and chromium from high-chromium vanadium slag according to claim 1 or 2, characterized in that: After step S3, the method further includes: S4. Dissolving the second residue in water, filtering and collecting the filtrate, performing precipitation treatment on the filtrate, and recovering chromium in the precipitate.

4. A method for separating vanadium and chromium from high-chromium vanadium slag according to claim 1 or 2, characterized in that: Before step S1, the method further includes: The high chromium vanadium slag raw material is sieved and dried to obtain the high chromium vanadium slag.

5. The method for separating vanadium and chromium from high-chromium vanadium slag according to claim 1, characterized in that: The content of vanadium in the high-chromium vanadium slag is 10 wt% to 15 wt% as V2O5, and the content of chromium as Cr2O3 is 5 wt% to 10 wt%.

6. The method for separating vanadium and chromium from high-chromium vanadium slag according to claim 1, characterized in that: The sodium salt includes sodium carbonate, and the mass ratio of the sodium carbonate to the high-chromium vanadium slag is 0.2:1 to 0.6:

1.

7. The method for separating vanadium and chromium from high-chromium vanadium slag according to claim 1, characterized in that: In step S1, the oxidation roasting is carried out at a temperature of 700-1000° C. and for a time of 1.5-2.5 hours.

8. The method for separating vanadium and chromium from high-chromium vanadium slag according to claim 2, characterized in that: The mass ratio of the roasted clinker to the anhydrous aluminum chloride is 1:2, and the mass ratio of the anhydrous aluminum chloride to the sodium chloride is 3:

2.

9. The method for separating vanadium and chromium from high-chromium vanadium slag according to claim 2, characterized in that: In the step S2, the first temperature is 150-170° C., and the time is 1.5-2.5 hours; in the step S3, the second temperature is 230-250° C., and the time is 1.5-2.5 hours.

10. The method for separating vanadium and chromium from high-chromium vanadium slag according to claim 3, characterized in that: In step S4, the second residue is dissolved in water at a temperature of 80° C. for a time of 1.5 to 2.5 hours.