Waste vanadium catalyst recovery method based on low-temperature microwave pyrolysis-extraction process

Abstract

The invention relates to the field of waste vanadium catalyst recovery, in particular to a waste vanadium catalyst recovery method based on a low-temperature microwave pyrolysis-extraction process, which comprises the following steps: microwave pyrolysis, curing leaching, oxidation extraction, primary reverse extraction, ammoniation vanadium precipitation, self-reduction dissolution, secondary reverse extraction, purification and concentration crystallization. Wherein in the primary reverse extraction, a sulfuric acid solution and the extraction phase are mixed to obtain a primary reverse extraction phase and a primary reverse extraction residual phase; and secondary reverse extraction: adding an ammonia water solution into the primary reverse extraction residual phase to obtain a secondary reverse extraction phase. According to the method, the vanadium element is transferred into the primary back extraction phase through primary back extraction of the sulfuric acid solution, then the molybdenum element is transferred into the secondary back extraction phase through secondary back extraction of the ammonia water solution, the vanadium element and the molybdenum element are subjected to back extraction respectively through different characteristics of the two solutions, and separation of the vanadium element and the molybdenum element is achieved.

Description

Technical Field

[0001] This application relates to the field of waste vanadium catalyst recycling, specifically to a method for recycling waste vanadium catalysts based on a low-temperature microwave pyrolysis-extraction process. Background Technology

[0002] Hydrodesulfurization (HDS) catalysts are crucial in petroleum refining. After multiple cycles of use, these catalysts deactivate and become spent catalysts. The vanadium and molybdenum metals present in these spent catalysts have significant strategic importance and potential for secondary recovery. However, the aqueous solutions of vanadium and molybdenum are very similar, making separation difficult. Summary of the Invention

[0003] To address the issue of vanadium and molybdenum separation during the recovery of spent HDS catalysts, this application provides a method for recovering spent vanadium catalysts based on a low-temperature microwave pyrolysis-extraction process, employing the following technical solution: A method for recovering waste vanadium catalyst based on low-temperature microwave pyrolysis-extraction process includes the following steps: Microwave pyrolysis: Waste HDS catalyst is pyrolyzed by microwave, crushed while hot and then separated by cyclone to obtain deoiled waste vanadium catalyst; Maturation leaching: The degreased waste vanadium catalyst is placed in a maturation agent and heated to mature, then water is added for leaching, and then the leaching solution is obtained by filtration; the components of the maturation agent include sulfuric acid, water, and at least one of phosphoric acid, sodium pyrosulfate and sodium thiosulfate; Oxidative extraction: The pH of the leachate is adjusted to 1.5-2.5, hydrogen peroxide is added for oxidation to obtain an aqueous phase; N235, TBP and sulfonated kerosene are mixed to obtain an organic phase; the aqueous phase and the organic phase are mixed to obtain the extract phase. First back-extraction: The sulfuric acid solution is mixed with the extraction phase to obtain a first back-extraction phase and a first back-extraction residue phase; Ammoniation precipitation of vanadium: Ammonia water is added to the primary back-extraction phase, and the mixture is filtered and dried to obtain vanadium precipitate; Self-reducing dissolution: The vanadium precipitate is subjected to a preset pressure of 0.02-0.12 MPa and a preset temperature of 400-650℃ to promote the self-reduction of the vanadium precipitate and obtain a vanadium self-reduced product; when the vanadium self-reduced product is cooled to 60-110℃, sulfuric acid solution is added to obtain a vanadium electrolyte. Secondary back-extraction: An ammonia solution is added to the residual phase of the primary back-extraction to obtain a secondary back-extraction phase; Purification: A purifying agent is added to the secondary back-extraction phase to produce impurity precipitates, and the filtrate is obtained by filtration; the purifying agent includes at least one of aluminum salt, oxalate and polyacrylamide; Concentration and crystallization: The filtrate is concentrated and crystallized, filtered, and dried to obtain ammonium molybdate.

[0004] Preferably, in the first back-extraction step, the sulfuric acid in the sulfuric acid solution accounts for 4%-10% by volume.

[0005] Preferably, in the ammoniation precipitation step, after adding ammonia, the pH of the primary back-extraction phase is adjusted to 1.5-2.3.

[0006] Preferably, in the secondary back-extraction step, the concentration of the ammonia solution is 4-8 mol / L.

[0007] Preferably, in the purification step, the purifying agent is a mixture of aluminum salt, oxalate and polyacrylamide.

[0008] Preferably, in the purification step, the solid-liquid ratios of each component of the purifying agent to the secondary back-extraction phase are: aluminum salt 20-40 mg / L, oxalate 2-4 mg / L, and the volume ratio of 0.1% polyacrylamide to the secondary back-extraction phase is 50:1-3.

[0009] Preferably, in the microwave pyrolysis step, the temperature range of the microwave pyrolysis is 600-700℃.

[0010] Preferably, in the aging and leaching step, the heating and aging temperature range is 80-160°C.

[0011] Preferably, in the oxidative extraction step, the hydrogen peroxide is oxidized at a temperature range of 25-60°C.

[0012] Preferably, in the self-reducing dissolution step, the ammonia gas generated to promote the self-reduction of vanadium precipitate can be prepared as an ammonia solution and added to the residual phase of the first back-extraction.

[0013] In summary, this application has the following beneficial effects: This application utilizes sulfuric acid solution for a single back-extraction to transfer vanadium to the primary back-extraction phase, and then uses ammonia solution for a second back-extraction to transfer molybdenum to the secondary back-extraction phase. By utilizing the different properties of the two solutions, vanadium and molybdenum are back-extracted separately, thus achieving the separation of the two elements. This application utilizes the ammonia gas generated from the self-reduction of vanadium precipitate to prepare ammonia water, which can be added to the residual phase of the first back-extraction for secondary extraction, thereby achieving interconversion between resources and reducing recycling costs. Detailed Implementation

[0014] Example 1 A method for recovering waste vanadium catalyst based on low-temperature microwave pyrolysis-extraction process, characterized by comprising the following steps: Microwave pyrolysis: 100g of waste HDS catalyst was subjected to microwave pyrolysis at a temperature of 650℃ for 1 hour. The catalyst was then crushed while hot and separated by cyclone to obtain de-oiled waste vanadium catalyst. Maturation leaching: 50g of degreased waste vanadium catalyst was placed in 150mL of aging agent and heated to mature at a temperature of 130℃. Then water was added for leaching, and the leachate was obtained by filtration. The aging agent consisted of 25% sulfuric acid, 1% phosphoric acid, 2g sodium pyrosulfate, and 1g sodium thiosulfate, with the remainder being water. Oxidative extraction: The pH of the leachate was adjusted to 2, hydrogen peroxide was added and oxidized at 40°C to obtain an aqueous phase; 20 wt% N235, 10 wt% TBP and 70 wt% sulfonated kerosene were mixed to obtain an organic phase; the aqueous phase and the organic phase were mixed to obtain the extract phase. First back-extraction: Mix 10% by volume of sulfuric acid solution with the extraction phase to obtain a first back-extraction phase and a first back-extraction residue phase; Ammoniation precipitation of vanadium: Ammonia water is added to the primary back-extraction phase to adjust the pH to 2, which promotes the precipitation of vanadium. The vanadium precipitate is obtained by filtration and drying. Self-reducing dissolution: The vanadium precipitate is subjected to a preset pressure of 0.10 MPa and a preset temperature of 550℃ to promote the self-reduction of the vanadium precipitate and obtain vanadium self-reduced product; when the vanadium self-reduced product is cooled to 80℃, sulfuric acid solution is added to obtain vanadium electrolyte; Secondary back-extraction: A 6 mol / L ammonia solution is added to the residual phase of the primary back-extraction to obtain a secondary back-extraction phase; Purification: A purifying agent is added to the secondary back-extraction phase to produce impurity precipitate, and the filtrate is obtained by filtration; the purifying agent is 30 mg aluminum salt, 3 mg oxalate and 1 mL of 0.1% polyacrylamide solution; Concentration and crystallization: The filtrate is concentrated and crystallized at 95°C, filtered, and dried to obtain ammonium molybdate.

[0015] The vanadium content in the collected vanadium electrolyte and the molybdenum content in ammonium molybdate were determined and compared with the vanadium and molybdenum content in the waste HDS catalyst. The results showed that the vanadium collection rate was 92.3% and the molybdenum collection rate was 89.4%.

[0016] Example 2 A method for recovering waste vanadium catalyst based on low-temperature microwave pyrolysis-extraction process, characterized by comprising the following steps: Microwave pyrolysis: 100g of waste HDS catalyst was subjected to microwave pyrolysis at a temperature of 650℃ for 1 hour. The catalyst was then crushed while hot and separated by cyclone to obtain de-oiled waste vanadium catalyst. Maturation leaching: 50g of degreased waste vanadium catalyst was placed in 150mL of aging agent and heated to mature at a temperature of 130℃. Then water was added for leaching, and the leachate was obtained by filtration. The aging agent consisted of 25% sulfuric acid, 1% phosphoric acid, 2g sodium pyrosulfate, and 1g sodium thiosulfate, with the remainder being water. Oxidative extraction: The pH of the leachate was adjusted to 2.5, hydrogen peroxide was added and oxidized at 40°C to obtain an aqueous phase; 20 wt% N235, 10 wt% TBP and 70 wt% sulfonated kerosene were mixed to obtain an organic phase; the aqueous phase and the organic phase were mixed to obtain the extract phase. First back-extraction: A 4% (by volume) sulfuric acid solution is mixed with the extractant phase to obtain a first back-extraction phase and a first back-extraction residue phase; Ammoniation precipitation of vanadium: Ammonia water is added to the primary back-extraction phase to adjust the pH to 2, which promotes the precipitation of vanadium. The vanadium precipitate is obtained by filtration and drying. Self-reducing dissolution: The vanadium precipitate is subjected to a preset pressure of 0.08 MPa and a preset temperature of 400℃ to promote the self-reduction of the vanadium precipitate and obtain vanadium self-reduced product; when the vanadium self-reduced product is cooled to 60℃, sulfuric acid solution is added to obtain vanadium electrolyte; Secondary back-extraction: A 6 mol / L ammonia solution is added to the residual phase of the primary back-extraction to obtain a secondary back-extraction phase; Purification: A purifying agent is added to the secondary back-extraction phase to produce impurity precipitate, and the filtrate is obtained by filtration; the purifying agent is 30 mg aluminum salt, 3 mg oxalate and 1 mL of 0.1% polyacrylamide solution; Concentration and crystallization: The filtrate is concentrated and crystallized at 95°C, filtered, and dried to obtain ammonium molybdate.

[0017] The vanadium content in the collected vanadium electrolyte and the molybdenum content in ammonium molybdate were determined and compared with the vanadium and molybdenum content in the waste HDS catalyst. The vanadium collection rate was found to be 86.1% and the molybdenum collection rate was 83.7%.

[0018] Example 3 A method for recovering waste vanadium catalyst based on low-temperature microwave pyrolysis-extraction process, characterized by comprising the following steps: Microwave pyrolysis: 100g of waste HDS catalyst was subjected to microwave pyrolysis at a temperature of 650℃ for 1 hour. The catalyst was then crushed while hot and separated by cyclone to obtain de-oiled waste vanadium catalyst. Maturation leaching: 50g of degreased waste vanadium catalyst was placed in 150mL of aging agent and heated to mature at a temperature of 130℃. Then water was added for leaching, and the leachate was obtained by filtration. The aging agent consisted of 25% sulfuric acid, 1% phosphoric acid, 2g sodium pyrosulfate, and 1g sodium thiosulfate, with the remainder being water. Oxidative extraction: The pH of the leachate was adjusted to 2, hydrogen peroxide was added and oxidized at 25°C to obtain an aqueous phase; 20 wt% N235, 10 wt% TBP and 70 wt% sulfonated kerosene were mixed to obtain an organic phase; the aqueous phase and the organic phase were mixed to obtain the extract phase. First back-extraction: Mix 8% by volume of sulfuric acid solution with the extract phase to obtain a first back-extraction phase and a first back-extraction residue phase; Ammoniation precipitation of vanadium: Ammonia water is added to the primary back-extraction phase to adjust the pH to 1.5, which promotes the precipitation of vanadium. The vanadium precipitate is obtained by filtration and drying. Self-reducing dissolution: The vanadium precipitate is subjected to a preset pressure of 0.12 MPa and a preset temperature of 650℃ to promote the self-reduction of the vanadium precipitate and obtain vanadium self-reduced product; when the vanadium self-reduced product is cooled to 110℃, sulfuric acid solution is added to obtain vanadium electrolyte; Secondary back-extraction: A 6 mol / L ammonia solution is added to the residual phase of the primary back-extraction to obtain a secondary back-extraction phase; Purification: A purifying agent is added to the secondary back-extraction phase to produce impurity precipitate, and the filtrate is obtained by filtration; the purifying agent is 30 mg aluminum salt, 3 mg oxalate and 1 mL of 0.1% polyacrylamide solution; Concentration and crystallization: The filtrate is concentrated and crystallized at 95°C, filtered, and dried to obtain ammonium molybdate.

[0019] The vanadium content in the collected vanadium electrolyte and the molybdenum content in ammonium molybdate were determined and compared with the vanadium and molybdenum content in the waste HDS catalyst. The results showed that the vanadium collection rate was 91.6% and the molybdenum collection rate was 88.9%.

[0020] Example 4 A method for recovering waste vanadium catalyst based on low-temperature microwave pyrolysis-extraction process, characterized by comprising the following steps: Microwave pyrolysis: 100g of waste HDS catalyst was subjected to microwave pyrolysis at a temperature of 650℃ for 1 hour. The catalyst was then crushed while hot and separated by cyclone to obtain de-oiled waste vanadium catalyst. Maturation leaching: 50g of degreased waste vanadium catalyst was placed in 150mL of aging agent and heated to mature at a temperature of 130℃. Then water was added for leaching, and the leachate was obtained by filtration. The aging agent consisted of 25% sulfuric acid, 1% phosphoric acid, 2g sodium pyrosulfate, and 1g sodium thiosulfate, with the remainder being water. Oxidative extraction: The pH of the leachate was adjusted to 2, hydrogen peroxide was added and oxidized at 60°C to obtain an aqueous phase; 20 wt% N235, 10 wt% TBP and 70 wt% sulfonated kerosene were mixed to obtain an organic phase; the aqueous phase and the organic phase were mixed to obtain the extract phase. First back-extraction: Mix 8% by volume of sulfuric acid solution with the extract phase to obtain a first back-extraction phase and a first back-extraction residue phase; Ammoniation precipitation of vanadium: Ammonia water is added to the primary back-extraction phase to adjust the pH to 2, which promotes the precipitation of vanadium. The vanadium precipitate is obtained by filtration and drying. Self-reducing dissolution: The vanadium precipitate is subjected to a preset pressure of 0.10 MPa and a preset temperature of 550℃ to promote the self-reduction of the vanadium precipitate and obtain vanadium self-reduced product; when the vanadium self-reduced product is cooled to 80℃, sulfuric acid solution is added to obtain vanadium electrolyte; Secondary back-extraction: A 4 mol / L ammonia solution is added to the residual phase of the primary back-extraction to obtain a secondary back-extraction phase; Purification: A purifying agent is added to the secondary back-extraction phase to produce impurity precipitate, and the filtrate is obtained by filtration; the purifying agent is 30 mg aluminum salt and 2 mL of 0.1% polyacrylamide solution; Concentration and crystallization: The filtrate is concentrated and crystallized at 95°C, filtered, and dried to obtain ammonium molybdate.

[0021] The vanadium content in the collected vanadium electrolyte and the molybdenum content in ammonium molybdate were determined and compared with the vanadium and molybdenum content in the waste HDS catalyst. The results showed that the vanadium collection rate was 91.8% and the molybdenum collection rate was 86.5%.

[0022] Example 5 A method for recovering waste vanadium catalyst based on low-temperature microwave pyrolysis-extraction process, characterized by comprising the following steps: Microwave pyrolysis: 100g of waste HDS catalyst was subjected to microwave pyrolysis at a temperature of 700℃ for 1 hour. The catalyst was then crushed while hot and separated by cyclone to obtain de-oiled waste vanadium catalyst. Maturation leaching: 50g of degreased waste vanadium catalyst was placed in 150mL of aging agent and heated to mature at a temperature of 130℃. Then water was added for leaching, and the leachate was obtained by filtration. The aging agent consisted of 25% sulfuric acid, 1% phosphoric acid, 2g sodium pyrosulfate, and 1g sodium thiosulfate, with the remainder being water. Oxidative extraction: The pH of the leachate was adjusted to 2, hydrogen peroxide was added and oxidized at 40°C to obtain an aqueous phase; 20 wt% N235, 10 wt% TBP and 70 wt% sulfonated kerosene were mixed to obtain an organic phase; the aqueous phase and the organic phase were mixed to obtain the extract phase. First back-extraction: Mix 8% by volume of sulfuric acid solution with the extract phase to obtain a first back-extraction phase and a first back-extraction residue phase; Ammoniation precipitation of vanadium: Ammonia water is added to the primary back-extraction phase to adjust the pH to 2, which promotes the precipitation of vanadium. The vanadium precipitate is obtained by filtration and drying. Self-reducing dissolution: The vanadium precipitate is subjected to a preset pressure of 0.10 MPa and a preset temperature of 550℃ to promote the self-reduction of the vanadium precipitate and obtain vanadium self-reduced product; when the vanadium self-reduced product is cooled to 80℃, sulfuric acid solution is added to obtain vanadium electrolyte; Secondary back-extraction: Add 8 mol / L ammonia solution to the residual phase of the primary back-extraction to obtain the secondary back-extraction phase; Purification: A purifying agent is added to the secondary back-extraction phase to produce impurity precipitate, and the filtrate is obtained by filtration; the purifying agent is 30 mg aluminum salt and 3 mg oxalate. Concentration and crystallization: The filtrate is concentrated and crystallized at 95°C, filtered, and dried to obtain ammonium molybdate.

[0023] The vanadium content in the collected vanadium electrolyte and the molybdenum content in ammonium molybdate were determined and compared with the vanadium and molybdenum content in the waste HDS catalyst. The vanadium collection rate was 92.1% and the molybdenum collection rate was 90.6%.

[0024] Example 6 A method for recovering waste vanadium catalyst based on low-temperature microwave pyrolysis-extraction process, characterized by comprising the following steps: Microwave pyrolysis: 100g of waste HDS catalyst was subjected to microwave pyrolysis at a temperature of 600℃ for 1 hour. The catalyst was then crushed while hot and separated by cyclone to obtain the de-oiled waste vanadium catalyst. Maturation leaching: 50g of degreased waste vanadium catalyst was placed in 150mL of aging agent and heated to mature at a temperature of 130℃. Then water was added for leaching, and the leachate was obtained by filtration. The aging agent consisted of 25% sulfuric acid, 1% phosphoric acid, 2g sodium pyrosulfate, and 1g sodium thiosulfate, with the remainder being water. Oxidative extraction: The pH of the leachate was adjusted to 2, hydrogen peroxide was added and oxidized at 40°C to obtain an aqueous phase; 20 wt% N235, 10 wt% TBP and 70 wt% sulfonated kerosene were mixed to obtain an organic phase; the aqueous phase and the organic phase were mixed to obtain the extract phase. First back-extraction: Mix 10% by volume of sulfuric acid solution with the extraction phase to obtain a first back-extraction phase and a first back-extraction residue phase; Ammoniation precipitation of vanadium: Ammonia water is added to the primary back-extraction phase to adjust the pH to 2, which promotes the precipitation of vanadium. The vanadium precipitate is obtained by filtration and drying. Self-reducing dissolution: The vanadium precipitate is subjected to a preset pressure of 0.10 MPa and a preset temperature of 550℃ to promote the self-reduction of the vanadium precipitate and obtain vanadium self-reduced product; when the vanadium self-reduced product is cooled to 80℃, sulfuric acid solution is added to obtain vanadium electrolyte; Secondary back-extraction: A 6 mol / L ammonia solution is added to the residual phase of the primary back-extraction to obtain a secondary back-extraction phase; Purification: A purifying agent is added to the secondary back-extraction phase to produce impurity precipitate, and the filtrate is obtained by filtration; the purifying agent is 30 mg aluminum salt, 3 mg oxalate and 3 mL of 0.1% polyacrylamide solution; Concentration and crystallization: The filtrate is concentrated and crystallized at 95°C, filtered, and dried to obtain ammonium molybdate.

[0025] The vanadium content in the collected vanadium electrolyte and the molybdenum content in ammonium molybdate were determined and compared with the vanadium and molybdenum content in the waste HDS catalyst. The results showed that the vanadium collection rate was 92.3% and the molybdenum collection rate was 89.4%.

[0026] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A method for recovering waste vanadium catalyst based on low-temperature microwave pyrolysis-extraction process, characterized in that, Includes the following steps: Microwave pyrolysis: Waste HDS catalyst is pyrolyzed by microwave, crushed while hot and then separated by cyclone to obtain deoiled waste vanadium catalyst; Maturation leaching: The degreased waste vanadium catalyst is placed in a maturation agent and heated to mature, then water is added for leaching, and then the leaching solution is obtained by filtration; the components of the maturation agent include sulfuric acid, water, and at least one of phosphoric acid, sodium pyrosulfate and sodium thiosulfate; Oxidative extraction: The pH of the leachate is adjusted to 1.5-2.5, hydrogen peroxide is added for oxidation to obtain an aqueous phase; N235, TBP and sulfonated kerosene are mixed to obtain an organic phase; the aqueous phase and the organic phase are mixed to obtain the extract phase. First back-extraction: The sulfuric acid solution is mixed with the extraction phase to obtain a first back-extraction phase and a first back-extraction residue phase; Ammoniation precipitation of vanadium: Ammonia water is added to the primary back-extraction phase, and the mixture is filtered and dried to obtain vanadium precipitate; Self-reducing dissolution: The vanadium precipitate is subjected to a preset pressure of 0.02-0.12 MPa and a preset temperature of 400-650℃ to promote the self-reduction of the vanadium precipitate and obtain a vanadium self-reduced product; when the vanadium self-reduced product is cooled to 60-110℃, sulfuric acid solution is added to obtain a vanadium electrolyte. Secondary back-extraction: An ammonia solution is added to the residual phase of the primary back-extraction to obtain a secondary back-extraction phase; Purification: A purifying agent is added to the secondary back-extraction phase to produce impurity precipitates, and the filtrate is obtained by filtration; the purifying agent includes at least one of aluminum salt, oxalate and polyacrylamide; Concentration and crystallization: The filtrate is concentrated and crystallized, filtered, and dried to obtain ammonium molybdate.

2. The method for recovering waste vanadium catalyst based on low-temperature microwave pyrolysis-extraction process according to claim 1, characterized in that: In one back-extraction step, the sulfuric acid in the sulfuric acid solution accounts for 4%-10% by volume.

3. The method for recovering waste vanadium catalyst based on low-temperature microwave pyrolysis-extraction process according to claim 2, characterized in that: In the ammoniation precipitation step, after adding ammonia, the pH of the primary back-extraction phase is adjusted to 1.5-2.

3.

4. The method for recovering waste vanadium catalyst based on low-temperature microwave pyrolysis-extraction process according to claim 1, characterized in that: In the secondary back-extraction step, the concentration of the ammonia solution is 4-8 mol / L.

5. The method for recovering waste vanadium catalyst based on low-temperature microwave pyrolysis-extraction process according to claim 1, characterized in that: In the purification step, the purifying agent is a mixture of aluminum salt, oxalate and polyacrylamide.

6. The method for recovering waste vanadium catalyst based on low-temperature microwave pyrolysis-extraction process according to claim 5, characterized in that: In the purification step, the solid-liquid ratios of each component of the purifying agent to the secondary back-extraction phase are as follows: aluminum salt 20-40 mg / L, oxalate 2-4 mg / L, and the volume ratio of 0.1% polyacrylamide to the secondary back-extraction phase is 50:1-3.

7. The method for recovering waste vanadium catalyst based on low-temperature microwave pyrolysis-extraction process according to claim 1, characterized in that: In the microwave pyrolysis step, the temperature range of microwave pyrolysis is 600-700℃.

8. The method for recovering waste vanadium catalyst based on low-temperature microwave pyrolysis-extraction process according to claim 1, characterized in that: In the aging and leaching step, the temperature range of the heating and aging process is 80-160°C.

9. The method for recovering waste vanadium catalyst based on low-temperature microwave pyrolysis-extraction process according to claim 1, characterized in that: In the oxidative extraction step, the hydrogen peroxide is oxidized at a temperature range of 25-60°C.

10. The method for recovering waste vanadium catalyst based on low-temperature microwave pyrolysis-extraction process according to claim 1, characterized in that: In the self-reducing dissolution step, the ammonia gas generated by promoting the self-reduction of vanadium precipitate can be prepared into an ammonia solution and added to the residual phase of the first back-extraction.