Novel impurity removal and vanadium precipitation process for directly preparing high-purity vanadium pentoxide

Abstract

The invention relates to a process for extracting vanadium from stone coal and smelting to prepare vanadium pentoxide, in particular to an impurity removal and vanadium precipitation process for an alkaline desorption solution. According to the method, the special impurity removal agent is adopted, according to the technological requirements, the quantitative special impurity removal agent is added into the alkaline desorption solution, sectional type impurity removal is adopted, and compared with an existing technology, the whole impurity removal and vanadium precipitation process is more thorough in impurity removal, better in vanadium precipitation effect and lower in vanadium content of vanadium precipitation tail water by controlling technological parameters such as the PH value and the temperature of the impurity removal and vanadium precipitation technology; the method has the advantages that the impurity removal slag amount is small, the vanadium content in the slag is low, the finished vanadium pentoxide product has few impurities and good quality, and 99.50% high-purity vanadium pentoxide can be directly prepared without secondary vanadium precipitation.

Description

Technical Field

[0001] The technical invention relates to a process for extracting vanadium from stone coal and smelting vanadium pentoxide, and specifically to a process for removing impurities and precipitating vanadium with an alkaline analytical solution. Background Art

[0002] With the application of all-vanadium liquid flow batteries in the field of energy storage, the demand for vanadium pentoxide products has increased significantly, especially high-purity vanadium pentoxide products with a purity of 99.50%. Due to limited production capacity, the product is in short supply and the price is about RMB 30,000 / ton more expensive than 98% vanadium pentoxide.

[0003] Vanadium pentoxide products are mainly produced by the following two processes: One method is to produce vanadium pentoxide using vanadium slag as raw material. The vanadium precipitation process of this method is basically acidic ammonium salt precipitation. It is based on controlling the reaction temperature above 90°C in a solution with a pH of 2-3. Polyvanadates react with ammonium salts to form hexavanadate ammonium precipitate. The product purity can reach 98%, and the excellent ones can reach 99%. However, due to the high potassium and sodium inclusions in the product, it is not suitable for directly preparing the electrolyte of all-vanadium liquid flow batteries.

[0004] A process for producing vanadium pentoxide using stone coal as raw material. This process mostly uses aluminum salt impurity removal process before vanadium precipitation. The vanadium precipitation process is basically weak alkaline ammonium salt vanadium precipitation. It is based on the reaction with ammonium salt in a weak alkaline metavanadic acid solution with a pH of 8-9 to generate ammonium vanadate precipitate. The product purity can reach 98%, 98.5%, and the excellent ones can reach 99%. However, due to process control reasons, the product contains impurities such as sodium, aluminum, silicon, and phosphorus, which are difficult to meet the standards and are not suitable for directly preparing all-vanadium liquid flow battery electrolyte.

[0005] The vanadium pentoxide products of the above two processes must be purified at a high cost because of excessive impurities. This is why the price of 99.50% pure vanadium pentoxide is about 30,000 yuan / ton more expensive than 98% pure vanadium pentoxide. Therefore, it is necessary to find a method to directly produce 99.50% high-purity vanadium pentoxide without secondary purification.

[0006] The present invention develops a new process technology for impurity removal and vanadium precipitation in the process of vanadium extraction and smelting from stone coal. Without changing other process technical conditions, only through the innovation of impurity removal and vanadium precipitation process, impurities are removed more thoroughly and vanadium precipitation effect is better. 99.50% high-purity vanadium pentoxide can be directly prepared without secondary vanadium precipitation. Summary of the invention

[0007] The present invention improves and innovates the impurity removal and vanadium precipitation process for vanadium extraction from stone coal based on a thorough study and understanding of the current domestic and foreign processes for removing impurities and vanadium from alkaline analytical liquid, and proposes a new process route for removing impurities and vanadium from stone coal. The process route has the advantages of less slag, low vanadium content in slag, low vanadium content in liquid after vanadium precipitation, low impurity content in finished products, high quality, and low cost.

[0008] This impurity removal and vanadium precipitation process is suitable for the impurity removal and vanadium precipitation process of alkaline analytical solution for vanadium extraction from stone coal.

[0009] This impurity removal and vanadium precipitation process is suitable for alkaline analytical solution with a vanadium content of 60-120g / L.

[0010] The impurity remover used in this impurity removal and vanadium precipitation process is a special aluminum salt, the main chemical component of which is aluminum sulfate. The impurity remover is prepared and added in the following way: a certain amount of aluminum hydroxide is dissolved in hot sulfuric acid to prepare the impurity remover; sulfuric acid containing a certain amount of impurity remover is added during the pH value adjustment of the analytical solution to remove impurities. The amount of impurity remover added: the weight ratio of aluminum hydroxide to the impurity content (silicon, phosphorus, arsenic) in the analytical solution is 3:1. Aluminum hydroxide meets the quality requirements of AH-1 in GB / T4294-2010.

[0011] The vanadium precipitation agent used in this impurity removal and vanadium precipitation process is ammonium sulfate, which is added according to the ammonium-vanadium weight ratio of (2.5-3.5):1. The quality grade of ammonium sulfate meets the Type 1 quality requirements in GB / T535-2020.

[0012] The process flow of impurity removal and vanadium precipitation: ① Add a certain amount of sulfuric acid containing a decontamination agent according to the impurity content in the alkaline analytical solution and stir; ② Adjust the pH value to 9.5-10.0 with sulfuric acid and continue stirring for 30 minutes; ③ Adjust the pH value to 7.8-8.6 with sulfuric acid, continue stirring for 30 minutes, cool the solution to 0-20℃, stop stirring and let it stand; ④ Solid-liquid separation; ⑤ Adjust the solution pH by 0.5-1 to pH8.8-9.1, and measure the vanadium content of the solution; ⑥ According to the vanadium content of the solution, add ammonium sulfate and stir to precipitate vanadium, cool the solution to 0-20℃, and stop stirring when it is consistent with or slightly higher than the end point temperature of impurity removal; ⑦ The subsequent step is the conventional ammonium vanadium precipitation process operation.

[0013] This process is different from the known alkaline analytical solution impurity removal and vanadium precipitation process in the following ways: ① Preparation of special impurity remover and method of adding impurity remover: In the known process, aluminum sulfate or aluminum chloride is directly added to the alkaline analytical solution. This method of addition has the problems of large amount of aluminum salt added, slow dissolution, incomplete dissolution, severe gelation of the solution after dissolution, difficulty in solid-liquid separation, large amount of slag, high vanadium content in the slag, and low yield. This process dissolves a certain amount of aluminum hydroxide in hot sulfuric acid to prepare an impurity remover, and adds sulfuric acid containing a certain amount of impurity remover to remove impurities during the pH adjustment of the alkaline analytical solution. This process uses a small amount of impurity remover, dissolves quickly, is easy to separate solid and liquid, has a small vanadium content in the slag, and has a high yield.

[0014] ② Segmented impurity removal, more thorough impurity removal, better impurity removal effect: It is known that the impurity removal process controls the pH value at 10-9.50, and the silicon removal effect is good, but the removal of phosphorus and arsenic is not ideal. Unlike the existing impurity removal process that controls the pH value at 10-9.50, this process removes impurities in stages at pH 9.50-10.00 and pH 7.80-8.50, removes impurities in the pH 9.50-10.00 range, mainly removing silicon, and then adjusts to pH 7.80-8.50 to remove impurities such as phosphorus and arsenic. Compared with the original process, segmented impurity removal is more thorough and has better impurity removal effect.

[0015] ③ The requirements for temperature control are different from those of the known impurity removal and vanadium precipitation processes: the original process has no clear requirements for the end temperature of impurity removal and vanadium precipitation. In actual operation, the end temperature of impurity removal is much higher than the end temperature of vanadium precipitation, and the end temperature of vanadium precipitation is actually controlled to be room temperature or even higher than room temperature. However, this process controls the end temperature of impurity removal at 0-20℃, and the end temperature of vanadium precipitation is consistent with or slightly higher than the end temperature of impurity removal. The end temperature of vanadium precipitation is ≧ the end temperature of impurity removal. This temperature control makes the impurity removal effect better. The lower the end temperature of vanadium precipitation, the lower the vanadium content of the tail water of vanadium precipitation. The control of the end temperature of vanadium precipitation effectively reduces the vanadium content in the tail water of vanadium precipitation and improves the vanadium recovery rate of the process.

[0016] ④ The requirements for PH control are different from those of the known impurity removal and vanadium precipitation processes: the known process directly precipitates vanadium after impurity removal, and the vanadium precipitation end point PH is between 8-9, and there is no precise requirement for PH. In actual operation, the PH value of the impurity removal end point is much greater than the vanadium precipitation end point PH; the impurity removal end point PH value of this process is 7.8-8.6, and the PH value is increased by 0.5-1 to PH8.8-9.1 during vanadium precipitation, and then the vanadium precipitation agent is added for vanadium precipitation, and the vanadium precipitation end point PH value ≧ the impurity removal end point PH value, and the vanadium precipitation end point PH is between 8-9. This process setting makes the vanadium precipitation have less impurity content of ammonium metavanadate, and the finished product meets the quality standard of 99.50% high-purity vanadium pentoxide.

[0017] This impurity removal and vanadium precipitation process changes the preparation of special impurity removers and the addition method of impurity removers. According to the requirements of this process, impurities are removed in stages, and the pH value of impurity removal and vanadium precipitation and the temperature of impurity removal and vanadium precipitation are precisely controlled. Compared with the existing process, the entire impurity removal and vanadium precipitation process is more thorough and the vanadium precipitation effect is better. The vanadium content in the vanadium precipitation tail water is lower, the amount of impurity removal slag is small, the vanadium content in the slag is low, the finished vanadium pentoxide has less impurities and better quality, and 99.50% high-purity vanadium pentoxide can be directly produced without secondary vanadium precipitation.

Claims

1. This technical invention relates to a process for extracting vanadium from stone coal and smelting vanadium pentoxide, and specifically to a process for removing impurities and precipitating vanadium in an alkaline analytical solution. Its characteristics are: ① Preparation of special impurity remover and impurity remover addition method: dissolve a certain amount of aluminum hydroxide in hot sulfuric acid to prepare the impurity remover. The impurity remover is added in the process of adjusting the pH value of the alkaline analytical solution. Sulfuric acid containing a certain amount of impurity remover is added, stirred, and then sulfuric acid is added to adjust the pH value, stirred, and impurities are removed. ② Segmented impurity removal. This process removes impurities in stages at pH 9.50-10.00 and pH 7.80-8.50: impurities are removed in the pH range of 9.50-10.00, mainly removing silicon, and then adjusting the pH value to 7.80-8.50 to remove impurities such as phosphorus and arsenic. ③ Requirements for temperature control of this impurity removal and vanadium precipitation process: This process controls the impurity removal endpoint temperature to 0-20℃, and the vanadium precipitation endpoint temperature is controlled to be consistent with the impurity removal endpoint temperature or slightly higher. The vanadium precipitation endpoint temperature must not be lower than the impurity removal endpoint temperature. This temperature control makes the impurity removal effect better, and the vanadium content in the vanadium precipitation tail water can also be well controlled. The lower the vanadium precipitation temperature, the lower the vanadium content in the vanadium precipitation tail water. ④ The end point pH value of this process is 7.8-8.

6. When vanadium is precipitated, the pH value is increased by 0.5-1 to pH8.8-9.1, and then the vanadium precipitation agent is added to precipitate vanadium. The end point pH value of vanadium precipitation is ≧ the end point pH value of impurity removal. The end point pH value of vanadium precipitation is between 8-9.

2. The new process technology for removing impurities and vanadium precipitation according to claim 1 is characterized in that: Preparation of special impurity remover and method of adding impurity remover. The existing process directly adds aluminum sulfate or aluminum chloride to the alkaline analytical solution. This method of adding has the problems of large amount of aluminum salt added, slow dissolution, incomplete dissolution, serious colloidization of the solution after dissolution, difficulty in solid-liquid separation, large amount of slag, high vanadium content in the slag, and low yield. This process dissolves a certain amount of aluminum hydroxide in hot sulfuric acid to prepare a special impurity remover. The impurity remover is added by adding sulfuric acid containing a certain amount of impurity remover during the pH value adjustment of the alkaline analytical solution to remove impurities. This process uses a small amount of impurity remover, dissolves quickly, is easy to separate solid and liquid, has a small vanadium content in the slag, and has a high yield.

3. The new process technology for removing impurities and precipitating vanadium according to claim 1 is characterized in that: The segmented impurity removal is more thorough and has better impurity removal effect. It is known that the impurity removal process controls the pH value at 10-9.

50. The silicon removal effect is better under this pH, but the removal of phosphorus and arsenic is not ideal. Unlike the existing impurity removal process that controls the pH value at 10-9.50, this process removes impurities in stages at pH 9.50-10.00 and pH 7.80-8.

50. In the pH 9.50-10.00 range, the impurity removal is mainly silicon removal, and then adjusted to pH 7.80-8.50 to effectively remove impurities such as phosphorus and arsenic. Compared with the original process, the segmented impurity removal is more thorough and has better impurity removal effect.

4. The new process technology for removing impurities and vanadium precipitation according to claim 1 is characterized in that: Different from the existing impurity removal and vanadium precipitation process, the original process has no detailed requirements for the impurity removal and vanadium precipitation end temperature. In the actual operation process, the impurity removal end temperature is higher than the vanadium precipitation end temperature, and the vanadium precipitation end temperature is actually controlled to be room temperature or even higher than room temperature. However, this process controls the impurity removal end temperature at 0-20℃, and the vanadium precipitation end temperature is consistent with or slightly higher than the impurity removal end temperature. The vanadium precipitation end temperature ≧ the impurity removal end temperature. This temperature control makes the impurity removal effect better. The lower the vanadium precipitation end temperature, the lower the vanadium content in the vanadium precipitation tail water. The control of the vanadium precipitation end temperature effectively reduces the vanadium content in the vanadium precipitation tail water and improves the vanadium recovery rate of the process.

5. The new process technology for removing impurities and precipitating vanadium according to claim 1 is characterized in that: The requirements for pH control of the existing impurity removal and vanadium precipitation process are different. The existing process directly precipitates vanadium after impurity removal, and controls the pH to be between 8-9. In actual operation, the pH value of the impurity removal endpoint is much higher than the pH of the vanadium precipitation endpoint. The pH value of the impurity removal endpoint of this process is 7.8-8.

6. When vanadium is precipitated, the pH value is increased by 0.5-1 to pH8.8-9.1, and then a vanadium precipitation agent is added to precipitate vanadium. The pH value of the vanadium precipitation endpoint is ≧ the pH value of the impurity removal endpoint, and the pH of the vanadium precipitation endpoint is between 8-9. This is one of the characteristics of this process that distinguishes it from the existing process. This process setting makes the content of ammonium metavanadate impurities in vanadium precipitation less, and the finished product meets the quality standard of 99.50% high-purity vanadium pentoxide.