Method for removing aluminum trichloride from crude vanadium oxychloride

Abstract

The invention provides a method for removing aluminum trichloride from crude vanadium oxychloride, which comprises the following steps: (1) taking crude vanadium oxychloride containing aluminum trichloride impurities as a raw material, injecting the raw material into a crystallizer, quickly cooling and growing crystal to form an aluminum trichloride crystal nucleus, and then carrying out gradient cooling and crystal growth; and (2) pumping out crystal slurry from the crystallizer, and filtering to obtain separated and purified vanadium oxychloride. The method has the beneficial effects that the problems of high cost, high difficulty, long period and high vanadium loss of the existing method for removing aluminum from crude vanadium oxychloride are well solved; the method has the advantages of simple separation process flow, no use of any solvent in the crystallization process, cost saving, high product quality and easiness in industrialization.

Description

Technical Field

[0001] The invention relates to a method for removing aluminum trichloride from crude vanadium oxychloride, belonging to the field of solid waste resource utilization. Background Art

[0002] The chlorination process for preparing high-purity vanadium pentoxide mainly involves chlorinating vanadium-containing raw materials to obtain an intermediate product, crude vanadium trichloride, which is then further refined to obtain high-purity vanadium trichloride, and finally the high-purity vanadium trichloride is converted to obtain high-purity vanadium pentoxide. Therefore, high-purity vanadium trichloride is the basic prerequisite for the preparation of high-purity vanadium pentoxide.

[0003] The solubility of aluminum chloride is affected by temperature and pH value. At room temperature, it has a higher solubility in weakly acidic solvents. In the pH range of 3 to 6, the solubility of aluminum chloride is about 60 to 90 g / L; when the pH value is between 7 and 9, the solubility of aluminum chloride is 30 to 50 g / L; and when the pH value is greater than 9, the solubility of aluminum chloride will be greatly reduced to only about 10 g / L. In addition, aluminum chloride is also related to temperature. As the temperature increases, the solubility of aluminum chloride will also increase. At 10°C, its solubility is 120 g / L; at 50°C, the solubility is 320 g / L; at 90°C, the solubility can reach more than 400 g / L. In short, the solubility of aluminum chloride is affected by the pH value and temperature of the solution. At room temperature, it has a higher solubility in acidic solvents, and the solubility of aluminum chloride will also drop significantly when the temperature decreases.

[0004] Since the vanadium-containing raw materials contain a certain amount of impurities, the impurities are chlorinated to varying degrees during the chlorination process, forming corresponding chlorides (such as AlCl3) that enter the crude vanadium oxychloride, which needs to be purified and refined to obtain high-purity vanadium oxychloride. For aluminum trichloride, the solubility of vanadium oxychloride is relatively large when acidic vanadium oxychloride is used as a solvent, and excessive aluminum trichloride in vanadium oxychloride will easily lead to saturated crystal precipitation at low temperatures, and the deposition will adhere to the inner wall of the heat exchanger pipe, which will greatly reduce the heat exchange effect of the heat exchanger on the one hand, and may block the pipe on the other hand, seriously affecting production.

[0005] Patent CN115947370A provides a method for preparing refined vanadium oxychloride using vanadium-containing refined tailings. This method only uses filtration to remove solid impurities in crude vanadium oxychloride, and does not consider impurities dissolved in the vanadium oxychloride; Patent CN114380331A, a method for purifying crude vanadium oxychloride, and CN114380332A, a method for purifying crude vanadium oxychloride, use a distillation method to remove some dissolved impurities in the crude vanadium oxychloride. This method has the disadvantages of low impurity removal efficiency and high energy consumption; CN112142107A, a method for preparing high-purity vanadium oxychloride using vanadium-containing refined tailings, uses a hydrolysis + distillation method to remove impurities from the crude vanadium oxychloride. This method has a high vanadium loss rate and high energy consumption. Summary of the invention

[0006] The present invention provides a method for removing aluminum trichloride from crude vanadium oxychloride. The method mainly removes aluminum trichloride by gradient crystallization, and the method has reliable process principle, simple process flow and low production cost.

[0007] The present invention adopts the following technical solutions:

[0008] (1) The external inert atmosphere is connected to the inert gas inlet 3 and the inert gas outlet 6 to replace the crystallizer, so that the system maintains an inert gas atmosphere state.

[0009] (2) Inject crude vanadium trichloride into the crystallizer at 2 / 3 liquid level through the raw material inlet 5, and close the raw material inlet; turn on the magnetic stirring 9, turn on the refrigerator 1, and inject it into the crystallizer interlayer through the freezing liquid inlet 2, and circulate cooling through the freezing liquid outlet 7, and control the freezing liquid temperature to cool the crude vanadium trichloride according to a certain temperature gradient to crystallize aluminum trichloride. Observe the internal temperature through the thermometer 4, and cool the crude vanadium trichloride to 10°C for crystal cultivation.

[0010] (3) After the crystal growth is completed, the discharge port 8 is opened to discharge the crystal slurry into a collecting bottle 10 with a filter cloth.

[0011] (4) After filtration, remove the filter cloth and test the vanadium content after acid leaching.

[0012] 2. The method for removing aluminum chloride from crude vanadium trichloride according to claim 1, characterized in that: the inert gas in step (1) can be nitrogen or argon, the nitrogen purity is ≥99%, the argon purity is ≥99%, the water vapor after replacement in the system is ≤1ppm, and there is no oxygen in the system.

[0013] 3. The method for removing aluminum chloride from crude vanadium oxychloride according to claim 1, characterized in that: step (2) uses a gradient crystallization method to crystallize aluminum chloride in the crude vanadium oxychloride, and the specific operation is as follows:

[0014] i. Crystal growth stage: Rapidly cool to 10°C at a cooling rate of 3-4°C / min, with a magnetic stirring speed of 100-120rpm to ensure uniform internal temperature, and grow the crystal at low temperature for 30 minutes to form crystal nuclei of aluminum chloride.

[0015] ii. Crystal growth stage: The magnetic stirring speed is controlled at 30-80 rpm. A low speed is conducive to crystal growth. The cooling rate is 0.5-1°C / min. After cooling to -15°C, keep it for 60 minutes.

[0016] 4. The method for removing aluminum chloride from crude vanadium oxychloride according to claim 1, characterized in that: in step (3), the filtration connecting pipeline is a sandwich tube, and a -15°C refrigerant is passed into the sandwich for cold preservation, the pore size of the filter cloth used for filtration is 3-6μm, the vanadium loss is less than 3g / L, and the aluminum content in the vanadium oxychloride after filtration is ≤0.001%.

[0017] 5. The method for removing aluminum chloride from crude vanadium oxychloride according to claim 1, characterized in that the filter cloth is subjected to acid leaching after filtration, and the acid is 1+1 hydrochloric acid.

[0018] The beneficial effect of the present invention is that the gradient crystallization method is adopted to control the gradient crystallization, precipitation and filtration of aluminum trichloride in crude vanadium oxychloride at low temperature to achieve the purpose of impurity removal. The process principle of the method is reliable, the process flow is simple, the production cost is relatively low, and it is easy to industrialize. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is a schematic diagram of the device for removing aluminum trichloride from crude vanadium oxychloride in this patent. DETAILED DESCRIPTION

[0020] In order to make the technical solution of the method for removing aluminum trichloride from crude vanadium oxychloride described in this patent clearer, the technical solution of the present invention is further described below in conjunction with specific implementation methods.

[0021] Embodiment 1:

[0022] Select nitrogen with a purity of more than 99% as an inert gas source and continuously pass it into the crystallizer through the nitrogen inlet and the nitrogen outlet to keep the device in an inert atmosphere; turn on the refrigerator to circulate the freezing liquid to the crystallizer jacket through the freezing liquid inlet and the freezing liquid outlet; inject crude vanadium trichloride to 2 / 3 through the raw material inlet, and close the crystallizer; turn on the magnetic stirring and set the speed to 100rpm, turn on the refrigerator to cool, cool at a rate of 3℃ / min, observe the thermometer display, and when it reaches 10℃, maintain this temperature for 30min. Then cool at a rate of 0.5℃ / min, and the stirring speed is reduced to 30rpm. After dropping to -15℃, keep it at this temperature for 60min, discharge the vanadium trichloride and filter it. The pore size of the filter cloth is between 3-6μm to obtain pure vanadium trichloride. Use 50ml of hydrochloric acid with a ratio of 1:1 to acid leaching and detect the vanadium content in the solution to calculate the vanadium loss.

[0023] Embodiment 2:

[0024] Select nitrogen with a purity of more than 99% as an inert gas source and continuously pass it into the crystallizer through the nitrogen inlet and the nitrogen outlet to keep the device in an inert atmosphere; turn on the refrigerator to circulate the freezing liquid to the crystallizer jacket through the freezing liquid inlet and the freezing liquid outlet; inject crude vanadium trichloride to 2 / 3 through the raw material inlet, and close the crystallizer; turn on the magnetic stirring and set the speed to 100rpm, turn on the refrigerator to cool, cool at a rate of 3℃ / min, observe the thermometer display, and when it reaches 10℃, maintain this temperature for 30min. Then cool at a rate of 0.5℃ / min, and the stirring speed is reduced to 30rpm. After dropping to -10℃, keep it at this temperature for 60min, discharge the vanadium trichloride and filter it. The pore size of the filter cloth is between 3-6μm to obtain pure vanadium trichloride. Use 50ml of hydrochloric acid with a ratio of 1:1 to acid leaching and detect the vanadium content in the solution to calculate the vanadium loss.

[0025] Embodiment 3:

[0026] Select nitrogen with a purity of more than 99% as an inert gas source and continuously pass it into the crystallizer through the nitrogen inlet and the nitrogen outlet to keep the device in an inert atmosphere; turn on the refrigerator to circulate the freezing liquid to the crystallizer jacket through the freezing liquid inlet and the freezing liquid outlet; inject crude vanadium trichloride to 2 / 3 through the raw material inlet, and close the crystallizer; turn on the magnetic stirring and set the speed to 100rpm, turn on the refrigerator to cool, cool at a rate of 3℃ / min, observe the thermometer display, and when it reaches 10℃, maintain this temperature for 30min. Then cool at a rate of 0.5℃ / min, and the stirring speed is reduced to 30rpm. After dropping to -5℃, keep at this temperature for 60min, discharge the vanadium trichloride for filtration, the pore size of the filter cloth is between 3-6μm, and pure vanadium trichloride is obtained. After leaching with 50ml of hydrochloric acid with a ratio of 1:1, the vanadium content in the solution is detected to calculate the vanadium loss.

[0027] Embodiment 4:

[0028] Nitrogen with a purity of more than 99% is selected as an inert gas source and continuously introduced into the crystallizer through a nitrogen inlet and a nitrogen outlet to place the device under an inert atmosphere; a refrigerator is turned on to circulate and supply a freezing liquid to the jacket of the crystallizer through a freezing liquid inlet and a freezing liquid outlet; crude vanadium trichloride is injected to 2 / 3 through a raw material inlet, and the crystallizer is closed; a magnetic stirring is turned on and a speed is set to 100 rpm, and a refrigerator is turned on for refrigeration, and the temperature is directly reduced to -15°C, and after being kept at this temperature for 60 minutes, the vanadium trichloride is discharged for filtration, and the pore size of the filter cloth is between 3-6 μm to obtain pure vanadium trichloride, and the vanadium content in the solution is detected after acid leaching with 50 ml of hydrochloric acid at a ratio of 1:1 to calculate the vanadium loss.

[0029] Embodiment 5:

[0030] Nitrogen with a purity of more than 99% is selected as an inert gas source and continuously introduced into the crystallizer through a nitrogen inlet and a nitrogen outlet to place the device under an inert atmosphere; a refrigerator is turned on to circulate and supply a freezing liquid to the jacket of the crystallizer through a freezing liquid inlet and a freezing liquid outlet; crude vanadium trichloride is injected to 2 / 3 through a raw material inlet, and the crystallizer is closed; a magnetic stirring is turned on and a speed is set to 100 rpm, and a refrigerator is turned on for refrigeration, and the temperature is directly reduced to -15°C, and after being kept at this temperature for 60 minutes, the vanadium trichloride is discharged for filtration, and the pore size of the filter cloth is between 1-3 μm to obtain pure vanadium trichloride, and the vanadium content in the solution is detected after acid leaching with 50 ml of hydrochloric acid at a ratio of 1:1 to calculate the vanadium loss.

[0031] Embodiment 6:

[0032] Nitrogen with a purity of more than 99% is selected as an inert gas source and continuously introduced into the crystallizer through a nitrogen inlet and a nitrogen outlet to place the device under an inert atmosphere; a refrigerator is turned on to circulate and supply a freezing liquid to the jacket of the crystallizer through a freezing liquid inlet and a freezing liquid outlet; crude vanadium trichloride is injected to 2 / 3 through a raw material inlet, and the crystallizer is closed; a magnetic stirring is turned on and a speed is set to 100 rpm, and a refrigerator is turned on for refrigeration, and the temperature is directly reduced to -15°C, and after being kept at this temperature for 60 minutes, the vanadium trichloride is discharged for filtration, and the pore size of the filter cloth is between 7 and 10 μm to obtain pure vanadium trichloride, and the vanadium content in the solution is detected after acid leaching with 50 ml of hydrochloric acid at a ratio of 1:1 to calculate the vanadium loss.

[0033] Embodiment 7:

[0034] Nitrogen with a purity of more than 99% is selected as an inert gas source and continuously introduced into the crystallizer through a nitrogen inlet and a nitrogen outlet to place the device under an inert atmosphere; a refrigerator is turned on to circulate and supply a freezing liquid to a jacket of the crystallizer through a freezing liquid inlet and a freezing liquid outlet; crude vanadium trichloride is injected to 2 / 3 through a raw material inlet, and the crystallizer is closed; a magnetic stirring is turned on and a speed is set to 100 rpm, and a refrigerator is turned on for refrigeration, and the temperature is directly reduced to -15°C, and after being kept at this temperature for 60 minutes, the vanadium trichloride is discharged for filtration, and the pore size of the filter cloth is between 10-15 μm to obtain pure vanadium trichloride, and the vanadium content in the solution is detected after acid leaching with 50 ml of hydrochloric acid at a ratio of 1:1 to calculate the vanadium loss.

[0035] The effect of removing aluminum chloride from vanadium oxychloride in Examples 1-4 is shown in Table 1:

[0036] The influence of different filtration temperatures is shown in Table 1:

[0037] Cooling temperature(℃) <![CDATA[AlCl3 before crystallization]]> Filter cloth aperture <![CDATA[AlCl3 after crystallization]]> Vanadium loss (g / L) Example 1 -15 0.3361％ 3-6μm 0.0007％ 2.14 Example 2 -10 0.3024％ 3-6μm 0.0112％ 1.99 Example 3 -5 0.2803％ 3-6μm 0.0343％ 2.34

[0038] The effect of gradient crystallization on impurity removal is shown in Table 2:

[0039]

[0040]

[0041] The effect of filter cloth pore size on impurity removal is shown in Table 3:

[0042] <![CDATA[AlCl3 before crystallization]]> Filter cloth aperture <![CDATA[AlCl3 after crystallization]]> Vanadium loss Example 1 0.3464％ 3-6μm 0.0007％ 2.47 Example 2 0.3054％ 7-10μm 0.0172％ 2.22 Example 3 0.3376％ 10-15μm 0.0212％ 1.84

[0043] It can be seen from the comparative data of the embodiments in Table 1 that the best removal effect of aluminum chloride is achieved when the final temperature of the crystal growth stage is -15°C; it can be seen from the data in Table 2 that gradient crystallization is significantly better than direct cooling crystallization. Due to direct cooling crystallization, the vanadium trichloride after direct cooling can also achieve a better removal rate by using a smaller filter cloth to filter, but the vanadium loss is too high. It can be seen from the comparative data in Table 3 that the best removal effect of aluminum chloride is achieved when the pore size of the filter cloth is 3-6μm. In summary, the impurity removal effect is best under these conditions of Example 1.

[0044] The above are only preferred specific embodiments of the present invention, which are all different implementations based on the overall concept of the present invention, and the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed by the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A method for removing aluminum chloride from crude vanadium oxychloride, utilizing the property that the solubility of low-temperature aluminum chloride in crude vanadium oxychloride is reduced, adopting a gradient crystallization method to crystallize aluminum chloride, and then removing it by filtering, comprising the following steps: (1) The external inert atmosphere is connected to the inert gas inlet 3 and the inert gas outlet 6 to replace the crystallizer, so that the system maintains an inert gas atmosphere state; (2) Inject crude vanadium trichloride into the crystallizer at 2 / 3 liquid level through the raw material inlet 5, and close the raw material inlet; turn on the magnetic stirring 9, turn on the refrigerator 1 and inject the cryogenic liquid into the crystallizer interlayer through the cryogenic liquid inlet 2, and circulate and cool it through the cryogenic liquid outlet 7, and control the cryogenic liquid temperature to cool the crude vanadium trichloride according to a certain temperature gradient to crystallize aluminum trichloride. Observe the internal temperature through the thermometer 4, and cool the crude vanadium trichloride to 10°C for crystal cultivation; (3) After the crystal growth is completed, the discharge port 8 is opened to discharge the crystal slurry into a collection bottle 10 with a filter cloth; (4) After filtration, remove the filter cloth and test the vanadium content after acid leaching.

2. The method for removing aluminum chloride from crude vanadium oxychloride according to claim 1, characterized in that: The inert gas in step (1) can be nitrogen or argon, the purity of nitrogen is ≥99%, the purity of argon is ≥99%, the water vapor after replacement in the system is ≤1ppm, and there is no oxygen in the system.

3. The method for removing aluminum chloride from crude vanadium oxychloride according to claim 1, characterized in that: Step (2) uses a gradient crystallization method to crystallize aluminum trichloride in crude vanadium oxychloride, and the specific operation is as follows: i. Crystal growth stage: Rapidly cool to 10°C at a cooling rate of 3-4°C / min, with a magnetic stirring speed of 100-120rpm to ensure uniform internal temperature, and grow the crystal at low temperature for 30 minutes to form crystal nuclei of aluminum chloride; ii. Crystal growth stage: The magnetic stirring speed is controlled at 30-80 rpm. A low speed is conducive to crystal growth. The cooling rate is 0.5-1°C / min. After cooling to -15°C, keep it for 60 minutes.

4. The method for removing aluminum chloride from crude vanadium oxychloride according to claim 1, characterized in that: In step (3), the filtration connecting pipeline is a sandwich tube, and a -15°C refrigerant needs to be passed into the sandwich for cold preservation. The pore size of the filter cloth used for filtration is 3-6 μm, the vanadium loss is less than 3 g / L, and the aluminum content in the vanadium trichloride after filtration is ≤0.001%.

5. The method for removing aluminum chloride from crude vanadium oxychloride according to claim 1, characterized in that: After filtration, the filter cloth is treated with acid leaching, and the acid is 1+1 hydrochloric acid.

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