Method and device for preparing ammonium polyvanadate by crystallizing sodium vanadate solution

Abstract

The invention discloses a method and device for preparing ammonium polyvanadate by crystallizing a sodium vanadate solution, and the method comprises the following steps: 1) adding ammonium sulfate and sulfuric acid into the sodium vanadate solution for premixing to obtain a mixed vanadium solution; the molar ratio of ammonium ions to vanadium in the mixed vanadium liquid is 0.6-1.2, the pH value is 2.2-2.9, the premixing temperature is controlled to be 35-65 DEG C, and it is guaranteed that no crystal precipitate is generated in the mixed vanadium liquid; and 2) crystallizing the mixed vanadium liquid under the conditions that the temperature is 92-100 DEG C and the pH value is 1.9-2.1 to obtain the ammonium polyvanadate slurry. According to the method, after ammonium sulfate and concentrated sulfuric acid are sequentially added into the sodium vanadate solution, no crystal precipitate is generated, the stability of the ammonium polyvanadate crystallization process can be improved, the particle size of the ammonium polyvanadate can be increased to reduce the cleaning difficulty, the stability and purity of the ammonium polyvanadate crystallization process are improved, and meanwhile the particle size of the ammonium polyvanadate is increased.

Description

Technical Field

[0001] The invention relates to the technical field of fine chemical industry, in particular to a method and a device for preparing ammonium polyvanadate through crystallization of sodium vanadate solution. Background Art

[0002] Ammonium polyvanadate (English name: Ammonium Polyvanadate, molecular formula is (NH4)2V6O 16 ) is usually produced from vanadium-containing molten iron converter steelmaking to obtain vanadium slag as raw material, which is then subjected to sodium roasting and water leaching to obtain a vanadium-containing leachate. The ammonium salt precipitation method is used to separate vanadium from the sodium vanadate solution to obtain ammonium polyvanadate.

[0003] The representative methods of vanadium precipitation process are as follows: Pakhomov et al. treated ammonium vanadate with dilute sulfuric acid and separated the generated vanadic acid precipitate from the mother liquor (US Pat. No. 3728442). Nasyrov et al. treated sodium vanadate solution with ammonium sulfate at a pH of 4 to 6 to obtain sodium ammonium decavanadate precipitate, which was dissolved in hot water and then sulfuric acid was added to generate ammonium polyvanadate precipitate, reducing the sodium impurity content (US Pat. No. 4039582).

[0004] At present, the ammonium polyvanadate production process commonly used in industry is indirect acidic ammonium salt precipitation of vanadium. Sodium vanadate solution uses ammonium sulfate as the ammonium ion source, reacts under acidic and high temperature conditions to obtain ammonium polyvanadate crystal precipitation, and then obtains ammonium polyvanadate after filtration and drying. The process includes: injecting clarified sodium vanadate solution, ammonium sulfate, and concentrated sulfuric acid into the reactor in sequence, adjusting the pH value of the mixed vanadium solution to 1.9-2.1, boiling the solution in the reactor for 20-30 minutes, performing solid-liquid separation, washing and drying to obtain ammonium polyvanadate. An inherent disadvantage of this method is that when the end point pH value of the solution is 1.9-2.0, a small amount of reddish-brown precipitate is produced and adheres to the wall of the reactor, resulting in a low vanadium conversion rate. The reddish-brown precipitate falls off, resulting in an increase in the sodium impurity content in the ammonium polyvanadate. Another disadvantage is that the vanadium concentration in the sodium vanadate solution is low (≤35g / kg H2O), and the amount of wastewater generated per ton of vanadium is large (40m 3 Wastewater / tV2O5), as well as increased energy consumption in the production process such as heating and pumping. In addition, according to this method, during the direct steam heating and vanadium precipitation process of the mixed vanadium liquid after adding ammonium sulfate and concentrated sulfuric acid, ammonium polyvanadate explodes into nuclei, making filtration and washing difficult and increasing the amount of washing wastewater generated; during the drying process, impurities in the crystallization mother liquor remain inside the ammonium polyvanadate crystals, affecting the quality of downstream vanadium products, and waste will also be generated.

[0005] In recent years, domestic scientific and technological workers have proposed improved processes to address the problems of the above-mentioned processes. For example, Publication No. CN117602671A discloses a method and device for improving the quality stability of ammonium polyvanadate, wherein ammonium sulfate solid and sulfuric acid are sequentially added to the preheated acidic vanadium liquid, and the liquid overflows to multiple parallel vanadium precipitation tanks to improve the quality stability of the ammonium polyvanadate product. Publication No. CN102502823A discloses a method for preparing ammonium polyvanadate with high tap density, wherein ammonium polyvanadate seeds and a small amount of ammonium sulfate are added to a weakly acidic vanadium liquid at 60 to 90°C, and the temperature is raised to 90 to 95°C after sulfuric acid is added to generate partial ammonium polyvanadate precipitation, and the particle size of the ammonium polyvanadate is increased while the content of Na2O impurities is reduced by adding ammonium sulfate; however, the consumption of ammonium sulfate is large and the operation process is complicated. Publication No. CN115072778A discloses a continuous reaction crystallization process of ammonium polyvanadate, in which seed crystals are added to a weakly acidic vanadium solution, and dilute sulfuric acid is added to adjust the pH value of the slurry to control the reaction crystallization rate, thereby obtaining ammonium polyvanadate with uniform particle size. Publication No. CN114229893A discloses a preparation method of ammonium polyvanadate, in which a mixed solution of sodium vanadate and ammonium sulfate is passed through an acid conditioning reactor with a partition to prevent local over-acidification from causing bad materials; however, a large amount of sodium ammonium decavanadate precipitates are produced in both the primary and secondary acid conditioning zones, which clog the acid conditioning reactor and are doped into the ammonium polyvanadate slurry, causing the process to fail to proceed smoothly. Summary of the invention

[0006] The technical problem to be solved by the present invention is to provide a method for preparing ammonium polyvanadate by crystallizing sodium vanadate solution, which can improve the stability of the ammonium polyvanadate crystallization process; the present invention also provides a device for preparing ammonium polyvanadate by crystallizing sodium vanadate solution.

[0007] In order to solve the above technical problems, the technical solution adopted by the method of the present invention comprises the following steps: 1) adding ammonium sulfate and sulfuric acid to a sodium vanadate solution for premixing to obtain a mixed vanadium liquid; the molar ratio of ammonium ions to vanadium in the mixed vanadium liquid is 0.6-1.2, the pH value is 2.2-2.9, and the premixing temperature is controlled at 35-65° C. to ensure that no crystal precipitation is generated in the mixed vanadium liquid; 2) The mixed vanadium solution is crystallized at 92-100° C. and pH 1.9-2.1 to obtain ammonium polyvanadate slurry.

[0008] Furthermore, in step 2), the mixed vanadium liquid is subjected to continuous crystallization.

[0009] Furthermore, the mixed vanadium liquid is continuously injected into a continuous crystallization reactor for continuous crystallization, and the residence time of the mixed vanadium liquid in the continuous crystallization reactor is 10 to 40 minutes.

[0010] Furthermore, in step 2), sulfuric acid is used to adjust the pH value of the mixed vanadium solution.

[0011] In order to solve the above technical problems, the technical solution adopted by the device of the present invention is: it includes a premixing tank, a liquid storage tank, a reactor and a filter press; the premixing tank is provided with an inlet for sodium vanadate solution, an inlet for ammonium sulfate and an inlet for sulfuric acid, the outlet of the premixing tank is connected to the inlet of the liquid storage tank, the outlet of the liquid storage tank is connected to the inlet of the reactor, and the outlet of the reactor is connected to the inlet of the filter press; the reactor is provided with a heating structure and a sulfuric acid inlet.

[0012] Furthermore, the filtrate outlet of the filter press is connected to the ammonium sulfate inlet of the premixing tank.

[0013] Furthermore, a dryer is provided; the solid material outlet of the filter press is connected to the inlet of the dryer, and the steam outlet of the dryer is connected to the ammonium sulfate inlet of the premixing tank.

[0014] The beneficial effect produced by adopting the above technical scheme is that: after the present invention sequentially adds ammonium sulfate and concentrated sulfuric acid to the sodium vanadate solution, no crystal precipitation is produced, the stability of the ammonium polyvanadate crystallization process and the particle size of the ammonium polyvanadate can be improved to reduce the difficulty of cleaning, which not only improves the stability and purity of the ammonium polyvanadate crystallization process, but also increases the particle size of the ammonium polyvanadate. The present invention prepares ammonium polyvanadate from the sodium vanadate solution, the median particle size D50 increases from 119 μm to 141 μm, the amount of washing water is reduced by about 50%, the impurity content of Na2O+K2O is reduced to less than 0.29 wt%, and the purity of V2O5 after the ammonium polyvanadate is calcined and deaminated is greater than 99.3 wt%. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] The present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments.

[0016] Figure 1 It is a structural schematic diagram of the device of the present invention.

[0017] In the figure: premixing tank 1; liquid storage tank 2; reactor 3; filter press 4; dryer 5. DETAILED DESCRIPTION

[0018] Figure 1As shown, the device for preparing ammonium polyvanadate by crystallization of sodium vanadate solution comprises a premixing tank 1, a liquid storage tank 2, a reactor 3 and a filter press 4. The top of the premixing tank 1 is provided with an inlet for sodium vanadate solution, an inlet for ammonium sulfate and an inlet for sulfuric acid, and the bottom is provided with an outlet; the inlet for sodium vanadate solution is connected to a sodium vanadate solution supply source, the inlet for ammonium sulfate is connected to an ammonium sulfate supply source, and the inlet for sulfuric acid is connected to a sulfuric acid supply source; the premixing tank 1 is provided with a temperature control structure. The outlet of the premixing tank 1 is connected to the inlet at the top of the liquid storage tank 2, the outlet at the bottom of the liquid storage tank 2 is connected to the inlet at the top of the reactor 3, and the outlet at the bottom of the reactor 3 is connected to the inlet of the filter press 4. The liquid storage tank 2 is provided with a temperature control structure. The reactor 3 is provided with a heating structure, which can be a jacket heating structure or a steam pipeline directly connected to the inside of the reactor 3; the reactor 3 is provided with a sulfuric acid inlet, which is connected to a sulfuric acid supply source; the reactor 3 is preferably a continuous crystallization reactor. The filtrate outlet of the filter press 4 is connected to the ammonium sulfate inlet of the premixing tank 1. A dryer 5 is also provided; the solid material outlet of the filter press 4 is connected to the inlet of the dryer 5, and the steam outlet of the dryer 5 is connected to the ammonium sulfate inlet of the premixing tank 1. The premixing tank 1, the liquid storage tank 2 and the reactor 3 are all provided with stirring devices.

[0019] Figure 1 As shown, the method for preparing ammonium polyvanadate by crystallization of sodium vanadate solution adopts the device of the above structure, comprising the following steps: 1) injecting sodium vanadate solution, ammonium sulfate or ammonium sulfate solution, and sulfuric acid into the premixing tank 1 in sequence, stirring evenly, and obtaining a mixed vanadium liquid. The vanadium concentration in the sodium vanadate solution is 28-40 g / L, the concentration of ammonium sulfate solid or ammonium sulfate solution is 300-450 g / L, and the concentration of concentrated sulfuric acid is 90-98 wt%. The amount of ammonium sulfate added to the mixed vanadium liquid is to control the molar ratio of ammonium ions to vanadium to be 0.6-1.2, and the time for adding ammonium sulfate is 1-10 min; the amount of sulfuric acid added to the mixed vanadium liquid is to control the pH value of the mixed vanadium liquid to be 2.2-2.9, and the time for adding sulfuric acid is 2-10 min. In the initial stage of acid addition, the generated solid increases with the decrease of pH. When the pH value decreases to 2.2-2.9, the solid phase is completely dissolved, and the mixed vanadium liquid is in a red and clear state. The temperature in the premixing tank 1 needs to be strictly controlled to reduce the precipitation of bright yellow solids during the mixing process. The solubility of the salt is greatly affected by temperature and is unstable. The residual bright yellow solids lead to excessively high potassium and sodium impurity content in the subsequent ammonium polyvanadate precipitation. Therefore, the premixing temperature of the premixing tank 1 is controlled to be 35-65°C to ensure that no crystal precipitation occurs in the mixed vanadium liquid. The stirring time of the mixed vanadium liquid in the premixing tank 1 is 1-10 minutes.

[0020] 2) The mixed vanadium liquid is introduced into the liquid storage tank 2 as a continuous crystallizer feed to prevent the temperature in the reactor 3 from rising sharply and causing explosion nucleation. The temperature in the liquid storage tank 2 is maintained at 35-80°C.

[0021] 3) The mixed vanadium liquid in the liquid storage tank 2 is continuously injected into the reactor 3, and sulfuric acid is added at 92-100°C to adjust the pH value to 1.9-2.1, and vanadium precipitation reaction is carried out to continuously crystallize, the liquid residence time is 10-40 minutes, and the stirring rate is 40-260r / min to obtain ammonium polyvanadate slurry. The sulfuric acid is preferably dilute sulfuric acid with a concentration of 20-75wt%.

[0022] 4) After crystallization in the reaction kettle 3, the slurry is sent to the filter press 4 for filtration and washing, and then to the dryer 5 for drying to obtain large-particle high-purity ammonium polyvanadate.

[0023] 5) The filtrate from the filter press 4 returns to the pre-mixing tank 1 , and the steam generated by the dryer 5 returns to the pre-mixing tank 1 . Example 1

[0024] Add 45ml of 28g / L sodium vanadate solution to the premixing tank, control the temperature in the tank at 40℃, slowly add 300g / L ammonium sulfate solution to the premixing tank, control the molar ratio of ammonium ions and vanadium to 0.7; then slowly add 98wt% concentrated sulfuric acid until the pH value of the mixed vanadium solution is 2.7; keep the stirring speed at 40r / min, continue stirring for 3min, and pump the mixed vanadium solution into the liquid storage tank after clarification, and control the temperature of the liquid storage tank to 55℃. The mixed vanadium solution in the liquid storage tank is continuously pumped into the continuous crystallization reactor, and the residence time is controlled to 20min. The reactor is directly heated by steam, the temperature is controlled at 95℃, the stirring speed is 150r / min, and 20wt% sulfuric acid is added to maintain the pH value of the solution at 1.9. The slurry after the reaction flows from the reactor to the filter press for filtration and washing, and then to the dryer for drying to obtain ammonium polyvanadate. Compared with the intermittent acidic ammonium salt vanadium precipitation, the ammonium polyvanadate obtained in this embodiment has a Na2O impurity content reduced to 0.2wt%, a median particle size D50 increased from 119μm to 138μm, and a V2O5 content of 99.3wt% after calcination and deammoniation. Example 2

[0025] Add 45ml of 35g / L sodium vanadate solution to the premixing tank, control the temperature in the tank at 50℃, slowly add ammonium sulfate solid to the premixing tank, control the molar ratio of ammonium ions and vanadium to 0.9; then slowly add 98% concentrated sulfuric acid until the pH value of the mixed solution is 2.4; keep the stirring speed at 50r / min, continue stirring for 4min, and pump the mixed vanadium liquid into the liquid storage tank after the solution is clarified, and control the temperature of the liquid storage tank to 70℃. Continuously pump the mixed vanadium liquid into the reactor, control the residence time to 25min; the reactor is directly heated by steam, control the solution temperature to 100℃, the stirring speed to 50r / min, and add 50wt% sulfuric acid to maintain the solution pH at 2.0. The slurry after the reaction is pumped from the bottom of the reactor into the filter press for filtration and washing, and then dried in the dryer to obtain ammonium polyvanadate. Since there is a certain concentration of potassium impurities in the industrial sodium vanadate solution, the above process reduces the Na2O content while reducing the K2O content. Compared with the intermittent acidic ammonium salt vanadium precipitation, the ammonium polyvanadate obtained in this embodiment has a Na2O+K2O content reduced to 0.28%, a median particle size D50 increased to 138 μm, and a purity of V2O5 after calcination and deammoniation of 99.42 wt%. Example 3

[0026] Add 45ml of 35g / L sodium vanadate solution to the premixing tank, control the temperature in the tank to 43℃, slowly add 400g / L ammonium sulfate solution to the premixing tank, control the molar ratio of ammonium ions and vanadium to 1.1; then slowly add 98wt% concentrated sulfuric acid until the pH value of the mixed solution is 2.7; keep the stirring speed at 60r / min, continue stirring for 5min, and pump the mixed vanadium liquid into the storage tank after the solution is clarified, and control the temperature of the storage tank to 65℃. The mixed vanadium liquid in the storage tank is continuously pumped into the continuous crystallization reactor, and the residence time is controlled to 30min. The reactor is heated by water bath, the temperature is controlled to 92℃, the stirring speed is 230r / min, and 63wt% sulfuric acid is added to maintain the pH value of the solution at 1.9. The slurry after the reaction flows from the reactor to the filter press for filtration and washing, and then to the dryer for drying to obtain ammonium polyvanadate. Compared with the intermittent acidic ammonium salt vanadium precipitation, the ammonium polyvanadate obtained in this example has a Na2O+K2O content reduced to 0.26wt%, a median particle size D50 increased to 143μm, and a V2O5 content of 99.47wt% after calcination and deamination. Example 4

[0027] Add 45ml of 40g / L sodium vanadate solution to the premixing tank, control the temperature in the tank at 35℃, slowly add 450g / L ammonium sulfate solution to the premixing tank, control the molar ratio of ammonium ions and vanadium to 0.6; then slowly add 95wt% concentrated sulfuric acid until the pH value of the mixed vanadium solution is 2.2; keep the stirring speed at 100r / min, continue stirring for 10min, and pump the mixed vanadium solution into the storage tank after clarification, and control the temperature of the storage tank at 35℃. The mixed vanadium solution in the storage tank is continuously pumped into the continuous crystallization reactor, and the residence time is controlled to be 20min. The reactor is directly heated by steam, the temperature is controlled at 94℃, the stirring speed is 40r / min, and 75wt% sulfuric acid is added to maintain the pH value of the solution at 2.0. The slurry after the reaction flows from the reactor to the filter press for filtration and washing, and then to the dryer for drying to obtain ammonium polyvanadate. Compared with the intermittent acidic ammonium salt vanadium precipitation, the ammonium polyvanadate obtained in this example has a Na2O+K2O content reduced to 0.25%, a median particle size D50 increased to 141 μm, and a V2O5 content of 99.41 wt % after calcination and deamination. Example 5

[0028] Add 45ml of 30g / L sodium vanadate solution to the premixing tank, control the temperature in the tank to 65℃, slowly add ammonium sulfate solid to the premixing tank, control the molar ratio of ammonium ions and vanadium to 1.2; then slowly add 90% concentrated sulfuric acid until the pH value of the mixed solution is 2.9; keep the stirring speed at 260r / min, continue stirring for 1min, and pump the mixed vanadium liquid into the liquid storage tank after the solution is clarified, and control the temperature of the liquid storage tank to 80℃. Continuously pump the mixed vanadium liquid into the reactor, control the residence time to 25min; the reactor is directly heated by steam, the solution temperature is controlled to 98℃, the stirring speed is 260r / min, and 40wt% sulfuric acid is added to maintain the pH value of the solution at 2.1. The slurry after the reaction is pumped from the bottom of the reactor into the filter press for filtration and washing, and then dried in the dryer to obtain ammonium polyvanadate. Compared with the intermittent acidic ammonium salt vanadium precipitation, the ammonium polyvanadate obtained in this example has a Na2O+K2O content reduced to 0.27%, a median particle size D50 increased to 137 μm, and a purity of V2O5 of 99.43 wt % after calcination and deammoniation.

Claims

1. A method for preparing ammonium polyvanadate by crystallization of sodium vanadate solution, characterized in that: The method comprises the following steps: 1) adding ammonium sulfate and sulfuric acid to a sodium vanadate solution for premixing to obtain a mixed vanadium liquid; the molar ratio of ammonium ions to vanadium in the mixed vanadium liquid is 0.6-1.2, the pH value is 2.2-2.9, and the premixing temperature is controlled at 35-65° C. to ensure that no crystal precipitation is generated in the mixed vanadium liquid; 2) The mixed vanadium solution is crystallized at 92-100° C. and pH 1.9-2.1 to obtain ammonium polyvanadate slurry.

2. The method for preparing ammonium polyvanadate by crystallization of sodium vanadate solution according to claim 1, characterized in that: In the step 2), the mixed vanadium solution is subjected to continuous crystallization.

3. The method for preparing ammonium polyvanadate by crystallization of sodium vanadate solution according to claim 2, characterized in that: The mixed vanadium liquid is continuously injected into a continuous crystallization reactor for continuous crystallization, and the residence time of the mixed vanadium liquid in the continuous crystallization reactor is 10 to 40 minutes.

4. The method for preparing ammonium polyvanadate by crystallization of sodium vanadate solution according to claim 1, 2 or 3, characterized in that: In the step 2), sulfuric acid is used to adjust the pH value of the mixed vanadium solution.

5. A device for preparing ammonium polyvanadate by crystallization of sodium vanadate solution, characterized in that: The invention comprises a premixing tank (1), a liquid storage tank (2), a reactor (3) and a filter press (4); the premixing tank (1) is provided with a sodium vanadate solution inlet, an ammonium sulfate inlet and a sulfuric acid inlet; the outlet of the premixing tank (1) is connected to the inlet of the liquid storage tank (2); the outlet of the liquid storage tank (2) is connected to the inlet of the reactor (3); the outlet of the reactor (3) is connected to the inlet of the filter press (4); the reactor (3) is provided with a heating structure and a sulfuric acid inlet.

6. The device for preparing ammonium polyvanadate by crystallization of sodium vanadate solution according to claim 5, characterized in that: The filtrate outlet of the filter press (4) is connected to the ammonium sulfate inlet of the premixing tank (1).

7. The device for preparing ammonium polyvanadate by crystallization of sodium vanadate solution according to claim 5 or 6, characterized in that: A dryer (5) is also provided; the solid material outlet of the filter press (4) is connected to the inlet of the dryer (5), and the steam outlet of the dryer (5) is connected to the ammonium sulfate inlet of the premixing tank (1).

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