Method and device for preparing high-purity potassium metavanadate from sodium vanadate in short process

Abstract

The invention discloses a method and device for preparing high-purity potassium metavanadate from sodium vanadate in a short process, and the method comprises the following steps: 1) mixing a sodium vanadate solution and potassium sulfate according to the molar ratio of potassium ions to vanadium of 0.34-1.0, adding concentrated sulfuric acid until the pH value is 1.9-2.5, reacting at 90-100 DEG C, crystallizing and separating to obtain a potassium polyvanadate solid; and 2) adding the potassium polyvanadate solid into a potassium hydroxide solution according to the molar ratio of potassium ions to vanadium of 0.5-1.0, heating to 80-100 DEG C, and carrying out digestion reaction to obtain a potassium metavanadate solution. The potassium metavanadate is prepared from the sodium vanadate solution leached through sodium salt roasting in a short process, reducing gas NH3 and low-valence vanadium are not generated in the preparation process, the potassium metavanadate precipitation process is changed, spherical potassium metavanadate solid particles uniform in particle size and good in fluidity can be prepared, the stability of the potassium metavanadate crystallization process is improved, the vanadium recovery rate is increased, and the method is suitable for industrial production. The purity of the obtained potassium metavanadate product is greater than 99.5 wt%, and the vanadium recovery rate is greater than 99%.

Description

Technical Field

[0001] The invention belongs to the technical field of fine chemical industry, in particular to a method and a device for preparing high-purity potassium metavanadate with sodium vanadate in a short process. Background Art

[0002] Potassium metavanadate, English name: Potassium metavanadate, molecular formula is KVO 3 , which is widely used in glaze, chemical catalyst, medical and other fields. At present, the production process of potassium metavanadate includes solid phase melting method and alkali dissolution crystallization method: the solid phase melting method is to convert ammonium polyvanadate (NH 4 ) 2 V 6 O 16 )、Ammonium metavanadate (NH 4 VO 3 ) or vanadium pentoxide (V 2 O 5 ) and potassium carbonate (K 2 CO 3 ) are mixed in a stoichiometric ratio and heated to a molten state, and then cooled and recrystallized in an aqueous medium to obtain KVO 3 The alkali dissolution crystallization method is usually used in industry to obtain (NH 4 ) 2 V 6 O 16 NH 4 VO 3 or V 2 O 5 As raw material, react in potassium hydroxide solution at 80-100°C for 1-2h, filter out insoluble impurities such as low-valent vanadium oxides to obtain a clear potassium metavanadate solution, evaporate and concentrate until the solution is supersaturated, cool and crystallize to obtain potassium metavanadate.

[0003] In the above method, the production raw material V 2 O 5 Most of them are (NH 4 ) 2 V 6 O 16 or NH 4 VO 3 An inherent disadvantage of this method is that at a calcination temperature of 550°C, ammonium polyvanadate or ammonium metavanadate decomposes to produce NH 3 and V 2 O 5 , NH 3 As a reducing agent, a small amount of V 2 O 5Reduced to low-valent vanadium oxide. The low-valent vanadium oxide does not react with potassium hydroxide solution, and is suspended in the potassium metavanadate solution in a solid phase, which needs to be filtered and then evaporated, concentrated and crystallized. Due to the high viscosity of high-concentration potassium metavanadate solution, it is difficult to filter the low-valent vanadium oxide, which reduces the production efficiency and vanadium yield.

[0004] Similarly, with (NH 4 ) 2 V 6 O 16 or NH 4 VO 3 As raw material, the alkali dissolution process decomposes a large amount of NH 3 , a small amount of NH4 remaining in the potassium metavanadate solution + It combines with metavanadate and precipitates with potassium metavanadate crystals, causing the nitrogen impurity content in the potassium metavanadate product to exceed the standard.

[0005] Another disadvantage is that due to the high solubility and supersaturation of potassium metavanadate, seed crystals are added during the cooling crystallization process to promote the crystallization of potassium metavanadate, and the high-concentration potassium metavanadate crystallization mother liquor is returned to the alkaline dissolution tank for recycling, resulting in a decrease in the dissolution rate of the solid phase vanadium raw material and accumulation of impurities in the potassium metavanadate solution, affecting production efficiency and product quality.

[0006] In recent years, domestic scientific and technological workers have proposed improved processes to address the problems existing in the above processes. For example, publication number CN108975398A provides a high-density potassium metavanadate and a preparation method thereof. H is added during the heating alkali dissolution process. 2 O 2 Solution, low-valent vanadium oxide and H 2 O 2 The reaction produces potassium metavanadate; this method increases the vanadium yield, but H 2 O 2 It is easy to decompose into water and oxygen, reducing the oxidizability, but still needs to be filtered to remove unreacted low-valent vanadium oxides. "Feasibility Study on Preparation Process of Potassium Metavanadate [J]" (Ferroalloys, 2022, 53(01): 24-27), Mu Xiaoling added potassium carbonate to the sodium roasting leaching solution, adjusted the pH value to 1.5-1.8 with concentrated sulfuric acid, hydrolyzed the precipitated vanadium to obtain sodium-containing potassium polyvanadate, mixed with potassium carbonate and melted, and recrystallized in an aqueous medium system to obtain potassium metavanadate product; this process does not produce reducing agent NH 3 , but the product has a high sodium impurity content. Publication No. CN102531055A provides a method for preparing sodium metavanadate / potassium metavanadate, wherein calcium chloride is added to a sodium vanadate solution to obtain a calcium vanadate solid, which is reacted with a potassium bicarbonate solution to obtain a potassium metavanadate solution and a calcium bicarbonate precipitate; the system generates a large amount of chlorine-containing wastewater, and when calcium vanadate is re-dissolved, due to Ca(HCO 3 ) 2It has a certain solubility, which leads to an increase in the Ca content in the potassium metavanadate product. Summary of the invention

[0007] The technical problem to be solved by the present invention is to provide a method for preparing high-purity potassium metavanadate by a short process using sodium vanadate with pure product; the present invention also provides a device for preparing high-purity potassium metavanadate by a short process using sodium vanadate.

[0008] In order to solve the above technical problems, the technical scheme adopted by the method of the present invention comprises the following steps: 1) mixing sodium vanadate solution and potassium sulfate at a molar ratio of potassium ions to vanadium of 0.34 to 1.0, adding concentrated sulfuric acid to a pH value of 1.9 to 2.5, reacting, crystallizing, and separating at 90 to 100° C. to obtain potassium polyvanadate solid; 2) adding potassium polyvanadate solid to potassium hydroxide solution at a molar ratio of potassium ion to vanadium of 0.5 to 1.0, heating to 80 to 100° C. for digestion reaction to obtain potassium metavanadate solution.

[0009] Furthermore, in step 2), the pH value of the digestion reaction endpoint solution is 7.0 to 9.0.

[0010] Furthermore, in step 2), the obtained potassium metavanadate solution is concentrated and dried to obtain high-purity potassium metavanadate.

[0011] In order to solve the above technical problems, the technical scheme adopted by the device of the present invention is: comprising a crystallization reactor, a No. 1 filter device, a digestion reactor and a No. 2 filter device; the crystallization reactor is provided with a sodium vanadate solution inlet, a potassium sulfate inlet and a concentrated sulfuric acid inlet, and is provided with a heating mechanism; the digestion reactor is provided with a potassium polyvanadate inlet and a potassium hydroxide solution inlet, and is provided with a heating mechanism; the outlet at the bottom of the crystallization reactor is connected to the inlet of the No. 1 filter device, the solid material outlet of the No. 1 filter device is connected to the potassium polyvanadate inlet of the digestion reactor, and the outlet at the bottom of the digestion reactor is connected to the inlet of the No. 2 filter device; the solid material outlet of the No. 2 filter device is connected to the potassium polyvanadate inlet of the digestion reactor.

[0012] Furthermore, an evaporation concentration device and a spray drying device are also provided; the liquid outlet of the second filtering device is connected to the inlet of the evaporation concentration device, and the outlet of the evaporation concentration device is connected to the inlet of the spray drying device.

[0013] Furthermore, a condenser is provided; the steam outlet of the evaporation concentration device and the steam outlet of the spray drying device are connected to the potassium hydroxide solution inlet of the digestion reaction kettle through the condenser.

[0014] The beneficial effects of the above technical solution are as follows: Different from the traditional solid phase melting method and alkali dissolution crystallization method, the present invention innovatively uses high-purity potassium polyvanadate as the vanadium raw material of the alkali dissolution process, and adds excess potassium polyvanadate in the digestion reaction to accurately control the potassium-vanadium ratio of the potassium metavanadate solution, thereby obtaining high-purity potassium metavanadate. The present invention uses the sodium vanadate solution leached by sodiumization roasting as the raw material to prepare potassium metavanadate in a short process, and no reducing gas NH is generated during the preparation process. 3 The invention uses high-purity potassium polyvanadate as the vanadium raw material of the alkali dissolution process, avoids the introduction of ammonium salts to cause vanadium reduction in the deamination process, can prepare spherical potassium metavanadate solid particles with uniform particle size and good fluidity, improves the stability of the potassium metavanadate crystallization process and the vanadium recovery rate, and the obtained potassium metavanadate product has a purity of more than 99.5wt% and a vanadium recovery rate of more than 99%. 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 schematic structural diagram of the device of the present invention.

[0017] In the figure: crystallization reactor 1; No. 1 filtering device 2; digestion reactor 3; No. 2 filtering device 4; evaporation concentration device 5; spray drying device 6; condenser 7. DETAILED DESCRIPTION

[0018] The method for preparing high-purity potassium metavanadate by a short process of sodium vanadate comprises the following steps: 1) mixing a sodium vanadate solution and potassium sulfate at a molar ratio of potassium ions to vanadium of 0.34 to 1.0, adding concentrated sulfuric acid to a pH value of 1.9 to 2.5, reacting and crystallizing at 90 to 100° C. and 30 to 300 r / min with stirring, and the reaction is completed when the reaction liquid changes from red to light yellow; separating to obtain a potassium polyvanadate solid; the vanadium (V) concentration in the sodium vanadate solution is 8 to 45 g / L, potassium sulfate is added in solid form, and the concentrated sulfuric acid concentration is 85 to 98 wt %.

[0019] 2) adding potassium polyvanadate solid to potassium hydroxide solution at a molar ratio of potassium ion to vanadium of 0.5 to 1.0, heating to 80 to 100° C., stirring at a rate of 50 to 400 r / min, performing a digestion reaction, the digestion reaction being performed for at least 1 hour, the pH value of the solution at the end point of the digestion reaction being 7.0 to 9.0, and obtaining a potassium metavanadate solution; the concentration of the KOH solution being 20 to 80 g / L.

[0020] 3) The potassium metavanadate solution is evaporated and concentrated at a temperature of 80 to 100° C., and the concentration of the potassium metavanadate solution after evaporation and concentration is 300 to 400 g / L; and then dried at a drying temperature of 150 to 350° C. to obtain high-purity potassium metavanadate; the purity of the obtained potassium metavanadate product is greater than 99.5wt%, and the vanadium recovery rate is greater than 99%.

[0021] Figure 1 As shown, the device for preparing high-purity potassium metavanadate from sodium vanadate in a short process includes a crystallization reactor 1, a No. 1 filter 2, a digestion reactor 3 and a No. 2 filter 4. The crystallization reactor 1 is provided with an inlet for sodium vanadate solution, an inlet for potassium sulfate and an inlet for concentrated sulfuric acid. The inlet for sodium vanadate solution is connected to a sodium vanadate solution source, the inlet for potassium sulfate is connected to a potassium sulfate source, and the inlet for concentrated sulfuric acid is connected to a concentrated sulfuric acid source; and a heating mechanism is provided, and the heating mechanism is preferably a structure for direct steam heating or a structure for jacket heating. The digestion reactor 3 is provided with an inlet for potassium polyvanadate and an inlet for potassium hydroxide solution, and the inlet for potassium hydroxide solution is connected to a potassium hydroxide solution source; and a heating mechanism is provided, and the heating mechanism is preferably a structure for jacket heating. The outlet at the bottom of the crystallization reactor 1 is connected to the inlet of the No. 1 filter 2, the solid material outlet of the No. 1 filter 2 is connected to the potassium polyvanadate inlet of the digestion reactor 3, and the outlet at the bottom of the digestion reactor 3 is connected to the inlet of the No. 2 filter 4; the solid material outlet of the No. 2 filter 4 is connected to the potassium polyvanadate inlet of the digestion reactor 3. It is best that both the No. 1 filtering device 2 and the No. 2 filtering device 4 are filter presses.

[0022] Figure 1 As shown, the device for preparing high-purity potassium metavanadate from sodium vanadate in a short process is also provided with an evaporation concentration device 5 and a spray drying device 6. The liquid outlet of the second filtering device 4 is connected to the inlet of the evaporation concentration device 5, and the outlet of the evaporation concentration device 5 is connected to the inlet of the spray drying device 6. The evaporation concentration device 5 is provided with a heating mechanism, and the heating mechanism is preferably a jacket heating structure. The spray drying device 6 is preferably dried by directly blowing hot air.

[0023] Figure 1 As shown, the device for preparing high-purity potassium metavanadate from sodium vanadate in a short process is also provided with a condenser 7; the steam outlet of the evaporation concentration device 5 and the steam outlet of the spray drying device 6 are connected to the potassium hydroxide solution inlet of the digestion reaction kettle 3 through the condenser 7.

[0024] The preparation process of the device for preparing high-purity potassium metavanadate using the sodium vanadate short process is as follows: 1) Sodium vanadate solution, potassium sulfate solid and concentrated sulfuric acid are sequentially injected into a crystallization reactor 1, and the temperature is raised to cause potassium polyvanadate to crystallize. After the reaction, the solution enters a first filtering device 2 for filtration to obtain potassium polyvanadate solid; 2) adding potassium polyvanadate solid and potassium hydroxide solution into a digestion reactor 3, heating and heating to obtain a reaction solution; filtering the reaction solution through a second filtering device 4 to obtain a potassium metavanadate solution and undissolved potassium polyvanadate solid; and feeding the undissolved potassium polyvanadate solid back into the digestion reactor 3; 3) The potassium metavanadate solution is pumped into an evaporation concentration device 5 for evaporation concentration, and then enters a spray drying device 6 for drying to obtain high-purity potassium metavanadate particles; 4) In step 3), the water vapor generated by the evaporation concentration device 5 and the spray drying device 6 is condensed by the condenser 7, and the condensed water is returned to the digestion reactor 3 for recycling. Example 1

[0025] Add 1L of sodium vanadate solution with a vanadium concentration of 35g / L and 59.68g of potassium sulfate solid to the crystallization reactor in sequence, with a potassium and vanadium molar ratio of 1.0, and slowly add 98wt% concentrated sulfuric acid until the solution pH is 1.9, with a stirring speed of 50r / min and a temperature of 40°C. After the solution is clarified, heat it to 90°C. When the reaction solution changes from red to light yellow, pump the slurry from the bottom of the reactor into a filter press for filtration and washing to obtain potassium polyvanadate solid. Add 0.5L of KOH solution with a concentration of 50.0g / L to the digestion reactor, slowly add excess potassium polyvanadate solid, control the potassium and vanadium molar ratio in the digestion reactor to 1.0, heat it to 80°C, stir at a rate of 100r / min, react for 1h, and pump the potassium metavanadate solution with a pH of 8.0 at the end of the reaction into the evaporation concentration device; the concentrated 380g / L KVO 3 The solution was slowly pumped into a 250°C spray dryer to obtain KVO 3 The purity of the solid was 99.68 wt % and the vanadium recovery rate was 99.35 %. Example 2

[0026] Add 1L of sodium vanadate solution with a vanadium concentration of 28g / L and 32.54g of potassium sulfate solid to the crystallization reactor in sequence, with a potassium to vanadium molar ratio of 0.68, slowly add 98wt% concentrated sulfuric acid until the solution pH is 2.1, stir at 100r / min, and the temperature is 40°C. After the solution is clarified, heat to 93°C. When the reaction solution changes from red to light yellow, pump the slurry from the bottom of the reactor into a filter press for filtration and washing to obtain potassium polyvanadate solid. Add 0.5L of KOH solution with a concentration of 20.0g / L to the digestion reactor, slowly add potassium polyvanadate solid, control the potassium to vanadium molar ratio in the digestion reactor to 0.70, heat to 90°C, stir at 200r / min, react for 1h, filter the excess potassium polyvanadate back to the digestion reactor, and pump the potassium metavanadate solution with a pH of 7.1 into the evaporation concentration device; concentrate 340g / L of KVO 3The solution was slowly pumped into a 280°C spray dryer to obtain KVO 3 The purity of the solid was 99.52 wt % and the vanadium recovery rate was 99.16 %. Example 3

[0027] Add 1L of sodium vanadate solution with a vanadium concentration of 35g / L (0.686mol) and 20.67g of potassium sulfate solid to the crystallization reactor in sequence, the molar ratio of potassium ions to vanadium is 0.346, slowly add 98wt% concentrated sulfuric acid until the pH value of the solution is 2.5, the stirring speed is 200r / min, and the temperature is 40℃. After the solution is clarified, heat it to 100℃. When the reaction solution changes from red to light yellow, pump the slurry from the bottom of the reactor into the filter press for filtration and washing to obtain potassium polyvanadate solid. Add 0.5L of KOH solution with a concentration of 60.0g / L to the digestion reactor, slowly add potassium polyvanadate solid, control the molar ratio of potassium and vanadium in the digestion reactor to 0.5, heat it to 100℃, stir it at a rate of 230r / min, react for 1h, and control the molar ratio of potassium and vanadium in the solution to 1.0. The excess potassium polyvanadate was filtered and returned to the digestion reactor, and the potassium metavanadate solution with a pH value of 8.0 was pumped into the evaporation concentration device; the concentrated 310g / L KVO 3 The solution was slowly pumped into a 320℃ spray dryer to obtain KVO 3 The purity of the solid was 99.61 wt % and the vanadium recovery rate was 99.28 %. Example 4

[0028] Add 1L of sodium vanadate solution with a vanadium concentration of 33g / L and 41.36g of potassium sulfate solid to the crystallization reactor in sequence, with a potassium to vanadium molar ratio of 0.73, slowly add 98wt% concentrated sulfuric acid until the solution pH is 2.0, stir at 50r / min, and the temperature is 40°C. After the solution is clarified, heat to 95°C. When the reaction solution changes from red to light yellow, pump the slurry from the bottom of the reactor into a filter press for filtration and washing to obtain potassium polyvanadate solid. Add 0.5L of KOH solution with a concentration of 80.0g / L to the digestion reactor, slowly add excess potassium polyvanadate solid, control the potassium to vanadium molar ratio in the digestion reactor to 0.6, heat to 91°C, stir at 100r / min, react for 1h, and pump the potassium metavanadate solution with a pH of 8.9 at the end of the reaction into the evaporation concentration device; the concentrated 380g / L KVO 3 The solution was slowly pumped into a 245℃ spray dryer to obtain KVO 3 The purity of the solid was 99.65 wt % and the vanadium recovery rate was 99.34 %.

Claims

1. A method for preparing high-purity potassium metavanadate from sodium vanadate in a short process, characterized in that: The method comprises the following steps: 1) mixing a sodium vanadate solution and potassium sulfate according to a molar ratio of potassium ions to vanadium of 0.34 to 1.0, adding concentrated sulfuric acid to a pH value of 1.9 to 2.5, reacting at 90 to 100° C., crystallizing, and separating to obtain a potassium polyvanadate solid; 2) adding potassium polyvanadate solid to potassium hydroxide solution at a molar ratio of potassium ion to vanadium of 0.5 to 1.0, heating to 80 to 100° C. for digestion reaction to obtain potassium metavanadate solution.

2. The method for preparing high-purity potassium metavanadate by a short-process of sodium vanadate according to claim 1, characterized in that: In the step 2), the pH value of the digestion reaction endpoint solution is 7.0 to 9.

0.

3. The method for preparing high-purity potassium metavanadate by a short-process of sodium vanadate according to claim 1, characterized in that: In the step 2), the obtained potassium metavanadate solution is concentrated and dried to obtain high-purity potassium metavanadate.

4. A device for preparing high-purity potassium metavanadate from sodium vanadate in a short process, characterized in that: The invention comprises a crystallization reactor (1), a first filtering device (2), a digestion reactor (3) and a second filtering device (4); the crystallization reactor (1) is provided with a sodium vanadate solution inlet, a potassium sulfate inlet and a concentrated sulfuric acid inlet, and is provided with a heating mechanism; the digestion reactor (3) is provided with a potassium polyvanadate inlet and a potassium hydroxide solution inlet, and is provided with a heating mechanism; the outlet at the bottom of the crystallization reactor (1) is connected to the inlet of the first filtering device (2), the solid material outlet of the first filtering device (2) is connected to the potassium polyvanadate inlet of the digestion reactor (3), the outlet at the bottom of the digestion reactor (3) is connected to the inlet of the second filtering device (4); the solid material outlet of the second filtering device (4) is connected to the potassium polyvanadate inlet of the digestion reactor (3).

5. The device for preparing high-purity potassium metavanadate by a short process of sodium vanadate according to claim 4, characterized in that: An evaporation concentration device (5) and a spray drying device (6) are also provided; the liquid material outlet of the second filtering device (4) is connected to the inlet of the evaporation concentration device (5), and the outlet of the evaporation concentration device (5) is connected to the inlet of the spray drying device (6).

6. The device for preparing high-purity potassium metavanadate by a short process of sodium vanadate according to claim 5, characterized in that: A condenser (7) is also provided; the steam outlet of the evaporation concentration device (5) and the steam outlet of the spray drying device (6) are connected to the potassium hydroxide solution inlet of the digestion reaction kettle (3) through the condenser (7).

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