Device for preparing high-purity potassium metavanadate from sodium vanadate in short process

Abstract

The utility model discloses a device for preparing high-purity potassium metavanadate from sodium vanadate in a short process. The device comprises a crystallization reaction kettle, a first filtering device, a digestion reaction kettle and a second filtering device, the crystallization reaction kettle is provided with a sodium vanadate solution inlet, a potassium sulfate inlet, a concentrated sulfuric acid inlet and a heating mechanism; the digestion reaction kettle is provided with a potassium polyvanadate inlet, a potassium hydroxide solution inlet and a heating mechanism; an outlet in the bottom of the crystallization reaction kettle is communicated with an inlet of the first filtering device, a solid material outlet of the first filtering device is connected with a potassium polyvanadate inlet of the digestion reaction kettle, and an outlet in the bottom of the digestion reaction kettle is communicated with an inlet of the second filtering device; a solid material outlet of the No.2 filtering device is connected with a potassium polyvanadate inlet of the digestion reaction kettle. According to the device, spherical potassium metavanadate solid particles with uniform particle size and good fluidity can be prepared, the stability of the potassium metavanadate crystallization process and the vanadium recovery rate are improved, 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 utility model belongs to fine chemical technology field especially a kind of device for the preparation of high-purity potassium metavanadate of sodium vanadate short process. BACKGROUND

[0002] Potassium metavanadate, English name: Potassium metavanadate, molecular formula is KVO3, is widely used in glaze, chemical catalyst, medical field etc..At present, the production process of potassium metavanadate has solid phase fusion method and alkali dissolution crystallization method: solid phase fusion method is to mix ammonium polyvanadate ((NH4)2V6O 16 ), ammonium metavanadate (NH4VO3) or di vanadium pentoxide (V2O5) with potassium carbonate (K2CO3) according to stoichiometric ratio and heat to melt state, recrystallization is obtained KVO3 in water medium system after cooling. 16 Industrial alkali dissolution crystallization method is generally used, with (NH4)2V6O 16 , NH4VO3 or V2O5 as raw material, reacts in 80~100 ℃ potassium hydroxide solution for 1~2h, filters to obtain clear potassium metavanadate solution with low-valence vanadium oxide and other insoluble impurities, evaporates and concentrates to solution supersaturation, and crystallizes to obtain potassium metavanadate after cooling.

[0003] In the above method, V2O5 production raw material is usually prepared by calcining (NH4)2V6O 16 Or NH4VO3. One inherent defect of this method is that, at 550 ℃ calcination temperature, ammonium polyvanadate or ammonium metavanadate decomposes to obtain NH3 and V2O5, and NH3 reduces a small amount of V2O5 to low-valence vanadium oxide as reducing agent. The low-valence vanadium oxide does not react with potassium hydroxide solution, and is suspended in potassium metavanadate solution in solid phase, which needs to be filtered and then evaporated and concentrated to crystallize. Due to the high viscosity of high-concentration potassium metavanadate solution, low-valence vanadium oxide is difficult to filter, which reduces production efficiency and vanadium yield.

[0004] Similarly, with (NH4)2V6O + Or NH4VO3 as raw material, a large amount of NH3 is decomposed in alkali dissolution process, and a small amount of NH4 In potassium metavanadate solution combines with metavanadate, and is precipitated with potassium metavanadate, which causes the nitrogen impurity content in potassium metavanadate product to exceed the standard.

[0005] Another defect is that, due to the high solubility and supersaturation of potassium metavanadate, seed crystal is added to promote the crystallization and precipitation of potassium metavanadate in the cooling crystallization process, and high-concentration potassium metavanadate crystallization mother liquor is returned to alkali dissolution tank for recycling, which reduces the dissolution rate of solid-phase vanadium raw material and accumulates impurities in potassium metavanadate solution, and affects production efficiency and product quality.

[0006] In recent years, domestic scientific and technological workers have proposed improved processes to address the problems of the above processes. For example, the publication number CN108975398A provides a high-density potassium metavanadate and a preparation method thereof. In the heating alkali solution process, H2O2 solution is added, and low-valence vanadium oxide reacts with H2O2 to obtain potassium metavanadate. This method improves the vanadium yield, but H2O2 is easy to decompose into water and oxygen at high temperature, reducing the oxidizing property, and unreacted low-valence vanadium oxide still needs to be removed by filtration. The feasibility study of potassium metavanadate preparation process [J] (Iron Alloy, 2022, 53(01): 24~27), Mu Xiaoling adds potassium carbonate to the sodium roasting leaching solution, adjusts the pH value to 1.5~1.8 with concentrated sulfuric acid, and hydrolyzes and precipitates vanadium to obtain sodium-containing polyvanadate, mixes with potassium carbonate, melts, and recrystallizes in a water medium system to obtain potassium metavanadate product; This process does not produce reducing agent NH3, but the sodium impurity content in the product is high. The publication number CN102531055A provides a preparation method of sodium metavanadate / potassium metavanadate. Calcium chloride is added to sodium vanadate solution to obtain calcium vanadate solid, which reacts with potassium bicarbonate solution to obtain potassium metavanadate solution and calcium bicarbonate precipitate; This system generates a large amount of wastewater containing chlorine, and when the calcium vanadate is returned to solution, due to the solubility of Ca(HCO3)2, the Ca content in the potassium metavanadate product increases. Practical new type content

[0007] The technical problem to be solved by the present utility model is to provide a device for preparing high-purity potassium metavanadate from sodium vanadate with a short process and pure product.

[0008] To solve the above technical problems, the technical scheme adopted by the present utility model is: including a crystallization reaction kettle, a first filter device, a digestion reaction kettle and a second filter device; the crystallization reaction kettle 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 reaction kettle is provided with a polyvanadate inlet and a potassium hydroxide solution inlet, and is provided with a heating mechanism; the outlet at the bottom of the crystallization reaction kettle is connected to the inlet of the first filter device, the solid material outlet of the first filter device is connected to the polyvanadate inlet of the digestion reaction kettle, and the outlet at the bottom of the digestion reaction kettle is connected to the inlet of the second filter device; the solid material outlet of the second filter device is connected to the polyvanadate inlet of the digestion reaction kettle.

[0009] Further, an evaporation and concentration device and a spray drying device are also provided; the liquid material outlet of the second filter device is connected to the inlet of the evaporation and concentration device, and the outlet of the evaporation and concentration device is connected to the inlet of the spray drying device.

[0010] Further, a condenser is also provided; the steam outlet of the evaporation and 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.

[0011] The beneficial effects produced by the above technical scheme are as follows: different from the traditional solid-phase melting method and alkali-dissolution crystallization method, the high-purity potassium polyvanadate is used as the alkali-dissolution process vanadium raw material, the excessive potassium polyvanadate is added in the digestion reaction to accurately control the potassium-vanadium ratio of the potassium metavanadate solution, and the high-purity potassium metavanadate is obtained. The sodium vanadate solution obtained by the sodium roasting and leaching is used as the raw material to prepare the potassium metavanadate in a short process, no reducing gas NH3 and low-valence vanadium is generated in the preparation process, the potassium metavanadate precipitation process is changed, and the potassium metavanadate in the solution is completely precipitated. The high-purity potassium polyvanadate is used as the alkali-dissolution process vanadium raw material, the introduction of the ammonium salt is avoided to prevent the vanadium from being reduced in the deamination process, the spherical potassium metavanadate solid particles with uniform particle size and good fluidity can be prepared, the stability of the potassium metavanadate crystallization process and the vanadium recovery rate are improved, the obtained potassium metavanadate product has a purity greater than 99.5wt% and a vanadium recovery rate greater than 99%. BRIEF DESCRIPTION OF DRAWINGS

[0012] The utility model will be explained further in detail below in combination with the drawings and specific embodiments.

[0013] Figure 1 It is the structure schematic diagram of the device of the utility model.

[0014] In the drawing: crystallization reaction kettle 1; No. 1 filter device 2; digestion reaction kettle 3; No. 2 filter device 4; evaporation concentration device 5; spray drying device 6; condenser 7. PREFERRED EMBODIMENT

[0015] Figure 1 As shown in the drawing, the device for preparing high-purity potassium metavanadate from sodium vanadate in a short process includes a crystallization reaction kettle 1, a No. 1 filter device 2, a digestion reaction kettle 3 and a No. 2 filter device 4. The crystallization reaction kettle 1 is provided with a sodium vanadate solution inlet, a potassium sulfate inlet and a concentrated sulfuric acid inlet, the sodium vanadate solution inlet is connected with a sodium vanadate solution source, the potassium sulfate inlet is connected with a potassium sulfate source, and the concentrated sulfuric acid inlet is connected with a concentrated sulfuric acid source; and a heating mechanism is arranged, which is preferably a structure directly connected with steam heating or a jacket heating structure. The digestion reaction kettle 3 is provided with a potassium polyvanadate inlet and a potassium hydroxide solution inlet, the potassium hydroxide solution inlet is connected with a potassium hydroxide solution source; and a heating mechanism is arranged, which is preferably a jacket heating structure. The outlet at the bottom of the crystallization reaction kettle 1 is connected with the inlet of the No. 1 filter device 2, the solid material outlet of the No. 1 filter device 2 is connected with the potassium polyvanadate inlet of the digestion reaction kettle 3, and the outlet at the bottom of the digestion reaction kettle 3 is connected with the inlet of the No. 2 filter device 4; and the solid material outlet of the No. 2 filter device 4 is connected with the potassium polyvanadate inlet of the digestion reaction kettle 3. The No. 1 filter device 2 and the No. 2 filter device 4 preferably both adopt a filter press.

[0016] Figure 1As shown, the device for preparing high-purity potassium metavanadate from sodium metavanadate by short process further comprises an evaporation and 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 and concentration device 5, and the outlet of the evaporation and concentration device 5 is connected to the inlet of the spray drying device 6. The evaporation and concentration device 5 is provided with a heating mechanism, which is preferably a jacketed heating structure. The spray drying device 6 preferably adopts a direct hot air blowing method for drying.

[0017] Figure 1 As shown, the device for preparing high-purity potassium metavanadate from sodium metavanadate by short process further comprises a condenser 7. The steam outlet of the evaporation and concentration device 5 and the steam outlet of the spray drying device 6 are connected to the inlet of the potassium hydroxide solution of the digestion reaction kettle 3 through the condenser 7.

[0018] The preparation process of the device for preparing high-purity potassium metavanadate from sodium metavanadate by short process is as follows:

[0019] 1) Sodium metavanadate solution, potassium sulfate solid, and concentrated sulfuric acid are sequentially injected into the crystallization reaction kettle 1. The dosages of the sodium metavanadate solution and the potassium sulfate solid are determined to ensure that the molar ratio of potassium ions to vanadium is 0.34-1.0, and concentrated sulfuric acid is added to achieve a pH value of 1.9-2.5. The temperature is raised to 90-100°C, and the potassium polyvanadate is crystallized under stirring at a speed of 30-300 r / min. The reaction solution is filtered through the first filtering device 2 to obtain potassium polyvanadate solid. The vanadium concentration in the sodium metavanadate solution is 8-45 g / L, the potassium sulfate is added in solid form, and the concentration of the concentrated sulfuric acid is 85-98 wt%.

[0020] 2) The potassium polyvanadate solid and the potassium hydroxide solution are added to the digestion reaction kettle 3 at a molar ratio of potassium ions to vanadium of 0.5-1.0. The digestion reaction is carried out at a temperature of 80-100°C and a stirring speed of 50-400 r / min. The digestion reaction lasts for at least 1 h, and the pH value of the end solution is 7.0-9.0. The reaction solution is filtered through the second filtering device 4 to obtain potassium metavanadate solution and undissolved potassium polyvanadate solid. The undissolved potassium polyvanadate solid is re-fed into the digestion reaction kettle 3. The concentration of the KOH solution is 20-80 g / L.

[0021] 3) The potassium metavanadate solution is pumped into the evaporation and concentration device 5 for evaporation and concentration at a temperature of 80-100°C. The concentration of the potassium metavanadate solution after evaporation and concentration is 300-400 g / L. Then, the solution is dried in the spray drying device 6 at a temperature of 150-350°C to obtain high-purity potassium metavanadate particles. The purity of the obtained potassium metavanadate product is greater than 99.5 wt%, and the vanadium recovery rate is greater than 99%.

[0022] 4) The water vapor generated by the evaporation and concentration device 5 and the spray drying device 6 in step 3) is condensed through the condenser 7, and the condensed water is returned to the digestion reaction kettle 3 for recycling.

Claims

1. A device for preparing high-purity potassium metavanadate by a short process of sodium vanadate, characterized in that: It include crystallization reactor (1), the first filter device (2), digestion reactor (3) and the second filter device (4);The crystallization reactor (1) is equipped with sodium vanadate solution inlet, potassium sulfate inlet and concentrated sulfuric acid inlet, and is equipped with heating mechanism;The digestion reactor (3) is equipped with polyvanadic potassium inlet and potassium hydroxide solution inlet, and is equipped with heating mechanism;The outlet of the bottom of the crystallization reactor (1) is communicated with the inlet of the first filter device (2), the solid material outlet of the first filter device (2) is connected with the polyvanadic potassium inlet of the digestion reactor (3), and the outlet of the bottom of the digestion reactor (3) is communicated with the inlet of the second filter device (4);The solid material outlet of the second filter device (4) is connected with the polyvanadic potassium inlet of the digestion reactor (3). 2.The device for preparing high-purity potassium metavanadate by a short process of sodium vanadate according to claim 1, characterized in that: It is also equipped with evaporation concentration device (5) and spray drying device (6);The liquid material outlet of the second filter device (4) is communicated with the inlet of the evaporation concentration device (5), and the outlet of the evaporation concentration device (5) is communicated with the inlet of the spray drying device (6). 3.The device for preparing high-purity potassium metavanadate by a short process of sodium vanadate according to claim 2, characterized in that: It is also equipped with condenser (7);The steam outlet of the evaporation concentration device (5) and the steam outlet of the spray drying device (6) are communicated with the potassium hydroxide solution inlet of the digestion reactor (3) through the condenser (7).

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