Safe decomposition method of niobium-tantalum-iron alloy

Abstract

The invention provides a safe decomposition method of a niobium-tantalum-iron alloy, and relates to the technical field of niobium product production, and the safe decomposition method comprises the following steps: step 1, mixing the niobium-tantalum-iron alloy with water according to a preset solid-to-liquid ratio to prepare slurry; 2, starting exhaust equipment, and controlling the interior of the reactor to keep a micro-negative pressure state; 3, dropwise adding sulfuric acid into the slurry to improve the acidity of the solution; 4, hydrofluoric acid is added into the slurry in two stages; wherein the adding amount of hydrofluoric acid in the first stage is larger than that in the second stage, and the adding rate of hydrofluoric acid in the first stage is smaller than that in the second stage; 5, after hydrofluoric acid in the second stage is added, if no obvious reaction exists on the surface of the solution, the hydrogen concentration is lower than the preset hydrogen concentration threshold value, and the obtained extraction stock solution meets the preset concentration threshold value, the reaction is finished, and the extraction stock solution containing fluorine niobic acid, fluorine tantalic acid and fluorine ferrite products is obtained. According to the scheme, the safety of decomposing the niobium-tantalum-iron alloy can be improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of niobium product production, and particularly relates to a safe decomposition method of niobium-tantalum-iron alloy. BACKGROUND

[0002] As an important strategic resource, niobium-tantalum is widely used in metallurgy, electronics, military industry, aerospace and many other fields due to its unique physical and chemical properties. So far, China's tantalum and niobium smelting capacity ranks first in the world, and 70% of the global primary products come from China. However, the production capacity of niobium ore raw materials in China is less than 5% of the smelting capacity, and more than 80% of the raw materials used by domestic tantalum and niobium smelting enterprises come from imports. In recent years, as a strategic scarce resource, the acquisition of niobium ore resources has become a bottleneck restricting the development of China's niobium industry. However, niobium-tantalum-iron alloy, as a primary product of niobium resources, has a smooth access channel, so using niobium-tantalum-iron as a substitute raw material can break through the bottleneck restricting the development of China's niobium industry. That is, using niobium-tantalum-iron alloy as a raw material, niobium products are obtained by decomposition.

[0003] At present, the commonly used decomposition method of niobium-tantalum-iron alloy is hydrofluoric acid-sulfuric acid decomposition method, that is, after the niobium-tantalum-iron alloy is slurried, hydrofluoric acid and sulfuric acid are used for decomposition in a decomposition tank. However, in the decomposition process of niobium-tantalum-iron alloy, a large amount of hydrogen gas is generated due to the reaction of iron, tantalum, niobium and other substances with acid. In the decomposition process currently adopted, the method is to directly add the niobium-tantalum-iron alloy slurry into the decomposition tank containing hydrofluoric acid, and then supplement sulfuric acid in the subsequent process. This method can cause the concentration of released hydrogen gas to change greatly and be difficult to control, and a large amount of hydrogen gas gathered can easily cause explosion, which has high safety hazards. SUMMARY

[0004] Therefore, in view of the above problems, it is necessary to provide a safe decomposition method of niobium-tantalum-iron alloy to improve the safety of decomposing niobium-tantalum-iron alloy.

[0005] The present application provides a safe decomposition method of niobium-tantalum-iron alloy, comprising the following steps: Step 1: mixing niobium-tantalum-iron alloy with water according to a preset solid-liquid ratio to prepare a slurry, and placing the slurry in a reactor; Step 2: starting an exhaust equipment, and keeping the reactor in a micro-negative pressure state by controlling the exhaust equipment; Step 3: uniformly adding a preset proportion of sulfuric acid into the slurry to improve the acidity of the solution; Step 4: Hydrofluoric acid is added to the slurry in two stages according to a preset mass-volume ratio of the niobium-tantalum-iron alloy to the hydrofluoric acid; wherein the amount of hydrofluoric acid added in the first stage is greater than that in the second stage, and the addition rate of hydrofluoric acid in the first stage is less than that in the second stage; after the addition of hydrofluoric acid in the first stage is completed, when the hydrogen release amount is significantly reduced or there is no obvious reaction phenomenon, the addition of hydrofluoric acid in the second stage is started; Step 5: After the addition of hydrofluoric acid in the second stage, if there is no obvious reaction on the surface of the solution, and the hydrogen concentration is lower than the preset hydrogen concentration threshold, and the obtained extraction stock solution meets the preset concentration threshold, the reaction is ended, and an extraction stock solution containing fluoroniobate, fluorotantalate and fluoroironate products is obtained.

[0006] Preferably, the step 1 specifically comprises: S11: The niobium-tantalum-iron alloy raw material is crushed and ball milled to a particle size of 100-200 mesh; S12: The ball milled niobium-tantalum-iron alloy is mixed with deionized water according to a solid-liquid ratio of 1 kg:(2-3) L, and stirred uniformly to prepare a slurry.

[0007] Preferably, sodium hexametaphosphate or polyvinylpyrrolidone is added during mixing in step S12 to prevent particle agglomeration and improve dispersibility; wherein the addition amount of sodium hexametaphosphate or polyvinylpyrrolidone is 0.1%-0.3% of the mass of the slurry.

[0008] Preferably, in step 2, the exhaust equipment is a water ring vacuum pump matched with a buffer tank to stabilize the pressure and avoid frequent start-stop of the vacuum pump; an exhaust pipeline is arranged at the top of the reactor, and the exhaust rate is matched with the air extraction amount of the water ring vacuum pump to timely exhaust the hydrogen generated in the reactor; wherein the micro-negative pressure state maintained in the reactor is-50 Pa to-200 Pa.

[0009] Preferably, the step 3 specifically comprises: using a high-precision peristaltic pump to uniformly drop 98% concentrated sulfuric acid into the slurry at a speed of 1 L / (45-60) min, and stirring at a speed of 300-400 rpm during the dropping process of concentrated sulfuric acid to make the sulfuric acid disperse quickly; wherein the mass-volume ratio of niobium-tantalum-iron alloy to concentrated sulfuric acid is 1 kg:(0.8-1.2) L; the dropping tube of the high-precision peristaltic pump is inserted into the slurry liquid surface by 5-10 cm to avoid the contact of sulfuric acid with air to generate acid mist.

[0010] Preferably, in step 4, the mass-volume ratio of niobium-tantalum-iron alloy to hydrofluoric acid is 1 kg:(1-2) L; the step 4 specifically comprises: S41: After the sulfuric acid dropping is completed for a preset time, 2 / 3 volume of hydrofluoric acid is added to the slurry at a dropping rate of 250-300 ml / hour; S42: When the hydrogen release amount is obviously reduced or there is no obvious reaction phenomenon on the liquid surface, the remaining 1 / 3 volume of hydrofluoric acid is added to the slurry at a dropping rate of 300-400 ml / hour.

[0011] Preferably, the temperature in the reactor is monitored in real time during the hydrofluoric acid dropping process, and the temperature sensor is linked with the hydrofluoric acid dropping pump; when the temperature rises to 68℃, the hydrofluoric acid dropping pump automatically reduces the speed by 10-15% and works; when the temperature is greater than 70℃, the hydrofluoric acid dropping pump stops adding hydrofluoric acid, and resumes adding hydrofluoric acid when the temperature is reduced to below 65℃.

[0012] Preferably, the reactor uses a jacketed water bath reactor, and cooling coils are arranged in the jacket to start cooling water to reduce the temperature when the temperature is greater than 70℃; wherein the top, middle and bottom of the reactor are provided with temperature sensors, and the average value of the detection results of the three temperature sensors is taken as the basis for controlling the hydrofluoric acid dropping pump and starting the cooling water.

[0013] Preferably, in step 5, if there is obvious reaction on the surface of the solution or the hydrogen concentration is greater than the preset hydrogen concentration threshold value, hydrofluoric acid is continuously added to the slurry to continue the reaction; if there is no obvious reaction on the surface of the solution and the hydrogen concentration is lower than the preset hydrogen concentration threshold value, sulfuric acid and hydrofluoric acid are added to the solution to make the final concentration of sulfuric acid and hydrofluoric acid in the extraction stock solution reach the preset concentration threshold value, and the reaction is ended.

[0014] Preferably, the preset hydrogen concentration threshold value is 0.1%; the sulfuric acid concentration threshold value in the extraction stock solution is 3.75-4.25 mol / L, and the hydrofluoric acid concentration threshold value is 5.5-6.5 mol / L.

[0015] According to the technical scheme, the safety decomposition method of the niobium-tantalum-iron alloy provided by the embodiment of the present application first mixes the niobium-tantalum-iron alloy with water according to a preset solid-liquid ratio to prepare slurry, and then places the slurry in a reactor, and then starts an exhaust device, and controls the exhaust device to keep the reactor in a micro-negative pressure state. Further, a preset proportion of sulfuric acid is uniformly added to the slurry to oxidize the iron in the niobium-tantalum-iron alloy and increase the acidity of the solution. Then, according to a preset mass-volume ratio of the niobium-tantalum-iron alloy to hydrofluoric acid, the hydrofluoric acid is added to the slurry in two stages. After the addition of the hydrofluoric acid in the second stage, if there is no obvious reaction on the surface of the solution, the hydrogen concentration is lower than a preset hydrogen concentration threshold, and the obtained extraction stock solution meets a preset concentration threshold, the reaction is ended, and the extraction stock solution containing fluoroniobate, fluorotantalate and fluoroferate products is obtained. According to the technical scheme, the hydrogen generated in the reaction is continuously extracted by the exhaust device in the present scheme, and the reactor is kept in a micro-negative pressure state, which ensures that the hydrogen concentration in the reactor is below the safety value, thereby avoiding the occurrence of explosion accidents and improving the safety of the decomposition of the niobium-tantalum-iron alloy. At the same time, the present scheme adopts the way of adding hydrofluoric acid in batches, and the hydrofluoric acid is added at a low drop rate in the first stage of the main reaction, which can reduce the violent reaction between the hydrofluoric acid and the alloy surface with high initial activity, reduce the hydrogen release peak, and thus reduce the probability of explosion accidents caused by rapid accumulation of hydrogen, thereby also improving the safety of the decomposition of the niobium-tantalum-iron alloy. In addition, before adding the hydrofluoric acid, the sulfuric acid is first added. The addition of sulfuric acid not only reduces the subsequent violent reaction between hydrofluoric acid and iron, but also increases the acidity of the solution, provides hydrogen ions for the solution, and reduces the volatilization of hydrofluoric acid. The amount of hydrofluoric acid added is greatly reduced. The cost of hydrofluoric acid is much higher than that of sulfuric acid, so the decomposition of the niobium-tantalum-iron alloy based on the present scheme can also help to reduce the decomposition cost. BRIEF DESCRIPTION OF DRAWINGS

[0016] Figure 1 A flow chart of a safety decomposition method of a niobium-tantalum-iron alloy provided by the embodiment of the present application. DETAILED DESCRIPTION

[0017] In order to more clearly illustrate the technical scheme of the embodiment of the present application, the following will briefly introduce the drawings needed to be used in the embodiment. Obviously, the drawings described below are some embodiments of the present application, and other drawings can also be obtained by those skilled in the art without creating laborious work.

[0018] As shown in Figure 1 The embodiment of the present application provides a safety decomposition method of a niobium-tantalum-iron alloy, which can include the following steps: Step 1: mix the ferroniobium-tantalum alloy with water according to a preset solid-liquid ratio to prepare a slurry, and place the slurry in a reactor; Step 2: start the exhaust equipment, and keep the reactor in a micro-negative pressure state by controlling the exhaust equipment; Step 3: uniformly drop a preset proportion of sulfuric acid into the slurry to increase the solution acidity; Step 4: add hydrofluoric acid to the slurry in two stages according to a preset mass-volume ratio of the ferroniobium-tantalum alloy to the hydrofluoric acid; the first-stage hydrofluoric acid addition amount is greater than the second-stage hydrofluoric acid addition amount, and the first-stage hydrofluoric acid addition rate is less than the second-stage hydrofluoric acid addition rate; after the first-stage hydrofluoric acid addition is completed, when the hydrogen release amount is obviously reduced or there is no obvious reaction phenomenon, the second-stage hydrofluoric acid addition is started; Step 5: after the second-stage hydrofluoric acid addition, if there is no obvious reaction on the surface of the solution, the hydrogen concentration is lower than a preset hydrogen concentration threshold, and the obtained extraction stock solution meets a preset concentration threshold, the reaction is ended, and an extraction stock solution containing fluoroniobate, fluorotantalate and fluoroferrate products is obtained.

[0019] In this embodiment, the hydrogen generated in the reaction is continuously extracted by the exhaust equipment, and the reactor is kept in a micro-negative pressure state, which ensures that the hydrogen concentration in the reactor is below a safety value, thereby avoiding the occurrence of explosion accidents and helping to improve the safety of the ferroniobium-tantalum alloy decomposition. At the same time, the present scheme adopts the way of adding hydrofluoric acid in batches, and the first stage of the main reaction is added at a lower drop rate, which can reduce the violent reaction of hydrofluoric acid with the alloy surface with high initial activity, reduce the hydrogen release peak, and thus reduce the probability of explosion accidents caused by rapid accumulation of hydrogen, thereby also improving the safety of the ferroniobium-tantalum alloy decomposition. In addition, before adding the hydrofluoric acid, the sulfuric acid is added first. The addition of sulfuric acid not only preferentially reacts with iron in the alloy to reduce the subsequent violent reaction of hydrofluoric acid with iron. At the same time, the addition of sulfuric acid can increase the acidity of the solution and provide hydrogen ions for the solution, thereby reducing the volatilization of hydrofluoric acid and greatly reducing the amount of hydrofluoric acid added. The cost of hydrofluoric acid is much higher than that of sulfuric acid, so based on the present scheme, the decomposition of the ferroniobium-tantalum alloy also helps to reduce the decomposition cost.

[0020] For step 1, when preparing the slurry, the following steps can be implemented: S11: crush and ball mill the ferroniobium-tantalum alloy raw material to a particle size of 100-200 mesh; S12: mix the ball-milled ferroniobium-tantalum alloy with deionized water according to a solid-liquid ratio of 1 kg:(2-3) L, and stir uniformly to prepare the slurry.

[0021] In this embodiment, the jaw crusher is considered to be used to crush the raw material of the niobium-tantalum-iron alloy, which is crushed to a particle size of less than 5 mm, and then ground by a planetary ball mill. When the ball mill is used for fine grinding, the ball mill medium is zirconia ball, the ball-to-material ratio is 3:1, the rotation speed is 300-400 rpm, and the ball milling time is 2-3 hours. During ball milling, samples can be taken every 30 minutes for detection by a laser particle size analyzer to ensure that more than 95% of the particles have a particle size of 100-200 mesh, avoiding incomplete reaction caused by too coarse particle size or agglomeration caused by too fine particle size.

[0022] At the same time, deionized water is considered to be used to prepare the slurry to avoid the combination of calcium and magnesium ions in the water with fluorine ions to form a precipitate, affecting the effective concentration of hydrofluoric acid. When stirring, an anchor stirrer is considered to be used, the stirring speed is 300-500 rpm, the stirring time is 20-30 minutes, and the solid-liquid mixture is uniformly mixed to control the slurry viscosity at 500-800 mPa.s.

[0023] In order to further improve the uniformity of the slurry mixing, in one embodiment, sodium hexametaphosphate or polyvinylpyrrolidone is added during the mixing of step S12 to prevent particle agglomeration and improve dispersibility; sodium hexametaphosphate can form an electrostatic repulsive force by adsorbing on the surface of alloy particles to prevent particle agglomeration, and can be suitable for high-hardness alloys in this scheme; while polyvinylpyrrolidone can disperse particles through steric hindrance effect, and is suitable for the fine-grained raw materials used in this scheme. Among them, the addition amount of sodium hexametaphosphate or polyvinylpyrrolidone is 0.1%-0.3% of the mass of the slurry, so as to ensure the dispersion effect while avoiding excessive addition which may cause organic phase emulsification during subsequent extraction.

[0024] For step 2, when micro-negative pressure control is performed, it is considered to reduce the hydrogen concentration in the reactor by continuous exhaust, while avoiding reaction gas leakage to the workshop. Specifically, a water ring vacuum pump (5-10 m 3 / h) can be used, matched with a buffer tank (volume 50-100 L) to stabilize the pressure and avoid frequent start-stop of the vacuum pump. A digital vacuum gauge is installed on the reactor to display the pressure in the reactor in real time, and the data is synchronized to the control system. An exhaust pipeline (diameter 100-150 mm) is provided at the top of the reactor, and the exhaust rate is matched with the air extraction amount of the water ring vacuum pump, so that the hydrogen generated in the reactor can be timely discharged to the corresponding hydrogen collection equipment.

[0025] In order to ensure the safety of the reaction, the micro-negative pressure state in the reactor is considered to be controlled at-50 Pa to-200 Pa, and the exhaust rate is greater than the air penetration rate, so that the hydrogen concentration in the reactor can be always lower than 4% of the lower explosive limit.

[0026] For step 3, when adding sulfuric acid to the slurry, a high-precision peristaltic pump can be used to add 98% concentrated sulfuric acid to the slurry at a uniform speed, with a drop rate of 1 L / (45-60) min. The specific drop rate can be adjusted according to the iron content to ensure uniform pre-reaction of iron. At the same time, stirring is carried out at a speed of 300-400 rpm during the drop process of concentrated sulfuric acid to quickly disperse the sulfuric acid and avoid local overheating, preventing sulfuric acid decomposition or volatilization. In addition, the mass-volume ratio of niobium-tantalum-iron alloy to concentrated sulfuric acid can be 1 kg:(0.8-1.2) L, and the drop tube of the high-precision peristaltic pump is inserted 5-10 cm below the slurry surface to avoid acid mist generated by the contact of sulfuric acid with air.

[0027] In this step, by adding sulfuric acid to the slurry first, the acidity of the solution can be increased, providing a large number of hydrogen ions for the solution, thereby reducing the subsequent volatilization of hydrofluoric acid, and thus reducing the amount of hydrofluoric acid added. Moreover, the cost of hydrofluoric acid is much higher than that of sulfuric acid, and the reduction of the amount of hydrofluoric acid added can also greatly reduce the cost of niobium-tantalum-iron alloy decomposition.

[0028] For step 4, when adding hydrofluoric acid, consider adding it in stages to match the reaction kinetics and reduce the amount of hydrogen gas released instantaneously. Specifically, the mass-volume ratio of niobium-tantalum-iron alloy to hydrofluoric acid is 1 kg:(1-2) L, which can be added to the slurry by the following method: S41: After the sulfuric acid drop is completed for a predetermined time, add 2 / 3 of the volume of hydrofluoric acid to the slurry at a drop rate of 250-300 ml / hour; S42: When the amount of hydrogen gas released is significantly reduced or there is no obvious reaction phenomenon on the liquid surface, add the remaining 1 / 3 of the volume of hydrofluoric acid to the slurry at a drop rate of 300-400 ml / hour.

[0029] In this embodiment, the first stage usually starts 5-10 minutes after the completion of sulfuric acid drop, at which time the pre-reaction of iron has been 30-40%. The initial alloy surface is highly active, and considering the lower drop rate of hydrofluoric acid in the first stage, the intense reaction between hydrofluoric acid and the fresh surface can be reduced, thereby reducing the hydrogen gas release peak. At the same time, the first stage is also a necessary reaction stage, and slowly adding hydrofluoric acid can avoid the safety hazards of large instantaneous release of hydrogen gas and intense reaction. When entering the second stage, the reaction is almost over, and the alloy surface is gradually covered with reaction products, and the reaction is slow. Increasing the drop rate can improve efficiency.

[0030] In addition, considering that temperature is also a core factor affecting reaction rate and side reactions, such as excessive temperature leading to intensified volatilization of hydrofluoric acid and generation of insoluble tantalum niobium oxides, and the higher the temperature, the higher the risk of reaction. Therefore, the temperature during the reaction needs to be monitored and controlled. Specifically, the temperature in the reactor can be monitored in real time during the dropping process of hydrofluoric acid, and the temperature sensor is linked with the hydrofluoric acid dropping pump; when the temperature rises to 68℃, the hydrofluoric acid dropping pump automatically reduces the speed by 10-15%; when the temperature is greater than 70℃, the hydrofluoric acid dropping pump stops adding hydrofluoric acid, and resumes adding acid when the temperature is reduced to below 65℃.

[0031] Further, the reactor can adopt a jacketed water bath reactor, and cooling coils are arranged in the jacket to start cooling water to reduce the temperature when the temperature is greater than 70℃. The flow rate of the cooling water can be controlled at 2-3L / min, and the cooling rate is controlled at 2-3℃ / min to avoid sudden cooling leading to particle sedimentation. In addition, temperature sensors can be arranged at the top, middle and bottom of the reactor, and the average value of the detection results of the three temperature sensors is taken as the basis for controlling the hydrofluoric acid dropping pump and starting the cooling water to avoid local temperature misjudgment.

[0032] For step 5, when determining the reaction endpoint, consider verifying from multiple dimensions, so that the reaction endpoint determination needs to consider the completeness of the reaction and the subsequent extraction requirements, to avoid premature termination leading to low leaching rate, or too late termination causing reagent waste. Specifically, when determining the reaction endpoint, if there is no obvious reaction on the surface of the solution, and the hydrogen concentration is lower than the preset hydrogen concentration threshold, and the obtained extraction stock solution meets the preset concentration threshold, it means that the reaction is completed, and the extraction stock solution containing fluoroniobate, fluorotantalate and fluoroferrate products is obtained. If there is obvious reaction on the surface of the solution, or the hydrogen concentration is greater than the preset hydrogen concentration threshold, it means that the niobium tantalum iron alloy has not been fully reacted, so hydrofluoric acid is continuously added to the slurry to continue the reaction. If there is no obvious reaction on the surface of the solution, and the hydrogen concentration is lower than the preset hydrogen concentration threshold, then sulfuric acid and hydrofluoric acid are added to the solution to make the concentration of sulfuric acid and hydrofluoric acid in the final extraction stock solution reach the preset concentration threshold, and the reaction is completed.

[0033] In this embodiment, the preset hydrogen concentration threshold can be 0.1%; the sulfuric acid concentration threshold in the extraction stock solution can be 3.75-4.25mol / L, and the hydrofluoric acid concentration threshold can be 5.5-6.5mol / L. In this way, the addition of sulfuric acid and hydrofluoric acid to the solution can provide a stable hydrogen ion environment for the solution, inhibit the hydrolysis of fluorine complexes, and ensure that they exist in the form of extractable ions. That is, it provides a stable medium environment for the subsequent extraction process, ensuring the separation efficiency of niobium, tantalum and iron and the purity of the products.

[0034] The following will further illustrate the scheme through specific examples. Example 1

[0035] (1) The niobium-tantalum-iron alloy raw material is crushed and ball milled to a particle size of 150 mesh or less; (2) The ball-milled niobium-tantalum-iron alloy is mixed with deionized water at a solid-liquid ratio of 1 kg:2.5 L, and stirred uniformly to form a slurry.

[0036] (3) A dispersing agent, sodium hexametaphosphate, is added, and the amount of the dispersing agent is controlled to be 0.2% of the mass of the slurry, to further improve the uniformity of the slurry.

[0037] (4) A vacuum pump is started, and the gas in the reactor is pumped out through a vacuum system to maintain a slightly negative pressure environment in the reactor.

[0038] (5) The vacuum degree is adjusted to control the pressure in the reactor to reach -100 Pa.

[0039] (6) 98% concentrated sulfuric acid is slowly added to the reactor, and the dropping time is 45 minutes. The volume-mass ratio of sulfuric acid to niobium-tantalum-iron alloy is 1 L:1 kg.

[0040] (7) Two-thirds of the total amount of hydrofluoric acid is added at a rate of 280 ml / hour.

[0041] (8) When the amount of hydrogen released is significantly reduced or there is no obvious reaction phenomenon on the liquid surface, the remaining one-third of the hydrofluoric acid is added at a rate of 360 ml / hour. The volume-mass ratio of hydrofluoric acid to niobium-tantalum-iron alloy is 1.5 L:1 kg.

[0042] (9) The reaction temperature is maintained at 62-73℃. When the temperature is ≥73℃, the addition of hydrofluoric acid is paused. When the temperature drops to below 62℃, the addition of acid is resumed.

[0043] (10) The sample is taken, and the hydrogen concentration at the end of the reaction is detected using a gas chromatograph.

[0044] (11) If the hydrogen concentration is higher than 0.1%, the temperature is adjusted to below 62℃, and the addition of acid is resumed.

[0045] (12) If the hydrogen concentration is lower than 0.1%, sulfuric acid and hydrofluoric acid are added to make the final extraction stock solution meet the requirements of 3.75-4.25 mol / L for the concentration of sulfuric acid and 5.5-6.5 mol / L for the concentration of hydrofluoric acid. The reaction is ended when the leaching rate of tantalum and niobium reaches 99%. Example 2

[0046] (1) The niobium-tantalum-iron alloy raw material is crushed and ball milled to a particle size of 180 mesh or less; (2) The ball-milled niobium-tantalum-iron alloy is mixed with deionized water at a solid-liquid ratio of 1 kg:3 L, and stirred uniformly to form a slurry.

[0047] (3) Add dispersant sodium hexametaphosphate, control the amount of dispersant to be 0.3% of the mass of the slurry, and further improve the uniformity of the slurry.

[0048] (4) Start the vacuum pump, and extract the gas in the reactor through the vacuum system to maintain a micro-negative pressure environment in the reactor.

[0049] (5) Adjust the vacuum degree, and control the pressure in the reactor to be-150 Pa.

[0050] (6) Slowly add 98% concentrated sulfuric acid into the reactor, the dropping time is 55 minutes, and the volume-mass ratio of sulfuric acid to niobium-tantalum-iron alloy is 1L:1kg.

[0051] (7) Add 2 / 3 of the total amount of hydrofluoric acid at a rate of 270ml / hour.

[0052] (8) When the hydrogen release amount is obviously reduced or there is no obvious reaction phenomenon on the liquid surface, add the remaining 1 / 3 of the hydrofluoric acid at a rate of 380ml / hour, wherein the volume-mass ratio of hydrofluoric acid to niobium-tantalum-iron alloy is 1.5L:1kg.

[0053] (9) The reaction temperature is maintained at 65-75℃, when the temperature is ≥75℃, the addition of hydrofluoric acid is paused, and after the temperature drops to below 65℃, the addition of acid is resumed.

[0054] (10) Take samples and use a gas chromatograph to detect the hydrogen concentration at the end of the reaction.

[0055] (11) If the hydrogen concentration is higher than 0.1%, adjust the temperature to below 65℃, and resume the addition of acid.

[0056] (12) If the hydrogen concentration is lower than 0.1%, add sulfuric acid and hydrofluoric acid to make the final extraction stock solution meet the requirements of 3.75-4.25mol / L of sulfuric acid concentration and 5.5-6.5mol / L of hydrofluoric acid concentration, and the niobium-tantalum leaching rate reaches 98%.

[0057] The following will further illustrate the scheme combined with specific experiments.

[0058] Experiment 1: 100g of niobium-tantalum-iron alloy was weighed in a beaker, 150mL of HF was slowly added, the temperature was controlled within 65℃, and HF was slowly added. After testing, the consumption of hydrofluoric acid was 92.65%, the leaching rate of tantalum and niobium was 95.60%, the total acid consumption rate was 89.85%, and the hydrogen gas generated during the acid addition process accounted for 1.5%~3.0% of the volume in the atmosphere (the explosion limit of hydrogen gas is 4%~75%); the extraction acidity requirement is 13-15mol / L, of which sulfuric acid is 3.75-4.25mol / L, HF acid is 5.5-6.5mol / L, in order to meet the extraction acidity requirement, concentrated sulfuric acid needs to be supplemented by 34.74% of the volume of the leaching solution, and hydrofluoric acid needs to be supplemented by 25.05% of the volume of the leaching solution.

[0059] Experiment 2: 100g of niobium-tantalum-iron alloy was weighed in a beaker, 150mL of HF was slowly added, the temperature was controlled within 65℃, and HF was slowly added. After testing, the consumption of hydrofluoric acid was 96.95%, the leaching rate of tantalum and niobium was 95.22%, the total acid consumption rate was 85.85%, and the hydrogen gas generated during the acid addition process accounted for 1.5%~3.0% of the volume in the atmosphere (the explosion limit of hydrogen gas is 4%~75%); the extraction acidity requirement is 13-15mol / L, of which sulfuric acid is 3.75-4.25mol / L, HF acid is 5.5-6.5mol / L, in order to meet the extraction acidity requirement, concentrated sulfuric acid needs to be supplemented by 35.73% of the volume of the leaching solution, and HF acid needs to be supplemented by 28.61% of the volume of the leaching solution.

[0060] Experiment 3: 100g of niobium-tantalum-iron alloy was weighed in a beaker, 300mL of water was added to make a slurry, 50mL of concentrated sulfuric acid was slowly added to the slurry, and then 300mL of HF was slowly added, the temperature was controlled within 65℃, and HF was slowly added. After testing, the consumption of sulfuric acid was 79.55%, the consumption of hydrofluoric acid was 43.06%, the leaching rate of tantalum and niobium was 99.52%, the total acid consumption rate was 48.87%, and the hydrogen gas generated during the acid addition process accounted for 1.5%~3.0% of the volume in the atmosphere (the explosion limit of hydrogen gas is 4%~75%); the extraction acidity requirement is 13-15mol / L, of which sulfuric acid is 3.75-4.25mol / L, HF acid is 5.5-6.5mol / L, in order to meet the extraction acidity requirement, concentrated sulfuric acid needs to be supplemented by 28.70% of the volume of the leaching solution, and HF acid needs to be supplemented by 8.08% of the volume of the leaching solution.

[0061] Experiment 4: 100g of niobium-tantalum-iron alloy was weighed into a beaker, 300mL of water was added for slurry, 100mL of concentrated sulfuric acid was slowly added to the slurry, and then 200mL of HF was slowly added, the temperature was controlled within 65℃, and the HF was slowly added. After detection, the sulfuric acid consumption rate was 52.76%, the consumption of hydrofluoric acid was 37.23%, the tantalum-niobium leaching rate was 98.57%, the total acid consumption rate was 42.86%, and the volume ratio of hydrogen gas generated during the acid addition process in the atmosphere was 1.5%~3.0% (the explosion limit of hydrogen gas is 4%~75%); the extraction acidity requirement is 13-15mol / L, of which sulfuric acid is 3.75-4.25mol / L and HF acid is 5.5-6.5mol / L. In order to meet the extraction acidity requirement, 22.96% of the volume of the leaching solution needs to be supplemented with concentrated sulfuric acid, and 9.16% of the volume of the leaching solution needs to be supplemented with HF acid.

[0062] Experiment 5: 100g of niobium-tantalum-iron alloy was weighed into a beaker, 80mL of concentrated sulfuric acid was added for slurry, and then 150mL of HF was slowly added, the temperature was controlled within 54℃, and the HF was slowly added. After detection, the sulfuric acid consumption rate was 51.62%, the consumption of hydrofluoric acid was 69.83%, the tantalum-niobium leaching rate was 95.57%, the total acid consumption rate was 62.96%, and the volume ratio of hydrogen gas generated during the acid addition process in the atmosphere was 1.5%~3.0% (the explosion limit of hydrogen gas is 4%~75%); the extraction acidity requirement is 13-15mol / L, of which sulfuric acid is 3.75-4.25mol / L and HF acid is 5.5-6.5mol / L. In order to meet the extraction acidity requirement, 13.15% of the volume of the leaching solution needs to be supplemented with concentrated sulfuric acid, and 7.08% of the volume of the leaching solution needs to be supplemented with HF acid.

[0063] Experiment 6: 100g of niobium-tantalum-iron alloy was weighed into a beaker, 80mL of concentrated sulfuric acid was added for slurry, and then 150mL of HF was slowly added, the temperature was controlled within 65℃, and the HF was slowly added. After detection, the sulfuric acid consumption rate was 84.91%, the consumption of hydrofluoric acid was 72.75%, the tantalum-niobium leaching rate was 97.32%, the total acid consumption rate was 66.02%, and the volume ratio of hydrogen gas generated during the acid addition process in the atmosphere was 1.5%~3.0% (the explosion limit of hydrogen gas is 4%~75%); the extraction acidity requirement is 13-15mol / L, of which sulfuric acid is 3.75-4.25mol / L and HF acid is 5.5-6.5mol / L. In order to meet the extraction acidity requirement, 14.67% of the volume of the leaching solution needs to be supplemented with concentrated sulfuric acid, and 9.05% of the volume of the leaching solution needs to be supplemented with HF acid.

[0064] The experiment 1 and the experiment 2 are the traditional mode of adding only hydrofluoric acid in the decomposition reaction, the experiment 3 and the experiment 4 are the mode of the present scheme, the experiment 5 and the experiment 6 are the mode of using concentrated sulfuric acid instead of deionized water for slurry. Through the comparison of the six groups of experiments, it can be known that the addition of sulfuric acid can improve the leaching efficiency of tantalum and niobium to different degrees, and the consumption rate of hydrofluoric acid and total acid is reduced by more than 50%, and the proportion of the leaching liquid volume of the added sulfuric acid and hydrofluoric acid is reduced by more than 20%. At the same time, through the experiment 5 and the experiment 6, it can be known that the mode of using deionized water for slurry can also significantly improve the leaching efficiency of tantalum and niobium, and the consumption rate of hydrofluoric acid and total acid is also obviously reduced, so the mode can be used for safely decomposing tantalum and niobium iron alloy. Further comparing the present scheme, the present scheme can further improve the leaching efficiency of tantalum and niobium, and reduce the consumption rate of hydrofluoric acid and total acid, so it is more advantageous.

[0065] The modules or units in the device embodiment of the present application can be combined, divided, and deleted according to actual needs. The above disclosed is only the preferred embodiment of the present application, and of course cannot limit the scope of the rights of the present application, and those skilled in the art can understand that all or part of the above-mentioned embodiments can be implemented, and equivalent changes made according to the claims of the present application still belong to the scope covered by the present application.

Claims

1. A safe decomposition method for niobium-tantalum-iron alloy, characterized in that: The following steps are involved: Step 1: mixing niobium-tantalum-iron alloy and water according to a preset solid-liquid ratio to prepare a slurry, and placing the slurry in a reactor; Step 2: Turn on the exhaust equipment and control the exhaust equipment to maintain a slightly negative pressure in the reactor; Step 3: adding a preset ratio of sulfuric acid to the slurry at a uniform rate to increase the acidity of the solution; Step 4: adding hydrofluoric acid to the slurry in two stages according to a preset mass-to-volume ratio of the niobium-tantalum-iron alloy to the hydrofluoric acid; wherein the amount of hydrofluoric acid added in the first stage is greater than the amount of hydrofluoric acid added in the second stage, and the rate of hydrofluoric acid addition in the first stage is less than the rate of hydrofluoric acid addition in the second stage; after the first stage of hydrofluoric acid addition is completed, the second stage of hydrofluoric acid addition is started when the amount of hydrogen released is significantly reduced or no obvious reaction occurs; Step 5: After the addition of hydrofluoric acid in the second stage, if there is no obvious reaction on the surface of the solution, the hydrogen concentration is lower than the preset hydrogen concentration threshold, and the obtained extraction solution meets the preset concentration threshold, the reaction is terminated to obtain an extraction solution containing fluoroniobic acid, fluorotantalic acid and fluoroferric acid products.

2. The safe decomposition method of niobium-tantalum-iron alloy according to claim 1, characterized in that: The step 1 specifically includes: S11: crushing and ball-milling the niobium-tantalum-iron alloy raw material to a particle size of 100-200 mesh; S12: The ball-milled niobium-tantalum-iron alloy is mixed with deionized water at a solid-liquid ratio of 1 kg:(2-3) L, and stirred evenly to prepare a slurry.

3. The safe decomposition method of niobium-tantalum-iron alloy according to claim 2, characterized in that: In step S12, sodium hexametaphosphate or polyvinyl pyrrolidone is added during mixing to prevent particle agglomeration and improve dispersibility; wherein, the amount of sodium hexametaphosphate or polyvinyl pyrrolidone added is 0.1%-0.3% of the mass of the slurry.

4. The safe decomposition method of niobium-tantalum-iron alloy according to claim 1, characterized in that: In step 2, the exhaust equipment is a water ring vacuum pump with a supporting buffer tank to stabilize the pressure and avoid frequent start and stop of the vacuum pump; an exhaust duct is provided on the top of the reactor, and the exhaust rate matches the suction volume of the water ring vacuum pump to discharge the hydrogen generated in the reactor in time; wherein, the slightly negative pressure state maintained in the reactor is -50Pa to -200Pa.

5. The safe decomposition method of niobium-tantalum-iron alloy according to claim 1, characterized in that: The step 3 specifically includes: using a high-precision peristaltic pump to uniformly add 98% concentrated sulfuric acid to the slurry at a dropping speed of 1 L / (45-60) min, and stirring at a speed of 300-400 rpm during the addition of the concentrated sulfuric acid to quickly disperse the sulfuric acid; wherein the mass volume ratio of the niobium tantalum iron alloy to the concentrated sulfuric acid is 1 kg:(0.8-1.2) L; and the dropping tube of the high-precision peristaltic pump is inserted 5-10 cm below the slurry liquid surface to prevent the sulfuric acid from contacting the air and generating acid mist.

6. The safe decomposition method of niobium-tantalum-iron alloy according to claim 1, characterized in that: In step 4, the mass volume ratio of the niobium-tantalum-iron alloy to the hydrofluoric acid is 1 kg: (1-2) L; step 4 specifically includes: S41: After the sulfuric acid is added dropwise for a preset time, 2 / 3 of the volume of hydrofluoric acid is added to the slurry at a dropwise rate of 250-300 ml / hour; S42: When the amount of hydrogen released is significantly reduced or there is no obvious reaction on the liquid surface, the remaining 1 / 3 volume of hydrofluoric acid is added to the slurry at a dropwise rate of 300-400 ml / hour.

7. The safe decomposition method of niobium-tantalum-iron alloy according to claim 6, characterized in that: During the hydrofluoric acid addition process, the temperature in the reactor is monitored in real time, and the temperature sensor is linked to the hydrofluoric acid addition pump; when the temperature rises to 68°C, the hydrofluoric acid addition pump automatically reduces the rate by 10-15%; when the temperature is greater than 70°C, the hydrofluoric acid addition pump suspends the addition of hydrofluoric acid and resumes acid addition when the temperature drops below 65°C.

8. The safe decomposition method of niobium-tantalum-iron alloy according to claim 7, characterized in that: The reactor adopts a jacketed water bath reactor, and a cooling coil is provided in the jacket to open the cooling water for cooling when the temperature is greater than 70°C; wherein, temperature sensors are provided at the top, middle and bottom of the reactor, and the average value of the detection results of the three temperature sensors is taken as the basis for regulating the hydrofluoric acid addition pump and opening the cooling water.

9. The method for safe decomposition of niobium-tantalum-iron alloy according to claim 1, characterized in that: In step 5, if there is an obvious reaction on the surface of the solution, or the hydrogen concentration is greater than the preset hydrogen concentration threshold, hydrofluoric acid is continued to be added to the slurry to continue the reaction; if there is no obvious reaction on the surface of the solution and the hydrogen concentration is lower than the preset hydrogen concentration threshold, sulfuric acid and hydrofluoric acid are added to the solution so that the concentrations of sulfuric acid and hydrofluoric acid in the final extraction solution reach the preset concentration threshold, and the reaction is terminated.

10. The safe decomposition method of niobium-tantalum-iron alloy according to claim 9, characterized in that: The preset hydrogen concentration threshold is 0.1%; the sulfuric acid concentration threshold in the extraction solution is 3.75-4.25 mol / L, and the hydrofluoric acid concentration threshold is 5.5-6.5 mol / L.

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