Tantalum oxide with low Fisher particle size and preparation method thereof

Abstract

The invention provides tantalum oxide with low Fisher particle size and a preparation method thereof, and the preparation method mainly comprises the following steps: by taking fluotantalic acid as a raw material, neutralizing and precipitating by ammonia gas with the pressure intensity of 0.3-0.5 MPa and the fluotantalic acid to generate tantalum hydroxide, regulating and washing the tantalum hydroxide by dilute ammonia water with the concentration of 0.4-0.5 mol / L to remove fluorine, blow-drying by compressed air with the pressure intensity of 0.5-0.6 MPa, and drying by microwaves to obtain the tantalum oxide with low Fisher particle size. Calcining in a rotary furnace, and grinding. The low-Fisher-particle-size tantalum oxide prepared by the method can meet the particle size requirement on the raw material tantalum oxide during tantalum carbide production, has low apparent density, can be uniformly mixed with carbon, and avoids cracking of crucible equipment in the reduction process.

Description

Technical Field

[0001] The invention relates to tantalum oxide, in particular to a tantalum oxide with low Fischer-Strauss particle size and a preparation method thereof. Background Art

[0002] Tantalum niobium concentrate is decomposed by hydrofluoric acid and sulfuric acid, and then extracted and separated to obtain fluorotantalate liquid. Ammonia precipitant is added to the fluorotantalate liquid to obtain tantalum hydroxide, which is then washed to remove fluorine, dried and calcined to obtain tantalum oxide. Tantalum oxide can be used to produce lithium tantalate crystals, tantalum carbide, tantalum powder, tantalum bars, capacitors, and as an additive for optical glass. In addition, tantalum oxide is mixed with carbon and carbonized once and twice at high temperature and under hydrogen protection to produce tantalum carbide with high hardness, high melting point and good high temperature resistance. The particle size of tantalum oxide is an important factor affecting the quality of tantalum carbide.

[0003] Tantalum oxide produced by using liquid ammonia to precipitate fluorotantalate has a large Fresnel particle size. Tantalum oxide cannot be mixed with auxiliary material carbon black to achieve uniformity during use. During carbon reduction, it will cause local violent reactions and powder leakage. Severe powder leakage will cause blockage of the exhaust holes. In addition, due to uneven mixing and too high loose density of tantalum oxide, tantalum oxide will react with the crucible, causing the material to adhere to the crucible, which can easily lead to cracking of the crucible and shorten the service life of the crucible.

[0004] Chinese patent CN115893492B provides a tantalum oxide and a preparation method thereof, wherein the method allows a fluorotantalate solution to be subjected to a first precipitation at a pH value of 3-6, and a second precipitation at a pH value of 8-10, and adopts a five-stage calcination, and the equipment investment required for the calcination adopted by this method is too large. Chinese patent CN118479537A provides a production method of tantalum oxide and niobium oxide, wherein a synthesizing agent and a hydrolyzing agent are sequentially added to a fluorotantalate solution to obtain tantalum hydroxide, and the fluorotantalate solution generates tantalum hydroxide, and this method adds a step of removing sodium fluoride, which makes the risk of excessive sodium content in tantalum oxide relatively high. Summary of the invention

[0005] The technical problem to be solved by the present invention is to provide a method for preparing tantalum oxide with low Fischer-Strauss particle size. The prepared tantalum oxide with low Fischer-Strauss particle size can meet the particle size requirements of the raw material tantalum oxide in the production of tantalum carbide, and has a small bulk density and can be evenly mixed with carbon, thereby avoiding cracking of the crucible equipment during the reduction process.

[0006] In order to solve the above technical problems, the technical solution of the present invention is:

[0007] A method for preparing tantalum oxide with low Fischer-Strauss particle size comprises the following steps:

[0008] S1. Pump the aqueous solution of tantalum fluoride into a neutralization precipitation tank, introduce ammonia gas and start stirring until the pH value of the aqueous solution of tantalum fluoride reaches 9 - 10 to obtain tantalum hydroxide precipitate;

[0009] S2. Transfer the tantalum hydroxide precipitate obtained in step S1 into a No. 1 filter press, wash it with water for 35 - 45 min, then wash it with dilute ammonia water for 35 - 45 min, and then dry it with compressed air for 25 - 35 min to obtain a tantalum hydroxide filter cake;

[0010] S3. Add pure water into a pulping tank, then add concentrated ammonia water, start stirring and add the tantalum hydroxide filter cake obtained in step S2, and pulp for 35 - 45 min to obtain a tantalum hydroxide slurry;

[0011] S4. Pump the tantalum hydroxide slurry obtained in step S3 into a No. 2 filter press, dry it with compressed air for 5 - 15 min, then wash it with pure water in a circulating manner for 35 - 45 min, and then dry it with compressed air for 1.5 - 2.5 h to obtain tantalum hydroxide;

[0012] S5. Dry the tantalum hydroxide obtained in step S4 with a microwave drying device, and then transfer it into a rotary kiln for calcination for 1.2 - 2 h to obtain tantalum oxide;

[0013] S6. Grind the tantalum oxide obtained in step S5 with a crushing and vibrating sieving mill to obtain tantalum oxide with a low Fisher particle size.

[0014] Further, in step S1 of the present invention, the acidity of the aqueous solution of tantalum fluoride is 0.9 - 1.5 mol / L; when the concentration of tantalum oxide in terms of the aqueous solution of tantalum fluoride is 26 - 50 g / L, the volume of the aqueous solution of tantalum fluoride loaded in a single neutralization precipitation tank is 3 - 4 m 3 , when the concentration of tantalum oxide in terms of the aqueous solution of tantalum fluoride is 50 - 90 g / L, the volume of the aqueous solution of tantalum fluoride loaded in a single neutralization precipitation tank is 2.6 - 3 m 3 .

[0015] Further, in step S1 of the present invention, the neutralization precipitation tank is a steel-lined plastic reaction tank with an inner diameter of 1.8 m and a height of 2 m, the pressure of ammonia gas is 0.3 - 0.5 MPa, the introduction time of ammonia gas is 0.9 - 2.6 h, and the stirring frequency is 42 Hz.

[0016] Further, in step S2 of the present invention, the concentration of the dilute ammonia water is 0.4 - 0.5 mol / L, which is diluted from the concentrated ammonia water with a concentration of 12 mol / L before use; the pressure of the compressed air is 0.5 - 0.6 MPa.

[0017] Further, in step S3 of the present invention, the concentration of the concentrated ammonia water is 12 mol / L, the volume ratio of pure water to concentrated ammonia water is 20:1, and the stirring frequency is 42 Hz.

[0018] Further, in step S4 of the present invention, the pressure of the compressed air is 0.5 - 0.6 MPa.

[0019] Further, in step S5 of the present invention, the temperatures of the three zones of the microwave drying equipment are 70°C, 85°C, and 70°C, the speed of the material conveying belt is 3 - 5 m / h, and the frequency of the feeding motor is 1 - 5 Hz.

[0020] Further, in step S5 of the present invention, the temperatures of the three zones of the rotary kiln are 850°C, 850°C, and 750°C.

[0021] Further, in step S6 of the present invention, the crushing vibrating sieving machine is equipped with a 70 - mesh stainless - steel sieve.

[0022] Another technical problem to be solved by the present invention is to provide tantalum oxide with low Fisher grain size prepared by the above - mentioned preparation method.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] 1) The Fisher grain size of the tantalum oxide with low Fisher grain size prepared by the present invention is less than 1 μm, and the apparent density can reach 0.6 - 0.9 g / cm 3 .

[0025] 2) The filter press used in the present invention has two functions of pressing and air - blowing. Drying the tantalum hydroxide filter cake with compressed air is conducive to realizing on - line production control.

[0026] 3) In the tantalum oxide grinding step of the present invention, the original 60 - mesh stainless - steel sieve is changed to a 70 - mesh stainless - steel sieve, taking into account both the grinding output and the factor that 100% of the finished product grain size passes through a 60 - mesh sieve. Specific Embodiments

[0027] The following will describe the present invention in detail with reference to specific embodiments. Here, the illustrative embodiments of the present invention and the descriptions are used to explain the present invention, but not to limit the present invention.

[0028] Example 1

[0029] Prepare tantalum oxide with low Fisher grain size according to the following steps:

[0030] S1. Pump the aqueous solution of tantalum fluoride with a concentration of 38.4 g / L of 9000 L of tantalum pentoxide and an acidity of 1.2 mol / L into neutralization and precipitation tanks No. 1 - 3 evenly by a pump, and pump the aqueous solution of tantalum fluoride with a concentration of 51.8 g / L of 2700 L of tantalum pentoxide and an acidity of 1.5 mol / L into neutralization and precipitation tank No. 4 by a pump. Introduce ammonia gas with a pressure of 0.4 MPa into neutralization and precipitation tanks No. 1 - 4 respectively and start stirring until the pH value of the aqueous solution of tantalum fluoride reaches 9.5 to obtain tantalum hydroxide precipitate. When the pH value of the solution is detected with a pH test paper to be 9.5, the time taken for neutralization and precipitation tanks No. 1 - 4 is 1.25 h, 1.2 h, 1.3 h, and 1.5 h respectively, and the precipitation end temperatures are 66 °C, 65 °C, 67 °C, and 70 °C respectively; among them, the neutralization and precipitation tank is a steel - lined plastic reaction tank with an inner diameter of 1.8 m and a height of 2 m, and the stirring frequency is 42 Hz;

[0031] S2. Transfer the tantalum hydroxide precipitate obtained in step S1 into Filter Press No. 1 (model: XAYZGM80 / 1000 - UK), wash it with water for 40 min and then wash it with 10 m 3 dilute ammonia water with a concentration of 0.4 mol / L for 40 min, and then blow it dry with compressed air with a pressure of 0.5 MPa for 30 min to obtain tantalum hydroxide filter cake; among them, the dilute ammonia water is diluted from concentrated ammonia water with a concentration of 12 mol / L before use;

[0032] S3. Add 10 m 3 pure water into the pulping tank, then add 0.5 m 3 concentrated ammonia water with a concentration of 12 mol / L, start stirring and add the tantalum hydroxide filter cake obtained in step S2. The stirring frequency is 42 Hz, and pulp for 40 min to obtain tantalum hydroxide slurry;

[0033] S4. Pump the tantalum hydroxide slurry obtained in step S3 into Filter Press No. 2 (model: XAYZGM80 / 1000 - UK), blow it dry with compressed air with a pressure of 0.5 MPa for 10 min and then wash it with 10 m 3 pure water in a cycle for 40 min (the discharged washing water is used as recycled water for the next batch), and then blow it dry with compressed air with a pressure of 0.5 MPa for 2 h to obtain tantalum hydroxide;

[0034] S5. Dry the tantalum hydroxide obtained in step S4 with a microwave drying device, and then transfer it to a rotary kiln for calcination for 1.5 h to obtain tantalum oxide; among them, the three - zone temperature of the microwave drying device is 70 °C, 85 °C, 70 °C, the speed of the material conveyor belt is 5 m / h, the frequency of the feeding motor is 2 Hz, and the three - zone temperature of the rotary kiln is 850 °C, 850 °C, 750 °C;

[0035] S6. Grind the tantalum oxide obtained in step S5 with a crushing and vibrating sieve powder machine equipped with a 70 - mesh stainless - steel screen to obtain tantalum oxide with a low Fisher particle size.

[0036] The Fisher size of the tantalum oxide with low Fisher size prepared in Example 1 is 0.95 μm, and the loose bulk density is 0.86 g / cm 3 , and the D50 analyzed by a laser particle size analyzer is 2.28 μm.

[0037] Example 2

[0038] The tantalum oxide with low Fisher size is prepared according to the following steps:

[0039] S1. The aqueous solution of fluotantalic acid with a concentration of 37.1 g / L and an acidity of 1.1 mol / L of 12800 L of tantalum oxide is evenly pumped into neutralization and precipitation tanks No. 1-4 by a pump, and ammonia gas with a pressure of 0.5 MPa is introduced into neutralization and precipitation tanks No. 1-4 respectively, and stirring is started until the pH value of the aqueous solution of fluotantalic acid reaches 10 to obtain tantalum hydroxide precipitate. When the pH value of the solution is detected with a pH test paper to be 10, the time used for neutralization and precipitation tanks No. 1-4 is 1.3, 1.2, 1.3, and 1.25 h respectively, and the precipitation end temperatures are 64, 65, 64, and 66 °C respectively; among them, the neutralization and precipitation tank is a steel-lined plastic reaction tank with an inner diameter of 1.8 m and a height of 2 m, and the stirring frequency is 42 Hz;

[0040] S2. The tantalum hydroxide precipitate obtained in step S1 is transferred into Filter Press No. 1 (model XAYZGM80 / 1000-UK), washed with water for 35 min and then washed with 10 m 3 dilute ammonia water with a concentration of 0.5 mol / L for 35 min, and then dried with compressed air with a pressure of 0.6 MPa for 25 min to obtain a tantalum hydroxide filter cake; among them, the dilute ammonia water is diluted from concentrated ammonia water with a concentration of 12 mol / L before use;

[0041] S3. 10 m 3 pure water is added into the pulping tank, and then 0.5 m 3 concentrated ammonia water with a concentration of 12 mol / L is added. After starting stirring, the tantalum hydroxide filter cake obtained in step S2 is added, and the stirring frequency is 42 Hz. Pulping is carried out for 35 min to obtain a tantalum hydroxide slurry;

[0042] S4. The tantalum hydroxide slurry obtained in step S3 is pumped into Filter Press No. 2 (model XAYZGM80 / 1000-UK), dried with compressed air with a pressure of 0.6 MPa for 5 min and then washed with 10 m 3 pure water by circulating washing for 35 min (the discharged washing water is used as recycled water for the next batch), and then dried with compressed air with a pressure of 0.6 MPa for 1.5 h to obtain tantalum hydroxide;

[0043] S5. Dry the tantalum hydroxide obtained in step S4 using a microwave drying equipment, and then transfer it to a rotary kiln for calcination for 1.2 h to obtain tantalum oxide. Among them, the temperatures of the three zones of the microwave drying equipment are 70 °C, 85 °C, and 70 °C, the speed of the material conveying belt is 3 m / h, the frequency of the feeding motor is 5 Hz, and the temperatures of the three zones of the rotary kiln are 850 °C, 850 °C, and 750 °C;

[0044] S6. Grind the tantalum oxide obtained in step S5 using a crushing and vibrating sieving machine equipped with a 70-mesh stainless steel screen to obtain tantalum oxide with a low Fisher particle size.

[0045] The Fisher particle size of the tantalum oxide with a low Fisher particle size prepared in Example 2 is 0.87 μm, and the loose bulk density is 0.84 g / cm 3 , and the D50 analyzed by a laser particle size analyzer is 2.08 μm.

[0046] Example 3

[0047] Prepare tantalum oxide with a low Fisher particle size according to the following steps:

[0048] S1. Use a pump to evenly pump 8600 L of an aqueous solution of fluotantalic acid with a tantalum pentoxide concentration of 68 g / L and an acidity of 1.5 mol / L into neutralization precipitation tanks No. 1-2. Introduce ammonia gas with a pressure of 0.3 MPa into neutralization precipitation tanks No. 1-2 respectively and start stirring until the pH value of the aqueous solution of fluotantalic acid reaches 9 to obtain tantalum hydroxide precipitate. When the pH value of the solution is detected with a pH test paper to be 9, the time taken for neutralization precipitation tanks No. 1-3 is 2.3, 2.2, and 2.5 h respectively, and the precipitation end temperatures are 75, 73, and 76 °C respectively. Among them, the neutralization precipitation tank is a steel-lined plastic reaction tank with an inner diameter of 1.8 m and a height of 2 m, and the stirring frequency is 42 Hz;

[0049] S2. Transfer the tantalum hydroxide precipitate obtained in step S1 to a No. 1 filter press (model XAYZGM80 / 1000-UK), wash it with water for 45 min, then wash it with 10 m 3 dilute ammonia water with a concentration of 0.4 mol / L for 45 min, and then blow it dry with compressed air with a pressure of 0.5 MPa for 35 min to obtain a tantalum hydroxide filter cake. Among them, the dilute ammonia water is diluted from concentrated ammonia water with a concentration of 12 mol / L before use;

[0050] S3. Add 10 m 3 pure water into the pulping tank, then add 0.5 m 3 concentrated ammonia water with a concentration of 12 mol / L, start stirring and add the tantalum hydroxide filter cake obtained in step S2, with a stirring frequency of 42 Hz, and pulp for 45 min to obtain a tantalum hydroxide slurry;

[0051] S4. Pump the tantalum hydroxide slurry obtained in step S3 into a No. 2 filter press (model XAYZGM80 / 1000-UK), blow it dry with compressed air at a pressure of 0.6 MPa for 15 min, and then wash it with 10 m 3 pure water in a circulating manner for 45 min (the discharged washing water is used as recycled water for the next batch), and then blow it dry with compressed air at a pressure of 0.5 MPa for 1.5 h to obtain tantalum hydroxide;

[0052] S5. Dry the tantalum hydroxide obtained in step S4 with a microwave drying device, and then transfer it to a rotary kiln for calcination for 2 h to obtain tantalum oxide; among them, the temperatures of the three zones of the microwave drying device are 70 °C, 85 °C, and 70 °C, the speed of the material conveying belt is 4 m / h, the frequency of the feeding motor is 1 Hz, and the temperatures of the three zones of the rotary kiln are 850 °C, 850 °C, and 750 °C;

[0053] S6. Grind the tantalum oxide obtained in step S5 with a crushing and vibrating sieve powder machine equipped with a 70-mesh stainless steel screen to obtain tantalum oxide with a low Fisher particle size.

[0054] The Fisher particle size of the tantalum oxide with a low Fisher particle size prepared in Example 3 is 0.75 μm, and the loose bulk density is 0.79 g / cm 3 , and the D50 analyzed by a laser particle size analyzer is 1.76 μm.

[0055] Comparative Example 1

[0056] Prepare tantalum oxide according to the following steps:

[0057] S1. Pump 8600 L of an aqueous solution of fluotantalic acid with a concentration of 68 g / L of tantalum oxide and an acidity of 1.5 mol / L into neutralization precipitation tanks No. 1-2 on average, introduce ammonia gas with a pressure of 0.2 MPa into neutralization precipitation tanks No. 1-2 respectively, and start stirring until the pH value of the aqueous solution of fluotantalic acid reaches 9.5 to obtain tantalum hydroxide precipitate. When the pH value of the solution is detected with a pH test paper to be 9.5, the times used for neutralization precipitation tanks No. 1-2 are 3.6 and 4 h respectively, and the precipitation end temperatures are 72 and 74 °C respectively; among them, the neutralization precipitation tank is a steel-lined plastic reaction tank with an inner diameter of 1.8 m and a height of 2 m, and the stirring frequency is 42 Hz;

[0058] S2. Transfer the tantalum hydroxide precipitate obtained in step S1 into a No. 1 filter press (model XAYZGM80 / 1000-UK), wash it with water for 40 min, then wash it with dilute ammonia water for 40 min, and then blow it dry with compressed air at a pressure of 0.5 MPa for 30 min to obtain a tantalum hydroxide filter cake; among them, the concentration of the dilute ammonia water is 0.4 mol / L, and it is diluted from concentrated ammonia water with a concentration of 12 mol / L before use;

[0059] S3. Add 10 m 3 pure water into the pulping tank, and then add 0.5 m3 Add the tantalum hydroxide filter cake obtained in step S2 to concentrated ammonia water with a concentration of 12 mol / L, start stirring, with a stirring frequency of 42 Hz, and prepare a tantalum hydroxide slurry for 40 min to obtain a tantalum hydroxide slurry;

[0060] S4. Pump the tantalum hydroxide slurry obtained in step S3 into a No. 2 filter press (model XAYZGM80 / 1000-UK), dry it with compressed air at a pressure of 0.5 MPa for 10 min, and then wash it with 10 m 3 of pure water in a circulating manner for 40 min (the discharged washing water is used as recycled water for the next batch), and then dry it with compressed air at a pressure of 0.5 MPa for 2 h to obtain tantalum hydroxide;

[0061] S5. Dry the tantalum hydroxide obtained in step S4 with a microwave drying device, and then transfer it to a rotary kiln for calcination for 1.5 h to obtain tantalum oxide; among them, the temperatures of the three zones of the microwave drying device are 70 °C, 85 °C, and 70 °C, the speed of the material conveying belt is 5 m / h, the frequency of the feeding motor is 2 Hz, and the temperatures of the three zones of the rotary kiln are 850 °C, 850 °C, and 750 °C;

[0062] S6. Grind the tantalum oxide obtained in step S5 with a crushing and vibrating sieve powder machine equipped with a 70-mesh stainless steel screen to obtain tantalum oxide with a low Fisher particle size.

[0063] The Fisher particle size of the tantalum oxide prepared in Comparative Example 1 is 1.5 μm, and the apparent density is 1.36 g / cm 3 , and the D50 analyzed by a laser particle size analyzer is 0.9 μm.

[0064] Comparative Example 2

[0065] Prepare tantalum oxide according to the following steps:

[0066] S1. Pump 7800 L of an aqueous solution of fluotantalic acid with a tantalum pentoxide concentration of 29 g / L and an acidity of 0.9 mol / L into neutralization precipitation tanks 1-2 on average by a pump, and pump 7100 L of an aqueous solution of fluotantalic acid with a tantalum pentoxide concentration of 37.4 g / L and an acidity of 1.0 mol / L into neutralization precipitation tanks 3-4 by a pump. Use liquid ammonia for precipitation, set the stirring frequency at 42 HZ, open the liquid ammonia valve leading to the aqueous solution of fluotantalic acid to 6-8%, and continuously introduce liquid ammonia until the pH value of the aqueous solution of fluotantalic acid reaches 9.5 to obtain a tantalum hydroxide precipitate. When the pH value of the solution is detected with a pH test paper to be 9.5, the times taken for neutralization precipitation tanks 1-4 are 1.6, 1.7, 1.5, and 1.6 h respectively, and the precipitation end temperatures are 69, 68, 65, and 68 °C respectively; among them, the neutralization precipitation tank is a steel-lined plastic reaction tank with an inner diameter of 1.8 m and a height of 2 m;

[0067] S2. Transfer the tantalum hydroxide precipitate obtained in step S1 into Filter Press No. 1 (model: XAYZGM80 / 1000-UK), wash it with water for 40 min, then wash it with dilute ammonia water for 40 min, and then dry it with compressed air at a pressure of 0.5 MPa for 30 min to obtain a tantalum hydroxide filter cake; wherein, the concentration of the dilute ammonia water is 0.4 mol / L, and it is diluted from concentrated ammonia water with a concentration of 12 mol / L before use;

[0068] S3. Add 10 m 3 of pure water into the pulping tank, then add 0.5 m 3 of concentrated ammonia water with a concentration of 12 mol / L. After starting the stirring, add the tantalum hydroxide filter cake obtained in step S2, and the stirring frequency is 42 Hz. Pulp for 40 min to obtain a tantalum hydroxide slurry;

[0069] S4. Pump the tantalum hydroxide slurry obtained in step S3 into Filter Press No. 2 (model: XAYZGM80 / 1000-UK), dry it with compressed air at a pressure of 0.5 MPa for 10 min, then wash it with 10 m 3 of pure water in a circulating manner for 40 min (the discharged washing water is used as the recycled water for the next batch), and then dry it with compressed air at a pressure of 0.5 MPa for 2 h to obtain tantalum hydroxide;

[0070] S5. Dry the tantalum hydroxide obtained in step S4 with a microwave drying device, and then transfer it into a rotary kiln for calcination for 1.5 h to obtain tantalum oxide; wherein, the temperatures of the three zones of the microwave drying device are 70 °C, 85 °C, and 70 °C, the speed of the material conveying belt is 5 m / h, the frequency of the feeding motor is 2 Hz, and the temperatures of the three zones of the rotary kiln are 850 °C, 850 °C, and 750 °C;

[0071] S6. Grind the tantalum oxide obtained in step S5 with a crushing and vibrating sieving machine equipped with a 70-mesh stainless steel screen to obtain tantalum oxide with a low Fisher particle size.

[0072] The Fisher particle size of the tantalum oxide prepared in Comparative Example 2 is 2.3 μm, and the loose bulk density is 1.5 g / cm 3 , and the D50 analyzed by a laser particle size analyzer is 0.81 μm.

[0073] Comparing Comparative Example 1 with Example 1, in Comparative Example 1, the volume of the liquid material precipitated in a single precipitation tank is relatively large, and the ammonia pressure is relatively small, resulting in a relatively long precipitation time for the whole process. Finally, the Fisher particle size and loose bulk density of the calcined tantalum oxide do not meet the usage requirements. Comparing Comparative Example 2 with Example 1, in Comparative Example 2, liquid ammonia is used to precipitate the tantalum solution, and the precipitation completion time is relatively short. After the calcined tantalum oxide is ground, the tantalum oxide product has a relatively obvious hard granular situation in terms of touch, a large loose bulk density, and a relatively large Fisher particle size. While the tantalum oxide samples produced in Examples 1-3 of the present invention are in a loose cotton shape, the Fisher particle sizes are all less than 1 μm, and the loose bulk densities are 0.6 - 0.9 g / cm3 , which can meet the usage requirements of customers.

[0074] The above embodiments merely illustrate the principles and effects of the present invention and are not intended to limit the present invention. Any person familiar with this technology can modify or change the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or changes made by those with ordinary knowledge in the technical field without departing from the spirit and technical idea disclosed by the present invention should still be covered by the claims of the present invention.

Claims

1. A method for preparing tantalum oxide with low Fischer-Strauss particle size, characterized in that: The following steps are involved: S1. Pumping the fluorotantalate aqueous solution into a neutralization precipitation tank, introducing ammonia gas and stirring until the pH value of the fluorotantalate aqueous solution reaches 9-10 to obtain tantalum hydroxide precipitate; S2. The tantalum hydroxide precipitate obtained in step S1 is transferred to filter press No. 1, washed with water for 35-45 min, then washed with dilute ammonia for 35-45 min, and then dried with compressed air for 25-35 min to obtain a tantalum hydroxide filter cake; S3. Add pure water to the slurry tank, then add concentrated ammonia, start stirring and add the tantalum hydroxide filter cake obtained in step S2, and slurry for 35-45min to obtain tantalum hydroxide slurry; S4. The tantalum hydroxide slurry obtained in step S3 is pumped into filter press No. 2, dried with compressed air for 5-15 min, then washed with pure water for 35-45 min, and then dried with compressed air for 1.5-2.5 h to obtain tantalum hydroxide; S5. The tantalum hydroxide obtained in step S4 is dried by a microwave drying device and then transferred to a rotary kiln for calcination for 1.2-2h to obtain tantalum oxide; S6. Grind the tantalum oxide obtained in step S5 with a crushing and vibrating sieving machine to obtain tantalum oxide with low Fischer-Strauss particle size.

2. The method for preparing tantalum oxide with low Fischer-Strauss particle size according to claim 1, characterized in that: In step S1, the acidity of the fluorotantalate aqueous solution is 0.9-1.5 mol / L; when the concentration of the fluorotantalate aqueous solution converted to tantalum oxide is 26-50 g / L, the volume of the fluorotantalate aqueous solution loaded into a single neutralization precipitation tank is 3-4 m 3 When the concentration of tantalum oxide in fluorotantalate aqueous solution is 50-90 g / L, the volume of fluorotantalate aqueous solution loaded into a single neutralization precipitation tank is 2.6-3 m 3 .

3. The method for preparing tantalum oxide with low Fischer-Strauss particle size according to claim 1, characterized in that: In step S1, the neutralization precipitation tank is a steel-lined plastic reaction tank with an inner diameter of 1.8 meters and a height of 2 meters, the pressure of ammonia is 0.3-0.5 MPa, the introduction time of ammonia is 0.9-2.6 hours, and the stirring frequency is 42 Hz.

4. The method for preparing tantalum oxide with low Fischer-Strauss particle size according to claim 1, characterized in that: In step S2, the concentration of the dilute ammonia water is 0.4-0.5 mol / L, and it is diluted with concentrated ammonia water with a concentration of 12 mol / L before use; the pressure of the compressed air is 0.5-0.6 MPa.

5. The method for preparing tantalum oxide with low Fischer-Strauss particle size according to claim 1, characterized in that: In step S3, the concentration of concentrated ammonia water is 12 mol / L, the volume ratio of pure water to concentrated ammonia water is 20:1, and the stirring frequency is 42 Hz.

6. The method for preparing tantalum oxide with low Fischer-Strauss particle size according to claim 1, characterized in that: In step S4, the pressure of the compressed air is 0.5-0.6 MPa.

7. The method for preparing tantalum oxide with low Fischer-Strauss particle size according to claim 1, characterized in that: In step S5, the temperatures of the three zones of the microwave drying equipment are 70° C., 85° C., and 70° C., the speed of the material conveyor belt is 3-5 m / h, and the frequency of the feed motor is 1-5 Hz.

8. The method for preparing tantalum oxide with low Fischer-Strauss particle size according to claim 1, characterized in that: In step S5, the temperatures of the three zones of the rotary kiln are 850°C, 850°C, and 750°C.

9. The method for preparing tantalum oxide with low Fischer-Strauss particle size according to claim 1, characterized in that: In step S6, the crushing and vibrating powder screening machine is equipped with a 70-mesh stainless steel screen.

10. Tantalum oxide with low Fresnel particle size obtained by the preparation method according to claims 1 to 9.