Cooling crystallization process for potassium fluotantalate

Abstract

The invention provides a potassium fluotantalate cooling crystallization process which comprises the following steps: adding hydrofluoric acid and water vapor into a fluotantalic acid solution, adjusting the mass concentration of tantalum in a mixed solution to be 30-40g / L and the acidity to be 2.0-2.5 mol / L, then adding potassium chloride, and carrying out conversion reaction on the mixed solution to prepare a potassium fluotantalate solution; transferring the potassium fluotantalate solution into a jacket cooling crystallization tank, and cooling in three steps: (1) naturally cooling the potassium fluotantalate solution from 90-100 DEG C to 50-55 DEG C; (2) introducing tap water with the temperature of 20-30 DEG C into a jacket of the jacket cooling crystallization tank, and cooling the potassium fluotantalate solution to 20-30 DEG C; and (3) introducing chilled water with the temperature of 3-8 DEG C into a jacket of the jacket cooling crystallization tank, and cooling the potassium fluotantalate solution to 3-8 DEG C to obtain the potassium fluotantalate crystal. By controlling the concentration of the raw material tantalum liquid and the cooling crystallization process, the potassium fluotantalate product with the granularity meeting customer requirements is prepared, the granularity of the potassium fluotantalate product passing through a 10-100-mesh sieve is 95% or above, the granularity of the potassium fluotantalate product larger than 10 meshes is 0, and the granularity of the potassium fluotantalate product smaller than 100 meshes is 5% or below.

Description

Technical Field

[0001] The invention belongs to the technical field of potassium fluorotantalate preparation, and more specifically relates to a potassium fluorotantalate cooling crystallization process. Background Art

[0002] Potassium fluorotantalate is mainly used to prepare metallic tantalum and other tantalum compounds. High specific capacity metallic tantalum powder is used to make tantalum electrolytic capacitors. Its quality will directly affect the performance of tantalum electrolytic capacitors.

[0003] At present, the preparation process of potassium fluorotantalate is: decomposing tantalum-niobium ore by mixed acid of hydrofluoric acid and sulfuric acid, extracting, pickling, de-niobium and de-tantalum in hydrofluoric acid-sulfuric acid-sec-octanol or methyl isobutyl ketone system to obtain tantalum liquid, adding hydrofluoric acid and water vapor to the tantalum liquid to adjust the mass concentration and acidity of tantalum, heating the solution to 90-100°C, adding potassium chloride or potassium fluoride and stirring to convert the solution, and after the solution conversion is completed, pouring the coolant into a cooling crystallization tank, letting it cool naturally for 4-6 hours, and then forcibly cooling it for 12-16 hours, that is, completing the entire potassium fluorotantalate crystallization process, and then extracting the crystallization mother liquor, and then transferring the potassium fluorotantalate crystals to a washing and filtration tank, washing, filtering and drying to obtain the potassium fluorotantalate product.

[0004] The particle size of the prepared potassium fluorotantalate product is an important indicator to measure the performance of the potassium fluorotantalate product. At present, our company adopts the conventional potassium fluorotantalate preparation process to produce potassium fluorotantalate, and adds hydrofluoric acid and water vapor to the raw tantalum liquid to adjust the mass concentration of tantalum to 40-45g / L (calculated as tantalum oxide). However, the particle size of the prepared potassium fluorotantalate product is difficult to meet the customer's requirements: more than 95% pass through a 10-100 mesh sieve, 0% are larger than 10 mesh, and less than 5% are smaller than 100 mesh. Summary of the invention

[0005] The object of the present invention is to provide a potassium fluorotantalate cooling crystallization process, so as to prepare a potassium fluorotantalate product with a particle size that meets customer requirements by controlling the concentration of the raw material tantalum liquid and the cooling crystallization process: more than 95% of the particles passing through a 10-100 mesh sieve, 0% of the particles larger than 10 mesh, and less than 5% of the particles smaller than 100 mesh.

[0006] To achieve the above object, the present invention provides a cooling crystallization process of potassium fluorotantalate, comprising the following steps:

[0007] Adding hydrofluoric acid and water vapor to the fluorotantalate solution to adjust the mass concentration of tantalum in the mixed solution to 30-40 g / L and the acidity to 2.0-2.5 mol / L, then adding potassium chloride to make the mixed solution undergo a conversion reaction to prepare a potassium fluorotantalate solution;

[0008] The potassium fluorotantalate solution is transferred into a jacket cooling crystallization tank and cooled in three steps:

[0009] (1) naturally cooling the potassium fluorotantalate solution from 90-100° C. to 50-55° C.;

[0010] (2) introducing tap water at 20-30° C. into the jacket of the jacket cooling crystallization tank to cool the potassium fluorotantalate solution to 20-30° C.;

[0011] (3) introducing 3-8° C. chilled water into the jacket of the jacket cooling crystallization tank to cool the potassium tantalate solution to 3-8° C. to obtain potassium tantalate crystals.

[0012] Furthermore, the room temperature during the natural cooling process is 20-35° C., and the stirring speed during the cooling process is 0-17 r / min.

[0013] Furthermore, the stirring speed of the tap water cooling process is 0-10r / min.

[0014] Furthermore, the stirring speed of the chilled water cooling process is 0-5r / min.

[0015] Furthermore, the stirring speed during the three-step cooling process is gradually reduced.

[0016] Furthermore, the stirring speed of the natural cooling process is 10-17 r / min, the stirring speed of the tap water cooling process is 5-10 r / min, and the stirring speed of the chilled water cooling process is 1-5 r / min.

[0017] Furthermore, based on the molar amount of potassium ions, the amount of potassium chloride added is 1.1-1.2 times the theoretical calculated amount.

[0018] Furthermore, the temperature of the conversion reaction is 90-100° C., and the reaction time is 0.5-1 h.

[0019] Furthermore, the mass concentration of tantalum in the mixed solution is 32-35 g / L.

[0020] Compared with the prior art, the present invention has the following technical effects:

[0021] The potassium fluorotantalate cooling crystallization process of the present invention adjusts the mass concentration of tantalum in the mixed solution to 30-40 g / L and the acidity to 2.0-2.5 mol / L, and transfers the potassium fluorotantalate solution into a jacketed cooling crystallization tank for cooling in three steps, so that the particle size of the prepared potassium fluorotantalate product meets the requirements of customers, that is, the potassium fluorotantalate product passing through a 10-100 mesh sieve is more than 95%, the potassium fluorotantalate product larger than 10 mesh is 0, and the potassium fluorotantalate product smaller than 100 mesh is less than 5%. DETAILED DESCRIPTION

[0022] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0023] The terms used in the embodiments of the present invention are only for the purpose of describing specific embodiments, and are not intended to limit the present invention. The singular forms "a", "said" and "the" used in the embodiments of the present invention and the appended claims are also intended to include plural forms, unless the context clearly indicates other meanings.

[0024] The embodiment of the present invention provides a cooling crystallization process of potassium fluorotantalate, comprising the following steps:

[0025] 1) adding hydrofluoric acid and water vapor to a fluorotantalate solution to adjust the mass concentration of tantalum in the mixed solution to 30-40 g / L and the acidity to 2.0-2.5 mol / L, then adding potassium chloride to allow the mixed solution to undergo a conversion reaction to prepare a potassium fluorotantalate solution;

[0026] 2) The potassium fluorotantalate solution is transferred into a jacket cooling crystallization tank and cooled in three steps:

[0027] (1) Naturally cool the potassium fluorotantalate solution from 90-100°C to 50-55°C;

[0028] (2) introducing tap water at 20-30° C. into the jacket of the jacket cooling crystallization tank to cool the potassium fluorotantalate solution to 20-30° C.;

[0029] (3) introducing 3-8° C. chilled water into the jacket of the jacket cooling crystallization tank to cool the potassium fluorotantalate solution to 3-8° C. to obtain potassium fluorotantalate crystals.

[0030] In the above step 1), the fluorotantalate solution of the embodiment of the present invention is obtained from the tantalum-niobium hydrometallurgy, that is, the tantalum-niobium ore raw material is decomposed and leached with hydrofluoric acid and sulfuric acid, and the leached ore pulp is extracted with octanol as an extractant, and the extract is subjected to acid washing, impurity removal, and de-niobium to obtain a fluoroniobic acid solution and an organic phase after de-niobium, and the organic phase after de-niobium is de-tantalized to obtain a fluorotantalate solution. The tantalum content (in terms of Tb) in the fluorotantalate solution is 1.3477 W / m2. 2 O 5The mass concentration of tantalum in the mixed solution is adjusted to 30-40 g / L and the acidity to 2.0-2.5 mol / L by adding hydrofluoric acid and water vapor to the fluorotantalate solution. The inventors have found that if the mass concentration of tantalum in the mixed solution is controlled to be relatively high, such as generally controlled to be above 40-45 g / L, the pass rate of the prepared potassium fluorotantalate product with a particle size between 10-100 mesh is usually below 60%, which is difficult to meet the customer's requirement of more than 95%. This may be because when the mass concentration of tantalum in the mixed solution is relatively high, potassium fluorotantalate is more easily hydrolyzed in the subsequent conversion reaction to form white powder 4KF·Ta 2 O 5 2TaF 5 The substance results in a decrease in the yield of potassium fluorotantalate products, and the particle size is difficult to meet production requirements. Therefore, in the embodiment of the present invention, the mass concentration of tantalum in the mixed solution is adjusted to 30-40 g / L, preferably, the mass concentration of tantalum in the mixed solution is 32-35 g / L, and the acidity is controlled to 2.0-2.5 mol / L, so as to facilitate the preparation of potassium fluorotantalate products that meet customer requirements.

[0031] In the above step 1), the amount of potassium chloride added is calculated according to the required stoichiometric amount of the conversion to generate potassium fluorotantalate. In the embodiment of the present invention, the amount of potassium chloride added is 1.1-1.2 times the theoretical calculated amount based on the molar amount of potassium ions.

[0032] In the above step 1), the embodiment of the present invention controls the temperature of the conversion reaction to be 90-100° C. and the reaction time to be 0.5-1 h. Under the conversion reaction conditions, fluorotantalate and potassium chloride in the solution undergo a chemical reaction to generate a potassium fluorotantalate product.

[0033] In the above step 2), the embodiment of the present invention cools the prepared potassium fluorotantalate solution in three steps respectively to prepare a potassium fluorotantalate product with a particle size that meets the requirements. In the natural cooling process of step (1), the room temperature of the natural cooling process of the embodiment of the present invention is 20-35°C, and the stirring speed of the cooling process is controlled to be 0-17r / min. In the tap water cooling process of step (2), the stirring speed of the tap water cooling process is controlled to be 0-10r / min. In the chilled water cooling process of step (3), the stirring speed of the chilled water cooling process is controlled to be 0-5r / min. In these three cooling processes, the stirring speed is gradually reduced. Preferably, the stirring speed of the natural cooling process is 10-17r / min, the stirring speed of the tap water cooling process is 5-10r / min, and the stirring speed of the chilled water cooling process is 1-5r / min.

[0034] In the above step 2), the volume of the jacket cooling crystallization tank used in the embodiment of the present invention is 1.98m 3, specifications are Φ1200*1870.

[0035] In the three-step cooling process of step 2), the control of cooling temperature and the control of stirring speed have an important influence on the particle size of the prepared potassium fluorotantalate product. The inventors have found that the conventional one-step natural cooling or the conventional two-step cooling or improper control of stirring speed during the cooling process will result in the particle size of the prepared potassium fluorotantalate product failing to meet customer requirements.

[0036] A cooling crystallization process of potassium fluorotantalate according to an embodiment of the present invention is illustrated below by using a plurality of specific embodiments.

[0037] Example 1

[0038] Embodiment 1 of the present invention provides a cooling crystallization process for potassium fluorotantalate, comprising the following steps:

[0039] (1) adding hydrofluoric acid and water vapor to a fluorotantalate solution to adjust the mass concentration of tantalum in the mixed solution to 35 g / L and the acidity to 2.2 mol / L, then adding potassium chloride in an amount of 1.1 times the theoretical amount in terms of the molar amount of potassium ions; reacting the mixed system at 95° C. for 1 hour to prepare a potassium fluorotantalate solution;

[0040] (2) The potassium fluorotantalate solution is transferred into a jacket cooling crystallization tank and cooled in three steps:

[0041] Step 1: Allow the potassium fluorotantalate solution to cool naturally from 95°C to 55°C, the room temperature for natural cooling is 28°C, and the stirring speed during the natural cooling process is 15r / min;

[0042] Step 2: Add 25°C tap water into the jacket of the jacket cooling crystallization tank to cool the potassium fluorotantalate solution to 25°C. The stirring speed during the tap water cooling process is 8r / min.

[0043] Step 3: Pass 5°C chilled water into the jacket of the jacket cooling crystallization tank to cool the potassium fluorotantalate solution to 5°C. The stirring speed of the chilled water cooling process is 5r / min to obtain potassium fluorotantalate crystals. Screening and testing of potassium fluorotantalate crystals: 97% of the potassium fluorotantalate products passed through a 10-100 mesh sieve, 0% of the potassium fluorotantalate products larger than 10 mesh, and 3% of the potassium fluorotantalate products smaller than 100 mesh.

[0044] Example 2

[0045] Embodiment 2 of the present invention provides a cooling crystallization process for potassium fluorotantalate, comprising the following steps:

[0046] (1) adding hydrofluoric acid and water vapor to a fluorotantalate solution to adjust the mass concentration of tantalum in the mixed solution to 32 g / L and the acidity to 2.1 mol / L, then adding potassium chloride in an amount of 1.2 times the theoretical amount in terms of the molar amount of potassium ions; reacting the mixed system at 90° C. for 1 hour to prepare a potassium fluorotantalate solution;

[0047] (2) The potassium fluorotantalate solution is transferred into a jacket cooling crystallization tank and cooled in three steps:

[0048] Step 1: Naturally cool the potassium fluorotantalate solution from 90°C to 50°C, the room temperature for natural cooling is 29°C, and the stirring speed during the natural cooling process is 15r / min;

[0049] Step 2: Add 25°C tap water into the jacket of the jacket cooling crystallization tank to cool the potassium fluorotantalate solution to 25°C. The stirring speed during the tap water cooling process is 8r / min.

[0050] Step 3: Pass 5°C chilled water into the jacket of the jacket cooling crystallization tank to cool the potassium fluorotantalate solution to 5°C. The stirring speed of the chilled water cooling process is 3r / min to obtain potassium fluorotantalate crystals. Screening and testing of potassium fluorotantalate crystals: 96% of the potassium fluorotantalate products passed through a 10-100 mesh sieve, 0% of the potassium fluorotantalate products larger than 10 mesh, and 4% of the potassium fluorotantalate products smaller than 100 mesh.

[0051] Example 3

[0052] Embodiment 3 of the present invention provides a cooling crystallization process for potassium fluorotantalate, comprising the following steps:

[0053] (1) adding hydrofluoric acid and water vapor to a fluorotantalate solution to adjust the mass concentration of tantalum in the mixed solution to 38 g / L and the acidity to 2.2 mol / L, then adding potassium chloride in an amount of 1.2 times the theoretical amount in terms of the molar amount of potassium ions; reacting the mixed system at 95° C. for 0.5 h to prepare a potassium fluorotantalate solution;

[0054] (2) The potassium fluorotantalate solution is transferred into a jacket cooling crystallization tank and cooled in three steps:

[0055] Step 1: Naturally cool the potassium fluorotantalate solution from 95°C to 50°C, the room temperature for natural cooling is 27°C, and the stirring speed during the natural cooling process is 12r / min;

[0056] Step 2: Add 25°C tap water into the jacket of the jacket cooling crystallization tank to cool the potassium fluorotantalate solution to 25°C. The stirring speed during the tap water cooling process is 6r / min.

[0057] Step 3: Pass 5°C chilled water into the jacket of the jacket cooling crystallization tank to cool the potassium fluorotantalate solution to 5°C. The stirring speed of the chilled water cooling process is 2r / min to obtain potassium fluorotantalate crystals. Screening and testing of potassium fluorotantalate crystals: 95% of the potassium fluorotantalate products pass through a 10-100 mesh sieve, 0% of the potassium fluorotantalate products are larger than 10 mesh, and 5% of the potassium fluorotantalate products are smaller than 100 mesh.

[0058] Comparative Example 1

[0059] The difference from Example 1 is that in step (1), the mass concentration of tantalum in the mixed solution is adjusted to 45 g / L. The other steps are the same, and the potassium fluorotantalate crystals are screened and tested: the potassium fluorotantalate product passing through a 10-100 mesh sieve is 56%.

[0060] Comparative Example 2

[0061] The difference from Example 1 is that in step (2), the potassium fluorotantalate solution is transferred into a jacketed cooling crystallization tank and directly cooled naturally from 95° C. to room temperature 28° C. in one step, and the stirring speed during the natural cooling process is 15 r / min. The other steps are the same, and the potassium fluorotantalate crystals are screened and tested: the potassium fluorotantalate product passing through a 10-100 mesh sieve is 45%.

[0062] Comparative Example 3

[0063] The difference from Example 1 is that in step (2), the potassium tantalate fluoroate solution is transferred into a jacket cooling crystallization tank and cooled in two steps:

[0064] Step 1: Allow the potassium fluorotantalate solution to cool naturally from 95°C to 55°C, the room temperature for natural cooling is 28°C, and the stirring speed during the natural cooling process is 15r / min;

[0065] Step 2: Add 25°C tap water into the jacket of the jacket cooling crystallization tank to cool the potassium fluorotantalate solution to 25°C. The stirring speed during the tap water cooling process is 8r / min. The other steps are the same, and the potassium fluorotantalate crystals are screened and tested: 75% of the potassium fluorotantalate product passes through a 10-100 mesh sieve.

[0066] Comparative Example 4

[0067] The difference from Example 1 is that in step (2), the potassium tantalate fluoroate solution is transferred into a jacket cooling crystallization tank and cooled in two steps:

[0068] Step 1: Allow the potassium fluorotantalate solution to cool naturally from 95°C to 55°C, the room temperature for natural cooling is 28°C, and the stirring speed during the natural cooling process is 15r / min;

[0069] Step 2: Pass 5°C chilled water into the jacket of the jacket cooling crystallization tank to cool the potassium fluorotantalate solution to 5°C. The stirring speed during the chilled water cooling process is 5r / min. The other steps are the same, and the potassium fluorotantalate crystals are screened and tested: the potassium fluorotantalate product passing the 10-100 mesh sieve is 43%.

[0070] Comparative Example 5

[0071] The difference from Example 1 is that the stirring speed controlled in the three cooling processes is 15 r / min. The other steps are the same, and the potassium fluorotantalate crystals are screened and tested: the potassium fluorotantalate product passing through a 10-100 mesh sieve is 88%.

[0072] Comparative Example 6

[0073] The difference from Example 1 is that the stirring speed controlled in the three cooling processes is 5 r / min. The other steps are the same, and the potassium fluorotantalate crystals are screened and tested: 92% of the potassium fluorotantalate product passes through a 10-100 mesh sieve.

[0074] Comparative Example 7

[0075] The difference from Example 1 is that no stirring is performed during the three cooling steps, that is, the product is allowed to cool naturally. The other steps are the same, and the potassium fluorotantalate crystals are screened and tested: the potassium fluorotantalate product passing through a 10-100 mesh sieve is 81%.

[0076] Comparative Example 8

[0077] The difference between this embodiment and Example 1 is that the three-step cooling process is controlled as follows:

[0078] Step 1: Naturally cool the potassium fluorotantalate solution from 95°C to 65°C, the room temperature for natural cooling is 28°C, and the stirring speed during the natural cooling process is 15r / min;

[0079] Step 2: Add 30°C tap water into the jacket of the jacket cooling crystallization tank to cool the potassium fluorotantalate solution to 30°C. The stirring speed during the tap water cooling process is 8r / min.

[0080] Step 3: Pass 15°C chilled water into the jacket of the jacket cooling crystallization tank to cool the potassium fluorotantalate solution to 15°C. The stirring speed of the chilled water cooling process is 5r / min to obtain potassium fluorotantalate crystals. The other steps are the same, and the potassium fluorotantalate crystals are screened and tested: 90% of the potassium fluorotantalate product passes through a 10-100 mesh sieve.

[0081] The above embodiments only express several implementation methods of the present invention, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the present invention. It should be pointed out that, for a person of ordinary skill in the art, several modifications and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the present invention patent shall be subject to the attached claims.

Claims

1. A cooling crystallization process of potassium fluorotantalate, characterized in that: The following steps are involved: Adding hydrofluoric acid and water vapor to the fluorotantalate solution to adjust the mass concentration of tantalum in the mixed solution to 30-40 g / L and the acidity to 2.0-2.5 mol / L, then adding potassium chloride to make the mixed solution undergo a conversion reaction to prepare a potassium fluorotantalate solution; The potassium fluorotantalate solution is transferred into a jacket cooling crystallization tank and cooled in three steps: (1) naturally cooling the potassium fluorotantalate solution from 90-100° C. to 50-55° C.; (2) introducing tap water at 20-30° C. into the jacket of the jacket cooling crystallization tank to cool the potassium fluorotantalate solution to 20-30° C.; (3) introducing 3-8° C. chilled water into the jacket of the jacket cooling crystallization tank to cool the potassium tantalate solution to 3-8° C. to obtain potassium tantalate crystals.

2. A potassium fluorotantalate cooling crystallization process as claimed in claim 1, characterized in that: The room temperature during the natural cooling process is 20-35° C., and the stirring speed during the cooling process is 0-17 r / min.

3. A potassium fluorotantalate cooling crystallization process as claimed in claim 1, characterized in that: The stirring speed of the tap water cooling process is 0-10r / min.

4. A potassium fluorotantalate cooling crystallization process as claimed in claim 1, characterized in that: The stirring speed of the chilled water cooling process is 0-5r / min.

5. A potassium fluorotantalate cooling crystallization process as claimed in claim 1, characterized in that: The stirring speed during the three-step cooling process is gradually reduced.

6. A potassium fluorotantalate cooling crystallization process as claimed in claim 1, characterized in that: The stirring speed of the natural cooling process is 10-17 r / min, the stirring speed of the tap water cooling process is 5-10 r / min, and the stirring speed of the chilled water cooling process is 1-5 r / min.

7. A potassium fluorotantalate cooling crystallization process as claimed in claim 1, characterized in that: Calculated on the molar amount of potassium ions, the amount of potassium chloride added is 1.1-1.2 times the theoretical calculated amount.

8. The potassium fluorotantalate cooling crystallization process according to claim 1, characterized in that: The temperature of the conversion reaction is 90-100° C., and the reaction time is 0.5-1 h.

9. A cooling crystallization process for potassium fluorotantalate according to any one of claims 1 to 8, characterized in that: The mass concentration of tantalum in the mixed solution is 32-35 g / L.