A potassium chloroaluminate molten salt and a method for preparing the same

Abstract

This invention provides a potassium chloroaluminate molten salt and its preparation method. The preparation method includes: uniformly mixing dry AlCl3 and KCl raw materials and adding them to a crucible; heating the mixture in the crucible to melt the raw materials and form an AlCl3-KAlCl4 mixed molten salt; adding KCl to the molten salt in small amounts several times until no volatiles are produced in the crucible, forming a KAlCl4 molten salt; and then hot-filtering the pure KAlCl4 molten salt to obtain a pure, transparent, and impurity-free potassium chloroaluminate salt. The raw materials require an appropriate excess of AlCl3 to ensure the quality of the raw materials. After the melt is formed, there is a small amount of free AlCl3 in the molten salt. The free AlCl3 is combined with KCl by adding small amounts of KCl in multiple batches to form pure KAlCl4. This avoids the formation of free KCl due to insufficient AlCl3 in the molten salt, which would lead to high viscosity, poor fluidity, and free particles clogging the pipes and valves of the equipment. The molten salt prepared by this invention is free of free KCl, precipitates and other impurities, has low vapor pressure and good fluidity, and can be used for the molten salt distillation separation of zirconium hafnium chloride, ensuring the operating efficiency of the distillation tower and avoiding secondary pollution of zirconium hafnium chloride.

Description

Technical Field

[0001] This invention relates to the field of chemical technology, and in particular to a potassium chloroaluminate molten salt and its preparation method. Background Technology

[0002] Potassium chloroaluminate (KAlCl4) molten salt has the characteristics of low melting point, good high-temperature fluidity, low viscosity, low vapor pressure, and high solubility for zirconium hafnium chloride. It is an ideal molten salt for the distillation and separation of zirconium hafnium chloride, and can also be used in molten salt electrolytic refining, electroplating and other fields.

[0003] However, the following problems exist in the preparation process of potassium chloroaluminate molten salt:

[0004] 1) AlCl3 easily sublimates (sublimation point is about 190℃). During the heating process, AlCl3 will inevitably volatilize, resulting in an excess or deficiency of AlCl3 in the molten salt. When there is insufficient AlCl3 in the molten salt, free KCl is easy to precipitate. Since the distillation temperature is lower than the melting point of KCl, the free solid KCl can easily cause blockage of pipes, sieves, and valves in the distillation equipment. When there is an excess of AlCl3 in the molten salt, the free AlCl3 will volatilize, causing ZrCl4 and HfCl4 to be contaminated by AlCl3 during distillation.

[0005] 2) AlCl3 is hygroscopic, and after absorbing moisture, it forms HCl gas and Al(OH)3. Al(OH)3 decomposes (at 200~250℃) to produce fine, dispersed black alumina precipitate in the molten salt. This black alumina precipitate can also cause blockage of pipes, sieves, and valves in the distillation equipment, reducing distillation efficiency.

[0006] It is evident that the quality of potassium chloroaluminate molten salt directly determines the separation effect of zirconium-hafnium chloride distillation; obtaining high-quality potassium chloroaluminate molten salt is a key factor in ensuring the distillation separation effect of zirconium-hafnium molten salt. Summary of the Invention

[0007] In view of the above-mentioned problems in the prior art, the present invention provides a potassium chloroaluminate molten salt and its preparation method, so as to achieve the controllable preparation of high-quality potassium chloroaluminate salt.

[0008] The specific details of the invention are as follows:

[0009] In a first aspect, the present invention provides a method for preparing potassium chloroaluminate molten salt, the method comprising:

[0010] S1. Dry AlCl3 and KCl raw materials are mixed evenly at a mass ratio of (1.82~1.93):1 and then added to a crucible. The crucible is then heated to melt the mixed raw materials in the crucible to form an AlCl3-KAlCl4 mixed molten salt.

[0011] S2. Add KCl to the AlCl3-KAlCl4 mixed molten salt in small amounts several times until no volatiles appear in the crucible to obtain KAlCl4 molten salt;

[0012] S3. The KAlCl4 molten salt is subjected to hot filtration to remove precipitates and impurities, resulting in pure and transparent potassium chloroaluminate.

[0013] Optionally, in step S1, the heating treatment of the crucible includes:

[0014] First, heat the crucible to 300-350℃ and hold for 10-30 minutes until the solid material inside is completely melted. Then, heat the crucible to 450-500℃ and hold for 30-60 minutes.

[0015] Optionally, the heat treatment is carried out in a pit-type resistance furnace.

[0016] Optionally, in step S2, the mass of KCl added each time does not exceed 0.05% of the total mass of the AlCl3-KAlCl4 mixed molten salt;

[0017] After each addition of KCl, keep warm and stir for 5-10 minutes. If volatile substances still appear, continue adding KCl until no volatile substances are produced in the molten salt.

[0018] Optionally, before performing the thermal filtration, the method further includes:

[0019] The KAlCl4 molten salt is heated to 500~550℃ and then subjected to hot filtration.

[0020] Alternatively, the heat filtration may be performed using a 316L stainless steel screen or foam ceramic.

[0021] Optionally, when the heat filtration uses a 316L stainless steel screen, the screen mesh size is 200-800 mesh.

[0022] Optionally, when the thermal filtration uses foam ceramic, the material of the foam ceramic is alumina, zirconium oxide, or silicon carbide;

[0023] The pore density of the foam ceramic should be higher than 5~20 ppi.

[0024] Optionally, the number of thermal filtration cycles is 1 to 5.

[0025] In a second aspect, the present invention provides a potassium chloroaluminate molten salt for distillation separation of zirconium hafnium chloride, wherein the potassium chloroaluminate molten salt is obtained by the preparation method described in the first aspect above.

[0026] Compared with the prior art, the present invention has the following advantages:

[0027] This invention provides a potassium aluminate molten salt and its preparation method. The preparation method includes: S1, mixing dry AlCl3 and KCl raw materials in a mass ratio of (1.82~1.93):1 and adding the mixture to a crucible, then heating the crucible to melt the mixed raw materials to form an AlCl3-KAlCl4 mixed molten salt; S2, adding KCl to the AlCl3-KAlCl4 mixed molten salt in small amounts several times until no volatiles appear in the crucible, obtaining KAlCl4 molten salt; S3, hot filtering the KAlCl4 molten salt to remove precipitates and impurities, obtaining pure and transparent potassium aluminate molten salt. In the preparation method provided by the present invention, an appropriate excess of AlCl3 is required in the raw materials to ensure that after the KCl and AlCl3 mixture forms a melt, a small amount of free AlCl3 in the molten salt continues to volatilize. Subsequent small-scale addition of KCl can effectively combine the free AlCl3 to form KAlCl4. This can effectively avoid the formation of free KCl due to insufficient AlCl3 in the molten salt, which would result in high viscosity, poor fluidity, and free particles clogging pipes and valves. The molten salt prepared by the present invention is free of free KCl, precipitates, and other impurities, has low vapor pressure, and good fluidity. It can be used for the molten salt distillation separation of zirconium hafnium chloride, ensuring the operating efficiency of the distillation tower and avoiding secondary pollution of zirconium hafnium chloride. Attached Figure Description

[0028] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0029] Figure 1 A flowchart illustrating the preparation method of potassium chloroaluminate molten salt provided in an embodiment of the present invention is shown;

[0030] Figure 2 The image shows physical photos of the potassium chloroaluminate molten salt obtained before and after hot filtration by the preparation method provided in the embodiment of the present invention;

[0031] Figure 3 The image shows the black precipitate in the molten salt obtained by hot filtration using the preparation method provided in this embodiment of the invention.

[0032] Figure 4 The diagram shows the phase analysis of the black precipitate in the molten salt obtained by hot filtration using the preparation method provided in this embodiment of the invention. Detailed Implementation

[0033] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the present invention or its application or use. Based on the embodiments of the present invention, any product that is the same as or similar to the present invention, derived by any person under the guidance of the present invention or by combining the features of the present invention with other prior art, falls within the protection scope of the present invention. Furthermore, all other embodiments obtained by those skilled in the art without inventive effort are within the protection scope of the present invention.

[0034] Specific experimental steps or conditions are not specified in the embodiments; they can be performed according to the conventional experimental steps or conditions described in the prior art. Reagents and other instruments used, unless otherwise specified, are all commercially available conventional reagent products. Furthermore, the accompanying drawings are merely illustrative diagrams of the embodiments of the present invention and are not necessarily drawn to scale. The same reference numerals in the drawings denote the same or similar parts, and therefore, repeated descriptions of them will be omitted. Some block diagrams shown in the drawings are functional entities and do not necessarily correspond to physically or logically independent entities.

[0035] Techniques, methods, and devices known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and devices should be considered part of this specification.

[0036] In the description of this invention, it should be understood that the use of terms such as "first" and "second" to define components is merely for the purpose of distinguishing the corresponding components. Unless otherwise stated, the above terms have no special meaning and therefore should not be construed as limiting the scope of protection of this invention.

[0037] Furthermore, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0038] Before providing a detailed description of the potassium chloroaluminate molten salt for distillation separation of zirconium hafnium chloride and its preparation method provided by the present invention, it is necessary to explain the relevant technologies as follows:

[0039] In industrial production, the separation of zirconium and hafnium is a key technology in the nuclear industry. Zirconium (Zr) and hafnium (Hf) are among the most difficult element pairs to separate due to their extremely similar chemical properties (almost identical ionic radii and highly consistent chemical behavior); nuclear-grade zirconium materials require a hafnium content of less than 0.01%.

[0040] Currently, molten salt distillation is the only industrially applied pyrometallurgical separation technology for zirconium-hafnium chloride. It utilizes the difference in vapor pressure between ZrCl4 and HfCl4 in molten salt for distillation separation. The key device in this process for separating and collecting zirconium-hafnium chloride is the distillation column. Potassium chloroaluminate molten salt, as an ideal molten salt for zirconium-hafnium chloride distillation separation, has the most prominent advantages of low melting point, low vapor pressure, and high fluidity—its melting point of 250℃ is much lower than that of the traditional NaCl-KCl system (approximately 650℃), reducing energy consumption and equipment requirements. Furthermore, its low viscosity facilitates sufficient heat and mass transfer between ZrCl4 / HfCl4 vapor and molten salt on the sieve plate.

[0041] However, the conventional direct chemical method for preparing potassium chloroaluminate molten salt has the following problems: The prepared KAlCl4 easily contains free AlCl3, leading to unstable molten salt composition; the collected ZrCl4 / HfCl4 products contain volatile AlCl3, causing secondary contamination; furthermore, the volatile AlCl3 components condense and deposit in the system's cold zone, causing blockages in the pipes and valves of the distillation equipment; additionally, because AlCl3 is hygroscopic, it absorbs moisture to form HCl gas and Al(OH)3. Al(OH)3 decomposes during the heating process of molten salt preparation, generating fine, dispersed black alumina precipitate. This black alumina precipitate also causes blockages in the pipes, sieves, and valves of the distillation equipment, reducing distillation efficiency. When there is insufficient AlCl3 in the molten salt, free KCl easily precipitates. Since the distillation temperature is below the melting point of KCl, the free solid KCl also causes blockages in the pipes, sieves, and valves of the distillation equipment.

[0042] It is evident that high-quality potassium aluminate molten salt is a key factor in ensuring the effective separation of zirconium and hafnium chlorides through distillation. Therefore, this invention aims to provide a method for preparing potassium aluminate molten salt. The obtained potassium aluminate molten salt, after heating and melting, exhibits a stable composition, effectively preventing the formation of free KCl due to insufficient AlCl3 in the molten salt. This avoids the formation of molten salt with high viscosity and poor fluidity, and also prevents a large amount of particulate KCl from clogging the filter medium during subsequent hot filtration. When the potassium aluminate molten salt prepared by this invention is used in the distillation separation of zirconium and hafnium chlorides, no KCl precipitation or AlCl3 volatilization occurs in the molten salt, effectively ensuring the operating efficiency of the distillation column and the purity of the zirconium and hafnium chlorides. Detailed implementation methods are described below:

[0043] In a first aspect, the present invention provides a method for preparing potassium chloroaluminate molten salt. Figure 1 A flowchart illustrating the preparation method of potassium chloroaluminate molten salt provided in an embodiment of the present invention is shown, as follows: Figure 1 As shown, the preparation method includes:

[0044] S1. Dry AlCl3 and KCl raw materials are mixed evenly at a mass ratio of (1.82~1.93):1 and then added to a crucible. The crucible is then heated to melt the solid material inside the crucible to form a mixed molten salt of AlCl3-KAlCl4.

[0045] In the specific implementation of this step, when preparing the solid materials, AlCl3 should be in appropriate excess (the molar ratio of AlCl3 to KCl is 1.02-1.08:1). The excess of AlCl3 in the solid materials can ensure that no free KCl exists after the KCl and AlCl3 mixture forms a melt. The slightly excess AlCl3 in the molten salt (sublimation point is about 190℃) will continue to volatilize and produce white smoke, which makes it easier to judge the reaction endpoint of effectively combining free AlCl3 to form KAlCl4 by adding small amounts of KCl in multiple times.

[0046] It should be noted that before preparing the solid materials, AlCl3 and KCl need to be dried separately to ensure that no moisture is present. This is to prevent AlCl3 from absorbing moisture and forming HCl gas and Al(OH)3. Al(OH)3 will decompose during the preparation of molten salt, generating fine black alumina precipitate that is dispersed in the molten salt.

[0047] In some embodiments, the heating treatment of the solid material in the crucible is carried out in a pit-type resistance furnace. During the heating process, the crucible containing the molten salt should be covered to avoid a large amount of AlCl4 volatilization.

[0048] The specific heating procedure includes: first, heating to 300-350℃ and holding for 10-30 minutes to completely melt the solid material in the crucible; based on the molar ratio of AlCl3 to KCl of (1.02-1.08):1, a slight excess of AlCl3 is used so that the loss of AlCl3 due to sublimation at this temperature does not affect the complete combination of AlCl3 with KCl, ensuring that there is no free KCl in the melt; after the solid material in the crucible has completely melted, the temperature is then raised to 450-500℃ and held for 30-60 minutes. The melt is further homogenized at the higher temperature.

[0049] S2. Add KCl to the AlCl3-KAlCl4 mixed molten salt in small amounts several times until no volatiles appear in the crucible to obtain KAlCl4 molten salt;

[0050] In this specific implementation step, to remove volatile impurities (mainly unreacted AlCl3 and its dimer Al2Cl6) from the AlCl3-KAlCl4 mixed molten salt, KCl is added in small amounts multiple times. The added KCl reacts with the free AlCl3 / Al2Cl6, converting it into non-volatile KAlCl4. The mass of KCl added each time does not exceed 0.05% of the total mass of the AlCl3-KAlCl4 mixed molten salt. If too much KCl is added at once, it will cause local areas to instantly form alkaline molten salt (such as K3AlCl6) or free KCl, producing insoluble impurities and destroying the composition of the molten salt.

[0051] In some implementations, after each addition of KCl, the mixture is kept warm and stirred for 5-10 minutes. If volatile substances still appear, KCl is added again. During this process of adding KCl in small, multiple amounts, the decision to continue adding KCl is primarily based on observing whether volatile substances appear in the melt; the absence of volatile substances is a direct indicator of the reaction endpoint. Adding KCl in small, multiple amounts also allows for fine-tuning of the molten salt composition until the free AlCl3 is nearly exhausted.

[0052] S3. The KAlCl4 molten salt is subjected to hot filtration to remove precipitates and impurities, resulting in pure and transparent potassium chloroaluminate.

[0053] In this step, the second molten salt precursor is subjected to hot filtration. The insoluble substances inherent in the raw materials AlCl3 and KCl (such as Al2O3 and SiO2), as well as the hydrolysis products caused by the absorption of moisture by the raw materials or the introduction of trace amounts of moisture during operation (such as AlOCl and Al(OH)3) are effectively retained during the hot filtration process. The number of hot filtrations is 1 to 5.

[0054] It should be noted that thermal filtration must be performed under a strictly anhydrous and oxygen-free inert atmosphere using a filtration device that is resistant to high temperatures and strong acid molten salt corrosion. Thermal filtration uses 316L stainless steel screens or foam ceramics. When using 316L stainless steel screens, the mesh size should be 200-800 mesh. When using foam ceramics, the material should be alumina, zirconium oxide, or silicon carbide. The pore density of the foam ceramics should be higher than 5-20 ppi.

[0055] In some embodiments, before hot filtration, the method further includes heating the second molten salt precursor to 500-550°C before filtration. If the second molten salt precursor contains trace amounts of Al(OH)3, heating to 500-550°C causes the Al(OH)3 to decompose, forming fine, dispersed black Al2O3 precipitates. These black Al2O3 precipitates then flocculate and grow, becoming visible to the naked eye. Hot filtration effectively separates and removes the Al2O3 precipitates, resulting in a pure, transparent KAlCl4 molten salt free of impurities and volatiles. Furthermore, low viscosity is crucial for ensuring the feasibility and efficiency of hot filtration, and the viscosity of molten salt decreases significantly with increasing temperature. Heating the second molten salt precursor to 500-550°C before filtration effectively improves the hot filtration efficiency.

[0056] In a second aspect, the present invention provides a potassium chloroaluminate molten salt, which is obtained by the preparation method described in the first aspect above.

[0057] To enable those skilled in the art to more clearly understand the present invention, the following embodiments are provided to illustrate in detail the potassium chloroaluminate molten salt and its preparation method according to the present invention.

[0058] Example 1

[0059] Mix 500.0g AlCl3 and 274.7g KCl (mass ratio 1.82:1) thoroughly, then place the mixture into a crucible and cover it. Place the crucible into a pit furnace. Heat to 350 ℃ and hold for 10 min. After the material has completely melted, raise the temperature to 450 ℃ and hold for 60 min.

[0060] The crucible lid was opened, and 0.39 g of KCl was added each time, stirring for 5 min to adjust the composition of the molten salt. This process was repeated four times. No more volatiles were produced in the molten salt, and no white free KCl particles were observed. The molten salt was then heated to 550 °C. Fine, dispersed black precipitates appeared in the molten salt. After holding at this temperature for 5 min, the black precipitates flocculated and grew, becoming visible to the naked eye (see [link to relevant documentation]). Figure 2 (Left); At this point, the mixture was heat-filtered four times using a 200-mesh stainless steel sieve to obtain a clear, transparent KAlCl4 molten salt with a slightly yellowish-green tint (see...). Figure 2 (Right). The black precipitate in the molten salt obtained from hot filtration is shown. Figure 3 Phase analysis was performed on the filtered black precipitate, and the results are shown in the figure. Figure 4 ,from Figure 4 As can be seen from the XRD pattern shown, the main phase is Al2O3.

[0061] Example 2

[0062] Mix 500.0 g AlCl3 and 268.8 g KCl (mass ratio 1.86:1) thoroughly, then place the mixture into a crucible and cover it. Place the crucible into a pit furnace. Heat to 300 ℃ and hold for 20 min. After the material has completely melted, raise the temperature to 500 ℃ and hold for 30 min.

[0063] The crucible lid was opened, and 0.38 g of KCl was added each time, stirring for 5 min to adjust the composition of the molten salt. After a total of 6 additions, the molten salt no longer produced volatiles, and there were no white free KCl particles in the molten salt. The molten salt was then heated to 500 ℃ and held for 5 min. After that, it was filtered 5 times using 20 ppi zirconia foam ceramic to obtain pure and transparent KAlCl4 molten salt.

[0064] Example 3

[0065] Mix 500.0 g AlCl3 and 265.9 g KCl (mass ratio 1.88:1) thoroughly, then place the mixture into a crucible and cover it. Place the crucible into a pit furnace. Heat to 350 ℃ and hold for 30 min. After the material has completely melted, raise the temperature to 480 ℃ and hold for 60 min.

[0066] The crucible lid was opened, and 0.38 g of KCl was added each time, stirring for 5 minutes to adjust the composition of the molten salt. After a total of 6 additions, the molten salt no longer produced volatiles, and there were no white free KCl particles in the molten salt. The molten salt was then heated to 550 °C and held for 5 minutes. After that, it was filtered once using 5 ppi zirconia foam ceramic to obtain pure and transparent KAlCl4 molten salt.

[0067] Example 4

[0068] Mix 500.0 g AlCl3 and 263.2 g KCl (mass ratio 1.90:1) thoroughly, then place the mixture into a crucible and cover it. Place the crucible into a pit furnace. Heat to 330 ℃ and hold for 20 min. After the material has completely melted, raise the temperature to 460 ℃ and hold for 45 min.

[0069] The crucible lid was opened, and 0.38 g of KCl was added each time, stirring for 5 min to adjust the composition of the molten salt. After adding KCl five times, the molten salt no longer produced volatiles, and there were no white free KCl particles in the molten salt. The molten salt was then heated to 550 °C and held for 5 min. After that, it was filtered three times using 10 ppi alumina foam ceramic to obtain pure and transparent KAlCl4 molten salt.

[0070] Example 5

[0071] Mix 500.0 g AlCl3 and 259.1 g KCl (mass ratio 1.93:1) thoroughly, then place the mixture into a crucible and cover it. Place the crucible into a pit furnace. Heat to 350 ℃ and hold for 10 min. After the material has completely melted, raise the temperature to 450 ℃ and hold for 30 min.

[0072] The crucible lid was opened, and 0.38 g of KCl was added each time, stirring for 5 min to adjust the composition of the molten salt. After a total of 8 additions, the molten salt no longer produced volatiles, and there were no white free KCl particles in the molten salt. The molten salt was then heated to 500 ℃ and held for 5 min. After that, it was filtered 5 times using 20 ppi silicon carbide foam ceramic to obtain pure and transparent KAlCl4 molten salt.

[0073] Example 6

[0074] Mix 500.0 g AlCl3 and 261.8 g KCl (mass ratio 1.91:1) thoroughly, then place the mixture into a crucible and cover it. Place the crucible into a pit furnace. Heat to 300 ℃ and hold for 30 min. After the material has completely melted, raise the temperature to 490 ℃ and hold for 40 min.

[0075] The crucible lid was opened, and 0.38 g of KCl was added each time, stirring for 5 min to adjust the composition of the molten salt. After a total of 9 additions, the molten salt no longer produced volatiles, and there were no white free KCl particles in the molten salt. The molten salt was then heated to 550 ℃ and held for 5 min. After that, it was hot-filtered once through an 800-mesh 316 stainless steel sieve to obtain pure and transparent KAlCl4 molten salt.

[0076] Example 6

[0077] Mix 500.0 g AlCl3 and 259.1 g KCl (mass ratio 1.93:1) thoroughly, then place the mixture into a crucible and cover it. Place the crucible into a pit furnace. Heat to 310 ℃ and hold for 25 min. After the material has completely melted, raise the temperature to 450 ℃ and hold for 40 min.

[0078] The crucible lid was opened, and 0.38 g of KCl was added each time, stirring for 5 min to adjust the composition of the molten salt. After 10 additions, the molten salt no longer produced volatiles, and there were no white free KCl particles in the molten salt. The molten salt was then heated to 520 ℃ and held for 5 min. After that, it was hot-filtered twice through a 325-mesh 316 stainless steel sieve to obtain pure and transparent KAlCl4 molten salt.

[0079] Example 7

[0080] Mix 500.0 g AlCl3 and 268.8 g KCl (mass ratio 1.86:1) thoroughly, then place the mixture into a crucible and cover it. Place the crucible into a pit furnace. Heat to 350 ℃ and hold for 15 min. After the material has completely melted, raise the temperature to 500 ℃ and hold for 60 min.

[0081] The crucible lid was opened, and 0.38g of KCl was added each time, stirring for 5 minutes to adjust the composition of the molten salt. After three additions, the molten salt no longer produced volatiles, and there were no white free KCl particles in the molten salt. The molten salt was then heated to 550 ℃ and held for 5 minutes. After that, it was hot-filtered twice through a 400-mesh 316 stainless steel sieve to obtain pure and transparent KAlCl4 molten salt.

[0082] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. In addition, those skilled in the art can combine and integrate the different embodiments or examples described in this specification.

[0083] For the sake of simplicity, the method embodiments are described as a series of actions. However, those skilled in the art should understand that the present invention is not limited to the described order of actions, as some steps can be performed in other orders or simultaneously according to the present invention. Furthermore, those skilled in the art should also understand that the embodiments described in the specification are preferred embodiments, and the actions and components involved are not necessarily essential to the present invention.

[0084] The foregoing has provided a detailed description of the potassium chloroaluminate molten salt for distillation separation of zirconium hafnium chloride and its preparation method. Specific examples have been used to illustrate the principles and implementation methods of the present invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of the present invention. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the ideas of the present invention. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A method for preparing potassium chloroaluminate molten salt, characterized in that, The preparation method includes: S1. Mix the dry AlCl3 and KCl raw materials evenly at a mass ratio of (1.82~1.93):1, add them to a crucible, cover the crucible, and then heat the crucible to melt the mixed raw materials in the crucible to form an AlCl3-KAlCl4 mixed molten salt. S2. Add KCl to the AlCl3-KAlCl4 mixed molten salt in small amounts and multiple times. The mass of KCl added each time shall not exceed 0.05% of the total mass of the AlCl3-KAlCl4 mixed molten salt, until no volatiles appear in the crucible, and obtain KAlCl4 molten salt. S3. The KAlCl4 molten salt is subjected to hot filtration to remove precipitates and impurities, resulting in pure and transparent potassium chloroaluminate. The heat treatment is carried out in a pit-type resistance furnace.

2. The method for preparing potassium chloroaluminate molten salt according to claim 1, characterized in that, In step S1, the heating treatment of the crucible includes: First, heat the crucible to 300-350℃ and hold for 10-30 minutes until the solid material inside is completely melted. Then, heat the crucible to 450-500℃ and hold for 30-60 minutes.

3. The method for preparing potassium chloroaluminate molten salt according to claim 1, characterized in that, In step S2, after each addition of KCl, keep warm and stir for 5 to 10 minutes. If volatile substances still appear, continue adding KCl until no volatile substances are produced in the molten salt.

4. The method for preparing potassium chloroaluminate molten salt according to claim 1, characterized in that, Before performing the thermal filtration, the method further includes: The KAlCl4 molten salt is heated to 500~550℃ and then subjected to hot filtration.

5. The method for preparing potassium chloroaluminate molten salt according to claim 4, characterized in that, The heat filtration is performed using a 316L stainless steel screen or foam ceramic.

6. The method for preparing potassium chloroaluminate molten salt according to claim 5, characterized in that, When the heat filtration uses a 316L stainless steel screen, the screen mesh size is 200~800 mesh.

7. The method for preparing potassium chloroaluminate molten salt according to claim 5, characterized in that, When the thermal filtration uses foam ceramics, the foam ceramics are made of alumina, zirconium oxide, or silicon carbide. The pore density of the foam ceramic should be higher than 5~20 ppi.

8. The method for preparing potassium chloroaluminate molten salt according to claim 1, characterized in that, The number of heat filtration cycles is 1 to 5.

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