Potassium chloroaluminate fused salt and preparation method thereof

Abstract

The invention provides a potassium chloroaluminate fused salt and a preparation method thereof, and the preparation method comprises the following steps: uniformly mixing dried AlCl3 and KCl raw materials, adding into a crucible, and heating to melt the mixed raw materials in the crucible to form an AlCl3-KAlCl4 mixed fused salt; the method comprises the following steps: adding a small amount of KCl into molten salt for multiple times until no volatile matter is generated in a crucible to form KAlCl4 molten salt, and carrying out hot filtration on the pure KAlCl4 molten salt to obtain pure, transparent and impurity-free potassium chloroaluminate; wherein the AlCl3 in the raw materials needs to be appropriately excessive, so that after the raw materials form a melt, a small amount of free AlCl3 exists in the molten salt, and pure KAlCl4 is formed by adding a small amount of KCl for multiple times in the subsequent process to chemically combine the free AlCl3; in this way, it can be avoided that due to the fact that AlCl3 in molten salt is insufficient, free KCl is formed, the molten salt is large in viscosity and poor in flowability, and free particles block pipelines and valves of equipment; the prepared fused salt is free of free KCl, precipitates and other impurities, low in vapor pressure and good in fluidity, and can be used for fused salt rectification separation of the zirconium-hafnium chloride, the operation efficiency of a rectification tower device is guaranteed, and secondary pollution of the zirconium-hafnium chloride is avoided.

Description

Technical Field

[0001] The present invention relates to the technical field of chemical industry, and in particular to a potassium chloroaluminate molten salt and a preparation method thereof. Background Art

[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 in zirconium and hafnium chloride. It is an ideal molten salt for the distillation separation of zirconium and hafnium chloride, and can also be used in molten salt electrolytic refining, electroplating and other fields.

[0003] However, potassium chloroaluminate molten salt has the following problems during the preparation process: 1) AlCl3 is easy to sublime (the sublimation point is about 190℃). AlCl3 will inevitably volatilize during the heating process, resulting in excessive or insufficient AlCl3 in the molten salt. When AlCl3 is insufficient in the molten salt, free KCl is easy to precipitate. Since the distillation temperature is lower than the melting point of KCl, free solid KCl can easily cause the pipes, sieve plates, and valves of the distillation equipment to be blocked. When AlCl3 is excessive in the molten salt, free AlCl3 will volatilize, causing ZrCl4 and HfCl4 to be contaminated by AlCl3 during distillation.

[0004] 2) AlCl₃ easily absorbs moisture, which forms HCl gas and Al(OH)₃. Al(OH)₃ decomposes (at 200-250°C) to form fine black alumina precipitates dispersed in the molten salt. This black alumina precipitate can also clog pipes, sieve plates, and valves in distillation equipment, reducing distillation efficiency.

[0005] It can be seen that the quality of potassium chloroaluminate molten salt directly determines the separation effect of zirconium and hafnium chloride distillation separation; obtaining high-quality potassium chloroaluminate molten salt is the key factor to ensure the distillation separation effect of zirconium and hafnium molten salt. Summary of the Invention

[0006] In view of the above problems existing in the prior art, the present invention provides a potassium chloroaluminate molten salt and a preparation method thereof, so as to achieve controllable preparation of high-quality potassium chloroaluminate salt.

[0007] The specific content of the invention is as follows: In a first aspect, the present invention provides a method for preparing potassium chloroaluminate molten salt, the preparation method comprising: S1, dry AlCl3 and KCl raw materials are mixed in a mass ratio of (1.82-1.93): 1 and added to a crucible, and then the crucible is heated to melt the mixed raw materials in the crucible to form an AlCl3-KAlCl4 mixed molten salt; S2, adding KCl in small amounts and multiple times to the AlCl3-KAlCl4 mixed molten salt until no volatile matter appears in the crucible, thereby obtaining KAlCl4 molten salt; S3. Hot filtering the KAlCl4 molten salt to remove precipitates and impurities therein to obtain pure, transparent potassium chloroaluminate salt.

[0008] Optionally, in step S1, the heating treatment of the crucible includes: First, heat to 300-350°C and keep warm for 10-30 minutes. After the solid material in the crucible is completely melted, heat to 450-500°C and keep warm for 30-60 minutes.

[0009] Optionally, the heating treatment is carried out in a pit-type resistance furnace.

[0010] Optionally, in step S2, the mass of the KCl added each time does not exceed 0.05% of the total mass of the AlCl3-KAlCl4 mixed molten salt; After each addition of KCl, the mixture was stirred for 5 to 10 minutes at a temperature of 5 to 10 minutes. If volatile matter still appeared, KCl was continued to be added until no volatile matter was produced in the molten salt.

[0011] Optionally, before performing the hot filtration, the method further comprises: The KAlCl4 molten salt is heated to 500-550°C and then hot filtered.

[0012] Optionally, the hot filtration is performed using a 316L stainless steel mesh or foam ceramic.

[0013] Optionally, when a 316L stainless steel screen is used for the hot filtration, the mesh size of the screen is 200-800 meshes.

[0014] Optionally, when foam ceramics are used for the heat filtration, 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.

[0015] Optionally, the hot filtration is performed 1 to 5 times.

[0016] In a second aspect, the present invention provides a potassium chloroaluminate molten salt for distillation separation of zirconium and hafnium chlorides, wherein the potassium chloroaluminate molten salt is obtained by the preparation method described in the first aspect.

[0017] Compared with the prior art, the present invention has the following advantages: The present invention provides a potassium chloroaluminate molten salt and a preparation method thereof. The preparation method comprises the following steps: S1, uniformly mixing dried AlCl3 and KCl raw materials in a mass ratio of (1.82-1.93):1, adding the mixture to a crucible, and then heating the crucible to melt the mixed raw materials in the crucible to form an AlCl3-KAlCl4 mixed molten salt; S2, adding KCl in small amounts and multiple times to the AlCl3-KAlCl4 mixed molten salt until no volatile matter appears in the crucible, thereby obtaining a KAlCl4 molten salt; S3, hot filtering the KAlCl4 molten salt to remove precipitates and impurities therein, thereby obtaining a pure and transparent potassium chloroaluminate salt; the present invention provides a potassium chloroaluminate molten salt and a preparation method thereof. In the preparation method provided by Ming, an appropriate excess of AlCl3 needs to be added to 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, and the subsequent small and multiple additions 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, resulting in high viscosity and poor fluidity of the formed molten salt, and free particles clogging pipes and valves; the molten salt prepared by the present invention does not contain impurities such as free KCl and precipitates, has a low vapor pressure and good fluidity, and can be used for molten salt distillation separation of zirconium and hafnium chloride, ensuring the operating efficiency of the distillation tower device and avoiding secondary pollution of zirconium and hafnium chloride. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0019] Figure 1 A flow chart of a method for preparing potassium chloroaluminate molten salt provided in an embodiment of the present invention is shown; Figure 2 The figure shows the physical image of potassium chloroaluminate molten salt obtained before and after hot filtration by the preparation method provided in the embodiment of the present invention; Figure 3 The black precipitate in the molten salt filtered out by hot filtration according to the preparation method provided in an embodiment of the present invention is shown; Figure 4 The diagram shows a phase analysis of a black precipitate in the molten salt filtered out by hot filtration according to the preparation method provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0020] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, not all of the embodiments. The following description of at least one exemplary embodiment is actually only illustrative and is by no means a limitation on the present invention and its application or use. Based on the embodiments of the present invention, any product that is identical or similar to the present invention and is obtained by anyone under the inspiration of the present invention or by combining the features of the present invention with other prior arts falls within the scope of protection of the present invention. In addition, all other embodiments obtained by ordinary technicians in this field without carrying out creative work fall within the scope of protection of the present invention.

[0021] Where specific experimental steps or conditions are not specified in the examples, the conventional experimental steps or conditions described in the prior art in the art may be used. Reagents and other instruments used, for which the manufacturer is not specified, are commercially available conventional reagent products. Furthermore, the accompanying drawings are merely schematic illustrations of embodiments of the present invention and are not necessarily drawn to scale. Identical reference numerals in the figures denote identical or similar parts, and their repeated descriptions will be omitted. Some block diagrams shown in the accompanying drawings are functional entities and do not necessarily correspond to physically or logically independent entities.

[0022] Technologies, methods, and equipment known to those skilled in the art may not be discussed in detail, but where appropriate, such technologies, methods, and equipment should be considered part of the description of the present invention.

[0023] In the description of the present invention, it should be understood that the use of terms such as "first" and "second" to limit components is only for the convenience of distinguishing the corresponding components. Unless otherwise stated, the above terms have no special meaning and therefore cannot be understood as limiting the scope of protection of the present invention.

[0024] In addition, 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.

[0025] Before describing in detail the potassium chloroaluminate molten salt for distillation separation of zirconium and hafnium chloride and its preparation method provided by the present invention, it is necessary to describe the related technologies as follows: In industrial production, the separation of zirconium and hafnium is a key technology in the nuclear industry. Zirconium (Zr) and hafnium (Hf) are one of 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%.

[0026] Currently, molten salt distillation is the only industrially applied pyrometallurgical separation technology for zirconium and hafnium chloride. This process utilizes the difference in vapor pressure between ZrCl₄ and HfCl₄ in molten salt for distillation separation. The key device for separating and collecting zirconium and hafnium chlorides in this process is the distillation column. Potassium chloroaluminate, an ideal molten salt for distillation separation of zirconium and hafnium chlorides, offers the following advantages: a low melting point, low vapor pressure, and high fluidity. Its melting point of 250°C is significantly lower than that of the traditional NaCl-KCl system (approximately 650°C), reducing energy consumption and equipment requirements. Furthermore, its low viscosity facilitates efficient heat and mass transfer between the ZrCl₄ / HfCl₄ vapor and the molten salt on the sieve plate.

[0027] However, the conventional direct reaction method for preparing potassium chloroaluminate molten salt presents the following problems: Free AlCl₃ is easily present in the prepared KAlCl₄, leading to unstable molten salt composition. Volatile AlCl₃ is present in the collected ZrCl₄\HfCl₄ products, causing secondary contamination of the product. Furthermore, the volatile AlCl₃ component condenses and deposits in the cold zone of the system, causing blockage of pipes and valves in the distillation equipment. Furthermore, AlCl₃ is easily deliquescent, forming HCl gas and Al(OH)₃ upon absorbing moisture. Al(OH)₃ decomposes during the heating process of the molten salt preparation, forming fine black alumina precipitates that are dispersed throughout the molten salt. This black alumina precipitate can also clog pipes, sieve plates, and valves in the distillation equipment, reducing distillation efficiency. When AlCl₃ is insufficient in the molten salt, free KCl is easily precipitated. Since the distillation temperature is below the melting point of KCl, the free, solid KCl can also clog pipes, sieve plates, and valves in the distillation equipment.

[0028] It can be seen that high-quality potassium chloroaluminate molten salt is a key factor in ensuring the distillation and separation effect of zirconium and hafnium molten salt; based on this, the present invention hopes to provide a method for preparing potassium chloroaluminate molten salt. The obtained potassium chloroaluminate molten salt has a stable composition after heating and melting, which can effectively avoid the formation of free KCl due to insufficient AlCl3 in the molten salt, resulting in high viscosity and poor fluidity of the formed molten salt, and also avoids a large amount of granular KCl clogging the filter medium during the subsequent hot filtration process; when the potassium chloroaluminate molten salt prepared by the present invention is used in the distillation and separation process of zirconium and hafnium chloride, there is no precipitation of KCl in the molten salt, and no volatilization of AlCl3, which effectively ensures the operating efficiency of the distillation tower device and the purity of zirconium and hafnium chloride. The specific implementation method is introduced as follows: In a first aspect, the present invention provides a method for preparing potassium chloroaluminate molten salt. Figure 1 The flow chart of the preparation method of potassium chloroaluminate molten salt provided in the embodiment of the present invention is shown as follows: Figure 1 As shown, the preparation method comprises: S1, dry AlCl3 and KCl raw materials are mixed in a mass ratio of (1.82-1.93):1 and added to a crucible, and then the crucible is heated to melt the solid material in the crucible to form an AlCl3-KAlCl4 mixed molten salt; During the specific implementation of this step, when preparing the solid material, AlCl3 is appropriately excessive (the molar ratio of AlCl3 to KCl is 1.02-1.08:1). The excess AlCl3 in the solid material can ensure that no free KCl exists after the KCl and AlCl3 mixture forms a melt; the slightly excessive AlCl3 (sublimation point is about 190°C) in the molten salt continues to evaporate and produce white smoke, which facilitates the determination of the reaction endpoint of the subsequent small and multiple additions of KCl to effectively combine the free AlCl3 with KAlCl4.

[0029] It should be noted that before preparing the solid material, AlCl3 and KCl need to be dried separately to ensure that there is no moisture present, so as to avoid the formation of HCl gas and Al(OH)3 after AlCl3 absorbs moisture. Al(OH)3 will decompose during the molten salt preparation process to form fine black alumina precipitates dispersed in the molten salt.

[0030] In some embodiments, the solid material in the crucible is heated in a pit-type resistance furnace. During the heating process, the crucible containing the molten salt should be covered to prevent a large amount of AlCl4 from volatilizing.

[0031] The specific heating procedure includes: first raising the temperature to 300-350°C and holding it for 10-30 minutes to completely melt the solid material in the crucible; based on a molar ratio of AlCl3 to KCl of 1.02-1.08:1, a slight excess of AlCl3 is added so that any loss of AlCl3 through sublimation at this temperature does not affect its complete combination with KCl, ensuring that there is no free KCl in the melt; after the solid material in the crucible is completely melted, the temperature is then raised to 450-500°C and held for 30-60 minutes. The melt is further homogenized at this higher temperature.

[0032] S2, adding KCl in small amounts and multiple times to the AlCl3-KAlCl4 mixed molten salt until no volatile matter appears in the crucible, thereby obtaining KAlCl4 molten salt; During the specific implementation of this step, in order to remove volatile impurities (mainly unreacted AlCl3 and its dimer Al2Cl6) in the AlCl3-KAlCl4 mixed molten salt, a method of adding KCl in small amounts and multiple times is adopted. The added KCl reacts with free AlCl3 / Al2Cl6 to convert 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 one time, alkaline molten salt (such as K3AlCl6) or free KCl will be instantly formed in local areas, generating insoluble impurities and destroying the composition of the molten salt; In some embodiments, after each addition of KCl, the mixture is stirred for 5-10 minutes. If volatiles are present, further KCl addition is performed. During the process of adding KCl in small amounts and multiple times, the decision to continue KCl addition is primarily based on observing the presence of volatiles in the melt; the absence of volatiles is a direct indicator of the reaction endpoint. By adding KCl in small amounts and multiple times, the molten salt composition can be finely adjusted until the free AlCl3 is nearly depleted.

[0033] S3. Hot filtering the KAlCl4 molten salt to remove precipitates and impurities therein to obtain pure, transparent potassium chloroaluminate salt.

[0034] During the specific implementation of this step, the second molten salt precursor is subjected to hot filtration. Insoluble substances inherent in the raw materials AlCl3 and KCl (such as Al2O3 and SiO2) and hydrolysis products (such as AlOCl and Al(OH)3) caused by moisture absorption of the raw materials or introduction of trace amounts of water during operation are effectively retained during the hot filtration process. The number of hot filtrations is 1 to 5 times.

[0035] It should be noted that hot filtration needs to be carried out in a strictly water-free and oxygen-free inert atmosphere, using a filtration device that is resistant to high temperature and strong acidic molten salt corrosion. Hot filtration is carried out using 316L stainless steel screen or foam ceramic. When 316L stainless steel screen is used for hot filtration, the mesh size is 200~800 mesh; when foam ceramic is used for hot filtration, the material of the foam ceramic is alumina, zirconium oxide or silicon carbide; the pore density of the foam ceramic should be higher than 5~20ppi.

[0036] In some embodiments, before performing hot filtration, the method further includes: heating the second molten salt precursor to 500-550°C and then filtering. If the second molten salt precursor contains a trace amount of Al(OH)3, after heating to 500-550°C, Al(OH)3 decomposes to form a fine and dispersed black Al2O3 precipitate, and the black Al2O3 precipitate flocculates and grows, becoming visible to the naked eye; the hot filtration method can effectively separate and remove the Al2O3 precipitate, thereby preparing a pure, transparent KAlCl4 molten salt free of impurities and volatiles. In addition, low viscosity is the key to ensuring that hot filtration is feasible and efficient, and the viscosity of molten salt decreases significantly with increasing temperature; the present invention heats the second molten salt precursor to 500-550°C and then filters it, which can effectively improve the efficiency of hot filtration.

[0037] 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.

[0038] In order to enable those skilled in the art to more clearly understand the present invention, the potassium chloroaluminate molten salt and the preparation method thereof according to the present invention are now described in detail through the following examples.

[0039] Example 1 Mix 500.0g AlCl₃ and 274.7g KCl (mass ratio 1.82:1) and place in a crucible. Secure the crucible lid and place the crucible in a pit furnace. Heat to 350°C and hold for 10 minutes. Once the mixture is completely melted, raise the temperature to 450°C and hold for 60 minutes.

[0040] The crucible lid was opened, and 0.39 g of KCl was added each time with stirring for 5 minutes to adjust the composition of the molten salt. After adding the material 4 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. Small, dispersed black precipitates appeared in the molten salt. After holding the temperature for 5 minutes, the black precipitates flocculated and grew, becoming visible to the naked eye (see Figure 2 Left); At this time, hot filtration was performed 4 times using a 200-mesh stainless steel sieve to obtain a slightly yellowish-green clear KAlCl4 molten salt (see Figure 2 Right). The black precipitate in the hot filtered molten salt is Figure 3 The black precipitate was analyzed and the results are shown in Figure 4 ,from Figure 4 It can be seen from the XRD pattern shown that the main phase is Al2O3.

[0041] Example 2 Mix 500.0 g of AlCl₃ and 268.8 g of KCl (mass ratio 1.86:1) and place in a crucible. Secure the crucible lid and place the crucible in a pit furnace. Heat to 300°C and hold for 20 minutes. Once the mixture is completely melted, raise the temperature to 500°C and hold for 30 minutes.

[0042] The crucible lid was opened, and 0.38 g of KCl was added at a time with stirring for 5 minutes to adjust the composition of the molten salt. After six additions, the molten salt no longer produced volatiles and contained no white free KCl particles. The molten salt was then heated to 500°C and held for 5 minutes. The mixture was then hot-filtered five times through a 20 ppi zirconia foam ceramic to obtain a pure, transparent KAlCl₄ molten salt.

[0043] Example 3 Mix 500.0 g of AlCl₃ and 265.9 g of KCl (mass ratio 1.88:1) and place in a crucible. Secure the crucible lid and place the crucible in a pit furnace. Heat to 350°C and hold for 30 minutes. Once the mixture is completely melted, raise the temperature to 480°C and hold for 60 minutes.

[0044] The crucible lid was opened, and 0.38 g of KCl was added at a time with stirring for 5 minutes to adjust the composition of the molten salt. After six additions, the molten salt no longer produced volatiles and contained no white free KCl particles. The molten salt was then heated to 550°C and held for 5 minutes. The mixture was then hot-filtered once through a 5 ppi zirconia foam ceramic to obtain pure, transparent KAlCl₄ molten salt.

[0045] Example 4 Mix 500.0 g of AlCl₃ and 263.2 g of KCl (mass ratio 1.90:1) and place in a crucible. Secure the crucible lid and place the crucible in a pit furnace. Heat to 330°C and hold for 20 minutes. Once the mixture is completely melted, raise the temperature to 460°C and hold for 45 minutes.

[0046] The crucible lid was opened, and 0.38 g of KCl was added at a time with stirring for 5 minutes to adjust the composition of the molten salt. After five additions, the molten salt no longer produced volatiles and contained no white free KCl particles. The molten salt was then heated to 550°C and held for 5 minutes. The mixture was then hot-filtered three times through a 10 ppi alumina foam ceramic to obtain a pure, transparent KAlCl₄ molten salt.

[0047] Example 5 Mix 500.0 g of AlCl₃ and 259.1 g of KCl (mass ratio 1.93:1) and place in a crucible. Secure the crucible lid and place the crucible in a pit furnace. Heat to 350°C and hold for 10 minutes. Once the mixture is completely melted, raise the temperature to 450°C and hold for 30 minutes.

[0048] The crucible lid was opened, and 0.38 g of KCl was added at a time with stirring for 5 minutes to adjust the composition of the molten salt. After eight additions, the molten salt no longer produced volatiles and contained no white free KCl particles. The molten salt was then heated to 500°C and held for 5 minutes. The mixture was then hot-filtered five times through a 20 ppi silicon carbide foam ceramic to obtain pure, transparent KAlCl₄ molten salt.

[0049] Example 6 Mix 500.0 g of AlCl₃ and 261.8 g of KCl (mass ratio 1.91:1) and place in a crucible. Secure the crucible lid and place the crucible in a pit furnace. Heat to 300°C and hold for 30 minutes. Once the mixture is completely melted, raise the temperature to 490°C and hold for 40 minutes.

[0050] The crucible lid was opened, and 0.38 g of KCl was added at a time with stirring for 5 minutes to adjust the composition of the molten salt. After nine additions, the molten salt no longer produced volatiles and contained no white free KCl particles. The molten salt was then heated to 550°C and held at that temperature for 5 minutes. The mixture was then hot-filtered once through an 800-mesh 316 stainless steel mesh to obtain pure, transparent KAlCl₄ molten salt.

[0051] Example 6 Mix 500.0 g of AlCl₃ and 259.1 g of KCl (mass ratio 1.93:1) and place in a crucible. Secure the crucible lid and place the crucible in a pit furnace. Heat to 310°C and hold for 25 minutes. Once the mixture is completely melted, raise the temperature to 450°C and hold for 40 minutes.

[0052] The crucible lid was opened, and 0.38 g of KCl was added at a time with stirring for 5 minutes to adjust the composition of the molten salt. After 10 additions, the molten salt no longer produced volatiles and contained no white free KCl particles. The molten salt was then heated to 520°C and held for 5 minutes. The mixture was then hot-filtered twice through a 325-mesh 316 stainless steel sieve to obtain pure, transparent KAlCl₄ molten salt.

[0053] Example 7 Mix 500.0 g of AlCl₃ and 268.8 g of KCl (mass ratio 1.86:1) and place in a crucible. Secure the crucible lid and place the crucible in a pit furnace. Heat to 350°C and hold for 15 minutes. Once the mixture is completely melted, raise the temperature to 500°C and hold for 60 minutes.

[0054] Open the crucible lid and add 0.38g of KCl at a time, stirring for 5 minutes to adjust the composition of the molten salt. Add the additions three times until the molten salt produces no more volatiles and contains no white free KCl particles. Heat the molten salt to 550°C, hold for 5 minutes, and then filter it twice using a 400-mesh 316 stainless steel sieve to obtain pure, transparent KAlCl₄ molten salt.

[0055] In the description of this specification, the reference terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" mean that the specific features, structures, materials, or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in any appropriate manner in any one or more embodiments or examples. In addition, those skilled in the art can combine and combine different embodiments or examples described in this specification.

[0056] For simplicity of description, the method embodiments are described as a series of actions. However, those skilled in the art should be aware that the present invention is not limited by the order of the actions described, as certain steps can be performed in other orders or simultaneously according to the present invention. Furthermore, those skilled in the art should also be aware that the embodiments described in this specification are preferred embodiments, and the actions and components involved are not necessarily required for the present invention.

[0057] The above is a detailed introduction to a potassium chloroaluminate molten salt for distillation separation of zirconium and hafnium chloride provided by the present invention and its preparation method. Specific examples are used herein to illustrate the principles and implementation methods of the present invention. The description of the above embodiments is only used to help understand the method of the present invention and its core idea. At the same time, for those skilled in the art, according to the ideas of the present invention, there will be changes in the specific implementation methods and application scopes. In summary, the content of this specification should not be understood as limiting the present invention.

Claims

1. A method for preparing potassium chloroaluminate molten salt, characterized in that, The preparation method comprises: S1, dry AlCl3 and KCl raw materials are mixed in a mass ratio of (1.82-1.93): 1 and added to a crucible, and then the crucible is heated to melt the mixed raw materials in the crucible to form an AlCl3-KAlCl4 mixed molten salt; S2, adding KCl in small amounts and multiple times to the AlCl3-KAlCl4 mixed molten salt until no volatile matter appears in the crucible, thereby obtaining KAlCl4 molten salt; S3. Hot filtering the KAlCl4 molten salt to remove precipitates and impurities therein to obtain pure, transparent potassium chloroaluminate salt.

2. The method for preparing potassium chloroaluminate molten salt according to claim 1, wherein In step S1, the crucible is subjected to a heating treatment, comprising: First, heat to 300-350°C and keep warm for 10-30 minutes. After the solid material in the crucible is completely melted, heat to 450-500°C and keep warm for 30-60 minutes.

3. The method for preparing potassium chloroaluminate molten salt according to claim 1 or 2, wherein The heating treatment is carried out in a pit-type resistance furnace.

4. The method for preparing potassium chloroaluminate molten salt according to claim 1, wherein In step S2, the mass of the KCl added each time does not exceed 0.05% of the total mass of the AlCl3-KAlCl4 mixed molten salt; After each addition of KCl, the mixture was stirred for 5 to 10 minutes at a temperature of 5 to 10 minutes. If volatile matter still appeared, KCl was continued to be added until no volatile matter was produced in the molten salt.

5. The method for preparing potassium chloroaluminate molten salt according to claim 1, wherein Before performing the hot filtration, the method further comprises: The KAlCl4 molten salt is heated to 500-550°C and then hot filtered.

6. The method for preparing potassium chloroaluminate molten salt according to claim 5, wherein The hot filtration is performed using a 316L stainless steel mesh or foam ceramic.

7. The method for preparing potassium chloroaluminate molten salt according to claim 6, wherein When the hot filtration uses a 316L stainless steel screen, the mesh number of the screen is 200-800 meshes.

8. The method for preparing potassium chloroaluminate molten salt according to claim 6, wherein When foam ceramics are used for the heat filtration, the material of the foam ceramics is alumina, zirconium oxide or silicon carbide; The pore density of the foam ceramic should be higher than 5-20 ppi.

9. The method for preparing potassium chloroaluminate molten salt according to claim 1, wherein The number of times of hot filtration is 1 to 5 times.

10. A potassium chloroaluminate molten salt, characterized in that The potassium chloroaluminate molten salt is obtained by the preparation method described in any one of claims 1 to 9.

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