Method for separating zirconium tetrachloride and hafnium tetrachloride

Abstract

The invention relates to the technical field of zirconium and hafnium separation, in particular to a method for separating zirconium tetrachloride and hafnium tetrachloride. The method for separating zirconium tetrachloride and hafnium tetrachloride comprises the following steps: (a) carrying out first heating treatment on a mixed system containing crude zirconium tetrachloride salt and alkali metal chlorate to obtain a first mixed system; (b) introducing crude zirconium tetrachloride gas into the first mixed system to carry out gas-liquid mass transfer exchange; zirconium tetrachloride gas generated in the gas-liquid mass transfer exchange process is collected; (c) carrying out second heating treatment on the reaction system after the gas-liquid mass transfer exchange is finished; and (d) carrying out third heating treatment on the reaction system subjected to the second heating treatment, and collecting hafnium tetrachloride gas generated in the third heating treatment process. The method for separating zirconium tetrachloride and hafnium tetrachloride is short in separation process, high in separation efficiency, high in product purity, high in operability, low in cost and capable of achieving continuous and large-scale production.

Description

Technical Field

[0001] The present invention relates to the technical field of zirconium and hafnium separation, and in particular to a method for separating zirconium tetrachloride and hafnium tetrachloride. Background Art

[0002] Zirconium and hafnium possess high-temperature, radiation-resistant, and corrosion-resistant properties, as well as unique nuclear properties. In the atomic energy industry, zirconium alloys are used in reactor cladding and structural materials, while hafnium is used as a reactor control material. Zirconium and hafnium are also widely used in the chemical, metallurgical, and electronic industries. Zirconium and hafnium coexist in ores, making them difficult to separate using conventional methods. For use in atomic energy, zirconium must be separated from hafnium, ensuring that the hafnium content in the zirconium is no more than one part per ten thousand by mass.

[0003] Currently, there are numerous technologies for separating zirconium and hafnium, primarily pyrolysis and hydrolysis (aqueous separation). Pyrolysis has a short process flow and can be directly integrated into the metal reduction process, but it requires high equipment requirements and suffers from poor purification and impurity removal. Hydrolysis, however, is less effective, with high costs, lengthy processes, and potential environmental pollution, making it difficult to implement on a large scale.

[0004] The raw material for zirconium and hafnium separation is generally zirconium tetrachloride containing hafnium tetrachloride. Usually, zirconium tetrachloride contains 0.8% to 1% hafnium tetrachloride. Since the sublimation temperatures of ZrCl4 and HfCl4 are extremely similar, the sublimation temperature of ZrCl4 is 331°C and the sublimation temperature of HfCl4 is 317°C, and the two substances only exist in solid and gaseous states, they cannot be separated by ordinary distillation.

[0005] The existing molten salt distillation method for separating zirconium and hafnium has the following disadvantages: high requirements for equipment and materials, poor purification and impurity removal, many purification stages, large investment, strict temperature control, and difficulty in actual industrial production.

[0006] In view of this, the present invention is proposed. Summary of the Invention

[0007] In order to overcome the problems of high equipment requirements, large investment, low separation efficiency, and strict temperature control in the existing zirconium and hafnium separation process, the present invention provides a method for separating zirconium tetrachloride and hafnium tetrachloride. The method has a short zirconium and hafnium separation process, high separation efficiency, high product purity, strong operability, low cost, and can be continuously and large-scaled produced.

[0008] In order to achieve the above-mentioned purpose of the present invention, the following technical solutions are adopted:

[0009] One aspect of the present invention relates to a method for separating zirconium tetrachloride and hafnium tetrachloride, comprising the following steps:

[0010] (a) subjecting a mixed system containing crude zirconium tetrachloride salt and alkali metal chloride salt to a first heating treatment to obtain a first mixed system;

[0011] (b) introducing crude zirconium tetrachloride gas into the first mixed system for gas-liquid mass transfer exchange; collecting the zirconium tetrachloride gas generated during the gas-liquid mass transfer exchange;

[0012] (c) subjecting the reaction system to a second heating treatment after the gas-liquid mass transfer exchange is completed; heating to remove impurities and accelerate the reaction and decomposition of small molecular clusters containing zirconium;

[0013] (d) performing a third heat treatment on the reaction system after the second heat treatment, and collecting hafnium tetrachloride gas generated during the third heat treatment.

[0014] The method for separating zirconium tetrachloride and hafnium tetrachloride has the advantages of short separation process, high separation efficiency, high product purity, strong operability, low cost, and can be produced continuously and on a large scale.

[0015] Preferably, the alkali metal chloride salt includes potassium chloride and sodium chloride.

[0016] Preferably, in step (a), the molar ratio of the crude zirconium tetrachloride salt, the potassium chloride and the sodium chloride is 60-65:17.5-20:17.5-20.

[0017] Preferably, the temperature of the first heat treatment is 250-320°C.

[0018] Preferably, the first heating treatment lasts for 3 to 5 hours.

[0019] Preferably, when the gas-liquid mass exchange is performed, the temperature of the crude zirconium tetrachloride gas is ≥331°C, and the temperature of the first mixed system is 350-500°C.

[0020] Preferably, the temperature of the second heat treatment is 500-600°C.

[0021] Preferably, the second heating treatment lasts for 6 to 8 hours.

[0022] Preferably, the temperature of the third heat treatment is 600-850°C.

[0023] Preferably, the third heating treatment lasts for 8 to 12 hours.

[0024] Preferably, the gas-liquid mass transfer exchange is carried out in a distillation tower.

[0025] Preferably, the number of the distillation towers is 3 to 4; the total number of plates of the distillation towers is 9 to 48.

[0026] Preferably, the crude zirconium tetrachloride salt contains 1% to 2% of hafnium tetrachloride.

[0027] Preferably, the crude zirconium tetrachloride gas contains 1% to 2% of hafnium tetrachloride.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] (1) The method for separating zirconium tetrachloride and hafnium tetrachloride provided by the present invention has a short separation process, high separation efficiency, high product purity, strong operability, low cost, and can be produced continuously and on a large scale.

[0030] (2) The method for separating zirconium tetrachloride and hafnium tetrachloride provided by the present invention comprises first adding an alkali metal chloride to form a relatively stable macromolecular complex salt of zirconium and hafnium, and then introducing crude zirconium tetrachloride gas containing hafnium tetrachloride into the macromolecular complex salt of zirconium and hafnium. The metallic activity of hafnium is greater than that of zirconium. Therefore, hafnium tetrachloride can continuously replace zirconium tetrachloride in the complex salt, thereby continuously purifying the zirconium tetrachloride, and finally obtaining nuclear-grade zirconium tetrachloride, while hafnium is enriched in the molten salt.

[0031] (3) The method for separating zirconium tetrachloride and hafnium tetrachloride provided by the present invention is as follows: when the concentration of hafnium in the molten salt is enriched to a sufficiently high level, the molten salt still contains a small amount of zirconium. At this time, by increasing the temperature of the molten salt, the zirconium composite salt with a relatively small molecular weight is first decomposed, so that the purity of the hafnium in the molten salt is further improved, and finally nuclear-grade hafnium tetrachloride is obtained. DETAILED DESCRIPTION

[0032] The technical scheme of the present invention will be clearly and completely described below in conjunction with specific embodiments, but it will be understood by those skilled in the art that the following described embodiments are part of embodiments of the present invention, rather than all embodiments, and are only used to illustrate the present invention, and should not be considered as limiting the scope of the present invention. Based on the embodiments in the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative work premise belong to the scope of protection of the present invention. Those who do not specify specific conditions in the embodiments are carried out according to normal conditions or the conditions recommended by the manufacturer. Those whose reagents or instruments are not specified by the manufacturer are conventional products that can be purchased commercially.

[0033] One aspect of the present invention relates to a method for separating zirconium tetrachloride and hafnium tetrachloride, comprising the following steps:

[0034] (a) subjecting a mixed system containing crude zirconium tetrachloride salt and alkali metal chloride salt to a first heating treatment to obtain a first mixed system;

[0035] (b) introducing crude zirconium tetrachloride gas into the first mixed system for gas-liquid mass transfer exchange; collecting the zirconium tetrachloride gas generated during the gas-liquid mass transfer exchange;

[0036] (c) performing a second heating treatment on the reaction system after the gas-liquid mass transfer exchange is completed;

[0037] (d) performing a third heat treatment on the reaction system after the second heat treatment, and collecting hafnium tetrachloride gas generated during the third heat treatment.

[0038] The method for separating zirconium tetrachloride and hafnium tetrachloride has the advantages of short separation process, high separation efficiency, high product purity, strong operability, low cost, and can be produced continuously and on a large scale.

[0039] The crude zirconium tetrachloride salt containing hafnium tetrachloride forms a low temperature eutectic with alkali metal chloride, so that ZrCl4 and HfCl4 form relatively stable ZrCl4 macromolecular complex salts (M n1 ZrCl n2 ) and HfCl4 macromolecular complex salt (M n1 HfCl n2 ).

[0040] The relative atomic mass of Zr is 91.22, and the relative atomic mass of Hf is 178.5. Therefore, the relative molecular mass of the ZrCl4 macromolecular complex salt is smaller than that of the HfCl4 macromolecular complex salt. The larger the relative molecular mass of the macromolecular complex salt, the higher the decomposition temperature of the macromolecular complex salt. Therefore, the decomposition temperature of the HfCl4 macromolecular complex salt is much higher than that of the ZrCl4 macromolecular complex salt, with a temperature difference greater than 100°C. By controlling the temperature, the separation of zirconium and hafnium is made easier.

[0041] The method separates zirconium and hafnium in a constant temperature distillation tower. The bottom of the distillation tower is a mixed salt. Crude zirconium tetrachloride gas containing hafnium tetrachloride is introduced from the bottom of the No. 1 distillation tower. The mixed salt flows down from the top of the tower. The tower has trays. The mixed salt and crude zirconium tetrachloride gas undergo gas-liquid mass transfer exchange on the trays. Each tray undergoes the following replacement reaction:

[0042] HfCl4+M n1 ZrCl n2 →ZrCl4↑+M n1 HfCl n2 .

[0043] Most of the ZrCl4 gas flows out from the top of the tower through the tower plates and enters the No. 2 distillation tower. After continuous replacement through the multi-stage tower plates of multiple distillation towers, the hafnium-free ZrCl4 gas flows out from the top of the last distillation tower, is condensed and collected, and at the same time, hafnium-rich molten salt containing a small amount of ZrCl4 is obtained at the bottom of the No. 1 distillation tower.

[0044] By controlling the temperature of the No. 1 distillation tower, the M n1 ZrCl n2Decompose into ZrCl4 gas, further purify the molten salt to obtain zirconium-free HfCl4 molten salt. The decomposition reaction is as follows:

[0045] M n1 ZrCl n2 →ZrCl4↑+M n1 Cl (n2-4) .

[0046] The zirconium-free HfCl4 molten salt is pumped into the heating furnace and the M n1 HfCl n2t The molten salt is decomposed and HfCl4 gas is collected to obtain nuclear-grade HfCl4.

[0047] Furthermore, the alkali metal chloride salt includes potassium chloride and sodium chloride.

[0048] Furthermore, in step (a), the molar ratio of the crude zirconium tetrachloride salt, the potassium chloride and the sodium chloride is 60-65:17.5-20:17.5-20, including but not limited to 60:17.5:20, 61:18:19.5, 62:18.5:19, 63:19:18.5, 64:19.5:18 or 65:20:17.5.

[0049] Furthermore, the temperature of the first heat treatment is 250-320°C.

[0050] In some specific embodiments, the temperature of the first heat treatment may be, for example, but not limited to, 250°C, 260°C, 270°C, 280°C, 290°C, 300°C, 310°C or 320°C.

[0051] Furthermore, the first heating treatment lasts for 3 to 5 hours.

[0052] In some specific embodiments, the time of the first heating treatment may be, for example, but not limited to, 3 hours, 4 hours or 5 hours.

[0053] Furthermore, when the gas-liquid mass exchange is performed, the temperature of the crude zirconium tetrachloride gas is ≥331°C, and the temperature of the first mixed system is 350-500°C.

[0054] In some specific embodiments, when the gas-liquid mass exchange is carried out, the temperature of the crude zirconium tetrachloride gas may be, for example, but not limited to, 331°C, 340°C, 350°C, 360°C, 380°C, 400°C, 430°C, 450°C, 480°C or 500°C, and the temperature of the first mixed system may be, for example, but not limited to, 350°C, 370°C, 390°C, 410°C, 430°C, 450°C, 470°C, 490°C or 510°C.

[0055] Furthermore, the temperature of the second heat treatment is 500-600°C, including but not limited to 500°C, 510°C, 520°C, 530°C, 540°C, 550°C, 560°C, 570°C, 580°C, 590°C or 600°C.

[0056] Furthermore, the second heating treatment time is a cycle time of 6 to 8 hours (for example, but not limited to 6 hours, 6.5 hours, 7 hours, 7.5 hours or 8 hours), so that the concentration of molten salt HfCl4 in the bottom of tower No. 1 is qualified.

[0057] Furthermore, the temperature of the third heat treatment is 600-850°C, including but not limited to 600°C, 620°C, 640°C, 660°C, 680°C, 700°C, 720°C, 740°C, 760°C, 780°C, 800°C, 820°C or 850°C.

[0058] Furthermore, the third heating treatment is performed for 8 to 12 hours, including but not limited to 8 hours, 9 hours, 10 hours, 11 hours or 12 hours.

[0059] Furthermore, the gas-liquid mass transfer exchange is carried out in a distillation tower.

[0060] Furthermore, the number of the distillation towers is 3 to 4, and the total number of stages of the distillation tower is 9 to 48 (for example, but not limited to, 9, 12, 15, 18, 21, 24, 27, 30, 33, 36, 39, 42, 45, or 48). Generally, a total number of 27 stages is sufficient to achieve nuclear-grade HfCl4 standards.

[0061] Furthermore, the crude zirconium tetrachloride salt contains 1% to 2% (for example, but not limited to 1%, 1.2%, 1.4%, 1.6%, 1.8% or 2%) of hafnium tetrachloride.

[0062] Furthermore, the crude zirconium tetrachloride gas contains 1% to 2% (for example, but not limited to 1%, 1.2%, 1.4%, 1.6%, 1.8% or 2%) of hafnium tetrachloride.

[0063] The embodiments of the present invention will be described in detail below with reference to specific examples and comparative examples.

[0064] Example 1

[0065] The method for separating zirconium tetrachloride and hafnium tetrachloride provided in this embodiment comprises the following steps:

[0066] 1. Dry NaCl and KCl at 130℃ for 2h;

[0067] 2. Mix crude zirconium tetrachloride salt, NaC, and KCl in a molar ratio of 63:18.5:18.5, mix well, and add to the kettle;

[0068] 3. Heating and dissolving salt: heating the bottom of the tower to 285℃ and keeping the temperature constant for 4 hours, observing the melting of the molten salt in the bottom of the tower. After it is completely melted, regulating the temperature of the distillation tower to 320℃ and keeping the temperature constant to obtain the first mixed system;

[0069] 4. Turn on the molten salt pump to circulate inside the tower. There is a heating device outside the tower to keep the tower body at a constant temperature with the tower kettle;

[0070] 5. Crude zirconium tetrachloride gas is introduced from the bottom of Tower 1. The temperature of the added crude zirconium tetrachloride gas is maintained at 331°C. The first mixed system is allowed to flow down from the top of the tower. After the crude zirconium tetrachloride gas is introduced, the temperature of the first mixed system at the bottom of the tower is increased and maintained at 475°C.

[0071] 6. The crude zirconium tetrachloride gas is distilled on the 3-stage tray of the No. 1 distillation tower. The first mixed system and the crude zirconium tetrachloride gas undergo gas-liquid mass transfer exchange on the tray. The following replacement reaction is carried out on each tray:

[0072] HfCl4+M n1 ZrCl n2 →ZrCl4↑+M n1 HfCl n2 ;

[0073] 7. The crude zirconium tetrachloride gas after the first distillation is discharged from the top of the No. 1 distillation tower and introduced into the bottom of the No. 2 distillation tower, and distilled on the three-stage tray of the No. 2 distillation tower. The mixed salt at the bottom of the No. 2 tower and the crude zirconium tetrachloride gas are further exchanged by gas-liquid mass transfer on the tray;

[0074] 8. The crude zirconium tetrachloride gas after the second distillation is discharged from the top of the No. 2 distillation tower and introduced into the bottom of the No. 3 distillation tower, and distilled on the three stages of the No. 3 distillation tower. The mixed salt at the bottom of the No. 3 distillation tower and the crude zirconium tetrachloride gas are further exchanged by gas-liquid mass transfer on the trays;

[0075] 9. The gas discharged from the top of the No. 3 distillation tower enters the condenser and is collected to obtain hafnium-free zirconium tetrachloride. The purity standard for sampling and analysis is: ZrCl4 contains HfCl4 ≤ 0.16%;

[0076] 10. By continuously adding crude zirconium tetrachloride gas, HfCl4 is enriched at the bottoms of the No. 1, No. 2, and No. 3 distillation towers, wherein the enrichment concentration of HfCl4 in the No. 1 distillation tower accounts for more than 50% of the total enrichment concentration of the three distillation towers; when the molar amount of HfCl4 added is greater than or equal to one times the molar amount of molten salt ZrCl4 configured at the bottom of the No. 1 distillation tower, the ZrCl4 in the No. 1 distillation tower is completely replaced by HfCl4, and Zr-free HfCl4 molten salt is obtained at the bottom of the tower. The molten salt is heated at 500°C for 6 hours, and the impurity content is detected. The impurities Fe≤0.06%, Cr≤0.01%, and Al≤0.0075% are considered qualified; the HfCl4 at the bottoms of the No. 2 and 3 distillation towers is enriched accordingly;

[0077] 11. The molten salt at the bottom of the No. 1 distillation tower is pumped into the heating furnace and evaporated at high temperature at 750℃ for 13 hours. n1 HfCl n2t The molten salt decomposes, and the steam enters the condenser for condensation. The HfCl4 gas is collected to obtain nuclear-grade HfCl4. After sampling and analysis, the purity standard is: HfCl4 contains ZrCl4 ≤ 10.7%.

[0078] Example 2

[0079] The method for separating zirconium tetrachloride and hafnium tetrachloride provided in this embodiment comprises the following steps:

[0080] 1-5, same as Example 1;

[0081] 6. The crude zirconium tetrachloride gas is distilled on the 6th stage of the No. 1 distillation tower. The first mixed system and the crude zirconium tetrachloride gas undergo gas-liquid mass transfer exchange on the stage. Each stage undergoes the following replacement reaction:

[0082] HfCl4+M n1 ZrCl n2 →ZrCl4↑+M n1 HfCl n2 ;

[0083] 7. The crude zirconium tetrachloride gas after the first distillation is discharged from the top of the No. 1 distillation tower and introduced into the bottom of the No. 2 distillation tower, and distilled on the 6-stage tray of the No. 2 distillation tower. The mixed salt at the bottom of the No. 2 tower and the crude zirconium tetrachloride gas are further exchanged by gas-liquid mass transfer on the tray;

[0084] 8. The crude zirconium tetrachloride gas after the second distillation is discharged from the top of the No. 2 distillation tower and introduced into the bottom of the No. 3 distillation tower, and distilled on the 6-stage tray of the No. 3 distillation tower. The mixed salt at the bottom of the No. 3 tower and the crude zirconium tetrachloride gas are further exchanged by gas-liquid mass transfer on the tray;

[0085] 9. The gas discharged from the top of the No. 3 distillation tower enters the condenser and is collected to obtain hafnium-free zirconium tetrachloride. The purity standard for sampling and analysis is: ZrCl4 contains HfCl4 ≤ 0.02%;

[0086] 10-11. Same as Example 1.

[0087] Example 3

[0088] The method for separating zirconium tetrachloride and hafnium tetrachloride provided in this embodiment comprises the following steps:

[0089] 1-5, same as Example 1;

[0090] 6. The crude zirconium tetrachloride gas is distilled on the 9th stage of the No. 1 distillation tower. The first mixed system and the crude zirconium tetrachloride gas undergo gas-liquid mass transfer exchange on the trays. Each tray undergoes the following replacement reaction:

[0091] HfCl4+M n1 ZrCl n2 →ZrCl4↑+M n1 HfCl n2 ;

[0092] 7. The crude zirconium tetrachloride gas after the first distillation is discharged from the top of the No. 1 distillation tower and introduced into the bottom of the No. 2 distillation tower, and distilled on the 9-stage tray of the No. 2 distillation tower. The mixed salt at the bottom of the No. 2 tower and the crude zirconium tetrachloride gas are further exchanged by gas-liquid mass transfer on the tray;

[0093] 8. The crude zirconium tetrachloride gas after the second distillation is discharged from the top of the No. 2 distillation tower and introduced into the bottom of the No. 3 distillation tower, and distilled on the 9-stage tray of the No. 3 distillation tower. The mixed salt at the bottom of the No. 3 tower and the crude zirconium tetrachloride gas are further exchanged by gas-liquid mass transfer on the tray;

[0094] 9. The gas discharged from the top of the No. 3 distillation tower enters the condenser and is collected to obtain hafnium-free zirconium tetrachloride. The purity standard for sampling and analysis is: ZrCl4 contains HfCl4 ≤ 0.003%;

[0095] 10-11. Same as Example 1.

[0096] Example 4

[0097] The method for separating zirconium tetrachloride and hafnium tetrachloride provided in this embodiment comprises the following steps:

[0098] 1-5, same as Example 1;

[0099] 6. The crude zirconium tetrachloride gas is distilled on the 12-stage tray of the No. 1 distillation tower. The first mixed system and the crude zirconium tetrachloride gas undergo gas-liquid mass transfer exchange on the trays. The following replacement reaction occurs on each tray:

[0100] HfCl4+M n1ZrCl n2 →ZrCl4↑+M n1 HfCl n2 ;

[0101] 7. The crude zirconium tetrachloride gas after the first distillation is discharged from the top of the No. 1 distillation tower and introduced into the bottom of the No. 2 distillation tower, and distilled on the 12-stage tray of the No. 2 distillation tower. The mixed salt at the bottom of the No. 2 tower and the crude zirconium tetrachloride gas are further exchanged by gas-liquid mass transfer on the trays;

[0102] 8. The crude zirconium tetrachloride gas after the second distillation is discharged from the top of the No. 2 distillation tower and introduced into the bottom of the No. 3 distillation tower, and distilled on the 12-stage tray of the No. 3 distillation tower. The mixed salt at the bottom of the No. 3 tower and the crude zirconium tetrachloride gas are further exchanged by gas-liquid mass transfer on the tray;

[0103] 9. The gas discharged from the top of the No. 3 distillation tower enters the condenser and is collected to obtain hafnium-free zirconium tetrachloride. The purity standard for sampling and analysis is: ZrCl4 contains HfCl4 ≤ 0.001%;

[0104] 10-11. Same as Example 1.

[0105] Example 5

[0106] The method for separating zirconium tetrachloride and hafnium tetrachloride provided in this embodiment comprises the following steps:

[0107] 1. Dry NaCl and KCl at 150℃ for 2h;

[0108] 2. Mix crude zirconium tetrachloride salt, NaC and KCl in a molar ratio of 60:20:20, mix well and add to the kettle;

[0109] 3. Heating the salt: heating the tower bottom to 320℃ and keeping the temperature constant for 3 hours, observing the melting of the molten salt in the tower bottom. After it is completely melted, regulating the tower bottom temperature to 320℃ and keeping the temperature constant to obtain the first mixed system;

[0110] 4. Same as Example 4;

[0111] 5. Crude zirconium tetrachloride gas is introduced from the bottom of Tower 1. The temperature of the added crude zirconium tetrachloride gas is maintained at 345°C. The first mixed system is allowed to flow down from the top of the tower. After the crude zirconium tetrachloride gas is introduced, the temperature of the first mixed system at the bottom of the tower is increased and maintained at 600°C.

[0112] 6. Same as Example 4;

[0113] 7. Same as Example 4;

[0114] 8. Same as Example 4;

[0115] 9. The gas discharged from the top of the No. 3 distillation tower enters the condenser and is collected to obtain hafnium-free zirconium tetrachloride. The purity standard for sampling and analysis is: ZrCl4 contains HfCl4 ≤ 0.0003%;

[0116] 10. By continuously adding crude zirconium tetrachloride gas, HfCl4 is simultaneously enriched at the bottoms of the No. 1, No. 2, and No. 3 distillation towers, wherein the enrichment concentration of HfCl4 in the No. 1 distillation tower accounts for more than 50% of the total enrichment concentration of the three distillation towers; when the molar amount of HfCl4 added is greater than or equal to one times the molar amount of molten salt ZrCl4 configured at the bottom of the No. 1 distillation tower, the ZrCl4 in the No. 1 distillation tower is completely replaced by HfCl4, and Zr-free HfCl4 molten salt is obtained at the bottom of the tower. The molten salt is heated at 600°C for 8 hours, and the impurity content is tested. The impurities Fe ≤ 0.06%, Cr ≤ 0.01%, and Al ≤ 0.0075% are considered qualified; the HfCl4 at the bottoms of the No. 2 and No. 3 distillation towers is accordingly enriched;

[0117] 11. The molten salt at the bottom of the No. 1 distillation tower is pumped into the heating furnace and evaporated at high temperature at 600℃ for 20 hours. n1 HfCl n2t The molten salt decomposes, the steam enters the condenser for condensation, and the HfCl4 gas is collected to obtain nuclear-grade HfCl4. After sampling and analysis, the purity standard is: HfCl4 contains ZrCl4 ≤ 0.4%.

[0118] Example 6

[0119] The method for separating zirconium tetrachloride and hafnium tetrachloride provided in this embodiment comprises the following steps:

[0120] 1. Dry NaCl and KCl at 100°C for 2 hours;

[0121] 2. Mix crude zirconium tetrachloride salt, NaC and KCl in a mass ratio of 65:17.5:17.5, mix well, and add to the kettle;

[0122] 3. Heating the salt: Raise the temperature of the tower kettle to 250°C and keep the temperature constant for 5 hours. Observe the melting of the molten salt in the tower kettle. After it is completely melted, adjust the temperature of the tower kettle to 320°C and keep the temperature constant to obtain the first mixed system.

[0123] 4. Same as Example 4;

[0124] 5. Crude zirconium tetrachloride gas is introduced from the bottom of Tower 1. The temperature of the added crude zirconium tetrachloride gas is maintained at 338°C. The first mixed system is allowed to flow down from the top of the tower. After the crude zirconium tetrachloride gas is introduced, the temperature of the first mixed system at the bottom of the tower is increased and maintained at 350°C.

[0125] 6. Same as Example 4;

[0126] 7. Same as Example 4;

[0127] 8. Same as Example 4;

[0128] 9. The gas discharged from the top of the No. 3 distillation tower enters the condenser and is collected to obtain hafnium-free zirconium tetrachloride. The purity standard for sampling and analysis is: ZrCl4 contains HfCl4 ≤ 0.0002%;

[0129] 10. By continuously adding crude zirconium tetrachloride gas, HfCl4 is simultaneously enriched at the bottoms of the No. 1, No. 2, and No. 3 distillation towers, wherein the enrichment concentration of HfCl4 in the No. 1 distillation tower accounts for more than 50% of the total enrichment concentration of the three distillation towers; when the molar amount of HfCl4 added is greater than or equal to one times the molar amount of molten salt ZrCl4 configured at the bottom of the No. 1 distillation tower, the ZrCl4 in the No. 1 distillation tower is completely replaced by HfCl4, and Zr-free HfCl4 molten salt is obtained at the bottom of the tower. The molten salt is heated at 550°C for 7 hours, and the impurity content is tested. The impurities Fe ≤ 0.06%, Cr ≤ 0.01%, and Al ≤ 0.0075% are considered qualified; the HfCl4 at the bottoms of the No. 2 and 3 distillation towers is correspondingly enriched;

[0130] 11. The molten salt at the bottom of the No. 1 distillation tower is pumped into the heating furnace and evaporated at high temperature at 850℃ for 6 hours. n1 HfCl n2t The molten salt decomposes, the steam enters the condenser for condensation, and the HfCl4 gas is collected to obtain nuclear-grade HfCl4. After sampling and analysis, the purity standard is: HfCl4 contains ZrCl4 ≤ 0.2%.

[0131] Comparative Example 1

[0132] The difference between this comparative example and Example 4 is only in step (5), in which the temperature of the first mixed system at the bottom of the tower is increased and maintained at 650° C., and zirconium tetrachloride and hafnium tetrachloride are separated. The purity standards of sampling and analysis are: ZrCl4 contains HfCl4 ≤ 0.4%; HfCl4 contains ZrCl4 ≤ 15%.

[0133] By comparing the separation effects and separation purities of the embodiments and comparative examples, it can be seen that:

[0134] 1. With the increase of the number of distillation tower plates, the concentration of hafnium tetrachloride enriched in molten salt increases.

[0135] 2. As the temperature of the distillation tower kettle increases, the separation effect becomes better.

[0136] 3. The collection effect of hafnium tetrachloride is better as the temperature increases.

[0137] Although the present invention has been illustrated and described using specific embodiments, it should be appreciated that the above embodiments are merely intended to illustrate the technical solutions of the present invention rather than to limit them. Those skilled in the art should understand that the technical solutions described in the above embodiments may be modified, or some or all of the technical features thereof may be replaced by equivalents, without departing from the spirit and scope of the present invention. However, these modifications or replacements do not deviate from the essence of the corresponding technical solutions within the scope of the technical solutions of the embodiments of the present invention. Therefore, this means that all such replacements and modifications within the scope of the present invention are included in the appended claims.

Claims

1. A method for separating zirconium tetrachloride and hafnium tetrachloride, characterized in that: The following steps are involved: (a) subjecting a mixed system containing crude zirconium tetrachloride salt and alkali metal chloride salt to a first heating treatment to obtain a first mixed system; (b) introducing crude zirconium tetrachloride gas into the first mixed system for gas-liquid mass transfer exchange; collecting zirconium tetrachloride gas generated during the gas-liquid mass transfer exchange process; (c) performing a second heating treatment on the reaction system after the gas-liquid mass transfer exchange is completed; (d) performing a third heat treatment on the reaction system after the second heat treatment, and collecting hafnium tetrachloride gas generated during the third heat treatment.

2. The method for separating zirconium tetrachloride and hafnium tetrachloride according to claim 1, wherein The alkali metal chloride salts include potassium chloride and sodium chloride.

3. The method for separating zirconium tetrachloride and hafnium tetrachloride according to claim 2, wherein: In step (a), the molar ratio of the crude zirconium tetrachloride salt, the potassium chloride and the sodium chloride is 60-65:17.5-20:17.5-20.

4. The method for separating zirconium tetrachloride and hafnium tetrachloride according to claim 1, characterized in that The temperature of the first heating treatment is 250-320°C; And / or, the first heating treatment time is 3 to 5 hours.

5. The method for separating zirconium tetrachloride and hafnium tetrachloride according to claim 1, characterized in that: When the gas-liquid mass exchange is performed, the temperature of the crude zirconium tetrachloride gas is ≥331°C, and the temperature of the first mixed system is 350-500°C.

6. The method for separating zirconium tetrachloride and hafnium tetrachloride according to claim 1, characterized in that: The temperature of the second heat treatment is 500-600°C; And / or, the second heating treatment time is 6 to 8 hours.

7. The method for separating zirconium tetrachloride and hafnium tetrachloride according to claim 1, characterized in that: The temperature of the third heat treatment is 600-850°C; And / or, the third heating treatment is performed for 8 to 12 hours.

8. The method for separating zirconium tetrachloride and hafnium tetrachloride according to claim 1, characterized in that: The gas-liquid mass transfer exchange is carried out in a distillation tower; The number of the distillation towers is 3 to 4; the total number of plates of the distillation towers is 9 to 48.

9. The method for separating zirconium tetrachloride and hafnium tetrachloride according to claim 1, characterized in that: The crude zirconium tetrachloride salt contains 1% to 2% of hafnium tetrachloride; And / or, the crude zirconium tetrachloride gas contains 1% to 2% of hafnium tetrachloride.