Fused salt extractive distillation separation device for zirconium-hafnium tetrachloride

Abstract

The invention provides a fused salt extractive distillation separation device for zirconium and hafnium tetrachloride, which comprises a rectifying tower, a reboiler, a reflux tank, a circulating tank, a sublimator, a gas preheater and a condenser, and during installation, all the parts are sequentially connected to obtain the complete zirconium and hafnium tetrachloride fused salt extractive distillation separation device. The device is simple in structure, easy and convenient to operate, convenient to connect and suitable for molten salt extractive distillation separation of zirconium-hafnium tetrachloride.

Description

Technical Field

[0001] The present application relates to the technical field of chemical separation of metal compounds, and in particular to a molten salt extraction and distillation separation device for zirconium and hafnium tetrachloride. Background Art

[0002] Zirconium (Zr) and hafnium (Hf) have good corrosion resistance, high temperature resistance and radiation resistance. They are widely used in atomic energy, aerospace, high-power lasers, integrated circuits and other fields. They are important strategic metal resources.

[0003] At present, the separation technology of zirconium and hafnium is divided into two types: wet method and pyrolysis. The wet separation technology of zirconium and hafnium is a solvent extraction technology represented by MIBK, TBP, etc., which realizes the separation of zirconium and hafnium by selectively extracting zirconium or hafnium into the organic phase. The pyrolysis separation technology of zirconium and hafnium mainly uses the subtle differences in the redox reaction characteristics, volatility characteristics and electrochemical characteristics between zirconium and hafnium compounds at high temperature to achieve separation. The pyrolysis molten salt extraction distillation is carried out at high temperature (300 ℃~500 ℃) and corrosive chloride melt / vapor environment, and because the relative volatility of zirconium and hafnium is relatively small (1.1~1.3), the complexity of the distillation device and the number of plates required are also significantly more than those of general distillation towers. In addition, the rationality of the distillation tower design also directly determines the separation efficiency and economic benefit indicators of zirconium and hafnium tetrachloride. Therefore, the distillation device is the core of the molten salt extraction and distillation separation technology of zirconium and hafnium.

[0004] The core of the molten salt distillation device is to achieve efficient circulation of molten salt, while strengthening the heat / mass transfer of gas-liquid phase on the tower plate to improve the distillation separation efficiency. At present, the circulation of molten salt generally adopts molten salt pumps, but molten salt pumps have relatively high requirements for the type, temperature, viscosity, and corrosion characteristics of molten salt, and the long-term operation process is prone to high-temperature reliability degradation (such as mechanical wear and component failure), leading to molten salt leakage and other problems. In addition, after the design and process parameters of conventional distillation towers are finalized, the efficiency of the entire tower is basically fixed. If the tower plate structure or process parameters are not selected reasonably, it may directly lead to insufficient gas-liquid phase exchange and low separation efficiency. Therefore, designing a molten salt distillation device that can achieve molten salt circulation and high separation efficiency in a simple and reliable way is an important direction for the development of zirconium and hafnium molten salt distillation separation technology. Summary of the invention

[0005] In order to solve the above problems, the present application provides a molten salt extraction and distillation separation device for zirconium and hafnium tetrachloride. The device has a simple structure and is easy to assemble. It can form a complete molten salt extraction and distillation separation system for zirconium and hafnium tetrachloride, and does not require a molten salt pump. It overcomes the problems existing in the use of molten salt pumps, achieves efficient separation, and enhances the purification effect. It provides a useful reference for the design and manufacture of zirconium and hafnium molten salt distillation industrial equipment, and is of great significance to promoting the high-quality, green and sustainable development of my country's zirconium and hafnium industry.

[0006] The present application provides a molten salt extraction and distillation separation device for zirconium and hafnium tetrachloride, the device comprising: A distillation tower (1), a reboiler (5), a reflux tank (3), a circulation tank (6), a sublimator (2), a gas preheater (7) and a condenser (4); The distillation tower (1) is composed of a distillation section (12) and a stripping section (13) connected to each other, wherein the distillation section (12) is used to extract hafnium tetrachloride, and the stripping section (13) is used to extract zirconium tetrachloride; The rectifying section (12) is connected to the first end of the reflux drum (3), the stripping section (13) is connected to the first end of the reboiler (5), and the connection between the rectifying section (12) and the stripping section (13) is connected to the sublimator (2); The second end of the reflux tank (3) is connected to the condenser (4), and the reflux tank (3) is used to transport molten salt to the distillation tower (1); The first end of the circulation tank (6) is connected to the second end of the reboiler (5); the second end of the circulation tank (6) is provided with a steam pipeline (61); the first end of the steam pipeline (61) is provided with a molten salt circulation pipeline (62); and the second end is connected to a gas preheater (7); the circulation tank (6) is used to store the molten salt transported by the reboiler (5); and the gas preheater (7) is used to heat the protective gas; One end of the molten salt circulation pipeline (62) away from the steam pipeline (61) is connected to the second end of the reflux tank (3), and the molten salt circulation pipeline (62) is used to transport the molten salt stored in the circulation tank (6) to the reflux tank (3).

[0007] Furthermore, a gas pipeline (11) is connected to the rectifying section (12) at a position close to the reflux tank (3), and a first end of the gas pipeline (11) is in communication with the rectifying section (12) and a second end extends into the reflux tank (3).

[0008] Furthermore, the shape of the gas pipeline (11) is L-shaped.

[0009] Furthermore, a circulation pipe (63) is provided at the third end of the steam pipeline (61), one end of the circulation pipe (63) is connected to the steam pipeline (61), and the other end of the circulation pipe (63) is connected to the stripping section (13).

[0010] Furthermore, a sleeve (64) is provided in the pipeline connecting the steam pipeline (61) and the circulation tank (6), one end of the sleeve (64) extends into the circulation tank (6), and the other end is connected to the molten salt circulation pipeline (62).

[0011] Furthermore, a plurality of feed ports (14) are respectively provided on the rectifying section (12) and the stripping section (13), and the gas outlet of the sublimator (2) is connected to the feed ports (14).

[0012] Furthermore, a molten salt draining tank (9) is provided at the third end of the circulation tank (6), and one end of the molten salt draining tank (9) is connected to the third end of the circulation tank (6).

[0013] Furthermore, the trays in the distillation tower (1) are sieve trays, float valves or barbs; The number of the tower plates is 20 to 30.

[0014] Furthermore, a throttle valve (15) is provided at a position of the rectification section (12) close to the reflux tank (3).

[0015] Furthermore, the device is made of high borosilicate glass, high-purity quartz glass, 316L stainless steel or nickel-based alloy.

[0016] In summary, the present application includes at least one of the following beneficial technical effects: 1. The present application provides a molten salt extraction and distillation separation device for zirconium and hafnium tetrachloride. During installation, the various components are connected separately to obtain a complete molten salt extraction and distillation separation system for zirconium and hafnium tetrachloride. The device has a simple structure and is easy to connect. It is suitable for molten salt extraction and distillation separation of industrial-grade zirconium and hafnium tetrachloride. 2. The device provided in the present application includes a reflux tank, a circulation tank, a molten salt circulation pipeline and a gas preheater. When performing molten salt extraction and distillation separation of zirconium and hafnium tetrachloride, the molten salt in the circulation tank is transported to the reflux tank along the molten salt circulation pipeline by gas pressure transportation. The molten salt in the reflux tank flows downward into the distillation tower for distillation treatment, thereby realizing the reflux and circulation of the molten salt. By adjusting the flow rate and pressure of the gas, the circulation rate of the molten salt can be more easily controlled, thereby realizing the control and adjustment of the reflux ratio. 3. The efficiency of distillation is determined by the degree of contact between the gas and liquid phases on the plates in the distillation tower during the distillation process. The more complete the contact, the closer the plates are to the theoretical number of plates. The present application provides a distillation separation device with a molten salt circulation function. Gas pipelines and steam pipelines are respectively arranged at the top and bottom of the distillation tower. The hafnium chloride at the top and the zirconium chloride at the bottom can be transported back to the distillation tower to exchange heat and substances between the gas and liquid phases, thereby improving the degree of contact between the gas and liquid phases and improving the distillation efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the description of the embodiments of the present application will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0018] Figure 1 A zirconium-hafnium molten salt extraction, distillation and separation device proposed in an embodiment of the present application is shown.

[0019] Description of reference numerals: 1. Distillation tower; 11. Gas pipeline; 12. Distillation section; 13. Stripping section; 14. Feed inlet; 15. Throttle valve; 2. Sublimator; 3. Reflux tank; 4. Condenser; 41. Vacuum pump interface; 5. Reboiler; 6. Circulation tank; 61. Steam pipeline; 62. Molten salt circulation pipeline; 63. Circulation pipe; 64. Casing; 7. Gas preheater; 8. Heating furnace; 9. Molten salt drain tank. DETAILED DESCRIPTION

[0020] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0021] In the drawings, the size of the constituent elements, the thickness of the layer or the area may be exaggerated for the sake of clarity. Therefore, any implementation of the present disclosure is not necessarily limited to the size shown in the drawings, and the shapes and sizes of the components in the drawings do not reflect the true proportions. In addition, the drawings schematically show ideal examples, and any implementation of the present disclosure is not limited to the shapes or values ​​shown in the drawings.

[0022] In the related technologies, zirconium (Zr) and hafnium (Hf) have good corrosion resistance, high temperature resistance and radiation resistance, and are widely used in atomic energy, aerospace, high-power lasers, integrated circuits and other fields, and are important strategic metal resources. Hafnium and zirconium have similar chemical properties and coexist in natural minerals, but their neutron absorption characteristics are completely opposite. The neutron absorption cross section of zirconium is only 0.18b, while that of hafnium is as high as 105b. In addition, the optical and electrical properties of zirconium and hafnium oxides are also different. Therefore, zirconium and hafnium must be deeply separated before they can be used in the above fields. Zirconium and hafnium separation technology is a key technology for the preparation of high-quality zirconium and hafnium materials. Since the 1950s, countries around the world have done a lot of research in the field of zirconium and hafnium separation, and currently two major separation technologies have been formed: wet method and pyrolysis.

[0023] The wet separation technology of zirconium and hafnium is a solvent extraction technology represented by MIBK and TBP. It selectively extracts zirconium or hafnium into the organic phase to achieve zirconium and hafnium separation. It is currently the most widely used zirconium and hafnium separation technology. Westinghouse Electric Company and Huachang Company in the United States, and China National Nuclear Corporation Weike, China Nuclear Jinghuan, Nanjing Youtian, etc., all use wet solvent extraction technology to separate zirconium and hafnium. However, this wet solvent extraction technology has problems such as large environmental pollution, high production cost, and long production process.

[0024] The typical representative of zirconium and hafnium pyrometallurgical separation technology is molten salt extraction and distillation separation technology. This technology uses the difference in volatility of zirconium tetrachloride / hafnium in molten salt to achieve distillation separation. Since hafnium tetrachloride is more volatile than zirconium tetrachloride, hafnium tetrachloride will be enriched at the top of the distillation tower, and zirconium tetrachloride will be enriched at the bottom of the distillation tower. Compared with wet extraction, pyrometallurgical molten salt extraction and distillation technology has less environmental pollution and low production cost. The separated raw materials and products can be directly connected with the carbon chlorination and magnesium thermal reduction distillation steps in the current preparation process of metal zirconium and hafnium, which has a significant effect on shortening the zirconium and hafnium manufacturing process and reducing production costs. France's Cezos is the only company in the world that has mastered this technology and achieved industrial production of nuclear-grade zirconium tetrachloride / hafnium.

[0025] However, unlike conventional distillation, molten salt extraction distillation is carried out at high temperature (300 ℃~500 ℃) and in a corrosive chloride melt / vapor environment. In addition, due to the low relative volatility of zirconium and hafnium (1.1~1.3), the complexity of the distillation unit and the number of plates required are significantly more than those of a general distillation tower. In addition, the rationality of the distillation tower design directly determines the separation efficiency and economic benefit indicators of zirconium and hafnium tetrachloride. Therefore, the distillation unit is the core of the molten salt extraction and distillation separation technology of zirconium and hafnium. However, there are currently few literature reports on the design of molten salt extraction and distillation equipment for zirconium and hafnium, and the research and development of molten salt separation technology for zirconium and hafnium in China is also in its infancy. Therefore, mastering the design and manufacturing of key core equipment for molten salt extraction and distillation of zirconium and hafnium is of great significance for my country to break through the molten salt extraction and distillation technology of zirconium and hafnium, thereby further promoting the high-quality, green and sustainable development of my country's zirconium and hafnium industry.

[0026] See also Figure 1 , Figure 1 A zirconium-hafnium molten salt extraction and distillation separation device proposed in an embodiment of the present application is shown, which specifically includes: The device comprises: Distillation tower 1, reboiler 5, reflux tank 3, circulation tank 6, sublimator 2, gas preheater 7 and condenser 4; The distillation tower 1 is composed of a distillation section 12 and a stripping section 13 connected to each other, wherein the distillation section 12 is used to extract hafnium tetrachloride, and the stripping section 13 is used to extract zirconium tetrachloride; The rectifying section 12 is connected to the first end of the reflux drum 3, the stripping section 13 is connected to the first end of the reboiler 5, and the connection between the rectifying section 12 and the stripping section 13 is connected to the sublimator 2; The second end of the reflux tank 3 is connected to the condenser 4, and the reflux tank 3 is used to transport molten salt to the distillation tower 1; The first end of the circulation tank 6 is connected to the second end of the reboiler 5, the second end of the circulation tank 6 is provided with a steam pipeline 61, the first end of the steam pipeline 61 is provided with a molten salt circulation pipeline 62, and the second end is connected to the gas preheater 7, the circulation tank 6 is used to store the molten salt transported by the reboiler 5, and the gas preheater 7 is used to heat the protective gas; One end of the molten salt circulation pipeline 62 away from the steam pipeline 61 is connected to the second end of the reflux tank 3 , and the molten salt circulation pipeline 62 is used to transport the molten salt stored in the circulation tank 6 to the reflux tank 3 .

[0027] The device has a simple connection method, and after connection, it forms a complete system capable of realizing molten salt extraction and distillation separation of zirconium and hafnium tetrachloride. It has a simple structure, is easy to install, has strong applicability, and can achieve an efficient separation effect.

[0028] In specific implementation, the device is used for molten salt extraction and distillation separation of a mixture of zirconium tetrachloride and hafnium tetrachloride. The extractant used for distillation is chloride molten salt. Hafnium tetrachloride is enriched at the top of the distillation section 12, and zirconium tetrachloride is enriched at the bottom of the stripping section 13.

[0029] In specific implementation, the reboiler 5 is used to heat the extractant, i.e., the chloride molten salt, so that the molten salt melts into a liquid state for subsequent transportation.

[0030] In a specific implementation, the sublimator 2 is used to heat the zirconium-hafnium tetrachloride, so that the zirconium-hafnium tetrachloride is vaporized and then enters the distillation tower 1 for distillation treatment.

[0031] In specific implementation, the embodiment of the present application utilizes the difference in vapor pressure of zirconium hafnium tetrachloride in chloride molten salt, so that the more volatile hafnium tetrachloride is enriched at the top of the distillation section 12, while the less volatile zirconium tetrachloride is enriched at the bottom of the stripping section 13, specifically dissolved in the molten salt in the reboiler 5, to achieve the separation of zirconium and hafnium. The method system applicable to the device is complete and simple to operate. It can be applied to industrial-grade molten salt extraction and distillation separation, and can also be applied to laboratory-grade molten salt extraction and distillation separation, and its application range is wider and broader. Using the device of the present application and the method applicable to the device for molten salt extraction and distillation separation, the separation efficiency is greatly improved, and the energy consumption is low and the economic benefits are better.

[0032] In specific implementation, the condenser 4 is used to recover the hafnium tetrachloride evaporated from the distillation section 12 .

[0033] In specific implementation, except for the condenser 4, the remaining components need to be placed in the heating furnace 8, the purpose of which is to ensure that the material is always in liquid and gaseous state during the distillation process, and the heating device can accurately control the temperature to achieve temperature control of the distillation process.

[0034] During specific implementation, the heating temperature of the reboiler is 450°C~500°C, the heating temperature of the reflux tank is 300°C~350°C, the top temperature of the distillation tower 1 is the same as the reflux tank 3, and the bottom temperature is the same as the reboiler 5. The temperature control method in the tower is: the temperature decreases linearly with the height from the bottom to the top of the tower, the heating temperature of the circulation tank is 500°C~550°C, the heating temperature of the gas preheater is 500~550°C, the heating temperature of the molten salt circulation pipeline is 300°C~350°C, and the heating temperature of the sublimator is 250°C-400°C.

[0035] During specific implementation, nitrogen or argon is filled into the gas preheater 7. After being heated by the gas preheater 7, the nitrogen or argon enters the circulation tank 6 along the steam pipeline 61, and the molten salt in the circulation tank 6 is pressed into the molten salt circulation pipeline 62, and finally pressed into the reflux tank 3 at the top of the distillation tower 1, so as to realize the circulation of the molten salt.

[0036] In specific implementation, reflux is the key to the distillation process, but there is no liquid phase in zirconium hafnium tetrachloride at normal pressure, and it can only be sublimated directly from the solid phase to the gas phase. Therefore, zirconium hafnium tetrachloride itself cannot reflux, and reflux can only be achieved through the circulation of molten salt. However, the extraction medium used in the distillation of zirconium hafnium molten salt is chloride molten salt, the operating temperature of which is between 300 ° C and 500 ° C, and it is highly corrosive, and conventional liquid transmission pumps cannot be used. The molten salt pump has relatively high requirements for the type, temperature, viscosity, and corrosion characteristics of the molten salt, and the long-term operation process is prone to high-temperature reliability degradation. The embodiment of the present application adopts a method of gas pressure delivery, which uses air pressure to transfer the molten salt from the circulation tank 6 at the bottom of the distillation tower 1 to the reflux tank 3 at the top of the tower, thereby realizing the reflux of the molten salt, solving the problem that the above-mentioned transmission pump cannot be used, overcoming the problems existing when the molten salt pump is used, and the flow rate of the molten salt circulation can be debugged by controlling the air intake, which is beneficial to process control.

[0037] In some embodiments, the rectifying section 12 is provided with a throttle valve 15 near the reflux tank 3. By adjusting the throttle valve 15, the flow rate of the molten salt in the reflux tank 3 to the rectifying tower 1 can be more accurately controlled. After the molten salt forms a stable flow rate, the vaporized zirconium hafnium tetrachloride is transported to the rectifying tower 1 for extractive distillation treatment. Controlling the flow rate of the molten salt is conducive to obtaining a more suitable reflux ratio, thereby improving the separation efficiency.

[0038] In some embodiments, a gas pipeline 11 is connected to the rectifying section 12 near the reflux tank 3 , a first end of the gas pipeline 11 is connected to the rectifying section 12 , and a second end of the gas pipeline 11 extends into the reflux tank 3 .

[0039] In specific implementation, a gas pipeline 11 is provided on the distillation tower 1, so that the upper end of the distillation tower 1 is connected to the tower top reflux tank 3, and a small amount of zirconium hafnium tetrachloride produced at the tower top is transported back to the reflux tank 3, dissolved in the molten salt, and returned to the distillation tower 1 for separation. It also helps to balance the gas pressure of the distillation tower 1 and the reflux tank 3, and avoid flooding in the distillation tower to a certain extent.

[0040] During specific implementation, the molten salt in the circulation tank 6 is transported to the reflux tank 3 along the molten salt circulation pipeline 62, and the gas pipeline 11 extends into one end of the reflux tank 3 and is inserted below the molten salt liquid level in the reflux tank 3 to increase the gas-liquid contact area and improve the mass transfer efficiency.

[0041] In some embodiments, the gas pipeline 11 is L-shaped.

[0042] By providing the L-shaped gas pipeline 11, the gas flow path is optimized and the pressure drop of the gas in the pipeline is reduced, which helps to maintain the flow pressure of the gas in the distillation tower 1 and ensure the stability of the distillation process.

[0043] In some embodiments, a circulation pipe 63 is disposed at the third end of the steam pipeline 61 , and one end of the circulation pipe 63 is connected to the steam pipeline 61 , and the other end of the circulation pipe 63 is connected to the distillation section 13 .

[0044] In specific implementation, part of the vaporized zirconium and hafnium tetrachloride introduced into the distillation tower 1 will dissolve in the descending molten salt and enter the reboiler 5, and the bottom of the stripping section 13 is connected to the circulation tank 6 by setting a circulation pipe 63. Since the temperature of the circulation tank 6 is relatively high, the molten salt will produce zirconium and hafnium tetrachloride vapor after stripping treatment, and the vapor will be transported back to the distillation tower 1 along the circulation pipe 63 for separation.

[0045] In a specific implementation, the zirconium-hafnium tetrachloride vapor produced by the molten salt stripping in the reboiler 5 is directly transported upward to the distillation tower 1 for separation.

[0046] In specific implementation, the degree of contact between the gas and liquid phases on the tower plate during the distillation process determines the efficiency of the distillation. The more complete the contact, the closer the tower plate is to the theoretical plate. The embodiment of the present application provides a distillation device with a molten salt circulation function, in which a gas pipeline 11 and a steam pipeline 61 are respectively arranged at the top and bottom of the distillation tower 1, so that the zirconium hafnium tetrachloride part enriched at the top and bottom of the tower can be transported back to the distillation tower 1 to exchange heat and substances between the gas and liquid phases, thereby improving the degree of contact between the gas and liquid phases and improving the distillation efficiency.

[0047] In some embodiments, a plurality of feed ports 14 are respectively provided on the rectifying section 12 and the stripping section 13 , and the gas outlet of the sublimator 2 is connected to the feed ports 14 .

[0048] In specific implementation, since hafnium tetrachloride is easier to evaporate, when hafnium tetrachloride with higher purity is to be prepared, the feed position is selected at a position closer to the reboiler 5, that is, the sublimator 2 is connected to the feed port 14 at the position of the stripping section 13 closer to the reboiler 5, the number of plates of the rectifying section 12 is relatively increased, and zirconium tetrachloride is dissolved in the molten salt as much as possible to be removed, so that the vapor rises more and more, and the hafnium tetrachloride therein is increasingly concentrated from plate to plate, so that the obtained purity is higher; while zirconium tetrachloride is more difficult to volatilize, when zirconium tetrachloride with higher purity is to be obtained, the feed position is selected at a position closer to the reflux tank 3, that is, the sublimator 2 is connected to the feed port 14 at the position of the rectifying section 12 closer to the reflux tank 3, the number of plates of the stripping section 13 is relatively increased, and the liquid flows more and more downward, and the zirconium tetrachloride therein is gradually concentrated, so as to obtain zirconium tetrachloride with higher purity. Therefore, in the embodiment of the present application, a plurality of feed ports 14 are provided on the distillation tower 1, and the feed position can be adjusted according to the composition of the raw materials and the target purity of the separated products, thereby effectively reducing the number of plates of the distillation tower 1 required to achieve the target separation efficiency.

[0049] In some embodiments, the trays in the distillation tower 1 are sieve trays, float valves or barbs; The number of the tower plates is 20 to 30.

[0050] In some embodiments, a sleeve 64 is provided in the pipeline connecting the steam pipeline 61 and the circulation tank 6 , one end of the sleeve 64 extends into the circulation tank 6 , and the other end is connected to the molten salt circulation pipeline 62 .

[0051] In specific implementation, by providing a casing 64, the molten salt is compressed by gas from the casing 64 to the molten salt circulation pipeline 62, and the zirconium and hafnium tetrachloride evaporated from the molten salt is discharged into the circulation pipe 63 along the gap between the outer wall of the casing 64 and the circulation tank 6 and the steam pipeline 61, so that the gas-liquid separation is achieved, and the zirconium and hafnium tetrachloride evaporated from the stripping can enter the distillation tower 1 for further separation, thereby improving the efficiency of comprehensive separation.

[0052] In some embodiments, a molten salt draining tank 9 is provided at the third end of the circulation tank 6 , and one end of the molten salt draining tank 9 is connected to the third end of the circulation tank 6 .

[0053] By setting up the molten salt emptying tank 9, when the gas in the molten salt is fully extracted, all the molten salt is discharged into the molten salt emptying tank 9 for cooling. When the next test is conducted, the cooled molten salt is discharged into the reboiler 5 to realize the repeated use of the molten salt.

[0054] In specific implementation, the reboiler 5 can be removed, and the molten salt draining tank 9 can be installed at the original position of the reboiler 5, so that the molten salt can be reused repeatedly.

[0055] In some embodiments, a vacuum pump interface 41 is provided at the upper end of the condenser 4. After the interface 41 is connected to the vacuum pump, the vacuum pump is started to enhance the diffusion effect of the steam.

[0056] In some embodiments, after the distillation is completed, the condenser 4 and the sublimator 2 are removed, and the condenser 4 is installed at the position of the original sublimator 2, and the material recovered in the condenser 4 is transported to the distillation tower 1 for secondary distillation and purification to improve the comprehensive purity of the separated products hafnium tetrachloride and zirconium tetrachloride.

[0057] In some embodiments, the condenser 4 may be air-cooled or water-cooled.

[0058] In some embodiments, valves are provided on the connecting pipe diameter between the condenser 4 and the reflux tank 3, on the connecting pipe diameter between the sublimator 2 and the distillation tower 1, on the connecting pipe diameter between the circulation pipe 63 and the distillation section 13, on the connecting path between the reboiler 5 and the circulation tank 6, and on the connecting path between the gas preheater 7 and the steam pipeline 61, so as to control the flow rate of gas and liquid.

[0059] In some embodiments, the molten salt circulation pipeline 62, the gas pipeline 11 and the steam pipeline 61 are also arranged in the heating furnace 8. The molten salt distillation temperature is an important parameter of the distillation process. Since the melting point of the chloride used in the distillation is between 250°C and 300°C, the molten salt must be kept in a molten state during the distillation process. Therefore, the various components, pipelines and valves of the distillation device provided by the present invention are all externally provided with the heating furnace 8, which can accurately control the temperature and ensure that the molten salt can always circulate normally during the distillation process.

[0060] In some embodiments, the device is made of high borosilicate glass, high purity quartz glass, 316L stainless steel or nickel-based alloy. The above materials are all suitable for use as materials for preparing a molten salt extraction and distillation separation device for zirconium and hafnium tetrachloride provided in an embodiment of the present application.

[0061] In specific implementation, the sublimator 2, reboiler 5, molten salt emptying tank 9, circulation tank 6, and condenser 4 provided in the embodiment of the present application are of unified specifications and can be used interchangeably, which is convenient for repeated use of molten salt and multiple distillation operations of raw materials.

[0062] The specific application method of the molten salt extraction and distillation separation device of zirconium and hafnium tetrachloride provided in the embodiment of the present application includes: Step 1: Follow Figure 1 Connect all parts of the device to ensure good air tightness. The total height of the equipment is about 3.6 m, the width is 1.5 m, and the length is 1.8 m. The total number of plates in the rectifying section 12 and the stripping section 13 in the rectifying tower 1 is 24; Step 2, using industrial-grade zirconium tetrachloride with a hafnium content of 2% as a separation raw material, loading it into a sublimator 2 in a glove box with a water and oxygen content of <1ppm, using NaCl-AlCl3 mixed salt as a molten salt distillation extractant, mixing NaCl-AlCl3 evenly in a glove box with a water and oxygen content of <1ppm, and then adding it to a reboiler 5. After the materials are filled, all valves are opened to start the vacuum pump, and the device is evacuated. When the vacuum degree reaches -0.1MPa, dry high-purity nitrogen is filled in to replace the residual air; Step 3, then start the heating furnace 8 of each component, wherein the heating temperature of the reboiler 5 is 450°C~500°C, the temperature of the reflux tank 3 is 300°C~350°C, the top temperature of the rectifying section 12 of the rectifying tower 1 is consistent with the reflux tank 3, the bottom temperature of the stripping section 13 is consistent with the temperature of the reboiler 5, and the temperature from the bottom of the tower to the top of the tower decreases linearly with the height, the temperature of the circulation tank 6 is 500°C~550°C, the temperature of the gas preheater 7 is 500°C~550°C, the temperature of the molten salt circulation pipeline 62 is 300°C~350°C, the sublimator 2 is first preheated to 250°C, and the feeding position is the feeding port 14 in the middle of the rectifying tower 1; Step 4, when the temperature of each component of the distillation device reaches the preset temperature, the molten salt in the reboiler 5 is in a liquid phase. At this time, about 2 / 3 of the molten salt in the reboiler 5 is placed in the circulation tank 6, the valve between the reboiler 5 and the circulation tank 6 and the valve of the tower bottom steam pipeline 61 are closed, the gas preheater 7 valve is opened, and nitrogen is slowly introduced at 1 L / min. At this time, the molten salt in the circulation tank 6 will enter the sleeve 64 due to the gas pressure, and then be transported to the top of the tower along the molten salt circulation pipeline 62. Finally, 2 / 3 of the molten salt in the circulation tank 6 can be pressed into the reflux tank 3, and the opening of the throttle valve 15 at the top of the distillation tower 1 is adjusted to control the molten salt reflux flow rate to 0.1 L / min~5 L / min; Step 5, when the molten salt is stably transmitted in the distillation tower 1, the temperature of the sublimator 2 is increased from 250°C to 400°C, at which time a large amount of zirconium hafnium tetrachloride will volatilize into the middle of the distillation tower 1, and contact the molten salt at each stage of the tower plate to transfer heat and mass. During the distillation process, whenever the amount of molten salt in the reboiler 5 reaches 2 / 3 of the total volume, half of the molten salt is discharged into the circulation tank 6, and the zirconium hafnium tetrachloride dissolved in the molten salt is first stripped, and the steam enters the steam pipeline 61 along the gap between the outer wall of the sleeve 64 and the circulation tank 6, and finally re-enters the distillation tower 1 along the circulation pipe 63, and then the stripped molten salt is pressed into the reflux tank 3 by nitrogen; Step 6, until all materials in the sublimator 2 are sublimated, the molten salt in the top reflux tank 3 is emptied, the temperature of the reboiler 5 and the circulation tank 6 is adjusted to 350 ° C, and the light component (i.e., hafnium tetrachloride) in the distillation tower 1 is condensed in the condenser 4. When the light component is condensed, a new condenser is replaced, and the temperature of the reboiler 5 and the circulation tank 6 is adjusted to 550 ° C, and the zirconium chloride dissolved in the molten salt is evaporated and solidified in the condenser 4; Step 7: Finally, all the molten salt is discharged into the molten salt emptying tank 9, and the distillation device can be cooled down in a vacuum or nitrogen atmosphere.

[0063] After one distillation separation, a hafnium tetrachloride enrichment with a content of 2.96% is obtained at the top of the tower, and a zirconium tetrachloride enrichment is obtained at the bottom of the tower, and the hafnium content decreases from 2% to 1.81%. It can be calculated that the zirconium enrichment at the bottom of the tower is circulated into the distillation tower 1 for separation 8 to 12 times to obtain zirconium tetrachloride with a hafnium content of less than 100ppm, thereby achieving efficient separation of zirconium and hafnium tetrachloride.

[0064] In summary, the embodiment of the present application provides a molten salt extraction, distillation and separation device of zirconium and hafnium tetrachloride, which has a simple structure, a simple connection method, and low assembly difficulty, and can be better applied to the molten salt extraction, distillation and separation method of zirconium and hafnium tetrachloride. The embodiment of the present application designs multiple feed positions on the distillation tower, each position corresponds to a different number of distillation section and stripping section plates, and the feed position can be adjusted according to the feed composition, the expected separation target, etc., to improve the separation efficiency; by feeding the top of the tower and the top product as raw materials multiple times, high-purity zirconium tetrachloride and hafnium tetrachloride can be prepared, and the device can provide a useful reference for the design and manufacture of zirconium and hafnium molten salt distillation industrial devices.

[0065] The various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referenced to each other.

[0066] Although the preferred embodiments of the present application have been described, those skilled in the art may make additional changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the embodiments of the present application.

[0067] Finally, it should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or terminal device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or terminal device. In the absence of further restrictions, the elements defined by the sentence "including one..." do not exclude the existence of other identical elements in the process, method, article or terminal device including the elements.

[0068] The above is a detailed introduction to a molten salt extraction, distillation and separation device for zirconium and hafnium tetrachloride provided by the present application. Specific examples are used in this article to illustrate the principles and implementation methods of the present application. The description of the above embodiments is only used to help understand the method and core idea of ​​the present application. At the same time, for those skilled in the art, according to the idea of ​​the present application, there will be changes in the specific implementation method and application scope. In summary, the content of this specification should not be understood as a limitation on the present application.

Claims

1. A molten salt extraction and distillation separation device for zirconium and hafnium tetrachloride, characterized in that: The device comprises: A distillation tower (1), a reboiler (5), a reflux tank (3), a circulation tank (6), a sublimator (2), a gas preheater (7) and a condenser (4); The distillation tower (1) is composed of a distillation section (12) and a stripping section (13) connected to each other, wherein the distillation section (12) is used for refining hafnium tetrachloride, and the stripping section (13) is used for concentrating zirconium tetrachloride; The rectifying section (12) is connected to the first end of the reflux drum (3), the stripping section (13) is connected to the first end of the reboiler (5), and the connection between the rectifying section (12) and the stripping section (13) is connected to the sublimator (2); The second end of the reflux tank (3) is connected to the condenser (4), and the reflux tank (3) is used to transport molten salt to the distillation tower (1); The first end of the circulation tank (6) is connected to the second end of the reboiler (5), the second end of the circulation tank (6) is provided with a steam pipeline (61), the first end of the steam pipeline (61) is provided with a molten salt circulation pipeline (62), and the second end is connected to the gas preheater (7), the circulation tank (6) is used to store the molten salt transported by the reboiler (5), and the gas preheater (7) is used to heat the protective gas; One end of the molten salt circulation pipeline (62) away from the steam pipeline (61) is connected to the second end of the reflux tank (3), and the molten salt circulation pipeline (62) is used to transport the molten salt stored in the circulation tank (6) to the reflux tank (3).

2. The molten salt extraction and distillation separation device of zirconium and hafnium tetrachloride according to claim 1, characterized in that: A gas pipeline (11) is connected to the rectifying section (12) at a position close to the reflux tank (3); a first end of the gas pipeline (11) is in communication with the rectifying section (12) and a second end extends into the reflux tank (3).

3. The molten salt extraction and distillation separation device of zirconium and hafnium tetrachloride according to claim 2, characterized in that: The shape of the gas pipeline (11) is L-shaped.

4. The molten salt extraction, rectification and separation device of zirconium and hafnium tetrachloride according to claim 1, characterized in that: A circulation pipe (63) is provided at the third end of the steam pipeline (61), one end of the circulation pipe (63) is connected to the steam pipeline (61), and the other end of the circulation pipe (63) is connected to the stripping section (13).

5. The molten salt extraction and distillation separation device of zirconium and hafnium tetrachloride according to claim 1, characterized in that: A sleeve (64) is provided in the pipeline connecting the steam pipeline (61) and the circulation tank (6); one end of the sleeve (64) extends into the circulation tank (6) and the other end is connected to the molten salt circulation pipeline (62).

6. The molten salt extraction and distillation separation device of zirconium and hafnium tetrachloride according to claim 1, characterized in that: The rectifying section (12) and the stripping section (13) are respectively provided with a plurality of feed ports (14), and the gas outlet of the sublimator (2) is connected to the feed ports (14).

7. The molten salt extraction and distillation separation device of zirconium and hafnium tetrachloride according to claim 1, characterized in that: A molten salt draining tank (9) is provided at the third end of the circulation tank (6), and one end of the molten salt draining tank (9) is connected to the third end of the circulation tank (6).

8. The molten salt extraction and distillation separation device of zirconium and hafnium tetrachloride according to claim 1, characterized in that: The trays in the distillation tower (1) are sieve trays, float valves or barbs; The number of the tower plates is 20 to 30.

9. The molten salt extraction, rectification and separation device of zirconium and hafnium tetrachloride according to claim 1, characterized in that: A throttle valve (15) is provided at a position of the rectification section (12) close to the reflux tank (3).

10. The molten salt extraction, rectification and separation device of zirconium and hafnium tetrachloride according to claim 1, characterized in that: The material of the device is high borosilicate glass, high-purity quartz glass, 316L stainless steel or nickel-based alloy.

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