A molten salt extraction and distillation separation device for zirconium and hafnium tetrachloride

Abstract

The present application provides a molten salt extraction and distillation separation device for zirconium and hafnium tetrachloride, comprising a distillation tower, a reboiler, a reflux tank, a circulation tank, a sublimator, a gas preheater, and a condenser. During installation, the various components are connected in sequence to obtain a complete molten salt extraction and distillation separation device for zirconium and hafnium tetrachloride. The device has a simple structure, is easy to operate, and is convenient to connect, and is suitable for the molten salt extraction and distillation separation of zirconium and 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] Currently, there are two types of zirconium and hafnium separation technologies: wet and pyrolysis. Wet zirconium and hafnium separation technology, exemplified by solvent extraction techniques such as MIBK and TBP, achieves zirconium and hafnium separation by selectively extracting zirconium or hafnium into an organic phase. Pyrolysis separation technology primarily exploits subtle differences in the redox reaction, volatility, and electrochemical properties of zirconium and hafnium compounds at high temperatures. Pyrolysis molten salt extraction and distillation is performed at high temperatures (300°C–500°C) in a corrosive chloride melt / vapor environment. Due to the low relative volatility of zirconium and hafnium (1.1–1.3), the distillation unit is significantly more complex and requires significantly more plates than conventional distillation towers. Furthermore, the rationality of the distillation tower design directly determines the separation efficiency and economic benefits of zirconium and hafnium tetrachloride. Therefore, the distillation unit is the core of zirconium and hafnium molten salt extraction and distillation separation technology.

[0004] The core of a molten salt distillation unit is to achieve efficient circulation of molten salt while enhancing heat and mass transfer between the gas and liquid phases on the trays, thereby improving distillation and separation efficiency. Currently, molten salt circulation generally utilizes molten salt pumps, but these pumps have relatively high requirements for the type, temperature, viscosity, and corrosion characteristics of the molten salt. Furthermore, long-term operation can easily lead to a decrease in high-temperature reliability (e.g., mechanical wear and component failure), resulting in molten salt leakage and other issues. Furthermore, once the design and process parameters of a conventional distillation tower are finalized, the overall tower efficiency is essentially fixed. Improper selection of the tray structure or process parameters can directly lead to insufficient gas-liquid exchange and low separation efficiency. Therefore, designing a molten salt distillation unit that can achieve molten salt circulation and high separation efficiency in a simple and reliable manner is an important direction for the development of zirconium and hafnium molten salt distillation and separation technology. Summary of the Invention

[0005] 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 industrial zirconium and hafnium molten salt distillation 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:

[0007] 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);

[0008] 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;

[0009] The rectifying section (12) is connected to the first end of the reflux tank (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);

[0010] 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);

[0011] 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;

[0012] 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).

[0013] Furthermore, 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).

[0014] Furthermore, the shape of the gas pipeline (11) is L-shaped.

[0015] 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 is connected to the stripping section (13).

[0016] 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).

[0017] 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).

[0018] Furthermore, a molten salt emptying tank (9) is provided at the third end of the circulation tank (6), and one end of the molten salt emptying tank (9) is connected to the third end of the circulation tank (6).

[0019] Furthermore, the trays in the distillation tower (1) are sieve trays, float valves or barbs;

[0020] The number of the tower plates is 20 to 30.

[0021] Furthermore, a throttle valve (15) is provided at a position of the rectifying section (12) close to the reflux tank (3).

[0022] Furthermore, the material of the device is high borosilicate glass, high-purity quartz glass, 316L stainless steel or nickel-based alloy.

[0023] In summary, this application includes at least one of the following beneficial technical effects:

[0024] 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 the molten salt extraction and distillation separation of industrial-grade zirconium and hafnium tetrachloride.

[0025] 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 along the molten salt circulation pipeline to the reflux tank by gas pressure delivery. 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 rate of molten salt circulation can be more easily controlled, and the reflux ratio can be controlled and adjusted.

[0026] 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. The more complete the contact, the closer the plates are to the theoretical number of plates. This application provides a distillation separation device with a molten salt circulation function. Gas and steam pipelines are provided at the top and bottom of the distillation tower, respectively. Hafnium chloride at the top and zirconium chloride at the bottom can be transported back into the distillation tower for heat and material exchange 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

[0027] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following briefly introduces the drawings required for use in the description of the embodiments of the present application. 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 any creative work.

[0028] Figure 1 A zirconium-hafnium molten salt extraction, distillation and separation device proposed in an embodiment of the present application is shown.

[0029] Description of reference numerals:

[0030] 1. Distillation tower; 11. Gas pipeline; 12. Distillation section; 13. Stripping section; 14. Feed inlet; 15. Throttle valve;

[0031] 2. Sublimator; 3. Reflux tank;

[0032] 4. Condenser; 41. Vacuum pump interface;

[0033] 5. Reboiler;

[0034] 6. Circulation tank; 61. Steam pipeline; 62. Molten salt circulation pipeline; 63. Circulation pipe; 64. Casing;

[0035] 7. Gas preheater;

[0036] 8. Heating furnace;

[0037] 9. Molten salt emptying tank. DETAILED DESCRIPTION

[0038] The following will be combined with the drawings in the embodiments of this application to clearly and completely describe the technical solutions in the embodiments of this application. Obviously, the embodiments described are part of the embodiments of this application, not all of them. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0039] In the drawings, the sizes of components, layer thicknesses, or regions may be exaggerated for clarity. Therefore, any implementation of the present disclosure is not necessarily limited to the dimensions shown in the drawings, and the shapes and sizes of components in the drawings do not reflect true proportions. Furthermore, the drawings schematically illustrate idealized examples, and any implementation of the present disclosure is not limited to the shapes or values ​​shown in the drawings.

[0040] In related technologies, zirconium (Zr) and hafnium (Hf) have excellent corrosion resistance, high temperature resistance, and radiation resistance. They are widely used in fields such as atomic energy, aerospace, high-power lasers, and integrated circuits, and are important strategic metal resources. Hafnium and zirconium have similar chemical properties and coexist in natural minerals. However, their neutron absorption characteristics are diametrically opposed. 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 also differ. Therefore, zirconium and hafnium must be deeply separated before they can be used in the above-mentioned 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 conducted extensive research in the field of zirconium and hafnium separation, and currently two major separation technologies have been developed: wet separation and pyrolysis.

[0041] Wet solvent extraction, exemplified by MIBK and TBP, is the most widely used technology for separating zirconium and hafnium by selectively extracting zirconium or hafnium into an organic phase. Westinghouse Electric and Huachang Electric in the United States, as well as domestic companies like China National Nuclear Corporation (CNNC) Weike, China National Nuclear Corporation (CNNC) Jinghuan, and Nanjing Youtian all use wet solvent extraction to separate zirconium and hafnium. However, this technology is associated with significant environmental pollution, high production costs, and lengthy production processes.

[0042] A typical example of pyrometallurgical separation technology for zirconium and hafnium is molten salt extraction and distillation. This technology exploits the difference in volatility between zirconium tetrachloride and hafnium in molten salt to achieve distillation separation. Since hafnium tetrachloride is more volatile than zirconium tetrachloride, hafnium tetrachloride concentrates at the top of the distillation column, while zirconium tetrachloride concentrates at the bottom. Compared to wet extraction, pyrometallurgical molten salt extraction and distillation technology offers reduced environmental pollution and lower production costs. The separation of raw materials and products can be directly integrated into the existing carbon chlorination and magnesium thermal reduction distillation steps in the production process for metallic zirconium and hafnium, significantly shortening the zirconium and hafnium manufacturing process and reducing production costs. The French company, Cezos, is the only company in the world to have mastered this technology and achieved industrial production of nuclear-grade zirconium and hafnium tetrachloride.

[0043] However, unlike conventional distillation, molten salt extraction distillation is carried out at high temperatures (300°C–500°C) in a corrosive chloride melt / vapor environment. Furthermore, due to the relatively low relative volatility of zirconium and hafnium (1.1–1.3), the distillation unit is significantly more complex and requires significantly more plates than a typical distillation column. Furthermore, the rationality of the distillation column design directly determines the separation efficiency and economic benefits of zirconium and hafnium tetrachloride. Therefore, the distillation unit is the core of zirconium and hafnium molten salt extraction and distillation separation technology. However, there are currently few reports on the design of equipment for molten salt extraction and distillation of zirconium and hafnium by pyrometallurgical separation, and research and development of zirconium and hafnium pyrometallurgical separation technology in China is still in its infancy. Therefore, mastering the design and manufacture of key core equipment for molten salt extraction and distillation of zirconium and hafnium is crucial for achieving breakthroughs in molten salt extraction and distillation technology in my country, thereby further promoting the high-quality, green, and sustainable development of the zirconium and hafnium industry.

[0044] See also Figure 1 , Figure 1 The present invention provides a zirconium-hafnium molten salt extraction and distillation separation device, which specifically includes:

[0045] The device comprises:

[0046] Distillation tower 1, reboiler 5, reflux tank 3, circulation tank 6, sublimator 2, gas preheater 7 and condenser 4;

[0047] 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;

[0048] The rectifying section 12 is connected to the first end of the reflux tank 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;

[0049] 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;

[0050] 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.

[0051] 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 . The molten salt circulation pipeline 62 is used to transport the molten salt stored in the circulation tank 6 to the reflux tank 3 .

[0052] The device has a simple connection method and, after connection, 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.

[0053] 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.

[0054] 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.

[0055] In a specific implementation, the sublimator 2 is used to heat the zirconium and hafnium tetrachloride, so that the zirconium and hafnium tetrachloride is vaporized and then enters the distillation tower 1 for distillation treatment.

[0056] In specific implementation, the embodiment of the present application utilizes the difference in vapor pressure of zirconium and 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. Its scope of application 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.

[0057] In specific implementation, the condenser 4 is used to recover the hafnium tetrachloride distilled from the distillation section 12 .

[0058] In specific implementation, except for the condenser 4, the remaining components need to be placed in the heating furnace 8. The purpose is to ensure that the material is always in liquid and gaseous state during the distillation process. The heating device can accurately control the temperature to achieve temperature control of the distillation process.

[0059] During specific implementation, the reboiler heating temperature is 450°C~500°C, the reflux tank heating temperature 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 height from the bottom to the top of the tower, the circulation tank heating temperature is 500°C~550°C, the gas preheater heating temperature is 500~550°C, the molten salt circulation pipeline heating temperature is 300°C~350°C, and the sublimator heating temperature is 250°C-400°C.

[0060] 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, thereby realizing the circulation of the molten salt.

[0061] During specific implementation, reflux is the key to the distillation process, but at normal pressure, zirconium hafnium tetrachloride does not exist in liquid phase and can only be sublimed directly from the solid phase to the gas phase. Therefore, zirconium hafnium tetrachloride itself cannot reflux and can only be refluxed through the circulation of molten salt. However, the extraction medium used in the distillation of zirconium hafnium molten salt is chloride molten salt, which has an operating temperature of 300 ℃ ~ 500 ℃ and is highly corrosive. Conventional liquid transmission pumps cannot be used, and 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. The embodiment of the present application adopts a method of gas pressure delivery, which utilizes 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.

[0062] In some embodiments, a throttle valve 15 is provided in the distillation section 12 near the reflux drum 3. By adjusting the throttle valve 15, the flow rate of the molten salt in the reflux drum 3 into the distillation tower 1 can be more accurately controlled. After the molten salt reaches a stable flow rate, the vaporized zirconium and hafnium tetrachloride is transported to the distillation tower 1 for extractive distillation. Controlling the flow rate of the molten salt facilitates obtaining a more appropriate reflux ratio, thereby improving separation efficiency.

[0063] 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 in communication with the rectifying section 12 , and a second end of the gas pipeline 11 extends into the reflux tank 3 .

[0064] In practice, a gas pipeline 11 is installed on the distillation tower 1, connecting the upper end of the distillation tower 1 to the tower top reflux tank 3. This allows the small amount of zirconium and hafnium tetrachloride produced at the top of the tower to be re-transferred to the reflux tank 3, where it is dissolved in the molten salt and then returned to the distillation tower 1 for separation. This also helps balance the gas pressure in the distillation tower 1 and the reflux tank 3, thus preventing flooding in the distillation tower to a certain extent.

[0065] 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.

[0066] In some embodiments, the gas pipeline 11 is L-shaped.

[0067] 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.

[0068] In some embodiments, a circulation pipe 63 is provided 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 stripping section 13 .

[0069] In a 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. By setting a circulation pipe 63, the bottom of the distillation section 13 is connected to the circulation tank 6. Due to the high temperature of the circulation tank 6, the molten salt will produce zirconium and hafnium tetrachloride vapor after stripping treatment. The vapor is transported back to the distillation tower 1 along the circulation pipe 63 for separation.

[0070] In a specific implementation, the zirconium and hafnium tetrachloride vapor generated by the molten salt stripping in the reboiler 5 is directly transported upward to the distillation tower 1 for separation.

[0071] 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. A gas pipeline 11 and a steam pipeline 61 are respectively provided at the top and bottom of the distillation tower 1. The zirconium and hafnium tetrachloride enriched at the top and bottom of the tower can be partially transported back to the distillation tower 1 for heat and material exchange between the gas and liquid phases, thereby improving the degree of contact between the gas and liquid phases and improving the distillation efficiency.

[0072] 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 .

[0073] In specific implementation, since hafnium tetrachloride is easier to evaporate, when hafnium tetrachloride of higher purity is to be prepared, the feed position is selected to be closer to the reboiler 5, that is, the sublimator 2 is connected to the feed port 14 of the stripping section 13 closer to the reboiler 5, and the number of trays of the rectifying section 12 is relatively increased, so that zirconium tetrachloride is dissolved in the molten salt as much as possible and removed, so that the hafnium tetrachloride therein becomes increasingly concentrated as the vapor rises, thereby obtaining a higher purity; and zirconium tetrachloride is more difficult to volatilize, so when zirconium tetrachloride of higher purity is to be obtained, the feed position is selected to be closer to the reflux tank 3, that is, the sublimator 2 is connected to the feed port 14 of the rectifying section 12 closer to the reflux tank 3, and the number of trays of the stripping section 13 is relatively increased, so that the zirconium tetrachloride therein becomes increasingly concentrated as the liquid flows downward, thereby obtaining zirconium tetrachloride of higher purity. Therefore, in the embodiment of the present application, multiple 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.

[0074] In some embodiments, the trays in the distillation tower 1 are sieve trays, float valves, or barbs;

[0075] The number of the tower plates is 20 to 30.

[0076] 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 .

[0077] In a specific implementation, by providing a casing 64, the molten salt is compressed by gas from the casing 64 into 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, thereby achieving gas-liquid separation. The zirconium and hafnium tetrachloride evaporated from the stripping can enter the distillation tower 1 for further separation, thereby improving the efficiency of the comprehensive separation.

[0078] In some embodiments, a molten salt emptying tank 9 is provided at the third end of the circulation tank 6 , and one end of the molten salt emptying tank 9 is connected to the third end of the circulation tank 6 .

[0079] 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 carried out, the cooled molten salt is discharged into the reboiler 5 to achieve the repeated use of the molten salt.

[0080] In specific implementation, the reboiler 5 can be disassembled 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.

[0081] 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.

[0082] In some embodiments, after the distillation is completed, the condenser 4 and the sublimator 2 are removed, and the condenser 4 is installed in the position of the original sublimator 2. The material recovered in the condenser 4 is then 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.

[0083] In some embodiments, the condenser 4 may be air-cooled or water-cooled.

[0084] 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.

[0085] In some embodiments, the molten salt circulation line 62, the gas line 11, and the steam line 61 are also disposed in the heating furnace 8. The molten salt distillation temperature is a critical parameter in 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 throughout the distillation process. Therefore, all components, pipelines, and valves of the distillation apparatus provided by the present invention are externally located in the heating furnace 8, enabling precise temperature control and ensuring that the molten salt can circulate normally during the distillation process.

[0086] In some embodiments, the device is made of borosilicate glass, high-purity quartz glass, 316L stainless steel, or nickel-based alloy. All of the above materials are suitable for use as materials for preparing a molten salt extraction, rectification, and separation device for zirconium and hafnium tetrachloride provided in the embodiments of the present application.

[0087] 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 have unified specifications and can be used interchangeably to facilitate the repeated use of molten salt and multiple distillation operations of raw materials.

[0088] 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:

[0089] Step 1: Follow Figure 1 Connect all parts of the device to ensure good airtightness. 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 of the distillation tower 1 is 24.

[0090] 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 <1 ppm, using a 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 <1 ppm, and then adding it to a reboiler 5. After the material is filled, all valves are opened and the vacuum pump is started to evacuate the device. When the vacuum reaches -0.1 MPa, dry high-purity nitrogen is filled in to replace the residual air;

[0091] Step 3, then start the heating furnace 8 of each component, wherein the heating temperature of the reboiler 5 is 450 ℃ ~ 500 ℃, the temperature of the reflux tank 3 is 300 ℃ ~ 350 ℃, the top temperature of the rectifying section 12 of the distillation 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 decreases linearly with the height, the temperature of the circulation tank 6 is 500 ℃ ~ 550 ℃, the temperature of the gas preheater 7 is 500 ℃ ~ 550 ℃, the temperature of the molten salt circulation pipeline 62 is 300 ℃ ~ 350 ℃, the sublimator 2 is first preheated to 250 ℃, and the feeding position is the feed port 14 in the middle of the distillation tower 1;

[0092] 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 under 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;

[0093] Step 5: After the molten salt is stably transported in the distillation tower 1, the temperature of the sublimator 2 is increased from 250°C to 400°C. At this time, a large amount of zirconium and hafnium tetrachloride will volatilize into the middle of the distillation tower 1 and contact the molten salt at each stage 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. The zirconium and hafnium tetrachloride dissolved in the molten salt are first stripped. 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. The stripped molten salt is then pressed into the reflux tank 3 using nitrogen;

[0094] Step 6: After all materials in the sublimator 2 have been sublimed, the molten salt in the reflux tank 3 at the top of the tower is drained, and the temperature of the reboiler 5 and the circulation tank 6 is adjusted to 350°C. The light component (i.e., hafnium tetrachloride) in the distillation tower 1 will condense 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. The zirconium chloride dissolved in the molten salt is evaporated and solidified in the condenser 4.

[0095] 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.

[0096] After a single distillation separation, a hafnium tetrachloride concentrate with a 2.96% hafnium content is obtained at the top of the tower, and a zirconium tetrachloride concentrate is obtained at the bottom of the tower, with the hafnium content reduced from 2% to 1.81%. It can be calculated that the zirconium concentrate at the bottom of the tower can be recycled into distillation tower 1 for 8 to 12 separations to obtain zirconium tetrachloride with a hafnium content of less than 100 ppm, achieving efficient separation of zirconium and hafnium tetrachloride.

[0097] In summary, the embodiment of the present application provides a molten salt extraction, distillation and separation device for zirconium and hafnium tetrachloride, which has a streamlined 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 corresponding to a different number of distillation sections 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. The device can provide a useful reference for the design and manufacture of industrial zirconium and hafnium molten salt distillation equipment.

[0098] 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.

[0099] Although preferred embodiments of the present invention have been described, those skilled in the art may make additional changes and modifications to these embodiments once they become aware of the basic inventive concepts. 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 invention.

[0100] Finally, it should be noted that, in this document, relational terms such as first and second, etc., are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the terms "comprises," "includes," or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article, or terminal device that includes a series of elements includes not only those elements, but also other elements not explicitly listed, or elements that are inherent to such process, method, article, or terminal device. In the absence of further restrictions, an element defined by the phrase "comprises a ..." does not exclude the presence of additional identical elements in the process, method, article, or terminal device that includes the element.

[0101] The above is a detailed introduction to the molten salt extraction and distillation separation device for zirconium and hafnium tetrachloride provided by the present application. Specific examples are used herein 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 ideas of the present application, 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 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 tank (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, rectification and separation device of zirconium and hafnium tetrachloride according to claim 1, characterized in that: The rectifying section (12) is connected to a gas pipeline (11) at a position close to the reflux tank (3). The first end of the gas pipeline (11) is in communication with the rectifying section (12), and the second end extends into the reflux tank (3).

3. The molten salt extraction, rectification and 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, rectification and separation device for 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 communicated with the molten salt circulation pipeline (62).

6. The molten salt extraction, rectification and separation device for zirconium and hafnium tetrachloride according to claim 1, characterized in that: 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).

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

10. The molten salt extraction, rectification and separation device for 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.

Images