Rectification system and method for producing boron isotope

Abstract

The invention provides a rectification system and method for producing boron isotopes, and belongs to the technical field of boron isotope preparation. The rectifying system comprises a rectifying tower and a condensing device; the rectifying tower comprises a tower body, a BF3 condenser positioned at the top of the tower body and a reboiler positioned at the bottom of the tower body; the condensing device comprises a liquid nitrogen storage tank and an intermediate condenser, the intermediate condenser is provided with a first heat exchange area and a second heat exchange area, the first heat exchange area is communicated with the second heat exchange area, and the first heat exchange area is configured to be capable of exchanging heat with liquid nitrogen provided by the liquid nitrogen storage tank. After heat exchange, at least part of the gaseous medium located in the first heat exchange area is cooled and liquefied to obtain a liquid medium, the liquid medium is collected to the second heat exchange area, and the second heat exchange area is configured to be capable of conducting heat exchange with gaseous BF3 in the BF3 condenser through the liquid medium; the rectification system can solve the problem that the rectification tower cannot operate normally due to freezing of BF3 in the process of preparing the boron isotope.

Description

Technical Field

[0001] This application relates to the technical field of boron isotope preparation, and specifically, to a rectification system and method for producing boron isotopes. Background Art

[0002] In nature, boron has 10 B and 11 B, two stable isotopes with abundances of 19.8% and 80.2% respectively. Boron isotopes are widely used in many fields, especially playing a huge role in the nuclear industry, medicine, and semiconductors. Specifically, in the nuclear industry, 10 B, due to its high neutron absorption characteristics, is used in controlling nuclear reactors and as a shielding material; in medicine, 10 B is used in boron neutron capture therapy (BNCT) to treat cancer; in the semiconductor field, 11 B is used as a boron dopant for silicon ion implantation to manufacture high-integration, high-density, and small-volume chips.

[0003] Currently, existing boron isotope separation and enrichment methods include cryogenic rectification, chemical exchange rectification, ion exchange chromatography, laser method, and centrifugation, etc. Industrial applications mainly focus on chemical exchange rectification and cryogenic rectification. Among them, the mainstream technology of chemical exchange rectification is the anisole complex exchange method. This method has a complex process flow, high operating requirements, and it is difficult to avoid moisture during the rectification process. The by-product (HF) generated has strong corrosiveness; compared with the chemical exchange rectification method, the cryogenic rectification method mainly uses BF 3 rectification method. F has only one stable isotope, and B has only two stable isotopes. During the entire separation process, there are only 11 BF 3 and 10 BF 3 two substances (specifically, collecting 10 BF 3 at the bottom and 11 BF 3 ) at the top). The component composition is relatively simple, and no chemical changes occur during the entire separation process to generate by-products, making the product have the advantages of less impurities and high purity. In addition, the cryogenic rectification method also has the advantage of being easy to scale up. Therefore, the cryogenic rectification method is expected to become the most ideal preparation process for industrial production of boron isotopes in the future.

[0004] However, during the process of preparing boron isotopes by the cryogenic rectification method, the separation coefficient is small, only 1.0075, and the reflux condensation must be carried out between the melting point (-127°C) and the normal boiling point (-101°C) of BF 3 . Currently, liquid nitrogen is usually used as a refrigerant. However, the temperature of liquid nitrogen is usually -198°C, which is likely to cause BF during the preparation process.3 "Freezes" (i.e., is converted to a solid state after cooling) inside the rectification column, thereby causing the rectification column to operate abnormally. 3 After cooling, it is converted into a solid state, which further causes the rectification column to be difficult to operate normally. Summary of the Invention

[0005] The purpose of this application is to provide a rectification system and method for producing boron isotopes. This rectification system can solve the problem that the rectification column is prone to abnormal operation due to "freezing" of BF during the preparation of boron isotopes. 3 The problem that it cannot operate normally due to "freezing".

[0006] The embodiments of this application are implemented as follows:

[0007] In a first aspect, an embodiment of this application provides a rectification system for producing boron isotopes, including a rectification column and a condensation device. The rectification column includes a column body and a BF condenser located at the top of the column body and a reboiler located at the bottom of the column body; the condensation device includes a liquid nitrogen storage tank and an intermediate condenser. The liquid nitrogen storage tank is used to communicate with a liquid nitrogen source, and the intermediate condenser is used to communicate with a gaseous medium source. The intermediate condenser has a first heat exchange area and a second heat exchange area, and the first heat exchange area and the second heat exchange area are connected. The first heat exchange area is configured to be able to exchange heat with the liquid nitrogen provided by the liquid nitrogen storage tank, so that at least part of the gaseous medium in the first heat exchange area is cooled and liquefied to obtain a liquid medium after heat exchange and is collected in the second heat exchange area. The second heat exchange area is configured to be able to exchange heat with the gaseous BF in the BF condenser using the liquid medium, so that the liquid medium provided by the second heat exchange area is heated and vaporized and returns to the first heat exchange area after heat exchange. 3 In the above technical solution, a condensation device is added to the rectification system on the basis of a conventional rectification column. Specifically, the condensation device includes a liquid nitrogen storage tank and an intermediate condenser. Among them, the liquid nitrogen storage tank is used to communicate with a liquid nitrogen source, and the intermediate condenser is used to communicate with a gaseous medium source. The intermediate condenser has a connected first heat exchange area and a second heat exchange area. The first heat exchange area is configured to be able to exchange heat with the liquid nitrogen provided by the liquid nitrogen storage tank, so that at least part of the gaseous medium in the first heat exchange area is cooled and liquefied to obtain a liquid medium after heat exchange and is collected in the second heat exchange area. The second heat exchange area is configured to be able to exchange heat with the gaseous BF in the BF condenser using the liquid medium, so that the liquid medium provided by the second heat exchange area is heated and vaporized and returns to the first heat exchange area after heat exchange; by adding an intermediate condenser, that is, using the heat exchange medium in the intermediate condenser as an intermediate bridge, so that the gaseous BF in the BF condenser 3 The gaseous BF in the BF condenser 3 is used for heat exchange, so that the liquid medium provided by the second heat exchange area is heated and vaporized and returns to the first heat exchange area after heat exchange.

[0008] In the above technical solution, a condensation device is added to the rectification system on the basis of a conventional rectification column. Specifically, the condensation device includes a liquid nitrogen storage tank and an intermediate condenser. Among them, the liquid nitrogen storage tank is used to communicate with a liquid nitrogen source, and the intermediate condenser is used to communicate with a gaseous medium source. The intermediate condenser has a connected first heat exchange area and a second heat exchange area. The first heat exchange area is configured to be able to exchange heat with the liquid nitrogen provided by the liquid nitrogen storage tank, so that at least part of the gaseous medium in the first heat exchange area is cooled and liquefied to obtain a liquid medium after heat exchange and is collected in the second heat exchange area. The second heat exchange area is configured to be able to exchange heat with the gaseous BF in the BF condenser using the liquid medium, so that the liquid medium provided by the second heat exchange area is heated and vaporized and returns to the first heat exchange area after heat exchange; by adding an intermediate condenser, that is, using the heat exchange medium in the intermediate condenser as an intermediate bridge, so that the gaseous BF in the BF condenser 3 The gaseous BF in the BF condenser 3 is used for heat exchange, so that the liquid medium provided by the second heat exchange area is heated and vaporized and returns to the first heat exchange area after heat exchange; by adding an intermediate condenser, that is, using the heat exchange medium in the intermediate condenser as an intermediate bridge, so that the gaseous BF in the BF condenser 3 The gaseous BF in the BF condenser 3The heat exchange medium for heat exchange is not liquid nitrogen but a liquid medium with a temperature higher than that of liquid nitrogen (obtained by liquefying the gaseous medium after heat exchange with liquid nitrogen), so as to solve the problem that the distillation column is prone to abnormal operation due to "icing" during the preparation of boron isotopes. 3 The problem that it cannot operate normally due to "icing".

[0009] In some alternative embodiments, along the height direction of the tower body, from top to bottom, the liquid nitrogen storage tank, the intermediate condenser, and the BF 3 condenser are connected in sequence. Among them, the first heat exchange area is located at the top of the intermediate condenser, the second heat exchange area is located at the bottom of the intermediate condenser, the liquid nitrogen storage tank is connected to the first heat exchange area, and the BF 3 condenser is connected to the second heat exchange area.

[0010] In the above technical solution, the liquid nitrogen storage tank, the intermediate condenser, and the BF 3 condenser are connected in sequence from top to bottom, that is, the three are set in an integrated form, which has the advantages of a relatively compact overall structure and a small space occupation.

[0011] In some alternative embodiments, the liquid nitrogen storage tank is sleeved on the first heat exchange area, and the second heat exchange area is sleeved on the BF 3 condenser, and the connection surfaces corresponding to both between the liquid nitrogen storage tank and the first heat exchange area and between the second heat exchange area and the BF3 condenser are used as heat exchange places.

[0012] In some alternative embodiments, the first heat exchange area is sleeved on the liquid nitrogen storage tank, the BF 3 condenser is sleeved on the second heat exchange area, and the connection surfaces corresponding to both between the liquid nitrogen storage tank and the first heat exchange area and between the second heat exchange area and the BF3 condenser are used as heat exchange places.

[0013] In the above technical solution, the liquid nitrogen storage tank, the intermediate condenser, and the BF 3 condenser are sequentially sleeved and the connection surfaces are used as heat exchange places, which has the advantages of a relatively compact overall structure, a reasonable layout, high connection stability, and high heat exchange efficiency; at the same time, this setting can also make the heat exchange medium contained in the intermediate condenser more convenient for self-circulation, that is, the gaseous medium at the top is cooled and transformed into a liquid medium and collected at the bottom, and the liquid medium at the bottom is heated and transformed back into a gaseous medium and returns to the top.

[0014] In some alternative embodiments, the liquid nitrogen storage tank is also provided with a pressure detection unit or / and a temperature detection unit.

[0015] In the above technical solution, after the liquid nitrogen is heat-exchanged, both the pressure and temperature in the liquid nitrogen storage tank will rise. A pressure detection unit or / and a temperature detection unit is added to the liquid nitrogen storage tank to realize real-time monitoring of the state in the liquid nitrogen storage tank, so as to facilitate judging whether new liquid nitrogen needs to be replenished according to the pressure and temperature indicators.

[0016] In some alternative embodiments, along the height direction of the tower body, from top to bottom, the intermediate condenser includes a first heat exchange area, a second heat exchange area, and a feeding area located between the two. The inner diameter of the feeding area is smaller than the inner diameter of the first heat exchange area and the inner diameter of the second heat exchange area.

[0017] In the above technical solution, the feeding area in the intermediate condenser does not participate in heat exchange. By setting its inner diameter to be smaller than the inner diameters of the first heat exchange area and the second heat exchange area at both ends, that is, presenting a form with a smaller middle and larger ends as a whole, it can reduce manufacturing consumables and lower the manufacturing cost. At the same time, it also enables the intermediate condenser to have a higher heat exchange efficiency.

[0018] In some alternative embodiments, along the height direction of the tower body, the feeding area includes a buffer section and equal-diameter feeding sections located at both ends of the buffer section, and the inner diameter of the buffer section is larger than the inner diameter of the equal-diameter feeding sections. The equal-diameter feeding section at the upper end is communicated with the first heat exchange area, and the equal-diameter feeding section at the lower end is communicated with the second heat exchange area.

[0019] In the above technical solution, the feeding area is set in a form where the buffer section and the equal-diameter feeding sections cooperate with each other. Among them, the inner diameter of the buffer section is larger than the inner diameter of the equal-diameter feeding sections, that is, the feeding area as a whole presents a form with a larger middle and smaller ends. The buffer section can temporarily store a part of the liquid medium, and can better maintain the temperature stability of the distillation column when the liquid nitrogen quantity is insufficient.

[0020] In some alternative embodiments, the nitrogen outlet of the liquid nitrogen storage tank is communicated with the heat exchange medium inlet of the reboiler through a compressor.

[0021] In the above technical solution, the nitrogen outlet of the liquid nitrogen storage tank is communicated with the heat exchange medium inlet of the reboiler, that is, the nitrogen generated after the liquid nitrogen is heat-exchanged is used as the heat source of the reboiler to realize the secondary utilization of nitrogen, which can save the manufacturing cost; at the same time, the nitrogen outlet of the liquid nitrogen storage tank and the heat exchange medium inlet of the reboiler are communicated through a compressor, which is convenient to adjust the nitrogen temperature so that the nitrogen has a more appropriate temperature when it reaches the reboiler, thereby better heating the liquid boron trifluoride and vaporizing it.

[0022] In some alternative embodiments, the liquid nitrogen storage tank, the intermediate condenser and BF 3The condensers are evenly spaced; the internal cavity of the middle condenser is used to communicate with the gaseous medium source. The first heat exchange area is located at the top of the middle condenser, and the second heat exchange area is located at the bottom of the middle condenser. The side wall of the cavity corresponding to the first heat exchange area has a first fluid channel capable of exchanging heat with the cavity. The first fluid channel is connected to the liquid nitrogen storage tank to introduce liquid nitrogen into the first fluid channel, so that at least part of the gaseous medium in the first heat exchange area is cooled and liquefied after heat exchange and collected in the second heat exchange area. The side wall of the cavity corresponding to the second heat exchange area has a second fluid channel, and the second fluid channel is configured to be able to transport the liquid medium to BF 3 condenser, for heat exchange with BF 3 the gaseous BF in the condenser 3 for heat exchange, and it can also make the liquid medium vaporize and return to the first heat exchange area after heat exchange.

[0023] In the above technical solution, the liquid nitrogen storage tank, the middle condenser and BF 3 condensers are evenly spaced, that is, they are set in a split form and connected and heat exchanged through pipelines, which is convenient for the assembly and layout of the rectification system when the longitudinal space is insufficient.

[0024] In a second aspect, an embodiment of the present application provides a method for producing boron isotopes, which is produced using the rectification system provided in the embodiment of the first aspect, and includes the following steps:

[0025] Transport the raw materials into the tower body for rectification. First, use the liquid nitrogen provided by the liquid nitrogen storage tank to exchange heat with the gaseous medium in the first heat exchange area, so that at least part of the gaseous medium in the first heat exchange area is cooled and liquefied to obtain a liquid medium and collected in the second heat exchange area. Among them, the liquefaction temperature of the gaseous medium is -100 to -120 °C; then use the liquid medium in the second heat exchange area to exchange heat with the gaseous BF 3 in the condenser 3 so that the liquid medium provided by the second heat exchange area vaporizes and returns to the first heat exchange area after heat exchange.

[0026] In the above technical solution, the method for producing boron isotopes is produced using the rectification system provided in the embodiment of the first aspect. Since an intermediate condenser is added on the basis of a conventional rectification column, and the liquefaction temperature of the heat exchange medium in the intermediate condenser is -100 to -120 °C, that is, the overall heat exchange process is: liquid nitrogen first exchanges heat with the gaseous medium to cool and liquefy the gaseous medium into a liquid medium with a temperature close to -100 °C, and then passes through the liquid medium to exchange heat with the gaseous BF 3 in the condenser 3 so as to make it exchange heat with the gaseous BF 3 in the condenser 3The heat exchange medium for heat exchange is not liquid nitrogen but a liquid medium with a temperature of about -100°C, thus solving the problem that direct heat exchange between liquid nitrogen and BF 3 gaseous BF in the condenser 3 causes "icing" inside the distillation column during heat exchange.

[0027] In some alternative embodiments, the gaseous medium includes a heat exchange gaseous medium and a buffer gaseous medium, and the volume ratio of the buffer gaseous medium is greater than that of the heat exchange gaseous medium. Among them, the heat exchange gaseous medium is selected from at least one of nitrogen trifluoride, carbon tetrafluoride, methane, ethylene, and oxygen, and the buffer gaseous medium is selected from at least one of hydrogen, neon, and helium.

[0028] In the above technical solution, the gaseous medium is composed of the heat exchange gaseous medium and the buffer gaseous medium of the above types, and the volume ratio of the buffer gaseous medium is greater than that of the heat exchange gaseous medium, so that the overall pressure change of the gaseous medium during liquefaction and gasification is small (pressure change will cause temperature change), and then the temperatures of the first heat exchange zone and the second heat exchange zone of the intermediate condenser are both maintained within a suitable range, which helps to improve the stability of the distillation system.

[0029] In some alternative embodiments, after the heat exchange gaseous medium in the intermediate condenser is liquefied, the pressure in the intermediate condenser is 1 - 50 bar.

[0030] Optionally, the heat exchange gaseous medium is oxygen. After the heat exchange gaseous medium in the intermediate condenser is liquefied, the pressure in the intermediate condenser is 5 - 10 bar.

[0031] Optionally, the heat exchange gaseous medium is ethylene. After the heat exchange gaseous medium in the intermediate condenser is liquefied, the pressure in the intermediate condenser is 1 - 2 bar.

[0032] Optionally, the heat exchange gaseous medium is nitrogen trifluoride or / and carbon tetrafluoride. After the heat exchange gaseous medium in the intermediate condenser is liquefied, the pressure in the intermediate condenser is 2 - 6 bar.

[0033] Optionally, the heat exchange gaseous medium is methane. After the heat exchange gaseous medium in the intermediate condenser is liquefied, the pressure in the intermediate condenser is 15 - 30 bar.

[0034] In the above technical solution, after the heat exchange gaseous medium in the intermediate condenser is liquefied, the pressure in the intermediate condenser is controlled within the above range so that the temperature of the liquid medium is closer to -100°C, thereby more accurately controlling the temperature of the distillation column at a suitable separation temperature; further, for different types of heat exchange gaseous media, the pressure of the gaseous medium after liquefaction is respectively limited within the above range, which can make the temperature of the liquid medium closer to -100°C.

[0035] In some alternative embodiments, the nitrogen outlet of the liquid nitrogen storage tank is connected to the heat exchange medium inlet of the reboiler through a compressor, and the compression ratio of the compressor is 2 to 20.

[0036] In the above technical solution, the compression ratio of the compressor is limited within the above range so that the temperature of the nitrogen reaches the reboiler within the range of -55°C to -95°C, facilitating heat exchange with liquid boron trifluoride and vaporizing it. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] To more clearly illustrate the technical solutions of the embodiments of the present application, the following will briefly introduce the drawings required for use in the embodiments. It should be understood that the following drawings only show certain embodiments of the present application and should not be regarded as limiting the scope. For those of ordinary skill in the art, other related drawings can be obtained based on these drawings without creative efforts.

[0038] Figure 1 Structural schematic diagram of the first rectification system provided by an embodiment of the present application;

[0039] Figure 2 Structural schematic diagram of the second rectification system provided by an embodiment of the present application;

[0040] Figure 3 Structural schematic diagram of the first intermediate condenser provided by an embodiment of the present application;

[0041] Figure 4 Structural schematic diagram of the second intermediate condenser provided by an embodiment of the present application;

[0042] Figure 5 Structural schematic diagram of the third rectification system provided by an embodiment of the present application;

[0043] Figure 6 Structural schematic diagram of the fourth rectification system provided by an embodiment of the present application.

[0044] Reference Signs: 10 - rectification system; 100 - rectification column; 110 - column body; 120 - BF 3 condenser; 130 - reboiler; 140 - adiabatic diaphragm; 200 - condensation device; 210 - liquid nitrogen storage tank; 220 - intermediate condenser; 221 - first heat exchange area; 222 - second heat exchange area; 223 - feeding area; 223a - buffer section; 223b - equal-diameter feeding section; 300 - compressor; 400 - first-stage vacuum cover; 500 - second-stage vacuum cover. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0045] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the following will clearly and completely describe the technical solutions in the embodiments of this application with reference to the accompanying drawings in the embodiments of this application. Obviously, the described embodiments are some, but not all, of the embodiments of this application. The components of the embodiments of this application usually described and illustrated in the accompanying drawings here can be arranged and designed in various different configurations.

[0046] Therefore, the following detailed description of the embodiments of this application provided in the accompanying drawings is not intended to limit the scope of this application that is claimed, but merely represents selected embodiments of this application. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in this application without creative efforts fall within the scope of protection of this application.

[0047] It should be noted that similar reference numerals and letters denote similar items in the following drawings. Therefore, once an item is defined in one drawing, it does not need to be further defined and explained in subsequent drawings.

[0048] In the description of this application, it should be noted that the orientation or positional relationship indicated by the terms "upper", "lower", "inner", "outer", etc. is based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship in which the product of this application is usually placed during use. It is only for the convenience of describing this application and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application. In addition, the terms "first", "second", etc. are only used for descriptive distinction and should not be construed as indicating or implying relative importance.

[0049] In the description of this application, it should also be noted that unless otherwise clearly specified and limited, the terms "set", "installed", "connected", and "connected" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be directly connected, or indirectly connected through an intermediate medium, and it can be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0050] In the prior art, during the process of preparing boron isotopes by the low-temperature rectification method, liquid nitrogen is usually directly used as the heat exchange medium of the BF 3 condenser. Since the temperature of liquid nitrogen is usually -198°C, it is easy to cause the BF 3 to "freeze" in the rectification column during the preparation process, thereby making it difficult for the rectification column to operate normally.

[0051] Based on this, the inventor found through research that by modifying a conventional rectification column (i.e., the column body and the BF located at the top of the column body) 3Optimize the structure of the condenser and the reboiler located at the bottom of the tower body, specifically by additionally installing an intermediate condenser to make it compatible with BF 3 The gaseous BF in the condenser 3 The heat exchange medium for heat exchange is not liquid nitrogen but other media with a temperature higher than liquid nitrogen, which can solve the problem that the distillation column is prone to abnormal operation due to BF 3 "icing" during the process of preparing boron isotopes.

[0052] The following specifically describes a distillation system and method for producing boron isotopes according to the present application.

[0053] Refer to Figure 1 , in the first aspect, an embodiment of the present application provides a distillation system 10 for producing boron isotopes, including a distillation column 100 and a condensation device 200. The distillation column 100 includes a tower body 110, a BF 3 condenser 120 located at the top of the tower body 110, and a reboiler 130 located at the bottom of the tower body 110 (wherein, a feed channel is provided in the middle of the tower body 110, and discharge ports are respectively provided at the top and the bottom of the tower body 110); the condensation device 200 includes a liquid nitrogen storage tank 210 and an intermediate condenser 220. The liquid nitrogen storage tank 210 is used to communicate with a liquid nitrogen source, and the intermediate condenser 220 is used to communicate with a gaseous medium source. The intermediate condenser 220 has a first heat exchange area 221 and a second heat exchange area 222, and the first heat exchange area 221 and the second heat exchange area 222 are connected. The first heat exchange area 221 is configured to be able to exchange heat with the liquid nitrogen provided by the liquid nitrogen storage tank 210, so that at least part of the gaseous medium located in the first heat exchange area 221 cools and liquefies to obtain a liquid medium and collects in the second heat exchange area 222. The second heat exchange area 222 is configured to be able to use the liquid medium to exchange heat with the gaseous BF 3 The gaseous BF in the BF condenser 120 3 for heat exchange, so that the liquid medium provided by the second heat exchange area 222 is heated and vaporized and returns to the first heat exchange area 221 after heat exchange.

[0054] In the present application, a condensation device 200 is additionally installed on the basis of the conventional distillation column 100 in the distillation system 10. Specifically, the condensation device 200 includes a liquid nitrogen storage tank 210 and an intermediate condenser 220. Among them, the liquid nitrogen storage tank 210 is used to communicate with a liquid nitrogen source, and the intermediate condenser 220 is used to communicate with a gaseous medium source. The intermediate condenser 220 has a connected first heat exchange area 221 and a second heat exchange area 222. The first heat exchange area 221 is configured to be able to exchange heat with the liquid nitrogen provided by the liquid nitrogen storage tank 210, so that at least part of the gaseous medium located in the first heat exchange area 221 cools and liquefies to obtain a liquid medium and collects in the second heat exchange area 222. The second heat exchange area 222 is configured to be able to use the liquid medium to exchange heat with the gaseous BF in the BF3 condenser 1203 Heat exchange is carried out so that the liquid medium provided by the second heat exchange area 222 is heated and vaporized after heat exchange and returns to the first heat exchange area 221; by adding an intermediate condenser 220, that is, using the heat exchange medium in the intermediate condenser 220 as an intermediate bridge to make it in contact with BF 3 The gaseous BF in the condenser 120 3 The heat exchange medium for heat exchange is not liquid nitrogen but a liquid medium with a temperature higher than that of liquid nitrogen (obtained by liquefying the gaseous medium after heat exchange with liquid nitrogen), so that the problem that the distillation column 100 is prone to abnormal operation due to BF 3 "icing" can be solved.

[0055] It should be noted that the heat exchange medium in the intermediate condenser 220 always circulates by itself between the gaseous and liquid states. Specifically, it cools down in the first heat exchange area 221 and is converted from the gaseous state to the liquid state and gathers in the second heat exchange area 222. The liquid medium exchanges heat with BF 3 The gaseous BF in the condenser 120 3 After heat exchange, it is heated and converted from the liquid state to the gaseous state and returns to the first heat exchange area 221. Therefore, it is only necessary to introduce the heat exchange medium into the intermediate condenser 220 once.

[0056] It should be noted that the relative positional relationship between the intermediate condenser 220 and the BF 3 condenser 120 is not limited. For example, it can be in a split form or an integrated form, and can be adjusted adaptively according to actual needs.

[0057] Refer to Figure 1 , as an example, along the height direction of the tower body 110, from top to bottom, the liquid nitrogen storage tank 210, the intermediate condenser 220 and the BF 3 condenser 120 are connected in sequence. Among them, the first heat exchange area 221 is located at the top of the intermediate condenser 220, the second heat exchange area 222 is located at the bottom of the intermediate condenser 220, the liquid nitrogen storage tank 210 is connected to the first heat exchange area 221, and the BF 3 condenser 120 is connected to the second heat exchange area 222.

[0058] In this embodiment, the liquid nitrogen storage tank 210, the intermediate condenser 220 and the BF 3 condenser 120 are connected in sequence from top to bottom, that is, the three are set in an integrated form, which has the advantages of a relatively compact overall structure and a small space occupation.

[0059] It should be noted that the liquid nitrogen storage tank 210, the intermediate condenser 220 and the BF 3The heat exchange method of the condenser 120 is not limited. For example, the connection surface can be used as the heat exchange site, or it can be in the form of being connected by pipelines for heat exchange. Specifically, it can be adjusted adaptively according to actual needs.

[0060] Refer to Figure 1 , as an example, the liquid nitrogen storage tank 210 is sleeved on the first heat exchange area 221, and the second heat exchange area 222 is sleeved on the BF 3 condenser 120, and between the liquid nitrogen storage tank 210 and the first heat exchange area 221, and between the second heat exchange area 222 and the BF 3 condenser 120, the corresponding connection surfaces are used as the heat exchange sites.

[0061] In this embodiment, the liquid nitrogen storage tank 210, the intermediate condenser 220, and the BF 3 condenser 120 are sequentially sleeved and the connection surfaces are used as the heat exchange sites, which has the advantages of a relatively compact overall structure, a more reasonable layout, high connection stability, and high heat exchange efficiency; at the same time, this setting can also make the heat exchange medium contained in the intermediate condenser 220 circulate more conveniently by itself, that is, the gaseous medium at the top cools down and is converted into a liquid medium and gathers at the bottom, and the liquid medium at the bottom warms up and is converted into a gaseous medium and returns to the top.

[0062] Refer to Figure 2 , in other possible embodiments, it can also be that the first heat exchange area 221 is sleeved on the liquid nitrogen storage tank 210, and the BF 3 condenser 120 is sleeved on the second heat exchange area 222, and between the liquid nitrogen storage tank 210 and the first heat exchange area 221, and between the second heat exchange area 222 and the BF 3 condenser 120, the corresponding connection surfaces are used as the heat exchange sites.

[0063] As an example, the liquid nitrogen storage tank 210 is also provided with a pressure detection unit or / and a temperature detection unit.

[0064] In this embodiment, after the heat exchange of the liquid nitrogen, the pressure and temperature in the liquid nitrogen storage tank 210 will both rise. The liquid nitrogen storage tank 210 is additionally provided with a pressure detection unit or / and a temperature detection unit to realize the real-time monitoring of the state in the liquid nitrogen storage tank 210, so as to facilitate judging whether new liquid nitrogen needs to be supplemented according to the pressure and temperature indicators.

[0065] Refer to Figure 3 , as an example, along the height direction of the tower body 110, from top to bottom, the intermediate condenser 220 includes a first heat exchange area 221, a second heat exchange area 222, and a feeding area 223 located between the two. The inner diameter of the feeding area 223 is smaller than the inner diameter of the first heat exchange area 221 and the inner diameter of the second heat exchange area 222.

[0066] In this embodiment, the feeding area 223 in the intermediate condenser 220 does not participate in heat exchange. Its inner diameter is set to be smaller than that of the first heat exchange area 221 and the second heat exchange area 222 at both ends, that is, it has a form of being smaller in the middle and larger at both ends as a whole. This can reduce manufacturing consumables and lower the manufacturing cost. At the same time, it also enables the intermediate condenser 220 to have a higher heat exchange efficiency.

[0067] Refer to Figure 4 , where Figure 4 the liquid level in indicates that there is a part of the liquid medium temporarily stored in the buffer section 223a. As an example, along the height direction of the tower body 110, the feeding area 223 includes a buffer section 223a and equal-diameter feeding sections 223b at both ends of the buffer section 223a, and the inner diameter of the buffer section 223a is larger than that of the equal-diameter feeding sections 223b. The upper equal-diameter feeding section 223b is communicated with the first heat exchange area 221, and the lower equal-diameter feeding section 223b is communicated with the second heat exchange area 222.

[0068] In this embodiment, the feeding area 223 is set in a form where the buffer section 223a and the equal-diameter feeding sections 223b cooperate with each other. Among them, the inner diameter of the buffer section 223a is larger than that of the equal-diameter feeding sections 223b, that is, the feeding area 223 has a form of being larger in the middle and smaller at both ends as a whole. The buffer section 223a can temporarily store a part of the liquid medium, and can better maintain the temperature stability of the distillation column 100 when the liquid nitrogen amount is insufficient.

[0069] It should also be noted that since a large amount of refrigerant is required for the preparation of boron isotopes by the low-temperature distillation method and the cost is relatively high, how to reduce costs and increase efficiency is also a major problem faced by this preparation method. Based on this, the structure of the low-temperature distillation system 10 can be further optimized.

[0070] Refer to Figure 5 , as an example, the nitrogen outlet of the liquid nitrogen storage tank 210 is communicated with the heat exchange medium feed inlet of the reboiler 130 through a compressor 300.

[0071] In this embodiment, the nitrogen outlet of the liquid nitrogen storage tank 210 is communicated with the heat exchange medium feed inlet of the reboiler 130, that is, the nitrogen generated after the liquid nitrogen is heat-exchanged is used as the heat source of the reboiler 130 to realize the secondary utilization of nitrogen, which can save the manufacturing cost; at the same time, the nitrogen outlet of the liquid nitrogen storage tank 210 and the heat exchange medium feed inlet of the reboiler 130 are communicated through a compressor 300, which is convenient for adjusting the nitrogen temperature so that the nitrogen has a more appropriate temperature after reaching the reboiler 130, thereby better heating the liquid boron trifluoride and vaporizing it.

[0072] It should be noted that according to statistics, by using the nitrogen gas after heat exchange with liquid nitrogen as the heat exchange medium of the reboiler 130 for reuse, the energy consumption can be reduced by about 20%. On this basis, if photovoltaic power generation and energy storage technologies can be jointly used with the cryogenic distillation system 10 in the future, it is expected to further reduce the energy consumption.

[0073] As an example, the liquid nitrogen storage tank 210, the intermediate condenser 220 and the BF 3 condenser 120 are all spaced apart; the internal cavity of the intermediate condenser 220 is used to communicate with the gaseous medium source. The first heat exchange area 221 is located at the top of the intermediate condenser 220, and the second heat exchange area 222 is located at the bottom of the intermediate condenser 220. The side wall of the cavity corresponding to the first heat exchange area 221 has a first fluid channel capable of heat exchange with the cavity. The first fluid channel is connected to the liquid nitrogen storage tank 210 to introduce liquid nitrogen into the first fluid channel, so that at least part of the gaseous medium in the first heat exchange area 221 is cooled and liquefied after heat exchange and collected in the second heat exchange area 222. The side wall of the cavity corresponding to the second heat exchange area 222 has a second fluid channel, and the second fluid channel is configured to be able to transport the liquid medium to the BF 3 condenser 120 to 3 carry out heat exchange with the gaseous BF 3 in the condenser 120, and it can also make the liquid medium vaporize and return to the first heat exchange area 221 after heat exchange.

[0074] In this embodiment, the liquid nitrogen storage tank 210, the intermediate condenser 220 and the BF 3 condenser 120 are all spaced apart, that is, they are set in a split form and are connected and heat-exchanged through pipelines, which is convenient for the assembly and layout of the distillation system 10 when the longitudinal space is insufficient.

[0075] It should be noted that for the structural or functional units in the distillation system 10 that are not specifically described or limited, they can be set according to the conventional selection in the art.

[0076] As an example, the height of the tower body 110 is 50 - 300 m, the inner diameter of the tower body 110 is 10 - 150 mm, and the tower body 110 can be in an integral form with the same inner diameter or in a form of splicing multiple tower sections with gradually decreasing inner diameters.

[0077] It should be noted that the tower body 110 can be a plate tower or a packed tower, and a liquid distribution device is arranged in the tower body 110 at intervals in the height direction of the tower body 110. Among them, the liquid distribution device can be a spray head type, a disk type, a tube type, a trough type or a trough-disk type.

[0078] As an example, the number of theoretical plates of the tower body 110 is 1800 - 3600.

[0079] Refer to Figure 6 , as an example, the rectification system 10 further includes a nested first-stage vacuum hood 400 and a second-stage vacuum hood 500, and both the first-stage vacuum hood 400 and the second-stage vacuum hood 500 are respectively connected to a vacuum unit. Among them, the rectification tower 100 and the condensation device 200 are both located inside the first-stage vacuum hood 400, and the second-stage vacuum hood 500 is sleeved outside the first-stage vacuum hood 400.

[0080] Refer to Figure 6 , as an example, the outer wall of the tower body 110 is further coated with a heat-insulating diaphragm 140, where the heat-insulating diaphragm 140 can be a single-sided metal-sprayed film, a plastic film or a corrugated aluminum-sprayed film.

[0081] As an example, the rectification system 10 is made of materials such as stainless steel, copper or titanium alloy that are resistant to low temperature and corrosion by boron trifluoride.

[0082] In a second aspect, the embodiments of the present application provide a method for producing boron isotopes, which is produced by using the rectification system provided in the embodiments of the first aspect, and includes the following steps:

[0083] Transport the raw materials into the tower body for rectification. First, use the liquid nitrogen provided by the liquid nitrogen storage tank to exchange heat with the gaseous medium in the first heat exchange area, so that at least part of the gaseous medium in the first heat exchange area cools down and liquefies after heat exchange to obtain a liquid medium and collect it in the second heat exchange area, where the liquefaction temperature of the gaseous medium is -100 to -120 °C; then use the liquid medium in the second heat exchange area to exchange heat with the gaseous BF 3 in the BF 3 condenser, so that the liquid medium provided by the second heat exchange area warms up and vaporizes after heat exchange and returns to the first heat exchange area.

[0084] In the present application, the method for producing boron isotopes is produced by using the rectification system provided in the embodiments of the first aspect. Since an intermediate condenser is added on the basis of a conventional rectification tower, and the liquefaction temperature of the heat exchange medium in the intermediate condenser is -100 to -120 °C, that is, the overall heat exchange process is: liquid nitrogen first exchanges heat with the gaseous medium to cool the gaseous medium and liquefy it into a liquid medium with a temperature close to -100 °C, and then the liquid medium exchanges heat with the gaseous BF 3 in the BF 3 condenser, so that the heat exchange medium for exchanging heat with the gaseous BF 3 in the BF 3 condenser is not liquid nitrogen but a liquid medium with a temperature of about -100 °C, thus solving the problem of "icing" inside the rectification tower caused by direct heat exchange between liquid nitrogen and the gaseous BF 3 in the BF 3 condenser.

[0085] As an example, the gaseous medium includes a heat-exchanging gaseous medium and a buffer gaseous medium, and the volume proportion of the buffer gaseous medium is greater than that of the heat-exchanging gaseous medium. Among them, the heat-exchanging gaseous medium is selected from at least one of nitrogen trifluoride, carbon tetrafluoride, methane, ethylene, and oxygen, and the buffer gaseous medium is selected from at least one of hydrogen, neon, and helium.

[0086] In this embodiment, the gaseous medium is composed of the heat-exchanging gaseous medium and the buffer gaseous medium of the above types, and the volume proportion of the buffer gaseous medium is greater than that of the heat-exchanging gaseous medium, so that the overall pressure change of the gaseous medium during the liquefaction and vaporization processes is relatively small (pressure change will cause temperature change), and further the temperatures of the first heat-exchanging zone and the second heat-exchanging zone of the intermediate condenser are both maintained within a suitable range, which helps to improve the stability of the rectification system.

[0087] As an example, after the heat-exchanging gaseous medium in the intermediate condenser is liquefied, the pressure in the intermediate condenser is 1 to 50 bar, for example but not limited to any one of the point values of 1 bar, 5 bar, 10 bar, 20 bar, 30 bar, 40 bar, and 50 bar or the range values between any two of them.

[0088] In this embodiment, after the heat-exchanging gaseous medium in the intermediate condenser is liquefied, the pressure in the intermediate condenser is controlled within the above range so that the temperature of the liquid medium is relatively close to -100 °C, thereby more accurately controlling the temperature of the rectification column at a suitable separation temperature.

[0089] As an example, when the heat-exchanging gaseous medium is oxygen, after the heat-exchanging gaseous medium in the intermediate condenser is liquefied, the pressure in the intermediate condenser is 5 to 10 bar, for example but not limited to any one of the point values of 5 bar, 6 bar, 7 bar, 8 bar, 9 bar, and 10 bar or the range values between any two of them.

[0090] As an example, when the heat-exchanging gaseous medium is ethylene, after the heat-exchanging gaseous medium in the intermediate condenser is liquefied, the pressure in the intermediate condenser is 1 to 2 bar, for example but not limited to any one of the point values of 1 bar, 1.2 bar, 1.4 bar, 1.6 bar, 1.8 bar, and 2.0 bar or the range values between any two of them.

[0091] As an example, the heat-exchanging gaseous medium is carbon tetrafluoride or / and nitrogen trifluoride. After the heat-exchanging gaseous medium in the intermediate condenser is liquefied, the pressure in the intermediate condenser is 2 to 6 bar, such as but not limited to any one of the point values of 2 bar, 2.5 bar, 3 bar, 3.5 bar, 4 bar, 4.5 bar, 5 bar, 5.5 bar and 6 bar or the range values between any two of them.

[0092] As an example, the heat-exchanging gaseous medium is methane. After the heat-exchanging gaseous medium in the intermediate condenser is liquefied, the pressure in the intermediate condenser is 15 to 30 bar, such as but not limited to any one of the point values of 15 bar, 18 bar, 20 bar, 22 bar, 24 bar, 26 bar, 28 bar and 30 bar or the range values between any two of them.

[0093] In this embodiment, for different types of heat-exchanging gaseous media, the pressure of the gaseous medium after liquefaction is respectively limited within the above range, which can make the temperature of the liquid medium closer to -100 °C.

[0094] As an example, the nitrogen outlet of the liquid nitrogen storage tank is connected to the heat-exchanging medium inlet of the reboiler through a compressor, and the compression ratio of the compressor is 2 to 20, such as but not limited to any one of the point values of 2, 4, 6, 8, 10, 12, 14, 16, 18 and 20 or the range values between any two of them.

[0095] In this embodiment, the compression ratio of the compressor is limited within the above range so that the temperature of the nitrogen reaches the reboiler and is maintained within the range of -55 to -95 °C, thereby facilitating heat exchange with liquid boron trifluoride and gasifying it.

[0096] As an example, a liquid distribution device is arranged in the tower body at intervals along the height direction of the tower body so that the pressure drop in the tower body is 0.5 to 250 Pa / m.

[0097] In this embodiment, limiting the pressure drop in the tower body within the above range helps to reduce energy consumption and production costs.

[0098] As an example, the number of theoretical plates of the tower body is 1800 to 3600, so that the reflux ratio of the tower body is 200 to 1000.

[0099] As an example, in the step of rectification treatment, the ratio of the distillate to the feed rate is set to 0.75 to 0.95.

[0100] As an example, the rectification system further includes a nested first-stage vacuum hood and a second-stage vacuum hood, and both the first-stage vacuum hood and the second-stage vacuum hood are respectively connected to a vacuum unit. Among them, the rectification column and the condensation device are both located inside the first-stage vacuum hood, the second-stage vacuum hood is sleeved outside the first-stage vacuum hood, and the vacuum degree inside the first-stage vacuum hood is 10 -2 ~10 -4 Pa, and the vacuum degree inside the second-stage vacuum hood is 10 -1 ~10 -3 Pa.

[0101] It should be noted that for the processes or steps not specifically described or limited during the production process, they can be set according to the conventional selection in this field.

[0102] The above are only the preferred embodiments of the present application and are not used to limit the present application. For those skilled in the art, various changes and modifications can be made to the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included within the protection scope of the present application.

Claims

1. A distillation system for producing boron isotopes, characterized in that: include: A distillation tower, comprising a tower body, a BF3 condenser located at the top of the tower body, and a reboiler located at the bottom of the tower body; A condensing device, the condensing device includes a liquid nitrogen storage tank and an intermediate condenser, the liquid nitrogen storage tank is used to communicate with a liquid nitrogen source, the intermediate condenser is used to communicate with a gaseous medium source, the intermediate condenser has a first heat exchange zone and a second heat exchange zone, the first heat exchange zone is connected to the second heat exchange zone, the first heat exchange zone is configured to be able to perform heat exchange with the liquid nitrogen provided by the liquid nitrogen storage tank, so that the gaseous medium located in the first heat exchange zone is at least partially cooled and liquefied to obtain liquid medium after the heat exchange and is collected in the second heat exchange zone, the second heat exchange zone is configured to be able to use the liquid medium to perform heat exchange with the gaseous BF3 in the BF3 condenser, so that the liquid medium provided by the second heat exchange zone is heated and vaporized after the heat exchange and returns to the first heat exchange zone.

2. The distillation system for producing boron isotopes according to claim 1, characterized in that: Along the height direction of the tower body, from top to bottom, the liquid nitrogen storage tank, the intermediate condenser and the BF3 condenser are connected in sequence, wherein the first heat exchange zone is located at the top of the intermediate condenser, the second heat exchange zone is located at the bottom of the intermediate condenser, the liquid nitrogen storage tank is connected to the first heat exchange zone, and the BF3 condenser is connected to the second heat exchange zone.

3. The distillation system for producing boron isotopes according to claim 2, characterized in that: The liquid nitrogen storage tank is sleeved on the first heat exchange zone, the second heat exchange zone is sleeved on the BF3 condenser, and the corresponding connecting surfaces between the liquid nitrogen storage tank and the first heat exchange zone, and between the second heat exchange zone and the BF3 condenser are used as heat exchange places.

4. The distillation system for producing boron isotopes according to claim 2, characterized in that: The first heat exchange zone is sleeved on the liquid nitrogen storage tank, the BF3 condenser is sleeved on the second heat exchange zone, and corresponding connecting surfaces between the liquid nitrogen storage tank and the first heat exchange zone, and between the second heat exchange zone and the BF3 condenser are used as heat exchange places.

5. The distillation system for producing boron isotopes according to any one of claims 2 to 4, characterized in that: The liquid nitrogen storage tank is also provided with a pressure detection unit and / or a temperature detection unit.

6. The distillation system for producing boron isotopes according to any one of claims 2 to 4, characterized in that: Along the height direction of the tower body, from top to bottom, the intermediate condenser includes the first heat exchange zone, the second heat exchange zone and a feed zone located therebetween, and the inner diameter of the feed zone is smaller than the inner diameter of the first heat exchange zone and the inner diameter of the second heat exchange zone.

7. The distillation system for producing boron isotopes according to claim 6, characterized in that: Along the height direction of the tower body, the feed zone includes a buffer section and equal-diameter feed sections located at both ends of the buffer section, and the inner diameter of the buffer section is larger than the inner diameter of the equal-diameter feed section. The equal-diameter feed section located at the upper end is connected to the first heat exchange zone, and the equal-diameter feed section located at the lower end is connected to the second heat exchange zone.

8. The distillation system for producing boron isotopes according to any one of claims 1 to 4, characterized in that: The nitrogen outlet of the liquid nitrogen storage tank is connected to the heat exchange medium feed port of the reboiler through a compressor.

9. The distillation system for producing boron isotopes according to claim 1, characterized in that: The liquid nitrogen storage tank, the intermediate condenser and the BF3 condenser are all distributed at intervals; The internal cavity of the intermediate condenser is used to communicate with the gaseous medium source, the first heat exchange zone is located at the top of the intermediate condenser, and the second heat exchange zone is located at the bottom of the intermediate condenser. The side wall of the cavity corresponding to the first heat exchange zone has a first fluid channel that can perform heat exchange with the cavity. The first fluid channel is connected to the liquid nitrogen storage tank to pass liquid nitrogen into the first fluid channel, so that the gaseous medium located in the first heat exchange zone is at least partially cooled and liquefied after heat exchange and collected in the second heat exchange zone. The side wall of the cavity corresponding to the second heat exchange zone has a second fluid channel, and the second fluid channel is configured to be able to transport the liquid medium to the BF3 condenser to perform heat exchange with the gaseous BF3 in the BF3 condenser, and can also allow the liquid medium to be heated and vaporized after heat exchange and return to the first heat exchange zone.

10. A method for producing boron isotopes, characterized in that: The production is carried out using the distillation system as claimed in any one of claims 1 to 9, comprising the following steps: The raw materials are transported into the tower body for rectification, and the liquid nitrogen provided by the liquid nitrogen storage tank is first used to perform heat exchange with the gaseous medium in the first heat exchange zone, so that the gaseous medium in the first heat exchange zone is at least partially cooled and liquefied after the heat exchange to obtain the liquid medium and collected in the second heat exchange zone, wherein the liquefaction temperature of the gaseous medium is -100 to -120°C; Then, the liquid medium in the second heat exchange zone is used to perform heat exchange with the gaseous BF3 in the BF3 condenser, so that the liquid medium provided by the second heat exchange zone is heated up and vaporized after the heat exchange and returns to the first heat exchange zone.

11. The method for producing boron isotopes according to claim 10, characterized in that: The gaseous medium includes a heat exchange gaseous medium and a buffer gaseous medium, and the volume proportion of the buffer gaseous medium is greater than the volume proportion of the heat exchange gaseous medium, wherein the heat exchange gaseous medium is selected from at least one of nitrogen trifluoride, carbon tetrafluoride, methane, ethylene and oxygen, and the buffer gaseous medium is selected from at least one of hydrogen, neon and helium.

12. The method for producing boron isotopes according to claim 11, characterized in that: After the heat exchange gaseous medium in the intermediate condenser is liquefied, the pressure in the intermediate condenser is 1 to 50 bar; Optionally, the heat exchange gaseous medium is oxygen, and after the heat exchange gaseous medium in the intermediate condenser is liquefied, the pressure in the intermediate condenser is 5 to 10 bar; Optionally, the heat exchange gaseous medium is ethylene, and after the heat exchange gaseous medium in the intermediate condenser is liquefied, the pressure in the intermediate condenser is 1 to 2 bar; Optionally, the heat exchange gaseous medium is nitrogen trifluoride or / and carbon tetrafluoride, and after the heat exchange gaseous medium in the intermediate condenser is liquefied, the pressure in the intermediate condenser is 2 to 6 bar; Optionally, the heat exchange gaseous medium is methane, and after the heat exchange gaseous medium in the intermediate condenser is liquefied, the pressure in the intermediate condenser is 15 to 30 bar.

13. The method for producing boron isotopes according to any one of claims 10 to 12, characterized in that: The nitrogen outlet of the liquid nitrogen storage tank is connected to the heat exchange medium feed port of the reboiler through a compressor, and the compression ratio of the compressor is 2-20.

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