A system for preparing high-abundance carbon-13 isotopes using carbon tetrafluoride as a medium and a refrigerant

Abstract

The present application discloses a system for preparing high-abundance carbon-13 isotopes using carbon tetrafluoride as a medium and a refrigerant, including: a microchannel distillation device, the microchannel distillation device includes a distillation unit, a reboiler and a condenser, the raw material of the microchannel distillation device is a first carbon tetrafluoride with natural abundance, the condenser is configured to condense the gaseous component in the first carbon tetrafluoride to be distilled into a liquid, the reboiler is configured to heat the liquid component into a gas, and the refrigerant in the condenser is a second carbon tetrafluoride. The device adopts a microchannel distillation method to not only significantly reduce the height of the distillation tower, but also achieve mass production and reduce energy consumption.

Description

Technical Field

[0001] The present application relates to the technical field of isotope separation, and in particular to a system for preparing high-abundance carbon-13 isotopes using carbon tetrafluoride as a medium and a refrigerant. Background Art

[0002] Carbon is an essential element in organic compounds and constitutes the carbon cycle of the biosphere. Its stable isotopes have a wide range of applications and considerable potential demand in the fields of medical diagnosis, agricultural ecology, food safety, etc. The main application of stable carbon isotopes is carbon-13 isotope labeled compounds. Since carbon-13 isotopes do not have any radioactivity, they have unique advantages in today's era when living standards and safety awareness have greatly improved. In addition, due to the existence of multiple allotropes of carbon and its diverse structural characteristics, its isotope effect has also received attention in basic scientific research, so the demand for high-abundance carbon-13 isotopes will become increasingly strong.

[0003] At present, the industrial production methods of carbon-13 isotopes include cryogenic distillation and centrifugation. However, cryogenic distillation of carbon-13 requires a high height of the distillation tower, which requires a unique geographical advantage, such as abandoned mines. Traditional distillation towers require hundreds or even thousands of meters in height, and the distillation equipment is too large, which is very difficult for actual engineering applications. For the centrifugal method to produce high-abundance carbon-13, it is necessary to purchase centrifuges, which has high equipment procurement costs and low mass production capacity.

[0004] Therefore, there is an urgent need in this field to develop a system for preparing high-abundance carbon-13 isotopes using carbon tetrafluoride as a medium and a refrigerant. The device uses a microchannel distillation method, which can not only significantly reduce the height of the distillation tower, but also achieve mass production and reduce energy consumption. Summary of the invention

[0005] The purpose of the present application is to provide a system for preparing high-abundance carbon-13 isotopes using carbon tetrafluoride as a medium and a refrigerant. The device adopts a microchannel distillation method, which can not only significantly reduce the height of the distillation tower, but also achieve mass production and reduce energy consumption.

[0006] The present application provides a system for preparing high-abundance carbon-13 isotopes using carbon tetrafluoride as a medium and a refrigerant, comprising:

[0007] A microchannel distillation device, the microchannel distillation device comprising a distillation unit, a reboiler and a condenser, the raw material of the microchannel distillation device is a first carbon tetrafluoride with natural abundance, the condenser is configured to condense the gaseous component in the first carbon tetrafluoride to be distilled into a liquid, the reboiler is configured to heat the liquid component into a gas, and the refrigerant in the condenser is a second carbon tetrafluoride;

[0008] The distillation unit comprises a plurality of microtubes stacked together, wherein the diameter of the microtubes is in the range of 0.3 mm to 1 mm, and a gas-liquid exchange hole is arranged on the tube wall of each microtube so that during the distillation process of carbon tetrafluoride to be distilled, the microtubes provide a liquid phase channel for liquid flow under the action of the capillary force of the microtubes and the surface tension of the gas-liquid exchange holes, and the external space outside the microtubes is configured for gas flow.

[0009] In another preferred example, the microchannel distillation device further comprises a shell, and the micro-tube distillation unit is arranged in the shell.

[0010] In another preferred example, the system further comprises a refrigeration cycle device, wherein the refrigeration cycle device is used for refrigerating and circulating the second carbon tetrafluoride required by the condenser, and the refrigeration cycle device comprises a compressor, a cooler, and a throttling device.

[0011] In another preferred example, the compressor is fluidly connected to the condenser and the cooler, the cooler is also fluidly connected to the throttling device, and the throttling device is also fluidly connected to the condenser.

[0012] In another preferred example, the compressor is used to compress the low-temperature and low-pressure gaseous second carbon tetrafluoride discharged from the condenser, the cooler is located downstream of the compressor, the cooler is used to cool the high-temperature and high-pressure gaseous second carbon tetrafluoride from the compressor, and the throttling device is located downstream of the cooler and upstream of the condenser.

[0013] In another preferred embodiment, the throttling device is used to cool down and reduce the pressure of the second carbon tetrafluoride from the cooler, and the second carbon tetrafluoride after cooling and reducing the pressure is transported to the condenser to be used as a refrigerant.

[0014] In another preferred embodiment, the distillation unit has a first end and a second end opposite to the first end. During the distillation process, the heavy components condensed into liquid at the second end 13 CF 4 Under the action of the capillary force of the microtube and the surface tension of the gas-liquid phase exchange hole, the liquid flows in the liquid phase channel along the first axial direction of the rectification unit and is heated to gas at the first end. 12 CF 4 Under the action of pressure difference, the microtube moves in the external space outside the microtube along the second axial direction of the distillation unit, and the second axial direction is opposite to the first axial direction.

[0015] In another preferred example, the first axial direction is a direction flowing from the second end to the first end, and the second axial direction is a direction flowing from the first end to the second end.

[0016] In another preferred embodiment, the first end is the heavy fraction end, and the second end is the light fraction end.

[0017] In another preferred example, the gas moves along the second axial direction, and the liquid moves along the first axial direction.

[0018] In another preferred example, the microtube includes a gas-liquid exchange section. When the gas in the external space and the liquid in the liquid phase channel flow, heat and mass transfer are carried out in the gas-liquid exchange section of the microtube through the gas-liquid exchange holes, so that the heavy component gas located in the external space is converted into liquid and enters the liquid phase channel, and the light component liquid located in the liquid phase channel is converted into gas and enters the external space, and separation and purification are achieved by repeated reciprocation.

[0019] In another preferred embodiment, the gas-liquid exchange section of the microtube is a part of the microtube.

[0020] In another preferred embodiment, the distillation unit is placed horizontally, inclined, or vertically.

[0021] In another preferred example, during the distillation process, the plurality of microtubes are placed horizontally or tilted, and the first end of the distillation unit and the second end of the distillation unit are at substantially the same height level or at different height levels.

[0022] In another preferred embodiment, the distillation unit is placed horizontally or inclined.

[0023] In another preferred embodiment, during the distillation process, the housing and the distillation unit are placed flat on a horizontal plane.

[0024] In another preferred example, the first axial direction and the second axial direction are both parallel to a horizontal plane.

[0025] In another preferred embodiment, the length of the microtube is in the range of 500 mm-1000 mm.

[0026] In another preferred embodiment, the plurality of microtubes are stacked together to form a cylinder, and the distance between the centers of two adjacent microtubes is in the range of 1 mm to 2 mm.

[0027] In another preferred embodiment, the pore size of the gas-liquid exchange hole is in the range of 0.02 mm-0.05 mm.

[0028] In another preferred embodiment, the gas-liquid phase exchange holes are evenly arranged in the circumferential direction and the axial direction of the microtube.

[0029] In another preferred embodiment, the center distance between two adjacent gas-liquid exchange holes in the axial direction of the microtube is 0.05 mm-0.1 mm.

[0030] In another preferred embodiment, the center distance between two adjacent gas-liquid exchange holes in the circumferential direction of the microtube is 0.05 mm-0.1 mm.

[0031] In another preferred embodiment, the distance between two adjacent gas-liquid exchange holes on the microtube wall of the same cross section of the microtube is 0.05 mm-0.1 mm.

[0032] In another preferred embodiment, the capillary force should be greater than or equal to the gas-liquid phase pressure difference, and the gas-liquid phase pressure difference refers to the difference between the static pressure head of the liquid in the liquid phase channel and the static pressure head of the gas flowing in the external space outside the microtube.

[0033] In another preferred embodiment, the total number of the microtubes is between 100 and 200, and the distillation unit includes a heavy fraction end (i.e., the first end) and a light fraction end (i.e., the second end), and carbon tetrafluoride with a carbon-13 isotope abundance higher than 99% is obtained at the heavy fraction end (i.e., the first end).

[0034] In another preferred example, the number of the distillation units is one or more. When the number of the distillation units is multiple, the multiple distillation units constitute the separation device of the microchannel distillation device in a series or parallel manner, that is, multiple distillation units are connected in parallel to form a separation unit, and multiple separation units are connected in series to form the separation device.

[0035] In another preferred embodiment, the liquid at the first end can be used to continuously evaporate to generate gas, and can also be collected to become the product of the micro-tubular distillation device. 13 CF 4 .

[0036] It should be understood that within the scope of the present invention, the above-mentioned technical features of the present invention and the technical features specifically described below (such as embodiments) can be combined with each other to form a new or preferred technical solution. Due to space limitations, they will not be described one by one here. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the prior art descriptions are briefly introduced below. It should be understood that the drawings described below are only some implementation examples of the present invention, and ordinary technicians in this field can also obtain other implementation examples based on these drawings without paying creative work.

[0038] Figure 1 It is a schematic diagram of the structure of a system for preparing high-abundance carbon-13 isotopes using carbon tetrafluoride as a medium and a refrigerant according to the present application;

[0039] Figure 2is a schematic structural diagram of a distillation unit (housing not shown) of a microchannel distillation device according to the present application;

[0040] Figure 3 is a partial structural schematic diagram of a distillation unit according to the present application;

[0041] Figure 4 It is a schematic diagram of the structure of the micro-tube of the distillation unit according to the present application.

[0042] In the accompanying drawings, the following are marked:

[0043] 1-Distillation unit

[0044] 11-First End

[0045] 12-Second end

[0046] 2-Microtubules

[0047] 21-Gas-liquid phase exchange hole

[0048] 200-Liquid Phase Channel

[0049] 3-Reboiler

[0050] 4-Condenser

[0051] 5-Compressor

[0052] 6-Cooler

[0053] 7-Throttle valve DETAILED DESCRIPTION

[0054] Through extensive and in-depth research, the inventors have developed for the first time a system for preparing high-abundance carbon-13 isotopes using carbon tetrafluoride as a medium and a refrigerant. The device includes a microchannel distillation device, which is a device for separating carbon-13 isotopes based on capillary force. The microchannel distillation method can not only significantly reduce the height of the traditional distillation tower (its size is much smaller than that of the traditional distillation tower), but also achieve mass production and reduce energy consumption. In addition, carbon tetrafluoride is used as both a medium and a refrigerant, which avoids the need for additional charging of other refrigerants.

[0055] In the following description, many technical details are provided to help readers better understand the present application. However, those skilled in the art can understand that the technical solution claimed in the present application can be implemented even without these technical details and various changes and modifications based on the following embodiments.

[0056] the term

[0057] As used herein, the term “axial direction” refers to a direction along its length, and the term “circumferential direction” refers to a direction of its circumference, which is a direction perpendicular to the axial direction.

[0058] As used herein, the terms "distillation unit" and "microtubular distillation unit" are used interchangeably.

[0059] As used herein, a "distillation process" is a process that achieves separation based on the differences in boiling points of different isotopes of carbon tetrafluoride.

[0060] It should be noted that in the application documents of this patent, relational terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that the process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the sentence "including one" do not exclude the existence of other identical elements in the process, method, article or device including the elements. In the application documents of this patent, if it is mentioned that an action is performed according to an element, it means that the action is performed at least according to the element, which includes two situations: performing the action only according to the element, and performing the action according to the element and other elements. Expressions such as multiple, multiple, and multiple include 2, 2 times, 2 kinds, and more than 2, more than 2 times, and more than 2 kinds.

[0061] In the present invention, all directional indications (such as up, down, left, right, front, back, etc.) are only used to explain the relative position relationship, movement status, etc. between the components in a certain specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indication will also change accordingly.

[0062] This application has at least one of the following advantages

[0063] (a) The system for preparing high-abundance carbon-13 isotopes using carbon tetrafluoride as a medium and a refrigerant in the present application realizes that carbon tetrafluoride is used as both a medium and a refrigerant, thereby avoiding the need for additional charging of other refrigerants and realizing the maximum utilization value of carbon tetrafluoride;

[0064] (b) The microchannel distillation device of the system of the present application can be used for purification of carbon isotope separation;

[0065] (c) The microchannel distillation device of the system of the present application provides a distillation unit with an ingenious structure, which utilizes the combined effect of the capillary force and surface tension of the microtubes and / or the gravity of the liquid to achieve the distillation process, improve the separation efficiency, and be able to prepare high-abundance carbon-13 isotopes at a low price and with low energy consumption;

[0066] (d) The distillation unit in the microchannel distillation device of the system of the present application can achieve the separation and purification of carbon-13 in carbon tetrafluoride by placing it horizontally or slightly tilted. Compared with the traditional distillation tower, it does not need to occupy space in the height direction and has more practical engineering applications.

[0067] To make the purpose, technical solution and advantages of the present invention clearer, the embodiments of the present invention will be further described in detail below in conjunction with the accompanying drawings. It should be understood that these are only some examples that the present invention may take for the reader, but are not intended to limit the scope of the present invention.

[0068] A system for preparing high-abundance carbon-13 isotopes using carbon tetrafluoride as a medium and a refrigerant

[0069] See also Figure 1 The present application provides a system for preparing high-abundance carbon-13 isotopes using carbon tetrafluoride as a medium and a refrigerant. The system includes a microchannel distillation device MCD and a refrigeration cycle device. The microchannel distillation device includes a distillation unit 1, a reboiler 3 and a condenser 4.

[0070] The raw material of the microchannel distillation device is the first carbon tetrafluoride with natural abundance, and the condenser 4 is configured to convert the heavy components in the first carbon tetrafluoride to be distilled into a gaseous state. 13 CF 4 The reboiler 3 is configured to condense the light components in the first carbon tetrafluoride to be distilled into liquid. 12 CF 4 After heating into gas, the gaseous first carbon tetrafluoride is introduced into the microchannel distillation device MCD as the working medium. The first carbon tetrafluoride is separated into multiple channels by capillary force using low temperature distillation method to obtain concentrated / depleted carbon isotopes. The purified gaseous carbon tetrafluoride is introduced into the microchannel distillation device. The binary components with different relative molecular weights in the carbon tetrafluoride will form different distributions in the temperature field. Light component 12 CF 4 In the reboiler, it is heated and evaporated first, and the heavy components 13 CF 4 It is first condensed when it encounters cold in the condenser, and the gas-liquid two phases conduct heat and mass transfer through multiple channels, and the heavy components are gradually gathered in order to achieve the separation of the heavy components and the light components. The number of microtubes in the distillation unit for separating the carbon-13 isotope is between 100 and 200. In one embodiment, a first carbon tetrafluoride raw material with a natural abundance of carbon-13 isotope and a pressure of 0.2 MPa is supplied to the microchannel distillation device, and carbon tetrafluoride with a carbon-13 isotope abundance higher than 99% is obtained at the heavy fraction end (the specific structure of the microchannel distillation device will be described in detail below).

[0071] Refrigeration cycle device

[0072] The refrigerant in the condenser 4 in the microchannel distillation device MCD is the second carbon tetrafluoride.

[0073] The cooling capacity of the condenser comes from the compression refrigeration of the second carbon tetrafluoride. The refrigeration cycle of the second carbon tetrafluoride is as follows: Compression process: The low-temperature and low-pressure gaseous second carbon tetrafluoride refrigerant enters the compressor 5. At this time, the temperature of the refrigerant is about -125°C (slightly lower than the temperature required to be maintained by the condenser in order to absorb heat), and the pressure is 0.1MPa (absolute pressure). In the compressor 5, the second carbon tetrafluoride is adiabatically compressed, and the compressor 5 works on the refrigerant to increase its pressure and temperature. The compressed second carbon tetrafluoride becomes a high-temperature and high-pressure gas, the temperature rises to about 50°C, and the pressure rises to about 2.0MPa (absolute pressure). Condensation process: The high-temperature and high-pressure gaseous second carbon tetrafluoride enters the cooler 6, in which the gaseous second carbon tetrafluoride exchanges heat with the cooling medium (such as air or other cooling liquids) and releases heat to the cooling medium. Since the temperature of the cooling medium is relatively low, the second carbon tetrafluoride is gradually cooled, and the temperature drops to about 30°C, which is close to the temperature of the cooling medium, and the pressure is still maintained at about 2.0 MPa (absolute pressure). Throttling process: After the high-pressure second carbon tetrafluoride comes out of the cooler 6, it enters the throttling device (such as the throttling valve 7). In the throttling device, the pressure of the second carbon tetrafluoride drops sharply. Since the throttling process is adiabatic and no work is done to the outside, according to the law of conservation of energy, its enthalpy value remains unchanged. However, the pressure reduction causes the temperature to drop significantly. After throttling, the second carbon tetrafluoride becomes a low-temperature and low-pressure gas-liquid two-phase mixture, the temperature drops to about -128°C, and the pressure drops to about 0.1 MPa (absolute pressure). Evaporation process: The low-temperature and low-pressure gas-liquid two-phase second carbon tetrafluoride enters the condenser 4 of the microchannel distillation device. The second carbon tetrafluoride exchanges heat with the first carbon tetrafluoride to be distilled in the microchannel distillation device that needs to be cooled, and absorbs the heat of the first carbon tetrafluoride to be distilled. The liquid second carbon tetrafluoride continues to evaporate and become gaseous, thereby providing cooling capacity for the condenser of the microchannel distillation device and maintaining its temperature at -120°C. The second carbon tetrafluoride completely changes into a low-temperature and low-pressure gas, and the temperature is maintained at about -120°C (slightly lower than the temperature of the cooled material to ensure heat transfer), and the pressure is still about 0.1MPa (absolute pressure). Then the gaseous second carbon tetrafluoride enters the compressor 5 again to start the next refrigeration cycle. In the entire refrigeration cycle, it is necessary to accurately control the pressure and temperature of each link to ensure the efficient operation of the refrigeration system and the stable working temperature of the distillation device condenser at -120°C. At the same time, it is also necessary to consider the physical characteristics of the second carbon tetrafluoride and the pressure resistance and low temperature resistance of the equipment.

[0074] In one embodiment, the compression process can be single-stage compression or multi-stage compression; in one embodiment, the compression refrigeration cycle can be a single-stage cycle or a cascade refrigeration cycle formed by series and parallel connection.

[0075] Microchannel distillation device (MCD device)

[0076] The present application provides a microchannel distillation device (MCD device), which includes a distillation unit 1 and a shell (not shown), a reboiler 3 and a condenser 4.

[0077] See also Figure 2-3 A microtube distillation unit 1 is arranged in the outer shell, and the distillation unit 1 is formed by stacking a plurality of microtubes 2; the diameter of the microtube 2 is in the range of 0.3 mm-1 mm, and a gas-liquid exchange hole 21 is arranged on the tube wall of each microtube 2, so that during the distillation process of the carbon tetrafluoride to be distilled, the microtube 2 provides a liquid phase channel 200 for liquid flow under the action of the capillary force of the microtube 2 and the surface tension of the gas-liquid exchange hole 21, and the external space outside the microtube 2 is configured for gas flow; preferably, a plurality of microtubes 2 are stacked together to form a cylinder, and the center distance between two adjacent microtubes 2 is in the range of 1 mm-2 mm.

[0078] The distillation unit 1 has a first end 11 (i.e., a heavy fraction end) and a second end 12 (i.e., a light fraction end) opposite to the first end 11. The first end 11 and the second end 12 of the microtube are fixed by two sieve plates, respectively. During the distillation process, the carbon tetrafluoride to be distilled, which is condensed into a liquid at the second end 12, flows in the liquid phase channel 200 along the first axial direction of the distillation unit 1 under the action of the capillary force of the microtube 2 and the surface tension of the gas-liquid phase exchange hole 21, and the carbon tetrafluoride to be distilled, which is heated into a gas at the first end 11, moves in the second axial direction of the distillation unit 1 in the external space outside the microtube 2 under the action of the pressure difference. The second axial direction is opposite to the first axial direction. That is, the gas moves along the second axial direction, and the liquid moves along the first axial direction. The first axial direction is the direction from the second end 12 to the first end 11, and the second axial direction is the direction from the first end 11 to the second end 12.

[0079] Specifically, the condenser 4 is located at the second end 12 of the distillation unit 1 and is configured to convert the heavy components of the carbon tetrafluoride to be distilled into a gaseous state. 13 CF 4 The reboiler 3 is located at the first end 11 of the distillation unit 1 and is configured to condense the liquid in the carbon tetrafluoride to be distilled. 12 CF 4Heated into gas. When the distillation starts, the gas is cooled and liquefied into liquid through the condenser 4 located at the second end 12. The liquid flows downward in the microtube to the first end 11 of the distillation unit 1 by gravity (when the distillation unit 1 is tilted) and capillary force. The light components in the liquid at the first end 11 are heated by the reboiler 3 to generate gas. The gas flows toward the second end 12 (along the second axial direction) outside the microtube by pressure difference to reach the second end 12. The gas-liquid flow process transfers heat and mass through the gas-liquid phase exchange hole 21 to bring the heavy components to the liquid phase and the light components to the gas phase. The separation and purification are achieved by repeated reciprocation, so that the liquid at the first end 11 (heavy fraction end) of the distillation unit 13 CF 4 In one embodiment, the feed inlet is located at the upper part or top of the microchannel distillation device (depending on whether the distillation unit 1 is placed horizontally, inclined or vertically), the heavy component outlet is located at the lower part or bottom (i.e., the first end) of the microchannel distillation device, and the upper part or top is close to the second end of the distillation unit. 13 CF 4 The flow rate is 0.05 to 0.3 times the feed flow rate. The outlet abundance of the heavy component at the bottom of the tower can be changed by changing the number of distillation tubes of the distillation unit.

[0080] Preferably, the total number of microtubes is between 100 and 200, and carbon tetrafluoride with a carbon-13 isotope abundance higher than 99% is obtained at the heavy fraction end of the distillation unit 1. In one embodiment, the number of distillation units is 1, and the number of microtubes is between 100 and 200. In other embodiments, the number of distillation units 1 is multiple, and when the number of distillation units 1 is multiple, the multiple distillation units 1 form a separation device of the microchannel distillation device in a series or parallel manner, that is, multiple distillation units 1 are connected in parallel to form a separation unit, and multiple separation units are connected in series to form the separation device.

[0081] Preferably, the microtube 2 includes a gas-liquid exchange section, and the gas-liquid exchange section of the microtube 2 is a part of the microtube 2. When the gas in the external space and the liquid in the liquid phase channel 200 flow, heat and mass transfer are carried out in the gas-liquid exchange section of the microtube 2 through the gas-liquid exchange hole 21, so that the heavy component gas in the external space is converted into liquid and enters the liquid phase channel 200, and the light component liquid in the liquid phase channel 200 is converted into gas and enters the external space. Specifically, the opening (gas-liquid exchange hole 21) on the tube wall is a gas-liquid exchange interface, which facilitates heat and mass transfer between gas and liquid. The liquid phase flows horizontally in the tube, and the gas phase flows horizontally outside the tube, and gas-liquid exchange is carried out at the opening.

[0082] In one embodiment, a plurality of microtubes 2 are placed horizontally or obliquely on a horizontal plane, that is, the distillation unit 1 is placed horizontally or slightly obliquely on a horizontal plane. By placing the distillation unit horizontally or obliquely to achieve distillation, compared with a traditional vertically placed distillation tower, the space requirement for height is low and it has more practical application value. The first end 11 of the distillation unit 1 and the second end 12 of the distillation unit are at the same height level or different height levels (in the case of oblique placement). In one embodiment, the inclination angle of the oblique placement can be 0-45 degrees. In one embodiment, when a plurality of microtubes 2 are placed horizontally on a horizontal plane, the first axial direction and the second axial direction are parallel to the horizontal plane.

[0083] In one embodiment, the length of the micro tube 2 is in the range of 500 mm to 1000 mm as required.

[0084] In this application, in order to achieve the desired gas-liquid mass transfer efficiency, a microtube 2 composed of uniform openings is constructed. By adjusting the spacing and pore size between the openings, the permeability between the microtubes 2 can be freely set. Based on the effective medium approximation theory (EMA), on a scale much larger than the opening spacing, such a microtube 2 can be considered to be uniform and isotropic with a constant effective permeability.

[0085] In the microtube structure, the key to preventing flooding is to control the pressure difference between the liquid phase and the gas phase and to use capillary force to maintain the flow of the liquid in the microchannel. The capillary force can absorb the liquid into the microchannel (liquid phase channel 200). In order to prevent the liquid phase from entering the gas phase, the capillary force must be large enough to overcome the pressure difference between the gas phase and the liquid phase. This pressure difference is generated by the flow of the liquid in the liquid phase channel 200.

[0086] The capillary force must be able to maintain the flow of the liquid in the liquid phase channel 200 without causing the liquid to overflow into the gas phase channel (the external space outside the microtube 2). This requires that the size and structure of the liquid phase channel 200 of the microtube be properly designed so that the liquid can flow stably in the microchannel.

[0087] The pressure difference generated by the flow of liquid in the liquid phase channel 200 is the same as the pressure difference between the gas and liquid phases. In the distillation unit composed of a plurality of microtubes 2 of the present application, the flow of liquid and gas is interrelated. The pressure difference generated by the flow of liquid in the liquid phase channel 200 must be balanced with the pressure difference between the gas and liquid phases to maintain a stable flow and separation process. If these two pressure differences are inconsistent, the flow of liquid or gas will be unstable, affecting the separation efficiency.

[0088] In the liquid phase channel 200, there is a phase interface between the liquid and the gas. Capillary force plays a key role at this phase interface, maintaining the flow of the liquid in the liquid phase channel 200 while preventing the liquid from entering the gas phase channel. The force balance at this phase interface requires that the pressure difference (capillary force) generated by the liquid flow matches the pressure difference between the gas and liquid phases.

[0089] The gas-liquid phase pressure difference ΔP is the difference between the liquid static pressure head and the vapor static pressure head:

[0090]

[0091] in, and are the liquid and vapor densities respectively, g is the gravitational acceleration, and h is the height of the liquid column, the height of the liquid in the direction of the microtube diameter.

[0092] The pressure difference due to capillary force is calculated as follows:

[0093]

[0094] in, is the tension coefficient of the liquid in the microtube, and R is the size and radius of the gas-liquid exchange hole 21 on the tube wall.

[0095] Therefore, in the design of the microtube 2, it is necessary to ensure that the capillary force is greater than or equal to the gas-liquid phase pressure difference. Based on the above, preferably, the microtube 2 is set to the following size, the gas-liquid phase exchange holes 21 are evenly arranged in the circumferential direction and axial direction of the microtube, the pore size of the gas-liquid phase exchange holes 21 is in the range of 0.02mm-0.05mm, and the center distance between two adjacent gas-liquid phase exchange holes 21 in the axial direction of the microtube 2 is 0.05mm-0.1mm. The center distance between two adjacent gas-liquid phase exchange holes 21 in the circumferential direction of the microtube 2 is 0.05mm-0.1mm.

[0096] The specification of this application records a large number of technical features, which are distributed in various technical solutions. If all possible combinations of technical features (i.e., technical solutions) of this application are listed, the specification will be too long. In order to avoid this problem, the various technical features disclosed in the above invention content of this application, the various technical features disclosed in the various embodiments and examples below, and the various technical features disclosed in the drawings can be freely combined with each other to form various new technical solutions (these technical solutions are all deemed to have been recorded in this specification), unless such a combination of technical features is technically infeasible. For example, in one example, feature A+B+C is disclosed, and in another example, feature A+B+D+E is disclosed. Features C and D are equivalent technical means that play the same role. Technically, only one of them can be used, and it is impossible to use them at the same time. Feature E can be combined with feature C technically. Then, the solution of A+B+C+D should not be deemed to have been recorded because it is technically infeasible, while the solution of A+B+C+E should be deemed to have been recorded.

[0097] All documents mentioned in this application are considered to be included in the disclosure of this application as a whole, so that they can be used as the basis for modification when necessary. In addition, it should be understood that after reading the above disclosure of this application, those skilled in the art can make various changes or modifications to this application, and these equivalent forms also fall within the scope of protection claimed in this application.

Claims

1. A system for preparing high-abundance carbon-13 isotopes using carbon tetrafluoride as a medium and a refrigerant, characterized in that: include: A microchannel distillation device, the microchannel distillation device comprising a distillation unit (1), a reboiler (3) and a condenser (4), the raw material of the microchannel distillation device is a first carbon tetrafluoride with natural abundance, the condenser (4) is configured to condense the components in the first carbon tetrafluoride to be distilled in a gaseous state into a liquid, the reboiler (3) is configured to heat the components in the liquid state into a gas, and the refrigerant in the condenser (4) is a second carbon tetrafluoride; The distillation unit (1) comprises a plurality of microtubes (2) stacked together, the diameter of the microtubes (2) being in the range of 0.3 mm to 1 mm, and a gas-liquid phase exchange hole (21) being arranged on the wall of each microtube (2), so that during the distillation process of carbon tetrafluoride to be distilled, under the action of the capillary force of the microtube (2) and the surface tension of the gas-liquid phase exchange hole (21), the microtube (2) provides a liquid phase channel (200) for liquid flow, and the external space outside the microtube (2) is configured to allow gas flow; The distillation unit (1) has a first end (11) and a second end (12) opposite to the first end (11). During the distillation process, the heavy components condensed into liquid at the second end (12) 13 CF4 flows in the liquid phase channel (200) along the first axial direction of the rectification unit (1) under the action of the capillary force of the microtube (2) and the surface tension of the gas-liquid phase exchange hole (21), and is heated at the first end (11) to become a gas. 12 Under the action of the pressure difference, CF4 moves in the external space outside the micro-tube (2) along the second axial direction of the distillation unit (1), and the second axial direction is opposite to the first axial direction.

2. The system according to claim 1, characterized in that The system further comprises a refrigeration cycle device, which is used for refrigerating and circulating the second carbon tetrafluoride required by the condenser (4), and the refrigeration cycle device comprises a compressor, a cooler, and a throttling device.

3. The system according to claim 2, characterized in that The compressor is in fluid communication with the condenser and the cooler, the cooler is also in fluid communication with the throttling device, and the throttling device is also in fluid communication with the condenser.

4. The system according to claim 3, characterized in that The microtube (2) comprises a gas-liquid phase exchange section. When the gas in the external space and the liquid in the liquid phase channel (200) flow, heat and mass transfer are performed in the gas-liquid phase exchange section of the microtube (2) through the gas-liquid phase exchange holes, so that the heavy component gas in the external space is converted into liquid and enters the liquid phase channel (200), and the light component liquid in the liquid phase channel (200) is converted into gas and enters the external space, and separation and purification are achieved by repeated reciprocation.

5. The system according to claim 1, wherein: During the distillation process, the plurality of microtubes (2) are placed horizontally or tilted, and the first end (11) of the distillation unit (1) and the second end (12) of the distillation unit are at substantially the same height level or at different height levels.

6. The system according to claim 5, characterized in that The plurality of microtubes (2) are stacked together to form a cylinder, and the distance between the centers of two adjacent microtubes (2) is within a range of 1 mm to 2 mm.

7. The system according to claim 6, characterized in that The diameter of the gas-liquid phase exchange hole (21) is in the range of 0.02 mm to 0.05 mm.

8. The system according to claim 7, characterized in that The gas-liquid phase exchange holes (21) are evenly arranged in the circumferential direction and the axial direction of the microtube.

9. The system according to claim 1, characterized in that The capillary force should be greater than or equal to the gas-liquid phase pressure difference, where the gas-liquid phase pressure difference refers to the difference between the static pressure head of the liquid in the liquid phase channel (200) and the static pressure head of the gas flowing in the external space outside the microtube (2).

10. The system according to claim 1, wherein: The total number of the microtubes is between 100 and 200. The distillation unit (1) comprises a heavy fraction end and a light fraction end. Carbon tetrafluoride having a carbon-13 isotope abundance higher than 99% is obtained at the heavy fraction end.

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