A microchannel cryogenic distillation apparatus for silicon isotope enrichment

Abstract

This application discloses a microchannel cryogenic distillation device for silicon isotope enrichment, comprising: a feed inlet, a bottom feed outlet, a top feed outlet, and a distillation column. The feed inlet is configured to introduce high-purity SiF4 gas with natural abundance. The distillation column includes multiple helical inner columns, each comprising a dry reboiler, a helical packed section, and a condenser. The helical packed section is obtained by 3D printing, and the packing material of the helical packed section is a first porous thin-walled structure. The first porous thin-walled structure includes a first thin wall and a gas channel formed by the first thin wall for gas flow. The first thin wall is configured as a surface for liquid flow. This device has a high degree of miniaturization, outstanding space utilization and manufacturing cost advantages, and uses silicon tetrafluoride as the core working fluid to achieve silicon isotope enrichment.

Description

Technical Field

[0001] This application relates to the field of isotope separation technology, and in particular to a microchannel cryogenic distillation apparatus for silicon isotope enrichment. Background Technology

[0002] Silicon isotopes ( 28 Si、 29 Si、 30 Si, as a key strategic material, has irreplaceable application value in the fields of semiconductors, nuclear industry, quantum technology, and precision testing: In the semiconductor industry, high abundance... 28 Si (abundance > 99.99%) has high atomic mass uniformity, which can significantly reduce wafer lattice defects and improve the high-frequency performance and stability of chips; the research and development and production of second-generation quantum systems (including quantum computer chips and quantum sensors) rely on it. 28 The acquisition of Si (silicon-28) material. The core technology of this type of quantum computer lies in using trapped electrons as qubits and manipulating quantum states through electron spin. 28 The core advantages of Si are mainly reflected in three characteristics: 1) It is a zero-nuclear spin-stable isotope. 28 Si and 30 Silicon crystals, composed of Si, are ideal carriers for spin qubits because their host atomic nuclei do not generate spin interference. 28 When Si has an abundance ≥99.9999% (6N level), it can eliminate nuclear spin interference, improving the coherence time of qubits by more than 10 times (>1 second) from milliseconds. Besides quantum computing, 28 The spin vacuum environment of Si can also be used to stabilize silicon-based optically active quantum dots. 2) 28 Si (abundance > 99.995%) can break through the thermal conductivity limit of naturally abundant silicon, further improving the performance of semiconductor integrated circuit hardware. For example... 28 The thermal conductivity of Si (99.995% abundance) is 450 ± 10 W / cm² at 21 K. -1 K -1 This value is approximately 10 times that of naturally abundant Si under the same conditions, exceeding... 12 C diamond at 104 K has a 410 W / cm². -1 K -1 This surpasses the previous record, becoming the highest thermal conductivity of a dielectric ever measured. This property offers potential for performance improvements in cryogenic applications, such as high-energy laser optical systems in vacuum environments: when irradiated by a laser, energy can dissipate rapidly from the irradiation point, effectively reducing the risk of thermal stress or equipment damage. 28Si (99.9% abundance) has a thermal conductivity 10 ± 2% higher than naturally abundant Si at 300 K. 3) Photoluminescence spectroscopy analysis shows that pure Si (99.896%) has a higher thermal conductivity than naturally abundant Si. 28 The homogeneous distribution of Si atoms in the crystal lattice causes a 58 meV shift in the band gap. High-energy measurements further reveal that the nonphonon-assisted photoluminescence spectral lines of bound excitons possess a finer, more concise structure. This optimized spectral fine structure allows for high-resolution studies of exciton processes in isotopically pure materials (such as in quantum sensing applications).

[0003] In the nuclear industry, 30 Due to its low neutron absorption cross section, silicon is a core material for nuclear reactor cladding and neutron detectors; it also plays a significant role in quantum computing and nuclear magnetic resonance (NMR) fields. 29 Si (spin quantum number I = 1 / 2) is a key probe for analyzing the molecular structure of solid-state qubit carriers and materials. However, silicon isotopes exist in a mixed state in nature ( 28 Si is approximately 92.23%. 29 Si is approximately 4.67%. 30 Since silicon is about 3.10%, it needs to be purified to a high abundance through enrichment technology. Therefore, the development of efficient, low-consumption, and miniaturized silicon isotope enrichment equipment has become a core demand of industry and scientific research.

[0004] Currently, silicon isotope enrichment technologies are mainly divided into three categories, but all of them have significant bottlenecks and cannot meet the needs of industrialization and miniaturization: 1) Chemical exchange method: This method relies on the isotopic distribution differences of silicon compounds (such as silanes and organosilicones) in different phases to achieve separation. It requires multiple chemical reactions (such as hydrogenation and halogenation), resulting in problems such as large reagent consumption, long reaction cycles (single enrichment requires several weeks), and easy introduction of impurities into the product. It also cannot achieve continuous production and is only suitable for small-batch preparation in the laboratory; 2) Electromagnetic separation method: This method uses the deflection differences of isotope ions in a magnetic field for separation. Although it can achieve high abundance enrichment, the energy consumption of a single device is as high as several thousand kilowatts, the production capacity is extremely low (the average daily output is only in the gram level), and the equipment manufacturing cost exceeds ten million yuan, making it completely unworthy of industrial promotion; 3) Low temperature distillation method: This method is based on the vapor pressure difference of silicon isotope compounds at low temperatures (i.e., the "isotope effect") to achieve separation. It has advantages such as being green and environmentally friendly (no chemical reagent consumption), capable of continuous operation, and easy to scale up production capacity. It is currently the only silicon isotope enrichment technology with industrialization potential. Silicon tetrafluoride (SiF4) is an ideal enrichment medium for this technology—because it contains only fluorine. 19 F is a stable isotope that does not introduce additional mass interference, and SiF4 exhibits a "reverse isotope effect" (heavy silicon isotope) at low temperatures (-120℃ to -80℃). 30 SiF4 is more volatile than its light isotopes. 28SiF4 can be efficiently enriched by distillation to achieve high concentration of heavy isotopes.

[0005] However, existing low-temperature distillation devices for SiF4 still suffer from the following key technical challenges, severely restricting silicon isotope enrichment efficiency and industrial applications: 1) Low separation efficiency and high equipment and energy costs: Traditional SiF4 distillation devices use randomly packed columns such as Heli-Pak #3013 (e.g., the Los Alamos laboratory prototype), with a single-stage equivalent theoretical plate height (HETP) as high as 2-4 cm. If it is necessary to... 30 Increasing Si abundance from 3.10% to 90% requires hundreds of theoretical trays, resulting in an effective tower height exceeding 10 meters. This not only significantly increases equipment manufacturing costs but also leads to a more than 30% increase in system cooling loss (energy consumption for maintaining low-temperature environments) due to the excessively large tower size. 2) Poor media compatibility and limited mass transfer efficiency: Existing devices have not optimized their structure for the low-temperature physical characteristics of SiF4 (viscosity of 0.015 mPa·s and surface tension of 12 mN / m at -100℃). The pore size and channel design of traditional packing cannot achieve SiF4 gas-liquid transfer. Sufficient contact between the two phases leads to low gas-liquid mass transfer efficiency and is prone to "flooding" (liquid blocking gas channels) or "dry walls" (liquid not covering the packing surface), further reducing separation stability; 3) Limited manufacturing process and poor structural integrity: Traditional devices use separate manufacturing of the packing and shell (the packing is machined and then installed into the metal shell), which cannot realize the processing of complex three-dimensional topological structures (such as biomimetic honeycomb, spiral channels), and there are gaps between the packing and the shell, which easily lead to cold leakage and fluid wall flow; at the same time, traditional processes cannot make the packing micropores The equivalent pore size is reduced to the optimal permeability pore size range in the SiF4 liquid film, and the gas-liquid contact surface area is only 100~200m² / m³, far lower than the 500m² / m³ or more required for efficient separation; 4) The existing device's reboiler (providing vaporization power) relies on an external pump to achieve fluid circulation, adding an extra 20% to energy consumption, and pump vibration easily leads to gas-liquid flow turbulence; at the same time, the reboiler's liquid holdup (>100mL) is mismatched with the low liquid holdup (<10mL) characteristics of the microchannel packed tower, and the system response lag time exceeds 1 hour, making it difficult to... Rapid adjustment to a stable separation state results in isotope abundance fluctuations of ±5%, thus the existing system has insufficient adaptability and poor operational stability; 5) Existing internal tower cascading schemes are limited, only capable of pure vertical gravity drive or pure horizontal cascading: the vertical scheme can utilize gravity to promote fluid flow, but the vertical space occupancy rate inside the vacuum hood is high; the horizontal scheme saves vertical space, but cannot optimize the flow pattern with the help of gravity. Neither of them can adapt to the limited space of the distillation column vacuum hood, resulting in low space utilization inside the vacuum hood and difficulty in achieving efficient separation in miniaturized equipment.

[0006] Therefore, there is an urgent need in this field to develop a microchannel cryogenic distillation device for silicon isotope enrichment. This device has a high degree of miniaturization, outstanding advantages in space utilization and manufacturing cost, and uses silicon tetrafluoride as the core working fluid to achieve silicon isotope enrichment. Summary of the Invention

[0007] The purpose of this application is to provide a microchannel cryogenic distillation device for silicon isotope enrichment. This device has a high degree of miniaturization, outstanding advantages in space utilization and manufacturing cost, and uses silicon tetrafluoride (SiF4) as the core working fluid to achieve silicon isotope enrichment.

[0008] This application provides a microchannel cryogenic distillation apparatus for silicon isotope enrichment, comprising: a feed inlet, a bottom feed outlet, a top feed outlet, and a distillation column, wherein the feed inlet is configured to introduce high-purity SiF4 gas of natural abundance.

[0009] The distillation column includes multiple helical inner columns, each helical inner column including a dry reboiler, a helical packed section, and a condenser. The helical packed section is obtained by 3D printing, and the packing of the helical packed section is a first porous thin-walled structure. The first porous thin-walled structure includes a first thin wall and a gas channel for gas flow enclosed by the first thin wall. The first thin wall is configured as a surface for liquid flow.

[0010] The dry reboiler is located at the bottom of the helical packing section and is configured to heat the liquid flowing downward along the first thin wall of the helical packing section under the action of gravity and the capillary force of the first porous thin-walled structure. The condenser is located at the top of the helical packing section and is configured to condense the gas flowing upward through the gas passage into liquid. The bottom outlet is configured to output the enriched liquid. 28 The SiF4 product, the top feed port of the column is configured to output enriched SiF4 product. 29 SiF4 and 30 SiF4 gaseous products.

[0011] In another preferred embodiment, the bottom feed port is configured to output enriched [material]. 28 SiF4 liquid or gaseous products.

[0012] In another preferred embodiment, the spiral-shaped inner towers are connected in series or in parallel.

[0013] In another preferred embodiment, the distillation column is located in a vacuum hood, and the cryogenic distillation apparatus may include multiple distillation columns as needed.

[0014] In another preferred embodiment, the spiral packing section is spiral in shape.

[0015] In another preferred embodiment, the porosity of the first porous thin-walled structure is between 10% and 85%, and the equivalent pore size of the first porous thin-walled structure is between 5 and 200 micrometers, and the permeability is between 6%. 10 -16 -5 10 -10 m 2 between.

[0016] Preferably, the capillary number Ca of the first porous thin-walled structure is less than 10. -4 Specific surface area > 800 m² / g, Laplace pressure of capillary force > 10 kPa.

[0017] In another preferred embodiment, the equivalent pore size of the first thin wall of the first porous thin-walled structure is between 5 and 200 micrometers.

[0018] In another preferred embodiment, the equivalent pore size of the first porous thin-walled structure is between 5 and 100 micrometers.

[0019] More preferably, the equivalent pore size of the first porous thin-walled structure is between 5 and 30 micrometers.

[0020] In another preferred embodiment, the thickness of the first thin wall of the first porous thin-walled structure is between 50 μm and 300 μm.

[0021] In another preferred embodiment, the first porous thin-walled structure is a honeycomb porous thin-walled structure obtained by 3D printing an alloy.

[0022] In another preferred embodiment, the helical inner tower is one or more of a double-helix structure, a triple-helix structure, and a quadruple-helix structure.

[0023] In another preferred embodiment, when the helical inner tower has a double-helix structure, the helical inner tower includes a first dry reboiler and a second dry reboiler, a first helical packing section and a second helical packing section, a first condenser and a second condenser. The first and second helical packing sections are helical in shape. The first dry reboiler is located at the bottom of the first helical packing section, the first condenser is located at the top of the first helical packing section, the second dry reboiler is located at the bottom of the second helical packing section, and the second condenser is located at the top of the second helical packing section. The same applies when the helical inner tower has a triple-helix structure.

[0024] In another preferred embodiment, the helical inner tower further includes an inner tower shell, the helical packing segment being integrally formed from the inner tower shell and the alloy using 3D printing.

[0025] In another preferred embodiment, the dry reboiler includes: a second porous thin-walled structure and a heating support; wherein,

[0026] The heating support includes a liquid collection surface. The second porous thin-walled structure is connected to the heating support and located above the liquid collection surface of the heating support. The second porous thin-walled structure is configured to provide a capillary surface for liquid flow and to draw the liquid located on the liquid collection surface from bottom to top into the second thin wall of the second porous thin-walled structure by capillary force, thereby enabling heat and mass transfer between the gas and liquid flowing in the second porous thin-walled structure.

[0027] The porosity of the second porous thin-walled structure is between 10% and 85%, and the equivalent pore size of the second thin wall of the second porous thin-walled structure is between 5 and 200 micrometers, and the permeability is between 6%. 10 -16 -5 10 -10 m 2 between.

[0028] Preferably, the capillary number Ca of the second porous thin-walled structure is less than 10. -4 Specific surface area > 800 m² / g, Laplace pressure of capillary force > 10 kPa.

[0029] In another preferred embodiment, the heating support is equipped with a heating rod, and the heating support is further configured to transfer heat to the liquid collection surface of the heating support and the second porous thin-walled structure through the heating rod, thereby causing the liquid located in the liquid collection surface and the second porous thin-walled structure to vaporize.

[0030] In another preferred embodiment, the second porous thin-walled structure includes a second thin wall and a second gas channel formed by the second thin wall for gas flow. During the distillation process, gas flows from bottom to top into the helical packing section of the helical inner tower through the second gas channel. Liquid located at the liquid collection surface is drawn from bottom to top onto the second thin wall by capillary force, or liquid from the helical packing section of the helical inner tower flows onto the second thin wall.

[0031] In another preferred embodiment, the second porous thin-walled structure has the same structure as the first porous thin-walled structure.

[0032] In another preferred embodiment, the dry reboiler further includes a reboiler shell, which is cylindrical, and the second porous thin-walled structure is filled in the reboiler shell, and / or the heating support is cylindrical, and the heating support is provided with heating rod holes for assembling the heating rod.

[0033] It should be understood that, within the scope of this invention, the above-described technical features of this invention and the technical features specifically described below (such as in the embodiments) can be combined with each other to form new or preferred technical solutions. Due to space limitations, they will not be described in detail here. Attached Figure Description

[0034] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below. It should be understood that the accompanying drawings described below are merely some implementation examples of the present invention, and those skilled in the art can obtain other implementation examples based on these drawings without creative effort.

[0035] Figure 1 This is a schematic diagram of a microchannel cryogenic distillation apparatus for silicon isotope enrichment according to an embodiment of this application.

[0036] Figure 2 This is a schematic diagram of the spiral inner column of a cryogenic distillation apparatus according to an embodiment of this application;

[0037] Figure 3 This is a physical schematic diagram of the packing material of the helical packing section of a helical inner tower according to an embodiment of this application;

[0038] Figure 4 This is a schematic cross-sectional view of the helical packing section of a helical inner tower according to another embodiment of this application;

[0039] Figure 5 This is a schematic diagram of the structure of a dry reboiler according to an embodiment of this application;

[0040] Figure 6 yes Figure 5 A schematic diagram of the linear structure of a dry reboiler.

[0041] In each of the attached figures, the markings are as follows:

[0042] 1-Inlet

[0043] 2-Bottom of the tower, material inlet

[0044] 3-Mid-section sampling port

[0045] 4-Top feed inlet

[0046] 5-Vacuum Shield

[0047] 6-Helical Inner Tower

[0048] 61-Dry Reboiler

[0049] 611-Second Porous Thin-Wall Structure

[0050] 612-Heating Support

[0051] 6121-Liquid Collection Surface

[0052] 62-Helical packing section

[0053] 63-Condenser

[0054] 7-Heat Exchanger Detailed Implementation

[0055] Through extensive and in-depth research, the inventors have developed a microchannel cryogenic distillation apparatus for silicon isotope enrichment. This apparatus uses silicon tetrafluoride (SiF4) as the core working fluid and targets silicon isotopes (SiF4). 28 Si、 29 Si、 30 To meet the industrial demand for Si enrichment, a high-efficiency, low-consumption, and miniaturized cryogenic distillation device is constructed using 3D printing of porous structures, cascaded packed towers, and dry reboilers. This device is fully compatible with the reverse isotope effect of SiF4 in the temperature range of 189-206 K (-84.15℃~-67.15℃) (heavy isotopes are more volatile), and can also be extended to the cryogenic distillation enrichment of other isotopes.

[0056] In the following description, many technical details are presented to help the reader better understand this application. However, those skilled in the art will understand that the technical solutions claimed in this application can be implemented even without these technical details and various variations and modifications based on the following embodiments.

[0057] the term

[0058] As used herein, the terms "spiral packing section" and "packing section" are used interchangeably;

[0059] As used herein, the term "equivalent pore size" refers to the equivalent pore size of the pores in the thin wall of a porous thin-walled structure, where the thin wall is a porous medium material.

[0060] In this invention, all directional indicators (such as up, down, left, right, front, back, etc.) are only used to explain the relative positional relationship and movement of each component in a certain specific posture (as shown in the figure). If the specific posture changes, the directional indicator will also change accordingly.

[0061] This application has at least one of the following advantages:

[0062] (a) The cryogenic distillation apparatus of this application uses silicon tetrafluoride (SiF4) as the core working fluid, because fluorine only contains 19F is a single isotope with no additional mass interference, and SiF4 exhibits a reverse isotope effect (heavy isotopes are more volatile) in the temperature range of 189-206 K (-84.15℃~-67.15℃), with its relative volatility deviation (ε) 28 Si / 30 Si =0.0018) is more than twice that of SiH4 (ε=0.00061) and SiCl4 (ε=0.00036), which can maximize the isotope separation potential; while traditional devices often fail to achieve high abundance enrichment due to improper medium selection (such as SiH4) or failure to fully utilize the reverse isotope effect of SiF4.

[0063] (b) The cryogenic distillation apparatus of this application has a high degree of miniaturization, with outstanding advantages in space utilization and manufacturing cost. Specifically, the distillation apparatus of this application overcomes the traditional apparatus's dilemma of "high HETP → large column body → high cost" through "low HETP reducing column height + hybrid cascade optimization of space + 3D printing integrated manufacturing." Because the distillation column HETP of the distillation apparatus of this application is ≤1 cm (compared to 2~4 cm for traditional apparatuses), it achieves the same enrichment target (e.g., 28 When the Si abundance is 99.9%, the effective height of the tower body of this application is only 1 / 3 to 1 / 4 of that of the conventional device (the conventional tower needs to be more than 10 meters, while this application only needs to be less than 3 meters), and the equipment footprint is reduced by more than 60%.

[0064] (c) The low-temperature distillation apparatus of this application has various spiral cascade structures (double spiral, triple spiral, quadruple spiral structures in series and parallel). The spiral packing section has a certain inclination angle and uses gravity to drive the flow of the working fluid. A channel length of more than 3 meters can be achieved in a vacuum hood 1 meter high. The space utilization rate is 2 to 3 times higher than that of traditional distillation columns with purely vertical and / or purely horizontal packing sections.

[0065] (e) The cryogenic distillation apparatus of this application uses 3D printing technology to manufacture the inner tower packing and shell in one piece, and the honeycomb thin-walled structure (thickness 50~100μm) achieves a larger air-liquid contact area with less material, reducing the equipment manufacturing cost by 30%~40% compared with traditional apparatus;

[0066] (f) The dry reboiler of this application has a liquid volume of only 10 mL, which is perfectly matched with the low liquid holdup (<10 mL) of the microchannel column, greatly shortening the isotope abundance equilibrium time in the reboiler. The equilibrium time of the traditional reboiler is about 96 hours, while the equilibrium time of the distillation column system of the dry reboiler is about 36 hours.

[0067] To make the objectives, technical solutions, and advantages of the present invention clearer, embodiments of the present invention will be described in further detail below with reference to the accompanying drawings. It should be understood that these are merely examples provided to the reader of possible implementations of the present invention and are not intended to limit the scope of the invention.

[0068] A microchannel cryogenic distillation apparatus for silicon isotope enrichment

[0069] See Figures 1-4 This application provides a microchannel cryogenic distillation device for silicon isotope enrichment. The device includes a closed-loop design of "raw material pretreatment - cryogenic distillation - product collection - energy recovery". The device includes a feed inlet 1, a bottom feed outlet 2, a top feed outlet 3, and a distillation column. The feed inlet 1 is configured to introduce high-purity SiF4 gas with natural abundance.

[0070] The distillation column includes multiple helical inner columns 6 and a vacuum shroud 5, with the multiple helical inner columns 6 disposed within the vacuum shroud 5. Each helical inner column 6 includes a dry reboiler 61, a helical packed section 62, and a condenser 63. The helical packed section 62 is obtained through 3D printing, and the packing of the helical packed section 62 is a first porous thin-walled structure. The first porous thin-walled structure includes a first thin wall and gas channels formed by the first thin wall for gas flow. The first thin wall is configured as a surface for liquid flow.

[0071] The dry reboiler 61 is located at the bottom of the helical packing section 62 and is configured to heat the liquid flowing downward along the first thin wall of the helical packing section 62 under the action of gravity and the capillary force of the first porous thin-walled structure. The condenser 63 is located at the top of the helical packing section 62 and is configured to condense the gas flowing upward through the gas passage into liquid. The bottom outlet 2 is configured to output the enriched liquid. 28 The SiF4 liquid product, with top feed port 3 configured to output enriched product. 29 SiF4 and 30 SiF4 gaseous products.

[0072] Specifically, inlet 1 is introduced with SiF4 product gas of natural abundance (containing... 28 SiF4 is approximately 92.2%. 29 SiF4 is approximately 4.7%. 30 The SiF4 content is approximately 3.1%. The product gas first undergoes drying and impurity removal pretreatment (to remove trace amounts of moisture and acidic impurities to prevent equipment corrosion) before entering the heat exchanger. The SiF4 product gas is discharged from the top of the heat exchanger absorption tower, where the heavier components (enriched) are removed. 29 SiF4 / 30 The cooling capacity of SiF4 is reduced by pre-cooling to near the operating temperature range of the distillation column (approximately -90°C), thus minimizing cooling capacity loss in the distillation column; simultaneously, the light components (high abundance) at the bottom of the column are pre-cooled. 28SiF4 vapor is collected after being heated to room temperature (e.g.) Figure 1 (2) at the bottom of the tower to avoid the waste of cold energy caused by the direct discharge of low-temperature gas.

[0073] The distillation column is the core separation unit of the silicon isotope enrichment microchannel cryogenic distillation device of this application. It integrates 3D-printed microchannel packing and a hybrid cascade structure to achieve efficient mass transfer between the SiF4 gas and liquid phases, and to concentrate light isotopes. 28 SiF4 is enriched in the liquid phase, heavy isotopes 29 SiF4 / 30 SiF4 migrates in the vapor phase. High abundance is output from the bottom of the distillation column. 28 SiF4 liquid product (target abundance can be adjusted to over 99.9% as needed), discharged from the top of the column rich in... 29 SiF4 / 30 SiF4 component vapor.

[0074] In one embodiment, the helical inner columns 6 are connected in series or in parallel. In one embodiment, the distillation column is located in a vacuum hood 5; depending on the requirements, the cryogenic distillation apparatus may include multiple distillation columns.

[0075] In one embodiment, the helical inner tower 6 can be a double-helix, triple-helix, or quadruple-helix structure. The double-helix structure is suitable for small-scale enrichment (e.g., laboratory-scale, capacity <100 g / d), while the quadruple-helix structure is suitable for large-scale industrial production (capacity >1 kg / d). The separation capacity can be expanded by increasing the number of helices, and each helical channel operates independently to avoid mutual interference.

[0076] In one embodiment, when the helical inner tower 6 has a double-helix structure, the helical inner tower 6 includes a first dry reboiler and a second dry reboiler, a first helical packing section and a second helical packing section, a first condenser and a second condenser. The first and second helical packing sections are helical in shape. The first dry reboiler is located at the bottom of the first helical packing section, the first condenser is located at the top of the first helical packing section, the second dry reboiler is located at the bottom of the second helical packing section, and the second condenser is located at the top of the second helical packing section. When the helical inner tower 6 has a triple-helix structure, the same applies.

[0077] Preferably, this application utilizes the structural freedom of 3D printing, and the helical inner tower 6 is designed as a cascaded structure (series or parallel structure) of various helical shapes (double helix structure, triple helix structure, or quadruple helix structure), solving the problem of "gravity drive and space utilization being incompatible" in traditional cascade schemes. The helical inner tower 6 is placed entirely inside the vacuum shroud 5, wherein the helical packing section has a certain inclination angle, using gravity to drive the liquid to flow downward (without external power), while the vapor flows upward along the helical channel, forming a stable countercurrent flow state; within the limited vertical space of the vacuum shroud, the channel length is expanded (e.g., if the vacuum shroud is 1 meter high, the helical shape can achieve a channel length of more than 3 meters), increasing the number of theoretical plates.

[0078] The hybrid cascade scheme of the spiral inner tower 6 achieves the synergy of gravity drive and space utilization. Compared with pure vertical cascade, the space utilization rate of the vacuum chamber is increased by 2 to 3 times. For example, in the limited vertical space of the vacuum chamber (such as 1 meter in height), the channel length is more than 3 meters. Compared with pure horizontal cascade, the liquid flow resistance is reduced by more than 50%, and no siphon device is required. The flow stability is significantly improved (isotope abundance fluctuation range < ±1%).

[0079] In one embodiment, the helical packing section 62 of the helical inner tower 6 is manufactured using powder laser sintering 3D printing technology to achieve integrated manufacturing of the inner tower packing and the inner tower shell, i.e., 3D printing of the packing and the inner tower shell. Preferably, alloy powders resistant to low temperatures and SiF4 corrosion (such as nickel-based alloys, Hastelloy, and stainless steel) are selected, and sintered layer by layer using laser selective melting technology: during sintering, the laser power is controlled (for the packing area: low power for rapid scanning to form a porous structure; for the shell area: high power for complete melting to form a dense and impermeable shell) to ensure that there are no gaps between the packing and the shell, avoiding cold leakage and fluid wall flow.

[0080] In one embodiment, the packing of the spiral packing section 62 of this application is a first porous thin-walled structure, which is a microchannel structure. The first porous thin-walled structure enhances gas-liquid mass transfer through "small channels + high specific surface area". The first porous thin-walled structure is obtained by 3D printing alloy.

[0081] The porosity of the first porous thin-walled structure is between 10% and 85%, and the equivalent pore size of the first porous thin-walled structure is between 5 and 200 micrometers, with a permeability of 6. 10 -16 -5 10 -10 m². Preferably, the capillary number Ca of the first porous thin-walled structure is <10. -4 Specific surface area > 800 m² / g, Laplace pressure of capillary force > 10 kPa.

[0082] The first porous thin-walled structure includes a thin wall and gas channels enclosed by the thin wall. The thin wall has a surface for liquid flow, and gas flows within the gas channels. Preferably, the thickness of the gas channels ranges from 0.1 mm to 3 mm (microchannel scale), employing an open flow channel design to ensure that SiF4 vapor (low viscosity and high fluidity at low temperatures) can flow uniformly upwards, avoiding flooding. The inner wall of the flow channel is polished to reduce vapor flow resistance. The thickness of the thin wall ranges from 50 μm to 300 μm, and it is designed to alternate with the gas channels. Liquid flows downwards within the thin wall along the direction of gravity, forming a counter-current contact with the vapor in the gas channels. Preferably, the material of the first porous thin-walled structure in this application is a metal film obtained by powder laser sintering, with an adjustable pore gradient and high porosity near the gas channel side (facilitating liquid permeation and vapor contact).

[0083] Preferably, the first porous thin-walled structure is a honeycomb thin-walled structure obtained by 3D printing alloy (e.g., Figure 4 The hexagonal honeycomb unit (with a thin wall thickness of only 50-300 μm) is preferred, and the equivalent pore size of the honeycomb unit is 5-30 μm (matching the molecular free path of SiF4). This structure uses minimal material to form the largest gas-liquid exchange surface area (specific surface area > 800 m²). 2 / m 3 It is 4 to 5 times that of traditional packings, significantly enhancing heat and mass transfer efficiency; at the same time, the regular arrangement of honeycomb units avoids the "channeling" problem of traditional random packings, ensuring uniform gas-liquid contact.

[0084] Through the microchannel structure design of the packing, the SiF4 distillation column of this application (1.5 meters effective length) achieves HETP ≤ 1 cm, which is far superior to the 2~4 cm of the traditional Heli-Pak #3013 packing. The smaller HETP means that, for the same enrichment target, the column height can be reduced to 1 / 3~1 / 4 of that of conventional devices (if...). 28 With a Si abundance of 99.9%, this application requires only 3 meters of height, while traditional towers need to be 10 meters high, significantly reducing equipment size and cold energy loss (energy consumption is reduced by about 40%).

[0085] In other embodiments, the first porous thin-walled structure can adjust its three-dimensional topology (e.g., circular or triangular honeycomb units) according to the distillation working medium (e.g., other isotope compounds), and the pore size and wall thickness can also be precisely controlled by 3D printing parameters (laser power, scanning speed, powder particle size) (e.g., when separating isotopes with low surface tension, the pore size can be reduced).

[0086] The entire cryogenic distillation unit operates within a cryogenic range of -270℃ to -20℃, with the core operating temperature zone of the distillation column precisely controlled between 189-206 K (-84.15℃ to -67.15℃) – this temperature range is where the reverse isotope effect of SiF4 is most significant, maximizing its effectiveness. 28SiF4 and 29 SiF4 / 30 The relative volatility difference of SiF4 provides a thermodynamic basis for efficient separation.

[0087] Dry reboiler

[0088] In one embodiment, see Figure 5 and Figure 6 The reboiler of this application is a dry reboiler 61, which includes a second porous thin-walled structure 611 and a heating support 612. The heating support 612 includes a liquid collection surface 6121. The second porous thin-walled structure 611 is connected to the heating support 612 and is located above the liquid collection surface 6121 of the heating support 612. The second porous thin-walled structure 611 is configured to provide a capillary surface for liquid flow and to draw the liquid located on the liquid collection surface 6121 from bottom to top into the second thin wall of the second porous thin-walled structure 611 by capillary force, thereby enabling heat and mass transfer between the gas and liquid flowing in the second porous thin-walled structure 611.

[0089] The porosity of the second porous thin-walled structure is between 10% and 85%, and the equivalent pore size of the second thin wall is between 5 and 200 micrometers, with a permeability of 6. 10 -16 -5 10 -10 m 2 Preferably, the capillary number Ca of the second porous thin-walled structure is less than 10. -4 Specific surface area > 800 m² / g, Laplace pressure of capillary force > 10 kPa.

[0090] The heating support 612 is equipped with a heating rod, and the heating support 612 is also configured to transfer heat to the liquid collection surface 6121 and the second porous thin-walled structure 611 of the heating support 612 through the heating rod, thereby causing the liquid located in the liquid collection surface 6121 and the second porous thin-walled structure 611 to vaporize. The liquid rapidly vaporizes SiF4, which has a boiling point of about -86°C at 0.3 atm, and the generated vapor enters the spiral packing section 62 of the spiral inner tower 6 to participate in mass transfer.

[0091] The second porous thin-walled structure 611 includes a second thin wall and a second gas channel formed by the second thin wall for gas flow. During the distillation process, the gas flows from bottom to top into the helical packing section 62 of the helical inner tower 6 through the second gas channel. The liquid located at the liquid collection surface 6121 is drawn from bottom to top onto the second thin wall by capillary force, or the liquid from the helical packing section 62 of the helical inner tower 6 flows onto the second thin wall, thereby transferring heat and mass with the gas flowing in the second porous thin-walled structure, making the dry reboiler space an "effective distillation section".

[0092] Preferably, the second porous thin-walled structure is the same as the first porous thin-walled structure. The second porous thin-walled structure is also a honeycomb porous thin-walled structure obtained through 3D printing of an alloy. This allows the dry reboiler to achieve rapid vaporization to reduce liquid holdup. Simultaneously, its large specific surface area enhances gas-liquid heat and mass exchange, using its own space as an effective rectification section, equivalent to providing an additional 2-3 theoretical plates, thus improving the overall separation efficiency of the distillation column. Specifically, the capillary action of the honeycomb porous material draws the liquid from the bottom of the reboiler to the thin wall of the second porous thin-walled structure 611, resulting in rapid vaporization and minimal liquid holdup. The gas-liquid mixture naturally returns to the distillation column due to the density difference, eliminating the need for external pump power and reducing energy consumption. The high-efficiency heat transfer characteristics of the thin-walled structure allow for rapid adjustment of the vaporization rate when the load changes. The high-velocity gas-liquid mixture washes over the thin wall and tube wall, significantly reducing the risk of scaling (especially suitable for materials that easily crystallize at low temperatures).

[0093] Preferably, the heating support 612 is provided with heating rod holes for mounting heating rods. The hole layout ensures uniform heat distribution and avoids localized overheating. The heating rod and the heating rod holes are made of compatible materials and must have good thermal conductivity (such as metal) to ensure efficient heat transfer to the honeycomb porous material and the liquid collection surface of the heating support 612.

[0094] The heating support 612, located below the second porous thin-walled structure 611 and including a liquid collection surface, bears the initial heating process of the liquid. It is directly connected to the second porous thin-walled structure 611, transferring heat to it. Simultaneously, it serves as the starting point for liquid circulation, driving natural circulation by utilizing density differences (the density of the gas-liquid mixture decreases after vaporization). The heating support 612, made of a highly thermally conductive metal material (such as an alloy), forms a "fluid-side fin" structure when connected to the 3D-printed honeycomb alloy material (second porous thin-walled structure 611), enhancing heat exchange efficiency.

[0095] In one embodiment, the second porous thin-walled structure 611 of the dry reboiler has the same structure as the packing of the helical packing section of the helical inner tower 6. In one embodiment, the second porous thin-walled structure 611 and the packing of the helical packing section 62 (the first porous thin-walled structure) can be 3D printed separately, and then the reboiler is welded together with the helical packing section 62.

[0096] In other embodiments, the helical packing section of the helical inner tower 6 and the second porous thin-walled structure of the dry reboiler are integrally sintered using 3D-printed alloy material.

[0097] Preferably, the porosity of the packing (first porous thin-walled structure) and the second porous thin-walled structure 611 of the spiral packing section 62 is >70%, and the equivalent pore size is 5~30 μm, so that the spiral packing section 62 and the second porous thin-walled structure 611 of the dry reboiler serve as the core area for liquid vaporization and heat and mass exchange.

[0098] The liquid phase retention of the dry reboiler in this application is more than 90% lower than that of the conventional reboiler. The minimum start-up capacity of the distillation column with the dry reboiler (liquid phase volume of about 10 mL, without macroscopic liquid level) is much lower than that of the minimum start-up capacity of the ordinary reboiler (100 mL).

[0099] It should be noted that in this patent application, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one" does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element. In this patent application, if it refers to performing an action according to an element, it means performing the action at least according to that element, including two cases: performing the action only according to that element, and performing the action according to that element and other elements. Expressions such as "multiple," "repeatedly," and "various" include two, two times, two kinds, and more than two, more than two times, and more than two kinds.

[0100] All documents mentioned in this application are considered to be incorporated in their entirety into the disclosure of this application so that they can serve as a basis for modifications if necessary. Furthermore, it should be understood that after reading the foregoing disclosure of this application, those skilled in the art can make various alterations or modifications to this application, and these equivalent forms also fall within the scope of protection claimed in this application.

Claims

1. A microchannel cryogenic distillation apparatus for silicon isotope enrichment, characterized in that, include: The column includes a feed inlet (1), a bottom feed outlet (2), a top feed outlet (3), and a distillation column, wherein the feed inlet (1) is configured to introduce high-purity SiF4 gas of natural abundance. The distillation column includes multiple helical inner columns (6), each helical inner column (6) including a dry reboiler (61), a helical packing section (62), and a condenser (63). The helical packing section (62) is obtained by 3D printing. The packing of the helical packing section (62) is a first porous thin-walled structure. The first porous thin-walled structure includes a first thin wall and a gas channel for gas flow enclosed by the first thin wall. The first thin wall is configured as a surface for liquid flow. The thin wall of the first porous thin-walled structure is a porous medium material. The thickness of the first thin wall ranges from 50μm to 300μm. It is designed to be arranged alternately with the gas channel. The helical packing section has an inclination angle. It uses gravity to drive the liquid to flow downward in the direction of gravity within the first thin wall, while the vapor flows upward along the helical channel, forming a counter-current contact with the vapor in the gas channel. The dry reboiler (61) is located at the bottom of the helical packing section (62) and is configured to heat the liquid flowing downward along the first thin wall of the helical packing section (62) under the action of gravity and the capillary force of the first porous thin-walled structure. The condenser (63) is located at the top of the helical packing section (62) and is configured to condense the gas flowing upward through the gas channel into liquid. The bottom feed port (2) is configured to output the enriched liquid. 28 The SiF4 product, the top feed port (3) of the column is configured to output enriched SiF4 product. 29 SiF4 and 30 SiF4 gaseous products.

2. The cryogenic distillation apparatus as described in claim 1, characterized in that, The porosity of the first porous thin-walled structure is between 10% and 85%, and the equivalent pore size of the first porous thin-walled structure is between 5 and 200 micrometers, and the permeability is between 6. 10 -16 -5 10 -10 m 2 between.

3. The cryogenic distillation apparatus as described in claim 2, characterized in that, The equivalent pore size of the first porous thin-walled structure is between 5 and 100 micrometers.

4. The cryogenic distillation apparatus as described in claim 2, characterized in that, The thickness of the first thin wall in the first porous thin-walled structure is between 50 μm and 300 μm.

5. The cryogenic distillation apparatus as described in claim 1, characterized in that, The spiral inner tower (6) is one or more of a double spiral structure, a triple spiral structure, and a quadruple spiral structure.

6. The cryogenic distillation apparatus as described in claim 1, characterized in that, The helical inner tower (6) also includes an inner tower shell, and the helical packing section (62) is integrally formed by 3D printing alloy and the inner tower shell.

7. The cryogenic distillation apparatus as described in claim 1, characterized in that, The dry reboiler (61) includes: a second porous thin-walled structure (611) and a heating support (612); wherein, The heating support (612) includes a liquid collection surface (6121). The second porous thin-walled structure (611) is connected to the heating support (612) and located above the liquid collection surface (6121) of the heating support (612). The second porous thin-walled structure (611) is configured as a capillary surface for liquid flow, and the liquid located on the liquid collection surface (6121) is drawn from bottom to top into the second thin wall of the second porous thin-walled structure (611) by capillary force, thereby enabling the gas and liquid flowing in the second porous thin-walled structure (611) to transfer heat and mass. The porosity of the second porous thin-walled structure is between 10% and 85%, and the equivalent pore size of the second thin wall of the second porous thin-walled structure is between 5 and 200 micrometers, and the permeability is between 6%. 10 -16 -5 10 -10 m 2 between.

8. The cryogenic distillation apparatus as described in claim 7, characterized in that, The heating support (612) is equipped with a heating rod, and the heating support (612) is also configured to transfer heat through the heating rod to the liquid collection surface (6121) of the heating support (612) and the second porous thin-walled structure (611), thereby causing the liquid located in the liquid collection surface (6121) and the second porous thin-walled structure (611) to vaporize.

9. The cryogenic distillation apparatus as described in claim 8, characterized in that, The second porous thin-walled structure (611) includes a second thin wall and a second gas channel formed by the second thin wall for gas flow. During the distillation process, the gas flows from bottom to top into the helical packing section (62) of the helical inner tower (6) through the second gas channel. The liquid located on the liquid collection surface (6121) is drawn from bottom to top to the second thin wall by capillary force or the liquid from the helical packing section (62) of the helical inner tower (6) flows to the second thin wall.

10. The cryogenic distillation apparatus as described in claim 9, characterized in that, The second porous thin-walled structure (611) has the same structure as the first porous thin-walled structure.

Images