A method and apparatus for low temperature rectification separation of silicon isotopes

Abstract

The application provides a method and device for separating silicon isotopes by low-temperature rectification, and the method comprises the following steps: feeding SiF4 raw material into a first separation tower to perform first low-temperature rectification, so as to obtain first tower bottom 28 SiF4 concentrate and first tower top lean material; feeding the first tower bottom 28 SiF4 concentrate into a second separation tower to perform second low-temperature rectification, so as to obtain second tower bottom 28 SiF4 concentrate and second tower top lean material; feeding the second tower bottom 28 SiF4 concentrate into a third separation tower to perform third low-temperature rectification, so as to obtain third tower bottom 28 SiF4 concentrate and third tower top lean material; the third tower top lean material is reused in the second separation tower. By performing three-stage low-temperature rectification on natural abundance SiF4 raw material, the separation efficiency of silicon isotopes is improved, and high abundance 28 SiF4 product is efficiently produced.

Description

Technical Field

[0001] This invention belongs to the field of isotope separation technology, and relates to a method and apparatus for separating silicon isotopes by low-temperature distillation. Background Technology

[0002] Silicon is an important semiconductor material widely used in electronics, semiconductors, photovoltaics, communications, and other fields. Natural silicon exists primarily in four stable isotopes: 28 Si、 29 Si、 30 Si and 32 Si. Among them 28 Si is the most common isotope, accounting for approximately 92.23%. However, recent studies have found that using high-abundance Si... 28 Semiconductor devices made from silicon (e.g., 99.85% or higher) offer significant performance advantages. For example, at room temperature, their thermal conductivity can be 10% to 60% higher than that of natural silicon, with even greater increases at certain specific temperatures; the reverse breakdown voltage of diodes made from this material can be more than 80% higher than that of natural silicon diodes manufactured using the same process. Furthermore, using silicon with an abundance of 99% or higher... 28 Silicon (Si) can be used to prepare silicon crystals, which can reduce phonon scattering, improve thermal conductivity, lower gate voltage, increase switching speed, and increase chip frequency. This allows for the manufacture of high-speed CPUs, high-power devices, and high-performance sensors. In the field of quantum information, high abundance... 28 Si can be used to fabricate devices with long spin coherence times, removing... 29 Interference from Si.

[0003] However, despite high abundance 28 Si has enormous potential for improving the performance of semiconductor devices, but its industrial production still faces many challenges. Currently, there are many methods for enriching silicon isotopes both domestically and internationally, including cryogenic distillation (SiH4, SiCl4, SiF4, or SiH3CH3 systems), gas centrifugation (with SiF4 or SiHCl3 as the medium), chemical exchange (separation systems of SiF4 and different complexing agents), laser methods (Si2F6, SiF4), and electromagnetic methods (SiH4). Among these, cryogenic distillation utilizes the minute differences in saturated vapor pressure between isotope atoms or molecules to achieve the separation of isotopic components. For example, in the silicon tetrafluoride system, 28 The volatility of Si is relatively... 29 Si is 0.9990, relative to 30 Since Si has a concentration of 0.9982, SiF4 is considered a practical method for enriching silicon isotopes. However, existing methods for separating silicon isotopes by cryogenic distillation suffer from low separation efficiency, complex processes, and high costs, and have not yet achieved a breakthrough in industrial production.

[0004] In summary, the development of a highly efficient and easy-to-operate separation method is crucial. 28 The development of methods and apparatus for separating Si isotopes has become a pressing technical problem in this field. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide a method and apparatus for low-temperature distillation separation of silicon isotopes. By performing three-stage low-temperature distillation on naturally abundant SiF4 feedstock, the separation efficiency of silicon isotopes is improved, thereby achieving high-abundance separation. 28 High-efficiency production of SiF4 products.

[0006] To achieve this objective, the present invention employs the following technical solution:

[0007] In a first aspect, the present invention provides a method for separating silicon isotopes by low-temperature distillation, the method comprising the following steps:

[0008] (1) The SiF4 raw material is fed into the first separation column for first low-temperature distillation to obtain the first column bottom. 28 SiF4 concentrate and lean feed from the top of the first tower;

[0009] (2) The first tower bottom of step (1) 28 The SiF4 concentrate is fed into the second separation column for a second cryogenic distillation, yielding the bottom product of the second column. 28 SiF4 concentrate and second tower top lean feed;

[0010] (3) The second tower bottom in step (2) 28 The SiF4 concentrate is fed into the third separation column for third cryogenic distillation, yielding the bottom product. 28 SiF4 concentrate and lean feed at the top of the third tower;

[0011] The lean feed from the top of the third tower is recycled to the second separation tower.

[0012] The method provided by this invention improves the separation efficiency of silicon isotopes by performing three-stage low-temperature distillation on naturally abundant SiF4 feedstock, thereby achieving high abundance. 28 The efficient production of SiF4 products solves the problems of high production cost, complex material circulation and many impurities in existing chemical exchange, gas centrifugation and laser methods.

[0013] It should be noted that by performing low-temperature distillation on the SiF4 raw material, 28The SiF4 concentrate is enriched at the bottom of the column. By combining a first, second, and third cryogenic distillation process, silicon isotopes are separated at each stage, thereby progressively improving the separation purity of silicon isotopes. This reduces the theoretical plate number of the distillation column, lowers engineering and operating costs, and significantly reduces energy consumption. Furthermore, it enables continuous production of silicon isotope separation, meeting the needs of large-scale production.

[0014] As a preferred technical solution of the present invention, in step (1) the SiF4 raw material 28 The abundance of SiF4 is ≥90%, for example, it can be 90.2%, 90.5%, 90.6%, 90.8%, 91%, 91.5%, 92%, 92.5% or 93%, etc.

[0015] In this invention, the SiF4 raw material is a purified raw material.

[0016] Preferably, before conveying the material to the first separation tower in step (1), the process further includes: heating and pressurizing the SiF4 raw material in the first cold trap and then conveying it to the first separation tower.

[0017] Preferably, the temperature of the SiF4 raw material after being heated and pressurized by the first cold trap is -10 to -30°C, for example, it can be -12°C, -15°C, -16°C, -18°C, -20°C, -22°C, -25°C, -26°C or -28°C, etc., and the pressure is 0.6 to 0.8 MPa, for example, it can be 0.62 MPa, 0.65 MPa, 0.66 MPa, 0.68 MPa, 0.7 MPa, 0.72 MPa, 0.75 MPa, 0.76 MPa or 0.78 MPa, etc.

[0018] It should be noted that after the material is heated and pressurized in a cold trap, it can be cooled to a lower temperature and the vaporization rate of the material will be accelerated. Then, low-temperature distillation can improve the separation effect and efficiency of silicon isotopes and reduce the energy consumption in the distillation process.

[0019] As a preferred technical solution of the present invention, before conveying to the second separation tower in step (2), the method further includes: conveying the bottom of the first tower to the second separation tower. 28 The SiF4 concentrate is heated and pressurized in the second cold trap and then transported to the second separation tower.

[0020] Preferably, the first tower bottom 28The SiF4 concentrate, after being heated and pressurized by the second cold trap, has a temperature of -10 to -30°C, for example, -12°C, -15°C, -16°C, -18°C, -20°C, -22°C, -25°C, -26°C, or -28°C, and a pressure of 0.6 to 0.8 MPa, for example, 0.62 MPa, 0.65 MPa, 0.66 MPa, 0.68 MPa, 0.7 MPa, 0.72 MPa, 0.75 MPa, 0.76 MPa, or 0.78 MPa.

[0021] As a preferred technical solution of the present invention, before conveying to the third separation tower in step (3), the method further includes: conveying the bottom of the second tower to the third separation tower. 28 The SiF4 concentrate is heated and pressurized in the third cold trap and then transported to the third separation tower.

[0022] Preferably, the second tower bottom 28 The SiF4 concentrate, after being heated and pressurized by the third cold trap, has a temperature of -10 to -30°C, for example, -12°C, -15°C, -16°C, -18°C, -20°C, -22°C, -25°C, -26°C, or -28°C, and a pressure of 0.6 to 0.8 MPa, for example, 0.62 MPa, 0.65 MPa, 0.66 MPa, 0.68 MPa, 0.7 MPa, 0.72 MPa, 0.75 MPa, 0.76 MPa, or 0.78 MPa.

[0023] As a preferred embodiment of the present invention, the top pressure of the first separation tower, the second separation tower, and the third separation tower is 0.35 to 0.65 MPa, for example, it can be 0.36 MPa, 0.38 MPa, 0.4 MPa, 0.42 MPa, 0.45 MPa, 0.46 MPa, 0.48 MPa, 0.5 MPa, 0.55 MPa, 0.6 MPa, 0.62 MPa, or 0.64 MPa, etc.

[0024] Preferably, the top temperatures of the first separation tower, the second separation tower, and the third separation tower are all between -65 and -80°C, for example, -66°C, -68°C, -70°C, -72°C, -75°C, -76°C, or -78°C.

[0025] Preferably, the bottom temperature of the first separation tower, the second separation tower, and the third separation tower is -65 to -80°C, for example, it can be -66°C, -68°C, -70°C, -72°C, -75°C, -76°C, or -78°C.

[0026] It should be noted that by controlling the pressure and temperature of the first, second, and third separation towers within a specific range, efficient distillation separation of silicon isotopes under low-temperature conditions is achieved, and the efficiency is improved. 28Abundance of SiF4.

[0027] Preferably, the vacuum degree of the first separation tower, the second separation tower and the third separation tower is 0.0001 to 10 Pa, for example, it can be 0.0005 Pa, 0.001 Pa, 0.005 Pa, 0.01 Pa, 0.05 Pa, 0.1 Pa, 0.5 Pa, 1 Pa or 5 Pa (absolute pressure).

[0028] As a preferred technical solution of the present invention, the reflux ratio of the first separation tower in step (1) is 10-100, for example, it can be 20, 30, 40, 50, 60, 70, 80 or 90, etc.

[0029] Preferably, the reflux ratio of the second separation tower in step (2) is 1800-2200, for example, it can be 1850, 1900, 1950, 2000, 2050, 2100 or 2150, etc.

[0030] Preferably, the reflux ratio of the third separation tower in step (3) is 5000-7000, for example, it can be 5200, 5500, 5600, 5800, 6000, 6200, 6500, 6600 or 6800, etc.

[0031] It should be noted that by controlling the reflux ratios of the first, second, and third separation towers within a specific range, the following can be achieved: 28 SiF4 is enriched at the bottom of the column, ensuring higher purity of the bottom product and reducing the amount of heating steam and cooling source required, thus lowering energy consumption. If the reflux ratio is too high, excessive energy consumption leads to increased production costs; if the reflux ratio is too low, decreased separation efficiency results in lower bottom product concentration. 28 The SiF4 abundance does not meet the requirements.

[0032] As a preferred technical solution of the present invention, step (1) the first tower bottom 28 The abundance of SiF4 concentrate is >96%, for example, it can be 96.2%, 96.4%, 96.5%, 96.6%, 96.8%, 97%, 97.2%, 97.4% or 97.5%, etc.

[0033] Preferably, in step (2), the second tower bottom 28 The abundance of SiF4 concentrate is >98%, for example, it can be 98.1%, 98.2%, 98.3%, 98.4%, 98.5%, 98.6%, 98.7%, 98.8%, 99%, or 99.2%, etc.

[0034] Preferably, the third tower bottom in step (3) 28The abundance of SiF4 concentrate is >99%, for example, it can be 99.1%, 99.2%, 99.3%, 99.4%, 99.5%, 99.6%, 99.7% or 99.8%, etc.

[0035] In a second aspect, the present invention provides an apparatus for low-temperature distillation separation of silicon isotopes, which applies the method for low-temperature distillation separation of silicon isotopes as described in the first aspect. The apparatus includes a first separation tower, a second separation tower, and a third separation tower connected in series.

[0036] The first, second, and third separation towers are all equipped with condensation devices at the top and reboiling devices at the bottom.

[0037] The first separation tower is equipped with a raw material inlet;

[0038] The bottom of the third separation tower is equipped with 28 SiF4 product export;

[0039] The top of the third separation tower is connected to the bottom of the second separation tower.

[0040] In this invention, the condenser condenses the rising steam entering the top of the column, and part of the condensate flows into the column as reflux liquid and part is collected as the top product; the reboiling device heats the bottom liquid to boiling and provides a certain flow of rising steam, while part of the bottom liquid is collected as the bottom product.

[0041] The apparatus provided by this invention, through the sequentially connected first, second, and third separation towers, not only reduces complex material circulation and high / low temperature tower equipment but also enables continuous production of silicon isotope products. The apparatus features a simple process, convenient operation, low cost, and high safety, and can meet the requirements for high abundance... 28 Requirements for SiF4 preparation process.

[0042] As a preferred embodiment of the present invention, a first cold trap is provided on the pipeline connecting the raw material inlet and the first separation tower.

[0043] Preferably, the bottom of the first separation tower is connected to the middle of the second separation tower, and a second cold trap is provided on the connecting pipeline.

[0044] Preferably, the bottom of the second separation tower is connected to the middle of the third separation tower, and a third cold trap is provided on the connecting pipeline.

[0045] As a preferred embodiment of the present invention, the first separation tower, the second separation tower and the third separation tower are all packed towers, and a liquid distributor is provided inside the packed tower.

[0046] In this invention, liquid distributors can be installed at certain intervals within the packed tower to evenly distribute the liquid flowing down from the top of the tower, thereby increasing the heat and mass transfer efficiency.

[0047] Preferably, the theoretical plate number of the first separation tower, the second separation tower and the third separation tower is 600 to 1200, for example, it can be 650, 700, 750, 800, 850, 900, 950, 1000, 1050, 1100 or 1150, etc.

[0048] In this invention, by using a three-stage separation tower in combination to separate silicon isotopes, the theoretical plate number of the separation tower can be reduced, thereby reducing costs and energy consumption.

[0049] Preferably, the surfaces of the first, second, and third separation towers are all covered with an aluminum polyester film.

[0050] In this invention, an aluminum polyester film is used to coat the surface of the tower body to reduce radiative heat loss.

[0051] Preferably, the first separation tower, the second separation tower and the third separation tower are all provided with tower well vacuum jackets, and an outer jacket is also provided outside the tower well vacuum jacket.

[0052] In this invention, a vacuum jacket is set in the tower well to draw a vacuum, thereby reducing heat loss through conduction; an outer jacket is set on its outer surface to protect the separation tower and prevent corrosion from water and air.

[0053] The numerical range described in this invention includes not only the point values ​​listed above, but also any point values ​​within the numerical ranges not listed above. Due to space limitations and for the sake of brevity, this invention will not exhaustively list all the specific point values ​​included in the range.

[0054] Compared with the prior art, the present invention has the following beneficial effects:

[0055] (1) The method provided by the present invention involves low-temperature distillation of SiF4 raw material. 28 The SiF4 concentrate is concentrated at the bottom of the column. By combining a first, second, and third cryogenic distillation process, the separation efficiency of silicon isotopes is improved, thereby achieving high abundance. 28 High-efficiency production of SiF4 products; the final separation tower can extract SiF4 with an abundance >99%. 28 SiF4 products;

[0056] (2) The device provided by the present invention, by setting up a first separation tower, a second separation tower and a third separation tower connected in series, not only reduces the complex material circulation and high and low temperature tower equipment, but also enables continuous production of silicon isotope products; the materials of each separation tower are transported to the separation tower after being heated and pressurized by the cold trap, which reduces energy consumption and improves production efficiency. Attached Figure Description

[0057] Figure 1 This is a schematic diagram of the structure of the apparatus for low-temperature distillation separation of silicon isotopes provided by the present invention;

[0058] Wherein, 1-first cold trap, 2-first reboiler, 3-first condenser, 4-first separation tower, 5-second cold trap, 6-second reboiler, 7-second condenser, 8-second separation tower, 9-third cold trap, 10-third reboiler, 11-third condenser, 12-third separation tower. Detailed Implementation

[0059] It should be understood that in the description of this invention, the terms "center," "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0060] It should be noted that, in the description of this invention, unless otherwise explicitly specified and limited, the terms "set," "connected," and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0061] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0062] This invention provides a device for the low-temperature distillation separation of silicon isotopes, wherein the device (e.g.) Figure 1 (As shown) includes a first separation tower 4, a second separation tower 8, and a third separation tower 12 connected in series.

[0063] The first separation tower 4 is provided with a raw material inlet; a first cold trap 1 is provided on the pipeline connecting the raw material inlet and the first separation tower 4.

[0064] The bottom of the first separation tower 4 is connected to the middle of the second separation tower 8, and a second cold trap 5 is provided on the connecting pipe; the bottom of the second separation tower 8 is connected to the middle of the third separation tower 12, and a third cold trap 9 is provided on the connecting pipe.

[0065] The bottom of the third separation tower 12 is provided with 28 SiF4 product export;

[0066] The top of the third separation tower 12 is connected to the bottom of the second separation tower 8;

[0067] The first separation tower 4 is independently equipped with a first reboiler 2 and a first condenser 3 at its bottom and top, respectively;

[0068] The second separation tower 8 is independently equipped with a second reboiler 6 and a second condenser 7 at its bottom and top, respectively;

[0069] The third separation tower 12 is independently equipped with a third reboiler 10 and a third condenser 11 at its bottom and top, respectively.

[0070] The loads of the first reboiling device 2, the second reboiling device 6, and the third reboiling device 10 are all 6.5 kW;

[0071] The first separation tower 4, the second separation tower 8, and the third separation tower 12 are all packed towers, and liquid distributors are installed inside the packed towers;

[0072] The surfaces of the first separation tower 4, the second separation tower 8, and the third separation tower 12 are all covered with an aluminum polyester film;

[0073] The first separation tower 4, the second separation tower 8 and the third separation tower 12 are all equipped with tower well vacuum jackets, and an outer jacket is also provided outside the tower well vacuum jacket.

[0074] In the following examples and comparative examples, the SiF4 raw materials were purified before being introduced. The composition and flow rate of the purified SiF4 raw materials are shown in Table 1.

[0075] Table 1

[0076] <![CDATA[SiF4]]> 92.23 4.67 3.1 10

[0077] Example 1

[0078] This embodiment provides a method for separating silicon isotopes by low-temperature distillation, using the aforementioned apparatus, wherein the theoretical plate number of the first separation column, the second separation column, and the third separation column is 700.

[0079] The method includes the following steps:

[0080] (1) The SiF4 raw material at a temperature of -75℃ is heated and pressurized in the first cold trap and then transported to the first separation column for the first low-temperature distillation to obtain the bottom of the first column. 28 SiF4 concentrate and first tower top lean feed (output flow rate of 9.9 kg / h) 28 SiF4 abundance was 92.18%;

[0081] The SiF4 raw material is heated and pressurized by the first cold trap to a temperature of -20℃ and a pressure of 0.7MPa.

[0082] The reflux ratio of the first separation column is 17, the pressure at the top of the column is 0.35 MPa, the temperature at the top of the column is -79℃, the temperature at the bottom of the column is -77℃, and the vacuum degree is 0.03 Pa (absolute pressure).

[0083] (2) The first tower bottom of step (1) 28 After being heated and pressurized in the second cold trap, the SiF4 concentrate is conveyed to the third separation column for a second cryogenic distillation, yielding the bottom product of the second column. 28 SiF4 concentrate and second tower top lean feed (output flow rate of 0.09 kg / h) 28 SiF4 abundance was 96.0%;

[0084] Among them, the first tower base 28 The SiF4 concentrate, after being heated and pressurized in the second cold trap, reaches a temperature of -20℃ and a pressure of 0.7MPa.

[0085] The reflux ratio of the second separation column is 2000, the pressure at the top of the column is 0.35 MPa, the temperature at the top of the column is -79℃, the temperature at the bottom of the column is -78℃, and the vacuum degree is 0.03 Pa (absolute pressure).

[0086] (3) The second tower bottom in step (2) 28 After being heated and pressurized in the third cold trap, the SiF4 concentrate is conveyed to the third separation column for third cryogenic distillation to obtain the bottom product of the third column. 28 SiF4 concentrate and third tower top lean feed (outflow rate 0.03 kg / h), 28 SiF4 abundance was 97.9%;

[0087] Among them, the second tower base 28 The SiF4 concentrate, after being heated and pressurized in the second cold trap, reaches a temperature of -20℃ and a pressure of 0.7MPa.

[0088] The reflux ratio of the third separation column is 6000, the pressure at the top of the column is 0.35 MPa, the temperature at the top of the column is -79℃, the temperature at the bottom of the column is -77℃, and the vacuum degree is 0.03 Pa (absolute pressure).

[0089] The lean feed from the top of the third tower is recycled to the second separation tower.

[0090] Example 2

[0091] This embodiment provides a method for separating silicon isotopes by low-temperature distillation, using the aforementioned apparatus, wherein the theoretical plate number of the first separation column, the second separation column, and the third separation column is 1000.

[0092] The method includes the following steps:

[0093] (1) The SiF4 raw material at a temperature of -75℃ is heated and pressurized in the first cold trap and then transported to the first separation column for the first low-temperature distillation to obtain the bottom of the first column. 28 SiF4 concentrate and first tower top lean feed (output flow rate of 9.9 kg / h) 28 SiF4 abundance was 92.18%;

[0094] The SiF4 raw material is heated and pressurized by the first cold trap to a temperature of -20℃ and a pressure of 0.7MPa.

[0095] The reflux ratio of the first separation column is 17, the pressure at the top of the column is 0.55 MPa, the temperature at the top of the column is -71℃, the temperature at the bottom of the column is -69℃, and the vacuum degree is 0.03 Pa (absolute pressure).

[0096] (2) The first tower bottom of step (1) 28 After being heated and pressurized in the second cold trap, the SiF4 concentrate is conveyed to the third separation column for a second cryogenic distillation, yielding the bottom product of the second column. 28 SiF4 concentrate and second tower top lean feed (output flow rate of 0.09 kg / h) 28 SiF4 abundance was 97.3%;

[0097] Among them, the first tower base 28 The SiF4 concentrate, after being heated and pressurized in the second cold trap, reaches a temperature of -20℃ and a pressure of 0.7MPa.

[0098] The reflux ratio of the second separation column is 2000, the pressure at the top of the column is 0.55 MPa, the temperature at the top of the column is -71℃, the temperature at the bottom of the column is -69℃, and the vacuum degree is 0.03 Pa (absolute pressure).

[0099] (3) The second tower bottom in step (2) 28After being heated and pressurized in the third cold trap, the SiF4 concentrate is conveyed to the third separation column for third cryogenic distillation to obtain the bottom product of the third column. 28 SiF4 concentrate and third tower top lean feed (outflow rate 0.03 kg / h), 28 SiF4 abundance was 99.1%;

[0100] Among them, the second tower base 28 The SiF4 concentrate, after being heated and pressurized in the second cold trap, reaches a temperature of -20℃ and a pressure of 0.7MPa.

[0101] The reflux ratio of the third separation column is 6000, the pressure at the top of the column is 0.55 MPa, the temperature at the top of the column is -71℃, the temperature at the bottom of the column is -69℃, and the vacuum degree is 0.03 Pa (absolute pressure).

[0102] The lean feed from the top of the third tower is recycled to the second separation tower.

[0103] Example 3

[0104] This embodiment provides a method for separating silicon isotopes by low-temperature distillation. Except for adjusting the number of theoretical plates in the first separation column to 1000, all other conditions are the same as in Embodiment 1.

[0105] Example 4

[0106] This embodiment provides a method for separating silicon isotopes by low-temperature distillation. Except for adjusting the theoretical plate number of the first, second, and third separation columns to 1000, all other conditions are the same as in Embodiment 1.

[0107] Example 5

[0108] This embodiment provides a method for separating silicon isotopes by low-temperature distillation. Except for adjusting the reflux ratio of the first separation column to 5, all other conditions are the same as in Embodiment 1.

[0109] Example 6

[0110] This embodiment provides a method for separating silicon isotopes by low-temperature distillation. Except for adjusting the reflux ratio of the second separation column to 800, all other conditions are the same as in Embodiment 1.

[0111] Example 7

[0112] This embodiment provides a method for separating silicon isotopes by low-temperature distillation. Except for adjusting the reflux ratio of the third separation column to 4000, all other conditions are the same as in Example 1.

[0113] Comparative Example 1

[0114] This comparative example provides a method for separating silicon isotopes by low-temperature distillation, except that the apparatus used does not include a second and third separation column, and the bottom of the first column is used to separate silicon isotopes. 28 The SiF4 concentrate is returned to the feed inlet of the first separation tower for cryogenic distillation, and the above operation is repeated twice. All other conditions are the same as in Example 1.

[0115] Comparative Example 2

[0116] This comparative example provides a method for separating silicon isotopes by low-temperature distillation. Except that the apparatus used does not have a third separation tower, all other conditions are the same as in Example 1.

[0117] The tower bases at each level in the above embodiments and comparative examples 28 The outflow rate of SiF4 concentrate was statistically analyzed, and mass spectrometry was used to detect the bottom flow rate of each stage of the tower. 28 Abundance values ​​of SiF4 concentrate. The results are shown in Table 2.

[0118] Table 2

[0119]

[0120]

[0121] In Table 2, " / " indicates that there are no corresponding results.

[0122] As shown in Table 2:

[0123] (1) The method and apparatus provided in Embodiments 1-4 of this invention employ a process combining first, second, and third low-temperature distillation, achieving efficient separation of silicon isotopes under specific reflux ratios, temperatures, and pressures, and realizing continuous production of silicon isotope separation; wherein, the extracted 28 The abundance of SiF4 products is >99%.

[0124] (2) A comparison of Examples 1 and 5-7 shows that if the reflux ratio of the first separation tower, the second separation tower, or the third separation tower is too low, the separation efficiency will decrease, leading to the final bottom of the tower. 28 The abundance of SiF4 products does not meet the requirements.

[0125] (3) A comparison of Example 1 and Comparative Example 1 shows that if the second and third separation towers are not set up, and low-temperature distillation is only repeated in the first separation tower, the product will be less effective due to the lack of cascade technology. 28 The abundance of SiF4 products decreased.

[0126] (4) A comparison of Example 1 and Comparative Example 2 shows that if a third separation tower is not installed, there is a problem with the extraction... 28The abundance of SiF4 products is less than 99%, which cannot meet the requirements for subsequent use.

[0127] The applicant declares that the above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A method for separating silicon isotopes by low-temperature distillation, characterized in that, The method includes the following steps: (1) The SiF4 raw material is heated and pressurized in the first cold trap and then transported to the first separation tower for the first low-temperature distillation to obtain the bottom of the first tower. 28 SiF4 concentrate and lean feed from the top of the first tower; The SiF4 raw material, after being heated and pressurized in the first cold trap, has a temperature of -10 to -30°C and a pressure of 0.6 to 0.8 MPa. (2) Take the first tower bottom from step (1) 28 After being heated and pressurized in the second cold trap, the SiF4 concentrate is conveyed to the second separation column for second cryogenic distillation to obtain the bottom product of the second column. 28 SiF4 concentrate and second tower top lean feed; First Tower Base 28 The SiF4 concentrate, after being heated and pressurized in the second cold trap, has a temperature of -10 to -30°C and a pressure of 0.6 to 0.8 MPa. (3) Take the second tower bottom from step (2) 28 After being heated and pressurized in the third cold trap, the SiF4 concentrate is conveyed to the third separation column for third cryogenic distillation to obtain the bottom product of the third column. 28 SiF4 concentrate and third column top lean feed; the third column top lean feed is recycled to the second separation column; Second Tower Base 28 The SiF4 concentrate, after being heated and pressurized in the third cold trap, has a temperature of -10 to -30°C and a pressure of 0.6 to 0.8 MPa. The top pressure of the first separation tower, the second separation tower, and the third separation tower are all 0.35~0.65MPa, the top temperature of the tower is -65~-80℃, and the bottom temperature of the tower is -65~-80℃. The reflux ratio of the first separation tower is 10-100; the reflux ratio of the second separation tower is 1800-2200; and the reflux ratio of the third separation tower is 5000-7000.

2. The method according to claim 1, characterized in that, In step (1), the SiF4 raw material 28 The abundance of SiF4 is ≥90%.

3. The method according to claim 1, characterized in that, The vacuum levels of the first separation tower, the second separation tower, and the third separation tower are all 0.0001~10 Pa.

4. The method according to claim 1, characterized in that, Step (1) First tower bottom 28 The abundance of SiF4 concentrate is >96%.

5. The method according to claim 1, characterized in that, Step (2) The second tower bottom 28 The abundance of SiF4 concentrate is >98%.

6. The method according to claim 1, characterized in that, The third tower base mentioned in step (3) 28 The abundance of SiF4 concentrate is >99%.

7. The method according to claim 1, characterized in that, The first, second, and third separation towers are all equipped with condensation devices at the top and reboiling devices at the bottom. The first separation tower is provided with a raw material inlet; a first cold trap is provided on the pipeline connecting the raw material inlet and the first separation tower. The bottom of the first separation tower is connected to the middle of the second separation tower, and a second cold trap is installed on the connecting pipeline; The bottom of the second separation tower is connected to the middle of the third separation tower, and a third cold trap is installed on the connecting pipeline; The bottom of the third separation tower is equipped with 28 SiF4 product export; The top of the third separation tower is connected to the bottom of the second separation tower.

8. The method according to claim 7, characterized in that, The first separation tower, the second separation tower and the third separation tower are all packed towers, and liquid distributors are installed inside the packed towers.

9. The method according to claim 7, characterized in that, The theoretical plate number of the first, second, and third separation towers is 600-1200.

10. The method according to claim 7, characterized in that, The surfaces of the first, second, and third separation towers are all covered with an aluminum polyester film.

11. The method according to claim 7, characterized in that, The first separation tower, the second separation tower and the third separation tower are all equipped with tower well vacuum jackets, and an outer jacket is also provided outside the tower well vacuum jacket.

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