Method and device for separating silicon isotopes through low-temperature rectification
Through three-stage low-temperature distillation and cold trap heating and pressurization treatment, the separation efficiency of silicon isotopes is improved, solving the problems of low separation efficiency and high cost in existing technologies, and realizing efficient and continuous production of high-abundance 28SiF4.
Patent Information
- Application Number
- CN202511042514.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-07-28
- Publication Date
- 2025-09-05
AI Technical Summary
The existing method of separating silicon isotopes by cryogenic distillation has problems such as low separation efficiency, complex process and high cost, and has not yet achieved a breakthrough in industrial production.
A three-stage cryogenic distillation method is used to perform three-stage cryogenic distillation on naturally abundant SiF4 raw materials. Through the process of combining the first cryogenic distillation, the second cryogenic distillation and the third cryogenic distillation, the separation purity of silicon isotopes is gradually improved. Combined with the cold trap temperature and pressurization treatment, the theoretical plate number and energy consumption of the distillation tower are reduced.
It has achieved efficient production of high-abundance 28SiF4 products, reduced engineering investment and operating costs, met the needs of large-scale production, and realized continuous production of silicon isotope separation.
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Figure CN120586648A_ABST
Abstract
Description
Technical Field
[0001] The present invention belongs to the technical field of isotope separation, and relates to a method and device for separating silicon isotopes by cryogenic distillation. Background Art
[0002] Silicon is an important semiconductor material, widely used in electronics, semiconductors, photovoltaics, communications and other fields. Natural silicon mainly exists in four stable isotopes, namely 28 4. 29 4. 30 Si and 32 Si. Among them 28 Si is the most common isotope, accounting for about 92.23%. However, recent studies have found that using high abundance 28 Semiconductor devices made of Si (e.g., 99.85% or more) have significant performance advantages. For example, at room temperature, its thermal conductivity can increase by 10% to 60% compared to natural silicon, and even more at certain temperatures; the reverse breakdown voltage of the diode made of Si can be increased by more than 80% compared to natural silicon diodes made with the same process. In addition, the use of Si with an abundance of more than 99% 28 Si can be used to prepare silicon crystals, which can reduce phonon scattering, improve thermal conductivity, reduce gate voltage, increase switching speed, and increase chip frequency. It can be used to manufacture high-speed CPUs, high-power devices, high-performance sensors, etc. In the field of quantum information, high abundance 28 Si can be used to prepare devices with long spin coherence time, removing 29 Interference of Si.
[0003] However, despite the high abundance 28 Si has great potential in improving the performance of semiconductor devices, but its industrial production still faces many challenges. There are many methods for enriching silicon isotopes at home and abroad, including cryogenic distillation (SiH4, SiCl4, SiF4 or SiH3CH3 system), gas centrifugation (medium is SiF4 or SiHCl3), chemical exchange method (SiF4 and different complexing agent separation system), laser method (Si2F6, SiF4), electromagnetic method (SiH4), etc. Among them, cryogenic distillation method uses the slight difference in saturated vapor pressure between isotope atoms or molecules to achieve the separation between isotope components. For example, in the silicon tetrafluoride system, 28 The volatility of Si is relatively 29 Si is 0.9990, relative to 30 Si is 0.9982, so SiF4 is considered a practical method for silicon isotope enrichment as a separation medium. However, existing methods for separating silicon isotopes using cryogenic distillation suffer from low separation efficiency, complex processes, and high costs, and have yet to achieve a breakthrough in industrial production.
[0004] In summary, a method with high separation efficiency and simple operation is developed. 28 Si isotope separation methods and devices have become a technical problem that needs to be solved urgently in this field. Summary of the Invention
[0005] In view of the shortcomings of the prior art, the present invention aims to provide a method and apparatus for separating silicon isotopes by cryogenic distillation. By performing three-stage cryogenic distillation on naturally abundant SiF4 raw materials, the separation efficiency of silicon isotopes is improved, thereby achieving high abundance. 28 Efficient production of SiF4 products.
[0006] In order to achieve the purpose of the invention, the present invention adopts the following technical solutions:
[0007] In a first aspect, the present invention provides a method for separating silicon isotopes by cryogenic distillation, the method comprising the following steps:
[0008] (1) The SiF4 raw material is transported to the first separation tower and subjected to the first low-temperature distillation to obtain the first tower bottom 28 SiF4 concentrate and lean material from the top of the first tower;
[0009] (2) The first bottom of step (1) 28 SiF4 concentrate is transported to the second separation tower for the second low-temperature distillation to obtain the second bottom 28 SiF4 concentrate and second tower top lean material;
[0010] (3) The second bottom of step (2) 28 SiF4 concentrate is transported to the third separation tower for the third low-temperature distillation to obtain the third tower bottom 28 SiF4 fine material and lean material from the top of the third tower;
[0011] The lean material at the top of the third tower is recycled to the second separation tower.
[0012] The method provided by the present invention improves the separation efficiency of silicon isotopes by performing three-stage low-temperature distillation on naturally abundant SiF4 raw materials, thereby achieving high abundance 28 The efficient production of SiF4 products solves the problems of high production costs, complex material circulation and high impurities in existing chemical exchange, gas centrifuge and laser methods.
[0013] It should be noted that by performing low temperature distillation on SiF4 raw materials, 28SiF4 concentrate is concentrated at the bottom of the tower. By combining the first, second and third cryogenic distillation stages, silicon isotopes are separated at each stage, gradually improving the separation purity of silicon isotopes. This reduces the number of theoretical plates in the distillation tower, lowers engineering investment and operating costs, and significantly reduces energy consumption. Continuous silicon isotope separation can be achieved to meet the needs of large-scale production.
[0014] As a preferred technical solution of the present invention, the SiF4 raw material in step (1) 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 the present invention, the SiF4 raw material is a raw material that has been purified.
[0016] Preferably, before being transported to the first separation tower, step (1) further includes: heating and pressurizing the SiF4 raw material in a first cold trap and then transporting it to the first separation tower.
[0017] Preferably, the temperature of the SiF4 raw material after heating and pressurizing in 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, and the pressure is 0.6 to 0.8MPa, for example, it can be 0.62MPa, 0.65MPa, 0.66MPa, 0.68MPa, 0.7MPa, 0.72MPa, 0.75MPa, 0.76MPa or 0.78MPa, etc.
[0018] It should be noted that after the material is heated and pressurized in the 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 be carried out, which can improve the separation effect and efficiency of silicon isotopes and reduce energy consumption in the distillation process.
[0019] As a preferred technical solution of the present invention, before the step (2) is transported to the second separation tower, the step further includes: 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 bottom 28The temperature of the SiF4 concentrate after heating and pressurizing in the second 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, 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.
[0021] As a preferred technical solution of the present invention, before the step (3) is transported to the third separation tower, the step further includes: 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 bottom 28 The temperature of the SiF4 concentrate after being heated and pressurized in the third 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, 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.
[0023] As a preferred technical solution of the present invention, the top pressures of the first separation tower, the second separation tower and the third separation tower are all 0.35-0.65 MPa, for example, 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 -65 to -80°C, for example, -66°C, -68°C, -70°C, -72°C, -75°C, -76°C or -78°C.
[0025] Preferably, the bottom temperatures of the first separation tower, the second separation tower and the third separation tower are all -65 to -80°C, for example, -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 separation tower, the second separation tower and the third separation tower within a specific range, efficient distillation separation of silicon isotopes is achieved under low temperature conditions, and the efficiency is improved. 28Abundance of SiF4.
[0027] Preferably, the vacuum degrees of the first separation tower, the second separation tower and the third separation tower are all 0.0001 to 10 Pa, for example, 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.
[0031] It should be noted that by controlling the reflux ratio of the first separation tower, the second separation tower and the third separation tower within a specific range, 28 SiF4 is enriched at the bottom of the tower, ensuring a higher purity of the bottom product. It can also reduce the amount of heating steam and cooling source, thereby reducing energy consumption. If the reflux ratio is too large, the energy consumption will increase, resulting in increased production costs; if the reflux ratio is too small, the separation efficiency will decrease, resulting in the bottom of the tower being 28 The SiF4 abundance does not meet the requirements.
[0032] As a preferred technical solution of the present invention, step (1) the first bottom 28 The abundance of SiF4 concentrate is greater than 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 bottom 28 The abundance of SiF4 concentrate is greater than 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 bottom of step (3) 28The abundance of SiF4 concentrate is greater than 99%, for example, it can be 99.1%, 99.2%, 99.3%, 99.4%, 99.5%, 99.6%, 99.7% or 99.8%.
[0035] In a second aspect, the present invention provides an apparatus for separating silicon isotopes by cryogenic distillation, applying the method for separating silicon isotopes by cryogenic distillation as described in the first aspect, wherein the apparatus comprises a first separation tower, a second separation tower, and a third separation tower connected in series.
[0036] The tops of the first separation tower, the second separation tower and the third separation tower are all provided with condensing devices, and the bottoms of the towers are all provided with reboilers;
[0037] The first separation tower is provided with a raw material inlet;
[0038] The bottom of the third separation tower is provided with 28 Export of SiF4 products;
[0039] The top of the third separation tower is connected to the bottom of the second separation tower.
[0040] In the present invention, the condensing device condenses the rising steam entering the top of the tower, and part of the condensate flows into the tower as reflux liquid, and part is produced as the top product; the reboiling device heats the bottom liquid to boiling, providing a certain flow of rising steam, and at the same time, part of the bottom liquid is produced as the bottom product.
[0041] 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 can continuously produce silicon isotope products. The device has a simple process, convenient operation, low cost, high safety, and can meet the needs of high abundance 28 Requirements for SiF4 preparation process.
[0042] As a preferred technical solution 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 technical solution of the present invention, the first separation tower, the second separation tower and the third separation tower are all packed towers, and liquid distributors are provided in the packed towers.
[0046] In the present invention, liquid distributors may be installed at certain heights in 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 numbers of the first separation tower, the second separation tower and the third separation tower are all 600 to 1200, for example, 650, 700, 750, 800, 850, 900, 950, 1000, 1050, 1100 or 1150.
[0048] In the present invention, the three-stage separation tower is used in combination to separate silicon isotopes, which can reduce the number of theoretical plates of the separation tower, thereby reducing costs and energy consumption.
[0049] Preferably, the tower bodies of the first separation tower, the second separation tower and the third separation tower are all covered with aluminum polyester film.
[0050] In the present invention, the surface of the tower body is coated with an aluminum polyester film to reduce the loss of radiant heat.
[0051] Preferably, the first separation tower, the second separation tower and the third separation tower are all provided with a tower well vacuum jacket, and an outer jacket is further provided outside the tower well vacuum jacket.
[0052] In the present invention, a tower well vacuum jacket is provided and vacuum is drawn by the well vacuum jacket to reduce conductive heat loss; an outer jacket is provided on its outer surface to protect the separation tower and avoid corrosion from water and air.
[0053] The numerical range described in the present invention includes not only the point values listed above, but also any point values between the above numerical ranges that are not listed. Due to space limitations and for the sake of simplicity, the present invention no longer exhaustively lists 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 is to perform low temperature distillation on SiF4 raw materials. 28 The SiF4 concentrate is concentrated at the bottom of the tower. The process of combining the first cryogenic distillation, the second cryogenic distillation and the third cryogenic distillation improves the separation efficiency of silicon isotopes, thereby achieving high abundance. 28 Efficient production of SiF4 products; the last stage separation tower can produce SiF4 with an abundance of >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 can continuously produce silicon isotope products; the materials of each separation tower are heated and pressurized by a cold trap and then transported to the separation tower, which reduces energy consumption and improves production efficiency. BRIEF DESCRIPTION OF THE DRAWINGS
[0057] Figure 1 Schematic diagram of the structure of the device for separating silicon isotopes by cryogenic distillation provided by the present invention;
[0058] Among them, 1-first cold trap, 2-first reboiling device, 3-first condensing device, 4-first separation tower, 5-second cold trap, 6-second reboiling device, 7-second condensing device, 8-second separation tower, 9-third cold trap, 10-third reboiling device, 11-third condensing device, 12-third separation tower. DETAILED DESCRIPTION
[0059] It should be understood that, in the description of the present invention, the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating the orientation or position relationship, are based on the orientation or position relationship shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention.
[0060] It should be noted that, in the description of the present invention, unless otherwise expressly specified or limited, the terms "disposed," "connected," and "connected" should be understood in a broad sense. For example, they may refer to fixed connections, detachable connections, or integral connections; mechanical connections or electrical connections; direct connections or indirect connections through an intermediate medium; and internal connections between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on specific circumstances.
[0061] The technical solution of the present invention is further described below by way of specific embodiments. It should be understood by those skilled in the art that the embodiments are merely to help understand the present invention and should not be regarded as specific limitations of the present invention.
[0062] A specific embodiment of the present invention provides a device for separating silicon isotopes by cryogenic distillation, wherein the device (such as Figure 1 ) comprises 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 pipeline; 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 pipeline;
[0065] The bottom of the third separation tower 12 is provided with 28 Export of SiF4 products;
[0066] The top of the third separation tower 12 is connected to the bottom of the second separation tower 8;
[0067] The bottom and top of the first separation tower 4 are independently provided with a first reboiler 2 and a first condenser 3;
[0068] The bottom and top of the second separation tower 8 are independently provided with a second reboiler 6 and a second condenser 7;
[0069] The bottom and top of the third separation tower 12 are independently provided with a third reboiler 10 and a third condenser 11;
[0070] The loads of the first reboiler 2, the second reboiler 6 and the third reboiler 10 are all 6.5kW;
[0071] The first separation tower 4, the second separation tower 8 and the third separation tower 12 are all packed towers, and a liquid distributor is provided in the packed tower;
[0072] The surfaces of the first separation tower 4, the second separation tower 8 and the third separation tower 12 are all covered with aluminum polyester film;
[0073] The first separation tower 4, the second separation tower 8 and the third separation tower 12 are all provided with a tower well vacuum jacket, and an outer jacket is further provided outside the tower well vacuum jacket.
[0074] In the following examples and comparative examples, the SiF4 raw material was purified before being introduced. The composition and flow rate of the purified SiF4 raw material are shown in Table 1.
[0075] Table 1
[0076] raw material <![CDATA[ 28 SiF4(%)]]> <![CDATA[ 29 SiF4(%)]]> <![CDATA[ 30 SiF4(%)]]> Inlet flow rate (kg / h) <![CDATA[SiF4]]> 92.23 4.67 3.1 10
[0077] Example 1
[0078] This embodiment provides a method for separating silicon isotopes by cryogenic distillation, which is performed using the aforementioned apparatus, wherein the number of theoretical plates of the first separation tower, the second separation tower, and the third separation tower are all 700;
[0079] The method comprises the following steps:
[0080] (1) The SiF4 raw material at a temperature of -75°C 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 first tower bottom 28 SiF4 concentrate and lean material from the first tower top (with an extraction flow rate of 9.9 kg / h, 28 SiF4 abundance is 92.18%);
[0081] The temperature of the SiF4 raw material after being heated and pressurized in the first cold trap is -20°C and the pressure is 0.7 MPa;
[0082] The reflux ratio of the first separation tower was 17, the tower top pressure was 0.35 MPa, the tower top temperature was -79°C, the tower bottom temperature was -77°C, and the vacuum degree was 0.03 Pa (absolute pressure);
[0083] (2) The first bottom of step (1) 28 The SiF4 concentrate is heated and pressurized in the second cold trap and then transported to the third separation tower for the second low-temperature distillation to obtain the second tower bottom 28 SiF4 concentrate and second tower top lean material (with an extraction flow rate of 0.09 kg / h, 28 SiF4 abundance is 96.0%);
[0084] Among them, the bottom of the first tower 28 The temperature of SiF4 concentrate after being heated and pressurized in the second cold trap is -20℃ and the pressure is 0.7MPa;
[0085] The reflux ratio of the second separation tower was 2000, the tower top pressure was 0.35 MPa, the tower top temperature was -79°C, the tower bottom temperature was -78°C, and the vacuum degree was 0.03 Pa (absolute pressure);
[0086] (3) The second bottom of step (2) 28 The SiF4 concentrate is heated and pressurized in the third cold trap and then transported to the third separation tower for the third low-temperature distillation to obtain the third tower bottom 28 SiF4 concentrate and lean material from the top of the third tower (with an extraction flow rate of 0.03 kg / h, 28 SiF4 abundance is 97.9%);
[0087] Among them, the second tower bottom 28 The temperature of SiF4 concentrate after being heated and pressurized in the second cold trap is -20℃ and the pressure is 0.7MPa;
[0088] The reflux ratio of the third separation tower is 6000, the tower top pressure is 0.35 MPa, the tower top temperature is -79°C, the tower bottom temperature is -77°C, and the vacuum degree is 0.03 Pa (absolute pressure);
[0089] The lean material at 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 cryogenic distillation, which is performed using the aforementioned apparatus, wherein the number of theoretical plates of the first separation tower, the second separation tower, and the third separation tower are all 1000;
[0092] The method comprises the following steps:
[0093] (1) The SiF4 raw material at a temperature of -75°C 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 first tower bottom 28 SiF4 concentrate and lean material from the first tower top (with an extraction flow rate of 9.9 kg / h, 28 SiF4 abundance is 92.18%);
[0094] The temperature of the SiF4 raw material after being heated and pressurized in the first cold trap is -20°C and the pressure is 0.7 MPa;
[0095] The reflux ratio of the first separation tower was 17, the tower top pressure was 0.55 MPa, the tower top temperature was -71°C, the tower bottom temperature was -69°C, and the vacuum degree was 0.03 Pa (absolute pressure);
[0096] (2) The first bottom of step (1) 28 The SiF4 concentrate is heated and pressurized in the second cold trap and then transported to the third separation tower for the second low-temperature distillation to obtain the second tower bottom 28 SiF4 concentrate and second tower top lean material (with an extraction flow rate of 0.09 kg / h, 28 SiF4 abundance is 97.3%);
[0097] Among them, the bottom of the first tower 28 The temperature of SiF4 concentrate after being heated and pressurized in the second cold trap is -20℃ and the pressure is 0.7MPa;
[0098] The reflux ratio of the second separation tower was 2000, the tower top pressure was 0.55 MPa, the tower top temperature was -71°C, the tower bottom temperature was -69°C, and the vacuum degree was 0.03 Pa (absolute pressure);
[0099] (3) The second bottom of step (2) 28The SiF4 concentrate is heated and pressurized in the third cold trap and then transported to the third separation tower for the third low-temperature distillation to obtain the third tower bottom 28 SiF4 concentrate and lean material from the top of the third tower (with an extraction flow rate of 0.03 kg / h, 28 SiF4 abundance is 99.1%);
[0100] Among them, the second tower bottom 28 The temperature of SiF4 concentrate after being heated and pressurized in the second cold trap is -20℃ and the pressure is 0.7MPa;
[0101] The reflux ratio of the third separation tower is 6000, the tower top pressure is 0.55 MPa, the tower top temperature is -71°C, the tower bottom temperature is -69°C, and the vacuum degree is 0.03 Pa (absolute pressure);
[0102] The lean material at 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 cryogenic distillation. Except for adjusting the number of theoretical plates of the first separation tower to 1000, other conditions are the same as those in Example 1.
[0105] Example 4
[0106] This embodiment provides a method for separating silicon isotopes by cryogenic distillation. Except for adjusting the theoretical plate numbers of the first separation tower, the second separation tower, and the third separation tower to 1000, other conditions are the same as those in Example 1.
[0107] Example 5
[0108] This embodiment provides a method for separating silicon isotopes by cryogenic distillation. Except for adjusting the reflux ratio of the first separation tower to 5, other conditions are the same as those in Example 1.
[0109] Example 6
[0110] This embodiment provides a method for separating silicon isotopes by cryogenic distillation. Except for adjusting the reflux ratio of the second separation tower to 800, other conditions are the same as those in Example 1.
[0111] Example 7
[0112] This embodiment provides a method for separating silicon isotopes by cryogenic distillation. Except for adjusting the reflux ratio of the third separation tower to 4000, other conditions are the same as those in Example 1.
[0113] Comparative Example 1
[0114] This comparative example provides a method for separating silicon isotopes by cryogenic distillation, except that the device used is not provided with a second separation tower and a third separation tower, and the bottom of the first tower is used to separate silicon isotopes. 28 The SiF4 concentrate was returned to the raw material inlet of the first separation tower for cryogenic distillation again, and the above operation was repeated twice. Other conditions were the same as those in Example 1.
[0115] Comparative Example 2
[0116] This comparative example provides a method for separating silicon isotopes by cryogenic distillation. Except that the device used is not provided with a third separation tower, other conditions are the same as those in Example 1.
[0117] The bottom of each stage in the above embodiments and comparative examples 28 The extraction flow of SiF4 concentrate is counted and the mass spectrometry is used to detect the flow at the bottom of each tower. 28 The abundance values of SiF4 concentrate are shown in Table 2.
[0118] Table 2
[0119]
[0120]
[0121] In Table 2, “ / ” indicates that there is no corresponding result.
[0122] From Table 2 we can see that:
[0123] (1) The method and apparatus provided in Examples 1-4 of the present invention adopt a process combining the first cryogenic distillation, the second cryogenic distillation and the third cryogenic distillation to achieve efficient separation of silicon isotopes under specific reflux ratio, temperature and pressure conditions, and realize continuous production of silicon isotope separation; wherein, the extracted 28 The abundance of SiF4 product is >99%.
[0124] (2) It can be seen from the comparison between Example 1 and Examples 5-7 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, resulting in the final tower bottom 28 The abundance of SiF4 products does not meet the requirements.
[0125] (3) From the comparison between Example 1 and Comparative Example 1, it can be seen that if the second separation tower and the third separation tower are not set, and low-temperature distillation is repeated only in the first separation tower, the cascade technology is not implemented, resulting in the production of 28 The abundance of SiF4 products decreases.
[0126] (4) From the comparison between Example 1 and Comparative Example 2, it can be seen that if the third separation tower is not set, there is a 28The abundance of SiF4 products is less than 99%, which cannot meet the requirements of subsequent use.
[0127] The applicant declares that the above is only a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention fall within the scope of protection and disclosure of the present invention.
Claims
1. A method for separating silicon isotopes by cryogenic distillation, characterized in that: The method comprises the following steps: (1) The SiF4 raw material is transported to the first separation tower and subjected to the first low-temperature distillation to obtain the first tower bottom 28 SiF4 concentrate and lean material from the top of the first tower; (2) The first bottom of step (1) 28 SiF4 concentrate is transported to the second separation tower for the second low-temperature distillation to obtain the second bottom 28 SiF4 concentrate and second tower top lean material; (3) The second bottom of step (2) 28 SiF4 concentrate is transported to the third separation tower for the third low-temperature distillation to obtain the third tower bottom 28 SiF4 fine material and lean material from the top of the third tower; The lean material at the top of the third tower is recycled to the second separation tower.
2. The method according to claim 1, characterized in that In the SiF4 raw material of step (1) 28 The abundance of SiF4 is ≥90%; Preferably, before the step (1) is transported to the first separation tower, the step further includes: heating and pressurizing the SiF4 raw material in the first cold trap and then transporting it to the first separation tower; Preferably, the temperature of the SiF4 raw material after being heated and pressurized in the first cold trap is -10 to -30°C and the pressure is 0.6 to 0.8 MPa.
3. The method according to claim 1 or 2, characterized in that Before the step (2) is transported to the second separation tower, the step further includes: 28 The SiF4 concentrate is heated and pressurized in the second cold trap and then transported to the second separation tower; Preferably, the first bottom 28 The temperature of the SiF4 concentrate after being heated and pressurized in the second cold trap is -10 to -30°C and the pressure is 0.6 to 0.8 MPa.
4. The method according to any one of claims 1 to 3, characterized in that Before the step (3) is transported to the third separation tower, the step further includes: 28 The SiF4 concentrate is heated and pressurized in the third cold trap and then transported to the third separation tower; Preferably, the second bottom 28 The temperature of the SiF4 concentrate after being heated and pressurized by the third cold trap is -10 to -30°C and the pressure is 0.6 to 0.8 MPa.
5. The method according to any one of claims 1 to 4, characterized in that The top pressures of the first separation tower, the second separation tower, and the third separation tower are all 0.35-0.65 MPa; Preferably, the top temperatures of the first separation tower, the second separation tower and the third separation tower are all -65 to -80°C; Preferably, the bottom temperatures of the first separation tower, the second separation tower and the third separation tower are all -65 to -80°C; Preferably, the vacuum degrees of the first separation tower, the second separation tower and the third separation tower are all 0.0001-10 Pa.
6. The method according to any one of claims 1 to 5, characterized in that The reflux ratio of the first separation tower in step (1) is 10-100; Preferably, the reflux ratio of the second separation tower in step (2) is 1800-2200; Preferably, the reflux ratio of the third separation tower in step (3) is 5000-7000.
7. The method according to any one of claims 1 to 6, characterized in that Step (1) the first tower bottom 28 The abundance of SiF4 concentrate is >96%; Preferably, in step (2), the second bottom 28 The abundance of SiF4 concentrate is >98%; Preferably, the third bottom of step (3) 28 The abundance of SiF4 concentrate is >99%.
8. A device for separating silicon isotopes by cryogenic distillation, characterized in that: A method for separating silicon isotopes by cryogenic distillation according to any one of claims 1 to 7, wherein the device comprises a first separation tower, a second separation tower, and a third separation tower connected in series; The tops of the first separation tower, the second separation tower and the third separation tower are all provided with condensing devices, and the bottoms of the towers are all provided with reboilers; The first separation tower is provided with a raw material inlet; The bottom of the third separation tower is provided with 28 Export of SiF4 products; The top of the third separation tower is connected to the bottom of the second separation tower.
9. The device according to claim 8, characterized in that A first cold trap is provided on the pipeline connecting the raw material inlet and the first separation tower; 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; 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.
10. The device according to claim 8 or 9, characterized in that The first separation tower, the second separation tower and the third separation tower are all packed towers, and a liquid distributor is provided in the packed tower; Preferably, the theoretical plate numbers of the first separation tower, the second separation tower and the third separation tower are all 600 to 1200; Preferably, the tower bodies of the first separation tower, the second separation tower and the third separation tower are all covered with aluminum polyester film; Preferably, the first separation tower, the second separation tower and the third separation tower are all provided with a tower well vacuum jacket, and an outer jacket is further provided outside the tower well vacuum jacket.