Boron trifluoride / methyl isobutyl ketone exchange constant cycle boron stable isotope separation method

Abstract

The separation of the boron isotopes by adopting the boron trifluoride / methyl isobutyl ketone exchange system is realized by countercurrent gas-liquid cascade contact in a packed tower and chemical exchange between the two-phase boron isotopes: boron trifluoride 10 is enriched in a liquid phase, and boron trifluoride 11 is enriched in a gas phase. In addition to the exchange column, two auxiliary systems are also required, the first is a reboiling stripping column which separates the composites by heating and simultaneously provides two substances: boron trifluoride gas is refluxed to the product end of the exchange column for cascade connection; and 2, recovery of methyl isobutyl ketone. And after distillation, the methyl isobutyl ketone without the boron trifluoride gas is recycled to a complexing cooling tower of a second auxiliary system and reacts with the tail part of the boron trifluoride to form a liquid complex, and then the liquid complex flows back to the tail end of the cascaded boron trifluoride 11. And the other two complexing towers are recombined and need to be cooled to remove reaction heat and control the temperature which is approximately the temperature used by the exchange tower.

Description

Technical Field

[0001] Stable isotopes belong to the high-tech industry of new materials in advanced manufacturing of nuclear technology. Isotope-grade pure new materials have their unique properties. With the rapid development of science and technology in recent years, a variety of isotope-pure new material products have been widely used, especially in the emerging field of nuclear medicine science, making great contributions and having important significance for the national economy and people's livelihood.

[0002] "Stable Isotope Production and Application Technology" is a project encouraged by the national development plan. The state clearly pointed out in relevant documents that "isotope medicine" is a high-tech industry with priority development. A variety of stable isotopes directly serve nuclear medicine and have occupied a certain share in my country's medical and health industry market, and are showing a rapid upward trend. The overall trend of the industry is high investment and high returns. As early as 2005, my country's medical and health industry market has become the world's third largest medical and health industry market after the United States and Japan. Background Art

[0003] Boron-10 is the best material for absorbing neutrons, shielding neutrons and gamma rays, and protecting people from radiation damage. Therefore, it is widely used in the nuclear industry, military engineering and other special industries. In the world today, only the United States and Russia have industrial-scale production, and the United States almost monopolizes the production of boron-10, with an annual output of about 10 tons. It is basically prohibited to sell it to my country for military reasons. Even if a small amount is imported, the price is very expensive.

[0004] Boron-11 is the opposite of boron-10. It hardly absorbs neutrons. In the process of manufacturing semiconductor devices, it is used as an isotope purity dopant. Since there is no background charge collection Qcoll caused by boron-10, the background soft error of the chip is eliminated, which can greatly improve the conductivity and radiation resistance and anti-interference ability of semiconductor devices. Therefore, boron-11 is an important supporting material for the development of the next generation of ultra-large-scale integrated circuit processes and aerospace, nuclear energy materials, and optical fiber technology. High-purity boron with a purity of 99.9999% is a necessary material for the upgrading technology of heavily doped boron silicon single crystals. The purity and abundance of boron-11 directly affect the properties of silicon semiconductor materials, and then affect the performance of semiconductor devices and the whole machine. Therefore, boron-11 is the best material for radiation-resistant aerospace semiconductor chips. Research and development of high-abundance boron-11 isotope doping sources is an inevitable trend in the development of boron-based semiconductor materials in the future.

[0005] At present, industrialized production is still not possible in China. Domestic universities and research institutions, such as Shanghai Institute of Chemical Technology, School of Chemical Engineering of Tianjin University, and Dalian Institute of Chemical Technology have been working hard on research for many years. Several companies are using the technologies of the above-mentioned institutions for further development, but there are only a small number of trial products. Currently, China can only use natural boron as a substitute, and the effect cannot reach 20%.

[0006] With the advent of the era of fourth-generation nuclear power plant fast neutron reactors and the need to build new nuclear submarines and nuclear aircraft carriers, natural boron is simply unable to meet the requirements. Therefore, there is an urgent need to independently develop large-scale industrial production of boron-10.

[0007] Boron-10 and boron-11 isotope products have important uses in the application fields of nuclear materials and semiconductor materials. Boron-10 and boron-11 isotope products have great strategic significance for the development of related fields in my country. Localization can effectively fill the technological gap in the fields of nuclear materials and semiconductor isotopes in my country, and completely end the history of relying entirely on imports for this series of products.

[0008] The development of boron trifluoride boron isotope separation technology began in the 1930s with the development of Manhattan nuclear industry technology. The mature mass production technology was first successfully developed by the United States and Russia. The general development process is as follows:

[0009] 1) The first generation technology uses ether as an intermediate complex.

[0010] 2) The second generation technology uses methyl ether as an intermediate complex.

[0011] 3) The third generation technology uses anisole as an intermediate complex and has been successfully mass-produced in the United States. Summary of the invention

[0012] A method for separating stable boron isotopes by constant cycle of boron trifluoride / methyl isobutyl ketone exchange: bottled boron trifluoride gas is used as a raw material and methyl isobutyl ketone liquid is used as an intermediate, and the two are subjected to gas / liquid countercurrent exchange, thereby separating two stable isotopes of boron trifluoride-10 and boron trifluoride-11 and obtaining both at the same time.

[0013] This method complies with the national industrial policy, and the product complies with the product catalog of the "Industrial Structure Adjustment Guidance Catalog (2005 Edition)". The project technology is advanced, the technology is forward-looking, the process technology is reliable, the economic benefits are significant, and it is environmentally friendly. The market demand for the product is steadily increasing in nuclear power, electronics industry, medical and civilian products, and it has excellent economic and social benefits. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 It is a process flow chart of the present invention. Figure 2Actual photos of the laboratory using this method.

[0014] 1. The molar ratio of boron trifluoride / methyl isobutyl ketone is 1.1:1. Boron trifluoride is first subjected to ultra-low temperature refining for desulfurization and impurity removal, and then enters the exchange tower for gas / liquid exchange with methyl isobutyl ketone. Methyl isobutyl ketone is dehydrated by molecular sieve, then subjected to low temperature refining, dehydration and impurity removal, and then enters the cooling tower for gas / liquid exchange. Required equipment: ① exchange tower, ② complexing tower, ③ cooling extraction tower, ④ low temperature stripping tower, ⑤ low temperature reboiling tower, ⑥ high temperature stripping tower, ⑦ high temperature reboiling tower, ⑧ boron trifluoride refining tank, ⑨ methyl isobutyl ketone refining tank, ⑩ molecular sieve trace water removal device.

[0015] 2. The whole system is purged with high-purity nitrogen, and each equipment is tested and qualified by a dew point meter. The methyl isobutyl ketone solution is dehydrated to ≮50ppm by a molecular sieve to remove trace water device and a methyl isobutyl ketone refining tank, and enters the system from the top of the cooling extraction tower to establish a liquid circulation. Samples are taken at the bottom of each tower for analysis, and the water content is ≮50ppm to meet the standard. If it does not meet the standard, the circulating liquid is drawn and then enters the molecular sieve to remove trace water device and methyl isobutyl ketone refining tank for dehydration until it meets the standard.

[0016] 3. After the boron trifluoride is refined, it enters from the bottom of the exchange tower and countercurrently exchanges with the methyl isobutyl ketone solvent from the top of the tower, so that the boron trifluoride-10 is gathered in the liquid state. The liquid enriched with boron 10 first enters the low-temperature stripping tower-low-temperature reboiling tower, the temperature is controlled at 65-75°C, and about 20% of the gas is separated, and then enters the high-temperature stripping tower-high-temperature reboiling tower, the temperature is controlled at 115.8°C, and the gas / liquid is completely separated. The gas separated by the high-temperature stripping tower enters the bottom of the low-temperature stripping tower. A cooler is set at the top section of the low-temperature stripping tower, and the qualified boron trifluoride-10 will be diverted here to the stable recovery device.

[0017] 4. The methyl isobutyl ketone solvent output from the bottom of the high-temperature reboiling tower enters the molecular sieve dehydration device after cooling, and after being refined, enters the top of the cooling extraction tower and intersects with the boron trifluoride-11 from bottom to top. The boron trifluoride-11 gas is led to the stable recovery device here.

[0018] 5. The liquid output at the bottom of the extraction tower enters the complexation tower and undergoes complexation reaction with the boron trifluoride gas output from the exchange tower to completely separate the two isotopes, so that boron trifluoride-10 is completely enriched in the liquid state, and boron trifluoride-11 is enriched in the gas state.

[0019] 6. This method uses a boron trifluoride / methyl isobutyl ketone exchange system, and the water content of the system cannot be ≯50ppm. The system pressure is controlled at 100kpa~0.3mpa. The operating temperature is controlled at 20~30℃. The maximum reboiling decomposition temperature is ≯115.8℃. At room temperature and pressure, except for the reboiling and stripping parts, the entire separation device is completely operated in a low-temperature state, in a closed-loop cycle, and a mature combined tower separation process is adopted to obtain boron trifluoride-10 and boron trifluoride-11 stable isotopes at the same time. DETAILED DESCRIPTION

[0020] The pilot plant for the separation of stable isotopes of boron trifluoride (100 kg / year) was designed in January 2021, the equipment was manufactured in August, and the installation began in November. Due to the long search for an institution willing and capable of testing the isotopes of boron trifluoride gas, it will not be put into operation until May 2022. From September 17 to 26, 2022, the gas intake was continuously operated for 9 days, a total of 210 hours.

[0021] The pilot plant follows the idea from initial design, construction, and trial operation: using a boron trifluoride / methyl isobutyl ketone exchange system. Due to the height limit of the experimental site, the tower body can only be no more than 3.2 meters. The water content of the system cannot be ≯50ppm. The operating temperature of the system can be controlled at 20-30℃. The reboiling decomposition temperature is ≯115.8℃. Under the influence of insufficient tower height, the system pressure is planned to be controlled in the range of 100kpa-0.3mpa. Due to funding reasons, it is decided that all pipes, fittings, valve materials and equipment materials are made of 304 material (this is not the best manufacturing material, but it can be used for short-term experiments). The filler is 316 mesh and the sealing material is polytetrafluoroethylene.

[0022] The pilot plant is equipped with an electromagnetic heating system, a circulating water system with adjustable temperature at 21-30°C, and a freezing liquid system that can be cooled to -35°C. A molecular sieve dehydration system is also developed and manufactured to dehydrate the methyl isobutyl ketone raw material to less than 50ppm. Under normal temperature and pressure, closed-loop circulation and mature combined tower separation technology are used to obtain boron trifluoride-10 and boron trifluoride-11 at the same time. There is no waste gas or waste liquid emission, energy saving and environmental protection, and low raw material consumption.

Claims

1. A method for separating stable boron isotopes by constant cycle exchange using boron trifluoride / methyl isobutyl ketone: using bottled boron trifluoride gas as raw material and methyl isobutyl ketone liquid as intermediate, the two are subjected to gas / liquid countercurrent exchange, thereby separating two stable isotopes of boron trifluoride-10 and boron trifluoride-11 and obtaining both at the same time. The molar ratio of boron trifluoride / methyl isobutyl ketone is 1.1:

1. Boron trifluoride is first subjected to ultra-low temperature refined desulfurization and impurity removal, and then enters the exchange tower for gas / liquid exchange with methyl isobutyl ketone. Methyl isobutyl ketone is dehydrated by molecular sieve, then subjected to low temperature refined dehydration and impurity removal, and then enters the cooling tower for gas / liquid exchange. Required equipment: ① exchange tower, ② complexing tower, ③ cooling extraction tower, ④ low-temperature stripping tower, ⑤ low-temperature reboiling tower, ⑥ high-temperature stripping tower, ⑦ high-temperature reboiling tower, ⑧ boron trifluoride refining tank, ⑨ methyl isobutyl ketone refining tank, ⑩ molecular sieve trace water removal device.

2. The whole system is purged with high-purity nitrogen, and each equipment is tested and qualified by a dew point meter. The methyl isobutyl ketone solution is dehydrated to ≮50ppm by a molecular sieve to remove trace water device and a methyl isobutyl ketone refining tank, and enters the system from the top of the cooling extraction tower to establish a liquid circulation. Samples are taken at the bottom of each tower for analysis, and the water content is ≮50ppm to meet the standard. If it does not meet the standard, the circulating liquid is drawn and then enters the molecular sieve to remove trace water device and methyl isobutyl ketone refining tank for dehydration until it meets the standard.

3. After the boron trifluoride is refined, it enters from the bottom of the exchange tower and countercurrently exchanges with the methyl isobutyl ketone solvent from the top of the tower, so that the boron trifluoride-10 is gathered in the liquid state. The liquid enriched with boron 10 first enters the low-temperature stripping tower-low-temperature reboiling tower, the temperature is controlled at 65-75°C, and about 20% of the gas is separated, and then enters the high-temperature stripping tower-high-temperature reboiling tower, the temperature is controlled at 115.8°C, and the gas / liquid is completely separated. The gas separated by the high-temperature stripping tower enters the bottom of the low-temperature stripping tower. A cooler is set at the top section of the low-temperature stripping tower, and the qualified boron trifluoride-10 will be diverted here to the stable recovery device.

4. The methyl isobutyl ketone solvent output from the bottom of the high-temperature reboiling tower enters the molecular sieve dehydration device after cooling, and after being refined, enters the top of the cooling extraction tower and intersects with the boron trifluoride-11 from bottom to top. The boron trifluoride-11 gas is led to the stable recovery device here.

5. The liquid is output from the bottom of the extraction tower and enters the complexation tower to react with the boron trifluoride gas output from the exchange tower to completely separate the two isotopes. According to the separation rate of 0.6% / 24 hours, it takes 133 to 134 days for the abundance of boron trifluoride-10 to reach 99.9% from 19.8%. It takes 32 to 33 days for the abundance of boron trifluoride-11 to reach 99.9% from 80.2%.

6. This method uses a boron trifluoride / methyl isobutyl ketone exchange system, and the water content of the system cannot be ≯50ppm. The system pressure is controlled at 100kpa~0.3mpa. The operating temperature is controlled at 20~30℃. The maximum decomposition temperature of reboiling is ≯115.8℃. At room temperature and pressure, except for the reboiling and stripping parts, the other parts of the entire separation device are completely operated in a low-temperature state, closed-loop circulation, and a mature combined tower separation process is adopted to obtain boron trifluoride-10 and boron trifluoride-11 stable isotopes at the same time. There is no waste gas or waste liquid emission, energy saving and environmental protection, and low raw material consumption.

7. This method has strict requirements on the material of the equipment. 316L must be used in the room temperature part, and specially selected materials must be used in the special part. This is the key condition for the process to operate stably for a long period of time and thus obtain stable isotopes of boron trifluoride-10 and boron trifluoride-11.

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