A synergic purification device and method for nitrogen trifluoride

Abstract

A synergistic purification device and method of nitrogen trifluoride, the device comprising a residual cold recycling unit, a deep cooling separation unit, an extractive rectification unit and an adsorption unit; the deep cooling separation unit comprising refrigeration equipment with gradually reduced temperature; the extractive rectification unit comprising extractive rectification equipment and solvent recovery rectification equipment, the extractive rectification equipment being connected with the discharge port of the refrigeration equipment through a feed line, and the discharge line being connected with the feed port of the solvent recovery rectification equipment, and the solvent recovery line of the solvent recovery rectification equipment being connected with the recycling port of the extractive rectification equipment; the adsorption unit being connected with the discharge port of the solvent recovery rectification equipment through a gas inlet pipeline; the residual cold recycling unit comprising refrigerant, a first cooling section and a second cooling section, the first cooling section and the second cooling section being in communication, the first cooling section being heat-exchanged with the extractive rectification unit, and the second cooling section being heat-exchanged with the deep cooling separation unit. The present application can simplify the process flow, reduce the purification energy consumption of nitrogen trifluoride, and improve the purification quality and efficiency.

Description

Technical Field

[0001] This invention belongs to the field of nitrogen trifluoride purification technology, specifically relating to a synergistic purification device and method for nitrogen trifluoride. Background Technology

[0002] Nitrogen trifluoride (NF3), a key fluorine-containing electronic specialty gas, is widely used in high-end manufacturing fields such as integrated circuits, transistors, optical fibers, and photovoltaic cells due to its advantages such as high etching rate, excellent selectivity, and no residual pollution after use. With the rapid development of the semiconductor industry, the market demand for nitrogen trifluoride continues to grow, and the industry's development prospects are very broad. However, high-end manufacturing fields have extremely stringent purity requirements for nitrogen trifluoride, and the crude raw materials contain complex components. Existing purification processes have many shortcomings, and the industry urgently needs to develop efficient and stable new purification technologies.

[0003] The main impurities in the crude nitrogen trifluoride gas include oxygen, nitrogen, carbon monoxide, carbon tetrafluoride, carbon dioxide, nitrous oxide, sulfur hexafluoride, and hydrogen fluoride. Among them, carbon tetrafluoride and nitrogen trifluoride have very similar physicochemical properties. Carbon tetrafluoride has a boiling point of -128℃ and a molecular diameter of 4.8 Å, while nitrogen trifluoride has a boiling point of -129℃ and a molecular diameter of 4.5 Å. Separating the two is extremely difficult and is the core technical challenge in the purification process of nitrogen trifluoride.

[0004] Currently, the main industrial methods for purifying nitrogen trifluoride are azeotropic distillation and adsorption, both of which have significant drawbacks. Regarding distillation, patent application CN101920944A discloses a technique for separating nitrogen trifluoride and carbon tetrafluoride using extractive distillation to prepare high-purity nitrogen trifluoride. This technique uses hydrogen chloride as an azeotropic agent, which, along with the feed gas, enters the distillation column. The azeotrope formed by carbon tetrafluoride and hydrogen chloride is collected from the top of the column, while high-purity nitrogen trifluoride is produced in the bottom. However, this process introduces hydrogen chloride, making precise control of the finished product's acidity difficult. In case of abnormal operating conditions, a water-alkali washing process is required for deep acid removal. Furthermore, the azeotrope collected from the top of the column requires membrane separation equipment to recover the azeotropic agent. Overall, the process is cumbersome and has low production efficiency.

[0005] In the field of adsorption purification, the limitations of existing technologies are also prominent. For example, patent CN106276828B discloses a method for adsorbing and purifying nitrogen trifluoride, which uses 5A molecular sieve combined with cerium tetradecyl phosphate as the carrier raw material, and then loads zinc dialkyl dithiophosphate and 3-fluoro-nitro-methylaniline onto the carrier by liquid-phase sedimentation to obtain the adsorbent. The crude nitrogen trifluoride is then adsorbed in an adsorption column packed with the adsorbent. This process not only continuously consumes inert gas and has high energy consumption in the desorption stage, but also requires frequent switching between adsorption and desorption conditions, making continuous production difficult. At the same time, conventional molecular sieves themselves cannot effectively adsorb carbon tetrafluoride, and even with modified adsorbents, it is difficult to achieve deep separation of the two substances, limiting the upper limit of product purification.

[0006] Currently, the industry also uses a purification process that couples distillation and adsorption. For example, patent CN102101656A discloses a technology for preparing high-purity nitrogen trifluoride by distillation and adsorption purification. However, this process has also revealed several technical defects in practical applications. First, the process adopts an intermittent operation mode, with crude nitrogen trifluoride flowing sequentially through multiple processing towers. The residence time of the raw gas in a single tower is as long as 20 minutes. After multiple devices are connected in series, the overall processing cycle increases significantly, resulting in low production efficiency and making it unsuitable for the continuous, large-scale production requirements of the industry. Second, the process only sets up a single-stage hydrogen fluoride removal tower, requiring the equipment to maintain a cryogenic condition of -90°C for a long time, resulting in high refrigeration energy consumption. Moreover, the single-tower structure makes it difficult to achieve gradient removal of impurities, and the removal effect on hydrogen fluoride and moisture is limited. Residual impurities not only easily corrode subsequent equipment but also affect the quality of the final product. Finally, the entire process involves eight sets of tower equipment in series, including a hydrogen fluoride removal tower, a high-temperature cracking tower, an oxidation tower, a reduction tower, an alkaline washing tower, a low-temperature dehydration tower, a distillation tower, and a molecular sieve adsorption tower. The number of supporting pipelines, valves, and auxiliary devices is also large, which not only significantly increases equipment investment, floor space, and operation and maintenance costs, but also increases the risk of gas leakage due to the excessive number of connection interfaces. At the same time, the process control nodes are complicated, and fluctuations in the operating conditions of a single piece of equipment can affect the entire production line, resulting in poor overall operational stability.

[0007] In summary, current nitrogen trifluoride purification processes generally suffer from problems such as complex processes, redundant equipment configurations, low purification efficiency, and high overall energy consumption. Therefore, providing a nitrogen trifluoride purification technology with a simplified process flow, lower energy consumption, and higher purification efficiency is a pressing technical problem to be solved in this field. Summary of the Invention

[0008] To address the shortcomings of the existing technology, this invention provides a synergistic purification apparatus and method for nitrogen trifluoride. This simplifies the process flow, reduces energy consumption in nitrogen trifluoride purification, and improves purification efficiency.

[0009] In a first aspect, the present invention provides a synergistic purification device for nitrogen trifluoride, comprising a residual cold recycling unit, and a cryogenic separation unit, an extractive distillation unit, and an adsorption unit connected sequentially along the purification direction. The cryogenic separation unit comprises at least two refrigeration units connected in series with progressively decreasing temperatures; The extraction distillation unit includes an extraction distillation device and a solvent recovery distillation device. The feed line of the extraction distillation device is connected to the outlet of the refrigeration equipment with the lowest temperature, and the outlet line is connected to the feed line of the solvent recovery distillation device. The solvent recovery line of the solvent recovery distillation device is connected to the reuse port of the extraction distillation device. The adsorption unit is connected to the outlet of the solvent recovery distillation equipment via an inlet pipe; The residual cold recycling unit includes a refrigerant, a first cooling section, and a second cooling section. The first cooling section and the second cooling section are connected. The first cooling section exchanges heat with the extraction and distillation unit, and the second cooling section exchanges heat with the cryogenic separation unit. The refrigerant passes through the first cooling section and the second cooling section in sequence.

[0010] Furthermore, the cryogenic separation unit satisfies at least one of the following: 1) The temperature of the cryogenic separation unit is 0~-90℃; 2) The cryogenic separation unit includes three refrigeration units connected in series with progressively decreasing temperatures. The temperatures of the three refrigeration units are 0~-20℃, -40~-60℃, and -70~-90℃, respectively. 3) The pressure of the refrigeration equipment is 0.95~1.50MPa.

[0011] Furthermore, the extractive distillation unit satisfies at least one of the following: 1) The bottom of the extractive distillation equipment is equipped with a first reboiler, which heats the heavy components of the extractive distillation equipment and generates vapor reflux; 2) The solvent recovery distillation equipment is equipped with a second reboiler at the bottom. The second reboiler heats the heavy components of the solvent recovery distillation equipment and generates vapor reflux. 3) The extraction distillation equipment and / or solvent recovery distillation equipment are equipped with packed distillation columns, and the materials of the packed distillation columns are any one or more of nickel, stainless steel, and Monel.

[0012] Furthermore, the extractive distillation unit satisfies at least one of the following: 1) The top of the extractive distillation equipment is equipped with a first condenser and a first reflux condenser. The first condenser exchanges heat with the first cooling section. The first condenser cools the light component material of the extractive distillation equipment and refluxes it through the first reflux condenser. 2) The solvent recovery distillation equipment is equipped with a second condenser and a second reflux device at the top. The second condenser exchanges heat with the first cooling section. The second condenser cools the light component material of the solvent recovery distillation equipment and refluxes it into the adsorption unit through the second reflux device.

[0013] Furthermore, the temperature of the first condenser is -160 to -180°C.

[0014] Furthermore, the temperature of the second condenser is -90 to -100°C.

[0015] Furthermore, the adsorption unit is filled with at least one of Zr-MOF metal-organic framework material, phosphate-supported modified 5A molecular sieve, and carbon molecular sieve adsorbent.

[0016] Furthermore, the adsorption unit is filled with Zr-MOFs metal-organic framework material, which is a metal-organic framework material with Zr as the central metal and oxalic acid as the organic ligand.

[0017] Furthermore, Zr-MOF metal-organic framework materials satisfy at least one of the following: 1) The material density is 2.35~2.81 g / cm³. 3 ; 2) Aperture is 6~6.5 Å; 3) Specific surface area is 1200~1300 m² 2 / g; 4) Porosity is 0.4~0.5; 5) The free volume of the pore is 0.2~0.25 cm³. 3 / g.

[0018] Furthermore, the extractive distillation unit also satisfies at least one of the following: 1) The internal pressure of the extractive distillation equipment is 0.9~1.0 MPa, the top temperature is -150~-170℃, and the bottom temperature is -80~-90℃; 2) The internal pressure of the solvent recovery distillation equipment is 0.8~0.9 MPa, the top temperature is -80~-90℃, and the bottom temperature is -75~-85℃.

[0019] Secondly, the present invention also provides a synergistic purification method using the above-mentioned synergistic purification device, comprising the following steps: S1. Cryogenic separation: The crude nitrogen trifluoride gas to be purified is passed into the cryogenic separation unit to remove heavy component impurities; S2, Extractive distillation: S2.1 The outlet gas after cryogenic separation enters the extractive distillation equipment through the feed pipeline, and at the same time, the extractant is introduced into the extractive distillation equipment; S2.2 The heavy components of the extractive distillation equipment enter the solvent recovery distillation equipment through the discharge pipeline; the extractant enriched in the solvent recovery distillation equipment flows back to the extractive distillation equipment along the solvent recovery pipeline; S2.3 The light component material of the solvent recovery distillation equipment enters the adsorption unit through the gas inlet pipeline; S3, Adsorption and Purification: The light component material entering the solvent recovery distillation equipment of the adsorption unit is purified to produce nitrogen trifluoride within the adsorption unit.

[0020] Furthermore, at least one of the following must be met: 1) By volume percentage, the crude nitrogen trifluoride gas consists of 25%~50% NF3, 45%~70% N2, 2%~4% CF4, 0.5~5 ppmv HF, and 1%~2% H2O; 2) The extractant is 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, and the feed volume ratio of the extractant to the crude nitrogen trifluoride gas is 0.5~2; 3) In the gas purified by adsorption in step S3, the volume content of nitrogen trifluoride is above 99.99%, preferably above 99.995%, and the volume content of carbon tetrafluoride is below 10 ppm.

[0021] The present invention provides a synergistic purification apparatus and method for nitrogen trifluoride, which has at least the following beneficial effects: (1) Through a three-stage purification process of cryogenic separation, extractive distillation, and adsorption, crude nitrogen trifluoride gas is purified efficiently and stably. Compared with existing single or two-stage purification processes, this solves the problem of low separation efficiency of carbon tetrafluoride, and the overall process flow is simple. At the same time, the solvent recovery distillation equipment can realize the recovery of high-purity extractant, which is returned to the extractive distillation equipment for reuse via the solvent recovery pipeline, resulting in high extractant recovery efficiency. In addition, the refrigerant is matched with the energy of the cryogenic separation unit and the extractive distillation unit to avoid energy waste. Compared with a single distillation process, the overall energy consumption is reduced, and the cost advantage is significant.

[0022] (2) The material after being removed by deep cryogenic separation unit can be directly entered into extraction and distillation unit for extraction and distillation without the need for additional cooling equipment. This simplifies equipment configuration, shortens process flow, and reduces refrigeration energy consumption and equipment maintenance costs.

[0023] (3) By using Zr-MOFs metal-organic framework materials, CF4 impurities can be removed efficiently, and the adsorption loss of NF3 is low, which can significantly improve the product yield of nitrogen trifluoride, reduce raw material loss, and effectively improve the overall economic benefits of the process. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the connection of the nitrogen trifluoride synergistic purification device of the present invention; Figure 2 This is a flowchart of the nitrogen trifluoride synergistic purification method of the present invention.

[0025] Explanation of reference numerals in the attached figures: 100 - Residual cold recycling unit, 200 - Cryogenic separation unit, 300 - Extractive distillation unit, 400 - Adsorption unit; 1-Raw gas, 2-Feed pipeline, 3-Solvent recovery pipeline, 4-First reflux pipe, 5-Production line, 6-Discharge pipeline, 7-Second reflux pipe, 8-Production pipeline, 9-First refrigeration equipment, 10-Second refrigeration equipment, 11-Third refrigeration equipment, 12-Extraction distillation equipment, 13-Solvent recovery distillation equipment, 14-First condenser, 15-Second condenser, 16-First reflux, 17-Second reflux, 18-First reboiler, 19-Second reboiler, 20-Adsorption equipment. Detailed Implementation

[0026] To better understand the above technical solutions, a detailed description of the solutions will be provided below in conjunction with the accompanying drawings and specific embodiments. Obviously, the described embodiments are merely some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0027] The terminology used in the embodiments of this invention is for the purpose of describing particular embodiments only and is not intended to limit the invention. The singular forms “a,” “the,” and “the” as used in the embodiments of this invention and the appended claims are also intended to include the plural forms, and “multiple” generally includes at least two unless the context clearly indicates otherwise.

[0028] It should also be noted that the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that an article or device that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such an article or device. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the article or device that includes said element.

[0029] like Figure 1 As shown, the present invention provides a synergistic purification device for nitrogen trifluoride, including a residual cold recycling unit 100, and a cryogenic separation unit 200, an extractive distillation unit 300 and an adsorption unit 400 connected sequentially along the purification direction. The cryogenic separation unit 200 includes at least two refrigeration units connected in series with progressively decreasing temperatures; The extraction distillation unit 300 includes an extraction distillation device 12 and a solvent recovery distillation device 13. The feed line 2 of the extraction distillation device 12 is connected to the outlet of the refrigeration equipment with the lowest temperature, the outlet line 6 is connected to the feed inlet of the solvent recovery distillation device 13, and the solvent recovery line 3 of the solvent recovery distillation device 13 is connected to the reuse port of the extraction distillation device 12. The adsorption unit 400 is connected to the outlet of the solvent recovery distillation equipment 13 via an inlet pipe; The residual cold recycling unit 100 includes a refrigerant, a first cooling section and a second cooling section (not shown). The first cooling section and the second cooling section are connected. The first cooling section exchanges heat with the extraction distillation unit 300, and the second cooling section exchanges heat with the cryogenic separation unit 200. The refrigerant passes through the first cooling section and the second cooling section in sequence.

[0030] The crude nitrogen trifluoride gas 1 is pretreated by a series of cooling devices with progressively decreasing temperatures. The material then sequentially enters the extractive distillation unit 12 and the solvent recovery distillation unit 13 (also known as the extractant recovery distillation unit), before being fed into the adsorption unit 400 for deep purification of nitrogen trifluoride. Finally, high-purity nitrogen trifluoride product is collected from the output pipeline 8. The extractant, after recovery, can be recycled back to the extractive distillation unit 12 via the solvent recovery pipeline 3 for reuse. Simultaneously, the cooling medium used to cool the extractive distillation unit 300, regulated and distributed by the residual cold reuse unit 100, can supply cooling to the multi-stage cooling equipment at the front end. This deep collaboration and coordinated operation between the units enables continuous material processing, closed-loop extraction, and tiered reuse of cooling capacity. This not only simplifies configuration and reduces equipment investment but also significantly reduces cooling capacity loss and reagent consumption, effectively compressing operating costs while ensuring purification efficiency.

[0031] The cryogenic separation unit 200 meets at least one of the following conditions: 1) The temperature of the cryogenic separation unit 200 is 0 to -90℃; 2) The cryogenic separation unit 200 includes three refrigeration devices connected in series with progressively decreasing temperatures, namely, the first refrigeration device 9, the second refrigeration device 10, and the third refrigeration device 11. The temperature of the first refrigeration device 9 is 0 to -20℃, the temperature of the second refrigeration device 10 is -40 to -60℃, and the temperature of the third refrigeration device 11 is -70 to -90℃; 3) The pressure of each refrigeration device is 0.95 to 1.50 MPa. The operating temperature range of the cryogenic separation unit 200 is set to 0 to -90℃. This low-temperature operating condition can effectively condense and remove moisture, hydrogen fluoride, sulfur hexafluoride, and various high-boiling-point impurities from the nitrogen trifluoride crude gas 1, completing preliminary purification. The cryogenic separation unit 200 includes three refrigeration devices, with temperatures sequentially controlled at 0~-20℃, -40~-60℃, and -70~-90℃. This gradient cooling operation mode enables the staged removal of impurities, avoiding problems such as impurity condensation and pipeline blockage caused by sudden temperature drops, and further improving the uniformity and depth of impurity removal. In addition, the operating pressure of all cooling devices is maintained within the range of 0.95~1.50MPa. This high-pressure environment significantly enhances the mass transfer between the gas and liquid phases, improves gas liquefaction efficiency and impurity separation effect, and effectively reduces the processing load of subsequent distillation and adsorption stages.

[0032] The extractive distillation unit 300 satisfies at least one of the following: 1) The bottom of the extractive distillation device 12 is provided with a first reboiler 18, which heats the heavy components of the extractive distillation device 12 and generates vapor reflux; 2) The bottom of the solvent recovery distillation device 13 is provided with a second reboiler 19, which heats the heavy components of the solvent recovery distillation device 13 and generates vapor reflux; 3) The extractive distillation device 12 and / or the solvent recovery distillation device 13 are provided with packed distillation columns, and the material of the packed distillation columns is any one or more of nickel, stainless steel, and Monel. Both the extractive distillation unit 12 and the solvent recovery distillation unit 13 are equipped with reboilers (first column reboiler 18 and second column reboiler 19) at the bottom. These reboilers can heat the distillation unit to form a vapor-phase reflux, stabilizing the contact state between the gas and liquid phases within the extractive distillation unit 300. This ensures continuous and stable mass and heat transfer in the distillation system, effectively improving component separation accuracy. Simultaneously, it maintains the operational balance within the extractive distillation unit 300, guaranteeing stable operation for continuous production. Furthermore, the use of packed distillation columns inside the extractive distillation unit 12 and / or the solvent recovery distillation unit 13 significantly increases the gas-liquid contact area, optimizes fluid distribution, and enhances mass transfer efficiency. This reduces the pressure drop in the extractive distillation unit 300 while further improving extraction separation and extractant recovery, achieving efficient purification and extractant recycling.

[0033] Furthermore, the extractive distillation unit 300 satisfies at least one of the following: 1) The extractive distillation device 12 is equipped with a first condenser 14 at the top for heat exchange with a first cooling section. The first condenser 14 cools the light component material of the extractive distillation device 12 and, after passing through the first reflux device 16, part of it is returned to the extractive distillation device 12 via the first reflux pipe 4, and part of it is collected through the collection line 5; the temperature of the first condenser 14 is -160~-180℃; 2) The solvent recovery distillation device 13 is equipped with a second condenser 15 and a second reflux device 17 at the top. The second condenser 15 exchanges heat with the first cooling section. The second condenser 15 cools the light component material of the solvent recovery distillation device 13, and part of it is returned to the solvent recovery distillation device 13 via the second reflux pipe 7 through the second reflux device 17, and part of it is introduced into the adsorption unit 400; the temperature of the second condenser 15 is -90~-100℃. The first condenser 14 and the first reflux 16 installed at the top of the extractive distillation unit 12, and the second condenser 15 and the second reflux 17 installed at the top of the solvent recovery distillation unit 13, can condense the rising light components (gas phase components) into liquid phases and achieve liquid phase reflux through the reflux condensers, continuously maintaining the dynamic balance between the gas and liquid phases within the unit, ensuring the stable operation of the distillation process, further enhancing the component separation effect, and improving the accuracy of product purification and extractant recovery. Specifically, the temperature of the first condenser 14 at the top of the extractive distillation unit 12 is controlled at -160~-180℃, which allows for sufficient condensation of nitrogen trifluoride components in an ultra-low temperature environment, reducing the loss of target products with the gas phase. The temperature of the second condenser 15 at the top of the solvent recovery distillation unit 13 is -90~-100℃, which allows for targeted condensation of extractant components, ensuring efficient recovery of the extractant while reasonably controlling refrigeration energy consumption.

[0034] Furthermore, the extractive distillation unit 300 also meets at least one of the following requirements: 1) The internal pressure of the extractive distillation equipment 12 is 0.9~1.0 MPa, the top temperature is -150~-170℃, and the bottom temperature is -80~-90℃; the pressure range of the extractive distillation equipment 12 can improve the condensation effect of the gas phase components and enhance the gas-liquid mass transfer; the extractive distillation equipment 12 forms a significant temperature gradient, the low temperature environment at the top can fully condense the nitrogen trifluoride components and reduce the volatilization loss of the target product, while the temperature at the bottom matches the component separation requirements, which can efficiently remove light component impurities such as carbon tetrafluoride, difluorohydrazine, and carbon monoxide in the system, ensuring the efficient operation of the extractive distillation process and achieving effective separation of nitrogen trifluoride from impurities. 2) The solvent recovery distillation unit 13 has an internal pressure of 0.8~0.9 MPa, a top temperature of -80~-90℃, and a bottom temperature of -75~-85℃. The pressure and temperature range of the solvent recovery distillation unit 13 is adapted to the physicochemical properties of the extractant, ensuring both complete vaporization and separation of the extractant, and condensation and recovery of the extractant at the top of the unit, guaranteeing the extractant recovery rate. Simultaneously, the mild operating conditions of the solvent recovery distillation unit 13 reduce refrigeration and heating energy consumption, thereby extending the equipment's service life. Overall, the extraction distillation unit 300, through the extraction distillation unit 12 and the solvent recovery distillation unit 13, employs differentiated pressure and stepped temperature distributions to form a dedicated operating system adapted to the separation target. The extraction distillation unit 12 relies on a high-pressure and large-temperature-difference environment to achieve deep separation of the main product and impurities, while the solvent recovery distillation unit 13 achieves efficient recovery and recycling of the extractant under relatively low-pressure and small-temperature-change conditions. The extraction distillation unit 300 can ensure separation accuracy and extractant recycling rate while achieving reasonable distribution of cold and heat, effectively balancing purification effect and operating energy consumption, and ensuring continuous, stable and economical operation of the entire distillation system.

[0035] The adsorption unit 400 includes an adsorption device 20, which is filled with at least one of Zr-MOFs metal-organic framework material, phosphate-supported modified 5A molecular sieve, and carbon molecular sieve adsorbent. Preferably, the adsorption unit 400 is filled with Zr-MOFs metal-organic framework material, which is a metal-organic framework material with Zr as the central metal and oxalic acid as the organic ligand. It can selectively adsorb trace impurities such as carbon tetrafluoride remaining in the gas after passing through the cryogenic separation unit 200 and the extractive distillation unit 300, efficiently achieving deep purification. Simultaneously, its adsorption loss for nitrogen trifluoride is extremely low, thereby effectively improving product yield and overall purification quality. The Zr-MOFs metal-organic framework material satisfies at least one of the following: 1) the material density is 2.35~2.81 g / cm³. 3 Preferably, the material density is 2.58 g / cm³. 3The material structure at this density is compact and stable, ensuring that the Zr-MOF metal-organic framework material is not prone to pulverization or loss after loading, thus guaranteeing the long-term stable operation of the adsorption unit 400. 2) The pore size is 6~6.5 Å, preferably 6.25 Å; this allows for precise sieving and selective adsorption by taking advantage of the molecular size differences between impurities and the target product (nitrogen trifluoride), enhancing the separation effect of CF4 and NF3. 3) The specific surface area is 1200~1300 m². 2 / g, preferably, the specific surface area is 1253.1m². 2 / g; can provide sufficient active sites for the adsorption process of adsorption unit 400, greatly improving the adsorption capacity and adsorption efficiency of adsorption unit 400. 4) Porosity is 0.4~0.5, preferably 0.44; 5) Pore free volume is 0.2~0.25cm³. 3 / g, preferably, the pore free volume is 0.22cm³. 3 / g; This porous structure can optimize the flow of gas within Zr-MOFs metal-organic framework materials, reduce airflow resistance, ensure mass transfer efficiency, and avoid excessive pressure drop, making it suitable for continuous production conditions.

[0036] The residual heat recovery unit 100 also includes a refrigerant pipeline for transporting refrigerant. The refrigerant pipeline is connected to the first condenser 14, the second condenser 15, and the heat exchange coils of the refrigeration equipment. The refrigerant circulates and exchanges heat through the refrigerant pipeline and the heat exchange coils of the first condenser 14, the second condenser 15, and the refrigeration equipment. The heat exchange coils of the first condenser 14 and the second condenser 15 correspond to the first cooling section of the residual heat recovery unit 100, and the heat exchange coils of the refrigeration equipment correspond to the second cooling section of the residual heat recovery unit 100. When a first refrigeration unit 9, a second refrigeration unit 10, and a third refrigeration unit 11 are provided, the refrigerant passes through the heat exchange coils of the first refrigeration unit 9, the second refrigeration unit 10, and the third refrigeration unit 11 in reverse order of decreasing temperature via the refrigerant pipeline, thereby achieving temperature control of multiple refrigeration units. In a preferred embodiment, valves are installed at the inlet and outlet of the heat exchange coils of the first condenser 14, the second condenser 15, the first refrigeration unit 9, the second refrigeration unit 10, and the third refrigeration unit 11 to regulate the refrigerant flow in the heat exchange coils, thereby achieving further temperature control.

[0037] In this invention, all pipelines connecting the various devices in the co-purification apparatus are made of stainless steel. To avoid the risk of corrosion from HF in the material, the cryogenic separation unit 200 is lined with polytetrafluoroethylene (PTFE). All pressure-controlled devices in the co-purification apparatus are equipped with safety valves, and the set pressure is set to the container's design pressure to prevent overpressure explosions. The cryogenic separation unit 200 and the residual cold recycling unit 100 are also covered with a 50mm thick polyurethane insulation layer to ensure the outer wall temperature is ≥5℃, thereby preventing frostbite to personnel.

[0038] See appendix Figure 2 The present invention also provides a synergistic purification method using the above-mentioned synergistic purification device, comprising the following steps: S1. Cryogenic separation: The crude nitrogen trifluoride gas 1 to be purified is passed into the cryogenic separation unit 200 to remove heavy component impurities; wherein, by volume percentage, the composition of the crude nitrogen trifluoride gas 1 includes 25%~50% NF3, 45%~70% N2, 2%~4% CF4, 0.5~5ppmv HF, and 1%~2% H2O; S2, Extractive distillation: S2.1 The outlet gas after cryogenic separation enters the extractive distillation equipment 12 through the feed pipeline 2, and at the same time, the extractant is introduced into the extractive distillation equipment 12. The extractant can be 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, and the feed volume flow ratio of the extractant to the crude nitrogen trifluoride gas 1 is 0.5~2. S2.2 The heavy component material of the extractive distillation equipment 12 enters the solvent recovery distillation equipment 13 through the discharge pipeline 6; the extractant enriched in the solvent recovery distillation equipment 13 flows back to the extractive distillation equipment 12 along the solvent recovery pipeline 3; S2.3 The light component material of the solvent recovery distillation equipment 13 enters the adsorption unit 400 through the gas inlet pipe; S3, Adsorption: Light component materials from the solvent recovery distillation equipment entering the adsorption unit 400 are purified to produce nitrogen trifluoride within the adsorption unit 400.

[0039] The extractant and adsorbent of this invention exhibit stable performance and excellent selectivity. In the NF3 / CF4 system, the Zr-MOF metal-organic framework material achieves an adsorption separation coefficient of 50.15 for CF4, efficiently removing impurities while reducing adsorption loss on NF3, effectively improving NF3 yield, reducing resource waste, and further enhancing the economic efficiency of the process. Furthermore, the process route of this invention is simple and continuous. Each unit / equipment is assembled into an integrated system via pipelines according to its function. The design is scientifically sound and easy to operate, enabling continuous production and effectively reducing parameter fluctuations during production, thus improving the stability and reliability of production operation. In addition, the synergistic purification method of this invention has strong adaptability to crude NF3 gases with different compositions, flexibly addressing fluctuations in impurity content in crude nitrogen trifluoride gas, and offering high operational flexibility. The overall purification process generates no toxic or harmful pollutants, the extractant is recycled, and energy is efficiently recovered, conforming to the production concept of green chemistry.

[0040] Example 1 The main components of crude nitrogen trifluoride gas are: 1.85% CF4, 1 ppm vHF, 1% H2O, 55.95% N2, and 41.2% NF3. Other impurities are present in negligible amounts. A three-stage refrigeration system is installed, and the refrigerant inlet and outlet valves are opened. The temperatures are stabilized at 0℃, -40℃, and -70℃ respectively. Then, the feed valve of the refrigeration system is opened, and the material (crude nitrogen trifluoride gas) enters the system through the feed inlet at a flow rate of 500 Nm³. 3 The process involves a 3-stage cryogenic separation process at a temperature of 25°C and a pressure of 1 MPa. During this process, a large amount of water and hydrogen fluoride, along with other heavy components, condenses into droplets or solidifies and is collected at the bottom of the cryogenic equipment. The outlet material is maintained at -70°C for pre-cooling before entering the extractive distillation unit. After the co-purification unit stabilizes, the outlet pipeline of the 3-stage cryogenic equipment is opened. After cryogenic separation, the H2O and HF in the crude nitrogen trifluoride gas decrease to 5 ppmv and 0.06 ppmv, respectively. 99.95% of the water and approximately 94% of the hydrogen fluoride are removed. The outlet material from the cryogenic equipment is discharged at -70°C and 495 Nm³ / h. 3The feed is introduced into the extractive distillation unit at a rate of 10354 kg / h along the feed line. Simultaneously, extractant C5H4F8O is introduced at the extractant inlet below the feed inlet to alter the relative volatility between nitrogen trifluoride and carbon tetrafluoride. The top temperature and pressure of the extractive distillation unit are -150℃ and 0.900 MPa, while the bottom temperature and pressure are -80℃ and 0.902 MPa. Under these conditions, NF3 has a high affinity for C5H4F8O and dissolves in the extractant, accumulating as a heavy component at the bottom of the extractive distillation unit. The top material of the extractive distillation unit consists of carbon tetrafluoride and a small amount of light components. Light components such as N2 and CF4 are condensed in the first condenser at the top, and the volumetric reflux ratio is controlled to 5 via the first reflux condenser. The distillate composition is analyzed to be 93.25% N2, 3.08% CF4, and other impurities (such as SF6 and CO2). The total flow rate is 300 Nm³. 3 The bottom of the extractive distillation unit contains a liquid mixture of extractant and nitrogen trifluoride, with a discharge flow rate of 10990.9 kg / h. The material enters from the inlet in the middle of the solvent recovery distillation unit along the discharge pipeline. The top temperature and pressure of the solvent recovery distillation unit are -80℃ and 0.800 MPa, while the bottom temperature and pressure are -75℃ and 0.801 MPa. High-purity nitrogen trifluoride is collected from the top of the solvent recovery distillation unit, and the extractant C5H4F8O is enriched at the bottom and transported to the recycling port through the solvent recovery pipeline for solvent recycling. The high-purity nitrogen trifluoride after extractive distillation is passed into an adsorption unit filled with Zr-MOFs metal-organic framework material. The temperature of the adsorption unit is controlled at 20℃ and the pressure at 0.75 MPa. After adsorption purification, electronic-grade nitrogen trifluoride product gas composition is obtained with 99.999% NF3 and 8 ppmv CF4.

[0041] Example 2 The difference from Example 1 is that a two-stage refrigeration system is set up, and the refrigerant inlet and outlet valves of the two-stage refrigeration system are opened to control the temperature to stabilize at -30°C and -80°C respectively. Then, the feed valve of the refrigeration system is opened, and the material (nitrogen trifluoride crude gas) enters from the feed inlet of the refrigeration system along its pipeline, with a feed flow rate of 500 Nm³. 3 The process involves a refrigeration system operating at 25°C and 1 MPa per hour. During this initial stage, the material undergoes a two-stage cryogenic separation process. Large amounts of water and hydrogen fluoride, among other heavy components, condense into droplets or solidify and are collected at the bottom of the refrigeration unit. The outlet material is maintained at -80°C for pre-cooling before entering the extraction and distillation unit. After the co-purification unit stabilizes, the outlet pipeline of the two-stage refrigeration unit is opened. After cryogenic separation, the H2O and HF in the crude nitrogen trifluoride gas decrease to 10 ppmv and 0.08 ppmv, respectively. 99.9% of the water and 92% of the hydrogen fluoride are removed. The outlet material from the refrigeration unit is maintained at -80°C and 495 Nm³ / h. 3The feed is introduced into the extraction and distillation unit via the feed pipeline at a rate of / h. The remaining steps are basically the same as in Example 1. After adsorption and purification, the electronic-grade nitrogen trifluoride product gas composition is 99.998% NF3 and 10 ppm vCF4.

[0042] Example 3 The difference from Example 1 is that: Nitrogen trifluoride crude gas containing 1.84% CF4, 1 ppmv HF, 1% H2O, 52.86% N2, and 44.3% NF3 was used as raw material, and the temperatures of the three-stage refrigeration equipment were controlled and stabilized at -15℃, -50℃, and -80℃, respectively. After cryogenic separation, the H2O and HF in the crude gas were reduced to 1 ppmv and 0.025 ppmv, respectively, with 99.99% moisture removal and 97.5% hydrogen fluoride removal. The outlet material of the refrigeration equipment was -80℃, 495 Nm³ / h. 3 The extractant C5H4F8O is fed into the extractive distillation unit at a flow rate of 10354 kg / h. The top temperature and pressure of the extractive distillation unit are -165℃ and 0.950 MPa, and the bottom temperature and pressure are -85℃ and 0.952 MPa. The volumetric reflux ratio controlled by the first reflux device is 7. The components in the distillate are 88.1% N2 and 3.06% CF4. The total flow rate is 300 Nm³. 3 The bottom of the extractive distillation unit contains a liquid mixture of extractant and nitrogen trifluoride, with a discharge flow rate of 10945.1 kg / h. The solvent recovery distillation unit has a top temperature of -88℃ and a pressure of 0.850 MPa, and a bottom temperature of -85℃ and a pressure of 0.851 MPa. The adsorption unit has a temperature of 25℃ and a pressure of 0.8 MPa. After adsorption purification, the electronic-grade nitrogen trifluoride product gas composition is 99.9992% NF3 and 6 ppmv CF4.

[0043] Example 4 The difference from Example 1 is that: Nitrogen trifluoride crude gas containing 2.81% CF4, 1 ppm vHF, 1% H2O, 62.39% N2, and 33.8% NF3 was used as raw material, and the temperatures of the three-stage refrigeration equipment were adjusted to -20℃, -60℃, and -90℃, respectively. After cryogenic separation, the impurities in the crude gas were 0.02 ppm vH2O and 0.01 ppm vHF, with 99.999% moisture and 99% hydrogen fluoride removed. The material after cryogenic separation entered the extractive distillation unit, accompanied by a feed of 10354 kg / h of C5H4F8O. The reflux ratio of the first reflux unit was adjusted to 10, while other parameters remained unchanged. The distillate composition at the top of the extractive distillation unit was 94.53% N2 and 4.25% CF4, with a total flow rate of 330 Nm³. 3 / h. After solvent recovery, the high-purity nitrogen trifluoride produced at the top of the solvent recovery distillation unit is fed into the adsorption unit. The temperature of the adsorption unit is 25℃ and the pressure is 0.8Mpa. After adsorption and purification, the electronic-grade nitrogen trifluoride product gas composition is 99.999% NF3 and 8ppmvCF4.

[0044] Comparative Example 1 The difference from Example 3 is that the cryogenic separation unit and cryogenic separation steps are omitted, and only a two-stage synergistic purification process of extractive distillation-adsorption purification is used to purify the crude nitrogen trifluoride gas. The crude gas, after being pre-cooled at -20℃, directly enters the extractive distillation unit. The top temperature of the extractive distillation unit is controlled at -165℃ and the pressure at 0.950 MPa, while the bottom temperature is -85℃ and the pressure at 0.952 MPa. The reflux volume ratio of the first reflux unit is 5. The light component content of the recovered (distillate) from the first reflux unit is 88.1% N2 and 3.06% CF4. The heavy components at the bottom enter the solvent recovery distillation unit. The top temperature of the solvent recovery distillation unit is -88℃ and the pressure is 0.850 MPa, while the bottom temperature is -85℃ and the pressure is 0.851 MPa. The bottom gas is transported to the reuse port of the extractive distillation unit through the solvent recovery pipeline. The nitrogen trifluoride product gas extracted from the top has the following composition: 93.2% NF3, 10 ppmv CF4, 0.06 ppmv HF, and 6000 ppmv H2O. As the device operates, moisture continuously accumulates in the circulating extractant, further increasing the moisture impurities in the crude nitrogen trifluoride product. Even after further purification by the adsorption unit, it is still difficult to reduce the moisture content to the electronic grade. This process cannot completely remove moisture from the crude gas, which has a significant impact on the purity of the product.

[0045] Comparative Example 2 Using the crude gas from Example 3 as raw material, a conventional low-temperature distillation process was employed for separation. A dual-tower distillation column for removing light components and a column for removing heavy components were set up. The top temperature of the light component removal column was -160°C and the pressure was 0.900 MPa, while the bottom temperature was -85°C and the pressure was 0.903 MPa. After pre-cooling, the material entered the light component removal column, where the light component N2 was collected at the top, and a mixture of CF4 and NF3 was enriched at the bottom. The top temperature of the heavy component removal column was -120°C and the pressure was 0.85 MPa, while the bottom temperature was -115°C and the pressure was 0.854 MPa. The liquid material from the bottom of the light component removal column entered the heavy component removal column, where NF3 was collected at the top and CF4 was enriched at the bottom. Analysis of the top material showed NF3: 99.993% and CF4: 68 ppmv. This product was used only as a low-purity product. Furthermore, since CF4 and NF3 have similar boiling points, the distillation column requires more than 120 theoretical trays, resulting in large equipment investment and high energy consumption.

[0046] Comparative Example 3 The difference from Example 1 is that the adsorption unit and adsorption purification steps are omitted, and only a two-stage purification process of cryogenic separation-extractive distillation is used to purify the crude nitrogen trifluoride gas. The crude gas undergoes three-stage cryogenic separation to remove 99.95% water and 94% hydrogen fluoride, with a feed flow rate of 500 Nm³. 3 The material is fed into a cryogenic separation unit at a temperature of 25°C and a pressure of 1 MPa for cryogenic separation. Then it enters an extractive distillation unit with an extractant C5H4F8O feed rate of 10354 kg / h. After separating the light components N2 and CF4 at the top of the extractive distillation unit, the bottom material enters a solvent recovery distillation unit. The product gas nitrogen trifluoride is directly collected from the top of the solvent recovery distillation unit, with the composition of 99.995% NF3 and 48 ppmv CF4.

[0047] This invention employs a three-stage synergistic process of cryogenic separation, extractive distillation, and adsorption for efficient and stable purification of crude nitrogen trifluoride gas. Compared to existing single or two-stage purification processes, it solves the problem of low separation efficiency for carbon tetrafluoride. The overall process is simple, scientifically sound, and the equipment is simple and compact. Both the extractant and refrigerant are fully utilized during the purification process, effectively avoiding energy waste. The final nitrogen trifluoride product gas exhibits a stable nitrogen trifluoride volume content of over 99.99%, preferably greater than 99.995%, while the carbon tetrafluoride volume content can be reduced to below 10 ppmv.

[0048] Although preferred embodiments of the invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including both the preferred embodiments and all changes and modifications falling within the scope of the invention. Clearly, those skilled in the art can make various alterations and modifications to the invention without departing from its spirit and scope. Thus, if these modifications and modifications of the invention fall within the scope of the claims and their equivalents, the invention is also intended to include these modifications and modifications.

Claims

1. A synergistic purification apparatus for nitrogen trifluoride, characterized in that, It includes a residual cold recycling unit, as well as a cryogenic separation unit, an extractive distillation unit, and an adsorption unit connected sequentially along the purification direction; The cryogenic separation unit comprises at least two refrigeration units connected in series with progressively decreasing temperatures; The extraction distillation unit includes an extraction distillation device and a solvent recovery distillation device. The feed line of the extraction distillation device is connected to the outlet of the refrigeration equipment with the lowest temperature, and the outlet line is connected to the feed line of the solvent recovery distillation device. The solvent recovery line of the solvent recovery distillation device is connected to the reuse port of the extraction distillation device. The adsorption unit is connected to the outlet of the solvent recovery distillation equipment via an inlet pipe; The residual cold recycling unit includes a refrigerant, a first cooling section, and a second cooling section. The first cooling section and the second cooling section are connected. The first cooling section exchanges heat with the extraction and distillation unit, and the second cooling section exchanges heat with the cryogenic separation unit. The refrigerant passes through the first cooling section and the second cooling section in sequence.

2. The co-purification apparatus as described in claim 1, characterized in that, The cryogenic separation unit satisfies at least one of the following: 1) The temperature of the cryogenic separation unit is 0~-90℃; 2) The cryogenic separation unit includes three refrigeration units connected in series with progressively decreasing temperatures. The temperatures of the three refrigeration units are 0~-20℃, -40~-60℃, and -70~-90℃, respectively. 3) The pressure of the refrigeration equipment is 0.95~1.50MPa.

3. The co-purification apparatus as described in claim 1, characterized in that, The extractive distillation unit satisfies at least one of the following: 1) The bottom of the extractive distillation equipment is equipped with a first reboiler, which heats the heavy components of the extractive distillation equipment and generates vapor reflux; 2) The solvent recovery distillation equipment is equipped with a second reboiler at the bottom. The second reboiler heats the heavy components of the solvent recovery distillation equipment and generates vapor reflux. 3) The extraction distillation equipment and / or solvent recovery distillation equipment are equipped with packed distillation columns, and the materials of the packed distillation columns are any one or more of nickel, stainless steel, and Monel.

4. The co-purification apparatus as described in claim 1, characterized in that, The extractive distillation unit also satisfies at least one of the following: 1) The top of the extractive distillation equipment is equipped with a first condenser and a first reflux condenser. The first condenser exchanges heat with the first cooling section. The first condenser cools the light component material of the extractive distillation equipment and refluxes it through the first reflux condenser. 2) The solvent recovery distillation equipment is equipped with a second condenser and a second reflux device at the top. The second condenser exchanges heat with the first cooling section. The second condenser cools the light component material of the solvent recovery distillation equipment and refluxes it into the adsorption unit through the second reflux device.

5. The co-purification apparatus as described in claim 1, characterized in that, The adsorption unit is filled with at least one of Zr-MOFs metal-organic framework material, phosphate-supported modified 5A molecular sieve, and carbon molecular sieve adsorbent.

6. The co-purification apparatus as described in claim 5, characterized in that, The adsorption unit is filled with Zr-MOFs metal-organic framework material, which is a metal-organic framework material with Zr as the central metal and oxalic acid as the organic ligand.

7. The co-purification apparatus as described in claim 6, characterized in that, Zr-MOFs metal-organic framework materials satisfy at least one of the following: 1) The material density is 2.35~2.81 g / cm³. 3 ; 2) Aperture is 6~6.5 Å; 3) Specific surface area is 1200~1300 m² 2 / g; 4) Porosity is 0.4~0.5; 5) The free volume of the pore is 0.2~0.25 cm³. 3 / g.

8. The co-purification apparatus as described in any one of claims 1 to 7, characterized in that, The extractive distillation unit also satisfies at least one of the following: 1) The internal pressure of the extractive distillation equipment is 0.9~1.0 MPa, the top temperature is -150~-170℃, and the bottom temperature is -80~-90℃; 2) The internal pressure of the solvent recovery distillation equipment is 0.8~0.9 MPa, the top temperature is -80~-90℃, and the bottom temperature is -75~-85℃.

9. A method for co-purification using the co-purification apparatus as described in any one of claims 1 to 8, characterized in that, Includes the following steps: S1. Cryogenic separation: The crude nitrogen trifluoride gas to be purified is passed into the cryogenic separation unit to remove heavy component impurities; S2, Extractive distillation: S2.1 The outlet gas after cryogenic separation enters the extractive distillation equipment through the feed pipeline, and at the same time, the extractant is introduced into the extractive distillation equipment; S2.2 The heavy components of the extractive distillation equipment enter the solvent recovery distillation equipment through the discharge pipeline; the extractant enriched in the solvent recovery distillation equipment flows back to the extractive distillation equipment along the solvent recovery pipeline; S2.3 The light component material of the solvent recovery distillation equipment enters the adsorption unit through the gas inlet pipeline; S3, Adsorption and Purification: The light component material entering the solvent recovery distillation equipment of the adsorption unit is purified to produce nitrogen trifluoride within the adsorption unit.

10. The synergistic purification method as described in claim 9, characterized in that, Meet at least one of the following: 1) By volume percentage, the crude nitrogen trifluoride gas consists of 25%~50% NF3, 45%~70% N2, 2%~4% CF4, 0.5~5 ppmv HF, and 1%~2% H2O; 2) The extractant is 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, and the feed volume ratio of the extractant to the crude nitrogen trifluoride gas is 0.5~2; 3) In the gas purified by adsorption in step S3, the volume content of nitrogen trifluoride is above 99.99%, and the volume content of carbon tetrafluoride is below 10 ppm.

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