Method and device for separating and refining nitrogen trifluoride and carbon tetrafluoride

Abstract

The invention relates to a method and a device for separating and refining nitrogen trifluoride and carbon tetrafluoride. The crude nitrogen trifluoride gas enters an adsorber in an adsorption state, an adsorbent selectively adsorbs carbon tetrafluoride, and a high-purity nitrogen trifluoride product is obtained at an outlet; meanwhile, hot inert gas is utilized to purge the adsorber in a desorption state, outlet regenerated gas enters a compressor after being cooled, and the regenerated gas enters a membrane separation assembly after being compressed; carbon tetrafluoride is used as permeation gas to permeate through the separation membrane, and residual waste gas is discharged to an incinerator. Main equipment comprises an adsorber in an adsorption state, an adsorber in a desorption state, a regeneration gas heater, a regeneration gas cooler, a compressor, a membrane separation assembly and the like. According to the method, nitrogen trifluoride and carbon tetrafluoride are separated through temperature swing and pressure swing adsorption, carbon tetrafluoride is efficiently and selectively adsorbed through the adsorbent to obtain the high-purity nitrogen trifluoride product, carbon tetrafluoride is separated and recycled through the membrane separation assembly, and the method has the advantages of being high in product purity and yield, low in cost and simple in process.

Description

TECHNICAL FIELD

[0001] The present application relates to a method and device for separating and purifying nitrogen trifluoride and carbon tetrafluoride, in particular to a nitrogen trifluoride and carbon tetrafluoride purification process with high product purity, high yield, low cost and simple process. BACKGROUND

[0002] Nitrogen trifluoride (NF3) is a colorless, odorless, non-toxic and non-combustible gas at normal temperature and pressure. NF3 has excellent etching rate and selectivity for silicon and tungsten, and can be used as a plasma etchant. It can also be used as a cleaning agent, which has the advantages of high cleaning rate and no trace left on the surface. NF3 can also be used as a fluorinating agent in electrochemical fluorination process to produce perfluorinated organic compounds and inorganic compounds. In addition, NF3 can also be used as an oxidizing agent for hydrogen fluoride laser and as an oxidizing agent and combustion aid in rocket launch.

[0003] Carbon tetrafluoride (CF4) is the main impurity in the production of NF3, and its concentration has an important influence on the etching process of NF3. If the concentration of CF4 impurity is too high, it will cause the etching line to widen, reduce the information storage capacity of the device, and seriously affect the quality of the semiconductor element. Moreover, the emission of CF4 will cause the greenhouse effect, it can exist stably in the atmosphere for a long time, and its greenhouse effect is thousands of times that of carbon dioxide, so its content must be strictly controlled. CF4 is also an electronic special gas, which can be used in the manufacture of semiconductor products such as integrated circuits and crystal diodes, used as an insulating medium in high-voltage switchgear such as circuit breakers and gas-insulated switch cabinets, and can also be used as a low-temperature coolant.

[0004] Currently, the main methods for producing NF3 in industry are electrolysis and chemical fluorination. Both methods require carbon materials as anodes. Due to the damage of carbon anodes during the preparation process, CF4 is inevitably introduced into the NF3 product. Therefore, regardless of which method is used, the generated NF3 will contain impurities such as CF4, and the content of impurities is about 5%. The separation methods used in industry mainly include deep cooling method, azeotropic distillation method and adsorption method.

[0005] CN116216666A reports a method for preparing high-purity nitrogen trifluoride. In a protective gas (nitrogen, argon, etc.), fluorine gas and ammonia gas are introduced in sequence to generate a mixture of HF, NF3 and protective gas. A custom adsorbent (polyacrylonitrile + alkali / alkaline earth metal fluoride) is used to adsorb and remove HF, and then NF3 is obtained by two-stage deep cooling condensation. This method requires maintaining a deep cooling medium at -150℃, which has high energy consumption; the product has high impurity content, more than 50 PPM, which is difficult to meet the quality requirements of high-end electronic special gas.

[0006] CN101258104B reports a method for purifying NF3. Liquid NF3 is boiled at 35-45 atm and -38 to -50℃, NF3 is selectively separated by using the difference in vaporization characteristics of CF4 and NF3, and inert gas is introduced in a bubbling manner to further increase the separation capacity of CF4 and NF3. This method requires maintaining a low temperature below -38℃, which consumes a lot of energy; 35-45 atm requires high sealing and pressure resistance of the equipment, which increases the safety risk and manufacturing cost; the waste gas from rectification stripping carries a large amount of NF3, and the yield is low.

[0007] CN105384153A reports a method for separating NF3 and CF4 by pressure swing adsorption, which selects a material that preferentially adsorbs NF3 compared to CF4 as the adsorbent, and NF3 is adsorbed by the adsorbent after the raw material gas is introduced into the adsorbent to reach a specified pressure, and the unadsorbed gas is discharged. Then the system is depressurized, and NF3 is regenerated from the adsorbent to obtain high-purity NF3 product. The adsorbent material in this process preferentially adsorbs NF3, resulting in a large amount of unadsorbed gas, which contains much more CF4 than the CF4 content in the raw material, making it difficult to further process, causing waste of raw material, and resulting in low yield of high-purity NF3 product.

[0008] In view of the problems of high impurity content, complex process, low yield, and difficulty in large-scale industrial production in the current nitrogen trifluoride refining process, the present application proposes a method and device for purifying NF3 by temperature swing adsorption and pressure swing adsorption based on CF4 preferentially adsorbing adsorbent material. This method does not require harsh conditions such as low temperature and high pressure, and has the advantages of high purity, high yield, low cost, and simple process. SUMMARY

[0009] In view of the deficiencies of the prior art, the present application proposes a method and device for separating and refining nitrogen trifluoride and carbon tetrafluoride. The method selects an adsorbent that preferentially adsorbs CF4, and through a temperature swing adsorption and pressure swing adsorption process, the temperature and pressure of the adsorption process are periodically changed to obtain high-purity carbon trifluoride; and four fluorides are recovered by using a separation membrane with high selectivity for permeating nitrogen tetrafluoride.

[0010] To achieve the above-mentioned purposes, the technical solutions of the present application are as follows:

[0011] A method for separating and refining nitrogen trifluoride and carbon tetrafluoride; comprising the following steps:

[0012] (1) Two adsorbers are configured, one in an adsorption state and the other in a regeneration state, and the states of the two adsorbers are switched in time sequence; a molecular sieve or metal-organic framework adsorbent is configured in the adsorber;

[0013] (2) Crude nitrogen trifluoride gas enters the adsorber in the adsorption state, where the adsorbent selectively adsorbs carbon tetrafluoride; high-purity nitrogen trifluoride product is obtained at the outlet of the adsorber.

[0014] (3) While crude nitrogen trifluoride gas enters the adsorber in the adsorption state, the adsorber bed in the regeneration state is purged with a hot inert atmosphere to desorb the carbon tetrafluoride adsorbed in the adsorber bed in the regeneration state, thus completing the regeneration of the adsorber in the regeneration state.

[0015] (4) The regenerated gas discharged from the adsorber in the regeneration state enters the cooler for cooling, and after cooling, it enters the compressor. After compression, the regenerated gas enters the membrane separation module. In the membrane separation module, carbon tetrafluoride is used as permeate gas to pass through the separation membrane to obtain high-purity carbon tetrafluoride product. The residual waste gas is discharged to the incinerator for incineration.

[0016] The adsorbent material used is a molecular sieve or a metal-organic framework material, including one or more of the following: mordenite molecular sieve, ZSM-5 molecular sieve, JUCXEK metal-organic framework material, ECUDOX metal-organic framework material, OXUPUT metal-organic framework material, and NIBXUT metal-organic framework material; the materials used are modified based on the above-mentioned mordenite molecular sieve, ZSM-5 molecular sieve, JUCXEK metal-organic framework material, ECUDOX metal-organic framework material, OXUPUT metal-organic framework material, or NIBXUT metal-organic framework material.

[0017] The method for separating and purifying nitrogen trifluoride and carbon tetrafluoride is described above; the adsorption temperature of the adsorber in the adsorption state is 25~80℃, and the adsorption pressure is 0.5~10 barG.

[0018] The method for separating and purifying nitrogen trifluoride and carbon tetrafluoride, wherein the inert gas in the regenerated adsorber is heated to a temperature of 80~200℃.

[0019] The method for separating and purifying nitrogen trifluoride and carbon tetrafluoride is described above; the pressure of the adsorber bed in the regenerated state is -0.75~0 barG.

[0020] The method for separating and purifying nitrogen trifluoride and carbon tetrafluoride, wherein the inert atmosphere is one of nitrogen, methane, ethane, and propane, and the inert atmosphere flow rate is 5% to 20% of the crude nitrogen trifluoride feed rate.

[0021] The method for separating and purifying nitrogen trifluoride and carbon tetrafluoride; in step (4), the regenerated gas is cooled to 25~50℃ before entering the compressor; the compressor inlet pressure is -0.75~0 barG, the outlet pressure is 1~5 barG; the membrane module permeate pressure is -0.5~2 barG, and the permeate side pressure is 1~5 barG.

[0022] The method for separating and purifying nitrogen trifluoride and carbon tetrafluoride; in step (5), the membrane material is in the form of an organic membrane, an inorganic membrane, or an organic-inorganic composite membrane.

[0023] This invention provides a nitrogen trifluoride and carbon tetrafluoride separation and purification apparatus, comprising an adsorber in an adsorption state, an adsorber in a regeneration state, a regeneration gas heater, a regeneration gas cooler, a regeneration gas compressor, a membrane separation assembly, a compressor reflux control valve, and related feed and discharge valves. The crude nitrogen trifluoride feed line is divided into two branches, connected to the feed valve of the adsorber in the adsorption state and the feed valve of the adsorber in the regeneration state, respectively. The outlet line of the adsorber feed valve in the adsorption state is divided into two branches, connected to the adsorber in the adsorption state and the regeneration gas outlet valve of the adsorber in the adsorption state, respectively. The outlet line of the adsorber in the regeneration state is divided into two branches, connected to the adsorber in the regeneration state and the regeneration gas outlet valve of the adsorber in the regeneration state, respectively. The outlet of the adsorber in the adsorption state is divided into two branches, connected to the regeneration gas inlet valve and the discharge valve of the adsorber in the adsorption state, respectively. The adsorber outlet in the regeneration state is divided into two branches, which are connected to the adsorber discharge valve and the adsorber regeneration inlet gas valve respectively. The adsorber regeneration gas outlet valve in the adsorption state is divided into two branches, which are connected to the adsorber regeneration gas outlet valve and the cooler respectively. The adsorber regeneration gas outlet valve in the regeneration state is divided into two branches, which are connected to the adsorber regeneration gas outlet valve and the cooler respectively. The regeneration gas feed is connected to the heater feed. The heater outlet is divided into two branches, which are connected to the adsorber regeneration gas inlet valve and the adsorber regeneration inlet gas valve respectively. The cooler outlet is divided into two branches, which are connected to the compressor inlet and the compressor reflux control valve respectively. The compressor outlet is connected to the membrane module inlet. The permeate side of the membrane module is connected to the purified carbon tetrafluoride pipeline. The residual permeate side of the membrane module is divided into two branches, which are connected to the compressor reflux control valve and the exhaust gas pipeline respectively.

[0024] This invention employs, as follows Figure 1The apparatus shown for separating and purifying nitrogen trifluoride and carbon tetrafluoride includes: an adsorber 1 in an adsorption state, an adsorber 2 in a regeneration state, a regeneration gas heater 3, a regeneration gas cooler 4, a regeneration gas compressor 5, a membrane separation assembly 6, a compressor reflux control valve 7, a feed switch valve for adsorber 1 in the adsorption state 8, a feed switch valve for adsorber 2 in the regeneration state 9, a regeneration gas outlet switch valve for adsorber 1 in the adsorption state 10, a regeneration gas outlet switch valve for adsorber 2 in the regeneration state 11, a regeneration gas inlet switch valve for adsorber 1 in the adsorption state 12, a discharge switch valve for adsorber 1 in the adsorption state 13, a discharge switch valve for adsorber 2 in the regeneration state 14, and a regeneration gas inlet switch valve for adsorber 2 in the regeneration state 15.

[0025] The crude nitrogen trifluoride feed line is divided into two branches, connected to feed valve 8 of adsorber 1 in adsorption state and feed valve 9 of adsorber 2 in regeneration state, respectively. The outlet line of feed valve 8 of adsorber 1 in adsorption state is divided into two branches, connected to adsorber 1 in adsorption state and regeneration gas outlet valve 10 of adsorber 1 in adsorption state, respectively. The outlet line of feed valve 9 of adsorber 2 in regeneration state is divided into two branches, connected to adsorber 2 in regeneration state and regeneration gas outlet valve 11 of adsorber 2 in regeneration state, respectively. The outlet of adsorber 1 in adsorption state is divided into two branches, connected to regeneration gas inlet valve 12 and adsorption discharge valve 13 of adsorber 1 in adsorption state, respectively. The outlet of adsorber 2 in regeneration state is divided into two branches, connected to adsorption discharge valve 14 and regeneration inlet valve 14 of adsorber 2 in regeneration state, respectively. Valve 15 is connected; the outlet of the regeneration gas outlet switch valve 10 of the adsorber 1 in the adsorption state is divided into two branches, which are respectively connected to the regeneration gas outlet switch valve 11 of the adsorber 2 in the regeneration state and the cooler 4; the outlet of the regeneration gas outlet switch valve 11 of the adsorber 2 in the regeneration state is divided into two branches, which are respectively connected to the regeneration gas outlet switch valve 10 of the adsorber 1 in the adsorption state and the cooler 4; the regeneration gas feed is connected to the feed of the heater 3; the outlet of the heater 3 is divided into two branches, which are respectively connected to the regeneration gas inlet switch valve 12 of the adsorber 1 in the adsorption state and the regeneration gas inlet switch valve 15 of the adsorber 2 in the regeneration state; the outlet of the cooler 4 is divided into two branches, which are respectively connected to the inlet of the compressor 5 and the compressor reflux control valve 7; the outlet of the compressor 5 is connected to the inlet of the membrane module 6; the permeate side of the membrane module 6 is connected to the purified carbon tetrafluoride; the residual permeate side of the membrane module 6 is divided into two branches, which are respectively connected to the compressor reflux control valve 7 and the waste gas pipeline.

[0026] The process includes the following:

[0027] (1) Provide a material that preferentially adsorbs carbon tetrafluoride as an adsorbent. The adsorbent material is a molecular sieve or a metal-organic framework material. The adsorbent material includes one or more of the following: mordenite molecular sieve, ZSM-5 molecular sieve, JUCXEK metal-organic framework material, ECUDOX metal-organic framework material, OXUPUT metal-organic framework material, and NIBXUT metal-organic framework material; or a modified material based on the above materials.

[0028] (2) Configure two adsorbers, namely adsorber 1 in the adsorption state and adsorber 2 in the regeneration state, and switch the state of the two adsorbers according to the time sequence.

[0029] (3) Open the feed valve 8 of the adsorber 1 in the adsorption state, close the feed valve 9 of the adsorber 2 in the regeneration state, and close the regeneration gas outlet valve 10 of the adsorber 1 in the adsorption state. Crude nitrogen trifluoride gas enters the adsorber 1 in the adsorption state, where the adsorbent selectively adsorbs carbon tetrafluoride. Close the regeneration gas inlet valve 12 of the adsorber 1 in the adsorption state, and open the outlet valve 13 of the adsorber 1 in the adsorption state. High-purity nitrogen trifluoride product is obtained at the outlet of the adsorber 1 in the adsorption state.

[0030] (4) While crude nitrogen trifluoride gas enters the adsorber in the adsorption state, open the regeneration gas outlet valve 11 of the adsorber 2 in the regeneration state and close the discharge valve 14 of the adsorber 2 in the regeneration state to reduce the pressure of the adsorber 2 in the regeneration state. Open the regeneration inlet valve 15 of the adsorber 2 in the regeneration state and use hot inert gas to purge the bed of the adsorber 2 in the regeneration state to desorb the carbon tetrafluoride adsorbed in the bed of the adsorber 2 in the regeneration state, thus completing the regeneration of the adsorber 2 in the regeneration state.

[0031] (5) The regenerated gas discharged from the adsorber 2 in the regeneration state enters the cooler 4 for cooling, and then enters the compressor 5. After compression, the regenerated gas enters the membrane separation module 6. In the membrane separation module 6, carbon tetrafluoride is used as permeate gas to pass through the separation membrane to obtain high-purity carbon tetrafluoride product. The residual waste gas is discharged to the incinerator for incineration. The compressor inlet pressure is controlled by the compressor reflux control valve 7.

[0032] The crude nitrogen trifluoride feed gas comes from the NF3 synthesis section and has undergone preliminary purification. The feed valve 8 of adsorber 1 in adsorption mode is opened, the feed valve 9 of adsorber 2 in regeneration mode is closed, and the regeneration gas outlet valve 10 of adsorber 1 in adsorption mode is closed. The crude nitrogen trifluoride gas enters adsorber 1 in adsorption mode, where the adsorbent selectively adsorbs carbon tetrafluoride. The regeneration gas inlet valve 12 of adsorber 1 in adsorption mode is closed, and the outlet valve 13 of adsorber 1 in adsorption mode is opened. High-purity nitrogen trifluoride product is obtained at the outlet of adsorber 1 in adsorption mode.

[0033] While crude nitrogen trifluoride gas enters the adsorber in the adsorption state, the regeneration gas outlet valve 11 of the adsorber 2 in the regeneration state is opened, and the discharge valve 14 of the adsorber 2 in the regeneration state is closed to reduce the pressure of the adsorber 2 in the regeneration state. The regeneration inlet valve 15 of the adsorber 2 in the regeneration state is opened to purge the bed of the adsorber 2 in the regeneration state with hot inert gas, desorbing the carbon tetrafluoride adsorbed in the bed of the adsorber 2 in the regeneration state, thus completing the regeneration of the adsorber 2 in the regeneration state.

[0034] The regenerated gas discharged from the adsorber 2 during the regeneration process enters the cooler 4 for cooling, and then enters the compressor 5. After compression, the regenerated gas enters the membrane separation module 6. Inside the membrane separation module 6, carbon tetrafluoride permeates through the separation membrane as permeate gas to obtain high-purity carbon tetrafluoride product. The residual permeate is discharged to the incinerator for combustion. The compressor is equipped with a return line, and the inlet and outlet pressures of the compressor are stabilized by adjusting the return line circulation volume.

[0035] The feed valve 8 of adsorber 1 in the adsorption state, the feed valve 9 of adsorber 2 in the regeneration state, the regeneration gas outlet valve 10 of adsorber 1 in the adsorption state, the regeneration gas outlet valve 11 of adsorber 2 in the regeneration state, the regeneration gas inlet valve 12 of adsorber 1 in the adsorption state, the discharge valve 13 of adsorber 1 in the adsorption state, the discharge valve 14 of adsorber 2 in the regeneration state, and the regeneration gas inlet valve 15 of adsorber 2 in the regeneration state are all track ball valves, and are controlled by an automated program.

[0036] Based on the above scheme, the impurity content of the refined NF3 product produced by this invention is <10 ppm, and the yield is ≥92.5%.

[0037] The technical advantages and beneficial effects of this invention are as follows:

[0038] Compared to other methods for preparing high-purity NF3 using adsorption, the greatest advantage of this invention is the use of a unique material that preferentially adsorbs CF4 as the adsorbent, overcoming the problems of large waste gas volume and low yield associated with traditional methods that preferentially adsorb NF3. Furthermore, a variable temperature and pressure method is employed to regenerate the adsorbent, significantly improving the regeneration efficiency and reducing the regeneration gas flow rate. A membrane separation unit is used to recover the regenerated CF4, allowing for the simultaneous production of both high-purity NF3 and CF4 products. The refined NF3 product produced by this method has an impurity purity of <10 ppm, an NF3 yield ≥92.5%, and advantages such as simple process, low energy consumption, low equipment investment, and easy scalability. Attached Figure Description

[0039] Figure 1 An apparatus for the separation and purification of nitrogen trifluoride and carbon tetrafluoride.

[0040] The diagram shows: 1. Adsorber in adsorption state; 2. Adsorber in regeneration state; 3. Regeneration gas heater; 4. Regeneration gas cooler; 5. Regeneration gas compressor; 6. Membrane separation assembly; 7. Compressor reflux control valve; 8. Feed valve for adsorber 1 in adsorption state; 9. Feed valve for adsorber 2 in regeneration state; 10. Regeneration gas outlet valve for adsorber 1 in adsorption state; 11. Regeneration gas outlet valve for adsorber 2 in regeneration state; 12. Regeneration gas inlet valve for adsorber 1 in adsorption state; 13. Discharge valve for adsorber 1 in adsorption state; 14. Discharge valve for adsorber 2 in regeneration state; 15. Regeneration gas inlet valve for adsorber 2 in regeneration state. Detailed Implementation

[0041] Specific embodiments of the present invention Figure 1 Further description, but the scope of the invention is not limited thereto. The crude NF3 feedstock from the synthesis section enters the adsorber 1 in an adsorption state. In the adsorber 1, the adsorbent selectively adsorbs CF4, and high-purity NF3 product is obtained at the outlet of the adsorber 1. Simultaneously with adsorption in the adsorber, inert regeneration gas enters the heater 3, and after heating, enters the adsorber 2 in a regeneration state to regenerate the adsorbed CF4. The regeneration gas at the outlet of the adsorber 2 in a regeneration state is cooled and enters the cooler 4, then enters the compressor 5. After being pressurized by the compressor, it enters the membrane separation module 6. In the membrane separation module, CF4 permeates through the separation membrane as permeate gas, and the residual waste gas is discharged to the incinerator for incineration. A return line is set to regulate the circulation volume and stabilize the compressor inlet and outlet pressures. The above process requires the use of switching valves, and the states of each switching valve are as follows:

[0042] (1) When adsorber 1 is in the adsorption state and adsorber 2 is in the regeneration state

[0043] The following valves are in the open state: the adsorber feed valve 8 in the adsorption state, the adsorber regeneration gas outlet valve 11 in the regeneration state, the adsorber discharge valve 13 in the adsorption state, and the adsorber regeneration inlet valve 15 in the regeneration state; the adsorber feed valve 9 in the regeneration state, the adsorber regeneration gas outlet valve 10 in the adsorption state, the adsorber regeneration gas inlet valve 12 in the adsorption state, and the adsorber discharge valve 14 in the regeneration state.

[0044] (2) When adsorber 1 is in the regeneration state and adsorber 2 is in the adsorption state

[0045] The adsorber feed valve 8 (in adsorption state), the adsorber regeneration gas outlet valve 11 (in regeneration state), the adsorber discharge valve 13 (in adsorption state), and the adsorber regeneration inlet valve 15 (in regeneration state) are in the closed state; the adsorber feed valve 9 (in regeneration state), the adsorber regeneration gas outlet valve 10 (in adsorption state), the adsorber regeneration gas inlet valve 12 (in adsorption state), and the adsorber discharge valve 14 (in regeneration state) are in the open state.

[0046] Example 1:

[0047] In this embodiment, the NF3 feed gas comes from the NF3 synthesis section and undergoes preliminary purification, with a CF4 impurity content of 5% and a flow rate of 1150 kg / h. The adsorbent is JUCXEK metal-organic framework material.

[0048] Open the feed valve 8 of adsorber 1 in adsorption mode, close the feed valve 9 of adsorber 2 in regeneration mode, and close the regeneration gas outlet valve 10 of adsorber 1 in adsorption mode. Crude nitrogen trifluoride gas enters adsorber 1 in adsorption mode, where the adsorbent selectively adsorbs carbon tetrafluoride. Close the regeneration gas inlet valve 12 of adsorber 1 in adsorption mode, and open the outlet valve 13 of adsorber 1 in adsorption mode. High-purity nitrogen trifluoride product is obtained at the outlet of adsorber 1 in adsorption mode. The adsorption pressure of adsorber 1 in adsorption mode is 0.5 barG, and the adsorption temperature is 25℃.

[0049] While crude nitrogen trifluoride gas enters the adsorber in the adsorption state, the regeneration gas outlet valve 11 of the adsorber 2 in the regeneration state is opened, and the discharge valve 14 of the adsorber 2 in the regeneration state is closed, reducing the pressure of the adsorber 2 in the regeneration state to -0.75 barG. The regeneration inlet valve 15 of the adsorber 2 in the regeneration state is opened, and inert gas heated to 200°C is used to purge the bed of the adsorber 2 in the regeneration state, desorbing the carbon tetrafluoride adsorbed in the bed of the adsorber 2 in the regeneration state, thus completing the regeneration of the adsorber 2 in the regeneration state. The inert regeneration gas is nitrogen, and the flow rate is 5% of the feed gas.

[0050] The regenerated gas discharged from the adsorber 2 in the regeneration state enters the cooler 4 for cooling. After being cooled to 40°C, it enters the compressor 5. The regenerated gas is then compressed to 4 barG and enters the membrane separation unit 6. Inside the membrane separation unit 6, carbon tetrafluoride is used as permeate gas and passes through the separation membrane to obtain high-purity carbon tetrafluoride product. The permeate side pressure is -0.5 barG. The residual permeate gas is discharged to the incinerator for combustion, with a residual side pressure of 4 barG. The compressor is equipped with a return line. The compressor inlet and outlet pressures are stabilized by adjusting the return line circulation volume, which is 50% of the regeneration gas flow rate.

[0051] The feed valve 8 of adsorber 1 in the adsorption state, the feed valve 9 of adsorber 2 in the regeneration state, the regeneration gas outlet valve 10 of adsorber 1 in the adsorption state, the regeneration gas outlet valve 11 of adsorber 2 in the regeneration state, the regeneration gas inlet valve 12 of adsorber 1 in the adsorption state, the discharge valve 13 of adsorber 1 in the adsorption state, the discharge valve 14 of adsorber 2 in the regeneration state, and the regeneration gas inlet valve 15 of adsorber 2 in the regeneration state are all track ball valves, which are automatically controlled by a program. The switching time of the adsorber is 24 hours.

[0052] In this embodiment, the impurity content of the NF3 product was 8 ppm, and the yield was 94%.

[0053] Example 2:

[0054] In this embodiment, the NF3 feed gas comes from the NF3 synthesis section and undergoes preliminary purification, with a CF4 impurity content of 5.5% and a flow rate of 1000 kg / h. The adsorbent is a composite material of JUCXEK metal-organic framework and mordenite molecular sieve.

[0055] Open the feed valve 8 of adsorber 1 in adsorption mode, close the feed valve 9 of adsorber 2 in regeneration mode, and close the regeneration gas outlet valve 10 of adsorber 1 in adsorption mode. Crude nitrogen trifluoride gas enters adsorber 1 in adsorption mode, where the adsorbent selectively adsorbs carbon tetrafluoride. Close the regeneration gas inlet valve 12 of adsorber 1 in adsorption mode, and open the outlet valve 13 of adsorber 1 in adsorption mode. High-purity nitrogen trifluoride product is obtained at the outlet of adsorber 1 in adsorption mode. The adsorption pressure of adsorber 1 in adsorption mode is 5 barG, and the adsorption temperature is 80℃.

[0056] While crude nitrogen trifluoride gas enters the adsorber in the adsorption state, the regeneration gas outlet valve 11 of the adsorber 2 in the regeneration state is opened, and the discharge valve 14 of the adsorber 2 in the regeneration state is closed, reducing the pressure of the adsorber 2 in the regeneration state to 0 barG. The regeneration inlet valve 15 of the adsorber 2 in the regeneration state is opened, and inert gas heated to 80°C is used to purge the bed of the adsorber 2 in the regeneration state, desorbing the carbon tetrafluoride adsorbed in the bed of the adsorber 2 in the regeneration state, thus completing the regeneration of the adsorber 2 in the regeneration state. The inert regeneration gas is methane, and the flow rate is 20% of the feed gas.

[0057] The regenerated gas discharged from the adsorber 2 in the regeneration state enters the cooler 4 for cooling. After being cooled to 50°C, the gas enters the compressor 5, where it is compressed to 1 barG and then enters the membrane separation unit 6. Inside the membrane separation unit 6, carbon tetrafluoride permeates through the separation membrane as permeate gas to obtain high-purity carbon tetrafluoride product; the permeate-side pressure is 0 barG. The residual permeate gas is discharged to the incinerator for combustion; the residual permeate-side pressure is 1 barG. The compressor is equipped with a return line, and the compressor inlet and outlet pressures are stabilized by adjusting the return line circulation rate, which is 55% of the regeneration gas flow rate.

[0058] The feed valve 8 of adsorber 1 in the adsorption state, the feed valve 9 of adsorber 2 in the regeneration state, the regeneration gas outlet valve 10 of adsorber 1 in the adsorption state, the regeneration gas outlet valve 11 of adsorber 2 in the regeneration state, the regeneration gas inlet valve 12 of adsorber 1 in the adsorption state, the discharge valve 13 of adsorber 1 in the adsorption state, the discharge valve 14 of adsorber 2 in the regeneration state, and the regeneration gas inlet valve 15 of adsorber 2 in the regeneration state are all track ball valves, which are automatically controlled by a program. The switching time of the adsorber is 24 hours.

[0059] In this embodiment, the impurity content of the NF3 product was 7 ppm, and the yield was 93.5%.

[0060] Example 3:

[0061] In this embodiment, the NF3 feed gas comes from the NF3 synthesis section and undergoes preliminary purification, with a CF4 impurity content of 4.5% and a flow rate of 1500 kg / h. The adsorbent is a composite material of ECUDOX metal-organic framework and mordenite molecular sieve.

[0062] Open the feed valve 8 of adsorber 1 in adsorption mode, close the feed valve 9 of adsorber 2 in regeneration mode, and close the regeneration gas outlet valve 10 of adsorber 1 in adsorption mode. Crude nitrogen trifluoride gas enters adsorber 1 in adsorption mode, where the adsorbent selectively adsorbs carbon tetrafluoride. Close the regeneration gas inlet valve 12 of adsorber 1 in adsorption mode, and open the outlet valve 13 of adsorber 1 in adsorption mode. High-purity nitrogen trifluoride product is obtained at the outlet of adsorber 1 in adsorption mode. The adsorption pressure of adsorber 1 in adsorption mode is 10 barG, and the adsorption temperature is 45℃.

[0063] While crude nitrogen trifluoride gas enters the adsorber in the adsorption state, the regeneration gas outlet valve 11 of the adsorber 2 in the regeneration state is opened, and the discharge valve 14 of the adsorber 2 in the regeneration state is closed, reducing the pressure of the adsorber 2 in the regeneration state to -0.3 barG. The regeneration inlet valve 15 of the adsorber 2 in the regeneration state is opened, and inert gas heated to 120°C is used to purge the bed of the adsorber 2 in the regeneration state, desorbing the carbon tetrafluoride adsorbed in the bed of the adsorber 2 in the regeneration state, thus completing the regeneration of the adsorber 2 in the regeneration state. The inert regeneration gas is ethane, and the flow rate is 15% of the feed gas.

[0064] The regenerated gas discharged from the adsorber 2 in the regeneration state enters the cooler 4 for cooling. After being cooled to 25°C, it enters the compressor 5. The regenerated gas is compressed to 5 barG and then enters the membrane separation unit 6. Inside the membrane separation unit 6, carbon tetrafluoride is used as permeate gas and passes through the separation membrane to obtain high-purity carbon tetrafluoride product. The permeate side pressure is 2 barG. The residual permeate gas is discharged to the incinerator for combustion. The residual permeate side pressure is 5 barG. The compressor is equipped with a return line. The compressor inlet and outlet pressures are stabilized by adjusting the return line circulation volume. The circulation volume is 30% of the regenerated gas flow rate.

[0065] The feed valve 8 of adsorber 1 in the adsorption state, the feed valve 9 of adsorber 2 in the regeneration state, the regeneration gas outlet valve 10 of adsorber 1 in the adsorption state, the regeneration gas outlet valve 11 of adsorber 2 in the regeneration state, the regeneration gas inlet valve 12 of adsorber 1 in the adsorption state, the discharge valve 13 of adsorber 1 in the adsorption state, the discharge valve 14 of adsorber 2 in the regeneration state, and the regeneration gas inlet valve 15 of adsorber 2 in the regeneration state are all track ball valves, which are automatically controlled by a program. The switching time of the adsorber is 24 hours.

[0066] In this embodiment, the impurity content of the NF3 product was 6 ppm, and the yield was 94.5%.

[0067] The technical solutions disclosed and proposed in this invention can be implemented by those skilled in the art by appropriately modifying the conditions and routes, etc. Although the methods and preparation techniques of this invention have been described through preferred embodiments, those skilled in the art can obviously modify or recombine the methods and technical routes described herein without departing from the content, spirit, and scope of this invention to achieve the final preparation technique. It should be particularly noted that all similar substitutions and modifications are obvious to those skilled in the art and are considered to be included within the spirit, scope, and content of this invention.

Claims

1. A method for separating and purifying nitrogen trifluoride and carbon tetrafluoride; characterized in that, Includes the following steps: (1) Configure two adsorbers, one in the adsorption state and the other in the regeneration state, and switch the state of the two adsorbers in sequence; the adsorbers are equipped with molecular sieves or metal-organic framework materials as adsorbents. (2) Crude nitrogen trifluoride gas enters the adsorber in the adsorption state, where the adsorbent selectively adsorbs carbon tetrafluoride; high-purity nitrogen trifluoride product is obtained at the outlet of the adsorber. (3) While crude nitrogen trifluoride gas enters the adsorber in the adsorption state, the adsorber bed in the regeneration state is purged with a hot inert atmosphere to desorb the carbon tetrafluoride adsorbed in the adsorber bed in the regeneration state, thus completing the regeneration of the adsorber in the regeneration state. (4) The regenerated gas discharged from the adsorber in the regeneration state enters the cooler for cooling, and after cooling, it enters the compressor. After compression, the regenerated gas enters the membrane separation module. In the membrane separation module, carbon tetrafluoride is used as permeate gas to pass through the separation membrane to obtain high-purity carbon tetrafluoride product. The residual waste gas is discharged to the incinerator for incineration.

2. The method for separating and purifying nitrogen trifluoride and carbon tetrafluoride as described in claim 1; characterized in that, The adsorbent material used is a molecular sieve or a metal-organic framework material, including one or more of the following: mordenite molecular sieve, ZSM-5 molecular sieve, JUCXEK metal-organic framework material, ECUDOX metal-organic framework material, OXUPUT metal-organic framework material, and NIBXUT metal-organic framework material; the materials used are modified based on the above-mentioned mordenite molecular sieve, ZSM-5 molecular sieve, JUCXEK metal-organic framework material, ECUDOX metal-organic framework material, OXUPUT metal-organic framework material, or NIBXUT metal-organic framework material.

3. The method for separating and purifying nitrogen trifluoride and carbon tetrafluoride as described in claim 1; characterized in that, The adsorption temperature of the adsorber in the adsorption state is 25~80℃, and the adsorption pressure is 0.5~10 barG.

4. The method for separating and purifying nitrogen trifluoride and carbon tetrafluoride as described in claim 1; characterized in that, The temperature of the inert gas in the regenerated adsorber is 80~200℃ after being heated.

5. The method for separating and purifying nitrogen trifluoride and carbon tetrafluoride as described in claim 1; characterized in that, The pressure of the adsorber bed in the regenerated state is -0.75~0 barG.

6. The method for separating and purifying nitrogen trifluoride and carbon tetrafluoride as described in claim 1; characterized in that, The inert atmosphere is one of nitrogen, methane, ethane, or propane, and the inert atmosphere flow rate is 5% to 20% of the crude nitrogen trifluoride feed rate.

7. The method for separating and purifying nitrogen trifluoride and carbon tetrafluoride as described in claim 1; characterized in that, In step (4), the regenerated gas is cooled to 25~50℃ before entering the compressor; the compressor inlet pressure is -0.75~0 barG and the outlet pressure is 1~5 barG; the membrane module permeate pressure is -0.5~2 barG and the permeate side pressure is 1~5 barG.

8. The method for separating and purifying nitrogen trifluoride and carbon tetrafluoride as described in claim 1; characterized in that, In step (5), the membrane material is in the form of an organic membrane, an inorganic membrane, or an organic-inorganic composite membrane.

9. A device for separating and purifying nitrogen trifluoride and carbon tetrafluoride, characterized in that, This includes an adsorber in the adsorption state, an adsorber in the regeneration state, a regeneration gas heater, a regeneration gas cooler, a regeneration gas compressor, a membrane separation unit, a compressor reflux control valve, and related feed and discharge valves; the crude nitrogen trifluoride feed line is divided into two branches, connected to the feed valves of the adsorber in the adsorption state and the adsorber in the regeneration state, respectively; the outlet line of the adsorber in the adsorption state feed valve is divided into two branches, connected to the adsorber in the adsorption state and the adsorber in the adsorption state regeneration gas outlet valve, respectively; the outlet line of the adsorber in the regeneration state feed valve is divided into two branches, connected to the adsorber in the regeneration state and the adsorber in the regeneration state regeneration gas outlet valve, respectively; the adsorber outlet in the adsorption state is divided into two branches, connected to the adsorber in the adsorption state regeneration gas inlet valve and the adsorber in the adsorption state discharge valve, respectively; the adsorber outlet in the regeneration state... Two valves are connected to the absorber discharge valve and the absorber regeneration inlet valve, respectively, in the regeneration state. The absorber regeneration outlet valve in the adsorption state is divided into two branches, which are connected to the absorber regeneration outlet valve and the cooler, respectively. The absorber regeneration outlet valve in the regeneration state is divided into two branches, which are connected to the absorber regeneration outlet valve and the cooler, respectively. The regeneration gas feed is connected to the heater feed. The heater outlet is divided into two branches, which are connected to the absorber regeneration inlet valve and the absorber regeneration inlet valve, respectively, in the adsorption state. The cooler outlet is divided into two branches, which are connected to the compressor inlet and the compressor reflux control valve, respectively. The compressor outlet is connected to the membrane module inlet. The membrane module permeate side is connected to the purified carbon tetrafluoride pipeline. The membrane module residual side is divided into two branches, which are connected to the compressor reflux control valve and the exhaust gas pipeline, respectively.

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