A method of manufacturing a hollow fiber membrane separator and a method for separating sulfur hexafluoride and nitrogen

Abstract

The application discloses a preparation method of a hollow fiber membrane separator and a method for separating sulfur hexafluoride and nitrogen, and belongs to the field of sulfur hexafluoride purification, and comprises the following steps: (1) a hollow fiber membrane precursor is prepared through a nonsolvent phase inversion method, comprising the steps of preparing a casting solution, spinning, solidification molding and the like, and the precursor is dried and then sintered at high temperature to obtain a hollow fiber membrane filament; (2) a plurality of hollow fiber membrane filament assemblies are packaged, and two end tube-side feed and discharge side heads are additionally arranged to obtain a hollow fiber membrane separator; (3) SF6 and N2 mixed gas is introduced from a tube-side inlet of the hollow fiber membrane separator, SF6 gas flows along the tube-side, N2 is discharged to a shell-side through holes on the hollow fiber membrane in the tube-side, SF6-rich retentate gas is discharged from a high-pressure side of the tube-side, N2-rich permeate gas is discharged from a low-pressure side of the shell-side, the SF6-rich retentate gas is separated again through a secondary hollow fiber membrane separator, and finally, the content of sulfur hexafluoride is more than 99.9%, and the content of nitrogen is less than 0.1%.

Description

Technical Field

[0001] This invention belongs to the field of sulfur hexafluoride purification, and particularly relates to a method for preparing a hollow fiber membrane separator and a method for separating sulfur hexafluoride and nitrogen. Background Technology

[0002] Sulfur hexafluoride (SF6) possesses excellent electrical insulation and arc-quenching properties, and is primarily used in electrical power, microelectronics, aerospace, and medical research. Due to its high thermal stability, it does not decompose even at temperatures above 500℃. At normal pressure, SF6's insulation capacity is 2.5 times that of air, and its arc-quenching capacity is equivalent to 100 times that of air. When used as an electrical insulating gas, SF6 is typically mixed with a certain amount of nitrogen. Separating the nitrogen from SF6 and purifying it into high-purity SF6 can reduce greenhouse gas emissions from SF6, making it an important method for recycling SF6 and increasing its reuse cycles.

[0003] There are generally three methods for separating sulfur hexafluoride (SF6) and nitrogen. The first method relies on traditional adsorption and distillation processes to remove nitrogen, but adsorption and distillation require a lot of equipment, are complex, and are difficult to operate. The second method uses physical methods to pressurize and liquefy SF6 to separate nitrogen, but this requires a large amount of cooling capacity, has high energy consumption, is uneconomical, poses safety risks due to low temperature and high pressure, and results in excessively high equipment costs. The third method uses membrane separation to separate SF6 and nitrogen (publication number CN). Patent specification 115569490A discloses a method and apparatus for online purification of sulfur hexafluoride (SF6) using inorganic molecular sieve membranes. SF6 is obtained through pretreatment and single-stage or multi-stage membrane separation. However, the inorganic membranes used are selected from commercially available mature membrane separation devices such as SSZ-13, DDR, and LTA. While these molecular sieve membranes are stable, their separation effect is generally poor, and the internal membrane components are brittle and easily damaged. Using only these membrane separation devices makes it difficult to achieve the required purity of SF6, limiting their application scope and operational capabilities. Patent specification CN119656884A discloses an SSZ-13 molecular sieve membrane, its preparation method, and its application in SF6. This method synthesizes SSZ-13 molecular sieve membranes via hydrothermal synthesis and uses them for the separation of impurities in SF6. The average nitrogen / SF6 selectivity can reach 325. However, the zeolite membrane synthesized by the hydrothermal method is relatively rough, with zeolite crystals exhibiting poor adhesion, uneven membrane thickness, and a tendency for the frame to collapse and block microchannels, making long-term use difficult. Although membrane separation is a novel and efficient separation method, current membranes used for the separation of sulfur hexafluoride (SF6) and nitrogen are generally commercially available pre-packaged membrane equipment. While the membrane parameters are stable, the separation effect is generally mediocre, and detailed subsequent control of the membrane parameters is not possible. Therefore, it is necessary to prepare high-efficiency membranes for separating SF6 and nitrogen using new membrane fabrication methods, and to package the membrane fibers into membrane equipment for the separation of SF6 and nitrogen, thereby reducing SF6 emissions and enabling the reuse of SF6. Summary of the Invention

[0004] The first technical problem to be solved by the present invention is to provide a method for preparing a hollow fiber membrane separator. The hollow fiber membrane has a dense outer layer and a reduced pore size, which can selectively allow small molecules such as nitrogen to pass through while retaining large molecules such as sulfur hexafluoride, thereby achieving rapid separation of sulfur hexafluoride and nitrogen.

[0005] The second technical problem this invention aims to solve is to provide a method for separating sulfur hexafluoride and nitrogen using the hollow fiber membrane separator. This method can purify sulfur hexafluoride to over 99.9%, is simple to operate, and has a fast nitrogen removal speed and high efficiency.

[0006] To solve the first technical problem mentioned above, the technical solution of the present invention is a method for preparing a hollow fiber membrane separator, comprising the following steps:

[0007] (1) Hollow fiber membrane precursors are prepared by a non-solvent phase inversion method, including steps such as preparing casting solution, spinning, and curing. The precursors are dried naturally and then sintered at high temperature to obtain hollow fiber membrane fibers.

[0008] (2) Encapsulate multiple sets of hollow fiber membrane filament assemblies, seal the membrane filaments with epoxy resin, and install end caps for the feed and discharge sides of the tubes at both ends to make a hollow fiber membrane separator.

[0009] The casting solution is prepared by mixing and stirring ceramic powder, inorganic nanoparticles, solubilizing additives, organic polymers, and organic solvents. The ceramic powder is one or more of Al2O3, TiO2, ZrO2, SiO2, Y2O3, etc.; the inorganic nanoparticles are one or more of MgO, MnO2, ZnO, NiO, Fe2O3, CuO, CoO, etc.; the solubilizing additives are one or more of polyethylene glycol (PEG), ethanol, tetrahydrofuran, polyvinylpyrrolidone (PVP), etc.; the organic polymers are one or more of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyacrylonitrile (PAN), polyetheramide (PEBA), poly(m-phenylenetrilamide) (PMIA), polyethyleneimine (PEI), polyethersulfone (PES), etc.; and the organic solvents are one or more of N-methylpyrrolidone (NMP), N,N-dimethylacetamide (DMAC), N,N-dimethylformamide (DMF), etc.

[0010] The casting solution comprises the following mass percentages: ceramic powder 50%~70%, inorganic nanoparticles 0%~5%, solubilizing additives 0%~5%, organic polymers 20%~40%, and organic solvents 10%~30%.

[0011] The solidification molding process is carried out by solution cooling molding in an external coagulation bath. The raw materials of the external coagulation bath are selected from one or more of water, ethanol, methanol, ethylene glycol, octanol, glycerol, etc.

[0012] Preferably, the stirring temperature of the casting solution is 50~90℃, and the temperature of the external coagulation bath is 30~70℃.

[0013] Preferably, the high-temperature sintering temperature of the membrane fiber is 500~1500℃.

[0014] The hollow fiber membrane separator preferably has 400 to 800 membrane filaments inside, and the membrane filament length is preferably 0.8 to 1.4 m.

[0015] To solve the second technical problem mentioned above, the technical solution of the present invention is a method for separating sulfur hexafluoride and nitrogen using a hollow fiber membrane separator, comprising the following steps: a mixture of sulfur hexafluoride and nitrogen is introduced into the tube side inlet of the hollow fiber membrane separator; the sulfur hexafluoride gas flows along the tube side; the nitrogen gas is discharged to the shell side through the pores on the hollow fiber membrane in the tube side; the sulfur hexafluoride-rich permeate gas is discharged from the high-pressure side of the tube side; the nitrogen-rich permeate gas is discharged from the low-pressure side of the shell side; the sulfur hexafluoride-rich permeate gas is further separated by a two-stage hollow fiber membrane separator, ultimately achieving a sulfur hexafluoride content of over 99.9% and a nitrogen content of less than 0.1%.

[0016] Preferably, the sulfur hexafluoride and nitrogen mixture contains 80% to 90% sulfur hexafluoride and 10% to 20% nitrogen, the hollow fiber membrane separator has a temperature of 25 to 55°C, a pressure of 0.8 to 1.6 MPa, and a gas flow rate of 50 to 100 L / min.

[0017] When a hollow fiber membrane separator is used to separate sulfur hexafluoride (SF6) and nitrogen, the mixed feed gas enters from the tube side of the membrane separator. SF6 flows inside the membrane fibers and exits through the tube side. Nitrogen enters the membrane fibers and diffuses into the shell side through channels perpendicular to the membrane fibers. SF6 is eventually discharged from the tube side as a gas rich in SF6 on the permeate side, while nitrogen is discharged from the shell side as a gas rich in nitrogen on the permeate side. The gas rich in SF6 on the permeate side after passing through the first membrane separator passes through a second membrane separator to achieve deep removal of nitrogen from the SF6. Ultimately, the purity of SF6 can reach over 99.9%.

[0018] Furthermore, the present invention provides a method for separating sulfur hexafluoride and nitrogen using a hollow fiber membrane separator, comprising the following steps:

[0019] (1) A casting solution is prepared by mixing and stirring ceramic powder, inorganic nanoparticles, solubilizing additives, organic polymers and organic solvents. The solution is allowed to stand, defoamed, and the temperature of the casting solution and the external coagulation bath is controlled. The casting solution is spun out from the spinneret and the support together, passes through the air passage, and enters the external coagulation bath to induce solvent-non-solvent diffusion. The spinning solution is solidified into a membrane fiber precursor. The precursor is arranged by a winding wheel and then the membrane fiber is removed and dried naturally to obtain the hollow fiber membrane fiber precursor. The dried membrane fiber precursor is sintered to remove the organic polymers and residual organic solvents in the membrane fiber, and finally the hollow fiber membrane fiber product is obtained for use.

[0020] (2) Arrange the hollow fiber membrane filaments neatly and place them into the membrane separator shell assembly. Inject epoxy resin into the port at the lower end of the shell assembly. After the epoxy resin solidifies, perform the same treatment on the upper end of the shell assembly. After the epoxy resin at both ends solidifies, cut off the excess membrane filaments and install end caps on the feed side and discharge side to assemble a hollow fiber membrane separator.

[0021] (3) A mixture of sulfur hexafluoride and nitrogen is introduced into the feed end cap of the hollow fiber membrane separator. The mixture enters the membrane fiber. Sulfur hexafluoride flows along the inside of the membrane fiber and enters the outlet end cap to become permeate gas. Nitrogen diffuses to the outside of the membrane fiber through the micropores distributed on the membrane fiber and accumulates in the shell side to become permeate gas. The permeate gas is separated again through a secondary membrane separator. The permeate gas discharged from the secondary membrane separator is the product gas rich in sulfur hexafluoride. The sulfur hexafluoride content can reach more than 99.9%.

[0022] Compared with the prior art, the present invention has the following advantages:

[0023] (1) The hollow fiber membrane of the present invention regulates the pore size distribution and channel size of the hollow fiber membrane by adding metal oxide nanoparticles and using solubilizing additives to assist in regulation, so that a dense layer is formed on the outer surface of the hollow fiber membrane, the pore size is reduced, and small molecules such as nitrogen can selectively pass through while retaining sulfur hexafluoride, thereby achieving rapid separation of sulfur hexafluoride and nitrogen.

[0024] (2) The hollow fiber membrane separator provided by the present invention removes sulfur hexafluoride and nitrogen. When the mixed gas passes through the membrane filaments inside the membrane separator, the smaller nitrogen molecules can diffuse to the shell side of the membrane separator through the micropores perpendicular to the membrane filaments. The sulfur hexafluoride has a larger diameter than the micropores perpendicular to the membrane filaments and can only flow along the inside of the membrane filaments, thus achieving the separation of sulfur hexafluoride and nitrogen. This separation method is simple and easy to operate, and the separation speed of the two gases is fast and the separation effect is good. Detailed Implementation

[0025] To more clearly illustrate the background technology and the technical solutions of the embodiments of the present invention, the embodiments of the present invention will be described in detail below. The embodiments are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0026] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" or "a number" means two or more, unless otherwise explicitly specified.

[0027] Example 1

[0028] A method for preparing a membrane for the separation of sulfur hexafluoride and nitrogen includes the following steps:

[0029] (1) Preparation of hollow fiber membrane. First, a casting solution was prepared, which was mixed according to the following mass percentages: 55% ceramic powder, 2% inorganic nanoparticles, 5% solubilizer, 25% organic polymer, and 13% organic solvent. The mixture was heated and stirred in a ball mill at a temperature of 60°C. The ceramic powder was ZrO2, the inorganic nanoparticles were MnO2, the solubilizer was PEG, the organic polymer was PES, and the organic solvent was NMP. After the casting solution is mixed and stirred, it is allowed to stand for 8 hours and then vacuum degassed for 8 hours to remove air bubbles. Once there are no air bubbles in the casting solution, the casting solution is heated to 65℃ and the external coagulation bath temperature is set to 40℃. The external coagulation bath uses an aqueous solution. After adjusting the flow rate and pressure of the casting solution, it is spun from the spinneret. After passing through an air path of 10 cm, it enters the external coagulation bath to induce solvent-non-solvent diffusion, which solidifies the spinning solution into a hollow fiber membrane precursor. The membrane precursor is naturally dried for 12 hours and then sent to a muffle furnace for high-temperature sintering to remove polymers and residual organic solvents. The muffle furnace is programmed to heat up to 1200℃ within 2 hours, hold at 1200℃ for 6 hours, cool down to 600℃ within 2 hours and hold for 4 hours, and finally terminate the heating program and allow it to cool naturally to room temperature to obtain the hollow fiber membrane.

[0030] (2) Assemble the hollow fiber membrane separator. Arrange 400 hollow fiber membrane filaments with a length of 1m neatly into the membrane separator shell assembly. Inject epoxy resin into the injection port at the lower end of the shell assembly to fix the membrane filaments and the shell. After standing for 8 hours, inject epoxy resin into the other end of the shell assembly. After the resin at both ends solidifies, cut off the excess membrane filaments at both ends to make the membrane filaments neatly arranged. Finally, the effective length of a single membrane filament inside the membrane separator is 0.8m, the outer diameter is 0.0012m, and the number is 400. After the cutting is completed, install the feed side and discharge side end caps to complete the overall encapsulation of the membrane separator.

[0031] (3) The mixed gas is introduced into the hollow fiber membrane separator for separation and testing. The mixed gas containing 90% sulfur hexafluoride and 10% nitrogen is sent into the membrane fiber inside the membrane separator through the tube side inlet at the end cap. The membrane separator temperature is 30℃, the tube side pressure is 1.2MPa, and the mixed gas flow rate is 60L / min. After passing through the membrane separator, the sulfur hexafluoride content in the permeate side gas is 98.2%, and the nitrogen content is 1.8%. The permeate side gas is then subjected to further separation in a secondary membrane separator. The secondary membrane separator temperature is 30℃, the tube side pressure is 1.18MPa, and the flow rate is 55L / min. After passing through the secondary membrane separator, the sulfur hexafluoride content in the permeate side gas is 99.92%, and the nitrogen content is 0.08%, which meets the requirements for sulfur hexafluoride finished gas.

[0032] Example 2

[0033] (1) Preparation of hollow fiber membrane. First, a casting solution was prepared, which was mixed according to the following mass percentages: 58% ceramic powder, 1% inorganic nanoparticles, 4% solubilizer, 25% organic polymer, and 12% organic solvent. The mixture was heated and stirred in a ball mill at a temperature of 65°C. The ceramic powder was TiO2, the inorganic nanoparticles were Fe2O3, the solubilizer was PEG, the organic polymer was PEBA, and the organic solvent was DMAC. After the casting solution is mixed and stirred, it is allowed to stand for 8 hours and then vacuum degassed for 8 hours to remove air bubbles. Once there are no air bubbles in the casting solution, the casting solution is heated to 70℃ and the external coagulation bath solution is heated to 45℃. The external coagulation bath is an aqueous solution. After adjusting the flow rate and pressure of the casting solution, it is spun from the spinneret. After passing through an air path of 10cm, it enters the external coagulation bath to induce solvent-non-solvent diffusion, which solidifies the spinning solution into a hollow fiber membrane precursor. The membrane precursor is naturally dried for 12 hours and then sent to a muffle furnace for high-temperature sintering to remove polymers and residual organic solvents. The muffle furnace is programmed to heat up to 1200℃ within 2 hours, hold at 1200℃ for 6 hours, cool down to 600℃ within 2 hours and hold for 4 hours, and finally terminate the heating program and allow it to cool naturally to room temperature to obtain the hollow fiber membrane.

[0034] (2) Assemble the hollow fiber membrane separator. Arrange 450 hollow fiber membrane filaments with a length of 1.2m neatly into the membrane separator shell assembly. Inject epoxy resin into the injection port at the lower end of the shell assembly to fix the membrane filaments and the shell. After standing for 8 hours, inject epoxy resin into the other end of the shell assembly. After the resin at both ends solidifies, cut off the excess membrane filaments at both ends to make the membrane filaments neatly arranged. Finally, the effective length of a single membrane filament inside the membrane separator is 1.1m, the outer diameter is 0.0012m, and the number is 450. After the cutting is completed, install the feed side and discharge side end caps to complete the overall encapsulation of the membrane separator.

[0035] (3) The mixed gas is introduced into the hollow fiber membrane separator for separation and testing. The mixed gas containing 85% sulfur hexafluoride and 15% nitrogen is sent into the membrane fiber inside the membrane separator through the tube side inlet at the end cap. The membrane separator temperature is 30℃, the tube side pressure is 1.2MPa, and the mixed gas flow rate is 60L / min. After passing through the membrane separator, the sulfur hexafluoride content in the permeate side gas is 98.7%, and the nitrogen content is 1.3%. The permeate side gas is then subjected to further separation in a secondary membrane separator. The secondary membrane separator temperature is 30℃, the tube side pressure is 1.18MPa, and the flow rate is 55L / min. After passing through the secondary membrane separator, the sulfur hexafluoride content in the permeate side gas is 99.91%, and the nitrogen content is 0.09%, which meets the requirements for sulfur hexafluoride finished gas.

[0036] Example 3

[0037] (1) Preparation of hollow fiber membrane. First, a casting solution was prepared, which was mixed according to the following mass percentages: 62% ceramic powder, 1% inorganic nanoparticles, 3% solubilizer, 22% organic polymer, and 12% organic solvent. The mixture was heated and stirred in a ball mill at a temperature of 65°C. The ceramic powder was Al2O3, the inorganic nanoparticles were CuO, the solubilizer was tetrahydrofuran, the organic polymer was PVDF, and the organic solvent was DMF. After the casting solution is mixed and stirred, it is allowed to stand for 8 hours and then vacuum degassed for 8 hours to remove air bubbles. Once there are no air bubbles in the casting solution, the casting solution is heated to 70℃ and the external coagulation bath solution is heated to 35℃. The external coagulation bath uses an ethanol solution. After adjusting the flow rate and pressure of the casting solution, it is spun from the spinneret. After passing through an air path of 10cm, it enters the external coagulation bath to induce solvent-non-solvent diffusion, which solidifies the spinning solution into a hollow fiber membrane precursor. The membrane precursor is naturally dried for 12 hours and then sent to a muffle furnace for high-temperature sintering to remove polymers and residual organic solvents. The muffle furnace is programmed to heat up to 1200℃ within 2 hours, hold at 1200℃ for 6 hours, cool down to 600℃ within 2 hours and hold for 4 hours, and finally terminate the heating program and allow it to cool naturally to room temperature to obtain the hollow fiber membrane filaments.

[0038] (2) Assemble the hollow fiber membrane separator. Arrange 450 hollow fiber membrane filaments with a length of 1.2m neatly into the membrane separator shell assembly. Inject epoxy resin into the injection port at the lower end of the shell assembly to fix the membrane filaments and the shell. After standing for 8 hours, inject epoxy resin into the other end of the shell assembly. After the resin at both ends solidifies, cut off the excess membrane filaments at both ends to make the membrane filaments neatly arranged. Finally, the effective length of a single membrane filament inside the membrane separator is 1.1m, the outer diameter is 0.0012m, and the number is 450. After the cutting is completed, install the feed side and discharge side end caps to complete the overall encapsulation of the membrane separator.

[0039] (3) The mixed gas is introduced into the hollow fiber membrane separator for separation and testing. The mixed gas containing 90% sulfur hexafluoride and 10% nitrogen is sent into the membrane fiber inside the membrane separator through the tube side inlet at the end cap. The membrane separator temperature is 30℃, the tube side pressure is 1.2MPa, and the mixed gas flow rate is 60L / min. After passing through the membrane separator, the sulfur hexafluoride content in the permeate side gas is 98.8%, and the nitrogen content is 1.3%. The permeate side gas is then subjected to further separation in a secondary membrane separator. The secondary membrane separator temperature is 30℃, the tube side pressure is 1.18MPa, and the flow rate is 55L / min. After passing through the secondary membrane separator, the sulfur hexafluoride content in the permeate side gas is 99.95%, and the nitrogen content is 0.05%, which meets the requirements for sulfur hexafluoride finished gas.

[0040] Example 4

[0041] (1) Preparation of hollow fiber membrane. First, a casting solution was prepared, which was mixed according to the following mass percentages: 50% ceramic powder, 1% inorganic nanoparticles, 5% solubilizer, 28% organic polymer, and 16% organic solvent. The mixture was heated and stirred in a ball mill at a temperature of 60°C. The ceramic powder was SiO2, the inorganic nanoparticles were ZnO, the solubilizer was PEG, the organic polymer was PVDF, and the organic solvent was DMAC. After the casting solution is mixed and stirred, it is allowed to stand for 8 hours and then vacuum degassed for 8 hours to remove air bubbles. Once there are no air bubbles in the casting solution, the casting solution is heated to 70℃ and the external coagulation bath solution is heated to 45℃. The external coagulation bath is an aqueous solution. After adjusting the flow rate and pressure of the casting solution, it is spun from the spinneret. After passing through an air path of 10 cm, it enters the external coagulation bath to induce solvent-non-solvent diffusion, which solidifies the spinning solution into a hollow fiber membrane precursor. The membrane precursor is naturally dried for 12 hours and then sent to a muffle furnace for high-temperature sintering to remove polymers and residual organic solvents. The muffle furnace is programmed to heat up to 1000℃ within 2 hours, hold at 1000℃ for 6 hours, cool down to 500℃ within 2 hours and hold for 4 hours, and finally terminate the heating program and allow it to cool naturally to room temperature to obtain the hollow fiber membrane filaments.

[0042] (2) Assemble the hollow fiber membrane separator. Arrange 500 hollow fiber membrane filaments with a length of 1.2m neatly into the membrane separator shell assembly. Inject epoxy resin into the injection port at the lower end of the shell assembly to fix the membrane filaments and the shell. After standing for 8 hours, inject epoxy resin into the other end of the shell assembly. After the resin at both ends solidifies, cut off the excess membrane filaments at both ends to make the membrane filaments neatly arranged. Finally, the effective length of a single membrane filament inside the membrane separator is 1.1m, the outer diameter is 0.0012m, and the number is 500. After the cutting is completed, install the feed side and discharge side end caps to complete the overall encapsulation of the membrane separator.

[0043] (3) The mixed gas is introduced into the hollow fiber membrane separator for separation and testing. The mixed gas containing 90% sulfur hexafluoride and 10% nitrogen is sent into the membrane fiber inside the membrane separator through the tube side inlet at the end cap. The membrane separator temperature is 30℃, the tube side pressure is 1.2MPa, and the mixed gas flow rate is 60L / min. After passing through the membrane separator, the sulfur hexafluoride content in the permeate side gas is 98.5%, and the nitrogen content is 1.5%. The permeate side gas is then subjected to further separation in a secondary membrane separator. The secondary membrane separator temperature is 30℃, the tube side pressure is 1.18MPa, and the flow rate is 55L / min. After passing through the secondary membrane separator, the sulfur hexafluoride content in the permeate side gas is 99.96%, and the nitrogen content is 0.04%, which meets the requirements for sulfur hexafluoride finished gas.

[0044] Example 5

[0045] (1) Preparation of hollow fiber membrane. First, a casting solution was prepared, which was mixed according to the following mass percentages: 60% ceramic powder, 1% inorganic nanoparticles, 5% solubilizer, 22% organic polymer, and 12% organic solvent. The mixture was heated and stirred in a ball mill at a temperature of 60°C. The ceramic powder was SiO2, the inorganic nanoparticles were NiO, the solubilizer was PEG, the organic polymer was PVDF, and the organic solvent was DMAC. After the casting solution is mixed and stirred, it is allowed to stand for 8 hours and then vacuum degassed for 8 hours to remove air bubbles. Once there are no air bubbles in the casting solution, the casting solution is heated to 70℃ and the external coagulation bath solution is heated to 45℃. The external coagulation bath is an aqueous solution. After adjusting the flow rate and pressure of the casting solution, it is spun from the spinneret. After passing through an air path of 10cm, it enters the external coagulation bath to induce solvent-non-solvent diffusion, which solidifies the spinning solution into a hollow fiber membrane precursor. The membrane precursor is naturally dried for 12 hours and then sent to a muffle furnace for high-temperature sintering to remove polymers and residual organic solvents. The muffle furnace is programmed to heat up to 1400℃ within 2 hours, hold at 1400℃ for 6 hours, cool down to 500℃ within 2 hours and hold for 4 hours, and finally terminate the heating program and allow it to cool naturally to room temperature to obtain the hollow fiber membrane filaments.

[0046] (2) Assemble the hollow fiber membrane separator. Arrange 500 hollow fiber membrane filaments with a length of 1.2m neatly into the membrane separator shell assembly. Inject epoxy resin into the injection port at the lower end of the shell assembly to fix the membrane filaments and the shell. After standing for 8 hours, inject epoxy resin into the other end of the shell assembly. After the resin at both ends solidifies, cut off the excess membrane filaments at both ends to make the membrane filaments neatly arranged. Finally, the effective length of a single membrane filament inside the membrane separator is 1.1m, the outer diameter is 0.0012m, and the number is 500. After the cutting is completed, install the feed side and discharge side end caps to complete the overall encapsulation of the membrane separator.

[0047] (3) The mixed gas is introduced into the hollow fiber membrane separator for separation and testing. The mixed gas containing 90% sulfur hexafluoride and 10% nitrogen is sent into the membrane fiber inside the membrane separator through the tube side inlet at the end cap. The membrane separator temperature is 30℃, the tube side pressure is 1.2MPa, and the mixed gas flow rate is 60L / min. After passing through the membrane separator, the sulfur hexafluoride content in the permeate side gas is 98.6%, and the nitrogen content is 1.4%. The permeate side gas is then subjected to further separation in a secondary membrane separator. The secondary membrane separator temperature is 30℃, the tube side pressure is 1.18MPa, and the flow rate is 55L / min. After passing through the secondary membrane separator, the sulfur hexafluoride content in the permeate side gas is 99.94%, and the nitrogen content is 0.06%, which meets the requirements for sulfur hexafluoride finished gas.

[0048] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A method for preparing a hollow fiber membrane separator, characterized in that, Includes the following steps: (1) Hollow fiber membrane precursor is prepared by non-solvent phase inversion method, including the steps of preparing casting solution, spinning, and solidification molding. The precursor is naturally dried and then sintered at high temperature to obtain hollow fiber membrane filaments. (2) Encapsulate multiple sets of hollow fiber membrane filament assemblies, seal the membrane filaments with epoxy resin, and install end caps for the feed and discharge sides of the tubes at both ends to make a hollow fiber membrane separator; The casting solution is prepared by mixing and stirring ceramic powder, inorganic nanoparticles, solubilizing additives, organic polymers and organic solvents. The mass percentage composition of the casting solution is as follows: ceramic powder 50%~70%, inorganic nanoparticles 1%~2%, solubilizing additives 3%~5%, organic polymers 20%~40%, and organic solvents 10%~30%; The ceramic powder is one or more of Al2O3, TiO2, ZrO2, SiO2, and Y2O3; the inorganic nanoparticles are one or more of MgO, MnO2, ZnO, NiO, Fe2O3, CuO, and CoO; the solubilizer is one or more of polyethylene glycol (PEG), ethanol, tetrahydrofuran, and polyvinylpyrrolidone (PVP); the organic polymer is one or more of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyacrylonitrile (PAN), polyetheramide (PEBA), poly(m-phenylenetrilamide) (PMIA), polyethyleneimine (PEI), and polyethersulfone (PES); and the organic solvent is one or more of N-methylpyrrolidone (NMP), N,N-dimethylacetamide (DMAC), and N,N-dimethylformamide (DMF). The hollow fiber membrane separator prepared by the method described above is used to separate sulfur hexafluoride and nitrogen gas, and includes the following steps: (1) A casting solution is prepared by mixing and stirring ceramic powder, inorganic nanoparticles, solubilizing additives, organic polymers and organic solvents. The solution is allowed to stand, defoamed, and the temperature of the casting solution and the external coagulation bath is controlled. The casting solution is spun out from the spinneret and the support together, passes through the air passage, and enters the external coagulation bath to induce solvent-non-solvent diffusion. The spinning solution is solidified into a membrane fiber precursor. The precursor is arranged by a winding wheel and then the membrane fiber is removed and dried naturally to obtain the hollow fiber membrane fiber precursor. The dried membrane fiber precursor is sintered to remove the organic polymers and residual organic solvents in the membrane fiber, and finally the hollow fiber membrane fiber product is obtained for use. (2) Arrange the hollow fiber membrane filaments neatly and place them into the membrane separator shell assembly. Inject epoxy resin into the port at the lower end of the shell assembly. After the epoxy resin solidifies, perform the same treatment on the upper end of the shell assembly. After the epoxy resin at both ends solidifies, cut off the excess membrane filaments and install end caps on the feed side and discharge side to assemble a hollow fiber membrane separator. (3) A mixture of sulfur hexafluoride and nitrogen is introduced into the feed end cap of the hollow fiber membrane separator. The mixture enters the membrane fiber. Sulfur hexafluoride flows along the inside of the membrane fiber and enters the outlet end cap to become permeate gas. Nitrogen diffuses to the outside of the membrane fiber through the micropores distributed on the membrane fiber and accumulates in the shell side to become permeate gas. The permeate gas is separated again through a secondary membrane separator. The permeate gas discharged from the secondary membrane separator is the product gas rich in sulfur hexafluoride. The sulfur hexafluoride content can reach more than 99.9%.

2. The preparation method according to claim 1, characterized in that, The solidification molding process is carried out using an external coagulation bath for solution cooling molding. The raw materials for the external coagulation bath are selected from one or more of water, ethanol, methanol, ethylene glycol, octanol, and glycerol.

3. The preparation method according to claim 2, characterized in that, The stirring temperature of the casting solution is 50~90℃, and the temperature of the external coagulation bath is 30~70℃.

4. The preparation method according to claim 1, characterized in that, The high-temperature sintering temperature is 500~1500℃.

5. The preparation method according to claim 1, characterized in that, The hollow fiber membrane separator contains 400 to 800 membrane filaments, with a filament length of 0.8 to 1.4 m.

6. A method for separating sulfur hexafluoride and nitrogen using a hollow fiber membrane separator prepared by any one of claims 1 to 5, characterized in that, The process includes the following steps: A mixture of sulfur hexafluoride (SF6) and nitrogen is introduced into the tube side of a hollow fiber membrane separator. The SF6 gas flows along the tube side, while the nitrogen gas is discharged to the shell side through the pores on the hollow fiber membrane in the tube side. The SF6-rich permeate gas is discharged from the high-pressure side of the tube side, while the nitrogen-rich permeate gas is discharged from the low-pressure side of the shell side. The SF6-rich permeate gas is then further separated by a two-stage hollow fiber membrane separator, ultimately achieving a SF6 content of over 99.9% and a nitrogen content of less than 0.1%.

7. The method according to claim 6, characterized in that, The sulfur hexafluoride and nitrogen mixture contains 80% to 90% sulfur hexafluoride and 10% to 20% nitrogen.

8. The method according to claim 6, characterized in that, The hollow fiber membrane separator has a temperature of 25~55℃, a pressure of 0.8~1.6MPa, and a mixed gas flow rate of 50~100L / min.