JP2000185212A - Method for separating and recovering perfluoro compound gas and device therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To efficiently separate and recover a perfluoro compound gas from a mixed gas by supplying a mixed gas to an asymmetrical hollow fiber carbon membrane to unload a gas consisting of a carrier gas from the permeation side of the membrane and at the same time, recovering the concentrated gas of a perfluoro compound from the non-permeation side of the membrane. SOLUTION: A mixed gas consisting of SF6 as a perfluoro gas and at least a single kind of carrier gas is continuously supplied from the mixed gas supply aperture 3 of a gas separation device 1 and is caused to flow to the non-permeable gas discharge aperture 4 side passing through the inside of a hollow fiber 2. Next, the gas which selectively permeates through a separation membrane is discharged from a permeable gas discharge aperture 5, and at the same time, the gas which does not permeate through the separation membrane is discharged from the non-permeable gas discharge aperture 4. Thus SF6 whose permeation rate is low is separated and recovered from the non-permeable gas discharge aperture 4. In this case, the resin wall 7 of the gas separation device 1 is formed in the cylindrical shape by setting both end parts of the hollow fiber 2 with an appropriate heat-curable resin and at the same time, is airtightly bonded to the inner wall of an airtight container 6 with the help of an adhesive or the like.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method and an apparatus for efficiently separating and recovering a perfluoro compound gas from a gas mixture by a carbon membrane.

[0002]

2. Description of the Related Art SF ₆ (sulfur hexafluoride) gas, chlorofluorocarbon gas, and tetrachloride are used as electrical insulating gases for gas-insulated electrical devices such as gas-insulated switchgears, gas circuit breakers, gas-insulated transformers, and pipeline air transmission. Halogen compounds mainly using carbon gas are used. Recently, in order to reduce the amount of global warming gas that has become an issue on a global scale, a mixture of halogen compounds and other electrically insulating gases is used for gas-insulated electrical equipment in order to reduce its usage. Attempts have been made.

In the semiconductor industry, in a semiconductor process involving gas, CF and CF are used for etching and cleaning.
Perfluoro compounds such as ₄ , C ₂ F ₆ , C ₃ F ₈ , C ₄ F ₁₀ , SF ₆ , and NF ₃ are being used exclusively. These perfluorocompound gases may be in pure form or diluted, for example, with air, nitrogen or other inert gases,
Alternatively, it is used in the form of a mixture with another perfluoro compound gas or another carrier gas (for example, an inert gas).

[0004] Most of these perfluoro compound gases contained in the carrier gas are gases that have an adverse effect on the environment, such as global warming, and must be recovered and reused without being discharged into the atmosphere.

As a conventional separation method, Japanese Patent Application Laid-Open No. Hei 9-103633 describes a general method for recovering a perfluoro compound using a gas separation membrane.

[0006]

However, the separation membrane exemplified in the above-mentioned publication is a separation membrane formed of a general organic substance, and is improved in selectivity at the time of separation.
More efficient separation and recovery is desired.

An object of the present invention is to provide a method and an apparatus for efficiently separating and recovering a perfluoro compound gas from a mixture gas of a perfluoro compound gas and a carrier gas.

[0008]

SUMMARY OF THE INVENTION The present invention provides at least one
A gas mixture comprising at least one perfluoro compound gas and at least one carrier gas is supplied to an asymmetric hollow fiber carbon membrane, and at least one carrier gas having a reduced perfluoro compound content from the permeate side of the membrane. And recovering a gas substantially enriched with at least one type of perfluoro compound from the non-permeate side of the membrane.

[0009] The present invention also relates to the above-mentioned perfluoropolymer, wherein a hollow fiber carbon membrane having an asymmetric structure obtained by partially carbonizing an asymmetric hollow fiber membrane made of aromatic polyimide is used as the asymmetric hollow fiber carbon membrane. The present invention relates to a method for separating and recovering compound gas.

[0010] Further, the asymmetric hollow fiber carbon membrane comprises an asymmetric hollow fiber membrane made of an aromatic polyimide in the range of 250 to 49.
A pre-heat treatment at a temperature in the range of 5 ° C. and at a temperature at which the asymmetric structure of the hollow fiber membrane is maintained, and in an atmosphere of an oxygen-containing gas; It is preferable to use a hollow fiber carbon membrane having an asymmetric structure obtained by partially carbonizing the fiber membrane at 500 to 900 ° C. in an atmosphere of an inert gas.

Further, as the perfluoro compound gas,
It is preferably selected from the group consisting of fluorocarbons, SF ₆ and mixtures thereof.

The carrier gas may be N ₂ , A
It is preferable to select from the group consisting of r, He, CO ₂ , and air.

Further, the present invention provides an asymmetric carbon membrane in the form of a large number of hollow fibers in a sealed container, wherein a gas supply port and a non-permeate gas outlet communicating inside the hollow fibers are provided. A gas separation device having at least one permeate gas outlet on the outside of the hollow fiber from a gas supply port of the gas separation device, the gas mixture comprising at least one perfluoro compound gas and at least one carrier gas. And a gas comprising at least one carrier gas having a reduced perfluoro compound content was taken out from the permeate side of the membrane, and substantially at least one perfluoro compound was concentrated from the non-permeate side of the membrane. The present invention relates to a perfluoro compound gas separation / recovery device for recovering a gas.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail. The method for separating and recovering a perfluoro compound gas of the present invention comprises: mixing a mixed gas containing at least one perfluoro compound gas and at least one carrier gas;
A gas comprising at least one carrier gas having a reduced perfluoro compound content is supplied from the permeate side of the membrane to the asymmetric hollow fiber carbon membrane, and substantially at least one gas is extracted from the non-permeate side of the membrane. The method is characterized in that a gas enriched with a fluoro compound is recovered.

When the gas mixture is separated, the gas mixture may be supplied from the outside of the hollow fiber and the permeated gas may be taken out from the inside (hole side) of the hollow fiber, or the gas mixture may be separated from the inside of one of the hollow fibers. May be carried out by flowing the permeated gas to the outside of the hollow fiber while supplying the gas from the inside and flowing through the hollow fiber and discharging from the inside of the other, but the latter method is more efficient This is preferable.

The asymmetric hollow fiber carbon membrane to be used is obtained by heat treatment of an organic polymer (polyimide, polypyrrololone, polyacrylonitrile, etc.) in an inert gas, or by plasma treatment of glassy carbon. There are things that can be done.

Among them, in particular, an asymmetric hollow fiber carbon membrane obtained by partially carbonizing a polyimide separation membrane has extremely excellent heat resistance and solvent resistance, and also has a perfluoro compound gas and a carrier gas such as nitrogen. Gas separation performance at a high level, such as when a perfluoro compound gas is separated from a mixed gas of the above.

[0018] Further, the separation membrane is formed by heating the asymmetric hollow fiber membrane made of aromatic polyimide at a temperature in the range of 250 to 495 ° C and maintaining the asymmetric structure of the hollow fiber membrane; Preliminary heat treatment in a gas-containing atmosphere for thermal stabilization, followed by partial carbonization of the preheat-treated hollow fiber membrane at 500 to 900 ° C. in an inert gas atmosphere It is preferably a hollow fiber membrane.

The asymmetric hollow fiber carbon membrane obtained by carbonizing the polyimide will be described in more detail.

In the present invention, the asymmetric hollow fiber membrane comprising the aromatic polyimide is disclosed in JP-A-60-1508.
No. 06, JP-A-61-133106, etc., the asymmetry of a single structure (single asymmetric structure comprising a dense layer on the surface and a porous layer inside) manufactured by a method as described in JP-A-61-133106, etc. Hollow fiber membrane, or Japanese Patent Application Laid-Open No. H2-169019
And a two-layer extruded structure manufactured by the method described in Japanese Patent Application No. 1-70446 (the outer layer is composed of a dense layer on the surface and the inner porous layer, and the inner layer is the porous layer). Asymmetric hollow fiber membrane having a two-layer extrusion asymmetric structure).

The method for producing an asymmetric hollow fiber membrane having a single membrane structure includes, for example, an aromatic tetracarboxylic acid component such as biphenyltetracarboxylic dianhydride, diaminodimethyldiphenylene sulfone, diaminodiphenylmethane,
An aromatic diamine component such as 4,4′-diaminodiphenyl ether is polymerized and imidized in a substantially equimolar phenolic solvent such as parachlorophenol to prepare a solution of a soluble aromatic polyimide. Is used as a dope solution for film formation, extruded from a tube-in-orifice type spinning nozzle into a hollow fiber into a nitrogen atmosphere, and then coagulated in a coagulating solution composed of an aqueous ethanol solution to form an asymmetric structure. A hollow fiber membrane is formed, and finally, the hollow fiber membrane is washed with ethanol to extract and remove a phenolic solvent, and after replacing the ethanol with an isooctane solvent, drying and further heat treatment, A method for producing an asymmetric hollow fiber membrane having a gas permeation rate and a selective permeability can be mentioned.

In the method for producing an asymmetric hollow fiber membrane having a two-layer extruded asymmetric structure, two kinds of soluble aromatic polyimide solutions are prepared in the same manner as in the method for producing a hollow fiber membrane having a single structure. In the same manner as in the above-described method of manufacturing a hollow fiber membrane having a single structure, except that a two-layer extrusion spinning nozzle capable of performing two-layer extrusion is used, a two-layer extrusion asymmetric structure is formed. And a method for producing a hollow fiber membrane having the same.

The asymmetric hollow fiber carbon membrane of the present invention has an outer diameter of 100 to 2000 μm, particularly 150 to 1000 μm.
m, and the film thickness is 10 to 5
It is preferably about 00 μm, especially about 20 to 200 μm.

In the production method of the present invention, for example, an asymmetric hollow fiber membrane made of the aromatic polyimide produced as described above is prepared, and the asymmetric hollow fiber membrane is subjected to 25
0 to 495 ° C., preferably 260 to 450 ° C., and at a temperature at which the asymmetric structure of the hollow fiber membrane is maintained, and 0.1 to 495 ° C. in an oxygen gas-containing atmosphere.
100 hours (especially 0.3 to 50 hours), heat-stabilize by pre-heat treatment, and then the pre-heat-treated hollow fiber membrane is
The hollow fiber carbon film is preferably formed in a temperature range of 500 to 900 ° C., preferably 550 to 800 ° C., and in an atmosphere of an inert gas such as a nitrogen gas, a helium gas, and an argon gas.

In the production method of the present invention, the preliminary heat treatment (thermal stabilization treatment) in the oxygen-containing gas is performed so that the asymmetric structure of the hollow fiber membrane can be maintained in the next carbonization treatment step. Partially cross-linked and / or partially cyclized aromatic polyimide forming the hollow fiber membrane, or
In order to infusibilize or insolubilize to obtain a thermally stable aromatic polyimide, the heat treatment is performed at a temperature in the range of 250 to 495 ° C., which is a temperature at which the asymmetric structure of the hollow fiber membrane is maintained. .

The temperature at which the above-mentioned asymmetric structure of the hollow fiber membrane is maintained is, for example, when the polyimide has a softening temperature measured by a measuring method described later, the temperature is lower than the softening temperature of the polyimide by 5%. ° C or lower, especially 10 ° C or lower, and when the polyimide has substantially no softening temperature or second-order transition temperature, the asymmetric structure of the polyimide hollow fiber membrane may be Any temperature may be used as long as it is a temperature at which it is not significantly deformed by observation with an electron microscope or the like, or a temperature at which the average pore diameter of the porous layer is not significantly reduced (to 50% or less).

If the preliminary heat treatment is within the above-mentioned temperature range, for example, the preliminary heat treatment is performed by gradually increasing the temperature from a temperature around 200 ° C. to a high temperature around 450 ° C. 0.5 at 350 ° C
Heat treatment for 100 hours (preferably 1 to 50 hours),
Next, a preliminary heat treatment performed in a plurality of stages, such as a heat treatment at a temperature of 350 to 490 ° C. for 10 to 300 minutes (preferably 20 to 200 minutes), may be used.

The preliminary heat treatment of the asymmetric hollow fiber membrane is performed by
The aromatic polyimide hollow fiber membrane (elongated hollow fiber) can be continuously supplied to a high-temperature heating furnace to be continuously performed, and a bundle of a plurality of asymmetric hollow fiber membranes can be formed. Once formed, the yarn bundle can be placed in a heating furnace at an appropriate temperature and left in the heating furnace for a certain period of time to perform batch heat treatment.

As the oxygen-containing gas used in the preheating treatment, for example, air or various mixing ratios of oxygen and another inert gas such as nitrogen (particularly, the oxygen-containing ratio;
5 to 30% by volume). In the production method of the present invention, if the preliminary heat treatment in the oxygen-containing gas is not performed, in the subsequent carbonization step,
It is not appropriate because the asymmetric structure of the hollow fiber membrane is impaired, and if the preliminary heat treatment is performed at too high a temperature, the asymmetric hollow fiber membrane made of aromatic polyimide cannot maintain the asymmetric structure optimally, and In some cases, the asymmetric hollow fiber carbon membrane becomes a low-performance gas separation membrane, which is not suitable because the non-crystalline structure may be impaired or the gas separation performance may be significantly inferior.

The carbonization of the preheated asymmetric hollow fiber membrane made of aromatic polyimide is carried out by heating the hollow fiber membrane (long hollow fiber) in a high-temperature heating furnace in the same manner as in the preheating described above. It can be supplied continuously and can be carried out continuously.Also, a plurality of asymmetric hollow fiber membrane yarn bundles are formed, and the yarn bundles are heated in a heating furnace at an appropriate temperature for a certain time. High heat treatment (carbonization) can also be performed batchwise by leaving it in a furnace.

In the production method of the present invention, the asymmetric hollow fiber carbon membrane produced as described above is further subjected to 250 to 4
At a temperature of 50 ° C. (particularly 300 to 400 ° C.) in an oxygen-containing gas atmosphere for 0.2 to 50 hours, especially 0.5 to 50 ° C.
Post heat treatment may be performed for 10 hours.

The perfluoro compound gas is preferably selected from the group consisting of fluorocarbon, SF ₆ , NF ₃ and mixtures thereof. Examples of the fluorocarbon include CF ₄ , C ₂ F ₆ , C ₃ F ₈ , and C ₄ F ₁₀ . SF ₆ gas is a colorless, odorless, and non-toxic inert gas that exhibits excellent dielectric strength by increasing the air pressure, has a low liquefaction temperature, and can be used under pressure even at low temperatures, so it is preferably used as an electrical insulating gas. Is done.

Further, examples of the carrier gas include nitrogen gas, carbon dioxide gas, helium gas, argon gas, air and the like. The combination of SF ₆ and these gases has a large dielectric strength and a large transmission speed ratio to the membrane, and is a preferable combination for gas-insulated electric equipment.
In particular, nitrogen gas is preferably used because it has no toxicity and is easily available. The mixed gas is not limited to the above-mentioned gas for electric insulation, and may include other gases used in a semiconductor process or the like. The concentration of the perfluoro compound gas is not particularly limited.

The asymmetric hollow fiber carbon membrane is, for example, a hollow fiber membrane bundle formed by cutting hollow fibers into an appropriate length and bundling a large number (100 to 100,000) so that the hollows (holes) at both ends thereof are not blocked. The two ends are integrally fixed with a resin such as an epoxy resin to form a module, and the module is provided in a container having at least a gas mixture (raw material gas) supply port, a non-permeate gas discharge port, and a permeate gas discharge port. It is stored and used as a gas separation and recovery device.

One embodiment of the gas separation apparatus of the present invention is shown in FIG.
It was shown to. Taking SF ₆ as an example of perfluoro gas,
This will be described below. The gas separation device 1 has a separation membrane in the form of a large number of hollow fibers 2 built in a sealed container 6,
_A mixed gas comprising ₆ and one or more other types of carrier gas is continuously supplied from a mixed gas supply port 3 of the gas separation device 1, and the inside of the hollow fiber 2 is caused to flow to a non-permeate gas discharge port 4 side to be separated. The gas that has selectively permeated the membrane is the permeated gas outlet 5
By discharging the gas that has been discharged through the separation membrane through the non-permeate gas discharge port 4, the SF that has a low permeation rate is discharged.
₆ can be separated and recovered from the non-permeate gas outlet 4. The resin wall 7 shown in FIG. 1 is a disc-shaped resin wall formed by solidifying an appropriate thermosetting resin such as an elastomer resin, an acrylate resin, an epoxy resin, or a phenol resin at both ends of the hollow fiber 2. Thus, each hollow fiber penetrates through the resin wall, and a hole in the hollow fiber opens toward the outside of the resin wall. The resin wall 7 is hermetically fixed to the inner wall of the sealed container 6 using an adhesive or the like. In order to further enhance the separation and recovery efficiency, it is effective to connect a vacuum pump or the like to the permeated gas discharge port 5 in the gas separation device 1 to collect and reduce the permeated gas under reduced pressure. Alternatively, another type of gas not contained in the mixed gas may be supplied as a purge gas from one of the outlets and discharged together with the permeated gas from the other of the permeated gas outlets.

[0036]

EXAMPLES The present invention will be described in more detail with reference to Examples and Examples. However, the present invention is not limited by those embodiments. For the asymmetric hollow fiber membrane (uncarbonized hollow fiber membrane), the asymmetric hollow fiber carbon membrane, and the like, the permeation performance of each gas was measured by the following method.

[Gas Permeation Performance] First, a hollow fiber element for evaluating permeation performance was prepared by using the hollow fiber membrane produced in the following examples, a stainless steel pipe, and an epoxy resin-based adhesive. The permeation performance was measured at 50 ° C. using a pure gas such as N ₂ , SF ₆ , C ₂ F ₆ , or CF ₄ by attaching a hollow fiber element of a hollow fiber membrane for permeation performance evaluation to a stainless steel container. Temperature, 10kgf / cm ² or 2
A gas permeation test was performed at a pressure of kgf / cm ² , and a gas permeation rate and a permeation rate ratio of each gas (indicating selective permeability and separation degree) were calculated.

Reference Example 1 [Preparation of Polyimide Solution 1] As an acid component, 3,3 ′,
4,4'-biphenyltetracarboxylic dianhydride (BP
DA) 20 mmol, 2,2′-bis (3,4-dicarboxyphenyl) hexafluoropropane dianhydride (6FDA) 70 mmol, pyromellitic dianhydride (PMDA) 10 mmol, and as a diamine component, Dimethyl-3,7-diaminodibenzothiophene-5,5
-100 mmol of dioxide (TSN), together with 331 g of parachlorophenol, was placed in a separable flask equipped with a stirrer and a nitrogen gas inlet tube, and a nitrogen gas was flowed while stirring the reaction solution at 180 ° C. Polymerization is performed at the polymerization temperature for 18 hours, and the aromatic polyimide concentration becomes 16
A weight percent aromatic polyimide solution was prepared. This polyimide solution had a rotational viscosity at 100 ° C. of 1600 poise. This aromatic polyimide solution was filtered through a 400-mesh stainless steel mesh to obtain a dope solution 1 for spinning.
Was prepared.

[Preparation of Polyimide Solution 2] As acid components, 20 mmol of 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride (BPDA) and 2,2′-bis (3,4-di (Carboxyphenyl) hexafluoropropane dianhydride (6FDA) 70 mmol, pyromellitic dianhydride (PMDA) 10 mmol, and dimethyl-3,7-diaminodibenzothiophene-5,5-dioxide (TSN) as a diamine component 100 mmol and 252 g of parachlorophenol were put into a separable flask equipped with a stirrer and a nitrogen gas inlet tube, and nitrogen gas was flown thereinto while stirring the reaction solution.
Polymerization was performed at a polymerization temperature of 0 ° C. for 18 hours to prepare an aromatic polyimide solution having an aromatic polyimide concentration of 20% by weight. This polyimide solution has a rotational viscosity of 2 at 100 ° C.
It was 700 poise. This aromatic polyimide solution,
The solution was filtered through a stainless steel mesh of 400 mesh to prepare a dope solution 2 for spinning.

[Method for producing an asymmetric hollow fiber membrane having an asymmetric structure of two-layer extrusion] A spinning nozzle for two-layer extrusion (outer diameter of outer circular opening 1700 μm, slit width of outer circular opening 150 μm)
m, outer diameter of inner circular opening: 1200 μm, slit width of inner circular opening: 300 μm, outer diameter of core opening: 400 μm
m), the spinning dope solutions 1 and 2
The spinning dope 1 is discharged from the slit at the outer circular opening of the spinning nozzle, and the spinning dope 2 is discharged into the hollow fiber through the slit at the inner circular opening. After passing through the atmosphere, it is immersed in a primary coagulation liquid (0 ° C.) composed of a 65% by weight aqueous solution of ethanol, and further in a secondary coagulation liquid (0 ° C.) in a secondary coagulation apparatus equipped with a pair of guide rolls. Then, the solidification of the hollow fiber body was completed by reciprocating between the guide rolls, and the spinning was performed while the hollow fiber membrane made of the aromatic polyimide was taken up by the take-up roll (take-up speed: 15 m / min).

Finally, the hollow fiber membrane is wound around a bobbin, and after sufficiently washing the coagulation solvent and the like with ethanol, the ethanol is replaced with isooctane (substitution solvent).
The hollow fiber membrane is heated to 100 ° C to evaporate isooctane.
After drying, the hollow fiber membrane was heat-treated at a temperature of 300 ° C. for 30 minutes, and the dried and heat-treated aromatic polyimide asymmetric hollow fiber membrane (outer diameter of the hollow fiber membrane: 42)
0 μm, and its film thickness: 110 μm).

Reference Example 2 [Preparation of polyimide solution] As an acid component of a polyimide raw material, 40 mmol of 3,3 ', 4,4'-biphenyltetracarboxylic dianhydride (BPDA) and 2,2'-bis (3 , 4-Dicarboxyphenyl) hexafluoropropane dianhydride (6FDA) 45 mmol, pyromellitic dianhydride (PMDA) 15 mmol, dimethyl-3,7-diaminodibenzothiophene-5,5-dioxide (diamine component) TSN) 50 mmol,
2,2 ', 5,5'-tetrachlorobenzidine (TC
B) A polyimide dope solution was prepared in the same manner as in the preparation of the polyimide solution 2 of Reference Example 1 except that 50 mmol was used.

[Production of Single-Structure Asymmetric Hollow Fiber Membrane] The dope for spinning was poured into a hollow fiber spinning nozzle (outer diameter of circular opening: 1000 μm, slit width of circular opening: 20).
0 μm, outer diameter of core opening: 400 μm), and the mixture is discharged in a hollow fiber form from the spinning nozzle, and after passing the hollow fiber body in a nitrogen atmosphere, 65% by weight. Immersed in a primary coagulation liquid (0 ° C.) composed of an aqueous ethanol solution, and further reciprocated between guide rolls in a secondary coagulation liquid (0 ° C.) in a secondary coagulation apparatus equipped with a pair of guide rolls to form a hollow. After the coagulation of the filamentous body was completed, the spinning was performed while the aromatic polyimide hollow fiber membrane was being taken up by a take-up roll (take-up speed: 15 m / min).

Finally, the hollow fiber membrane is wound around a bobbin, and after thoroughly washing the coagulation solvent and the like with ethanol, the ethanol is replaced with isooctane (substitution solvent).
The hollow fiber membrane is heated to 100 ° C to evaporate isooctane.
After drying, the hollow fiber membrane was heat-treated at a temperature of 300 ° C. for 30 minutes, and the dried and heat-treated aromatic polyimide asymmetric hollow fiber membrane (outer diameter of the hollow fiber membrane: 42)
0 μm, and its film thickness: 110 μm).

Reference Example 3 As an acid component of a polyimide raw material, 3,3 ′, 4,4′-
Biphenyltetracarboxylic dianhydride (BPDA) 1
00 mmol, dimethyl-3,7- as diamine component
Diaminodibenzothiophene-5,5-dioxide (T
SN) A polyimide hollow fiber membrane was produced in the same manner as in Reference Example 2, except that 90 mmol and 4,4'-diaminodiphenyl ether (DADE) 10 mmol were used.

Example 1 The asymmetric hollow fiber membrane obtained in Reference Example 1 was subjected to a heat treatment at 270 ° C. for 38 hours in an air atmosphere oven without tension, followed by a preliminary heat treatment at 400 ° C. for 30 minutes. Stabilized. Next, the preheat-treated asymmetric hollow fiber membrane is placed in a quartz glass tube at 550 ° C. and maintained in a nitrogen atmosphere in an electric tubular furnace at a rate of 20 cm / min between a feed roll and a take-off roll. The mixture was passed at a speed to carry out carbonization treatment for a residence time of 4 minutes to produce an asymmetric hollow fiber carbon membrane.

Using the electron microscope, a photograph of the asymmetric hollow fiber carbon membrane produced as described above is taken at a magnification of 10,000 times the cross section of the hollow fiber carbon membrane, and the cross section of the hollow fiber carbon membrane in the photograph is observed. This confirmed an asymmetric structure composed of a carbonized dense layer (surface layer) and a partially carbonized porous layer (porous layer adjacent to the dense layer).

The permeation performance of the hollow fiber carbon membrane was measured according to the permeation performance measurement method. Table 1 shows the results.

Example 2 The hollow fiber carbon film obtained in Example 1 was immersed in a solution of silicone oil in isooctane, heated to 100 ° C. to evaporate the isooctane, and the surface of the hollow fiber carbon film was coated with silicone oil. . The permeation performance of the hollow fiber carbon membrane was measured according to the permeation performance measurement method. Table 1 shows the results.

Example 3 A hollow fiber carbon membrane produced in the same manner as in Example 1 except that the carbonization temperature was set to 600 ° C. was immersed in an isooctane solution of silicone oil, and heated to 100 ° C. to evaporate the isooctane. The surface of the hollow fiber carbon membrane was coated with silicone oil. The permeation performance of the hollow fiber carbon membrane was measured according to the permeation performance measurement method. Table 1 shows the results.

Example 4 A hollow fiber carbon membrane coated with silicone oil was prepared in the same manner as in Example 3 except that the carbonization temperature was 700 ° C. The permeation performance of the hollow fiber carbon membrane was measured according to the permeation performance measurement method. Table 1 shows the results.

Example 5 A hollow fiber carbon was produced in the same manner as in Example 1 except that the asymmetric hollow fiber membrane obtained in Reference Example 2 was used instead of the asymmetric hollow fiber membrane obtained in Reference Example 1. A film was prepared.

For the produced asymmetric hollow fiber carbon membrane,
Using an electron microscope, the cross section of the hollow fiber carbon membrane was 10,000
Take a 2 × photograph and observe the cross section of the hollow fiber carbon membrane in the photograph to obtain a carbonized dense layer (surface layer).
An asymmetric structure composed of a partially carbonized porous layer (porous layer adjacent to the dense layer) was confirmed. The permeation performance of the hollow fiber carbon membrane was measured according to the permeation performance measurement method. Table 1 shows the results.

Example 6 A hollow fiber carbon membrane was produced in the same manner as in Example 5, except that the carbonization temperature was changed to 600 ° C. The permeation performance of the hollow fiber carbon membrane was measured according to the permeation performance measurement method. Table 1 shows the results.

Comparative Examples 1 to 3 The polyimide hollow fiber membranes obtained in Reference Examples 1 to 3 before carbonization were immersed in a solution of silicone oil in isooctane.
Isooctane was evaporated by heating to 100 ° C., and the surface of the hollow fiber was coated with silicone oil. The permeation performance of these films was measured according to the permeation performance measurement method. Table 1 shows the results.

It can be seen that the carbonized membrane has a higher N ₂ permeation rate and is much better at separating perfluoro compounds than the conventional non-carbonized separation membrane.

[0057]

[Table 1]

[0058]

As can be seen from Table 1, the use of an asymmetric hollow fiber carbon membrane allows a mixture gas containing a perfluoro compound gas to obtain a high separation coefficient and a high permeation rate, which cannot be achieved by a conventional organic membrane. Thus, the perfluoro compound gas can be separated and recovered with high efficiency.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing one example of an apparatus for separating and recovering a perfluoro compound gas of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1; Gas separation device 2: Carbon membrane hollow fiber 3: Source gas supply port (mixed gas supply port) 4: Non-permeate gas outlet 5; Permeate gas outlet 6; Sealed container 7; Resin wall

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4D006 GA41 HA02 HA18 KE06P MA01 MA25 MA31 MA33 MB03 MB04 MB13 MB15 MC05X MC39 MC58X MC89 NA04 NA10 NA62 NA63 NA64 PA02 PB19 PB70 PC01

Claims (6)

[Claims] A mixed gas containing at least one perfluoro compound gas and at least one carrier gas is supplied to an asymmetric hollow fiber carbon membrane, and the content of the perfluoro compound is reduced from the permeation side of the membrane. At least one
A method for separating and recovering a perfluoro compound gas, comprising extracting a gas composed of a kind of carrier gas and collecting a gas substantially enriched with at least one kind of perfluoro compound from the non-permeate side of the membrane. 2. The asymmetric hollow fiber carbon membrane is a hollow fiber carbon membrane having an asymmetric structure obtained by partially carbonizing an asymmetric hollow fiber membrane made of an aromatic polyimide. The method for separating and recovering a perfluoro compound gas described in the above. 3. An asymmetric hollow fiber carbon membrane comprising an aromatic polyimide and an asymmetric hollow fiber membrane at a temperature in the range of 250 to 495 ° C., and the asymmetric structure of the hollow fiber membrane is maintained. Preliminary heat treatment is performed at a temperature and in an atmosphere of an oxygen-containing gas to stabilize the heat. Then, the pretreated hollow fiber membrane is partially carbonized at 500 to 900 ° C. in an atmosphere of an inert gas. 2. The method for separating and recovering perfluoro compound gas according to claim 1, wherein the hollow fiber carbon membrane has an asymmetric structure obtained by the above method. 4. The method according to claim 1, wherein the perfluoro compound gas is selected from the group consisting of fluorocarbon, SF ₆ and a mixture thereof. 5. The method according to claim 1, wherein the carrier gas is N ₂ , Ar, He, C.
4. The method for separating and recovering perfluoro compound gas according to claim 1, which is selected from the group consisting of O ₂ and air. 6. An asymmetric carbon membrane in the form of a large number of hollow fibers is housed in a sealed container, and a gas supply port and a non-permeate gas outlet communicating with the inside of the hollow fiber, and at least one non-permeable gas outlet outside the hollow fiber. A gas mixture comprising at least one perfluoro compound gas and at least one carrier gas, which is introduced from the gas supply port of the gas separator into the inside of the hollow fiber, the membrane comprising: Extracting a gas comprising at least one carrier gas having a reduced perfluoro compound content from the permeate side of the membrane, and recovering a gas substantially enriched with at least one perfluoro compound from the non-permeate side of the membrane. An apparatus for separating and recovering a perfluoro compound gas.