JPS6242723A - Method for dehumidifying mixed gas - Google Patents

Abstract

PURPOSE:To miniaturize the apparatus and to control the waste of a dry gas by using a gas separation membrane made of an aromatic polyimide and having more than a specified ratio in the gas permeation velocity of steam to methane and dehumidifying a mixed gas while passing a small amt. of dry gas along the permeated gas side of the membrane. CONSTITUTION:A mixture of an aromatic tetracarboxylic acid component such as biphenyltetracarboxylic dianhydride, and an aromatic diamine component such as a diamino-dimethyl-diphenylen sulfone and 2,6-diaminopyridine are polymerized and iminated to obtain an aromatic polyimide which is formed into a membrane. Consequently, a gas separation membrane having >=200 ratio in the gas permeation velocity of steam to methane can be obtained. The membrane 2 is housed in a gas separator 1 and a steam-contg. mixed gas is supplied from a mixed gas supply port 3. Less then 10vol% dry gas, based on the mixed gas, is supplied from a dry gas supply port 6, passed along the permeated gas side of the membrane 2 and discharged from a discharge port 5 along with the steam permeated through the membrane 2. The dehumidified nonpermeated gas is discharged from a discharge port 4.

Description

Detailed Description of the Invention [Field of Application of the Invention] This invention relates to a gas separation membrane (hollow fiber, spiral membrane,
Selective separation of water vapor from various gas mixtures containing water vapor (e.g., air, natural gas, associated gas during crude oil extraction, fermentation gas, etc.) using a gas separation device containing a flat membrane (e.g., flat membrane) The present invention provides a method for removing mixed gas and drying the mixed gas.

[Description of prior art]

Conventionally, glycol absorption methods, molecular sieve adsorption methods, and the like have been generally employed as methods for dehumidifying hydrocarbon gases such as natural gas.

However, all of these methods require fairly large equipment, high equipment costs, and sufficient land for factory construction, making them difficult to use for offshore gas extraction where space is limited. Not suitable, but also the complexity of operation,
There were also problems in terms of operational safety and difficulty in maintenance.

In contrast to the above-mentioned absorption or adsorption methods, gas separation modules with built-in gas separation membranes have recently been developed as a method that can be made into small, lightweight equipment, easy to maintain, and highly safe. Some methods have been proposed to dehumidify or dry the mixed gas.

Methods for dehumidifying a mixed gas using such a gas separation membrane include, for example, fa) pressurizing a mixed gas containing water vapor to an extremely high pressure and supplying it to a gas separation device;
By significantly reducing the pressure on the permeate side of the membrane (Japanese Patent Laid-Open No. 54-15
2679 Publication), a method of dehumidifying a mixed gas by increasing the pressure difference of water vapor between the supply side and the permeation side of a gas separation membrane (bl. The permeability of water vapor (methane gas) is relatively high, and the selective permeability of water vapor (PH
A method of dehumidifying a mixed gas using a gas separation membrane having a PCI4) of 200 to 400
3835), and (C) a method of dehumidifying the mixed gas by supplying a large amount of purge gas to the i3 side of the gas separation membrane to lower the partial pressure of the permeated water vapor (see Japanese Patent Application Laid-open No. 1983- (see Japanese Patent No. 2674) and the like are known.

However, in the above-mentioned known method (a), the gas content M
In areas where the concentration of water vapor is high on the gas permeation side of the membrane (near the permeate gas outlet), water vapor may not be able to be removed from the mixed gas at a sufficiently high removal rate;
In addition, with the method (b) mentioned above, it is difficult to manufacture a gas separation membrane with gas separation performance compatible with this method, or the main component of the mixed gas is The drawback was that a large amount of the effective gas component was lost.

Furthermore, the method (c) described above has the disadvantage of consuming a considerable amount of purge gas.

[Requirements and effects of the present invention]

As a result of intensive research into a practical dehumidification method that overcomes the shortcomings of the aforementioned "mixed gas dehumidification method using a gas separation membrane," the inventors found that the water vapor permeability (velocity) is sufficiently high. We use a gas separation device that has a built-in gas separation membrane (hollow fiber membrane or spiral gas separation membrane) made of aromatic polyimide, which has high water vapor permeability and extremely high selective permeability for water vapor relative to other gas components. A small amount of dry gas supplied from the outside is passed along the gas permeation side of the gas separation membrane of the gas separation device, while a mixed gas is made to flow along the gas supply side of the gas separation membrane to pass through the gas separation membrane. The present invention was completed based on the discovery that the mixed gas can be effectively dehumidified or dried by selectively permeating water vapor in the mixed gas.

That is, this invention provides a permeated gas outlet and a dry gas supply port that communicate with the gas permeation side of the gas separation membrane, and a mixed gas supply port and non-permeated gas exhaust that communicate with the gas supply side of the gas separation membrane. A gas separation membrane made of aromatic polyimide with a permselectivity of 200 or more, expressed as the ratio of gas permeation rates of water vapor and methane (PH20/PCH4), is built into a sealed container with an outlet. Using a separation device, a mixed gas containing water vapor is supplied from the mixed gas supply port of the gas separation device and allowed to flow along the gas supply side of the gas separation membrane, while % or less of dry gas is supplied from the dry gas supply port and is caused to flow along the gas permeation side of the gas separation membrane, while water vapor of the mixed gas that has passed through the gas separation membrane is removed. Relating to a gas dehumidification method.

The method of the present invention uses a gas separation membrane made of aromatic polyimide that has excellent water vapor permselectivity, and dehumidifies a mixed gas while flowing dry gas through the gas permeation side of the gas separation membrane. (a) The gas separation membrane built into the gas separation device can be used effectively, and the membrane tank of the gas separation membrane that is layered inside the entire gas separation device can be made smaller, so the gas separation ('h) It is possible to use relatively low-pressure raw material gas;
In addition, it is possible to dehumidify the mixed gas without increasing the differential pressure between the raw material gas supply side and the gas permeation side so much, and (C) dry gas (supplied from the outside to the gas permeation side and circulated). Advantages include that sufficient dehumidification can be achieved even when the amount of purge gas (purge gas) is relatively small relative to the supply gas, and waste of drying gas can be suppressed.

Furthermore, the aromatic polyimide gas separation membrane used in the method of the present invention has extremely excellent properties such as durability, heat resistance, chemical resistance, and moisture resistance.
Another advantage is that the mixed gas can be dehumidified stably over a long period of time.

[Detailed explanation of each requirement of the present invention]

Hereinafter, each requirement of the present invention will be explained in more detail with reference to the drawings.

In the gas separation device used in the present invention, for example, as shown in FIG. Gas separation device 1 built in
It is.

The gas separation membrane has a gas overspeed ratio (PH2) of water vapor and methane measured by the gas permeation test method described below.
A gas separation membrane made of aromatic polyimide (for example, a hollow fiber membrane) having a permselectivity (gas separation performance) indicated by , spiral film, flat film, etc.).

The gas separation membrane has a permeation rate of water stem air at 25°C (PH2
0i (according to the gas permeation test method described below) is approximately I
O-5cil/d ・sec ・cml 1g or more,
In particular, 1×l Q-'~5×10-2d/cd・
It is preferable that the amount is about sec.cm/1 g.

In the gas separation membrane, its permselectivity (PH20/
PCI! 4) is less than 200, it is not suitable because the mixed gas cannot be dehumidified sufficiently effectively.

The sealed container also includes an exhaust port 5J for permeated gas (such as water vapor) that has passed through the gas separation membrane and a supply port 6J for dry gas (purge gas), which are in communication with the gas permeation side of the gas separation membrane 2. In addition, a sealed container (for example,
It may be a cylindrical container, etc.).

In the gas separation device described above, both ends of the gas separation membrane (such as a bundle of hollow fibers) 2 are formed by solidifying a suitable thermosetting resin such as an elastomer resin, an acrylate resin, an epoxy resin, or a phenol resin. The gas separation membrane element is formed by binding the disc-shaped resin walls 8. The hole is open to the outside of the resin wall, and the element is sealed at the 8,8° portion of the resin wall as shown in Figure 1, using adhesive or the like if necessary. It suffices if it is sealed and fixed integrally to the inner wall of the container 7.

The gas separation membrane made of aromatic polyimide is produced by polymerizing (and imidizing) an acid component such as an aromatic tetracarboxylic acid or its acid dianhydride and an aromatic diamine component.
Using the aromatic polyamic acid (or aromatic polymide) solution obtained by It is a composite separation membrane manufactured by forming a thin homogeneous layer on the surface of a porous membrane made of a suitable material using an aromatic polyimide solution or an aromatic polyimide solution. Examples include gas separation membranes that have excellent gas separation performance.

The aromatic polyimide mentioned above is especially r5-1 or -3
The aromatic diamine containing the divalent group j of O2- is
The product obtained by polymerizing and imidizing approximately equimolar amounts of an aromatic diamine component and an aromatic tetracarboxylic acid component containing 0 to 100 mol%, preferably 40 to 100 mol%, has a water vapor transmission rate. It is extremely suitable in many respects.

Examples of the aromatic diamines include diamino-dibenzothiophene or its derivatives, diamino-diphenylene sulfone or its derivatives, diamino-diphenyl sulfide or its derivatives, diamino-diphenyl sulfone or its iM4 form, diamino-thioxanthin or its derivatives, etc. Examples include derivatives.

In particular, diamino-dibenzothiophenes or derivatives thereof include diamino-dibenzothiophenes represented by the general formula or diamino-diphenylene sulfones represented by the general formula. However, in the above general formula, R, R'
is hydrogen, a hydrocarbon substituent having 1 to 6 carbon atoms (alkyl group, alkylene group, aryl group, etc.), 1 carbon number
Examples include alkoxy groups having 6 to 6, and preferred examples include methyl, ethyl, and propyl groups.

The diamino-dibenzothiophenes include 3,
7-Diami2,8-dimethyl-dibenzothiophene, 3,7-Diami2,6-dimethyl-dibenzothiophene, 2,8-Diamino-3,7-dimethyl-dibenzothiophene, 3,7-Diami2, 8-diethyl-
Examples of the diamino-diphenylene sulfones include dibenzothiophene, 3,
7-Diamitwo-2,8-dimethyl-diphenylenesulfone, 3,7-diamitwo-2,8-diethyl-diphenylenesulfone, 3,7-diamitwo-2,8-dipropyl-
Diphenylene sulfone, 2,8-diamino-3゜7-dimethyl-diphenylene sulfone, 3,7-diamino-2
, 8-dimethoxy-diphenylene sulfone, and the like.

Furthermore, the diphenyl sulfide or its derivative includes 4,4'-diamino-diphenyl sulfone,
Diamino-diphenyl sulfones such as 3,3°-diamino-diphenyl sulfone, 3,5-diamino-diphenyl sulfone, 3.4″-diamino-diphenyl sulfone, and 4,4′-diamino-diphenyl sulfide; 3. 3”-diamino-diphenyl sulfide, 3.
Diamino-diphenyl sulfides such as 5-diamino-diphenyl sulfide and 3.4'-diamino-diphenyl sulfide can be mentioned;
Cyamitsu-thioxanthin-5,5-dioxide, 2.
8-diamino-thioxanthine-5,5-dioxide,
3.7-cyamino-thioxanthone-5,5-dioxide, 2.8-diamino-thioxanthone-5,5-dioxide, 3.7-cyamino-phenoxanthone-5.5-
Dioxide, 2,8-diamino-phenoxatin-5,
5-dioxide, 2,7-cyamitsuthianthurene, 2
．． 8-Diamino-thianthrene, 3,7-diamitul
O-methyl-phenothiazine-5,5-dioxide and the like can be mentioned.

Furthermore, examples of aromatic diamines include bis((p-aminophenoxy)phenyl)sulfide and bis((p-aminophenoxy)phenyl)sulfone.

As the aromatic diamine component, other aromatic diamines can be used together with the aromatic diamines containing the above-mentioned "-3-1 or -502-〇 divalent group". Aromatic diamines include 4,4'-diamino-diphenyl ether, 3,3'-dimethyl-4,4
1-diamino-diphenyl ether, 3,3'-jethoxy-4,4'-diamino-diphenyl ether, 3,
Diphenyl ether compounds such as 3°-diamino-diphenyl ether, diphenylmethane compounds such as 4,4°-diamino-diphenylmethane, 3,3”-diamino-diphenylmethane, 4I4′-diamino-benzophenone, 3,3°-diamino-benzophenone benzophenone compounds such as 2,2-bis(3-aminophenyl)propane, 2,2-bis(4-aminophenyl)propane, 2,2-bis(4-(4'-aminophenoxy)
2,2-bis(phenyl)propane-based compounds such as phenyl]propane, 0-1m-1p-phenylenediamine, 3,5-diaminobenzoic acid, 2,6-diamitupyridine, o-)lysine, etc. be able to.

The aromatic tetracarboxylic acid component used in the production of the aromatic polyimide is 3.3', 4.4''-biphenyltetracarboxylic acid, or 2,3.3', 4''-biphenyltetracarboxylic acid.
'-Biphenyltetracarboxylic acids, their dianhydrides, or their lower alcohol esters, 3°3", 4.4
'-benzophenonetetracarboxylic acid, or 2,3.
3′,4″-benzophenonetetracarboxylic acids, their dianhydrides, or benzophenonetetracarboxylic acids such as lower alcohol esters thereof;
Furthermore, pyromellitic acids such as pyromellitic acid, its dianhydride, or its esterified product can be mentioned.

In particular, in this invention, an aromatic polyimide obtained from an aromatic tetracarboxylic acid component containing 50 to 100 mol%, especially 80 to 100 mol% of biphenyltetracarboxylic acids, and the above-mentioned aromatic diamine component is used. , has excellent solubility in organic solvents such as phenolic compounds, so gas separation membranes made of such aromatic polyimides are stable! l! It is suitable from the viewpoint of film forming, such as preparation of a dope solution for a film and film forming properties.

The gas separation polyimide membrane used in this invention comprises an aromatic polyamic acid (polyimide precursor) obtained from the above-mentioned aromatic diamine component and aromatic tetracarboxylic acid component;
Alternatively, an organic solvent solution such as aromatic polyimide soluble in an organic solvent is used as a dope solution for film formation, a thin film of the dope solution is formed, and a drying process is performed in which the solvent is removed from the thin film of the dope solution and solidified. Dry film forming method, which mainly forms film.
Alternatively, it is possible to manufacture polyimide separation membranes with various structures by forming them into flat membranes or hollow fibers using a wet membrane-forming method in which the TA membrane of the dope solution is brought into contact with a coagulating liquid to coagulate and form a membrane. .

For example, the method for producing the gas separation polyimide membrane used in the present invention includes the above-mentioned aromatic diamine component (which may contain other aromatic diamines) and the above-mentioned biphenyltetracarboxylic acids. and an aromatic tetracarboxylic acid component mainly containing approximately equimolar amounts of a phenolic compound in an organic solvent at a temperature of about 140° C. or higher in one step to produce an aromatic polyimide,
A solution of the aromatic polyimide (concentration: about 3 to 30% by weight)
) is used as a dope liquid and coated or cast on a substrate at a temperature of about 30 to 150°C or extruded into a hollow fiber shape to form a thin film (flat film or hollow fiber) of the dope liquid, and then The thin film is immersed in a coagulation liquid to form a coagulation film, and the solvent, coagulation liquid, etc. are evaporated and removed from the coagulation film, and finally, it is thoroughly dried and heat-treated at a temperature of 150 to 400℃, especially 170 to 350℃. For example, a membrane forming method for forming an asymmetric gas separation membrane made of aromatic polyimide can be mentioned.

In the method of this invention, a gas separation device incorporating the aforementioned aromatic polyimide gas separation membrane is used, and as shown in FIG. 1, a mixed gas containing water vapor is passed through the gas separation device 1. The mixed gas is continuously supplied from the mixed gas supply port 3 and allowed to flow along the gas supply side of the gas separation membrane 2, while at most 10% by volume, preferably from 0.5 to 8% by volume of the mixed gas. A proportionate amount of dry gas is supplied from the dry gas supply port 6, and while flowing along the gas permeation side of the gas separation membrane, the water vapor components of the mixed gas that has passed through the gas separation membrane 2 are removed as described above. The mixed gas is removed by being discharged from the permeated gas outlet 5 along with the dry gas, and the mixed gas that has not passed through the gas separation membrane (non-permeable gas) is discharged from the non-permeable gas outlet 4, thereby dehumidifying the mixed gas. It dries.

In this invention, the mixed gas has a water vapor content close to a saturated state at the temperature and pressure during dehumidification (e.g., a saturated content of water vapor in the mixed gas that is the raw material gas at the temperature during the dehumidification operation). It is sufficient that it is contained in a mixed gas mainly composed of hydrocarbons, natural gas, petroleum gas, etc., at a content rate of at least 70% or more of its saturated content rate.

In this invention, if the amount of drying gas supplied is too large compared to the amount of mixed gas supplied as raw material gas, the efficiency of removing water vapor from the mixed gas will not improve, and only the consumption of drying gas will increase. This is not appropriate because the amount increases unnecessarily, and if the amount of drying gas supplied becomes too small, it is not preferable because the water vapor itself will not be removed sufficiently. In this invention, the amount of drying gas supplied is approximately 0.5 to 8% by volume relative to the amount of raw material gas (mixed gas) supplied.
At the same time, the drying gas is supplied at an appropriate gas velocity (preferably from 0.1 to 10 m/sec, particularly preferably from 0.1 to 10 m/sec, particularly preferably from 0.1 to 10 m/sec, so that the supply rate is such that It is preferable to supply the gas at a gas velocity of about .5 to 8 m/sec.

In this invention, the drying gas refers to a mixed gas having the same composition as the raw material gas, in which the water vapor content is approximately 300 ppm or less, particularly 200 ppm or less, and further approximately 1 to 1100 ppm, or nitrogen gas or argon gas. , neon gas, or other inert gas. Therefore, in some cases, as shown in FIG. , it may be supplied as a dry gas to the permeate gas side of the gas separation membrane.

In this invention, the pressure of the mixed gas supplied to the gas separation device is adjusted to remove water vapor by the amount of drying gas supplied to the permeate gas side of the gas separation membrane or the pressure when the permeate gas is discharged. However, in this invention, when the pressure at the time of exhausting the permeated gas is near atmospheric pressure, the range is not particularly limited and may be within a wide range.
g/cd or more, particularly about 10 to 100 kg/c+J, is preferable in order to increase the water vapor removal rate.

Further, the supply amount of the mixed gas is such that the supply ratio to the effective area of the gas separation membrane (the hollow fiber to the membrane area) is approximately 0.05 to 100 ad/c+J-see, particularly 0.1 ~10cIIl/clI! - It is preferable that the supply amount be about sec.

〔Example〕

In this invention, the gas permeation test uses a gas separation device as shown in Fig. 1, which is equipped with a gas separation membrane (hollow fiber) made of each aromatic polyimide, to conduct a mixed gas containing water vapor for approximately 60 minutes. While supplying to the gas separation device at a supply pressure of ~52 kg/cdG and a temperature of 25°C, gas separation was performed while supplying dry gas to the inside of the hollow fiber, and each composition and The amount of permeation of each component (the analysis of water vapor was performed using a DuPont Model 303 hygrometer, and the analysis of other gases was performed using gas chromatography) was used to measure the rate of water vapor permeation through the gas separation membrane. .

Examples 1-3 Hollow fiber A made of aromatic polyimide was prepared.

The hollow fiber A contains 100 parts by weight of biphenyltetracarboxylic dianhydride,
80 parts by weight of diamino-dimethyl-diphenylene sulfone isomer mixture and 20 i of 2,6-cyamitubiridine!
It is made of aromatic polyimide formed from 31 parts, effective length: 5.6eai, outer diameter: 305μ, inner diameter: 90
μ, and the water vapor transmission rate at a measurement temperature of 25°C; 6.5 X10
''''cl/ cd ・see ・emHg).

One of the hollow fibers A (effective membrane area: 0.54 cd) is
Using a gas separation device whose both ends are sealed with epoxy resin and built into a sealed container of the same type as shown in Figure 1, the mixed gas supply port of the gas separation device is connected to the gas shown in Table 1. 52k of mixed gas containing water vapor and methane as the main component
g/ejG, a temperature of about 25° C., and a gas flow rate shown in Table 1 to flow along the outer surface (gas supply side) of the hollow fiber, while containing only about 10 ppm or less of water vapor. Dry argon gas (dry gas) that has not been used is supplied from the dry gas supply port of the gas separation device at a flow rate shown in Table 1, and while flowing along the inner surface (gas permeation side) of the internal hole of the hollow fiber, The permeated gas containing water vapor, etc. that has permeated through the gas separation membrane is recovered from the permeated gas outlet at approximately normal pressure, and the non-permeated gas (dehumidified gas) that has not permeated through the gas separation membrane is collected in the gas separation device. Collected from non-permeable gas outlet.

The compositions and flow rates of the permeate gas and non-permeate gas were measured, and the results are shown in Table 1.

Comparative Example 1 Water vapor was removed from the mixed gas in the same manner as in Example 1, except that no drying gas was supplied. The results are shown in Table 1.

Examples 4-5 Hollow fiber B made of aromatic polyimide was prepared.

The hollow fiber B contains 90 parts by weight of biphenyltetracarboxylic dianhydride and 10 parts by weight of pyromellitic dianhydride, 90 M parts of a diamino-dimethyl-diphenylene sulfone isomer mixture and 10 parts by weight of 4,4'-diaminodiphenyl ether. Made of aromatic polyimide formed from parts by weight, effective length: 5.15ao, outer diameter: 434μ, inner diameter: 19
0 μ, and the water vapor transmission rate at a measurement temperature of 25°C; 7.4 Xl 0
-'ad/ cd -sec -aaHg).

One of the hollow fibers B (effective membrane area 50.70 aJ) is
Using a gas separation device whose both ends are sealed with epoxy resin and built into a sealed container of the same type as shown in Figure 1, the mixed gas supply port of the gas separation device is connected to the gas shown in Table 1. A mixed gas containing water vapor and mainly composed of methane is supplied at the gas flow rate shown in Table 1, and dry argon gas (dry gas) is supplied from the dry gas supply port of the gas separation device at the flow rate shown in Table 1. Except for the supply, the permeated gas was recovered from the permeated gas outlet at normal pressure in the same manner as in Example 1, and the non-permeated gas (dehumidified gas) was recovered from the non-permeated gas outlet of the gas separation device. .

The compositions and flow rates of the permeate gas and non-permeate gas were measured, and the results are shown in Table 1.

Comparative Example 2 Water vapor was removed from the mixed gas in the same manner as in Example 4, except that no drying gas was supplied. The results are shown in Table 1.

Examples 6 to 7 A gas separation device incorporating hollow fibers B' having the same shape and material as Example 4, except that the effective length of the hollow fibers is 11.0 cm and the effective membrane area is 1.50 cd. using
In addition, a mixed gas having the water vapor content shown in Table 1 was used as the raw material gas, the supply amount of the mixed gas was changed as shown in Table 1, and the supply pressure of the mixed gas was 6 kg/c.
11G and the amount of drying gas supplied was changed in the same manner as in Example 4 to remove water vapor from the mixed gas. The results are shown in Table 1.

Comparative Example 3 Water vapor was removed from the mixed gas in the same manner as in Example 6, except that no drying gas was supplied. The results are shown in Table 1.

Examples 8-10 Hollow fibers C made of aromatic polyimide were prepared.

The hollow fiber C contains 100 parts by weight of biphenyltetracarboxylic dianhydride,
Made of aromatic polyimide formed from 80 parts by weight of a diamino-dimethyl-diphenylene sulfone isomer mixture and 20 parts by weight of 2,6-diamitupyridine, effective length: approximately 25.3 C11, outer diameter: 454μ, Inner diameter: 230μ, and water vapor transmission rate at a measurement temperature of 25°C: 5-6 xl
0-'ad/cj-sec-cmHg).

A bundle of 30 hollow fibers C (effective membrane area: 108c)
111), whose both ends are tightly bonded with epoxy resin,
A gas separation device built in a sealed container of the same type as shown in Figure 1 is used, and the mixed gas supply port of the gas separation device contains water vapor shown in Table 1 and contains methane as the main component. A mixed gas of
The permeate gas was recovered at normal pressure from the permeate gas outlet in the same manner as in Example 1, except that dry argon gas (dry gas) was supplied from the dry gas supply port of the gas separation device at the flow rate shown in Table 1. In addition, non-permeable gas (dehumidified gas) was recovered from the non-permeable gas outlet of the gas separation device.

The compositions and flow rates of the permeate gas and non-permeate gas were measured, and the results are shown in Table 1.

Comparative Example 4 Water vapor was removed from the mixed gas in the same manner as in Example 8 except that the drying gas was not completely supplied. The results are shown in Table 1.

Examples 11-12 A hollow fiber made of aromatic polyimide was prepared.

The hollow fibers are made of aromatic polyimide formed from 100 parts by weight of biphenyltetracarboxylic dianhydride vA and 100 parts by weight of a diamino-dimethyl-diphenylene sulfone isomer mixture, and have an effective length of approximately 4.1 am. , outer diameter: 22oμ, inner diameter: 1
30μ and the water vapor transmission rate at a measurement temperature of 25°C; 5. OXl
0-'cd/·see-cmllg).

A bundle of 6 hollow fibers (effective membrane area: 1°70cm)
ffl) is tightly bonded at both ends with epoxy resin,
Using a gas separator built in a sealed container of the same type as shown in FIG. 1, and using a device as shown in FIG. A mixed gas containing water vapor as shown in Table 1 and containing methane as a main component was supplied at the gas flow rate shown in Table 1, the supply pressure of the mixed gas was set to 1"01qr/cfflG, and the gas mixture was as shown in FIG. The procedure was the same as in Example 1, except that the non-permeable gas partially branched from the non-permeable gas line was supplied as dry gas via the circulation line from the dry gas supply port of the gas separation device at the flow rate shown in Table 1. Then, the permeated gas was recovered from the permeated gas outlet at normal pressure, and the non-permeated gas (dehumidified gas) was recovered from the non-permeated gas outlet of the gas separation device.

The compositions and flow rates of the permeate gas and non-permeate gas were measured, and the results are shown in Table 1.

Comparative Example 5 Example 11 except that no drying gas was supplied.
Water vapor from the mixed gas was removed in the same manner as above. The results are shown in Table 1.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing an example of a gas separation apparatus used in the method of the present invention. FIG. 2 is a flow diagram when a part of the non-permeable gas (dehumidified gas) coming out of the non-permeable gas outlet of the gas separation device is recirculated and used as drying gas in the method of the present invention. The outline is shown below. 1; Gas separation device, 2; Hollow fiber, 3; Raw material gas supply port (
mixed gas supply port), 4; non-permeable gas discharge port, 5; permeated gas discharge port, 6; dry gas supply port, 7; sealed container, 8; resin wall.

Claims (1)

[Claims] A permeated gas outlet and a dry gas supply port that communicate with the gas permeation side of the gas separation membrane, and a mixed gas supply port and non-permeated gas exhaust that communicate with the gas supply side of the gas separation membrane. A gas separation membrane made of aromatic polyimide with a permselectivity of 200 or more, expressed as the ratio of gas permeation rates of water vapor and methane (PH_2O/PCH_4), is built into a sealed container with an outlet. Using a separation device, a mixed gas containing water vapor is supplied from the mixed gas supply port of the gas separation device and allowed to flow along the gas supply side of the gas separation membrane, while % or less of dry gas is supplied from the dry gas supply port and is caused to flow along the gas permeation side of the gas separation membrane, while water vapor of the mixed gas that has passed through the gas separation membrane is removed. Gas dehumidification method.