JP2000140558A - Method and device for separating/recovering gas for electrical insulation - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable SF6 to be efficiently separated/recovered and thereby reduce the emission amount of the SF6 into an atmosphere by supplying a mixed gas made up of an electrically insulating gas containing a specific amount of the SF6 to a gas separating membrane to establish their mutual contact and recovering a gas containing the SF6 of a specific purity from the impermeable side of the membrane. SOLUTION: When SF6 is efficiently recovered by separation, a mixed gas consisting of the SF6 and another gas is supplied from the mixed gas supply aperture 3 of a gas separation device 1 and is fluidized to an impermeable gas discharge aperture 4 side through the inside of a hollow fiber 2. The gas permeating through a separation membrane is discharged from a permeable gas discharge aperture 5, while the gas not permeating through the separation membrane is discharged from an impermeable gas discharge aperture 4 and thus the SF6 whose permeation velocity is low is recovered by separation. In this case, the concentration of the SF6 in the mixed gas is set to be 6-60 vol.% and the SF6 amount to be discharged from the membrane permeation side is set to be 3 vol.% or less of the mixed gas before separation. Besides, the mixed gas is treated so that the purity of the SF6 in the SF6-rich gas to be recovered to the membrane impermeation side is equivalent to 80 vol.% or more.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for separating and recovering a halogen compound from a mixed gas containing a halogen compound used in an electric insulation system.

[0002]

2. Description of the Related Art Gas insulated switchgears, gas circuit breakers, gas shutoffs
Electrical insulation of gas-insulated electrical equipment such as edge transformers and pipeline air transmission
SF as an edge gas₆(Sulfur hexafluoride) gas, Freon
Halogen compounds such as gas and carbon tetrachloride gas
Is used. In particular, SF ₆Is to raise the air pressure
Shows better dielectric strength and has a liquefied
12 and lower than carbon tetrachloride.
Because it can be used, it is widely used as an electric insulating gas.
However, global warming, which has recently become a global issue
There is a pressing need for countermeasures as chemical gas. One measure
As SF₆SF to reduce the use of₆And beyond
Gas-insulated electric machine
Attempts have been made to use them in vessels.

In this case, the halogen compound needs to be separated from other gases, recovered and reused. As a method therefor, a pressure cooling method (liquefaction method) has been conventionally studied.

However, in the case of the pressurized cooling method, an extremely high pressure and a low temperature are generally required, and the higher the pressure and the lower the temperature, the more the separation and recovery of the target halogen compound is to be increased to reduce the recovery loss. Is required, and in practice, the recovery loss of the halogen compound is extremely large. For example, H. Hama et al., "Application problems of SF6
/ N2 mixtures to gas insulated bus ", 8th Internatio
nal Symposium on Gaseous Dielectrics, Virginia Bea
ch, June 22-I (1998) states that a mixed gas containing SF ₆ of 7% or less liquefies even at a low temperature of 3.5 MPa and -50 ° C.
F ₆ is 0%, and in a mixed gas of SF ₆ of 10% or less,
Recovery is disclosed to be substantially difficult. Also, 5
3.5 MPa, -10 ° C. even with a mixed gas of 0% SF ₆
Discloses that the liquefaction rate is less than 50%. As described above, normally, the recovery loss of SF ₆ by the pressurized cooling method is extremely large, about 50%.

[0005] For recovery loss in the that will be released into the atmosphere, recovery loss less efficient separation recovery method and apparatus of SF ₆ in view of global warming is demanded.

[0006]

SUMMARY OF THE INVENTION The present invention is expected to increase the amount of halogen compound gas harmful to the global environment, especially from the use of insulating mixed gas used for gas-insulated electric equipment and the like. It is an object of the present invention to provide a method and an apparatus for efficiently separating and recovering SF ₆ and dramatically reducing the amount of SF ₆ released into the atmosphere.

[0007]

The present invention SUMMARY OF] is a mixed gas consisting of other at least one or more electrically insulating gas SF ₆ of 3 to 60% by volume is contacted with feed to the gas separation membrane, the membrane From the non-permeate side, a gas containing SF ₆ with a purity of 80% by volume or more is recovered at a recovery rate of SF ₆ of 80% or more, and the amount of SF ₆ gas discharged to the permeate side of the gas separation membrane is equal to the total mixed gas amount. The present invention relates to a method for separating and recovering a gas for electric insulation, which is not more than 3% by volume.

[0008] The present invention also relates to the above-mentioned method for separating and recovering a gas for electrical insulation, wherein the gas separation membrane is an aromatic polyimide separation membrane.

Further, the present invention, the electrically insulating gas other than the SF ₆ is nitrogen gas, carbon dioxide gas, helium gas, hydrogen gas, sulfur dioxide gas, characterized in that at least one of the air The present invention relates to a method for separating and recovering an electric insulating gas.

[0010] Further, the present invention provides a separation membrane in the form of a large number of hollow fibers, which is contained in a sealed container, and has a gas supply port and a non-permeate gas outlet communicating with the inside of the hollow fibers, and further, an outside of the hollow fibers. A gas separation device having at least one permeate gas outlet, wherein SF ₆ gas and at least one other
A mixed gas composed of more than one kind of electrically insulating gas is introduced into the inside of the hollow fiber from the gas supply port of the gas separator, and the electrically insulating gas whose SF ₆ gas amount is 3% by volume or less of the supplied mixed gas is permeated gas. The present invention relates to a device for separating and recovering a gas for electrical insulation, wherein a gas discharged from an outlet and containing SF ₆ having a purity of 80% by volume or more is recovered from a non-permeate gas outlet.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention relates to a method of contacting a gas mixture comprising SF ₆ used as an electric insulating gas of gas-insulated electric equipment and at least one other kind of electric insulating gas with a gas separation membrane, A gas rich in an electrically insulating gas other than SF ₆ is discharged to the permeation side of the membrane, and SF ₆ is discharged from the non-permeation side of the membrane.
This is a method for separating and recovering a gas rich in water.

The SF ₆ gas is a colorless, odorless and non-toxic inert gas, exhibits excellent dielectric strength by increasing the pressure, has a low liquefaction temperature, and can be used under pressure even at a low temperature. It is preferably used as

The possibility of using a mixed gas containing SF ₆ for electrical insulation is currently being studied, and types of gases other than SF ₆ used as the mixed gas include nitrogen gas, carbon dioxide gas, helium gas, and the like. Examples include hydrogen gas, sulfur dioxide gas, and air. 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 the separation and recovery of the present invention. 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 electric insulating gas.

The concentration of SF ₆ in the electric insulating mixed gas supplied to the gas separation membrane is 3 to 60% by volume, preferably 5 to 50% by volume. At lower concentrations, the electrical insulation is reduced, at higher concentrations the use of SF ₆ increases,
This is because the loss of SF ₆ increases. Some of the SF ₆ is chlorofluorocarbon, four with an electrically insulating halogen compounds other than SF _6, such as carbon tetrachloride may be a gas composition was replaced by 50%.

The amount of SF ₆ discharged to the permeation side of the membrane is directly related to the problem of air pollution, and the smaller the better, the better. However, the volume of SF ₆ is preferably 3% by volume or less of the mixed gas before separation, and more preferably 1% by volume or less. preferable.

Further, the purity of SF _6-rich gas SF ₆ recovered on the non-permeate side is preferably 80 vol% or more. Not only it requires only a small storage tank when stored at higher gas state high purity SF _6, SF ₆
The higher the purity, the easier it is to liquefy, which is advantageous when stored in a liquid state.

[0017] As the gas separation membrane, one of the transmission speed greater film than transmission rate of SF ₆ of electrically insulating gas other than SF ₆ is used. For example, polyamide, cellulose, cellulose acetate, polyimide film and the like can be mentioned. Among these, permeation rate ratio of the gas component and SF ₆ except SF ₆ is large, further, modularization can be increased membrane area per easy unit volume, and heat resistance, excellent in durability aromatic polyimide gas separation Membranes are preferred. Since the aromatic polyimide film has a very high water vapor transmission rate that causes a decrease in dielectric strength when present in an electric insulating gas, the water vapor accompanies the gas having a high transmission rate in the mixed gas to form a SF. ₆ and separated. For this reason, it is particularly preferably used for separating and recovering SF ₆ used for an electric insulating gas. The aromatic polyimide gas separation membrane contains an aromatic tetracarboxylic acid skeleton and an aromatic diamine skeleton, and can be manufactured by a known method.

Examples of the acid which forms the group of the aromatic tetracarboxylic acid skeleton include biphenyltetracarboxylic acids, for example, 3,
2,3,3 ', 4'-biphenyltetracarboxylic acid, acid anhydrides, esters, etc., such as 3', 4,4'-biphenyltetracarboxylic acid and acid anhydrides and esters; bis (dicarboxyphenyl) Propanes, such as 2,2
-Bis (3,4-dicarboxyphenyl) propane and acid anhydrides and esters thereof, such as 2,2-bis (3,4-dicarboxyphenyl) hexafluoropropane and acid anhydrides and esters thereof; pyromellitic acids Benzophenone tetracarboxylic acids such as 3,3 ′, 4,4′-benzophenonetetracarboxylic acid and acid anhydrides and esters such as 2,3,3 ′, Bis (dicarboxyphenyl) sulfones, for example, bis (3,4-dicarboxyphenyl) sulfone and its acid anhydrides and esters; bis (dicarboxyphenyl) Phenyl) ethers, for example, bis (3,4-dicarboxyphenyl) ether and its anhydrides and esters And the like.

As the diamine serving as the group of the aromatic diamine skeleton, an aromatic diamine compound having one and / or two or more benzene rings is used. Specifically, for example,
4,4'-diaminodiphenyl ether, 3,4'-
Diaminodiphenyl ether, 3,3′-diaminodiphenyl ether, 3,3′-dimethyl-4,4′-diaminodiphenyl ether, 3,3′-dimethoxy-4,
Diphenyl ether compounds such as 4'-diaminodiphenyl ether; 4,4'-diaminodiphenylmethane, 3,3'-diaminodiphenylmethane, 2,2'-
Diphenylmethane compounds such as diaminodiphenylmethane and 2,4'-diaminodiphenylmethane; 4,4 '
-Diaminobibenzyl, 4,4'-diamino-2,2 '
Bibenzyl compounds such as dimethylbibenzyl; 4,
Benzophenone compounds such as 4'-diaminobenzophenone, 3,3'-diaminobenzophenone, and 2,2'-diaminobenzophenone; 2,2-bis (3-aminophenyl) propane, 2,2-bis [4- (4 2,2-bis (phenyl) propane-based compounds such as' -aminophenoxy) phenyl] propane; benzidine-based compounds such as 3,3'-dimethylbenzidine and 3,3'-dimethoxybenzidine;3,3'- Diaminodiphenyl sulfide, 4,4′-diaminodiphenyl sulfide, 3,
Diaminodiphenylsulfide compounds such as 3′-diaminodiphenylsulfone and 4,4′-diaminodiphenylsulfone; phenylenediamine compounds such as o-, m- and p-phenylenediamine; 3,5-diaminobenzoic acid; Diaminobenzoic acid compounds such as 4-diaminobenzoic acid and 2,3-diaminobenzoic acid; 2,6-diaminopyridine, 2,5-diaminopyridine, 2,3-
Examples thereof include diaminopyridine-based compounds such as diaminopyridine. These aromatic diamines may be used alone or in combination of two or more.

The hollow fiber polyimide separation membrane is prepared by dissolving a polyimide solution obtained by polymerizing and imidizing substantially equimolar amounts of a tetracarboxylic acid component and a diamine component in the presence of an organic polar solvent. It is used as a dope liquid, extruded from a hollow fiber forming nozzle to form a hollow fiber, coagulated in a coagulating liquid, then removed and dried.

The hollow fiber polyimide separation membrane is formed, for example, by cutting a hollow fiber into an appropriate length to prepare a large number (100 to 100,000).
Hollow fiber membrane bundles formed by bundling
The two ends are integrally fixed with a resin such as an epoxy resin so as not to be blocked, and are modularized, and this is at least a gas mixture (raw material gas) supply port, a non-permeate gas discharge port, and a permeate gas discharge port. And used as a gas separation and recovery device. When separating gas mixtures,
The gas mixture is supplied from the outside of the hollow fiber and the permeated gas is taken out from the inside (hole side) of the hollow fiber. Alternatively, the gas mixture is supplied from one inside of the hollow fiber and flows through the hollow fiber. And let it drain from the other inside,
The permeation gas may be permeated to the outside of the hollow fiber, but the latter method is preferred because it is more efficient.

The gas separation device includes a hollow fiber, a spiral membrane,
There is no particular limitation as long as it is contained in a sealed container such as a flat membrane, but the use of a hollow fiber membrane is preferred in that the membrane area per unit volume can be increased.

One embodiment of the gas separation device of the present invention is shown in FIG.
It was shown to. The gas separation device 1 has a separation membrane in the form of a large number of hollow fibers 2 incorporated in a sealed container 6. The gas separation device 1 converts a mixed gas composed of SF ₆ and at least one other gas into a gas.
Is continuously supplied from the mixed gas supply port 3 to flow the inside of the hollow fiber 2 to the non-permeate gas discharge port 4 side, and the gas selectively permeating the separation membrane is discharged from the permeate gas discharge port 5 and separated. By discharging the gas that has not passed through the membrane from the non-permeate gas outlet 4, SF ₆ having a low permeation rate 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.

[0024]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to embodiments.

Example 1 As a hollow fiber membrane, 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride (hereinafter referred to as s-BPDA) 30 mmol, 2,2′-bis (3,4-diphenyl) Carboxyphenyl) hexafluoropropane dianhydride (hereinafter 6FD
A) 55 mmol, pyrometic acid dianhydride (hereinafter referred to as PM
DA) formed from 15 mmol, 50 mmol 3,7-diamino-2,8-dimethyldiphenylene sulfone (hereinafter, TSN), and 50 mmol 2,2,2,5,5'-tetrachlorobenzidine (hereinafter, TCB). Aromatic polyimide made was used. The outer diameter of the hollow fiber membrane is 410
μm, the inner diameter is 280 μm, and SF _{6 at} 40 ° C.
Gas transmission rate is 4.8 × 10 ^-7 cm ³ / cm ² · sec · c
mHg, nitrogen gas permeation rate is 2 × 10 ⁻⁵ cm ³ / cm ²
· Sec · cmHg. A yarn bundle was formed using this hollow fiber, and both ends were adhered to each other with an epoxy resin, and the resulting bundle was housed in a sealed container of the same type as that shown in FIG. 1 to manufacture a gas separation device. The effective membrane area was 60 m ² .

A mixed gas comprising 10% by volume of SF ₆ gas and 90% by volume of nitrogen gas was supplied from the gas supply port of the gas separator at a pressure of 5 kg / cm ² G, a flow rate of 12 Nm ³ / h and a temperature of 40 ° C. The permeated gas is collected from the permeated gas outlet at normal pressure,
The non-permeate gas was recovered from the non-permeate gas outlet. Table 1 shows the flow rate of each gas and the SF ₆ gas concentration. The SF ₆ gas in the supply gas is separated and recovered as a non-permeate gas. Of the SF ₆ gas in the supply gas, the one recovered from the non-permeate gas outlet is shown in Table 1 at the same time as the SF ₆ recovery rate. In addition, the ratio of SF ₆ gas discharged from the permeated gas outlet to the total supply mixed gas is expressed by S
It is shown Similarly in Table 1 as F ₆ losses.

Example 2 The pressure of the supplied mixed gas was 6 kg / cm ² G and the temperature was 120.
C. and the same procedure as in Example 1 except that the effective film area was 28 m ² . The permeation rate of SF ₆ gas at a temperature of 120 ° C. is 5.5 × 10 ⁻⁷ cm ³ / cm ² · sec · cmH
g, the permeation rate of nitrogen gas is 4.5 × 10 ⁻⁵ cm ³ / cm ²
· Sec · cmHg. The results are shown in Table 1.

Example 3 The supplied mixed gas was SF₆Gas 10% by volume, carbon dioxide
90 volume%, pressure 6kg / cm^TwoG, effective film surface
3.7m product^TwoThe procedure was the same as in Example 1 except that
Was. The permeation rate of carbon dioxide gas at a temperature of 40 ° C. is 5 × 1
0^-Fourcm^Three/ cm ^Two· Sec · cmHg. Table 1 shows the results
It was shown to.

Example 4 Example 1 was repeated except that the supplied mixed gas was 10% by volume of SF ₆ gas, 90% by volume of helium gas, the pressure was 6 kg / cm ² G, and the effective film area was 2.6 m ^2. Was performed in the same manner as described above. The helium gas permeation rate at a temperature of 40 ° C. was 1 × 10 ⁻³ cm ³ / cm ² · sec · cmHg. The results are shown in Table 1.

[0030]

[Table 1]

[0031]

Industrial Applicability According to the present invention, high-concentration SF ₆ can be efficiently and easily recovered from an insulating gas composed of a mixture of SF ₆ and other electric insulating gas used for gas-insulated electric equipment with a small recovery loss. Can be separated and recovered.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an example of an apparatus for separating and recovering a halogen compound gas according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1: Gas separation apparatus 2: Hollow fiber 3: Raw material gas supply port (mixed gas supply port) 4: Non-permeate gas discharge port 5: Permeate gas discharge port 6: Sealed container 7: Resin wall

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4D006 GA41 HA02 HA41 HA61 KE03Q KE03R MA01 MA33 MB04 MC58 NA10 NA12 NA64 NA75 PA04 PB20 PB63 PB64 PB66 PB70

Claims (4)

[Claims] 1. A gas mixture comprising 3 to 60% by volume of SF ₆ and at least one other electrically insulating gas is supplied to a gas separation membrane and brought into contact with the gas separation membrane. recovery of% more gas containing SF ₆ SF ₆ 8
SF recovered at 0% or more and discharged to the permeate side of the gas separation membrane
_{(6) A} method for separating and recovering a gas for electrical insulation, wherein a gas amount is 3% by volume or less of a total mixed gas amount. 2. The method according to claim 1, wherein the gas separation membrane is an aromatic polyimide separation membrane. 3. The method according to claim 1, wherein the electrically insulating gas is nitrogen gas, carbon dioxide gas,
3. The method according to claim 1, wherein the gas is at least one of helium gas, hydrogen gas, sulfur dioxide gas, and air. 4. A plurality of hollow fiber-shaped separation membranes are 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 outside of the hollow fiber are provided. A gas separation device having a permeated gas outlet,
A mixed gas consisting of SF ₆ gas and at least one other kind of electrically insulating gas is introduced into the hollow fiber from the gas supply port of the gas separator, and the SF ₆ gas amount is 3% by volume or less of the supplied mixed gas. An apparatus for separating and recovering a gas for electrical insulation, wherein a certain electrically insulating gas is discharged from a permeated gas outlet, and a gas containing SF ₆ having a purity of 80% by volume or more is recovered from a non-permeated gas outlet.