JP2000210527A - Mixed gas separated and separating system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To put a mixed gas apparatus to practical use by realizing a safety disposal of recycling, disposal or the like of sulfur hexafluoride gas by a method wherein a container in which an inlet of a mixed gas and a supply opening of a heavy gas are formed downward, and a container to which a supply opening of the light gas is formed and a continuous porous body filled in the container are provided upward. SOLUTION: A continuous porous body 1 comprises a porous material such as active carbon, spongy body or the like including, for example, those in a gas chromatograph, and is filled inside a container 2. To this container 2, upper and lower both outlet openings 3, 4 are formed, and an inlet 5 is formed downward. Then, a mixed gas is sucked from the inlet 5, and sulfur hexafluoride gas (SF6 gas) being a heavy gas in the mixed gas blows out often from the lower outlet opening 4. Nitrogen gas being a light gas blows out often from the upper outlet opening 3 contrary thereto. That is, a mass difference or the like of both gases is used, and both gases are efficiently separated. Thereby a safety disposal such as recycling, decomposition or the like of the SF6 gas being an artificial gas which is excellent in an electric insulation property can be realized, and a mixed gas apparatus is put to practical use.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a separation apparatus and a separation system for recovering a mixed gas of sulfur hexafluoride gas and nitrogen gas.

[0002]

2. Description of the Related Art In recent years, power transmission systems have become longer and longer distances, and the power system has been increasingly increased in voltage. Therefore, it is an absolute condition that the medium to be filled into the device has excellent electric insulation properties. As a gas medium satisfying such conditions, sulfur hexafluoride gas (hereinafter referred to as “SF6”) which is an artificial gas having excellent electric insulation properties is used. Gas)) is generally used.

[0003] However, although SF6 gas uses a smaller amount of carbon dioxide than carbon dioxide gas, it has a global warming coefficient of 20,000 or more times that of carbon dioxide gas. Emissions are regulated together with carbon dioxide
It has been designated as one of the six gases.

There are various possible directions for developing such regulations. As one of them, from the viewpoint of reducing the amount of SF6 gas used even a little, a technology using a mixed gas of SF6 gas and nitrogen gas (hereinafter referred to as “mixed gas”) as an insulating medium has been developed. No. 10-49156).

[0005]

Here, the technique using the mixed gas as the insulating medium has an advantage that the absolute amount of SF6 gas released into the environment in the event of an accident or other unexpected situation is small. However, on the other hand, since it is composed of two types of gases with completely different physical properties, it is inconvenient for the gas to be recovered during maintenance, etc., even if it is disposed of in a mixed state for recycling. If it is disposed of, it will fall down at the end of the course and will be against the flow of SF6 gas emission regulations.

Accordingly, the present invention provides a simple apparatus for separating a mixed gas of SF6 gas and nitrogen gas, and also provides a separation system using the apparatus so as to recycle or discard SF6 gas. The purpose is to realize safe disposal and to use the mixed gas equipment for practical application.

[0007]

In order to achieve the above object, according to the present invention, as a first aspect of the present invention, a gas inlet port for drawing a mixed gas downward and a heavier gas in the mixed gas are blown. A container forming a gas outlet for discharging the gas and forming a gas outlet for discharging a lighter gas in the mixed gas above, and a continuous porous body filled in the container. The present invention provides a mixed gas separation device characterized by the following. In such a configuration, it is possible to separate the mixed gas by utilizing the difference between the mass and the diameter of the gas.

Further, in the present invention, as a second aspect of the present invention, a gas inlet for introducing the mixed gas is formed, a gas outlet for blowing out a heavier gas in the mixed gas, and a gas outlet for discharging the mixed gas. A container forming a gas outlet for blowing a lighter gas, a gas outlet for blowing a heavier gas in the mixed gas, and a gas outlet for blowing a lighter gas in the mixed gas Are separated by a diffusion membrane in the container. In such a configuration, it is possible to separate the mixed gas by utilizing the difference between the molecular diameters of the gases.

Further, in the present invention, according to a third aspect of the present invention, the container is provided with a means for heating an upper portion of the container. Provide equipment. In such a configuration,
Providing a temperature gradient in the mixed gas enables efficient mixed gas separation.

Further, in the present invention, as a fourth aspect of the present invention, there is provided a container having a rotating body therein, a gas inlet for drawing a mixed gas from the outside of the container, and an outside of the container formed near the rotation axis. A mixed gas separation device having a rotating body formed with a gas outlet to the outside and a gas outlet to the outside of the container formed in the vicinity of the peripheral wall of the rotating body, and a drive unit for rotating the rotating body. I do. In such a configuration, it is possible to separate the mixed gas using the difference in the mass of the gas.

[0011] In the present invention, as the invention of claim 5, the gas separation device is connected in multiple stages in a plurality of stages, and the mixed gas is subjected to a plurality of separation processes and a plurality of feedback processes. A mixed gas separation system according to any one of claims 1 to 4, characterized by: In such a configuration, high-precision separation that can satisfy the actual concentration condition can be performed regardless of the separation efficiency per unit.

Further, in the present invention, as a sixth aspect of the present invention, there is provided a hollow fiber bundle comprising a plurality of hollow fibers provided with a gas inlet and a gas outlet at both ends for introducing a mixed gas, and Gas separation characterized by having a container housed in a sealed manner and having an outlet for blowing out gas permeated from the hollow fiber membrane and a gas inlet and a gas outlet forming both ends of the hollow fiber. Provide equipment. In such a configuration, it is possible to efficiently separate the mixed gas by utilizing the difference in the transmittance of the mixed gas between the hollow fiber membranes.

In the present invention, a mixed gas separator for increasing the SF6 concentration of the mixed gas to a predetermined value, and a mixed gas having a high SF6 concentration outputted from this device are processed at a low temperature or a high pressure. And a liquefaction device for liquefying the mixed gas. In such a system, the gas once concentrated in the SF6 concentration can be processed in the liquefaction device by the separation device, so that the equipment such as the compressor can be reduced in size and energy can be saved.

In the present invention, a mixed gas separating apparatus for increasing the SF6 concentration of the mixed gas to a predetermined value, and a mixed gas having a high SF6 concentration outputted from this apparatus are processed at a low temperature or a high pressure. And a liquefier that liquefies the mixture gas, wherein the mixed gas separation device is the separation device or the separation system according to any one of claims 1 to 6, provide. Even in such a system, once the separation device
Since the gas enriched in SF6 concentration can be processed by the liquefaction equipment,
Equipment such as a compressor can be reduced in size and energy can be saved.

According to the present invention, a mixed gas having a low SF6 concentration discharged from the system is sent to a chemical reaction step with calcium monoxide or the like. A mixed gas separation system according to claim 8 is provided. In such a system, simple and safe SF6 disposal of a mixed gas having a low SF6 concentration, which is difficult to treat not only a liquefier but also a separator, becomes possible.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a first embodiment of the present invention will be described with reference to FIG. The continuous porous body 1 is made of, for example, a gas chromatograph, activated carbon, a spongy body, or another porous material, and is filled in the container 2. An upper outlet 3 and a lower outlet 4 are respectively formed in the container 2, and an inlet 5 is formed below.
When the mixed gas is sucked into the apparatus having such a configuration through the inlet 5, a larger amount of SF6 gas, which is the heavier gas in the mixed gas, is blown out from the lower outlet 4, whereas the lighter gas in the mixed gas is blown out. Is blown out from the upper outlet 3 in large quantities. This is thought to be due to differences in the mass, molecular diameter and adsorption power observed in both gases (nitrogen gas and SF).
The molecular weights of the six gases are 28 and 146, respectively, and the molecular diameters are 4 Å and 6 Å, respectively). Therefore, according to the present embodiment, it is possible to efficiently separate the two gases by utilizing the difference in mass and the like.

Next, a second embodiment of the present invention will be described with reference to FIG. Here, FIG. 2 shows an apparatus utilizing a difference in the transmittance of both gases to the diffusion film 11 and the like, in which an upper outlet 13 and a lower outlet 14 are respectively formed on one surface of a container 12 and the other surface. An inlet 15 is formed at the bottom. Also,
In the container 12, the diffusion film 11 is provided between the upper chamber to which the upper outlet 13 belongs and the lower chamber to which the lower outlet 14 belongs. By providing such a diffusion membrane 11, separation of the two gases becomes possible due to a difference in the molecular diameter of the two gases or a difference in the permeability into the membrane. For example, when a diffusion film 11 having a fine network structure is installed between the upper outlet 13 and the lower outlet 14, nitrogen molecules having a smaller diameter can be separated from SF6 gas by the small diameter. Becomes Also, as a material for the diffusion membrane, improvement of the separation efficiency was confirmed with a semipermeable membrane material such as cellophane, but the permeability of the mixed gas changes depending on the molecular diameter or the difference in the permeability. Any object may be used.

Further, in the container 12, a heating means such as a heater 16 may be provided in the upper chamber. Such heater 16
In the case of installation, etc., a temperature gradient can be created between the upper part and the lower part in the container 12, so that the lighter nitrogen gas diffuses more efficiently into the upper chamber, and the separation efficiency to the upper outlet 13 is further improved I do.

Next, a third embodiment of the present invention will be described with reference to FIG. Here, FIG. 3 shows a centrifugal separator utilizing the mass difference between the two gases, and a driving unit 26 including a motor and a belt transmission mechanism and the like, and a cylinder which is rotated by the rotation in a cylindrical container 22. A rotating body 21 is provided. Inside the rotating body 21, an inlet 25 for supplying a mixed gas from the outside, a nitrogen outlet 23 communicating from the vicinity of the rotation axis to the outside, and an SF6 communicating from the vicinity of the cylindrical inner peripheral wall to the outside.
An outlet 24 is provided. However, since the vicinity of the rotating shaft is in a low pressure state, a vacuum pump (not shown) is attached to the nitrogen outlet 23.

The inlet of the centrifugal separator having the above configuration
When the mixed gas is supplied to 25, the rotating body rotating at high speed
In the area 21, under the influence of the gravitational field due to the strong centrifugal force, the heavier gas SF6 gas is located near the inner peripheral wall of the cylinder, and the lighter nitrogen gas is located near the axis near the vacuum.
Each is efficiently separated. Therefore, by extracting these gases from the vicinity of the inner peripheral wall of the cylinder or from the vicinity of the axis, respectively, it is possible to obtain SF6 gas and nitrogen gas which are considerably separated from each other. According to the separation device of the present embodiment, since a considerably strong gravitational field can be created depending on the adjustment of the rotation speed of the rotating body 21, the separation coefficient is larger than that of the gas diffusion method or the like. Therefore, the power consumption required for the separation step is small.

Next, a fourth embodiment of the present invention will be described with reference to FIG. In other words, all of the first to third embodiments make it possible to efficiently separate a mixed gas by utilizing a clear mass difference between SF6 gas and nitrogen gas. A complete separation operation is not possible only by itself. Therefore, as shown in Fig. 4, a plurality of these single units are connected in multiple stages to form a plant (cascade), and the gas is subjected to the separation process or the feedback process many times, thereby affecting the separation efficiency per single unit. Therefore, high-precision separation that can satisfy the actual concentration condition can be performed.

Next, a fifth embodiment of the present invention will be described with reference to FIG. Here, FIG. 5 shows an apparatus for performing gas separation by utilizing a difference in the permeability of a mixed gas when a hollow fiber membrane material is used, and a hollow fiber bundled with hollow fibers in a cylindrical container 32. A yarn bundle 31 is hermetically arranged, and at both ends of the hollow fiber bundle 31, a suction port 35 for drawing a mixed gas from outside the container 32 and an outlet 34 for blowing SF6 gas out of the container 32 are formed. FIG. 1 shows a structure in which a nitrogen outlet 33 for blowing nitrogen gas is formed.

Here, in order to increase the separation efficiency, the hollow fiber bundle 31
Although it is desirable to arrange the devices compactly while keeping the distance as much as possible, if they are arranged randomly, it will be impossible to perform later maintenance and inspection. Therefore, in order to arrange the hollow fiber bundles 31 neatly, in this embodiment, a spiral arrangement is adopted as shown in the figure.

FIG. 3 is an enlarged view of the hollow fiber bundle 31.
Figure 6 shows. Here, inside the hollow fiber 36 per unit, the mixed gas is blown in at a high pressure, and nitrogen gas is continuously blown out from the surface of the skin. In order to increase the separation efficiency, the more unit hollow fibers, the better. The stopper 37 is used for the maintenance and inspection of the hollow fiber bundle 31.

FIG. 7 is a conceptual diagram showing the mechanism of permeation of nitrogen gas 39 through the thread 38 of the hollow fiber 36. Here, (a) shows micropores formed in the epidermis 38 that are smaller than the molecular diameter of SF6 gas 40,
FIG. 3B shows a state where only nitrogen 39 permeates, and FIG. 4B shows a state where nitrogen gas 39 easily dissolves into the thread 38. The transmission principle is the same as that of the diffusion film 11 of the second embodiment described above.

In the present embodiment, the optimum design of the hollow fibers, the number of the hollow fibers, and the adjustment of the overall length make it possible to improve the separation efficiency per unit without forming a cascade as shown in the fourth embodiment. .

The above first to fifth embodiments are all separation techniques focusing on the difference in characteristics between SF6 gas and nitrogen gas. Needless to say, the present invention can be applied if there is a similar relationship between the gas characteristic differences. Next, still another embodiment of the present invention will be described. With regard to technology for separating mixed gases, focusing on the difference between the condensation points of the two gases, cooling and / or pressurization of the mixed gas removes only the SF6 gas with a higher condensation point by liquefaction and removal. Has been proposed. But the problem here is that
As shown in FIG. 8, the pressure required for liquefaction of SF6 is required in a form that is almost inversely proportional to the concentration of SF6 gas in the mixed gas. That is, in order to separate the mixed gas having a low SF6 gas concentration, the output of the compressor becomes excessive, so that the equipment becomes large and enormous energy is consumed.

FIG. 9 shows a system in which the separation apparatuses and the like according to the first to fifth embodiments are combined in order to efficiently use such a liquefaction separation technique. That is, the mixed gas recovered from the insulating device 41 is made clean by passing it through an adsorption tank 42 for removing moisture and decomposition gas and a filter 43 for removing dust such as carbon powder. In this case, the adsorption tank 42 and the filter 43 may be arranged first, or may be arranged in multiple stages, depending on the properties of dust and the like.
Thereafter, the mixed gas is input to the separator 44, where the SF6
The concentration is increased to a predetermined value (the predetermined value varies depending on the output scale of the liquefaction device 45 described later). After that, the concentrated mixed gas is input to a refrigerator 46 or a liquefaction device 45 provided with a liquid nitrogen cylinder (not shown), and is cooled and pressurized here to liquefy only SF6. Here, the liquefied SF6 is filled in the SF6 tank 47 to perform a subsequent reuse process. On the other hand, most of the gas remaining as residue in the liquefaction apparatus 45 is nitrogen, but a trace amount of SF6 vapor remains. This SF
6 It is sufficient to return to the feedback step of sending gas to the separation device 44 again to remove the vapor. Further, since the SF6 concentration is very small (usually determined in relation to the saturated vapor pressure), if this feedback increases the cost instead, the mixed gas is sent to the chemical treatment device 48. Here, a chemical reaction with calcium monoxide (CaO) etc. is made,
A trace amount of SF6 is decomposed into solid calcium fluoride (CaF2) and the like. Although the reaction was confirmed at a specific reaction temperature of 300 ° C when a specific catalyst was used, 50
It was confirmed that the reaction was promoted in a high-temperature atmosphere at 0 ° C. Now,
The gas leaving the chemical treatment unit 48 is no longer released into the environment as pure nitrogen gas.

Here, if the separation apparatus described in the first to fifth embodiments (separation system in the multi-staged fourth embodiment) is used as the separation apparatus 44, a certain amount of SF6 enrichment can be performed on the mixed gas. Therefore, the liquefaction step of the mixed gas sent to the liquefaction apparatus 45 after that becomes easy as described above. That is, it is possible to reduce the size of the system including the compressor and the like, and to save energy at the time of separation.

Further, it was difficult to separate a mixed gas having a low concentration of SF6 using not only the liquefaction unit 45 but also the separation unit 44 (even if a cascade is formed, the plant becomes a large-scale plant). Here, in order to efficiently remove such a mixed gas, the solidification disposal by the chemical treatment device 48 is appropriately incorporated into the system, so that the entire system becomes more environmentally safe. Therefore, the chemical treatment device 48 may be incorporated in the step of releasing nitrogen gas from the separation device 44.

[0031]

As described above, in the separation apparatus of the present invention, SF6
By utilizing the characteristic difference such as the mass difference between the gas and the nitrogen gas, it is possible to efficiently separate the mixed gas composed of both gases, and to reduce the mixed gas concentrated to a certain value in combination with the apparatus. Since it is possible to propose a separation system that can be liquefied, it is also possible to realize safe disposal such as recycling or decomposition of SF6 gas.

[Brief description of the drawings]

FIG. 1 is a view showing a mixed gas separation device according to a first embodiment of the present invention utilizing a mass difference or the like.

FIG. 2 is a diagram showing a mixed gas separation device according to a second embodiment of the present invention using an average speed difference and the like.

FIG. 3 is a diagram showing a mixed gas separation device according to a third embodiment of the present invention using a mass difference.

FIG. 4 shows a multi-stage mixed gas separation apparatus according to the present invention.
FIG. 9 is a state diagram showing the fourth embodiment.

FIG. 5 is a view showing a mixed gas separation device according to a fifth embodiment of the present invention, utilizing a difference in the transmittance of a mixed gas to a hollow fiber membrane material.

FIG. 6 is an enlarged view of a hollow fiber bundle in which hollow fibers are bundled.

FIG. 7 is a conceptual diagram showing a mechanism of nitrogen gas permeation through the hollow fiber thread.

FIG. 8 is a diagram showing a correlation between a mixing ratio required for liquefaction and a liquefaction pressure of a mixed gas composed of nitrogen and SF6 at an isothermal time.

FIG. 9 is a conceptual diagram showing a liquefaction separation system of the present invention.

[Explanation of symbols]

1 ... continuous porous body, 11 ... diffusion film, 21 ... rotating body, 31
・ ・ ・ Gas separation unit, 2, 12, 22, 32 ・ ・ ・ Container, 3, 13, 2
3, 33 ・ ・ ・ Nitrogen outlet, 4, 14, 24, 34 ・ ・ ・ SF6 outlet
5, 15, 25, 35 ... Inlet, 44 ... Separation device, 45 ... Liquefaction device, 48 ... Chemical treatment device.

Continued on the front page (72) Inventor Hiroshi Murase 2-1 Ukishima-cho, Kawasaki-ku, Kawasaki-shi, Kanagawa Prefecture Inside the Toshiba Hamakawasaki Plant (72) Inventor Kazuyuki Suzuki 1-1-1, Shibaura, Minato-ku, Tokyo Stock Company Toshiba head office F-term (reference) 4D002 AA01 AA22 AC10 BA04 BA14 CA07 DA05 DA11 EA01 FA02 GA02 GA03 GB02 GB03 GB04 4D006 GA41 GA48 HA08 HA18 HA41 KA53 KA55 KA56 MA01 MA03 MC14X PA04 PB19 PB63 PB70 4D047 A0309

Claims (9)

[Claims] 1. A gas inlet for drawing a mixed gas downward and a gas outlet for blowing a heavier gas in the mixed gas are formed, and a lighter gas in the mixed gas is blown upward. A mixed gas separation device, comprising: a container forming the gas outlet of (1); and a continuous porous body filled in the container. 2. A gas inlet for drawing a mixed gas and a gas outlet for blowing a heavier gas in the mixed gas and a gas outlet for blowing a lighter gas in the mixed gas. A container to be formed, a gas outlet for blowing out a heavier gas in the mixed gas, and a gas outlet for blowing out a lighter gas in the mixed gas are separated by a diffusion film in the container. A mixed gas separation device, comprising: 3. The mixed gas separation apparatus according to claim 2, wherein said container is provided with means for heating an upper portion of said container. 4. A container having a rotating body therein, a gas inlet for drawing a mixed gas from outside the container, a gas outlet formed outside the container near the axis of rotation, and formed near a peripheral wall of the rotating body. A mixed gas separation device, comprising: a rotating body formed with a gas outlet to the outside of the container, and a driving unit for rotating the rotating body. 5. The gas separation apparatus according to claim 1, wherein the gas separation device is connected in a plurality of stages, and the mixed gas is subjected to a plurality of separation steps and a plurality of feedback steps. 2. The mixed gas separation system according to item 1. 6. A hollow fiber bundle comprising a plurality of hollow fibers bundled with a gas inlet and a gas outlet for drawing a mixed gas at both ends, and a hollow fiber bundle which is hermetically stored and which is capable of transmitting gas permeated from the hollow fiber membrane. A gas separation device comprising: a container having an air outlet for blowing out and a gas inlet and a gas outlet forming both ends of the hollow fiber. 7. A mixing device comprising: a mixed gas separator for increasing the SF6 concentration of the mixed gas to a predetermined value; and a liquefaction device for liquefying the mixed gas having a high SF6 concentration output from the device by low-temperature or high-pressure processing. Gas separation system. 8. A mixed gas separation device for increasing the SF6 concentration of the mixed gas to a predetermined value, and a liquefaction device for liquefying the mixed gas having a high SF6 concentration output from the device by cooling or pressurizing the mixed gas. And the mixed gas separation device,
7. A mixed gas separation system, which is the separation device or the separation system according to any one of 1 to 6. 9. The mixed gas separation system according to claim 7, wherein the mixed gas having a low SF6 concentration discharged from the system is sent to a chemical reaction step with calcium monoxide or the like.