JP2000334247A - Apparatus for recovering gaseous sf6 - Google Patents

Abstract

PROBLEM TO BE SOLVED: To recover almost all of a gaseous SF6 in a short time without leaking to the atmosphere not only by pressurizing the gaseous SF6 in a vessel to be recovered such as a transformer and a breaker in a pressurizing part and cooling and condensing the pressurized gas but also by separating the gaseous SF6 in a gas separating part. SOLUTION: In the case of recovering the gaseous SF6 in the vessel 1 to be recovered, the gas to be recovered is introduced from the vessel 1 to the pressurizing part 2 and pressurized in the pressurizing part 2 provided with a buffer tank 28 and a pressurizing pump 30. The pressurized gas is cooled to below 20 deg.C and condensed in a condensing part provided with a cooling part 31 and a condensing tank 32, which is then stored in a liquid storage tank 5 as a condensed SF6. When the SF6 concentration of the gas to be recovered is 50 vol.% or higher and the internal pressure of the vessel 1 is 0 MPa.G, gas is sent from a gas supply part 7 to the vessel 1 and mixed with the gaseous SF6 to discharge the mixed gas to the pressurizing part 2. Meanwhile when the SF6 concentration is lower than 50 vol.%, such a gas is introduced to the gas separating part 3 to adsorb and separate the gaseous SF6.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to the recovery of SF6 gas (sulfur hexafluoride gas, the same applies hereinafter).

[0002]

2. Description of the Related Art SF6 gas is filled into a high-voltage power transformer or a circuit breaker of a power circuit, and the thermal stability, electrical stability, and high withstand voltage of the device make use of the device, thereby enabling downsizing of the device. The contribution is significant in reducing the volume of substations. The purity of SF6 gas in transformers and circuit breakers is 1
Some of them are 00%, and others are appropriately filled with nitrogen gas. These gases must be extracted when inspecting, maintaining, or repairing the equipment that uses them. However, conventionally, these gases have been released to the atmosphere because there is little harm to the human body. . However, since SF6 gas is an expensive gas, there has been a recovery device in a range where it can be easily recovered and reused cost-effectively, and has been recovered and reused.
In other words, there was an apparatus for liquefying and recovering by extracting and pressurizing and compressing and cooling. However, the inside of the container to be recovered was sucked and collected to a high vacuum area, or a gas mixed with other gas was separated and SF
There was no device for collecting only six gases.

[0003] That is, when the concentration of SF6 gas is reduced due to the mixing of other gases, the partial pressure of the SF6 gas is reduced, so that the gas is compressed to a high pressure, and cooling to a low temperature is required. , Had not been made. Conventionally, when SF6 gas is used, SF4, sulfur dioxide, S
Decomposed gases such as OF2 may cause degradation of the characteristics of the equipment used. Therefore, there was an apparatus for removing such gases to prevent this, but there was no apparatus for separation and purification at the time of recovery.

In recent years, the emission of carbon dioxide and the like due to the prevention of global warming has been regulated. The 1997 World Environment Conference was held in Kyoto, resulting in 240 carbon dioxide emissions.
The emission of SF6 gas, which has a global warming potential of 00 times, has also become strictly regulated. In order to prevent the SF6 gas from leaking into the atmosphere, "a" eliminate the gas leaking from the sealing section of the filling device. [B] It is important to eliminate gas that is wasted when installing or maintaining equipment, dismantling and dismantling, etc., when filling and extracting gas. Regarding “A”, the number is very low at present due to the improvement of the seal portion of the device. Regarding "b", the electric power industry voluntarily enacted the "Standards for Handling SF6 Gas for Electric Power" in December 1998 by the Joint Research Institute of Electric Power, and decided to regulate its emissions. That is, 0.01 for inspection and repair
5MPa · abs (recovery rate of 97vol% or more) A voluntary standard was created to suction and recover up to a vacuum area of 0.005MPa · abs (recovery rate of 99vol% or more) when dismantling and removing. Recovering to a high vacuum region has the disadvantage of requiring a long recovery time. The low recovery rate at the time of inspection is a compromise value for minimizing the time of the power failure due to the stoppage of the apparatus, and sufficient time is taken for evacuation at the time of removal. In other words, the liquid is sucked and collected up to the high vacuum region, and the amount of leakage to the atmosphere is reduced.

[0005] The electric power industry will develop and implement a recovery device that meets the above criteria by 2005. Even if 50 vol% of nitrogen gas, which is an inert gas, is mixed, the impulse breakdown voltage is 85% when SF6 gas alone is used.
%, The commercial frequency breakdown voltage is 96.6%, and there is little deterioration in performance. Therefore, manufacturers who use SF6 gas with nitrogen gas when encapsulating SF6 gas in transformers and circuit breakers and those who use high-purity SF6 gas There is. Conventionally, such gas containing nitrogen gas has been difficult to recover, so most of them have been released to the atmosphere and discarded during inspection and disposal.

[0006]

The object of the present invention is to recover at least 99 vol% of SF6 gas from a container to be recovered, which is a transformer or a circuit breaker, without almost leaking into the atmosphere.
In addition, it can be collected in a short time. In addition, even if nitrogen gas or air is mixed in the gas to be collected, it must be separated and collected.

[0007]

Means for Solving the Problems To solve the above problems, an object of the present invention is to provide a critical temperature of 45.64 ° C., a critical pressure of 3.75 MPa · G, a melting point of −50.8 ° C., and a sublimation point of −6.
In consideration of the characteristics of SF6 gas at 3.8 [deg.] C., the transformer or circuit breaker of the electric circuit as a container to be recovered is a closed container in which SF6 gas has a high pressure (about 0.6 MPa.G to 0.
3 MPa · G). And the filling gas is a small amount by the mixed nitrogen gas and electric discharge, but SF6 gas is decomposed, SF4, SOF2, sulfur dioxide are present,
Water may also be mixed. However, there is a separate removing means for removing the decomposition gas, SF4, SOF2, and sulfur dioxide from the SF6 gas, and most of them can be removed therefrom, but detailed description is omitted here. It is the second most important issue after the main performance of recovering SF6 gas to minimize the time of power outage during inspection, maintenance or repair of the equipment used for the equipment related to the public infrastructure of power supply. In consideration of these problems, an efficient recovery apparatus has been invented.

As described above, the container to be recovered (transformer, circuit breaker, etc.) is filled with the gas to be recovered (SF6 gas) at a high pressure as described above. And SF6 gas is a liquefied gas,
A pressurizing section for pressurizing the gas and a liquefying section for cooling and liquefaction are provided, and in a range where the concentration of SF6 gas in the gas to be recovered is high,
Since the partial pressure of SF6 gas in the pressurized gas is also increased, the liquefied gas can be easily liquefied and recovered in a relatively low pressure range or a relatively high liquefaction temperature range due to the relationship between the liquefaction temperature and the pressure of the liquefied gas. First, the container is collected by the above method until the internal pressure in the container reaches a pressure range in which the container can be liquefied by the pressurizing pump. As described above, the gas to be recovered may be diluted with 100% SF6 gas or nitrogen gas.
Even if this mixed gas exists, a gas separation unit for separating the mixed gas from the SF6 gas is provided. The gas separation unit is a PSA method (pressure sw.) Using an adsorbent that adsorbs a specific gas.
ing Adsorption). When a mixed gas containing a specific gas is fed to the adsorption column filled with the adsorbent while applying pressure, the specific gas is adsorbed and removed by the adsorbent, and the non-adsorbed gas is separated and taken out from the other end of the adsorption column. It is. This step is called an adsorption step. Shortly before the specific gas is adsorbed by the adsorbent and the mixture (raw material) gas is stopped being filled, and the pressure of the adsorbent is reduced from the inlet of the adsorbent, the specific gas adsorbed by the adsorbent is reduced. Is released from the adsorbent and discharged, and the adsorption capacity of the adsorbent is regenerated. This is called a regeneration step. Since the gas is separated while repeating the adsorption step and the regeneration step, that is, while applying or reducing pressure to the adsorption column, the pressure is reduced.
re Swing Adoption (PS for short)
A) It is called (pressure fluctuation adsorption) method.

The adsorbent is SF6, which is a target gas.
There are an adsorbent that adsorbs a gas and does not adsorb a mixed gas, and an adsorbent that adsorbs another mixed gas without adsorbing the SF6 gas as a target gas. The method for extracting the target gas differs slightly depending on the adsorbent used. For example SF
When six gases are used as target gases, the former includes molecular sieve charcoal in which activated carbon has a molecular sieve function. The latter has 5 of zeolite
There are A type, 4A type and others. In the former case, the SF6 gas, which is the target gas, is adsorbed on the adsorbent and is separated, so that the SF6 gas concentrated in the step of separating from the adsorbent in the reduced pressure regeneration step is recovered. In the latter case, the SF6 gas is separated from the other end of the adsorption cylinder and comes out in the pressure adsorption step, so that it is obtained in the adsorption step. Zeolite adsorbs and removes nitrogen gas, carbon dioxide gas, and moisture well without adsorbing SF6 gas. Gas that separates SF6 gas from SF6 gas and a mixture of these gases because oxygen gas adsorbs slightly. Used as an adsorbent in the separation section.

[0010] However, a case where air is mixed in the SF6 gas may occur. Air is 78% nitrogen and oxygen 2
Since it is 1%, zeolite that adsorbs a large amount of nitrogen is first placed on the upstream side of the adsorption column, and then molecular sieve charcoal that strongly adsorbs oxygen is placed downstream as an adsorbent. So that oxygen whose partial pressure has been increased by molecular sieving can be efficiently adsorbed and removed.
By combining and arranging the kinds of adsorbents upstream and downstream as described above, a gas separation unit capable of efficiently separating and removing air is constituted. Then, the SF separated in the gas separation unit
The gases other than the six gases are nitrogen gas and oxygen gas, which are the same as the constituent gases of the atmosphere, and are discharged into the atmosphere. In the regeneration step, this exhaust gas released into the atmosphere is SF
It is necessary to eliminate 6 gases, and a pressure equalization step is inserted between the adsorption step and the regeneration step so that no SF6 gas remains in the adsorption cylinder after the adsorption step.

That is, using a plurality of adsorption cylinders filled with an adsorbent in the gas separation unit, supplying the gas to be recovered to the adsorption cylinder in one pressurization step, adsorbing the mixed gas in SF6 gas to the adsorbent, Before the adsorbent becomes full with the adsorbed gas, supply of the gas to be recovered is stopped, and the adsorber is connected to the inlet and outlets and outlets of another regeneration process, and the gas in the adsorber is completed. After performing the pressure equalizing step of transferring the gas to the adsorption column after the regeneration step, the pressure of the adsorption column after the adsorption step is reduced, the regeneration step is started, and the gas adsorbed by the adsorbent is desorbed to the atmosphere. At this time, the pressure may be reduced to a vacuum range by a vacuum pump for regeneration. Then, the adsorption cylinder after the regeneration step enters the adsorption step, supplies the gas to be recovered, and
Separate 6 gases. After introducing the equalizing step, the SF6 gas present in the inlet, outlet and respective conduits of the adsorption cylinder after the adsorption step is transferred to the adsorption cylinder after the regeneration step (after removing the SF6 gas), In the regeneration step, the adsorbed gas containing no SF6 gas is discharged into the atmosphere.

The gas to be recovered (S
F6 gas) remains in the gas in the container to be recovered even if the internal pressure in the container to be recovered is recovered to the atmospheric pressure level.
At the time of disassembly, the pressure is reduced to a vacuum range of 0.005 MPa · abs and collected, and self-regulation is set to reduce the dissipation of SF6 gas to the atmosphere. However, as the vacuum value increases, the gas expands, It takes a long time. Therefore, as a result of intensive research, the gas that can be separated in the gas separation unit is filled in the container to be recovered, the pressure of the container to be recovered is increased to a positive pressure or a pressure close to the positive pressure, and the gas that can be separated in the separation unit is SF6. The SF6 gas is recovered to a target recovery level (residual gas level) in a short period of time by being derived by mixing with the gas.
Therefore, a gas supply unit is provided. As the gas in the gas supply unit, nitrogen gas or air can be used in combination with the capacity of the gas separation unit.

[0013] In order to efficiently recover the gas in a short time, it is possible to easily liquefy and recover the SF6 gas in the range where the concentration of the SF6 gas in the recovery container is high. Cool and liquefy in the liquefaction section and collect. By this method, the internal pressure in the container to be recovered is recovered to a pressure range that can be liquefied by the pressure pump. (However, it should be noted that this pressure varies depending on the cooling capacity (temperature) of the liquefaction unit.) When the pressure in the collection container falls below a certain value, gas is supplied from the gas supply unit to the collection container. The pressure is increased and the pressure is increased by the pressure unit. At this time, the non-liquefied gas is extracted from the liquefied part. This gas is returned to the upstream side of the pressurizing section, and is again put into the cycle of pressurized cooling and liquefaction.

[0014] As the concentration of SF6 gas in the gas to be recovered decreases, the partial pressure of SF6 gas decreases, so that the pressure for liquefaction increases, and the temperature required for liquefaction decreases. Then, the gas to be recovered is led to the gas separation unit, and the SF6 gas is concentrated and then added to the pressurization unit. Recovery is continued by this method, and the concentration of SF6 gas in the gas to be recovered is determined to be 0.015 MPa · ab.
It is determined whether the collection up to s has been completed, and the collection is completed. According to such a method, the gas to be recovered can be derived at a positive pressure without using an expensive vacuum pump capable of drawing a high vacuum from the container to be recovered, and the gas can be recovered below the target level in a short time.

[0015] That is, in the SF6 gas recovery device composed of the gas supply unit and the gas separation unit, the high pressure gas regulated by the gas supply unit is supplied to the recovery container, and the gas to be recovered mixed with the SF6 gas. Is taken out from the gas outlet and separated into a gas containing a large amount of SF6 and a gas containing almost no SF6 in a gas separation section.
Emission of gas containing almost no SF6 into the atmosphere, SF
The gas containing 6 is recovered. "I" SF6 comprising a PSA-type gas separation unit and a gas supply unit having an adsorption cylinder filled with an adsorbent for adsorbing SF6 gas or mixed gas (nitrogen gas, air, carbon dioxide gas, etc.) in the container to be recovered. In the gas recovery device, the high pressure gas regulated by the gas supply unit is supplied to the container to be recovered, and SF6 is supplied.
The gas to be recovered mixed with the gas is taken out, sent to the gas separation unit, and the easily adsorbed gas in the container to be recovered is adsorbed by the adsorbent in the adsorption cylinder in the pressure adsorption step to be separated from the non-adsorbed gas. The pressure in the adsorption cylinder was reduced in the pressure reduction regeneration step, the gas adsorbed on the adsorbent was desorbed, and the mixed gas separated from the SF6 gas was discharged to the atmosphere. "U" In a SF6 gas recovery system consisting of a gas separation unit using PSA and a nitrogen gas supply unit having an adsorption cylinder filled with zeolite as an adsorbent, nitrogen gas whose pressure has been regulated by the nitrogen gas supply unit is supplied to the container to be recovered. Then, the gas to be recovered mixed with a gas mainly containing SF6 gas filled in the container to be recovered is taken out, sent to the gas separation section, and nitrogen gas or the like is adsorbed in the adsorption cylinder in the pressure adsorption step. The adsorbent was adsorbed and removed to separate it from SF6 gas, and the adsorber was depressurized in a depressurizing step to desorb nitrogen gas and the like adsorbed by the adsorbent and release it to the atmosphere.

Further, in the SF6 gas recovery apparatus comprising a PSA type gas separation unit and a gas supply unit having two adsorption cylinders filled with an adsorbent for adsorbing a gas other than the SF6 gas in the container to be recovered, Supplying a high-pressure gas whose pressure has been adjusted by the gas supply unit to the container to be recovered, taking out a gas to be recovered mixed with a gas mainly containing SF6 gas filled in the container to be recovered from the outlet, and supplying the gas to the gas separation unit. Then, the gas other than SF6 gas is adsorbed by the adsorbent in the adsorption cylinder and separated from the SF6 gas by the adsorption cylinder in one pressure adsorption step, and the adsorbent of the adsorption cylinder is full of the adsorption gas. The supply of the to-be-recovered gas is stopped before the pressure is reduced, and the inlet and outlet and the outlet are connected to each other on which the decompression regeneration step has been completed, and the gas on the adsorption cylinder on which the adsorption step has been completed has been decompressed. After performing the pressure equalization process, Completed the adsorption column in step enters the vacuum regeneration step, the adsorbed gas in the adsorbent is discharged into the atmosphere, finished adsorption column depressurization regeneration step enters the adsorption step, SF to supply the collected gas
Six gases were separated. "O" In a SF6 gas recovery device comprising a PSA-type gas separation unit and a high-pressure air supply unit having two adsorption columns filled with zeolite on the upstream side and molecular sieves on the downstream side, a high-pressure air supply unit Higher-pressure air at a more constant pressure is supplied to mix with SF6 gas, the gas to be recovered is taken out from the outlet, fed into the gas separation section, and nitrogen gas, Oxygen gas and the like are adsorbed by the adsorbent in the adsorption cylinder to separate it from SF6 gas, and before the adsorbent in the adsorption cylinder becomes full of the adsorption gas, the supply of the gas to be recovered is stopped. After performing the pressure equalizing step of connecting the inlet and outlet and the outlets of the completed adsorption column and transferring the gas of the adsorption column completed with the adsorption process to the adsorption column completed with the decompression and regeneration process, the adsorption column with the completed adsorption process Entered the reduced pressure regeneration process and was adsorbed by the adsorbent The gas was discharged into the atmosphere, and the gas to be recovered was supplied to the adsorption column after the decompression regeneration step, and the adsorption step was started to separate the SF6 gas.

[0017] Furthermore, "KA" SF6 composed of a gas separation unit, a pressurization unit and a liquefaction unit
In the gas recovery device, SF taken out of the container to be recovered
The gas to be recovered containing 6 is supplied to the gas separation unit, separated into SF6 gas and gas not containing SF6, the gas containing no SF6 is discharged into the atmosphere, and the SF6 gas is pressurized by the pressurizing unit. Thereafter, the liquefied part is sent to a liquefier, which is attached to an atmosphere of latent heat of vaporization of liquid nitrogen gas mainly from a liquid nitrogen tank to cool the liquefied part and liquefy the SF6 gas. The liquefied nitrogen was pressurized and supplied to the container to be recovered. "K" In the SF6 gas recovery device composed of a gas separation unit, a pressurization unit, a liquefaction unit, and a gas supply unit,
When the F6 gas concentration is high, the gas to be recovered is directly pressurized in the pressurizing section, then cooled and liquefied in the liquefying section, and the non-liquefied gas in the cooling section is returned to the upstream side from the pressurizing section. This is performed until the internal pressure in the container to be recovered becomes substantially atmospheric pressure (about 0 MPa · G). Thereafter, a gas at a constant pressure is supplied from the gas supply unit into the container to be recovered, mixed with SF6 gas, and the pressure is increased. Liquefaction recovery by pressurized cooling is continued, and SF6
When the gas concentration falls below a certain value, the gas to be recovered is sent to the gas separation unit, the SF6 gas and the mixed gas are separated, the mixed gas is discharged into the atmosphere, and the SF6 gas is pressurized by the pressurizing unit. Then, it is cooled and liquefied in a liquefaction unit.

[0018]

FIG. 1 shows a flow sheet of an SF6 gas recovery apparatus according to a preferred embodiment. This is for recovering SF6 gas filled in the collection container 1 which is a transformer or a circuit breaker. The configuration of the recovery device includes a gas separation unit 3, a gas supply unit 7, a pressurizing unit 2, a liquefaction unit 4, and a reservoir 5 for storing liquefied SF6 gas. The container to be recovered 1 is usually SF6 at a pressure of 0.3 MPa · G to 0.6 MPa · G.
Gas is enclosed. Its concentration is from 100 vol%, and even if diluted with nitrogen gas, it is sealed at a concentration of 50 vol% or more. The SF6 gas has a critical temperature of 45.
64 ° C., critical pressure 3.75 MPa · G, critical molar volume 2
01 mL / mol, melting point -50.8 ° C, sublimation point -63.
8 ° C.

The vapor pressure of SF6 gas is, for example, 1.
Since the pressure is 22 MPa · G, the gas to be recovered is extracted, pressurized to 2.44 MPa · G in the pressurizing section 2 and cooled to 0 ° C. or lower in the cooling section 4, and SF6 gas of 50 vol% or more can be liquefied and recovered. . For this reason, the gas to be recovered is introduced into the pressurizing section 2 from the container 1 to be recovered, and is pressurized to 2.44 MPa · G by the pressurizing section 2 composed of a return circuit including the buffer tank 28, the pressurizing pump 30 and the constant pressure valve 29. This is the cooling unit 3
1. The liquefaction unit 4 including the liquefaction tank 32 and the solenoid valves 33 and 34 cools the liquefaction unit 4 to 20 ° C. or lower to liquefy and collect SF6. The liquefied SF 6 is stored in the reservoir 5.

The SF6 concentration of the gas to be recovered is 50 vol%
In the above case, when the internal pressure in the container to be collected becomes 0 MPa · G, gas is supplied from the gas supply unit 7 through the inlet 36 and S
Mixed with F6 gas, taken out from the outlet 35, and pressurized
And the method of cooling in the liquefaction section is continued, and the SF6 gas is liquefied and collected. Since the non-liquefied gas (nitrogen gas) remains in the liquefaction tank 32, this gas is returned to the upstream side of the pressurizing section (not shown). When the concentration of the SF6 gas in the gas to be recovered becomes 50 vol% or less, liquefaction and recovery cannot be performed at the above-mentioned pressure and temperature, and the gas to be recovered is introduced by closing the solenoid valve 10 and opening 9 in the gas separation section 3, Separate the gas. That is, adsorption tubes 19 and 2 filled with an adsorbent that adsorbs nitrogen gas and the like other than SF6 gas.
When the solenoid valve 21 is opened and introduced into one of the adsorption tubes 19 of the gas separation unit 3 composed of the vacuum pump 15, the electromagnetic valves 18, 21 to 27, and the adsorbent in the adsorption tube 19, Since gases other than SF6 are adsorbed and removed, SF6
The gas is concentrated and the solenoid valves 25, 2
7, which is referred to as an adsorption step.

The derived gas is stored in the buffer tank 28 of the pressurizing section 2 and then pressurized. Immediately before nitrogen gas or the like is adsorbed on the adsorbent of the adsorption cylinder 19 and becomes full, the solenoid valves 9 and 27 are closed, the introduction of the gas to be recovered and the derivation of SF6 gas are stopped, and the regeneration process is completed. The electromagnetic valves 21 and 23 at the inlet of the adsorption cylinder 20 and the electromagnetic valves 25 and 26 at the outlet are opened to move the adsorption cylinder 19 from the adsorption step to the adsorption cylinder 20 from which the regeneration step has been completed. After performing a pressure equalizing step of moving the SF6 gas remaining in the outlet conduit to the adsorption cylinder 20, the electromagnetic valves 21 and 25 of the adsorption cylinder 19 are closed, and the electromagnetic valves 22 and 18 are opened to open to the atmosphere. Suction cylinder 1
When the pressure in Step 9 is reduced to atmospheric pressure, nitrogen gas or the like adsorbed on the adsorbent is released and discharged into the atmosphere. Subsequently, the electromagnetic valve 18 is closed, and the adsorbent is sufficiently regenerated by pulling down to a vacuum region by the vacuum pump 15. (Regeneration process)

The adsorption cylinder 20 opens the solenoid valves 9 and 27, introduces the gas to be recovered from the solenoid valves 9 and 23, introduces the concentrated gas into the buffer tank 28 from the solenoid valves 26 and 27, Pressurize by 30 and liquefy and separate by the same method as before. The gas supply unit 7 is composed of a nitrogen cylinder 13 and a pressure regulating valve 14. When nitrogen gas is introduced into the container to be recovered and mixed, the gas supply unit 7 separates SF6 gas and nitrogen gas. The agent may be zeolite, and any other agent that adsorbs nitrogen gas can be used. There are 13X type and 5A type, and 5A type is used in this example.

The inlet (upstream) of the gas to be recovered in the adsorption column
Zeolite on the side and molecular sieve (CMS ・
・ Carbon, Molecular, Seaves)
Is filled so that nitrogen gas and oxygen gas can be adsorbed and removed, a compressed air generator 6 using air can be used instead of the gas supply unit 7 using nitrogen gas. This is constituted by a compressor 12 and an air dryer. The dried air is fed into the container 1 to be recovered at a regulated pressure, and SF6
After mixing with the gas, the SF6 gas can be separated and recovered according to the same principle as the method using the nitrogen gas, so that it can be performed using ubiquitous air.

The concentration of SF 6 gas in the mixed gas is 0.015 MPa · ab of pure SF 6 gas in terms of atmospheric pressure.
When the pressure is about 5% of the pressure corresponding to s, and the pressure is high by the pressure introduced into the PSA gas separation unit, one-fourth of the pressure
It is necessary to lower to the concentration multiplied by. Further, a compressor for increasing the pressure to a pressure required for gas separation can be provided between the container 1 to be recovered and the inlet to the gas separation section.
In this case, since the pressure in the container 1 can be set to the atmospheric pressure, the process can be completed when the pressure reaches about 5%.

FIG. 2 shows a flow sheet of an SF6 gas recovery apparatus according to another preferred embodiment. The configuration of this SF6 gas recovery apparatus is composed of a gas separation unit 3, a gas supply unit 7, a pressurization unit 2, a liquefaction unit 4, and a reservoir 5 for storing liquefied SF6 gas. It has the same configuration, but the gas separation unit 3 fills the adsorption tubes 19 and 20 with molecular sieve charcoal that adsorbs SF6 gas as an adsorbent. Except for the operation here, the operation is the same as that of the first embodiment, and therefore the description will be made focusing on this gas separation portion. When the concentration of the SF6 gas in the gas to be recovered decreases, the solenoid valve 10 of the gas separation unit is closed, and the gas valve 9 is opened to introduce the gas to be recovered and separate the SF6 gas. That is, the adsorption cylinder 1 filled with an adsorbent for adsorbing SF6 gas
9, 20 and the solenoid valves 12, 21 to 27, and the vacuum pump 15, the one of the adsorption cylinders 19 of the gas separation unit 3 is provided with the solenoid valve 2
1, the SF6 gas in the to-be-recovered gas is adsorbed by the adsorbent in the adsorption cylinder 19 and is removed by passing through the solenoid valves 25 and 27 from the other end outlet of the adsorption cylinder where the SF6 gas is removed. Gas (gas not containing SF6 gas) is derived.
This is called an adsorption step.

The SF 6 gas is adsorbed on the adsorbent of the adsorption cylinder 19, the solenoid valves 9, 21, 25, 27 are closed before the adsorbent is full, and the solenoid valves 23, 2 of the adsorption cylinder 20 after the regeneration process is completed.
4 and 26 are closed, the solenoid valve 37 is opened, and the cylinders 19 and 2 are closed.
The pressure is equalized to zero, and the non-adsorbed gas in the adsorption cylinder 19 is moved into the adsorption cylinder 20 with the center as the center. This step serves to increase the concentration of SF6 gas in the adsorption cylinder after the completion of the adsorption step. Thereafter, the next step can be performed to further increase the concentration of SF6 gas. That is, the solenoid valves 12, 21 are opened and SF
This is a step of purging the interior of the adsorption column 19 with the six gases and driving out the mixed gas in the adsorption column 19 toward the adsorption column 20. If the SF6 gas has reached the liquefiable concentration, all or a part of the pressure equalizing step and the purging step can be omitted. Thereafter (at this time, the SF6 gas also partially moves), the solenoid valves 21 and 1
The valves 2 and 37 are closed, the solenoid valves 22 and 11 are opened, and the SF6 gas in the inside of the adsorption cylinder 19 is led out by the vacuum pump 15 and sent to the buffer tank 28, which is pressurized by the pressurizing section. The adsorption cylinder 19 is sufficiently evacuated to recover the SF6 gas and regenerate the adsorbent. The adsorption cylinder 20 is provided with the solenoid valves 9 and 2
3, 26 and 27 are opened, the gas to be recovered is introduced, and the adsorption process is performed in the same manner as in the adsorption column 19. As described above, since the molecular sieve that adsorbs SF6 gas is used as the adsorbent used in the gas separation unit, the operation is the same as that of Example 1 except that the recovery of SF6 gas is performed in the regeneration step.

Further, the temperatures of the cooling unit 31 and the liquefaction tank 32 of the liquefaction unit 4 must be reduced to required values.
Usually, cooling is performed using an electric refrigerator. However, as described above, since the gas is supplied to the container to be recovered, the latent heat of evaporation using liquid nitrogen 40 is used as a cooling heat source for the liquefaction unit using the evaporator 41. Efficiency can be improved by introducing the evaporated nitrogen gas into the container to be recovered from the nitrogen gas outlet 43 and using the gas supply source. The liquefied part must be airtight and must withstand a certain pressure.

[0028]

[Effect of the Invention] By implementing the present invention,
What required long time and difficult or incomplete recovery or expensive installation can recover SF6 gas almost completely and in a relatively short time with a relatively simple recovery device. It has an excellent effect.

[Brief description of the drawings]

FIG. 1 is a flow sheet of a preferred embodiment of the present invention.

FIG. 2 is a flow sheet of another preferred embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Recovered container 2 Pressurization part 3 Gas separation part 4 Liquefaction part 5 Reservoir 6 High pressure air supply part 7 Gas supply part 8, 9, 10 Solenoid valve 11 Air dryer 12 Compressor 13 Nitrogen cylinder 14 Pressure regulating valve 15 Vacuum pump 16 Exhaust port 1 17 Exhaust port 2 18 Solenoid valve 19.20 Suction cylinder 21 to 27 Solenoid valve 28 Buffer tank 29 Constant pressure valve 30 Pressurizing pump 31 Cooling unit 32 Liquefaction tank 33, 34 Solenoid valve 35 Outlet 36 Inlet 40 Liquid Nitrogen tank 41 Evaporator 42 Nitrogen gas outlet in liquefaction part 43 Nitrogen gas outlet from liquefaction part 44 Gas inlet

Claims (8)

[Claims] 1. An S gas comprising a gas supply section and a gas separation section.
In the F6 gas recovery device, a high-pressure gas whose pressure has been adjusted by the gas supply unit is supplied to the recovery container, the recovery gas mixed with the SF6 gas is taken out from the gas outlet, and the SF is recovered by the gas separation unit.
An SF6 gas recovery apparatus that separates a gas containing much SF6 and a gas containing little SF6, discharges a gas containing little SF6 into the atmosphere, and recovers a gas containing SF6. 2. An SF6 gas recovery apparatus comprising a PSA-type gas separation unit and a gas supply unit having an adsorption cylinder filled with an adsorbent for adsorbing SF6 gas or mixed gas in a recovery container, A high-pressure gas regulated by a gas supply unit is supplied to the tank, and a gas to be recovered mixed with SF6 gas is taken out and sent to the gas separation unit, and the easily adsorbed gas in the gas to be recovered is adsorbed in the pressure adsorption step. Adsorbed by the adsorbent in the cylinder and separated from non-adsorbed gas, decompressed in the adsorption cylinder in the decompression regeneration step, desorbed gas adsorbed by the adsorbent, separated and mixed SF6 gas and mixed gas An SF6 gas recovery device that discharges gas into the atmosphere. 3. An SF6 gas recovery apparatus comprising a PSA-type gas separation section and a nitrogen gas supply section having an adsorption cylinder filled with zeolite as an adsorbent, and a nitrogen gas whose pressure is regulated by a nitrogen gas supply section in a container to be recovered. The gas to be recovered is mixed with a gas mainly containing SF6 gas filled in the container to be recovered, and is sent to the gas separation unit. In the pressure adsorption step, nitrogen gas or the like is introduced into the adsorption cylinder. SF6 gas recovery device that adsorbs and removes from the adsorbent and separates it from SF6 gas, depressurizes the adsorption column in the decompression step, desorbs nitrogen gas and the like adsorbed by the adsorbent, and releases it to the atmosphere . 4. An SF6 gas recovery apparatus comprising a PSA-type gas separation unit and a gas supply unit having two adsorption cylinders filled with an adsorbent for adsorbing a gas other than SF6 gas in a container to be recovered. The container is supplied with a high-pressure gas whose pressure has been adjusted by a gas supply unit, and SF6 filled in the container to be recovered is filled.
The gas to be recovered mixed with the gas mainly is taken out from the outlet, sent to one of the adsorption columns of the gas separation unit, and a gas other than SF6 gas is adsorbed by the adsorption column in the pressure adsorption step. It is adsorbed by the adsorbent in the cylinder and is separated from SF6 gas. The supply of the gas to be collected is stopped before the adsorbent of the adsorption cylinder becomes full of the adsorbed gas, and the other adsorption cylinder and the inlet where the pressure reduction regeneration process is completed are completed. After performing the pressure equalization step of coupling the gas and the outlets of the adsorption cylinders having completed the adsorption step to the adsorption cylinders of which the pressure reduction regeneration step has been completed, the adsorption cylinders having completed the adsorption step enter a pressure reduction regeneration step, The gas adsorbed by the adsorbent is discharged into the atmosphere, and the adsorption column after the decompression regeneration step enters the adsorption step, in which a gas to be recovered is supplied to separate the SF6 gas.
Gas recovery device. 5. An SF6 gas recovery unit comprising a PSA-type gas separation unit and a high-pressure air supply unit having two adsorption tubes filled with zeolite on the upstream side and molecular sieve on the downstream side, and the high-pressure air is supplied to the container to be recovered. A high-pressure air at a constant pressure is supplied from a supply unit, mixed with SF6 gas, a gas to be recovered is taken out from an outlet, fed into the gas separation unit, and nitrogen is adsorbed in an adsorption cylinder in one pressure adsorption process. Gas, oxygen gas and the like are adsorbed by the adsorbent in the adsorption column to separate from SF6 gas, and before the adsorbent in the adsorption column becomes full of the adsorption gas, the supply of the gas to be recovered is stopped, and the other pressure is reduced. After performing the pressure equalizing step in which the adsorption column, in which the regeneration step is completed, the inlets and the outlets are connected, and the gas in the adsorption column in which the adsorption step is completed is transferred to the adsorption cylinder in which the pressure reduction regeneration step is completed, the adsorption step is completed. The adsorption cylinder enters the decompression regeneration process and absorbs the adsorbent. An SF6 gas recovery device that discharges the deposited gas to the atmosphere, supplies the gas to be recovered to the adsorption column after the decompression regeneration process is completed, enters the adsorption process, and separates the SF6 gas. 6. An SF6 gas recovery apparatus comprising a gas separation section, a pressurization section, and a liquefaction section, supplies a gas to be recovered containing SF6 taken out of a recovery container to the gas separation section,
6 gas and a gas not containing SF6, the gas containing no SF6 is discharged into the atmosphere, and the SF6 gas is pressurized by a pressurizing unit and then sent to a liquefying unit. An SF6 gas recovery device in which the liquefied portion is attached to an atmosphere mainly of latent heat of vaporization of liquid nitrogen gas to cool the liquefied portion and liquefy the SF6 gas. 7. An SF6 gas recovery apparatus comprising a gas separation section, a pressurization section, and a liquefaction section, supplies a gas to be recovered including SF6 taken out from a recovery container to the gas separation section,
6 gas and a gas containing no SF6, the gas containing no SF6 is discharged into the atmosphere, the SF6 gas is pressurized by a pressurizing unit, and then sent to a liquefying unit. The liquefied portion is attached to an atmosphere of latent heat of vaporization of the liquefied nitrogen gas, and the liquefied portion is cooled to liquefy the SF6 gas, and pressurized gasified liquefied nitrogen is supplied to the container to be recovered. SF6 gas recovery device. 8. In an SF6 gas recovery apparatus comprising a gas separation section, a pressurization section, a liquefaction section and a gas supply section, when the concentration of SF6 gas in the collection container is high, the gas to be recovered is directly sent to the pressurization section. After the pressurization, it is cooled and liquefied in the liquefaction unit, and the non-liquefied gas in the cooling unit is configured to be returned to the upstream side from the pressurization unit, and the internal pressure in the container to be recovered becomes approximately atmospheric pressure (about 0 MPa · G). After that, a constant pressure gas is supplied from the gas supply unit into the container to be recovered, mixed with SF6 gas to increase the pressure, and the liquefaction and recovery by the pressurized cooling is continued. When the concentration falls below a certain value, the gas to be recovered is sent to the gas separation unit, the SF6 gas and the mixed gas are separated, the mixed gas is discharged into the atmosphere, and the SF6 gas is pressurized by the pressurizing unit. A SF6 gas recovery device that is cooled and liquefied in a liquefaction unit.