JP2002355518A - Equipment for recovering specified gas - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an equipment for recovering a specified gas from which any of the specified gas is not released to the atmosphere even when some specified gas is not yet separated at a step to separate the specified gas from other mixed gas in a gas separating part when the specified gas is recovered in a vessel 26 to be collected. SOLUTION: At the step to separate the specified gas from other mixed gases in the gas separating part 21, exhaust gas in which a little specified gas is mixed together with other mixed gas such as nitrogen gas is stored temporarily in an exhaust gas tank 6 in the part 21 through an exhaust gas inlet 20, which is then made to flow to another vessel 26 through an exhaust gas outlet 2 again.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to the separation and recovery of a specific gas. The specific gas refers to a gas that is subject to emission control into the atmosphere due to prevention of global warming and destruction of the ozone layer, or toxicity or odor of the gas, and relates to separation and recovery of this gas.

[0002]

2. Description of the Related Art Toxic gases, odorous gases, and other gases that have an adverse effect on living organisms in specific gases are collected or detoxified or deodorized so as not to be released. However, gas that was released into the atmosphere until recently because it was harmless and odorless,
From the environmental point of view, some of them have become emission control gases.

That is, the following gases have been subject to emission control at the Kyoto Conference on Global Warming Prevention.

[0004]

Embedded image

The following gases have been subject to emission control to prevent the destruction of the ozone layer.

[0006]

Embedded image

[0007] Among these gases, the desired effects are great due to the properties of these gases, and there are no alternatives that can be found.
Or, even if alternatives are found, there are many that are likely to have similar environmental impacts, and many would require similar release controls. Since the regulation has been set in recent years, there is no technology for separating and recovering these gases without releasing them into the atmosphere. If this technology can be established, the technical role will be significant.

If these specific gases are used in a 100% pure state, there is little problem since they can be extracted, stored and reused as they are. However, when these gases are mixed with other gases, a difficult problem arises in separation and recovery. Separation of gas mixtures depends on their physical, scientific,
Alternatively, various methods for separating using electric properties can be considered.

For example, a cryogenic separation method in which separation is performed according to a difference in vaporization temperature after high-pressure cooling and liquefaction, a separation membrane method using molecular size or the like, or a solubility, a PSA separation method using an adsorbent,
There is a liquefaction method using a difference in liquefaction temperature. Further, there is also a method of separating them by combining them. However, it is usually difficult to separate a plurality of mixed gases into two 100% pure gases. When the mixed gas of A and B is separated, A can be separated into a dense gas and B can be separated into a rich gas. However, B is contained in A and A is contained in dense B. When one A is darkened (the component of B is reduced), the A increases in the other B. The opposite is also true. When the emission control gas is released into the atmosphere, this slightly contained gas becomes a problem. Conventionally, a great deal of energy has been spent on keeping the concentration of the trace gas released into the atmosphere low, and advanced technology has been required.

[0010]

SUMMARY OF THE INVENTION To recover a specific gas without leaking into the atmosphere.

[Means for Solving the Problems]

Gas separation techniques for separating and recovering a specific gas include, for example, a PSA method using an adsorbent and a liquefaction method based on a difference in liquefaction temperature. Even with these separation means, it is necessary to change one or two parameters in the separation means depending on the concentration of the target gas contained in the gas to be separated.
There is an optimal and efficient value corresponding to that concentration. Even if the concentration changes, if a parameter value corresponding to the concentration is controlled, the mixed gas of A and B can be changed to A and B within a certain concentration range.
B can be optimally separated. However, as mentioned above, B in A
However, A is somewhat contained in B. Instead of releasing this B, it is returned to the collection container.

That is, in a specific gas recovery device having a gas separation unit and a pump, a gas to be recovered containing a specific gas is introduced into the gas separation unit from a recovery container and separated into a specific gas and another mixed gas. A specific gas recovery apparatus configured to recover the specific gas and return the mixed gas to the container to be recovered by the pump. By doing so, the concentration of the specific gas A in the container to be recovered decreases, but by controlling the gas separation unit corresponding to the concentration, the concentrated specific gas A is recovered.

That is, in a specific gas recovery apparatus having a gas separation section and a pump, a gas to be recovered containing a specific gas is introduced into the gas separation section from a recovery container and separated into a specific gas and another mixed gas. While recovering the specific gas, configured to return the mixed gas to the container to be recovered by the pump,
The specific gas recovery device is configured such that the concentration of the gas to be recovered is measured and the control of the gas separation unit is changed according to the concentration value.

When recovering a specific gas in a container to be recovered,
Even if the gas in this container is recovered to atmospheric pressure, the specific gas still remains in it. Therefore, it is necessary to evacuate the inside of the container to pump out a specific gas, but this evacuation takes a long time. Further, the container may be damaged if the container is not constructed to withstand vacuum evacuation. For this reason, if the mixed gas to be mixed with the specific gas is a gas such as nitrogen that exists in the natural world, this gas is supplied, and instead of vacuuming, a diluent gas is supplied from the gas supply unit to reduce the concentration, then the gas is extracted. Separate and concentrate in the separation section and collect.

That is, in a specific gas recovery device having a gas separation unit, a pump, and a gas supply unit, a gas to be recovered including a specific gas is introduced from a recovery container into the gas separation unit, and the specific gas and another mixed gas ( (Diluent gas) to collect the specific gas, and further return the mixed gas to the container to be recovered by the pump, and the pressure of the gas to be recovered introduced into the gas separation unit is lower than a predetermined pressure value. A specific gas recovery device configured to introduce the gas in the gas supply unit to the container to be recovered in the event of the occurrence. The constant pressure value is a pressure value required in the gas separation unit, a constant pressure value determined at a pressure equal to or lower than the atmospheric pressure or a vacuum pressure resistance value of the apparatus, and is a constant pressure value determined technically.

In the case of recovering the separated specific gas, a step of cooling under pressure, liquefying and recovering is often added.
In this liquefaction stage, the concentration of the mixed gas is increased as much as the specific gas is liquefied and separated, so this processing is performed as follows. That is, in a specific gas recovery device having a gas separation unit, a pressurization unit, and a liquefaction unit, in the process of separating the specific gas and another mixed gas in the gas separation unit, and in the process of liquefying the specific gas in the liquefaction unit The specific gas recovery device is configured to return the diluted specific gas to the container to be recovered because the specific gas concentration decreases.

[0017]

In this embodiment, SF6 gas is taken as an example of a specific gas. And the gas separation part is PS
The case where the A-type gas separation method is used will be described.

SF6 gas is charged into a high-voltage power transformer or a circuit breaker of a power circuit, and its thermal stability, electrical stability,
Utilizing the high insulation pressure resistance, it is possible to reduce the size of the equipment, and its contribution is significant in reducing the volume of substations in cities. The SF6 gas filled in the transformer or the circuit breaker may be one having a purity of 100% or one which is appropriately diluted with nitrogen gas. These gases must be extracted at the time of inspection, maintenance and repair of the equipment in which they are used. However, conventionally, these gases are released to the atmosphere because there is little influence on the human body and the like by these gases.

However, SF6 gas is almost 100% pure.
%, And since it is an expensive gas, there has been a recovery apparatus in a range where it can be easily recovered and reused cost-effectively, and has been recovered and reused. In other words, there was a device that withdrawn and liquefied and recovered by pressurization and compression cooling.However, the inside of the container to be recovered was suctioned and recovered to a high vacuum range, or a mixed gas containing other gases was separated. There was no device for collecting only SF6 gas.

The electric power industry voluntarily enacted the "Standards for Handling SF6 Gas for Electric Power" in December 1998 by the Joint Research Institute of Electricity, and decided to regulate its emission. That is, at the time of repair and inspection, 0.015 MPa · abs (recovery rate of 97 vol% or more), and at the time of dismantling and removal, 0.005 MPa · abs (recovery rate of 9 vol.
A voluntary standard for suctioning up to a vacuum region of 9 vol% or more was created. Recovering to a high vacuum region has the disadvantage of requiring a long time for recovery. 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. That is, the liquid is suctioned and collected up to a high vacuum region, and the amount of leakage into the atmosphere is reduced.

The SF6 gas is characterized by a critical temperature of 45.64 ° C., a critical pressure of 3.66 MPa · G, a melting point of −50.8 ° C., and a sublimation point of −63.8 ° C. A liquefaction unit for cooling and liquefaction is provided. In the range where the concentration of SF6 gas in the gas to be recovered is high, the pressure to be applied is relatively low due to the relationship between the liquefaction temperature and pressure of the liquefied gas, and the liquefaction temperature is relatively high. It can be easily liquefied and recovered.

First, by the above method, the internal pressure in the container to be recovered is recovered by the suction pump until the internal pressure becomes within a pressure range in which the liquid can be liquefied in the liquefaction unit. As described above, the gas to be recovered may be a gas in which SF6 gas is 100% or a gas diluted with nitrogen gas. Even if this mixed gas exists,
A gas separation unit for separating the six gases from other separated gases is provided.

The gas separation section is performed by a PSA method using an adsorbent for adsorbing a specific gas. In the PSA method, when a mixed gas containing a specific gas is sent while applying pressure to an adsorption column filled with the adsorbent, the specific gas is adsorbed and removed by the adsorbent, and the non-adsorbed gas is removed from the other end of the adsorption column. Is separated and taken out. This step is called an adsorption step. Then, shortly before the adsorbent adsorbs the adsorbed gas, the supply of the mixed (raw material) gas is stopped, and the pressure of the adsorbent is reduced from the inlet of the adsorbent. The adsorbed gas released from the adsorbent is discharged and the adsorbent's adsorption capacity is regenerated. This step is called a regeneration step. Since the gas is separated while repeating the adsorption step and the regeneration step, that is, applying or decreasing pressure to the adsorption column.
Pressure Swing Adsorption "Pressure fluctuation adsorption" method.

The adsorbent is SF6, which is the target gas.
There are an adsorbent that adsorbs a gas and does not adsorb a mixed gas, and an adsorbent that adsorbs another mixed (diluted) gas that is mixed without adsorbing the SF6 gas as the target gas. The method of extracting the target gas differs slightly depending on the adsorbent used. For example, when targeting SF6 gas, the former includes molecular sieve charcoal in which activated carbon has a molecular sieve function. The latter includes zeolite 5A type, 4A type and others.

In the former case, the SF6 gas is adsorbed and separated by the adsorbent, so that the SF6 gas is recovered in the step of separating from the adsorbent in the pressure reduction regeneration step. In the latter case, the SF6 gas is not adsorbed by the adsorbent in the pressure adsorption step, and is separated from the other end of the adsorption cylinder and comes out. In the SF6 gas separation by the PSA method, the separated diluent gas, that is, the SF6 gas is slightly present on the exhaust gas side.
Disposal into the atmosphere is a problem because it contains gases. The amount of SF6 gas contained in this exhaust gas is ppm
It is technically difficult to keep it low to order.
For this reason, a small amount of separated exhaust gas containing SF6 gas is not released to the atmosphere but returned to the container to be recovered.

In the process of liquefying SF6 gas by pressurizing and cooling, gas such as nitrogen contained in the gas is not liquefied in the upper space of the liquefaction tank. Since the gas concentration increases, the gas is extracted and returned to the container to be recovered in the same manner as in the case of the separated exhaust gas.

[0027]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described with reference to the drawings. However, this is one embodiment for explanation, and the present invention is not limited to this embodiment. FIG. 1 shows a case where a PSA gas separation method is used with SF6 gas as a specific gas.
2 is a flow sheet showing a configuration of the present example including a liquefier 2 and a liquefaction unit 23.

The details of the gas separation unit 21 in FIG.
(A) or FIG. 2 (B) shows a flow sheet. The recovered gas is connected to the recovered gas inlet 1 of the gas separation unit 21 from the outlet of the recovered container 26, and the SF concentrated in the gas separation unit 21.
Six gases are introduced into the pressurizing section 22 from the outlet 3, and the pressurizing section includes a buffer tank 30, a pressurizing pump 31, and a pressure reducing valve 32 as a return circuit so as not to overpressurize to a certain pressure or more.

The pressurized SF6 gas is sent to a liquefaction unit 23 where it is cooled and liquefied and stored in a storage tank 24. Liquefaction unit 2
3 is a cooler 33, solenoid valves 34, 36, 37, liquefaction tank 35
It is cooled by a cooler 33 and sent to a liquefaction tank 35 for cooling. As long as the SF6 gas entering the liquefaction unit 23 is not 100% pure, the SF6 gas is temporarily stored in the liquefaction tank 35.
When the gas is liquefied and taken out to the storage tank 24, the concentration of the impurity gas in the liquefaction tank increases, and the liquefaction temperature and pressure increase. Therefore, the impurity gas is taken out by opening the solenoid valve 36 and returned to the gas separation part. It is necessary to put the waste gas into the exhaust gas tank 6 in the gas separation unit 21 through the exhaust gas inlet 20 and return the waste gas to the collection container 26 by the pump 7.

Since the pressure of the container to be recovered decreases as the SF6 gas is liquefied and taken out, when the pressure becomes lower than a certain value, the solenoid valve 29 is opened from the gas supply unit 25 to introduce the gas, and the gas is separated. The gas pressure is maintained so as not to affect the operation of the unit. It is preferable that the gas supply unit 25 be constituted by, for example, a nitrogen cylinder and a pressure reducing valve. FIG. 2 (A)
The target gas (SF6 gas) is strongly adsorbed on the adsorbent and mixed gas
2 shows a flow sheet of a gas separation unit using molecular sieve charcoal that only slightly adsorbs (nitrogen gas).

In this method, a gas from a container to be recovered such as a transformer is introduced from a gas inlet 1 to be recovered, and the solenoid valves 8 and 10 are opened to adsorb the SF6 gas into the adsorption cylinder 4 and a nitrogen gas partially containing the SF6 gas. Exhaust gas separated from SF6 gas and the like is stored in an exhaust gas tank 6 through solenoid valves 14 and 9. This is pressurized and discharged from the exhaust gas outlet 2 by the pump 7. This is returned to the collection container 26 of FIG.

The gas to be recovered is introduced into the adsorption column 4, the introduction is stopped before the adsorbent adsorbs the SF6 gas and becomes full, and a pressure equalization step is performed between the adsorbent and the adsorption column 5 after the regeneration process. Perform That is, the electromagnetic valves 8, 10, 16, 11, and 14 are closed, all the electromagnetic valves of the adsorption cylinder 5 are closed, the equalizing electromagnetic valve 17 is opened, and the nitrogen gas floating in the adsorption cylinder 4 is adsorbed. It is moved to the cylinder 5 together with a part of SF6 gas. Thereafter, the electromagnetic valve 17 is closed, the SF6 gas adsorbed on the adsorbent of the adsorption cylinder 4 opens the electromagnetic valves 11 and 18, and the concentrated SF6 gas is sent from the outlet 3 to the storage tank 30 of FIG. This step is called a regeneration step because the SF6 gas adsorbed from the adsorbent is decompressed and released from the adsorbent, taken out from the outlet 3 and the capacity of the adsorbent is regenerated.

The adsorption cylinder 5 introduces the gas to be recovered from the electromagnetic valve 12, adsorbs the SF 6 gas to the adsorbent, and sets the electromagnetic valves 15, 9.
Is opened, and nitrogen gas is sent to the exhaust gas tank 6 and sent from the exhaust gas outlet 2 to the container 26 to be recovered in FIG. As described above, the pressure adsorption step, the pressure equalization step, and the regeneration step are repeated to separate the gas. In this way, the raw material gas is taken in from the to-be-collected gas inlet 1 by gas separation, and SF
The six gases are adsorbed and separated, taken out in the regeneration step, and sent out from the outlet 3. On the other hand, the nitrogen gas, which is a mixed gas, is stored in an exhaust gas tank 6 and is pumped by a pump 7.
Returned to 6. Of course, the specific gas concentration in the container to be recovered falls, but the concentration is detected, and the cycle time of the gas separation unit, or the amount of gas at the time of introduction and discharge is changed according to the concentration, and controlled so that it can be separated appropriately. I do.

FIG. 2 (B) shows a flow sheet of a separation unit using a zeolite in which the adsorbent hardly adsorbs the target gas (SF6 gas) and adsorbs a mixed gas of nitrogen gas. Raw material gas is introduced from the recovered gas inlet 1,
The solenoid valves 8 and 10 are opened and guided to the adsorption cylinder 4 to adsorb nitrogen gas or the like to the adsorbent, SF6 gas is concentrated from the other end, and the buffer tank 30 of FIG. Sent out to. Shortly before the adsorbent of the adsorption cylinder 4 becomes full of the separated exhaust gas such as nitrogen gas, the introduction of the raw material gas is stopped, and a pressure equalization step is performed with the adsorption cylinder 5 after the regeneration step.

That is, the solenoid valves 8, 18, 11, and 13 are closed, the solenoid valves 14, 15, and 10 and 12 are opened, and SF6 gas floating in the adsorption cylinder 4 is supplied to the adsorption cylinder 5 with a part of nitrogen gas. And the solenoid valves 10, 14, and 13 are closed, and the solenoid valves 11, 9, 8, 12, 15, and 18 are opened,
The source gas is introduced into the adsorption column 5 and the concentrated SF 6 gas is discharged from the outlet 3 through the solenoid valves 15 and 18.

Thus, the adsorption cylinder 5 enters the adsorption step. The separated exhaust gas adsorbed by the adsorption column 4 is released from the exhaust gas outlet 2 by the pump 7 after the nitrogen gas or the like adsorbed by the adsorbent is released and stored in the exhaust gas tank 6 through the solenoid valves 11 and 9. 26. Thus, the adsorption step, the pressure equalization step, and the regeneration step are repeated to separate the gas. The decrease in the concentration of the specific gas in the container to be recovered is the same as in the case described above, and the control of the gas separation unit is similarly performed based on the concentration value.

The pressure equalizing step in the description of the flow sheet shown in FIGS. 2A and 2B can be omitted because of the capability of pressurizing and liquefying SF6 gas.

[0038]

EFFECT OF THE INVENTION Specific gas, SF6 gas and other mixed gas
(E.g., nitrogen gas) in a gas separation section by the PSA method, it is technically difficult to achieve 100% perfect separation, but even in such a case, the present invention should be practiced. Thereby, the separation and recovery processing of the SF6 gas in the container to be recovered can be performed without releasing the mixed gas containing the diluted SF6 gas into the atmosphere.

[Brief description of the drawings]

FIG. 1 is a flow sheet showing an overall configuration of a gas separation section for separating a specific gas according to the present invention when a PSA method is used.

FIG. 2 is a flow sheet for detailed explanation of a gas separation unit 21; FIG. 2A is a flow sheet in the case where a specific gas is mainly adsorbed to the adsorbent using molecular sieve charcoal as the adsorbent, and FIG. 2B is a flow sheet mainly using the zeolite as the adsorbent except for the specific gas. 5 is a flow sheet when the nitrogen gas or the like is adsorbed by the adsorbent.

[Explanation of symbols]

 Reference Signs List 1 recovered gas inlet 2 exhaust gas outlet 3 outlet 4, 5 adsorption tube 6 exhaust gas tank 7, 7 'pump 8 to 19 solenoid valve 20 exhaust gas inlet 21 gas separation unit 22 pressurization unit 23 liquefaction unit 24 storage tank 25 gas supply unit 26 Container to be recovered 27 Nitrogen cylinder 28 Pressure reducing valve 30 Buffer tank 31 Pressurizing pump 32 Pressure reducing valve 33 Cooler 34, 36, 37 Solenoid valve 35 Liquefaction tank

Claims (4)

[Claims] In a specific gas recovery apparatus having a gas separation unit and a pump, a gas to be recovered containing a specific gas is introduced from a recovery container into the gas separation unit and separated into a specific gas and another mixed gas. A specific gas recovery apparatus, wherein the specific gas is recovered and the mixed gas is returned to the container to be recovered by the pump. 2. A specific gas recovery apparatus having a gas separation unit and a pump, wherein a gas to be recovered containing a specific gas is introduced from a recovery container into the gas separation unit and separated into a specific gas and another mixed gas. The specific gas is recovered, and the mixed gas is returned to the container to be recovered by the pump, the concentration of the recovered gas is measured, and the control of the gas separation unit is changed according to the concentration value. A specific gas recovery device characterized by the above-mentioned. 3. A specific gas recovery device having a gas separation unit, a pump and a gas supply unit, wherein a gas to be recovered containing a specific gas is introduced into the gas separation unit from a container to be recovered, and the specific gas and another mixed gas are introduced. When the specific gas is recovered by separating the mixed gas, the mixed gas is returned to the container to be recovered by the pump, and the pressure of the gas to be recovered introduced into the gas separation unit becomes lower than a predetermined value. And a gas recovery unit configured to introduce the gas in the gas supply unit into the container to be recovered. 4. In a specific gas recovery device having a gas separation unit, a pressurizing unit and a liquefaction unit, a process of separating the specific gas and another mixed gas in the gas separation unit, and liquefying the specific gas in the liquefaction unit A specific gas recovery device configured to return the diluted specific gas generated in the process of performing the recovery to the container to be recovered.