JPH10286425A - Separation method of gaseous mixture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for separating a gaseous mixture good in recovery efficiency and without lowering the blower efficiency by using two adsorption vessels. SOLUTION: The left and right adsorption vessels 3, 4 and a receiver tank 7 are provided, after the following five stages have been operated in this order, the adsorption vessels 3 and 4 are reversed, the following five stages are operated in the order and the total ten stages are executed repeatedly. Namely, product gaseous oxygen remaining in the left adsorption vessel 3 is recovered in the right adsorption vessel 4 and the right vessel, 4 is evacuated, desorbed and exhausted in the first stage (A). Raw air is introduced into the right adsorption vessel 4 and the evacuation, desorption and exhaustion are continued in the left adsorption vessel 3 in the second stage (B). The product gaseous oxygen is introduced into the right adsorption vessel 4 from the receiver tank 7 and the evacuation, desorption and exhaustion are continued in the left adsorption vessel 3 in the third stage (C). Gaseous nitrogen is adsorbed on an adsorbent in the right adsorption vessel 4, the gaseous oxygen is generated as the product gas and the evacuation, desorption and exhaustion are continued in the left adsorption vessel 3 in the fourth stage (D). A part of the product gaseous oxygen generated from the right adsorption vessel 4 is introduced into the left adsorption vessel 3 and the evacuation, desorption and exhaustion are continued in the left adsorption vessel 3 in the fifth stage (E).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for separating a mixed gas by a pressure swing adsorption method (PSA method).

[0002]

2. Description of the Related Art Conventionally, various methods have been used as a method for separating a product gas such as oxygen from a gas mixture such as air. Because of the low cost, a separation method using an adsorbent is widely used. The separation method using this adsorbent is generally called a pressure swing adsorption method (PSA method),
A plurality of adsorption tanks are filled with an adsorbent for selectively adsorbing nitrogen gas, and air is introduced into each adsorption tank, nitrogen gas is adsorbed by pressurization, nitrogen gas is desorbed by depressurization (regeneration of adsorption tank), and pressure is increased. By repeating such operations, oxygen gas is separated and generated. In such a PSA method, a method using three or more adsorption tanks is mainly used.
Recently, many methods have been devised which use two adsorption tanks which are effective in reducing the scale of the apparatus and equipment costs.

As a method using two adsorption tanks as described above, a separation method disclosed in Japanese Patent Application Laid-Open No. Hei 7-265635 has been proposed. This separation method uses two beds 31, 32, a product reservoir 33, a feed blower 34 and a vacuum pump 35, as shown in FIG. 11, and first feed air (ambient air) is compressed by the feed blower 34. Then, the mixture is introduced into the first bed 31 which has been already pressurized to the adsorption pressure, adsorbs nitrogen in the air to the adsorbent, and oxygen in the air not adsorbed by the adsorbent is used as product oxygen via the manifold 36 as product oxygen. Pull out to product reservoir 33. At this time, the second floor 32
Is evacuated by a vacuum pump 35. Next, in the latter half of the oxygen production in the first bed 31, a part of the product oxygen is sent to the second bed 32 via the manifold 37 as a purge gas. Next, feed air compressed by a feed blower 34 is introduced into the second bed 32, while the first
And the outlets of the second floors 31 and 32 are connected to each other, and the residual gas in the first floor 31 is recovered to the second floor 32 via the manifold 38, and the first floor 31 is connected to the vacuum pump 35. Evacuate under reduced pressure. Next, the connection between the outlets of the first and second floors 31 and 32 is interrupted, and the first
, And the introduction of feed air to the second bed 32 is continued. After that, the first floor 31 and the second floor 32 are exchanged, and the above method is repeated.
In this separation method, the feed blower 34 and the vacuum pump 35 operate continuously.

[0004] An adsorption method disclosed in JP-A-8-71350 has also been proposed. That is, in step 1, the gas taken out from the second bed at the upper supply pressure by the co-current depressurization (residual gas release from the upper end of the second bed) is collected at the upper end of the first bed at the lower desorption pressure. I do. In this stage 1, the supply blower and the exhaust blower are in an unloaded state. Next, in Step 1A (overlapping step), Step 1 is continued, and at the same time, the supply gas is introduced into the lower end of the first bed by the supply blower, and the gas is evacuated and reduced from the second bed by the exhaust blower. Stage 2 is reached when the first bed reaches the upper adsorption pressure. In this stage 2, additional feed air is introduced at the lower end of the first bed and product gas (a component that is not easily adsorbed in the feed gas) is withdrawn from the upper end. Next, in step 3, the additional supply of the supply gas is continued. Then, a part of the product gas recovered from the upper end of the first bed is diverted to the upper end of the second bed as a purge gas. Upon completion of Step 3, regeneration of the first bed begins with Step 4, a co-current depressurization-pressure equalization step, in which residual gas in the first bed is withdrawn from the top of the first bed and a second gas is removed. Collect at the top of the floor (during this period the supply and exhaust blowers are unloaded). After such a stage 4, the first floor is replaced with the second floor, and the above method is repeated.

[0005]

However, in the above separation method, the residual gas in the first bed 31 is removed from the second bed 32.
Since the feed air compressed by the feed blower 34 is also introduced from the inlet of the second bed 32 at the same time when the feed gas is recovered from the outlet of the second bed 32, there is a problem that the recovery efficiency of the residual gas is poor. That is, the recovery of the residual gas is performed by connecting the outlets of the first and second beds 31 and 32 to each other,
Utilizing the vacuum of the bed 32 (ie, the first and second
Using the pressure difference between the floors 31 and 32).
This is because, when the feed air is also introduced during the recovery of the residual gas, the internal pressure of the second bed 32 immediately rises and a large pressure difference cannot be obtained for a long time. On the other hand, in the above-mentioned adsorption method, the exhaust blower is in a no-load state when the residual gas is recovered, and there are problems such as a decrease in blower efficiency and wasteful consumption of power. That is, the fact that the exhaust blower is in a no-load state means that the exhaust blower is normally operating without a load, not at all, and the exhaust blower is wastefully used. This is because adverse effects such as a decrease in blower efficiency and wasteful power consumption appear.

The present invention has been made in view of such circumstances, and an object of the present invention is to provide a mixed gas separation method that uses two adsorption tanks, has a high recovery efficiency, and does not cause a decrease in blower efficiency. I do.

[0007]

In order to achieve the above object, a mixed gas separation method according to the present invention comprises a first and a second adsorption tank filled with an adsorbent for selectively adsorbing a specific gas and a product gas. A storage tank is provided, and the following five steps (A) to (E) are operated in this order, then the first adsorption tank and the second adsorption tank are reversed, and the following five steps (A) to (E) are performed again. The configuration is such that ten steps of operating in this order are repeatedly performed. (A) The gas remaining in the second adsorption tank is recovered in the first adsorption tank through communication between the gas outlet of the first adsorption tank that has been decompressed and exhausted and the gas outlet of the second adsorption tank that has been adsorbed. (2) a step of depressurizing and desorbing the specific gas adsorbed by the adsorbent of the second adsorption tank from the gas inlet of the adsorption tank and exhausting the gas. (B) a step of introducing a raw material gas into the gas inlet of the first adsorption tank where the recovery of the residual gas is continued, and continuing the decompression / desorption exhaust in the second adsorption tank; (C) A step in which the product gas in the product gas storage tank is introduced into the gas outlet of the first adsorption tank where the recovery of the residual gas is completed and the introduction of the source gas is continued, and the desorption / desorption exhaust in the second adsorption tank is continued. (D) The specific gas in the raw material gas is adsorbed by the adsorbent in the first adsorption tank in which the introduction of the product gas is completed and the introduction of the raw material gas is continued, and a gas not adsorbed by the adsorbent is generated from the gas outlet as a product gas. And introducing the product gas into the product gas storage tank and continuing the decompression and desorption in the second adsorption tank. (E) A part of the product gas generated from the gas outlet of the first adsorption tank, which continues the introduction of the raw material gas and the generation of the product gas, is introduced into the gas outlet of the second adsorption tank, and desorbed and decompressed in the second adsorption tank. The process of continuing exhaust.

That is, according to the mixed gas separation method of the present invention, the first gas filled with an adsorbent for selectively adsorbing a specific gas is used.
And a second adsorption tank and a product gas storage tank. After the following five steps (A) to (E) are operated in this order, the first adsorption tank and the second adsorption tank are reversed, and the following five steps (A) to (E) are again operated in this order. 10 to do
The process is repeated. That is,
In the step (A), in order to increase the recovery rate of the product gas, the gas (gas containing a large amount of product components) remaining in the second adsorption tank (pressurized state) after the adsorption is removed from the first adsorption tank after the decompression and desorption is completed. The water is collected in the adsorption tank (under reduced pressure) using the pressure difference between both tanks. At this time, the introduction of the raw material gas into the first adsorption tank is stopped, and the recovery using a larger pressure difference can be performed. In addition, the decompression and desorption of the second adsorption tank is started. As a result, the pressure in the first adsorption tank increases, the pressure in the second adsorption tank decreases, and the pressures in both tanks are equalized.
In the step (B), pressure equalization is continued until the pressures in both tanks become substantially equal, and further recovery is performed. Further, the introduction of the raw material gas into the first adsorption tank is started, whereby it is possible to introduce a larger amount of the raw material gas while shortening the pressure rising time of the first adsorption tank. The introduction of the raw material gas into the first adsorption tank may be started at the same time as the equalization or after the end. (C)
In the process, the equalization and recovery of both tanks have been completed, and in this state, while continuing the introduction of the raw material gas into the first adsorption tank, a high-concentration product gas is supplied from the product gas storage tank to the first adsorption tank. Introduce. By this operation, the pressure of the first adsorption tank is increased without impairing the capacity of the adsorption tank, and in the next step (D),
Product gas can be generated stably. Also, the second
The vacuum desorption of the adsorption tank is further continued. In the step (D), the introduction of the raw material gas into the first adsorption tank is continued, and the product gas is generated stably and supplied to the product gas storage tank. Further, the decompression and desorption of the second adsorption tank is further continued. In the step (E), while continuing the state of the step (D), a part of the product gas is introduced into the second adsorption tank, and the partial pressure of the product gas is increased, so that the adsorbed specific gas is desorbed under reduced pressure. Facilitate.

As described above, according to the present invention, the product gas can be stably separated and generated by the PSA method using two adsorption tanks. Moreover, in the recovery step, while the introduction of the raw material gas into one of the adsorption tanks is stopped, the residual gas is recovered from the other adsorption tank to the one adsorption tank, so that a large pressure difference is used. Can be collected. Therefore, the recovery efficiency in the recovery step is good, and the product gas can be efficiently separated and generated from the raw material gas with a smaller amount of adsorbent and less power. Further, the vacuum desorption / exhaust of both adsorption tanks is not paused, the power is not wasted for the vacuum desorption / exhaustion, and the efficiency of the vacuum desorption / exhaust means (blower, etc.) is reduced. Absent. The present invention is mainly used for separating and generating oxygen gas from air, but can also be used for separating and generating more useful component gas than mixed gas.

[0010]

Next, an embodiment of the present invention will be described in detail with reference to the drawings.

FIG. 1 shows a mixed gas separation apparatus used in the mixed gas separation method of the present invention. In the drawing, reference numeral 1 denotes a raw air blower which takes in raw air (atmospheric air) from the outside, compresses the raw air, and sends it to a raw air intake pipe 11. Reference numerals 3 and 4 denote a pair of left and right adsorption tanks having the same structure. Each of the adsorption tanks 3 and 4 has a lower alumina layer 5 filled with an adsorbent for dehumidification (activated alumina).
And an upper adsorbent layer 6 (placed on the lower alumina layer 5) filled with an adsorbent (zeolite) for nitrogen adsorption are housed in a vertically stacked manner. Reference numeral 7 denotes a receiver tank (product oxygen gas storage tank).
The product oxygen gas produced in the above is stored. Reference numeral 8 denotes a vacuum pump, which evacuates the inside of both adsorption tanks 3 and 4 under reduced pressure.

Reference numeral 12 denotes a first introduction pipe having an automatic opening / closing valve 12a for connecting the raw material air intake pipe 11 and an entrance pipe 3c (extending from the entrance end 3a) of the left adsorption tank 3.
Of the raw material air intake pipe 11 and the right adsorption tank 4 (the inlet end 4a
Automatic opening / closing valve 1 for connecting an inlet pipe 4c)
It is a 2nd introduction pipe with 3a. Reference numeral 14 denotes a first exhaust pipe with an automatic opening / closing valve 14a for connecting the inlet pipe 3c of the left adsorption tank 3 and the inlet pipe 8a of the vacuum pump 8;
Is a second exhaust pipe with an automatic opening / closing valve 15a connecting the inlet pipe 4c of the right adsorption tank 4 and the inlet pipe 8a of the vacuum pump 8. In the drawing, reference numeral 22 denotes a return pipe with an automatic opening / closing valve 22a for connecting the upstream portion and the downstream portion of the original air blower 1.

Reference numeral 16 denotes a first outlet pipe with an automatic opening / closing valve 16a for connecting an outlet pipe 3d (extending from the outlet end 3b) of the left adsorption tank 3 and an inlet pipe 7a of the receiver tank 7, and 17 denotes a right adsorption tank 4 (Extends from the exit end 4b)
Outlet pipe 4d and inlet pipe 7a of receiver tank 7
And a second lead-out pipe with an automatic opening / closing valve 17a. Reference numeral 18 denotes a first connection pipe having an automatic opening / closing valve 18a and a manual flow control valve 18b for connecting an intermediate portion of the outlet pipe 3d of the left adsorption tank 3 and an intermediate portion of the exit pipe 4d of the right adsorption tank 4, and 19 denotes a left connection pipe. This is a second connection pipe with an automatic opening / closing valve 19a and a manual flow control valve 19b for connecting the tip of the outlet pipe 3d of the adsorption tank 3 and the tip of the outlet pipe 4b of the right adsorption tank 4. Reference numeral 20 denotes an automatic opening / closing valve provided on the inlet pipe 7a of the receiver tank 7, and the upstream side portion and the downstream side portion of the automatic opening / closing valve 20 are connected by a bypass pipe 21 with a manual flow control valve 21a. The flow rate of the manual flow control valve 21a of the bypass pipe 21 is controlled by the automatic on-off valve 2.
The flow rate is set smaller than the flow rate setting of 0.

Using the above mixed gas separation apparatus, oxygen gas and nitrogen gas can be separated from the raw air in the following manner. That is, in the first step (see FIG. 2),
The automatic opening / closing valves 12a, 15a, 16a, 20 are opened, and the automatic opening / closing valves 13a, 14a, 17a, 18a, 19a, 2
2a is closed. In this state, the raw air taken in by the raw air blower 1 is compressed and sent out to the raw air intake pipe 11, and supplied to the left adsorption tank 3 from the inlet end 3a via the first inlet pipe 12 and the inlet pipe 3c. In the left adsorption tank 3, the supplied raw air (compressed air) is first passed through the lower alumina layer 5, and the adsorbent of the lower alumina layer 5 adsorbs and removes moisture, carbon dioxide, and the like in the raw air. Then, the mixture is passed through the upper adsorbent layer 6 to mainly adsorb nitrogen in the compressed air with the adsorbent of the upper adsorbent layer 6, and then remove oxygen not adsorbed by the lower alumina layer 5 and the upper adsorbent layer 6. It is extracted from the outlet end 3b as product oxygen gas (purity of about 93%) (adsorption separation step). The product oxygen gas extracted from the outlet end 3b is supplied to the outlet pipe 3d and the first outlet pipe 1
6, supply to the receiver tank 7 via the inlet pipe 7a. On the other hand, the inside of the right adsorption tank 4 is evacuated to a reduced pressure by the vacuum pump 8 through the inlet pipe 4c, the second exhaust pipe 15, and the inlet pipe 8a, and the water adsorbed by the adsorbent of the lower alumina layer 5 is removed. , Carbon dioxide and the like, and nitrogen and the like adsorbed on the adsorbent of the upper adsorbent layer 6 are desorbed (reduced pressure regeneration step).

In the second step (see FIG. 3), the above-mentioned adsorption separation step is continued in the left adsorption tank 3. On the other hand, in the right adsorption tank 4, the automatic opening / closing valve 19a is opened at the final stage of the above-mentioned decompression regeneration step, and a part of the product oxygen gas passing through the outlet pipe 3d is supplied to the second connecting pipe 19 and the outlet pipe 4d.
To the right adsorption tank 4 from the outlet end 4b. By supplying the product oxygen gas, the desorption of nitrogen from the adsorbent of the upper adsorbent layer 6 is promoted, and the regeneration efficiency is improved (product purging step).

In the third step (see FIG. 4), the automatic on-off valve 1
4a, 18a are opened, and the automatic on-off valves 12a, 15a, 1
6a and 19a are closed, and the negative pressure (vacuum pressure) of the right adsorption tank 4 is used to open the left adsorption tank 3 (the above-mentioned adsorption separation step is completed).
The gas having a relatively high oxygen purity (oxygen purity: about 21 to 93%) remaining at the top of the column is passed through the first connecting pipe 18 (the above-described reduced pressure regeneration step has been completed, and the right adsorption tank 4
Is not exhausted by the vacuum pump 8).
From the outlet pipe 4d (first half of the recovery process). On the other hand, the inside of the left adsorption tank 3 is evacuated and reduced by the vacuum pump 8 through the inlet pipe 3c, the first exhaust pipe 14, and the inlet pipe 8a. Therefore, the automatic on-off valve 22a is opened, and the original air blower 1 for the left adsorption tank 3 is opened.
Of supply of raw material air from is stopped.

In the fourth step (see FIG. 5), the automatic on-off valve 1
3a is opened, the automatic on-off valve 22a is closed, and the raw air taken in by the raw air blower 1 is supplied to the right adsorption tank 4 from the inlet pipe 4c. At this time, the outlet end 3b of the left adsorption tank 3
, The residual gas is continuously supplied to the outlet end 4b of the right adsorption tank 4 (the latter half of the recovery process).

In the fifth step (see FIG. 6), the automatic on-off valve 1
8a is closed, and the supply of the residual gas from the left adsorption tank 3 to the right adsorption tank 4 is terminated. At this point, the inside of the right adsorption tank 4 is still under a negative pressure, and in order to restore the pressure to near atmospheric pressure, the automatic opening and closing valve 17a is opened, the automatic opening and closing valve 20 is closed, and the receiver is closed. The product oxygen gas in the tank 7 is supplied to the inlet pipe 7a, the bypass pipe 21, the second outlet pipe 1
7. Supply to the right adsorption tank 4 via the outlet pipe 4d.
At this time, the raw air taken in by the raw air blower 1 is continuously supplied from the inlet end 4a of the right adsorption tank 4 (pressure recovery step).

In the sixth step (see FIG. 7), the automatic on-off valve 2
0 is opened. That is, as a whole, the automatic on-off valve 1
3a, 14a, 17a and 20 are opened, and the automatic on-off valve 12 is opened.
a, 15a, 16a, 18a, 19a and 22a are closed. In this state, the compressed air sent from the raw air blower 1 is supplied to the right adsorption tank 4 from the inlet end 4a via the raw material air intake pipe 11 and the second introduction pipe 13, and product oxygen gas is extracted from the outlet end 4b. This sixth step is a step corresponding to the above-mentioned first step, in which the operations of both adsorption tanks 3 and 4 are interchanged. And, even after the sixth step, the second to second steps
A step similar to the fifth step (a step in which the operations of the two adsorption tanks 3 and 4 are switched in the second to fifth steps) is performed. In this way, the first to fifth steps are repeated to separate oxygen gas and nitrogen gas from the raw material air.

As described above, in this embodiment, the product oxygen gas can be separated and generated stably at low cost by the PSA method using the two adsorption tanks 3 and 4. Moreover, the product oxygen gas can be efficiently separated and generated from the raw material air with high recovery efficiency, a smaller amount of adsorbent and less power. Furthermore, the vacuum pump 8 is not stopped, and power is not wasted. Also,
By sufficiently drawing out and utilizing the capacity of the adsorbent, a target component gas having an effective concentration and a high concentration can be separated and generated from the mixed gas.

FIG. 8 shows another embodiment of the present invention. In this embodiment, in the mixed gas separation device of FIG. 1, a branch pipe 25 with an automatic opening / closing valve 25a branches from an upstream side of the automatic opening / closing valve 13a of the second introduction pipe 13, and is opened to the atmosphere. In this embodiment, in the fourth and fifth steps, the automatic on-off valve 25a
Is opened, atmospheric air is allowed to flow naturally into the branch pipe 25 by utilizing the negative pressure (vacuum pressure) in the right adsorption tank 4, and then the air flows right from the inlet end 4 a via the second introduction pipe 13. It is introduced into the adsorption tank 4 (FIGS. 9 and 10).
reference). Other parts are the same as those of the embodiment shown in FIG. 1, and the same parts are denoted by the same reference numerals. (That is, steps other than the fourth step and the fifth step are the same as the steps shown in FIGS. 2 to 4 and FIG. 7)

This embodiment has the same operation and effect as the embodiment shown in FIG. Moreover, in this embodiment, in the fourth step and the fifth step, the original air blower 1 is used.
When the raw material air is supplied to the right adsorption tank 4 by the above method, the atmospheric air is also supplied simultaneously (without passing through the original air blower 1) by the negative pressure (vacuum pressure) in the right adsorption tank 4, so that the original air Blower 1
Capacity can be reduced. Therefore, when the original air blower 1 having the same capacity as the conventional one is used, the production efficiency of the product oxygen gas is improved.

In the embodiment shown in FIG. 8, the automatic opening / closing valve 25a of the branch pipe 25 may be opened and closed only in one of the fourth step and the fifth step.

The separation of the mixed gas to which the present invention is applied includes, for example, separation of oxygen gas from air or specific effective gas (for example, hydrogen, carbon monoxide, Concentration and recovery of any effective gas such as hydrocarbons, or purification of a gas containing a toxic gas. Examples of the adsorbent used in the present invention include granules such as zeolite, silica gel, activated alumina, and activated carbon, and they are used alone or in combination. For example, zeolite is used as a nitrogen adsorbent, carbon is used as an oxygen adsorbent, zeolite is used as a carbon dioxide adsorbent, and the like. Silica gel and activated alumina are preferably used for dehumidification, and activated carbon or the like is used for adsorption of hydrocarbons in the air.

[0025]

As described above, according to the mixed gas separation method of the present invention, the PSA method using two adsorption tanks can be used.
Product gas can be separated and generated stably. Moreover, in the recovery step, while the introduction of the raw material gas into one of the adsorption tanks is stopped, the residual gas is recovered from the other adsorption tank to the one adsorption tank, so that a large pressure difference is used. Can be collected. Therefore, the recovery efficiency in the recovery step is good, and the product gas can be efficiently separated and generated from the raw material gas with a smaller amount of adsorbent and less power. Further, the vacuum desorption / exhaust of both adsorption tanks is not paused, the power is not wasted for the vacuum desorption / exhaustion, and the efficiency of the vacuum desorption / exhaust means (blower, etc.) is reduced. Absent. The present invention is mainly used for separating and generating oxygen gas from air, but can also be used for separating and generating more useful component gas than mixed gas.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a mixed gas separation device used in the present invention.

FIG. 2 is an explanatory diagram showing the operation of the mixed gas separation device.

FIG. 3 is an explanatory diagram showing an operation of the mixed gas separation device.

FIG. 4 is an explanatory diagram showing the operation of the mixed gas separation device.

FIG. 5 is an explanatory diagram showing the operation of the mixed gas separation device.

FIG. 6 is an explanatory view showing the operation of the mixed gas separation device.

FIG. 7 is an explanatory view showing the operation of the mixed gas separation device.

FIG. 8 is a configuration diagram showing another embodiment of the mixed gas separation device.

FIG. 9 is an explanatory diagram showing the operation of the other embodiment.

FIG. 10 is an explanatory diagram showing the operation of the other embodiment.

FIG. 11 is an explanatory diagram showing the operation of a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Original air blower 3 Left adsorption tank 4 Right adsorption tank 7 Receiver tank 10 Vacuum pump

 ────────────────────────────────────────────────── ─── Continuing from the front page (72) Nobuyuki Oyagi, Inventor 2-6-6 Chikushinmachi, Sakai-shi, Osaka Daido Hokusan Co., Ltd. Sakai Plant

Claims (1)

[Claims] 1. A first and a second adsorption tank filled with an adsorbent for selectively adsorbing a specific gas and a product gas storage tank are provided, and the following five steps (A) to (E) are operated in this order. After that, the first adsorption tank and the second adsorption tank are reversed, and the following five steps (A) to (E) are operated again in this order.
A mixed gas separation method characterized by repeating the steps. (A) The gas remaining in the second adsorption tank is recovered in the first adsorption tank through communication between the gas outlet of the first adsorption tank that has been decompressed and exhausted and the gas outlet of the second adsorption tank that has been adsorbed. (2) a step of depressurizing and desorbing the specific gas adsorbed by the adsorbent of the second adsorption tank from the gas inlet of the adsorption tank and exhausting the gas. (B) a step of introducing a raw material gas into the gas inlet of the first adsorption tank where the recovery of the residual gas is continued, and continuing the decompression / desorption exhaust in the second adsorption tank; (C) A step in which the product gas in the product gas storage tank is introduced into the gas outlet of the first adsorption tank where the recovery of the residual gas is completed and the introduction of the source gas is continued, and the desorption / desorption exhaust in the second adsorption tank is continued. (D) The specific gas in the raw material gas is adsorbed by the adsorbent in the first adsorption tank in which the introduction of the product gas is completed and the introduction of the raw material gas is continued, and a gas not adsorbed by the adsorbent is generated from the gas outlet as a product gas. And introducing the product gas into the product gas storage tank and continuing the decompression and desorption in the second adsorption tank. (E) A part of the product gas generated from the gas outlet of the first adsorption tank, which continues the introduction of the raw material gas and the generation of the product gas, is introduced into the gas outlet of the second adsorption tank, and desorbed and decompressed in the second adsorption tank. The process of continuing exhaust.