JPH10211412A - Method for separating mixed gas - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for separating a mixed gas which is capable of regulating a gas concentration gradient in an adsorption tower. SOLUTION: This method for separating a mixed gas comprises repeating the cycle of an adsorptive separation step, a vacuum regeneration step and a pressure restoration step in that order, in a pair of right/left adsorption towers 3, 4. A feedstock air is supplied to the right adsorption tower 4 which is already through with the vacuum regeneration step from the inlet end 4a of the tower 4, and a finished product oxygen gas is supplied from the outlet end 4b of the tower 4. Further, a residual gas contained in the left adsorption tower 3 which is already through with the adsorptive separation step is supplied to the right adsorption tower 4 from its intermediate part, and thereby the pressure restoration step is performed.

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, nitrogen,
Various methods have been used as a method for separating product gas such as oxygen, but recently, the separation method by the PSA method has been widely used because of the easiness of apparatus design and the low equipment cost. As such a separation method, Japanese Patent Laid-Open No.
A concentrated oxygen recovery method disclosed in JP-A-236914 has been proposed. This concentrated oxygen recovery method includes two adsorption tanks 30,
First, in step 1 (see FIG. 14), the mixed gas is pressurized by the blower 33 and the one adsorber tank 30 is used.
To adsorb and remove nitrogen gas to concentrate oxygen gas.
This concentrated oxygen gas is stored in the concentrated oxygen gas storage tank 32.
On the other hand, a vacuum pump 3
4 to desorb under reduced pressure to regenerate the adsorbent. Then process 2
In (see FIG. 15), at the end of the desorption step of the other adsorption tank 31, a part of the concentrated oxygen gas flows backward from the concentrated oxygen gas storage tank 32 to wash the other adsorption tank 31. Next, step 3
(See FIG. 16) In one of the adsorption tanks 30 where the adsorption has been completed.
A part of the residual oxygen gas in the inside is recovered to the outlet end of the other adsorption tank 31. At this time, the other adsorption tank 31 is still being desorbed by the vacuum pump 34. Next, step 4 (FIG. 17)
), The residual oxygen gas in one adsorption tank 30 is collected at the inlet end of the other adsorption tank 31. At the same time, a part of the concentrated oxygen gas is transferred from the concentrated oxygen gas storage tank 32 to the other adsorption tank 3.
1 to the outlet end. At this time, one adsorption tank 30
Then, vacuum desorption by the vacuum pump 34 is started from the inlet end. Next, in step 5 (see FIG. 18), the reverse flow of the concentrated oxygen gas is continued from the concentrated oxygen gas storage tank 32, and when the gas recovery from one adsorption tank 30 is completed, the other adsorption tank 3
A mixed gas is introduced into the inlet end of the first through a blower 33,
The pressure is increased in preparation for the adsorption step. These steps are repeated to collect the concentrated oxygen gas from the mixed gas.

[0003]

However, according to the above method, when the pressure of the other adsorption tank 31 (30) is restored, one of the adsorption tanks 30 (30) is placed above or below this adsorption tank 31 (30).
The residual oxygen gas of (31) must be introduced, and the concentration gradient of the oxygen gas in the other adsorption tank 31 (30) becomes uneven. For this reason, the performance of the adsorbent in each of the adsorption tanks 30 and 31 cannot be fully utilized, and the concentrated oxygen is reduced by increasing the amount of the adsorbent or reducing the regeneration pressure (increase the vacuum pump capacity). It is necessary to ensure gas purity and flow, which results in increased initial running costs of the device.

The present invention has been made in view of such circumstances, and has as its object to provide a mixed gas separation method capable of adjusting a gas concentration gradient in an adsorption tower.

[0005] In order to achieve the above object, the mixed gas separation method of the present invention comprises a plurality of adsorption towers, and each adsorption tower repeats an adsorption separation step, a decompression regeneration step, and a pressure recovery step in this order. In the mixed gas separation method so as to be performed, the raw material mixed gas is supplied from the inlet end to the adsorption tower after the reduced pressure regeneration step, and the product gas is supplied from the outlet end,
A configuration is adopted in which the pressure recovery step is performed by supplying the residual gas of another adsorption tower that has completed the adsorption separation step from the intermediate portion.

[0006] That is, the mixed gas separation method of the present invention comprises:
To the adsorption tower that has completed the decompression regeneration step, a raw material mixed gas is supplied from its inlet end, a product gas is supplied from its outlet end, and residual gas from another adsorption tower that has completed the adsorption separation step is supplied from its intermediate part. (This residual gas is a raw material mixed gas in the middle of the adsorption separation when the adsorption separation step is completed,
Relatively high purity. Particularly, the gas remaining in the vicinity of the outlet end has high purity. Therefore, when the residual gas is introduced, it is preferable to supply the residual gas from the outlet end of the other adsorption tower. Therefore, in the adsorbent in the adsorption tower after the pressure recovery step, a portion near the inlet end where the raw material mixed gas is supplied,
In the middle portion where the residual gas is supplied, and in the portion near the outlet end where the product gas is supplied, the gas concentration increases in that order, and the gas concentration becomes uniform (the gas concentration increases from the inlet end to the outlet end). Distribution. By adjusting the concentration gradient to such a state, the utilization efficiency of the adsorbent in the next adsorption separation step can be increased, and the adsorbent performance can be sufficiently exhibited. In addition, since the utilization efficiency of the adsorbent is improved, the amount of adsorbent to be charged can be reduced and the capacity of the vacuum pump can be reduced. As a result, the initial running cost of the apparatus can be reduced.

Further, in the present invention, the above-mentioned pressure recovery step includes
When dividing into a pre-process in which the supply of the product gas and the supply of the residual gas are simultaneously performed, and a post-process in which the supply of the raw material mixed gas and the supply of the product gas are simultaneously performed, the gas concentration gradient is surely adjusted. it can. In particular, the gas concentration near the outlet end can be reliably increased, and the utilization efficiency of the adsorbent can be further increased. In the present invention, when the supply of the raw material mixed gas, the supply of the product gas, and the supply of the residual gas are simultaneously performed in the pressure recovery step, the steps can be simplified.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, embodiments 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 numeral 2 denotes a cooler, which cools the raw material air passing through the raw material air intake pipe 11 and cools the raw material air to a predetermined temperature (20 to 40 ° C.) by the cooling heat of the cooling water passing therethrough. 3,4
Is a pair of left and right adsorption towers having the same structure. As shown in FIG. 2 (this FIG. 2 shows the internal structure of the left adsorption tower 3, the internal structure of the right adsorption tower 4 has the same structure) as shown in FIG. 2. Lower alumina layer 5 in which an adsorbent (activated alumina) for dehumidification is filled.
(Disposed below the adsorption towers 3 and 4) and an upper adsorbent layer 6 filled with an adsorbent (zeolite) for nitrogen adsorption (placed on the lower alumina layer 5, The upper surface of each of the adsorption towers 3 and 4 is accommodated in a vertically stacked manner. Both sides)
The gas inlet end 7a protrudes from one lateral side (the right side in the left adsorption tower 3 and the left side in the right adsorption tower 4), as well as a large number of discharge ports (not shown). The projecting position of the gas inlet end 7a substantially corresponds to the intermediate height position of each of the adsorption towers 3 and 4.)
Are arranged. Reference numeral 8 denotes a receiver tank (product oxygen gas storage tank) which stores the product oxygen gas produced in both adsorption towers 3 and 4. Reference numeral 9 denotes an oxygen blower which takes out product oxygen gas from the receiver tank 8, raises the temperature to a predetermined pressure, and supplies it to the demand side. Reference numeral 10 denotes a vacuum pump, which evacuates the insides of both adsorption towers 3 and 4 under reduced pressure.

Reference numeral 12 denotes a first equipped with an automatic opening / closing valve 12a for connecting the raw material air intake pipe 11 and the inlet end 3a of the left adsorption tower 3.
An introduction pipe 13 is a second introduction pipe with an automatic opening / closing valve 13a for connecting the raw material air intake pipe 11 and the inlet end 4a of the right adsorption tower 4. 14 is the inlet end 3 of the left adsorption tower 3
is a first exhaust pipe with an automatic opening / closing valve 14a connecting the inlet pipe 10a of the vacuum pump 10 with the inlet end 4a of the right adsorption tower 4 and the inlet pipe 10 of the vacuum pump 10.
and a second exhaust pipe with an automatic opening / closing valve 15a for connecting the first exhaust pipe to the second exhaust pipe. 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 an automatic on-off valve 1 for connecting the outlet end 3b of the left adsorption tower 3 and the inlet pipe 8a of the receiver tank 8.
Reference numeral 6 denotes a first pressure-reducing pipe with a reference numeral 17 denotes an outlet end 4b of the right adsorption tower 4 and an automatic opening / closing valve 16a of the first pressure-reducing pipe 16.
It is a second pressure recovery pipe with an automatic opening / closing valve 17a connecting the upstream side portion. Reference numeral 18 denotes a first outlet pipe with an automatic opening / closing valve 18a connecting the outlet end 3b of the left adsorption tower 3 and the inlet pipe 8a of the receiver tank 8, and 19 denotes a right adsorption tower 4
End 4b and the automatic opening / closing valve 18a of the first outlet pipe 18
It is a second outlet pipe with an automatic on-off valve 19a for connecting to a downstream portion. Reference numeral 20 denotes a first connection pipe having an automatic opening / closing valve 20a and a flow control valve 20b for connecting the outlet end 3b of the left adsorption tower 3 and the intermediate height portion (the gas inlet end 7a of the gas discharge section 7) of the right adsorption tower 4. And 21 is an intermediate height portion between the outlet end 4b of the right adsorption tower 4 and the left adsorption tower 3 (the gas inlet end 7 of the gas discharge section 7).
a) an automatic on-off valve 21a and a flow control valve 21b
Attached second connecting pipe. Each of the flow control valves 20b,
21b regulates a flow rate of a residual gas, which will be described later, passing through the connecting pipes 20, 21 to which the pipe 21b is attached. In the figure, reference numeral 23 denotes an automatic opening / closing valve provided at an upstream portion of the first condensing pipe 16 to the second condensing pipe 17.
The upstream side part and the downstream side part 3 are connected by a bypass pipe 24 with a manual control valve 24a. The manual control valve 24a is a valve for adjusting the flow rate of the product oxygen gas when purging the product with the product oxygen gas at the final stage of the pressure reduction regeneration process, and has an opening degree previously adjusted.
The automatic on-off valve 23 is a valve used when introducing product oxygen gas in the pressure recovery step. At this time, the product oxygen gas also flows through the manual control valve 24a.

Using the above mixed gas separation apparatus, oxygen gas and nitrogen gas can be separated from raw air in the following manner. That is, in the first step (see FIG. 3),
The automatic opening / closing valves 12a, 15a, 18a are opened, and the automatic opening / closing valves 13a, 14a, 16a, 17a, 19a, 20a,
The valves 21a, 22a and 23 are closed. In this state, the raw air taken in by the raw air blower 1 is compressed, sent out to the raw air intake pipe 11, introduced into the cooler 2, cooled down to a predetermined temperature, and then fed into the raw air intake pipe 11, the first introduction. The water is supplied to the left adsorption tower 3 from the inlet end 3a via the pipe 12. In the left adsorption tower 3, the supplied raw material 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 gas, and the like in the raw material air. After passing through the upper adsorbent layer 6, the upper adsorbent layer 6 mainly adsorbs nitrogen in the compressed air.
Oxygen not adsorbed by the lower alumina layer 5 and the upper adsorbent layer 6 is used as product oxygen gas (purity of about 93%) as the outlet end 3.
b) (adsorption separation step). Then, the product oxygen gas extracted from the outlet end 3b is passed through the first outlet pipe 1
8. Store in the receiver tank 8 via the inlet pipe 8a. On the other hand, in the right adsorption tower 4, the inside thereof is connected to the vacuum pump 10 through the second exhaust pipe 15 and the inlet pipe 10a.
To desorb water, carbon dioxide, etc. adsorbed by the adsorbent of the lower alumina layer 5 and nitrogen etc. adsorbed by the adsorbent of the upper adsorbent layer 6 (decompression step).

In the second step (see FIG. 4), the above-mentioned adsorption separation step is continued in the left adsorption tower 3. On the other hand, in the right adsorption tower 4, in the final stage of the above-mentioned decompression regeneration step, the automatic opening / closing valve 17a is opened, and a part of the product oxygen gas collected in the receiver tank 8 is supplied to the inlet pipe 8a and the first pressure reducing pipe. The water is supplied from the outlet end 4b to the right adsorption tower 4 via the bypass pipe 16, the bypass pipe 24, and the second pressure recovery pipe 17. 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. 5), the automatic on-off valve 1
4a, 20a and 23 are opened, and the automatic on-off valves 12a and 15 are opened.
The valves a and 18a are closed, and the gas having a relatively high oxygen purity (oxygen purity: about 21 to 93%) remaining at the top of the left adsorption tower 3 (where the above-mentioned adsorption / separation step has been completed) is taken as the first gas. Via the connecting pipe 20 (the above-mentioned reduced pressure regeneration step has been completed)
The gas is supplied to the gas discharge section 7 from the gas inlet end 7a (that is, the middle height of the right adsorption tower 4) as the recompressed gas of the right adsorption tower 4, and the upper adsorbent layer is supplied from a number of discharge ports of the gas discharge section 7. Send it into 6. At this time, the product oxygen gas in the receiver tank 8 is continuously supplied from the outlet end 4b of the right adsorption tower 4 (this product oxygen gas is also used as a decompression gas). In the third step, since the automatic on-off valve 23 is opened, a larger amount of product oxygen gas is supplied than in the second step.
Supplied to As described above, in the third step, the supply of the residual gas from the gas discharge unit 7 and the supply of the product oxygen gas from the outlet end 4b are performed simultaneously (the first half of the pressure recovery step). On the other hand, the inside of the left adsorption tower 3 is evacuated and evacuated by the vacuum pump 10 through the first exhaust pipe 14 and the inlet pipe 10a. Therefore, the automatic on-off valve 22a is opened,
The supply of raw air from the raw air blower 1 to the left adsorption tower 3 is stopped.

In the fourth step (see FIG. 6), the automatic on-off valve 2
The valve 0a is closed, and the supply of the residual gas from the left adsorption tower 3 to the gas discharge section 7 of the right adsorption tower 4 is terminated. At this point, the inside of the right adsorption tower 4 is still under a negative pressure, and in order to restore the pressure to near atmospheric pressure, the automatic opening and closing valve 13a is opened, the automatic opening and closing valve 22a is closed, and the original pressure is reduced. Raw air taken in by the empty blower 1 (via the cooler 2) is supplied to the right adsorption tower 4 from the inlet end 4a. At this time, the outlet end 4 of the right adsorption tower 4
From b, the product oxygen gas in the receiver tank 8 is continuously supplied. Thus, in the fourth step, the inlet end 4a
And the supply of the product oxygen gas from the outlet end 4b are performed simultaneously (the latter half of the pressure recovery step). When the fourth step is completed, the gas concentration distribution in the upper adsorbent layer 6 of the right adsorption tower 4 is as shown in FIG. That is, the upper part of the upper adsorbent layer 6 into which the product oxygen gas is sent has an oxygen concentration of about 93%, and the middle part of the upper adsorbent layer 6 into which the residual gas is sent from the left adsorption tower 3 has an oxygen concentration of about 21 to 93%. The lower portion of the upper adsorbent layer 6 into which the raw material air is sent has an oxygen concentration of about 21%.

In the fifth step (see FIG. 8), the automatic on-off valve 1
9a is opened and the automatic on-off valves 17a and 23 are closed. That is, as a whole, the automatic on-off valves 13a, 14a, 1
9a is opened and the automatic on-off valves 12a, 15a, 16a, 1
7a, 18a, 20a, 21a, 22a and 23 are closed. In this state, the compressed air sent from the raw air blower 1 is cooled to a predetermined temperature by the cooler 2 and then supplied to the right adsorption tower 4 from the inlet end 4a via the raw air intake pipe 11 and the second introduction pipe 13. Then, product oxygen gas is extracted from the outlet end 4b. This fifth step is a step corresponding to the above-mentioned first step, in which the operations of both adsorption towers 3 and 4 are interchanged. Then, in the fifth and subsequent steps, the second to fourth steps are also performed.
The same step as the step (the step in which the operations of the adsorption towers 3 and 4 are switched in the second to fourth steps) is performed. In this way, the first to fourth steps are repeated to separate oxygen gas and nitrogen gas from the raw material air. In the fifth step (that is, the first step), the upper adsorbent layer 6 in the adsorption towers 3 and 4 has the oxygen gas concentration gradient shown in FIG. Efficiency is improved.

As described above, in this embodiment, when the pressure reduction regeneration step of one adsorption tower 4 (3) ends and the adsorption separation step of the other adsorption tower 3 (4) ends, one of the adsorption towers 3 (4) ends. In order to restore the pressure in the adsorption tower 4 (3), the raw material air is supplied from the inlet end 4a (3a) of one of the adsorption towers 4 (3), and the product in the receiver tank 8 is supplied from the outlet end 4b (3b). Oxygen gas is supplied, and residual gas at the top of the other adsorption tower 3 (4) is supplied from the intermediate height part (that is, the gas discharge part 7). Therefore, the concentration gradient of the oxygen gas in the upper adsorbent layer 6 of one adsorption tower 4 (3) can be adjusted,
In the next adsorption / separation step, the utilization efficiency of the adsorbent in the upper adsorbent layer 6 can be increased, and the adsorbent performance can be sufficiently exhibited. In addition, by improving the utilization efficiency of the adsorbent, it is possible to reduce the amount of adsorbent and reduce the capacity of the vacuum pump, thereby reducing the initial running cost of the apparatus. . In addition, while the residual gas is being supplied from the other adsorption tower 3 (4) to the one adsorption tower 4 (3), the other adsorption tower 3 (4) is depressurized and exhausted. Can be shortened, and there is no need to perform a no-load operation of the vacuum pump 10, and the pressure reduction regeneration becomes efficient.

FIG. 9 shows another embodiment of the present invention. In this embodiment, in the third step, the automatic opening / closing valve 13a is opened and the automatic opening / closing valve 22a is closed,
Cooler 2 after taking in from outside with original sky blower 1
Is supplied from the inlet end 4a to the right adsorption tower 4 via the second introduction pipe 13. The 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, the steps other than the third step are the same as those of FIGS. 3, 4, 6, and 6). 8 is the same as the step shown in FIG. 8).

This embodiment has the same operation and effect as the embodiment shown in FIG. Moreover, in this embodiment, since the raw air is supplied to the right adsorption tower 4 by the raw air blower 1, the pressure of the right adsorption tower 4 is quickly restored in the third step. Therefore, the amount of product oxygen gas supplied from the receiver tank 8 to the right adsorption tower 4 decreases, and the amount of product oxygen gas that can be taken out of the receiver tank 8 by the oxygen blower 9 increases accordingly.

FIG. 10 shows still another embodiment of the present invention. In this embodiment, in the above-described third step, the automatic on-off valve 14a is closed, and the vacuum pump 10 is in the idle operation. The 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, the steps other than the third step are the same as those of FIGS. 3, 4, 6, and 6). 8 is the same as the step shown in FIG. 8).

This embodiment has the same operation and effect as the embodiment shown in FIG. Moreover, in this embodiment, since the vacuum pump 10 is stopped, almost all the residual gas at the top of the left adsorption tower 3 is introduced into the right adsorption tower 4 in the third step, and the oxygen gas concentration gradient Is performed reliably, and the efficiency of generating product oxygen gas is improved.

FIG. 11 shows still another embodiment of the present invention. In this embodiment, in the mixed gas separator of FIG. 1, the automatic opening / closing valve 13a of the second introduction pipe 13 is used.
A branch pipe 27 with an automatic opening / closing valve 27 a branches from the upstream portion and is connected to a filter 26. In this embodiment, in the above-described fourth step, the automatic on-off valve 27a is opened, and the negative air in the right adsorption tower 4 is used to separate the atmospheric air purified by the filter 26 into the branch pipe 27.
, And is introduced into the right adsorption tower 4 from the inlet end 4a via the second introduction pipe 13 (see FIG. 12). 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 are described in FIGS. 3 to 5.
(Same as the process shown in FIG. 8)

This embodiment has the same operation and effect as the embodiment shown in FIG. In addition, in this embodiment, when the raw air is supplied to the right adsorption tower 4 by the raw air blower 1 in the fourth step, the atmospheric air is also released by the negative pressure in the right adsorption tower 4 (the raw air blower 1 is removed). Since they are supplied simultaneously (without passing through), the capacity of the original air blower 1 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.

FIG. 13 shows a modification of the adsorption towers 3 and 4. In this modification, the upper adsorbent layers 6 of both adsorption towers 3 and 4 are
The gas discharge unit 7 disposed at the top has a large number of discharge ports (not shown) opened on the upper side and four lateral sides, but not on the lower side. The other parts are the same as those of the adsorption tower 3 shown in FIG. 2, and the same parts are denoted by the same reference numerals. Further, as another modified example of the adsorption towers 3, 4, a large number of discharge ports may be opened on the lower side and four lateral sides of the gas discharge section 7, and the discharge ports may not be opened on the upper side. The same operation and effect as those of the above-described embodiments can be obtained by using both of these modified examples.

In each of the above embodiments, the position where the gas discharge section 7 is disposed on the upper adsorbent layer 6 is not limited to the center of the upper adsorbent layer 6 in the height direction. The position may be closer to the upper side or slightly lower. Further, in the mixed gas separation device shown in FIG. 11, the third step may be replaced with the step shown in FIG. 9 or FIG.

The separation of the mixed gas targeted by the present invention includes, for example, separation of oxygen gas from air or specific effective gas (for example, hydrogen, carbon monoxide) from mixed gas during industrial gas production. , Hydrocarbons, etc.), and purification of gas containing 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.

[0027]

As described above, according to the mixed gas separation method of the present invention, in the adsorbent in the adsorption tower after the pressure recovery step, the portion near the inlet end where the raw material mixed gas is supplied and the residual gas are removed. The gas concentration becomes higher and uniform (the gas concentration becomes higher from the inlet end to the outlet end) in that order in the portion near the supplied intermediate portion and the portion near the outlet end where the product gas is supplied.
It becomes a gas concentration distribution. By adjusting the concentration gradient to such a state, the utilization efficiency of the adsorbent in the next adsorption separation step can be increased, and the adsorbent performance can be sufficiently exhibited. In addition, since the utilization efficiency of the adsorbent is improved, the amount of adsorbent to be charged can be reduced and the capacity of the vacuum pump can be reduced. As a result, the initial running cost of the apparatus can be reduced. Further, in the present invention, when the pressure recovery step is divided into a pre-process in which the supply of the product gas and the supply of the residual gas are simultaneously performed, and a post-process in which the supply of the raw material mixed gas and the supply of the product gas are simultaneously performed. Can reliably adjust the gas concentration gradient. In particular, the gas concentration near the outlet end can be reliably increased, and the utilization efficiency of the adsorbent can be further increased. In the present invention, in the pressure recovery step,
When the supply of the raw material mixed gas, the supply of the product gas, and the supply of the residual gas are performed at the same time, the process can be simplified.

[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 of the inside of an adsorption tower used in 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 diagram of a gas concentration distribution of an upper adsorbent layer.

FIG. 8 is an explanatory view showing the operation of the mixed gas separation device.

FIG. 9 is a process chart showing another embodiment of the mixed gas separation device.

FIG. 10 is a process chart showing still another embodiment of the mixed gas separation device.

FIG. 11 is a configuration diagram showing still another embodiment of the mixed gas separation device.

FIG. 12 is a process chart of the still another embodiment.

FIG. 13 is an explanatory view showing a modification of the adsorption tower.

FIG. 14 is an explanatory diagram showing the operation of a conventional example.

FIG. 15 is an explanatory diagram showing the operation of a conventional example.

FIG. 16 is an explanatory diagram showing the operation of a conventional example.

FIG. 17 is an explanatory view showing the operation of the conventional example.

FIG. 18 is an explanatory diagram showing the operation of a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Original air blower 3, 4 Adsorption tower 4a Inlet end 4b Outlet end 8 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 (3)

[Claims] 1. A mixed gas separation method comprising a plurality of adsorption towers, each of which repeatedly performs an adsorption separation step, a decompression regeneration step, and a pressure recovery step in this order. The mixed gas is supplied from the inlet end of the adsorption tower, the product gas is supplied from the outlet end, and the residual gas of the other adsorption tower that has completed the adsorption / separation step is supplied from an intermediate portion thereof. A mixed gas separation method, wherein a pressure recovery step is performed. 2. The pressure recovery step is divided into a pre-process in which the supply of the product gas and the supply of the residual gas are simultaneously performed, and a post-process in which the supply of the raw material mixed gas and the supply of the product gas are simultaneously performed. The method for separating a mixed gas according to claim 1. 3. The mixed gas separation method according to claim 1, wherein in the pressure recovery step, the supply of the raw material mixed gas, the supply of the product gas, and the supply of the residual gas are performed simultaneously.