JPH10216453A - Separation of gas - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase regenerating efficiency of an adsorbent and to improve product yield by providing at least two adsorption columns with the adsorbent packed in a form like column and introducing a part of a product gas obtained at one adsorption tower and from which unnecessary gas components in a gaseous mixture are removed to the other adsorption tower during regeneration to subject to the regeneration. SOLUTION: At least two towers of the adsorption tower A and B in which the adsorbent capable of selectively adsorbing the unnecessary gas components in the gaseous mixture consisting of more than two gas components is packed in the form like column are prepared, and the gaseous mixture is introduced to one adsorption tower A under pressure with a pump 11 to adsorb the unnecessary gas components to the adsorbent, and desired gas components are discharged from a tower outlet as the product gas. During this operation, the adsorption tower B is vacuumized by an actuation of the pump 11, and a part of the product gas is supplied to a counterflow direction as a purge gas for regeneration of the adsorption tower B in a vacuum state to desorb (purge) the unnecessary gas components remaining in the adsorbent to execute the regeneration of the adsorbent.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gas separation method, and more particularly, to pressure oscillations (fluctuations, oscillations, etc.) for separating a desired gas from a mixture of two or more gases.
Swing) Pressure Swing Adsorption (PS)
A) is a gas separation method using, for example, can efficiently produce oxygen using air as a raw material,
The present invention relates to a gas separation method that can provide an automatic gas separation device that is easy to handle and safe.

[0002]

2. Description of the Related Art For example, oxygen, which is an air separation product, is used in small batches or continuously in a limited space in a room or a building, such as for medical use, consumer use, laboratory use, and light industrial use. In order to meet these needs, there is currently only a supply means using a cylinder or a liquid container (liquid oxygen), which is inconvenient to handle and has problems in safety management.

In recent years, along with the miniaturization, sophistication, and diversification of various types of consumer equipment and production equipment, these equipment and equipment have been integrated or automatically integrated with the main equipment at any time or continuously. There is an increasing demand for various types of gas separators from small gas separators to large gas separators that can be used. For the demand of medium to large capacity oxygen, the configuration is simple and the installation space is small,
It is expected that a new type of oxygen production apparatus which can be operated safely and of course be manufactured at a lower cost than the prior art and which has a low running cost, as well as being safe.

[0004] Conventionally, a number of gas separation methods using a pressure vibration adsorption method (PSA method) for separating a desired gas from a mixture of two or more gases have been proposed (for example, see Japanese Patent Application Laid-Open No. Hei 3- No. 52615). The prior art will be described below.

FIG. 1 is a diagram showing a basic system A of a gas separation apparatus used for implementing the conventional method and the method of the present invention. 2 to 3 are diagrams showing modified examples of the basic system A used for implementing the conventional method and the method of the present invention. FIGS. 6A and 6B are valve sequence diagrams for implementing the related art.

In FIG. 1, (A) and (B) show an adsorption tower in which an adsorbent for selectively adsorbing unnecessary gas components is packed in a column. When oxygen is produced from air, moisture is dried. An adsorbent such as silica gel or activated alumina as an adsorbent is filled on the inlet end side of the adsorption tower, and MS-5A, MS-13X or the like as a nitrogen selective adsorbent is packed in layers thereon. 11 is a pump, 1 to 10 are automatic valves, and 14 and 15 are needle valves.

The separation operation will be described below with reference to an example in which oxygen is produced from air using the standard configuration system shown in FIG. 1 (note that the valve sequence is shown in FIGS. 6A and 6B). Focusing on the adsorption tower (A), it comprises the following six steps. Source gas pressurization process Product removal process Purge providing process Temporary holding process Decompression process Purge process

Source gas pressurizing process The source air is supplied from the automatic valve 10 and the pump 1 in the direction indicated by the arrow.
1. Pressurized and sent to the inlet end of the adsorption tower (A) via the automatic valve 1 [the inlet valve of the adsorption tower (A)]. At this time, the other automatic valves (2, 3, 4) around the adsorption tower (A) are in a closed state. The pressurized air first comes into contact with a moisture adsorbent (activated alumina) at the inlet end of the adsorption tower (A), and the moisture in the air is adsorbed and removed. Next, nitrogen in the air is adsorbed by the nitrogen selective adsorbent (MS-5A), and an adsorbed gas zone is formed in the adsorption layer. The composition of the gas phase portion in the column becomes gradually rich in nitrogen and becomes oxygen-rich toward the outlet end of the adsorption tower (A).

Product Removal Step When the pressure in the adsorption tower (A) reaches a predetermined operating pressure (maximum pressure), the automatic valve 1 is closed. During or immediately after pressurization of the adsorption tower (A), the automatic valve 2 is opened and product oxygen is collected, sent in the direction indicated by the arrow, and stored in a reservoir (not shown). At the same time as the pressurization of the adsorption tower (A) is stopped, the automatic valves 8 and 9 are opened, the automatic valve 10 is closed, and the pump 1
In 1, the operation is switched from pressurization of the adsorption tower (A) to depressurization and evacuation of the adsorption tower (B), and the exhaust is exhausted through the automatic valve 9 in the direction indicated by the arrow.

Purge providing step The automatic valve 3 (automatic valve 7) is a purge providing valve. Subsequent to the product removal process, the automatic valve 3 is opened for a certain short period of time, and a part of the product oxygen is supplied from the outlet end of the adsorption tower (A) in the direction of the arrow to the outlet end of the adsorption tower (B). Purging is performed in a counter-current direction. The purge amount of the adsorption tower (B) is adjusted by adjusting the opening time of the automatic valve 3 and the opening of the needle valve (14). In many cases, the needle valve (14) is unnecessary, and when the needle valve (14) is not provided, the purge flow rate can be adjusted by intermittently opening and closing the automatic valve 3 (FIG. 6).
(Indicated by a ₁ and a ₂ in (B)). Immediately after the purging step, the adsorption tower (B) is pressurized with product oxygen. This is performed by closing the automatic valve 8 for a fixed short period of time while keeping the automatic valve 3 open (FIG. 6 (A),
(Indicated by b in (B)).

Temporary holding step After a series of operations of the automatic valve 3 for the purge supply step and the subsequent product oxygen pressurization, the valves (1, 2,...) Around the adsorption tower (A) are operated.
3 and 4) are all closed for a certain period of time, and the pressure in the adsorption tower (A) is kept constant (during this time, the “raw material pressurizing step” of the adsorption tower (B) is performed).

Depressurization Step The automatic valves 4 and 9 of the adsorption tower (A) are opened (the automatic valve 10 is closed), the adsorption tower (A) is depressurized and evacuated in the countercurrent direction by the pump 11, and the exhaust gas is exhausted. The gas is exhausted through the automatic valve 9 in the direction indicated by the arrow.

Purge Step At the end of the depressurization of the adsorption tower (A), the automatic purge valve 7 of the adsorption tower (B) is opened, and a part of the product oxygen is discharged from the outlet end of the adsorption tower (B) in the pressurizing process. It is supplied into the adsorption tower (A) from the outlet end of the adsorption tower (A) in the direction of the arrow. The product oxygen supplied into the adsorption tower (A) is in a vacuum state.
Flows counter-currently through the reactor and the nitrogen (N
₂ ) The desorption is promoted, and the desorbed nitrogen (H ₂ O, N ₂ ) is released (purged) into the atmosphere together with the desorbed gas (H ₂ O, N ₂ ) via the automatic valve 4 → the pump 11 → the automatic valve 9.

Thus, the adsorption tower (A) returned to a usable state again (one cycle). While the adsorption tower (A) goes through the above-mentioned six steps, the adsorption tower (B) also has just one cycle.
The same six steps (1) to (4) are performed with a delay of / 2 cycle.

Either the adsorption tower (A) or the adsorption tower (B) is always in a pressurized state (a state in which the product can be sent out), and the product oxygen thus collected is sent to the consumption end via a reservoir (not shown). .

In the above prior art, during the "temporary holding step", the inside of the adsorption tower (A) (especially at the upper end)
Still a considerable amount of valuable gases (oxygen-rich components) remain.
Since this is released to the atmosphere via the automatic valve 4 → the pump 11 → the automatic valve 9 in the “decompression step”, there is a problem that the product is lost (the yield is reduced).

[0017]

In order to meet the various needs from small to large, as described above, it has a simple structure, is easy to manufacture, has low installation and utility costs, and has a low overall running cost. There is a need for a significantly improved oxygen production system. For this purpose, it is necessary to increase the productivity of the adsorbent represented by the following formula (1) and to increase the product yield represented by the following formula (2). Adsorbent productivity = product gas (liter) / kg-adsorbent (H) (1) That is, an object of the present invention is to separate a desired gas from a mixture of two or more gases by a pressure vibration adsorption method (PSA).
Method), which can improve both productivity (adsorbent productivity) and product yield by a system that is simple and can be miniaturized and an improved operation method. For example, it is an object of the present invention to provide a gas separation method capable of stably and efficiently producing high-purity oxygen from air as a raw material, and providing a safe and easy automatic gas separation apparatus.

[0018]

Therefore, the inventor of the present invention, as a pre-stage of the present invention, used the system shown in FIG. 1 as an experimental device and used a valve sequence shown in FIG. Preparative test). FIG. 8 shows the experimental results.

Fractionation (split sampling) test method and its results. That is, the apparatus shown in FIG. 1 is operated with the valve sequence shown in FIG. Was. At this time, the automatic valve 8
(Alternatively, the automatic valve 4), the composition change of the gas released from the apparatus through the pump 11 to the atmosphere was measured. Experimental conditions: 1 cycle = 16 seconds Raw material pressurization time (of FIG. 7) = 2.5 seconds Depressurization / purge time (+ of FIG. 7) = 5.5 seconds

The horizontal axis of FIG. 8 showing the experimental results is the amount (integrated value, unit: cc) of the outflow gas from the automatic discharge valve 8 (or the automatic valve 4) in one cycle, and the vertical axis is the oxygen in the outflow gas. Indicates the concentration. P indicates the opening point of the purge valve (automatic valve 3 or automatic valve 7). In FIG. 8, the automatic valve 8
(Or the automatic valve 4) is opened, and when the line where the oxygen concentration 21% line intersects the curve A perpendicularly to the curve A intersects the horizontal axis is B, OB is the first discharge in the depressurization step. It is assumed that the line is a gas portion (R-1), and a point where a line having an oxygen concentration of 21% intersects with the curve A perpendicularly to a point where the line intersects the horizontal axis is C
And the automatic valve 8 (or the automatic valve 4) is closed at D, and C
If -D is the final exhaust gas portion (R-2) of the pressure reduction step, it can be seen that the oxygen (valuable component) concentration in the exhaust gas between OB and CD is high.

Therefore, this valuable component R-1 and / or R
-2 is collected in the column again, that is, the valuable components flowing out of the adsorption tower (A) and the adsorption tower (B) are collected by the automatic valve 4 (or the automatic valve 8), the pump 11 and the automatic valve 5 (or the automatic valve 5). The recovery was carried out to the adsorption tower (B) [or the adsorption tower (A)] via the valve 1). However, when purging is not performed, it becomes as shown by the dotted line (E) in FIG.
₂ ) Desorption stops.

As a result of the above experiments, it was found that, in the case of pressure fluctuations from vacuum to higher than atmospheric pressure, the pressure fluctuation range was reduced to near atmospheric pressure to reduce abrupt pressure changes. By recycling the active components (gas rich in product gas) in the discarded gas to other towers, the product yield is improved, the product oxygen yield is greatly increased, and adsorption is achieved, compared to the conventional technology. The present inventors have found that the productivity of the agent is also improved, and have accomplished the present invention.

That is, the invention of claim 1 of the present invention provides
At least two adsorption towers (A and B) in which an adsorbent capable of selectively adsorbing unnecessary gas components in the gas mixture composed of the above gas components are packed in a column shape are prepared, and one of the adsorption towers (A and B) is prepared. About A) (1) The gas mixture is introduced under pressure from the inlet of the adsorption tower, and an unnecessary gas component is selectively adsorbed to the inlet end of the adsorbent to form an adsorbed gas zone, and the gas mixture is introduced. To increase the pressure in the tower while advancing the tip of the adsorption gas zone, and to stop the feed of the raw material at a predetermined pressure. Immediately after the end of the process, a desired gas component is taken out from the outlet of the adsorption tower at the end of the adsorption tower (A), and the product is collected as a product gas. (3) Following the above step, a part of the product gas is depressurized. Purge gas for regeneration of the adsorption tower (B) (4) Depressurizing step of depressurizing the adsorption tower (A) using a pump following the above step (5) Part of product gas collected in the product gas collecting step of the adsorption tower (B) Is introduced from the outlet end of the adsorption tower (A) in the countercurrent direction (the opposite direction to the raw material supply flow), and is circulated to desorb unnecessary components remaining in the adsorbent in the adsorption tower (A). A purge step of discharging the gas into the atmosphere from the inlet end of the tower (A).
Swing A (Pressure Swing A)
In the (desorption, PSA method) (−− = pressurization process, − = decompression process), the atmospheric release gas in the −decompression process is divided into the initial release gas (R-1), the final release gas (R-2), and others. R- containing many useful components
A gas separation method comprising recycling and recovering 1 and / or R-2 from one adsorption tower to another adsorption tower via a pump.

The concentration of the useful component in the gas released into the atmosphere by the above-mentioned depressurization step fluctuates over time. Since the initial decompressed gas (R-1) and the final decompressed gas (R-2) among them have a high useful component concentration, this decompressed gas is divided into R-1, R-2 and others, and R- By recycling and recovering 1 and / or R-2 from one adsorption tower to another adsorption tower via a pump, or into the system, loss of useful components can be reduced. Note that the concentration of the useful components of R-1 and R-2 is not strictly defined as being equal to or higher than the target component in the raw material gas, and the gases of R-1 and R-2 are generally regarded as effective components. It shows a rich split gas. For example, when the raw material gas is air, even if the oxygen is separated and the oxygen concentration becomes about 21% or less, the unused gas still contains a considerable amount of unused oxygen. In the present invention, these include cases where the recovery is widely measured as R-1 and R-2.

According to a second aspect of the present invention, there is provided the gas separation method according to the first aspect, wherein the gas separation operation is performed under the same specification.
It is characterized in that it is carried out by a system composed of one adsorption tower and one pump (for both pressurization and vacuuming).

According to a third aspect of the present invention, there is provided the gas separation method according to the first aspect, wherein the gas separation operation is performed under the same specifications.
It is characterized in that it is carried out by a system composed of the above adsorption tower and two kinds of pumps (one for pressurization and the other for vacuum).

According to a fourth aspect of the present invention, in the gas separation method according to any one of the first to third aspects, the gas flow rate of the R-1 and / or R-2 is adjusted by using an adsorption tower (A) -pump-adsorption. It is controlled by the opening time of the automatic valve on the gas supply line connecting the tower (B).

According to a fifth aspect of the present invention, in the gas separation method according to any one of the first to fourth aspects, the order of recycle of R-1 and R-2 is divided gas containing a large amount of useful components. Is delivered to the outlet end of the adsorption tower undergoing recycling, and the divided gas containing relatively little useful component is delivered to the inlet end of the adsorption tower undergoing recycling. The suction pressure of the recycling pump in the recycling operation is -0.5 kgG / cm < ² > (36
0 Torr) to +0.5 kgG / cm ² .

According to a sixth aspect of the present invention, there is provided the gas separation method according to the first aspect, wherein the adsorbent column has a structure in which two types of adsorbents are packed in layers, one of which is silica gel;
One is a desiccant such as activated alumina, and the other is a nitrogen selective adsorbent such as molecular sieve zeolite. The former is located at the inlet end (lower layer) of the adsorption tower, and the latter is the adsorption tower filled in the upper layer. Using the system according to claim 2 or claim 3 to separate oxygen using air as a raw material.

According to a seventh aspect of the present invention, the idling of the pumps is avoided by expressing the relationship between the compression capacities of the two types of pumps according to the third aspect by the following equation. A method according to claim 1, claim 3 to claim 6. Formula: Pvac = kPcom where Pvac indicates the compression capacity (liter / minute or m ³ / minute) of the vacuum pump near the atmospheric pressure.
com indicates the compression capacity (liter / min or m ³ / min) of the pressurizing pump near the atmospheric pressure, and k is 1 to 5
It is.

[0031]

[Action]

1) Operating pressure range is 150 Torr to +2.0 kgG / cm
² ) It is advantageous in terms of energy because it is set in the vicinity of the atmosphere and in the region where the pump performance can be exhibited most. 2) By using one pump for "pressurizing" and "evacuating" or one of the two pumps is "pressurizing"
The other is used for "vacuum quoting", which facilitates the alternating operation of pressurization and decompression, shortens cycle time, and increases adsorbent productivity. 3) The above pump is used not only for pressurization and evacuation but also for the recycling operation unique to the present invention, and to recover valuable components (oxygen when oxygen is produced) in the gas released to the atmosphere when depressurized. Thereby, the product yield can be improved. 4) That is: a) The adsorbent productivity was improved, so that the apparatus could be further downsized (reduction in apparatus cost). b) The unit power consumption (KWH / m ³ product gas) was reduced by improving the product yield. c) The total cost was reduced by a) and b).

[0032]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The method of the present invention is shown in FIGS.
This will be described in detail below with reference to FIG. FIG. 1 shows a system (basic system A) of a gas separation apparatus, which has already been described in the section of the prior art and is composed of two columns having the same specifications and one pump, which is suitable for implementing the present invention. 2 and 3
FIG. 1 shows a modified example of the basic system A shown in FIG. 1 (one pump). FIG. 4 shows another system (basic system B) of a gas separation apparatus which is composed of two columns and two pumps having the same specifications and is suitable for implementing the present invention. FIG.
A modified example of the basic system B shown in (2 pumps) is shown. 9 to 13 show a valve sequence (valve opening time to time relationship). FIG. 9 is a drawing showing a valve sequence of the basic system A shown in FIG. 1 (one pump). FIG.
FIG. 3 is a view showing a valve sequence of a modified example of the basic system A shown in FIG. 2 (one pump). FIG. 11 corresponds to FIG.
It is a drawing showing a valve sequence of another modification of the basic system A shown in FIG. FIG. 12 is a drawing showing a valve sequence of the basic system B shown in FIG. 4 (two pumps). FIG. 13 is a drawing showing a valve sequence of a modified example of the basic system B shown in FIG. 5 (two pumps).

(Embodiment 1) One embodiment of the method of the present invention for separating oxygen from air using the basic system A shown in FIG. 1 and the valve sequence shown in FIG. 9 will be described in detail. The separation operation by the adsorption tower (A) and the adsorption tower (B) in the basic system A shown in FIG. 1 is performed in the following ten steps (10) to (10). Time (sec) Raw material gas pressurization step (1.5) Recycle pressurization step (1.0) Product removal step from adsorption tower (B) to adsorption tower (A) (2.0) Purge providing step (1.5 ) Valuable gas recovery step (0.5) From adsorption tower (A) to adsorption tower (B) Temporary stop step (1.5) Recycling pressure reduction step (1.0) From adsorption tower (A) to adsorption tower (B) Decompression step (2.0) Purge step (1.5) (10) Valuable gas recovery step (0.5) From adsorption tower (B) to adsorption tower (A) The steps will be described below in the order of the steps.

Regarding the adsorption tower (A), the raw material gas pressurizing step 1.5 seconds The raw material air is supplied from the automatic valve 1
0, the pump 11 and the automatic valve 1 are fed under pressure to the inlet end of the adsorption tower (A) [at this time, the automatic valves 2, 3, and 4 attached to the adsorption tower (A) are closed]. Pressurized air first
Water at the inlet end of the adsorption tower (A) comes into contact with a water adsorbent (eg, activated alumina) to adsorb and remove water in the air. Then
Nitrogen in the air is adsorbed by the upper nitrogen selective adsorbent (MS-5A), and a nitrogen adsorption zone is formed in the adsorption layer. The nitrogen adsorption zone advances toward the outlet end of the adsorption tower (A) as the pressurized feeding is continued. The composition of the gas phase portion in the adsorption column becomes oxygen-rich as the amount of nitrogen gradually decreases from the air composition (oxygen = 21%) at the inlet end toward the outlet end.

Recycling pressurization step 1.0 seconds The automatic valve 10 is closed while the automatic valve 1 for supplying raw materials is opened, and the automatic valve 8 is opened to remove the residual valuable gas in the adsorption tower (B). ) -Automatic valve 8 -Pump 11 -Automatic valve 1 is sent to the adsorption tower (A) by recycling pressurization. The pressure in the adsorption tower (B) decreases, the pressure in the adsorption tower (A) increases,
Reach the maximum pressure of operation. When the above continuous operation is completed, the automatic valve 1 is closed and the automatic valve 9 is opened. The pressurization of the adsorption tower (A) is completed.
At reduced pressure.]

Product removal process 2.0 seconds Automatic valve 2 is opened during or immediately after pressurization of adsorption tower (A), and product oxygen is collected. Product oxygen is sent to the consumer end via a product reservoir (not shown) or directly.

Purge providing step 1.5 seconds The automatic valves 3 and 7 are valves for supplying a purge. The automatic valve 3 is opened for a certain short period of time following the step, and a part of the product oxygen is discharged from the outlet end of the adsorption tower (A) to the adsorption tower (B).
At the outlet end of the column, and the gas is purged by flowing in the column in the countercurrent direction. The purge amount to the adsorption tower (B) is adjusted by adjusting the opening time of the automatic valve 3 and the opening of the needle valve 14.

Valuable gas recovery step Immediately after the 0.5 second purge supply operation, the residual oxygen at the outlet end of the adsorption tower (A) is transferred toward the outlet end of the adsorption tower (B) by the differential pressure between the two towers. Recover valuable gas. This is performed by closing the automatic valve 8 for a fixed short period of time while keeping the automatic valve 3 open.

Temporary stop step 1.5 seconds After a series of operations in which the purge supply step and the valuable gas recovery step are continued (the automatic valve 3 is closed), the automatic valves (1, 2, 3,. 4) is closed for a certain period of time, and the pressure in the adsorption tower (A) is kept constant. [When the adsorption A tower is in operation, the pump 11 is operating and the raw material gas pressurizing step of the adsorption tower (B) is being performed. Automatic valve 1
0 and the automatic valve 5 are being opened. ]

When the operation of the recycle pressure reducing step 1.0 seconds is completed, the automatic valve 10 is closed, the automatic valves 4 and 5 are opened (the automatic valve 9 is closed), and the residual valuable gas in the adsorption tower (A) is automatically discharged. Valve 4-Pump 11 → Via automatic valve 5,
It is fed under pressure from the inlet end in the adsorption tower (B).

Following the 2.0-second pressure reduction step, the automatic valve 9 is opened (the automatic valve 4 is kept open through the two operations of the recycling pressure reduction step and the pressure reduction step), and the pressure reduction operation of the adsorption tower (A) is started. Done. The adsorption tower (A) is depressurized through the automatic valve 4-pump 11 → automatic valve 9-
It is evacuated.

Purge step 1.5 seconds At the end of depressurization of the adsorption tower (A), the automatic purge valve 7 of the adsorption tower (B) is opened, and the product is discharged from the outlet end of the adsorption tower (B) in the pressurizing process. Adsorption tower (A) where part of oxygen is in the process of decompression
Is supplied to the adsorption tower (A) from the outlet end of the column. The product oxygen supplied into the adsorption tower (A) flows countercurrently in the adsorption tower (A) to promote the desorption of nitrogen remaining in the adsorbent column, and the automatic valve 4 → the pump 11 → the automatic valve 9 After that, it is released (purged) into the atmosphere together with the desorbed nitrogen.

(10) Valuable gas recovery step Immediately after the operation for 0.5 seconds, the residual oxygen at the outlet end of the adsorption tower (B) is immediately discharged toward the outlet end of the adsorption tower (A) by the pressure difference between the two towers. Transfer and recover valuable gas. This is performed by closing the automatic valve 4 for a fixed short period of time while keeping the automatic valve 7 open. Thus, the adsorption tower (A) was returned to a usable state again through the one cycle process of (10).

In the adsorption tower (A), 10 of the above (10)
The same 10 steps are carried out in the adsorption tower (B) just one-half cycle later during one cycle of the step. Either the adsorption tower (A) or the adsorption tower (B) is always in a pressurized state (a state in which the product can be delivered), and product oxygen is collected every half cycle. The collected oxygen is usually kept at a constant pressure via a reservoir (not shown) and sent to the consumption end.

FIG. 9 shows the relationship (valve sequence) of the "opening time of each valve to time" in the one-cycle operation described above. 9, the vertical axis indicates the valve number of the automatic valve shown in FIG. 1, and the horizontal axis indicates time (second). The hatched portion indicates the open state of each automatic valve. In addition, (10) in FIG. 9 shows the process symbol in the above description.

(Embodiment 2) The two pumps shown in FIG.
Details of another embodiment of the method of the present invention for separating oxygen from air using a basic system B using columns [adsorption tower (A) and adsorption tower (B)] and a standard valve sequence shown in FIG. Will be described. Adsorption tower (A) in basic system B
The separation operation by the adsorption tower (B) is performed sequentially in the following 9 steps.

Time (sec) Source gas pressurization step (3.5) Product removal (or delivery) step (1.0) Purge supply step (0.5) Valuable gas recovery step (0.5) Adsorption tower (A) ) To adsorption tower (B) Recycle pressure reduction step (1.5) Pressure reduction step from adsorption tower (A) to adsorption tower (B) (3.0) Purge step (0.5) Valuable gas recovery step (0.5 ) From the adsorption tower (B) to the adsorption tower (A) Recycle pressurization step (1.5) From the adsorption tower (B) to the adsorption tower (A) Hereinafter, the steps will be described in order (see FIG. 12).

With respect to the adsorption tower (A), the raw material gas pressurizing step 3.5 seconds The raw material air passes through the pump 11a and the automatic valve 1 and flows into the adsorption tower (A).
Into the inlet end of the underpressure. The pressure in the adsorption tower (A) rises.

Product take-out (or delivery) step 1.0 second When the pressure in the adsorption tower (A) reaches a predetermined pressure, the automatic valve 2 is opened, and product oxygen is taken out from the end of the adsorption tower (A). .

Purge providing step 0.5 seconds Following the closing of the automatic valve 2 for product delivery, the automatic valve 3 for purge is opened for a short time, and a part of product oxygen is discharged from the outlet end of the adsorption tower (A). From the outlet end of the adsorption tower (B) in a vacuum state, it flows in the counterflow direction into the tower, and the adsorption tower (B) is purged.

Valuable gas recovery step 0.5 seconds Following the above operation, if the automatic valve 8 is closed for a short time while the automatic valve 3 is open (the automatic valve 4 is then opened), the outlet of the adsorption tower (A) The valuable gas at the end flows counter-currently from the outlet end of the adsorption tower (B) into the tower and is collected. During this short-time operation, the automatic valves 18 and 19 are kept open.

Recycling pressure reduction step 1.5 seconds In parallel with the above operation, the automatic valves 4 and 17 are opened, and valuable gas remaining in the adsorption tower (A) is discharged from the inlet end of the adsorption tower (A). From the inlet through the automatic valve 4-pump 11b-automatic valve 17 to the inlet end of the adsorption tower (B).
This operation ends when the automatic valve 17 is closed and the automatic valve 18 is opened.

Depressurization step 3.0 seconds This operation is started by opening the automatic valve 18. Unwanted gas in the adsorbent of the adsorption tower (A) is supplied to the automatic valve 4-pump 11
b-released to atmosphere via automatic valve 18;

Purge step 0.5 sec When the adsorption tower (A) is at the end of evacuation, the automatic valve 7 for purging of the adsorption tower (B) is opened for a short period of time and the outlet end of the adsorption tower (B) is opened. Part of the product oxygen flows from the outlet end of the adsorption tower (A) in the counterflow direction into the tower to promote desorption of the adsorbed nitrogen gas.

Valuable gas recovery step 0.5 seconds The automatic valve 4 is closed, the automatic valve 19 is opened, and the valuable gas in the adsorption tower (B) passes through the automatic valve 7 for purging the adsorption tower (B). It flows into A) in a countercurrent direction to the column and is collected.

Recycling pressurization step 1.5 seconds The automatic valves 8 and 16 are opened, and the residual gas in the adsorption tower (B) passes through the automatic valve 8 → the pump 11b → the automatic valve 1 and is discharged from the adsorption tower (A). It flows in from the entrance end. The adsorption tower (A) is pressurized and the adsorption tower (B) is depressurized.

As described above, for the adsorption tower (A), the same applies to the adsorption tower (B) while the steps (1) to (5) are performed.
Is performed.

FIG. 12 shows the relationship (valve sequence) between "opening time of each valve and time" in the one-cycle operation described above.
Shown in The hatched portion indicates the opening time of each automatic valve. In FIG. 12, “-” indicates the process number in the above description. In Example 2 (two pumps), as shown in FIG.
Every 1.5 cycles with pump 11a (for pressurization) for 1.5 seconds,
The pump 11b (for both vacuuming and recycling) generates an idle time of 0.5 seconds, which is not preferable in terms of energy. During the recycle operation, when the pump 11a is operated simultaneously with the pump 11b, the compression ratio is reduced within a short period of time.
The work required for gas supply varies greatly from 1 to 3 for 1a and from 1 to 10 for pump 11b, and the two greatly differ. If the two pump specifications are the same, the gas supply power of the pump 11a is far superior, and the recycle operation by the pump 11b is hindered.
Therefore, it is necessary to increase the supply capacity of the latter and make the capabilities of both the same. When the gas compression capacity (liter / minute or m ³ / minute) of the above two types of pumps near the atmospheric pressure is Pcom for the pressurizing pump and Pvac for the evacuation / recycling pump, respectively, Pvac = kPcom
(K ≒ 1-5). Generally, to maximize the overall efficiency of the separation operation, the valve sequence and the compression capacity of the two pumps are designed to be in harmony, while at the same time avoiding pump idling.

Next, modifications of the method of the present invention (modifications of the system configuration and its operation software) will be described below with reference to FIGS. 2, 3 to 5, 10, 11, and 13 to 17. I do. Although various modifications are conceivable, all that fall within the basic concept of the present invention belong to the scope of the present invention. FIG. 14 is a standard valve sequence diagram for performing the recovery operation of R-1 and R-2 using the basic system A of FIG. FIG.
FIG. 5 is a standard valve sequence diagram for performing a recovery operation of R-1 and R-2 using the basic system B of FIG.
FIG. 16 is a modification of the basic system B of FIG. FIG. 17 shows the relationship between R-1 and R using the system of FIG.
FIG. 4 is a standard valve sequence diagram for performing the recovery operation of FIG. The symbols (10) on each valve sequence diagram correspond to the process numbers in the description of each embodiment. That is, the numbers 1 to 10 for the 1-pump system, and the numbers 10 for the 2-pump system.

1) Combination of FIG. 2 (System Configuration) -FIG. 10 (Valve Sequence) FIG. 2 shows two equalizing valves (automatic valve 12, automatic valve 12) known in the basic system A (two towers, one pump) of FIG. An example in which an automatic valve 13) is added is shown.

2) Combination of FIG. 3 (System Configuration) -FIG. 11 (Valve Sequence) FIG. 3 shows the basic system A of FIG.
An example is shown in which an additional valve (automatic valve 12 ', automatic valve 13') is added. In this example, valuable gas is sent from the outlet end of one column to the inlet end of another column, which is a so-called "cocurrent recovery".

3) Combination of FIG. 5 (System Configuration) -FIG. 13 (Valve Sequence) FIG. 5 shows a basic system B (two towers, two pumps) (see FIG. 4) with two valuable gas recovery valves (automatic valve). 12 'and an automatic valve 13') are shown.

4) Combination of FIG. 1 (System Configuration) -FIG. 14 (Valve Sequence) or FIG. 4 (System Configuration) -FIG. 15 (Valve Sequence) This combination is a valuable gas (R-1) at the beginning of depressurization and an end of decompression. An example in which valuable gas (R-2) is recovered will be described.

5) Combination of FIG. 16 (System Configuration) -FIG. 17 (Valve Sequence) This combination shows an example of recovering valuable gas via a pump and an intermediate reservoir (RS).

6) Although the configuration and its valve sequence may be any of a number of small modifications other than those described above, they are included in the scope of the present invention as long as the basic separation concept is based on the present invention.

7) The present invention can be applied to any two columns of a PAS system having three or more columns. Further, the number of pumps can be increased to three or more. However, three towers, etc.
As the number of towers increases, it becomes easier to avoid idling of the pump, and the product yield improves, but the equipment configuration becomes complicated,
In some cases, there is a disadvantage of increased equipment cost,
In the present invention, the two-tower configuration is usually adopted as a standard system configuration in many cases, but it is preferable to design the system configuration in response to various needs.

Example 3 Using the apparatus shown in FIG. 1, oxygen was produced from air by the gas separation method of the present invention carried out in Example 1. Gas separation device configuration: Adsorption tower: Stainless steel cylinder 5.3 cm in diameter and 23 cm in length Adsorbent: MS-5A Filling amount: 247 g to adsorption tower (A), 25 to adsorption tower (B)
1 g (Activated alumina was filled up to 15% of the bed height at the inlet end of adsorption tower (A) and adsorption tower (B)) All valves were solenoid valves Pumps used both diaphragm type compression and vacuum evacuation Valve sequence implemented Are shown in Table 1.

[0068]

[Table 1]

As a result, 1.46% of oxygen having a purity of 90% was obtained.
(L / min). The production amount (yield) increased by 50% as compared with Comparative Example 1 described below.

Comparative Example 1 Using the same experimental apparatus as in Example 3, a gas separation test according to the prior art was performed to produce oxygen gas from air. The implemented valve sequence is shown in Table 2.

[0071]

[Table 2]

As a result, oxygen having a purity of 90.4% was reduced to 0.9%.
7 (l / min).

[0073]

According to the gas separation method of the present invention, it is possible to continuously and stably produce useful components from a gas mixture consisting of two or more gas components with a simple system, such as producing oxygen with higher purity than air. it can. Since the gas separation method of the present invention has high adsorbent productivity, the whole apparatus can be made small and compact. Therefore, the portable type, the desktop type, the indoor installation, and the installation in a limited area in the building can be realized. In the case of a large-capacity machine, the installation area can be small, and a large site is not required. Since the system using the gas separation method of the present invention has a simple configuration, the price of the apparatus can be reduced. Also, useful components such as oxygen can be supplied at low cost in combination with a high product yield. The gas separation method of the present invention has a low operating pressure, and the separation operation of all devices is automatically controlled by one valve sequence.
Therefore, the driving operation is only on-off by the button, and the driving security is simple and the handling is safe.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing a basic system (basic system A) of an apparatus used for performing a conventional method and a method of the present invention.

FIG. 2 is an explanatory diagram showing a modification of the basic system A.

FIG. 3 is an explanatory diagram showing another modification of the basic system A.

FIG. 4 is an explanatory diagram showing a basic system (basic system B) of an apparatus used to carry out the method of the present invention.

FIG. 5 is an explanatory diagram showing a modification of the basic system B.

FIGS. 6A and 6B are explanatory diagrams showing an operation state (valve sequence) of an automatic valve in one cycle for performing a conventional method using a basic system A. FIGS.

FIG. 7 is an explanatory diagram showing a valve sequence when an experiment according to the present invention is performed using the basic system A shown in FIG.

FIG. 8 is a (cured gas amount-oxygen concentration) relationship curve showing experimental results performed using the basic system A shown in FIG. 1 and the valve sequence shown in FIG.

FIG. 9 is an explanatory diagram showing a standard valve sequence for implementing the present invention using the basic system A shown in FIG.

FIG. 10 is an explanatory diagram showing a standard valve sequence for implementing the present invention using a modification of the basic system A shown in FIG. 2;

FIG. 11 is an explanatory diagram showing a standard valve sequence for implementing the present invention using another modification of the basic system A shown in FIG. 3;

12 is an explanatory view showing a standard valve sequence for implementing the present invention using the basic system B shown in FIG.

FIG. 13 is an explanatory diagram showing a standard valve sequence for implementing the present invention using a modification of the basic system B shown in FIG. 5;

14 is a diagram showing an example of R-1 using the basic system A shown in FIG.
FIG. 9 is an explanatory diagram showing a standard valve sequence for performing a recovery operation of R-2 and R-2.

15 is a diagram showing an example of R-1 using the basic system B shown in FIG.
FIG. 9 is an explanatory diagram showing a standard valve sequence for performing a recovery operation of R-2.

FIG. 16 is an explanatory diagram showing a modification of the basic system B shown in FIG.

FIG. 17 is an explanatory diagram showing a standard valve sequence for performing a recovery operation of R-1 and R-2 using a modification of the basic system B shown in FIG. 16;

[Explanation of symbols]

A, B adsorption towers 1 to 10, 12, 13, 12 ', 13', 16 to 19,
18a, 19a Automatic valve 11, 11a, 11b Pump 14, 15 Needle valve R-1 Valuable gas at the beginning of decompression R-2 Valuable gas at the end of decompression RS reservoir

Claims (7)

[Claims] 1. At least two adsorption columns (A and B) packed in a column with an adsorbent capable of selectively adsorbing unnecessary gas components in a gas mixture composed of two or more gas components.
Preparing one of the adsorption towers (A) (1) The gas mixture is pressurized and introduced from the inlet of the adsorption tower, and the unnecessary gas components are selectively adsorbed at the inlet end of the adsorbent, thereby adsorbing the gas mixture. And the introduction of the gas mixture is continued to increase the pressure in the column while advancing the tip of the adsorption gas zone, and to stop the feed of the raw material at a predetermined pressure. In the middle of the pressurizing step or immediately after the pressurizing step is completed, a desired gas component is taken out from the outlet of the adsorption tower at the end of the adsorption tower (A) and collected as a product gas. A purge providing step in which a part of the product gas is supplied as a purge gas for regeneration of the adsorption tower (B) in the pressure reducing step (4) a pressure reducing step in which the adsorption tower (A) is depressurized using a pump following the above step (5) In the product gas collection process of the adsorption tower (B) A part of the product gas to be collected is introduced from the outlet end of the adsorption tower (A) in the countercurrent direction (the direction opposite to the raw material supply flow) and circulated, so as to be introduced into the adsorbent in the adsorption tower (A). A purging step of desorbing the remaining unnecessary components and releasing it into the atmosphere from the inlet end of the adsorption tower (A). The two columns are alternately formed by reducing the time so that the purging step and the purging step proceed simultaneously. Above ~
Swing A (Pressure Swing A)
dsorption, PSA method), the atmospheric release gas in the decompression step is divided into an initial release gas (R-1), an end release gas (R-2), and others, and R-1 and / or R containing a large amount of useful components. -2 is recycled from one adsorption tower to another adsorption tower via a pump. 2. The gas separation operation according to claim 1, wherein the gas separation operation is performed by a system composed of two adsorption towers having the same specification and one pump (for both pressurization and vacuuming). Method. 3. The gas separation operation according to claim 1, which is performed by a system including two or more adsorption towers of the same specification and two pumps (one for pressurization and the other for vacuum). The method of claim 1, wherein: 4. The gas flow rate of said R-1 and / or R-2 is controlled by the opening time of an automatic valve on a gas supply line connecting the adsorption tower (A) -pump-adsorption tower (B). The method according to claim 1, wherein the method comprises: 5. The recycling sequence of R-1 and R-2 is such that the divided gas containing a large amount of useful components is delivered to the outlet end of the adsorption tower to be recycled, and the divided gas containing a relatively small amount of useful components is recycled. 5. The process according to claim 1, wherein the recycled gas is delivered to an inlet end of the adsorption tower which is recycled. 6. The adsorbent column according to claim 1, wherein the adsorbent column has a structure in which two kinds of adsorbents are packed in layers, one of which is a desiccant such as silica gel, activated alumina, and the other is a molecular sieve. A nitrogen selective adsorbent such as zeolite, wherein the former is at the inlet end (lower layer) of the adsorption tower, and the latter includes the adsorption tower filled in the upper layer thereof. The method according to claim 1, wherein oxygen is separated from air. 7. The pump according to claim 1, wherein the relationship between the compression capacities of the two pumps according to claim 3 is represented by the following equation so as to avoid idling of the pumps. Item 7. The method according to Item 6. Formula: Pvac = kPcom where Pvac indicates the compression capacity (liter / minute or m ³ / minute) of the vacuum pump near the atmospheric pressure.
com indicates the compression capacity (liter / min or m ³ / min) of the pressurizing pump near the atmospheric pressure, and k is 1 to 5
It is.