JPS6238281B2 - - Google Patents

Description

Detailed Description of the Invention The present invention uses a mixed gas mainly containing nitrogen and oxygen, such as air, as a raw material, and passes the raw material through an adsorbent that selectively adsorbs nitrogen, thereby selectively adsorbing mainly nitrogen components. It relates to a method of removing and enriching and concentrating oxygen components, and more specifically, an oxygen enrichment method using a pressure fluctuation adsorption method that aims to increase the oxygen concentration and improve the yield for a mixed gas feedstock consisting of oxygen and nitrogen. It is.

Generally, when concentrating a specific component in a mixed gas,
Multiple adsorption beds filled with adsorbents that selectively adsorb components other than specific components in a mixed gas are installed in parallel, and raw materials are supplied under pressure to each of these adsorption beds to remove specific components that are difficult to adsorb. Pressure fluctuation adsorption method (pressure fluctuation adsorption method) involves continuous operation by sequentially switching and repeating the adsorption process of concentrating and collecting, followed by the regeneration process such as depressurization, scavenging, vacuum evacuation, and repressurization.
Swing Adsorption (hereinafter referred to as PSA) is adopted.

When concentrating oxygen from a mixed gas of oxygen and nitrogen such as air using this method, synthetic or natural zeolite selectively adsorbs nitrogen at room temperature, so the zeolite is used as an adsorbent to fill an adsorption bed. However, when a mixed gas of oxygen and nitrogen, such as air, is introduced into the adsorption bed, nitrogen is adsorbed and removed, and oxygen, which is difficult to adsorb, is concentrated and enriched and led out from the adsorption bed. When the adsorption capacity of the adsorbent in the adsorption bed deteriorates, in order to regenerate the adsorbent, depressurization, scavenging or evacuation, and further pressurization and regeneration steps are performed. A plurality of adsorption beds are provided to continuously collect concentrated oxygen, and each bed is sequentially switched to the above-mentioned process for operation.

However, in the above-mentioned mixed gas separation and concentration using PSA, when regenerating the adsorbent that has adsorbed the easily adsorbed nitrogen component, it is difficult to sufficiently desorb the easily adsorbed nitrogen component from the adsorbent, and the easily adsorbed nitrogen component remains on the adsorbent. In the adsorption process carried out in the process, easily adsorbed nitrogen components cannot be sufficiently adsorbed and removed, and they are accompanied by oxygen, which is a difficult to adsorb component to be collected, resulting in a decrease in purity, making it particularly difficult to obtain highly pure components. . Therefore, a method has been proposed in which the adsorption bed is evacuated to atmospheric pressure during regeneration, but in this method, the interior of the adsorption bed is pressurized in the previous adsorption process prior to evacuation. The gas in the adsorption bed is released to reduce the pressure to atmospheric pressure. However, the gas released from this adsorption bed contains oxygen, which is a component that is difficult to adsorb and is effective as a product that remains in the space of the adsorption bed during the adsorption process.Therefore, it is difficult to release this into the atmosphere immediately because of the yield. undesirable. For this reason, when regenerating the adsorption bed by evacuation after the adsorption process, the gas to reduce the pressure of the adsorption bed to atmospheric pressure prior to evacuation is not immediately released into the atmosphere, but instead a separate adsorption bed is used. Attempts are being made to introduce it and use it effectively.

On the other hand, during regeneration, it is difficult to immediately supply raw materials to the adsorption bed after it has been evacuated and raise the pressure to a pressurized state in the next adsorption process, because the pressure difference between vacuum and pressurization is large. The rapid flow of the raw material into the gas stream reduces the adsorption effect and reduces the purity of the product oxygen-enriched gas, which not only reduces the yield of product oxygen with the desired purity, but also causes inconveniences such as wear of the adsorbent. Therefore, it is necessary to gradually increase the pressure to the adsorption pressure without immediately increasing the pressure to the adsorption pressure.

Based on the operational needs of the two adsorption beds described above, an operation has been proposed in which these two adsorption beds are related to each other so as to satisfy the necessary operating conditions for both. One method is to regenerate the adsorption bed that has completed the adsorption process, and to reduce the internal pressure of the bed from the adsorption process pressure to almost atmospheric pressure before evacuation. A separate adsorption bed containing a gas containing many components,
It is introduced into an adsorption bed that has already been evacuated for regeneration and is in a vacuum state, and is operated to equalize the pressure of both adsorption beds, so that the adsorption bed that is operated from the adsorption process to the evacuation process is gradually moved. One stage of depressurization,
Moreover, effective oxygen components in the released gas at this time are effectively recovered. On the other hand, there is a method in which the vacuum evacuation process has already been completed and the pressure of the adsorption bed, which is to be used in the next adsorption process, is gradually increased to form one stage. However, such conventional methods have the disadvantage that not only a sufficient yield cannot be obtained, but also the yield of product oxygen per unit adsorbent is low. That is, this is the first
Two conventionally used methods will be explained by illustrating them in the figure.

In the figure, a shows an adsorption bed in a pressurized state after completing the adsorption process, and b shows another adsorption bed in a vacuum state after the inside of the bed has been evacuated to regenerate the adsorbent. Mazu
In pressure equalization between both adsorption beds using method (i), the gas in the bed is led out in parallel flow to reduce the pressure in the bed from the pressurized adsorption bed a (generally when the adsorption process is finished). In the adsorption bed, nitrogen, which is an easily adsorbed component, is adsorbed in a high concentration at the raw material introduction end, and gradually becomes less adsorbed toward the end where oxygen, which is a difficult adsorbed component, is taken out.
Therefore, in order to recover oxygen that is useful as a product, it is preferable to conduct it in the same direction as the flow of the raw material, so-called parallel flow. ), the gas is placed in a separate vacuum bed b
is introduced in parallel flow direction to equalize the pressure on both beds. However, because the pressure difference between adsorption bed a in a pressurized state and adsorption bed b in a vacuum state is large, the gas flow flowing from adsorption bed a to adsorption bed b becomes much faster.As a result, in adsorption bed a, the adsorbent A large amount of the nitrogen component adsorbed in the adsorbent is desorbed, and oxygen, which is effective as a product existing in the space, is extracted and carried into the adsorption bed b. On the other hand, in adsorption bed b, as a result of the introduction of oxygen-enriched gas containing nitrogen, which is an easily adsorbed component, from adsorption bed a at a rapid space velocity, the adsorption front of nitrogen, which is an easily adsorbed component, on bed b The gas (hatched area in the figure) not only reaches close to the product gas outlet, but also diffuses into the floor.

Therefore, even if product oxygen is subsequently introduced into the bed b in a countercurrent manner to raise the pressure of the bed b to the adsorption pressure, the pressurizing pressure range by the product oxygen gas is smaller than the pressure range due to the pressure equalization, and this Therefore, the extension and diffusion of the nitrogen adsorption front in the bed caused by the pressure equalization cannot be eliminated, and therefore the purity of the product oxygen obtained in the adsorption step in the next step does not reach the desired purity of 90% or more. In addition, in order to obtain the desired high-purity oxygen, it is necessary to keep the supply flow rate of raw air low, which reduces the amount of air processed per unit time, reducing operational efficiency. Become.

For this reason, as shown in (ii), product oxygen is first introduced countercurrently into the adsorption bed b which is in a vacuum state to break the vacuum state of the bed and bring the pressure to approximately normal pressure, and then the adsorption bed b is placed in a pressurized state. A method has been proposed in which the pressure of both beds is equalized by introducing gas from adsorption bed a into bed a in parallel flow. In this method, after the adsorption bed B is brought to almost normal pressure, the pressure of both beds is equalized by introducing nitrogen-containing oxygen-enriched gas released in parallel from the adsorption bed A. Although the pressure difference is not as large as in the method (i) above, the pressure equalization operation is performed in a vacuum state in the method (i) above, and in the method (ii) the difference is only due to the pressure from normal pressure. The disadvantages of the method (i) above are hardly resolved. Therefore, after introducing product oxygen into adsorption bed b in a vacuum state and raising the pressure of bed b to above normal pressure by the method (ii) above, adsorption bed a and adsorption bed b are equalized by the method described above. There is also a method of resolving the above-mentioned disadvantages by pressurizing, but this method prevents the long extension of the nitrogen adsorption front and diffusion within the adsorption bed B, but it does not substantially reduce the effectiveness of the product from the adsorption bed A. The amount of released gas containing oxygen introduced into the adsorption bed b and recovered is reduced, resulting in a reduction in yield.

In view of the above, the present invention has made various attempts and has discovered a pressure equalization method that eliminates the above-mentioned drawbacks. That is, this will be explained with reference to FIG.

In the figure, a indicates an adsorption bed which is in a pressurized state after completing the adsorption process as in FIG. 1, and b indicates an adsorption bed which has been evacuated to regenerate the adsorbent and is in a vacuum state. When adsorption bed a finishes the adsorption process and adsorption bed b finishes the evacuation process, the product oxygen output end of adsorption bed a (upper end in the figure) and the raw material supply end of adsorption bed B (lower end in the figure) part), and the nitrogen-containing oxygen-enriched gas led out from the adsorption bed a in parallel flow through the adsorption bed b.
At the same time, product oxygen is introduced into the adsorption bed b in a countercurrent direction from the product oxygen outlet end (upper end in the figure) of the bed. In this state, the operation is continued until the pressures of adsorption bed a and adsorption bed b are equalized. As a result, the vacuum in adsorption bed b, which was in a vacuum state, is broken by the oxygen-enriched gas containing nitrogen and the product oxygen from adsorption bed a, and the pressure is increased. Oxygen-enriched gas containing nitrogen, which is an easily adsorbed component, is introduced into adsorption bed a, but at the same time, product oxygen is introduced into adsorption bed b in the countercurrent direction.
The adsorption front (hatched area in the figure) formed on adsorption bed b by nitrogen contained in the oxygen-enriched gas from adsorption bed a that is introduced into adsorption bed b in parallel flow is
At the same time, the product oxygen introduced in the countercurrent direction suppresses diffusion into the bed, suppresses rapid elongation, and prevents product oxygen from being pushed up to the product oxygen outlet end of adsorption bed b. It is formed by being pressed against the lower raw material supply end, and the effective bed capacity for adsorbing nitrogen in the subsequent adsorption process of bed b increases. In addition, the flow rate of the oxygen-enriched gas derived from adsorption bed a and staying in the bed a space is suppressed by the product oxygen flowing countercurrently to adsorption bed b, so that it is not adsorbed by the adsorbent of adsorption bed a. Therefore, the amount of nitrogen, which is an easily adsorbed component, accompanying the oxygen-enriched gas introduced from adsorption bed A to adsorption bed B is small, and adsorption bed B is contaminated with nitrogen in this process. As the area becomes smaller, the effective bed capacity for nitrogen adsorption in the subsequent adsorption process is further increased, high purity oxygen can be collected, and the bed can be filled with more mixed gas until it is penetrated by the nitrogen adsorption front. This makes it possible to separate and treat the gas, substantially increasing the amount of gas separated per unit amount of adsorbent and improving operational efficiency.

Based on the above-mentioned new knowledge, the present invention utilizes a mixed gas of mainly oxygen and nitrogen, such as air, as a raw material, and a pressurized adsorption process in which nitrogen is selectively adsorbed and removed by an adsorbent to concentrate and continuously collect oxygen; The oxygen enrichment method uses PSA operation, which includes the process of vacuum evacuation and regeneration of the adsorbent that has adsorbed nitrogen, and by adopting the new pressure equalization process mentioned above, the entire process can be operated economically and efficiently while improving the yield. This is an oxygen enrichment method. The oxygen concentrating method of the present invention is shown below in Figures 3 and 4.
This will be explained in detail with reference to the drawings.

FIG. 3 is a system diagram showing an example of an apparatus for implementing the method of the present invention, and FIG. 4 is a process operation sequence diagram of an example of implementing the method of the present invention. In Fig. 3, A, B, C, and D are adsorption beds each filled with an adsorbent that selectively adsorbs nitrogen, such as natural or synthetic zeolite, 1 is a compressor, and 2 is a discharge port of the compressor 1. Feed air is transferred to each adsorption bed A, B, C,
Main raw material supply pipes that supply to D, 3A, 3 respectively
B, 3C, and 3D are supply pipes branched from the main raw material supply pipe 2, and each pipe 3A to 3D is connected to a valve 4.
Each adsorption bed A, B, through A, 4B, 4C, 4D
It is connected to C and D. 5A, 5B, 5C, 5
D is a pipe for deriving concentrated product oxygen from the adsorption beds A, B, C, and D, respectively, and each pipe 5A to 5D is connected to the main derivation pipe 7 via valves 6A, 6B, 6C, and 6D, and the main derivation pipe 7 is connected to a product tank 9 via a valve 8. 10A, 10B, 10C, 1
0D is the adsorption bed A, B, C, D and each valve 4A, 4
B, 4C, 4D between each pipe 3A, 3B, 3C,
A discharge pipe branched from 3D, each discharge pipe having a valve 1
It is connected via 1A, 11B, 11C, and 11D to a main discharge pipe 12 whose one end opens to the atmosphere. 1
3A, 13B, 13C, 13D are the discharge pipes 10
Similar to A, 10B, 10C, 10D, each adsorption bed A,
B, C, D and valves 4A, 4B, 4C, 4D are exhaust pipes branched from each pipe 3A, 3B, 3C, 3D, and each exhaust pipe is connected to valves 14A, 14B, 14C, 14.
It is connected to a main exhaust pipe 15 via D, and the main exhaust pipe is further connected to a vacuum pump 16.

On the other hand, valves 6 are provided in each outlet pipe 5A, 5B, 5C, and 5D for discharging product oxygen from each adsorption bed A, B, C, and D.
Between A, 6B, 6C, 6D and each adsorption bed, pipes 17A, 17 for equalizing the pressure with other beds, respectively.
B, 17C, and 17D are branched, and each pipe is connected to each supply conduit 3C, 3D, 3A, and adsorption bed C, adsorption bed D, adsorption bed A, and adsorption bed B through valves 18A, 18B, 18C, and 18D. Connected to 3B. In addition, the product outlet pipes 5A, 5B, 5C, and 5D of each of the adsorption beds A, B, C, and D are connected to a backfilling main pipe 2 connected from the raw material tank 9 via a valve 19, respectively.
Pipes 21A, 21B, 2 branched from 0
1C and 21D are valves 22A, 22B, and 22, respectively.
C, 22D, and each of the product outlet pipes 5A, 5B, 5C, and 5D is provided with a valve 2.
4A, 24B, 24C, 24D and flow rate adjustment valve 2
Repressurization pipes 23A, 2 communicating with the product oxygen deriving main pipe 7 via 5A, 25B, 25C, 25D
3B, 23C, and 23D are arranged in series.

When the oxygen concentrating method of the present invention is operated using the apparatus as described above as follows, concentrated oxygen can be obtained continuously. That is, for example, the adsorption beds A, B, C, and D each have a pressure adsorption () process, a pressurized adsorption () process, a cocurrent depressurization process, a countercurrent depressurization process, a countercurrent exhaust process, a countercurrent exhaust process, and a pressure equalization process. The eight steps of the pressurization process and the repressurization process are sequentially switched and circulated according to the above process order, and the four beds are arranged so that the processes at the same time are two steps before or after the order of the eight steps. In the process state, that is, when bed A is the pressure adsorption () process, bed B is the pressure equalization process two steps before the pressure adsorption () process in the process order, and bed C is the pressure equalization process two steps before the pressure adsorption () process in the process order. The countercurrent evacuation process before the process and the bed D are operated so that the processes of each bed are combined at the same time so that the bed D is in the state of the cocurrent depressurization process two processes before.

The state of the adsorption bed in the 8 steps is as follows.

That is, pressurized adsorption ()...a process in which raw materials are supplied under pressure to one end of the adsorption bed, nitrogen is adsorbed and removed by the bed, and concentrated oxygen is collected from the other end; pressurized adsorption ()... The raw material is supplied under pressure from one end of the adsorption bed, concentrated oxygen is collected from the other end, and a part of the collected concentrated oxygen is divided and supplied to the repressurization process where the pressure is increased to the adsorption pressure of another column. Process, co-current depressurization...The supply of raw materials to the adsorption bed is stopped, the pressurized gas in the bed is co-currently led out from the concentrated oxygen outlet end of the adsorption bed, the bed is depressurized, and the discharged gas is evacuated. Countercurrent depressurization...The raw material supply end of the adsorption bed is communicated with the atmosphere, and the gas in the bed is circulated countercurrently and released to the atmosphere to bring the inside of the bed to almost atmospheric pressure. Countercurrent exhaust: A process of exhausting the gas in the adsorption bed at almost atmospheric pressure in a countercurrent direction from the raw material supply end using a vacuum pump. Pressure equalization: As shown in Figure 2 above. In the unique process of the present invention, the cocurrent depressurized gas from the other bed is introduced from the raw material supply end into the adsorption bed in a vacuum state, and at the same time, concentrated oxygen is introduced countercurrently from the raw material tank through the concentrated oxygen outlet end to raise the pressure. At the same time, there is a process of equalizing the pressure with the bed in the co-current depressurization process, repressurization... from the concentrated oxygen outlet end of the adsorption bed, a part of the concentrated oxygen collected from the bed in the repressurization process The state of the adsorption bed is maintained in each step, such as the step of introducing the adsorbent into the bed countercurrently and increasing the pressure within the bed to the adsorption pressure.

Next, an example will be described in which the above-mentioned eight steps are continuously operated using, for example, four adsorption beds A, B, C, and D.

First, in the first step, valves 4A, 6A, 8, 14C,
18D, 19, and 22B are open, the other valves are closed, and a mixed gas such as air mainly consisting of oxygen and nitrogen components is supplied to the adsorption bed A from the compressor 1 at a pressure of 1.5 to 3 Kg/cm ² G. It is compressed and introduced through the main raw material supply pipe 2, branch pipe 3A, and valve 4A,
In the bed A, nitrogen is adsorbed by the adsorbent in the bed, and oxygen concentrated to about 90% or more is discharged from the discharge pipe 5A and stored in the product tank 9 via the valve 6A, the main discharge pipe 7, and further through the valve 8. Then, a pressure adsorption () process is performed.
The adsorption bed B is in a vacuum state as the inside of the bed has been regenerated by evacuation in the previous step, and the raw material supply pipe 3B of the bed communicates with the outlet pipe 5D of the adsorption bed D via the pipe 17D and the valve 18A. The adsorption bed D, which was maintained at a pressure of 1.5 to 3 Kg/cm ² G after completing the pressurized adsorption () process in the previous process, has a higher oxygen purity than the raw material staying in the space of the bed D, but it has a higher purity than the product oxygen. Oxygen-enriched gas with low oxygen purity is introduced into the adsorption bed B in parallel flow, and at the same time a pipe 21B is branched from the backfill main pipe 20 extending from the raw material tank 9 via the valve 19 to the outlet pipe 5B of the adsorption bed B.
are in communication via valve 22B, and product oxygen gas is introduced from product tank 9 into adsorption bed B in a countercurrent direction. As a result, the vacuum state of the adsorption bed B is broken, and a pressure equalization process is performed in which the pressure is equalized to about 1 to 1.5 kg/cm ² G between the adsorption bed B and the adsorption bed D.
In addition, the pressure inside the adsorption bed C has been reduced to approximately atmospheric pressure in the previous step, and by opening the valve 14C, the bed C
The pipe 3C at the raw material introduction end is connected to the exhaust main pipe 15 via a pipe 13C and a valve 14C, and further to a vacuum pump 16.
The inside of the adsorption bed C is evacuated to a pressure of 100 to 150 torr in the countercurrent direction by a vacuum pump 16, whereby the nitrogen adsorbed by the adsorbent in the adsorption bed C is desorbed and exhausted. The process is carried out. Furthermore, the adsorption bed D was subjected to a pressurized adsorption ( ) step in the previous step, and the pressure inside the bed was 1.5 to 3 Kg/cm ² G.
By opening D, the pipe 5 at the product oxygen outlet end of the bed D is opened.
D communicates through valves 17D and 18D with the pipe 3B at the raw material supply end of the adsorption bed B, which is in a vacuum state and is pressurized and equalized, to obtain a higher oxygen purity than the raw material remaining in the space within the adsorption bed D. Oxygen-enriched gas with higher oxygen purity and lower oxygen purity than product oxygen flows cocurrently in bed D and is led out.
Adsorption bed B is introduced co-currently. Then, as described above, co-current depressurization is carried out to equalize the pressure to 1 to 1.5 Kg/cm ² G with the adsorption bed B.

After the above steps are performed on each adsorption bed for the same period of time, each adsorption bed is switched to the next second step.

That is, in the second step, valves 4A, 6A, 8, 11D,
14C and 24B are opened, and the other valves are closed. Adsorption bed A is compressor 1 as in the first step.
The raw material compressed to 1.5-3Kg/cm ² G is transferred to pipes 2 and 3.
A. Introduced through valve 4A, adsorbing and removing nitrogen in the bed, leading out concentrated oxygen with an oxygen purity of 90% or more through pipe 5A, and passing through valve 6A, pipe 7, and further valve 8 to the product tank. 9, the concentrated oxygen is collected as a product, and a part of the concentrated oxygen is branched from the main outlet pipe 7 and distributed to the pipe 5B of the adsorption bed B via the pipe 23B, valve 24B, and flow rate adjustment valve 25B, and is adsorbed. Floor B
In order to increase the pressure of the bed B to an adsorption pressure of 1.5 to 3 kg/cm ² G, pressurized adsorption () is performed in which the pressure is introduced in the countercurrent direction.
During this period, adsorption bed B undergoes a repressurization process in which a part of the product oxygen derived from adsorption bed A is introduced countercurrently to increase the pressure within the bed to an adsorption pressure of 1.5 to 3 Kg/cm ² G as described above. As in the first step, the adsorption bed C continues to undergo a countercurrent evacuation process in which the inside of the bed is evacuated in a countercurrent direction using a vacuum pump, and the adsorption bed D is evacuated in parallel with the previous step by opening the valve 11D. The inside of the bed, which has a pressure of 1 to 1.5 Kg/cm ² G due to flow reduction, communicates with the atmosphere through the pipe 10D, the valve 11D, and the main discharge pipe 12, so that the gas in the bed flows countercurrently within the bed. A countercurrent depressurization process is performed in which the pressure inside the bed is reduced to approximately atmospheric pressure. Subsequently, after a certain period of time, each adsorption bed is switched to the third step.

In the third step, valves 4B, 6B, 8, 14D, 18
A, 19, and 22C are opened, and the other valves are closed, and adsorption bed A is used for pressurized adsorption () in the previous process.
In the process, the oxygen-enriched gas remaining in the bed is led out in parallel flow and introduced into adsorption bed C via pipe 17A and valve 18A, and the pressure inside adsorption bed A is adjusted to 1.5 to 3 Kg/cm ² of the previous step.
A cocurrent depressurization process is performed to reduce the pressure from the pressure of G to 1.0 to 1.5 Kg/cm ² G, and the adsorption bed B is connected to the pipe 2,
3B, feedstock pressurized to a pressure of 1.5 to 3 Kg/cm ² G is introduced via valve 4B, nitrogen content is adsorbed and removed in bed B, and concentrated oxygen concentrated to 90% or more is passed through pipe 5B. Pressurized adsorption () in which the product is extracted and collected as a product into the product tank 9 via the valve 6B, pipe 7, and valve 8.
The process is carried out, and the adsorption bed C has been made into a vacuum state in the previous process, and the oxygen-enriched gas derived from the cocurrent pressure reduction process in the adsorption bed A is passed through the pipe 17A and the valve 18A.
At the same time, from the product tank 9, a valve 19,
Through pipe 20, pipe 21C, and valve 22C, product oxygen is introduced countercurrently into the adsorption bed C from the outlet pipe 5C, so that the bed C breaks the vacuum and is pressurized to the adsorption bed A. A pressurization and equalization process is performed to equalize the pressure to 0.5 to 1.5 Kg/cm ² G between the adsorption bed D and the adsorption bed D is connected to the vacuum pump 16 via a pipe 13D, a valve 14D, and a pipe 15. Then, the inside of the bed is evacuated in a countercurrent direction, and a vacuum evacuation process is performed to desorb and eliminate nitrogen adsorbed on the adsorbent in the bed and regenerate the bed. After operating these third steps for a certain period of time, each adsorption bed is operated in a fourth step.

In the fourth step, valves 4B, 6B, 8, 11A, 14
D, 24C are opened and the other valves are closed, adsorption bed A is communicated with the atmosphere through pipe 10A, valve 11A and pipe 12, and the gas in bed A is directed towards bed A. A depressurization step is carried out in which the raw material is discharged into the atmosphere and depressurized to atmospheric pressure, and the adsorption bed B is filled with raw material pressurized to 1.5 to 3 Kg/cm ² G by the compressor 1, as in the third step, and then transferred to the pipe 2. , 3B, is introduced via valve 4B, nitrogen is adsorbed and removed in bed B, and concentrated oxygen concentrated to 90% or more is led out from pipe 5B, and is sent to the product tank via valve 6B, pipe 7, and valve 8. 9 as a product, and a part of it is branched from pipe 7 to pipe 23C,
A process of pressurized adsorption () is performed in which the gas for repressurization is supplied to the adsorption bed C via the valve 24C and the flow rate control valve 25C, and the adsorption bed C is subjected to the pressurized adsorption () in the adsorption bed B.
A part of the concentrated oxygen obtained in the process is branched from the pipe 7 to the pipe 23C as described above, and introduced countercurrently into the adsorption bed C through the valve 24C and the flow rate adjustment valve 25C, respectively, to achieve an adsorption pressure of 1.5 to 3 Kg/cm. A repressurization process is performed to increase the pressure to ² G, and the adsorption bed D is connected to the main exhaust pipe 15 via the pipe 13D and valve 14D, and the raw material introduction end of the adsorption bed D is connected to the main exhaust pipe 15 through the pipe 13D and the valve 14D. A countercurrent evacuation process is continued in which the bed is evacuated in a countercurrent manner by a vacuum pump 16 connected to the pump 16 to regenerate the bed.

In this manner, the valves are switched and operated at predetermined time intervals thereafter so that each adsorption bed is sequentially operated in accordance with the eight process sequences. That is, in the subsequent fifth step, valves 4C, 6C, 8, 14A, 1
8B, 19, and 22D are operated in the open state, and the other valves are operated in the closed state, so that adsorption bed A undergoes a countercurrent exhaust process, adsorption bed B performs a cocurrent depressurization process, and adsorption bed C performs a pressurized adsorption () process. , the adsorption bed D is operated in a pressure equalization step, and in the sixth step, valves 4C, 6C, 8, 11B,
14A and 24D are opened, and the other valves are closed. Adsorption bed A undergoes a countercurrent evacuation step following the fifth step, and adsorption bed B undergoes a countercurrent depressurization step. Bed C undergoes a pressurized adsorption ( ) step, adsorption bed D undergoes a repressurization step, and in the subsequent seventh step, valves 4D, 6D, 8, 14B, 18C,
19 and 22A are operated in the open state, and the other valves are operated in the closed state, respectively, so that adsorption bed A undergoes the pressure equalization process, adsorption bed B performs the countercurrent evacuation process, and adsorption bed C performs the cocurrent depressurization process. In addition, the adsorption bed D is operated in the pressurized adsorption () step, respectively. Furthermore, in the eighth step, valves 4D and 6
D, 8, 11C, 14B, and 24A are opened, and the other valves are closed, so that adsorption bed A undergoes a repressurization process, and adsorption bed B continues a countercurrent exhaust process. In bed C, a countercurrent depressurization process is operated, and in adsorption bed D, a pressurized adsorption () process is operated.

Thereafter, each valve is switched at predetermined intervals and operated continuously so that each adsorption bed is circulated and operated in the operating state of each step from the first step to the eighth step. As a result, concentrated oxygen concentrated to 90% or more is continuously collected and stored in the product tank 9. Of the valves to be switched, valve 8
is a manual on-off valve that is always kept open during operation; valves 19, 25A, 25B, 25C, and 25D are flow rate adjustment valves that keep the flow constant; the other valves are solenoid valves; A method of automatically opening and closing operations according to a time sequence is adopted so that the operation is performed according to the process order.

Although the above description has been made of the case where four adsorption beds are used to continuously collect concentrated oxygen, the present invention is not limited to this, and if multiple adsorption beds are installed, the present invention It is quite clear that any suitable implementation may be made without departing from the spirit.

Next, an example in which the oxygen concentrating method of the present invention as described above was carried out will be shown below.

Number of adsorption beds installed: 4 beds Adsorbent used and amount used: Linde, Molecular Sieve 5A, 25Kg/1 bed Amount of air processed: 19.9 to 21.3Nm ³ /hr Adsorption bed: 2.5Kg/cm ² G, Exhaust vacuum: 130 Torr Equalization pressure: 1.5Kg/cm ² G, temperature 15℃ Operation Product oxygen yield: 3.1Nm ³ /hr Product oxygen purity: 92% Yield: 69% Product oxygen yield per unit amount of adsorbent :31/Kg.

As described above, according to the oxygen concentration method of the present invention,
Not only is it possible to collect product oxygen with high purity, but the method of the present invention also solves the problem that conventional methods of the same type reduce the yield when trying to obtain high purity product oxygen. Now, the oxygen gas, which is effective as a product and remains in the adsorption bed space after the adsorption process is completed, can be used in the subsequent pressure equalization process without being discarded, and it can also be collected to a large extent by the unique pressure equalization process of the present invention. It became possible to improve the ratio. Furthermore, the pressure equalization process adopted in the present invention introduces the product oxygen gas in a counterflow at the same time as the oxygen-enriched gas consisting of effective oxygen components into the bed, thereby eliminating impurity components contained in the oxygen-enriched gas. This prevents nitrogen, which is an easily adsorbed component, from diffusing into the bed, suppresses the extension of its adsorption front, and reduces the entrainment of impure nitrogen components from the bed from which the oxygen-enriched gas used for this is derived. As a result, the effective capacity of the bed for adsorbing and removing impure nitrogen in the subsequent adsorption process is increased, making it possible not only to stably collect oxygen with a high purity of 90% or more, but also to improve the processing efficiency. As is clear from the above examples, a product yield of 31/hr per 1 kg of adsorbent was obtained, which is 2.5 to 2.5% more than the product yield of 90% or more obtained by conventional methods. The yield is three times higher,
This is a device that has substantially improved its performance, and is extremely effective as an industrially practical device.

[Brief explanation of the drawing]

Figure 1 is a diagram explaining the conventional pressure equalization method, Figure 2
The figure is a diagram explaining the pressure equalization method adopted in the present invention,
FIG. 3 is a system diagram illustrating the method of the present invention, and FIG. 4 is a process operation sequence diagram of the method of the present invention. A, B, C, D are adsorption beds, 1 is a compressor, 2 is a raw material supply main pipe, 3A to 3D are supply conduits, 4A to 4D, 6A to 6D, 8, 11A to 11D, 1
4A to 14D, 18, 19, 22A to 22
D, 24A to 24D are valves, 5A to 5D, 17
A to 17D, 21A to 21D are pipes, 7 is a main outlet pipe, 9 is a product tank, 10A to 10D are discharge pipes, 12 is a main discharge pipe, 13A to 13D are exhaust pipes, 15 is a main exhaust pipe, 16 is a vacuum pump, 20 is the main pipe for reverse filling, 23A to 23D are the pipes for repressurization,
25A to 25D are flow rate regulating valves.

Claims (1)

[Scope of Claims] 1. Consisting of a plurality of adsorption beds filled with an adsorbent that selectively adsorbs nitrogen, a mixed gas such as air containing oxygen and nitrogen is introduced under pressure and passed through the adsorption beds to absorb nitrogen. Concentrating oxygen by sequentially switching over each of the plurality of adsorption beds, a step of collecting concentrated oxygen by adsorption and removal, and a step of regenerating the adsorption bed by desorbing the nitrogen adsorbed in the step by vacuum suction. In the method, each adsorption bed is subjected to (a) a pressurized adsorption step in which a pressurized mixed gas is introduced into the bed from one end of the adsorption bed and concentrated oxygen is collected from the other end; (b) introduction of the mixed gas; A cocurrent depressurization process in which the gas is discharged in a cocurrent direction from the concentrated oxygen outlet end of the adsorption bed and supplied for pressure equalization of other columns; (c) Mixed gas introduction into the adsorption bed (d) A countercurrent depressurization process in which the end of the adsorption bed is communicated with the atmosphere and the gas in the bed is discharged in a countercurrent direction to reduce the pressure to approximately atmospheric pressure. Countercurrent exhaust step in which exhaust is carried out in the countercurrent direction, (e) Gas from the cocurrent depressurization step in another bed is introduced from the mixed gas inlet end of the adsorption bed, and at the same time, the gas obtained from the pressurized adsorption step is introduced from the concentrated oxygen outlet end. (f) A pressure equalization step in which a part of the concentrated oxygen is introduced to equalize the pressure with other beds in the cocurrent depressurization step; A repressurization step of introducing a part of the obtained concentrated oxygen to pressurize the inside of the bed to an adsorption pressure.