JPH04322713A - Method and equipment for separating gaseous nitrogen - Google Patents

Abstract

PURPOSE:To provide a method and equipment for separating gaseous nitrogen capable of increasing separation efficiency of gaseous nitrogen to power source in separation of gaseous nitrogen from feed gas whose main components are nitrogen and oxygen by molecular sieve carbon. CONSTITUTION:A connecting pipe 26 connecting gaseous nitrogen takeoff parts of an adsorption tank 3 and an adsorption tank 4, the first two valves 11, 12, and a branch pipe 27 branching from between the first valves 11, 12 are provided. A holding tank 6 is provided at the end of the branch pipe 27, and the second valve 13 is provided for the branch pipe 27. In the adsorption tank 3 and the adsorption tank 4 in gaseous nitrogen separation equipment of the above constitution, when adsorption, equalization and regeneration processes are repeated to separate gaseous nitrogen, gaseous nitrogen of relatively low concentration in the adsorption tank where adsorption and pressure-equalizing processes are completed successively is transferred to the holding tank 6, then after the regeneration process is completed, gaseous nitrogen of relatively low concentration in the holding tank 6 is again transferred to the adsorption tank.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention utilizes the selective adsorption properties of molecular sieve carbon to produce a mixed gas containing nitrogen and oxygen as main components (
The present invention relates to a method and apparatus for separating nitrogen from (eg air).

0002

[Prior art] Carbon molecular sieve (CARBON MOLE)
The pressure fluctuation adsorption method (PRESS) utilizes the selective adsorption characteristics of CULAR SEIVES (hereinafter referred to as CMS).
A method of separating nitrogen gas from a mixed gas such as air using URE SWING ADSORPTION (hereinafter referred to as PSA) has been widely known. This device is relatively small and has been put into practical use as a means of continuously supplying inexpensive nitrogen gas by placing it near consumers.

Although the equilibrium adsorption amounts of oxygen and nitrogen in CMS are almost the same if the temperature and adsorption pressure are specified, there is a noticeable difference in the adsorption amounts at the initial stage of adsorption. FIG. 3 shows an example of the adsorption characteristics of this CMS. As shown in the figure, CMS adsorbs oxygen gas to almost the equilibrium adsorption amount in a relatively short time after the start of adsorption, but conversely, it takes a relatively long time to adsorb nitrogen gas to almost the equilibrium adsorption amount. Therefore, the time for adsorbing oxygen to CMS is usually set to about 60 seconds to about 240 seconds, which is the time when the difference in the amount of adsorption between oxygen and nitrogen is large.

[0004] By the way, in a PSA device using this CMS, if the raw material gas supply amount and adsorption tank capacity are regulated,
The amount of nitrogen gas taken out and its nitrogen gas concentration have the relationship shown in FIG. That is, when the amount of nitrogen gas taken out is increased, the nitrogen gas concentration decreases, and when the amount of nitrogen gas taken out is decreased, the nitrogen gas concentration increases. Since consumers usually desire any nitrogen gas concentration, the amount of nitrogen gas taken out at that concentration is regulated.

Conventionally, in this nitrogen gas separation apparatus, the problem has been how to increase the amount of nitrogen gas taken out at a predetermined concentration with respect to the predetermined supply amount of raw material gas. In other words, the operating cost of the device is almost the same as the power cost of the compressor for supplying the raw material gas, so by increasing the amount of nitrogen gas extracted, the power consumption per unit amount of nitrogen gas used ( This makes it possible to reduce the unit power cost (hereinafter referred to as unit power cost).

[0006] Conventionally, various operating methods have been studied for nitrogen gas separation apparatuses using a plurality of adsorption tanks in order to reduce the unit power cost. For example,
In the method described in Publication No. 204, when a substance is adsorbed at a relatively high pressure and desorbed at a relatively low pressure, the pressure is lowered to an intermediate level between the relatively high pressure and the relatively low pressure. , removing at least a portion of the desorbed material (hereinafter referred to as a pressure equalization step), subsequently reducing the pressure to said relatively low pressure, and improving unit power costs by removing the remaining desorbed material. There is.

The method described above can also be applied to nitrogen gas separation technology using the PSA method, and has been confirmed to be effective to some extent. That is, the PSA nitrogen gas separation apparatus is equipped with at least two adsorption tanks, and a step (hereinafter referred to as adsorption) in which raw material gas is supplied to both adsorption tanks and the CMS adsorbs oxygen gas to separate nitrogen gas. (hereinafter referred to as a step), a step (hereinafter referred to as
The process (referred to as the regeneration process) is repeated alternately, but the nitrogen gas in the adsorption tank A is transferred to the adsorption tank B by communicating the adsorption tank A after the adsorption process and the adsorption tank B after the regeneration process. (Pressure equalization process) The above-mentioned effects were obtained.

Further, at the beginning of the adsorption step, at the same time as the raw material gas is supplied to the adsorption tank, nitrogen gas of a predetermined concentration is introduced from the opposite side, so that the concentration of the nitrogen gas sent out is set to the predetermined concentration from the beginning. Things are being done.

[0009]

[Problems to be Solved by the Invention] However, the above-mentioned conventional method has the following problems. That is, when transferring nitrogen gas from adsorption tank A to adsorption tank B in the pressure equalization process mentioned above, there is a limit to the amount of nitrogen gas that can be transferred, and if this is exceeded, the amount of nitrogen gas that can be transferred is then transferred to adsorption tank B. The concentration of nitrogen gas that can be extracted by performing the adsorption process is extremely reduced. Therefore, there was naturally a limit to the above-mentioned improvement in unit power costs.

[0010] This is because when the adsorption tank is in the adsorption process, the gas in the adsorption tank flows from the raw material gas supply side to the nitrogen gas extraction side, so the nitrogen gas concentration in the adsorption tank is low enough to allow sufficient adsorption time. The concentration on the extraction side is high, and conversely the concentration on the raw material gas supply side is low. For example, if this is moved from the nitrogen gas extraction side of adsorption tank A to the nitrogen gas extraction side of adsorption tank B as described above, This is based on the fact that nitrogen gas with a high concentration is located on the raw material supply side of adsorption tank B, and nitrogen gas with a low concentration is located on the nitrogen gas extraction side, so that when the adsorption process is subsequently performed, nitrogen gas with a low concentration is initially extracted. .

Furthermore, if the amount of nitrogen gas transferred during the pressure equalization step is increased, a large amount of oxygen gas will be adsorbed by the CMS on the nitrogen gas extraction side of the adsorption tank that is the transfer source, and the CMS will be removed during the regeneration step.
There was a problem that oxygen gas was not sufficiently desorbed from the gas. For this reason, in the next adsorption step, oxygen gas is not sufficiently adsorbed by the CMS on the nitrogen gas extraction side of the adsorption tank, and nitrogen gas with a desired concentration cannot be obtained. In addition, when nitrogen gas of a predetermined concentration is introduced at the beginning of the adsorption process, by being filled with nitrogen gas of a predetermined concentration, the CMS on the nitrogen gas extraction side of the adsorption tank desorbs the adsorbed oxygen gas. , the nitrogen gas concentration in the same area decreases.

The present invention has been made in view of the above-mentioned circumstances, and an object of the present invention is to provide a method and apparatus for separating nitrogen gas that can improve the efficiency of separating nitrogen gas from a power source.

[0013]

[Means for Solving the Problems] A first invention of the present invention for achieving the above object is an invention of a method, in which two
In the method of supplying raw material gas containing nitrogen gas and oxygen gas as main components to adsorption tanks A and B, and separating nitrogen gas using carbon molecular sieve filled in adsorption tanks A and B, the following The gist is to carry out the steps sequentially and continuously.

a) Adsorption tank A that has completed adsorption and is in a pressurized state
A first step of communicating the gas in the adsorption tank A with the adsorption tank B, which has completed the transfer of gas from the retention tank after completion of regeneration, to transfer the gas in the adsorption tank A to the adsorption tank B.

b) A second step for communicating the adsorption tank A and the retention tank to transfer gas from the adsorption tank A to the retention tank, while supplying the raw material gas to the adsorption tank B and separating nitrogen gas.
Process.

c) A third step of releasing the residual gas in the adsorption tank A to the atmosphere while continuously supplying the raw material gas to the adsorption tank B to separate nitrogen gas.

d) The adsorption tank A and the retention tank are communicated, and gas is transferred from the retention tank to the adsorption tank A, while the raw material gas is continuously supplied to the adsorption tank B, and nitrogen The fourth step is to separate the gas.

e) The adsorption tank B, which has completed adsorption and is in a pressurized state, is communicated with the adsorption tank A, which has completed the gas transfer from the retention tank, and the gas in the adsorption tank B is transferred to the adsorption tank A. Fifth step of transferring.

f) A sixth step of communicating the adsorption tank B and the retention tank to transfer gas from the adsorption tank B to the retention tank, while supplying the raw material gas to the adsorption tank A and separating nitrogen gas.
Process.

g) A seventh step of releasing the residual gas in the adsorption tank B to the atmosphere while continuously supplying the raw material gas to the adsorption tank A to separate nitrogen gas.

h) The adsorption tank B and the retention tank are communicated and gas is transferred from the retention tank to the adsorption tank B, while the raw material gas is continuously supplied to the adsorption tank A, and the nitrogen gas is 8th step of separating.

[0022] In addition to the configuration of the first invention, the second invention also provides a structure in which nitrogen gas is added to the adsorption tank A in the third step and the adsorption tank B in the seventh step after the residual gas is released into the atmosphere. The purpose is to have the documents sent.

[0023] Furthermore, in the third invention, raw material gas containing nitrogen gas and oxygen gas as main components is alternately supplied from one side to the two adsorption tanks A and B arranged in parallel, and the other A device for extracting nitrogen gas separated from the side, comprising: a connecting pipe connecting the nitrogen gas extracting parts of the adsorption tank A and the adsorption tank B; two first valves provided on the connecting pipe; The gist of the present invention is to include a branch pipe branching from between the valves, a retention tank provided at an end of the branch pipe, and a second valve provided in the branch pipe.

[0024]

[Operation] The operation of the present invention will be explained below. According to the first invention and the third invention, firstly, the
The first valve is opened, and adsorption tank A, which has completed adsorption and is in a pressurized state, is communicated with adsorption tank B, which has completed regeneration and has completed gas transfer from the retention tank. Concentrated nitrogen gas is transferred to adsorption tank B from the nitrogen gas extraction section.

Next, the first valve and the second valve on the adsorption tank A side are connected to each other.
Adsorption tank A is opened by opening the valve to connect adsorption tank A and retention tank.
While transferring the relatively low concentration nitrogen gas in the tank to the retention tank,
The raw material gas is supplied to the adsorption tank B to separate nitrogen gas.

Next, the gas still remaining in the adsorption tank A is released to the atmosphere, and the gas adsorbed by the CMS is desorbed and regenerated, while the adsorption tank B is continuously supplied with the raw material. Supply gas and separate nitrogen gas.

Next, the first valve and the second valve on the adsorption tank A side are connected again.
The valve is opened to connect the adsorption tank A and the retention tank to transfer relatively low concentration nitrogen gas in the retention tank to the adsorption tank A.
The raw material gas is continuously supplied to the adsorption tank B to separate nitrogen gas.

Next, the two first valves are opened to connect adsorption tank B, which has completed adsorption and is in a pressurized state, with adsorption tank A, which has completed regeneration and has completed gas transfer from the retention tank. Then, nitrogen gas at a predetermined concentration in adsorption tank B is transferred to adsorption tank A. As a result, in the adsorption tank A, nitrogen gas with a relatively low concentration exists at a position away from the nitrogen gas extraction part, and nitrogen gas with a predetermined concentration exists at a position close to the nitrogen gas extraction part.

Next, the first valve and the second valve on the adsorption tank B side are opened, and the adsorption tank B and the retention tank are communicated with each other, so that the comparatively low concentration nitrogen gas in the adsorption tank B is transferred to the retention tank. While being transferred, raw material gas is supplied to adsorption tank A to separate nitrogen gas. Here, since nitrogen gas of a predetermined concentration is transferred to a position close to the nitrogen gas extraction part in the adsorption tank A, the nitrogen gas of a predetermined concentration can be extracted even at the beginning of nitrogen gas extraction after the raw material gas is supplied. is possible.

Next, the gas still remaining in the adsorption tank B is released to the atmosphere, and the gas adsorbed by the CMS is desorbed and regenerated, while the raw material gas is continuously supplied to the adsorption tank A. and separate nitrogen gas.

Next, the first valve and the second valve on the adsorption tank B side are connected again.
The valve is opened to connect the adsorption tank B and the retention tank to transfer relatively low concentration nitrogen gas in the retention tank to the adsorption tank B,
Raw material gas is continuously supplied to adsorption tank A to separate nitrogen gas.

Thereafter, by sequentially and continuously carrying out the above steps, it is possible to continuously separate nitrogen gas at a predetermined concentration.

Further, according to the second invention, by feeding nitrogen gas from the nitrogen gas take-off section of the adsorption tank in a regenerated state, the partial pressure of oxygen gas in the adsorption tank is lowered, and the CM
Oxygen gas can be forcibly desorbed from S. As a result, the amount of oxygen gas that can be adsorbed by CMS is increased, and the separation efficiency can be improved.

[0034]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Examples of the present invention will be described below with reference to the accompanying drawings. First, an apparatus for carrying out the present invention will be explained.

FIG. 2 is an explanatory diagram showing an embodiment of the apparatus of the present invention. As shown in the figure, the nitrogen gas separation device according to the example includes two adsorption tanks A (3) and B (4), and a compressor (1) that supplies air as a raw material gas under pressure.
, a raw material tank (2) that temporarily stores pressurized air, a product tank (5) that temporarily stores nitrogen gas separated from adsorption tank A (3) and adsorption tank B (4), and adsorption tank A ( 3) and a retention tank (6) for temporarily storing relatively low concentration nitrogen gas separated from adsorption tank B (4), and a retention tank (6) provided above the adsorption tank A (3) and adsorption tank B (4). This device consists of an extraction piping section (A), an intake piping section (B) and an exhaust piping section (C) provided below adsorption tank A (3) and adsorption tank B (4). Each part will be explained below.

[0036] The product tank (5) is equipped with a product outlet pipe (29) having a valve (16) at its lower part.

The take-out piping section (A) has a valve (14) and an take-out pipe (23) connected to the upper part of the adsorption tank A (3), and a valve (15), and also has a valve (15) and a take-out pipe (23) connected to the upper part of the adsorption tank B (4). It has a take-out pipe (24) connected to the upper part of the take-out pipe (23), a take-out pipe (28) that connects these take-out pipes (23), (24) and the product tank (5), and a throttle valve (17). ), (24), a connecting pipe (26) having valves (11), (12) and connecting the extraction pipes (23), (24), and the valve (11). , (12) connecting pipe (2
6) and a branch pipe (27) which is connected to the retention tank (6) via a valve (13).

The intake piping section (B) has a valve (7) and an intake pipe (21) connected to the lower part of the adsorption tank A (3), and a valve (9) and connects the adsorption tank B (
4), and an intake pipe (19) that connects these intake pipes (21), (22) and the raw material tank (2).

[0039] The exhaust piping section (C) is connected to the adsorption tank A (
3), an exhaust pipe (21a) branching from the intake pipe (21) between the valve (7) and having the valve (8), and an intake pipe between the valve (9) and the lower part of the adsorption tank B (4). an exhaust pipe (22a) branching from (22) and having a valve (10);
It is composed of an exhaust pipe (20) connected to both of these exhaust pipes (21a) and (22a).

[0040] The adsorption tank A (3) and the adsorption tank B (4)
) is a hermetically sealed hollow cylindrical member, the inside of which is filled with CMS.

Next, FIG. 1 shows an example of carrying out the method of the present invention using a nitrogen gas separation apparatus having the above configuration.
The explanation will be based on. FIG. 1 is an explanatory diagram showing the steps in a nitrogen gas separation apparatus in chronological order, focusing on each adsorption tank. Hereinafter, the periods T1 to T2, T2 to T3, and T shown in the same figure are as follows.
3~T4, T4~T5, T5~T6, T6~T7, T7
-T8, and the operating state of the device at T8-T9 will be explained. Note that the valve (16) is always open.

[0042] Also, the opening degree of the throttle valve (17) is adjusted appropriately to ensure that nitrogen gas constantly flows from the adsorption tank on the high pressure side where the adsorption process is being carried out to the adsorption tank on the low pressure side where the regeneration process is being carried out. ing. The flow rate varies depending on the desired product nitrogen gas concentration and ranges from 10% to 50% of the withdrawal flow rate.

1) Period T1-T2 During this period, an adsorption step is performed on adsorption tank A (3), and three pressure equalization steps are performed on adsorption tank B (4). In addition, the valve (11) of the separation device in Figure 2 before this period
, (12) are open and valves (7), (8), (9),
(10), (13), (14), and (15) are closed.

First, the operation of adsorption tank A(3) will be explained. Open the valve (7) at the bottom of adsorption tank A (3) and open the raw material tank (
2), high-pressure air is fed into the adsorption tank A (3). At the same time, open the valve (14) at the top of adsorption tank A (3) and product tank (5).
) is fed into the adsorption tank A (3). Through this operation, the adsorption tank A (3) is pressurized, and the raw material tank (2)
, the pressure is approximately equal to that of the product tank (5). Since the compressor (1) is in continuous operation, the pressure in the adsorption tank A (3) is further increased.

The inside of adsorption tank A (3) is filled with CMS, and as a result of this CMS adsorbing oxygen gas by pressurizing it for a predetermined period of time, nitrogen gas of a predetermined concentration passes through the extraction pipe (23). After that, it is stored in the product tank (5). This operation continues during periods T1-T4. Therefore, the description of the adsorption tank A(3) during the period T2 to T3 and the period T3 to T4 will be omitted. On the other hand, in adsorption tank B (4), by opening the valves (12) and (13) at the top of adsorption tank B (4), relatively low concentration nitrogen gas in adsorption tank B (4) can be removed. is connected to the retention tank (6) via the connecting pipe (26) and branch pipe (27).
).

2) Period T2-T3 During this period, the valves (7) and 2 in FIG. Open (10) and (14) and close the remaining valves.

Since the adsorption tank B (4) which has completed the pressure equalization step 3 has a higher pressure than the atmospheric pressure, when the valve (10) is opened, the residual gas in the adsorption tank B (4) is discharged through the intake pipe (22), The gas is discharged into the atmosphere through an exhaust pipe (22a) and an exhaust pipe (20) that branch from this. Through this operation, the oxygen gas adsorbed on the CMS is desorbed, and the CMS is regenerated. At this time, nitrogen gas at a predetermined concentration is flowing from adsorption tank A (3) on the high pressure side to adsorption tank B (4) via the throttle valve (17). As a result, the partial pressure of oxygen gas in adsorption tank B (4) decreases, so oxygen gas is forcibly desorbed from CMS, and C
MS is regenerated with high efficiency.

3) Period T3 to T4 During this period, the valve (7) in FIG. ), (12), (13), (14),
Close the remaining valves.

By opening the valves (12) and (13), relatively low concentration nitrogen gas in the retention tank (6) flows into the branch pipe (2).
7), is sent to the adsorption tank B (4) via the connecting pipe (26) and the take-out pipe (24).

4) Period T4-T5 In this period, adsorption tank A (3) and adsorption tank B (4
) Open the valves (11) and (12) in FIG. 2 and close the remaining valves to carry out two pressure equalization steps for both.

The nitrogen gas extraction side of adsorption tank A (3) where the adsorption process has been completed is filled with nitrogen gas at high pressure and a predetermined concentration, and the extraction pipe (23), connecting pipe (26), and extraction pipe (24) are This is sent to the adsorption tank B (4) where the first pressure equalization step has been completed. As a result, the relatively low concentration nitrogen gas that was previously sent to adsorption tank B (4) is transferred to the lower part of the tank.
That is, it is moved to the source gas supply side, and the upper part of the tank, ie, the nitrogen gas extraction side, is filled with nitrogen gas at a predetermined concentration.

5) Period T5-T6 During this period, the valves in FIG. Open (9), (11), (13), (15),
Close the remaining valves. Adsorption tank A (3
) is filled with relatively low concentration nitrogen gas, which is fed into the retention tank (6) via the take-out pipe (23), the connecting pipe (26), and the branch pipe (27).

On the other hand, the valve (9) at the bottom of the adsorption tank B(4) is opened to send high pressure air from the raw material tank (2) into the adsorption tank B(4). At the same time, the valve (15) at the top of adsorption tank B (4)
) is opened and high-pressure nitrogen gas is introduced from the product tank (5) into the adsorption tank B (
4).

[0054] Through this operation, the relatively low concentration nitrogen gas is pushed further downward, and the nitrogen gas in adsorption tank B (4
) is pressurized to approximately the same pressure as the raw material tank (2) and product tank (5). Since the compressor (1) is in continuous operation, the pressure in adsorption tank B (4) is further increased, and the pressure in adsorption tank B (4) is increased.
When the pressure of B exceeds the pressure of product tank (5), adsorption tank B (4)
Nitrogen gas is taken out from the tank via the take-out pipe (24), but as mentioned above, the nitrogen gas take-out side of adsorption tank B (4) is filled with nitrogen gas at a predetermined concentration, so it is necessary to take out nitrogen gas from the beginning. Can be done. As a result of the CMS being pressurized for a predetermined period of time and adsorbing oxygen gas, nitrogen gas of a predetermined concentration passes through the take-out pipe (24) to the product tank (
5).

[0055] In the subsequent period T6 to T9, the steps performed for adsorption tank A (3) and adsorption tank B (4) in the above-mentioned period T2 to T5 are reversed, and the steps performed for adsorption tank A (3) and adsorption tank B (4) are reversed. In (3), a regeneration step, a pressure equalization step, and a pressure equalization step 2 are carried out, and an adsorption step and a pressure equalization step 2 are carried out in the adsorption tank B (4), and the details thereof will be omitted.

[0056] From then on, adsorption tank A (3) and adsorption tank B
In contrast to (4), by alternately repeating the steps shown in FIG. 1, nitrogen gas can be continuously extracted.

FIG. 5 shows the results of producing nitrogen gas according to the example detailed above. Figure 5 shows pressure equalization 2 process and pressure equalization 3.
The horizontal axis indicates the transfer rate in the process (gas amount in the adsorption tank = 100%), and the vertical axis indicates the amount of nitrogen gas extracted (expressed as a ratio where the amount of nitrogen gas extracted by the conventional method = 100). As shown in the figure, when using the retention tank according to the method of the present invention, the extraction amount increases by about 8% compared to the conventional method, and in addition to this, when the inside of the adsorption tank is purged with nitrogen gas at a specified concentration in the regeneration process. , the amount taken out increased by about 20% compared to the conventional method.

[0058]

Effects of the Invention As detailed above, according to the present invention, at the beginning of the adsorption process, the adsorption tank on the nitrogen gas extraction side is filled with nitrogen gas at a predetermined concentration from the beginning. can be extracted, the amount of nitrogen gas separated can be increased, and manufacturing costs can be reduced. In addition, in the regeneration process, we decided to scavenge the inside of the adsorption tank with nitrogen gas at a predetermined concentration.
As a result of being able to regenerate CMS with high efficiency, the amount of CMS adsorbed is increased, the amount of nitrogen gas separated can be increased, and as described above, manufacturing costs can be reduced.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing steps performed for each adsorption tank of a nitrogen gas separation device.

FIG. 2 is an explanatory diagram schematically showing an embodiment of the device of the present invention.

FIG. 3 is a graph showing the adsorption characteristics of CMS.

FIG. 4 is a graph showing the relationship between the amount of gas transferred in the pressure equalization step (the amount of gas in the adsorption tank=100%) and the concentration of oxygen gas contained in the gas.

FIG. 5 is a graph showing the amount of nitrogen gas taken out in the method of the present invention.

FIG. 6 is a graph showing the relationship between the amount of nitrogen gas taken out of the nitrogen gas separation device and the nitrogen gas concentration.

[Explanation of symbols]

1 Compressor 2 Raw material tank 3 Adsorption tank A 4 Adsorption tank B 5 Product tank 6 Retention tank 11 Valve 12 Valve 13 Valve 17 Throttle valve 26 Connecting pipe 27 Branch pipe

Claims (3)

[Claims] [Claim 1] Two adsorption tanks A and B installed in parallel.
In the method of supplying a raw material gas containing nitrogen gas and oxygen gas as main components and separating nitrogen gas using carbon molecular sieves filled in adsorption tank A and adsorption tank B, the following steps are sequentially and continuously carried out. A nitrogen gas separation method characterized by: a) Adsorption tank A, which has completed adsorption and is in a pressurized state, is communicated with adsorption tank B, which has completed regeneration and has completed transfer of gas from the retention tank, to transfer the gas in adsorption tank A to adsorption tank B. The first step is to b) A second step of communicating the adsorption tank A and the retention tank to transfer gas from the adsorption tank A to the retention tank, while supplying the raw material gas to the adsorption tank B and separating nitrogen gas. c) While releasing the residual gas in the adsorption tank A to the atmosphere,
A third step of continuously supplying the raw material gas to the adsorption tank B and separating nitrogen gas. d) Connecting the adsorption tank A and the retention tank to transfer gas from the retention tank to the adsorption tank A, while continuously supplying the raw material gas to the adsorption tank B to separate nitrogen gas. The fourth step. e) A step in which the adsorption tank B, which has completed adsorption and is in a pressurized state, and the adsorption tank A, which has completed gas transfer from the retention tank, are communicated, and the gas in the adsorption tank B is transferred to the adsorption tank A. 5 steps. f) A sixth step of communicating the adsorption tank B and the retention tank to transfer gas from the adsorption tank B to the retention tank, while supplying the raw material gas to the adsorption tank A and separating nitrogen gas. g) While releasing the residual gas in the adsorption tank B to the atmosphere,
A seventh step of continuously supplying the raw material gas to the adsorption tank A and separating nitrogen gas. h) Connecting the adsorption tank B and the retention tank to transfer gas from the retention tank to the adsorption tank B, while continuously supplying the raw material gas to the adsorption tank A and separating nitrogen gas. Eighth step. 2. For the adsorption tank A in the third step and the adsorption tank B in the seventh step after the residual gas is released into the atmosphere,
The nitrogen gas separation method according to claim 1, wherein nitrogen gas is passed through. [Claim 3] Two adsorption tanks A and B arranged in parallel.
In the apparatus for alternately supplying a raw material gas mainly composed of nitrogen gas and oxygen gas from one side of the tank and taking out the separated nitrogen gas from the other side, the nitrogen gas take-off portion of the adsorption tank A and the adsorption tank B a connecting pipe connecting the connecting pipes, two first valves provided on the connecting pipe, a branch pipe branching from between the first valves, and a retention tank provided at the end of the branch pipe;
and a second valve provided in the branch pipe.