JP2021107058A - Nitrogen gas separation method and nitrogen gas separation device - Google Patents

Abstract

To provide a nitrogen gas separation device and a nitrogen gas separation method capable of obtaining more product gases while suppressing the pressure reduction of a product gas to be taken out.SOLUTION: In a nitrogen gas separation method, a raw material gas containing nitrogen gas and oxygen gas is supplied under pressure into two or more adsorption towers 3A, 3B filled with an adsorbent; an adsorption step, a pressure equalization step, a desorption step and a pressure equalization step are repeated in each adsorption tower 3A, 3B; and a product gas containing nitrogen gas having higher concentration than the raw material gas is obtained. The adsorption step is performed in a second time longer than a first time being the execution time of the adsorption step for taking out the product gas having first concentration at a first flow rate when the product gas is taken out from a product tank at a second flow rate larger than the first flow rate.SELECTED DRAWING: Figure 1

Description

The present invention relates to a nitrogen gas separation method and a nitrogen gas separation device.

In recent years, nitrogen gas has been used in a wide range of fields from industrial gas used for heat treatment of metals, manufacturing of semiconductors, explosion-proof seals of chemical plants, etc. to filling gas for food preservation, and the amount used is increasing year by year. ing. As a method for producing this nitrogen gas, high-pressure air, which is a raw material gas, is sent into an adsorption tank filled with molecular sieve carbon, which is a speed-separating type adsorbent, and oxygen gas is adsorbed on the adsorbent to produce nitrogen gas. A so-called pressure fluctuation adsorption (PSA) type manufacturing method for separating is used. As such a nitrogen gas separation method by the PSA method, for example, the one described in Patent Document 1 is known.

The nitrogen gas separation method of Patent Document 1 aims to always stably supply high-purity nitrogen gas (for example, 99.99%).

Japanese Unexamined Patent Publication No. 2005-270953

On the other hand, there is a demand from users who want to take out a large amount of nitrogen gas even if the purity of nitrogen gas is not high. In order to meet such demands of users, a method of obtaining a large amount of low-purity nitrogen gas by increasing the flow rate of nitrogen gas taken out as a product gas can be considered.

However, in this case, since the amount of nitrogen gas taken out increases, the pressure of the nitrogen gas taken out as the product gas decreases, and there is a problem that the pressure of the product gas desired by the user cannot be obtained.

Therefore, the present invention has been made based on the above-mentioned problems, and an object of the present invention is a nitrogen gas separation method capable of obtaining a larger amount of product gas while suppressing a decrease in the pressure of the product gas to be taken out. And to provide a nitrogen gas separator.

In the nitrogen gas separation method according to the present invention, a raw material gas containing nitrogen gas and oxygen gas is supplied under pressure to two or more adsorption towers filled with an adsorbent, and each adsorption tower has an adsorption step and a pressure equalizing step. This is a nitrogen gas separation method for obtaining a product gas containing a higher concentration of nitrogen gas than the raw material gas by repeating the desorption step and the pressure equalizing step. When the product gas is taken out from the product tank at a second flow rate, which is a flow rate larger than the first flow rate, the adsorption step is the implementation time of the adsorption step for taking out the product gas having the first concentration at the first flow rate. Perform the second hour, which is longer than the first hour.

According to the present invention, since the product gas is taken out from the product tank at the second flow rate, which is a flow rate larger than the first flow rate, even a large amount of the product gas having a lower concentration than when the product gas having the first concentration is taken out. It is possible to meet the user's request to take out the product gas of. Moreover, since the adsorption step is performed for the second time, which is longer than the first time, which is the execution time of the adsorption step for taking out the product gas of the first concentration at the first flow rate, compared with the case of taking out the product gas of the first concentration. Therefore, it is possible to suppress a decrease in the pressure of the product gas.

In the above configuration, in the adsorption step, a part of the product gas may be sent as a cleaning gas from the adsorption tower attached to the adsorption step to the adsorption tower attached to the desorption step. The flow rate of the cleaning gas sent to the adsorption tower attached to the desorption step is set to a flow rate that decreases according to the ratio or difference of the length of the second time to the first time.

According to this configuration, in the adsorption step, the product gas is taken out from the product tank for a second time, which is longer than the first time, which is the execution time of the adsorption step for taking out the product gas of the first concentration at the first flow rate, but is washed. In order to reduce the gas flow rate, the amount of cleaning gas sent to the adsorption tower attached to the desorption process does not increase. Moreover, since the flow rate of the cleaning gas is set to be a flow rate that becomes smaller according to the ratio or difference of the length of the second time to the first time, cleaning when a part of the product gas having the first concentration is sent as the cleaning gas. It can be as much as the amount of gas. Therefore, in the adsorption step, it is possible to prevent a part of the product gas from being discharged as a cleaning gas more than necessary.

In the above configuration, in the adsorption step, a part of the product gas is sent as a cleaning gas from the adsorption tower attached to the adsorption step to the adsorption tower attached to the desorption step, while the cleaning gas is sent. Sending to the adsorption tower attached to the desorption step may be temporarily stopped. The stop time may be a time that increases according to the difference or ratio of the length of the second time to the first time.

According to this configuration, in the adsorption step, the product gas is taken out from the product tank for the second hour, which is longer than the first time, which is the execution time of the adsorption step for taking out the product gas of the first concentration at the first flow rate, but is desorbed. Since the sending of the cleaning gas to the adsorption tower attached to the process is temporarily stopped, the amount of the cleaning gas sent to the adsorption tower attached to the desorption process does not increase. Moreover, since the stop time is set to be a time that increases according to the difference or ratio of the length of the second time to the first time, the amount of the cleaning gas is a cleaning gas for a part of the product gas having the first concentration. The amount can be the same as the amount of cleaning gas when it is sent as. Therefore, in the adsorption step, it is possible to prevent a part of the product gas from being discharged as a cleaning gas more than necessary.

In the nitrogen gas separation method according to the present invention, a raw material gas containing nitrogen gas and oxygen gas is supplied under pressure to two or more adsorption towers filled with an adsorbent, and each adsorption tower has an adsorption step and a pressure equalizing step. This is a nitrogen gas separation method for obtaining a product gas containing a higher concentration of nitrogen gas than the raw material gas by repeating the desorption step and the pressure equalizing step. In the nitrogen gas separation method, the flow rate of the product gas is measured by a flow meter, the pressure of the product gas is detected by the pressure gauge, and the flow rate measured by the flow meter is the product gas having the first concentration in the adsorption step. Is larger than the first flow rate when the gas is taken out from the product tank for the first hour, and the pressure detected by the pressure gauge is the pressure of the product gas taken out from the product tank when the adsorption step for the first hour is performed. When the pressure is lower than a certain first pressure, the time of the suction step is extended so that the length of the suction step becomes the second time longer than the first time.

According to the present invention, since the product gas is taken out from the product tank at a flow rate larger than the first flow rate of the product gas when the product gas having the first concentration is taken out from the product tank, the nitrogen gas concentration in the taken out product gas is the first. It is lower than 1 concentration. When taking out this product gas, the flow rate measured by the flow meter is larger than the first flow rate when taking out the product gas of the first concentration from the product tank for the first hour in the adsorption step, and the pressure detected by the pressure gauge. Is lower than the first pressure, which is the pressure of the product gas taken out from the product tank when the adsorption step is performed for the first hour, so that the length of the adsorption step is longer than the first hour in the second hour. Extend the time of the adsorption process. Therefore, as compared with the case where the product gas having the first concentration is taken out at the first pressure, a larger amount of product gas can be obtained while suppressing a decrease in the pressure of the product gas.

The nitrogen gas separator according to the present invention contains a first adsorption tower filled with an adsorbent and at least introduced with a raw material gas containing nitrogen gas and oxygen gas, and an adsorbent filled with at least nitrogen gas and oxygen gas. A second adsorption tower into which the raw material gas is introduced, a control unit that controls the first adsorption tower and the second adsorption tower to repeatedly perform the adsorption step, the pressure equalizing step, the desorption step, and the pressure equalizing step, and the first A product tank into which a product gas containing nitrogen gas obtained from a raw material gas is introduced in the first adsorption tower and the second adsorption tower, a flow meter for measuring the flow rate of the product gas, and a pressure for detecting the pressure of the product gas. It is equipped with a total. In the control unit, the flow rate measured by the flow meter was larger than the first flow rate when the product gas having the first concentration was taken out from the product tank for the first hour in the adsorption step, and was detected by the pressure gauge. When the pressure is lower than the first pressure, which is the pressure of the product gas taken out from the product tank when the adsorption step of the first hour is performed, the length of the adsorption step is longer than that of the first hour. Extend the time of the adsorption process so that it is time.

According to the present invention, since the product gas is taken out from the product tank at a flow rate larger than the first flow rate of the product gas when the product gas having the first concentration is taken out from the product tank, the nitrogen gas concentration in the taken out product gas is the first. It is lower than 1 concentration. When taking out this product gas, the flow rate measured by the flow meter is larger than the first flow rate when taking out the product gas of the first concentration from the product tank for the first hour in the adsorption step, and the pressure detected by the pressure gauge. Is lower than the first pressure, which is the pressure of the product gas taken out from the product tank when the adsorption step of the first hour is performed, the length of the adsorption step becomes the second time longer than the first hour. As such, the time of the adsorption process is extended. Therefore, as compared with the case where the product gas having the first concentration is taken out at the first pressure, a larger amount of product gas can be obtained while suppressing a decrease in the pressure of the product gas.

In the above configuration, the control unit controls to send a part of the product gas as a cleaning gas from the adsorption tower attached to the adsorption step to the adsorption tower attached to the desorption step in the adsorption step. May be done. The flow rate of the cleaning gas sent to the adsorption tower attached to the desorption step may be a flow rate that becomes smaller depending on the ratio or difference of the length of the second time to the first time.

According to this configuration, in the adsorption step, the product gas is taken out from the product tank for a second time, which is longer than the first time, which is the execution time of the adsorption step for taking out the product gas of the first concentration at the first flow rate, but is washed. In order to reduce the gas flow rate, the amount of cleaning gas sent to the adsorption tower attached to the desorption process does not increase. Moreover, since the flow rate of the cleaning gas is set to be a flow rate that becomes smaller according to the ratio or difference of the length of the second time to the first time, cleaning when a part of the product gas having the first concentration is sent as the cleaning gas. It can be as much as the amount of gas. Therefore, in the adsorption step, it is possible to prevent a part of the product gas from being discharged as a cleaning gas more than necessary.

In the above configuration, the control unit controls to send a part of the product gas as a cleaning gas from the adsorption tower attached to the adsorption step to the adsorption tower attached to the desorption step in the adsorption step. On the other hand, control may be performed to temporarily stop sending the cleaning gas to the adsorption tower attached to the desorption step. The stop time may be a time that increases according to the difference or ratio of the length of the second time to the first time.

According to this configuration, in the adsorption step, the product gas is taken out from the product tank for the second hour, which is longer than the first time, which is the execution time of the adsorption step for taking out the product gas of the first concentration at the first flow rate, but is desorbed. Since the sending of the cleaning gas to the adsorption tower attached to the process is temporarily stopped, the amount of the cleaning gas sent to the adsorption tower attached to the desorption process does not increase. Moreover, since the stop time is set to be a time that increases according to the difference or ratio of the length of the second time to the first time, the amount of the cleaning gas is a cleaning gas for a part of the product gas having the first concentration. The amount can be the same as the amount of cleaning gas when it is sent as. Therefore, in the adsorption step, it is possible to prevent a part of the product gas from being discharged as a cleaning gas more than necessary.

According to the present invention, more product gas can be obtained while suppressing a decrease in the pressure of the product gas to be taken out.

It is a figure which shows the structure of the nitrogen gas separation apparatus which concerns on 1st Embodiment of this invention. It is a figure which shows the structure of the nitrogen gas separation apparatus which concerns on 2nd Embodiment of this invention.

Hereinafter, each embodiment of the present invention will be described with reference to the drawings. However, for convenience of explanation, each figure referred to below is a simplified representation of the main components required for explaining the nitrogen gas separator according to the embodiment of the present invention. Therefore, the nitrogen gas separator according to each embodiment of the present invention may include any component not shown in each of the figures referenced herein. Hereinafter, the nitrogen gas separation device of the first embodiment will be described with reference to FIG.

(First Embodiment)
The nitrogen gas separation device 10 separates nitrogen gas from a raw material gas containing nitrogen gas and oxygen gas to obtain a product gas containing nitrogen gas. As the raw material gas, for example, air can be used, but the raw material gas is not limited to this, and any gas containing at least nitrogen gas and oxygen gas may be used.

As shown in FIG. 1, the nitrogen gas separation device 10 includes a raw material gas supply unit 2, a first adsorption tower 3A, a second adsorption tower 3B, a product gas take-out line L3, a product tank 4, and a control unit 20. And. A total of three or more first and second adsorption towers 3A and 3B may be provided.

The raw material gas supply unit 2 is a first unit that connects the gas supply machine 1, the raw material gas supply line L1 connected to the discharge port of the gas supply machine 1, the raw material gas supply line L1 and the inlet of the first adsorption tower 3A. It has an adsorption tower inlet line L1A and a second adsorption tower inlet line L1B connecting the raw material gas supply line L1 and the inlet of the second adsorption tower 3B.

The gas supply machine 1 sucks the raw material gas from the suction port, pressurizes the sucked raw material gas and discharges it from the discharge port, and passes through the raw material gas supply line L1 and the first and second adsorption tower inlet lines L1A and L1B. The raw material gas at a predetermined pressure is supplied to the first and second adsorption towers 3A and 3B. When air is used as the raw material gas, the gas supply machine 1 sucks air from the atmosphere. When a gas other than air is used as the raw material gas, for example, the gas supply machine 1 is connected to the raw material gas source 7 containing the raw material gas in a container (see FIG. 1). The gas supply machine 1 may be composed of a compressor, a booster, or a blower.

A first intake valve CV1 is provided on the first suction tower inlet line L1A. A second intake valve CV3 is provided on the second suction tower inlet line L1B. Further, a first pressure equalizing line L7 connecting the first suction tower inlet line L1A and the second suction tower inlet line L1B is provided. A first pressure equalizing valve CV7 is provided on the first pressure equalizing line L7. The raw material gas discharge line L2 is connected to the first and second adsorption tower inlet lines L1A and L1B.

The raw material gas discharge line L2 includes a first discharge line L2A connected to the downstream side of the first intake valve CV1 on the first suction tower inlet line L1A and a second intake valve CV3 on the second suction tower inlet line L1B. It has a second discharge line L2B connected to the downstream side and a discharge merging line L2C connected to a confluence of the first discharge line L2A and the second discharge line L2B.

The first adsorption tower 3A and the second adsorption tower 3B are filled with an adsorbent that adsorbs oxygen gas. When the raw material gas is supplied, the first adsorption tower 3A and the second adsorption tower 3B adsorb the oxygen gas in the raw material gas to the adsorbent to generate a product gas containing nitrogen gas with high purity. As the adsorbent filled in the first and second adsorption towers 3A and 3B, any adsorbent can be used as long as it can adsorb oxygen gas, and for example, molecular sieve carbon can be used.

Molecular sieve carbon is a wood-based or coal-based carbon whose pore diameter is adjusted to about 3 to 5 angstroms by carbonizing raw materials such as charcoal, coal, coke, coconut shell, resin, and pitch having a large number of pores at high temperature. It is a resin-based or pitch-based adsorbent. Such molecular sieve carbon has a property of adsorbing oxygen gas more easily than nitrogen gas, and has a property of selectively adsorbing oxygen gas from a mixed gas containing nitrogen gas such as air and oxygen gas. .. Further, the molecular sieve carbon has an increased ability to adsorb oxygen gas under high pressure conditions. Therefore, the molecular sieve carbon can adsorb a large amount of oxygen gas by pressurizing the insides of the first and second adsorption towers 3A and 3B, and then by depressurizing the insides of the first and second adsorption towers 3A and 3B. Oxygen gas can be desorbed.

The product gas generated in the first and second adsorption towers 3A and 3B is supplied to the user through the product gas take-out line L3. The product gas take-out line L3 includes a first suction tower outlet line L3A connected to the outlet of the first suction tower 3A, a second suction tower outlet line L3B connected to the outlet of the second suction tower 3B, and a first suction. It has a product gas merging line L3C at which the tower outlet line L3A and the second adsorption tower outlet line L3B merge.

A first take-out valve CV5 is provided on the first suction tower outlet line L3A. A second take-out valve CV6 is provided on the second suction tower outlet line L3B. Further, a second pressure equalizing line L8 is provided to connect the upstream side of the first take-out valve CV5 in the first suction tower outlet line L3A and the upstream side of the second take-out valve CV6 in the second suction tower outlet line L3B. ing. A second pressure equalizing valve CV8 is provided on the second pressure equalizing line L8. These valves CV1 to CV8 are composed of valves that can be opened and closed.

A cleaning gas flow rate adjusting line L5 is connected to the second pressure equalizing line L8 so as to bypass the second pressure equalizing valve CV8 in the second pressure equalizing line L8. The cleaning gas flow rate adjusting line L5 is configured to have a smaller pipe diameter than the second pressure equalizing line L8. That is, since the cleaning gas flow rate adjusting line L5 is a line for cleaning gas, the flow rate of the cleaning gas flowing as a part of the product gas is set to be smaller than the flow rate of the product gas flowing through the second pressure equalizing line L8.

The cleaning gas flow rate adjusting line L5 is provided with a cleaning gas flow rate adjusting valve 5. The cleaning gas flow rate adjusting valve 5 sends a part of the product gas as cleaning gas from the adsorption tower attached to the adsorption step to the adsorption tower attached to the desorption step, and enters the adsorption tower attached to the desorption step. It is provided to promote the discharge of residual raw material gas. The cleaning gas flow rate adjusting valve 5 is configured so that the opening degree of the cleaning gas flow rate adjusting line L5 can be adjusted by the control of the control unit 20 described later. The cleaning gas flow rate adjusting valve 5 and the cleaning gas flow rate adjusting line L5 may be omitted. That is, the configuration may be such that the cleaning gas does not flow.

A product tank 4 is arranged on the product gas merging line L3C. The product tank 4 is composed of a container having a primary storage space for appropriately storing the supplied product gas, and leveles the nitrogen gas concentration in the product gas stored in the product tank 4.

An oxygen concentration meter 21, a flow meter 22, and a product gas flow rate adjusting valve CV9 are provided on the downstream side of the product tank 4 in the product gas merging line L3C. The product gas flow rate adjusting valve CV9 is configured so that the opening degree can be adjusted. By adjusting the opening degree of the product gas flow rate adjusting valve CV9, the flow rate of the product gas taken out from the product tank 4 can be adjusted. The flow rate of the product gas taken out from the product tank 4 can be appropriately set according to the needs of the user.

The oxygen concentration meter 21 is for measuring the oxygen gas concentration contained in the product gas taken out from the product tank 4 and calculating the nitrogen gas concentration in the product gas. The oxygen concentration meter 21 is arranged on the downstream side of the product tank 4 on the product gas merging line L3C.

The flow meter 22 measures the flow rate of the product gas taken out from the product tank 4. The flow meter 22 is arranged between the oxygen concentration meter 21 and the product gas flow rate adjusting valve CV9 on the product gas confluence line L3C. The flow meter 22 is for grasping the flow rate of the product gas taken out from the product tank 4, and measures the flow rate in the product gas taken out from the product tank 4. The flow meter 22 may be arranged between the product tank 4 and the oxygen concentration meter 21 on the product gas merging line L3C.

The control unit 20 is electrically connected to the valves CV1 to CV8 and the cleaning gas flow rate adjusting valve 5, and performs the suction step, the pressure equalizing step, the desorption step, and the pressure equalizing step in the first and second suction towers 3A and 3B. The opening and closing of the valves CV1 to CV8 and the opening degree of the cleaning gas flow rate adjusting valve 5 are controlled so that the operation can be repeated.

Specifically, when the first suction tower 3A is attached to the suction step and the second suction tower 3B is attached to the attachment / detachment step, the control unit 20 uses the first intake valve CV1, the first take-out valve CV5, and the second discharge valve CV4. At the same time as opening, the second intake valve CV3, the first take-out valve CV6, and the first discharge valve CV2 are closed.

When the first suction tower 3A is attached to the attachment / detachment step and the second suction tower 3B is attached to the suction step, the control unit 20 closes the first intake valve CV1, the first take-out valve CV5, and the second discharge valve CV4, and the second suction valve CV4. The intake valve CV3, the second take-out valve CV6, and the first discharge valve CV2 are opened.

When the first and second suction towers 3A and 3B are subjected to the pressure equalizing step, the control unit 20 closes the first intake valve CV1, the second intake valve CV3, the first take-out valve CV5, and the second take-out valve CV6. , The first pressure equalizing valve CV7 and the second pressure equalizing valve CV8 are opened.

When the nitrogen gas separation device 10 is started, the control unit 20 controls to maintain the open / closed state of the valves CV1 to CV8 so that each step is performed for a preset time. Further, when the nitrogen gas separation device 10 is started, the control unit 20 controls to adjust the cleaning gas flow rate adjusting valve 5 to a preset opening degree.

Next, a nitrogen gas separation method using the nitrogen gas separation device 10 configured as described above will be described.

First, when the nitrogen gas separation device 10 is started, the adsorption step, the pressure equalizing step, the desorption step, and the pressure equalizing step are repeatedly performed for a preset time. At this time, the opening degree of the cleaning gas flow rate adjusting valve 5 is also adjusted to a preset opening degree in the adsorption step.

For example, when the adsorption step is performed in the first adsorption tower 3A, the desorption step is performed in the second adsorption tower 3B. The adsorption step is a step of separating nitrogen gas from the raw material gas to generate a product gas containing nitrogen gas. The desorption step is a step of regenerating the adsorbent by desorbing the oxygen gas adsorbed on the adsorbent from the adsorbent.

In the suction step of the first suction tower 3A and the attachment / detachment step of the second suction tower 3B, the first intake valve CV1, the first take-out valve CV5, the second discharge valve CV4, and the cleaning gas flow rate adjusting valve 5 are opened, and the first discharge It is started by closing the valve CV2, the second intake valve CV3, the first take-out valve CV6, and the first and second pressure equalizing valves CV7 and CV8.

In the adsorption step of the first adsorption tower 3A, first, the raw material gas is supplied from the raw material gas source 7 to the first adsorption tower 3A through the raw material gas supply line L1 and the first adsorption tower inlet line L1A. In the raw material gas supplied to the first adsorption tower 3A, the oxygen gas in the raw material gas is adsorbed by the adsorbent, so that the nitrogen gas is separated from the raw material gas to generate a product gas containing the nitrogen gas. The product gas generated in the first adsorption tower 3A is supplied to the product tank 4 through the first adsorption tower outlet line L3A and the product gas merging line L3C, leveled, and flows out from the product tank 4 through the product gas merging line L3C. .. A part of the product gas generated in the first adsorption tower 3A is sent to the second adsorption tower 3B as a cleaning gas via the cleaning gas flow rate adjusting line L5.

On the other hand, in the desorption step of the second adsorption tower 3B, the raw material gas in the second adsorption tower 3B passes through the second adsorption tower inlet line L1B, the second discharge line L2B, and the discharge confluence line L2C together with the cleaning gas in the second adsorption tower. It is discharged to the outside by a pressure difference lower than the pressure in 3B. As a result, the pressure inside the second adsorption tower 3B is reduced, and the oxygen gas adsorbed on the adsorbent is desorbed from the adsorbent. The desorbed oxygen gas is discharged from the first adsorption tower 3B together with the raw material gas and the cleaning gas. As a result, the adsorbent in the first adsorption tower 3B is regenerated.

When the adsorption step and the desorption step are completed, the pressure equalizing step of moving the gas in the first adsorption tower 3A to the second adsorption tower 3B is started. The pressure equalizing step is started by closing the first intake valve CV1, the first take-out valve CV5, the second discharge valve CV4, and the cleaning gas flow rate adjusting valve 5, and opening the first and second pressure equalizing valves CV7 and CV8. NS.

In the pressure equalizing step, the gas filled in the first adsorption tower 3A moves to the second adsorption tower 3B through the first pressure equalizing line L7 and the second pressure equalizing line L8.

When the pressure equalizing step is completed, the desorption step of the first suction tower 3A and the suction step of the second suction tower 3B are performed. In the attachment / detachment step of the first suction tower 3A and the suction step of the second suction tower 3B, the first discharge valve CV2, the second intake valve CV3, the second take-out valve CV6, and the cleaning gas flow rate adjusting valve 5 are opened, and the first and second suction towers 3B are opened. It is started by closing the second pressure equalizing valves CV7 and CV8.

In the adsorption step of the second adsorption tower 3B, the raw material gas is supplied to the second adsorption tower 3B from the raw material gas source 7 through the raw material gas supply line L1 and the second adsorption tower inlet line L1B. At this time, the oxygen gas in the raw material gas is adsorbed on the adsorbent, and the nitrogen gas is separated from the raw material gas to generate a product gas containing the nitrogen gas. The product gas generated in the second adsorption tower 3B is supplied to the product tank 4 through the second adsorption tower outlet line L3B and the product gas merging line L3C, leveled, and flows out from the product tank 4 through the product gas merging line L3C. NS. A part of the product gas having the second concentration generated in the second adsorption tower 3B is sent to the first adsorption tower 3A via the cleaning gas flow rate adjusting line L5.

On the other hand, in the desorption step of the first adsorption tower 3A, the raw material gas in the first adsorption tower 3A passes through the first adsorption tower inlet line L1A, the first discharge line L2A, and the discharge confluence line L2C together with the cleaning gas in the first adsorption tower. It is discharged to the outside by a pressure difference lower than the pressure in 3A. As a result, the pressure in the first adsorption tower 3A is reduced, and the oxygen gas adsorbed on the adsorbent is desorbed from the adsorbent. The desorbed oxygen gas is discharged from the first adsorption tower 3A together with the raw material gas and the cleaning gas. As a result, the adsorbent in the first adsorption tower 3A is regenerated.

When the desorption step of the first adsorption tower 3A and the adsorption step of the second adsorption tower 3B are completed, a pressure equalizing step of moving the gas in the second adsorption tower 3B to the first adsorption tower 3A is performed.

When the pressure equalization step is completed, the suction step of the first suction tower 3A and the desorption step of the second suction tower 3B are performed. After that, the above cycle is repeated in the first and second adsorption towers 3A and 3B.

In the nitrogen gas separator 10, the product gas having the first concentration is taken out from the product tank 4 at the first flow rate, and the product gas having the second concentration lower than the first concentration is taken out from the product tank at the second flow rate larger than the first flow rate. It can also be taken out from the tank 4. The first concentration is, for example, the nitrogen gas concentration in the product gas in the range of 99% or more and 99.999% or less. The first concentration may be, for example, higher than 99% and less than or equal to 99.999%. The second concentration is a concentration lower than the first concentration, for example, a concentration in the range of 90% or more and 99% or less. The first flow rate and the second flow rate may be appropriately set according to the size and performance of the nitrogen gas separator 10, respectively, but the second flow rate is a flow rate larger than the first flow rate, for example, the first flow rate. It may be about 1.2 times to 10.0 times.

When taking out the product gas of the first concentration from the product tank 4 at the first flow rate, the control unit 20 starts the nitrogen gas separation device 10 in the mode of taking out the product gas of the first concentration at the first flow rate, and at the same time, starts the product. The opening degree of the product gas flow rate adjusting valve CV9 is adjusted to the first opening degree so that the flow rate of the product gas taken out from the tank 4 becomes the first flow rate. At this time, the control unit 20 performs the adsorption step for the first time, which is a preset time, and adjusts the cleaning gas flow rate adjusting valve 5 to the preset opening degree.

On the other hand, when the product gas having the second concentration is taken out from the product tank 4 at the second flow rate, the control unit 20 starts the nitrogen gas separation device 10 in the mode of taking out the product gas having the second concentration at the second flow rate. The opening degree of the product gas flow rate adjusting valve CV9 is adjusted to the second opening degree so that the flow rate of the product gas taken out from the product tank 4 becomes a second flow rate larger than the first flow rate. At this time, the control unit 20 performs the adsorption step for the second time, which is a preset time. The second hour is longer than the first hour. At the same time, the control unit 20 adjusts the cleaning gas flow rate adjusting valve 5 to a preset opening degree. At this time, when the adsorption step of the first hour is performed so that the opening degree of the cleaning gas flow rate adjusting valve 5 is the same as the amount of the cleaning gas when the adsorption step of the first hour is performed. It is adjusted to be smaller than.

In the initial stage of the adsorption step of the first adsorption tower 3A, the oxygen gas is sufficiently adsorbed by the adsorbent, so that the product gas containing high-purity nitrogen gas is supplied from the first adsorption tower 3A to the product tank 4. NS.

In the adsorption step, the adsorption capacity of the adsorbent decreases as the oxygen gas is adsorbed by the adsorbent, so the concentration of nitrogen gas in the product gas supplied from the first adsorption tower 3A to the product tank 4 is increased. It gradually decreases. In the adsorption step, the time set so as to end the adsorption step when the nitrogen gas concentration does not fall below an acceptable concentration is the first hour. When the product gas is taken out from the product tank 4 at the first flow rate, the nitrogen gas concentration in the product gas taken out from the product tank 4 when the nitrogen gas separation device 10 is operated in a cycle in which the adsorption step time is set to the first hour. The average concentration of is the first concentration. When the product gas is taken out from the product tank 4 at the first flow rate, the average pressure of the product gas taken out from the product tank 4 when the nitrogen gas separation device 10 is operated in a cycle in which the adsorption step time is set to the first hour is the first. 1 pressure. The first flow rate, the first time, and the first concentration can be appropriately set according to the user's request.

When the product gas is taken out from the product tank 4 at a second flow rate larger than the first flow rate, the nitrogen gas concentration in the product gas decreases and the pressure of the product gas in the product tank 4 tends to decrease. Therefore, by performing the adsorption step for the second time, which is longer than the first time, the pressure of the product gas in the product tank 4 can be raised to a pressure substantially equal to the first pressure. Therefore, when the product gas is taken out from the product tank 4 at the second flow rate, the adsorption step for the second time, which is longer than the first time, is performed. As a result, the concentration of nitrogen gas in the product gas taken out from the product tank 4 at the second flow rate is lower than that when the product gas is taken out from the product tank 4 at the first flow rate, but it is taken out from the product tank 4 at the second flow rate. It is possible to prevent the pressure of the product gas from being lowered as compared with the first pressure of the product gas taken out from the product tank 4 at the first flow rate.

When taking out from the product tank 4 at the second flow rate, the opening degree of the cleaning gas flow rate adjusting valve 5 is adjusted. At this time, the opening degree of the cleaning gas flow rate adjusting valve 5 is such that the amount of cleaning gas is about the same as the amount of cleaning gas used in the entire adsorption process when the product gas is taken out from the product tank 4 at the first flow rate. In addition, the flow rate of the cleaning gas is adjusted to decrease according to the ratio of the length of the second hour to the first hour.

For example, when the length of the adsorption process in the first hour is set to 40 seconds and the length of the adsorption process in the second hour is set to 80 seconds, the length of the adsorption process in the second hour is the second. It is twice the length of the one-hour adsorption process. Therefore, the opening degree of the cleaning gas flow rate adjusting valve 5 when performing the adsorption step for the second hour is halved from the opening degree of the cleaning gas flow rate adjusting valve 5 when performing the adsorption step for the first hour. .. The opening degree of the cleaning gas flow rate adjusting valve 5 when performing the adsorption step for the second hour is halved from the opening degree of the cleaning gas flow rate adjusting valve 5 when performing the adsorption step for the first hour. It does not have to be adjusted.

Further, when the length of the adsorption step in the first hour is set to 40 seconds and the length of the adsorption step in the second hour is set to 120 seconds, the length of the adsorption step in the second hour is the second. It is three times the length of the one-hour adsorption process. Therefore, the opening degree of the cleaning gas flow rate adjusting valve 5 when performing the adsorption step for the second hour is set to 1/3 of the opening degree of the cleaning gas flow rate adjusting valve 5 when performing the adsorption step for the first hour. .. In this case, the opening degree of the cleaning gas flow rate adjusting valve 5 when performing the adsorption step for the second hour is 1/3 of the opening degree of the cleaning gas flow rate adjusting valve 5 when performing the adsorption step for the first hour. It does not have to be adjusted to be. For example, the opening degree of the cleaning gas flow rate adjusting valve 5 may be adjusted so that the flow rate of the cleaning gas becomes smaller according to the difference in length between the first time and the second time.

In the nitrogen gas separation method of the first embodiment, the product gas can be taken out from the product tank 4 at a second flow rate, which is a flow rate larger than the first flow rate, so that it is lower than the case where the product gas having the first concentration is taken out. It is possible to meet the user's desire to take out a large amount of product gas even if the product gas has a high concentration. Moreover, since the adsorption step is performed for the second time, which is longer than the first time, which is the execution time of the adsorption step for taking out the product gas of the first concentration at the first flow rate, compared with the case of taking out the product gas of the first concentration. Therefore, it is possible to suppress a decrease in the pressure of the product gas.

In the nitrogen gas separation method of the first embodiment, in the adsorption step, the product gas is stored in the product tank for a second hour, which is longer than the first hour, which is the implementation time of the adsorption step for taking out the product gas having the first concentration at the first flow rate. However, since the flow rate of the cleaning gas is reduced, the amount of cleaning gas sent to the adsorption tower attached to the desorption step does not increase. Moreover, since the flow rate of the cleaning gas is set to be a flow rate that becomes smaller according to the ratio or difference of the length of the second time to the first time, cleaning when a part of the product gas having the first concentration is sent as the cleaning gas. It can be as much as the amount of gas. Therefore, in the adsorption step, it is possible to prevent a part of the product gas from being discharged as a cleaning gas more than necessary.

The nitrogen gas separation method using the nitrogen gas separation device 10 described above is an embodiment of the present invention, and the specific configuration thereof can be appropriately changed without departing from the spirit of the present invention. Hereinafter, a nitrogen gas separation method using the nitrogen gas separation device 10 according to the modified example of the first embodiment will be described. In the modified example of the first embodiment, the elements corresponding to the first embodiment are designated by the same reference numerals as those of the first embodiment, and the description thereof will be omitted. Hereinafter, the differences from the first embodiment will be described.

(Modified example of the first embodiment)
In the first embodiment, the flow rate of the cleaning gas is controlled to be smaller according to the ratio or difference of the length of the second time to the first time, but the cleaning gas is adsorbed in the desorption step. It may be controlled to temporarily stop sending to the tower. In this case, the cleaning gas flow rate adjusting valve 5 may be configured as a simple on-off valve. The time to stop is controlled to a time that increases according to the difference in length between the first time and the second time. For example, when the first time is 40 seconds and the second time is set to 80 seconds, the difference in length of the second time from the first time is 40 seconds. In this case, the stop time is set to 40 seconds. Further, when the first time is 40 seconds and the second time is set to 120 seconds, the difference in the length of the second time from the first time is 80 seconds. In this case, the stop time is set to 80 seconds. The time for stopping the sending of the cleaning gas to the adsorption tower attached to the desorption step does not have to be strictly adjusted to these times. For example, the time to stop may be adjusted to increase according to the ratio of the length of the second time to the first time.

In the modified example of the first embodiment, in the adsorption step, the product gas is taken out from the product tank for the second hour, which is longer than the first hour, which is the implementation time of the adsorption step for taking out the product gas of the first concentration at the first flow rate. However, since the sending of the cleaning gas to the adsorption tower attached to the desorption step is temporarily stopped, the amount of the cleaning gas sent to the adsorption tower attached to the desorption step does not increase. Moreover, since the stop time is set to be a time that increases according to the difference or ratio of the length of the second time to the first time, the amount of the cleaning gas is a cleaning gas for a part of the product gas having the first concentration. The amount can be the same as the amount of cleaning gas when it is sent as. Therefore, in the adsorption step, it is possible to prevent a part of the product gas from being discharged as a cleaning gas more than necessary.

(Second Embodiment)
Next, a nitrogen gas separation method using the nitrogen gas separation device 200 and the nitrogen gas separation device 200 of the second embodiment will be described. In the second embodiment, the elements corresponding to the first embodiment are designated by the same reference numerals as those in the first embodiment, and the description of the first embodiment is incorporated. Hereinafter, the differences between the nitrogen gas separator 200 of the second embodiment and the first embodiment will be described.

As shown in FIG. 2, the nitrogen gas separator 200 of the second embodiment is further provided with a pressure gauge 201 for detecting the pressure of the product gas, and the flow rate measured by the flow meter 22 and the pressure gauge 201 are detected. It differs from the nitrogen gas separation device 10 of the first embodiment in that it is determined whether or not to perform the adsorption step for the second time, which is longer than the first time, based on the pressure.

The flow meter 22 is connected to the control unit 20 and is configured to transmit flow rate information indicating the measured flow rate to the control unit 20.

The pressure gauge 201 is installed in the product tank 4 so as to measure the pressure of the product gas in the product tank 4. The pressure gauge 201 may be installed on the downstream side of the product tank 4 in the product gas merging line L3C. The pressure gauge 201 is connected to the control unit 20 and is configured to transmit pressure information indicating the detected pressure to the control unit 20.

When the flow rate information received from the flow meter 22 indicates the first flow rate, the control unit 20 controls to perform the adsorption step for the first hour.

In the control unit 20, when the flow rate measured by the flow meter 22 is larger than the first flow rate and the pressure detected by the pressure gauge 201 is lower than the first pressure, the length of the suction step is the second time. Control is performed to extend the time of the adsorption step so as to have the length of. Specifically, the control unit 20 controls to maintain the open / closed state of the valves CV1 to CV8 when the suction step is performed for the first hour until the suction step elapses for the second time. Since the method of adjusting the cleaning gas flow rate adjusting valve 5 is the same as that of the first embodiment, it will be omitted.

In the nitrogen gas separation device 200 and the nitrogen gas separation method of the second embodiment, the product gas is taken out from the product tank 4 at a second flow rate larger than the first flow rate of the product gas when the product gas having the first concentration is taken out from the product tank 4. Since it is taken out from, the nitrogen gas concentration in the product gas taken out is lower than the first concentration. When the product gas is taken out, if the flow rate measured by the flow meter 22 is larger than the first flow rate and the pressure detected by the pressure gauge 201 is lower than the first pressure, the length of the adsorption step is the second. Extend the time of the adsorption process to the length of time. Therefore, as compared with the case where the product gas having the first concentration is taken out from the product tank 4 at the first pressure, more product gas can be obtained while suppressing a decrease in the pressure of the product gas.

In the nitrogen gas separation device 200 and the nitrogen gas separation method of the second embodiment, the flow rate measured by the flow meter 22 is larger than the first flow rate, and the pressure detected by the pressure gauge 201 is lower than the first pressure. In this case, the time of the suction step was extended so that the length of the suction step was the length of the second time, but the suction step was controlled to be performed until the pressure detected by the pressure gauge 201 reached the first pressure. May be done.

In this way, the pressure of the product gas of the second concentration taken out from the product tank 4 at the second flow rate larger than the first flow rate becomes the same as the pressure of the product gas taken out from the product tank 4 at the first flow rate. Be retained. Therefore, it becomes easy to obtain a larger amount of product gas while suppressing a decrease in the pressure of the product gas to be taken out.

The pressure of the product gas taken out from the product tank 4 in the adsorption step is based on the assumption that the flow rate and pressure of the raw material gas supplied from the gas supply machine 1 to the first and second adsorption towers 3A and 3B are constant. , It changes according to the flow rate of the product gas taken out from the product tank 4 and the time of the adsorption step. Hereinafter, an example specifically carried out using the nitrogen gas separator 10 shown in FIG. 1 will be described.

(Example 1)
In the first embodiment, the pressure and the flow rate of the air as the raw material gas supplied from the gas supply machine 1 to the first and second adsorption towers 3A and 3B are 0.725 MPa and 5.75 m ³ / min, respectively. The gas supply machine 1 was set. The product gas flow rate adjusting valve CV9 was adjusted so that the second flow rate measured by the flow meter 22 in the adsorption step was 100 Nm ^{3 / h.} This flow rate is larger than the first flow rate (60 Nm ³ / h). Further, the second time, which is the time of the adsorption step, was set to 60 seconds.

(Example 2)
Example 2 is different from Example 1 in that the second time, which is the time of the adsorption step, is set to 80 seconds. Other conditions of Example 2 are the same as those of Example 1.

(Example 3)
In Example 3, the second flow rate is ^{set to a larger flow rate (125 Nm 3} / h) than in Examples 1 and 2, and the second time, which is the time of the adsorption step, is longer than in Examples 1 and 2. It differs from Examples 1 and 2 in that it is set to (180 seconds).

(Comparison example)
The comparative example differs from Examples 1 and 2 in that the second time, which is the time of the adsorption step, is set to the same length (40 seconds) as the first time. Other conditions of the comparative example are the same as those of the first and second embodiments.

Table 1 shows the nitrogen gas concentration calculated from the oxygen gas concentration measured by the oxygen gas concentration meter 21 and the average pressure of the product gas in the product tank 4 in Examples 1 to 3 and Comparative Example, respectively.

In this test, as a reference, the first flow rate of the product gas was set to 60 Nm ³ / h, the first concentration was set to 99.99%, and the first time, which is the adsorption process time, was set to 40 seconds. As shown in Table 1, in Example 1, the ^{nitrogen gas separation device 10 is operated in a cycle in which the flow rate of the product gas is 100 Nm 3} / h (second flow rate) and the adsorption process time is 60 seconds (second time). The average concentration of the product nitrogen gas was 99%, and the average pressure of the product gas was 0.51 MPa. Therefore, in Example 1, the average pressure of the product gas having the second concentration in the product tank 4 is the product gas having the first concentration (99.99%) at ^{the first flow rate (60 Nm 3 / h).} It can be seen that the average pressure (0.55 MPa) in the product tank 4 at the time of taking out (reference time) in the adsorption process time of time (40 seconds) is almost the same.

In Example 2, it can be seen that the average pressure of the product gas having the second concentration in the product tank 4 is 0.62 MPa, which is almost the same as the average pressure of the product gas at the reference time (0.55 MPa) (Table). 1).

Similarly to the above, in Example 3, the average pressure of the product gas having the second concentration in the product tank 4 is 0.55 MPa, which is about the same as the average pressure (0.55 MPa) in the product tank 4 at the time of reference. (See Table 1). From this, the average pressure of the product gas of the second concentration in the product tank 4 is the product at the time of reference by increasing the length of the adsorption process even if the flow rate of the product gas taken out from the product tank 4 is increased. It can be seen that the pressure can be set to the same level as the average pressure in the tank 4.

In the comparative example, the average pressure of the product gas having the second concentration in the product tank 4 is 0.37 MPa, which is lower than the average pressure (0.55 MPa) in the product tank 4 at the time of reference (5). See Table 1). In the comparative example, the adsorption process time is set to the same length as the first hour (40 seconds) even though the product gas is taken out from the product tank 4 at a second flow rate larger than the first flow rate. Therefore, it is considered that the adsorption step was completed before the average pressure of the product gas having the second concentration in the product tank 4 rose to the same pressure as the average pressure in the product tank 4 at the reference time.

From this, even if the product gas is taken out from the product tank 4 at a second flow rate larger than the first flow rate, the length of the adsorption step is longer than the first time in the second hour as in Examples 1 to 3. By setting the length, it is possible to suppress a decrease in the pressure of the product gas as compared with the case where the product gas having the first concentration is taken out.

3A 1st adsorption tower 3B 2nd adsorption tower 4 Product tank 10 Nitrogen gas separator 20 Control unit 22 Flow meter 201 Pressure gauge

Claims (7)

A raw material gas containing nitrogen gas and oxygen gas is supplied under pressure to two or more adsorption towers filled with an adsorbent, and each adsorption tower repeats an adsorption step, a pressure equalizing step, a desorption step, and a pressure equalizing step. A nitrogen gas separation method for obtaining a product gas containing a higher concentration of nitrogen gas than the raw material gas.
When the product gas is taken out from the product tank at a second flow rate, which is a flow rate larger than the first flow rate, the adsorption step is the implementation time of the adsorption step for taking out the product gas having the first concentration at the first flow rate. Do the second hour, which is longer than the first hour,
Nitrogen gas separation method. In the adsorption step, a part of the product gas is sent as a cleaning gas from the adsorption tower attached to the adsorption step to the adsorption tower attached to the desorption step.
The flow rate of the cleaning gas sent to the adsorption tower attached to the desorption step is set to a flow rate that becomes smaller according to the ratio or difference of the length of the second time to the first time, according to claim 1. The nitrogen gas separation method according to the above. In the adsorption step, a part of the product gas is sent as a cleaning gas from the adsorption tower attached to the adsorption step to the adsorption tower attached to the desorption step, while the cleaning gas is attached to the desorption step. Temporarily stop sending to the adsorption tower
The nitrogen gas separation method according to claim 1, wherein the stop time is a time that increases according to the difference or ratio of the length of the second time to the first time. A raw material gas containing nitrogen gas and oxygen gas is supplied under pressure to two or more adsorption towers filled with an adsorbent, and each adsorption tower repeats an adsorption step, a pressure equalizing step, a desorption step, and a pressure equalizing step. A nitrogen gas separation method for obtaining a product gas containing a higher concentration of nitrogen gas than the raw material gas.
Measure the flow rate of the product gas with a flow meter and
The pressure of the product gas is detected by a pressure gauge,
The flow rate measured by the flow meter is larger than the first flow rate when the product gas having the first concentration is taken out from the product tank for the first hour in the adsorption step, and the pressure detected by the pressure gauge is the first. When the pressure of the product gas taken out from the product tank is lower than the first pressure when the time adsorption step is performed, the length of the adsorption step is set to the second time longer than the first time. A nitrogen gas separation method that extends the time of the adsorption process. The first adsorption tower, which is filled with an adsorbent and introduces a raw material gas containing at least nitrogen gas and oxygen gas,
A second adsorption tower filled with an adsorbent and into which a raw material gas containing at least nitrogen gas and oxygen gas is introduced.
A control unit that controls to repeatedly perform the adsorption step, the pressure equalizing step, the desorption step, and the pressure equalizing step in the first suction tower and the second suction tower.
A product tank into which a product gas containing a nitrogen gas obtained from a raw material gas is introduced in the first adsorption tower and the second adsorption tower, and a product tank.
A flow meter that measures the flow rate of the product gas and
A pressure gauge for detecting the pressure of the product gas is provided.
The control unit
The flow rate measured by the flow meter is larger than the first flow rate when the product gas having the first concentration is taken out from the product tank for the first hour in the adsorption step, and the pressure detected by the pressure gauge is the first. When the pressure of the product gas taken out from the product tank is lower than the first pressure when the time adsorption step is performed, the length of the adsorption step is set to the second time longer than the first time. A nitrogen gas separator that extends the time of the adsorption process. In the adsorption step, the control unit controls to send a part of the product gas as a cleaning gas from the adsorption tower attached to the adsorption step to the adsorption tower attached to the desorption step.
The flow rate of the cleaning gas sent to the adsorption tower attached to the desorption step is set to a flow rate that becomes smaller according to the ratio or difference of the length of the second time to the first time, according to claim 5. The nitrogen gas separator according to the description. In the adsorption step, the control unit controls to send a part of the product gas as a cleaning gas from the adsorption tower attached to the adsorption step to the adsorption tower attached to the desorption step. , Control is performed to temporarily stop sending the cleaning gas to the adsorption tower attached to the desorption step.
The nitrogen gas separation device according to claim 5, wherein the stop time is a time that increases according to the difference or ratio of the length of the second time to the first time.

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