JP2013240728A - Separating apparatus and method of mixed gas - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a separating apparatus of mixed gas capable of further reducing power consumption according to a using condition of separated product gas.SOLUTION: A separating apparatus of mixed gas has two or more of adsorbing towers 7A, 7B filled with adsorbent for separating components which can be hardly absorbed by adsorbing and removing components which can be easily absorbed from the compressed mixed gas supplied from a compressor 1, and a valve system for operating an adsorbing step introducing the mixed gas into the adsorbing towers 7A, 7B and making the adsorbent adsorb the components which can be easily absorbed and an exhausting step introducing purge gas into the adsorbing towers 7A, 7B and desorbing the components which can be easily adsorbed by the adsorbent and exhausting the same alternatively sifting the steps in the two or more of the adsorbing towers 7A, 7B, the valve system controls so as to complete the discharging step in one adsorbing towers 7A, 7B and switch to a stagnation step stagnating gas in the adsorbing towers 7A, 7B while the other adsorbing towers 7A, 7B continue the adsorbing step along with the reduction of flowing rate of the separated product gas.

Description

The present invention relates to a mixed gas separation apparatus and method for generating a nitrogen gas or an oxygen gas by separating a mixed gas typified by air.

  As means for separating a target gas such as nitrogen gas from a mixed gas typified by air, there is a pressure swing adsorption (PSA) separation method.

  The PSA nitrogen gas generator using the PSA method supplies pressurized air to an adsorption tower filled with an adsorbent, adsorbs oxygen molecules in the air to the adsorbent, and separates the nitrogen gas that has not been adsorbed. Thus, nitrogen gas can be obtained.

  In such a PSA-type nitrogen gas generator, generally, at least two adsorption towers are prepared and switched alternately at a constant period of about 1 to 2 minutes. Thereby, each process of adsorption | suction-equal pressure-exhaust-pressure equalization is repeated by each adsorption tower, and obtaining the target nitrogen gas is performed.

  FIG. 1A shows a conventional PSA type nitrogen gas generator.

  In this example, a first adsorption tower 7A and a second adsorption tower 7B are provided. The first adsorption tower 7A and the second adsorption tower 7B are filled with an adsorbent that can selectively adsorb oxygen molecules such as molecular sieve carbon.

  The compressed air supplied from the inverter type compressor 1 is supplied to the first adsorption tower 7A and the second adsorption tower 7B via the first intake valve 2A and the second intake valve 2B. The nitrogen gas separated by the adsorption of oxygen in the first adsorption tower 7A and the second adsorption tower 7B is temporarily stored in the product tank 10 via the first extraction valve 4A and the second extraction valve 4B. . The nitrogen gas stored in the product tank 10 is supplied to a facility for using nitrogen gas (not shown) via the pressure reducing valve 11 and the flow rate sensor 13. Reference numeral 12 denotes an oxygen concentration meter 12 for measuring the nitrogen purity of nitrogen gas supplied from the product tank 10 to the facility using nitrogen gas.

  While the adsorption process is performed in the first adsorption tower 7A, the exhaust process is performed in the second adsorption tower 7B. At this time, a part of the nitrogen gas generated in the first adsorption tower 7A is introduced into the second adsorption tower 7B through the orifice 9 as a purge gas. In the second adsorption tower 7B, the oxygen gas adsorbed to the adsorbent by the purge gas is desorbed and discharged as exhaust gas via the second exhaust valve 3B and the silencer 8.

  While the adsorption process is performed in the second adsorption tower 7B, the exhaust process is performed in the first adsorption tower 7A. At this time, a part of the nitrogen gas generated in the second adsorption tower 7B is introduced into the first adsorption tower 7A through the orifice 9 as a purge gas. In the first adsorption tower 7B, the oxygen gas adsorbed to the adsorbent by the purge gas is desorbed and discharged as exhaust gas via the first exhaust valve 3A and the silencer 8.

  In the first adsorption tower 7A and the second adsorption tower 7B, the adsorption process and the exhaust process are switched alternately. The adsorption step is performed in a pressurized state with compressed air introduced into the first adsorption tower 7A and the second adsorption tower 7B. On the other hand, the exhaust process is performed under atmospheric pressure by opening the first adsorption tower 7A and the second adsorption tower 7B to the atmosphere with the first exhaust valve 3A and the second exhaust valve 3B.

  Between the adsorption process and the exhaust process, a pressure equalization process is performed in which the first adsorption tower 7A and the second adsorption tower 7B are communicated to equalize the pressure difference between the first adsorption tower 7A and the second adsorption tower 7B. . In the pressure equalization process, the lower pressure equalization valve 5 and the upper pressure equalization valve 6 are opened, and the lower part and the upper part of the cylinders of the first adsorption tower 7A and the second adsorption tower 7B are communicated with each other. This is performed by moving the gas in the cylinder from one of the adsorption towers to the other adsorption tower where the exhaust process has been performed.

FIG. 1B is a diagram showing the open / close state of the valve in each step in the conventional apparatus.
FIG. 2 is a diagram showing a gas flow in each step in the conventional apparatus.
(A) is when the 1st adsorption tower 7A is an adsorption process, and the 2nd adsorption tower 7B is an exhaust process.
(B) is when the first adsorption tower 7A is in the exhaust process and the second adsorption tower 7B is in the adsorption process.
(C) is a pressure equalizing step.

  As shown in FIG. 1B, when the first adsorption tower 7A is the adsorption process and the second adsorption tower 7B is the exhaust process, the first intake valve 2A is opened and the second intake valve 2B is closed. Further, the first exhaust valve 3A is closed and the second exhaust valve 3B is opened. Further, the first extraction valve 4A is opened, and the second extraction valve 4B is closed. The lower pressure equalizing valve 5 and the upper pressure equalizing valve 6 are closed.

  As shown in FIG. 2 (A), in this state, compressed air supplied from the compressor 1 is introduced into the first adsorption tower 7A, where nitrogen gas adsorbed and separated is temporarily stored in the product tank 10. Stored. A part of the nitrogen gas obtained in the first adsorption tower 7A is introduced into the second adsorption tower 7B as a purge gas, used for desorption, and then discharged as exhaust gas.

  As shown in FIG. 1B, when the first adsorption tower 7A is in the exhaust process and the second adsorption tower 7B is in the adsorption process, the first intake valve 2A is closed and the second intake valve 2B is open. Further, the first exhaust valve 3A is opened and the second exhaust valve 3B is closed. Further, the first extraction valve 4A is closed and the second extraction valve 4B is open. The lower pressure equalizing valve 5 and the upper pressure equalizing valve 6 are closed.

  As shown in FIG. 2 (B), in this state, compressed air supplied from the compressor 1 is introduced into the second adsorption tower 7B, where nitrogen gas adsorbed and separated is temporarily stored in the product tank 10. Stored. Part of the nitrogen gas obtained in the second adsorption tower 7B is introduced into the first adsorption tower 7A as a purge gas, used for desorption, and then discharged as exhaust gas.

  As shown in FIG. 1B, both the first intake valve 2A and the second intake valve 2B are closed during the pressure equalization step. Further, both the first exhaust valve 3A and the second exhaust valve 3B are closed. Further, both the first extraction valve 4A and the second extraction valve 4B are closed. Then, both the lower pressure equalizing valve 5 and the upper pressure equalizing valve 6 are opened.

  As shown in FIG. 2C, in this state, the gas in the cylinder moves from one adsorption tower that has been performing the adsorption process to the other adsorption tower that has been performing the exhaust process until then. The in-cylinder pressures of the adsorption tower 7A and the second adsorption tower 7B are made uniform.

  The following patent documents 1 to 4 are disclosed as prior art documents relating to such a gas separation method.

Japanese Examined Patent Publication No. 4-69085 JP 2002-167204 A JP 2008-80260 A JP 2010-207750 A

  As a problem in Patent Document 1, the PSA nitrogen gas generator has the following problems.

  That is, when the amount of nitrogen gas consumed in the facility using nitrogen gas is less than the amount of nitrogen gas generated in the specification, the generated nitrogen gas is surplus. Then, the nitrogen gas having the specified concentration is not produced excessively, but the nitrogen purity of the generated nitrogen gas becomes higher than necessary. Operating the compressor 1 at the same rotation speed in such a state leads to wasted power consumption.

  Here, when the switching cycle between the adsorption process and the exhaust process is made constant, the flow rate of nitrogen gas used and the nitrogen purity are in an inversely proportional relationship. In order to make the nitrogen purity constant, the switching period may be extended as the amount of nitrogen used decreases. When the switching period is extended, the amount of raw material air consumed per hour is reduced. Depending on the amount of air used, the motor speed of the inverter type compressor 1 is reduced, so that power consumption is reduced.

  The conventional control method disclosed in Patent Document 1 is as follows.

  During normal operation, the valve is controlled to open and close at the switching cycle shown in FIG. At this time, the switching cycle is determined by the set time of the program in the control means (not shown). The set time can be arbitrarily changed.

  Extend the switching cycle according to the nitrogen flow rate. That is, both the adsorption process / exhaust process time are extended.

  The extension time is determined as follows. First, the control means detects the flow rate pulse signal from the flow rate sensor 13 and calculates the flow rate of the nitrogen gas being used. The control means calculates the nitrogen flow rate generated at the normal switching cycle when the specified flow rate is generated. Then, the control means compares the nitrogen flow rate generated in the switching cycle with the flow rate of the nitrogen gas used, and (1) whether the used nitrogen flow rate reaches the nitrogen flow rate generated in the switching cycle or (2 The time of the adsorption process / exhaust process is extended until either the set maximum extension time is reached or (3) the oxygen concentration detected by the oxygen concentration meter 12 reaches the set value.

  As a result of extending the cycle period, the flow rate of the raw material air is reduced and the power consumption is reduced.

  However, depending on the usage of nitrogen gas, which is a separate product gas, it is necessary to reduce the amount of generated nitrogen gas and further reduce power consumption while sufficiently satisfying specifications of nitrogen gas such as purity and pressure. It becomes.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide a mixed gas separation apparatus and method that can further reduce power consumption in accordance with the use state of the separated product gas.

In order to achieve the above object, the mixed gas separation apparatus of the present invention is provided with an adsorbent for adsorbing and removing an easily adsorbed component from a pressurized mixed gas supplied from a pressurizing means and separating a difficultly adsorbed component. Two or more filled adsorption containers;
An adsorption step of introducing a mixed gas into the adsorption vessel and adsorbing the easy-adsorption component to the adsorbent; and an exhausting step of introducing a purge gas into the adsorption vessel and desorbing and evacuating the easy-adsorption component adsorbed by the adsorbent, A valve system for switching and operating alternately in the two or more adsorption vessels,
As the flow rate of the separated product gas decreases, the valve system ends the exhaust process in the other adsorption container while one adsorption container continues the adsorption process, and removes the gas in the other adsorption container. The gist is to perform control so as to switch to the staying process.

In order to achieve the above object, the method for separating a mixed gas according to the present invention comprises an adsorbent for adsorbing and removing an easily adsorbed component from a pressurized mixed gas supplied from a pressurizing means and separating a difficultly adsorbed component. Two or more filled adsorption containers;
An adsorption step of introducing a mixed gas into the adsorption vessel and adsorbing the easy-adsorption component to the adsorbent; and an exhausting step of introducing a purge gas into the adsorption vessel and desorbing and evacuating the easy-adsorption component adsorbed by the adsorbent, Preparing a valve system for switching and operating alternately in the two or more adsorption vessels,
As the flow rate of the separated product gas decreases, the valve system ends the exhaust process in the other adsorption container while one adsorption container continues the adsorption process, and removes the gas in the other adsorption container. The gist is to perform control so as to switch to the staying process.

  According to the present invention, as the flow rate of the separated product gas decreases, while the one adsorption container continues the adsorption process, the exhaust process is terminated in the other adsorption container, and the gas in the other adsorption container is retained. By switching to the staying process, the amount of the mixed gas that is a raw material is reduced by the amount that wasteful exhaust gas emission is reduced. Therefore, when the amount of the separated product gas used decreases, the operation of the pressurizing means can be reduced while maintaining the concentration of the separated product gas, and the power consumption can be reduced.

In the present invention, when the valve system terminates the exhaust process in the other adsorption container and switches to the retention process by stopping the introduction of the purge gas from one adsorption container to the other adsorption container,
The operation of the pressurizing means can be reduced while maintaining the concentration of the separated product gas, and the power consumption can be reduced. That is, the purge gas that flows to the adsorption container needs to flow in a predetermined amount in order to regenerate the adsorbent, but conversely, if the flow exceeds the predetermined amount, the effect of regenerating the adsorbent does not increase. Therefore, by stopping the introduction of useless purge gas when the amount of the separated product gas used is reduced, the operation of the pressurizing means is reduced while maintaining the concentration of the separated product gas, and the power consumption is reduced. Can do.

In the present invention, when the valve system terminates the exhaust process in the other adsorption container and switches to the retention process by stopping the discharge of the exhaust gas from the other adsorption container,
The operation of the pressurizing means can be reduced while maintaining the concentration of the separated product gas, and the power consumption can be reduced. That is, when the exhaust gas discharge is stopped, the adsorption container is hermetically sealed, and the gas is desorbed from the regeneration-side adsorbent, so that the pressure in the adsorption container gradually increases. When the pressure in the adsorption container on the regeneration side becomes high, the pressure in the adsorption container at the time of shifting to the adsorption process is increased by that amount, and the pressure necessary for the adsorption process is reached earlier. The fact that the pressure in the adsorption container increases quickly means that the operation of the pressurizing means can be saved, and the power consumption decreases accordingly.

In the present invention, the valve system extends the switching time for switching between the adsorption process and the exhaust process as the flow rate of the separated product gas decreases, and completes the exhaust process in the other adsorption container during the extended time. When switching to the retention process,
The following effects (1) and (2) can be obtained.
(1) By stopping the purge gas during the extended time, the consumption of the mixed gas is reduced. Although the predetermined amount of purge gas regenerates the adsorbent, even if a purge gas exceeding a predetermined amount flows, it will not be regenerated further. Therefore, the regeneration of the adsorbent is completed during the normal switching time, and it is not necessary to flow the purge gas until the extended time. Therefore, unnecessary purge gas that does not affect the quality of the product gas can be stopped, and power consumption can be reduced while maintaining the quality.
(2) By stopping the exhaust of the regeneration-side adsorption container, the adsorption container is sealed, gas is desorbed from the regeneration-side adsorption during the extended time, and the pressure in the adsorption container gradually increases. If the regeneration-side adsorption container internal pressure increases, the adsorption container internal pressure when the process proceeds to the adsorption process also increases. Since the pressure in the adsorption container at the start of the adsorption process is high, the pressure required for the adsorption process is reached earlier. The fact that the pressure in the adsorption container increases quickly means that the operation of the pressurizing means can be saved, and the power consumption decreases accordingly.

(A) is a block diagram which shows an example of the separation apparatus of the conventional mixed gas. (B) is a figure explaining control of a valve system. It is a figure explaining the flow of gas in the separation device of the conventional mixed gas. (A) is the first adsorption tower and the second adsorption tower is the evacuation process, (B) is the first adsorption tower is the evacuation process and the second adsorption tower is the adsorption process, and (C) is the pressure equalization process. (A) is a block diagram which shows an example of the separation apparatus of the mixed gas of this invention. (B) is a figure explaining control of a valve system. It is a figure explaining the flow of the gas in the separation apparatus of the mixed gas of the present invention. (A) is the first adsorption tower is the adsorption process and the second adsorption tower is the exhaust process, (B) is the first adsorption tower is the adsorption process and the second adsorption tower is the retention process, (C) is the first adsorption tower is the exhaust process. In the process, the second adsorption tower is the adsorption process, (D) is the first adsorption tower is the retention process, the second adsorption tower is the adsorption process, and (E) is the pressure equalizing process. It is a figure which shows the relationship between the amount of nitrogen generation and power consumption in Example 1 and Comparative Example 1. It is a figure which shows the relationship between the nitrogen generation amount and power consumption in Example 2 and Comparative Example 2. It is a figure which shows the pressure in the adsorption tower in Example 2 and Comparative Example 2.

  Next, the best mode for carrying out the present invention will be described.

  FIG. 3A is a diagram showing a configuration of a mixed gas separation device according to an embodiment of the present invention.

  This example is applied to an air separation device that uses air as a mixed gas as a raw material and generates nitrogen gas as a product gas by adsorbing oxygen in the air.

  In this embodiment, the parts denoted by the same reference numerals as those in FIG. 1 are the same as those in the conventional apparatus. In the following description, overlapping description may be omitted.

  This air separation device is supplied with air mainly composed of nitrogen and oxygen as a mixed gas which is a raw material gas from a compressor 1 which is a pressurizing means. Adsorption towers 7A and 7B, which are two adsorption vessels filled with an adsorbent for adsorbing and removing an easily adsorbed component from a supplied pressurized mixed gas and separating a difficultly adsorbed component, are provided.

  The first adsorption tower 7A and the second adsorption tower 7B are filled with molecular sieve carbon that preferentially adsorbs oxygen in the air as an adsorbent. Therefore, when pressurized air is introduced into the first adsorption tower 7A and the second adsorption tower 7B, oxygen in the air is adsorbed by the adsorbent, and nitrogen gas is obtained as a product gas.

  In this embodiment, air as a mixed gas is introduced into the adsorption towers 7A and 7B to adsorb oxygen as an easily adsorbed component to the adsorbent, and a purge gas is introduced into the adsorption towers 7A and 7B as an adsorbent. There is provided a valve system for switching and operating alternately in the two adsorption towers 7A and 7B an exhaust process for desorbing and exhausting oxygen, which is an easily adsorbed component.

  The valve system includes the following components.

The first intake valve 2A and the second intake valve 2B supply the compressed air supplied from the inverter compressor 1 to the first adsorption tower 7A and the second adsorption tower 7B.
The first take-off valve 4A and the second take-off valve 4B pass when the nitrogen gas separated by the adsorption of oxygen in the first adsorption tower 7A and the second adsorption tower 7B is temporarily stored in the product tank 10. .
The pressure reducing valve 11 and the flow rate sensor 13 pass through when the nitrogen gas stored in the product tank 10 is supplied to a nitrogen gas using facility (not shown). The oxygen concentration meter 12 measures the nitrogen purity of the nitrogen gas supplied from the product tank 10 to the facility using the nitrogen gas.
The purge valve 15 and the orifice 9 are supplied from the first adsorption tower 7A performing the adsorption process to the second adsorption tower 7B performing the exhaust process, or from the second adsorption tower 7B performing the adsorption process to the first adsorption tower 7A performing the exhaust process. , Via when introducing purge gas.
The first outflow check valve 16A and the second inflow check valve 17B prevent the backflow of purge gas sent from the first adsorption tower 7A performing the adsorption process to the second adsorption tower 7B performing the exhaust process.
The second outflow check valve 16B and the first inflow check valve 17A prevent the backflow of purge gas sent from the second adsorption tower 7B performing the adsorption process to the first adsorption tower 7A performing the exhaust process.
The first exhaust valve 3A and the second exhaust valve 3B pass through when the purge gas introduced into the first adsorption tower 7A and the second adsorption tower 7B during the exhaust process is discharged. The silencer 8 passes when the exhaust gas that has passed through the first exhaust valve 3A and the second exhaust valve 3B is discharged.
The lower pressure equalization valve 5 and the upper pressure equalization valve 6 are opened when the pressure equalization process is performed between the adsorption process and the exhaust process, and the first adsorption tower 7A and the second adsorption tower 7B are communicated with each other, thereby providing the first adsorption tower 7A. And the pressure difference between the second adsorption tower 7B is equalized.

  In the valve system, opening / closing control of each valve is performed, and the same adsorption process, discharge process, and pressure equalization process as described above are performed.

  In the present invention, the above valve system exhausts in the other adsorption tower (7B or 7A) while one adsorption tower (7A or 7B) continues the adsorption process as the flow rate of the separated product gas decreases. Control is performed so that the process is terminated and the process is switched to a retention process for retaining the gas in the other adsorption tower (7B or 7A).

  Switching to the retention process can be realized by the following two controls.

  First, the valve system stops the introduction of purge gas from one adsorption tower (7A or 7B) to the other adsorption tower (7B or 7A), so that the other adsorption tower (7B or 7A) The exhaust process can be terminated and switched to the residence process. Specifically, the introduction of the purge gas is stopped by closing the purge valve 15.

  Second, the valve system stops exhausting the exhaust gas from the other adsorption tower (7B or 7A), thereby terminating the exhaust process in the other adsorption tower (7B or 7A) and entering the residence process. Can be switched. Specifically, exhaust gas exhaust can be stopped by closing the second exhaust valve 3B or the first exhaust valve 3A.

  Further, switching to the residence process can be performed during the extended time by extending the switching time between the adsorption process and the exhaust process.

  That is, the valve system extends the switching time for switching between the adsorption process and the exhaust process as the flow rate of the separated product gas decreases, and during the extended time, the exhaust process in the other adsorption tower (7B or 7A). To complete the dwell process.

FIG. 3B is a diagram showing a state in which the valve is opened and closed in each process under the control of the valve system.
FIG. 4 is a diagram showing a gas flow in each step in the apparatus of the present embodiment.
(A) is when the 1st adsorption tower 7A is an adsorption process, and the 2nd adsorption tower 7B is an exhaust process.
(B) is when the 1st adsorption tower 7A is an adsorption process and the 2nd adsorption tower 7B is a residence process.
(C) is when the first adsorption tower 7A is in the exhaust process and the second adsorption tower 7B is in the adsorption process.
(D) is when the 1st adsorption tower 7A is a residence process, and the 2nd adsorption tower 7B is an adsorption process.
(E) is a pressure equalizing step.

  As shown in FIG. 3B, when the first adsorption tower 7A is the adsorption process and the second adsorption tower 7B is the exhaust process, the first intake valve 2A is opened and the second intake valve 2B is closed. Further, the first exhaust valve 3A is closed and the second exhaust valve 3B is opened. Further, the first extraction valve 4A is opened, and the second extraction valve 4B is closed. The lower pressure equalizing valve 5 and the upper pressure equalizing valve 6 are closed. Further, the purge valve 15 is opened, and the purge gas passes through the first outflow check valve 16A and the second inflow check valve 17B and is sent from the first adsorption tower 7A to the second adsorption tower 7B.

  As shown in FIG. 4A, in this state, compressed air supplied from the compressor 1 is introduced into the first adsorption tower 7A, and nitrogen gas adsorbed and separated here is temporarily supplied to the product tank 10. Stored. A part of the nitrogen gas obtained in the first adsorption tower 7A is introduced into the second adsorption tower 7B as a purge gas, used for desorption, and then discharged as exhaust gas.

  As shown in FIG. 3B, when the first adsorption tower 7A is in the adsorption process and the second adsorption tower 7B is switched from the exhaust process to the retention process, the first intake valve 2A is opened and the second intake valve 2B is opened. Is kept closed. Further, the first exhaust valve 3A is kept closed, and the second exhaust valve 3B is closed. Further, the state where the first extraction valve 4A is opened and the second extraction valve 4B is closed is maintained. The lower pressure equalizing valve 5 and the upper pressure equalizing valve 6 are kept closed. Further, the purge valve 15 is closed.

  As shown in FIG. 4 (B), in this state, compressed air supplied from the compressor 1 is introduced into the first adsorption tower 7A, where nitrogen gas adsorbed and separated is temporarily stored in the product tank 10. Stored. The introduction of the purge gas from the first adsorption tower 7A to the second adsorption tower 7B is stopped, and the exhaust gas discharge from the second adsorption tower 7B is also stopped.

  In the 2nd adsorption tower 7B, the timing which switches from an exhaust process to a residence process can be performed as follows, for example. That is, as the flow rate of the product gas detected by the flow sensor 13 decreases below a predetermined value, the switching time for switching between the adsorption process and the exhaust process is extended, and the second adsorption tower 7B is removed from the exhaust process during the extended time. It is possible to switch to a residence process.

  At this time, it is possible to switch from the exhaust process to the retention process simultaneously with the start of the extension, or to switch from the exhaust process to the retention process after a while has passed since the extension started. Further, the extension time can be determined according to the flow rate of the product gas.

  Further, when switching from the exhaust process to the retention process in the second adsorption tower 7B, the purge valve 15 and the second exhaust valve 2B can be closed simultaneously, or the purge valve 15 and the second valve can be closed. Some time lag can be provided between the exhaust valve 2B and the valve. When providing a time lag, the purge valve 15 may be closed first and then the second exhaust valve 2B may be closed, or the second exhaust valve 2B may be closed first and then the purge valve 15 may be closed. May be.

  As shown in FIG. 3B, when the first adsorption tower 7A is in the exhaust process and the second adsorption tower 7B is in the adsorption process, the first intake valve 2A is closed and the second intake valve 2B is open. Further, the first exhaust valve 3A is opened and the second exhaust valve 3B is closed. Further, the first extraction valve 4A is closed and the second extraction valve 4B is open. The lower pressure equalizing valve 5 and the upper pressure equalizing valve 6 are closed. The purge valve 15 is opened, and the purge gas passes through the second outflow check valve 16B and the first inflow check valve 17A and is sent from the second adsorption tower 7B to the first adsorption tower 7A.

  As shown in FIG. 4C, in this state, compressed air supplied from the compressor 1 is introduced into the second adsorption tower 7B, where nitrogen gas adsorbed and separated is temporarily stored in the product tank 10. Stored. Part of the nitrogen gas obtained in the second adsorption tower 7B is introduced into the first adsorption tower 7A as a purge gas, used for desorption, and then discharged as exhaust gas.

  As shown in FIG. 3B, when the second adsorption tower 7B is in the adsorption process and the first adsorption tower 7A is switched from the exhaust process to the retention process, the second intake valve 2B is opened and the first intake valve 2A is opened. Is kept closed. Further, the second exhaust valve 3B is kept closed, and the first exhaust valve 3A is closed. Further, the state where the second extraction valve 4B is opened and the first extraction valve 4A is closed is maintained. The lower pressure equalizing valve 5 and the upper pressure equalizing valve 6 are kept closed. Further, the purge valve 15 is closed.

  As shown in FIG. 4D, in this state, compressed air supplied from the compressor 1 is introduced into the second adsorption tower 7B, where nitrogen gas adsorbed and separated is temporarily supplied to the product tank 10. Stored. The introduction of the purge gas from the second adsorption tower 7B to the first adsorption tower 7A is stopped, and the exhaust gas discharge from the first adsorption tower 7A is also stopped.

  In the 1st adsorption tower 7A, the timing which switches from an exhaust process to a residence process can be performed as follows, for example. That is, as the flow rate of the product gas detected by the flow sensor 13 decreases below a predetermined value, the switching time for switching between the adsorption process and the exhaust process is extended, and the first adsorption tower 7A is removed from the exhaust process during the extended time. It is possible to switch to a residence process.

  At this time, it is possible to switch from the exhaust process to the retention process simultaneously with the start of the extension, or to switch from the exhaust process to the retention process after a while has passed since the extension started. Further, the extension time can be determined according to the flow rate of the product gas.

  Further, when switching from the exhaust process to the residence process in the first adsorption tower 7A, the purge valve 15 can be closed and the first exhaust valve 3A can be closed at the same time. A slight time lag may be provided between the exhaust valve 3A and the closed valve. When providing a time lag, the purge valve 15 may be closed first and then the first exhaust valve 3A may be closed, or the first exhaust valve 3A may be closed first and then the purge valve 15 may be closed. May be.

  As shown in FIG. 3B, both the first intake valve 2A and the second intake valve 2B are closed during the pressure equalization step. Further, both the first exhaust valve 3A and the second exhaust valve 3B are closed. Further, both the first extraction valve 4A and the second extraction valve 4B are closed. Then, both the lower pressure equalizing valve 5 and the upper pressure equalizing valve 6 are opened.

  As shown in FIG. 4 (E), in this state, the gas in the cylinder moves from one adsorption tower that has been performing the adsorption process to the other adsorption tower that has been performing the exhaust process until then. The in-cylinder pressures of the adsorption tower 7A and the second adsorption tower 7B are made uniform.

  In the present embodiment, as the flow rate of the separated product gas decreases, while the one adsorption tower (7A or 7B) continues the adsorption process, the exhaust process is terminated in the other adsorption tower (7B or 7A). By switching to the residence process in which the gas in the other adsorption tower (7B or 7A) is retained, the amount of the mixed gas that is a raw material is reduced by the amount that wasteful exhaust gas emission is reduced. Therefore, when the usage amount of the separated product gas decreases, the operation of the compressor 1 can be reduced while maintaining the concentration of the separated product gas, and the power consumption can be reduced.

Further, the valve system stops the introduction of purge gas from one adsorption tower (7A or 7B) to the other adsorption tower (7B or 7A), thereby evacuating the other adsorption tower (7B or 7A). To end the process and switch to the retention process,
The operation of the compressor 1 can be reduced while maintaining the concentration of the separated product gas, and the power consumption can be reduced. That is, the purge gas flowing through the adsorption tower (7B or 7A) needs to flow in a predetermined amount in order to regenerate the adsorbent, but conversely, even if it exceeds the predetermined amount, the effect of regenerating the adsorbent is enhanced. is not. Therefore, when the amount of the separated product gas used is reduced, the introduction of useless purge gas is stopped, thereby reducing the operation of the compressor 1 while maintaining the concentration of the separated product gas, thereby reducing the power consumption. it can.

Further, the valve system terminates the exhaust process in the other adsorption tower (7B or 7A) and stops the exhaust process from the other adsorption tower (7B or 7A) to switch to the residence process. ,
The operation of the compressor 1 can be reduced while maintaining the concentration of the separated product gas, and the power consumption can be reduced. That is, when the exhaust gas discharge is stopped, the adsorption tower (7B or 7A) is in a sealed state, the gas is desorbed from the regeneration side adsorbent, and the pressure in the adsorption tower (7B or 7A) gradually increases. When the pressure in the regeneration-side adsorption tower (7B or 7A) increases, the pressure in the adsorption tower (7B or 7A) at the time of shifting to the adsorption process increases correspondingly, and reaches the necessary pressure for the adsorption process earlier. The fact that the pressure in the adsorption tower (7B or 7A) is increased quickly can save the operation of the compressor 1, and the power consumption is reduced accordingly.

The valve system extends the switching time for switching between the adsorption process and the exhaust process as the flow rate of the separated product gas decreases, and during the extended time, the exhaust process in the other adsorption tower (7B or 7A). To end the process and switch to the retention process,
The following effects (1) and (2) can be obtained.
(1) By stopping the purge gas during the extended time, the consumption of the mixed gas is reduced. Although the predetermined amount of purge gas regenerates the adsorbent, even if a purge gas exceeding a predetermined amount flows, it will not be regenerated further. Therefore, the regeneration of the adsorbent is completed during the normal switching time, and it is not necessary to flow the purge gas until the extended time. Therefore, unnecessary purge gas that does not affect the quality of the product gas can be stopped, and power consumption can be reduced while maintaining the quality.
(2) By stopping the exhaustion of the regeneration side adsorption tower (7B or 7A), the adsorption tower (7B or 7A) is in a sealed state, and gas is desorbed from the regeneration side adsorption during the extended time, and gradually the adsorption tower (7B or 7A) The internal pressure increases. When the pressure in the regeneration-side adsorption tower (7B or 7A) increases, the pressure in the adsorption tower (7B or 7A) also increases when the process proceeds to the adsorption step. Since the pressure in the adsorption tower (7B or 7A) at the start of the adsorption process is high, the pressure required for the adsorption process is reached earlier. The fact that the pressure in the adsorption tower (7B or 7A) is increased quickly can save the operation of the compressor 1, and the power consumption is reduced accordingly.

  Next, examples will be described.

The nitrogen gas generator shown in FIG. 3 having the following specifications was prepared.
Nitrogen gas generation amount: 30 Nm ³ / h
Nitrogen gas pressure: 0.5 MPa
Nitrogen gas purity: 99% vol or more Inverter type compressor:
Main motor nominal output 11 kW
As other conditions, the purity and pressure of the nitrogen gas were in a state satisfying the specification values of the product gas.

  On the other hand, as the comparative example 1, the nitrogen gas generator shown in FIG.

The amount of nitrogen gas generated was reduced from 30 Nm ³ / h (100%) to 22.5 Nm ³ / h (75%) and 15 Nm ³ / h (50%), extending the adsorption / exhaust process. In each state, power consumption was measured.

  FIG. 5 shows the relationship between the amount of nitrogen gas generated and the power consumption in Example 1 and Comparative Example 1. It can be seen that in Example 1, the reduction in power is greater when the amount of nitrogen gas generated is smaller.

The nitrogen gas generator shown in FIG. 3 having the following specifications was prepared.
Nitrogen gas generation amount: 20 Nm ³ / h
Nitrogen gas pressure: 0.5 MPa
Nitrogen gas purity: 99.99% vol or more Inverter type compressor (with dryer):
Main motor nominal output 11 kW
Nominal output of dryer 0.5 kW
As other conditions, the purity and pressure of the nitrogen gas were in a state satisfying the specification values of the product gas.

  On the other hand, as the comparative example 2, the nitrogen gas generator shown in FIG.

The amount of nitrogen gas generated was reduced from 20 Nm ³ / h (100%) to 15 Nm ³ / h (75%), 10 Nm ³ / h (50%), 5 Nm ³ / h (25%), and the cycle period was extended. . In each state, power consumption was measured.

  FIG. 6 shows the relationship between the amount of nitrogen gas generated and the power consumption in Example 2 and Comparative Example 2. It turns out that the fall of electric power is larger in Example 2 when the amount of nitrogen gas generation decreases.

FIG. 7 shows the pressure fluctuation of each adsorption tower in Example 2 and Comparative Example 2. In Example 2, it turns out that the pressure in an adsorption tower is rising in a residence process.

1 Compressor 2A 1st intake valve 2B 2nd intake valve 3A 1st exhaust valve 3B 2nd exhaust valve 4A 1st extraction valve
4B 2nd extraction valve 5 Lower pressure equalizing valve 6 Upper pressure equalizing valve 7A 1st adsorption tower 7B 2nd adsorption tower 8 Silencer 9 Orifice 10 Product tank 11 Pressure reducing valve 12 Oxygen concentration meter 13 Flow rate sensor 15 Purge valve 16A First outflow check valve 16B Second outflow check valve 17A First inflow check valve 17B Second inflow check valve

Claims (5)

Two or more adsorption containers filled with an adsorbent for adsorbing and removing the easily adsorbed component from the pressurized mixed gas supplied from the pressurizing means and separating the difficultly adsorbed component;
An adsorption step of introducing a mixed gas into the adsorption vessel and adsorbing the easy-adsorption component to the adsorbent; and an exhausting step of introducing a purge gas into the adsorption vessel and desorbing and evacuating the easy-adsorption component adsorbed by the adsorbent, A valve system for switching and operating alternately in the two or more adsorption vessels,
As the flow rate of the separated product gas decreases, the valve system ends the exhaust process in the other adsorption container while one adsorption container continues the adsorption process, and removes the gas in the other adsorption container. A separation apparatus for a mixed gas, wherein control is performed so as to switch to a retention step for retention.   The mixed gas separation according to claim 1, wherein the valve system terminates the exhaust process in the other adsorption container and switches to the residence process by stopping the introduction of the purge gas from the one adsorption container to the other adsorption container. apparatus.   3. The mixed gas separation device according to claim 1, wherein the valve system stops exhaust of the exhaust gas from the other adsorption container, thereby ending the exhaust process in the other adsorption container and switching to the retention process.   As the flow rate of the separated product gas decreases, the valve system extends the switching time for switching between the adsorption process and the exhaust process, and ends the exhaust process in the other adsorption vessel during the extended time and enters the residence process. The mixed gas separation device according to any one of claims 1 to 3, wherein switching is performed. Two or more adsorption containers filled with an adsorbent for adsorbing and removing the easily adsorbed component from the pressurized mixed gas supplied from the pressurizing means and separating the difficultly adsorbed component;
An adsorption step of introducing a mixed gas into the adsorption vessel and adsorbing the easy-adsorption component to the adsorbent; and an exhausting step of introducing a purge gas into the adsorption vessel and desorbing and evacuating the easy-adsorption component adsorbed by the adsorbent, Preparing a valve system for switching and operating alternately in the two or more adsorption vessels,
As the flow rate of the separated product gas decreases, the valve system ends the exhaust process in the other adsorption container while one adsorption container continues the adsorption process, and removes the gas in the other adsorption container. A method for separating a mixed gas, wherein control is performed so as to switch to a retention step for retention.

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