JP2015024349A - Nitrogen gas concentration system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a nitrogen gas concentration system excellent in energy efficiency by which a separated nitrogen gas can be efficiently collected, and consumption of the time required for obtaining high-density nitrogen gas or required electric energy is suppressed less.SOLUTION: There is provided a nitrogen gas concentration system in which the adsorption and desorption of oxygen gas included in a raw material gas are alternately repeated between two or more adsorption towers filled with molecular sieving carbon to concentrate the nitrogen gas. The system comprises: a storage provided with a storage space for storing the nitrogen gas; a gas circulation route; a nitrogen separation device including two or more adsorption towers; a blower feeding the sucked raw material gas to the nitrogen separation device so that the pressure in the adsorption tower becomes 0.05-0.15 MPa; and a vacuum pump for desorbing the oxygen gas adsorbed onto the molecular sieving carbon.

Description

  The present invention relates to a nitrogen gas concentration system. More specifically, the present invention relates to a nitrogen gas concentrating system capable of separating and concentrating nitrogen gas from a raw material gas containing nitrogen gas and oxygen gas and storing a product gas containing high concentration nitrogen gas in an internal space such as a warehouse.

  2. Description of the Related Art Conventionally, there has been known a technique for improving the preservability of fruits and vegetables arranged, for example, in a warehouse by storing high concentration nitrogen gas in an internal space such as a warehouse. In general, such a high-concentration nitrogen gas is generated by repeating the operation of replacing the nitrogen gas separated from the raw material gas (usually air) by the nitrogen separator and the gas in the warehouse. Thus, a pressure swing adsorption method (hereinafter also referred to as a PSA (Pressure Swing Adsorption) method) has attracted attention as a method for increasing the nitrogen gas concentration in the storage.

  In the PSA method, usually two adsorption towers packed with molecular sieve carbon are used. Specifically, in the PSA method, air is pressurized and supplied to one adsorption tower to adsorb oxygen gas, and mainly nitrogen gas is separated and taken out as product gas, while the other adsorption tower is desorbed in the meantime. In addition, by alternately repeating adsorption and desorption of oxygen gas between both adsorption towers, nitrogen gas is continuously obtained using the difference in adsorption speed between oxygen gas and nitrogen gas by molecular sieve carbon ( Patent Document 1).

In addition, two adsorption towers and a warehouse are connected by a circulation line, the pressure at the time of oxygen gas adsorption in one adsorption tower is 0.2 to 0.3 MPa ( ^{2 to 3} kg / cm ² ), and the other adsorption A circulation system that evacuates the tower to about 50 Torr and desorbs oxygen gas is also known (Patent Document 2).

JP 2002-159820 A JP-A-62-236414

  However, in the conventional PSA method for increasing the nitrogen gas concentration in the warehouse, the pressure at the time of adsorption in the adsorption tower is set to about 0.7 to 0.9 MPa, and the pressure at the time of desorption is set to 100 Torr (−0.09 MPa to atmospheric pressure (0 MPa). In such conditions, since the pressure during adsorption is high, the amount of adsorbent can be reduced, and the size of the nitrogen separation device can be reduced compared to the system of Patent Document 2. Although the gas can be reduced, the nitrogen gas stored in the storage is not circulated and used, and instead of supplying the newly separated nitrogen gas into the storage, some of the gas in the storage is exhausted. There is a problem in that the gas in the warehouse where the nitrogen concentration is increasing is exhausted and the efficiency is poor, and in the circulation system described in Patent Document 2, two adsorption towers are communicated between adsorption and desorption. When During the pressure equalization), a residual pressure of the gas containing nitrogen gas separated from the raw material gas is generated in each adsorption tower. Since the gas in the tower (including the separated nitrogen gas) is exhausted because it is subjected to the process, the conventional circulation system cannot efficiently recover the separated nitrogen gas and has a high concentration. There is a problem that the time and electric energy required to obtain the nitrogen gas increase, resulting in poor energy efficiency.

  The present invention has been made in view of such a conventional situation. The separated nitrogen gas can be efficiently recovered, the time and electric energy required to obtain a high concentration of nitrogen gas can be suppressed, and the energy efficiency can be reduced. The object is to provide a good nitrogen gas enrichment system.

  The nitrogen gas concentrating system of one aspect of the present invention that solves the above-described problem is the adsorption of the oxygen gas among the source gases containing nitrogen gas and oxygen gas between two or more adsorption towers packed with molecular sieve carbon. A nitrogen gas concentration system for concentrating the nitrogen gas by alternately repeating desorption and desorption, the storage having a storage space for storing the concentrated nitrogen gas, and one end and the other end connected to the storage space A gas circulation path, a nitrogen separation apparatus including the two or more adsorption towers disposed in the gas circulation path, and the raw material disposed upstream of the nitrogen separation apparatus in the gas circulation path. A blower for sucking gas and supplying the nitrogen separation device so that the pressure in the adsorption tower is 0.05 to 0.15 MPa, and a vacuum pump for desorbing the oxygen gas adsorbed on the molecular sieve carbon Characterized in that it obtain.

  According to such a nitrogen gas concentration system, the pressure in the adsorption tower at the time of adsorption is lower than that of the conventional system. Is unlikely to occur. For this reason, the amount of nitrogen gas separated from the raw material gas is reduced and efficiently recovered. Compared to the case of using a compressor or the like at a high pressure as in the prior art, when the raw material gas is supplied to the adsorption tower by operating the blower in the above pressure range, the separated nitrogen gas obtained from the same raw material gas amount The amount increases and the target nitrogen gas concentration is efficiently achieved. As a result, the operation time of the system of the nitrogen gas concentration system of the present invention is shortened compared with the conventional system. Therefore, according to the nitrogen gas concentration system of the present invention, excellent energy efficiency is achieved.

  In the above-described configuration, the nitrogen gas concentration system is disposed on the downstream side of the two or more adsorption towers and on the upstream side of the storage, the oxygen concentration meter for measuring the oxygen gas concentration in the storage space, It is preferable to further include a flow rate adjusting device that controls the flow rate of the concentrated nitrogen gas supplied into the storage space according to the detected value of the oximeter.

  According to such a nitrogen gas concentration system, for example, when the oxygen gas concentration in the storage space is high (that is, when the nitrogen gas concentration is low), the nitrogen gas flow rate supplied to the storage space is controlled to increase. When the nitrogen gas concentration is quickly increased and then the oxygen gas concentration in the storage space becomes low (that is, when the nitrogen gas concentration is increased), the flow rate of nitrogen gas supplied to the storage space is reduced. Control can increase the replacement efficiency. As a result, the nitrogen gas concentration is efficiently increased, and the system operation time is further shortened.

  Said structure WHEREIN: It is preferable that a nitrogen gas concentration system is further provided with the cooling device which cools the said raw material gas arrange | positioned in the downstream of the said blower, and is supplied to the said nitrogen separation apparatus. Such a cooling device can lower the temperature of the source gas pressurized by the blower. As a result, the amount of oxygen gas adsorbed in the adsorption tower increases, and the amount of nitrogen gas separated increases.

  In the above configuration, the nitrogen gas concentrating system includes a connection pipe connecting the upstream side and the downstream side of the blower, and the raw material gas disposed in the connection pipe and discharged from the blower. It is preferable to further include a raw material gas pressure adjusting device that returns to the upstream side.

  Such a raw material gas pressure adjusting device circulates the raw material gas before and after the blower when the supply of the raw material gas to the adsorption tower is shut off, for example, in a pressure equalizing process for communicating two adsorption towers. I can leave it to you. As a result, it is possible to prevent the source gas from being pressurized more than necessary on the upstream side of the adsorption tower and to prevent the blower from being broken. In addition, there is an excess of pressurized source gas, such as a pressure equalization step in which source gas is not supplied or the latter half of the adsorption step in which the pressure in the adsorption tower is increased and the source gas becomes difficult to be supplied. In this case, it is possible to prevent the surplus source gas from being released into the atmosphere by the blower. Thereby, the inhalation of atmospheric gas into the nitrogen separator can be reduced, and the performance degradation of the nitrogen separator can be prevented. Furthermore, when the cooling device is provided, the burden on the cooling device is reduced. Alternatively, the raw material gas is sufficiently cooled by the cooling device, and the adsorption rate of the oxygen gas in the adsorption tower can be improved.

  The storage is preferably a storage for storing fruits and vegetables. In this case, the nitrogen gas concentration system can efficiently increase the nitrogen gas concentration in the storage space so that the nitrogen gas concentration necessary for the fruit and vegetable storage is obtained.

  It is preferable that the storage is a processing cabinet for performing fumigation of books, fumigation of cigarettes, or insecticidal treatment of cultural properties. In this case, the nitrogen gas concentrating system can, for example, maintain the nitrogen gas concentration in the storage space so as to obtain the nitrogen gas concentration necessary for fumigation of books stored in the library, fumigation of cigarettes or insecticidal treatment of cultural properties. The concentration can be increased efficiently.

  ADVANTAGE OF THE INVENTION According to this invention, the isolate | separated nitrogen gas can be collect | recovered efficiently, the time and electric energy which are required in order to obtain high concentration nitrogen gas can be suppressed, and an energy efficient nitrogen gas concentration system can be provided.

FIG. 1 is a schematic diagram of a nitrogen gas concentration system according to an embodiment (first embodiment) of the present invention. FIG. 2 is a flowchart showing a process of separating nitrogen gas from source gas. FIG. 3 is a schematic diagram of a nitrogen gas concentration system according to an embodiment (second embodiment) of the present invention. FIG. 4 is a graph showing temporal changes in the nitrogen gas concentration in the product gas and the nitrogen gas concentration in the storage space during operation of the nitrogen gas concentration system in Example 1. FIG. 5 is a graph showing the relationship between the time required for the nitrogen gas concentration to reach 98% by volume (arrival time) and the pressure during adsorption. FIG. 6 is a graph showing the relationship between the power consumption required for the nitrogen gas to reach 98% by volume and the pressure during adsorption. FIG. 7 is a schematic view of a conventional nitrogen gas concentration system.

(First embodiment)
<Nitrogen gas concentration system>
Hereinafter, embodiments of the nitrogen gas concentration system of the present invention will be described with reference to the drawings. FIG. 1 is a schematic diagram of a nitrogen gas concentration system according to an embodiment of the present invention.

  As shown in FIG. 1, the nitrogen gas concentration system 100 includes a storage 200, a gas circulation path 300, a blower 400, a nitrogen separator 500, and a vacuum pump 600. The nitrogen gas concentrating system 100 includes a gas circulation path 300 that connects the storage 200 and the nitrogen separation device 500, and a raw material gas that is circulated in the gas circulation path 300 by the blower 400 (stored in the storage 200 described later). A mixed gas of a gas and a gas (atmosphere) sucked from the outside, including oxygen gas and nitrogen gas (the same applies hereinafter) is pressurized and supplied to the nitrogen separator 500. The nitrogen separator 500 prepares a product gas in which nitrogen gas is separated and concentrated by adsorbing oxygen gas from the raw material gas. The vacuum pump 600 assists desorption of the adsorbed oxygen gas. The obtained product gas flows through the gas circulation path 300 and is returned to the storage 200. The product gas returned to the storage 200 is circulated again as a raw material gas through the circulation path 300 as necessary, and the nitrogen gas concentration is increased and finally stored as a product gas having a desired nitrogen gas concentration. . In the nitrogen gas concentration system 100 of this embodiment, in particular, the raw material gas is appropriately pressurized by the blower 300 and supplied to the nitrogen separation device 500. As a result, a product gas containing a high concentration of nitrogen gas can be obtained in a shorter time and with a smaller amount of electric power than before. Hereinafter, the details of this mechanism will be described along the gas flow direction starting from the storage 200.

(Storage)
The storage 200 is a relatively large box including a storage space 210 in which gas (including raw material gas and product gas described later) circulating in the gas circulation path 300 is stored. The storage 200 may be provided with various measuring instruments such as an oxygen concentration meter, a pressure gauge, and a hygrometer for measuring the oxygen gas concentration in the storage space 210. When the storage 200 is provided with a door member (not shown) for closing an opening (not shown) of the storage space 210, the storage 200 is used for an application (for example, a fruit and vegetable storage) described later. , A storage object (for example, fruits and vegetables) can be carried in and out.

(Gas circulation path)
The gas circulation path 300 is an annular path through which the gas in the storage space 210 and the gas such as the sucked air circulate. One end and the other end of the gas circulation path 300 are respectively connected to the storage space 210, and the gas stored in the storage space 210 circulates through the gas circulation path 300 and is supplied to the storage space 210 again. Has been. Further, the gas circulation path 300 is provided with an outside air inlet for sucking outside air (atmosphere) into the path at any position. In the present embodiment, an outside air inlet 700 is provided on the downstream side of the storage 200 and the upstream side of the blower 400 via the connection pipe line 710. From such an outside air inlet, outside air is sucked so that the inside of the storage 200 does not become a negative pressure. The intake of outside air is performed by driving a blower 400 described later to generate a suction force. Further, the inside of the storage space 210 of the above-described storage 200 is adjusted to a slightly pressurized state so that the outside air is prevented from entering and the storage 200 itself is not destroyed by being pressurized or vacuumed. Has been. Therefore, when the suction force is generated by driving the blower 400, the gas pushed out from the slightly pressurized storage space 210 circulates mainly in the circulation path 300, and the shortage as the raw material gas is sucked into the outside air. It is supplemented by outside air sucked from the mouth 700. In the present embodiment, for the sake of clarity, the gas flowing through the gas circulation path 300 from the storage 200 to the adsorption tower of the nitrogen separation device 500 described later is referred to as “source gas”, and the nitrogen separation device. The gas that is increased in the nitrogen gas concentration by the 500 adsorption towers and flows through the gas circulation path 300 up to the storage 200 is referred to as “product gas”. Therefore, when the product gas supplied to the storage 200 is circulated from the storage 200 through the gas circulation path 300 toward the nitrogen separation device 500 again, such product gas is handled as a raw material gas.

  The raw material gas that circulates in the gas circulation path 300 is a mixed gas of the gas stored in the storage 200 and the gas (atmosphere) sucked from the outside as described above, and includes oxygen gas and nitrogen gas. The source gas may contain a small amount of other gases such as carbon dioxide.

(Blower)
The blower 400 is a blower facility arranged on the upstream side of a nitrogen separation device 500 described later, pressurizes the raw material gas, and supplies it to the nitrogen separation device 500. In the present embodiment, the blower 400 supplies the raw material gas to the nitrogen separator 500 so that the pressure in the adsorption tower provided in the nitrogen separator 500 is 0.05 to 0.15 MPa. The range of the pressure may be 0.05 to 0.15 MPa from the viewpoint of energy saving, but it is preferably 0.05 to 0.13 MPa in consideration of further energy efficiency, and 0.05 to 0. More preferably, it is 10 MPa. In consideration of the device design such as the thickness of the pipe, it is more preferable that the pressure is 0.08 to 0.10 MPa. The blower 400 supplies the raw material gas so that the pressure in the adsorption tower is 0.05 to 0.15 MPa lower than the conventional pressure, so that the pressure in the two adsorption towers is equalized after the adsorption of the oxygen gas. The pressure becomes substantially atmospheric pressure or negative pressure (see the steps (ii) and (iv) described later). As a result, the residual pressure of the product gas existing in the adsorption tower in the pressure equalization step is reduced, and the amount of product gas exhausted in the subsequent desorption step can be reduced. Therefore, since the amount of atmospheric gas sucked down and the oxygen concentration in the raw material gas decreases, a product gas containing a high concentration of nitrogen gas can be obtained efficiently, and energy efficiency is improved.

(Nitrogen separator)
The nitrogen separation apparatus 500 is an apparatus disposed in the gas circulation path 300, and separates and concentrates the nitrogen gas by removing oxygen gas from the raw material gas, thereby producing a product gas having an increased nitrogen gas concentration. It is a device for doing. The nitrogen separation device 500 includes two adsorption towers (an adsorption tower 510 a and an adsorption tower 510 b), a product tank 520, an oxygen concentration meter 530, and a flow meter 540. Each component is connected by a gas circulation path 300 that branches appropriately. Valves V <b> 1 to V <b> 10 for opening and closing the path are installed in the gas circulation path 300 in the nitrogen separator 500. The valves V1 to V10 are valves (for example, electromagnetic valves) that are independently controlled. Specifically, the valves V1 and V3 are inlet valves that open and close the gas circulation path 300 through which the raw material gas supplied to the adsorption tower 510a and the adsorption tower 510b passes, respectively. The valves V2 and V4 are exhaust valves that open and close the gas circulation path 300 through which the gas exhausted from the adsorption tower 510a and the adsorption tower 510b passes, respectively. The valves V5 and V6 are outlet valves that open and close the gas circulation path 300 through which the product gas taken out from the adsorption tower 510a and the adsorption tower 510b passes, respectively. The valves V7 and V8 are pressure equalizing valves that open and close the gas circulation path 300 through which gas passes in a pressure equalizing process described later. The valve V9 is an outside air supply valve that opens and closes a supply pipe 320 for supplying outside air (air), which will be described later, to the exhaust pipe 310. The valve V <b> 10 is a control valve that opens and closes the gas circulation path 300 through which the product gas supplied to the storage space 210 passes. These valves V1 to V10 can be electrically opened and closed by a control device (not shown) set with a timer.

  The adsorption tower 510a and the adsorption tower 510b are each filled with molecular sieve carbon that adsorbs oxygen gas. Molecular sieve carbon is a wood-based, coal-based, resin that is carbonized with charcoal, coal, coke, coconut husk, resin, pitch, etc., with many pores, and carbonized at a high temperature to adjust the pore diameter to about 3-5 mm. Adsorbents such as a system and a pitch system. 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. . In addition, molecular sieve carbon has an increased ability to adsorb oxygen gas under high pressure conditions. Therefore, molecular sieve carbon can adsorb a large amount of oxygen gas by pressurizing the inside of the adsorption tower, and then desorb the oxygen gas by reducing the pressure inside the adsorption tower. Specific examples of such molecular sieve carbon include trade names GN-UC-H, 1.5GN-H, and 1.5GN-S manufactured by Kuraray Chemical Co., Ltd. In the nitrogen separation apparatus 500, adsorption and desorption of oxygen gas are alternately repeated by the adsorption tower 510a and the adsorption tower 510b, and the product gas is prepared by separating and concentrating the nitrogen gas from the raw material gas.

  With reference to FIG. 2 in addition to FIG. 1, the flow of separating and concentrating nitrogen gas from the source gas in the nitrogen gas concentration system 100 will be specifically described. FIG. 2 is a flowchart showing a process of separating nitrogen gas from source gas. Nitrogen gas is separated and concentrated from the raw material gas in each adsorption tower through a process in which an adsorption process, a pressure equalization process (release), a desorption process, and a pressure equalization process (recovery) are performed as one cycle. At that time, while one of the adsorption towers is subjected to the adsorption process, each valve described above is controlled so that the other adsorption tower is subjected to the desorption process.

  Specifically, as shown in FIG. 2, while the adsorption tower 510a is subjected to the adsorption process, the adsorption tower 510b is subjected to the desorption process (stage (i)). Further, while the adsorption tower 510a is subjected to the pressure equalization process (release), the adsorption tower 510b is subjected to the pressure equalization process (recovery) (stage (ii)), and the adsorption tower 510a is subjected to the desorption process. While the adsorption tower 510b is subjected to the adsorption process (stage (iii)), and while the adsorption tower 510a is subjected to the pressure equalization process (recovery), the adsorption tower 510b is subjected to the pressure equalization process (release). (Stage (iv)). Hereinafter, each step will be described in detail.

<Stage (i)>
The stage (i) is a stage where the adsorption tower 510a is subjected to the adsorption process and the adsorption tower 510b is subjected to the desorption process. Specifically, in the stage (i), the valve V2, the valve V3, and the valves V6 to V9 are closed, and the valve V1, the valve V4, the valve V5, and the valve V10 are opened. Therefore, the source gas supplied to the nitrogen separation device 500 is supplied to the adsorption tower 510a. In the adsorption tower 510a, oxygen gas is adsorbed among the supplied raw material gases, and the separated nitrogen gas is sent to the product tank 520. The product tank 520 is a box having a primary storage space 521 for appropriately storing the separated nitrogen gas as a product gas. Thereafter, the product gas flows through the gas circulation path 300 and is supplied to the storage space 210. At this time, as described above, when the blower 400 or the raw material gas pressure adjusting device 900 described later is provided so that the pressure in the adsorption tower 510a is in the range of 0.05 to 0.15 MPa, the raw material is used. It is adjusted according to the operating conditions of the gas pressure adjusting device 900. On the other hand, the oxygen gas adsorbed by the adsorption tower 510b is sucked by the vacuum pump 600, desorbed from the adsorption tower 510b, and released to the outside of the nitrogen separation device 500 (usually in the atmosphere).

<Stage (ii)>
The stage (ii) is a stage where the adsorption tower 510a is subjected to a pressure equalization process (release) and the adsorption tower 510b is subjected to a pressure equalization process (recovery). Specifically, in the stage (ii), the valves V1 to V6 are closed, and the valves V7 to V9 and the valve V10 are opened. Therefore, the adsorption tower 510a and the adsorption tower 510b communicate with each other, and the pressure inside the both adsorption towers is equalized. At this time, since the adsorption tower 510a that has been subjected to the adsorption process immediately before has a higher pressure than the adsorption tower 510b, the gas in the adsorption tower 510a flows into the adsorption tower 510b.

  However, according to the nitrogen gas concentration system 100 of the present embodiment, the pressure in the adsorption tower 510a at the time of adsorption is controlled to 0.05 to 0.15 MPa, which is lower than the conventional pressure as described above. Therefore, even when the adsorption towers communicate with each other in the pressure equalization step, the amount of gas (including the separated nitrogen gas) flowing from the adsorption tower 510a to the adsorption tower 510b is small, and is substantially equal to atmospheric pressure or negative pressure. The pressure is equalized.

<Stage (iii)>
The stage (iii) is a stage where the adsorption tower 510a is subjected to the desorption process and the adsorption tower 510b is subjected to the adsorption process. Specifically, in the stage (iii), the valve V1, the valve V4, the valve V5, and the valves V7 to V9 are closed, and the valve V2, the valve V3, the valve V6, and the valve V10 are opened. Therefore, the source gas supplied to the nitrogen separation device 500 is supplied to the adsorption tower 510b. In the adsorption tower 510b, oxygen gas is adsorbed among the supplied source gases, and the separated nitrogen gas is sent to the product tank 520. Thereafter, the product gas flows through the gas circulation path 300 and is supplied to the storage space 210. At this time, as in the step (i), the blower 400 or the raw material gas pressure adjusting device 900 described later is provided so that the pressure in the adsorption tower 510b is in the range of 0.05 to 0.15 MPa. If it is, it is adjusted according to the operating conditions of the raw material gas pressure adjusting device 900. On the other hand, the oxygen gas adsorbed on the adsorption tower 510a is sucked by the vacuum pump 600, desorbed from the adsorption tower 510a, and released to the outside of the nitrogen separation device 500 (usually in the atmosphere). In the nitrogen gas concentration system 100, when the pressure is equalized in the stage (ii), the inside of the adsorption tower 510b is almost atmospheric pressure or negative pressure, and a large residual pressure as in the conventional system is generated. Absent. Therefore, the amount of nitrogen gas exhausted from the adsorption tower 510a in the stage (iii) is less than that of a conventional system that generates a large residual pressure during the pressure equalization process.

<Stage (iv)>
The stage (iv) is a stage where the adsorption tower 510a is subjected to a pressure equalization process (recovery) and the adsorption tower 510b is subjected to a pressure equalization process (release). Specifically, in the stage (iv), the valves V1 to V6 are closed, and the valves V7 to V9 and the valve V10 are opened. Therefore, the adsorption tower 510a and the adsorption tower 510b communicate with each other, and the pressure inside the both adsorption towers is equalized. At this time, since the adsorption tower 510b that has been subjected to the adsorption process immediately before has a higher pressure than the adsorption tower 510a, the gas in the adsorption tower 510b flows into the adsorption tower 510a.

  However, according to the nitrogen gas concentration system 100 of the present embodiment, the pressure in the adsorption tower 510b at the time of adsorption is controlled to 0.05 to 0.15 MPa, which is lower than the conventional pressure as described above. Therefore, even when the adsorption towers communicate with each other in the pressure equalization process, the amount of gas (including the separated nitrogen gas) flowing from the adsorption tower 510b to the adsorption tower 510a is small, and is approximately atmospheric pressure or negative pressure. The pressure is equalized.

  With the above stages (i) to (iv) as one cycle, adsorption and desorption of oxygen gas are alternately repeated in the adsorption tower 510a and the adsorption tower 510b, and the product gas obtained by separating and concentrating nitrogen gas from the raw material gas is obtained. Prepared. In the stage (i) performed again, as described in the stage (iii), when the pressure is equalized in the stage (iv), the inside of the adsorption tower 510b becomes substantially atmospheric pressure or negative pressure. Thus, no large residual pressure is generated as in the conventional system. Therefore, there is little nitrogen gas exhausted from the adsorption tower 510b in the step (i) again.

  In addition, 1 cycle can be implemented in 82 to 260 seconds, for example. In this case, the adsorption process (stage (i)) of the adsorption tower 510a is performed in 40 to 120 seconds, the pressure equalization process (release) (stage (ii)) is performed in 1 to 10 seconds, and the desorption process ((iii) ) Can be performed in 40 to 120 seconds, and the pressure equalization step (recovery) (stage (i)) can be performed in 1 to 10 seconds.

  Further, the nitrogen separation device 500 may be configured so that the adsorption and desorption of oxygen gas can be alternately repeated by at least two adsorption towers. Therefore, the number of adsorption towers is not particularly limited as long as it is two or more. In this case, for example, two nitrogen separation devices including two adsorption towers may be provided in parallel and connected to the blower 400, and the nitrogen gas may be separated and concentrated using a total of four adsorption towers. Three or more adsorption towers may be installed in the nitrogen separator. The number of adsorption towers is appropriately selected according to the size of the installation space of the nitrogen gas concentration system, the amount of nitrogen gas to be separated and concentrated, the volume of the storage space, and the like.

  Returning to the description of the nitrogen separator 500, the nitrogen separator 500 is preferably provided with a flow meter 540 on the downstream side of the product tank 520. Further, it is preferable that an oxygen concentration meter 530 is connected to the gas circulation path 300 that connects the downstream side of the product tank 520 and the upstream side of the flow meter 540. The flow meter 540 measures the flow rate of the product gas supplied from the primary storage space 521 to the storage space 210 from the product tank 520. The oxygen concentration meter 530 measures the oxygen gas concentration of the product gas. The flow meter 540 and the oxygen concentration meter 530 appropriately manage the flow rate of the product gas supplied to the storage space 210 of the storage 200 and the oxygen gas concentration in the product gas.

(Vacuum pump)
The vacuum pump 600 is a device for assisting desorption of oxygen gas adsorbed on the molecular sieve carbon of the adsorption tower. One end of the vacuum pump 600 is connected to the gas circulation path 300 on the upstream side of the adsorption tower in the nitrogen separator 500, and the other end is provided in the middle of the exhaust pipe 310 opened to the outside. In the exhaust pipe 310, on the upstream side of the vacuum pump 600, a supply pipe 320 for supplying outside air (air) to the exhaust pipe 310 and a valve (the above-described valve V9) installed in the pipe are provided. It has been.

  The vacuum pump 600 is used in the desorption process. That is, in the nitrogen gas concentrating system 100 of the present embodiment, as described in the stages (ii) and (iv), in the pressure equalizing process (release), the inside of both adsorption towers is set to approximately atmospheric pressure or negative pressure. Under such a pressure, oxygen gas may not be sufficiently desorbed from molecular sieve carbon. Therefore, in the present embodiment, the inside of the adsorption tower (for example, the adsorption tower 510b in the stage (i)) subjected to the desorption process by the vacuum pump 600 is decompressed to assist the desorption of oxygen gas. As a result, more oxygen gas can be desorbed than when desorbed at normal pressure (about 0 MPa). As a result, the amount of oxygen gas that can be adsorbed from the source gas per unit volume increases. In the stage (ii) or (iv), the adsorption tower and the vacuum pump 600 are not communicated with each other. Therefore, outside air is sucked from the supply pipe 320 in order to reduce the load on the vacuum pump.

  According to the nitrogen gas concentrating system 100 of the present embodiment, by repeating the steps (i) to (iv) while circulating the gas through the gas circulation path 300, high concentration nitrogen is obtained using air as a source gas. Product gas containing gas can be produced. At that time, in the nitrogen gas concentrating system 100 of the present embodiment, the raw material gas is supplied by the blower 400 so that the pressure in the adsorption tower 510a or the adsorption tower 510b in the adsorption step becomes 0.05 to 0.15 MPa. The Further, while one adsorption tower is subjected to the adsorption process, the other adsorption tower is subjected to the desorption process and is evacuated by the vacuum pump 600. For this reason, the pressure in the two adsorption towers, which is equalized after the adsorption of oxygen gas, is approximately atmospheric pressure or negative pressure. As a result, the residual pressure of the product gas existing in the adsorption tower at the time of pressure equalization is reduced, so that the amount of product gas exhausted in the subsequent desorption process can be reduced. Therefore, since the amount of atmospheric gas sucked down and the oxygen concentration in the raw material gas decreases, a product gas containing a high concentration of nitrogen gas can be obtained efficiently, and energy efficiency is improved. In particular, when the pressure in the two adsorption towers becomes negative during the pressure equalization process, the absolute value of the adsorption pressure reached at the end of the adsorption process is compared with the absolute value of the desorption pressure reached at the end of the desorption process. In addition, the absolute value of the desorption pressure is larger than the absolute value of the adsorption pressure. Thus, the energy-saving effect is obtained by lowering the desorption pressure than by increasing the adsorption pressure. Further, when the adsorption pressure is low, the specification pressure of the blower 400 can also be lowered. Therefore, the temperature rise of the raw material gas pressurized by the blower 400 is prevented, and the load on the cooling device 800 is reduced.

  Next, a configuration that the nitrogen gas concentration system 100 of the present embodiment preferably includes will be described. The nitrogen gas concentration system 100 preferably includes a cooling device 800, a connecting pipe line 910, and a raw material gas pressure adjusting device 900.

(Cooling device 800)
The nitrogen gas concentration system 100 of the present embodiment preferably includes a cooling device 800. The source gas supplied from the blower 400 to the nitrogen separation device 500 is preferably adjusted to a temperature of about 20 to 50 ° C., for example, in order to improve the adsorption efficiency of the oxygen gas in the adsorption tower. Therefore, the nitrogen gas concentration system 100 preferably includes a cooling device 800 on the downstream side of the blower 400. According to the cooling device 800, since the source gas pressurized by the blower 400 can be adjusted within the above temperature range, oxygen gas is easily adsorbed in the adsorption tower, and the separation and concentration efficiency of nitrogen gas increases. In addition, it does not specifically limit as the cooling device 800, For example, the well-known cooling device which employ | adopted the air cooling system, the water cooling system, etc. can be used.

(Raw gas pressure regulator)
The nitrogen gas concentration system 100 of the present embodiment preferably includes a raw material gas pressure adjustment device 900.

  That is, when the nitrogen gas is separated and concentrated from the raw material gas, a pressure equalizing step for connecting the two adsorption towers is performed (see FIG. 2). At this time, the supply of the raw material gas to the nitrogen separation device 500 is shut off. If the source gas continues to flow in the gas circulation path 300 in such a state, the source gas pressure increases on the upstream side of the nitrogen separation device 500, which may cause a failure or the like. Therefore, when the supply of the source gas to the nitrogen separation device 500 is shut off, it is preferable to circulate the source gas before and after the blower 400.

  Therefore, in the nitrogen gas concentrating system 100, a connecting pipe 910 that connects the downstream side and the upstream side of the blower 400 is provided on the downstream side of the blower 400, and the raw material gas pressure adjusting device 900 is provided in the connecting pipe 910. Is preferably provided. By providing such a connection pipe 910 and the raw material gas pressure adjusting device 900, in the nitrogen gas concentration system 100, part or all of the raw material gas supplied from the blower 400 to the nitrogen separation device 500 is again upstream of the blower 400. It can be returned to the side. As a result, it is possible to prevent the source gas from being pressurized more than necessary on the upstream side of the adsorption tower and to prevent the blower 400 from malfunctioning. In addition, there is an excess of pressurized source gas, such as a pressure equalization step in which source gas is not supplied or the latter half of the adsorption step in which the pressure in the adsorption tower is increased and the source gas becomes difficult to be supplied. In such a case, it is possible to prevent excess source gas from being released into the atmosphere by the blower 400. In addition, this can reduce the supply of atmospheric gas to the nitrogen separation device 500 and prevent the performance of the nitrogen separation device 500 from deteriorating. It should be noted that the position where the connecting pipe 910 is connected on the downstream side of the blower 400 may be on the upstream side of the cooling device 800 or on the downstream side of the cooling device 800. When the connection pipe 910 is connected to the upstream side of the cooling device 800, the burden on the cooling device 800 is reduced. Further, when the connection pipe line 910 is connected to the downstream side of the cooling device 800, the raw material gas is sufficiently cooled by the cooling device 800, and the adsorption rate of oxygen gas in the adsorption tower can be improved.

<Application of nitrogen gas concentration system>
Next, the use of the nitrogen gas concentration system 100 of this embodiment will be described. The nitrogen gas concentration system 100 can store a product gas containing a high concentration of nitrogen gas in the storage space 210 of the storage 200. Therefore, the storage 200 can be suitably used for an application in which a desired effect can be obtained by using a nitrogen gas atmosphere.

  As such a use, for example, a use as a storage for storing fruits and vegetables can be cited. In this case, the nitrogen gas concentrating system 100 can suppress respiration of fruits and vegetables carried into the storage space 210 and prevent a decrease in freshness by setting the inside of the storage space 210 to a high-concentration nitrogen gas atmosphere.

  In addition, the storage 200 has a use as a processing container for performing fumigation of books, fumigation of cigarettes, or insecticidal treatment of cultural properties. In this case, the nitrogen gas concentrating system 100 can fumigate books and cigarettes carried into the storage space 210 or perform an insecticidal treatment on cultural assets by setting the storage space 210 to a high-concentration nitrogen gas atmosphere. it can. In this specification, the cultural property refers to cultural products such as paintings, sculptures, crafts, and handwriting.

(Second Embodiment)
Next, another embodiment of the nitrogen gas concentration system of the present invention will be described with reference to the drawings. FIG. 3 is a schematic diagram of a nitrogen gas concentration system according to an embodiment of the present invention.

  As shown in FIG. 3, the nitrogen gas concentrating system 101 of this embodiment is provided with a flow rate adjusting device 541 in place of the flow meter 540 and the valve V10 in the nitrogen gas concentrating system 100 of the first embodiment. The configuration is the same as that of the nitrogen gas concentration system 100 of the first embodiment except that the oxygen concentration meter 220 is provided in the storage 200. For this reason, the same reference numerals are assigned to overlapping components, and the description thereof is omitted as appropriate.

(Oxygen concentration meter)
In the nitrogen gas concentration system 101 of this embodiment, an oxygen concentration meter 220 is installed in the storage space 210. The oxygen concentration meter 220 is connected to a flow rate adjusting device 541 described later by wire or wirelessly, and feeds back a measured value of the oxygen concentration in the storage space 210 to the flow rate adjusting device 541.

(Flow control device)
Further, the nitrogen separation device 501 of this embodiment includes a flow rate adjusting device 541 on the downstream side of the product tank 520. The flow rate adjusting device 541 can adjust the flow rate of the product gas supplied to the storage space 210 stepwise in response to feedback of the measured value of the oxygen concentration measured by the oximeter 220.

  Specifically, for example, when the oxygen gas concentration in the storage space 210 is high (that is, when the nitrogen gas concentration is low), the flow control device 541 adjusts the flow rate so that a large amount of product gas is supplied to the storage space 210. The nitrogen gas concentration in the storage space 210 can be quickly increased by adjusting. Thereafter, when the oxygen gas concentration in the storage space 210 is low (that is, when the nitrogen gas concentration is increased), the flow control device 541 is configured so that the flow rate of the product gas supplied to the storage space 210 decreases. The replacement efficiency can be increased by adjusting to As a result, the nitrogen gas concentration system 101 can efficiently increase the nitrogen gas concentration in the product gas in the storage space 210. More specifically, for example, when the nitrogen gas concentration system 101 is operated so that product gas containing 98% by volume of nitrogen gas is stored in the storage space 210, the nitrogen gas concentration of the product gas is 98 volume. It is necessary to make the concentration higher than% (for example, 99% by volume). Here, when the operation of the nitrogen gas concentration system 101 is started, air (oxygen gas concentration of about 20% by volume) exists in the storage space 210, and the oxygen gas concentration is high. Therefore, first, the flow rate adjusting device 541 is controlled so that the flow rate of the product gas supplied to the storage space 210 is increased, so that the replacement efficiency between the air in the storage space 210 and the product gas can be increased. In this case, when the flow rate of the product gas supplied from the nitrogen separation device 501 increases, the nitrogen gas concentration in the product gas is estimated to be low (may be less than 98% by volume). Nitrogen gas replacement efficiency is improved. On the other hand, if the nitrogen gas concentration in the storage space 210 is increased to some extent, the product gas concentration stored in the storage space 210 is set to the above-mentioned 98% by volume unless a product gas having a high nitrogen gas concentration is supplied. It can not be. Therefore, the flow control device 541 performs a step when the oxygen concentration meter 220 feeds back that the oxygen gas concentration of the product gas in the storage space 210 has become a certain value or less (for example, 10% by volume or less in the product gas). In particular, it is preferable to increase the nitrogen gas concentration in the product gas by reducing the flow rate of the product gas. Thereby, the nitrogen gas concentration in the product gas in the storage space 210 can be efficiently increased without significantly reducing the replacement efficiency, and can reach the target nitrogen gas concentration of 98% by volume.

  As described above, according to the nitrogen gas concentration system 101 of the present embodiment, the flow rate of the product gas supplied to the storage space 210 can be adjusted according to the detected value of the oxygen concentration in the storage space 210. As a result, the nitrogen gas concentration of the product gas stored in the storage space 210 can be increased efficiently. Therefore, the operation time of the nitrogen gas concentration system 101 is further shortened, and the energy efficiency is further improved.

  EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples.

Example 1
Using the nitrogen gas concentration system 100 shown in FIG. 1, a mixed gas of a gas stored in the storage 200 and a gas (atmosphere) sucked from the outside is used as a raw material gas, and the nitrogen gas is separated and concentrated from the raw material gas. A product gas containing nitrogen gas that changes to 97.8 to 99.4% by volume over time was supplied to the storage space 210. The adsorption and desorption cycle time in both adsorption towers at that time was 126 seconds. The breakdown was 60 seconds for the oxygen gas adsorption process, 3 seconds for the pressure equalization process (release), 60 seconds for the desorption process, and 3 seconds for the pressure equalization process (recovery). The raw material gas was supplied by the blower 400 so that the pressure of the adsorption tower at the time of adsorption was 0.05 MPa, and the pressure was reduced by the vacuum pump 600 until the pressure of the adsorption tower at the time of desorption was -0.09 MPa. The pressure in both adsorption towers during the pressure equalization step was -0.02 MPa. The volume of the storage space 210 was 350 m ³ . The supply amount of the product gas was 45 Nm ³ / hr. The nitrogen gas concentration system 100 was operated until the nitrogen gas concentration of the product gas in the storage space 210 reached 98% by volume. FIG. 4 shows the nitrogen gas concentration in the product gas and the nitrogen gas concentration in the storage space 210 when the nitrogen gas concentration system 100 is in operation. FIG. 5 shows the relationship between the time required for the nitrogen gas concentration to reach 98% by volume (arrival time) and the pressure during adsorption. Furthermore, the relationship between the amount of power consumption and the pressure at the time of adsorption | suction is shown in FIG.

(Example 2)
The nitrogen gas concentration system 100 was operated in the same manner as in Example 1 except that the pressure of the adsorption tower during adsorption was 0.1 MPa. The pressure in both adsorption towers during the pressure equalization step was 0.01 MPa. FIG. 5 shows the relationship between the arrival time and the pressure at the time of adsorption. FIG. 6 shows the relationship between the power consumption and the pressure during adsorption.

Example 3
The nitrogen gas concentration system 100 was operated in the same manner as in Example 1 except that the pressure of the adsorption tower at the time of adsorption was 0.15 MPa. The pressure in both adsorption towers during the pressure equalization step was 0.03 MPa. FIG. 5 shows the relationship between the arrival time and the pressure at the time of adsorption. FIG. 6 shows the relationship between the power consumption and the pressure during adsorption.

(Comparative Example 1)
The nitrogen gas concentration system 100 was operated in the same manner as in Example 1 except that the pressure of the adsorption tower at the time of adsorption was 0.01 MPa. The pressure in both adsorption towers during the pressure equalization step was -0.04 MPa. FIG. 5 shows the relationship between the arrival time and the pressure at the time of adsorption. FIG. 6 shows the relationship between the power consumption and the pressure during adsorption.

(Comparative Example 2)
The nitrogen gas concentration system 100 was operated in the same manner as in Example 1 except that the pressure of the adsorption tower during adsorption was 0.2 MPa. The pressure in both adsorption towers during the pressure equalization step was 0.06 MPa. FIG. 5 shows the relationship between the arrival time and the pressure at the time of adsorption. FIG. 6 shows the relationship between the power consumption and the pressure during adsorption.

(Comparative Example 3)
The nitrogen gas concentration system 100 was operated in the same manner as in Example 1 except that the pressure of the adsorption tower at the time of adsorption was 0.25 MPa. The pressure in both adsorption towers during the pressure equalization step was 0.08 MPa. FIG. 5 shows the relationship between the arrival time and the pressure at the time of adsorption. FIG. 6 shows the relationship between the power consumption and the pressure during adsorption.

(Comparative Example 4)
Using the nitrogen gas concentration system 102 shown in FIG. 7, nitrogen gas was separated and concentrated using air as a raw material gas, and a product gas containing 99% by volume of nitrogen gas was prepared and supplied to the storage space 210. In this nitrogen gas concentrating system 102, the raw material gas (air) taken in from the air compressor 401 (compressor) is dried by a drying device 801 (drying condition: atmospheric pressure dew point of −17 ° C. or lower). Was concentrated and supplied to the storage space 210. The storage space 210 was connected with an internal pressure adjusting device 601 that discharges the gas in the storage space 210 to the outside by a connection pipe line 602 provided with a valve V11. The internal pressure adjustment device 601 increased the nitrogen gas concentration in the storage space 210 while exchanging the supplied product gas and the gas stored in the storage space 210 as needed. The time until the nitrogen gas concentration in the storage space 210 reaches 98% by volume is comparable to that of the nitrogen gas concentrating system 100 of the first embodiment. . The cycle time of the adsorption tower of the nitrogen separator 502 was 126 seconds. The breakdown was 60 seconds for the oxygen gas adsorption process, 3 seconds for the pressure equalization process (release), 60 seconds for the desorption process, and 3 seconds for the pressure equalization process (recovery). The pressure of the adsorption tower at the time of adsorption was 0.70 MPa, and the pressure of the adsorption tower at the time of desorption was 0 MPa. The pressure in both adsorption towers during the pressure equalization step was 0.30 MPa. The volume of the storage space 210 was 350 m ³ . The supply amount of the product gas was 50 Nm ³ / hr. The nitrogen gas concentration system 102 was operated until the nitrogen gas concentration of the product gas in the storage space 210 reached 98% by volume. FIG. 5 shows the relationship between the arrival time and the pressure at the time of adsorption. FIG. 6 shows the relationship between the power consumption and the pressure during adsorption.

Example 4
The nitrogen gas concentration system 101 shown in FIG. 3 was used, and the nitrogen gas flow rate was gradually reduced from 50 Nm ³ / hr to 45 Nm ³ / hr using the nitrogen gas concentration system 101 in the same manner as in Example 2. Drove. Specifically, the operation was performed at a nitrogen gas flow rate of 50 Nm ³ / hr for 5.2 hr from the start of operation. After confirming that the oxygen gas concentration in the storage space 210 was 10% by volume with an oximeter installed in the storage space 210, the nitrogen gas flow rate was 49 Nm ³ / hr until 5.2 to 10.3 hr. Drove as. After confirming that the oxygen gas concentration in the storage space 210 became 5% by an oxygen concentration meter installed in the storage space 210, the nitrogen gas flow rate was 48 Nm ³ / hr from 10.3 to 15.6 hr. Drove as. After the oxygen gas concentration in the storage space 210 by the oxygen concentration meter which is installed in the storage space 210 became 2.5% by volume was confirmed, 45 Nm nitrogen gas flow rate to the arrival time of 15.6hr ³ / Driving as hr. FIG. 5 shows the relationship between the arrival time and the pressure at the time of adsorption. FIG. 6 shows the relationship between the power consumption and the pressure during adsorption.

  As shown in FIG. 5, according to the system of Examples 1 to 4 adjusted so that the pressure in the adsorption tower in the adsorption process is 0.05 to 0.15 MPa by the blower, the nitrogen gas concentration in the product gas The time (arrival time) required to reach 98% by volume was as short as 17 to 21.5 hours. On the other hand, according to the systems of Comparative Examples 1 to 3 in which the pressure in the adsorption tower was adjusted to be out of the above range, the arrival time was 27 to 36.5 hours, which was a long time. In particular, in the system of Comparative Example 3 in which the pressure in the adsorption tower was 0.25 MPa as in the prior art, the arrival time was as long as 36.5 hours.

  Moreover, as shown in FIG. 6, according to the system of Examples 1-4 adjusted so that the pressure in the adsorption tower in an adsorption process may be 0.05-0.15 MPa with a blower, nitrogen in product gas The power consumption until the gas concentration reached 98% by volume was as small as 95 to 115 kWh. On the other hand, according to the systems of Comparative Examples 1 to 3 in which the pressure in the adsorption tower was adjusted to deviate from the above range, the power consumption was as large as 155 to 250 kWh. In particular, in the system of Comparative Example 3 in which the pressure in the adsorption tower was 0.25 MPa as in the prior art, the power consumption was as large as 250 kWh.

  Further, in the system of Comparative Example 4 in which the pressure in the adsorption tower in the adsorption process is 0.7 MPa using a compressor (air compression device 401) as in the prior art, as shown in FIG. In the case of the device configuration of the air compression device 401 and the nitrogen separation device 502, which is the same level as the system 1, it was found that the power consumption is extremely large as 375 kWh as shown in FIG. 6. This is presumed to be because there is no evacuation and the gas stored in the storage space 210 is not circulated and used, so that a large amount of source gas is required and the power consumption (power consumption) of the air compressor 401 increases. .

  From these results, it was found that according to the nitrogen gas concentration systems of Examples 1 to 4 of the present invention, the product gas containing 98% by volume of nitrogen gas can be adjusted in a short time and with excellent energy efficiency. That is, despite the fact that molecular sieve carbon has the property of increasing the adsorption capacity of oxygen gas under high pressure conditions, in the nitrogen gas concentration system of the present invention, the pressure in the adsorption tower in the adsorption process is conventionally reduced by the blower. It has been found that the effect of separating and concentrating nitrogen gas is enhanced and the power consumption can be suppressed when adjusted to be lower than that. Further, as can be seen from the results of Example 2 and Example 4, the arrival time is further shortened and the power consumption is suppressed by adjusting the flow rate of the product gas supplied to the storage space in stages. I found out.

  The present invention is a nitrogen gas concentrating system capable of separating and concentrating nitrogen gas from a raw material gas containing nitrogen gas and oxygen gas and storing a product gas containing high concentration nitrogen gas in an internal space such as a warehouse. Therefore, the present invention is suitably used in a technical field that provides, for example, a storage for storing high-concentration nitrogen gas to preserve fruits and vegetables, a storage for performing fumigation of books and cigarettes, or insecticidal treatment of cultural assets, and the like. be able to.

100, 101, 102 Nitrogen gas concentrating system 200 Storage 210 Storage space 220, 530 Oxygen concentration meter 300 Gas circulation path 310 Exhaust pipe 320 Supply pipe 400 Blower 401 Air compressor 500, 501, 502 Nitrogen separator 510a, 510b Adsorption tower 520 Product tank 521 Primary storage space 540 Flow meter 541 Flow control device 600 Vacuum pump 601 Internal pressure adjustment device 602 Connection pipe 700 Outside air inlet 710 Connection pipe 800 Cooling device 801 Drying apparatus 900 Raw material gas pressure adjustment apparatus 910 Connection pipe Road V1-V11 valve

Claims (6)

A nitrogen gas concentrating system for concentrating the nitrogen gas by alternately repeating adsorption and desorption of the oxygen gas among the source gas containing nitrogen gas and oxygen gas between two or more adsorption towers packed with molecular sieve carbon Because
A storage comprising a storage space in which the concentrated nitrogen gas is stored;
A gas circulation path in which one end and the other end are connected to the storage space;
A nitrogen separator including the two or more adsorption towers arranged in the gas circulation path;
It arrange | positions in the upstream of the said nitrogen separation apparatus among the said gas circulation paths, attracts | sucks the said source gas, and supplies it to the said nitrogen separation apparatus so that the pressure in the said adsorption tower may be 0.05-0.15 MPa. With the blower,
A vacuum pump for desorbing the oxygen gas adsorbed on the molecular sieve carbon;
Nitrogen gas enrichment system. An oxygen concentration meter for measuring the oxygen gas concentration in the storage space;
The flow rate of the concentrated nitrogen gas, which is disposed downstream of the two or more adsorption towers and upstream of the storage, and is supplied into the storage space according to a detection value of the oximeter. The nitrogen gas concentration system according to claim 1, further comprising: a flow rate control device that controls the flow rate.   The nitrogen gas concentration system according to claim 1, further comprising a cooling device that is disposed downstream of the blower and that cools the source gas supplied to the nitrogen separation device. A connecting pipe connecting the upstream side and the downstream side of the blower;
The raw material gas pressure adjusting device which is arrange | positioned in the said connection pipe line and returns the said raw material gas discharged | emitted from the said blower to the upstream of the said blower is further provided. Nitrogen gas concentration system.   The nitrogen gas concentration system according to any one of claims 1 to 4, wherein the storage is a storage for storing fruits and vegetables.   5. The nitrogen gas concentration system according to claim 1, wherein the storage is a processing chamber for performing fumigation of books, fumigation of cigarettes, or insecticidal processing of cultural properties.

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