Nitrogen gas generation apparatus, system, and method using catalytic combustion

Abstract

Provided is a nitrogen gas generation apparatus which makes it possible to use a combustion catalyst to stably, continuously, and reliably generate high-purity nitrogen gas. This nitrogen gas generation apparatus comprises: an oxygen delivery amount restriction means that takes in air or gas which contains nitrogen and oxygen, and that delivers the air or the gas while restricting the delivery amount of oxygen contained in the air or the gas; and a catalytic combustion means that reacts the delivered air or gas with fuel gas which contains intake hydrogen on a combustion catalyst to convert the air or the gas into nitrogen-enriched gas, which has an increased nitrogen concentration. The oxygen delivery amount restriction means makes the oxygen concentration of the air or the gas equal to or smaller than the maximum oxygen concentration that is determined on the basis of a set or desired upper temperature limit for the combustion catalyst or the catalytic combustion reaction, and / or makes the flow rate of the air or the gas equal to or smaller than the maximum flow rate that is determined on the basis of a set or desired upper temperature limit for the combustion catalyst or the catalytic combustion reaction.

Description

Apparatus, system and method for generating nitrogen gas using catalytic combustion

[0001] The present invention relates to a technique for producing highly pure nitrogen gas.

[0002] This application claims the benefit of priority under the Paris Convention to Japanese Patent Application JP2024-151407, filed on September 3, 2024, which is incorporated herein by reference in its entirety pursuant to PCT Rule 20.6.

[0003] In recent years, hydrogen energy has been attracting attention as a means of achieving carbon neutrality and ultimately carbon zero. By utilizing this hydrogen energy, it is possible to produce useful materials and energy without emitting carbon dioxide. The present inventors have focused on hydrogen energy and have developed a variety of devices and systems using fuel cells that generate electricity using hydrogen energy, as disclosed in Patent Documents 1 to 11. In particular, as disclosed in Patent Documents 6 and 7, they have developed a nitrogen gas generator that applies exhaust gas extracted from a fuel cell to an oxygen removal filter and extracts gas with an increased nitrogen concentration from the filter. Furthermore, as disclosed in Patent Documents 8 and 10, they have invented a configuration in which the dehumidification process of exhaust gas, which is important in nitrogen gas generation, is performed using a water seal pump or a dry filter. Furthermore, as disclosed in Patent Documents 9 and 11, they have also developed a nitrogen gas generator that performs the dehumidification process using a water exchange process.

[0004] JP 2013-233549 A JP 2016-164987 A JP 2017-084796 A JP 2018-163890 A JP 2019-129110 A JP 2020-149838 A JP 2021-136084 A JP 2022-114256 A JP 2023-101132 A International Publication No. 2021 / 172260 International Publication No. 2023 / 132193

[0005] The present inventors are currently focusing on catalytic combustion as a promising gas processing method for generating nitrogen gas using hydrogen energy. Catalytic combustion is a process in which a target gas is combusted with hydrogen gas over a combustion catalyst to decompose, remove, or reduce unwanted components in the target gas. The present inventors believe that using such catalytic combustion may enable stable or continuous production of nitrogen gas with a purity of, for example, 4N (99.99 vol%) or 5N (99.999 vol%).

[0006] Therefore, an object of the present invention is to provide a nitrogen gas generating device, system, and method that can stably, continuously, or reliably generate high-purity nitrogen gas using a combustion catalyst.

[0007] According to the present invention, there is provided a nitrogen gas generating device or system comprising: an oxygen content delivery amount limiting means for taking in air or a gas containing nitrogen and oxygen, and delivering the air or gas while limiting the amount of oxygen content in the air or gas delivered; and a catalytic combustion means for reacting the delivered air or gas with a fuel gas containing hydrogen taken in on a combustion catalyst to convert the air or gas into a nitrogen-enriched gas having a higher nitrogen concentration, wherein the oxygen content delivery amount limiting means limits the oxygen concentration of the air or gas to a maximum oxygen concentration determined based on a set or desired upper limit temperature for the combustion catalyst or the reaction, and / or limits the flow rate of the air or gas to a maximum flow rate determined based on a set or desired upper limit temperature for the combustion catalyst or the reaction.

[0008] In one embodiment of the nitrogen gas generating device or system according to the present invention, the catalytic combustion means converts the air or gas into a nitrogen-enriched gas having an oxygen concentration equal to or less than a set or desired upper limit oxygen concentration, and the oxygen content delivery amount limiting means preferably limits the oxygen concentration of the air or gas to a maximum oxygen concentration determined based on the set or desired upper limit temperature of the combustion catalyst or the reaction and the set or desired upper limit oxygen concentration, and / or limits the flow rate of the air or gas to a maximum flow rate determined based on the set or desired upper limit temperature of the combustion catalyst or the reaction and the set or desired upper limit oxygen concentration.

[0009] In another embodiment of the nitrogen gas generating device or system according to the present invention, it is also preferable that the oxygen content delivery amount limiting means includes a fuel cell that takes in the air or gas and delivers the air or gas with a reduced oxygen concentration as exhaust gas.

[0010] Furthermore, in an embodiment including the above fuel cell, it is also preferable that the fuel cell takes in a fuel gas containing hydrogen at a flow rate equal to or greater than the flow rate that enables all of the oxygen contained in the taken-in air or gas to be converted into water, allows a current to flow between the electrodes in an amount that would flow if all of the oxygen were converted into water, and discharges the air or gas with a reduced oxygen concentration as exhaust gas.

[0011] In yet another embodiment of the nitrogen gas generating device or system according to the present invention, it is also preferable that the oxygen delivery amount restriction means includes an oxygen filtering means which has filters with different permeabilities for nitrogen and oxygen, and which acts on the taken-in air or gas through the filters to deliver air or gas with a reduced oxygen concentration.

[0012] Furthermore, in yet another embodiment of the nitrogen gas generating device or system according to the present invention, it is also preferable that the oxygen content delivery amount restriction means includes: a fuel cell that takes in the air or gas and delivers the air or gas with a reduced oxygen concentration as exhaust gas; and oxygen filtering means that has filters with different permeabilities for nitrogen and oxygen, and that acts on the filter with the taken-in air or gas as exhaust gas to deliver the air or gas with an even lower oxygen concentration.

[0013] In yet another embodiment of the nitrogen gas generation device or system according to the present invention, the oxygen content delivery amount restriction means includes a second catalytic combustion means that reacts the taken-in air or gas with the taken-in fuel gas containing hydrogen on a second combustion catalyst and delivers the air or gas with a reduced oxygen concentration, and it is also preferable that the second catalytic combustion means has a set or desired second upper limit temperature for the second combustion catalyst or the reaction, which second upper limit temperature exceeds the upper limit temperature for the above-mentioned catalytic combustion means (first catalytic combustion means).

[0014] Furthermore, in yet another embodiment of the nitrogen gas generation device or system according to the present invention, the oxygen content delivery amount restriction means includes: a fuel cell that takes in the air or gas and delivers the air or gas with a reduced oxygen concentration as exhaust gas; and second catalytic combustion means that reacts the taken-in air or gas as exhaust gas with taken-in fuel gas containing hydrogen on a second combustion catalyst and delivers the air or gas with an even lower oxygen concentration, and it is also preferable that the second catalytic combustion means has a set or desired second upper limit temperature for the second combustion catalyst or the reaction, which second upper limit temperature exceeds the upper limit temperature of the above-mentioned catalytic combustion means (first catalytic combustion means).

[0015] In yet another embodiment of the nitrogen gas generating device or system according to the present invention, the oxygen content delivery amount restriction means includes: oxygen filtering means having filters with different permeabilities for nitrogen and oxygen, which act on the taken-in air or gas through the filters to deliver the air or gas with a reduced oxygen concentration; and second catalytic combustion means which reacts the air or gas with a reduced oxygen concentration with the taken-in fuel gas containing hydrogen on a second combustion catalyst to deliver the air or gas with an even lower oxygen concentration, and it is also preferable that the second catalytic combustion means has a set or desired second upper limit temperature for the second combustion catalyst or the reaction, which second upper limit temperature exceeds the upper limit temperature of the above-mentioned catalytic combustion means (first catalytic combustion means).

[0016] Furthermore, in yet another embodiment of the nitrogen gas generating apparatus or system according to the present invention, it is preferable that the nitrogen gas generating apparatus or system further comprises gas filtering means that includes filters having different permeabilities for nitrogen and hydrogen and for nitrogen and oxygen, and that applies the introduced nitrogen-enhancing gas to the filters to deliver a nitrogen-enhancing gas with a higher nitrogen concentration, or a nitrogen-enhancing gas from which hydrogen has been removed or a nitrogen-enhancing gas with a lower hydrogen concentration, if the introduced nitrogen-enhancing gas contains hydrogen.

[0017] In yet another embodiment of the nitrogen gas generating device or system according to the present invention, it is also preferable that the nitrogen gas generating device or system further comprises a dehumidifying means for removing or reducing the moisture or water vapor content contained in the nitrogen enrichment gas that is taken in.

[0018] Furthermore, as yet another embodiment of the nitrogen gas generation device or system according to the present invention, it is also preferable that the nitrogen gas generation device or system further comprises: a pressure boosting means that is provided upstream of the oxygen content delivery amount restriction means or upstream of the catalytic combustion means, and that increases the pressure of the air or gas that has been taken in or delivered, and delivers the increased pressure air or gas toward the oxygen content delivery amount restriction means or the catalytic combustion means; and a pressure control means that is provided downstream of the catalytic combustion means, and that controls the increased pressure of the air or gas in the section from the pressure boosting means to its installation position.

[0019] The present invention also provides a nitrogen gas generating device or system comprising: an oxygen content delivery amount limiting means for taking in air or a gas containing nitrogen and oxygen, and delivering the air or gas while limiting the amount of oxygen content delivered from the air or gas; and a catalytic combustion means for reacting the delivered air or gas with a fuel gas containing hydrogen taken in on a combustion catalyst to convert the air or gas into a nitrogen-enriched gas having an oxygen concentration equal to or lower than a set or desired upper limit oxygen concentration, wherein the oxygen content delivery amount limiting means limits the oxygen concentration of the air or gas to a maximum oxygen concentration determined based on the set or desired upper limit oxygen concentration, and / or limits the flow rate of the air or gas to a maximum flow rate determined based on the set or desired upper limit oxygen concentration.

[0020] According to the present invention, there is further provided a nitrogen gas generation method comprising: a first step of taking in air or a gas containing nitrogen and oxygen and delivering the air or gas while limiting the amount of oxygen in the air or gas delivered; and a second step of reacting the delivered air or gas with a fuel gas containing hydrogen taken in over a combustion catalyst to convert the air or gas into a nitrogen-enriched gas having a higher nitrogen concentration, wherein in the first step, the oxygen concentration of the air or gas is set to or below a maximum oxygen concentration determined based on a set or desired upper limit temperature of the combustion catalyst or the reaction, and / or the flow rate of the air or gas is set to or below a maximum flow rate determined based on a set or desired upper limit temperature of the combustion catalyst or the reaction.

[0021] According to the nitrogen gas generating device, system, and method of the present invention, it is possible to stably, continuously, or reliably generate high-purity nitrogen gas using a combustion catalyst.

[0022] FIG. 1 is a schematic diagram showing one embodiment of a nitrogen gas generation device and system according to the present invention. FIG. 2 is a schematic diagram showing another embodiment of a nitrogen gas generation device and system according to the present invention. FIGS. 3(A) and 3(B) are a schematic diagram and graph illustrating an example of catalytic combustion treatment using a catalytic combustion unit according to the present invention. FIGS. 4(A) and 4(B) are graphs illustrating an example of oxygen filtering treatment using an oxygen filtering unit according to the present invention. FIG. 4(C) is a schematic diagram illustrating an embodiment of a gas filter arrangement according to the present invention. FIG. 5 is a graph illustrating an example of oxygen reduction and removal treatment using a fuel cell according to the present invention. FIG. 6 is a schematic diagram showing yet another embodiment of a nitrogen gas generation device and system according to the present invention. FIG. 7 is a schematic diagram showing yet another embodiment of a nitrogen gas generation device and system according to the present invention. FIG. 8 is a schematic diagram showing yet another embodiment of a nitrogen gas generation device and system according to the present invention. FIG. 9 is a schematic diagram showing yet another embodiment of a nitrogen gas generation device and system according to the present invention. FIG. 10 is a schematic diagram showing yet another embodiment of a nitrogen gas generation device and system according to the present invention. FIG. 11 is a schematic diagram for explaining another embodiment of the fuel cell unit according to the present invention.

[0023] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[0024] [Nitrogen Gas Generating Apparatus and System] FIG. 1 is a schematic diagram showing one embodiment of a nitrogen gas generating apparatus and system according to the present invention.

[0025] The nitrogen gas generator 1 shown in FIG. 1 as one embodiment of the present invention includes: (A) oxygen content delivery amount restriction means (102, 103, ...) that takes in air or a gas containing nitrogen (N2) and oxygen (O2) (hereinafter referred to as nitrogen-containing gas) and delivers the air or nitrogen-containing gas to a subsequent stage while restricting the amount of oxygen (O2) content in the air or nitrogen-containing gas that is delivered to a subsequent stage; and (B) a catalytic combustion unit (U) 109 that reacts the delivered air or nitrogen-containing gas with taken-in fuel gas containing hydrogen (H2) on a combustion catalyst to convert the air or nitrogen-containing gas into a nitrogen-enriched gas having a higher nitrogen (N2) concentration, or in this embodiment, a nitrogen-enriched gas having an oxygen (O2) concentration not exceeding a set or desired "upper oxygen concentration limit."

[0026] Here, as a preferred embodiment, the oxygen delivery amount limiting means (102, 103, ...) preferably performs at least one of the following: (A11) setting the oxygen (O2) concentration of the air or nitrogen-containing gas to a maximum oxygen concentration determined based on a set or desired upper limit temperature in the combustion catalyst or catalytic combustion reaction, and (A12) setting the flow rate of the air or nitrogen-containing gas to a maximum flow rate determined based on a set or desired upper limit temperature in the combustion catalyst or catalytic combustion reaction.

[0027] The oxygen delivery amount limiting means (102, 103, ...) limits the amount of oxygen (O2) in the air or nitrogen-containing gas delivered to the catalytic combustion unit 109, thereby keeping the temperature of the combustion catalyst or catalytic combustion reaction in the catalytic combustion unit 109 below the "upper limit temperature." As a result, the nitrogen gas generator 1 can stably or continuously generate high-purity nitrogen gas.

[0028] Generally, in catalytic combustion processing in a catalytic combustor, as the amount of oxygen (O2) per unit time in the introduced air or nitrogen-containing gas, i.e., the introduction flow rate of oxygen (O2), increases, the catalytic combustion reaction becomes larger, the reaction heat increases, and the reaction temperature, and ultimately the temperature of the combustion catalyst, also increases. If this temperature becomes too high, there is a possibility that the support of the combustion catalyst, etc., may be deformed or deteriorated. Therefore, in catalytic combustors, a predetermined "upper limit temperature" is set for the combustion catalyst or catalytic combustion reaction to ensure stable or continuous catalytic combustion reaction, and it is desirable or necessary to use the combustion catalyst or catalytic combustion reaction at or below this "upper limit temperature."

[0029] For example, in the case of combustion catalysts with a metal support such as stainless steel, which are said to be capable of efficiently removing or reducing trace amounts of oxygen (O2), a "maximum temperature" of, for example, 300°C is often set or recommended (for example, by combustion catalyst manufacturers) on the assumption of continuous use. When air is introduced at a desired flow rate into a catalytic combustor using such a metal-supported combustion catalyst, the temperature of the combustion catalyst or catalytic combustion reaction often exceeds the set or recommended "maximum temperature."

[0030] Therefore, the nitrogen gas generating device 1 of this embodiment uses an oxygen content delivery amount limiting means (102, 103, ...) to limit the amount of oxygen (O2) in the air or nitrogen-containing gas delivered to the catalytic combustion unit 109, making it possible to keep the temperature of the combustion catalyst or catalytic combustion reaction in the limited catalytic combustion unit 109 below the "upper limit temperature."

[0031] Furthermore, as another preferred embodiment, the oxygen delivery amount limiting means (102, 103, ...) preferably performs at least one of the following: (A21) setting the oxygen (O2) concentration of the air or nitrogen-containing gas to be equal to or less than a "maximum oxygen concentration" determined based on the set or desired "upper limit temperature" of the combustion catalyst or catalytic combustion reaction and the above-mentioned "upper limit oxygen concentration" in the nitrogen-enriched gas produced; and (A22) setting the flow rate of the air or nitrogen-containing gas to be equal to or less than a "maximum flow rate" determined based on the set or desired "upper limit temperature" of the combustion catalyst or catalytic combustion reaction and the above-mentioned "upper limit oxygen concentration" in the nitrogen-enriched gas produced.

[0032] By limiting the amount of oxygen (O2) in the air or nitrogen-containing gas sent to the catalytic combustion unit 109, the oxygen content limiting means (102, 103, ...) can suppress the temperature of the combustion catalyst or catalytic combustion reaction in the catalytic combustion unit 109 to an "upper limit temperature" and can keep the oxygen (O2) concentration of the nitrogen-enriched gas extracted from the catalytic combustion unit 109 below the "maximum oxygen concentration." As a result, the nitrogen gas generator 1 can stably, continuously, and reliably generate high-purity nitrogen gas.

[0033] Generally, in catalytic combustion treatment in a catalytic combustor, the smaller the amount of oxygen (O2) per unit time in the introduced air or nitrogen-containing gas, i.e., the smaller the introduction flow rate of the oxygen (O2), the more reliably the introduced oxygen (O2) can be used for the reaction, and the more reduced the oxygen (O2) concentration in the gas extracted after catalytic combustion treatment.

[0034] Therefore, the oxygen content delivery amount limiting means (102, 103, ...) limits the amount of oxygen (O2) in the air or nitrogen-containing gas delivered to the catalytic combustion unit 109 as described above in (A21) and / or (A22), thereby making it possible to keep the oxygen (O2) concentration of the nitrogen-enriched gas extracted from the catalytic combustion unit 109 below the "upper limit oxygen concentration."

[0035] As a result, the nitrogen gas generator 1 can more reliably generate nitrogen gas with high purity. For example, as will be described later, it is possible to reliably generate nitrogen gas with a purity of 5N (99.999 vol%) or higher, which is the specification required by a certain supplier.

[0036] Furthermore, as another preferred embodiment, the oxygen content delivery amount limiting means (102, 103, ...) implements at least one of the following: (A31) setting the oxygen (O2) concentration of the air or nitrogen-containing gas to be equal to or less than the "maximum oxygen concentration" determined based on the above-mentioned "upper limit oxygen concentration", and (A32) setting the flow rate of the air or nitrogen-containing gas to be equal to or less than the "maximum flow rate" determined based on the above-mentioned "upper limit oxygen concentration", thereby limiting the amount of oxygen (O2) content in this air or nitrogen-containing gas delivered to the catalytic combustion unit 109, and causing this catalytic combustion unit 109 to generate a nitrogen-enriched gas having an oxygen (O2) concentration equal to or less than the "upper limit oxygen concentration".

[0037] By limiting the amount of oxygen (O2) in the air or nitrogen-containing gas sent to the catalytic combustion unit 109, the oxygen (O2) concentration of the nitrogen-enriched gas extracted from the catalytic combustion unit 109 can be kept below the "upper limit oxygen concentration." As a result, the nitrogen gas generator 1 can reliably generate high-purity nitrogen gas. For example, as one embodiment, as described below, it is possible to reliably generate nitrogen gas having a purity of 5N (99.999 vol%) or higher, which is the specification required by a certain supplier.

[0038] Here, the oxygen content delivery amount limiting means (102, 103, ...) will be described in detail later using Figures 1, 2, 6, 7, 8 and 9, and can be at least one of a fuel cell unit (103, 203), an oxygen filtering unit (106, 306, 403'), an oxygen content limiting catalytic combustion unit (205, 405), and a flow controller (102, 107, 107', 202, 207, 302, 307, 402, 407). Of course, a combination of at least two of these is also preferable.

[0039] In the embodiments shown in Figures 1, 2, 6, 7, 8, and 9, which will be described in detail later, all of the components are combined to form a single device (nitrogen gas generator). However, in other embodiments, at least one of the components may be included in a device separate from the other components. For example, the oxygen delivery amount limiting means (102, 103, ...) may be included in a device separate from the device including the catalytic combustion unit (109, 209, 309, 409). In such a case, these devices together constitute the nitrogen gas generation system (1, 1', 2, 3, 4, 4') according to the present invention.

[0040] The terms "high purity" and "high purity" used above and below refer to a state in which the oxygen and hydrogen concentrations in nitrogen gas (nitrogen-enhancing gas) are sufficiently reduced. Specifically, the nitrogen concentration (in ml per 100 ml of medium, expressed in vol%) in "high purity" nitrogen gas (nitrogen-enhancing gas) or "high purity" nitrogen gas (nitrogen-enhancing gas) is sometimes specified as 95 vol% or more, 99 vol% (2N) or more, or even 99.9 vol% (3N) or more, or 99.999 vol% (5N) or more, depending on the field and application of the nitrogen gas.

[0041] In this specification, the nitrogen concentration value is a value measured and calculated without taking into account residual elements in the nitrogen gas (nitrogen-enriched gas), such as argon (Ar) and carbon dioxide (CO2) originally contained in the air. In other words, the nitrogen concentration value (e.g., 99.999 vol% (5N)) in this specification is a value that takes into account only oxygen (O2) and hydrogen (H2) as highly active impurities that should be reduced or removed.

[0042] Furthermore, below, gas pressure values ​​for air, hydrogen gas, etc. are absolute pressure values ​​based on a vacuum, i.e., atmospheric pressure is 1 atmosphere (approximately 0.1 megapascals (MPa)). For example, the "0.5 MPa (approximately 5 atmospheres)" shown below is the measured value by a pressure gauge installed in the piping for air, hydrogen gas, etc., i.e., the gauge pressure value is approximately 0.4 MPa (approximately 4 atmospheres).

[0043] [Device / System Configuration] The nitrogen gas generating device (system) 1 of this embodiment shown in Figure 1 has a pressure boosting unit 101, a flow rate controller 102, a fuel cell unit 103, a dehumidifier 104, a dehumidification unit 105, an oxygen filtering unit 106, a flow rate controller 107, a hydrogen recovery unit 108, a catalytic combustion unit 109, a dehumidification unit 110, a hydrogen filtering unit 111, a pressure controller 112, a nitrogen gas tank 113, and an overall control unit 121, and is capable of taking in air and a fuel gas, which is hydrogen gas in this embodiment, and generating a nitrogen-enhancing gas, which is high-purity nitrogen gas in this embodiment, and providing it to the outside.

[0044] As described above, in this embodiment, air is used as the raw material gas for nitrogen gas generation. However, it is also possible to use a nitrogen-containing gas, such as a mixture of nitrogen gas and oxygen gas. In this embodiment, hydrogen gas taken from an external source, for example, a hydrogen station, is used as the fuel gas. However, in another embodiment, a hydrogen-containing gas can be generated from a hydrocarbon gas, such as city gas or liquefied petroleum (LP) gas, by a steam reforming reaction, and this hydrogen-containing gas can be used as the fuel gas. The transfer of materials and energy and the process flow, shown by arrows connecting the components in the device (or system) configuration diagram of FIG. 1, can also be understood as one embodiment of the nitrogen gas generation method according to the present invention.

[0045] 1 , the pressure boosting unit 101 is provided upstream of the fuel cell unit 103 as an oxygen delivery amount limiting means, and increases the pressure of air taken in from the atmosphere and delivers the high-pressure air to the fuel gas chamber side of the fuel cell 103f of the fuel cell unit 103. Specifically, the pressure boosting unit 101 may include a gas compressor 101p that includes a compressor that compresses the air taken in from the atmosphere and delivers the generated compressed air toward the fuel cell unit 103, and an electric motor for operating the compressor. Here, various types of compressors can be used, such as a reciprocating type, a scroll type, a screw type, a rotary type, a swing type, or a combination of two or more of these.

[0046] In the nitrogen gas generator (system) 1 of this embodiment, compressed air generated by the pressure booster unit 101 passes through various units while maintaining a high pressure state and is converted into nitrogen-enriched gas, which in this embodiment is high-purity nitrogen gas. The pressure booster unit 101 creates this high-pressure state, and a pressure controller 112 provided downstream of the hydrogen filtering unit 111 controls this high-pressure state as back pressure control, as will be described later. The gas pressure value in this high-pressure state can be, for example, 0.2 to 1 MPa (approximately 2 to 10 atmospheres).

[0047] Incidentally, as intermediate pressure control, it is also preferable that the pressure controller PL provided in the upstream stage of the dehumidification unit 105 controls the back pressure of the fuel cell 103f. Furthermore, it is also preferable that the overall control unit 121 adjusts the pressure boosting operation of the pressure boosting unit 101 (for example, driving the electric motor that operates the compressor) and the pressure control operation of the pressure controller PL and the pressure controller 112, and controls so that the set high pressure state is realized in each unit.

[0048] The booster unit 101 of this embodiment may also have a buffer tank in which the generated compressed air is temporarily stored. It is also preferable to pass the compressed air taken out of the buffer tank through an air filter and an oil filter to remove fine particles of dust and oil components before sending the compressed air to the fuel cell unit 103. If, for example, a compressed air supply facility is available at the site where the nitrogen gas generator (system) 1 is delivered or installed, the booster unit 101 may be omitted.

[0049] 1, the flow rate controller 102 includes, for example, a gas regulator and a mass flow controller or a flow switch, and controls the flow rate of compressed air supplied from the pressure booster unit 101 to the fuel cell unit 103. Here, the flow rate controller 102 in this embodiment can be understood as an oxygen delivery amount limiting means that takes in air, limits the amount of oxygen delivered in the taken-in air, and delivers this air.

[0050] Specifically, in this embodiment, the flow controller 102 functions as an oxygen content delivery amount limiting means by limiting the flow rate of this air to a maximum flow rate determined based on: (a) a set or desired upper limit temperature of the combustion catalyst 109c or catalytic combustion reaction in the catalytic combustion unit 109, and / or (in this embodiment, and) (b) a set or desired upper limit oxygen concentration in the high-purity nitrogen gas that is finally output.

[0051] <Fuel Cell Unit> Also in Figure 1, the fuel cell unit 103 is equipped with a fuel cell 103f, and compressed air having a high pressure (e.g., 0.2 to 1 MPa) is introduced into the oxidizing gas chamber from an air intake on the air electrode side of the fuel cell 103f, and high-pressure hydrogen gas having a pressure equivalent to that of the compressed air is introduced into the fuel gas chamber from a hydrogen intake on the hydrogen electrode side of the fuel cell 103f, causing a fuel cell reaction in the fuel cell 103f.

[0052] As a result of this fuel cell reaction, fuel cell 103f outputs high-pressure (e.g., 0.2 to 1 MPa) air with a reduced oxygen concentration as exhaust gas from an exhaust gas outlet on the air electrode side, and discharges high-pressure hydrogen electrode-side exhaust gas with a pressure equivalent to that of the air with a reduced oxygen concentration from an exhaust gas outlet on the hydrogen electrode side. Incidentally, hereinafter, this air with a reduced oxygen concentration (exhaust gas) may also be referred to as "exhaust-depleted oxygen air."

[0053] Here, the fuel cell unit 103 of this embodiment can be regarded as an oxygen content delivery amount limiting means that takes in air, limits the amount of oxygen content in the air that is delivered, and delivers this air. Specifically, in this embodiment, the fuel cell unit 103 functions as an oxygen content delivery amount limiting means by limiting the oxygen concentration of this air to not more than (a) a set or desired upper limit temperature of the combustion catalyst 109c in the catalytic combustion unit 109 or the catalytic combustion reaction, and / or (in this embodiment, and) (b) a "maximum oxygen concentration" that is determined based on a set or desired upper limit oxygen concentration in the high-purity nitrogen gas that is finally output.

[0054] In this embodiment, as will be described later, not only the fuel cell unit 103 but also the oxygen filtering unit 106 function as oxygen delivery amount limiting means. Therefore, the above-mentioned "maximum oxygen concentration" is a value related to the oxygen concentration after oxygen reduction processing in the fuel cell unit 103. The oxygen filtering unit 106 takes in air (exhaust gas) having an oxygen concentration equal to or lower than this "maximum oxygen concentration," and sends the air (exhaust gas) having an oxygen concentration equal to or lower than the maximum oxygen concentration determined for the entire oxygen delivery amount limiting means (103, 106) toward the catalytic combustion unit 109.

[0055] Furthermore, it is preferable that the exhausted low-oxygen air, which is the exhaust gas on the air electrode side, then has condensed water removed to a certain extent, for example, via a drain, and is further dehumidified by a dehumidifier 104 equipped with an air-water separator (water exchanger) and a dehumidifying agent cartridge, etc. Here, if the dehumidifier 104 includes an air-water separator (water exchanger), the dehumidifier 104 can perform air-water separation (water exchange) between the exhausted low-oxygen air as the exhaust gas and the compressed air before it is taken into the fuel cell unit 103.

[0056] Incidentally, in this embodiment, the exhaust gas from the cathode, i.e., the low-oxygen air after exhaust, is subsequently subjected to oxygen filtering, catalytic combustion, and hydrogen filtering processes before being converted into high-purity nitrogen gas. However, to prevent the moisture and water vapor contained in the air from becoming a major obstacle to these processes, the air is subjected to a dehumidification process.

[0057] The fuel cell 103f may have a known configuration. For example, it may have a configuration in which multiple cells, each having an electrolyte membrane sandwiched between an air electrode (oxygen electrode, negative electrode, cathode) and a hydrogen electrode (fuel electrode, positive electrode, anode), are stacked with a separator interposed between them. In this case, each cell has an oxidizing gas chamber on the air electrode side and a fuel gas chamber on the hydrogen electrode side, sandwiching the electrolyte membrane.

[0058] Furthermore, although the fuel cell 103f is a polymer electrolyte fuel cell (PEFC) in this embodiment, it is of course possible to use a solid oxide fuel cell (SOFC), a phosphoric acid fuel cell (PAFC), a molten carbonate fuel cell (MCFC), etc. Incidentally, the PEFC employed in this embodiment operates at a relatively low temperature and can be made compact in size, and is therefore also used in many fuel cell vehicles, for example.

[0059] Furthermore, as described above, the fuel cell 103f of this embodiment is a high-pressure compatible fuel cell that receives high-pressure (e.g., 0.2 to 1 MPa) compressed air and high-pressure (e.g., 0.2 to 1 MPa) hydrogen gas, and discharges high-pressure (e.g., 0.2 to 1 MPa) exhaust gas from the oxidizing gas chamber and the fuel gas chamber.

[0060] Furthermore, the fuel cell unit 103 equipped with the fuel cell 103f described above preferably includes a group of measuring devices and sensors that can measure (a) the flow rate, pressure, temperature, and humidity of the compressed air or high-pressure hydrogen gas introduced into the fuel cell 103f, (b) the flow rate, pressure, temperature, and humidity of the exhaust gas discharged from the fuel cell 103f, and (c) the complex impedance, voltage, and current between the hydrogen electrode and the air electrode of the fuel cell 103f. Furthermore, it is also preferable that the operation of the fuel cell 103f be controlled according to settings by the overall control unit 121 that receives measurement information from this group of measuring devices and sensors.

[0061] Furthermore, the fuel cell unit 103 of this embodiment can be provided with a heat exchanger that circulates a heat exchange medium such as water, located within or around the fuel cell 103f, to extract thermal energy from the fuel cell reaction in the operating fuel cell 103f and provide this thermal energy to the outside. In this case, hot water, hot water, or a high-temperature heat exchange medium other than water output from the heat exchanger may be supplied to the outside. Usable heat exchangers include a multi-tube heat exchanger such as a shell-and-tube heat exchanger and a plate heat exchanger such as an Alfa Laval brazed plate heat exchanger.

[0062] Furthermore, instead of a heat exchanger, a heat transfer system connecting the separator of the fuel cell 103f to a heat pipe may be used to extract thermal energy from the fuel cell 103f and supply this thermal energy to the outside from one end of the heat pipe. In either case, such heat transfer means not only makes it possible to provide thermal energy to, for example, consumers, but also to control the cell temperature of the fuel cell 103f below a predetermined upper limit temperature (e.g., 80°C for a PEFC) and maintain optimal operation of the fuel cell 103f. Alternatively, as a simpler configuration, water (cooling water) taken in from the outside may be heated in the fuel cell 103f and supplied to the outside as warm water or hot water.

[0063] Furthermore, in this embodiment, it is also preferable that the thermal energy extracted by the heat transfer means such as the heat exchanger or heat conduction system described above is sent to a temperature regulator that adjusts the temperature of the gas (exhaust gas on the air electrode side) supplied to the oxygen filtering unit 106, catalytic combustion unit 109, and hydrogen filtering unit 111 provided downstream, and used to adjust the temperature of this gas (exhaust gas on the air electrode side) to a temperature suitable for each process. Here, this temperature regulator may be equipped with a thermometer that monitors the temperature of this gas (exhaust gas on the air electrode side) and reports the temperature to the overall control unit 121 as appropriate.

[0064] In this embodiment, the power generated by the fuel cell reaction in the fuel cell 103f is adjusted by a power adjustment unit before being provided to the outside. Here, this power adjustment unit may have, for example, a storage battery and an inverter, and may temporarily store DC power from the fuel cell 103f and then convert it into AC power for external use. In addition, it is also preferable that the pressure booster unit 101 of this embodiment be operated by power from the fuel cell 103f or by a combination of this power and commercial power.

[0065] <Dehumidification Means> Also referring to Figure 1, the dehumidification unit 105 of this embodiment includes a dry filter 105d, which reduces the moisture or water vapor content in the low-oxygen exhaust air delivered from the cathode side of the fuel cell 103f. The dry filter 105d receives high-pressure (e.g., 0.2 to 1 MPa) low-oxygen exhaust air and ejects it through small holes in the filter, causing it to expand adiabatically. Condensed water is then removed from the ejected low-oxygen exhaust air, dehumidifying it. For example, it is possible to reduce the relative humidity of gas with a relative humidity of 100% to approximately 15%.

[0066] The dry filter 105d is not limited to the adiabatic expansion and condensation type as described above, and may be, for example, a membrane separation type dry filter equipped with a hollow fiber membrane such as a fluorine-based non-porous membrane, or a dry filter equipped with a water absorbing agent such as zeolite. However, in this embodiment, the adiabatic expansion and condensation type dry filter 105d is adopted because it has the advantage of being largely maintenance-free.

[0067] As described above, the dehumidification unit 105 of this embodiment can dehumidify high-pressure gas (e.g., 0.2 to 1 MPa). It is also preferable that the pressure value (e.g., 0.2 to 1 MPa) of the exhausted, low-oxygen air introduced into the dry filter 105d be equal to or greater than the minimum pressure required to achieve a target or desired relative humidity at a set introduction flow rate. Thus, the dehumidification unit 105 is highly suitable for incorporation into a series of high-pressure systems, including the fuel cell unit 103, oxygen filtering unit 106, and catalytic combustion unit 109, located between the pressure booster unit 101 and pressure controller 112.

[0068] If one of the dehumidifier 104 and the dehumidifying unit 105 is sufficient to dehumidify the exhausted low-oxygen air, the other may be omitted. Also, if the fuel cell 103f is an SOFC, the dehumidifier 104 and the dehumidifying unit 105 may be omitted.

[0069] 1, the oxygen filtering unit 106 of this embodiment is equipped with a gas filter 106f having different permeability rates for nitrogen and oxygen, and exhausted low-oxygen air with a reduced oxygen concentration and high pressure (e.g., 0.2 to 1 MPa) that has been dehumidified is applied to this gas filter 106f, and high-pressure air with an even lower oxygen concentration (e.g., 0.2 to 1 MPa) is extracted and sent out from this gas filter 106f. Incidentally, hereinafter, this air with an even lower oxygen concentration will also be referred to as "filtered air."

[0070] Here, the oxygen filtering unit 106 in this embodiment can be considered as an oxygen content delivery amount limiting means that takes in exhausted low-oxygen air, limits the amount of oxygen in this air that is delivered, and delivers filtered air. Specifically, in this embodiment, the fuel cell unit 103 functions as an oxygen content delivery amount limiting means by limiting the oxygen concentration of this exhausted low-oxygen air to or below (a) a set or desired upper limit temperature of the combustion catalyst 109c or catalytic combustion reaction in the catalytic combustion unit 109, and / or (in this embodiment, and) (b) a maximum oxygen concentration determined based on a set or desired upper limit oxygen concentration in the high-purity nitrogen gas that is ultimately output.

[0071] Specifically, the gas filter 106f comprises: (a) a hollow fiber section (106fa in FIG. 4(C) described later) having different permeability rates for nitrogen (N2) and oxygen (O2); (b) a filter inlet section (106fb in FIG. 4(C) described later) for introducing high-pressure (e.g., 0.2 to 1 MPa) exhausted low-oxygen air to act on the hollow fiber section of (a) above; and a filter outlet section (106fc in FIG. 4(C)) for extracting high-pressure (e.g., 0.2 to 1 MPa) filtered air with a reduced oxygen concentration (i.e., a higher nitrogen concentration) from the hollow fiber section; (c) A filter purge section (106fd in FIG. 4(C)) is provided for extracting the oxygen (O2)-containing gas (hereinafter sometimes referred to as "filter exhaust gas") separated from the exhausted low-oxygen air by the hollow fiber section (a) above, separately from the filtered air extracted in (b) above.

[0072] Of these, the hollow fiber fiber portion (a) is a hollow fiber polymer fiber that preferentially allows oxygen (O) to permeate over nitrogen (N). As high-pressure (e.g., 0.2 to 1 MPa) exhaust-depleted oxygen-rich air flows through the hollow fiber fiber portion from the filter inlet, oxygen (O) selectively permeates the polymer fiber and exits. Finally, filtered air with a reduced oxygen concentration, i.e., a higher nitrogen concentration, is extracted from the filter outlet. Incidentally, the hollow fiber fiber portion may also selectively allow water (H2O) and hydrogen (H2) to permeate in addition to oxygen (O). In this case, filtered air with a reduced relative humidity and hydrogen concentration can also be obtained.

[0073] Furthermore, experiments have confirmed that in such a hollow fiber section, the higher the pressure of the exhausted low-oxygen air being introduced (inlet pressure), the smaller the flow rate of the extracted filtered air (outlet flow rate), and the lower the oxygen concentration of the exhausted low-oxygen air being introduced (inlet oxygen concentration), the more filtered air with a reduced oxygen concentration (outlet oxygen concentration) can be extracted from the filter outlet, i.e., with a higher nitrogen concentration (outlet nitrogen concentration).

[0074] From the viewpoint of the dependency of the outlet oxygen concentration on the introduced oxygen concentration, the gas filter 106f (oxygen filtering unit 106) and the fuel cell 103f (fuel cell unit 103), which reduces the oxygen concentration of the air in advance, are a very suitable combination for ultimately producing high-purity nitrogen gas having a low oxygen concentration (required by specifications). Therefore, it can be understood that the combination of the two constitutes a more suitable oxygen delivery amount limiting means.

[0075] Furthermore, it has been experimentally confirmed that the recovery rate (= outlet flow rate / inlet flow rate) of the gas filter 106f increases as the introduced oxygen concentration decreases. Therefore, from the viewpoint of recovery rate, the gas filter 106f (oxygen filtering unit 106) and the fuel cell 103f (fuel cell unit 103) in the preceding stage are an extremely suitable combination for recovering a sufficient amount (flow rate) of high-purity nitrogen gas (required as a specification).

[0076] If the oxygen concentration of the low-oxygen post-exhaust air discharged from the fuel cell unit 103 is low enough to keep the temperature of the combustion catalyst 109c or catalytic combustion reaction below an upper limit temperature, or to keep the oxygen concentration of the high-purity nitrogen gas finally output below an upper limit oxygen concentration, the oxygen filtering unit 106 can be omitted. An example of such a fuel cell unit 103 will be described later with reference to FIG. 5.

[0077] 1, in this embodiment, the filtered air with a reduced oxygen concentration extracted from the oxygen filtering unit 106 has its flow rate controlled by a flow rate controller 107 and is sent to a catalytic combustion unit 109. Here, the flow rate controller 107 may include, for example, a gas regulator and a mass flow controller or a flow switch.

[0078] The flow rate controller 107 may also function as an oxygen delivery rate limiting means by setting the flow rate of the filtered air with a reduced oxygen concentration to a maximum flow rate determined based on: (a) a set or desired upper limit temperature of the combustion catalyst 109c or catalytic combustion reaction in the catalytic combustion unit 109, and / or (in this embodiment, and) (b) a set or desired upper limit oxygen concentration in the high-purity nitrogen gas that is finally output.

[0079] <Catalytic Combustion Means> Also referring to FIG. 1, the catalytic combustion unit 109 is equipped with a combustion catalyst 109c, and the filtered air sent out from the oxygen filtering unit 106 reacts with the taken-in hydrogen gas on the combustion catalyst 109c to convert the filtered air into a nitrogen-enriched gas having an oxygen concentration equal to or lower than a set or desired upper limit oxygen concentration, which in this embodiment is high-purity nitrogen gas.

[0080] Specifically, the catalytic combustion unit 109 of this embodiment brings high-pressure (e.g., 0.2 to 1 MPa) filtered air into contact with high-pressure (e.g., 0.2 to 1 MPa) hydrogen gas on the surface of the combustion catalyst 109c, causing a catalytic combustion reaction, which further consumes oxygen (O2) in the filtered air and outputs high-pressure (e.g., 0.2 to 1 MPa) high-purity nitrogen gas. In this way, in the catalytic combustion unit 109 of this embodiment, high-pressure (e.g., 0.2 to 1 MPa) gases come into contact with each other on the combustion catalyst, which increases the reaction rate of the catalytic combustion reaction and further accelerates the reaction, thereby further reducing the oxygen concentration in the ultimately produced nitrogen gas, i.e., improving the nitrogen purity.

[0081] In this embodiment, the oxygen content delivery amount restriction means (102, 103, 106, 107) including the fuel cell unit 103 and oxygen filtering unit 106 controls the oxygen concentration and / or flow rate of the filtered air delivered to the catalytic combustion unit 109 as described above. As a result, the catalytic combustion unit 109 can: (a) suppress the temperature of the combustion catalyst 109c or the catalytic combustion reaction to a set or desired upper limit temperature or lower, and / or (in this embodiment, and) (b) keep the oxygen concentration in the high-purity nitrogen gas that is finally delivered to a set or desired upper limit oxygen concentration or lower.

[0082] The combustion catalyst 109c of this embodiment is a solid catalyst with a support of a metal such as stainless steel, which is capable of efficiently removing and reducing trace amounts of oxygen (O2). In the catalytic combustion unit 109 of this embodiment equipped with this combustion catalyst 109c, the upper limit temperature during continuous use is set to 300°C, and the upper limit oxygen concentration of the generated nitrogen gas is set to 10 ppm vol (equivalent to a nitrogen purity of 5N).

[0083] In contrast, in this embodiment, the above-mentioned oxygen delivery amount limiting means (102, 103, 106, 107) limits the temperature of the combustion catalyst 109c or catalytic combustion reaction to 300°C or less, and further limits the oxygen concentration of the air with a lower oxygen concentration (filtered air in this embodiment) delivered to the catalytic combustion unit 109 to a maximum oxygen concentration (e.g., 3 vol%) or less in order to obtain high-purity nitrogen gas with an oxygen concentration of 10 ppm vol or less at the desired flow rate.

[0084] Here, the temperature of the combustion catalyst 109c or catalytic combustion reaction in the catalytic combustion unit 109 would greatly exceed the upper limit temperature (300°C) if it directly received post-exhaust low-oxygen air with an oxygen concentration of, for example, 6 to 10 vol% sent from the fuel cell unit 103. In contrast, in this embodiment, the catalytic combustion unit 109 receives filtered air with an oxygen concentration reduced to, for example, 0.5 to 3 vol% from the oxygen-oxygen filtering unit 106.

[0085] Therefore, the temperature of the combustion catalyst 109c or the catalytic combustion reaction is kept below the upper limit temperature (300°C). As a result, the catalytic combustion unit 109 continuously and stably causes the catalytic combustion reaction, and is able to continuously and stably generate and supply high-purity nitrogen gas, for example, nitrogen gas with a purity of 5N or higher in this embodiment.

[0086] As will be described later, it has been experimentally confirmed that when a plurality of combustion catalysts 109c are arranged in series inside the reaction tube, the temperature of the reaction tube due to the heat of reaction is significantly higher at the outlet side of the reaction tube where the introduced gas that has been in the fuel catalyst environment for a long time is present than at the inlet side. Therefore, it is also preferable that the upper limit temperatures of the combustion catalyst 109c and the reaction tube be determined taking into consideration the temperature at the outlet side of the reaction tube. Incidentally, it is also preferable that the temperatures of the combustion catalyst 109c and the reaction tube are measured by a thermometer TM, appropriately notified to the overall control unit 121, and monitored and managed by the overall control unit 121.

[0087] Furthermore, in the catalytic combustion unit 109 of this embodiment, in order to achieve a continuous and stable catalytic combustion reaction, the lower limit temperature of the combustion catalyst 109c and the reaction tube containing the combustion catalyst 109c is set to 100°C. To achieve a catalytic combustion reaction that achieves a temperature above this lower limit temperature, the oxygen delivery amount limiting means (102, 103, 106, 107) preferably sets the oxygen concentration of the filtered air delivered to the catalytic combustion unit 109 to a set minimum oxygen concentration (e.g., 0.5 vol%) or higher. This ensures that the temperatures of the combustion catalyst 109c and the reaction tube are above the lower limit temperature (100°C), eliminating the need to heat the combustion catalyst 109c and the reaction tube, for example, by electrical power. In this way, when the temperatures of the combustion catalyst 109c and the reaction tube are set above the lower limit temperature without heating them by electrical power, it is important to appropriately determine the minimum oxygen concentration at the set inlet flow rate (of the filtered air).

[0088] However, it is also possible to adopt an embodiment in which the oxygen concentration of the filtered air sent to the catalytic combustion unit 109 is sufficiently low (for example, 0.01 vol%), while the combustion catalyst 109c and the reaction tube are heated, for example, by an electric heater or electromagnetic induction, using commercial power or power from the fuel cell unit 103. The combustion catalyst 109c and the reaction tube may also be heated using thermal energy from the fuel cell unit 103. In particular, when the fuel cell 103f is an SOFC, the temperature of the fuel cell reaction becomes very high, for example, about 700°C. As a result, a sufficient amount of thermal energy can be extracted from the fuel cell 103f and used for the catalytic combustion reaction. Furthermore, it is also possible to use the thermal energy of the very high-temperature exhaust gas for the catalytic combustion reaction.

[0089] As described above, the combustion catalyst 109c of this embodiment is a solid catalyst with a metal support such as stainless steel. Specifically, the combustion catalyst 109c can be a metal honeycomb with numerous fine holes and a catalyst such as platinum (Pt), palladium (Pd), or nickel (Ni) supported on the surface, including the interior of these holes. Alternatively, the combustion catalyst 109c may be a honeycomb-shaped ceramic support supporting platinum (Pt), palladium (Pd), or nickel (Ni). It may also be equipped with a granular catalyst. In any case, the combustion catalyst 109c must be used at a temperature below a predetermined or desired upper limit temperature.

[0090] 1, the catalytic combustion unit 109 of this embodiment takes in high-pressure (e.g., 0.2 to 1 MPa) hydrogen gas as the combustion gas used in the catalytic combustion reaction from the hydrogen recovery unit 108. The hydrogen recovery unit 108 uses a hydrogen gas filter, an executor, etc. to extract and recover unreacted residual hydrogen gas from the exhaust gas taken out from the exhaust gas outlet on the hydrogen electrode side of the fuel cell 103f.

[0091] The hydrogen gas recovered by the hydrogen recovery unit 108 may be sent to a hydrogen mixer, mixed with hydrogen gas supplied from outside, and then reused in the fuel cell 103f. In this embodiment, the pressure of the hydrogen gas (back pressure of the fuel cell 103f) is controlled by a pressure controller PL provided upstream of the hydrogen recovery unit 108. In this embodiment, the hydrogen gas recovered by the hydrogen recovery unit 108 is also sent to the catalytic combustion unit 109.

[0092] Furthermore, like the fuel cell unit 103, the catalytic combustion unit 109 of this embodiment may take in high-pressure (e.g., 0.2 to 1 MPa) hydrogen gas from the outside, for example, from a hydrogen station. A hydrogen gas tank or hydrogen storage tank may be provided to temporarily store the taken-in hydrogen gas. A hydrogen compression pump may also be provided to adjust the hydrogen gas delivered to the catalytic combustion unit 109 or the fuel cell unit 103 to a predetermined high pressure (e.g., 0.2 to 1 MPa). As described above, the fuel cell unit 103 and catalytic combustion unit 109 are an extremely suitable combination, also because they can utilize hydrogen gas from the same hydrogen gas source.

[0093] The high-purity nitrogen gas (nitrogen-enriched gas) delivered from the catalytic combustion unit 109 typically contains moisture or water vapor produced by the catalytic combustion reaction. Therefore, in this embodiment, a dehumidifying unit 110 provided downstream of the catalytic combustion unit 109 reduces or removes this moisture or water vapor to a level that does not impede subsequent processing. This dehumidifying unit 110 includes a dry filter 110d similar to the dry filter 105d described above in this embodiment. This dry filter 110d reduces the moisture or water vapor content in the high-pressure (e.g., 0.2 to 1 MPa) high-purity nitrogen gas (nitrogen-enriched gas) delivered from the catalytic combustion unit 109.

[0094] Here, it is also preferable that the pressure value (e.g., 0.2 to 1 MPa) of the high-purity nitrogen gas (nitrogen-enriched gas) introduced into the dry filter 110d be equal to or higher than the minimum pressure required to achieve a target or desired relative humidity at a set introduction flow rate in the dry filter 110d. In this way, like the dehumidification unit 105, the dehumidification unit 110 is also very suitable for incorporation into a series of high-pressure systems including the fuel cell unit 103, the oxygen filtering unit 106, and the catalytic combustion unit 109 between the pressure booster unit 101 and the pressure controller 112 as described above.

[0095] In this embodiment, the high-purity nitrogen gas (nitrogen-enriched gas) introduced into the dry filter 110d is heated to an extremely high temperature due to the catalytic combustion reaction. Therefore, the dehumidification unit 110 may be provided with a cooling means, such as a water-cooling means, to lower the temperature of the high-purity nitrogen gas (nitrogen-enriched gas) sent to the hydrogen filtering unit 111 (described later) to a temperature suitable for the gas filter 111f. In another embodiment, the dehumidification unit 110 may be provided with a heat exchanger that exchanges heat between the high-purity nitrogen gas (nitrogen-enriched gas) and a refrigerant such as water to lower the temperature of the high-purity nitrogen gas (nitrogen-enriched gas) and dehumidify it. The combustion catalyst unit 109 also preferably has an automatic drain for removing condensed water generated in the high-purity nitrogen gas (nitrogen-enriched gas) being sent out.

[0096] Furthermore, the high-purity nitrogen gas (nitrogen-enriched gas) delivered from the catalytic combustion unit 109 often contains residual hydrogen gas that was not used in the catalytic combustion reaction. This is because, in catalytic combustion reactions, it is generally very difficult to adjust the flow rate of the introduced hydrogen gas to cause the desired catalytic combustion reaction while keeping the amount of residual hydrogen gas small, for example, to the order of 10 ppm vol. Therefore, in this embodiment, a hydrogen filtering unit 111 is provided downstream of the dehumidification unit 110 to remove or reduce this residual hydrogen gas.

[0097] <Gas Filtering Means> Also in FIG. 1 , the hydrogen filtering unit 111 is a gas filtering means that applies high-pressure (e.g., 0.2 to 1 MPa) high-purity nitrogen gas (nitrogen-enriched gas) taken in from the dehumidification unit 110 via the flow rate controller FL to a gas filter 111f to generate and deliver high-purity nitrogen gas (nitrogen-enriched gas) with a higher nitrogen concentration, and that, when the nitrogen-enriched gas received from the dehumidification unit 110 contains hydrogen (H2), generates and delivers high-purity nitrogen gas (nitrogen-enriched gas) from which hydrogen (H2) has been removed or which has a lower hydrogen concentration.

[0098] Here, the gas filter 111f is a gas filter with different permeability for nitrogen (N) and hydrogen (H) and for nitrogen (N) and oxygen (O). Alternatively, the gas filter 111f may be a hydrogen filter with different permeability for nitrogen (N) and oxygen (O), but not for nitrogen (N) and hydrogen (H). In either case, the hydrogen filtering unit 111 generates and delivers high-purity nitrogen gas (nitrogen-enriched gas) from which hydrogen (H) has been removed or which has a lower hydrogen concentration.

[0099] Furthermore, by providing such a hydrogen filtering unit 111 downstream of the catalytic combustion unit 109, the catalytic combustion unit 109 does not need to be required to perform such sophisticated control over the amount (flow rate) of hydrogen gas introduced. In this way, the catalytic combustion unit 109 and the downstream hydrogen filtering unit 111 form an excellent combination that can increase the efficiency of generating high-purity nitrogen gas in a simple manner.

[0100] Furthermore, the gas filter 111f of this embodiment may be the same filter as the gas filter 106f of the oxygen filtering unit 106 described above. For example, the gas filter 111f and the gas filter 106f may be a UBE N2 separator manufactured by UBE using aromatic polyimide hollow fibers, or a N2 membrane module / nitrogen gas filter manufactured by Polypla-Evonik, also using aromatic polyimide hollow fibers. When a filter using such aromatic polyimide hollow fibers is used as the gas filter 111f, the hydrogen concentration of a gas having a hydrogen concentration of approximately 1 vol% can be reduced to a few ppm vol. Furthermore, for gases having a hydrogen concentration of less than 1 vol%, the hydrogen concentration can be reduced to below the detection limit (1 ppm vol).

[0101] Furthermore, it has been confirmed through experiments that the higher the pressure of the gas introduced into the gas filter 111f, the lower the hydrogen concentration of this gas (introduced hydrogen concentration), and the smaller the flow rate of this gas (introduced flow rate), the more the hydrogen concentration of the gas delivered from the gas filter 111f is reduced. Here, it has also been confirmed through experiments that the hydrogen reduction effect of the gas filter 111f is extremely significant when the introduced gas has a pressure equal to or greater than a predetermined pressure threshold (e.g., approximately 0.75 MPa) and a hydrogen concentration equal to or less than a predetermined hydrogen concentration threshold determined according to this pressure.

[0102] Furthermore, in this embodiment, the oxygen concentration and hydrogen concentration of the high-purity nitrogen gas (nitrogen-enriched gas) delivered from the hydrogen filtering unit 111 are measured by an oxygen concentration meter O2 and a hydrogen concentration meter H2, respectively. Here, it is also preferable that the overall control unit 121 monitors the final purity of the high-purity nitrogen gas (nitrogen-enriched gas) based on these measured values ​​received from the oxygen concentration meter O2 and the hydrogen concentration meter H2.

[0103] In addition, the hydrogen filtering unit 111 can be omitted if the high-purity nitrogen gas (nitrogen-enriched gas) delivered from the catalytic combustion unit 109 contains almost no hydrogen gas, has a hydrogen concentration below a set or desired upper limit hydrogen concentration, or it is preferable for the gas to contain a considerable amount of hydrogen gas.

[0104] <Pressure Control Means> Also in FIG. 1, the pressure controller 112 is a pressure control means that controls the increased pressure of the gas (air, nitrogen-enriched gas) flowing in the section from the pressure boosting unit 101 to its own installation position, i.e., the downstream position of the hydrogen filtering unit 111.

[0105] Specifically, the pressure controller 112 of this embodiment is equipped with a back pressure valve and a back pressure gauge, and controls the back pressure of a series of high-pressure systems including the fuel cell unit 103, the dehumidification unit 105, the oxygen filtering unit 106, the combustion catalyst unit 109, the dehumidification unit 110, and the hydrogen filtering unit 111.

[0106] Furthermore, the pressure controller 112 of this embodiment controls the pressure of the gas in each unit so that the oxygen concentration of the gas discharged from each of the fuel cell unit 103, the oxygen filtering unit 106, and the combustion catalyst unit 109 is equal to or less than the maximum oxygen concentration set for each unit. Here, the maximum oxygen concentration in each unit is set so that high-purity nitrogen gas having an oxygen concentration equal to or less than the set or desired upper limit oxygen concentration can be ultimately obtained. Also, the pressure controller 112 controls the pressure of the gas in the hydrogen filtering unit 111 so that the hydrogen concentration of the gas discharged from the hydrogen filtering unit 111 is equal to or less than the maximum hydrogen concentration set for the hydrogen filtering unit 111. Here, the maximum hydrogen concentration in the hydrogen filtering unit 111 is also set so that high-purity nitrogen gas having an oxygen concentration equal to or less than the set or desired upper limit oxygen concentration can be ultimately obtained.

[0107] Furthermore, pressure controller 112 controls the pressure of the gas in dehumidification unit 105 and dehumidification unit 110 so that the relative humidity of the gas discharged from dehumidification unit 105 and dehumidification unit 110 is equal to or less than the maximum relative humidity set for the gas introduced into oxygen filtering unit 106 and hydrogen filtering unit 111, respectively, or is within a set allowable relative humidity range. As described above, pressure controller 112 controls the back pressure of the series of high-pressure systems, thereby controlling the pressure of the gas in each unit in the high-pressure systems, thereby contributing to the final production of high-purity nitrogen gas having an oxygen concentration equal to or less than the set or desired upper limit oxygen concentration.

[0108] 1, the nitrogen gas tank 113 is a tank that temporarily stores high-pressure (e.g., 0.2 to 1 MPa) high-purity nitrogen gas having an oxygen concentration equal to or lower than a set or desired upper limit oxygen concentration, which is delivered from the hydrogen filtering unit 111. The nitrogen gas tank 113 in this embodiment is equipped with a gas regulator and a mass flow controller or a flow switch, and, for example, receives instructions from the overall control unit 121 and delivers the stored high-purity nitrogen gas at a predetermined stable pressure and flow rate to an external supply destination.

[0109] [Another Embodiment of Nitrogen Gas Generating Apparatus and System] FIG. 2 is a schematic diagram showing another embodiment of a nitrogen gas generating apparatus and system according to the present invention.

[0110] The nitrogen gas generator (system) 1' of this embodiment shown in Figure 2 is configured such that the pressure booster unit 101 provided upstream of the fuel cell unit 103 and the flow rate controller 107 provided downstream of the oxygen filtering unit 106 in the nitrogen gas generator (system) 1 shown in Figure 1 are not employed, and instead the pressure booster unit 101' and the flow rate controller 107' are provided between the fuel cell unit 103 and the dehumidification unit 105.

[0111] In other words, the nitrogen gas generator (system) 1 shown in FIG. 1 is provided with a pressure boosting means upstream of the oxygen content delivery amount limiting means (102, 103, 106, 107), whereas the nitrogen gas generator (system) 1' shown in FIG. 2 is provided with a pressure boosting means upstream of the catalytic combustion unit 109 and within the oxygen content delivery amount limiting means (102, 103, 107', 106).

[0112] The oxygen content delivery amount restriction means (102, 103, 107', 106) of such a nitrogen gas generator (system) 1' also controls the oxygen concentration and / or flow rate of the filtered air delivered to the catalytic combustion unit 109 in the same manner as the oxygen content delivery amount restriction means (102, 103, 106, 107) shown in Fig. 1. As a result, the catalytic combustion unit 109 can: (a) suppress the temperature of the combustion catalyst 109c or the catalytic combustion reaction to a set or desired upper limit temperature or lower, and / or (in this embodiment, and) (b) keep the oxygen concentration in the high-purity nitrogen gas that is finally delivered to a set or desired upper limit oxygen concentration or lower.

[0113] Furthermore, this enables the nitrogen gas generating device (system) 1' of this embodiment to deliver high-purity nitrogen gas having a set or desired purity from the nitrogen gas tank 113 to an external supply destination at a predetermined stable pressure and flow rate.

[0114] In the nitrogen gas generating device (system) 1′, a series of high-pressure systems including a dehumidifying unit 105, an oxygen filtering unit 106, a combustion catalyst unit 109, a dehumidifying unit 110, and a hydrogen filtering unit 111 are configured between the pressure boosting unit 101′ and the pressure controller 112. The pressure controller 112 of this embodiment controls the back pressure of this series of high-pressure systems.

[0115] Specifically, the pressure controller 112 of this embodiment controls the pressure of the gas in each of the oxygen filtering unit 106 and the combustion catalyst unit 109 so that the oxygen concentration of the gas discharged from each of the oxygen filtering unit 106 and the combustion catalyst unit 109 is equal to or less than the maximum oxygen concentration set in each unit. Here, the maximum oxygen concentration in each unit is set so that high-purity nitrogen gas having an oxygen concentration equal to or less than the set or desired upper limit oxygen concentration can ultimately be obtained. Also, the pressure controller 112 controls the pressure of the gas in the hydrogen filtering unit 111 so that the hydrogen concentration of the gas discharged from the hydrogen filtering unit 111 is equal to or less than the maximum hydrogen concentration set in the hydrogen filtering unit 111. Here, the maximum hydrogen concentration in the hydrogen filtering unit 111 is set so that high-purity nitrogen gas having an oxygen concentration equal to or less than the set or desired upper limit oxygen concentration can ultimately be obtained.

[0116] Furthermore, the pressure controller 112 controls the gas pressure in the dehumidification units 105 and 110 so that the relative humidity of the gases discharged from the dehumidification units 105 and 110 is equal to or less than the maximum relative humidity set for the gases introduced into the oxygen filtering unit 106 and hydrogen filtering unit 111, respectively, or within the allowable relative humidity range. As described above, the pressure controller 112 controls the back pressure of the high-pressure system, thereby controlling the gas pressure in each unit within the high-pressure system, thereby contributing to the final production of high-purity nitrogen gas having an oxygen concentration equal to or less than the set or desired upper limit oxygen concentration. Incidentally, since the gas compressor 101p in the pressure booster unit 101′ compresses the exhaust gas from the fuel cell 103f, which has a high relative humidity, it is also preferable to have an automatic drain to remove condensed water generated by compression. Furthermore, it is also preferable to use a rust-resistant, stainless steel tank for the compressor tank in the gas compressor 101p.

[0117] The fuel cell unit 103 of this embodiment does not belong to the series of high-pressure systems described above, and as a result, the fuel cell 103f does not need to be a high-pressure compatible type. Therefore, it is preferable to use a solid oxide fuel cell (SOFC), which is generally considered difficult to make into a high-pressure compatible type, as this fuel cell 103f. Of course, a non-high-pressure compatible solid polymer fuel cell (PEFC) may also be used.

[0118] [Embodiment of Catalytic Combustion Means] FIG. 3 is a schematic diagram and graphs for explaining an embodiment of catalytic combustion processing by the catalytic combustion unit 109 according to the present invention.

[0119] In this example, a honeycomb catalyst (Pt coated) D3HPT2S40C manufactured by Tanaka Kikinzoku Kogyo Co., Ltd. was used as the combustion catalyst 109c, and ten combustion catalysts 109c were arranged in series in a stainless steel reaction tube as shown in Figure 3(A). Air with a reduced oxygen concentration was then introduced into this reaction tube to cause a catalytic combustion reaction.

[0120] The combustion catalyst 109c manufactured by Tanaka Kikinzoku Kogyo Co., Ltd. is a solid catalyst with a metal (stainless steel) support, and is designed for continuous use with an upper temperature limit of 300°C. When dehumidified low-oxygen exhaust air with an oxygen concentration of approximately 10 vol% that was delivered from the fuel cell unit 103 was first introduced into a reaction tube equipped with such a combustion catalyst 109c, the temperature inside the reaction tube, particularly near the inlet, far exceeded the upper temperature limit of 300°C.

[0121] Next, the dehumidified low-oxygen exhaust air sent from the fuel cell unit 103 was introduced into the oxygen filtering unit 106, and the filtered air with an oxygen concentration of approximately 1.77 vol% sent from the oxygen filtering unit 106 was introduced into the reaction tube. Hydrogen gas was also introduced into the reaction tube at a predetermined flow rate in accordance with the filtered air. The pressure inside the reaction tube was 0.73 MPa. The experimental results are shown in Figure 3(B).

[0122] Specifically, the graph in FIG. 3(B) shows the temperature inside the reaction tube, the flow rate of the exhausted oxygen-depleted air at the catalyst inlet, the oxygen concentration at the catalyst outlet, and the relative humidity of the high-purity nitrogen gas (humidity at the catalyst outlet) discharged from the reaction tube from 65 minutes after the start of the oxygen concentration of the high-purity nitrogen gas (oxygen concentration at the catalyst outlet) falling below 10 ppm vol to 400 minutes after the start of the oxygen concentration of the high-purity nitrogen gas discharged from the reaction tube (oxygen concentration at the catalyst outlet).

[0123] According to the graph in Figure 3(B), the temperature inside the reaction tube remained generally stable between 65 and 400 minutes, at approximately 230°C, below the upper limit temperature (300°C). Furthermore, the oxygen concentration of the high-purity nitrogen gas discharged from the reaction tube (outlet oxygen concentration) tended to decrease over time, eventually dropping below 2 ppm vol. This indicates that, ignoring residual hydrogen gas, high-purity nitrogen gas was obtained with a purity exceeding 5N and approaching 6N.

[0124] The catalyst inlet flow rate of the exhausted low-oxygen air was generally stable at approximately 20 L / min between 65 and 400 minutes. The relative humidity of the discharged high-purity nitrogen gas was approximately 4%, but this was the value after dehumidification by the dehumidification unit 110 installed downstream of the reaction tube. Experiments have also confirmed that the oxygen concentration of the high-purity nitrogen gas discharged from the reaction tube (outlet oxygen concentration) decreases with increasing pressure inside the reaction tube and decreasing catalyst inlet flow rate. When filtered air with an oxygen concentration of approximately 3 vol% was introduced into the reaction tube under the same conditions, the temperature inside the reaction tube was between 280°C and 300°C (the upper limit temperature), i.e., below the upper limit temperature (300°C).

[0125] [Example of Oxygen Filtering Means] FIG. 4 is a graph illustrating an example of oxygen filtering processing by the oxygen filtering unit 106 according to the present invention, and a schematic diagram illustrating an embodiment of the arrangement of the gas filter 106f according to the present invention.

[0126] 4A and 4B, an example of oxygen filtering using the gas filter 106f will be described. In this example, compressed air at a pressure of approximately 0.7 MPa was introduced into a PEFC-type fuel cell 103f with a rated output of 1 kilowatt (kW). Then, exhausted low-oxygen air at a pressure of approximately 0.7 MPa was extracted from the fuel cell 103f. The oxygen concentration of this exhausted low-oxygen air was approximately 16-17 vol%.

[0127] Next, this exhausted low-oxygen air with a pressure of about 0.7 MPa is sent to a gas filter 106f, and the outlet flow rate is 0.24 to 1.9 normal lube (Nm 3 The oxygen concentration of the filtered air discharged from the gas filter 106f, i.e., the outlet oxygen concentration, was investigated as a function of the outlet flow rate. A 2-inch UBE N2 separator manufactured by UBE was used as the gas filter 106f.

[0128] As shown in FIG. 4A, in this embodiment, the outlet oxygen concentration decreases as the outlet flow rate decreases, and 3 / hour, the outlet flow rate is further reduced to 0.24 Nm 3 / hour, the outlet oxygen concentration drops to 109 ppm vol. It has also been found, though not based on other experimental results, that the outlet oxygen concentration decreases as the filter internal pressure or inlet pressure increases. It has also been found that the outlet oxygen concentration decreases as the inlet oxygen concentration decreases.

[0129] In this way, it can be understood that the oxygen concentration of the filtered air delivered from the gas filter 106f is further reduced by taking in air with a reduced oxygen concentration (exhaust low-oxygen air) from the fuel cell 103f and by throttling the outlet flow rate under higher internal filter pressure, and as a result, filtered air with a reduced oxygen concentration can be delivered to the catalytic combustion unit 109.

[0130] Next, in this embodiment, using the experimental results described above, the relationship between the outlet oxygen concentration and the outlet flow rate was investigated when using a PEFC-type fuel cell 103f with a rated output of 10 kW, which is capable of delivering low-oxygen air at a larger flow rate after exhaust.

[0131] 4B is a graph showing the relationship between the filtering effect index and the oxygen concentration of the exhaust-depleted oxygen air introduced into the gas filter 106f, i.e., the introduced oxygen concentration. This graph was determined from experimental values. The filtering effect index is defined by the following equation (1): (filtering effect index) = (outlet oxygen concentration at the time of air introduction) / (outlet oxygen concentration at the time of target gas introduction).

[0132] The "outlet oxygen concentration at the time of introduction of the target gas" in the above formula (1) is the outlet oxygen concentration when the target gas for which this index is to be calculated (evaluation target gas; in this embodiment, exhausted low-oxygen air) is introduced into the gas filter 106f. Furthermore, the "outlet oxygen concentration at the time of introduction of air" is the outlet oxygen concentration when air is introduced into the gas filter 106f under the same filter internal pressure and outlet flow rate as the evaluation target gas. For example, if the filtering effect index of a certain evaluation target gas is X, then the outlet oxygen concentration when this evaluation target gas is introduced into the gas filter 106f will be 1 / X of the outlet oxygen concentration when air is introduced into the gas filter 106f.

[0133] According to Figure 4(B), the filtering effect index increases rapidly as the oxygen concentration of the exhausted hypoxic air (evaluation target gas) introduced into the gas filter 106f, i.e., the introduced oxygen concentration, decreases. This means that reducing the introduced oxygen concentration significantly improves the filtering effect. For example, the filtering effect index for exhausted hypoxic air with an introduced oxygen concentration of 3 vol% is approximately 7. In other words, the oxygen concentration of this exhausted hypoxic air after filtering is reduced to approximately one-seventh of the oxygen concentration of the air after filtering.

[0134] From the above results, it can be understood that in order to send filtered air with a lower oxygen concentration to the catalytic combustion unit 109, it is also preferable for the gas filter 106f of the oxygen filtering unit 106 to receive air with a lower oxygen concentration (exhaust low-oxygen air) from the fuel cell 103f of the fuel cell unit 103.

[0135] The filtering effectiveness index curve of the graph shown in FIG. 4(B) was determined based on experimental data points obtained when the gas filter 106f was made of (a) a UBE N2 separator (2-inch diameter) manufactured by UBE and using polyimide hollow fibers, and (b) an N2 membrane module nitrogen gas filter (Selective 6-inch diameter) manufactured by Polypla-Evonik, also using polyimide hollow fibers.

[0136] In the graph, it can be seen that the data points for the Polypla-Evonik filter indicated as "6-inch diameter" and the data points for the other 2-inch diameter filter manufactured by UBE are both generally on the same filtering effect index curve. From this, it can be considered that the relationship between the filtering effect index and the introduced oxygen concentration shown in Figure 4(B) (filtering effect index curve) represents a universal and essential characteristic of polyimide hollow fiber filters, regardless of, for example, the filter manufacturer or filter diameter.

[0137] Next, a preferred embodiment of the arrangement of the gas filter 106f will be described using Figure 4(C). As shown in Figure 4(C), in this embodiment, three gas filters 106f1, 106f2, and 106f3 are arranged in parallel with the flow of introduced low-oxygen exhaust air to perform oxygen filtering. Specifically, the low-oxygen exhaust air discharged from the fuel cell unit 103 is divided into three flows, which are introduced into the hollow fiber section through the filter inlets of the gas filters 106f1, 106f2, and 106f3, respectively.

[0138] Next, the gases discharged from each hollow fiber section through each filter outlet section are combined to become filtered air to be sent to the catalytic combustion unit 109. Meanwhile, the gases coming out of each filter purge section are also combined and discharged as filter exhaust gas.

[0139] This allows a larger amount (flow rate) of exhausted low-oxygen air to be subjected to oxygen filtering. As a result, a larger amount (flow rate) of filtered air can be sent to the catalytic combustion unit 109, and as a result, a larger amount (flow rate) of high-purity nitrogen gas can be generated and provided. Of course, the number of gas filters 106f arranged in parallel is not limited to three, and two or four or more gas filters 106f may be arranged in parallel.

[0140] [Example of operation of fuel cell 103f]

[0141] FIG. 5 is a graph for explaining an example of oxygen reduction and removal processing by the fuel cell 103f according to the present invention.

[0142] In this example, a fuel cell 103f with a rated output of 1 kW was used, and the air inlet flow rate was gradually decreased from 100.0 L / min. The oxygen concentration of the discharged low-oxygen air was measured for each air inlet flow rate. The fuel cell 103f was maintained at a constant current of 90 amperes (A), a constant power of 900 W, and a constant hydrogen gas inlet flow rate of 20 L / min, allowing the fuel cell reaction to continue. The internal pressure of the air and hydrogen gas (internal fuel cell pressure) was approximately 0.1 MPa. Because the current (power) and hydrogen gas inlet flow rate were kept constant, the oxygen (O2) consumption by the fuel cell 103f was also constant.

[0143] As shown in the graph in Figure 5, when the air inlet flow rate was 100.0 L / min, the measured oxygen concentration of the exhaust gas (low-oxygen exhaust air) was 16.8 vol%. This indicates that the introduced hydrogen gas flow rate (20 L / min) was unable to consume most of the oxygen (O2) in the introduced air, resulting in a large amount of oxygen (O2) remaining in the exhaust gas (low-oxygen exhaust air). Here, when the residual oxygen concentration in the exhaust gas (low-oxygen exhaust air) was theoretically calculated using the applied current (90 A) when the air inlet flow rate was 100.0 L / min, the theoretically calculated residual oxygen concentration was 16.2%, which roughly agreed with the measured value (16.8 vol%).

[0144] Next, as the inlet air flow rate decreased from 100.0 L / min, the oxygen concentration of the exhaust gas (low-oxygen exhaust air) also decreased. When the inlet air flow rate was 20.0 L / min, the measured oxygen concentration of the exhaust gas (low-oxygen exhaust air) was 0.0 vol% (below the measurement limit of the oxygen concentration meter). As described above, in this embodiment, the oxygen (O2) consumption rate by the fuel cell 103f was constant. Therefore, under these conditions, the inlet air flow rate at which all of the oxygen (O2) contained in the exhaust gas was consumed was theoretically calculated from the applied current (90 A). This inlet flow rate (theoretical calculation value) was 22.5 L / min.

[0145] Therefore, the experimental result that the oxygen concentration of the exhaust gas (low-oxygen exhaust air) is 0.0 vol% when the air inlet flow rate is 2.5 L / min less than the theoretically calculated value (22.5 L / min), i.e., when the air inlet flow rate is 20.0 L / min, is generally consistent with the theoretical result. Furthermore, as shown in the graph in Figure 5, the measured oxygen concentration of the exhaust gas (low-oxygen exhaust air) at air inlet flow rates of 20.0 to 100.0 L / min also generally agrees with the theoretically calculated value. Incidentally, the discrepancy (in the 0.1 vol% range) between the two values ​​at air inlet flow rates of 40.0 L / min or greater is likely due to measurement errors of the oxygen concentration meter.

[0146] From the above, it can be understood that when the flow rate of introduced air shown in the graph of FIG. 5 is 20.0 L / min, or more specifically, 22.5 L / min (the theoretically calculated value), that is, when the oxygen concentration of the exhaust gas (low-oxygen air after exhaust) is 0.0 vol%, in the fuel cell 103f, (α) hydrogen gas is taken in at a flow rate equal to or greater than the flow rate that enables all of the oxygen (O2) contained in the taken-in air to be converted into water (H2O), and (β) a current flows between the electrodes in an amount that would flow when all of the oxygen (O2) contained in the taken-in air is converted into water (H2O).

[0147] As described above, it can be seen that the fuel cell 103f of this embodiment can generate nitrogen gas (low-oxygen air after exhaust) with a considerably high purity, in this embodiment, 3N or more, by realizing the above states (α) and (β). Whether the fuel cell reaction is in a normal state, in which the above current (β) flows as set, can be determined using the measured value of the complex impedance between the electrodes of the fuel cell 103f. For example, the overall control unit 121 may measure the complex impedance and determine whether the fuel cell reaction is in a normal state, and then notify an external administrator of the determination result (maintenance and inspection result) via a communication network such as wireless communication.

[0148] Furthermore, when the fuel cell 103f that embodies the above states (α) and (β) is used as a high-pressure compatible type in the embodiment shown in Fig. 1, or as a non-high-pressure compatible type in the embodiment shown in Fig. 2, the fuel cell unit 103 alone can serve as a means for reducing the oxygen concentration, and air with a sufficiently reduced oxygen concentration can be sent to the catalytic combustion unit 109. In other words, in this case, the fuel cell unit 103 (and the flow rate controller) alone can constitute the oxygen delivery amount limiting means, and therefore the oxygen filtering unit 106 can be omitted.

[0149] Even if the above states (α) and (β) are not reached, when the oxygen concentration of the exhaust gas (low-oxygen air after exhaust) falls below a set maximum oxygen concentration (e.g., 3 vol%), it is possible to configure the oxygen delivery amount limiting means using only this fuel cell unit 103 (and flow rate controller). Furthermore, in the embodiment shown in Figure 6, which will be described later, it is also possible to employ a fuel cell 203f that embodies the above states (α) and (β).

[0150] [Yet Another Embodiment of Nitrogen Gas Generating Apparatus and System] FIG. 6 is a schematic diagram showing yet another embodiment of a nitrogen gas generating apparatus and system according to the present invention.

[0151] The nitrogen gas generator (system) 2 shown in Figure 6, like the nitrogen gas generator (system) 1 shown in Figure 1, is a device (system) that takes in air and hydrogen gas, generates a nitrogen-enhancing gas, and in this embodiment, high-purity nitrogen gas, and can provide it to the outside. Here, the nitrogen gas generator (system) 2 of this embodiment does not employ the dehumidification unit 105 and oxygen filtering unit 106 in the nitrogen gas generator (system) 1 shown in Figure 1, and instead, in the positions of these units, an oxygen content limiting catalytic combustion unit 205 as second catalytic combustion means and a dehumidification unit 206 downstream thereof are provided.

[0152] 6 does not include an oxygen filtering unit as the oxygen content delivery amount limiting means (202, 203, 205, 207) according to the present invention, but includes a fuel cell unit 203 and an oxygen content limiting catalytic combustion unit 205. In this embodiment, the pressure booster unit 201, the flow rate controller 202, the fuel cell unit 203 including a fuel cell 203f, the dehumidifier 204, the flow rate controller 207, the hydrogen recovery unit 208, the catalytic combustion unit 209 including a combustion catalyst unit 209c, the dehumidifier unit 210 including a dry filter 210d, the hydrogen filtering unit 211 including a gas filter 211f, the pressure controller 212, the nitrogen gas tank 213, and the overall control unit 221 have the same configurations and perform the same functions as the units or devices of the same names in FIG. Furthermore, dehumidification unit 206 including dry filter 206d may have the same configuration and function as dehumidification unit 110 including dry filter 110d shown in Fig. 1. Alternatively, dehumidification unit 206 may be provided with a heat exchanger that performs heat exchange between the catalytic combustion treated air (hereinafter also referred to as post-catalytic combustion air) sent from oxygen content limiting catalytic combustion unit 205 and a refrigerant such as water, thereby lowering the temperature of the post-catalytic combustion air and dehumidifying it.

[0153] The oxygen content limiting catalytic combustion unit 205 serves as a second catalytic combustion means that reacts the low-oxygen air taken in as exhaust gas with hydrogen gas received from the hydrogen recovery unit 208 and / or from an external source such as a hydrogen station on a combustion catalyst (second combustion catalyst) 205c, and outputs air with a lower oxygen concentration. The oxygen content limiting catalytic combustion unit 205 of this embodiment has a set or desired second upper limit temperature for the combustion catalyst 205c or catalytic combustion reaction, and in this embodiment, this second upper limit temperature exceeds the upper limit temperature (first upper limit temperature) of the catalytic combustion unit 209 serving as the first catalytic combustion means.

[0154] Specifically, in this embodiment, combustion catalyst 209c serving as the first combustion catalyst is a solid catalyst with stainless steel (metal) as a support, and as a result, the upper limit temperature (first upper limit temperature) of catalytic combustion unit 209 serving as first catalytic combustion means is set to 300° C. Meanwhile, in this embodiment, oxygen content limiting catalytic combustion unit 205 serving as second catalytic combustion means is equipped with combustion catalyst (second combustion catalyst) 205c with a ceramic support such as calcium aluminate (CaO.Al2O3), fused silica (SiO2), or titanium dioxide (TiO2).

[0155] The second upper limit temperature in the oxygen content limiting catalytic combustion unit 205 is set to a value between 550°C and 850°C, for example, higher than the first upper limit temperature of 300°C, because the ceramic carrier has high heat resistance. Incidentally, while it is not easy to favorably support metal catalysts such as platinum (Pt) and palladium (Pd) on ceramic surfaces, it is relatively easy to favorably support them on metal surfaces such as stainless steel. Therefore, it is generally believed that metal-supported solid catalysts can more efficiently remove and reduce trace amounts of oxygen (O2) than ceramic-supported solid catalysts.

[0156] As described above, the second upper limit temperature in the oxygen content limiting catalytic combustion unit 205 can be set to a sufficiently high temperature, so that the temperature of the combustion catalyst 205c or the catalytic combustion reaction can be kept below the second upper limit temperature (e.g., 550°C) even when the oxygen content limiting catalytic combustion unit 205 receives post-exhaust low-oxygen air with an oxygen concentration of, for example, 6 to 10 vol% sent from the fuel cell unit 203. As a result, the oxygen content limiting catalytic combustion unit 205 can continuously and stably cause a catalytic combustion reaction using a larger amount of oxygen and hydrogen, and can continuously and stably send post-catalytic combustion air with a lower oxygen concentration, for example, an oxygen concentration of 3 vol% or less, to the catalytic combustion unit 209.

[0157] In this embodiment, it is also preferable that the dehumidification unit 206 sufficiently lowers the temperature of the post-catalytic combustion air so that the temperature involved in the catalytic combustion process in the catalytic combustion unit 209 does not exceed a first upper limit temperature (e.g., 300°C). Furthermore, the oxygen content limiting catalytic combustion unit 205 may be capable of heating the combustion catalyst 209c and reaction tube using electric power or thermal energy from the fuel cell unit 203, or even commercial electric power, to support the high-temperature environment of the catalytic combustion process. Furthermore, the amount of hydrogen gas introduced into the oxygen content limiting catalytic combustion unit 205 does not need to be an amount sufficient to consume all of the oxygen in the low-oxygen exhaust air being introduced, but may be an amount sufficient to leave some residual hydrogen in the post-catalytic combustion air.

[0158] On the other hand, the temperature of the combustion catalyst 209c or catalytic combustion reaction in the catalytic combustion unit 209 would greatly exceed the first upper limit temperature (300°C) if the catalytic combustion unit 209 directly received post-exhaust low-oxygen air with an oxygen concentration of, for example, 6 to 10 vol% sent from the fuel cell unit 203. In contrast, in this embodiment, the catalytic combustion unit 209 receives post-catalytic combustion air with an oxygen concentration reduced to, for example, 3 vol% or less, for example, 0.01 to 3 vol%, from the oxygen content limiting catalytic combustion unit 205.

[0159] Therefore, the temperature of the combustion catalyst 209c or the catalytic combustion reaction is kept below the first upper limit temperature (300°C). As a result, the catalytic combustion unit 209 continuously and stably induces the catalytic combustion reaction, enabling it to continuously and stably generate and provide high-purity nitrogen gas having an oxygen concentration below a set or desired upper limit, e.g., nitrogen gas with a purity of 5N or higher. Furthermore, it is also preferable to set the oxygen concentration of the post-catalytic combustion air received by the catalytic combustion unit 209 to a set minimum oxygen concentration (e.g., 0.5 vol%) or higher, e.g., 0.5 to 3 vol%. Here, this minimum oxygen concentration (e.g., 0.5 vol%) is set so that the temperature of the combustion catalyst 209c or the catalytic combustion reaction is above a set lower limit temperature (e.g., 100°C).

[0160] Next, an example of catalytic combustion processing in the oxygen content limiting catalytic combustion unit 205 will be described. In this example, a ceramic-supported honeycomb platinum catalyst manufactured by Nagamine Manufacturing Co., Ltd. was used as the second combustion catalyst 205c. Specifically, six such second combustion catalysts 205c were installed in series within a reaction tube, and dehumidified exhaust gas (exhaust-depleted oxygen-rich air) from the fuel cell 203f was introduced into the reaction tube. The oxygen concentration of this exhaust-depleted oxygen-rich air was 8.1 vol%. The pressure within the reaction tube was adjusted to approximately 0.75 MPa by back pressure control. Furthermore, in this example, the reaction tube (second combustion catalyst 205c) was not heated by electric power or the like.

[0161] Here, 20 minutes after the start of the catalytic combustion reaction, the oxygen concentration of the post-catalytic combustion air extracted from the reaction tube was 2.61 vol% under the conditions of post-exhaust low-oxygen air and hydrogen gas inlet flow rates of 16 L / min and 4 L / min, respectively. The temperature of the reaction tube (second combustion catalyst 205c) was 277°C, below the second upper temperature limit (e.g., 550°C). Furthermore, when this post-catalytic combustion air was dehumidified using the dry filter 206d, the temperature of the dehumidified post-catalytic combustion air decreased to 27.3°C and the relative humidity decreased to 9.3%. Thus, in this example, post-catalytic combustion air was generated that was highly suitable for delivery to the catalytic combustion unit 209 (equipped with a stainless steel (metal)-supported combustion catalyst 209) in terms of oxygen concentration, temperature, and relative humidity.

[0162] In this example, under the condition that the hydrogen gas inlet flow rate was 4 L / min as described above, the residual hydrogen concentration in the post-catalytic combustion air after dehumidification was 2.87 vol%. This residual hydrogen content was utilized for catalytic combustion in the downstream catalytic combustion unit 209. When the hydrogen gas inlet flow rate was increased to 9 L / min, the oxygen concentration in the post-catalytic combustion air extracted from the reaction tube decreased to the 1 vol% range, but the residual hydrogen concentration exceeded 10 vol%. Furthermore, the temperature of the reaction tube (second combustion catalyst 205c) remained around 300°C, below the second upper limit temperature (e.g., 550°C). When the ratio of the hydrogen gas inlet flow rate to the post-exhaust oxygen-depleted air inlet flow rate was further increased to reduce the oxygen concentration in the post-catalytic combustion air extracted from the reaction tube to less than 0.1 vol%, the temperature of the reaction tube (second combustion catalyst 205c) exceeded 500°C.

[0163] As another embodiment, in the nitrogen gas generating apparatus (system) 1' shown in Figure 2, it is possible to eliminate the dehumidifying unit 105 and the oxygen filtering unit 106 and instead provide the above-described oxygen content limiting catalytic combustion unit 205 and the subsequent dehumidifying unit 206 in their place. This type of apparatus (system) also makes it possible to continuously and stably generate and provide high-purity nitrogen gas.

[0164] Furthermore, in an embodiment in which the oxygen content delivery amount limiting means does not include an oxygen filtering unit, such as the present embodiment shown in Figure 6, there is no air or exhaust gas that is not recovered in the gas filter and is ultimately discarded without becoming high-purity nitrogen gas, making it possible to generate high-purity nitrogen gas from air more efficiently.

[0165] [Yet Another Embodiment of Nitrogen Gas Generating Apparatus and System] FIG. 7 is a schematic diagram showing yet another embodiment of a nitrogen gas generating apparatus and system according to the present invention.

[0166] Like the nitrogen gas generator (system) 1 shown in Fig. 1, the nitrogen gas generator (system) 3 shown in Fig. 7 is a device (system) that takes in air and hydrogen gas, generates a nitrogen-enhancing gas, and in this embodiment, high-purity nitrogen gas, and can provide it to the outside. Here, the nitrogen gas generator (system) 3 of this embodiment has a configuration in which the fuel cell unit 103, dehumidifier 104, dehumidification unit 105, and hydrogen recovery unit 108 of the nitrogen gas generator (system) 1 shown in Fig. 1 are omitted.

[0167] 7 does not include a fuel cell unit as the oxygen delivery amount limiting means (302, 306, 307) according to the present invention, but includes an oxygen filtering unit 306. In this embodiment, the pressure boosting unit 301, the flow rate controller 302, the oxygen filtering unit 306 including the gas filter 306f, the flow rate controller 307, the catalytic combustion unit 309 including the combustion catalyst unit 309c, the dehumidifying unit 310 including the dry filter 310d, the hydrogen filtering unit 311 including the gas filter 311f, the pressure controller 312, the nitrogen gas tank 313, and the overall control unit 321 have the same configurations and perform the same functions as the units or devices (1**(#), where * is a number and # is an English letter) of the same names in FIG. In this embodiment, the catalytic combustion unit 309 naturally does not receive high-pressure hydrogen gas from the hydrogen recovery unit, but rather receives it from an external source, such as a hydrogen station, or from the high-pressure water electrolysis unit 502 (Figure 10) described below.

[0168] Here, the oxygen filtering unit 306 of this embodiment takes in compressed air from the pressure boosting unit 301, and while limiting the amount of oxygen in this compressed air that is delivered, delivers the filtered air to the catalytic combustion unit 309. Specifically, in this embodiment, the oxygen filtering unit 306 independently adjusts the oxygen concentration of the taken-in air to be equal to or less than the maximum oxygen concentration (e.g., 3 vol%), for example, 0.1 to 3 vol%, determined based on: (a) a set or desired upper limit temperature of the combustion catalyst 309c or catalytic combustion reaction in the catalytic combustion unit 309, and / or (in this embodiment, and) (b) a set or desired upper limit oxygen concentration in the high-purity nitrogen gas that is finally output.

[0169] As a result, the catalytic combustion unit 309 that receives filtered air from the oxygen filtering unit 306 can: (a) suppress the temperature of the combustion catalyst 309c or the catalytic combustion reaction to a set or desired upper limit temperature or lower, and / or (in this embodiment, and) (b) suppress the oxygen concentration in the high-purity nitrogen gas that is ultimately delivered to a set or desired upper limit oxygen concentration or lower.

[0170] In this embodiment, the combustion catalyst 309c of the catalytic combustion unit 309 can be a solid catalyst supported by a metal such as stainless steel. However, if the oxygen concentration in the high-purity nitrogen gas that is ultimately delivered can be kept below a set or desired upper limit of the oxygen concentration, the combustion catalyst 309c can also be a solid catalyst supported by a ceramic material that has a higher upper limit temperature.

[0171] In any case, the catalytic combustion unit 309 of this embodiment can keep the temperature of the combustion catalyst 309c or the catalytic combustion reaction at or below a set upper limit temperature, thereby continuously and stably causing the catalytic combustion reaction and continuously and stably generating and supplying high-purity nitrogen gas having an oxygen concentration below a set or desired upper limit oxygen concentration, for example, nitrogen gas with a purity of 5N or higher.

[0172] As another embodiment, in the nitrogen gas generating apparatus (system) 3 shown in FIG. 7, the oxygen filtering unit 306 and the flow rate controller 307 may be omitted, and the oxygen delivery amount limiting means according to the present invention may be the flow rate controller 302 alone.

[0173] In this case, however, the flow rate controller 302 must be able to keep the flow rate of the compressed air received from the pressure booster unit 301 equal to or less than a "maximum flow rate" determined based on: (a) a set or desired upper limit temperature of the combustion catalyst 309c or catalytic combustion reaction in the catalytic combustion unit 309, and / or (in this embodiment, and) (b) a set or desired upper limit oxygen concentration in the high-purity nitrogen gas that is finally output. Also, it is necessary to employ a catalytic combustion unit 309 in which such a "maximum flow rate" is determined as a practical value.

[0174] For example, a catalytic combustion unit 309 equipped with a combustion catalyst 309c having a ceramic carrier, whose upper limit temperature is high enough to allow combustion with air (with an oxygen concentration of approximately 20 vol%) and which is appropriately adjusted to be able to efficiently remove and reduce trace amounts of oxygen (O2), can be used in an apparatus (system) in which only the flow controller 302 is used as the oxygen delivery amount limiting means.

[0175] [Yet Another Embodiment of Nitrogen Gas Generating Apparatus and System] FIG. 8 is a schematic diagram showing yet another embodiment of a nitrogen gas generating apparatus and system according to the present invention.

[0176] The nitrogen gas generator (system) 4 shown in Fig. 8 is also a device (system) that takes in air and hydrogen gas, generates a nitrogen-enhancing gas, and in this embodiment, high-purity nitrogen gas, and can provide it to the outside, similar to the nitrogen gas generator (system) 1 shown in Fig. 1. Here, the nitrogen gas generator (system) 4 of this embodiment has a configuration in which the fuel cell unit 203, dehumidifier 204, and hydrogen recovery unit 208 in the nitrogen gas generator (system) 2 shown in Fig. 6 are omitted.

[0177] 8 does not include a fuel cell unit as the oxygen content delivery amount limiting means (402, 405, 407) according to the present invention, but includes an oxygen content limiting catalytic combustion unit 405. In this embodiment, the pressure boosting unit 401, the flow rate controller 402, the oxygen content limiting catalytic combustion unit 405 including a combustion catalyst 405c, the dehumidification unit 406 including a dry filter 406d, the flow rate controller 407, the catalytic combustion unit 409 including a combustion catalyst unit 409c, the dehumidification unit 410 including a dry filter 410d, the hydrogen filtering unit 411 including a gas filter 411f, the pressure controller 412, the nitrogen gas tank 413, and the overall control unit 421 have the same configurations and perform the same functions as the units or devices of the same names in FIG. Incidentally, the oxygen content limiting catalytic combustion unit 405 and the catalytic combustion unit 409 naturally do not receive high-pressure hydrogen gas from the hydrogen recovery unit, but rather receive it from an external source, such as a hydrogen station, or from the high-pressure water electrolysis unit 502 (Figure 10) described below.

[0178] Here, the catalytic combustion unit 405 for limiting the oxygen content in this embodiment takes in compressed air from the pressure boosting unit 401, and while limiting the amount of oxygen content in this compressed air that is delivered, delivers the post-catalytic combustion air to the catalytic combustion unit 409. Specifically, in this embodiment, the catalytic combustion unit 405 for limiting the oxygen content controls the oxygen concentration of the air it takes in independently, without the aid of a fuel cell, to: (a) a set or desired upper limit temperature in the combustion catalyst 409c or catalytic combustion reaction in the catalytic combustion unit 409, and / or (in this embodiment, and) (b) a maximum oxygen concentration (e.g., 3 vol%) or less, for example, 0.01 to 3 vol%, determined based on a set or desired upper limit oxygen concentration in the high-purity nitrogen gas that is finally output.

[0179] As a result, the catalytic combustion unit 409 that receives post-catalytic combustion air from the oxygen content limiting catalytic combustion unit 405 can: (a) suppress the temperature of the combustion catalyst 409c or catalytic combustion reaction to a set or desired upper limit temperature or lower, and / or (in this embodiment, and) (b) keep the oxygen concentration in the high-purity nitrogen gas that is ultimately delivered to a set or desired upper limit oxygen concentration or lower.

[0180] In addition, in this embodiment, the combustion catalyst 405c of the oxygen content limiting catalytic combustion unit 405 and the combustion catalyst 409c of the catalytic combustion unit 409 can be a solid catalyst with a ceramic support and a solid catalyst with a metal support such as stainless steel, respectively, similar to the combustion catalyst 205c of the oxygen content limiting catalytic combustion unit 205 and the combustion catalyst 209c of the catalytic combustion unit 209 shown in Figure 6.

[0181] In this case, even when the oxygen content limiting catalytic combustion unit 405 receives compressed air from the pressure boosting unit 401, the set second upper limit temperature is sufficiently high, for example, between 550°C and 850°C, so it is possible to keep the temperature of the combustion catalyst 405c or the catalytic combustion reaction at or below this second upper limit temperature. As a result, the oxygen content limiting catalytic combustion unit 405 can continuously and stably cause a catalytic combustion reaction using a larger amount of oxygen and hydrogen, and continuously and stably send post-catalytic combustion air with a reduced oxygen concentration to the catalytic combustion unit 409.

[0182] This also makes it possible to keep the temperature of the combustion catalyst 409c or the catalytic combustion reaction in the catalytic combustion unit 409 at or below a set first upper limit temperature (e.g., 300°C). As a result, the catalytic combustion unit 409 can continuously and stably cause the catalytic combustion reaction to occur, and continuously and stably generate and supply high-purity nitrogen gas having an oxygen concentration equal to or lower than a set or desired upper limit oxygen concentration, for example, nitrogen gas with a purity of 5N or higher.

[0183] Furthermore, it is also preferable to set the oxygen concentration of the post-catalytic combustion air received by the catalytic combustion unit 409 to a set minimum oxygen concentration (e.g., 0.5 vol%) or higher, e.g., 0.5 to 3 vol%. Here, this minimum oxygen concentration (e.g., 0.5 vol%) is set so that the temperature of the combustion catalyst 409c or the catalytic combustion reaction is equal to or higher than a set lower limit temperature (e.g., 100°C).

[0184] The amount of hydrogen gas introduced into the oxygen content limiting catalytic combustion unit 405 does not need to be an amount sufficient to consume all of the oxygen content of the introduced air, but may also be an amount sufficient to leave a certain amount of residual hydrogen in the air after catalytic combustion.

[0185] Furthermore, in an embodiment in which the oxygen content delivery amount limiting means does not include an oxygen filtering unit, such as the present embodiment shown in Figure 8, there is no air or exhaust gas that is not recovered in the gas filter and is ultimately discarded without becoming high-purity nitrogen gas, making it possible to generate high-purity nitrogen gas from air more efficiently.

[0186] [Yet Another Embodiment of Nitrogen Gas Generating Apparatus and System] FIG. 9 is a schematic diagram showing yet another embodiment of a nitrogen gas generating apparatus and system according to the present invention.

[0187] The nitrogen gas generator (system) 4' shown in Figure 9, like the nitrogen gas generator (system) 1 shown in Figure 1, is a device (system) that takes in air and hydrogen gas, generates a nitrogen-enhancing gas, and in this embodiment, high-purity nitrogen gas, and can provide it to the outside. Here, the nitrogen gas generator (system) 4' of this embodiment is configured by providing an oxygen filtering unit 403' including a gas filter 403f' between the flow rate controller 402 and the oxygen content limiting catalytic combustion unit 405 in the nitrogen gas generator (system) 4 shown in Figure 8. Here, the oxygen filtering unit 403' has a configuration similar to that of the oxygen filtering unit 306 shown in Figure 7 and the oxygen filtering unit 106 shown in Figure 1, and is a component that performs the same functions.

[0188] 9 includes an oxygen content limiting catalytic combustion unit 405 and an oxygen filtering unit 403' in front of it as oxygen content limiting means (402, 403', 405, 407) according to the present invention. The oxygen content limiting catalytic combustion unit 405 of this embodiment takes in filtered air with a reduced oxygen concentration from the oxygen filtering unit 403', and limits the amount of oxygen content in the filtered air while sending the catalytically combusted air toward the catalytic combustion unit 409.

[0189] Specifically, in this embodiment, the oxygen content limiting catalytic combustion unit 405 adjusts the oxygen concentration of the filtered air it receives to a maximum oxygen concentration (e.g., 3 vol%) or less, for example, 0.01 to 3 vol%, determined based on: (a) a set or desired upper limit temperature of the combustion catalyst 409c or catalytic combustion reaction in the catalytic combustion unit 409, and / or (in this embodiment, and) (b) a set or desired upper limit oxygen concentration in the high-purity nitrogen gas that is ultimately output. In this case, because the oxygen content limiting catalytic combustion unit 405 receives filtered air with a reduced oxygen concentration, it is easier to adjust the oxygen concentration of the filtered air to a maximum oxygen concentration (e.g., 3 vol%) or less, for example, 0.01 to 3 vol%, compared to the embodiment of FIG. 8, which receives raw air.

[0190] Also in this embodiment, the catalytic combustion unit 409 that receives post-catalytic combustion air from the oxygen content limiting catalytic combustion unit 405 can: (a) suppress the temperature of the combustion catalyst 409c or catalytic combustion reaction to a set or desired upper limit temperature or lower, and / or (in this embodiment, and) (b) make the oxygen concentration in the high-purity nitrogen gas that is finally delivered lower than a set or desired upper limit oxygen concentration.

[0191] In this embodiment, the combustion catalyst 405c of the oxygen content limiting catalytic combustion unit 405 and the combustion catalyst 409c of the catalytic combustion unit 409 can be a solid catalyst with a ceramic support and a solid catalyst with a metal support such as stainless steel, respectively. In this case, as described above, the oxygen content limiting catalytic combustion unit 405 can keep the temperature of the combustion catalyst 405c or the catalytic combustion reaction at or below the second upper limit temperature (e.g., 550°C), and the catalytic combustion unit 409 can also keep the temperature of the combustion catalyst 409c or the catalytic combustion reaction at or below the first upper limit temperature (e.g., 300°C).

[0192] As a result, the catalytic combustion unit 409 can continuously and stably cause a catalytic combustion reaction, and continuously and stably generate and provide high-purity nitrogen gas having an oxygen concentration below a set or desired upper limit oxygen concentration, for example, nitrogen gas with a purity of 5N or higher.

[0193] Furthermore, it is also preferable to set the oxygen concentration of the post-catalytic combustion air received by the catalytic combustion unit 409 to a set minimum oxygen concentration (e.g., 0.5 vol%) or higher, e.g., 0.5 to 3 vol%. Here, this minimum oxygen concentration (e.g., 0.5 vol%) is set so that the temperature of the combustion catalyst 409c or the catalytic combustion reaction is equal to or higher than a set lower limit temperature (e.g., 100°C).

[0194] [Embodiment Including High-Pressure Water Electrolysis Means] FIG. 10 is a schematic diagram showing yet another embodiment of a nitrogen gas generation device and system according to the present invention.

[0195] In this embodiment, the nitrogen gas generator / system (1, 1', 2, 3, 4, 4') described above is further provided with a high-pressure water electrolysis unit 502 shown in Fig. 10. Specifically, this high-pressure water electrolysis unit 502 outputs the generated high-pressure hydrogen gas to the fuel cell unit (103, 203), the oxygen content limiting catalytic combustion unit (205, 405), and the catalytic combustion unit (109, 209, 309, 409).

[0196] The high-pressure water electrolysis unit 502 electrolyzes supplied water or water vapor, or an electrolysis target containing water or water vapor, in a limited space (electrolysis cell) to generate high-pressure hydrogen gas at a pressure equal to or greater than a set pressure threshold. Specifically, the high-pressure water electrolysis unit 502 of this embodiment includes a high-pressure water electrolyzer 502E having a configuration in which multiple electrolysis cells are stacked (laminated), each of which has a structure in which an ion exchange membrane 502Ec such as a solid polymer membrane is sandwiched between catalysts and electrodes (cathode 502Ea and anode 502Eb) on both sides of the membrane. Of course, various other configurations and methods can be used for the high-pressure water electrolyzer 502E as long as they are capable of generating high-pressure hydrogen gas. For example, a water electrolysis method using an anion exchange membrane (AEM) or a proton exchange membrane (PEM) may be used.

[0197] Furthermore, when the high-pressure water electrolysis unit 502 generates high-pressure hydrogen gas, for example, at several hundred atmospheres, the pressure of the generated high-pressure hydrogen gas may be reduced to approximately the same pressure (for example, 0.2 to 1 MPa) as the compressed air sent out from the pressure boosting unit (101, 201, 301, 401) by a pressure controller PL equipped with a buffer tank and a pressure adjustment valve provided downstream. The flow rate of this high-pressure hydrogen gas is controlled by a flow rate controller FL provided downstream of the high-pressure water electrolysis unit 502.

[0198] Furthermore, in order to improve the electrolysis efficiency (hydrogen generation efficiency), the high-pressure water electrolysis unit 502 may generate high-temperature water or steam and electrolyze it to generate high-pressure hydrogen gas. In this case, it is preferable that the high-pressure water electrolysis unit 502 receives thermal energy transferred by a heat transfer means such as a heat exchanger or a heat conduction system from the fuel cell unit (103, 203), the catalytic combustion unit for oxygen content limitation (205, 405), or the catalytic combustion unit (109, 209, 309, 409), and uses at least this thermal energy to generate high-temperature water or steam or to increase the temperature in the electrolysis cell to further increase the pressure of the hydrogen gas.

[0199] The high-pressure water electrolysis unit 502 also preferably receives power generated by the fuel cell unit (103, 203) and performs water electrolysis using this power or this power in combination with commercial power drawn from an external source. It is also preferable to use this power for electrothermal heating to generate high-temperature water or steam. Furthermore, water (pure water) extracted from the drain of the fuel cell (103f, 203f) or the dry filter (105d, 110d, 206d, 210d, 310d, 406d, 410d) may also be electrolyzed.

[0200] In this way, by having the high-pressure water electrolysis unit 502 receive and utilize thermal energy, electricity, and water from the components of the nitrogen gas generation device / system (1, 1', 2, 3, 4, 4'), it is possible to significantly reduce or even eliminate the amount of thermal energy, electricity, and water that must be supplied from outside the device / system for the electrolysis process.

[0201] As described above, the high-pressure water electrolysis unit 502, the fuel cell unit (103, 203), the oxygen content limiting catalytic combustion unit (205, 405), and the catalytic combustion unit (109, 209, 309, 409) are capable of seamlessly exchanging high-pressure hydrogen gas, water (pure water), thermal energy, and electricity, and can also form a series of high-pressure systems, making them an extremely suitable combination.

[0202] For example, it is also preferable to integrate, in terms of pressure and thermal energy, a high-pressure water electrolysis unit 502 in which the high-pressure water electrolyzer 502E is an SOEC (Solid Oxide Electrolysis Cell), a fuel cell unit 103 in which the fuel cell 103f is a Solid Oxide Fuel Cell (SOFC), and a catalytic combustion unit 109 in which the combustion catalyst 109c is a ceramic-supported solid catalyst (having a high upper limit temperature). Such integration makes it possible to produce high-purity nitrogen gas more efficiently and simply.

[0203] As also shown in FIG. 10 , the high-pressure water electrolysis unit 502 of this embodiment is supplied with power from a natural energy power generation unit 501. The natural energy power generation unit 501 may be a solar cell power generation unit equipped with a solar cell and converting sunlight into electricity, a wind power generation unit using wind power to rotate a rotor with blades to drive a generator to generate electricity, or a micro-hydro power generation unit using water power to rotate a turbine to drive a generator to generate electricity. Furthermore, various other power generation units can be used as the natural energy power generation unit 501 as long as they ultimately convert the light energy of sunlight or the kinetic energy of wind and water currents into electrical energy. Furthermore, the natural energy power generation unit 501 may be a combination of two or more of the power generation units described above.

[0204] In addition, the natural energy power generation unit 501 of this embodiment is equipped with a storage battery 501b, which is a secondary battery such as a lithium (Li) battery or a lead (Pb) storage battery, and stores the electricity it generates in the storage battery 501b (after converting it to DC power using a converter in the case of AC power).

[0205] Furthermore, the natural energy power generation unit 501 of this embodiment is equipped with a power generation meter that measures its own power generation amount and a power storage meter that measures the amount of power stored in the storage battery 501b, making it possible to measure the amount of power generation and the amount of power stored at each point in time. In this embodiment, the overall control unit (121, 221, 321, 421) checks the measured amount of power generation and the amount of power stored, and then supplies the necessary power from the storage battery 501b to the high-pressure water electrolysis unit 502 when power is required for electrolysis, or to the pressure booster unit (101, 101', 201, 301, 401) when power is required for compressed air generation. Of course, commercial power may also be supplied here (to make up for any shortfall).

[0206] In any case, the combination of the natural energy power generation unit 501, high-pressure water electrolysis unit 502, fuel cell unit (103, 203), oxygen content limiting catalytic combustion unit (205, 405), and catalytic combustion unit (109, 209, 309, 409) described above generates and burns hydrogen gas required to produce high-purity nitrogen gas while emitting as little greenhouse gas as possible, such as carbon dioxide (CO2). In other words, it is a suitable configuration that matches the coming carbon-neutral society, carbon-zero society, and even hydrogen society.

[0207] [Another Embodiment of Fuel Cell Unit] FIG. 11 is a schematic diagram for explaining another embodiment of the fuel cell unit according to the present invention.

[0208] The fuel cell unit 103 of this embodiment shown in Figure 11 includes a fuel cell 103f and control units 103Ca, 103Cb, and 103Cc. The fuel cell 103f includes multiple cells, which are structural units each including a hydrogen electrode and an air electrode sandwiched between two electrolyte membranes. These cells are stacked, and are designed so that hydrogen gas and air pass through the hydrogen electrode and air electrode in each cell, from the cell on the upstream side to the cell on the downstream side of the fuel supply.

[0209] The entire set of cells is divided into a plurality of functional cell sections, which are a power generation priority cell section 103fa, an intermediate cell section 103fb, and an oxygen removal cell section 103fc in Fig. 11. Each of these functional cell sections (103fa, 103fb, 103fc) includes one or a series of multiple cells (two or three in Fig. 11, but actually, for example, several to a dozen or so), and is not electrically connected in series with other functional cell sections, but is electrically connected to its own individual power generation control section (103Ca, 103Cb, 103Cc).

[0210] 11, the control units 103Ca, 103Cb, and 103Cc receive electromotive forces generated between the hydrogen electrodes and the air electrodes in the power generation priority cell unit 103fa, the intermediate cell unit 103fb, and the oxygen removal cell unit 103fc, respectively, and output power (current) appropriate for the functional cell unit they are responsible for. It is also preferable to measure the complex impedance of the functional cell unit they are responsible for and control and manage the functional cell unit accordingly.

[0211] In contrast to the fuel cell 103f of this embodiment, conventional fuel cells, particularly PEFC-type fuel cells, have a configuration in which, for example, tens to hundreds of cells are electrically connected in series to ensure the power required as an actual power source, since the electromotive force of a single cell is usually less than 1 volt (V). Here, naturally, the amount of power that can be generated is smaller in the cells in the later stages, where the amount of oxygen supplied is small. However, the power generation efficiency (relative to the amount of hydrogen supplied) of the entire series-connected cells, including such cells, is significantly reduced because the amount of power generated by each cell must be somewhat uniform.

[0212] Furthermore, if the oxygen deficiency in the downstream cell in the latter stage increases, the fuel cell reaction becomes unstable. In fact, in a fuel cell with an output of 5 kW or more and having several tens of cells, for example, a fuel cell with an output of 6 kW and having 50 cells, it has been confirmed that if the amount of oxygen in the downstream cell in the latter stage becomes too small, the power generation operation becomes unstable.

[0213] In contrast, in the fuel cell 103f of this embodiment, (a) the power generation priority cell section 103fa, which has a large oxygen supply amount (the oxygen in the supplied air has not yet been consumed much), (b) the intermediate cell section 103fb, which is intermediate in terms of the oxygen supply amount, and (c) the oxygen removal cell section 103fc, which has a small oxygen supply amount (the oxygen in the supplied air has been considerably consumed), can each be individually controlled for the power generation amount (current amount) that is suited to the oxygen supply amount.

[0214] Furthermore, by controlling the amount of power generation (current) in this manner, it is possible to maximize or improve both the oxygen reduction efficiency and the power generation efficiency (relative to the amount of hydrogen supply) in the fuel cell 103f. Furthermore, by controlling the amount of power generation (including the amount of current) in each control unit (103Ca, 103Cb, 103Cc) in combination, it is also possible to adjust the oxygen concentration (outlet oxygen concentration) of the exhaust gas (exhaust-depleted oxygen air) to a desired value. As such, the fuel cell unit 103 of this embodiment is a fuel cell system that is extremely suitable for generating high-purity nitrogen gas.

[0215] Of course, the number of functional cell sections in the fuel cell 103f of this embodiment is not limited to three, but may be two, four, or more. For example, among the several hundred rows of cells, the group of 150 cells on the lower side and the remaining group of cells on the upper side may be the second functional cell section and the first functional cell section, respectively.

[0216] As a simpler modification, multiple functional cell units (103fa, 103fb, and 103fc in FIG. 1) can be electrically connected in parallel to a single power generation control unit (e.g., 103Ca). This configuration also improves the power generation efficiency relative to the amount of hydrogen supply compared to a configuration in which a series of cells are electrically connected in series.

[0217] As a further modification, each of the multiple functional cell units (103fa, 103fb, and 103fc in FIG. 1 ) may be replaced by multiple fuel cells. In this case, these fuel cells are physically connected in series. Specifically, the cathode exhaust gas of one fuel cell is introduced into the cathode inlet of the subsequent fuel cell. Furthermore, all of the serially connected cells in each fuel cell may be electrically connected to a separate power generation control unit for each fuel cell, or may be electrically connected in parallel to a single shared power generation control unit. Here, each fuel cell may preferably be a fuel cell with a dozen or so cell stages and an output of less than 5 kW, such as a 2.5 kW fuel cell with 15 cell stages, rather than a fuel cell with several dozen cell stages and an output of 5 kW or more, as described above. This ensures stable power generation operation of each fuel cell.

[0218] [Overall Control Means] The overall control unit (121, 221, 321, 421) controls the operation of each of the above-mentioned units and controllers. In particular, it is preferable that the oxygen delivery amount limiting means controls the oxygen concentration of the delivered air to be equal to or less than the "maximum oxygen concentration" determined based on the "upper limit temperature" and / or the "upper limit oxygen concentration." It is also preferable that the flow rate of the delivered air be equal to or less than the "maximum flow rate" determined based on the "upper limit temperature" and / or the "upper limit oxygen concentration."

[0219] Specifically, in order to perform the above control, the overall control unit (121, 221, 321, 421) monitors the oxygen concentration and flow rate of the air with reduced oxygen concentration that is discharged from the oxygen content discharge amount limiting means using an oxygen concentration meter and flow meter provided immediately after the oxygen content discharge amount limiting means, and further, based on these monitored values, (a) if the oxygen content discharge amount limiting means includes a fuel cell unit, adjusts the pressure and flow rate of the air and hydrogen gas introduced into the fuel cell, the amount of power generated by the fuel cell, etc.; (b) if the oxygen content discharge amount limiting means includes an oxygen content limiting catalytic combustion unit, adjusts the pressure and flow rate of the air introduced into the reaction tube containing the combustion catalyst, the exhausted low-oxygen air, or the filtered air, or the temperature of the combustion catalyst or catalytic combustion reaction; and (c) if the oxygen content discharge amount limiting means includes an oxygen filtering unit, it is preferable to be able to adjust the pressure and flow rate of the air introduced into the gas filter or the exhausted low-oxygen air.

[0220] The overall control unit (121, 221, 321, 421) may be equipped with a processor and memory, and the processor may execute a control program stored in the memory to perform the above-mentioned control and adjustment.

[0221] As described above in detail, the nitrogen gas generating device, system, and method of the present invention can stably, continuously, or reliably generate high-purity nitrogen gas using a combustion catalyst. Furthermore, the present invention, as merely one embodiment, can efficiently or simply generate and provide high-purity nitrogen gas by utilizing hydrogen gas, which will be inexpensive and easily available in the coming hydrogen gas society, and can also provide thermal energy, pure water, and, in some embodiments, electricity.

[0222] In other words, this invention is expected to contribute greatly to the establishment of a carbon-free, locally produced and consumed energy and product supply and demand system, which is considered to be one ideal future model. Furthermore, it is expected to be of great help in realizing carbon neutrality, which is an urgent issue.

[0223] It should be noted that the above-described embodiments are merely illustrative of the present invention and are not limiting, and the present invention can be embodied in various other modified and altered forms. Therefore, the scope of the present invention is defined only by the claims and their equivalents.

[0224] 1, 1', 2, 3, 4, 4' Nitrogen gas generator (system) 101, 101' 201, 301, 401 Pressure booster unit (U) 101p, 101p', 201p, 301p, 401p Gas compressor 102, 107, 107' 202, 207, 302, 307, 402, 407 Flow rate controller 103, 203 Fuel cell unit 103f, 203f Fuel cell 103fa Power generation priority cell section 103fb Intermediate cell section 103fc Oxygen removal cell section 103Ca, 103Cb, 103Cc Control section 104, 204 Dehumidifier 105, 110, 206, 210, 310, 406, 410 Dehumidification unit 105d, 110d, 206d, 210d, 310d, 406d, 410d Dry filter 106, 306, 403' Oxygen filtering unit 106f, 106f1, 106f2, 106f3, 306f, 403f' Gas filter 106fa Hollow fiber section 106fb Filter inlet section 106fc Filter outlet section 106fd Filter purge section 108, 208 Hydrogen recovery unit 109, 209, 309, 409 Catalytic combustion unit 109c, 209c, 309c, 409c Combustion catalyst 111, 211, 311, 411 Hydrogen filtering unit 111f, 211f, 311f, 411f Gas filter 112, 212, 312, 412 Pressure controller 113, 213, 313, 413 Nitrogen gas tank 121, 221, 321, 421 Overall control unit 205, 405 Catalytic combustion unit for oxygen content limitation 205c, 405c Combustion catalyst 501 Natural energy power generation unit 501b Storage battery 502 High-pressure water electrolysis unit 502E High-pressure water electrolyzer 502Ea Cathode 502Eb Anode 502Ec Ion exchange membrane

Claims

1. A nitrogen gas generator comprising: an oxygen content delivery amount limiting means for taking in air or a gas containing nitrogen and oxygen, and delivering the air or gas while limiting the amount of oxygen content in the air or gas delivered; and a catalytic combustion means for reacting the delivered air or gas with a fuel gas containing hydrogen taken in on a combustion catalyst to convert the air or gas into a nitrogen-enriched gas having a higher nitrogen concentration, wherein the oxygen content delivery amount limiting means limits the oxygen concentration of the air or gas to a maximum oxygen concentration determined based on a set or desired upper limit temperature for the combustion catalyst or the reaction, and / or limits the flow rate of the air or gas to a maximum flow rate determined based on a set or desired upper limit temperature for the combustion catalyst or the reaction.

2. The nitrogen gas generating device of claim 1, characterized in that the catalytic combustion means converts the air or gas into a nitrogen-enriched gas having an oxygen concentration below a set or desired upper limit oxygen concentration, and the oxygen content delivery amount limiting means limits the oxygen concentration of the air or gas to a maximum oxygen concentration determined based on a set or desired upper limit temperature of the combustion catalyst or the reaction and the set or desired upper limit oxygen concentration, and / or limits the flow rate of the air or gas to a maximum flow rate determined based on a set or desired upper limit temperature of the combustion catalyst or the reaction and the set or desired upper limit oxygen concentration.

3. A nitrogen gas generating device as described in claim 1 or 2, characterized in that the oxygen content delivery amount limiting means includes a fuel cell that takes in the air or gas and delivers the air or gas with a reduced oxygen concentration as exhaust gas.

4. The nitrogen gas generating device described in claim 3, characterized in that the fuel cell takes in fuel gas containing hydrogen at a flow rate equal to or greater than the flow rate that enables all of the oxygen contained in the taken-in air or gas to be converted into water, allows a current to flow between the electrodes in an amount that would flow if all of the oxygen were converted into water, and sends out the air or gas with a reduced oxygen concentration as exhaust gas.

5. A nitrogen gas generating device as described in claim 1 or 2, characterized in that the oxygen delivery amount limiting means is provided with filters having different degrees of permeability for nitrogen and oxygen, and includes oxygen filtering means that acts on the taken-in air or gas through the filter to deliver air or gas with a reduced oxygen concentration.

6. The nitrogen gas generating device according to claim 1 or 2, characterized in that the oxygen content delivery amount limiting means comprises: a fuel cell that takes in the air or gas and delivers the air or gas with a reduced oxygen concentration as exhaust gas; and oxygen filtering means that has filters with different permeabilities for nitrogen and oxygen, and that acts on the filter with the taken-in air or gas as exhaust gas, thereby delivering the air or gas with an even lower oxygen concentration.

7. The nitrogen gas generating device according to claim 1 or 2, characterized in that the oxygen content delivery amount limiting means includes a second catalytic combustion means that reacts the taken-in air or gas with the taken-in fuel gas containing hydrogen on a second combustion catalyst and delivers the air or gas with a reduced oxygen concentration, and the second catalytic combustion means has a second upper limit temperature that is set or desired for the second combustion catalyst or the reaction and that exceeds the upper limit temperature.

8. The nitrogen gas generating device according to claim 1 or 2, characterized in that the oxygen content delivery amount limiting means includes: a fuel cell that takes in the air or gas and delivers the air or gas with a reduced oxygen concentration as exhaust gas; and second catalytic combustion means that reacts the taken-in air or gas as exhaust gas with taken-in fuel gas containing hydrogen on a second combustion catalyst and delivers the air or gas with an even lower oxygen concentration, and the second catalytic combustion means has a second upper limit temperature that is a set or desired second upper limit temperature for the second combustion catalyst or the reaction and that exceeds the upper limit temperature.

9. The nitrogen gas generating device according to claim 1 or 2, characterized in that the oxygen content delivery amount limiting means comprises: oxygen filtering means having filters with different degrees of permeability for nitrogen and oxygen, which act on the taken-in air or gas through the filters to deliver the air or gas with a reduced oxygen concentration; and the oxygen content delivery amount limiting means comprises second catalytic combustion means which reacts the air or gas with a reduced oxygen concentration with the taken-in fuel gas containing hydrogen on a second combustion catalyst to deliver the air or gas with an even lower oxygen concentration, and the second catalytic combustion means has a second upper limit temperature which is a set or desired second upper limit temperature for the second combustion catalyst or the reaction, and which exceeds the upper limit temperature.

10. The nitrogen gas generating apparatus according to claim 1, further comprising gas filtering means for filtering the nitrogen-enhancing gas taken in through filters having different permeabilities for nitrogen and hydrogen, and for filtering the nitrogen-enhancing gas taken in through the filters, and delivering nitrogen-enhancing gas having a higher nitrogen concentration, or nitrogen-enhancing gas having a lower hydrogen concentration, when the nitrogen-enhancing gas taken in contains hydrogen.

11. The nitrogen gas generating apparatus according to claim 1, further comprising a dehumidifying means for removing or reducing the moisture or water vapor content contained in the nitrogen enrichment gas taken in.

12. A nitrogen gas generating device as described in claim 1, 2, 10 or 11, further comprising: a pressure boosting means provided upstream of the oxygen content delivery amount limiting means or the catalytic combustion means, which increases the pressure of the air or gas that has been taken in or delivered, and delivers the increased pressure air or gas toward the oxygen content delivery amount limiting means or the catalytic combustion means; and a pressure control means provided downstream of the catalytic combustion means, which controls the increased pressure of the air or gas in the section from the pressure boosting means to its own installation position.

13. A nitrogen gas generator comprising: an oxygen content delivery amount limiting means for taking in air or a gas containing nitrogen and oxygen, and delivering the air or gas while limiting the amount of oxygen content in the air or gas delivered; and a catalytic combustion means for reacting the delivered air or gas with taken-in fuel gas containing hydrogen on a combustion catalyst to convert the air or gas into a nitrogen-enriched gas having an oxygen concentration equal to or lower than a set or desired upper limit oxygen concentration, wherein the oxygen content delivery amount limiting means limits the oxygen concentration of the air or gas to a maximum oxygen concentration determined based on the set or desired upper limit oxygen concentration, and / or limits the flow rate of the air or gas to a maximum flow rate determined based on the set or desired upper limit oxygen concentration.

14. A nitrogen gas generation system comprising: an oxygen content delivery amount limiting means for taking in air or a gas containing nitrogen and oxygen, and delivering the air or gas while limiting the amount of oxygen content in the air or gas delivered; and a catalytic combustion means for reacting the delivered air or gas with a fuel gas containing hydrogen taken in on a combustion catalyst to convert the air or gas into a nitrogen-enriched gas having a higher nitrogen concentration, wherein the oxygen content delivery amount limiting means limits the oxygen concentration of the air or gas to a maximum oxygen concentration determined based on a set or desired upper limit temperature for the combustion catalyst or the reaction, and / or limits the flow rate of the air or gas to a maximum flow rate determined based on a set or desired upper limit temperature for the combustion catalyst or the reaction.

15. A method for generating nitrogen gas, comprising: a first step of taking in air or a gas containing nitrogen and oxygen and discharging the air or gas while limiting the amount of oxygen in the air or gas discharged; and a second step of reacting the discharged air or gas with a fuel gas containing hydrogen taken in over a combustion catalyst to convert the air or gas into a nitrogen-enriched gas having a higher nitrogen concentration, wherein in the first step, the oxygen concentration of the air or gas is set to or below a maximum oxygen concentration determined based on a set or desired upper limit temperature for the combustion catalyst or the reaction, and / or the flow rate of the air or gas is set to or below a maximum flow rate determined based on a set or desired upper limit temperature for the combustion catalyst or the reaction.

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