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

Abstract

The present invention provides a nitrogen gas generator capable of stably, continuously, and reliably producing high-purity nitrogen gas using a combustion catalyst. [Solution] This nitrogen gas generator includes an oxygen output limiting means that takes in air or a gas containing nitrogen and oxygen, and outputs the air or the gas while limiting the amount of oxygen output from the air or the gas, and a catalytic combustion means that reacts the output air or the gas and the intake hydrogen-containing fuel gas on a combustion catalyst to convert the air or the gas into a nitrogen-enhanced gas with a higher nitrogen concentration. Here, the oxygen output limiting means sets the oxygen concentration of the air or the gas to be less than or equal to the maximum oxygen concentration determined based on a set or desired upper limit temperature in the combustion catalyst or catalytic combustion reaction, and / or sets the flow rate of the air or the gas to be less than or equal to the maximum flow rate determined based on a set or desired upper limit temperature in the combustion catalyst or catalytic combustion reaction.

Description

Technical Field

[0001] The present invention relates to a technology for generating high-purity nitrogen gas.

Background Art

[0002] In recent years, hydrogen energy has been in the spotlight towards the realization of carbon neutrality and ultimately carbon zero. By utilizing this hydrogen energy, it becomes possible to generate useful substances and energy without emitting carbon dioxide.

[0003] The inventors of the present application have focused on such hydrogen energy and, as disclosed in Patent Documents 1 to 11, have developed various devices and systems using fuel cells that generate electricity by hydrogen energy. In particular, as disclosed in Patent Documents 6 and 7, a nitrogen gas generation device has been developed that acts exhaust gas taken out from a fuel cell on an oxygen removal filter and takes out a gas with an increased nitrogen concentration from this filter. Also, as disclosed in Patent Documents 8 and 10, a configuration has been invented in which the dehumidification treatment of exhaust gas, which is important in the generation of nitrogen gas, is carried out using a water seal pump or a dry filter. Furthermore, as disclosed in Patent Documents 9 and 11, a nitrogen gas generation device that carries out the same dehumidification treatment by a water exchange treatment has also been developed.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Patent Document 5

Patent Document 6

[0005] The inventors of this application are currently focusing on catalytic combustion as a promising gas treatment method for nitrogen gas generation using hydrogen energy. Catalytic combustion is a process in which a target gas is burned together with hydrogen gas on a combustion catalyst to decompose, remove, or reduce unwanted components in the target gas. The inventors of this application believe that by using such catalytic combustion, it may be possible to stably or continuously generate nitrogen gas with a purity of, for example, 4N (99.99 vol%) or 5N (99.999 vol%).

[0006] Therefore, the present invention aims to provide a nitrogen gas generation apparatus, system, and method that can stably, continuously, or reliably generate high-purity nitrogen gas using a combustion catalyst. [Means for solving the problem]

[0007] According to the present invention, an oxygen content limiting means takes in air or a gas containing nitrogen and oxygen, and delivers the air or gas while limiting the amount of oxygen delivered in the air or gas, A catalytic combustion means that reacts the supplied air or gas with the intake hydrogen-containing fuel gas on a combustion catalyst to convert the air or gas into a nitrogen-enhanced gas with a higher nitrogen concentration. It has, The oxygen supply limiting means limits the oxygen concentration of the air or gas to a maximum oxygen concentration determined based on the set or desired upper temperature limit in the combustion catalyst or reaction, and / or limits the flow rate of the air or gas to a maximum flow rate determined based on the set or desired upper temperature limit in the combustion catalyst or reaction. A nitrogen gas generating apparatus or system characterized by the above is provided.

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

[0009] Furthermore, in another embodiment of the nitrogen gas generating apparatus or system according to the present invention, the oxygen output limiting means may also include a fuel cell that takes in the air or gas and sends out the air or gas with reduced oxygen concentration as exhaust gas.

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

[0011] As yet another further embodiment of the nitrogen gas generation device or system according to the present invention, the oxygen component delivery amount limiting means preferably includes an oxygen filtering means that includes a filter having different degrees of permeability for nitrogen and oxygen, and acts on the taken-in air or gas with the filter to deliver the air or gas with reduced oxygen concentration.

[0012] Furthermore, as yet another further embodiment of the nitrogen gas generation device or system according to the present invention, the oxygen component delivery amount limiting means includes a fuel cell that takes in the air or gas and delivers the air or gas with reduced oxygen concentration as exhaust gas, and an oxygen filtering means that includes a filter having different degrees of permeability for nitrogen and oxygen, and acts on the taken-in air or gas as exhaust gas with the filter to deliver the air or gas with further reduced oxygen concentration. It is also preferable to include.

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

[0014] Furthermore, as yet another further embodiment of the nitrogen gas generation device or system according to the present invention, the oxygen component delivery amount limiting means includes a fuel cell that takes in the air or gas and delivers the air or gas with reduced oxygen concentration as exhaust gas, and a second catalytic combustion means that reacts the taken-in air or gas as exhaust gas and a fuel gas containing taken-in hydrogen on a second combustion catalyst to deliver the air or gas with further reduced oxygen concentration. including The second catalytic combustion means preferably has a second upper limit temperature which is the second combustion catalyst or the set or desired second upper limit temperature in the reaction and exceeds the upper limit temperature in the above-mentioned catalytic combustion means (first catalytic combustion means).

[0015] Further, as still another embodiment of the nitrogen gas generation device or system according to the present invention, the oxygen content delivery amount limiting means comprises a filter with different degrees of permeability for nitrogen and oxygen, and oxygen filtering means for acting on the taken-in air or gas with the filter to send out the air or gas with reduced oxygen concentration; The oxygen content delivery amount limiting means includes second catalytic combustion means for reacting the air or gas with reduced oxygen concentration and the fuel gas containing taken-in hydrogen on the second combustion catalyst to send out the air or gas with further reduced oxygen concentration including The second catalytic combustion means preferably has a second upper limit temperature which is the second combustion catalyst or the set or desired second upper limit temperature in the reaction and exceeds the upper limit temperature in the above-mentioned catalytic combustion means (first catalytic combustion means).

[0016] Furthermore, as still another embodiment of the nitrogen gas generation device or system according to the present invention, the nitrogen gas generation device or system comprisesa gas filtering means for acting on the taken-in nitrogen increasing gas with a filter having different degrees of permeability for nitrogen and hydrogen and for nitrogen and oxygen, to send out a nitrogen increasing gas with a higher nitrogen concentration, which is the taken-in nitrogen increasing gas with removed hydrogen or with a lower hydrogen concentration when the taken-in nitrogen increasing gas contains hydrogen.

[0017] Further, as still another embodiment of the nitrogen gas generation device or system according to the present invention, the nitrogen gas generation device or system preferably further has a dehumidifying means for removing or reducing the moisture or water vapor content contained in the taken-in nitrogen increasing gas.

[0018] Furthermore, in yet another embodiment of the nitrogen gas generating apparatus or system according to the present invention, the nitrogen gas generating apparatus or system is provided prior to the oxygen supply limiting means or prior to the catalytic combustion means, and includes a pressure boosting means that increases the pressure of the intake or delivery of the air or gas, and delivers the increased-pressure air or gas toward the oxygen supply limiting means or toward the catalytic combustion means, A pressure control means is provided downstream of the catalytic combustion means and controls the increased pressure of the air or gas in the section from the pressure boosting means to its own installation position. It is also preferable to have further.

[0019] According to the present invention, the present invention also includes an oxygen content limiting means for taking in air or a gas containing nitrogen and oxygen, and for sending out the air or gas while limiting the amount of oxygen content sent out in the air or gas, A catalytic combustion means that reacts the supplied air or gas with the intake hydrogen-containing fuel gas on a combustion catalyst to convert the air or gas into a nitrogen-enhanced gas having an oxygen concentration below a set or desired upper limit oxygen concentration. It has, The oxygen supply 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. A nitrogen gas generating apparatus or system characterized by the above is provided.

[0020] According to the present invention, the invention further includes 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 discharged from the air or gas, A second step involves reacting the supplied air or gas with the intake hydrogen-containing fuel gas on a combustion catalyst to convert the air or gas into a nitrogen-enhanced gas with a higher nitrogen concentration. It has, In the first step, the oxygen concentration of the air or gas is set to be less than or equal to the maximum oxygen concentration determined based on the set or desired upper temperature limit in the combustion catalyst or the reaction, and / or the flow rate of the air or gas is set to be less than or equal to the maximum flow rate determined based on the set or desired upper temperature limit in the combustion catalyst or the reaction. A method for generating nitrogen gas is provided, characterized by the following features. [Effects of the Invention]

[0021] According to the nitrogen gas generation apparatus, system, and method of the present invention, high-purity nitrogen gas can be stably, continuously, or reliably generated using a combustion catalyst. [Brief explanation of the drawing]

[0022] [Figure 1] This is a schematic diagram showing one embodiment of the nitrogen gas generating apparatus and system according to the present invention. [Figure 2] This is a schematic diagram showing another embodiment of the nitrogen gas generating apparatus and system according to the present invention. [Figure 3] These are schematic diagrams and graphs illustrating one embodiment of catalytic combustion treatment using the catalytic combustion unit according to the present invention. [Figure 4] This is a graph illustrating one embodiment of oxygen filtering processing using the oxygen filtering unit according to the present invention, and a schematic diagram illustrating one embodiment of the arrangement of the gas filter according to the present invention. [Figure 5] This graph illustrates one embodiment of the oxygen reduction and removal treatment using a fuel cell according to the present invention. [Figure 6] This is a schematic diagram illustrating yet another embodiment of the nitrogen gas generating apparatus and system according to the present invention. [Figure 7] This is a schematic diagram illustrating yet another embodiment of the nitrogen gas generating apparatus and system according to the present invention. [Figure 8] This is a schematic diagram illustrating yet another embodiment of the nitrogen gas generating apparatus and system according to the present invention. [Figure 9] This is a schematic diagram illustrating yet another embodiment of the nitrogen gas generating apparatus and system according to the present invention. [Figure 10] This is a schematic diagram illustrating yet another embodiment of the nitrogen gas generating apparatus and system according to the present invention. [Figure 11] This is a schematic diagram illustrating another embodiment of the fuel cell unit according to the present invention. [Modes for carrying out the invention]

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

[0024] [Nitrogen gas generator / system] Figure 1 is a schematic diagram showing one embodiment of the nitrogen gas generating apparatus and system according to the present invention.

[0025] The nitrogen gas generator 1 shown in Figure 1, as one embodiment of the present invention, (A) An oxygen content limiting means (102, 103, ...) that takes in air or a gas containing nitrogen (N2) and oxygen (O2) (hereinafter abbreviated as nitrogen-containing gas), and sends the air or nitrogen-containing gas to the downstream stage while limiting the amount of oxygen (O2) content in the air or nitrogen-containing gas sent to the downstream stage, (B) A catalytic combustion unit (U) 109 reacts the supplied air or nitrogen-containing gas with the intake hydrogen (H2) fuel gas on a combustion catalyst to convert the air or nitrogen-containing gas into a nitrogen-enhanced gas with a higher nitrogen (N2) concentration, or a nitrogen-enhanced gas having an oxygen (O2) concentration below a set or desired "upper limit oxygen concentration" in this embodiment. It has.

[0026] Here, in a preferred embodiment, the oxygen output limiting means (102, 103, ...) is (A11) The oxygen (O2) concentration of the air or nitrogen-containing gas shall be less than or equal to the "maximum oxygen concentration" determined based on the set or desired "upper temperature limit" in the combustion catalyst or catalytic combustion reaction, and (A12) The flow rate of air or nitrogen-containing gas shall be less than or equal to the "maximum flow rate" determined based on the set or desired "upper temperature limit" in the combustion catalyst or catalytic combustion reaction. It is also preferable to implement at least one of the following.

[0027] The oxygen supply limiting means (102, 103, ...) limit the amount of oxygen (O2) supplied from the air or nitrogen-containing gas 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 produce high-purity nitrogen gas.

[0028] Generally, in catalytic combustion treatment in a catalytic combustor, increasing the amount of oxygen (O2) per unit time in the introduced air or nitrogen-containing gas, i.e., the flow rate of introduced oxygen (O2), leads to a larger catalytic combustion reaction, increased reaction heat, and consequently, an increase in the reaction temperature and, consequently, the temperature of the combustion catalyst. If this temperature becomes too high, there is a possibility that the support material of the combustion catalyst may deform or deteriorate. Therefore, in catalytic combustors, a predetermined "upper temperature limit" is usually set for the combustion catalyst or catalytic combustion reaction to ensure a stable or continuous catalytic combustion reaction, and it is desirable or necessary to use the catalyst below this "upper temperature limit".

[0029] For example, in the case of combustion catalysts using metal supports such as stainless steel, which are said to be able to efficiently remove or reduce trace amounts of oxygen (O2), a "maximum temperature" of, for example, 300°C is often set or recommended (by the combustion catalyst manufacturer) for 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 the catalytic combustion reaction often exceeds the set or recommended "maximum temperature."

[0030] Therefore, the nitrogen gas generator 1 of this embodiment limits the amount of oxygen (O2) supplied to the catalytic combustion unit 109 from the air or nitrogen-containing gas by means of oxygen supply limiting means (102, 103, ...), making it possible to keep the temperature of the combustion catalyst or catalytic combustion reaction in the limiting catalytic combustion unit 109 below the "upper limit temperature".

[0031] Furthermore, the oxygen output limiting means (102, 103, ...) can be, in other preferred embodiments, (A21) The oxygen (O2) concentration of the air or nitrogen-containing gas shall be less than or equal to the "maximum oxygen concentration" determined based on the set or desired "upper temperature limit" in the combustion catalyst or catalytic combustion reaction, and the "upper oxygen concentration limit" in the nitrogen-enhanced gas produced, and (A22) The flow rate of air or nitrogen-containing gas shall be less than or equal to the "maximum flow rate" determined based on the set or desired "upper temperature limit" in the combustion catalyst or catalytic combustion reaction, and the "upper oxygen concentration limit" in the nitrogen-enhanced gas produced. It is also preferable to implement at least one of the following.

[0032] The oxygen supply limiting means (102, 103, ...) limit the amount of oxygen (O2) supplied from the air or nitrogen-containing gas to the catalytic combustion unit 109, thereby suppressing the temperature of the combustion catalyst or catalytic combustion reaction in the catalytic combustion unit 109 to the "upper limit temperature" and keeping the oxygen (O2) concentration of the nitrogen-enhanced 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 produce high-purity nitrogen gas.

[0033] Generally speaking, 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 oxygen (O2) introduction flow rate, the more reliably the introduced oxygen (O2) can be used in the reaction, and the lower the oxygen (O2) concentration in the gas after catalytic combustion treatment.

[0034] Therefore, the oxygen supply limiting means (102, 103, ...) can limit the amount of oxygen (O2) supplied to the catalytic combustion unit 109 from the air or nitrogen-containing gas as described in (A21) and / or (A22) above, thereby making the oxygen (O2) concentration of the nitrogen-enhanced gas taken out from the catalytic combustion unit 109 less than or equal to the "upper limit oxygen concentration".

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

[0036] Furthermore, the oxygen output limiting means (102, 103, ...) can be, in other preferred embodiments, (A31) The oxygen (O2) concentration of air or nitrogen-containing gas shall be less than or equal to the "maximum oxygen concentration" determined based on the "upper limit oxygen concentration" above, and (A32) The flow rate of air or nitrogen-containing gas shall be less than or equal to the "maximum flow rate" determined based on the "upper limit oxygen concentration" above. It is also preferable to limit the amount of oxygen (O2) in the air or nitrogen-containing gas supplied to the catalytic combustion unit 109 by implementing at least one of the above, thereby causing the catalytic combustion unit 109 to generate a nitrogen-enhanced gas having an oxygen (O2) concentration below the "upper limit oxygen concentration".

[0037] The oxygen output limiting means (102, 103, ...) limit the amount of oxygen (O2) in the air or nitrogen-containing gas supplied to the catalytic combustion unit 109, thereby making the oxygen (O2) concentration of the nitrogen-enhanced gas extracted from the catalytic combustion unit 109 below the "upper limit oxygen concentration". As a result, the nitrogen gas generator 1 can reliably produce high-purity nitrogen gas. For example, although this is only one embodiment, as will be described later, it is possible to reliably produce nitrogen gas with a purity of 5N (99.999 vol%) or higher, which is the specification required by a certain supplier.

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

[0039] Furthermore, in the embodiments shown in Figures 1, 2, 6, 7, 8, and 9, which will be described in detail later, all the components together constitute a single device (nitrogen gas generator). However, in other embodiments, at least one of the components may be included in a separate device from the other components. For example, the oxygen output limiting means (102, 103, ...) may be included in a separate device from the device containing the catalytic combustion units (109, 209, 309, 409). In such cases, 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-enhanced gas) have been sufficiently reduced. Specifically, the nitrogen concentration (in ml per 100 ml of medium, in units of vol%) in "high purity" nitrogen gas (nitrogen-enhanced gas) or "high-purity" nitrogen gas (nitrogen-enhanced gas) may be specified as 95 vol% or higher, 99 vol% (2N) or higher, or even 99.9 vol% (3N) or higher, or 99.999 vol% (5N) or higher, depending on the field and application of the nitrogen gas.

[0041] Incidentally, in this specification, the nitrogen concentration values ​​are measured and calculated without considering residual elements in the nitrogen gas (increased nitrogen gas), such as argon (Ar) and carbon dioxide (CO2) that were originally present in the air. In other words, in this specification, the nitrogen concentration value (e.g., 99.999 vol% (5N)) is a value that considers only oxygen (O2) and hydrogen (H2) as highly reactive impurities that should be reduced or removed.

[0042] Furthermore, the gas pressure values ​​for air, hydrogen gas, etc., listed below are absolute pressure values ​​based on a vacuum, meaning atmospheric pressure is set at 1 atmosphere (approximately 0.1 megapascals (MPa)). For example, the "0.5 MPa (approximately 5 atmospheres)" shown below corresponds to a gauge pressure value of approximately 0.4 MPa (approximately 4 atmospheres) when measured by a pressure gauge installed in a pipe containing air or hydrogen gas.

[0043] [Device / System Configuration] The nitrogen gas generator (system) 1 of this embodiment, shown in Figure 1, includes a pressure boosting unit 101, a flow controller 102, a fuel cell unit 103, a dehumidifier 104, a dehumidification unit 105, an oxygen filtering unit 106, a flow 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. It takes in air and fuel gas, and in this embodiment, hydrogen gas, to generate nitrogen-enhanced gas, and in this embodiment, high-purity nitrogen gas, which can be supplied to the outside.

[0044] In this embodiment, as described above, air is used as the raw material gas for nitrogen gas production, but it is also possible to use a nitrogen-containing gas such as a mixture of nitrogen gas and oxygen gas. Furthermore, in this embodiment, hydrogen gas taken in from an external source, such as a hydrogen station, is used as the fuel gas. However, in other embodiments, it is also possible to produce hydrogen-containing gas from hydrocarbon gases such as city gas or LP (Liquefied Petroleum) gas through a steam reforming reaction, and use this hydrogen-containing gas as the fuel gas. In addition, the flow of material and energy transfer and the processing performed, shown by connecting the components with arrows in the apparatus (or system) configuration diagram of Figure 1, can also be understood as one embodiment of the nitrogen gas production method according to the present invention.

[0045] <Means of increasing pressure> Also in Figure 1, the pressure boosting unit 101 is located upstream of the fuel cell unit 103, which serves as a means for limiting the amount of oxygen delivered. It 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 equipped with a compressor that compresses air taken in from the atmosphere and delivers the generated compressed air toward the fuel cell unit 103, and an electric motor for operating this compressor. Various types of compressors can be used, such as reciprocating, scroll, screw, rotary, or swing types, or combinations of two or more of these.

[0046] Furthermore, in the nitrogen gas generation apparatus (system) 1 of this embodiment, the compressed air generated by the pressure boosting unit 101 is converted into nitrogen-enhanced gas, or in this embodiment, high-purity nitrogen gas, by passing through various units while maintaining a high-pressure state. Here, the pressure boosting unit 101 creates this high-pressure state, and the pressure controller 112, located downstream of the hydrogen filtering unit 111, controls this high-pressure state as back pressure control, as will be described later. Here, 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, it is also preferable that, as intermediate pressure control, a pressure controller PL located upstream 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 pressure controller 112, so that the set high-pressure state is achieved in each unit.

[0048] Furthermore, the pressure boosting unit 101 of this embodiment may have a buffer tank, and the generated compressed air may be temporarily stored in this buffer tank. It is also preferable to pass the compressed air taken from this buffer tank through an air filter and an oil filter to remove fine dust and oil components, and then send the compressed air to the fuel cell unit 103. Incidentally, if there is, for example, a compressed air supply facility at the site where the nitrogen gas generation device (system) 1 is brought in or installed, this pressure boosting unit 101 can be omitted.

[0049] <Flow rate control means> Also in Figure 1, the flow controller 102 includes, for example, a gas regulator and a mass flow controller or flow switch, and controls the flow rate of compressed air supplied from the pressure boosting unit 101 to the fuel cell unit 103. In this embodiment, the flow controller 102 can be considered as an oxygen output limiting means that takes in air, limits the amount of oxygen output from the taken-in air, and then outputs this air.

[0050] Specifically in this embodiment, the flow rate controller 102 controls the flow rate of this air. (a) The combustion catalyst 109c in the catalytic combustion unit 109 or the set or desired upper limit temperature in the catalytic combustion reaction, and / or (in this embodiment, and) (b) The set or desired upper limit oxygen concentration in the final output high-purity nitrogen gas By keeping the flow rate below the maximum flow rate determined based on [the relevant factor], it functions as a means of limiting the amount of oxygen delivered.

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

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

[0053] Here, the fuel cell unit 103 of this embodiment can be considered as an oxygen output limiting means that takes in air, limits the amount of oxygen output from the air, and outputs this air. Specifically, in this embodiment, the fuel cell unit 103 controls the oxygen concentration of this air, (a) The combustion catalyst 109c in the catalytic combustion unit 109 or the set or desired upper limit temperature in the catalytic combustion reaction, and / or (in this embodiment, and) (b) The set or desired upper limit oxygen concentration in the final output high-purity nitrogen gas By keeping the oxygen supply below the "maximum oxygen concentration" determined based on this, it functions as a means of limiting the amount of oxygen delivered.

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

[0055] Furthermore, it is preferable that the exhaust gas from the air electrode side, which is post-exhaust low-oxygen air, is subsequently subjected to further dehumidification by a dehumidifier 104 equipped with a gas-water separator (water exchanger) and a desiccant cartridge, for example, to remove some of the condensed water in a drain, and then further dehumidified. Here, if the dehumidifier 104 includes a gas-water separator (water exchanger), the dehumidifier 104 can perform gas-water separation (water exchange) between the post-exhaust low-oxygen air as exhaust gas and the compressed air before it is taken into the fuel cell unit 103.

[0056] Incidentally, the exhaust gas from the air electrode side, which is post-exhaust low-oxygen air, is subsequently subjected to oxygen filtering, catalytic combustion, and hydrogen filtering in this embodiment to be converted into high-purity nitrogen gas. However, dehumidification is performed to prevent the moisture and water vapor content from becoming a major obstacle to these processes.

[0057] Furthermore, the fuel cell 103f may have a known configuration. For example, it may have a configuration in which multiple cells, each having a structure in which an electrolyte membrane is sandwiched between an air electrode (oxygen electrode, cathode) and a hydrogen electrode (fuel electrode, anode), are stacked (laminated) with a separator in between. In this case, in each cell, an oxidizing gas chamber on the air electrode side and a fuel gas chamber on the hydrogen electrode side are provided so as to sandwich the electrolyte membrane.

[0058] Furthermore, while fuel cell 103f is a polymer electrolyte fuel cell (PEFC) in this embodiment, it can of course also be a solid oxide fuel cell (SOFC), a phosphoric acid fuel cell (PAFC), or a molten carbonate fuel cell (MCFC). Incidentally, the PEFC used in this embodiment operates at relatively low temperatures and allows for a compact battery size, and is therefore 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 compressed air at high pressure (e.g., 0.2 to 1 MPa) and hydrogen gas at high pressure (e.g., 0.2 to 1 MPa), and discharges high-pressure exhaust gas (e.g., 0.2 to 1 MPa) from the oxidation gas chamber and fuel gas chamber.

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

[0061] Furthermore, the fuel cell unit 103 of this embodiment can also have a heat exchanger that circulates a heat exchange medium such as water placed inside or around the fuel cell 103f, thereby extracting thermal energy from the fuel cell reaction from the operating fuel cell 103f and providing this thermal energy to the outside. In this case, hot water, steam, or a high-temperature heat exchange medium other than water may be supplied to the outside. Examples of usable heat exchangers include multi-tube heat exchangers such as shell-and-tube heat exchangers, and plate heat exchangers such as Alfa Laval brazed plate heat exchangers.

[0062] Furthermore, instead of a heat exchanger, a heat conduction system connecting the separator of the fuel cell 103f and a heat pipe may be used to extract thermal energy from within the fuel cell 103f, and this thermal energy may be supplied to the outside from one end of the heat pipe. In any case, such a heat transfer means can not only provide thermal energy to, for example, consumers, but also control the temperature of the cells of the fuel cell 103f to below a predetermined upper limit temperature (for example, 80°C for a PEFC), thereby maintaining optimal operation of the fuel cell 103f. Alternatively, in 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 hot water or hot water.

[0063] Furthermore, in this embodiment, it is preferable that the thermal energy extracted by the heat transfer means such as the heat exchanger and heat conduction system described above is sent to a temperature controller 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, which are located downstream, and is used for temperature adjustment to bring the temperature of this gas (exhaust gas on the air electrode side) to a temperature suitable for each process. Here, the temperature controller may be equipped with a thermometer to monitor the temperature of this gas (exhaust gas on the air electrode side) and report it to the overall control unit 121 as appropriate.

[0064] Furthermore, 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 supplied to the outside. Here, this power adjustment unit may, for example, have a storage battery and an inverter, and temporarily store the DC power from the fuel cell 103f and then convert it into AC power in a form that can be used externally. It is also preferable that the pressure boosting unit 101 of this embodiment be operated by the power from the fuel cell 103f, or by this power and commercial power.

[0065] <Dehumidification means> Also in Figure 1, the dehumidification unit 105 of this embodiment is equipped with a dry filter 105d, which reduces the moisture or water vapor content in the post-exhaust low-oxygen air discharged from the air electrode side of the fuel cell 103f. The dry filter 105d receives the high-pressure (e.g., 0.2 to 1 MPa) post-exhaust low-oxygen air, ejects it through small holes in the filter, and expands it adiabatically. The condensed water generated is shaken off from the flow after the ejection of this post-exhaust low-oxygen air, thereby dehumidifying the post-exhaust low-oxygen air. For example, it is possible to reduce the relative humidity of a gas with a relative humidity of 100% to about 15%.

[0066] The dry filter 105d is not limited to the adiabatic expansion and condensation type described above, but may also be 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 requiring virtually no maintenance.

[0067] Furthermore, as described above, the dehumidification unit 105 of this embodiment can dehumidify high-pressure gas (e.g., 0.2 to 1 MPa). Here, it is also preferable that the pressure value of the exhaust low-oxygen air introduced (e.g., 0.2 to 1 MPa) be greater than or equal to the lower limit pressure required to achieve the target or desired relative humidity under the set introduction flow rate in the dry filter 105d. Thus, the dehumidification unit 105 is a unit that is very suitable for integration into a series of high-pressure systems that include the fuel cell unit 103, oxygen filtering unit 106, and catalytic combustion unit 109 between the pressure boosting unit 101 and the pressure controller 112 as described above.

[0068] Furthermore, if the dehumidifier 104 and the dehumidification unit 105 adequately dehumidify the low-oxygen air after exhaust, the other can be omitted. Also, if the fuel cell 103f is an SOFC, the dehumidifier 104 and the dehumidification unit 105 can be omitted.

[0069] <Oxygen filtering means> Also in Figure 1, the oxygen filtering unit 106 of this embodiment is equipped with gas filters 106f with different degrees of permeability for nitrogen and oxygen. Exhaust low-oxygen air with reduced oxygen concentration and dehumidification at high pressure (e.g., 0.2 to 1 MPa) is passed through these gas filters 106f, and air with an even lower oxygen concentration at high pressure (e.g., 0.2 to 1 MPa) is extracted from these gas filters 106f and sent out. Incidentally, this air with an even lower oxygen concentration may hereafter be referred to as "filtered air".

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

[0071] Specifically, gas filter 106f is, (a) Hollow fiber sections with different degrees of permeability to nitrogen (N2) and oxygen (O2) (106fa in Figure 4(C) described later), (b) A filter inlet (106fb in Figure 4(C), described later) for introducing high-pressure (e.g., 0.2-1 MPa) exhaust low-oxygen air to act on the hollow fiber section described in (a), and a filter outlet (106fc in Figure 4(C)) for extracting filtered air with a lower oxygen concentration (i.e., a higher nitrogen concentration) at high pressure (e.g., 0.2-1 MPa) from this hollow fiber section, (c) A filter purge section (106fd in Figure 4(C)) for extracting the gas containing oxygen (O2) separated from the low-oxygen air after exhaust by the hollow fiber section of (a) above (hereinafter sometimes referred to as "filter exhaust gas"), separately from the filtered air extracted in (b) above. It is equipped with.

[0072] Of these, the hollow fiber portion described in (a) above is a polymer fiber made of hollow fibers that preferentially permeates oxygen (O2) over nitrogen (N2). As the low-oxygen air after exhaust at high pressure (e.g., 0.2 to 1 MPa) flows from the filter inlet through this hollow fiber portion, oxygen (O2) selectively permeates through the polymer fibers and exits. As a result, filtered air with a lower oxygen concentration and a higher nitrogen concentration is ultimately extracted from the filter outlet. Incidentally, this hollow fiber portion may also selectively permeate water (H2O) and hydrogen (H2) in addition to oxygen (O2). In this case, it is also possible to obtain filtered air with lower relative humidity and hydrogen concentration.

[0073] Experiments have confirmed that in such hollow fiber sections, the higher the pressure of the exhaust low-oxygen air introduced (introduction pressure), the lower the flow rate of the filtered air taken out (outlet flow rate), and the lower the oxygen concentration of the exhaust low-oxygen air introduced (introduction oxygen concentration), the more filtered air with a reduced oxygen concentration (outlet oxygen concentration), i.e., a higher nitrogen concentration (outlet nitrogen concentration), can be taken out from the filter outlet.

[0074] From the perspective of the dependence of the outlet oxygen concentration on the input oxygen concentration, the gas filter 106f (oxygen filtering unit 106) and the fuel cell 103f (fuel cell unit 103), which pre-reduces the oxygen concentration of the air beforehand, are a very suitable combination for ultimately producing high-purity nitrogen gas with a low oxygen concentration (as required by the specifications). Therefore, it is understood that combining the two results in a more suitable oxygen output limiting means.

[0075] Furthermore, experiments have confirmed that with the gas filter 106f, the recovery rate (= outlet flow rate / introduction flow rate) increases as the introduced oxygen concentration decreases. Therefore, from the standpoint of recovery rate, the gas filter 106f (oxygen filtering unit 106) and the preceding fuel cell 103f (fuel cell unit 103) are a very suitable combination for recovering a sufficient amount (flow rate) of high-purity nitrogen gas (as required by the specifications).

[0076] Furthermore, if the oxygen concentration of the low-oxygen air after exhaust discharge from the fuel cell unit 103 is low enough to keep the temperature of the combustion catalyst 109c or the catalytic combustion reaction below the upper limit temperature, or to keep the oxygen concentration of the final output high-purity nitrogen gas below the upper limit oxygen concentration, the oxygen filtering unit 106 can be omitted. An example of such a fuel cell unit 103 will be explained later with reference to Figure 5.

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

[0078] Furthermore, the flow controller 107 controls the flow rate of filtered air with a lower oxygen concentration. (a) The combustion catalyst 109c in the catalytic combustion unit 109 or the set or desired upper limit temperature in the catalytic combustion reaction, and / or (in this embodiment, and) (b) The set or desired upper limit oxygen concentration in the final output high-purity nitrogen gas It may also function as an oxygen delivery rate limiting means by keeping the flow rate below the maximum flow rate determined based on [the relevant factor].

[0079] <Catalytic combustion method> Also in Figure 1, the catalytic combustion unit 109 is equipped with a combustion catalyst 109c, and reacts filtered air sent from the oxygen filtering unit 106 with the intake hydrogen gas on the combustion catalyst 109c to convert this filtered air into a nitrogen-enhanced gas having an oxygen concentration below a set or desired upper limit oxygen concentration, which in this embodiment is high-purity nitrogen gas.

[0080] In this embodiment, the catalytic combustion unit 109 specifically brings filtered air at high pressure (e.g., 0.2 to 1 MPa) and hydrogen gas at high pressure (e.g., 0.2 to 1 MPa) into contact on the surface of the combustion catalyst 109c to cause a catalytic combustion reaction, further consuming oxygen (O2) in the filtered air and delivering 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, since high-pressure (e.g., 0.2 to 1 MPa) gases come into contact on the combustion catalyst, the reaction rate of the catalytic combustion reaction is increased, the reaction is further promoted, and the effect of reducing the oxygen concentration in the nitrogen gas produced, i.e., the effect of improving nitrogen purity, is further increased.

[0081] In this embodiment, the oxygen output limiting means (102, 103, 106, 107), including the fuel cell unit 103 and the oxygen filtering unit 106, controls the oxygen concentration and / or flow rate of the filtered air sent to the catalytic combustion unit 109 as described above. As a result, the catalytic combustion unit 109, (a) The temperature of the combustion catalyst 109c or the catalytic combustion reaction can be kept below a set or desired upper limit temperature, and / or (in this embodiment, and) (b) The oxygen concentration in the high-purity nitrogen gas finally delivered can be set to or below a set or desired upper limit oxygen concentration.

[0082] Furthermore, the combustion catalyst 109c in this embodiment is a solid catalyst supported by 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 such a combustion catalyst 109c, the upper limit temperature for continuous use is set to 300°C, and the upper limit oxygen concentration of the nitrogen gas produced is set to 10 ppm vol (corresponding to a nitrogen purity of 5N).

[0083] In contrast, the oxygen supply limiting means (102, 103, 106, 107) described above, in this embodiment, suppress the temperature of the combustion catalyst 109c or the catalytic combustion reaction to 300°C or less, and further, in order to obtain high-purity nitrogen gas with a desired flow rate and an oxygen concentration of 10 ppm vol or less, suppress the oxygen concentration of the air with a reduced oxygen concentration (filtered air in this embodiment) supplied to the catalytic combustion unit 109 to the maximum oxygen concentration (for example, 3 vol%) or less.

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

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

[0086] As will be described later, when multiple combustion catalysts 109c are arranged in series inside the reaction tube, experiments have confirmed that the temperature of the reaction tube due to the heat of reaction is considerably higher at the outlet side of the reaction tube, where the introduced gas has been in the fuel catalyst environment for a long time, than at the inlet side. Therefore, it is preferable that the upper limit temperature of the combustion catalysts 109c and the reaction tube be determined taking into account the temperature at the outlet side of the reaction tube. Incidentally, it is also preferable that the temperature of the combustion catalysts 109c and the reaction tube be measured by a thermometer TM, notified to the overall control unit 121 as appropriate, 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. In order to cause a catalytic combustion reaction that achieves a temperature above this lower limit temperature, it is also preferable in this embodiment for the oxygen supply limiting means (102, 103, 106, 107) to set the oxygen concentration of the filtered air supplied to the catalytic combustion unit 109 to be above the set minimum oxygen concentration (e.g., 0.5 vol%). As a result, the temperature of the combustion catalyst 109c and the reaction tube will be above the lower limit temperature (100°C), eliminating the need to heat the combustion catalyst 109c and the reaction tube, for example, with electricity. Thus, when the temperature of the combustion catalyst 109c and the reaction tube is to be above the lower limit temperature without heating them with electricity or the like, it is important to appropriately determine the above minimum oxygen concentration at the set introduction flow rate (of 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, to 0.01 vol%), while the combustion catalyst 109c and reaction tubes are heated, for example, by an electric heater or by electromagnetic induction using commercial power or power from the fuel cell unit 103. Alternatively, the thermal energy from the fuel cell unit 103 may be used to heat the combustion catalyst 109c and reaction tubes. 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, and furthermore, the thermal energy of the exhaust gas, which is at a very high temperature, can also be used for the catalytic combustion reaction.

[0089] Incidentally, as mentioned above, the combustion catalyst 109c in this embodiment is a solid catalyst supported by a metal such as stainless steel. Specifically, the combustion catalyst 109c can be a metal honeycomb with numerous fine holes, on which metals such as platinum (Pt), palladium (Pd), or nickel (Ni) are supported as catalysts on the surface, including the inside of these holes. In another embodiment, the combustion catalyst 109c may be a honeycomb-shaped ceramic support on which platinum (Pt), palladium (Pd), or nickel (Ni) is supported. It may also be equipped with a granular catalyst. In any case, the combustion catalyst 109c needs to be used at a temperature below the upper limit temperature set or deemed desirable for itself.

[0090] As also shown in Figure 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 extracts and recovers 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 using a hydrogen gas filter, executor, etc.

[0091] The hydrogen gas recovered by the hydrogen recovery unit 108 may be sent to a hydrogen mixer, mixed with hydrogen gas supplied from an external source, 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 located 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, the catalytic combustion unit 109 of this embodiment, like the fuel cell unit 103, may take in high-pressure (e.g., 0.2 to 1 MPa) hydrogen gas from an external source, such as 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 bring the hydrogen gas supplied to the catalytic combustion unit 109 and 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 the catalytic combustion unit 109 are a very suitable combination, especially since they can utilize hydrogen gas from the same hydrogen gas source.

[0093] The high-purity nitrogen gas (increased nitrogen gas) discharged from the catalytic combustion unit 109 typically contains moisture or water vapor generated by the catalytic combustion reaction. Therefore, in this embodiment, a dehumidification unit 110 located downstream of the catalytic combustion unit 109 reduces or removes this moisture or water vapor to an extent that does not hinder subsequent processing. This dehumidification unit 110 is equipped with a dry filter 110d similar to the dry filter 105d described above, and 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 (increased nitrogen gas) discharged 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-enhanced gas) introduced into the dry filter 110d be greater than or equal to the lower limit pressure required to achieve the target or desired relative humidity under the set introduction flow rate in the dry filter 110d. Thus, the dehumidification unit 110, like the dehumidification unit 105, is a unit that is very suitable for integration into a series of high-pressure systems that include the fuel cell unit 103, oxygen filtering unit 106, and catalytic combustion unit 109 between the pressure boosting unit 101 and the pressure controller 112 as described above.

[0095] In this embodiment, the high-purity nitrogen gas (increased nitrogen gas) introduced into the dry filter 110d is extremely hot due to the catalytic combustion reaction. Therefore, the dehumidification unit 110 may be equipped with a cooling means, such as a water cooling means, to lower the temperature of the high-purity nitrogen gas (increased nitrogen gas) sent to the hydrogen filtering unit 111, which will be described later, to a temperature suitable for the gas filter 111f. Incidentally, in another embodiment, the dehumidification unit 110 may be equipped with a heat exchanger capable of exchanging heat between the high-purity nitrogen gas (increased nitrogen gas) and a refrigerant such as water to lower the temperature of the high-purity nitrogen gas (increased nitrogen gas) and dehumidify it. Furthermore, it is preferable that the combustion catalyst unit 109 is equipped with an auto-drain for removing condensed water generated in the high-purity nitrogen gas (increased nitrogen gas) being sent out.

[0096] Furthermore, the high-purity nitrogen gas (increased nitrogen 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, generally, in a catalytic combustion reaction, it is very difficult to control the flow rate of the hydrogen gas introduced to bring about the desired catalytic combustion reaction and then reduce the amount of residual hydrogen gas to, for example, 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 Figure 1, the hydrogen filtering unit 111 is a gas filtering means that takes high-pressure (e.g., 0.2 to 1 MPa) high-purity nitrogen gas (nitrogen-enhanced gas) taken in from the dehumidification unit 110 via the flow controller FL and applies it to the gas filter 111f to generate and send out high-purity nitrogen gas (nitrogen-enhanced gas) with a higher nitrogen concentration, and if the nitrogen-enhanced gas received from the dehumidification unit 110 contains hydrogen (H2), then hydrogen (H2) is removed or the hydrogen concentration is lower.

[0098] Here, the gas filter 111f is a gas filter that has different degrees of permeability for nitrogen (N2) and hydrogen (H2), and for nitrogen (N2) and oxygen (O2). As a modification, the gas filter 111f may be a hydrogen filter that has different degrees of permeability for nitrogen (N2) and hydrogen (H2), but is not limited to nitrogen (N2) and oxygen (O2). In any case, the hydrogen filtering unit 111 generates and sends out high-purity nitrogen gas (nitrogen-enhanced gas) from which hydrogen (H2) has been removed or which has a lower hydrogen concentration.

[0099] Furthermore, by placing 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 highly sophisticated control over the amount (flow rate) of hydrogen gas introduced. In this way, the catalytic combustion unit 109 and the subsequent hydrogen filtering unit 111 form an excellent combination that can improve the efficiency of high-purity nitrogen gas production in a simpler manner.

[0100] Furthermore, the gas filter 111f in this embodiment may be the same filter as the gas filter 106f of the oxygen filtering unit 106 described above. For example, as gas filters 111f and 106f, UBE N2 separators using aromatic polyimide hollow fibers manufactured by UBE, or N2 membrane modules / nitrogen gas filters using aromatic polyimide hollow fibers manufactured by Polypla Evonik, can be used. When such filters using aromatic polyimide hollow fibers are used as gas filter 111f, for example, the hydrogen concentration of a gas with a hydrogen concentration of approximately 1 vol% can be reduced to several ppm vol. Also, for gases with a hydrogen concentration of less than 1 vol%, it is possible to reduce the hydrogen concentration to below the detection limit (1 ppm vol).

[0101] Furthermore, experiments have confirmed that the higher the pressure of the gas introduced into the gas filter 111f, the lower the hydrogen concentration of the gas (introduced hydrogen concentration), and the smaller the flow rate of the gas (introduced flow rate), the greater the reduction in the hydrogen concentration of the gas discharged from the gas filter 111f. Experiments have also confirmed that the hydrogen reduction effect of the gas filter 111f is particularly pronounced when the introduced gas has a pressure above a predetermined pressure threshold (for example, approximately 0.75 MPa) and a hydrogen concentration below 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-enhanced gas) discharged 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-enhanced gas) based on these measurements received from the oxygen concentration meter O2 and the hydrogen concentration meter H2.

[0103] Furthermore, if the high-purity nitrogen gas (nitrogen-enhanced gas) delivered from the catalytic combustion unit 109 does not contain hydrogen gas in general, has a hydrogen concentration below the set or desired upper limit hydrogen concentration, or if it is preferable that it contains a considerable amount of hydrogen gas, the hydrogen filtering unit 111 can be omitted.

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

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

[0106] Furthermore, the pressure controller 112 of this embodiment controls the gas pressure within each unit so that the oxygen concentration of the gas delivered from each of the fuel cell unit 103, oxygen filtering unit 106, and combustion catalyst unit 109 is less than or equal to 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 less than or equal to the set or desired upper limit oxygen concentration can ultimately be obtained. In addition, the pressure of the gas within the hydrogen filtering unit 111 is controlled so that the hydrogen concentration of the gas delivered from the hydrogen filtering unit 111 is less than or equal to the maximum hydrogen concentration set in 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 less than or equal to the set or desired upper limit oxygen concentration can ultimately be obtained.

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

[0108] Also in Figure 1, the nitrogen gas tank 113 is a tank for temporarily storing high-pressure (e.g., 0.2 to 1 MPa) high-purity nitrogen gas having an oxygen concentration below 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 flow switch, and, for example, upon instruction from the overall control unit 121, it delivers the stored high-purity nitrogen gas to an external supply destination at a predetermined stable pressure and flow rate.

[0109] [Other embodiments of nitrogen gas generators and systems] Figure 2 is a schematic diagram showing another embodiment of the 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, eliminates the use of the pressure boosting unit 101 located upstream of the fuel cell unit 103 and the flow rate controller 107 located downstream of the oxygen filtering unit 106, as in the nitrogen gas generator (system) 1 shown in Figure 1. Instead, the pressure boosting unit 101' and the flow rate controller 107' are installed between the fuel cell unit 103 and the dehumidification unit 105.

[0111] In other words, the nitrogen gas generator (system) 1 shown in Figure 1 is equipped with a pressure boosting means before the oxygen output limiting means (102, 103, 106, 107), whereas the nitrogen gas generator (system) 1' shown in Figure 2 is equipped with a pressure boosting means before the catalytic combustion unit 109 and within the oxygen output limiting means (102, 103, 107', 106).

[0112] The oxygen output limiting 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 sent toward the catalytic combustion unit 109 in the same manner as the oxygen output limiting means (102, 103, 106, 107) shown in Figure 1. As a result, the catalytic combustion unit 109, (a) The temperature of the combustion catalyst 109c or the catalytic combustion reaction can be kept below a set or desired upper limit temperature, and / or (in this embodiment, and) (b) The oxygen concentration in the high-purity nitrogen gas finally delivered can be set to or below a set or desired upper limit oxygen concentration.

[0113] Furthermore, this enables the nitrogen gas generator (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 with a predetermined stable pressure and flow rate.

[0114] In the nitrogen gas generator (system) 1', a series of high-pressure systems, including a dehumidification unit 105, an oxygen filtering unit 106, a combustion catalyst unit 109, a dehumidification 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 in this embodiment controls the back pressure of this series of high-pressure systems.

[0115] Specifically, the pressure controller 112 of this embodiment controls the gas pressure within each unit so that the oxygen concentration of the gas delivered from the oxygen filtering unit 106 and the combustion catalyst unit 109 is less than or equal to 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 less than or equal to the set or desired upper limit oxygen concentration can ultimately be obtained. Furthermore, the pressure of the gas within the hydrogen filtering unit 111 is controlled so that the hydrogen concentration of the gas delivered from the hydrogen filtering unit 111 is less than or equal to 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 less than or equal to the set or desired upper limit oxygen concentration can ultimately be obtained.

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

[0117] Furthermore, the fuel cell unit 103 in 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 also preferable to use a solid oxide fuel cell (SOFC), which is generally not considered easy to make compatible with high pressures, as the fuel cell 103f. Of course, a non-high-pressure compatible polymer electrolyte fuel cell (PEFC) may also be used.

[0118] [Examples of catalytic combustion means] Figure 3 is a schematic diagram and graph illustrating one embodiment of catalytic combustion treatment using the catalytic combustion unit 109 according to the present invention.

[0119] In this embodiment, a honeycomb catalyst (Pt coated) D3HPT2S40C manufactured by Tanaka Kikinzoku Kogyo Co., Ltd. was used as the combustion catalyst 109c, and as shown in Figure 3(A), 10 combustion catalysts 109c were arranged in series inside a stainless steel reaction tube. Next, air with a reduced oxygen concentration was introduced into this reaction tube to induce a catalytic combustion reaction.

[0120] Here, 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 exhaust low-oxygen air with an oxygen concentration of approximately 10 vol%, which has been dehumidified and initially sent from the fuel cell unit 103, was introduced into the reaction tube lined with these combustion catalysts 109c, the temperature inside the reaction tube, especially near the inlet, significantly exceeded the upper temperature limit of 300°C.

[0121] Next, dehumidified, low-oxygen exhaust air from the fuel cell unit 103 was introduced into the oxygen filtering unit 106. Filtered air with an oxygen concentration of approximately 1.77 vol% from this oxygen filtering unit 106 was then introduced into the reaction tube. Hydrogen gas was also introduced into the reaction tube at a predetermined flow rate, matching the amount of 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 Figure 3(B) shows the temperature inside the reaction tube, the flow rate of the low-oxygen air after exhaust to the catalyst, the oxygen concentration at the catalyst outlet, and the relative humidity of the discharged high-purity nitrogen gas (humidity at the catalyst outlet) from 65 minutes (the time when the oxygen concentration of the high-purity nitrogen gas discharged from the reaction tube (oxygen concentration at the catalyst outlet) began to fall below 10 ppm vol) to 400 minutes.

[0123] According to the graph in Figure 3(B), the temperature inside the reaction tube remained generally stable for 65 to 400 minutes, staying 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 falling below 2 ppm vol. This indicates that, excluding residual hydrogen gas, a high-purity nitrogen gas exceeding 5N and approaching 6N was obtained.

[0124] Incidentally, the catalyst inlet flow rate of the low-oxygen air after exhaust remained generally stable at approximately 20 L / min for a period of 65 to 400 minutes. The relative humidity of the discharged high-purity nitrogen gas was approximately 4%, which is the value after dehumidification by the dehumidification unit 110 located downstream of the reaction tube. It was also confirmed by experiment that the oxygen concentration of the high-purity nitrogen gas discharged from the reaction tube (outlet oxygen concentration) decreases as the pressure inside the reaction tube increases and as the catalyst inlet flow rate decreases. Furthermore, when filtered air with an oxygen concentration of approximately 3 vol% was introduced into the reaction tube under the same conditions as above, the temperature inside the reaction tube was between 280°C and 300°C (upper limit temperature), meaning it remained below the upper limit temperature (300°C).

[0125] [Examples of oxygen filtering means] Figure 4 is a graph illustrating one embodiment of the oxygen filtering process using the oxygen filtering unit 106 according to the present invention, and a schematic diagram illustrating one embodiment of the arrangement of the gas filter 106f according to the present invention.

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

[0127] Next, this exhaust low-oxygen air with a pressure of approximately 0.7 MPa is sent to gas filter 106f, with an outlet flow rate of 0.24 to 1.9 normal cubic meters (Nm³). 3 The system was introduced to vary within the range of ) / hour, and the dependence of the outlet flow rate on the oxygen concentration of the filtered air delivered from the gas filter 106f, i.e., the outlet oxygen concentration, was investigated. A 2-inch diameter UBE N2 separator manufactured by UBE Corporation was used as the gas filter 106f.

[0128] As shown in Figure 4(A), in this embodiment, the outlet oxygen concentration decreases as the outlet flow rate decreases, and when the outlet flow rate is 0.8 Nm³ 3 This results in approximately 1000 ppm vol per hour. Furthermore, the outlet flow rate is further reduced to 0.24 Nm³. 3 Assuming a flow rate of 109 ppm vol / hour, the outlet oxygen concentration decreases to 109 ppm vol. Furthermore, in other experimental results, it has been found that this outlet oxygen concentration decreases as the filter internal pressure or inlet pressure increases. Additionally, it has been found that the outlet oxygen concentration decreases as the inlet oxygen concentration decreases.

[0129] Thus, the oxygen concentration of the filtered air sent out from the gas filter 106f is further reduced by taking in air with a reduced oxygen concentration (low-oxygen air after exhaust) from the fuel cell 103f, and by restricting the outlet flow rate under a higher filter internal pressure. As a result, filtered air with an even lower oxygen concentration can be sent to the catalytic combustion unit 109.

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

[0131] Figure 4(B) is a graph showing the relationship between the filtering efficiency index and the oxygen concentration of the post-exhaust low-oxygen air introduced into the gas filter 106f, i.e., the introduced oxygen concentration. This graph was determined from experimental values. Here, the filtering efficiency index is given by the following equation: (1) (Filtering effectiveness index) = (Outlet oxygen concentration when air is introduced) / (Outlet oxygen concentration when target gas is introduced) It is defined by [this].

[0132] In equation (1) above, "outlet oxygen concentration when target gas is introduced" is the target gas for which this index is to be calculated (evaluation target gas; in this embodiment, it is the outlet oxygen concentration when exhaust low-oxygen air is introduced into the gas filter 106f). Also, "outlet oxygen concentration when air is introduced" is the outlet oxygen concentration when air is introduced into the gas filter 106f under the same filter pressure and outlet flow rate as the evaluation target gas described above. For example, if the filtering efficiency 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] As shown in Figure 4(B), this filtering efficiency index increases sharply as the oxygen concentration of the exhaust low-oxygen air (the gas being evaluated) 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 efficiency index for exhaust low-oxygen air with an introduced oxygen concentration of 3 vol% is approximately 7. In other words, the oxygen concentration of this exhaust low-oxygen air after filtering is reduced to about one-seventh of the oxygen concentration of the air after filtering.

[0134] From the above results, it is understood that in order to supply 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 (low-oxygen air after exhaust) from the fuel cell 103f of the fuel cell unit 103.

[0135] Here, the filtering effect exponential curve in the graph shown in Figure 4(B) is for gas filter 106f, (a) UBE N2 separator (2-inch diameter) using polyimide hollow fiber manufactured by UBE, and (b) N2 membrane module nitrogen gas filter (Selective 6-inch diameter) manufactured by Polypla Evonik, also using polyimide hollow fibers. It is determined based on experimental data points obtained using [the specified method].

[0136] In the same graph, it can be seen that the data points for the Polypla Evonik filter labeled "6-inch diameter," as well as the data points for the other UBE 2-inch diameter filters, generally lie on a single filtering efficiency index curve. From this, it can be concluded that the relationship between the filtering efficiency index and the introduced oxygen concentration (filtering efficiency index curve) shown in Figure 4(B) 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 filters 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 to the flow of exhaust low-oxygen air being introduced, and perform oxygen filtering. Specifically, the exhaust low-oxygen air sent from the fuel cell unit 103 is divided into three flows and introduced into the hollow fiber sections from 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 are combined and 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 filtered exhaust gas.

[0139] This allows for oxygen filtering treatment of a larger volume (flow rate) of exhaust low-oxygen air. As a result, a larger volume (flow rate) of filtered air can be sent to the catalytic combustion unit 109, and consequently, a larger volume (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; two or four or more gas filters 106f may be used in parallel.

[0140] [An example of fuel cell 103f operation]

[0141] Figure 5 is a graph illustrating one embodiment of the oxygen reduction and removal treatment using the fuel cell 103f according to the present invention.

[0142] In this embodiment, a fuel cell 103f with a standard output of 1kW was used, and the oxygen concentration of the exhaust hypoxic air was measured at each air intake rate, starting from 100.0 L / min and gradually decreasing. In the fuel cell 103f, the current was kept constant at 90 amperes (A), the power at 900W, and the hydrogen gas intake rate at 20 L / min to continue the fuel cell reaction. The cell pressure (fuel cell pressure) for air and hydrogen gas was approximately 0.1 MPa. Since the current (power) and hydrogen gas intake 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 intake flow rate was 100.0 L / min, the measured oxygen concentration of the exhaust gas (low-oxygen air after exhaust) was 16.8 vol%. This indicates that the flow rate of the introduced hydrogen gas (20 L / min) was insufficient 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 air after exhaust). Here, when the residual oxygen concentration in the exhaust gas (low-oxygen air after exhaust) was theoretically calculated from the applied current value (90 A) when the air intake flow rate was 100.0 L / min, the theoretically calculated residual oxygen concentration was 16.2%, which was in good agreement with the measured value (16.8 vol%).

[0144] Next, as the air intake flow rate decreased from 100.0 L / min, the oxygen concentration of the exhaust gas (low-oxygen air after exhaust) also decreased accordingly. When the air intake flow rate was 20.0 L / min, the measured oxygen concentration of the exhaust gas (low-oxygen air after exhaust) was 0.0 vol% (below the detection limit of the oxygen concentration meter). In this embodiment, as described above, the amount of oxygen (O2) consumed by the fuel cell 103f is constant. Under these conditions, the air intake flow rate at which all the contained oxygen (O2) is consumed was theoretically calculated from the current value (90A), and this intake flow rate (theoretical calculated value) was found to be 22.5 L / min.

[0145] Therefore, the experimental result that the oxygen concentration of the exhaust gas (low-oxygen air after exhaust) becomes 0.0 vol% when the air intake flow rate is 2.5 L / min less than the theoretically calculated value (22.5 L / min), i.e., when the air intake flow rate is 20.0 L / min, is generally consistent with the theory. Furthermore, as shown in the graph in Figure 5, the measured values ​​of the oxygen concentration of the exhaust gas (low-oxygen air after exhaust) when the air intake flow rate is between 20.0 and 100.0 L / min also generally match the theoretically calculated value. Incidentally, the difference between the two (around 0.1 vol%) when the air intake flow rate is 40.0 L / min or higher is generally thought to be due to measurement errors of the oxygen concentration by the oxygen concentration meter.

[0146] Furthermore, as stated above, when the air intake flow rate shown in the graph of Figure 5 is 20.0 L / min, or more specifically, when it is 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%, then in fuel cell 103f, (α) A flow rate of hydrogen gas is taken in that is greater than the flow rate that can convert all the oxygen (O2) contained in the intake air into water (H2O), and (β) The current flowing between the electrodes is the amount that would flow if all the oxygen (O2) in the intake air were converted into water (H2O). This is understood.

[0147] As described above, the fuel cell 103f of this embodiment makes it possible to generate nitrogen gas of considerably high purity, in this embodiment 3N or higher (low-oxygen air after exhaust), by realizing the states (α) and (β) above. The determination of whether the fuel cell reaction state is a normal state in which the current (β) above flows as set can be performed 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 state is normal, and notify an external administrator of the determination result (maintenance inspection result), for example, via a communication network such as wireless communication.

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

[0149] Furthermore, even without reaching the states described in (α) and (β) above, if the oxygen concentration of the exhaust gas (low-oxygen air after exhaust) falls below the set maximum oxygen concentration (for example, 3 vol%), it is possible to configure the oxygen output limiting means using only such a fuel cell unit 103 (and flow controller). Moreover, 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 states described in (α) and (β) above.

[0150] [Further Other Embodiments of Nitrogen Gas Generators and Systems] Figure 6 is a schematic diagram showing yet another embodiment of the 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 to produce nitrogen-enhanced gas, in this embodiment high-purity nitrogen gas, and can provide it to the outside. In this embodiment, the nitrogen gas generator (system) 2 eliminates the use of the dehumidification unit 105 and the oxygen filtering unit 106 in the nitrogen gas generator (system) 1 shown in Figure 1, and instead, an oxygen-limiting catalytic combustion unit 205 as a second catalytic combustion means and a subsequent dehumidification unit 206 are provided in the positions of these units.

[0152] In other words, the nitrogen gas generator (system) 2 shown in Figure 6 does not include an oxygen filtering unit as an oxygen output limiting means (202, 203, 205, 207) according to the present invention, but instead includes a fuel cell unit 203 and an oxygen limiting catalytic combustion unit 205. Incidentally, in this embodiment, the pressure boosting unit 201, flow controller 202, fuel cell unit 203 including fuel cell 203f, dehumidifier 204, flow controller 207, hydrogen recovery unit 208, catalytic combustion unit 209 including combustion catalyst unit 209c, dehumidification unit 210 including dry filter 210d, hydrogen filtering unit 211 including gas filter 211f, pressure controller 212, nitrogen gas tank 213, and overall control unit 221 have the same configuration as the units or devices of the same name in Figure 1 (1**(#), * is a number, # is an English letter) and perform the same functions. Furthermore, the dehumidification unit 206, which includes the dry filter 206d, may have the same configuration and perform the same function as the dehumidification unit 110, which includes the dry filter 110d shown in Figure 1. Alternatively, the dehumidification unit 206 may be equipped with a heat exchanger capable of exchanging heat between the post-catalytic combustion air (hereinafter sometimes referred to as post-catalytic combustion air) sent from the oxygen-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] Furthermore, the oxygen-limiting catalytic combustion unit 205 is a second catalytic combustion means that reacts the low-oxygen post-exhaust air, which is the intake 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 to deliver air with an even lower oxygen concentration. In this embodiment, the oxygen-limiting catalytic combustion unit 205 has a set or desired second upper limit temperature in the combustion catalyst 205c or the catalytic combustion reaction, but in this embodiment, this second upper limit temperature is a value that exceeds the upper limit temperature (first upper limit temperature) of the catalytic combustion unit 209, which is the first catalytic combustion means.

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

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

[0156] As described above, since the second upper limit temperature in the oxygen-limiting catalytic combustion unit 205 can be set to a sufficiently high temperature, even when the oxygen-limiting catalytic combustion unit 205 receives exhaust low-oxygen air with an oxygen concentration of, for example, 6-10 vol%, sent from the fuel cell unit 203, it is possible to keep the temperature of the combustion catalyst 205c or the catalytic combustion reaction below the second upper limit temperature (for example, 550°C). As a result, the oxygen-limiting catalytic combustion unit 205 can continuously and stably induce a catalytic combustion reaction using more oxygen and hydrogen, and can continuously and stably send post-catalytic combustion air with an even 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 related to the catalytic combustion process in the catalytic combustion unit 209 does not exceed the first upper limit temperature (e.g., 300°C). Furthermore, the oxygen-limiting catalytic combustion unit 205 may be capable of heating the combustion catalyst 209c and reaction tube using electricity or thermal energy from the fuel cell unit 203, or even commercial electricity, in order to assist in the high-temperature environment of the catalytic combustion process. Moreover, the amount of hydrogen gas introduced into the oxygen-limiting catalytic combustion unit 205 does not need to be enough to consume all the oxygen in the low-oxygen post-exhaust air that is introduced; on the other hand, it may be an amount that leaves a certain amount of residual hydrogen in the post-catalytic combustion air.

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

[0159] Therefore, the temperature of the combustion catalyst 209c or the catalytic combustion reaction will remain below the first upper limit temperature (300°C). As a result, the catalytic combustion unit 209 can continuously and stably induce the catalytic combustion reaction and continuously and stably produce and supply high-purity nitrogen gas, for example, nitrogen gas with a purity of 5N or higher, having an oxygen concentration below the set or desired upper limit oxygen concentration. Furthermore, it is preferable to set the oxygen concentration of the post-catalytic combustion air received by the catalytic combustion unit 209 to be above the set minimum oxygen concentration (e.g., 0.5 vol%), for example, 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 the set lower limit temperature (e.g., 100°C).

[0160] Next, an example of catalytic combustion treatment in the oxygen-limiting catalytic combustion unit 205 will be described. In this example, a honeycomb platinum catalyst with a ceramic support, manufactured by Nagamine Seisakusho Co., Ltd., was used as the second combustion catalyst 205c. Specifically, six such second combustion catalysts 205c were arranged in series in a reaction tube, and dehumidified exhaust gas (low-oxygen post-exhaust air) from the fuel cell 203f was introduced into this reaction tube. The oxygen concentration of this low-oxygen post-exhaust air was 8.1 vol%. The pressure inside 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 electricity or the like.

[0161] Here, 20 minutes after the start of the catalytic combustion reaction, under conditions where the introduction flow rates of exhaust low-oxygen air and hydrogen gas were 16 L / min and 4 L / min, respectively, the oxygen concentration in the post-catalytic combustion air taken out of the reaction tube was 2.61 vol%. Furthermore, the temperature of the reaction tube (second combustion catalyst 205c) was 277°C, which is below the second upper limit temperature (e.g., 550°C). When this post-catalytic combustion air was subjected to dehumidification treatment using a dry filter 206d, the temperature of the post-catalytic combustion air after dehumidification treatment decreased to 27.3°C and the relative humidity decreased to 9.3%. Thus, in this embodiment, it was possible to generate post-catalytic combustion air that is very suitable for delivery to the catalytic combustion unit 209 (equipped with a combustion catalyst 209 supported by stainless steel (metal)) in terms of oxygen concentration, temperature, and relative humidity.

[0162] In this embodiment, under the condition that the hydrogen gas introduction 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 will be used for catalytic combustion in the subsequent catalytic combustion unit 209. Incidentally, when the hydrogen gas introduction flow rate was increased to 9 L / min, the oxygen concentration in the post-catalytic combustion air removed from the reaction tube decreased to around 1 vol%, but the residual hydrogen concentration exceeded 10 vol%. Also, the temperature of the reaction tube (second combustion catalyst 205c) remained around 300°C, below the second upper limit temperature (e.g., 550°C). Incidentally, when the ratio of the hydrogen gas introduction flow rate to the introduction flow rate of low-oxygen air after exhaust was further increased, and the oxygen concentration in the post-catalytic combustion air removed from the reaction tube was reduced to less than 0.1 vol%, the temperature of the reaction tube (second combustion catalyst 205c) exceeded 500°C.

[0163] In another embodiment, in the nitrogen gas generator (system) 1' shown in Figure 2, the dehumidification unit 105 and the oxygen filtering unit 106 can be omitted, and instead, the oxygen-limiting catalytic combustion unit 205 and the subsequent dehumidification unit 206 described above can be installed in their place. Even with such a device (system), it is possible to continuously and stably generate and provide high-purity nitrogen gas.

[0164] Furthermore, in embodiments where the oxygen output limiting means does not include an oxygen filtering unit, as shown in Figure 6, no air or exhaust gas is generated that is not recovered in the gas filter and is ultimately discarded without becoming high-purity nitrogen gas. This makes it possible to generate high-purity nitrogen gas more efficiently from air.

[0165] [Further Other Embodiments of Nitrogen Gas Generators and Systems] Figure 7 is a schematic diagram showing yet another embodiment of the nitrogen gas generating apparatus and system according to the present invention.

[0166] The nitrogen gas generator (system) 3 shown in Figure 7, like the nitrogen gas generator (system) 1 shown in Figure 1, is a device (system) that takes in air and hydrogen gas to produce nitrogen-enhanced gas, in this embodiment high-purity nitrogen gas, and can provide it to the outside. In this embodiment, the nitrogen gas generator (system) 3 has a configuration that eliminates the use of the fuel cell unit 103, dehumidifier 104, dehumidification unit 105, and hydrogen recovery unit 108 compared to the nitrogen gas generator (system) 1 shown in Figure 1.

[0167] In other words, the nitrogen gas generator (system) 3 shown in Figure 7 does not have a fuel cell unit as an oxygen output limiting means (302, 306, 307) according to the present invention, but it does have an oxygen filtering unit 306. Incidentally, in this embodiment, the pressure boosting unit 301, flow controller 302, oxygen filtering unit 306 including gas filter 306f, flow controller 307, catalytic combustion unit 309 including combustion catalyst unit 309c, dehumidification unit 310 including dry filter 310d, hydrogen filtering unit 311 including gas filter 311f, pressure controller 312, nitrogen gas tank 313, and overall control unit 321 have the same configuration as the units or devices of the same name in Figure 1 (1**(#), * is a number, # is an English letter), and perform the same functions. Furthermore, 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), which will be described later.

[0168] In this embodiment, the oxygen filtering unit 306 takes in compressed air from the pressure boosting unit 301, limits the amount of oxygen released from this compressed air, and sends the filtered air toward the catalytic combustion unit 309. Specifically, in this embodiment, the oxygen filtering unit 306 independently controls the oxygen concentration of the intake air without the assistance of a fuel cell. (a) The combustion catalyst 309c in the catalytic combustion unit 309 or the set or desired upper limit temperature in the catalytic combustion reaction, and / or (in this embodiment and) (b) The set or desired upper limit oxygen concentration in the final output high-purity nitrogen gas The maximum oxygen concentration determined based on (e.g., 3 vol%) should be less than or equal to 0.1 to 3 vol%, for example.

[0169] As a result, the catalytic combustion unit 309, which receives filtered air from the oxygen filtering unit 306, (a) The temperature of the combustion catalyst 309c or the catalytic combustion reaction can be kept below a set or desired upper limit temperature, and / or (in this embodiment, and) (b) The oxygen concentration in the high-purity nitrogen gas finally delivered can be set to or below the set or desired upper limit oxygen concentration.

[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 ultimately delivered can be kept below a set or desired upper limit oxygen concentration, the combustion catalyst 309c can also be a solid catalyst supported by ceramics with 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 below a set upper limit temperature. As a result, it is also possible to continuously and stably induce the 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.

[0172] Incidentally, in another embodiment, in the nitrogen gas generator (system) 3 shown in Figure 7, it is possible to omit the use of the oxygen filtering unit 306 and the flow rate controller 307, and to use only the flow rate controller 302 as the oxygen output limiting means according to the present invention.

[0173] However, in this case, the flow controller 302 controls the flow rate of compressed air received from the pressure boosting unit 301. (a) The combustion catalyst 309c in the catalytic combustion unit 309 or the set or desired upper limit temperature in the catalytic combustion reaction, and / or (in this embodiment, and) (b) The set or desired upper limit oxygen concentration in the final output high-purity nitrogen gas It must be possible to keep the flow rate below the "maximum flow rate" determined based on the above. Furthermore, it is necessary to employ a catalytic combustion unit 309 such that such a "maximum flow rate" is determined to be a practical value.

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

[0175] [Further Other Embodiments of Nitrogen Gas Generators and Systems] Figure 8 is a schematic diagram showing yet another embodiment of the nitrogen gas generating apparatus and system according to the present invention.

[0176] The nitrogen gas generator (system) 4 shown in Figure 8, like the nitrogen gas generator (system) 1 shown in Figure 1, is a device (system) that takes in air and hydrogen gas to produce nitrogen-enhanced gas, and in this embodiment, high-purity nitrogen gas, which can be supplied to the outside. 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 are omitted from the nitrogen gas generator (system) 2 shown in Figure 6.

[0177] In other words, the nitrogen gas generator (system) 4 shown in Figure 8 does not have a fuel cell unit as an oxygen content limiting means (402, 405, 407) according to the present invention, but does have an oxygen content limiting catalytic combustion unit 405. Incidentally, in this embodiment, the pressure boosting unit 401, the flow controller 402, the oxygen content limiting catalytic combustion unit 405 including the combustion catalyst 405c, the dehumidification unit 406 including the dry filter 406d, the flow controller 407, the catalytic combustion unit 409 including the combustion catalyst unit 409c, the dehumidification unit 410 including the dry filter 410d, the hydrogen filtering unit 411 including the gas filter 411f, the pressure controller 412, the nitrogen gas tank 413, and the overall control unit 421 have the same configuration as the units or devices of the same name (2**(#), * is a number, # is an English letter) in Figure 6, and perform the same functions. Incidentally, the oxygen-limiting catalytic combustion unit 405 and the catalytic combustion unit 409, as you might expect, do not receive high-pressure hydrogen gas from the hydrogen recovery unit, but rather from an external source such as a hydrogen station, or from the high-pressure water electrolysis unit 502 (Figure 10), which will be described later.

[0178] In this embodiment, the oxygen-limiting catalytic combustion unit 405 takes in compressed air from the pressure boosting unit 401, limits the amount of oxygen supplied from this compressed air, and sends the post-catalytic combustion air toward the catalytic combustion unit 409. Specifically, in this embodiment, the oxygen-limiting catalytic combustion unit 405 independently controls the oxygen concentration of the intake air without the assistance of a fuel cell. (a) The combustion catalyst 409c in the catalytic combustion unit 409 or the set or desired upper temperature in the catalytic combustion reaction, and / or (in this embodiment and) (b) The set or desired upper limit oxygen concentration in the final output high-purity nitrogen gas The oxygen concentration should be less than or equal to the maximum oxygen concentration determined based on (e.g., 3 vol%), for example, between 0.01 and 3 vol%.

[0179] As a result, the catalytic combustion unit 409, which receives post-catalytic combustion air from the oxygen-limiting catalytic combustion unit 405, (a) The temperature of the combustion catalyst 409c or the catalytic combustion reaction can be kept below a set or desired upper limit temperature, and / or (in this embodiment, and) (b) The oxygen concentration in the high-purity nitrogen gas finally delivered can be set to or below the set or desired upper limit oxygen concentration.

[0180] Furthermore, in this embodiment, the combustion catalyst 405c of the oxygen-limiting catalytic combustion unit 405 and the combustion catalyst 409c of the catalytic combustion unit 409 can be solid catalysts supported by ceramics and solid catalysts supported by metals such as stainless steel, respectively, similar to the combustion catalyst 205c of the oxygen-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-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, making it possible to keep the temperature of the combustion catalyst 405c or the catalytic combustion reaction below this second upper limit temperature. As a result, the oxygen-limiting catalytic combustion unit 405 can continuously and stably induce a catalytic combustion reaction using more oxygen and hydrogen, and can continuously and stably supply post-catalytic combustion air with a lower oxygen concentration to the catalytic combustion unit 409.

[0182] Furthermore, this makes it possible to keep the temperature of the combustion catalyst 409c or the catalytic combustion reaction in the catalytic combustion unit 409 below a set first upper limit temperature (e.g., 300°C). As a result, the catalytic combustion unit 409 can continuously and stably induce the catalytic combustion reaction and continuously and stably produce and provide high-purity nitrogen gas, for example, nitrogen gas with a purity of 5N or higher, having an oxygen concentration below a set or desired upper limit oxygen concentration.

[0183] Furthermore, it is preferable to set the oxygen concentration of the post-catalytic combustion air received by the catalytic combustion unit 409 to be above a set minimum oxygen concentration (e.g., 0.5 vol%), for example, 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 above a set lower limit temperature (e.g., 100°C).

[0184] Furthermore, the amount of hydrogen gas introduced into the oxygen-limiting catalytic combustion unit 405 does not need to be enough to consume all the oxygen in the introduced air; on the other hand, it may be an amount that leaves a certain amount of residual hydrogen in the air after catalytic combustion.

[0185] Furthermore, in embodiments where the oxygen output limiting means does not include an oxygen filtering unit, as shown in Figure 8, no air or exhaust gas is generated that is not recovered in the gas filter and is ultimately discarded without becoming high-purity nitrogen gas. This makes it possible to generate high-purity nitrogen gas more efficiently from air.

[0186] [Further Other Embodiments of Nitrogen Gas Generators and Systems] Figure 9 is a schematic diagram showing yet another embodiment of the 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 to produce nitrogen-enhanced gas, in this embodiment high-purity nitrogen gas, and can provide it to the outside. In this embodiment, the nitrogen gas generator (system) 4' has a configuration in which an oxygen filtering unit 403', including a gas filter 403f', is provided between the flow controller 402 and the oxygen-limiting catalytic combustion unit 405, as in the nitrogen gas generator (system) 4 shown in Figure 8. Here, the oxygen filtering unit 403' has the same configuration as the oxygen filtering unit 306 shown in Figure 7 and the oxygen filtering unit 106 shown in Figure 1, and performs the same function.

[0188] In other words, the nitrogen gas generator (system) 4 shown in Figure 9 includes an oxygen content limiting catalytic combustion unit 405 and an oxygen filtering unit 403' upstream of it, as the oxygen content limiting means (402, 403', 405, 407) according to the present invention. In this embodiment, the oxygen content limiting catalytic combustion unit 405 takes in filtered air with reduced oxygen concentration from the oxygen filtering unit 403', and sends the post-catalytic combustion air toward the catalytic combustion unit 409 while limiting the amount of oxygen delivered in this filtered air.

[0189] Specifically, in this embodiment, the oxygen-limiting catalytic combustion unit 405 adjusts the oxygen concentration of the received filtered air, (a) The combustion catalyst 409c in the catalytic combustion unit 409 or the set or desired upper temperature in the catalytic combustion reaction, and / or (in this embodiment and) (b) The set or desired upper limit oxygen concentration in the final output high-purity nitrogen gas The oxygen concentration is set to be less than or equal to the maximum oxygen concentration (e.g., 3 vol%) determined based on the above, for example, 0.01 to 3 vol%. In this case, since the oxygen-limiting catalytic combustion unit 405 receives filtered air with reduced oxygen concentration, it becomes easier to set the oxygen concentration of this filtered air to be less than or equal to the maximum oxygen concentration (e.g., 3 vol%), for example, 0.01 to 3 vol%, compared to the embodiment in Figure 8 where the air itself is received.

[0190] In this embodiment as well, the catalytic combustion unit 409, which receives post-catalytic combustion air from the oxygen-limiting catalytic combustion unit 405, (a) The temperature of the combustion catalyst 409c or the catalytic combustion reaction can be kept below a set or desired upper limit temperature, and / or (in this embodiment, and) (b) The oxygen concentration in the high-purity nitrogen gas finally delivered can be set to or below a set or desired upper limit oxygen concentration.

[0191] In this embodiment as well, the combustion catalyst 405c of the oxygen-limiting catalytic combustion unit 405 and the combustion catalyst 409c of the catalytic combustion unit 409 can be solid catalysts supported by ceramics and solid catalysts supported by metals such as stainless steel, respectively. In this case, as described above, the oxygen-limiting catalytic combustion unit 405 can keep the temperature of the combustion catalyst 405c or the catalytic combustion reaction 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 below the first upper limit temperature (e.g., 300°C).

[0192] As a result, the catalytic combustion unit 409 can continuously and stably induce a catalytic combustion reaction, and can also 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 preferable to set the oxygen concentration of the post-catalytic combustion air received by the catalytic combustion unit 409 to be above a set minimum oxygen concentration (e.g., 0.5 vol%), for example, 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 above a set lower limit temperature (e.g., 100°C).

[0194] [Embodiment including high-pressure water electrolysis means] Figure 10 is a schematic diagram showing yet another embodiment of the nitrogen gas generating apparatus and system according to the present invention.

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

[0196] Here, the high-pressure water electrolysis unit 502 electrolyzes supplied water or steam, or an electrolytic target containing water or steam, in a limited space (electrolytic cell) to generate high-pressure hydrogen gas having a pressure above a set pressure threshold. Specifically, the high-pressure water electrolysis unit 502 of this embodiment includes a high-pressure water electrolyzer 502E having a structure in which multiple electrolytic cells are stacked (laminated), each having 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 course, various other configurations and methods can be used as the high-pressure water electrolyzer 502E as long as they can generate high-pressure hydrogen gas. For example, as the water electrolysis method, a water electrolysis method using AEM (Anion Exchange Membrane) or a water electrolysis method using PEM (Proton Exchange Membrane) may be used.

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

[0198] Furthermore, the high-pressure water electrolysis unit 502 may generate high-temperature water or steam and electrolyze it to produce high-pressure hydrogen gas in order to improve the electrolysis efficiency (hydrogen generation efficiency). In this case, it is preferable that the high-pressure water electrolysis unit 502 receives thermal energy transferred from the fuel cell units (103, 203), oxygen-limiting catalytic combustion units (205, 405), and catalytic combustion units (109, 209, 309, 409) by heat transfer means such as heat exchangers and heat conduction systems, and use at least this thermal energy to generate high-temperature water or steam, or to raise the temperature inside the electrolytic cell to increase the pressure of the hydrogen gas.

[0199] Furthermore, it is preferable that the high-pressure water electrolysis unit 502 receives electricity generated by the fuel cell units (103, 203) and performs water electrolysis using this electricity, or using this electricity in combination with commercial electricity drawn from an external source. It is also preferable to perform electric heating using such electricity to generate high-temperature water or steam. In addition, it is preferable to receive water (pure water) extracted from the drains of the fuel cells (103f, 203f) or from the dry filters (105d, 110d, 206d, 210d, 310d, 406d, 410d) and use this water as a target for electrolysis.

[0200] In this way, the high-pressure water electrolysis unit 502 receives and utilizes thermal energy, electricity, and water from the components of the nitrogen gas generation device / system (1,1',2,3,4,4'), making it possible to significantly reduce, or even reduce to almost zero, the amount of thermal energy, electricity, and water that needs to be supplied from outside the device / system for the electrolysis process.

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

[0202] For example, it is preferable to integrate, in terms of pressure and thermal energy, a high-pressure water electrolysis unit 502 in which the high-pressure water electrolysis unit 502E is an SOEC (Solid Oxide Electrolytic 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 solid catalyst on a ceramic support (having a high upper temperature limit). Such integration makes it possible to produce high-purity nitrogen gas with higher efficiency and more simply.

[0203] As also shown in Figure 10, the high-pressure water electrolysis unit 502 of this embodiment is supplied with power from the natural energy power generation unit 501. The natural energy power generation unit 501 may be a solar cell power generation unit equipped with solar cells that convert sunlight into electricity, a wind power generation unit that generates electricity by rotating a rotor with blades using wind power to drive a generator, or a micro-hydroelectric power generation unit that generates electricity by rotating a turbine using water power to drive a generator. Furthermore, any other type of power generation unit that ultimately converts the light energy of sunlight or the kinetic energy of wind and water flow into electrical energy can be used as the natural energy power generation unit 501. Moreover, the natural energy power generation unit 501 may be a combination of two or more of the power generation units described above.

[0204] Furthermore, 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) battery, and stores the power it generates in the storage battery 501b (after converting AC power to DC power using a converter).

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

[0206] In any case, the combination of the renewable energy power generation unit 501 described above, the high-pressure water electrolysis unit 502, the fuel cell units (103, 203), the oxygen-restricting catalytic combustion units (205, 405), and the catalytic combustion units (109, 209, 309, 409) generates and burns hydrogen gas, which is necessary for producing high-purity nitrogen gas, while minimizing the emission of greenhouse gases 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] [Other embodiments of fuel cell units] Figure 11 is a schematic diagram illustrating 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 comprises a fuel cell 103f and control units 103Ca, 103Cb, and 103Cc. The fuel cell 103f comprises multiple cells, which are constituent units including a hydrogen electrode and an air electrode with an electrolyte membrane in between. These cells are stacked, and are designed so that hydrogen gas and air pass through the hydrogen electrode and air electrode within each cell sequentially, from the cell on the upper side to the cell on the lower side, respectively, for fuel supply.

[0209] Furthermore, the entirety of these multiple cells is divided into multiple functional cell sections, in Figure 11, the power generation priority cell section 103fa, the intermediate cell section 103fb, and the oxygen removal cell section 103fc. Each of these functional cell sections (103fa, 103fb, 103fc) contains one or a series of cells (two or three in Figure 11, but actually several to a dozen or so), and is not electrically connected in series with the other functional cell sections, but is electrically connected to a power generation control unit (103Ca, 103Cb, 103Cc) that is provided individually for each.

[0210] As shown in Figure 11, the control units 103Ca, 103Cb, and 103Cc each receive the electromotive force generated between the hydrogen electrode and air electrode in the power generation priority cell section 103fa, the intermediate cell section 103fb, and the oxygen removal cell section 103fc, respectively, and output power (current) corresponding to the functional cell section they are responsible for. It is also preferable to measure the complex impedance of the functional cell section they are responsible for and perform control and management according to that functional cell section.

[0211] In contrast to the fuel cell 103f of this embodiment, conventional fuel cells, especially PEFC type fuel cells, typically have an electromotive force of less than 1 volt (V) in a single cell. Therefore, in order to secure the power required as an actual power source, for example, tens to hundreds of cells are electrically connected in series. In this configuration, the amount of power that can be generated is naturally smaller in the lower-level cells with less oxygen supply. However, the power generation efficiency (relative to the amount of hydrogen supplied) of the entire series of cells, including these lower-level cells, is considerably impaired because the power generation of each cell needs to be somewhat equalized.

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

[0213] In contrast, in the fuel cell 103f of this embodiment, (a) A power generation priority cell section 103fa with a large oxygen supply (where the oxygen in the supplied air has not yet been consumed much), (b) With respect to the oxygen supply, the intermediate cell section 103fb is an intermediate cell section, (c) The oxygen removal cell section 103fc has a low oxygen supply (a considerable amount of oxygen in the supplied air is consumed) However, it can receive individual control over the amount of power generated (current) to match the oxygen supply.

[0214] Furthermore, by implementing this power generation (current) control, it becomes possible to maximize or improve both the oxygen reduction efficiency and the power generation efficiency (relative to the hydrogen supply) in the fuel cell 103f. In addition, by coordinating the power generation (including current) control in each control unit (103Ca, 103Cb, 103Cc), it becomes possible to adjust the oxygen concentration (outlet oxygen concentration) of the exhaust gas (low-oxygen air after exhaust) to a desired value. Thus, the fuel cell unit 103 of this embodiment is a fuel cell system that is very suitable for generating high-purity nitrogen gas.

[0215] Incidentally, the number of functional cell sections in the fuel cell 103f of this embodiment is not limited to three, but can be two or four or more. For example, out of several hundred cell stages, the lower 150 cell stage group and the upper remaining cell stage group can be designated as the second functional cell section and the first functional cell section, respectively.

[0216] Furthermore, as a simpler modification, it is also possible to electrically connect multiple functional cell units (103fa, 103fb, and 103fc in Figure 1) in parallel to a single power generation control unit (e.g., 103Ca). In this case as well, the power generation efficiency relative to the hydrogen supply can be improved 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 sections (103fa, 103fb, and 103fc in Figure 1) may be a multiple fuel cell. In this case, these fuel cells are physically connected in series. Specifically, the exhaust gas from the air electrode side of one fuel cell is introduced into the air electrode side inlet of a subsequent fuel cell. The entire series-connected cells in each fuel cell may be electrically connected to a power generation control unit provided individually for each fuel cell, or they may be electrically connected in parallel to a single power generation control unit provided for common use. Here, it is also preferable that each fuel cell is not a fuel cell with dozens of cells and an output of 5kW or more as described above, but rather a fuel cell with a dozen or so cells and an output of less than 5kW, for example, a fuel cell with 15 cells and an output of 2.5kW. This ensures the stability of the 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 units and controllers described above. In particular, it is preferable that the oxygen output limiting means controls the oxygen concentration of the air being supplied so that it is less than or equal to the "maximum oxygen concentration" determined based on the "upper temperature limit" and / or the "upper oxygen concentration limit". It is also preferable that the flow rate of the air being supplied is less than or equal to the "maximum flow rate" determined based on the "upper temperature limit" and / or the "upper oxygen concentration limit".

[0219] Specifically, the overall control unit (121, 221, 321, 421) monitors the oxygen concentration and flow rate of the reduced-oxygen-concentration air delivered from the oxygen supply limiting means using an oxygen concentration meter and flow meter installed immediately after the oxygen supply limiting means, and further, based on these monitored values, (a) If the oxygen supply limiting means includes a fuel cell unit, 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. are adjusted. (b) If the oxygen supply limiting means includes an oxygen limiting catalytic combustion unit, the pressure and flow rate of the air introduced into the reaction tube housing the combustion catalyst, the low-oxygen air after exhaust, or the filtered air, and the temperature of the combustion catalyst or the catalytic combustion reaction are adjusted. (c) If the oxygen supply limiting means includes an oxygen filtering unit, adjust the pressure and flow rate of the air introduced into the gas filter or the low-oxygen air after exhaust. It is preferable that this be possible.

[0220] Furthermore, the overall control unit (121, 221, 321, 421) may be equipped with a processor and memory, and this processor may perform the control and adjustment described above by executing a control program stored in this memory.

[0221] As described in detail above, the nitrogen gas generation apparatus, system, and method of the present invention can stably, continuously, and reliably generate high-purity nitrogen gas using a combustion catalyst. Furthermore, although this invention is only one embodiment, it is possible to efficiently and simply generate and provide high-purity nitrogen gas using hydrogen gas, which will be readily and inexpensively available in the coming hydrogen gas society, and at the same time, it is also possible to provide thermal energy, pure water, and, depending on the embodiment, electricity.

[0222] In other words, this invention is expected to make a significant contribution to building a locally produced and consumed, carbon-free energy and product supply and demand system, which is considered an ideal model for the future. Furthermore, it is expected to be of great help in achieving carbon neutrality, which is an urgent issue.

[0223] Furthermore, all embodiments described above are illustrative and not limiting of the present invention, and the present invention can be implemented in various other variations and modifications. Accordingly, the scope of the present invention is defined solely by the claims and their equivalents. [Explanation of symbols]

[0224] 1, 1', 2, 3, 4, 4' Nitrogen gas generator (system) 101, 101'201, 301, 401 Pressure Boosting Unit (U) 101p, 101p', 201p, 301p, 401p gas compressors 102, 107, 107', 202, 207, 302, 307, 402, 407 Flow controllers 103, 203 Fuel Cell Units 103f, 203f fuel cell 103fa Power Generation Priority Cell Section 103fb Intermediate cell section 103fc Oxygen Removal Cell Section 103Ca, 103Cb, 103Cc control unit 104, 204 Dehumidifier 105, 110, 206, 210, 310, 406, 410 Dehumidification Unit 105d, 110d, 206d, 210d, 310d, 406d, 410d dry filters 106, 306, 403' Oxygen Filtering Unit 106f, 106f1, 106f2, 106f3, 306f, 403f' gas filters 106fa Hollow fiber section 106fb filter inlet 106fc filter outlet 106fd Filter Purge Unit 108, 208 Hydrogen Recovery Units 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 filters 112, 212, 312, 412 pressure controllers 113, 213, 313, 413 Nitrogen gas tanks 121, 221, 321, 421 Overall control unit 205, 405 Oxygen-restricted catalytic combustion unit 205c, 405c Combustion catalyst 501 Renewable 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. An oxygen content output limiting means that takes in air or a gas containing nitrogen and oxygen, and outputs the air or gas while limiting the amount of oxygen output from the air or gas, A catalytic combustion means that reacts the supplied air or gas with the intake hydrogen-containing fuel gas on a combustion catalyst to convert the air or gas into a nitrogen-enhanced gas with a higher nitrogen concentration. It has, The oxygen supply limiting means limits the oxygen concentration of the air or gas to a maximum oxygen concentration determined based on the set or desired upper temperature limit in the combustion catalyst or reaction, and / or limits the flow rate of the air or gas to a maximum flow rate determined based on the set or desired upper temperature limit in the combustion catalyst or reaction. A nitrogen gas generating apparatus characterized by the following features.

2. The catalytic combustion means converts the air or gas into a nitrogen-enhanced gas having an oxygen concentration below a set or desired upper limit oxygen concentration. The oxygen supply limiting means sets the oxygen concentration of the air or gas to be less than or equal to the maximum oxygen concentration determined based on the set or desired upper limit temperature in the combustion catalyst or reaction, and / or the flow rate of the air or gas to be less than or equal to the maximum flow rate determined based on the set or desired upper limit temperature in the combustion catalyst or reaction, and the set or desired upper limit oxygen concentration. The nitrogen gas generating apparatus according to feature 1.

3. The nitrogen gas generating apparatus according to claim 1 or 2, characterized in that the oxygen output limiting means includes a fuel cell that takes in the air or gas and sends out the air or gas with reduced oxygen concentration as exhaust gas.

4. The nitrogen gas generating device according to claim 3, characterized in that the fuel cell takes in a hydrogen-containing fuel gas at a flow rate greater than or equal to the flow rate that would be sufficient to convert all the oxygen contained in the intake air or gas into water, and allows an amount of current that would flow when all the oxygen is converted into water to flow between the electrodes, thereby discharging the air or gas with reduced oxygen concentration as exhaust gas.

5. The nitrogen gas generator according to claim 1 or 2, characterized in that the oxygen output limiting means includes filters with different degrees of permeability for nitrogen and oxygen, and includes an oxygen filtering means that causes the intake air or gas to act on the filters to deliver air or gas with reduced oxygen concentration.

6. The oxygen supply amount limiting means is A fuel cell that takes in the air or gas and discharges the air or gas with reduced oxygen concentration as exhaust gas, The system includes filters with different degrees of permeability for nitrogen and oxygen, and an oxygen filtering means that applies the intake exhaust gas (air or gas) to the filters to deliver air or gas with a reduced oxygen concentration. A nitrogen gas generating apparatus according to claim 1 or 2, characterized by including the following:

7. The oxygen supply limiting means includes a second catalytic combustion means that reacts the intake air or gas with the intake hydrogen-containing fuel gas on a second combustion catalyst to supply the air or gas with a reduced oxygen concentration. The second catalytic combustion means has a second upper limit temperature that is greater than the set or desired second upper limit temperature in the second combustion catalyst or the reaction. A nitrogen gas generating apparatus according to claim 1 or 2.

8. The oxygen supply amount limiting means is A fuel cell that takes in the air or gas and discharges the air or gas with reduced oxygen concentration as exhaust gas, A second catalytic combustion means that reacts the air or gas taken in as exhaust gas with the fuel gas containing hydrogen taken in on a second combustion catalyst, and delivers the air or gas with a reduced oxygen concentration. Includes, The second catalytic combustion means has a second upper limit temperature that is greater than the set or desired second upper limit temperature in the second combustion catalyst or the reaction. A nitrogen gas generating apparatus according to claim 1 or 2.

9. The oxygen supply amount limiting means is An oxygen filtering means is provided which filters have different degrees of permeability for nitrogen and oxygen, and which applies the intake air or gas to the filters to deliver the air or gas with reduced oxygen concentration. The oxygen supply limiting means includes a second catalytic combustion means that reacts the air or gas with reduced oxygen concentration with the intake hydrogen-containing fuel gas on a second combustion catalyst to supply the air or gas with an even lower oxygen concentration. Includes, The second catalytic combustion means has a second upper limit temperature that is greater than the set or desired second upper limit temperature in the second combustion catalyst or the reaction. A nitrogen gas generating apparatus according to claim 1 or 2.

10. The nitrogen gas generator according to claim 1, further comprising a gas filtering means that includes filters with different degrees of permeability to nitrogen and hydrogen and to nitrogen and oxygen, and which causes the introduced nitrogen-enhanced gas to act on the filters to deliver a nitrogen-enhanced gas with a higher nitrogen concentration, and in the case that the introduced nitrogen-enhanced gas contains hydrogen, a nitrogen-enhanced gas from which hydrogen has been removed or a nitrogen-enhanced gas with a lower hydrogen concentration.

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

12. A pressure boosting means is provided prior to the oxygen supply limiting means or prior to the catalytic combustion means, which increases the pressure of the intake or discharged air or gas, and discharges the increased-pressure air or gas toward the oxygen supply limiting means or toward the catalytic combustion means, A pressure control means is provided downstream of the catalytic combustion means and controls the increased pressure of the air or gas in the section from the pressure boosting means to its own installation position. A nitrogen gas generating apparatus according to claim 1, 2, 10, or 11, further comprising the above.

13. An oxygen content output limiting means that takes in air or a gas containing nitrogen and oxygen, and outputs the air or gas while limiting the amount of oxygen output from the air or gas, A catalytic combustion means that reacts the supplied air or gas with the intake hydrogen-containing fuel gas on a combustion catalyst to convert the air or gas into a nitrogen-enhanced gas having an oxygen concentration below a set or desired upper limit oxygen concentration. It has, The oxygen output limiting means controls the oxygen concentration of the air or gas to be less than or equal to the maximum oxygen concentration determined based on the set or desired upper limit oxygen concentration, and / or controls the flow rate of the air or gas to be less than or equal to the maximum flow rate determined based on the set or desired upper limit oxygen concentration. A nitrogen gas generating apparatus characterized by the following features.

14. An oxygen content output limiting means that takes in air or a gas containing nitrogen and oxygen, and outputs the air or gas while limiting the amount of oxygen output from the air or gas, A catalytic combustion means that reacts the supplied air or gas with the intake hydrogen-containing fuel gas on a combustion catalyst to convert the air or gas into a nitrogen-enhanced gas with a higher nitrogen concentration. It has, The oxygen supply limiting means limits the oxygen concentration of the air or gas to a maximum oxygen concentration determined based on the set or desired upper temperature limit in the combustion catalyst or reaction, and / or limits the flow rate of the air or gas to a maximum flow rate determined based on the set or desired upper temperature limit in the combustion catalyst or reaction. A nitrogen gas generation system characterized by the following features.

15. A first step involves taking in air or a gas containing nitrogen and oxygen, and discharging the air or gas while limiting the amount of oxygen discharged from the air or gas. A second step involves reacting the supplied air or gas with the intake hydrogen-containing fuel gas on a combustion catalyst to convert the air or gas into a nitrogen-enhanced gas with a higher nitrogen concentration. It has, In the first step, the oxygen concentration of the air or gas is set to be less than or equal to the maximum oxygen concentration determined based on the set or desired upper temperature limit in the combustion catalyst or the reaction, and / or the flow rate of the air or gas is set to be less than or equal to the maximum flow rate determined based on the set or desired upper temperature limit in the combustion catalyst or the reaction. A method for producing nitrogen gas characterized by the features described above.

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