Nitrogen gas generation apparatus and system using fuel cell

Abstract

Provided is a nitrogen gas generation apparatus capable of generating and supplying high-purity nitrogen gas using a fuel cell, with higher efficiency or simplicity. This nitrogen gas generation apparatus comprises: a fuel cell that operates by taking in air or a gas containing nitrogen and oxygen, and a fuel gas; and a catalytic combustion means for reacting nitrogen-enriched gas, which is taken out from the fuel cell as exhaust gas and has an increased nitrogen concentration, on a combustion catalyst by using a residual fuel gas component and / or the fuel gas, the residual fuel gas component being a fuel gas component remaining in the nitrogen-enriched gas, to turn the nitrogen-enriched gas into a high-concentration nitrogen-enriched gas having a higher nitrogen concentration. The fuel cell is a solid oxide fuel cell (SOFC). Preferably, the exhaust gas from the air electrode side is sent to a subsequent stage without being subjected to dehumidification treatment. Also preferably, the fuel cell operates by taking in an amount of the fuel gas such that the fuel gas still remains in the nitrogen-enriched gas introduced into the catalytic combustion means.

Description

Nitrogen gas generating device and system using fuel cells

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

[0002] In recent years, hydrogen energy has been attracting attention as a way to achieve carbon neutrality and ultimately carbon zero. Fuel cells that utilize this hydrogen energy enable highly efficient power generation without emitting carbon dioxide, and are a key technology in the coming hydrogen society.

[0003] The inventors of the present application have focused on the potential of fuel cells and have developed a variety of devices and systems that utilize fuel cells, as described in Patent Documents 1 to 10. For example, as disclosed in Patent Documents 6 to 10, they have developed a nitrogen gas generator that applies exhaust gas extracted from a fuel cell to a nitrogen filter and extracts gas with an increased nitrogen concentration from the filter. Furthermore, as disclosed in Patent Documents 8 to 10, they have invented a configuration in which a water ring pump and a water exchanger are used to perform the dehumidification process of exhaust gas, which is important in generating nitrogen gas.

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

[0005] High-purity nitrogen gas is a very useful inert gas that does not have any combustion-supporting or combustion-assisting properties, and there is a great demand for it in various fields. However, currently, high-purity nitrogen gas is produced using air as a raw material by pressure swing adsorption (PSA), cryogenic air separation, membrane separation, etc.

[0006] In contrast, if exhaust gas from a fuel cell is used instead of air as the raw material, high-purity nitrogen gas can be produced more efficiently. Furthermore, high-purity nitrogen gas produced using a fuel cell can be supplied to various production and service sites at lower cost.

[0007] One issue that needs to be addressed is how to efficiently reduce the oxygen concentration in the exhaust gas from a fuel cell. The nitrogen gas generators and systems disclosed in, for example, Patent Documents 6 to 10, are of course important solutions to this issue. However, the inventors of the present application have been searching for a more suitable configuration for generating nitrogen gas using a fuel cell, specifically, a configuration that is more efficient or simple.

[0008] Therefore, an object of the present invention is to provide a nitrogen gas generating device and system that can generate and supply high-purity nitrogen gas with greater efficiency or ease using a fuel cell.

[0009] According to the present invention, there is provided a nitrogen gas generator comprising: a fuel cell that operates by taking in air or a gas containing nitrogen and oxygen, and a fuel gas; and catalytic combustion means that reacts a nitrogen-enriched gas, which has an increased nitrogen concentration compared to the air or gas extracted as exhaust gas from the fuel cell, on a combustion catalyst with a residual fuel gas portion and / or the fuel gas that remains in the nitrogen-enriched gas, to produce a high-concentration nitrogen-enriched gas with an even higher nitrogen concentration.

[0010] It is also preferable that the fuel cell according to the present invention is a solid oxide fuel cell (SOFC), and that the exhaust gas from the air electrode side is sent to a subsequent stage without being subjected to a dehumidification treatment.

[0011] In one embodiment of the nitrogen gas generator according to the present invention, the fuel cell is preferably operated by taking in an amount of fuel gas that will cause the fuel gas to remain in the nitrogen-enriched gas introduced into the catalytic combustion means.Furthermore, the fuel cell is preferably operated by taking in an amount of fuel gas that is equal to or greater than the amount that allows all of the oxygen contained in the taken-in air or gas to be converted into water.

[0012] It is also preferable that the nitrogen gas generator further comprises pressure boosting means for increasing the pressure of the nitrogen-enriching gas, and that the catalytic combustion means reacts the pressurized nitrogen-enriching gas on a combustion catalyst.

[0013] Furthermore, in another embodiment of the nitrogen gas generating device according to the present invention, the nitrogen gas generating device further comprises exhaust gas combustion means for combusting the nitrogen-enhancing gas extracted from the fuel cell and the residual fuel exhaust gas extracted from the fuel cell as exhaust gas, thereby reducing the oxygen concentration of the nitrogen-enhancing gas, and it is also preferable that the catalytic combustion means reacts the nitrogen-enhancing gas with the reduced oxygen concentration on a combustion catalyst.

[0014] Furthermore, as yet another embodiment of the nitrogen gas generator according to the present invention, it is also preferable that the nitrogen gas generator further comprises a reforming means for reforming the supplied hydrocarbon gas using the combustion heat received from the exhaust gas combustion means to generate the fuel gas.

[0015] Furthermore, as yet another embodiment of the nitrogen gas generator according to the present invention, the nitrogen gas generator is provided with filters having different permeabilities for nitrogen and oxygen, and it is also preferable that the nitrogen gas generator further has filtering means for converting the high-concentration nitrogen-enriched gas into a high-concentration nitrogen-enriched gas having a higher nitrogen concentration.

[0016] Here, in the above embodiment provided with a filtering means, it is also preferable that the catalytic combustion means reacts the nitrogen-enriched gas on the combustion catalyst with a sufficient amount of the residual fuel gas and / or the fuel gas until a fuel gas portion remains after the catalytic combustion reaction, the filter has different permeability for nitrogen and oxygen and for nitrogen and hydrogen, and the filtering means converts the high-concentration nitrogen-enriched gas into a high-concentration nitrogen-enriched gas having a higher nitrogen concentration and from which hydrogen has been removed or a high-concentration nitrogen-enriched gas having a lower hydrogen concentration.

[0017] It is also preferable that the nitrogen gas generator further comprises heat exchange means for exchanging heat between the nitrogen-enriching gas and the air or gas before it is introduced into the fuel cell, thereby reducing the temperature of the nitrogen-enriching gas and increasing the temperature of the air or gas.

[0018] Furthermore, it is also preferable that the nitrogen gas generator further comprises heat exchange means for exchanging heat between the finally produced high-concentration nitrogen-enriched gas and the high-concentration nitrogen-enriched gas extracted from the catalytic combustion means, thereby increasing the temperature of the finally produced high-concentration nitrogen-enriched gas.

[0019] In yet another embodiment of the nitrogen gas generator according to the present invention, the nitrogen gas generator preferably further comprises a water electrolysis means for electrolyzing supplied water vapor to generate the fuel gas, and the fuel cell preferably operates by taking in the generated fuel gas. It is also preferable that the water electrolysis means comprises a solid oxide electrolyzer (SOEC).

[0020] Here, in the above embodiment equipped with water electrolysis means, it is also preferable that the nitrogen gas generation device further comprises exhaust gas combustion means for combusting the nitrogen-enhancing gas extracted from the fuel cell and at least the residual fuel exhaust gas extracted from the fuel cell as exhaust gas, thereby reducing the oxygen concentration of the nitrogen-enhancing gas, and heating means for generating steam from supplied water or increasing the temperature of the supplied steam, using combustion heat received from the exhaust gas combustion means, wherein the water electrolysis means generates the fuel gas using the generated or heated steam, and the catalytic combustion means reacts the nitrogen-enhancing gas with reduced oxygen concentration on a combustion catalyst.

[0021] The present invention also provides a nitrogen gas generation system having: a fuel cell that operates by taking in air or a gas containing nitrogen and oxygen, and a fuel gas; and catalytic combustion means that reacts a nitrogen-enriched gas, which has an increased nitrogen concentration compared to the air or gas extracted as exhaust gas from the fuel cell, on a combustion catalyst with a residual fuel gas portion and / or the fuel gas that remains in the nitrogen-enriched gas, to produce a high-concentration nitrogen-enriched gas with an even higher nitrogen concentration.

[0022] According to the nitrogen gas generating device and system of the present invention, it is possible to generate and supply highly pure nitrogen gas more efficiently or simply by using a fuel cell.

[0023] FIG. 1 is a schematic diagram showing one embodiment of a nitrogen gas generator and a nitrogen gas generation system according to the present invention. FIG. 2 is a schematic diagram for explaining a combustion catalyst mechanism used in an example of catalytic combustion treatment by catalytic combustion means according to the present invention. FIG. 3 is a graph showing the processing results in one example of catalytic combustion treatment by catalytic combustion means according to the present invention. FIG. 4 is a graph showing the processing results in another example of catalytic combustion treatment by catalytic combustion means according to the present invention. FIG. 5 is a graph showing one example of gas filtering treatment by a gas filter according to the present invention. FIG. 6 is a schematic diagram for explaining one embodiment of the arrangement of a gas filter according to the present invention. FIG. 7 is a schematic diagram showing another embodiment of the installation position of a pressure boosting means according to the present invention. FIG. 8 is a schematic diagram showing another embodiment of a high-concentration nitrogen-enriched gas that is finally generated. FIG. 9 is a schematic diagram showing another embodiment of a nitrogen gas generator and a nitrogen gas generation system according to the present invention. FIG. 10 is a schematic diagram showing yet another embodiment of a nitrogen gas generator and a nitrogen gas generation system according to the present invention.

[0024] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[0025] [Nitrogen Gas Generating Apparatus and System] FIG. 1 is a schematic diagram showing one embodiment of a nitrogen gas generating apparatus and a nitrogen gas generating system according to the present invention.

[0026] The nitrogen gas generator 1 according to one embodiment of the present invention shown in Figure 1 includes: (A) a fuel cell 103a that operates by taking in "air or a gas containing nitrogen and oxygen" and "fuel gas" (hydrogen gas in this embodiment); (B) a catalytic combustion unit (U) 108 that converts a "nitrogen-enriched gas," which has an increased nitrogen concentration compared to the "air or a gas containing nitrogen and oxygen" and is extracted as exhaust gas from the fuel cell 103a, into a "high-concentration nitrogen-enriched gas" with an increased nitrogen concentration by reacting the "nitrogen-enriched gas" with a "residual fuel gas" and / or "fuel gas" remaining in the "nitrogen-enriched gas" on a combustion catalyst. Furthermore, in this embodiment, (C) the fuel cell 103a is a solid oxide fuel cell (SOFC), and exhaust gas from the air electrode side of the fuel cell 103a is sent to a subsequent stage without being subjected to dehumidification treatment.

[0027] In this embodiment, the "nitrogen-enhancing gas" includes both exhaust gas from the cathode side and exhaust gas from the anode side. However, in another embodiment, only exhaust gas from the cathode side can be introduced into the catalytic combustion unit U108 as the "nitrogen-enhancing gas."

[0028] In this embodiment, the catalytic combustion U108 of (B) brings the "nitrogen-enriched gas" into contact with the surface of a combustion catalyst (solid catalyst 108a in this embodiment) to cause a catalytic combustion reaction, thereby further reducing the oxygen concentration, i.e., further increasing the nitrogen concentration, in the "nitrogen-enriched gas" with reduced oxygen concentration (i.e., increased nitrogen concentration) extracted from the fuel cell 103a.

[0029] As will be explained in more detail later using the graph in Figure 4, the lower the oxygen concentration of the "nitrogen-enriched gas" extracted from the fuel cell 103a and introduced into the catalytic combustion U108, the lower the oxygen concentration of the "nitrogen-enriched gas" exhausted from the catalytic combustion U108. In this way, by combining the fuel cell 103a, which reduces the oxygen concentration, with the catalytic combustion U108, which further reduces the oxygen concentration, a "high-concentration nitrogen-enriched gas," such as high-purity nitrogen gas, can be generated and supplied with greater efficiency or with greater ease (e.g., because air is used as the raw material and no cryogenic means are required). Therefore, it can be understood that this combination is an excellent combination for generating a "high-concentration nitrogen-enriched gas," such as high-purity nitrogen gas.

[0030] Furthermore, as shown in (C) above, the fuel cell 103a of this embodiment is an SOFC, and the exhaust gas from the cathode side is dry. As a result, when this exhaust gas is transferred to the downstream stage as (part of) the nitrogen-enriching gas, there is no need to dehumidify this exhaust gas. Incidentally, a polymer electrolyte fuel cell (PEFC), for example, can also be used as the fuel cell 103a. However, in this case, the exhaust gas (nitrogen-enriching gas) from the cathode side has a relative humidity of approximately 100%. Therefore, in order to effectively and continuously perform the subsequent catalytic combustion process, it is important to dehumidify this exhaust gas (nitrogen-enriching gas) from the cathode side. This dehumidification can be performed using, for example, a dry filter or a water seal pump.

[0031] Furthermore, since the fuel cell 103a of this embodiment is an SOFC, its exhaust gas (nitrogen-enriched gas) is a high-temperature gas (several hundred degrees Celsius, for example, approximately 700 degrees Celsius). On the other hand, it is preferable that the temperature of the combustion catalyst and its surroundings in the catalytic combustion U108 is also high (for example, 100 degrees Celsius or higher), as will be described later. Thus, it can be seen that the fuel cell 103a and the catalytic combustion U108 are a very suitable combination, even from the viewpoint of gas temperature.

[0032] Furthermore, in this embodiment, the nitrogen gas generator 1 further includes (D) a filter having different permeability for nitrogen (N2) and oxygen (O2), which is a hydrogen / nitrogen gas filter 110a in this embodiment, and a hydrogen / nitrogen filtering unit U110 that converts the "high-concentration nitrogen-enriched gas" extracted from the catalytic combustion U108 into a "high-concentration nitrogen-enriched gas" having a higher nitrogen concentration. Also, in this embodiment, (D') the hydrogen / nitrogen gas filter 110a is a filter having different permeability for nitrogen (N2) and oxygen (O2) and for nitrogen (N2) and hydrogen (H2).

[0033] In the catalytic combustion U108 of this embodiment, as will be described in detail later, in order to consume as much oxygen (O) as possible in the "nitrogen-enhancing gas," the "nitrogen-enhancing gas" is reacted on the combustion catalyst using a sufficient amount of "residual fuel gas" (and / or fuel gas (hydrogen gas)) until a fuel gas (hydrogen (H)) portion remains after the catalytic combustion reaction. As a result, a portion of the fuel gas (hydrogen gas) remains in the "enriched nitrogen-enhancing gas" extracted from the catalytic combustion U108. For example, if the "nitrogen-enhancing gas" is reacted on the combustion catalyst in the catalytic combustion U108 using an amount of hydrogen (H) greater than or equal to the amount sufficient to convert all of the oxygen (O) contained in the nitrogen-enhancing gas to water (H2O), some hydrogen (H2) will remain in the exhausted "enriched nitrogen-enhancing gas," due in part to the fact that not all of the hydrogen (H2) actually contributes to the catalytic combustion reaction.

[0034] In contrast, the hydrogen / nitrogen gas filter 110a (D') described above, which will also be described in detail later, simultaneously reduces or removes the oxygen (O2) and hydrogen (H2) contents in the "high-concentration nitrogen-enriched gas" discharged from the catalytic combustion U108. This makes it possible to produce a "high-concentration nitrogen-enriched gas" from which hydrogen has been removed or which has a lower hydrogen concentration, i.e., high-purity nitrogen gas in this embodiment.

[0035] In this way, it can be seen that the catalytic combustion U108 in the nitrogen gas generator 1 and the subsequent hydrogen / nitrogen filtering U110 are an excellent combination that is highly efficient in generating high-purity nitrogen gas and is also highly convenient (in the sense that hydrogen and oxygen are reduced and removed simultaneously in one go).

[0036] In this embodiment, the fuel cell 103a, catalytic combustion U108, and hydrogen / nitrogen filtering U110 described above are all combined to form a single device (nitrogen gas generator 1). However, in other embodiments, at least one of the fuel cell 103a, catalytic combustion U108, and hydrogen / nitrogen filtering U110 may be included in a device separate from the other components. In this case, these devices as a whole constitute the nitrogen gas generation system 1 according to the present invention. For example, the nitrogen gas generation system 1 may be composed of a device including the fuel cell 103a and a device including the catalytic combustion U108 and hydrogen / nitrogen filtering U110.

[0037] Furthermore, the terms "high purity" and "high purity" used herein refer to a state in which the oxygen concentration and hydrogen concentration in the nitrogen-enhancing gas are sufficiently reduced. Specifically, the nitrogen concentration (amount of nitrogen (ml) per 100 ml of gas, expressed in vol%) in "high purity" nitrogen gas (nitrogen-enhancing gas) or "high purity" nitrogen gas (nitrogen-enhancing gas) may be, for example, 95 vol% or more, 99 vol% (2N) or more, or even 99.9 vol% (3N) or more, or 99.999 vol% (5N) or more, depending on the field and application of the nitrogen gas. The nitrogen concentration values ​​described herein are measured and calculated values ​​without taking into account inert gases such as argon (Ar), which are naturally present in air and therefore are contained in the nitrogen-enhancing gas.

[0038] Furthermore, the pressure values ​​(gas pressure values) of air, hydrogen gas, nitrogen-enhancing gas, etc. described in this specification are absolute pressure values ​​based on a vacuum, i.e., atmospheric pressure is 1 atmosphere (approximately 0.1 megapascals (MPa)). For example, the "0.5 MPa" shown below is the measurement value using a gas pressure gauge installed in the piping with atmospheric pressure as the reference (zero), i.e., the gauge pressure value is approximately 0.4 MPa (approximately 4 atmospheres).

[0039] [Device / System Configuration] As also shown in FIG. 1 , the nitrogen gas generating device (system) 1 of this embodiment has: (a) a heat exchanger 102; (b) a fuel cell U103 equipped with a fuel cell 103a; (c) a heat exchanger 104; (d) an exhaust gas combustion section 105 equipped with a gas burner 105a; (e) a heat exchanger 106; (f) a pressure booster U107 equipped with a compression pump 107a; (g) a catalytic combustion U108 equipped with a solid catalyst 108a; (h) a heat exchanger HT; (i) a gas-liquid separator U109; (j) a hydrogen / nitrogen filtering U110 equipped with a hydrogen / nitrogen gas filter 110a; and (k) an overall control U131. The nitrogen gas generating device (system) 1 of this embodiment takes in air or a gas containing nitrogen and oxygen, and a fuel gas, generates high-purity nitrogen gas, and can provide it to the outside.

[0040] In this embodiment, air is used as the gas containing nitrogen and oxygen, but other gases, such as a mixture of air or nitrogen gas with oxygen gas, can also be used. In this embodiment, hydrogen gas taken in from an external source, such as a hydrogen station or hydrogen storage facility, is used as the fuel gas. However, as will be described later with reference to FIG. 9 , it is also possible to generate hydrogen gas (hydrogen-containing gas) from taken-in hydrocarbon gas, such as city gas or LP (Liquefied Petroleum) gas, through a steam reforming reaction and use this hydrogen gas (hydrogen-containing gas) as the fuel gas.

[0041] Incidentally, the transfer of matter and energy shown by connecting the components with arrows in the configuration diagram of the device (or system) shown in Figure 1, and the flow of the processes carried out, can also be understood as one embodiment of the nitrogen gas generation method according to the present invention.

[0042] <Heat Exchanger 102> In this embodiment, the heat exchanger 102 exchanges heat between: (a) air supplied from outside, temporarily stored (buffered) in an air tank 101 equipped with a pump, and before being introduced into the fuel cell 103a, the air having a flow rate controlled by a flow controller FCa; and (b) a high-temperature (e.g., several hundred degrees Celsius) nitrogen-enriching gas discharged from the fuel cell 103a and subjected to exhaust gas combustion treatment in an exhaust gas combustion section 105. The heat exchanger 102 heats the air (a) to increase its temperature, while decreasing the temperature of the nitrogen-enriching gas (b). In this embodiment, the overall control U131 monitors and manages the temperature of the heated air using a thermometer Ta.

[0043] In this way, the heat exchanger 102 can supply the SOFC fuel cell 103a (described later) with suitable high-temperature air, i.e., air whose temperature approaches the SOFC reaction temperature (several hundred degrees Celsius, e.g., approximately 700 degrees Celsius), and also serves to reduce the temperature of the nitrogen enrichment gas to a temperature (e.g., several tens of degrees Celsius) acceptable for the downstream compressor pump 107a.

[0044] It is also preferable that the heat exchanger 102 converts the water vapor contained in the nitrogen-enriched gas (b) into water by reducing the temperature of the nitrogen-enriched gas to less than 100°C, and removes this water using a dehumidifying means, such as a drain, provided at the outlet.

[0045] The flow controllers (FCa, FCb, FCc, FCd) installed in the nitrogen gas generating apparatus (system) 1, including the flow controller FCa described above in (a), are equipped with, for example, a gas regulator and a mass flow controller (or a flow switch), and are devices that control the flow rate and pressure of the nitrogen-enriched gas at the installation location.

[0046] <Fuel Cell Unit> Also in FIG. 1 , the fuel cell U103 includes a fuel cell 103a which is an SOFC in this embodiment, and (a) introduces high-temperature air from a heat exchanger 102 into the air electrode side of the fuel cell 103a, and (b) introduces hydrogen gas, which is supplied from the outside and temporarily stored (buffered) in a hydrogen tank 121 equipped with a pump, and whose flow rate is controlled by a flow controller FCd, into the combustion electrode side of the fuel cell 103a, causing a fuel cell reaction in the fuel cell 103a to generate electricity.

[0047] A heat exchanger may be provided to exchange heat between the hydrogen gas (b) and the high-temperature nitrogen-enriched gas. In this case, the temperature of this hydrogen gas is sufficiently high, approaching the temperature of the fuel cell (SOFC) reaction (several hundred degrees Celsius, e.g., approximately 700 degrees Celsius). In this embodiment, the fuel cell U103 uses a backpressure controller, including a backpressure valve and a backpressure gauge, to set the air and hydrogen gas pressure to approximately 0.1 to 0.2 MPa. Of course, higher gas pressures can be used to further improve the efficiency of the fuel cell reaction. However, in this case, it is important to set the air and hydrogen gas pressure to a value that does not damage the electrolyte layer, which is a thin ceramic layer such as yttria-stabilized zirconia (YSZ, ZrO2 + YO3). An appropriate sealing structure must also be employed to seal the entire fuel cell 103a.

[0048] The SOFC fuel cell 103a has a structure in which a plurality of stacks are formed by stacking a plurality of unit cells, each of which includes a stacked cathode, an electrolyte layer, and an anode, in series via a connecting member (interconnect). The stack structure may be an electrolyte-supported flat-plate type, an anode-supported flat-plate type, a cylindrical vertical-striped type, a cylindrical flat-plate vertical-striped type, a cylindrical horizontal-striped type, or a cylindrical flat-plate horizontal-striped type.

[0049] The fuel cell (SOFC) reaction that occurs in such a fuel cell 103a is as follows: First, oxygen (O2) in the air on the cathode side is transported to the cathode and electrons (e - ) to obtain oxygen ions (O 2- ) Then, oxygen ions (O 2-) and hydrogen (H2) of hydrogen gas, electrons (e - ) to the fuel electrode, which reacts to produce water (HO). This generates an electromotive force between the air electrode (cathode) and the fuel electrode (anode), allowing power to be supplied to the outside. The rated voltage of one single cell is, for example, 0.7 to 0.85 volts (V).

[0050] The exhaust gas from the cathode side is dry, high-temperature air (several hundred degrees Celsius, for example, about 700 degrees Celsius) with a reduced oxygen concentration, i.e., an increased nitrogen concentration. The residual oxygen concentration in the air serving as (a part of) this nitrogen-enriched gas can be reduced to a sufficiently small value (for example, about 4 vol%) by adjusting the SOFC reaction. Meanwhile, the exhaust gas from the anode side contains water vapor (HO).

[0051] Furthermore, the fuel cell U103 equipped with the fuel cell 103a described above preferably includes a group of measuring devices and sensors capable of measuring (a) the flow rate, pressure, temperature, and humidity of the air and hydrogen gas introduced into the fuel cell 103a, (b) the flow rate, pressure, temperature, and humidity of the exhaust gas discharged from the fuel cell 103a, and (c) the complex impedance, voltage, and current between the air electrode and the combustion electrode of the fuel cell 103a. In this case, the overall control U131, which receives measurement information from these measuring devices and sensors, can control the operation of the fuel cell 103a according to settings.

[0052] It is also preferable that the fuel cell U103 includes a heat exchanger for circulating a heat exchange medium disposed within or around the fuel cell 103a to extract thermal energy generated by the fuel cell reaction from the operating fuel cell 103a and provide this thermal energy to the outside. Examples of heat exchangers that can be used include a shell-and-tube heat exchanger or a plate heat exchanger such as an Alfa Laval brazed plate heat exchanger. Furthermore, instead of a heat exchanger, a heat conductor connecting the interconnect of the fuel cell 103a to a heat pipe may be used to extract thermal energy from the fuel cell 103a and provide this thermal energy to the outside from one end of the heat pipe. In either case, such heat transfer means not only enables the provision of thermal energy to, for example, consumers, but also enables the temperature of the single cell of the fuel cell 103a to be controlled within a predetermined temperature range, thereby maintaining optimal operation of the fuel cell 103a.

[0053] Furthermore, in this embodiment, the thermal energy extracted by the heat transfer means such as the heat exchanger or heat conductor is preferably sent to (a) a temperature regulator TCa in the exhaust gas combustion unit 105, which adjusts the temperature of the gas burner 105a and the exhaust gas introduced therein (e.g., by raising it to a set value), and (b) a temperature regulator TCb in the catalytic combustion unit U108, which adjusts the temperature of the solid catalyst 108a, reaction tube, nitrogen augmentation gas introduced therein (e.g., by raising it to a set value). For example, this thermal energy may be used to change the temperature of a metal capillary tube through which the nitrogen augmentation gas passes, thereby adjusting the temperature. These temperature regulators TCa and TCb may each be equipped with a thermometer to monitor the temperatures of the gas burner 105a, solid catalyst 108a, reaction tube, nitrogen augmentation gas, etc., and report the results to the overall control unit U131 as appropriate.

[0054] In this embodiment, the power generated by the fuel cell reaction in the fuel cell 103a is adjusted by a power adjustment unit PW and can be supplied to an external source, such as a consumer. The power adjustment unit PW may include, for example, a storage battery and an inverter, and temporarily store DC power from the fuel cell 103a and then convert it into AC power for external use. The booster U107 in this embodiment may also operate its own compressor pump 107a using power from the fuel cell 103a, or using this power in combination with power (renewable energy power) from an externally installed solar power generation system, wind power generation system, or micro-hydroelectric power generation system, or commercial power drawn from an external source.

[0055] <Heat Exchanger 104> In this embodiment, the heat exchanger 104 exchanges heat between the exhaust gas from the combustion electrode side, which is high-temperature (several hundred degrees Celsius, for example, approximately 700 degrees Celsius) exhaust gas from the fuel cell 103a, and a heat exchange medium. A portion of the thermal energy of this exhaust gas is transferred to the catalytic combustion unit 108 via the heat exchange medium. This effectively promotes the catalytic combustion reaction in the catalytic combustion unit 108, as will be described in detail later. Alternatively, the exhaust gas from the air electrode side may also exchange heat with the heat exchange medium of the heat exchanger 104. However, as in this embodiment, by introducing the exhaust gas from the air electrode side at a high temperature into the exhaust gas combustion unit 105 without introducing it into the heat exchanger 104, the large thermal energy of the exhaust gas from the air electrode side can be utilized in the exhaust gas combustion process, thereby improving the efficiency of the exhaust gas combustion process.

[0056] It is also preferable that the heat exchanger 104 reduces the temperature of the exhaust gas from the combustion electrode side to less than 100°C, converts the water vapor generated by the fuel cell reaction and contained in the exhaust gas into water, and removes this water using a dehumidifying means, such as a drain, provided at the outlet.

[0057] 1 , the exhaust gas combustion unit 105 of this embodiment takes in exhaust gas from the air electrode side and exhaust gas from the combustion electrode side as nitrogen-enriched gas from the fuel cell U103 and heat exchanger 104, respectively. The exhaust gas combustion unit 105 then uses a gas burner 105a to mix and burn these exhaust gases (nitrogen-enriched gas), thereby reducing the oxygen concentration of the exhaust gases (nitrogen-enriched gas). Here, in this embodiment, the exhaust gas from the combustion electrode side is a fuel exhaust gas containing residual hydrogen gas (fuel gas).

[0058] Thus, to allow a sufficient amount of hydrogen gas (fuel gas) to remain in the exhaust gas from the combustion electrode side and be used in the exhaust gas combustion process, the fuel cell 103a of this embodiment operates by introducing an amount of hydrogen gas (fuel gas) that will result in hydrogen gas (fuel gas) remaining in the nitrogen-enriched gas introduced into the exhaust gas combustion unit 105 (and, in this embodiment, also in the nitrogen-enriched gas introduced into the catalytic combustion unit 108 via the exhaust gas combustion unit 105). For example, it is preferable to operate by introducing an amount of hydrogen gas (fuel gas) that is greater than or equal to the amount that can convert all of the oxygen (O2) contained in the introduced air to water. In this case, since in an actual fuel cell not all of the introduced hydrogen (H2) contributes to the fuel cell reaction, the exhaust gas (fuel exhaust gas) from the combustion electrode side will contain residual hydrogen gas (residual fuel gas).

[0059] Here, the exhaust gas combustion unit 105 may combust the nitrogen-enhancing gas by also using hydrogen gas (fuel gas) taken in from the hydrogen tank 121. In another embodiment, the exhaust gas combustion unit 105 does not take in exhaust gas (fuel exhaust gas) from the combustion electrode side, but takes in exhaust gas (nitrogen-enhancing gas) from the air electrode side and hydrogen gas (fuel gas) from the hydrogen tank 121, mixes these gases (nitrogen-enhancing gas), and burns them to reduce the oxygen concentration of these gases (nitrogen-enhancing gas).

[0060] In yet another embodiment, it is possible not to provide the exhaust gas combustion unit 105 described above downstream of the fuel cell U103. Specifically, in this embodiment, the exhaust gas from the air electrode side and the exhaust gas from the combustion electrode side of the fuel cell 103a are introduced into the catalytic combustion U108 as nitrogen-enriched gas without passing through the exhaust gas combustion means.

[0061] In this embodiment, too, in order to leave a sufficient amount of hydrogen gas (fuel gas) in the exhaust gas from the combustion electrode side for use in catalytic combustion, the fuel cell 103a operates by taking in an amount of hydrogen gas (fuel gas) that will leave some hydrogen gas (fuel gas) in the nitrogen-enriched gas discharged from the fuel cell U103 and introduced into the catalytic combustion U108. For example, it is also preferable to operate by taking in an amount of hydrogen gas (fuel gas) that is greater than or equal to the amount that can convert all of the oxygen (O2) contained in the introduced air to water. In this case, in an actual fuel cell, not all of the introduced hydrogen (H2) contributes to the fuel cell reaction, and therefore the exhaust gas from the combustion electrode side will contain residual hydrogen gas (residual fuel gas).

[0062] The exhaust gas combustion section 105 may also use other combustion means, such as an electric wire heater, instead of the gas burner 105a to combust the introduced nitrogen-enriched gas.

[0063] 1 , the various filter unit FLa is a unit that processes the nitrogen-enriched gas, which will subsequently be introduced into the catalytic combustion unit U108 and the hydrogen / nitrogen filtering unit U110, to remove or reduce sulfides, chlorides, hydrocarbons, fluorides, strong alkaline compounds, and other substances that are harmful to the catalytic combustion process and gas filtering process. Specifically, the various filter unit FLa may include, for example, an activated carbon filter to remove or reduce the above-mentioned impurities in the exhaust gas. Furthermore, the various filter unit FLa may also include a mist filter and a dust filter to remove or reduce mist, such as water mist, solvent mist, or oil mist, in the nitrogen-enriched gas.

[0064] <Heat Exchanger 106> In this embodiment, the heat exchanger 106 exchanges heat between the nitrogen-enhancing gas delivered from the heat exchanger 102 and the supplied water. Using a portion of the thermal energy of the nitrogen-enhancing gas, which has been heated by the heat generated in the fuel cell reaction and the exhaust gas combustion reaction, the supplied water is converted into hot or heated water and supplied to the outside. This makes it possible to provide hot or heated water to consumers, for example. Furthermore, the temperature of the nitrogen-enhancing gas can be reduced to a temperature below the upper limit temperature (e.g., several tens of degrees Celsius) of the compression pump 107a of the booster U107, which is installed downstream of the heat exchanger 106. In this case, it is also preferable to dehumidify the nitrogen-enhancing gas using a dehumidifying means, such as a drain, installed at the outlet of the heat exchanger 106. Incidentally, if the temperature of the nitrogen-enhancing gas is sufficiently reduced by the upstream heat exchanger 102, the heat exchanger 106 may be omitted.

[0065] 1 , the pressure intensifier (U107) of this embodiment takes in nitrogen augmentation gas, the flow rate of which is controlled by the flow controller (FCb), from the heat exchanger (106), increases the pressure of this nitrogen augmentation gas using the compressor pump (107a), and delivers the high-pressure nitrogen augmentation gas to the catalytic combustion (U108). The overall control (U131) of this embodiment controls the operation of the compressor pump (107a) and the pressure controller (PCa) so that the pressure of the nitrogen augmentation gas introduced into the catalytic combustion (U108) and the hydrogen / nitrogen filtering (U110), both of which are downstream of the pressure intensifier (U107), meets the gas pressure value conditions (e.g., a gas pressure of 0.8 MPa or greater) set for each of these units. Thus, the pressure intensifier (U107) of this embodiment increases the pressure of the nitrogen augmentation gas, thereby simultaneously increasing the efficiency of the catalytic combustion and filtering processes to set or desired values.

[0066] Specifically, the booster U107 may include a flow control valve, a compressor pump 107a with a built-in tank, and a buffer tank. The compressor pump 107a with a built-in tank increases the pressure of the nitrogen-enhancing gas introduced into the booster U107 and delivers the nitrogen-enhancing gas at a high pressure (e.g., 0.3 to 1 MPa). It is also preferable that the compressor pump 107a receives power generated by the fuel cell 103a and operates on this power, or on a combination of this power and power (renewable energy power) from an externally installed solar power generation system, wind power generation system, or micro-hydroelectric power generation system, or on commercial power drawn from an external source.

[0067] The nitrogen-enhancing gas discharged from the fuel cell 103a and introduced into the booster unit 107 at a predetermined flow rate must be delivered to the catalytic combustion unit 108 as high-pressure gas at a predetermined flow rate without stagnation. Therefore, for example, the operation and stop of the compressor pump 107a may be controlled by a programmable logic controller (PLC) based on the flow rate of the nitrogen-enhancing gas. However, the booster unit 107 of this embodiment does not require such burdensome control, and can deliver high-pressure nitrogen-enhancing gas to the downstream unit at a predetermined flow rate while continuously operating the compressor pump 107a.

[0068] Specifically, in this embodiment, the booster U107 continuously operates the compressor pump 107a at a rotational speed roughly suited to the flow rate of the nitrogen augmentation gas discharged from the fuel cell 103a. Then, the flow rate of the nitrogen augmentation gas flowing into the compressor pump 107a is finely adjusted by the flow control valve VL, and high-pressure nitrogen augmentation gas having a predetermined pressure (e.g., 0.3 to 1 MPa) is temporarily stored in the compressor pump 107a's built-in tank. Finally, the booster U107 delivers this stored nitrogen augmentation gas to the catalytic combustion U108 at a predetermined pressure and flow rate, for example, via a buffer tank.

[0069] In this embodiment, the flow rate of the nitrogen augmentation gas being delivered is measured and monitored by a flow meter Fa. The pressure of the nitrogen augmentation gas being delivered is monitored by a gas pressure meter Pb installed downstream of the catalytic combustion unit U108 and the hydrogen / nitrogen filtering unit U110, and is set to a predetermined value by back pressure control by a pressure controller PCa also installed downstream, and by operation control of the compression pump 107a.

[0070] <Catalytic Combustion Means> Also referring to FIG. 1 , the catalytic combustion unit (U108) of this embodiment uses the residual hydrogen gas (residual fuel gas) remaining in the nitrogen-enhancing gas taken from the booster (U107) to react on the surface of the solid catalyst (108a), which is the combustion catalyst of this embodiment, to further reduce the oxygen concentration in the nitrogen-enhancing gas, i.e., to further increase the nitrogen concentration. The solid catalyst (108a) may be a metal or ceramic honeycomb with numerous fine holes and a large surface area, including the interior of these holes, supporting a metal catalyst such as platinum (Pt), palladium (Pd), or nickel (Ni). It is also preferable to use high-pressure (e.g., 0.3-1 MPa) hydrogen gas taken from the hydrogen tank (121), which has been increased in pressure by the booster (U122) and whose flow rate is monitored by a flow meter (Fc), to react the nitrogen-enhancing gas on the solid catalyst (U108a).

[0071] In this embodiment, in the catalytic combustion U108, high-pressure gas (e.g., 0.3 to 1 MPa) contacts the surface of the solid catalyst 108a. This allows more gas molecules to participate in the catalytic combustion reaction, increasing the reaction rate and accelerating the catalytic combustion reaction. As a result, the oxygen concentration in the nitrogen-enriched gas is reduced. Furthermore, even if the oxygen concentration is reduced to the same extent as in the case of low-pressure gas (e.g., 0.1 to 0.2 MPa), the suction volume (SV) and catalyst volume (V) of the solid catalyst 108a can be reduced, thereby further reducing the cost of the solid catalyst 108a, which uses expensive catalytic materials such as platinum (Pt). The overall control U131 monitors the gas pressure in the catalytic combustion U108 using a gas pressure gauge Pa.

[0072] In addition, the catalytic combustion U108 of this embodiment reacts the introduced nitrogen-enhancing gas on the combustion catalyst with a sufficient amount of residual hydrogen gas (and, in some cases, hydrogen gas from the hydrogen tank 121) until only hydrogen gas (fuel gas) remains after the catalytic combustion reaction, thereby sufficiently reducing the oxygen concentration of the nitrogen-enhancing gas. For example, it is preferable to react the introduced nitrogen-enhancing gas on the combustion catalyst with an amount of hydrogen (H) that is sufficient to convert all of the oxygen (O) contained in the nitrogen-enhancing gas to water (H2O).

[0073] Furthermore, as described above, the fuel cell 103a of this embodiment operates by taking in an amount of hydrogen gas that leaves a predetermined amount of hydrogen gas remaining in the nitrogen-enriching gas discharged from the exhaust gas combustion unit 105 and introduced into the catalytic combustion unit U108. As a result, this predetermined amount of hydrogen gas remains in the nitrogen-enriching gas taken into the catalytic combustion unit U108. It is preferable that this predetermined amount be set to an amount sufficient to leave hydrogen gas (fuel gas) remaining after the catalytic combustion reaction in the catalytic combustion unit U108. This allows the catalytic combustion unit U108 of this embodiment to perform an optimal catalytic combustion process using only the remaining hydrogen gas (remaining fuel gas) in the nitrogen-enriching gas or by minimizing the amount of hydrogen gas used from the hydrogen tank 121.

[0074] However, in order to ultimately produce high-purity nitrogen gas, it is necessary to remove or reduce the amount of hydrogen gas (fuel gas) remaining after this catalytic combustion reaction. In this embodiment, this role is also fulfilled by the hydrogen / nitrogen filtering U110, which is provided in the subsequent stage and further reduces the oxygen concentration of the nitrogen-enriched gas.

[0075] In another embodiment, the catalytic combustion unit 108 can take in only exhaust gas (nitrogen-enhancing gas) from the cathode side of the fuel cell 103a and react this nitrogen-enhancing gas on the solid catalyst 108a with hydrogen gas (fuel gas) taken in from the hydrogen tank 121. In this case, the exhaust gas combustion unit 105 may be omitted. Alternatively, the exhaust gas (nitrogen-enhancing gas) from the cathode side can be introduced into the heat exchanger 104, and a portion of the thermal energy of this high-temperature nitrogen-enhancing gas can be transferred from the heat exchanger 104 to the catalytic combustion unit 108 for use in the catalytic combustion reaction.

[0076] 1, the catalytic combustion reaction in the solid catalyst 108a, which is the combustion catalyst of this embodiment, increases in reaction rate and is further accelerated as the temperature inside the reaction tube containing the solid catalyst 108a increases. It has also been found that when the temperature inside the reaction tube falls below 100°C, water (HO) generated by the catalytic combustion reaction and water (HO) carried in by the nitrogen-enhancing gas tend to inhibit the catalytic combustion reaction. Therefore, the catalytic combustion unit 108 of this embodiment captures thermal energy from the exhaust gas of the fuel cell 103a via the heat exchange medium of the heat exchanger 104 and uses this thermal energy to heat the atmosphere inside the reaction tube containing the solid catalyst 108a to the required temperature (e.g., 60 to 200°C). For example, heating may be achieved by wrapping the piping of the heat exchange medium of the heat exchanger 104 around the solid catalyst 108a or the reaction tube.

[0077] As described above, the temperature controller TCb takes in thermal energy from the fuel cell 103a via a heat transfer means to heat the solid catalyst 108a and the reaction tubes, thereby controlling their temperatures. Furthermore, the nitrogen-enhancing gas sent from the pressure booster U107 is also at a high temperature, for example, above 100°C, and this contributes greatly to increasing the temperatures of the solid catalyst 108a and the reaction tubes.

[0078] Furthermore, the above-described heating treatment may be performed by wrapping a heating wire around the solid catalyst 108a or the reaction tube and applying power from the fuel cell U103 to the heating wire, or by applying this power together with power (renewable energy) from an externally installed solar power generation system, wind power generation system, or micro-hydroelectric power generation system, or commercial power. It is also possible to perform induction heating by irradiating an electromagnetic field onto an iron-based alloy disposed inside or around the carrier of the solid catalyst 108a. Incidentally, the temperatures of the solid catalyst 108a and the reaction tube rise due to the reaction heat of catalytic combustion itself, so the above-described heating treatment must be performed taking into account the temperature increase due to this reaction heat itself. The overall control U131 uses a thermometer Tb to monitor the temperature inside the reaction tube containing the solid catalyst 108a during catalytic combustion U108.

[0079] Fig. 2 is a schematic diagram for explaining the combustion catalyst mechanism used in an example of catalytic combustion treatment by catalytic combustion U108. Fig. 3 is a graph showing the processing results of one example of catalytic combustion treatment. Fig. 4 is a graph showing the processing results of another example of catalytic combustion treatment.

[0080] In the example shown in Figure 3, a honeycomb catalyst (Pt-coated) D3HPT manufactured by Tanaka Kikinzoku Kogyo Co., Ltd. was used as the solid catalyst 108a. As shown in Figure 2, two solid catalysts 108a (cylindrical, 5 cm diameter and height) were arranged in series in a stainless steel reaction tube. A nitrogen-oxygen mixture with an oxygen concentration of 11.2 vol% was generated to simulate the exhaust gas from the fuel cell 103a (Figure 1). This mixture was then introduced into the reaction tube as a nitrogen-enhancing gas. Hydrogen gas was introduced into the reaction tube at a flow rate slightly varied from a reference flow rate expected to consume exactly all of the oxygen in the nitrogen-enhancing gas. The pressure inside the reaction tube (intratube pressure) was varied between 0.22 and 0.50 MPa, and the pressure dependence of the residual oxygen and hydrogen concentrations in the gas emitted from catalytic combustion U108 was investigated. The temperature inside the reaction tube was 99 to 106°C.

[0081] According to the graph in Figure 3, the higher the residual hydrogen concentration, the lower the residual oxygen concentration, since the catalytic combustion reaction proceeds under a sufficient amount of hydrogen (H). Furthermore, for the same residual hydrogen concentration, the higher the pressure inside the tube, the lower the residual oxygen concentration, since the catalytic combustion reaction proceeds under a higher density of gas molecules. For example, when the pressure inside the tube is 0.50 MPa, the inlet flow rates of the nitrogen-enhancing gas and hydrogen gas are 6.4 liters (L) / min and 1.4 L / min, respectively, and the residual hydrogen concentration is approximately 10,000 ppm vol, the residual oxygen concentration is very low, at approximately 200 ppm vol.

[0082] In the example shown in Figure 4, nitrogen-oxygen mixed gases with oxygen concentrations of 3.385 vol%, 1.425 vol%, and 0.654 vol% were generated. These nitrogen-oxygen mixed gases were each treated as nitrogen-enhancing gases and introduced into the reaction tube at a flow rate of 2.0 L / min. Hydrogen gas was then introduced into the reaction tube at a flow rate expected to consume exactly all of the oxygen in the nitrogen-enhancing gas. The temperature inside the reaction tube was then varied to determine the residual oxygen concentration in the nitrogen-enhancing gas after the catalytic combustion reaction. The pressure inside the reaction tube was approximately 0.19 MPa. In this example, ten solid catalysts 108a were arranged in series inside the reaction tube.

[0083] 4, it can be seen that the residual oxygen concentration decreases as the introduced oxygen concentration, which is the oxygen concentration in the introduced nitrogen-enriched gas, decreases and as the temperature inside the reaction tube increases. For example, when the introduced oxygen concentration is 0.654 vol%, if the temperature inside the reaction tube is increased to 100°C, the residual oxygen concentration becomes approximately 10 ppm vol, and it becomes possible to produce nitrogen gas with high purity (5N, 99.999 vol%) with respect to nitrogen (N).

[0084] As explained above, in the catalytic combustion process in catalytic combustion U108, by increasing the pressure (pressure inside the reaction tube) of the nitrogen-enriching gas introduced and by increasing the temperature inside the reaction tube containing the solid catalyst 108a, it is possible to further reduce the residual oxygen concentration and produce, for example, very high-purity nitrogen gas. Furthermore, depending on the specifications required for the nitrogen gas to be provided (for example, the allowable ranges for the residual oxygen concentration and the residual hydrogen concentration), it is also possible to omit the hydrogen / nitrogen filtering U110, which will be explained later, and provide the high-purity nitrogen gas discharged from catalytic combustion U108 to the outside.

[0085] Returning to FIG. 1 , the heat exchanger HT of this embodiment exchanges heat between the high-temperature (e.g., 100 to several hundred degrees Celsius) nitrogen-enriched gas discharged from the catalytic combustion unit (U108) and the heat exchange medium, reducing the temperature of this nitrogen-enriched gas to a temperature (e.g., 40 to 70 degrees Celsius) suitable for the downstream hydrogen / nitrogen gas filter 110a. The heat exchanger HT may provide thermal energy to the outside via the heated heat exchange medium, or it may be preferable to use water as the heat exchange medium to supply warm or hot water to the outside. In this embodiment, the overall control unit (U131) monitors the temperature of this nitrogen-enriched gas using a downstream thermometer (Tc).

[0086] <Gas-Liquid Separation Means> The nitrogen-enriched gas delivered from the heat exchanger HT still contains water (HO) generated by the catalytic combustion reaction and water (HO) carried in by the nitrogen-enriched gas. Meanwhile, the hydrogen / nitrogen gas filter 110a to be used subsequently has an allowable humidity range for the introduced gas. Therefore, the gas-liquid separation unit U109 of this embodiment performs a dehumidification process on the nitrogen-enriched gas to remove moisture and water vapor, and delivers the nitrogen-enriched gas, whose humidity is now within the allowable humidity range of the hydrogen / nitrogen gas filter 110a, to the hydrogen / nitrogen filtering unit U110.

[0087] Here, the dehumidification process in the gas-liquid separator U109 of this embodiment can be performed using, for example, a dehumidifier using silica gel or zeolite, a dehumidification device equipped with a pressurizing mechanism, a gas-liquid separator (such as a gravity separation type, centrifugal separation type, mist eliminator pad type, blade-type separation type, or air pressure separation coalescer type), or a dry filter device.

[0088] <Hydrogen / Nitrogen Filtering Means> Also in FIG. 1 , the hydrogen / nitrogen filtering unit U110 of this embodiment is a unit that converts high-pressure (e.g., 0.3 to 1 MPa) nitrogen-enriched gas, which has its flow rate controlled by the flow controller FCc and is sent from the catalytic combustion unit U108 via the gas-liquid separation unit U109, into a nitrogen-enriched gas with a higher nitrogen concentration, i.e., high-purity nitrogen gas in this embodiment, using a hydrogen / nitrogen gas filter 110a.

[0089] The hydrogen-nitrogen gas filter 110a is a filter with different permeability rates for nitrogen (N) and oxygen (O), and reduces the oxygen concentration and increases the nitrogen concentration of the introduced nitrogen-enriched gas, thereby producing and delivering high-purity nitrogen gas in this embodiment. Furthermore, the hydrogen-nitrogen gas filter 110a of this embodiment is a filter with different permeability rates not only for nitrogen (N) and oxygen (O), but also for nitrogen (N) and hydrogen (H). As a result, the hydrogen-nitrogen gas filter 110a can produce and deliver high-purity nitrogen gas from which hydrogen (H) has been removed or from which the hydrogen concentration has been further reduced.

[0090] In this embodiment, as described above, the catalytic combustion U108 discharges a nitrogen-enriched gas containing residual hydrogen gas (residual fuel gas). In contrast, the hydrogen / nitrogen gas filter 110a can remove or reduce this residual hydrogen gas. That is, the oxygen (O2) and hydrogen (H2) contents of the nitrogen-enriched gas taken in from the catalytic combustion U108 can be simultaneously reduced or removed. Another advantage of this configuration is that the catalytic combustion U108 does not require highly sophisticated control of the amount (flow rate) of hydrogen gas introduced. Thus, it can be seen that the catalytic combustion U108 and the hydrogen / nitrogen filtering U110 of this embodiment are an excellent combination in that they use sufficient hydrogen (H2) to consume most of the oxygen (O2) and then simultaneously remove most of the remaining oxygen (H2, O2).

[0091] 1, the hydrogen / nitrogen gas filter 110a of this embodiment comprises: (a) a hollow fiber fiber section (110a1-b in FIG. 6, which will be described later) having different permeability rates for nitrogen (N2) and oxygen (O2) and for nitrogen (N2) and hydrogen (H2); (b) a filter inlet section (110a1-a in FIG. 6) for introducing a high-pressure (e.g., 0.3 to 1 MPa) nitrogen-enhancing gas to act on the hollow fiber fiber section of (a), and a filter outlet section (110a1-c in FIG. 6) for extracting the high-pressure (e.g., 0.3 to 1 MPa) nitrogen-enhancing gas having a higher nitrogen concentration, which in this embodiment is high-purity nitrogen gas, from the hollow fiber fiber section; (c) A filter purge section (110a1-d in FIG. 6) that extracts a gas containing oxygen (O2) and hydrogen (H2) separated from the nitrogen (N2) in the nitrogen-enriched gas by the hollow fiber section of (a) (hereinafter referred to as the filter exhaust gas) separately from the high-purity nitrogen gas extracted in (b).

[0092] Of these, the hollow fiber portion (a) is a hollow fiber polymer fiber that preferentially allows oxygen (O) and hydrogen (H) to permeate over nitrogen (N). As high-pressure (e.g., 0.3 to 1 MPa) nitrogen-enriched gas flows from the filter inlet through this hollow fiber portion, oxygen (O) and hydrogen (H) selectively permeate the polymer fiber and exit, ultimately resulting in high-purity nitrogen gas being extracted from the filter outlet.

[0093] Furthermore, it has been experimentally confirmed that in this hollow fiber section, the higher the pressure of the nitrogen-enhancing gas introduced (inlet pressure), the smaller the flow rate of the high-purity nitrogen gas extracted (outlet flow rate), and the lower the oxygen concentration of the nitrogen-enhancing gas introduced (inlet oxygen concentration), the lower the nitrogen concentration of the nitrogen-enhancing gas extracted from the filter outlet.

[0094] From the viewpoint of the outlet oxygen concentration, it can be seen that the hydrogen / nitrogen gas filter 110a (hydrogen / nitrogen filtering U110) and the catalytic combustion U108 upstream thereof, which significantly reduces the oxygen concentration of the nitrogen-enriched gas in advance, are a very suitable combination for producing nitrogen gas with a very low oxygen concentration, as required by specifications. Furthermore, experiments have confirmed that the recovery rate (= outlet flow rate / inlet flow rate) of the hydrogen / nitrogen gas filter 110a increases as the introduced oxygen concentration decreases. Therefore, from the viewpoint of recovery rate, the hydrogen / nitrogen gas filter 110a (hydrogen / nitrogen filtering U110) and the catalytic combustion U108 upstream thereof are a very suitable combination for recovering a sufficient amount (flow rate) of high-purity nitrogen gas as required by specifications.

[0095] If the catalytic combustion unit (U108) delivers nitrogen gas with a target, preset, or desired high purity, the hydrogen / nitrogen filter (U110) may be installed solely for the purpose of reducing or removing hydrogen (H2) from the nitrogen gas. In an experiment, an argon / hydrogen mixed gas with a hydrogen concentration of approximately 30 vol% was introduced into the hydrogen / nitrogen gas filter (U110a), a 4-inch diameter filter using aromatic polyimide hollow fibers, at a pressure of 0.5 MPa and a flow rate of 10 L / min. The outlet hydrogen concentration was reduced to 6 ppm vol. If the hydrogen concentration of the introduced gas was below a few vol%, the outlet hydrogen concentration could be reduced to below the measurement limit (1 ppm vol). The argon (Ar) and nitrogen (N2) separation rates of the filters used were roughly equivalent, and it is clear that similar results could be obtained if the introduced gas was a nitrogen / hydrogen mixed gas with a hydrogen concentration of approximately 30 vol.

[0096] Furthermore, as described above, the hydrogen / nitrogen gas filter 110a of this embodiment further reduces the oxygen concentration in a high-pressure (e.g., 0.3 to 1 MPa) nitrogen-enriched gas. The pressure value (e.g., 0.3 to 1 MPa) of the introduced nitrogen-enriched gas is equal to or greater than the lower limit pressure value determined by the characteristics of the hollow fiber, which is required to achieve a target, set, or desired nitrogen concentration (purity) in the hydrogen / nitrogen gas filter 110a at a set introduction flow rate.

[0097] For example, if a hydrogen / nitrogen gas filter 110a is used that requires an inlet pressure of 0.8 MPa or higher (i.e., a lower limit pressure of 0.8 MPa) to extract high-purity nitrogen gas at a desired flow rate with a desired low oxygen concentration, the nitrogen-enriched gas introduced into the hydrogen / nitrogen gas filter 110a can be a gas having a pressure (inlet pressure) of, for example, 0.8 to 0.85 MPa. In this case, it is also preferable that the pressure booster U107 generates a nitrogen-enriched gas having a pressure equal to or higher than a pressure threshold (e.g., 0.85 MPa) set based on this lower limit pressure (0.8 MPa) and taking into account the pressure loss in the intermediate catalytic combustion U108, and delivers the nitrogen-enriched gas to the catalytic combustion U108 and the downstream hydrogen / nitrogen filtering U110.

[0098] As the hydrogen / nitrogen gas filter 110a described above, which allows oxygen (O) and hydrogen (H) to pass through preferentially over nitrogen (N), it has been confirmed that the UBE N2 separator manufactured by UBE (formerly Ube Industries) using aromatic polyimide hollow fibers, and the N2 membrane module nitrogen gas filter manufactured by Polypla-Evonik, which also uses aromatic polyimide hollow fibers, can be used.

[0099] Fig. 5 is a graph showing an example of gas filtering processing by the hydrogen / nitrogen gas filter 110a, and Fig. 6 is a schematic diagram for explaining an embodiment of the arrangement of the gas filter according to the present invention.

[0100] First, the specific details of the gas filtering process using the hydrogen / nitrogen gas filter 110a in this embodiment will be described. In this embodiment, nitrogen-enriched gas with oxygen concentrations (introduced oxygen concentrations) of 1.0 vol%, 2.0 vol%, and 10.0 vol% and a pressure of approximately 0.7 MPa is introduced into this hydrogen / nitrogen gas filter 110a at an outlet flow rate of 2.4 to 19.0 normal lube (Nm 3 The hydrogen / nitrogen gas filter 110a was introduced so that the flow rate varied within a range of 1 / hour. Here, the oxygen concentration of the high-purity nitrogen gas discharged from the filter outlet of the hydrogen / nitrogen gas filter 110a, i.e., the outlet flow rate dependency of the outlet oxygen concentration, was investigated. A 2-inch diameter UBE N2 separator manufactured by UBE was used as the hydrogen / nitrogen gas filter 110a.

[0101] According to the graph in Figure 5, the outlet oxygen concentration decreases as the outlet flow rate decreases and as the introduced oxygen concentration decreases. Specifically, this is as follows: (a) Under the condition that the filter internal pressure is about 0.7 MPa, the introduced oxygen concentration is 10 vol%, and the outlet flow rate is 2.4 Nm 3 / hour, the outlet oxygen concentration is 62 ppm vol. Also, under the same conditions, the outlet flow rate is 10 Nm 3 Even if the flow rate is increased to 1000 ppm / hr, the outlet oxygen concentration is low at about 1000 ppm vol, and nitrogen gas with a purity of about 3N (99.9 vol% or higher) can be generated. (b) Under conditions of a filter internal pressure of about 0.7 MPa, the inlet oxygen concentration is set to 2 vol%, and the outlet flow rate is set to 2.4 Nm 3 / hour, the outlet oxygen concentration is 12 ppm vol. Also, under the same conditions, the outlet flow rate is 10 Nm 3 Even if the flow rate is increased to 1000ppm / hr, the outlet oxygen concentration is low at about 200ppm vol, and nitrogen gas with a purity of about 4N (99.99vol% or higher) can be generated. (c) When the filter pressure is about 0.7MPa, the introduced oxygen concentration is 1vol%, and the outlet flow rate is 2.4Nm 3 / hour, the outlet oxygen concentration will be reduced to 7 ppm vol, and it will be possible to generate nitrogen gas with a purity of 5N (99.999 vol% or higher).

[0102] From the above results, it can be seen that catalytic combustion U108 (Figure 1) can be omitted depending on the specifications required for the high-purity nitrogen gas provided. For example, even if the oxygen concentration of the nitrogen-enriched gas discharged from the fuel cell 103a is 10 vol% as described above (a), high-purity nitrogen gas of approximately 3N can be produced using only hydrogen / nitrogen filtering U110, i.e., without catalytic combustion U108 (Figure 1). Furthermore, if the oxygen concentration of the nitrogen-enriched gas discharged from the fuel cell 103a can be reduced to, for example, approximately 2-4 vol%, high-purity nitrogen gas of approximately 4N can be produced using only hydrogen / nitrogen filtering U110, i.e., without catalytic combustion U108 (Figure 1).

[0103] Next, a preferred embodiment of the arrangement of the hydrogen / nitrogen gas filter 110a will be described using FIG. 6. As shown in FIG. 6, in this embodiment, three hydrogen / nitrogen gas filters 110a1, 110a2, and 110a3 are arranged in parallel with the flow of nitrogen-enriched gas introduced to perform gas filtering. Specifically, the nitrogen-enriched gas discharged from the catalytic combustion unit 108 (FIG. 1) is divided into three streams and introduced into the hollow fiber fiber sections of the hydrogen / nitrogen gas filters 110a1, 110a2, and 110a3 from their filter inlets. The gases discharged from each hollow fiber fiber section through their respective filter outlets are then combined to form high-purity nitrogen gas. Meanwhile, the gases discharged from each filter purge section are also combined and discharged as filter exhaust gas.

[0104] This allows a larger amount (flow rate) of nitrogen-enriched gas to be subjected to gas filtering. As a result, it is possible to employ a larger, more powerful fuel cell 103a and generate and provide a larger amount (flow rate) of high-purity nitrogen gas. Of course, the number of hydrogen / nitrogen gas filters 110a arranged in parallel is not limited to three, and two or four or more hydrogen / nitrogen gas filters 110a may be arranged in parallel.

[0105] The various devices provided downstream of the hydrogen / nitrogen filtering unit U110 will be described below.

[0106] Returning to FIG. 1 , the pressure controller PCa of this embodiment is equipped with a back pressure valve and a back pressure gauge and controls the outlet pressure (pressure of the extracted high-purity nitrogen gas) of the hydrogen / nitrogen filtering unit U110, i.e., the back pressure. Here, this back pressure value (outlet pressure value) is monitored by a gas pressure gauge Pb. In this embodiment, the pressure controller PCa also serves to introduce high-pressure (e.g., 0.3 to 1 MPa) nitrogen-enriched gas, whose pressure is equal to or exceeds the lower limit pressure set in the catalytic combustion unit U108 or the hydrogen / nitrogen filtering unit U110, into the catalytic combustion unit U108 or the hydrogen / nitrogen filtering unit U110. In other words, the pressure controller PCa serves as pressure control means for maintaining and managing these units as a series of high-pressure systems.

[0107] 1, the nitrogen gas tank 111 of this embodiment is a tank that temporarily stores high-pressure (e.g., 0.3 to 1 MPa) high-purity nitrogen gas delivered from the hydrogen / nitrogen filtering unit U110. This nitrogen gas tank 111 is equipped with a gas regulator and a mass flow controller (or a flow switch), and preferably supplies the stored high-purity nitrogen gas to the outside at a predetermined stable pressure and flow rate, for example, in response to instructions from the overall control unit U131.

[0108] In this embodiment, the overall control U131 monitors and manages the flow rate, residual oxygen concentration, and residual hydrogen concentration of the high-purity nitrogen gas introduced into the nitrogen gas tank 111 using a flow meter Fb, an oxygen concentration meter Oa, and a hydrogen concentration meter Ha, respectively, and checks whether the high-purity nitrogen gas to be provided to the outside is being generated in a set amount (flow rate) and whether it meets the purity specifications. It is also preferable to provide a dehumidifying means such as a dry filter and a hygrometer downstream of the hydrogen / nitrogen filtering U110, and the overall control U131 checks, based on the monitored value from the hygrometer, whether the high-purity nitrogen gas dehumidified by this dehumidifying means meets the humidity specifications (e.g., a dew point of −60°C or lower).

[0109] Furthermore, in this embodiment, a branch pipe is provided that branches off from the pipe connecting the hydrogen / nitrogen filtering U110 to the back pressure valve of the downstream pressure controller PCa. This branch pipe is used to extract the high-pressure, high-purity nitrogen gas delivered from the hydrogen / nitrogen filtering U110. The nitrogen gas tank 111 receives the high-pressure, high-purity nitrogen gas through this branch pipe. A check valve Vn is provided midway along this branch pipe to prevent backflow of the high-purity nitrogen gas from the nitrogen gas tank 110.

[0110] By adopting such a structure using branch piping, it is possible to store the high-purity nitrogen gas delivered from the hydrogen / nitrogen filtering U110 in the nitrogen gas tank 111 by utilizing its high pressure as is, without using, for example, a boost compression pump. Here, it is also preferable to provide a gas pressure gauge in the nitrogen gas tank 111 to monitor the pressure inside the tank, and set it so that high-purity nitrogen gas continues to flow from the hydrogen / nitrogen filtering U110 at a predetermined flow rate while the pressure inside the tank is below a predetermined upper limit (for example, 0.65 MPa).

[0111] As described above in detail, the nitrogen gas generator (system) 1 of this embodiment is an apparatus (system) that can provide not only high-purity nitrogen gas but also electric power and thermal energy to consumers with high efficiency and ease. It is also possible to provide consumers with water (pure water) generated and recovered by the fuel cell 103a, exhaust gas combustion unit 105, and catalytic combustion unit 108. In this case, the apparatus (system) functions as, for example, a nitrogen gas, electric power, heat, and pure water supply apparatus (system).

[0112] [Another embodiment of the installation position of the pressure boosting means] FIG. 7 is a schematic diagram showing another embodiment of the installation position of the pressure boosting means according to the present invention.

[0113] In the embodiment shown in FIG. 7, the booster U107′ equipped with the compressor pump 107a′ has the same configuration and function as the booster U107 (FIG. 1) equipped with the compressor pump 107a (FIG. 1), but unlike the booster U107 (FIG. 1), it is installed after the catalytic combustion U108 and before the hydrogen / nitrogen filtering U110.

[0114] As a result, the nitrogen-enriched gas discharged from the fuel cell 103a and passing through the exhaust gas combustion unit 105, heat exchanger 102, and heat exchanger 106 undergoes catalytic combustion treatment in catalytic combustion unit 108, and is then introduced into pressure booster unit 107', where it is brought to a high pressure (e.g., 0.3 to 1 MPa). This high-pressure nitrogen-enriched gas is then introduced into hydrogen / nitrogen filtering unit 110, where it is subjected to gas filtering treatment under high pressure (e.g., 0.3 to 1 MPa), and as a result, high-purity nitrogen gas is sent out from hydrogen / nitrogen filtering unit 110.

[0115] In this manner, in this embodiment as well, it is possible to perform gas filtering processing on the nitrogen-enriched gas whose oxygen concentration has been reduced by catalytic combustion processing at a gas pressure (which provides a higher filtering effect) that is equal to or higher than the lower limit pressure value set in the hydrogen / nitrogen gas filter 110a, and as a result, it is possible to produce a nitrogen-enriched gas with an even lower oxygen concentration (and hydrogen concentration), i.e., a high-purity nitrogen gas.

[0116] In this embodiment, the heat exchanger HT serves to lower the temperature of the nitrogen-enriched gas discharged from the catalytic combustion unit 108 to a temperature below the upper limit temperature (e.g., several tens of degrees Celsius) of the compression pump 107a' of the pressure booster unit 107' provided downstream of the heat exchanger HT. Also, in this embodiment, the pressure booster unit 122 for hydrogen gas (FIG. 1) can be omitted.

[0117] [High-Temperature Nitrogen Gas] FIG. 8 is a schematic diagram showing another embodiment of the ultimately generated high-concentration nitrogen-enriched gas.

[0118] According to FIG. 8, the heat exchanger HT of this embodiment exchanges heat between: (a) the finally generated high-concentration nitrogen-enriched gas, which in this embodiment is high-purity nitrogen gas; and (b) the nitrogen-enriched gas discharged from the catalytic combustion U108, thereby increasing the temperature of the finally generated high-purity nitrogen gas.

[0119] The high-temperature (e.g., tens to hundreds of degrees Celsius) high-purity nitrogen gas thus produced is a high-temperature inert gas that is very suitable for supplying to, for example, reflow soldering equipment and atmospheric furnaces for firing various products and components such as multilayer capacitors.

[0120] The finally generated high-purity nitrogen gas may be heated and utilized at the destination by thermal energy supplied from the nitrogen gas generator (system) 1. For example, the high-purity nitrogen gas may be supplied from the nitrogen gas generator (system) 1 to the destination via a gas pipe. On the other hand, the thermal energy generated in the fuel cell 103a, the exhaust gas combustion unit 105, or the catalytic combustion unit 108 may be supplied from the nitrogen gas generator (system) 1 to the destination via a heat transfer means such as a heat exchanger or a heat pipe heat conductor, and the temperature of the supplied high-purity nitrogen gas may be increased at the destination.

[0121] [Another embodiment of the device / system] Figure 9 is a schematic diagram showing another embodiment of the nitrogen gas generator and nitrogen gas generation system according to the present invention. Here, in the nitrogen gas generator (system) 2 shown in Figure 9, components with reference numerals including "2#*" (where # and * are numbers) have the same configuration and function as the components with the same reference numerals including "1#*" in the nitrogen gas generator (system) 1 shown in Figure 1.

[0122] The nitrogen gas generator (system) 2 of this embodiment shown in Figure 9 differs from the nitrogen gas generator (system) 1 shown in Figure 1 in that it has a mixer 221, a reforming tube 205b, and a poison gas remover 222. This nitrogen gas generator (system) 2: (a) uses city gas, the main component of which is methane (CH4), or gas containing propane (C3H8) and butane (C4H), which is supplied from the outside, as a poison gas remover. 10(b) Hydrogen gas (hydrogen-containing gas) is generated by a steam reforming reaction from a hydrocarbon gas such as LP gas, which is the heat exchanger (202, 204, 206, HT), and (b) water or steam supplied from the outside and / or water or steam extracted from a dehumidifying means such as a drain installed at the outlet of the heat exchanger (202, 204, 206, HT), and the generated hydrogen gas (hydrogen-containing gas) is introduced as a fuel gas into the fuel electrode side of the fuel cell 203a.

[0123] Specifically, in this embodiment, the hydrocarbon gas (a) and the water or steam (b) are mixed in a mixer 221, and the resulting mixed gas is introduced into the reforming tube 205b while the flow rate is controlled by a flow controller FCd. The reforming tube 205b then reforms the introduced mixed gas (hydrocarbon gas) through a steam reforming reaction using combustion heat received from the gas burner 205a (or an electric wire heater) of the exhaust gas combustion section 205, thereby producing hydrogen gas (hydrogen-containing gas). Furthermore, the poison gas remover 222 removes poison gases such as carbon monoxide (CO) gas generated by the steam reforming reaction from the produced hydrogen gas (hydrogen-containing gas).

[0124] The steam reforming reaction described above, when methane (CH4) is used as the hydrocarbon gas, is represented by the following chemical reaction formula (2): CH4 + 2H2O → 4H2 + CO2. Thus, hydrogen (H2) and carbon dioxide (CO2) are produced by the steam reforming reaction. However, in reality, methane (CH4) that did not contribute to the reaction and carbon monoxide (CO) that was not completely oxidized are also discharged from the reforming tube 205a. Therefore, the poison gas remover 222 of this embodiment is equipped with a hydrogen separation membrane, a CH4 / CO / CO2 absorbent, and / or a PSA (Pressure Swing Absorption) mechanism, etc., and is capable of removing or separating not only carbon monoxide (CO) but also methane (CH4), carbon dioxide (CO2), etc., discharged from the reforming tube 205a.

[0125] As described above, the reformer 205b of this embodiment uses combustion heat from the gas burner 205a (or electric wire heater) of the exhaust gas combustion unit 205 to promote the steam reforming reaction. Furthermore, the reformer 205b may receive heat generated by the fuel cell 203a or catalytic combustion unit 208 via heat transfer means such as a heat exchanger or a heat pipe heat conductor, and use this heat to promote the steam reforming reaction. In this way, according to this embodiment, the heat generated within the device (system) 2 is used to promote the steam reforming reaction, making it possible to generate hydrogen gas (fuel gas) with higher efficiency.

[0126] [Still Another Embodiment of the Apparatus / System] Figure 10 is a schematic diagram showing still another embodiment of the nitrogen gas generator and nitrogen gas generation system according to the present invention. Here, in the nitrogen gas generator (system) 3 shown in Figure 10, components with reference numerals including "3#*" (where # and * are numbers) have the same configuration and function as the components with the same reference numerals including "1#*" in the nitrogen gas generator (system) 1 shown in Figure 1.

[0127] The nitrogen gas generator (system) 3 of this embodiment shown in Figure 10 differs from the nitrogen gas generator (system) 1 shown in Figure 1 in that it includes a water electrolysis unit U351 equipped with a water vapor generator VP, a heater 305c, and a solid oxide electrolyzer (SOEC) 351c. The solid oxide electrolyzer 351c has a structure in which a plurality of stacks are formed by stacking a plurality of unit cells in series via connecting members (interconnects), each unit cell including a stacked cathode (hydrogen electrode), a ceramic electrolyte layer, and an anode (oxygen electrode). The operating temperature of the solid oxide electrolyzer 351c is also high (several hundred degrees Celsius, for example, approximately 700 degrees Celsius), similar to that of the SOFC fuel cell 303a.

[0128] Specifically, in this embodiment, the solid oxide electrolyzer 351c takes in high-temperature (e.g., several hundred degrees Celsius) water vapor supplied from the heater 305c to the cathode side, electrolyzes the taken-in water vapor using the supplied power, generates high-temperature (e.g., several hundred degrees Celsius, approximately 700 degrees Celsius) hydrogen gas (fuel gas), and sends it out from the cathode side.

[0129] On the other hand, the fuel cell 303a of this embodiment is an SOFC that operates by taking in the generated high-temperature (several hundred degrees Celsius, for example, approximately 700 degrees Celsius) hydrogen gas (fuel gas) and discharging high-temperature (several hundred degrees Celsius, for example, approximately 700 degrees Celsius) nitrogen-enriched gas as exhaust gas. The hydrogen gas (fuel gas) generated in the solid oxide electrolyzer 351c is introduced into the fuel cell 303a after its flow rate is controlled by a flow controller FCe. A hydrogen tank or a hydrogen storage alloy cylinder may be provided between the water electrolysis unit U351 and the fuel cell U303 to temporarily store the hydrogen gas (fuel gas) generated in the solid oxide electrolyzer 351c and appropriately send it to the fuel cell 303a.

[0130] The heater 305c includes, for example, a large number of long fine tubes, and uses combustion heat received from the gas burner 305a (or an electric wire heater) of the exhaust gas combustion unit 305 to increase the temperature of the steam supplied through these fine tubes. The high-temperature (e.g., several hundred degrees Celsius) steam is then introduced into the solid oxide electrolyzer 351c. In this embodiment, the steam supplied to the heater 305c is generated by a steam generator VP. The steam generator VP is a heat exchanger that performs heat exchange between (a) water supplied from outside and whose flow rate is controlled by a flow rate controller FCd, and (b) high-temperature nitrogen-enriched gas discharged from the catalytic combustion unit 308, thereby generating steam from the water (a) and reducing the temperature of the nitrogen-enriched gas (b) to a temperature suitable for the downstream hydrogen / nitrogen gas filter 310a.

[0131] As a further modification, the heater 305c may heat the water supplied through the fine tubes using combustion heat received from the gas burner 305a (or an electric wire heater) of the exhaust gas combustion unit 305 to generate high-temperature (e.g., several hundred °C) water vapor. The solid oxide electrolyzer 351c may also receive heat generated by the fuel cell 303a or catalytic combustion unit 308 via heat transfer means such as a heat exchanger or a heat pipe heat conductor, and use this heat to promote the water electrolysis reaction. In any case, this embodiment uses the heat generated within the device (system) 3 to promote the water electrolysis reaction, enabling the generation of high-temperature (several hundred °C, e.g., approximately 700 °C) hydrogen gas (fuel gas) with higher efficiency.

[0132] Furthermore, the water supplied to the steam generator VP (or heater 305c) may be water received from the outside, but it is also preferable that at least a portion of the water is taken out from a dehumidifying means such as a heat exchanger (302, 304, 306) or a drain installed at the outlet of the steam generator VP itself. Furthermore, the power supplied to the solid oxide electrolyzer 351c may be commercial power or power (renewable energy power) from an externally installed solar power generation device, wind power generation device, micro-hydroelectric power generation device, or the like, but it is also preferable that it includes power generated by the fuel cell 303a. Furthermore, the oxygen gas delivered from the anode side of the solid oxide electrolyzer 351c may also be temporarily stored in an oxygen tank, for example, and then supplied to the outside.

[0133] In this embodiment, the pressure of the hydrogen gas (fuel gas) introduced from the solid oxide electrolyzer 351c to the fuel cell 303a is set to approximately 0.1 to 0.2 MPa by a back pressure controller including a back pressure valve and a back pressure gauge provided in the fuel cell U303. However, it goes without saying that a higher gas pressure value can be used to improve the efficiency of the water electrolysis reaction and the fuel cell reaction. For example, the solid oxide electrolyzer 351c may have a high-pressure seal structure, and the pressure of the introduced water vapor may be increased by a booster pump or the like, thereby generating hydrogen gas (fuel gas) at a high pressure within a range that will not damage the thin ceramic electrolyte layer.

[0134] As described above, the solid oxide electrolyzer 351c of this embodiment can more efficiently or more easily introduce high-temperature (several hundred degrees Celsius, for example, about 700 degrees Celsius) hydrogen gas into the SOFC fuel cell 303a by using the heat in the device (system) 3, and in some cases, water or electricity generated in the device (system) 3. This also promotes the fuel cell reaction in the fuel cell 303a, making it possible to more efficiently or more easily generate nitrogen-enriched gas with an increased nitrogen concentration, and thus high-purity nitrogen gas.

[0135] In another embodiment, the water electrolyzer U351 may include a water electrolyzer other than an SOEC, such as a polymer electrolyte electrolyzer (PEEC). The fuel cell 303a may also be a PEFC other than an SOFC. Even in such an embodiment, a nitrogen-enriched gas with an increased nitrogen concentration, and thus high-purity nitrogen gas, can be produced with high efficiency or ease. However, as can be seen from the above, the water electrolyzer U351 including the solid oxide electrolyzer 351c and the fuel cell U303 including the SOFC fuel cell 303a in this embodiment are an excellent combination in that they can deliver fuel gas at a desirable high temperature and, in some cases, at a high pressure.

[0136] [Overall Control Means] The following describes the overall control U331 of the nitrogen gas generator (system) 3 shown in Fig. 10. The control content described below also applies to the control of common units and devices performed by the overall control U131 shown in Fig. 1 and the overall control U231 shown in Fig. 9.

[0137] The overall control U331 of this embodiment shown in FIG. 10 includes an integrated circuit (IC) such as a processor and memory. A nitrogen gas generation control program for performing the monitoring, adjustment, and control described below is installed in the memory, and the program is executed by the IC. At least a portion of the monitoring, adjustment, and control may be implemented using wired logic. Furthermore, the nitrogen gas generation control program may execute the monitoring, adjustment, and control processes using a machine learning model for nitrogen gas generation control, for example, a model constructed using a trained deep neural network (DNN) algorithm, in which measurement data from various measuring instruments and control devices are used as explanatory variables and adjustment and control instruction information is used as a target variable.

[0138] Here, the overall control U331 of this embodiment: (a) uses the flow controller FCa to control the flow rate of air introduced from the air tank 301 to the fuel cell U303; (b) uses the flow controller FCd, a means for adjusting the amount of power supplied to the water electrolysis U351, and the flow controller FCe to control the flow rate of hydrogen gas produced in the solid oxide electrolyzer 351c and introduced into the fuel cell U303; (c) uses the back pressure controller of the fuel cell U303 to control the pressure inside the solid oxide electrolyzer 351c, the pressure inside the fuel cell 303a, and the pressure of the exhaust gas (nitrogen-enriched gas) discharged from the fuel cell 303a, and controls the residual oxygen concentration (nitrogen concentration) of the nitrogen-enriched gas discharged from the fuel cell 303a by this control together with the above controls (a) and (b); (d) Using the temperature controller TCa, the residual oxygen concentration (nitrogen concentration) of the nitrogen-enriched gas discharged from the exhaust gas combustion section 305 is controlled, and the temperature of the steam introduced from the heater 305c to the water electrolysis section U351 is also controlled; (e) Using the flow controller FCb, a means for adjusting the amount of power supplied to the compression pump 307a, the pressure controller PCa, and the temperature controller TCb, the flow rate and pressure of the nitrogen-enriched gas introduced to the catalytic combustion section U308 and the temperature of the reaction tube containing the solid catalyst 308c are controlled, thereby controlling the oxygen concentration (nitrogen concentration) of the nitrogen-enriched gas discharged from the catalytic combustion section U308; (f) Using the flow controller FCc, a means for adjusting the amount of power supplied to the compression pump 307a, and the pressure controller PCa, the flow rate and pressure of the nitrogen-enriched gas introduced to the hydrogen / nitrogen filtering section U310 is controlled, thereby controlling the residual oxygen concentration (nitrogen concentration) of the nitrogen-enriched gas, which in this embodiment is high-purity nitrogen gas, delivered from the hydrogen / nitrogen filtering section U310.

[0139] Furthermore, the overall control U331 of this embodiment can communicate with the water electrolysis U351, fuel cell U303, heater 305c, pressure booster U307, catalytic combustion U308, and hydrogen / nitrogen filtering U310, as well as various measuring instruments and control devices (including those shown in FIG. 10) provided inside these units and equipment or in the upstream or downstream stages thereof, via a wired or wireless communication network. Furthermore, the overall control U331 of this embodiment generates control and adjustment instruction signals based on measurement data from these various measuring instruments, and transmits the generated control and adjustment instruction signals to the above-mentioned units and equipment and various control devices to perform various control operations, thereby generating high-purity nitrogen gas having a target, set, or desired purity.

[0140] In particular, in this embodiment, the overall control U331 adjusts the amount (flow rate) of the above-mentioned (b) hydrogen gas introduced to the combustion electrode side of the fuel cell U303 to an amount (flow rate) that will allow a hydrogen gas portion (fuel gas portion) to remain in the nitrogen-enriched gas that is introduced to the catalytic combustion U308 after passing through the fuel cell reaction in the fuel cell U303 and the exhaust gas combustion reaction in the exhaust gas combustion unit 105. Here, it is also preferable that the overall control U331 determines and adjusts the amount (flow rate) of hydrogen gas introduced to the combustion electrode side of the fuel cell 303a based on: (h1) residual hydrogen concentration information in the exhaust gas (fuel exhaust gas) from the fuel electrode side of the fuel cell 303a, obtained from a hydrogen concentration meter installed at the outlet of the fuel cell U303, and (h2) residual hydrogen concentration information in the nitrogen-enriched gas discharged from the exhaust gas combustion unit 305, obtained from a hydrogen concentration meter installed at the outlet of the exhaust gas combustion unit 305.

[0141] Furthermore, it is also preferable that the overall control U331 determines and adjusts the amount (flow rate) of hydrogen gas to be introduced into the combustion electrode side of the fuel cell 303a so that the amount (concentration) of hydrogen gas (fuel gas) remaining in the nitrogen-enhancing gas introduced into the catalytic combustion U308 is an amount (concentration) that enables all of the remaining oxygen (O2) to be converted into water (H2O) by the subsequent catalytic combustion reaction, based on (h3) residual hydrogen concentration information in the nitrogen-enhancing gas discharged from the catalytic combustion U308 obtained from a hydrogen concentration meter installed at the outlet of the catalytic combustion U308.

[0142] Furthermore, it is also preferable that the overall control U331 determines and adjusts the amount (flow rate) of hydrogen gas to be introduced into the combustion electrode side of the fuel cell 303a so that the residual hydrogen concentration in the finally generated high-purity nitrogen gas is equal to or less than a set upper limit value (e.g., 10 ppm vol) based on (h4) residual hydrogen concentration information in the finally generated high-purity nitrogen gas obtained from a hydrogen concentration meter Ha installed downstream of the hydrogen / nitrogen filtering U310.

[0143] The above-described control of the amount (flow rate) of hydrogen gas introduced into the combustion electrode side can of course also be carried out in the overall control U131 (FIG. 1) or the overall control U231 (FIG. 9).

[0144] In this embodiment, the overall control unit U331 treats the catalytic combustion unit U108, the gas-liquid separation unit U309 (including a dry filter device, etc.), and the hydrogen / nitrogen filtering unit U310 as a single high-pressure system. The overall control unit U331 transmits pressure and flow rate adjustment and control command signals to the flow controller FCb, the pressure booster U107, the flow controller FCc, and the pressure controller PCa, etc., to ensure that the nitrogen-enhanced gas pressure is consistently maintained between, for example, 0.3 and 1 MPa, or even between, for example, 0.7 and 1 MPa. Furthermore, the overall control unit U331 preferably determines and adjusts the pressure (gas pressure) so that the catalytic combustion process and gas filtering process are performed under sufficiently high gas pressure, and the residual oxygen concentration (measured by the oxygen concentration meter Oa) of the resulting high-purity nitrogen gas is below a preset upper limit (e.g., 10 ppm vol).

[0145] It is also preferable that the overall control U331 transmits temperature adjustment / control instruction signals to the temperature regulators TCa and TCb, etc., so that the temperature of the nitrogen enrichment gas along the way falls within the preferred temperature range set for each unit / device. In any case, the overall control U331 of this embodiment controls the purity and amount (flow rate) of the high-purity nitrogen gas that is ultimately produced so that they meet the required specifications.

[0146] As described above in detail, the nitrogen gas generating device and system of the present invention can generate and supply highly pure nitrogen gas with greater efficiency and ease using a fuel cell.

[0147] Furthermore, the present invention, as merely one embodiment thereof, makes it possible to efficiently or simply generate and provide high-purity nitrogen gas by utilizing hydrogen gas, which will become inexpensive and easily available in the coming hydrogen gas society, and at the same time to provide electric power, thermal energy, and in some cases, pure water.

[0148] In other words, this invention is expected to contribute greatly to the establishment of a carbon-free, locally produced and consumed energy and product supply and demand system, which is considered to be one ideal future model. Furthermore, it is expected to be of great help in realizing carbon neutrality, which is an urgent issue.

[0149] It should be noted that the above-described embodiments are merely illustrative of the present invention and are not limiting, and the present invention can be embodied in various other modified and altered forms. Therefore, the scope of the present invention is defined only by the claims and their equivalents.

[0150] 1, 2, 3 Nitrogen gas generator / system 101, 201, 301 Air tank 102, 104, 106, 202, 204, 206, 302, 304, 306 Heat exchanger 103, 203, 303 Fuel cell unit (U) 103a, 203a, 303a Fuel cell 105, 205, 305 Exhaust gas combustion section 105a, 205a, 305a Gas burner 107, 122, 107', 207, 222, 307, 322 Pressure booster U 107a, 107a', 207a, 307a Compressor pump 108, 208, 308 Catalytic combustion U 108a, 208a, 308a Solid catalyst 109, 209, 309 Gas-liquid separation U 110, 210, 310 Hydrogen / nitrogen filtering U 110a, 110a1, 110a2, 110a3, 210a, 310a Hydrogen / nitrogen gas filter 110a1-a Filter inlet section 110a1-b Hollow fiber section 110a1-c Filter outlet section 110a1-d Filter purge section 111, 211, 311 Nitrogen gas tank 121 Hydrogen tank 131, 231, 331 Overall control U 205b Reforming tube 221 Mixer 305c Heater 351 Water electrolysis U 351a Solid oxide electrolyzer

Claims

1. A nitrogen gas generation device, comprising: a fuel cell that operates by taking in air or a gas containing nitrogen and oxygen, and a fuel gas; and catalytic combustion means that uses a residual fuel gas component, which is a component of the fuel gas remaining in the nitrogen-increased gas taken out as exhaust gas from the fuel cell and having a higher nitrogen concentration than the air or the gas, and / or the fuel gas, and reacts them on a combustion catalyst to convert the nitrogen-increased gas into a high-concentration nitrogen-increased gas having an even higher nitrogen concentration.

2. The nitrogen gas generation device according to claim 1, wherein the fuel cell is a solid oxide fuel cell (SOFC), and the exhaust gas from the air electrode side is sent to the subsequent stage without undergoing a dehumidification treatment.

3. The nitrogen gas generation device according to claim 1, wherein the fuel cell operates by taking in an amount of the fuel gas such that the fuel gas still remains in the nitrogen-increased gas introduced into the catalytic combustion means.

4. The nitrogen gas generation device according to claim 1, wherein the fuel cell operates by taking in an amount of the fuel gas that is equal to or greater than an amount that enables all of the oxygen contained in the taken-in air or the gas to be converted into water.

5. The nitrogen gas generation device according to claim 1, further comprising pressure increasing means for increasing the pressure of the nitrogen-increased gas, wherein the catalytic combustion means reacts the nitrogen-increased gas at a higher pressure on a combustion catalyst.

6. The nitrogen gas generation device according to any one of claims 1 to 5, further comprising exhaust gas combustion means for burning the nitrogen-increased gas taken out from the fuel cell and the fuel exhaust gas with the fuel gas remaining therein, which is taken out as exhaust gas from the fuel cell, to reduce the oxygen concentration of the nitrogen-increased gas, wherein the catalytic combustion means reacts the nitrogen-increased gas with a reduced oxygen concentration on a combustion catalyst.

7. The nitrogen gas generation device according to claim 6, further comprising reforming means for reforming the supplied hydrocarbon gas using the combustion heat received from the exhaust gas combustion means to generate the fuel gas.

8. The nitrogen gas generation device according to any one of claims 1 to 5, further comprising filtering means provided with a filter having different degrees of permeability for nitrogen and oxygen, and converting the high-concentration nitrogen-increased gas into a high-concentration nitrogen-increased gas having an even higher nitrogen concentration.

9. The catalytic combustion means reacts the nitrogen-increasing gas on a combustion catalyst using a sufficient amount of the residual fuel gas component and / or the fuel gas until a fuel gas component remains after the catalytic combustion reaction. The filter is a filter with different degrees of permeability for nitrogen and oxygen and for nitrogen and hydrogen. The filtering means makes the high-concentration nitrogen-increasing gas into a high-concentration nitrogen-increasing gas with a higher nitrogen concentration, in which hydrogen has been removed or the hydrogen concentration is lower. The nitrogen gas generation device according to claim 8, characterized in that.

10. The nitrogen gas generation device according to any one of claims 1 to 5, further comprising heat exchange means for performing heat exchange between the nitrogen-increasing gas and the air or the gas before being introduced into the fuel cell, reducing the temperature of the nitrogen-increasing gas, and increasing the temperature of the air or the gas.

11. The nitrogen gas generation device according to any one of claims 1 to 5, further comprising heat exchange means for performing heat exchange between the finally generated high-concentration nitrogen-increasing gas and the high-concentration nitrogen-increasing gas taken out from the catalytic combustion means, and increasing the temperature of the finally generated high-concentration nitrogen-increasing gas.

12. The nitrogen gas generation device according to any one of claims 1 to 5, further comprising water electrolysis means for electrolyzing the supplied water vapor to generate the fuel gas, and the fuel cell operates by taking in the generated fuel gas.

13. The nitrogen gas generation device according to claim 12, characterized in that the water electrolysis means has a solid oxide electrolyzer (SOEC).

14. Exhaust gas combustion means for burning the nitrogen-increasing gas taken out from the fuel cell and at least the fuel exhaust gas remaining the fuel gas taken out as exhaust gas from the fuel cell to reduce the oxygen concentration of the nitrogen-increasing gas, and heating means for generating water vapor from the supplied water or increasing the temperature of the supplied water vapor using the combustion heat received from the exhaust gas combustion means. The water electrolysis means generates the fuel gas using the generated or heated water vapor. The catalytic combustion means reacts the nitrogen-increasing gas with a reduced oxygen concentration on a combustion catalyst. The nitrogen gas generation device according to claim 12, characterized in that.

15. A fuel cell that operates by taking in air or a gas containing nitrogen and oxygen and a fuel gas, and catalytic combustion means for reacting, on a combustion catalyst, a nitrogen-increased gas taken out as exhaust gas from the fuel cell and having a nitrogen concentration higher than that of the air or the gas, using a residual fuel gas component that is the fuel gas component remaining in the nitrogen-increased gas and / or the fuel gas, to convert the nitrogen-increased gas into a high-concentration nitrogen-increased gas with an even higher nitrogen concentration. A nitrogen gas generation system characterized by comprising the above.

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