Nitrogen gas generating device and method for filtering fuel cell exhaust gas

Abstract

To provide a device which surely and stably generates highly pure nitrogen gas by using a fuel battery.SOLUTION: A nitrogen gas generation device includes: a fuel battery that is operated by taking air (or gas containing nitrogen and oxygen) and fuel gas; dehumidifying means (gas liquid separation U) of reducing a moisture content or a moisture vapor in exhaust gas taken out of the fuel battery and having an oxygen concentration lower than that of air; and filtering means (nitrogen filter U) having a filter using a fiber with different penetration degrees for nitrogen and oxygen and changing the exhaust gas having been reduced in moisture contant or moisture vapor into gas increased in nitrogen concentration. Here, the filter is preferably a filter in which as an oxygen concentration of a filtering object air is lower, a collection rate becomes higher. Further, the dehumidifying means is preferably a pump unit including a water sealing type pump. In addition, it is preferable that the exhaust gas taken out of the fuel battery is provided in an adiabatic expansion chamber that is adiabatically expanded.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] In recent years, the use of fuel cells has been actively promoted. For example, fuel cell vehicles have been put into practical use, and fuel cell equipment for home and industrial use is also becoming more widespread. Fuel cells not only enable highly efficient power generation, but also, unlike conventional power generation methods using internal combustion engines, make it possible to reduce carbon dioxide emissions to almost zero. For these reasons, fuel cell technology is expected to significantly contribute to the realization of a carbon-zero society.

[0003] The inventors of the present application have focused on the potential of fuel cells and have invented a soldering device that utilizes a fuel cell, as described in Patent Documents 1 and 2. This soldering device utilizes not only the electricity generated by the fuel cell, but also the exhaust gases generated by the power generation, which are supplied to the soldering device.

[0004] The present inventors have also invented a power generation device that uses a fuel cell to supply inert gas and electricity to a processing device that processes an object to be heated by electrically heating the object in the inert gas, as described in Patent Documents 3 and 4. This power generation device can remove or reduce the oxygen, water vapor, and moisture contained in the exhaust gas from the fuel cell, and convert the exhaust gas into an inert gas suitable for use in the processing device.

[0005] Furthermore, the inventors of the present application have also invented an electric power and gas supply device capable of supplying low-oxygen gas with a sufficiently small amount of oxygen by connecting N fuel cell units from a first fuel cell unit to an Nth fuel cell unit, as described in Patent Document 5. Furthermore, as described in Patent Document 6, the inventors have also invented a nitrogen gas generation device that supplies air and fuel gas having a pressure above atmospheric pressure to a fuel cell to operate the fuel cell, and applies the exhaust gas having a pressure above atmospheric pressure extracted from the fuel cell to a nitrogen filter at a pressure above atmospheric pressure, and extracts gas with an increased nitrogen concentration from the filter. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2013-233549 [Patent Document 2] Japanese Patent Application Laid-Open No. 2016-164987 [Patent Document 3] Japanese Patent Application Laid-Open No. 2017-084796 [Patent Document 4] Japanese Patent Application Laid-Open No. 2018-163890 [Patent Document 5] Japanese Patent Application Publication No. 2019-129110 [Patent Document 6] Japanese Patent Publication No. 2020-149838 Summary of the Invention [Problem to be solved by the invention]

[0007] Thus, the inventors of the present application have come to the realization that by using fuel cells, it will be possible to supply highly pure nitrogen gas, which is in high demand at various production and service sites.

[0008] Such high-purity nitrogen gas is an inert gas that has no combustion-supporting or combustion-promoting properties, making it a very useful gas. However, at present, it is produced using air as a raw material through methods such as pressure swing adsorption (PSA), cryogenic air separation, and membrane separation.

[0009] Here, we thought that if we used the exhaust gas from a fuel cell instead of using air as a raw material as in the past, we might be able to efficiently produce high-purity nitrogen gas. And of course, because we use a fuel cell, it would be possible to supply electricity along with the high-purity nitrogen gas.

[0010] However, the exhaust gas extracted from a fuel cell usually contains a large amount of water (H2O) generated in the fuel cell reaction, and its relative humidity is approximately 100%. Therefore, if left as is, this will hinder the subsequent high-purity treatment, making it difficult to carry out this treatment reliably and stably.

[0011] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide an apparatus, system and method for reliably and stably generating high-purity nitrogen gas using a fuel cell. [Means for solving the problem]

[0012] According to the present invention, the device operates by taking in air or a gas containing nitrogen and oxygen, and a fuel gas. and discharges exhaust gas with a lower oxygen concentration than air or the gas in question. a fuel cell; a first flow control means for controlling the flow rate of air or the gas introduced into the fuel cell; It is equipped with a filter using fibers with different permeability to nitrogen and oxygen. , this a filtering means for converting the exhaust gas into a gas having an increased nitrogen concentration; 、 a second flow control means for controlling the flow rate of the nitrogen-enriched gas delivered from the filtering means; With death, the second flow control means controls the flow rate of the gas with increased nitrogen concentration so that the nitrogen concentration of the gas with increased nitrogen concentration becomes the "target nitrogen concentration" under the condition that the pressure of the exhaust gas introduced into the filtering means is a predetermined pressure and the oxygen concentration of the exhaust gas is the "low oxygen concentration" realized by the flow rate control by the first flow control means; The first flow control means controls the flow rate of the air or gas so that the oxygen concentration of the exhaust gas becomes the above-mentioned "low oxygen concentration" under the condition that the pressure of the air or gas introduced into the fuel cell is a predetermined pressure. It is characterized by A nitrogen gas generator is provided. Here, in one embodiment of the nitrogen gas generating device according to the present invention, the fuel cell is preferably a solid oxide fuel cell (SOFC). In another embodiment of the nitrogen gas generator according to the present invention, it is also preferable that the nitrogen gas generator further comprises a dehumidifying means for reducing the moisture or water vapor content in the exhaust gas extracted from the fuel cell. Furthermore, as still another embodiment of the nitrogen gas generator according to the present invention, The nitrogen gas generator further includes catalytic combustion means for reacting the gas having an increased nitrogen concentration with the fuel gas on a combustion catalyst to convert the gas having an increased nitrogen concentration into a gas having a lower oxygen concentration, The "target nitrogen concentration" in the gas with an increased nitrogen concentration is a nitrogen concentration at which the nitrogen concentration of the gas with an increased nitrogen concentration, having the target nitrogen concentration, is introduced into the catalytic combustion means, and the nitrogen concentration of the gas with a lower oxygen concentration that is extracted from the catalytic combustion means becomes the target or desired high nitrogen concentration. It is also preferable. In yet another embodiment of the nitrogen gas generator according to the present invention, it is also preferable that the second flow control means controls the flow rate of the gas with increased nitrogen concentration under the conditions so that the nitrogen concentration of the gas with increased nitrogen concentration becomes the "target nitrogen concentration" and the recovery rate becomes the target or desired recovery rate.

[0013] Also, Nitrogen gas generator according to the present invention Further other In one embodiment, the device , this It is also preferable that the system further comprises a pressure increasing means for increasing the pressure of the exhaust gas, and the filtering means converts the pressurized exhaust gas into gas having an increased nitrogen concentration.

[0020] In yet another embodiment of the nitrogen gas generating device according to the present invention, the device is configured to generate nitrogen gas by using air having a pressure above atmospheric pressure. or the and a fuel gas having a pressure above atmospheric pressure is supplied to the fuel cell. provide It is also preferred that the apparatus further comprises a pressure control means for filtering the exhaust gas having a pressure above atmospheric pressure into a gas having an increased concentration of nitrogen.

[0022] Furthermore, as yet another embodiment of the nitrogen gas generating device according to the present invention, the fuel cell comprises a plurality of cells, which are structural units each including two electrodes sandwiching an electrolyte, and the entirety of the plurality of cells is divided into a plurality of functional cell sections, and each functional cell section includes one or a plurality of consecutive cells, is not electrically connected in series with other functional cell sections, and is electrically connected to an individual power generation control section.

[0023] According to the present invention, the fuel cell can be operated by taking in air or a gas containing nitrogen and oxygen, and a fuel gas. and discharges exhaust gas with a lower oxygen concentration than air or the gas in question. a fuel cell; a first flow control means for controlling the flow rate of air or the gas introduced into the fuel cell; It is equipped with a filter using fibers with different permeability to nitrogen and oxygen. , this a filtering means for converting the exhaust gas into a gas having an increased nitrogen concentration; 、 a second flow control means for controlling the flow rate of the nitrogen-enriched gas delivered from the filtering means; With death, the second flow control means controls the flow rate of the gas with increased nitrogen concentration so that the nitrogen concentration of the gas with increased nitrogen concentration becomes the "target nitrogen concentration" under the condition that the pressure of the exhaust gas introduced into the filtering means is a predetermined pressure and the oxygen concentration of the exhaust gas is the "low oxygen concentration" realized by the flow rate control by the first flow control means; The first flow control means controls the flow rate of the air or gas so that the oxygen concentration of the exhaust gas becomes the above-mentioned "low oxygen concentration" under the condition that the pressure of the air or gas introduced into the fuel cell is a predetermined pressure. It is characterized by A nitrogen gas generating system is provided.

[0024] According to the present invention, further a first step of introducing air or a gas containing nitrogen and oxygen into a fuel cell while controlling the flow rate of the air or the gas; a second step of operating a fuel cell that takes in air or the gas and a fuel gas, and extracting from the fuel cell an exhaust gas having an oxygen concentration lower than that of the air or the gas; a third step of passing the exhaust gas through a filter using fibers having different permeabilities for nitrogen and oxygen to convert the exhaust gas into a gas having an increased nitrogen concentration; a fourth step of controlling the flow rate of the nitrogen-enriched gas exiting the filter; and In a fourth step, under the condition that the pressure of the exhaust gas introduced into the filter is a predetermined pressure and the oxygen concentration of the exhaust gas is the "low oxygen concentration" realized by the flow rate control in the first step, the flow rate of the gas with increased nitrogen concentration is controlled so that the nitrogen concentration of the gas with increased nitrogen concentration becomes the "target nitrogen concentration", In the first step, the flow rate of the air or gas is controlled so that the oxygen concentration of the exhaust gas becomes the above-mentioned "low oxygen concentration" under the condition that the pressure of the air or gas introduced into the fuel cell is a predetermined pressure. A method for generating nitrogen gas is provided. [Effects of the Invention]

[0025] According to the present invention, it is possible to reliably and stably generate highly pure nitrogen gas using a fuel cell. [Brief explanation of the drawings]

[0026] [Figure 1] 1 is a schematic diagram showing one embodiment of a nitrogen gas generator system according to the present invention. [Figure 2] 1 is a graph for explaining Example 1 of the nitrogen gas generation process according to the present invention. [Figure 3] 1 is a graph for explaining Example 1 of the nitrogen gas generation process according to the present invention. [Figure 4] 1 is a graph for explaining Example 1 of the nitrogen gas generation process according to the present invention. [Figure 5] 10 is a graph illustrating Example 2 in which the recovery rate of a nitrogen gas filter in a nitrogen gas generation process according to the present invention was examined. [Figure 6] FIG. 10 is a schematic diagram for explaining another embodiment of the dehumidifying means according to the present invention. [Figure 7]1 is a schematic diagram for explaining an embodiment of a gas-liquid separator U as a dehumidifying means according to the present invention. FIG. [Figure 8] FIG. 10 is a schematic diagram for explaining another embodiment of the filtering means according to the present invention. [Figure 9] FIG. 10 is a schematic diagram illustrating yet another embodiment of the nitrogen gas generator system according to the present invention. [Figure 10] FIG. 10 is a schematic diagram illustrating another embodiment of a fuel cell according to the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0027] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. In each drawing, the same components are designated by the same reference numerals. In addition, components that may have similar structures and functions may also be designated by the same reference numerals. Furthermore, dimensional ratios within and between components in the drawings are arbitrary for ease of viewing the drawings.

[0028] [Nitrogen gas generator / system] FIG. 1 is a schematic diagram showing one embodiment of a nitrogen gas generator system according to the present invention.

[0029] The nitrogen gas generator 1 (or nitrogen gas generation system 1) according to one embodiment of the present invention shown in FIG. 1 includes: (A) A "fuel cell (in the fuel cell unit U (11)") that operates by taking in "air or a gas containing nitrogen and oxygen" and "fuel gas" (hydrogen in this embodiment), (B) A dehumidifying means (gas-liquid separator U122 in FIG. 1, water ring pump U30 in FIG. 6) for reducing the moisture or water vapor content in the exhaust gas (off-gas) extracted from the fuel cell and having an oxygen concentration lower than that of air; (C) A "nitrogen gas filter 12f" is provided using fibers (e.g., hollow fiber fibers) with different permeability for nitrogen and oxygen, and is a filtering means (nitrogen filter U12 in Figure 1) that converts the "exhaust gas" with reduced moisture or water vapor content into gas with increased nitrogen concentration. It is characterized by having:

[0030] Here, the "nitrogen gas filter 12f" in (C) above is a filter that uses fibers with different degrees of permeability for nitrogen and oxygen, as described above, and the inventors of the present application have confirmed through experiments, as will be described in detail later, that in a filter that uses such fibers, the "oxygen concentration reduction index" of "exhaust gas" that has an oxygen concentration (in ml per 100 ml of medium, expressed in volume (vol)%) lower than that of air increases the lower the oxygen concentration.

[0031] In this way, the nitrogen gas generating device (system) 1 makes it possible to efficiently generate nitrogen gas with a low oxygen concentration, i.e., high purity, by combining a fuel cell and a nitrogen gas filter 12f, which are highly compatible from the perspective of low oxygen concentration.

[0032] Incidentally, as will be explained in more detail later, the inventors of the present application have confirmed through experiments that by applying "exhaust gas" with an oxygen concentration of 2.5 vol% or less to "nitrogen gas filter 12f," it is possible to extract "exhaust gas" from "nitrogen gas filter 12f" with an oxygen concentration that is 1 / 10 or less of the result when air is applied.

[0033] Furthermore, the inventors of the present application have experimentally confirmed that the nitrogen gas filter 12f used in this embodiment has a higher recovery rate as the oxygen concentration of the gas to be filtered decreases. Therefore, by using such a nitrogen gas filter 12f to filter exhaust gases having an oxygen concentration lower than that of air, it is possible to further increase the recovery rate of high-purity nitrogen gas. This recovery rate will also be described in detail later.

[0034] As described above, the "nitrogen gas filter 12f" is a filter using fibers with different degrees of permeability for nitrogen and oxygen, and the inventors have experimentally confirmed that, in a filter using such fibers, the higher the pressure of the "exhaust gas" acting on the filter, the lower the oxygen concentration of the "exhaust gas" extracted from the filter, i.e., the higher the purity of the nitrogen gas obtained. Therefore, in this embodiment, a pressure booster U124 is provided upstream of the nitrogen filter U to increase the pressure of the "exhaust gas" acting on the filter, making it possible to efficiently produce nitrogen gas with a low oxygen concentration, i.e., high purity.

[0035] Incidentally, as will be explained in more detail later, experiments have confirmed that it is also preferable to set the pressure of the "exhaust gas" acting on the "nitrogen gas filter 12f" to a pressure value that exceeds a pressure threshold determined by the "nitrogen gas filter 12f," a pressure threshold that increases as the flow rate of the "exhaust gas" when extracted from the "nitrogen gas filter 12f" increases.

[0036] The terms "high purity" and "high purity" used above refer to a state in which the oxygen concentration in the nitrogen gas is sufficiently reduced. Specifically, the nitrogen concentration (in ml per 100 ml of medium, expressed as vol%) in the "high purity" or "high purity" nitrogen gas produced in this embodiment may be, for example, 95 vol% or more, 99 vol% or more, or even 99.9 vol% or more, or 99.99 vol% or more, depending on the field and application of the nitrogen gas.

[0037] Furthermore, the dehumidifying means (B) reduces the moisture or water vapor content in the "exhaust gas," which normally has a relative humidity of approximately 100%, thereby ensuring that the subsequent purification process can be carried out reliably and stably without being adversely affected by the moisture or water vapor content, and is an important means for efficiently producing high-purity nitrogen gas. Here, as this important dehumidifying means, it is also preferable to use a water ring pump U30, which includes a water ring pump, as will be described in detail later using Figure 6.

[0038] [Devices and system configuration] As also shown in FIG. 1, the nitrogen gas generating device (system) 1 of this embodiment includes: (a) a fuel cell U (unit) 11 having a "fuel cell"; (b) A natural energy power generation unit U101, a power storage unit U101s, a hydrogen generation unit U102, a hydrogen generation reformer U103, a hydrogen tank 104, a flow control unit U105, an air compressor U106, an air tank 107, a filter U108, and a flow control unit U109 are provided in a position preceding the fuel cell U11. (c) A drain 111, a pressure control unit U113, a gas-liquid separation unit U114, and a hydrogen recovery unit U115 are provided at the downstream side of the hydrogen electrode of the fuel cell U11. (d) At a position downstream of the air electrode side of the fuel cell U11, there are provided a drain 112, a pressure control U121, a gas-liquid separation U122, an off-gas buffer tank 123, a pressure booster U124, a corrosive gas removal unit U125, a temperature adjustment unit U126, a flow control unit U127, a nitrogen filter U12 equipped with a nitrogen gas filter 12f, a pressure booster U128, and a nitrogen tank 129. (e) Overall control U131 and It is a device (system) equipped with the above, and is capable of taking in natural energy such as air, water, and sunlight, and in some cases city gas and even commercial electricity, and supplying highly pure nitrogen gas, electricity, and thermal energy to the outside.

[0039] In other words, the nitrogen gas generating device (system) 1 of this embodiment is also capable of providing the electric power and thermal energy generated by the operating "fuel cell" to the outside in addition to the generated nitrogen gas, and can also be considered as a nitrogen gas, electric power and heat supply device (system).

[0040] The nitrogen gas generator (system) 1 may include at least the fuel cell U11 and components directly connected thereto, the gas-liquid separator U122, and the nitrogen filter U12, and may also constitute a nitrogen gas generation system together with at least an external natural energy generator U101. For example, the nitrogen gas generator (system) 1 may be a device (system) that includes all components except the natural energy generator U101, the power storage U101s, the hydrogen generator U102, the hydrogen generator / reformer U103, the hydrogen tank 104, the air compressor U106, the air tank 107, the pressure booster U128, and the nitrogen tank 129.

[0041] The nitrogen gas generating device (system) 1 may also be provided with a piping joint as an exhaust gas intake that can be connected to an exhaust gas outlet of an externally installed fuel cell, and can be a device (system) that takes in exhaust gas discharged from this external fuel cell and outputs nitrogen gas with a reduced oxygen concentration. In other words, it may be a "fuel cell-mounted filtering device (system)" that can be attached to a fuel cell.

[0042] In other words, in this case, the nitrogen gas generating device (system) 1 is a device (system) having (a) an exhaust gas intake port for receiving exhaust gas discharged from an external fuel cell, (b) a dehumidification means for reducing the moisture or water vapor content in the received exhaust gas, and (c) a filter made of fibers with different degrees of permeability for nitrogen and oxygen, which outputs gas with an increased nitrogen concentration by applying the exhaust gas with reduced moisture or water vapor content to the filter.

[0043] Incidentally, the material and energy transfers and processing flows shown by connecting the components with arrows in the device and system configuration diagram of Figure 1 can also be understood as one embodiment of the nitrogen gas generation method according to the present invention.

[0044] Also in Figure 1, the natural energy power generation unit U101 may be a solar cell power generation unit equipped with a solar cell and converting sunlight into electricity, or a wind power generation unit that uses wind power to rotate a rotor with blades to drive a generator and generate electricity, or a micro-hydro power generation unit that uses water flow (hydropower) to rotate a turbine (water wheel) to drive a generator and generate electricity.

[0045] Also, various other power generation units can be adopted as the natural energy power generation unit 101 as long as they ultimately convert the light energy of sunlight or the kinetic energy of wind and water currents into electrical energy. Furthermore, the natural energy power generation unit 101 may be a combination of two or more of the power generation units described above. In any case, it is preferable that the output section of the generated power is equipped with a wattmeter so that it is possible to measure whether or not power is being generated at each point in time and the amount of power generated.

[0046] The power storage unit U101s is equipped with a secondary battery such as a lithium (Li) battery or a lead (Pb) battery, and is a power storage unit that stores and preserves the power supplied from the natural energy power generation unit 101. The power storage unit U101s also preferably has a power storage meter that can measure the amount of power stored at any given time and whether it is fully charged. Here, power is supplied from the power storage unit U101s to the hydrogen generator U102 (which performs water electrolysis) and the air compressor U106, which will be described later, but instead of or in addition to these, commercial power may be supplied to the hydrogen generator U102 and the air compressor U106.

[0047] Furthermore, it is also preferable to supply power directly from the renewable energy power generation unit 101 to the hydrogen generator U102 and air compressor U106 without using a storage battery U101s with a secondary battery, which has a certain limit on the amount of stored power (or is provided only as an auxiliary). In this case, renewable energy is directly converted into the chemical energy of hydrogen and the physical energy of compressed air and then used.

[0048] When the renewable energy power generation unit 101 generates AC power (for example, when it is equipped with an AC generator), this AC power or commercial power is converted to DC by a converter and then supplied to the power storage U101s or hydrogen generation U102. Also, when the air compressor U106 is equipped with a DC-driven compressor 22, the power is also converted to DC and then supplied to the air compressor U106.

[0049] In any case, the overall control U131 can appropriately switch and control the power supply to the hydrogen generation U102 and air compression U106 as described above, while monitoring, for example, the power generation status in the natural energy power generation unit 101 and the power storage status in the power storage U101s.

[0050] 1, the hydrogen generator U102 is a hydrogen supply unit equipped with an electrolysis section capable of generating hydrogen and oxygen by electrolyzing the obtained water using supplied power. Various known electrolysis methods can be used here, but for example, electrolysis may be performed using a stack of multiple electrolysis cells, each having a structure in which a solid polymer electrolyte membrane is sandwiched between catalysts and electrodes on both sides.

[0051] The hydrogen generator U102 is also preferably equipped with a dehumidifying unit that removes moisture from the generated hydrogen and oxygen. Furthermore, a mechanism may be provided in which the moisture removed here is returned to the electrolysis unit for electrolysis. It is also preferable to have a wattmeter that can measure the amount of power consumed at each point in time and whether or not power is being consumed, and may also have a flow meter or gas pressure meter that can measure the amount of hydrogen and oxygen generated and whether or not they are being generated.

[0052] The hydrogen generation reformer U103 takes in a hydrocarbon gas such as city gas or LPG, mixes this hydrocarbon gas with steam, and generates a hydrogen-containing gas containing hydrogen (H2) as a main component from this mixed gas through a steam reforming reaction. It is also preferable to have a mechanism for reducing the carbon monoxide gas content in the generated hydrogen-containing gas using a CO conversion catalyst or the like, and further reducing the carbon monoxide concentration using a CO selective oxidation catalyst.

[0053] Incidentally, if an SOFC (solid oxide fuel cell) is used as the "fuel cell" of the fuel cell U11 described below, the high temperature (large amount of heat) required for steam reforming in the hydrogen generation reformer U103 can be met by the exhaust heat from this "fuel cell."

[0054] The nitrogen gas generating system 1 may be equipped with either a hydrogen generation unit 102 or a hydrogen generation and reforming unit 103 as a hydrogen (fuel) supply source, or it is preferable to have both units to ensure a variety of supply sources. Furthermore, instead of or in addition to these supply sources, hydrogen gas itself may be supplied from another system or device.

[0055] The hydrogen tank 104 is a gas tank that temporarily stores and preserves the hydrogen gas supplied from the hydrogen generator U102 or hydrogen generator / reformer U103 in a compressed (high-pressure) state, and may be equipped with a hydrogen storage alloy cylinder. It is also preferable that the hydrogen tank 104 is equipped with a gas pressure gauge so that the gas pressure inside the tank can be measured at any time.

[0056] The flow control U105 is a unit that controls the pressure and flow rate of hydrogen gas supplied from the hydrogen tank 104 to the fuel cell U11. Specifically, it may be equipped with a hydrogen gas regulator and a hydrogen gas mass flow controller (or flow switch).

[0057] Here, hydrogen gas may be supplied to the hydrogen electrode side of fuel cell U11 at a high pressure (e.g., 1.1 to 7 atmospheres, approximately 0.11 to 0.7 MPa) exceeding atmospheric pressure (1 atmosphere, approximately 0.1 MPa). That is, in this embodiment, the back pressure of the "fuel cell" provided in fuel cell U11 can be set to, for example, atmospheric pressure or a pressure exceeding atmospheric pressure. Note that this back pressure is set to 1 atmosphere (approximately 0.1 MPa) when the outlet side of the "fuel cell" is in an open state, i.e., when the exhaust gas pressure is atmospheric pressure.

[0058] However, when a mass flow controller is used in the flow control U105, a pressure difference loss usually occurs here, so it is also preferable to receive hydrogen gas from the hydrogen tank 104 at a pressure, for example, 1 to 2 atmospheres (approximately 0.1 to 0.2 MPa) higher than the set pressure (back pressure), adjust that pressure with a regulator, and then flow that hydrogen gas to the mass flow controller. Incidentally, it has been found through experiments that the above-mentioned pressure difference loss increases as the flow rate decreases (the flow is throttled).

[0059] Also in Figure 1, the air compressor U106 is a unit equipped with a compressor that compresses (high-pressures) air taken in from the atmosphere and supplies it to an air tank 107. As a compression method for this compressor, various methods can be used, such as a reciprocating type, scroll type, screw type, rotary type, swing type, or a combination of two or more of these.

[0060] The air tank 107 is a gas tank that temporarily stores and preserves the compressed air supplied from the air compressor U106 in a compressed state. It is also preferable that the air tank 107 is provided with a gas pressure gauge so that the gas pressure inside the tank can be measured at any time.

[0061] The filter U108 is a unit that includes an air filter and an oil filter, and removes minute dust particles, oil components, and the like from the high-pressure air supplied from the air tank 107 using these filters.

[0062] The flow control U109 is a unit that controls the pressure and flow rate of compressed air supplied from the air tank 107 to the air electrode side of the fuel cell U11 via the filter U108. Specifically, it may be equipped with a gas regulator and a mass flow controller (or a flow switch).

[0063] In this embodiment, this compressed air may also be supplied to the air electrode side of the fuel cell U11 (set with a back pressure exceeding atmospheric pressure, for example) while still in a high pressure state (for example, 1.1 to 7 atmospheres, about 0.11 to 0.7 MPa) exceeding atmospheric pressure (1 atmosphere, about 0.1 MPa). In this case, taking into account the pressure differential loss of the mass flow controller, compressed air at a pressure, for example, 1 to 2 atmospheres (about 0.1 to 0.2 MPa) higher than the set back pressure may be received from the air tank 107, and the pressure may be adjusted by a regulator before the compressed air is passed to the mass flow controller, just as in the case of hydrogen gas described above.

[0064] Also in Figure 1, fuel cell U11 is a unit that has a "fuel cell" and extracts and outputs exhaust gas having an oxygen concentration lower than that of air, electricity, heat, and water (water vapor) from this "fuel cell."

[0065] Of course, this fuel cell U11 can be used with the back pressure of the "fuel cell" set to atmospheric pressure (1 atmosphere, approximately 0.1 MPa). However, as a preferred embodiment, (a) A back pressure exceeding atmospheric pressure (e.g., 1.1 to 7 atmospheres, approximately 0.11 to 0.7 MPa) is set, (b) It receives hydrogen gas having a pressure above atmospheric pressure (e.g., 1.1 to 7 atmospheres, approximately 0.11 to 0.7 MPa) from the flow control U105, and further receives compressed air having a pressure above atmospheric pressure (e.g., 2 to 7 atmospheres) from the flow control U109, and operates; (c) Discharge exhaust gases with pressures exceeding atmospheric pressure (e.g., 1.1 to 7 atmospheres, approximately 0.11 to 0.7 MPa). It is also preferable that the unit is equipped with a "fuel cell."

[0066] Here, this "fuel cell" may be of a known configuration, and may have a structure in which multiple cells, each having a structure in which an electrolyte is sandwiched between a hydrogen electrode (fuel electrode, positive electrode, anode) and an air electrode (oxygen electrode, negative electrode, cathode), are stacked (laminated) with separators interposed between them.

[0067] Furthermore, as the cell type for "fuel cells," various types of fuel cells can be used, including polymer electrolyte fuel cells (PEFCs), solid oxide fuel cells (SOFCs), phosphoric acid fuel cells (PAFCs), and molten carbonate fuel cells (MCFCs). Of these, SOFCs have high power generation efficiency and typically operate at approximately 700 to 1000°C, making them capable of supplying considerably high-temperature exhaust gases. As mentioned above, when hydrogen gas is produced from city gas or the like using hydrogen generation reforming (U103), SOFCs can also provide the large amount of heat required for the steam reforming. Furthermore, the PEFC system operates at relatively low temperatures and allows for compact cell size, which is why it is used in many fuel cell vehicles, for example.

[0068] If the "fuel cell" in Fuel Cell U11 is a PEFC, it is also possible to use, for example, a JARI-type fuel cell developed for research and development by the Japan Automobile Research Institute (JARI), a general incorporated foundation. JARI-type fuel cells are designed to be able to increase back pressure and apply pressure to the cell, and also to recover all exhaust gases with high back pressure.

[0069] Furthermore, as the "fuel cell," it is also possible to adopt a fuel cell with a maximum output of over 10 kW, such as that manufactured by PowerCell, a Swedish fuel cell manufacturer. For example, in a 96-cell PowerCell fuel cell with a maximum output of 12.9 kW, the hydrogen gas flow rate and air flow rate required to output 10 kW of electricity are 150 liters / minute (L / min) and 500 L / min, respectively, and in this case, the flow rate of nitrogen gas contained in the exhaust gas is 400 L / min. Furthermore, the flow rate of water vapor contained in the exhaust gas is 150 L / min, which is equivalent to 5.3 liters / hour (L / h) of water.

[0070] Incidentally, a dehumidifying means (gas-liquid separator U122 in FIG. 1, water ring pump U30 in FIG. 6) is required to reduce the large amount of water vapor and moisture discharged from the fuel cell and ensure stable and reliable nitrogen gas generation. It is also preferable that the water recovered by the dehumidifying means be provided to the outside as pure water or highly purified water. It is also preferable that both air and hydrogen gas be introduced into such a fuel cell via a humidifier (not shown) to prevent a decrease in the proton conductivity of the electrolytic membrane (due to lack of humidification), which causes heat loss in the fuel cell reaction.

[0071] In this embodiment, the pressure inside the "fuel cell", i.e., the back pressure, is adjusted and controlled by the back pressure valve of the pressure control U113 and the back pressure valve of the pressure control U121, which will be described later. (a) The back pressure on the hydrogen electrode side, which is mainly adjusted by the back pressure valve of the pressure control U113, (b) The back pressure on the air electrode side, which is mainly adjusted by the back pressure valve of the pressure control U121, and It is also preferable to control the back pressures so that they are nearly equal. In fact, if there is a difference of about 0.1 atmospheres (0.01 MPa) between the two back pressures, some gas leakage may occur from the "fuel cell," but it has been experimentally shown that if the two back pressures are equal, no problems will occur even with a fairly high back pressure. In particular, if the "fuel cell" is a PEFC, it is more preferable to make the two back pressures equal, since its electrolytic membrane is relatively thin.

[0072] In addition, the fuel cell U11 equipped with the "fuel cell" described above is (a) The flow rate, pressure, and / or temperature of the hydrogen gas and air introduced into the "fuel cell"; (b) The flow rate, pressure, and / or temperature of exhaust gases and water vapor / moisture emitted from the "fuel cell"; and (c) Complex impedance between the hydrogen electrode and the air electrode of a fuel cell It is also preferable that the fuel cell is provided with a measuring system and a group of sensors capable of measuring the above, and that the operation of the "fuel cell" is controlled by an overall control U131 that receives information from the measuring system and group of sensors.

[0073] For example, as a simple example of control, a machine learning model (using, for example, a DNN (Deep Neural Network) algorithm) may be constructed using the above (b) and (c) as explanatory variables and the above (a) as the objective variable, and the constructed model may be used to adjust the flow rate, pressure, and / or temperature of the hydrogen gas or air supplied to the "fuel cell" so that the "fuel cell" produces the desired output. It is also preferable to perform control such as stopping the supply of hydrogen gas and shutting down the "fuel cell" when the complex impedance value of above (c) falls outside a predetermined allowable range.

[0074] It is also preferable that a heat exchanger that circulates a heat exchange medium such as water is placed inside or around the fuel cell U11 to extract heat from the operating fuel cell and transfer it to the outside of the unit. Examples of heat exchangers that can be used here include multi-tube heat exchangers such as shell-and-tube heat exchangers and plate heat exchangers such as Alfa Laval brazed plate heat exchangers.

[0075] Alternatively, instead of a heat exchanger, a heat conduction system can be used that connects a conductive separator in the fuel cell with a heat pipe, allowing the heat inside the fuel cell to be directly extracted to the outside. In either case, such heat exchange / conduction means can control the temperature of the fuel cell cells to a predetermined temperature (e.g., 80°C) or below, thereby maintaining optimal operation of the fuel cell. When water (cooling water) is used as the heat exchange medium, it is also preferable to use an ion exchanger to remove ions (cations and anions) from the circulating cooling water.

[0076] Incidentally, the heat transferred by the heat exchange medium or heat pipe in this way is supplied not only to the outside but also to within the system for use, and in this embodiment, it is supplied to an off-gas buffer tank 123, which will be described later, and makes it possible to further increase the temperature (for example, 45°C) of the exhaust gas supplied to the nitrogen filter U12. Of course, if the temperature of the exhaust gas is sufficiently high, such heating treatment in the off-gas buffer tank 123 is not necessary.

[0077] The heat can also be transferred to the hydrogen generation reformer U103 using such a heat exchange medium or heat pipe to replenish the heat required for steam reforming. Furthermore, the heat can be used to convert the water to be electrolyzed in the hydrogen generation unit U102 into steam or to raise the temperature of the water, thereby improving the efficiency of hydrogen generation during electrolysis.

[0078] In this case, in order to achieve and stably maintain the desired hydrogen generation efficiency, it is also preferable to monitor the temperature of the electrolytic cell with an installed temperature sensor and control the electrolysis operation with the overall control U131. Furthermore, it is also possible to perform electrolysis without using an electrolyte by increasing the voltage applied between the electrodes, thereby eliminating the need for monitoring and maintenance of the electrolyte.

[0079] Furthermore, the high-temperature medium from the heat exchanger or the high-temperature medium that has received heat transferred by the heat pipe can be used to heat the facility in which the device (system) 1 is installed, or this high-temperature medium can be introduced into a cooling tower to lower its temperature, and the low-temperature medium can be used to generate cool air in a condenser / evaporator and air conditioning unit, for example, to cool the facility. In this case, the nitrogen gas generator (system) 1 can also use power from the "fuel cell" to assist in the operation of these heating and cooling equipment, and therefore can function as an energy-saving device within the facility.

[0080] Furthermore, as another embodiment of the fuel cell U11, two or more "fuel cells" can be connected in series, and exhaust gas from the preceding fuel cell can be sequentially taken in and used for the cell reaction, making it easy to ultimately extract exhaust gas with a lower oxygen concentration, for example, exhaust gas with an oxygen concentration of 2.5 vol% or less. The inventors of the present application have disclosed a fuel cell system with this configuration that they invented in JP 2019-129110 A.

[0081] Also in FIG. 1, drains 111 and 112 are provided at the fuel passage outlet (on the hydrogen electrode side) and the air passage outlet (on the air electrode side) of the "fuel cell" in fuel cell U11, respectively, to recover water produced by condensation of water vapor contained in the exhaust gas (which usually has a relative humidity of approximately 100%). This makes it possible to suppress adverse effects on the cell reaction due to the so-called flooding phenomenon. The water recovered in this way may also be sent to hydrogen generator U102 and reused as a hydrogen generating material.

[0082] Here, by setting the back pressure of the "fuel cell" to a value exceeding atmospheric pressure (for example, 2 to 7 atmospheres, approximately 0.2 to 0.7 MPa), the dew point can be raised to increase the amount of water that falls into drains 111 and 112, thereby enhancing the dehumidification effect. It is also preferable that drains 111 and 112 have an auto-drain function that automatically discharges water to the outside when a predetermined amount of water has accumulated.

[0083] The pressure control U113 is a unit for returning the hydrogen gas that has been dehumidified in the drain 111 to the fuel line inlet (on the hydrogen electrode side) of the fuel cell (for example, downstream of the flow control U105) via, for example, a hydrogen mixer, while maintaining the set back pressure of the fuel cell. Specifically, the pressure control U113 is equipped with a back pressure valve and a pressure gauge, and controls the pressure (back pressure) within the fuel cell, particularly on the hydrogen electrode side, by adjusting this back pressure valve.

[0084] The gas-liquid separator U114 is a unit for removing residual water vapor and moisture from the exhaust gas discharged from the fuel passage outlet (on the hydrogen electrode side) of the fuel cell and passing through the drain 111 and pressure control U113. Specifically, water vapor and moisture can be removed using a dehumidifier, a dehumidifier equipped with a pressurizing mechanism, a gas-liquid separator, or a dry filter. Dehumidifiers containing silica gel and / or zeolite can be used. The gas-liquid separator can be a gravity separator, a centrifugal separator, a mist eliminator pad, a vane separator, or a pneumatic separator coalescer.

[0085] The hydrogen recovery unit U115 uses a known hydrogen gas filter and executor to extract and reuse unreacted residual hydrogen gas from the exhaust gas discharged from the fuel passage outlet (on the hydrogen electrode side). The extracted hydrogen gas can be sent back to the hydrogen mixer downstream of the flow control unit U105, for example. The extracted hydrogen gas may also be discharged to the outside.

[0086] The pressure control U121 is a unit for sending the exhaust gas (on the cathode side) that has been dehumidified in the drain 112 to the gas-liquid separator U122 while maintaining the set back pressure of the "fuel cell." Specifically, like the pressure control U113, this pressure control U121 is also equipped with a back pressure valve and a pressure gauge, and by adjusting this back pressure valve, the pressure (back pressure) within the "fuel cell," particularly on the cathode side, is controlled.

[0087] Also in Figure 1, the gas-liquid separator U122 is a unit for removing residual water vapor and moisture from the exhaust gas that is discharged from the air passage outlet (on the air electrode side) of the "fuel cell" and passes through the drain 112 and pressure control U121. Specifically, the water vapor and moisture can be removed using a dehumidifier, a dehumidifying device equipped with a pressurizing mechanism, or a gas-liquid separator. Incidentally, as one standard, the gas-liquid separator U122 may be one that suppresses the relative humidity in the exhaust gas to 60% or less, more preferably 30% or less.

[0088] As will be described in detail later with reference to FIG. 7, the gas-liquid separator U122 may be a dry filter unit using a dry filter 122f (FIG. 7). As another preferred embodiment, as will be described in detail later with reference to FIG. 6, a water ring pump U30 equipped with a water ring pump 301 may be used as a dehumidifying means instead of the gas-liquid separator U122. Furthermore, the gas-liquid separator U122 may be a pump unit equipped with a dry vacuum pump. A dry vacuum pump is a vacuum pump that does not use oil or liquid in the vacuum chamber and can be used, for example, to evacuate water vapor. For example, an air-cooled dry vacuum pump such as the NeoDry 60E manufactured by Kashiyama Kogyosho may be used as such a dry vacuum pump. This air-cooled dry vacuum pump has a structure in which a pair of multi-stage roots rotors rotate without contact to compress and evacuate gas.

[0089] The off-gas buffer tank 123 is a gas tank that temporarily preserves and stores the exhaust gas introduced from the gas-liquid separator U122. This exhaust gas is introduced into the off-gas buffer tank 123 until the pressure becomes the same as the set back pressure (e.g., 1.1 to 7 atmospheres, approximately 0.11 to 0.7 MPa). Furthermore, in order to allow the exhaust gas to flow into the nitrogen filter U12 (described later) at a desired pressure (e.g., 7 atmospheres, approximately 0.7 MPa), it is also preferable that the flow rate of this exhaust gas into the off-gas buffer tank 123 be set to a flow rate equal to or exceeding the required introduction flow rate into the nitrogen filter U12.

[0090] Incidentally, when the "fuel cell" is stopped, the pressure in the piping to the off-gas buffer tank 123 returns to, for example, atmospheric pressure. Therefore, it is preferable that the off-gas buffer tank 123 is equipped with a check valve to prevent backflow of exhaust gas to the "fuel cell." It is also preferable that the off-gas buffer tank 123 is equipped with a gas pressure gauge so that the gas pressure in the tank can be measured at each point in time.

[0091] Furthermore, it is also preferable that the off-gas buffer tank 123 uses a "heating means" capable of performing a heating process using the heat generated by the "fuel cell" in the fuel cell U11 to heat the exhaust gas in the tank to a temperature higher than room temperature (for example, 30 to 45°C). This makes it possible to supply exhaust gas at a temperature suitable for nitrogen filtering to the nitrogen gas filter 12f of the nitrogen filter U12, which will be described later.

[0092] Here, the above-mentioned "heating means" may be a heat exchanger or a separator-heat pipe connection system, as already explained. This makes it possible to effectively utilize the heat of the "fuel cell" to perform an appropriate nitrogen filtering process without using an energy consuming means such as an electric heater. Of course, if the temperature of the exhaust gas introduced into the off-gas buffer tank 123 is sufficiently high, such heating means is not necessary.

[0093] The booster U124 further boosts the exhaust gas extracted from the "fuel cell" of the fuel cell U11, with its moisture or water vapor content reduced (for example, to a pressure of 7 atmospheres (approximately 0.7 MPa)), and supplies it to the nitrogen filter U12. A known compression pump, such as Hitachi Industrial Equipment Systems' Bebicon (registered trademark) POD-7.5VNB, can be used as this booster U124. Alternatively, a known booster valve, such as SMC's inert gas booster valve VB11A or VBA42, can also be used. It is also preferable to provide a pressure gauge to monitor the boosted exhaust gas pressure.

[0094] Here, most of the known booster valves are of the air-driven type, and in this case, the booster valve may be driven using a portion of the compressed air supplied to the "fuel cell", i.e., compressed air taken out from the air tank 107, as support gas. This eliminates the need for additional power consumption for driving the booster valve. It is also preferable to use a booster-type compressor as the booster valve U124.

[0095] As mentioned above, if the pressure of the exhaust gas from the off-gas buffer tank 123 is sufficiently high (for example, 7 atmospheres (approximately 0.7 MPa)), the pressure booster U124 is of course not necessary. Also, although care must be taken in handling it, it is possible to use hydrogen gas extracted from the hydrogen tank 104 as this support gas.

[0096] Also in Figure 1, the corrosive gas removal unit U125 is a unit that can perform processing to remove or reduce at least one of sulfides, chlorides, hydrocarbons, fluorides, and strong alkaline compounds from exhaust gas (extracted from the "fuel cell") that is then to be applied to the nitrogen gas filter 12f of the nitrogen filter U12.

[0097] For example, if hydrogen gas is generated from city gas or other sources using the hydrogen generation reformer U103 and used as fuel in a fuel cell, the resulting exhaust gas will contain various gas components other than hydrogen gas, such as hydrogen sulfide, sulfur dioxide, hydrocarbon gases such as methane, ammonia, and formaldehyde. Furthermore, if an SOFC is used in a fuel cell, nitrogen gas in the air can combine with oxygen in a high-temperature atmosphere of around 800°C, generating nitrogen oxides (NOx). These gases not only become impurities in the final nitrogen gas product, but also pose a risk of adversely affecting the hollow fiber fibers of the nitrogen gas filter 12f.

[0098] Therefore, the corrosive gas removal unit U125 is equipped with, for example, an activated carbon filter, and serves to remove or minimize the amount of impurity gases in the exhaust gas. Incidentally, one standard for the corrosive gas removal unit U125 is to limit the concentration of hydrocarbon gases to 0.013 mg / Nm3. 3 It is also preferable to keep the concentrations of strongly acidic gases such as hydrogen sulfide, sulfur dioxide, hydrogen chloride, and fluorine, and strongly alkaline gases such as amines, ammonia, and caustic soda below the detection limit of a predetermined detection method.

[0099] Furthermore, as shown in Figure 1, it is also preferable to install a mist filter and a dust filter before and after the corrosive gas removal unit U125. Of these, the mist filter is a filter that removes or reduces mist such as water mist, solvent mist, and oil mist in the exhaust gas. As one standard, this mist filter reduces the concentration of residual oil from these mist to 0.01 mg / Nm3. 3 It is also preferable to keep it to 0.008 ppm wt or less. On the other hand, a dust filter is a filter that removes or reduces dust in exhaust gas. As one standard, it is also preferable for a dust filter to remove almost all particles with a particle size of 0.01 μm or more.

[0100] The temperature regulator U126 is a unit equipped with, for example, an electric heater, for adjusting the temperature of the exhaust gas taken in to approach or match a preset suitable temperature based on the characteristics of the nitrogen gas filter 12f, and supplying the temperature-adjusted exhaust gas to the nitrogen filter U12. In one preferred embodiment, the temperature regulator U126 may receive heat supplied from the fuel cell U11 via a heat exchanger and use it for temperature adjustment, or may adjust the exhaust gas temperature using power supplied from the fuel cell U11.

[0101] Incidentally, the UBE N2 separator NM-B01A manufactured by Ube Industries, which can be used as the nitrogen gas filter 12f (described in detail later), is said to have a high filtering effect when the temperature of the introduced gas is 30 to 45°C, which is higher than room temperature (25°C). In this case, when the exhaust gas from the "fuel cell" is higher than room temperature (25°C), it is possible to enjoy this high filtering effect without using the temperature adjustment unit U126. It is also possible to reduce the amount of power consumed for temperature adjustment.

[0102] It is also known that in the nitrogen gas filter 12f, which uses fibers with different permeabilities for nitrogen and oxygen, the recovery rate drops significantly as the temperature of the introduced exhaust gas increases. Therefore, depending on the nitrogen gas output performance set in this system, it may be possible to maintain the temperature of the exhaust gas at approximately the same temperature as in the off-gas buffer tank 123 without using the temperature regulator U126 in order to ensure a predetermined recovery rate.

[0103] Also in Figure 1, the nitrogen filter U12 is a unit that applies exhaust gas supplied from the flow control U127 to a nitrogen gas filter 12f made of fibers with different permeability to nitrogen and oxygen, and extracts exhaust gas with an increased nitrogen concentration, i.e., high-purity nitrogen gas in this embodiment, from this nitrogen gas filter 12f.

[0104] Specifically, in this embodiment, the nitrogen filter U12 is (a) a nitrogen gas filter 12f; (b) a filter input / output section that introduces exhaust gas into the nitrogen gas filter 12f to act on it and extracts exhaust gas with an increased nitrogen concentration from the nitrogen gas filter 12f; (c) A filter purge section that extracts gas containing oxygen molecules (hereinafter referred to as filter exhaust gas) separated from nitrogen molecules (in the exhaust gas) by the nitrogen gas filter 12f separately from the exhaust gas extracted in (b) above. It is equipped with:

[0105] Specifically, the nitrogen gas filter 12f can be a hollow fiber filter (hollow fiber filter) made of a polymer fiber material that allows oxygen molecules to pass through preferentially over nitrogen molecules. For example, the UBE N2 Separator NM-B01A manufactured by Ube Industries, Ltd., which uses polyimide hollow fibers, can be used. As high-pressure exhaust gas flows through the hollow fibers, oxygen molecules selectively pass through the hollow fiber membrane, ultimately extracting highly purified nitrogen gas from the hollow fiber outlet.

[0106] Of course, the nitrogen gas filter 12f is not limited to this separator. For example, a separator from the UBE N2 Separator NM series manufactured by Ube Industries, a SEPURAN N2 membrane module manufactured by Daicel-Evonik, or a selective-type nitrogen gas filter also manufactured by Daicel-Evonik can also be used as the nitrogen gas filter 12f.

[0107] Here, in such a nitrogen gas filter 12f, (a) The oxygen concentration of the introduced exhaust gas (introducing oxygen concentration), the pressure of the introduced exhaust gas (introducing pressure), and the flow rate of the exhaust gas at the outlet of the filter 12f (outlet flow rate), (b) The oxygen concentration of the exhaust gas at the outlet of the filter 12f (outlet oxygen concentration) and the recovery rate of the filter 12f The relationship between these factors will be explained in detail later using examples shown in Figures 2 to 5. Various conditions for obtaining highly pure nitrogen gas will also be explained there.

[0108] The outlet flow rate (a) above can be measured by a flow meter installed on the outlet side of the nitrogen filter U12 and controlled by the flow control U127 described below. Similarly, the outlet oxygen concentration (b) above can be measured by an oxygen concentration meter installed on the outlet side of the nitrogen filter U12. Of course, it is also preferable to install the flow control U127 immediately after these oxygen concentration meter and flow meter.

[0109] Furthermore, in this embodiment, based on the outlet oxygen concentration measured by this oxygen concentration meter, the overall control U131 can, for example, control the back pressure valve of the pressure control U121 to adjust the set back pressure of the "fuel cell", or control the mass flow controller of the flow control U127 to adjust the exhaust gas flow rate to the filter, thereby making it possible to supply high-purity nitrogen gas with the desired extremely low oxygen concentration.

[0110] 1, the flow control U127 is a unit that controls the flow rate of the exhaust gas with an increased nitrogen concentration generated by the nitrogen filter U12, i.e., high-purity nitrogen gas in this embodiment, and sends the nitrogen gas to the nitrogen tank 129 via the pressure booster U128. That is, as described above, this is a unit that controls the outlet flow rate (f_out) of the nitrogen gas filter 12f. Specifically, it can be equipped with a gas regulator and a mass flow controller (or a flow switch).

[0111] In this embodiment, the pressure booster U128 is a unit that further boosts the pressure of the high-purity nitrogen gas whose flow rate has been controlled by the flow control U127 (for example, to a pressure of 8 to 15 atmospheres (approximately 0.8 to 1.5 MPa)) and sends it to the nitrogen tank 129, thereby preserving and storing a larger amount of high-purity nitrogen gas in the nitrogen tank 129. For example, a boost pressure booster valve or a boost compressor can be used as this pressure booster U128. For example, the Booster Bebicon (registered trademark) OBB-7.5GP manufactured by Hitachi Industrial Equipment Systems Co., Ltd., which can boost the pressure to 10 atmospheres (approximately 1.0 MPa) or more, may be used. It is also preferable that a pressure gauge be provided to monitor the pressure boost.

[0112] The nitrogen tank 129 temporarily stores and preserves the high-purity nitrogen gas supplied from the nitrogen filter U12 via the pressure booster U128, and serves as a nitrogen gas supply interface that stably supplies the high-purity nitrogen gas to the outside, for example, under the control of the overall control U131. It is also preferable that the nitrogen tank 129 is provided with a gas pressure gauge so that the gas pressure inside the tank can be measured at any time.

[0113] It is also possible to supply the generated nitrogen gas directly to the outside from the nitrogen filter U12 via a predetermined flow control means without using the nitrogen tank 129 (and pressure booster U128) as such a nitrogen gas supply interface. For example, if the supply destination is a soldering device or the like, high-purity nitrogen gas that is supplied directly and has a temperature at least above room temperature (25°C) is more preferable because it saves the amount of heat required to further increase the temperature when used as a soldering atmosphere.

[0114] The overall control U131 is capable of communicating with the major components including the fuel cell U11 and nitrogen filter U12 described above, and preferably with all components (including, for example, the water ring pump U30 (Figure 6)) via a wired or wireless communication network, and is a control unit that receives measured quantities output from the measuring units and sensors of each component, such as pressure, gas flow rate, temperature, nitrogen concentration, oxygen concentration, hydrogen concentration, and the presence or absence of hydrogen leakage, and monitors them as appropriate to monitor and control each component.

[0115] For example, it is also preferable that the overall control U131 is equipped with a processor and memory, and that the memory stores and is equipped with a nitrogen gas generation system monitoring and control program for monitoring and controlling each component, and that the program is executed by the processor.

[0116] The control performed by the overall control U131 includes adjustment and control of the pressure, gas flow rate, temperature, nitrogen concentration, oxygen concentration, hydrogen concentration, etc., in each component and between each component. In particular, it is also preferable to control the back pressure in the "fuel cell" of the fuel cell U11 and to control the balance between the back pressure on the hydrogen electrode side and the back pressure on the air electrode side.

[0117] It is also preferable that the overall control U131 monitors the temperature (cell temperature) of the "fuel cell" of the fuel cell U11, the temperature of the exhaust gas introduced into the nitrogen gas filter 12f of the nitrogen filter U12, and the temperature of the hydrogen generation U102, etc., to appropriately control the fuel cell reaction, filtering operation, and hydrogen generation (electrolysis) reaction in the nitrogen gas generation device (system) 1. Furthermore, it is also preferable to monitor the presence or absence of hydrogen leakage in each component and between each component, and if it is determined that a problem has occurred, to send an alarm containing information about the location of the hydrogen leakage to the outside.

[0118] [Example 1] 2 to 4 are graphs for explaining Example 1 of the nitrogen gas generation process according to the present invention.

[0119] In Example 1, the measurement results and analysis results of which are shown in FIGS. 2 to 4, a UBE N2 separator NM-B01A manufactured by Ube Industries was used as the nitrogen gas filter 12f (FIG. 1). Air having an oxygen concentration of 20.8 vol% and three types of mixed gases of nitrogen gas and oxygen gas having oxygen concentrations of 10.3 vol%, 5.1 vol%, and 1.1 vol%, respectively, were introduced into this nitrogen gas filter 12f at room temperature (25°C). (a) The oxygen concentration of the introduced gas (introduced oxygen concentration c_in_O2 (vol%)), the pressure of the introduced gas (introduced pressure p_in (atmospheric pressure)), and the flow rate of the exhaust gas at the outlet of the nitrogen gas filter 12f (outlet flow rate f_out (L / min, liters / minute)), (b) Oxygen concentration of the gas at the outlet of the nitrogen gas filter 12f (outlet oxygen concentration c_out_O2 (ppm vol)) We measured the above and investigated the relationship between (a) and (b).

[0120] Incidentally, the oxygen concentrations of 10.3 vol%, 5.1 vol%, and 1.1 vol% in the introduced gas are all values that are realized in the exhaust gas of an actual "fuel cell."

[0121] Figures 2(A), (B), and (C) show graphs showing the relationship between the inlet oxygen concentration c_in_O2 and the outlet oxygen concentration c_out_O2 when the outlet flow rate f_out is 2.0 L / min, 1.5 L / min, and 1.0 L / min, respectively.

[0122] According to these graphs, (a) The smaller the introduced oxygen concentration c_in_O2, (b) The larger the introduction pressure p_in, (c) The smaller the outlet flow rate f_out, It can be seen that the outlet oxygen concentration c_out_O2 becomes smaller, and nitrogen gas with higher purity is output from the nitrogen gas filter 12f.

[0123] For example, if the inlet oxygen concentration c_in_O2 is 1.1%, the inlet pressure p_in is 7.0 atmospheres (approximately 0.7 MPa), and the outlet flow rate f_out is 1.0 L / min, the outlet oxygen concentration c_out_O2 (as shown in Figure 2(C)) is 325 ppm (0.0325 vol%). It has also been shown that if the outlet flow rate f_out is set to an even smaller value of 0.75 L / min under the same inlet oxygen concentration and inlet pressure, the outlet oxygen concentration c_out_O2 becomes a very small value of 190 ppm (0.0190 vol%), resulting in high-purity nitrogen gas with an extremely low oxygen concentration. It has been experimentally confirmed that this tendency in results remains roughly unchanged even when the temperature of the gas introduced into the nitrogen gas filter 12f is 40°C or 50°C.

[0124] <Outlet flow rate and outlet oxygen concentration> First, a more specific relationship between the outlet flow rate f_out and the outlet oxygen concentration c_out_O2 will be described. From the data of the graphs shown in Figures 2(A) to 2(C), the relationship between the two is expressed by the following equation: (1) (c_out_O2)=C·(f_out) a It is derived that the relationship expressed as follows holds. The coefficient C of the (a) term takes a positive value, and the smaller the introduced oxygen concentration c_in_O2 is and the larger the introduced pressure p_in is, the smaller the value becomes. For example, when the introduced oxygen concentration c_in_O2 is 1.1% and the introduced pressure p_in is 7.0 atmospheres (approximately 0.7 MPa), the C value becomes 319 (ppm), which is a very small value. (b) The power coefficient a is almost independent of the introduced oxygen concentration c_in_O2, and is around 1.6 when the introduced pressure p_in is 4.0 atmospheres (approximately 0.4 MPa). The larger the introduced pressure p_in, the larger the value becomes, reaching around 2.0 when the introduced pressure p_in is 7.0 atmospheres (approximately 0.7 MPa).

[0125] Therefore, in any case, it can be understood that the smaller the outlet flow rate f_out, the smaller the outlet oxygen concentration c_out_O2 can be, that is, high-purity nitrogen gas with a lower oxygen concentration can be obtained. Here, since the power coefficient a is determined only by the introduction pressure p_in, the mechanism by which the outlet flow rate contributes to the outlet oxygen concentration is thought to be dynamic and related to the state of the fibers of the filter 12f, which is determined by the introduction pressure.

[0126] <Introduced oxygen concentration and filtering effect> Next, the relationship between the introduced oxygen concentration c_in_O2 and the filtering effect of the nitrogen gas filter 12f, that is, the degree of the oxygen concentration reduction effect, will be described using the analysis results shown in FIG.

[0127] 3(A), (B), and (C) show graphs illustrating the relationship between the introduced oxygen concentration c_in_O2 and the oxygen concentration reduction index when the outlet flow rate f_out is 2.0 L / min, 1.5 L / min, and 1.0 L / min, respectively. Note that the four curves shown in each of these graphs are power approximation curves for data points when the introduced pressure p_in is 4.0 atmospheres (approximately 0.40 MPa), 5.0 atmospheres (approximately 0.51 MPa), 6.0 atmospheres (approximately 0.61 MPa), and 7.0 atmospheres (approximately 0.71 MPa), respectively.

[0128] Here, the oxygen concentration reduction index is calculated by the following formula, where c_out_O2(Air) is the outlet oxygen concentration when air with an oxygen concentration of 20.8 vol% is introduced into the nitrogen gas filter 12f. (2) (Oxygen concentration reduction index)=c_out_O2(Air) / c_out_O2 It is an index calculated by taking the result of filtering with air as the standard and expressing the absolute degree of reduction in oxygen concentration due to filtering, that is, the magnitude of the filtering effect (relative to the case of air as the standard).

[0129] According to the graphs in Figures 3(A), (B) and (C), (a) The oxygen concentration reduction index increases as the introduced oxygen concentration c_in_O2 decreases. In particular, the rate of increase becomes rapidly larger when the introduced oxygen concentration c_in_O2 exceeds 10 vol%. (b) The oxygen concentration reduction index does not show a significant dependency on the inlet pressure p_in. (c) The oxygen concentration reduction index does not show any significant dependency on the outlet flow rate f_out. Incidentally, the introduced oxygen concentration c_in_O2=10 vol%, at which the rate of increase of the oxygen concentration reduction index in (a) above begins to increase sharply, roughly corresponds to the oxygen concentration in the exhaust gas of a "fuel cell" with an oxygen utilization rate of 50%.

[0130] Furthermore, from the above analysis results, it can be seen that, for example, to find filtering conditions that result in an oxygen concentration reduction index of 10, i.e., a filtering effect 10 times greater (one order of magnitude higher) than that of air, the introduced oxygen concentration c_in_O2 should be set to 2.5 vol% or less, regardless of the settings of the introduced pressure p_in or the outlet flow rate f_out. Here, the value c_in_O2 = 2.5 vol% is the average of the introduced oxygen concentration values for which the oxygen concentration reduction index is 10 in the four power approximation curves in each graph. Incidentally, the horizontal axis intercept of the tangent line at around c_in_O2 = 1.1 vol% in each graph curve also has a value near 2.5 vol% (= c_in_O2).

[0131] Therefore, in the nitrogen gas generator (system) 1 of the embodiment shown in Figure 1, by applying exhaust gas with an oxygen concentration of 2.5 vol% or less to the nitrogen gas filter 12f, it is possible to extract exhaust gas from this filter 12f with an oxygen concentration of 1 / 10 or less compared to the result when air is applied. Incidentally, it has been confirmed through experiments that the graph of Figure 3 described above is generally consistent, especially in the low oxygen concentration range, even when the temperature of the gas introduced into the nitrogen gas filter 12f is 40°C and 50°C.

[0132] <Inlet pressure and outlet oxygen concentration> Next, the relationship between the introduction pressure p_in and the outlet oxygen concentration c_out_O2 will be explained using the analysis results shown in FIG.

[0133] FIG. 4 shows the ratios of the quadratic coefficients to the linear coefficients in the four polynomial (quadratic) approximation equations corresponding to the four graph curves in each of the graphs shown in FIGS. 2(A) to 2(C). Relationship between inlet pressure p_in and (second-order coefficient) / (first-order coefficient) The graph shows:

[0134] 2(A) to 2(C) show four graph curves that represent the relationship between the inlet oxygen concentration c_in_O2 and the outlet oxygen concentration c_out_O2 when the inlet pressure p_in is 4.0 atmospheres (approximately 0.40 MPa), 5.0 atmospheres (approximately 0.51 MPa), 6.0 atmospheres (approximately 0.61 MPa), and 7.0 atmospheres (approximately 0.71 MPa), and furthermore, a polynomial (quadratic) approximation formula corresponding to the graph curve is written near each graph curve. For example, near the graph curve for p_in=7.0 atmospheres (and f_out=1.0 L / min) in the graph of FIG. 2(C), (3) y=6.6246x 2 +161.96 where y is c_out_O2 (vol%) and x is c_in_O2 (vol%) In this case, the quadratic coefficient is 6.6246 and the linear coefficient is 161.96.

[0135] As described above, the introduced oxygen concentration c_in_O2 not only contributes (proportionally) to the outlet oxygen concentration c_out_O2 as a linear term, but also has an effect as a quadratic term. In other words, if the introduced oxygen concentration c_in_O2 becomes 1 / N, the outlet oxygen concentration c_out_O2 does not simply become 1 / N, but the quadratic term of the introduced oxygen concentration c_in_O2 affects the outlet oxygen concentration c_out_O2.

[0136] The ratio of the second-order coefficient to the first-order coefficient, (second-order coefficient) / (first-order coefficient), as described above, was calculated for each curve in each of the graphs in Figures 2(A) to (C), and these calculated values were plotted on a graph with the vertical axis representing (second-order coefficient) / (first-order coefficient) and the horizontal axis representing the introduction pressure p_in, resulting in the graph in Figure 4.

[0137] According to the graph in Figure 4, three graph curves (straight lines in Figure 4) are obtained where the outlet flow rates f_out are 1.0 L / min, 1.5 L / min, and 2.0 L / min, respectively, and it can be seen that the graph points in Figure 4 can be approximated by a linear approximation formula determined for each outlet flow rate.

[0138] According to these graph curves (straight lines), the (quadratic coefficient) / (linear coefficient) ratio increases as the inlet pressure p_in increases and as the outlet flow rate f_out decreases. Therefore, it can be seen that the quadratic term of the inlet oxygen concentration c_in_O2 contributes to reducing the outlet oxygen concentration c_out_O2.

[0139] From this, it can be understood that in order to obtain nitrogen gas with higher purity (to reduce the outlet oxygen concentration c_out_O2), it is preferable to increase the proportion of the quadratic term in the inlet oxygen concentration c_in_O2, i.e., (quadratic coefficient) / (linear coefficient), in positive values, and that it is important to set it to a value exceeding 0 (zero), at which the contribution of the quadratic term disappears. In other words, it is preferable to express the quadratic term exceeding a positive value.

[0140] Therefore, from the graph of FIG. 4, the conditions under which the (second-order coefficient) / (first-order coefficient) ratio exceeds 0 (zero) were found. It was found that the conditions are when the inlet pressure p_in exceeds 2.94 atmospheres (approximately 0.298 MPa), 3.40 atmospheres (approximately 0.344 MPa), and 3.86 atmospheres (approximately 0.391 MPa) when the outlet flow rate f_out is 1.0 L / min, 1.5 L / min, and 2.0 L / min, respectively. It can also be seen that these pressure thresholds take larger values as the outlet flow rate f_out increases. In other words, when the outlet flow rate f_out is set to a smaller value, it becomes possible to set the inlet pressure p_in based on the smaller pressure threshold.

[0141] Furthermore, from the above analysis results, it can be understood that in the nitrogen gas generation device (system) 1 of the embodiment shown in Figure 1, it is also preferable to set the exhaust gas pressure (inlet pressure) acting on the nitrogen gas filter 12f to a pressure value that exceeds the pressure threshold determined by the nitrogen gas filter 12f, and which increases as the flow rate (outlet flow rate) of the exhaust gas when extracted from the nitrogen gas filter 12f increases.

[0142] [Example 2] FIG. 5 is a graph for explaining Example 2 in which the recovery rate of the nitrogen gas filter 12f in the nitrogen gas generation process according to the present invention was examined.

[0143] In Example 2, the recovery rate of the nitrogen gas filter 12f is measured using the same system as in Example 1, with the same conditions set as in Example 1 for the introduced oxygen concentration, introduction pressure, and outlet flow rate. However, in Example 2, measurements are also made when the introduced oxygen concentration c_in_O2=0 (zero), that is, when pure nitrogen gas is introduced into the filter 12f. The recovery rate, which is a measurement item in Example 2, is the degree of gas recovery in the filter 12f, and is calculated using the following equation, where the flow rate of the introduced gas at the inlet of the filter 12f (introduced flow rate) is f_in: (4) (recovery rate) = (f_out) / (f_in) The ratio is calculated as follows:

[0144] Figures 5(A), (B), and (C) show graphs showing the relationship between the introduced oxygen concentration c_in_O2 and the recovery rate under conditions where the outlet flow rate f_out is 2.0 L / min, 1.5 L / min, and 1.0 L / min, respectively.

[0145] According to these graphs, (a) (Although there may be some deviations under the condition of 4.0 atmospheres (approximately 0.40 MPa)) The smaller the introduced oxygen concentration c_in_O2, (b) (Although the difference between 4.0 atmospheres (approximately 0.40 MPa) and 5.0 atmospheres (approximately 0.51 MPa) is very small) the smaller the introduction pressure p_in, (c) (This is highly probable given the definition of recovery rate) The larger the outlet flow rate f_out, The recovery rate becomes larger, and it can be seen that even if a predetermined flow rate of exhaust gas is introduced into the nitrogen gas filter 12f, a larger amount of nitrogen gas (which is exhaust gas with a reduced oxygen concentration) is obtained.

[0146] Regarding the inlet oxygen concentration c_in_O2 in (a) above, the direction of increasing the recovery rate and the direction of decreasing the outlet oxygen concentration c_out_O2 (as shown in FIG. 2, for example) are consistent. Specifically, by decreasing the inlet oxygen concentration c_in_O2, it is possible to further reduce the outlet oxygen concentration and increase the recovery rate. Therefore, in order to generate more nitrogen gas with higher purity, it is more preferable to use a nitrogen gas filter that increases the recovery rate as the oxygen concentration of the gas to be filtered decreases.

[0147] This also shows that a combined system of a "fuel cell" that outputs exhaust gas with a low oxygen concentration and the above-mentioned "nitrogen gas filter" that utilizes that exhaust gas is a very compatible system, in other words, a system that can efficiently generate nitrogen gas, from the standpoint of both the outlet oxygen concentration and the recovery rate.

[0148] On the other hand, with regard to the inlet pressure p_in (b) and the outlet flow rate f_out (c) above, the direction of increasing the recovery rate and the direction of decreasing the outlet oxygen concentration c_out_O2 (as shown in Figure 2, for example) are opposite directions, and the recovery rate and the outlet oxygen concentration c_out_O2 are in a so-called trade-off relationship.

[0149] Therefore, for example, if the inlet pressure p_in is increased, high-purity nitrogen gas with a lower oxygen concentration can be obtained, but on the other hand, the amount of exhaust gas required to obtain a predetermined amount of that nitrogen gas, and therefore the amount of air required to be input into the ``fuel cell'', will increase.

[0150] Therefore, it is also preferable to adjust the settings of the inlet pressure p_in and the outlet flow rate f_out to ensure a predetermined recovery rate while realizing a desired low outlet oxygen concentration c_out_O2 in accordance with the nitrogen gas output performance set in the nitrogen gas generator (system) 1 (FIG. 1). For example, it is also preferable to determine while controlling the inlet pressure p_in and the outlet flow rate f_out (and the recovery rate, which depends on them) in order to achieve the performance content of producing nitrogen gas of a predetermined purity or higher (e.g., 99.9 vol% or higher) at a predetermined production cost (e.g., at a production cost equal to or lower than that of a PSA device, as described below).

[0151] Regarding the trade-off between the recovery rate and the outlet oxygen concentration c_out_O2 with respect to the inlet pressure p_in in (b) above, the inventors of the present application believe that this is also related to the fact that in the nitrogen gas filter 12f of Example 2 (Example 1), in which the filter fibers are hollow fibers, as the inlet pressure p_in increases, the hollow fibers expand, causing changes not only in the oxygen molecule selectivity of the filter fibers but also in their permeability to molecules other than oxygen molecules.

[0152] Furthermore, with regard to the recovery rate described above, the inventors of the present application have confirmed that the higher the temperature of the gas introduced into the nitrogen gas filter 12f, the smaller the recovery rate becomes, and that the recovery rate drops significantly at temperatures above a certain level. Therefore, it is also preferable that the temperature adjuster U126 (FIG. 1) installed upstream of the nitrogen filter U12 in the nitrogen gas generator (system) 1 (FIG. 1) adjusts the temperature of the exhaust gas, taking into consideration the need to ensure a predetermined recovery rate in the nitrogen gas filter 12f.

[0153] Regarding the effect of the temperature of the introduced gas on the recovery rate, the inventors of the present application believe that as the temperature increases, the hollow fibers of the nitrogen gas filter 12f expand, which changes not only the oxygen molecule selectivity of the filter fibers but also their permeability to molecules other than oxygen molecules.

[0154] 2 to 5, Examples 1 and 2 have been described above. Based on the findings obtained from these experiments, the inventors of the present application have succeeded in generating high-purity nitrogen gas having a purity (nitrogen concentration) exceeding 99.9 vol% and an oxygen concentration of less than 0.1 vol% (1000 ppm vol) using a nitrogen gas generation device (system) 1. Such high-purity nitrogen gas can be used in reflow soldering equipment, which has strict purity requirements. Incidentally, even in reflow soldering equipment, nitrogen gas with a purity (nitrogen concentration) of 99 vol% can be used, depending on the type of solder paste used.

[0155] Needless to say, the demand for nitrogen gas is not limited to electronic and electrical fields that use soldering equipment. In fact, nitrogen gas is used for a variety of purposes in a wide range of fields, including the metal and resin fields, which use nitrogen gas for laser processing and heat treatment, the transportation field, which requires nitrogen gas for tire filling and shipboard purging equipment, the chemical field, which uses nitrogen gas as a process gas, pressure transport gas, and cooling gas, the machinery field, which requires nitrogen gas for dry cutting equipment, and the food field, which uses nitrogen gas for food preservation and gas filling, and in CA (Controlled Atmosphere) storage atmosphere supply equipment and fryer equipment.

[0156] Therefore, the required purity (nitrogen concentration) of nitrogen gas also varies depending on the field and application. For example, in some cases the concentration of oxygen gas as an impurity gas (oxygen concentration) is required to be on the order of 0.01 vol% (100 ppm vol), while in other cases an oxygen concentration of up to a few vol% is acceptable.

[0157] In such a situation, the nitrogen gas generator (system) 1 can appropriately provide nitrogen gas in which the residual oxygen is suppressed to the required upper limit of the oxygen concentration by adjusting, for example, the inlet oxygen concentration c_in_O2, the inlet pressure p_in, and the outlet flow rate f_out. For example, in a case where the oxygen concentration can be as low as a few vol%, it is possible to increase the recovery rate by setting the inlet oxygen concentration c_in_O2 to, for example, 10 vol%, suppressing the inlet pressure p_in lower, and increasing the outlet flow rate f_out.

[0158] Furthermore, the nitrogen gas generator (system) 1 can also provide the electricity and heat required for the generated nitrogen gas, depending on the field and application. In this regard, it is naturally difficult or impossible for conventional nitrogen gas generators to provide such energy supplies.

[0159] Furthermore, based on the findings described above, the inventors have confirmed that the nitrogen gas generation system 1 according to the present invention can significantly reduce the cost of generating nitrogen gas. For example, according to research by the inventors, the current selling price of a nitrogen gas cylinder is, for example, 430 yen / Nm 3 The selling price of liquid nitrogen is about 120 yen / Nm 3 In addition, the cost of generating nitrogen gas using a PSA (pressure swing adsorption) device, which is a widely used nitrogen gas generating device, is about 48 yen / Nm 3 It will be about that amount.

[0160] In response to these issues, calculations have confirmed that with the nitrogen gas generator (system) 1, by setting appropriate conditions, including the standard output of the "fuel cell," the possible exhaust gas flow rate, and even the expected hydrogen procurement cost, it is possible to achieve generation costs that are equal to or lower than those of, for example, the PSA device described above. Furthermore, in cases where the nitrogen gas generator (system) 1 also provides the (required) electricity and heat, as described above, the overall procurement costs, including these, can be significantly reduced compared to conventional methods.

[0161] [Another embodiment of the dehumidifying means: Water ring pump U] FIG. 6 is a schematic diagram for explaining another embodiment of the dehumidifying means according to the present invention.

[0162] First, FIG. 6(A) shows a water ring pump U30 that receives exhaust gas extracted from the air electrode side (drain 112) of the "fuel cell" of the fuel cell U11 via a flow control valve, reduces the moisture or water vapor content in the exhaust gas, and sends the dehumidified exhaust gas toward the off-gas buffer tank 123.

[0163] Here, the water ring pump U30 is equipped with a water ring pump 301, which is a water ring vacuum pump, and a gas-liquid separation tank 302, and further incorporates a heat exchanger (part of the heat exchanger U40) for cooling the circulating sealing liquid.

[0164] Of these, the water ring pump 301 is (a) The sealing liquid (sealing water) contained in the pump casing forms a crescent-shaped water film inside the pump due to the centrifugal force caused by the eccentric rotation of the impeller 301a, which is the impeller. (b) The volume of the sealed space formed between this water film of sealing liquid and two adjacent blades of the impeller 301a changes periodically with the eccentric rotation of the impeller 301a, causing this water film of sealing liquid to act as a piston and seal, specifically drawing exhaust gas into the casing, compressing it within the casing, and then discharging it outside the casing together with the sealing liquid. Of course, the structure of the water ring pump 301 is not limited to that shown in Fig. 6(A), and various structures related to water ring pumps can be used.

[0165] The gas-liquid separation tank 302 receives the mixture of exhaust gas and sealing liquid discharged from the water ring pump 301, separates the water and steam content in the exhaust gas from the sealing liquid, and serves as a water storage tank for storing the separated sealing liquid (containing water and steam). The stored sealing liquid is returned to the water ring pump 301 by a pump (via a heat exchanger that is part of the heat exchanger U40) and is used again. When the stored sealing liquid exceeds a predetermined amount, part of it is discharged to the outside of the tank as overflow water.

[0166] In the water ring pump 301, the impeller 301a is rotated at high speed by a motor, and the temperature of the sealing liquid usually rises due to frictional heat, and if it is not cooled, the sealing liquid may boil. Therefore, for example, if the sealing liquid reaches a predetermined temperature (for example, 50°C) or higher, it is cooled by passing it through a heat exchanger (part of the heat exchanger U40).

[0167] The heat exchanger U40 thus adjusts (cools) the temperature of the sealing liquid in the water seal pump U30, but in the embodiment shown in Figure 6(A), it also extends another heat exchanger that is part of itself into the fuel cell U11, and adjusts (cools) the temperature of the "fuel cell."

[0168] That is, the heat exchanger U40 can be configured by arranging a heat exchanger connected to the water seal pump U30 and a heat exchanger connected to the fuel cell U11 in series, using a common chiller pump, for example, to receive heat from the seal liquid and the fuel cell and simultaneously adjust (cool) their temperatures. Alternatively, both heat exchangers can be arranged in parallel to simultaneously adjust (cool) their temperatures. Of course, it is also possible to control each heat exchanger independently. Furthermore, the heat exchanger U40 can supply the recovered heat to external devices or facilities, or it can be used for heating and cooling within the facility where the system 1 is installed. In this case, the chiller can be omitted.

[0169] The water ring pump 301 described above makes it possible to suck in exhaust gas, dehumidify it, and transfer it to the off-gas buffer tank 123 by its vacuum pumping action, even when the outlet pressure on the air electrode side of the fuel cell is in a "low pressure" state close to atmospheric pressure (approximately 0.1 MPa). Here, in the case of such "low pressure," the outlet pressure on the air electrode side of the "fuel cell" falls below 1 atmosphere (approximately 0.1 MPa) due to the suction action of the water ring pump 301, and as a result, gas after the fuel cell reaction in the cells of the "fuel cell" is actively drawn out, which is expected to improve the power generation efficiency of the "fuel cell."

[0170] In this way, the water ring pump 301 is extremely suitable for use with a "fuel cell." In fact, when the exhaust gas from a "fuel cell" with an outlet pressure of 1.2 atmospheres (approximately 0.12 MPa) and a relative humidity of approximately 100% was dehumidified using the water ring vacuum pump LEH100SMS manufactured by Kashiyama Kogyo Co., Ltd., the exhaust gas obtained had a relative humidity (several tens of percent) similar to that of the typical value in the atmosphere, and it was possible to quickly store this exhaust gas in the tank 123.

[0171] Incidentally, if the vacuum pumping action of the water ring pump 301 is too great, it may draw out too much gas from the cells of the "fuel cell," which may cause problems with the fuel cell reaction. Therefore, it is preferable to adjust the rotation speed of the impeller 301a of the water ring pump 301 so that the transfer flow rate to the off-gas buffer tank 123 does not exceed the reference value of the introduction flow rate. In order to appropriately perform such adjustments, it is also preferable to install a flow meter and a pressure meter just before the intake port and just after the outlet port of the water ring pump U30, respectively, to monitor the flow rate and pressure of the exhaust gas.

[0172] Next, in the embodiment shown in FIG. 6(B), an adiabatic expansion chamber 50 is provided between the fuel cell U11 and the water ring pump U30. Here, exhaust gas extracted from the cathode side of the "fuel cell" via a flow control valve is drawn into this adiabatic expansion chamber 50 by the suction force of the water ring pump 301. At this time, the drawn-in exhaust gas is suddenly released into the adiabatic expansion chamber 50, which has a predetermined volume, from the cathode side outlet pipe, causing it to expand adiabatically and lower its temperature. As a result, some of the moisture and water vapor contained in the exhaust gas condenses due to a decrease in saturated water vapor density and accumulates in the lower part of the adiabatic expansion chamber 50. Here, if the vacuum pumping action (the rotation speed of the impeller 301a) of the water ring pump 301 is increased within a predetermined limit and the flow rate of the exhaust gas flowing into the adiabatic expansion chamber 50 is adjusted by the flow control valve to cause a rapid drop in the exhaust gas pressure, the degree of adiabatic expansion will increase, and the dehumidification effect due to condensation will also be enhanced. For example, it is possible to lower the temperature of the exhaust gas by several tens of degrees Celsius, condensing a large amount of water vapor and removing it from the exhaust gas.

[0173] In this way, the adiabatic expansion chamber 50 functions as a dehumidifying means for the exhaust gas upstream of the water ring pump U30. In this case, the water ring pump U30 takes in the exhaust gas with reduced moisture and water vapor content after adiabatically expanding, thereby further reducing the moisture and water vapor content of the exhaust gas. In other words, by providing the adiabatic expansion chamber 50, it becomes possible to send exhaust gas with a lower relative humidity to the off-gas buffer tank 123.

[0174] In this embodiment, (a) A heat exchanger incorporated in the water ring pump U30, a heat exchanger installed in the adiabatic expansion chamber 50 (tube bundle 501 in FIG. 6(B)), and a heat exchanger incorporated in the fuel cell U11 are arranged in series (or in parallel), (b) Receives heat from the sealing liquid of the water ring pump U30 and the "fuel cell" and transfers the heat to the adiabatic expansion chamber 50, thereby adjusting the temperatures of the sealing liquid, the adiabatic expansion chamber 50, and the "fuel cell" all at once. A heat exchanger U60 is provided.

[0175] Here, the heat exchanger U60 also uses a chiller pump to perform the above temperature adjustment, but because the heat exchange medium is cooled in the adiabatic expansion chamber 50, a chiller pump with low power consumption can be used. Furthermore, in the heat exchanger U60, the heat recovered in this way can of course be supplied to external devices or facilities, or it can be used for heating and cooling within the facility where the device (system) 1 is installed. In this case, it is also possible to omit the chiller.

[0176] As a modification, the heat exchanger in the "fuel cell" can be omitted from the heat exchanger U60, and the heat exchanger U60 can be used as a heat transfer means that absorbs heat from the sealing liquid of the water ring pump U30 and transfers the heat to the adiabatic expansion chamber 50. Here, in this case too, it is possible to omit the chiller or reduce power consumption.

[0177] Furthermore, in another embodiment in which the adiabatic expansion chamber 50 is used as the dehumidifying means, the water ring pump U30 is omitted from the configuration of FIG. 6(B), and further, (a) The pressure of the exhaust gas from the "fuel cell" of the fuel cell U11 is set to a pressure exceeding atmospheric pressure (1 atmosphere, approximately 0.1 MPa), for example, a pressure of 3 atmospheres (approximately 0.3 MPa) or more (i.e., the "fuel cell" is driven under high pressure using the pressure control U121 and pressure control U113 (Figure 1)), (b) The high-pressure exhaust gas is released into the adiabatic expansion chamber 50 to remove a considerable amount of moisture and water vapor from the exhaust gas. In this case, it is possible to reliably proceed with the dehumidification process of the exhaust gas without using the water ring pump U30, which requires a lot of driving power.

[0178] 6(A) and 6(B), a dehumidification means using a water ring pump 301 has been described. In both embodiments shown in these figures, at least a portion of the power required to drive the water ring pump U30 and chiller pump can be supplied from a fuel cell, or alternatively, from a natural energy generator U101 (FIG. 1) or a battery U101s (FIG. 1). It is also preferable to provide a pure water recovery means (specifically, piping, a pump, a filter, and the like) for recovering water discharged from the fuel cell, water extracted (e.g., overflowed) from the adiabatic expansion chamber 50 (in the case of FIG. 6(B)), or even overflow water from the gas-liquid separation tank 302 (if the water is highly pure), and providing the water as pure water or highly pure water to the outside. In this case, the present system 1 also functions as a pure water supply system.

[0179] [An embodiment of the gas-liquid separation unit: dry filter] FIG. 7 is a schematic diagram for explaining one embodiment of the gas-liquid separator U122 as the dehumidifying means according to the present invention.

[0180] In the embodiment shown in Fig. 7, the gas-liquid separator U122 is a dry filter unit using a dry filter 122f. (a) receiving exhaust gas having a pressure exceeding atmospheric pressure (1 atmosphere, approximately 0.1 MPa), for example, a pressure of 3 atmospheres (approximately 0.3 MPa) or more; (b) The exhaust gas is abruptly redirected at the bottom of the vessel to separate water, oil and other fine particles from the exhaust gas; (c) The exhaust gas that has changed direction and entered the mesh pipe 122f1 is filtered by the mesh of the mesh pipe 122f1 and the hollow fiber filter inside it (which allows more water vapor to pass through than air) to remove fine particles, moisture, and water vapor from the exhaust gas. (d) Furthermore, the heat generated during filtration evaporates the water in the exhaust gas. This is a filter that makes it possible to

[0181] The moisture and water vapor extracted from the exhaust gas is discharged to the outside of the filter 122f through the drain 122f2, but this may also be supplied to the outside as pure water or highly pure water. The structure of the dry filter 122f is not limited to that shown in Fig. 7, and various known dry filter structures may be used.

[0182] In this embodiment, in order to supply high-pressure exhaust gas (for example, 3 to 7 atmospheres (approximately 0.3 to 0.7 MPa)) to the dry filter 122f, as shown in FIG. (a) Using the pressure control U121 and the pressure control U113, high pressure (for example, 3 to 7 atmospheres (approximately 0.3 to 0.7 MPa) air (or gas containing nitrogen and oxygen) and high pressure (for example, 3 to 7 atmospheres (approximately 0.3 to 0.7 MPa) hydrogen (fuel gas)) are supplied to the "fuel cell", (b) High-pressure (e.g., 3 to 7 atmospheres (approximately 0.3 to 0.7 MPa) exhaust gas is extracted from the "fuel cell" and sent to the dry filter 122f. This is how it works.

[0183] In this way, the high-pressure compatible "fuel cell" and dry filter 112f are an ideal combination, as they are part of a high-pressure system that can efficiently remove the moisture and water vapor that is generated while promoting the efficiency of the cell reaction.

[0184] In this embodiment, the high-pressure exhaust gas with reduced moisture or water vapor content discharged from the dry filter 112f is sent to the nitrogen filter U12 without (or may be sent through) the off-gas buffer tank 123. As described above, the higher the pressure of the exhaust gas acting on the nitrogen gas filter 12f of the nitrogen filter U12, the lower the oxygen concentration of the extracted exhaust gas, i.e., the higher the purity of nitrogen gas obtained. Therefore, it can be understood that a very suitable combination can be achieved by forming the dry filter 112f and the nitrogen filter U12 into a single high-pressure system.

[0185] [Another embodiment of the nitrogen filter U] Another preferred embodiment of the nitrogen filter U12 will be described below. As described above, the nitrogen filter U12 shown in Fig. 1 is equipped with a filter purge section that extracts a "filter discharge gas" containing oxygen molecules that have been separated from nitrogen molecules (in the exhaust gas) by passing through the hollow fiber fibers of the nitrogen gas filter 12f. Here, the "filter discharge gas" discharged from this filter purge section contains a considerable amount of oxygen molecules, and is therefore a gas that can be reused in the fuel cell reaction or can be subjected to another filtering process.

[0186] Incidentally, when a UBE N2 separator NM-B01A manufactured by Ube Industries was used as the nitrogen gas filter 12f, gas with an oxygen concentration of 10.2 vol% was introduced into this nitrogen gas filter 12f under conditions of an inlet pressure of 6.0 atmospheres (approximately 0.61 MPa) and an outlet flow rate of 1.0 L / min, and the oxygen concentration of the filter exhaust gas discharged from there was measured. The experimental result was 14.9 vol%, and the recovery rate was also obtained as 0.29. Furthermore, it was confirmed through experiments that the oxygen concentration of the filter exhaust gas increases as (a) the inlet oxygen concentration increases, (b) the inlet pressure decreases, and (c) the outlet flow rate increases.

[0187] If we assume that almost all of the oxygen molecules in the introduced gas are discharged from the filter purge section of the nitrogen gas filter 12f (because the oxygen concentration at the outlet of the filter 12f is orders of magnitude smaller), the oxygen concentration in the filter discharge gas is calculated to be 0.102 / 0.71 = 14.4 using the recovery rate (0.29) obtained from the above experiment, which roughly matches the 14.9 vol% obtained from the above experiment. Therefore, it can be seen that almost all of the oxygen gas separated as unnecessary is recovered from the filter purge section of the nitrogen gas filter 12f.

[0188] Therefore, the nitrogen gas generating device (system) 1 of this embodiment is provided with a gas return passage as shown by the circled "B" in FIG. 1, and this filter exhaust gas is (a) Returning the gas to the flow control U109 located before the cathode of the Fuel Cell to be reused in the Fuel Cell as a gas containing oxygen and nitrogen; and / or (b) Return the exhaust gas to the off-gas buffer tank 123 installed in front of the nitrogen filter U12, and let it act on the nitrogen gas filter 12f again together with the exhaust gas. This makes it possible to use oxygen gas more effectively and extract nitrogen gas with a lower oxygen concentration.

[0189] If the filter exhaust gas, which has a lower oxygen concentration than air, is reused in a fuel cell, the exhaust gas from the fuel cell can be made into exhaust gas with a lower oxygen concentration. This increases the recovery rate in the nitrogen gas filter 12f into which such exhaust gas is introduced (as explained using FIG. 5), making it possible to ultimately extract more nitrogen gas. Furthermore, although this depends on the settings of various conditions in the nitrogen gas generator (system) 1, increasing the final recovery rate in the nitrogen gas filter 12f in this way can also significantly reduce the cost of generating nitrogen gas.

[0190] Incidentally, under conditions where the oxygen concentration of the exhaust gas from the "fuel cell" is about 15 vol%, and the oxygen concentration of the filter exhaust gas is, for example (typically) 1.4 times the introduced oxygen concentration c_in_O2, the oxygen concentration of the filter exhaust gas will be the same as or higher than that of air (20.8 vol%), and as a result, it can be seen that the above-mentioned benefits of returning the filter exhaust gas to the air electrode side of the "fuel cell" do not arise.

[0191] On the other hand, if the oxygen concentration of the filter exhaust gas is also 1.4 times the inlet oxygen concentration, and the oxygen concentration of the exhaust gas from the "fuel cell" is about 10 vol%, the oxygen concentration of the filter exhaust gas will be around 14 vol% (<20.8 vol%), and the above-mentioned return of the filter exhaust gas becomes meaningful. Furthermore, if the oxygen concentration of the exhaust gas from the "fuel cell" is about 5 vol%, the oxygen concentration of the filter exhaust gas will be around 7 vol%, which not only is expected to improve the recovery rate, but depending on the system settings, it may also have the economic effect of significantly reducing the cost of generating nitrogen gas.

[0192] Further, another embodiment of the nitrogen filter U12 will be described below. Figure 8 is a schematic diagram for explaining another embodiment of the filtering means according to the present invention.

[0193] 8(A), the nitrogen filter U12 is provided with three nitrogen gas filters 12f1, 12f2, and 12f3 connected in parallel. Of course, the number of nitrogen gas filters connected in parallel is not limited to three, and may be two or four or more.

[0194] Specifically, the exhaust gas supplied to the nitrogen filter U12 is divided and taken into each of the three nitrogen gas filters 12f1, 12f2, and 12f3, and each nitrogen gas filter acts on the portion of the exhaust gas that has been taken into it to produce gas with an increased nitrogen concentration, i.e., high-purity nitrogen gas, and finally these high-purity nitrogen gases join together and are sent toward the nitrogen tank 129.

[0195] It is also preferable that the filter exhaust gas discharged from each of the three nitrogen gas filters 12f1, 12f2, and 12f3 be returned to the flow control U109 (FIG. 1) upstream of the fuel cell and / or the off-gas buffer tank 123 (FIG. 1) upstream of the nitrogen filter U12 for reuse. Furthermore, if the oxygen concentration in the filter exhaust gas discharged from these nitrogen gas filters is above a predetermined level, the filter exhaust gas may be sent to an external oxygen tank for storage. In any case, this type of processing makes it possible to more effectively utilize the oxygen gas or to extract nitrogen gas with a lower oxygen concentration.

[0196] In this way, by arranging multiple nitrogen gas filters in parallel and performing filtering, it is possible to simultaneously take in large amounts of exhaust gas and provide more high-purity nitrogen gas to the outside.For example, according to the catalog values of a 4-inch diameter nitrogen gas filter manufactured by Daicel-Evonik, when it receives air at 7 atmospheres (approximately 0.7 MPa) at a flow rate of 40 L / min, it will discharge high-purity nitrogen gas with an oxygen concentration of approximately 0.1 vol% at a flow rate of approximately 10 L / min (assuming a recovery rate of approximately 0.25).

[0197] For example, by arranging three such nitrogen gas filters in parallel and feeding exhaust gas (with an oxygen concentration lower than that of air, e.g., 5-10 vol%) to each nitrogen gas filter at 7 atmospheres (approximately 0.7 MPa) and a flow rate of 40 L / min, high-purity nitrogen gas with an oxygen concentration of 0.01 vol% (100 ppm vol) or significantly less than 0.1 vol% (1000 ppm vol) can be supplied to the outside at a total flow rate of approximately 30 (= 10 × 3) L / min. Here, the exhaust gas flows into each nitrogen gas filter at a flow rate of one-third of the original total flow rate of 120 (= 40 × 3) L / min, thereby improving the oxygen separation ability of each nitrogen gas filter compared to using a single nitrogen gas filter. Of course, using a nitrogen gas filter with a larger diameter (e.g., 6 inches) would enable the supply of even larger amounts of high-purity nitrogen gas. Furthermore, for example, the selective type 6-inch diameter nitrogen gas filter manufactured by Daicel-Evonik has a recovery rate of approximately 0.32, which is significantly improved compared to the recovery rate of a 4-inch diameter nitrogen gas filter (approximately 0.25), making it possible to provide more high-purity nitrogen gas to the outside world.

[0198] 8(B), the nitrogen filter U12 is provided with three nitrogen gas filters 12f1, 12f2, and 12f3 connected in cascade. Specifically, the exhaust gas taken into the nitrogen filter U12 is first introduced into the nitrogen gas filter 12f1, and the filter exhaust gas discharged from this nitrogen gas filter 12f1 is introduced into the next nitrogen gas filter 12f1.

[0199] Furthermore, the filter exhaust gas discharged from this nitrogen gas filter 12f2 is introduced into the final nitrogen gas filter 12f3, and the filter exhaust gas discharged from this nitrogen gas filter 12f3 is sent back to the flow control U109 (Figure 1) in front of the "fuel cell" and / or the off-gas buffer tank 123 (Figure 1) in front of the nitrogen filter U12, and is reused.

[0200] Furthermore, if the oxygen concentration in the filter exhaust gas discharged from nitrogen gas filter 12f3 is above a predetermined level, the filter exhaust gas may be sent to an external oxygen tank for storage. In either case, such processing makes it possible to more effectively utilize the oxygen gas or to extract nitrogen gas with a lower oxygen concentration. The exhaust gases with increased nitrogen concentrations that have come out of nitrogen gas filters 12f1, 12f2, and 12f3 are combined and output as high-purity nitrogen gas.

[0201] In addition, since the flow rate of the introduced gas (introduced flow rate) decreases from nitrogen gas filter 12f1 to 12f3, it is preferable to use, for example, nitrogen gas filter 12f2 that is smaller than 12f1 (compatible with small flow rates), and further, to use nitrogen gas filter 12f3 that is smaller than 12f2 (compatible with small flow rates).

[0202] Naturally, the number of nitrogen gas filters used in this embodiment is not limited to 3. Specifically, it is possible to use N nitrogen gas filters, from the first nitrogen gas filter to the Nth nitrogen gas filter (N is an integer of 2 or more).

[0203] Various embodiments relating to the nitrogen filter U12 have been described above, but even in these embodiments, it is preferable that the overall control U131 (Figure 1) constantly monitors the oxygen concentration, pressure, and flow rate of the exhaust gas from the "fuel cell," as well as the inlet oxygen concentration, inlet pressure, inlet flow rate, inlet gas temperature, outlet oxygen concentration, outlet pressure, outlet flow rate, etc. of each nitrogen gas filter, and controls each unit so that a predetermined amount (predetermined flow rate) of nitrogen gas having a predetermined high nitrogen concentration can be provided at the appropriate time.

[0204] [Controlled by machine learning] Hereinafter, we will explain the machine learning control of the nitrogen gas generation process in the nitrogen gas generation device (system) 1, which uses a water ring pump U30 (FIG. 6(A)) as the dehumidifying means according to the present invention and converts the exhaust gas dehumidified by the water ring pump U30 into high-purity nitrogen gas using a nitrogen filter U12 (FIG. 1). This control can be implemented in the overall control U131 (FIG. 1).

[0205] First, consider a state in which a nitrogen gas generator (system) 1 having a predetermined configuration that takes in air and hydrogen to generate high-purity nitrogen gas is operating stably. (a) The flow rate of air introduced into the "fuel cell" in fuel cell U11 (Fig. 1); (b) Complex impedance value between the hydrogen electrode and the air electrode of the "fuel cell" (c) "Fuel Cell" temperature, (d) the amount of electricity generated by the "fuel cell"; (e) the outlet flow rate of the exhaust gas at the cathode side of the "fuel cell"; (f) the outlet pressure of the exhaust gas at the cathode side of the "fuel cell"; (g) the rotation speed (or driving power) of the impeller 301a in the water ring pump 301; (h) The temperature of the sealing liquid at the position of the water ring pump 301 or the position of the gas-liquid separation tank 302, (i) the relative humidity of the exhaust gas at the outlet of the water ring pump U30; (j) the temperature of the inlet exhaust gas at the nitrogen filter U12; (k) the pressure of the exhaust gas introduced into the nitrogen filter U12; (l) the outlet flow rate (of nitrogen gas) at the nitrogen filter U12, and (m) Outlet oxygen concentration (of nitrogen gas) at nitrogen filter U12 Prepare a large dataset of measurements.

[0206] Next, it is also preferable to use these data sets to construct a nitrogen gas generation model using, for example, a DNN (Deep Neural Network) algorithm, and use a control program incorporating this model to control the operating state of the nitrogen gas generation device (system) 1. Here, in this nitrogen gas generation model, for example, the above (a) to (k) can be set as explanatory variables, and the above (l) and (m) can be set as response variables.

[0207] By inputting information on the operating conditions of the fuel cell U11, the water ring pump U30, and the nitrogen filter U12 into this model, the performance of the device (system) 1 can be calculated. (l') The supply flow rate of high-purity nitrogen gas that can be supplied to the outside, and (m') Purity (or oxygen concentration) of high-purity nitrogen gas that can be supplied externally It is possible to know or predict the above. Here, it is preferable to adopt at least (a) and (g) above as explanatory variables when building a model and predicting performance. In addition, either (l) or (m) above may be set as the objective variable.

[0208] As a further modification, it is also possible to construct a nitrogen gas generation control model using the above (b) to (f) and (h) to (m) as explanatory variables and the above (a) and (g) as target variables, and to use a control program incorporating this model to control the operating state of the nitrogen gas generator (system) 1. This allows the necessary parameters to be calculated to achieve the target supply flow rate and target purity (or oxygen concentration) of the high-purity nitrogen gas to be supplied. (a) the flow rate of air introduced into the "fuel cell"; and (g) Rotational speed (or driving power) of the impeller 301a in the water ring pump 301 can be obtained, and the target can be achieved by performing control in accordance with this. Here, it is preferable to adopt at least one of the above (l) and (m) as an explanatory variable when building a model and predicting controlled variables. Also, one of the above (a) and (g) may be set as the objective variable.

[0209] As already mentioned, nitrogen gas users' requirements for nitrogen gas purity and supply amount (flow rate) vary widely depending on the field and specific application. In some cases, the overall control U131 (Figure 1) may construct a nitrogen gas generation model and a nitrogen gas generation control model to meet the requirements of each individual user, and use a control program incorporating a model that matches the user's desired performance to enable the nitrogen gas generator (system) 1 to provide high performance that meets the user's requirements.

[0210] [Another embodiment using catalytic combustion] FIG. 9 is a schematic diagram illustrating yet another embodiment of a nitrogen gas generator system according to the present invention.

[0211] In the embodiment shown in Fig. 9, a catalytic combustion unit U90 is provided downstream of the nitrogen filter U12 (for example, immediately after the flow control unit U127) in the nitrogen gas generation device (system) 1 shown in Fig. 1. Here, this catalytic combustion unit U90 is a unit that brings hydrogen gas into contact with oxygen in the exhaust gas on a combustion catalyst made of a compound of a noble metal such as palladium (Pd) or platinum (Pt), or a compound of another transition metal, to perform catalytic combustion, which is an oxidation reaction that is more controlled than flame combustion.

[0212] Specifically, in this embodiment, the catalytic combustion U90 is (a) Nitrogen gas with a low oxygen concentration (for example, an oxygen concentration of 0.1 to several vol%) extracted from the nitrogen filter U12, (b) Hydrogen gas extracted from the hydrogen electrode side outlet of the fuel cell U11, passed through the drain 111, pressure control U113, and gas-liquid separation U114, and then recovered in the hydrogen recovery U115, and then sent through the flow control U902 and check valve. The nitrogen gas and hydrogen gas are brought into contact on the surface of a solid catalyst 90a, which is a combustion catalyst installed inside the unit, causing a catalytic combustion reaction, and ultimately outputting high-purity nitrogen gas with an extremely low oxygen concentration (for example, an oxygen concentration on the order of 0.01 vol% (100 ppm vol)) and a small amount of water vapor to the outside. Of course, instead of the hydrogen gas in (b) above, hydrogen gas can also be supplied to the catalytic combustion unit 90 from, for example, the hydrogen generation unit 102 or the hydrogen generation and reforming unit 103.

[0213] Here, the solid catalyst 90a, which is the combustion catalyst installed in the catalytic combustion unit 90, is preferably a ceramic honeycomb with many fine holes and a metal such as platinum (Pt) or palladium (Pd) supported as a catalyst on the surface, including the inside of the holes. For example, NA honeycomb, an oxidation catalyst (platinum catalyst) manufactured by Nagamine Manufacturing Co., Ltd., can be used as this solid catalyst 90a.

[0214] As stated in the catalog, NA honeycomb is a solid catalyst in which platinum group metals such as platinum (Pt) and palladium (Pd) are supported on the surface of a support whose main components are calcium aluminate (CaO Al2O3), fused silica (SiO2), and titanium dioxide (TiO2). The support has a honeycomb shape, which provides a very large contact area for the supported platinum group metals, allowing for efficient oxidation reactions. Incidentally, the optimum operating temperature for NA honeycomb is said to be 200-850°C.

[0215] In this embodiment, hydrogen is burned with a small amount of oxygen, and the heat of reaction is much smaller than that of general catalytic combustion. Therefore, the solid catalyst 90a is heated to, for example, 250°C before being used as a catalyst for catalytic combustion. Here, this heating can be performed, for example, by an electric heating method in which an electric heating wire is wrapped around the solid catalyst 90a and electrically heated.

[0216] As another preferred embodiment of this heating, the solid catalyst 90a may be subjected to induction heating. Specifically, iron (Fe) or an iron-based alloy such as stainless steel is mixed into the carrier of the solid catalyst 90a, and a magnetic field (electromagnetic field) of, for example, several tens of kilohertz (kHz) to several hundred kHz is applied to the solid catalyst 90a using an electromagnetic field generator, and Joule heat due to eddy currents generated by the principle of electromagnetic induction is used to directly heat the solid catalyst 90a.

[0217] Here, in consideration of the skin effect of electromagnetic induction, it is also preferable to disperse iron powder or iron flakes or an iron-based alloy such as powdered or flake stainless steel near the surface of the support of the solid catalyst 90a, for example, inside the support to a depth at least equal to or greater than the penetration depth δ. This allows the portion of the solid catalyst 90a near the surface that should be heated to a high temperature to be heated to a predetermined high temperature with uniform temperature distribution.

[0218] Alternatively, a plate of iron or an iron-based alloy such as stainless steel may be placed in contact with, for example, the side surface of the solid catalyst 90a, and the solid catalyst 90a may be induction-heated via the plate by electromagnetic induction. In either case, induction heating of the solid catalyst 90a does not require wiring such as heating wires for each solid catalyst 90a, even when a plurality of solid catalysts 90a are used, and the plurality of solid catalysts 90a can be heated simultaneously and easily.

[0219] As described above, in this embodiment, the solid catalyst 90a is heated to promote catalytic combustion. However, to reduce the power required for heating, it is possible to set the oxygen concentration of the nitrogen gas extracted from the nitrogen filter U12 slightly higher. Increasing the oxygen concentration in this way increases the heat generated by catalytic combustion, which in turn reduces the power required to heat the solid catalyst 90a. In any case, it is important to appropriately adjust the filtering conditions of the nitrogen filter U12 (e.g., the inlet flow rate of the exhaust gas) and the catalytic combustion conditions (e.g., the temperature of the solid catalyst 90a) taking into account the purity and supply amount (flow rate) required for the nitrogen gas to be ultimately supplied.

[0220] Furthermore, the extremely low-oxygen-concentration nitrogen gas output from the catalytic combustion U90 is at a high temperature, and this heat may be recovered by a plate-type or multi-tube heat exchanger 901 installed at the outlet of the catalytic combustion U90. In this case, the heat recovered by the heat exchanger 901, like the heat recovered from the fuel cell U11, is preferably supplied to the off-gas buffer tank 123 and used to further heat the exhaust gas to be supplied to the nitrogen filter U12 (for example, 45°C), or it may be supplied to the outside. Note that if the temperature of the nitrogen gas output from the catalytic combustion U90 is not very high, it may be sent to the hydrogen filter U903 (described later) without passing through the heat exchanger 901.

[0221] Here, the extremely low-oxygen nitrogen gas output from the catalytic combustion unit 90 typically contains residual hydrogen gas that was not burned in the catalytic combustion reaction. In this embodiment, the hydrogen filter 903 takes in this high-purity nitrogen gas that has passed through the heat exchanger 901, and separates the residual hydrogen gas from the extremely low-oxygen nitrogen gas using a known hydrogen gas filter installed inside, outputting nitrogen gas of higher purity. This output high-purity nitrogen gas is then preferably stored in a nitrogen tank 129 (FIG. 1) via a check valve, an oxygen concentration meter, a flow meter, and a pressure booster 128 (FIG. 1), and is then provided to the outside as appropriate.

[0222] The hydrogen gas filter may be a filter equipped with a palladium (Pd)-based hydrogen permeable membrane, or a hydrogen gas filter equipped with an aromatic polyimide-based gas separation membrane. For example, UBE GAS SEPARATOR manufactured by Ube Industries, which uses a pipe made of bundled hollow fiber membranes, or SEPURUN Noble manufactured by EVONIK can be used.

[0223] In this embodiment, the hydrogen gas separated from the nitrogen gas by the hydrogen filter U903 is sent via the flow control U904 to the hydrogen recovery U115, where it can be reused in the fuel cell U11 or subjected to catalytic combustion again in the catalytic combustion U90. If a reducing atmosphere is required at the destination of the nitrogen gas supply, for example, if the nitrogen gas supply destination is an anti-oxidizing atmosphere furnace or fryer, it is possible to set the supplied nitrogen gas to contain a small amount of hydrogen while ensuring safety.

[0224] Furthermore, as described above, by employing catalytic combustion U90 in the nitrogen gas generator (system) 1 (FIG. 1), it is also possible to improve the recovery rate in the nitrogen gas filter 12f (FIG. 1) of the nitrogen filter U12. That is, if the oxygen concentration of the gas output from the nitrogen gas filter 12f is set to, for example, several vol%, with the ultimate goal of achieving an extremely low oxygen concentration in catalytic combustion U90, it becomes possible to introduce a significantly large flow rate (outlet flow rate) of exhaust gas into the nitrogen gas filter 12f (as can be seen from the graph in FIG. 2). As a result, the recovery rate in the nitrogen gas filter 12f can be increased (as can be seen from the graph in FIG. 5).

[0225] 9, it is also possible to efficiently generate nitrogen gas with a lower oxygen concentration using only the fuel cell U11 and catalytic combustion U90, without using the nitrogen filter U12. In any case, it is understood that the combination of "fuel cell" and "catalytic combustion" is extremely advantageous in that it allows the necessary hydrogen gas to be shared and enables efficient generation of nitrogen gas.

[0226] Incidentally, although this is an embodiment that does not use a fuel cell, it is also possible to adopt an apparatus (system) that efficiently generates high-purity nitrogen gas with sufficiently reduced moisture or water vapor content by omitting the fuel cell U11 from the apparatus (system) configuration of Figure 9, i.e., an apparatus (system) that includes a nitrogen filter U12 and catalytic combustion U90 as its main components.

[0227] [Another embodiment of the fuel cell] FIG. 10 is a schematic diagram for explaining another embodiment of the "fuel cell" according to the present invention.

[0228] Figure 10 shows fuel cell 11F, which is suitable as the "fuel cell" included in fuel cell U11 (Figure 1). Fuel cell 11F has multiple cells, which are structural units each including a hydrogen electrode and an air electrode with an electrolyte sandwiched between them, and these cells are stacked so that hydrogen (fuel gas) and air (gas containing nitrogen and oxygen) pass through the hydrogen electrode and air electrode, respectively, in the cells, from the cell on the upstream side to the cell on the downstream side of the fuel supply.

[0229] The entire cell is divided into a plurality of functional cell sections, namely, a power generation priority cell section 11Fa, an intermediate cell section 11Fb, and an oxygen removal cell section 11Fc in Fig. 10. Each of these functional cell sections (11Fa, 11Fb, 11Fc) includes one or a plurality of consecutive cells (two or three in Fig. 10, but actually, for example, several to several hundred), and is not electrically connected in series with other functional cell sections, but is electrically connected to an individually provided power generation amount control section (11Ca, 11Cb, 11Cc).

[0230] 10, the control units 11Ca, 11Cb, and 11Cc receive the electromotive force generated between the hydrogen electrode and the air electrode in the power generation priority cell unit 11Fa, the intermediate cell unit 11Fb, and the oxygen removal cell unit 11Fc, respectively, and output power appropriate for the functional cell unit they are responsible for. It is also preferable to measure the complex impedance of the functional cell unit they are responsible for and perform control and management appropriate for that functional cell unit.

[0231] On the other hand, conventional fuel cells, especially PEFC-type fuel cells, are composed of a series of, for example, several hundred cells electrically connected in series to ensure the required power as an actual power source, since the electromotive force of a single cell is usually less than 1 V (volt). Here, naturally, the amount of power that can be generated is small in cells with a small oxygen supply, but the power generation efficiency (relative to the amount of hydrogen supply) of the entire series-connected cells, including such cells, is significantly reduced because the power generation amount of each cell must be somewhat uniform.

[0232] In contrast, in the case of fuel cell 11F, (a) a power generation priority cell section 11Fa having a large supply of oxygen (where the oxygen in the supplied air has not yet been consumed to a large extent); (b) an intermediate cell portion 11Fb which is intermediate in terms of oxygen supply amount; (c) The oxygen removal cell portion 11Fc in which the amount of oxygen supplied is small (the oxygen in the supplied air is considerably consumed) However, the amount of power generation can be controlled in accordance with the amount of oxygen supplied. Therefore, by implementing such power generation control, it is possible to maximize or improve both the oxygen reduction efficiency and the power generation efficiency (relative to the amount of hydrogen supplied) in the fuel cell 11F.

[0233] Thus, fuel cell 11F is well suited to be used as the "fuel cell" of fuel cell U11 (FIG. 1), i.e., for producing high-purity nitrogen gas, although of course fuel cell 11F can also be used for other general purposes as a suitable fuel cell that allows for optimization of power generation efficiency.

[0234] Incidentally, the number of functional cell units in the fuel cell 11F is not limited to three, and can be two or four or more. For example, among several hundred rows of cells, the group of 150 cells on the lower side and the remaining group of cells on the upper side can be the first functional cell unit and the second functional cell unit, respectively.

[0235] As explained in detail above, according to the present invention, it is possible to reliably and stably generate high-purity nitrogen gas using a fuel cell. In particular, by dehumidifying the exhaust gas from the fuel cell using a water seal pump or a dry filter, and further using a nitrogen gas filter or catalytic combustion, it is possible to more reliably, stably, and efficiently generate even higher-purity nitrogen gas.

[0236] Furthermore, in the future, when a hydrogen gas society and a carbon-free society arrives, the use of fuel cells that use hydrogen gas as a fuel gas is expected to become widespread everywhere. In such an era, this invention will make a significant contribution to the efficient production of nitrogen gas. Naturally, it will also be possible to meet the need for on-site supply of electricity, heat, and, in some cases, pure water. In other words, this invention is expected to greatly contribute to the establishment of a local production-for-local consumption, carbon-free energy and product supply and demand system, which is considered an ideal form for the future.

[0237] Furthermore, although this is merely one embodiment of the present invention, it is also possible to supply hydrogen gas as fuel gas to a fuel cell by using a hydrogen generator U equipped with an electrolysis unit. This configuration is also expected to be widely used in the hydrogen gas society and carbon-zero society described above.

[0238] 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. [Explanation of symbols]

[0239] 1. Nitrogen Gas Generator / System 101 Renewable Energy Power Generation Unit (U) 101s Energy storage U 102 Hydrogen Generation U 103 Hydrogen Generation and Reforming U 104 Hydrogen Tank 105, 109, 127, 902, 904 Flow Control U 106 Air Compressor U 107 Air Tank 108 Filter U 11 Fuel Cell U 11Ca, 11Cb, 11Cc control unit 11F Fuel cell 11Fa Power Generation Priority Cell Section 11Fb Intermediate cell 11Fc Oxygen removal cell 111, 112 Drain 113, 121 Pressure Control U 114, 122 Gas-liquid separation U 115 Hydrogen Recovery U 12 Nitrogen Filter U 12f, 12f1, 12f2, 12f3 Nitrogen Gas Filter 122f Dry Filter 122f1 mesh tube 122f2 Drain 123 Offgas buffer tank 124, 128 Pressure Booster U 125 Corrosive gas removal U 126 Temperature adjustment U 129 Nitrogen Tank 131 Overall Control U 30 Water ring pump U 301 Water ring pump 301a impeller 302 Gas-liquid separation tank 40, 60, 901 Heat exchange U 50 Insulated expansion chamber 501 Tube bundle 90 Catalytic Combustion U 90a Solid catalyst 903 Hydrogen Filter U

Claims

1. a fuel cell that operates by taking in air or a gas containing nitrogen and oxygen and a fuel gas and discharging an exhaust gas having an oxygen concentration lower than that of the air or the fuel gas; a first flow control means for controlling the flow rate of air or the gas introduced into the fuel cell; a filtering means for converting the exhaust gas into a gas having an increased nitrogen concentration, the filtering means including a filter using fibers having different permeabilities for nitrogen and oxygen; a second flow control means for controlling the flow rate of the nitrogen-enriched gas delivered from the filtering means; and the second flow control means controls the flow rate of the gas with increased nitrogen concentration so that the nitrogen concentration of the gas with increased nitrogen concentration becomes a target nitrogen concentration under conditions where the pressure of the exhaust gas introduced into the filtering means is a predetermined pressure and the oxygen concentration of the exhaust gas is a low oxygen concentration realized by flow rate control by the first flow control means; The first flow control means controls the flow rate of the air or the gas so that the oxygen concentration of the exhaust gas becomes the low oxygen concentration under the condition that the pressure of the air or the gas introduced into the fuel cell is a predetermined pressure. A nitrogen gas generator characterized by:

2. A nitrogen gas generating device as described in Claim 1, characterized in that the fuel cell is a solid oxide fuel cell (SOFC).

3. A nitrogen gas generating device as described in claim 1, characterized in that it further has a dehumidifying means for reducing the moisture or water vapor content in the exhaust gas extracted from the fuel cell.

4. The method further comprises catalytic combustion means for reacting the nitrogen-enriched gas with the fuel gas on a combustion catalyst to convert the nitrogen-enriched gas into a gas having a lower oxygen concentration; The target nitrogen concentration in the nitrogen-enriched gas is a nitrogen concentration at which the nitrogen concentration of the gas having the target nitrogen concentration is introduced into the catalytic combustion means, and the nitrogen concentration of the gas having a lower oxygen concentration that is extracted from the catalytic combustion means becomes the target or desired high nitrogen concentration.

4. The nitrogen gas generating device according to claim 1, wherein the nitrogen gas generating device is a nitrogen gas generating device.

5. A nitrogen gas generating device as described in any one of claims 1 to 4, characterized in that the second flow control means controls the flow rate of the gas with increased nitrogen concentration so that, under the conditions, the nitrogen concentration of the gas with increased nitrogen concentration becomes the target nitrogen concentration and the recovery rate becomes the target or desired recovery rate.

6. Further comprising a pressure increasing means for increasing the pressure of the exhaust gas, The filtering means converts the pressurized exhaust gas into a gas having an increased nitrogen concentration.

6. The nitrogen gas generator according to claim 1, wherein the nitrogen gas generator is a gas generating device.

7. The fuel cell further includes a pressure control means for supplying air or a gas having a pressure exceeding atmospheric pressure and a fuel gas having a pressure exceeding atmospheric pressure to the fuel cell, The filtering means converts the exhaust gas having a pressure above atmospheric pressure into a gas having an increased concentration of nitrogen.

7. The nitrogen gas generator according to claim 1, wherein the nitrogen gas generator is a gas generating device.

8. The nitrogen gas generator according to any one of claims 1 to 7, characterized in that the fuel cell comprises a plurality of cells, which are structural units each including two electrodes sandwiching an electrolyte, and the entire set of cells is divided into a plurality of functional cell sections, each of which includes one or a plurality of consecutive cells, is not electrically connected in series with other functional cell sections, and is electrically connected to an individual power generation amount control unit.

9. a fuel cell that operates by taking in air or a gas containing nitrogen and oxygen and a fuel gas and discharging an exhaust gas having an oxygen concentration lower than that of the air or the fuel gas; a first flow control means for controlling the flow rate of air or the gas introduced into the fuel cell; a filtering means for converting the exhaust gas into a gas having an increased nitrogen concentration, the filtering means including a filter using fibers having different permeabilities for nitrogen and oxygen; a second flow control means for controlling the flow rate of the nitrogen-enriched gas delivered from the filtering means; and the second flow control means controls the flow rate of the gas with increased nitrogen concentration so that the nitrogen concentration of the gas with increased nitrogen concentration becomes a target nitrogen concentration under conditions where the pressure of the exhaust gas introduced into the filtering means is a predetermined pressure and the oxygen concentration of the exhaust gas is a low oxygen concentration realized by flow rate control by the first flow control means; The first flow control means controls the flow rate of the air or the gas so that the oxygen concentration of the exhaust gas becomes the low oxygen concentration under the condition that the pressure of the air or the gas introduced into the fuel cell is a predetermined pressure. A nitrogen gas generation system.

10. A method for producing a fuel cell, comprising: a first step of introducing air or a gas containing nitrogen and oxygen into a fuel cell while controlling the flow rate of the air or the gas; a second step of operating the fuel cell taking in air or the gas and a fuel gas, and extracting from the fuel cell an exhaust gas having an oxygen concentration lower than that of the air or the gas; a third step of passing the exhaust gas through a filter using fibers having different permeabilities for nitrogen and oxygen to convert the exhaust gas into a gas having an increased nitrogen concentration; a fourth step of controlling the flow rate of the nitrogen-enriched gas exiting the filter; and In a fourth step, under the condition that the pressure of the exhaust gas introduced into the filter is a predetermined pressure and the oxygen concentration of the exhaust gas is the low oxygen concentration realized by the flow rate control in the first step, the flow rate of the gas with increased nitrogen concentration is controlled so that the nitrogen concentration of the gas with increased nitrogen concentration becomes a target nitrogen concentration; In the first step, the flow rate of the air or gas introduced into the fuel cell is controlled so that the oxygen concentration of the exhaust gas becomes the low oxygen concentration under the condition that the pressure of the air or gas introduced into the fuel cell is a predetermined pressure. A method for generating nitrogen gas.

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