Apparatus for producing hydrogen gas, apparatus for supplying hydrogen gas, fuel cell system, movable body, and method for producing hydrogen gas

Abstract

To provide a small and simple apparatus for producing hydrogen gas small in power consumed, capable of removing nitrogen without using a high pressure compressor, and without separately needing a pressure-reducing machine for forming a differential pressure between an upstream side and a downstream side of a separation membrane so as to flow a gas successively generated from liquefied ammonia as a raw material to a downstream side without stagnating.SOLUTION: An apparatus for producing hydrogen gas of an embodiment includes a tank of liquefied ammonia, a primary purification part and a secondary purification part for removing residual ammonia gas and nitrogen gas from decomposition gas of ammonia gas, and a pressure reducing machine. A separation membrane of the purification part where the nitrogen gas is removed separates the hydrogen gas from the nitrogen gas by a pressure difference between an upstream side and a downstream side of the separation membrane. The pressure reducing machine is provided on a purified gas line where the hydrogen gas flows, and reduces the pressure on the upstream side of the pressure reducing machine. The pressure difference is formed as a part of a pressure difference formed between a pressure in the tank and a pressure on the upstream side of the pressure reducing machine.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a hydrogen gas production device that produces hydrogen gas using liquefied ammonia as a raw material, a hydrogen gas supply device, a fuel cell system, a mobile body, and a hydrogen gas production method. [Background technology]

[0002] Due to the trend toward carbon neutrality, fuel cells are widely used in fuel cell vehicles (FCVs) and on-site facilities for home or commercial use. One method for producing hydrogen gas, which serves as fuel gas for fuel cells, without generating carbon dioxide is to produce hydrogen gas using ammonia as a raw material. This method generally involves bringing heated ammonia gas into contact with a catalyst and decomposing it to produce a mixed gas consisting primarily of hydrogen gas and nitrogen gas.

[0003] Ammonia decomposition gas contains undecomposed residual ammonia in addition to nitrogen gas. When the residual ammonia is supplied to the negative electrode (fuel electrode) of a fuel cell together with hydrogen gas, the platinum catalyst at the negative electrode is poisoned, reducing its catalytic activity and causing a problem of reduced power generation performance of the fuel cell. Therefore, it is preferable to thoroughly remove the ammonia remaining in the ammonia decomposition gas. Conventionally, it has been known to adsorb ammonia onto an adsorbent such as zeolite and remove it from the ammonia decomposition gas (for example, Non-Patent Documents 1 and 3, Patent Documents 1 to 3).

[0004] Furthermore, if nitrogen gas is not removed from the ammonia decomposition gas, the maximum output during power generation will decrease, and therefore it is preferable to remove the nitrogen gas from the ammonia decomposition gas. Conventionally, it has been known to remove the nitrogen gas from the ammonia decomposition gas by using a pressure swing air (PSA) method or a cryogenic separation method (for example, Non-Patent Documents 1 and 2, and Patent Document 3). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 2017-104778 [Patent Document 2] International Publication No. 2023 / 022995 [Patent Document 3] Japanese Patent Application Publication No. 54-126689 [Non-patent literature]

[0006] [Non-Patent Document 1] Taiyo Nippon Sanso Corporation, Cabinet Office, Cross-ministerial Strategic Innovation Promotion Program (SIP), Project "Energy Carriers", Research Theme "Ammonia Hydrogen Station Fundamental Technology" Final Report (public), March 25, 2019 [Non-patent document 2] Akihiro Numata, "Hydrogen Recovery by Cryogenic Separation", Hitachi Review, Vol. 53, No. 12, p. 1164-1971 (1971) [Non-patent document 3] Junyoung Cha et al., “Ammonia as an efficient COx-free hydrogen carrier Fundamentals and feasibility analyzes for fuel cell applications”, Applied Energy, Vol. 224, p. 194-204 (2018) Summary of the Invention [Problem to be solved by the invention]

[0007] Patent Documents 1, 3, and Non-Patent Document 1 disclose hydrogen production processes using liquefied ammonia as a feedstock. These processes involve catalytic decomposition of ammonia to generate hydrogen, followed by removal of residual ammonia by adsorption using an adsorbent, and separation and removal of nitrogen by a PSA method or cryogenic separation method. The purified hydrogen obtained by these processes can be used as fuel for polymer electrolyte fuel cells (PEFCs), which are widely used as small, highly efficient power generation systems. Non-Patent Document 2 also discloses details of related cryogenic separation methods. Nitrogen removal using the PSA and cryogenic separation methods generally requires a high-pressure compressor, which requires installation space. Furthermore, the PSA method removes nitrogen by repeatedly adsorbing nitrogen onto an adsorbent under pressure and desorbing and discharging nitrogen from the adsorbent at reduced pressure. This requires frequent startup and continuous operation of the compressor, consuming a large amount of power. Furthermore, the cryogenic separation method also consumes a large amount of power because nitrogen is liquefied or adsorbed onto an adsorbent under extremely high-pressure conditions or under cooling conditions using adiabatic expansion from a high-pressure state, resulting in significant power consumption. To perform the PSA method or cryogenic separation method, which require such operations, large equipment is required, which is difficult to install or install on a mobile body or small on-site facility.

[0008] On the other hand, Non-Patent Document 3 discloses a hydrogen production process using liquefied ammonia as a feedstock. The process consists of only a hydrogen production step by catalytic decomposition of ammonia and a subsequent step of removing residual ammonia gas by adsorption using an adsorbent, and omits the nitrogen separation step using the PSA method or cryogenic separation method, which require large equipment and consumes a lot of power. In the hydrogen production process disclosed in Non-Patent Document 3, when the produced hydrogen is used as fuel for a polymer electrolyte fuel cell (PEFC), the residual ammonia gas that poisons the anode catalyst of the fuel cell (PEFC) is removed, so the produced hydrogen can be used as fuel for the fuel cell (PEFC). Furthermore, the process consumes little power, allowing the device to be small and lightweight, and can be installed or mounted on a mobile vehicle or small on-site facility. However, because the process disclosed in Non-Patent Document 3 does not perform nitrogen separation, nitrogen remains in the produced hydrogen at a molar ratio of hydrogen:nitrogen = 75:25. Therefore, in the process of Non-Patent Document 3, when the produced hydrogen is supplied to a fuel cell (PEFC) to generate electricity, the presence of nitrogen increases concentration polarization due to a decrease in hydrogen concentration at the negative electrode, resulting in a significant decrease in power generation efficiency, especially at high output.

[0009] Furthermore, Patent Document 2, like Non-Patent Document 3, omits the nitrogen separation step described above, and discloses an embodiment in which nitrogen-containing hydrogen produced by a hydrogen production process consisting only of a hydrogen generation step by catalytic decomposition of ammonia and a step of adsorption and removal of residual ammonia gas is supplied to a fuel cell (PEFC) to generate electricity, and in particular discloses an embodiment in which the aforementioned decrease in power generation efficiency is improved by, for example, modifying the negative electrode on the fuel cell (PEFC) by cutting a groove or by intermittently purging nitrogen that accumulates in high concentrations at the negative electrode during power generation. However, even with such an embodiment, a decrease in power generation efficiency due to increased concentration polarization is essentially unavoidable, and the very fact that a special fuel cell (PEFC) different from the specifications generally available on the market is required presents a problem in terms of versatility.

[0010] The present invention aims to provide a small, simple hydrogen gas production device that consumes little power, and that can remove nitrogen without using a high-pressure compressor, by creating a pressure difference between the vapor pressure in the liquefied ammonia tank and the pressure downstream of the separation membrane when producing hydrogen gas while supplying liquefied ammonia as a raw material, and by creating a pressure difference between the upstream and downstream sides of the separation membrane as part of this pressure difference, which eliminates the need to use a pressure reducer separate from the pressure reducer used to create the pressure difference. Also, the present invention aims to provide a hydrogen gas supply device, a fuel cell system, a mobile body, and a hydrogen gas production method. [Means for solving the problem]

[0011] The present disclosure encompasses the following aspects. Aspect 1 A hydrogen gas production apparatus for producing hydrogen gas by supplying liquefied ammonia as a raw material, the supplied liquefied ammonia, ammonia gas obtained by vaporizing the liquefied ammonia, a decomposition gas obtained by decomposing the ammonia gas, and a purified gas obtained by purifying the decomposition gas, in one direction, a tank for storing liquefied ammonia; a raw ammonia line for guiding the liquefied ammonia from the tank downstream; a vaporizer provided in the raw ammonia line for vaporizing the liquefied ammonia into ammonia gas; a heater for heating the vaporized ammonia gas to a temperature for decomposition; an ammonia decomposition unit connected to the raw ammonia line downstream of the vaporizer, for decomposing the ammonia gas heated to the decomposition temperature by bringing the ammonia gas into contact with a catalyst to generate a decomposed gas containing hydrogen gas, nitrogen gas, and residual ammonia gas; a decomposition gas line connected to the ammonia decomposition unit and guiding the decomposition gas downstream; a cooler provided in the decomposition gas line for cooling the decomposition gas; a primary purification section connected to the cracked gas line downstream of the cooler, for removing one of the residual ammonia gas and the nitrogen gas from the cooled cracked gas to generate a primary purified gas; a primary purified gas line connected to the primary purification section and guiding the primary purified gas downstream; a secondary purification unit connected to the primary purified gas line, for removing the other of the residual ammonia gas and the nitrogen gas from the primary purified gas to generate a secondary purified gas; a secondary purified gas line connected to the secondary purification section, which guides the secondary purified gas downstream and discharges it; the purification section from which the residual ammonia gas is removed out of the first purification section and the second purification section is an ammonia adsorption section having an adsorbent that adsorbs the residual ammonia gas, a hydrogen separation unit, wherein one of the primary purification unit and the secondary purification unit from which the nitrogen gas is removed has a separation membrane, and the separation membrane is configured to selectively allow the hydrogen gas to permeate and separate it from the nitrogen gas by a pressure difference created between an upstream side and a downstream side of the separation membrane; the hydrogen gas production apparatus further includes a pressure reducer provided in a purified gas line, one of the primary purified gas line and the secondary purified gas line, that is connected to the hydrogen separation unit and through which the hydrogen gas that has permeated the separation membrane flows, the pressure reducer sucking in the purified gas flowing through the purified gas line and discharging it downstream to reduce the pressure of the purified gas upstream of the pressure reducer; a hydrogen gas production apparatus in which the pressure upstream of the pressure reducer is reduced, thereby creating a pressure difference between the vapor pressure of ammonia gas evaporated in the tank and the pressure upstream of the pressure reducer, so that the liquefied ammonia and the gas flow downstream from the tank to the secondary purified gas line, and the differential pressure is formed as part of the pressure difference.

[0012] Aspect 2 2. The hydrogen gas production device according to aspect 1, wherein a compressor for increasing the pressure of the decomposed gas or the primary purified gas is not provided upstream of the separation membrane.

[0013] Aspect 3 2. The hydrogen gas production device according to aspect 1, further comprising a compressor upstream of the hydrogen separation unit for increasing the pressure of the cracked gas or the primary purified gas.

[0014] Aspect 4 3. The hydrogen gas production apparatus according to claim 1, wherein the tank includes a heater for heat retention that maintains the vapor pressure by heating the inside of the tank so that the flow of the liquefied ammonia and the gas downstream from the tank to the secondary purified gas line is maintained.

[0015] Aspect 5 the cooler and the vaporizer constitute a first heat exchanger having a first high-temperature side flow path through which the cracked gas flows and a first low-temperature side flow path through which the liquefied ammonia flows, 5. The hydrogen gas production apparatus according to any one of aspects 1 to 4, wherein the first heat exchanger is configured to cool the decomposition gas and heat and vaporize the liquefied ammonia by heat exchange between the decomposition gas flowing through the first high-temperature side flow path and the liquefied ammonia flowing through the first low-temperature side flow path.

[0016] Aspect 6 The hydrogen gas production apparatus according to aspect 5, wherein the cooler is referred to as a first cooler, and further comprises a second cooler that is provided upstream or downstream of the first cooler in the decomposition gas line and cools the decomposition gas.

[0017] Aspect 7 7. The hydrogen gas production apparatus according to claim 6, wherein the decomposition gas passing through the second cooler is cooled by heat exchange with external air or a liquid refrigerant cooled by heat exchange with external air.

[0018] Aspect 8 the heater for raising the temperature is provided downstream of the vaporizer in the raw ammonia line, a combustor that combusts a portion of any of the cracked gas, the primary purified gas, and the secondary purified gas, which are extracted from the ammonia decomposition section or downstream of the ammonia decomposition section, together with air, and discharges the combustion gas; a combustion gas line connected to the combustor and through which the combustion gas flows, a part of the combustion gas line and the heater for temperature increase constitute a second heat exchanger having a second high-temperature side flow path through which the combustion gas flows and a second low-temperature side flow path through which the ammonia gas flows, Aspect 8. The hydrogen gas production apparatus according to any one of aspects 1 to 7, wherein the second heat exchanger is configured to cool the combustion gas and raise the temperature of the ammonia gas by heat exchange between the combustion gas flowing through the second high-temperature side passage and the ammonia gas flowing through the second low-temperature side passage.

[0019] Aspect 9 the ammonia adsorption unit includes a regeneration heater that heats the adsorbent that has adsorbed the residual ammonia gas, an inert gas introduction line that introduces an inert gas from the outside, and a desorbed ammonia discharge line through which the residual ammonia gas desorbed from the adsorbent flows; Aspect 8. The hydrogen gas production apparatus of any one of aspects 1 to 7, wherein the ammonia adsorption unit is configured so that, when heated by the regeneration heater, the residual ammonia gas adsorbed by the adsorbent is desorbed from the adsorbent and discharged from the ammonia adsorption unit through the desorbed ammonia discharge line together with the inert gas introduced through the inert gas inlet line.

[0020] Aspect 10 a combustor that combusts a portion of any of the cracked gas, the primary purified gas, and the secondary purified gas extracted from the ammonia decomposition section or downstream of the ammonia decomposition section, together with air, and discharges the combustion gas; Aspect 10. The hydrogen gas generating apparatus according to aspect 9, wherein the residual ammonia gas discharged together with the inert gas is introduced into the combustor and combusted.

[0021] Aspect 11 the heater for raising the temperature is provided downstream of the vaporizer in the raw ammonia line, the hydrogen gas production apparatus further includes a combustion gas line connected to the combustor and through which the combustion gas flows; a part of the combustion gas line and the heater for temperature increase constitute a second heat exchanger having a second high-temperature side flow path through which the combustion gas flows and a second low-temperature side flow path through which the ammonia gas flows, A hydrogen gas production apparatus according to aspect 10, wherein the second heat exchanger is configured to cool the combustion gas and raise the temperature of the ammonia gas by heat exchange between the combustion gas flowing through the second high-temperature side passage and the ammonia gas flowing through the second low-temperature side passage.

[0022] Aspect 12 a re-liquefaction unit connected to the desorbed ammonia discharge line and the tank, and configured to liquefy the residual ammonia gas desorbed from the adsorbent to separate it from the inert gas; Aspect 12. The hydrogen gas production apparatus according to any one of aspects 9 to 11, wherein the residual ammonia gas discharged together with the inert gas is guided to the re-liquefaction section, liquefied to be separated from the inert gas, and recovered in the tank.

[0023] Aspect 13 the ammonia adsorption unit has a plurality of ammonia adsorbers arranged in parallel in the one direction, each of the plurality of ammonia adsorbers includes the adsorbent, the inert gas introduction line, and the desorbed ammonia discharge line; ammonia adsorption unit is configured such that, in one or more ammonia adsorbers among the plurality of ammonia adsorbers, the residual ammonia gas desorbed from the adsorbent by heating with the regenerative heater is discharged through the desorbed ammonia discharge line together with the inert gas introduced from the inert gas inlet line, while the decomposed gas or the primary purified gas is introduced into the remaining ammonia adsorbers, the residual ammonia gas in the gas is adsorbed by the adsorbent of the ammonia adsorber and removed, and the decomposed gas or the primary purified gas from which the residual ammonia gas has been removed is guided downstream of the ammonia adsorption unit, and the one or more ammonia adsorbers and the remaining ammonia adsorbers are switchable among the plurality of ammonia adsorbers.

[0024] Aspect 14 14. The hydrogen gas production apparatus according to any one of aspects 1 to 13, wherein the ammonia adsorption unit includes a plurality of ammonia adsorbers arranged in series in the same direction, and each of the plurality of ammonia adsorbers includes the adsorbent.

[0025] Aspect 15 15. The hydrogen gas production apparatus according to any one of aspects 1 to 14, further comprising: a flow rate regulator provided in the raw ammonia line downstream of the vaporizer to regulate a flow rate of the ammonia gas; and / or an upstream pressure regulator provided in the gas line through which the gas introduced to the hydrogen separation unit flows to regulate a pressure of the gas flowing in the gas line.

[0026] Aspect 16 16. The hydrogen gas production device according to any one of aspects 1 to 15, wherein the primary purification unit is the ammonia adsorption unit, and the secondary purification unit is the hydrogen separation unit.

[0027] Aspect 17 A hydrogen gas supply device that supplies hydrogen gas to a supply destination, The hydrogen gas production apparatus according to any one of aspects 1 to 16; a final gas discharge line connected to a secondary purified gas line of the hydrogen gas production apparatus, which guides the secondary purified gas discharged from the secondary purified gas line toward the supply destination and discharges it, the final gas discharge line having a branch portion that branches off so that the secondary purified gas flows to a side different from the supply destination; a purified gas tank connected to the branching portion and configured to store the secondary purified gas flowing to the different side; a compressor provided upstream of the branched portion in the final gas discharge line, for pressurizing the secondary purified gas into the purified gas tank; a set of switching valves that are provided in the final gas discharge line and that switch the flow path of the secondary purified gas flowing through the final gas discharge line, switching between flowing the secondary purified gas discharged from the secondary purified gas line toward the purified gas tank, guiding the secondary purified gas in the purified gas tank to the supply destination side and discharging it, or guiding the secondary purified gas discharged from the secondary purified gas line to the supply destination side and discharging it.

[0028] Aspect 18 The hydrogen gas production apparatus according to any one of aspects 1 to 16 or the hydrogen gas supply apparatus according to aspect 17; a polymer electrolyte fuel cell having an anode and a cathode, the anode and the cathode being connected to an external load, and configured to generate electricity by supplying secondary purified gas discharged from the hydrogen gas production device or the hydrogen gas supply device to the anode and air to the cathode.

[0029] Aspect 19 The fuel cell system includes: a purified gas supply line connected to a secondary purified gas line of the hydrogen gas production device or a final gas discharge line of the hydrogen gas supply device, for guiding the secondary purified gas discharged from the line to the negative electrode; a hydrogen-containing gas discharge line provided with a flow path switch, which guides a hydrogen-containing gas containing surplus hydrogen gas, which is not consumed during the power generation and is discharged from the negative electrode, and nitrogen gas, which is contained in the secondary purified gas and has permeated a separation membrane of the hydrogen gas production device, to the secondary purified gas line or the final gas discharge line connected to the purified gas supply line and merges with the secondary purified gas; a hydrogen-containing gas treatment line that branches off from the hydrogen-containing gas discharge line via the flow path switch and discharges the hydrogen-containing gas to the outside, the flow path switch is configured to switch the flow direction of the hydrogen-containing gas to one of the secondary purified gas line side or the final gas discharge line side and the hydrogen gas treatment line side; the flow direction of the hydrogen-containing gas is switched to the side of the secondary purified gas line or the final gas discharge line, so that the hydrogen-containing gas is circulated and supplied to the negative electrode together with the secondary purified gas discharged from the secondary purified gas line or the final gas discharge line; When the amount of electricity generated by the polymer electrolyte fuel cell or the elapsed time during the power generation from the time when the flow direction of the hydrogen-containing gas is switched to the second purified gas line or the final gas discharge line reaches a predetermined value, the flow direction of the hydrogen-containing gas is switched to the hydrogen-containing gas treatment line side, and the hydrogen-containing gas containing the concentrated nitrogen gas from that time is discharged to the outside, A fuel cell system as described in aspect 18, configured so that upon completion of discharge of the hydrogen-containing gas containing the concentrated nitrogen gas from the hydrogen-containing gas processing line to the outside, the flow direction of the hydrogen-containing gas switches to the side of the secondary purification line or the final gas discharge line.

[0030] Aspect 20 The primary purification unit of the hydrogen gas production device and the hydrogen gas supply device is an ammonia adsorption unit, and the secondary purification unit is a hydrogen separation unit, a purified gas supply line connected to a secondary purified gas line of the hydrogen gas production device or a final gas discharge line of the hydrogen gas supply device, for guiding the secondary purified gas discharged from the line to the negative electrode; a hydrogen-containing gas discharge line provided with a flow path switch, which guides a hydrogen-containing gas containing surplus hydrogen gas, which is not consumed during the power generation and is discharged from the negative electrode, and nitrogen gas, which is contained in the secondary purified gas and has permeated a separation membrane of the hydrogen gas production device, to the secondary purified gas line or the final gas discharge line connected to the purified gas supply line and merges with the secondary purified gas; a hydrogen-containing gas treatment line branching from the hydrogen-containing gas discharge line via the flow path switch and connected to a primary purified gas line of the hydrogen gas production device or the hydrogen gas supply device, the flow path switch is configured to switch the flow direction of the hydrogen-containing gas to one of the secondary purified gas line side or the final gas discharge line side and the hydrogen gas treatment line side; the flow direction of the hydrogen-containing gas is switched to the side of the secondary purified gas line or the final gas discharge line, so that the hydrogen-containing gas is circulated and supplied to the negative electrode together with the secondary purified gas discharged from the secondary purified gas line or the final gas discharge line; When the amount of electricity generated by the polymer electrolyte fuel cell or the elapsed time during the power generation from the time point when the flow direction of the hydrogen-containing gas is switched to the second purified gas line or the final gas discharge line side reaches a predetermined value, the flow direction of the hydrogen-containing gas is switched to the hydrogen-containing gas treatment line side, and the hydrogen-containing gas containing the concentrated nitrogen gas from that point on is led to the first purified gas line via the hydrogen-containing gas treatment line, merges with the first purified gas flowing in the first purified line, and is led to the hydrogen separation unit, where the nitrogen gas is separated and removed by the separation membrane, and the merged gas from which the nitrogen gas has been separated and removed is supplied to the negative electrode via the second purified gas line or the final gas discharge line and the hydrogen gas supply line, A fuel cell system as described in aspect 18, configured so that upon completion of the separation and removal of the nitrogen gas from the gas after the merger, the flow direction of the hydrogen-containing gas is switched to the side of the secondary purified gas line or the final gas discharge line.

[0031] Aspect 21 A mobile object, a fuel cell system according to aspect 20; and a motor connected to the negative and positive electrodes of the fuel cell system, driven by the power generated by the fuel cell of the fuel cell system, and generating power to propel the mobile body.

[0032] Aspect 22 A hydrogen gas production method for producing hydrogen gas by supplying liquefied ammonia as a raw material, and sequentially flowing the supplied liquefied ammonia, ammonia gas obtained by vaporizing the liquefied ammonia, a cracked gas obtained by decomposing the ammonia gas, and a purified gas obtained by purifying the cracked gas in one direction, A step of guiding the liquefied ammonia from a tank storing the liquefied ammonia downstream and vaporizing the liquefied ammonia into ammonia gas; heating the vaporized ammonia gas to a decomposition temperature; a step of bringing the ammonia gas heated to the decomposition temperature into contact with a catalyst to decompose the ammonia gas, thereby generating a decomposed gas containing hydrogen gas, nitrogen gas, and residual ammonia gas; cooling the cracked gas; removing one of the residual ammonia gas and the nitrogen gas from the cooled decomposition gas to generate a primary purified gas; removing the other of the residual ammonia gas and the nitrogen gas from the primary purified gas to generate a secondary purified gas; a step of removing the residual ammonia gas from the step of generating the primary purified gas and the step of generating the secondary purified gas, the step of using an adsorbent that adsorbs the residual ammonia gas to adsorb the residual ammonia gas onto the adsorbent; the step of removing the nitrogen gas from the step of generating the primary purified gas and the step of generating the secondary purified gas is a step of separating the hydrogen gas from the nitrogen gas by selectively allowing the hydrogen gas to permeate using a separation membrane due to a pressure difference created between an upstream side and a downstream side of the separation membrane; The hydrogen gas production method further includes a step of reducing the pressure of the purified gas upstream by sucking in the purified gas containing the hydrogen gas that has permeated the separation membrane and discharging it downstream, a pressure difference is formed between the vapor pressure of ammonia gas evaporated in the tank and the pressure on the upstream side, and the pressure difference is formed as part of the pressure difference, so that the liquefied ammonia and the gas flow downstream from the tank to the downstream side of the separation membrane by reducing the pressure on the upstream side. [Effects of the Invention]

[0033] According to the hydrogen gas production apparatus and method of the above aspects, when hydrogen gas is produced while supplying liquefied ammonia as a raw material, a pressure difference is established between the vapor pressure in the liquefied ammonia tank and the pressure on the downstream side of the separation membrane, so that gas produced sequentially using the liquefied ammonia as a raw material flows downstream without stagnation, and by forming a differential pressure between the upstream and downstream sides of the separation membrane as part of this pressure difference, it is not necessary to use a pressure reducer separate from the pressure reducer used to form the pressure difference.In addition, nitrogen removal can be performed without using a high-pressure compressor, thereby reducing power consumption and making the equipment smaller and simpler.Furthermore, a hydrogen gas supply apparatus, a fuel cell system, and a mobile object equipped with such a hydrogen gas production apparatus can be obtained. [Brief explanation of the drawings]

[0034] [Figure 1] 1 is a diagram showing the configuration of a hydrogen gas production device A1 according to one embodiment. [Figure 2] FIG. 1 is a diagram showing the configuration of a hydrogen gas production device A5 according to an embodiment. [Figure 3] FIG. 1 is a diagram showing the configuration of a hydrogen gas production device A2 according to an embodiment. [Figure 4] FIG. 1 is a diagram showing the configuration of a hydrogen gas production device A3 according to an embodiment. [Figure 5] FIG. 1 is a diagram showing the configuration of a hydrogen gas production device A4 according to an embodiment. [Figure 6] FIG. 2 is a diagram showing the configuration of a hydrogen gas supply device B1 according to an embodiment. [Figure 7] FIG. 2 is a diagram showing the configuration of a hydrogen gas supply device B2 according to an embodiment. [Figure 8] FIG. 1 is a diagram showing the configuration of a fuel cell system C1 according to an embodiment. [Figure 9] FIG. 2 is a diagram showing the configuration of a fuel cell system C2 according to an embodiment. [Figure 10] FIG. 2 is a diagram showing the configuration of a fuel cell system C3 according to an embodiment. [Figure 11] FIG. 2 is a diagram showing the configuration of a fuel cell system C4 according to an embodiment. [Figure 12] FIG. 2 is a diagram showing the configuration of a fuel cell system C5 according to an embodiment. [Figure 13] FIG. 1 is a diagram showing the configuration of a fuel cell system C6 according to an embodiment. [Figure 14] FIG. 2 is a diagram showing the configuration of a fuel cell system C7 according to an embodiment. [Figure 15] FIG. 1 is a diagram showing the configuration of a fuel cell system C9 according to an embodiment. [Figure 16] FIG. 2 is a diagram showing the configuration of a fuel cell system C8 according to an embodiment. [Figure 17] FIG. 1 is a diagram showing the configuration of a fuel cell system C10 according to an embodiment. [Figure 18] FIG. 1 is a diagram showing the configuration of a fuel cell system C11 according to an embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0035] Hereinafter, a hydrogen gas production device, a hydrogen gas supply device, a fuel cell system, a mobile body, and a hydrogen gas production method according to embodiments will be described.

[0036] 1 shows the configuration of a hydrogen gas production apparatus A1 according to one embodiment. In the following description, the hydrogen gas production apparatuses An (n is an integer of 1 to 5) may be collectively referred to as hydrogen gas production apparatus A.

[0037] The hydrogen gas production apparatus A1 is an apparatus for producing hydrogen gas by supplying liquefied ammonia as a raw material and sequentially flowing the supplied liquefied ammonia, ammonia gas obtained by vaporizing the liquefied ammonia, cracked gas obtained by decomposing the ammonia gas, and purified gas obtained by purifying the cracked gas in one direction. "One direction" refers to the direction in which the liquefied ammonia, ammonia gas, cracked gas, and purified gas flow through each part (including lines and equipment) that constitutes the hydrogen gas production apparatus A1 (hereinafter also referred to as the gas flow direction).

[0038] The hydrogen gas production apparatus A1 includes a tank 1, a raw ammonia line 3, a vaporizer 5, a heater 7 for heating, an ammonia decomposition section 9, a decomposition gas line 11, a cooler 13, a primary purification section 15, a primary purified gas line 17, a secondary purification section 19, and a secondary purified gas line 21.

[0039] Tank 1 is a container for storing liquefied ammonia. The ammonia to be liquefied may be synthesized using the Haber-Bosch process, which uses hydrogen gas obtained from natural gas, coal gas, etc. through a steam reforming reaction or a shift reaction, and nitrogen gas from the air, or may be synthesized using hydrogen gas obtained by water electrolysis and nitrogen gas from the air; the synthesis method is not limited. Tank 1 generally has a nozzle with an openable valve (not shown) for replenishing the liquefied ammonia from the outside when the amount of liquefied ammonia inside decreases.

[0040] The liquefied ammonia stored in the tank 1 is preferably prepared from ammonia from which components such as carbon monoxide and sulfur compounds, such as hydrogen sulfide and sulfur dioxide, have been sufficiently removed in advance. The secondary purified gas, which is produced by the hydrogen gas production apparatus A1 using liquefied ammonia as a raw material and will be described later, is primarily composed of hydrogen gas and is used, for example, as fuel gas for polymer electrolyte fuel cells (PEFCs). If the secondary purified gas contains the above-mentioned components as impurities, the PEFC anode may be poisoned, resulting in reduced power generation performance. Therefore, the liquefied ammonia stored in the tank 1 is preferably prepared from ammonia from which impurities have been sufficiently removed to the extent that electrode poisoning is not a problem. Ammonia obtained by synthesizing hydrogen gas obtained by water electrolysis with nitrogen gas is unlikely to contain the above-mentioned impurities and is therefore preferable as the liquefied ammonia used as the raw material for the secondary purified gas. Ammonia synthesized by the Haber-Bosch process from raw materials such as natural gas and coal gas can generally contain the above-mentioned impurities to an acceptable level by carefully controlling the purity at each synthesis step.

[0041] Liquefied ammonia is stored in tank 1 so that a gas phase space filled with vaporized ammonia gas is formed above the liquid surface, and the liquid phase liquefied ammonia and the gas phase ammonia gas form a gas-liquid equilibrium state at the temperature inside tank 1. During operation of hydrogen gas production apparatus A1, tank 1 is normally sealed except for supply valve 4, which will be described later. The pressure of the gas phase inside tank 1 during operation of hydrogen gas production apparatus A1 (hereinafter also referred to as internal tank pressure) is maintained at the saturated vapor pressure of ammonia at the temperature inside tank 1, except in cases such as when the supply amount of liquefied ammonia fluctuates suddenly. As will be described later, this internal tank pressure becomes part of the driving force that moves gas within the system during the process of producing hydrogen gas from liquefied ammonia in hydrogen gas production apparatus A1.

[0042] The raw ammonia line 3 is a line that guides liquefied ammonia from the tank 1 to the downstream side. In this specification, the term "line" includes not only piping but also a valve provided in the piping. The raw ammonia line 3 is provided with a supply valve 4 that is opened when the liquefied ammonia in the tank 1 is supplied to the downstream side.

[0043] The vaporizer 5 is provided in the raw ammonia line 3 and vaporizes the liquefied ammonia to produce ammonia gas. The vaporizer 5 is equipped with a heating mechanism and can provide the liquefied ammonia with a heat quantity greater than the latent heat of vaporization of the liquefied ammonia. The heating mechanism can be a heat exchanger (e.g., the first heat exchanger 25 shown in FIG. 5, which will be referred to later) that exchanges heat between the liquefied ammonia and a high-temperature gas, an electric heater, or the like, or a combination of these. The heat exchanger is not limited to the first heat exchanger 25. If there is an external heat source with a sufficient heat quantity and temperature for the vaporization, the heat medium, which is a fluid, heated by the heat source can be introduced into the heat exchanger of the vaporizer 5 to vaporize the liquefied ammonia (this embodiment is not shown). This heat exchanger is preferably used both during startup and steady-state operation (during operation other than startup) of the hydrogen gas production apparatus A1.

[0044] Heating heater 7 is a device that heats vaporized ammonia gas to a decomposition temperature. The decomposition temperature is the temperature required for the ammonia gas decomposition reaction (reaction equation 2NH3 → 3H2 + N2) in ammonia decomposition section 9, and is set according to the performance of the catalyst, etc., so as to obtain a sufficient decomposition rate of ammonia gas. Heating heater 7 may be provided downstream of vaporizer 5 in raw ammonia line 3 to heat the ammonia gas flowing in raw ammonia line 3, or may be provided in ammonia decomposition section 9 to heat the equipment of ammonia decomposition section 9 (for example, a decomposition tower described below), or may be provided in both of these locations, as in the example shown in FIG. 1.

[0045] The heater 7 for heating can be an electric heater or a heat exchanger (e.g., the second heat exchanger 33 shown in FIG. 5) that exchanges heat between ammonia gas and a high-temperature gas, or both. Among these, an electric heater is preferably used in the ammonia decomposition section 9 because, when the ammonia decomposition section 9 is installed, it can be heated independently by applying electricity during startup of the hydrogen gas production apparatus A1, facilitating the decomposition reaction. Furthermore, when an external heat source with sufficient heat quantity and temperature for the temperature increase is available, the second heat exchanger 33 can heat the ammonia gas to a predetermined decomposition temperature by introducing a fluid heat medium heated by the heat source into the second heat exchanger 33. Such a second heat exchanger 33 is preferably used both during startup and steady-state operation (operation other than startup) of the hydrogen gas production apparatus A1. Furthermore, combustion gas (described later) can be used as a heat source for heating in the second heat exchanger 33. In this case, the second heat exchanger 33 is preferably used during steady-state operation of the hydrogen gas production apparatus A1.

[0046] According to one embodiment, as shown in FIG. 2, the temperature-raising heater 7 may be configured for autothermal reforming (ATR), in which a portion of the ammonia gas introduced into the ammonia decomposition unit 9 is combusted with air to heat the remaining ammonia gas to a decomposition temperature. This configuration may also be used in combination with an electric heater, a second heat exchanger 33, or the like. FIG. 2 is a diagram showing the configuration of a hydrogen gas production apparatus A5. In the hydrogen gas production apparatus A5, the temperature-raising heater 7 provided in the ammonia decomposition unit 9 is a combination of an autothermal reforming configuration (ATR) and an electric heater provided in the device (e.g., a decomposition tower) of the ammonia decomposition unit 9, but the electric heater may be omitted. In the hydrogen gas production apparatus A5, an outside air introduction line 10 for introducing external air is connected to the ammonia decomposition unit 9 to perform autothermal reforming. A combustion oxidation catalyst for promoting the combustion of ammonia gas may be provided in the ammonia decomposition unit 9 upstream of a catalyst for promoting the decomposition reaction, which will be described later. The combustion oxidation catalyst may be a carrier made of porous ceramics molded into a granulated or honeycomb shape, or a honeycomb-shaped carrier made of a nitridation-resistant metal (for example, nickel (Ni), nickel alloys such as Inconel (registered trademark) 600, 625, 718, and 750, Incoloy (registered trademark) 800 and 825, Hastelloy (registered trademark) C276 and C22, Nimonic (registered trademark) 75, 80A, and 90, or stainless steel such as SUS310S), carrying ultrafine particle catalyst particles made of at least one of precious metals such as platinum (Pt), palladium (Pd), ruthenium (Ru), rhodium (Rh), and iridium (Ir), and oxides of metals such as manganese (Mn), cobalt (Co), chromium (Cr), and copper (Cu). Furthermore, with the autothermal reforming configuration (ATR), the device of the ammonia decomposition unit 9 that is in a stopped state can be quickly heated, and the ammonia decomposition unit 9 can be started up.

[0047] Returning to Figure 1, ammonia decomposition unit 9 is connected to raw ammonia line 3 downstream of vaporizer 5, and is a section where ammonia gas heated to a decomposition temperature is brought into contact with a catalyst to decompose (crack) it, thereby generating a cracked gas containing hydrogen gas, nitrogen gas, and residual ammonia gas. Ammonia decomposition unit 9 preferably uses a cracking tower in which ammonia gas is brought into contact with a catalyst arranged inside while flowing from below to above, and decomposed.

[0048] The catalyst used for ammonia decomposition is preferably an oxide or oxynitride of an element such as sodium (Na), potassium (K), rubidium (Ru), cesium (Cs), magnesium (Mg), calcium (Ca), strontium (St), barium (Ba), a rare earth element (e.g., cerium (Ce), lanthanum (La), yttrium (Y), etc.), aluminum (Al), silicon (Si), titanium (Ti), or zirconium (Zr), or a composite oxide or composite oxynitride of these elements, or a catalyst in which ultrafine particles of a catalyst component are dispersed and supported on a support having a large specific surface area, such as zeolites, graphite, activated carbon, or nanocarbons (e.g., vapor-grown carbon fiber, carbon nanotube, carbon nanohorn, or graphene). Furthermore, as a support component that provides a high promoter effect, materials containing amides and imides of alkali metals and alkaline earth metals (e.g., NaNH2, Ca(NH2)2, Mg(NH2)2, CaNH, LiCaN, etc.) may be used as a support or mixed with the above-mentioned support. Ultrafine particles of the catalyst component are used, such as iron (Fe) oxide, nickel (Ni), cobalt (Co), ruthenium (Ru), palladium (Pd), rhodium (Rh), iridium (Ir), and platinum (Pt), having a very small particle size (1 nm or more and less than 1 μm). Ultrafine particles of ruthenium (Ru) are preferred, as they can particularly accelerate the decomposition reaction at low temperatures and lower the decomposition temperature. The decomposition temperature when using a catalyst supporting ultrafine particles of ruthenium (Ru) is affected by the material, composition, and structure of the support. For ruthenium (Ru)-supported catalysts that exhibit excellent performance, the decomposition temperature is set to, for example, 500 to 600°C. This makes it easier to decompose ammonia gas at a high decomposition rate (for example, about 95 to 99% at an absolute pressure of 1 MPa or less, although this rate also depends on the pressure inside the ammonia decomposition unit 9).

[0049] The catalyst used in the ammonia decomposition unit 9 may be packed in granular form or may be arranged in a honeycomb shape so as to reduce the pressure loss of the ammonia gas flowing inside the device of the ammonia decomposition unit 9, and various other forms can be used. The catalyst formed in a honeycomb shape may be a catalyst carrier supporting the above-mentioned ultrafine particle catalyst for ammonia decomposition formed into a honeycomb shape, or may be a metal honeycomb having nitriding resistance coated with a catalyst carrier supporting the ultrafine particle catalyst for ammonia decomposition.

[0050] The decomposition gas mainly contains hydrogen gas and nitrogen gas in a molar ratio of 75:25, for example, in accordance with the production ratio in the reaction formula 2NH3 → 3H2 + N2, and when produced in the ammonia decomposition unit 9, it also contains a small amount (for example, 1000 volume ppm to 5 volume %) of undecomposed residual ammonia gas that can poison the electrodes of a polymer electrolyte fuel cell (PEFC).

[0051] The decomposed gas line 11 is connected to the ammonia decomposing section 9 and is a line that guides the decomposed gas downstream.

[0052] The cooler 13 is a device provided in the cracked gas line 11 and cools the cracked gas. By cooling the cracked gas to, for example, less than 100°C, preferably to room temperature (approximately 25°C) or lower, a larger amount of residual ammonia gas can be adsorbed onto the adsorbent in the ammonia adsorption section described below, thereby improving the removal rate of the residual ammonia gas. Furthermore, by cooling the cracked gas, a larger amount of hydrogen gas can be separated from nitrogen gas in the hydrogen separation section described below, thereby improving the removal rate of nitrogen gas. Furthermore, if the hydrogen separation section includes a polymer separation membrane or a resin container that is sensitive to heat, cooling can also prevent deterioration of these materials.

[0053] The primary purification section 15 is connected to the cracked gas line 11 downstream of the cooler 13 and removes either the residual ammonia gas or the nitrogen gas from the cooled cracked gas to produce a primary purified gas. Furthermore, the secondary purification section 19, located downstream of the primary purification section 15, removes the remaining one of the residual ammonia gas and the nitrogen gas from the primary purified gas to produce a secondary purified gas. Below, the hydrogen gas production apparatus A1 will be described in detail for the case where the residual ammonia gas is removed in the primary purification section 15 and the nitrogen gas is removed in the secondary purification section 19.

[0054] The primary purification section 15 of the hydrogen gas production apparatus A1 shown in Fig. 1 is an ammonia adsorption section that removes residual ammonia gas. In the following description, the ammonia adsorption section that is the primary purification section 15 will be referred to as the ammonia adsorption section 15. The ammonia adsorption section 15 has an adsorbent that adsorbs the residual ammonia gas. The ammonia adsorption section 15 uses an adsorption tower that adsorbs the residual ammonia gas onto the adsorbent arranged inside while flowing the cracked gas from the inlet side to the outlet side.

[0055] The adsorbent used in the ammonia adsorption section 15 is preferably a porous adsorbent with many Lewis acid sites, such as X-type or A-type zeolite. Zeolites with many pores with pore diameters of approximately 5 to 20 Å, such as zeolite 13X, are particularly suitable. These zeolites preferably contain at least one cation selected from the group consisting of lithium (Li), calcium (Ca), and sodium (Na). These adsorbents can be regenerated by adsorbing residual ammonia gas and the like and then heating them at the point where they reach breakthrough, thereby desorbing the ammonia gas and the like, making them reusable. If the cracked gas contains moisture as an impurity or a by-product of ammonia decomposition in the autothermal reforming (ATR) configuration, not only the residual ammonia gas but also the moisture is adsorbed by the adsorbent in the ammonia adsorption section 15 and removed from the cracked gas.

[0056] When the above-described autothermal reforming (ATR) configuration is adopted for the heating heater 7, water vapor is also adsorbed by the adsorbent in addition to the residual ammonia gas, and therefore the breakthrough time of the adsorbent in the ammonia adsorption section 15 is shortened. Therefore, when the autothermal reforming (ATR) configuration is adopted for the heating heater 7, it may be necessary to increase the frequency of the adsorbent regeneration process.

[0057] The primary purified gas, which has passed through the ammonia adsorption section 15 and from which residual ammonia gas has been removed, is a mixed gas consisting of approximately 75% by volume of hydrogen gas and 25% by volume of nitrogen gas. When the secondary purified gas obtained by further purifying the primary purified gas in a subsequent stage (downstream) is used as fuel gas for a polymer electrolyte fuel cell (PEFC), the concentration of residual ammonia gas that will poison the electrodes in the primary purified gas is, for example, less than several hundred ppb by volume, and preferably less than 100 ppb by volume.

[0058] The primary purified gas line 17 is connected to the primary purification section 15 and is a line that guides the primary purified gas downstream.

[0059] The secondary purification section 19 is connected to the primary purified gas line 17 and removes either the residual ammonia gas or the nitrogen gas from the primary purified gas to produce a secondary purified gas. Here, we will particularly describe the removal of nitrogen gas from the primary purified gas from which residual ammonia gas has already been removed. The secondary purification section 19 of the hydrogen gas production apparatus A1 shown in FIG. 1 is a hydrogen separation section that removes nitrogen gas. In the following description, the hydrogen separation section that is the secondary purification section 19 will be referred to as the hydrogen separation section 19. The hydrogen separation section 19 has a separation membrane and is configured to selectively allow hydrogen gas to permeate and separate it from nitrogen gas by using a differential pressure (hereinafter simply referred to as differential pressure) created between the upstream and downstream sides of the separation membrane. The hydrogen separation section 19 has an inlet for the primary purified gas and an outlet for the secondary purified gas (hereinafter referred to as the inlet and outlet, respectively). A flow-type gas separation membrane module is used in which a separation membrane configured to permeate and separate hydrogen gas from the purified gas is arranged midway along the flow path of the purified gas flowing from the inlet to the outlet.

[0060] Gas is injected into the separation membrane module installed inside the hydrogen separation section 19 from the inlet, and due to the pressure difference between the upstream side (inlet side) and downstream side (outlet side) of the module separated by the separation membrane, hydrogen gas selectively permeates the separation membrane from the components contained in the gas, while nitrogen gas hardly permeates and is discharged from each exhaust line.

[0061] Separation membranes for separating hydrogen gas generally include membranes made of palladium (Pd) or palladium alloys, membranes made of crystalline or amorphous ceramics such as zeolite, porous silica, porous alumina, and porous aluminosilicate, and porous polymer membranes having a separation layer made of aromatic polyamide, aromatic polyimide, polytetrafluoroethylene (PTFE), etc. Separation membranes that have a high performance (selective permeability) of allowing more hydrogen gas to permeate than nitrogen gas at a predetermined differential pressure and that allow a large amount of hydrogen gas to permeate (high permeation rate) are preferably used.

[0062] Among the separation membranes mentioned above, membranes made of palladium (Pd) or palladium alloys have particularly excellent hydrogen gas selective permeability, enabling the production of high-purity hydrogen gas of 99.97% by volume or higher, as specified in the international standard ISO14687-2 2012 Grade D (hereinafter referred to as ISO14687-2), in a single pass. However, palladium (Pd) is rare and expensive, making it difficult to fabricate membranes with large surface areas. Furthermore, the hydrogen gas permeation rate is extremely slow, especially at room temperature (approximately 25°C), requiring the application of an extremely large differential pressure. Therefore, they are not suitable for rapidly purifying the large amounts of hydrogen gas required for the operation of fuel cell systems and mobile vehicles, as described below. Furthermore, to separate hydrogen gas using a palladium (Pd) or palladium alloy separation membrane, the cracked gas must be heated to a high temperature upstream of the hydrogen separation unit 19. For this reason, palladium (Pd) or palladium alloy separation membranes are excluded from the separation membranes used in the hydrogen separation unit 19.

[0063] On the other hand, separation membranes with separation layers made of crystalline or amorphous ceramics such as zeolite (e.g., SOD-type zeolite), porous silica, porous alumina, or porous aluminosilicate, and porous polymer separation membranes with separation layers made of aromatic polyamide, aromatic polyimide, polytetrafluoroethylene (PTFE), etc., are less expensive than palladium (Pd) or palladium alloy separation membranes and are less restricted in raw material resources. These separation membranes have a large number of micropores with pore sizes on the angstrom level (1 angstrom or greater, less than 100 nm), enabling separation based on differences in the molecular sizes of gas components. These micropores are particularly preferred for their narrow pore size distribution of approximately 3 Å, which corresponds to the midpoint between the molecular diameters of hydrogen and nitrogen. Therefore, ceramic separation membranes or polymer separation membranes with the above-mentioned specifications are preferably used as the separation membrane for the hydrogen separation unit 19.

[0064] In particular, polymer separation membranes are generally lightweight and can be molded into a variety of shapes (e.g., thin, narrow hollow fibers). Separation membrane modules, in which such hollow fiber membranes are bundled and enclosed in a container, allow separation membranes with large surface areas to be efficiently enclosed in the container, thereby increasing the hydrogen gas permeation rate per module size. This is advantageous for installing on-site facilities in confined spaces or on mobile vehicles. Furthermore, some polymer separation membranes have been subjected to surface treatments to increase the selective permeability and permeation rate (permeation rate) of hydrogen gas. Such polymer separation membranes achieve sufficient hydrogen gas permeation rates at room temperature (approximately 25°C) even under relatively small differential pressure conditions. This eliminates the need to pressurize the primary purified gas upstream of the hydrogen separation section 19, reducing the power required to produce hydrogen gas and contributing to reduced manufacturing costs. Therefore, polymer separation membranes with the above-described specifications are particularly preferred.

[0065] The magnitude of the differential pressure between the upstream and downstream sides of the separation membrane is set to an appropriate value so as to obtain a predetermined permeation rate of hydrogen gas. For example, when separation is performed at around room temperature (about 25°C) using a polymer separation membrane with good performance, the differential pressure is set, for example, within the range of about 0.5 to 0.9 MPa.

[0066] Selective permeability and permeation amount (permeation rate) are generally affected by temperature, and as temperature increases, selective permeability decreases slightly while permeation amount (permeation rate) often increases. Therefore, it is preferable to determine the temperature of the gas introduced into the separation membrane module taking into consideration the balance between these two. Furthermore, when separation is performed using a polymer separation membrane, which generally has lower heat resistance than separation membranes made of ceramic or the like, it is preferable that the hydrogen gas production apparatus A1 can be suitably operated, for example, at around room temperature (approximately 25°C), and that sufficient selective permeability and permeation amount (permeation rate) of hydrogen gas can be achieved at the same time within that temperature range.

[0067] The amount of secondary purified gas permeated per unit time, which is separated and permeated by the separation membrane, is determined by the permeation area of ​​the separation membrane, the permeation coefficient of the secondary purified gas in the separation membrane, and the magnitude of the differential pressure, as shown in the following formula 1. Here, the permeation coefficient is the permeation area specific to the separation membrane, the differential pressure, and the amount of secondary purified gas permeated per unit time. Formula 1: (Secondary purified gas permeation rate per unit time through separation membrane [kg-H2 / h]) = (separation membrane permeation area [m 2 ]) × (permeability coefficient of secondary purified gas [kg-H2 / (m 2 ·MPa·h)]) ×(Differential pressure [MPa]) In the hydrogen gas production apparatus A1, the amount of secondary purified gas permeated per unit time corresponds to the amount of secondary purified gas produced per unit time. Therefore, the amount of secondary purified gas produced per unit time is also given by Equation 1.

[0068] To ensure the desired permeation amount (permeation rate) of the secondary purified gas, a sufficient membrane area is required. Therefore, if a sufficient membrane area cannot be ensured with just one separation membrane module, the hydrogen separation section 19 may be configured with multiple separation membrane modules arranged in parallel in the gas flow direction. Based on the above-mentioned equation 1, the required number of separation membrane modules to be arranged in parallel can be determined using the value calculated using the following equation 2 as a guide. Note that the decimal point of the calculation result is rounded up. Formula 2: (Number of parallel separation membrane modules required) = (target amount of secondary purified gas permeated per unit time [kg-H2 / h]) / {(Separation membrane permeation area per separation membrane module [m 2 ]) × (permeation area of ​​the separation membrane specific to the separation membrane module, differential pressure and unit time, Secondary purified gas permeation rate [kg-H2 / (m 2 ·MPa·h)]) × (Set differential pressure [MPa])

[0069] Suitable polymer separation membranes that can be used include, for example, the "Polymer Separation Membrane Module for Hydrogen Gas Separation" manufactured by Toray Industries, Inc., which is a modularized hollow fiber polymer membrane, and the "Poreflon Nano 0.3" manufactured by Sumitomo Electric Fine Polymer Co., Ltd.

[0070] The secondary purified gas is produced by the hydrogen gas production apparatus A1 and discharged from the hydrogen gas production apparatus A1. The secondary purified gas is substantially free of residual ammonia gas, which can poison the anode when used as fuel gas in a polymer electrolyte fuel cell (PEFC). Furthermore, the majority of the nitrogen gas has been removed by the hydrogen separation unit 19, resulting in a mixed gas (hydrogen-based gas) primarily composed of hydrogen gas. The mixed gas (hydrogen-based gas) used as the secondary purified gas is composed of, for example, approximately 95 to 98 volume % hydrogen gas and approximately 2 to 5 volume % nitrogen gas. Therefore, the amount of nitrogen gas contained in the secondary purified gas is significantly reduced compared to when nitrogen removal is not performed (nitrogen concentration: approximately 25 volume %). Therefore, when the secondary purified gas is used as fuel gas in a polymer electrolyte fuel cell (PEFC), concentration polarization is suppressed compared to when nitrogen removal is not performed, thereby maintaining high power generation efficiency and reducing the likelihood of a decrease in maximum power output during power generation. Furthermore, since the energy density of the secondary purified gas increases compared to when nitrogen removal is not performed, the amount of energy that can be stored when the secondary purified gas is filled into an external tank (for example, a purified gas tank (including a high-pressure hydrogen tank) described below) is greatly improved.

[0071] ISO14687-2 specifies the allowable concentrations of impurities such as ammonia, which have the effect of poisoning the electrodes of polymer electrolyte fuel cells (PEFCs), and also stipulates that the hydrogen purity must be 99.97% or higher. According to this standard, the allowable concentration of helium is less than 300 ppm by volume, and the combined allowable concentration of nitrogen and argon is less than 100 ppm by volume, but these trace components only slightly dilute the concentration of hydrogen gas, and even if they are contained in the secondary purified gas, they have almost no effect on the characteristics of polymer electrolyte fuel cells (PEFCs). On the other hand, most of the nitrogen gas contained in the primary purified gas has been removed from the secondary purified gas (e.g., the hydrogen gas concentration is approximately 95-98% by volume). When the secondary purified gas is used as fuel gas in a polymer electrolyte fuel cell (PEFC), concentration polarization at the anode is significantly reduced compared to when nitrogen removal is not performed (hydrogen gas concentration is approximately 75% or less). Consequently, the power generation efficiency and maximum power output during power generation are not significantly different from those when high-purity hydrogen specified in ISO 14687-2 is used. Therefore, when generating power using a polymer electrolyte fuel cell (PEFC) with secondary purified gas as fuel, the special polymer electrolyte fuel cell (PEFC) described in Non-Patent Document 3, which has grooves on the anode, is not particularly required. Furthermore, the energy density when filled in an external tank at high pressure and the fluid properties, such as the flow path resistance at room temperature (approximately 25°C) generated by the flow of the secondary purified gas, are not significantly different from those of high-purity hydrogen gas that meets the above standards.

[0072] The secondary purified gas line 21 is connected to the secondary purification section 19 (hydrogen separation section) and is a line that guides the secondary purified gas downstream and discharges it from the hydrogen gas production apparatus A1. The discharged secondary purified gas may be supplied directly to a supply destination (for example, a fuel cell or a high-pressure hydrogen tank, which will be described later) or may be stored in a purified gas tank of a hydrogen gas supply apparatus, which will be described later.

[0073] Liquefied ammonia, ammonia gas, cracked gas, primary purified gas, and secondary purified gas (hereinafter, these gases may be collectively referred to as a series of gases) are configured to flow downstream via raw ammonia line 3, cracked gas line 11, primary purified gas line 17, and secondary purified gas line 21 due to the pressure difference between the vapor pressure of ammonia in tank 1 and the pressure on the downstream side of the separation membrane (upstream side of pressure reducer 22) reduced by pressure reducer 22, which is provided downstream of the separation membrane and reduces the pressure and exhausts the secondary purified gas. The pressure difference that serves as the driving force for hydrogen separation by the separation membrane is formed as a pressure drop between the upstream and downstream sides of the separation membrane caused by the pressure reduction and exhaust by pressure reducer 22. In other words, the pressure difference is formed as part of the pressure difference. Here, the pressure on the upstream side of the separation membrane refers to the gas pressure on the downstream side of the portion closest to hydrogen separation unit 19 (upstream pressure regulator 18 in the example shown in FIG. 1 ) on primary purified gas line 17, which is connected to the hydrogen separation unit upstream of hydrogen separation unit 19. In addition, the downstream side of the separation membrane means the gas pressure upstream of the point closest to the hydrogen separation section 19 (downstream pressure regulator 20 in the example shown in Figure 1) on the secondary purified gas line 21 connected to the hydrogen separation section 19 downstream of the hydrogen separation section 19.

[0074] The pressure difference for separating and permeating hydrogen through the separation membrane is directly adjusted by adjusting or driving the upstream pressure regulator 18 , the pressure reducer 22 , and the downstream pressure regulator 20 .

[0075] The upstream pressure regulator 18 is a device that adjusts the pressure upstream of the hydrogen separation section 19 to an appropriate pressure by adjusting the opening of the flow path between the primary purification section 15 (ammonia adsorption section 15) and the hydrogen separation section 19. A general pressure regulating valve (pressure reducing valve) can be used for the upstream pressure regulator 18, but it is more preferable that it also have a function of detecting the mass flow rate of the gas flowing through the upstream pressure regulator 18 before hydrogen separation.

[0076] Pressure reducer 22 is a device that reduces the pressure upstream of pressure reducer 22 (i.e., downstream of hydrogen separation unit 19) by sucking in the secondary purified gas containing hydrogen gas that has permeated the separation membrane in hydrogen separation unit 19 and discharging it downstream. Pressure reducer 22 may be, for example, a pump. Pressure reducer 22 reduces the pressure upstream of pressure reducer 22, creating a reduced-pressure state downstream of the separation membrane that generates the differential pressure as part of the pressure difference. In this way, the differential pressure is created using a common pressure reducer 22 to create the pressure difference that is formed so that liquefied ammonia, ammonia gas, cracked gas, primary purified gas, and secondary purified gas flow downstream from tank 1 to secondary purified gas line 21. Therefore, there is no need to separately install a pressure reducer, such as a pressure reducer pump, downstream of the separation membrane to create the differential pressure. In other words, in hydrogen gas production apparatus A1, pressure reducer 22 is used as both the pressure reducer for creating the pressure difference and the pressure reducer for creating the differential pressure.

[0077] Downstream pressure regulator 20 is a device that adjusts the aperture of the flow path between hydrogen separation section 19 and pressure reducer 22 to alleviate the reduced pressure created by pressure reducer 22, appropriately adjusts the pressure downstream of hydrogen separation section 19, and controls the flow rate of the secondary purified gas that permeates the separation membrane to a predetermined flow rate. Like upstream pressure regulator 18, downstream pressure regulator 20 can be a general pressure regulating valve (pressure reducing valve), but it is more preferable that it also have a function to detect the mass flow rate of the secondary purified gas flowing through downstream pressure regulator 20. This appropriately adjusts the differential pressure across the separation membrane in hydrogen separation section 19, and the secondary purified gas containing hydrogen gas that permeates the separation membrane at a flow rate determined based on that differential pressure is passed by pressure reducer 22 through secondary purified gas line 21 and discharged.

[0078] The hydrogen gas production apparatus A1 further includes a nitrogen gas discharge line 23 for discharging to the outside a gas containing nitrogen as a main component (nitrogen-based gas) from which most of the hydrogen gas has been separated by the hydrogen separation unit 19. Hereinafter, the "nitrogen-based gas" may be simply referred to as "nitrogen gas." The nitrogen gas discharge line 23 is connected to an outlet for the nitrogen-based gas from the hydrogen separation unit 19 so that the nitrogen-based gas is discharged to the outside of the hydrogen separation unit 19. A nitrogen discharge pressure regulator 24 is provided on the nitrogen gas discharge line 23. Nitrogen discharge pressure regulator 24 is a device that adjusts the aperture of the flow path of nitrogen gas discharge line 23 to maintain the pressure at the nitrogen-based gas outlet of hydrogen separation section 19 at a pressure slightly lower than the pressure at the inlet to hydrogen separation section 19 of the primary purified gas before hydrogen separation, which is adjusted by upstream pressure regulator 18, and adjusts the flow rate of the nitrogen-based gas flowing through nitrogen gas discharge line 23 to a flow rate obtained by subtracting the flow rate of the secondary purified gas flowing through downstream pressure regulator 20 from the flow rate of the primary purified gas before hydrogen separation, which flows through upstream pressure regulator 18. Although a general pressure adjusting valve (pressure reducing valve) can be used for nitrogen discharge pressure regulator 24, it is more preferable that the nitrogen discharge pressure regulator 24 also has the function of detecting the mass flow rate of the nitrogen-based gas flowing through it and controlling the flow rate of the nitrogen-based gas so that this flow rate is equal to the value obtained by subtracting the mass flow rate of the secondary purified gas flowing through downstream pressure regulator 20 from the mass flow rate of the primary purified gas before hydrogen separation, which flows through upstream pressure regulator 18. The nitrogen-based gas is continuously discharged from the hydrogen separation section 19 through the nitrogen gas discharge line 23 by the nitrogen discharge pressure regulator 24 .

[0079] In the hydrogen gas production apparatus A1, the pressure difference between the internal pressure (vapor pressure) of tank 1 and the pressure upstream of pressure reducer 22, formed by the decompression and exhaust of pressure reducer 22, serves as a driving force for liquefied ammonia and the series of gases flowing downstream. The gas flowing downstream is ammonia gas generated in raw ammonia line 3 downstream of vaporizer 5, which is converted to decomposition gas in decomposition gas line 11 downstream of ammonia decomposition section 9, converted to primary purified gas in primary purified gas line 17 downstream of primary purification section 15 (ammonia adsorption section 15 in this example), and converted to secondary purified gas in secondary purified gas line 21 downstream of secondary purification section (hydrogen separation section 19 in this example). Throughout this process of sequential gas transformation, the internal pressure (vapor pressure) of tank 1 must be maintained at a predetermined supply pressure so that liquefied ammonia and the series of gases can flow smoothly downstream from tank 1 to secondary purified gas line 21. Furthermore, the pressure difference is adjusted as described above by upstream pressure regulator 18 and downstream pressure regulator 20. This allows a series of gas flows from the tank 1 to the downstream side, and allows the production of second purified gas at a predetermined production amount per unit time by the separation membrane.

[0080] During operation of the hydrogen gas production apparatus A1, as liquefied ammonia flows downstream from the tank 1, the gas volume increases due to evaporation of the liquefied ammonia, the temperature rise and decomposition of the ammonia gas, and the gas volume decreases due to cooling in the cooler 13. Even with such state changes, these gases do not stagnate or backflow within the hydrogen gas production apparatus A1, and it is preferable that the processing capacity (processing amount per unit time) and flow path resistance (pressure loss) of each device within the hydrogen gas production apparatus A1, as well as the flow path resistance (pressure loss) of each gas line, be appropriately designed and controlled so that the gas pressure always decreases sequentially as it proceeds downstream, in addition to the internal pressure (vapor pressure) of the tank 1 and the pressure reduction and exhaust capacity of the pressure reducer 22.

[0081] The hydrogen gas production apparatus A1 can create a pressure difference between the internal pressure (vapor pressure) of the tank 1 and the pressure downstream of the separation membrane, which is reduced by the pressure reducer 22. This pressure difference allows hydrogen gas to be separated using a separation membrane. Therefore, it does not require a high-pressure compressor (e.g., one that pressurizes to 1 MPa or more) typically used for hydrogen gas separation by pressure swing air (PSA) or cryogenic separation, nor does it require frequent startup and continuous operation of a high-pressure compressor, as is the case with PSA. Furthermore, it does not require cooling under even higher pressure conditions or using adiabatic expansion from a high-pressure state, as is the case with cryogenic separation. Therefore, the hydrogen gas production apparatus A1 can reduce the power consumed to increase the pressure upstream of the separation membrane and the energy consumed for hydrogen gas production. Furthermore, while the high-pressure compressors required for PSA and cryogenic separation are large, the hydrogen gas production apparatus A1 does not require such a compressor, thereby eliminating the installation space required, allowing the hydrogen gas production apparatus A1 to be made smaller and simpler. In other words, according to the hydrogen gas production device A1, when hydrogen gas is produced using liquefied ammonia as a raw material, nitrogen gas can be removed (hydrogen gas can be separated) without using a high-pressure compressor, etc., which reduces the amount of power consumed and makes the hydrogen gas production device A1 small and simple.

[0082] Such a hydrogen gas production device A1 is small and can be mounted on mobile objects such as fuel cell vehicles (FCVs) and fuel cell (FC) ships. The hydrogen gas production device A1 can continuously separate hydrogen gas using a separation membrane, making it suitable for continuously supplying fuel gas to a polymer electrolyte fuel cell (PEFC), for example.

[0083] The hydrogen gas production apparatus A1 may also include a compressor 17a that pressurizes the primary purified gas, as shown in parentheses on the primary purified gas line 17 in Fig. 1. The primary purified gas is pressurized by the compressor 17a to, for example, 0.1 to 0.5 MPa. The compressor 17a may be, for example, a pump or a compressor.

[0084] In this case, the internal pressure (vapor pressure) of tank 1 is maintained at a predetermined supply pressure so that liquefied ammonia and other gases flow smoothly downstream from tank 1 through secondary purified gas line 21. This allows liquefied ammonia and other gases to flow downstream of tank 1, enabling the permeation and production of secondary purified gas at a predetermined throughput per unit time through the separation membrane. That is, by providing compressor 17a, the internal pressure (vapor pressure) of tank 1 can be reduced by the amount of pressurization by compressor 17a (e.g., 0.1 to 0.5 MPa) compared to when compressor 17a is not provided. As a result, the pressure in ammonia decomposition section 9 downstream of tank 1 is also reduced by the amount of pressurization compared to when compressor 17a is not provided. The ammonia decomposition reaction (2NH3 → 3H2 + N2) in ammonia decomposition section 9 is a reaction in which the gas volume increases as the reaction proceeds. Therefore, at a given decomposition temperature, the lower the pressure, the higher the ammonia decomposition rate, producing more hydrogen gas and reducing the amount of residual ammonia gas. Therefore, by providing the pressurizer 17a, the pressure in the ammonia decomposition section 9 can be reduced, and as a result, the ammonia decomposition rate in the ammonia decomposition section 9 can be improved. Furthermore, by providing the pressurizer 17a, even if the differential pressure required for hydrogen separation in the separation membrane is insufficient due to an unexpected decrease in the internal pressure (vapor pressure) of the tank 1 caused by a sudden drop in the external environmental temperature, the pressurizer 17a can compensate for the pressure deficiency and maintain the throughput of membrane separation. Note that the above bracketed elements in Figure 1 indicate optional components, and whether or not the pressurizer 17a is provided in the hydrogen gas production apparatus A1 can be selected taking into consideration the advantages and disadvantages described above.

[0085] According to one embodiment, the tank 1 preferably has a heater 1a for keeping warm, as shown in FIG. 3. FIG. 3 is a diagram showing a hydrogen gas production apparatus A2 according to one embodiment. The heater 1a for keeping warm is a device that heats the inside of the tank 1 to maintain the vapor pressure so that the flow of liquefied ammonia and a series of gases downstream from the tank 1 to the secondary purified gas line 21 is maintained. Specifically, the heater 1a for keeping warm is a device that heats and maintains the temperature inside the tank 1 at a predetermined temperature so that the tank internal pressure (vapor pressure) is maintained at the supply pressure when the secondary purified gas is produced at a predetermined production amount per unit time, both in the case where the compressor 17a is not provided and in the case where it is provided. As described above, this supply pressure is a pressure at which the liquefied ammonia and a series of gases flow downstream without stagnation from the tank 1 to the secondary purified gas line 21. The heater 1a for heat retention increases the vapor pressure of liquefied ammonia in the tank 1, heating the tank 1 to a temperature where the internal tank pressure becomes the supply pressure and maintaining that temperature. This allows the liquefied ammonia and a series of other gases to flow downstream of the tank 1, enabling the production of secondary purified gas at a predetermined throughput per unit time through the separation membrane. Furthermore, by providing the heater 1a for heat retention, even if a sudden drop in the external environmental temperature occurs, the internal pressure (vapor pressure) can be stabilized by controlling the temperature of the tank 1 to be constant. Even if the differential pressure required for hydrogen separation through the separation membrane is insufficient, the pressure shortfall can be compensated for by heating the tank 1, thereby maintaining the throughput of membrane separation. Suppressing fluctuations in the tank internal pressure in this way stabilizes the throughput of liquefied ammonia per unit time and the production volume of secondary purified gas.

[0086] 3, when the hydrogen gas production apparatus A2 is operated without the pressure compressor 17a and using only the pressure reduced by the pressure reducer 22 as the pressure that, together with the tank internal pressure, forms the pressure difference, the temperature inside the tank 1 is preferably maintained at, for example, about 40 to 50°C by the heater 1a for heat retention so that the tank internal pressure is maintained at the supply pressure. By maintaining the temperature inside the tank 1 at a temperature slightly higher than the normal outside air temperature in this manner, the internal pressure of the tank 1 is maintained at about 1.6 to 2 MPa, and as a result, the internal pressure in the downstream ammonia decomposition section 9 is, for example, about 1.1 to 1.5 MPa. Furthermore, a differential pressure (for example, about 0.5 to 0.9 MPa) required for hydrogen separation of a predetermined throughput per unit time can be applied to the separation membrane of the downstream hydrogen separation section 19.

[0087] On the other hand, in the hydrogen gas production apparatus A2 shown in Fig. 3, when the pressure generator 17a is provided in addition to the pressure generator 22, as described above, the internal pressure (vapor pressure) of the tank 1 can be reduced compared to when the pressure generator 17a is not provided, and the pressure in the ammonia decomposition section 9 is also reduced. As a result, the ammonia decomposition rate in the ammonia decomposition section 9 is improved, more hydrogen gas is produced, and the amount of residual ammonia gas can be reduced. At this time, the inside of the tank 1 is heated and maintained by the heater 1a for heat retention so that the internal pressure (vapor pressure) of the tank 1 is maintained at the supply pressure.

[0088] When the pressurizer 17a is installed, the temperature inside the tank 1 is preferably maintained at approximately 35 to 40°C so that the tank internal pressure is maintained at the supply pressure. By maintaining the temperature inside the tank 1 at a temperature slightly higher than the normal ambient temperature, the internal pressure of the tank 1 is maintained at approximately 1.4 to 1.6 MPa. As a result, the pressure in the downstream ammonia decomposition section 9 is also reduced to, for example, approximately 0.9 to 1.1 MPa. Therefore, when a particularly high-performance decomposition catalyst is used, the decomposition rate of the ammonia decomposition reaction can be maintained at a high level of approximately 97 to 99%. Furthermore, the downstream separation membrane can also be applied with a differential pressure (e.g., 0.5 to 0.9 MPa) required for hydrogen separation at a predetermined throughput per unit time. Note that, if the pressurizer 17a is not installed and the heating temperature inside the tank 1 is set to approximately 40 to 50°C, the pressure in the ammonia decomposition section 9 will be, for example, approximately 1.1 to 1.5 MPa. Even when the above-mentioned high-performance decomposition catalyst is used, the decomposition rate of the ammonia decomposition reaction will be approximately 95 to 97%.

[0089] The heater 1a for warmth can be placed on the outside or inside of the container body of the tank 1. The heater 1a for warmth preferably indirectly heats the liquefied ammonia. The heater 1a for warmth may be, for example, a heating mechanism such as a heat exchanger or heater having a temperature control function, or a heat insulating material covering the outside of the container body of the tank 1, or a combination of these may be used. Heating of the inside of the tank 1 by the heater 1a for warmth can be performed intermittently or continuously during operation of the hydrogen gas production apparatus A2. When performed intermittently, heating starts when the temperature or internal tank pressure in the tank 1 measured during operation of the hydrogen gas production apparatus A2 reaches a predetermined lower limit and ends when it reaches a predetermined upper limit.

[0090] As the amount of liquefied ammonia in tank 1 decreases due to the continuous supply of liquefied ammonia downstream, the liquefied ammonia in tank 1 typically vaporizes to fill the gas phase space within tank 1, and the heat of vaporization is removed during this process, causing cooling within tank 1. For this reason, the temperature and pressure within tank 1 will gradually decrease during operation unless the heat of vaporization is compensated for by external heating. For this reason, during operation of hydrogen gas production apparatus A2, the temperature and pressure within tank 1 can be prevented from progressing and the temperature and internal pressure within tank 1 can be maintained by continuously heating the interior of tank 1 with heat retention heater 1a to compensate for the heat of vaporization.

[0091] In the above embodiments, the primary purification section 15 is an ammonia adsorption section 15, and the secondary purification section 19 is a hydrogen separation section 19, as in the hydrogen gas production apparatuses A1 and A2. According to these embodiments, residual ammonia gas is removed in the ammonia adsorption section 15 before hydrogen gas is separated in the hydrogen separation section 19. Therefore, the nitrogen-based gas separated from hydrogen gas in the hydrogen separation section 19 contains almost no residual ammonia gas. The residual ammonia gas concentration (less than several hundred ppb by volume, preferably less than 100 ppb by volume, after removal of the residual ammonia gas) is low enough not to violate, for example, odor regulations (Japan's Offensive Odor Prevention Act regulates site boundaries at 2 ppm by volume in industrial and exclusively industrial areas, and 1 ppm by volume elsewhere). If the hydrogen gas concentration in the nitrogen-based gas is below the lower flammability limit, the nitrogen-based gas can be directly released into the atmosphere. Therefore, there is no need to remove residual ammonia gas from the nitrogen-based gas separated from hydrogen gas in the hydrogen separation section 19, simplifying the equipment.

[0092] Meanwhile, according to an embodiment different from the embodiment described above, the primary purification section 15 may be a hydrogen separation section, and the secondary purification section 19 may be an ammonia adsorption section, as shown in Fig. 4. Fig. 4 is a diagram showing a hydrogen gas production apparatus A3 of one embodiment. Fig. 4 shows a case where the aforementioned compressor 17a is not provided upstream of the separation membrane of the hydrogen separation section, but the compressor 17a may also be provided, and the effects in each case are similar to those described above. In this embodiment, too, liquefied ammonia, ammonia gas, cracked gas, primary purified gas (here, a gas mainly composed of hydrogen gas and containing residual ammonia gas not decomposed in ammonia decomposition section 9), and secondary purified gas (here, a gas mainly composed of hydrogen obtained by removing residual ammonia gas from the primary purified gas) flow downstream via raw ammonia line 3, cracked gas line 11, primary purified gas line 17, and secondary purified gas line 21 due to the pressure difference between the vapor pressure of ammonia gas evaporated in tank 1 and the pressure upstream of pressure reducer 22, which is provided downstream of the separation membrane of primary purification section (hydrogen separation section) 15 and reduces the pressure of the primary purified gas. The pressure difference, which serves as the driving force for hydrogen separation by the separation membrane, is formed as a pressure drop between the upstream and downstream sides of the separation membrane that occurs when pressure reducer 22 reduces the pressure and exhausts the gas. In other words, the pressure difference is formed as part of the pressure difference. Throughout the above process, the internal pressure (vapor pressure) of tank 1 must be maintained at a predetermined supply pressure so that liquefied ammonia and a series of gases can flow smoothly downstream from tank 1 to secondary purified gas line 21. For this reason, tank 1 is preferably further provided with the aforementioned heater 1a for heat retention to maintain the required internal pressure (vapor pressure) (not shown in FIG. 3). In hydrogen gas production apparatus A3, the permeation amount per unit time of the hydrogen-based gas containing a trace amount of residual ammonia gas separated and permeated by the separation membrane (approximately equal to the production amount of secondary purified gas per unit time of hydrogen gas production apparatus A3) and the required number of parallel separation membrane modules are determined by the above-mentioned formulas 1 and 2, respectively.

[0093] According to one embodiment, as shown in FIG. 5, the cooler 13 and the vaporizer 5 preferably constitute a first heat exchanger 25 having a first high-temperature side passage through which the cracked gas flows and a first low-temperature side passage through which the liquefied ammonia flows. FIG. 5 is a diagram showing a hydrogen gas production apparatus A4 according to one embodiment. The first heat exchanger 25 is configured to cool the cracked gas and heat the liquefied ammonia by heat exchange between the cracked gas flowing through the first high-temperature side passage and the liquefied ammonia flowing through the first low-temperature side passage. According to this embodiment, the heat source required for vaporizing the liquefied ammonia is obtained within the hydrogen gas production apparatus A4, and the heat of the high-temperature cracked gas can be effectively utilized, thereby improving energy efficiency in producing hydrogen gas. Note that in FIG. 5 and the drawings referred to hereinafter, for lines that are shown with a portion interrupted, such as the raw ammonia line 3, lines that appear at the same height or horizontal position are portions of the same line.

[0094] In this embodiment, when the cooler 13 is referred to as the first cooler 13, the hydrogen gas production apparatus A4 may further include a second cooler 27, as shown in FIG. 5, which is provided upstream or downstream of the first cooler 13 in the cracked gas line 11 and cools the cracked gas. In the hydrogen gas production apparatus A4 shown in FIG. 5, the second cooler 27 is provided downstream of the first cooler 13. The removal rate of residual ammonia gas by the ammonia adsorption unit 15 increases as the temperature of the cracked gas decreases, preferably when the temperature is around room temperature (about 25°C) or lower. Therefore, when the cooling capacity of the first cooler 13 is insufficient and the temperature of the cracked gas after cooling is several tens of degrees Celsius or more higher than room temperature (for example, about 25°C), cooling by the second cooler 27 can compensate for the insufficient cooling by the first cooler 13 and increase the removal rate of residual ammonia gas.

[0095] Furthermore, in this embodiment, the second cooler 27 may be one having a heat exchanger structure, a forced air-cooling structure using an air-cooling fan or the like to blow outside air, or even one using electronic cooling. Among these, the cracked gas passing through the second cooler 27 having a heat exchanger structure is preferably cooled by heat exchange with outside air or a liquid refrigerant cooled by heat exchange with outside air. When the second cooler 27 is provided upstream of the first cooler 13, it is preferable to use air introduced into the second cooler 27 from the outside as the refrigerant. When the second cooler 27 is provided downstream of the first cooler 13, it is preferable to use a liquid refrigerant, such as cooling water cooled by heat exchange with outside air in a radiator (not shown), as the refrigerant. After heat exchange with the cracked gas in the second cooler 27, the liquid refrigerant is returned to the radiator, where it is cooled again by heat exchange with outside air, and can be circulated for use in the second cooler 27.

[0096] According to one embodiment, the temperature-raising heater 7 is provided downstream of the vaporizer 5 in the raw ammonia line 3, and the hydrogen gas production apparatus A4 further includes a combustor 29 and a combustion gas line 31, as shown in FIG. The combustor 29 is a device that combusts a portion of any of the cracked gas, primary purified gas, and secondary purified gas (hereinafter also referred to as off-gas) extracted from the ammonia decomposition section 9 or downstream of the ammonia decomposition section 9, together with air, and discharges the combustion gas. The off-gas may be extracted directly from the ammonia decomposition section 9, or may be extracted from any position on the line downstream of the ammonia decomposition section 9, such as the upstream or downstream side of the first cooler 13, the downstream side of the ammonia adsorption section 15, or the downstream side of the hydrogen separation section 19. In the example shown in FIG. 5 , the off-gas is extracted from a midpoint of the cracked gas line 11 and guided to the combustor 29 through a branch gas line 30 that branches off from a portion of the cracked gas line 11 downstream of the second cooler 27. The branch gas line 30 connects the combustor 29 to the ammonia decomposition section 9 or the line from which the off-gas is extracted. An outside air introduction line 32 that introduces air from the outside is connected to the combustor 29. The off-gas contains highly combustible hydrogen gas and can be burned together with air.

[0097] The combustion gas line 31 is connected to the combustor 29 and is a line through which the combustion gas flows. A portion of the combustion gas line 31 and the heating heater 7 preferably constitute a second heat exchanger 33 having a second high-temperature side passage through which the combustion gas flows and a second low-temperature side passage through which the ammonia gas flows. The second heat exchanger 33 is configured to cool the combustion gas and heat the ammonia gas by heat exchange between the combustion gas flowing through the second high-temperature side passage and the ammonia gas flowing through the second low-temperature side passage. The combustion gas can be produced using gas produced within the hydrogen gas production apparatus A4 as fuel, so the heat source required to heat the ammonia gas can be obtained within the hydrogen gas production apparatus A4. The combustion of the off-gas by the combustor 29 is continuously performed during steady-state operation of the hydrogen gas production apparatus A, except during startup of the hydrogen gas production apparatus A.

[0098] The amount of air introduced from outside into the combustor 29 is preferably an amount such that the amount of oxygen in the air is equal to or greater than the stoichiometric ratio for combustion relative to the amount of off-gas introduced into the combustor 29. By supplying a sufficient amount of oxygen (air) necessary for combustion, incomplete combustion of the off-gas can be suppressed.

[0099] A combustion oxidation catalyst for promoting the combustion of ammonia gas may be provided upstream inside the combustor 29. By providing a combustion oxidation catalyst inside the combustor 29, the decomposition gas can be efficiently combusted even when the hydrogen gas concentration in the decomposition gas is low and the ammonia gas concentration is high during start-up of the hydrogen gas production apparatus A, and the ammonia gas can be heated and raised in temperature in the second heat exchanger 33. As with the above-mentioned combustion oxidation catalyst provided in the ammonia decomposition section 9, the combustion oxidation catalyst may be a carrier of porous ceramics molded into a granulated or honeycomb shape, or a honeycomb-shaped carrier of a nitridation-resistant metal (e.g., nickel (Ni), nickel alloys such as Inconel (registered trademark) 600, 625, 718, and 750, Incoloy (registered trademark) 800 and 825, Hastelloy (registered trademark) C276 and C22, Nimonic (registered trademark) 75, 80A, and 90, stainless steel such as SUS310S, etc.), on which ultrafine particle catalysts made of at least one of precious metals such as platinum (Pt), palladium (Pd), ruthenium (Ru), rhodium (Rh), iridium (Ir), and oxides of metals such as manganese (Mn), cobalt (Co), chromium (Cr), and copper (Cu) are supported. If the above-mentioned combustion oxidation catalyst is not provided in the combustor 29, another independent heating means such as electric heating must be provided in the temperature-raising heater 7, and the ammonia gas must be heated and raised in temperature by this means when the hydrogen gas production apparatus A is started.

[0100] The combustion gas may contain nitrogen oxides (NOx) generated by nitrogen gas mixed in the cracked gas or nitrogen gas in the air. Therefore, a denitration device (not shown) may be installed in the combustor 29. The denitration device removes NOx using a catalyst that decomposes NOx, such as three-way catalytic decomposition or selective catalytic reduction (SCR). This allows denitration to be performed in parallel with the combustion of the off-gas. When denitration is performed using the SCR method, residual ammonia gas contained in gases such as cracked gas acts as a reducing agent that selectively reduces NOx to harmless nitrogen gas and water vapor. Therefore, if the amount of residual ammonia gas is insufficient compared to the amount of NOx in the combustion gas, liquefied ammonia can be supplied from the tank 1 through an appropriate line (not shown) to the denitration device in the combustor 29 to make up for the shortage.

[0101] 5, the ammonia adsorption unit 15 preferably includes a regeneration heater 35 that heats the adsorbent that has adsorbed residual ammonia gas, an inert gas inlet line 37 for introducing an inert gas from the outside, and a desorbed ammonia discharge line 39 through which the residual ammonia gas desorbed from the adsorbent flows. The ammonia adsorption unit 15 is configured so that the residual ammonia gas adsorbed in the adsorbent is desorbed from the adsorbent by heating it with the regeneration heater 35, and is discharged from the ammonia adsorption unit 15 through the desorbed ammonia discharge line 39 together with the inert gas introduced through the inert gas inlet line 37. In this way, when the adsorbent in the ammonia adsorption unit 15 reaches breakthrough due to adsorption of residual ammonia gas, etc., the adsorbent can be heated to desorb the adsorbed residual ammonia gas, etc., and the adsorbent can be regenerated and reused.

[0102] For example, an electric heater can be used as the regeneration heater 35. In the example shown in Fig. 5, the regeneration heater 35 is provided in the device of the ammonia adsorption section 15 (for example, the above-mentioned adsorption tower), and heats the adsorbent together with the device of the ammonia adsorption section 15. For example, when the adsorbent is X-type zeolite, 90% or more of the adsorbed ammonia gas is desorbed by heating it to approximately 400°C or higher.

[0103] In the example shown in Fig. 5, the inert gas introduction line 37 is connected to the primary purified gas line 17. The portion of the inert gas introduction line 37 extending from the connection position with the primary purified gas line 17 to the ammonia adsorption section 15 shares a part of the flow path with the primary purified gas line 17. In the example of Fig. 5, the inert gas passes through the inert gas introduction line 37, flows through this flow path in the opposite direction to the primary purified gas, and is introduced into the ammonia adsorption section 15. The inert gas is preferably a gas that is chemically non-reactive with ammonia and does not substantially inhibit the adsorption of ammonia gas onto the adsorbent; preferably, nitrogen gas or a rare gas such as argon gas or helium gas is used. Nitrogen gas is shown as an example in the drawing.

[0104] 5, the desorbed ammonia discharge line 39 is connected to the cracked gas line 11. The portion of the desorbed ammonia discharge line 39 extending from the ammonia adsorption unit 15 to the connection position with the cracked gas line 11 shares a part of the flow path with the cracked gas line 11. The portion of the desorbed ammonia discharge line 39 extending from this connection position toward the combustor shares a flow path with the branch gas line 30. In the example of FIG. 5, the desorbed ammonia gas flows together with the inert gas in the former flow path in the opposite direction to the cracked gas, and further flows in the latter flow path in the same direction as the off-gas, and is discharged through the desorbed ammonia discharge line 39.

[0105] 5, the inert gas may be introduced from the upstream side of the ammonia adsorbing section 15 in the same direction as the decomposition gas (in this case, the inert gas introduction line 37 is connected to the upstream side of the ammonia adsorbing section 15). In this case, the ammonia gas desorbed from the ammonia adsorbing section 15 flows together with the inert gas toward the downstream side of the ammonia adsorbing section 15 in the same direction as the flow of the primary purified gas, and is discharged (in this case, the desorbed ammonia discharge line 39 is connected to the downstream side of the ammonia adsorbing section 15).

[0106] In this embodiment, the hydrogen gas production apparatus A4 preferably further includes the combustor 29 described above. The ammonia gas discharged together with the inert gas is introduced into the combustor 29 and combusted. The off-gas supplied to the combustor 29 contains highly combustible hydrogen gas, so the ammonia gas desorbed from the adsorbent in the ammonia adsorption section 15 and discharged can be combusted together with the hydrogen gas to render it harmless and odorless. This allows ammonia gas, the release of which into the atmosphere is restricted, to be disposed of by incineration. The configuration of this embodiment can be designed to be relatively compact, so the hydrogen gas production apparatus A4 can be suitably used in small on-site facilities and mobile vehicles.

[0107] Furthermore, in this embodiment, the heating heater 7 is provided downstream of the vaporizer in the raw ammonia line 3, and the hydrogen gas production apparatus A4 is further equipped with a combustion gas line 31 connected to the combustor 29 and through which the combustion gas flows, and it is preferable that a part of the combustion gas line 31 and the heating heater 7 constitute the above-mentioned second heat exchanger 33.

[0108] According to one embodiment, in the above embodiment in which the ammonia adsorption unit 15 includes a regenerator 35, an inert gas introduction line 37, and a desorbed ammonia discharge line 39, the hydrogen gas production apparatus A further includes a reliquefaction unit (gas-liquid separator) 41 connected to the desorbed ammonia discharge line 39 and the tank 1, as shown in FIGS. 12 and 13 (see below), configured to liquefy the ammonia gas desorbed from the adsorbent and separate it from the inert gas. The ammonia gas discharged together with the inert gas is introduced to the reliquefaction unit (gas-liquid separator) 41, where it is liquefied and separated from the inert gas, and then recovered in the tank 1. The inert gas separated from the liquefied ammonia in the reliquefaction unit (gas-liquid separator) 41 has residual ammonia removed by adsorption or the like, and is then discharged outside the system. The desorbed ammonia discharge line 39 is preferably provided with a compressor 42 for compressing the ammonia gas and a cooler 43. This allows the ammonia gas desorbed from the adsorbent, discharged, and compressed to be efficiently cooled, liquefied, and recovered. According to this embodiment, ammonia gas, the release of which into the atmosphere is restricted, is returned to the liquefied ammonia in the tank 1, which serves as a raw material for hydrogen gas, thereby minimizing the outflow of desorbed ammonia gas into the external environment. A pump, for example, is used as the compressor 42. Since the reliquefaction section (gas-liquid separator) 41 is generally a relatively large device, the hydrogen gas production apparatus A of this embodiment can be suitably used in slightly large on-site facilities or slightly large mobile bodies (such as ships). Furthermore, the configuration of this embodiment can also be used in combination with the configuration of the above-described embodiment, in which the ammonia gas discharged from the ammonia adsorption section 15 is combusted in a combustor 29, as shown in FIG. 13 .

[0109] In the above-described embodiment employing the embodiment in which the residual ammonia gas discharged from the ammonia adsorption unit 15 is combusted by the combustor 29, the ammonia adsorption unit 15 preferably has a plurality of ammonia adsorbers 15A, 15B arranged in parallel with the gas flow direction, as shown in Fig. 16 which will be referred to later. The above-described adsorption tower is preferably used for each of the plurality of ammonia adsorbers 15A, 15B. The number of the plurality of ammonia adsorbers included in the ammonia adsorption unit 15 is two in the illustrated example, but is not limited to two and may be three, four or more.

[0110] The plurality of ammonia adsorbers 15A each have the above-described adsorbent, an inert gas introduction line 37A, and a desorbed ammonia discharge line 39A. The plurality of ammonia adsorbers 15B each have the above-described adsorbent, an inert gas introduction line 37B, and a desorbed ammonia discharge line 39B. The adsorbents of the ammonia adsorbers 15A and 15B each have the same configuration as the above-described adsorbent, and the same type of adsorbents can be used for both adsorbents.

[0111] 16, the inert gas introduction lines 37A, 37B are portions that branch off from an inert gas supply port 37c and extend to the ammonia adsorbers 15A, 15B, and are connected to each other at the supply port 37c. The inert gas supplied from the supply port 37c is introduced from the supply port 37c through the inert gas introduction lines 37A, 37B into the ammonia adsorbers 15A, 15B. In the example shown in FIG. 16, the primary purified gas line 17 extends from the ammonia adsorbers 15A, 15B, joins with the ammonia adsorbers 15A, 15B, and extends toward the hydrogen separation unit 19. The portions of the primary purified gas line 17 extending from the ammonia adsorbers 15A, 15B are connected to the inert gas introduction lines 37A, 37B and share a flow path with the inert gas introduction lines 37A, 37B.

[0112] In the example shown in Fig. 16, the desorbed ammonia discharge lines 39A and 39B extend from the ammonia adsorbers 15A and 15B, respectively, join together, and extend toward the combustor 29. In the example shown in Fig. 16, the cracked gas line 11 branches into two on its way from the ammonia decomposition section 9 toward the ammonia adsorption section 15, and is connected to the ammonia adsorbers 15A and 15B, respectively. The portions of the cracked gas line 11 connected to the ammonia adsorbers 15A and 15B share a flow path with the inert gas introduction lines 37A and 37B. In the example shown in Fig. 16, the branched gas line 30 is connected to the portion where the desorbed ammonia discharge lines 39A and 39B join together, and shares a flow path with the desorbed ammonia discharge lines 39A and 39B.

[0113] The ammonia adsorption unit 15 is preferably configured such that, in one or more ammonia adsorbers, residual ammonia gas desorbed from the adsorbent by heating with the regenerative heater 35 is discharged through the desorbed ammonia discharge line 39 together with inert gas introduced from the inert gas introduction line 37, while the cracked gas or the primary purified gas is introduced into the remaining ammonia adsorbers, and the residual ammonia gas in the gas is adsorbed by the adsorbent of the ammonia adsorber and removed, and the cracked gas or the primary purified gas from which the residual ammonia gas has been removed is guided downstream of the ammonia adsorption unit. The ammonia adsorption unit 15 is preferably configured such that, among the multiple ammonia adsorbers 15A and 15B, switching between the one or more ammonia adsorbers and the remaining ammonia adsorbers is possible. This switching is performed by the coordinated switching operation of valves (e.g., three-way valves) at the branching point of the cracked gas line 11 and the joining point of the desorbed ammonia discharge line 39 before the adsorbent currently adsorbing ammonia gas reaches breakthrough. According to this embodiment, by repeatedly switching between the ammonia adsorber that adsorbs residual ammonia gas (using the adsorbent) and the ammonia adsorber that desorbs residual ammonia gas (regenerating the adsorbent), the use and regeneration of the adsorbent can be performed simultaneously, eliminating the need to stop the operation of the hydrogen gas production apparatus A and allowing continuous operation for long periods of time. According to this embodiment, the operation of the hydrogen gas production apparatus A does not need to be stopped. A portion of the combustion gas generated by combusting the off-gas in the combustor 29 is guided to the heating heater 7 through the combustion gas line 31, where the ammonia gas is heated in the heating heater 7. Meanwhile, a portion of the remaining combustion gas is guided to the ammonia adsorber that regenerates the adsorbent through the regeneration treatment gas line 28, where it is heated by contacting the outer wall surface of the ammonia adsorber (adsorption tower). The regeneration treatment gas line 28 extends from the combustor 29 toward the ammonia adsorption unit 15, branches into two branches along the way, and is connected to the ammonia adsorbers 15A and 15B, respectively.Such a configuration contributes to reducing energy loss when adsorption of residual ammonia gas at low temperatures and desorption of residual ammonia gas at high temperatures are carried out in parallel.

[0114] 16, the inert gas passes through inert gas inlet line 37A or 37B, flows through primary purified gas line 17 in the opposite direction to the primary purified gas, and is introduced into ammonia adsorber 15A or 15B. Furthermore, in the example of FIG. 16, the desorbed ammonia gas flows together with the inert gas through cracked gas line 11 in the opposite direction to the cracked gas, and then flows through desorbed ammonia exhaust line 39A or 39B in the same direction as the off-gas, and is then discharged. However, the inert gas does not necessarily have to be introduced into ammonia adsorber 15A or 15B in this direction; the inert gas may be introduced from the upstream side of ammonia adsorber 15A or 15B in the same direction as the cracked gas (in this case, inert gas inlet line 37A or 37B is connected upstream of ammonia adsorber 15A or 15B). In this case, the desorbed ammonia gas from the ammonia adsorbers 15A, 15B flows together with the inert gas toward the downstream side of the ammonia adsorbers 15A, 15B in the same direction as the primary purified gas and is discharged (in this case, the desorbed ammonia discharge lines 39A, 39B are connected to the downstream side of the ammonia adsorption unit 15).

[0115] According to one embodiment, as shown in FIG. 15, the ammonia adsorption unit 15 has two ammonia adsorbers 15X and 15Y arranged in series in the gas flow direction, and each of the two ammonia adsorbers 15X and 15Y preferably contains an adsorbent. Each of the multiple ammonia adsorbers 15X and 15Y has a structure similar to the adsorption tower described above. In the example shown in FIG. 15, the two ammonia adsorbers 15X and 15Y are connected to each other in the gas flow direction by a connection line 15a. The gas from which residual ammonia gas has been adsorbed in the ammonia adsorber 15X is led to the ammonia adsorber 15Y through the connection line 15a.

[0116] According to this embodiment, the small amount of residual ammonia gas remaining in the gas that has passed through the upstream ammonia adsorber (hereinafter referred to as the primary adsorber) 15X is removed by adsorption onto an adsorbent in the downstream ammonia adsorber (hereinafter referred to as the secondary adsorber) 15Y, thereby further reducing the concentration of residual ammonia gas in the purified gas. The residual ammonia in the purified gas that has passed through the secondary adsorber 15Y is preferably less than 100 ppb by volume. This improves the effectiveness of preventing electrode poisoning by residual ammonia gas when the secondary purified gas is supplied to a polymer electrolyte fuel cell (PEFC).

[0117] The adsorbent for the primary adsorber 15X is preferably a solid Lewis acid adsorbent similar to that used in the single adsorber described above. Specifically, a porous adsorbent with many Lewis acid sites, such as X-type or A-type zeolites, is used. Zeolites with many pores with pore diameters of approximately 5 to 20 Å, such as zeolite 13X, are particularly suitable. These zeolites preferably contain at least one cation selected from the group consisting of lithium (Li), calcium (Ca), and sodium (Na). These adsorbents can be regenerated by desorbing ammonia gas and the like by heating them when breakthrough is reached through adsorption of ammonia gas and the like. Therefore, they can be reused.

[0118] The adsorbent used in the secondary adsorber 15Y is preferably a Bronsted acid type adsorbent, specifically an adsorbent having Bronsted acid sites and high acidity and large exchange capacity, such as activated alumina, silica-alumina gel, activated carbon whose surface is treated with a strong non-volatile acid such as sulfuric acid or phosphoric acid, or activated carbon impregnated with such an acid, silica gel, alumina gel, or an ion exchange resin having a strong or ultra-strong acid ion exchange group (e.g., a hydrocarbon or fluorocarbon polymer having many sulfonic acid or sulfate groups). When the adsorbent reaches breakthrough in the secondary adsorber 15Y, it is removed from the secondary adsorber 15Y and replaced with a new one. Alternatively, if the secondary adsorber 15Y is configured so that it can be operated to flow a liquid strong acid or super strong acid stronger than the adsorbent described above, or during the shutdown of the hydrogen gas production apparatus A, the ammonium ions (NH4 + ) to hydrogen ions (H + ) and regenerate it. Furthermore, the adsorbent removed at the time of breakthrough may be regenerated and reused by performing the above-mentioned offline ion exchange regeneration treatment. For adsorbents such as activated alumina and silica-alumina gel, offline regeneration treatment by calcination may also be effective. Since the majority of residual ammonia gas is usually adsorbed by the primary adsorber 15X, the actual amount of residual ammonia gas adsorbed by the adsorbent in the secondary adsorber 15Y is very small. Therefore, even a small amount of adsorbent in the secondary adsorber 15Y can often be used for a relatively long period of time.

[0119] According to one embodiment, the hydrogen gas production apparatus A preferably includes a flow rate regulator 6, which is provided downstream of the vaporizer 5 in the raw ammonia line 3 and regulates the flow rate of the ammonia gas, as shown in FIG.

[0120] The flow rate regulator 6 is a device that adjusts the flow rate of ammonia gas to a predetermined flow rate. A mass flow meter, an ultrasonic flow meter, an electromagnetic flow meter, or the like can be used as the flow rate regulator 6. The throughput of liquefied ammonia per unit time is set in accordance with the mass flow rate of ammonia gas adjusted by the flow rate regulator 6. The throughput of liquefied ammonia per unit time is determined by the following formula based on the throughput per unit time of the primary purified gas in the separation membrane of the hydrogen separation section 19, etc. Formula 3: (Liquid ammonia treatment amount per unit time [kg-NH3 / h]) = (ammonia adsorption amount per unit time in the ammonia adsorption section 15 [kg-NH3 / h]) + (Primary purified gas throughput per unit time in the hydrogen separation section 19 separation membrane [kg-H2 / h]) + (Amount of off-gas removed per unit time [kg / h])

[0121] In Equation 3, the amount of ammonia adsorption per unit time in the first term is approximately equal to the amount of ammonia remaining per unit time in the ammonia decomposition section 9 (= decomposition gas flow rate × residual ammonia gas concentration). The amount of off-gas taken out per unit time in the third term needs to be taken into consideration when the off-gas is branched downstream of the ammonia decomposition section 9 in order to obtain a heat medium for heating the ammonia gas in the first heat exchanger 25 and a combustion gas required for incinerating the ammonia gas desorbed from the adsorbent in the ammonia adsorption section 15.

[0122] Based on the processing amount of liquefied ammonia per unit time determined by Equation 3, (i) the amount of heat exchanged per unit time in each section that performs heat exchange (e.g., first heat exchanger 25, second heat exchanger 33), (ii) the required amount of catalyst based on the flow rate of the gas to be processed in the ammonia decomposition section 9, (iii) the required amount of adsorbent in the ammonia adsorption section 15, and (iv) the required number of parallel separation membrane modules in the hydrogen separation section (according to Equation 2 above) are also set.

[0123] (Hydrogen gas supply device) Next, a hydrogen gas supply device according to an embodiment will be described.

[0124] A hydrogen gas supply device B1 according to one embodiment is shown in Fig. 6. A hydrogen gas supply device B2 according to one embodiment is shown in Fig. 7. In the following description, the hydrogen gas supply devices B1 and B2 may be collectively referred to as the hydrogen gas supply device B. The hydrogen gas supply device B1 is a device that supplies hydrogen gas to a supply destination. The hydrogen gas supply device B1 includes the above-mentioned hydrogen gas production device A, a final gas discharge line 61, a purified gas tank 63, a compressor 65, and a set of switching valves 67.

[0125] The final gas discharge line 61 is connected to the secondary purified gas line 21 of the hydrogen gas production apparatus A, and guides and discharges the secondary purified gas discharged from the secondary purified gas line 21 toward a supply destination, and has a branching section 61a that branches so that the secondary purified gas flows to a side different from the supply destination. Examples of supply destinations include a fuel cell and a high-pressure hydrogen tank, which will be described later.

[0126] The purified gas tank 63 is a container connected to the branching portion 61a and stores the secondary purified gas that flows to a side different from the supply destination. The purified gas tank 63 may be, for example, a high-pressure tank that is filled with the secondary purified gas and maintains an internal pressure of, for example, 80 MPa to 90 MPa, or a simple tank (buffer tank) for temporarily storing a small amount of secondary purified gas (for example, the purified gas tank 63 shown in FIG. 10 , which will be referred to later). The high-pressure tank can be suitably used as the purified gas tank 63 when the hydrogen gas supply device B is installed in, for example, a hydrogen station that supplies hydrogen gas to mobile objects such as fuel cell vehicles (FCVs). The hydrogen gas supply device B in the illustrated example includes only one purified gas tank 63, but the hydrogen gas supply device B may include two, three, or more purified gas tanks. The hydrogen gas supply device B may include, as the multiple purified gas tanks 63, for example, multiple small tanks connected in parallel to the branching portion 61a. As the small tank, for example, a pressure accumulator that stores the second purified gas at a high pressure of about 10 to 90 MPa can be used.

[0127] The compressor 65 is provided upstream of the branch 61a in the final gas discharge line 61 and is a device that pressurizes the secondary purified gas into the purified gas tank 63. The compressor 65 can be a pump, a compressor, or a combination of these. In the examples shown in FIGS. 6 and 7 , the purified gas tank 63 is the high-pressure tank, and the compressor 65 is a compressor that can pressurize the secondary purified gas into the purified gas tank 63 at high pressure. The compressor 65 can not only increase the pressure downstream of the compressor 65 compared to the upstream side, but also reduce the pressure upstream of the compressor 65. This allows the compressor 65 to double as the pressure reducer 22 provided in the secondary purified gas line 21, and the pressure reducer 22 can sometimes be omitted from the secondary purified gas line 21. In an apparatus that does not include the pressure reducer 22, the pressure reducer 22 of the hydrogen gas production apparatus A is composed of the compressor 65, and the secondary purified gas line 21 of the hydrogen gas production apparatus A is composed of the secondary purified gas line 21 and the final gas discharge line 61.

[0128] 6 and 7, the set of switching valves 67 includes a valve 67a provided upstream of a branched portion 61a of the final gas discharge line 61, a valve 67b provided at the branched portion 61a, and a valve 67c provided downstream of the branched portion 61a of the final gas discharge line 61. The set of switching valves 67 is configured to switch between flowing the secondary purified gas discharged from the secondary purified gas line 21 toward the purified gas tank 63, guiding the secondary purified gas in the purified gas tank 63 to the supply destination side and discharging it, or guiding the secondary purified gas discharged from the secondary purified gas line 21 to the supply destination side and discharging it, by switching the open / closed states of these valves 67a to 67c.

[0129] The hydrogen gas supply device B is suitably used as an on-site hydrogen station that supplies hydrogen gas to a mobile object such as a fuel cell vehicle (FCV). The liquefied ammonia supplied from outside to the tank 1 of the hydrogen gas production device A can be transported using transportation means such as a tank truck.

[0130] According to one embodiment, a third cooler 69 is preferably provided in the final gas discharge line 61 downstream of the branching portion 61a. This prevents the external tank from being overheated due to adiabatic compression of the secondary purified gas in the external tank when the high-pressure secondary purified gas stored in the purified gas tank 63 is rapidly supplied and stored in the external tank. Cooling by the third cooler 69 is effective when the purified gas tank 63 is the high-pressure tank. The external tank may be, for example, a high-pressure hydrogen tank mounted on a mobile object such as a fuel cell vehicle (FCV). The secondary purified gas is cooled to a cooling temperature of, for example, −40 to −30°C by the third cooler 69. The third cooler 69 may be, for example, a heat exchanger that exchanges heat between the secondary purified gas and a refrigerant. The refrigerant used is a refrigerant that is cooled by a powerful external cold source (for example, a refrigerator) and is usable at the cooling temperature.

[0131] According to one embodiment, a fourth cooler 62 is preferably provided in the final gas discharge line 61 upstream of the compressor 65. When the purified gas tank 63 is the above-mentioned high-pressure tank and the compressor 65 is a compressor capable of injecting the secondary purified gas into the purified gas tank 63 at high pressure, the secondary purified gas is pre-cooled by the fourth cooler 62 before being compressed by the compressor 65, thereby preventing the purified gas tank 63 from being overheated due to the adiabatic compression of the secondary purified gas by the compressor 65. The secondary purified gas is cooled to a cooling temperature of, for example, −40 to −30°C. The fourth cooler 62 can be, for example, a heat exchanger that exchanges heat between the secondary purified gas and a refrigerant. The refrigerant used is the above-mentioned refrigerant that is cooled by a powerful external cold source (e.g., a refrigerator) separately provided and that can be used at the cooling temperature.

[0132] (Fuel cell system) Next, a fuel cell system C according to an embodiment will be described.

[0133] 8 to 18 show fuel cell systems C1 to C11. FIG. 8 is a diagram showing the configuration of a fuel cell system C1 according to one embodiment. FIG. 9 is a diagram showing the configuration of a fuel cell system C2 according to one embodiment. FIG. 10 is a diagram showing the configuration of a fuel cell system C3 according to one embodiment. FIG. 11 is a diagram showing the configuration of a fuel cell system C4 according to one embodiment. FIG. 12 is a diagram showing the configuration of a fuel cell system C5 according to one embodiment. FIG. 13 is a diagram showing the configuration of a fuel cell system C6 according to one embodiment. FIG. 14 is a diagram showing the configuration of a fuel cell system C7 according to one embodiment. FIG. 15 is a diagram showing the configuration of a fuel cell system C8 according to one embodiment. FIG. 16 is a diagram showing the configuration of a fuel cell system C9 according to one embodiment. FIG. 17 is a diagram showing the configuration of a fuel cell system C10 according to one embodiment. FIG. 18 is a diagram showing the configuration of a fuel cell system C11 according to one embodiment. In the following description, fuel cell systems C1 to C11 will be collectively referred to as fuel cell system C.

[0134] The fuel cell system C includes the above-mentioned hydrogen gas production device A or the above-mentioned hydrogen gas supply device B, and a polymer electrolyte fuel cell (PEFC) 81. Because a polymer electrolyte fuel cell (PEFC) has high power generation efficiency, a low operating temperature, and is lightweight and compact, the fuel cell system C is suitable for use as a power generation system for mobile objects such as fuel cell vehicles (FCVs) and for on-site facilities for home or commercial use.

[0135] The polymer electrolyte fuel cell (PEFC) 81 has an anode and a cathode, and the anode and cathode are connected to an external load 91. The PEFC is configured to generate electricity by supplying hydrogen gas discharged from the hydrogen gas production device A or the hydrogen gas supply device B to the anode and air to the cathode. When the polymer electrolyte fuel cell 81 generates electricity, the required flow rate of hydrogen gas supplied from the hydrogen gas production device A or the hydrogen gas supply device B is determined according to its output current value.

[0136] The polymer electrolyte fuel cell (PEFC) 81 has a single cell formed by stacking catalyst layers with gas diffusion layers provided on both sides of a polymer electrolyte membrane and separators serving as current collectors, and preferably forms a bipolar cell stack in which multiple single cells are stacked in series. The cell stack has a negative electrode terminal connected to the negative electrode of each single cell and a positive electrode terminal connected to the positive electrode of each single cell. The polymer electrolyte fuel cell (PEFC) 81 shown in the figure forms a cell stack, and the negative electrode terminal and positive electrode terminal are connected to an external load 91.

[0137] The negative electrode catalyst layer of the single cell is, for example, a layer made of carbon black carrying a catalyst, which is ultrafine particles of a platinum group metal such as platinum (Pt), and the positive electrode catalyst layer is, for example, a layer made of carbon black carrying a catalyst, which is ultrafine particles of a platinum group metal oxide such as iridium (Ir) oxide. These layers are bonded to both sides of the electrolyte membrane, respectively, to form the negative electrode and positive electrode of the polymer electrolyte fuel cell (PEFC) 81. The electrolyte membrane is made of a very strong acidic fluorocarbon polymer mainly having ion exchange groups such as sulfonic acid groups and carboxyl groups, and has a high hydrogen ion (hydronium ion HO) exchange rate. + ) conductivity. Separators are often made of thin plates made of graphite, carbonaceous materials, or composite materials containing these, which have sufficient electronic conductivity and mechanical strength and are chemically stable in the bonding with a very strong acidic electrolyte and in the reducing / oxidizing environments at the anode and cathode. An external load 91 is connected between the anode and cathode terminals, and hydrogen gas and oxygen gas are supplied to the anode and cathode, respectively, to output DC power and generate electricity. If the hydrogen gas supplied to the anode of a polymer electrolyte fuel cell (PEFC) 81 contains gas components such as carbon monoxide, ammonia, hydrogen sulfide, or sulfur compounds such as sulfur dioxide, these gas components severely poison the platinum and other anode catalysts, reducing their catalytic activity and significantly reducing the power generation performance of the PEFC. Therefore, the concentrations of these gas components in the secondary purified gas must be reduced to within the allowable concentration range that does not cause such poisoning. For example, it is preferable that the concentration be within the allowable range specified in ISO 14687-2, the international standard for hydrogen gas for fuel cells.

[0138] A hydrogen gas supply pump 79 is provided in the final gas discharge line 61 downstream of the pressure reducer 22. The hydrogen gas supply pump 79 is a device for supplying a secondary purified gas containing a high concentration of hydrogen gas to a polymer electrolyte fuel cell (PEFC) 81. The secondary purified gas of fuel supplied to the polymer electrolyte fuel cell 81 generally contains hydrogen ions (hydronium ions HO) in the electrolyte membrane. + ) is added to the air, but lines for adding this moisture (water vapor) are omitted in FIGS. 8 to 18.

[0139] A hydrogen gas supply line 83, which is connected to the final gas discharge line 61 via a hydrogen gas supply pump 79, is connected to a hydrogen gas supply port of the solid polymer fuel cell (PEFC) 81, which supplies the second purified gas to the negative electrode of the solid polymer fuel cell (PEFC) 81. Meanwhile, a hydrogen gas discharge line 84 is connected to a hydrogen gas discharge port of the solid polymer fuel cell 81, which discharges gas containing excess hydrogen gas not consumed during power generation from the negative electrode of the solid polymer fuel cell 81 (hereinafter referred to as hydrogen-containing gas). A pressure regulator 85 is provided in the hydrogen gas discharge line 84, and the hydrogen gas discharge line 84 is connected to the final gas discharge line 61 downstream of the pressure regulator 85 so as to merge. The merged hydrogen-containing gas is supplied to the negative electrode of the solid polymer fuel cell 81 together with the second purified gas discharged from the final gas discharge line 61, thereby forming a hydrogen gas circulation loop via the negative electrode. Furthermore, a flow path switch 86 is provided in the hydrogen gas discharge line 84, and a hydrogen gas treatment line 87 branches off from the hydrogen gas discharge line 84 via the flow path switch 86 and discharges the hydrogen-containing gas to the outside. As the flow path switch 86, for example, a three-way valve can be used. The flow path switch 86 switches the flow path of the hydrogen-containing gas so that the hydrogen-containing gas flows in either a direction toward the final gas discharge line 61 or a direction toward the outside. Under normal operating conditions, the flow path switch 86 is set so that the hydrogen-containing gas flows from the hydrogen gas discharge line 84 toward the final gas discharge line 61, forming the above-mentioned circulation loop.

[0140] The hydrogen-containing gas that flows from the hydrogen gas discharge line 84 to the final gas discharge line 61 is circulated and supplied to the anode of the polymer electrolyte fuel cell 81 by the hydrogen gas supply pump 79 together with the secondary purified gas supplied from the final gas discharge line 61, and reused for power generation. The pressure regulator 85 regulates the pressure of the hydrogen-containing gas discharged from the polymer electrolyte fuel cell 81. The pressure regulator 85 maintains the pressure of the secondary purified gas at the anode at a constant pressure of approximately several hundred kPa during power generation by the polymer electrolyte fuel cell (PEFC) 81. The circulation loop effect ensures that the amount of secondary purified gas supplied to the anode per unit time is sufficiently excessive relative to the amount of secondary purified gas consumed per unit time required to obtain the output current of the polymer electrolyte fuel cell 81. Furthermore, the regulator maintains a pressure balance with the air pressure supplied to the cathode side via the electrolyte membrane and also contributes to regulating the amount of moisture in the anode. The pressure regulator 85 uses a pressure regulating valve that maintains a constant primary pressure upstream of the pressure regulator 85. Most of the water generated at the positive electrode during power generation in a polymer electrolyte fuel cell (PEFC) is discharged from the air outlet on the positive electrode side, along with the oxygen and nitrogen gas in the air that is not consumed at the positive electrode.

[0141] In the normal operating state of the fuel cell system C1 shown in FIG. 8 , as described above, the flow path of the hydrogen-containing gas switched by the flow path selector 86 is maintained in the direction from the hydrogen gas discharge line 84 toward the final gas discharge line 61, thereby forming the hydrogen gas circulation loop. At this time, a stable, high output is obtained for a while after the start of power generation by the polymer electrolyte fuel cell (PEFC) 81. However, the secondary purified gas that permeates the separation membrane of the secondary purification section and is supplied to the polymer electrolyte fuel cell 81 via the final gas discharge line 61 and the hydrogen gas supply line 83 contains a small amount of nitrogen gas, about 2 to 5 volume %, along with hydrogen gas, which is the main component. Therefore, during power generation by the polymer electrolyte fuel cell 81, the secondary purified gas containing nitrogen gas is supplied and continues to be circulated and supplied to the polymer electrolyte fuel cell 81 via the hydrogen gas discharge line 84 and the like. During this time, only hydrogen gas is consumed as fuel at the anode of the polymer electrolyte fuel cell 81, so that the nitrogen gas concentration gradually increases from the initial concentration of about 2 to 5 volume % within the circulation loop. Such an increase in nitrogen gas concentration can increase concentration polarization at the negative electrode of the polymer electrolyte fuel cell 81 and reduce power generation efficiency, so it is necessary to reduce the nitrogen gas concentration in the circulation loop before the effect reaches an unacceptable level.

[0142] As described above, the fuel cell system C1 includes a flow path switch 86 in the hydrogen gas discharge line 84, and a hydrogen gas treatment line 87 that branches off from the hydrogen gas discharge line 84 via the flow path switch 86 and discharges the hydrogen-containing gas to the outside. Before the increase in nitrogen gas concentration described above progresses and the decrease in power generation efficiency exceeds an allowable level, the flow path of the hydrogen-containing gas is switched by the flow path switch 86 so that the direction of the hydrogen-containing gas is toward the hydrogen gas treatment line 87. This allows the nitrogen-enriched gas that has been residing in the circulation loop to be discharged to the outside of the system by the hydrogen gas supply pump 79. When the discharge of the hydrogen-containing gas residing in the circulation loop to the outside (outside) is completed and the inside of the circulation loop is completely replaced with the secondary purified gas supplied by the supply pump 79, the nitrogen gas concentration in the hydrogen-containing gas residing in the circulation loop returns to approximately its initial state (e.g., approximately 2 to 5% by volume). At that point, the flow path switch 86 is returned to the normal position of the final gas discharge line 61. Even during the series of processes described above, it is possible to continue power generation in the polymer electrolyte fuel cell 81. The configuration of the fuel cell system C1 described above, which intermittently discharges concentrated nitrogen gas to the outside of the system, makes it possible to restore the nitrogen gas concentration that has increased in the first circulation loop to its initial state (for example, about 2 to 5% by volume), prevents an increase in concentration polarization at the negative electrode of the polymer electrolyte fuel cell 81 and a decrease in power generation efficiency, and maintains stable, high-output power generation.

[0143] In the above-described configuration, the hydrogen-containing gas discharged from the hydrogen gas treatment line 87 still contains a high concentration of hydrogen gas and is flammable. For this reason, when discharging the hydrogen-containing gas, it is preferable to take fire prevention measures, such as mixing the hydrogen-containing gas with a gas mainly composed of low-flammability nitrogen gas discharged from the nitrogen gas discharge line 23 of the hydrogen separation unit 19 of the hydrogen gas production device A or the hydrogen gas supply device B provided in the fuel cell system C1, mixing the gas with a large amount of air under conditions where fire, static electricity, etc. are sufficiently eliminated, and discharging the gas outside the system. In addition, it is preferable to provide a flame arrester, for example, to prevent flashback, at the tip of the pipe from which the gas is finally discharged outside the system.

[0144] The configuration of the fuel cell system C1, which intermittently discharges concentrated nitrogen gas outside the system, is similar to the embodiment disclosed in Patent Document 2, which intermittently purges nitrogen gas accumulated at the anode during power generation in a polymer electrolyte fuel cell. However, while the initial concentration of nitrogen gas in the fuel gas supplied to the polymer electrolyte fuel cell is high at approximately 25% by volume in Patent Document 2, the fuel cell system C1 of the present invention has a much lower concentration of nitrogen gas, for example, approximately 2-5% by volume. Therefore, concentration polarization at the anode during normal operation is suppressed compared to Patent Document 2, resulting in higher power efficiency. Furthermore, due to the difference in the initial nitrogen gas concentration, the fuel cell system C1 of the present invention requires less frequent discharge to restore the nitrogen gas concentration compared to Patent Document 2, and therefore the amount of hydrogen gas lost due to discharge outside the system is significantly less than that of Patent Document 2. The fuel cell systems C3 to C11 in FIGS. 10 to 18 also show examples in which a configuration similar to that of the fuel cell system C1 is provided, in which concentrated nitrogen gas is intermittently discharged to the outside of the system.

[0145] FIG. 9 shows another fuel cell system C2 that can prevent an increase in concentration polarization and a decrease in power generation efficiency at the negative electrode of a polymer electrolyte fuel cell 81 and maintain stable, high-output power generation. Because the fuel cell system C2 utilizes the separation membrane of the hydrogen separation unit after removal of residual ammonia gas, the hydrogen gas production device A or hydrogen gas supply device B provided therein preferably has an ammonia adsorption unit as the primary purification unit 15 and a hydrogen separation unit as the secondary purification unit. Instead of the configuration of the fuel cell system C1 shown in FIG. 8, in which nitrogen-enriched gas is intermittently discharged to the outside of the system, the fuel cell system C2 has a hydrogen gas treatment line 87 that branches off from the hydrogen gas discharge line 84 via a flow path switch 86 and merges with the secondary purified gas line 21 upstream of the separation membrane of the secondary purification unit 19 (hydrogen separation unit). The flow path switch 86 can be, for example, a three-way valve. The hydrogen gas treatment line 87 is provided with a reflux pump 88, and further provided with a pressure adjusting valve 89 and a check valve 90 at a portion before joining the secondary purified gas line 21.

[0146] In fuel cell system C2, before the increase in nitrogen gas concentration described above continues and the decrease in power generation efficiency exceeds an allowable level, flow path selector 86 switches the flow path so that the hydrogen-containing gas is discharged toward hydrogen gas treatment line 87, and reflux pump 88 is started. The hydrogen-containing gas in which nitrogen gas has been concentrated and has been staying in the circulation loop is pressurized by reflux pump 88, passes through hydrogen gas treatment line 87, and merges with the primary purified gas passing through primary purified gas line 17 upstream of the separation membrane of hydrogen separation unit 19. In the portion of hydrogen gas treatment line 87 before this merger, pressure regulator valve 89 adjusts the pressure of the hydrogen-containing gas in which nitrogen gas has been concentrated in hydrogen gas treatment line 87 so that it is equal to the pressure of the primary purified gas in the primary purified gas line. This pressure adjustment prevents the hydrogen-containing gas from flowing upstream of primary purified gas line 17 and the primary purified gas from flowing into hydrogen gas treatment line 87. Thereafter, the hydrogen-containing gas in which nitrogen gas has been concentrated is separated together with the primary purified gas by a separation membrane to separate the nitrogen gas contained therein (at this time, the primary purified gas becomes a secondary purified gas from which nitrogen gas has been separated), and the gas is then supplied as fuel gas by a supply pump 79 to a polymer electrolyte fuel cell 81 via a final gas discharge line 61 and a hydrogen gas supply line 83. In the above, the flow rate per unit time of the hydrogen-containing gas in which nitrogen gas has been concentrated, transported by a reflux pump 88, needs to be limited to a level that does not exceed the separation processing capacity of the separation membrane when the two gases join together.

[0147] When the circulation loop is completely replaced with the second purified gas and the hydrogen-containing gas from which nitrogen gas has been removed, supplied by the supply pump 79, the nitrogen gas concentration in the gas remaining in the circulation loop returns to approximately its initial state (for example, about 2 to 5% by volume), the flow path switch 68 is returned to the normal final gas discharge line 61 side, and the reflux pump 88 is stopped. Here, the check valve 90 prevents the first purified gas from flowing into the hydrogen gas treatment line 87, which would cause a drop in pressure in the hydrogen gas treatment line 87 after the reflux pump 88 is stopped.

[0148] Even during the series of processes described above, it is possible to continue power generation in the polymer electrolyte fuel cell 81. The configuration of the fuel cell system C2 described above, which removes nitrogen gas from nitrogen-enriched gas, makes it possible to restore the nitrogen gas concentration that has increased in the first circulation loop to its initial state (for example, about 2 to 5% by volume), preventing an increase in concentration polarization at the negative electrode of the polymer electrolyte fuel cell 81 and a decrease in power generation efficiency, and maintaining stable, high-output power generation.

[0149] The fuel cell system C2 described above, which removes nitrogen gas from nitrogen-enriched gas, has a slightly more complicated configuration than the fuel cell system C1, but has the advantage of using only the components of the fuel cell system C2, thereby reducing the amount of hydrogen gas lost by being discharged outside the system to almost zero. A configuration similar to this fuel cell system C2 can also be applied to the fuel cell systems C3 to C11 shown in Figures 10 to 18, replacing the configuration similar to the fuel cell system C1, which intermittently discharges nitrogen-enriched gas outside the system.

[0150] In the above-mentioned fuel cell system C1 and fuel cell system C2, in order to reduce the dead volume that is difficult to discharge when discharging gas remaining in the circulation loop, it is preferable that the piping length between the confluence of the hydrogen gas discharge line 84 and the final gas discharge line 61 and the flow path switch 86 be as short as possible.

[0151] Next, in the above-mentioned fuel cell system C1 and fuel cell system C2, the timing at which the flow path switch 86 is switched from the state in which the circulation loop is formed during normal operation (in the fuel cell system C2, the reflux pump 88 is started at the same time) to process the nitrogen gas in the circulation loop into concentrated gas (hereinafter referred to as the "start of processing"), and the timing at which the processing is completed and the flow path switch 86 is switched back again to its original state (in the fuel cell system C2, the reflux pump 88 is stopped at the same time; hereinafter referred to as the "end of processing") will be explained.

[0152] In fuel cell system C1 and fuel cell system C2, during power generation, the flow path switch 86 is set so that the direction of the hydrogen-containing gas changes from the hydrogen gas treatment line 87 side to the final gas discharge line 61 side (at which point the circulation loop is formed, hereafter referred to as the "circulation loop formation point"). As power generation progresses, the nitrogen gas concentration in the gas residing in the circulation loop gradually increases from its initial state (e.g., approximately 2 to 5% by volume). This increase in nitrogen gas concentration in the circulation loop increases the concentration polarization of hydrogen gas at the anode of the polymer electrolyte fuel cell 81, reducing power generation efficiency. The point at which this reduction in power generation efficiency reaches an unacceptable level is the "treatment start point." This "unacceptable level" is arbitrary and can be determined as appropriate depending on the target and purpose of the generated power supply. The nitrogen gas concentration in the circulation loop when the power generation efficiency drops to the assumed "unacceptable level" is the upper limit of the allowable nitrogen gas concentration, and the "start point of treatment" is the point at which the nitrogen gas concentration in the circulation loop reaches this upper limit of the allowable nitrogen gas concentration.

[0153] The nitrogen gas concentration in the circulation loop can be monitored by installing a specific concentration detection means within the circulation loop, but it is preferable to use an indicator that allows for easier detection. Hereinafter, the nitrogen gas concentration in the circulation loop at a certain point during power generation after the circulation loop is formed is a function of the volume of the circulation loop (including the gas phase volume of the negative electrode of the polymer electrolyte fuel cell 81), the initial concentration of nitrogen gas in the circulation loop (approximated by the nitrogen gas concentration in the secondary purified gas supplied as fuel, e.g., approximately 2 to 5% by volume), and the amount of electricity generated by the polymer electrolyte fuel cell 81 from the time the circulation loop was formed to that point. Of these, the volume of the circulation loop and the initial concentration of nitrogen gas in the circulation loop are preset values ​​for this fuel cell system and are constants. The output current of the polymer electrolyte fuel cell 81 is generally a preset value as a power generation condition and is constantly monitored. Therefore, the amount of electricity generated by the polymer electrolyte fuel cell 81 can also be easily and constantly monitored as the integral of the output current over time. As described above, the nitrogen gas concentration in the circulation loop is a function of the amount of electricity generated and the elapsed time since the circulation loop was established, both of which can be easily monitored continuously. Therefore, if the amount of electricity generated and the elapsed time since the circulation loop was established at the time when the decrease in power generation efficiency reaches the unacceptable level are experimentally determined as predetermined values, these can be used as indicators that can be monitored continuously in place of the upper limit of the allowable nitrogen gas concentration. Therefore, the "treatment start point" in the fuel cell systems C1 and C2 is detected as the point when the flow path switch 86 is set so that the direction of the hydrogen-containing gas changes from the final gas discharge line 61 to the hydrogen gas treatment line 87, and the amount of electricity generated or the elapsed time since the circulation loop was established reaches the predetermined value. At this timing, the flow path switch 86 can be switched.

[0154] As described above, in the fuel cell system C1, the gas that has reached the upper limit of the allowable nitrogen gas concentration and is residing in the circulation loop at the "start of treatment" is discharged entirely from the system, and in the fuel cell system C2, the nitrogen gas concentrated in the entire amount is separated and removed using the separation membrane, thereby allowing the nitrogen gas concentration in the circulation loop to be roughly restored to the initial nitrogen gas concentration (e.g., approximately 2 to 5 volume %). The "end of treatment" is the time when the above treatment is completed. The mass of gas that has reached the upper limit of the allowable nitrogen gas concentration and is residing in the circulation loop at this "start of treatment" is roughly calculated using the following equation 4. Formula 4: (Mass [kg] of the gas with the maximum allowable nitrogen gas concentration remaining in the circulation loop) ≒(circulation loop volume [m 3 ]) × (gas density at circulation loop internal pressure and temperature [kg / m 3 ]) ≒(circulation loop volume [m 3 ]) × (nitrogen gas density at circulation loop internal pressure and temperature [kg / m 3 ])

[0155] On the right side of Equation 4, "gas density at the internal pressure and temperature of the circulation loop" is the density of the gas at the maximum allowable nitrogen gas concentration at the internal pressure and temperature of the circulation loop. Because nitrogen gas has a density at least one order of magnitude greater than hydrogen gas, when the nitrogen gas concentration rises to, for example, approximately 20-30% by volume, the contribution of the nitrogen gas density becomes dominant in the gas density. Therefore, although the actual value of the maximum allowable nitrogen gas concentration is unknown, we will assume here that it is approximated by the density of pure nitrogen gas. Furthermore, the nitrogen gas density at the internal pressure and temperature of the circulation loop can be calculated using the following Equation 5:

[0156] Formula 5: (Nitrogen gas density at circulation loop internal pressure and temperature [kg / m 3 ]) = (Nitrogen gas density 1.250 kg / m at standard condition 0.1013 MPa, 0°C) 3 ]) ×273.2 / (273.2 + temperature inside the circulation loop [℃]) × (circulation loop internal pressure [MPa]) / (0.1013 [MPa])

[0157] In Equation 5, the pressure inside the circulation loop can be approximated by the primary pressure of the pressure regulator 85, and the temperature inside the circulation loop can be approximated by the temperature inside the polymer electrolyte fuel cell, which is often monitored. Therefore, Equations 4 and 5 can be used to calculate an approximate value for the mass of the gas with the upper limit of the allowable nitrogen gas concentration residing in the circulation loop. In fuel cell systems C1 and C2, when treating a hydrogen-containing gas containing nitrogen gas with the upper limit of the allowable nitrogen gas concentration residing in the circulation loop, the mass flow rate per unit time of the gas in the hydrogen gas treatment line 87 can be measured, for example, by providing a mass flow meter (not shown). The treatment is estimated to be approximately completed by performing the treatment for a time period calculated by dividing, for example, approximately twice the mass of the gas with the upper limit of the allowable nitrogen gas concentration residing in the circulation loop estimated by Equations 4 and 5 by the measured mass flow rate per unit time. This is considered the "treatment completion point," and the flow path switch 86 can be switched again at this timing.

[0158] (Mobile) Next, the moving body of the embodiment will be described. The moving body includes the above-mentioned fuel cell system C and a motor.

[0159] The motor is a device that is driven by the supply of electric power generated by the polymer electrolyte fuel cell (PEFC) and generates power to propel a moving object. The motor is a load that is connected to the negative and positive electrodes of the fuel cell system C. The motor is preferably connected to the negative and positive terminals of the polymer electrolyte fuel cell (PEFC) that make up the cell stack. When power is supplied from the polymer electrolyte fuel cell (PEFC), the motor drives the motor (for example, by rotating the rotating shaft in a rotary motor or by moving linearly in a linear motor) to output mechanical power.

[0160] The mobile object preferably further comprises a motor and a secondary battery connected to the polymer electrolyte fuel cell (PEFC). The secondary battery is generally connected in parallel to the motor and the polymer electrolyte fuel cell (PEFC), and a floating charge configuration is often adopted in which the secondary battery can be charged while the motor is driven by the polymer electrolyte fuel cell (PEFC) (not shown). This makes it possible to stabilize the power supplied to the motor even if the output of the polymer electrolyte fuel cell (PEFC) or the rotation speed of the motor fluctuates.

[0161] Examples of mobile bodies include airspace mobile bodies such as aircraft, helicopters, and drones, land mobile bodies such as vehicles (passenger cars, trucks, buses, etc.), railroad vehicles, and cargo handling machines, and water mobile bodies such as ships. The mobile body further includes a driving body that is driven by the transmission of mechanical power output from the motor to propel the mobile body. For airspace mobile bodies such as aircraft, helicopters, and drones, the driving body is a propeller or rotor that propels the flight of the mobile body; for land mobile bodies such as vehicles (passenger cars, trucks, buses, etc.), railroad vehicles, and cargo handling machines, the driving body is a wheel or caterpillar that propels the movement of the mobile body; and for water mobile bodies such as ships, the driving body is a screw or water jet mechanism that propels the navigation of the mobile body.

[0162] The mobile body may further include a tank for storing at least a portion of the secondary purified gas discharged from the hydrogen gas production device A or the hydrogen gas supply device B (the high-pressure hydrogen tank described above).

[0163] The tank 1 of the fuel cell system C may be filled with liquefied ammonia as cargo or fuel for the mobile body and installed on the mobile body.

[0164] (Hydrogen gas production method) Next, a hydrogen gas production method according to an embodiment will be described. The hydrogen gas production method of the embodiment is a method for producing hydrogen gas by supplying liquefied ammonia as a raw material, and sequentially flowing the supplied liquefied ammonia, ammonia gas obtained by vaporizing the liquefied ammonia, decomposed gas obtained by decomposing the ammonia gas, and purified gas obtained by purifying the decomposed gas in one direction.

[0165] The hydrogen gas production method includes the following steps S1 to S7. Step S1: Liquefied ammonia is guided downstream from a tank storing the liquefied ammonia and vaporized to form ammonia gas. Step S2: Heating the vaporized ammonia gas to a temperature for decomposition. Step S3: bringing the ammonia gas heated to the decomposition temperature into contact with a catalyst to decompose it, thereby generating a decomposed gas containing hydrogen gas, nitrogen gas, and residual ammonia gas. Step S4 of cooling the cracked gas. Step S5: removing one of the residual ammonia gas and the nitrogen gas from the cooled cracked gas to generate a primary purified gas. Step S6 of removing the other of the residual ammonia gas and the nitrogen gas from the primary purified gas to generate a secondary purified gas. Step S7: reducing the pressure of the purified gas upstream by sucking in the purified gas containing hydrogen gas that has permeated the separation membrane and discharging it downstream.

[0166] Of step S5 for producing a primary purified gas and step S6 for producing a secondary purified gas, the step for removing residual ammonia gas is a step for adsorbing the residual ammonia gas onto an adsorbent using an adsorbent that adsorbs the residual ammonia gas. Of step S5 for producing a primary purified gas and step S6 for producing a secondary purified gas, the step for removing nitrogen gas is a step in which a separation membrane is used to selectively allow hydrogen gas to permeate by creating a pressure difference between the upstream and downstream sides of the separation membrane, thereby separating hydrogen gas from nitrogen gas.

[0167] By performing the decompression (evacuation) in step S7 of decompressing, a pressure difference is formed between the vapor pressure in the tank and the pressure downstream of the separation membrane so that liquefied ammonia, ammonia gas, cracked gas, primary purified gas, and secondary purified gas flow downstream from the tank to the downstream side of the separation membrane. The pressure difference is formed as a pressure drop between the upstream and downstream sides of the separation membrane caused by the decompression and exhaust. In other words, the hydrogen gas production method of the embodiment in which the pressure difference is formed as part of the pressure difference can be performed using, for example, any of the hydrogen gas production apparatus A, hydrogen gas supply apparatus B, and fuel cell system C described above.

[0168] According to the hydrogen gas production method of the embodiment, when hydrogen gas is produced while supplying liquefied ammonia as a raw material, a pressure difference is established between the vapor pressure in the liquefied ammonia tank and the pressure on the downstream side of the separation membrane, so that gas generated sequentially using the liquefied ammonia as a raw material flows downstream without stagnation. By creating a pressure difference between the upstream and downstream sides of the separation membrane as part of this pressure difference, it is not necessary to use a pressure reducer separate from the pressure reducer used to create the pressure difference. In addition, hydrogen gas separation (removal of nitrogen gas) can be performed without using a high-pressure compressor (e.g., one that applies pressure of 1 MPa or more), thereby consuming less power. Furthermore, hydrogen gas can be produced using small, simple equipment.

[0169] The above describes the hydrogen gas production device, hydrogen gas supply device, fuel cell system, mobile body, and hydrogen gas production method of the present invention, but the present invention is not limited to the above embodiments, and various improvements and modifications may be made within the scope of the gist of the present invention. [Explanation of symbols]

[0170] 1 tank 1a Heater for keeping warm 3. Raw ammonia line 4 Supply valve 5. Vaporizer 6 Flow regulator 7 Heating heater 9. Ammonia decomposition section 10. Outside air intake line 11 Decomposition gas line 13 Cooler 15 Primary purification section (ammonia adsorption section shown in figures other than Figure 4) 15A, 15B, 15X, 15Y Ammonia Adsorber 15a connecting line 17 Primary refined gas line 17a Pressurizer 18 Upstream pressure regulator 19 Secondary purification section (hydrogen separation section shown in figures other than Figure 4) 20 Downstream pressure regulator 21 Secondary purified gas line 22 Pressure reducer 23 Nitrogen gas discharge line 24 Nitrogen discharge regulator 25 1st heat exchanger 27 Second cooler 28 Regeneration gas line 29 Combustor 30 Branch gas line 31 Combustion gas line 32 Outside air intake line 33 Second heat exchanger 35 Regeneration heater 37, 37A, 37B Inert gas introduction line 37c supply port 39, 39A, 39B Desorbed ammonia discharge line 41 Reliquefaction section 42 Compressor 43 Cooler 61 Final gas discharge line 62 4th cooler 63 Refined Gas Tank 65 Pressurizer 67 A set of switching valves 67a, 67b, 67c valves 69 Third cooler 79 Purified gas supply pump 81 Solid polymer fuel cell 83 Purified gas supply line 84 Hydrogen-containing gas discharge line 86 Flow path switch 88 Reflux Pump 87 Hydrogen-containing gas treatment line 91 External load

Claims

1. A hydrogen gas production apparatus for producing hydrogen gas by supplying liquefied ammonia as a raw material, the supplied liquefied ammonia, ammonia gas obtained by vaporizing the liquefied ammonia, a decomposition gas obtained by decomposing the ammonia gas, and a purified gas obtained by purifying the decomposition gas, in one direction, a tank for storing liquefied ammonia; a raw ammonia line for guiding the liquefied ammonia from the tank downstream; a vaporizer provided in the raw ammonia line for vaporizing the liquefied ammonia into ammonia gas; a heater for heating the vaporized ammonia gas to a temperature for decomposition; an ammonia decomposition unit connected to the raw ammonia line downstream of the vaporizer, for decomposing the ammonia gas heated to the decomposition temperature by bringing the ammonia gas into contact with a catalyst to generate a decomposed gas containing hydrogen gas, nitrogen gas, and residual ammonia gas; a decomposition gas line connected to the ammonia decomposition unit and guiding the decomposition gas downstream; a cooler provided in the decomposition gas line for cooling the decomposition gas; a primary purification section connected to the cracked gas line downstream of the cooler, for removing one of the residual ammonia gas and the nitrogen gas from the cooled cracked gas to produce a primary purified gas; a primary purified gas line connected to the primary purification section and guiding the primary purified gas downstream; a secondary purification unit connected to the primary purified gas line, for removing the other of the residual ammonia gas and the nitrogen gas from the primary purified gas to generate a secondary purified gas; a secondary purified gas line connected to the secondary purification section, which guides the secondary purified gas downstream and discharges it; the refining section from which the residual ammonia gas is removed out of the primary refining section and the secondary refining section is an ammonia adsorption section having an adsorbent that adsorbs the residual ammonia gas, a hydrogen separation unit, wherein one of the primary purification unit and the secondary purification unit from which the nitrogen gas is removed has a separation membrane, and the separation membrane is configured to selectively allow the hydrogen gas to permeate and separate it from the nitrogen gas by a pressure difference created between an upstream side and a downstream side of the separation membrane; the hydrogen gas production apparatus further includes a pressure reducer provided in a purified gas line, one of the primary purified gas line and the secondary purified gas line, that is connected to the hydrogen separation unit and through which the hydrogen gas that has permeated the separation membrane flows, the pressure reducer sucking in the purified gas flowing through the purified gas line and discharging it downstream to reduce the pressure of the purified gas upstream of the pressure reducer; a hydrogen gas production apparatus in which the pressure upstream of the pressure reducer is reduced, thereby creating a pressure difference between the vapor pressure of ammonia gas evaporated in the tank and the pressure upstream of the pressure reducer, so that the liquefied ammonia and the gas flow downstream from the tank to the secondary purified gas line, and the differential pressure is formed as part of the pressure difference.

2. 2. The hydrogen gas production device according to claim 1, wherein a compressor for increasing the pressure of the decomposed gas or the primary purified gas is not provided upstream of the separation membrane.

3. 2. The hydrogen gas production device according to claim 1, further comprising a compressor for increasing the pressure of the cracked gas or the primary purified gas, provided upstream of the hydrogen separation section.

4. 3. The hydrogen gas production device according to claim 1, wherein the tank has a heater for heat retention that maintains the vapor pressure by heating the inside of the tank so that the flow of the liquefied ammonia and the gas downstream from the tank to the secondary purified gas line is maintained.

5. the cooler and the vaporizer constitute a first heat exchanger having a first high-temperature side passage through which the cracked gas flows and a first low-temperature side passage through which the liquefied ammonia flows, 3. The hydrogen gas production device according to claim 1, wherein the first heat exchanger is configured to cool the decomposition gas and heat and vaporize the liquefied ammonia by heat exchange between the decomposition gas flowing through the first high-temperature side flow path and the liquefied ammonia flowing through the first low-temperature side flow path.

6. The hydrogen gas production device according to claim 5, further comprising a second cooler provided upstream or downstream of the first cooler in the decomposition gas line to cool the decomposition gas, when the cooler is referred to as a first cooler.

7. 7. The hydrogen gas production device according to claim 6, wherein the decomposition gas passing through the second cooler is cooled by heat exchange with external air or a liquid refrigerant cooled by heat exchange with external air.

8. the heater for raising the temperature is provided downstream of the vaporizer in the raw ammonia line, a combustor that combusts, together with air, a portion of any of the cracked gas, the primary purified gas, and the secondary purified gas extracted from the ammonia decomposition section or downstream of the ammonia decomposition section, and discharges a combustion gas; a combustion gas line connected to the combustor and through which the combustion gas flows, a part of the combustion gas line and the heater for temperature increase constitute a second heat exchanger having a second high-temperature side passage through which the combustion gas flows and a second low-temperature side passage through which the ammonia gas flows, 3. The hydrogen gas production device according to claim 1, wherein the second heat exchanger is configured to cool the combustion gas and raise the temperature of the ammonia gas by heat exchange between the combustion gas flowing through the second high-temperature side flow path and the ammonia gas flowing through the second low-temperature side flow path.

9. the ammonia adsorption unit includes a regeneration heater that heats the adsorbent that has adsorbed the residual ammonia gas, an inert gas introduction line that introduces an inert gas from the outside, and a desorbed ammonia discharge line through which the residual ammonia gas desorbed from the adsorbent flows; 2. The hydrogen gas production apparatus according to claim 1, wherein the ammonia adsorption unit is configured such that, when heated by the regeneration heater, the residual ammonia gas adsorbed by the adsorbent is desorbed from the adsorbent and discharged from the ammonia adsorption unit through the desorbed ammonia discharge line together with the inert gas introduced through the inert gas inlet line.

10. a combustor that combusts a portion of any of the cracked gas, the primary purified gas, and the secondary purified gas extracted from the ammonia decomposition section or downstream of the ammonia decomposition section, together with air, and discharges the combustion gas; 10. The hydrogen gas production device according to claim 9, wherein the residual ammonia gas discharged together with the inert gas is introduced into the combustor and combusted.

11. the heater for raising the temperature is provided downstream of the vaporizer in the raw ammonia line, the hydrogen gas production apparatus further includes a combustion gas line connected to the combustor and through which the combustion gas flows; a part of the combustion gas line and the heater for temperature increase constitute a second heat exchanger having a second high-temperature side passage through which the combustion gas flows and a second low-temperature side passage through which the ammonia gas flows, 11. The hydrogen gas production device according to claim 10, wherein the second heat exchanger is configured to cool the combustion gas and raise the temperature of the ammonia gas by heat exchange between the combustion gas flowing through the second high-temperature side passage and the ammonia gas flowing through the second low-temperature side passage.

12. a re-liquefaction unit connected to the desorbed ammonia discharge line and the tank, and configured to liquefy the residual ammonia gas desorbed from the adsorbent to separate it from the inert gas; 10. The hydrogen gas production device according to claim 9, wherein the residual ammonia gas discharged together with the inert gas is guided to the re-liquefaction section, liquefied and separated from the inert gas, and recovered in the tank.

13. the ammonia adsorption unit has a plurality of ammonia adsorbers arranged in parallel in the one direction, each of the plurality of ammonia adsorbers includes the adsorbent, the inert gas introduction line, and the desorbed ammonia discharge line; 13. The hydrogen gas production apparatus according to claim 9, wherein the ammonia adsorption unit is configured such that, in one or more ammonia adsorbers among the plurality of ammonia adsorbers, the residual ammonia gas desorbed from the adsorbent by heating by the regenerative heater is discharged through the desorbed ammonia discharge line together with the inert gas introduced from the inert gas inlet line, while the decomposed gas or the primary purified gas is introduced into the remaining ammonia adsorbers, the residual ammonia gas in the gas is adsorbed by the adsorbent of the ammonia adsorber and removed, and the decomposed gas or the primary purified gas from which the residual ammonia gas has been removed is guided downstream of the ammonia adsorption unit, and the one or more ammonia adsorbers and the remaining ammonia adsorbers are switchable among the plurality of ammonia adsorbers.

14. 3. The hydrogen gas production device according to claim 1, wherein the ammonia adsorption unit includes a plurality of ammonia adsorbers arranged in series in the one direction, and each of the plurality of ammonia adsorbers includes the adsorbent.

15. 3. The hydrogen gas production apparatus according to claim 1, further comprising: a flow rate regulator provided in the raw ammonia line downstream of the vaporizer to regulate a flow rate of the ammonia gas; and / or an upstream pressure regulator provided in the gas line through which the gas guided to the hydrogen separation section flows to regulate a pressure of the gas flowing in the gas line.

16. 3. The hydrogen gas production device according to claim 1, wherein the primary purification section is the ammonia adsorption section, and the secondary purification section is the hydrogen separation section.

17. A hydrogen gas supply device that supplies hydrogen gas to a supply destination, The hydrogen gas production device according to claim 1; a final gas discharge line connected to a secondary purified gas line of the hydrogen gas production apparatus, which guides and discharges the secondary purified gas discharged from the secondary purified gas line toward the supply destination, the final gas discharge line having a branch portion that branches off so that the secondary purified gas flows to a side different from the supply destination; a purified gas tank connected to the branching portion and configured to store the secondary purified gas flowing to the different side; a compressor provided in the final gas discharge line upstream of the branching portion, for pressurizing the secondary purified gas into the purified gas tank; a set of switching valves provided in the final gas discharge line for switching the flow path of the secondary purified gas flowing through the final gas discharge line, the set of switching valves switching whether the secondary purified gas discharged from the secondary purified gas line flows toward the purified gas tank, the secondary purified gas in the purified gas tank is guided to the supply destination side and discharged, or the secondary purified gas discharged from the secondary purified gas line is guided to the supply destination side and discharged.

18. The hydrogen gas production device according to claim 1 or the hydrogen gas supply device according to claim 17; a polymer electrolyte fuel cell having an anode and a cathode, the anode and the cathode being connected to an external load, and configured to generate electricity by supplying secondary purified gas discharged from the hydrogen gas production device or the hydrogen gas supply device to the anode and air to the cathode.

19. The fuel cell system includes: a purified gas supply line connected to a secondary purified gas line of the hydrogen gas production device or a final gas discharge line of the hydrogen gas supply device, for guiding the secondary purified gas discharged from the line to the negative electrode; a hydrogen-containing gas discharge line provided with a flow path switch, which guides a hydrogen-containing gas containing surplus hydrogen gas, which is not consumed during the power generation and is discharged from the negative electrode, and nitrogen gas, which is contained in the secondary purified gas and has permeated a separation membrane of the hydrogen gas production device, to the secondary purified gas line or the final gas discharge line connected to the purified gas supply line, and merges the hydrogen-containing gas with the secondary purified gas; a hydrogen-containing gas treatment line that branches off from the hydrogen-containing gas discharge line via the flow path switch and discharges the hydrogen-containing gas to the outside, the flow path switch is configured to switch the flow direction of the hydrogen-containing gas to one of the secondary purified gas line side or the final gas discharge line side and the hydrogen gas treatment line side; the flow direction of the hydrogen-containing gas is switched to the side of the secondary purified gas line or the final gas discharge line, so that the hydrogen-containing gas is circulated and supplied to the negative electrode together with the secondary purified gas discharged from the secondary purified gas line or the final gas discharge line; When the amount of electricity generated by the polymer electrolyte fuel cell or the elapsed time during the power generation from the time when the flow direction of the hydrogen-containing gas is switched to the secondary purified gas line or the final gas discharge line reaches a predetermined value, the flow direction of the hydrogen-containing gas is switched to the hydrogen-containing gas treatment line side, and the hydrogen-containing gas containing the concentrated nitrogen gas from that time is discharged to the outside, 19. The fuel cell system of claim 18, wherein the flow direction of the hydrogen-containing gas is switched to the side of the secondary purification line or the final gas discharge line upon completion of discharge of the hydrogen-containing gas containing the concentrated nitrogen gas from the hydrogen-containing gas processing line to the outside.

20. the primary purification unit of the hydrogen gas production device and the hydrogen gas supply device is an ammonia adsorption unit, and the secondary purification unit is a hydrogen separation unit; a purified gas supply line connected to a secondary purified gas line of the hydrogen gas production device or a final gas discharge line of the hydrogen gas supply device, for guiding the secondary purified gas discharged from the line to the negative electrode; a hydrogen-containing gas discharge line provided with a flow path switch, which guides a hydrogen-containing gas containing surplus hydrogen gas, which is not consumed during the power generation and is discharged from the negative electrode, and nitrogen gas, which is contained in the secondary purified gas and has permeated a separation membrane of the hydrogen gas production device, to the secondary purified gas line or the final gas discharge line connected to the purified gas supply line, and merges the hydrogen-containing gas with the secondary purified gas; a hydrogen-containing gas treatment line branching from the hydrogen-containing gas discharge line via the flow path switch and connected to a primary purified gas line of the hydrogen gas production apparatus or the hydrogen gas supply apparatus, the flow path switch is configured to switch the flow direction of the hydrogen-containing gas to one of the secondary purified gas line side or the final gas discharge line side and the hydrogen gas treatment line side; the flow direction of the hydrogen-containing gas is switched to the side of the secondary purified gas line or the final gas discharge line, so that the hydrogen-containing gas is circulated and supplied to the negative electrode together with the secondary purified gas discharged from the secondary purified gas line or the final gas discharge line; When the amount of electricity generated by the polymer electrolyte fuel cell or the elapsed time during the power generation from the time point when the flow direction of the hydrogen-containing gas is switched to the side of the secondary purified gas line or the final gas discharge line reaches a predetermined value, the flow direction of the hydrogen-containing gas is switched to the side of the hydrogen-containing gas treatment line, and the hydrogen-containing gas containing the concentrated nitrogen gas from that point is introduced into the primary purified gas line via the hydrogen-containing gas treatment line, merges with the primary purified gas flowing in the primary purified line, and is introduced into the hydrogen separation unit, where the nitrogen gas is separated and removed by the separation membrane, and the gas after the merger from which the nitrogen gas has been separated and removed is supplied to the negative electrode via the secondary purified gas line or the final gas discharge line and the hydrogen gas supply line, 19. The fuel cell system of claim 18, wherein the flow direction of the hydrogen-containing gas is switched to the side of the secondary purified gas line or the final gas discharge line upon completion of the separation and removal of the nitrogen gas from the gas after the joining.

21. A mobile object, a fuel cell system according to claim 18; a motor connected to the negative and positive electrodes of the fuel cell system, driven by the power generated by the fuel cell of the fuel cell system, and generating power to propel the mobile body.

22. A hydrogen gas production method for producing hydrogen gas by supplying liquefied ammonia as a raw material, and sequentially flowing the supplied liquefied ammonia, ammonia gas obtained by vaporizing the liquefied ammonia, a cracked gas obtained by decomposing the ammonia gas, and a purified gas obtained by purifying the cracked gas in one direction, A step of guiding the liquefied ammonia from a tank storing the liquefied ammonia downstream and vaporizing the liquefied ammonia into ammonia gas; heating the vaporized ammonia gas to a decomposition temperature; a step of bringing the ammonia gas heated to the decomposition temperature into contact with a catalyst to decompose the ammonia gas, thereby generating a decomposed gas containing hydrogen gas, nitrogen gas, and residual ammonia gas; cooling the cracked gas; removing one of the residual ammonia gas and the nitrogen gas from the cooled cracked gas to generate a primary purified gas; removing the other of the residual ammonia gas and the nitrogen gas from the primary purified gas to generate a secondary purified gas; a step of removing the residual ammonia gas from the step of generating the primary purified gas and the step of generating the secondary purified gas, the step of removing the residual ammonia gas from the residual ammonia gas by using an adsorbent that adsorbs the residual ammonia gas; the step of removing the nitrogen gas from the step of generating the primary purified gas and the step of generating the secondary purified gas is a step of separating the hydrogen gas from the nitrogen gas by selectively allowing the hydrogen gas to permeate using a separation membrane due to a pressure difference created between an upstream side and a downstream side of the separation membrane; The hydrogen gas production method further includes a step of reducing the pressure of the purified gas upstream by sucking in the purified gas containing the hydrogen gas that has permeated the separation membrane and discharging it downstream, a pressure difference is formed between the vapor pressure of ammonia gas evaporated in the tank and the pressure on the upstream side, and the pressure difference is formed as part of the pressure difference, so that the liquefied ammonia and the gas flow downstream from the tank to the downstream side of the separation membrane by reducing the pressure on the upstream side.

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