Solid oxide fuel cell stack, fuel cell module, and fuel cell device

Abstract

Hydrogen supplied through a hydrogen supply port is injected together with water supplied through a water supply port into this solid oxide fuel cell stack. The solid oxide fuel cell stack generates power using hydrogen as a raw fuel.

Description

Solid oxide fuel cell stack, fuel cell module, and fuel cell device CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to Japanese Patent Application No. 2024-004173, filed on January 15, 2024, the entire disclosure of which is incorporated herein by reference.

[0002] The present disclosure relates to a solid oxide fuel cell stack, a fuel cell module, and a fuel cell device.

[0003] 2. Description of the Related Art A solid oxide fuel cell that generates electricity using hydrogen as a raw fuel is known (see Patent Document 1).

[0004] Special table 2019-530137 publication

[0005] In the solid oxide fuel cell stack according to the first aspect, hydrogen supplied from the hydrogen supply port is injected together with water supplied from the water supply port, and the hydrogen is used as a raw fuel to generate electricity.

[0006] In order to solve the above-mentioned problems, a fuel cell module according to a second aspect includes a solid oxide fuel cell stack into which hydrogen supplied from a hydrogen supply port is injected together with water supplied from a water supply port, and the hydrogen is used as a raw fuel to generate electricity.

[0007] In order to solve the above-mentioned problems, a fuel cell device according to a third aspect comprises a fuel cell module having a solid oxide fuel cell stack into which hydrogen supplied from a hydrogen supply port is injected together with water supplied from a water supply port, and which generates electricity using the hydrogen as a raw fuel, and auxiliary equipment for operating the fuel cell module.

[0008] 1 is a schematic diagram of a fuel cell module including a solid oxide fuel cell stack according to an embodiment of the present invention.

[0009] Hereinafter, embodiments of a solid oxide fuel cell stack and a fuel cell module to which the present disclosure is applied will be described with reference to the drawings.

[0010] 1 , a fuel cell module 11 including a solid oxide fuel cell stack 10 according to an embodiment of the present disclosure is configured to include the solid oxide fuel cell stack 10, a mixing section 12, and a combustion section 13. The fuel cell module 11 may constitute a fuel cell device together with auxiliary equipment for operating the fuel cell module 11.

[0011] Hydrogen is injected into the solid oxide fuel cell stack 10 through a hydrogen supply port 14 together with water supplied through a water supply port 15. Hydrogen released from an organic hydride, ammonia, or the like, or synthesized hydrogen may be supplied to the hydrogen supply port 14. Liquid water or water vapor may be supplied to the water supply port 15.

[0012] The solid oxide fuel cell stack 10 generates electricity by an electrochemical reaction between injected hydrogen as a raw fuel and an oxygen-containing gas contained in the air. The solid oxide fuel cell stack 10 may also generate water by an electrochemical reaction.

[0013] As will be described later, hydrogen and water as raw fuel may be mixed and then supplied to the solid oxide fuel cell stack 10. The amount of hydrogen supplied to the solid oxide fuel cell stack 10 may be adjusted according to the required power. The amount of water supplied to the solid oxide fuel cell stack 10 may be constant.

[0014] Since the solid oxide fuel cell stack 10 undergoes an electrochemical reaction at a relatively high temperature, the water produced may be water vapor. The solid oxide fuel cell stack 10 discharges exhaust gas containing at least unreacted raw fuel, unreacted oxygen, and water vapor. The solid oxide fuel cell stack 10 may discharge the unreacted raw fuel and water vapor from a fuel off-gas outlet 16. The solid oxide fuel cell stack 10 may discharge unreacted oxygen from an oxygen off-gas outlet 17.

[0015] The solid oxide fuel cell stack 10 may have a single fuel off-gas discharge port 16 or may have multiple fuel off-gas discharge ports 16. In a configuration having multiple fuel off-gas discharge ports 16, the solid oxide fuel cell stack 10 may have a fuel off-gas discharge manifold connected to the multiple fuel off-gas discharge ports 16.

[0016] At least a portion of the raw fuel and water discharged from the fuel off-gas outlet 16 may be re-supplied to the solid oxide fuel cell stack 10. At least a portion of the raw fuel and water may be re-supplied somewhere between the hydrogen supply port 14 and the water supply port 15 and the solid oxide fuel cell stack 10. At least a portion of the raw fuel and water may be provided immediately before the solid oxide fuel cell stack 10, specifically downstream of a mixer 12 described below.

[0017] For example, a discharge pipe 18 that discharges raw fuel and water from the solid oxide fuel cell stack 10 may be provided with a recirculation path 20 that connects to a fuel supply port 19 for the raw fuel to the solid oxide fuel cell stack 10. The raw fuel and water may be sent from the recirculation path 20 to the fuel supply port 19 using a booster such as a pump. The discharge pipe 18 and the recirculation path 20 may be connected via a flow control valve 21. The fuel supply port 19 and the fuel off-gas discharge port 16 may be provided on the same surface of the solid oxide fuel cell stack 10. Furthermore, the oxygen off-gas discharge port 17 may also be provided on the same surface as the fuel supply port 19 and the fuel off-gas discharge port 16.

[0018] The solid oxide fuel cell stack 10 may be configured by stacking a plurality of solid oxide fuel cells. The solid oxide fuel cells may have any known shape, such as a flat plate type, a cylindrical type, or a cylindrical-flat plate type. Therefore, the solid oxide fuel cell stack 10 may be a flat plate type, a cylindrical type, or a cylindrical-flat plate type. A flat plate type solid oxide fuel cell may be rectangular.

[0019] The mixing unit 12 may mix the raw fuel and water. Therefore, as described above, the raw fuel and water may be mixed and supplied to the solid oxide fuel cell stack 10. The mixing unit 12 may discharge the raw fuel and water as a gaseous mixture. The mixing unit 12 may be provided in the vicinity of the solid oxide fuel cell stack 10. The mixing unit 12 may be provided vertically above or to the side of the solid oxide fuel cell stack 10 in close proximity when the solid oxide fuel cell stack 10 is installed as a fuel cell device.

[0020] The mixing section 12 may also function as a vaporizing section that vaporizes water supplied in liquid form. The heat required for vaporizing the water may be obtained from the solid oxide fuel cell stack 10 operating at a high temperature. Furthermore, the heat required for vaporizing the water may be obtained from the combustion section 13, which will be described later.

[0021] The combustion unit 13 may combust unreacted raw fuel, i.e., hydrogen, in the solid oxide fuel cell stack 10. The combustion unit 13 may use unreacted oxygen in the solid oxide fuel cell stack 10 to combust the unreacted raw fuel.

[0022] The combustion section 13 may be disposed between the solid oxide fuel cell stack 10 and the mixing section 12. It may be assumed that the combustion section 13 is disposed vertically above the solid oxide fuel cell stack 10 when the solid oxide fuel cell stack 10 is installed as a fuel cell device.

[0023] In the solid oxide fuel cell stack 10 of this embodiment configured as described above, hydrogen supplied from the hydrogen supply port 14 is injected together with water supplied from the water supply port 15, and the hydrogen is used as a raw fuel to generate electricity. The electromotive force in the solid oxide fuel cell stack 10 can be calculated using the Nernst equation. Specifically, the electromotive force can be calculated using the following equation (1):

[0024] Electromotive force=-ΔG / nF+(RT / nF)×ln{P(H ２ ) x P ０．５ (O ２ ) / p(H ２ 0) (1)

[0025] In equation (1), ΔG is the Gibbs free energy change [kJ / mol], n is the number of electrons involved in the reaction, T is the battery temperature (temperature between cells) [°C], F is the Faraday constant (= 96484.56 [C / mol]), R is the gas constant (8.3145 [J / (mol × K)]), and P() is the partial pressure of each gas.

[0026] In a configuration in which only high-purity hydrogen gas is supplied to a solid oxide fuel cell stack, very little water is generated near the anode inlet. Therefore, as can be seen from equation (1), the electromotive force near the anode inlet becomes large. Under such conditions, when the solid oxide fuel cell stack generates electricity, the amount of current flowing near the anode inlet increases, causing a temperature rise near the anode inlet due to Joule heat. This temperature rise may result in a decrease in the performance and shortened lifespan of the solid oxide fuel cell stack. Meanwhile, in the solid oxide fuel cell stack 10 having the above-described configuration, water may also be present near the anode inlet. Therefore, as can be seen from equation (1), the solid oxide fuel cell stack 10 can reduce the electromotive force near the anode inlet compared to a configuration in which only high-purity hydrogen gas is supplied to the anode. This prevents the current flowing near the anode inlet from concentrating and the temperature rise near the anode inlet due to Joule heat. As a result, the solid oxide fuel cell stack 10 can have improved performance and a longer lifespan.

[0027] Furthermore, in the solid oxide fuel cell stack 10, the raw fuel and water are mixed together before being supplied to the solid oxide fuel cell stack 10. With this configuration, the solid oxide fuel cell stack 10 can suppress an increase in electromotive force by uniformly dispersing the raw fuel and water within the anode.

[0028] Furthermore, in the solid oxide fuel cell stack 10, a mixing section 12 that mixes the raw fuel and water is disposed near the solid oxide fuel cell stack 10. With this configuration, the solid oxide fuel cell stack 10 can heat the raw fuel and water supplied thereto by heat transfer at the operating temperature of the solid oxide fuel cell stack 10 during power generation.

[0029] Furthermore, in the solid oxide fuel cell stack 10, a combustion section 13 that combusts unreacted raw fuel in the solid oxide fuel cell stack 10 is disposed between the solid oxide fuel cell stack 10 and the mixing section 12. With this configuration, the solid oxide fuel cell stack 10 can further heat the raw fuel and water supplied to the mixing section 12 by burning the unreacted raw fuel in the combustion section 13.

[0030] Furthermore, in the solid oxide fuel cell stack 10, the amount of water supplied through the water supply port 15 is constant. Bumping may occur in the mixing section 12 if the amount of water supplied is insufficient relative to the amount of heat applied from the outside. Therefore, if the heat generated in the combustion section 13 increases, it is possible to increase the amount of water supplied. However, because there is generally a difference in response speed between a water pump and a hydrogen pump, hunting or overshooting may occur when attempting to synchronize the water supply with the hydrogen supply. Therefore, the solid oxide fuel cell stack 10 having the above-described configuration can achieve stable control while reducing the possibility of bumping by supplying a sufficient, constant amount of water even when the hydrogen supply is increased by a normally required amount from the current value.

[0031] Furthermore, in the solid oxide fuel cell stack 10, at least a portion of the raw fuel and water discharged from the solid oxide fuel cell stack 10 is re-supplied to the solid oxide fuel cell stack 10. With this configuration, the solid oxide fuel cell stack 10 can improve the utilization rate of the raw fuel.

[0032] Furthermore, in the solid oxide fuel cell stack 10, a discharge pipe 18 that discharges raw fuel and water from the solid oxide fuel cell stack 10 is provided with a recirculation path 20 that connects to a fuel supply port 19 for the raw fuel to the solid oxide fuel cell stack 10. With this configuration, the solid oxide fuel cell stack 10 can more efficiently supply at least a portion of the raw fuel and water discharged from the solid oxide fuel cell stack 10 to the fuel supply port 19 for the raw fuel, thereby further improving the utilization rate of the raw fuel.

[0033] In the solid oxide fuel cell stack 10, the discharge pipe 18 and the recirculation path 20 are connected via a flow control valve 21. With this configuration, the solid oxide fuel cell stack 10 can adjust the amount of raw fuel to be recirculated and the amount of raw fuel to be combusted in the combustion section 13.

[0034] Furthermore, the solid oxide fuel cell stack 10 is flat, and the fuel off-gas outlet 16 and the fuel supply port 19, which discharge the raw fuel and water from the solid oxide fuel cell stack 10, are provided on the same surface of the solid oxide fuel cell stack 10. This configuration allows the solid oxide fuel cell stack 10 to shorten the length of piping. Furthermore, because the water concentration is low on the fuel supply port 19 side, the electromotive force is large according to formula (1). Under such circumstances, when the solid oxide fuel cell stack 10 generates electricity, the current flowing on the fuel supply port 19 side tends to concentrate, and the temperature on the fuel supply port 19 side tends to rise due to Joule heat. On the other hand, in the solid oxide fuel cell stack 10 configured as described above, the electromotive force is reduced according to formula (1) at the fuel off-gas outlet 16, where the water concentration is high, and the current flowing on the fuel off-gas outlet 16 side of the anode is small, so the temperature on the fuel off-gas outlet 16 side tends to be less likely to rise. To cope with such an event, the solid oxide fuel cell stack 10 can offset temperature variations in the direction perpendicular to the same plane (e.g., the stacking direction) by providing the fuel off-gas exhaust port 16 and the fuel supply port 19 on the same plane, thereby preventing deterioration and a decrease in power generation efficiency in the solid oxide fuel cell stack 10.

[0035] In one embodiment, (1) the solid oxide fuel cell stack receives hydrogen supplied from a hydrogen supply port together with water supplied from a water supply port, and generates electricity using the hydrogen as a raw fuel.

[0036] (2) In the solid oxide fuel cell stack of (1) above, the raw fuel and the water are mixed together and then supplied to the solid oxide fuel cell stack.

[0037] (3) In the solid oxide fuel cell stack of (2) above, a mixer that mixes the raw fuel and the water is disposed near the solid oxide fuel cell stack.

[0038] (4) In the solid oxide fuel cell stack of (3) above, a combustion section that combusts the unreacted raw fuel in the solid oxide fuel cell stack is disposed between the solid oxide fuel cell stack and the mixing section.

[0039] (5) In the solid oxide fuel cell stack of (4) above, the amount of water supplied through the water supply port is constant.

[0040] (6) In the solid oxide fuel cell stack according to any one of (1) to (5) above, at least a portion of the raw fuel and water discharged from the solid oxide fuel cell stack is resupplied to the solid oxide fuel cell stack.

[0041] (7) In the solid oxide fuel cell stack of (6) above, a discharge pipe for discharging raw fuel and water from the solid oxide fuel cell stack is provided with a recirculation path that connects to a raw fuel supply port to the solid oxide fuel cell stack.

[0042] (8) In the solid oxide fuel cell stack of (7) above, the discharge pipe line and the recirculation line are connected via a flow rate adjustment valve.

[0043] (9) In the solid oxide fuel cell stack of (7) or (8) above, the solid oxide fuel cell stack is a flat plate type, and the outlet for discharging raw fuel and water from the solid oxide fuel cell stack and the supply port are provided on the same surface of the solid oxide fuel cell stack.

[0044] In one embodiment, (10) a fuel cell module includes a solid oxide fuel cell stack according to any one of (1) to (9) above.

[0045] In one embodiment, a (11) fuel cell device includes the fuel cell module of (10) and accessories for operating the fuel cell module.

[0046] The drawings illustrating the embodiments of the present disclosure are schematic, and the dimensional ratios and the like in the drawings do not necessarily correspond to the actual ones.

[0047] Although the embodiments of the present disclosure have been described based on the drawings and examples, it should be noted that those skilled in the art could make various modifications or alterations based on the present disclosure. Therefore, it should be noted that these modifications or alterations are included in the scope of the present disclosure. For example, the functions included in each component can be rearranged so as not to cause logical inconsistencies, and multiple components can be combined or divided into one.

[0048] All of the features described in this disclosure and / or all steps of all of the disclosed methods or processes may be combined in any combination except combinations in which these features are mutually exclusive. Furthermore, each feature described in this disclosure may be replaced by an alternative feature serving the same, equivalent, or similar purpose, unless expressly denied. Thus, unless expressly denied, each disclosed feature is only one example of a generic series of identical or equivalent features.

[0049] Furthermore, embodiments of the present disclosure are not limited to the specific configurations of any of the above-described embodiments, but rather extend to any novel feature or combination thereof described in the present disclosure, or any novel method or process step or combination thereof described.

[0050] For example, in the above embodiment, the solid oxide fuel cell stack 10 may be glass-sealed to a fuel supply manifold, and hydrogen may be supplied to the cell stack from the fuel supply manifold. With this configuration, current flowing near the anode inlet is concentrated, and Joule heat causes a temperature rise near the anode inlet, which can prevent stress from being generated in the glass seal and the resulting cracks.

[0051] REFERENCE SIGNS LIST 10 Solid oxide fuel cell stack 11 Fuel cell module 12 Mixing section 13 Combustion section 14 Hydrogen supply port 15 Water supply port 16 Fuel off-gas outlet 17 Oxygen off-gas outlet 18 Exhaust pipe 19 Fuel supply port 20 Recirculation path 21 Flow rate adjustment valve

Claims

1. A solid oxide fuel cell stack in which hydrogen supplied from a hydrogen supply port is injected together with water supplied from a water supply port, and power is generated using the hydrogen as a primary fuel.

2. The solid oxide fuel cell stack according to claim 1, wherein the primary fuel and the water are supplied to the solid oxide fuel cell stack after being mixed.

3. The solid oxide fuel cell stack according to claim 2, wherein a mixing section for mixing the primary fuel and the water is disposed in the vicinity of the solid oxide fuel cell stack.

4. The solid oxide fuel cell stack according to claim 3, wherein a combustion section for burning unreacted primary fuel in the solid oxide fuel cell stack is disposed between the solid oxide fuel cell stack and the mixing section.

5. The solid oxide fuel cell stack according to claim 4, wherein the supply amount of water mixed from the water supply port is constant.

6. The solid oxide fuel cell stack according to any one of claims 1 to 5, wherein at least a part of the primary fuel and water discharged from the solid oxide fuel cell stack is re-supplied to the solid oxide fuel cell stack.

7. The solid oxide fuel cell stack according to claim 6, wherein a discharge pipe for discharging the primary fuel and water from the solid oxide fuel cell stack is provided with a recirculation path connected to a supply port of the primary fuel to the solid oxide fuel cell stack.

8. The solid oxide fuel cell stack according to claim 7, wherein the discharge pipe and the recirculation path are connected via a flow rate adjustment valve.

9. The solid oxide fuel cell stack according to claim 7 or 8, wherein the solid oxide fuel cell stack is of a flat plate type, and a discharge port for discharging the primary fuel and water from the solid oxide fuel cell stack and the supply port are provided on the same surface of the solid oxide fuel cell stack.

10. A fuel cell module comprising the solid oxide fuel cell stack according to any one of claims 1 to 9.

11. A fuel cell device comprising the fuel cell module according to claim 10 and auxiliary equipment for operating the fuel cell module.

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