Fuel cell device

Abstract

This fuel cell device has a fuel cell and a current adjustment unit. The fuel cell generates power by using fuel gas that is based on methane concentration-variable fuel. The current adjustment unit adjusts a current value generated by the fuel cell so as to maintain the current value at a first current value when a required load is a prescribed value or greater after the start of power generation by the fuel cell.

Description

fuel cell device CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to Japanese Patent Application No. 2024-013545, filed on January 31, 2024, the entire disclosure of which is incorporated herein by reference.

[0002] The present disclosure relates to fuel cell devices.

[0003] A fuel cell system, which combines a fuel cell such as a solid oxide fuel cell with a reformer, is supplied with raw fuel and water to generate fuel gas to be supplied to the fuel cell. Fuel cell systems are generally designed to perform operational control that balances stable operation, power generation efficiency, and other factors. The operating conditions that optimize operational stability and power generation efficiency vary depending on the calorific value of the raw fuel. Therefore, it has been proposed to change the supply amounts of raw fuel and water depending on the calorific value of the raw fuel.

[0004] Japanese Patent Application Laid-Open No. 2019-067617

[0005] A fuel cell device according to a first aspect includes: a fuel cell that generates electricity using fuel gas based on a methane concentration varying fuel; and a current adjustment unit that adjusts a current value generated by the fuel cell to maintain it at a first current value when a required load is equal to or greater than a predetermined value after the fuel cell starts generating electricity.

[0006] The fuel cell device according to the present invention is configured to operate in a manner that allows the current to be adjusted by the control unit in the fuel cell device.

[0007] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. In the following drawings, the same components are denoted by the same reference numerals.

[0008] 1 , a fuel cell device 10 according to an embodiment of the present disclosure includes a fuel cell 11 and a current adjusting unit 12. The fuel cell device 10 may further include a combustion unit 13, a reformer 14, a first supply unit 15, a second supply unit 16, a first detection unit 17, and a control unit 18.

[0009] The fuel cell 11 generates power through an electrochemical reaction using fuel gas and air. Specifically, the fuel cell 11 performs an electrochemical reaction using oxygen gas in the air. The fuel cell 11 may include a fuel cell unit. The fuel cell 11 may include a plurality of fuel cell units. The plurality of fuel cell units may form a cell stack. The cell stack may have any shape, such as a hollow plate, a flat plate, a metal support, or a cylinder. The fuel cell unit may be a solid oxide fuel cell unit. In the fuel cell 11, not all of the fuel gas and oxygen gas in the air may undergo an electrochemical reaction, and unreacted fuel gas and oxygen gas may be discharged. The discharged unreacted fuel gas may include methane that was not reformed in the reformer 14 described below.

[0010] The current adjustment unit 12 adjusts the current value of the power generated by the fuel cell 11. The current adjustment unit 12 may adjust the current value based on the required load of the fuel cell device 10. The required load is the power value requested of the fuel cell device 10 by a customer facility using the fuel cell device 10. If the required load is equal to or greater than a predetermined value after the fuel cell 11 starts generating power, the current adjustment unit 12 adjusts the power value to maintain it at a first current value. In this application, the start of power generation by the fuel cell 11 refers to the start of power supply from the fuel cell device 10 to the customer facility via the current adjustment unit 12, and does not include the start of the fuel cell 11 being started. When starting to maintain the first current value, the current adjustment unit 12 may notify the control unit 18 of the start of maintaining the first current value. The current adjustment unit 12 is, for example, a power conditioner.

[0011] The combustion unit 13 may combust unreacted fuel gas in the fuel cell 11 using unreacted oxygen gas. The combustion unit 13 may heat the fuel cell 11 and the reformer 14 using heat generated by burning the unreacted fuel gas. The combustion unit 13 may stabilize the temperature of the fuel cell 11 by heating the fuel cell 11. The combustion unit 13 may provide energy for a steam reforming reaction in the reformer 14 by heating the reformer 14. The combustion unit 13 may be located in the opposite direction from the reformer 14 in the first direction to effectively heat the reformer 14. In the fuel cell device 10, the first direction is a direction in which the fuel cell device 10 is expected to be oriented vertically upward when installed. The combustion unit 13 may be, for example, a space in the first direction from the fuel cell 11. Unreacted fuel gas and unreacted oxygen gas injected from an outlet of the fuel cell 11 may be combusted in this space. Alternatively, the combustion unit 13 may be, for example, a burner located in a first direction from the fuel cell 11 .

[0012] The reformer 14 may generate fuel gas by steam reforming the methane concentration-varying fuel and water. Specifically, the reformer 14 may contain a reforming catalyst. The reforming catalyst may generate fuel gas from the methane concentration-varying fuel and water. In other words, in the fuel cell device 10, the fuel gas is based on the methane concentration-varying fuel. Steam may be supplied to the reformer 14 as liquid reforming water and vaporized into steam in a vaporization unit provided in the reformer 14. The fuel gas may include, for example, hydrogen gas.

[0013] The variable methane concentration fuel may be, for example, biogas, which may be produced by fermentation of organic fertilizer, biodegradable materials, sludge, wastewater, etc. The variable methane concentration fuel mainly contains methane and carbon dioxide. The variable methane concentration fuel may have a variable methane concentration.

[0014] The first supply unit 15 may supply the variable methane concentration fuel to the fuel cell 11. The supply of the variable methane concentration fuel from the first supply unit 15 to the fuel cell 11 may be direct, or may be indirect via the reformer 14. The first supply unit 15 may adjust the amount of the variable methane concentration fuel supplied to the reformer 14. The first supply unit 15 may be, for example, a pump whose duty ratio is changeable.

[0015] The second supply unit 16 may supply water to the reformer 14. The second supply unit 16 may adjust the amount of water supplied to the reformer 14. The second supply unit 16 may be, for example, a pump whose duty ratio is variable.

[0016] The first detector 17 may detect the supply amount of the variable methane concentration fuel supplied to the fuel cell 11. The first detector 17 is, for example, a mass flow meter or a volume flow meter.

[0017] The control unit 18 is configured to include at least one processor, at least one dedicated circuit, or a combination of these. The processor is a general-purpose processor such as a CPU (Central Processing Unit) or a GPU (Graphics Processing Unit), or a dedicated processor specialized for specific processing. The dedicated circuit may be, for example, an FPGA (Field-Programmable Gate Array), an ASIC (Application Specific Integrated Circuit), or the like. The control unit 18 may control the operation of the fuel cell device 10.

[0018] The control unit 18 may further include a storage unit. The storage unit may include any storage device, such as a RAM (Random Access Memory) or a ROM (Read Only Memory). The storage unit may store various programs that cause the control unit 18 to function and various information used by the control unit 18.

[0019] The control unit 18 may start the fuel cell device 10 through a predetermined process after starting up the fuel cell device 10. After starting up is complete, the control unit 18 may notify the current adjustment unit 12 of the start of power generation.

[0020] The control unit 18 may control the first supply unit 15 to maintain the temperature of the combustion unit 13 within a specific temperature range while the power generated by the fuel cell 11 is adjusted to be maintained at the first current value. The specific temperature range may be a temperature determined according to the first current value. In the fuel cell 11, an appropriate temperature for heating the reformer 14 is designed according to the current value. The specific temperature range is a temperature range having a certain width centered on the appropriate temperature designed for the first current value. The certain width is, for example, 600 to 700°C.

[0021] The control unit 18 may control the second supply unit 16 to adjust the amount of water supplied to the reformer 14 in accordance with the amount of supply of the variable methane concentration fuel detected by the first detection unit 17. Specifically, the control unit 18 may increase the amount of water supplied to the reformer 14 as the amount of supply of the variable methane concentration fuel detected by the first detection unit 17 increases.

[0022] The control unit 18 may adjust the amount of water supplied to the reformer 14 so as to vary the first ratio. The first ratio is the ratio of the amount of substance of water supplied to the reformer 14 to the amount of substance of carbon in the methane contained in the methane concentration varying fuel. Alternatively, the control unit 18 may adjust the amount of water supplied to the reformer 14 so as to maintain the second ratio constant. The second ratio is the ratio of the amount of substance of water supplied to the reformer 14 to the amount of substance of carbon contained in the methane concentration varying fuel. A value for the second ratio that improves power generation efficiency while suppressing carbon deposition in the fuel cell 11 and the reformer 14 may be calculated in advance and stored as information in the memory unit.

[0023] The control unit 18 may estimate the methane concentration contained in the variable methane concentration fuel based on the supply amount of the variable methane concentration fuel detected by the first detection unit 17. To estimate the methane concentration, the control unit 18 may first estimate the consumption amount of fuel gas in the fuel cell 11 and the consumption amount of unreacted fuel gas combusted in the combustion unit 13.

[0024] The control unit 18 may calculate the consumption amount of fuel gas (methane) consumed in the fuel cell 11 based on the current value of the fuel cell 11 obtained as information from the current adjustment unit 12. There is a correspondence relationship between the current value of the fuel cell 11 and the consumption amount of fuel gas, and this correspondence relationship may be calculated in advance and stored in the memory unit. The control unit 18 may calculate the consumption amount of fuel gas by reading out the consumption amount corresponding to the current value obtained from the current adjustment unit 12.

[0025] The control unit 18 may calculate the consumption amount of unreacted fuel gas combusted in the combustion unit 13 based on the temperature of the combustion unit 13. There is a correspondence relationship between the temperature of the combustion unit 13 and the consumption amount of unreacted fuel gas, and this correspondence relationship may be calculated in advance and stored in the memory unit. The control unit 18 may calculate the consumption amount of unreacted fuel gas by reading out the consumption amount corresponding to the temperature obtained from a temperature sensor provided in the combustion unit 13.

[0026] Next, the control unit 18 may calculate the methane content in the variable methane concentration fuel by summing the amount of fuel gas consumed in the fuel cell 11 and the amount of unreacted fuel gas burned in the combustion unit 13. Furthermore, the control unit 18 may estimate the methane concentration contained in the variable methane concentration fuel by dividing the calculated methane content by the supply amount of variable methane concentration fuel detected by the first detection unit 17. The control unit 18 may determine the total supply amount of variable methane concentration fuel to be supplied from the estimated methane concentration.

[0027] Next, the first start process executed by the current adjusting unit 12 in this embodiment will be described with reference to the flowchart of Fig. 2. The first start process is started, for example, periodically after the fuel cell device 10 starts to start up.

[0028] In step S100, the current adjustment unit 12 determines whether the fuel cell 11 has already started power generation. The current adjustment unit 12 may determine whether power generation has already started based on a notification from the control unit 18 that power generation has started. If power generation has already started, the process proceeds to step S101. If power generation has not started, the first start process ends.

[0029] In step S101, the current adjusting unit 12 determines whether the requested load acquired as information from the customer facility is equal to or greater than a predetermined value. If the requested load is equal to or greater than the predetermined value, the process proceeds to step S102. If the requested load is not equal to or greater than the predetermined value, the first start process ends.

[0030] In step S102, the current adjusting unit 12 starts adjusting the current value of the fuel cell 11 to the first current value. After the adjustment starts, the first start process ends.

[0031] Next, the second start process executed by the control unit 18 in this embodiment will be described with reference to the flowchart in Fig. 3. The second start process is started, for example, when a notification of the start of maintaining the first current value is received from the current adjustment unit 12.

[0032] In step S200, the control unit 18 starts maintaining the temperature of the combustion unit 13 within a specific temperature range. Specifically, the control unit 18 adjusts the supply amount of variable methane concentration fuel so as to maintain the temperature of the combustion unit 13 within the specific temperature range. After starting the maintenance, the process proceeds to step S201.

[0033] In step S201, the control unit 18 starts maintaining the second ratio constant. Specifically, the control unit 18 may calculate the amount of water to be supplied based on the supply amount of variable methane concentration fuel adjusted in step S200 and the second ratio. The control unit 18 controls the second supply unit 16 to supply water in the calculated amount. After the maintenance starts, the second start process ends.

[0034] The fuel cell device 10 of this embodiment, configured as described above, includes a fuel cell 11 that generates electricity using fuel gas based on a methane concentration-varying fuel, and a current adjustment unit 12 that adjusts the current value generated by the fuel cell 11 to maintain a first current value when the required load is equal to or greater than a predetermined value after the fuel cell 11 starts generating electricity. In the fuel cell device 10, the methane in the methane concentration-varying fuel, which is the basis of the fuel gas, is used for power generation in the fuel cell 11 and combustion in the combustion unit 13. Appropriate amounts of methane used for power generation in the fuel cell 11 and combustion in the combustion unit 13 can be estimated based on a balance between stable operation and improved power generation efficiency. However, in a configuration using a methane concentration-varying fuel, it is difficult to grasp the amount of methane, making stable operation difficult. In response to such an event, the fuel cell device 10 configured as described above fixes the current value of the fuel cell 11, which is normally the target of control, to a first current value, thereby substantially stabilizing the amount of fuel gas consumed by the fuel cell 11. Therefore, the fuel cell device 10 can stabilize its operation.

[0035] The fuel cell device 10 further comprises a combustion unit 13 that combusts unreacted fuel gas in the fuel cell 11, a first supply unit 15 that supplies variable methane concentration fuel to the fuel cell 11, and a control unit 18 that controls the first supply unit 15 to maintain the temperature of the combustion unit 13 within a specific temperature range determined in accordance with the first current value. As described above, the amount of fuel gas consumed in the fuel cell 11 is substantially constant, and therefore the fuel cell device 10 can adjust the amount of variable methane concentration fuel supplied in accordance with the temperature of the combustion unit 13, for example, by feedback, and can therefore be operated simply and efficiently.

[0036] The fuel cell device 10 also includes a first detection unit 17 that detects the supply amount of variable methane concentration fuel supplied to the fuel cell 11, a reformer 14 that produces fuel gas by steam reforming the variable methane concentration fuel, and a second supply unit 16 that supplies water to the reformer 14, and a control unit 18 controls the second supply unit 16 to adjust the amount of water supplied to the reformer 14 in accordance with the supply amount detected by the first detection unit 17. With this configuration, the fuel cell device 10 can perform control to suppress carbon deposition in the fuel cell 11 and the reformer 14.

[0037] Furthermore, in the fuel cell device 10, the control unit 18 increases the amount of water supplied to the reformer 14 as the supply amount detected by the first detection unit 17 increases. With this configuration, the fuel cell device 10 can suppress carbon deposition in the fuel cell 11 and the reformer 14.

[0038] Furthermore, in the fuel cell device 10, the control unit 18 maintains a constant second ratio, which is the ratio of water supplied to the reformer 14 to carbon contained in the variable methane concentration fuel. With this configuration, the fuel cell device 10 can easily improve power generation efficiency while suppressing carbon deposition in the fuel cell 11 and the reformer 14.

[0039] Furthermore, in the fuel cell device 10, the control unit 18 estimates the methane concentration contained in the variable methane concentration fuel based on the supply amount detected by the first detection unit 17. With this configuration, the fuel cell device 10 can obtain information that can contribute to improving the operation of the fuel cell device 10 itself and the operation of the production equipment for variable methane concentration fuel.

[0040] The above has described an embodiment of the fuel cell device 10, but embodiments of the present disclosure can also be embodied as a method or program for implementing the device, as well as a storage medium on which a program is recorded (for example, an optical disk, a magneto-optical disk, a CD-ROM, a CD-R, a CD-RW, a magnetic tape, a hard disk, or a memory card, etc.).

[0041] Furthermore, the implementation form of the program is not limited to application programs such as object code compiled by a compiler or program code executed by an interpreter, but may also be in the form of a program module incorporated into an operating system. Furthermore, the program may or may not be configured so that all processing is performed solely by the CPU on the control board. The program may also be configured so that part or all of it is executed by another processing unit mounted on an expansion board or expansion unit added to the board as needed.

[0042] 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.

[0043] 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.

[0044] All of the features described in this disclosure and / or all steps of all 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.

[0045] 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 herein, or any novel method or process step or combination thereof described herein.

[0046] In this disclosure, descriptions such as "first" and "second" are identifiers for distinguishing the configuration. In this disclosure, configurations distinguished by descriptions such as "first" and "second" can have their numbers exchanged. For example, a first supply unit can exchange the identifiers "first" and "second" with a second supply unit. The exchange of identifiers is performed simultaneously. The configurations remain distinguished even after the identifier exchange. Identifiers may be deleted. A configuration from which an identifier has been deleted is distinguished by a symbol. The descriptions of identifiers such as "first" and "second" in this disclosure should not be used solely to interpret the order of the configurations or to justify the existence of an identifier with a smaller number.

[0047] REFERENCE SIGNS LIST 10 fuel cell device 11 fuel cell 12 current adjustment section 13 combustion section 14 reformer 15 first supply section 16 second supply section 17 first detection section 18 control section

Claims

1. A fuel cell device comprising: a fuel cell that generates electricity using fuel gas based on a variable methane concentration fuel; and a current adjustment unit that adjusts the current value generated by the fuel cell to maintain it at a first current value when the required load is equal to or greater than a predetermined value after the fuel cell starts generating electricity.

2. A fuel cell device according to claim 1, further comprising: a combustion section that combusts the unreacted fuel gas in the fuel cell; a first supply section that supplies the methane concentration varying fuel to the fuel cell; and a control section that controls the first supply section so as to maintain the temperature of the combustion section within a specific temperature range determined according to the first current value.

3. A fuel cell device according to claim 2, comprising: a first detection unit that detects the supply amount of the methane concentration varying fuel supplied to the fuel cell; a reformer that generates the fuel gas by steam reforming the methane concentration varying fuel; and a second supply unit that supplies water to the reformer, wherein the control unit controls the second supply unit to adjust the amount of water supplied to the reformer in accordance with the supply amount detected by the first detection unit.

4. A fuel cell device according to claim 3, wherein the control unit increases the amount of water supplied to the reformer as the supply amount detected by the first detection unit increases.

5. A fuel cell device according to claim 3, wherein the control unit varies a first ratio, which is the ratio of water supplied to the reformer to carbon in methane contained in the methane concentration varying fuel.

6. A fuel cell device according to claim 3, wherein the control unit maintains a second ratio, which is the ratio of water supplied to the reformer to carbon contained in the methane concentration varying fuel, constant.

7. A fuel cell device according to claim 3, wherein the control unit estimates the methane concentration contained in the variable methane concentration fuel based on the supply amount detected by the first detection unit.

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