Fuel battery apparatus

Abstract

This fuel battery apparatus has a fuel battery, a supply device, a combustion unit, a reformer, and a control device. The control device executes first control for reducing the amount of fuel gas supplied to the fuel battery when the temperature of the combustion unit is equal to or higher than a first temperature. The control device executes, in preference to the first control, second control for increasing the amount of fuel gas to be supplied to the fuel battery when the temperature of the fuel battery is lower than a second temperature or expected to drop to lower than or equal to the second temperature.

Description

fuel cell device CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to Japanese Patent Application No. 2023-108874, filed on June 30, 2023, the entire disclosure of which is incorporated herein by reference.

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

[0003] In solid oxide fuel cells, fuel gas is generated from raw fuel by steam reforming to be supplied to the fuel cell. The steam reforming reaction is an endothermic reaction, and the heat required for the reaction is supplied by combustion of off-gas discharged from the fuel cell and unreacted gas contained in the off-gas. In such solid oxide fuel cells, it has been proposed to adjust the amount of raw fuel supplied under specific conditions in order to suppress deterioration of the fuel cell (see Patent Document 1).

[0004] Patent No. 5597628

[0005] A fuel cell device according to a first aspect comprises: a fuel cell that generates electricity using fuel gas and air; a supply device that supplies fuel gas to the fuel cell; a combustion section that combusts unreacted fuel gas in the fuel cell; a reformer that is located in a first direction from the combustion section and contains a reforming catalyst that is heated by heat generated by combustion in the combustion section; and a control device that executes a first control to reduce the amount of fuel gas supplied to the fuel cell when the temperature of the combustion section is equal to or higher than a first temperature, and executes a second control, in priority to the first control, to increase the amount of fuel gas supplied to the fuel cell when the temperature of the fuel cell is lower than a second temperature or when the temperature of the fuel cell is expected to fall to or below the second temperature.

[0006] It is a configuration diagram showing a schematic configuration of a fuel cell device according to the present embodiment. It is a flowchart for explaining a heating process executed by the control device of Figure 1. It is a flowchart for explaining an overheating prevention process executed by the control device of Figure 1. It is a flowchart for explaining a heating process executed by the control device of Figure 1.

[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, a first supply device (supply device) 12, a combustion section 13, a reformer 14, and a control device 15. The fuel cell device 10 may further include a first temperature sensor 16, a second temperature sensor 17, a second supply device 18, and a third supply device 19.

[0009] The fuel cell 11 generates electricity through an electrochemical reaction using fuel gas and 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, for example, a hollow plate, a flat plate, a metal support, a cylinder, or the like. The fuel cell unit may be a solid oxide fuel cell unit. In the fuel cell 11, all of the fuel gas and oxygen gas in the air may not undergo an electrochemical reaction, and unreacted fuel gas and oxygen gas may be discharged.

[0010] The first supply device 12 directly or indirectly supplies fuel gas to the fuel cell 11. For example, the first supply device 12 supplies raw fuel to a reformer 14, thereby supplying fuel gas obtained by reforming the raw fuel as described below to the fuel cell 11. The first supply device 12 may directly or indirectly adjust the amount of fuel gas supplied to the fuel cell 11. The first supply device 12 may be, for example, a pump with a variable duty ratio.

[0011] The combustion unit 13 burns unreacted fuel gas in the fuel cell 11 using unreacted oxygen gas. The combustion unit 13 can heat the reformer 14 using the heat generated by burning the unreacted fuel gas. The combustion unit 13 may heat the reformer 14 to provide energy for causing a steam reforming reaction in the reformer 14.

[0012] The reformer 14 is located in a first direction from the combustion section 13. In the fuel cell device 10, the first direction is a direction that is assumed to be directed vertically upward when the fuel cell device 10 is installed. The reformer 14 contains a reforming catalyst. The reforming catalyst may generate fuel gas by steam reforming using raw fuel and steam. The reforming catalyst is heated by heat generated by combustion in the combustion section 13 to carry out the steam reforming reaction. For example, a Ru-based catalyst may be used as the reforming catalyst.

[0013] The raw fuel includes, for example, light hydrocarbons such as methane, ethane, propane, and butane. The raw fuel is, for example, city gas, LPG, biogas, or the like containing the light hydrocarbons. The water vapor may be supplied to the reformer 14 as liquid reforming water and vaporized into water vapor in a vaporization unit provided in the reformer 14. The fuel gas includes, for example, hydrogen gas.

[0014] The first temperature sensor 16 may detect the temperature of the combustion section 13. The second temperature sensor 17 may detect the temperature of the fuel cell 11. The first temperature sensor 16 and the second temperature sensor 17 are, for example, thermocouples.

[0015] The second supply device 18 may adjust the amount of water supplied to the water reformer 14. The second supply device 18 may be, for example, a pump with a variable duty ratio.

[0016] The third supply device 19 may adjust the amount of air supplied to the fuel cell 11. The third supply device 19 may be, for example, a blower with a variable duty ratio.

[0017] The control device 15 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 device 15 may control the operation of the fuel cell device 10.

[0018] After starting up the fuel cell device 10, the control device 15 may control each component of the fuel cell device 10, such as the voltage or current of the fuel cell 11, and the amount of supply from the first supply device 12, the second supply device 18, and the third supply device 19, so as to generate power of the current value of the required load. In the following description of the present application, the supply amount may mean the flow rate, i.e., the amount that flows per short period of time.

[0019] The control device 15 executes a first control, a second control, a third control, and a fourth control. In the first control, the control device 15 controls the first supply device 12 to reduce the amount of fuel gas supplied to the fuel cell 11. In the second control and the fourth control, the control device 15 controls the first supply device 12 to increase the amount of fuel gas supplied to the fuel cell 11. The control device 15 may execute a third control under conditions different from those of the second control and the fourth control, as described below, and in the third control, the control device 15 controls the first supply device 12 to increase the amount of fuel gas supplied to the fuel cell 11.

[0020] The control device 15 executes the first control when the temperature of the combustion unit 13 is equal to or higher than a first temperature. The first temperature is set to a temperature that can suppress deterioration of the reforming catalyst. The first temperature may be set depending on the type of reforming catalyst, and is, for example, 700 to 750°C for the above-mentioned Ru-based catalyst.

[0021] The control device 15 may execute the first control when the current of the power generated by the fuel cell 11 is equal to or less than a current threshold. The control device 15 may acquire the current of the power generated by the fuel cell 11 as information from a current sensor or an external device. The control device 15 may acquire the current from, for example, a current sensor built into the fuel cell device 10 or a current sensor provided external to the fuel cell device 10. The control device 15 may also acquire the current of the power generated by the fuel cell 11 from, for example, another information processing device.

[0022] The control device 15 executes the second control in preference to the first control when the temperature of the fuel cell 11 is lower than the second temperature or when it is expected that the temperature of the fuel cell 11 will drop to or below the second temperature. In other words, even if the temperature of the combustion unit 13 is higher than the first temperature, the control device 15 executes the second control without executing the first control when the temperature of the fuel cell 11 is lower than the second temperature or when it is expected that the temperature of the fuel cell 11 will drop to or below the second temperature. The second temperature may be determined, for example, based on the temperature of the fuel cell 11 when the fuel cell device 10 starts generating electricity.

[0023] The temperature of the fuel cell 11 may drop below the second temperature if the necessary fuel gas is not supplied to the fuel cell 11 due to, for example, an error in the gas flow meter or a gas leak caused by a crack in the fuel cell 11. Furthermore, if the necessary fuel gas is not supplied to the fuel cell 11, a misfire occurs and the temperature of the combustion section 13 drops. Therefore, if the temperature of the combustion section 13 detected by the first temperature sensor 16 continues to drop, it can be expected that the fuel cell 11 will drop below the second temperature.

[0024] The control device 15 may execute the third control when the temperature of the combustion unit 13 drops below the first temperature after the first control is executed. The control device 15 may increase the fuel gas so that the increase in the fuel gas in the third control is less than the decrease in the fuel gas in the first control executed immediately before the third control.

[0025] Furthermore, the control device 15 may increase the fuel gas so that the time for which the fuel gas is increased in the third control is shorter than the time for which the fuel gas was decreased in the first control executed immediately before the third control. When the time for which the fuel gas is increased in the third control is kept shorter than the time for which the fuel gas is decreased in the first control, the absolute value of the increase in the amount of fuel gas supply in the third control, in other words, the increase in the flow rate, may be the same as the absolute value of the decrease in the amount of fuel gas supply in the first control, in other words, the decrease in the flow rate.

[0026] Alternatively, the control device 15 may increase the fuel gas so that the time for which the fuel gas is increased in the third control is equal to or longer than the time for which the fuel gas was decreased in the first control executed immediately before the third control. When the control is performed so that the time for which the fuel gas is increased in the third control is equal to or longer than the time for which the fuel gas was decreased in the first control, the absolute value of the increase in the amount of fuel gas supply in the third control may be greater than the absolute value of the decrease in the amount of fuel gas supply in the first control.

[0027] Furthermore, the control device 15 may execute the fourth control with priority over the first control until a predetermined time has elapsed since the fuel cell 11 started generating electricity.

[0028] If the temperature of the fuel cell 11 becomes equal to or higher than the second temperature after the second control or the fourth control is performed, the control device 15 may return the increased amount of fuel gas supply to the original amount.

[0029] Next, the heating process executed by the control device 15 in this embodiment will be described with reference to the flowchart of Fig. 2. The heating process is started, for example, periodically while the fuel cell device 10 is in operation.

[0030] In step S100, the control device 15 determines whether the temperature of the fuel cell 11 is less than a second temperature. If it is less than the second temperature, the process proceeds to step S101. If it is not less than the second temperature, the heating process ends.

[0031] In step S101, the control device 15 determines whether the first control is being executed. If the first control is being executed, the process proceeds to step S102. If the first control is not being executed, the process proceeds to step S103.

[0032] In step S102, the control device 15 stops the first control. In other words, the control device 15 stops the reduction of the gas supply amount that is being executed in step S204 of the superheat suppression control described below, and returns the gas supply amount to the amount before the reduction. After the reduction, the process proceeds to step S103.

[0033] In step S103, the control device 15 stores the gas supply amount. After storing the amount, the process proceeds to step S104.

[0034] In step S104, the control device 15 increases the gas supply amount by a predetermined increment. After the increase, the process proceeds to step S105.

[0035] In step S105, the control device 15 waits for a predetermined waiting time. After the waiting time has elapsed, the process proceeds to step S106.

[0036] In step S106, the control device 15 determines whether the temperature of the fuel cell 11 is less than the second temperature. If it is less than the second temperature, the process returns to step S105. If it is not less than the second temperature, the process proceeds to step S107.

[0037] In step S107, the control device 15 returns the gas supply amount to the supply amount stored in step S103, and then the heating process is completed.

[0038] Next, the overheating prevention process executed by the control device 15 in this embodiment will be described with reference to the flowchart of Fig. 3. The overheating prevention process is started, for example, periodically while the fuel cell device 10 is in operation.

[0039] In step S200, the control device 15 determines whether the current of the fuel cell 11 is less than the current threshold. If it is not less than the current threshold, the overheat suppression process ends. If it is less than the current threshold, the process proceeds to step S202.

[0040] In step S201, the control device 15 determines whether the temperature of the combustion unit 13 is equal to or higher than a first temperature. If the temperature is equal to or higher than the first temperature, the process proceeds to step S202. If the temperature is not equal to or higher than the first temperature, the superheat suppression process ends.

[0041] In step S202, the control device 15 determines whether the second control is being executed. If the second control is not being executed, the process proceeds to step S203. If the second control is being executed, the overheating prevention process ends.

[0042] In step S203, the control device 15 stores the gas supply amount. After storing the amount, the process proceeds to step S204.

[0043] In step S204, the control device 15 reduces the gas supply amount by a predetermined amount. After the reduction, the process proceeds to step S205.

[0044] In step S205, the control device 15 waits for a predetermined waiting time. After the waiting time has elapsed, the process proceeds to step S206.

[0045] In step S206, the control device 15 determines whether the temperature of the combustion section 13 is equal to or higher than the first temperature. If the temperature is equal to or higher than the first temperature, the process returns to step S205. If the temperature is not equal to or higher than the first temperature, the process proceeds to step S207.

[0046] In step S207, the control device 15 detects the elapsed time since the gas supply rate was reduced in step S204. Furthermore, the control device 15 determines the heating time based on the calculated elapsed time. After the determination, the process proceeds to step S208.

[0047] In step S208, the control device 15 increases the gas supply amount from the gas supply amount stored in step S203 by an increase amount that is the same as the predetermined decrease amount by which the gas supply amount was decreased in step S204. After the increase, the process proceeds to step S209.

[0048] In step S209, the control device 15 waits until the heating time determined in step S207 has elapsed. After the heating time has elapsed, the process proceeds to step S210.

[0049] In step S210, the control device 15 returns the gas supply amount to the supply amount stored in step S203. After returning the gas supply amount to the supply amount, the superheat suppression process ends.

[0050] Next, the heating process executed by the control device 15 in this embodiment will be described with reference to the flowchart of Fig. 4. The heating process is started, for example, periodically while the fuel cell device 10 is in operation.

[0051] In step S300, the control device 15 determines whether a predetermined time has elapsed since the fuel cell 11 started generating electricity. If the predetermined time has not elapsed, the process proceeds to step S301. If the predetermined time has elapsed, the heating process ends.

[0052] In step S301, the control device 15 stores the gas supply amount. After storing the amount, the process proceeds to step S302.

[0053] In step S302, the control device 15 increases the gas supply amount by a predetermined increment. After the increase, the process proceeds to step S303.

[0054] In step S303, the control device 15 waits for a predetermined waiting time. After the waiting time has elapsed, the process proceeds to step S304.

[0055] In step S304, the control device 15 determines whether the temperature of the fuel cell 11 is less than the second temperature. If it is less than the second temperature, the process returns to step S303. If it is not less than the second temperature, the process proceeds to step S305.

[0056] In step S305, the control device 15 returns the gas supply amount to the supply amount stored in step S301. After returning the gas supply amount to the supply amount, the heating process ends.

[0057] The fuel cell device 10 of this embodiment configured as described above executes a first control that reduces the amount of fuel gas supplied to the fuel cell 11 when the temperature of the combustion unit 13 is equal to or higher than a first temperature, and executes a second control that increases the amount of fuel gas supplied to the fuel cell 11 when the temperature of the fuel cell 11 is lower than a second temperature or when the temperature of the fuel cell 11 is expected to drop to or below the second temperature, in priority over the first control. When the temperature of the combustion unit 13 becomes high, the reformer 14 overheats, which accelerates the deterioration of the reforming catalyst contained in the reformer 14 and increases the temperature of the fuel gas discharged from the reformer 14, thereby increasing the temperature difference between different parts of the fuel cell 11. Furthermore, in the fuel cell device 10, it is desirable to prioritize power generation amount and power generation efficiency over suppressing both the deterioration of the reforming catalyst and the increase in the temperature difference between the fuel cell 11. In view of such events and circumstances, the fuel cell device 10 having the above-described configuration can determine the situation in which it is desirable to improve the amount of power generated and the power generation efficiency of the fuel cell 11, and prioritize the execution of the second control, while, in situations where the second control is feasible, suppressing the deterioration of the reforming catalyst and the increase in the temperature difference in the fuel cell 11. Therefore, the fuel cell device 10 can suppress the deterioration of parts other than the fuel cell 11.

[0058] Furthermore, the fuel cell device 10 of this embodiment executes the first control when the current of the electric power generated by the fuel cell 11 is equal to or less than the current threshold. In other words, the fuel cell device 10 does not execute the first control when the current of the electric power generated by the fuel cell 11 is greater than the current threshold. Reducing the amount of fuel gas when the current is not equal to or less than the current threshold may result in a misfire. In such an event, the fuel cell device 10 having the above-described configuration can reduce the possibility of a misfire.

[0059] Furthermore, the fuel cell device 10 of this embodiment executes a third control to increase the amount of fuel gas supplied to the fuel cell 11 if the temperature of the combustion unit 13 drops below the first temperature after the first control is executed. An excessive drop in the temperature of the combustion unit 13 causes a temperature drop in the fuel cell 11. A temperature drop in the fuel cell 11 makes it difficult to respond to load fluctuations. In response to such an event, the fuel cell device 10 having the above-described configuration can bring the combustion unit 13 closer to an appropriate temperature in response to an excessive temperature drop in the combustion unit 13 caused by the execution of the first control. Therefore, the fuel cell device 10 makes it easier to respond to load fluctuations.

[0060] Furthermore, the fuel cell device 10 of this embodiment increases the fuel gas so that the increase in the fuel gas in the third control is less than the decrease in the fuel gas in the first control executed immediately before the third control. When the fuel gas is increased in the third control, the temperature of the combustion unit 13 may again exceed the first temperature, and thereafter, the temperature of the combustion unit 13 may repeatedly decrease and increase. In response to such an event, the fuel cell device 10 having the above-described configuration can reduce the possibility that the temperature of the combustion unit 13 will again exceed the first temperature. Therefore, the fuel cell device 10 contributes to stabilizing the temperature of the combustion unit 13.

[0061] Furthermore, the fuel cell device 20 of this embodiment increases the fuel gas so that the time for increasing the fuel gas in the third control is less than the time for decreasing the fuel gas in the first control executed immediately before the third control. With this configuration, the fuel cell device 10 can suppress the increase in the fuel gas in the third control to be less than the decrease in the fuel gas in the first control executed immediately before the third control, even in a simplified configuration, such as a configuration in which the absolute values ​​of the increase and decrease in the fuel gas supply amount (flow rate) are the same.

[0062] Furthermore, in the fuel cell device 10 of this embodiment, a fourth control, which increases the amount of fuel gas supplied to the fuel cell 11, is executed in priority over the first control until a predetermined time has elapsed since the start of power generation of the fuel cell 11. Immediately after the start of power generation, the ceramic portion of the fuel cell 11 has a low temperature, resulting in a high internal resistance, and the fuel cell 11 cannot output a large current. Therefore, by increasing the amount of fuel gas for a predetermined time after the start of power generation, rated power generation is achieved early. In this control, the temperature of the combustion section 13 may temporarily rise above the first temperature. However, in the fuel cell device 10, it is desirable to prioritize power generation amount and power generation efficiency over suppressing both deterioration of the reforming catalyst and an increase in the temperature difference of the fuel cell 11. In response to such events and demands, the fuel cell device 10 having the above-described configuration can execute the first control while prioritizing power generation amount and power generation efficiency.

[0063] 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.).

[0064] 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.

[0065] 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.

[0066] 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.

[0067] 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.

[0068] 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.

[0069] In this disclosure, descriptions such as "first" and "second" are identifiers for distinguishing the configuration. Configurations distinguished by descriptions such as "first" and "second" in this disclosure can have their numbers exchanged. For example, a first supply device can exchange the identifiers "first" and "second" with a second supply device. 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.

[0070] REFERENCE SIGNS LIST 10 fuel cell device 11 fuel cell 12 first supply device 13 combustion section 14 reformer 15 control device 16 first temperature sensor 17 second temperature sensor 18 second supply device 19 third supply device

Claims

1. A fuel cell device comprising: a fuel cell that generates electricity using fuel gas and air; a supply device that supplies fuel gas to the fuel cell; a combustion section that combusts unreacted fuel gas in the fuel cell; a reformer located in a first direction from the combustion section and containing a reforming catalyst that is heated by heat generated by combustion in the combustion section; and a control device that executes a first control to reduce the amount of fuel gas supplied to the fuel cell when the temperature of the combustion section is equal to or higher than a first temperature, and executes a second control in priority to the first control to increase the amount of fuel gas supplied to the fuel cell when the temperature of the fuel cell is lower than a second temperature or when the temperature of the fuel cell is expected to drop below the second temperature.

2. A fuel cell device according to claim 1, wherein the control device executes the first control when the current of the electric power generated by the fuel cell is equal to or lower than a current threshold.

3. A fuel cell device as claimed in claim 1 or 2, wherein the control device executes a third control to increase the amount of the fuel gas supplied to the fuel cell when the temperature of the combustion section falls below the first temperature after execution of the first control.

4. A fuel cell device as described in claim 3, wherein the control device increases the fuel gas so that the amount of increase in the fuel gas in the third control is less than the amount of decrease in the fuel gas in the first control executed immediately before the third control.

5. A fuel cell device as described in claim 4, wherein the control device increases the fuel gas so that the time for which the fuel gas is increased in the third control is less than the time for which the fuel gas was decreased in the first control executed immediately before the third control.

6. A fuel cell device as described in claim 1, wherein the control device executes a fourth control, which increases the amount of fuel gas supplied to the fuel cell, in priority over the first control for a predetermined time after the fuel cell starts generating electricity.