Fuel cell system

Abstract

A fuel cell system (200) of the present disclosure is provided with a fuel cell (100), a fuel gas path (1), a gas opening / closing portion (2), a recirculation path (3), a first discharge path (4), a first discharge portion (5), a second discharge path (6), a second discharge portion (7), and a control portion (8). A state in which the gas opening / closing portion (2) is in a first closed state, the first discharge portion (5) is in a second closed state, and the second discharge portion (7) is in a third closed state is an initial state. In a case where a water discharge operation of discharging condensed water in the fuel gas path (1), the fuel cell (100), and the recirculation path (3) is performed during power generation stop of the fuel cell (100), the control portion (8) switches the gas opening / closing portion (2) from the first closed state to a first flow-through state and the first discharge portion (5) from the second closed state to a second flow-through state from the initial state.

Description

Technical Field

[0001] This disclosure relates to a fuel cell system. Background Technology

[0002] Patent Document 1 discloses a residual water discharge device for a fuel cell, which includes: a reactant gas supply unit that supplies reactant gas to the fuel cell via a gas flow path; and a gas pressure control unit that, when the fuel cell stops operating, increases the gas pressure of the reactant gas supplied from the reactant gas supply unit and then supplies the pressurized reactant gas to the gas flow path, thereby discharging residual water in the gas flow path to the outside.

[0003] Existing technical documents

[0004] Patent documents

[0005] Patent Document 1: Japanese Patent Application Publication No. 2002-305017 Summary of the Invention

[0006] This disclosure provides a technique for discharging condensate while suppressing fuel cell degradation and the outflow of combustible gases from the system during periods when the fuel cell system is not in operation.

[0007] The fuel cell system disclosed herein comprises: a fuel cell that uses hydrogen-containing gas to generate electricity; a fuel gas path connected to the fuel cell for allowing hydrogen-containing gas to flow through; a gas opening and closing section disposed in the fuel gas path for switching between a first flow state allowing hydrogen-containing gas to flow through the fuel gas path and a first closed state closing the hydrogen-containing gas in the fuel gas path; and a recirculation path connected to the fuel gas path at a position between the gas opening and closing section and the fuel cell for allowing hydrogen-containing gas not used in the power generation of the fuel cell to flow back to the fuel gas path.

[0008] In addition, the fuel cell system includes: a first discharge path connected to a recirculation path for discharging condensate generated by water vapor contained in hydrogen-containing gas to the outside; a first discharge unit disposed in the first discharge path for switching between a second flow state in which hydrogen-containing gas flows through the first discharge path and a second closed state in which hydrogen-containing gas is blocked in the first discharge path; a second discharge path disposed in the recirculation path for discharging hydrogen-containing gas flowing through the fuel gas path to the outside; a second discharge unit disposed in the second discharge path for switching between a third flow state in which hydrogen-containing gas flows through the second discharge path and a third closed state in which hydrogen-containing gas is blocked in the second discharge path; and a control unit for operating the gas opening / closing unit, the first discharge unit, and the second discharge unit.

[0009] The initial state is characterized by the gas opening / closing section being in a first closed state, the first discharge section being in a second closed state, and the second discharge section being in a third closed state. When a drainage operation is performed to discharge condensate from the fuel gas path, the fuel cell, and the recirculation path during a period when the fuel cell's power generation is stopped, the control unit switches the gas opening / closing section from the first closed state to a first flow state and the first discharge section from the second closed state to a second flow state, starting from the initial state.

[0010] According to the fuel cell system of this disclosure, condensate can be discharged while suppressing fuel cell degradation and leakage of flammable gases outside the fuel cell system during periods of system shutdown. Therefore, the decrease in the durability of the fuel cell system can be suppressed. Furthermore, situations where unsafe conditions arise due to the leakage of flammable gases outside the fuel cell system can be prevented. Attached Figure Description

[0011] Figure 1 This is a structural diagram of the fuel cell system according to Embodiment 1 of this disclosure.

[0012] Figure 2 This is a flowchart relating to the pressure detection-based drainage operation in Embodiment 1 of this disclosure.

[0013] Figure 3 It is shown Figure 2 A graph showing the pressure changes during the drainage process.

[0014] Figure 4 This is a flowchart relating to time-elapsed control in Embodiment 1 of this disclosure.

[0015] Figure 5 This is a flowchart related to the drainage operation based on water level detection in Embodiment 1 of this disclosure.

[0016] Figure 6 It is shown Figure 5 A diagram showing the water level changes during the drainage process.

[0017] Figure 7 This is a flowchart related to the pressure detection-based drainage operation of Embodiment 1.

[0018] Figure 8 It is shown Figure 7 The graph shows the pressure change over time during the drainage process. Detailed Implementation

[0019] The embodiments will now be described in detail with reference to the accompanying drawings. However, sometimes unnecessary detailed descriptions are omitted. For example, detailed descriptions of well-known matters or repeated descriptions of substantially the same structures are sometimes omitted.

[0020] Furthermore, the accompanying drawings and the following description are provided to enable those skilled in the art to fully understand this disclosure and are not intended to limit the scope of the claims.

[0021] (Implementation Method 1)

[0022] [1-1. Structure]

[0023] Figure 1 This is a structural diagram of the fuel cell system in Embodiment 1 of this disclosure.

[0024] exist Figure 1 In the fuel cell system 200, there are a fuel cell 100, a fuel gas path 1, a gas opening and closing unit 2, a recirculation path 3, a first discharge path 4, a first discharge unit 5, a second discharge path 6, a second discharge unit 7, a control unit 8, a gas circulation device 9, a pressure detection unit 10, a tank 11, a water level detection unit 12, and an operation unit 20.

[0025] Fuel cell 100 is a fuel cell that uses hydrogen-containing gas to generate electricity. Specifically, fuel cell 100 uses hydrogen contained in hydrogen-containing gas supplied from the outside to generate electricity through a chemical reaction. Furthermore, in the chemical reaction of fuel cell 100, not all the hydrogen-containing gas supplied to fuel cell 100 is used; rather, a portion of the hydrogen-containing gas that is not used in fuel cell 100 is discharged from fuel cell 100.

[0026] The fuel cell 100 in this embodiment is, for example, a solid polymer fuel cell. However, the fuel cell 100 is not limited to the above; for example, it may also be a solid oxide fuel cell.

[0027] Fuel gas path 1 is a path connected to fuel cell 100 and used for the flow of hydrogen-containing gas. Hydrogen-containing gas is supplied to fuel cell 100, for example, from a hydrogen storage tank via fuel gas path 1.

[0028] The gas opening / closing unit 2 is a valve installed in the fuel gas path 1. The gas opening / closing unit 2 switches between a flow state allowing hydrogen-containing gas to flow through the fuel gas path 1 and a closed state that blocks the hydrogen-containing gas from entering the fuel gas path 1. In this embodiment, the gas opening / closing unit 2 is, for example, a solenoid valve.

[0029] Recirculation path 3 is a path connecting the gas opening / closing section 2 and the fuel cell 100, used to allow a portion of the hydrogen-containing gas that is not used in the chemical reaction during the power generation of the fuel cell 100 to flow to fuel gas path 1.

[0030] The first discharge path 4 is connected to the recirculation path 3 and is used to discharge condensate generated by water vapor contained in the hydrogen-containing gas flowing in the recirculation path 3 to the outside.

[0031] The first discharge section 5 is a valve installed on the first discharge path 4. The first discharge section 5 switches between a flow state that allows hydrogen-containing gas to circulate in the first discharge path 4 and a closed state that blocks the hydrogen-containing gas in the first discharge path 4. In this embodiment, the first discharge section 5 is, for example, a solenoid valve.

[0032] The second discharge path 6 is connected to the recirculation path 3 and is used to discharge the hydrogen-containing gas flowing in the recirculation path 3 to the outside.

[0033] Here, during power generation by the fuel cell 100, hydrogen is used in the fuel cell 100. Therefore, the hydrogen concentration of the hydrogen-containing gas flowing in the recirculation path 3 becomes relatively low compared to the hydrogen concentration of the hydrogen-containing gas supplied to the fuel cell 100. The hydrogen-containing gas supplied to the fuel cell 100 mixes with the hydrogen-containing gas flowing in the recirculation path 3, which has a relatively lower hydrogen concentration. Therefore, the hydrogen concentration of the hydrogen-containing gas supplied to the fuel cell 100 gradually decreases as the fuel cell 100 generates electricity.

[0034] The hydrogen-containing gas with reduced hydrogen concentration is discharged through the second discharge path 6 at fixed intervals, thereby suppressing the decrease in the output of the fuel cell 100. Furthermore, the fixed interval is, for example, every 3 minutes.

[0035] The second discharge section 7 is a valve provided on the second discharge path 6. The second discharge section 7 switches between a flow state that allows hydrogen-containing gas to circulate in the second discharge path 6 and a closed state that blocks the hydrogen-containing gas in the second discharge path 6. In this embodiment, the second discharge section 7 is, for example, a solenoid valve.

[0036] The control unit 8 activates the gas opening / closing unit 2, the first discharge unit 5, and the second discharge unit 7. In this embodiment, the control unit 8 is, for example, composed of a DSP (Digital Signal Processor) including an A / D conversion circuit, an input / output circuit, an arithmetic circuit, and a storage device.

[0037] The gas recirculation device 9 is a pump located between the fuel cell 100 and the first discharge path 4, used to circulate hydrogen-containing gas from the recirculation path 3 to the fuel gas path 1. In this embodiment, the gas recirculation device 9 is, for example, a diaphragm pump.

[0038] The pressure detection unit 10 is a pressure gauge installed between the gas opening / closing unit 2 and the fuel cell 100, used to measure the pressure of the hydrogen-containing gas flowing in the fuel gas path 1. In this embodiment, the pressure detection unit 10 is, for example, a pulse output pressure sensor.

[0039] Tank 11 is a tank provided in the recirculation path 3 for storing condensate produced by water vapor contained in the hydrogen-containing gas flowing in the recirculation path 3. Alternatively, in this embodiment, tank 11 may be omitted, and the condensate may be stored in the first discharge path 4 instead.

[0040] The water level detection unit 12 is a sensor installed inside the tank 11 and used to detect the water level of the condensate stored in the tank 11. In this embodiment, the water level detection unit 12 is, for example, a float switch. Furthermore, if the fuel cell system 200 does not have a tank 11, the water level detection unit 12 may also be installed in the first discharge path 4. In this case, the water level detection unit 12 may also be configured to detect the water level of the condensate stored in the first discharge path 4.

[0041] The operation unit 20 receives user instructions. Instructions received by the operation unit 20 from the user are sent to the control unit 8. In this embodiment, the operation unit 20 is, for example, a PC application program.

[0042] [1-2. Actions]

[0043] Below, refer to Figures 2-8 The operation of the fuel cell 100 configured as described above will now be explained. Furthermore, when the same process is shown in different figures, the same reference numerals may be used for explanation or the explanation may be omitted.

[0044] Furthermore, during the period when the fuel cell 100 stops operating, the gas opening / closing section 2 is in a closed state, the first discharge section 5 is in a closed state, and the second discharge section 7 is in a closed state. In this embodiment 1, the above-mentioned states during the period when the fuel cell 100 stops operating are defined as the initial state.

[0045] Figure 2 This is a flowchart illustrating the pressure detection-based drainage operation of Embodiment 1. Figure 3 This is a graph showing the pressure change over time during the drainage operation based on pressure detection in Embodiment 1.

[0046] First, in step S01, the control unit 8 switches the gas opening / closing unit 2 from a closed state to a flowing state, causing the process to proceed to step S02. At this time, as... Figure 3As shown, the pressure in fuel gas path 1 gradually increases from an initial pressure value, P1. Furthermore, the initial pressure value P1 is, for example, 1 kPa. Additionally, the control unit 8 can also perform step S01 if the user operates the operation unit 20 and sends an instruction to the control unit 8 to begin the drainage operation.

[0047] Next, in step S02, the control unit 8 determines whether the pressure of the fuel gas path 1, i.e. the pressure value P measured by the pressure detection unit 10, exceeds the threshold P2.

[0048] If the pressure value P of fuel gas path 1 exceeds the threshold P2 (step S02: "Yes"), the control unit 8 moves the process to step S03. On the other hand, if the pressure value P of fuel gas path 1 is below the threshold P2 (step S02: "No"), the control unit 8 moves the process to step S02 and repeats the process until the pressure value P of fuel gas path 1 exceeds the threshold P2.

[0049] Next, in step S03, the control unit 8 switches the first discharge unit 5 from a closed state to a flowing state, so that the processing moves to step S04.

[0050] Through the control of step S03, the gas opening / closing section 2 becomes open, the first discharge section 5 becomes open, and the second discharge section 7 becomes closed. Therefore, the first discharge path 4 becomes open to the atmosphere. At this time, since the pressure within the first discharge path 4 is higher than atmospheric pressure, condensate generated in the fuel gas path 1, the fuel cell 100, and the recirculation path 3 begins to be discharged through the first discharge path 4. At this time, the pressure in the fuel gas path 1 remains close to the value of P2. In this disclosure, the action of discharging condensate from the fuel gas path 1, the fuel cell 100, and the recirculation path 3 is defined as a drainage action. Furthermore, the threshold pressure P2 is, for example, 3 kPa. The value of P2 is determined based on the power generation of the fuel cell 100 and the length of the first discharge path 4.

[0051] Next, in step S04, the control unit 8 switches the gas opening / closing section 2 from the flowing state to the closed state and switches the first discharge section 5 from the flowing state to the closed state. That is, the control unit 8 restores the gas opening / closing section 2 and the first discharge section 5 to their initial states. Thus, the drainage operation is completed. At this time, as... Figure 3 As shown, the pressure in fuel gas path 1 gradually decreases from P2 towards P3. Furthermore, the pressure value P3 is, for example, 2 kPa. Additionally, the control unit 8 can also perform step 04 if the user operates the operation unit 20 and sends an instruction to the control unit 8 to stop the drainage operation.

[0052] Figure 4This is a flowchart related to the time-based control in Embodiment 1.

[0053] First, in step S05, the control unit 8 switches the gas opening / closing unit 2 from a closed state to a flowing state and switches the first discharge unit 5 from a closed state to a flowing state, thus moving the processing to step S06. As a result, the drainage operation begins.

[0054] Next, in step S06, the control unit 8 determines whether the elapsed time t from the start of the drainage operation has exceeded a predetermined time t1. Furthermore, the predetermined time t1 is a shorter time than the time required until almost all the condensate stored in the first discharge path 4 or tank 11 is discharged to the outside of the fuel cell system 200. The predetermined time t1 is, for example, 3 minutes. Moreover, the predetermined time t1 is determined based on factors such as the pressure within the fuel gas path 1 and the length of the first discharge path 4.

[0055] If the elapsed time t exceeds the predetermined time t1 (step S06: "Yes"), that is, if the drainage operation for the predetermined period has been performed, the control unit 8 moves the process to step S04. On the other hand, if the elapsed time t is less than or equal to the predetermined time t1 (step S06: "No"), the control unit 8 moves the process to step S06 and repeats the process until the elapsed time t exceeds the predetermined time t1.

[0056] Figure 5 This is a flowchart related to the drainage operation based on water level detection in Embodiment 1. Figure 6 It is shown Figure 5 The graph shows the change in the water level of the condensate stored in the first discharge path 4 during the drainage operation over time.

[0057] First, in step S05, the control unit 8 switches the gas opening / closing unit 2 from a closed state to a flowing state, and switches the first discharge unit 5 from a closed state to a flowing state, moving the process to step S07. At this time, the first discharge path 4 is open to the atmosphere, and the pressure of the hydrogen-containing gas is higher than atmospheric pressure. Therefore, the condensate stored in the first discharge path 4 or tank 11 is discharged, such as... Figure 6 As shown, the water level H of the condensate begins to decrease from the initial water level H1 toward the specified water level H2.

[0058] Next, in step S07, the control unit 8 determines whether the water level H of the condensate stored in the first discharge path 4 or tank 11 is lower than the specified water level H2. Furthermore, the water level when there is no stored condensate in the first discharge path 4 is set to 0, and the specified water level H2 is, for example, about 5 cm.

[0059] If the condensate water level H is lower than the specified water level H2 (step S07: "Yes"), the control unit 8 moves the process to step S04. On the other hand, if the condensate water level H is higher than the specified water level H2 (step S07: "No"), the control unit 8 moves the process to step S07 and repeats the process until the condensate water level H is lower than the specified water level H2.

[0060] Figure 7 This is a flowchart related to the pressure detection-based drainage operation of Embodiment 1. Figure 8 It is shown Figure 7 The graph shows the pressure change over time in fuel gas path 1 during the drainage operation.

[0061] First, in step S01, the control unit 8 switches the gas opening / closing unit 2 from a closed state to a flowing state, causing the process to proceed to step S02. At this time, as... Figure 8 As shown, the pressure in fuel gas path 1 gradually increases from the initial pressure value, P1.

[0062] Next, in step S02, the control unit 8 determines whether the pressure value P measured by the pressure detection unit 10 exceeds the threshold P2.

[0063] If the pressure value P of fuel gas path 1 exceeds the threshold P2 (step S02: "Yes"), the control unit 8 moves the process to step S08. On the other hand, if the pressure value P of fuel gas path 1 is below the threshold P2 (step S02: "No"), the control unit 8 moves the process to step S02 and repeats the process until the pressure value P of fuel gas path 1 exceeds the threshold P2.

[0064] Next, in step S08, the control unit 8 switches the gas opening / closing section 2 from the flowing state to the closed state and switches the first discharge section 5 from the closed state to the flowing state, thus moving the processing to step S09. As a result, the drainage operation begins. Furthermore, by switching the gas opening / closing section 2 from the flowing state to the closed state, such as... Figure 8 As shown, the pressure P in fuel gas path 1 gradually decreases from P2 towards P4. Furthermore, the threshold P4 is, for example, 2 kPa, or any value higher than atmospheric pressure. When P4 equals atmospheric pressure, almost all the condensate in the first discharge path 4 is discharged to the outside of the first discharge path 4, making the first discharge path 4 open to the atmosphere.

[0065] Next, in step S09, the control unit 8 determines whether the pressure value P measured by the pressure detection unit 10 is lower than the threshold P4.

[0066] If the pressure value P of fuel gas path 1 is lower than the threshold P4 (step S09: "Yes"), the control unit 8 moves the process to step S04. On the other hand, if the pressure value P of fuel gas path 1 is higher than the threshold P4 (step S09: "No"), the control unit 8 moves the process to step S09 and repeats the process until the pressure value P of fuel gas path 1 is lower than the threshold P4.

[0067] [1-3. Effects, etc.]

[0068] As described above, in this embodiment, the fuel cell system 200 includes: a fuel cell 100 that uses hydrogen-containing gas to generate electricity; a fuel gas path 1 connected to the fuel cell 100 for allowing hydrogen-containing gas to flow; a gas opening / closing section 2 disposed in the fuel gas path 1 for switching between a first flow state allowing hydrogen-containing gas to flow in the fuel gas path 1 and a first closed state blocking hydrogen-containing gas in the fuel gas path 1; and a recirculation path 3 connected to the fuel gas path 1 at a position between the gas opening / closing section 2 and the fuel cell 100 for allowing hydrogen-containing gas not used in the power generation of the fuel cell 100 to flow to the fuel gas path 1.

[0069] In addition, the fuel cell system 200 also includes: a first discharge path 4 connected to the recirculation path 3 for discharging condensate generated by water vapor contained in hydrogen-containing gas to the outside; a first discharge section 5 disposed in the first discharge path 4 for switching between a second flow state in which hydrogen-containing gas flows through the first discharge path 4 and a second closed state in which hydrogen-containing gas is blocked in the first discharge path 4; a second discharge path 6 disposed in the recirculation path 3 for discharging hydrogen-containing gas flowing through the fuel gas path 1 to the outside; a second discharge section 7 disposed in the second discharge path 6 for switching between a third flow state in which hydrogen-containing gas flows through the second discharge path 6 and a third closed state in which hydrogen-containing gas is blocked in the second discharge path 6; and a control section 8 for operating the gas opening / closing section 2, the first discharge section 5, and the second discharge section 7.

[0070] The initial state is characterized by the gas opening and closing part 2 being in a first closed state, the first discharge part 5 being in a second closed state, and the second discharge part 7 being in a third closed state.

[0071] When a drainage operation is performed to discharge condensate from fuel gas path 1, fuel cell 100 and recirculation path 3 during the period when power generation of fuel cell 100 is stopped, control unit 8 switches gas opening and closing unit 2 from first closed state to first open state and first discharge unit 5 from second closed state to second open state from the initial state.

[0072] Therefore, condensate can be discharged without opening the first discharge path 4 to the atmosphere. Thus, when the first discharge path 4 is under positive pressure, hydrogen-containing gas is not discharged outside the fuel cell system 200, suppressing unsafe events such as smoke and fire. Furthermore, when the first discharge path 4 is under negative pressure, air will not reach the fuel cell 100 from the outside via the first discharge path 4, suppressing the degradation of the electrolyte membrane inside the fuel cell 100. Moreover, shortly after the fuel cell system 200 stops operating, for example, after only about 30 minutes, the temperature of the fuel gas path 1 and the recirculation path 3 decreases from a high temperature, causing the volume of hydrogen-containing gas within the paths to shrink, thus making the first discharge path 4 negative pressure.

[0073] In this embodiment, the fuel cell system 200 may also include a gas recirculation device 9, which is disposed between the fuel cell 100 and the first discharge path 4, for circulating hydrogen-containing gas from the recirculation path 3 to the fuel gas path 1.

[0074] Alternatively, after the control unit 8 switches the gas opening / closing unit 2 from the first closed state to the first open state and the first discharge unit 5 from the second closed state to the second open state from the initial state, it causes the gas circulation device 9 to operate to perform the drainage operation.

[0075] This increases the pressure of the hydrogen-containing gas in the first discharge path 4, thus allowing for faster discharge of condensate.

[0076] Alternatively, in this embodiment, the fuel cell system 200 may also include a pressure detection unit 10, which is disposed between the gas opening / closing unit 2 and the fuel cell 100, and is used to measure the pressure of the hydrogen-containing gas flowing in the fuel gas path 1.

[0077] Alternatively, if the control unit 8 switches the gas opening / closing unit 2 from the first closed state to the first open state from the initial state, and the measured value of the pressure detection unit 10 exceeds the predetermined value P2, then after switching the first discharge unit 5 from the second closed state to the second open state, it performs a drainage operation.

[0078] Therefore, since the drainage action is performed based on the pressure value of fuel gas path 1, the drainage rate of condensate can be adjusted. Thus, condensate drainage can be performed efficiently by setting P2 to an appropriate value.

[0079] Alternatively, in this embodiment, after the control unit 8 has switched the gas opening / closing unit 2 from the first closed state to the first open state and the first discharge unit 5 from the second closed state to the second open state from the initial state, and has performed a drainage operation for a predetermined period of time, it may switch the gas opening / closing unit 2 from the first open state to the first closed state and the first discharge unit 5 from the second open state to the second closed state to stop the drainage operation.

[0080] Therefore, condensate can be discharged without opening the first discharge path 4 to the atmosphere. This prevents hydrogen-containing gas from leaking out of the fuel cell system 200.

[0081] Alternatively, in this embodiment, the fuel cell system 200 may also include: a tank 11 disposed in the recirculation path 3 for storing condensate; and a water level detection unit disposed inside the tank 11 for detecting the water level of the condensate stored in the tank 11.

[0082] Alternatively, after the control unit 8 switches the gas opening / closing unit 2 from the first closed state to the first flowing state and the first discharge unit 5 from the second closed state to the second flowing state from the initial state, if the water level in the tank 11 drops to the predetermined water level H2 during the drainage operation, the control unit 8 switches the gas opening / closing unit 2 from the first flowing state to the first closed state and the first discharge unit 5 from the second flowing state to the second closed state to stop the drainage operation.

[0083] Therefore, condensate can be discharged without opening the first discharge path 4 to the atmosphere. This prevents hydrogen-containing gas from leaking out of the fuel cell system 200.

[0084] Alternatively, in this embodiment, if the pressure detection unit 10's measured value is lower than the predetermined value P4 after the drainage operation is performed, the control unit 8 may switch the gas opening and closing unit 2 from the first flow state to the first closed state and switch the first discharge unit 5 from the second flow state to the second closed state to stop the drainage operation.

[0085] Therefore, condensate can be discharged without opening the first discharge path 4 to the atmosphere. This prevents hydrogen-containing gas from leaking out of the fuel cell system 200.

[0086] (Other implementation methods)

[0087] The above-described embodiments are used to illustrate the technology in this disclosure, and therefore various changes, substitutions, additions, omissions, etc., can be made within the scope of the claims or their equivalents.

[0088] Industrial availability

[0089] The fuel cell system disclosed herein can be applied, for example, to stationary fuel cell systems and automotive fuel cell systems that use solid polymer fuel cells or solid oxide fuel cells.

[0090] Explanation of reference numerals in the attached figures

[0091] 1: Fuel gas path; 2: Gas opening and closing unit; 3: Recirculation path; 4: First discharge path; 5: First discharge unit; 6: Second discharge path; 7: Second discharge unit; 8: Control unit; 9: Gas circulation device; 10: Pressure detection unit; 11: Tank; 12: Water level detection unit; 20: Operation unit; 100: Fuel cell; 200: Fuel cell system.

Claims

1. A fuel cell system comprising: Fuel cells use hydrogen-containing gas to generate electricity; A fuel gas path, which is connected to the fuel cell, is used to allow the hydrogen-containing gas to flow; A gas opening and closing section is provided in the fuel gas path, which switches between a first flow state in which the hydrogen-containing gas flows in the fuel gas path and a first closed state in which the hydrogen-containing gas is blocked in the fuel gas path. A recirculation path, located at the position between the gas opening / closing part and the fuel cell in the fuel gas path, is used to allow hydrogen-containing gas that is not used in the power generation of the fuel cell to flow into the fuel gas path. A first discharge path, which is connected to the recirculation path, is used to discharge condensate generated by water vapor contained in the hydrogen-containing gas to the outside. A first discharge section is disposed in the first discharge path, which switches between a second flow state in which the hydrogen-containing gas flows through the first discharge path and a second closed state in which the hydrogen-containing gas is blocked in the first discharge path. A second discharge path is provided in the recirculation path for discharging the hydrogen-containing gas flowing in the fuel gas path to the outside. A second discharge section, disposed in the second discharge path, switches between a third flow state in which the hydrogen-containing gas flows through the second discharge path and a third closed state in which the hydrogen-containing gas is blocked in the second discharge path; and The control unit activates the gas opening / closing unit, the first discharge unit, and the second discharge unit. The initial state is defined as the state in which the gas opening and closing part is in the first closed state, the first discharge part is in the second closed state, and the second discharge part is in the third closed state. When a drainage operation is performed to discharge the condensate from the fuel gas path, the fuel cell, and the recirculation path during the period when the power generation of the fuel cell is stopped, the control unit switches the gas opening and closing section from the first closed state to the first flowing state and switches the first discharge section from the second closed state to the second flowing state from the initial state.

2. The fuel cell system according to claim 1, wherein, It also includes a gas recirculation device, which is disposed between the fuel cell and the first discharge path, for circulating the hydrogen-containing gas from the recirculation path to the fuel gas path. After the control unit switches the gas opening / closing part from the first closed state to the first flowing state and the first discharge part from the second closed state to the second flowing state from the initial state, it causes the gas circulation device to operate to perform the drainage operation.

3. The fuel cell system according to claim 1 or 2, wherein, It also includes a pressure detection unit, which is disposed between the gas opening / closing unit and the fuel cell, for measuring the pressure of the hydrogen-containing gas flowing in the fuel gas path. When the control unit switches the gas opening / closing part from the first closed state to the first flowing state from the initial state, and the measured value of the pressure detection unit exceeds the first predetermined value, the control unit performs the drainage operation after switching the first discharge part from the second closed state to the second flowing state.

4. The fuel cell system according to claim 1 or 2, wherein, If the control unit performs the drainage operation for a predetermined period after switching the gas opening / closing part from the first closed state to the first flowing state and the first discharge part from the second closed state to the second flowing state from the initial state, the control unit switches the gas opening / closing part from the first flowing state to the first closed state and the first discharge part from the second flowing state to the second closed state to stop the drainage operation.

5. The fuel cell system according to claim 2, further comprising: A tank, disposed in the recirculation path, is used to store the condensate; and A water level detection unit, located inside the tank, is used to detect the water level of the condensate stored in the tank. After the control unit switches the gas opening / closing part from the first closed state to the first flowing state and the first discharge part from the second closed state to the second flowing state from the initial state, if the water level in the tank drops to a predetermined water level during the drainage operation, it switches the gas opening / closing part from the first flowing state to the first closed state and the first discharge part from the second flowing state to the second closed state to stop the drainage operation.

6. The fuel cell system according to claim 3, wherein, If the pressure detection unit's measured value is lower than the second predetermined value after the drainage operation is performed, the control unit switches the gas opening and closing unit from the first flow state to the first closed state and switches the first discharge unit from the second flow state to the second closed state to stop the drainage operation.

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