WO2013183745A1 - Fuel cell system - Google Patents

Fuel cell system Download PDF

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Publication number
WO2013183745A1
WO2013183745A1 PCT/JP2013/065783 JP2013065783W WO2013183745A1 WO 2013183745 A1 WO2013183745 A1 WO 2013183745A1 JP 2013065783 W JP2013065783 W JP 2013065783W WO 2013183745 A1 WO2013183745 A1 WO 2013183745A1
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WO
WIPO (PCT)
Prior art keywords
fuel cell
gas
oxidant
cell stack
cell system
Prior art date
Application number
PCT/JP2013/065783
Other languages
French (fr)
Japanese (ja)
Inventor
竜也 菅原
金沢　卓磨
Original Assignee
本田技研工業株式会社
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Publication of WO2013183745A1 publication Critical patent/WO2013183745A1/en

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M8/00—Fuel cells; Manufacture thereof
    • H01M8/04—Auxiliary arrangements, e.g. for control of pressure or for circulation of fluids
    • H01M8/04082—Arrangements for control of reactant parameters, e.g. pressure or concentration
    • H01M8/04089—Arrangements for control of reactant parameters, e.g. pressure or concentration of gaseous reactants
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M8/00—Fuel cells; Manufacture thereof
    • H01M8/04—Auxiliary arrangements, e.g. for control of pressure or for circulation of fluids
    • H01M8/04298—Processes for controlling fuel cells or fuel cell systems
    • H01M8/043—Processes for controlling fuel cells or fuel cell systems applied during specific periods
    • H01M8/04303—Processes for controlling fuel cells or fuel cell systems applied during specific periods applied during shut-down
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M8/00—Fuel cells; Manufacture thereof
    • H01M8/04—Auxiliary arrangements, e.g. for control of pressure or for circulation of fluids
    • H01M8/04223—Auxiliary arrangements, e.g. for control of pressure or for circulation of fluids during start-up or shut-down; Depolarisation or activation, e.g. purging; Means for short-circuiting defective fuel cells
    • H01M8/04228—Auxiliary arrangements, e.g. for control of pressure or for circulation of fluids during start-up or shut-down; Depolarisation or activation, e.g. purging; Means for short-circuiting defective fuel cells during shut-down
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M8/00—Fuel cells; Manufacture thereof
    • H01M8/10—Fuel cells with solid electrolytes
    • H01M2008/1095—Fuel cells with polymeric electrolytes
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/30—Hydrogen technology
    • Y02E60/50—Fuel cells

Definitions

  • the present invention relates to a fuel cell system including a fuel cell that generates electricity by electrochemically reacting a fuel gas and an oxidant gas.
  • a fuel cell system equipped with a polymer-electrolyte fuel cell (PEFC)
  • hydrogen fuel gas
  • oxygen oxidant gas
  • the fuel gas and the oxidant gas are reacted electrochemically to generate electricity.
  • the applicant of the present application has proposed a cross leak detection technique according to Patent Document 1 as one approach for detecting a phenomenon (cross leak) that induces such a problem.
  • a cross leak detection technique according to Patent Document 1
  • Patent Document 1 does not describe or suggest technical matters for suppressing deterioration of the electrolyte membrane.
  • An object of the present invention is to provide a fuel cell system that contributes to extending the life of a fuel cell.
  • the invention according to (1) includes a fuel cell that generates electricity by electrochemically reacting a fuel gas and an oxidant gas, and an oxidant gas for supplying the fuel cell to the fuel cell.
  • An oxidant gas supply flow path, an oxidant off gas discharge flow path for discharging the reacted oxidant off gas from the fuel cell, and the oxidant gas supply flow path are provided to oxidize the fuel cell.
  • a circulating flow path communicating with the circulating flow path, and a circulation pump for sending an oxidant off-gas from the branching section to the merging section; and a circulation pump disposed in the circulating flow path from the divergence section to the merging section.
  • a check valve that suppresses the flow of the oxidant off-gas in the direction, and a control unit that performs control to drive the circulation pump when the fuel cell is stopped.
  • a fuel cell system having a long-life fuel cell can be obtained.
  • the invention according to (2) is the fuel cell system according to (1), which is disposed on the downstream side of the compressor and the upstream side of the merging portion in the oxidant gas supply flow path.
  • An inlet side sealing valve that seals the flow of the oxidant gas from the compressor to the inlet side of the fuel cell through the junction, and the downstream side of the branch part of the oxidant off-gas discharge channel.
  • an outlet side sealing valve that seals a flow of the oxidant off-gas from the outlet side of the fuel cell to the exhaust side through the branch portion.
  • the oxidant off-gas can be circulated without introducing new oxygen using the circulation flow path as a closed space, oxygen remaining on the cathode side of the fuel cell
  • a fuel cell system having a long-life fuel cell can be obtained by quickly removing hydrogen and hydrogen.
  • the invention according to (3) is the fuel cell system according to (1), wherein the circulation pump adopts a can structure in which a rotor and a stator of a motor unit are sealed with a can.
  • the circulation pump adopts a can structure in which the rotor and stator of the motor unit are sealed with a can, the life of the motor unit in the fuel cell and the circulation pump is further extended. Can be achieved.
  • the invention according to (4) is the fuel cell system according to (2), wherein the circulation pump adopts a can structure in which a rotor and a stator of a motor unit are sealed with a can.
  • the circulation pump adopts a can structure in which the rotor and the stator of the motor unit are sealed with a can, oxygen and hydrogen remaining on the cathode side of the fuel cell can be quickly removed. In addition to the removal effect, the life of the motor unit in the fuel cell and the circulation pump can be further extended.
  • a fuel cell system having a long-life fuel cell can be obtained.
  • FIG. 1 is a schematic configuration diagram of a fuel cell system according to an embodiment of the present invention. It is explanatory drawing showing the internal structure of a circulation pump. In the fuel cell system concerning the embodiment of the present invention, it is an explanatory view showing the flow of the air at the time of normal operation. In the fuel cell system concerning the embodiment of the present invention, it is an explanatory view showing the flow of the air at the time of operation stop. It is a flowchart figure showing the flow of the EGR process performed at the time of the driving
  • the present inventors have proposed that oxygen and hydrogen (cross leak) remaining at the cathode of the fuel cell when the fuel cell is stopped. I thought it was important to remove as early as possible from the time of shutdown.
  • a circulation channel for circulating the oxidant off-gas is provided on the cathode side of the fuel cell, and provided in the circulation channel when the fuel cell is stopped. The idea that the oxidant off-gas should be circulated to the cathode side of the fuel cell by driving the circulation pump has been obtained.
  • a fuel cell system includes a fuel cell that generates electricity by electrochemically reacting a fuel gas and an oxidant gas, and an oxidant for supplying the oxidant gas to the fuel cell.
  • the branch portion disposed in the oxidant off-gas discharge passage, and the junction portion disposed on the downstream side of the compressor in the oxidant gas supply passage are the electric compressor for supplying the gas.
  • a circulation channel that communicates with the circulation channel, a circulation pump that is disposed in the circulation channel and that feeds an oxidant off-gas from the branch portion to the merge portion, and is disposed in the circulation channel and is coupled to the merge portion from the branch portion.
  • the order toward the club A check valve that suppresses the flow of the oxidant off-gas that is in the opposite direction to the direction, and a control unit that performs control to drive the circulation pump when the fuel cell is stopped. The most important feature.
  • oxygen and hydrogen remaining on the cathode side of the fuel cell can be quickly removed by circulating the oxidant off-gas to the cathode side of the fuel cell.
  • FIG. 1A is a schematic configuration diagram of a fuel cell system 11 according to an embodiment of the present invention.
  • FIG. 1B is an explanatory diagram illustrating the internal configuration of the circulation pump 69.
  • a fuel cell system 11 includes a fuel cell stack (corresponding to a “fuel cell” of the present invention) 13, an anode gas supply / exhaust system 15, and a cathode gas supply / exhaust system.
  • a system 17, a diluter 19, and a control unit 21 are provided.
  • the fuel cell system 11 is mounted as a power source in an unillustrated automobile.
  • the fuel cell stack 13 is a polymer electrolyte fuel cell (Polymer Fuel Cell: PEFC), and is configured by stacking a plurality of fuel cells 23 as shown in FIG. 1A. In the example of the fuel cell stack 13 in FIG. 1A, one fuel cell 23 is representatively shown.
  • the fuel battery cell 23 shown in FIG. 1A is configured by sandwiching, for example, a fluororesin-based solid polymer electrolyte membrane 29 between flat plate-like anodes 25 and a cathode 27 provided to face each other. The anode 25 and the cathode 27 are sandwiched from the outside by a pair of separators 30a and 30b.
  • As anode 25 and cathode 27 what carried platinum or a platinum alloy as a catalyst on conductive carbon can be used, for example.
  • hydrogen H 2 (corresponding to “fuel gas” of the present invention) is supplied to the anode 25, thereby causing an oxidation reaction of hydrogen H 2 shown in the formula (1). .
  • oxygen O 2 (corresponding to the “oxidant gas” of the present invention) is supplied to the cathode 27, whereby the reduction of oxygen O 2 shown in the formula (2) is performed.
  • a reaction takes place.
  • 2H + (hydrogen ion; proton) in the formula (2) is supplied from the anode 25 side through the solid polymer electrolyte membrane 29 having cation exchange properties (proton conductivity).
  • 2e ⁇ (electron charge) in the formula (2) is supplied from the anode 25 side through a conductive line (not shown).
  • the anode 25 and the cathode 27 are supplied.
  • An electric potential difference (OCV; Open Circuit Voltage) is generated between the fuel cell stack 13 and the fuel cell stack 13 can generate power.
  • the anode 25 and the cathode 27 of the fuel cell stack 13 in a state capable of generating power in this way are electrically connected to an electric load (for example, a battery or a motor for driving an automobile not shown) via a conductive wire (not shown). Then, the DC power generated by the fuel cell stack 13 is configured to be supplied to the electric load.
  • the anode gas supply / exhaust system 15 has a function of supplying or discharging hydrogen (fuel gas) to the anode 25 side of the fuel cell stack 13. As shown in FIG. 1A, the anode gas supply / exhaust system 15 having such a function communicates between a hydrogen tank 31 that stores high-pressure hydrogen (fuel gas) and the hydrogen tank 31 and the inlet side 13a1 of the fuel cell stack 13.
  • the hydrogen discharge pipe 39 communicating between the side 13a2 and the diluter 19, the gas-liquid separator 41 and the purge valve 43 disposed in the hydrogen discharge pipe 39, and the gas-liquid separator 41 and the ejector 35 are communicated.
  • a hydrogen reflux pipe 45 to be connected.
  • the hydrogen tank 31 functions as a hydrogen (fuel gas) supply source.
  • the shut-off valve 34 has a function of supplying high-pressure hydrogen stored in the hydrogen tank 31 to an appropriate pressure, or shutting off the supply.
  • the ejector 35 has a function of mixing and recirculating the hydrogen supplied from the hydrogen tank 31 and the hydrogen (fuel offgas) recirculated through the hydrogen recirculation pipe 45.
  • the hydrogen mixed by the ejector 35 is supplied to the anode 25 of the fuel cell stack 13.
  • the anode gas circulation part 37 has a function of bringing hydrogen (anode gas) flowing therethrough into direct contact with the anode 25.
  • the gas-liquid separator 41 has a function of separating water (condensation water) contained therein from hydrogen (anode offgas) discharged from the fuel cell stack 13.
  • the water separated and recovered by the gas-liquid separator 41 is temporarily stored in a tank section (not shown) of the gas-liquid separator 41, for example, and then discharged to the diluter 19 via a pipe (not shown). .
  • the purge valve 43 has a function of discharging (purging) impurities such as nitrogen contained in hydrogen (fuel offgas) discharged from the fuel cell stack 13 during normal operation of the fuel cell stack 13 (during normal power generation). .
  • the purge valve 43 is closed at normal times when the impurity concentration in the fuel off-gas is not more than a predetermined value. In other words, the purge valve 43 operates so as to be opened at the time of abnormality when the impurity concentration in the fuel off gas exceeds a predetermined value.
  • the impurity concentration in the fuel off gas may be calculated based on the detection value of a hydrogen concentration sensor (not shown) that detects the concentration of hydrogen in the anode off gas.
  • the cathode gas supply / exhaust system 17 has a function of supplying air (oxidant gas) containing oxygen to the cathode 27 of the fuel cell stack 13 and discharging the supplied air containing oxygen from the cathode 27.
  • the cathode gas supply / exhaust system 17 having such a function includes an electric compressor 51 and an air supply pipe (communication gas oxidizer gas of the present invention) that connects the compressor 51 and the fuel cell stack 13 in communication.
  • An air recirculation pipe (this corresponds to an “off gas discharge flow path”) 59, an outlet side sealing valve 61, a back pressure valve 63, a humidifier 65, an air supply pipe 53 and an air discharge pipe 59.
  • 67 (corresponding to “circulation flow path” of the invention), a circulation pump 69, and a check valve 71.
  • the compressor 51 has a function of compressing the air taken in from the air introduction port 51 a and sending it out to the fuel cell stack 13.
  • the inlet side sealing valve 55 is disposed in the air supply pipe 53 on the downstream side of the compressor 51 and on the upstream side of the merging portion 75.
  • the inlet-side sealing valve 55 has a function of sealing a flow of new air (oxidant gas) from the compressor 51 to the inlet side 13c1 of the fuel cell stack 13 via a junction 75 described later.
  • the inlet side sealing valve 55 is opened during normal power generation of the fuel cell stack 13. However, the inlet side sealing valve 55 operates so as to be closed when power generation of the fuel cell stack 13 is stopped. The reason will be described later in detail.
  • the cathode gas circulation unit 57 is provided along the cathode 27 of the fuel cell stack 13 and has a function of bringing air containing oxygen (cathode gas) flowing therethrough directly into contact with the cathode 27.
  • the outlet side sealing valve 61 is disposed on the downstream side of the branching portion 73 and on the upstream side of the humidifier 65 in the air discharge pipe 59.
  • the outlet side sealing valve 61 has a function of sealing the flow of old air (oxidant offgas) from the outlet side 13c2 of the fuel cell stack 13 to the exhaust side of the diluter 19 through a branching portion 73 described later.
  • the outlet side sealing valve 61 is opened during normal power generation of the fuel cell stack 13, similarly to the inlet side sealing valve 55. However, similarly to the inlet side sealing valve 55, the outlet side sealing valve 61 operates so as to be closed when the operation of the fuel cell stack 13 is stopped (when power generation is stopped). The reason will be described later in detail.
  • a normally closed solenoid valve can be suitably used as the inlet-side sealing valve 55 and the outlet-side sealing valve 61.
  • the inlet side sealing valve 55 and the outlet side sealing valve 61 are preferably kept closed when the operation of the fuel cell stack 13 is stopped. When this closing action is continued, no power is required and power is saved. It is because it can contribute to.
  • the back pressure valve 63 is disposed downstream of the humidifier 65 and upstream of the diluter 19 in the air discharge pipe 59.
  • the back pressure valve 63 has a function of adjusting the flow velocity (pressure) of air in the cathode gas circulation portion 57.
  • the back pressure valve 63 can be configured by, for example, a throttle valve that can variably adjust the throttle amount.
  • the humidifier 65 is disposed so as to straddle the air supply pipe 53 and the air discharge pipe 59.
  • the humidifier 65 has a function of humidifying the air from the compressor 51 toward the cathode gas circulation part 57.
  • the solid polymer electrolyte membrane 29 used in the present embodiment works to increase the power generation efficiency of the fuel cell stack 13 by exhibiting good cation exchange properties (proton conductivity) in a water-containing state. Therefore, the humidifier 65 can increase the power generation efficiency of the fuel cell stack 13 by maintaining the solid polymer electrolyte membrane 29 in a water-containing state during normal operation of the fuel cell stack 13.
  • the humidifier 65 has a hollow fiber membrane (not shown) inside. Through this hollow fiber membrane, moisture is exchanged between the air (relatively dry) toward the cathode gas circulation part 57 and the humid air (oxidant off-gas) discharged from the cathode gas circulation part 57. It is configured to be
  • the circulation pump 69 is provided in the air recirculation pipe 67.
  • the circulation pump 69 is driven by a motor unit 93 (see FIG. 1B) described later to discharge air (oxidant) from the outlet side 13c2 of the fuel cell stack 13. Off-gas) from the branching portion 73 toward the merging portion 75.
  • the circulation pump 69 includes an air supply turbine 81, a drive shaft 83 fixed to the air supply turbine 81, a pair of bearings 85 and 87, a rotor 89, and a stator 91 in a casing 79.
  • a motor unit 93 configured to include the motor unit 93.
  • the drive shaft 83 of the air supply turbine 81 is rotatably supported via a pair of bearings 85 and 87, for example.
  • the drive shaft 83 is rotationally driven by the motor unit 93.
  • the air supply turbine 81 is rotationally driven by the motor unit 93 via the drive shaft 83.
  • the inlet side sealing valve 55 and the outlet side sealing valve 61 close the air supply pipe 53 and the air discharge pipe 59, respectively.
  • the air supply pipe 53 ⁇ the inlet side 13c1 of the fuel cell stack 13 ⁇ the cathode gas circulation part 57 ⁇ the outlet side 13c2 of the fuel cell stack 13 ⁇ the air discharge pipe 59 ⁇ the branching part 73 ⁇ air reflux.
  • An annular air flow passage 77 (see FIG. 1A) is formed that sequentially passes through the pipe 67 ⁇ the joining portion 75 ⁇ the air supply pipe 53.
  • the gas remaining in the air flow passage 77 is configured to circulate in the closed air flow passage 77 for a predetermined time described later when the operation of the fuel cell stack 13 is stopped.
  • a pump having a can structure in which the rotor 89 and the stator 91 of the motor section 93 are sealed via a cylindrical can (partition wall) 95 is used as the circulation pump 69.
  • the air (oxidant off-gas) delivered by the circulation pump 69 contains more moisture than the air introduced into the fuel cell stack 13. When this moisture enters the stator 91 of the motor part 93 in the circulation pump 69, the motor part 93 is damaged. Therefore, by adopting the above can structure as the circulation pump 69, the life of the motor section 93 is extended.
  • the check valve 71 is provided in the air recirculation pipe 67.
  • the check valve 71 has a function of suppressing the air flow in the reverse direction with respect to the forward direction from the branching portion 73 toward the merging portion 75 during normal operation of the fuel cell stack 13 (during normal power generation).
  • the check valve 71 is provided for the purpose of suppressing a decrease in power generation efficiency in the fuel cell stack 13.
  • a mechanical valve that does not require power can be preferably used from the viewpoint of contributing to power saving.
  • a T-shaped joint can be used as the branch part 73 and the junction part 75.
  • the branch portion 73 is preferably provided in the vicinity of the outlet side 13c2 of the fuel cell stack 13 in the air discharge pipe 59.
  • the merging portion 75 is preferably provided in the vicinity of the inlet side 13 c 1 of the fuel cell stack 13 in the air supply pipe 53.
  • the diluter 19 discharges the fuel off-gas (hydrogen) introduced into the diluter 19 when the purge valve 43 is open from the outlet side 13c2 of the fuel cell stack 13 through the air discharge pipe 59. It has a function of diluting with (air).
  • the fuel off-gas (hydrogen) diluted to a predetermined concentration or less with the oxidant off-gas (air) is exhausted into the atmosphere.
  • the control unit 21 has a function of controlling the operation of each member including valves and motors belonging to the anode gas supply / exhaust system 15 and the cathode gas supply / exhaust system 17.
  • the control unit 21 includes a CPU (Central processing Unit) (not shown), a ROM (Read Only Memory), a RAM (Random Access Memory), an input / output circuit (including an A / D converter and a D / A converter), and the like. Configured.
  • the CPU executes operation control of each member including a valve and a motor using the RAM as a work area in accordance with a program stored in the ROM.
  • control unit 21 performs a control to open the purge valve 43 when an impurity concentration (such as nitrogen) in the fuel off gas exceeds a predetermined value.
  • control unit 21 performs control to drive the motor unit of the compressor 51 during normal power generation of the fuel cell stack 13.
  • control unit 21 performs control to open the inlet side sealing valve 55 and the outlet side sealing valve 61 during normal power generation of the fuel cell stack 13 while closing the fuel cell stack 13 when power generation is stopped.
  • control unit 21 performs control to adjust the throttle amount of the back pressure valve (throttle valve) 63 during normal power generation of the fuel cell stack 13.
  • control part 21 performs control which drives the motor part 93 of the circulation pump 69 at the time of the electric power generation stop of the fuel cell stack 13.
  • FIG. 2A is an explanatory diagram showing the air flow during normal operation in the fuel cell system 11 according to the embodiment of the present invention.
  • FIG. 2B is an explanatory diagram showing the flow of air when operation is stopped in the fuel cell system 11 according to the embodiment of the present invention.
  • FIG. 3 is a flowchart showing the flow of the EGR process that is executed when the operation of the fuel cell system 11 according to the embodiment of the present invention is stopped.
  • the operation for quickly removing oxygen and hydrogen remaining on the cathode 27 side of the fuel cell stack 13 is performed in the cathode gas supply / exhaust system 17. Therefore, the anode gas supply / exhaust system 15 is not shown in FIGS. 2A and 2B.
  • each part during normal operation of the fuel cell system 11 is as follows. That is, as shown in FIG. 2A, the compressor 51 sends air to the fuel cell stack 13 through the air supply pipe 53 (the inlet side sealing valve 55 is opened). The air sent out by the compressor 51 is humidified through the humidifier 65 and then introduced into the inlet side 13 c 1 of the fuel cell stack 13. Thereafter, the oxygen-containing air introduced into the cathode gas circulation part 57 of the fuel cell stack 13 contacts the cathode 27 and is used for an electrochemical reaction (oxygen reduction reaction).
  • Used air that has passed through the cathode gas circulation part 57 is discharged from the outlet side 13c2 of the fuel cell stack 13 through the air discharge pipe 59 (the outlet side sealing valve 61 is opened).
  • the air thus discharged is introduced into the diluter 19 through the back pressure valve 63 after humidifying the newly supplied air in the humidifier 65.
  • the circulation pump 69 sends out air (oxidant offgas) discharged from the outlet side 13 c 2 of the fuel cell stack 13 from the branch portion 73 toward the junction portion 75. At this time, both the inlet side sealing valve 55 and the outlet side sealing valve 61 are closed. Therefore, the air (oxidant off-gas) sent out by the circulation pump 69 is introduced into the inlet side 13 c 1 of the fuel cell stack 13.
  • the air supply pipe 53 ⁇ the inlet side 13c1 of the fuel cell stack 13 ⁇ the cathode gas circulation part 57 ⁇ the outlet side 13c2 of the fuel cell stack 13 ⁇ the air discharge pipe 59 ⁇ the branch part 73 ⁇ the air recirculation pipe.
  • An annular air flow passage 77 (see FIGS. 1A and 2B) is formed that sequentially passes through 67 ⁇ merging portion 75 ⁇ air supply pipe 53.
  • the gas remaining in the air flow passage 77 operates so as to circulate in the closed air flow passage 77 when the operation of the fuel cell stack 13 is stopped.
  • the gas remaining in the air flow passage 77 (hydrogen generated on the cathode 27 side due to oxygen and cross leak) introduced into the cathode gas circulation portion 57 of the fuel cell stack 13 is blocked.
  • the air flow passage 77 it contacts the cathode 27 and is repeatedly used for electrochemical reaction (oxygen reduction reaction). Then, the amount (concentration) of oxygen and hydrogen in the gas remaining in the air flow passage 77 through the promotion of an electrochemical reaction (oxygen reduction reaction) in the sense of increasing the chance of contact with the cathode 27 (contact time). Reduce. Therefore, oxygen and hydrogen remaining on the cathode 27 side of the fuel cell stack 13 can be quickly removed.
  • FIG. 3 is a flowchart showing the flow of the EGR process that is executed when the operation of the fuel cell system 11 according to the embodiment of the present invention is stopped.
  • the EGR (Exhaust Gas Recirculation) process in the embodiment of the present invention refers to a process of recirculating exhaust gas when the fuel cell system 11 is stopped.
  • step S ⁇ b> 11 the control unit 21 monitors whether or not a command signal related to operation stop is input during normal operation of the fuel cell system 11. For example, when the ignition switch 101 (see FIG. 1A) is turned off, the control unit 21 considers that a command signal related to operation stop has been input, and starts the EGR process (“Yes” in step S11). See). That is, as a result of the monitoring in step S11, the control unit 21 advances the process flow to step S12 when the ignition switch 101 is turned off.
  • step S12 the control unit 21 operates to close the inlet side sealing valve 55.
  • the inlet side sealing valve 55 seals the flow of new air (oxidant gas) from the compressor 51 via the junction 75 to the inlet side 13c1 of the fuel cell stack 13.
  • step S13 the control unit 21 operates to close the outlet side sealing valve 61.
  • the outlet side sealing valve 61 seals the flow of old air (oxidant off-gas) from the outlet side 13c2 of the fuel cell stack 13 to the exhaust side of the diluter 19 via the branching portion 73.
  • steps S12 and S13 described above may be performed simultaneously in time, or may be performed sequentially with a time interval therebetween. Further, in the case of adopting a mode of sequentially performing time intervals with each other, the process of step S12 may be performed after step S13.
  • step S14 the control unit 21 operates to drive the motor unit 93 of the circulation pump 69.
  • the circulation pump 69 sends out air (oxidant off-gas) discharged from the outlet side 13c2 of the fuel cell stack 13 from the branching portion 73 toward the joining portion 75.
  • an annular air flow passage 77 (see FIGS. 1A and 2B) is formed in the fuel cell system 11. Therefore, the gas remaining in the air flow passage 77 circulates in the closed air flow passage 77 when the operation of the fuel cell stack 13 is stopped.
  • step S15 the control unit 21 determines whether or not a predetermined time set in advance has elapsed since the start of driving of the circulation pump 69.
  • This predetermined time takes into account the capacity of the air flow passage 77, the component ratio of oxygen and hydrogen in the remaining gas, the delivery speed of the circulation pump 69, the activity of the catalyst (for example, platinum), etc. Based on the results of verification by (simulation), taking into account that the oxygen and hydrogen concentrations related to the electrochemical reaction through the catalyst in the remaining gas are sufficiently reduced, the time can be changed as appropriate (For example, 1 to 3 minutes) may be set.
  • step S15 If it is determined in step S15 that a predetermined time has elapsed since the start of driving of the circulation pump 69, the control unit 21 advances the process flow to step S16.
  • step S16 the control unit 21 operates to stop the driving of the circulation pump 69. Thereby, the circulation pump 69 stops its drive. As a result, the gas remaining in the air flow passage 77 stays in the closed air flow passage 77 as it is. However, in the gas remaining in the air flow passage 77, the concentration of the gas (oxygen and hydrogen) contributing to the reaction on the cathode 27 side is sufficiently reduced.
  • step S16 ends the control unit 21 ends the flow of the EGR process. Note that, when the operation of the fuel cell stack 13 is stopped, the inlet side sealing valve 55 and the outlet side sealing valve 61 continue to close. This is to prevent new air from being introduced into the annular air flow passage 77 when the fuel cell stack 13 is shut down.
  • a fuel cell system 11 includes a fuel cell stack 13 that generates electricity by electrochemically reacting a fuel gas (hydrogen) and an oxidant gas (oxygen), and an oxidant for the fuel cell stack 13.
  • a fuel gas hydrogen
  • an oxidant gas oxygen
  • Agent A recirculation pump 69 that sends out gas (air) and a reverse passage that is disposed in the circulation flow path 67 and suppresses the flow of oxidant off-gas (air) that is in the reverse direction to the forward direction from the branch portion 73 toward the junction portion 75. It is characterized by comprising a stop valve 71 and a control unit 21 that controls to drive the circulation pump 69 when the operation of the fuel cell stack 13 is stopped.
  • the control unit 21 performs control for driving the circulation pump 69.
  • the gas oxygen and hydrogen generated on the cathode 27 side due to cross leak, etc.
  • the cathode contacts with the cathode 27 and is repeatedly used for electrochemical reaction (oxygen reduction reaction).
  • the amount (concentration) of oxygen and hydrogen in the gas remaining in the air flow passage 77 through the promotion of an electrochemical reaction (oxygen reduction reaction) in the sense of increasing the chance of contact with the cathode 27 (contact time).
  • the flow of the oxidant off-gas (air) in the reverse direction with respect to the forward direction from the branching portion 73 toward the merging portion 75 is suppressed in the circulation flow path 67.
  • the structure which provides the check valve 71 is employ
  • the oxidant gas supply channel 53 is disposed on the downstream side of the compressor 51 and on the upstream side of the merging portion 75, and the fuel passes through the merging portion 75 from the compressor 51.
  • An inlet side sealing valve 55 that seals the flow of the oxidant gas (air) toward the inlet side 13c1 of the battery stack 13 and the downstream side of the branching portion 73 of the oxidant offgas discharge flow path 59 are provided.
  • the configuration further includes an outlet side sealing valve 61 that seals the flow of the oxidant off-gas from the outlet side 13c2 of the battery stack 13 to the exhaust side of the diluter 19 through the branch portion 73.
  • the air flow passage 77 including the circulation flow path 67 is formed as a narrow closed space, and the oxidant off-gas can be circulated without introducing new oxygen. Therefore, the gas (oxygen and hydrogen) remaining on the cathode 27 side of the fuel cell stack 13 can be quickly removed. Thereby, the deterioration suppression effect of the above-mentioned solid polymer electrolyte membrane 29 can be further enhanced.
  • the circulation pump 69 adopts a configuration in which a can structure in which the rotor 89 and the stator 91 of the motor section 93 are sealed with a can 95 is adopted. According to the fuel cell system 11 according to the embodiment of the present invention, the life of the motor unit 93 in the fuel cell stack 13 and the circulation pump 69 can be further extended.
  • Fuel Cell System 13 Fuel Cell Stack (Fuel Cell) 21 Control Unit 23 Fuel Cell 25 Anode 27 Cathode 29 Solid Polymer Electrolyte Membrane 51 Compressor 53 Air Supply Pipe (Oxidant Gas Supply Channel) 55 Inlet side sealing valve 59 Air discharge piping (oxidant off-gas discharge flow path) 61 Outlet side sealing valve 67 Circulation flow path 69 Circulation pump 71 Check valve 73 Branching section 75 Merging section

Abstract

[Problem] To obtain a fuel cell system (11) having a long-lifespan fuel cell stack (13). [Solution] The fuel cell system (11) is provided with: the fuel cell stack (13); an oxidant gas feed channel (53) for feeding an oxidant gas to the fuel cell stack (13); an oxidant off-gas discharge channel (59) for discharging the post-reaction oxidant off-gas (air) from the fuel cell stack (13); a compressor (11); a circulation channel (67) communicating between a branching part (73) and a confluence part (75); a circulation pump (69) for sending the oxidant off-gas (air) from the branching part (73) to the confluence part (75); a check valve (71) for suppressing the flow of the oxidant off-gas (air) in the reverse direction with respect to the forward direction from the branching part (73) to the confluence part (75); and a controller (21) for performing control to drive the circulation pump (69) when the fuel cell stack (13) is not in operation.

Description

燃料電池システムFuel cell system
　本発明は、燃料ガスと酸化剤ガスとを電気化学的に反応させて発電する燃料電池を備えた燃料電池システムに関する。 The present invention relates to a fuel cell system including a fuel cell that generates electricity by electrochemically reacting a fuel gas and an oxidant gas.
　例えば、固体高分子型燃料電池（Polymer Electrolyte Fuel Cell：ＰＥＦＣ）を備えた燃料電池システムでは、燃料電池のアノードに水素（燃料ガス）を供給すると共に、燃料電池のカソードに酸素（酸化剤ガス）を供給し、これらの燃料ガスと酸化剤ガスとを電気化学的に反応させて発電する。 For example, in a fuel cell system equipped with a polymer-electrolyte fuel cell (PEFC), hydrogen (fuel gas) is supplied to the anode of the fuel cell and oxygen (oxidant gas) is supplied to the cathode of the fuel cell. The fuel gas and the oxidant gas are reacted electrochemically to generate electricity.
　こうした燃料電池システムでは、例えば燃料電池の発電（運転）停止時において、燃料電池に残存しているアノードの燃料ガスが電解質膜を透過してカソードへ、カソードの酸化剤ガスが電解質膜を透過してアノードへ相互に移動する現象（クロスリーク）を生じる場合がある。このような現象（クロスリーク）が生じると、カソードで水素と酸素とが反応（酸素の還元反応過程）して過酸化水素（Ｈ2 Ｏ2 ）が生成される。すると、このＨ2 Ｏ2 由来のヒドロキシルラジカル（・ＯＨ）などのラジカル類が、電解質膜を劣化（酸化）させるという課題がある。 In such a fuel cell system, for example, when power generation (operation) of the fuel cell is stopped, anode fuel gas remaining in the fuel cell permeates the electrolyte membrane to the cathode, and cathode oxidant gas permeates the electrolyte membrane. In some cases, the phenomenon of mutual movement to the anode (cross leak) may occur. When such a phenomenon (cross leak) occurs, hydrogen and oxygen react at the cathode (oxygen reduction reaction process) to generate hydrogen peroxide (H 2 O 2 ). Then, there is a problem that radicals such as hydroxyl radicals (.OH) derived from H 2 O 2 deteriorate (oxidize) the electrolyte membrane.
　こうした課題を誘発させる現象（クロスリーク）を検出するためのアプローチのひとつとして、本願出願人は、特許文献１に係るクロスリーク検出技術を提案している。特許文献１に係るクロスリーク検出方法では、周期的に検出される第２セルペア電圧が前回検出時までの第２セルペア電圧よりも高くなったときに、クロスリークの発生はないと判断する。所定の時間が経過するまでに、第２セルペア電圧が前回検出時までの第２セルペア電圧よりも高くならなかったときには、クロスリークが発生したものと判断する。 The applicant of the present application has proposed a cross leak detection technique according to Patent Document 1 as one approach for detecting a phenomenon (cross leak) that induces such a problem. In the cross leak detection method according to Patent Document 1, it is determined that no cross leak occurs when the periodically detected second cell pair voltage is higher than the second cell pair voltage until the previous detection. If the second cell pair voltage does not become higher than the second cell pair voltage until the previous detection by the time the predetermined time has elapsed, it is determined that a cross leak has occurred.
　特許文献１に係る技術によれば、複数枚のセルの合計セル電圧を検出する場合であっても、正確にクロスリークを検出することができる。 According to the technique according to Patent Document 1, even when the total cell voltage of a plurality of cells is detected, a cross leak can be accurately detected.
特開２０１０－１０３０６３号公報JP 2010-103063 A
　ところで、燃料電池の運転停止時にクロスリークが生じた場合であっても、電解質膜の劣化を抑制することができれば、燃料電池の長寿命化に寄与することができる。この点、特許文献１では、電解質膜の劣化を抑制するための技術的事項については、記載も示唆もしてない。 By the way, even if a cross leak occurs when the operation of the fuel cell is stopped, if the deterioration of the electrolyte membrane can be suppressed, it can contribute to the extension of the life of the fuel cell. In this regard, Patent Document 1 does not describe or suggest technical matters for suppressing deterioration of the electrolyte membrane.
　本発明は、燃料電池の長寿命化に寄与する燃料電池システムを提供することを目的とする。 An object of the present invention is to provide a fuel cell system that contributes to extending the life of a fuel cell.
　上記目的を達成するために、（１）に係る発明は、燃料ガスおよび酸化剤ガスを電気化学的に反応させて発電する燃料電池と、前記燃料電池に対して酸化剤ガスを供給するための酸化剤ガス供給流路と、前記燃料電池から反応後の酸化剤オフガスを排出するための酸化剤オフガス排出流路と、前記酸化剤ガス供給流路に配設され、前記燃料電池に対して酸化剤ガスを供給するコンプレッサと、前記酸化剤オフガス排出流路に配設される分岐部、および、前記酸化剤ガス供給流路のうち前記コンプレッサの下流側に配設される合流部、の間を連通する循環流路と、前記循環流路に配設され、前記分岐部から前記合流部へと酸化剤オフガスを送り出す循環ポンプと、前記循環流路に配設され、前記分岐部から前記合流部へ向かう順方向に対して逆方向となる酸化剤オフガスの流れを抑制する逆止弁と、前記燃料電池の運転停止時に、前記循環ポンプを駆動させる制御を行う制御部と、を備えて構成されることを最も主要な特徴とする。 To achieve the above object, the invention according to (1) includes a fuel cell that generates electricity by electrochemically reacting a fuel gas and an oxidant gas, and an oxidant gas for supplying the fuel cell to the fuel cell. An oxidant gas supply flow path, an oxidant off gas discharge flow path for discharging the reacted oxidant off gas from the fuel cell, and the oxidant gas supply flow path are provided to oxidize the fuel cell. Between the compressor for supplying the oxidant gas, the branch portion disposed in the oxidant off-gas discharge flow path, and the merging portion disposed on the downstream side of the compressor in the oxidant gas supply flow path. A circulating flow path communicating with the circulating flow path, and a circulation pump for sending an oxidant off-gas from the branching section to the merging section; and a circulation pump disposed in the circulating flow path from the divergence section to the merging section. Against the forward direction A check valve that suppresses the flow of the oxidant off-gas in the direction, and a control unit that performs control to drive the circulation pump when the fuel cell is stopped. To do.
　（１）に係る発明によれば、長寿命の燃料電池を有する燃料電池システムを得ることができる。 According to the invention according to (1), a fuel cell system having a long-life fuel cell can be obtained.
　また、（２）に係る発明は、（１）に記載の燃料電池システムであって、前記酸化剤ガス供給流路のうち前記コンプレッサの下流側かつ前記合流部の上流側に配設され、前記コンプレッサから前記合流部を経て前記燃料電池の入口側へ向かう酸化剤ガスの流れを封止する入口側封止弁と、前記酸化剤オフガス排出流路のうち前記分岐部の下流側に配設され、前記燃料電池の出口側から前記分岐部を経て排気側へ向かう酸化剤オフガスの流れを封止する出口側封止弁と、をさらに備えることを特徴とする。 The invention according to (2) is the fuel cell system according to (1), which is disposed on the downstream side of the compressor and the upstream side of the merging portion in the oxidant gas supply flow path. An inlet side sealing valve that seals the flow of the oxidant gas from the compressor to the inlet side of the fuel cell through the junction, and the downstream side of the branch part of the oxidant off-gas discharge channel. And an outlet side sealing valve that seals a flow of the oxidant off-gas from the outlet side of the fuel cell to the exhaust side through the branch portion.
　（２）に係る燃料電池システムによれば、循環流路を閉空間として新たな酸素を導入することなく酸化剤オフガスの循環を行うことができるので、燃料電池のカソード側に残存している酸素および水素を速やかに除いて、長寿命の燃料電池を有する燃料電池システムを得ることができる。 According to the fuel cell system according to (2), since the oxidant off-gas can be circulated without introducing new oxygen using the circulation flow path as a closed space, oxygen remaining on the cathode side of the fuel cell In addition, a fuel cell system having a long-life fuel cell can be obtained by quickly removing hydrogen and hydrogen.
　また、（３）に係る発明は、（１）に記載の燃料電池システムであって、前記循環ポンプは、モータ部のロータおよびステータをキャンで密閉したキャン構造を採る、ことを特徴とする。 Further, the invention according to (3) is the fuel cell system according to (1), wherein the circulation pump adopts a can structure in which a rotor and a stator of a motor unit are sealed with a can.
　（３）に係る燃料電池システムによれば、前記循環ポンプは、モータ部のロータおよびステータをキャンで密閉したキャン構造を採るため、燃料電池、および、循環ポンプにおけるモータ部の一層の長寿命化を図ることができる。 According to the fuel cell system according to (3), since the circulation pump adopts a can structure in which the rotor and stator of the motor unit are sealed with a can, the life of the motor unit in the fuel cell and the circulation pump is further extended. Can be achieved.
　また、（４）に係る発明は、（２）に記載の燃料電池システムであって、前記循環ポンプは、モータ部のロータおよびステータをキャンで密閉したキャン構造を採る、ことを特徴とする。 The invention according to (4) is the fuel cell system according to (2), wherein the circulation pump adopts a can structure in which a rotor and a stator of a motor unit are sealed with a can.
　（４）に係る燃料電池システムによれば、前記循環ポンプは、モータ部のロータおよびステータをキャンで密閉したキャン構造を採るため、燃料電池のカソード側に残存している酸素および水素を速やかに除く効果に加えて、燃料電池、および、循環ポンプにおけるモータ部の一層の長寿命化を図ることができる。 According to the fuel cell system according to (4), since the circulation pump adopts a can structure in which the rotor and the stator of the motor unit are sealed with a can, oxygen and hydrogen remaining on the cathode side of the fuel cell can be quickly removed. In addition to the removal effect, the life of the motor unit in the fuel cell and the circulation pump can be further extended.
　本発明によれば、長寿命の燃料電池を有する燃料電池システムを得ることができる。 According to the present invention, a fuel cell system having a long-life fuel cell can be obtained.
本発明の実施形態に係る燃料電池システムの概略構成図である。1 is a schematic configuration diagram of a fuel cell system according to an embodiment of the present invention. 循環ポンプの内部構成を表す説明図である。It is explanatory drawing showing the internal structure of a circulation pump. 本発明の実施形態に係る燃料電池システムにおいて、通常運転時の空気の流れを表す説明図である。In the fuel cell system concerning the embodiment of the present invention, it is an explanatory view showing the flow of the air at the time of normal operation. 本発明の実施形態に係る燃料電池システムにおいて、運転停止時の空気の流れを表す説明図である。In the fuel cell system concerning the embodiment of the present invention, it is an explanatory view showing the flow of the air at the time of operation stop. 本発明の実施形態に係る燃料電池システムの運転停止時に実行される、ＥＧＲ処理の流れを表すフローチャート図である。It is a flowchart figure showing the flow of the EGR process performed at the time of the driving | operation stop of the fuel cell system which concerns on embodiment of this invention.
　以下、本発明の実施形態に係る燃料電池システムについて、図面を参照して詳細に説明する。 Hereinafter, a fuel cell system according to an embodiment of the present invention will be described in detail with reference to the drawings.
〔本発明の実施形態に係る燃料電池システムの概要〕
　本発明者らの研究によると、燃料電池システムでは、燃料電池の運転停止時において、クロスリークが生じると、カソードで水素と酸素とが反応（酸素の還元反応過程）して過酸化水素（Ｈ2 Ｏ2 ）が生成される。このＨ2 Ｏ2 由来のヒドロキシルラジカル（・ＯＨ）などのラジカル類が、電解質膜を劣化（酸化）させる要因となることがわかった。 [Outline of Fuel Cell System According to Embodiment of the Present Invention]
According to the study by the present inventors, in the fuel cell system, when a cross leak occurs when the fuel cell is stopped, hydrogen reacts with oxygen at the cathode (oxygen reduction reaction process) to generate hydrogen peroxide (H 2 O 2 ) is produced. It has been found that radicals such as hydroxyl radicals (.OH) derived from H 2 O 2 cause deterioration (oxidation) of the electrolyte membrane.
　そこで、本発明者らは、電解質膜の劣化を抑制して燃料電池の長寿命化を図るには、燃料電池の運転停止時において、燃料電池のカソードに残存している酸素および水素（クロスリークによる）を、運転停止時を始期としてできるだけ早期に除くことが重要であると考えた。 Therefore, in order to suppress the deterioration of the electrolyte membrane and extend the life of the fuel cell, the present inventors have proposed that oxygen and hydrogen (cross leak) remaining at the cathode of the fuel cell when the fuel cell is stopped. I thought it was important to remove as early as possible from the time of shutdown.
　また、燃料電池のカソードに残存している酸素および水素を除くには、燃料電池のカソード側に酸化剤オフガスを循環させる循環流路を設け、燃料電池の運転停止時に、循環流路に設けた循環ポンプを駆動させることによって、燃料電池のカソード側に酸化剤オフガスを循環させればよいのでは、との着想を得るに至った。 In addition, in order to remove oxygen and hydrogen remaining on the cathode of the fuel cell, a circulation channel for circulating the oxidant off-gas is provided on the cathode side of the fuel cell, and provided in the circulation channel when the fuel cell is stopped. The idea that the oxidant off-gas should be circulated to the cathode side of the fuel cell by driving the circulation pump has been obtained.
　上記を踏まえて、本発明者らは、さらなる検討を加えた結果、本発明の実施形態に係る燃料電池システムを完成させた。すなわち、本発明の実施形態に係る燃料電池システムは、燃料ガスおよび酸化剤ガスを電気化学的に反応させて発電する燃料電池と、前記燃料電池に対して酸化剤ガスを供給するための酸化剤ガス供給流路と、前記燃料電池から反応後の酸化剤オフガスを排出するための酸化剤オフガス排出流路と、前記酸化剤ガス供給流路に配設され、前記燃料電池に対して酸化剤ガスを供給する電動式のコンプレッサと、前記酸化剤オフガス排出流路に配設される分岐部、および、前記酸化剤ガス供給流路のうち前記コンプレッサの下流側に配設される合流部、の間を連通する循環流路と、前記循環流路に配設され、前記分岐部から前記合流部へと酸化剤オフガスを送り出す循環ポンプと、前記循環流路に配設され、前記分岐部から前記合流部へ向かう順方向に対して逆方向となる酸化剤オフガスの流れを抑制する逆止弁と、前記燃料電池の運転停止時に、前記循環ポンプを駆動させる制御を行う制御部と、を備えて構成されることを最も主要な特徴とする。 Based on the above, the present inventors have further studied and completed the fuel cell system according to the embodiment of the present invention. That is, a fuel cell system according to an embodiment of the present invention includes a fuel cell that generates electricity by electrochemically reacting a fuel gas and an oxidant gas, and an oxidant for supplying the oxidant gas to the fuel cell. A gas supply channel, an oxidant off-gas discharge channel for discharging the reacted oxidant off-gas from the fuel cell, and the oxidant gas supply channel; Between the electric compressor for supplying the gas, the branch portion disposed in the oxidant off-gas discharge passage, and the junction portion disposed on the downstream side of the compressor in the oxidant gas supply passage. A circulation channel that communicates with the circulation channel, a circulation pump that is disposed in the circulation channel and that feeds an oxidant off-gas from the branch portion to the merge portion, and is disposed in the circulation channel and is coupled to the merge portion from the branch portion. The order toward the club A check valve that suppresses the flow of the oxidant off-gas that is in the opposite direction to the direction, and a control unit that performs control to drive the circulation pump when the fuel cell is stopped. The most important feature.
　本発明によれば、燃料電池の運転停止時において、燃料電池のカソード側に酸化剤オフガスを循環させることにより、燃料電池のカソード側に残存している酸素および水素を速やかに除くことができるため、電解質膜の劣化（酸化）を抑制して、長寿命の燃料電池を有する燃料電池システムを得ることができる。 According to the present invention, when the fuel cell is stopped, oxygen and hydrogen remaining on the cathode side of the fuel cell can be quickly removed by circulating the oxidant off-gas to the cathode side of the fuel cell. In addition, it is possible to obtain a fuel cell system having a long-life fuel cell by suppressing deterioration (oxidation) of the electrolyte membrane.
〔本発明の実施形態に係る燃料電池システム１１の概略構成〕
　次に、本発明の実施形態に係る燃料電池システム１１の概略構成について、図１Ａおよび図１Ｂを参照して説明する。図１Ａは、本発明の実施形態に係る燃料電池システム１１の概略構成図である。図１Ｂは、循環ポンプ６９の内部構成を表す説明図である。 [Schematic Configuration of Fuel Cell System 11 According to Embodiment of the Present Invention]
Next, a schematic configuration of the fuel cell system 11 according to the embodiment of the present invention will be described with reference to FIGS. 1A and 1B. FIG. 1A is a schematic configuration diagram of a fuel cell system 11 according to an embodiment of the present invention. FIG. 1B is an explanatory diagram illustrating the internal configuration of the circulation pump 69.
　本発明の実施形態に係る燃料電池システム１１は、図１Ａに示すように、燃料電池スタック（本発明の“燃料電池”に相当する）１３と、アノードガス給排気系１５と、カソードガス給排気系１７と、希釈器１９と、制御部２１と、を備えている。なお、燃料電池システム１１は、不図示の自動車に動力源として搭載される。 As shown in FIG. 1A, a fuel cell system 11 according to an embodiment of the present invention includes a fuel cell stack (corresponding to a “fuel cell” of the present invention) 13, an anode gas supply / exhaust system 15, and a cathode gas supply / exhaust system. A system 17, a diluter 19, and a control unit 21 are provided. The fuel cell system 11 is mounted as a power source in an unillustrated automobile.
　燃料電池スタック１３は、固体高分子型燃料電池（Polymer Electrolyte Fuel Cell：ＰＥＦＣ）であり、図１Ａに示すように、燃料電池セル２３を複数積層して構成される。図１Ａの燃料電池スタック１３の例では、ひとつの燃料電池セル２３を代表的に示している。図１Ａに示す燃料電池セル２３は、相互に対向させて設けた平板状のアノード２５およびカソード２７の間に、例えばフッ素樹脂系の固体高分子電解質膜２９を挟んで構成されている。アノード２５およびカソード２７は、一対のセパレータ３０ａ，３０ｂにより外方側から挟恃される。アノード２５およびカソード２７としては、例えば、導電性カーボン上に、触媒としての白金や白金合金を担持させたものを用いることができる。 The fuel cell stack 13 is a polymer electrolyte fuel cell (Polymer Fuel Cell: PEFC), and is configured by stacking a plurality of fuel cells 23 as shown in FIG. 1A. In the example of the fuel cell stack 13 in FIG. 1A, one fuel cell 23 is representatively shown. The fuel battery cell 23 shown in FIG. 1A is configured by sandwiching, for example, a fluororesin-based solid polymer electrolyte membrane 29 between flat plate-like anodes 25 and a cathode 27 provided to face each other. The anode 25 and the cathode 27 are sandwiched from the outside by a pair of separators 30a and 30b. As anode 25 and cathode 27, what carried platinum or a platinum alloy as a catalyst on conductive carbon can be used, for example.
　燃料電池セル２３のアノード２５では、アノード２５に対して水素Ｈ２　（本発明の“燃料ガス”に相当する）が供給されることにより、式（１）に示す水素Ｈ２　の酸化反応が起こる。
　Ｈ２　　→　２Ｈ＋　　＋　２ｅ－　　　　　　　　　　　　　式（１） In the anode 25 of the fuel cell 23, hydrogen H 2 (corresponding to “fuel gas” of the present invention) is supplied to the anode 25, thereby causing an oxidation reaction of hydrogen H 2 shown in the formula (1). .
H 2 → 2H + + 2e - Formula (1)
　一方、燃料電池セル２３のカソード２７では、カソード２７に対して酸素Ｏ２　（本発明の“酸化剤ガス”に相当する）が供給されることにより、式（２）に示す酸素Ｏ２　の還元反応が起こる。
　２Ｈ＋　　＋　（１／２）Ｏ２　＋　２ｅ－　　→　Ｈ２　Ｏ　　　式（２）
　なお、式（２）中の２Ｈ＋　（水素イオン；プロトン）は、陽イオン交換性（プロトン伝導性）を有する固体高分子電解質膜２９を通してアノード２５の側から供給される。また、式（２）中の２ｅ－　（電子の電荷）は、不図示の導電線を介してアノード２５の側から供給される。 On the other hand, at the cathode 27 of the fuel cell 23, oxygen O 2 (corresponding to the “oxidant gas” of the present invention) is supplied to the cathode 27, whereby the reduction of oxygen O 2 shown in the formula (2) is performed. A reaction takes place.
2H + + (1/2) O 2 + 2e − → H 2 O Formula (2)
2H + (hydrogen ion; proton) in the formula (2) is supplied from the anode 25 side through the solid polymer electrolyte membrane 29 having cation exchange properties (proton conductivity). Further, 2e − (electron charge) in the formula (2) is supplied from the anode 25 side through a conductive line (not shown).
　要するに、燃料電池セル２３において、アノード２５に対して水素Ｈ２　（燃料ガス）が供給される一方、カソード２７に対して酸素Ｏ２　（酸化剤ガス）が供給されると、アノード２５およびカソード２７の間に電位差（ＯＣＶ；Open Circuit Voltage）が生じて、燃料電池スタック１３が発電可能な状態となる。こうして発電可能な状態になった燃料電池スタック１３のアノード２５およびカソード２７が、導電線（不図示）を介して電気負荷（例えば、不図示のバッテリや自動車走行用モータ）に電気的に接続されると、燃料電池スタック１３で発電した直流電力が電気負荷に供給されるように構成されている。 In short, in the fuel cell 23, when hydrogen H 2 (fuel gas) is supplied to the anode 25 and oxygen O 2 (oxidant gas) is supplied to the cathode 27, the anode 25 and the cathode 27 are supplied. An electric potential difference (OCV; Open Circuit Voltage) is generated between the fuel cell stack 13 and the fuel cell stack 13 can generate power. The anode 25 and the cathode 27 of the fuel cell stack 13 in a state capable of generating power in this way are electrically connected to an electric load (for example, a battery or a motor for driving an automobile not shown) via a conductive wire (not shown). Then, the DC power generated by the fuel cell stack 13 is configured to be supplied to the electric load.
〔アノードガス給排気系１５の説明〕
　アノードガス給排気系１５は、燃料電池スタック１３のアノード２５側に対して水素（燃料ガス）を供給しまたは排出する機能を有する。かかる機能を有するアノードガス給排気系１５は、図１Ａに示すように、高圧の水素（燃料ガス）を貯蔵する水素タンク３１と、水素タンク３１および燃料電池スタック１３の入口側１３ａ１の間を連通接続する水素供給配管３３と、水素供給配管３３に配設される遮断弁３４およびエゼクタ３５と、燃料電池スタック１３のアノード２５に沿って設けられるアノードガス流通部３７と、燃料電池スタック１３の出口側１３ａ２および希釈器１９の間を連通接続する水素排出配管３９と、水素排出配管３９に配設される気液分離器４１およびパージ弁４３と、気液分離器４１およびエゼクタ３５の間を連通接続する水素還流配管４５と、を備えている。 [Description of Anode Gas Supply / Exhaust System 15]
The anode gas supply / exhaust system 15 has a function of supplying or discharging hydrogen (fuel gas) to the anode 25 side of the fuel cell stack 13. As shown in FIG. 1A, the anode gas supply / exhaust system 15 having such a function communicates between a hydrogen tank 31 that stores high-pressure hydrogen (fuel gas) and the hydrogen tank 31 and the inlet side 13a1 of the fuel cell stack 13. A hydrogen supply pipe 33 to be connected, a shut-off valve 34 and an ejector 35 provided in the hydrogen supply pipe 33, an anode gas circulation part 37 provided along the anode 25 of the fuel cell stack 13, and an outlet of the fuel cell stack 13 The hydrogen discharge pipe 39 communicating between the side 13a2 and the diluter 19, the gas-liquid separator 41 and the purge valve 43 disposed in the hydrogen discharge pipe 39, and the gas-liquid separator 41 and the ejector 35 are communicated. And a hydrogen reflux pipe 45 to be connected.
　水素タンク３１は、水素（燃料ガス）の供給源としての機能を有する。遮断弁３４は、水素タンク３１に貯蔵された高圧の水素を、適正な圧力に調整して供給し、または、供給を遮断する機能を有する。エゼクタ３５は、水素タンク３１から供給される水素と、水素還流配管４５を介して還流される水素（燃料オフガス）とを混合して再循環させる機能を有する。エゼクタ３５で混合された水素は、燃料電池スタック１３のアノード２５に供給される。アノードガス流通部３７は、そこに流通する水素（アノードガス）をアノード２５に対して直に接触させる機能を有する。 The hydrogen tank 31 functions as a hydrogen (fuel gas) supply source. The shut-off valve 34 has a function of supplying high-pressure hydrogen stored in the hydrogen tank 31 to an appropriate pressure, or shutting off the supply. The ejector 35 has a function of mixing and recirculating the hydrogen supplied from the hydrogen tank 31 and the hydrogen (fuel offgas) recirculated through the hydrogen recirculation pipe 45. The hydrogen mixed by the ejector 35 is supplied to the anode 25 of the fuel cell stack 13. The anode gas circulation part 37 has a function of bringing hydrogen (anode gas) flowing therethrough into direct contact with the anode 25.
　気液分離器４１は、燃料電池スタック１３から排出されてきた水素（アノードオフガス）から、そこに含まれる水分（結露水）を分離する機能を有する。気液分離器４１で分離回収された水分は、例えば、気液分離器４１が有する不図示のタンク部に一時的に貯留された後、不図示の配管を介して希釈器１９に排出される。 The gas-liquid separator 41 has a function of separating water (condensation water) contained therein from hydrogen (anode offgas) discharged from the fuel cell stack 13. The water separated and recovered by the gas-liquid separator 41 is temporarily stored in a tank section (not shown) of the gas-liquid separator 41, for example, and then discharged to the diluter 19 via a pipe (not shown). .
　パージ弁４３は、燃料電池スタック１３の通常運転時（通常発電時）において、燃料電池スタック１３から排出されてきた水素（燃料オフガス）に含まれる窒素等の不純物を排出（パージ）する機能を有する。 The purge valve 43 has a function of discharging (purging) impurities such as nitrogen contained in hydrogen (fuel offgas) discharged from the fuel cell stack 13 during normal operation of the fuel cell stack 13 (during normal power generation). .
　なお、パージ弁４３は、燃料オフガス中の不純物濃度が所定値以下である通常時には閉止されている。換言すれば、パージ弁４３は、燃料オフガス中の不純物濃度が所定値を超える異常時に開放されるように動作する。燃料オフガス中の不純物濃度は、アノードオフガス中の水素の濃度を検出する不図示の水素濃度センサの検出値に基づいて算出すればよい。 The purge valve 43 is closed at normal times when the impurity concentration in the fuel off-gas is not more than a predetermined value. In other words, the purge valve 43 operates so as to be opened at the time of abnormality when the impurity concentration in the fuel off gas exceeds a predetermined value. The impurity concentration in the fuel off gas may be calculated based on the detection value of a hydrogen concentration sensor (not shown) that detects the concentration of hydrogen in the anode off gas.
〔カソードガス給排気系１７の説明〕
　カソードガス給排気系１７は、燃料電池スタック１３のカソード２７に酸素を含む空気（酸化剤ガス）を供給すると共に、該供給した酸素を含む空気をカソード２７から排出する機能を有する。かかる機能を有するカソードガス給排気系１７は、図１Ａに示すように、電動式のコンプレッサ５１と、コンプレッサ５１および燃料電池スタック１３の間を連通接続する空気供給配管（本発明の“酸化剤ガス供給流路”に相当する）５３と、入口側封止弁５５と、カソードガス流通部５７と、燃料電池スタック１３および希釈器１９の間を連通接続する空気排出配管（本発明の“酸化剤オフガス排出流路”に相当する）５９と、出口側封止弁６１と、背圧弁６３と、加湿器６５と、空気供給配管５３および空気排出配管５９の間を連通接続する空気還流配管（本発明の“循環流路”に相当する）６７と、循環ポンプ６９と、逆止弁７１と、を備えている。 [Description of Cathode Gas Supply / Exhaust System 17]
The cathode gas supply / exhaust system 17 has a function of supplying air (oxidant gas) containing oxygen to the cathode 27 of the fuel cell stack 13 and discharging the supplied air containing oxygen from the cathode 27. As shown in FIG. 1A, the cathode gas supply / exhaust system 17 having such a function includes an electric compressor 51 and an air supply pipe (communication gas oxidizer gas of the present invention) that connects the compressor 51 and the fuel cell stack 13 in communication. (Corresponding to the “supply channel”) 53, the inlet side sealing valve 55, the cathode gas flow part 57, and the air discharge pipe (the “oxidant” of the present invention) that connects the fuel cell stack 13 and the diluter 19 in communication. An air recirculation pipe (this corresponds to an “off gas discharge flow path”) 59, an outlet side sealing valve 61, a back pressure valve 63, a humidifier 65, an air supply pipe 53 and an air discharge pipe 59. 67 (corresponding to “circulation flow path” of the invention), a circulation pump 69, and a check valve 71.
　コンプレッサ５１は、空気導入口５１ａから取り込んだ空気を圧縮して、燃料電池スタック１３へと送り出す機能を有する。 The compressor 51 has a function of compressing the air taken in from the air introduction port 51 a and sending it out to the fuel cell stack 13.
　入口側封止弁５５は、空気供給配管５３のうちコンプレッサ５１の下流側かつ合流部７５の上流側に配設されている。入口側封止弁５５は、コンプレッサ５１から後記する合流部７５を経て燃料電池スタック１３の入口側１３ｃ１へ向かう新しい空気（酸化剤ガス）の流れを封止する機能を有する。 The inlet side sealing valve 55 is disposed in the air supply pipe 53 on the downstream side of the compressor 51 and on the upstream side of the merging portion 75. The inlet-side sealing valve 55 has a function of sealing a flow of new air (oxidant gas) from the compressor 51 to the inlet side 13c1 of the fuel cell stack 13 via a junction 75 described later.
　なお、入口側封止弁５５は、燃料電池スタック１３の通常発電時には開放されている。ただし、入口側封止弁５５は、燃料電池スタック１３の発電停止時に、閉止されるように動作する。その理由について、詳しくは後記する。カソードガス流通部５７は、燃料電池スタック１３のカソード２７に沿って設けられ、そこに流通する酸素を含む空気（カソードガス）をカソード２７に対して直に接触させる機能を有する。 The inlet side sealing valve 55 is opened during normal power generation of the fuel cell stack 13. However, the inlet side sealing valve 55 operates so as to be closed when power generation of the fuel cell stack 13 is stopped. The reason will be described later in detail. The cathode gas circulation unit 57 is provided along the cathode 27 of the fuel cell stack 13 and has a function of bringing air containing oxygen (cathode gas) flowing therethrough directly into contact with the cathode 27.
　出口側封止弁６１は、空気排出配管５９のうち分岐部７３の下流側かつ加湿器６５の上流側に配設されている。出口側封止弁６１は、燃料電池スタック１３の出口側１３ｃ２から後記する分岐部７３を経て希釈器１９の排気側へ向かう古い空気（酸化剤オフガス）の流れを封止する機能を有する。 The outlet side sealing valve 61 is disposed on the downstream side of the branching portion 73 and on the upstream side of the humidifier 65 in the air discharge pipe 59. The outlet side sealing valve 61 has a function of sealing the flow of old air (oxidant offgas) from the outlet side 13c2 of the fuel cell stack 13 to the exhaust side of the diluter 19 through a branching portion 73 described later.
　なお、出口側封止弁６１は、入口側封止弁５５と同様に、燃料電池スタック１３の通常発電時には開放されている。ただし、出口側封止弁６１は、入口側封止弁５５と同様に、燃料電池スタック１３の運転停止時（発電停止時）に、閉止されるように動作する。その理由について、詳しくは後記する。 The outlet side sealing valve 61 is opened during normal power generation of the fuel cell stack 13, similarly to the inlet side sealing valve 55. However, similarly to the inlet side sealing valve 55, the outlet side sealing valve 61 operates so as to be closed when the operation of the fuel cell stack 13 is stopped (when power generation is stopped). The reason will be described later in detail.
　入口側封止弁５５および出口側封止弁６１としては、常時閉止式（ノーマルクローズ）の電磁弁を好適に用いることができる。入口側封止弁５５および出口側封止弁６１は、燃料電池スタック１３の運転停止時において、閉止動作を継続することが望ましいところ、この閉止動作を継続させる際に、電力を要せず節電に寄与することができるからである。 As the inlet-side sealing valve 55 and the outlet-side sealing valve 61, a normally closed solenoid valve can be suitably used. The inlet side sealing valve 55 and the outlet side sealing valve 61 are preferably kept closed when the operation of the fuel cell stack 13 is stopped. When this closing action is continued, no power is required and power is saved. It is because it can contribute to.
　背圧弁６３は、空気排出配管５９のうち加湿器６５の下流側かつ希釈器１９の上流側に配設されている。背圧弁６３は、カソードガス流通部５７における空気の流速（圧力）を調整する機能を有する。背圧弁６３は、例えば、絞り量を可変調整可能な絞り弁により構成することができる。 The back pressure valve 63 is disposed downstream of the humidifier 65 and upstream of the diluter 19 in the air discharge pipe 59. The back pressure valve 63 has a function of adjusting the flow velocity (pressure) of air in the cathode gas circulation portion 57. The back pressure valve 63 can be configured by, for example, a throttle valve that can variably adjust the throttle amount.
　加湿器６５は、空気供給配管５３および空気排出配管５９を跨ぐように配設されている。加湿器６５は、コンプレッサ５１からカソードガス流通部５７へ向う空気を加湿する機能を有する。本実施形態で用いられる固体高分子電解質膜２９は、含水状態において良好な陽イオン交換性（プロトン伝導性）を発揮して、燃料電池スタック１３の発電効率を高めるように働く。したがって、加湿器６５は、燃料電池スタック１３の通常運転時において、固体高分子電解質膜２９を含水状態に維持することを通じて、燃料電池スタック１３の発電効率を高めることができる。 The humidifier 65 is disposed so as to straddle the air supply pipe 53 and the air discharge pipe 59. The humidifier 65 has a function of humidifying the air from the compressor 51 toward the cathode gas circulation part 57. The solid polymer electrolyte membrane 29 used in the present embodiment works to increase the power generation efficiency of the fuel cell stack 13 by exhibiting good cation exchange properties (proton conductivity) in a water-containing state. Therefore, the humidifier 65 can increase the power generation efficiency of the fuel cell stack 13 by maintaining the solid polymer electrolyte membrane 29 in a water-containing state during normal operation of the fuel cell stack 13.
　詳しく述べると、加湿器６５は、不図示の中空糸膜を内部に有する。この中空糸膜を介して、カソードガス流通部５７に向う（比較的乾燥した）空気と、カソードガス流通部５７から排出された多湿の空気（酸化剤オフガス）との間で水分の交換が行われるように構成されている。 More specifically, the humidifier 65 has a hollow fiber membrane (not shown) inside. Through this hollow fiber membrane, moisture is exchanged between the air (relatively dry) toward the cathode gas circulation part 57 and the humid air (oxidant off-gas) discharged from the cathode gas circulation part 57. It is configured to be
　循環ポンプ６９は、空気還流配管６７に設けられている。循環ポンプ６９は、燃料電池スタック１３の運転停止時（発電停止時）に、後記のモータ部９３（図１Ｂ参照）の駆動によって、燃料電池スタック１３の出口側１３ｃ２から排出された空気（酸化剤オフガス）を、分岐部７３から合流部７５へ向けて送り出す機能を有する。循環ポンプ６９は、図１Ｂに示すように、ケーシング７９内に、送気タービン８１と、送気タービン８１に固着される駆動軸８３と、一対の軸受け８５，８７と、ロータ８９およびステータ９１を含んで構成されるモータ部９３と、を備えて構成されている。 The circulation pump 69 is provided in the air recirculation pipe 67. When the operation of the fuel cell stack 13 is stopped (when power generation is stopped), the circulation pump 69 is driven by a motor unit 93 (see FIG. 1B) described later to discharge air (oxidant) from the outlet side 13c2 of the fuel cell stack 13. Off-gas) from the branching portion 73 toward the merging portion 75. As shown in FIG. 1B, the circulation pump 69 includes an air supply turbine 81, a drive shaft 83 fixed to the air supply turbine 81, a pair of bearings 85 and 87, a rotor 89, and a stator 91 in a casing 79. A motor unit 93 configured to include the motor unit 93.
　送気タービン８１の駆動軸８３は、例えば一対の軸受け８５，８７をそれぞれ介して回転自在に軸支される。駆動軸８３は、モータ部９３により回転駆動される。要するに、送気タービン８１は、駆動軸８３を介して、モータ部９３により回転駆動される。 The drive shaft 83 of the air supply turbine 81 is rotatably supported via a pair of bearings 85 and 87, for example. The drive shaft 83 is rotationally driven by the motor unit 93. In short, the air supply turbine 81 is rotationally driven by the motor unit 93 via the drive shaft 83.
　図１Ｂに示す循環ポンプ６９の駆動時（燃料電池スタック１３の運転停止時）において、入口側封止弁５５および出口側封止弁６１は、空気供給配管５３および空気排出配管５９をそれぞれ閉止するように動作する。その結果、燃料電池システム１１には、空気供給配管５３→燃料電池スタック１３の入口側１３ｃ１→カソードガス流通部５７→燃料電池スタック１３の出口側１３ｃ２→空気排出配管５９→分岐部７３→空気還流配管６７→合流部７５→空気供給配管５３を順次通る環状の空気流通路７７（図１Ａ参照）が形成される。これにより、空気流通路７７に残留した気体は、燃料電池スタック１３の運転停止時に、閉塞された空気流通路７７内を、後記の所定時間にわたり循環するように構成されている。 When the circulation pump 69 shown in FIG. 1B is driven (when the operation of the fuel cell stack 13 is stopped), the inlet side sealing valve 55 and the outlet side sealing valve 61 close the air supply pipe 53 and the air discharge pipe 59, respectively. To work. As a result, in the fuel cell system 11, the air supply pipe 53 → the inlet side 13c1 of the fuel cell stack 13 → the cathode gas circulation part 57 → the outlet side 13c2 of the fuel cell stack 13 → the air discharge pipe 59 → the branching part 73 → air reflux. An annular air flow passage 77 (see FIG. 1A) is formed that sequentially passes through the pipe 67 → the joining portion 75 → the air supply pipe 53. As a result, the gas remaining in the air flow passage 77 is configured to circulate in the closed air flow passage 77 for a predetermined time described later when the operation of the fuel cell stack 13 is stopped.
　循環ポンプ６９としては、図１Ｂに示すように、モータ部９３のロータ８９およびステータ９１を、円筒状のキャン（隔壁）９５を介して密閉したキャン構造を採るものを用いる。循環ポンプ６９により送出される空気（酸化剤オフガス）は、燃料電池スタック１３に導入される空気と比べて水分を多く含んでいる。この水分が循環ポンプ６９におけるモータ部９３のステータ９１へと進入すると、モータ部９３の損傷を招来する。そこで、循環ポンプ６９として前記のキャン構造を採用することにより、モータ部９３の長寿命化を図っている。 As the circulation pump 69, as shown in FIG. 1B, a pump having a can structure in which the rotor 89 and the stator 91 of the motor section 93 are sealed via a cylindrical can (partition wall) 95 is used. The air (oxidant off-gas) delivered by the circulation pump 69 contains more moisture than the air introduced into the fuel cell stack 13. When this moisture enters the stator 91 of the motor part 93 in the circulation pump 69, the motor part 93 is damaged. Therefore, by adopting the above can structure as the circulation pump 69, the life of the motor section 93 is extended.
　逆止弁７１は、空気還流配管６７に設けられている。逆止弁７１は、燃料電池スタック１３の通常運転時（通常発電時）において、分岐部７３から合流部７５へ向かう順方向に対して逆方向となる空気の流れを抑制する機能を有する。燃料電池スタック１３の通常運転時において、分岐部７３から合流部７５へ向かう順方向に対して逆方向となる空気の流れが生じると、カソードガス流通部５７に向う空気の流量が減少する。その結果、燃料電池スタック１３における発電効率の低下を招来する。要するに、逆止弁７１は、燃料電池スタック１３における発電効率の低下を抑制する目的で設けられている。
　逆止弁７１としては、節電に寄与する観点から、動力を要しない機械式のものを好適に用いることができる。 The check valve 71 is provided in the air recirculation pipe 67. The check valve 71 has a function of suppressing the air flow in the reverse direction with respect to the forward direction from the branching portion 73 toward the merging portion 75 during normal operation of the fuel cell stack 13 (during normal power generation). During the normal operation of the fuel cell stack 13, if an air flow is generated that is in the opposite direction to the forward direction from the branching portion 73 toward the merging portion 75, the air flow rate toward the cathode gas circulation portion 57 decreases. As a result, the power generation efficiency in the fuel cell stack 13 is reduced. In short, the check valve 71 is provided for the purpose of suppressing a decrease in power generation efficiency in the fuel cell stack 13.
As the check valve 71, a mechanical valve that does not require power can be preferably used from the viewpoint of contributing to power saving.
　分岐部７３および合流部７５としては、例えば、Ｔ字形状の継手を用いることができる。分岐部７３は、空気排出配管５９のうち、燃料電池スタック１３の出口側１３ｃ２近傍に設けるのが好ましい。同様に、合流部７５は、空気供給配管５３のうち、燃料電池スタック１３の入口側１３ｃ１近傍に設けるのが好ましい。環状の空気流通路７７を狭隘な（容積の小さい）閉空間とすることにより、閉塞された空気流通路７７に残留した気体中の、カソード２７側で反応に寄与するガス（酸素および水素）の濃度を速やかに低下させることができるからである。 As the branch part 73 and the junction part 75, for example, a T-shaped joint can be used. The branch portion 73 is preferably provided in the vicinity of the outlet side 13c2 of the fuel cell stack 13 in the air discharge pipe 59. Similarly, the merging portion 75 is preferably provided in the vicinity of the inlet side 13 c 1 of the fuel cell stack 13 in the air supply pipe 53. By making the annular air flow passage 77 a narrow (small volume) closed space, the gas (oxygen and hydrogen) contributing to the reaction on the cathode 27 side in the gas remaining in the closed air flow passage 77 is reduced. This is because the concentration can be lowered quickly.
　希釈器１９は、パージ弁４３が開放状態のときに希釈器１９に導入される燃料オフガス（水素）を、空気排出配管５９を介して燃料電池スタック１３の出口側１３ｃ２から排出される酸化剤オフガス（空気）で希釈する機能を有する。酸化剤オフガス（空気）で所定の濃度以下まで希釈された燃料オフガス（水素）は、大気中に排気される。 The diluter 19 discharges the fuel off-gas (hydrogen) introduced into the diluter 19 when the purge valve 43 is open from the outlet side 13c2 of the fuel cell stack 13 through the air discharge pipe 59. It has a function of diluting with (air). The fuel off-gas (hydrogen) diluted to a predetermined concentration or less with the oxidant off-gas (air) is exhausted into the atmosphere.
　制御部２１は、アノードガス給排気系１５およびカソードガス給排気系１７に属する弁やモータを含む各部材の動作制御を行う機能を有する。制御部２１は、不図示のＣＰＵ（Central processing Unit）、ＲＯＭ（Read Only Memory）、ＲＡＭ（Random Access Memory）、入出力回路（Ａ／Ｄ変換器およびＤ／Ａ変換器を含む）などを備えて構成される。ＣＰＵは、ＲＯＭに格納されたプログラムに従って、ＲＡＭを作業領域として用いて、弁やモータを含む各部材の動作制御を実行する。 The control unit 21 has a function of controlling the operation of each member including valves and motors belonging to the anode gas supply / exhaust system 15 and the cathode gas supply / exhaust system 17. The control unit 21 includes a CPU (Central processing Unit) (not shown), a ROM (Read Only Memory), a RAM (Random Access Memory), an input / output circuit (including an A / D converter and a D / A converter), and the like. Configured. The CPU executes operation control of each member including a valve and a motor using the RAM as a work area in accordance with a program stored in the ROM.
　詳しく述べると、制御部２１は、燃料オフガス中の不純物濃度（窒素など）が所定値を超える異常時にパージ弁４３を開放動作させる制御を行う。また、制御部２１は、燃料電池スタック１３の通常発電時に、コンプレッサ５１のモータ部を駆動させる制御を行う。また、制御部２１は、入口側封止弁５５および出口側封止弁６１を、燃料電池スタック１３の通常発電時に開放させる一方、燃料電池スタック１３の発電停止時に閉止させる制御を行う。また、制御部２１は、燃料電池スタック１３の通常発電時に、背圧弁（絞り弁）６３の絞り量を調整させる制御を行う。そして、制御部２１は、燃料電池スタック１３の発電停止時に、循環ポンプ６９のモータ部９３を駆動させる制御を行う。 More specifically, the control unit 21 performs a control to open the purge valve 43 when an impurity concentration (such as nitrogen) in the fuel off gas exceeds a predetermined value. In addition, the control unit 21 performs control to drive the motor unit of the compressor 51 during normal power generation of the fuel cell stack 13. In addition, the control unit 21 performs control to open the inlet side sealing valve 55 and the outlet side sealing valve 61 during normal power generation of the fuel cell stack 13 while closing the fuel cell stack 13 when power generation is stopped. Further, the control unit 21 performs control to adjust the throttle amount of the back pressure valve (throttle valve) 63 during normal power generation of the fuel cell stack 13. And the control part 21 performs control which drives the motor part 93 of the circulation pump 69 at the time of the electric power generation stop of the fuel cell stack 13. FIG.
〔本発明の実施形態に係る燃料電池システム１１の動作〕
　上述のように構成された本発明の実施形態に係る燃料電池システム１１の動作について、図２Ａ、図２Ｂ、および図３を参照して説明する。図２Ａは、本発明の実施形態に係る燃料電池システム１１において、通常運転時の空気の流れを表す説明図である。図２Ｂは、本発明の実施形態に係る燃料電池システム１１において、運転停止時の空気の流れを表す説明図である。図３は、本発明の実施形態に係る燃料電池システム１１の運転停止時に実行される、ＥＧＲ処理の流れを表すフローチャート図である。 [Operation of Fuel Cell System 11 According to Embodiment of the Present Invention]
The operation of the fuel cell system 11 according to the embodiment of the present invention configured as described above will be described with reference to FIGS. 2A, 2B, and 3. FIG. FIG. 2A is an explanatory diagram showing the air flow during normal operation in the fuel cell system 11 according to the embodiment of the present invention. FIG. 2B is an explanatory diagram showing the flow of air when operation is stopped in the fuel cell system 11 according to the embodiment of the present invention. FIG. 3 is a flowchart showing the flow of the EGR process that is executed when the operation of the fuel cell system 11 according to the embodiment of the present invention is stopped.
　なお、本発明の実施形態に係る燃料電池システム１１において、燃料電池スタック１３のカソード２７側に残存している酸素および水素を速やかに除くための動作は、カソードガス給排気系１７において行われる。そのため、図２Ａおよび図２Ｂにおいて、アノードガス給排気系１５の図示を省略している。 In the fuel cell system 11 according to the embodiment of the present invention, the operation for quickly removing oxygen and hydrogen remaining on the cathode 27 side of the fuel cell stack 13 is performed in the cathode gas supply / exhaust system 17. Therefore, the anode gas supply / exhaust system 15 is not shown in FIGS. 2A and 2B.
　燃料電池システム１１の通常運転時における各部の動作は以下の通りである。すなわち、図２Ａに示すように、コンプレッサ５１は、空気供給配管５３（入口側封止弁５５は開放）を通して燃料電池スタック１３へと空気を送り出す。コンプレッサ５１により送り出された空気は、加湿器６５を通って加湿された後、燃料電池スタック１３の入口側１３ｃ１に導入される。その後、燃料電池スタック１３のカソードガス流通部５７に導入された酸素を含む空気は、カソード２７に接触して電気化学反応（酸素の還元反応）に利用される。 The operation of each part during normal operation of the fuel cell system 11 is as follows. That is, as shown in FIG. 2A, the compressor 51 sends air to the fuel cell stack 13 through the air supply pipe 53 (the inlet side sealing valve 55 is opened). The air sent out by the compressor 51 is humidified through the humidifier 65 and then introduced into the inlet side 13 c 1 of the fuel cell stack 13. Thereafter, the oxygen-containing air introduced into the cathode gas circulation part 57 of the fuel cell stack 13 contacts the cathode 27 and is used for an electrochemical reaction (oxygen reduction reaction).
　カソードガス流通部５７を通過した使用済みの空気は、燃料電池スタック１３の出口側１３ｃ２から空気排出配管５９（出口側封止弁６１は開放）を通して排出される。こうして排出された空気は、加湿器６５において新たに供給される空気を加湿した後、背圧弁６３を通して希釈器１９へと導入される。 Used air that has passed through the cathode gas circulation part 57 is discharged from the outlet side 13c2 of the fuel cell stack 13 through the air discharge pipe 59 (the outlet side sealing valve 61 is opened). The air thus discharged is introduced into the diluter 19 through the back pressure valve 63 after humidifying the newly supplied air in the humidifier 65.
　要するに、燃料電池システム１１の通常運転時には、図２Ａに示すように、コンプレッサ５１→加湿器６５→空気供給配管５３の入口側封止弁５５→燃料電池スタック１３の入口側１３ｃ１→カソードガス流通部５７→燃料電池スタック１３の出口側１３ｃ２→空気排出配管５９の出口側封止弁６１→（背圧弁６３→希釈器１９→排気；ただし、本かっこ内の経路は図２Ａにおいて省略のため、図１Ａ参照）を順次通る空気流通路９７（図１Ａおよび図２Ａ参照）が形成される。 In short, during normal operation of the fuel cell system 11, as shown in FIG. 2A, compressor 51 → humidifier 65 → air supply piping 53 inlet side sealing valve 55 → fuel cell stack 13 inlet side 13c1 → cathode gas circulation section 57 → outlet side 13c2 of the fuel cell stack 13 → outlet side sealing valve 61 of the air discharge pipe 59 → (back pressure valve 63 → diluter 19 → exhaust; however, the path in the parenthesis is omitted in FIG. 1A) (see FIG. 1A), an air flow passage 97 (see FIGS. 1A and 2A) is formed.
　一方、燃料電池システム１１の運転停止時における各部の動作は、以下の通りである。すなわち、図２Ｂに示すように、循環ポンプ６９は、燃料電池スタック１３の出口側１３ｃ２から排出された空気（酸化剤オフガス）を、分岐部７３から合流部７５へ向けて送り出す。このとき、入口側封止弁５５および出口側封止弁６１は、共に閉止されている。そのため、循環ポンプ６９により送り出された空気（酸化剤オフガス）は、燃料電池スタック１３の入口側１３ｃ１に導入される。 On the other hand, the operation of each part when the operation of the fuel cell system 11 is stopped is as follows. That is, as shown in FIG. 2B, the circulation pump 69 sends out air (oxidant offgas) discharged from the outlet side 13 c 2 of the fuel cell stack 13 from the branch portion 73 toward the junction portion 75. At this time, both the inlet side sealing valve 55 and the outlet side sealing valve 61 are closed. Therefore, the air (oxidant off-gas) sent out by the circulation pump 69 is introduced into the inlet side 13 c 1 of the fuel cell stack 13.
　したがって、燃料電池システム１１には、空気供給配管５３→燃料電池スタック１３の入口側１３ｃ１→カソードガス流通部５７→燃料電池スタック１３の出口側１３ｃ２→空気排出配管５９→分岐部７３→空気還流配管６７→合流部７５→空気供給配管５３を順次通る環状の空気流通路７７（図１Ａおよび図２Ｂ参照）が形成される。これにより、空気流通路７７に残留した気体は、燃料電池スタック１３の運転停止時に、閉塞された空気流通路７７内を循環するように動作する。 Therefore, in the fuel cell system 11, the air supply pipe 53 → the inlet side 13c1 of the fuel cell stack 13 → the cathode gas circulation part 57 → the outlet side 13c2 of the fuel cell stack 13 → the air discharge pipe 59 → the branch part 73 → the air recirculation pipe. An annular air flow passage 77 (see FIGS. 1A and 2B) is formed that sequentially passes through 67 → merging portion 75 → air supply pipe 53. Thus, the gas remaining in the air flow passage 77 operates so as to circulate in the closed air flow passage 77 when the operation of the fuel cell stack 13 is stopped.
　この循環の際に、燃料電池スタック１３のカソードガス流通部５７に導入される、空気流通路７７に残留した気体（酸素、および、クロスリークなどによりカソード２７側に生じた水素）は、閉塞された空気流通路７７内において、カソード２７に接触して電気化学反応（酸素の還元反応）に繰り返し利用される。すると、空気流通路７７に残留した気体中の酸素や水素は、カソード２７に対する接触機会（接触時間）を増やすという意味での電気化学反応（酸素の還元反応）の促進を通じて、その量（濃度）を低減させる。したがって、燃料電池スタック１３のカソード２７側に残存している酸素および水素を速やかに除くことができる。 During this circulation, the gas remaining in the air flow passage 77 (hydrogen generated on the cathode 27 side due to oxygen and cross leak) introduced into the cathode gas circulation portion 57 of the fuel cell stack 13 is blocked. In the air flow passage 77, it contacts the cathode 27 and is repeatedly used for electrochemical reaction (oxygen reduction reaction). Then, the amount (concentration) of oxygen and hydrogen in the gas remaining in the air flow passage 77 through the promotion of an electrochemical reaction (oxygen reduction reaction) in the sense of increasing the chance of contact with the cathode 27 (contact time). Reduce. Therefore, oxygen and hydrogen remaining on the cathode 27 side of the fuel cell stack 13 can be quickly removed.
〔ＥＧＲ処理の流れ〕
　次に、燃料電池システム１１の運転停止時に実行される、ＥＧＲ処理の流れについて、図３を参照して説明する。図３は、本発明の実施形態に係る燃料電池システム１１の運転停止時に実行される、ＥＧＲ処理の流れを表すフローチャート図である。
　なお、本発明の実施形態でいうＥＧＲ（Exhaust Gas Recirculation）処理とは、燃料電池システム１１の運転停止時に、排気を再循環させる処理をいう。 [Flow of EGR processing]
Next, the flow of the EGR process that is executed when the operation of the fuel cell system 11 is stopped will be described with reference to FIG. FIG. 3 is a flowchart showing the flow of the EGR process that is executed when the operation of the fuel cell system 11 according to the embodiment of the present invention is stopped.
The EGR (Exhaust Gas Recirculation) process in the embodiment of the present invention refers to a process of recirculating exhaust gas when the fuel cell system 11 is stopped.
　ステップＳ１１において、制御部２１は、燃料電池システム１１の通常運転中に、運転停止に係る指令信号が入力されたか否かを監視している。なお、制御部２１は、例えば、イグニッションスイッチ１０１（図１Ａ参照）のオフが入力された場合に、運転停止に係る指令信号が入力されたとみなして、ＥＧＲ処理を開始（ステップＳ１１の“Ｙｅｓ”参照）させる。つまり、制御部２１は、ステップＳ１１の監視の結果、イグニッションスイッチ１０１のオフが入力された場合に、処理の流れをステップＳ１２へと進ませる。 In step S <b> 11, the control unit 21 monitors whether or not a command signal related to operation stop is input during normal operation of the fuel cell system 11. For example, when the ignition switch 101 (see FIG. 1A) is turned off, the control unit 21 considers that a command signal related to operation stop has been input, and starts the EGR process (“Yes” in step S11). See). That is, as a result of the monitoring in step S11, the control unit 21 advances the process flow to step S12 when the ignition switch 101 is turned off.
　ステップＳ１２において、制御部２１は、入口側封止弁５５を閉止させるように動作する。これにより、入口側封止弁５５は、コンプレッサ５１から合流部７５を経て燃料電池スタック１３の入口側１３ｃ１へ向かう新しい空気（酸化剤ガス）の流れを封止する。 In step S12, the control unit 21 operates to close the inlet side sealing valve 55. Thereby, the inlet side sealing valve 55 seals the flow of new air (oxidant gas) from the compressor 51 via the junction 75 to the inlet side 13c1 of the fuel cell stack 13.
　ステップＳ１３において、制御部２１は、出口側封止弁６１を閉止させるように動作する。これにより、出口側封止弁６１は、燃料電池スタック１３の出口側１３ｃ２から分岐部７３を経て希釈器１９の排気側へ向かう古い空気（酸化剤オフガス）の流れを封止する。 In step S13, the control unit 21 operates to close the outlet side sealing valve 61. Thereby, the outlet side sealing valve 61 seals the flow of old air (oxidant off-gas) from the outlet side 13c2 of the fuel cell stack 13 to the exhaust side of the diluter 19 via the branching portion 73.
　なお、前記したステップＳ１２およびＳ１３の処理は、時間的に同時に行ってもよいし、相互に時間間隔をおいて順次行ってもよい。また、相互に時間間隔をおいて順次行う態様を採用する場合に、ステップＳ１３の後に、ステップＳ１２の処理を行ってもよい。 Note that the processes of steps S12 and S13 described above may be performed simultaneously in time, or may be performed sequentially with a time interval therebetween. Further, in the case of adopting a mode of sequentially performing time intervals with each other, the process of step S12 may be performed after step S13.
　ステップＳ１４において、制御部２１は、循環ポンプ６９のモータ部９３を駆動させるように動作する。これにより、循環ポンプ６９は、燃料電池スタック１３の出口側１３ｃ２から排出された空気（酸化剤オフガス）を、分岐部７３から合流部７５へ向けて送り出す。その結果、燃料電池システム１１には、環状の空気流通路７７（図１Ａおよび図２Ｂ参照）が形成される。したがって、空気流通路７７に残留した気体は、燃料電池スタック１３の運転停止時に、閉塞された空気流通路７７内を循環する。 In step S14, the control unit 21 operates to drive the motor unit 93 of the circulation pump 69. As a result, the circulation pump 69 sends out air (oxidant off-gas) discharged from the outlet side 13c2 of the fuel cell stack 13 from the branching portion 73 toward the joining portion 75. As a result, an annular air flow passage 77 (see FIGS. 1A and 2B) is formed in the fuel cell system 11. Therefore, the gas remaining in the air flow passage 77 circulates in the closed air flow passage 77 when the operation of the fuel cell stack 13 is stopped.
　ステップＳ１５において、制御部２１は、循環ポンプ６９の駆動開始時点から予め設定される所定時間が経過したか否かを判定する。この所定時間は、空気流通路７７の容量、残留した気体中の酸素および水素の成分比、循環ポンプ６９の送出速度、触媒（例えば白金など）の活性などを考慮して、例えば実験や模擬試験（シミュレーション）による検証結果を踏まえて、残留した気体中の、触媒を介した電気化学的な反応に関連する酸素および水素の濃度が十分に低下することを考慮して、適宜変更可能な時間長（例えば１～３分間など）に設定すればよい。 In step S15, the control unit 21 determines whether or not a predetermined time set in advance has elapsed since the start of driving of the circulation pump 69. This predetermined time takes into account the capacity of the air flow passage 77, the component ratio of oxygen and hydrogen in the remaining gas, the delivery speed of the circulation pump 69, the activity of the catalyst (for example, platinum), etc. Based on the results of verification by (simulation), taking into account that the oxygen and hydrogen concentrations related to the electrochemical reaction through the catalyst in the remaining gas are sufficiently reduced, the time can be changed as appropriate (For example, 1 to 3 minutes) may be set.
　ステップＳ１５の判定の結果、循環ポンプ６９の駆動開始時点から予め設定される所定時間が経過した旨の判定が下された場合に、制御部２１は、処理の流れをステップＳ１６へと進ませる。 If it is determined in step S15 that a predetermined time has elapsed since the start of driving of the circulation pump 69, the control unit 21 advances the process flow to step S16.
　ステップＳ１６において、制御部２１は、循環ポンプ６９の駆動を停止させるように動作する。これにより、循環ポンプ６９は、その駆動を停止する。その結果、空気流通路７７に残留した気体は、閉塞された空気流通路７７内にそのまま滞留する。ただし、空気流通路７７に残留した気体中について、カソード２７側で反応に寄与するガス（酸素および水素）の濃度は十分に低下している。 In step S16, the control unit 21 operates to stop the driving of the circulation pump 69. Thereby, the circulation pump 69 stops its drive. As a result, the gas remaining in the air flow passage 77 stays in the closed air flow passage 77 as it is. However, in the gas remaining in the air flow passage 77, the concentration of the gas (oxygen and hydrogen) contributing to the reaction on the cathode 27 side is sufficiently reduced.
　ステップＳ１６に係る処理が終了すると、制御部２１は、ＥＧＲ処理の流れを終了させる。
　なお、燃料電池スタック１３の運転停止時において、入口側封止弁５５および出口側封止弁６１は、閉止動作を継続している。燃料電池スタック１３の運転停止時において、新しい空気が、環状の空気流通路７７内に導入されるのを防ぐためである。 When the process related to step S16 ends, the control unit 21 ends the flow of the EGR process.
Note that, when the operation of the fuel cell stack 13 is stopped, the inlet side sealing valve 55 and the outlet side sealing valve 61 continue to close. This is to prevent new air from being introduced into the annular air flow passage 77 when the fuel cell stack 13 is shut down.
〔本発明の実施形態に係る燃料電池システム１１の作用効果〕
　本発明の実施形態に係る燃料電池システム１１は、燃料ガス（水素）および酸化剤ガス（酸素）を電気化学的に反応させて発電する燃料電池スタック１３と、燃料電池スタック１３に対して酸化剤ガス（酸素）を供給するための酸化剤ガス供給流路５３と、燃料電池スタック１３から反応後の酸化剤オフガス（空気）を排出するための酸化剤オフガス排出流路５９と、酸化剤ガス供給流路５３に配設され、燃料電池スタック１３とに対して酸化剤ガス（酸素）を供給するコンプレッサ１１と、酸化剤オフガス排出流路５９に配設される分岐部７３、および、酸化剤ガス供給流路５３のうちコンプレッサ５１の下流側に配設される合流部７５、の間を連通する循環流路６７と、循環流路６７に配設され、分岐部７３から合流部７５へと酸化剤オフガス（空気）を送り出す循環ポンプ６９と、循環流路６７に配設され、分岐部７３から合流部７５へ向かう順方向に対して逆方向となる酸化剤オフガス（空気）の流れを抑制する逆止弁７１と、燃料電池スタック１３の運転停止時に、循環ポンプ６９を駆動させる制御を行う制御部２１と、を備えて構成されることを特徴とする。 [Operation and Effect of Fuel Cell System 11 According to Embodiment of the Present Invention]
A fuel cell system 11 according to an embodiment of the present invention includes a fuel cell stack 13 that generates electricity by electrochemically reacting a fuel gas (hydrogen) and an oxidant gas (oxygen), and an oxidant for the fuel cell stack 13. An oxidant gas supply channel 53 for supplying gas (oxygen), an oxidant offgas discharge channel 59 for discharging the reacted oxidant offgas (air) from the fuel cell stack 13, and an oxidant gas supply Compressor 11 that is disposed in flow path 53 and supplies oxidant gas (oxygen) to fuel cell stack 13, branch 73 disposed in oxidant off-gas discharge flow path 59, and oxidant gas Of the supply flow channel 53, a circulation flow channel 67 that communicates between the merge portion 75 disposed on the downstream side of the compressor 51, a circulation flow channel 67, and oxidation from the branch portion 73 to the merge portion 75. Agent A recirculation pump 69 that sends out gas (air) and a reverse passage that is disposed in the circulation flow path 67 and suppresses the flow of oxidant off-gas (air) that is in the reverse direction to the forward direction from the branch portion 73 toward the junction portion 75. It is characterized by comprising a stop valve 71 and a control unit 21 that controls to drive the circulation pump 69 when the operation of the fuel cell stack 13 is stopped.
　本発明の実施形態に係る燃料電池システム１１では、制御部２１は、循環ポンプ６９を駆動させる制御を行う。その結果、燃料電池スタック１３の運転停止時に、循環流路６７を含む空気流通路７７に残留した気体（酸素、および、クロスリークなどによりカソード２７側に生じた水素）は、空気流通路７７内において、カソード２７に接触して電気化学反応（酸素の還元反応）に繰り返し利用される。すると、空気流通路７７に残留した気体中の酸素や水素は、カソード２７に対する接触機会（接触時間）を増やすという意味での電気化学反応（酸素の還元反応）の促進を通じて、その量（濃度）を低減させる。 In the fuel cell system 11 according to the embodiment of the present invention, the control unit 21 performs control for driving the circulation pump 69. As a result, when the operation of the fuel cell stack 13 is stopped, the gas (oxygen and hydrogen generated on the cathode 27 side due to cross leak, etc.) remaining in the air flow passage 77 including the circulation flow path 67 flows into the air flow passage 77. In FIG. 5, the cathode contacts with the cathode 27 and is repeatedly used for electrochemical reaction (oxygen reduction reaction). Then, the amount (concentration) of oxygen and hydrogen in the gas remaining in the air flow passage 77 through the promotion of an electrochemical reaction (oxygen reduction reaction) in the sense of increasing the chance of contact with the cathode 27 (contact time). Reduce.
　したがって、燃料電池スタック１３のカソード２７側に残存している酸素および水素を速やかに除くことができるため、固体高分子電解質膜２９の劣化（酸化）を抑制して、長寿命の燃料電池スタック１３を有する燃料電池システム１１を得ることができる。 Therefore, since oxygen and hydrogen remaining on the cathode 27 side of the fuel cell stack 13 can be quickly removed, deterioration (oxidation) of the solid polymer electrolyte membrane 29 is suppressed, and the long-life fuel cell stack 13 is suppressed. Can be obtained.
　また、本発明の実施形態に係る燃料電池システム１１では、循環流路６７に、分岐部７３から合流部７５へ向かう順方向に対して逆方向となる酸化剤オフガス（空気）の流れを抑制する逆止弁７１を設ける構成を採用している。このため、燃料電池スタック１３の通常運転時において、分岐部７３から合流部７５へ向かう順方向に対して逆方向となる空気の流れを抑制することができる。 Further, in the fuel cell system 11 according to the embodiment of the present invention, the flow of the oxidant off-gas (air) in the reverse direction with respect to the forward direction from the branching portion 73 toward the merging portion 75 is suppressed in the circulation flow path 67. The structure which provides the check valve 71 is employ | adopted. For this reason, during the normal operation of the fuel cell stack 13, it is possible to suppress the flow of air that is in the reverse direction with respect to the forward direction from the branch portion 73 toward the junction portion 75.
　したがって、循環流路６７に逆止弁７１を設けない場合と比べて、順方向に対して逆方向となる空気の流れを抑制することができるため、上述の固体高分子電解質膜２９の劣化抑制効果に加えて、燃料電池スタック１３における発電効率の低下を抑制することができる。 Therefore, compared with the case where the check valve 71 is not provided in the circulation channel 67, the flow of air in the reverse direction with respect to the forward direction can be suppressed, so that the deterioration of the solid polymer electrolyte membrane 29 is suppressed. In addition to the effect, a decrease in power generation efficiency in the fuel cell stack 13 can be suppressed.
　また、本発明の実施形態に係る燃料電池システム１１では、酸化剤ガス供給流路５３のうちコンプレッサ５１の下流側かつ合流部７５の上流側に配設され、コンプレッサ５１から合流部７５を経て燃料電池スタック１３の入口側１３ｃ１へ向かう酸化剤ガス（空気）の流れを封止する入口側封止弁５５と、酸化剤オフガス排出流路５９のうち分岐部７３の下流側に配設され、燃料電池スタック１３の出口側１３ｃ２から分岐部７３を経て希釈器１９の排気側へ向かう酸化剤オフガスの流れを封止する出口側封止弁６１と、をさらに備える構成を採用している。 In the fuel cell system 11 according to the embodiment of the present invention, the oxidant gas supply channel 53 is disposed on the downstream side of the compressor 51 and on the upstream side of the merging portion 75, and the fuel passes through the merging portion 75 from the compressor 51. An inlet side sealing valve 55 that seals the flow of the oxidant gas (air) toward the inlet side 13c1 of the battery stack 13 and the downstream side of the branching portion 73 of the oxidant offgas discharge flow path 59 are provided. The configuration further includes an outlet side sealing valve 61 that seals the flow of the oxidant off-gas from the outlet side 13c2 of the battery stack 13 to the exhaust side of the diluter 19 through the branch portion 73.
　本発明の実施形態に係る燃料電池システム１１によれば、循環流路６７を含む空気流通路７７を狭溢な閉空間とし、新たな酸素を導入することなく酸化剤オフガスの循環を行うことができるので、燃料電池スタック１３のカソード２７側に残存している気体（酸素および水素）を速やかに除くことができる。これにより、上述の固体高分子電解質膜２９の劣化抑制効果を一層高めることができる。 According to the fuel cell system 11 according to the embodiment of the present invention, the air flow passage 77 including the circulation flow path 67 is formed as a narrow closed space, and the oxidant off-gas can be circulated without introducing new oxygen. Therefore, the gas (oxygen and hydrogen) remaining on the cathode 27 side of the fuel cell stack 13 can be quickly removed. Thereby, the deterioration suppression effect of the above-mentioned solid polymer electrolyte membrane 29 can be further enhanced.
　また、本発明の実施形態に係る燃料電池システム１１では、循環ポンプ６９は、モータ部９３のロータ８９およびステータ９１をキャン９５で密閉したキャン構造を採る、構成を採用することとした。本発明の実施形態に係る燃料電池システム１１によれば、燃料電池スタック１３、および、循環ポンプ６９におけるモータ部９３の一層の長寿命化を図ることができる。 In the fuel cell system 11 according to the embodiment of the present invention, the circulation pump 69 adopts a configuration in which a can structure in which the rotor 89 and the stator 91 of the motor section 93 are sealed with a can 95 is adopted. According to the fuel cell system 11 according to the embodiment of the present invention, the life of the motor unit 93 in the fuel cell stack 13 and the circulation pump 69 can be further extended.
〔その他の実施形態〕
　以上説明した実施形態は、本発明の具現化例を示したものである。したがって、これらによって本発明の技術的範囲が限定的に解釈されることがあってはならない。本発明はその要旨またはその主要な特徴から逸脱することなく、様々な形態で実施することができるからである。 [Other Embodiments]
The embodiment described above shows an embodiment of the present invention. Therefore, the technical scope of the present invention should not be limitedly interpreted by these. This is because the present invention can be implemented in various forms without departing from the gist or main features thereof.
　１１　　燃料電池システム
　１３　　燃料電池スタック（燃料電池）
　２１　　制御部
　２３　　燃料電池セル
　２５　　アノード
　２７　　カソード
　２９　　固体高分子電解質膜
　５１　　コンプレッサ
　５３　　空気供給配管（酸化剤ガス供給流路）
　５５　　入口側封止弁
　５９　　空気排出配管（酸化剤オフガス排出流路）
　６１　　出口側封止弁
　６７　　循環流路
　６９　　循環ポンプ
　７１　　逆止弁
　７３　　分岐部
　７５　　合流部 11 Fuel Cell System 13 Fuel Cell Stack (Fuel Cell)
21 Control Unit 23 Fuel Cell 25 Anode 27 Cathode 29 Solid Polymer Electrolyte Membrane 51 Compressor 53 Air Supply Pipe (Oxidant Gas Supply Channel)
55 Inlet side sealing valve 59 Air discharge piping (oxidant off-gas discharge flow path)
61 Outlet side sealing valve 67 Circulation flow path 69 Circulation pump 71 Check valve 73 Branching section 75 Merging section

Claims (4)

  1. 　燃料ガスおよび酸化剤ガスを電気化学的に反応させて発電する燃料電池と、
    　前記燃料電池に対して酸化剤ガスを供給するための酸化剤ガス供給流路と、
    　前記燃料電池から反応後の酸化剤オフガスを排出するための酸化剤オフガス排出流路と、
    　前記酸化剤ガス供給流路に配設され、前記燃料電池に対して酸化剤ガスを供給するコンプレッサと、
    　前記酸化剤オフガス排出流路に配設される分岐部、および、前記酸化剤ガス供給流路のうち前記コンプレッサの下流側に配設される合流部、の間を連通する循環流路と、
    　前記循環流路に配設され、前記分岐部から前記合流部へと酸化剤オフガスを送り出す循環ポンプと、
    　前記循環流路に配設され、前記分岐部から前記合流部へ向かう順方向に対して逆方向となる酸化剤オフガスの流れを抑制する逆止弁と、
    　前記燃料電池の運転停止時に、前記循環ポンプを駆動させる制御を行う制御部と、
    　を備えて構成されることを特徴とする燃料電池システム。     A fuel cell that generates electricity by electrochemically reacting fuel gas and oxidant gas;
    An oxidant gas supply channel for supplying an oxidant gas to the fuel cell;
    An oxidant off-gas discharge passage for discharging the oxidant off-gas after reaction from the fuel cell;
    A compressor that is disposed in the oxidant gas supply flow path and supplies an oxidant gas to the fuel cell;
    A circulation passage that communicates between a branch portion disposed in the oxidant off-gas discharge passage and a merging portion disposed on the downstream side of the compressor in the oxidant gas supply passage;
    A circulation pump which is disposed in the circulation flow path and sends out an oxidant off-gas from the branch portion to the junction portion;
    A check valve that is disposed in the circulation flow path and suppresses a flow of an oxidant off-gas that is in a reverse direction with respect to a forward direction from the branch portion toward the merge portion;
    A control unit that performs control to drive the circulation pump when the fuel cell is stopped;
    A fuel cell system comprising:
  2. 　請求項１に記載の燃料電池システムであって、
    　前記酸化剤ガス供給流路のうち前記コンプレッサの下流側かつ前記合流部の上流側に配設され、前記コンプレッサから前記合流部を経て前記燃料電池の入口側へ向かう酸化剤ガスの流れを封止する入口側封止弁と、
    　前記酸化剤オフガス排出流路のうち前記分岐部の下流側に配設され、前記燃料電池の出口側から前記分岐部を経て排気側へ向かう酸化剤オフガスの流れを封止する出口側封止弁と、
    　をさらに備えることを特徴とする燃料電池システム。     The fuel cell system according to claim 1,
    The oxidant gas supply flow path is disposed on the downstream side of the compressor and the upstream side of the merging portion, and seals the flow of the oxidant gas from the compressor to the inlet side of the fuel cell through the merging portion. An inlet-side sealing valve that
    An outlet-side sealing valve that is disposed on the downstream side of the branch part in the oxidant off-gas discharge channel and seals the flow of the oxidant off-gas from the outlet side of the fuel cell to the exhaust side through the branch part. When,
    A fuel cell system, further comprising:
  3. 　請求項１に記載の燃料電池システムであって、
    　前記循環ポンプは、モータ部のロータおよびステータをキャンで密閉したキャン構造を有する、
    　ことを特徴とする燃料電池システム。     The fuel cell system according to claim 1,
    The circulation pump has a can structure in which the rotor and stator of the motor unit are sealed with a can.
    A fuel cell system.
  4. 　請求項２に記載の燃料電池システムであって、
    　前記循環ポンプは、モータ部のロータおよびステータをキャンで密閉したキャン構造を有する、
    　ことを特徴とする燃料電池システム。     The fuel cell system according to claim 2, wherein
    The circulation pump has a can structure in which the rotor and stator of the motor unit are sealed with a can.
    A fuel cell system.
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