JP4938987B2 - Fuel cell system and method for stopping the same - Google Patents

Description

  The present invention relates to a fuel cell system and a stopping method thereof.

  Generally, a fuel cell is configured by laminating a plurality of single cells so as to be electrically in series. This single cell is formed by sandwiching a membrane electrode assembly (MEA; Membrane Electrode Assembly) between a pair of conductive separators. This membrane electrode structure is formed by sandwiching one surface side of a proton conductive polymer electrolyte membrane (PEM; Polymer Exchange Membrane) with a cathode electrode and the other surface side with an anode electrode.

By the way, in a fuel cell during power generation, hydrogen, which is a fuel gas, is supplied to an anode electrode, and air (oxygen), which is an oxidant gas, is supplied to an adjacent electrode through a flow path formed in a separator. Has been.
When stopping the fuel cell during power generation, the power supply to the connected external load circuit is cut off, and then the anode-side flow path (hereinafter referred to as the anode system) is compressed with compressed air. Perform air scavenging. This is because hydrogen gas circulates in the anode system at all times and moisture generated by the electrode reaction stays in the anode system. If the remaining moisture remains in this state and the fuel cell is stopped and left at a temperature below freezing, the moisture will condense and block the anode system after a while. This is because the fuel cell cannot be started from the next time because the supply is hindered.
JP-A-10-284104 (Claims 1, 2, paragraphs 0003 to 0005)

  However, as described above, if air scavenging is repeated in order to discharge the moisture remaining in the anode system, there is a problem that the components of the fuel cell such as the membrane electrode structure and the separator are corroded. To do. This is because when the boundary between the hydrogen-containing gas phase originally filled in the anode system and the air layer newly introduced by scavenging is formed in the anode system, this boundary is formed on the inner wall in the anode system. It is thought that this is caused by the occurrence of a local potential difference at the site of contact.

  Therefore, the present invention aims to solve the above-described problems, and even if air scavenging is performed when the fuel cell system is stopped, the components of the fuel cell are prevented from being corroded and effective from the aspect of energy management. An object of the present invention is to provide a fuel cell system and a method for stopping the fuel cell system.

In order to solve the problems described above, a fuel cell system of the present invention has a fuel gas flow path and an oxidant gas flow path, and is connected to the anode electrode from the inlet of the fuel gas flow path through the fuel gas flow path. fuel gas is supplied, the oxygen-containing gas to the cathode electrode through the oxidizing gas channel is supplied, the fuel supplying power obtained by the reaction of the fuel gas及 beauty the oxygen-containing gas to an external load circuit A battery, a fuel gas discharge path connected to an outlet of the fuel gas flow path, a discharge side shut-off valve provided in the fuel gas discharge path, and at least a resistor capable of being electrically connected to the fuel cell An auxiliary circuit including: a first switch member for electrically connecting / disconnecting the external load circuit and the fuel cell; and a second switch for electrically connecting / disconnecting the auxiliary circuit and the fuel cell. and member, wherein By supplying the agent gas from the inlet of the fuel gas passage to the anode electrode, an anode for discharging the wind pressure of the oxidant gas moisture remaining in the said fuel gas passage from the discharge-side shut-off valve Before operating the scavenging means, the switching means for switching the supply of the oxidizing gas to the anode electrode or the cathode electrode, and the switching means so that the oxidizing gas is supplied to the anode electrode, while the first switch member in electrical connection, characterized in that it comprises a control unit for the second switch member to the electrical connection.

  By having such a configuration, a potential difference locally generated in the anode system due to air scavenging is eliminated by the conduction of electrons through an external load circuit electrically connected to the fuel cell. Become.

In addition, the present invention is characterized by comprising a data storage unit that records a history of scavenging by the anode scavenging means .

According to the present invention, the external load circuit includes at least a chargeable power storage device .
By having such a configuration, energy based on a potential difference locally generated in the anode system due to air scavenging is stored in a storage device connected to the outside of the fuel cell. The energy is effectively used.

  According to the present invention, local potential generated in the anode system during air scavenging can be eliminated by electronic circulation using an external load circuit, so that corrosion of fuel cell components can be prevented and eliminated. Can be shortened. Further, an excellent effect is exhibited from the viewpoint of effective use of energy.

FIG. 1 is an overall configuration diagram showing the fuel cell system of the present embodiment, FIG. 2 is an exploded perspective view showing the fuel cell, and FIG. 3 is a flowchart showing processing in the control unit. In the following description, a case where the fuel cell system 1 is mounted on a vehicle will be described as an example.
As shown in FIG. 1, the fuel cell system 1 of this embodiment includes a fuel cell FC, an air supply unit 10, a hydrogen supply unit 20, an auxiliary circuit 30, and a control unit 40.

  As shown in FIG. 2, the fuel cell FC includes a plurality of single cells (SC) 8 each having a membrane electrode structure (MEA) 7 sandwiched between conductive cathode separators 5 and anode separators 6 in the thickness direction. It is constructed by stacking. The membrane electrode structure (MEA) 7 is configured such that one side of the electrolyte membrane (PEM) 2 is sandwiched between a cathode electrode 3 containing a catalyst and the other side is sandwiched between an anode electrode 4 containing a catalyst. The single cells 8, 8... Are stacked on each other so as to be electrically in series.

  In the cathode separator 5, a plurality of flow paths 5 a, 5 a, 5 a... Through which air as an oxidant gas flows are formed on the surface facing the cathode electrode 3 so as to extend linearly in parallel with each other. In the cathode separator 5, air flows in the same direction from the inlet 5a1 formed on one side to the outlet 5a2 formed on the other side of each flow path 5a. The inlet 5a1 is connected to the air introduction path 16 (see FIG. 1), and the outlet 5a2 is connected to the air exhaust path 17.

  In the anode separator 6, a plurality of flow paths 6 a, 6 a, 6 a... Through which hydrogen gas as a fuel gas flows are formed on the surface facing the anode electrode 4 so as to extend linearly in parallel with each other. Also in this anode separator 6, hydrogen gas flows in the same direction from one inlet 6a1 to the other outlet 6a2 with respect to each flow path 6a. The inlet 6a1 is connected to the hydrogen supply path 26 (see FIG. 1), and the outlet 6a2 is connected to the circulation path 25.

As shown in FIG. 1, the air supply means 10 supplies air as an oxidant gas to the cathode electrode 3 (see FIG. 2) of the fuel cell FC via the air introduction path 16. It consists of a vessel 12, a humidifier 13, and the like.
The compressor 11 is a mechanical supercharger and sucks and pressurizes atmospheric air (outside air). The cooler 12 cools pressurized hot air (compressed air) to a temperature suitable for power generation in the fuel cell FC. The humidifier 13 humidifies the air cooled by the cooler 12 to a humidity suitable for power generation in the fuel cell FC, particularly to a humidity at which the ionic conductivity of the electrolyte membrane 2 (see FIG. 2) can be sufficiently exhibited. .

  The air supply means 10 includes an anode scavenging path (anode scavenging means) 14 for introducing air sucked by the compressor 11 into the hydrogen supply path 26 and scavenging air to the anode electrode 4 (see FIG. 2) of the fuel cell FC. Is provided. In addition, a switching valve (switching means) 15 is provided at the base end of the anode scavenging passage 14, and the supply of air is switched to the anode electrode 4 or the cathode electrode 3 according to an instruction from the control unit 40. ing. When air is supplied to the cathode electrode 3, the air (oxidizing gas) flows through the flow paths 5a, 5a, and contributes to the power generation reaction of the fuel cell FC. When air is supplied to the anode electrode 4, air scavenging is performed in which moisture staying in the anode system is discharged from the discharge side shut-off valve 27 described later by the wind pressure.

The hydrogen supply means 20 supplies hydrogen as fuel gas to the anode electrode 4 (see FIG. 2) of the fuel cell FC, and includes a hydrogen tank 21, a supply-side shut-off valve 22, a pressure control valve 23, an ejector 24, and a circulation. The passage 25, the hydrogen supply passage 26, and the discharge side shut-off valve 27 are configured.
The hydrogen tank 21 is configured by filling a metal container with high-purity hydrogen gas at a high pressure, and the supply-side shut-off valve 22 is a valve for shutting off or supplying hydrogen to the fuel cell FC. The pressure control valve 23 is a valve that controls the supply amount of hydrogen gas supplied to the fuel cell FC. Further, the ejector 24 recirculates unused hydrogen gas discharged from the fuel cell FC via the circulation path 25 so as to prevent the fuel gas (hydrogen gas) from being discharged wastefully. It has become.

  The discharge side shut-off valve 27 is provided in a midway path on the fuel cell FC side of the circulation path 25, and is shut off during normal power generation of the fuel cell FC. The discharge-side shut-off valve 27 is opened in synchronization with the operation of the switching valve 15 during air scavenging, and the water that stays in the hydrogen supply path 26 and the anode-electrode-side flow path 6a together with the compressed air is discharged to the outside. It is.

In the fuel cell system 1, the fuel cell FC is electrically connected to the external load circuit 50 through conductive cables C1 and C2. For example, the cable C1 connects the negative pole of the fuel cell FC and the negative pole of the external load circuit 50, and the cable C2 connects the positive pole of the fuel cell FC and the positive pole of the external load circuit 50.
The external load circuit 50 may be an energy storage system (power storage device) such as a capacitor capable of charging electric energy in addition to the motor of the compressor 11 and a travel motor (not shown). The cables C1 and C2 include a first switch S1 and a second switch S2 (switch member) that can switch the connection between the fuel cell FC and the external load circuit 50 between a closed state (ON state) and an open state (OFF state). I have.

The auxiliary circuit 30 includes a resistor 31, a third switch S3, and conductive cables C3 and C4. One end of the cable C3 is connected to the resistor 31, the other end is connected to the cable C1, and one end of the cable C4 is connected to the resistor 31, and the other end is connected to the cable C2. The third switch S3 can switch the connection between the cable C1 and the resistor 31 between an ON state and an OFF state, and is provided on the cable C3.
The connection point P1 between the cable C1 and the cable C3 is formed closer to the fuel cell FC with respect to the first switch S1, and the connection point P2 between the cable C2 and the cable C4 is a fuel cell with respect to the second switch S2. It is formed near FC.

The control unit 40 is connected to the compressor 11, the switching valve 15, the supply side cutoff valve 22, the pressure control valve 23, the discharge side cutoff valve 27, and the first to third switches S <b> 1 to S <b> 3. . By the control of the control unit 40, the output of the motor of the compressor 11 is controlled, the switching operation of the switching valve 15 and the discharge side shut-off valve 27 are controlled in synchronism, the opening / closing operation of the supply side shut-off valve 22 is controlled, and the pressure The pressure of the control valve 23 is controlled to control the supply amount of hydrogen, and the opening / closing operations of the first to third switches S1 to S3 are respectively controlled.
The control data storage unit 41 stores information executed by the control unit 40 one by one, and feeds back this information to the control unit 40 to reflect it in the control executed by the control unit 40.

  Next, the operation of the fuel cell system 1 of the present embodiment will be described with reference to FIG. 3 (refer to FIGS. 1 and 2 as appropriate). FIG. 3 is a flowchart showing processing in the control unit in the present embodiment.

  First, hydrogen is supplied to the anode electrode 4 and air (oxygen) is supplied to the cathode electrode 3, and generated power from the fuel cell FC is supplied to the external load circuit 50 via the cables C 1 and C 2. The battery system 1 is in an operating state (S11). At this time, the first and second switches S1 and S2 shown in FIG. 1 are set to be closed (ON), and the third switch S3 is set to be open (OFF).

Next, in order to stop the fuel cell system 1, the supply to the external load circuit 50 of the fuel cell FC is interrupted to enter an ignition-off (IG-OFF) state (S12). At this time, the first to third switches S1, S2, and S3 are all set to open (OFF).
Then, the control unit 40 determines whether or not the anode air scavenging is necessary. If it is determined that the anode air scavenging is unnecessary, the subsequent operation flow is not executed and the job is ended (S13: No). When it is determined that the anode air scavenging is necessary (S13: Yes), the switches S1 and S2 are reset (ON), and the external load circuit 50 and the fuel cell FC are electrically connected (S14). . Further, the third switch S3 is set to be closed (ON), and the resistor 31 and the fuel cell FC are electrically connected (S15).

  Next, the switching valve 15 is switched to switch the flow path from the air introduction path 16 to the anode scavenging path 14 so that the air supplied from the compressor 11 is supplied to the anode electrode 4, and the discharge side shut-off valve 27 is Opening and air scavenging in the anode system is started (S16). Then, air scavenging is continued until a predetermined time has elapsed (S17). As a result, the inside of the flow path 6a on the anode electrode side is completely replaced from the hydrogen-containing gas phase to the air phase. Until the both gas phases are completely replaced in this way, A local potential difference is generated at a portion where the inner wall surface of the flow path 6a is in contact, but electrons are conducted through the cables C1, C2, C3, and C4 so that the potential difference is canceled by the external load circuit 50 and the resistor 31. In order to work, the components of the fuel cell FC are not corroded.

  In addition, unlike when the current flows only through the resistor 31 of the auxiliary circuit 30, the current also flows through the external load circuit 50. Incidentally, if the ignition switch is repeatedly turned on and off at short time intervals, the life of the resistor 31 is likely to decrease due to heat generation. Even in such a case, the current generated by the resistor 31 and the external load circuit 50 is shared. Therefore, even if a small-capacitance resistor 31 is used, it is possible to avoid a decrease in life.

  After the air scavenging in the anode system is completed (S18), in order to leave a record of the fact that the inside of the anode system is completely replaced with the air phase from the hydrogen-containing gas phase, the air scavenging is performed on the data storage unit 60. A history is recorded (S19). The recorded execution history is used as information when starting the fuel cell FC next time.

  Thereafter, the resistor 31 and the fuel cell FC are electrically disconnected (S20), then the external load circuit 50 and the fuel cell FC are electrically disconnected (S21), and a series of operation flow is completed. The fuel cell system 1 is completely stopped. At this time, the first to third switches S1, S2, S3 are all set to open (OFF).

  Thus, in the fuel cell system 1 of the present embodiment, the fuel cell FC and the external load circuit 50 are electrically connected before air scavenging in the anode system when the fuel cell system 1 is stopped. As a result, the local potential in the anode system generated by air scavenging is eliminated by the conduction of electrons to the connected external load circuit 50. Further, energy is consumed for driving an external load by electrons conducting the external load circuit 50, or if an energy storage device (power storage device) such as a capacitor is connected as the external load circuit 50, these are charged, It is also excellent in terms of energy management.

  In addition, in order to avoid corrosion of the fuel cell FC due to electromotive force generated during air scavenging, it also leads to a reduction in the load of the resistor 31 that is normally used. This improves the durability of the resistor 31 and reduces the processing time. The advantage of shortening is also derived.

  In this embodiment, the fuel cell system for vehicles has been described as an example. However, the present invention is not limited to this, and may be a fuel cell system for vehicles such as ships and airplanes, or a stationary fuel. A battery system may be used.

It is a whole lineblock diagram showing the fuel cell system of this embodiment. It is a disassembled perspective view which shows a fuel cell. It is a flowchart which shows the process in a control part.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Fuel cell system 3 Cathode electrode 4 Anode electrode 10 Air supply means 14 Anode scavenging path (anode scavenging means)
15 Switching valve (switching means)
20 Hydrogen supply means 30 Auxiliary circuit 31 Resistor 40 Control unit 50 External load circuit (power storage device)
FC fuel cell S1 1st switch (switch member)
S2 Second switch (switch member)
S3 3rd switch

Claims (5)

A fuel gas channel and an oxidant gas channel, wherein a fuel gas is supplied from an inlet of the fuel gas channel to the anode electrode via the fuel gas channel, and the cathode electrode via the oxidant gas channel oxidant gas is supplied, and a fuel cell for supplying power obtained by the reaction of the fuel gas及 beauty the oxygen-containing gas to an external load circuit,
A fuel gas discharge path connected to an outlet of the fuel gas flow path;
A discharge-side shut-off valve provided in the fuel gas discharge path;
An auxiliary circuit including at least a resistor capable of being electrically connected to the fuel cell;
A first switch member for electrically connecting / disconnecting the external load circuit and the fuel cell;
A second switch member for electrically connecting / disconnecting the auxiliary circuit and the fuel cell;
By supplying the oxidant gas from the inlet of the fuel gas flow path to the anode electrode, moisture remaining in the fuel gas flow path is discharged from the discharge side shut-off valve by the wind pressure of the oxidant gas. Anode scavenging means;
Switching means for switching the supply of the oxidant gas to the anode electrode or the cathode electrode;
Before operating the switching means so that the oxidant gas is supplied to the anode electrode, the first switch member is brought into an electrically connected state before the second switch member is electrically connected. the fuel cell system characterized by comprising a control unit, the to state. The fuel cell system according to claim 1, further comprising a data storage unit that records a history of scavenging performed by the anode scavenging means. The external load circuit, the fuel cell system according to claim 1 or 2, characterized in that it comprises at least chargeable power storage device. Fuel gas is supplied from the inlet of the fuel gas flow path of the fuel cell to the anode electrode via the fuel gas flow path, and oxidant gas is supplied to the cathode electrode via the oxidant gas flow path of the fuel cell. the Rukoto, a generator supplying electric power to the fuel cell is generating power to an external load circuit,
A power supply stop step of cutting off the supply of power to the external load circuit;
By supplying the oxidant gas from the inlet of the fuel gas flow path to the anode electrode, moisture remaining in the fuel gas flow path is supplied to the fuel gas discharge path connected to the outlet of the fuel gas flow path. Before exhausting from the provided shut-off valve by the wind pressure of the oxidant gas , the external load circuit and the fuel cell are electrically connected , and at least the auxiliary circuit including the resistor and the fuel cell are electrically connected. An anode scavenging step connected to the fuel cell system. 5. The method of stopping a fuel cell system according to claim 4, further comprising a data storage step of recording an execution history of anode scavenging in the data storage unit after the anode scavenging step.

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