JP5311974B2 - Starting method of fuel cell system - Google Patents

Description

  The present invention has an oxidant gas flow path for supplying an oxidant gas to the cathode side electrode and a fuel gas flow path for supplying a fuel gas to the anode side electrode, and an electrochemical reaction between the oxidant gas and the fuel gas. A fuel cell system start-up method comprising a fuel cell stack in which a plurality of fuel cells for power generation are stacked, the operation being stopped in a state where the oxidant gas flow path and the fuel gas flow path are filled with the oxidant gas About.

  A fuel cell supplies a fuel gas (mainly hydrogen-containing gas) and an oxidant gas (mainly oxygen-containing gas) to the anode-side electrode and the cathode-side electrode and causes them to react electrochemically. It is a system that obtains electrical energy.

  For example, in a polymer electrolyte fuel cell, an electrolyte membrane / electrode structure (MEA) provided with an anode electrode and a cathode electrode on both sides of an electrolyte membrane made of a polymer ion exchange membrane is sandwiched by separators. Has a cell. This type of power generation cell is normally used as a fuel cell stack by alternately laminating a predetermined number of electrolyte membrane / electrode structures and separators.

  In this type of fuel cell, when power generation (operation) is stopped, supply of fuel gas and oxidant gas to the fuel cell is stopped, but the fuel gas remains on the anode side electrode, while the cathode side The oxidant gas remains on the electrode. For this reason, there is a problem that the cathode side is held at a high potential while the fuel cell is stopped, and the electrode catalyst is deteriorated.

  Thus, for example, a fuel cell system disclosed in Patent Document 1 is known. As shown in FIG. 6, the fuel cell system includes a fuel cell stack 1. Hydrogen is supplied from the hydrogen tank 2 to the fuel cell stack 1 as fuel, and discharged from the fuel cell stack 1. The unused hydrogen is circulated and supplied to the fuel cell stack 1 via the circulation pump 3. The output of the fuel cell stack 1 is connected to a load (not shown) via a power switch 4, while being switched to and connected to the discharge resistors 5 a and 5 b via the power switch 4.

  When the system is stopped, when the control device 6 detects a stop signal, the hydrogen supply of the fuel cell stack 1 is stopped, the output of the fuel cell stack 1 is switched by the power switch 4 and connected to the discharge resistor 5a. ing. Further, by switching the discharge resistance from the discharge resistance 5a to the discharge resistance 5b, the discharge is continuously performed until the residual hydrogen concentration becomes substantially 0%.

JP 2001-345114 A

  In the above Patent Document 1, the discharge resistors 5 a and 5 b are connected to the fuel cell stack 1. Specifically, as shown in FIG. 7, the fuel cell stack 1 includes a plurality of fuel cells 1 a stacked, and the fuel cell 1 a includes an oxidant gas channel 8 a and a fuel gas channel 8 b on both sides of the MEA 7. Is provided.

  On one end side of the fuel cell stack 1 in the stacking direction of the fuel cells 1a, an oxidant gas manifold 9a for supplying an oxidant gas and a fuel gas manifold 9b for supplying a fuel gas are provided. Therefore, the oxidant gas is supplied from the oxidant gas manifold 9a to the oxidant gas flow path 8a of each fuel cell 1a, while the fuel gas is supplied from the fuel gas manifold 9b to the fuel gas flow path 8b of each fuel cell 1a. ing.

  In the above-mentioned Patent Document 1, discharge resistances 5a and 5b are connected to both ends in the stacking direction of the plurality of fuel cells 1a, that is, the plurality of fuel cells 1a are collectively discharged.

  However, in particular, in the fuel cell 1a arranged on the side opposite to the fuel gas manifold 9b side (on the opposite manifold side), the supply of fuel gas is delayed compared to the fuel cell 1a on the gas manifold side. For this reason, there is a possibility that the fuel cell 1a on the side opposite to the manifold has a reversal (cell voltage is negative), and the anode side electrode is deteriorated due to oxidation.

  The present invention solves this type of problem, and is a fuel cell system capable of satisfactorily discharging a plurality of fuel cells and preventing deterioration of an electrode catalyst as much as possible with a simple process. It aims at providing the starting method of.

  The present invention has an oxidant gas flow path for supplying an oxidant gas to the cathode side electrode and a fuel gas flow path for supplying a fuel gas to the anode side electrode, and an electrochemical reaction between the oxidant gas and the fuel gas. A fuel cell system start-up method comprising a fuel cell stack in which a plurality of fuel cells for power generation are stacked, the operation being stopped in a state where the oxidant gas flow path and the fuel gas flow path are filled with the oxidant gas It is about.

This starting method includes a step of connecting a discharge resistor for each fuel cell or a predetermined number of fuel cells, and a step of supplying an oxidant gas to the oxidant gas flow channel while supplying a fuel gas to the fuel gas flow channel. And a step of detecting a cell voltage for each of the fuel cells or the predetermined number of fuel cells, and a step of cutting the discharge resistance when the detected cell voltage becomes negative . .

Further, the fuel cell stack is provided with a manifold that supplies at least fuel gas on one end side in the stacking direction, and the discharge resistance can be cut off when the voltage of the fuel cell disposed at least on the other end side in the stacking direction becomes negative. preferable.

  In the present invention, the cell voltage is detected for each fuel cell or for each predetermined number of fuel cells, and each discharge resistor is disconnected or connected based on the detected cell voltage. For this reason, at the time of start-up, it is possible to reliably prevent the reversal of the fuel cell, and it is possible to prevent deterioration of the electrode catalyst as much as possible with a simple process.

  FIG. 1 is a schematic configuration diagram of a fuel cell system 10 to which a startup method according to the first embodiment of the present invention is applied.

  The fuel cell system 10 includes a fuel cell stack 12, an oxidant gas supply device 14 for supplying an oxidant gas to the fuel cell stack 12, a fuel gas supply device 16 for supplying a fuel gas to the fuel cell stack 12, And a controller 18 that controls the entire fuel cell system 10.

  The fuel cell stack 12 is configured by stacking a plurality of fuel cells 20 in the direction of arrow A. Each fuel cell 20 includes, for example, an electrolyte membrane / electrode structure 28 in which a solid polymer electrolyte membrane 22 in which a perfluorosulfonic acid thin film is impregnated with water is sandwiched between a cathode side electrode 24 and an anode side electrode 26. The electrolyte membrane / electrode structure 28 is sandwiched between a pair of separators 30a and 30b.

  The cathode side electrode 24 and the anode side electrode 26 are uniformly coated on the surface of the gas diffusion layer with a gas diffusion layer (not shown) made of carbon paper or the like and porous carbon particles carrying platinum alloy on the surface. An electrode catalyst layer (not shown). The electrode catalyst layers are formed on both surfaces of the solid polymer electrolyte membrane 22.

  Between the electrolyte membrane / electrode structure 28 and the separator 30a, an oxidant gas passage 32 for supplying an oxidant gas to the cathode electrode 24 is formed, and the electrolyte membrane / electrode structure 28 and the separator 30b are formed. A fuel gas flow path 34 for supplying fuel gas to the anode side electrode 26 is formed between the two.

  An end plate 35 a is disposed at one end (manifold side) of the fuel cell stack 12 in the stacking direction. The end plate 35a has an oxidant gas inlet communication hole 36a for supplying an oxidant gas such as air (oxygen-containing gas) to the oxidant gas flow path 32, and a fuel gas such as a hydrogen-containing gas. A fuel gas inlet communication hole 38a for supplying to the passage 34 is formed.

  An end plate 35b is disposed at the other end portion (on the opposite side of the manifold) of the fuel cell stack 12 in the stacking direction. The end plate 35b includes an oxidant gas outlet communication hole 36b for discharging the oxidant gas from the oxidant gas flow path 32, and a fuel gas outlet communication hole 38b for discharging the fuel gas from the fuel gas flow path 34. And are formed. In the fuel cell stack 12, a cooling medium flow path (not shown) is provided for flowing a cooling medium between the fuel cells 20 or for each of the plurality of fuel cells 20.

  The oxidant gas supply device 14 includes an air compressor 40 that compresses and supplies air from the atmosphere, and the air compressor 40 is disposed in the air supply flow path 42. The air supply channel 42 is provided with a valve 44 as necessary, and the air supply channel 42 communicates with the oxidant gas inlet communication hole 36 a of the fuel cell stack 12.

  The oxidant gas supply device 14 includes an air discharge channel 46 that communicates with the oxidant gas outlet communication hole 36b. The air discharge channel 46 includes a valve (back pressure control valve) 48 with an adjustable opening for adjusting the pressure of air supplied from the air compressor 40 through the air supply channel 42 to the fuel cell stack 12. Is provided.

  The fuel gas supply device 16 includes a hydrogen tank 50 that stores high-pressure hydrogen (hydrogen-containing gas). The hydrogen tank 50 communicates with the fuel gas inlet communication hole 38 a of the fuel cell stack 12 via the hydrogen supply flow path 52. To do. The hydrogen supply channel 52 is provided with a valve 54 and an ejector 56. The hydrogen supply channel 52 and the air supply channel 42 can communicate with each other via a connection channel 58, and a valve 60 is disposed in the connection channel 58.

  The off gas passage 62 communicates with the fuel gas outlet communication hole 38b. A hydrogen circulation path 64 communicates with the off-gas flow path 62, and the hydrogen circulation path 64 communicates with an ejector 56. The off-gas flow path 62 is provided with a purge valve 65 that is opened when the fuel gas is discharged to the outside.

  The ejector 56 supplies the hydrogen gas supplied from the hydrogen tank 50 to the fuel cell stack 12 through the hydrogen supply flow path 52, and exhaust gas containing unused hydrogen gas that has not been used in the fuel cell stack 12. Then, the gas is sucked from the hydrogen circulation path 64 and supplied again as fuel gas to the fuel cell stack 12.

  The fuel cell stack 12 is provided with a discharge circuit 66 for each predetermined number of fuel cells 20 (see FIG. 2). Each discharge circuit 66 includes an open / close switch 68 and a discharge resistor 70. The discharge circuit 66 is controlled by the controller 18. The controller 18 detects the cell voltage of each fuel cell 20 and also detects the average cell voltage or the lowest cell voltage in the fuel cell block 72 to which each discharge circuit 66 is connected.

  The operation of the fuel cell system 10 configured as described above will be described below with reference to the flowchart shown in FIG. 3 in relation to the activation method according to the first embodiment of the present invention.

  When the operation of the fuel cell system 10 is stopped, as will be described later, the oxidant gas passage 32 and the fuel gas passage 34 are filled with an oxidant gas (hereinafter also referred to as air).

  Therefore, when an activation signal (for example, an ignition ON signal) of the fuel cell system 10 is input to the controller 18 (step S1), the process proceeds to step S2 and the open / close switch 68 that opens and closes each discharge circuit 66 is closed ( Switch ON).

  Then, the oxidant gas supply device 14 and the fuel gas supply device 16 are driven to supply air and fuel gas to the fuel cell stack 12 (step S3). Specifically, the valve 60 is closed while the valves 44 and 54 are opened. For this reason, in the oxidant gas supply device 14, air is sent to the air supply flow path 42 via the air compressor 40. This air is supplied to an oxidant gas flow path 32 provided in each fuel cell 20 in the fuel cell stack 12.

  On the other hand, in the fuel gas supply device 16, the fuel gas is supplied from the hydrogen tank 50 to the hydrogen supply passage 52. This fuel gas is supplied to a fuel gas flow path 34 provided in the fuel cell 20 in the fuel cell stack 12.

  As a result, the air supplied to the cathode side electrode 24 and the fuel gas supplied to the anode side electrode 26 react electrochemically to generate power.

  The cell voltage of each fuel cell 20 is detected by the controller 18, and this controller 18 detects the average cell voltage or the lowest cell voltage in the fuel cell block 72 to which each discharge circuit 66 is connected.

  Next, the process proceeds to step S5, where it is determined whether or not the detected average cell voltage or minimum cell voltage is positive. If it is determined that the average cell voltage or the lowest cell voltage in any one of the fuel cell blocks 72 is negative (NO in step S5), the process proceeds to step S6, and the discharge connected to the fuel cell block 72 is performed. The open / close switch 68 of the circuit 66 is opened (switch OFF). For this reason, it is possible to reliably prevent inversion of the fuel cell 20 at the time of start-up, and to prevent deterioration of the electrode catalyst constituting the anode-side electrode 26 as much as possible with a simple process. It becomes possible.

  Here, in the fuel cell stack 12, a plurality of fuel cells 20 are stacked in the arrow A direction. In the fuel cell 20 disposed on the end plate 35b side, which is the side opposite to the manifold, the fuel gas supplied to the fuel gas flow path 34 is delayed as compared with the fuel cell 20 disposed on the end plate 35a side which is the manifold side. It is easy to generate. For this reason, in the fuel cell 20 arranged on the end plate 35b side, inversion due to a delay in the supply of fuel gas is likely to occur.

  In this case, in the first embodiment, a discharge circuit 66 is provided for each predetermined number of fuel cells 20, and the cell voltage of each fuel cell 20 is detected by the controller 18. Therefore, in the fuel cell block 72 including the fuel cell 20 in which the detected cell voltage is negative, the open / close switch 68 of the discharge circuit 66 connected to the fuel cell block 72 is opened to open the fuel cell 20. Inversion can be effectively prevented.

At that time, it is preferable to detect the cell voltages of all the fuel cells 20, but in order to simplify the system , for example, the cell voltages of the fuel cells 20 arranged on the end plate 35b side from the substantially central portion in the stacking direction are used. it may be the only detection. This is because the reversal due to the fuel gas supply delay is likely to occur in the fuel cell 20 on the end plate 35b side.

  On the other hand, if it is determined in step S5 that the detected average cell voltage or minimum cell voltage is positive (YES in step S5), the process proceeds to step S7, and the open / close switch 68 constituting all the discharge circuits 66. Is closed.

  Further, the process proceeds to step S8, and if it is determined that the average cell voltage or the lowest cell voltage in each fuel cell block is a threshold value (for example, 0.2V to 0.8V) (YES in step S8), step Proceeding to S9, the open / close switch 68 constituting each discharge circuit 66 is opened. Thereby, the fuel cell system 10 becomes a normal power generation operation, and can supply power to a desired load.

  By the way, when the power generation by the fuel cell stack 12 is stopped, the valve 54 is closed and the valve 60 is opened as shown in FIG. For this reason, the air supplied to the air supply flow path 42 via the air compressor 40 is supplied to the oxidant gas flow path 32 in the fuel cell stack 12, while part of the air passes through the connection flow path 58 to form hydrogen. The fuel is supplied from the supply passage 52 to the fuel gas passage 34 in the fuel cell stack 12. Therefore, the oxidant gas passage 32 and the fuel gas passage 34 are purged with air, and the operation of the fuel cell system 10 is stopped.

  FIG. 4 is an explanatory diagram of the fuel cell stack 12 and the discharge circuit 82 that constitute the fuel cell system 80 to which the startup method according to the second embodiment of the present invention is applied. The same components as those of the fuel cell system 10 according to the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted.

  The fuel cell stack 12 constituting the fuel cell system 80 is provided with a discharge circuit 82 for each fuel cell 20. The controller 18 detects the cell voltage of each fuel cell 20 and performs open control of the open / close switch 68 that constitutes each discharge circuit 82.

  In the second embodiment configured as described above, activation is performed according to the flowchart shown in FIG.

  First, when the activation signal of the fuel cell system 80 is input to the controller 18 (step S11), the process proceeds to step S12, and the open / close switch 68 constituting each discharge circuit 82 is closed.

  Further, fuel gas and air are supplied to the fuel cell stack 12 (step S13), and the controller 18 detects the cell voltage of each fuel cell 20 (step S14). Then, the controller 18 compares the cell voltage for each fuel cell 20 with a threshold (for example, 0.2 V to 0.8 V), and determines that the cell voltage exceeds the threshold (YES in step S15). ) The fuel cell 20 proceeds to step S16, and the open / close switch 68 is opened, whereby the discharge process is completed.

  Thereby, in the second embodiment, the cell voltage is detected for each fuel cell 20 and the opening / closing operation of the open / close switch 68 is performed for each discharge circuit 82 connected to each fuel cell 20. Therefore, a desired discharge process can be performed efficiently and reliably for each fuel cell 20, and the startability of the entire fuel cell system 80 can be improved satisfactorily.

  In the second embodiment, as in the first embodiment, it is determined whether or not the cell voltage of each fuel cell 20 is positive (see step S5), and the cell voltage is negative. In the determined fuel cell 20, the opening / closing switch 68 may be opened / closed to prevent deterioration of the electrode catalyst due to the reversal of the fuel cell 20.

1 is a schematic configuration diagram of a fuel cell system to which a startup method according to a first embodiment of the present invention is applied. It is explanatory drawing of the fuel cell stack and discharge circuit which comprise the said fuel cell system. It is a flowchart explaining the said starting method. It is explanatory drawing of the fuel cell stack and discharge circuit which comprise the fuel cell system with which the starting method which concerns on the 2nd Embodiment of this invention is applied. It is a flowchart explaining the said starting method. 2 is an explanatory diagram of a fuel cell system disclosed in Patent Document 1. FIG. It is explanatory drawing of the fuel cell stack which comprises the said fuel cell system.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10,80 ... Fuel cell system 12 ... Fuel cell stack 14 ... Oxidant gas supply device 16 ... Fuel gas supply device 18 ... Controller 20 ... Fuel cell 22 ... Solid polymer electrolyte membrane 24 ... Cathode side electrode 26 ... Anode side electrode 28 ... Electrolyte membrane / electrode structure 30a, 30b ... Separator 32 ... Oxidant gas passage 34 ... Fuel gas passage 40 ... Air compressor 42 ... Air supply passage 46 ... Air discharge passage 50 ... Hydrogen tank 52 ... Hydrogen supply flow Path 56 ... Ejector 62 ... Off gas flow path 66, 82 ... Discharge circuit 68 ... Open / close switch 70 ... Discharge resistor 72 ... Fuel cell block

Claims (2)

A plurality of oxidant gas flow paths for supplying an oxidant gas to the cathode side electrode and a fuel gas flow path for supplying a fuel gas to the anode side electrode, and generating a plurality of power by an electrochemical reaction of the oxidant gas and the fuel gas. A starting method of a fuel cell system comprising a fuel cell stack in which fuel cells are stacked, the operation being stopped in a state where the oxidant gas flow path and the fuel gas flow path are filled with the oxidant gas,
Connecting a discharge resistor for each fuel cell or for each predetermined number of fuel cells;
Supplying the oxidant gas to the oxidant gas flow path while supplying the fuel gas to the fuel gas flow path;
Detecting a cell voltage for each fuel cell or for each predetermined number of fuel cells;
Cutting the discharge resistance when the detected cell voltage becomes negative ;
A starting method for a fuel cell system, comprising: In starting method of claim 1 Symbol placement, the fuel cell stack is provided with a manifold for supplying at least the fuel gas in the stacking direction one end side,
A method of starting a fuel cell system, comprising: cutting off the discharge resistance when the voltage of the fuel cell disposed at least on the other end side in the stacking direction becomes negative.

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