JP2009301751A - Starting method of fuel cell system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent deterioration of an electrode catalyst as much as possible and maintain power generation performance excellently by a simple process. <P>SOLUTION: The starting method of a fuel cell system 10 includes a process in which hydrogen gas is supplied by replacing air simultaneously in an oxidant gas passage 32 and a fuel gas passage 34 of a fuel cell stack 12 where the air is filled up while the system is shutdown, a process in which the air is supplied to the oxidant gas passage 32 after the supply of the hydrogen gas to the oxidant gas passage 32 is shutdown, and a process in which a load 66 is connected with the fuel cell stack 12 to start power generation by the fuel cell stack 12. <P>COPYRIGHT: (C)2010,JPO&INPIT

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. The present invention relates to a starting method of a fuel cell system that includes a fuel cell that generates electric power, and is shut down in a state where the oxidant gas channel and the fuel gas channel are filled with the oxidant gas.

  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, a polymer electrolyte fuel cell includes a power generation cell in which an electrolyte membrane / electrode structure provided with an anode side electrode and a cathode side electrode is sandwiched between separators on both sides of an electrolyte membrane made of a polymer ion exchange membrane. ing. 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 layer is deteriorated.

  Therefore, for example, as disclosed in Patent Document 1, when the fuel cell stack is stopped, the anode-side supply line and the cathode-side supply line are purged with air after the temperature of the cooling medium has dropped to a set temperature or lower. Fuel cell systems are known.

US Pat. No. 7,270,904

  However, in Patent Document 1 described above, when the fuel cell is started in a state where air is present in the cathode side electrode and the anode side electrode, fuel gas and air are mixed in the anode side electrode. For this reason, in particular, the cathode catalyst is likely to be at a high potential, and the electrode catalyst may be deteriorated (damaged) in the cathode electrode in which a catalyst having a higher activity than the anode electrode is used. As a result, there is a problem in that the power generation performance of the fuel cell is reduced.

  The present invention solves this type of problem, and provides a method for starting a fuel cell system capable of preventing deterioration of an electrode catalyst as much as possible and maintaining good power generation performance with a simple process. The purpose is to do.

  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. The present invention relates to a method of starting a fuel cell system that includes a fuel cell that generates electric power, and that is shut down in a state where the oxidant gas passage and the fuel gas passage are filled with the oxidant gas.

  This starting method includes a step of simultaneously supplying fuel gas to the oxidant gas flow path and the fuel gas flow path, and after stopping the supply of the fuel gas to the oxidant gas flow path, the oxidant gas flow A step of supplying an oxidant gas to the road, and a step of connecting a load to the fuel cell and starting power generation by the fuel cell.

  The starting method preferably includes a step of making the moving speeds of the interfaces between the oxidant gas and the fuel gas the same when simultaneously supplying the fuel gas to the oxidant gas channel and the fuel gas channel.

  Further, in this activation method, when the fuel gas is simultaneously supplied to the oxidant gas flow channel and the fuel gas flow channel, the oxidant gas supplied to the bypass flow channel branched from the upstream side of the oxidant gas flow channel is supplied. And a step of diluting the fuel gas discharged from the fuel cell.

  In the present invention, by simultaneously supplying (purging) the fuel gas to the oxidant gas flow path and the fuel gas flow path, the oxidant gas remaining in the oxidant gas flow path and the fuel gas flow path is Replaced with fuel gas. Therefore, while the oxidant gas is supplied to the oxidant gas flow path without purging with the fuel gas, it is possible to suppress a partial potential increase compared to the case where the fuel gas is supplied to the fuel gas flow path. It is possible to suppress deterioration of the electrode catalyst.

  Next, an oxidant gas is supplied to the oxidant gas flow path. For this reason, fuel gas and oxidant gas are mixed in the oxidant gas flow path, and a high potential is likely to be generated in the anode side electrode. In that case, since the activity of the anode side electrode can be set lower than that of the cathode side electrode, it is possible to prevent the electrode catalyst of the anode side electrode from deteriorating. Thereby, it becomes possible to prevent deterioration of the electrode catalyst as much as possible and maintain good power generation performance 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. 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 a 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 side 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.

  At one end of the fuel cell stack 12 in the stacking direction, 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 such as a hydrogen-containing gas. A fuel gas inlet communication hole 38 a for supplying gas to the fuel gas channel 34 is formed. At the other end in the stacking direction of the fuel cell stack 12, an oxidant gas outlet communication hole 36 b for discharging the oxidant gas from the oxidant gas channel 32 and a fuel gas for discharging from the fuel gas channel 34. A fuel gas outlet communication hole 38b is 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 the ejector 56. A purge valve 65 that is opened when the fuel gas is supplied to the fuel gas passage 34 is disposed in the off gas passage 62.

  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.

  For example, a load 66 such as a drive motor is provided in the fuel cell stack 12 through a switch 68 so as to be electrically disconnected and connectable.

  The operation of the fuel cell system 10 configured as described above will be described below along the flowchart shown in FIG. 2 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 the activation signal of the fuel cell system 10 is input to the controller 18, the valves 54 and 60 are opened and the valve 44 is closed as shown in FIG. Therefore, fuel gas (hereinafter also referred to as hydrogen gas) is supplied from the hydrogen tank 50 to the hydrogen supply flow path 52.

  The hydrogen gas is supplied to the fuel gas inlet communication hole 38a of the fuel cell stack 12 through the hydrogen supply flow path 52, and is branched at the connection flow path 58, and passes through the air supply flow path 42 to the fuel cell stack. 12 oxidant gas inlet communication holes 36a. Accordingly, in the fuel cell stack 12, hydrogen is supplied to the fuel gas channel 34 and the oxidant gas channel 32 of each fuel cell 20 (step S1 in FIG. 2).

  At that time, the opening degree control of the valve 48 arranged in the air discharge channel 46 is performed. As shown in FIG. 4, when hydrogen gas is supplied to the oxidant gas flow path 32 and the fuel gas flow path 34 filled with air, the interfaces 70a and 70b between the air and the hydrogen gas are directed in the direction of arrow A. Moving. Therefore, by controlling the opening degree of the valve 48, the hydrogen gas / air interface 70a in the oxidant gas flow channel 32 and the air / hydrogen gas interface 70b in the fuel gas flow channel 34 are directed in the direction of arrow A. Are set to the same speed (step S2). Thereby, fuel gas can be simultaneously supplied to the oxidant gas flow path 32 and the fuel gas flow path 34. Instead of controlling the opening degree of the valve 48, it is also possible to supply fuel gas at the same time by providing a pressure loss member (not shown) in the oxidant gas flow path 32.

  Next, the process proceeds to step S3, where it is determined whether or not the supply of hydrogen gas to the oxidant gas flow path 32 is terminated. Here, for example, when it is determined that a predetermined amount (predetermined stack pipe volume) of hydrogen gas has been supplied to the fuel cell stack 12, or when the hydrogen gas satisfies a predetermined time (to satisfy the above volume). When it is determined that only the required time has been supplied, it is determined that the supply of hydrogen gas to the oxidant gas flow path 32 has been completed (YES in step S3), and the process proceeds to step S4, where the oxidant gas flow The supply of hydrogen gas to the passage 32 is stopped. Specifically, the air supply flow path 42 and the hydrogen supply flow path 52 are blocked by closing the valve 60.

  Then, as shown in FIG. 5, when the valve 44 is opened, air is sent to the air supply channel 42 via the air compressor 40. This air is supplied to the oxidant gas flow path 32 provided in each fuel cell 20 in the fuel cell stack 12 (step S5).

  Accordingly, air is supplied to the oxidant gas passage 32 and hydrogen gas is supplied to the fuel gas passage 34. In this state, the switch 68 is closed, whereby the fuel cell stack 12 is electrically connected to the load 66 (see step S6 and FIG. 6). For this reason, activation of the fuel cell stack 12 is started.

  At the start-up, the oxidant gas is sent to the oxidant gas flow path 32 of each fuel cell 20 and supplied along each cathode side electrode 24. On the other hand, the fuel gas is supplied to each fuel gas channel 34 of the fuel cell 20 and supplied along each anode side electrode 26. 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.

  Further, 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.

  In this case, in the first embodiment, when the operation of the fuel cell system 10 is stopped, the oxidant gas flow paths 32 and the fuel gas flow paths 34 of the fuel cell stack 12 are filled with air. When starting the fuel cell system 10, first, hydrogen gas is simultaneously supplied to the oxidant gas passage 32 and the fuel gas passage 34.

  For this reason, the air remaining in the oxidant gas flow path 32 and the fuel gas flow path 34 is replaced with hydrogen gas, and then air is supplied only to the oxidant gas flow path 32. Therefore, compared with a case where hydrogen gas is supplied to the fuel gas flow channel 34 and air is supplied to the oxidant gas flow channel 32 in a state where air exists in the oxidant gas flow channel 32 and the fuel gas flow channel 34, respectively. Thus, a partial increase in potential can be suppressed, and deterioration of the electrode catalyst layer can be suppressed.

  In addition, after the oxidant gas flow path 32 and the fuel gas flow path 34 are replaced with hydrogen gas, air is supplied to the oxidant gas flow path 32. And air are mixed, and a high potential is easily generated in the anode side electrode 26. At that time, since the activity of the anode side electrode 26 can be set lower than that of the cathode side electrode 24, it is possible to satisfactorily prevent the electrode catalyst of the anode side electrode 26 from deteriorating.

  As a result, in the first embodiment, it is possible to obtain an effect that the degradation of the electrode catalyst can be prevented as much as possible by a simple process, and the power generation performance of the entire fuel cell stack 12 can be maintained satisfactorily.

  Further, the opening degree of the valve 48 is controlled in order to simultaneously supply hydrogen gas to the oxidant gas passage 32 and the fuel gas passage 34. Therefore, as shown in FIG. 4, in the oxidant gas flow channel 32 and the fuel gas flow channel 34, the air and hydrogen gas interfaces 70a and 70b are controlled to have the same speed at which they move in the direction of arrow A. There is an advantage that a partial increase in potential is surely suppressed.

  FIG. 8 is a schematic configuration diagram of a fuel cell system 80 to which the activation method according to the second embodiment of the present invention is applied. Note that the same components as those of the fuel cell system 10 used in the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted.

  The fuel cell system 80 includes a dilution box 82 to which the air discharge channel 46 and the off-gas channel 62 are connected. The dilution box 82 is connected to the air supply passage 42 by a bypass passage 84 that is positioned between the air compressor 40 and the valve 44, and the bypass passage 84 is provided with a valve 86. Arranged.

  In the second embodiment configured as described above, when purging the oxidant gas flow path 32 and the fuel gas flow path 34 with hydrogen gas, the valve 44 is closed, while the valves 54, 60, 48 and 86 are Opened. Therefore, the hydrogen gas supplied from the hydrogen tank 50 to the hydrogen supply flow path 52 is supplied to the fuel gas flow path 34 and the oxidant gas flow path 32, and the surplus hydrogen gas is discharged to the off-gas flow path 62 and the air discharge. It is introduced into the dilution box 82 via the flow path 46.

  At that time, the air compressor 40 is driven and air is introduced into the dilution box 82 through the bypass channel 84. Therefore, in the dilution box 82, the discharged hydrogen gas is sufficiently diluted with air and then discharged out of the system.

  For this reason, in the second embodiment, the hydrogen gas discharged from the fuel cell stack 12 in the hydrogen gas purge can be sufficiently diluted with air while having the same effect as the first embodiment. It is possible to obtain an effect that the treatment of the discharged hydrogen gas is favorably and easily performed.

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 a flowchart explaining the said starting method. It is explanatory drawing of the purge process by hydrogen gas. It is explanatory drawing of the interface of hydrogen gas and air in the said purge process. It is explanatory drawing at the time of supplying air to the oxidant gas flow path purged with hydrogen gas. It is explanatory drawing at the time of starting a connection by connecting load to a fuel cell stack. It is explanatory drawing at the time of stopping driving | operation of the said fuel cell system. It is a schematic block diagram of the fuel cell system with which the starting method which concerns on the 2nd Embodiment of this invention is applied.

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 channel 34 ... Fuel gas channel 40 ... Air compressor 42 ... Air supply channel 44, 48, 54, 60, 86 ... Valve 46 ... Air exhaust Channel 50 ... Hydrogen tank 52 ... Hydrogen supply channel 56 ... Ejector 62 ... Off-gas channel 66 ... Load 82 ... Dilution box 84 ... Bypass channel

Claims (3)

A fuel cell having 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 generating electric power by an electrochemical reaction of the oxidant gas and the fuel gas A starting method of a fuel cell system, wherein the operation is stopped in a state where the oxidant gas flow path and the fuel gas flow path are filled with the oxidant gas,
Simultaneously supplying the fuel gas to the oxidant gas flow path and the fuel gas flow path;
Supplying the oxidant gas to the oxidant gas flow path after stopping the supply of the fuel gas to the oxidant gas flow path;
Connecting a load to the fuel cell and starting power generation by the fuel cell;
A starting method for a fuel cell system, comprising:   2. The starting method according to claim 1, wherein when the fuel gas is simultaneously supplied to the oxidant gas flow path and the fuel gas flow path, the moving speed of the interface between the oxidant gas and the fuel gas is made equal. A starting method for a fuel cell system, comprising:   The start-up method according to claim 1 or 2, wherein when supplying the fuel gas simultaneously to the oxidant gas flow path and the fuel gas flow path, the bypass flow path branches from the upstream side of the oxidant gas flow path. A method for starting a fuel cell system, comprising the step of diluting the fuel gas discharged from the fuel cell through the supplied oxidant gas.

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