JP5118370B2 - Anode scavenging system for fuel cell - Google Patents

Description

  The present invention relates to a fuel cell anode scavenging system that scavenges residual hydrogen in an anode system including an anode electrode of a fuel cell and a fuel gas (hydrogen) supply passage in the vicinity thereof.

  In general, a fuel cell has a plurality of cells stacked in series with a cathode electrode supplied with oxygen in the air on one side and an anode electrode supplied with hydrogen on the other side across a polymer electrolyte membrane. It is composed of a stack structure. The fuel cell generates electric power by the electrochemical reaction of each cell, and supplies the load with electric energy generated by the stack in which the cells are connected in series. For reasons such as improving fuel efficiency, hydrogen discharged from the fuel cell is recirculated using an ejector or the like disposed in a hydrogen supply path that is a fuel gas supply path immediately before the stack.

  The fuel cell uses a catalyst such as platinum as an electrode in order to promote an electrochemical reaction. However, when the power generation of the fuel cell is stopped, if hydrogen remains in each cell of the stack, the performance of the catalyst and the polymer electrolyte membrane deteriorates. Therefore, from the cathode gas supply device, it enters the stack and the anode system near the stack. Scavenging is performed by supplying air to exhaust residual hydrogen in the stack and the anode system.

  Conventionally, when scavenging the inside of the anode system, in order to secure a flow rate of air for scavenging, the air supply path immediately before the cathode electrode of the stack is connected to the hydrogen supply path immediately before the anode electrode of the stack and downstream of the ejector. A scavenging valve is installed in the pipeline. On the other hand, the secondary shut-off valve that closes the pipe in the anode system connected to the stack when power generation of the fuel cell is stopped is arranged in the hydrogen supply path via the heat exchanger, filter, and secondary regulator upstream from the ejector. ing.

In addition, there exist the following patent document 1 and patent document 2 as literature well-known invention concerning this application.
JP 2006-147213 A (see FIG. 1) Japanese Patent Laying-Open No. 2005-302609 (see FIG. 1)

  By the way, according to the above-described conventional configuration, the scavenging air supplied from the cathode gas supply device scavenges the stack and the inside of the conduit from the ejector to the stack, but the heat exchanger, filter, secondary, upstream from the ejector. Hydrogen in the pipe line leading to the regulator and the secondary shut-off valve remains sealed even during scavenging and cannot be scavenged. Therefore, after scavenging, the trapped hydrogen may spontaneously diffuse into the stack and the hydrogen gas concentration in the stack may be about 5% at the maximum.

  FIG. 7 is a graph showing the relationship between the hydrogen gas concentration [%] (horizontal axis) and the cathode potential [V] (vertical axis) in the stack when the fuel cell system is stopped.

  As shown in FIG. 7, when residual hydrogen remains in the stack at a predetermined concentration (for example, gas concentration of 0.5%) or more, the cathode potential in the stack increases greatly. Then, a phenomenon occurs in which a part of the metal of the catalyst in the electrode is ionized and moves into the polymer electrolyte membrane, and OH radicals are generated by a chemical reaction between the ionized metal and oxygen and hydrogen in the polymer electrolyte membrane. Then, the polymer electrolyte membrane is decomposed. Therefore, there is a possibility that the performance of the catalyst in the electrode deteriorates and the polymer electrolyte membrane deteriorates.

  In view of the above circumstances, the present invention prevents the deterioration of catalyst performance and polymer electrolyte membrane due to residual hydrogen in the anode system when the fuel cell system is stopped, and improves the performance and durability of the fuel cell anode. The purpose is to provide a system scavenging system.

In order to achieve the above object, an anode scavenging system for a fuel cell according to the present invention was obtained by a reaction between a fuel gas supplied to an anode electrode through a fuel gas supply passage and an oxidant gas supplied to a cathode electrode. An anode system scavenging system for a fuel cell having a fuel cell for supplying current to an external load circuit and scavenging an anode electrode and a fuel gas supply path in the vicinity thereof with an oxidant gas, and is provided in the fuel gas supply path And is connected to a fuel gas supply path immediately after the shut-off means, and is connected to an oxidant gas supply path to the cathode electrode during the first scavenging process. A first introduction part for supplying an oxidant gas to the fuel gas supply channel, and an oxidant gas can be introduced by the first introduction part during the first scavenging process, while at the second scavenging process A first valve to preclude the introduction of the oxidant gas, the oxidant gas from being connected to the fuel gas supply passage oxidizing gas supply passage when the second scavenging process, the blocking means and the anode electrode in the fuel gas supply passage The second introduction part introduced between the ejector and the anode electrode provided between the anode and the anode electrode, the second valve enabling the introduction of the oxidant gas by the second introduction part, and the anode electrode were discharged A circulation flow path for circulating the fuel exhaust gas to the anode electrode through the ejector , and a control device for controlling the first scavenging process and the second scavenging process, and the first introduction part immediately after the shut-off means In addition, the control device is connected to the fuel gas supply path upstream of the ejector, and the control device closes the shut-off means and the second valve during the first scavenging process, and sends the oxidant gas immediately after the shut-off means from the first introduction unit. Supply to the gas supply path, during the second scavenging process, While closing the shut-off means, the second valve is opened, the oxidant gas is introduced from the second introduction part into the fuel gas supply path downstream of the ejector and supplied to the anode electrode, and when the power generation of the fuel cell is stopped, Control is performed so that the second scavenging process is performed after the first scavenging process .

  According to the fuel system anode scavenging system of the first aspect of the present invention, since the first introduction part and the first valve are provided, the anode system including the anode electrode of the fuel cell and the fuel gas supply path in the vicinity thereof is provided. When scavenging, it is possible to surely scavenge residual hydrogen in the fuel gas supply path that is difficult to scavenge from the shutoff means in the fuel gas supply path to the anode electrode at the stack inlet, preventing stack deterioration and catalyst deterioration. is there.

In addition , by installing the valves separately in the second introduction part of the scavenging passage in the stack of the fuel cell and the first introduction part of the scavenging passage from the shut-off means of the fuel gas supply passage to the anode electrode at the stack inlet The scavenging flow rate for each flow path can be adjusted and the scavenging timing can be controlled, so that the optimum scavenging can be performed.

According to the anode scavenging system for a fuel cell according to claim 2 of the present invention, the first valve is constituted by a simple check valve, and the cost can be reduced.

  Embodiments of the present invention will be described below with reference to the accompanying drawings.

  A fuel cell system 1 according to an embodiment to which the present invention is applied includes a fuel cell 2 for supplying electric energy to a load of an external load circuit such as a travel motor, as shown in FIG. 2 (to be described later) cathode gas supply device 3 for supplying oxygen in the oxidant gas to the cathode electrode (oxygen electrode) 2c of the 2S, and fuel to the anode electrode (hydrogen electrode) 2b of the stack 2S of the fuel cell 2 It comprises an anode gas supply device 4 for supplying gaseous hydrogen, and a control device 5 for controlling both the supply devices 3 and 4 and an external load circuit.

  The fuel cell 2 includes a membrane electrode structure in which one side of a solid polymer electrolyte membrane 2a having ionic conductivity is sandwiched between an anode electrode 2b containing a catalyst and the other side of a cathode electrode 2c containing a catalyst. Many cells, for example, 200 cells stacked in series, are formed in a structure of a stack 2S in which both surfaces of (MEA) are sandwiched between conductive separators (not shown). The separator is formed with a hydrogen passage, an air passage, and a cooling water passage. Air, hydrogen supplied from a cathode gas supply device 3, an anode gas supply device 4, and a cooling water circulation device (not shown), respectively. The water is circulated so as not to mix.

  This fuel cell 2 is supplied with hydrogen from the anode gas supply device 4 to the anode electrode 2b and air is supplied from the cathode gas supply device 3 to the cathode electrode 2c. And the electric current is taken out from the fuel cell 2 to the load, and the supplied hydrogen and oxygen are consumed. If no current is taken out from the fuel cell 2, the supplied hydrogen and oxygen are not consumed and are discharged from the fuel cell 2 as exhaust hydrogen and exhaust air. Further, for reasons such as improving fuel efficiency, the hydrogen discharged from the fuel cell 2 is recirculated and used using an ejector (described later) disposed in the hydrogen supply path immediately before the stack.

  Here, in the fuel cell system 1, the performance of the fuel cell 2 caused by the deterioration of the catalyst and the polymer electrolyte membrane due to the residual hydrogen in the stack 2 </ b> S when the power generation of the fuel cell 2 is stopped and the pipe connected to the stack 2 </ b> S. A scavenging process is performed to discharge residual hydrogen in the stack 2S and the hydrogen supply path (fuel gas supply path) near the stack 2S to the dilution box (described later) while power generation of the fuel cell 2 is stopped for the purpose of preventing the decrease. It has been broken.

[First embodiment (reference embodiment) ]
FIG. 2 shows the configuration of the fuel cell 2 in the fuel cell system according to the first embodiment around the stack 12S and the anode gas supply device 4 in the vicinity of the stack 12S, and the flow of hydrogen, air, and scavenging gas in the piping. It is a conceptual block diagram.

  The fuel cell system stack 12S of the first embodiment and the anode gas supply device 4 near the stack 12S are provided in a hydrogen supply path from a hydrogen supply source such as a high-pressure hydrogen tank as shown in FIG. The secondary regulator 13 that performs the above operation, the filter 14 that is provided immediately downstream of the secondary regulator 13 and prevents foreign matter from entering the stack 12S, and the hydrogen that is provided and supplied to the hydrogen supply path downstream of the filter 14 is supplied to the electric power of the fuel cell 2. A heat exchanger 15 for heating to a temperature suitable for a chemical reaction, a secondary shutoff valve (shutoff means) 16 provided in a hydrogen supply path downstream of the heat exchanger 15 and shutting off the supply of hydrogen when the fuel cell 2 is stopped, An ejector 17 that is provided immediately downstream of the secondary shutoff valve 16 and recirculates the hydrogen discharged from the stack 12S, and a hydrogen and supply supplied by connecting a pipe downstream of the ejector 17 are connected. The stack 12S for generating power by the electrochemical reaction with the generated oxygen, and the scavenging pipe for supplying scavenging air connected to the pipe H1 for supplying hydrogen to the anode electrode (hydrogen electrode) 12b of the stack 12S (first introduction part) ) S1 and an intake scavenging valve (first valve) 18 provided in the scavenging pipe S1 and opened during scavenging, and disposed in a pipe between the stack 12S and the dilution box B and opened during scavenging to discharge the scavenging gas to the dilution box B And a discharge gas scavenging valve 19 to be configured.

  Power generation in the fuel cell system of the first embodiment is performed as follows. During power generation of the fuel cell 2, the secondary shutoff valve 16 is opened to supply fuel gas hydrogen, and the scavenging process is not performed, so that the inlet scavenging valve 18 and the outlet scavenging valve 19 are closed.

  The hydrogen sent from the hydrogen supply source to the secondary regulator 13 is depressurized to 1 MPa in the secondary regulator 13 and the foreign matter is removed by the filter 14 and then sent to the heat exchanger 15 through the piping as shown by the arrow. It is done. The hydrogen sent to the heat exchanger 15 is heated to a temperature suitable for the electrochemical reaction of the fuel cell 2, for example, 80 to 90 degrees, and is sent to the secondary shutoff valve 16 through the pipe as shown by an arrow. Via the ejector 17, as indicated by an arrow, it is sent to the anode electrode (hydrogen electrode) 12 b of the stack 12 </ b> S through a pipe. In addition, the hydrogen sent to the anode electrode (hydrogen electrode) 12b of the stack 12S is decompressed to 130 kPa.

  On the other hand, the air supplied from the cathode gas supply device 3 is sent to the cathode electrode (oxygen electrode) 12c of the stack 12S as shown by the arrow through the pipe. When the fuel cell 2 is requested to receive a current from the load, hydrogen supplied to the anode electrode (hydrogen electrode) 12b of the stack 12S and oxygen in the air supplied to the cathode electrode (oxygen electrode) 12c become the stack 12S. Each cell in the inside performs an electrochemical reaction through the solid polymer electrolyte membrane 12a to generate electric power, and supply a current required for the load.

  Next, the scavenging process performed while the fuel cell system is stopped will be described. Since the fuel cell system is stopped, the secondary shutoff valve 16 is closed, the supply of hydrogen from the hydrogen supply source is stopped, and scavenging is performed, so that the inlet scavenging valve 18 and the outlet scavenging valve 19 are opened. It is.

  At the time of scavenging, scavenging air is sent from the cathode gas supply device 3 through a pipe to the cathode electrode (oxygen electrode) 12c of the stack 12S as shown by an arrow a11, and is also shown by an arrow a12 through the scavenging pipe S1. As described above, the air is sent to the pipe H1 downstream of the ejector 17 through the intake / scavenging valve 18, and is sent to the anode electrode (hydrogen electrode) 12b of the stack 12S as indicated by an arrow a13.

  Thus, the scavenging air sent to the stack 12S scavenges the residual hydrogen in the stack 12S and is discharged to the dilution box B through the piping through the outlet / scavenging valve 19, as indicated by an arrow a14. Further, a part of the scavenged air sent to the stack 12S is sent to the ejector 17 through a pipe as shown by an arrow a15, and again as shown by an arrow a13, the anode electrode (hydrogen electrode) of the stack 12S through the pipe H1. 12b and scavenging is performed.

  According to the configuration of the first embodiment, as shown in FIG. 2, the secondary shutoff valve 16 is disposed upstream of the hydrogen supply path in the vicinity of the ejector 17 and the scavenging of the scavenging process is guided to the pipe H <b> 1 downstream of the ejector 17. A scavenging pipe S1 and an intake scavenging valve 18 are provided, and the residual hydrogen scavenging system (the flow of scavenging of arrows a11, a12, a13, a14, a15) when power generation is stopped is shut off after power generation of the stack 12S is stopped. The system is arranged in the immediate vicinity of the shutoff valve 16 downstream.

  Therefore, the volume of the hydrogen supply pipe upstream of the ejector 17 at the time of scavenging can be virtually eliminated. Therefore, the hydrogen supply path from the secondary shut-off valve 16 that was difficult to scavenge when performing the anode scavenging to the inlet of the stack 12S. The residual hydrogen in the inside can be surely scavenged. Therefore, the deterioration of the polymer electrolyte membrane in the fuel cell 2 and the deterioration of the performance of the catalyst in the electrode can be prevented, and the performance and durability of the fuel cell 2 can be improved.

[Second Embodiment]
FIG. 3 is a view showing the configuration of the fuel cell 2 according to the second embodiment around the stack 22S of the fuel cell 2 and the anode gas supply device 4 in the vicinity of the stack 22S and the flow of hydrogen, air, and scavenging in the pipes by arrows. FIG.

In the second embodiment, the position of the secondary shutoff valve 16 in the first embodiment (see FIG. 2) is changed, and a scavenging pipe (first introduction portion of claim 1 ) S21 and an additional intake scavenging valve (claim) 1 and the other components are the same as those of the first embodiment, and the same constituent elements are designated by reference numerals 10 in FIG. 2 of the first embodiment. The place is changed to the number of 20 places, and detailed explanation is omitted.

  As shown in FIG. 3, in the second embodiment, the secondary shutoff valve 26 is provided upstream of the secondary regulator 23 in the hydrogen supply pipe. Further, a scavenging pipe S21 for supplying scavenging air is disposed so as to be connected to a hydrogen supply pipe H21 connecting the secondary regulator 23 and the secondary shutoff valve 26, and an additional inlet scavenging valve is connected to the scavenging pipe S21. 21 is provided.

  During power generation of the fuel cell 2 of the fuel cell system of the second embodiment, the secondary shut-off valve 26 is opened to supply hydrogen, and the inlet / outlet scavenging valve 28, the outlet / outlet scavenging valve 29, and the additional inlet / outlet scavenging valve 21 are closed. . The fuel gas hydrogen is supplied to the anode electrode of the stack 22S through the hydrogen supply pipe via the secondary shutoff valve 26, the secondary regulator 23, the filter 24, the heat exchanger 25, and the ejector 27 constituting the anode gas supply device 4. While supplying to (hydrogen electrode) 22b, air is supplied from the cathode gas supply device 3 to the cathode electrode 22c (oxygen electrode) of the stack 22S, and electricity is generated in each cell in the stack 22S to supply current to the load.

  Next, the scavenging process performed during the power generation stop of the fuel cell system according to the second embodiment will be described.

  Since power generation is stopped, the secondary shutoff valve 26 is closed, and supply of hydrogen from the anode gas supply device 4 to the anode electrode (hydrogen electrode) 22b of the stack 22S is stopped. In scavenging, first, residual hydrogen in the hydrogen supply pipe is scavenged. That is, the inlet / outlet scavenging valve 28 is closed, the outlet / outlet scavenging valve 29 and the additional inlet / outlet scavenging valve 21 are opened, and air is supplied from the cathode gas supply device 3 through the additional inlet / outlet scavenging valve 21 through the scavenging pipe S21 as indicated by arrows a21 and a22. Thus, the hydrogen is supplied to the hydrogen supply pipe H21 connecting the secondary regulator 23 and the secondary shutoff valve 26. The supplied air is then sent to the anode electrode (hydrogen electrode) 22b of the stack 22S through the hydrogen supply pipe via the secondary regulator 23, the filter 24, the heat exchanger 25, and the ejector 27 as indicated by an arrow a23. The hydrogen supply path downstream of the secondary shutoff valve 26 is scavenged. Thereafter, the air sent to the anode electrode (hydrogen electrode) 22b is further scavenged in the stack 22S, and then discharged to the dilution box B through the piping through the outlet / scavenging valve 29 as indicated by an arrow a24.

  Subsequently, scavenging of the circulation part is performed. That is, the additional scavenging inlet valve 21 is closed and the inlet scavenging valve (second valve of claim 2) 28 is opened, and the scavenging air is supplied from the cathode gas supply device 3 through the pipe as shown by an arrow a25 in the stack 22S. To the cathode electrode (oxygen electrode) 22c, and, as indicated by an arrow a26, the scavenging pipe (second introduction portion of claim 2) S22 is sent to the pipe H22 downstream of the ejector 27 through the scavenging valve 28, As shown by an arrow a23, it is sent to the anode 22 (hydrogen electrode) 22b of the stack 22S through the pipe H22. Thereafter, the scavenging air sent to the stack 22S scavenges residual hydrogen in the stack 22S and is discharged to the dilution box B through the piping through the outlet / scavenging valve 29 as indicated by an arrow a24. Further, after scavenging the inside of the stack 22S, a part of the scavenging air sent to the stack 22S is sent again to the ejector 27 through the piping as indicated by the arrow a27, and again as shown by the arrow a23. The gas is sent to the anode electrode (hydrogen electrode) 22b of the stack 22S through the supply pipe H22, and scavenging in the stack 22S is performed.

  According to the second embodiment, in the scavenging process, first, the additional inlet scavenging valve 21 is opened, the scavenging air is sent through the pipe S21, and the anode electrode (hydrogen electrode) 22b at the entrance of the stack 22S from downstream of the secondary shutoff valve 26. Then, the additional supply scavenging valve 21 is closed and the input scavenging valve 28 is opened, and the circulation part having the stack 22S and the ejector 27 is scavenged by the scavenging air. Therefore, scavenging in the entire system where residual hydrogen remains is possible.

  Further, the scavenging of the circulation section including the stack 22S and the scavenging in the hydrogen supply path from the secondary shutoff valve 26 to the stack 22S are divided, and the scavenging valve 28 and the additional scavenging inlet valve 21 are provided in each scavenging flow path. By installing, the adjustment of the scavenging flow rate and the scavenging timing for each scavenging flow path can be controlled, and the optimum scavenging is possible.

[Third Embodiment (Reference Embodiment) ]
FIG. 4 is a diagram showing the configuration of the fuel cell 2 according to the third embodiment around the stack 32S of the fuel cell 2 and the anode gas supply device 4 in the vicinity of the stack 32S and the flow of hydrogen, air, and scavenging gas in the pipes by arrows. FIG.

The third embodiment has a configuration in which a backflow prevention valve 31 is provided instead of the secondary shutoff valve 16 in the first embodiment (see FIG. 2), and the other configurations are the same as those in the first embodiment. Therefore, the same constituent elements are shown by changing the numbered 10's place in FIG. 2 of the first embodiment to the number of the 30th place, and detailed description thereof will be omitted.

As shown in FIG. 4, in the third embodiment, the hydrogen supply pipe connecting the heat exchanger 35 and Ezeku motor 3 7 are provided check valve 31, upstream of the hydrogen supply channel of the secondary regulator 33 Is provided with a shut-off valve 36. Here, the backflow prevention valve 31 enables fluid to flow from the heat exchanger 35 side upstream of the hydrogen supply path to the ejector 37 side downstream of the hydrogen supply path, and from the ejector 37 downstream of the hydrogen supply path upstream of the hydrogen supply path. This prevents fluid from flowing into the heat exchanger 35 side. Further, when the supply of hydrogen is stopped, the backflow prevention valve 31 causes hydrogen in the hydrogen supply path on the heat exchanger 35 side upstream from the backflow prevention valve 31 to flow into the hydrogen supply path on the ejector 37 side downstream from the backflow prevention valve 31. It is set not to flow.

  In the power generation of the fuel cell 2 of the fuel cell system of the third embodiment, the shutoff valve 36 is opened to supply hydrogen, the inlet / outlet scavenging valve 38 and the outlet / outlet scavenging valve 39 are closed, and hydrogen is supplied to the anode gas supply device 4. While supplying the cut-off valve 36, the secondary regulator 33, the filter 34, the heat exchanger 35, and the ejector 37 to the anode electrode (hydrogen electrode) 32b of the stack 32S through the hydrogen supply pipe, air is supplied to the cathode gas supply device. 3 is supplied to the cathode electrode 32c (oxygen electrode) of the stack 32S, and power is generated in each cell in the stack 32S to supply current to the load.

  Next, the scavenging process performed during the power generation stop of the fuel cell system according to the third embodiment will be described.

  Since the power generation is stopped, the shutoff valve 36 is closed, and the supply of hydrogen from the anode gas supply device 4 to the anode electrode (hydrogen electrode) 32b of the stack 32S is stopped. In the scavenging process, the inlet scavenging valve 38 is opened, and the scavenging air is sent from the cathode gas supply device 3 to the cathode electrode (oxygen electrode) 32c of the stack 32S through the pipe as shown by the arrow a31, and the arrow a32 As shown in FIG. 5, the gas is sent to the pipe H31 downstream of the ejector 37 through the scavenging pipe S3 through the inlet / scavenging valve 38, and sent to the anode electrode (hydrogen electrode) 32b of the stack 32S through the pipe H31 as shown by an arrow a33. Thus, the scavenging air sent to the stack 32S scavenges residual hydrogen in the stack 32S and is discharged to the dilution box B through the piping through the outlet / scavenging valve 39 as indicated by an arrow a34. Further, a part of the scavenged air sent to the stack 32S is scavenged in the stack 32S, and then sent again to the ejector 37 through the pipe (circulation flow path of claim 3) H32 as shown by the arrow a35. As shown in FIG. 4, the gas is sent to the anode electrode (hydrogen electrode) 32b of the stack 32S through the pipe H31, and scavenging in the stack 32S is performed. In this case, the backflow prevention valve 31 is provided in the hydrogen supply pipe upstream of the ejector 37, and the backflow in which the remaining hydrogen flows into the hydrogen supply path upstream of the backflow prevention valve 31 is prevented. Further, since the backflow prevention valve 31 is stopped from supplying hydrogen, it prevents the hydrogen in the hydrogen supply path upstream from the backflow prevention valve 31 from flowing into the hydrogen supply path downstream from the backflow prevention valve 31. Thus, scavenging of the circulating portion including the stack 32S and the ejector 37 downstream from the backflow prevention valve 31 is performed smoothly.

  According to the third embodiment, the backflow prevention valve 31 blocks the flow of fluid between the circulation unit having the stack 32S and the ejector 37 and the hydrogen supply path upstream from the backflow prevention valve 31 during the scavenging process. Residual hydrogen in the downstream circulation section is smoothly scavenged, and residual hydrogen in the hydrogen supply path upstream from the backflow prevention valve 31 can be prevented from diffusing into the circulation section. That is, with the simple configuration provided with the backflow prevention valve 31, it is possible to prevent the residual hydrogen in the hydrogen supply path that has been difficult to scavenge from diffusing to the stack 32S side.

[Fourth Embodiment]
FIG. 5 is a diagram showing the configuration of the fuel cell 2 according to the fourth embodiment around the stack 42S of the fuel cell 2 and the anode gas supply device 4 in the vicinity of the stack 42S and the flow of hydrogen, air, and scavenging in the pipes by arrows. FIG.

As shown in FIG. 5, in the fourth embodiment, the position of the secondary shutoff valve 16 in the first embodiment (see FIG. 2) is changed, and a scavenging pipe S41 and an additional scavenging check valve (reverse of claim 2 ) are used. Stop valve) 41 is provided, and other configurations are the same as those of the first embodiment. Therefore, the same constituent elements are designated by 10 in the numbering of FIG. 2 of the first embodiment. The number is changed to the 40's place and detailed description is omitted.

  In the fourth embodiment, the secondary shutoff valve 46 is provided upstream of the secondary regulator 43 in the hydrogen supply pipe. Further, a scavenging pipe S41 is provided for connecting a pipe for supplying air connected to the cathode electrode 42c (oxygen electrode) of the stack 42S and a hydrogen supply pipe H41 for connecting the secondary regulator 43 and the secondary shutoff valve 46. An additional scavenging check valve 41 is provided in the scavenging pipe S41. Here, the additional scavenging check valve 41 prevents hydrogen in the hydrogen supply path from flowing to the air supply path side through the scavenging pipe S41. Further, the additional scavenging check valve 41, when generating power is stopped and scavenging air is sent to the scavenging pipe S41, the air pressure on the air supply path side becomes larger than the hydrogen pressure in the hydrogen supply path including the hydrogen supply pipe H41. The scavenging air is configured to flow toward the hydrogen supply path.

  When generating power in the fuel cell 2 of the fuel cell system of the fourth embodiment, the secondary shut-off valve 46 is opened to supply hydrogen, and the inlet and outlet scavenging valves 48 and 49 are closed. Then, hydrogen from a hydrogen supply source such as a high-pressure hydrogen tank is supplied to a hydrogen supply pipe via a secondary shut-off valve 46, a secondary regulator 43, a filter 44, a heat exchanger 45, and an ejector 47 constituting the anode gas supply device 4. And supply air to the cathode electrode 42c (oxygen electrode) of the stack 42S from the cathode gas supply device 3 to generate electricity in each cell in the stack 42S and load. To supply current.

  Here, during power generation, the additional scavenging is performed because the hydrogen pressure on the hydrogen supply path side is greater than the air pressure on the air supply path side of the scavenging pipe S41, with the additional scavenging check valve 41 in the scavenging pipe S41 as a boundary. The check valve 41 is kept closed, and air on the air supply side is prevented from flowing into the hydrogen supply pipe H41 through the scavenging pipe S41.

  Next, the residual hydrogen scavenging process performed while the power generation of the fuel cell 2 of the fuel cell system according to the fourth embodiment is stopped will be described.

  Since power generation is stopped, the secondary shutoff valve 46 is closed, and supply of hydrogen from the anode gas supply device 4 to the anode electrode (hydrogen electrode) 42b of the stack 42S is stopped. In the scavenging process, first, scavenging of the hydrogen supply path downstream of the secondary shutoff valve 46 is performed. That is, in the state where the inlet / scavenging valve 48 is closed, the scavenging air is supplied from the cathode gas supply device 3 through the scavenging pipe S41 via the additional scavenging check valve 41 as shown by the arrow a41, and the secondary shutoff valve 46. And a hydrogen supply pipe H41 to which the secondary regulator 43 is connected. The scavenging air then passes through the hydrogen supply pipe via the secondary regulator 43, the filter 44, the heat exchanger 45, and the ejector 47 as indicated by arrows a42 and a43, and the anode electrode (hydrogen electrode) of the stack 42S. ) 42b and the hydrogen supply path to the anode electrode (hydrogen electrode) 42b downstream of the secondary shutoff valve 46 is scavenged. Thereafter, the scavenging air scavenges the inside of the stack 42S and is discharged to the dilution box B through the piping through the outlet / scavenging valve 49 as indicated by an arrow a44.

  Here, during the scavenging, the secondary shutoff valve 46 is closed, and the scavenging pipe is determined from the hydrogen pressure on the hydrogen supply path side of the scavenging pipe S41 with the additional scavenging check valve 41 in the scavenging pipe S41 as a boundary. Since the pressure of air on the air supply path side in S41 is larger, the scavenging air on the air supply side flows into the hydrogen supply pipe H41 through the scavenging pipe S41 via the additional scavenging check valve 41.

  Thereafter, scavenging of the circulating portion including the stack 42S and the ejector 47 is performed. That is, the scavenging air is sent from the cathode gas supply device 3 to the cathode electrode (oxygen electrode) 42c of the stack 42S through the pipe as shown by an arrow a45, and the intake and scavenging valve 48 is opened as shown by an arrow a46. Then, the gas is sent to the pipe H42 downstream of the ejector 47 through the scavenging pipe S42 via the inlet / scavenging valve 48, and sent to the anode electrode (hydrogen electrode) 42b of the stack 42S through the pipe H42 as indicated by an arrow a43. Thus, the scavenging air sent to the stack 42S scavenges residual hydrogen in the stack 42S and is discharged to the dilution box B through the piping through the outlet / scavenging valve 49 as indicated by an arrow a44. Further, after scavenging the inside of the stack 42S, a part of the scavenging air sent to the stack 42S is sent again to the ejector 47 through the pipe as shown by the arrow a47, and again as shown by the arrow a43. The gas is sent to the anode electrode (hydrogen electrode) 42b of the stack 42S through H42, and scavenging in the stack 42S is performed.

  According to the fourth embodiment, a scavenging pipe S41 that supplies scavenging air is connected to the hydrogen supply pipe H41 that connects the secondary shut-off valve 46 and the secondary regulator 43, and additional scavenging is added to the scavenging pipe S41. A check valve 41 is provided. Since the additional scavenging check valve 41 sends scavenging air to the hydrogen supply pipe H41 connecting the secondary shut-off valve 46 and the secondary regulator 43 during scavenging, scavenging is difficult. It is possible to scavenge residual hydrogen in the hydrogen supply path from the secondary shutoff valve 26 to the anode electrode (hydrogen electrode) 42b at the entrance of the stack 22S.

  Further, the additional scavenging check valve 41 that is a simple check valve can replace the additional scavenging valve 21 exemplified in the second embodiment, and the cost can be reduced.

[Fifth Embodiment (Reference Embodiment) ]
FIG. 6 shows, by arrows, the configuration around the stack 52S of the fuel cell 2 and the anode gas supply device 4 in the vicinity of the stack 52S and the flow of hydrogen, air, and scavenging in the pipe of the fuel cell system according to the fifth embodiment. It is a conceptual block diagram.

As shown in FIG. 6, the fifth embodiment, the second embodiment while changing the position of the secondary shut-off valve 16 in (see FIG. 2), the scavenging valve 5 1 out newly piping S 51 and additional scavenging Since the other configuration is the same as the configuration of the first embodiment, the similar components are designated by the 10th digit in the numbering of FIG. The detailed description will be omitted.

In the fifth embodiment, the secondary shutoff valve 56 is provided upstream of the secondary regulator 53 in the hydrogen supply pipe. Further, a scavenging pipe S51 for connecting the hydrogen supply pipe H51 for connecting the secondary shutoff valve 56 and the secondary regulator 53 and the pipe for connecting the outlet scavenging valve 59 and the dilution box B is provided. An additional discharge gas scavenging valve 51 is provided in the pipe S51.

When power is generated by the fuel cell 2 of the fuel cell system of the fifth embodiment, the secondary shutoff valve 56 is opened to supply hydrogen, and the inlet / outlet scavenging valve 58, the outlet scavenging valve 59, and the additional outlet scavenging valve 51 are closed. . Then, hydrogen from a hydrogen supply source such as a high-pressure hydrogen tank is supplied to a hydrogen supply pipe via a secondary shut-off valve 56, a secondary regulator 53, a filter 54, a heat exchanger 55, and an ejector 57 constituting the anode gas supply device 4. And supply air to the cathode electrode 52c (oxygen electrode) of the stack 52S from the cathode gas supply device 3 to generate power in each cell in the stack 52S. To supply current.

  Next, a residual hydrogen scavenging process that is performed while the fuel cell 2 of the fuel cell system according to the fifth embodiment is stopped will be described.

  Since the power generation is stopped, the secondary shutoff valve 56 is closed, and the supply of hydrogen from the anode gas supply device 4 to the anode electrode (hydrogen electrode) 52b of the stack 52S is stopped. Then, in order to perform scavenging, the inlet scavenging valve 58, the outlet scavenging valve 59, and the additional outlet scavenging valve 51 are opened, and the scavenging air is supplied from the cathode gas supply device 3 to the cathode electrode of the stack 52S as indicated by an arrow a51. 52c (oxygen electrode), and as indicated by an arrow a52, the hydrogen supply for connecting the ejector 57 and the stack 52S through the scavenging pipe 58 (second introduction portion of claim 5) S52 through the scavenging valve 58 Flow in pipe H52. The scavenging air sent to the hydrogen supply pipe H52 is diverted to flow to the anode electrode (hydrogen electrode) 52b of the stack 52S as indicated by an arrow a53, and the hydrogen supply path is routed through a wavy arrow a54. As shown in FIG. 4, the gas flows backward through the hydrogen supply pipe via the ejector 57, the heat exchanger 55, the filter 54, and the secondary regulator 53, and flows upstream of the hydrogen supply path.

  Thus, one scavenging air sent to the anode electrode (hydrogen electrode) 52b of the stack 52S scavenges residual hydrogen in the stack 52S together with the scavenging air sent to the cathode electrode 52c (oxygen electrode). Then, as shown by an arrow a55, it is discharged to the dilution box B through the piping through the outlet / scavenging valve 59. Further, after scavenging the stack 52S, a part of the scavenging air sent to the stack 52S is sent again to the ejector 57 through the piping as shown by the arrow a56, and again as shown by the arrow a53. The gas is sent to the anode electrode (hydrogen electrode) 52b of the stack 52S through the supply pipe H52, and scavenging in the stack 52S is performed.

  On the other hand, as indicated by a dashed arrow a54, the other scavenging air flowed upstream of the hydrogen supply path is supplied with hydrogen via an ejector 57, a heat exchanger 55, a filter 54, and a secondary regulator 53. After passing through the piping, as shown by an arrow a56, the additional scavenging valve 51 is passed through the scavenging piping S51 to be flown to the piping connecting the outlet scavenging valve 59 and the dilution box B, and discharged to the dilution box B. Is done.

  According to the fifth embodiment, in the scavenging process, the ejector 57, the heat exchanger 55, the filter 54, the secondary regulator 53, and the hydrogen supply path downstream of the secondary shut-off valve 56, in which residual hydrogen is difficult to escape by scavenging air, Residual hydrogen can be discharged out of the system from the hydrogen supply pipe connecting them.

  In addition, since the circulation part including the ejector 57 and the stack 52S can be scavenged, scavenging of both the circulation part and the hydrogen supply path that is difficult to scavenge is possible.

  The outlet / scavenging valve may also serve as a purge valve provided in the middle of the circulation path that guides the hydrogen discharged from the fuel cell 2 to the ejector.

1 is an overall configuration conceptual diagram showing a fuel cell system according to an embodiment of the present invention. The conceptual block diagram which represented the structure of the fuel cell stack of the first embodiment, the configuration around the anode gas supply device in the vicinity of the stack, and the flow of hydrogen, air, and scavenging in the pipes by arrows. The conceptual structure figure which represented the structure of the fuel cell stack of the second embodiment, the structure around the anode gas supply device in the vicinity of the stack, and the flow of hydrogen, air, and scavenging in the pipe by arrows. The conceptual structure figure which represented the structure of the fuel cell stack of 3rd Embodiment, the structure around the anode gas supply apparatus of the stack vicinity, and the flow of the hydrogen in the piping, air, and scavenging by the arrow. The conceptual block diagram which represented the structure of the surroundings of the stack of the fuel cell in the fuel cell system of 4th Embodiment, and the anode gas supply apparatus of the stack, and the flow of hydrogen, air, and scavenging in piping by the arrow. The conceptual structure figure which represented the flow of the stack of the fuel cell in the fuel cell system of 5th Embodiment, the anode gas supply apparatus of the stack vicinity, and the flow of hydrogen, air, and scavenging in piping. The figure which showed the relationship between the hydrogen gas density | concentration [%] (horizontal axis) and the cathode pole potential [V] (vertical axis) in the stack in which the fuel cell system is stopped.

Explanation of symbols

2 Fuel cell 12b Anode electrode (hydrogen electrode)
12c Cathode electrode (oxygen electrode)
16 Secondary shut-off valve (shut-off means)
18 Inlet scavenging valve (first valve)
21 Additional intake and scavenging valve (first valve of claim 2)
28 Inlet scavenging valve (second valve of claim 2)
31 Backflow prevention valve (check valve of claim 3)
37 Ejector (Circulation means of claim 3)
41 Additional scavenging check valve (check valve according to claim 4)
51 Additional outlet scavenging valve (third valve of claim 5)
56 Secondary shutoff valve (Cutoff means of claim 5)
58 Inlet scavenging valve (second valve of claim 5)
12b Anode electrode (hydrogen electrode)
12c Cathode electrode (oxygen electrode)
H32 piping (circulation flow path of claim 3)
S1 Scavenging piping (first introduction part)
S21 Scavenging piping (first introduction part of claim 2)
S22 Scavenging piping (second introduction part of claim 2)
S51 Scavenging piping (Delivery part of claim 5)
S52 Scavenging piping (second introduction part of claim 5)

Claims (2)

A fuel cell for supplying an external load circuit with a current obtained by a reaction between a fuel gas supplied to the anode electrode through a fuel gas supply path and an oxidant gas supplied to the cathode electrode; and the anode electrode and its vicinity An anode-based scavenging system for a fuel cell that performs a scavenging process on the fuel gas supply path with the oxidant gas,
A blocking means provided in the fuel gas supply path, for blocking the supply of the fuel gas to the anode electrode when the fuel cell is stopped;
A first introduction part connected to the fuel gas supply path immediately after the shut-off means, and supplying the oxidant gas from the oxidant gas supply path to the cathode electrode during the first scavenging process;
A first valve that allows the introduction of the oxidant gas by the first introduction unit during the first scavenging process, while disabling the introduction of the oxidant gas during the second scavenging process;
An ejector connected to the fuel gas supply path and configured to supply the oxidant gas from the oxidant gas supply path during the second scavenging process , between the shut-off means and the anode electrode in the fuel gas supply path ; A second introduction part for introducing the anode electrode from between the anode electrode and the anode electrode;
A second valve that enables introduction of oxidant gas by the second introduction part;
A circulation flow path for circulating the fuel exhaust gas discharged from the anode electrode to the anode electrode through the ejector ;
A control device that controls the first scavenging process and the second scavenging process;
The first introduction part is connected to a fuel gas supply path immediately after the blocking means and upstream of the ejector,
The controller is
During the first scavenging process, the shut-off means and the second valve are closed, and the oxidant gas is supplied from the first introduction part to the fuel gas supply path immediately after the shut-off means,
During the second scavenging process, the shut-off means is closed, the second valve is opened, and the oxidant gas is introduced from the second introduction part into the fuel gas supply path downstream of the ejector. Supplying the anode electrode ;
An anode-based scavenging system for a fuel cell , wherein the second scavenging process is controlled after the first scavenging process when power generation of the fuel cell is stopped . 2. The fuel cell anode scavenging system according to claim 1, wherein the first valve is a check valve that allows the oxidant gas to communicate only during the first scavenging process.

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