JP4602052B2 - Fuel cell system and scavenging method for fuel cell. - Google Patents

Description

  The present invention relates to a fuel cell scavenging method used in a fuel cell vehicle or the like and a fuel cell system using the method.

  A fuel cell mounted in a fuel cell vehicle or the like causes a chemical reaction between a fuel gas and an oxidant gas, and takes out the energy generated during this reaction directly as electric energy to an external circuit. In this type of fuel cell, an anode electrode and a cathode electrode are usually arranged on both sides of a solid polymer electrolyte membrane, and hydrogen is supplied as a fuel gas to the anode electrode side, while an oxidant gas is provided to the cathode electrode side. Air containing oxygen is supplied.

  Further, as a fuel cell system using such a fuel cell, there is a fuel cell system in which unreacted fuel gas that has passed through the anode electrode is returned to the inlet side of the anode electrode so as to use the fuel gas efficiently. The fuel cell system includes a fuel gas circulation passage that connects the outlet side and the inlet side of the anode electrode, and the fuel gas containing the reacted gas is repeatedly circulated through the passage, so that the anode electrode outlet including the circulation passage portion is provided. Moisture and other impurities gradually increase in the side passage. For this reason, the passage on the outlet side of the anode electrode is provided with a mechanism for appropriately discharging and purging the internal gas to the outside.

  Also, in this type of fuel cell system, when the operation of the fuel cell is stopped, moisture remaining in the anode electrode side and cathode electrode side passages is surely discharged to the outside, and the inside of the passage when the operation is resumed. It is necessary to prevent water clogging and freezing. As a countermeasure, a fuel cell system has been developed in which a scavenging gas is introduced to the anode side when the fuel cell is stopped, and water and other impurities in the passage are scavenged by the scavenging gas (see, for example, Patent Document 1). .

The fuel cell system described in Patent Document 1 supplies hydrogen gas from a hydrogen tank to the anode electrode, while supplying air to the cathode electrode by a compressor to generate power by the fuel cell. A large flow of air is sent simultaneously to the cathode and anode, thereby scavenging both electrodes.
JP 2003-331893 A

  However, since the scavenging method employed in this conventional fuel cell system supplies a large flow of air to the cathode and anode simultaneously by a common compressor (oxidant gas supply means), sufficient air is supplied to both electrodes. The compressor must be operated at a high output so that it can be supplied. For this reason, when the conventional scavenging method is adopted, there is a problem that the vibration and noise of the compressor, which is the oxidizing gas supply means, increase.

  Therefore, the present invention enables both the cathode electrode and the anode electrode to be surely scavenged while suppressing the operation output of the oxidant gas supply means, and achieves both the sure scavenging of both electrodes and the reduction of vibration and noise during scavenging. It is an object of the present invention to provide a fuel cell scavenging method and a fuel cell system using the scavenging method.

In order to achieve the above object, the invention described in claim 1 is directed to a fuel cell that generates power by reacting a fuel gas supplied to the anode electrode and an oxidant gas supplied to the cathode electrode, and the anode electrode. Fuel gas supply means for supplying fuel gas; oxidant gas supply means for supplying oxidant gas to the cathode electrode; and an introduction passage for introducing oxidant gas from the oxidant gas supply means to the anode electrode side; the provided, in a fuel cell system that performs the oxidant gas scavenging of the anode electrode and the cathode electrode supplied from the oxidant gas supply means, when the scavenging of the fuel cell, the cathode electrode from the oxidizing gas supply means after the oxidant gas supply to the scavenging flow control means for switching from said oxidant gas supply means to the oxygen-containing gas supply for scavenging to the anode electrode, before A fuel gas dilution means for diluting the fuel gas discharged from the anode electrode with an oxidant gas and discharging the fuel gas to the outside, and the anode electrode and the fuel gas dilution means are connected, and the fuel gas discharged from the anode electrode is A fuel gas discharge passage for flowing into the fuel gas dilution means, the cathode electrode and the fuel gas dilution means are connected, and an oxidant gas discharge for allowing the oxidant gas that has passed through the cathode electrode to flow into the fuel gas dilution means. And the scavenging flow rate control means includes a fuel gas discharge side valve that opens and closes the fuel gas discharge passage, and an oxidant gas side valve that opens and closes the oxidant gas discharge passage. When the oxidant gas supply means supplies the oxidant gas from the oxidant gas supply means to the cathode electrode, the flow rate control means fully opens the oxidant side valve to scavenge the cathode electrode. Thereafter, the oxidant side valve is set as a first opening area, which is narrowed to be smaller than the fully opened state, the supply of the oxidant gas to the anode electrode side is ensured, and the fuel gas discharge side valve is set as the second opening area. The anode electrode fuel gas is opened from the fully closed state, the oxidant gas is allowed to flow into the anode electrode from the introduction passage, and the anode gas fuel gas is diluted to a concentration not more than a specified value in the fuel gas dilution means. Is discharged to the fuel gas diluting means, and when performing switching for scavenging to the anode electrode, the oxidant side valve is set to a third opening area smaller than the first opening area, In order to increase the supply amount of the oxidant gas to the anode electrode side, the fuel gas discharge side valve is further throttled down to a fourth opening area larger than the second opening area. The oxidant gas is caused to flow into the anode electrode from the introduction passage, and scavenging of the anode electrode is performed.

In the case of the present invention, when scavenging the fuel cell, by the control by the scavenging flow rate control means, first, the oxidant gas is supplied to the cathode electrode, the cathode electrode side is scavenged, and then the anode electrode is oxidized for scavenging. The agent gas is supplied and the anode electrode side is scavenged. At this time, since the cathode electrode and the anode electrode are not simultaneously scavenged by the large flow rate of the oxidant gas, the maximum output requirement for the oxidant gas supply means becomes small.
In addition, the remaining fuel gas on the anode side can be allowed to flow into the fuel gas dilution means at a minute flow rate during the scavenging of the cathode electrode, and the fuel gas flowing into the fuel gas dilution means has a relatively high concentration, but the fuel gas Fully diluted by gas dilution means. Therefore, at this time, the exhaust gas concentration discharged to the outside through the fuel gas dilution means can be suppressed to a specified value or less. In addition, since the fuel gas on the anode electrode side can be flowed to the fuel gas dilution means side at a minute flow rate, the concentration of the fuel gas on the anode electrode side can be gradually reduced. Therefore, when the scavenging gas flow control means is switched to supply a large flow of oxidant gas from the oxidant gas supply means to the anode electrode side after that, the fuel gas on the anode electrode side can be diluted to some extent. Therefore, when the anode electrode is scavenged at once with a large flow of oxidant gas, the fuel gas diluted to some extent flows into the fuel gas dilution means, so the concentration of the fuel gas discharged from the fuel gas dilution means is regulated. It can be suppressed below the value.

According to a second aspect of the present invention, in the first aspect of the present invention, fuel consumption means for continuing power generation consumption is provided during scavenging of the fuel cell.
In this case, it is possible to gradually decrease the fuel gas concentration on the anode electrode side by continuing the power generation consumption.

According to a third aspect of the present invention, there is provided a fuel cell for generating power by reacting a fuel gas supplied to the anode electrode and an oxidant gas supplied to the cathode electrode, and a fuel gas supply for supplying the fuel gas to the anode electrode Means, an oxidant gas supply means for supplying an oxidant gas to the cathode electrode, and an introduction passage for introducing the oxidant gas from the oxidant gas supply means to the anode electrode side. In the fuel cell system in which the cathode electrode and the anode electrode are scavenged by the oxidant gas supplied from the means, the oxidant gas is supplied from the oxidant gas supply means to the cathode electrode during the scavenging of the fuel cell. After that, scavenging flow rate control means for switching from the oxidant gas supply means to oxidant gas supply for scavenging to the anode electrode, and the exhaust gas discharged from the anode electrode A fuel gas dilution means for diluting a fuel gas with an oxidant gas and discharging the gas to the outside; and the anode electrode and the fuel gas dilution means are connected, and the fuel gas discharged from the anode electrode is connected to the fuel gas dilution means An inflow fuel gas discharge passage; and an oxidant gas discharge passage for connecting the cathode electrode and the fuel gas diluting means and allowing the oxidant gas that has passed through the cathode electrode to flow into the fuel gas diluting means. A scavenging method for a fuel cell in a fuel cell system, wherein the scavenging flow rate control means comprises: a fuel gas discharge side valve for opening and closing the fuel gas discharge passage; and an oxidant gas side valve for opening and closing the oxidant gas discharge passage. When the oxidant gas is supplied from the oxidant gas supply means to the cathode electrode, the scavenging flow rate control means controls the oxidant side valve. After opening and scavenging the cathode electrode, the oxidant side valve is throttled smaller than the fully open state as the first opening area to ensure supply of the oxidant gas to the anode side and to discharge the fuel gas The side valve is opened from the fully closed state as the second opening area, the oxidant gas is caused to flow into the anode electrode from the introduction passage, and the fuel gas at the anode electrode is diluted to a concentration not more than a specified value in the fuel gas dilution means. Therefore, when performing the step of discharging the fuel gas of the anode electrode to the fuel gas dilution means and the switching for scavenging to the anode electrode, the scavenging flow rate control means causes the oxidant side valve to be turned on. In order to increase the supply amount of the oxidant gas to the anode electrode side as a third opening area that is smaller than the first opening area, the fuel is further reduced and the fuel is reduced. Opening the gas discharge side valve as a fourth opening area larger than the second opening area, and flowing the oxidant gas from the introduction passage into the anode electrode to scavenge the anode electrode; It is characterized by having.

According to the first and second aspects of the present invention, the oxidant gas is first supplied from the oxidant gas supply means to the cathode electrode, and after the scavenging of the cathode electrode is finished, the oxidant gas supply means from the same oxidant gas supply means has a time difference. Since the oxidant gas for scavenging is supplied to the gas, an increase in the maximum output demand for the oxidant gas supply means can be suppressed while securing a sufficient scavenging flow rate at each electrode. Therefore, it is possible to achieve both the positive scavenging of both poles and the reduction of noise and vibration during scavenging.
Further, when supplying the oxidant gas from the oxidant gas supply means to the cathode electrode, the fuel gas on the anode side is discharged to the fuel gas dilution means at a minute flow rate, so that when the cathode electrode is scavenged, the anode side Since the dilution can be performed in parallel, the scavenging time on the anode electrode side can be shortened without causing a large increase in the exhaust concentration of the fuel gas.

According to the second aspect of the present invention, the fuel gas on the anode electrode side can be consumed by the power generation consumption means before the anode electrode side is scavenged with the oxidant gas, so that the scavenging time on the anode electrode side is shortened. As a result, the remaining fuel gas on the anode electrode side can be effectively used.

  An embodiment of the present invention will be described below with reference to FIGS. In addition, embodiment described below is an aspect of the fuel cell system mounted in a fuel cell vehicle.

FIG. 1 is an overall configuration diagram of a fuel cell system according to the present invention.
As shown in the figure, the fuel cell 1 includes a solid polymer electrolyte membrane 1a (hereinafter referred to as “electrolyte membrane 1a”) made of a solid polymer ion exchange membrane or the like sandwiched between an anode 1b and a cathode 1c from both sides. Is formed by a stack in which a plurality of cells formed in (1) are stacked (schematically depicted as a single cell in the figure).

In the fuel cell 1, hydrogen gas is supplied as fuel gas to the anode 1b, and air containing oxygen as oxidant gas is supplied to the cathode 1c. When hydrogen gas is supplied to the anode 1b, hydrogen ions generated by the catalytic reaction at the anode 1b pass through the electrolyte membrane 1a and move to the cathode 1c, and electrochemical reaction with oxygen in the air at the cathode 1c. To generate electricity.
During power generation, water is generated on the cathode electrode 1c side, and a part of the generated water is reversely diffused to the anode electrode 1b side through the electrolyte membrane 1a.

  A fuel gas supply passage 2 for supplying hydrogen gas as a fuel gas is connected to the anode electrode 1b of the fuel cell 1, and an oxidant gas supply for supplying air as an oxidant gas to the cathode electrode 1c. A passage 3 is connected.

  A hydrogen tank 4 (fuel gas supply means in the present invention) for storing hydrogen gas is connected to the upstream side of the fuel gas supply passage 2 via an open / close valve 5. The opening / closing valve 5 is controlled to be opened / closed by a controller (not shown) so that hydrogen gas can be supplied from the hydrogen tank 4 to the anode 1b side by opening the opening / closing valve 5.

  The anode electrode 1b is connected to a fuel gas circulation passage 6 for returning unreacted hydrogen gas that has passed through the anode electrode 1b to the inlet side of the anode electrode 1b again. The fuel gas circulation passage 6 is joined and connected to the fuel gas supply passage 2 via the ejector 7 on the inlet side of the anode 1b, and unreacted hydrogen gas is mixed with fresh hydrogen and re-supplied to the anode 1b. .

  Further, a fuel gas discharge passage 9 is branched from the outlet side portion of the anode 1b of the fuel gas circulation passage 6. Three branch passages 9a, 9b, and 9c are provided in the middle of the fuel gas discharge passage 9, and a drain valve 10, a purge valve 11, and an air discharge valve 12 are interposed in the branch passages 9a, 9b, and 9c, respectively. Yes.

  The drain valve 10 is mainly intended to discharge the water accumulated in the fuel gas circulation passage 6 to the catch tank 13, and has the smallest opening area among the three valves 10, 11, and 12. It has become.

  The purge valve 11 is mainly intended to appropriately discharge moisture and other impurities mixed in the fuel gas circulation passage 6 to the outside during the operation of the fuel cell system. The three valves 10, 11, Of the twelve, the opening area is intermediate.

  The air discharge valve 12 discharges the gas scavenged in the fuel gas circulation passage 6 to the outside when the fuel cell is stopped, and has the largest opening area among the three valves 10, 11, and 12. .

  The branch passages 9a, 9b, and 9c join again at the downstream side of the valves 10, 11, and 12, and are connected to an exhaust gas inlet 14a of a dilution box 14 that will be described later, which is an oxidant gas dilution means. In this embodiment, the openings 10a, 11a, 12a through which the gas flows from the valves 10, 11, 12 constitute an exhaust port.

  On the other hand, on the upstream side of the oxidant gas supply passage 3, a compressor 8 (oxidant gas supply means in the present invention) for pressurizing and feeding air is connected. An oxidant gas discharge passage 16 is connected to the cathode 1c of the fuel cell 1 for discharging the air that has passed through the cathode 1c to the outside. A back pressure control valve 17 is provided in the middle of the oxidant gas discharge passage 16 to adjust the internal pressure of the cathode electrode 1c, and the downstream side of the oxidant gas discharge passage 16 is the dilution gas inlet 14b of the dilution box 14. It is connected to the.

  The dilution box 14 includes a discharge port 14c in addition to the exhaust gas introduction port 14a connected to the fuel gas discharge passage 9 and the dilution gas introduction port 14b connected to the oxidant gas discharge passage 16 as described above. The discharge port 14c is connected to a dilution discharge passage 18 that opens to the outside of the system. In the dilution box 14, the hydrogen gas on the fuel gas circulation passage 6 side flowing from the exhaust gas introduction port 14 a is mixed with the flow of air flowing from the dilution gas introduction port 14 b to the discharge port 14 c, and the diluted hydrogen gas is diluted therewith. It discharges outside the system through the discharge passage 18. A hydrogen concentration sensor 19 is provided in the dilution discharge passage 18 on the downstream side of the dilution box 14, and the detection signal is input to a controller (not shown).

  The oxidant gas supply passage 3 is provided with a branch passage 20 for introducing air (oxidant gas) fed from the compressor 15 to the inlet side of the anode 1b. An air introduction valve 21 that is controlled to be opened and closed by a controller is interposed in the introduction passage 20. The air introduction valve 21 normally closes the introduction passage 20 and opens the introduction passage 20 under the control of the controller when the fuel cell 1 is stopped.

  By the way, in the fuel cell system of this embodiment, scavenging of the cathode electrode 1b and the anode electrode 1c is performed by a large flow of air supplied from the compressor 8 when the fuel cell 1 is stopped. During scavenging of the electrodes 1b and 1c, on / off control of the on-off valve 5 in the hydrogen gas supply line, flow control of the compressor 8, on / off control of the air introduction valve 21 in the introduction passage 20, drain on the fuel gas discharge passage 9 The on / off control of the valve 10, the purge valve 11, and the air discharge valve 12, and the control of the back pressure control valve 17 on the oxidant gas discharge passage 16 are performed by a controller of a controller (not shown). In this embodiment, the controller of the controller, the valves 5, 21, 10, 11, 12, 17 and the drive unit of the compressor 8 constitute the scavenging flow rate control means in the present invention.

  Next, control of the fuel cell system when the fuel cell vehicle stops will be described according to the flowchart of FIG. 2 with reference to the timing chart of FIG. When the ignition switch of the fuel cell vehicle is ON, basically, the air introduction valve 21, the drain valve 10, the purge valve 11, and the air discharge valve 12 are all closed, and the open / close valve 5 is open.

  When the ignition switch is turned off, the controller first closes the opening / closing valve 5 and increases the flow rate of the compressor 15 in step 100. When the flow rate of the compressor 15 increases in this way, a large amount of air flows into the cathode 1c, and the cathode 1c and the oxidizing gas discharge passage 16 are scavenged by the air. In the next step 101, it is determined whether or not the elapsed time T from the closing of the opening / closing valve 5 has reached a predetermined time T1, and the process proceeds to the next step 102 after waiting for the predetermined time T1 to be reached. Until the process proceeds to step 102, the fuel cell system continues to generate power by a load (fuel consumption means) such as auxiliary equipment.

  In step 102, the power consumption due to the load is slightly reduced, the drain valve 10 and the air introduction valve 21 are opened, and the back pressure control valve 17 is slightly throttled. At this time, part of the air pumped from the compressor 8 flows through the introduction passage 20 into the anode 1b and further into the fuel gas circulation passage 6, and the hydrogen gas in the fuel gas circulation passage 6 is diluted by the air. While being discharged from the drain valve 10 to the dilution box 14 at a minute flow rate. At this time, since the back pressure control valve 17 is slightly throttled, the air flow rate on the cathode side slightly decreases as shown in FIG. 3, whereas a slight gas flow occurs on the anode side. This state continues until the elapsed time T reaches T2 in step 103, and proceeds to the next step 104 when T2 is reached. Until advancing to step 104, a part of the air pumped from the compressor 8 flows into the anode 1b side, but since a large amount of air still flows into the cathode 1c side, the air on the cathode 1c side still flows. Scavenging continues at this time.

In step 102, when the drain valve 10 is opened, the gas in the fuel gas circulation passage 6 flows into the exhaust gas inlet 14 of the dilution box 14. At this time, the opening area of the drain valve 10 is small, and the drain Since hydrogen gas gradually flows into the dilution box 14 from the valve 10, the hydrogen gas is sufficiently diluted in the dilution box 14 by the air introduced from the dilution gas inlet 14b. For this reason, the peak of the discharge concentration of the hydrogen gas discharged from the dilution discharge passage 18 is suppressed to a specified value or less as shown in FIG.
In this specification, “scavenging” means flowing a large flow of oxidant gas (air containing oxygen in this embodiment) to the cathode electrode or the anode electrode, and step 102 of this embodiment. , 103 is not included in “scavenging”.

  When the predetermined time has elapsed and the routine proceeds to step 104, the controller stops the power generation consumption by the load, and simultaneously opens the purge valve 11 and the air discharge valve 12, and further throttles the back pressure control valve 17. At this time, when the back pressure control valve 17 is greatly throttled, the air flow rate on the cathode side is greatly reduced as shown in FIG. 3, and as a result, scavenging of the cathode 1c is completed. On the other hand, on the anode side, since the purge valve 11 and the air discharge valve 12 having a large opening area are opened simultaneously, the inside thereof is scavenged by a large flow of air flowing into the anode electrode 1 b and the fuel gas circulation passage 6.

  At this time, a large amount of gas flows from the fuel gas circulation passage 6 into the dilution box 14, but the fuel gas circulation passage 6 has already been diluted to some extent by the introduced air from the compressor 8 in the preceding steps (S102, S103). Therefore, the hydrogen gas is sufficiently diluted by further air mixing in the dilution box 14. Therefore, the discharge concentration of the hydrogen gas discharged from the dilution discharge passage 18 at this time is also suppressed to a specified value or less (see FIG. 3). At this time, since the gas in the fuel gas circulation passage 6 is exhausted at once through the purge valve 11 and the air discharge valve 12, impurities such as moisture remaining in the fuel gas circulation passage 6 are reliably discharged to the outside at this time. Is done.

  This state is continued until the elapsed time T reaches T3 in step 105. When the elapsed time T reaches T3, the process proceeds to the next step 106, where the air introduction valve 21, the drain valve 10, the purge valve 11, the air discharge valve. All currently open valves such as 12 are closed and control is terminated at this stage.

  In this embodiment, the timing for switching from scavenging of the cathode electrode 1c to scavenging of the anode electrode 1b is determined by managing the elapsed time (see step 103 in FIG. 2), but downstream of the dilution box 14. The hydrogen gas concentration on the side is managed based on the detection signal of the hydrogen concentration sensor 19, and the scavenging on the cathode electrode 1c side is switched to the scavenging on the anode electrode 1b side when the hydrogen gas concentration falls below a set value. good.

  As described above, in this fuel cell system, when the ignition switch is turned off, the air supply flow rate by the compressor 8 is increased, and after scavenging the cathode electrode 1c side with a large flow of air first, Since the supply air flow rate from the compressor 8 to the anode electrode 1b side is rapidly increased by the control of the back pressure control valve 17 and the like, the anode electrode 1b side is scavenged all at once. The air can be surely scavenged by the air, and the output of the compressor 8 can be suppressed smaller than when the cathode 1c and the anode 1b are simultaneously scavenged. Therefore, in the case of this fuel cell system, the vibration and noise of the compressor 8 during scavenging can be greatly reduced.

  In this fuel cell system, a minute flow of air is introduced into the anode 1b through the introduction passage 20 (air introduction valve 21) in the latter half of the scavenging of the cathode electrode 1c, and the gas in the fuel gas circulation passage 6 is further removed. Since the exhaust gas is discharged little by little to the dilution box 14, the hydrogen gas in the cathode electrode 1c and the fuel gas circulation passage 6 is diluted little by little before shifting to scavenging of the anode electrode 1b, and the next anode electrode 1b. And the concentration of the exhaust hydrogen gas during this period can be suppressed to a specified value or less. In the next scavenging of the anode 1b, the remaining hydrogen gas in the fuel gas circulation passage 6 is diluted to some extent, so that the scavenging time of the anode 1b can be shortened.

  Furthermore, in the case of this embodiment, since the power generation consumption by the load (fuel consumption means) such as auxiliary devices is continued immediately before the scavenging of the cathode electrode 1c to the scavenging of the anode electrode 1b, the anode electrode 1b before the start of scavenging is started. The hydrogen gas concentration on the side can be further reduced, and the amount of hydrogen gas that is exhausted as it is can be reduced to effectively use energy.

  The present invention is not limited to the above embodiment, and various design changes can be made without departing from the scope of the invention. For example, although the above embodiment applies the fuel cell system and the scavenging method according to the present invention to a fuel cell vehicle, the present invention can also be applied to devices other than the fuel cell vehicle.

1 is a schematic configuration diagram of a fuel cell system showing an embodiment of the present invention. The flowchart which shows a part of processing content in the embodiment. The timing chart which shows the change of system states, such as the operation state of various valves in the embodiment, a power generation state, and a hydrogen concentration state.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Fuel cell 1b ... Anode electrode 1c ... Cathode electrode 4 ... Hydrogen tank 5 ... Opening / closing valve (scavenging flow control means) 8 ... Compressor 10 Drain valve (scavenging flow control means) 11 ... Purge valve (scavenging flow control means) 12 ... Air Discharge valve (scavenging flow rate control means) 17 ... back pressure control valve (scavenging flow rate control means) 14 ... dilution box (fuel gas dilution means) 20 ... air introduction passage (introduction passage)

Claims (3)

A fuel cell that generates electricity by reacting a fuel gas supplied to the anode electrode and an oxidant gas supplied to the cathode electrode; and
Fuel gas supply means for supplying fuel gas to the anode electrode;
An oxidant gas supply means for supplying an oxidant gas to the cathode electrode;
An introduction passage for introducing an oxidant gas from the oxidant gas supply means to the anode electrode side,
In the fuel cell system to perform scavenging of the anode electrode and the cathode electrode by the oxidant gas supplied from the oxidant gas supply means,
During scavenging of the fuel cell, after the oxidant gas supply from the oxidant gas supply means to said cathode electrode, switching from the oxidant gas supply means to the oxygen-containing gas supply for scavenging to the anode electrode Scavenging flow rate control means ;
A fuel gas dilution means for diluting the fuel gas discharged from the anode electrode with an oxidant gas and discharging it to the outside;
A fuel gas discharge passage for connecting the anode electrode and the fuel gas dilution means, and allowing the fuel gas discharged from the anode electrode to flow into the fuel gas dilution means;
An oxidant gas discharge passage for connecting the cathode electrode and the fuel gas diluting means and allowing the oxidant gas that has passed through the cathode electrode to flow into the fuel gas diluting means;
The scavenging flow rate control means includes
A fuel gas discharge side valve for opening and closing the fuel gas discharge passage, and an oxidant gas side valve for opening and closing the oxidant gas discharge passage,
The scavenging flow rate control means includes
When supplying the oxidant gas from the oxidant gas supply means to the cathode electrode, the oxidant side valve is fully opened to scavenge the cathode electrode, and then the oxidant side valve is used as the first opening area. The throttle is made smaller than in the fully open state to ensure the supply of the oxidant gas to the anode electrode side, and the fuel gas discharge side valve is opened from the fully closed state as the second opening area, and the oxidant gas is supplied from the introduction passage. Inflowing into the anode electrode and discharging the anode electrode fuel gas to the fuel gas dilution means in order to dilute the fuel gas of the anode electrode to a concentration below a specified value in the fuel gas dilution means,
When switching for scavenging to the anode electrode, supply of the oxidant gas to the anode electrode side with the oxidant side valve as a third opening area smaller than the first opening area In order to increase the amount, the fuel gas discharge side valve is further opened as a fourth opening area larger than the second opening area, and the oxidant gas is caused to flow into the anode electrode from the introduction passage. A fuel cell system for scavenging the anode electrode . 2. The fuel cell system according to claim 1 , further comprising fuel consuming means for continuing power generation consumption during scavenging of the fuel cell. A fuel cell for generating power by reacting a fuel gas supplied to the anode electrode and an oxidant gas supplied to the cathode electrode, a fuel gas supply means for supplying fuel gas to the anode electrode, and an oxidant to the cathode electrode An oxidant gas supply means for supplying a gas, and an introduction passage for introducing the oxidant gas from the oxidant gas supply means to the anode electrode side, and the oxidant gas supplied from the oxidant gas supply means In the fuel cell system for scavenging the cathode electrode and the anode electrode, the oxidant gas supply unit is configured to supply the oxidant gas from the oxidant gas supply unit to the cathode electrode when scavenging the fuel cell. Scavenging flow rate control means for switching to supply of oxidant gas for scavenging from the anode to the anode electrode, and fuel gas discharged from the anode electrode by oxidant gas A fuel gas diluting means for diluting and discharging to the outside, and a fuel gas discharge passage for connecting the anode electrode and the fuel gas diluting means to allow the fuel gas discharged from the anode electrode to flow into the fuel gas diluting means And an oxidant gas discharge passage for connecting the cathode electrode and the fuel gas diluting means and allowing the oxidant gas that has passed through the cathode electrode to flow into the fuel gas diluting means, and the scavenging flow rate control means A scavenging method for a fuel cell in a fuel cell system, comprising: a fuel gas discharge side valve for opening and closing the fuel gas discharge passage; and an oxidant gas side valve for opening and closing the oxidant gas discharge passage,
When supplying the oxidant gas from the oxidant gas supply means to the cathode electrode, the scavenging flow rate control means fully opens the oxidant side valve to scavenge the cathode electrode, and then the oxidant side valve. Is made smaller than the fully opened state as the first opening area to ensure the supply of the oxidant gas to the anode electrode side, and the fuel gas discharge side valve is opened from the fully closed state as the second opening area, An oxidant gas is caused to flow from the introduction passage into the anode electrode, and the fuel gas at the anode electrode is supplied to the fuel gas dilution means in order to dilute the fuel gas at the anode electrode to a concentration not more than a specified value in the fuel gas dilution means. Discharging process;
When performing switching for scavenging to the anode electrode, the scavenging flow rate control means sets the oxidant side valve to a third opening area smaller than the first opening area, and the anode electrode side. In order to increase the supply amount of the oxidant gas to the gas, the fuel gas discharge side valve is further opened as a fourth opening area larger than the second opening area, and the oxidant gas is opened from the introduction passage. And a step of scavenging the anode electrode by flowing the gas into the anode electrode .

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