JP4202219B2 - Discharge device and discharge method for fuel cell system - Google Patents

Description

  The present invention relates to a discharge device and a discharge method for discharging water and impurities (such as nitrogen) from a fuel gas circulation system of a fuel cell system.

  A fuel cell mounted on a fuel cell vehicle or the like includes an anode and a cathode on both sides of a solid polymer electrolyte membrane, a fuel gas (for example, hydrogen gas) is supplied to the anode, and an oxidant gas (for example, oxygen or oxygen) is supplied to the cathode. There is a type in which chemical energy related to the oxidation-reduction reaction of these gases is directly extracted as electric energy. In this fuel cell, hydrogen gas is ionized at the anode and moves through the solid polymer electrolyte, and electrons move to the cathode through an external load and react with oxygen to produce water to generate water. Electric energy can be taken out.

  Further, in this type of fuel cell, the gas discharged from the anode after being used for power generation, that is, the anode off-gas contains unreacted fuel gas. Therefore, in order to reduce fuel gas consumption, In many cases, a fuel cell system (hereinafter referred to as a hydrogen circulation type fuel cell system) is assembled that recycles the anode off-gas, mixes it with fresh fuel gas, and supplies the fuel cell again.

  By the way, as described above, water is generated on the cathode side for power generation in the fuel cell, but a part of the generated water on the cathode side passes through the solid polymer electrolyte membrane and moves to the anode side. If a part of the anode side gas passage in the fuel cell is blocked by the generated water, the amount of fuel gas supplied to the fuel cell decreases, which may adversely affect the power generation performance.

In addition, when a fuel gas containing a small amount of impurities (for example, oxygen, chlorine, ammonia, nitrogen, etc.) other than hydrogen is used in a hydrogen circulation fuel cell system, the concentration of the impurities increases due to circulation of the anode off-gas. However, the power generation performance of the fuel cell may become unstable, which may adversely affect the power generation performance.
Therefore, as disclosed in Patent Document 1, a discharge passage is connected to the fuel gas circulation passage, and if necessary, a discharge valve of the discharge passage is opened so that the generated water and impurities are part of the anode offgas. In addition, a fuel cell system has been devised that prevents the gas passage in the fuel cell from being blocked by the generated water, thereby reducing the impurity concentration in the fuel gas.
Japanese Patent Laid-Open No. 9-22714

When the generated water and impurities are discharged together with the anode off gas from the discharge valve in this way, hydrogen as fuel is also discharged, which affects fuel consumption. Therefore, in order to improve fuel efficiency, it is necessary to reduce the amount of hydrogen discharged from the discharge valve as much as possible. Conventionally, as a countermeasure, hydrogen discharge is minimized by providing an orifice in the discharge section or precisely controlling the opening / closing and opening of the discharge valve.
However, as long as water and impurities are discharged from the discharge valve together with the anode off gas containing hydrogen, in principle, the amount of hydrogen discharged cannot approach zero as much as possible, compared to the amount of product water and impurities to be discharged. It cannot be denied that the amount of discharged hydrogen is relatively large, and there is room for improvement in terms of improving fuel consumption.

However, if the discharge frequency and discharge amount of anode off gas from the discharge valve are limited to improve fuel efficiency, the power generation state of the fuel cell becomes unstable, and power supply to the drive source (motor) of the fuel cell vehicle is reduced. If it is performed, it may affect acceleration response and power performance.
Accordingly, the present invention provides a fuel cell system discharge apparatus and discharge method capable of reducing the amount of hydrogen released while ensuring the stability of power generation by reliably discharging water and impurities from the fuel cell system. It is.

In order to solve the above-mentioned problem, the invention according to claim 1 is directed to a cathode (for example, a fuel gas (for example, hydrogen gas in an embodiment to be described later) supplied to an anode (for example, an anode 2b in an embodiment to be described later). A fuel cell (for example, a fuel cell 2 in an embodiment to be described later) that is supplied with an oxidant gas (for example, air in an embodiment to be described later) to a cathode 2c) in an embodiment to be described later; A fuel gas supply passage (for example, a hydrogen supply passage 21 in an embodiment described later) for supplying fuel gas to the anode of the fuel cell, and an anode off-gas discharged from the anode of the fuel cell to the fuel gas supply passage An anode off-gas passage (for example, anode anode in an embodiment described later) for supplying the anode again. A fuel gas supply control means (for example, hydrogen in an embodiment to be described later) provided in the fuel gas supply passage upstream of the confluence of the gas passage 22) and the anode off-gas passage. A fuel cell system (for example, an embodiment to be described later) having a supply control valve V1) and a discharge valve (for example, an exhaust valve V2 in an embodiment to be described later) for discharging the gas in the anode off-gas passage. In the discharge device of the fuel cell system 1), the fuel gas supply control means reduces the fuel gas supply amount before discharging the gas in the anode off-gas passage by opening the discharge valve , When the ratio of the amount of hydrogen supplied to the fuel cell to the amount of hydrogen consumed by the fuel cell becomes 1, the supply amount of the fuel gas decreases And features that you stop.
By configuring in this way, the concentration of the fuel gas in the anode off-gas passage can be temporarily reduced to 0 compared with that during normal operation before the discharge valve is opened, and then the discharge valve is opened. The amount of fuel gas discharged from the discharge valve can be reduced.

According to a second aspect of the present invention, in the first aspect of the present invention, the amount of fuel gas reduced by the fuel gas supply control means is less than the amount of fuel gas supplied by the fuel cell during normal power generation. It is characterized by.
By configuring in this way, the ratio of the amount of hydrogen supplied to the fuel cell to the amount of hydrogen consumed by the fuel cell, that is, the stoichiometry can be made closer to “1”, and the amount of fuel gas that is wasted wasted more. Can be reduced.

According to a third aspect of the present invention, in the first or second aspect of the present invention, the supply amount of the fuel gas before the decrease is reduced by the fuel gas supply control means substantially simultaneously with the opening of the discharge valve. It is characterized by increasing above.
By configuring in this way, the pressure in the anode off-gas passage decreases when the fuel gas supply amount is decreased, but the fuel gas supply amount is increased more than during normal power generation almost simultaneously with opening the discharge valve. Then, the supply amount of the fuel gas temporarily increases, and the flow rate of the gas flowing through the anode of the fuel cell can be increased. Therefore, the generated water accumulated in the anode of the fuel cell can be surely and sufficiently removed from the fuel cell. Can be discharged.

The invention according to claim 4 is a fuel cell in which fuel gas is supplied to the anode and oxidant gas is supplied to the cathode to generate power; a fuel gas supply passage for supplying fuel gas to the anode of the fuel cell; An anode off-gas passage for returning the anode off-gas discharged from the anode of the fuel cell to the fuel gas supply passage and supplying the anode again to the anode, and the fuel gas supply passage upstream of the junction of the anode off-gas passage A fuel cell system discharge method comprising: a fuel gas supply control means for controlling a supply amount of the fuel gas; and a discharge valve for discharging a gas in the anode off-gas passage. Thus, before discharging the gas in the anode off-gas passage, the fuel gas supply control means supplies the fuel gas. The amount reduces, the ratio of the amount of hydrogen supplied to the fuel cell for the amount of hydrogen consumed by the fuel cell is characterized that you stop a decrease in the supply amount of the fuel gas when a 1.
By configuring in this way, the concentration of the fuel gas in the anode off-gas passage can be temporarily reduced to 0 compared with that during normal operation before the discharge valve is opened, and then the discharge valve is opened. The amount of fuel gas discharged from the discharge valve can be reduced.

According to the first aspect of the present invention, the fuel gas supply amount is decreased before the discharge valve is opened, so that the concentration of the fuel gas in the anode off-gas passage is temporarily operated normally before the discharge valve is opened. also can be brought close to zero by reducing from time, it is possible to reduce the amount of fuel gas discharged from the discharge valve when opened the discharge valve after this, reduce the amount of fuel gas being discarded wastefully be able to. Therefore, when it is employed in a fuel cell system that supplies electric power to a drive source of a fuel cell vehicle, fuel efficiency is improved.

According to the second aspect of the present invention, the stoichiometric ratio can be made close to “1” by making the fuel gas supply amount smaller than the fuel gas supply amount during normal power generation. It can be reduced more.
According to the invention of claim 3, substantially simultaneously with the opening of the discharge valve, the fuel gas supply control means increases the supply amount of the fuel gas above the supply amount before the decrease, thereby temporarily Since the supply amount of the fuel gas increases and the flow velocity of the gas flowing through the anode of the fuel cell can be increased, the generated water accumulated in the anode of the fuel cell can be surely and sufficiently discharged out of the fuel cell. .

According to the invention of claim 4, the fuel gas supply amount is reduced before the discharge valve is opened, so that the concentration of the fuel gas in the anode off-gas passage is temporarily operated normally before the discharge valve is opened. when also can be brought close to zero by reducing from, it is possible to reduce the amount of fuel gas discharged from the discharge valve when opened the discharge valve after this, the amount of fuel gas being discarded wastefully Can be reduced. Therefore, when it is employed in a fuel cell system that supplies electric power to a drive source of a fuel cell vehicle, fuel efficiency is improved.

Embodiments of a discharge device and a discharge method of a fuel cell system according to the present invention will be described below with reference to the drawings of FIGS. In addition, the fuel cell system in this embodiment is an aspect mounted in the fuel cell vehicle.
FIG. 1 is a schematic configuration diagram of a hydrogen circulation type fuel cell system 1.
The fuel cell 2 is a stack formed by stacking a plurality of cells formed by sandwiching a solid polymer electrolyte membrane 2a made of a solid polymer ion exchange membrane or the like from both sides between an anode 2b and a cathode 2c (in FIG. 1, a single cell). When hydrogen gas is supplied as fuel gas to the anode 2b and air containing oxygen as oxidant is supplied to the cathode 2c, hydrogen ions generated by the catalytic reaction at the anode 2b are converted into a solid polymer electrolyte membrane. Passing through 2a and moving to the cathode 2c, the cathode 2c causes an electrochemical reaction with oxygen to generate electric power, thereby generating water. Part of the generated water passes through the solid polymer electrolyte membrane 2a and also moves to the anode 2b side.
The fuel cell 2 includes cell voltage detection means 8 that detects the voltage of each cell.

The hydrogen gas stored in the high-pressure hydrogen tank (fuel supply means) 3 flows through the hydrogen supply passage (fuel gas supply passage) 21 and passes through the anode-side gas passage 2d in the fuel cell 2 to the anode 2b of each cell. Supplied. The hydrogen supply passage 21 is provided with a hydrogen supply control valve V1 and an ejector 4 in order from the side close to the high-pressure hydrogen tank 3.
The hydrogen supply control valve V1 controls the flow rate of hydrogen gas supplied from the high-pressure hydrogen tank 3 to the fuel cell 2, and the ejector 4 supplies the anode off-gas discharged from the anode side gas passage 2d of the fuel cell 2 with hydrogen. This is for returning to the passage 21.

  Of the hydrogen gas supplied to the anode 2b of the fuel cell 2, the hydrogen gas that has not been used for power generation, that is, unreacted hydrogen is discharged from the fuel cell 1 to the anode off-gas passage 22 as the anode off-gas. The anode off-gas passage 22 is provided with a hydrogen circulation pump 5 and a backflow prevention valve 6. The anode offgas discharged from the fuel cell 2 is boosted by the hydrogen circulation pump 5, and then passes through the backflow prevention valve 6 to be ejector. 4 is combined with fresh hydrogen gas supplied from the high-pressure hydrogen tank 3 and supplied again to the anode 2 b of the fuel cell 2. That is, the anode offgas discharged from the fuel cell 2 circulates in the fuel cell 2 through the anode offgas passage 22 and the hydrogen supply passage 21 downstream of the ejector 4. In this embodiment, the fuel gas circulation passage 20 is constituted by the hydrogen supply passage 21 and the anode off-gas passage 22 downstream of the ejector 4.

In the anode off gas passage 22, a pressure sensor 11 for detecting the hydrogen pressure in the anode off gas passage 22 is installed upstream of the hydrogen circulation pump 5. In the following description, the pressure detected by the pressure sensor 11 is referred to as pump inlet pressure.
A discharge valve V2 is provided in the discharge passage 23 branched from the anode off-gas passage 22. The discharge valve V2 is normally closed and is controlled by an electronic control unit (ECU) 10 so as to open when a purge request is made, as will be described later.

On the other hand, air is pressurized to a predetermined pressure by the air compressor 7, passes through the air passage 31, passes through the cathode side gas passage 2 e in the fuel cell 2, and is supplied to the cathode 2 c of each cell. After the air supplied to the fuel cell 2 is used for power generation, it is discharged from the fuel cell 2 as a cathode offgas to the cathode offgas passage 32 and is discharged via the pressure control valve V3.
Output signals and the like from the pressure sensor 11 and the cell voltage detection means 8 are input to the ECU 10, and the ECU 10 controls the hydrogen supply control valve V1, the discharge valve V2, and the pressure control valve V3 based on these output signals and the like.

  In this fuel cell system 1, when the cell voltage of the fuel cell 2 drops to a predetermined value, water has accumulated in the anode side gas passage 2d in the fuel cell 2, or the impurity concentration in the hydrogen gas has increased. Therefore, the discharge valve V2 is opened to discharge moisture and impurities out of the system (hereinafter referred to as purge). In particular, in this embodiment, the amount of hydrogen discharged together with water and impurities when the discharge valve V2 is opened by controlling the hydrogen supply amount to the fuel cell 2 to a predetermined level before and after the opening of the discharge valve V2. Can be made as close to zero as possible.

A method for controlling the hydrogen supply amount before and after the opening of the discharge valve V2 and the principle of reducing the hydrogen discharge amount will be described with reference to the schematic diagrams of FIGS. 2 to 4, the hydrogen circulation pump 5 and the backflow prevention valve 6 are omitted.
2 to 4 are diagrams showing an example of the mass ratio of hydrogen, water vapor, and nitrogen (impurities) in the fluid flowing through each part of the hydrogen flow path. FIG. 2 is for normal power generation and FIG. 3 is for opening the discharge valve V2. FIG. 4 shows immediately before and immediately after opening the discharge valve V2.
At the time of normal power generation shown in FIG. 2, the amount of fresh hydrogen supplied from the high-pressure hydrogen tank 3 is “10”, the amount of hydrogen discharged from the fuel cell 2 to the anode off-gas passage 22 and sucked into the ejector 4 is “5”, It is assumed that the amount of hydrogen consumed in the fuel cell 2 is “10”, the amount of water vapor contained in the anode off-gas discharged from the fuel cell 2 at this time is “5”, and the amount of nitrogen is “2”. In this case, since the total amount of hydrogen supplied to the fuel cell 2 is “15”, the ratio of the amount of hydrogen supplied to the fuel cell 2 to the amount of hydrogen consumed by the fuel cell 2, that is, the stoichiometry is 15/10. = 1.5.

When there is a purge request during the normal power generation operation, before the discharge valve V2 is opened, control is performed to reduce the amount of fresh hydrogen supplied from the high-pressure hydrogen tank 3 and temporarily reduce stoichiometry.
For example, as shown in FIG. 3, if the amount of fresh hydrogen supplied from the high-pressure hydrogen tank 3 is reduced to “5” while maintaining the amount of hydrogen consumed in the fuel cell 2 at “10”, the normal power generation Since hydrogen of “5”, which is sometimes discharged from the fuel cell 2 and remains in the anode off-gas passage 22, is sucked into the ejector 4 and supplied to the fuel cell 2, the total amount of hydrogen supplied to the fuel cell 2 is “10 The stoichiometry at this time is “1.0”. However, in this case, after reducing the amount of fresh hydrogen supplied from the high-pressure hydrogen tank 3 to “5”, the amount of hydrogen discharged from the fuel cell 2 to the anode off-gas passage 22 becomes “0”. Further, the amount of water vapor and the amount of nitrogen contained in the anode off-gas are the same as those during normal power generation, the water vapor amount is “5”, and the nitrogen amount is “2”.
Thus, by reducing the stoichiometry, the amount of hydrogen in the anode off-gas passage 22 before opening the exhaust valve V2 is made as close to “0” as possible, and the inside of the anode off-gas passage 22 is made only with impurities such as water vapor and nitrogen. .

  In this state, by opening the exhaust valve V2, only impurities such as water vapor and nitrogen filled in the anode off-gas passage 22 can be discharged, and the amount of hydrogen discharged from the discharge valve V2 is limited to “0”. ”. When the discharge valve V2 is opened, the supply amount of fresh hydrogen temporarily supplied from the high-pressure hydrogen tank 3 is increased from that during normal power generation to increase the stoichiometry. This is because the generated water accumulated in the fuel cell 2 is reliably and sufficiently discharged from the fuel cell 2 by increasing the flow velocity of the gas flowing in the fuel cell 2. More specifically, when the hydrogen supply amount before opening the discharge valve V2 is decreased, the pressure in the anode off-gas passage 22 is lowered. Here, if the hydrogen supply amount is increased more than that during normal power generation substantially simultaneously with opening the discharge valve V2, the flow rate of the hydrogen gas flowing through the anode 2b of the fuel cell 2 temporarily increases. The generated water accumulated in the anode 2b can be reliably and sufficiently discharged from the fuel cell 2 to the anode off-gas passage 22.

  For example, as shown in FIG. 4, when the amount of fresh hydrogen supplied from the high-pressure hydrogen tank 3 is increased to “12” while the amount of hydrogen consumed in the fuel cell 2 is maintained at “10”, the discharge valve Since V2 is open, gas is not sucked from the anode off-gas passage 22 into the ejector 4, so that the total amount of hydrogen supplied to the fuel cell 2 is "12", and the stoichiometry at this time is "1.2". Note that due to the presence of the backflow prevention valve 6, hydrogen does not flow from the hydrogen supply passage 21 into the anode offgas passage 22 via the ejector 4. In this case, the amount of hydrogen discharged from the fuel cell 2 to the anode off-gas passage 22 after increasing the amount of fresh hydrogen supplied from the high-pressure hydrogen tank 3 to “12” is “2”. Paying attention to the amount of hydrogen in the gas discharged from the exhaust valve V2, the amount of hydrogen in the anode off-gas passage 22 is described as “0”.

  Further, if the valve opening time of the exhaust valve V2 is kept too long, the gas including the hydrogen amount “2” discharged from the fuel cell 2 after increasing the stoichiometry to “1.2” (hereinafter, for convenience of explanation, Since the scavenging gas is discharged from the discharge valve V2, it is preferable to control the discharge valve V2 to be closed immediately before the scavenging gas reaches the discharge valve V2.

Next, a specific example of purge process control of the fuel cell system 1 will be described with reference to the flowchart of FIG.
The purge process control routine shown in the flowchart of FIG. 5 is repeatedly executed by the ECU 10 at regular intervals.
First, in step S101, based on each cell voltage detected by the cell voltage detection means 8, it is determined whether there is a cell voltage lower than a preset threshold value. When the cell voltage is lower than the threshold value, it is determined that there is a purge request because water has accumulated in the anode gas passage 2d of the fuel cell 2 or the impurity concentration in the hydrogen gas has increased.

If the determination result in step S101 is “NO” (no purge request), the execution of this routine is temporarily terminated.
If the determination result in step S101 is “YES” (with a purge request), the process proceeds to step S102, where the supply amount of fuel gas (hydrogen gas) is reduced by controlling the opening of the hydrogen supply control valve V1, Execute stoichiometric reduction control.
In step S103, it is determined whether the stoichiometric value is “1”. As a method for calculating the stoichiometry, the amount of hydrogen supplied to the fuel cell 2 and the amount of hydrogen discharged from the fuel cell 2 may be detected by a hydrogen flow meter and calculated based on this, or the fuel cell 2 Since the pressure in the anode off-gas passage 22 decreases when the amount of hydrogen discharged from the exhaust gas decreases, the stoichiometry can be calculated based on the degree of decrease in the pump inlet pressure detected by the pressure sensor 11.

If the determination result in step S103 is “NO” (stoichi ≠ 1), the process returns to step S102 and the fuel gas supply amount reduction is continued.
When the determination result in step S103 is “YES” (stoichiometric = 1), the process proceeds to step S104, and the supply amount of fuel gas (hydrogen gas) is increased by controlling the opening degree of the hydrogen supply control valve V1, The stoichiometric increase control is executed and the discharge valve V2 is opened.

Next, it progresses to step S105 and it is determined whether the system scavenging was complete | finished. As described above, the end point of the in-system scavenging is preferably immediately before the scavenging gas reaches the discharge valve V2, and the following method can be exemplified as a method for detecting this end point.
(1) The flow rate of gas discharged from the exhaust valve V2 is measured with a flow meter, and the flow rate is determined by the fuel cell 2 while the volume from the outlet of the fuel cell 2 to the discharge valve V2 and the discharge valve V2 is open. When the sum of the consumed hydrogen amount is reached, it is determined as the end point of the system scavenging.
(2) When the scavenging gas flows into the anode off-gas passage 22, the pressure in the anode off-gas passage 22 rises, so that the system scavenging is completed based on the degree of increase in the pump inlet pressure detected by the pressure sensor 11. Determine if it is a point.
(3) The purge time is mapped in advance in relation to the stoichiometric value or the like by experiment, the purge time corresponding to the purge processing condition is obtained with reference to this map, and when the purge time has passed, The end point is determined.

When the determination result in step S105 is “NO”, since the end point of the system scavenging has not been reached, the open state of the discharge valve V2 is maintained and the system scavenging is continued.
If the determination result in step S105 is “YES”, since the end point of the system scavenging has been reached, the process proceeds to step S106, the exhaust valve V2 is closed to end the system scavenging, and the execution of this routine is temporarily ended. To do.

  According to the discharge device and discharge method of the fuel cell system of this embodiment, the anode off-gas passage is temporarily set before the discharge valve V2 is opened by reducing the supply amount of hydrogen gas before the discharge valve V2 is opened. The concentration of hydrogen gas in 22 can be reduced as compared with the normal operation. Therefore, since the amount of hydrogen gas discharged from the discharge valve V2 when the discharge valve V2 is opened thereafter can be reduced, the amount of fuel gas that is wasted can be reduced. Therefore, the fuel consumption of the fuel cell vehicle is improved.

  In particular, in this embodiment, the fuel gas supply amount is made smaller than the fuel gas supply amount at the time of normal power generation before the discharge valve V2 is opened, and the hydrogen gas supply amount is reduced until the stoichiometric value becomes almost “1”. Therefore, the amount of hydrogen gas in the anode off-gas passage 22 can be as close to “0” as possible, and the amount of hydrogen gas discharged from the discharge valve V2 can be as close as possible to “0”. Therefore, the fuel consumption of the fuel cell vehicle can be further improved.

  In this embodiment, since the supply amount of hydrogen gas is increased by the hydrogen supply control valve V2 more than the supply amount at the time of normal power generation almost simultaneously with the opening of the discharge valve V2, the fuel cell 2 temporarily By increasing the flow rate of the hydrogen gas flowing through the anode, the generated water accumulated in the anode of the fuel cell 2 can be reliably and sufficiently discharged from the fuel cell 2 to the anode off-gas passage 22.

[Other Examples]
The present invention is not limited to the embodiment described above.
For example, in the above-described embodiment, the fuel gas supply control means for controlling the supply amount of the fuel gas is configured by the hydrogen supply control valve. However, the present invention is not limited to this, and supply of the fuel gas before joining the anode off gas Other configurations that can control the amount are also possible.
In the above-described embodiment, the target value of stoichiometry when the supply amount of fuel gas is reduced before opening the discharge valve is set to “1”, but this is an ideal value and is at least more than the stoichiometric value during normal power generation. If the smaller value is set as the target value for stoichiometry, the value is not particularly limited to “1”.
The present invention can also be applied to fuel cell systems other than those for vehicles.

It is a block diagram of the discharge device of the fuel cell system according to the present invention. It is FIG. (1) for demonstrating the principle of the hydrogen emission reduction by the discharge method of the fuel cell system which concerns on this invention. It is FIG. (2) for demonstrating the principle of the hydrogen emission amount reduction by the discharge method of the fuel cell system which concerns on this invention. It is FIG. (3) for demonstrating the principle of the hydrogen emission reduction by the discharge method of the fuel cell system which concerns on this invention. It is an example of the flowchart of the purge process for enforcing the discharge method of the fuel cell system concerning this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Fuel cell system 2 Fuel cell 2b Anode 2c Cathode 2d Anode side gas passage 7 Gas-liquid separation tank 21 Hydrogen supply passage (fuel gas supply passage)
22 Anode off-gas passage V1 Hydrogen supply control valve (fuel gas supply control means)
V2 discharge valve

Claims (4)

A fuel cell in which fuel gas is supplied to the anode and oxidant gas is supplied to the cathode to generate electricity; and
A fuel gas supply passage for supplying fuel gas to the anode of the fuel cell;
An anode offgas passage for returning the anode offgas discharged from the anode of the fuel cell to the fuel gas supply passage and supplying the anode offgas again to the anode;
Fuel gas supply control means for controlling the supply amount of the fuel gas provided in the fuel gas supply passage upstream of the junction with the anode off-gas passage;
A discharge valve for discharging the gas in the anode off-gas passage;
In the discharge device of the fuel cell system comprising
Before the gas in the anode off-gas passage is discharged by opening the discharge valve, the fuel gas supply control means decreases the supply amount of the fuel gas, and the fuel cell with respect to the amount of hydrogen consumed in the fuel cell discharge device for a fuel cell system characterized that you stop a decrease in the supply amount of the fuel gas when the ratio of supplied hydrogen amount becomes 1 in.   2. The fuel cell discharge device according to claim 1, wherein the fuel gas supply amount reduced by the fuel gas supply control means is less than the fuel gas amount supplied by the fuel cell during normal power generation.   3. The fuel according to claim 1, wherein the fuel gas supply control means increases the supply amount of the fuel gas more than the supply amount before the decrease by the fuel gas supply control means substantially simultaneously with the opening of the discharge valve. Battery discharge device. A fuel cell in which fuel gas is supplied to the anode and an oxidant gas is supplied to the cathode to generate power, a fuel gas supply passage for supplying fuel gas to the anode of the fuel cell, and an exhaust from the anode of the fuel cell Amount of fuel gas provided in the fuel gas supply passage upstream from the junction of the anode offgas passage for returning the anode offgas to the fuel gas supply passage and supplying the anode offgas again to the anode In a discharge method of a fuel cell system, comprising: a fuel gas supply control means for controlling the gas; and a discharge valve for discharging the gas in the anode off-gas passage.
Before the gas in the anode off-gas passage is discharged by opening the discharge valve, the fuel gas supply control means decreases the supply amount of the fuel gas, and the fuel cell with respect to the amount of hydrogen consumed in the fuel cell discharge method of the fuel cell system the ratio of the supplied amount of hydrogen is characterized that you stop a decrease in the supply amount of the fuel gas when it becomes a 1 in.

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