JP2006155917A - Fuel cell system and operating method for fuel cell system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel cell system capable of preventing the deterioration of a fuel cell body by preventing aeration caused by the dispersion of hydrogen and oxygen even if the fuel cell system is left at it is after emergency shut down. <P>SOLUTION: This fuel cell system comprises a fuel cell 1 generating an electromotive force by the reaction of hydrogen and oxygen, an exhaust pipe 12 discharging anode off-gas discharged from the fuel cell 1 to air, a normally-closed first relief valve 10 provided in the exhaust pipe 12 and closed in a nonconductive state, a normally-open second relief valve 11 provided in a branch exhaust pipe 15 branched from the exhaust pipe 12 in parallel with the first relief valve 10 and opened in the nonconductive state and a liquid pool 14 pooling liquid 30 to block a flow passage of the exhaust pipe 12 or the branch exhaust pipe 15 when power generation is stopped in the fuel cell 1 and power supply is cut off provided in the upstream or the lower stream or both of them of the second relief valve 12. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a fuel cell system and a method for operating the fuel cell system, and more particularly to a technique for suppressing deterioration of the fuel cell during an emergency stop of the fuel cell system.

  In recent years, fuel cells that generate power using fuel gas (hydrogen gas) and oxidant gas (air) have been put into practical use as power sources for mounting on automobiles. Fuel cells are attracting attention from the viewpoint of protecting the global environment because no harmful exhaust gas is generated with power generation.

  Such a fuel cell forms a fuel cell stack by stacking a plurality of fuel cell single cells, which are the basic unit of power generation, and generates a predetermined electromotive force by introducing fuel gas and oxidant gas into the fuel cell stack. Arise. A fuel cell single cell has, for example, a membrane electrode assembly (MEA) in which an anode electrode (hydrogen electrode) and a cathode electrode (oxygen electrode) are joined to both surfaces of a solid polymer electrolyte membrane. Electricity is generated by supplying hydrogen gas as a fuel gas to the anode electrode and oxygen as an oxidant gas to the cathode electrode.

In such a fuel cell system, when control of the power plant system becomes impossible, for example, during an emergency stop, the anode line is connected to stop the system so that the differential pressure between the anode and cathode does not become excessive. A normally open anode purge valve is set (see, for example, Patent Document 1).
JP-A-62-108466 (2nd and 3rd pages, Fig. 4)

  However, in the technique described in Patent Document 1, since the purge valve set in the anode line is set to normally open, after the power plant system is stopped, air diffuses into the anode line and enters the fuel cell stack. Problems that cause the life of the main body to accelerate occur.

  In order to prevent this, if a normally closed purge valve is set instead of a normally open, the power plant system control during an emergency stop etc. becomes impossible and the system is stopped. While maintaining the pressure, it was impossible to remove hydrogen from the anode, and the fuel cell body could be damaged during an emergency stop.

  Accordingly, the present invention provides, for example, a fuel cell system capable of preventing deterioration of the fuel cell main body by preventing air from being mixed due to diffusion of hydrogen and oxygen even when the fuel cell system is left after an emergency stop. And it aims at providing the operating method of a fuel cell system.

  A fuel cell system according to the present invention is provided in a fuel cell that generates an electromotive force by reacting hydrogen and oxygen, an exhaust pipe that discharges anode off-gas discharged from the fuel cell to the atmosphere, and an exhaust pipe that is not energized A normally closed first relief valve that is closed in a state; a normally opened second relief valve that is provided in parallel with the first relief valve in a branch exhaust pipe branched from the exhaust pipe and is opened in a non-energized state; A liquid reservoir for accumulating liquid and closing the flow path of the exhaust pipe or the branch exhaust pipe at the time of normal stop of the system and at the time of emergency stop by system abnormality diagnosis upstream or downstream of the second relief valve or both. Prepare.

  According to the fuel cell system of the present invention, while the fuel cell system is left after being stopped, liquid is accumulated in the liquid reservoir provided upstream, downstream, or both of the normally open second relief valve, and the exhaust pipe is caused by this liquid. Therefore, mixing of outside air (air) and hydrogen on the anode side is prevented, diffusion of air into the anode is suppressed, and deterioration of the fuel cell main body after the system is stopped can be prevented.

  Hereinafter, specific embodiments to which the present invention is applied will be described in detail with reference to the drawings. In the present embodiment, the fuel cell system according to the present invention is applied to a fuel cell vehicle.

“First Embodiment”
FIG. 1 is a block diagram showing a schematic configuration of the fuel cell system according to the first embodiment, and FIG. 2 is an enlarged cross-sectional view of a main part of a liquid reservoir portion formed upstream and downstream of the first relief valve, respectively. .

  The fuel cell system according to the first embodiment includes a fuel cell 1 that generates an electromotive force by reacting hydrogen and oxygen, a cathode supply path that supplies oxygen to the fuel cell 1, and hydrogen that is supplied to the fuel cell 1. The main configuration is an anode supply path, a cathode offgas exhaust path for discharging the cathode offgas discharged from the fuel cell 1 to the atmosphere, and an anode offgas exhaust path for discharging the anode offgas discharged from the fuel cell 1 to the atmosphere.

  The cathode supply path is a path for supplying the air pressurized by the compressor 2 from the cathode IN3 to the fuel cell 1. The cathode offgas exhaust path is a path for discharging the cathode offgas discharged from the fuel cell 1 to the atmosphere through the cathode EX4.

  The anode supply path is a path through which hydrogen supplied from the hydrogen tank 5 passes through the hydrogen pipe 6 and is regulated by the pressure regulating valve 7 and then supplied from the anode IN8 to the fuel cell 1. In addition, the anode supply path is provided with a path for discharging hydrogen remaining not used for power generation through the anode EX9, adjusting the pressure by the booster 13, and circulating it to the anode IN8.

  The anode off-gas exhaust path is a path that is branched from the anode EX9 and discharges the anode off-gas to the atmosphere through the exhaust pipe 12 having an open end opened to the atmosphere. A first relief valve 10 is provided in the middle of the exhaust pipe 12, and a branch exhaust pipe 15 that branches so as to bypass the first relief valve 10 is provided. A second relief valve 11 arranged in parallel with the relief valve 10 is provided.

  The first relief valve 10 is a normally closed relief valve that closes in a non-energized state. The normally closed as defined here means that the valve is closed when electricity is not passed (for example, when the fuel cell system is stopped), and the valve is opened by energization. Therefore, the first relief valve 10 is in a state where the valve is ON-OFF while the fuel cell system is in operation and the fuel cell 1 is generating electric power. Therefore, the anode off-gas flows from the exhaust pipe 12 to the atmosphere. Since the valve is closed when the fuel cell system is normally stopped and during an emergency stop due to the system abnormality diagnosis, the anode off gas flows into the branch exhaust pipe 15.

  The second relief valve 11 is a normally open relief valve that opens in a non-energized state. The normal open defined here means that the valve is open when electricity is not conducted (for example, when the fuel cell system is stopped), and the valve is closed when energized. Accordingly, since the second relief valve 11 is in a closed state while the fuel cell system is operating and the fuel cell 1 is generating power, the anode off-gas does not flow through the branch exhaust pipe 15 but is mainstream. Since the valve is opened during normal stop of the fuel cell system and emergency stop by system abnormality diagnosis through the exhaust pipe 12, the anode off gas flows through the branch exhaust pipe 15.

  In both the upstream and downstream sides of the second relief valve 11, there is a liquid that accumulates liquid and closes the exhaust pipe 12 and the branch exhaust pipe 15 when the fuel cell system is normally stopped and during an emergency stop due to system abnormality diagnosis. A reservoir portion 14 is formed. The liquid reservoirs 14 are provided at positions upstream and downstream of the connecting portion of the branch exhaust pipe 15 connected to the exhaust pipe 12. As shown in FIG. 2, the liquid reservoir 14 is formed by curving a part of the exhaust pipe 12 in a substantially U shape (or a substantially V shape) toward the vehicle lower side, and the liquid 30 fills. When this is done, the exhaust pipe 12 is closed.

  In the fuel cell system configured as described above, the water reservoir generated during fuel cell operation is filled in the liquid reservoir 14 when the system is normally stopped or during an emergency stop due to system abnormality diagnosis. Since the exhaust pipe 12 and the branch exhaust pipe 15 are completely closed by submerging the liquid reservoir portion 14, the outside air and the hydrogen on the anode side are directly mixed with the generated water accumulated during standing after the system operation is stopped. Can be prevented. Accordingly, since hydrogen and air are not in direct contact with each other, it is possible to prevent the diffusion of air into the anode, and it is possible to prevent damage to the fuel cell main body even when left after the system is stopped.

  Further, at the time of starting the fuel cell system, the liquid 30 accumulated in the liquid reservoir 14 can be blown off with the internal pressure, so that the functions of the first relief valve 10 and the second relief valve 11 are not hindered.

  On the other hand, in the operation method of the fuel cell system, the liquid reservoir 14 provided in the exhaust pipe 12 that discharges the anode off-gas discharged from the fuel cell 1 to the atmosphere at the normal stop of the system and at the emergency stop by the system abnormality diagnosis. In addition, the generated water generated during the fuel cell operation and the condensed water (liquid 30) in the pipe flow down and accumulate in the liquid reservoir 14, and the liquid reservoir 14 is submerged. Therefore, in the state of being left after the fuel cell system is stopped, the liquid reservoir 14 is submerged by the liquid 30 and the exhaust pipe 12 and the branch exhaust pipe 15 are closed, thereby preventing air from diffusing into the anode. Shortening the life of the fuel cell is avoided.

  As described above, in the present embodiment, since water (liquid 30) generated by the power generation by the fuel cell 1 is used, no special equipment for submerging the liquid reservoir 14 is required. The structure of the fuel cell system itself can be simplified.

“Second Embodiment”
FIG. 3 is a block diagram showing a schematic configuration of the fuel cell system according to the second embodiment.

  In the fuel cell system of the second embodiment, in addition to the configuration of the fuel cell system of the first embodiment, a reservoir tank 16 in which an antifreeze liquid (Long Life Cloolant) that is a liquid 30 is stored, and the reservoir tank 16 An antifreeze liquid supply pipe 17 for supplying the antifreeze liquid to the liquid reservoir 14 and a control valve 18 for controlling the supply of the antifreeze liquid to the liquid reservoir 14 during a normal stop of the fuel cell system and an emergency stop by a system abnormality diagnosis. Yes.

  The reservoir tank 16 is filled with antifreeze for preventing water discharged from the fuel cell 1 from freezing even when the fuel cell system is placed below the freezing point. The antifreeze liquid is controlled by a control valve 18 installed in the vicinity of the liquid reservoir 14 and supplied from the reservoir tank 16 to the liquid reservoir 14 through the antifreeze liquid supply pipe 17. The timing at which the antifreeze liquid is supplied to the liquid reservoir 14 is a normal stop of the fuel cell system and an emergency stop by a system abnormality diagnosis. Further, as shown in FIG. 2, the supply amount of the antifreeze liquid is an amount of water in which the liquid reservoir 14 is submerged and the exhaust pipe 12 is closed.

  In the fuel cell system according to the second embodiment, antifreeze liquid is applied to the liquid reservoir 14 when the fuel cell system is normally stopped and during an emergency stop due to system abnormality diagnosis, compared to the fuel cell system according to the first embodiment. The fuel cell system according to the first embodiment and the fuel cell system according to the first embodiment can be started without causing pipe clogging at the time of start-up due to freezing under conditions such as a cold region where the outside air temperature is below freezing point. It is possible to ensure the same effect and cope with low temperatures. That is, according to the fuel cell system of this embodiment, the exhaust pipe 12 can be blocked by the antifreeze liquid stored in the liquid reservoir 14, thereby preventing the outside air and the anode from diffusing, and further freezing can be prevented even at extremely low temperatures. At the same time, it is possible to ensure the same exhaust at the start of cryogenic temperatures.

“Third Embodiment”
FIG. 4 is a block diagram showing a schematic configuration of the fuel cell system according to the third embodiment.

  The fuel cell system according to the third embodiment includes, in addition to the configuration of the fuel cell system according to the second embodiment, a temperature sensor 19 that is an outside air temperature detecting means for detecting an outside air temperature, and a signal from the temperature sensor 19. Is used to estimate the occurrence of icing in the fuel cell 1 (determining whether the fuel cell is icing) or not. If it is determined that there is no risk of icing, water generated during power generation of the fuel cell 1 is When it is determined that there is a risk of freezing in the liquid reservoir 14, the control valve 18 is opened to control the computer 20 as a controller for controlling to store the antifreeze liquid in the liquid reservoir 14.

  The temperature sensor 19 is provided in a part of the body of the automobile and detects the temperature of the outside air. The computer 20 reads the sensor signal detected by the temperature sensor 19 and determines whether or not the water in the exhaust pipe 12 is frozen. If it is determined that there is a possibility of freezing, the control valve 18 is opened and the reservoir tank is opened. When the antifreeze liquid is supplied from 16 to the liquid reservoir 14 and it is determined that there is no possibility of freezing, the generated water generated by the fuel cell 1 is supplied to the liquid reservoir 14 without supplying the antifreeze liquid.

  In the fuel cell system according to the third embodiment, since the outside air temperature is detected and the possibility of freezing is determined to determine whether or not the antifreeze liquid is supplied to the liquid reservoir 14, the temperature environment Depending on the state, it is possible to select whether to supply antifreeze or to supply generated water generated by the fuel cell 1. Therefore, in a temperature environment where there is no concern about icing, the generated water that is generated by the fuel cell and does not run out during operation is used, and the use of the antifreeze stored in the reservoir tank 16 is saved and the frequency of replenishment of the antifreeze is reduced. Less economics can be ensured. In addition, under the temperature environment where icing occurs, icing can be prevented by the antifreeze liquid, and thus the same effect as the fuel cell system of the second embodiment can be obtained.

  Of course, according to the fuel cell system of the third embodiment, either the water generated selectively from the fuel cell 1 or the antifreeze liquid is filled in the liquid reservoir 14 by determining whether or not there is a possibility of freezing. By closing the exhaust pipe 12, it is possible to prevent the air from diffusing into the anode that is left unattended after a normal stop of the fuel cell system and after an emergency stop due to a system abnormality diagnosis.

"Other embodiments"
Although specific embodiments to which the present invention is applied have been described above, the present embodiments are not limited to the above-described embodiments, and various modifications can be made.

  For example, in the first to third embodiments described above, the liquid reservoir 14 is formed both upstream and downstream of the first relief valve 10, but the liquid reservoir 14 is formed in at least one of them. If it does, there can exist the effect of this invention.

  Further, since the first relief valve 10 uses a normally closed relief valve that closes the valve when the fuel cell system is normally stopped and at the time of emergency stop by system abnormality diagnosis, the first relief valve 10 is used. The same effect can be obtained by providing the liquid reservoir 14 in the branch exhaust pipe 15 that is bypassed from the exhaust pipe 12 provided with the. In this case, the liquid reservoir 14 is provided in the branch exhaust pipe 15 upstream, downstream, or both of the second relief valve 11.

It is a block diagram which shows schematic structure of the fuel cell system of 1st Embodiment. It is a principal part expanded sectional view of the liquid reservoir part each formed in the upstream and downstream of the 1st relief valve in the fuel cell system of 1st Embodiment. It is a block diagram which shows schematic structure of the fuel cell system of 2nd Embodiment. It is a block diagram which shows schematic structure of the fuel cell system of 3rd Embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Fuel cell 2 ... Compressor 3 ... Cathode IN
4 ... Cathode EX
5 ... Hydrogen tank 8 ... Anode IN
9 ... Anode EX
DESCRIPTION OF SYMBOLS 10 ... 1st relief valve 11 ... 2nd relief valve 12 ... Exhaust pipe 14 ... Liquid reservoir 15 ... Branch exhaust pipe 16 ... Reservoir tank (tank)
18 ... Control valve 19 ... Temperature sensor (outside air temperature detection means)
20: Computer (control unit)
30 ... Liquid (water, antifreeze)

Claims (10)

A fuel cell that reacts hydrogen and oxygen to generate an electromotive force; and
An exhaust pipe for releasing the anode off-gas discharged from the fuel cell to the atmosphere;
A normally closed first relief valve provided in the exhaust pipe and closed in a non-energized state;
A normally open second relief valve provided in parallel with the first relief valve on the branch exhaust pipe branched from the exhaust pipe and opened in a non-energized state;
A liquid reservoir for accumulating liquid and closing the flow path of the exhaust pipe or the branch exhaust pipe at the time of normal stop of the system and emergency stop by system abnormality diagnosis, upstream or downstream of the second relief valve or both. A fuel cell system comprising: The fuel cell system according to claim 1,
The liquid reservoir is formed by bending a part of the exhaust pipe or the branch exhaust pipe. The fuel cell system according to claim 1 or 2, wherein
The liquid is water generated during power generation of the fuel cell. The fuel cell system. The fuel cell system according to claim 1 or 2, wherein
The fuel cell system, wherein the liquid is an antifreeze liquid. The fuel cell system according to claim 1 or 2, wherein
A tank of antifreeze and
Piping for supplying antifreeze liquid from the tank to the liquid reservoir;
A fuel cell system comprising: a control valve that controls supply of the antifreeze liquid to the liquid reservoir when the system is normally stopped and during an emergency stop by a system abnormality diagnosis. The fuel cell system according to claim 5, wherein
An outside air temperature detecting means for detecting the outside air temperature;
If the signal from the outside air temperature detecting means is monitored to estimate the occurrence of icing in the fuel cell and it is determined that there is no risk of icing, water generated during power generation of the fuel cell is stored in the liquid reservoir. A fuel cell system comprising: a control unit that controls to open the control valve and store the antifreeze liquid in the liquid storage unit when it is determined that there is a risk of storage and freezing. In a method of operating a fuel cell system in which hydrogen and oxygen are supplied to a fuel cell to generate power and an anode off gas generated by the power generation is released to the atmosphere.
A liquid reservoir provided in an exhaust pipe that discharges the anode off-gas discharged from the fuel cell to the atmosphere collects the liquid and closes the flow path at the time of normal stop of the system and emergency stop by system abnormality diagnosis. A method for operating a fuel cell system, characterized in that: A method for operating a fuel cell system according to claim 7,
Water generated during power generation of the fuel cell is used as the liquid. A method of operating a fuel cell system. A method for operating a fuel cell system according to claim 7,
An antifreeze is used as the liquid. A method for operating a fuel cell system. A method for operating a fuel cell system according to claim 7,
If it is determined that there is no risk of icing of the fuel cell by detecting the outside air temperature, water generated during power generation of the fuel cell is stored in the reservoir, and if it is determined that there is a risk of icing A method of operating a fuel cell system, wherein the antifreeze is stored in the liquid reservoir.

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