JP2004193102A - Fuel cell operating method, and fuel cell operating device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel cell operating method capable of preventing freezing of a reaction gas passage, and minimizing energy necessary for drainage by draining water in a system only when it is necessary. <P>SOLUTION: In the operating method for a fuel cell 1, gaseous hydrogen and air are supplied as reaction gases to each reaction gas passage 5 and 6, and power generation is carried out by electrochemical reaction. It is characterized by that water in the reaction gas passages 5 and 6 are drained and operation of the fuel cell 1 is stopped by cutting off electric power supply from the fuel cell 1, detecting an outside air temperature, and supplying the reaction gases to the reaction gas passages 5 and 6 in response to the outside air temperature. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

  The present invention relates to a fuel cell operation method and a fuel cell operation device.

In order to prevent freezing of the fuel cell, a technique has been proposed in which water is discharged from a reaction gas flow channel of the fuel cell before at least a part of the solid polymer electrolyte membrane of the fuel cell becomes 0 ° C. or less (for example, And Patent Document 1.).
JP 2000-512068 A

However, the above prior art does not disclose a specific method for drainage, and when such a fuel cell is applied to a fuel cell vehicle, the solid polymer electrolyte membrane always has a temperature of 0 ° C. There is a problem that wasteful energy is consumed because water is always discharged though it is not less.
Therefore, the present invention provides a fuel cell operating method and a fuel cell that can prevent freezing of a reaction gas flow path and minimize energy required for draining by draining water in the system only when necessary. A driving device is provided.

In order to solve the above problem, the invention according to claim 1 is directed to a fuel gas (for example, hydrogen in the embodiment) as a reaction gas in each of the reaction gas channels (for example, the reaction gas channels 5 and 6 in the embodiment). A fuel cell (e.g., the fuel cell 1 in the embodiment) that supplies an oxidizing gas (e.g., air in the embodiment) and an oxidant gas (e.g., air in the embodiment) to generate electric power by an electrochemical reaction. Shutting off the supply, detecting the outside air temperature, discharging the water in the reaction gas passage by supplying the reaction gas to the reaction gas passage according to the outside air temperature, and shutting down the fuel cell. Features.
With this configuration, the reaction gas is supplied in accordance with the outside air temperature, thereby discharging the water in the reaction gas flow path and shutting down the fuel cell, so that even if the fuel cell falls below freezing, Since the water is discharged, the reaction gas flow path can be prevented from freezing.

The invention according to claim 2 is characterized in that water is not discharged when the outside air temperature is equal to or higher than a predetermined temperature.
With such a configuration, drainage treatment can be eliminated when there is no concern that the reaction gas flow path freezes.

The invention according to claim 3 is characterized in that the treatment time for discharging water is made longer as the outside air temperature is lower.
With this configuration, the processing time for discharging water is lengthened, paying attention to the fact that the lower the outside air temperature, the higher the possibility of freezing the reaction gas flow path.

The invention according to claim 4 is characterized in that the treatment time for discharging water is made constant when the outside air temperature is lower than a predetermined temperature.
With this configuration, when the outside air temperature is lower than the predetermined temperature, the water discharge time is made constant, and the water in the reaction gas flow path is discharged.

The invention according to claim 5 is characterized in that the supply amount of the reaction gas is set according to the outside air temperature.
With this configuration, by setting the supply amount of the reaction gas in accordance with the outside air temperature, it is possible to always equalize the time required when the operation of the fuel cell is stopped.

The invention according to claim 6 is characterized in that the supply amount of the reaction gas is increased as the outside air temperature is lower.
With this configuration, it is necessary to perform drainage more carefully as the outside air temperature is lower. Therefore, by increasing the supply amount of the reaction gas, the drainage can be completed in the same time as the normal temperature state. .

The invention according to claim 7 is characterized in that a fuel gas (for example, hydrogen gas in the embodiment) and an oxidant gas (for example, hydrogen gas in the embodiment) are used as the reaction gas in each of the reaction gas passages (for example, the reaction gas passages 5 and 6 in the embodiment). A fuel cell (for example, the fuel cell 1 in the embodiment) that supplies the air with the air in the embodiment and generates an electric power by an electrochemical reaction, and an outside air temperature detecting unit (for example, the outside air temperature sensor 20 in the embodiment) that detects the outside air temperature ) And gas supply control means (for example, the compressor 7 and the hydrogen pump 14 in the embodiment) for controlling the supply of the reaction gas, in which the supply of electric power from the fuel cell is cut off. The gas supply control unit is controlled in accordance with a detection value of the outside air temperature detection unit, and the operation of the fuel cell is stopped.
With this configuration, the reaction gas is supplied in accordance with the outside air temperature, thereby discharging the water in the reaction gas flow path and shutting down the fuel cell, so that even if the fuel cell falls below freezing, Since the water is discharged, the reaction gas flow path can be prevented from freezing.

According to the first aspect of the present invention, it is assumed that the reaction gas is supplied in accordance with the outside air temperature, the water in the reaction gas flow path is discharged, the operation of the fuel cell is stopped, and then the fuel cell is below freezing. Also, since water is discharged, the reaction gas flow path can be prevented from freezing. In addition, the energy required for drainage can be minimized as compared with the case where water is constantly drained when the operation is stopped, the load on the fuel cell can be reduced, and the restartability of the fuel cell below freezing can be improved. effective.
Furthermore, draining the water in the system only when necessary, has the effect of minimizing the energy required for drainage.

  According to the second aspect of the present invention, when the outside air temperature when the operation of the fuel cell is stopped is higher than the predetermined temperature, the drainage processing is not performed, so that the possibility that the reaction gas flow path of the fuel cell is frozen is sufficiently low. In some cases, it is possible to eliminate the power consumption of the compressor and the like necessary for the wastewater treatment, and it is possible to minimize the load on the fuel cell.

  According to the third aspect of the invention, the lower the outside air temperature when the operation of the fuel cell is stopped, the higher the possibility of the freezing of the reaction gas flow path. The freezing of the reaction gas flow path can be reliably prevented.

  According to the invention according to claim 4, when the outside air temperature is lower than the predetermined temperature, the wastewater treatment can be performed for a fixed treatment time, so that the wastewater treatment can be performed without excess or shortage of the treatment time. The water can be drained, and the freezing of the reaction gas channel can be prevented.

  According to the invention according to claim 5, by setting the supply amount of the reaction gas in accordance with the outside air temperature, the time required when the operation of the fuel cell is stopped can be always equalized, so that the commerciality is improved. improves. In particular, when mounted on a fuel cell vehicle, it is possible to prevent the driver from feeling uncomfortable when the operation of the fuel cell is stopped.

  According to the invention according to claim 6, since it is necessary to perform drainage more carefully as the outside air temperature is lower, by increasing the supply amount of the reaction gas as the outside air temperature is lower, the drainage can be performed in the same time as the normal temperature state. It can be completed.

According to the invention according to claim 7, since the water in the reaction gas flow path is discharged by supplying the reaction gas in accordance with the outside air temperature and the operation of the fuel cell is stopped, the fuel cell is below freezing point thereafter. Since the water is discharged, the reaction gas channel can be prevented from freezing. In addition, the energy required for drainage can be minimized as compared with the case where water is constantly drained when the operation is stopped, the load on the fuel cell can be reduced, and the restartability of the fuel cell below freezing can be improved. effective.
Furthermore, draining the water in the system only when necessary, has the effect of minimizing the energy required for drainage.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a schematic configuration diagram of a fuel cell system mounted on a fuel cell vehicle.
The fuel cell 1 is configured by stacking a plurality of cells formed by sandwiching a solid polymer electrolyte membrane 2 made of, for example, a solid polymer ion exchange membrane or the like between an anode 3 and a cathode 4 from both sides (FIG. 1). Only a single cell is shown), hydrogen gas is supplied as a fuel gas to the reaction gas flow path 5 of the anode 3, and air containing oxygen is supplied as an oxidant gas to the reaction gas flow path 6 of the cathode 4. Hydrogen ions generated by the catalytic reaction pass through the solid polymer electrolyte membrane 2 and move to the cathode 4 to cause an electrochemical reaction with oxygen at the cathode 4 to generate power, thereby generating water. Since a part of the generated water generated on the cathode side is diffused back to the anode side through the solid polymer electrolyte membrane 2, the generated water also exists on the anode side.

  The air is pressurized to a predetermined pressure by a compressor 7 such as a supercharger (S / C) and supplied to a reaction gas flow path 6 of the cathode 4 of the fuel cell 1 through an air supply flow path 8. After the air supplied to the fuel cell 1 is used for power generation, the air is discharged from the fuel cell 1 to the air discharge passage 9 together with the water generated on the cathode side, and introduced into the exhaust gas treatment device 10. Hereinafter, the air supplied to the fuel cell 1 is identified as supply air, and the air exhausted from the fuel cell 1 is identified as exhaust air.

  On the other hand, the hydrogen gas supplied from the hydrogen tank (H2) 11 is supplied to the reaction gas flow path 5 of the anode 3 of the fuel cell 1 through the hydrogen gas supply flow path (fuel gas supply flow path) 12. The unreacted hydrogen gas that has not been consumed together with the generated water on the anode side passes through the hydrogen gas discharge flow path (fuel gas discharge flow path) 16 from the anode side to the hydrogen gas circulation flow path (fuel gas circulation flow path) 13. And merges with the hydrogen gas supply channel 12 via a hydrogen pump 14 provided in the hydrogen gas circulation channel 13. That is, the hydrogen gas discharged from the fuel cell 1 merges with the fresh hydrogen gas supplied from the hydrogen tank 11 and is supplied again to the reaction gas flow path 5 of the anode 3 of the fuel cell 1.

  A hydrogen gas purge channel 22 having a purge valve 15 is branched from the hydrogen gas circulation channel 13, and the hydrogen gas purge channel 22 is connected to the exhaust gas treatment device 10. In the exhaust gas treatment device 10, the exhaust air discharged from the air discharge passage 9 of the fuel cell 1 and the hydrogen gas discharged from the hydrogen gas purge passage 22 are diluted and discharged. Reference numeral 17 denotes a shutoff valve for shutting off hydrogen gas supplied from the hydrogen tank 11, and reference numeral 18 denotes a motor for driving a vehicle driven by electric energy of the fuel cell 1.

  The fuel cell 1 is controlled by an ECU 19 which is a control unit. Therefore, a signal from an outside air temperature sensor 20 is input to the ECU 19, and the number of revolutions of the compressor 7, the number of revolutions of the hydrogen pump 14, the opening / closing of the shut-off valve 17, and the purge The opening and closing of the valve 15 is performed. Further, it controls the motor 18 according to an acceleration request input from the accelerator pedal 21.

Next, the fuel cell operation stop processing of the fuel cell vehicle will be described based on the flowchart of FIG. The description will be made with reference to the time chart of FIG. 3 and the graphs of FIGS. 4 and 6.
In step S1, the fuel cell vehicle stops, the ignition switch is turned off (IG-OFF), and the supply of power from the fuel cell 1 is cut off (at the point X in FIG. 3). At this time, the shutoff valve 17 provided in the hydrogen gas supply passage 12 is shut off, and the supply of hydrogen from the hydrogen tank 11 is stopped.
In the next step S2, it is determined whether or not the outside air temperature is equal to or higher than 15 ° C. (predetermined temperature). If the determination result is “NO” and the temperature is less than 15 ° C., the process proceeds to step S3, and if the determination result is “YES”. If it is 15 ° C. or higher, the process proceeds to step S5.

  Here, as shown in FIG. 3, the power generation current is the idle power generation current i (0 after X) until the ignition switch is turned off (IGSWOFF). The compressor 7 has idle speeds a and b, respectively. Note that the purge valve 15 is closed.

  In step S3, the rotation speed (rotation speed d (d> b) in FIG. 3) of the compressor 7 used for the stop processing according to the outside air temperature and the rotation speed of the hydrogen pump 14 (rotation speed e (e in FIG. 3) = A)) and a processing time timer (time indicated by t1 in FIG. 3) are set, and the process proceeds to step S4. Here, the set value of the processing time timer has a characteristic that the temperature gradually decreases to 15 ° C. as shown in FIG. In this case, the processing time is set to 0.

  In other words, the lower the outside air temperature when the fuel cell vehicle is stopped, the lower the temperature of the fuel cell 1 and the higher the possibility that the reactant gas flow path freezes. I do. When the temperature is 15 ° C. or higher, the possibility of freezing of the reaction gas flow path of the fuel cell 1 is sufficiently low, so that the processing time can be reduced to zero and the power consumption of the compressor 7 and the like required for wastewater treatment can be eliminated. Thus, the load on the fuel cell 1 can be minimized.

The set value of the processing time timer is not limited to the example shown in FIG. 4A, but may be the following modified examples.
As a first modification, for example, as shown in FIG. 4B, when the temperature is 15 ° C. or more, the processing time for discharging water is set to the first processing time, and when the temperature is lower than 15 ° C., The second processing time may be set to be longer than the first processing time. In other words, the lower the outside air temperature when the fuel cell vehicle is stopped, the more likely the reaction gas flow path of the fuel cell 1 is frozen, so that the water discharge process is performed for a longer time. Further, when the outside air temperature is lower than the predetermined temperature (15 ° C.), the processing time is set to a constant value, so that the water discharging process can be performed without any shortage of the processing time.

  As a second modification, for example, as shown in FIG. 4C, when the temperature is higher than 15 ° C., the processing time for discharging water is set to the first processing time, and when the temperature is lower than 0 ° C., the first processing time is set. The second processing time may be set to be longer than the first processing time. By doing so, the lower the outside air temperature when the fuel cell vehicle is stopped, the higher the possibility that the reactant gas flow path of the fuel cell 1 freezes. The reaction gas can be discharged, and freezing of the reaction gas flow path can be reliably prevented. When the outside air temperature is lower than a second predetermined temperature (0 ° C.) lower than the first predetermined temperature (15 ° C.), the drainage treatment is performed at a second predetermined time longer than the first predetermined time. Since the time is set, the time required for the wastewater treatment can be minimized, and the power consumption of the compressor 7 and the like can be minimized without taking the wastewater treatment time too long.

  In the case of the first and second modifications, steps S1 to S3 in the operation stop processing are as shown in FIG. That is, after the ignition switch is turned off in step S1, the outside air temperature is read in step S2, and in step S3, the rotation speed of the compressor 7 used for the stop processing and the rotation speed of the hydrogen pump 14 are set in accordance with the outside air temperature. Setting and setting of a processing time timer are performed, and the process proceeds to step S4. Since step S4 and subsequent steps are the same as those in the flowchart of FIG. 2, illustration and description are omitted.

Further, the set values of the rotation speed of the compressor 7 and the rotation speed of the hydrogen pump 14 according to the outside air temperature can be set as shown in FIG. 6, the horizontal axis represents the outside air temperature, and the vertical axis represents the rotation speed of the compressor 7 or the hydrogen pump 14.
In the example of FIG. 6A, the rotation speed is set to the first rotation speed higher than the idling rotation speed when the rotation speed is equal to or higher than 15 ° C., and the rotation speed is set lower than the first rotation speed when the rotation speed is lower than 0 ° C. The second rotation speed is set to a high value, and is set so as to gradually increase continuously as the outside air temperature decreases between 0 ° C. and 15 ° C.
In the example of FIG. 6B, the rotation speed is set to a first rotation speed higher than the idling rotation speed when the temperature is higher than 15 ° C., and gradually lower as the temperature becomes lower when the temperature is lower than 15 ° C. To be higher.
In the example of FIG. 6C, the rotation speed is set to a first rotation speed higher than the idling rotation speed when the rotation speed is equal to or higher than 15 ° C., and the rotation speed is set lower than the first rotation speed when the rotation speed is lower than 15 ° C. At a high rotation speed, and the rotation speed is increased stepwise at predetermined temperature intervals.
However, when the processing time timer is set to 0 when the outside air temperature is 15 ° C. or more as shown in FIG. 4A, the outside air temperature of the hydrogen pump 14 is 15 ° C. or more. At this time, the first rotation speed is set to zero.

The lower the outside air temperature when the fuel cell vehicle is stopped, the higher the possibility that the reactant gas flow path of the fuel cell 1 is frozen. Therefore, it is necessary to carefully drain water. By increasing the supply speed of the compressed air or hydrogen gas by increasing the rotation speed of the pump 14, it is possible to reliably discharge water, and to reliably prevent the reaction gas flow path from freezing. Also, by increasing the supply amount of compressed air or hydrogen gas, it is possible to shorten the time required for discharging water, so that the outside air temperature is lower than when the supply amount is constant regardless of the outside air temperature. The set value of the processing time timer, which is set when the time is low, can be shortened.
Also, as the outside air temperature becomes lower, the rotation speed of the compressor 7 and the hydrogen pump 14 is increased, and the supply amount of the compressed air and hydrogen gas is increased. Therefore, it is possible to make the set value of the processing time timer constant when the outside air temperature is 15 ° C. or less, and to always equalize the time required when the operation of the fuel cell 1 is stopped. It becomes possible.

  In step S4, the compressor 7 and the hydrogen pump 14 are driven at the rotation speed set in step S3, and are operated until the processing time timer becomes 0 (until the time t1 elapses) (step S5), and the process proceeds to step S6. . As a result, air is supplied to the reaction gas passage 6 in a compressed state, and the water in the reaction gas passage 6 is discharged by the compressed air having the secured flow velocity. Further, since the shutoff valve 17 is closed in the hydrogen gas circulation channel 13 so that hydrogen is not supplied from the hydrogen tank 11, the hydrogen gas remaining in the hydrogen gas circulation channel 13 is circulated to the fuel cell 1. By re-supplying the hydrogen gas discharged from the fuel cell 1, water in the hydrogen gas circulation channel 13 is collected near the purge valve 15.

Here, since the reaction gas is supplied to the reaction gas flow paths 5 and 6 after the operation of the fuel cell 1 is stopped, the compressor 7 and the hydrogen pump 14 are operated by electric energy from an auxiliary power supply such as a capacitor and a battery (not shown). Is
The water remaining in each of the reaction gas flow paths 5, 6 can be discharged by the reaction gas (hydrogen gas, oxidizing gas) supplied to the fuel cell 1, so that it is not necessary to newly provide an auxiliary device for drainage.

  In step S6, the hydrogen pump 14 is stopped (the rotation speed of the hydrogen pump = 0 at the point of time Y in FIG. 3), and in step S7, a discharge process by the purge valve 15 (opening of the purge valve 15 in FIG. 3) is performed. Thereby, the hydrogen gas is sent from the hydrogen gas purge channel 22 to the exhaust gas treatment device 10. At this time, the compressor 7 is operating at the rotational speed d.

Then, in step S8, the compressor 7 is operated from the time point Y in FIG. 3 until the compressor drive time timer becomes zero. Thus, the exhaust gas can be processed by supplying the exhaust air in an amount corresponding to the amount of hydrogen discharged to the exhaust gas processing apparatus 10 to the exhaust gas processing apparatus 10. The set value t2 of the compressor drive time timer is determined according to the amount of hydrogen discharged to the exhaust gas processing device 10. At this time, since the water in the hydrogen gas circulation channel 13 is collected near the purge valve 15, it is possible to discharge the water at an early stage and to suppress the amount of discharged hydrogen with a small amount. Therefore, the driving time of the compressor 7 during the subsequent dilution process can be shortened.
Then, in step S9, the compressor 7 is stopped (at the time point Z in FIG. 3), and the operation stop processing ends.

  According to the above embodiment, by supplying the reaction gas to the reaction gas flow paths 5 and 6 according to the outside air temperature, the water in the reaction gas flow paths 5 and 6 is discharged, and the operation of the fuel cell 1 is stopped. Then, even if the fuel cell 1 is below the freezing point, since the water is discharged, the reaction gas flow paths 5, 6 do not freeze. Therefore, the energy required for drainage can be minimized as compared with the case where water is constantly drained when the operation is stopped, the load on the fuel cell 1 can be suppressed, and the restartability of the fuel cell 1 below freezing can be improved. Can be improved. In addition, when necessary, draining the water in the system for a necessary time can minimize the energy required for draining.

  Here, the oxidizing gas of the reaction gas is compressed air, and the compressed air is supplied, so that the compressed air can drain the reaction gas flow path 6 with a sufficient flow velocity secured. Therefore, the water inside the reaction gas flow path 6 for the oxidizing gas can be reliably discharged.

  Further, the hydrogen pump 14 provided in the hydrogen gas circulation channel 13 is operated for a predetermined time t1 to circulate the hydrogen gas into the hydrogen gas circulation channel 13 by the hydrogen pump 14, After the remaining water is collected, the reaction gas flow path 5 of the fuel cell 1 can be drained, so that the water inside the reaction gas flow path 5 for the hydrogen gas can be reliably discharged, and the collected water causes the drainage. Time can be reduced.

  Note that the present invention is not limited to the above-described embodiment. For example, the predetermined outside air temperature of 15 ° C. is merely an example, and can be changed depending on the region where it is used. Further, in the present invention, the drainage treatment may be performed according to the outside air temperature, and various modifications other than the example shown in FIGS. 4A to 4C are possible. For example, in FIGS. 4B and 4C, when the temperature is equal to or higher than a predetermined temperature (15 ° C.), the drainage processing may not be performed, and the processing time may be increased as the outside air temperature decreases. The processing time may be extended.

1 is a schematic configuration diagram of a fuel cell system mounted on a fuel cell vehicle according to an embodiment of the present invention. FIG. 4 is a flowchart illustrating a process of stopping operation of a fuel cell mounted on the fuel cell vehicle according to the embodiment of the present invention. It is a time chart figure of an embodiment of the present invention. It is a graph figure of embodiment of this invention, (a) shows the relationship between the processing time and the outside air temperature at the time of a stop, (b), (c) shows a modification. FIG. 9 is another example of a flowchart illustrating a fuel cell operation stop process. It is a graph figure of an embodiment of this invention, (a) shows the relation between the number of rotations of a compressor or a hydrogen pump, and the outside air temperature at the time of stop, and (b), (c) shows a modification.

Explanation of reference numerals

1 fuel cells 5, 6 reaction gas flow path 7 compressor (gas supply control means)
14 Hydrogen pump (gas supply control means)
18 Motor 20 Outside temperature sensor (outside temperature detection means)

Claims (7)

A method of operating a fuel cell that supplies a fuel gas and an oxidizing gas as a reaction gas to each reaction gas flow path and generates power by an electrochemical reaction,
The power supply from the fuel cell is cut off, the outside air temperature is detected, and the reaction gas is supplied into the reaction gas passage according to the outside air temperature to discharge the water in the reaction gas passage, and the fuel is discharged. A method of operating a fuel cell, comprising shutting down the operation of a battery.   2. The method according to claim 1, wherein water is not discharged when the outside air temperature is equal to or higher than a predetermined temperature.   The fuel cell operating method according to claim 1 or 2, wherein the processing time for discharging water is set longer as the outside air temperature is lower.   4. The fuel cell operating method according to claim 1, wherein the processing time for discharging water is constant when the outside air temperature is lower than a predetermined temperature.   2. The fuel cell operating method according to claim 1, wherein the supply amount of the reaction gas is set according to the outside air temperature.   The fuel cell operation method according to claim 5, wherein the supply amount of the reaction gas is increased as the outside air temperature is lower. A fuel cell that supplies fuel gas and oxidant gas as a reaction gas to each reaction gas flow path and generates power by an electrochemical reaction;
An outside air temperature detecting means for detecting an outside air temperature;
Gas supply control means for controlling the supply of the reaction gas,
A fuel cell operation device, wherein the supply of electric power from the fuel cell is cut off, the gas supply control means is controlled in accordance with a detection value of the outside air temperature detection means, and the operation of the fuel cell is stopped.

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