JP2004179102A - Control method of exhaust gas treatment device of fuel cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a control method of an exhaust gas treatment device which exhausts the hydrogen left in the diluting container after the stop of generation of the fuel cell while monitoring and reducing the concentration thereof. <P>SOLUTION: The exhaust gas treatment device of a fuel cell introduces hydrogen gas exhausted from the fuel cell stack 4 from the entrance part 12 and keeps the hydrogen gas in a reservoir chamber 13, and mixes the hydrogen gas introduced in the above reservoir chamber 13 with a cathode off-gas of the fuel cell and diluted, and then dilutes and exhausts the above to the outside. When the fuel cell stack 4 stops the generation of power, the time of exhaust treatment of the residual hydrogen remained in the reservoir chamber 13 is set according to the concentration of remaining hydrogen so as to set into long time when the concentration of residual hydrogen is high, at least by one of a ventilating means 18 of a box 2 that houses the fuel cell stack 4 or by an air supply means 16 supplying the air to the fuel cell stack 4. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for controlling an exhaust gas treatment device for a fuel cell, which is a power source of an electric vehicle.
[0002]
[Prior art]
When a fuel cell system serving as a power source of an electric vehicle (hereinafter, referred to as “vehicle”) uses, for example, pure hydrogen (hereinafter, referred to as “hydrogen”) as a fuel, the supply of hydrogen to the fuel cell system is performed by A circulation system is adopted in the anode piping system to increase the utilization efficiency (improve fuel efficiency).
As a circulation system, a blower for pressurizing hydrogen, an ejector for generating a negative pressure to suction hydrogen, a vacuum pump, or the like is used. In the circulation system, if the recirculation is continued for a long time, the concentration of impurities in hydrogen, for example, nitrogen, increases, and the efficiency of power generation may be reduced. Since this hydrogen has a high concentration even if it contains impurities, it is often inconvenient to discharge high concentration hydrogen to the atmosphere as it is.
Therefore, hydrogen is retained in a diluter, diluted to a low concentration, and then discharged to the atmosphere (for example, see Patent Document 1). In addition, water may accumulate and impede the flow of hydrogen in the anode piping system of the fuel cell stack. This water is also discharged to the atmosphere through a diluter.
[0003]
[Patent Document 1]
JP-A-2002-289237 (text version, page 12, FIG. 7)
[0004]
[Problems to be solved by the invention]
However, after the operation of the vehicle is stopped, hydrogen remains in the diluter. This hydrogen may diffuse naturally and flow back into the piping or the fuel cell stack constituting the fuel cell.
On the other hand, when purging hydrogen accumulated in the diluter, it is necessary to perform a purging operation so that hydrogen having a high concentration is not discharged at one time.
[0005]
Accordingly, an object of the present invention is to provide a control method of an exhaust gas treatment device that discharges a reduced amount of hydrogen while monitoring the concentration of hydrogen remaining in a diluter after stopping power generation of a fuel cell.
[0006]
[Means for Solving the Problems]
As a means for solving the above-mentioned problems, a control method of an exhaust gas treatment apparatus for a fuel cell according to claim 1 of the present invention is directed to introducing a hydrogen gas purged from a fuel cell stack from an inlet to a residence chamber. In the fuel cell exhaust gas treatment device that mixes the hydrogen gas introduced into the retention chamber with the cathode off-gas of the fuel cell, dilutes the mixture, and discharges the diluted gas to the atmosphere, the power generation of the fuel cell stack was stopped. When, at least one of the ventilation means of the box containing the fuel cell stack and the air supply means to the fuel cell stack, the time for discharging residual hydrogen in the retention chamber, according to the concentration of the residual hydrogen, When the residual hydrogen concentration is high, it is set to a long time.
[0007]
With such a configuration, in the control method of the exhaust gas treatment apparatus for a fuel cell according to the first aspect of the present invention, after the purge, the residual hydrogen concentration in the retaining chamber decreases with time. Therefore, the residual hydrogen concentration when the fuel cell stops generating power can be predicted. If the predicted value of the residual hydrogen concentration is known, the time for discharging the residual hydrogen can be set according to the predicted value. Therefore, after the power generation of the fuel cell stack is stopped, it is possible to minimize the power consumption of equipment (at least one of the ventilation means and the air supply means) that is continuously operated to discharge the hydrogen accumulated in the accumulation chamber. Become. Thus, for example, the capacity of the storage battery is not consumed unnecessarily to discharge the hydrogen retained in the retention chamber, so that it is easy to secure a necessary amount of electricity at the time of restart.
[0008]
In the control method of the exhaust gas treatment apparatus for a fuel cell according to the second aspect of the present invention, hydrogen gas purged from the fuel cell stack is introduced from the inlet portion, retained in the retention chamber, and introduced into the retention chamber. In a fuel cell exhaust gas treatment device that mixes the hydrogen gas with a cathode off gas of the fuel cell, dilutes the gas, and discharges the diluted gas to the atmosphere, when power generation of the fuel cell stack is stopped, a box containing the fuel cell stack is The time for exhausting residual hydrogen in the storage chamber by at least one of the ventilation means and the air supply means for the fuel cell stack is long immediately after the purge according to the elapsed time from the final purge during power generation of the fuel cell. It is characterized in that it is set to time.
[0009]
With such a configuration, in the control method of the exhaust gas treatment apparatus for a fuel cell according to the second aspect of the present invention, the amount of hydrogen remaining in the retention chamber is large immediately after the purge, and a long time after the purge. It will decrease over time. That is, the amount of hydrogen remaining in the retention chamber when the fuel cell stops generating power can be determined by the elapsed time from the purge performed immediately before the fuel cell stopped generating power. When the amount of residual hydrogen is known from the elapsed time, the operation time of the equipment (at least one of the ventilation means and the air supply means) continuously operated to discharge the hydrogen retained in the retention chamber after the power generation of the fuel cell stack is stopped is determined. Can be set. That is, it is possible to optimize the time for the process of discharging the hydrogen remaining in the retaining chamber. Thus, for example, the capacity of the storage battery is not consumed unnecessarily to discharge the hydrogen retained in the retention chamber, so that it is easy to secure a necessary amount of electricity at the time of restart.
[0010]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, an embodiment of a control method of an exhaust gas treatment apparatus for a fuel cell according to the present invention will be described with reference to the drawings.
[0011]
In the drawings to be referred to, FIG. 1 is a diagram showing a layout of a fuel cell system box including an exhaust fuel dilutor in a fuel cell electric vehicle, and FIG. 2 is a system diagram of a fuel cell. First, an exhaust gas treatment device for a fuel cell will be described.
[0012]
As shown in FIG. 1, a fuel cell system box 2 is mounted substantially below the floor of a fuel cell electric vehicle 1 at the center. Inside the fuel cell system box 2, a fuel cell system, that is, a temperature controller 3, a fuel cell stack 4, a humidifier 5, and an exhaust fuel dilutor 6 are placed in order from the front to the rear of the vehicle 1. ing. The fuel cell system includes an air supply means such as a high pressure hydrogen container 15, a supercharger (S / C) 16 for supplying air to the fuel cell stack 4, and a ventilation fan 18 for ventilating the fuel cell system box 2. And a radiator (not shown) for cooling the fuel cell stack 4.
[0013]
As shown in FIG. 2, the fuel cell stack 4 is supplied with hydrogen serving as fuel stored in the high-pressure hydrogen container 15 and air taken in from outside the vehicle and compressed by the supercharger 16 to generate electric power. Supplies electricity to drive the In order to operate the fuel cell stack 4 suitably, the temperature of the hydrogen and air supplied to the fuel cell stack 4 is adjusted by the temperature controller 3 (see FIG. 1), and the temperature of the hydrogen and air supplied to the fuel cell stack 4 is supplied by the humidifier 5. Humidified hydrogen and air. The discharged fuel dilutor 6 discharges and retains purge hydrogen from the anode piping system, mixes and dilutes with discharged air, and discharges the diluted hydrogen to the atmosphere.
[0014]
Hydrogen once used in the fuel cell stack 4 is returned to the upstream side of the humidifier 5 by a pipe 7 to form a circulation system in order to increase the utilization efficiency (improve fuel efficiency). In addition, since hydrogen that has been recirculated for a long time has a high impurity concentration or water accumulates therein, a purge hydrogen pipe 8 branched from a pipe 7 of the circulation system is discharged to purge the hydrogen and water. It is connected to the fuel diluter 6. The purge hydrogen pipe 8 is provided with an on-off valve 9 and is connected to control means such as an ECU (Electronic Control Unit) 10 and is normally closed and opened when purging hydrogen gas.
[0015]
A cathode offgas pipe 11 for discharging the cathode offgas discharged from the fuel cell stack 4 passes through the discharged fuel dilutor 6 and opens to the atmosphere. The diameter of the cathode offgas pipe 11 is reduced after the cathode offgas pipe 11 enters the exhaust fuel dilutor 6. As a result, the flow rate of the cathode off-gas flowing in the cathode off-gas pipe 11 increases, and the pressure decreases. In the cathode off-gas pipe 11 in the exhaust fuel diluter 6, a hole (not shown) for sucking hydrogen retained in the exhaust fuel diluter 6 (retention chamber 13), and condensation generated in the fuel cell stack 4. An unillustrated drainage hole for draining water is provided.
Above the discharged fuel diluter 6, an inlet 12 for purge hydrogen discharged from the purge hydrogen pipe 8 of the circulation system is provided. The inside of the discharged fuel dilutor 6 becomes a retention chamber 13 for hydrogen released from the inlet 12.
[0016]
The configuration of the fuel cell system box 2 is substantially as described above. The purge hydrogen discharged into the retention chamber 13 in the exhausted fuel diluter 6 stays for a while as it diffuses and expands in volume. Thereafter, since the exhaust air flows through the cathode off-gas pipe 11 introduced into the exhaust fuel diluter 6, the purge hydrogen is sucked from a hole (not shown) and mixed with the exhaust air to be diluted to have a low concentration. And is released to the atmosphere.
Condensed water in the exhaust air from the humidifier 5 and the fuel cell stack 4 is also discharged together with the exhaust air.
[0017]
As shown in FIG. 7, the exhausted fuel diluter 6 purges residual hydrogen mixed with impurities at predetermined time intervals T _PIO when the vehicle stops at a traffic light. By the way, when the ignition switch is turned off and the power generation of the fuel cell stack 4 is completely stopped, the flow of the exhaust air (cathode off-gas) stops, so that the hydrogen that has not been discharged to the atmosphere remains in the discharged fuel diluter 6. Become.
Therefore, even after the power generation of the fuel cell stack 4 is stopped, the supercharger 16 is continuously operated to continuously supply the cathode off-gas from the fuel cell stack 4 to the exhausted fuel diluter 6 through the cathode off-gas pipe 11. After the power generation is stopped, the ventilation means such as the ventilation fan 18 for ventilating the inside of the fuel cell system box 2 is continuously operated. Part of the ventilation air from the ventilation fan 18 penetrates through the fuel cell system box 2 through the hydrogen discharge pipe 17 and opens to the atmosphere. Then, the hydrogen discharge pipe 17 and the discharged fuel dilutor 6 are connected by a control pipe 19, and the pressure can be adjusted in the control pipe 19 (the pressure of the cathode off gas supplied by the supercharger 16 is reduced). A relief valve 20, such as a vent valve, which opens and closes due to differences, is provided. The relief valve 20 closes when the signal pressure (cathode pressure) from the supercharger 16 is, for example, 15 kPa or more (during power generation) and becomes 5 kPa or less (when the vehicle stops or power generation is stopped). Has been adjusted.
Exhaust of hydrogen gas using the ventilation fan 18 will be described as a first embodiment, and exhaust of hydrogen gas using the supercharger 16 will be described as a second embodiment later.
[0018]
In addition, an ejector 21 having a throat portion 21a having an inner diameter smaller than that of the hydrogen discharge pipe 17 was provided at a connection portion between the control pipe 19 and the hydrogen discharge pipe 17. By doing so, since the throat portion 21a of the ejector 21 (see FIG. 2) is narrower than the hydrogen discharge pipe 17, the wind speed blown by the ventilation fan 18 is increased, and the discharge fuel dilutor 6 side Even the pressure drops. Therefore, a suction force is generated in the throat portion 21a, and the residual hydrogen remaining in the storage chamber 13 in the discharged fuel diluter 6 is sucked out by the suction force.
A hydrogen sensor 22 is provided in the storage chamber 13, detects the amount of residual hydrogen in the storage chamber 13, sends a signal to the ECU 10, and detects the hydrogen concentration. The hydrogen concentration may not be directly detected but may be obtained as a predicted value by a method described later.
Reference numeral 23 denotes a cathode outlet, reference numeral 24 denotes an outlet of the hydrogen discharge pipe 17, and reference numeral 25 denotes a ventilation outlet in the fuel cell system box 2.
[0019]
Next, a first embodiment of the control method of the exhaust gas treatment apparatus for a fuel cell according to the present invention will be described with reference to the flowchart of FIG. Note that the first embodiment is an embodiment in which the discharge time is determined according to the predicted value of the residual hydrogen concentration in the retention chamber 13.
When the ignition switch is turned off to stop the power generation of the fuel cell stack 4 (S1), the operation of the supercharger 16 is stopped, but the ventilation fan 18 is continuously operated. Then, as shown in FIG. 4, the ECU 10 (see FIG. 2) measures a time T _PI from the final purge of hydrogen performed immediately before the ignition switch is turned off until the ignition switch is turned off (S2). Next, from the time T _PI , the flow rate of air into the retaining chamber 13 by the supercharger (S / C) 16 before the ignition switch is turned off, and the purge hydrogen amount, the ECU 10 determines the hydrogen concentration in the retaining chamber 13 by the ECU 10. Predict (S3). This is based on an algorithm that, as shown in FIG. 7, the concentration increases when purging is performed, and decreases when the purging is not performed (gradually).
From the obtained hydrogen concentration and the transition curve of the predicted concentration of residual hydrogen shown in FIG. 5, the time until the hydrogen concentration decreases to the target low hydrogen concentration is calculated (S4). Then, the ventilation fan 18 is driven for the calculated time (driving time of the ventilation fan 18) (S5), and the residual hydrogen in the stagnant chamber 13 is released by the relief valve 20 (the relief valve 20 is open to stop power generation), After passing through the control pipe 19 and the ejector 21, it is mixed and diluted with the air flowing in the hydrogen discharge pipe 17, and has a low concentration and is discharged from the discharge port 24 to the atmosphere.
As shown in FIG. 5, when the ventilation hydrogen 18 discharges residual hydrogen from the retention chamber 13, the residual hydrogen concentration is set to be longer when the predicted value (initial concentration) of the residual hydrogen concentration is large.
[0020]
According to the first embodiment, when the predicted value (initial concentration) of the residual hydrogen in the retaining chamber 13 is large, the driving of the ventilation fan 18 is performed for a longer time to discharge the residual hydrogen to the atmosphere. When the predicted value (initial concentration) of the residual hydrogen concentration in the fuel cell 13 is small, the driving time of the ventilation fan 18 is shortened. Therefore, the power consumption of the ventilation fan 18 is suppressed to the minimum, and the capacity of the storage battery (not shown) is more than necessary. Power consumption can be ensured at the time of restart.
[0021]
Next, a second embodiment of the control method of the exhaust gas treatment apparatus for a fuel cell according to the present invention will be described with reference to the flowchart of FIG. Note that the second embodiment is an embodiment in which the discharge processing time of the residual hydrogen in the retention chamber 13 is determined according to the elapsed time from the last purge.
When the ignition switch is turned off and the power generation of the fuel cell stack 4 is stopped (S11), the ventilation fan 18 is stopped, and the supercharger 16 is continuously operated. Then, as shown in FIG. 7, the time T _PI from the final purge of hydrogen was carried out just before turning off the ignition switch to the off ignition switch is measured by the ECU 10 (see FIG. 2) (S12). Then, the ECU 10 determines whether or not the time T _PI from the last purge to turning off the ignition switch is, for example, 10 seconds or more (S13). If it is longer than 10 seconds (YES), it is determined that there is no need to drive the supercharger 16, so the supercharger 16 is stopped (S14).
However, if the time T _PI from the last purge until the ignition switch is turned off is, for example, less than 10 seconds (NO), the drive time T _SC of the supercharger 16 is calculated as follows (S15).
[0022]
That is, in step S15, as shown in FIG. 7, the time T _PI from the last purge of hydrogen to turning off the ignition switch is compared with the time T _PIO between the last purge and the immediately preceding purge, and The operation time of the charger 16 is calculated. Then, it is driven at a rotational speed in a time period _{T SC} with the supercharger 16 with the calculated (S16). As a result, the residual hydrogen in the retention chamber 13 is sucked into the cathode off-gas pipe 11, mixed with air and diluted, becomes a low concentration, and is discharged from the cathode outlet 23 to the atmosphere.
When the supercharger 16 to drive the in time to discharge treated residual hydrogen in the retention chamber 13 (drive time T _SC of the supercharger _16), as shown in FIG. 8, immediately after purging (T _PI is on short side ) Is longer.
[0023]
On the other hand, in step S15, the time T _PI from the final purge of hydrogen to the turning off of the ignition switch shown in FIG. 7 is compared with the time T _PIO between the final purge and the immediately preceding purge, and if the driving time _{T SC} of the charger 16 is calculated as "0" (S13), drives the time _{T SC} only the super-charger 16. That is, if the time _TSC is 0, the supercharger 16 is not driven.
[0024]
According to the second embodiment, there is determined whether the elapsed time (10 seconds), yet only a minimum time T _SC, to continue operating the supercharger 16, the discharge of residual hydrogen in the holding chamber 13 Since the processing is performed, the power consumption is suppressed to the minimum and the capacity of the storage battery is not consumed more than necessary, so that a necessary amount of electricity can be secured at the time of restart.
[0025]
In the first embodiment, a ventilation fan (ventilation means) 18 is used, and in the second embodiment, a supercharger (air supply means) 16 is used to discharge residual hydrogen in the retention chamber 13. Although the case in which the processing is performed has been described, in both embodiments, the ventilation fan (ventilation means) 18 and the supercharger (air supply means) 16 are simultaneously used to shorten the discharge processing of the residual hydrogen in the retention chamber 13. You may make it perform efficiently between. Further, in the first embodiment, the supercharger 16 may be used instead of the ventilation fan 18, and in the second embodiment, the ventilation fan 18 may be used instead of the supercharger 16. Is also good.
[0026]
【The invention's effect】
As described above, in the exhaust gas treatment apparatus for a fuel cell according to the first aspect of the present invention, when the amount of residual hydrogen is large, the hydrogen discharge time is lengthened, so that the hydrogen remaining in the retention chamber is reliably discharged. be able to. Therefore, the power consumption of at least one of the ventilation means and the air supply means which continuously operates can be suppressed to the minimum. For this reason, for example, since the capacity of the storage battery is not consumed more than necessary, a necessary amount of electricity can be secured at the time of restart.
[0027]
In the fuel cell exhaust gas treatment device according to the second aspect of the present invention, even when the elapsed time from the hydrogen purge immediately before the stop of power generation is long, the hydrogen discharge time is extended, so that the hydrogen remaining in the retention chamber is reduced. It can be discharged reliably. Therefore, since at least one of the ventilation means and the air supply means is continuously operated for the required time, power consumption can be suppressed to the minimum. For this reason, for example, since the capacity of the storage battery is not consumed more than necessary, a necessary amount of electricity can be secured at the time of restart.
[Brief description of the drawings]
FIG. 1 is a diagram showing a layout of a fuel cell system box according to the present invention in a fuel cell electric vehicle.
FIG. 2 is a system diagram of the fuel cell of the present invention.
FIG. 3 is a flowchart showing a method of controlling a ventilation fan.
FIG. 4 is a time chart when the ventilation means is operated for a predetermined time.
FIG. 5 is a graph showing a predicted concentration of hydrogen in a retention chamber.
FIG. 6 is a flowchart illustrating a supercharger control method.
FIG. 7 is a time chart when the supercharger is operated for a predetermined time.
FIG. 8 is a graph showing a predicted concentration of hydrogen in the retention chamber.
[Explanation of symbols]
1: Fuel cell electric vehicle (vehicle)
2: Fuel cell system box 4: Fuel cell stack 6: Discharged fuel dilutor 8: Purge hydrogen pipe 11: Cathode off-gas pipe 12: Inlet 13: Retention chamber 16: Supercharger (air supply means)
17: Hydrogen discharge pipe 18: Ventilation fan (ventilation means)
20: relief valve 22: hydrogen sensor 23: cathode outlet

Claims (2)

Hydrogen gas purged from the fuel cell stack is introduced from the inlet portion and retained in the retention chamber, and the hydrogen gas introduced into the retention chamber is mixed with the cathode off gas of the fuel cell, diluted, and discharged to the atmosphere. In an exhaust gas treatment device for a fuel cell,
When the power generation of the fuel cell stack is stopped, at least one of ventilation means of a box containing the fuel cell stack and air supply means to the fuel cell stack, the time for discharging residual hydrogen in the storage chamber, According to the concentration of the residual hydrogen, when the residual hydrogen concentration is large, set to a long time,
A method for controlling an exhaust gas treatment device for a fuel cell, comprising: Hydrogen gas purged from the fuel cell stack is introduced from the inlet portion and retained in the retention chamber, and the hydrogen gas introduced into the retention chamber is mixed with the cathode off gas of the fuel cell, diluted, and discharged to the atmosphere. In an exhaust gas treatment device for a fuel cell,
When the power generation of the fuel cell stack is stopped, at least one of ventilation means of a box containing the fuel cell stack and air supply means to the fuel cell stack, the time for discharging residual hydrogen in the storage chamber, According to the elapsed time from the last purge during power generation of the fuel cell, set a long time immediately after the purge,
A method for controlling an exhaust gas treatment device for a fuel cell, comprising:

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