JP2004281237A - Exhaust gas treatment device for fuel cell - Google Patents

Abstract

An object of the present invention is to provide an exhaust gas treatment device for a fuel cell, which makes it possible to sufficiently extract the capacity of a diluter.
An exhaust gas treatment device (25) includes an exhaust fuel dilutor (6) in which hydrogen intermittently purged from a circulation pipe is stored, and an exhaust fuel dilutor (6) using a part of exhaust air from a fuel cell (4) as stirring air. The exhaust pipe includes an agitation pipe 19 to be introduced into the upper part of the diluter 6 and an exhaust pipe 14 in which a suction port 17 for sucking hydrogen in the exhaust fuel dilutor 6 is formed. Further, the exhaust gas processing device 25 includes an adjusting valve 19a for adjusting the amount of the stirring air, and a hydrogen concentration detecting device for detecting a hydrogen concentration of a mixture of the exhaust air and the hydrogen sucked from the inlet 17. And a control device 27 for controlling the regulating valve 19a based on the detection signal from the hydrogen concentration detector 26.
[Selection diagram] FIG.

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a fuel cell exhaust gas treatment apparatus that dilutes hydrogen purged from a fuel cell to a predetermined concentration and then discharges the diluted hydrogen.
[0002]
[Prior art]
In general, a fuel cell is configured such that a cathode is partitioned on one side and a anode is partitioned on the other side with a proton conductive polymer electrolyte membrane (PEM membrane) interposed therebetween, and is supplied to the cathode. Electric power is generated by an electrochemical reaction between oxygen in the air and hydrogen in the fuel gas supplied to the anode. In the field of such fuel cells, as a technique for diluting unreacted hydrogen and discharging it to the atmosphere, hydrogen discharged from the fuel cell is mixed with air in a diluter to reduce the hydrogen concentration, Is known (for example, see Patent Document 1).
[0003]
[Patent Document 1]
JP-A-11-191422 (paragraph number [0024], FIG. 2)
[0004]
[Problems to be solved by the invention]
By the way, in the technique as described above, in order to maintain the hydrogen concentration in the exhaust gas discharged from the diluter to the atmosphere below a predetermined limit value, and to mix and dilute as much purge hydrogen as possible. It has been desired that the concentration of hydrogen in the exhaust gas be controlled with higher precision and the capacity of the diluter be sufficiently utilized.
[0005]
Accordingly, an object of the present invention is to provide an exhaust gas treatment device for a fuel cell, which makes it possible to sufficiently draw out the capacity of a diluter.
[0006]
[Means for Solving the Problems]
According to the first aspect of the present invention that solves the above problem, the hydrogen gas purged from the fuel cell is retained in a retention chamber, mixed with the cathode off gas of the fuel cell, diluted, and discharged to the atmosphere. In a fuel cell exhaust gas treatment device having a diluting device, a stirring pipe for introducing a stirring gas for stirring hydrogen gas retained in the retention chamber, an adjustment valve for adjusting the amount of the stirring gas, A hydrogen concentration detector that detects the hydrogen concentration of the exhaust gas discharged to the atmosphere, and a control device that controls the adjustment valve based on a detection signal from the hydrogen concentration detector. I do.
[0007]
According to the first aspect of the invention, when the hydrogen gas in the dilutor is mixed with the cathode off-gas and discharged to the outside, the hydrogen concentration of the discharged gas is detected by the hydrogen concentration detector. Then, the control device appropriately controls the adjustment valve based on the detection signal from the hydrogen concentration detector, whereby the amount of the stirring gas is increased or decreased, and the amount of hydrogen contained in the exhaust gas is adjusted. That is, by increasing the amount of the stirring gas, the hydrogen accumulated in the upper portion is stirred to increase the amount of hydrogen in the exhaust gas. The amount of hydrogen in the exhaust gas is reduced by increasing the amount of hydrogen.
[0008]
The invention according to claim 2 is the exhaust gas treatment device for a fuel cell according to claim 1, wherein the control device is configured such that an amount of the stirring gas supplied to the dilutor is equal to or less than a lower limit, and When it is determined that the hydrogen concentration is higher than a predetermined value, the flow rate varying means is controlled to increase the amount of the cathode off-gas.
[0009]
Here, the "flow rate varying means" refers to, for example, a compressor that supplies air in an amount corresponding to the rotation speed, a flow rate adjustment valve that can adjust the flow rate, and the like.
[0010]
According to the invention described in claim 2, for example, when the hydrogen concentration detected by the hydrogen concentration detector is high, the amount of the stirring gas is reduced when the amount of the stirring gas is reduced to reduce the amount of hydrogen in the exhaust gas. When it cannot be reduced above, that is, when it is equal to or less than the lower limit, the flow rate varying means is controlled to increase the amount of cathode offgas.
[0011]
According to a third aspect of the present invention, there is provided an exhaust gas for a fuel cell having a dilutor for retaining hydrogen gas purged from a fuel cell in a retention chamber, mixing with a cathode off-gas of the fuel cell, diluting the gas, and discharging the diluted gas to the atmosphere. In the processing apparatus, a stirring pipe for introducing a stirring gas for stirring the hydrogen gas retained in the retention chamber, and an adjustment valve for adjusting the amount of the stirring gas are provided to execute hydrogen purging from the fuel cell. The introduction of the stirring gas is controlled accordingly.
[0012]
According to the third aspect of the invention, when hydrogen is purged from the fuel cell, the introduction of the stirring gas into the diluter is controlled according to the execution of the hydrogen purge. That is, for example, by performing control to close the adjustment valve in accordance with the execution of the hydrogen purge, the pressure in the diluter is reduced to a predetermined value or less, and the purged hydrogen is sufficiently taken into the diluter.
[0013]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, with reference to the drawings, details of an exhaust gas treatment device for a fuel cell according to the present invention will be described. In the drawings to be referred to, FIG. 1 is a plan view showing a fuel cell vehicle equipped with a fuel cell exhaust gas treatment device according to the present invention, and FIG. 2 is an explanatory diagram showing a fuel cell system having the exhaust gas treatment device. . FIG. 3 is a schematic explanatory view showing the movement of the stirring air and purge hydrogen in the discharged fuel dilutor. Note that FIG. 3 merely schematically illustrates each component in order to particularly express the movement of the stirring air and the purge hydrogen, and the positional relationship between the components is not limited to this. In particular, the structure of the exhaust fuel dilutor 6 and the exhaust pipe 14 may be such that the exhaust pipe 14 penetrates the exhaust fuel diluter 6 as shown in FIG. The exhaust pipe 14 may be joined to the lower surface.
[0014]
As shown in FIG. 1, a fuel cell vehicle (hereinafter, referred to as “vehicle”) 1 is provided with a fuel cell system box 2 under a floor substantially in 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 arranged in order from the front to the rear of the vehicle 1. ing. In addition, the fuel cell system includes a radiator (not shown) for cooling the fuel cell stack 4 in addition to the devices 3 to 6, a high-pressure hydrogen container 23 shown in FIG. Flow rate varying means) 21 and the like.
[0015]
As shown in FIG. 2, the fuel cell stack 4 performs an electrochemical reaction between hydrogen serving as a fuel stored in the high-pressure hydrogen container 23 and air supplied from the compressor 21 (hereinafter, referred to as “supply air”). It generates electricity. Further, an anode drain pipe 10 for discharging a drain such as water generated along with power generation to a discharge fuel dilutor 6 is connected to a lower portion of the fuel cell stack 4. The water generated in the fuel cell stack 4 flows to the exhausted fuel diluter 6 by manually or automatically opening and closing an on-off valve 12 provided at an appropriate position of the anode drain pipe 10.
[0016]
On the anode side of the fuel cell stack 4, a hydrogen supply pipe 22 for guiding hydrogen from the high-pressure hydrogen container 23 is connected to an inlet of the fuel cell stack 4, and a circulation pipe (recirculation system) for returning hydrogen to the fuel cell stack 4 at an outlet thereof. 7) is connected. The circulation pipe 7 has a purge hydrogen pipe 8 for discharging hydrogen containing impurities in hydrogen stored therein and water generated in the fuel cell stack 4 to the discharge fuel diluter 6. Is connected. The hydrogen in the circulation pipe 7 is opened and closed at predetermined intervals by a signal from a control device 27 to be described later, and a purge valve 9 provided at an appropriate position of the purge hydrogen pipe 8 is opened and closed by a discharge fuel dilutor. 6 is intermittently purged (discharged).
[0017]
An air supply pipe 24 for guiding supply air from the compressor 21 is connected to the cathode side of the fuel cell stack 4 at its inlet, and air discharged from the fuel cell stack 4 (hereinafter, “exhausted air (cathode off-gas) ) ") Is connected to an exhaust pipe 14 for guiding the outside. The exhaust pipe 14 is disposed so as to pass below the exhaust fuel diluter 6, so that exhaust air flowing inside the exhaust pipe 14 is guided to the outside through the lower side of the exhaust fuel dilutor 6. In addition, the exhaust pipe 14 is formed with a suction port 17 for sucking an air-fuel mixture containing hydrogen, water, and the like in the exhaust fuel diluter 6, and a part of the exhaust air flowing through the exhaust pipe 14 is agitated. A stirring pipe 19 is introduced from the upstream side of the exhausted fuel diluter 6 to be introduced into the upper part of the exhausted fuel diluter 6 as air for use. A backfire prevention filter 15 is provided on the outlet side of the exhaust pipe 14.
[0018]
The humidifier 5 is provided at an appropriate position of the hydrogen supply pipe 22, and a humidifier drain pipe 11 for discharging a drain such as water to the discharge fuel diluter 6 is connected to a lower portion of the humidifier 5. The drain in the humidifier 5 flows to the discharged fuel diluter 6 by manually or automatically opening and closing an on-off valve 13 provided at an appropriate position of the humidifier drain pipe 11. Although not shown, the air supply pipe 24 is also provided with a humidifier 5, a humidifier drain pipe 11, and an on-off valve 13, and the drain of the humidifier 5 is discharged to the discharged fuel diluter 6. It has become.
[0019]
The discharged fuel diluter 6 is a container having a retention chamber for temporarily storing and retaining hydrogen mainly intermittently purged from the circulation pipe 7, and is a core of the exhaust gas treatment device 25 described later. Things. Further, a communication hole 6a communicating with the suction port 17 of the exhaust pipe 14 is formed in a lower portion of the exhaust fuel diluter 6 (see FIG. 3).
[0020]
As shown in FIG. 3, the exhaust gas treatment device 25 includes the exhaust fuel dilutor 6, the stirring pipe 19, the exhaust pipe 14, and the compressor 21 as well as an adjustment valve 19a, an air amount detector 19b, and a hydrogen concentration. It has a detector 26 and a control device 27. The adjustment valve 19a is provided at an appropriate position of the stirring pipe 19, and adjusts the amount of stirring air by controlling the opening degree of the valve based on a control signal transmitted from the control device 27.
[0021]
The air amount detector 19b is provided inside the regulating valve 19a, detects the opening degree of the valve, detects the amount of stirring air supplied into the exhausted fuel diluter 6, and controls the detection signal. Output to the device 27. The hydrogen concentration detector 26 is provided on the outlet side of the exhaust pipe 14, specifically, on the downstream side of the inlet 17, and detects the hydrogen concentration of a mixture of exhaust air and hydrogen sucked from the inlet 17. (The hydrogen concentration after dilution with the discharged air) and outputs a detection signal to the control device 27.
[0022]
The control device 27 controls the valve opening of the regulating valve 19a based on the detection signal from the hydrogen concentration detector 26, and controls the compressor 21 based on the detection signals from the air amount detector 19b and the hydrogen concentration detector 26. The rotation speed is controlled. In addition, the control device 27 opens the purge valve 9 to discharge hydrogen by transmitting a signal to the purge valve 9 when the power generation of the fuel cell is abnormal (the power generation voltage is reduced) or every predetermined time. Further, the control device 27 determines that hydrogen has been purged when transmitting a signal to the purge valve 9, and controls the regulating valve 19a in accordance with the result (execution of hydrogen purge) to discharge the stirring air. The introduction to the fuel dilutor 6 is controlled. Specifically, the control device 27 performs control according to the control flow shown in FIG.
[0023]
Next, a method of treating the purged hydrogen by the exhaust gas treatment device 25 will be described with reference to FIGS.
First, it is determined whether hydrogen has been purged from the circulation pipe 7 (step S1). This purging process is performed when the power generation voltage drops or at predetermined time intervals (for example, once every 5 to 10 seconds). If it is detected in step S1 that hydrogen has been purged (Yes), the control device 27 closes the adjustment valve 19a to stop the supply of the stirring air into the exhausted fuel dilutor 6 (step S1). S2). As a result, the pressure in the exhaust fuel diluter 6 drops to a predetermined value or less, and the purged hydrogen is sufficiently taken into the exhaust fuel diluter 6.
[0024]
If the hydrogen has not been purged in step S1 (No), the hydrogen concentration is detected by the hydrogen concentration detector 26 (step S3), and the hydrogen concentration is within a predetermined range, for example, 1 to 1.5%. It is determined by the control device 27 whether it is within the range (step S4). If it is determined in step S4 that the hydrogen concentration is within the predetermined range, the control ends.
[0025]
If it is determined in step S4 that the hydrogen concentration is lower than the predetermined range, hydrogen having a specific gravity lighter than air is stored in the upper portion of the exhaust fuel diluter 6 so that the amount of hydrogen sucked through the inlet 17 is reduced. Is determined to be low, the control device 27 opens the regulating valve 19a by a predetermined amount to increase the flow rate of the stirring air supplied into the exhausted fuel diluter 6 (step S5), and the hydrogen is supplied to the suction port. Send to 17. Thereafter, the flow returns to step S3 to detect the hydrogen concentration. In step S4, it is determined whether or not the hydrogen concentration falls within a predetermined range. The increased stirring air increases the hydrogen concentration to within the predetermined range. If so, this control ends.
[0026]
As shown in FIG. 4, when it is determined in step S4 that the hydrogen concentration is higher than the predetermined range, it is determined that the hydrogen is excessively supplied to the inlet 17 by the stirring air, and the control device 27 The control valve 19a is closed by a predetermined amount to reduce the flow rate of the stirring air supplied into the exhausted fuel dilutor 6 (step S6). Next, it is determined whether or not the flow rate of the stirring air is equal to or less than a lower limit value (for example, zero) based on a detection signal from the air amount detector 19b (step S7). (No), the process returns to step S3 again to detect the hydrogen concentration, and determines in step S4 whether the hydrogen concentration has fallen within a predetermined range.
[0027]
When it is determined in step S7 that the flow rate of the stirring air is equal to or lower than the lower limit (Yes), the hydrogen concentration is detected again by the hydrogen concentration detector 26 (step S8), and the hydrogen concentration is set to a predetermined value, for example, 1 It is determined whether it is higher than 0.5% (step S9). If it is determined in step S9 that the hydrogen concentration is equal to or lower than the predetermined value (No), the process returns to steps S3 and S4. Since this hydrogen concentration is within the predetermined range in step S4, this control is performed. It will end as it is.
[0028]
If it is determined in step S9 that the hydrogen concentration is higher than the predetermined value (Yes), the control device 27 increases the rotation speed of the compressor 21 by increasing the rotation speed of the compressor 21 because the stirring air cannot be reduced any more. A process is performed to decrease the hydrogen concentration by increasing the amount of exhaust air mixed with the hydrogen coming in from step 17 (step S10). Then, when returning to steps S3 and S4 again, if the hydrogen concentration is reduced to within a predetermined range by the increased discharged air, this control is terminated as it is.
[0029]
FIG. 5 is a time chart showing changes in purge hydrogen and stirring air. As shown in FIG. 5, the supply of the stirring air is prohibited during the purging of hydrogen (between T1 and T2, between T3 and T4), and according to the detected value of the hydrogen concentration during non-purge (between T2 and T3). The amount of stirring air is increased or decreased. Immediately after the end of the purge (T2, T4), the amount of the stirring air gradually increases because the hydrogen concentration is often equal to or higher than a predetermined value because the stirring air is set to zero. FIG. 5A shows a case where a linear valve is used as the adjustment valve 19a. In this case, the amount of stirring air is continuously increased. FIG. 5B shows a case where a duty valve is used as the adjustment valve 19a. In this case, the ON / OFF ratio of the valve 19a is gradually increased.
[0030]
As described above, the following effects can be obtained in the present embodiment.
(1) The control device 27 controls the adjustment valve 19a based on the detection signal from the hydrogen concentration detector 26 to control the amount of stirring air, whereby the amount of hydrogen sucked into the exhaust pipe 14 is adjusted. Therefore, the hydrogen concentration of the mixture discharged to the outside can be controlled so as to be within a predetermined range. That is, it is possible to increase the limit value of the amount of hydrogen purged from the fuel cell by maintaining the concentration of hydrogen discharged to the atmosphere below a predetermined limit value and mixing and diluting as much purge hydrogen as possible. it can. Further, when power generation is unstable such as when the power generation voltage of the fuel cell is lowered or power generation is started, more hydrogen is purged, so that power generation can be controlled stably.
[0031]
(2) Even if the hydrogen concentration of the air-fuel mixture discharged to the outside cannot be reduced by controlling the regulating valve 19a, the amount of the discharged air is increased by controlling the compressor 21. It can be within a predetermined range.
(3) By controlling the regulating valve 19 a based on the control of the purge valve 9, the pressure in the exhausted fuel diluter 6 can be reduced, so that the purged hydrogen is sufficiently taken into the exhausted fuel diluter 6. be able to.
[0032]
As described above, the present invention is not limited to the above embodiment, but may be embodied in various forms.
In the present embodiment, the exhaust air of the fuel cell is used as the stirring air, but the present invention is not limited to this, and supply air may be used.
[0033]
【The invention's effect】
According to the first aspect of the present invention, the amount of hydrogen in the exhaust gas is adjusted by the control device controlling the adjustment valve based on the detection signal from the hydrogen concentration detector. The hydrogen concentration of the exhaust gas can be controlled so as to fall within a predetermined range, so that the capacity of the dilutor can be sufficiently obtained.
[0034]
According to the second aspect of the present invention, even when the hydrogen concentration of the exhaust gas discharged to the outside cannot be reduced by the control of the regulating valve, the amount of the cathode off-gas is increased by the control of the flow rate variable means. The hydrogen concentration of the exhaust gas can be reliably kept within a predetermined range.
[0035]
According to the third aspect of the present invention, by controlling the introduction of the stirring gas, the purged hydrogen can be sufficiently taken into the diluter, and the capacity of the diluter can be sufficiently extracted.
[Brief description of the drawings]
FIG. 1 is a plan view showing a fuel cell vehicle equipped with a fuel cell exhaust gas treatment device according to the present invention.
FIG. 2 is an explanatory diagram showing a fuel cell system having an exhaust gas treatment device.
FIG. 3 is a schematic explanatory view showing movements of stirring air and purge hydrogen in a discharged fuel diluter.
FIG. 4 is a control flow chart showing a method for treating purged hydrogen by the exhaust gas treatment apparatus according to the present invention.
FIG. 5 is a time chart (a) showing changes in the stirring air and purge hydrogen adjusted by the adjustment valve according to the present embodiment, and the stirring air and purge adjusted by the adjustment valve according to another embodiment. It is a time chart (b) showing change of hydrogen.
[Explanation of symbols]
4 Fuel cell stack 6 Exhaust fuel dilutor 7 Circulation piping (circulation system)
14 exhaust pipe 17 suction port 19 stirring pipe 19a regulating valve 19b air amount detector 21 compressor (flow rate variable means)
25 Exhaust gas treatment device 26 Hydrogen concentration detector 27 Control device

Claims (3)

In a fuel cell exhaust gas treatment apparatus having a dilutor for retaining hydrogen gas purged from a fuel cell in a retention chamber and mixing it with a cathode off gas of the fuel cell, diluting and discharging the air to the atmosphere,
A stirring pipe for introducing a stirring gas for stirring the hydrogen gas retained in the retention chamber, an adjustment valve for adjusting the amount of the stirring gas, and hydrogen for detecting a hydrogen concentration of the exhaust gas discharged to the atmosphere And a concentration detector,
A control device for controlling the regulating valve based on a detection signal from the hydrogen concentration detector. An exhaust gas treatment device for a fuel cell according to claim 1,
The control device includes:
When it is determined that the amount of the stirring gas supplied to the diluter is equal to or less than a lower limit value and the hydrogen concentration is higher than a predetermined value, controlling the flow rate varying means to increase the amount of the cathode off-gas. An exhaust gas device for a fuel cell, characterized in that: In a fuel cell exhaust gas treatment apparatus having a dilutor for retaining hydrogen gas purged from a fuel cell in a retention chamber and mixing it with a cathode off gas of the fuel cell, diluting and discharging the air to the atmosphere,
A stirring pipe for introducing a stirring gas for stirring the hydrogen gas retained in the retention chamber, and an adjustment valve for adjusting the amount of the stirring gas is provided,
An exhaust gas treatment apparatus for a fuel cell, wherein the introduction of the stirring gas is controlled in accordance with execution of a hydrogen purge from the fuel cell.

Images