JPH08293312A - Fuel cell system - Google Patents

Abstract

PURPOSE: To avoid or suppress the CO poisoning of a catalyst in a fuel cell. CONSTITUTION: A fuel cell system 10 has a CO transformer 48, a temperature sensor 50, a CO sensor 52 and a passage selector valve 60 from a reforming device 20 side on a hydrogen gas feed line 44 between the reforming device 26 for generating hydrogen rich gas and a fuel cell 40. The passage selector valve 60 is provided in the branched position of a hydrogen gas refluxing line 62 branched from the hydrogen gas feed line 62 and extended to the burner 24 of the reforming device 26 to switch both the lines. When either of the detected temperature βt and the detected CO concentration αt by the temperature sensor 50 and the CO sensor 62 is out of the allowable temperature range or allowable CO concentration in the steady state of the fuel cell 40 when the fuel cell 40 is started, the designation of hydrogen rich gas from the reforming device 20 is switched from the fuel cell 40 to the burner 24, so that no hydrogen rich gas containing a high concentration CO is supplied to the fuel cell 40.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reformer for supplying a supplied hydrocarbon compound to a reforming reaction to produce a hydrogen-rich gas, and a fuel cell supplied with the produced hydrogen-rich gas as a fuel gas. And a fuel cell system having:

[0002]

2. Description of the Related Art A fuel cell using hydrogen-rich gas as a fuel gas has an electrolyte and an electrode that permeate hydrogen ions in a hydrated state of H ⁺ ( _x H ₂ O), and the electrolyte is sandwiched between the electrodes. Prepare Although there are various types of such fuel cells (for example, polymer electrolyte fuel cells, phosphoric acid fuel cells, etc.) depending on the type of electrolyte used, the electrode reactions that proceed at both the anode and cathode electrodes are as follows. Is the street.

[0003] The ^{_{anode: 2H 2 → 4H + + 4e}} - ... ^{cathode: 4H + + 4e - + O} 2 → 2H 2 O ...

When hydrogen gas is supplied to the anode, the reaction formula in the anode proceeds and hydrogen ions are generated. The generated hydrogen ions permeate (diffuse) the electrolyte (a solid polymer electrolyte membrane in the case of a solid polymer electrolyte fuel cell) in the hydrated state of H ⁺ ( _x H ₂ O), and reach the cathode. When an oxygen-containing gas such as air is supplied, the reaction formula at the cathode proceeds. this,
The fuel cell exhibits an electromotive force by the electrode reaction of (1) proceeding at each electrode.

The presence of a catalyst such as platinum is indispensable for the smooth progress of the above electrode reaction, and a catalyst layer carrying this catalyst is interposed between the electrolyte and the electrode. ing.

By the way, in the reformer which is a supply source of the hydrogen rich gas to the fuel cell, when the hydrocarbon compound is reformed to generate hydrogen (gas), a small amount of a trace amount is generated in the process of the reforming reaction. It is well known that carbon oxide (CO) is produced as an intermediate product. Since this CO is supplied to the anode of the fuel cell together with hydrogen gas, it causes CO poisoning of the catalyst in the catalyst layer of the anode.

When such a situation occurs, the function of the catalyst deteriorates, and the electrode reaction of the anode slows down, resulting in a decrease in electromotive force and eventually a stop of power generation. Therefore, various techniques for avoiding CO poisoning of this catalyst have been conventionally proposed. For example, Japanese Patent Laid-Open No. 5-251104 proposes a technique of installing a methanation reactor in front of a fuel cell in addition to a CO shift converter. This CO transformer
CO at a given temperature in the presence of oxygen is used as a catalyst (eg Ru
It is used to oxidize carbon dioxide (CO ₂ ) by a catalyst or Pt catalyst) to reduce carbon monoxide in passing hydrogen gas, and is generally arranged in front of the fuel cell. Also,
In the methanation reactor, CO is used as a catalyst (for example, at a predetermined temperature).
(Ru catalyst, Pt catalyst, etc.) to react with hydrogen in the gas and reduce it to methane (CH ₄ ) to reduce carbon monoxide in the passing hydrogen gas. That is, JP-A-5-25110
4, in this way, the CO poisoning of the catalyst in the catalyst layer of the anode is prevented by reducing the CO in the gas.

[0008]

The fuel cell does not emit environmentally unfriendly gases such as NOx during energy acquisition. Therefore, from the viewpoint of environmental protection, fuel cells are rapidly becoming widespread as an energy source for power plants as large plants and vehicles replacing internal combustion engines. In this case, in the case of a power plant, so-called all-day operation is performed not only in the fuel cell but also in the reformer, and the operation is stopped only during maintenance / inspection of the plant. On the other hand, when the fuel cell is mounted on a vehicle or the like and used as an energy source, the fuel cell is frequently operated and stopped. For this reason, in a fuel cell system in which the fuel cell is frequently operated and stopped, the CO shift converter and the methanation reactor are cooled during the operation stop and are not yet heated to a predetermined temperature during the initial operation start period. The hydrogen-rich gas is supplied to the fuel cell from the reformer while the CO reduction by the CO shifter and the methanation reactor is insufficient. Therefore, the catalyst is poisoned during the initial stage of the operation, and the electrode reaction thereafter is hindered, resulting in a decrease in output.

However, if the CO shift converter and the methanation reactor are constantly maintained at a predetermined temperature even during the period when the fuel cell is stopped, CO reduction can be achieved even at the initial stage of the operation described above. You can However, this is not a practical solution because it requires equipment for temperature maintenance and its control.

Further, not only when the fuel cell is not in a steady state as in the initial stage of operation, but also when the fuel cell is in a steady state, poisoning of the catalyst may cause harmful effects. When the operating condition of the fuel cell is in a steady state, for example, if the load of the motor or the like connected to the fuel cell fluctuates, the reforming device suppresses the progress of the reforming reaction in accordance with the fluctuation of the load or Promote. During this transition, the amount of CO in the hydrogen rich gas also changes. In order to deal with this CO fluctuation, it may be necessary to promote the reduction of CO in the CO shift converter and the methanation reactor.
In such a case, the supply of oxygen to the CO shifter increases, and the chances of reaction between this oxygen and hydrogen in the hydrogen-rich gas increase. For this reason, the CO reduction efficiency in the CO transformer is reduced. On the other hand, since the reaction between CO and hydrogen is promoted in the methanation reactor, the amount of hydrogen in the hydrogen-rich gas supplied to the fuel cell is reduced, and the amount of hydrogen supplied to the fuel cell and fluctuations in load are reduced. Correspondence collapses.

Therefore, even if the CO amount transiently fluctuates when the operating state of the fuel cell is in a steady state, the CO shifter or the methanation reactor uniformly promotes the CO reduction in accordance with the CO amount fluctuation. I can't plan. Therefore, CO in the hydrogen-rich gas may poison the catalyst in the catalyst layer.

The present invention has been made to solve the above problems, and an object thereof is to avoid or suppress CO poisoning of a catalyst in a fuel cell.

[0013]

[Means for Solving the Problems] In order to achieve the above object, the means adopted in the fuel cell system according to claim 1 is a modification for producing a hydrogen rich gas by subjecting a supplied hydrocarbon compound to a reforming reaction. A fuel cell system having a quality device and a fuel cell supplied with the produced hydrogen-rich gas as a fuel gas, the operating state detecting means detecting an operating state of the fuel cell, and the fuel cell being supplied to the fuel cell. A gas property detecting means for detecting the property of the hydrogen-rich gas, and the detected operating condition is not in a steady operating condition, and the detected gas property is different from the gas property during steady operation of the fuel cell, the generation And a switching means for switching the supply destination of the hydrogen-rich gas thus supplied to other than the fuel cell.

Further, the means adopted in the fuel cell system according to claim 2 is to provide a reformer for producing the hydrogen-rich gas by subjecting the supplied hydrocarbon compound to the reforming reaction, and the produced hydrogen-rich gas. A fuel cell system having a fuel cell supplied as fuel gas, the operating state detecting means detecting an operating state of the fuel cell, and detecting a carbon monoxide concentration in a hydrogen-rich gas supplied to the fuel cell. Concentration detecting means, a gas branch introducing means for branching in front of the fuel cell, and introducing the generated hydrogen rich gas other than the fuel cell, a flow rate of the hydrogen rich gas flowing into the gas branch introducing means, and Flow rate adjusting means for adjusting the flow rate ratio with the flow rate of the hydrogen-rich gas supplied to the fuel cell, and the detected operating state is a steady operating state When the carbon oxides concentration exceeds a predetermined concentration, and its gist in that it comprises a flow control means the flow rate for controlling the flow rate adjusting means on the side of increasing the hydrogen rich gas flowing into the gas branch introduction means.

The means adopted in the fuel cell system according to claim 3 are a reformer for producing a hydrogen-rich gas by subjecting the supplied hydrocarbon compound to a reforming reaction, and the produced hydrogen-rich gas as a fuel gas. A fuel cell system supplied with the fuel cell as a fuel cell system, wherein the fuel cell system has an operating load detecting means for detecting an operating load of the fuel cell and a branch in front of the fuel cell to generate the hydrogen-rich gas as the fuel. The gas branch introducing means introduced into other than the cell, the flow rate adjusting means adjusting the flow rate ratio of the flow rate of the hydrogen rich gas flowing into the gas branch introducing means and the flow rate of the hydrogen rich gas supplied to the fuel cell, When the operating load fluctuates, the flow rate control means for controlling the flow rate adjusting means on the side where the flow rate of the hydrogen rich gas flowing into the gas branch introducing means increases. When, as its gist in that it comprises.

In the fuel cell system according to a fourth aspect, the hydrogen rich gas supply destination other than the fuel cell switched by the switching means and the hydrogen rich gas introduction destination other than the fuel cell introduced by the gas branch introducing means are set to The burner was used for the reforming reaction in the reformer.

In the fuel cell system according to the present invention, the gas property detecting means includes a concentration detecting means for detecting a carbon monoxide concentration in the hydrogen-rich gas supplied to the fuel cell and a gas temperature of the hydrogen-rich gas. It has at least one of the temperature detecting means.

[0018]

According to the fuel cell system of the present invention having the above-mentioned structure, the hydrogen-rich gas property detected by the gas property detection unit is detected when the operation condition of the fuel cell detected by the operation condition detection unit is not a steady operation condition. Is different from the gas property during the steady operation of the fuel cell, the switching means switches the supply destination of the hydrogen-rich gas from the fuel cell to another. Therefore, the hydrogen-rich gas having a property not suitable for the steady operation state of the fuel cell is not supplied to the fuel cell when the operation state of the fuel cell is not the steady operation state.

According to another aspect of the fuel cell system of the present invention, the operating state detecting means detects the operating state of the fuel cell,
The concentration detecting means detects the concentration of carbon monoxide in the hydrogen-rich gas. When the carbon monoxide concentration exceeds the predetermined concentration while the operation state is the steady operation state, the flow rate control means controls the inflow amount of the hydrogen-rich gas into the gas branch introduction means branched in front of the fuel cell. It is increased through the control of the flow rate adjusting means. Therefore, in a situation in which the concentration of carbon monoxide increases and CO poisoning of the catalyst may be caused, the supply amount of the hydrogen-rich gas supplied to the fuel cell itself is reduced by the amount of the inflow to the gas branch introducing means, Reduce the total amount of carbon monoxide reaching the battery.

In the fuel cell system according to the third aspect, the operating load detecting means detects the operating load of the fuel cell, and when the operating load changes, the gas branch introducing means branched in front of the fuel cell. The inflow amount of the hydrogen-rich gas is increased by controlling the flow rate adjusting means by the flow rate controlling means. Therefore, in a situation in which the carbon monoxide concentration is expected to increase with a change in the operating load and CO poisoning of the catalyst may be caused, the supply amount of the hydrogen-rich gas supplied to the fuel cell itself is supplied to the gas branch introduction means. CO poisoning of the catalyst is suppressed by reducing the total amount of carbon monoxide reaching the fuel cell.

In the fuel cell system according to the fourth aspect, the hydrogen-rich gas that has not been supplied to the fuel cell through the switching means or the gas branch introducing means is supplied or introduced into the burner for the reforming reaction in the reformer. . Therefore, not only hydrogen in the hydrogen-rich gas but also carbon monoxide is burned as fuel for the burner.

In the fuel cell system according to the fifth aspect of the present invention, the properties of the hydrogen-rich gas detected by the gas-property detecting means include the concentration of carbon monoxide in the hydrogen-rich gas detected by the concentration detecting means and the hydrogen-rich gas detected by the temperature detecting means. At least one of the gas temperatures. Therefore, when the concentration of carbon monoxide in the hydrogen-rich gas or the gas temperature of the hydrogen-rich gas differs from that during the steady operation of the fuel cell, the supply destination of the hydrogen-rich gas is switched from the fuel cell to another. If the gas temperature of the hydrogen-rich gas is too high or too low, it can be assumed that the reforming reaction in the reformer is in an unstable state.In such a case, carbon monoxide produced as an intermediate product is generated. May increase. Therefore, in both cases of detecting the carbon monoxide concentration and detecting the gas temperature, the hydrogen-rich gas is not supplied to the fuel cell through the switching of the supply destination of the hydrogen-rich gas.

[0023]

Preferred embodiments of the present invention will be described below in order to further clarify the structure and operation of the present invention described above. FIG. 1 is a block diagram illustrating a schematic configuration of a fuel cell system 10 according to an embodiment. As shown
The fuel cell system 10 receives supply of reforming material methanol and water at a predetermined molar ratio, and reforms methanol with steam to produce a hydrogen rich gas (hereinafter, simply referred to as hydrogen gas).
And a solid polymer fuel cell (hereinafter simply referred to as a fuel cell) 40 that exhibits an electromotive force through a reaction between hydrogen and oxygen.

The fuel cell 40 comprises a solid polymer electrolyte membrane 40.
a is sandwiched between positive and negative electrodes of an anode 40b and a cathode 40c, and an oxygen gas supply conduit 42 is provided to the cathode 40c.
Air from the hydrogen gas supply line 44 to the anode 40b.
Hydrogen gas is supplied from. And the fuel cell 40
Generates an electromotive force by advancing the above electrode reactions of (1) and (2) with positive and negative electrodes, and drives an external drive device, for example, a motor in an electric vehicle, via a wiring (not shown).

The reformer 20 comprises a reformer 22 filled with a carrier carrying a catalyst for reforming methanol (eg, a Cu--Zn catalyst), and the reformer 22 for reforming methanol. A burner 24 for heating to a suitable temperature (about 250 to 300 ° C.). The reformer 22 receives the supply of methanol and water via the reforming material supply pipe 15 by a pump not shown. Then, the reformer 22 advances the reforming reaction of methanol through the reforming catalyst to steam reform the methanol to generate hydrogen gas. The generated hydrogen gas is sent to the hydrogen gas supply pipe line 44.
The burner 24 burns hydrogen and methanol in the excess hydrogen gas that has not been consumed in the electrode reaction at the anode 40b, and heats the reformer 22. The surplus hydrogen gas is supplied to the burner 24 from the surplus gas recirculation conduit 26 from the fuel cell 40, and the methanol is supplied to the burner 24 from a combustion methanol supply conduit 28 by a pressure feed pump (not shown). The supply of the surplus hydrogen gas and methanol to the burner 24 is performed as follows by the drive control of the pressure feed pump by the control device 70 described later.

At the beginning of the operation of the fuel cell 40,
Since the surplus hydrogen gas is not discharged from the fuel cell 40 or the amount thereof is small, methanol is supplied to the burner 24 and burned to heat the reformer 22. However, when the operating state of the fuel cell 40 shifts to a steady state and the surplus hydrogen gas is stably discharged, the supply amount of methanol is gradually reduced to burn the surplus hydrogen gas. Thereby, consumption of methanol can be suppressed. Further, when the load of the fuel cell 40 fluctuates (increases) and the hydrogen in the surplus hydrogen gas decreases, the heat quantity for heating the reformer 22 becomes insufficient, so the supply quantity of methanol is increased and a sufficient heat quantity is obtained. Is configured to obtain.

A CO shifter 48 for reducing carbon monoxide in the hydrogen gas in the pipeline passes through the pipeline of the hydrogen gas supply pipeline 44 between the fuel cell 40 and the reformer 20. A temperature sensor 50 that detects the temperature of the gas and a CO sensor 52 that detects the CO concentration in the passing gas are provided. The CO shift converter 48 uses a catalyst (for example, Ru) that oxidizes a small amount of carbon monoxide into carbon dioxide in the presence of oxygen.
It further comprises a carrier carrying a catalyst, a Pt catalyst, etc.) to further reduce carbon monoxide in passing hydrogen gas. CO transformer 48
Air is introduced from the air introduction pipe 56 to oxygen in the air to oxidize carbon monoxide, and the amount of air introduced is adjusted by the flow rate adjusting valve 58 of the air introduction pipe 56. The CO shift converter 48 is maintained at a temperature suitable for the reaction required for reducing carbon monoxide, and the amount of air introduced into the CO shift converter 48 is controlled by the control device 70 described later by the CO sensor 5
2 is determined according to the detected CO concentration.

Further, in the pipeline of the hydrogen gas supply pipeline 44,
A flow path switching valve 60 is provided in front of the fuel cell 40, and a hydrogen gas recirculation pipe line 62 extending from the flow path switching valve 60 to the burner 24 is provided. The flow path switching valve 60 is configured to switch the gas flow path to either the hydrogen gas supply pipeline 44 or the hydrogen gas recirculation pipeline 62, and to change the gas flow rate ratio flowing through both pipelines. Therefore, the flow passage switching valve 60 switches the flow passage to the hydrogen gas recirculation conduit 62, or the hydrogen gas recirculation conduit 62.
Is set, the burner 24 receives excess hydrogen gas from the excess gas recirculation pipeline 26 and methanol from the combustion methanol supply pipeline 28 as well as hydrogen rich gas from the hydrogen gas recirculation pipeline 62. Is supplied. It should be noted that the flow passage switching and flow ratio adjustment by the flow passage switching valve 60 will be described later.

In addition, the fuel cell system 10 includes a voltmeter 64, an impedance meter 66, a CPU, and a CPU for detecting the operating state of the fuel cell 40 and the variation of its load.
A control device 70 is provided which is mainly composed of a ROM and a RAM and is configured as a logical operation circuit. The control device 70 receives signals from I / O ports mutually connected to them via a common bus, sensors such as the temperature sensor 50, the CO sensor 52, the voltmeter 64, and the impedance meter 66, and other sensors and switches (not shown). Input the signal. And the control device 7
0 drives and controls the flow rate adjusting valve 58 of the air introducing pipe 56, the flow passage switching valve 60 of the hydrogen gas supply pipe line 44, and the like in accordance with these input signals and a preset control program.

Next, the operation control routine and the operation end control routine performed by the fuel cell system 10 will be described with reference to FIG.
It will be described based on the following flowcharts. The operation control routine is repeatedly executed every predetermined time after the ignition switch is turned on when the start switch (not shown) and the fuel cell system 10 are mounted on the vehicle. Then, when this routine is started, as shown in FIG. 2, first, the sensors such as the temperature sensor 50, the CO sensor 52, the voltmeter 64, and the impedance meter 66 are scanned (step S100) to execute this routine. Get the required sensor input. Then, from the sensor outputs of the voltmeter 64 and the impedance meter 66, the fuel cell 40
It is determined whether the operating state of is in the starting state or in the steady state (step S110). Here, if it is the operating state at the time of starting, the process at the time of starting from step S120 is performed, and if it is the steady state, the process proceeds to step S160.

Subsequent to the judgment that the operating state is at the time of starting, it is judged whether or not the detected CO concentration αt of the CO sensor 52 is below a predetermined CO concentration α (for example, 10 ppm) (step S120). It is sequentially determined whether or not the temperature βt detected by the temperature sensor 50 is within a predetermined temperature range (step S130). This predetermined CO concentration α
Is the CO concentration in the hydrogen-rich gas supplied to the anode 40b when the fuel cell 40 continues the steady operation. If the CO concentration is lower than this CO concentration α, the operation of the fuel cell 40 is not hindered. Means that. In other words, the CO concentration α is also the CO poisoning allowable concentration of the catalyst of the catalyst layer of the electrode in the anode 40b of the fuel cell 40.
In addition, the specified temperature range (lower limit: β0, upper limit: βT)
Is the range of the gas temperature of the hydrogen-rich gas supplied to the anode 40b when the fuel cell 40 continues the steady operation, and means that there is no hindrance to the operation of the fuel cell 40 within this temperature range. To do. In other words, this temperature range is also the allowable temperature range of the hydrogen-rich gas supplied to the anode 40b of the fuel cell 40.

When the operating state is at the time of starting, the above-mentioned judgment is made with respect to the detected CO concentration αt and the detected temperature βt.
For the following reasons. That is, in this case, the reformer 2
Because the reforming reaction of methanol in the reformer 22 of 0 is unstable, the CO concentration may be temporarily high or the gas temperature may be low. In addition, CO reduction may be insufficient due to insufficient temperature rise of the CO shift converter 48.

When a negative determination is made in any of steps S120 and 130 described above, either the CO concentration of the hydrogen-rich gas from the reformer 20 or the gas temperature is not during steady operation of the fuel cell 40. Therefore, assuming that such a hydrogen-rich gas should not be supplied to the fuel cell 40, the flow path switching valve 60 is drive-controlled to switch the pipeline to the hydrogen gas recirculation pipeline 62 side (step S14).
0). That is, the hydrogen gas supply pipeline 44 is closed to make its flow rate zero (0%), and the hydrogen gas recirculation pipeline 62 is opened to make its flow volume full (100%). As a result, the supply destination of the hydrogen-rich gas from the reformer 20 is switched from the fuel cell 40 to the burner 24, and the burner 24
Then, the hydrogen-rich gas is supplied via the hydrogen gas reflux pipe 62. After the execution of step S140, this routine is temporarily terminated without performing the subsequent processing, and the processing from step S100 described above is repeated. Therefore, while the negative determination is made in steps S120 and 130, the hydrogen-rich gas from the reformer 20 remains in the fuel cell 4.
It is not supplied to 0, but is supplied to the burner 24 for combustion and is used for heating the reformer 22.

On the other hand, the above steps S120, 130
If both are positive, the CO concentration and the gas temperature of the hydrogen-rich gas from the reformer 20 are within the permissible range even if the operating state is at the time of starting, and the fuel cell 40 is in a steady operation. Therefore, there is no problem such as CO poisoning of the catalyst. Therefore, in this case, in order to supply the hydrogen-rich gas to the fuel cell 40, the flow path switching valve 60 is drive-controlled to switch the pipeline to the hydrogen gas supply pipeline 44 side (step S150). That is, the hydrogen gas recirculation pipeline 62 is closed to make its flow rate zero (0%), and the hydrogen gas supply pipeline 44 is opened to make its flow volume full (100%). As a result, in addition to the supply of air to the cathode 40c, the hydrogen-rich gas is supplied to the anode 40b, so the above electrode reaction occurs and the fuel cell 40 starts to start.

Subsequent to step S150, it is judged again whether the detected CO concentration αt is lower than the predetermined CO concentration α (step S160), and after the start of the fuel cell 40 or in step S110. Fuel cell 40
The quality of the CO concentration during the normal operation of is judged. Here, in the case of affirmative determination, the CO concentration of the hydrogen-rich gas from the reformer 20 is within the allowable range, so the catalyst C
O There is no problem such as poisoning. Therefore, in this case, this routine is once ended without performing the subsequent processing, and the processing from step S100 is repeated. In other words, upon receiving an affirmative judgment in steps S120 and S130, the pipeline is switched to the hydrogen gas supply pipeline 44, and the anode 40b
After starting the supply of the hydrogen rich gas to the fuel cell 40 and starting the fuel cell 40, the hydrogen rich gas from the reformer 20 is
As long as a positive determination is made in step S160, the fuel cell 40 is continuously supplied.

However, if the CO concentration becomes high for some reason during the supply of the hydrogen-rich gas to the fuel cell 40 and the fuel cell 40 is not in the steady operation, the negative determination is made in step S160. Then, in this case, the flow path switching valve 60 is drive-controlled to change the flow rate ratio between the hydrogen gas supply conduit 44 and the hydrogen gas reflux conduit 62 (step S170). At this time, the hydrogen gas supply line 44
The flow rate up to that time in
Increase the flow rate of 2 from zero flow rate. As a result, the amount of hydrogen-rich gas supplied to the fuel cell 40 decreases,
The total amount of CO that reaches the anode 40b of the fuel cell 40 can be reduced, and the degree of CO poisoning of the catalyst can be suppressed. After the execution of this step S170, this routine is ended, and the processing from step S100 described above is repeated. In addition,
The flow rate ratio of the above two pipes by the flow passage switching valve 60 is detected C
It is determined by the O concentration αt, and if the detected CO concentration αt becomes higher, the flow rate of the hydrogen gas recirculation line 62 increases and the flow rate of the hydrogen gas supply line 44 decreases.

Next, the operation end control routine executed by the fuel cell system 10 will be described. This operation end control routine is executed only when a start switch (an ignition switch in the vehicle) not shown is turned off. Then, when this routine is started, as shown in FIG. 3, first, the flow path switching valve 60 is drive-controlled to switch the pipeline to the hydrogen gas recirculation pipeline 62 side (step S200), and the fuel is fed until then. The supply of the hydrogen-rich gas that has been continued to the battery 40 is stopped. As a result, the fuel cell 40 stops its operation, and the supply destination of the hydrogen rich gas generated in the reformer 20 after the start switch is turned off is switched to the burner 24.

After that, the pump for pumping the reforming raw material of methanol and water (reforming raw material pump) is driven for a predetermined time (several seconds to several tens of seconds) to send the reforming raw material to the reforming device 20 (step S210), the inside of the heat exchanger, which is a component of the reformer 20, is filled with methanol and water. Therefore, the hydrogen-rich gas generated in the reformer 20 is supplied to the burner 24 for combustion for a predetermined time (several seconds to several tens of seconds) after the start switch is turned off. Therefore, even when the CO concentration in the hydrogen-rich gas is high immediately before the operation of the fuel cell 40 is stopped, the hydrogen-rich gas having such a high CO concentration is burned immediately after the operation of the fuel cell 40 is stopped and the hydrogen-rich gas supply pipe 44 is Is reduced from. Therefore, the switching period of the gas supply destination to the burner 24 in step S140 of the operation control routine when the operation is restarted is shortened.

Subsequent to step S210, the flow path switching valve 60 is drive-controlled to switch the pipeline to the hydrogen gas supply pipeline 44 side (step S220), and this routine ends. That is, the supply destination of the hydrogen-rich gas is returned to the fuel cell 40 to prepare for restart of operation.

The fuel cell system 1 of the embodiment described above
At 0, the CO concentration in the hydrogen-rich gas is high or the gas temperature is outside the predetermined temperature range and the CO concentration in the hydrogen-rich gas is high at the time of start-up when the operation state of the fuel cell 40 is not in the steady operation state. As predicted, the supply destination of the hydrogen-rich gas from the reformer 20 is switched from the fuel cell 40 to the burner 24 by the passage switching valve 60.
Therefore, according to the fuel cell system 10, the fuel cell 4
At the start of 0, the hydrogen rich gas containing high concentration of CO is not supplied to the fuel cell 40, so that the catalyst in the anode 40b of the fuel cell 40 is not poisoned by CO.

Further, in the fuel cell system 10, when switching the supply destination of the hydrogen rich gas, the supply destination of the hydrogen rich gas is selected not only when the CO concentration in the hydrogen rich gas is high but also when the gas temperature is out of a predetermined range. Switch to burner 24. Therefore, even if the CO sensor 52 has a failure (abnormality) and the CO concentration is high, the detected C
Even when the O concentration αt is low, the hydrogen-rich gas is not supplied to the fuel cell 40 in which the gas temperature is out of the predetermined temperature range and the CO concentration in the hydrogen-rich gas is expected to be high.
Therefore, according to the fuel cell system 10, the fuel cell 4
It is possible to surely avoid CO poisoning of the catalyst in the zero anode 40b. In addition, if the gas temperature is out of the predetermined range even if the CO concentration is low, the hydrogen-rich gas is not supplied to the fuel cell 40. Therefore, according to the fuel cell system 10, it is possible to avoid flooding caused by water vapor in the hydrogen-rich gas at the anode 40b of the fuel cell 40.

In the fuel cell system 10 of this embodiment, the CO concentration (detected CO concentration αt) exceeds the predetermined concentration (permissible concentration α) for some reason even when the fuel cell 40 is in the steady operation state. When a situation occurs, the flow rate switching valve 60 increases the flow rate of the hydrogen rich gas to the hydrogen gas recirculation conduit 62 from zero, and the amount of the hydrogen rich gas supplied to the fuel cell 40 itself is reduced by the increase. Therefore, according to the fuel cell system 10, the total amount of CO reaching the fuel cell 40 is reduced, and CO poisoning of the catalyst in the anode 40b of the fuel cell 40 is suppressed.

Further, in the fuel cell system 10 of this embodiment, the hydrogen rich gas supplied to the burner 24 instead of the fuel cell 40 is burned by the burner 24. Therefore,
According to the fuel cell system 10, the reforming reaction can be promoted by efficiently preheating the reforming raw material such as methanol and water in the reforming apparatus 20 by the combustion of the hydrogen-rich gas. The reforming reaction in the vessel 22 can be stabilized in an early stage.

Further, in the fuel cell system 10, even if the CO concentration exceeds the predetermined concentration when the fuel cell 40 is in the steady operation state, the total amount of CO reaching the fuel cell 40 is reduced as described above. The increase of the oxygen supply amount for promoting the reduction of CO by the CO shift converter 48 can be minimized. Therefore, the fuel cell system 10 of the present embodiment
According to this, since the chance of reaction between oxygen and hydrogen in the hydrogen-rich gas in the CO shift converter 48 is not inadvertently increased, hydrogen shortage in the fuel cell 40 can be suppressed.

Further, in the fuel cell system 10, the hydrogen-rich gas is supplied to the burner 24 and burned for a predetermined time (several seconds to several tens of seconds) after the operation of the fuel cell 40 is stopped, and immediately before the operation of the fuel cell 40 is stopped. CO in hydrogen rich gas
Even when the concentration is high, the hydrogen rich gas having such a high CO concentration is reduced from the inside of the hydrogen gas supply pipe line 44. Therefore, according to the fuel cell system 10, by shortening the switching period of the gas supply destination to the burner 24 in step S140 of the operation control routine at the time of restarting the operation,
The startability of the fuel cell 40 when the operation is restarted can be improved.

Further, according to the fuel cell system 10, at the beginning of the operation of the fuel cell 40, the consumption of methanol in the burner 24 can be reduced through the combustion of the hydrogen-rich gas, and the operating state of the fuel cell 40 becomes steady. In the state, the consumption of methanol in the burner 24 can be reduced by burning the surplus hydrogen gas from the fuel cell 40.

Next, a fuel cell system 10 of another embodiment (second embodiment) will be described. In the fuel cell system 10 of the second embodiment, instead of the processing of steps S160 and 170 in the above-mentioned operation control routine, FIG.
The configuration is different in that the processing shown in FIG. That is,
In the fuel cell system 10 of the second embodiment, following the valve switching in step S150, the impedance meter 66 is used to determine whether or not the load on the fuel cell 40 is reduced and its extent.
Judgment from the transition of the sensor output of (step S36
0). When it is determined in step S360 that the load is not reduced or the degree of reduction is small, the progress of the reforming reaction in the reformer 22 of the reformer 20 does not change and CO is generated. Assuming that the amount does not change, this routine is temporarily terminated without any processing.

However, if the load is significantly reduced in step S360, the progress of the reforming reaction in the reformer 22 of the reformer 20 changes according to this load fluctuation, and CO in hydrogen-rich gas is produced. The quantity may increase. Therefore, in this case, the flow path switching valve 60 is drive-controlled to change the flow rate ratio between the hydrogen gas supply conduit 44 and the hydrogen gas recirculation conduit 62 (step S370), and this routine is ended.
When the flow rate ratio is changed, the flow rate up to that point in the hydrogen gas supply pipeline 44 is reduced and the flow rate in the hydrogen gas recirculation pipeline 62 is increased from zero. As a result, the amount of hydrogen-rich gas supplied to the fuel cell 40 decreases, so the total amount of CO that reaches the anode 40b of the fuel cell 40 decreases. The flow rate ratio of the two flow paths by the flow path switching valve 60 is determined by the degree of decrease of the load. If the degree of decrease is large, the flow rate of the hydrogen gas recirculation line 62 is increased and the flow rate of the hydrogen gas supply line 44 is increased. The flow rate is determined to be reduced.

Therefore, according to the fuel cell system 10 of the second embodiment as well, when the load of the fuel cell 40 is suddenly reduced when the fuel cell 40 is in the steady operation state, the fuel cell 4
The total amount of CO reaching 0 is reduced to suppress CO poisoning of the catalyst in the anode 40b of the fuel cell 40.

The embodiments of the present invention have been described above.
The present invention is not limited to these examples, and it goes without saying that the present invention can be implemented in various modes without departing from the scope of the present invention.

For example, the CO concentration α when comparing the detected CO concentrations αt in steps S120 and 160 and the lower limit value (lower limit temperature) β0 and the upper limit value (upper limit temperature) βT when comparing the detection temperature βt in step S130 are set. Alternatively, the fuel cell 40 may be variably configured according to the temperature of the fuel cell 40 itself, its operating state, and the like.

Further, in step S110, the voltmeter 6
4. The operating state of the fuel cell 40 is determined based on the sensor output of the impedance meter 66, but the following configuration may be used. That is, the fuel cell 40 is in the operating state at the time of starting for a predetermined time after the start switch is turned on, and if the predetermined time has elapsed, it is determined that the fuel cell 40 is in the normal operating state. You can also

Further, the fuel cell system 10 is not limited to one mounted on a vehicle, and may be a stationary fuel cell system, and a phosphoric acid type fuel cell other than the polymer electrolyte fuel cell may be used. Needless to say, the system may have one.

Although the burner 24 is used as the supply destination of the hydrogen-rich gas at the time of starting the fuel cell 40, it may also be used as a heat source for humidifying the gas as a gas humidifier for humidifying the supply gas to the fuel cell 40. it can.

[0055]

As described above, in the fuel cell system according to the first aspect, at the beginning of the operation when the operation state of the fuel cell is not in the steady operation state, the fuel cell system is not suitable for the steady operation state of the fuel cell. Do not supply hydrogen rich gas to the fuel cell. As a result, according to the fuel cell system of the first aspect, CO poisoning of the catalyst in the fuel cell does not occur when the operating state is not in the steady operating state as at the beginning of the operation of the fuel cell.

In the fuel cell system according to the second aspect, when the carbon monoxide concentration exceeds a predetermined concentration while the operating state of the fuel cell is in the steady operating state, the amount of hydrogen rich gas flowing into the gas branch introducing means is increased. The amount of hydrogen-rich gas supplied to the fuel cell itself is decreased by increasing Therefore, according to the fuel cell system of the second aspect, the total amount of carbon monoxide reaching the fuel cell is reduced and CO poisoning of the catalyst is suppressed.

In the fuel cell system according to the third aspect, when the operating load of the fuel cell fluctuates, the supply amount of the hydrogen rich gas to the fuel cell itself is increased by increasing the inflow amount of the hydrogen rich gas to the gas branch introducing means. To reduce.
Therefore, according to the fuel cell system of the third aspect, the total amount of carbon monoxide reaching the fuel cell is reduced, and the CO of the catalyst is reduced.
Control poisoning.

In the fuel cell system according to the fourth aspect, the hydrogen-rich gas that is no longer supplied to the fuel cell is supplied or introduced into the burner of the reformer to burn hydrogen and carbon monoxide in the hydrogen-rich gas. Therefore, according to the fuel cell system of the fourth aspect, the reforming reaction in the reforming device can be stabilized in an early stage by preheating the hydrocarbon compound and promoting the reforming reaction.

In the fuel cell system according to the fifth aspect, when the carbon monoxide concentration in the hydrogen-rich gas and the gas temperature of the hydrogen-rich gas are different from those during the steady operation of the fuel cell, the operating state of the fuel cell becomes the steady operating state. At the beginning of no operation, such hydrogen-rich gas is not supplied to the fuel cell. As a result, according to the fuel cell system of the fifth aspect, CO poisoning of the catalyst in the fuel cell does not occur when the operating state is not in the steady operating state as at the beginning of the operation of the fuel cell.

[Brief description of drawings]

FIG. 1 is a block diagram illustrating a schematic configuration of a fuel cell system 10 according to an embodiment.

FIG. 2 is a flowchart showing an operation control routine performed by the fuel cell system 10.

FIG. 3 is a flowchart showing an operation end control routine executed by the fuel cell system 10.

FIG. 4 is a flowchart showing a process of a main part of an operation control routine performed by the fuel cell system 10 of the second embodiment.

[Explanation of symbols]

 10 ... Fuel cell system 15 ... Reforming material supply pipe 20 ... Reforming device 22 ... Reformer 24 ... Burner 26 ... Excess gas recirculation pipe 28 ... Combustion methanol supply pipe 40 ... Fuel cell 40a ... Solid polymer Electrolyte membrane 40b ... Anode 40c ... Cathode 42 ... Oxygen gas supply pipeline 44 ... Hydrogen gas supply pipeline 48 ... CO shifter 50 ... Temperature sensor 52 ... CO sensor 56 ... Air introduction pipe 58 ... Flow rate adjusting valve 60 ... Flow path switching Valve 62 ... Hydrogen gas recirculation pipe 64 ... Voltmeter 66 ... Impedance meter 70 ... Control device

Claims (5)

[Claims] 1. A fuel cell system having a reformer for producing a hydrogen-rich gas by subjecting the supplied hydrocarbon compound to a reforming reaction, and a fuel cell for receiving the produced hydrogen-rich gas as a fuel gas. The operating state detecting means for detecting the operating state of the fuel cell, a gas property detecting means for detecting the property of the hydrogen-rich gas supplied to the fuel cell, and the detected operating state is not in a steady operating state. When the detected gas property is different from the gas property at the time of steady operation of the fuel cell, switching means for switching the supply destination of the generated hydrogen-rich gas to other than the fuel cell,
A fuel cell system comprising: 2. A fuel cell system having a reformer for producing a hydrogen-rich gas by subjecting the supplied hydrocarbon compound to a reforming reaction, and a fuel cell for receiving the produced hydrogen-rich gas as a fuel gas. The operating state detecting means for detecting the operating state of the fuel cell, the concentration detecting means for detecting the carbon monoxide concentration in the hydrogen-rich gas supplied to the fuel cell, and branching in front of the fuel cell And a flow ratio of the flow rate of the hydrogen rich gas flowing into the gas branch introducing means and the flow rate of the hydrogen rich gas supplied to the fuel cell, and the gas branch introducing means for introducing the generated hydrogen rich gas to other than the fuel cell. Flow rate adjusting means for adjusting the gas, and when the detected operating state is a steady operating state and the detected carbon monoxide concentration exceeds a predetermined concentration, the gas And flow control means for the flow rate of the hydrogen rich gas flowing into Toki introducing means controls the flow rate adjusting means on the side of increasing,
A fuel cell system comprising: 3. A fuel cell system having a reformer for producing a hydrogen-rich gas by subjecting the supplied hydrocarbon compound to a reforming reaction, and a fuel cell for receiving the produced hydrogen-rich gas as a fuel gas. Wherein the operating load detecting means for detecting an operating load of the fuel cell, and a gas branch introducing means for branching in front of the fuel cell and introducing the generated hydrogen-rich gas to other than the fuel cell, Flow rate adjusting means for adjusting the flow rate ratio of the flow rate of the hydrogen rich gas flowing into the gas branch introducing means and the flow rate of the hydrogen rich gas supplied to the fuel cell; and when the detected operating load changes, the gas branch A fuel cell system, comprising: a flow rate control means for controlling the flow rate adjusting means on the side where the flow rate of the hydrogen-rich gas flowing into the introducing means increases. . 4. The fuel cell system according to claim 1, wherein a hydrogen rich gas supply destination other than the fuel cell switched by the switching means and a fuel introduced by the gas branch introducing means. A fuel cell system in which a hydrogen-rich gas other than a battery is introduced into a burner for a reforming reaction in the reformer. 5. The fuel cell system according to claim 1, wherein the gas property detection means detects the concentration of carbon monoxide in the hydrogen-rich gas supplied to the fuel cell and the hydrogen-rich gas. A fuel cell system having at least one of temperature detecting means for detecting a gas temperature.