JP2005285692A - Fuel cell system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress deterioration of an anode side caused by insufficiency of hydrogen, while improving fuel use rate and system efficiency. <P>SOLUTION: This fuel cell system is provided with a fuel cell 10, constituted of one or more unit cells 10a and receiving supply of anode gas and cathode gas to generate electricity, a voltage sensor 50 for detecting voltage in one or a plurality of unit cells 10a connected in series of the fuel cell 10, and a CO<SB>2</SB>concentration detector 40 for detecting CO<SB>2</SB>concentration in anode exhaust gas exhausted from the fuel cell 10. It is also provided with a deterioration determining means 60 for determining the deterioration of anode of the fuel cell 10 according to the output of the voltage sensor 50 and output of the CO<SB>2</SB>concentration detector 40. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a fuel cell system. In particular, the present invention relates to a configuration for determining deterioration in an anode of a fuel cell.

  In a fuel cell, the output current and the amount of reaction gas consumed are proportional to each other, and therefore it is necessary to supply a reaction gas corresponding to the output current. If the amount of hydrogen supplied to the fuel cell is insufficient with respect to the amount of hydrogen required by the fuel cell, so-called hydrogen deficiency results in significant deterioration and power generation in the fuel cell becomes impossible. The problem of hydrogen deficiency has been addressed by supplying more hydrogen to the fuel cell. In other words, an amount of hydrogen exceeding the amount commensurate with the output current to the fuel cell was supplied to the fuel cell so as not to be deficient in hydrogen.

However, when the hydrogen supply amount is controlled in this way, the fuel utilization rate in the fuel cell becomes low, and the power generation efficiency cannot be improved. Therefore, as a conventional system, whether or not the hydrogen supply amount in the first unit cell is insufficient is determined by supplying the anode gas flowing through the first unit cell and insulating the first unit cell. Judgment is made based on the voltage of the two cells. The hydrogen concentration of the gas introduced from one first cell corresponding to the second cell to the hydrogen electrode side can be estimated from the voltage of the second cell. Therefore, the determination means estimates the hydrogen concentration from the voltage of the second cell, and determines that the amount of hydrogen supplied to the first cell is insufficient when the estimated value of the hydrogen concentration falls below a predetermined reference value, for example. (For example, refer to Patent Document 1).
JP 2003-157886 A

  However, even if the amount of anode gas supplied from the outside is sufficient, there is a possibility that the cathode gas is not sufficiently supplied to the reaction field due to the presence of condensed water or the like inside the fuel cell, and the voltage may decrease. Therefore, it is difficult to determine the deterioration of the anode using only the voltage value.

  In view of the above problems, an object of the present invention is to provide a fuel cell system that can determine deterioration of an anode while improving fuel utilization and system efficiency.

The present invention comprises one or more unit cells, a fuel cell that generates power by receiving supply of anode gas and cathode gas, and voltages of one or a plurality of unit cells connected in series of the fuel cell. Voltage detecting means for detecting. Further, CO ₂ concentration detection means for detecting the carbon dioxide concentration in the anode exhaust gas discharged from the fuel cell, the output of the voltage detection means and the output of the CO ₂ concentration detection means in accordance with the output of the anode of the fuel cell Deterioration determining means for determining deterioration.

  By measuring both the voltage of one or a plurality of unit cells connected in series and the carbon dioxide concentration of the anode exhaust gas, it is possible to accurately determine whether the abnormality is on the anode side or the cathode side. Therefore, an increase in the supply amount of the anode gas can be suppressed, and the catalyst deterioration reaction at the anode can be suppressed while improving the fuel utilization rate and the system efficiency.

  This embodiment will be described. The configuration of the fuel cell system is shown in FIG.

A fuel cell 10 that generates power using an anode gas and a cathode gas is provided. The fuel cell 10 is configured by a stack in which a plurality of unit cells (not shown) are stacked. An anode side inlet pipe 21 is provided on the anode upstream side of the fuel cell 10. Further, an anode gas supply amount adjusting means 23 for adjusting the flow rate of the supplied anode gas, an anode gas humidifying means 24 for humidifying the anode gas, and a humidification amount control means 25 for controlling the humidification amount are provided. On the anode downstream side of the fuel cell 10, an anode side outlet pipe 22 that is a flow path of anode exhaust gas is provided. The anode-side outlet pipe 22, provided with a CO ₂ concentration detector 40 for detecting a CO ₂ concentration in the anode in the exhaust gas discharged.

  A cathode side inlet pipe 31 is provided on the cathode upstream side of the fuel cell 10. Further, a cathode gas supply amount adjusting means 33 for adjusting the flow rate of the supplied cathode gas, a cathode gas humidifying means 34 for humidifying the anode gas, and a humidification amount control means 35 for controlling the humidification amount are provided. On the downstream side of the cathode of the fuel cell 10, a cathode side outlet pipe 32, which is a flow path for cathode exhaust gas, is provided.

  In addition, as the anode gas humidifying means 24 and the cathode humidifying means 34, for example, a humidifier, a water injector or the like is used. The respective means for humidifying the anode and the cathode are not limited to this, and the fuel cell 10 may be internally humidified. The anode gas supply amount adjusting means 23 and the cathode gas supply amount adjusting means 33 include, for example, a flow meter and a valve whose opening / closing is controlled according to the output thereof.

  Furthermore, a voltage sensor 50 that detects the voltage of the fuel cell 10 is provided. Here, the voltage sensor 50 is configured as shown in FIG. That is, only the stack end where it is difficult to uniformly supply the reaction gas is monitored in detail. At the stack end, the cell voltage is detected for each unit cell 10a, and the voltages of a plurality of unit cells 10a connected in series are detected near the center of the stack. Thereby, the monitor location of a voltage can be reduced. The configuration of the voltage sensor 50 is not limited to this, and the cell voltage may be detected for all the unit cells 10a. Alternatively, the cell voltage may be detected for each unit cell 10a so as to be dense at the end portion and for every plurality of unit cells 10a so as to be coarse in the center portion. Alternatively, the voltages of a plurality of unit cells 10a connected in series may be detected. Further, a current control means 52 for controlling a current value taken out from the fuel cell 10 to the load 51 is provided.

Furthermore, an arithmetic processing system 60 for controlling such a fuel cell system is provided. In the arithmetic processing system 60, the deterioration of the anode of the fuel cell 10 is determined based on the outputs of the CO ₂ concentration detector 40 and the voltage sensor 50.

Here, when a carbon corrosion reaction (C + 2H ₂ O → CO ₂ + 4H ⁺ + 4e ⁻ ) occurs due to hydrogen deficiency in the anode, the concentration of CO ₂ in the anode exhaust gas increases. In addition, as the carbon corrosion reaction becomes more serious, the potential difference between the anode and the cathode becomes smaller, and further the polarity is reversed.

Therefore, when the voltage decreases and the CO ₂ concentration increases, it is determined that a serious carbon corrosion reaction has occurred at the anode. At this time, the output current is suppressed and the anode gas supply amount introduced into the fuel cell 10 is increased. Further, the humidification on the anode side is suppressed. Here, the humidification amount of the anode gas is reduced to reduce the water clogging, and the hydrogen deficiency due to the diffusion decrease of the anode gas is eliminated. When the voltage is normal and the CO ₂ concentration is increased, it is determined that a small amount of carbon corrosion reaction has occurred at the anode. At this time, the supply amount of the anode gas is increased and the humidification on the anode side is suppressed. When the voltage is reduced and the CO ₂ concentration is normal, it is determined that no carbon corrosion reaction has occurred at the anode. At this time, since the cause of the voltage drop is considered to be the cathode side, the water clogging is eliminated by increasing the supply amount of the cathode gas. Also, the output current is suppressed.

  Next, the flow of the anode deterioration determination method as described above will be described with reference to the flowchart of FIG. Here, this flow is executed every predetermined time (for example, 10 msec).

  In step S1, it is determined whether or not the voltage value is abnormal. It is determined whether or not the output of the voltage sensor 50 is smaller than a predetermined range. The predetermined range of the voltage value is a voltage range in which it can be determined that the fuel cell 10 is operating normally, and is set in advance according to the output. Here, since voltages at a plurality of locations in the fuel cell 10 are detected, when it is determined that one or more detected voltage values are not within the predetermined range, it is determined that the voltage value is abnormal. If the voltage value is smaller than the predetermined range, it is determined that there is an abnormality in the fuel cell 10 and the process proceeds to step S2.

In step S2, it is determined whether or not there is an abnormality in the CO ₂ concentration in the anode exhaust gas. It is determined whether or not the output of the CO ₂ concentration detector 40 exceeds a predetermined range. Predetermined range of CO ₂ concentration, CO in the anode gas introduced into the fuel cell 10, is set in advance in accordance with the CO ₂ concentration. If the CO ₂ concentration is higher than the predetermined range, it is determined that an abnormality has occurred on the anode side. That is, it is determined that hydrogen deficiency has occurred and serious carbon corrosion has occurred.

  If it is determined that a serious carbon corrosion reaction has occurred on the anode side, the process proceeds to step S3, where the flow rate of the anode gas is increased to suppress hydrogen deficiency. Further, by suppressing the humidification of the anode gas, the clogging on the anode side is eliminated, and the hydrogen deficiency due to the clogging is eliminated. Further, the output current is suppressed to prevent a carbon corrosion reaction from occurring.

Next, in step S4, it is determined whether or not the CO ₂ concentration of the anode exhaust gas is within a predetermined normal value range. If the CO ₂ concentration does not recover to the predetermined concentration range, this flow is terminated and the operation stop control is started. When the CO ₂ concentration in the anode exhaust gas recovers within the predetermined concentration range, the process proceeds to step S5. In step S5, it is determined whether or not the voltage value has been recovered. If the voltage value has been recovered, this flow is terminated and normal operation control is continued.

On the other hand, if the voltage value does not recover after the CO ₂ concentration becomes normal, it is determined that there is an abnormality on the cathode side, and the process proceeds to step S6. In step S6, the cathode gas is increased. Thereby, when the water clogging has arisen on the cathode side, this is eliminated. Further, by reducing the humidification amount in the cathode gas humidification means 34 by the humidification control means 35, the humidification amount on the cathode side is suppressed, and water clogging is suppressed. Note that the cathode gas increase and the humidification suppression operation in step S6 may be either one.

  In step S7, the voltage value is determined again. When the voltage value is within the predetermined range, this flow ends. On the other hand, when the voltage value does not recover, this flow is finished and the operation shifts to the operation stop control of the fuel cell 10. Alternatively, processing such as setting an output limit or outputting a warning signal may be performed.

On the other hand, in step S1, if the voltage value is within the predetermined range and no abnormality is recognized, the process proceeds to step S8, and it is determined whether or not an abnormality has occurred in the CO ₂ concentration. If there is an abnormality only in the CO ₂ concentration, it is determined that a slight carbon corrosion reaction has occurred. Therefore, in step S9, by increasing the anode gas flow rate, hydrogen deficiency is suppressed, and humidification of the anode gas is suppressed to eliminate clogging on the anode side.

Next, in step S10, it is determined whether or not the CO ₂ concentration has returned to a normal range. If it has not returned, the present flow is terminated and the operation is stopped. When the CO ₂ concentration returns to the normal range, this flow is terminated and normal operation is continued.

On the other hand, if it is determined in steps S1 and S2 that the voltage value is abnormal but the CO ₂ concentration is not abnormal, it is determined that there is no abnormality on the anode side but an abnormality has occurred on the cathode side. To do. Accordingly, in step S11, the cathode gas supply amount is increased to eliminate the clogging of the cathode and suppress the output current.

  Next, in step S7, it is determined whether or not the voltage value is within a predetermined normal value. When it recovers within the normal value, this flow is terminated and normal operation is continued. On the other hand, when the voltage value does not recover, there is a possibility that the output is reduced due to damage to the fuel cell 10 itself. In such a case, this flow is finished and the operation shifts to the operation stop control of the fuel cell 10. Alternatively, processing such as setting an output limit or outputting a warning signal may be performed.

In this way, by detecting both the voltage value and the CO ₂ concentration, the degree of the carbon corrosion reaction of the anode that has occurred is determined, and processing corresponding to that is performed.

If it takes a long time for the recovery after the CO ₂ concentration and voltage recovery process is performed, it is determined whether or not the recovery has occurred after waiting for a predetermined time until the recovery (S4, S5, S7, S10). It is preferred to do so. For example, if it takes time until the carbon corrosion reaction is actually reduced after performing the hydrogen deficiency recovery process in step S3, the process waits for a predetermined time until the determination in step S4 is made. Alternatively, a predetermined time limit may be set in advance, and this flow may be controlled to end if the CO ₂ concentration and voltage value monitored during this time are not reduced to a predetermined range. At this time, during the predetermined time limit, the increase amount of the supply amount of the anode gas or the cathode gas may be gradually increased according to the elapsed time.

  Next, the effect of this embodiment will be described.

The voltage of the fuel cell 10 which is composed of one or more unit cells 10a and generates power by receiving supply of anode gas and cathode gas, and the voltage of one or a plurality of unit cells 10a connected in series. It includes a voltage sensor 50 for detecting a CO ₂ concentration detector 40 for detecting a CO ₂ concentration of the anodes in the exhaust gas discharged from the fuel cell 10, a. In addition, deterioration determination means (S1, S2, S8) for determining deterioration of the anode of the fuel cell 10 according to the output of the voltage sensor 50 and the output of the CO ₂ concentration detector 40 is provided. As a result, the degree of carbon corrosion reaction occurring at the anode of the fuel cell 10 can be determined. As a result, treatment according to the degree of the carbon corrosion reaction can be performed, and an increase in the supply amount of the anode gas can be suppressed, and the carbon corrosion reaction at the anode can be suppressed while improving the fuel utilization rate and the system efficiency.

The deterioration determination means is based on a combination of a determination as to whether or not the output of the voltage sensor 50 has fallen below a predetermined range and a determination as to whether or not the output of the CO ₂ concentration detector 40 exceeds a predetermined range. Determine deterioration. As a result, an appropriate recovery process can be performed with respect to the abnormality of the fuel cell 10, the deterioration of the fuel cell 10 can be suppressed, and the efficiency can be maintained. When the output of the voltage sensor 50 is smaller than the predetermined range, it is determined that an abnormality has occurred in the fuel cell 10. When the output of the CO ₂ concentration detector 40 exceeds the predetermined range, it is determined that the anode of the fuel cell 10 is in a hydrogen deficient state and a carbon corrosion reaction has occurred.

Gas supply amount adjusting means for adjusting the supply amount of at least one of the anode gas and the cathode gas is provided. Gas supply amount adjustment based on the combination of the determination of whether or not the output of the voltage sensor 50 falls below a predetermined range and the determination of whether or not the output of the CO ₂ concentration detector 40 exceeds the predetermined range The gas supply amount is changed by the means. As the gas supply amount adjusting means, an anode gas supply amount adjusting means 23 for adjusting the supply amount of the anode gas is provided, and when the output of the CO ₂ concentration detector 40 is higher than a predetermined range, the anode gas supply amount is increased. When the output of the voltage sensor 50 is smaller than the predetermined range and the output of the CO ₂ concentration detector 40 is higher than the predetermined range, it can be determined that a carbon corrosion reaction has occurred on the anode side, and the anode gas supply amount is By increasing, hydrogen deficiency can be suppressed. Further, as the gas supply amount adjusting means, a cathode gas supply amount adjusting means 33 for adjusting the supply amount of the cathode gas is provided, the output of the voltage sensor 50 is smaller than the predetermined range, and the output of the CO ₂ concentration detector 40 is within the predetermined range. In this case, the cathode gas supply amount is increased. When the output of the voltage sensor 50 is smaller than the predetermined range and the output of the CO ₂ concentration detector 40 is within the predetermined range, it can be determined that the cause of the abnormality of the fuel cell 10 is not the anode side but the cathode side. By increasing the cathode gas supply amount, water clogging on the cathode side can be eliminated and the voltage drop can be recovered.

Anode-side humidified state adjusting means for adjusting the humidified state on the anode side is provided. Here, anode gas humidifying means 24 for humidifying the anode gas and anode gas humidification amount control means 25 for controlling the humidification amount in the anode gas humidification means 24 are provided. Humidification on the anode side is based on the combination of the determination of whether the output of the voltage sensor 50 is lower than the predetermined range and the determination of whether the output of the CO ₂ concentration detector 40 exceeds the predetermined range. Change state. When the output of the CO ₂ concentration detector 40 exceeds a predetermined range, humidification on the anode side is suppressed. Thus, when it is determined that hydrogen deficiency has occurred on the anode side and a carbon corrosion reaction has occurred, humidification on the anode side is suppressed to eliminate water clogging that may cause hydrogen deficiency.

Current suppression means 52 that suppresses the output current is provided, and the output current is suppressed when the output of the voltage sensor 50 is smaller than the predetermined range and the output of the CO ₂ concentration detector 40 exceeds the predetermined range. Thus, by suppressing the output, the power generation reaction can be suppressed and the carbon corrosion reaction can be reduced. Further, current suppression means 52 that suppresses the output current is provided, and the output current is suppressed when the output of the voltage sensor 50 is smaller than the predetermined range and the output of the CO ₂ concentration detector 40 is within the predetermined range. This can prevent the fuel cell 10 from deteriorating due to excessive output.

An anode gas supply amount adjusting means 23 for adjusting the supply amount of the anode gas and a cathode gas supply amount adjusting means 33 for adjusting the supply amount of the cathode gas are provided. Further, a cathode side humidification state adjusting means for adjusting the humidification state on the cathode side is provided. Here, as the cathode side humidification state adjusting means, a cathode gas humidifying means 34 for humidifying the cathode gas and a cathode gas humidifying amount control means 35 for controlling the humidification amount in the cathode gas humidifying means 34 are provided. Furthermore, the current suppression means 35 which suppresses output current is provided. When the output of the voltage sensor 50 is smaller than the predetermined range and the output of the CO ₂ concentration detector 40 exceeds the predetermined range, the output current is suppressed and the supply amount of the anode gas is increased, and the CO ₂ concentration detector When the output of 40 falls within the predetermined range, it is determined again whether the output of the voltage sensor 50 is within the predetermined range. If the output of the voltage sensor 50 remains smaller than the predetermined range, the cathode gas supply amount At least one of increase or suppression of humidification on the cathode side is performed. As described above, even when abnormality occurs on both the anode side and the cathode side, both of them can be eliminated.

  The fuel cell 10 is composed of a stack formed by stacking a plurality of unit cells 10a, and the voltage sensor 50 detects the cell voltage roughly with respect to the number of cells toward the center in the stacking direction of the unit cells 10a. At the end, the cell voltage is densely detected with respect to the number of cells. Alternatively, the fuel cell 10 is configured by a stack in which a plurality of unit cells 10a are stacked, and the voltage sensor 50 is a voltage for each of the plurality of unit cells 10a connected in series in the vicinity of the center in the unit cell 10a stacking direction. And the voltage for each unit cell 10a is detected at the end in the stacking direction. As a result, it is possible to more accurately determine the end portion where the gas supply is likely to vary, and it is possible to suppress the entire monitor location, thereby making it possible to reduce the size and cost of the system.

In the present embodiment, a stack formed by stacking a plurality of unit cells 10a is used as a fuel cell. However, the present invention is not limited to this, and the present invention can also be applied to a case where a unit cell 10a is used. Further, the voltage sensor 50 is provided at each end for each unit cell 10a. However, the present invention is not limited to this. The voltage sensor 50 may be configured to detect a plurality of voltages. Further, when the anode gas is generated by reforming a hydrocarbon compound or the like and the supplied anode gas contains CO ₂ , voltage detection means is provided on the inlet side of the fuel cell 10, and the fuel cell 10 The increase in the carbon corrosion reaction may be determined by detecting the amount of increase in the CO ₂ concentration inside.

  Thus, the present invention is not limited to the best mode for carrying out the invention, and various modifications can be made within the scope of the technical idea described in the claims. Not too long.

  The present invention can be applied to a fuel cell system. In particular, the present invention can be applied to fuel cell deterioration determination.

It is a figure which shows the structure of the fuel cell system used for this embodiment. It is a figure which shows the state which installed the voltage sensor used for this embodiment. It is a flowchart for suppressing the carbon corrosion reaction of this embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Fuel cell 23 Anode gas supply amount adjustment means 24 Anode gas humidification means (Anode side humidification state adjustment means)
25 Humidification amount control means (Anode side humidification state adjustment means)
33 Cathode gas supply amount adjustment means 34 Cathode gas humidification means (cathode side humidification state adjustment means)
35 Humidification amount control means (Cathode side humidification state adjustment means)
40 CO ₂ concentration detector (CO ₂ concentration detection means)
50 Voltage sensor (voltage detection means)
52 Current control means Degradation determining means S1, S2, S8

Claims (12)

A fuel cell composed of one or more unit cells and generating power by receiving supply of anode gas and cathode gas;
Voltage detecting means for detecting the voltage of one or a plurality of unit cells connected in series of the fuel cell;
CO ₂ concentration detection means for detecting the carbon dioxide concentration in the anode exhaust gas discharged from the fuel cell;
A fuel cell system comprising: a deterioration determination unit that determines deterioration of the anode of the fuel cell according to the output of the voltage detection unit and the output of the CO ₂ concentration detection unit. The deterioration determination means is a combination of a determination as to whether or not the output of the voltage detection means is lower than a predetermined range and a determination as to whether or not the output of the CO ₂ concentration detection means exceeds a predetermined range. The fuel cell system according to claim 1, wherein deterioration is determined based on the determination. A gas supply amount adjusting means for adjusting the supply amount of at least one of the anode gas and the cathode gas;
3. The fuel cell system according to claim 1, wherein the gas supply amount is changed by the gas supply amount adjustment unit based on an output of the deterioration determination unit. As the gas supply amount adjusting means, an anode gas supply amount adjusting means for adjusting the supply amount of the anode gas is provided,
4. The fuel cell system according to claim 3, wherein the anode gas supply amount is increased when the output of the CO ₂ concentration detection means is higher than a predetermined range. As the gas supply amount adjusting means, a cathode gas supply amount adjusting means for adjusting the supply amount of the cathode gas is provided,
The fuel cell system according to claim 3 or 4, wherein when the output of the voltage detection means is smaller than a predetermined range and the output of the CO ₂ concentration detection means is within a predetermined range, the cathode gas supply amount is increased. An anode side humidification state adjusting means for adjusting the humidification state on the anode side is provided,
The fuel cell system according to claim 1 or 2, wherein the humidification state on the anode side is changed based on the output of the deterioration determination means. The fuel cell system according to claim 6, wherein humidification on the anode side is suppressed when the output of the CO ₂ concentration detecting means exceeds a predetermined range. Provided with current suppressing means for suppressing the output current,
The fuel cell system according to claim 1 or 2, wherein the output current is suppressed when the output of the voltage detection means is smaller than a predetermined range and the output of the CO ₂ concentration detection means exceeds a predetermined range. Provided with current suppressing means for suppressing the output current,
The fuel cell system according to claim 1 or 2, wherein the output current is suppressed when the output of the voltage detection means is smaller than a predetermined range and the output of the CO ₂ concentration detection means is within the predetermined range. An anode gas supply amount adjusting means for adjusting the supply amount of the anode gas;
Cathode gas supply amount adjusting means for adjusting the supply amount of the cathode gas;
Cathode side humidification state adjusting means for adjusting the humidification state on the cathode side;
Current suppression means for suppressing the output current,
When the output of the voltage detection means is smaller than a predetermined range and the output of the CO ₂ concentration detection means exceeds a predetermined range,
Suppressing the output current and increasing the supply amount of anode gas, when the output of the CO ₂ concentration detection means falls within a predetermined range, it is determined again whether the output of the voltage detection means is within the predetermined range, 3. The fuel cell system according to claim 1, wherein when the output of the voltage detection means remains smaller than a predetermined range, at least one of increasing the cathode gas supply amount or suppressing humidification on the cathode side is performed. The fuel cell is composed of a stack formed by stacking a plurality of unit cells,
The voltage detection means detects a cell voltage roughly with respect to the number of cells toward the center in the unit cell stacking direction, and detects a cell voltage densely with respect to the number of cells at the end in the stacking direction. 3. The fuel cell system according to 2. The fuel cell is constituted by a stack formed by laminating a plurality of unit cells,
The voltage detection means detects a voltage of a plurality of unit cells connected in series in the vicinity of a central portion in the unit cell stacking direction, and detects a voltage of one unit cell at an end in the stacking direction. The fuel cell system described in 1.

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