JPH1167255A - Defective cell detecting method of phosphoric acid fuel cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To discriminate a cell which may cause cross leakage in the earlier stage than a normal cell in the normal state operation because of less amount of phosphoric acid in a phosphoric acid electrolyte layer compared with the normal cell although cross leakage does not occur in the normal operation state. SOLUTION: This fuel cell has a cell which has a fuel electrode on one surface of a phosphoric acid electrolyte layer and oxygen electrode on the other surface, and has a fuel gas flow path for a fuel gas on the fuel electrode side and an oxygen-containing gas flow path for an oxygen-containing gas on the air electrode side. The variation of the open circuit voltage of the cell produced by varying the flow state of the fuel gas flowing through the fuel gas flow path is found as discrimination information in the state that the flow rate of the oxygen-containing gas flowing through the oxygen-containing gas flow path is decreased to the reference value Fh or less for discriminating a defective cell smaller than the value Fs in the normal operation state, and the defective cell is discriminated, based on the discrimination information obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a phosphoric acid electrolyte layer comprising a fuel electrode on one surface and an oxygen electrode on the other surface,
In addition, a fuel gas flow path through which a fuel gas containing hydrogen gas flows is provided on the fuel electrode side, and a cell having an oxygen-containing gas flow path through which an oxygen-containing gas flows is provided on the oxygen electrode side. The present invention relates to a method for detecting a defective cell in a phosphoric acid fuel cell, which determines the quality of the cell in the phosphoric acid fuel cell.

[0002]

2. Description of the Related Art Conventionally, in a state where a cell is operated in a normal operation state, that is, a fuel gas flows through a fuel gas flow path at a flow rate in a normal operation state, and a fuel gas flows in an oxygen-containing gas flow path in a normal operation state. With the flow of the oxygen-containing gas at a flow rate and the connection of a load device that consumes the output power to the cell, the output voltage of the cell is measured, and the quality of the cell is determined based on the measurement information.

[0003]

The causes of cell failure include deterioration of the electrode catalyst of the oxygen electrode and the fuel electrode, and cross leak (fuel gas) caused by a decrease in phosphoric acid held in the phosphoric acid electrolyte layer. May occur from the fuel electrode side to the oxygen electrode side through the phosphoric acid electrolyte layer, or conversely, a phenomenon in which the oxygen-containing gas leaks from the oxygen electrode side to the fuel electrode side through the phosphoric acid electrolyte layer). In a state where the cell is operated in the normal operation state, the cell in which the electrode catalyst is deteriorated is
Output voltage drops. Further, in a state where the cell is operated in the normal operation state, the output voltage of the cell in which the cross leak has occurred decreases. Therefore, according to the conventional detection method, a defective cell can be determined based on a decrease in the output voltage of the cell due to deterioration of the electrode catalyst or occurrence of cross leak.

The oxygen-containing gas flowing out of the oxygen-containing gas flow path and the fuel gas flowing out of the fuel gas flow path during operation have a small amount of phosphoric acid retained in the phosphoric acid electrolyte layer. Since it flows out in a contained state, the amount of phosphoric acid in the phosphoric acid electrolyte layer gradually decreases as the operation time elapses. On the other hand, the cross leak is more likely to occur as the amount of phosphoric acid in the phosphoric acid electrolyte layer is smaller. In the cell, in the state of operating in the normal operation state, cross leak does not occur, but the amount of phosphoric acid retained in the phosphate electrolyte layer is smaller than in the normal cell, and when the cell is operated in the normal operation state There is a cell in which a cross leak may occur earlier than a normal cell (hereinafter, sometimes referred to as a cross leak early occurrence cell). If it is possible to discriminate such a cell in which cross-leakage occurs early in the shipping inspection of the phosphoric acid type fuel cell, take measures such as replenishing the phosphoric acid electrolyte layer with phosphoric acid or replacing it with another cell. Thus, it is possible to prevent a problem that a cross leak occurs early during operation and the output voltage drops. In addition, in the periodic inspection of the phosphoric acid type fuel cell during operation, if the cell in which the cross leak occurs early can be determined, the above-described measures must be taken to reduce the output voltage during operation and stop the operation. Such troubles can be prevented. However, with the conventional inspection method, it was not possible to determine the cell where the cross leak occurred early.

The present invention has been made in view of such circumstances, and has as its object the purpose of preventing cross-leak from occurring in a normal operation state of a cell, but making the phosphoric acid electrolyte layer of the phosphoric acid electrolyte layer have a higher concentration than a normal cell. When the cell is operated in a normal operation state with a small amount of the cell, it is possible to determine a cell in which a cross leak may occur earlier than a normal cell.

[0006]

According to the first aspect of the present invention, the flow rate of the oxygen-containing gas flowing through the oxygen-containing gas flow path is equal to or less than a reference value for quality determination which is smaller than a value in a normal operation state. When the flow state of the fuel gas flowing through the fuel gas flow path is changed in this state, no cross leak occurs in a normal cell, but the amount of phosphoric acid in the phosphoric acid electrolyte layer is lower than in a normal cell. If you drive in normal operating conditions,
In the case of a cell in which a cross leak can occur earlier than a normal cell (a cross leak early occurrence cell), the fuel gas leaks from the fuel electrode side to the oxygen electrode side through the phosphoric acid electrolyte layer and cross leak occurs. The amount of fuel gas leaking from the fuel electrode side to the oxygen electrode side through the phosphoric acid electrolyte layer (hereinafter sometimes referred to as the fuel gas cross leak amount)
Changes according to the change in the flow state of the fuel gas. still,
The flow state of the fuel gas flowing through the fuel gas flow path includes the flow rate or the pressure of the fuel gas. When the cross leak occurs, the open circuit voltage (voltage in a no-load state where no load is connected to the cell) decreases, and the amount of the decrease increases as the cross leak amount increases in accordance with the cross leak amount. Therefore, when the flow state of the fuel gas flowing through the fuel gas flow path is changed while the flow rate of the oxygen-containing gas flowing through the oxygen-containing gas flow path is equal to or less than the reference value for quality determination, By determining the change in the open circuit voltage, the cell in which the cross leak occurs early can be determined. Also, the smaller the amount of phosphoric acid in the phosphoric acid electrolyte layer, the greater the amount of cross leak, and the greater the amount of decrease in open circuit voltage. Therefore, since the amount of phosphoric acid in the phosphoric acid electrolyte layer can be evaluated based on the amount of decrease in the open circuit voltage, for example, the phosphoric acid in the phosphoric acid electrolyte layer decreases so that phosphoric acid needs to be replenished. Can be determined.

That is, the inventors of the present invention set the flow rate of the oxygen-containing gas flowing through the oxygen-containing gas flow path in the normal operating state in a state in which the fuel gas flows through the fuel gas flow path in a predetermined flow state. If the value is less than a certain value (corresponding to the reference value for pass / fail determination) less than the value in the above, the cross leak does not occur in the normal cell, but in the cell in which the cross leak occurs early, the fuel gas is supplied from the fuel electrode side to the phosphoric acid electrolyte. It has been found that cross leaks occur significantly due to leakage to the oxygen electrode side through the layer. When a cross leak occurs in the cell, the open circuit voltage decreases. FIG. 5 shows such a behavior. In a state where the fuel gas flows through the fuel gas flow path in a predetermined flow state, the flow rate of the oxygen-containing gas flowing through the oxygen-containing gas flow path is usually reduced. Value F in operating state
When the flow rate of the oxygen-containing gas decreases in both the normal cell and the early-cross-leakage cell, the open-circuit voltage decreases when the value is less than or equal to the value Fh smaller than s. It can be seen that the amount of occurrence of the open circuit voltage is larger than that of the normal cell by the amount of occurrence.

In a state in which the fuel gas is caused to flow through the fuel gas flow path in a predetermined flow state and the flow rate of the oxygen-containing gas flowing through the oxygen-containing gas flow path is set to be equal to or less than the reference value for quality determination, FIG. As shown in (1), when the amount of phosphoric acid held in the phosphoric acid electrolyte layer becomes less than a predetermined amount (for example, about 50% of the initial amount), a cross leak occurs, and the amount of the cross leak decreases. The smaller the amount, the larger the amount, and the larger the cross leak amount, the larger the amount of decrease in the open circuit voltage.
In FIG. 6, the amount of phosphoric acid in the phosphoric acid electrolyte layer is shown as a ratio to the initial amount.

The present invention has been made on the basis of the above aspects. That is, when the flow rate of the oxygen-containing gas flowing through the oxygen-containing gas flow path is set to be smaller than the value Fs in the normal operation state, the flow rate Fh at which the cross leak is likely to occur remarkably in the early cell where the cross leak occurs is determined by the pass / fail determination. Set as the reference value. Then, the flow rate of the oxygen-containing gas flowing through the oxygen-containing gas flow path is set to be equal to or less than the quality determination reference value, a cross leak is generated in the cross leak early occurrence cell, the open circuit voltage is measured, and the open circuit voltage is measured. Is determined based on the decrease in the number of cells in which a cross leak occurs early. Incidentally, for example, the flow rate Fs in the normal operation state is 5c as the flow rate per unit area of the oxygen electrode.
In the case of c / mim · cm ² , the reference value Fh for quality judgment
Is set to about 1 cc / min · cm ² .

According to the second aspect of the present invention, in the state where the flow state of the fuel gas flowing through the fuel gas flow path is kept constant, the oxygen-containing gas flow path is supplied to the oxygen-containing gas flow path at a normal flow rate. When the gas is allowed to flow, no cross leak occurs in either the normal cell or the cross leak early generation cell, but the oxygen-containing gas is maintained in a state where the flow state of the fuel gas flowing through the fuel gas flow path is kept constant. When an oxygen-containing gas is passed through the flow path at a flow rate equal to or less than the pass / fail determination reference value, no cross leak occurs in a normal cell,
In the cell in which the cross-leakage occurs early, the fuel gas leaks to the oxygen electrode side through the phosphoric acid electrolyte layer, causing cross-leakage, and the open circuit voltage decreases. Therefore, in a state where the flow state of the fuel gas flowing through the fuel gas flow path is kept constant, the flow rate of the oxygen-containing gas flowing through the oxygen-containing gas flow path is set to the value in the normal operation state and the reference value for the pass / fail determination. By determining the change in the open circuit voltage in the cell when the following change is made, it is possible to determine the cell in which the cross leak occurs early. Also, the smaller the amount of phosphoric acid in the phosphoric acid electrolyte layer, the greater the amount of cross leak and the greater the amount of decrease in the open circuit voltage, so that the amount of phosphoric acid in the phosphoric acid electrolyte layer is determined based on the amount of decrease in the open circuit voltage. The quantity can be evaluated.

According to the third aspect of the present invention, the flow rate of the oxygen-containing gas flowing through the oxygen-containing gas flow path while maintaining the flow state of the fuel gas flowing through the fuel gas flow path constant. Is changed under the condition of being equal to or less than the pass / fail determination reference value, a cross leak does not occur in a normal cell, but in a cell in which a cross leak occurs early, the fuel gas flows from the fuel electrode side to the oxygen electrode through the phosphoric acid electrolyte layer. Side leaks and cross leaks occur, and the amount of cross leaks
The open circuit voltage changes in accordance with the change in the flow rate of the oxygen-containing gas, and decreases in accordance with the cross leak amount as the cross leak amount increases. Therefore, in a state where the flow state of the fuel gas flowing through the fuel gas flow path is kept constant, the flow rate of the oxygen-containing gas flowing through the oxygen-containing gas flow path is smaller than the value in the normal operation state. By determining the change in the open circuit voltage in the cell when the cell is changed under the condition that the value is equal to or less than the value, it is possible to determine the cell in which the cross leak occurs early. Also, the smaller the amount of phosphoric acid in the phosphoric acid electrolyte layer, the greater the amount of cross leak and the greater the amount of decrease in the open circuit voltage, so that the amount of phosphoric acid in the phosphoric acid electrolyte layer is determined based on the amount of decrease in the open circuit voltage. The quantity can be evaluated.

According to the fourth aspect of the present invention, the oxygen-containing gas is supplied to the oxygen-containing gas flow path in the normal operation state while the flow state of the fuel gas flowing through the fuel gas flow path is kept constant. When the flow of the oxygen-containing gas in the oxygen-containing gas flow path is stopped from the state in which the flow is performed at the flow rate, the cross leak does not occur in the normal cell, but the fuel gas is The gas leaks from the side through the phosphoric acid electrolyte layer to the oxygen electrode side to generate cross leak, and as time passes, the amount of fuel gas existing on the oxygen electrode side increases. Then, in the normal cell, the amount of the oxygen-containing gas present on the oxygen electrode side is reduced, and accordingly, the open circuit voltage is reduced. As the amount of gas decreases and the amount of fuel gas present on the oxygen electrode side increases with the cross leak,
The open circuit voltage decreases faster than the open circuit voltage decreases in the normal cell. Therefore, in a state where the flow state of the fuel gas flowing through the fuel gas flow path is kept constant,
The rate of change of the open circuit voltage in the cell when the flow of the oxygen-containing gas in the oxygen-containing gas flow path is stopped from the state in which the oxygen-containing gas flows at the flow rate in the normal operation state through the oxygen-containing gas flow path. By determining the value, the cell in which the early occurrence of the cross leak has occurred can be determined. Also, the smaller the amount of phosphoric acid in the phosphoric acid electrolyte layer, the greater the amount of cross leak, and the faster the rate of decrease of the open circuit voltage,
The amount of phosphoric acid in the phosphoric acid electrolyte layer can be evaluated.

According to the fifth aspect of the present invention, a state in which the flow rate of the oxygen-containing gas flowing through the oxygen-containing gas flow path is maintained at a constant value equal to or less than a quality determination reference value smaller than the value in the normal operation state. When the fuel gas flows through the fuel gas flow path at the flow rate in the normal operation state, no cross leak occurs in the normal cell, but in the early cell where the cross leak occurs, the fuel gas flows from the fuel electrode side to the phosphoric acid. Since the cross leak has occurred due to leakage to the oxygen electrode side through the electrolyte layer, when the flow of the fuel gas in the fuel gas flow path is stopped from that state, the open circuit voltage in the normal cell in the early stage of the cross leak occurs. The open circuit voltage drops at a rate faster than the drop rate. Therefore, in a state where the flow rate of the oxygen-containing gas flowing through the oxygen-containing gas flow path is maintained at a constant value equal to or less than the quality determination reference value smaller than the value in the normal operation state, the fuel gas is supplied to the fuel gas flow path in the normal operation state. From the state of flow at the flow rate in the above, when the flow of the fuel gas in the fuel gas flow path is stopped, the rate of change of the open circuit voltage in the cell is determined to determine the cell in which the early occurrence of cross leak has occurred. Can be.

According to the characteristic structure of the sixth aspect, a plurality of cells are provided. Then, the plurality of cells are divided into blocks composed of a plurality of cells,
The open circuit voltage is measured for each block. The measurement information of the open circuit voltage differs depending on whether or not the block includes the cell in which the cross leak early occurrence cell is included. The discrimination information obtained from the measurement information of the open circuit voltage also includes the cross leak early occurrence cell in the block. Whether the block is good or not can be determined. Since the number of cells constituting the block is smaller than the number of cells of the entire phosphoric acid type fuel cell, the early occurrence of the cross leak can be easily determined in the block determined to be defective.

That is, generally, in a phosphoric acid type fuel cell,
The output voltage of one cell is low, and in order to obtain an output voltage necessary for practical use, 150 to 300 cells are provided in an electrically connected state in series. Then, it is necessary to measure the open circuit voltage of the cell in order to obtain the determination information for determining the quality of the cell. In such a case, cell 1
Measuring the open circuit voltage for each unit complicates the measurement operation. On the other hand, according to the characteristic configuration of the present invention, since the open circuit voltage is measured for each block, the work of measuring the open circuit voltage to obtain the discrimination information can be simplified.

According to the seventh aspect of the present invention, the temperature of the cell is maintained so as to be lower than the temperature in the normal operation state, so that the deterioration of the electrode catalyst can be prevented. Therefore, when performing the inspection, it is possible to reliably prevent a problem such as shortening of the life of the cell.

[0017]

Embodiments of the present invention will be described below with reference to the drawings. First, the configuration of the phosphoric acid fuel cell will be described with reference to FIGS. A fuel electrode 2 is provided on one surface of the phosphoric acid electrolyte layer 1 and an oxygen electrode 3 is provided on the other surface, and a fuel gas flow path f through which a fuel gas containing hydrogen gas flows is provided on the fuel electrode 2 side. A plurality of rectangular plate-shaped cells C provided with an oxygen-containing gas flow path s through which oxygen-containing gas flows on the oxygen electrode 3 side are provided in the thickness direction in a state of being electrically connected in series, A cell stack T is formed.

In forming the cell stack T,
A plurality of (for example, six in this embodiment) cells C are arranged in the thickness direction in a state of being electrically connected in series to form a sub-stack Ts.
The cooling units 7 having conductivity are arranged between each other, and are arranged side by side in the thickness direction in a state of being electrically connected in series by the cooling units 7. Furthermore, in the cell stack T, the cell stack T
There is provided a current collecting plate 8 for extracting electric power from the power supply.

The cell C will be described. Cell C is
A fuel electrode 2 is provided on one surface of the phosphoric acid electrolyte layer 1, an oxygen electrode 3 is provided on the other surface, and a fuel-side flow path forming member is formed to form a fuel gas flow path f on the fuel electrode 2 side. 4, and an oxygen-side flow path forming member 5 is formed to form an oxygen-containing gas flow path s on the oxygen electrode 3 side. Phosphoric acid electrolyte layer 1
Is formed by holding the matrix layer impregnated with phosphoric acid. The fuel electrode 2 and the oxygen electrode 3 are formed of carbon in a porous shape, and a catalyst layer is formed on the side in contact with the phosphoric acid electrolyte layer 1 by supporting platinum as an electrode catalyst.

The fuel-side flow path forming member 4 is formed of a conductive material in a state where a plurality of concave grooves functioning as fuel gas flow paths f are provided on one surface in parallel at a distance from each other. It is. Further, the oxygen-side flow path forming member 5 has a plurality of grooves on one surface that function as oxygen-containing gas flow paths s, and the gaps are orthogonal to the respective grooves of the fuel-side flow path forming member 4. It is made of a conductive material so as to be provided in a parallel state with a space therebetween.

A plurality of cells C formed as described above are
The separators 6 having a rectangular plate shape and having conductivity are arranged between each other, and are arranged in the thickness direction.

Although not shown, the cooling section 7 is provided with a flow section for cooling water inside a box made of a conductive material in a state of being electrically insulated from the box. It is composed.

Each of the four sides of the cell stack T includes:
A box-shaped member 9 having one surface opened is attached with its opening facing the side surface of the cell stack T. Then, the fuel gas supply pipe 10 is connected to the box-shaped member 9 attached to the side surface at which one end of the fuel gas passage f opens, and the inside of the box-shaped member 9 is connected to each cell. C
Similarly, the fuel gas discharge pipe 11 is connected to the box-shaped member 9 attached to the side surface where the other end of the fuel gas flow path f is opened. The inside of the box-shaped member 9 is connected to function as a fuel gas discharge chamber 15 communicating with the fuel gas flow path f of each cell C. Further, an oxygen-containing gas supply pipe 12 is connected to a box-shaped member 9 attached to a side surface at which one end of the oxygen-containing gas flow path s is opened, in a state of communicating with the inside thereof.
The inside of the box-shaped member 9 functions as an oxygen-containing gas supply chamber 16 communicating with the oxygen-containing gas flow path s of each cell C,
Similarly, the oxygen-containing gas discharge pipe 1 is attached to the box-shaped member 9 attached to the side face where the other end of the oxygen-containing gas flow path s opens.
3 is connected to allow the inside of the box-shaped member 9 to function as an oxygen-containing gas discharge chamber 17 communicating with the oxygen-containing gas flow path s of each cell C.

Then, the fuel gas is supplied to the fuel gas supply chamber 14 through the fuel gas supply pipe 10, and the fuel gas is caused to flow through the fuel gas flow path f of each cell C, and then discharged to the fuel gas discharge chamber 15. Then, the fuel gas is discharged to the outside through the fuel gas discharge pipe 11, and air as the oxygen-containing gas is supplied to the oxygen-containing gas supply chamber 16 through the oxygen-containing gas supply pipe 12, and the oxygen-containing gas flow path s Then, the gas is discharged to the oxygen-containing gas discharge chamber 17 and discharged to the outside through the oxygen-containing gas discharge pipe 13. In each cell C, hydrogen in the fuel gas and oxygen in the air are allowed to react with each other, so that DC power can be obtained.

Next, a description will be given of the configuration of a device (hereinafter, referred to as a detecting device) for detecting a cell in which a cross leak occurs early from the cell stack T. As shown in FIG. 3, terminals 18 for open circuit voltage measurement are electrically connected to cells C at both ends in the cell arrangement direction in each subtack Ts, and each terminal 18 is connected to a multi-input voltmeter 19. Thus, the open circuit voltage can be measured for each sub-tack Ts. Therefore, the sub-tack Ts has a plurality of cells C
Corresponds to the block B composed of Note that a load device (not shown) for consuming output power is not connected to the cell stack T in order to measure the open circuit voltage.

As shown in FIG. 4, a hydrogen cylinder 20 is connected to the fuel gas supply pipe 10, and hydrogen gas is supplied to the fuel gas supply pipe 10 as a fuel gas.
Is connected to a blower 21 to supply air to the oxygen-containing gas supply pipe 12 as oxygen-containing gas. The fuel gas supply pipe 10 is provided with a fuel gas flow rate adjusting valve 22 for adjusting the flow rate of the fuel gas flowing through the fuel gas channel f.
The fuel gas discharge pipe 11 has a fuel gas pressure adjustment for adjusting the pressure of the fuel gas flowing through the fuel gas passage f by adjusting the pressure of the fuel-side exhaust gas discharged from the fuel gas passage f. Valves 23 are provided respectively. In addition, the oxygen-containing gas supply pipe 12 has an oxygen-containing gas flow control valve 24 for adjusting the flow rate of the oxygen-containing gas s flowing through the oxygen-containing gas flow path s, and the oxygen-containing gas discharge pipe 13 has By adjusting the pressure of the oxygen-side exhaust gas discharged from the oxygen-containing gas s, the oxygen-containing gas pressure regulating valves 25 for adjusting the pressure of the oxygen-containing gas flowing through the oxygen-containing gas flow path s are respectively provided. I have.

Further, the fuel-side exhaust gas is sampled for each block B in the fuel gas discharge chamber 15 to measure the oxygen concentration in the fuel-side exhaust gas, or the oxygen-side exhaust gas is blocked in the oxygen-containing gas discharge chamber 17 for the block B. A gas analyzer 26 is provided for sampling each time and detecting the hydrogen concentration in the oxygen-side exhaust gas.

Hereinafter, a method of detecting a cell in which a cross leak has occurred early will be described using the detection device configured as described above. When each of the following detection methods is performed, the temperature of the cell C is the temperature in the normal operation state (for example, 2
Temperature lower than about 00 ° C (for example, 40 to 60 °).
C) is maintained.

[First Detection Method] A flow rate of hydrogen gas (for example, 2 cc / mi) in a normal operation state is supplied to the fuel gas passage f.
m · cm ² ), and air flows through the oxygen-containing gas flow path s in the normal operation state at a flow rate Fs.
(For example, about 5 cc / mim · cm ² ) and a reference flow rate Fh (for example, 1 cc / m
im ・ cm ² )
The voltmeter 19 measures the open circuit voltage of each block B. Then, based on the measurement information, the cell is changed from a state in which air flows through the oxygen-containing gas flow path s at the flow rate Fs in the normal operation state to a state in which air flows through the reference flow rate Fh for pass / fail determination. A change in the open circuit voltage at C is obtained, and a block B having the change equal to or more than the first set value is detected as a defective block including a cell having an early occurrence of cross leak. Further, in the defective block, under the same conditions as above, the flow rate of air flowing through the oxygen-containing gas flow path s is changed while the hydrogen gas flows through the fuel gas flow path f at the flow rate in the normal operation state. , The change in the open circuit voltage in cell C
Cell C which is obtained for each cell and whose change is equal to or greater than the first set value.
Is detected as a cell in which a cross leak occurs early.

FIG. 7 shows the open circuit voltage of the cell C in each block B when air is passed at the flow rate Fs in the normal operation state, and the flow rate in each block B when the air is passed at the reference flow rate Fh for pass / fail determination. A cell in each block B when a load device (not shown) in a rated state is connected to the open circuit voltage of the cell C and the cell stack T, and both air and hydrogen gas flow at a flow rate in a normal operation state. C indicates an output voltage (hereinafter, may be referred to as a load voltage). However, in FIG. 7, the open circuit voltage and the load voltage are indicated by values per cell obtained by dividing the measured value of each block B by the number of cells C included in the block B.

As shown in FIG. 7, there is no significant difference between the blocks in the on-load voltage and the open circuit voltage when the air flow rate is the flow rate Fs in the normal operation state. The open circuit voltage at the reference flow rate Fh is 2
The eighth block B is particularly lower than the other blocks B. Accordingly, regarding the change in the open circuit voltage when the air flow rate is changed from the flow rate Fs in the normal operation state to the reference flow rate Fh for quality determination, blocks other than No. 28
While the difference between the blocks is small at about 6 to 12 mV,
The 28th block B is about 37 mV, which is particularly large with respect to the other blocks B. Therefore, the block B of the 28th
Can be determined as a defective block including a cell in which a cross leak early occurrence cell is included.

Further, as the amount of phosphoric acid in the phosphoric acid electrolyte layer 1 is smaller, the amount of cross leak increases, and the amount of decrease in the open circuit voltage increases. The amount of phosphoric acid in layer 1 can be evaluated.

[Second detection method] The flow rate of hydrogen gas in the normal operation state (for example, 2 cc / mi)
m · cm ² ), and the flow rate of the air flowing through the oxygen-containing gas flow path s is determined by the reference flow rate Fh for pass / fail determination.
(For example, about 1 cc / mim · cm ² ) or less, and the voltmeter 19 measures the open circuit voltage of each block B in each case. Then, based on the measurement information, when the air flow rate is changed, the cell C
, The block B having the change equal to or more than the second set value is detected as a defective block including a cell in which a cross leak early occurrence cell is included.

The measurement results are not shown. However, as shown in FIG. 5, when the air flow rate is smaller than the reference flow rate Fh for pass / fail determination, the amount of decrease in the open circuit voltage of the cell in which the early occurrence of the cross leak is larger than that of the normal cell and the air flow rate Is smaller than the reference flow rate Fh for pass / fail determination, the amount of decrease in the open circuit voltage of the cells in which the early-stage cross-leakage occurs is large. It turns out that it becomes larger than a normal block.

Further, as the amount of phosphoric acid in the phosphoric acid electrolyte layer 1 is smaller, the amount of cross leak increases, and the amount of decrease in the open circuit voltage increases. The amount of phosphoric acid in layer 1 can be evaluated.

[Third Detection Method] The flow rate of air flowing through the oxygen-containing gas flow path s is determined by a reference flow rate Fh (for example,
(About 1 cc / mim · cm ² ), and the flow rate of hydrogen gas flowing through the fuel gas passage f is 0.16 cc / mi.
The voltmeter 19 measures the open circuit voltage of each block B when the voltage is changed to m · cm ² and 0.32 cc / mim · cm ² , respectively. Then, based on the measurement information, the flow rate of the hydrogen gas flowing through the fuel gas flow path f is set to 0.16 cc / mim · cm ² and 0.32 cc / mim.
The change of the open circuit voltage in the cell C when the change is changed to cm ² is obtained, and the block B in which the change is equal to or more than the third set value is detected as a defective block including the cell in which the cross leak early occurrence cell is included. Further, in the defective block, under the same conditions as described above, the flow rate of the hydrogen gas flowing through the fuel gas flow path f is set to a value equal to or less than the reference flow rate Fh for determining whether the air flows through the oxygen-containing gas flow path s. 0.16cc / m flow rate
im · cm ² and 0.32 cc / mim · cm ² to determine the change in open-circuit voltage for each cell C, and the cell C whose change is equal to or greater than the third set value occurs early in the cross leak. Detect as a cell.

FIG. 8 shows that the hydrogen gas flow rate is 0.16 cc / m
The open circuit voltage of cell C in each block B at im · cm ² , the open circuit voltage of cell C in each block B at 0.32 cc / mim · cm ² , and the open circuit between both 3 shows a change in voltage. However, in FIG. 8, as in FIG. 7, the open circuit voltage is represented by a value per cell by dividing the measured value of each block B by the number of cells C included in the block B. I have.

As shown in FIG. 8, with respect to the change in the open circuit voltage, the difference between the blocks is about 0 to 3 mV for the blocks other than the 28th block, while the block B for the 28th block is about 12 mV. , Especially for the other blocks B. Therefore, the 28th block B can be determined as a defective block including the cell in which the cross leak early occurrence cell is included.

Furthermore, the smaller the amount of phosphoric acid in the phosphoric acid electrolyte layer 1, the greater the amount of cross leakage and the greater the amount of decrease in the open circuit voltage. The amount of phosphoric acid in layer 1 can be evaluated.

[Fourth detection method] Flow through fuel gas passage f
Constant fuel gas flow (for example, under normal operating conditions)
2cc / mim · cm^TwoDegree)
In this state, air is supplied to the oxygen-containing gas flow path s in the normal operation state.
Fs (for example, 5 cc / mim · cm ^Twodegree)
From the state where the oxygen-containing gas flows,
When fully closed, the flow rate of air in the oxygen-containing gas flow path s is reduced.
From the time of stopping, with the passage of time, the voltmeter 19
Then, the open circuit voltage of each block B is measured. And that
Of the open circuit voltage in the cell C based on the measurement information of
The speed of change of the open circuit voltage is determined by the fourth setting.
Block B exceeding the specified value is included in cells that
Detected as a defective block.

Furthermore, the smaller the amount of phosphoric acid in the phosphoric acid electrolyte layer 1, the greater the amount of cross leak and the faster the decrease in the open circuit voltage. can do.

[Fifth detection method] The flow rate of air flowing through the oxygen-containing gas flow path s is determined by a reference flow rate Fh (for example,
While maintaining constant the 1cc / mim · cm ² or so) or less, the flow rate in the normal operation state of hydrogen gas to the fuel gas passage f (e.g., from a state in which flow through at 2cc / mim · cm ² or so), the fuel With the passage of time, the open circuit voltage of each block B is measured with the voltmeter 19 from the time when the flow of the hydrogen gas in the fuel gas flow path f is stopped by fully closing the gas flow control valve 22. I do. Then, based on the measurement information, the speed of the change in the open circuit voltage in the cell C is obtained, and the block B in which the speed of the change in the open circuit voltage is equal to or more than the fifth set value includes the cell in which the cross leak early occurrence cell is included. Detected as a bad block.

[Sixth Detection Method] During the execution of any one of the first to fifth detection methods described above, the oxygen-side exhaust gas is sampled for each block B, and the oxygen-containing exhaust gas is sampled by the gas analyzer 26. Detect hydrogen concentration in exhaust gas,
Block B whose detected value is equal to or larger than the sixth set value is detected as a defective block including a cell in which a cross leak early occurrence cell is included.

Illustration of the measurement results is omitted. However, as shown in FIG. 9, the amount of phosphoric acid retained in the phosphoric acid electrolyte layer is a predetermined amount (for example, about 50% of the initial amount).
Below this, cross leak occurs, the hydrogen concentration in the oxygen-side exhaust gas increases, and the amount of cross leak increases as the amount of phosphoric acid decreases, so that the hydrogen concentration increases. In FIG. 9, the amount of phosphoric acid in the phosphoric acid electrolyte layer is shown as a ratio to the initial amount. Therefore, the detected value of the hydrogen concentration is high in the defective block including the cell in which the cross leak occurs early.

Furthermore, the smaller the amount of phosphoric acid in the phosphoric acid electrolyte layer 1, the greater the amount of cross leak and the higher the concentration of hydrogen in the oxygen-side exhaust gas. The amount of phosphoric acid in layer 1 can be evaluated.

[Another Embodiment] Next, another embodiment will be described. (A) In the case where the cell stack T is divided into a plurality of blocks B, in the above-described embodiment, the case where one sub-stack Ts is divided as one block B has been described as an example. The sub-stack Ts may be divided so that a plurality of blocks B exist in one sub-stack Ts. Alternatively, the plurality of sub-stacks Ts may be divided as one block B.

(B) In the above embodiment, the cell stack T is divided into a plurality of blocks B,
Although the case where the open-circuit voltage is measured for each cell has been described as an example, the open-circuit voltage may be measured for each cell C instead of dividing the block B. However, in order to simplify the measurement operation, it is preferable to divide the circuit into blocks B and measure the open circuit voltage for each block B.

(C) The number of cells C constituting the block B can be set as appropriate. However, as the number of cells C constituting the block B increases, the operation of measuring the open circuit voltage can be simplified, but the detection accuracy of the defective block including the early-cross-leakage cell decreases. .

(D) In detecting a cell having an early occurrence of cross leak, any one of the first to fifth detection methods described above may be performed. In addition, the first
Alternatively, two or more of the fifth to fifth detection methods may be implemented in combination. In this case, it is possible to improve the detection accuracy of the cell in which the cross leak occurs early. Further, when the sixth detection method is used together, the detection accuracy can be further improved.

(E) In each of the first to fifth detection methods described above, when detecting an early occurrence cell of a cross leak from a defective block, the same detection method as that used for detecting the defective block is employed. Or another detection method may be adopted.

(F) In the above embodiment, pure hydrogen gas is used as the fuel gas. However, hydrocarbon gas such as natural gas is reformed and converted to hydrogen gas. And a reformed gas containing carbon dioxide gas and the like. Although the case where air is used as the oxygen-containing gas has been exemplified, pure oxygen gas and various other oxygen-containing gases containing oxygen gas can be used.

(G) The specific values of the flow rate of the hydrogen gas in the normal operation state, the flow rate Fs of the air in the normal operation state, and the reference flow rate Fh for determining the quality of the air are exemplified in the respective detection methods described above. The value is not limited to a specific value, and can be appropriately set according to the specifications and performance of the cell C, operating conditions in a normal operating state, and the like.

(H) In the first detection method described above, the flow rate of the hydrogen gas maintained constant is not limited to the flow rate in the normal operation state, but can be changed as appropriate.
However, even when the flow rate is lower than the flow rate in the normal operation state,
The higher the flow rate is, the more the cross leak is likely to occur in the cell where the cross leak occurs early. Therefore, it is preferable to increase the flow rate as much as possible. The flow rate at the time of reducing the flow rate of the air may be any flow rate as long as it is equal to or less than the reference flow rate Fh for quality determination. As the flow rate of the air is reduced, the cross leak is more likely to occur in the cell where the cross leak occurs earlier.

(I) In the above-described second detection method, the flow rate of the hydrogen gas maintained constant is not limited to the flow rate in the normal operation state, but can be changed as appropriate.
However, even when the flow rate is lower than the flow rate in the normal operation state,
The higher the flow rate is, the more the cross leak is likely to occur in the cell where the cross leak occurs early. Therefore, it is preferable to increase the flow rate as much as possible. Further, the flow rate of the air when it is changed under the condition of being equal to or less than the reference flow rate Fh for pass / fail determination may be any value as long as it is equal to or lower than the reference flow rate Fh for pass / fail determination.

(V) In the above third detection method, the flow rate of air may be any value as long as it is equal to or less than the reference flow rate Fh for pass / fail determination. Also, the value when changing the flow rate of the hydrogen gas can be changed to various values other than those exemplified in the above embodiment. Further, in the above embodiment, the case where the flow rate of the hydrogen gas is changed in order to change the flow state of the hydrogen gas has been described, but the pressure of the hydrogen gas may be changed instead.

(G) In the above-mentioned fourth detection method, the flow rate of the hydrogen gas maintained constant is not limited to the flow rate in the normal operation state, but can be changed as appropriate.
However, even when the flow rate is lower than the flow rate in the normal operation state,
The higher the flow rate is, the more the cross leak is likely to occur in the cell where the cross leak occurs early. Therefore, it is preferable to increase the flow rate as much as possible.

(ヲ) In the above first detection method,
In a state where the flow rate of the fuel gas flowing through the fuel gas flow path f is maintained at the value in the normal operation state, the flow rate of the oxygen-containing gas flowing through the oxygen-containing gas flow path s is determined to be equal to the value Fs in the normal operation state. The case where the change of the open circuit voltage in the cell C when it is changed to be equal to or less than the use reference value Fh is obtained, and the early occurrence cell of the cross leak is detected based on the change of the open circuit voltage is illustrated. Instead of this, when the fuel gas is caused to flow through the fuel gas flow path f at a flow rate in the normal operation state, and the oxygen-containing gas is caused to flow through the oxygen-containing gas flow path s at a flow rate equal to or less than the reference value Fh for quality determination. Alternatively, the open circuit voltage of the cell C may be measured, and the cell in which the cross leak occurs early may be detected based on the open circuit voltage itself. However, since the open circuit voltage varies between cells,
It is preferable to obtain the change in the open circuit voltage as in the above-described first detection method, because the influence of the variation can be eliminated in the detection of the cell in which the cross-leakage occurs early, and the detection accuracy can be improved. (W) The configuration of the cell C and the juxtaposed configuration for juxtaposing the plurality of cells C in the thickness direction to form the cell stack T are not limited to the configuration exemplified in the above embodiment, but may be various. Is possible. Further, the shape of the cell C can be various shapes such as a square plate shape and a rectangular plate shape close to a square.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a configuration of a sub stack of a phosphoric acid type fuel cell.

FIG. 2 is a partially cutaway perspective view showing the entire configuration of the phosphoric acid type fuel cell.

FIG. 3 shows a configuration for measuring an open circuit voltage.

FIG. 4 is a block diagram of a detection device.

FIG. 5 is a diagram showing a relationship between an open circuit voltage and an air flow rate.

FIG. 6 is a graph showing the relationship between the amount of phosphoric acid and the amount of cross leak.

FIG. 7 is a diagram showing an open circuit voltage when the air flow rate is changed.

FIG. 8 is a diagram showing an open circuit voltage when the hydrogen gas flow rate is changed.

FIG. 9 is a diagram showing the relationship between the amount of phosphoric acid and the concentration of hydrogen in the oxygen-side exhaust gas.

[Explanation of symbols]

 1 Phosphoric acid electrolyte layer 2 Fuel electrode 3 Oxygen electrode f Fuel gas flow path s Oxygen-containing gas flow path B Block C cell Fh Reference value for quality judgment Fs Value in normal operation state

Claims (7)

[Claims] 1. A fuel gas flow path through which a fuel electrode is provided on one surface of a phosphoric acid electrolyte layer and an oxygen electrode is provided on the other surface, and through which a fuel gas containing hydrogen gas flows. A phosphoric acid fuel cell provided with a cell provided with an oxygen-containing gas flow path through which the oxygen-containing gas flows on the oxygen electrode side, wherein the flow rate of the oxygen-containing gas flowing through the oxygen-containing gas flow path When the flow state of the fuel gas flowing through the fuel gas flow path is changed in a state where the value is equal to or less than the quality determination reference value smaller than the value in the normal operation state, the change in the open circuit voltage in the cell is A defective cell detection method for a phosphoric acid type fuel cell, wherein the method determines the quality of the cell based on the determination information. 2. A fuel gas flow path through which a fuel electrode is provided on one surface of a phosphoric acid electrolyte layer and an oxygen electrode is provided on the other surface, and a fuel gas containing hydrogen gas flows therethrough. In a phosphoric acid fuel cell provided with a cell having an oxygen-containing gas flow path through which the oxygen-containing gas flows on the oxygen electrode side, the flow state of the fuel gas flowing through the fuel gas flow path The cell when the flow rate of the oxygen-containing gas flowing through the oxygen-containing gas flow path is changed to a value in a normal operation state and a pass / fail determination reference value smaller than the value in a state where the oxygen-containing gas flow rate is maintained constant. A method for detecting a defective cell in a phosphoric acid type fuel cell, wherein a change in the open circuit voltage is determined as discrimination information, and the quality of the cell is discriminated based on the discrimination information. 3. A fuel gas flow path in which a fuel electrode is provided on one surface of the phosphoric acid electrolyte layer and an oxygen electrode is provided on the other surface and a fuel gas containing hydrogen gas flows therethrough is provided on the fuel electrode side. In a phosphoric acid fuel cell provided with a cell having an oxygen-containing gas flow path through which the oxygen-containing gas flows on the oxygen electrode side, the flow state of the fuel gas flowing through the fuel gas flow path The cell when the flow rate of the oxygen-containing gas flowing through the oxygen-containing gas flow path is changed under the condition that the flow rate of the oxygen-containing gas flowing through the oxygen-containing gas flow path is equal to or less than a reference value for quality determination that is smaller than the value in the normal operation state is maintained. A method for detecting a defective cell in a phosphoric acid type fuel cell, wherein a change in the open circuit voltage is determined as discrimination information, and the quality of the cell is discriminated based on the discrimination information. 4. A fuel gas flow path in which a fuel electrode is provided on one surface of the phosphoric acid electrolyte layer and an oxygen electrode is provided on the other surface, and a fuel gas containing hydrogen gas flows therethrough. In a phosphoric acid fuel cell provided with a cell having an oxygen-containing gas flow path through which the oxygen-containing gas flows on the oxygen electrode side, the flow state of the fuel gas flowing through the fuel gas flow path From a state in which the oxygen-containing gas flows through the oxygen-containing gas flow path at the flow rate in the normal operation state, while being kept constant,
When the flow rate of the oxygen-containing gas in the oxygen-containing gas flow path is stopped, the speed of change of the open circuit voltage in the cell is obtained as discrimination information, and the pass / fail of the cell is discriminated based on the discrimination information. Cell detection method for phosphoric acid type fuel cell. 5. A fuel gas flow path in which a fuel electrode is provided on one surface of a phosphoric acid electrolyte layer and an oxygen electrode is provided on the other surface, and a fuel gas flow path through which a fuel gas containing hydrogen gas flows is provided. A phosphoric acid fuel cell provided with a cell provided with an oxygen-containing gas flow path through which the oxygen-containing gas flows on the oxygen electrode side, wherein the flow rate of the oxygen-containing gas flowing through the oxygen-containing gas flow path In a state where the fuel gas is allowed to flow through the fuel gas flow path at a flow rate in the normal operation state in a state in which the fuel gas flow rate is maintained at or below the reference value for pass / fail determination smaller than the value in the normal operation state. A failure rate of the phosphoric acid type fuel cell which determines the speed of change of the open circuit voltage in the cell when the flow of the fuel gas is stopped as determination information, and determines the quality of the cell based on the measurement information. Cell detection method. 6. A plurality of said cells are provided, said plurality of cells are divided into blocks composed of a plurality of cells, and an open circuit voltage is measured for each of said blocks. And determining whether the block is good or bad based on the determination information.
6. The method for detecting a defective cell of a phosphoric acid fuel cell according to any one of items 5 to 5. 7. The method for detecting a defective cell in a phosphoric acid fuel cell according to claim 1, wherein the temperature of the cell is maintained lower than a temperature in a normal operation state.