JPH087911A - Method of detecting faulty cell in phosphoric acid type fuel cell - Google Patents

Abstract

PURPOSE:To detect a latent faulty cell by measuring the change of.output voltage at a fuel utilization factor close to operation limit value in every block, and comparing it with a set value. CONSTITUTION:A terminal for measuring voltage is connected to each of the cells at both ends of a sub stack constituting a block, and in case that the fuel utilization factor is 80% in normal operation value and is 95% in operation limit value, based on the detection information of a flow meter 26, the concentration of hydrogen gas is adjusted by adjusting the aperture of proportional valves 19 and 20 so that the fuel utilization factor may be 90-94%. And, by a volt meter 15, the output change from normal operation at this time is measured, and if the drop of the output voltage is more than the set value, it is judged to be faulty, regarding that a cell bad in fuel gas distribution equality is included in the block. Hereby, a user can surely detect such a latent faulty cell that the property deteriorates during operation.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel gas flow which has a fuel electrode on one surface of a phosphoric acid electrolyte layer and an oxygen electrode on the other surface, and through which a fuel gas containing hydrogen gas flows. A plurality of plate-shaped cells having a channel on the surface facing the fuel electrode and having an oxygen-containing gas passage through which the oxygen-containing gas containing oxygen gas flows, on the surface facing the oxygen electrode are juxtaposed in a stacked state. In this phosphoric acid fuel cell, a defective cell detecting method for a phosphoric acid fuel cell, which detects a defective cell among a plurality of cells juxtaposed in a stacked state.

[0002]

2. Description of the Related Art Generally, in a phosphoric acid fuel cell, the electromotive force of one cell is as low as about 0.65 V, and 150 to 300 cells are electrically connected to obtain an output voltage required for practical use. And are arranged side by side in a laminated state in a state of being connected in series with the above. In the following description, a plurality of cells arranged side by side in a stacked state may be referred to as a cell stack. Therefore, as a method for detecting defective cells in the cell stack before shipping the phosphoric acid fuel cell,
The following method was adopted.

The proportion of the fuel gas supplied to each fuel gas channel used in the cell reaction at the fuel electrode (hereinafter referred to as the fuel utilization rate), or the oxygen content supplied to each oxygen-containing gas channel. The proportion of oxygen gas in the gas used in the battery reaction at each oxygen electrode (hereinafter, referred to as oxygen utilization rate) is slightly smaller than the value during normal operation (hereinafter, may be referred to as normal operation value). It has been increased (for example, about 5% or less), and the output voltage change of each block at that time during normal operation is measured, and the defective cell is detected from the output voltage change. Further, a load larger than that during normal operation is connected to the fuel cell, the change in output voltage of each block at that time during normal operation is measured, and a defective cell is detected from the change in output voltage.

[0004]

According to the above-mentioned conventional detection method, an initial defective cell can be surely detected. On the other hand, a cell whose characteristic deterioration rate is slower than that of the initial defective cell due to the potential defect but slightly faster than that of the normal cell (hereinafter, may be referred to as latent defective cell) is The characteristics deteriorate and become defective at a relatively early stage after the start of operation. However, such a latent defective cell could not be detected by the conventional detection method because the output voltage change is almost the same as that of the normal cell. Therefore, in some cases, a user may have a defective cell during operation and must disassemble the cell stack to replace the defective cell, and improvement has been desired.

The latent defective cells include cells having a poor gas isotropy and cells having a poor gas diffusion property. In the cells, the introduced fuel gas and oxygen-containing gas must be in a state in which they are evenly distributed over the entire surface of each cell, that is, they must be excellent in gas equality. However, when there is a defect in the fuel electrode or the oxygen electrode, phosphoric acid oozes out from the phosphoric acid electrolyte layer into the fuel flow path or the oxygen-containing gas flow path, and the introduced fuel gas or oxygen-containing gas is applied to the cell surface. Uneven distribution occurs and the gas isotropic property deteriorates. Further, the fuel electrode and the oxygen electrode are formed of a porous body so that the introduced fuel gas and oxygen-containing gas diffuse through the porous body. In the cell, the introduced fuel gas or oxygen-containing gas must diffuse into the reaction region of the fuel electrode or the oxygen electrode, that is, the gas diffusivity must be excellent. However, if there is a defect in the fuel electrode or the oxygen electrode, phosphoric acid will enter the holes of the fuel electrode or the oxygen electrode from the phosphoric acid electrolyte layer, and the gas diffusibility will deteriorate.

When the gas isotropic property or the gas diffusibility is poor, the temperature distribution of the cell becomes unbalanced during operation, so that the defects further progress, and the gas isotropic property or the gas diffusivity is further deteriorated. The characteristics deteriorate and become defective.

The present invention has been made in view of the above circumstances, and an object thereof is to detect a defective defective cell of a phosphoric acid fuel cell capable of reliably detecting a latent defective cell whose characteristics are deteriorated during driving by a user. To provide a method.

[0008]

A first characteristic configuration of a defective cell detection method for a phosphoric acid fuel cell according to the present invention is to provide a fuel electrode on one surface of a phosphoric acid electrolyte layer and an oxygen electrode on the other surface. And an oxygen-containing gas flow path through which an oxygen-containing gas containing oxygen gas flows and which has a fuel gas flow path through which a fuel gas containing hydrogen gas flows and which faces the fuel electrode. In a phosphoric acid fuel cell in which a plurality of plate cells provided on the surface facing the pole are juxtaposed in a stacked state, each fuel gas flow is divided into one cell or a block composed of a plurality of cells. The fuel utilization rate, which indicates the proportion of the fuel gas supplied to the fuel cell used in the cell reaction at each fuel electrode, is increased from the value during normal operation to near the operation limit value, and the normal operation of each of the blocks at that time is increased. Measures output voltage change over time And, in that the output voltage change is poor settings or more blocks.

A second characteristic configuration is 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. A plurality of plate-shaped cells provided on the surface facing the fuel electrode and having an oxygen-containing gas flow path through which the oxygen-containing gas containing the oxygen gas flows, on the surface facing the oxygen electrode are juxtaposed in a stacked state. In the phosphoric acid fuel cell, the hydrogen gas concentration in the fuel gas supplied to the fuel gas flow passage is divided into blocks, each of which is divided into one cell or a block composed of a plurality of cells. Increase, measure the output voltage change of each of the blocks at that time during normal operation,
The point is that a block whose output voltage change is equal to or larger than a set value is defective.

A third characteristic constitution is a fuel gas flow passage 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. A plurality of plate-shaped cells provided on the surface facing the fuel electrode and having an oxygen-containing gas flow path through which the oxygen-containing gas containing the oxygen gas flows, on the surface facing the oxygen electrode are juxtaposed in a stacked state. In the phosphoric acid fuel cell, it is divided into blocks consisting of one cell or multiple cells, and the proportion of the fuel gas supplied to each fuel gas flow path that is used in the cell reaction at each fuel electrode The fuel utilization factor is greater than the value during normal operation, and the hydrogen gas concentration in the fuel gas is less than the value during normal operation, and the output voltage of each block at that time during normal operation is shown. Measure the change and output Change lies in the failure of the set value or more blocks.

A fourth characteristic configuration is 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. A plurality of plate-shaped cells provided on the surface facing the fuel electrode and having an oxygen-containing gas flow path through which the oxygen-containing gas containing the oxygen gas flows, on the surface facing the oxygen electrode are juxtaposed in a stacked state. In a phosphoric acid fuel cell, the cell is divided into blocks composed of one cell or a plurality of cells, and the battery is provided at each oxygen electrode of the oxygen gas in the oxygen-containing gas supplied to each oxygen-containing gas flow path. The oxygen utilization rate, which indicates the proportion used in the reaction, is increased from the value during normal operation to near the operating limit value, and the change in output voltage during normal operation of each of the blocks at that time is measured, and the output voltage change is set. Do not block more than the value There is a point to be.

A fifth characteristic configuration is 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. A plurality of plate-shaped cells provided on the surface facing the fuel electrode and having an oxygen-containing gas flow path through which the oxygen-containing gas containing the oxygen gas flows, on the surface facing the oxygen electrode are juxtaposed in a stacked state. In the phosphoric acid fuel cell, the oxygen gas concentration in the oxygen-containing gas supplied to the oxygen-containing gas flow path is divided into blocks composed of one cell or a plurality of cells, and the oxygen gas concentration is a value during normal operation. The output voltage change of each of the blocks at the time of the normal operation is measured, and the block having the output voltage change of the set value or more is determined to be defective.

A sixth characteristic constitution is 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. A plurality of plate-shaped cells provided on the surface facing the fuel electrode and having an oxygen-containing gas flow path through which the oxygen-containing gas containing the oxygen gas flows, on the surface facing the oxygen electrode are juxtaposed in a stacked state. In a phosphoric acid fuel cell, the cell is divided into blocks composed of one cell or a plurality of cells, and the battery is provided at each oxygen electrode of the oxygen gas in the oxygen-containing gas supplied to each oxygen-containing gas flow path. The oxygen utilization rate showing the ratio used in the reaction is made larger than the value during normal operation, and
By making the oxygen gas concentration in the oxygen-containing gas supplied to the oxygen-containing gas channel smaller than the value during normal operation,
The output voltage change of each of the blocks at that time during normal operation is measured, and a block having an output voltage change of a set value or more is determined to be defective.

[0014]

The operation of the first characteristic configuration is as follows. When the fuel utilization rate is increased, the hydrogen partial pressure in the vicinity of the outlet of the fuel gas flow channel is lowered, and the output voltage of the cell tends to be lowered, but the inventors of the present invention conducted various experiments, When increasing the fuel utilization rate, the degree of decrease in output voltage is the same in both normal cells and cells with poor gas isotropic distribution until slightly increased (for example, about 5%) from the normal operation value. It is possible to detect a cell with poor gas isotropic property by using the phenomenon that the output voltage of a cell with poor gas isotropic property decreases more than the normal cell when the value is raised to the limit value. I discovered that I can do it.
This phenomenon is greatly affected by the fact that cells with poor equiproportion of fuel gas have a higher fuel utilization rate than normal cells and the hydrogen partial pressure near the outlet of the fuel gas flow channel has decreased. It is thought to be due to. Incidentally, the operation limit value in the fuel utilization rate is a value in a state in which it is not preferable for continuous operation for a long time, when operating at that value, the gas isotropic property becomes too bad and the current density of the cell becomes large. .

FIG. 5 illustrates an example of the above phenomenon. In FIG. 5, the solid line shows the correlation between the fuel utilization rate and the cell output voltage in the normal cell, and the broken line shows the correlation between the fuel utilization rate and the cell output voltage in the cell with poor gas equidistributivity. The normal operation value and the operation limit value of the fuel utilization rate are slightly different depending on the cell specifications, but in FIG. 5, the normal operation value is about 80% and the operation limit value is about 95%, respectively. To do. As shown in FIG. 5, while increasing the fuel utilization rate from 80% to 85% of the normal operation value, the degree of decrease in the output voltage is the same in both the normal cells and the cells with poor gas isotropy. Therefore, as in the conventional case, the fuel utilization rate should be slightly lower than the normal operation value (for example, 5%).
However, it was not possible to detect cells with poor gas isotropy by the inspection method by increasing the size. However, when the fuel utilization rate is increased from 85% to 95% of the operating limit value, the degree of decrease in the output voltage of the cell having poor gas isotropy becomes larger than that of the normal cell.

The first characteristic configuration is based on the above viewpoint. That is, when the fuel utilization rate is increased from the normal operation value to near the operation limit value, the output voltage change with respect to the normal operation is a phenomenon in which a latent defective cell having poor gas isotropy of fuel gas is larger than a normal cell. Present. Therefore, the set value is set to such a value that it is possible to clearly distinguish between a block in which at least one cell having a poor equidistribution of the fuel gas is present and a block in which no cells are present at all.
Then, the fuel utilization rate is increased from the normal operation value to near the operation limit value, the output voltage change for each block at the time of the normal operation is measured, and the block whose output voltage change is the set value or more is regarded as defective. is there.

Although the acceleration test results when the fuel utilization rate is increased from the normal operation value, the inspection performed by the method according to the first characteristic configuration can be carried out in a short time. Even if the inspection is performed by operating at the operating limit value, there is almost no effect on the life of the cell and there is no problem, but the inspection is performed at a fuel utilization rate that is 1 to 2% smaller than the operating limit value. Is preferred. Therefore, in the example shown in FIG. 5, it is preferable to carry out the inspection by making the fuel utilization rate larger than the normal operation value by about 10 to 14%.

The operation of the second characteristic structure is as follows. The inventors of the present invention conducted various experiments,
If the hydrogen gas concentration in the fuel gas supplied to the fuel gas flow path is made higher than the normal operating value, the phenomenon that the output voltage of cells with poor gas diffusivity of fuel gas increases more than that of normal cells It was discovered that it is possible to detect cells with poor gas diffusivity using. This phenomenon is because when the hydrogen gas concentration is increased, the partial pressure of hydrogen actually used in the battery reaction rises, so the output voltage rises in all cells, but cells with poor gas diffusivity have higher hydrogen It is considered that this is due to the large effect of increasing the gas concentration. FIG. 6 illustrates the above phenomenon. In FIG. 6, the solid line shows the correlation between the hydrogen gas concentration and the cell output voltage in the normal cell, and the broken line shows the correlation between the hydrogen gas concentration and the cell output voltage in the cell with poor gas diffusibility. The normal operating value of hydrogen gas concentration varies slightly depending on the cell specifications.
In FIG. 6, about 65% will be described as an example. Figure 6
As shown in, when the hydrogen gas concentration is increased from 65% of the normal operation value to 100%, the degree of increase in the output voltage of the cell having poor gas diffusivity becomes larger than that of the normal cell.

The second characteristic structure is made based on the above viewpoint. That is, when the hydrogen gas concentration in the fuel gas is increased from 65% of the normal operation value to 100%, the output voltage change with respect to the normal operation is as follows. Also exhibits the phenomenon of becoming larger. Therefore, the set value is set to such a value that it is possible to clearly distinguish a block in which at least one cell having a poor gas diffusibility of fuel gas exists and a block in which no cell exists at all. Then, the hydrogen gas concentration in the fuel gas is increased from the normal operation value by about 35%, and the change in output voltage of each block at that time during normal operation is measured. To do.

The operation of the third characteristic configuration is as follows. If the hydrogen gas concentration in the fuel gas supplied to the fuel gas flow path is made smaller than the normal operation value, the output voltage of the cell will decrease. Therefore, if the fuel utilization rate is set higher than the value during normal operation and the hydrogen gas concentration in the fuel gas is set lower than the value during normal operation, the fuel utilization rate is increased and the gas distribution of the fuel gas is distributed. The influence given to the cell having poor property is promoted by reducing the hydrogen gas concentration. Therefore, even if the fuel utilization rate is not increased to near the operating limit value, it is possible to increase the output voltage difference between the normal cell and the cell with poor gas gas isotropy by only slightly increasing the normal operation value. Becomes clear. or,
Even for cells with poor gas diffusivity of fuel gas, the effect of reducing the hydrogen gas concentration is promoted by increasing the fuel utilization rate, and the difference in output voltage change between normal cells becomes clear. That is, the degree of decrease in the output voltage of a cell having poor gas isotropy or gas diffusivity is larger than that of a normal cell.

The third characteristic configuration is made based on the above viewpoint. That is, the set value is set to such a value that it is possible to clearly distinguish a block in which at least one cell having poor gas isotropy or gas diffusivity is present and a block in which no gas is present at all. Then, the fuel utilization rate is made higher than the value at the time of normal operation, and the hydrogen gas concentration in the fuel gas is made lower than the value at the time of normal operation. Is measured, and the block whose output voltage change is equal to or larger than the set value is determined to be defective.

The operation of the fourth characteristic configuration is as follows. When the oxygen utilization rate is increased, the oxygen partial pressure near the outlet of the oxygen-containing gas flow channel is reduced, and the output voltage of the cell tends to be reduced, but the inventors of the present invention conducted various experiments. However, when increasing the oxygen utilization rate, the degree of decrease in output voltage is the same in both normal cells and cells with poor gas isotropy until slightly increased from the normal operating value (for example, about 5%). If you raise it to near the operating limit,
It has been discovered that a cell having a poor gas isotropic property can be detected by utilizing the phenomenon that the degree of decrease in the output voltage of a cell having a poor gas isotropic property is larger than that of a normal cell. This phenomenon is due to the fact that cells with poor equiisotropy of oxygen-containing gas have a higher oxygen utilization rate than normal cells,
This is considered to be due to the large influence of the decrease in the oxygen partial pressure near the outlet of the oxygen-containing gas flow path.
The operation limit value in the oxygen utilization rate is a value in a state in which it is not preferable for continuous operation for a long time, when operating at that value, the gas isotropy becomes too bad and the current density of the cell increases. .

FIG. 7 illustrates the above phenomenon. In FIG. 7, the solid line shows the correlation between the oxygen utilization rate and the cell output voltage in the normal cell, and the broken line shows the correlation between the oxygen utilization rate and the cell output voltage in the cell in which the oxygen-containing gas has poor gas isotropy. Show the relationship. The normal operation value and the operation limit value of the oxygen utilization rate are slightly different depending on the cell specifications,
In FIG. 6, a normal operation value of about 60% and an operation limit value of about 80% will be described as examples. As shown in FIG. 7, the oxygen utilization rate is 60% to 65% of the normal operation value.
During the period up to, the degree of decrease in output voltage is the same in both normal cells and cells with poor gas isotropicity. Therefore, as in the conventional method, the method of inspecting by making the oxygen utilization rate slightly higher than the normal operation value (for example, about 5% or less) cannot detect the cell having poor gas isotropy. However, the oxygen utilization rate was increased from 65% to the operating limit value of 8
During the increase to 0%, the degree of decrease in the output voltage of the cell having a poor gas isotropy becomes larger than that of the normal cell.

The fourth characteristic structure is made based on the above viewpoint. That is, when the oxygen utilization rate is increased from the normal operation value to near the operation limit value, the output voltage change with respect to the normal operation is larger in the latent defective cell with poor gas isotropy of the oxygen-containing gas than in the normal cell. Exhibit a phenomenon. Therefore, the set value is set to such a value that it is possible to clearly distinguish between a block in which at least one cell having an oxygen-containing gas having a poor gas isotropic property exists and a block in which there is no such gas at all. Then, the oxygen utilization rate is increased from the normal operation value to near the operation limit value, and the output voltage change for each block at the time of the normal operation is measured. is there.

It should be noted that increasing the oxygen utilization rate from the normal operating value results in an accelerated test, but since the inspection performed by the method according to the third characteristic configuration can be carried out in a short time, the oxygen utilization rate can be reduced. Even if the inspection is performed by operating at the operation limit value, there is almost no effect on the life of the cell and there is no problem, but it is better to perform the inspection at an oxygen utilization rate that is 1 to 2% smaller than the operation limit value. preferable. Therefore, in the example shown in FIG. 7, it is preferable to carry out the inspection with the oxygen utilization rate increased by about 10 to 19% from the normal operation value.

The operation of the fifth characteristic configuration is as follows. The inventors of the present invention conducted various experiments,
When the oxygen gas concentration in the oxygen-containing gas supplied to the oxygen-containing gas flow path is made higher than the normal operation value, the degree of increase in the output voltage of the cell having poor gas diffusivity of oxygen gas becomes larger than that of the normal cell. It was discovered that the phenomenon can be used to detect cells with poor gas diffusivity. This phenomenon is because when the oxygen gas concentration is increased, the partial pressure of oxygen actually used in the battery reaction increases, so the output voltage rises in all cells, but cells with poor gas diffusivity are more oxygen-rich than normal cells. It is considered that this is due to the large effect of increasing the gas concentration. FIG. 8 illustrates the above phenomenon. In FIG. 8, the solid line shows the correlation between the oxygen gas concentration and the cell output voltage in the normal cell, and the broken line shows the correlation between the oxygen gas concentration and the cell output voltage in the cell where the gas diffusivity of oxygen gas is poor. Show. Although the normal operating value of the oxygen gas concentration is slightly different depending on the specifications of the cell, air is generally used as the oxygen-containing gas. Therefore, in FIG. 8, the normal operating value of the oxygen gas concentration is about 21%. . As shown in FIG. 8, when the oxygen gas concentration is increased from 21% of the normal operation value to 100%, the degree of increase in the output voltage of the cell having poor gas diffusivity of oxygen gas becomes larger than that of the normal cell.

The fifth characteristic configuration is based on the above viewpoint. That is, when the oxygen gas concentration in the oxygen-containing gas is increased from the normal operation value by about 80%, the output voltage change with respect to the normal operation is larger in the latent defective cell having the poor oxygen gas diffusivity than in the normal cell. Presents a phenomenon. Therefore, the set value is set to such a value that a block in which at least one cell having poor gas diffusivity of oxygen gas exists and a block in which no gas exists at all can be clearly distinguished. Then, the oxygen gas concentration in the oxygen-containing gas is increased from the normal operation value by about 80%, and the output voltage change for each block at that time during the normal operation is measured. And

The operation of the sixth characteristic structure is as follows. If the oxygen gas concentration in the oxygen-containing gas supplied to the oxygen-containing gas flow channel is made smaller than the normal operation value, the output voltage of the cell will decrease. Therefore, if the oxygen utilization rate is made higher than the value at the time of normal operation, and the oxygen gas concentration in the oxygen-containing gas is made lower than the value at the time of normal operation, the oxygen utilization rate is increased so that the gas of the oxygen-containing gas is increased. The influence given to the cell with poor equidistribution is promoted by reducing the oxygen gas concentration. Therefore, even if the oxygen utilization rate is not increased to near the operating limit value, the output voltage change between the normal cell and the cell with poor gas isotropy of the oxygen-containing gas can be obtained by only slightly increasing the oxygen operation rate. The difference becomes clear. Also, for cells with poor oxygen gas diffusivity, the effect of reducing the oxygen gas concentration is promoted by increasing the oxygen utilization rate, and the difference in output voltage change between normal cells becomes clear. . That is, the degree of decrease in the output voltage of a cell having poor gas isotropy or gas diffusivity is larger than that of a normal cell.

The sixth characteristic configuration is based on the above viewpoint. That is, the set value is set to such a value that it is possible to clearly distinguish a block in which there is at least one cell having a poor gas isotropic property or gas diffusibility of the oxygen-containing gas from a block in which it does not exist at all. Then, the oxygen utilization rate is made larger than the value at the time of normal operation, and the oxygen gas concentration in the oxygen-containing gas is made smaller than the value at the time of normal operation, and the output voltage for the normal operation of each block at that time. The change is measured, and the block in which the output voltage change is equal to or larger than the set value is determined to be defective.

[0030]

According to the first and fourth characteristic configurations, it is possible to reliably detect a latent defective cell whose gas isotropic property is poor and whose characteristics are deteriorated during operation by the user. Further, according to the second and fifth characteristic configurations, it is possible to reliably detect a latent defective cell having poor gas diffusibility and having characteristics deteriorated during operation by the user.
Further, according to the third and sixth characteristic configurations, while the influence on the life of the cell is minimized, the gas isotropy or gas diffusivity is poor, and the characteristics deteriorate during operation by the user. It has become possible to reliably detect such latent defective cells.

[0031]

Embodiments of the present invention will be described below with reference to the drawings. First, the configuration of a phosphoric acid fuel cell will be described with reference to FIGS. 1 and 2. In the cell C, a rectangular plate-shaped phosphoric acid electrolyte layer 1 impregnated with phosphoric acid is provided with a rectangular plate-shaped fuel electrode 2 on one surface, and a rectangular plate-shaped oxygen electrode 3 is provided on the other surface. Moreover, the fuel gas flow path f is formed on the surface facing the fuel electrode 2.
To form a rectangular plate shape. Further, a fuel gas flow path forming member 4 is provided to provide the oxygen gas flow path forming member 5 and an oxygen containing gas flow path forming member 5 is provided to provide the oxygen containing gas flow path s on the surface facing the oxygen electrode 3. is there. The fuel gas flow path constituting member 4 is formed of a conductive material in a state in which a large number of concave grooves functioning as fuel gas flow paths f are provided in parallel on one surface. Further, the fuel gas flow path constituting member 4 is attached to the fuel electrode 2 with the concave groove facing the fuel electrode 2. Further, the oxygen-containing gas flow path constituent member 5
Is formed of a conductive material in a state where a large number of concave grooves functioning as oxygen-containing gas flow paths s are provided in parallel on one surface. The oxygen-containing gas flow path constituting member 5 is attached to the oxygen electrode 3 in a state where the concave groove is orthogonal to the concave groove of the fuel gas flow path constituting member 4 and faces the oxygen electrode 3.

A plurality (six in this embodiment) of the cells C configured as described above are electrically connected in a state in which a plate-shaped conductive separator 6 is arranged between adjacent cells C. The sub-stacks Ts are configured by arranging them in a stacked state in the vertical direction in the state of being connected in series. And
A cell stack is formed by arranging a plurality of the sub-stacks Ts in the vertical direction in a state where the cooling unit 7 having conductivity is arranged between the adjacent sub-stacks Ts and in a state of being electrically connected in series. T is configured. or,
A current collector plate 8 is provided on each of the upper end surface and the lower end surface of the cell stack T.
Is attached in a state of being electrically connected. The cooling unit 7
It is configured to flow cooling water.

On each of the four side surfaces of the cell stack T,
The box-shaped member 9 having one surface opened is attached in an airtight state with its opening facing the side surface of the cell stack T. Then, the inside of the box-shaped member 9 attached to the side surface where one end of each of the fuel gas flow paths f opens is used as a fuel gas supply path 10 that communicates with each of the fuel gas flow paths f, and the other end of each of the fuel gas flow paths f The fuel gas discharge passage 11 that communicates the inside of the box-shaped member 9 attached to the side surface where the
It is configured to. Further, the inside of the box-shaped member 9 attached to the side surface where one end of each of the oxygen-containing gas flow paths s opens is used as an oxygen-containing gas supply path 12 that communicates with each of the oxygen-containing gas flow paths s. The insides of the box-shaped members 9 attached to the side surfaces of which the other ends thereof are open are configured to serve as oxygen-containing gas discharge passages 13 that communicate with the oxygen-containing gas passages s.

The fuel gas containing hydrogen gas is supplied to the fuel gas supply passage 10 through the fuel gas supply pipe 16 to flow the fuel gas through the fuel gas passage f of each cell C, and then the fuel gas discharge passage And the oxygen-containing gas supply pipe 2
1 to supply the air as the oxygen-containing gas to the oxygen-containing gas supply passage 12 so that the air flows through the oxygen-containing gas passage s of each cell C, and then is discharged to the oxygen-containing gas discharge passage 13. There is. Then, in each cell C, hydrogen in the fuel gas and oxygen in the air are electrochemically reacted to obtain direct-current power. The electromotive force of each cell C is about 0.65 V, and the cell C
By constructing the cell stack T by connecting 0 to 300 cells in series, the output voltage required for practical use is obtained.

Exhaust fuel gas discharged to the fuel gas discharge passage 11 is a heat source of a reformer (not shown) for reforming a raw fuel gas such as natural gas into a fuel gas containing hydrogen gas. That is, it is used as a combustion gas for a burner (not shown) for heating the reformer. The exhaust air exhausted to the oxygen-containing gas exhaust passage 13 is used as a heat source for air conditioning, hot water supply, etc. by recovering exhaust heat.

Next, a method for detecting a defective cell C in the cell stack T will be described with reference to FIGS. 3 and 4. First, the defective cell C is selected from the cell stack T.
A configuration of a device for detecting (hereinafter, abbreviated as a detection device) will be described. The terminals 14 for voltage measurement are electrically connected to the cells C at both ends of each sub-stack Ts. The terminal 14 is sandwiched between the cell C at the end of the sub-stack Ts and the cooling unit 7, and the terminal 14 is sandwiched between the cell C at the end of the sub-stack Ts and the current collector plate 8. It is electrically connected to the terminal 14. Each of the terminals 14 is connected to a multi-input voltmeter 15 so that the output voltage of each sub-stack Ts can be measured. Therefore, the sub-stack Ts corresponds to the block B composed of one or more cells C.

A hydrogen gas supply pipe 17 and a carbon dioxide gas supply pipe 18 are communicatively connected to a fuel gas supply pipe 16 for supplying a fuel gas to the fuel gas supply passage 10, and are connected to the fuel gas supply passage 10. A gas obtained by mixing hydrogen gas and carbon dioxide gas is supplied as a fuel gas. The hydrogen gas supply pipe 17 is provided with a proportional valve 19, and the carbon dioxide gas supply pipe 18 is provided with a proportional valve 20. Then, the fuel utilization rate and the hydrogen gas concentration in the fuel gas can be adjusted by adjusting the opening of each of the proportional valve 19 and the proportional valve 20. The fuel utilization rate increases as the supply amount of fuel gas decreases.

Further, the oxygen-containing gas supply pipe 21 for supplying the oxygen-containing gas to the oxygen-containing gas supply passage 12 is connected to the oxygen gas supply pipe 22 and the nitrogen gas supply pipe 23 so as to communicate with each other. On the other hand, a gas obtained by mixing oxygen gas and nitrogen gas is supplied as an oxygen-containing gas. The oxygen gas supply pipe 22 is provided with a proportional valve 24, and the nitrogen gas supply pipe 23 is provided with a proportional valve 25. The oxygen utilization rate and the oxygen gas concentration in the oxygen-containing gas can be adjusted by adjusting the opening of each of the proportional valve 24 and the proportional valve 25.
The oxygen utilization rate increases as the supply amount of the oxygen-containing gas decreases.

In the figure, 26 is a flow meter for detecting the flow rate of the fuel gas flowing through the fuel gas supply pipe 16, and 27 is
It is a flow meter that detects the flow rate of the oxygen-containing gas flowing through the oxygen-containing gas supply pipe 21. Further, 28 is a gas analyzer for measuring the hydrogen gas concentration in the fuel gas flowing through the fuel gas supply pipe 16 and the oxygen concentration in the oxygen-containing gas flowing through the oxygen-containing gas supply pipe 21. Further, 29 is a load device that consumes the output power of the phosphoric acid fuel cell, and the load device 29 is a load equivalent to the rated state of the phosphoric acid fuel cell.

Next, a method of detecting a defective cell C using the detecting device constructed as described above will be described. [First Detection Method] Based on the measurement information of the gas analyzer 28, while maintaining the hydrogen concentration at the normal operation value, the flow meter 26
Based on the detection information of 1, the opening of each of the proportional valve 19 and the proportional valve 20 is adjusted so that the fuel utilization rate becomes a value close to the operation limit value. For example, the hydrogen concentration is adjusted to 65%.
Further, as in the example shown in FIG. 5, when the normal operating value of the fuel utilization rate is 80% and the operating limit value is 95%, the fuel utilization rate is 90%.
Adjust to ~ 94%. And, the fuel utilization rate is 90-
The output voltage change rate of each of the blocks B at the time of about 94% with respect to the normal operation is measured, and the block B having the output voltage change rate of the set value or more is determined to be defective. The defective block B includes a cell C having a poor equidistribution of the fuel gas.

[Second Detection Method] While maintaining the fuel utilization rate to the normal operation value based on the detection information of the flow meter 26, the hydrogen concentration is made higher than the normal operation value based on the measurement information of the gas analyzer 28. Thus, the proportional valve 19 and the proportional valve 20
Adjust the opening of each. For example, the fuel utilization rate is adjusted to 80%. Further, as in the example shown in FIG. 6, when the normal operation value of the hydrogen concentration is 65%, the hydrogen concentration is increased to 100%. Then, the output voltage change rate of each block B when the hydrogen concentration is made higher than the normal operation value with respect to the normal operation is measured, and the block B having the output voltage change rate of the set value or more is determined to be defective. The defective block B includes a cell C having poor gas diffusivity of fuel gas.

[Third Detection Method] The fuel utilization rate is made higher than the normal operation value based on the detection information of the flow meter 26, and the hydrogen concentration is made higher than the normal operation value based on the measurement information of the gas analyzer 28. The opening of each of the proportional valve 19 and the proportional valve 20 is adjusted so as to reduce the opening. For example, as in the example shown in FIG. 5, when the normal operating value of the fuel utilization rate is 80% and the operating limit value is 95%, the fuel utilization rate is adjusted to 90%.
Further, for example, as in the example shown in FIG. 6, when the normal operation value of the hydrogen concentration is 65%, the hydrogen concentration is reduced to 50%.
Block B when the fuel utilization rate is higher than the normal operation value and the hydrogen concentration is lower than the normal operation value
The output voltage change rate for each normal operation is measured, and the block B having the output voltage change rate equal to or higher than the set value is determined to be defective. The defective block B includes a cell C having poor gas isotropy or gas diffusibility of the fuel gas.

[Fourth Detection Method] The oxygen utilization rate is close to the operation limit value based on the detection information of the flow meter 27 while maintaining the oxygen concentration at the normal operation value based on the measurement information of the gas analyzer 28. The opening of each of the proportional valve 24 and the proportional valve 25 is adjusted so that the value becomes a value. For example, the oxygen concentration is 21%
Adjust to. Further, as in the example shown in FIG. 7, when the normal operating value of the oxygen utilization rate is 60% and the operating limit value is 80%, the oxygen utilization rate is adjusted to about 70 to 79%. Then, the output voltage change rate in each of the blocks B when the oxygen utilization rate is set to about 70 to 79% with respect to the normal operation is measured, and the block B having the output voltage change rate of the set value or more is determined to be defective.
The defective block B includes a cell C having a poor gas isotropic distribution of the oxygen-containing gas.

[Fifth Detection Method] While maintaining the oxygen utilization rate at the normal operation value based on the detection information of the flow meter 27, the oxygen concentration is made higher than the normal operation value based on the measurement information of the gas analyzer 28. So that the proportional valve 24 and the proportional valve 25
Adjust the opening of each. For example, the oxygen utilization rate is adjusted to 60%. Further, as in the example shown in FIG. 8, when the normal operating value of the oxygen concentration is 21%, the oxygen concentration is increased to 100%. Then, the output voltage change rate in each of the blocks B when the oxygen concentration is made higher than the normal operation value with respect to the normal operation is measured, and the block B having the output voltage change rate of the set value or more is determined to be defective. The defective block B includes a cell C having poor gas diffusivity of oxygen gas.

[Sixth Detection Method] The oxygen utilization rate is made higher than the normal operation value based on the detection information of the flow meter 27, and the oxygen concentration is made higher than the normal operation value based on the measurement information of the gas analyzer 28. The opening of each of the proportional valve 24 and the proportional valve 25 is adjusted so as to reduce the opening. For example, as in the example shown in FIG. 7, when the normal operating value of the oxygen utilization rate is 60% and the operating limit value is 80%, the oxygen utilization rate is adjusted to 75%.
Further, for example, as in the example shown in FIG. 8, when the normal operation value of the oxygen concentration is 21%, the oxygen concentration is reduced to 10%.
Block B when the oxygen utilization rate is higher than the normal operation value and the oxygen concentration is lower than the normal operation value
The output voltage change rate for each normal operation is measured, and the block B having the output voltage change rate equal to or higher than the set value is determined to be defective. The defective block B includes a cell C having a poor gas isotropy or gas diffusivity of the oxygen-containing gas.

In each of the above inspection methods, the defective block B is replaced with a new block B. Alternatively, in the defective block B, the output voltage change rate of each cell C may be measured to identify the defective cell, and the defective cell may be replaced with a new cell C.

When the inspection for detecting the defective cell C in the cell stack T is performed, the defective block is detected by performing the first, second, fourth and fifth detection methods. Alternatively, defective blocks are detected by performing the second, third, fifth and sixth detection methods.

[Other Embodiments] Next, other embodiments will be listed. In the above embodiment, the case where one block B is configured by one sub-stack Ts has been exemplified, but instead of this, it is configured so that a plurality of blocks B are present in one sub-stack Ts. Is also good.

In the above embodiment, the block B is composed of a plurality of cells C, but the block B may be composed of one cell C instead.

When performing the inspection for detecting the defective cell C in the cell stack T, the above-mentioned first to sixth
Of the inspection methods described above, which inspection method is selected and executed can be variously changed in addition to the above-described embodiment. For example,
Since the third and sixth inspection methods can detect both the cell C having a poor gas isotropy and the cell C having a poor gas diffusivity, the inspection should be performed by a combination of the third and sixth inspection methods. You can In this case, the number of inspection methods to be performed is reduced, so that the inspection time is shortened and the inspection cost is reduced.

Further, an inspection method (first, second and third inspection methods) for inspecting the gas isotropy or gas diffusivity of the fuel gas, an inspection for inspecting the gas isochoricity or gas diffusivity of the oxygen-containing gas Only one of the methods (fourth, fifth and sixth inspection methods) may be performed. When only the inspection method for inspecting the gas isotropy or gas diffusivity of the fuel gas is performed, any one or a plurality of the first, second and third inspection methods can be performed.
When performing only the inspection method for inspecting the gas isotropy or gas diffusivity of the oxygen-containing gas, perform any one or more of the fourth, fifth and sixth inspection methods. You can

By performing all of the first, second, third, fourth, fifth and sixth inspection methods, highly accurate inspection can be performed.

It should be noted that although reference numerals are given in the claims for convenience of comparison with the drawings, the present invention is not limited to the configurations of the accompanying drawings by the entry.

[Brief description of drawings]

FIG. 1 is an exploded perspective view of a phosphoric acid fuel cell sub-stack.

FIG. 2 is a perspective view of a phosphoric acid fuel cell.

FIG. 3 is a side view of a phosphoric acid fuel cell stack.

FIG. 4 is a block diagram of a defective cell detection device for a phosphoric acid fuel cell.

FIG. 5 is a diagram showing a correlation between a fuel utilization rate and a cell output voltage.

FIG. 6 is a diagram showing a correlation between hydrogen gas concentration and cell output voltage.

FIG. 7 is a diagram showing a correlation between oxygen utilization rate and cell output voltage.

FIG. 8 is a diagram showing a correlation between oxygen gas concentration and cell output voltage.

[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 C Cell B Block

Claims (6)

[Claims] 1. A phosphoric acid electrolyte layer (1) is provided with a fuel electrode (2) on one surface and an oxygen electrode (3) on the other surface, and a fuel gas containing hydrogen gas flows therethrough. A surface facing the fuel electrode (2) with a fuel gas channel (f) and a surface facing the oxygen electrode (3) with an oxygen-containing gas channel (s) through which an oxygen-containing gas containing oxygen gas flows. In a phosphoric acid fuel cell in which a plurality of plate-shaped cells (C) provided in the above are juxtaposed in a stacked state, a block (B) composed of one cell (C) or a plurality of cells (C) The fuel utilization rate, which indicates the proportion of the fuel gas supplied to each fuel gas flow path (f) that was used in the cell reaction at each fuel electrode (2), is close to the operating limit value from the value during normal operation. The output voltage change of each of the blocks (B) at the time of normal operation Measured, bad cell detection method of the phosphoric acid fuel cell output voltage change is more than the set value of the block (B) and poor. 2. A fuel gas (2) having a fuel electrode (2) on one surface of the phosphoric acid electrolyte layer (1) and an oxygen electrode (3) on the other surface, and a fuel gas containing hydrogen gas flows therethrough. A surface facing the fuel electrode (2) with a fuel gas channel (f) and a surface facing the oxygen electrode (3) with an oxygen-containing gas channel (s) through which an oxygen-containing gas containing oxygen gas flows. In a phosphoric acid fuel cell in which a plurality of plate-shaped cells (C) provided in the above are juxtaposed in a stacked state, a block (B) composed of one cell (C) or a plurality of cells (C) And the hydrogen gas concentration in the fuel gas supplied to the fuel gas flow path (f) is made larger than the value during normal operation, and the output of each of the blocks (B) at that time during normal operation The voltage change is measured, and the line (B) whose output voltage change is equal to or higher than the set value becomes defective Bad cell detection method type fuel cell. 3. A phosphoric acid electrolyte layer (1) is provided with a fuel electrode (2) on one surface and an oxygen electrode (3) on the other surface, and a fuel gas containing hydrogen gas flows therethrough. A surface facing the fuel electrode (2) with a fuel gas channel (f) and a surface facing the oxygen electrode (3) with an oxygen-containing gas channel (s) through which an oxygen-containing gas containing oxygen gas flows. In a phosphoric acid fuel cell in which a plurality of plate-shaped cells (C) provided in the above are juxtaposed in a stacked state, a block (B) composed of one cell (C) or a plurality of cells (C) The fuel gas flow rate (f) supplied to each fuel gas flow path (f), and the fuel utilization rate indicating the ratio used in the cell reaction at each fuel electrode (2) is made larger than the value during normal operation, In addition, make the hydrogen gas concentration in the fuel gas smaller than the value during normal operation, and Block (B) measures the output voltage changes in each for normal operation, bad cell detection method of the phosphoric acid fuel cell output voltage change is more than the set value of the block (B) and poor. 4. A phosphoric acid electrolyte layer (1) is provided with a fuel electrode (2) on one surface and an oxygen electrode (3) on the other surface, and a fuel gas containing hydrogen gas flows therethrough. A surface facing the fuel electrode (2) with a fuel gas channel (f) and a surface facing the oxygen electrode (3) with an oxygen-containing gas channel (s) through which an oxygen-containing gas containing oxygen gas flows. In a phosphoric acid fuel cell in which a plurality of plate-shaped cells (C) provided in the above are juxtaposed in a stacked state, a block (B) composed of one cell (C) or a plurality of cells (C) The oxygen utilization rate, which indicates the proportion of the oxygen gas in the oxygen-containing gas supplied to each oxygen-containing gas flow channel (s), used in the battery reaction at each oxygen electrode (3) during normal operation From the value to near the operation limit value, and at the time of normal operation of each of the blocks (B) at that time Outputs the voltage change is measured, bad cell detection method of the phosphoric acid fuel cell output voltage change is more than the set value of the block (B) and poor against. 5. A phosphoric acid electrolyte layer (1) is provided with a fuel electrode (2) on one surface and an oxygen electrode (3) on the other surface, and a fuel gas containing hydrogen gas flows therethrough. A surface facing the fuel electrode (2) with a fuel gas channel (f) and a surface facing the oxygen electrode (3) with an oxygen-containing gas channel (s) through which an oxygen-containing gas containing oxygen gas flows. In a phosphoric acid fuel cell in which a plurality of plate-shaped cells (C) provided in the above are juxtaposed in a stacked state, a block (B) composed of one cell (C) or a plurality of cells (C) And the oxygen gas concentration in the oxygen-containing gas supplied to the oxygen-containing gas flow channel (s) is made larger than the value during normal operation, and the block (B) at that time is in normal operation. Output voltage change is measured, and block (B) whose output voltage change is greater than the set value is determined to be defective. Bad cell detection method Berlin acid fuel cell. 6. A phosphoric acid electrolyte layer (1) is provided with a fuel electrode (2) on one surface and an oxygen electrode (3) on the other surface, and a fuel gas containing hydrogen gas flows therethrough. A surface facing the fuel electrode (2) with a fuel gas channel (f) and a surface facing the oxygen electrode (3) with an oxygen-containing gas channel (s) through which an oxygen-containing gas containing oxygen gas flows. In a phosphoric acid fuel cell in which a plurality of plate-shaped cells (C) provided in the above are juxtaposed in a stacked state, a block (B) composed of one cell (C) or a plurality of cells (C) The oxygen utilization rate, which indicates the proportion of the oxygen gas in the oxygen-containing gas supplied to each oxygen-containing gas flow channel (s), used in the battery reaction at each oxygen electrode (3) during normal operation Acid in the oxygen-containing gas supplied to the oxygen-containing gas flow channel (s), which is larger than the value The gas concentration is made smaller than the value during the normal operation, and the output voltage change of each of the blocks (B) at that time during the normal operation is measured, and the block (B) whose output voltage change is equal to or more than the set value is determined to be defective. Method for detecting defective cells in phosphoric acid fuel cell.