JPH11260385A - Fuel cell protection method, protection device, and fuel cell device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To simplify the structure of a protection device and to lower its cost by monitoring output voltage of at least one cell belonging to the lower part of a fuel cell layered product in a layer-built type fuel cell by means of a voltage measurement device and stopping operation of the fuel cell by means of a controller when the output voltage decreases below a predetermined value. SOLUTION: This fuel cell device is provided with a voltage measurement device 7 connected to at least one cell belonging to a lower part C of a fuel cell layered product in a cell main body 1 and measuring output voltage of this cell, and a controller 8 stopping operation of the fuel cell, when the voltage measured by the voltage measurement device 7 decreases below a predetermined reference value. When a the supply quantity of fuel gas is reduced abnormally, for example reduced to 87% in terms of a hydrogen using ratio, a cell voltage of the lower part C of the fuel cell layered product becomes 4 times or more of that in another part such as an upper part A, then this voltage is detected by means of the voltage measurement device 7, and the operation of the fuel cell is stopped by means of a controller 8.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for protecting a fuel cell, and more particularly to a method and an apparatus for protecting a fuel cell, which detect an abnormal decrease in a reactant gas during the operation of the fuel cell and stop the operation of the fuel cell, and the fuel. The present invention relates to a battery device.

[0002]

2. Description of the Related Art Conventionally, in a fuel cell, a protection device is provided to prevent the performance of the whole cell from being deteriorated or an accident from occurring due to deterioration or malfunction of a unit cell constituting the fuel cell. I have.

[0003] For example, Japanese Patent Application Laid-Open No. 63-264875 discloses that the concentration of carbon monoxide or carbon dioxide is measured on the upstream and downstream sides of a battery, and when this concentration exceeds a predetermined value,
A fuel cell protection device is described in which it is determined that there is oxidative degradation of battery carbon due to a gas cloth or gas defect, and the operation of the fuel cell is stopped. A device similar to this protection device is also described in JP-A-59-149660.

FIG. 3 is a block diagram showing a fuel cell disclosed in Japanese Patent Application Laid-Open No. 63-264875, in which a cell body is composed of a plurality of cells each holding an electrolyte between a pair of gas diffusion electrodes. 1 includes an oxidant supply / discharge system 2 and a fuel supply / discharge system 3
And a gas concentration detection device 4 for detecting carbon monoxide and carbon dioxide is connected to the oxidant supply / discharge system 2 on the downstream side of the battery main body 1. This gas concentration detection device 4
Are also connected to a fuel supply / discharge system 3 on the upstream and downstream sides of the battery body 1.

In such a conventional fuel cell, when an oxidant and a fuel are supplied to the cell body 1 through an oxidant supply / discharge system 2 and a fuel supply / discharge system 3, an electrochemical reaction occurs in the cell body 1. Occurs and power is generated. In the case of phosphoric acid type fuel cells, the carbonaceous material of the electrode may be oxidized when the battery deteriorates, gas crosses, gas deficiency, etc. occur. The abnormal reaction products of carbon monoxide and / or carbon dioxide are discharged into the exhaust gas of the discharge systems 2 and 3. The abnormal reaction product discharged to the oxidant supply / discharge system 2 is detected by the gas concentration detection device 4 and the operation of the fuel cell is stopped. In the fuel supply / discharge system 3, it is necessary to distinguish between carbon monoxide and carbon dioxide contained in the fuel before the reaction and carbon monoxide and carbon dioxide as abnormal reaction products. For this reason, the gas concentration detecting device 4 detects the gas concentration of carbon monoxide and / or carbon dioxide in the fuel gas in the fuel supply / discharge system 3 on the upstream side of the battery body 1 and the fuel supply on the downstream side of the battery body 1. The gas concentration of carbon monoxide and / or carbon dioxide in the exhaust system 3 is detected, and the presence of an abnormal reaction product is determined from the difference between these gas concentrations. If it is determined that an abnormal reaction is occurring, The operation of the fuel cell is stopped.

[0006] In the safety protection device for a laminated fuel cell described in Japanese Patent Application Laid-Open No. 60-54176, a unit battery showing the lowest battery voltage at the time of initial operation or periodic inspection, or a battery block containing the unit battery is used. Based on the knowledge gained from the experience that the battery always deteriorates fastest in subsequent operation, the battery with the lowest shared voltage is selected at the time of initial operation or inspection, and the voltage of the selected battery is The operation of the battery is stopped when the voltage becomes equal to or lower than the voltage immediately before the start of the polarization.

[0007]

In the conventional fuel cell shown in FIG. 3, it is required to use a detector which detects the gas concentration of carbon monoxide and carbon dioxide quickly and with high sensitivity. Even if a simple detector is realized, it takes time to sample and detect the abnormal reaction gas generated by the abnormal reaction in the battery, and when the abnormal reaction gas is detected, the carbonaceous material in the battery has already been detected. After the occurrence of an abnormality such as oxidation wear, there is a problem that an abnormal reaction cannot be prevented in advance.

[0008] Further, in Japanese Patent Application Laid-Open No. 60-54176, all the cells or a plurality of cells are determined in order to determine which cell or group of cells should be selected as having the lowest shared voltage. There is a problem that a large number of voltage measurement lines for measuring the voltage of the battery group must be set in advance.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problem. An abnormality is detected by a simple device before the battery is worn out as described above due to a shortage of fuel gas during operation, for example. An object of the present invention is to provide a stacked fuel cell protection method and protection device capable of stopping operation, and a fuel cell device provided with the protection device.

[0010]

In order to solve the above-mentioned problems, a fuel cell protection method according to claim 1 includes a plurality of cells stacked vertically, and includes a vertically upper, middle, and lower cells. In order to protect a stacked fuel cell including a fuel cell stack that can be divided into a plurality of cells and a gas supply header for supplying a reaction gas commonly to the plurality of cells of the fuel cell stack from abnormal operation. Monitoring the output voltage of at least one unit cell belonging to the lower part of the fuel cell stack, and stopping the operation of the fuel cell when the output voltage drops below a predetermined value. .

According to a second aspect of the present invention, there is provided a fuel cell protection device including a plurality of cells stacked vertically, which can be vertically divided into an upper portion, a middle portion, and a lower portion. An apparatus for protecting a stacked fuel cell from abnormal operation, comprising a gas supply header for supplying a reaction gas to the plurality of cells in common, wherein at least one of the fuel cells stacked under the lower part of the fuel cell stack A voltage measuring device connected to the cell and measuring an output voltage of the cell; and a control device for stopping the operation of the fuel cell when detecting that the output voltage has dropped below a predetermined value. I have.

According to a third aspect of the present invention, there is provided a fuel cell device including a plurality of cells stacked vertically, which can be vertically divided into an upper portion, a middle portion, and a lower portion. A gas supply header for supplying a reaction gas to the plurality of cells in common, and a voltage connected to at least one cell belonging to the lower part of the fuel cell stack to measure an output voltage of the cells. A measuring device;
A controller for stopping the operation of the fuel cell when detecting that the output voltage has dropped below a predetermined value, thereby protecting the stacked fuel cell from abnormal operation.

[0013]

According to the fuel cell protection method of the first aspect, when the fuel gas is abnormally reduced during the operation of the stacked fuel cell, the cell voltage of the stacked battery falls below the other parts. The output voltage of at least one unit cell belonging to the lower part of the fuel cell stack is monitored based on the phenomenon that the fuel gas becomes large, and when the output voltage falls below a predetermined value, it is determined that the fuel gas has abnormally decreased. By judging and stopping the operation of the fuel cell, the fuel cell can be protected before an abnormality occurs.

In the fuel cell protection device according to the second aspect, the output voltage of at least one unit cell belonging to the lower part of the fuel cell stack is measured by a voltage measuring device, and the output voltage falls below a predetermined value. When the operation is detected, the operation of the fuel cell can be stopped by the control device to protect the fuel cell. In the fuel cell device according to the third aspect, when the output voltage of at least one unit cell belonging to the lower part of the fuel cell stack is measured by the voltage measurement device and it is detected that the output voltage has dropped below a predetermined value. Control unit stops operation of fuel cell and protects fuel cell

[0015]

FIG. 1 schematically shows a fuel cell device according to an embodiment of the present invention. The fuel cell device has a stacked cell body 1 including a number of unit cells. The cell body 1 includes a fuel cell stack (not shown) including a large number of cells stacked in a vertical direction, and a gas supply for supplying a reaction gas commonly to the plurality of cells of the fuel cell stack. It has a header (not shown), and has a general structure in which the oxidant supply / discharge system 2 and the fuel supply / discharge system 3 are connected. Battery body 1
For the sake of convenience of the description of the present invention, in FIG. 1, the battery body 1 is vertically divided into three parts vertically by a two-dot chain line into an upper part A, a middle part B and a lower part C. This is not to say that the overall height of the fuel cell stack of the cell body 1 is only shown in three equal parts, and the oxidant supply header and the fuel supply header are common to each cell. . An electric output line 5 is provided on the battery body 1 thus configured.
The load 6 is connected via the.

The fuel cell device of the present invention is connected to at least one unit cell belonging to the lower part C of the fuel cell stack of the cell body 1, for example, the lowest cell of the fuel cell stack, and connected to this unit. A voltage measuring device 7 for measuring the output voltage of the battery, and a control device 8 for stopping the operation of the fuel cell when the voltage measured by the voltage measuring device 7 falls below a predetermined reference value set in advance. . The predetermined reference value set in advance is a value lower than the battery voltage of the lower part C obtained when the operation state of the fuel cell is not abnormal, and higher than the battery voltage of the lower part C at the time of occurrence of the fuel gas supply abnormality.

If the fuel gas supplied from the fuel supply / discharge system 2 to the cell body 1 decreases for some reason during the operation of the fuel cell device, the output voltage generated by each cell decreases. According to the present invention, when the flow rate of the fuel gas with respect to the load is abnormally reduced, that is, when the hydrogen utilization rate is abnormally high, at least the lower part belonging to the vertically divided fuel cell stack into three equal parts is provided. It is based on newly obtained experimental results that the voltage drop of the output voltage of one cell is significantly greater than the voltage drop in the other part.

FIG. 2 shows a distribution curve of the amount of voltage change obtained by this experiment. In the experiment, a stacked fuel cell in which 324 cells having a common gas header were stacked was used, and the fuel was 61% H ₂ -15% CO ₂ -24% H _20.
Using a simulated fuel gas having the following composition, the distribution of the change in the cell output voltage in the stacking direction was examined by changing the fuel gas flow rate, that is, the hydrogen utilization rate. When the hydrogen utilization rate was changed from 55% to 75%, there was no difference in the change in the battery voltage depending on the position. However, when the hydrogen utilization rate was changed from 75% to 87%, a distribution curve of the voltage change amount as shown in FIG. 2 was obtained. In FIG. 2, when the fuel cell stack is vertically divided into three equal parts and divided into an upper part A, a middle part B, and a lower part C, the amount of decrease in the cell output voltage in the lower part C is lower than the upper part A and the middle part B. The remarkably large value was about four times larger than the amount of decrease in the battery output voltage. From this, it is clear that if at least one of the cells belonging to the lower part C of the fuel cell stack is selected and the decrease in the battery voltage is monitored, the abnormal decrease in the fuel gas can be reliably detected.

As described above, in the fuel cell device of the present invention, the flow rate of the fuel gas with respect to the load is reduced due to the irregular operation of the power generation system or the like, and the substantial hydrogen utilization rate in the battery body 1 is, for example, 75%. In this case, the change in the battery voltage does not change depending on the position, and the battery voltage at the lower part C of the battery does not significantly decrease as shown in FIG. Therefore, the battery voltage is higher than the predetermined reference value, and the operation of the control device 8 does not stop the operation of the fuel cell.

On the other hand, the fuel gas supply amount decreases abnormally,
For example, when the hydrogen utilization rate reaches 87%, the battery voltage of the lower part C of the fuel cell stack becomes about four times or more higher than that of the other part, for example, the battery voltage of the upper part A, and this voltage is detected by the voltage measuring device 7, It is detected that the voltage has become lower than a predetermined reference voltage value set in advance, and the control device 8 stops the operation of the fuel cell.

As described above, the battery to be subjected to voltage measurement in the present invention may be a single cell belonging to the lower part C, an arbitrary number of plural cells, or the lowermost cell may be selected. Alternatively, an adjacent battery may be selected or a non-adjacent battery may be selected. Further, the present invention can be applied to a power generation system including a plurality of battery bodies.

[0022]

As described above, according to the present invention, at least one member belonging to the lower portion of the fuel cell stack of the stacked fuel cell is provided.
The output voltages of the two cells are monitored by a voltage measurement device, and when the output voltage drops below a predetermined value, the operation of the fuel cell is stopped by the control device. Therefore, the structure of the protection device is simple and inexpensive, and can be installed without changing the design of the existing fuel cell. In particular, since the battery whose voltage is to be measured can be selected only by the position, it is extremely easy to select the battery to be measured. Also, since the battery voltage is detected instead of detecting the gas concentration due to the abnormal reaction, the abnormality is detected immediately before the abnormal reaction occurs and immediately after the abnormal decrease in the fuel gas occurs. Can be detected.

Further, according to the present invention, since the voltage drop of the unit cell on the lower side of the fuel cell stack in which the voltage drop due to the fuel gas shortage appears quickly as an index of abnormality, the fuel gas shortage is left unchecked. As a result, carbon, which is a constituent material of the fuel cell itself such as a unit cell or a separator, becomes “C + H ₂ O → CO” or “C + 2H ₂ O → CO”.
₂ ), hydrogen is generated while being consumed by the reaction, and this hydrogen is converted into hydrogen ions as in “H ₂ → 2H ⁺ + 2e ⁻ ” and used in the cell reaction, causing irreversible damage to the fuel cell itself. Fatal damage to the fuel cell itself, which would otherwise be caused, can be quickly avoided.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing one embodiment of a fuel cell device provided with a fuel cell protection device of the present invention.

FIG. 2 is a graph showing a distribution of a voltage change amount due to an abnormal decrease in a fuel gas supply amount of a stacked fuel cell, that is, an abnormal increase in a hydrogen utilization rate.

FIG. 3 is a schematic view showing a conventional fuel cell power generation system.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Battery main body 2 Fuel supply / discharge system 3 Oxidant supply / discharge system 7 Voltage measuring device 8 Control device

Claims (3)

[Claims] 1. A fuel cell stack including a plurality of cells stacked vertically and divided vertically into an upper part, a middle part, and a lower part; and a common cell for the plurality of cells of the fuel cell stack. A fuel cell protection method for protecting a stacked fuel cell provided with a gas supply header for supplying a reaction gas from abnormal operation, the method comprising: protecting at least one unit cell belonging to the lower portion of the fuel cell stack. A fuel cell protection method, comprising: a step of monitoring an output voltage; and a step of stopping operation of the fuel cell when the output voltage falls below a predetermined value. 2. A fuel cell stack including a plurality of cells stacked vertically and divided vertically into upper, middle and lower parts, and a common fuel cell for the plurality of cells of the fuel cell stack. A fuel cell protection device for protecting a stacked fuel cell provided with a gas supply header for supplying a reaction gas from abnormal operation, wherein the at least one unit cell belonging to the lower part of the fuel cell stacked body is provided. A fuel cell protection device, comprising: a connected voltage measurement device for measuring the output voltage of the unit cell; and a control device for stopping the operation of the fuel cell when detecting that the output voltage has dropped below a predetermined value. . 3. A fuel cell stack including a plurality of cells stacked vertically and divided vertically into upper, middle and lower parts, and a common cell for the plurality of cells of the fuel cell stack. A gas supply header for supplying a reaction gas, a voltage measuring device connected to at least one unit cell belonging to the lower part of the fuel cell stack, and measuring an output voltage of the unit cell; A fuel cell device comprising: a control device for stopping the operation of the fuel cell when detecting a decrease below a predetermined value and protecting the stacked fuel cell from abnormal operation.