JPH08213038A - Control method of fuel cell power generation device - Google Patents

Abstract

PURPOSE: To provide a control method by which protective operation can be safely performed without damaging a fuel cell main body even when a shortage of a supply oxygen is caused. CONSTITUTION: Unit cells 5 formed by sandwiching an electrolyte layer 2 by a fuel electrode 3 and an air electrode 4 are layered by plural layers by interposing a separator 6, and are formed by properly incorporating a cooling plate 7. In this fuel cell main body 1, an electric potential difference between a fuel gas outlet voltage sensor 8 and a fuel gas outlet voltage sensor 9 arranged in the outlet vicinity and the inlet vicinity of fuel gas of the fuel electrode 3 is measured. When a measured value exceeds a preset value A, a control signal is sent to a control valve 14 from a control device 12, and a flow rate of raw material fuel to be sent to a reforming system reactor 13 is increased. When the measured valve further exceeds a preset value B higher than A, a value of a load 10 is reduced by a control signal from the control device 12, and when the measured value further exceeds a preset value C higher than B, a load switch 11 is cut off by a control signal from the control device 12, and operation of a device is stopped.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for controlling a fuel cell power generator which sends a reaction gas to a fuel electrode and an air electrode sandwiching an electrolyte layer to obtain electric power by an electrochemical reaction.

[0002]

2. Description of the Related Art FIG. 2 is a schematic diagram showing the basic structure of a general fuel cell power generator. As shown in the figure, the fuel cell power generator includes a fuel cell main body 1 and a reaction gas supply for supplying reformed fuel gas obtained by reforming raw fuel in a reforming system reactor 13 and air to the fuel cell main body 1. System, a control inverter 20 that converts direct-current power obtained by an electrochemical reaction in the fuel cell main body 1 into alternating-current power and sends it to the load 10, and more mainly,
The cooling water system 30 removes heat generated by the electrochemical reaction.

FIG. 3 is a schematic diagram showing the basic structure of the fuel cell main body 1 and a control method of a fuel cell power generator which has been conventionally used. The fuel cell main body 1 includes a separator 6 and a unit cell 5 in which an electrolyte layer 2 is sandwiched between a fuel electrode 3 having a fuel gas passage hole 31 and an air electrode 4 having an air passage hole 41.
A plurality of layers are laminated with the interposing of the above, and the cooling plate 7 is appropriately incorporated therein. The reformed fuel gas is sent from one side surface of the stacked fuel cell body 1 to the opposite side surface through the fuel gas flow hole 31, and the air is supplied from one side surface orthogonal to these side surfaces. Air flow hole 41 to the other side
Sent through. When the reformed fuel gas and the air are allowed to flow in this manner, a DC power is generated by an electrochemical reaction in each unit cell 5 to generate a DC voltage between the fuel electrode 3 and the air electrode 4, and the cells are stacked. In the fuel cell main body 1, a DC voltage in which the DC voltage of each single cell is superimposed is obtained.

As described above, direct-current power can be obtained by passing the reformed fuel gas and air through the fuel cell body 1. However, in order to obtain normal power generation performance, the reformed fuel gas is used to provide a predetermined amount. Amount of hydrogen needs to be supplied. The amount of hydrogen supplied by the reformed fuel gas depends on the gas flow rate of the raw fuel supplied to the reforming reactor 13 and the reforming rate of the raw fuel in the reforming reactor 13 shown in FIG. Determined. Normal,
A method is used in which the operating conditions of the reforming reactor 13 are kept constant to avoid fluctuations in the reforming rate of the raw fuel, and the gas flow rate of the raw fuel is adjusted by a control valve to control the amount of hydrogen supplied. However, if the reforming rate of the raw fuel in the reforming reactor 13 is lowered for some reason, the supplied hydrogen amount is reduced, and the fuel cell body 1 may be operated in a hydrogen-deficient state. In particular, when operating in a state where the supplied hydrogen amount is extremely short, in order to make up for the shortage, the carbon material forming the fuel electrode 3 is

[0005]

## STR1 ## _{C + 2H 2 O → CO 2} + 4H + + 4e - In the reaction occurs as shown, the battery characteristic is subject to permanent damage. Therefore, in the conventional fuel cell power generator, in order to prevent such a situation from occurring, as shown in FIG. 3, the potential difference between the stacks of a plurality of single cells is constantly monitored, and this potential difference is constantly monitored. When the voltage drops below a predetermined voltage, a control signal is issued from the control device 15 to shut off the load switch 11 connected to the load 10 to stop the power generation device.

[0006]

As described above, if the method of constantly monitoring the potential difference of the laminated body of the single cells and stopping the power generator when the potential difference falls below a predetermined voltage is adopted,
Even if the reforming rate of the raw fuel is lowered for some reason, it is possible to prevent the fatal damage to the fuel cell main body 1 due to the shortage of the supplied hydrogen amount.

However, even in the above method, in order to detect that the potential difference drops below a predetermined voltage, it is necessary that the hydrogen utilization rate in a single cell is as high as 95% or more, and therefore, protection is required. There is a problem that the fuel cell main body is not a little damaged before the operation is performed. Further, in the fuel cell power generator, the cell voltage often decreases with the aging, but it is difficult to distinguish between the decrease in the potential difference due to the aging and the decrease in the potential difference due to the shortage of the supplied hydrogen amount. Although it can be used for detecting the shortage of the amount of hydrogen supply at the initial stage of the operation of the battery power generator, there is a drawback that it cannot be detected effectively as the operation progresses.

The present invention has been made in view of the above problems, and an object thereof is to keep safety without damaging the fuel cell body even when the amount of supplied hydrogen is insufficient as described above. Another object of the present invention is to provide a method of controlling a fuel cell power generation device capable of performing a protective operation.

[0009]

In order to achieve the above object, in the present invention, a fuel cell constructed by stacking a plurality of single cells in which an electrolyte layer is sandwiched between a fuel electrode and an air electrode. In a fuel cell power generator that supplies fuel gas to the fuel electrode of the main body and air to the air electrode to obtain electric power by an electrochemical reaction, measure the potential difference in the same electrode surface of the fuel cell main body, and measure the measured potential difference. The power generation state quantity is controlled according to the size.

Further, the potential difference in the same electrode plane is
The potential difference is within the same electrode surface of the fuel electrode. Further, the potential difference within the same electrode surface is defined as the potential difference between the vicinity of the fuel gas inlet and the vicinity of the fuel gas outlet of the fuel electrode. Further, as the power generation state quantity to be controlled, the flow rate of the raw fuel supplied to the reforming system reactor to generate the fuel gas, and the load current flowing in the load connected between both electrodes of the fuel cell main body At least one of the above is used.

[0011]

When the amount of hydrogen supplied to the stacked fuel cell bodies is insufficient due to a reduction in the reforming rate of the raw fuel or a decrease in the raw fuel flow rate, the amount of hydrogen at the fuel gas outlet side of the fuel electrode is reduced. Since the current decreases and the current concentrates on the fuel gas inlet side of the fuel electrode, the distribution of the potential difference on the same electrode surface changes. Therefore, by measuring the potential difference at a predetermined position on the same electrode surface, the shortage of the supplied hydrogen amount can be detected, and by controlling the power generation state amount of the fuel cell power generation device using this measurement value, the fuel cell power generation device is safe. Can be operated to protect.

Particularly, if the potential difference is measured within the same electrode surface of the fuel electrode, the potential difference due to the shortage of the amount of hydrogen supplied at that electrode can be directly measured, so that it can be detected more accurately. Moreover, if the potential difference between the vicinity of the fuel gas outlet and the vicinity of the fuel gas inlet is measured, the change in the potential difference due to the shortage of the supplied hydrogen amount can be measured with higher accuracy, so that the shortage of the supplied hydrogen amount can be detected with higher accuracy. Become.

Also, if the flow rate of the raw fuel supplied to the reforming reactor for producing the fuel gas is used as the power generation state quantity controlled based on the detection signal of the shortage of the supplied hydrogen quantity, the supplied hydrogen quantity is By controlling the flow rate of the raw fuel to increase as well as detecting the shortage, the shortage of the supplied hydrogen amount will be resolved. Further, if the load current flowing through the load connected between the electrodes of the fuel cell body is used as the power generation state amount to be controlled, the load current decreases with the detection of the shortage of the supplied hydrogen amount,
Alternatively, the protection operation can be safely performed by performing control such as interruption. In addition, if the raw fuel flow rate and the load current are controlled together, a safer protection operation can be performed.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a control method for a fuel cell power generator according to the present invention will be described below with reference to the drawings. FIG. 1 is a schematic diagram showing a basic configuration of a fuel cell body 1 and a control method according to the present invention. The basic configuration of the fuel cell body 1 shown in the figure is
The same components as those shown in FIG. 3 are already described, and the components having the same functions are designated by the same reference numerals, and the duplicated description will be omitted.

One of the differences between the control method according to the embodiment of the present invention shown in FIG. 1 and the control method according to the conventional example shown in FIG. 3 lies in the detection method of the shortage of the supplied hydrogen amount. This is a method of protection operation performed based on the detected signal. As a method of detecting the shortage of the amount of supplied hydrogen, in the conventional example, the potential difference between the stacked bodies of a plurality of single cells is constantly monitored, and a method of detecting the shortage of the amount of supplied hydrogen depending on whether or not the potential difference drops below a predetermined voltage. However, in the embodiment of the present invention shown in FIG. 1, the fuel gas of the fuel electrode 3 having the same potential as the potential measured by the fuel gas outlet voltage sensor 8 installed near the fuel gas outlet of the fuel electrode 3. A method is used in which a potential difference from the potential measured by the fuel gas inlet voltage sensor 9 installed near the inlet is obtained, and when the potential difference exceeds a predetermined voltage, it is detected that the amount of supplied hydrogen is insufficient. In this method, as described above, the potential difference between the two points where the fluctuation of the potential caused by the shortage of the supplied hydrogen amount is most noticeable is measured, so that the shortage of the supplied hydrogen amount can be effectively detected. . When the amount of supplied hydrogen decreases due to a decrease in the flow rate of raw fuel and a decrease in the reforming rate, and the hydrogen utilization rate in a single cell exceeds 90%,
It has been confirmed that the measured potential difference exceeds 10 mV. In order to detect the shortage of the supplied hydrogen amount by the method of the conventional example, it was necessary for the hydrogen utilization rate to exceed 95%, but in this embodiment, it is detected if it exceeds 90%, so it can be detected early. It is possible to perform the protective operation without causing a large damage to the battery body.

Next, as a protection operation performed based on the detected signal, in the conventional example, a control signal is issued from the control device 15 to shut off the load switch 11 connected to the load 10 to stop the power generation device. However, in the embodiment of FIG. 1, a control signal is issued from the control device 12 in accordance with the level of the measured potential difference to adjust the raw fuel flow rate or the load condition. The protective action of is adopted. That is, in the embodiment of FIG. 1, when the potential difference measured by the fuel gas outlet voltage sensor 8 and the fuel gas inlet voltage sensor 9 exceeds 8 mV, the control valve 14 is adjusted and supplied to the reforming system reactor 13. When the measured potential difference rises and exceeds 12 mV, the value of the load current flowing through the load 10 is reduced by 20%, and when the potential difference rises and exceeds 20 mV, the load switch 11 increases. The multi-stage protection operation is adopted to shut off the power and stop the power generation device.

As described above, if the method for controlling the fuel cell power generator shown in this embodiment is used, it is possible to detect a decrease in the amount of hydrogen supplied at an early stage, so that it is possible to carry out a fine protection operation and the fuel cell main body. Will be protected without damaging the. In addition, since this detection method is a method that detects the potential difference within the same electrode surface, it can be measured without being affected by the change in battery voltage due to aging as in the conventional method. Can be used for any purpose.

Although the potential difference is measured by the voltage sensors provided at the outlet and the inlet of the fuel electrode in the above embodiment, the present invention is not limited to this, and voltage sensors incorporated at two points in the same electrode may be used. If so, a decrease in the amount of supplied hydrogen can be similarly detected although there is a difference in sensitivity. Further, in the above embodiment, a plurality of protective operations such as the adjustment of the raw fuel flow rate or the adjustment of the load condition are incorporated as the protective operation, but the invention is not limited to this, and any one of them is performed. It goes without saying that may be.

[0019]

As described above, according to the present invention, the fuel gas is applied to the fuel electrode of the fuel cell body constituted by stacking a plurality of single cells in which the electrolyte layer is sandwiched between the fuel electrode and the air electrode. In addition, in a fuel cell power generator that supplies air to the air electrode to obtain electric power by an electrochemical reaction, the potential difference in the same electrode surface of the fuel cell body is measured, and the power generation state quantity is determined by the magnitude of the measured potential difference. Since the control is performed, a shortage of the amount of hydrogen supplied to the fuel electrode of the fuel cell main body is detected by the measured potential difference, and a control method of the fuel cell power generation device that can effectively perform the protective operation can be obtained. became.

Particularly, if the potential difference in the same fuel electrode surface, especially the potential difference between the fuel gas outlet and the fuel gas inlet, is measured, the shortage of the amount of hydrogen to be supplied can be confirmed quickly and surely. Therefore, the control method of the fuel cell power generation device capable of more effectively performing the protection operation can be obtained. Further, as the power generation state quantity to be controlled, the flow rate of the raw fuel supplied to the reforming system reactor to generate the fuel gas, and the load current flowing in the load connected between both electrodes of the fuel cell main body If at least one of them is used, the protection operation can be appropriately performed, and the control method of the fuel cell power generation device that can be operated safely can be obtained.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a basic configuration of a fuel cell main body and a control method of a fuel cell power generator according to the present invention.

FIG. 2 is a schematic diagram showing the basic configuration of a general fuel cell power generator.

FIG. 3 is a schematic diagram showing a basic configuration of a fuel cell main body and a control method of a fuel cell power generator conventionally used.

[Explanation of symbols]

 1 Fuel Cell Main Body 2 Electrolyte Layer 3 Fuel Electrode 4 Air Electrode 5 Single Cell 6 Separator 7 Cooling Plate 8 Fuel Gas Outlet Voltage Sensor 9 Fuel Gas Inlet Voltage Sensor 10 Load 11 Load Switch 12 Control Device 13 Reforming System Reactor 14 Control Valve 15 Control Device 20 Control Inverter 30 Cooling Water System 31 Fuel Gas Flow Hole 41 Air Flow Hole 71 Cooling Water Flow Path

Claims (4)

[Claims] 1. A fuel cell main body constructed by stacking a plurality of single cells in which an electrolyte layer is sandwiched between a fuel electrode and an air electrode to supply fuel gas to the fuel electrode and air to the air electrode. In the fuel cell power generation device that obtains electric power by an electrochemical reaction, the fuel is characterized in that the potential difference in the same electrode surface of the fuel cell body is measured, and the power generation state quantity is controlled according to the magnitude of the measured potential difference. A method for controlling a battery power generator. 2. The method of controlling a fuel cell power generator according to claim 1, wherein the potential difference within the same electrode surface is the potential difference within the same electrode surface of the fuel electrode. 3. The method of controlling a fuel cell power generator according to claim 2, wherein the potential difference within the same electrode surface is the potential difference between the vicinity of the fuel gas inlet and the vicinity of the fuel gas outlet of the fuel electrode. 4. The power generation state quantity to be controlled flows into a flow rate of a raw fuel supplied to a reforming system reactor to generate the fuel gas and into a load connected between both electrodes of a fuel cell body. The method for controlling a fuel cell power generator according to claim 1, 2 or 3, wherein at least one of the load current and the load current.