JPH0282459A - Fuel cell operation control device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an operation control system for a fuel cell, particularly an F4 fuel cell, which controls the operation of a phosphoric acid fuel cell so as to maintain its cell characteristics.

[Conventional technology]

A fuel cell generates electricity by causing a cell reaction by supplying air as an oxidant to the positive electrode, or oxidizer electrode, and hydrogen-containing fuel gas to the negative electrode, or fuel 1i, and a load circuit connected to the fuel cell. is supplying electricity to. In such a power supply state, a state in which at least either air or fuel gas is not supplied to the electrodes for some reason during power generation by the fuel cell in the amount necessary to obtain a stable output voltage of the cell, that is, a gas starvation state. When it is energized, the output voltage drops and eventually it becomes unable to generate electricity. In the process of decreasing the output voltage due to such a lack of gas, a change occurs in the temperature distribution within the battery surface. Figure 3 shows the single cell surface when a sufficient amount of fuel gas and air is supplied to the load current of the load circuit connected to a fuel cell, such as a phosphoric acid fuel cell, and the output voltage is stable. This is an example of the internal temperature distribution, and FIG. 4 is an example of the internal temperature distribution when the same cell is transmitting power in a state where hydrogen is insufficient. As can be seen from a comparison of these figures, when power is being transmitted in a state where there is a shortage of hydrogen, the temperature near the hydrogen cell entrance becomes abnormally high. This is thought to be because the hydrogen flow rate is low relative to the load (then power is generated only near the hydrogen inlet, resulting in local energy concentration).The same phenomenon occurs even when oxygen is insufficient.

If such an excessively high temperature condition occurs within the cell surface, the following effects will occur on a fuel cell, for example, a phosphoric acid fuel cell using phosphoric acid as an electrolyte. That is, the water vapor pressure in the phosphoric acid of the battery-reactive special electric bull increases and scatters, resulting in an increase in the concentration of phosphoric acid, a decrease in volume, and an increase in the internal resistance of the battery. Alternatively, the gas seal between air and fuel gas maintained by the phosphoric acid in the electrode becomes weaker, causing a direct reaction between oxygen and hydrogen through the electrode. Furthermore, sintering of platinum in the electrode catalyst layer is promoted, and the platinum surface area is reduced. Since all of these effects on the fuel cell deteriorate the cell output characteristics, it is necessary to avoid generating power and transmitting power to the load circuit when the fuel cell is out of gas. For this reason, conventionally, by monitoring the output voltage of the battery, power transmission to the load circuit is stopped when the battery is out of gas. The method for stopping power transmission is to gradually lower the output voltage when the flow rate of either air or fuel gas decreases relative to the load current, so when the output voltage drops to a predetermined value, the switch is automatically opened. The load circuit is separated from the fuel cell by using the following method.

The above method requires some time until the load circuit is disconnected, and during this time the battery is exposed to excessively high temperatures, accelerating the deterioration of battery characteristics.

As a solution to this drawback, a fuel cell operation control system as shown in FIG. 5 is known. In FIG. This is a fuel cell main body in which unit cells each consisting of a fuel electrode 4 are stacked.

The fuel cell main body 1 includes a supply pipe 5 for supplying air to the oxidizer electrode 3, a discharge pipe 6 for discharging unreacted air that does not contribute to the cell reaction from the oxidizer electrode 3, and a fuel type 8i4 for discharging fuel gas.
A supply pipe 7 for supplying fuel gas to the fuel electrode 4 and a discharge pipe 8 for discharging unreacted fuel gas that does not contribute to the cell reaction from the fuel electrode 4 are provided. Note that the supply pipe 5 is provided with an air flow rate sensor 9 for detecting the supply flow rate of air, and the supply pipe 7 is provided with a fuel flow rate sensor 10 for detecting the supply flow rate of fuel gas.

A load circuit 15 in which a load 11 and a switch 12 are connected in series is connected to the fuel cell main body 1 . Note that 13 is a current meter 'rj1 that detects a load current as a load amount.

With this configuration, the fuel cell main body 1 generates electricity through a cell reaction between air and fuel gas supplied through the supply pipes 5 and 7, respectively. Then, by closing the switch 12, power is transmitted to the load circuit 15, and the required power is supplied to the load 11. Note that unreacted air and fuel gas that do not contribute to the cell reaction are discharged from exhaust pipes 6.8, respectively.

In the operation of such a fuel cell, operation control when the flow rate of air or fuel gas corresponding to the load is insufficient will be explained. In FIG. 5, the fuel flow rate calculator 16. The air flow rate calculator 17 receives the output signal of the load current detected by the ammeter 13 manually, calculates the fuel gas flow rate and air flow rate that will not cause gas shortage in response to the load current, and calculates the calculated fuel gas flow rate and air flow rate. Outputs air flow rate. The comparator 18 inputs and compares the output signal of the measured fuel gas flow rate detected by the fuel flow sensor 10 and the output signal from the fuel flow calculator 16, and the measured fuel gas flow rate becomes the calculated fuel gas flow rate corresponding to the load current. When it is smaller, an output signal is output, and this output signal opens the switch 12. Note that when the measured fuel gas flow rate is greater than or equal to the calculated fuel gas flow rate corresponding to the load current, no output signal is output and the switch 12 is closed.

In comparison H19, the output signal of the measured air flow rate detected by the air flow rate sensor 9 and the output signal from the oxidizer flow rate calculator 17 are manually compared, and when the measured air flow rate is smaller than the calculated air flow rate corresponding to the load current, an output signal is generated. A signal is output, and the switch 12 is opened by this output signal. Note that when the measured air flow rate is greater than or equal to the calculated air flow rate corresponding to the load current, no output signal is output and the switch 12 is closed.

With such a system configuration, when the flow rate of fuel gas or air supplied to the fuel cell main body 1 is smaller than the flow rate calculated so as not to cause a gas shortage corresponding to the jX load 'gi flow, the comparator 1 day or The output signal from the comparator 19 immediately opens the switch 12 and disconnects the load circuit 15 from the fuel cell main body l.

[Invention tries to solve! ! ! ! [Question] In the above-mentioned salt l-1 battery, pure hydrogen is rarely used as the fuel gas supplied to the fuel cell body, and hydrogen-containing gas obtained by reforming natural gas or methanol is used instead. In most cases, . In this case, the fuel gas contains gases such as CQt, CO, and water vapor in addition to hydrogen, but the composition of these gases changes depending on the capacity and operating conditions of the reformer. Therefore, in the method of comparing the calculated value and the measured value of the air or fuel gas flow rate, it is difficult to detect a shortage of the hydrogen flow rate, especially on the fuel gas side, when the hydrogen concentration has decreased due to a reduction in the capacity of the reformer. This has the disadvantage that power is transmitted to the load circuit in a state of gas starvation, which deteriorates the battery characteristics.

Furthermore, by comparing the measured and calculated flow rates of fuel gas and air in the operation control system shown in FIG. Therefore, the fuel cell main body maintains a high voltage in the open circuit state, that is, a voltage of around 1 V on average for a single cell, and since the load is suddenly removed from the normal operating state, the fuel cell main body also reaches a temperature of 150°C or more. It has become.

Therefore, since the fuel cell is placed in a high voltage and high temperature state after the load is cut off, as is well known, the carbon that is the carrier of the catalyst in the electrode is extremely susceptible to corrosion, resulting in deterioration of the cell characteristics. Therefore, it is desired to prevent batteries from being left at high voltage and high temperature due to load interruption due to lack of gas.

An object of the present invention is to provide an operation control device for a fuel cell that can detect an insufficient amount of hydrogen in fuel gas supplied to a fuel cell and disconnect a load circuit, and a device that can disconnect a load circuit even when the load circuit is disconnected due to lack of gas. An object of the present invention is to provide a fuel cell operation control device that does not leave the fuel cell in a high voltage and high temperature state.

(Means for Solving the Problem!!!) In order to solve the above problem i, according to the present invention, a load circuit including a switch for generating electric power by a battery reaction caused by supply of fuel gas and oxidizing gas. In a fuel cell that supplies fuel gas, a fuel flow sensor detects the flow rate of fuel gas, a hydrogen concentration meter detects the amount of hydrogen contained in this fuel gas, and a hydrogen concentration meter and a fuel flow sensor calculate the hydrogen flow rate. a first computing unit, a load detector provided in the load circuit, a second computing unit that computes a hydrogen flow rate corresponding to the load detected by the detector, and first and second computing units. A comparison device that inputs and compares the output signals from the X-X, and outputs an output signal that opens the switch when the hydrogen flow rate calculated by the first X-operator is smaller than the hydrogen flow rate calculated by the second X-X operator. It shall consist of a container.

The present invention also provides a fuel cell that supplies electric power generated by a cell reaction caused by the supply of fuel gas and oxidant gas to a load circuit including a first switch, which includes a fuel flow sensor and an oxidant gas.
The measured fuel gas flow rate and the measured oxidizing gas flow rate detected by the sensor are calculated by calculating the calculated fuel gas flow rate and the calculated oxidizing gas flow rate, respectively, corresponding to the load amount detected by the load detector. When at least one of the measured fuel gas flow rate and the measured oxidizing gas flow rate is smaller than the calculated fuel gas flow rate and the calculated oxidizing gas flow rate, respectively, the data from the first or second comparator is compared. In a fuel cell operation control device that opens a first switch in response to an output signal, a voltage sensor that detects the output voltage of the fuel cell is connected in parallel to the load circuit, and a variable resistor is connected in series with the second switch. a discharge resistor circuit connected to a third computing unit that computes an electrical output corresponding to the measured fuel gas flow rate and the measured oxidizing gas flow rate, and a voltage sensor that calculates the electrical output calculated by this computing unit. a fourth arithmetic unit that outputs an output signal for setting the resistance of the variable resistor so that the detected output voltage is transmitted to the discharge resistance circuit; The switch shall be closed.

[Effect]

The fuel gas supplied to the fuel cell is hydrogen-rich gas obtained by reforming a reforming raw material in a reformer. Therefore, the hydrogen flow rate in the fuel gas is determined by providing a hydrogen concentration meter in the fuel gas supply system and determining the actual hydrogen flow rate from the fuel gas flow rate detected by the fuel flow rate sensor and the hydrogen concentration detected by the hydrogen concentration meter. If the measured hydrogen flow rate is smaller than the calculated hydrogen flow rate calculated to prevent gas shortage in accordance with the load amount of the load circuit, the load circuit switch is opened. Therefore, when the amount of hydrogen in the fuel gas decreases, power is not transmitted to the load circuit of the fuel cell, so that the cell characteristics are maintained well.

In addition, a discharge resistance circuit in which a switch and a variable resistor are connected in series is installed in parallel with the load circuit.The actual fuel gas flow rate and actual oxidation detected by the fuel flow rate sensor and oxidizer flow rate sensor supplied to the fuel cell are installed. If at least one of the oxidizing agent gas flow rate and the oxidizing agent gas flow rate is smaller than the calculated fuel gas flow rate or the calculated oxidizing gas flow rate, which is calculated to prevent gas shortage according to the load amount of the load circuit, the load circuit switch is opened. At the same time, the switch of the discharge resistance circuit is closed to transfer the power generated by the fuel cell from the load circuit to the discharge resistance circuit.

At this time, the electrical output that will not cause a gas shortage is calculated according to the measured fuel gas flow rate and the measured oxidant gas flow rate, and this electrical output is transmitted to the discharge resistance circuit at the output voltage when the load circuit is disconnected. Set the resistance of the variable resistor. Therefore, high voltage and high temperature of the battery do not occur as would occur when the load is cut off.

〔Example〕

Embodiments of the present invention will be described below based on the drawings.

FIG. 1 is a system diagram of a driving side m-device of a fuel cell according to an embodiment of claim 1 of the present invention. In FIG. 1 and FIG. 2, which will be described later, parts that are the same as those in the conventional example shown in FIG. In FIG. 1, a fuel gas supply pipe 7 includes a fuel flow sensor 10 for detecting the flow rate of fuel gas, and a hydrogen concentration meter 2 for detecting the hydrogen concentration in the fuel gas.
1 is provided. The output signals from the fuel flow rate sensor 10 and the hydrogen concentration meter 21 are inputted to an actual hydrogen flow rate calculator 22 which calculates the hydrogen flow rate in the fuel gas and outputs the result, and a load circuit detected by the ammeter 13. A calculated hydrogen flow rate calculator 23 is provided to calculate a hydrogen flow rate that does not cause gas shortage in response to a load current of 15, and the output signals from the actually measured and calculated hydrogen flow rate calculators 22 and 23 are inputted and compared. A comparator 24 is provided which outputs an output signal when the measured hydrogen flow rate calculated by the measured hydrogen flow rate calculator 22 is smaller than the calculated hydrogen flow rate calculated by the calculated hydrogen flow rate calculator 23.

Then, the switch 12 is opened by the output signal from the comparator 24.

With such a system configuration, fuel gas and oxidant gas are normally supplied to the fuel cell main body 1 to generate electricity through a cell reaction, and the switch 12 is closed to supply the generated electricity to the load circuit. At this time, the hydrogen flow rate in the fuel gas is calculated by the actually measured hydrogen flow rate calculator 22 based on the fuel gas flow rate and hydrogen concentration detected by the fuel flow rate sensor 10 and the hydrogen concentration meter 21. On the other hand, the load circuit 15 is calculated by calculating the hydrogen flow rate by the calculator 23.
The hydrogen flow rate corresponding to the load current detected by the ammeter 13 is calculated, and the measured hydrogen flow rate calculated by the measured hydrogen flow rate calculator 22 and the calculated hydrogen flow rate calculated by the calculated hydrogen flow rate calculator 23 are constantly compared to When the measured hydrogen flow rate becomes smaller than the calculated hydrogen flow rate, the comparator 24 outputs an output signal. Then, this output signal opens the switch 12 and disconnects the load circuit 15 from the fuel cell main body 1. Therefore, if the hydrogen flow rate in the fuel gas decreases for some reason relative to the load amount, the load circuit 15 is disconnected from the fuel cell main body 1. It is separated from the fuel cell main body 1 to prevent deterioration of battery characteristics.

FIG. 2 is a system diagram of a fuel cell operation control device according to an embodiment of claim 2 of the present invention. What is different from the conventional example shown in FIG. 5 in FIG. 2 is a voltmeter 20 that detects the output voltage of the fuel cell, and a discharge resistance circuit in which a switch 26 and a variable resistor 27 are connected in series in parallel to the load circuit 15. 28 and comparator 1
8 or the output signal from the comparator 19 closes the switch 26, and the fuel 1111! Output calculation that inputs the output signals from the E quantity sensor 10 and the air flow rate sensor 9, and calculates the electrical output that will not cause a gas shortage in response to the measured fuel gas flow rate and the measured air flow rate detected by these sensors. input the output signal from the output generator 29 and the output generator 29,
The electrical output calculated by the output calculator 29 is sent to the discharge resistance circuit 2.
With such a system configuration, during normal load operation, the switch 12 of the load circuit 15 is closed, and the switch 2 of the discharge resistance circuit 28 is closed.
6 is opened and power is transmitted to the load circuit 15. In this state, when the fuel gas flow rate or air flow rate supplied to the fuel cell main body l is smaller than the calculated fuel gas flow rate or calculated air flow rate calculated in accordance with the load amount of the load circuit 15, the comparator 18
Alternatively, the output signal from the comparator 19 opens the switch 12 and closes the switch 26 to disconnect the load circuit 15 from the fuel cell main body 1 and instead discharge the power generated by the fuel cell to the resistor circuit 28. Transmit electricity to At this time, the resistance of the variable resistor 27 of the discharge resistance circuit 28 is determined by the output voltage detected by the voltmeter 20 and the electrical output calculated by the output 64 calculator 29 corresponding to the measured fuel gas flow rate and the measured air flow rate. It is set by the output signal from the resistance value calculator 30 to transmit power to the circuit 28 . Therefore, the fuel cell transmits to the discharge resistor circuit 28 an electrical output that corresponds to the flow rate of the supplied fuel gas and air and does not cause a gas shortage.

〔Effect of the invention〕

As is clear from the above description, the present invention has the following effects.

In the fuel cell operation control device according to claim 1, hydrogen mff1 in the fuel gas supplied to the fuel cell is actually measured, and when the measured hydrogen flow rate is smaller than the hydrogen flow rate that does not cause gas shortage corresponding to the load amount of the load circuit. By opening the switch and disconnecting the load circuit from the fuel cell, negative ml
Since fuel gas with an insufficient amount of hydrogen is not supplied to the battery, there is no local excessive temperature rise on the battery surface, and battery characteristics can be stably maintained over a long period of time.

In the fuel cell operation control device of claim 2, the fuel gas flow rate or oxidant gas flow rate supplied to the fuel cell is smaller than the calculated fuel gas flow rate and calculated air flow rate that do not cause gas shortage corresponding to the load amount of the load circuit. When the load circuit is disconnected from the fuel cell by opening the load circuit switch, the discharge resistance circuit switch installed in parallel with the load circuit is closed and the switch is automatically switched to the discharge resistance circuit before the output voltage starts to drop, causing the discharge to start. In the resistance circuit, the resistance value of the variable resistor is set so that the electrical output that does not cause gas shortage corresponding to the flow rate of the fuel gas and oxidant gas supplied is transmitted at the output voltage when the load circuit is disconnected. Since the fuel cell is no longer transmitting power during this period, and the battery is not left exposed to high voltage and high temperature as it would be during load shedding, the battery characteristics can be maintained stably over a long period of time.

[Brief explanation of the drawing]

FIG. 1 is a system diagram of a fuel cell operation control device according to an embodiment of the present invention, FIG. 2 is a system diagram of a fuel cell operation control device according to a different embodiment of the present invention, and FIG. 3 is a system diagram of a fuel cell operation control device according to an embodiment of the present invention. Figure 4 is a distribution diagram showing the temperature distribution inside the cell when sufficient hydrogen is supplied to the load, Figure 4 is a distribution diagram of the temperature distribution inside the cell when insufficient hydrogen is supplied to the load, and Figure 5 is a distribution diagram showing the temperature distribution inside the cell when hydrogen is insufficiently supplied to the load. 1 is a system diagram of a conventional fuel cell operation control device. 1; Fuel cell, 9: Air 2i! slip sensor, 10: fuel flow sensor, 13: ammeter, 12.26: switch, 1
5: Load circuit, 16: Fuel flow rate calculator, 17: Air flow rate calculator, 18.19.14: Comparator, 20: Voltmeter,
21: Hydrogen concentration meter, 22: Actual hydrogen flow rate calculator, 23:
Calculation hydrogen flow calculator, 27; Variable resistance, 2nd: Release resistance circuit, 29: Output calculator, 30: Resistance value calculator. Figure 1 Figure 4

Claims (1)

[Claims] 1) In a fuel cell that supplies electricity to a load circuit equipped with a switch, which generates electricity through a cell reaction caused by the supply of fuel gas and oxidant gas, a flow rate sensor that detects the flow rate of supplied fuel gas; , a hydrogen concentration meter that detects the amount of hydrogen contained in this fuel gas, a first calculator that calculates the hydrogen flow rate using the fuel flow rate sensor and the hydrogen concentration meter, a load detector provided in the load circuit, and this detector. A second computing unit calculates the hydrogen flow rate corresponding to the load amount detected by inputting and comparing the output signals from the first and second computing units, and calculating the hydrogen flow rate calculated by the first computing unit. 1. A fuel cell operation control device comprising: a comparator that outputs an output signal that opens a switch when the hydrogen flow rate is smaller than the hydrogen flow rate calculated by the second calculation unit. 2) A fuel cell that supplies electric power generated by a cell reaction caused by the supply of fuel gas and oxidant gas to a load circuit including a first switch, which is detected by a fuel flow sensor and an oxidizer flow sensor. The measured fuel gas flow rate and the measured oxidizing gas flow rate are calculated by the first and second comparators, respectively, and the calculated fuel gas flow rate and the calculated oxidizing gas flow rate are calculated corresponding to the load amount detected by the load detector. When at least one of the measured fuel gas flow rate and the measured oxidizing gas flow rate is smaller than the calculated fuel gas flow rate and the calculated oxidizing gas flow rate, respectively, the first opening/closing is performed by the output signal from the first or second comparator. In a fuel cell operation control device that opens a fuel cell, a voltage sensor that detects the output voltage of the fuel cell is connected in parallel to the load circuit, and a second switch and a variable resistor are connected in series. A resistor circuit, a third computing unit that computes the electrical output corresponding to the measured fuel gas flow rate and the measured oxidant gas flow rate, and the electrical output calculated by this computing unit is discharged at the output voltage detected by the voltage sensor. and a fourth arithmetic unit that outputs an output signal for setting the resistance of the variable resistor so as to transmit power to the resistance circuit, and the second switch is closed by the output signal from the first or second comparator. A fuel cell operation control device characterized by: