JPS60198064A - Fuel cell system - Google Patents

Abstract

PURPOSE:To absorb transient pressure variation to improve safety by connecting in parallel volume elements to a fuel electrode line and an oxidizing agent electrode line through control valves, detecting differential pressure between both lines to control opening of each control valve. CONSTITUTION:Volume elements 16 and 17 are connected in parallel to an oxidizing agent line 14 and a fuel electrode line 15 in the outlet of a fuel cell containing an oxidizing agent electrode 12 and a fuel electrode 13 through control valves 18 and 19. The differential pressure between both lines 14 and 15 in the inlet of the fuel cell is detected with a differential pressure gauge. The signal detected is inputted to a dead zone circuit 21 of a controller 20. When the value of differential pressure exceeds a specified value, the opening of either control valve 18 or 19 is controlled through a signal recognition circuit 23. When pressure in either electrode is high, pressure variation is absorbed with either volume element 16 or 17 to prevent generation of crossover. Therefore, safety and reliability are improved.

Description

[Detailed description of the invention] [Technical field of invention] The present invention relates to a fuel cell device.

[Background of the invention and its problems] Conventionally, a device that directly converts the energy contained in fuel into electrical energy has been known. Usually, a pair of porous 7'I electrodes consisting of a fuel electrode and an oxidizer electrode are placed between the electrolytic negative layer, and a fluid fuel such as hydrogen is brought into contact with the back surface of one electrode, and the other electrode is placed in contact with a fluid fuel such as hydrogen. Bring a fluid oxidizer such as oxygen into contact with the back of the
The electrochemical reaction that occurs at this time is used to extract electrical energy from between the electrodes, and as long as the fuel and oxidizer are supplied, electrical energy can be extracted with high efficiency. It is possible.

FIG. 1 is a cross-sectional perspective view showing the structure of a unit cell of a Li/V acid fuel cell as an example.

In FIG. 1, an electrolyte layer 1 in which porous carbon vapor is impregnated with phosphoric acid as an electrolyte is sandwiched in a Zandwich shape, and a pair of electrodes, a fuel electrode 2 and an oxidizer electrode 3, coated with a platinum catalyst on both ends of the electrolyte layer 1 are sandwiched in between. Furthermore, a graphite plate interconnector 6.7 having a fuel flow groove 4 and an oxidizer flow groove 5 is installed on both sides of the ink connector 6. Air is passed through the groove 5 of the interconnector as an oxidizing agent.

As a result, at the fuel electrode 2 on the side through which fuel containing hydrogen as a main component flows, hydrogen gas is converted into ion by the following reaction.

1"2-+ 2 l-1" +22- ・=(1) These hydrogen ions pass through the electrolyte layer 1 and reach the oxidizer electrode 3 on the side through which air flows. On the other hand, due to the reaction in (1) above, The emitted electrons e''' pass through the external load circuit 8 and reach the oxidizer electrode 3.
water vapor is produced through the following chemical reaction with oxygen in the air.

J402 +2 days” +22−−+1−120 =12
1. The smallest unit required for this electrochemical reaction is called a cell. Since the voltage obtained from this unit cell 9 is about 1V at most, in practice, a stacked body of a plurality of unit cells 9 is assembled together as one battery, stored in a pressure vessel, and burned. 'M forms the battery body.

By the way, in such a fuel cell, the oxidant electrode 3
When the pressure imbalance of the gas flowing to the fuel electrode 2 side (hereinafter referred to as the interelectrode pressure difference) reaches a certain value or more, a so-called crossover phenomenon occurs in which the reactant gas passes through the electrolyte layer 1 without being ionized. It will cause it. This crossover phenomenon caused by an excessive differential pressure between the electrodes occurs especially in transient situations where the flow rate of the fuel electrode 2 or oxidizer electrode 3 line changes, such as when the fuel cell starts or stops or when the load suddenly changes. It is more likely to occur in When such a phenomenon occurs, hydrogen and oxygen mix in a gaseous state and may burn, which is not only dangerous, but also destroys the electrolytic layer 1 and prevents normal electrochemical reactions. There is a risk of loss of function.

[Purpose of the Invention] The present invention has been made to solve the above-mentioned problems, and its purpose is to suppress the generation of interelectrode pressure to a small level even when the system is in a transient state, and to reduce the electrolyte layer. The object of the present invention is to provide a highly safe fuel cell device that can prevent destruction of the fuel cell.

[Summary of the Invention] In order to achieve the above object, the present invention provides an electrolyte layer between a pair of electrodes, a fuel electrode and an oxidizer electrode, each having a fuel flow groove and an oxidizer flow groove through which fuel and an oxidizer flow. C
A fuel cell body is formed by stacking multiple unit cells of
In the original fuel cell, fuel and oxidant are supplied and discharged to the fuel electrode and oxidizer electrode through the fuel electrode line and oxidizer electrode line, and electrical energy is extracted from between the electrodes. and a volume element provided in parallel with the oxidizer electrode line, a control valve provided on the inlet side of each volume element, and a differential pressure for detecting the differential pressure between the fuel electrode line and the oxidizer electrode line. The present invention is characterized in that it is configured by adding a detector and a control device that controls the opening degree of the control valve in accordance with a differential pressure signal from the differential pressure detector.゛[Embodiments of the Invention] First, the present invention takes advantage of the fact that volume elements generally have the property of absorbing and mitigating line pressure fluctuations, and a volume element is installed in parallel with each electrode line, and a volume element is installed on the inlet side. The opening degree of the control valve is controlled by the interpole differential pressure signal.

An embodiment of the present invention shown in the drawings will be described below.

FIG. 2 shows an example of the configuration of a fuel cell device according to the present invention. In the figure, 11 is a fuel cell device formed by stacking a plurality of unit cells 9 shown in FIG. 1, and 12 and 13 are an oxidizer electrode and a fuel electrode thereof, respectively. Further, 31 and 32 are control valves that adjust the air flow rate and fuel flow rate to be supplied to the oxidizing agent 12 and the fuel electrode 13, respectively, and 33 and 34 are control valves that adjust the gas flow rate discharged from the respective poles 12 and 13. It is a control valve that

On the other hand, 14 and 15 are an oxidizer electrode line and a fuel electrode line, respectively, and volume elements 16 and 17 are arranged in parallel on the outlet side of the fuel cell main body 11 of each electrode line 14 and 15.
A control valve 18.19 is provided on the inlet side of each volume element 16.17.

Furthermore, 20 is a differential pressure gauge as a differential pressure detector installed at the entrance m of the fuel cell main body 11 and detects the differential pressure between the poles of each pole line 14, 15, and 30 is the output signal of this differential pressure gauge 120. This is a control device that controls the opening degree of the control valves 18 and 19 in accordance with the above.

Here, the control device 30 controls, when the output signal of the differential pressure 8120 exceeds a predetermined constant value on both the positive and negative sides,
A dead band circuit 21 that sends out an output signal 22 proportional to the exceeded signal, and an output signal 22 of this dead band circuit 21.
The above control valve 1 depends on whether it has a positive sign or a negative sign.
8 or 19 to be controlled, and controls the output signal 22 of the dead band circuit 21 for the determined one and outputs it as a 0 signal 24 or 25. A specific example of this is shown in Figure 3.
In FIG. 3, 26 is a switching circuit, and 27 is a code discrimination circuit.

Next, in the fuel 1'3I battery device configured as described above, the direction in which the pressure of the oxidizer electrode line 14 is high is determined by the differential pressure gauge 2.
It is assumed that the differential pressure between the electrodes is detected by the differential pressure gauge 20 as shown in FIG. 4, 20 in the transient state of the system. This differential pressure signal 20 is transmitted to a dead band circuit 21
As shown at 22 in FIG. 4, the signal 20 has a positive la P + .

Only signals exceeding a certain negative value P- are output.

This output signal 22 is then transferred to the signal discriminator circuit 23 in FIG.
When passing through the signal 22, the positive or negative sign of the signal 20 is determined and the signal 22 is
If it is positive, it is output as a control signal 24 to the control valve 18 to control the control valve 18 in the opening direction, and if it is one side, it is output as a control signal 25 to the control valve 19 to control the control valve 19 in the opening direction. be done.

That is, the signal discriminated by this signal discrimination circuit 23 has a waveform as shown at 24.25 in FIG. 4, and when the pressure on the oxidizer electrode line 14 side is large, the differential pressure signal 20 appears as a positive sign, and The glB valve 18 on the inlet side of the volume element 16 installed in parallel with the line 14 is operated in the same direction by the signal 24 according to the magnitude of the positive value, thereby absorbing the rise in differential pressure in the positive direction. suppress. Conversely, fuel electrode line 1
When the pressure on the side 5 is high, the differential pressure signal 20 appears as a negative sign, and the control valve 19 on the inlet side of the volume element 17 provided in parallel with the fuel electrode line 15 is controlled according to the magnitude of the negative value. 25 in the opening direction to absorb and suppress the rise in differential pressure in the negative direction.

As described above, this fuel cell power generation device includes an electrolyte layer arranged between a pair of electrodes of the fuel t11.3 and the oxidizer tii12, which have a fuel flow groove and an oxidizer flow groove through which the fuel and oxidizer flow. A fuel cell main body 11 is formed by stacking a plurality of unit cells, and fuel and oxidizer are supplied to and discharged from the fuel electrode 13 and the oxidizer electrode 12 through the fuel electrode line 15 and the oxidizer electrode line 14, and the fuel cell body 11 is formed by stacking a plurality of unit cells. Electrode 12.
In a conventional fuel cell that extracts electrical energy from between 13 and 13, volume elements 16 and 17 are provided in parallel with the fuel electrode line 15 and the oxidizer electrode line 14, respectively.
, control valves 18 and 19 provided on the inlet side of each of these volume elements 16 and 17, and the fuel electrode line 1
Differential pressure detection L that detects the differential pressure between 5 and the oxidizer electrode line 14
120, and determines the positive or negative sign of the differential pressure signal from this differential pressure detector 20, and when the magnitude of the signal exceeds a certain value, the magnitude of the signal proportional to the exceeded signal is determined. The control device 30 is configured to include a control device 30 that controls the opening degree of the control valve 18 or 19 depending on the situation.

Therefore, if the system enters a transient state for some reason and a large difference in pressure between the electrodes occurs due to changes in the flow rates of the oxidizer electrode and fuel electrode lines 14 and 15, the The adjustment piece 18 or 19 on the inlet side of the volume element 16 or 17 installed in parallel with the pole line 14 or 15 is controlled in the opening direction to absorb the change in pressure no. It is possible to prevent the occurrence of crossover phenomenon, which eliminates the conventional destruction of the electrolyte layer 1, maintains the original electrochemical reaction function, and prevents gas combustion, making it safe. It is possible to improve your sexuality.

In the above embodiment, the volume elements 16 and 17 are provided on the outlet side of the fuel cell main body 11, but they may also be provided on the inlet side.

[Effects of the Invention] As explained above, according to the present invention, even when the system is in a transient state, the generation of interelectrode pressure difference can be suppressed to a small level, and the electrolyte layer can be prevented from being destroyed. and a highly reliable fuel cell device can be provided.

[Brief explanation of the drawing]

Figure 1 shows the configuration of the unit cell of the phosphoric acid fuel cell.
11i plane perspective view, FIG. 2 is a configuration diagram showing an embodiment of the present invention, FIG. 3 is a block diagram showing an example of a control device in the embodiment, and FIG. 4 is a diagram for explaining the operation of the embodiment. FIG. DESCRIPTION OF SYMBOLS 1... Electrolyte layer, 2... Fuel electrode, 3... Oxidizer electrode, 4.5... Distribution groove, 6.7... Ink connector,
8... External load circuit, 9... Unit cell, 11...
Fuel 1 battery body, 12... Oxidizer electrode, 13... Fuel 31 pole, 14... Oxidizer electrode line, 15... Fuel 1'l + @ line, 16.17. ...Volume element, 18
, 19.31, 32, 33.34... control valve, 20.
... Differential pressure bath 1.21 ... Insensitization circuit, 22 ... Output signal of dead band circuit, 23 ... Signal discrimination circuit, 30 ...
·Control device. Applicant's agent Patent attorney Takehiko Suzue Figure 1 Figure 2 Figure 1

Claims (1)

[Claims] (l) I'A!: A fuel electrode J3 having a fuel electrode J3 and an oxidizer flow groove, through which tl and an oxidizer flow, and an oxidizer (between the pair of electrodes). A plurality of unit cells (6 layers are formed to form a fuel cell body) each having an electrolyte layer arranged thereon, and a salt line and an oxidizer line are connected to the fuel electrode and the oxidizer electrode. -U 9P4 material and oxidizing agent are supplied and discharged, and electrical energy is extracted from between the electrodes 43, and the fuel electrode line and (
l! Volume elements installed in parallel with the i-forming agent pole line, control valves straddled on the inlet side of each of these volume elements, and the fuel 1'l 111! and a control device for controlling the opening degree of the control valve in accordance with the differential pressure signal from the differential pressure detector. When the magnitude of the differential pressure signal from the differential pressure detector exceeds a certain amount, the control device sends out an output signal proportional to the exceeded signal. The output signal of this dead band circuit has a positive rG signal which is controlled by the load.
ii) a signal discrimination circuit which separates the valve by 1' and outputs a control signal;
1) Insert the fuel 81 battery as described in item 1).