JPS61116764A - Fuel cell system - Google Patents

Abstract

PURPOSE:To prevent a fuel cell main body from breakage to increase safety and reliability even if supply of active material gas is stopped by arranging an output controller which controls the output of a fuel cell main body. CONSTITUTION:Inactive gas N such as nitrogen is filled in a sealed container in which a fuel cell main body 11 is accommodated. When at least one of differential signals DELTAP1, DELTAP2 which are detected with a fuel gas side differential pressure gauge 26F and an oxidizing agent gas side differential pressure gauge 26A is decreased to dangerous differential pressure, a differential pressure controller 27 sends a valve opening signal to inactive gas supply valves 33F, 33A, and supplies inactive gas N' to a fuel gas supply part 11F and an oxidizing agent gas supply part 11A to prevent the fuel cell main body 11 from the dangerous differential pressure. When the differential pressure signals DELTAP1, DELTAP2 are not recovered for a long time, output voltage 36V applied to a load 35 is monitored with an output controller 34 to decrease output current 36I. Thereby, polarity conversion of the fuel cell main body 11 is prevented.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention provides a method for reducing fuel cell The present invention relates to a fuel cell device that can be operated or stopped safely without damaging the main body.

[Technical Background of the Invention] A fuel cell device directly converts the chemical energy of fuel into electrical energy.
A pair of porous electrodes are arranged, and a fuel gas such as hydrogen is brought into contact with the back surface of one electrode, and an oxidizing gas containing oxygen is brought into contact with the back surface of the other electrode to cause a chemical reaction.
The electrical energy generated at this time is extracted from the pair of porous electrodes. Electrolytes include molten salts, alkaline solutions, acidic solutions, etc.
Here, a fuel cell device using phosphoric acid as an electrolyte will be explained with reference to FIG.

In FIG. 2, 1 is an electrolyte layer made of a fibrous sheet or mineral powder impregnated with phosphoric acid. Further, in the figure, 2 is an anode, and 3 is a cathode. The anode 2 and cathode 3 are both carbonaceous porous electrodes, typically an electrolyte 111
Platinum as a catalyst is coated on the surface in contact with the metal. Furthermore, in the figure, 4 is a fuel gas inlet chamber into which a fuel gas F containing hydrogen is introduced, and 5 is an oxidizing gas inlet chamber into which an oxidizing gas (usually air) containing oxygen is introduced.

Therefore, the hydrogen of the fuel gas F that has flowed into the fuel gas inlet chamber 4 comes into contact with the catalyst through the pores of the anode 2, which is a porous electrode. Here, hydrogen is dissociated into hydrogen ions and electrons by the action of a catalyst. What is the reaction formula in this case?

H2-42H" + 28 = ll).Then, the hydrogen ions enter the electrolyte layer 1 and migrate toward the cathode 3 due to the action of the supervoltage and concentration diffusion. Furthermore, the electrons separated by the dissociation of the hydrogen ions are released to the outside. The oxygen in the oxidizing gas A that has flowed into the oxidizing gas inflow chamber 5 contacts the catalyst through the pores of the cathode 3, which is a porous electrode, and flows into the cathode 3. Together with the hydrogen ions migrating from the 2nd side and the electrons returning to the cathode 3 through the external power load 6, the next reaction occurs due to the action of the catalyst.

4H'' +4e +02-+2820 - (2) Thus, hydrogen is oxidized to water, and at the same time chemical energy is converted to electrical energy and provided to external power load 6.

At this time, part of the electrical energy is consumed in the electrolyte layer 1 by the external resistance of the battery. Therefore, in order to increase the efficiency of the battery, it is necessary to shorten the migration distance of hydrogen ions and reduce the resistance, and for this reason, the electrolyte layer 1 is formed extremely thin.

Further, the fuel gas F and the oxidizing gas A flowing into the inlet chamber 4.5 are normally pressurized to a diffused pressure in order to increase their concentration and increase the reaction rate.

By the way, as mentioned above, the electrolyte layer 1 is formed extremely thin, so if the pressure difference between the fuel gas F on the anode 2 side and the oxidant gas A on the cathode 3 side is large, the fuel gas F or the oxidant gas A will leak into the electrolyte layer. Resisting the surface tension of the phosphoric acid impregnated into the electrolyte layer 1, it becomes bubbles and permeates the electrolyte layer 1.
There is a risk of local combustion. Furthermore, there is a risk that the device may deteriorate or its performance may deteriorate. Therefore, the above pressure difference needs to be kept extremely small, for example, within 4001111MH20 (generally, the pressure of the oxidizing gas A is
pressure).

For this reason, the pressure difference between the fuel gas F and the oxidizing gas A is controlled. That is, as shown in FIG. 3, the fuel gas F flows from the fuel gas supply section 11f1 into the fuel gas reaction section 11'' in the fuel cell main body 11 through the fuel gas supply pipe 11F, and the fuel gas F reacted within the main body 11 is discharged as fuel gas. Part 1
1. Pass the fuel gas exhaust pipe 11F' from 2 to the combustor 12.
The remaining fuel components are combusted and enter the mixer 13. On the other hand, the oxidizing gas reaction section 1 in the fuel cell main body 11 is supplied from the oxidizing gas supply section 1181 through the oxidizing gas supply pipe 11A.
The oxidizing gas A that flows into the main body 11 and reacts in the main body 11 directly enters the mixer 13 from the oxidizing gas exhaust section 11a through the oxidizing gas exhaust pipe 11A'. Thus, the pressure of the residual fuel gas F and the pressure of the oxidizing gas A match in the mixer 13.

Note that 14 and 15 in the figure are the flow path resistances to the fuel gas F and the oxidizing gas A in the fuel cell main body 11, and 16 in the figure is the flow path resistance to the fuel gas F in the combustor 12. In addition, 17.18 in the figure indicates each discharge pipe 11F',
11A' are each inserted with an adjustable flow path resistance, such as a manual orifice or the like.

The flow path resistance 14.15 inside the fuel cell main body 11 is small, so it does not pose much of a problem when performing differential pressure control, but the flow path resistance 16 inside the combustor 12 is large, so the flow path resistance 17.1
8, the differential pressure between the fuel gas F and the oxidizing gas A within the fuel cell main body 11 is kept within a specified value.

Reference numerals 19 and 20 in the figure denote a fuel gas release valve and an oxidant gas release valve connected to the fuel gas supply pipe 11F and the oxidant gas supply pipe 11A, respectively, and these have the following functions. That is, in the fuel cell device shown in FIG. 3, the flow path resistance 16 in the combustor 12 is large, and therefore the pressure drop at the rated flow rate is several thousand 1 MH20 (for example, 3000 am+
H20).

Therefore, as shown in FIG. 4, by controlling the flow rates of the fuel gas F side and the oxidant gas A side in proportion to the output, the differential pressure ΔP is kept within a specified value (for example, 400RH20). It is difficult to control the flow rate with high precision, and the relationship between the flow rate and the pressure drop also deviates from the square-law characteristic approximation, especially on the fuel gas side because it passes through the combustor 12.

Therefore, controlling the flow rate of the fuel gas F or the oxidizing gas A alone cannot respond particularly to transient characteristics. Therefore,
When the differential pressure ΔP rises rapidly, the fuel gas release valve 19 or the oxidizing gas releasing valve 2o is operated to release the fuel gas F or the oxidizing gas A, thereby suppressing the rise in the differential pressure ΔP.

[Problems in the background art] As mentioned above, in the conventional fuel cell device, the fuel cell main body 1
When the differential pressure generated between the pressure of fuel gas F and the pressure of oxidant gas A in fuel cell main body 11 increases, the oxidizing gas release valve 2o provided on the gas supply side or gas discharge side of fuel cell main body 11 or the fuel gas A discharge valve 19 is operated to discharge the high-pressure side gas into the atmosphere.

However, this method requires a slight pressure difference of, for example, 200 to 500
It is sufficiently useful if the pressure difference is around AQ, but if a larger differential pressure occurs, it is difficult to deal with it because the amount of discharge is limited. Furthermore, if the supply of either or both of the fuel gas F and the oxidizing gas A is stopped for some reason, the generation of an excessive pressure difference cannot be avoided. Therefore, as a preventive measure, a method has been considered in which differential pressure is controlled by supplying an inert gas such as nitrogen as a differential pressure control gas to the pressure grinding system, but in this case, the differential pressure is very small. Even if the control is carried out, the reactant gas chamber will be diluted, so if the load continues, the voltage of the fuel cell will drop rapidly, and polarity reversal phenomenon (forcibly caused even though there is insufficient reactant gas) will occur. Since the output is extracted from the fuel cell body 11, the battery with relatively poor gas flow is no longer able to maintain its function as a battery, causing electrolysis and phosphoric acid concentration (phenomenon), which can be fatal to the fuel cell body 11. In some cases, it may be damaged so much that it cannot be reused.

[Object of the Invention] The present invention was made to solve the above-mentioned problems, and its purpose is to improve the differential pressure control function and to prevent the fuel cell main body from being destroyed even if the supply of raw material gas is stopped. An object of the present invention is to provide a fuel cell device that can improve safety and reliability without causing any damage.

[Summary of the Invention 1 To achieve the above object, the present invention has an inert gas supply section connected to a fuel gas supply section and an oxidizing gas supply section, and an inert gas supply section to each inert gas supply section. In addition to providing a supply valve, the fuel cell main body is housed in a sealed container, and the container is filled with an inert gas, and each pressure of the fuel gas and oxidizing gas and the above-mentioned standards are set using the inert gas pressure in the sealed container as a reference pressure. The differential pressure is detected by a differential pressure transmitter. If the differential pressure between the fuel gas side and the oxidizing gas side drops significantly for some reason, or if the supply of each gas is stopped, the differential pressure controller will control each gas based on the signals detected by the differential pressure detectors. By opening the inert gas supply valve connected to the gas system and supplying inert gas to the fuel cell main body, the pressure in each gas system is prevented from decreasing and dangerous pressure differentials are eliminated, and the inert gas is An output controller that monitors the fuel cell voltage and controls the output of the fuel cell to maintain it at a constant voltage in order to prevent polarity reversal caused by a decrease in the output of the fuel cell by supplying gas. The present invention is characterized in that it has a structure that prevents damage to the fuel cell main body.

[Embodiment of the Invention] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows an example of the configuration of a fuel cell device according to the present invention. Note that the same parts as in FIG. 3 are designated by the same reference numerals and their explanations will be omitted. In FIG. 1, the fuel cell main body 1
1 is housed in an airtight container 30, and the airtight container 30 is filled with an inert gas N such as nitrogen to maintain a constant pressure. Further, an inert gas supply pipe 3ON and an inert gas discharge pipe 3ON' are connected to the airtight container 30, and an adjustable flow path resistance 31 consisting of a manual orifice etc. is connected to the inert gas exhaust pipe 3ON'. In addition, a control valve 32 for controlling the inflow amount of the inert gas N is inserted into the inert gas supply pipe 3ON.

On the other hand, the fuel gas supply pipe 11F and the inert gas supply pipe 3
A fuel gas side differential pressure gauge 26F is inserted between the oxidizing gas supply pipe 11A and the inert gas supply pipe 3ON, and an oxidizing gas side differential pressure gauge 26A is inserted between the oxidizing gas supply pipe 11A and the inert gas supply pipe 3ON. Then, the fuel gas discharge part 11f of the fuel gas discharge pipe 11F'
2 and the combustor 12, and an oxidant gas release valve 29 between the oxidant gas discharge part 11a2 of the oxidant gas discharge pipe 11A and the mixer 13. are doing.

In general, the fuel gas supply section F and the oxidizing gas supply section A
are connected to inert gas supply parts 33N1 and 33N2, respectively, and these inert gas supply parts 33N1 and 33N2 are connected to
are provided with inert gas supply valves 33F and 33A, respectively. Moreover, 27 in the figure is a differential pressure controller, and each of the above-mentioned differential pressure gauges 26F.

Based on the detection signal from 26A, the inert gas supply valve 33F
, 33A to control the differential pressure ΔP1 between the fuel gas F and the inert gas N and the differential pressure ΔP between the oxidizing gas A and the inert gas N.
2 within a predetermined value and suppress the crime. moreover,
In the figure, 34 is an output controller that controls the output from the fuel cell main body 11, and 35 is a load. Here, the output controller 34 is constituted by, for example, an inverter, a timer, etc., and is activated by the inert gas supply valve control signal from the differential pressure controller 27, and even if a predetermined period of time has elapsed from the activation, the differential pressure ΔPi, It operates on the condition that ΔP2 does not fall within a predetermined value, and controls the power supplied from the fuel cell device 11 to the load 35.

In a fuel cell device having such a configuration, when at least one of the differential pressure signals ΔPi and ΔP2 detected by the fuel gas side differential pressure gauge 26F and the oxidizing gas side differential pressure gauge 26A decreases and exceeds a predetermined value to become a dangerous differential pressure. The differential pressure controller 27 that monitors this differential pressure gives a valve opening signal to at least one of the corresponding inert gas supply valves 33F and 33A, and sets the inert gas N (reference pressure) in the closed container 30 in advance. The inert gas N' maintained at the same pressure is supplied to the fuel gas side inert gas supply section 33N! and oxidizing gas side inert gas supply section 3
3N2 to the fuel gas supply section 11F and oxidizing gas supply section 11A.

In this state, the differential pressure controller 2
7 continues to give a valve opening signal to the inert gas supply valves 33F and 33A. As a result, the differential pressure ΔPi.

If ΔP2 falls within a predetermined value, the differential pressure controller 27 gives a valve opening signal to the inert gas supply valves 33F and 33A to stop the supply of the inert gas N'. By doing so, it is possible to prevent the fuel cell main body 11 from being exposed to a dangerous differential pressure.

Now, in this way, the inert gas N' is supplied to the fuel cell main body 11 to eliminate the dangerous differential pressure, but for example, if at least one of the supply of the fuel gas F and the oxidizing gas A is stopped, or If at least one of the fuel/gas flow rate adjustment valve 24 and the oxidant gas flow rate adjustment valve 25 becomes closed or close to it due to a failure, etc., the differential pressure Δ
Pi.

ΔP2 does not recover to within a predetermined value for a long time.

In this case, a large amount of inert gas N' is fed into the fuel cell main body 11, and the fuel gas and oxidizing gas become diluted. Then, as a matter of course, the output voltage 36V of the fuel cell main body 11 begins to decrease. This output voltage 36V and output current 361 are controlled by the output controller 34.
The load 35 is monitored by this output controller 34.
The output current 361 is lowered while monitoring the damage caused by the output voltage 36V supplied to the circuit. By doing so, it is possible to prevent the above-mentioned polarity change phenomenon in the fuel cell main body 11. Therefore, after that, it becomes possible to shut down the operation according to a normal safe shutdown procedure.

[Effects of the Invention] As explained above, according to the present invention, the differential pressure control function is improved, and even if the supply of raw material gas is stopped, the fuel cell main body is not destroyed, thereby improving safety and reliability. It is possible to provide a fuel cell device that can

[Brief explanation of the drawing]

Fig. 1 is a system diagram showing an embodiment of the present invention, Fig. 2 is a principle diagram of a fuel cell device, Fig. 3 is a system diagram showing a conventional example of a fuel cell device, and Fig. 4 is a diagram showing the relationship between flow rate and pressure drop. FIG. 3 is a graph diagram showing the relationship between the fuel gas side and the oxidizing gas side. 11... Fuel cell main body, 11f... Fuel gas reaction section, 11f1... Fuel gas supply section, 11f2... Fuel gas discharge section, 11a... Oxidizing gas reaction section, 11a1.
... Oxidizing gas supply section, 11a2... Oxidizing gas supply section,
12... Combustor, 13... Mixer, 26.26F,
26A...Differential pressure gauge, 27...Differential pressure controller, 28...
・Fuel gas release valve, 29... Oxidizing gas release valve, 30・
... airtight container, F... fuel gas, A... oxidizing gas,
N... Inert gas, 33N1... Fuel gas side inert gas supply section, 33N2... Oxidizing gas side inert gas supply section, 33F... Fuel gas side inert gas supply valve, 33A
... Oxidizing gas side inert gas supply valve, 34... Output controller, 36V... Output voltage, 361... Output current.

Claims (1)

[Claims] a fuel cell main body comprising a fuel gas reaction section to which a fuel gas supply section and a fuel gas discharge section are connected; and an oxidation gas reaction section to which an oxidation gas supply section and an oxidation gas discharge section are connected;
An airtight container that houses the fuel cell main body and is filled with an inert gas, and is connected between the fuel gas supply section or the fuel gas discharge section and the airtight container to supply the fuel gas and the inert gas inside the airtight container. and a fuel gas side differential pressure gauge connected between the oxidizing gas supply section or the oxidizing gas discharge section and the sealed container to detect the differential pressure between the oxidizing gas and the inert gas in the sealed container. An oxidizing gas side differential pressure gauge to be detected, each inert gas supplying section on the fuel gas and oxidizing gas side connected to the fuel gas supply section and the oxidizing gas supply section and supplying inert gas, and each of these inert gas supply sections Each inert gas supply valve on the fuel gas and oxidizing gas side provided in and a differential pressure controller that operates on the condition that the differential pressure does not fall within a predetermined value even after a predetermined period of time has elapsed from the control of the inert gas supply valve to supply a predetermined amount of power from the fuel cell main body to the load. 1. A fuel cell device comprising: an output controller for controlling the output value.