JP3784456B2 - Fuel cell power generator and method of operating the same - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a fuel cell power generator and an operation method thereof.
[0002]
[Prior art]
A fuel cell such as a solid polymer electrolyte fuel cell or a phosphoric acid fuel cell uses hydrogen as a fuel gas, and generates electricity by electrochemically reacting it with oxygen as an oxidant gas.
[0003]
[Problems to be solved by the invention]
The surplus hydrogen gas discharged from the fuel cell can be reused as fuel for the reformer that produces hydrogen, but when hydrogen is produced through a reforming reaction using water / methanol as a raw material, A large amount of by-products such as carbon dioxide is mixed in the reformed gas in addition to hydrogen. For this reason, when the reformed gas is used as the fuel gas of the fuel cell, the hydrogen concentration is low, and a constant hydrogen concentration cannot be obtained, so that it is difficult to constantly obtain a high output.
[0004]
Therefore, it is preferable to use pure hydrogen from a hydrogen cylinder as a fuel gas. However, according to the prior art, surplus hydrogen gas remaining after the power generation reaction is discharged from the fuel cell to the outside of the system. However, the so-called spilling of hydrogen gas is not preferable in terms of the utilization efficiency of hydrogen gas, and when a fuel cell is used as a drive source of an electric vehicle, air in a garage or an underground parking lot is used. Hydrogen will be discharged into a poorly circulated space .
[0005]
Although it is possible to configure the system so that surplus hydrogen gas is not discharged from the fuel cell, in this case, the partial pressure of nitrogen and water vapor in the fuel gas gradually increases, and the hydrogen partial pressure relatively decreases Therefore, the power generation performance is deteriorated.
[0006]
[Means for Solving the Problems]
Accordingly, the present invention provides a fuel cell power generator that can improve safety and hydrogen utilization efficiency by using a closed system that does not release hydrogen gas to the outside air, and can maintain stable power generation performance. Objective.
[0007]
That is, according to the present invention, in a power generation apparatus using a fuel cell using hydrogen as a fuel gas, the fuel gas whose hydrogen partial pressure has decreased due to power generation by the fuel cell is discharged from the fuel electrode side to the air electrode side through the valve means. And a control means for controlling opening and closing of the valve means .
[0008]
Here, the closed line means a flow path having no outlet other than the valve means . Therefore, when the valve means is closed, the entire amount of the fuel electrode exhaust gas discharged from the fuel electrode is supplied to the air electrode.
[0009]
The control means controls the valve means to be opened intermittently while the valve means is normally closed.
[0010]
Preferably, voltage measuring means for measuring the output voltage of the fuel cell is provided, and the control means receives the measurement result by the voltage measuring means, and valve means so as not to cause a substantial drop in the output voltage of the fuel cell. Open / close control.
[0011]
Alternatively, voltage measuring means for measuring the output voltage of the fuel cell is provided, and the control means substantially determines the output voltage when the fuel cell is operated with the valve means closed based on the measurement result by the voltage measuring means. Data of a time interval until a decrease is seen is created in advance, and the valve means is controlled to open and close at a cycle substantially the same as this time interval or slightly shorter.
[0012]
According to a further preferred embodiment, a circulation path connected to the intake side and the exhaust side of the air electrode of the fuel cell is provided. The circulation path is provided with an intake port for introducing air from outside the system, and an air An exhaust port for discharging the air electrode exhaust gas including reaction product water discharged from the electrode to the outside of the system is connected, and the reaction product water is contained by controlling the opening degree of at least one of the intake port and the exhaust port. The air electrode exhaust gas is configured to be reintroduced into the air electrode through a circulation path.
[0013]
The operating method of the fuel cell power generator according to the present invention is characterized in that after starting operation with the valve means closed, the valve means is intermittently opened for a predetermined time at a predetermined cycle.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is a schematic view showing a configuration example of a fuel cell power generator according to the present invention. Pure hydrogen gas from a hydrogen gas cylinder 5 is supplied to a fuel electrode 2 of a fuel cell 1 through a pressure regulating valve 6 and air. The pole 3 is supplied with oxygen as an oxidant gas. As is well known, power generation is performed by transferring hydrogen ions obtained at the fuel electrode 2 in the form of protons through the electrolyte 4 to the air electrode 3.
[0015]
Most of the hydrogen gas supplied to the fuel electrode 2 is used for power generation reaction and consumed, but the remaining surplus hydrogen gas flows through the closed line 7 and is introduced into the air electrode 3 through the valve 8. .
[0016]
The hydrogen gas introduced into the air electrode 3 burns on the air catalyst (Pt) and is converted into water. As a result, in the case of a solid polymer electrolyte fuel cell in which a solid polymer ion exchange membrane is used as the electrolyte 4, the water generated by the normal cell reaction at the air electrode 3 and the recovered water by the combustion of surplus hydrogen gas are Due to the difference in concentration, the electrolyte membrane 4 is humidified because it flows toward the electrolyte membrane 4 having a low water concentration. That is, the polymer solid electrolyte membrane 4 can be humidified from the air electrode 3 side in addition to the conventional humidification from the fuel electrode 2 side, or can be performed only from the air electrode 3 side. When humidification from the fuel electrode 2 side is not performed, it is not necessary to introduce water vapor into the hydrogen gas supplied to the fuel electrode 2 for humidification, so that the utilization efficiency of hydrogen gas is further improved and stabilized.
[0017]
The output voltage of the fuel cell 1 is monitored by a voltmeter 9. The control device 10 controls the opening and closing and the opening degree of the pressure regulating valve 6 and the valve 8 as described later.
[0018]
The operation of the fuel cell power generation device shown in FIG. 1 will be described. First, when starting up, the valve 8 is held closed so that the pressure regulating valve 6 supplies hydrogen to the fuel electrode 2 at a constant flow rate below the explosion limit. adjust.
[0019]
When the fuel cell 1 is operated with the valve 8 closed, the partial pressures of nitrogen and water vapor contained in trace amounts in the hydrogen gas gradually increase. That is, since the partial pressure of hydrogen consumed at the fuel electrode 2 gradually decreases, the output voltage also decreases accordingly, and a stable output cannot be obtained.
[0020]
Therefore, a time interval at which the output voltage starts to decrease when the fuel cell 1 is operated with the valve 8 closed is measured in advance, and the valve 8 is opened at a period substantially the same as or slightly shorter than the time interval. As described above, the fuel cell 1 is operated while the valve 8 is intermittently controlled to open and close.
[0021]
Alternatively, the control device 10 may analyze input data from the voltmeter 9 that constantly monitors the output voltage, and may control the valve 8 to be opened for a certain period of time simultaneously with the start of the decrease in the output voltage.
[0022]
FIG. 2 shows a configuration of a fuel cell power generator according to another embodiment of the present invention. In the embodiment of FIG. 1, pure hydrogen from a hydrogen gas cylinder 5 is supplied as a fuel gas, whereas a water / methanol mixture or the like The reformed raw material is reformed in the reformer 12 to generate a hydrogen-rich reformed gas, and this reformed gas is stored in the tank 13, and fuel is supplied via the pressure regulating valve 6 and the valve 8. Supply to the pole 2.
[0023]
The operation method of the fuel cell power generator according to this embodiment is the same as that described above with reference to FIG. 1 and will not be described. However, when the reformed gas is used as the fuel gas, in addition to hydrogen gas, water vapor, nitrogen , Carbon dioxide, carbon monoxide and the like are contained in a relatively large amount, and when the fuel cell 1 is operated with the valve 8 closed, the hydrogen partial pressure drop and the output voltage drop caused thereby are started in a relatively short time. Therefore, it is necessary to set a short period until the closed valve 8 is opened.
[0024]
FIG. 3 shows an embodiment configured as a circulation flow path for circulating the exhaust gas discharged from the air electrode 3 to the air electrode 3 as a modification of the embodiment shown in FIG. Such a configuration is suitably employed when a solid polymer electrolyte membrane is used as the electrolyte 4 and the humidification of the electrolyte membrane is performed exclusively from the air electrode 3 side.
[0025]
That is, the exhaust gas from the air electrode 3 is sent to the air discharge line 14, and this air discharge line 14 joins the air introduction line 15 to form a circulation path 16. The exhaust gas containing the generated reaction product water is introduced into the air electrode 3 so that the electrolyte membrane 4 can be humidified.
[0026]
An exhaust valve 17 is provided in connection with the circulation path 16, and a certain amount of exhaust gas from the air electrode is discharged out of the system according to the opening of the exhaust valve 17, and the remaining amount is the circulation path 16 and the air. It is reintroduced into the air electrode 3 through the introduction line 15. The opening degree of the exhaust valve 17 is controlled by the aforementioned control device 10 so as to give the optimal water balance condition to the fuel cell 1.
[0027]
According to such a structure, in addition to the water produced | generated when the hydrogen gas introduce | transduced into the air electrode 3 through the closed line 7 when the valve | bulb 8 is open is burned on an air catalyst, the circulation path 16 The reaction product water contained in the exhaust gas re-introduced into the air electrode 3 through the water exists as moisture in the air electrode 3, which permeates the electrolyte membrane 4 due to the water concentration difference and moves to the fuel electrode 2 side, Further, the moisture moved to the fuel electrode 2 side moves to the air electrode 3 side as electroosmotic water, and the humidification of the electrolyte membrane 4 is efficiently and averaged by the reciprocating movement of these moisture. For this reason, humidification from the fuel electrode 2 side becomes unnecessary, and it is not necessary to humidify the fuel gas itself, so that the hydrogen partial pressure can be increased and the power generation efficiency can be improved.
[0028]
In any of the embodiments shown in FIGS. 1 to 3, in any case, surplus hydrogen gas fed from the fuel electrode 2 through the closed line 7 when the valve 8 is opened passes through the air electrode 3 through a path different from oxygen. However, the surplus hydrogen gas may be joined to the oxygen introduction line. In particular, the configuration of introducing surplus hydrogen gas into an air supply manifold (not shown) provided adjacent to the air electrode 3 and introducing it into the air electrode 3 together with air (oxygen) can be simplified. This is preferable for downsizing.
[0029]
【The invention's effect】
According to the present invention, surplus hydrogen gas that has not been consumed in the battery reaction is consumed in the system of the fuel cell power generation apparatus without being released from the fuel electrode to the outside air, and therefore, it is extremely safe, so that it is particularly an electric vehicle. It is suitable for mounting as a drive source.
[0030]
In addition, an increase in the partial pressure of components other than hydrogen, such as water vapor and nitrogen in the fuel gas supplied to the fuel electrode, is suppressed, and the efficiency of using hydrogen in the fuel gas is improved and stabilized.
[0031]
Furthermore, in a polymer solid oxide fuel cell that uses a polymer solid ion exchange membrane as an electrolyte, surplus hydrogen gas introduced into the air electrode burns on the air catalyst and is converted to water, which is used for the electrolyte. Since the membrane can be humidified, humidification from the fuel electrode side becomes unnecessary. Therefore, it is possible to increase the hydrogen partial pressure in the fuel gas and further contribute to the improvement and stabilization of power generation efficiency.
[Brief description of the drawings]
FIG. 1 is a schematic diagram showing a schematic configuration of a fuel cell power generator according to an embodiment of the present invention.
FIG. 2 is a schematic diagram showing a schematic configuration of a fuel cell power generator according to a modification of the present invention.
FIG. 3 is a schematic diagram showing a schematic configuration of a fuel cell power generator according to still another embodiment of the present invention.
[Explanation of symbols]
1 Fuel Cell 2 Fuel Electrode 3 Air Electrode 4 Electrolyte (electrolyte membrane)
5 Hydrogen gas cylinder 6 Pressure regulating valve 7 Closed line 8 Valve 9 Voltmeter 10 Controller 12 Reformer 13 Reformed gas tank 14 Air discharge line 15 Air introduction line 16 Circulation path 17 Valve

Claims (6)

In a power generation apparatus using a fuel cell that uses hydrogen as a fuel gas, a closed line that discharges the fuel gas having a reduced hydrogen partial pressure accompanying the power generation of the fuel cell from the fuel electrode side to the air electrode side through the valve means; And a control means for controlling opening and closing of the valve means . 2. The fuel cell power generator according to claim 1, wherein the control means controls the valve means so as to be opened intermittently while the valve means is normally closed. Voltage measuring means for measuring the output voltage of the fuel cell is provided, and the control means receives the measurement result by the voltage measuring means and opens the valve means when the output voltage of the fuel cell decreases. 3. The fuel cell power generator according to claim 2, wherein the valve means is controlled. Voltage measuring means for measuring the output voltage of the fuel cell is provided, and the control means substantially controls the output voltage when the fuel cell is operated with the valve means closed based on a measurement result by the voltage measuring means. Data of a time interval until a typical decrease is seen is created in advance, and the valve means is controlled to open and close so that the valve means is opened at a period substantially the same as or slightly shorter than this time interval. The fuel cell power generator according to claim 2. A circulation path connected to the intake side and the exhaust side of the air electrode of the fuel cell is provided, and an intake port for introducing air from outside the system to the circulation path and reaction product water discharged from the air electrode An exhaust port for exhausting the air electrode exhaust gas containing gas to the outside of the system is connected, and by controlling the opening degree of at least one of the intake port and the exhaust port, the air electrode exhaust gas containing the reaction product water is passed through the circulation path. 5. The fuel cell power generator according to claim 1, wherein the fuel cell power generator is configured to be reintroduced into the air electrode through the air electrode. 2. The method of operating a fuel cell power generator according to claim 1, wherein the valve means is intermittently opened for a predetermined time at a predetermined cycle after the start-up operation with the valve means closed. Operation method of fuel cell power generator.

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