JP3530458B2 - Method and apparatus for starting polymer electrolyte fuel cell - Google Patents

Description

Detailed Description of the Invention

[0001]

The present invention relates to a solid polymer fuel cell having a reformer, an electric load connected to the solid polymer fuel cell, and a combustible gas generated in the solid polymer fuel cell. The present invention relates to a method for starting a polymer electrolyte fuel cell used in a polymer electrolyte fuel cell system including a gas burner that obtains heat energy by burning, a burner for heating a reformer, and the like, and an apparatus for starting the fuel cell. .

[0002]

2. Description of the Related Art Fuel cells include phosphoric acid type fuel cells and polymer electrolyte fuel cells. Hydrogen, which is a fuel gas, is also supplied to polymer electrolyte fuel cells from a hydrogen supply device such as a hydrogen cylinder. Type and a fuel gas such as natural gas, city gas, methanol, etc., which is constantly heated by a combustion device, undergoes a chemical reaction with equipment such as a reformer to reform it into hydrogen, which is then converted into hydrogen in the fuel cell. There is a type that is supplied as fuel.

Further, in order to effectively utilize the energy of the entire energy system including the fuel cell, the polymer electrolyte fuel cell is used to generate power, and the heat generated during power generation and the exhaust gas from combustion are used. A polymer electrolyte fuel cell system forming a cogeneration system for supplying hot water is also considered.

[0004]

However, in the conventional system using the polymer electrolyte fuel cell having the reformer, energy loss at the time of starting the polymer electrolyte fuel cell is unavoidable, and the solid polymer fuel cell has a high solid content. There is a problem that it takes time for the operation of the molecular fuel cell to reach the rated stable output state.

An object of the present invention is to solve the problems of the above-mentioned conventional techniques, to promptly shift the operation of the polymer electrolyte fuel cell to a steady operation state and start the fuel cell with a device configuration as simple as possible. It is an object of the present invention to provide a method for starting a polymer electrolyte fuel cell and an apparatus for the same, which can reduce the energy loss at the time of operation and increase the overall energy efficiency of the entire system.

[0006]

The invention according to claim 1 is
A polymer electrolyte fuel cell having a reformer, an electric load connected to the polymer electrolyte fuel cell, a gas burner for burning a combustible gas generated in the polymer electrolyte fuel cell to obtain heat energy, In a polymer electrolyte fuel cell system having a burner for heating a quality device, the reformed gas is burned by a gas burner that obtains the thermal energy until the function of the reformer becomes stable after the system is started, When the reformed gas of a predetermined quality is obtained from the pouch, the reformed gas is caused to flow through the fuel electrode of the polymer electrolyte fuel cell, and the exhaust gas is gradually burned while being burned by the gas burner for obtaining the thermal energy. When the electric load is increased and the temperature of the fuel cell is substantially stabilized at the operating temperature, the exhaust gas from the fuel electrode is burned by the heating burner of the reformer. It is a method.

According to a second aspect of the present invention, there are provided a polymer electrolyte fuel cell having a reformer, an electric load connected to the polymer electrolyte fuel cell, and a combustible gas generated in the polymer electrolyte fuel cell. It has a gas burner that burns to obtain heat energy and a burner for heating the reformer, and the heat energy is maintained until the function of the reformer becomes stable after the solid polymer fuel cell is started. Combusting the reformed gas with the obtained gas burner,
When a reformed gas of a predetermined quality is obtained from the reformer, the reformed gas is caused to flow through the fuel electrode of the polymer electrolyte fuel cell, and the exhaust gas is gradually burned while being burned by the gas burner for obtaining the thermal energy. In addition, when the electric load is increased and the fuel cell almost reaches the rated stable output state, it has a mechanism for switching the flow of exhaust gas from the fuel electrode to the heating burner side of the reformer. It is a starting device for a molecular fuel cell.

According to a third aspect of the present invention, there is provided a mechanism for increasing the electric load of the polymer electrolyte fuel cell according to the second aspect,
The electric load control device is characterized in that it is an electric load control device for increasing the current while keeping the output voltage of the polymer electrolyte fuel cell at a voltage above a certain level.

According to a fourth aspect of the invention, there is provided a mechanism for increasing the electric load of the polymer electrolyte fuel cell according to the second aspect,
The present invention is characterized in that the electric load control device increases the current in accordance with a rule previously obtained as a relation between the temperature and the output voltage of the polymer electrolyte fuel cell.

According to a fifth aspect of the present invention, the electric load according to any one of the second to fourth aspects is a load connected to an electric power system outside the polymer electrolyte fuel cell via an inverter. It is characterized by the fact that it is.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be applied to a polymer electrolyte fuel cell such as a polymer electrolight fuel cell (hereinafter referred to as a fuel cell) in a power generation system GS for a small household power source. An embodiment of the polymer electrolyte fuel cell system will be described with reference to the drawings.

In FIG. 1, reference numeral 100 indicates a building, and the building 100 is supplied with electric power from a commercial power source via a low-voltage light line 101, a watt hour meter 102, and a distribution board 103. . The electric power of the commercial power source is supplied to the air conditioner 105 and other electric devices via the first cable 104 shown by a thin line. The polymer electrolyte fuel cell system of this embodiment has a fuel cell 6 as will be described later.
In addition to the power generation system GS using the heat recovery device RD.

The electric power generated by the fuel cell 6 is DC / D
Via C converter 107, boosted to 180V,
It is sent to the grid interconnection inverter 108, and is supplied to electrical equipment such as the illumination 111 and the television 106 through the distribution board 103 and the second cable 110 shown by the thick line in FIG. The fuel cell power generation system GS is connected to a commercial power source via a grid interconnection inverter 108.

The heat recovery device RD is connected by a water circulation path including a hot water storage tank 50, heat exchangers 32 and 46, and pumps 33 and 47.

In the polymer electrolyte fuel cell system using such a fuel cell 6, city water is supplied into the hot water storage tank 50 through a water supply pipe 61 connected to the hot water storage tank 50. Obtained heat such as heat generated in the process of power generation by the fuel cell 6 or heat generated by burning gas generated in the polymer electrolyte fuel cell system for the city water supplied to the hot water storage tank 50. Energy and exhaust heat are recovered to heat water, the heated hot water is stored in the hot water storage tank 50, supplied to the bath 113, the kitchen 114, etc. via the hot water supply pipe 62,
The energy of the fuel used in the fuel cell 6 is effectively used.

FIG. 2 is a view showing an embodiment of such a polymer electrolyte fuel cell system of the present invention.

In FIG. 2, the fuel gas supply of the fuel cell 6 is as follows: natural gas, city gas, methanol, LPG,
Raw fuel such as butane is supplied to the desulfurizer 2 through the fuel pipe 1, where the sulfur component is removed from the raw fuel. The raw fuel that has passed through the desulfurizer 2 is pressurized by the booster pump 10 and supplied to the reformer 3.

Since the chemical reaction in the reformer 3 is an endothermic reaction, it has a burner 12 for continuing the chemical reaction while heating, to which fuel is supplied via a fuel pipe 13 and a fan 14 is connected. Combustion is performed by the combustion air supplied via the above. Reference numeral 15 is a pipe line to which unreacted hydrogen is supplied via the fuel electrode 6a.

The heat exchanger 17 is connected to the exhaust system 31 of the reformer 3, and when the water in the water tank 21 is supplied via the pump 22, the heat exchanger 17 vaporizes the water. .
This steam is mixed with the raw fuel that has passed through the desulfurizer 2 and the pump 10 and supplied to the reformer 3.

The raw fuel supplied to the reformer 3 undergoes a chemical reaction here to produce a reformed gas containing hydrogen, carbon dioxide and carbon monoxide. This reformed gas is supplied to the CO shift converter 4, where carbon monoxide contained in the fuel gas is transformed into carbon dioxide. The gas that has passed through the CO shift converter 4 is supplied to the CO remover 5, and here, the CO shift converter 4
The unmodified carbon monoxide in the gas that has passed through is oxidized to carbon dioxide. After passing through the CO remover 5, the carbon monoxide concentration becomes 1
The gas having a high hydrogen concentration (reformed gas) reduced to 0 ppm or less is supplied to the fuel electrode 6a of the polymer electrolyte fuel cell 6.

At this time, the amount of water added to the reformed gas is adjusted by adjusting the amount of treated water supplied from the water tank 21 to the reformer 3. For example, the ratio of the amount of steam supplied to the reformer 3 via the heat exchanger 17 to the amount of raw fuel gas (S / C ratio) is 2 to 3 which is the conventional S / C ratio.
If the S / C ratio is set to a value higher than the above value, for example, the amount of water contained in the reformed gas discharged from the reformer 3 can be increased.

The reformed gas discharged from the CO remover 5 is directly supplied to the fuel cell 6 so that a large amount of water is not lost from the reformed gas while passing through the CO shift converter 4 and the CO remover 5. However, when the reformed gas at a high temperature flows in and the fuel cell 6 becomes too hot and the function of the cell constituent material is deteriorated or the solid polymer membrane of the cell is damaged, A heat exchanger (not shown) is provided in the pipe 64 between the CO remover 5 and the fuel cell 6, and the water tank 21 is provided in this heat exchanger.
The temperature of the reformed gas is adjusted by exchanging heat with the reformed gas by flowing water.

When the S / C ratio is increased, a proper amount of moisture is given to the reformed gas supplied to the fuel electrode 6a of the fuel cell, even if an independent humidifying device for humidifying the reformed gas is not additionally provided. You can

When the power generation system GS is started, as described above, the raw fuel and the combustion air are supplied to the burner 12 for combustion, and when the operating temperature of the fuel cell 6 is stable after the start, the fuel pipe 13 The supply of fuel from the fuel cell is cut off, and instead, unreacted hydrogen gas (off gas) discharged from the fuel electrode 6a is supplied as fuel via the pipe 15, and combustion of the burner 12 is continued.

Since the chemical reaction performed in the CO shift converter 4 and the CO remover 5 is an exothermic reaction, for example, in the CO remover 5, a burner (not shown) is burned only when the system is started to generate combustion gas. The temperature of the CO remover 5 is raised to the reaction temperature by the heat of the combustion gas generated at this time.

After that, the reaction temperature is maintained by the heat of the exothermic reaction of itself. Cooling control is performed from the outside as necessary so that the CO shift converter 4 and the CO remover 5 do not rise above the reaction temperature.

The reaction air is supplied to the air electrode 6k by supplying air from the air pump 11 to the water tank 21 and sending the air to the gas phase portion 53 while bubbling the reaction air into the water in the water tank 21. Is performed, and the reaction air is supplied with water so that the reaction in the fuel cell 6 is appropriately maintained, and the reaction air is supplied to the air electrode 6k of the fuel cell through the conduit 25.

In the fuel cell 6, the hydrogen contained in the reformed gas supplied to the fuel electrode 6a and the oxygen contained in the air supplied to the air electrode 6k via the air pump 11 and the gas phase portion 53 of the water tank. While electricity is generated by the electrochemical reaction, the battery itself generates reaction heat due to the activation overvoltage, the concentration overvoltage, and the resistance overvoltage during the electrochemical reaction.

The cooling unit 6c of the fuel cell 6 has electrodes 6a, 6k of the fuel cell 6 in order to prevent the fuel cell 6 from overheating due to reaction heat of the cell itself after the fuel cell shifts to a steady operation state. Is a cooling device juxtaposed with each other, and the cooling unit 6c
The water in the water tank 21 is circulated as cooling water by the pump 48 so that the temperature in the fuel cell 6 can be maintained at a temperature suitable for power generation, for example, 70 ° C. to 80 ° C. with this cooling water. Cooling is controlled.

A heat exchanger 1 is provided between the reformer 3 and the CO shift converter 4, and between the CO shifter 4 and the CO remover 5, respectively.
8 and 19 are connected, and water is circulated from the water tank 21 to the heat exchangers 18 and 19 via the pumps 23 and 24,
The gas that has passed through the reformer 3 and the CO shift converter 4 is cooled.

In this way, the reformer 3, the CO shifter 4,
In the CO remover 5 and the fuel cell 6, a predetermined chemical reaction and power generation are continued.

Next, the starting control of the polymer electrolyte fuel cell used in the polymer electrolyte fuel cell system will be described.

As described above, at the time of starting the polymer electrolyte fuel cell system, the composition of the reformed gas that has passed through the reformer 3, the CO shift converter 4, and the CO remover 5 is not stable, so that the composition is stable. Until then, this gas cannot be supplied to the fuel cell 6. Therefore, the reformer 3, the CO converter 4, the CO
Until the temperature of each reactor of the remover 5 becomes stable, the reformed gas in an unstable gas composition state is fed through the pipe 35 and the on-off valve 36.
It is led to the PG burner 34 via the route and burned. Then, after the operation of each reactor is stabilized, the reformed gas is introduced into the fuel cell 6 to start power generation.

The introduction of the reformed gas does not immediately bring the fuel cell, which has started power generation, to the rated stable output state.
The output of power generation is small while the temperature of the fuel cell is low.
The unreacted gas not used for power generation in the fuel cell 6 at the time of start-up is guided to the PG burner 34 via the pipe 38 and the opening / closing valve 39 to be burned, and the temperature of the fuel cell 6 becomes the operating temperature (for example,
70 ° C. to 80 ° C.) and after reaching the rated output state, the flow of the unreacted gas discharged from the fuel electrode 6a is switched and introduced into the burner 12 of the reformer 3 via the pipe line 15. Then, switching control is performed so that the fuel is burned here.

The switching control of the reformed gas is performed by the controller 95.
Done by After activation of the polymer electrolyte fuel cell system, the control device 95 operates to close the on-off valve 91 and open the on-off valve 36 until the above reactors are stabilized in temperature. As a result, the reformed gas having an unstable composition is supplied to the PG burner 34 through the pipe 35 and the on-off valve 36 and burned, and the heat is recovered in the hot water storage tank 50 by the water circulating in the heat exchanger.

When the temperature of each reactor is stable, the controller 95 opens the on-off valves 91 and 39, introduces the reformed gas into the fuel electrode 6a, and closes the on-off valves 36 and 92.
The flow of the reformed gas is switched from the pipe line 35 to the pipe line 38, but is supplied to the PG burner 34 as in the case of the pipe line 38.
Combustion is continued here until the temperature of the fuel cell 6 stabilizes.

In this process, the controller 95 gradually increases the electric load on the fuel cell by monitoring the battery temperature with the sensor 115 and increasing the extraction current value according to the battery temperature at that time.

To take out such an electric load, for example, when the control device 95 opens the valve 91 to start flowing the reformed gas to the fuel electrode 6a as described above and then confirms the open voltage of the battery. Immediately in the form of cooperation from the open voltage to the power system via the inverter 108.

The control device 95 controls the inverter 108 to prevent the battery from being overloaded and being damaged, and the battery to reach the rated stable output state as soon as possible while preventing the battery from being rated stable. Until the temperature reaches the optimum temperature in the output state, the load temperature is controlled to be gradually increased by increasing the current.

In addition to the control of the temperature rise of the load of the fuel cell by the controller 95, in addition to this, the voltage of the cell is controlled so that the output voltage of the fuel cell is kept at a constant voltage value, for example, a voltage of 0.6 V or more per unit cell. That controls the inverter 108 by the control device 95 so as to obtain the maximum current that can be obtained within that range, and if the open voltage of the battery is confirmed, the load is mechanically changed from 0% to 100% at a certain speed. A method for controlling the inverter 108 so as to increase it, or a controller for controlling the amount of load applied to the fuel cell immediately after the start of power generation based on the data obtained as the characteristics of the fuel cell of the polymer electrolyte fuel cell system in advance. There is a method of controlling with 95.

In any of these cases, when the battery power generation is started and the open voltage is confirmed, the maximum load is generated within a range where the electric power is started from the small power generation capacity and the control device 95 does not damage the fuel cell 6. In order to apply a load to the fuel cell, the current is increased and the fuel cell 6 is heated by self-reaction heat to raise the temperature of the cell to the temperature of the rated stable output state as soon as possible, and the solid polymer fuel cell This is to shift the operation to a steady operation state, whereby the energy loss when starting the fuel cell can be minimized.

According to the load applying method and control of such a form, a heating device for raising the temperature of the battery is not required, and the heating energy is not required separately. No, there is an excessive load on the battery immediately,
The fuel cell 6 can be rapidly shifted to a steady operation state without damaging the cell.

After the temperature of the fuel cell 6 is stabilized and the rated power generation is continuously performed (the rated stable output state), most of the reformed gas is used for power generation, and the obtained power is obtained. As described above, it is supplied to a load such as an electric device via the DC / DC converter 107.

The flow of gas at this time is based on the on-off valves 91, 9
The unreacted gas (off-gas) that has not been converted into electric power in the fuel cell 6 is supplied to the burner 12 through the pipe 15 while the open / close valves 36 and 39 are closed while the valve 2 is opened.
Switching control is performed by the control device 95 so as to be used for heating.

Reference numeral 115 is a temperature sensor for inputting temperature information of the battery 6 to the controller 95.

In this way, the control device 95 controls the gas burner (PG burner 3 until the stable reformed gas is obtained from the reformer 3 after the solid polymer fuel cell 6 is started.
In step 4), the reformed gas having an unstable gas composition is burned, and the heat load connected to this burner, for example, the hot water storage tank 5
The control is performed so as to obtain heat energy such as 0.

When a reformed gas of a predetermined quality is obtained from a reactor such as the reformer 3, the reformed gas is caused to flow through the fuel electrode 6a of the polymer electrolyte fuel cell, and the exhaust gas is used as a gas burner ( The electric load of the fuel cell is increased by gradually increasing the current while burning it in the PG burner 34), and when the fuel cell 6 almost reaches the rated stable output state, the flow of the off gas from the fuel electrode 6a. The reformer heating burner 1
The control device 95 controls the switching to the 2 side. According to the method for starting a polymer electrolyte fuel cell of the present invention, the energy before the power generation is started is used instead of hot water, and the polymer electrolyte fuel cell is rapidly shifted to a steady operation. In addition, since the heat generated by the electric power and the fuel cell, the unused fuel gas, the reformed gas, and the like are used as a heat load, the energy of the fuel cell as a whole can be effectively utilized.

In addition to the power generation efficiency of the fuel cell alone, it is easy to take the form of a polymer electrolyte fuel cell system or the like, which is connected to the effective use of the energy of the supplied fuel,
It is possible to provide a cogeneration system that has a large effect on power generation and heat utilization.

[0049]

According to the present invention, in a fuel cell system incorporating a polymer electrolyte fuel cell, the polymer electrolyte fuel cell includes a reformer, an electric load connected to the fuel cell,
A burner for burning the combustible gas generated in the fuel cell to obtain heat energy, and a burner for heating the reformer,
A state in which the reformed gas is burned by a gas burner that obtains the thermal energy until the function of the reformer becomes stable after the start of the polymer electrolyte fuel cell, and the reformed gas of a predetermined quality is obtained from the reformer. Then, the reformed gas is caused to flow through the fuel electrode of the polymer electrolyte fuel cell, and the exhaust gas is burned by the gas burner for obtaining the thermal energy while gradually increasing the electric load of the fuel cell, and the temperature of the fuel cell is increased. Since the solid polymer electrolyte fuel cell is started by switching the exhaust gas from the fuel electrode to the heating burner of the reformer when the temperature stabilizes at about the operating temperature, the device configuration for starting the fuel cell becomes extremely simple.

Further, the operation of the polymer electrolyte fuel cell is promptly shifted to the steady operation state while preventing an excessive load from being applied to the fuel cell and damaging the fuel cell at the time of startup.
Energy loss when starting the fuel cell can be reduced.

Further, due to the heat load of the hot water supply device or the like in the polymer electrolyte fuel cell system, the heat generated during the transition from the startup of the polymer electrolyte fuel cell to the steady operation and the unstable components are modified. Since the energy of the quality gas is recovered as heat energy, it is possible to provide a polymer electrolyte fuel cell system in which the overall energy efficiency of the entire system using the fuel cell is increased.

[Brief description of drawings]

FIG. 1 is a system diagram when a polymer electrolyte fuel cell system according to the present invention is installed in a home.

FIG. 2 is a circuit diagram showing an embodiment of a polymer electrolyte fuel cell system.

[Explanation of symbols]

3 reformer 6 Fuel cell 6a Fuel electrode 12,34 burners 13, 15, 35, 38 pipelines 36, 39, 91, 92 Open / close valve 32,46 heat exchanger 50 hot water storage tank 95 Control device 107 DC / DC converter 108 Grid-connected inverter 115 Temperature sensor GS power generation system RD heat recovery device

─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Satoshi Yamamoto 2-5-5 Keihanhondori, Moriguchi-shi, Osaka Sanyo Electric Co., Ltd. (72) Inventor Akira Fujio 2-5-keihanmotodori, Moriguchi-shi, Osaka Sanyo Denki Co., Ltd. (72) Inventor Taketoshi Koki 2-5-5 Keihan Hondori, Moriguchi City, Osaka Prefecture Sanyo Denki Co., Ltd. (72) Inventor Katsuyuki Makihara 2-5 Keihan Hondori, Moriguchi City, Osaka Prefecture No. 5 within Sanyo Electric Co., Ltd. (56) Reference JP-A-8-162137 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) H01M 8/04 H01M 8/00 H01M 8 / 10 H01M 8/06

Claims (5)

(57) [Claims] 1. A polymer electrolyte fuel cell having a reformer, and an electric load connected to the polymer electrolyte fuel cell,
In a polymer electrolyte fuel cell system having a gas burner for obtaining heat energy by burning a combustible gas produced in a polymer electrolyte fuel cell, and a burner for heating a reformer, the reformer after the system is started. Until the function of is stabilized, burn the reformed gas with a gas burner that obtains the heat energy,
When a reformed gas of a predetermined quality is obtained from the reformer, the reformed gas is caused to flow through the fuel electrode of the polymer electrolyte fuel cell, and the exhaust gas is gradually burned while being burned by the gas burner for obtaining the thermal energy. Of the solid polymer fuel cell, wherein the electric load is increased and the exhaust gas from the fuel electrode is burned by the heating burner of the reformer when the temperature of the fuel cell is substantially stabilized at the operating temperature. starting method. 2. A polymer electrolyte fuel cell having a reformer, and an electric load connected to the polymer electrolyte fuel cell,
A reformer having a gas burner for obtaining heat energy by burning a combustible gas generated in the polymer electrolyte fuel cell, and a burner for heating the reformer, and the reformer after starting the polymer electrolyte fuel cell Until the function of is stabilized, the reformed gas is burned by the gas burner for obtaining the thermal energy, and when the reformed gas of a predetermined quality is obtained from the reformer, the fuel electrode of the polymer electrolyte fuel cell is The reformed gas is made to flow, and the exhaust gas is burned by the gas burner that obtains the thermal energy while gradually increasing the electric load, and when the fuel cell almost reaches the rated stable output state, the flow of the exhaust gas from the fuel electrode is modified. A starting device for a polymer electrolyte fuel cell, which has a mechanism for switching to a heating burner side of a quality device. 3. A mechanism for gradually increasing an electric load of a fuel cell while flowing a reformed gas through a fuel electrode of the polymer electrolyte fuel cell and burning the exhaust gas with a gas burner for obtaining the thermal energy. The starting device for a polymer electrolyte fuel cell according to claim 2, which is an electric load control device for increasing the current while keeping the output voltage of the polymer electrolyte fuel cell at a voltage higher than a certain level. 4. A mechanism for gradually increasing an electric load of a fuel cell while flowing a reformed gas through a fuel electrode of the polymer electrolyte fuel cell and burning the exhaust gas with a gas burner for obtaining the thermal energy. The polymer electrolyte fuel cell according to claim 2, wherein the polymer electrolyte fuel cell is an electric load control device that increases an electric current according to a rule previously determined as a relationship between the temperature and the output voltage of the polymer electrolyte fuel cell. Activation device. 5. The electric load connected to the polymer electrolyte fuel cell is a load connected to an electric power system outside the polymer electrolyte fuel cell via an inverter. The starting device for a polymer electrolyte fuel cell according to any one of claims 2 to 4.