JP2001291525A - Starting method of solid polymer-type fuel cell and its device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a starting method of a solid polymer-type fuel cell wherein energy loss is reduced in starting the fuel cell and in which the total energy efficiency is enhanced, by shifting the operation of the fuel cell into a stable operation state promptly. SOLUTION: In a solid polymer-type fuel cell system which has a fuel cell with a reformer, a gas burner to burn combustible gas generated by the fuel cell and a burner for the reformer, after exhaust gas transited through a fuel electrode is increasingly electrically loaded while burning with the burner, the flow of the exhaust gas is switched to the heating burner of the reformer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to 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. The present invention relates to a method and an apparatus for starting a solid polymer fuel cell used in a solid polymer fuel cell system comprising a gas burner for obtaining thermal energy by burning, a burner for heating a reformer, and the like. .

[0002]

2. Description of the Related Art There are two types of fuel cells: a phosphoric acid type fuel cell and a polymer electrolyte fuel cell. Hydrogen as a fuel gas is also supplied from a hydrogen supply device such as a hydrogen cylinder to the polymer electrolyte fuel cell. And a fuel gas, such as natural gas, city gas, methanol, etc., which is chemically heated by a reformer or other device to reform hydrogen into hydrogen while the fuel device is constantly heated by a combustion device. There is a type that supplies it as fuel.

Further, in order to effectively use the energy of the entire energy system including the fuel cell, power generation is performed using a polymer electrolyte fuel cell, and heat generated during the power generation and exhaust gas of combustion are used. A polymer electrolyte fuel cell system that forms a cogeneration system that supplies hot water by heating has also been considered.

[0004]

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

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems of the prior art, and to quickly shift the operation of a 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 and an apparatus for starting a polymer electrolyte fuel cell, which can reduce the energy loss at the time of performing the operation and increase the total energy efficiency of the entire system.

[0006]

According to the first aspect of the present invention,
A polymer electrolyte fuel cell having a reformer; an electric load connected to the polymer electrolyte fuel cell; and a gas burner for obtaining heat energy by burning combustible gas generated in the polymer electrolyte fuel cell. In a polymer electrolyte fuel cell system having a burner for heating a reformer, the reformed gas is burned by a gas burner that obtains the heat energy until the function of the reformer is stabilized after the system is started, and the reforming gas is burned. When a reformed gas of a predetermined quality is obtained from the reformer, the reformed gas is flowed through the fuel electrode of the polymer electrolyte fuel cell, and the exhaust gas is gradually burned with a gas burner for obtaining the thermal energy. The electric load is increased, and when 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 is 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. A gas burner that obtains thermal energy by burning, and a burner for heating the reformer, and the heat energy is supplied until the function of the reformer becomes stable after the start of the polymer electrolyte fuel cell. Burn 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 supplied to the fuel electrode of the polymer electrolyte fuel cell, and the exhaust gas is gradually burned by a gas burner for obtaining the thermal energy. A mechanism for switching the flow of exhaust gas from the fuel electrode to the heating burner side of the reformer when the fuel cell substantially reaches the rated stable output state. It is a starting device for a molecular fuel cell.

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

According to a fourth aspect of the present invention, the mechanism for increasing the electric load of the polymer electrolyte fuel cell according to the second aspect is as follows.
The present invention is characterized in that it is an electric load control device that increases the current in accordance with a rule previously determined as the relationship 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 following.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will now be described in which a polymer electrolyte fuel cell (hereinafter, referred to as a fuel cell) such as a polymer electrolite fuel cell is used in a power generation system GS for a small household power supply. An embodiment of the polymer electrolyte fuel cell system will be described with reference to the drawings.

In FIG. 1, reference numeral 100 denotes a building, and the building 100 is supplied with electric power from a commercial power supply via a low-voltage lamp 101, a watt-hour meter 102, and a distribution board 103. . The electric power of the commercial power supply 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 according to this embodiment includes a fuel cell 6 as described later.
And a heat recovery device RD in addition to the power generation system GS using the power generation system.

The electric power generated by the fuel cell 6 is DC / D
It is boosted to 180V via C converter 107,
The electric power is sent to the system interconnection inverter 108, and is supplied to the electric equipment such as the lighting 111 and the television 106 via the distribution board 103 and the second cable 110 shown by a thick line in FIG. 1. This fuel cell power generation system GS is connected to a commercial power supply via a system interconnection inverter 108.

The heat recovery device RD is connected to 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. The city water supplied to the hot water storage tank 50 is used to generate 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. Energy and waste heat are collected to heat the water, the heated water is stored in the hot water storage tank 50, and supplied to the bath 113, the kitchen 114, and the like 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 diagram showing an embodiment of such a polymer electrolyte fuel cell system of the present invention.

In FIG. 2, the fuel gas supplied from the fuel cell 6 is supplied from natural gas, city gas, methanol, LPG,
Raw fuel such as butane is supplied to a desulfurizer 2 via a fuel pipe 1, where sulfur components are removed from the raw fuel. The raw fuel that has passed through the desulfurizer 2 is pressurized by the pressurizing 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, in which fuel is supplied via a fuel pipe 13 and a fan 14 is provided. Combustion takes place with the combustion air supplied via. Reference numeral 15 denotes a pipeline to which unreacted hydrogen that has passed through the fuel electrode 6a is supplied.

A 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 water is turned into steam in the heat exchanger 17. .
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 converter 4, where carbon monoxide contained in the fuel gas is converted into carbon dioxide. The gas that has passed through the CO converter 4 is supplied to a CO remover 5, where the CO 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
A gas having a high hydrogen concentration (reformed gas) reduced to 0 ppm or less is supplied to the fuel electrode 6 a 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 (S / C ratio) between the amount of steam supplied to the reformer 3 via the heat exchanger 17 and the amount of raw fuel gas is changed to the conventional S / C ratio of 2 to 3
By setting the S / C ratio to a value higher than the value of, for example, 3 to 4, the amount of water contained in the reformed gas exiting the reformer 3 can be increased.

The reformed gas leaving the CO remover 5 is supplied directly to the fuel cell 6 so that a large amount of water is not lost from the reformed gas while passing through the CO converter 4 and the CO remover 5. However, when the reformed gas at a high temperature flows into the fuel cell 6 and the temperature of the fuel cell 6 becomes too high, the function of the battery constituent material may be reduced, or the solid polymer membrane of the battery may be damaged. A heat exchanger (not shown) is provided in a pipe 64 between the CO remover 5 and the fuel cell 6, and a water tank 21 is provided in the heat exchanger.
And heat exchange with the reformed gas by, for example, flowing water to adjust the temperature of the reformed gas.

When the S / C ratio is increased, it is possible to provide an appropriate moisture to the reformed gas supplied to the fuel electrode 6a of the fuel cell without specially providing an independent humidifier for humidifying the reformed gas. Can be.

When the power generation system GS is started, as described above, the raw fuel and the combustion air are supplied to the burner 12 to perform combustion. When the operating temperature of the fuel cell 6 is stabilized after the start, the fuel pipe 13 is used. The supply of fuel from the fuel cell is cut off, and the unreacted hydrogen gas (off-gas) discharged from the fuel electrode 6a is supplied as fuel through the pipe line 15, and the burner 12 continues burning.

Since the chemical reaction performed in the CO 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.

Thereafter, the reaction temperature is maintained by the heat of its own exothermic reaction. From the outside, cooling control is performed, if necessary, so that the temperature of the CO converter 4 and the CO remover 5 does not rise above the reaction temperature.

The reaction air is supplied to the air electrode 6k by supplying air to the water tank 21 from the air pump 11 and sending the reaction air to the gas phase 53 while bubbling the reaction air into the water in the water tank 21. Is performed, water is given 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 via the pipe 25.

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

The cooling section 6c of the fuel cell 6 is provided with electrodes 6a, 6k of the fuel cell 6 in order to prevent the fuel cell 6 from overheating due to the reaction heat of the cell itself after the fuel cell shifts to a steady operation state. 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 is maintained at a temperature suitable for power generation, for example, a temperature of 70 ° C. to 80 ° C. by the cooling water. Cooling control.

A heat exchanger 1 is provided between the reformer 3 and the CO converter 4 and between the CO converter 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 pumps 23 and 24,
The gas that has passed through the reformer 3 and the CO converter 4 is cooled.

Thus, the reformer 3, the CO converter 4,
In the CO remover 5 and the fuel cell 6, predetermined chemical reactions and power generation are continued.

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

As described above, when the polymer electrolyte fuel cell system is started, 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. Until this gas is supplied, the gas cannot be supplied to the fuel cell 6. Therefore, the reformer 3, the CO shift converter 4, the CO
Until the temperature of each reactor of the remover 5 is stabilized, the reformed gas in an unstable gas composition state is passed through the pipe 35 and the on-off valve 36.
The gas is guided to the PG burner 34 via the PG burner 34 for combustion. 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 mean that the fuel cell that has started generating power immediately enters the rated stable output state.
While the temperature of the fuel cell is low, the output of power generation is also small.
Unreacted gas not used for power generation in the fuel cell 6 at the time of startup is guided to the PG burner 34 via the pipe 38 and the opening / closing valve 39 for combustion, and the temperature of the fuel cell 6 becomes the operating temperature (for example,
After the temperature has stabilized near 70 ° C. to 80 ° C. and reached the rated output state, the flow of unreacted gas discharged from the fuel electrode 6 a is switched and introduced into the burner 12 of the reformer 3 via the pipe 15. Then, switching control is performed so as to cause combustion.

The switching control of the reformed gas is performed by the control unit 95.
Done by After the start 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 each of the above reactors is 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 burns, 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 stabilized, the control device 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 line 35 to the line 38, but is supplied to the PG burner 34 in the same manner as in the line 38,
Here, the combustion is continued until the temperature of the fuel cell 6 is stabilized.

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

For example, the controller 95 opens the valve 91 as described above to start flowing the reformed gas to the fuel electrode 6a, and then confirms the open voltage of the battery. Immediately in the form of a link from the open voltage to the power system via the inverter 108.

The control unit 95 controls the inverter 108 to prevent the battery from being overloaded and damaging the battery, and to make the battery into the rated stable output state as soon as possible. Until the output temperature reaches the optimum temperature, the load temperature is controlled so that the current is gradually increased to increase the load.

The control of the temperature rise of the load of the fuel cell by the control device 95 is performed by controlling the voltage of the fuel cell such that the output voltage of the fuel cell is maintained at a constant voltage value, for example, a voltage of 0.6 V or more per unit cell. While controlling the inverter 108 with the control device 95 so as to obtain the maximum current that can be taken in the range, or when the open voltage of the battery is confirmed, the load is mechanically increased from 0% to 100% at a certain speed. A method of controlling the inverter 108 so as to increase it, or a control device for controlling the amount of load applied to the fuel cell immediately after the start of power generation based on data obtained in advance as characteristics of the fuel cell of the polymer electrolyte fuel cell system 95, and the like.

In any of these, when the power generation of the battery is started and the open voltage thereof is confirmed, the electric power is started to be applied from the small power generation capacity, and the maximum value in a range where the fuel cell 6 is not damaged by the control device 95 is determined. In such a manner that a load is applied to the fuel cell, the current is increased, and the temperature of the fuel cell 6 is raised to the rated stable output state as soon as possible by self-reaction heat heating, so that the solid polymer fuel cell The operation is shifted to a steady operation state, whereby the energy loss at the time of starting the fuel cell can be minimized.

According to the load application method and the control in this manner, a heating device for raising the temperature of the battery is not required, and wasteful energy for heating is separately required. No, the battery is immediately overloaded,
The fuel cell 6 can be promptly shifted to a steady operation state without damaging the cell.

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

At this time, the gas flow is controlled by the on-off valves 91 and 9.
With the valve 2 open, the on-off valves 36 and 39 are closed, and the unreacted gas (off-gas) not converted into electric power by the fuel cell 6 is supplied to the burner 12 via the pipe 15 and the reformer 3
The switching is controlled by the control device 95 so as to be used for heating the.

A temperature sensor 115 inputs temperature information of the battery 6 to the controller 95.

As described above, the control device 95 operates the gas burner (PG burner 3) until the stable reformed gas is obtained from the reformer 3 after the start of the polymer electrolyte fuel cell 6.
The reformed gas having an unstable gas composition is burned in 4), and the heat load connected to this burner, for example, the hot water storage tank 5
Control is performed so as to obtain thermal energy at 0 or the like.

When a reformed gas of a predetermined quality can be obtained from a reactor such as the reformer 3 or the like, the reformed gas is flowed to the fuel electrode 6a of the polymer electrolyte fuel cell, and the exhaust gas is supplied to a gas burner ( The electric load of the fuel cell is increased by, for example, gradually increasing the current while burning with the PG burner 34). When the fuel cell 6 reaches the rated stable output state, the flow of the off-gas from the fuel electrode 6a To the reformer heating burner 1
Control for switching to the second side is performed by the control device 95. According to the startup method of the polymer electrolyte fuel cell of the present invention, the energy before the start of power generation is promptly shifted to the steady operation while the energy is used instead of hot water. In addition, since the electric power and the heat generated in the fuel cell, the unused fuel gas, the reformed gas, and the like are used for the heat load, the energy of the entire fuel cell can be effectively used.

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 that is linked to the effective use of the energy of the supplied fuel.
The present invention can provide a cogeneration system having a large power generation and heat utilization effect.

[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 gas burner that obtains thermal energy by burning combustible gas generated in the fuel cell, and a burner for heating the reformer,
Until the function of the reformer is stabilized after the start of the polymer electrolyte fuel cell, the reformed gas is burned by a gas burner that obtains the thermal energy, and a reformed gas of a predetermined quality is obtained from the reformer. Then, the reformed gas is passed through the fuel electrode of the polymer electrolyte fuel cell, and the exhaust gas is burned by a gas burner that obtains the thermal energy while gradually increasing the electric load of the fuel cell. When the operating temperature is almost stabilized, the exhaust gas from the fuel electrode is switched to the heating burner of the reformer to start the polymer electrolyte fuel cell, so that the equipment configuration for starting the fuel cell becomes extremely simple.

Further, the operation of the polymer electrolyte fuel cell is immediately shifted to a steady operation state while preventing the fuel cell from being damaged by applying an excessive load at the time of startup.
Energy loss when starting the fuel cell can be reduced.

Further, the thermal load of a hot water supply device or the like included in the polymer electrolyte fuel cell system can reduce the heat and unstable components generated during the transition from the startup of the polymer electrolyte fuel cell to the steady operation. Since the energy of the raw 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 the drawings]

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

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

[Explanation of symbols]

 3 Reformer 6 Fuel cell 6a Fuel electrode 12,34 Burner 13,15,35,38 Pipe line 36,39,91,92 Open / close valve 32,46 Heat exchanger 50 Hot water storage tank 95 Controller 107 DC / DC converter 108 Grid-connected inverter 115 Temperature sensor GS Power generation system RD Heat recovery unit

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Kazuhiro Tajima 2-5-5 Keihanhondori, Moriguchi-shi, Osaka Sanyo Electric Co., Ltd. (72) Satoshi Yamamoto 2-5-2 Keihanhondori, Moriguchi-shi, Osaka No. 5 Sanyo Electric Co., Ltd. (72) Inventor Akira Fujio 2-5-5 Keihan Hondori, Moriguchi-shi, Osaka Prefecture In-house Sanyo Electric Co., Ltd. 2-5-5 Sanyo Electric Co., Ltd. (72) Inventor Katsuyuki Makihara 2-5-5 Keihanhondori, Moriguchi-shi, Osaka Sanyo Electric Co., Ltd. F-term (reference) 5H026 AA06 5H027 AA06 BA09 KK46 KK54 MM26

Claims (5)

[Claims] 1. A polymer electrolyte fuel cell having a reformer, an electric load connected to the polymer electrolyte fuel cell,
In a polymer electrolyte fuel cell system having a gas burner that obtains thermal energy by burning combustible gas generated in a polymer electrolyte fuel cell, and a burner for heating the reformer, the reformer Until the function of stabilizes, burn the reformed gas with a gas burner that obtains the thermal energy,
When a reformed gas of a predetermined quality is obtained from the reformer, the reformed gas is supplied to the fuel electrode of the polymer electrolyte fuel cell, and the exhaust gas is gradually burned by a gas burner for obtaining the thermal energy. In the polymer electrolyte fuel cell, the electric load is increased, and when 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. starting method. 2. A polymer electrolyte fuel cell having a reformer, an electric load connected to the polymer electrolyte fuel cell,
A gas burner that obtains thermal energy by burning combustible gas generated in the polymer electrolyte fuel cell; and a burner for heating the reformer, and wherein the reformer is activated after the start of the polymer electrolyte fuel cell. Until the function is stabilized, the reformed gas is burned with a gas burner that obtains the heat energy, and when a reformed gas of a predetermined quality is obtained from the reformer, the reformed gas is applied to the fuel electrode of the polymer electrolyte fuel cell. The electric load is gradually increased while flowing the reformed gas and the exhaust gas is burned by a gas burner that obtains the thermal energy. When the fuel cell almost reaches the rated stable output state, the flow of the exhaust gas from the fuel electrode is improved. A starting device for a polymer electrolyte fuel cell, comprising a mechanism for switching to a heating burner side of a porcelain vessel. 3. A mechanism for 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, while gradually increasing the electric load of the fuel cell. 3. The starting device for a polymer electrolyte fuel cell according to claim 2, wherein the device is an electric load control device that increases the current while maintaining the output voltage of the polymer electrolyte fuel cell at a certain voltage or higher. 4. A mechanism for flowing a reformed gas through the fuel electrode of the polymer electrolyte fuel cell and burning the exhaust gas with a gas burner for obtaining the thermal energy, while gradually increasing the electric load of the fuel cell. 3. The polymer electrolyte fuel cell according to claim 2, wherein the polymer electrolyte fuel cell is an electric load control device that increases current according to a rule previously determined as a relationship between the temperature and the output voltage of the polymer electrolyte fuel cell. Starter. 5. The electric load connected to the polymer electrolyte fuel cell may be 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.