JP2006032173A - Fuel cell power generation system and stopping method for it - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel cell power generation system and a stopping method for it for safely, economically, and easily stopping the system with causing no damage in a reactor due to high-pressure gas or negative pressure gas generated in stopping or no deterioration of a catalyst by air or condensed water without assembling any nitrogen gas cylinder into the system. <P>SOLUTION: This fuel cell power generation system 1B is provided with a fuel reforming device 10 and a fuel cell 11. The fuel cell power generation system 1B is provided with a circulation gas circulation passage 18, which connects a fuel supply part 16 to the fuel reforming device 10 and a reformed gas discharge part 17 from the fuel reforming device 10 to each other, and a catalyst combustor 21 having an air introducing means 20 introducing air from the outside of the system. A check valve 30 is arranged in the circulation gas circulation passage 18 connecting the catalyst combustor 21 and the fuel reforming device 10 together. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a fuel cell power generation system suitable as, for example, a small power source for home use and a method for stopping the same.

  In recent years, a desulfurizer that removes sulfur contained in hydrocarbon fuel gases such as natural gas, city gas, methanol, LPG, and butane, and a reformer (RF that reacts the fuel gas with water vapor to reform hydrogen) ), A CO converter (SH) that converts carbon monoxide, a CO remover (PROX) that removes carbon monoxide, hydrogen (reformed gas) thus obtained, oxygen in the air, etc. There has been proposed a fuel cell power generation system as a small power source provided with a fuel cell that generates electricity by chemically reacting with an oxidant (see, for example, Patent Documents 1, 2, and 3).

  When a fuel gas containing hydrogen is supplied to the fuel electrode (AN) and air is supplied to the air electrode (CA), a fuel electrode reaction that decomposes hydrogen molecules into hydrogen ions and electrons at the fuel electrode, and oxygen and hydrogen ions at the air electrode Electrochemical reactions that generate water from the electrons are performed, and electric power is supplied to the load by electrons moving in the external circuit from the fuel electrode toward the air electrode, and water is generated on the air electrode side.

FIG. 11 shows a conventional fuel cell power generation system.
As shown in FIG. 11, after the fuel cell power generation system 1A desulfurizes natural gas, city gas, hydrocarbon fuel gas (LPG) such as methanol, LPG, butane, etc., through the shut-off valve 2 and desulfurizes it. The water is sent to the reformer (RF) through the check valve 40, while the water is sent to the vaporizer through the stop valve 1 and vaporized, and the water vapor is sent to the reformer (RF) through the check valve 50. After reforming the fuel gas to hydrogen, the resulting reformed gas is sent to the CO converter (SH) to transform carbon monoxide in the reformed gas, and then sent to the CO remover (PROX) to monoxide A fuel reformer 10 for removing carbon is provided.
The hydrogen obtained by reducing the CO concentration obtained in the fuel reformer 10 is sent to the fuel electrode (AN) of the fuel cell 11 through the shut-off valve 4, and the air is sent to the air electrode (CA) of the fuel cell 11, Power generation is performed by an electrochemical reaction between hydrogen in the reformed gas supplied to the fuel electrode (AN) and oxygen in the air supplied to the air electrode (CA).
The reaction by steam reforming is an endothermic reaction, and the reformer burner 12 is used as a heating medium for maintaining the reforming reaction.
Hydrogen gas (off-gas) discharged from the fuel cell 11 is supplied to the burner 12 through the shut-off valve 8, and fuel gas (LPG) is added to the burner 12 through the shut-off valve 3 as necessary to burn the combustion air. The amount of heat necessary for the reforming reaction of the reformer (RF) is supplied by combustion.

When the fuel cell power generation system 1A is stopped, flammable gas remains in the system, and liquid water that is not sufficiently vaporized remains in the system. When the inlet / outlet is closed, the reactor is caused by vaporization of water. If the pressure in the reactor rises or the temperature drops while the inlet / outlet is closed, the water vapor in the reactor will condense, resulting in a drop in pressure, causing the reactor to become negative pressure, damaging the reactor, Has a problem of adversely affecting the catalyst.
On the other hand, when the temperature is lowered with the outlet opened, the inside of the reactor becomes negative pressure, and there is a problem that external air is mixed into the reactor and the reaction catalyst deteriorates due to oxidation. When a catalyst or the like is used, there arises a problem that the reactor generates heat due to an oxidation reaction.

Therefore, a nitrogen supply path 13 from a nitrogen cylinder provided with an open / close valve is provided in front of the desulfurizer of the fuel gas supply unit, and an open / close valve is provided in the path 14 of hydrogen gas (off-gas) discharged from the fuel cell 11. A discharge path 15 is provided, and when the fuel cell power generation system 1A is stopped, the closing valves 1, 2, and 3 are closed, and nitrogen gas is sent from the nitrogen cylinder to the fuel reformer 10 and the fuel cell 11 through the fuel gas supply unit. The inside of the system is replaced with nitrogen gas by, for example, releasing it from the air to the atmosphere.
JP 2003-217620 A JP 2003-217623 A JP 2000-277137 A

  However, in the method of using a nitrogen gas cylinder incorporated in the system, it is necessary to check the amount of gas in the nitrogen gas cylinder, replace the nitrogen gas cylinder, etc., and there is a problem that the management of the system becomes complicated and the cost increases.

A first object of the present invention is a fuel cell power generation system capable of safely, economically and easily shutting down a system without incorporating a nitrogen gas cylinder into the system, and is generated when an inlet / outlet is closed at the time of stopping. The pressure drop in the reactor is suppressed, and the pressure drop in the reactor that occurs when the temperature drops with the inlet / outlet closed is suppressed, causing the reactor to be damaged or the condensed water adversely affecting the catalyst. It is also possible to provide a fuel cell power generation system that prevents the reaction catalyst from deteriorating due to oxidation due to negative pressure inside the reactor due to negative pressure inside the reactor, and preventing the reactor from generating heat due to oxidation reaction. ,
A second object of the present invention is to provide a method for economically and easily stopping a fuel cell power generation system.

In order to solve the above problems, a fuel cell power generation system according to claim 1 of the present invention comprises a fuel reformer for reforming a fuel gas into a hydrogen-rich reformed gas, an electrochemical reaction between the reformed gas and air. A fuel cell power generation system comprising a fuel cell that generates electricity by reacting automatically,
Provided with a catalytic combustor provided with a circulation gas circulation path for connecting a fuel gas supply unit to the fuel reformer and a reformed gas discharge unit from the fuel reformer and provided with air introduction means from outside the system And a check valve is provided in the circulating gas circulation path connecting the catalytic combustor and the fuel reformer.

  The fuel cell power generation system according to claim 2 of the present invention is the fuel cell power generation system according to claim 1, wherein a path branched from the circulation gas circulation path connecting the check valve and the catalytic combustor is provided. The branched path is provided with a shut-off valve and a buffer tank.

  A fuel cell power generation system according to a third aspect of the present invention is the fuel cell power generation system according to the second aspect, wherein a vacuum break valve is provided instead of the shut-off valve.

  A fuel cell power generation system according to a fourth aspect of the present invention is the fuel cell power generation system according to the second aspect, wherein a gas-liquid separation device is provided in the circulation gas circulation path.

  A fuel cell power generation system according to a fifth aspect of the present invention is the fuel cell power generation system according to any one of the second to fourth aspects, wherein pressure measurement means is provided in the circulation gas circulation path. And

  According to a sixth aspect of the present invention, immediately after the fuel reformer of the fuel cell power generation system according to the fifth aspect of the present invention is stopped, the buffer tank and the circulating gas circulation path are brought into communication with each other. When the pressure becomes equal to or higher than a first predetermined value set in advance, the buffer tank and the circulating gas circulation path are disconnected from each other, and the pressure in the circulating gas circulation path is set to a second predetermined value. When the fuel cell power generation system becomes lower than the value, the supply of air to the catalyst combustor is started by the air introduction means, and the buffer tank and the circulating gas circulation path are in communication with each other. Is the method.

  According to a seventh aspect of the present invention, in the stopping method according to the sixth aspect, the air supply to the catalytic combustor is stopped when the pressure in the circulating gas circulation path reaches a preset third specified value. The buffer tank and the circulating gas circulation path are not communicated with each other.

According to a first aspect of the present invention, there is provided a fuel cell power generation system that generates power by electrochemically reacting a reformed gas and air with a fuel reformer that reforms a fuel gas into a hydrogen-rich reformed gas. A fuel cell power generation system comprising a fuel cell,
Provided with a catalytic combustor provided with a circulation gas circulation path for connecting a fuel gas supply unit to the fuel reformer and a reformed gas discharge unit from the fuel reformer and provided with air introduction means from outside the system In addition, since a check valve is provided in the circulating gas circulation path that connects the catalytic combustor and the fuel reformer, a high pressure gas or a negative pressure gas generated at the time of stopping can be used without incorporating a nitrogen gas cylinder into the system. There is a remarkable effect that the fuel cell power generation system can be stopped safely, economically and easily without damaging the apparatus and without deteriorating the catalyst with air or condensed water.

That is, when the fuel cell power generation system is stopped, the supply of the raw material fuel gas and water vapor to the fuel cell power generation system is stopped, the supply of the combustion fuel gas to the burner that supplies the amount of heat necessary for the reforming reaction is stopped, and the fuel The supply of the reformed gas to the battery body is also stopped. When a gas mainly composed of a high-pressure reformed gas is generated by the vaporization of water in the fuel reformer or the reaction of the residual gas, the high-pressure gas is introduced into the circulation gas circulation path and relaxed. The gas will not damage the reactor.
Also, when the negative pressure increases due to condensation of water vapor, an appropriate amount of air necessary to compensate for this negative pressure is sent from outside the system to the catalytic combustor via the air introduction means. The reformed gas is combusted, oxygen in the air is consumed to form nitrogen, and the nitrogen can be repeatedly sent to the fuel reformer through the circulation gas circulation path. Prominent that negative pressure gas will not damage the reactor, negative pressure will not allow external air to enter the system and damage the reactor, and the catalyst will not be degraded by air or condensed water There is an effect.

The fuel cell power generation system according to claim 2 of the present invention is the fuel cell power generation system according to claim 1, wherein a path branched from the circulation gas circulation path connecting the check valve and the catalytic combustor is provided. Since the branch path is provided with a shut-off valve and a buffer tank, when a gas mainly composed of high-pressure reformed gas is generated when the fuel cell power generation system is stopped, the high-pressure gas is supplied to the circulation gas circulation path. Introducing, opening the shut-off valve of the branched path and putting it in the buffer tank can alleviate, so the reactor is not damaged by the gas mainly composed of high pressure reformed gas.
When water vapor is condensed or the negative pressure increases, an appropriate amount of air necessary to compensate for this negative pressure is sent from outside the system to the catalytic combustor through the air introduction means, The required amount of high-pressure reformed gas put into the catalyst is sent to the catalyst combustor to be burnt, and oxygen in the air is consumed to form nitrogen into the fuel reformer through the circulation gas circulation path. Since it can be sent repeatedly, the reactor will not be damaged by high pressure gas or negative pressure gas generated at the time of shutdown, and external air will be mixed into the system at negative pressure and the reactor will not be damaged. Further, there is a further remarkable effect that the catalyst can be prevented from being deteriorated by air or condensed water.

  The fuel cell power generation system according to claim 3 of the present invention is the fuel cell power generation system according to claim 2, wherein a vacuum break valve is provided instead of the shut-off valve. As a result, the power can be saved because the door is opened and closed.

  A fuel cell power generation system according to a fourth aspect of the present invention is the fuel cell power generation system according to the second aspect, wherein a gas-liquid separation device is provided in the circulation gas circulation path. The necessary amount of the high pressure reformed gas can be sent to the catalytic combustor through the gas-liquid separator and burned, and the oxygen in the air is consumed to form nitrogen, and the water vapor in the nitrogen is Can be separated by a gas-liquid separator, and nitrogen separated from the water can be repeatedly sent to the fuel reformer through the circulation gas circulation path so that the catalyst of the fuel reformer does not deteriorate with condensed water. There is a further remarkable effect that it is possible.

  The fuel cell power generation system according to claim 5 of the present invention is the fuel cell power generation system according to any one of claims 2 to 4, wherein pressure measurement means is provided in the circulation gas circulation path. The pressure in the circulating gas circulation path is measured by the pressure measuring means, and the on-off valve is opened and closed.For example, when the negative pressure increases, air is sent from outside the system to the catalytic combustor through the air introducing means. Or a high-pressure reformed gas placed in the buffer tank can be sent to the catalytic combustor.

  According to a sixth aspect of the present invention, immediately after the fuel reformer of the fuel cell power generation system according to the fifth aspect of the present invention is stopped, the buffer tank and the circulating gas circulation path are brought into communication with each other. When the pressure becomes equal to or higher than a first predetermined value set in advance, the buffer tank and the circulating gas circulation path are disconnected from each other, and the pressure in the circulating gas circulation path is set to a second predetermined value. When the fuel cell power generation system becomes lower than the value, the supply of air to the catalyst combustor is started by the air introduction means, and the buffer tank and the circulating gas circulation path are in communication with each other. It is a safe method without degrading the catalyst without incorporating a nitrogen gas cylinder into the system, damaging the reactor with high-pressure gas or negative-pressure gas generated at the time of shutdown. It can be stopped economically and easily the fuel cell power generation system, a marked effect of.

That is, when the fuel cell power generation system is stopped, the supply of the raw material fuel gas and water vapor to the fuel cell power generation system is stopped, the supply of the combustion fuel gas to the burner that supplies the amount of heat necessary for the reforming reaction is stopped, and the fuel The supply of the reformed gas to the battery body is also stopped. Since the gas mainly composed of high-pressure reformed gas is generated by the vaporization of water in the fuel reformer and the reaction of residual gas, the high-pressure gas is brought into communication between the buffer tank and the circulation gas circulation path. Is introduced into the circulating gas circulation path and placed in the buffer tank to relieve high pressure.
Then, the reformed gas introduced in a non-communication state between the buffer tank and the circulation gas circulation path when the pressure decreases and the pressure in the circulation gas circulation path becomes equal to or lower than a first predetermined value set in advance. Store.
Then, when the pressure further decreases and becomes negative pressure, and the pressure in the circulating gas circulation path becomes equal to or lower than a preset second specified value, this negative pressure is applied to the catalytic combustor from outside the system through the air introduction means. An appropriate amount of air necessary for compensation is sent, and a necessary amount of high-pressure reformed gas placed in the buffer tank with the buffer tank and the circulating gas circulation path in communication with each other is separated into gas and liquid. After the water is separated by the vessel, it is sent to the catalyst combustor for combustion.
Then, oxygen in the air is consumed to form nitrogen, and water vapor in the nitrogen is separated by a gas-liquid separator, and nitrogen separated from moisture is repeatedly sent to the fuel reformer through the circulation gas circulation path. As a result, the equipment is not damaged by the high-pressure gas or negative-pressure gas generated at the time of shutdown, and external air is mixed into the system due to negative pressure and equipment such as piping is not damaged. In addition, there is a remarkable effect that the respective catalysts are not deteriorated by condensed water.

  According to a seventh aspect of the present invention, in the stopping method according to the sixth aspect, after that, the air supply to the catalytic combustor is stopped when the pressure in the circulating gas circulation path reaches a preset third specified value. In addition, since the buffer tank and the circulating gas circulation path are in a non-communication state, the pressure in the buffer tank can be maintained, and the negative pressure can be eliminated by repeatedly using the gas in the buffer tank. There is a further remarkable effect.

Next, the present invention will be described in detail based on embodiments with reference to the drawings.
[First Embodiment]
FIG. 1 is an explanatory diagram schematically illustrating an example of a fuel cell power generation system according to the present invention.
As shown in FIG. 1, the fuel cell power generation system 1B of the present invention uses a hydrocarbon fuel gas (LPG) such as natural gas, city gas, methanol, LPG, butane, etc., and a shutoff valve 2 of the fuel gas supply unit 16. After being sent to the desulfurizer and desulfurized, it is sent to the reformer (RF) via the check valve 40, while water is sent to the vaporizer via the shutoff valve 1 and vaporized to form the check valve 50 as water vapor. Then, it is sent to the reformer (RF) and steam is added to reform the fuel gas to hydrogen, and the resulting reformed gas is sent to the CO converter (SH) to convert the carbon monoxide in the reformed gas. A fuel reformer 10 is provided that transforms and then sends to a CO remover (PROX) to remove carbon monoxide.
The hydrogen having a reduced CO concentration obtained by the fuel reformer 10 is sent to the fuel electrode (AN) of the fuel cell 11 through the shut-off valve 4 of the reformed gas supply path 19 of the reformed gas discharge unit 17 and air. Is sent to the air electrode (CA) of the fuel cell 11 by an electrochemical reaction between hydrogen in the reformed gas supplied to the fuel electrode (AN) and oxygen in the air supplied to the air electrode (CA). Power generation is performed.
The reaction by steam reforming is an endothermic reaction, and the reformer burner 12 is used as a heating medium for maintaining the reforming reaction.
Hydrogen gas (off-gas) discharged from the fuel cell 11 is supplied to the burner 12 via the shut-off valve 8 and, if necessary, fuel gas (LPG) is added to the burner 12 via the shut-off valve 3 and combustion air. The amount of heat necessary for the reforming reaction of the reformer (RF) is supplied by combustion.

The fuel cell power generation system 1B of the present invention is a circulating gas that communicates a fuel gas supply unit 16 that supplies fuel gas to the fuel reformer 10 and a reformed gas discharge unit 17 that discharges reformed gas from the fuel reformer 10. A circulation path 18 is provided separately from the reformed gas supply path 19 to the main body of the fuel cell 11.
In the circulating gas circulation path 18, a catalytic combustor (hydrogen is combusted) provided with a pressure measuring means 22, a check valve 30, a gas-liquid separator 23, and an air introduction means 20 (close valve 7) from outside the system. (For example, a platinum catalyst supported on a carrier is filled) 21, a gas-liquid separator 24, a shut-off valve 6 are provided, and a circulating gas circulation path 18 that connects the check valve 30 and the catalytic combustor 21 is provided. A path 25 branched from the circulating gas circulation path 18 is provided, and the shutoff valve 5 and the buffer tank 26 are provided in the branched path 25.
The circulation gas circulation path 18 is connected after the check valve 40 of the fuel gas supply unit 16 so that the gas in the circulation gas circulation path 18 can be circulated.

FIG. 2 is an explanatory diagram showing a graph showing changes over time in pressure and temperature in the fuel reformer when the fuel cell power generation system 1B shown in FIG. 1 is stopped, and a relationship between the open / close states of the respective shut-off valves. .
FIG. 3 is a flowchart showing the relationship between the open / close states of the shut-off valves when the fuel cell power generation system 1B shown in FIG. 1 is stopped.
In FIG. 2, the left vertical axis represents the pressure in the fuel reformer (solid line), the right vertical axis represents the reformer (RF) temperature (dashed line), the horizontal axis represents the elapsed time, and the temperature and pressure corresponding to the elapsed time. The open / closed states of the shut-off valves 1 to 8 are shown.

  As shown in FIGS. 2 and 3, when the fuel cell power generation system 1B is stopped, the closing valves 1, 2, 3, 4, and 8 are closed (the closing valves 6 and 7 are closed during operation). Then, the stop valve 5 is opened. In this way, the supply of the raw material fuel gas and water vapor is stopped, the supply of the combustion fuel gas to the burner that supplies the amount of heat necessary for the reforming reaction is stopped, and the reformed gas is also supplied to the fuel cell 11 body. When stopped, gas mainly composed of high-pressure reformed gas is generated by the vaporization of water in the fuel reformer 10 and the reaction of the residual gas. This high-pressure gas enters the circulating gas circulation path 18 and the check valve 30 is turned on. It enters into a path 25 branched through and is introduced into the buffer tank 26 through the closing valve 5. The high pressure is relieved, and the pressure and temperature in the fuel reformer 10 decrease with time.

When the pressure measured by the pressure measuring means 22 becomes 0 kPa or less (when the water pressure in the circulating gas circulation path 18 condenses or the negative pressure increases), the closing valve 7 and the closing valve 6 are opened.
Then, an appropriate amount of air necessary to compensate for this negative pressure is sent from outside the system to the catalytic combustor 21 through the air introduction means 20 (the shut-off valve 7).
At the same time, after passing the required amount of high-pressure reformed gas in the buffer tank 26 through the shut-off valve 5, water is separated by the gas-liquid separator 23 and sent to the catalytic combustor 21 to burn the reformed gas. The oxygen in the air is consumed, and the remaining gas is converted to a nitrogen-based gas.
The water vapor in the nitrogen is separated by the gas-liquid separator 24, and the nitrogen from which the water has been separated is sent to the fuel reformer 10 through the shut-off valve 6 and the circulation gas circulation path 18.

When the pressure measured by the pressure measuring means 22 becomes −0.5 kPa or more, the closing valve 7 is closed. Since the reformed gas can be supplied to the catalytic combustor 21 next time by holding the pressure in the buffer tank 26 when the closing valve 7 is closed, the closing valve 5 is also preferably closed.
When the pressure becomes -3 kPa or less, the shut-off valve 7 is opened and nitrogen separated from the water as described above is sent to the fuel reformer 10 through the shut-off valve 6 and the circulating gas circulation path 18. When the pressure becomes −0.5 kPa or more, the stop valve 7 is closed.
Then, the temperature is measured by a thermometer (not shown) of the reformer (RF) and this operation is repeated until the temperature reaches room temperature. When the temperature reaches room temperature, the closing valve 5 and the closing valve 6 are closed, and the next operation is awaited.
By shutting down the fuel cell power generation system in this way, it is safe and economical without incorporating nitrogen gas cylinders into the system, without damaging the equipment with high pressure gas or negative pressure gas, and without degrading each catalyst. And can be stopped easily.

[Second Embodiment]
FIG. 4 is a graph showing changes over time in the pressure and temperature in the fuel reformer when the fuel cell power generation system 1B shown in FIG. 1 is stopped, and the relationship between the open / close states of the shut-off valves. It is explanatory drawing which shows.
FIG. 5 is a flowchart showing the relationship between the open / close state of each shut-off valve when the fuel cell power generation system 1B shown in FIG. 1 is stopped according to another embodiment.
In FIG. 4, the left vertical axis represents the pressure in the fuel reformer (solid line), the right vertical axis represents the reformer (RF) temperature (dashed line), the horizontal axis represents the elapsed time, and the closing valve 1 corresponding to the elapsed time. -8 open / closed states are shown.

In the second embodiment, as the buffer tank 26 shown in FIG. 1, an expansion tank having a variable internal volume structure, for example, a water-sealable movable tank, a bellows type, a cylinder type, a balloon type or the like, which has a variable internal volume. It is the same as that of 1st Embodiment except having used the expansion tank which has a structure.
As shown in FIGS. 4 and 5, when the fuel cell power generation system 1B is stopped, the closing valves 1, 2, 3, 4, and 8 are closed (the closing valves 6 and 7 are closed during operation). Then, the stop valve 5 is opened. In this way, the supply of the raw material fuel gas and water vapor is stopped, the supply of the combustion fuel gas to the burner that supplies the amount of heat necessary for the reforming reaction is stopped, and the reformed gas is also supplied to the fuel cell 11 body. When stopped, gas mainly composed of high-pressure reformed gas is generated by the vaporization of water in the fuel reformer 10 and the reaction of the residual gas. This high-pressure gas enters the circulating gas circulation path 18 and the check valve 30 is turned on. It passes through the branched path 25 and is introduced into the buffer tank (expansion tank having a variable internal volume structure) 26 through the shut-off valve 5, and this high pressure is easily relieved to almost 0 kPa (atmospheric pressure), and the temperature is changed over time. Decreases with.

After the pressure measured by the pressure measuring means 22 becomes 0 kPa or less, the closing valve 7 and the closing valve 6 are opened as shown in FIG. Then, an appropriate amount of air necessary to compensate for this negative pressure is sucked into the catalytic combustor 21 from outside the system through the air introduction means 20 (the shut-off valve 7), and the high-pressure reforming put in the buffer tank 26. After passing the required amount of gas through the shut-off valve 5, water is separated by the gas-liquid separator 23 and sent to the catalytic combustor 21 to burn the reformed gas, consuming oxygen in the air, and residual gas Is converted into a gas mainly composed of nitrogen, the water vapor in the nitrogen is separated by the gas-liquid separator 24, and the nitrogen from which the moisture has been separated is sent to the fuel reformer 10 through the shut-off valve 6 and the circulation gas circulation path 18.
When the pressure measured by the pressure measuring means 22 becomes −0.5 kPa or more, the closing valve 7 is closed. Since the reformed gas can be supplied to the catalytic combustor 21 next time by holding the pressure in the buffer tank 26 when the closing valve 7 is closed, the closing valve 5 is also preferably closed.
When the pressure becomes -3 kPa or less, the shut-off valve 7 is opened and nitrogen separated from the water as described above is sent to the fuel reformer 10 through the shut-off valve 6 and the circulating gas circulation path 18. When the pressure becomes −0.5 kPa or more, the stop valve 7 is closed.
Then, the temperature is measured by a thermometer (not shown) of the reformer (RF) and this operation is repeated until the temperature reaches room temperature. When the temperature reaches room temperature, the closing valve 5 and the closing valve 6 are closed, and the next operation is awaited.
By shutting down the fuel cell power generation system in this way, it is safe and economical without incorporating nitrogen gas cylinders into the system, without damaging the equipment with high pressure gas or negative pressure gas, and without degrading each catalyst. And can be stopped easily.

[Third Embodiment]
FIG. 6 is a graph showing changes over time in the pressure and temperature in the fuel reformer when the fuel cell power generation system 1B shown in FIG. 1 is stopped, and the relationship between the open / close states of the shut-off valves. It is explanatory drawing which shows.
FIG. 7 is a flowchart showing the relationship between the open / close state of each shut-off valve when the fuel cell power generation system 1B shown in FIG. 1 is stopped according to another embodiment.
In FIG. 6, the left vertical axis represents the pressure in the fuel reformer (solid line), the right vertical axis represents the reformer (RF) temperature (dashed line), the horizontal axis represents the elapsed time, and the closing valve 1 corresponding to the elapsed time. -8 open / closed states are shown.

  As shown in FIGS. 6 and 7, when the fuel cell power generation system 1B is stopped, the closing valves 1, 2, 3, 4, and 8 are closed (the closing valves 6 and 7 are closed during operation). Then, the stop valve 5 is opened. In this way, the supply of the raw material fuel gas and water vapor is stopped, the supply of the combustion fuel gas to the burner that supplies the amount of heat necessary for the reforming reaction is stopped, and the reformed gas is also supplied to the fuel cell 11 body. When stopped, gas mainly composed of high-pressure reformed gas is generated by the vaporization of water in the fuel reformer 10 and the reaction of the residual gas. This high-pressure gas enters the circulating gas circulation path 18 and the check valve 30 is turned on. It enters into a path 25 branched through and is introduced into the buffer tank 26 through the closing valve 5. The high pressure is relaxed, and the pressure and temperature in the fuel reformer 10 decrease with time.

However, when the pressure measured by the pressure measuring means 22 becomes 40 kPa (example of the first specified value) or more due to vaporization of moisture or the like, the shutoff valve 5 is temporarily closed and the reformed gas is stored in the buffer tank 26.
When the pressure becomes 0 kPa (example of the second specified value) or less (when the water vapor in the circulation gas circulation path 18 is condensed or the negative pressure is increased), the closing valve 7, the closing valve 6, Open the shut-off valve 5.
Then, an appropriate amount of air necessary to compensate for this negative pressure is sent from the outside of the system to the catalytic combustor 21 via the air introduction means 20 (close valve 7), and the high-pressure reformed gas placed in the buffer tank 26 is supplied. After the required amount passes through the shut-off valve 5, the moisture is separated by the gas-liquid separator 23 and sent to the catalytic combustor 21 to burn the reformed gas, consuming oxygen in the introduced air, and the remaining The gas is a nitrogen-based gas, the water vapor in the nitrogen is separated by the gas-liquid separator 24, and the nitrogen from which the moisture has been separated is sent to the fuel reformer 10 through the closed valve 6 and the circulation gas circulation path 18.

When the pressure becomes -0.5 kPa (example of the third specified value) or more, the closing valve 5 and the closing valve 7 are closed. Since the reformed gas can be supplied to the catalytic combustor 21 next time by holding the pressure in the buffer tank 26 when the closing valve 7 is closed, the closing valve 5 is also preferably closed.
When the pressure becomes -3 kPa or less, the shutoff valve 5 and the shutoff valve 7 are opened, and nitrogen separated from the moisture is sent to the fuel reformer 10 through the circulation gas circulation path 18. When the pressure becomes −0.5 kPa or more, the closing valve 5 and the closing valve 7 are closed.
Then, as a result of temperature measurement by a thermometer (not shown) of the reformer (RF), when the temperature reaches room temperature, the shutoff valve 6 is closed and the next operation is awaited.
By shutting down the fuel cell power generation system in this way, it is safe and economical without incorporating nitrogen gas cylinders into the system, without damaging the equipment with high pressure gas or negative pressure gas, and without degrading each catalyst. And can be stopped easily.

[Fourth Embodiment]
FIG. 8 is an explanatory diagram schematically illustrating another example of the fuel cell power generation system of the present invention.
The fuel cell power generation system 1C according to the present invention shown in FIG. 8 is a vacuum breaker in which the shutoff valve 7 of the fuel cell power generation system 1B according to the present invention shown in FIG. It is the same except having replaced with valve 20A.
FIG. 9 is an explanatory diagram showing a graph showing changes in pressure and temperature with time in the fuel reformer when the fuel cell power generation system 1C shown in FIG. 8 is stopped, and a relationship between the open / close states of the respective shut-off valves. .
FIG. 10 is a flowchart showing the relationship between the open / close states of the shut-off valves when the fuel cell power generation system 1C shown in FIG. 8 is stopped.
In FIG. 9, the left vertical axis represents the pressure in the fuel reformer (solid line), the right vertical axis represents the reformer (RF) temperature (dashed line), the horizontal axis represents the elapsed time, and the closing valve 1 corresponding to the elapsed time. -8 open / closed states are shown.

As shown in FIGS. 9 and 10, when the fuel cell power generation system 1C is stopped, the closing valves 1, 2, 3, 4, and 8 are closed (the closing valve 6 is closed during operation). The vacuum break valve 20A is closed. Then, the stop valve 5 is opened.
In this way, the supply of the raw material fuel gas and water vapor is stopped, the supply of the combustion fuel gas to the burner that supplies the amount of heat necessary for the reforming reaction is stopped, and the reformed gas is also supplied to the fuel cell 11 body. When stopped, gas mainly composed of high-pressure reformed gas is generated by the vaporization of water in the fuel reformer 10 and the reaction of the residual gas. This high-pressure gas enters the circulating gas circulation path 18 and the check valve 30 is turned on. It enters into a path 25 branched through and is introduced into the buffer tank 26 through the closing valve 5. The high pressure is relaxed, and the pressure and temperature in the fuel reformer 10 decrease with time.

When the pressure measured by the pressure measuring means 22 becomes 0 kPa or less (when the negative pressure increases due to condensation of water vapor in the circulation gas circulation path 18), the closing valve 6 is opened.
Then, the vacuum break valve 20A automatically opens, and an appropriate amount of air necessary to compensate for this negative pressure is sent from the outside of the system through the vacuum break valve 20A to enter the buffer tank 26. After the necessary amount of the high pressure reformed gas passes through the shut-off valve 5, the moisture is separated by the gas-liquid separator 23 and sent to the catalyst combustor 21, where the reformed gas burns and is introduced into the introduced air. Oxygen is consumed, and the residual gas becomes a nitrogen-based gas. The water vapor in the nitrogen is separated by the gas-liquid separator 24, and the nitrogen from which the moisture has been separated passes through the shut-off valve 6 and the circulating gas circulation path 18 to improve the fuel. Sent to the quality device 10.
When the pressure measured by the pressure measuring means 22 increases and reaches a predetermined pressure (for example, −0.5 kPa or more), the vacuum break valve 20A is automatically closed, and this is repeated thereafter.
As a result of temperature measurement by a thermometer (not shown) of the reformer (RF), when the temperature reaches room temperature, the closing valve 5 and the closing valve 6 are closed, and the next operation is awaited.
By shutting down the fuel cell power generation system in this way, it is safe and economical without incorporating nitrogen gas cylinders into the system, without damaging the equipment with high pressure gas or negative pressure gas, and without degrading each catalyst. And can be stopped easily.

  The description of the above embodiment is for explaining the present invention, and does not limit the invention described in the claims or reduce the scope. Moreover, each part structure of this invention is not restricted to the said embodiment, A various deformation | transformation is possible within the technical scope as described in a claim.

The fuel cell power generation system of the present invention includes a fuel reformer that reforms a fuel gas into a hydrogen-rich reformed gas, and a fuel cell that generates electricity by electrochemically reacting the reformed gas and air. A fuel cell power generation system,
Provided with a catalytic combustor provided with a circulation gas circulation path for connecting a fuel gas supply unit to the fuel reformer and a reformed gas discharge unit from the fuel reformer and provided with air introduction means from outside the system In addition, since a check valve is provided in the circulating gas circulation path that connects the catalytic combustor and the fuel reformer, a high pressure gas or a negative pressure gas generated at the time of stopping can be used without incorporating a nitrogen gas cylinder into the system. There is a remarkable effect that the fuel cell power generation system can be shut down safely, economically and easily without damaging the equipment and without degrading the catalyst with air or condensed water. High value.

It is explanatory drawing which illustrates typically an example of the fuel cell power generation system of this invention. FIG. 2 is a graph showing changes in pressure and temperature with time in the fuel reformer when the fuel cell power generation system shown in FIG. It is a flowchart which shows the relationship with the opening-and-closing state of each closing valve at the time of the stop of the fuel cell power generation system shown in FIG. FIG. 5 is a graph showing changes in pressure and temperature with time in the fuel reformer when the fuel cell power generation system of the other embodiment shown in FIG. 1 is stopped, and an explanatory diagram showing the relationship between the open / close states of the shut-off valves. is there. It is a flowchart which shows the relationship with the open / close state of each closing valve at the time of the stop of the other embodiment of the fuel cell power generation system shown in FIG. FIG. 2 is a graph showing changes in pressure and temperature over time in the fuel reformer when the fuel cell power generation system shown in FIG. 1 is stopped, and an explanatory diagram showing the relationship between the open / close states of the shut-off valves. . It is a flowchart which shows the relationship with the open / close state of each closing valve at the time of the stop of the other embodiment of the fuel cell power generation system shown in FIG. It is explanatory drawing which illustrates typically the other example of the fuel cell power generation system of this invention. FIG. 9 is an explanatory diagram showing a graph showing changes over time in pressure and temperature in the fuel reformer when the fuel cell power generation system shown in FIG. 8 is stopped, and a relationship between open / closed states of the shut-off valves. It is a flowchart which shows the relationship with the opening / closing state of each closing valve at the time of the stop of the fuel cell power generation system shown in FIG. It is explanatory drawing which illustrates the conventional fuel cell power generation system typically.

Explanation of symbols

1A, 1B, 1C Fuel cell power generation systems 1-8 Stop valve 30, 40, 50 Check valve 10 Fuel reformer 11 Fuel cell 12 Burner 16 Fuel gas supply unit 17 Reformed gas discharge unit 18 Circulating gas circulation path 19 Gas supply path 20 Air introducing means 20A Vacuum break valve 21 Catalytic combustor 22 Pressure measuring means 23, 24 Gas-liquid separator 25 Branched path 26 Buffer tank

Claims (7)

A fuel cell power generation system comprising a fuel reformer that reforms a fuel gas into a hydrogen-rich reformed gas, and a fuel cell that generates electricity by electrochemically reacting the reformed gas and air,
Provided with a catalytic combustor provided with a circulation gas circulation path for connecting a fuel gas supply unit to the fuel reformer and a reformed gas discharge unit from the fuel reformer and provided with air introduction means from outside the system And a check valve is provided in the circulating gas circulation path connecting the catalytic combustor and the fuel reformer. 2. The fuel cell according to claim 1, wherein a path branched from the circulating gas circulation path connecting the check valve and the catalytic combustor is provided, and a stop valve and a buffer tank are provided in the branched path. Power generation system. The fuel cell power generation system according to claim 2, further comprising a vacuum breaker valve instead of the shut-off valve. The fuel cell power generation system according to claim 2, wherein a gas-liquid separator is provided in the circulation gas circulation path. The fuel cell power generation system according to any one of claims 2 to 4, wherein pressure measurement means is provided in the circulation gas circulation path. 6. A first state in which the buffer tank and the circulating gas circulation path are brought into communication immediately after the fuel reformer of the fuel cell power generation system according to claim 5 is stopped, and thereafter the pressure in the circulating gas circulation path is set in advance. The buffer tank and the circulating gas circulation path are disconnected from each other when the specified value or more is reached, and when the pressure in the circulating gas circulation path becomes equal to or lower than a second predetermined value set in advance. A method for stopping a fuel cell power generation system, characterized in that air supply to a catalyst combustor is started by air introduction means and the buffer tank and the circulating gas circulation path are in communication with each other. When the pressure in the circulating gas circulation path reaches a preset third specified value, the air supply to the catalytic combustor is stopped and the communication between the buffer tank and the circulating gas circulation path is not established. The stopping method according to claim 6.

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