JP2002117874A - Reforming fuel cell system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a surplus fuel flown into a burner from becoming excessive, even in case a load is stopped suddenly or slowed down suddenly. SOLUTION: A reforming fuel cell system is constituted with a reformer 1, which generates a reformed gas, a CO removal part 2, which reduces CO in the reformed gas and supplies it to a fuel cell stack, a burner 4 that burns air and a discharged gas or the reformed gas from the fuel cell stack 3, an evaporator 5, which sends a fuel steam to reformer 1 by an exhaust heat from the burner 4, a shut-off valve 8, which supplies selectively the reformed gas from the CO removal part 2 to the fuel cell stack 3, a shut-off valve 9, which is arranged in a flow way 40, which connects the CO removal part through the burner, and supplies the reformed gas selectively, and a small shut-off valve 10 as a stopper element in parallel with the shut-off valve 9.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in a reforming fuel cell system.

[0002]

2. Description of the Related Art As a conventional reforming type fuel cell system, Japanese Patent Application Laid-Open No. Hei 7-296834 is known.

[0003]

However, in the above-mentioned conventional example, when the load of the motor or the like connected to the fuel cell stack is suddenly stopped, or when the required output is suddenly reduced due to rapid deceleration, the fuel is not supplied. Excess fuel (hydrogen) discharged from the battery stack flows into the combustor at once,
There has been a problem that the temperature of the combustor rises excessively and durability decreases.

The present invention has been made in view of the above problems, and prevents an excessive amount of surplus fuel from flowing into a combustor even when a load is suddenly stopped or suddenly decelerated. The purpose is to:

[0005]

According to a first aspect of the present invention, there is provided a reformer for producing a reformed gas, a CO removing section for reducing CO in the reformed gas and supplying the reduced gas to a fuel cell stack, A combustor for burning the exhaust gas or the reformed gas and the air from the battery stack, an evaporator for sending fuel vapor to the reformer by exhaust heat from the combustor, and a fuel cell stack from the CO removal unit. A first valve for selectively supplying reformed gas, and a second valve for selectively supplying reformed gas interposed in a flow path communicating the CO removal unit and the combustor. In the reformed fuel cell system, a throttle element is provided in the flow path in which the second valve is provided.

In a second aspect based on the first aspect, the throttle element is constituted by a third valve arranged in parallel with the second valve.

In a third aspect based on the first aspect, the throttle element comprises a throttle arranged in series with the second valve.

A fourth aspect of the present invention provides a reformer for generating a reformed gas, a CO removing unit for reducing CO in the reformed gas and supplying it to a fuel cell stack, A combustor for burning exhaust gas or the reformed gas and air, an evaporator for sending fuel vapor to the reformer by exhaust heat from the combustor, and a reformed gas from the CO removal unit to a fuel cell stack A first valve for selectively supplying reformed gas, a second valve interposed in a flow path communicating between the CO removing unit and the combustor to selectively supply reformed gas, and a fuel cell stack and a combustion chamber. And a pressure control valve for regulating the reformed gas in the fuel cell stack, between the reactor and the fuel cell stack, when the pressure control valve is closed,
A throttle element is provided to regulate the reformed gas flowing into the combustor.

In a fifth aspect based on the fourth aspect, the throttle element comprises a fourth valve disposed in parallel with the pressure control valve.

In a sixth aspect based on the fourth aspect, the throttle element comprises a throttle arranged in parallel with the pressure control valve.

[0011]

Accordingly, the first aspect of the present invention is that the throttle element is disposed in the flow path that connects the CO removing section and the combustor, and the excess fuel is contained in the reformed gas discharged from the fuel cell stack. In a situation where the fuel gas suddenly increases, the first valve is closed, and the reformed gas can be gradually sent from the CO removing section to the combustor through the throttle element, and the amount of fuel flowing into the combustor can be increased. Can be prevented from rapidly increasing, the temperature of the combustor can be prevented from becoming excessively high, and the durability of the combustor can be ensured.

According to the second aspect of the present invention, the third valve disposed in parallel with the second valve functions as a throttle, so that the amount of surplus fuel in the reformed gas discharged from the fuel cell stack rapidly increases. In such a situation, the first valve and the second valve are closed, and the reformed gas can be gradually sent from the CO removing section to the combustor through the third valve, and flows into the combustor. It is possible to suppress a sudden increase in the amount of fuel to be generated, to surely prevent the temperature of the combustor from becoming excessive, and to ensure the durability of the combustor.

According to the third aspect of the present invention, since the throttle is arranged in series with the second valve, when a situation where surplus fuel rapidly increases in the reformed gas discharged from the fuel cell stack,
By closing the first valve and opening the second valve,
The reformed gas can be gradually sent from the CO removal unit to the combustor via the throttle, suppressing the sudden increase in the amount of fuel flowing into the combustor and ensuring that the temperature of the combustor becomes excessive. And the durability of the combustor can be ensured.

Further, according to a fourth aspect of the present invention, when the pressure control valve for regulating the reformed gas in the fuel cell stack is closed between the fuel cell stack and the combustor, the reformer that flows into the combustor is provided. The throttle element that regulates the quality gas is provided, so when the surplus fuel increases rapidly in the reformed gas discharged from the fuel cell stack, the pressure control valve is closed, and the fuel is passed through the throttle element. The reformed gas can be gradually sent from the battery stack to the combustor, suppressing the sudden increase in the amount of fuel flowing into the combustor, preventing the combustor temperature from becoming excessively high, and ensuring combustion. The durability of the vessel can be ensured.

According to a fifth aspect of the present invention, the fourth valve disposed in parallel with the pressure control valve functions as a throttle so that surplus fuel increases rapidly in the reformed gas discharged from the fuel cell stack. In such a situation, the reformed gas can be gradually sent to the combustor via the fourth valve, and the amount of fuel flowing into the combustor can be prevented from increasing rapidly, so that the temperature of the combustor becomes excessive. And the durability of the combustor can be ensured.

According to a sixth aspect of the present invention, the provision of the restrictor arranged in parallel with the pressure control valve allows a situation in which surplus fuel increases rapidly in the reformed gas discharged from the fuel cell stack. The reformed gas can be gradually sent to the combustor via the throttle, suppressing the sudden increase in the amount of fuel flowing into the combustor, and reliably preventing the temperature of the combustor from becoming excessive, The durability of the combustor can be ensured.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 shows a fuel cell system of a reforming type.
The reforming system for supplying the fuel (hydrogen) gas to the fuel cell stack 3 includes a gas from an evaporator 5 for vaporizing water for producing steam and methanol as a raw material, and a flow control valve 2.
Air from a compressor (not shown) which is pumped from the reactor 6 is subjected to a catalytic reaction in the reformer 1 to form a reformed gas. Further, air is supplied from the upstream of the CO removing section 2 and the reformed gas is supplied to the CO removing section 2. After removing the CO inside, the CO is supplied to an anode (not shown) of the fuel cell stack 3 via a shut-off valve 8 (a first valve which is a shut-off valve).

The reformed gas generated in the CO removing section 2 is supplied to the shut-off valve 9 (second
) Or the small shut-off valve 10 (third valve).

The shut-off valve 9 and the small shut-off valve 10 are arranged in parallel, and the cross-sectional area of the small shut-off valve 10 is set smaller than that of the shut-off valve 9, and the shut-off valve 9 is closed. At the time of valve opening, a flow path resistance is set such that the small shut-off valve 10 functions as a throttle element.

On the other hand, air (oxidizing gas) is supplied to a cathode (not shown) of the fuel cell stack 3 from a compressor or the like via a flow control valve 25.

Exhaust reformed gas containing excess fuel (hydrogen) discharged from the fuel cell stack 3 is sent to the combustor 4 via the pressure control valve 21.

The exhaust air discharged from the fuel cell stack 3 is sent to a combustor 4 via a pressure control valve 22, and the combustor 4 burns the exhaust reformed gas and the exhaust air to exhaust the exhaust gas. The exhaust gas is sent to the evaporator 5 and heated to evaporate methanol and water injected from the injectors 51 and 52.

The output of the fuel cell stack 3 drives a load 7 composed of a motor or the like.

The reforming fuel cell system as described above is
A control unit 6 (control means) constituted by a microcomputer or the like
The output of the fuel cell stack 3 is controlled by controlling the control valves and the injectors.

For this reason, the control unit 6 includes
Load state detection means 30 for detecting the operation state of the load 7 is connected.

The load state detecting means 30 is constituted by, for example, a power detecting device when the load 7 is an inverter, and is constituted by a rotation speed sensor when the load 7 is a motor.

The control unit 6 adjusts the gas pressure in the fuel cell stack 3 with the pressure control valves 21 and 22 based on the input from the load state detecting means 30 and sends the gas to the fuel cell stack 3 and the reformer 1. The amount of air to be supplied is adjusted by the flow control valves 25 and 26, and the reformed gas supplied from the CO removal unit 2 to the fuel cell stack 3 is controlled by the shut-off valve 8. Shutoff valve 9 and small shutoff valve 1
0 is controlled.

Here, when the reforming system and the fuel cell stack 3 are in a steady state, the control unit 6
While the shutoff valve 8 is opened, the shutoff valve 9 and the small shutoff valve 10 are closed to supply the reformed gas from the CO removing unit 2 to the fuel cell stack 3, and the pressure of the pressure control valve 21. The operation of the fuel cell stack 3 is performed by the control.

When the load state detecting means 30 detects a sudden stop or a sudden deceleration of the load 7 from this steady state, in other words, a sudden decrease in the required output of the load 7, the control unit 6
The shutoff valve 8 is closed to stop the supply of the reformed gas to the fuel cell stack 3, while the small shutoff valve 10 is closed.
Is opened.

Therefore, if the required output of the load 7 suddenly decreases, the excess hydrogen in the exhaust reformed gas increases in the conventional example. However, according to the present invention, when the required output of the load 7 decreases rapidly, The reformed gas from the CO removing unit 2 is gradually supplied to the combustor 4 through the small-sized shut-off valve 10 having a large resistance. It is possible to reliably prevent the temperature of the combustor 4 from becoming excessively high, and to ensure the durability of the combustor 4.

When the reforming system is started, the shut-off valve 8 is closed, while the shut-off valve 9 and the small shut-off valve 10 are opened to directly burn the reformed gas from the CO removing unit 2. The warm-up operation is performed by sending the small-size shut-off valve 10 to the small-size shut-off valve 10 in addition to the shut-off valve 9.
Also, by opening the valve, the flow path resistance of the reformed gas flowing from the CO removing unit 2 to the combustor 4 can be reduced, and the warm-up can be efficiently performed. When the required output decreases sharply, the small shut-off valve 10 can act as a throttle element to protect the combustor 4.

When the load state detecting means 30 detects a sudden decrease in the required output of the load 7 such as a sudden stop or a sudden deceleration of the load 7 from a steady state, the load of the reformed gas or exhaust reformed gas to the combustor 4 is detected. Although the inflow is suppressed, since the gas immediately before the required output sharply decreases is supplied from the evaporator 5, the reformed gas gradually flowing from the shutoff valve 10 is burned in the combustor 4, and the reformed gas is combusted in the evaporator 5. The cycle of producing gas lasts for a while.

FIG. 2 shows a second embodiment, in which the first
While the small shut-off valve 10 of the embodiment is abolished, a throttle 11 composed of an orifice or the like is provided downstream of the shut-off valve 9, and the other configuration is the same as that of the first embodiment.

The throttle 11 downstream of the shut-off valve 9 is
A flow path resistance is provided to regulate the flow rate of the reformed gas from the O removal unit 2 to the combustor 4 so as not to exceed the capacity of the combustor 4.

In this case, when the load 7 suddenly stops or decelerates from the steady state, the control unit 6 closes the shut-off valve 8 to stop the supply of the reformed gas to the fuel cell stack 3 while shutting down. The off valve 9 is opened.

Therefore, when the required output of the load 7 suddenly decreases, the reformed gas to the fuel cell stack 3 is shut off, and the reformed gas from the CO removing unit 2 is passed through the throttle 11 provided downstream of the shut-off valve 9. Is supplied to the combustor 4, the amount of hydrogen flowing into the combustor 4 is suppressed by the throttle 11, the temperature of the combustor 4 is reliably prevented from becoming excessive, and the durability of the combustor 4 is improved. Nature can be secured.

The throttle 11 may be disposed in series with the shut-off valve 9, for example, may be disposed upstream of the shut-off valve 9.

FIG. 3 shows a third embodiment, in which the second embodiment is used.
While the throttle 11 of the embodiment is abolished, the throttle 12 is provided in parallel with a pressure control valve 21 for controlling the pressure of the reformed gas discharged from the fuel cell stack 3. This is the same as the embodiment.

The throttle 1 arranged in parallel with the pressure control valve 21
2 indicates that the flow rate of the exhaust reformed gas from the fuel cell stack 3 to the combustor 4 when the pressure control valve 21 is closed
The flow path resistance is regulated so as not to exceed the capacity.

In this case, when the load 7 suddenly stops or decelerates from the steady state, the control unit 6 closes the pressure control valve 21 while keeping the shut-off valve 8 open.

Therefore, when the required output of the load 7 suddenly decreases, the reformed gas discharged from the fuel cell stack 3 is supplied to the combustor 4 through the throttle 12 arranged in parallel with the pressure control valve 21. That is, the amount of hydrogen flowing into the combustor 4 is suppressed by the restrictor 12, the temperature of the combustor 4 is reliably prevented from becoming excessive, and the durability of the combustor 4 can be ensured.

FIG. 4 shows a fourth embodiment, in which the third embodiment is used.
Instead of the throttle 12 of the embodiment, a small shut-off valve 1
3 (fourth valve) is provided, and the other configuration is the same as that of the third embodiment.

The cross-sectional area of the small shut-off valve 13 is as follows.
The pressure control valve 2 is set to be smaller than the pressure control valve 21.
When the valve 1 is closed, the fuel cell stack 3
It has a flow path resistance that regulates the flow rate of the exhaust reformed gas to not exceed the capacity of the combustor 4, and is configured to function as a throttle element.

In this case, when the load 7 suddenly stops or decelerates from the steady state, the control unit 6 closes the pressure control valve 21 and opens the small shut-off valve 13 while keeping the shut-off valve 8 open. Give a valve.

Therefore, when the required output of the load 7 suddenly decreases, the reformed gas discharged from the fuel cell stack 3 is sent to the combustor 4 via the small shut-off valve 13 arranged in parallel with the pressure control valve 21. As a result, the amount of hydrogen flowing into the combustor 4 is suppressed by the small shut-off valve 13 to reliably prevent the temperature of the combustor 4 from becoming excessively high, and the durability of the combustor 4 is improved. Can be secured.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a reformed fuel cell system showing one embodiment of the present invention.

FIG. 2 is a schematic diagram illustrating a reformed fuel cell system according to a second embodiment.

FIG. 3 is a schematic configuration diagram of a reformed fuel cell system according to a third embodiment.

FIG. 4 is a schematic diagram illustrating a reformed fuel cell system according to a fourth embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Reformer 2 CO removal part 3 Fuel cell stack 4 Combustor 5 Evaporator 8 Shutoff valve 10, 13 Small shutoff valve 11, 12 Restrictor 40 Bypass flow path

Claims (6)

[Claims] A reformer that generates a reformed gas; a CO removing unit that reduces CO in the reformed gas and supplies the reformed gas to a fuel cell stack; and an exhaust gas from the fuel cell stack or the reformed gas. A combustor for burning gas and air; an evaporator for sending fuel vapor to the reformer by exhaust heat from the combustor; and selectively supplying reformed gas from the CO removing unit to a fuel cell stack. A reforming type fuel cell system comprising: a first valve; and a second valve interposed in a flow path that connects the CO removing unit and the combustor and selectively supplying a reformed gas. A reforming fuel cell system, wherein a throttle element is provided in a flow path in which a second valve is provided. 2. The valve according to claim 1, wherein the throttle element is a third valve arranged in parallel with the second valve.
3. The reformed fuel cell system according to item 1. 3. The reforming fuel cell system according to claim 1, wherein the throttle element is a throttle arranged in series with the second valve. 4. A reformer that generates a reformed gas, a CO removing unit that reduces CO in the reformed gas and supplies the reduced gas to a fuel cell stack, and an exhaust gas from the fuel cell stack or the reformed gas. A combustor for burning gas and air; an evaporator for sending fuel vapor to the reformer by exhaust heat from the combustor; and selectively supplying reformed gas from the CO removing unit to a fuel cell stack. A first valve, a second valve interposed in a flow path that connects the CO removal unit and the combustor, and selectively supplies reformed gas, and a fuel cell stack and a combustor. A pressure control valve for regulating the reformed gas in the fuel cell stack, wherein the throttle element regulates the reformed gas flowing into the combustor when the pressure control valve is closed. Reformed fuel cell system Temu. 5. The reforming fuel cell system according to claim 4, wherein the throttle element is a fourth valve arranged in parallel with the pressure control valve. 6. The reforming fuel cell system according to claim 4, wherein the throttle element is a throttle arranged in parallel with the pressure control valve.