JP2001021112A - Combustion device of fuel cell system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a combustion device of a fuel cell system wherein temperature rising performance of a heater can be improved at a start-up, and heat deterioration of the heater during a normal operation can be suppressed, and moreover pressure losses of the fuel cell system can be suppressed. SOLUTION: At a start-up, methanol and air is heated by a heater 19 in operation and the methanol and air is fed to a combustion catalyst 29, whereby an oxidation reaction is accelerated by the catalyst and exhaust gas of combustion is discharged to the atmosphere from an exhaust pipe 31. During a normal operation, air passes through the heater 19 and flows into a second mixing chamber 23, and simultaneously exhaust reformed gas and exhaust air delivered from a stack is drawn into the chamber 23 so that these gases are mixed, and air, exhaust reformed gas, and exhaust air in the chamber 23 is drawn into the catalyst 29, where an oxidation reaction is accelerated by the catalyst 29 so that these gases are burnt and exhaust gas is discharged to the atmosphere from the pipe 31.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a combustor of a fuel cell system for burning exhaust reformed gas and exhaust air discharged from a fuel cell.

[0002]

2. Description of the Related Art Conventionally, as a combustor of a fuel cell system, one shown in FIG. 3 is known. This combustor 101
Then, air discharged from the compressor, methanol supplied via a methanol injector at the time of starting, exhaust reformed gas exhausted from the stack and exhaust air are sucked in front of the heater 103, and these gases are discharged by the heater 103. heating·
The combustion catalyst 105 is configured to promote the oxidation reaction and burn, and then exhaust the air to the atmosphere.

[0003]

However, in the conventional combustor of the fuel cell system, as shown in FIG. 3, exhaust air from the stack also flows into the heater 103 of the combustor at the time of starting. . For this reason, the air from the compressor and the exhaust air from the stack flow in with respect to the amount of methanol necessary for starting, and the air amount becomes excessive, and the temperature rise of the heater 103 deteriorates. As a result, there is a problem that the startability of the combustor deteriorates.

Further, during normal operation, the exhaust reformed gas and the exhaust air react (combust) in the heater 103, and the temperature in the heater rises significantly. For this reason, there has been a problem that thermal deterioration of the heater 103 and the catalyst applied to the heater 103 is increased.

Furthermore, since the exhaust reformed gas and the exhaust air always flow in the heater 103, there is a problem that the pressure loss in the heater 103 affects the fuel cell system.

[0006] The present invention has been made in view of the above,
It is an object of the present invention to provide a combustor for a fuel cell system which can improve the temperature rise of the heater at the time of starting, prevent thermal deterioration of the heater during normal operation, and suppress pressure loss of the fuel cell system. It is in.

[0007]

According to the first aspect of the present invention,
In order to solve the above problems, a heater for heating fuel and air supplied from the outside, a fuel and air provided downstream of the heater and heated by the heater, and a reformed gas discharged from a fuel cell And a mixing chamber for mixing the exhaust air and a combustion catalyst that combusts by promoting an oxidation reaction by a gas mixture from the mixing chamber.

According to a second aspect of the present invention, there is provided a heater for heating fuel and air supplied from the outside, and combusting by promoting an oxidation reaction by the fuel and air heated by the heater. A first combustion catalyst, a mixing chamber provided downstream of the heater, for mixing the combustion gas from the first combustion catalyst, the reformed gas discharged from the fuel cell, and the discharged air; And a second combustion catalyst that promotes an oxidation reaction by a mixed gas from the fuel and burns.

[0009]

According to the first aspect of the present invention, for example, at startup, fuel and air supplied from the outside are heated by the heater, and the fuel and air heated by the heater are passed through the mixing chamber. By promoting the oxidation reaction by the mixed gas from the mixing chamber and burning with the combustion catalyst, it is possible to improve the temperature rise of the heater at the time of starting. Also,
For example, during normal operation, air supplied from outside is passed through a heater, and the air that has passed through the heater, the reformed gas discharged from the fuel cell, and the discharged air are mixed in a mixing chamber, and mixed from the mixing chamber. By promoting the oxidation reaction by gas and burning by the combustion catalyst, thermal deterioration of the heater can be prevented during normal operation, and exhaust reformed gas and exhaust air do not pass through the heater, so pressure loss of the fuel cell system is reduced. Can be suppressed.

According to the present invention, for example, at the time of starting, the fuel and air supplied from the outside are heated by the heater, and the oxidation reaction by the fuel and air heated by the heater is promoted. As a result, the temperature can be raised by the first combustion catalyst, so that the temperature rise of the heater at the time of starting can be improved. Also, for example, during normal operation, air supplied from outside is passed through the heater and the first combustion catalyst,
The air from the first combustion catalyst, the exhaust reformed gas exhausted from the fuel cell, and the exhaust air are mixed in a mixing chamber, and an oxidation reaction by the mixed gas from the mixing chamber is promoted to be mixed by the second combustion catalyst. By burning, thermal deterioration of the heater can be prevented during normal operation, and since exhaust reformed gas and exhaust air do not pass through the inside of the heater, pressure loss of the fuel cell system can be suppressed.

[0011]

Embodiments of the present invention will be described below with reference to the drawings.

(First Embodiment) FIG. 1 is a diagram showing a configuration of a combustor of a fuel cell system according to a first embodiment of the present invention.

As shown in FIG. 1, the first mixing chamber 13 has
An inlet 15 for sucking air discharged from a compressor (not shown);
3 is provided.

A heater (EHC) 19 is provided on one side of the first mixing chamber 13 facing the inlet 15, and a temperature sensor 21 is mounted on the heater 19.

The heater 19 has one side facing the first mixing chamber 13 in contact with the second mixing chamber 23 and the second mixing chamber 2
An inlet 25 for sucking exhaust reformed gas discharged from a fuel electrode of a stack (not shown) is provided at an upper part of the stack 3, and a discharge port from an air electrode of the stack is provided at a lower part of the second mixing chamber 23. There is provided an inlet 27 for sucking exhaust air to be discharged.

The second mixing chamber 23 has one side facing the heater 19 in contact with a combustion catalyst 29. In the combustion catalyst 29, the exhaust reformed gas and the exhaust air react and burn, and the exhaust pipe 31 is exhausted.
Exhausted to the atmosphere via

Next, the operation and effect of the combustor of the fuel cell system according to the first embodiment of the present invention will be described with reference to FIG.

First, at the time of starting, the heater 19 is energized to be heated. At this time, air discharged from the compressor is sucked into the first mixing chamber 13 via the inlet 15, and methanol from a fuel tank (not shown) is injected into the first mixing chamber 13 via the methanol injector 17. The methanol and air are heated by the heater 19 during heating and burned. Further, methanol and air are sucked into the combustion catalyst 29, and the oxidation reaction is promoted by the combustion catalyst 29, and the burned exhaust gas is exhausted from the exhaust pipe 31 to the atmosphere.

Next, during normal operation, air discharged from the compressor is sucked into the first mixing chamber 13 through the inlet 15, passes through the heater 19, and flows into the second mixing chamber 23.
At the same time, the exhaust reformed gas discharged from the fuel electrode of the stack is sucked into the second mixing chamber 23 through the inlet 25, and the exhaust air discharged from the air electrode of the stack is discharged into the second mixing chamber 23 through the inlet 27.
These gases are sucked into the mixing chamber 23 and mixed. Further, the air, the exhaust reformed gas and the exhaust air in the second mixing chamber 23 are sucked into the combustion catalyst 29, the oxidation reaction is promoted by the combustion catalyst 29, and the exhaust gas is exhausted from the exhaust pipe 31 to the atmosphere.

As a result, the effect of the first embodiment is that when the combustor 11 is started, the amount of air passing through the heater 19 is smaller than in the prior art.
9 can be improved in temperature rising property. In addition, during normal operation, since there is no combustion in the heater 19, it is possible to prevent the heater 19 from being thermally degraded. Furthermore, during normal operation, since the exhaust reformed gas and the exhaust air do not pass through the heater 19, the pressure loss of the fuel cell system including the stack can be suppressed.

The heater 19 is controlled by using the temperature sensor 21.
When the failure diagnosis of the combustor 11 is performed by monitoring the temperature rise of the heater, the detection error of the heater temperature can be reduced because the exhaust reformed gas and the exhaust air discharged from the stack are not affected. As a result, a diagnosis error at the time of failure diagnosis can be reduced.

(Second Embodiment) FIG. 2 is a diagram showing a configuration of a combustor of a fuel cell system according to a second embodiment of the present invention. Note that the second embodiment has the same basic configuration as the combustor of the fuel cell system corresponding to the first embodiment shown in FIG. 1, and the same components are denoted by the same reference numerals. And a description thereof will be omitted.

A feature of the second embodiment is that, as shown in FIG. 2, a first combustion catalyst 53 which burns by promoting an oxidation reaction by air and fuel heated by a heater 19 at the time of startup.
A mixing chamber 55 for mixing the air that has passed through the first combustion catalyst 53 during operation, the exhaust reformed gas exhausted from the stack, and the exhaust air, and promotes an oxidation reaction by the mixed gas from the mixing chamber 55. And the second combustion catalyst 61 that burns.

Hereinafter, the first combustion catalyst 53 and the second combustion catalyst 6
1 will be specifically described.

The first combustion catalyst 53 is a first-stage combustion catalyst used for starting. Compared to the second-stage combustion catalyst, the first combustion catalyst 53 has a lower heat mass honeycomb and uses a low-temperature active catalyst washcoat. .

The second combustion catalyst 61 is a second-stage combustion catalyst used for the operation, is a catalyst that promotes an oxidation reaction by the exhaust reformed gas and air, and serves as a CO removal catalyst in the first stage of the first stage.
Compared with the combustion catalyst 53, a catalyst wash coat which is a honeycomb having a low pressure loss and excellent in high exhaust temperature durability is used.

Here, an example of the optimal arrangement of the first combustion catalyst 53 and the second combustion catalyst 61 will be described.

(1) Comparing the heat capacities of the honeycombs constituting both combustion catalysts,

The heat capacity of the honeycomb of the first combustion catalyst ≦ the heat capacity of the honeycomb of the second combustion catalyst.

(2) Comparing the ventilation resistance of the honeycombs constituting both combustion catalysts,

## EQU2 ## The ventilation resistance of the honeycomb of the first combustion catalyst ≧ the ventilation resistance of the honeycomb of the second combustion catalyst.

(3) Comparing the reaction temperature T50 at which the conversion of both combustion catalysts becomes 50%,

## EQU3 ## T50 of the first combustion catalyst ≦ T50 of the second combustion catalyst.

The first combustion catalyst may be a catalyst washcoat which emphasizes the temperature raising performance while lowering the durability at high temperatures.

Next, the operation and effect of the combustor of the fuel cell system according to the second embodiment of the present invention will be described with reference to FIG.

First, at the time of starting, the heater 19 is energized to be heated. At this time, air discharged from the compressor is sucked into the first mixing chamber 13 via the inlet 15, and methanol from a fuel tank (not shown) is injected into the first mixing chamber 13 via the methanol injector 17. The methanol and air are heated by the heater 19 during heating and burned. Further, methanol and air are sucked into the combustion catalyst 53, and the oxidation reaction is promoted by the honeycomb of the combustion catalyst 53, and the combustion is performed. Next, the unburned methanol and air are sucked into the combustion catalyst 61 from the second mixing chamber 55, and the oxidation reaction is promoted by the honeycomb of the combustion catalyst 61, and the burned exhaust gas is exhausted from the exhaust pipe 31 to the atmosphere. .

Next, during normal operation, air discharged from the compressor is sucked into the first mixing chamber 13 through the inlet 15 and passes through the heater 19 and the first combustion catalyst 53 to the second mixing chamber 55. Inflow. At the same time, the exhaust reformed gas discharged from the fuel electrode of the stack is sucked into the second mixing chamber 55 through the inlet 57, and the exhaust air discharged from the air electrode of the stack is discharged into the second mixing chamber 55 through the inlet 59. And these gases are mixed. Further, the air in the second mixing chamber 55, the exhaust reformed gas, and the exhaust air are sucked into the second combustion catalyst 61, and the oxidation reaction is promoted by the second combustion catalyst 55, and the exhaust gas is discharged from the exhaust pipe 31 to the atmosphere. Exhausted.

As a result, the effects of the second embodiment are the same as those of the first embodiment, and the honeycomb (carrier) of the combustion catalyst is constituted by arranging a plurality of combustion catalysts in series in multiple stages. ) And the catalyst washcoat can be optimally arranged in consideration of the three points of the temperature rising property, the durability, and the pressure loss performance.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of a combustor of a fuel cell system according to a first embodiment of the present invention.

FIG. 2 is a diagram showing a configuration of a combustor of a fuel cell system according to a second embodiment of the present invention.

FIG. 3 is a diagram showing a configuration of a combustor of a conventional fuel cell system.

[Explanation of symbols]

 13 First mixing chamber 15,25,27,57,59 Inlet 17 Methanol injector 19 Heater 21 Temperature sensor 23,55 Second mixing chamber 29 Combustion catalyst 31 Exhaust pipe 53 First combustion catalyst 61 Second combustion catalyst

Claims (2)

[Claims] 1. A heater for heating fuel and air supplied from outside, a fuel and air provided downstream of the heater and heated by the heater, a reformed gas discharged from the fuel cell, and a discharged gas. A combustor for a fuel cell system, comprising: a mixing chamber that mixes air; and a combustion catalyst that promotes an oxidation reaction by a mixed gas from the mixing chamber and burns. 2. A heater for heating fuel and air supplied from the outside, a first combustion catalyst for promoting oxidation by the fuel and air heated by the heater and burning, and a downstream side of the heater. A mixing chamber provided for mixing the combustion gas from the first combustion catalyst, the exhaust reformed gas discharged from the fuel cell, and the exhaust air; and promoting combustion by the oxidation reaction of the mixed gas from the mixing chamber. A combustor for a fuel cell system, comprising: a second combustion catalyst.