JP3578002B2 - Fuel cell system combustor - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a combustor for a fuel cell system that burns exhaust reformed gas and exhaust air discharged from a fuel cell.
[0002]
[Prior art]
Conventionally, a combustor shown in FIG. 3 has been known as a combustor for a fuel cell system. In this combustor 101, 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. Is heated and burned by the heater 103, accelerates the oxidation reaction by the combustion catalyst 105, burns, and then is exhausted to the atmosphere.
[0003]
[Problems to be solved by the invention]
However, in the combustor of the conventional fuel cell system, as shown in FIG. 3, at the time of starting, exhaust air from the stack also flows into the heater 103 of the combustor. For this reason, the air from the compressor and the exhaust air from the stack flow in with respect to the amount of methanol required for starting, and the amount of air 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.
[0004]
Also, 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 the thermal deterioration of the heater 103 and the catalyst applied to the heater 103 is increased.
[0005]
Further, 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, and has as its object to improve the temperature rise of the heater at the time of starting, prevent the heater from being deteriorated during normal operation, and suppress the pressure loss of the fuel cell system. It is an object of the present invention to provide a combustor of a fuel cell system that can perform the above.
[0007]
[Means for Solving the Problems]
According to a first aspect of the present invention, there is provided 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 fuel cell. And a combustion chamber that mixes the reformed exhaust gas and the exhaust air discharged from the mixing chamber and promotes an oxidation reaction by the mixed gas from the mixing chamber to burn.
[0008]
According to a second aspect of the present invention, there is provided a heater for heating fuel and air supplied from the outside, and a first fuel for burning by promoting an oxidation reaction by the fuel and air heated by the heater. A mixing chamber for mixing the combustion catalyst, the combustion gas from the first combustion catalyst provided downstream of the heater, and the exhaust reformed gas and exhaust air discharged from the fuel cell; and mixing from the mixing chamber. The gist of the present invention is that it comprises a second combustion catalyst that promotes oxidation by gas and burns.
[0009]
【The invention's effect】
According to the first aspect of the present invention, for example, at the time of 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 gas mixture and burning by the combustion catalyst, the temperature rise of the heater at the time of starting can be improved. Also, for example, during normal operation, air supplied from the 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. By promoting the oxidation reaction by the mixed gas of the above and burning by the combustion catalyst, it is possible to prevent the heater from deteriorating during normal operation, and because the exhaust reformed gas and the exhaust air do not pass through the heater, the fuel cell system Pressure loss can be suppressed.
[0010]
Further, according to the present invention, for example, at the time of start-up, 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, so that the first fuel and air are heated. The combustion can be performed by the combustion catalyst described above, so that the temperature rise of the heater at the time of starting can be improved. Further, for example, during normal operation, air supplied from outside is passed through the heater and the first combustion catalyst, and the air from the first combustion catalyst, the exhaust reformed gas discharged from the fuel cell, and the exhaust air are mixed. The mixture is mixed by the chamber, the oxidation reaction by the mixed gas from the mixing chamber is promoted, and combustion is performed by the second combustion catalyst, so that the heater can be prevented from being thermally degraded during the normal operation, and the inside of the heater can be exhausted reformed gas. And the exhaust air does not pass, so that the pressure loss of the fuel cell system can be suppressed.
[0011]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0012]
(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.
[0013]
As shown in FIG. 1, the first mixing chamber 13 has an inlet 15 for sucking air discharged from a compressor (not shown), and methanol as fuel is injected into the first mixing chamber 13 at a high speed. A methanol injector 17 is provided.
[0014]
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.
[0015]
The heater 19 has one side facing the first mixing chamber 13 in contact with the second mixing chamber 23, and an upper portion of the second mixing chamber 23 is provided with an exhaust gas discharged from a fuel electrode of a stack (not shown). An inlet 25 for sucking reformed gas is provided, and an inlet 27 for sucking exhaust air discharged from the air electrode of the stack is provided below the second mixing chamber 23.
[0016]
The second mixing chamber 23 has one side facing the heater 19 in contact with the combustion catalyst 29, where the exhaust reformed gas reacts with the exhaust air to be combusted, and is discharged to the atmosphere via the exhaust pipe 31. Exhausted.
[0017]
Next, with reference to FIG. 1, the operation and effect of the combustor of the fuel cell system according to the first embodiment of the present invention will be described.
[0018]
First, at the time of startup, the heater 19 is energized and 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.
[0019]
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. And these gases are 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.
[0020]
As a result, as an effect relating to the first embodiment, when starting the combustor 11, the amount of air passing through the heater 19 is reduced as compared with the conventional case, so that the temperature rise of the heater 19 can be improved. . In addition, during normal operation, since there is no combustion in the heater 19, thermal deterioration of the heater 19 can be prevented. Further, during the normal operation, since the exhaust reformed gas and the exhaust air do not pass through the inside of the heater 19, the pressure loss of the fuel cell system including the stack can be suppressed.
[0021]
Further, when the temperature rise of the heater 19 is monitored by using the temperature sensor 21 and the failure diagnosis of the combustor 11 is performed, the temperature is not affected by the exhaust reformed gas and the exhaust air discharged from the stack. The detection error can be reduced, and as a result, the diagnosis error at the time of failure diagnosis can be reduced.
[0022]
(Second embodiment)
FIG. 2 is a diagram illustrating 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.
[0023]
As shown in FIG. 2, the features of the second embodiment are, as shown in FIG. 2, a first combustion catalyst 53 that promotes an oxidation reaction by air and fuel heated by the heater 19 at the time of startup and burns the fuel. A mixing chamber 55 for mixing the air that has passed through the catalyst 53, the exhaust reformed gas exhausted from the stack, and the exhaust air; a second combustion catalyst 61 that promotes an oxidation reaction by the mixed gas from the mixing chamber 55 to burn; That you have.
[0024]
Hereinafter, the first combustion catalyst 53 and the second combustion catalyst 61 will be specifically described.
[0025]
The first combustion catalyst 53 is a first-stage combustion catalyst used for starting, has a lower heat mass honeycomb than the second-stage combustion catalyst, and uses a low-temperature active catalyst washcoat.
[0026]
The second combustion catalyst 61 is a second-stage combustion catalyst used for the operation, and is a catalyst that promotes an oxidation reaction by the exhaust reformed gas and the air. And a catalyst washcoat that is a low-pressure-drop honeycomb and excellent in high exhaust temperature durability.
[0027]
Here, an example of optimal arrangement of the first combustion catalyst 53 and the second combustion catalyst 61 will be described.
[0028]
(1) Comparing the heat capacities of the honeycombs constituting both combustion catalysts,
(Equation 1)
The heat capacity of the honeycomb of the first combustion catalyst ≦ the heat capacity of the honeycomb of the second combustion catalyst.
[0029]
(2) Comparing the ventilation resistance of the honeycombs constituting both combustion catalysts,
(Equation 2)
The ventilation resistance of the honeycomb of the first combustion catalyst ≧ the ventilation resistance of the honeycomb of the second combustion catalyst.
[0030]
(3) Comparing the reaction temperature T50 at which the conversion of both combustion catalysts becomes 50%,
(Equation 3)
T50 of first combustion catalyst ≦ T50 of second combustion catalyst
It becomes.
[0031]
The first combustion catalyst may be a catalyst washcoat that emphasizes the temperature-raising performance while reducing high-temperature durability.
[0032]
Next, with reference to FIG. 2, the operation and effect of the combustor of the fuel cell system according to the second embodiment of the present invention will be described.
[0033]
First, at the time of startup, the heater 19 is energized and 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. .
[0034]
Next, during normal operation, air discharged from the compressor is sucked into the first mixing chamber 13 via the inlet 15, passes through the heater 19 and the first combustion catalyst 53, and flows into the second mixing chamber 55. 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, the exhaust reformed gas, and the exhaust air in the second mixing chamber 55 are sucked into the second combustion catalyst 61, and the oxidation reaction is promoted by the second combustion catalyst 55 to be burned, and the exhaust gas is discharged from the exhaust pipe 31 to the atmosphere. Exhausted.
[0035]
As a result, in addition to the effects of the first embodiment, a plurality of combustion catalysts are arranged in multiple stages in series, so that the honeycomb (carrier) of the combustion catalyst and the catalyst can be obtained. The wash coat 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)

A heater for heating fuel and air supplied from the outside,
A mixing chamber that is provided downstream of the heater and mixes the fuel and air heated by the heater, and the exhaust reformed gas and the exhaust air discharged from the fuel cell;
And a combustion catalyst that promotes an oxidation reaction by the gas mixture from the mixing chamber and burns. A heater for heating fuel and air supplied from the outside,
A first combustion catalyst that promotes an oxidation reaction by the fuel and air heated by the heater and burns;
A mixing chamber provided downstream of the heater for mixing the combustion gas from the first combustion catalyst with the exhaust reformed gas and the exhaust air discharged from the fuel cell;
And a second combustion catalyst that promotes an oxidation reaction by the mixed gas from the mixing chamber and burns.

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