JP3240783B2 - Internal reforming fuel cell - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an internal reforming fuel cell, and more particularly, to a molten carbonate type fuel cell incorporating a reformer.

[0002]

2. Description of the Related Art Molten carbonate fuel cells have features that are not found in conventional power generation devices, such as high efficiency and little impact on the environment, and have attracted attention as power generation systems following hydro, thermal and nuclear power. Are being researched and developed in various countries around the world. In particular, in a power generation facility using a molten carbonate fuel cell using natural gas as a fuel, as shown in FIG. 2, a reformer 10 for reforming a fuel gas 1 such as natural gas into an anode gas 2 containing hydrogen, A fuel cell 12 generally generates electricity from the anode gas 2 and the cathode gas 3 containing oxygen, and the anode gas produced by the reformer is supplied to the fuel cell, and most of the anode gas is produced in the fuel cell ( After consuming 80%, for example, the combustion chamber C of the reformer 10 is used as the anode exhaust gas 4.
o. The fuel gas 1 is preheated by the fuel preheater 11 and enters the reforming chamber Re of the reformer. In the reformer, combustible components (hydrogen, carbon monoxide, methane, etc.) in the anode exhaust gas are burned in the combustion chamber, and the reforming chamber Re is heated by the high-temperature combustion gas to reform the fuel flowing inside. The combustion exhaust gas 5 that has exited the reforming chamber is heat-recovered by the air preheater 13, water is removed by the condenser 14 and the steam separator 15, and the air compressed by the turbine compressor (power recovery device 16) The mixed gas is heated by the air preheater 13 and merges with the cathode gas 3. As a result, carbon dioxide generated on the anode side of the battery enters the cathode gas 3 for the fuel cell via the combustion exhaust gas 5 and supplies carbon dioxide required for the cathode reaction of the fuel cell to the cathode side C. A part of the cathode gas 3 reacts in the fuel cell to become a cathode exhaust gas 7,
A part thereof is recirculated to the cathode inlet side, a part is supplied to the combustion chamber Co of the reformer 10 to burn the anode exhaust gas 4, and the remaining part is supplied to the power recovery unit 16 to be pressure-recovered. Is discharged. In the drawing, reference numeral 12a denotes a storage container of the fuel cell, and reference numeral 8 denotes a purge gas supplied to the storage container.

[0003]

The gas seal between the anode side A and the cathode side C in the molten carbonate type fuel cell can prevent electrolyte wetting (surface tension) at the operating temperature of the fuel cell (about 600 to 700 ° C.). ) (Wet seal). Therefore, the differential pressure between the anode and the cathode is, for example, 500 mmAq even in the case of the pressurizing operation.
It is necessary to control the pressure difference to be as small as about (0.05 kg / cm ² ). However, the above-described conventional power generation device has a problem that a pressure difference is easily generated between the anode side A and the cathode side C of the fuel cell 12. That is, as is apparent from FIG. 3 schematically showing the power generation device in FIG. 2, after the gas that has passed through the anode side A of the fuel cell 12 has passed through the combustion chamber Co and the like of the reformer 10, the fuel cell 12 Since the gas enters the cathode side C, the pressure on the anode side A is higher than that on the cathode side C by an amount corresponding to the pressure loss of the intermediate device and the flow path. For this reason, in the conventional power generation device, it was necessary to provide a valve and a blower in the high-temperature gas line and to constantly control the differential pressure between the anode and the cathode. However, such control needs to cope with various operating conditions of the fuel cell (for example, conditions at the time of startup and load change), and it is necessary to perform precise differential pressure control under pressurized operation. There was a problem that it was complicated and poor in reliability. In addition, in such a power generation facility, unless the reforming rate in the reformer 10 is maintained at a high level (for example, 90% or more), there is a problem that the hydrogen concentration of the anode gas 2 is low and the performance of the fuel cell is reduced.

On the other hand, an internal reforming fuel cell in which a reforming catalyst is directly filled in the anode side A of the fuel cell has been proposed and implemented (hereinafter, referred to as a direct internal reforming fuel cell).
In such a direct internal reforming fuel cell, since the hydrogen generated by the reforming is immediately consumed in the fuel cell, the operating temperature (about 600 to 700 ° C.) of the fuel cell is lower than the temperature of the reformer (for example, 800 ° C. or higher). ) Also has the advantage of a high reforming rate, but since the reforming catalyst is in direct contact with the electrolyte of the fuel cell, the reforming catalyst is easily contaminated, and as is clear from the schematic diagram shown in FIG. There is a problem that the pressure on the anode side A tends to be higher than that on the cathode side C.

Further, in order to avoid the problems of the direct internal reforming fuel cell, an indirect internal reforming fuel cell (FIG. 5) in which a reformer is incorporated between the fuel cells has been proposed. However, such an indirect internal reforming fuel cell has a problem that the reforming rate of the fuel gas 1 is low because the temperature of the fuel cell is low and the generated hydrogen is not consumed immediately. For this reason, in the conventional indirect internal reforming fuel cell, it was necessary to mix a large amount of steam into the fuel gas 1 to increase the S / C ratio (steam / carbon ratio) in the reforming beyond that required for the reaction. . However, when the S / C ratio is increased, there is a problem that the concentration of hydrogen contained in the anode gas 2 is reduced due to excess steam, and the performance of the fuel cell is reduced.

In the fuel cells shown in FIGS. 3 and 4,
Since the anode exhaust gas 4 that has passed through the fuel cell is burned in the combustion chamber Co and circulated to the cathode gas 3, the concentration of carbon dioxide (CO ₂ ) contained in the cathode gas 3 is low.

The present invention has been made to solve such a problem. That is, an object of the present invention is that the pressure difference between the anode and the cathode is essentially low, the reforming rate of the fuel gas is high, the reforming catalyst is not polluted, and the hydrogen concentration in the anode gas and the cathode gas An object of the present invention is to provide an internal reforming fuel cell having a high concentration of carbon dioxide.

[0008]

According to Means for Solving the Problems] The present invention, cathode gas containing oxygen and anode gas (2) containing hydrogen
A fuel cell (22) for generating electricity from (3) , and a fuel cell
A reformer (24 ) for reforming the fuel gas (1) with heat transferred from the (22) , wherein the reformer (24) comprises a reforming chamber (26) filled with a reforming catalyst. And a hydrogen chamber (2) holding a gas mainly composed of hydrogen separated from the reformed gas.
8) and a reforming chamber (26) and a hydrogen chamber in the reformer (24) .
(28) , a separation membrane (30) having a hydrogen separation function of separating a gas containing hydrogen as a main component from the reformed gas, and introducing the fuel gas (1) into the reforming chamber (26). Do
Passed through the fuel gas line (32) and the reforming chamber (26)
A combustor (34) for burning the fuel gas (1), and a combustor
Combustion exhaust gas discharged from (34) is mixed into cathode gas (3)
The cathode gas line (36) to be
8) Anode for introducing gas in anode to anode gas (2)
And a gas line (38) .

[0009]

[0010]

According to the structure of the present invention, the internal reforming fuel cell of the present invention includes the reformer (24) for reforming the fuel gas (1) with the heat transferred from the fuel cell (22). The reformer (24) partitions the interior of the reformer (24) into a reforming chamber (26) and a hydrogen chamber (28) and separates hydrogen-based gas from the reformed gas (). Separation membrane with function (3
0) , and the separation membrane (30) allows the reforming chamber (26)
Since the hydrogen generated in the fuel cell is immediately separated, the fuel cell (2
Even at the operation temperature 2) (about 650 ° C.), a high reforming rate can be obtained. The reforming catalyst is a fuel cell (2
Since it is filled in the reformer (24) separate from 2) , there is no direct contact with the electrolyte of the fuel cell (22) , and the reforming catalyst is not contaminated.

[0011] In particular, the internal reforming fuel cell of the present invention, the reforming chamber and the fuel gas line for introducing the fuel gas (1) to (26) (32), the fuel gas passing through the reforming chamber (26)
A combustor (34 ) for burning (1) , and a combustor (34)
A cathode gas line (36 ) for mixing the combustion exhaust gas discharged from the chamber with the cathode gas (3) , and an anode gas line (38) for introducing the gas in the hydrogen chamber (28) to the anode gas (2). The gas separated from the hydrogen chamber (28) by the separation membrane (30) is the anode gas (38).
And the fuel gas (1) that has passed through the reforming chamber (26) enters the cathode gas (3) after burning in the combustor (34) , so that the pressure difference between the anode gas (2) and the cathode gas (3) is Since only the difference between the pressure loss of the separation membrane (30) and the pressure loss of the combustor (34) is low and both are low (e.g.
The difference is even smaller. Therefore, the differential pressure between the anode and the cathode can always be kept essentially small without providing a valve or a blower in the high-temperature gas line and without using a special control device.

Further, since the gas containing hydrogen as a main component separated by the separation membrane (30) is introduced into the anode gas (2) , the amount of excess water vapor and carbon dioxide in the anode gas (2) is smaller than in the prior art. Hydrogen concentration can be increased. Further, the hydrogen component is separated by the separation membrane (30) , and the reforming chamber (2)
6) The fuel gas (1) that has passed through the combustor (34) enters the cathode gas (3) after combustion, and a high reforming rate can be obtained without increasing the S / C ratio. The concentration of carbon dioxide in the cathode gas (3) can be increased.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is an overall configuration diagram of an internal reforming fuel cell according to the present invention. In this figure, an internal reforming fuel cell 20 of the present invention generates a fuel cell 22 that generates electricity from an anode gas 2 containing hydrogen and a cathode gas 3 containing oxygen, and generates a fuel gas 1 by heat transferred from the fuel cell 22. And a reformer 24 for reforming. The fuel cell 22 and the reformer 24 are substantially integrally formed, and heat generated in the fuel cell 22 is transferred to the reformer 24, and the entire reformer 24 is the same as the fuel cell 22. (About 600 to 700 ° C.). For example, as shown in the drawing, the reformer 24 is configured in a planar shape, and is sandwiched between a plurality of single cells (anode A, a cathode C, and an electrolyte plate therebetween) constituting the fuel cell 20 every several cells. Is preferred.

The reformer 24 includes a reforming chamber 26 filled with a reforming catalyst, a hydrogen chamber 28 containing a gas containing hydrogen as a main component separated from the reformed gas, and a reformer 24. Quality room 26
And a separation membrane 30 having a hydrogen separation function of separating a gas containing hydrogen as a main component from the reformed gas. The separation membrane 30 is a porous membrane having a performance of selectively separating hydrogen at 600 to 700 ° C., and is preferably, for example, a porous glass membrane, a porous ceramics plate, a palladium film, a metal thin film, or the like. In FIG. 1, the reformer 24 is divided into three by two separation membranes 30, and two of them are
However, the present invention is not limited to such a configuration, and it is sufficient that at least one separation membrane 30, two reforming chambers 26, and two hydrogen chambers 28 are provided.

According to the above-described structure, since the hydrogen generated in the reforming chamber 28 is immediately separated by the separation membrane 30, a high reforming rate can be obtained even at the operating temperature of the fuel cell 22 (about 600 to 700 ° C.). Can be. Further, since the reforming catalyst is filled in the reformer 24 separate from the fuel cell 22, the reforming catalyst does not come into direct contact with the electrolyte of the fuel cell 22, and the reforming catalyst is not contaminated.

The internal reforming fuel cell 20 of the present invention further comprises a fuel gas line 32 for introducing the fuel gas 1 into the reforming chamber 26.
And a combustor 34 for burning the fuel gas that has passed through the reforming chamber 26,
And a cathode gas line 38 for introducing the gas in the hydrogen chamber 28 to the anode gas 2.

With this configuration, the gas separated from the hydrogen chamber 28 by the separation membrane 30 enters the anode gas 2, and the fuel gas passing through the reforming chamber 26 enters the cathode gas 3 after burning in the combustor 34. Anode gas 2 and cathode gas 3
Is substantially the only difference between the pressure loss of the separation membrane 30 and the pressure loss of the combustor 34, and both are low pressure losses (for example, 20
The difference is even smaller. Therefore, the differential pressure between the anode and the cathode can always be kept essentially small without providing a valve or a blower in the high-temperature gas line and without using a special control device.

The combustor 34 is preferably a catalytic combustor filled with a combustion catalyst. Thereby, the reforming rate and the hydrogen separation rate in the reformer 24 are high, and the combustible components in the fuel gas that has passed through the reforming chamber 26 are small (the calorific value is small).
Even in this case, stable combustion can be maintained. Air required for combustion is supplied to the combustor 34 from a line (not shown).

Air 6 is mixed into the cathode gas line 36 to become the cathode gas 3. As a result, the fuel gas that has separated the hydrogen component and passed through the reforming chamber enters the cathode gas after burning in the combustor, and a high reforming rate can be obtained without increasing the S / C ratio. ,
The concentration of carbon dioxide in the cathode gas can be increased. In addition, as shown in FIG. 1, a recycle line 35 for returning the gas that has passed through the reforming chamber 26 to the fuel gas line 32 for introducing the fuel gas 1 may be provided.

The anode gas line 38 may supply the gas in the hydrogen chamber 28 to the anode side A of the fuel cell 22 as it is, or may supply an appropriate dilution gas (for example, the fuel cell 22).
(A recycle gas that has once passed through the anode side of the above). With this configuration, the amount of excess water vapor and carbon dioxide is smaller than in the related art, and the hydrogen concentration in the anode gas can be increased.

[0021]

As described above, the internal reforming fuel cell of the present invention maintains the pressure difference between the anode and the cathode essentially low, increases the fuel gas reforming rate, and reduces contamination of the reforming catalyst. Has the effect of preventing and increasing the concentration of hydrogen in the anode gas and the concentration of carbon dioxide in the cathode gas, thereby enhancing the performance of the fuel cell and maintaining the performance stably for a long period of time. Has the effect.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram of an internal reforming fuel cell according to the present invention.

FIG. 2 is an overall configuration diagram of a power generation facility using a conventional molten carbonate fuel cell.

FIG. 3 is a configuration diagram schematically showing the power generator of FIG. 2;

FIG. 4 is an overall configuration diagram of a conventional direct internal reforming fuel cell.

FIG. 5 is an overall configuration diagram of a conventional indirect internal reforming fuel cell.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Fuel gas 2 Anode gas 3 Cathode gas 4 Anode exhaust gas 5 Combustion exhaust gas 6 Air 7 Cathode exhaust gas 8 Purge gas 10 Reformer 11 Fuel preheater 12 Fuel cell 12a Storage container 13 Air preheater 14 Condenser 15 Gas-water separator 16 Power Recovery device 20 Internal reforming fuel cell 22 Fuel cell 24 Reformer 26 Reforming chamber 28 Hydrogen chamber 30 Separation membrane 32 Fuel gas line 34 Combustor 36 Cathode gas line 38 Anode gas line Re Reforming chamber Co Combustion chamber A Anode side C Cathode side

Claims (1)

(57) [Claims] A fuel cell (2 ) that generates power from an anode gas (2) containing hydrogen and a cathode gas (3) containing oxygen.
2) and the fuel gas by heat transferred from the fuel cell (22)
A reformer (24 ) for reforming (1) , wherein the reformer (24) is a reforming chamber filled with a reforming catalyst.
(26) , a hydrogen chamber (28) holding a gas mainly composed of hydrogen separated from the reformed gas, and a reformer (24) into a reforming chamber (26) and a hydrogen chamber (28) . A separation membrane (30) having a hydrogen separation function for separating a gas containing hydrogen as a main component from the reformed gas, wherein a fuel gas (1) is introduced into the reforming chamber (26).
The fuel gas that has passed through the sling (32) and the reforming chamber (26)
A combustor (34) for burning the gas (1);
4) Mixing the flue gas that has exited into the cathode gas (3)
A cathode gas line (36) and the hydrogen chamber (28)
Gas that introduces the gas inside to the anode gas (2)
And a line (38) .