JP2737535B2 - Internal reforming molten carbonate 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 molten carbonate fuel cell, and more particularly to an internal reforming molten carbonate fuel cell in which a catalyst material for reforming a hydrocarbon-based source gas is disposed.

[0002]

2. Description of the Related Art As a fuel for a high-temperature fuel cell such as a molten carbonate fuel cell, a fuel gas mainly containing hydrogen gas is generally used. In other words, what is considered as a large-scale alternative molten salt fuel cell for central power generation uses synthetic gas containing hydrogen, which has been obtained by reforming petroleum gas or natural gas, as a fuel. In a battery (for on-site use), city gas (mainly methane) can be used after steam reforming. For on-site use, an internal reforming method for performing a reforming reaction inside the battery is usually considered to be practically promising in terms of compactness, system efficiency and cost, and is being studied.

[0003] This internal reforming method includes a direct internal reforming type,
There are two types, the indirect internal reforming type, and the direct internal reforming type has higher efficiency, but the problem is that the catalyst is installed in the power generation part and the reforming catalyst deteriorates due to electrolyte seepage and contact with electrolyte vapor. is there. On the other hand, the indirect internal reforming type is somewhat inferior to the former in terms of thermal efficiency, but is advantageous in that the power generation part and the reforming part are separated, so that the catalyst life is improved. Here, when using the indirect internal reforming type, an important factor is the balance between heat generation by the battery body and heat absorption by the reforming reaction. In other words, if these heat balances are not well maintained, a local temperature rise or temperature drop will occur in the plane of the unit cell, leading to a deterioration in the performance of the cell. This greatly depends on how the catalyst in the reforming zone is charged.

Until now, in the case of performing indirect internal reforming, there is a method of performing reforming using a plurality of catalysts having different catalytic actions as disclosed in Japanese Patent Application Laid-Open No. 61-34865. Is a measure against fuel diversification, and no measures have been taken to make the temperature distribution in the cell surface uniform. Further, Japanese Patent Application Laid-Open No. 63-31
As disclosed in Japanese Unexamined Patent Publication No. 0574, there is a case where a reforming catalyst having a lower carbon deposition property is disposed on the upstream side with respect to the flow direction of the raw material gas than on the downstream side. This takes into account that the reforming is performed with a small amount of water vapor, but no measures have been taken to make the temperature distribution in the battery surface uniform as in the above case.

[0005]

SUMMARY OF THE INVENTION Conventionally, JP-A-61-3
As disclosed in Japanese Patent No. 4865, a method of performing reforming using a plurality of catalysts having different catalytic actions,
As disclosed in Japanese Patent No. 310574, there is a method in which a reforming catalyst having a lower carbon deposition property is disposed on the upstream side with respect to the flow direction of the raw material gas than on the downstream side to perform reforming. Thus, although there is an advantage that various types of fuel gas can be handled, an extra catalyst is also filled together, which is not preferable in terms of cost and efficiency. Further, it is considered that a considerable temperature difference occurs in the plane because the temperature distribution in the plane of the battery is not considered. In the latter case, the upstream side where the water vapor tends to run short in the fuel gas flow direction is filled with a catalyst having a low carbon deposition property. Temperature control seems difficult.

[0006]

According to the present invention, a carbonate is used as a raw material.
Electrolyte layer and the fuel and oxidizer electrodes sandwiching it from both sides
Or a battery unit in which a plurality of unit cells are stacked
Internal reforming molten carbonate fuel consisting of a body and an internal reformer
In the battery, as the reformer, small cells having different reforming performances may be used.
Equipped with at least two types of reforming catalysts and mixing the reforming catalysts
Ratio is relatively superior in the reforming capacity to the flow direction of the raw material gas.
The mixing ratio was set so that the arranged density of the catalyst
It is characterized by using a plate-type reformer. to this
Therefore, when a single catalyst layer is used,
Avoid rapid temperature drop. Further, the present invention provides the
As a reformer, a catalyst with relatively excellent reforming capacity is used in the center.
In addition, a catalyst with relatively poor reforming capacity is
Use the reformer that has been formed.

Further, the temperature distribution in the reformer surface is controlled by changing the mixing ratio in the reformer surface.

[0008]

The internal reforming type fuel cell utilizes the fact that the heat generated by the reaction of the battery and the heat generated by the resistance of the battery members increase the temperature inside the cell, while the reforming reaction is an endothermic reaction, and the inside of the cell stack is utilized. In which a reforming reaction is carried out. Therefore, the internal reforming method does not require an external reforming device and also has the effect of cooling the battery. Such a method can directly supply city gas as fuel gas and can effectively use the heat generated by the battery, which is very advantageous in improving system efficiency, reducing costs, and improving compactness. However, in the case of indirect internal reforming, as described in the related art, the arrangement of the catalyst in the reformer laminated inside the battery main body is important for balancing the heat with the unit cell.

Here, the catalyst mixing ratio inside the reformer is
Of catalyst with relatively excellent reforming ability
By increasing the arrangement density , a sharp reforming reaction at the upstream portion of the catalyst layer is suppressed, and the temperature drop is reduced. Also, the reforming reaction proceeds in the downstream part, and the temperature of the entire reformer is made uniform. Mixing catalysts with different performances
High performance catalyst (eg noble metal supported catalyst)
Catalyst with lower performance than when only
(Catalyst) is mixed, which leads to a reduction in catalyst cost.

[0010] Furthermore, the internal reforming type melting is performed using this reformer.
When configuring a molten carbonate fuel cell, the thermal
Considering the cost, a catalyst with relatively excellent reforming capacity is
When filled, the temperature within the battery surface becomes uniform.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An internal reforming molten carbonate fuel cell using the present invention will be described below with reference to the drawings.

(Embodiment 1) FIG. 1 is a structural view of an internal reforming type molten carbonate fuel cell according to one embodiment, and FIG. 2 is an internal view of a reformer plate incorporated in the battery. It is shown. 1 and 2, the reformer plate 1 is sandwiched between the unit cells 2 and has a shape similar to that of the bipolar plate of the unit cell 2. Therefore, the fuel electrode 3, the electrolyte plate 4, and the oxidant electrode 5 can function as a part of the battery in combination. The reformer plate 1 and the unit cell 2 are both provided with a raw gas supply internal manifold hole 6, a fuel gas manifold hole 7, an oxidizing gas manifold 8 and their exhaust gas manifolds 9, which are installed through the stack. These gases are supplied or exhausted from a lower header 11.

The raw gas supply internal manifold hole 6 has an opening only inside the reformer plate, from which the raw material gas is supplied and not supplied to the unit cells. The raw material gas supplied into the reformer plate is supplied to the reforming catalyst 12a,
In the units 12b and 12c, the cells are reformed by utilizing the heat generated from the cells, and supplied to each unit cell from the outlet through the fuel manifold hole 7. In FIG. 2, when viewed as a bipolar plate, the fuel electrode 3 side is the upper surface and the oxidant electrode 5 side is the lower surface. The oxidizing gas is supplied to each unit cell from the oxidizing gas manifold 8, and the exhaust gas after the reaction is discharged from the fuel exhaust gas manifold 9 and the oxidizing exhaust gas manifold 10.

[0014] described embodiments such reformer plate 1 according to the present invention the internal reforming type fused carbonate fuel cell installed between the unit cell 2 2, according to FIG. Figure
2 are three types of reforming catalyst layers 12a, 1
2b and 12c are packed so that a catalyst layer having good reforming performance is located downstream with respect to the flow direction of the raw material gas (mainly methane). That is, 12a, 12b, 12
c. When the catalyst is packed in this way, it is possible to prevent a sharp drop in the temperature at the raw material gas inlet portion as compared with the case where a single catalyst is packed on the entire reformer plate. Moreover, since the more likely to occur reforming reaction of the downstream portion it was hard to occur in a single catalyst, thereby sufficiently pull out each catalyst performance.

FIG. 3 shows the structure of the catalyst layer in detail.
It is. Two types of catalysts 14a and 14b having different reforming performances
Are filled so that the ratio of the catalyst 14a having good reforming performance is increased in the flow direction of the raw material gas indicated by the arrow . Thereby, the temperature distribution in the reformer plate surface can be made more strictly uniform. By mixing and filling in this manner, the reforming reaction proceeds more smoothly. In addition, it leads to cost reduction of the reforming catalyst . here
Reforming catalysts with different performances all use different metals.
Or the amount of metal supported on the same catalyst
It may be different. Also, the shape is usually
Spherical or pellet-like materials used for quality
However, the present invention is not limited to this.

In addition, when a temperature distribution occurs in the unit cell surface due to the structure of the stack, the supply direction of the fuel gas and the oxidizing gas, etc., the catalyst is applied to the reformer plate at an appropriate mixing ratio. Filling can control the in-plane temperature distribution.
That is, by using this method, if the temperature distribution of the unit cell is known, a reforming catalyst corresponding to the temperature distribution can be selected and filled, and the temperature of the entire stack can be made uniform.

(Embodiment 2 ) FIG. 4 shows a state in which the reformer plate 1 is placed from above in the same manner as in Embodiment 1.
A schematic diagram when viewed is shown. By the way in the fuel cell is more generally saying example, if the peripheral portion there is a tendency that more of the central portion is high temperature. In the case of a large-sized stack, the temperature rising portion inside the unit cell changes depending on the supply direction of the fuel gas and the oxidizing gas, for example, whether it is a direct flow or a parallel flow, but the temperature from the center also tends to increase. . In particular, in the case of a relatively small-sized stack used for on-site power generation or the like, such a tendency is remarkable because the influence of heat radiation from the side surface of the stack becomes large. Therefore, by filling the two types of catalysts 14a and 14b having different reforming performances shown in Embodiment 1 as shown in FIG. 4 , it is possible to effectively suppress the temperature rise in the central part of the unit cell. In other words, by filling a reforming catalyst 14a having high performance in the center of the reformer plate and a reforming catalyst 14b having lower performance in the periphery thereof, heat generated in the center of the cell can be effectively converted. The temperature of the central part of the cell can be lowered, and the temperature in the cell plane can be made uniform.

[0018] Figure 5 shows the tactile filling rate and the methane conversion rate relation to the reformer of the medium when methane is one of the raw material gas of a hydrocarbon system was steam reforming. The reforming conditions are a steam / carbon ratio of 3.5 and a reaction temperature of 650 ° C. As can be seen from this figure, it was found that when the filling rate was 60% or more, the methane conversion rate was 90% or more and was almost constant. That is, in order to control the temperature distribution in the plane of the reformer and obtain a sufficient conversion, it was found that the catalyst filling rate was required to be 60% or more. Therefore, the filling rate is 60%
By doing the above, the reforming performance is fully exhibited,
Further, a battery having a uniform in-plane temperature distribution can be formed.

[0019]

As is clear from the above description of the embodiments,
According to the internal reforming type molten carbonate fuel cell of the present invention, the temperature of the whole cell can be made uniform only by changing the mixing ratio and arrangement of the reforming catalyst filled in the reformer plate. This can prevent a partial temperature rise of the battery and improve the reliability of the battery.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an internal reforming molten carbonate fuel cell according to one embodiment of the present invention.

FIG. 2 is a configuration diagram of a reformer plate in the embodiment.

FIG. 3 is a schematic view showing a main part of the reformer plate in a state where the catalyst is charged in the embodiment.

FIG. 4 is a schematic view showing a state in which a reformer plate according to another embodiment of the present invention is charged with a catalyst.

FIG. 5 is a characteristic diagram showing a relationship between a catalyst filling rate and a methane conversion rate of a reformer plate according to another embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Reformer plate 2 Unit cell 3 Fuel electrode 4 Electrolyte plate 5 Oxidant electrode 6 Internal manifold hole for raw material gas supply 7 Manifold hole for fuel gas 8 Manifold for oxidant gas 9 Manifold for fuel exhaust gas 10 Manifold for oxidant exhaust gas 11 Header 12a, 12b, 12c Reforming catalyst layer 13 End plate 14a, 14b Reforming catalyst

 ──────────────────────────────────────────────────の Continuing on the front page (72) Koji Gamo, Inventor 1006 Odakadoma, Kadoma, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (72) Kinichi Adachi, 1006 Odakadoma, Kadoma, Osaka Prefecture In-company (56) References JP-A-61-58174 (JP, A) JP-A-5-258758 (JP, A) JP-A-5-89896 (JP, A) )

Claims (2)

(57) [Claims] 1. A result of this and the electrolyte layer carbonate as a raw material and a fuel electrode sandwiching from both sides and the battery body in which a plurality stacked unit cells or battery cells made of an oxidizing agent electrode, the internal reformer, The reformer has at least two types having different reforming performances.
And the mixing ratio of the reforming catalyst is
Of catalyst with relatively excellent reforming ability in the flow direction
An internal reforming molten carbonate fuel cell, characterized in that it is a plate-type reformer with a mixing ratio such that the density increases gradually . 2. A consists carbonate electrolyte layer as a raw material and fuel electrode sandwiching it from both sides and the battery body in which a plurality stacked unit cells or battery cells made of an oxidizing agent electrode, the internal reformer, The reformer is a plate-type reformer in which a catalyst having a relatively excellent reforming ability is arranged in a central portion, and a catalyst having a relatively poor reforming ability is arranged in a peripheral portion thereof. Internal reforming molten carbonate fuel cell.