Chemistry: electrical current producing apparatus – product – and – Having magnetic field feature
Reexamination Certificate
1999-08-11
2002-10-29
Ryan, Patrick (Department: 1745)
Chemistry: electrical current producing apparatus, product, and
Having magnetic field feature
C429S006000, C429S047000
Reexamination Certificate
active
06472092
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a fuel-reforming apparatus, for producing a reformed gas containing hydrogen by reforming reformable fuel containing hydrocarbon.
2. Description of the Related Art
A fuel cell stack has been developed, which comprises, for example, a plurality of stacked fuel cells interposed by separators, the fuel cell including an anode electrode and a cathode electrode provided opposingly with a solid polymer electrolyte membrane interposed therebetween. Such a fuel cell stack has been practically used for a variety of applications.
The fuel cell stack of this type is constructed as follows. That is, a reformed gas (fuel gas) containing hydrogen, which is produced by reforming hydrocarbon, for example, an aqueous methanol solution with steam, is supplied to the anode electrode, while an oxygen-containing gas (air) is supplied to the cathode electrode. Thus, the hydrogen gas is ionized, and it flows through the solid polymer electrolyte membrane. Accordingly, the electric energy is obtained at the outside of the fuel cell.
The steam reforming reaction, in which the aqueous methanol solution is reformed to produce the reformed gas containing hydrogen as described above, is an endothermic reaction represented by CH
3
OH+H
2
O→CO
2
+3H
2
. Therefore, a complicated heat transfer structure is usually incorporated in the reformer in order to supply an amount of heat necessary for the reforming reaction. As a result, the structure is complicated.
In view of the above, an endothermic reaction apparatus is known, for example, as disclosed in Japanese Laid-Open Patent Publication No. 3-122001, comprising an endothermic reaction unit including a cylindrical container for surrounding a combustion chamber having a burner disposed at one end and a reaction chamber containing a catalyst for facilitating the endothermic reaction charged along an inner cylinder of the cylindrical container, and a heat-insulating container for accommodating a plurality of endothermic reaction units as described above. In this apparatus, the reaction chamber is formed along an inner wall of an intermediate cylinder provided in the cylindrical container. The intermediate cylinder and a brim-shaped partition plate are used to form a preheating chamber for raw material gas communicating with the inlet side of the reaction chamber and a reproducing chamber communicating with the outlet side of the reaction chamber. Further, a cover is provided to form a combustion gas passage on the outer circumferential side of the preheating chamber. In this apparatus, the thermal energy of the combustion gas is effectively utilized to preheat the raw material gas so that the heat consumption amount of the combustion chamber is reduced.
However, the apparatus concerning the conventional technique described above comprises the cylindrical container provided with the inner cylinder and the outer cylinder, the intermediate cylinder arranged in the cylindrical container, and the brim-shaped partition plate provided for the intermediate cylinder. Therefore, a problem is pointed out in that the number of parts is considerably increased, and the system is complicated.
Further, the outer circumferential wall is constructed by the heat-insulating container which has a relatively large wall thickness. Therefore, a problem arises in that the whole apparatus becomes large.
In another viewpoint, for example, as disclosed in Japanese Laid-Open Patent Publication Nos. 9-315801 and 7-335238, a method is known, in which oxygen is supplied to a raw material fuel gas containing hydrocarbon to perform the oxidation reaction as the exothermic reaction, and the amount of heat released by the oxidation reaction is utilized so that the reforming reaction as the endothermic reaction is performed for the raw material fuel gas. Accordingly, an advantage is obtained in that the structure can be simplified.
In general, the velocity of the oxidation reaction is larger than the velocity of the reforming reaction. Therefore, the temperature on the inlet side of the reforming catalyst tends to increase, while the temperature on the outlet side of the reforming catalyst, which is important for the reforming reaction, tends to decrease. However, in the conventional technique described above, the reforming catalyst (composed of pellets) is formed to be lengthy in the flow direction of the gas. For this reason, the difference in temperature is large in the flow direction of the gas in the reforming catalyst. Therefore, a problem is pointed out in that it is impossible to realize the desired reforming reaction over the entire region of the catalyst layer. Further, the pellet is inconvenient in that the compact property is inferior, and it is extremely difficult to obtain an equivalent temperature over the reforming catalyst.
In the case of such a system, when it is intended to control the temperature on the gas outlet side of the reforming catalyst in order to efficiently perform the reforming reaction, it is feared that the temperature on the gas inlet side of the reforming catalyst may be locally increased to be not less than the heat resistant temperature of the reforming catalyst. For this reason, a problem is pointed out in that the concentration of produced carbon monoxide is increased, and the reforming catalyst is quickly subjected to thermal deterioration. On the other hand, when it is intended to set the temperature on the gas outlet side of the reforming catalyst in order to avoid the thermal deterioration of the reforming catalyst, an inconvenience arises in that the reaction efficiency of the reforming catalyst is extremely lowered.
A structure is usually adopted for the reforming catalyst, in which plate-shaped reforming catalyst layers and catalytic combustion chambers are alternately stacked (see, for example, Japanese Laid-Open Patent Publication No. 8-253301). However, such a reforming catalyst layer is generally designed to have a rectangular plate-shaped configuration. Therefore, the entire case for constructing the reformer is rectangular. For this reason, the following problem arises. That is, the stress tends to concentrate in the case, the case inevitably has a large wall thickness, and it is impossible to miniaturize the entire reformer.
On the other hand, when the steam reforming for the aqueous methanol solution is started, it is necessary to heat the reforming catalyst to a predetermined temperature. For this purpose, an apparatus, which is disposed at the outside of the reformer, is usually used to supply the heat such as steam to the reformer. However, a compact reformer especially having a high efficiency is required for the fuel cell stack to be carried on vehicles or automobiles. In such a case, it is impossible to adopt the structure as described above.
As shown in
FIG. 34
, the reformer
1
for reforming the aqueous methanol solution is sometimes designed such that the cross-sectional area of a flow passage
2
for methanol mixed with steam (hereinafter referred to as “reformable fuel gas”) is smaller than the cross-sectional area of the reforming catalyst section
4
. In this arrangement, in order to uniformly supply the reformable fuel gas to the entire surface of the reforming catalyst section
4
, there is usually provided a region for widening the cross-sectional area of the flow passage, i.e., the cone section
6
on the upstream side of the reforming catalyst section
4
.
However, if the cone section
6
is not designed to be sufficiently long in the flow direction of the reformable fuel gas, the reformable fuel gas is not delivered uniformly over the entire cross-sectional area of the reforming catalyst section
4
. As a result, the reformable fuel gas flows through only a part of the reforming catalyst section
4
. It is feared that the whole surface of the reforming catalyst section
4
cannot be utilized effectively. Therefore, in fact, it is necessary to use a sufficiently long cone section
6
. A problem is pointed out in that the r
Iseki Eiji
Isove Shoji
Kotani Yasunori
Matsuda Kazuhito
Okada Hikaru
Arent Fox Kintner & Plotkin & Kahn, PLLC
Honda Giken Kogyo Kabushiki Kaisha
Ryan Patrick
Wills M.
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