JPH0652657B2 - Molten carbonate fuel cell with internal reforming - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an internal reforming fuel cell in which molten carbonate is used as an electrolyte and methane or natural gas is converted into hydrogen-rich gas inside the cell to be used as a fuel. In particular, it relates to a molten carbonate fuel cell having an anode chamber for carrying out a reforming reaction and an electrochemical reaction.

[Prior art and its problems]

An internal reforming fuel cell that reforms methane or natural gas into hydrogen-rich gas in a fuel cell to generate power is highly energy efficient because the heat generated during power generation can be used as is for the reforming reaction. It is attracting attention as a power generation method. In this type of fuel cell, a so-called molten carbonate fuel cell which uses molten carbonate as an electrolyte and is operated at around 650 ° C. is used because of heat balance. The reforming of methane and natural gas is performed in the anode chamber, and the following proposals have been made as a structure for causing this reaction. One method is to fill the anode chamber with a reforming catalyst (Japanese Patent Publication No. 47-25782). Another method is to put a porous corrugated material in the anode chamber and fill the grooves on the separator side with the reforming catalyst (Japanese Patent Laid-Open No. 58-10374). In the former case, the methane and natural gas to be supplied should be in contact with the anode without being completely reformed into hydrogen, and the reforming catalyst should be generated by the molten carbonate vapor and the molten carbonate exuded through the anode during the battery operation. There was a problem that it deteriorated and the battery could not be operated for a long time. The latter case is a partial improvement of the former proposal, but it uses a porous corrugated material, so that the gas that is not completely reformed is supplied to the anode at the portion in contact with the anode, and the porous material is also used. There is still a problem that the molten carbonate permeates through or the molten carbonate vapor passes through this and deteriorates the reforming catalyst. These problems must be solved in order to enable a molten carbon dioxide fuel cell that performs internal reforming to operate for a long time and to put it into practical use.

[Object of the Invention]

An object of the present invention is to eliminate the above-mentioned problems of the prior art and to provide a molten carbonate fuel cell that performs internal reforming and can operate the fuel cell stably for a long time.

[Outline of Invention]

The outline of the present invention will be described. A feature of the present invention is that the anode chamber is partitioned into a reforming reaction section and an electrochemical reaction section, the heat generated or consumed by each reaction is more effectively utilized, and the fuel cell has a long life. This is to achieve FIG. 1 shows a sectional structure of a fuel cell according to the present invention. Reference numeral 1 is an electrolyte layer in which a matrix plate is impregnated with molten carbonate, 2 is an anode, and 3 is a cathode. 4 and 5 are separators forming an anode chamber and a cathode chamber. A corrugated plate 7 is arranged in the anode chamber 6. The anode 2 is held by this corrugated plate 7. The space on the separator side of the corrugated plate 7 is filled with a reforming catalyst 8 such as methane or natural gas. FIG. 2 shows a vertical cross section of this battery, in which the left end of the corrugated plate 7 is an end communicating with the separator and the hydrogen-rich gas reformed on the reforming catalyst layer is U-turned. Then it returns to the space on the anode side. At this time, the reformed gas contacts the anode 2 and causes an electrochemical reaction to generate electricity. In this structure, even if the molten carbonate permeates through the anode, it is prevented by the corrugated sheet 7, so that the reforming catalyst does not deteriorate. Further, even if the molten carbonate becomes vapor and passes through the anode, it is discharged to the outside of the battery together with the reformed gas, so that there is no problem. Also, the reforming reaction is an endothermic reaction and generates heat during power generation of the battery, but considering the heat balance between the two, the reaction between hydrocarbons such as methane and natural gas and steam occurs near the inlet side to the anode chamber. Because it ’s easy
It requires more heat here. On the other hand, the heat generated in the battery is collected and carried by the reformed gas from the U-turn portion of the anode chamber toward the inlets of hydrocarbons and steam in order. Therefore, since the largest amount of heat can be supplied to the portion that requires the largest amount of heat, energy can be effectively used. This is a great feature of the present invention. Further, when the corrugated plate 7 is made of a conductive material, the separator and the anode can be electrically connected to each other, and it is not necessary to make an external electrical connection when laminating multiple layers.

In another structure of the present invention, the corrugated plate 7 is made of nickel, and the surface of the nickel corrugated plate on the side of the separator 4 has a porous unevenness. FIG. 3 shows a sectional view of a battery using the corrugated plate 7'of the present invention. The porous unevenness provided on the corrugated plate can be easily formed by Raney-nickeling the surface of the nickel plate, and has an advantage that the activity as a reforming catalyst is also high. As another method, there is a method in which nickel powder or hollow nickel powder is sintered and adhered to the surface of the nickel plate. Either method can achieve the object of the present invention.

Example of Invention

 Examples of the present invention will be described below.

Example (1) A mixture of lithium carbonate and potassium carbonate in a molar ratio of 2: 1 was used as the electrolyte 1, a nickel sintered plate having a porosity of about 65% was used for the anode 2, and nickel oxide was used for the cathode 3. A sintered plate doped with lithium was used. The separators 4 and 5 were processed using stainless steel (SUS-316). For the corrugated plate 7, stainless steel (SUS-316) having a thickness of about 0.5 mm was used. As the reforming catalyst 8, an alumina carrier carrying nickel was used, and a battery as shown in FIG. 1 was assembled to supply methane and steam. I chose a steam-carbon ratio of 3. A mixed gas of air and carbon dioxide was supplied to the cathode side, and continuous power generation was performed at 650 ° C. and a current density of 150 mA / cm ² . The symbol A shows the change over time in the battery voltage during continuous power generation. For comparison, the result of continuous power generation in a similar manner for a case in which the reforming catalyst is only filled in the anode chamber 6 without using a corrugated plate is shown by symbol B in FIG.

Example (2) The corrugated plate 7 used in Example 1 was made into a nickel plate having a thickness of about 2 mm, and aluminum was vapor-deposited on one surface of the plate to prepare an alloy of nickel aluminum. Next, this was dipped in an alkaline aqueous solution to elute aluminum to form porous irregularities on the surface. Others were the same as those shown in Example (1), and batteries were made. The continuous power generation performance of this battery is
It was almost the same as that shown by the symbol A in FIG.

〔The invention's effect〕

As is apparent from FIG. 4, the present invention has the effect of significantly improving the continuous power generation performance of the battery as compared with the conventional one. This effect is obtained because the reforming catalyst is prevented from being deteriorated by the molten carbonate.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a sectional view of a molten carbonate fuel cell according to the present invention, FIG. 2 is a longitudinal sectional view thereof, and FIG. 3 is a molten carbonate fuel cell having another structure of the present invention. 4 is a cross-sectional view of FIG. 4 and FIG. 4 is a diagram comparing the performances of the battery of the present invention and the conventional battery. DESCRIPTION OF SYMBOLS 1 ... Electrolyte layer, 2 ... Anode, 3 ... Cathode, 4 ... Anode side separator, 5 ... Cathode side separator, 6 ... Anode chamber, 7 ... Corrugated sheet, 8 ... Reforming catalyst, 7 '... Nickel corrugated sheet.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Koichi Miyoshi 4026 Kuji Town, Hitachi City, Hitachi, Ibaraki Prefecture Hitachi Research Institute Ltd. (72) Masato Takeuchi 4026 Kuji Town, Hitachi City, Ibaraki Prefecture Hitachi Ltd. Hitachi, Ltd. (56) Reference JP-A-58-119167 (JP, A)

Claims (1)

[Claims] 1. An electrolyte layer having a molten carbonate as an electrolyte between a pair of gas diffusion electrodes, a separator in contact with the pair of gas diffusion electrodes, and an anode of the pair of gas diffusion electrodes and adjacent thereto. In the molten carbonate fuel cell for internal reforming, the anode chamber is provided between the separators, and the cathode of the pair of gas diffusion electrodes and the cathode chamber is provided between the adjacent separators. The chambers on the anode side and the separator side that communicate with each other in the region of the corrugated plate tip end by the corrugated plates that do not reach the opposite side walls of the anode chamber, and that are in line contact with the anode and the separator alternately It is divided into chambers and holds a reforming catalyst for converting a fuel gas containing methane as a main component into hydrogen in the chamber on the side of the separator, and in the chamber on the side of the separator of the anode chamber. The internal reforming is characterized in that the supplied fuel gas containing methane as a main component is converted into hydrogen by the reforming catalyst and then introduced into the chamber on the anode side through the region at the tip of the corrugated plate. Perform molten carbonate fuel cell.