JPH05258758A - Internally reformed type molten carbonate fuel battery - Google Patents

Abstract

PURPOSE:To provide an internally reformed type molten carbonate fuel battery is simple in structure and in which the stack can be uniformly cooled. CONSTITUTION:Raw fuel gas is supplied, with an internal manifold system, to a reformer plate 1 and is thereby reformed, after which this reformed fuel gas is supplied to each elemental battery 2. Metallic support portions 13 are installed inside the reformer plate 1 over an entire region thereof to decrease the thermal and electrical resistances and simultaneously increase the mechanical strength as well. Further, the interior of the reformer plate 1 is divided into three gas channels, in only a central channel of which a reformer catalyst 12 is installed, thereby making even the cooling of the stack.

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 having an improved stack and reformer plate structure.

[0002]

2. Description of the Related Art A molten carbonate fuel cell uses a gas whose main component is hydrogen as a fuel gas. In large-scale molten carbonate fuel cell power generation, coal gas is used or natural gas is modified by a reformer. It has been considered to use it by converting it into a gas containing hydrogen as a main component. City gas (mainly composed of methane) is used as raw fuel for relatively small-scale power generation, especially for power generation in demand areas (on-site power generation), so it is necessary to reform it by methods such as steam reforming. .. However, in the case of a small-scale power generation device, installing a large-scale reformer separately from the power generation part brings down compactness, system efficiency, and cost. For this reason, a so-called internal reforming method in which reforming is performed inside the battery is often adopted especially for on-site use.

The internal reforming system takes advantage of the fact that the reforming reaction is an endothermic reaction, while the reaction heating of the fuel cell and the resistance heating of the cell member increase the temperature inside the cell.
This is a system in which a reforming reaction is performed inside the battery stack. Therefore, the internal reforming method does not require an external reforming device and has the effect of cooling the battery. Since such a system can directly supply city gas as a fuel gas and can effectively utilize the heat generation of the battery, it is very advantageous in improving system efficiency, reducing cost and improving compactness.

Therefore, two types of internal reforming systems, so-called direct internal reforming type and indirect internal reforming type, have been studied conventionally. The direct internal reforming type has high efficiency, but since the catalyst is installed in the power generation part, there is a problem that the reforming catalyst deteriorates due to electrolyte bleeding or contact with electrolyte vapor. On the other hand, the indirect internal reforming type is somewhat disadvantageous in terms of thermal efficiency, but is advantageous in terms of life because the power generation part and the reforming part are separated.

On the other hand, there are an external manifold system and an internal manifold system as a gas supply system to each unit cell which constitutes the stack. The external manifold system has a structure in which the fuel-side or oxidant-side air chambers of each cell are open on the side of the stack, and a box-shaped external manifold is attached here to distribute gas to each cell. is there. On the other hand, the internal manifold system is a system in which a gas flow hole is provided in the peripheral portion of the unit cell, and the gas is distributed to each unit cell from this hole (internal manifold).

When performing indirect internal reforming by an external manifold system, for example, there is a system in which the inside of the manifold is divided into two as disclosed in Japanese Patent Laid-Open No. 61-13576, but the manifold structure becomes complicated. It becomes difficult to make a reliable gas seal. Further, in the external manifold system, there is a disadvantage in that it is necessary to take a countermeasure because the electrolyte moves through the manifold seal material.

On the other hand, as a method of performing internal reforming with an internal manifold type, as disclosed in JP-A-3-105865, reforming is performed by dividing the inside of the unit cell into two and filling a reforming catalyst on the gas upstream side. There is a means such as providing a zone and reforming here. In addition, the inside of the reformer plate is divided into two parts along a plane, one side is filled with a reforming catalyst, and the other side is filled with a combustion catalyst for burning unreacted fuel discharged from the fuel electrode. It is also considered to install between them and reform with the heat of combustion and the heat of the battery.

[0008]

However, in the case of performing internal reforming with the internal manifold type, in the former method of the above-mentioned conventional methods, a part of the unit cell is applied to the reforming portion, so that the reforming section There was a problem in temperature uniformity such that the temperature decreased and one of the power generation sections increased in temperature. In the latter method, the combustion heat of the fuel exhaust gas can also be used for the reforming reaction,
While the unit cell in contact with the reforming side of the reformer plate is cooled, the unit cell in contact with the catalytic combustion portion, on the contrary, increases in temperature, which is not preferable. Further, in this method, there is a problem that the stack structure is slightly complicated because the fuel exhaust gas and the combustion air are supplied. Therefore, an object of the present invention is to avoid these problems and to obtain an internal reforming molten carbonate fuel cell having a simple structure and capable of uniformly cooling the stack.

[0009]

In order to achieve this object, an internal reforming molten carbonate fuel cell of the present invention includes a laminated unit cell and a reformer plate for reforming raw fuel, and a modified reformer plate. An internal manifold hole for supplying raw fuel gas, which is provided in a state of vertically penetrating a pledget plate, and a manifold hole for fuel gas and oxidant gas, wherein the unit cell is for fuel gas and oxidant gas, respectively. Each gas is supplied and discharged through the manifold hole of the reformer plate, the reformer plate is similar to the bipolar plate of the unit cell, and can be supplied and discharged only to the internal manifold hole for supplying the raw fuel gas and the manifold hole for the fuel gas. And has a simple structure that also functions as a bipolar plate and that supplies the fuel gas obtained by reforming the supplied raw fuel gas to each unit cell.

Further, upper and lower end plates are electrically connected to each other inside the reformer plate, and a plurality of supporting portions made of metal having mechanical strength are installed at a distance interval of 10 cm or less. The upper and lower end plates are connected thermally and electrically to improve the mechanical, thermal and electrical characteristics.

Further, the inside of the reformer plate is divided into three gas passages by a partition having a notch, the reforming catalyst is installed only in the central portion of the passage located at the center, and the raw fuel is provided at the outer edge portion thereof. The opening of the internal manifold hole for gas supply is provided,
The reformed fuel gas has a structure in which the flow is reversed from the notch through the gas passages on both sides and is supplied to each cell through the fuel manifold holes provided on both sides of the raw fuel gas supply internal manifold hole. Aim for uniform cooling of the stack.

[0012]

With this structure, the internal manifold hole for supplying raw fuel gas supplies the raw fuel to the reformer plate and the fuel gas reformed in the reformer plate to each unit cell. The reformer plate itself also functions as a bipolar plate.

A plurality of supporting parts installed inside the reformer plate electrically and thermally connect the upper and lower end plates to reduce the electric resistance and thermal resistance of the reformer plate. Further, since this support portion has mechanical strength, it prevents deformation of the reformer plate against stack pressure from above and below.

Of the three gas passages inside the reformer plate, the reforming catalyst reforms the raw fuel in the central passage, and at the same time, absorbs heat from the central portion of the unit cell groups that are in contact with each other vertically. The reformed fuel gas is supplied to each unit cell through the gas passages on both sides and the fuel manifold hole.

[0015]

Embodiments An internal reforming molten carbonate fuel cell according to an embodiment of the present invention will be described below with reference to the drawings.

(Embodiment 1) In FIGS. 1 and 2, the reformer plate 1 is sandwiched between the unit cells 2, and the unit cell 2
It has a structure similar to that of the bipolar plate. Therefore, it can function as a part of the battery in combination with the fuel electrode 3, the electrolyte plate 4, and the oxidant electrode 5. In addition, the reformer plate 1 and the unit cell 2 are both provided with a raw fuel gas supply internal manifold hole 6, a fuel gas manifold hole 7, an oxidant gas manifold 8 and their exhaust gas manifolds which are installed longitudinally through the stack. 9 and 10, these gases are supplied or discharged from the lower header 11.

With respect to the internal manifold hole 6 for supplying raw fuel gas, there is an opening 6c only inside the reformer plate 1,
Raw fuel is supplied from here, and is not supplied to the unit cell 2. The raw fuel supplied into the reformer plate 1 contacts the reforming catalyst 12 and is reformed by using the heat generated from the cell, and is passed from the outlet 6a to the fuel cell manifold hole 7 to each cell 2. Supplied. When viewed as a bipolar plate in FIG. 2, the fuel electrode 3 side is the upper surface, and the oxidizer electrode 5
The side is the bottom surface. The oxidant gas is supplied from the oxidant gas manifold 8 to each cell 2, and the exhaust gas after the reaction is a fuel exhaust gas manifold 9 and an oxidant exhaust gas manifold 1.
Emitted from 0.

As described above, in this embodiment, the reformer plate 1 having a bipolar plate structure is installed between the unit cells 2, and the internal manifold hole 6 for supplying the raw fuel gas is provided for each unit cell 2 and the reformer plate. The internal reforming type molten carbonate fuel cell by the internal manifold system has been realized with an extremely simple structure that is only additionally installed in 1. Further, the reformer plate 1 does not have a heat generating portion such as a power generation portion or a combustion portion, and the unit cell group in contact with the reformer plate 1 can be cooled substantially evenly, which is convenient for battery management. Moreover, the problems of gas leakage and corrosion associated with the seal as in the case of the external manifold can be greatly reduced.

(Embodiment 2) Next, Embodiment 2 in which the invention according to claim 2 is applied to a reformer plate of an internal reforming molten carbonate fuel cell having a structure similar to that of Embodiment 1 is shown in FIG. Follow the instructions below. FIG. 3 shows a state in which the end plate 14 on the fuel electrode side of the reformer plate 1 is removed, but it is actually joined to the outer edge portion 1a by welding or brazing so as to prevent gas leakage. The outer edge portion 1a and the end plate 14 of the reformer plate 1 are made of a heat-resistant alloy, and a support portion 13 made of the same material and having sufficient mechanical strength is in contact with the end plate 14 having a bipolar plate structure. It is installed at the height. Reformer plate 1 of this embodiment
Has a size of 40 cm square, a thickness of 1.2 cm, and the support portion 13 has a size of 1 cm square and is arranged at intervals of 5 cm. Reforming catalyst 1
No. 2 was filled on the entire surface of the reformer plate 1 leaving a space of 5 cm from the inner edge thereof.

The reformer plate 1 was placed in the center of a stack of 10 cells of a 40 cm square unit cell 2 and an operation test was conducted. As raw fuel gas, steam was added to desulfurized city gas (main component of methane) at a steam / carbon ratio of 3.0, preheated to 650 ° C., and reformed using the internal manifold hole 6 for supplying raw fuel. Pour plate 1 was supplied. As the oxidant gas, a mixed gas of 70% air and 30% carbon dioxide gas was also preheated and supplied. The stack pressure during operation was 4 tons (2.5 kg / cm ² ). The temperature distribution of the reformer plate 1 was measured in a state where the stack was steadily operated at an average temperature of 650 ° C. As a result, the high temperature portion was 660 ° C and the low temperature portion was 620 ° C, and the difference was about 40 ° C. Further, the voltage drop in the reformer plate 1 portion when a current of 100 A was taken out was as small as 5 mV. After the test, the appearance of the reformer plate 1 was inspected, but no deformation was found.

Further, for comparison, a reformer plate having no supporting portion 13 installed and a partitioning portion having a width of 1 cm for reinforcement arranged along the gas flow on the central symmetry line (not shown) is manufactured. Then, the same test was performed. As a result, the hot part,
The difference in the low temperature portion was about 70 ° C., and the voltage drop at the reformer plate portion when a current of 100 A was taken out was a very large value of 35 mA. After the test, the reformer plate was found to have a slight dent on the end plate where there was no partition. Since such deformation greatly hinders close contact with the unit cell,
It seems that the heat and electric resistance were high.

On the other hand, the reformer plate 1 according to the second embodiment
However, such deformation does not occur, and since the metal supporting portions 13 are present at intervals of 5 cm, this realizes reduction of heat and electric resistance, which leads to a more uniform temperature distribution and a small voltage drop.

(Embodiment 3) Next, Embodiment 3 in which the invention according to claim 3 is applied to the reformer plate 1 having the same structure as that of Embodiment 2 will be described with reference to FIG. FIG. 4 shows a state in which the end plate 14 on the fuel electrode side of the reformer plate 1 is removed. The interior of the reformer plate 1 is divided into three gas passages by a partition 16 having a notch 15, and the reforming catalyst 12 is installed only in the central portion of the passage located at the center. Further, the outer edge portion 1a of the reformer plate 1 has an opening (not shown, but see 6c in FIG. 2) to the internal manifold hole 6 for supplying raw fuel gas, from which the raw fuel is supplied, Of the reforming catalyst 12 after passing through the portion where the reforming catalyst 12 does not exist.
To be modified. The reformed fuel gas flows from the notch 15 through the gas passages on both sides to reverse the flow, and is supplied to each cell 2 from the fuel gas outlet through the fuel gas manifold hole 7.

From the viewpoint of the heat balance, from the viewpoint of the heat balance, the flow passage part without the reforming catalyst 12 from the internal manifold hole 6 for supplying the raw fuel gas, and the fuel gas after reforming pass through both gas flow passages to form the fuel. In the process of reaching the gas manifold hole 7, the unit cell 2
The heat exchange with the is extremely small, and a large heat absorption occurs near the center where the reforming is performed, and the vicinity of the center of the unit cell 2 is cooled intensively.

By the way, generally speaking, in the fuel cell, the temperature tends to be higher in the central portion than in the peripheral portion. In the case of a large stack, the unit cell 2 depends on the fuel gas and oxidant gas supply directions, for example, direct flow or parallel flow.
Although the internal temperature rise part changes, the tendency is that the part from the center also becomes hot. Especially in the case of a relatively small-scale stack used for on-site power generation, this tendency is remarkable because the influence of heat radiation from the side surface of the stack increases. Therefore, in the reformer plate 1 of the present embodiment, the heat absorption by the reforming reaction is concentrated near the center, and the heat exchange in the other gas flow paths is extremely small, so that the temperature rise in the central portion of the unit cell 2 is effectively suppressed. Therefore, it is possible to greatly contribute to the temperature uniformity of the stack.

Next, the result of the battery test according to this embodiment will be described. The size and test conditions of the reformer plate 1 are the same as in the second embodiment. When the temperature distribution of the reformer plate 1 was measured in a state where the stack average temperature was 650 ° C. in the steady operation, the high temperature part was 660 ° C. and the low temperature part was 630 ° C. The difference was about 30 ° C., which is great for temperature uniformity. It turned out to contribute.

Although the unit cell and the reformer plate described in the present embodiment are both rectangular, they may have other shapes such as a circle. Further, the shape of each manifold hole and its inlet / outlet may be any shape regardless of the present embodiment, and the arrangement may be any shape within the range in which the present invention can be carried out.

With respect to the structure of the reformer plate, in the case of the second embodiment, the partition of each flow path is substantially equal, but it may be divided at an appropriate ratio, and the partition may be partially or partially. The whole may be installed diagonally. Further, in the third embodiment, the notch is only at the end of the partition plate, but this may be at any position on the partition plate.

Although the reforming catalyst is shown as a granular one in this embodiment, it may have another shape, for example, a honeycomb shape. In addition to the catalyst, other objects such as a catalyst holding member and a carbonate vapor removing member may be present.

[0030]

As is apparent from the above description of the embodiments, according to the internal reforming molten carbonate fuel cell of the present invention, in particular, the structure of gas supply can be simplified and
It is possible to evenly cool the unit cells in contact with the reformer plate. It also has the advantage that the problems associated with gas sealing, such as with an external manifold, do not occur.

According to the second aspect of the present invention, the plurality of metal supporting portions provided inside the upper and lower end plates are electrically and thermally connected to each other to reduce electric resistance and thermal resistance of the reformer plate. Further, in order to improve the mechanical strength, the reformer plate is prevented from being deformed against stack pressure from above and below, and the contact with the unit cell group is maintained normally. As a result, the efficiency and reliability of the battery can be improved.

Further, when the reformer plate according to claim 3 is used, since the reforming catalyst is installed only in the central flow path, the heat absorption due to the reaction is concentrated near the center, which effectively raises the temperature in the central part of the unit cell. Therefore, it is possible to obtain a more uniform cooling effect, reduce the equipment for temperature control of the battery, and significantly improve the reliability.

[Brief description of drawings]

FIG. 1 is a perspective view showing the concept of the configuration of an internal reforming molten carbonate fuel cell according to an embodiment of the present invention.

FIG. 2 is a perspective view showing a cross-section with a part of the reformer plate of the first embodiment cut away.

FIG. 3 is a perspective view showing the internal structure of the reformer plate of Embodiment 2 with the fuel electrode side end plate removed.

FIG. 4 is a perspective view showing the internal structure of the reformer plate of Embodiment 3 with the end plate on the fuel electrode side removed.

[Explanation of symbols]

 1 reformer plate 2 unit cell 6 internal manifold hole for supplying raw fuel gas 7 manifold hole for fuel gas 8 manifold for oxidant gas 9 manifold for fuel exhaust gas 10 manifold for oxidant exhaust gas

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Eiichi Yasumoto Eiichi Yasumoto 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd.

Claims (3)

[Claims] 1. A stacked unit cell and a reformer plate for reforming raw fuel, an internal manifold hole for supplying raw fuel gas, which is provided in a state of vertically extending through the reformer plate, for fuel gas, and oxidation. And a manifold hole for the agent gas, the unit cell supplies and discharges each gas through the manifold holes for the fuel gas and the oxidant gas, and the reformer plate is a bipolar plate of the unit cell. Similar to the above, and has a structure that can be supplied and discharged only to the internal manifold hole for supplying the raw fuel gas and the manifold hole for the fuel gas, and also functions as a bipolar plate and is obtained by reforming the supplied raw fuel gas. An internal reforming molten carbonate fuel cell having a structure for supplying the produced fuel gas to each unit cell. 2. A plurality of supporting portions made of metal are installed inside the reformer plate at a distance of 10 cm or less, and upper and lower end plates of the reformer plate are thermally and electrically connected. 1. The internal reforming molten carbonate fuel cell according to 1. 3. The inside of the reformer plate is divided into three gas passages by a partition having a notch, and the reforming catalyst is installed only in the central portion of the passage located at the center, and the raw fuel is provided at the outer edge portion thereof. The opening of the internal manifold hole for gas supply is provided, and the reformed fuel gas flows through the gas passages on both sides from the notch to reverse the flow, and is used for the fuel provided on both sides of the internal manifold hole for raw fuel gas supply. The internal reforming molten carbonate fuel cell according to claim 1 or 2, further comprising a structure for supplying each unit cell through a manifold hole.