JPH03225767A - Internally reformed type fuel cell - Google Patents

Abstract

PURPOSE:To sufficiently advance reforming reaction and cell reaction while preventing the deterioration of cell characteristics by the evaporation of an electrolyte by charging specified materials to first and second passages on the face side of a fuel gas side electrode and the face side isolated from this electrode, respectively. CONSTITUTION:In an electrolyte layer 1, a material 11 having no chemical reaction with electrolytes, for example, MgO, LiAlO2, Al2O3, and a reforming catalyst 9 are charged in a first fuel gas passage 7a on the face side of a fuel gas side electrode 2 and a second fuel gas passage 7b isolated from the electrode 2, respectively, whereby an internally reformed type fuel cell capable of uniformly and sufficiently advancing reforming reaction and cell reaction in the cell while preventing the deterioration of cell characteristics by the evaporation of the layer 1 can be provided.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to an internal reforming fuel cell, and particularly to extending its life.

[Prior Art] FIG. 2 is a vertical plan view showing a part of an embodiment of a conventional internally modified battery disclosed in, for example, Japanese Patent Laid-Open No. 186471/1983. In the figure, (1) is the electrolyte layer, (
2) is a fuel gas side electrode, (3) is an oxidizing gas side electrode that faces the fuel gas side electrode (2) with the electrolyte layer (1) in between, and (4a) is an electrode that supports the fuel gas side electrode (2). and a fuel gas side current collector plate that allows the generated current to pass through (4b
) are oxidizing gas side current collector plates that support the oxidizing gas side electrode (3) and allow the generated current to pass; (5a), (5b
) are the fuel gas side flow path forming material and the oxidizing gas side flow path forming material for forming the fuel gas flow path and the oxidizing gas flow path, respectively, and (6) is the fuel provided opposite the fuel gas side electrode (2). a separator plate that separates the gas flow path (7) and the oxidation gas flow path (8) provided opposite to the oxidation gas side electrode (3);
(9) is a reforming catalyst, (10) is arranged between the reforming catalyst (9) and the fuel gas antistatic iii (2), and removes the electrolyte contained in the fuel gas or substances generated from the electrolyte from the fuel gas. It is an electrolyte removing substance that has the function of

Next, the operation will be explained. A fuel gas containing hydrocarbons or alcohol/steam as its main components is supplied from the direction of arrow B, and an oxidizing gas containing oxygen and carbon dioxide as its main components is supplied from the direction of arrow A, resulting in a cross flow of fuel gas. The oxidizing gas is introduced into the oxidizing gas flow path. Hydrocarbons in the fuel gas are converted to the following formula (1) by the action of the reforming catalyst (9):
As shown in (2) and (3), thermal energy produced as a by-product in a fuel gas whose main components are hydrogen and carbon oxide is directly utilized.

CHI +H20-+c.

+'3H2+49.3kcal/mol...(1
)Cn Hm + n H20-+ n CO+((m
+2n)/2) H2... (2) CO100 → CO2 +H2-9,8kcal/mol...(3)
According to the reactions shown in equations (1), (2), and (3), the hydrogen and carbon oxide generated in the fuel gas flow path and the oxygen and carbon dioxide in the oxidizing gas supplied by arrow A are respectively on the fuel gas side. Diffuse the holes in the current collector plate (4a) and the oxidant gas side current collector plate (4b) to connect the fuel gas side electrode (2) and the oxidant gas side electrode (
In 3), the following equations (4), (5), and (6) are used, respectively.
causes a reaction as shown in

Fuel gas side electrode H2+CO32-→H20+ C02+ 2 e
(4) CO+ H20-+ H2+ CO3... (
5) Oxidizing gas side electrode 1/202+ C02+ 2 e -) C032-(6
) Through these chemical and electrochemical reactions, the chemical energy of the fuel gas is converted into electrical energy and by-product thermal energy. As mentioned earlier, most of the by-product thermal energy is used for the reaction heat of hydrocarbon decomposition in the gas flow path, resulting in a significant improvement in thermal efficiency, which is one of the characteristics of the internal reforming method. ing.

At the same time, since the reformed gas is used at the fuel electrode, the reactions in equations (1) and (2) proceed to the right, and in internally reformed fuel cells, the hydrocarbons exceed the equilibrium at the cell operating temperature. An improvement in the reforming rate occurs and most of the hydrocarbons fed are reformed.

Here, the reforming catalyst (9) is, for example, one in which nickel having catalytic activity is supported on a carrier mainly composed of alumina or magnesia.

In general, such a reforming catalyst (9) is susceptible to electrolyte contamination, and its activity as a catalyst is significantly reduced by contamination with a trace amount of electrolyte. In this example, the electrolyte layer (1)
For example, Li2CO3 and K 2 G O
In order to prevent electrolytes such as 3 or substances generated from electrolytes such as LiOH or KOH from contaminating the reforming catalyst in the form of steam or droplets and reducing the activity of the reforming catalyst (9), An electrolyte removing substance (10) is placed between the electrode (9) and the electrode (2).

Further, FIG. 3 is a perspective view showing a part of another embodiment of the conventional internal reforming pond disclosed in Japanese Patent Application Laid-Open No. 1-122569. In the figure, (5a) is a fuel gas flow path forming material for forming a fuel gas flow path, (7a) is a first fuel gas flow path facing the fuel gas side electrode, (7b)
) indicates a second fuel gas flow path separated from the fuel gas side electrode by the fuel gas flow path forming material (5a). (
9) is a reforming catalyst, and (10) is an electrolyte removal substance.

Since the reforming catalyst (9) and the electrolyte removal substance (10) are filled in the second fuel gas flow path (7b) isolated from the fuel gas electrode, the fuel gas containing the electrolyte or a substance generated from the electrolyte is is supplied from the first fuel gas flow path (7a) to the second fuel gas flow path (7b) through the perforation provided in the fuel gas side flow path forming material (5a), and the electrolyte removal substance (10) After the electrolyte is removed by the reforming catalyst (9
).

[Problems to be Solved by the Invention] Since the conventional internal reforming fuel cell is configured as described above, an electrolyte removing substance ( 10), there is a problem in that the electrolyte or a substance generated from the electrolyte is removed from the fuel gas by the electrolyte removing substance, promoting evaporation of the electrolyte from the electrode. The same is true when the reforming catalyst (9) is filled instead of the part filled with the electrolyte removal substance (10) in Figure 2, and the reforming catalyst, which has the property of taking in electrolyte, prevents evaporation of the electrolyte. promoted.

Next, as shown in FIG. 3, when the portion of the fuel gas flow path that contacts the electrode is a gap flow path, an excessive amount of fuel gas flows into the gap, which tends to cause imbalance in fuel distribution. In order to avoid this, if a flow path configuration is adopted in which fuel gas can be evenly supplied to the first fuel gas flow path (7a) and the second fuel gas flow path (7b), the first fuel gas flow Although it is necessary to make the diameter of the channel at least 0.5 mm or less, it is difficult to manufacture a corrugated plate with such a shape, and it is also expensive. In addition, if the fuel gas flow rate in the gap is insufficient, the flow path may become laminar, resulting in insufficient gas exchange between the fuel gas side electrode and the fuel gas flow path.To avoid this, It is desirable to cause turbulence in the gas flow within the flow path.

This invention was made to solve the above-mentioned problems, and it is possible to uniformly and sufficiently advance the reforming reaction and battery reaction within the battery while preventing deterioration of battery characteristics due to evaporation of the electrolyte. The purpose of this study is to obtain an internal reforming fuel cell.

[Means for Solving the Problems] The internal reforming fuel cell according to the present invention has a fuel gas flow path that includes a first flow path facing the fuel gas side electrode and a second flow path isolated from the fuel gas side electrode. The first flow path is filled with a substance that has no chemical reactivity with the electrolyte, and the second flow path is filled with at least a reforming catalyst.

[Operation] In the present invention, the fuel gas flow path is divided into a first flow path facing the electrode and a second flow path isolated from the electrode. The difference in channel resistance between these channels is controlled by a substance that is not chemically reactive with the electrolyte (hereinafter referred to as a non-reactive substance) filled in the first channel. The retained non-reactive substances also cause turbulence in the gas flow within the fuel gas flow path to facilitate exchange of reactant gases. As the fuel gas flows downstream from the supply section, the gas reformed by the reforming catalyst filled in the flow path of jI2 and the gas used in the electrode are mixed and flowed into the first and second flow paths. Since it flows at an appropriate rate, the reforming reaction and battery reaction can proceed uniformly and sufficiently.

[Example] Hereinafter, an example of the present invention will be described with reference to the drawings. 1st
In the figure, (1) is the electrolyte layer, (2) is the fuel gas side electrode, (3) is the oxidizing gas side electrode, (4a) is the fuel gas side current collector plate, (4b) is the oxidizing gas side current collector plate, (5
a) is a fuel gas flow path forming material, (5b) is an oxidizing gas flow path forming material, and (7a) is a first electrode facing the fuel gas side electrode.
The fuel gas flow path (7b) is the fuel gas flow path forming material (5
a) is a second fuel gas flow path separated from the fuel gas side electrode; (8) is an oxidizing gas flow path; (9) is a reforming catalyst; and (11) is a non-reactive substance. Reforming catalyst (9
) is a non-reactive substance (1) in the second fuel gas flow path (7b).
1) is filled in the first fuel gas flow path (7a).

Next, the operation of the internal reforming fuel cell equipped with the non-reactive substance (11) according to this embodiment will be explained. Among fuel gases whose main components are hydrocarbons or alcohols,
The gas flowing into the second fuel gas flow path (7b) is caused by the action of the reforming catalyst (9) filled with the formula (1), (2
), (3), the fuel gas is transformed into a fuel gas mainly composed of hydrogen and carbon oxide, and flows into the downstream gas flow path. The fuel gas that has flowed into the first fuel gas flow path (7a) does not change in quality, but here, the gas containing hydrogen and carbon oxide that has been changed in the upstream is used for cell reactions at the fuel electrode, and further downstream. Provided to the fuel gas flow path. First fuel gas flow path (
Another first fuel gas flow path (7a) and a second fuel gas flow path (7b) are located downstream of the second fuel gas flow path (7a) and the second fuel gas flow path (7b), and the downstream side The first flow path and the second flow path
Similarly, gas is used in the reforming reaction and battery reaction in the flow path. The gas flowing out from the upstream fuel gas flow path is
The ratio of the amounts flowing downstream into the first fuel gas flow path (7a) and the second fuel gas flow path (7b) is determined by the amount of non-reactive material filled in the first fuel gas flow path (7a). (11)
can be controlled by the filling rate. When the first fuel gas flow path is a gap as in the conventional example shown in FIG.
The first fuel gas flow path (7a) and the second fuel gas flow path (
7b), for example, if a flow path configuration was adopted that could supply fuel gas evenly, it would be difficult and expensive to manufacture a corrugated plate of a suitable shape. Similar effects can be obtained with a very simple structure.

By controlling the distribution of fuel gas to the first and second flow paths in this manner, the reforming reaction can be made uniform, and an internal reforming fuel cell with a small temperature distribution can be obtained.

In addition, as already mentioned, one of the characteristics of internal reforming fuel cells is that the reforming rate is improved by subjecting the fuel gas to the cell reaction immediately after it is reformed. However, by controlling the flow of fuel gas using this method, a high reforming rate of fuel gas can be achieved. Furthermore, turbulence is caused in the gas flow within the fuel gas flow path to promote exchange of reactant gases.

In addition, there is a substance filled on the electrode side of the fuel gas flow path.

Since it does not react with the electrolyte, the electrolyte evaporated from the electrode or substances generated from the electrolyte are not directly removed from the fuel gas on the spot, and the evaporation of the electrolyte is not promoted.

Here, as an example of a substance that has no chemical reactivity with the electrolyte, in ceramics, for example, MgO or Li with a low specific surface area.
Examples include A I O2 and Al2O3. A material suitable for filling the first channel can be obtained by molding the powder of these substances into a pellet or disk shape and then firing it. The MgO pellets thus obtained are transferred to the first fuel gas flow path (7a).
When placed in
The amount of deposited electrolyte of the reforming catalyst mainly composed of 2O3 is sufficiently small compared to 8 wt% or more under similar conditions, and is suitable for use as a substance non-reactive with the electrolyte. Further, metals such as Ni can also be used as the substance filling the first flow path.

In this way, with a simple battery component configuration, it is possible to achieve a high reforming rate of fuel gas, prevent a reduction in the activity of the reforming catalyst due to contamination by the electrolyte or substances generated from the electrolyte, and suppress loss of electrolyte. , can operate stably for a long period of time.

[Effects of the Invention] As described above, according to the present invention, the fuel gas flow path is composed of the first flow path facing the fuel gas side electrode and the second flow path isolated from the fuel gas side electrode. Since the first flow path is filled with a substance that has no chemical reactivity with the electrolyte, and the second flow path is filled with at least a reforming catalyst, deterioration of battery characteristics due to evaporation of the electrolyte can be prevented. This has the effect of providing an internally reforming fuel cell in which the reforming reaction and cell reaction can proceed uniformly and sufficiently within the cell.

[Brief explanation of drawings]

FIG. 1 is a partially cutaway perspective view showing the main parts of an internal reforming fuel cell according to an embodiment of the present invention. FIG. 2 is a plan view showing the main parts of a conventional internally reforming fuel cell, and FIG. 3 is a perspective view showing the main parts of another conventional internally reforming fuel cell. (1)... Electrolyte layer, (2)... Fuel gas side electrode, (
3)... Oxidizing gas anti-static electrode, (4a)... Fuel gas side current collecting plate, (4b)... Oxidizing gas side current collecting plate, (5a)
...fuel gas flow path forming material, (5b)...oxidizing gas flow path forming material, (6)...separator plate, (7)...
Fuel gas flow path, (7a)...first fuel gas flow path,
(7b) Second fuel gas flow path, (8) Oxidizing gas flow path, (9) Reforming catalyst, (10) Electrolyte removal substance, (11) Non-reactive substance , A...fuel gas flow direction, B...oxidant gas flow direction. Note that the same reference numerals in each figure indicate the same or corresponding parts.

Claims (1)

[Claims] A unit cell having a fuel gas side electrode and an oxidizing gas side electrode facing each other with an electrolyte layer interposed therebetween, and a fuel gas passage provided opposite to the fuel gas side electrode and an oxidizing gas passage provided opposite to the oxidizing gas side electrode. in which separator plates are alternately stacked to separate the fuel gas flow path, the fuel gas flow path comprising a first flow path facing the fuel gas side electrode and a second flow path isolated from the fuel gas side electrode. 1. An internal reforming fuel cell, characterized in that the first channel is filled with a substance that has no chemical reactivity with the electrolyte, and the second channel is filled with at least a reforming catalyst.