JPH05135795A - Solid electrolyte fuel cell - Google Patents

Abstract

(57) [Summary] [Purpose] The reaction of gas and fuel within the cell surface of a solid oxide fuel cell is made uniform, temperature distribution and thermal stress distribution are relaxed, and durability and performance are improved. [Structure] The fuel gas and the oxidant gas were made to flow in the same direction, and the fuel gas and the oxidant gas discharged at the end of each unit cell were diffused to the outside and burned on the spot.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a solid oxide fuel cell.

[0002]

2. Description of the Related Art Recently, fuel cells, which use oxygen and hydrogen as fuels and directly convert the chemical energy originally possessed by the fuels into electricity, have been attracting attention from the viewpoints of resource saving and environmental protection.
Particularly, the solid oxide fuel cell has an operating temperature of 800 to 1
Since it is as high as 000 ° C, compared with phosphoric acid type and molten carbonate type fuel cells, power generation efficiency is higher in principle, waste heat can be effectively utilized, and the constituent materials are all solid Since it has many advantages such as being easy, research and development is progressing.

FIG. 4 is an exploded perspective view showing the basic structure of a conventional solid oxide fuel cell, in which a unit cell 12, a separator (also referred to as an interconnector) 13, a unit cell 12 and a separator 13 are laminated in this order from the upper layer, Solid electrolyte fuel cell fixed together (hereinafter abbreviated as stack)
Make up. In this structure, the separator 13 hermetically isolates the individual cells 12 from each other and electrically connects the adjacent single cells 12 in series one after another.

As shown in FIG. 4, the unit cell 12 has an air electrode 11a on the surface of the flat solid electrolyte layer 10 and a fuel electrode 11 on the back surface.
b and are arranged. An oxidant gas (air) 14 and a fuel gas 15 are formed on the respective surfaces of the electrodes 11a and 11b.
By circulating, the electromotive force can be generated between both electrodes. In order to make the reaction between the gas and the air electrode 11a or the fuel electrode 11b uniform and efficiently generate electromotive force, a plurality of grooves 16 are regularly formed on both surfaces of the separator 13 as shown in FIG. As shown in FIG. 4, a manifold (not shown) is attached to the outside of the stack, and gas (fuel gas and oxidant gas) is supplied from this manifold,
The gas is supplied to the air electrode 11a and the fuel electrode 11b through the groove 16 of the separator.

On the other hand, instead of supplying gas from the manifold, holes are provided in the peripheral portions of the unit cell and the separator,
There is also known a fuel cell having a structure in which when a unit cell and a separator are stacked, these holes are aligned to form a gas passage. For example, it is described in JP-A-3-225771.

[0006]

Conventionally, even if a plurality of rows of grooves 16 as gas passages are provided on the surface of the separator 13 and the gas is evenly supplied into the separator through the blow-out holes, the gas inlet side is not provided. There is a difference in the flow rate and concentration between the upstream side and the outlet side, which is the outlet side, and as a result, the cell reaction does not occur uniformly, and the temperature distribution inside the cells and even in the stack becomes non-uniform, which is high upstream and low downstream. ..

FIG. 5 shows an operating temperature distribution diagram of the stack shown in FIG. 4, and FIG. 5 (a) shows a cross-flow type operating temperature distribution diagram in which gas and air (oxidant gas) flow orthogonally in the separator. , (B) show a parallel flow type operating temperature distribution chart in which gas and air flow in parallel. In each figure, the inlet side is hot and the outlet side is cold. As a result, the planar thermal stress distribution of the stack becomes non-uniform, thermal strain occurs, durability deteriorates, and the output of the battery decreases.

The present invention has been made in view of the above points, and makes the reaction between the gas and the fuel in the cell surface of the solid oxide fuel cell uniform, thereby relaxing the temperature distribution and thus the thermal stress distribution. It is intended to improve the durability of and improve the output.

[0009]

In order to solve the above-mentioned problems, the present invention provides a plate-shaped unit cell in which a fuel electrode and an air electrode are arranged so as to sandwich a solid electrolyte layer, and the unit cell is electrically connected. In a solid oxide fuel cell, which is connected in series and distributes fuel gas to the fuel electrode of the unit cell, and is alternately laminated with separators that distribute oxidant gas to the air electrode,
A groove as a gas passage in the same direction is formed on the front surface and the back surface of the separator, and the fuel gas and the oxidant gas are caused to flow in the same direction, and the fuel gas and the oxidant exhausted at the gas discharge side end of the unit cell. The gas and the gas were diffused to the outside and burned on the spot.

[0010]

As described above, the fuel gas or the oxidant gas is made to flow in the same direction on each electrode surface of the unit cells of the stack,
Since the exhaust gas is released at the end of the unit cell and burned on the spot, the temperature of the downstream portion of the gas becomes high, the temperature difference between the upstream and downstream of the gas becomes small, and as a result, the thermal stress distribution is relaxed. It

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings.

In the stack of the solid oxide fuel cell according to the present invention, the unit cells 12 shown in FIG. 1 and the separator 9 shown in FIG. 2 are alternately laminated with a packing (not shown) interposed therebetween to form an integral body. It is fixed to.

FIG. 1 shows the unit cell 12, (a) is a plan view and (b) is a front view. The surface of the yttria-stabilized zirconia (YSZ) sintered body as the solid electrolyte layer 10 is coated with (La, Sr) MnO ₃ as the air electrode 11a and Ni / YSZ cermet as the fuel electrode 11b on the back surface by screen printing or the like. It is manufactured by baking in air at a predetermined temperature. Holes for gas supply / exhaust, that is, air supply holes 1 and fuel gas supply holes 2 are collectively formed on one side of the unit cell 12 at edges or sides where the electrodes 11a and 11b of the solid electrolyte layer 10 are not attached. Has been done. These air supply holes 1 and 2 are connected in the process of stacking the unit cells 12 to form a gas passage inside the stack.

2 and 3 show a separator, (a) is a plan view, (b) is a sectional view taken along line XX 'of (a),
(C) is a cross-sectional view taken along line YY 'of (a), (d) is Z of (a).
-Z 'sectional view, (e) is a WW' sectional view of (a). The separator 9 shown in FIG. 2 is one that is stacked in the middle of the stack, and the separator 9 ′ shown in FIG. 3 is that that is arranged on the uppermost lower surface of the stack.

The separators 9 and 9'are, for example, Japanese Patent Laid-Open No. 2-1.
A flat plate-like sintered body obtained by press-molding calcium dope plantan chromite disclosed in No. 11632 and then firing in air, in which holes for gas supply and exhaust, that is, electrodes of a single cell Air supply holes 1, fuel gas supply holes 2, air exhaust holes 3, fuel gas exhaust holes 4, air ejection holes 5, and fuel gas ejection holes 6 are formed in order to supply gas to the surface or collect exhaust gas. .. Further, in order to evenly distribute the gas throughout the electrode surface and to connect the unit cells in series, grooves 16 are formed on both surfaces of the separator 9 as shown in FIG. 'In Figure 3
As shown in (b), the groove 16 is formed only on one surface. The grooves 16 on the front side and the back side of the separator 9 are formed in parallel. In FIG. 2A, the air supply hole 1 and the fuel gas supply hole 2 are collectively provided on one side of the separator 9. Further, as shown in FIG. 2B, the air exhaust hole 3 and the fuel gas exhaust hole 4 are collectively formed on the front side and the back side of the separator 9 on the side opposite to the separator 9.

A solid oxide fuel cell according to the present invention can be assembled by alternately stacking the unit cells 12 and the separator 9 having the above-described structure with a packing sandwiched therebetween. When the fuel gas and the oxidant gas are made to flow in the same direction from the uppermost lower surface of the stack by the air supply pipe, they reach the ejection holes 5 and 6 of the separator. Each gas ejected from the ejection holes 5 and 6 is an air chamber 7 formed between the separator 9 and the unit cell 12.
Alternatively, the fuel gas enters the fuel gas chamber 8, flows on each electrode surface, and is consumed by the cell reaction. The cell reaction is strong in the upstream portion of the gas, that is, the portion near the air supply hole, and the temperature is high, and the temperature is low in the downstream portion of the gas, that is, near the exhaust hole. The exhaust gas collected in the exhaust ports 3 and 4 on one side of the separators 9 and 9'is discharged from here. That is, as shown in FIG. 2B as a cross-sectional view taken along the line XX ′, exhaust air is collected in the air exhaust holes 3 on the front side of one side of the separator 9, and the fuel gas exhaust holes on the back side are collected. Fuel exhaust gas gathers in 4. The two exhaust holes 3 and 4 are close to each other.

Since the fuel exhaust gas discharged from the exhaust hole 4 contains 10% or more of unreacted fuel, it is mixed with the air in the exhaust hole 3 and burns in the vicinity of the exhaust hole 4. As a result, the temperature of the terminal portion of the unit cell can be raised to approach the high temperature of the portion close to the air supply hole, and the temperature distribution in the cell surface can be relaxed.

[0018]

As described above in detail, in the present invention, the fuel gas and the oxidant gas (air) are made to flow in the same direction from the air supply holes to the unit cells in the stack, and the fuel gas and the oxidant gas (air) are made to flow in the same direction at the side ends of the unit cells. Since the fuel gas and air discharged from the exhaust port are released to the outside and burned on the spot,
Since the temperature of the portion of the unit cell 9 close to the exhaust hole becomes high and approaches the temperature of the portion close to the air supply port, the temperature distribution of the unit cell and the separator becomes relatively uniform, and thermal strain due to non-uniform thermal stress distribution occurs. It has the excellent effect of improving the stack durability and performance.

[Brief description of drawings]

FIG. 1 shows a structure of a unit cell of a solid oxide fuel cell according to the present invention, (a) is a plan view and (b) is a front view.

FIG. 2 shows a structure of a solid oxide fuel cell separator according to the present invention, (a) is a plan view, (b) is a sectional view taken along line XX ′ of (a), and (c) is (a). Is a sectional view taken along the line YY ', (d) is a sectional view taken along the line ZZ' of (a), and (e) is a sectional view taken along the line WW 'of (a).

FIG. 3 shows a structure of a separator arranged on the upper and lower surfaces of a solid oxide fuel cell according to the present invention, (a) is a plan view, (b) is a sectional view taken along line XX ′ of (a), 3C is a sectional view taken along the line YY ′ of FIG. 7A, FIG. 7D is a sectional view taken along the line ZZ ′ of FIG.

FIG. 4 is an exploded perspective view of a stack of a conventional solid oxide fuel cell stack.

FIG. 5 is an operating temperature distribution diagram of a conventional solid oxide fuel cell, in which (a) shows a cross flow type and (b) shows a parallel flow type.

[Explanation of symbols]

 1 Air Supply Hole 2 Fuel Gas Supply Hole 3 Air Exhaust Hole 4 Fuel Gas Exhaust Hole 5 Air Jet Hole 6 Fuel Gas Jet Hole 7 Air Chamber 8 Fuel Gas Chamber 9, 9 Separator 10 Solid Electrolyte Layer 11a Air Electrode 11b Fuel Electrode 12 Single battery

Claims (1)

[Claims] 1. A flat plate-shaped unit cell in which a fuel electrode and an air electrode are arranged so as to sandwich a solid electrolyte layer, and the unit cell is electrically connected in series and a fuel gas is distributed to the fuel electrode to form an air electrode. In a solid oxide fuel cell constituted by alternately stacking separators for distributing an oxidant gas, a groove as a gas passage in the same direction is formed on the front surface and the back surface of the separator, and the fuel gas and the oxidizer are formed. A solid electrolyte characterized in that the gas is made to flow in the same direction of the unit cell, the fuel gas and the oxidant gas exhausted at the gas discharge side end of the unit cell are diffused to the outside, and burned on the spot. Type fuel cell.