JPH1027619A - Cylindrical cell type solid electrolyte fuel cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase generation output and provide sufficient output in a small size by optimizing the rate of an interconnector in an inactive area, where no electrochemical burning reaction occurs, to the circumference of a cell. SOLUTION: A fuel cell consists of membrane air poles laminated in cylindrical multilayers, a solid electrolyte membrane and a fuel pole as well as an air pole and a band interconnector formed in membrane on the fuel pole and extended to the axial direction. it is satisfied with 0.10<=W/πD<=0.30, where D is the outline of the air pole or the fuel pole and W is the width of the band interconnector. In this case, the interconnector is in an inactive area where no electrochemical during reaction occurs and so, if the rate to the circumference of a cell is too large, cell output is decreased. On the other hand, if the width is too small, ohm resistance is increased and the cell output is worn by resistance heat. The width is thus optimized to increase generation output and provide sufficient output in a small size.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a solid oxide fuel cell of a cylindrical cell type. In particular, the present invention relates to a cylindrical cell-type solid oxide fuel cell (hereinafter, also referred to as T-SOFC) in which the width of an interconnector is optimized in order to maximize the power generation output per unit cell length.

[0002]

2. Description of the Related Art T-SOFC is disclosed in Japanese Patent Publication No. 1-59705.
And the like. The T-SOFC has a cylindrical cell composed of a porous support tube-air electrode-solid electrolyte-fuel electrode-interconnector. Flow oxygen (air) to the air electrode side,
When gaseous fuel (H ₂ , CO, etc.) is allowed to flow to the fuel electrode side, O ²⁻ ions move in this cell, causing chemical combustion, generating a potential between the air electrode and the fuel electrode and generating power. Will be There is also a type in which the air electrode also serves as a support tube. Demonstration tests of T-SOFC were conducted in 1993 at 25
Up to kw class cells (cell effective length 50 cm, number of cells 1152) are in progress.

[0003] At present, typical constituent materials of T-SOFC,
The thickness and manufacturing method are as follows (Proc. Of the
3rd Int. Symp. On SOFC, 1993). Support tube: ZrO ₂ (CaO), thickness 1.2 mm, extrusion Air electrode: La (Sr) MnO ₃ , thickness 1.4 mm, slurry coat Solid electrolyte: ZrO ₂ (Y ₂ O ₃ ), thickness 40 μm, E
VD interconnector: LaCr (Mg) O ₃ , thickness 40
μm, EVD fuel electrode: Ni—ZrO ₂ (Y ₂ O ₃ ), thickness 100 μm
m, slurry coat-EVD

FIGS. 2 and 3 are views showing the overall structure of a typical T-SOFC. This solid oxide fuel cell 1
The cylindrical cell assembly 101, which is the central part of the cell 10, has a large number of elongated cylindrical cells 3 (dimensions, diameter 15 mm × length 500
mm). The cylindrical cell 3 is a ceramic tube whose upper end is open and whose lower end is closed. The cross section of the cylindrical cell 3 has a multilayer cylindrical shape (see FIG. 3B), and the air electrode 1
1. Each layer of the solid electrolyte layer 13, the fuel electrode 15, and the interconnector 17 is laminated.

[0005] Each layer of the cylindrical cell is formed of a material mainly composed of an oxide having the required functions (conductivity, air permeability, solid electrolyte, electrochemical catalysis, etc.). Inside the cylindrical cell 3, an elongated air introduction pipe 5 for passing air is provided.
Is passing. The air introduction pipe 5 extends downward from the air distributor 121 at the top of the cylindrical cell 3 and reaches near the bottom of the cylindrical cell 3 tube. The air in the air distributor 121 is supplied into the cylindrical cell 3 tube by the air introduction pipe 5. The air supplied to the inside (bottom) of the tube is directed upward in the tube while contributing to the above-described power generation reaction, and exits from the cell upper end 21 to the exhaust combustion chamber 105. In the exhaust combustion chamber 105, fuel gas exhaust and air exhaust, which will be described later, are mixed, and oxygen and fuel components exhausted without being reacted in the cylindrical cell 3 burn (general combustion).

Fuel gas is supplied to the outer surface of the cylindrical cell 3 from the fuel header 137 below the fuel cell 110 and supplied to the above-described power generation. The unreacted portion of the fuel gas and the products of electrochemical combustion (CO ₂ , H ₂ O)
And the like) enter the exhaust combustion chamber 105 through a gap on the outer surface of the upper end of the cylindrical cell 3. In the exhaust combustion chamber 105, the unreacted fuel burns as described above. Combustion exhaust gas is exhaust port 1
It is discharged from 25. The sensible heat of the exhaust gas is used for residual heat of air and fuel gas supplied to the fuel cell, or sent to a power generation system using a normal steam boiler turbine for power generation.

The six rows of cylindrical cells 3 shown in FIG.
They are electrically connected to each other. That is, since the interconnector 17 of the right cylindrical cell is connected to the outer surface (external electrode, in this case, the fuel electrode) of the left cylindrical cell via the Ni felt 135, the six interconnectors of FIG. The cylindrical cells will be connected in series. In a normal solid oxide fuel cell, the power generation voltage in one cylindrical cell is about 1 volt, so that a required voltage is obtained by connecting many cylindrical cells in series. Cylindrical cell assembly 101
Current collector plates 131 and 131 'are provided outside the outermost row in contact with the cylindrical cell 3. From the current collector 131 and the current collector 133 connected to the current collector 131, the power generated by the cell assembly 1 is taken out.

The cross-sectional structure of the cell 3 will be described with reference to FIG. The cell 3 has a laminated structure of several layers (films). First, the air electrode 11 exists in the innermost ring shape. The air electrode 11 also has a role as a strength member (support) for supporting the cell. This air electrode 11 is made of strontium do plantan manganite (LSM)
And the like. The air electrode 11 serves as a cathode while air passes through it.

Next, the solid electrolyte membrane 13 is present in a substantially ring shape outside the air electrode 11. The solid electrolyte membrane 13 has a portion (a portion of the interconnector 17) that is partially interrupted on the left side of the drawing. The solid electrolyte membrane 13 is a dense membrane such as yttria-stabilized zirconia (YSZ). The solid electrolyte membrane 13 serves as a shielding membrane that allows O ²⁻ ions to pass through it and prevents the air inside the cell 3 and the fuel gas outside the cell 3 from directly mixing.

Next, the fuel electrode 15 exists in a substantially ring shape outside the solid electrolyte membrane 13. This fuel electrode 15
There is a part (part around the interconnector 17) that is partially interrupted on the left side of the figure. The fuel electrode 15 is made of Ni-YS
It is a porous film such as Z cermet. The fuel gas passes through the fuel electrode 15 and becomes an anode.

The interconnector 17 (FIG. 3A)
(B) (left side) is a film extending in the axial direction of the cell 3 in a band shape on the air electrode 11. The interconnector 17 is a dense film such as calcium dopantran chromite.
The interconnector 17 has a role of exposing the air electrode 11 to a conductive portion with the air electrode on the outer surface of the cell 3 and a function of airtightly shutting the inside and the outside of the cell 3. The interconnector 17 is not in contact with the fuel electrode 15 to avoid conduction.

Next, the structure of the cell 3 in the axial direction (vertical direction) will be described with reference to FIG. First, at the upper end (open end) of the cell 3, an open end non-power generation area 31 is provided.
Is provided. The non-power generation region 31 includes only the air electrode 11 and the solid electrolyte layer 13, and has no fuel electrode or interconnector. Therefore, the gas inside and outside the cell 3 is shut off, but no power is generated. Such a non-power generation area is also provided near the lower end (sealed end) 23 of the cell 3 (sealed end side non-power generation area 35). by this,
Heat spots near the cell sealing end and the open end are eliminated to prevent cracks.

Open end non-power generation area 31 and sealed end non-power generation area 3
The central part of the cell 3 excluding 5 is a power generation area 33. An air electrode 11, a solid electrolyte layer 13, a fuel electrode 15
And all of the interconnectors 17 are formed,
Power generation is performed.

[0014]

The above-mentioned cylindrical cell type solid oxide fuel cell is required to have a high output per unit cell length. To this end, optimizing the width of the interconnector in relation to the cell diameter (circumference) (percentage occupied) is one powerful factor. However, no systematic analysis and research on interconnect width optimization has been performed so far.

The present invention provides a small-sized, sufficient output cylindrical cell-type solid oxide fuel cell in which the width of the interconnector is optimized to maximize the power generation output per unit cell length. The purpose is to do.

[0016]

Means for Solving the Problems To solve the above problems, a cylindrical cell type solid electrolyte fuel cell of the present invention comprises a membrane-shaped air electrode, a solid electrolyte membrane and a fuel electrode laminated in a multilayer cylindrical shape. And a solid oxide fuel cell having a cylindrical cell having an axially extending strip-shaped interconnector formed on an air electrode or a fuel electrode;
When the outer diameter of the air electrode or the fuel electrode is D and the width of the strip-shaped interconnector is w, 0.10 ≦ w / πD ≦ 0.30.

Since the interconnector portion is an inactive region where an electrochemical combustion reaction does not occur, if the ratio of the interconnect to the cell circumference is too large, the cell output decreases. on the other hand,
If the width of the interconnect is too small, the ohmic resistance between the cells will increase, and the cell output will be exhausted due to electrical resistance heating. The inventor has succeeded in optimizing the interconnector width through various analyzes and experiments. From the above viewpoint, the range of w / πD is more preferably 0.15 to 0.25, and most preferably 0.17 to 0.22.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The following test cells were prepared and power generation tests were performed at various w / πD%. (1) Cell specifications Model: Self-supporting air electrode Air electrode: Material La _0.9 Sr _0.1 MnO ₃ , outer diameter 16
mm, thickness 1.5 mm, conductivity 60 S / cm, porosity 35%, extrusion → firing Solid electrolyte: material 8 mol% Y ₂ O ₃ stabilized ZrO ₂ ,
20μm thick, slurry coat → fired Interconnector: Material La _0.8 Ca _0.2 CrO
_3. Thickness 40μm, slurry coat → fired Fuel electrode: Material YSZ 30% by weight Ni cermet, thickness 60μm, conductivity 1,400S / cm, porosity 40%, slurry coat → fired

(2) Power generation conditions: Fuel: (H ₂ + 11% H ₂ O): N ₂ = 1: 2 Oxidant: Air Cell temperature: 1,000 ° C. Fuel utilization rate: 85%

(3) Power generation test result: FIG. 1 is a graph showing the power generation test result. The horizontal axis shows the w / πD ratio, and the vertical axis shows the output (W / cm) per unit cell length. This graph shows that an output of 1.2 W / cm can be achieved in the range of w / πD 0.10 to 0.30. Also, w / πD 0.15
Output 1.5W / cm, w / πD 0.17 ~ in the range of 0.25
It can be seen that an output of 1.6 W / cm can be achieved in the range of 0.22.

[0021]

As is clear from the above description, the present invention optimizes the width of the interconnector,
It is possible to provide a cylindrical cell-type solid oxide fuel cell having a high power generation output per unit cell length, a small size, and a sufficient output.

[Brief description of the drawings]

FIG. 1 is a graph showing a power generation test result of a solid oxide fuel cell according to one embodiment of the present invention. The horizontal axis represents the interconnector width w / πD ratio, and the vertical axis represents the output (W / cm) per unit cell length.

FIG. 2 is a diagram showing the entire structure of a typical cylindrical cell type solid oxide fuel cell.

FIG. 3 is a sectional view showing a structure of a cell of the fuel cell of FIG. 2; (A) is an overall longitudinal sectional view, and (B) is a transverse sectional view showing a BB section of (A).

[Explanation of symbols]

Reference Signs List 3 cylindrical cell 5 air introduction pipe 11 air electrode 13 solid electrolyte layer 15 fuel electrode 17 interconnector 21 cell upper end (open end) 23 cell lower end (sealed end) 25 introduction pipe tip 31 open end non-power generation area 33 power generation area 35 Non-power generation area on sealed end

Claims (3)

[Claims] 1. A film-like air electrode laminated in a multilayer cylindrical shape,
A solid electrolyte fuel cell having a cylindrical cell including a solid electrolyte membrane and a fuel electrode, and an axially extending strip-shaped interconnector formed on the air electrode or the fuel electrode; A cylindrical cell-type solid oxide fuel cell, wherein 0.10 ≦ w / πD ≦ 0.30, where D is the outer diameter of the pole and w is the width of the strip-shaped interconnector. 2. The cylindrical cell type solid oxide fuel cell according to claim 1, wherein 0.15 ≦ w / πD ≦ 0.25. 3. The fuel cell according to claim 1, wherein 0.17 ≦ w / πD ≦ 0.22.