JPH03238760A - Fuel cell of solid electrolyte type - Google Patents

Abstract

PURPOSE:To improve power generating efficiency by providing a turbulent flow generation means in the space of a cylinder for changing an oxide gas flow or a fuel gas flow to a turbulent flow. CONSTITUTION:In the solid electrolyte type fuel cell wherein a gas flow E passes the cylinder space 7 of a cylindrical solid electrolyte type fuel cell element, and fuel gas or oxide gas comes in contact with the external surface of the aforesaid element, a turbulent flow generation means 9 for changing a gas flow E to a turbulent flow is provided within the cylinder space 7. Namely, a solid circular cylinder body 9, for example, is so made as to pass through the center of the space 7 and fixed to the inner side of a cylindrical porous support body 1 with three plate-shaped ribs 10, thereby forming three oxide gas flow passages 12. Consequently, the sectional area of the flow passage 12 becomes smaller than that of the conventional passage and the mean flow velocity of the oxide gas becomes larger, thereby changing an oxide gas flow to a turbulent flow as shown by an arrow E. According to the aforesaid construction, an oxide gas or fuel gas flowing in the cylinder space 7 can be effectively used for power generation and the efficiency thereof can be increased.

Description

[Detailed description of the invention] (Industrial application field) The present invention relates to solid oxide fuel cells.

(Prior Art) Recently, fuel cells have been attracting attention as power generation devices. This is a device that can directly convert the chemical energy of fuel into electrical energy, and because it is not subject to the restrictions of the Carnot cycle, it has inherently high energy conversion efficiency and can be used for a variety of fuels (naphtha, natural gas, etc.). , methanol, coal reformed gas.

It is an extremely promising technology as it uses heavy oil (such as heavy oil), is low-pollution, and its power generation efficiency is not affected by the size of the facility.

In particular, solid oxide fuel cells (SOFC)
Because it operates at a high temperature of °C, the bridge reaction is extremely active, no expensive precious metal catalyst such as platinum is required, the polarization is small, and the output voltage is relatively high, so the energy conversion efficiency is higher than that of other fuel cells. significantly higher than that. Furthermore, since all the structural materials are made of solid materials, they are stable and have a long life.

FIG. 8 is a broken perspective view showing an example of such a cylindrical 5OFC element, and FIG. 9 is a cross-sectional view taken along a line in FIG. 8.

An air electrode pi5 is provided on the outer periphery of the cylindrical ceramic support l, a solid electrolyte t4 and a fuel electrode 3 are arranged along the outer periphery of the air electrode 5, and in the upper region in FIG. An interconnector 2 is provided on the interconnector 2, and a connecting terminal 6 is attached thereon. And cylindrical 5
To connect the OFC elements in series, connect the air electrode 5 of the 5 OFG element and the fuel electrode 3 of the adjacent 5 OFC element via the interconnector 2 and the connecting terminal 6, and also connect the cylindrical 5 op.
To connect the c elements in parallel, the fuel electrodes 3 of adjacent 5OFC elements are connected with Ni felt or the like.

(Problems to be Solved by the Invention) During operation of this cylindrical 5OFC, as shown in FIG. The oxidizing gas is caused to flow into the oxidizing gas passage 8 formed by the bay space 7 as shown by arrows A and B.

However, the flow of the oxidizing gas in the cylinder space 7 is rectified, has regular streamlines, and flows in a layered manner. Therefore, in the peripheral part of the cylinder interior space 7 near the porous support l, the arrow C
Oxygen is consumed sequentially as shown in the figure, and the oxygen concentration decreases as one moves to the right in the drawing, the electrode reaction becomes inactive and the temperature decreases, and this temperature drop makes the electrode reaction even more inactive. For this reason, the oxygen in the oxidizing gas flowing through the oxidizing gas flow path 8 is not used effectively enough, resulting in a decrease in power generation efficiency, and due to the thermal gradient between the active and inactive areas of the electrode reaction. A large thermal strain stress occurs in the 5OFC element.

Moreover, in the laminar flow as described above, the oxidizing gas flowing in the center of the cylinder space 7 hardly contributes to power generation, and furthermore, the flow velocity of the oxidizing gas is low at the periphery of the cylinder space 7, while the oxidizing gas flowing in the center part Since the flow rate of the oxidizing gas is high, more oxygen flows away without being used for power generation.

A problem similar to the above occurs also in the 5OPC, which has a configuration in which fuel gas flows into the cylinder space of a cylindrical 5OFC element and oxidizing gas flows around the outer periphery, resulting in a large loss of fuel gas.

The problem of the present invention is to provide a cylindrical solid electrolyte fuel cell.
It is an object of the present invention to provide a solid oxide fuel cell with high power generation efficiency, which effectively utilizes oxidizing gas or fuel gas flowing in a cylinder space for power generation to reduce loss of oxidizing gas or fuel gas.

(Means for Solving the Problems) In the present invention, an oxidizing gas flow or a fuel gas flow passes through an inner space of a cylindrical solid oxide fuel cell element, and an oxidizing gas flow or a fuel gas flow passes through an outer peripheral surface of the solid oxide fuel cell element. In a solid oxide fuel cell configured to be in contact with fuel gas or oxidizing gas,
The present invention relates to a solid oxide fuel cell in which a turbulent flow means for converting the oxidizing gas flow or the fuel gas flow into a turbulent flow is provided in the cylinder space.

(Example) FIG. 1 is a cutaway perspective view showing a cylindrical 5OFC according to an example of the present invention, and FIG. 2 is a sectional view taken along the line E in FIG. 1.

In this cylindrical 5OFC, a solid cylindrical body 9 is passed through the center of the cylinder interior space 7, and a cylindrical porous support l
It is fixed inside with three flat ribs 10 to form three oxidizing gas channels 12. porous support 1, cylindrical body 9,
It is preferable to integrally extrude the flat plate-shaped rib 10 from the viewpoint of manufacturing efficiency.

At this time, it is preferable that the porous support 1, the plate-like ribs 101, and the cylindrical body 9 be made of the same material, and this material is preferably electrically conductive for the reason described later. Such porous conductive materials include Sr-doped LaCr
0. Examples include LaMn0z.

The air electrode 5 is made of doped or undoped LaMn0. , CaMn0+, LaNi
0:++LaCo0++ Can be manufactured from LaCrO3 etc.
LaMnO3 doped with Sr is preferred. Disposed around the outer periphery of the air electrode 5 is an airtight solid electrolyte 4 typically made of yttria-stabilized zirconia and having a thickness of about 1 to 100 microns. In the solid electrolyte deposition step, a selected longitudinal section is masked and the interconnector 2 is deposited in this section. Interconnector 2 must be electrically conductive under oxygen and fuel atmospheres. Interconnector 2 preferably has a thickness of 5 to IOθ microns. The surface area of the solid electrolyte other than the cell interconnector 2 is surrounded by a fuel electrode 3, which acts as an anode. −
For boat fishing, the thickness of the fuel electrode 3 is 30 to 100 microns, and is generally made of nickel-zirconia cermet or cobalt-zirconia cermet.

A connecting terminal 6 is attached to the upper part of the interconnector 2. Examples of the material for the connection terminal 6 include nickel-zirconia cermet, cobalt-zirconia cermet, and nickel.

During operation, for example, fuel gas flows around the outer periphery of the fuel electrode 3 as shown by the arrow, and oxidizing gas flows as shown by the arrow E through each of the three oxidizing gas channels 12 divided by the cylindrical body 9 and the plate-like ribs 10. flows to Oxygen in the oxidizing gas passes through the porous support 1 and generates oxygen ions at the interface between the air electrode 5 and the solid electrolyte 4, and these oxygen ions move through the solid electrolyte 4 to the fuel electrode 3, It reacts with the fuel and emits electrons to the fuel electrode 3.

According to the cylindrical 5OFC of this example, the following effects can be achieved.

(1) Since the solid cylindrical body 9 is provided in the center of the cylinder space 7, oxidizing gas does not flow into the center of the cylinder space 7, and therefore the oxidizing gas flow in the center does not contribute to power generation. Can be blocked,
Oxidizing gas can be used efficiently and not wasted, improving power generation efficiency.

(2) Since the narrow oxidizing gas channel 12 is formed between the inner circumferential surface of the porous support 1 and the cylindrical body 9, the cross-sectional area of the oxidizing gas channel 12 is smaller than before, and the oxidizing gas The average flow velocity increases, and the oxidizing gas flow becomes turbulent as shown by arrow E. In general, in turbulent flow, momentum exchange occurs on a much larger scale than in laminar flow, and the flow becomes extremely irregular in time and space. Since the oxygen-depleted portion and the oxygen-consumed portion are mixed, it is possible to prevent the oxidizing gas with a reduced oxygen concentration from flowing in a laminar flow along the inner circumferential surface of the porous support 1 as in the conventional case. Therefore, it is possible to suppress a decrease in power generation efficiency due to inactivity of the electrode reaction and an increase in thermal strain stress due to a thermal gradient.

In order to appropriately generate turbulent flow as described above and to prevent waste of oxidizing gas, it is further preferred that the ratio of the diameter of the cylindrical portion 9 to the diameter of the cylinder interior space 7 be 0.3 or more. preferable.

(3) Since both ends of the cylindrical 5opc are open and the oxidizing gas is allowed to flow from one end to the other, there is no need for a step of sealing one end, and manufacturing costs can be reduced.

(4) It is very advantageous to integrally extrude the cylindrical body 9, the plate-shaped ribs 10, and the porous support 1, since it does not require much manufacturing time and a homogeneous porous support 1 can be obtained. .

(5) In addition, since the plate-like ribs 10 are made to protrude radially from the cylindrical body 9 and are shaped to support the porous support body 1 against pressure in the transverse direction, from a structural mechanical point of view, it is different from the conventional one. It has a higher radial crushing strength than a porous support. The number of these flat ribs can be varied.

(6) Conventionally, even if the porous support 1 was molded from a conductive material, current flowed circumferentially along the porous support 1.

On the other hand, when the flat rib 10, the porous support 1, and the cylindrical body 9 are molded from a porous conductive material, current flows through the flat rib 10 and the cylindrical body 9 as shown by arrow G. . Therefore, when a large number of cylindrical 5OFC elements shown in FIG. 1 are collected and connected in series, current loss can be reduced and the overall power generation efficiency can be further improved.

In the example shown in FIG. 1, an air electrode may be provided on the outer peripheral surface of the solid electrolyte 4, and a fuel electrode may be provided on the inner peripheral surface. In this case, fuel gas is supplied to the internal space of the 5OFC element, and oxidizing gas is supplied to the outside. In this case, the above (1) to (
It can achieve the same effect as 6) and also reduce H in the fuel gas.
2. It can prevent combustion sources such as Co from being wasted.
It is even more effective.

FIGS. 3 to 6 each show an example in which something other than a solid cylindrical body is used as the turbulence means.

In the example shown in FIG. 3, a hollow columnar body 19 formed by sealing both ends of a hollow cylinder 19b with sealing portions 19a is provided instead of a solid columnar body. The outer periphery of the hollow cylinder 19b is the first
The hollow cylinder 19b, the flat rib 10 and the porous support 1
can be extruded in one piece.

In FIG. 3, both ends of the hollow cylinder 19b are sealed with sealing parts 19a, but it is sufficient to seal at least the upstream end of the cylinder 19b.

In this embodiment, a hollow body is used instead of a solid body as a means for turbulating gas flow, so that thermal stress can be lowered structurally than a solid body, and it is strong against thermal shock. Therefore, it is more suitable for 5OFCs that operate at high temperatures for long periods of time.

In the example shown in FIG. 4, a solid cylindrical body 15 having a slope is provided in the cylinder interior space 7 and supported by a flat plate-like rib 1O. The narrow end of the solid cylindrical body 15 is disposed on the upstream side of the oxidizing gas flow, and the thick end thereof is disposed on the downstream side of the oxidizing gas flow. Therefore, the cross-sectional area of the oxidizing gas flow path 22 is large on the upstream side;
It gradually becomes smaller as it goes downstream. As a result, the oxidizing gas flowing into the oxidizing gas flow path 22 initially flows slowly in a layered manner, but as the oxygen is consumed, the oxidizing gas flows rapidly and becomes turbulent as indicated by arrow E.

In the embodiment shown in FIG.
The upstream opening of 5c is sealed with a sealing part 25a, and the downstream opening is sealed with a sealing part 25b having a larger diameter. Depending on the case, the sealing portion 25b on the downstream side may be removed.

In the example shown in FIG. 6, a rod 16 is fixed in the cylinder interior space 7, and a circular plate 17, for example, is fixed around the rod 16 at a predetermined interval. As a result, the oxidizing gas flow that has flowed into the cylinder interior space 7 in the direction of arrow A collides with the plate 17 and is disturbed, passes through the gap between the plate 17 and the porous support 1, and this movement It repeats this and flows downstream. As described above, due to the action of the plate 17, the oxidizing gas flow becomes turbulent as shown by arrow E, so it is possible to prevent the oxidizing gas from passing through the center of the cylinder space 7 as a laminar flow. At the same time, it is possible to prevent oxidizing gas with a reduced oxygen concentration from flowing along the circumferential surface of the porous support 1.

FIG. 7 is a partial sectional view showing an example in which the present invention is applied to a so-called multi-cell type 5OFC.

Air electrodes 3 are placed at predetermined intervals on the surface of the porous support l.
5 are provided at multiple locations, and a solid electrolyte 34 and a fuel electrode 33 are sequentially provided on each air electrode 35.
and adjacent air electrodes 35 are sequentially electrically connected by an interconnector 36.

The other parts are the same as 5OFG in FIG.
Three oxidizing gas channels 12 are formed.

In each of the above examples, the air electrode etc. were formed on the surface of the porous support, but it is also possible to use the cylindrical air electrode itself or the cylindrical fuel electrode itself as a rigid support and have a structure that can stand on its own with only the battery elements. good.

Instead of the cylindrical solid oxide fuel cell element, other shapes, such as square cylinders, hexagonal cylinders, etc., may be used.

(Effects of the Invention) According to the solid oxide fuel cell according to the present invention, since the turbulence means for converting the oxidizing gas flow or the fuel gas flow into the turbulent flow is provided in the cylinder space, the oxidizing gas flow or the fuel gas flow is Since the fresh part and the part with reduced concentration of the fuel gas flow are mixed, it is possible to prevent the oxidizing gas or fuel gas with reduced concentration from continuing to flow in a layered manner along the inner peripheral surface of the bay space. Therefore, it is possible to suppress the decrease in power generation efficiency due to the reduced gas concentration and the increase in thermal strain stress due to non-uniform electrode reactions, and it is also possible to prevent fresh gas from flowing through without being used for power generation. There is no waste, and power generation efficiency is greatly improved.

[Brief explanation of drawings]

FIG. 1 is a cutaway perspective view of a cylindrical 5OFC according to an embodiment of the present invention, FIG. 2 is a sectional view taken along the line E in FIG. 1, and FIGS. (corresponding to FIG. 2) FIG. 7 is a partial cross-sectional view showing an example in which the present invention is applied to a so-called multi-cell type 5OFC, and FIG. 8 is a cross-sectional view of a conventional 5OFC. The broken perspective view shown in FIG. 9 is a sectional view taken along a harbor line in FIG. 8. l, 21...Porous support 2...Interconnector 3.33...Fuel electrode 4.34...
Solid electrolyte 5.35... Air electrode 7... Cylinder space 8, 12.22... Oxidizing gas channel 9... Solid cylindrical body 10... Flat rib 1
5...Solid cylindrical body 19 with a slope...Hollow cylindrical body 17...Plates 19a, 25a, 25b - Sealing portion 25c...Cylindrical body 36 with a slope... Interconnectors A, B, E... Oxidizing gas flow C... Oxygen movement D... Fuel gas flow G... Current flow 351- Figure 3 Figure 4 Figure 9! <jJf Figure 5 Figure 6 35S Figure 7

Claims (1)

[Claims] 1. A structure in which an oxidizing gas flow or a fuel gas flow passes through the cylinder space of a cylindrical solid oxide fuel cell element, and the fuel gas or oxidizing gas comes into contact with the outer peripheral surface of the solid oxide fuel cell element. A solid oxide fuel cell according to the present invention, wherein a turbulent flow means for converting the oxidizing gas flow or the fuel gas flow into a turbulent flow is provided in the cylinder space.