JPH04303566A - Solid electrolyte fuel cell - Google Patents

Abstract

PURPOSE:To prevent the mixture of air with fuel gas due to air or fuel gas leakage resulting from sealing deterioration during operation, to perform good gas flow distribution, to improve generating capability and to simplify manufacture of an electrode. CONSTITUTION:Provided are fuel battery cells, air and fuel gas feed and exhaust manifolds 7, 9 and 8, 10 and inactive gas filling manifolds 11, 12, which are installed on one side and the other side, respectively, of the periphery of each separator 6 to partition the cells in stack. Gas passages 13, 14 are formed between an air pole 2 and the separator 6 and between a fuel pole 3 and the separator 6, respectively. Inactive gas filling grooves 15a, 15b, 16a, 16b are provided on the periphery of the fuel gas F feed and exhaust manifolds 8, 10 which are installed on the air pole 2 and on the periphery of the air feed and exhaust manifolds 7, 9 which are installed on the fuel pole 3.

Description

[Detailed description of the invention]

0001

[Field of Industrial Application] The present invention relates to fuel cells used in the energy sector for directly converting the chemical energy of fuel into electrical energy, and particularly to a flat solid oxide fuel cell using a solid electrolyte. .

0002

[Prior Art] Solid oxide fuel cells are a third generation fuel cell that replaces second generation molten carbonate fuel cells.
Studies are currently underway for its development.

[0003] Solid oxide fuel cells that are currently being studied include flat plate types and cylindrical types. Among these, an example of a flat plate type solid oxide fuel cell is shown in Fig. 6. For example, an air electrode 2 and a fuel electrode 3 are stacked on both sides of an electrolyte plate 1 to which an yttria-stabilized zirconia-based ionic conductor is applied, and a gas passage 4a is provided on the air electrode 2 side and the fuel electrode 3 side. Gas passage forming bodies 4 and 5 are arranged to form gas passages 5a and 5a, and air (O2 gas) is supplied to the gas passage 4a of the air electrode 2, and fuel gas (H2 gas) is supplied to the gas passage 5a of the fuel electrode 3. ) so that the oxygen ions O-- generated by the reaction on the air electrode 2 side reach the fuel electrode 3 side through the electrolyte plate 1. On the other hand, on the fuel electrode 3 side, the above-mentioned fuel gas H2 and The above oxygen ion O--
There is a structure in which one cell C is made up of a cell C in which H2 O is released as water H2O, and such a cell C is laminated in multiple layers with a separator 6 interposed therebetween to form a stack.

[0004] The above-mentioned flat plate type solid oxide fuel cell can produce a large amount of electric power with a small volume, and the thinner the cell C is, the more compact it can be when stacked. There is a characteristic that it can be obtained, especially,
The thinner the electrolyte plate 1 is, the better the passage of oxygen ions O-- can improve performance.

However, the conventional flat plate solid oxide fuel cell shown in FIG. 6 has a structure in which gas passages 4a and 5a are formed on each surface of the air electrode 2 and the fuel electrode 3. If an attempt is made to reduce the thickness of the cell C by making the fuel electrode 3 and the electrolyte plate 1 thinner, the flow of gas through the gas passages 4a and 5a will deteriorate, and the connection between the air electrode 2 and the fuel electrode 3 and the electrolyte plate 1 will deteriorate. If the contact is poor, the conductivity of electrons (or current) will be poor, and if the electrolyte plate 1 is made thinner than 100 μm for the purpose of improving the conductivity of oxygen ions O--, it will need to be supported. The air electrode 2 and fuel electrode 3 that support the electrolyte plate 1 are required to have strength, but in conventional systems, both the air electrode 2 and the fuel electrode 3 have a structure in which the uneven surfaces are in contact with the electrolyte plate 1. Therefore, electrolyte plate 1
There are problems such as the inability to support and provide strength.

[0006] In order to solve this problem, the air electrode 2
Alternatively, the fuel electrode 3 is made porous so that gas can pass therethrough, or a large number of through holes are provided in parallel inside the air electrode 2 and the fuel electrode 3, and the through holes are used as gas passages. By making the outer surface of each electrode smooth in this manner, the electrolyte plate 1, which is a thin film of 100 to 200 μm, can be reliably supported.

[0007]

[Problems to be Solved by the Invention] However, there is a problem in flowing gas through a porous electrode, and the gas flow is poor.
On the other hand, when providing through holes in parallel inside the air electrode 2 and fuel electrode 3, it is not only difficult to make holes inside the air electrode 2 and fuel electrode 3 with a thickness of 1 to 2 mm, but also for each electrode. It is necessary to provide a header part at one end of the battery, but this is also difficult, and furthermore, the header part on the air electrode 2 side is attached to the air supply manifold installed outside the battery, and the header part on the fuel electrode 3 side is also attached to the air supply manifold. Since it is necessary to connect each to the fuel gas supply manifold provided outside the battery, there are problems with the fabrication of the electrodes, the structure of the manifold is complicated, and gas passages are not secured. Otherwise, there are problems such as poor gas distribution and difficulty in improving power generation performance. Furthermore, in this type of solid oxide fuel cell, air and hydrogen as fuel flow, so if these gases leak from the flow path and come into contact with each other, there is a risk of combustion or explosion.

Therefore, the present invention provides a structure that can reliably and firmly support an electrolyte plate having a thin film structure, improves power generation performance by improving gas flow distribution, and is easy to manufacture. In addition, the structure of the manifold part is simplified, and even if a gas leak occurs in the manifold part, the flat plate type solid electrolyte fuel can be maintained by preventing contact between air and fuel gas. The aim is to provide batteries.

[0009]

[Means for Solving the Problems] In order to solve the above problems, the present invention sandwiches an electrolyte plate between an air electrode and a fuel electrode from both sides, and allows air to flow to the air electrode side and fuel gas to flow to the fuel electrode side. In a configuration in which each cell is stacked in multiple layers with a separator in between, air and fuel gas are supplied to both one side and the other side of the periphery of the cell and separator. A gas passage that forms a discharge manifold and a manifold for filling inert gas, and connects the air supply manifold and the discharge manifold between the air electrode and the separator of each cell. On the other hand, a gas passage is formed between the fuel electrode and the separator of each of the cells to communicate the fuel gas supply manifold and the exhaust manifold, and a gas passage is formed between the front and back of the air electrode of each of the cells. An inert gas filling groove is formed surrounding each fuel gas supply/discharge manifold and each air supply/discharge manifold on the front and back sides of the fuel electrode of each cell, and each inert gas filling groove is , and communicates with the manifold for charging the inert gas, so that the pressure of the inert gas is higher than the pressure of the air and fuel gas.

[0010] The gas passages may be formed by providing grooves on the surfaces of the air and fuel electrodes on the separator side, or may be formed by providing unevenness on both surfaces of the separators. .

[0011]

[Operation] Since it is an internal manifold type, air flows from the air supply manifold through the gas passage between the air electrode and the separator and is discharged from the discharge manifold on the opposite side. On the other hand, the fuel gas flows from the fuel gas supply manifold through the gas passage between the fuel electrode and the separator and is discharged from the discharge manifold on the opposite side. There are grooves filled with inert gas under high pressure around the air electrode fuel gas supply and discharge manifold and the fuel electrode air supply and discharge manifold.
Even if air or fuel gas leaks from the air or fuel gas supply/discharge manifold due to deterioration of sealing properties during fuel cell operation, high-pressure inert gas will flow to the air or fuel gas side. This can prevent contact between air and fuel gas. Furthermore, at the same time, the inert gas flows out and the sealing pressure of the inert gas decreases, making it possible to detect a leak.

Since the air and fuel gas flowing through each cell pass through the gas passages, the gas flow is good, and the smooth outer surfaces of the air electrode and fuel electrode are brought into contact with and supported by the electrolyte plate. This improves the passage of electrons (electricity) from the air electrode to the electrolyte plate, promoting reactions and improving electrochemical performance (power generation performance).

[0013]

Embodiments Hereinafter, embodiments of the present invention will be described with reference to the drawings.

1 to 5 show an embodiment of the present invention, in which an electrolyte plate 1 having a thin film structure having a thickness of 100 to 200 μm is sandwiched between an air electrode 2 and a fuel electrode 3 from both sides. One cell C is configured to supply air to the 2 side and fuel gas to the fuel electrode 3 side, and each cell C is stacked in multiple layers with a separator 6 in between. , a manifold 7 for supplying air A and a manifold 8 for supplying fuel gas F are provided on one side of the periphery of the electrolyte plate 1, and a manifold 9 for discharging air and a manifold 9 for discharging fuel gas are provided on the other side of the periphery. A discharge manifold 10 is provided, and a discharge manifold 10 is provided between manifolds 7 and 8 on one side of the periphery and manifolds 9 and 1 on the other side of the periphery.
0, manifolds 11 and 12 for sealing inert gas (nitrogen gas or argon gas) are provided. The air electrode 2 and the fuel electrode 3 are porous ceramic sintered bodies, and air and fuel gas supply/discharge ports provided on the electrolyte plate 1 are provided on one side and the other side of their respective peripheries. Manifold 7
, 8, 9, 10 and an inert gas filling manifold 11,
12, manifolds 7 and 9 for supplying and discharging air, manifolds 8 and 10 for supplying and discharging fuel gas, and manifolds 11 and 12 for filling in inert gas are provided, and around the separator 6 that partitions the cell C. Similarly, manifolds 7 and 9 for supplying and discharging air, manifolds 8 and 10 for supplying and discharging fuel gas, and manifolds 11 and 12 for filling in inert gas are provided on one side and the other side of the cell C as a separator. Each manifold 7, 8, 9, 10 and 11 when stacked through 6
, 12 are communicated in the stacking direction to form a series of flow paths. On the surface of the air electrode 2 opposite to the surface in contact with the electrolyte plate 1 (the surface on the separator 6 side), a large number of grooves 13a are provided in the center so as to extend in parallel from one side to the other.
and a bent groove 13 which is bent at both ends so as to concentrate the air in the supply manifold 7 and the discharge manifold 9.
A gas passage 1 connecting the manifolds 7 and 9 from
3, and similarly, on the surface of the fuel electrode 3 opposite to the surface in contact with the electrolyte plate 1 (the surface on the separator 6 side), a plate was provided in the center so as to extend in parallel from one side to the other side. Multiple grooves 1
4a and bent grooves 14b which are bent at both ends so that the fuel gas is concentrated in the supply manifold 8 and the discharge manifold 10, forming a gas passage 14 that communicates the manifolds 8 and 10, and Air A on the side and fuel gas F on the fuel electrode 3 side flow in parallel at the center,
Furthermore, around the manifolds 8 and 10 for supplying and discharging fuel gas on both the front and back surfaces of the air electrode 2, the manifolds 8,
Inert gas filling grooves 15a and 15 surround 10.
At the same time, inert gas filling grooves 16a and 16b are formed around the manifolds 7 and 9 for supplying and discharging air on both the front and back surfaces of the fuel electrode 3 so as to surround the manifolds 7 and 9. Then, the inert gas filling grooves 15a and 16a are connected to the inert gas filling manifold 11.
Furthermore, the inert gas filling grooves 15b and 16b are communicated with the inert gas filling manifold 12, and each inert gas filling groove 15a, 15b, 16a, 16b is filled with air A or fuel gas F. An inert gas is sealed at a pressure higher than that of the stack, and an inert gas filling pressure measuring device (not shown) is installed outside the stack.

Air (O2 gas) supplied to the air electrode 2
A is introduced into the gas passage 13 from the air supply manifold 7, and while flowing through the gas passage 13, oxygen is reduced by reaction and concentrated in the air discharge manifold 9,
It is discharged from the discharge manifold 9. During this time, oxygen ions O-- generated by reaction from air (O2 gas) that has passed through the air electrode 2 as a porous body and reached the electrolyte plate 1 are allowed to reach the fuel electrode 3 through the electrolyte plate 1. On the other hand, on the fuel electrode 3 side, fuel gas (H2 gas) F
is introduced from the fuel gas supply manifold 8 into the gas passage 14, and while flowing through the gas passage 14, oxygen ions O--
After being reacted with, the water is discharged from the discharge manifold 10 as water (containing some unreacted hydrogen).

In the above, when the cell C consisting of the electrolyte plate 1 sandwiched between the air electrode 2 and the fuel electrode 3 is stacked in multiple layers with the separator 6 in between, as shown in FIG. 9. Fuel gas F supply/discharge manifold 8,1
0 is a continuous flow path in the stacking direction, and for each cell C, air A is guided from the supply manifold 7 through the gas passage 13 to the discharge manifold 9, and fuel gas F is guided from the supply manifold 8 through the gas passage 14. The air is guided to the exhaust manifold 10 through the air supply and exhaust manifolds 7 and 9.
The sealability of the manifold part is important because if a leak occurs at the part or the part of the manifolds 8 and 10 for supplying and discharging fuel gas, and if air and fuel gas come into contact, there is a risk of combustion or explosion. During the operation of the solid oxide fuel cell, the air supply and exhaust manifold 7,
If an air or fuel gas leak occurs at the part 9 or the fuel gas supply/discharge manifolds 8 and 10,
Solid oxide fuel cells that have been proposed so far have the problem of mixing air and fuel gas due to leakage, but in the present invention, the air electrode 2 side has a structure around the manifolds 8 and 10 for supplying and discharging fuel gas F. Inert gas filling grooves 15a and 15b
In addition, inert gas filling grooves 16a and 16b are provided around the air A supply/discharge manifolds 7 and 9 on the fuel electrode 3 side, and the pressure of the sealed inert gas is adjusted to the air or Since the pressure is higher than that of the fuel gas,
Even if air or fuel gas leaks due to deterioration of sealing performance or the like, mixing of air and fuel gas due to the leak can be prevented. That is, if fuel gas leaks from the supply/discharge manifolds 8, 10 on the air electrode 2 side, the inert gas such as nitrogen or argon sealed in the inert gas filling grooves 15a, 15b will become under pressure. Due to the difference, the fuel gas flows to the manifolds 8 and 10 side, which prevents mixing of fuel gas and air.Also, even if air leaks on the fuel electrode 3 side, the air flows to the manifold 7 side. , 9 around the inert gas filling groove 16a,
The inert gas sealed in 16b will instead flow into the air manifolds 7 and 9, and mixing of air and fuel gas can be prevented. This can prevent combustion and explosion caused by mixture of fuel gas and air due to leakage. In addition, when the air or fuel gas leaks, the sealed inert gas flows into the air or fuel gas manifold, resulting in a drop in the sealed gas pressure. The occurrence of leakage of air or fuel gas can be detected by detecting it with an inert gas filling pressure measuring device (not shown).

[0017] In the above embodiment, the inert gas is filled in the inert gas filling grooves 15a, 16a and 15b, 16b every several layers of the cell C. Now, connect the gas passages 13 and 14 to the air electrode 2.
Although the above example shows the case in which these are formed on each side of the fuel electrode 3, it is also possible to form them separately on both the front and back sides of the separator 6, and the gas leak countermeasure adopted in the present invention is suitable for use in solid oxide fuel cells. Of course, it is also effective when applied to hydrogen production equipment and other places where hydrogen and oxygen may mix.

[0018]

[Effects of the Invention] As described above, according to the solid oxide fuel cell of the present invention, the cell is formed by sandwiching an electrolyte plate between an air electrode and a fuel electrode from both sides, and is stacked in multiple layers with a separator in between. In one configuration, air and fuel gas supply/discharge manifolds and inert gas filling manifolds are formed on one side and the other side of the periphery of the cell and the separator, and between the air electrode and the separator, A gas passage communicating between an air supply manifold and an air discharge manifold is formed so that both ends of the gas passage are concentrated in the supply and discharge manifold, and similarly, between the fuel electrode and the separator, A gas passage is formed that communicates the fuel gas supply manifold and the discharge manifold, and the gas passage is also concentrated at both ends in the supply and discharge manifold, and the fuel gas formed in the air electrode is Inert gas filling grooves are formed surrounding each manifold for supplying and discharging air, and around each manifold for supplying and discharging air formed in the fuel electrode, and the inert gas Since the structure is such that an inert gas having a pressure higher than that of air or fuel gas is sealed from the filling manifold to the inert gas filling groove, the following excellent effects can be achieved. (i) If air or fuel gas leaks from the manifold due to deterioration of sealing performance during operation, and there is a risk that air and fuel gas may mix due to the leak on the air electrode side or fuel electrode side, use an inert gas The inert gas sealed in the sealing groove flows into the air or fuel gas manifold side due to the pressure difference, which prevents air and fuel gas from mixing, and prevents the risk of combustion or explosion due to the mixing of the two. It can be prevented. (ii) The inert gas sealed in the inert gas filling groove is
When the leaked air or fuel gas flows into the manifold side, the pressure of the enclosed inert gas decreases, so that a leak in the fuel cell stack can be detected by this pressure decrease of the inert gas. (iii) Since the air electrode and fuel electrode can be brought into close contact with the electrolyte plate over the entire surface to ensure good contact, oxygen ions from the air electrode side pass through the electrolyte plate and are absorbed into the fuel. Electrons (electricity) as they reach the poles
Not only can the conductivity of the gas be improved, but also gas passages can be ensured to improve gas circulation, which can promote reactions and improve performance. (iv) Since the contact between the electrolyte plate and the electrode in (iii) above is improved, even if the electrolyte plate is a thin film, it can be strongly supported, and gas passages can be formed inside the electrode. Since there is no porosity, the manufacturability of the electrode can be improved. (v) Since the manifold is provided in the peripheral portion and the gas passages are concentrated in the manifold, the structure of the manifold portion can be simplified.

[Brief explanation of drawings]

FIG. 1 is a perspective view showing one embodiment of a solid oxide fuel cell of the present invention.

FIG. 2 is an exploded perspective view of FIG. 1;

FIG. 3 is a plan view of the air electrode.

FIG. 4 is a plan view of an electrolyte plate.

FIG. 5 is a plan view of the fuel electrode.

FIG. 6 is a schematic perspective view of a conventional solid oxide fuel cell.

[Explanation of symbols]

1 Electrolyte plate 2 Air electrode 3 Fuel electrode 6 Separator 7 Air supply manifold 8 Fuel gas supply manifold 9 Air discharge manifold 10 Fuel gas discharge manifold 11, 12 Inert gas filling manifold 13, 1
4 Gas passages 15a, 15b, 16a, 16b Inert gas filling groove C Cell A Air F Fuel gas

Claims (1)

[Claims] [Claim 1] An electrolyte plate is sandwiched between an air electrode and a fuel electrode from both sides, and air is allowed to flow to the air electrode side, and fuel gas is allowed to flow to the fuel electrode side, respectively, as one cell, and each cell is separated by a separator. In a solid oxide fuel cell that is stacked in multiple layers, manifolds for supplying and discharging air and fuel gas are formed on both one side and the other side of the periphery of the cell and separator, as well as manifolds for supplying and discharging inert gas. A gas passage is formed between the air electrode of each cell and the separator to communicate the air supply manifold and the exhaust manifold; A gas passage is formed in between to communicate the fuel gas supply manifold and the discharge manifold, and furthermore, a gas passage is formed between each of the fuel gas supply and discharge manifolds formed at the air electrode of each cell, and each cell. An inert gas filling groove is formed surrounding each manifold formed in the fuel electrode for supplying and discharging air, and each inert gas filling groove is communicated with the inert gas filling manifold to fill the inert gas. A solid electrolyte fuel cell characterized by having a configuration in which active gas is sealed at a higher pressure than air and fuel gas.