JP2018200748A - Fuel cell unit - Google Patents

Abstract

To provide an internal reforming type fuel cell unit capable of improving reforming efficiency of fuel gas and efficiently supplying a reformed fuel gas to a fuel electrode.SOLUTION: The fuel cell unit includes: a unit cell structure in which a fuel electrode layer, an electrolyte layer, and an air electrode layer are laminated in order; and a pair of separators disposed on both sides of the unit cell structure. Then, a fuel gas flow path is formed by the separators disposed on the fuel electrode layer side of the unit cell structure and the unit cell structure. The separators disposed on the fuel electrode layer side have protrusions protruding into the fuel gas flow path. Since the protrusions have a reforming catalyst on their surfaces and a flow of the fuel gas flowing in the fuel gas flow path is disturbed, it is possible to efficiently supply the reformed fuel gas with improved reforming efficiency to the fuel electrode.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a fuel cell unit, and more particularly to a fuel cell unit capable of reforming fuel gas in a gas flow path.

  Solid oxide fuel cells (SOFCs) can be expected to have high conversion efficiency because they operate at high temperatures. They are also adaptable to fuel, and reformed gases such as methane and other hydrocarbon fuels can be modified with nickel catalysts. Internal reforming type power generation is possible in which power generation is performed while obtaining hydrogen by reforming in a fuel cell unit using a catalyst.

  Japanese Patent Laid-Open No. 10-92477 of Patent Document 1 has an oxidant gas flow path on one side of a separator, a fuel gas flow path on the other side, and the separator and cathode current collector plate. It is disclosed that a cathode convex portion to be brought into contact is provided, and an internal reforming catalyst is filled in a concave portion on the back surface side of the cathode convex portion.

  And according to the said separator, since an internal reforming catalyst does not disturb a flow path, it describes that the pressure loss with respect to the flow of gas can be decreased.

Japanese Patent Laid-Open No. 10-92477

  However, a fuel gas containing a gas to be reformed such as methane, other hydrocarbons or alcohol fuel and hydrogen gas (hereinafter sometimes simply referred to as “fuel gas”) forms a laminar flow to form a gas flow. Circulate in the street.

  Of the fuel gas flowing in a laminar flow, the gas to be reformed flowing on the separator side is reformed by the reforming catalyst carried on the separator to generate hydrogen gas, as shown in FIG. However, the gas to be reformed flowing on the fuel electrode side is not easily brought into contact with the reforming catalyst supported on the separator and is difficult to generate hydrogen gas, and the hydrogen gas flowing on the fuel electrode side is consumed at the fuel electrode. .

  Therefore, the fuel gas flowing in the fuel gas channel has a high hydrogen concentration on the separator side and a high concentration of the reformed gas on the fuel electrode side and a low hydrogen concentration. A gradient occurs.

  And the laminar flow in the gas flow path has a slow flow rate near the wall and a high flow rate near the center, and the hydrogen gas on the separator side flows along the separator, so the transport of the hydrogen gas flowing near the separator to the fuel electrode is Transport resistance is increased due to diffusion.

  Thus, even if the reforming catalyst is provided in the separator, the reformed gas is difficult to contact the reforming catalyst of the separator and the reforming efficiency is lowered, and the reformed hydrogen gas is difficult to reach the fuel electrode. The transportation loss increases and the power generation efficiency decreases.

  The present invention has been made in view of such problems of the prior art, and an object of the present invention is to improve the reforming efficiency for generating hydrogen gas from the reformed gas and to add hydrogen to the fuel electrode. An object of the present invention is to provide a fuel cell unit that can efficiently supply gas.

  As a result of intensive studies to achieve the above object, the present inventor has found that the above object can be achieved by providing a protrusion having a reforming catalyst in the fuel gas flow path to disturb the flow of the fuel gas, The present invention has been completed.

That is, the fuel cell unit of the present invention includes a single cell structure in which a fuel electrode layer, an electrolyte layer, and an air electrode layer are sequentially laminated, and a pair of separators disposed on both sides of the single cell structure,
Is provided.
The separator disposed on the fuel electrode layer side of the single cell structure and the single cell structure form a fuel gas flow path, and the separator disposed on the fuel electrode layer side includes the fuel gas flow path. It has a protrusion protruding inward, and the protrusion has a reforming catalyst on its surface.

  According to the present invention, since the protrusion having the reforming catalyst is provided in the fuel gas flow path and the gas flow is disturbed and stirred, the reforming efficiency and the hydrogen gas transport efficiency can be increased. A fuel cell unit with high efficiency can be provided.

It is a disassembled perspective view which shows an example of the fuel cell unit of this invention. FIG. 2 is a cross-sectional view taken along the line A-A ′ of FIG. 1, illustrating a layer configuration of the fuel cell unit according to the present invention. It is a perspective view which shows an example of the principal part of the separator which arrange | positioned protrusion in zigzag. It is a figure explaining the relationship between the plate | board surface of a plate-shaped protrusion, and the main flow direction. It is a figure explaining the arrangement | positioning state of the protrusion seen from the main flow direction. It is a figure explaining the laminar flow which flows through a fuel gas flow path.

The fuel cell unit of the present invention will be described in detail.
As shown in FIG. 1, the fuel cell unit FC includes a single cell structure 1 and a pair of separators 2 a and 2 b disposed on both sides of the single cell structure.

  The single cell structure 1 has an electrolyte electrode layer 12 in which a fuel electrode layer 121, an electrolyte layer 122, and an air electrode layer 123 are stacked in this order.

  The single cell structure may be any of a metal support type in which an electrolyte electrode layer is supported by a metal support in addition to an electrolyte support type, a fuel electrode support type, and an air electrode support type.

  In particular, since the fuel cell support type single cell structure has a relatively large amount of catalyst in the fuel electrode layer, it is possible to efficiently reform the reformed gas in the fuel gas. However, it is necessary to increase the thickness of the fuel electrode layer in order to increase the strength of the single cell structure.

In the present invention, since the protrusion having the reforming catalyst is provided in the fuel gas flow path of the single cell structure, the gas to be reformed can be efficiently reformed even in the case of a metal support type single cell structure. Is possible.
And since it is a metal support type | mold, the whole single cell structure can be reduced in weight by a metal support body, and also it can be set as a fuel cell unit excellent in rapid startability (warm-up) by improving thermal conductivity. A metal support type single cell structure in which the electrolyte electrode layer is supported by a metal support from the fuel electrode layer side is preferable.

Hereinafter, a metal support type will be described as an example. FIG. 2 is a cross-sectional view taken along the line AA ′ of FIG.
A fuel gas flow path 3 is formed between the metal support 11 and the separator 2a disposed on the metal support side, and between the electrolyte electrode layer 12 and the separator 2b disposed on the electrolyte electrode layer side. An oxidant gas flow path 4 is formed. The fuel gas flow channel 3 and the oxidant gas flow channel 4 may be divided by a wave-shaped separator to form a plurality of flow channels, and one flow channel is formed on the entire surface of the electrolyte electrode layer by a flat plate separator. May be formed.

A fuel gas containing a gas to be reformed such as methane or other hydrocarbon fuel flows in the fuel gas flow path 3 in the direction indicated by a large arrow in FIG.
In the present invention, the direction indicated by the large arrow in FIG. 2 and flowing from the gas inlet to the outlet is referred to as the main flow direction.

  In the fuel cell unit FC of the present invention, as shown in FIG. 2, the separator 2a disposed on the metal support side is formed with a protrusion 21 protruding into the fuel gas flow path. A reforming catalyst (not shown) is included in at least a part of these.

  Since the protrusion protrudes into the fuel gas flow path, the fuel gas forms a laminar flow in the main flow direction, and the fuel gas hits the protrusion 21 locally as shown by a small solid arrow in FIG. The direction of flow changes, and as shown by a small dotted arrow, it flows in the main flow direction as a whole while forming a turbulent flow.

  Therefore, even if the hydrogen concentration in the fuel gas is higher on the separator side and lower on the metal support side on the upstream side than the protrusion 21, it is stirred with turbulent flow on the downstream side of the protrusion 21. Therefore, the gradient of the hydrogen concentration in the fuel gas in the thickness direction of the fuel cell unit in the fuel gas flow path is reduced.

  Therefore, the hydrogen gas in the fuel gas easily reaches the fuel electrode, the reformed gas easily comes into contact with the reforming catalyst on the surface of the protrusion, and is easily reformed to hydrogen gas. The improvement of the transport efficiency and the improvement of the reforming efficiency with the reforming catalyst greatly improve the power generation efficiency.

  The position where the protrusion is provided in the fuel gas flow path only needs to stir the laminar flow flowing in the main flow direction in the fuel gas flow path, such as the bottom surface of the fuel gas flow path, that is, the surface facing the metal support of the separator, Although it can be provided on any of the side surfaces of the fuel gas flow path, it preferably protrudes toward the metal support.

  Since the protrusion protrudes from the bottom surface of the fuel gas channel toward the metal support, a flow toward the metal support occurs in the flow of the fuel gas. The flowing hydrogen gas is easily supplied to the fuel electrode.

It is preferable that a plurality of protrusions are arranged in a staggered manner in the main flow direction of the fuel gas. FIG. 3 shows a separator having protrusions arranged in a staggered manner.
As shown in FIG. 3, the fuel gas flowing in the main flow direction indicated by the arrow in FIG. 3 has a path to a certain projection by alternately arranging the projections at half the pitch between the plurality of projections. It is blocked. Of the flow of fuel gas that hits one protrusion, the flow deviated to the side without facing the direction of the metal support hits the front of the other protrusion, so the fuel gas is efficiently reformed and stirred, The reformed hydrogen gas is easily supplied to the fuel electrode.

  The shape of the protrusion is not particularly limited as long as the flow of the fuel gas can be stirred.

  Since the three-dimensional protrusion can be easily formed and a metal plate can be formed by press molding, the manufacturing process can be simplified and the cost can be reduced.

Further, if the protrusions are plate-like, the occupied volume in the fuel gas flow path can be reduced, and the plate surface of the plate-like protrusions resists the main flow direction of the fuel gas as shown in FIG. By disposing in the direction, the fuel gas can be greatly stirred.
The plate-like projection can be formed by cutting and raising a projection from a metal plate, overlapping the flat metal plate, and closing the cut and raised portion with the flat metal plate.

  As shown in FIG. 4, it is preferable that the angle α on the upstream side rising from the separator is an obtuse angle. If the angle on the upstream side of the protrusion is from right angle to an acute angle, stagnation is likely to occur near the upstream base of the protrusion, but if the angle α on the upstream side is obtuse, the fuel gas will flow without stagnation. You can quality.

  The protrusion can contact the metal support. FIG. 5 is a cross-sectional view taken along the line B-B ′ of FIG.

  As shown in FIG. 5, the protrusion provided on a part of the fuel gas channel is in contact with the metal support so as not to block the entire fuel gas channel, so that the fuel gas channel is formed of the electrolyte electrode layer. Even when one channel is formed on the entire surface, the single cell structure can be supported and conduction between the metal support and the separator can be obtained.

  The protrusion is preferably a spring. Due to the elastic deformation of the protrusion, even when the fuel cell unit is deformed due to heat during assembly or operation of the fuel cell unit, the protrusion supports the single cell structure and absorbs the displacement. Damage to the battery unit can be prevented.

  In particular, if the protrusion is a plate-like cantilever spring as shown in FIG. 3, it can be easily manufactured, and damage to the fuel cell unit can be prevented with a simple configuration.

  The reforming catalyst is provided on at least a part of the surface of the protrusion. The position where the reforming catalyst is provided is preferably provided upstream of the protrusion in the main flow direction. Since the fuel gas flowing in the main flow direction collides with the upstream side of the protrusion, the reforming efficiency is improved by providing the reforming catalyst on the upstream side of the protrusion.

  In addition, the reforming catalyst can be provided not only on the upstream side of the protrusions but also on the downstream side, and further, can be provided on the bottom and side surfaces of the fuel gas flow path and on the entire fuel gas flow path side of the separator. By providing the reforming catalyst on the upstream and downstream sides of the protrusions or the entire fuel gas flow path, the reforming area is increased, and more efficient reforming of the fuel gas is possible. Further, by providing the reforming catalyst on the separator side, it is possible to prevent carbon from being deposited on the metal support or the fuel electrode layer, which occurs when the reforming catalyst is provided on the metal support or the fuel electrode layer.

The reforming catalyst generates hydrogen gas from the gas to be reformed, and examples thereof include nickel, ruthenium, rhodium, etc., and those obtained by applying the nickel, ruthenium, rhodium, etc. to the support surface such as alumina. be able to.
The said reforming catalyst can be provided by apply | coating to a separator, and drying and baking.

  Here, each member which comprises the said single cell structure is demonstrated.

(Metal support)
The metal support supports the single cell structure.
As said metal support body, the metal porous body which has many continuous holes penetrated in the lamination direction can be used.

  Examples of the metal porous body include those obtained by solidifying metal particles or metal fibers by sintering or pressing, or those obtained by forming holes in a metal plate by etching or mechanical treatment, etc. Can be used.

  Examples of the metal material constituting the metal porous body include metal materials such as stainless steel, iron (Fe), nickel (Ni), copper (Cu), platinum (Pt), and silver (Ag). it can.

(Electrolyte electrode layer)
The electrolyte electrode layer is formed by sequentially laminating a fuel electrode layer, an electrolyte, and an air electrode layer, and generates power by an electrochemical reaction.

(Fuel electrode layer)
As the fuel electrode layer, a metal catalyst made of metal and / or alloy having hydrogen oxidation activity and stable in a reducing atmosphere can be used.

  Examples of the metal catalyst include nickel (Ni), palladium (Pd), platinum (Pt), ruthenium (Ru), Ni—Fe alloy, Ni—Co alloy, Fe—Co alloy, Ni—Cu alloy, Pd— Pt alloy etc. can be mentioned.

(Electrolyte layer)
As the electrolyte layer, an oxide having oxygen ion conductivity and functioning as a solid electrolyte can be used.

For example, YSZ (yttria stabilized zirconia: Zr _1-x Y _x O ₂ ), SSZ (scandium stabilized zirconia: Zr _1-x Sc _x O ₂ ), SDC (samarium-doped ceria: Ce _1-x Sm _x O _2), GDC (gadolinium doped _{ceria: Ce 1-x Gd x O} 2), LSGM ( lanthanum strontium magnesium _{gallate: La 1-x Sr x Ga} 1-y Mg y O 3) , and the like.

(Air electrode layer)
Examples of the constituent material of the air electrode layer include perovskite oxides.
Examples of the perovskite oxide include perovskite oxides (for example, LSCF (lanthanum strontium cobalt iron oxide), LSM (lanthanum strontium manganese oxide), and the like.

  The electrolyte electrode layer can be formed by laminating on one surface of the metal support. The method for laminating the electrolyte electrode layer may be either a dry method or a wet method.

  In the fuel cell unit of the present invention, the fuel gas is agitated and flows by the protrusion having the reforming catalyst, so that the reforming efficiency of the fuel gas and the transport efficiency of the hydrogen gas are improved and the power generation efficiency is improved.

FC fuel cell unit 1 single cell structure 11 metal support 12 electrolyte electrode layer 121 fuel electrode layer 122 electrolyte layer 123 air electrode layer 2a separator 2b separator 21 protrusion 3 fuel gas flow path 4 oxidant gas flow path

Claims (11)

A single cell structure in which a fuel electrode layer, an electrolyte layer, and an air electrode layer are sequentially laminated;
A pair of separators disposed on both sides of the single cell structure;
A fuel cell unit comprising:
A fuel gas flow path is formed by the separator disposed on the fuel electrode layer side of the single cell structure and the single cell structure,
The separator disposed on the fuel electrode layer side has a protrusion protruding into the fuel gas flow path,
The fuel cell unit, wherein the protrusion has a reforming catalyst on a surface thereof.   2. The fuel cell unit according to claim 1, wherein the protrusion is a flow changing unit that locally changes the flow of the fuel gas in a direction different from the main flow direction of the fuel gas.   The fuel cell unit according to claim 1, wherein the protrusion protrudes in the direction of the single cell structure.   The fuel cell unit according to any one of claims 1 to 3, wherein a plurality of the protrusions are provided, and the protrusions are arranged in a staggered manner in the main flow direction of the fuel gas.   The fuel cell unit according to claim 1, wherein the protrusion has a conical shape.   The fuel cell unit according to any one of claims 1 to 5, wherein the protrusion is plate-shaped, and the plate surface is disposed in a direction against the flow of fuel gas.   The fuel cell unit according to any one of claims 1 to 6, wherein the upstream angle at which the protrusion rises from the separator is an obtuse angle.   The fuel cell unit according to any one of claims 1 to 7, wherein the protrusion has the reforming catalyst on upstream and downstream surfaces.   The fuel cell unit according to claim 1, wherein the protrusion is in contact with the single cell structure.   The fuel cell unit according to claim 1, wherein the protrusion is a spring.   The fuel cell unit according to any one of claims 1 to 10, further comprising a metal support, wherein the single cell structure is supported by the metal support from the fuel electrode layer side.

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