JP2002151106A - Fuel cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an SOFC simplifying the piping line of cells by collecting, having stack structure reducing the unburned gas as low as possible to enhance power generating efficiency, and uniformizing the flow or distribution of air and fuel gas in the cell to suppress generation of thermal stress. SOLUTION: A fuel gas passage is installed in the central part between disks stacked at the specified intervals, a ring-shaped separator made of metal is arranged between the disks, a space between the disks is divided into two horizontal planes to form a circular chamber type cell reaction passage being connected to the fuel gas passage and an air passage opened on the outer circumferential side, and the cell reaction passage and the air passage are arranged on both sides of the disk to be stacked to constitute the cell, and the cells are stacked.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a solid oxide fuel cell (Solid Oxide Fuel Cell).
s, hereinafter abbreviated as SOFC), a structure in which a large number of cells formed by disks stacked at predetermined intervals can be connected in series and in series, and the reaction of fuel gas is repeated in a closed loop to complete combustion. A disk stack structure that can greatly improve power generation efficiency, increase the resistance to thermal stress that occurs during high-temperature operation, and use metal materials as interconnect materials to enhance electrical conduction and improve battery performance. The present invention relates to a fuel cell having a basic configuration.

[0002]

2. Description of the Related Art The configuration of a SOFC that is currently in practical use includes a cermet porous body of nickel and yttria-stabilized zirconia as a fuel electrode, yttria-stabilized zirconia as a fixed electrolyte, lanthanum manganite as an air electrode, and an interconnect material. There is a so-called cylindrical SOFC in which a stack unit is formed by bundling a large number of cylindrical cells having one end closed using lanthanum chromite.

Further, a cell in which a fuel electrode made of a plate-shaped porous body, an electrolyte, and an oxygen electrode made of a porous body are sequentially stacked is sandwiched between dense interconnect plates, and these cells are stacked and arranged. Flat-plate SOFCs have been put to practical use.

[0004] The basic configuration of fuel cell power generation includes a fuel reformer, a battery body, and an inverter that converts direct current generated from the battery into alternating current as described above. SOFCs use hydrogen (H ₂ ) as a fuel in addition to hydrogen (H ₂ ). It is said that methane (CH ₄ ) or the like can be taken as fuel, and that the fuel gas can be reformed (internal reforming) also in the battery section. That is, the remaining unburned gas reacted in the battery is burned, and the heat of combustion can be used for the reforming reaction (endothermic reaction).

[0005]

The SOFC is expected to have a power generation efficiency of 50% or more due to its high heat utilization efficiency. Further, since the operating temperature of the battery is as high as 1000 ° C., the exhaust heat thereof can be reduced. It is considered that application to a cogeneration system in which high-temperature steam is recovered by a steam recovery device can be expected.

[0006] The cells are generally formed of solid ceramics in consideration of heat resistance. In addition, the cells are bundled or arranged in a stack for power generation efficiency. There is a need for measures against cracking.

The flat type SOFC can increase the cell density. However, because of the laminated structure, it is necessary to reduce the difference in the coefficient of thermal expansion of each part of the cell and the variation in the temperature distribution in the plane direction to improve the thermal cycle resistance. Is important, and there is basically a problem of poor thermal cycle resistance.

[0008] The cylindrical SOFC has a feature in that, when adopting a configuration in which only the upper end of the cell is fixed, the expansion and contraction in the longitudinal direction of the cylinder with respect to thermal cycle resistance is highly reliable. However, the structure in which a large number of cylindrical cells are bundled and arranged, and the structure in which air and fuel flow efficiently are complicated, space utilization efficiency is low, space is required, and power output is low due to poor electric conduction of ceramic materials. It is necessary to take special measures such as sandwiching nickel felt for electrical connection.

[0009] The SOFC burns the remaining unburned gas reacted by the battery and uses the combustion heat for the reforming reaction. The SOFC is combined with a gas turbine to provide a high-efficiency power generation system, and furthermore, the waste heat to recover steam. A configuration has been proposed in which a system for collecting high-temperature steam by a vessel is used. However, an SOFC having a configuration for reducing unburned gas in fuel gas has not been proposed.

An object of the present invention is to provide a basic configuration that can extremely simplify a cell piping system. Further, the present invention provides a SOFC having a stack structure for greatly reducing unburned gas in order to greatly improve power generation efficiency.
The purpose is to propose. Another object of the present invention is to propose an SOFC having a configuration in which the flow and distribution of air and fuel gas in a cell are made uniform and thermal stress is hardly generated.

[0011]

The inventor of the present invention has conducted various studies on the cell configuration for the purpose of achieving a stack structure capable of repeatedly burning fuel gas. As a result, the fuel cell penetrates through the central portion between disks stacked at a predetermined interval. A fuel gas passage is provided, a ring-shaped plate separator made of metal is arranged between the disks, and the spaces between the disks are divided into two parts by a horizontal plane to form an annular chamber type cell reaction passage connected to the fuel gas passage and an outer periphery. Open air passage can be formed on the part side,
It has been found that the configuration of the cells in which the battery reaction passage and the air passage are arranged sandwiching each disk to be stacked can be arranged in a stack.

The inventor of the present invention accommodates a stack unit in which disks are stacked and arranged in a cylinder, so that air can pass upward between the inner peripheral surface of the cylinder and the outer periphery of the stack unit. It is easy to introduce and discharge air into the open air passage, and fuel gas can be introduced and discharged from the center between the disks into the annular chamber type cell reaction passage. It has been found that it is possible to collect the fuel gas without taking it out and to make the battery react repeatedly and again, and to aim at complete combustion of the fuel gas.

Further, the inventor of the present invention arranges a number of disks horizontally stacked and arranged, and a metal separator which is divided into two by a horizontal plane between the disks, and further has a ring having dimples between the metal separator and the disks. By arranging a plate-shaped metal path separator and forming a battery reaction passage and an air passage as a reciprocating path capable of making a U-turn, two kinds of metal separators are arranged between disks as an interconnect material, and a stacked stack is formed. The cell compressive strength at the time can be good electrical conduction,
Since it is symmetrical in the radial direction of the disk around the fuel gas passage communicating vertically, the flow and distribution of air and fuel gas in the cell can be made uniform, the temperature distribution is uniform in the radial direction, and the heat The present inventors have found that the configuration is such that thermal stress and the like due to expansion are less likely to occur and thermal stress is hardly generated, and the present invention has been completed.

That is, according to the present invention, the fuel and the combustion gas pass through the central portion between the disks of a stack unit in which a required number of disks are stacked at a predetermined interval and communicate with each other in the radial direction between the disks and the disk stacking direction. Means for distributing and introducing fuel gas for forming a passage are arranged, and each disk-facing surface is divided into two parts on the outer peripheral side of the distributing introduction and discharge means between the disk-facing surfaces to form a fuel gas cell reaction passage. A fuel cell comprising a ring plate-like separator for forming an air passage, and means for allowing air to be introduced and discharged from an outer peripheral end of the stacked disks.

The present invention is also directed to the above structure, wherein: a ring plate-shaped path separator is arranged in the battery reaction passage and the air passage to form a reciprocating passage in the passage; A structure in which a metal or alloy material such as a stainless steel material or an Fe-Cr-W alloy material is selected as the material of the pass separator, and a means for distributing and introducing and discharging the fuel gas, which forms a fuel gas passage at the center of the disk. An axial through-hole, a plurality of combustion gas passages on the outer peripheral side of the through-hole in a direction parallel to the central axis, and a distribution inlet / outlet passage and a discharge inlet / outlet passage provided in the radial direction of the disk, and the through-holes are respectively provided. Or a configuration in which the fuel electrode and the air electrode are formed on both main surfaces of a disk made of a material containing an electrolyte. A structure in which the combustion gas passage on the outlet side of the flow-side unit is connected to the fuel gas passage on the inlet side of the downstream unit, and one or more stack units are arranged in the cylinder, and the fuel gas flows through the center of the cell. Through which the air passes through the cylinder.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the structure of the present invention will be described.
This will be described in detail with reference to the drawings. The fuel cell of the present invention shown in FIG. 1A is characterized in that thin disks 1 made of a known fixed electrolyte material or a porous base carrier capable of moving hydrogen or oxygen are stacked and used. The disk 1 may have a disk shape or a polygonal plate shape.

Here, it is a means for distributing and introducing and discharging fuel gas for forming a fuel and combustion gas passage.
As shown in FIGS. 1B and 1C, a short cylindrical passage member 10,
A disc 11 having a through hole 12 in the center and a passage hole formed in a predetermined pattern around the through hole 12 is laminated with the center axis thereof aligned.

Further, a ring plate for forming a fuel gas cell reaction passage 2 and an air passage 3 by dividing the space between each disk 1 facing surface into two portions on the outer peripheral side of the distribution introducing and discharging means between the disk 1 facing surfaces. Ring-shaped separators 20, 31 for vertically dividing the separators 20 into the battery reaction passage 2 and the air passage 3.
Is arranged.

The ring plate separator 20 is made of metal here and has flange portions 21 and 22 formed on the inner peripheral side and the outer peripheral side as shown in FIG. 1A, respectively. The space between the opposing surfaces is configured so that the space between the opposing surfaces of the disk 1 can be horizontally divided into two. In addition, the flange portions 21 and 22 are connected to the separator 2.
It has a function of joining and sealing the disk 0 and the disk 1. Further, the flange portions 21 and 22 may be shaped to seal with the passage members 10 and 11.

Ring plate-shaped path separators 30, 31
Is made of metal and has dimples 3 as shown in FIG. 1A.
2 is formed in a required pattern so as to fit between the opposing surfaces of the separator 20 and the disk 1, whereby the gap can be divided into two vertically. The passages divided by the path separators 30 and 31 form a reciprocating passage through which the fluid can make a U-turn.

The pass separator 30 in the fuel gas cell reaction passage 2 is connected to the separator 20 and the disk 1.
And between the opposing surfaces. Further, as shown in FIG. 3, the path separator 31 arranged in the air passage 3 is increased in outer diameter so as to be in contact with the inner peripheral surface of the cylindrical body 40 in which the fuel cell is housed. Unit 50
The air rising between the outer peripheral portion of the cylindrical body 40 and the inner peripheral surface of the cylindrical body 40 is taken into the air passage 3, and the path separator 31 forms a reciprocating passage and can be discharged. Further, as shown in FIG. 3, the outer peripheral portion of the pass separator 31 can be swaged by a bolt 34 shown in a simplified manner, and a bolt hole 35 can be provided in the outer peripheral portion of the pass separator 31.

The short cylindrical passage members 10 and 11 shown in FIGS. 1B and 1C have a through hole 12 in the center axis direction forming a fuel gas passage in the center of the disk 1 and a center axis on the outer peripheral side of the through hole 12. A plurality of combustion gas passages 13 are provided in a parallel direction, and a distribution introduction hole passage 14 and a discharge hole passage 15 are provided in the radial direction of the disk 1 and connected to the through hole 12 or the combustion gas passage 13 respectively.

The arrangement of the distribution introduction passage 14 and the discharge passage 15 in the radial direction of the disk 1 in the passage members 10 and 11 is as follows.
Depending on the configuration of the battery reaction passage 2 and the path separator 30, the fuel cell can be appropriately selected so that the fuel can be uniformly dispersed and introduced into and out of the battery reaction passage 2 arranged in a ring shape.

The fuel gas flows down through the through-holes 12 of the passage members 10 and 11 and enters the battery reaction passage 2 from the distribution / introduction passage 14 and makes a U-turn around the outer periphery of the disk 1 to discharge passages 15 of the passage member. From the combustion gas passage 13.

Here, it is possible to form a fuel cell by forming the disk 1 from a known fixed electrolyte material or the like and forming a fuel electrode on the upper surface and an air electrode on the lower surface from a known material. it can.

Further, the disk 1 can be formed of a porous base carrier through which hydrogen can move, and a fuel cell can be formed by sequentially forming a fuel electrode, an electrolyte membrane, and an air electrode on the upper surface. In the case of using a porous base carrier through which oxygen can move, a fuel cell can be formed by sequentially forming an air electrode, an electrolyte membrane, and a fuel electrode on the lower surface of the disk.

In selecting any of the base carrier material and the membrane material, a material having a similar thermal expansion coefficient to the material should be selected so as to take into account a difference in thermal expansion coefficient.

As described in detail above, a ring-shaped plate separator 20 made of metal is arranged between the disks 1, and the space between the disks 1 is divided into two parts by a horizontal plane to form a battery reaction passage 2 and an air passage 3. The cell structure in which the battery reaction passages 2 and the air passages 3 are arranged sandwiching each disk 1 to be stacked has a structure in which the cells are stacked. Can be introduced.

The fuel cell of FIG. 1 having a configuration in which cells according to the number of stacked disks 1 are stacked is arranged to flow down a through hole 12 (closed at the lower end of the cell) of a fuel gas passage at the center. The fuel is distributed and introduced into each cell reaction passage 2, and a cell reaction occurs with air introduced from the outer peripheral side of the disk 1, and the combustion gas flows down the combustion gas passage 13 at the center of the disk.

Here, as shown in the conceptual diagram of FIG. 4, when the stack units S1 and S2 of the cells are connected in series, the combustion gas passage 13 of the upper stack unit S1 is connected.
Through the through-holes 12 serving as lower fuel gas passages.
The fuel gas F once reacted can be reacted again to achieve complete combustion.

The fuel cell of the present invention shown in FIG. 2A is basically the same as the configuration of FIG. 1, except that the configuration of the separator 23 is changed. That is, here, the disk-shaped separator 2 having a hole corresponding to the passage unit at the center is provided.
3, the sealing of the battery reaction passage 2 is ensured by arranging a ring member 4 made of the same material as the disc material between the outer peripheral ends of the separator 23 and the disc 1 and joining them. .

When the disk-shaped separator 23 is used, only the path separator 31 having the dimples 32 arranged in the air passage 3 is laminated and arranged so that the disc 1 when the whole is closely adhered in the axial direction. Since there is a concern that the outer peripheral side strength is reduced, as shown in FIG. 2B, the strength can be maintained by arranging the support members 5 and 5 with the path separator 31 interposed therebetween.

Further, as shown in FIG. 2C, the pass separator 31 is replaced with tube plates 33, 33 made of a heat-resistant alloy.
By appropriately providing a plurality of reinforcing portions sandwiched and joined therebetween, it is possible to improve the compressive strength in a stack structure using the disc-shaped separator 23.

As the separator and the pass separator, known metal materials that can be used as an interconnect material can be appropriately selected. In consideration of heat resistance, corrosion resistance, and consistency of the coefficient of thermal expansion with other members, stainless steel, Fe −
A Cr-W alloy material is preferred.

As stainless steel materials, SUS430,
SUS304 and the like, and the Fe-Cr-W alloy material has a composition represented by Fe-18Cr-7W or the like,
It has heat resistance of 1200 ° C or more, and has an operating temperature of 700
It has excellent oxidation resistance at a temperature of from 1000C to 1000C, and has a characteristic that its thermal expansion coefficient is close to that of various ceramics known as a disk-based carrier.

The joining and sealing of the pass material and the separator serving as the disc material and the interconnect material are performed as follows.
Any known material such as a metal brazing material, a glass material, a ceramic glass, and a frit material for various ceramics can be appropriately selected and used according to conditions such as an application temperature and a thermal expansion coefficient.

By providing a corrugation or a flange portion by using the above-mentioned metal material in these separator materials, or by appropriately providing a fin-formed portion, thermal stress easily generated due to a difference in thermal expansion coefficient can be absorbed in the same portion. It can be alleviated.

When a deterioration preventing film is provided on a separator serving as an interconnect material as necessary so as not to form an insulating film by oxidation, any known material such as the glass material, ceramic glass, and frit material for various ceramics may be used. Can also be appropriately selected and used according to conditions such as an applied temperature and a coefficient of thermal expansion. In addition, a known method such as a coating sintering and a sol-gel method can be appropriately adopted according to a material type as a film forming method.

A general SOFC is calcium oxide Ca
Zirconium oxide ZrO ₂ (zirconia) in which a small amount of a divalent or trivalent metal oxide such as O or yttrium oxide Y ₂ O ₃ is dissolved as a solid solution exhibits high oxide ion O ₂ conductivity at a temperature of 1000 ° C. or more. Thus, a fuel cell using such a conductive solid oxide as an electrolyte is constituted.

In the present invention, the above-mentioned ceramics or the like is used as the material of the disk itself, and a fuel electrode, an air electrode and the like can be formed on a required surface. Also, using a material having the same coefficient of thermal expansion for the disk, an electrolyte and an air electrode can be respectively formed on the outer peripheral surface of the disk.

Further, the disk is formed by using a porous material made of various kinds of ceramics, metals, etc. which are known as a disk base carrier and capable of moving hydrogen, for example, and a fuel electrode, an electrolyte, an air electrode, etc. are formed on a required surface. It is also possible to form a film.

Conventionally, a cermet porous body of a metal such as nickel and ceramics has been used for the fuel electrode, and a composite oxide such as LaCoO ₃ and a perovskite oxide have been used for the air electrode. These pole materials have been improved in material and composition, and many materials have been proposed. For example, zirconia in which tetragonal crystals and cubic crystals are stabilized at a low temperature by adding yttria, calcia, magnesia, or the like such as yttria-stabilized zirconia (YSZ, 8V, 3Y) to an electrolyte is known.

The present invention is characterized in that the above-mentioned passage structure through which the fuel gas in the vertical direction and the air in the horizontal direction flow in and out is realized by a disk disposed in the center and a stack unit thereof. Needless to say, any known material can be appropriately selected and used as the material and material required for the SOFC.

[0044]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A stack unit having the structure shown in FIG.
It was formed by laminating two disks. Yttria stabilized zirconia (YSM) is used for the disc, and Y is used for the internal passage member.
It was fired using a zirconia ceramic material whose thermal expansion coefficient was adjusted to be equal to that of SM. In addition, Fe
-18Cr-7W-0.1Ce material (manufactured by Sumitomo Special Metals Co., Ltd.) and SUS430 as a pass separator.

The dimensions of the disk-stacked cell are as follows.
mm, and the disc interval is 7 mm. Ni—ZrO ₂ + Y ₂ O ₃ is used for the fuel electrode formed on each disk, and L is used for the air electrode.
Each of aSrMnO ₃ was formed.

The disk-stacked cell alone is at room temperature to 100
In the repeated test at 0 ° C., the thermal cycle test of 100 times was cleared. In particular, it was confirmed that the temperature distribution in the radial direction of the disk with respect to the repeated start-up and cooling was uniform in all directions. It was confirmed that the power generation efficiency of the fuel cell, which was a power generation unit using a stack unit having 50 disks stacked in two stages, exceeded 50%.

[0047]

The fuel cell according to the present invention has a piping system in the stacking direction at the center of the disk, and can distribute gas radially from the piping system at the center, allowing only the fuel gas to react in a closed chamber. In addition, the flow and distribution of air and fuel gas in the cells between the disks are made uniform, so that thermal stress hardly occurs. In addition, the structure is restricted only in the central piping system, there is no member that contacts or restricts in the radial direction of the disk, the temperature distribution is uniform in the radial direction, and the occurrence of thermal stress and the like accompanying thermal expansion is small, Excellent thermal cycle resistance.

According to the present invention, it is possible to construct a fuel cell system in which disk-stacked cells are arranged in multiple stages and accommodated in, for example, a cylinder through which air rises and passes, and the fuel reacted in the first disk cell is directly discharged from the cell. It is possible to collect the fuel gas without taking it out and react it many times in the stack unit connected in series, and to aim at complete combustion of the fuel gas.

According to the present invention, since a stainless steel material such as Fe-Cr-W is used as a separator material serving as an interconnect, the coefficient of thermal expansion can be approximated to that of a solid electrolyte, and the electric conductivity can be improved. It can prevent oxidation deterioration at high temperature by adopting glass coating material,
Furthermore, there is an advantage that the electric conduction can be improved and the thermal stress can be absorbed and reduced by the dimple molding.

[Brief description of the drawings]

FIG. 1A is a right vertical sectional view showing the configuration of a disk cell according to the present invention, and FIGS. 1B and 1C are perspective explanatory views of a passage member.

FIGS. 2A and 2C are right vertical sectional views showing another configuration of the disk cell according to the present invention, and B is a perspective explanatory view of a separator.

FIG. 3 is an explanatory view showing a configuration in which a disk-type stack unit according to the present invention is housed in a cylindrical body.

FIG. 4 is a conceptual explanatory view showing a flow of a fuel gas flowing in a stack unit.

[Description of Signs] 1 Disc 2 Battery reaction passage 3 Air passage 4 Ring member 5 Support member 10, 11 Passage member 12 Through hole 13 Combustion gas passage 14 Distribution introduction hole 15 Discharge hole 20, 23 Separator 21, 22 Flange 30, 31 Pass separator 32 Dimple 33 Tube plate 34 Bolt 35 Bolt hole 40 Cylindrical body 50 Fuel cell unit F Fuel gas S1, S2 Stack unit

Claims (8)

[Claims] 1. A fuel and combustion gas passage is formed at a central portion between disks of a stack unit in which a required number of disks are stacked at a predetermined interval and communicates in a radial direction between the disks and in a direction in which the disks are stacked. Means for distributing and introducing fuel gas for the fuel cell, and dividing the space between each disk facing surface into two on the outer peripheral side of the distributing introducing and discharging means between the disk facing surfaces to form a fuel gas cell reaction passage and an air passage. Fuel cell having means for arranging a ring-shaped separator for performing the operation and allowing air to be introduced / exited from the outer peripheral end side of the stacked disks. 2. The fuel cell according to claim 1, wherein a ring plate-shaped path separator is arranged in the cell reaction passage and the air passage, and a reciprocating passage is formed in the passage. 3. A metal or alloy material is used as a material for the ring-shaped separator and the pass separator.
Or the fuel cell according to claim 2. 4. A means for distributing and introducing fuel gas, comprising: a through hole in the center axis direction forming a fuel gas passage at the center of the disk; and a plurality of combustion gas passages on the outer peripheral side of the through hole in a direction parallel to the center axis. 2. The fuel cell according to claim 1, wherein a distribution introduction / outlet passage and a discharge / inlet passage are provided in a radial direction of the disk and connected to the through hole or the combustion gas passage, respectively. 3. 5. The fuel cell according to claim 1, wherein a fuel electrode and an air electrode are formed on both main surfaces of a disk made of a material containing an electrolyte. 6. The fuel cell according to claim 1, wherein a plurality of stack units are connected in series. 7. The fuel cell according to claim 6, wherein, when the stack units are connected in series, the outlet combustion gas passage of the upstream unit is connected to the inlet fuel gas passage of the downstream unit. 8. The fuel cell according to claim 1, wherein one or more stack units are arranged in the cylinder, and fuel gas passes through the center of the cell, and air passes through the cylinder.