JP5151273B2 - Solid oxide fuel cell - Google Patents

Description

  The present invention relates to a solid oxide fuel cell (SOFC), and more particularly to a solid oxide fuel cell having a preheating function.

  In recent years, solid oxide fuel cells have become capable of generating power even at temperatures of 600 ° C. to 800 ° C. as the low temperature performance of fuel cells, which are power generation elements, has improved. It has become possible to use a metal material such as ferritic stainless steel as a structural member such as a flange or a separator used in manufacturing the steel. By using a metal material for the constituent members of the stack in this manner, the heat capacity of the entire stack is reduced and the heat conduction is increased, so that the startability of the fuel cell can be improved.

  By the way, in a solid oxide fuel cell, the use of a metal material as a constituent member of the stack as described above is basically advantageous in improving the startability, but the temperature of the fuel cell is quickly increased. In order to improve the startability, it is more effective to preheat the fuel gas or oxidizing gas supplied to the fuel cell.

Therefore, as a conventional solid oxide fuel cell, a heat exchanger in which a heat accumulator containing a stack of fuel cells and a heat storage material for storing heat generated in the stack is provided in a heat insulating container and arranged outside the heat insulating container. In the heat exchanger, heat exchange between the heat stored in the regenerator and the fuel gas and the oxidizing gas supplied to the stack (see Patent Document 1), and in the heat insulating container, from the stack of fuel cells and the stack An off-gas combustor that burns the discharged off-gas is provided, and heat exchange is performed between the heat generated in the off-gas combustor and the fuel gas and oxidizing gas supplied to the stack in a heat exchanger arranged outside the insulated container. What to do (Patent Document 2) is disclosed.
Japanese Patent Laid-Open No. 2004-71312 JP 2004-71315 A

  However, in the conventional solid oxide fuel cell as described above, the heat from the regenerator or off-gas combustor in the heat insulation container is supplied to the heat exchanger outside the heat insulation container, so that heat loss There is a problem that the heating gas as a heat medium is easy to cool, and it is a problem to solve such a problem in order to further improve the temperature rise property of the combustion battery cell, that is, the startability of the fuel cell. It was.

  The present invention has been made in view of the above-described conventional situation, and an object of the present invention is to provide a solid oxide fuel cell excellent in temperature rise property, that is, startability of a fuel cell.

  In the solid oxide fuel cell of the present invention, a fuel cell comprising an electrolyte layer sandwiched between a fuel electrode and an air electrode is supported by a cell support plate, and on both sides of the cell support plate via respective porous bodies. Interconnectors are arranged, and a stack is formed by laminating them in multiple stages.

  In addition, the solid oxide fuel cell includes a first fuel gas passage for supplying fuel gas to the fuel electrode of the fuel cell between the cell support plate and the interconnector on the fuel electrode side, and a porous electrode on the fuel electrode side. A first fuel gas flow path for supplying fuel gas to the material, and a first oxidizing gas for supplying oxidizing gas to the air electrode of the fuel cell between the cell support plate and the interconnector on the air electrode side. A gas flow path and a second oxidizing gas flow path for supplying an oxidizing gas to the porous body on the air electrode side are provided, and an opening for communicating between the porous bodies on both sides is provided on the cell support plate ing.

  In the above solid oxide fuel cell, a power generation region by the fuel cell and a combustion region by the opening and the porous body are formed between the cell support plate and the interconnectors on both sides, and the second fuel is formed in the combustion region. The fuel gas from the gas flow path and the oxidizing gas from the second oxidizing gas flow path are mixed and burned, thereby preheating the fuel cell directly inside the fuel cell.

  According to the solid oxide fuel cell of the present invention, the fuel cell is provided with a power generation region, a combustion region in which the fuel gas and the oxidizing gas are mixed and burned, and the fuel cell is directly preheated by the heat. In addition, there is little heat loss, the temperature of the fuel cell can be raised efficiently and quickly, and the startability can be greatly enhanced.

  Hereinafter, an embodiment of a solid oxide fuel cell of the present invention will be described based on the drawings.

  A solid oxide fuel cell C1 shown in FIG. 1 includes a fuel cell 4 having an electrolyte layer 2 sandwiched between an air electrode (cathode) 1 and a fuel electrode (anode) 3, and a cell support plate 5 made of ceramics. In addition, the fuel battery cell 4 is supported by the cell support plate 5.

  In the fuel cell C 1, the interconnectors 8 and 9 are disposed on both sides of the cell support plate 5 via the gas-permeable metal porous bodies 6 and 7. A fuel electrode side current collector 11 is interposed therebetween, and an air electrode side current collector 10 is interposed between the air electrode 1 and the interconnector 8.

  Further, the fuel cell C1 includes a first fuel gas passage B1 for supplying fuel gas to the fuel electrode 3 of the fuel cell 4 between the cell support plate 5 and the fuel electrode side interconnector 9, and a fuel electrode side. The second fuel gas flow path B2 for supplying the fuel gas to the porous body 7 is provided, and the air electrode 1 of the fuel cell 4 is oxidized between the cell support plate 5 and the interconnector 8 on the air electrode side. A first oxidizing gas channel A1 that supplies gas and a second oxidizing gas channel A2 that supplies oxidizing gas to the porous body 6 on the air electrode side are provided.

  And the fuel cell C1 is provided with the opening part 12 which makes the cell support plate 5 connect between the porous bodies 6 and 7 of the both surfaces side.

  Here, in the fuel cell 4, for example, 8YSZ (8 mol% yttria stabilized zirconia) can be used for the electrolyte layer 2. Further, for example, Ni-8YSZ can be used for the fuel electrode 3, and LSM (lanthanum, strontium, manganese oxide) can be used for the air electrode 1, for example.

  Furthermore, for the cell support plate 5, for example, a thin plate made of ceramics such as yttria stabilized zirconia and magnesium stabilized zirconia can be used. The cell support plate 5 has a thermal expansion coefficient close to that of the electrolyte layer 2 and can be bonded to the fuel cell 4 well to make a thin joint, and also has excellent heat resistance and also in a high temperature environment. The fuel cell 4 can be stably supported while maintaining rigidity. Further, since the cell support plate 5 has excellent strength and toughness and is resistant to deformation, the cell support plate 5 can be thinned to about 50 to 100 μm, thereby reducing the volume and heat capacity of the fuel cell and thus the stack.

  Furthermore, for the current collector 11 on the fuel electrode side, for example, Ni felt, foam metal and mesh can be used, and for the current collector 10 on the air side, for example, a conductive oxide or the like can be used. A coated metal mesh or the like can be used.

  Furthermore, the interconnectors 8 and 9 also function as terminals for taking out the electricity generated in the fuel battery cell 4 to the outside via the current collectors 10 and 11, and naturally have conductivity. Although metals are used, it is more desirable to form a conductive oxide layer on the surface of a single metal because oxidation or corrosion occurs.

  The fuel cell C <b> 1 of this embodiment has a planar rectangular shape, and the fuel cell 4 is arranged at the center of the cell support plate 5, and the first side is located outside (on both sides) of the fuel cell 4. And the second oxidizing gas passages A1 and A2 and the first and second fuel gas passages B1 and B2, respectively, are arranged in parallel, and the respective pores are formed outside these passages A1, A2, B1 and B2. The mass bodies 6 and 7 and the opening 12 are arranged in parallel.

  At this time, each of the flow paths A1, A2, B1, and B2 is formed by the respective pipes P. The fuel cell 4 and the porous bodies 6 and 7 are formed by these pipes P on the fuel electrode side and the air electrode side, respectively. It has a structure in which the space between the two is hermetically closed. Note that an end portion (end portion in the direction perpendicular to the paper surface) of the fuel cell C1 that is not shown is hermetically closed to the outside, and the configuration can be changed according to the arrangement of the flow path and the porous body. .

  In addition, the pipe P of this embodiment has a triangular cross section, and the two are combined in a quadrangular shape on each of the fuel electrode side and the air electrode side, and in each set, the fuel battery cells 4 that are on the opposite sides of each other Gas supply holes (not shown) to the side and the porous bodies 6 and 7 are provided. Each set of pipes P may be integral or separate.

  The solid oxide fuel cell C1 having the above-described configuration forms a stack by stacking in multiple stages, and is housed in, for example, a heat insulating container. Further, as shown in FIG. 2, an oxidizing gas supply line LAi and The first and second oxidizing gas flow paths A1 and A2 are connected via respective flow control valves VA1 and VA2, and the fuel gas supply line LBi and the first and second fuel gas flow paths B1 and B2 are connected. B2 is connected through respective flow control valves VB1 and VB2, and an exhaust line LAe and a line LBe for oxidizing gas and fuel gas are connected.

  The fuel cell C1 supplies an oxidizing gas (air) from the first oxidizing gas channel A1 to the air electrode 1 of the fuel cell 4 and also supplies fuel from the first fuel gas channel B1 to the fuel cell 4. By supplying the fuel gas to the electrode 3, power generation by an electrochemical reaction is started in the fuel battery cell 4, but efficient power generation is possible if the fuel battery cell 4 does not reach a predetermined temperature at startup. Is not done.

  Therefore, the fuel cell C1 supplies the oxidizing gas from the second oxidizing gas channel A2 to the porous body 6 side, and supplies the fuel gas from the second fuel gas channel B2 to the porous body 7 side, The oxidizing gas and the fuel gas are mixed and burned in the opening 12. As a result, the fuel cell 4 is preheated by the heat generated by the combustion, and the fuel cell 4 is quickly heated with the start of the power generation, so that efficient power generation is performed.

  As described above, the fuel cell C1 has a power generation region by the fuel cell 4 and a combustion region by the porous bodies 6 and 7 and the opening 12 inside the fuel cell C1, and the fuel cell 4 is heated by the heat. Since it is directly preheated, for example, compared to a conventional fuel cell in which the supply gas is preheated in a heat exchanger arranged outside the heat insulating container, heat loss is reduced, and the fuel cell is efficiently and quickly operated. In addition, the temperature of the entire stack formed by stacking the fuel cells C1 can be raised uniformly, and the startability is excellent. In addition, since an external heat exchanger as in the prior art is not required, the structure is simple and it is possible to easily cope with reduction in size and weight.

  The fuel cell C1 supplies the fuel gas and the oxidizing gas to the second fuel gas channel B2 and the second oxidizing gas channel A2 after sufficiently heating the fuel cell 4 to a temperature suitable for power generation. Is stopped, the fuel cell 4 is not heated unnecessarily, and when the temperature of the fuel cell 4 becomes excessive, the oxidizing gas (air) is supplied to the second oxidizing gas channel A2. It is also possible to cool the fuel battery cell 4 by doing so.

  As described above, in order to automatically perform heating, stop heating, and cooling at the time of startup, a temperature sensor is disposed in an appropriate portion such as the inside of the fuel cell C1 or a flow path, and detection from these temperature sensors is performed. Based on the signal, the opening of each flow control valve VA1, VA2, VB1, VB2 shown in FIG. 2 may be controlled. That is, the fuel cell C1 can easily cope with the temperature control, and can realize a stable operation by the temperature control.

  Further, the fuel cell C1 described in this embodiment is configured such that the piping of the first and second fuel gas flow paths B1 and B2 is between the power generation region by the fuel cell 4 and the combustion region by the porous bodies 6 and 7. P and the pipes P of the first and second oxidizing gas flow paths A1 and A2 are integrated with each other, so that these pipes P are heated by combustion, and as a result, immediately before the fuel cell 4 is supplied. The fuel gas and the oxidizing gas can be sufficiently preheated to further increase the rapid temperature rise performance of the fuel cell 4. Further, the integration of the above-described piping P can simplify the supply system of each of the fuel gas and the oxidizing gas, and can contribute to further downsizing and weight reduction of the entire structure.

  Further, the fuel cell C1 can naturally generate the mixed combustion of the fuel gas and the oxidizing gas. However, since the metal porous bodies 6 and 7 are employed, these porous cells are porous. Ignition can be performed by energizing the masses 6 and 7.

  FIG. 3 is a diagram for explaining another embodiment of the solid oxide fuel cell of the present invention. Note that the same components as those of the previous embodiment are denoted by the same reference numerals, and detailed description thereof is omitted.

  The illustrated fuel cell C <b> 2 is provided with a plurality of openings 12 in the cell support plate 5 for communicating between the porous bodies 6 and 7 on both sides thereof. In the fuel cell C2, the fuel cell 4 is disposed in the center of the cell support plate 5, and the first oxidizing gas flow path is disposed outside the fuel cell 4 on the fuel electrode 3 side and the air electrode 1 side. A1 and the first fuel gas flow path B1 are disposed, the porous bodies 6 and 7 and the opening 12 are disposed outside the flow paths A1 and B1, and the second oxidizing property is disposed outside the porous bodies 6 and 7. A gas flow path A2 and a second fuel gas flow path B2 are arranged.

  Then, on each of the air electrode 1 side and the fuel electrode 3 side, the fuel cells 4 and the porous bodies 6 and 7 are formed by the pipes P and P forming the first oxidizing gas flow path A1 and the first fuel gas flow path B1. And the inside and outside of the battery are hermetically closed by pipes P and P forming the second oxidizing gas passage A2 and the second fuel gas passage B2. The pipe P of this embodiment has a rectangular cross section.

  The fuel cell C2 can obtain the same operations and effects as the fuel cell of the previous embodiment, and the piping of the first oxidizing gas passage A1 and the first fuel gas passage B1 depending on the combustion region. Since P and P are directly heated, the oxidizing gas and the fuel gas immediately before being supplied to the fuel battery cell 4 can be sufficiently heated, and the rapid temperature rise of the fuel battery cell 4 and thus the fuel battery C1 can be quickly Can be further improved.

  FIG. 4 is a diagram illustrating still another embodiment of the solid oxide fuel cell of the present invention. Note that the same components as those of the previous embodiment are denoted by the same reference numerals, and detailed description thereof is omitted.

  The illustrated fuel cell C3 has basically the same configuration as the fuel cell C1 of the embodiment shown in FIG. 1, and the cell support plate 5 communicates between the porous bodies 6 and 7 on both sides thereof. A plurality of openings 12 are provided, and the first and second oxidizing gas flow paths A1 and A2 and the pipes P forming the first and second fuel gas flow paths B1 and B2 are rectangular in cross section. Is made. Even in this fuel cell C3, the same operations and effects as those of the previous embodiments can be obtained.

  Note that the solid oxide fuel cell of the present invention is not limited to the details of the above-described embodiments, and the shape and material of each component can be changed as appropriate. The shape and arrangement of the oxidizing gas flow path and the porous body can be changed as appropriate.

  As Example 1, a solid oxide fuel cell having the structure shown in FIG.

In the fuel battery cell (4), the electrolyte (2) was made of 8YSZ (8 mol% yttria stabilized zirconia) as a material and had a thickness of 10 μm. The intermediate layer between the air electrode (1) and the electrolyte (2) was made of YDC (yttria cerium oxide) as a material and had a thickness of 4 μm. The fuel electrode (3) was made of Ni-8YSZ as a material and had a thickness of 500 μm. For the air electrode (1), LSCF (lanthanum, strontium, cobalt, iron oxide) was used as a material, the thickness was 30 μm, and the electrode area was 60 cm ² .

  As the cell support plate (5), a substrate having a thickness of 50 μm made of 3 mol% yttria stabilized zirconia was used, and an alumina layer having a thickness of 10 μm was formed on the front and back of the substrate. And the fuel cell (4) was joined using the metal brazing material.

  The gas flow path is divided into two parts inside a square pipe (P) having a cross section of 2 mm × 2 mm made of Fe-22Cr stainless steel, and the first and second oxidizing gas flow paths (A1, A2) having a triangular cross section. ) And the first and second fuel gas flow paths (B1, B2). These pipes (P) were joined to the cell support plate (5) and the interconnectors (8, 9) using a metal brazing material.

  The porous body (6, 7) is a porous metal body having a cross section of 2 mm x 4 mm made of Fe-22Cr stainless steel particles, and using a metal brazing material, the cell support plate (5) or the interconnector (8, 9). ).

   The interconnector (8, 9) uses an Fe-22Cr stainless steel sheet with a thickness of 250 μm, and the surface of the sheet on the fuel electrode (2) side is plated with Ni with a thickness of 5 μm, and the air electrode (3 ) LSM (lanthanum / strontium / manganese oxide) was baked to a thickness of 20 μm on the surface on the side.

  A Ni mesh with a mesh size of 16 was used for the current collector (11) on the fuel electrode (3) side. The current collector (10) on the air electrode (1) side was obtained by baking LSM (lanthanum / strontium / manganese oxide) with a thickness of 20 μm on a mesh made of Fe-22Cr having a mesh size of 16.

  Then, 10 fuel cells (C1) described above were stacked to form a stack, and the time required to reach a predetermined operating temperature from room temperature was evaluated.

  At this time, for preheating, hydrogen gas, which is a fuel gas, is supplied to the second fuel gas channel (B2) at 5 L / min, and the second oxidizing gas channel (A2) is an oxidizing gas. Air was supplied at 8 L / min, and the porous body (6, 7) was energized to mix and burn hydrogen gas and air. At the same time, for power generation, hydrogen gas is similarly supplied to the first fuel gas channel (B1) at 3 L / min, and air is also supplied to the first oxidizing gas channel (A1) at 6 L / min. Supplied.

The stack started power generation after 5 minutes by the above gas supply, and the power generation output was stabilized after 15 minutes. After 15 minutes, power generation with a voltage of 7 V and a current density of 0.3 A / cm ² was confirmed. The temperature of the stack at that time was about 770 ° C. This confirmed that the stack could be started in 15 minutes.

  Further, after 15 minutes from the start, the hydrogen gas in the second fuel gas channel (B2) and the air in the second oxidizing gas channel (A2) were shut off. After 10 minutes from the shut-off, the stack temperature reached about 790 ° C., so when air was supplied to the second oxidizing gas flow path (A2) at 8 L / min, about 5 minutes later, The temperature dropped to 770 ° C. Thereby, it was confirmed that the cell support plate (5) and the interconnectors (8, 9) can be cooled by supplying air to the second oxidizing gas channel (A2).

  Here, as Comparative Example 1, a stack was formed by stacking the fuel cells of Example 1, and a test for reducing the combustion gas flow rate was performed.

  For preheating, hydrogen gas as a fuel gas is supplied to the second fuel gas channel (B2) at 1 L / min, and 2 L of air as an oxidizing gas is supplied to the second oxidizing gas channel (A2). Hydrogen gas and air were mixed and combusted by supplying at / min and energizing the porous body (6, 7). At the same time, for power generation, hydrogen gas is similarly supplied to the first fuel gas channel (B1) at 3 L / min, and air is also supplied to the first oxidizing gas channel (A1) at 6 L / min. Supplied.

  In this case, almost no power generation output was obtained even after 60 minutes had elapsed from the gas supply, and the temperature after 60 minutes was about 480 ° C. This Comparative Example 1 supports that sufficient supply of the preheating fuel gas and oxidizing gas as in Example 1 achieves good temperature rise performance of the fuel battery cell (4) and good startability of the stack. It became.

  As Example 2, a solid oxide fuel cell having the structure shown in FIG. The fuel cell (4), the cell support plate (5), the interconnectors (8, 9) and the current collectors (10, 11) are the same as in the previous embodiment.

  The gas flow path is formed by square pipes (P) made of Fe-22Cr stainless steel and having a cross section of 2 mm × 2 mm. These pipes (P) are made of a metal brazing material and are used for the cell support plate (5) and the interface. Joined to connectors (8, 9).

  The porous body (6, 7) is a porous metal body having a cross section of 2 mm × 6 mm made of Fe-22Cr stainless steel particles, and using a metal brazing material, the cell support plate (5) and the interconnector (8, 9). ). In addition, three holes having a diameter of 1 mm were formed as openings (12) between the porous bodies (6, 7) in the cell support plate (5).

  Then, 10 stacks of the above fuel cells (C2) were formed to form a stack, and the time required to reach a predetermined operating temperature from room temperature was evaluated.

  At this time, for preheating, hydrogen gas, which is a fuel gas, is supplied to the second fuel gas channel (B2) at 5 L / min, and the second oxidizing gas channel (A2) is an oxidizing gas. Air was supplied at 8 L / min, and the porous body (6, 7) was energized to mix and burn hydrogen gas and air. At the same time, for power generation, hydrogen gas is similarly supplied to the first fuel gas channel (B1) at 3 L / min, and air is also supplied to the first oxidizing gas channel (A1) at 6 L / min. Supplied.

The stack started power generation after the elapse of 6 minutes by the above gas supply, and the power generation output was stabilized after 17 minutes. After 17 minutes, power generation with a voltage of 7 V and a current density of 0.3 A / cm ² was confirmed. The temperature of the stack at that time was about 760 ° C. This confirmed that the stack could be started in 17 minutes.

  As Example 3, a solid oxide fuel cell having the structure shown in FIG. The fuel cell (4), the cell support plate (5), the interconnectors (8, 9), and the current collectors (10, 11) are the same as those in the second embodiment.

  Then, 10 stacks of the above fuel cells (C3) were stacked to form a stack, and the time required to reach a predetermined operating temperature from room temperature was evaluated.

  At this time, for preheating, hydrogen gas, which is a fuel gas, is supplied to the second fuel gas channel (B2) at 5 L / min, and the second oxidizing gas channel (A2) is an oxidizing gas. Air was supplied at 8 L / min, and the porous body (6, 7) was energized to mix and burn hydrogen gas and air. At the same time, for power generation, hydrogen gas is similarly supplied to the first fuel gas channel (B1) at 3 L / min, and air is also supplied to the first oxidizing gas channel (A1) at 6 L / min. Supplied.

The stack started power generation after the elapse of 5 minutes due to the above gas supply, and the power generation output was stabilized after 12 minutes. After 12 minutes, power generation with a voltage of 7 V and a current density of 0.3 A / cm ² was confirmed. The temperature of the stack at that time was about 760 ° C. This confirmed that the stack could be started in 12 minutes.

It is sectional drawing (a) explaining one Embodiment of the solid oxide fuel cell of this invention, and sectional drawing (b) which expanded the edge part. It is explanatory drawing which shows the gas supply / exhaust system of the solid oxide fuel cell shown in FIG. It is sectional drawing of the one side omission explaining other embodiment of the solid oxide fuel cell of this invention. It is sectional drawing of the one side omission explaining further another embodiment of the solid oxide fuel cell of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Air electrode 2 Electrolyte layer 3 Fuel electrode 4 Fuel cell 5 Cell support plate 6 7 Porous body 8 9 Interconnector 12 Opening part A1 1st oxidizing gas flow path A2 2nd oxidizing gas flow path B1 1st fuel gas Channel B2 Second fuel gas channel C1 to C3 Solid oxide fuel cell P Piping

Claims (4)

A fuel cell comprising an electrolyte layer sandwiched between a fuel electrode and an air electrode is supported by a cell support plate, and an interconnector is disposed on both sides of the cell support plate via respective porous bodies, and the cell support plate and the fuel A first fuel gas passage for supplying fuel gas to the fuel electrode of the fuel cell and a second fuel gas passage for supplying fuel gas to the porous body on the fuel electrode side are provided between the electrode connector and the electrode connector. A first oxidizing gas passage for supplying an oxidizing gas to the air electrode of the fuel cell between the cell support plate and the air electrode side interconnector, and an oxidizing property for the porous body on the air electrode side A solid oxide fuel cell, characterized in that a second oxidizing gas flow path for supplying gas is provided, and an opening for communicating between the porous bodies on both sides is provided in the cell support plate. In the cell support plate, the first and second fuel gas flow paths and the first and second oxidizing gas flow paths are arranged outside the fuel cell, and the porous bodies and the openings are formed outside these flow paths. 2. The solid oxide fuel cell according to claim 1, wherein a portion is arranged and the space between the fuel cell and the porous body is closed by a pipe forming each flow path. In the cell support plate, the first fuel gas flow path and the first oxidizing gas flow path are disposed outside the fuel battery cell, and the porous body and the opening are disposed outside these flow paths. A second fuel gas flow channel and a second oxidizing gas flow channel are disposed outside, and a pipe that forms the first fuel gas flow channel and the first oxidizing gas flow channel is provided between the fuel cell and the porous body. 2. The solid oxide fuel cell according to claim 1, wherein the fuel cell is closed. The solid oxide fuel cell according to any one of claims 1 to 3, wherein the cell support plate is made of ceramics and the porous body is made of metal.

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