Solid acid fuel cells

Abstract

To provide a solid oxide fuel cell with which it is possible to suppress a decrease in temperature due to a bias in reforming reaction and suppress a decrease in power generation performance.SOLUTION: Provided is a solid oxide fuel cell 100 in which a plurality of power generation cells 2, each composed of an anode electrode disposed on one face of a solid electrolyte layer and a cathode electrode disposed on the other face of the solid electrolyte layer, are laminated via a separator 5. The solid oxide fuel cell 100 includes a flow channel forming member 3 that is disposed between the anode electrode and the separator 5 and that forms an anode flow channel 6 in which a fuel gas flows, with a reforming catalyst disposed in at least one of the anode electrode and the anode flow channel 6. The anode flow channel 6 includes a reforming reaction promotion unit 62 whose flow channel section area is large and a reforming reaction suppress unit 61 whose flow channel sectional area is smaller than the reforming reaction promotion unit 62, the reforming reaction promotion unit 62 and the reforming reaction suppress unit 61 being formed by changing the flow channel sectional area of the anode flow channel 6 by the separator 5 or the flow channel forming member 3.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] This invention relates to a solid oxide fuel cell. [Background technology]

[0002] In internally reformed solid oxide fuel cells (SOFCs) where the reforming catalyst is located on the anode side of the anode channel or electrolyte, the temperature of the part where the endothermic reforming reaction is likely to occur drops significantly, which may reduce power generation performance.

[0003] Patent Document 1 discloses a fuel cell in which a corrugated flow path forming member is placed between a separator and an electrode to form a fuel gas flow path on the electrode side (electrode-side flow path) and a fuel gas flow path on the separator side (separator-side flow path), and a reforming catalyst is placed in one of the flow paths. In this fuel cell, the flow path forming member is divided into an upstream side and a downstream side, and the upstream electrode-side flow path is connected to the downstream separator-side flow path by a half-pitch offset in a direction perpendicular to the gas flow direction, and the upstream separator-side flow path is connected to the downstream electrode-side flow path. As a result, half of the fuel gas passes through the flow path on the upstream side where the reforming catalyst is not placed, and is not reformed until it reaches the downstream side. In this way, the concentration of the reforming reaction is suppressed. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 1-140560 [Overview of the project] [Problems that the invention aims to solve]

[0005] In the fuel cell described in Patent Document 1, there is a portion where the upstream electrode-side flow path and the downstream electrode-side flow path overlap at the point where the flow path forming member is divided, and there is a risk that the reformed anode gas may mix into the downstream electrode-side flow path. As a result, the flow rate of fuel gas supplied from the upstream separator-side flow path to the downstream electrode-side flow path decreases, and there is still a risk that the power generation performance will decrease.

[0006] This invention addresses the above-mentioned problems and aims to provide a solid oxide fuel cell that can suppress temperature drops due to bias in the reforming reaction and suppress a decrease in power generation performance. [Means for solving the problem]

[0007] According to one aspect of the present invention, a solid oxide fuel cell is provided in which a plurality of power generation cells, each comprising a solid electrolyte layer, an anode electrode disposed on one side of the solid electrolyte layer, and a cathode electrode disposed on the other side of the solid electrolyte layer, are stacked via a separator. This solid oxide fuel cell includes a flow path forming member disposed between the anode electrode and the separator, forming an anode flow path through which fuel gas flows, and a reforming catalyst is disposed in at least one of the anode electrode and the anode flow path of the power generation cell. The anode flow path has a reforming reaction promoting section with a large flow path cross-sectional area and a reforming reaction suppressing section with a smaller flow path cross-sectional area than the reforming reaction promoting section, and the reforming reaction promoting section and the reforming reaction suppressing section are formed by changing the flow path cross-sectional area of ​​the anode flow path with a separator or a flow path forming member. [Effects of the Invention]

[0008] According to the present invention, the anode flow path has a reforming reaction promoting section with a large flow path cross-sectional area and a reforming reaction suppressing section with a smaller flow path cross-sectional area than the reforming reaction promoting section. As a result, the flow velocity of the fuel gas in the reforming reaction suppressing section becomes greater than the flow velocity in the reforming reaction promoting section, thus reducing the reforming rate in the reforming reaction suppressing section. Therefore, by forming the reforming reaction suppressing section near the part where the reforming reaction is likely to occur, the bias in the reforming reaction can be suppressed, the temperature drop due to reforming concentration can be suppressed, and the decrease in power generation performance can be suppressed. [Brief explanation of the drawing]

[0009] [Figure 1] Figure 1 is an exploded perspective view showing a solid oxide fuel cell according to a first embodiment of the present invention. [Figure 2] Figure 2 is an exploded perspective view of the cell unit. [Figure 3] Figure 3 is a schematic cross-sectional view of the anode channel. [Figure 4] Figure 4 illustrates the effects of the solid oxide fuel cell according to the first embodiment. [Figure 5] Figure 5 is a schematic cross-sectional view of the anode flow path in a solid oxide fuel cell according to a modified example of the first embodiment. [Figure 6] Figure 6 illustrates the effect of a solid oxide fuel cell according to a modified example of the first embodiment. [Figure 7] Figure 7 is a schematic cross-sectional view of the anode flow path in a solid oxide fuel cell according to the second embodiment. [Figure 8] Figure 8 is a top view of the channel forming member. [Figure 9] Figure 9 is a top view of a modified flow channel forming member. [Figure 10] Figure 10 is a schematic cross-sectional view of the anode flow path in a solid oxide fuel cell according to a modified example of the second embodiment. [Figure 11] Figure 11 is a top view of the channel forming member. [Figure 12] Figure 12 is a schematic cross-sectional view of the anode channel in a solid oxide fuel cell according to the third embodiment. [Figure 13] Figure 13 is a top view of the channel forming member. [Figure 14] Figure 14 is a top view of a modified flow channel forming member. [Figure 15] Figure 15 is a top view of a modified flow channel forming member. [Figure 16] Figure 16 is a top view of the flow channel forming member in a solid oxide fuel cell according to the fourth embodiment. [Figure 17] Figure 17 is a top view of the flow path forming member according to the modification. [Figure 18] Figure 18 is a schematic cross-sectional view of the anode flow path in the solid oxide fuel cell according to the fifth embodiment.

Mode for Carrying Out the Invention

[0010] Hereinafter, embodiments of the present invention will be described with reference to the drawings and the like.

[0011] (First Embodiment) Figure 1 is an exploded perspective view showing a solid oxide fuel cell 100 (hereinafter, also simply referred to as "fuel cell") according to the first embodiment of the present invention. As shown in Figure 1, the solid oxide fuel cell 100 is composed of a plurality of cell units 1 stacked in the vertical direction. Note that the solid oxide fuel cell 100 of the present embodiment is mainly mounted on a vehicle or the like, but is not limited thereto.

[0012] Figure 2 is an exploded perspective view of the cell unit 1 constituting the solid oxide fuel cell 100. As shown in Figure 2, the cell unit 1 includes a power generation cell 2, a metal anode flow path forming member (flow path forming member) 3, a metal cathode flow path forming member 4, a separator 5, an anode spacer 31, a cathode spacer 41, and the like.

[0013] The power generation cell 2 is composed of a membrane electrode assembly 21 (see Figure 3) in which an anode electrode is placed on one side of a solid electrolyte layer and a cathode electrode is placed on the other side. In this embodiment, the lower side of the power generation cell 2 is the anode electrode and the upper side is the cathode electrode. The power generation cell 2 is supplied with anode gas (fuel gas) and cathode gas (air), and the power generation cell 2 generates electricity based on the electrode reaction at the anode electrode and the cathode electrode. In this embodiment, the power generation cell 2 also includes metal support layers 22 and 23 (see Figure 3) that support the anode electrode and the cathode electrode, respectively. The material constituting the metal support layers 22 and 23 is preferably ferritic stainless steel, but is not limited thereto. Hereinafter, the anode electrode and the metal support layer 22 that supports the anode electrode are referred to as the anode electrode, and the cathode electrode and the metal support layer 23 that supports the cathode electrode are referred to as the cathode electrode. A reforming catalyst (not shown) is uniformly arranged on the anode electrode of the power generation cell 2.

[0014] Furthermore, the active area 24, which is the region of the power generation cell 2 that contributes to power generation, is fixed to a cell frame 25, which is a frame that surrounds the outer periphery of the active area 24. The cell frame 25 has a plurality of protrusions extending from its outer edge, and holes 26 are formed in the protrusions. The space between the power generation cell 2 and the cell frame 25 is sealed by a cell seal member 27.

[0015] The anode channel forming member 3 is made of a conductive material such as metal and is placed between the anode electrode of the power generation cell 2 and the separator 5 described later, forming an anode channel 6 (see Figure 3) through which fuel gas flows on the anode electrode side of the power generation cell 2. The anode channel forming member 3 is formed in a so-called wave shape, with linearly extending irregularities in the width direction of the power generation cell 2 repeated in the longitudinal direction. As a result, multiple anode channels 6 are partitioned between the anode electrode of the power generation cell 2 and the separator 5. A reforming catalyst is uniformly arranged on the inner circumferential surface of each anode channel 6. In this embodiment, the fuel gas is assumed to flow from the lower right to the upper left direction in Figure 2.

[0016] The cathode channel forming member 4 is made of a conductive material such as metal and is placed between the cathode electrode of the power generation cell 2 and the separator 5 (of the adjacent cell unit 1), forming a cathode channel through which cathode gas (air) flows towards the cathode electrode side of the power generation cell 2. The cathode channel forming member 4 is formed in a wave shape, similar to the anode channel forming member 3, and multiple cathode channels are partitioned between the cathode electrode of the power generation cell 2 and the separator 5. In this embodiment, the cathode gas (air) is assumed to flow from the lower right to the upper left in Figure 2. That is, the solid oxide fuel cell 100 of this embodiment is a co-flow fuel cell in which the fuel gas and air flow in the same direction.

[0017] As shown in Figure 2, the anode channel forming member 3 that forms the anode channel 6 and the cathode channel forming member 4 that forms the cathode channel are each divided into two parts, an upstream side and a downstream side, but this is not limited to this. For example, the anode channel 6 and the cathode channel may be formed by a single member. Also, in Figure 2, the two divided channel forming members 3 and 4 are spaced apart on the upstream and downstream sides, but the channel forming members 3 and 4 may be arranged close together without any gap between the upstream and downstream channel forming members.

[0018] The separator 5 is a conductive plate-shaped member, with one surface (upper surface) electrically bonded to the anode channel forming member 3. This electrically connects the separator 5 and the anode electrode of the power generation cell 2 via the anode channel forming member 3. Meanwhile, the other surface (lower surface) of the separator 5 is bonded to the cathode channel forming member 4 of the adjacent cell unit 1. Furthermore, a shim plate 51 is installed upstream of the anode channel 6 to increase the thickness of the separator 5 in the stacking direction.

[0019] Furthermore, the separator 5 has a plurality of protrusions extending from its outer edge, and holes 52 are formed in these protrusions at positions corresponding to the holes 26 of the cell frame 25. The overlap of the holes 52 of the separator 5 and the holes 26 of the cell frame 25 forms holes through which fuel gas supplied to the anode flow path 6 flows, and holes through which fuel gas exits the anode flow path 6. A sealing member 11 is provided around the holes formed by the overlap of the holes 52 of the separator 5 and the holes 26 of the cell frame 25.

[0020] The anode spacer 31 is a frame stacked on the outer circumference of the separator 5, positioned between the power generation cell 2 and the separator 5, and ensuring the height of the anode flow path 6. The anode spacer 31 is positioned so that its outer shape overlaps with the power generation cell 2 (cell frame 25) and the separator 5.

[0021] The cathode spacers 41 are positioned at both ends in the longitudinal direction of the cathode channel forming member 4, ensuring the height of the cathode channel and sealing both ends in the longitudinal direction of the cathode channel forming member 4.

[0022] As described above, the solid oxide fuel cell 100 of this embodiment includes a flow path forming member 3 that forms an anode flow path 6 between the anode electrode and the separator 5, and a reforming catalyst is arranged in the anode flow path 6 and the anode electrode of the power generation cell 2. In other words, the solid oxide fuel cell 100 is a so-called internal reforming type fuel cell in which the fuel gas is reformed in the anode flow path 6 and the anode electrode of the power generation cell 2.

[0023] Incidentally, in internally reforming solid oxide fuel cells, the temperature in the part where the endothermic reforming reaction is likely to occur drops significantly, which may reduce power generation performance. For example, if the reforming catalyst is uniformly distributed in the anode channel and anode electrode, reforming is more likely to occur near the inlet of the anode channel. As a result, the temperature upstream of the anode channel drops significantly, which may reduce power generation performance.

[0024] Therefore, in this embodiment, the separator 5 is used to change the flow velocity of the fuel gas in the anode flow path 6 by changing the flow cross-sectional area of ​​the anode flow path 6, thereby correcting the bias in the reforming reaction. Specifically, the thickness of the separator 5 is increased on the upstream side of the anode flow path 6 where the reforming reaction is likely to occur, making the flow cross-sectional area on the upstream side of the anode flow path 6 smaller than the flow cross-sectional area on the downstream side. As a result, the anode flow path 6 is formed with an upstream reforming reaction suppression section 61 (see Figure 3) with a smaller flow cross-sectional area than the downstream side, and a downstream reforming reaction promotion section 62 (see Figure 3) with a larger flow cross-sectional area than the upstream side. Consequently, the flow velocity of the fuel gas in the upstream reforming reaction suppression section 61 of the anode flow path 6 is greater than the flow velocity in the downstream reforming reaction promotion section 62 of the anode flow path 6, resulting in a lower reforming rate in the reforming reaction suppression section (upstream side) 61. Therefore, the reforming reaction can be suppressed on the upstream side of the anode channel 6, where the reforming reaction is likely to occur, and the bias in the reforming reaction is corrected. As a result, the temperature drop due to reforming concentration is suppressed, and the decrease in power generation performance is suppressed.

[0025] The details of the anode channel 6 are described below.

[0026] Figure 3 is a schematic cross-sectional view of the anode flow path 6, where (a) shows a portion of the cross-section along line AA in Figure 2 (upstream side of the anode flow path 6), (b) shows a portion of the cross-section along line BB in Figure 2 (downstream side of the anode flow path 6), and (c) shows a portion of the cross-section along line CC in Figure 2. In Figure 3(c), the fuel gas is assumed to flow from right to left in the diagram.

[0027] As shown in Figure 3, an anode channel forming member (channel forming member) 3 is positioned between the metal support 22 on the anode electrode side of the power generation cell 2 (membrane electrode assembly 21) and the separator 5. The channel forming member 3 has a portion that connects to the anode electrode (metal support 22) of the power generation cell 2 (first connection portion 32) and a portion that connects to the separator 5 (second connection portion 33), and the first connection portion 32 and the second connection portion 33 are connected by a connecting portion 34. As a result, multiple spaces are formed between the anode electrode and the separator 5: a space surrounded by the separator 5, the connecting portion 34 and the channel forming member 3 (first connection portion 32), and a space surrounded by the anode electrode, the connecting portion 34 and the channel forming member 3 (second connection portion 33). The space surrounded by the anode electrode, the connecting portion 34 and the channel forming member 3 (second connection portion 33) becomes the anode channel 6 through which the fuel gas flows. The reforming catalyst is uniformly distributed on the inner surface of the anode channel 6 and on the anode electrode, and the fuel gas flowing through the anode channel 6 is reformed within the anode channel 6 and on the anode electrode.

[0028] Furthermore, the flow path forming member 3 is welded to the metal support 22 at the first joint 32 and to the separator 5 at the second joint 33. This prevents displacement of the joints 32 and 33 and improves rigidity.

[0029] Furthermore, as shown in Figures 3(a) and 3(c), a shim plate 51 is installed on the separator 5 on the upstream side of the anode flow path 6 to increase the thickness of the separator 5 in the stacking direction. As a result, the flow cross-sectional area on the upstream side of the anode flow path 6 becomes smaller than the flow cross-sectional area on the downstream side, and the flow velocity on the upstream side becomes greater than the flow velocity on the downstream side. Therefore, the space velocity SV, which is expressed as the fuel gas flow rate divided by the volume of the space coated with the catalyst, is greater on the upstream side than on the downstream side.

[0030] Here, the reforming rate of the fuel gas decreases as the space velocity SV increases, so the reforming rate on the upstream side of the anode channel 6 is lower than the reforming rate on the downstream side. In other words, the anode channel 6 is formed with an upstream reforming reaction suppression section 61 where the reforming reaction is suppressed, and a downstream reforming reaction promotion section 62 where the reforming reaction is promoted.

[0031] When the reforming catalyst is uniformly distributed in the anode channel and anode electrode, if the cross-sectional area of ​​the anode channel is constant, reforming is more likely to occur near the inlet of the anode channel, which may cause a significant drop in temperature on the upstream side of the anode channel. In contrast, in the solid oxide fuel cell 100 of this embodiment, as described above, the anode channel 6 has a reforming reaction suppression section 61 with a small cross-sectional area on the upstream side and a reforming reaction promotion section 62 with a large cross-sectional area on the downstream side. As a result, the peak of the reforming reaction shifts from the upstream side to the downstream side, correcting the bias in the reforming reaction. Consequently, the temperature drop due to reforming concentration is suppressed.

[0032] Figure 4 is a graph illustrating the effect of the solid oxide fuel cell 100 of this embodiment, showing the temperature at each position in the anode flow path 6 during fuel gas supply. The horizontal axis of Figure 4 represents the distance from the inlet of the anode flow path 6 in the direction of fuel gas flow, and the vertical axis represents the temperature inside the anode flow path 6 during fuel gas supply. Note that 0 on the horizontal axis of Figure 4 is the inlet of the anode flow path 6, l out This is the outlet of the anode channel 6.

[0033] Curve C0 in Figure 4 is the temperature curve when the cross-sectional area of ​​the anode channel 6 is constant. As shown in Figure 4, when the cross-sectional area of ​​the anode channel 6 is constant, when fuel gas is supplied to the anode channel 6, the reforming reaction concentrates near the inlet of the channel, and the temperature of the anode channel 6 drops significantly. Also, power generation is concentrated downstream of the anode channel 6, and the temperature drops sharply at the outlet. out The closer you get to the source, the higher the temperature of the anode channel 6 becomes due to the heat generated by power generation. Therefore, if the cross-sectional area of ​​the anode channel 6 is constant, the temperature difference ΔT between the inlet and outlet of the channel is large.

[0034] On the other hand, curve C1 in Figure 4 is the temperature curve when the anode channel 6 has a reforming reaction suppression section 61 on the upstream side and a reforming reaction acceleration section 62 on the downstream side, as in this embodiment. When the anode channel 6 has a reforming reaction suppression section 61 with a small channel cross-sectional area on the upstream side and a reforming reaction acceleration section 62 with a large channel cross-sectional area on the downstream side, the bias in the reforming reaction is corrected, and as shown in curve C1, the temperature drop near the inlet of the channel is suppressed. In addition, because the temperature drop near the inlet is suppressed, the power generation performance on the upstream side is improved, and the concentration of power generation on the downstream side of the anode channel 6 is also suppressed. In this way, the concentration of the reforming reaction that causes a temperature drop and the concentration of power generation, which is an exothermic reaction, are suppressed, so the temperature near the inlet and outlet of the channel is lower compared to when the channel cross-sectional area of ​​the anode channel is constant. out The temperature difference ΔT in the vicinity decreases.

[0035] Here, the outlet temperature of the anode channel 6 when the cross-sectional area of ​​the anode channel 6 is constant is defined as the heat resistance limit temperature T of the anode channel 6. max Therefore, in this embodiment where the temperature difference ΔT is small, the average temperature of the flow path (fuel gas) can be raised to a higher temperature compared to the case where the flow path cross-sectional area is constant. That is, in the solid oxide fuel cell 100 of this embodiment, the average temperature of the flow path (fuel gas) can be raised from curve C1 to curve C2 in Figure 4. On the other hand, when the flow path cross-sectional area of ​​the anode flow path 6, where the temperature difference ΔT is large, is constant, raising the average temperature of the flow path (fuel gas) will raise the temperature of the outlet l out The temperature of the anode channel 6 in the vicinity reaches the heat resistance limit temperature T. max Because it would exceed a certain limit, the average temperature cannot be raised any further.

[0036] Thus, in the solid oxide fuel cell 100 of this embodiment, not only is it possible to suppress the temperature drop due to reforming concentration, but the average temperature of the fuel gas can also be increased, thus further improving power generation performance.

[0037] Furthermore, raising the average temperature of the fuel gas can be achieved, for example, by increasing the temperature of the fuel gas supplied to the fuel cell stack (solid oxide fuel cell 100) or by reducing the flow rate of the cooling air.

[0038] According to the solid oxide fuel cell 100 of the first embodiment described above, the following effects can be obtained.

[0039] The solid oxide fuel cell 100 is equipped with a flow path forming member 3 positioned between the anode electrode of the power generation cell 2 and the separator 5, forming an anode flow path 6 through which fuel gas flows. A reforming catalyst is placed in the anode electrode of the power generation cell 2 and in the anode flow path 6. The anode flow path 6 has a reforming reaction promoting section 62 with a large flow path cross-sectional area formed by changing the flow path cross-sectional area with the separator 5, and a reforming reaction suppressing section 61 with a smaller flow path cross-sectional area than the reforming reaction promoting section 62. As a result, the flow velocity of the fuel gas in the reforming reaction suppressing section 61 is greater than the flow velocity in the reforming reaction promoting section 62, thus reducing the reforming rate in the reforming reaction suppressing section 61. Therefore, by forming the reforming reaction suppressing section 61 near the part where the reforming reaction is likely to occur, the bias of the reforming reaction can be suppressed, the temperature drop due to reforming concentration can be suppressed, and the decrease in power generation performance can be suppressed.

[0040] Furthermore, the bias in the reforming reaction is suppressed, and the temperature drop due to reforming concentration is suppressed, resulting in a smaller temperature difference within the anode flow path 6 during fuel gas supply. Consequently, the average temperature of the fuel gas within the anode flow path 6 can be increased, further improving power generation performance.

[0041] In the solid oxide fuel cell 100, the separator 5 has a greater thickness in the stacking direction than the reforming reaction promoting section 62 in the reforming reaction suppression section 61. That is, by increasing the thickness of the separator 5, a reforming reaction suppression section 61 with a small flow path cross-sectional area is formed. Therefore, by increasing the thickness of the separator 5 near the area where the reforming reaction is likely to occur, the unevenness of the reforming reaction can be suppressed, and the temperature drop due to reforming concentration can be suppressed. That is, the decrease in power generation performance due to temperature drop can be suppressed.

[0042] In the solid oxide fuel cell 100, the fuel gas flowing through the anode channel 6 and the air flowing through the cathode channel flow in the same direction. The reforming reaction suppression section 61 is formed on the upstream side of the anode channel 6, and the reforming reaction acceleration section 62 is formed on the downstream side of the anode channel 6. This suppresses the reforming reaction on the upstream side of the anode channel 6, where reforming reactions tend to occur in co-flow fuel cells. Consequently, the bias in the reforming reaction is suppressed, and the temperature drop due to reforming concentration is suppressed. Therefore, the decrease in power generation performance due to temperature drop can be suppressed.

[0043] In this embodiment, the anode flow path 6 has a reforming reaction suppression section 61 with a small flow path cross-sectional area on the upstream side and a reforming reaction acceleration section 62 with a large flow path cross-sectional area on the downstream side, but it is not necessarily limited to this. For example, as described in the following modified example of the first embodiment, in a counterflow fuel cell where the flow direction of the fuel gas flowing through the anode flow path 6 and the flow direction of the air flowing through the cathode flow path are opposite, it is preferable to form the reforming reaction suppression section 61 near the flow path inlet and near the flow path outlet. Also, for example, unlike this embodiment, if the reforming catalyst is not uniformly arranged, the reforming reaction suppression section 61 may be formed in the area with a large amount of catalyst, and the reforming reaction acceleration section 62 may be formed in the area with a small amount of catalyst.

[0044] Furthermore, in this embodiment, the thickness of the separator 5 is increased by installing a shim plate 51, but this is not necessarily the only option. For example, a single separator 5 with increased thickness in the portion forming the reforming reaction suppression section 61 may be used.

[0045] Furthermore, in this embodiment, the reforming reaction suppression section 61 is formed by increasing the thickness of the separator 5, but this is not necessarily limited to this, as long as the cross-sectional area of ​​the anode channel 6 can be changed. For example, as in the second to fifth embodiments described later, the cross-sectional area of ​​the anode channel 6 may be changed using the channel forming member 3.

[0046] Furthermore, in this embodiment, the reforming catalyst is placed in the anode electrode and the anode channel 6 of the power generation cell 2, but this is not necessarily the case, and the reforming catalyst may be placed in only one of the anode electrode and the anode channel 6.

[0047] Furthermore, as in this embodiment, it is preferable that the flow path forming member 3 is welded to the metal support 22 and the separator 5 at the joint portions 32 and 33, respectively, but it is not necessarily limited to this, and (metal) joining may be done by methods other than welding, such as diffusion bonding or brazing.

[0048] Furthermore, while it is preferable for the power generation cell 2 to include metal supports 22 and 23, as in this embodiment, it is not necessarily limited to this, and a configuration without metal supports 22 and 23 is also possible.

[0049] (Modified version of the first embodiment) Referring to Figures 5 and 6, a modified solid oxide fuel cell 100 according to the first embodiment will be described. In this modified embodiment, the thickness of the separator 5 is increased in a location that differs from the first embodiment. The same reference numerals are used for elements that are the same as in the first embodiment, and their descriptions are omitted.

[0050] Figure 5 is a schematic cross-sectional view of the anode flow path 6 along the direction of fuel gas flow. In this modified example, the solid oxide fuel cell 100 is a so-called counterflow fuel cell in which the flow directions of the fuel gas flowing through the anode flow path 6 and the air flowing through the cathode flow path are opposite. Also, in Figure 5, the fuel gas flows from right to left in the figure. Note that in Figure 5, the flow path forming member 3 is not divided into two parts, unlike in the first embodiment, but it may be configured to be divided as in the first embodiment.

[0051] As shown in Figure 5, in this modified example, the separator 5 has shim plates 51 installed near the inlet 63 and outlet 64 of the anode channel 6 to increase the thickness of the separator 5 in the stacking direction. As a result, a reforming reaction suppression section 61 with a small channel cross-sectional area is formed near the inlet 63 and outlet 64 of the anode channel 6, and a reforming reaction promotion section 62 with a larger channel cross-sectional area than the reforming reaction suppression section 61 is formed in the central part 65 of the anode channel 6.

[0052] In this counterflow fuel cell, the inlet of the cathode channel, to which low-temperature air is supplied, and the outlet 64 of the anode channel 6 are adjacent to each other via the power generation cell 2. Therefore, the temperature near the outlet 64 of the anode channel 6 tends to decrease. Consequently, when the cross-sectional area of ​​the anode channel is constant, the temperature inside the anode channel during fuel gas supply is lower near the inlet and outlet of the anode channel, where reforming reactions are likely to occur, and higher in the center. On the other hand, in this embodiment, a reforming reaction suppression section 61 with a small cross-sectional area is formed near the inlet 63 and outlet 64 of the anode channel 6. As a result, the flow velocity near the inlet 63 and outlet 64 of the anode channel 6 decreases, and the reforming rate decreases. Consequently, the temperature drop near the inlet 63 and outlet 64 of the anode channel 6 is suppressed.

[0053] Figure 6 is a graph showing the temperature inside the anode flow path 6 during fuel gas supply in this modified embodiment. Similar to Figure 4, the horizontal axis represents the distance from the inlet 63 of the anode flow path 6 in the direction of fuel gas flow, and the vertical axis represents the temperature inside the anode flow path 6 during fuel gas supply. In Figure 6, 0 on the horizontal axis represents the distance from the inlet 63 of the anode flow path 6, l out This is the outlet 64 of the anode channel 6.

[0054] Curve C0 in Figure 6 is the temperature curve when the cross-sectional area of ​​the anode channel 6 is constant. As shown by curve C0 in Figure 6, in a counterflow fuel cell, when the cross-sectional area of ​​the anode channel is constant, when fuel gas is supplied to the anode channel, the reforming reaction concentrates near the inlet of the channel, causing a large decrease in the temperature inside the anode channel. Also, because the outlet of the anode channel and the inlet of the cathode channel, through which cold air flows, are close together, the temperature near the outlet of the anode channel also decreases significantly. Consequently, the temperature near the inlet and outlet of the anode channel becomes low, while the temperature in the center of the anode channel becomes high. Furthermore, because power generation is concentrated in the center of the anode channel, the heat generated by power generation further increases the temperature in the center of the anode channel 6. Therefore, when the cross-sectional area of ​​the anode channel is constant, the temperature difference ΔT between the inlet and outlet and the center of the channel is large.

[0055] On the other hand, curve C1 in Figure 6 is the temperature curve when, as in this embodiment, the anode flow path 6 has a reforming reaction suppression section 61 with a small flow path cross-sectional area near the inlet 63 and outlet 64, and a reforming reaction acceleration section 62 with a large flow path cross-sectional area in the central section 65. When the anode flow path 6 has a reforming reaction suppression section 61 near the inlet 63 and outlet 64 and a reforming reaction acceleration section 62 in the central section 65, the bias in the reforming reaction is corrected, and as shown in curve C1, the temperature drop near the inlet 63 and outlet 64 of the flow path is suppressed. In addition, because the temperature drop near the inlet 63 and outlet 64 is suppressed, the power generation performance near the inlet 63 and outlet 64 is improved, and the concentration of power generation in the central section 65 of the anode flow path 6 is also suppressed. Therefore, the temperature difference ΔT between the inlet 63 and outlet 64 and the central section 65 of the flow path becomes smaller compared to the case where the flow path cross-sectional area of ​​the anode flow path 6 is constant.

[0056] Here, the temperature at the center of the anode channel 6 when the cross-sectional area of ​​the anode channel 6 is constant is defined as the heat resistance limit temperature T of the anode channel 6. maxThen, in this embodiment where the temperature difference ΔT is small, the average temperature of the fuel gas in the flow channel can be raised to a higher temperature compared to the case where the flow channel cross-sectional area is constant. That is, in the solid oxide fuel cell 100 of this embodiment, the average temperature of the fuel gas in the flow channel can be increased from the curve C1 to the curve C2 in FIG. 6. On the other hand, when the temperature difference ΔT is large and the flow channel cross-sectional area of the anode flow channel 6 is constant, if the average temperature of the fuel gas in the flow channel is increased, the temperature of the anode flow channel 6 near the central part of the flow channel will exceed the heat resistance limit temperature T max and thus the average temperature cannot be increased any further.

[0057] Thus, in the solid oxide fuel cell 100 of this modified example as well, not only can the temperature drop due to reforming concentration be suppressed, but the average temperature of the fuel gas can be increased, and the power generation performance is further improved.

[0058] According to the solid oxide fuel cell 100 of the modified example of the first embodiment described above, the following effects can be obtained.

[0059] In the solid oxide fuel cell 100, the fuel gas flowing through the anode flow channel 6 and the air flowing through the cathode flow channel flow in opposite directions. The reforming reaction promoting part 62 is formed at the central part 65 in the anode flow channel 6, and the reforming reaction suppressing part 61 is formed near the flow channel inlet 63 and the flow channel outlet 64 in the anode flow channel 6. Thereby, the reforming reaction near the inlet 63 of the anode flow channel 6 where the reforming reaction is likely to occur, and the reforming reaction near the outlet 64 of the anode flow channel 6 where the temperature is likely to decrease in a counterflow fuel cell are suppressed, and the temperature drop near the inlet 63 and the outlet 64 of the anode flow channel 6 is suppressed. Therefore, the decrease in power generation performance due to temperature drop can be suppressed.

[0060] Also, since the temperature drop near the inlet 63 and the outlet 64 of the anode flow channel 6 is suppressed, the temperature difference in the anode flow channel 6 during fuel gas supply becomes small. Therefore, the average temperature of the fuel gas in the anode flow channel 6 can be increased, and the power generation performance can be further improved.

[0061] (Second Embodiment) The solid oxide fuel cell 100 of the second embodiment will be described with reference to Figures 7 and 8. This embodiment differs from the other embodiments in that the anode flow path forming member 3 is provided with openings 35 and 36. Elements similar to those in the other embodiments are denoted by the same reference numerals, and their descriptions are omitted.

[0062] Figure 7 is a schematic cross-sectional view of the anode flow path 6 in the solid oxide fuel cell 100 of the second embodiment, where (a) is a schematic view of a part of the cross-section along the direction perpendicular to the flow direction (corresponding to line AA in Figure 2) on the upstream side of the anode flow path 6, and (b) is a schematic view of a part of the cross-section along the direction perpendicular to the flow direction (corresponding to line BB in Figure 2) on the downstream side of the anode flow path 6. Figure 8 is a top view of the flow path forming member 3 as seen from the top surface of the first joint portion 32 where the flow path forming member 3 is joined to the anode electrode. In Figure 8, the fuel gas is assumed to flow from right to left in the figure, and the flow direction of the fuel gas and the air flowing in the cathode flow path are assumed to be the same (i.e., co-flow). Furthermore, the reforming catalyst is assumed to be uniformly arranged in the anode electrode, or in the anode electrode and the anode flow path 6.

[0063] As shown in Figures 7(b) and 8, the flow channel forming member 3, positioned between the anode electrode (metal support 22) and the separator 5, has an opening 35 that penetrates the flow channel forming member 3 in the stacking direction at the first joint portion 32 joined to the anode electrode on the downstream side of the anode flow channel 6. Furthermore, the second joint portion 33 joined to the separator 5 has an opening 36 that penetrates the flow channel forming member 3 in the stacking direction. On the other hand, as shown in Figures 7(a) and 8, on the upstream side of the anode flow channel 6, the first joint portion 32 and the second joint portion 33 of the flow channel forming member 3 are closed. As a result, the cross-sectional area on the downstream side of the anode flow channel 6 is larger than the cross-sectional area on the upstream side. The openings 35 and 36 can be formed by hollowing out the flow channel forming member 3, etc.

[0064] Thus, in this embodiment, the cross-sectional area of ​​the anode channel 6 is changed by providing or closing openings 35 and 36 in the channel forming member 3 at the first and second joints 32 and 33. Specifically, openings 35 and 36 are provided in the channel forming member 3 on the downstream side of the anode channel 6 to increase the channel cross-sectional area, while the channel forming member 3 on the upstream side closes the first and second joints 32 and 33, making the channel cross-sectional area smaller than that on the downstream side. Consequently, the flow velocity on the upstream side of the anode channel 6 is greater than the flow velocity on the downstream side, and the space velocity SV is greater on the upstream side than on the downstream side. As a result, the reforming rate on the upstream side of the anode channel 6 is lower than the reforming rate on the downstream side, and the anode channel 6 is formed with an upstream reforming reaction suppression section 61 where the reforming reaction is suppressed and a downstream reforming reaction promotion section 62 where the reforming reaction is promoted.

[0065] As mentioned above, in a coflow fuel cell, the reforming reaction is more likely to occur upstream of the anode flow path, while heat generation due to power generation is more likely to occur downstream. In contrast, in this embodiment, the anode flow path 6 has a reforming reaction suppression section 61 on the upstream side to suppress the reforming reaction, and a reforming reaction promotion section 62 on the downstream side of the anode flow path 6, where heat generation due to power generation is more likely to occur, to promote the reforming reaction. Therefore, it is possible to suppress the bias in the reforming reaction and the bias in heat generation due to power generation. In other words, it is possible to suppress the temperature drop due to the concentration of reforming, and thus suppress the decrease in power generation performance. In addition, since the temperature difference within the anode flow path 6 during fuel gas supply is reduced, the average temperature of the fuel gas can be increased, and power generation performance can be further improved.

[0066] In this embodiment, since an opening 35 is provided in the first joint portion 32 where the flow path forming member 3 is joined to the anode electrode, fuel gas can also flow into the space enclosed by the flow path forming member 3 and the separator 5 and be supplied to the anode electrode. That is, the space enclosed by the flow path forming member 3 and the separator 5 also becomes the anode flow path 6. Furthermore, on the downstream side of the anode flow path 6, the contact area between the fuel gas and the reforming catalyst placed on the anode electrode is larger than on the upstream side, which does not have an opening 35. As a result, the reforming reaction is further promoted in the reforming reaction promoting section 62 on the downstream side of the anode flow path 6. Consequently, the temperature difference between the upstream and downstream sides of the anode flow path 6 becomes smaller, and the average temperature inside the anode flow path 6 can be increased further.

[0067] According to the solid oxide fuel cell 100 of the second embodiment described above, the following effects can be obtained.

[0068] In the solid oxide fuel cell 100, the reforming catalyst is placed at the anode electrode, and the flow channel forming member 3 in the reforming reaction promoting section 62 has openings 35 and 36 that penetrate the flow channel forming member 3 in the stacking direction at the part that connects to the anode electrode (first connection part 32) and the part that connects to the separator 5 (second connection part 33). That is, the flow channel cross-sectional area of ​​the anode flow channel 6 is changed by whether or not openings 35 and 36 are provided in the flow channel forming member 3, thereby forming the reforming reaction suppression section 61 and the reforming reaction promoting section 62. Therefore, by closing the flow channel forming member 3 near the part where the reforming reaction is likely to occur and providing openings 35 and 36 in the flow channel forming member 3 near the part where heat generation due to power generation is likely to occur, the unevenness of the reforming reaction can be suppressed. Thus, the temperature drop due to reforming concentration can be suppressed, and the decrease in power generation performance due to the temperature drop can be suppressed.

[0069] Furthermore, since the temperature difference within the anode flow path 6 during fuel gas supply is reduced, the average temperature of the fuel gas can be increased, thereby further improving power generation performance.

[0070] Furthermore, in the reforming reaction accelerating section 62, where the flow path forming member 3 has an opening 35, the contact area between the fuel gas and the reforming catalyst placed on the anode electrode is increased. As a result, the reforming reaction is further accelerated in the reforming reaction accelerating section 62. Therefore, by forming the reforming reaction accelerating section 62 near the part where heat generation due to power generation is likely to occur, the temperature difference within the anode flow path 6 is reduced, the average temperature within the anode flow path 6 can be increased, and power generation performance can be further improved.

[0071] In this embodiment, the flow path forming member 3 is configured to have openings 35 and 36 (reform reaction promoting section 62) on the downstream side, but this is not necessarily the case. The locations where the reform reaction suppression section 61 and the reform reaction promoting section 62 are formed can be arbitrarily determined in accordance with the configuration of the solid oxide fuel cell 100. For example, in a counterflow fuel cell, as in the modified example of the first embodiment described above, it is preferable to provide openings 35 and 36 in the flow path forming member 3 in the central part of the anode flow path 6 to form the reform reaction promoting section 62. Also, for example, if the reforming catalyst is not uniformly arranged, the flow path forming member 3 in the part with a large amount of catalyst may be closed to form the reform reaction suppression section 61, and openings 35 and 36 may be provided in the flow path forming member 3 in the part with a small amount of catalyst to form the reform reaction promoting section 62. In addition, in all of the embodiments described below (modified version of the second embodiment, third to fifth embodiments), the anode channel 6 is configured to have a reforming reaction suppression section 61 on the upstream side and a reforming reaction acceleration section 62 on the downstream side. However, the configuration is not limited to these, and the locations where the reforming reaction suppression section 61 and the reforming reaction acceleration section 62 are formed can be determined arbitrarily.

[0072] Furthermore, although Figure 8 of this embodiment shows the flow channel forming member 3 divided into two parts, an upstream side and a downstream side, the invention is not limited to this. As shown in Figure 9 (top view of the flow channel forming member 3), the flow channel forming member 3 may be formed from a single member, and an opening 35 may be provided in the reforming reaction promoting section 62.

[0073] Furthermore, in this embodiment, it is preferable that the reforming catalyst be placed at the anode electrode, but it is not necessarily limited to this, and the reforming catalyst may be placed only in the anode flow path 6. Even with such a configuration, at least by changing the flow path cross-sectional area, the concentration of reforming can be mitigated, and the decrease in power generation performance due to temperature drop can be suppressed.

[0074] (Modified version of the second embodiment) A modified solid oxide fuel cell 100 according to the second embodiment will be described with reference to Figures 10 and 11. In this modified embodiment, the opening 35 is provided only in the first joint portion 32 that connects to the anode electrode in the anode flow path forming member 3, which is different from the second embodiment. Elements similar to those in other embodiments are denoted by the same reference numerals, and their descriptions are omitted.

[0075] Figure 10 is a schematic cross-sectional view of the anode flow path 6 of a solid oxide fuel cell 100, a modified example of the second embodiment, where (a) is a schematic view of a part of the cross-section along the direction perpendicular to the flow direction (corresponding to line AA in Figure 2) on the upstream side of the anode flow path 6, and (b) is a schematic view of a part of the cross-section along the direction perpendicular to the flow direction (corresponding to line BB in Figure 2) on the downstream side of the anode flow path 6. Figure 11 is a top view of the flow path forming member 3, as seen from the top surface of the first joint portion 32 where the flow path forming member 3 is joined to the anode electrode. In Figure 11, the fuel gas is assumed to flow from right to left in the figure, and the flow direction of the fuel gas and the air flowing through the cathode flow path is assumed to be the same (i.e., co-flow). The reforming catalyst is assumed to be uniformly arranged on the anode electrode (metal support 22), or on the inner circumferential surface of the anode electrode and the anode flow path 6.

[0076] Furthermore, as will be described later, in this modified example, similar to the second embodiment, the flow path forming member 3 also has an opening 35 at the first joint portion 32 that is joined to the anode electrode, so the space surrounded by the flow path forming member 3 and the separator 5 also becomes an anode flow path 6 through which fuel gas flows.

[0077] As shown in Figure 10(b) and Figure 11, in this modified example, the channel forming member 3 has an opening 35 that penetrates the channel forming member 3 in the stacking direction at the first joint 32 downstream of the anode channel 6. On the other hand, the channel forming member 3 is closed at the first joint 32 and second joint 33 upstream of the anode channel 6, and at the second joint 33 downstream of the anode channel 6. As a result, the cross-sectional area on the downstream side of the anode channel 6 is larger than the cross-sectional area on the upstream side, and the anode channel 6 is formed with an upstream reforming reaction suppression section 61 with a smaller channel cross-sectional area and a downstream reforming reaction promotion section 62 with a smaller channel cross-sectional area than the upstream side. That is, the reforming reaction is suppressed on the upstream side of the anode channel 6 where the reforming reaction is likely to occur, and the reforming reaction is promoted in the downstream reforming reaction promotion section 62 where the reforming reaction is less likely to occur. Therefore, the temperature drop due to the bias in the reforming reaction is suppressed, and the temperature difference between the upstream and downstream sides of the anode channel 6 is reduced, which allows the average temperature inside the anode channel 6 to be increased.

[0078] Furthermore, the contact area between the fuel gas and the reforming catalyst placed on the anode electrode is larger on the downstream side of the anode channel 6 than on the upstream side, which does not have an opening 35. As a result, the reforming reaction is further promoted in the reforming reaction promotion section 62 on the downstream side of the anode channel 6. Consequently, the temperature difference between the upstream and downstream sides of the anode channel 6 becomes smaller, and the average temperature inside the anode channel 6 can be increased further.

[0079] As described above, in this modified example, the reforming catalyst is placed at the anode electrode of the power generation cell 2, and the flow channel forming member 3 is provided with an opening 35 that penetrates the flow channel forming member 3 in the stacking direction at the portion (first joint portion 32) that is joined to the anode electrode in the reforming reaction promoting section 62. In other words, the flow channel cross-sectional area of ​​the anode flow channel 6 is changed by whether or not an opening 35 is provided at the first joint portion 32 of the flow channel forming member 3. This configuration also has the same effects as the second embodiment.

[0080] It is preferable to have a configuration in which openings are provided in both the first joint 32 and the second joint 33, as in the second embodiment, or a configuration in which the opening 35 is provided only in the first joint 32, as in a modified example of the second embodiment, but it is not limited to these, and a configuration in which the opening is provided only in the second joint 33 is also acceptable. Even with such a configuration, the cross-sectional area of ​​the anode flow path 6 can be changed, so the bias in the reforming reaction can be corrected to some extent.

[0081] Furthermore, in Figure 11 of this modified example, the flow path forming member 3 is divided into two parts, an upstream side and a downstream side, but the invention is not limited to this, and the flow path forming member 3 may be formed from a single member.

[0082] (Third embodiment) The third embodiment of the solid oxide fuel cell 100 will be described with reference to Figures 12 and 13. This embodiment differs from the second embodiment in that an opening is also provided in the anode channel forming member 3 on the upstream side of the anode channel 6. Elements similar to those in other embodiments are denoted by the same reference numerals, and their descriptions are omitted.

[0083] Figure 12 is a schematic cross-sectional view of the anode flow path 6 of the solid oxide fuel cell 100 of the third embodiment, where (a) is a schematic view of a part of the cross-section along the direction perpendicular to the flow direction (corresponding to line AA in Figure 2) on the upstream side of the anode flow path 6, and (b) is a schematic view of a part of the cross-section along the direction perpendicular to the flow direction (corresponding to line BB in Figure 2) on the downstream side of the anode flow path 6. Figure 13 is a top view of the flow path forming member 3 as seen from the top surface of the first joint portion 32 where the flow path forming member 3 is joined to the anode electrode. In Figure 13, the fuel gas is assumed to flow from right to left in the figure, and the flow direction of the fuel gas and the air flowing through the cathode flow path is assumed to be the same (i.e., co-flow). The reforming catalyst is assumed to be uniformly arranged on the anode electrode (metal support 22), or on the inner circumferential surface of the anode electrode and the anode flow path 6.

[0084] Furthermore, as will be described later, in this embodiment as well, the flow path forming member 3 has openings 35A and 35B in the first joint portion 32 that is joined to the anode electrode, so the space enclosed by the flow path forming member 3 and the separator 5 also becomes an anode flow path 6 through which fuel gas flows.

[0085] As shown in Figures 12(a) and 13, the flow channel forming member 3 has an opening 35A that penetrates the flow channel forming member 3 in the stacking direction at the first joint portion 32 that is joined to the anode electrode on the upstream side of the anode flow channel 6, and an opening 36A that penetrates the flow channel forming member 3 in the stacking direction at the second joint portion 33 that is joined to the separator 5. Furthermore, as shown in Figures 12(b) and 13, the flow channel forming member 3 has an opening 35B that penetrates the flow channel forming member 3 in the stacking direction at the first joint portion 32 that is joined to the anode electrode on the downstream side of the anode flow channel 6, and an opening 36B that penetrates the flow channel forming member 3 in the stacking direction at the second joint portion 33 that is joined to the separator 5.

[0086] Here, the openings 35B and 36B on the downstream side of the anode channel 6 have a larger opening width than the openings 35A and 36A on the upstream side. That is, the openings 35B and 36B on the downstream side of the anode channel 6 have a larger opening area than the openings 35A and 36A on the upstream side. As a result, the cross-sectional area on the downstream side of the anode channel 6 is larger than the cross-sectional area on the upstream side.

[0087] Thus, in this embodiment, the cross-sectional area of ​​the anode flow path 6 is changed by changing the size of the opening area (opening width) of the openings 35 and 36 of the flow path forming member 3. Specifically, the cross-sectional area of ​​the flow path is increased by increasing the opening width of the openings 35B and 36B of the flow path forming member 3 on the downstream side of the anode flow path 6, and the cross-sectional area of ​​the flow path is decreased by making the opening width of the openings 35A and 36A of the flow path forming member 3 on the upstream side smaller than the openings 35B and 36B on the downstream side. Consequently, the flow velocity of the fuel gas on the upstream side of the anode flow path 6 is greater than the flow velocity on the downstream side, and the space velocity SV is greater on the upstream side than on the downstream side. As a result, the reforming rate on the upstream side of the anode flow path 6 is lower than the reforming rate on the downstream side, and the anode flow path 6 is formed with an upstream reforming reaction suppression section 61 where the reforming reaction is suppressed and a downstream reforming reaction promotion section 62 where the reforming reaction is promoted. In other words, the reforming reaction is suppressed in the upstream side where it is more likely to occur, and the reforming reaction is promoted in the downstream side where heat generation from power generation is more likely to occur. This suppresses both the bias in the reforming reaction and the bias in heat generation from power generation. Therefore, the temperature drop due to the concentration of reforming can be suppressed, and the decrease in power generation performance can be suppressed. In addition, since the temperature difference in the anode flow path 6 during fuel gas supply is reduced, the average temperature of the fuel gas can be increased, and power generation performance can be further improved.

[0088] Furthermore, in the reforming reaction promotion section 62, where the opening width of the flow path forming member 3 is large, the diffusion distance of the fuel gas from the anode flow path 6 to the anode electrode is shorter compared to the reforming reaction suppression section 61, where the opening width is small (see the arrow in Figure 12). Therefore, in the reforming reaction promotion section 62, the fuel gas can more easily reach the reforming catalyst placed at the anode electrode, and the reforming reaction in the reforming reaction promotion section 62 is further promoted. On the other hand, in the reforming reaction suppression section 61, where the opening width is small, the fuel gas has difficulty reaching the reforming catalyst, and the reforming reaction is further suppressed. As a result, the temperature difference within the anode flow path 6 during fuel gas supply is reduced, and the thermal stress in the flow direction of the anode flow path 6 is alleviated. In addition, because the temperature difference is smaller, the average temperature of the fuel gas can be increased further, and the power generation performance can be further improved.

[0089] According to the solid oxide fuel cell 100 of the third embodiment described above, the following effects can be obtained.

[0090] In the solid oxide fuel cell 100, the reforming catalyst is placed at the anode electrode, and the flow channel forming member 3 has openings 35 and 36 that penetrate the flow channel forming member 3 at the part that connects to the anode electrode (first connection part 32) and the part that connects to the separator 5 (second connection part 33) in the reforming reaction promoting section 62 and the reforming reaction suppressing section 61. The openings 35B and 36B in the reforming reaction promoting section 62 have a larger opening area than the openings 35A and 36A in the reforming reaction suppressing section 61. Therefore, by providing openings 35A and 36A with a small opening area in the flow channel forming member 3 near the part where the reforming reaction is likely to occur, and openings 35B and 36B with a large opening area in the flow channel forming member 3 near the part where heat generation due to power generation is likely to occur, the unevenness of the reforming reaction can be suppressed. In other words, the temperature drop due to reforming concentration can be suppressed, and the decrease in power generation performance due to the temperature drop can be suppressed.

[0091] Furthermore, in the reforming reaction acceleration section 62, where the flow path forming member 3 has large openings 35B and 36B, the fuel gas can more easily reach the reforming catalyst placed at the anode electrode, and the reforming reaction in the reforming reaction acceleration section 62 is further accelerated. On the other hand, in the reforming reaction suppression section 61, where the flow path forming member 3 has small openings 35A and 36A, the fuel gas has difficulty reaching the reforming catalyst, and the reforming reaction is further suppressed. Consequently, the temperature difference within the anode flow path 6 during fuel gas supply is reduced, and thermal stress in the flow direction of the anode flow path 6 is alleviated. In addition, because the temperature difference is reduced, the average temperature of the fuel gas can be increased further, and power generation performance can be further improved.

[0092] In the solid oxide fuel cell 100, the reforming catalyst is placed at the anode electrode, and the flow channel forming member 3 has openings 35 and 36 that penetrate the flow channel forming member 3 at the part that connects to the anode electrode (first connection part 32) and the part that connects to the separator 5 (second connection part 33) in the reforming reaction promoting section 62 and the reforming reaction suppressing section 61. The openings 35B and 36B in the reforming reaction promoting section 62 have a larger opening width than the openings 35A and 36A in the reforming reaction suppressing section 61. Therefore, by providing openings 35A and 36A with a smaller opening width in the flow channel forming member 3 near the part where the reforming reaction is likely to occur, and openings 35B and 36B with a larger opening width in the flow channel forming member 3 near the part where heat generation due to power generation is likely to occur, the unevenness of the reforming reaction can be suppressed. In other words, the temperature drop due to reforming concentration can be suppressed, and the decrease in power generation performance due to the temperature drop can be suppressed.

[0093] In this embodiment, it is preferable that the reforming catalyst be placed at the anode electrode, but it is not necessarily limited to this, and the reforming catalyst may be placed only in the anode flow path 6. Even with such a configuration, at least by changing the flow path cross-sectional area, the concentration of reforming can be mitigated, and the decrease in power generation performance due to temperature drop can be suppressed.

[0094] Furthermore, in Figure 13 of this embodiment, the flow path forming member 3 is divided into two parts, an upstream side and a downstream side, and the width of the opening is changed in two stages. However, the embodiment is not limited to this, and as shown in Figure 14 (top view of the flow path forming member 3), the flow path forming member 3 may be formed from a single member, and the width of the opening may be changed in two stages.

[0095] Furthermore, although Figure 13 of this embodiment shows the opening width of the channel forming member 3 being changed in two stages, the invention is not limited to this, and the opening width may be changed in stages to three or more different widths. Also, as shown in Figure 15 (top view of the channel forming member 3), the opening widths of the openings 35 and 36 of the channel forming member 3 may be changed continuously. In this case, the portion of the opening widths of the openings 35 and 36 that is less than or equal to a predetermined length becomes the reforming reaction suppression section 61, and the portion that is greater than the predetermined length becomes the reforming reaction promotion section 62.

[0096] Furthermore, in this embodiment, the opening widths of the openings 35A and 36A in the reforming reaction suppression section 61 are reduced, and the opening widths of the openings 35B and 36B in the reforming reaction acceleration section 62 are increased, but this is not necessarily the only configuration. That is, any configuration is acceptable as long as the opening area of ​​the openings 35B and 36B in the reforming reaction acceleration section 62 is larger than the opening area of ​​the openings 35A and 36A in the reforming reaction suppression section 61 (see, for example, the fourth embodiment described later).

[0097] (Fourth Embodiment) Referring to Figure 16, the fourth embodiment of the solid oxide fuel cell 100 will be described. This embodiment differs from the third embodiment in that multiple openings 35A are provided at intervals on the upstream side (near the inlet) of the anode flow path 6. Elements similar to those in other embodiments are denoted by the same reference numerals, and their descriptions are omitted.

[0098] Figure 16 is a top view of the anode channel 6 in the solid oxide fuel cell 100 of the fourth embodiment, and is a view of the anode channel 6 from the top surface of the first joint 32 where the anode channel forming member 3 is joined to the anode electrode. In Figure 16, the fuel gas is assumed to flow from right to left in the figure, and the flow direction of the fuel gas and the air flowing in the cathode channel is assumed to be the same (i.e., co-flow). The reforming catalyst is assumed to be uniformly arranged in the anode electrode (metal support 22), or in the anode electrode and the anode channel 6.

[0099] Furthermore, as will be described later, in this embodiment as well as in the second and third embodiments, the flow path forming member 3 has openings 35A and 35B in the first joint portion 32 that is joined to the anode electrode, so the space enclosed by the flow path forming member 3 and the separator 5 also becomes an anode flow path 6 through which fuel gas flows.

[0100] As shown in Figure 16, the flow path forming member 3 has multiple openings 35A that penetrate the flow path forming member 3 in the stacking direction, spaced apart in the direction of fuel gas flow, on the upstream side (near the inlet) of the anode flow path 6. That is, the flow path forming member 3 on the upstream side (near the inlet) of the anode flow path 6 has multiple spaced openings 35A and beam portions 37 between the openings 35A. On the other hand, the flow path forming member 3 downstream of the portion where the openings 35A and beam portions 37 are formed (hereinafter referred to as the downstream side) has one opening 35B that penetrates the flow path forming member 3 in the stacking direction, along the anode flow path 6.

[0101] Here, on the upstream side (near the inlet) of the anode flow path 6, multiple openings 35A are provided at intervals, so the opening area per unit area of ​​the flow path forming member 3 for the openings 35A is smaller than the opening area of ​​the downstream openings 35B. Therefore, the average value of the flow path cross-sectional area of ​​the anode flow path 6 on the upstream side (near the inlet) where the openings 35A are provided is smaller than the average value of the flow path cross-sectional area of ​​the anode flow path 6 on the downstream side. In other words, the flow velocity of the fuel gas on the upstream side (near the inlet) of the anode flow path 6 is greater than the flow velocity on the downstream side. As a result, the reforming rate on the upstream side (near the inlet) of the anode flow path 6 is lower than the reforming rate on the downstream side, and the anode flow path 6 is formed with an upstream reforming reaction suppression section 61 where the reforming reaction is suppressed and a downstream reforming reaction promotion section 62 where the reforming reaction is promoted. In other words, the reforming reaction is suppressed in the upstream side (near the inlet) where it is likely to occur, and the reforming reaction is promoted in the downstream side where heat generation due to power generation is likely to occur. This suppresses both the bias in the reforming reaction and the bias in heat generation due to power generation. Therefore, the temperature drop due to the concentration of reforming can be suppressed, and the decrease in power generation performance can be suppressed. In addition, since the temperature difference in the anode flow path 6 during fuel gas supply is reduced, the average temperature of the fuel gas can be increased, and power generation performance can be further improved.

[0102] Furthermore, downstream of the anode channel 6, the opening 35B has a larger opening area than the opening 35A upstream (near the inlet), resulting in a larger contact area between the fuel gas and the reforming catalyst placed on the anode electrode. On the other hand, upstream of the anode channel 6 (near the inlet), the openings 35A are spaced apart, creating a region where the fuel gas and the reforming catalyst placed on the anode electrode do not come into contact. Consequently, the reforming reaction is further promoted in the reforming reaction promotion section 62 downstream of the anode channel 6, and the reforming reaction is further suppressed in the reforming reaction suppression section 61 upstream (near the inlet). As a result, the temperature difference between the upstream and downstream sides of the anode channel 6 becomes smaller, and the average temperature inside the anode channel 6 can be increased, thus improving power generation performance.

[0103] Furthermore, since the flow path forming member 3 on the upstream side (near the inlet) of the anode flow path 6 has a beam portion 37 between the openings 35A, the beam portion 37 becomes a conductive passage in the width direction of the anode flow path 6. As a result, the temperature rises in the reforming reaction suppression section 61 on the upstream side (near the inlet) of the anode flow path 6 due to Joule heating caused by resistance, further suppressing the temperature drop on the upstream side (near the inlet) and further suppressing the decrease in power generation performance.

[0104] According to the solid oxide fuel cell 100 of the fourth embodiment described above, the following effects can be obtained.

[0105] In the solid oxide fuel cell 100, the reforming catalyst is placed at the anode electrode, and multiple openings 35A are provided in the flow path forming member 3 in the reforming reaction suppression section 61, spaced apart in the direction of fuel gas flow in the anode flow path 6. This reduces the opening area of ​​the openings 35A in the reforming reaction suppression section 61. Therefore, by providing openings 35A with a small opening area in the flow path forming member 3 near the part where the reforming reaction is likely to occur, the unevenness of the reforming reaction can be suppressed. In other words, the temperature drop due to reforming concentration can be suppressed, and the decrease in power generation performance due to the temperature drop can be suppressed.

[0106] Furthermore, because the openings 35A in the reforming reaction suppression section 61 are spaced apart, a region is created in the reforming reaction suppression section 61 where the fuel gas and the reforming catalyst placed on the anode electrode do not come into contact. Consequently, the reforming reaction is further suppressed in the reforming reaction suppression section 61. Therefore, by forming the reforming reaction suppression section 61 near the area where the reforming reaction is likely to occur, the temperature difference within the anode flow path 6 can be reduced, and the average temperature within the anode flow path 6 can be increased. Thus, power generation performance is further improved.

[0107] Furthermore, since the openings 35A in the reforming reaction suppression section 61 are spaced apart, beam sections 37, which serve as conductive passages in the width direction of the anode flow path 6, are formed between the openings 35A in the reforming reaction suppression section 61. As a result, the temperature in the reforming reaction suppression section 61 rises due to Joule heating caused by resistance, further suppressing the temperature drop in the reforming reaction suppression section 61 and further suppressing the decrease in power generation performance.

[0108] In this embodiment, it is preferable that the reforming catalyst be placed at the anode electrode, but it is not necessarily limited to this, and the reforming catalyst may be placed only in the anode flow path 6. Even with such a configuration, at least by changing the flow path cross-sectional area, the concentration of reforming can be mitigated, and the decrease in power generation performance due to temperature drop can be suppressed.

[0109] Furthermore, in this embodiment, openings 35A and 35B are provided in the first joint 32 where the flow channel forming member 3 is joined to the anode electrode. However, similar openings may also be provided in the second joint 33 where the flow channel forming member 3 is joined to the separator 5. Moreover, it is also possible to provide similar openings only in the second joint 33. Even in this case, at least by changing the cross-sectional area of ​​the flow channel, the concentration of reforming can be mitigated, and the decrease in power generation performance due to temperature drop can be suppressed to some extent.

[0110] Furthermore, although the flow channel forming member 3 is divided into two parts, upstream and downstream, in Figure 16 of this embodiment, the invention is not limited to this. As shown in Figure 17 (top view of the anode flow channel 6), the flow channel forming member 3 may be formed from a single member, and openings 35A may be provided at intervals in the reforming reaction suppression section 61.

[0111] (Fifth embodiment) Referring to Figure 18, the solid oxide fuel cell 100 of the fifth embodiment will be described. In this embodiment, the anode channel forming member 3 is made of a porous material, which is different from the other embodiments. The same reference numerals are used for elements that are the same as in the other embodiments, and their descriptions are omitted.

[0112] Figure 18 is a schematic cross-sectional view of the anode flow path 6 along the direction of fuel gas flow. In Figure 18, the fuel gas is assumed to flow from right to left, and the flow direction of the fuel gas and the air flowing through the cathode flow path is assumed to be the same (i.e., co-flow). The reforming catalyst is assumed to be uniformly distributed on at least one of the anode electrode (metal support 22) and the inner surface of the anode flow path 6.

[0113] As shown in Figure 18, in this embodiment, the channel forming member 3 is a porous body made of a porous material.

[0114] Furthermore, as shown in Figure 18, the flow path forming member 3 is denser on the upstream side of the anode flow path 6 than on the downstream side. That is, the void ratio of the flow path forming member 3 on the upstream side of the anode flow path 6 is smaller than that on the downstream side. Consequently, the flow path cross-sectional area on the downstream side of the anode flow path 6 is larger than that on the upstream side. As a result, the flow velocity of the fuel gas on the upstream side of the anode flow path 6 is greater than that on the downstream side, and the reforming rate on the upstream side of the anode flow path 6 is lower than that on the downstream side. In this way, the anode flow path 6 is formed with an upstream reforming reaction suppression section 61 where the reforming reaction is suppressed and a downstream reforming reaction promotion section 62 where the reforming reaction is promoted. Consequently, the reforming reaction is suppressed on the upstream side where the reforming reaction is likely to occur, and the reforming reaction is promoted on the downstream side where heat generation due to power generation is likely to occur, thus suppressing the bias in the reforming reaction and the bias in heat generation due to power generation. Therefore, the temperature drop due to reforming concentration can be suppressed, and the decrease in power generation performance can be suppressed. Furthermore, since the temperature difference within the anode flow path 6 during fuel gas supply is reduced, the average temperature of the fuel gas can be increased, thereby further improving power generation performance.

[0115] Although embodiments of the present invention have been described above, these embodiments only represent a part of the application examples of the present invention, and are not intended to limit the technical scope of the present invention to the specific configurations of the above embodiments.

[0116] Although each of the embodiments described above has been explained as a standalone embodiment, they may be combined as appropriate. [Explanation of Symbols]

[0117] 1. Cell unit, 2. Power generation cell, 3. Anode channel forming member (channel forming member), 5. Separator, 6. Anode channel, 21. Membrane electrode assembly, 51. Shim plate, 61. Reforming reaction suppression unit, 62. Reforming reaction acceleration unit, 100. Solid oxide fuel cell

Claims

1. A solid oxide fuel cell is formed by stacking multiple power generation cells, each comprising a solid electrolyte layer, an anode electrode disposed on one side of the solid electrolyte layer, and a cathode electrode disposed on the other side of the solid electrolyte layer, with a separator in between. The system includes a flow path forming member that is positioned between the anode electrode and the separator and forms an anode flow path through which fuel gas flows, A reforming catalyst is placed in at least one of the anode electrode and the anode channel of the power generation cell. The anode channel has a reforming reaction promoting section with a large channel cross-sectional area and a reforming reaction suppressing section with a smaller channel cross-sectional area than the reforming reaction promoting section. The reforming reaction promoting section and the reforming reaction suppressing section are formed by changing the cross-sectional area of ​​the anode channel using the separator or the channel forming member. The reform reaction promoting unit is provided near a portion where the reform reaction is less likely to occur. The reforming reaction suppression unit is provided near the part where the reforming reaction is likely to occur. The flow channel forming member has a portion that is joined to the anode electrode and a portion that is joined to the separator. The channel forming member is provided with an opening that penetrates the channel forming member in the stacking direction at least one of the portions that are joined to the anode electrode and the separator in the reforming reaction promoting section. Solid oxide fuel cell.

2. A solid oxide fuel cell according to claim 1, The separator has a greater thickness in the stacking direction in the modification reaction suppression section than in the modification reaction acceleration section. Solid oxide fuel cell.

3. A solid oxide fuel cell according to claim 1, The reforming catalyst is placed at the anode electrode of the power generation cell. The channel forming member is provided with an opening that penetrates the channel forming member in the stacking direction at the portion that is joined to the anode electrode in the reforming reaction promoting section. Solid oxide fuel cell.

4. A solid oxide fuel cell according to claim 1, The channel forming member is provided with an opening that penetrates the channel forming member in at least one of the portions that are joined to the anode electrode and the separator in the reforming reaction promoting portion and the reforming reaction suppressing portion. In the reform reaction promoting section, the opening provided in the flow channel forming member has a larger opening area than the opening provided in the flow channel forming member in the reform reaction suppressing section. Solid oxide fuel cell.

5. A solid oxide fuel cell according to claim 4, In the reform reaction promoting section, the opening provided in the flow channel forming member has a larger opening width than the opening provided in the flow channel forming member in the reform reaction suppressing section. Solid oxide fuel cell.

6. A solid oxide fuel cell according to claim 4, In the reforming reaction suppression section, the openings provided in the flow path forming member are provided in multiple locations at intervals in the direction of fuel gas flow in the anode flow path. Solid oxide fuel cell.

7. A solid oxide fuel cell according to claim 1, The channel forming member is made of a porous material, and the porosity in the modification reaction suppression section is smaller than the porosity in the modification reaction acceleration section. Solid oxide fuel cell.

8. A solid oxide fuel cell according to claim 1, The system further comprises a cathode channel forming member, which is positioned between the cathode electrode and the separator and forms a cathode channel through which air flows. The fuel gas flowing through the anode channel and the air flowing through the cathode channel have the same flow direction. The reforming reaction suppression unit is formed on the upstream side of the anode channel, The reforming reaction promoting unit is formed on the downstream side of the anode channel. Solid oxide fuel cell.

9. A solid oxide fuel cell according to claim 1, The system further comprises a cathode channel forming member, which is positioned between the cathode electrode and the separator and forms a cathode channel through which air flows. The fuel gas flowing through the anode channel and the air flowing through the cathode channel have opposite flow directions. The reforming reaction promoting unit is formed in the central part of the anode channel, The reforming reaction suppression section is formed near the channel inlet and near the channel outlet in the anode channel. Solid oxide fuel cell.

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