A porous tubular methanol solid oxide fuel cell having a closed end

Abstract

The application discloses a porous tubular methanol solid oxide fuel cell with a closed end, which is a tubular solid oxide fuel cell (SOFC) cell stack, and a plurality of tubular SOFC single cells are contained in the tubular SOFC cell stack; the bottom end of the inner tube of the tubular SOFC single cell is open, the top end is closed, the inner tube wall is provided with a plurality of closed sections and a plurality of open sections, and the plurality of closed sections and the plurality of open sections are arranged alternately in sequence along the moving direction of fuel in the inner tube. The inner tube structure of the tubular SOFC single cell can effectively improve the uniformity of the distribution of methanol on the anode surface of the solid oxide fuel cell, thereby effectively overcoming the serious problem of carbon deposition caused by the uneven distribution of methanol on the anode surface of the solid oxide fuel cell.

Description

Technical Field

[0001] This invention relates to a porous tubular methanol solid oxide fuel cell with a closed end. Background Technology

[0002] Solid oxide fuel cells (SOFCs) are environmentally friendly power generation devices that convert the chemical energy of reactants into electrical energy through electrochemical reactions. Due to their high operating temperatures, SOFCs can use a variety of fuels, such as methane, methanol, ethanol, ammonia, vegetable oil, sugar, glucose, and propane. Methanol, being widely available and liquid at room temperature, has become one of the most ideal fuels for SOFCs. Studies have shown that while methanol itself does not produce carbon deposits, the CO produced by methanol cracking can lead to carbon buildup in SOFCs. In traditional tubular methanol SOFCs, methanol flows along the inner tube to the top of the anode and then flows back down the outer tube from top to bottom. Therefore, the methanol concentration is highest at the top of the anode, resulting in the fastest pyrolysis and the most severe carbon buildup (severe carbon buildup manifests as carbon formation on the surface of the anode active components, covering them and rendering them inactive, thus leading to performance degradation of the fuel cell). To address this issue, existing technologies propose a porous inner tube design. Some methanol can enter the anode through the porous area to participate in the reaction, but most of the methanol flows along the inner tube to the top of the anode and then back down the outer tube from top to bottom. While this method reduces carbon buildup at the top of the anode, it is still significant. Summary of the Invention

[0003] Purpose of the invention: The purpose of this invention is to provide a solid oxide fuel cell that can effectively alleviate the problem of carbon deposition on the anode of methanol SOFC, and solve the problem of performance degradation caused by carbon deposition in methanol solid oxide fuel cells, thereby shortening the battery life.

[0004] Technical solution: The methanol solid oxide fuel cell of the present invention is a tubular SOFC stack, which contains multiple tubular SOFC single cells. Along the direction of fuel movement in the inner tube, the bottom end of the inner tube of the tubular SOFC single cell is open and the top end is closed. The inner tube wall is provided with multiple closed areas and multiple open areas, which are arranged alternately. Among them, the area near the top end is the open area and the area near the bottom end is the closed area.

[0005] Each of the opening sections has a catalyst layer on the outside of the tube wall. The catalyst layer is made of anode material for solid oxide fuel cells, such as Ni / YSZ or Ni / BZCY catalyst layer.

[0006] The thickness of the catalyst layer is 550–600 μm.

[0007] The multi-segment opening area includes a first opening area near the top, a third opening area near the bottom, and a second opening area located between the first and third opening areas; wherein the porosity of the first opening area is 0.3 to 0.5, the porosity of the second opening area is 0.3 to 1.0, and the porosity of the third opening area is 0.5 to 0.6.

[0008] The diameter of the holes in the multi-segment opening area is not less than 1 μm.

[0009] The length of the first opening area is 11-25% of the total length of the inner tube, the length of the second opening area is 8-12% of the total length of the inner tube, and the length of the third opening area is 11-14% of the total length of the inner tube.

[0010] The multiple closed areas include a first closed area near the bottom, a second closed area located between the second and third opening areas, and a third closed area located between the first and second opening areas.

[0011] The lengths of the first, second, and third enclosed zones are 17-23% of the total length of the inner tube.

[0012] The inner tube has a wall thickness of 0.9–1.1 mm and an inner radius of 1.5–2.0 mm, while the anode tube has an inner radius of 4–6 mm.

[0013] Beneficial Effects: Compared with existing technologies, this invention has the following significant advantages: In the tubular SOFC single cell of this invention, methanol can only enter the anode through the porous structure of the inner tube, reducing the methanol concentration at the top of the anode. Compared with the porous inner tube design, the closed-end porous inner tube improves the uniformity of methanol distribution on the anode surface. Simultaneously, a catalyst layer of the same length as the porous structure region is added outside the porous inner tube. The addition of the catalyst layer allows methanol to be cracked before entering the anode, and the cracking products can directly enter the anode to participate in the electrochemical reaction, further reducing anode carbon deposition. Monitoring revealed that the maximum methanol concentration at the top, middle, and bottom of the anode is almost the same, indicating an effective improvement in the uniformity of methanol distribution on the anode surface. The inner tube structure of the tubular SOFC single cell of this invention can effectively improve the uniformity of methanol distribution on the anode surface of a solid oxide fuel cell, thereby effectively overcoming the serious carbon deposition problem caused by uneven methanol distribution on the anode surface of a solid oxide fuel cell (in areas with high methanol concentration, more CO is produced from methanol cracking, easily leading to severe carbon deposition). Attached Figure Description

[0014] Figure 1 This is a schematic diagram of the structure of the tubular SOFC single cell of the present invention;

[0015] Figure 2 The diagrams show a comparison of the carbon deposition activity of the corresponding anodes of the prior art porous inner tube, Comparative Example 1, and Example 1 with one end closed porous inner tube; a) shows the carbon deposition activity distribution of the prior art porous inner tube; b) shows the carbon deposition activity distribution of the porous inner tube of Comparative Example 1; c) shows the carbon deposition activity distribution of the porous inner tube with one end closed in Example 1.

[0016] Figure 3 The graphs show the methanol concentration distribution on the anode surface of the prior art porous inner tube, Comparative Example 1, and Example 1 with one end closed porous inner tube; a) shows the methanol concentration distribution on the anode surface corresponding to the prior art porous inner tube; b) shows the methanol concentration distribution on the anode surface corresponding to the porous inner tube of Comparative Example 1; c) shows the methanol concentration distribution on the anode surface corresponding to the porous inner tube with one end closed in Example 1.

[0017] Figure 4 The diagram shows the carbon deposition activity and methanol concentration distribution on the anode surface of the porous inner tube with one end closed in Example 2; a) shows the carbon deposition activity of the porous inner tube with one end closed in Example 2; b) shows the methanol concentration distribution on the anode surface corresponding to the porous inner tube with one end closed in Example 2.

[0018] Figure 5 The figures show a comparison of the carbon deposition activity of Example 2 (without a catalyst layer) and Example 3 (with a catalyst layer) with one end of a closed porous inner tube. Figure a shows the carbon deposition activity of Example 2 (without a catalyst layer) with one end of a closed porous inner tube; Figure b shows the carbon deposition activity of Example 3 (with a catalyst layer).

[0019] Figure 6 The figures show the methanol concentration distribution on the anode surface of Example 2 with a closed porous inner tube without a catalyst layer and Example 3 with a closed porous inner tube with a catalyst layer. Figure a shows the methanol concentration distribution on the anode surface of Example 2 with a closed porous inner tube without a catalyst layer and Figure b shows the methanol concentration distribution on the anode surface of Example 3 with a closed porous inner tube with a catalyst layer. Detailed Implementation

[0020] like Figure 1As shown, the present invention relates to a methanol solid oxide fuel cell, wherein the fuel cell is a tubular SOFC stack, and the tubular SOFC stack contains multiple tubular SOFC single cells 1. The cell structure, from the inside out, consists of an anode support layer 7, an anode functional layer 8, an electrolyte 9, a cathode functional layer 10, and a cathode support layer 11. The cavity 2 formed by the gap between the inner tube 3 and the anode support layer 7 is the anode reaction zone. Along the direction of fuel movement within the inner tube 3, the bottom end of the inner tube 3 of the tubular SOFC single cell is open, and the top end is closed. The inner tube 3 wall has multiple closed sections and multiple open sections, which are arranged alternately. Fuel flows in through the bottom opening of the inner tube 3 and enters the anode through the multiple open sections (first open section 4, second open section 5, and third open section 6) to participate in the reaction. The top end of the inner tube 3 is closed, and the closed top end is made of the same material as the closed section of the inner tube side wall, which can prevent fuel from flowing into the top of the anode, thereby effectively preventing the phenomenon of severe carbon accumulation on the top of the anode.

[0021] Example 1

[0022] In this embodiment, the multi-segment opening area includes a first opening area 4 near the top, a third opening area 6 near the bottom, and a second opening area 5 located between the first opening area 4 and the third opening area 6; the multi-segment closed area includes a first closed area 13 near the bottom, a second closed area 14 located between the second opening area 5 and the third opening area 6, and a third closed area 15 located between the first opening area 4 and the second opening area 5; the lengths of the first closed area 13, the second closed area 14, and the third closed area 15 are all 20 mm, and the lengths of the first opening area 4, the second opening area 5, and the third opening area 6 are all 10 mm; and the porosity of the first opening area 4, the second opening area 5, and the third opening area 6 is all ε = 0.5; the inner tube wall thickness w = 1 mm, the inner tube inner radius R = 1.5 mm, the inner radius of the anode tube is 4 mm, and there is a certain gap between the inner tube and the tubular solid oxide fuel cell anode tube.

[0023] Comparative Example 1

[0024] The only difference between Comparative Example 1 and Example 1 is that the top of the inner tube 3 is open; otherwise, the inner tube structure is exactly the same as that of Example 1.

[0025] The maximum carbon deposition activity and methanol concentration distribution of the anodes corresponding to the structures of the prior art, Comparative Example 1, and Example 1 are as follows: Figures 2-3 As shown. (Through) Figures 2-3It can be seen that, compared to the porous inner tube with open ends (the existing porous inner tube refers to the porous inner tube disclosed in application number 2021114213287, where the porous layer sidewall has a porosity of 0.5 and a thickness of 2mm; the inner wall of the inner tube (excluding the pipe with the porous layer sidewall) is coated with a methanol pyrolysis catalyst layer, and the ratio of the length of the inner tube in the battery reaction zone to the length of the pipe with the porous layer sidewall is 3:1, that is, if the lower half of the inner tube in the battery reaction zone is 9cm long, the length of the pipe with the porous layer sidewall is 3cm), the maximum carbon deposition activity of the anode corresponding to the porous inner tube with one end closed in Embodiment 1 of this invention is 51.8 ( Figure 2 a) decreased to 23.01 ( Figure 2 c) The maximum methanol concentration is 6.06 mol / m³. 3 ( Figure 3 a) Reduced to 4.15 mol / m 3 ( Figure 3 c). When the structure was changed to that of Comparative Example 1, the maximum carbon deposition activity of the anode actually increased, becoming 75.63 ( Figure 2 b) The maximum methanol concentration on the anode surface becomes 6.72 mol / m 3 ( Figure 3 b).

[0026] Example 2

[0027] In this embodiment, the multi-segment opening area includes a first opening area 4 near the top, a third opening area 6 near the bottom, and a second opening area 5 located between the first opening area 4 and the third opening area 6; the multi-segment closed area includes a first closed area 13 near the bottom, a second closed area 14 located between the second opening area 5 and the third opening area 6, and a third closed area 15 located between the first opening area 4 and the second opening area 5; the lengths of the first closed area 13, the second closed area 14, and the third closed area 15 are all 16 mm; the length of the first opening area 4 is 22 mm with a porosity of 0.5; the length of the second opening area 5 is 8 mm with a porosity of 0.3; the length of the third opening area 6 is 12 mm with a porosity of 0.5; the wall thickness of the inner tube 3 is w = 1 mm; the inner radius of the inner tube 3 is R = 1.5 mm; and the inner radius of the anode tube is 4 mm; the corresponding maximum carbon deposition activity and methanol concentration distribution are as follows: Figure 4 As shown.

[0028] pass Figure 4 It can be seen that, compared to Example 1, the maximum carbon deposition activity of the porous inner tube with one end closed in Example 2 is 23.01 ( Figure 2 c) decreased to 17.56 ( Figure 4 a) The maximum methanol concentration is 4.15 mol / m³. 3 ( Figure 3 c) Reduced to 3.63 mol / m3 ( Figure 4 b).

[0029] Example 3

[0030] In this embodiment, the multi-segment opening area includes a first opening area 4 near the top, a third opening area 6 near the bottom, and a second opening area 5 located between the first opening area 4 and the third opening area 6; the multi-segment closed area includes a first closed area 13 near the bottom, a second closed area 14 located between the second opening area 5 and the third opening area 6, and a third closed area 15 located between the first opening area 4 and the second opening area 5; the lengths of the first closed area 13, the second closed area 14, and the third closed area 15 are all 16 mm; the length of the first opening area 4 is 22 mm with a porosity of 0.3; the length of the second opening area 5 is 8 mm with a porosity of 1; and the length of the third opening area 6 is 12 mm with a porosity of 0.3. The rate is 0.5, the inner tube 3 wall thickness w = 1 mm, the inner radius R = 1.5 mm, and the inner radius of the anode tube is 4 mm; a catalyst layer 12 is provided on the outer wall of the tube corresponding to the first opening area 4 and the third opening area 6, and the laying length of the catalyst layer 12 is consistent with the length of the first opening area 4 and the third opening area 6; the material selected for the catalyst layer 12 is the anode material of solid oxide fuel cell, such as Ni / YSZ or Ni / BZCY catalyst layer; after thickness analysis, the thickness of the catalyst layer 12 is set to 550 μm. The addition of the catalyst layer allows methanol to be catalyzed by the catalyst layer before flowing into the anode from the opening area, and the generated synthesis gas products can directly enter the anode area for reaction, thereby reducing carbon deposition on the anode. In this embodiment, appropriately reducing the porosity of the first opening area 4 and then increasing the porosity of the second opening area 5 can help reduce carbon deposition. At this time, the maximum carbon deposition activity of the anode area is further reduced compared with Example 2 without a catalyst layer, see Figure 5 Furthermore, the methanol concentration distribution on the anode surface is more uniform, see Figure 6 .

[0031] pass Figures 5-6 It can be seen that, compared with the porous inner tube, the maximum methanol concentration in the porous inner tube with one end closed in Example 3 is 6.06 mol / m³. 3 ( Figure 3 a) Reduced to 1.48 mol / m 3 ( Figure 6 (b) decreased by 75.5%; in addition, the maximum carbon deposition activity also decreased from 51.8 ( Figure 2 a) decreased to 4.91 ( Figure 5 b).

[0032] This invention relates to a tubular solid oxide fuel cell (anode tube) with one end closed and the inner tube also closed at one end. The inner tube wall has a multi-segment porous structure, while the remaining part has a dense structure. Because the top of the inner tube is closed, fuel can only enter the anode to participate in the electrochemical reaction through the porous structure of the inner tube. By matching the porosity, thickness, length, and inner radius of the open area of ​​the inner tube, the uniformity of methanol concentration on the anode surface can be effectively improved. This alleviates the severe carbon deposition problem caused by excessive methanol concentration at the top of the anode in traditional tubular methanol solid oxide fuel cells, slows down the battery degradation rate, and extends battery life. In addition, this invention adds a catalyst layer outside the porous structure. The catalyst layer allows methanol to be catalytically cracked before entering the anode, and the cracking products directly enter the anode reaction, further reducing carbon deposition.

Claims

1. A porous tubular methanol solid oxide fuel cell with a closed end, wherein the fuel cell is a tubular SOFC stack, and the tubular SOFC stack contains a plurality of tubular SOFC single cells (1); characterized in that: Along the direction of fuel movement within the inner tube (3), the bottom of the inner tube of the tubular SOFC single cell (1) is open and the top is closed. The inner tube (3) wall is provided with multiple closed sections and multiple open sections, which are arranged alternately in sequence.

2. The porous tubular methanol solid oxide fuel cell according to claim 1, characterized in that: A catalyst layer (12) is provided on the outside of the tube wall corresponding to the opening area. The catalyst layer (12) is a Ni / YSZ catalyst layer or a Ni / BZCY catalyst layer.

3. The porous tubular methanol solid oxide fuel cell according to claim 2, characterized in that: The thickness of the catalyst layer (12) is 550-600 μm.

4. The porous tubular methanol solid oxide fuel cell according to claim 1, characterized in that: The multi-segment opening area includes a first opening area (4) near the top, a third opening area (6) near the bottom, and a second opening area (5) located between the first opening area (4) and the third opening area (6); wherein the porosity of the first opening area (4) is 0.3 to 0.5, the porosity of the second opening area (5) is 0.3 to 1.0, and the porosity of the third opening area (6) is 0.5 to 0.

6.

5. The porous tubular methanol solid oxide fuel cell according to claim 4, characterized in that: The diameter of the holes in the multi-segment opening area is not less than 1 μm.

6. The porous tubular methanol solid oxide fuel cell according to claim 4, characterized in that: The length of the first opening area (4) is 11-25% of the total length of the inner tube (3), the length of the second opening area (5) is 8-12% of the total length of the inner tube (3), and the length of the third opening area (6) is 11-14% of the total length of the inner tube (3).

7. The porous tubular methanol solid oxide fuel cell according to claim 1, characterized in that: The multi-segment closed area includes a first closed area (13) near the bottom, a second closed area (14) located between the second opening area (5) and the third opening area (6), and a third closed area (15) located between the first opening area (4) and the second opening area (5).

8. The porous tubular methanol solid oxide fuel cell according to claim 7, characterized in that: The lengths of the first closed area (13), the second closed area (14), and the third closed area (15) are 17 to 23% of the total length of the inner tube (3).

9. The porous tubular methanol solid oxide fuel cell according to claim 1, characterized in that: The wall thickness of the inner tube (3) is 0.9 to 1.1 mm.

10. The porous tubular methanol solid oxide fuel cell according to claim 1, characterized in that: The inner radius of the inner tube (3) is 1.5 to 2.0 mm; the inner radius of the outer anode tube of the inner tube (3) is 4 to 6 mm.

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