Electrochemical systems

Abstract

The present invention provides an electrochemical system that can reduce the variation in thermal energy exchanged per unit time in a heat exchanger. [Solution] The electrochemical system comprises a stack having multiple cells containing an electrolyte that separates a fuel electrode from an air electrode, a heat exchanger, and a tube through which the gas that has passed the fuel electrode flows, wherein the stack is located vertically above the heat exchanger, and the tube extends vertically downward from the stack to the heat exchanger. The tube may include a bent section between the stack and the heat exchanger.

Description

[Technical Field]

[0001] The present invention relates to an electrochemical system comprising a stack including a fuel electrode, an electrolyte, and an air electrode. [Background technology]

[0002] Prior art is disclosed in Patent Document 1 in which an electrochemical system comprising a stack having multiple cells containing an electrolyte that separates a fuel electrode and an air electrode is connected to a heat exchanger through which a pipe carrying gas after passing through the stack flows, and thermal energy is exchanged between the gas and the fluid in the heat exchanger. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2015-125890 [Overview of the project] [Problems that the invention aims to solve]

[0004] In prior art, water vapor contained in the gas condenses and accumulates in the pipes. This can block the pipes, hindering gas flow, or the accumulated water can suddenly flow into the heat exchanger, causing variations in the amount of thermal energy exchanged per unit time between the gas and fluid in the heat exchanger.

[0005] This invention was made to solve this problem and aims to provide an electrochemical system that can reduce the variation in thermal energy exchanged per unit time in a heat exchanger. [Means for solving the problem]

[0006] A first embodiment for achieving this objective comprises a stack having a plurality of cells containing an electrolyte that separates a fuel electrode from an air electrode, a heat exchanger, and a pipe through which the gas that has passed through the fuel electrode flows, wherein the stack is located vertically above the heat exchanger, and the pipe extends vertically downward from the stack to the heat exchanger.

[0007] In a second embodiment, the tube includes a bent portion between the stack and the heat exchanger, as in the first embodiment. [Effects of the Invention]

[0008] According to the present invention, the stack is positioned vertically above the heat exchanger, and the gas tubes extend vertically downward from the stack to the heat exchanger, thereby reducing the accumulation of water formed by the condensation of gas. This makes it less likely for water to clog the tubes or for accumulated water to suddenly flow into the heat exchanger, thus reducing the variation in thermal energy exchanged per unit time between the gas and fluid in the heat exchanger. [Brief explanation of the drawing]

[0009] [Figure 1] This is a side view of an electrochemical system in one embodiment. [Figure 2] This is a perspective view of the stack. [Figure 3] This is a cross-sectional view of the stack at line III-III. [Modes for carrying out the invention]

[0010] Preferred embodiments of the present invention will be described below with reference to the accompanying drawings. Figure 1 is a side view of an electrochemical system 10 in one embodiment. The electrochemical system 10 comprises a stack 11, a heat exchanger 13, and a pipe 14 connecting the stack 11 and the heat exchanger 13. The stack 11 is exemplified by a fuel cell or an electrolytic device.

[0011] Figure 2 is a perspective view of the stack 11. The stack 11 includes reaction units 30, a laminate 31 formed by stacking multiple reaction units 30 in the thickness direction, terminals 32 and 33 electrically connected to the laminate 31, and end plates 34 and 35 that sandwich the laminate 31 in the thickness direction. The laminate 31 is made up of, for example, 10 to 30 reaction units 30 stacked on top of each other. Bolts 36 are arranged around the periphery of the stack 11, penetrating the end plates 34 and 35 and the laminate 31 in the thickness direction. The stack 11 is fastened together by the bolts 36.

[0012] The four spaces that penetrate the periphery of the stack 11 in the thickness direction function as a passage 37 for supplying fuel gas from outside the stack 11 to the fuel chamber 51 (described later) of the reaction unit 30, a passage 38 for discharging gas from the fuel chamber 51 to outside the stack 11, a passage 39 for supplying oxidizer gas from outside the stack 11 to the air chamber 52 (described later) of the reaction unit 30, and a passage 40 for discharging gas from the air chamber 52 to outside the stack 11.

[0013] Figure 3 is a cross-sectional view of the stack 11 cut along the line III-III in Figure 2, passing through passages 37 and 38, and shows a portion of the laminate 31. The thickness of each part is exaggerated in Figure 3.

[0014] As shown in Figure 3, the reaction unit 30 includes, in order in the thickness direction, a fuel electrode frame 41, a first separator 42, an air electrode frame 43, and a second separator 44. Holes (passages 37-40) pass through the fuel electrode frame 41, the first separator 42, the air electrode frame 43, and the second separator 44. Inside the fuel electrode frame 41, the first separator 42, the air electrode frame 43, and the second separator 44, a cell 45, an interconnector 49, and a current collector 50 are arranged.

[0015] Cell 45 includes an electrolyte 46, a fuel electrode 47 and an air electrode 48 that are separated from each other in the thickness direction by the electrolyte 46. Although a flat plate-shaped cell 45 is described in the present embodiment, the cell 45 is not limited to this. The cell 45 may be of a metal-supported type (metal-supported flat plate type) that supports the electrode and the electrolyte with a porous body of metal such as Fe-Cr-based alloy. The cell 45 may be of an electrode-supported type or an electrolyte-supported type.

[0016] The material of the electrolyte 46 is a solid oxide, and examples thereof include stabilized zirconia, ceria-based solid solutions, and solid solutions of alumina with one or more selected from the group consisting of stabilized zirconia and ceria-based solid solutions. Examples of the stabilizer for stabilized zirconia include CaO, MgO, Y₂O₃, Sc₂O₃, and Yb₂O₃. Examples of elements that form a solid solution with ceria in the ceria-based solid solution include Gd, Sm, and Y.

[0017] Examples of the material of the fuel electrode 47 include those containing a Ni-containing catalyst and Y-doped zirconia, and those containing a Ni-containing catalyst and Gd-doped ceria. Examples of the catalyst include cermet which is a composite (sintered body) of Ni, Ni-based alloy, NiO and an oxide (solid electrolyte).

[0018] The material of the air electrode 48 is perovskite-type oxide La 1-X Sr X MnO 3-δ , La 1-X Sr X CoO 3-δ , La 1-X Sr X Co 1-Y Fe Y O 3-δ , Pr 1-X Sr X MnO 3-δ are exemplified.

[0019] The fuel electrode frame 41 is a frame-shaped member disposed between the second separator 44 and the first separator 42, and surrounding the cell 45 and the current collector 50. Stainless steel is exemplified as the material of the fuel electrode frame 41.

[0020] The first separator 42 is a frame-shaped member that is airtightly joined to the electrolyte 46 by brazing material or the like, avoiding the air electrode 48. Stainless steel is an example of a material for the first separator 42.

[0021] The air electrode frame 43 is a frame-shaped member positioned between the first separator 42 and the second separator 44, surrounding the interconnector 49. An example of the material for the air electrode frame 43 is an insulator such as mica.

[0022] The second separator 44 is a frame-shaped member and is airtightly joined to the interconnector 49 by brazing material or the like. Stainless steel is an example of a material for the second separator 44.

[0023] The current collector 50 electrically connects adjacent interconnectors 49 and fuel electrodes 47 in the thickness direction. The current collector 50 is exemplified by including a bent conductor and a spacer such as mica placed within the conductor. Examples of conductor materials include nickel, nickel-based alloys, and stainless steel. The interconnectors 49 electrically connect adjacent current collectors 50 and air electrodes 48 in the thickness direction. An example of interconnector material is stainless steel.

[0024] A fuel chamber 51 is provided inside the fuel electrode frame 41, and an air chamber 52 is provided inside the air electrode frame 43. Slits 53 and 54 are provided in the fuel electrode frame 41. Through slit 53, the fuel chamber 51 is connected to passage 37 (see Figure 1), and through slit 54, the fuel chamber 51 is connected to passage 38 (see Figure 1). The air chamber 52 is connected to passages 39 and 40 through slits (not shown) provided in the air electrode frame 43. The first separator 42 and the second separator 44 separate the fuel chamber 51 and the air chamber 52, preventing the fuel gas in the fuel chamber 51 and the oxidizer gas in the air chamber 52 from mixing.

[0025] If stack 11 is a fuel cell, examples of fuel gases include hydrogen, carbon monoxide, and hydrocarbons, and examples of oxidizer gases include oxygen and air. If stack 11 is an electrolytic device, examples of fuel gases include water vapor, carbon dioxide, and mixtures thereof, and examples of oxidizer gases include oxygen and air. Stack 11 also includes configurations that allow for reversible operation as both a fuel cell and an electrolytic device.

[0026] Multiple cells 45 are electrically connected in series between terminals 32 and 33 via an interconnector 49 and a current collector 50. When the stack 11 is an electrolytic device, when the positive electrode of a power supply (not shown) is connected to terminal 32 and the negative electrode of the power supply is connected to terminal 33, electrons flow out toward the fuel electrode 47 of the cell 45 at the cell 45's operating temperature. The fuel gas that enters the fuel chamber 51 is reduced by the fuel electrode 47. Since electrons are removed at the air electrode 48, oxide ions that have moved to the air electrode 48 via the electrolyte 46 are oxidized at the air electrode 48. This generates energy carriers such as hydrogen and hydrocarbons in the fuel chamber 51. The energy carriers generated in the fuel chamber 51 exit the stack 11 through the passage 38.

[0027] If the stack 11 is a fuel cell, when fuel gas is flowed into the fuel chamber 51 and oxidizer gas into the air chamber 52 at the operating temperature of the cell 45, gaseous oxygen reacts with electrons at the air electrode 48 to generate oxide ions. These oxide ions move through the electrolyte 46 and react with the fuel gas at the fuel electrode 47 to generate electrons. This causes current to flow to the load (not shown) connected to terminals 32 and 33 (see Figure 1).

[0028] Let's return to Figure 1 for explanation. The hot module 12 includes a stack 11, a heater (not shown) for heating the stack 11, a vaporizer (not shown) for generating steam, and an insulating material (not shown) in which the stack 11, heater, and vaporizer are placed. If the stack 11 is a fuel cell and carbon monoxide or hydrocarbons are the fuel gas, the hot module 12 further includes a reformer for steam reforming of the fuel gas.

[0029] The heat exchanger 13 is a device that exchanges thermal energy between the gas and fluid after it has passed through the fuel electrode 47 (see Figure 3) of the stack 11. The temperature of the gas after it has passed through the fuel electrode 47 is close to the operating temperature of the cell 45. The gas after it has passed through the fuel electrode 47 is supplied to the heat exchanger 13 through a pipe 14 connected to the passage 38 (see Figure 3) of the stack 11.

[0030] Examples of fluids that exchange thermal energy with the gas in the heat exchanger 13 include fuel gas and oxidizer gas supplied to the stack 11. The fluid (fuel gas and oxidizer gas) is supplied to the heat exchanger 13 through pipe 19. After passing through the fuel electrode 47, the exchange of thermal energy between the gas and the fluid causes the cooled gas to flow through pipe 18 and the heated fluid to be supplied to the hot module 12 through pipe 20.

[0031] In addition to heating the fluid flowing through the pipe 19, the heat exchanger 13 also heats the energy storage device 21. Examples of the energy storage device 21 include secondary batteries and electrochemical capacitors. When the stack 11 is a fuel cell, the energy storage device 21 stores the electricity generated by the stack 11, and when the stack 11 is an electrolytic device, it is an auxiliary power source that supplies power to the stack 11. The energy storage device 21 tends to have a reduced discharge capacity when the temperature is low, but because the energy storage device 21 is heated to near room temperature by the heat exchanger 13, a decrease in discharge capacity due to low temperature can be prevented. The hot module 12, the heat exchanger 13, and the energy storage device 21 are housed in the casing 22.

[0032] The stack 11 is located vertically above the heat exchanger 13. That is, the horizontal plane containing the stack 11 is located vertically above the horizontal plane containing the heat exchanger 13. The pipe 14 extends vertically downward from the stack 11 to the heat exchanger 13. That is, as the pipe 14 moves away from the stack 11 (as it approaches the heat exchanger 13), the vertical distance between the stack 11 and the pipe 14 gradually increases. Therefore, when gas condenses into water in the pipe 14, the water flows down the pipe 14 each time. This reduces the accumulation of water in the pipe 14, making it less likely for water to clog the pipe 14 or for water accumulated in the pipe 14 to suddenly flow into the heat exchanger 13. This reduces the variation in the amount of thermal energy exchanged per unit time between the gas and fluid in the heat exchanger 13.

[0033] The pipe 14 includes a vertical section 15 extending along a vertical line from the stack 11, a bent section 16 located below the vertical section 15, and an inclined section 17 extending from the bent section 16, intersecting the vertical line, to the heat exchanger 13. Because the pipe 14 includes a bent section 16 between the stack 11 and the heat exchanger 13, the pipe 14 can connect the stack 11 and the heat exchanger 13 when there is a horizontal distance between them.

[0034] Although the present invention has been described above based on embodiments, it can be easily inferred that the present invention is not limited in any way to the above embodiments, and that various improvements and modifications are possible without departing from the spirit of the present invention.

[0035] In this embodiment, the pipe 14 is described as being connected from the stack 11 to the heat exchanger 13 in the order of vertical section 15, bent section 16, and inclined section 17, but it is not necessarily limited to this. It is certainly possible to connect the pipe 14 from the stack 11 to the heat exchanger 13 in the order of inclined section 17, bent section 16, and vertical section 15.

[0036] In this embodiment, the case where the bent portion 16 of the pipe 14 is angular has been described, but this is not necessarily the only case. It is certainly possible to round the bent portion 16 and curve the pipe 14. Also, if the horizontal distance between the stack 11 and the heat exchanger 13 is long, it is certainly possible to provide multiple bent portions 16 in the pipe 14 connecting the stack 11 and the heat exchanger 13.

[0037] In the embodiment, the case where there is a horizontal distance between the stack 11 and the heat exchanger 13 has been described. However, if there is no horizontal distance between the stack 11 and the heat exchanger 13, and the stack 11 and the heat exchanger 13 are on a vertical line, it is naturally possible to omit the bent portion 16 and the inclined portion 17 and connect the stack 11 and the heat exchanger 13 with the vertical portion 15 of the pipe 14.

[0038] In this embodiment, we have described a case where a horizontal distance exists between the stack 11 and the heat exchanger 13, and the stack 11 and the heat exchanger 13 are connected by a pipe 14 that includes a vertical section 15, a bent section 16, and an inclined section 17. However, this is not necessarily the only option. It is certainly possible to omit the vertical section 15 and the bent section 16 and connect the stack 11 and the heat exchanger 13 using the inclined section 17 of the pipe 14.

[0039] In this embodiment, the case in which the heat exchanger 13 heats the energy storage device 21 has been described, but it is not necessarily limited to this. It is certainly possible to heat other heat-utilizing equipment with the heat exchanger 13. Examples of other heat-utilizing equipment include water heaters.

[0040] In this embodiment, the design of the cell 45 of the stack 11 was described as being flat, but it is not necessarily limited to this. It is certainly possible to make the cell 45 of the stack 11 into other designs such as cylindrical horizontal stripe or cylindrical vertical stripe.

[0041] In the embodiment, the case where cell 45 is a rectangle was described, but it is not necessarily limited to this. The shape of cell 45 may be a circle or an ellipse, or it may be a polygon other than a rectangle, such as a triangle or a pentagon.

[0042] In the embodiment, the case in which the gas passages 37, 38, 39, and 40 are built into the stack 11 has been described, but it is not necessarily limited to this. It is of course possible to connect the manifold as passages 37, 38, 39, and 40 to the cell and provide it outside the cell. Examples of manifold materials include ceramics with high high-temperature strength.

[0043] In the embodiment, a stack 11 including a solid oxide type cell 45 has been described, but it is not necessarily limited to this. It is certainly possible to apply the techniques of the embodiment to stacks including other types of cells, such as molten carbonate type cells. [Explanation of symbols]

[0044] 10 Electrochemical Systems 11 stacks 13 Heat exchanger 14 tubes 16. Bending section (the part that bends) 45 cells 46 Electrolytes 47 Fuel electrode 48 Air pole

Claims

1. A stack comprising multiple cells containing an electrolyte that separates the fuel electrode and the air electrode, Heat exchanger, An electrochemical system comprising a pipe through which the gas after passing the fuel electrode flows, The stack is located vertically above the heat exchanger, The tube is an electrochemical system extending vertically downward from the stack to the heat exchanger.

2. The electrochemical system according to claim 1, wherein the tube includes a bent portion between the stack and the heat exchanger.

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