Stacks, hot modules, and electrolytic devices

Abstract

The present invention provides a stack, hot module, and electrolytic device that can increase the amount of hydrogen produced downstream of the fuel electrode. [Solution] The stack consists of multiple reaction units connected in series in the thickness direction, each containing an electrolytic cell with an electrolyte that separates a fuel electrode and an air electrode in the thickness direction, a first current collector in contact with the fuel electrode, and a second current collector in contact with the air electrode. Fuel gas containing water vapor flows in parallel along the portion where the fuel electrode and the first current collector are in contact with each reaction unit. Each reaction unit includes an air supply passage that supplies fuel gas to the portion and an exhaust passage that discharges the gas that has flowed along the portion from the reaction unit, and in at least one reaction unit the exhaust passage is located along the portion.

Description

[Technical Field]

[0001] The present invention relates to a stack of electrolytic cells, a hot module, and an electrolytic device. [Background technology]

[0002] Prior art is disclosed in Patent Document 1, which involves supplying a fuel gas containing water vapor (water) to the fuel electrode of an electrolytic cell to generate hydrogen in a stack in which electrolytic cells containing an electrolyte that isolates a fuel electrode and an air electrode in the thickness direction are connected in series. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2020-38773 [Overview of the Initiative] [Problems that the invention aims to solve]

[0004] The hydrogen generated at the fuel electrode of the electrolytic cell is transported downstream by the fuel gas. As the hydrogen concentration downstream becomes higher than that upstream, the reaction rate for hydrogen generation is lower downstream of the fuel electrode compared to upstream. Therefore, the prior art reduces the amount of hydrogen generated downstream of the fuel electrode.

[0005] This invention was made to solve this problem and aims to provide a stack, hot module, and electrolytic device that can increase the amount of hydrogen generated downstream of the fuel electrode. [Means for solving the problem]

[0006] A first embodiment for achieving this objective is a stack in which a plurality of reaction units are connected in series in the thickness direction, each reaction unit including an electrolytic cell containing an electrolyte that isolates a fuel electrode and an air electrode in the thickness direction, a first current collector in contact with the fuel electrode, and a second current collector in contact with the air electrode, and a fuel gas containing water vapor flows in parallel along the portion where the fuel electrode and the first current collector are in contact with each reaction unit. Each reaction unit includes an air supply passage that supplies fuel gas to the portion and an exhaust passage that discharges the gas that has flowed along the portion from the reaction unit, and in at least one reaction unit the exhaust passage is located along the portion.

[0007] In a second embodiment, in the first embodiment, there are multiple exhaust passages in at least one reaction unit.

[0008] A third embodiment is a hot module comprising a stack according to the first or second embodiment, a vaporizer that generates water vapor contained in the fuel gas, a heat exchanger that exchanges heat with the gas supplied to the stack, a heater for heating the stack, and an insulating material in which the stack, vaporizer, heat exchanger, and heater are arranged.

[0009] A fourth embodiment is an electrolytic apparatus comprising the hot module of the third embodiment. [Effects of the Invention]

[0010] According to the present invention, the exhaust passage for discharging gas from the reaction unit is provided at a position along the portion where the fuel electrode and the first current collector are in contact. Since the hydrogen generated at the portion where the fuel electrode and the first current collector are in contact is more easily discharged through the exhaust passage, the difference between the hydrogen concentration downstream of the fuel electrode and the hydrogen concentration upstream of the fuel electrode can be reduced. The reaction rate for generating hydrogen downstream of the fuel electrode can be made so that it is not less than the reaction rate for generating hydrogen upstream of the fuel electrode, thereby increasing the amount of hydrogen generated downstream of the fuel electrode. [Brief explanation of the drawing]

[0011] [Figure 1] This is a perspective view of a stack in one embodiment. [Figure 2] This is a cross-sectional view of the stack along line II-II in Figure 1. [Figure 3] Figure 2 is a cross-sectional view of the stack along line III-III. [Figure 4] Figure 2 is a cross-sectional view of the stack along the IV-IV line. [Figure 5] This is a block diagram of an electrolytic device. [Modes for carrying out the invention]

[0012] Preferred embodiments of the present invention will be described below with reference to the accompanying drawings. Figure 1 is a perspective view of a stack 10 in one embodiment. The stack 10 includes reaction units 11, terminals 12 and 13 electrically connected to the reaction units 11, and end plates 14 and 15 that sandwich the reaction units 11 and terminals 12 and 13 in the thickness direction. The stack 10 consists of, for example, 10 to 30 reaction units 11 stacked in the thickness direction of the reaction units 11. Terminal 12 is positioned between the reaction units 11 and the end plate 14, and terminal 13 is positioned between the reaction units 11 and the end plate 15. Stainless steel is an example of a material for terminals 12 and 13.

[0013] Insulator 16 is positioned between terminal 12 and end plate 14, electrically insulating terminal 12 from end plate 14. Insulator 17 is positioned between terminal 13 and end plate 15, electrically insulating terminal 13 from end plate 15. Bolts 18 are positioned around the periphery of stack 10, penetrating the end plates 14, 15, insulators 16, 17, terminals 12, 13, and reaction unit 11 in the thickness direction. Stack 10 is fastened by bolts 18.

[0014] The four spaces at the periphery of the stack 10 extending in the thickness direction of the reaction unit 11 are an air supply side manifold 19 that supplies fuel gas from outside the stack 10 to the fuel chamber 37 (described later) of the reaction unit 11, an exhaust side manifold 20 that discharges gas from the fuel chamber 37 to the outside of the stack 10, an air supply side manifold 21 that supplies oxidant gas from outside the stack 10 to the air chamber 38 (described later) of the reaction unit 11, and an exhaust side manifold 22 that discharges gas from the air chamber 38 to the outside of the stack 10.

[0015] Figure 2 is a cross-sectional view of the stack 10 cut along the line II-II of Figure 1 passing through the air supply side manifold 19 and the exhaust side manifold 20, mainly showing the reaction unit 11. In Figure 2, the thickness of each part is exaggerated. The reaction unit 11 includes an electrolytic cell 23, a first current collector 27 and a second current collector 30 which are paths for flowing current between the electrolytic cell 23 and the terminals 12 and 13.

[0016] The electrolytic cell 23 includes a porous fuel electrode 24 in contact with the first current collector 27, a porous air electrode 25 in contact with the second current collector 30, and an electrolyte 26 that separates the fuel electrode 24 and the air electrode 25 in the thickness direction. In this embodiment, a flat plate-shaped electrolytic cell 23 is described, but it is not limited thereto. The electrolytic cell 23 may also be a metal-supported type (metal-supported flat plate type) that supports the electrodes and the electrolyte with a porous body of a metal such as an Fe-Cr system.

[0017] The material of the electrolyte 26 is a solid oxide, and examples include a solid solution of one or more selected from stabilized zirconia, ceria-based solid solution, stabilized zirconia and ceria-based solid solution and alumina. Examples of the stabilizer of stabilized zirconia are CaO, MgO, Y2O3, Sc2O3, Yb2O3. Examples of the elements dissolved in ceria of the ceria-based solid solution are Gd, Sm, Y.

[0018] Examples of the material of the fuel electrode 24 include those containing a catalyst containing Ni and zirconia in which Y is dissolved, and those containing a catalyst containing Ni and ceria in which Gd is dissolved. Examples of the catalyst are a cermet which is a composite (sintered body) of Ni, a Ni-based alloy, and a composite of NiO and an oxide (solid electrolyte).

[0019] The material of the air electrode 25 is a 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 is exemplified.

[0020] The first current collector 27 electrically connects the second current collector 30 and the fuel electrode 24 adjacent to each other in the thickness direction. The first current collector 27 includes a plate-shaped support portion 28 and a current collection portion 29 disposed between the support portion 28 and the fuel electrode 24. The current collection portion 29 is exemplified by including a bent conductor and a spacer such as mica disposed in the conductor. Examples of the materials of the support portion 28 and the conductor include nickel, nickel-based alloys, and stainless steel.

[0021] The second current collector 30 electrically connects the first current collector 27 and the air electrode 25 adjacent to each other in the thickness direction. In the present embodiment, the support portion 28 and the second current collector 30 are integrated. Examples of the material of the second current collector 30 include stainless steel.

[0022] The first separator 31 is a frame-shaped member disposed outside the air electrode 25 and is hermetically joined to the electrolyte 26 by a brazing material or the like. Examples of the material of the first separator 31 include stainless steel. The second separator 32 is a frame-shaped member disposed outside the portion where the current collection portion 29 is provided and is hermetically joined to the support portion 28 by a brazing material or the like. Examples of the material of the second separator 32 include stainless steel. The first separator 31 and the second separator 32 are penetrated by the air supply side manifold 19 and the exhaust side manifold 20.

[0023] The first frame 33 is a frame-shaped member that surrounds the fuel electrode 24, electrolyte 26, and current collector 29, and is positioned between the first separator 31 and the second separator 32. Stainless steel is an example of a material for the first frame 33. The intake manifolds 19, 21 (see Figure 1) and exhaust manifolds 20, 22 pass through the first frame 33. An intake passage 34 connected to the intake manifold 19 and an exhaust passage 35 connected to the exhaust manifold 20 are provided in the first frame 33.

[0024] The second frame 36 is a frame-shaped member that surrounds the air electrode 25, the second current collector 30, and the support portion 28, and is positioned between the first separator 31 and the second separator 32. The material of the second frame 36 is exemplified by an insulator such as mica. The intake manifolds 19, 21 (see Figure 1) and the exhaust manifolds 20, 22 pass through the second frame 36. An intake passage connected to the intake manifold 21 and an exhaust passage connected to the exhaust manifold 22 (neither of which are shown) are provided in the second frame 36.

[0025] A fuel chamber 37 is provided inside the first frame 33, and an air chamber 38 is provided inside the second frame 36. The fuel chamber 37 is connected to the intake manifold 19 through the intake passage 34 and to the exhaust manifold 20 through the exhaust passage 35. The first separator 31 and the second separator 32 separate the fuel chamber 37 and the air chamber 38, preventing the fuel gas in the fuel chamber 37 from mixing with the oxidizer gas in the air chamber 38. The fuel gas supplied to the fuel chamber 37 is a mixed gas containing water vapor, or water vapor, as an example. The oxidizer gas supplied to the air chamber 38 is oxygen, or air, as an example.

[0026] Multiple electrolytic cells 23 are electrically connected in series between terminals 12 and 13 via a first current collector 27 and a second current collector 30. When the positive electrode of a power supply (not shown) is connected to terminal 12 and the negative electrode of the power supply is connected to terminal 13, electrons flow out toward the fuel electrode 24 of the electrolytic cell 23. The fuel gas that enters the fuel chamber 37 is reduced at the fuel electrode 24. Since electrons are removed at the air electrode 25, oxide ions that have moved to the air electrode 25 via the electrolyte 26 are oxidized at the air electrode 25. H2O + 2e - →H2+O 2- Hydrogen is generated at the fuel electrode 24 through a chemical reaction.

[0027] The hydrogen generated at the fuel electrode 24 and the remaining reaction gases are carried by the fuel gas flow supplied from the upstream intake passage 34 to the fuel chamber 37, and exit the stack 10 through the downstream exhaust passage 35 and the exhaust manifold 20. If the hydrogen concentration downstream of the fuel electrode 24 is higher than the hydrogen concentration upstream of the fuel electrode 24, the reaction rate that produces hydrogen will be lower downstream of the fuel electrode 24 than upstream of the fuel electrode 24. As a result, the amount of hydrogen produced downstream of the fuel electrode 24 will decrease, and there is a risk that the amount of hydrogen produced will not be as designed.

[0028] Figure 3 is a cross-sectional view of the stack 10 along line III-III in Figure 2. Figure 4 is a cross-sectional view of the stack 10 along line IV-IV in Figure 2. In Figure 4, the positions of the air intake passage 34 and the exhaust passage 35 are shown by dashed lines. The current collectors 29 are arranged in a grid pattern with spacing between them between the support portion 28 and the fuel electrode 24 (see Figure 2). The bottom surface of the current collector 29 is in contact with the support portion 28, and the top surface of the current collector 29 is in contact with the fuel electrode 24. Therefore, the fuel gas that enters the fuel chamber 37 from the air intake passage 34 flows along the side surface of the current collector 29 (part of the first current collector 27) between the current collectors 29 and heads towards the exhaust passage 35.

[0029] The exhaust passage 35 is located along the current collector 29. Specifically, the exhaust passage 35 extends from the exhaust-side manifold 20 toward the portion of the fuel chamber 37 where the current collector 29 is located. In the projection view (equivalent to Figure 4) showing the current collector 29 projected in the thickness direction of the reaction unit 11 (see Figure 2), the range 40 is the downstream 1 / 3 of the entire range where the current collector 29 is located. The area of ​​range 40 is 1 / 3 of the total area where the current collector 29 is located. In the upstream 2 / 3 of the entire range where the current collector 29 is located, the fuel gas flows relatively freely.

[0030] However, in the downstream 1 / 3 of the range 40, the gas flow is more easily constrained to the position of the exhaust passage 35, so the gas moves mainly through range 44 towards the exhaust passage 35, colliding with the sides of the current collector 29. Range 44 is a roughly trapezoidal area enclosed by line segments 42 and 43 connecting both ends of the boundary 41 of range 40 and the center of the opening of the exhaust passage 35, and the boundary 41. To smooth the gas flow in range 40, it is preferable that the area of ​​the current collector 29 in range 44 be as large as possible. In particular, if the area of ​​the current collector 29 in range 44 is 81% or more of the area of ​​the current collector 29 in range 40, the concentration of hydrogen accumulating near the exhaust passage 35 can be further reduced. This ensures that the reaction rate for hydrogen generation downstream of the fuel electrode 24 is not too low compared to the reaction rate for hydrogen generation upstream of the fuel electrode 24. Since the amount of hydrogen generated downstream of the fuel electrode 24 can be increased, the amount of hydrogen generated can be made as designed.

[0031] The current collector 29 has a shape projected in the thickness direction of the reaction unit 11 (see Figure 2) (a rectangle in this embodiment), which extends along line segments 45 and 46 connecting the center of the opening of the air supply passage 34 and the center of the opening of the exhaust passage 35, respectively. The shape of the current collector 29 extending along line segments 45 and 46 means that the angle between the longer edge of the current collector 29 (the longer side of the rectangle in this embodiment) and line segments 45 and 46 is less than 45°. The shape of the current collector 29 extending along line segments 45 and 46 is preferable because it allows for smoother gas flow in the range 40.

[0032] In the stack 10, it is sufficient if the exhaust passage 35 of one of the multiple reaction units 11 is located along the current collector 29. This is because it ensures the amount of hydrogen produced in the electrolytic cell 23 arranged in that reaction unit 11. Alternatively, the exhaust passages 35 of all reaction units 11 arranged in the stack 10 may be located along the current collector 29. This is because it ensures the amount of hydrogen produced in the electrolytic cell 23 arranged in all reaction units 11.

[0033] Let's return to Figure 3 for explanation. The first frame 33 is constructed such that the cross-sectional area of ​​the exhaust passage 35 is larger than the cross-sectional area of ​​the intake passage 34. In this embodiment, there are multiple exhaust passages 35 in a single first frame 33.

[0034] The cross-sectional area of ​​the intake passage 34 is the cross-sectional area when the narrowest part of the intake passage 34 is cut horizontally. If there are multiple intake passages 34, the cross-sectional area of ​​the intake passage 34 is the sum of the cross-sectional areas of the narrowest parts of each individual intake passage 34. The cross-sectional area of ​​the exhaust passage 35 is the sum of the cross-sectional areas when the narrowest part of each individual exhaust passage 35 is cut horizontally. If individual intake passages 34 or exhaust passages 35 are branched, the cross-sectional area of ​​the intake passage 34 or exhaust passage 35 is the cross-sectional area of ​​the part that is the rate-limiting part of the gas flow.

[0035] Since the cross-sectional area of ​​the intake passage 34 is smaller than the cross-sectional area of ​​the intake-side manifold 19, the pressure of the fuel gas flowing through the intake-side manifold 19 can be maintained, and fuel gas can be supplied to all intake passages 34 branching from the intake-side manifold 19. Since the cross-sectional area of ​​the exhaust passage 35 is smaller than the cross-sectional area of ​​the fuel chamber 37, the exhaust passage 35 becomes the rate-limiting flow of gas in the fuel chamber 37. Since the cross-sectional area of ​​the exhaust passage 35 is larger than the cross-sectional area of ​​the intake passage 34, the concentration of hydrogen accumulating near the exhaust passage 35 in the fuel chamber 37 can be prevented from becoming as high as in the case where it were not. This allows for an even greater amount of hydrogen to be generated downstream of the fuel electrode 24.

[0036] Since there are multiple exhaust passages 35 in a single first frame 33, the cross-sectional area of ​​the exhaust passages 35 can be easily increased even if the cross-sectional area of ​​each exhaust passage 35 is about the same as the cross-sectional area of ​​each intake passage 34. Furthermore, having multiple exhaust passages 35 reduces hydrogen accumulation over a wide area of ​​the fuel chamber 37 compared to the case where there is only one exhaust passage 35, thus reducing the area where hydrogen production is reduced.

[0037] Figure 5 is a block diagram of an electrolytic device 50 equipped with a stack 10. The electrolytic device 50 is a device that produces hydrogen from water and is equipped with a hot module 51.

[0038] The hot module 51 comprises a stack 10, a vaporizer 52 that generates steam supplied to the stack 10, a heat exchanger 53 that performs heat exchange between the gas supplied to the stack 10 and the gas generated by the stack 10, and a heater 54 that heats the stack 10. To reduce heat dissipation, the hot module 51 has the stack 10, vaporizer 52, heat exchanger 53 and heater 54 arranged inside an insulating material 55.

[0039] The vaporizer 52 includes a heat exchanger that exchanges heat with the high-temperature gas containing oxygen produced by the stack 10, and heats water to produce steam. The steam produced by the vaporizer 52 contains hydrogen, which reduces the oxidation of the catalyst contained in the fuel electrode 24. The hydrogen-containing steam exchanges heat with the hydrogen and oxygen produced by the stack 10 by the heat exchanger 53, and is then heated by the heater 54 to the operating temperature of the stack 10 and supplied to the fuel chamber 37 of the stack 10. The air exchanges heat with the hydrogen and oxygen produced by the stack 10 by the heat exchanger 53, and is then heated by the heater 54 to the operating temperature of the stack 10 and supplied to the air chamber 38 of the stack 10.

[0040] Examples of the insulation material 55 include heat-resistant fibers such as ceramic wool, refractory ceramic fiber (RCF), and biosoluble fiber (AES), as well as heat-resistant containers formed from heat-resistant fibers. The heat-resistant fibers fill the gaps between the stack 10, the vaporizer 52, the heat exchanger 53, and the heater 54. The condenser 56 is a device for cooling hydrogen gas, and the liquefied water is supplied to the vaporizer 52 as raw water.

[0041] 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.

[0042] In the embodiment, the case where the shape of the electrolytic cell 23 (the shape projected in the thickness direction of the electrolytic cell 23) is rectangular was described, but it is not necessarily limited to this. The shape of the electrolytic cell 23 may be circular or elliptical, or it may be a polygon other than a rectangle, such as a triangle or pentagon.

[0043] In the embodiment described, the current collectors 29 are arranged in a grid pattern along the sides of the rectangular electrolytic cell 23 (the grid pattern intersects perpendicularly with the sides of the electrolytic cell 23), but this is not necessarily the only case. It is certainly possible to arrange the current collectors 29 so that the grid pattern formed by the alignment of the current collectors 29 intersects diagonally with the sides of the rectangular electrolytic cell 23.

[0044] In the embodiment, the case where the shape of the current collector 29 (the shape projected in the thickness direction of the electrolytic cell 23) is rectangular has been described, but it is not necessarily limited to this. The shape of the current collector 29 may be circular or elliptical, or it may be a square or parallelogram. Furthermore, it may be a polygon other than a quadrilateral, such as a triangle or pentagon. Regardless of the shape of the current collector 29, it is preferable that it extends along the line segments 45 and 46 connecting the center of the opening of the air supply passage 34 and the center of the opening of the exhaust passage 35, as this allows for smooth gas flow in the range 40.

[0045] In the embodiment, the case in which the current collectors 29 are scattered in a grid pattern with intervals between them has been described, but the invention is not necessarily limited to this. It is certainly possible to arrange the current collectors 29 in a striped pattern by connecting multiple current collectors 29 as described in the embodiment, and to arrange them with intervals between them so that they extend along line segments 45 and 46 connecting the centers of the openings of the air intake passage 34 and the exhaust passage 35, respectively. In this case as well, gas can be flowed along the current collectors 29 and between the current collectors 29.

[0046] In the embodiment described, a current collector 29, which is a separate component from the support 28, is placed between the support 28 and the fuel electrode 24 to constitute the first current collector 27. However, the invention is not necessarily limited to this configuration. It is, of course, possible to integrate the support 28 and the current collector 29.

[0047] In the embodiment, the case in which the support portion 28 and the second current collector 30 are integrated has been described, but this is not necessarily the only option. It is certainly possible to configure the second current collector 30 by placing a second current collector 30, which is a separate component from the support portion 28, between the support portion 28 and the air electrode 25.

[0048] In the embodiment, a case in which multiple exhaust passages 35 are provided (two in the embodiment) has been described, but it is not necessarily limited to this. There may be three or more exhaust passages 35, or there may be just one. Even when there is only one exhaust passage 35, the exhaust passage 35 is made such that its cross-sectional area is larger than that of the intake passage 34. This reduces separation of the fuel electrode 24, similar to the embodiment. When there is only one exhaust passage 35, the area 44 through which the gas mainly flows is a roughly triangular area enclosed by the boundary 41 of the range 40, the two line segments connecting the ends of the boundary 41 of the range 40 and the center of the opening of the exhaust passage 35, and the boundary 41 itself.

[0049] In the embodiment described, the case in which the intake manifolds 19, 21 and exhaust manifolds 20, 22 through which the gas passes are built into the stack 10 has been described, but it is not necessarily limited to this. It is of course possible to provide the intake manifolds 19, 21 and exhaust manifolds 20, 22 outside the first frame 33 and the second frame 36. Examples of manifold materials include ceramics with high high-temperature strength.

[0050] In the embodiment, a stack 10 including a solid oxide type electrolytic cell 23 has been described, but it is not necessarily limited to this. It is certainly possible to apply the technology according to the embodiment to a stack including other types of cells, such as a molten carbonate type. [Explanation of Symbols]

[0051] 10 stacks 23 Electrolytic Cells 24 Fuel electrode 25 Air pole 26 Electrolytes 27. First current collector 29 Current collector (part) 30 Second current collector 34 Air supply path 35 Exhaust passage 50 Electrolyzer 51 Hot Modules 52 Vaporizer 53 Heat exchanger 54 Heater 55 Insulation

Claims

1. An electrolytic cell containing an electrolyte that separates the fuel electrode and the air electrode in the thickness direction, A first current collector in contact with the fuel electrode, A stack comprising a second current collector in contact with the air electrode, wherein a plurality of reaction units are connected in series in the thickness direction, and a fuel gas containing water vapor flows in parallel to each reaction unit along the portion where the fuel electrode and the first current collector are in contact, The reaction unit includes an air supply passage for supplying the fuel gas to the portion and an exhaust passage for discharging the gas that has flowed along the portion from the reaction unit. A stack in which the exhaust passage is located along the portion in at least one of the reaction units.

2. The stack according to claim 1, wherein at least one of the reaction units has multiple exhaust passages.

3. A stack according to claim 1 or 2, A vaporizer that generates water vapor contained in the fuel gas, A heat exchanger that performs heat exchange with the gas supplied to the stack, A heater for heating the aforementioned stack, A hot module comprising the stack, the vaporizer, the heat exchanger, and the heater, and an insulating material in which these are arranged.

4. An electrolytic apparatus comprising the hot module described in claim 3.

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