Electrolytic module and electrolytic device

Abstract

To provide an electrolytic module and an electrolytic device which are capable of reducing heat dissipation from electrolytic cells.SOLUTION: An electrolysis module includes electrolytic cells in which elements including an electrolyte isolating two electrodes are arranged. Three or more electrolytic cells are arrayed. The elements are electrically connected in series. When the number of the electrolytic cells is divided equally into three parts, and the electrolytic cells are divided into a central portion and two end portions on both sides of the central portion in the direction in which the electrolytic cells are arranged, an average of the area of the elements included in the electrolytic cells in at least one of the two end portions is smaller than an average of the area of the elements included in the electrolytic cells in the central portion.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an electrolysis module in which electrolysis cells are arranged, and an electrolysis device. [Background technology]

[0002] An electrolysis module, which is an arrangement of electrolysis cells in which an element part containing an electrolyte that separates two electrodes is arranged, electrolyzes fuel gas in the element part to which a voltage is applied, and synthesizes energy carriers such as hydrogen and hydrocarbons (Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2023-72892 A Summary of the Invention [Problem to be solved by the invention]

[0004] In an electrolytic cell to which a voltage is applied to the element portion, heat dissipation from the center portion in the arrangement direction of the electrolytic cell is less than heat dissipation from the ends located on both sides of the arrangement direction of the center portion, so that the temperature in the center portion is likely to rise, which poses the problem of temperature variations easily occurring that affect the durability of the electrolytic cell.

[0005] The present invention has been made to solve this problem, and has an object to provide an electrolysis module and an electrolysis device that can reduce the temperature variation of the electrolysis cell. [Means for solving the problem]

[0006] A first aspect for achieving this object is an electrolysis module including an electrolysis cell in which an element portion containing an electrolyte separating two electrodes is arranged, in which three or more electrolysis cells are arranged and the element portions are electrically connected in series to each other, wherein when the number of electrolysis cells is divided into thirds to partition the electrolysis cell into a central portion and two end portions located on either side of the central portion in the direction in which the electrolysis cells are arranged, the average area of ​​the element portions included in the electrolysis cells at at least one of the two end portions is smaller than the average area of ​​the element portions included in the electrolysis cells at the central portion.

[0007] In the second embodiment, in the first embodiment, the average area of ​​the element portions included in the electrolysis cell at the two ends is smaller than the average area of ​​the element portions included in the electrolysis cell at the center.

[0008] In a third aspect, in the first or second aspect, the average area of ​​the element portions included in the electrolytic cell at the end portions is 40% or more of the average area of ​​the element portions included in the electrolytic cell at the central portion.

[0009] In a fourth aspect, in any one of the first to third aspects, the average area of ​​the element portions included in the electrolytic cell at the end portions is 97% or less of the average area of ​​the element portions included in the electrolytic cell at the central portion.

[0010] A fifth aspect is an electrolysis device comprising an electrolysis module according to any one of the first to fourth aspects, a power source that passes a current through a circuit connected to the electrodes, and an adjustment unit that adjusts the output of the power source, wherein the adjustment unit sets an average voltage of the central portion to a voltage lower than a thermal neutral point at which heat absorption and heat generation are balanced in the electrolysis module set to a predetermined temperature, and sets an average voltage of at least one end portion to a voltage higher than the thermal neutral point. Effect of the Invention

[0011] According to the present invention, when the number of electrolytic cells is divided into thirds and the electrolytic cell is divided into a central portion and two end portions located on either side of the central portion, the average area of ​​the element portions included in the electrolytic cells at the end portions is smaller than the average area of ​​the element portions included in the electrolytic cells at the central portion. Since the element portions are connected in series, the same current flows through the end portions and the central portion, and the current density of the element portions at the central portion can be made smaller than the current density of the element portions at the end portions. Since the Joule heat at the central portion can be made smaller than the Joule heat at the end portions, the temperature rise at the central portion, which dissipates less heat than the end portions, can be reduced, and the temperature variation of the electrolytic cells can be reduced. [Brief description of the drawings]

[0012] [Figure 1] FIG. 1 is a perspective view of an electrolysis module according to a first embodiment. [Diagram 2] FIG. 1 is a cross-sectional view of an electrolysis cell. [Diagram 3] 1 is a graph showing current-voltage characteristics and heat generation characteristics of an electrolysis module. [Figure 4] FIG. 1 is a block diagram of an electrolysis device. [Diagram 5] FIG. 11 is a plan view of an electrolysis module according to a second embodiment. [Figure 6] FIG. 1 is a perspective view of an electrolysis cell. [Figure 7] FIG. 13 is a side view of the electrolysis module according to the third embodiment. [Figure 8] FIG. 8 is a cross-sectional view of the electrolysis module taken along line VIII-VIII in FIG. [Figure 9] FIG. 13 is a perspective view of an electrolysis module according to a fourth embodiment. [Figure 10] FIG. 2 is an exploded view of the electrolysis cell. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Preferred embodiments of the present invention will now be described with reference to the accompanying drawings. FIG. 1 is a perspective view of an electrolysis module 10 in a first embodiment. The electrolysis module 10 includes a plurality of (three or more) electrolysis cells 11. The electrolysis cells 11 have element sections 13 arranged on a breathable support 12. The electrolysis module 10 includes a manifold 14 connected to one end of the support 12, and a manifold 15 connected to the other end of the support 12. The electrolysis cells 11 are arranged between the manifolds 14 and 15. In this embodiment, 20 electrolysis cells 11 are arranged in a row with spaces between each other.

[0014] FIG. 2 is a cross-sectional view of the electrolysis cell 11. The support 12 is provided with a plurality of cavities 16 with a circular cross section that connect the manifolds 14 and 15. An element unit 13 is provided on each of the outer surfaces (front and back) of the support 12. The support 12 has air permeability between the outer surface of the support 12 and the cavities 16. The element unit 13 includes, in order from the outer surface of the support 12, a fuel electrode 17, an electrolyte 18, and a cathode 19. In FIG. 2, the thickness of the element unit 13 is exaggerated. In this embodiment, the electrolysis cell 11 is a flat cylindrical horizontal stripe electrolysis cell in which the element units 13 are lined up along the cavities 16.

[0015] The support 12 is a member that does not have electronic conductivity, and an example of the material is stabilized zirconia. Examples of stabilizers for stabilized zirconia include CaO and MgO. Examples of the material for the fuel electrode include a material containing a catalyst containing Ni and zirconia with Y dissolved therein, and a material containing a catalyst containing Ni and ceria with Gd dissolved therein. Examples of the catalyst include Ni, Ni-based alloys, and cermets that are composites (sintered bodies) of NiO and oxides (solid electrolytes).

[0016] The material of the electrolyte 18 is a solid oxide, and examples thereof include stabilized zirconia, ceria-based solid solution, and a solid solution of one or more selected from stabilized zirconia and ceria-based solid solution and alumina. Examples of stabilizers for stabilized zirconia include CaO, MgO, YO, ScO, and YbO. Examples of elements dissolved in ceria in the ceria-based solid solution include Gd, Sm, and Y.

[0017] The material of the cathode 19 is a perovskite oxide called La 1-X Sr X MnO 3-δ ,La 1-X Sr X Chief of Staff 3-δ ,La 1-X Sr X Co 1-Y Fe Y O 3-δ ,Pr 1-X Sr X MnO 3-δ Examples are given below.

[0018] The interconnector 20 connects the air electrode 19 and the fuel electrode 17 of the adjacent element units 13. The material of the interconnector 20 is conductive La 1-X Sr X TiO 3-δ In one electrolysis cell 11, the element parts 13 are connected in series by an interconnector 20. In adjacent electrolysis cells 11, the element parts 13 are connected in series by a connecting member (not shown).

[0019] Returning to FIG. 1, the manifold 14 supplies fuel gas to each of the electrolysis cells 11. Examples of the fuel gas include water vapor, carbon dioxide, and a mixture of these. The spent fuel gas that has passed through each of the electrolysis cells 11 is supplied to the manifold 15. An oxidant gas flows outside the electrolysis cells 11. Examples of the oxidant gas include air and oxygen.

[0020] When the positive electrode of a power supply (not shown) is connected to the air electrode 19 (see FIG. 2) of the element unit 13 and the negative electrode of the power supply is connected to the fuel electrode 17, electrons flow toward the fuel electrode 17. The fuel gas that has passed through the support 12 is reduced at the fuel electrode 17. Since electrons are lost at the air electrode 19, oxide ions that have moved to the air electrode 19 via the electrolyte 18 are oxidized at the air electrode 19. As a result, energy carriers such as hydrogen and hydrocarbons are synthesized in the electrolysis cell 11.

[0021] 3 is a graph showing the current-voltage characteristics and heat generation characteristics of the electrolysis module 10. Since the electrolysis of water vapor, carbon dioxide, and the like contained in the fuel gas is an endothermic reaction, the temperature of the element unit 13 (the temperature of the exhaust gas entering the manifold 15) decreases with an increase in current density compared to the temperature at the open circuit voltage of the element unit 13 at which current begins to flow (the average voltage of the element unit 13 when the current density is 0). When the current density increases further, the temperature of the element unit 13 begins to rise due to Joule heat, and reaches a thermal neutral point N where the heat absorption and heat generation are balanced.

[0022] At the thermal neutral point N, the electrolytic cell 11 neither generates nor absorbs heat, but when the current density of the element unit 13 becomes lower than the current density of the element unit 13 at the thermal neutral point N, heat absorption becomes predominant in the electrolytic cell 11, and the temperature decreases. When the current density of the element unit 13 becomes higher than the current density of the element unit 13 at the thermal neutral point N, heat generation becomes predominant in the electrolytic cell 11, and the temperature increases.

[0023] Returning to FIG. 1 , the electrolysis module 10 has electrolysis cells 11 arranged therein. The electrolysis cells 11 are used in a state in which the element units 13 reach their operating temperature (for example, about 700°C). The element units 13 tend to lose more heat the closer they are to the ends in the arrangement direction of the electrolysis cells 11, and thus tend to lose more temperature, whereas the element units 13 tend to lose less heat the closer they are to the center in the arrangement direction of the electrolysis cells 11, and thus tend to lose more temperature. If any part of the electrolysis cells 11 has a higher temperature than necessary, this may reduce the durability of the electrolysis cells 11.

[0024] The central portion 21 is a portion located in the center in the direction in which the electrolytic cells 11 are arranged when the number of electrolytic cells 11 included in the electrolysis module 10 is divided into thirds and the electrolytic cells 11 are divided into three portions. The end portions 22, 23 are portions located on both sides of the central portion 21 when the number of electrolytic cells 11 included in the electrolysis module 10 is divided into thirds and the electrolytic cells 11 are divided into three portions.

[0025] The method of dividing the number of electrolytic cells 11 into thirds and dividing the area into the central portion 21 and the end portions 22 and 23 differs depending on whether the number of electrolytic cells 11 is a multiple of 3 or not. When the number of electrolytic cells 11 is a multiple of 3, the number of electrolytic cells 11 included in the central portion 21, the number of electrolytic cells 11 included in the end portions 22, and the number of electrolytic cells 11 included in the end portions 23 are equal.

[0026] When the number of electrolytic cells 11 is not a multiple of 3, the number of electrolytic cells 11 is divided by 3 to obtain a quotient and a remainder, and then the remainder is allocated to the central portion 21 or the ends 22, 23 so that the number of electrolytic cells 11 included in the end portion 22 is equal to the number of electrolytic cells 11 included in the end portion 23. The reason why the number of electrolytic cells 11 included in the end portion 22 is equal to the number of electrolytic cells 11 included in the end portion 23 is to fairly evaluate the areas of the element portions 13 of the electrolytic cells 11 included in the ends 22, 23.

[0027] For example, when the remainder when the number of electrolytic cells 11 is divided by 3 is 1, the number of electrolytic cells 11 included in the end portion 22 and the number of electrolytic cells 11 included in the end portion 23 are each set to the quotient, and the number of electrolytic cells 11 included in the central portion 21 is set to the quotient plus the remainder of 1. When the remainder when the number of electrolytic cells 11 is divided by 3 is 2, the number of electrolytic cells 11 included in the central portion 21 is set to the quotient, and the number of electrolytic cells 11 included in the end portion 22 and the number of electrolytic cells 11 included in the end portion 23 are each set to the quotient plus 1.

[0028] Since the electrolysis module 10 has 20 electrolytic cells 11, dividing 20 by 3 gives a quotient of 6 with a remainder of 2. Therefore, the number of electrolytic cells 11 included in the central portion 21 is 6, and the numbers of electrolytic cells 11 included in each of the end portions 22 and 23 are 7. The seventh electrolytic cells 11 from the end are included in the end portions 22 and 23, and the six electrolytic cells 11 inside the end portions 22 and 23 are included in the central portion 21.

[0029] In the electrolysis module 10, the average area of ​​the element units 13 included in the electrolytic cells 11 at at least one of the end parts 22, 23 is smaller than the average area of ​​the element units 13 included in the electrolytic cells 11 in the central part 21. The area of ​​the element units 13 refers to the area of ​​the portion where the electrolyte 18 (see FIG. 2 ), the fuel electrode 17, and the air electrode 19 overlap. The area of ​​the element units 13 can be changed, for example, by changing the area of ​​the fuel electrode 17 or the air electrode 19. The average area of ​​the element units 13 is the value obtained by dividing the sum of the areas of the element units 13 by the number of element units 13 for which the sum was calculated.

[0030] Since the element parts 13 of the electrolytic cell 11 are electrically connected in series, the same current flows through the element parts 13. Since the average area of ​​the element parts 13 included in the electrolytic cell 11 at least one of the ends 22, 23 is smaller than the average area of ​​the element parts 13 included in the electrolytic cell 11 at the central part 21, the current density of the element parts 13 at the central part 21 can be made smaller than the current density of the element parts 13 at least one of the ends 22, 23. As a result, the temperature of the central part 21, which dissipates less heat and is more likely to rise in temperature than the end parts 22, 23, can be reduced. This makes it possible to reduce the temperature variation between the end parts 22, 23 and the central part 21. Since overheating of the central part 21 can be reduced, the durability of the electrolytic cell 11 can be ensured.

[0031] In the electrolysis module 10, it is further preferable that the average area of ​​the element portion 13 included in the electrolytic cell 11 at the two end portions 22, 23 is smaller than the average area of ​​the element portion 13 included in the electrolytic cell 11 at the central portion 21. This is because the temperature variation between the end portions 22, 23 and the central portion 21 can be further reduced, and therefore overheating of the central portion 21 can be further reduced.

[0032] It is preferable that the average area of ​​the element parts 13 included in the electrolytic cell 11 at least one of the ends 22, 23 is 40% or more of the average area of ​​the element parts 13 included in the electrolytic cell 11 at the central portion 21, because this prevents the current density of the element parts 13 at at least one of the ends 22, 23 from becoming excessively large and reduces deterioration of the element parts 13 at at least one of the ends 22, 23. It is preferable that the average area of ​​the element parts 13 included in the electrolytic cell 11 at least one of the ends 22, 23 is 97% or less of the average area of ​​the element parts 13 included in the electrolytic cell 11 at the central portion 21, because this allows a difference to be made between the heat generation of the element parts 13 in the central portion 21 and the heat generation of the element parts 13 in at least one of the ends 22, 23.

[0033] Fig. 4 is a block diagram of the electrolysis device 30. The electrolysis device 30 includes an electrolysis module 10, a power supply 31 that supplies current to the element unit 13 of the electrolysis module 10, and an adjustment unit 33 that adjusts the output of the power supply 31. In Fig. 4, the element units 13 included in the electrolysis cell 11 in the central portion 21 and end portions 22, 23 of the electrolysis module 10 are represented by line segments. The length of the line segments indicates the average size of the area of ​​the element units 13 included in the electrolysis cell 11 in each portion.

[0034] An ammeter 32 for measuring a current flowing through the circuit is disposed in a circuit connected to the power supply 31 and the element section 13. The power supply 31 outputs a unipolar pulsating current, pulse, or direct current to the circuit.

[0035] The electrolysis device 30 is equipped with a thermometer 34 that detects the temperature of the electrolytic cell 11 (see FIG. 1). The thermometer 34 is disposed near the manifold 15, and detects the temperature of the exhaust gas entering the manifold 15 as a representative value of the temperature of the electrolytic cell 11. However, this is not limited to this, and it is of course possible to dispose the thermometer 34 in a location other than the manifold 15 and detect a representative value of the temperature of the electrolytic cell 11.

[0036] The electrolysis device 30 includes a heater (not shown) that heats the electrolytic cell 11. There are no limitations on the heater as long as it can heat the electrolytic cell 11. Examples of the heater include a heater that heats the fuel gas or oxidant gas supplied to the electrolytic cell 11 to heat the electrolytic cell 11, and a heater that is disposed in a heat-insulating container that houses the electrolytic cell 11 to heat the electrolytic cell 11 from the periphery of the electrolytic cell 11.

[0037] The adjustment unit 33 includes a CPU, a ROM, a RAM, and a backup RAM (none of which are shown). The adjustment unit 33 acquires the current detected by the ammeter 32, and adjusts the output of the power source 31 so that the average temperature of the element unit 13 (the temperature of the electrolytic cell 11) becomes a temperature equivalent to the thermal neutral point N (see FIG. 3). Since the area of ​​the element unit 13 is known, the current to be passed through the electrolytic cell 11 in order to make the average temperature of the element unit 13 become a temperature equivalent to the thermal neutral point N is determined in advance. The adjustment unit 33 adjusts the output of the power source 31 so that the current detected by the ammeter 32 becomes equal to the previously determined current.

[0038] Instead of the adjustment unit 33 adjusting the output of the power source 31 so that the current detected by the ammeter 32 is equal to the pre-determined current, the adjustment unit 33 may obtain the temperature detected by the thermometer 34 and adjust the output of the power source 31 so that the average temperature of the element unit 13 (the temperature of the electrolytic cell 11) becomes a temperature equivalent to the thermal neutral point N. The adjustment unit 33 may use both of these.

[0039] In the electrolysis module 10, the average area of ​​the element units 13 included in the electrolytic cell 11 at at least one of the ends 22, 23 is smaller than the average area of ​​the element units 13 included in the electrolytic cell 11 at the central portion 21. Therefore, when a current flows through the electrolytic cell 11 such that the average temperature of the element units 13 becomes a temperature equivalent to the thermal neutral point N, the average voltage of the element units 13 included in the central portion 21 becomes lower than the voltage equivalent to the thermal neutral point N. In addition, the average voltage of the element units 13 included in at least one of the ends 22, 23 becomes higher than the voltage equivalent to the thermal neutral point N.

[0040] As a result, the average temperature of the element units 13 included in the central portion 21 becomes lower than the temperature corresponding to the thermal neutral point N, and the average temperature of the element units 13 included in at least one of the end portions 22, 23 becomes higher than the temperature corresponding to the thermal neutral point N. This makes it possible to make the activation overvoltage of at least one of the end portions 22, 23 lower than the activation overvoltage of the central portion 21. As a result, for the energy input by the power source 31 to the electrolysis module 10, at least one of the end portions 22, 23 can synthesize energy carriers more efficiently than the central portion 21.

[0041] Furthermore, because the average temperature of the element parts 12 included in the central part 21 is lower than the temperature corresponding to the thermal neutral point N, it is possible to reduce the temperature variation between the central part 21 and at least one of the ends 22, 23, even if the heat dissipation from the central part 21 is less than the heat dissipation from the ends 22, 23. This makes it possible to reduce a decrease in durability of the electrolytic cell 11 caused by a part of the electrolytic cell 11 becoming hot.

[0042] Since the electrolysis device 30 performs electrolysis near the current density of the element unit 13 corresponding to the thermal neutral point N, the temperature of the element unit 13 can be maintained even with little new energy input. Therefore, the electrolysis efficiency can be ensured. Furthermore, the durability of the element unit 13 can be improved because the temperature change of the element unit 13 can be reduced.

[0043] An electrolysis module 40 in a second embodiment will be described with reference to Fig. 5 and Fig. 6. In the second embodiment, an electrolysis module 40 including cylindrical vertical stripe electrolysis cells 41 will be described. Fig. 5 is a plan view of the electrolysis module 40 in the second embodiment. The electrolysis module 40 includes a plurality of electrolysis cells 41. In this embodiment, a total of 18 electrolysis cells 41 are arranged, six vertically and three horizontally.

[0044] 6 is a perspective view of the electrolytic cell 41. The electrolytic cell 41 is cylindrical and includes an element section 42. The element section 42 includes, from the inside to the outside, an air electrode 43, an electrolyte 44, and an anode 45. An interconnector 46 is connected to the air electrode 43. The materials of the air electrode 43, the electrolyte 44, the anode 45, and the interconnector 46 are similar to those of the air electrode 19, the electrolyte 18, the anode 17, and the interconnector 20 of the electrolytic cell 11 in the first embodiment, and therefore will not be described.

[0045] Returning to Fig. 5, adjacent electrolytic cells 41 are connected by a conductor 47. The conductor 47 contacts the interconnector 46 and the fuel electrode 45 of adjacent electrolytic cells 41. The conductor 47 also has a function of buffering thermal expansion of the electrolytic cells 41. An example of the conductor 47 is a nonwoven fabric of metal fibers containing nickel or the like.

[0046] The electrolytic cells 41 adjacent to each other in a different direction via the conductor 47 are electrically insulated by the insulator 48. Examples of materials for the insulator 48 include alumina, mullite, magnesia, and zirconia. All of the electrolytic cells 41 are connected in series by the conductors 47 and the insulators 48. With an oxidant gas supplied into the electrolytic cell 41 and a fuel gas supplied to the outside of the electrolytic cell 41, electrolysis is performed in the element unit 42 to which a voltage is applied.

[0047] In the electrolysis module 40, when the number of electrolytic cells 41 is divided into three, that is, a central portion 49 located in the center in the direction in which the six electrolytic cells 11 are arranged, and end portions 50, 51 located on both sides of the central portion 49, the average area of ​​the element portions 42 included in the electrolytic cells 41 in at least one of the end portions 50, 51 is smaller than the average area of ​​the element portions 42 included in the electrolytic cells 41 in the central portion 49. Since the current density of the element portions 42 in the central portion 49 can be made smaller than the current density of the element portions 42 in at least one of the end portions 50, 51, it is possible to reduce a temperature rise of the element portions 42 in the central portion 49. Since the temperature of the central portion 49, which dissipates less heat and is more likely to rise in temperature than the end portions 50, 51, can be reduced, it is possible to reduce the temperature variation between the end portions 50, 51 and the central portion 40, and to reduce overheating of the central portion 49.

[0048] The electrolysis module 40 can also be divided into three parts by dividing the number of electrolytic cells 41 into three parts: a central part 52 located in the center of the direction in which the three electrolytic cells 41 are arranged, and end parts 53 and 54 located on both sides of the central part 52. In this case, if the average area of ​​the element parts 42 included in the electrolytic cells 41 at least in one of the end parts 53 and 54 is smaller than the average area of ​​the element parts 42 included in the electrolytic cells 41 in the central part 52, overheating of the central part 52 can be reduced, and the same action and effect can be obtained.

[0049] An electrolysis module 60 in a third embodiment will be described with reference to Figs. 7 and 8. In the first embodiment, a case where the set of electrolysis cells 11 is a 20x1 matrix consisting of 20 rows and 1 column has been described, and in the second embodiment, a case where the set of electrolysis cells 41 is a 3x6 matrix consisting of 3 rows and 6 columns has been described. In the first and second embodiments, the electrolysis cells 11 and 41 are arranged in rows and are arranged in a square shape as a whole. In contrast, in the third embodiment, an electrolysis module 60 will be described in which the set of electrolysis cells 61 is arranged in a substantially circular shape as a whole. The electrolysis cells 61 are cylindrical horizontal stripes. Fig. 7 is a side view of the electrolysis module 60 in the third embodiment. Fig. 8 is a cross-sectional view of the electrolysis module 60 taken along line VIII-VIII in Fig. 7.

[0050] In the electrolysis module 60, manifolds 63, 64 are connected to both ends of a plurality of cylindrical electrolysis cells 61 arranged at intervals from each other. The electrolysis cells 61 include a support and a plurality of element units 62 arranged on the support. The element units 62 include, in order from the outer surface of the support, a fuel electrode, an electrolyte, and a cathode, and adjacent element units 62 are connected by an interconnector (none of which are shown). The support, fuel electrode, electrolyte, cathode, and interconnector included in the electrolysis cell 61 are similar to the support 12, fuel electrode 17, electrolyte 18, cathode 19, and interconnector 20 of the electrolysis cell 11 in the first embodiment, and therefore description thereof will be omitted. All of the element units 62 are connected in series.

[0051] The manifold 63 supplies fuel gas into the electrolytic cells 61. The spent fuel gas that has passed through each of the electrolytic cells 61 is supplied to a manifold 64. An oxidant gas flows outside the electrolytic cells 61. Electrolysis takes place in the element section 62 to which a voltage is applied.

[0052] In the electrolysis module 60, when the number of electrolytic cells 61 is divided into three, that is, a central portion 65 located in the center of the set of electrolytic cells 61, and end portions 66, 67 located on both sides of the central portion 65, the average area of ​​the element portions 62 included in the electrolytic cells 61 in at least one of the end portions 66, 67 is smaller than the average area of ​​the element portions 62 included in the electrolytic cells 61 in the central portion 65. The method of dividing into three when the number of electrolytic cells 61 is not a multiple of three is similar to that in the first embodiment, and therefore description thereof will be omitted.

[0053] In this embodiment, the number of electrolytic cells 61 included in the electrolytic module 60 is "185", so the number of electrolytic cells 61 included in the end portions 66 and 67 is set to "62", and the number of electrolytic cells 61 included in the central portion 65 is set to "61", and a boundary between the end portion 66 and the central portion 65 and a boundary between the end portion 67 and the central portion 65 are set to partition the set of electrolytic cells 61 into three. In order to uniquely determine the boundaries of the three partitions, the boundaries are set to straight lines.

[0054] If the number of electrolytic cells 61 is counted from the left end of the set of electrolytic cells 61, and a straight line 68a between the end portion 66 and the central portion 65 is taken as the boundary, the number of electrolytic cells 61 included in the end portion 66 is "56", which is "6" less than the target value "62". If a straight line 68c that is parallel to the straight line 68a is taken as the boundary, the number of electrolytic cells 61 included in the end portion 66 is "66", which is "4" greater than the target value "62". Since it is desirable for the number of electrolytic cells 61 included in the end portion 66 to be closer to the target value, the straight line 68c, which has a smaller difference from the target value, is taken as the boundary between the end portion 66 and the central portion 65.

[0055] Similarly, counting the number of electrolytic cells 61 from the right end of the set of electrolytic cells 61, and taking the straight line 68b between the end portion 67 and the central portion 65 as the boundary, the number of electrolytic cells 61 included in the end portion 67 is "56", which is "6" smaller than the target value "62". Taking the straight line 68d, which is parallel to the straight line 68b, as the boundary, the number of electrolytic cells 61 included in the end portion 67 is "66", which is "4" larger than the target value "62". Since it is desirable for the number of electrolytic cells 61 included in the end portion 67 to be closer to the target value, the straight line 68d, which has a smaller difference from the target value, is taken as the boundary between the end portion 67 and the central portion 65.

[0056] In this embodiment, the difference between the number of electrolytic cells 61 included in the end portion 66 when the straight line 68a is the boundary and the target value is compared with the difference between the number of electrolytic cells 61 included in the end portion 66 when the straight line 68c is the boundary and the target value, and the straight line 68c with the smaller difference is set as the boundary between the end portion 66 and the central portion 65. If the difference between the number of electrolytic cells 61 included in the end portion 66 when the straight line 68a is the boundary and the target value is the same as the difference between the number of electrolytic cells 61 included in the end portion 66 when the straight line 68c is the boundary, the straight line 68c with the larger number of electrolytic cells 61 included in the end portion 66 is set as the boundary between the end portion 66 and the central portion 65. This is to increase the area of ​​the element portion 62 included in the end portion 66 to be evaluated.

[0057] In the case of this embodiment, it is of course possible to set the boundary between end portion 66 and central portion 65, or the boundary between end portion 67 and central portion 65, with a straight line that forms an angle of 45° with straight lines 68a, 68b, 68c, and 68d. This is because the boundaries of the three sections can also be set with straight lines in this case. Therefore, there are two ways to separate central portion 65 from end portions 66 and 67. The method of setting the boundaries of the three sections is as described above, so a description thereof will be omitted.

[0058] In all partitioning methods of the electrolysis module 60, the average area of ​​the element portion 62 included in the electrolytic cell 61 at at least one of the ends 66, 67 is not smaller than the average area of ​​the element portion 62 included in the electrolytic cell 61 at the central portion 65. There is only one combination that can be partitioned so that the average area of ​​the element portion 62 included in the electrolytic cell 61 at at least one of the ends 66, 67 is smaller than the average area of ​​the element portion 62 included in the electrolytic cell 61 at the central portion 65. This is because, with such a combination, the current density of the element portion 62 in the central portion 65 can be made smaller than the current density of the element portion 62 at at least one of the ends 66, 67, thereby reducing the temperature rise of the element portion 62 in the central portion 65 and reducing overheating of the central portion 65.

[0059] An electrolysis module 70 in a fourth embodiment will be described with reference to Fig. 9 and Fig. 10. In the fourth embodiment, an electrolysis module 70 including a flat plate-shaped electrolysis cell 71 will be described. Fig. 9 is a perspective view of the electrolysis module 70 in the fourth embodiment.

[0060] The electrolytic cell 71 includes a reaction unit 72 and end plates 73, 74 that sandwich the reaction unit 72 in the thickness direction. Bolts 75 are arranged on the periphery of the electrolytic cell 71, penetrating the reaction unit 72 and the end plates 73, 74 in the thickness direction. The reaction unit 72 and the end plates 73, 74 are fastened together by the bolts 75. In this embodiment, a plurality of reaction units 72 are stacked on top of each other.

[0061] The four spaces that penetrate the periphery of the electrolytic cell 71 in the thickness direction function as a passage 76 for gas to enter from outside the electrolytic cell 71 to a fuel chamber 90 (described later) of the reaction unit 72, a passage 77 for gas to exit from the fuel chamber 90 to the outside of the electrolytic cell 71, a passage 78 for gas to enter from outside the electrolytic cell 71 to an air chamber 92 (described later) of the reaction unit 72, and a passage 79 for gas to exit from the air chamber 92 to the outside of the electrolytic cell 71.

[0062] Fig. 10 is an exploded view of the electrolysis cell 71 taken along line XX in Fig. 9, passing through passages 76 and 77. Fig. 10 is a cross-sectional view taken along line XX, in which components constituting one reaction unit 72 are separated in the thickness direction. In Fig. 10, the thickness of each part is exaggerated. The reaction unit 72 includes, in order in the thickness direction, an interconnector 80, an anode frame 81, a cell 82 with separators, and an cathode frame 83.

[0063] The separator-equipped cell 82 includes an element portion 84 and a separator 88 arranged on the element portion 84. Holes (passages 76-78) penetrate the interconnector 80, the anode frame 81, the separator 88, and the cathode frame 83. The element portion 84 includes an electrolyte 85, and an anode 86 and an cathode 87 isolated by the electrolyte 85. The materials of the electrolyte 85, the anode 86, and the cathode 87 are similar to those of the electrolyte 18, the anode 17, and the cathode 19 of the electrolysis cell 11 in the first embodiment, and therefore will not be described.

[0064] The separator 88 is a frame-shaped member provided with an opening larger than the air electrode 87. The material of the separator 88 is, for example, stainless steel. The separator 88 is airtightly joined to the electrolyte 85 by brazing material or the like, avoiding the air electrode 87.

[0065] The interconnectors 80 are conductive plate-like members arranged on both sides in the thickness direction of the element section 84. The interconnectors 80 electrically connect the reaction units 72 adjacent to each other in the thickness direction. An example of the material of the interconnectors 80 is stainless steel.

[0066] The fuel electrode frame 81 is a frame-shaped member disposed between the interconnector 80 and the separator 88. The material of the fuel electrode frame 81 is, for example, stainless steel. The fuel electrode frame 81 surrounds the element portion 84 and a current collector 89 provided in the center of the interconnector 80.

[0067] The current collector 89 electrically connects the fuel electrode 86 and the interconnector 80. The material of the current collector 89 is, for example, a gas permeable porous body made of a metal such as Ni. A fuel chamber 90 surrounded by the interconnector 80 and the separator-equipped cells 82 is provided inside the fuel electrode frame 81.

[0068] The air electrode frame 83 is a frame-shaped member disposed between the interconnector 80 and the separator 88. The material of the air electrode frame 83 is, for example, an insulator such as mica. The air electrode frame 83 surrounds a current collector 91 provided in the center of the interconnector 80. The current collector 91 electrically connects the air electrode 87 and the interconnector 80. In this embodiment, the current collector 91 is formed integrally with the interconnector 80, but this is not limited to this. It is of course possible for the current collector 91 to be a member separate from the interconnector 80.

[0069] An air chamber 92 surrounded by the interconnector 80 and the separator-equipped cell 82 is provided inside the air electrode frame 83. The separator 88 separates the fuel chamber 90 from the air chamber 92, preventing the fuel gas in the fuel chamber 90 and the oxidizer gas in the air chamber 92 from mixing.

[0070] Returning to FIG. 9, the electrolytic cell 71 includes a terminal plate 93 arranged between the end plate 73 and the reaction unit 72, and a terminal plate 94 arranged between the end plate 74 and the reaction unit 72. The reaction units 72 are electrically connected in series between the terminal plates 93, 94. The terminal plate 93 is connected to the air electrode 87, and the terminal plate 94 is connected to the fuel electrode 86. The protruding portions of the terminal plates 93, 94 function as terminals. Holes (passages 76-78) penetrate the terminal plate 94. The element portions 84 included in the multiple electrolytic cells 71 are connected in series.

[0071] When the positive electrode of a power supply (not shown) is connected to terminal plate 93 and the negative electrode of the power supply is connected to terminal plate 94, electrons begin to flow toward the fuel electrode 86 of element unit 84. The fuel gas that has entered the fuel chamber 90 is reduced at the fuel electrode 86. As electrons are lost at the air electrode 87 of element unit 84, oxide ions that have moved to the air electrode 87 via the electrolyte 85 are oxidized at the air electrode 87. As a result, energy carriers such as hydrogen and hydrocarbons are synthesized in the electrolysis cell 71.

[0072] In the electrolysis module 70, when the number of electrolytic cells 71 is divided into three, that is, a central portion 95 located in the center of the set of electrolytic cells 71, and end portions 96, 97 located on both sides of the central portion 95, the average area of ​​the element portions 84 included in the electrolytic cells 71 in at least one of the end portions 96, 97 is smaller than the average area of ​​the element portions 84 included in the electrolytic cells 71 in the central portion 95. The method of dividing into three when the number of electrolytic cells 71 is not a multiple of three is similar to that in the first embodiment, and therefore will not be described.

[0073] In this embodiment, the set of electrolytic cells 71 is a 4×1 matrix consisting of four rows and one column. The electrolytic cells 71 are arranged in columns, and the whole is arranged in a square. According to the electrolytic module 70, the current density of the element unit 84 in the central portion 95 can be made larger than the current density of the element unit 84 in at least one of the end portions 96 and 97, so that the temperature rise of the element unit 84 in the central portion 95 can be reduced. Since the temperature of the central portion 95, which has less heat dissipation and is more likely to rise in temperature than the end portions 96 and 97, can be reduced, the temperature variation between at least one of the end portions 96 and 97 and the central portion 95 can be reduced. Since overheating of the central portion 95 can be reduced, the durability of the electrolytic cells 71 can be ensured.

[0074] The present invention has been described above based on an embodiment, but the present invention is in no way limited to the above embodiment, and it can be easily inferred that various improvements and modifications are possible within the scope of the present invention without departing from the spirit of the present invention.

[0075] The number and arrangement of the electrolytic cells 11, 41, 61, 71 in the embodiment are merely examples and are appropriately set according to the required characteristics of the electrolytic module. However, since the number of the electrolytic cells 11, 41, 61, 71 is divided into three equal parts, the number of the electrolytic cells 11, 41, 61, 71 is three or more.

[0076] In the first embodiment, the electrolysis module 10 in which a plurality of element units 13 are provided in one electrolysis cell 11 has been described, but the present invention is not necessarily limited to this. Electrolysis cells 11 provided with a single element unit 13 may be mixed and arranged with electrolysis cells 11 provided with a plurality of element units 13, or a plurality of electrolysis cells 11 provided with a single element unit 13 may be arranged.

[0077] In the first embodiment, the electrolytic cells 11 are arranged in a flat cylindrical horizontal stripe shape, but this is not necessarily limited to this. It is of course possible to change the design of the electrolytic cells 11 to a flat plate shape or a cylindrical horizontal stripe shape.

[0078] In the second embodiment, the electrolysis module 40 in which all 18 electrolysis cells 41 are connected in series has been described, but the present invention is not necessarily limited to this. For example, it is of course possible to create three sets of six electrolysis cells connected in series and connect the three sets in parallel. In this case, when the six electrolysis cells connected in series are divided into a central portion (two cells) and end portions (two cells each) on both sides of the central portion, the average area of ​​the element portions 42 included in the electrolysis cells 41 in the central portion is set to be smaller than the average area of ​​the element portions 42 included in the electrolysis cells 41 at the end portions.

[0079] In the third embodiment, the electrolytic cells 61 are clustered together, but this is not necessarily limited to this. It is of course possible to arrange the electrolytic cells 61 vertically and horizontally or in a single horizontal row.

[0080] In the fourth embodiment, the electrolytic cells 71 are arranged in a row, but this is not necessarily limited to this. It is of course possible to arrange the electrolytic cells 61 vertically and horizontally.

[0081] In the fourth embodiment, the electrolytic cell 71 has a flat plate design. The flat plate electrolytic cell 71 may be an electrode-supported type or an electrolyte-supported type. It may be a metal-supported type (metal-supported flat plate type) in which the electrodes and electrolyte are supported by a porous body of a metal such as an Fe-Cr-based metal.

[0082] In the fourth embodiment, the passages 76-79 through which the gas passes are built into the electrolytic cell 71, but this is not necessarily limited to this. It is of course possible to provide a manifold as the passages 76-79 outside the electrolytic cell by joining it to the electrolytic cell. Examples of materials for the manifold include ceramics that have high high-temperature strength.

[0083] In the fourth embodiment, the terminal plates 93, 94 including terminals to which a power source (not shown) is connected are disposed in the electrolytic cell 71, but this is not necessarily limited to the above. It is of course possible to omit the terminal plates 93, 94 and electrically connect the reaction units 72 to the end plates 73, 74, thereby using the end plates 73, 74 as terminals of the electrolytic cell 71.

[0084] Although explanation has been omitted for the second to fourth embodiments, as in the first embodiment, it is naturally possible to make both the average areas of the element portions 42, 62, 84 contained in the electrolytic cells 41, 61, 71 at the ends 50, 51, 53, 54, 66, 67, 96, 97 smaller than the average area of ​​the element portions 42, 62, 84 contained in the electrolytic cells 41, 61, 71 at the central portions 49, 52, 65, 95.

[0085] Although not explained in the embodiment, when the average area of ​​the element portions 13, 42, 62, 84 at one of the ends 22, 23, 50, 51, 53, 54, 66, 67, 96, 97 is smaller than the average area of ​​the element portions 13, 42, 62, 84 at the central portion 21, 49, 52, 65, 95, the average area of ​​the element portions 13, 42, 62, 84 at the other of the ends 22, 23, 50, 51, 53, 54, 66, 67, 96, 97 may be the same as the average area of ​​the element portions 13, 42, 62, 84 at the central portion 21, 49, 52, 65, 95, or may be larger than the average area of ​​the element portions 13, 42, 62, 84 at the central portion 21, 49, 52, 65, 95.

[0086] In the embodiment, the case where the element units 13, 42, 62, 84 of the electrolytic cells 11, 41, 61, 71 included in the electrolytic module 10, 40, 60, 70 are all connected in series, that is, the case where there is only one circuit in which the element units 13, 42, 62, 84 are connected in series in the electrolytic module 10, 40, 60, 70 has been described, but this is not necessarily limited to this. It is of course possible for the electrolytic module 10, 40, 60, 70 to have a plurality of circuits in which the element units 13, 42, 62, 84 are connected in series. In this case, the electrolytic cell including the element units constituting the circuit connected in series is divided into a center portion and an end portion, and the average area of ​​the element units included in the electrolytic cells in the center portion is made larger than the average area of ​​the element units included in the electrolytic cells in the end portions.

[0087] In the embodiment, the electrolyte 18, 44, 85 having oxide ion conductivity is used, but the present invention is not necessarily limited to this. It is of course possible to use the electrolyte 18, 44, 85 having proton conductivity under the operating conditions of the element unit 13, 42, 62, 84. Examples of substances that exhibit proton conductivity under the operating conditions of the element unit 13, 42, 62, 84 include perovskite-type oxides such as SrZrO3 and BaZrO3, pyrochlore-type oxides, and phosphates, in which the B site is substituted with trivalent metal ions such as Y and In.

[0088] Although not described in the embodiments, when a set of electrolytic cells is an m×n matrix (where m and n are natural numbers, and at least one of m and n is 3 or more) consisting of m rows and n columns as in the first, second, and fourth embodiments, and the entire set is arranged in a quadrangle, m or n, which is 3 or more, may be divided by 3 to obtain a quotient and a remainder, and the electrolytic cell may be divided into three by treating the rows or columns as a group unit. This is because in this case too, the electrolytic cell can be uniquely divided into three. [Explanation of symbols]

[0089] 10,40,60,70 Electrolytic Module 11,41,61,71 Electrolytic cell 13,42,62,84 Element section 17,45,86 Fuel electrode (electrode) 18,44,85 Electrolyte 19,43,87 Air electrode 21,49,52,65,95 Central part 22,23,50,51,53,54,66,67,96,97 End 30 Electrolyzer 31 Power supply 33 Adjustment part

Claims

1. An electrolysis module including an electrolysis cell in which an element unit including an electrolyte is disposed to separate two electrodes, the element unit being electrically connected in series with one another, the electrolysis cell being arranged in three or more, an electrolysis module in which, when the number of electrolysis cells is divided into thirds to partition the electrolysis cells into a central portion and two end portions located on either side of the central portion in the direction in which the electrolysis cells are arranged, the average area of ​​the element portions included in the electrolysis cells in at least one of the two end portions is smaller than the average area of ​​the element portions included in the electrolysis cells in the central portion.

2. The electrolysis module according to claim 1 , wherein an average area of ​​the element portions included in the electrolysis cell at the two ends is smaller than an average area of ​​the element portions included in the electrolysis cell at the center.

3. 3. The electrolysis module according to claim 1, wherein an average area of ​​the element portions included in the electrolysis cells at the end portions is 40% or more of an average area of ​​the element portions included in the electrolysis cells at the central portion.

4. 3. The electrolysis module according to claim 1, wherein an average area of ​​the element portions included in the electrolysis cells at the ends is 97% or less of an average area of ​​the element portions included in the electrolysis cells at the central portion.

5. An electrolysis module according to claim 1 or 2; A power source that applies a current to a circuit connected to the electrodes; An adjustment unit that adjusts the output of the power source, the adjustment unit sets an average voltage of the central portion to a voltage lower than a thermal neutral point at which heat absorption and heat generation are balanced in the electrolysis module, which is set to a predetermined temperature, and sets an average voltage of at least one of the ends to a voltage higher than the thermal neutral point.

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