Stack, hot module, and hydrogen production apparatus

Abstract

To provide a stack, a hot module, and a hydrogen production device capable of securing a supply amount of fuel gas in a downstream part.SOLUTION: A stacked body in which a plurality of reaction units are arranged in a thickness direction and the reaction units are connected to each other in series, each of the reaction units including a cell containing an electrolyte that separates a fuel electrode and an air electrode from each other in the thickness direction, an interconnector disposed at an interval from the fuel electrode in the thickness direction, and a spacer that electrically connects the interconnector and the fuel electrode and determines a height of a fuel chamber between the interconnector and the fuel electrode; When the number of the reaction units is divided into two equal parts in the thickness direction of the laminate to partition the reaction units into an upstream part and a downstream part of the fuel gas, the average thickness of the spacers in the downstream part is larger than the average thickness of the spacers in the upstream part.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a stack in which cells are stacked, a hot module, and a hydrogen production device. [Background technology]

[0002] In a stack comprising a stack in which reaction units are connected in series, each reaction unit including a cell containing an electrolyte that separates an anode and an cathode in the thickness direction, an interconnector spaced apart from the anode, and a spacer that electrically connects the interconnector and the anode and determines the height of the fuel chamber, and a manifold that supplies fuel gas to each fuel chamber, the prior art disclosed in Patent Document 1 reduces the variation in the thickness of the spacer so as to prevent a shortage of fuel gas supplied to the fuel chamber. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2017-228481 Summary of the Invention [Problem to be solved by the invention]

[0004] In the prior art, there is a risk of insufficient fuel gas being supplied downstream.

[0005] The present invention has been made to solve this problem, and has an object to provide a stack, a hot module, and a hydrogen production device that can ensure the supply of fuel gas downstream. [Means for solving the problem]

[0006] The first aspect for achieving this object is a stack comprising a stack in which reaction units are arranged in the thickness direction and connected in series to each other, the reaction units including cells containing an electrolyte that separates an anode and an cathode in the thickness direction, an interconnector arranged at a distance from the anode in the thickness direction, and a spacer that electrically connects the interconnector and the anode and determines the height of the fuel chamber between the interconnector and the anode, and a manifold that extends in the thickness direction of the stack, is connected to the fuel chamber provided in each of the reaction units, and supplies fuel gas flowing from one side to the other in the thickness direction to the anode, wherein when the number of reaction units is divided into two equal parts in the thickness direction of the stack and the reaction units are divided into upstream and downstream parts of the fuel gas, the average thickness of the spacers in the downstream part is greater than the average thickness of the spacers in the upstream part.

[0007] In a second embodiment, in the first embodiment, the thickness of all the spacers in the downstream portion is greater than the average thickness of the spacers in the upstream portion.

[0008] In a third embodiment, in the first or second embodiment, the number of reaction units is 13 or more.

[0009] In a fourth aspect, in any of the first to third aspects, the spacer comprises a conductor having a pair of opposing portions that face each other in the thickness direction and contact the fuel electrode and the interconnector, respectively, and a connecting portion that connects the pair of opposing portions, and an insert arranged between the opposing portions, and the average thickness of the insert in the downstream portion is greater than the average thickness of the insert in the upstream portion.

[0010] In a fifth aspect, in any one of the first to fourth aspects, the cell has a function of electrolyzing a fuel gas.

[0011] The sixth aspect is a hot module comprising a stack according to any one of the first to fifth aspects, a vaporizer that generates steam as a fuel gas, a heat exchanger that exchanges heat with the gas supplied to the stack, a heater for heating the stack, and insulation within which the stack, vaporizer, heat exchanger, and heater are disposed.

[0012] A seventh aspect is a hydrogen production device, which includes the hot module according to the sixth aspect. [Effects of the Invention]

[0013] According to the present invention, when the number of reaction units is divided into two equal parts in the thickness direction of the stack to divide the reaction units into upstream and downstream parts of the fuel gas, the average thickness of the spacers in the downstream part is greater than the average thickness of the spacers in the upstream part, thereby reducing friction loss in the fuel chamber in the downstream part and ensuring the supply of fuel gas to the downstream part. [Brief explanation of the drawings]

[0014] [Figure 1] FIG. 2 is a perspective view of a stack according to one embodiment. [Figure 2] FIG. 2 is a cross-sectional view of the laminate taken along line II-II. [Figure 3] 1A is a cross-sectional view of a spacer arranged in the downstream portion, and FIG. 1B is a cross-sectional view of a spacer arranged in the upstream portion. [Figure 4] FIG. 1A is a diagram showing the output of the stack in the example, and FIG. 1B is a diagram showing the output of the stack in the comparative example. [Figure 5] FIG. 1 is a block diagram of a hydrogen production device. DETAILED DESCRIPTION OF THE INVENTION

[0015] Preferred embodiments of the present invention will now be described with reference to the accompanying drawings. Fig. 1 is a perspective view of a stack 10 in one embodiment. The stack 10 includes a reaction unit 11, a stack 12 formed by stacking a plurality of reaction units 11 in the thickness direction, conductive plates 13 and 15 electrically connected to the stack 12, and end plates 17 and 18 that sandwich the stack 12 and the conductive plates 13 and 15 in the thickness direction. The stack 12 is formed by stacking, for example, approximately 10-30 reaction units 11.

[0016] Conductive plate 13 is disposed between laminate 12 and end plate 17, and conductive plate 15 is disposed between laminate 12 and end plate 18. Terminals 14 and 16 are connected to conductive plates 13 and 15, respectively. The conductive plates 13 and 15 and terminals 14 and 16 can be made of stainless steel, for example.

[0017] An insulator 19 disposed between the conductive plate 13 and the end plate 17 electrically insulates the conductive plate 13 from the end plate 17. An insulator 20 disposed between the conductive plate 15 and the end plate 18 electrically insulates the conductive plate 15 from the end plate 18. Bolts 21 are disposed around the periphery of the stack 10 and pass through the end plates 17, 18, insulators 19, 20, conductive plates 13, 15, and laminate 12 in the thickness direction. The stack 10 is fastened together by the bolts 21.

[0018] The four spaces that penetrate the periphery of the stack 10 in the thickness direction function as a manifold 22 that supplies fuel gas from outside the stack 10 to a fuel chamber 39 (described later) of the reaction unit 11, a manifold 23 that discharges gas from the fuel chamber 39 to outside the stack 10, a manifold 24 that supplies oxidant gas from outside the stack 10 to an air chamber 40 (described later) of the reaction unit 11, and a manifold 25 that discharges gas from the air chamber 40 to outside the stack 10.

[0019] Manifold 22 penetrates end plate 18, insulator 20, and conductive plate 15, and is closed by end plate 17, insulator 19, and conductive plate 13. Fuel gas supplied to stack 10 flows through manifold 22 from end plate 18 to end plate 17. For ease of explanation, if the number of reaction units 11 is divided into two equal parts in the thickness direction of stack 12 and the stack is divided into an upstream section 26 and a downstream section 27 of the fuel gas flow, in this embodiment, the stack is divided into an upstream section 26 close to end plate 18 and a downstream section 27 close to end plate 17.

[0020] If the number of reaction units 11 is even, the upstream section 26 is divided into two equal parts so that the number of reaction units 11 in the upstream section 26 is equal to the number of reaction units 11 in the downstream section 27. If the number of reaction units 11 is odd, the downstream section 27 is divided into two parts so that the number of reaction units 11 in the downstream section 27 is one more than the number of reaction units 11 in the upstream section 26. This is because attention is focused on the flow of fuel gas in the downstream section 27.

[0021] In this embodiment, manifold 23 penetrates end plate 18, insulator 20, and conductive plate 15, and is closed by end plate 17, insulator 19, and conductive plate 13. Similarly, manifold 24 penetrates end plate 18, insulator 20, and conductive plate 15, and is closed by end plate 17, insulator 19, and conductive plate 13. Manifold 25 penetrates end plate 18, insulator 20, and conductive plate 15, and is closed by end plate 17, insulator 19, and conductive plate 13.

[0022] 2 is a cross-sectional view of the laminate 12 taken along line II-II in FIG. 1, which passes through the manifolds 22 and 23, and illustrates a portion of the upstream portion 26 and downstream portion 27 of the laminate 12. In FIG. 2, the thickness of each portion is exaggerated.

[0023] 2, the reaction unit 11 includes, in order in the thickness direction, an anode frame 28, a first separator 29, an air electrode frame 30, and a second separator 31. Manifolds 22-25 penetrate the anode frame 28, the first separator 29, the air electrode frame 30, and the second separator 31. Cells 32, interconnectors 36, and spacers 37 and 38 are arranged inside the anode frame 28, the first separator 29, the air electrode frame 30, and the second separator 31. The spacer 37 is arranged in the upstream section 26, and the spacer 38 is arranged in the downstream section 27.

[0024] The cell 32 includes an electrolyte 33, and an anode 34 and cathode 35 separated in the thickness direction by the electrolyte 33. In this embodiment, a flat-plate type cell 32 is described, but the present invention is not limited to this. The cell 32 may also 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. The cell 32 may be an electrode-supported type or an electrolyte-supported type.

[0025] The electrolyte 33 is made of a solid oxide, and examples thereof include stabilized zirconia, ceria-based solid solution, and a solid solution of alumina with one or more selected from stabilized zirconia and ceria-based solid solutions. Examples of stabilizers for stabilized zirconia include CaO, MgO, YO, ScO, and YbO. Examples of elements dissolved in ceria in ceria-based solid solutions include Gd, Sm, and Y.

[0026] Examples of the material for the fuel electrode 34 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 cermet, which is a composite (sintered body) of NiO and an oxide (solid electrolyte).

[0027] The material of the cathode 35 is a perovskite oxide called La 1-X Sr X MnO 3-δ ,La 1-X Sr X CoO 3-δ ,La 1-X SrX Co 1-Y Fe Y O 3-δ ,Pr 1-X Sr X MnO 3-δ is exemplified.

[0028] The fuel electrode frame 28 is a frame-shaped member disposed between the second separator 31 and the first separator 29, and surrounds the cell 32 and the spacers 37 and 38. Stainless steel is an example of the material for the fuel electrode frame 28. The first separator 29 is a frame-shaped member, and is airtightly joined to the electrolyte 33 with brazing material or the like, avoiding the air electrode 35. Stainless steel is an example of the material for the first separator 29.

[0029] The cathode frame 30 is a frame-shaped member disposed between the first separator 29 and the second separator 31, and surrounds the interconnector 36. An example of the material for the cathode frame 30 is an insulator such as mica. The second separator 31 is a frame-shaped member, and is airtightly joined to the interconnector 36 with a brazing material or the like. An example of the material for the second separator 31 is stainless steel.

[0030] The spacers 37 and 38 electrically connect the interconnectors 36 adjacent to each other in the thickness direction to the fuel electrode 34. The interconnector 36 electrically connects the spacers 37 and 38 adjacent to each other in the thickness direction to the air electrode 35. The material of the interconnector 36 is, for example, stainless steel.

[0031] A fuel chamber 39 is provided inside the anode frame 28, and an air chamber 40 is provided inside the cathode frame 30. The fuel chamber 39 is connected to the manifolds 22 and 23, and the air chamber 40 is connected to the manifolds 24 and 25 (see FIG. 1). The first separator 29 and the second separator 31 isolate the fuel chamber 39 from the air chamber 40, preventing the fuel gas in the fuel chamber 39 and the oxidizer gas in the air chamber 40 from mixing.

[0032] When stack 10 is a fuel cell, examples of the fuel gas include hydrogen, carbon monoxide, and hydrocarbon, and examples of the oxidant gas include oxygen and air. When stack 10 is an electrolysis device (cell 32 is an electrolysis cell having the function of electrolyzing fuel gas), examples of the fuel gas include water vapor, carbon dioxide, and a mixture thereof, and examples of the oxidant gas include oxygen and air. Stack 10 also includes stacks that are capable of reversible operation as a fuel cell and an electrolysis device.

[0033] The multiple cells 32 are electrically connected in series between terminals 14 and 16 via interconnectors 36 and spacers 37 and 38. When the stack 10 is an electrolysis device, the positive electrode of a power supply (not shown) is connected to terminal 14, and the negative electrode of the power supply is connected to terminal 16, causing electrons to flow toward the fuel electrode 34 of the cell 32. The fuel gas that enters the fuel chamber 39 is reduced at the fuel electrode 34. Because electrons are removed at the air electrode 35, oxide ions that have migrated to the air electrode 35 via the electrolyte 33 are oxidized at the air electrode 35. As a result, energy carriers such as hydrogen and hydrocarbons are generated in the fuel chamber 39. The energy carriers generated in the fuel chamber 39 are exhausted to the outside of the stack 10 through the manifold 23.

[0034] When stack 10 is a fuel cell, when fuel gas is flowed through fuel chamber 39 and oxidant gas is flowed through air chamber 40, gas-phase oxygen reacts with electrons at air electrode 35 of cell 32 to generate oxide ions, and the oxide ions that have traveled through electrolyte 33 react with fuel gas at fuel electrode 34 to generate electrons. This causes a current to flow through a load (not shown) connected to terminals 14 and 16 (see FIG. 1).

[0035] Figure 3(a) is a cross-sectional view of a spacer 38 disposed in the downstream section 27 (see Figure 2). Figure 3(b) is a cross-sectional view of a spacer 37 disposed in the upstream section 26. The spacer 38 determines the height of a fuel chamber 39 between the interconnector 36 and the anode 34 in the downstream section 27. The height of the fuel chamber 39 in the downstream section 27 is equal to a thickness T2 of the spacer 38. The spacer 37 determines the height of the fuel chamber 39 between the interconnector 36 and the anode 34 in the upstream section 26. The height of the fuel chamber 39 in the upstream section 26 is equal to a thickness T1 of the spacer 37.

[0036] The average thickness T2 of the spacer 38 in the downstream portion 27 is greater than the average thickness T1 of the spacer 37 in the upstream portion 26. This allows the average height of the fuel chamber 39 (see FIG. 2) in the downstream portion 27 to be greater than the average height of the fuel chamber 39 in the upstream portion 26.

[0037] The distance that the fuel gas travels through the manifold 22 to reach the fuel chamber 39 is longer in the downstream section 27 than in the upstream section 26. Therefore, the friction loss of the fuel gas flowing through the manifold 22 to the downstream section 27 is likely to be greater than the friction loss of the fuel gas flowing through the manifold 22 to the upstream section 26. By making the average height of the fuel chamber 39 in the downstream section 27 greater than the average height of the fuel chamber 39 in the upstream section 26, the friction loss of the fuel chamber 39 in the downstream section 27 can be made smaller than the friction loss of the fuel chamber 39 in the upstream section 26. This ensures the supply of fuel gas to the downstream section 27, thereby reducing the variation in output of the stack 10 between the upstream section 26 and the downstream section 27.

[0038] The spacer 38 includes a conductor 41 having a pair of opposing portions 42 that face each other and contact the anode 34 and the interconnector 36, respectively, and a connecting portion 43 that connects the opposing portions 42, and an insert 45 that is disposed between the opposing portions 42. Examples of materials for the conductor 41 include metals such as nickel, nickel-based alloys, and stainless steel. Examples of materials for the insert 45 include insulators such as mica, and conductors such as nickel, nickel-based alloys, and stainless steel.

[0039] The spacer 37 includes a conductor 41 having a pair of opposing portions 42 and a connecting portion 43 that connects the opposing portions 42 together, and an insert 44 that is disposed between the opposing portions 42. Examples of materials for the insert 44 include an insulator such as mica, and a conductor such as nickel, a nickel-based alloy, or stainless steel.

[0040] The difference between the thickness T1 of the spacer 37 and the thickness T2 of the spacer 38 is the difference in thickness between the inserts 44 and 45. The spacers 37 and 38 use conductors 41 of the same dimensions, and by making the insert 45 of the spacer 38 thicker than the insert 44 of the spacer 37, the thickness T2 of the spacer 38 is made larger than the thickness T1 of the spacer 37. This makes it easier to manage the thickness T1 of the spacer 37 and the thickness T2 of the spacer 38.

[0041] Figure 4(a) is a diagram showing the output of the stack 10 in the example. Figure 4(b) is a diagram showing the output of a stack in the comparative example. The diagrams shown in Figures 4(a) and 4(b) are plots of the voltage of each cell 32 (left scale) and the thickness of the inserts 44, 45 for each reaction unit 11 (right scale) when hydrogen is supplied to the fuel chamber 39 and oxygen is supplied to the air chamber 40 of the stack 10 in which 25 reaction units 11 are connected in series.

[0042] The horizontal axis in Figures 4(a) and 4(b) represents the position of the reaction unit 11 in the stack. Moving to the left on the axis indicates that the reaction unit 11 is located closer to the conductive plate 15, and moving to the right on the axis indicates that the reaction unit 11 is located closer to the conductive plate 13. The upstream section includes 12 reaction units 11 including cells 32 adjacent to the conductive plate 15, and the downstream section includes 13 reaction units 11 including cells 32 adjacent to the conductive plate 13.

[0043] The cell voltage on the left scale shown in Figures 4(a) and 4(b) is the ratio of the voltage of the cell 32 plotted based on the voltage of the cell 32 adjacent to the conductive plate 15. The insert thickness on the right scale shown in Figures 4(a) and 4(b) is the ratio of the insert thickness plotted based on the thickness of the insert 45 of the reaction unit 11 adjacent to the conductive plate 13. The dashed line in Figure 4(a) represents the average thickness of the insert 44 in the upstream portion. The same conductors 41 were used for the upstream and downstream portions of the spacers 37 and 38.

[0044] As shown in Figure 4(a), in the stack 10 of the example, the average thickness of the inserts in the downstream portion, i.e., the average thickness of the spacers, was greater than the average thickness of the inserts in the upstream portion, i.e., the average thickness of the spacers. On the other hand, as shown in Figure 4(b), in the stack of the comparative example, the average thickness of the inserts in the downstream portion, i.e., the average thickness of the spacers, was the same as the average thickness of the inserts in the upstream portion, i.e., the average thickness of the spacers.

[0045] The cell voltage of the stack in the comparative example shown in Figure 4(b) showed a tendency to gradually decrease from the upstream to the downstream. In particular, the voltage of the fourth cell from the left in the downstream section, which had the thinnest insert, was the lowest of all the cells.

[0046] On the other hand, the cell voltage of the stack 10 in the example shown in Figure 4(a) was almost the same in the downstream section as in the upstream section. It is presumed that the cell voltage in the downstream section was made almost the same as the cell voltage in the upstream section because the amount of fuel gas supplied to the downstream section was secured by making the average spacer thickness in the downstream section larger than the average spacer thickness in the upstream section.

[0047] As shown in Figure 4(a), in the stack 10 of the example, the thickness of all the inserts in the downstream section, i.e., the thickness of all the inserts, was greater than the average insert thickness in the upstream section (the value shown by the dashed line), i.e., the average spacer thickness. This is thought to have prevented the example from having low voltage cells such as the fourth cell from the left in the downstream section in Figure 4(b), further reducing the variation in cell voltage in the downstream section.

[0048] The average thickness of the spacers 37 in the upstream section 26 is preferably 0.90 to 0.99, more preferably 0.93 to 0.98, and even more preferably 0.95 to 0.97, relative to the average thickness of the spacers 38 in the downstream section 27. This is to ensure the flow velocity of the fuel gas in the downstream section 27 while reducing friction loss.

[0049] In the examples, a stack 10 in which 25 reaction units 11 are stacked has been described, but there is no limit to the number of reaction units 11. However, the greater the number of reaction units 11, the more pronounced the effect of reducing the output variation. For example, if the number of reaction units 11 is 13 or more, the effect of reducing the output variation of the reaction units 11 becomes greater.

[0050] 5 is a block diagram of a hydrogen production device 50 including the stack 10. The hydrogen production device 50 is a device that produces hydrogen from water and includes a hot module 51.

[0051] The hot module 51 includes the stack 10, a vaporizer 52 that generates steam to be supplied to the stack 10, a heat exchanger 53 that exchanges heat 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. In the hot module 51, the stack 10, the vaporizer 52, the heat exchanger 53, and the heater 54 are arranged inside a heat insulating material 55 to reduce heat radiation.

[0052] 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 oxidation of the catalyst contained in the anode 34. The hydrogen-containing steam exchanges heat with the hydrogen and oxygen produced by the stack 10 in the heat exchanger 53, is then heated by the heater 54 to the operating temperature of the stack 10, and is supplied to the fuel chamber 39 of the stack 10. The air exchanges heat with the hydrogen and oxygen produced by the stack 10 in the heat exchanger 53, is then heated by the heater 54 to the operating temperature of the stack 10, and is supplied to the air chamber 40 of the stack 10.

[0053] Examples of heat insulating material 55 include heat-resistant fibers such as ceramic wool, refractory ceramic fiber (RCF), and biosoluble fiber (AES), and a heat-resistant container made of heat-resistant fibers. The heat-resistant fibers fill gaps between stack 10, vaporizer 52, heat exchanger 53, and heater 54. Condenser 56 is a device that cools hydrogen gas, and liquefied water is supplied to vaporizer 52 as raw water.

[0054] Even when the stack 10 is used in a hydrogen production device 50, the supply of fuel gas downstream can be secured, which clearly reduces the variation in the output of the reaction units 11 and the variation in the generation of energy carriers for each reaction unit 11.

[0055] The present invention has been described above based on the embodiments, but the present invention is not limited to the above embodiments, and it can be easily inferred that various improvements and modifications are possible within the scope of the present invention.

[0056] The present invention has been described above based on the embodiments, but the present invention is not limited to the above embodiments, and it can be easily inferred that various improvements and modifications are possible within the scope of the present invention.

[0057] In the embodiment, the manifold 22 penetrates the end plate 18, the insulator 20, and the conductive plate 15, and is closed by the end plate 17, the insulator 19, and the conductive plate 13, and the fuel gas supplied to the stack 10 flows through the manifold 22 from the end plate 18 to the end plate 17. However, this is not necessarily limited to this. It is of course possible for the manifold 22 to penetrate the end plate 17, the insulator 19, and the conductive plate 13, and be closed by the end plate 18, the insulator 20, and the conductive plate 15. In this case, the fuel gas supplied to the stack 10 flows through the manifold 22 from the end plate 17 to the end plate 18.

[0058] In the embodiment, the manifold 23 penetrates the end plate 18, the insulator 20, and the conductive plate 15, and is closed by the end plate 17, the insulator 19, and the conductive plate 13, and the gas flows through the manifold 23 from the end plate 17 to the end plate 18 and is exhausted to the outside of the stack 10. However, this is not necessarily limited to this. It is of course possible for the manifold 23 to penetrate the end plate 17, the insulator 19, and the conductive plate 13, and be closed by the end plate 18, the insulator 20, and the conductive plate 15. In this case, the gas flows through the manifold 23 from the end plate 18 to the end plate 17 and is exhausted to the outside of the stack 10. The direction of the gas flowing through the manifolds 24 and 25 is also set appropriately.

[0059] In the embodiment, the spacers 37, 38 are described as being made up of multiple components, each combining the conductor 41 and the inserts 44, 45, but this is not necessarily limited to this. It is of course possible to make the spacers 37, 38 of different heights from a single conductive component.

[0060] In the embodiment, the fuel chambers 39 are connected in parallel to the manifolds 22 and 23, but this is not necessarily limited to this. It is of course possible to connect the fuel chambers 39 to the manifolds 22 and 23 so that the flow of fuel gas is parallel and serial, as in Patent Document 1. In this case as well, the number of reaction units 11 is divided into two equal parts in the thickness direction of the stack 12 according to the flow of fuel gas, and the average thickness of the spacers in the downstream portion is set to be greater than the average thickness of the spacers in the upstream portion.

[0061] In the embodiment, the case where the shape of the cells 32 is a rectangle has been described, but this is not necessarily limited to this. The shape of the cells 32 may be a circle or an ellipse, or may be a polygon other than a rectangle, such as a triangle or a pentagon.

[0062] In the embodiment, the manifolds 22, 23, 24, and 25 through which gas passes are built into the stack 10, but this is not necessarily limited to this. It is of course possible to provide manifolds such as the manifolds 22, 23, 24, and 25 outside the cells by joining them to the cells. Examples of materials for the manifolds include ceramics with high high-temperature strength.

[0063] In the embodiment, the stack 10 including the solid oxide type cells 32 has been described, but this is not necessarily limited to this. It is of course 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]

[0064] 10 stacks 11 Reaction Units 12 Laminate 22 Manifold 26 Upper reaches 27 Downstream 32 cells 33 Electrolytes 34 Fuel electrode 35 Air electrode 36 Interconnector 37,38 Spacer 39 Fuel chamber 41 Conductors 42 Opposing part 43 Connection 44,45 insert 50 Hydrogen production equipment 51 Hot Module 52 Vaporizer 53 Heat exchanger 54 Heater 55 Insulation T1, T2 thickness

Claims

1. a cell including an electrolyte separating an anode and a cathode through its thickness; an interconnector disposed at a distance from the fuel electrode in the thickness direction; a stack in which a plurality of reaction units, each including a spacer that electrically connects the interconnector and the anode and determines the height of a fuel chamber between the interconnector and the anode, are arranged in the thickness direction, and the reaction units are connected in series to each other; a manifold extending in the thickness direction of the stack, connected to the fuel chamber provided in each of the reaction units, and supplying the fuel gas flowing from one side to the other in the thickness direction to the fuel electrode, A stack in which, when the number of reaction units is divided into two equal parts in the thickness direction of the stack and the reaction units are divided into upstream and downstream parts of the fuel gas, the average thickness of the spacers in the downstream part is greater than the average thickness of the spacers in the upstream part.

2. The stack of claim 1 , wherein the thickness of all of the spacers in the downstream portion is greater than the average thickness of the spacers in the upstream portion.

3. 3. The stack according to claim 1, wherein the number of reaction units is 13 or more.

4. the spacer has a pair of opposing portions that are opposed to each other in the thickness direction and that are in contact with the anode and the interconnector, respectively; a connecting portion that connects the pair of opposing portions; an insert disposed between the opposing portions, 3. The stack according to claim 1 or 2, wherein the average thickness of the insert in the downstream portion is greater than the average thickness of the insert in the upstream portion.

5. 3. The stack according to claim 1, wherein the cells have a function of electrolyzing the fuel gas.

6. A stack according to claim 1 or 2; a vaporizer for generating water vapor as the fuel gas; a heat exchanger that exchanges heat with the gas supplied to the stack; a heater for heating the stack; a hot module comprising a thermal insulator in which the stack, the vaporizer, the heat exchanger, and the heater are disposed;

7. A hydrogen production device comprising the hot module according to claim 6.

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