Electrochemical device, hydrogen production device, and method of controlling electrochemical device

Abstract

To provide an electrochemical device, a hydrogen production device and the electrochemical device, capable of improving the accuracy in control of cells.SOLUTION: The electrochemical device comprises: a laminate in which a plurality of cells including an electrolyte separating a fuel electrode and an air electrode in a thickness direction are disposed in the thickness direction, and the cells are connected to each other in series; two first terminals which are disposed outside in the thickness direction of the laminate and have polarities electrically connected to the cells; two second terminals which are provided inside the first terminals of the laminate in the thickness direction and are electrically connected to the cells; and a voltmeter which detects a potential between the second terminals.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to an electrochemical device having stacked cells, a hydrogen production method, and a method for controlling an electrochemical device. [Background technology]

[0002] Patent Document 1 discloses a hydrogen purification system (electrochemical apparatus) in which a hydrogen-containing gas containing carbon monoxide and water vapor is supplied to the fuel electrode of an electrochemical device in which a cell containing an electrolyte is arranged to separate the fuel electrode and the air electrode, and a power supply causes the required amount of current to flow between the fuel electrode and the air electrode. In the prior art disclosed in Patent Document 1, a voltmeter measures the voltage at the junction between the electrochemical device and the power supply, and a controller controls the flow rate and current of the hydrogen-containing gas. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2022-6765 Summary of the Invention [Problem to be solved by the invention]

[0004] In the prior art, when components between the power supply junction and the cell deteriorate and electrical resistance increases, the voltage detected by the controller increases when the current flowing through the cell is constant. This causes a change in the current that the power supply passes through the cell during constant voltage control, resulting in inaccurate control of the cell.

[0005] The present invention has been made to solve this problem, and has as its object to provide an electrochemical device, a hydrogen production device, and a method for controlling an electrochemical device that can improve the accuracy of cell control. [Means for solving the problem]

[0006] A first aspect for achieving this object is an electrochemical device comprising: a stack in which a plurality of cells containing an electrolyte that separates a fuel electrode and an air electrode in the thickness direction are arranged in the thickness direction and the cells are connected in series to each other; two first terminals of different polarities that are arranged on the outer side of the stack in the thickness direction and electrically connected to the cells; two second terminals that are arranged on the inner side of the first terminals in the thickness direction of the stack and electrically connected to the cells; and a voltmeter that detects the potential between the second terminals.

[0007] In a second aspect, in the first aspect, the voltmeter detects the potentials of the plurality of cells.

[0008] In a third aspect, in the first aspect, the voltmeter detects the potential of one cell.

[0009] In a fourth aspect, in any one of the first to third aspects, the cell has a function of electrolyzing a fuel gas.

[0010] A fifth aspect is a hydrogen production device, comprising the electrochemical device of the fourth aspect.

[0011] A sixth aspect is a method for controlling an electrochemical device, the electrochemical device comprising: a stack in which a plurality of cells containing an electrolyte that separates a fuel electrode and an air electrode in the thickness direction are arranged in the thickness direction and the cells are connected in series to each other; and two first terminals of different polarities that are arranged on the outside of the stack in the thickness direction and electrically connected to the cells; the potential between two second terminals that are arranged on the inside of the first terminal in the thickness direction of the stack and electrically connected to the cells is detected by a voltmeter; and at least one of the amount of gas supplied to the cells and the power input from the first terminal is adjusted so that the potential remains constant. [Effects of the Invention]

[0012] According to the present invention, two second terminals provided inside the first terminal in the thickness direction of the stack are electrically connected to the cell, and a voltmeter detects the potential between the second terminals. Control can be performed based on the potential between the second terminals, thereby improving the accuracy of cell control. [Brief explanation of the drawings]

[0013] [Figure 1] FIG. 2 is a perspective view of a stack of the electrochemical device according to the first embodiment. [Figure 2] FIG. 1 is a cross-sectional view of an electrochemical device. [Figure 3] FIG. 1 is an exploded view of the stack. [Figure 4] FIG. 4 is a cross-sectional view of an electrochemical device according to a second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0014] 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 11 of an electrochemical device 10 (see Fig. 2) according to a first embodiment. The stack 11 includes a reaction unit 12, a stack 13 formed by stacking a plurality of reaction units 12 in the thickness direction, conductive plates 14 and 16 electrically connected to the stack 13, and end plates 18 and 19 that sandwich the stack 13 and the conductive plates 14 and 16 in the thickness direction. The stack 13 is formed by stacking, for example, approximately 10-30 reaction units 12.

[0015] Conductive plate 14 is disposed between laminate 13 and end plate 18, and conductive plate 16 is disposed between laminate 13 and end plate 19. First terminals 15 and 17 are connected to conductive plates 14 and 16, respectively. The conductive plates 14 and 16 and first terminals 15 and 17 are made of, for example, stainless steel.

[0016] Insulator 20 is disposed between conductive plate 14 and end plate 18, providing electrical insulation between conductive plate 14 and end plate 18. Insulator 21 is disposed between conductive plate 16 and end plate 19, providing electrical insulation between conductive plate 16 and end plate 19. Bolts 22 are disposed around the periphery of stack 11, passing through end plates 18, 19, insulators 20, 21, conductive plates 14, 16, and laminate 13 in the thickness direction. Stack 11 is fastened together by bolts 22.

[0017] The four spaces that penetrate the periphery of the stack 11 in the thickness direction function as a passage 23 that supplies fuel gas from outside the stack 11 to a fuel chamber 40 (described later) of the reaction unit 12, a passage 24 that discharges gas from the fuel chamber 40 to outside the stack 11, a passage 25 that supplies oxidant gas from outside the stack 11 to an air chamber 41 (described later) of the reaction unit 12, and a passage 26 that discharges gas from the air chamber 41 to outside the stack 11, respectively.

[0018] Fig. 2 is a cross-sectional view of the electrochemical device 10, in which the stack 11 is cut along line II-II in Fig. 1, which passes through the passages 23 and 24. Fig. 3 is an exploded view of the stack 11, in which part of the stack 11 is not shown. In Figs. 2 and 3, the thickness of each part is exaggerated.

[0019] 3, the reaction unit 12 includes, in order in the thickness direction, an anode frame 27, a first separator 28, an air cathode frame 29, and a second separator 30. Holes (passages 23-26) penetrate the anode frame 27, the first separator 28, the air cathode frame 29, and the second separator 30.

[0020] Cells 31, interconnectors 35, and current collectors 36 are arranged inside a fuel electrode frame 27, a first separator 28, a cathode frame 29, and a second separator 30. A frame-shaped first member 37 is arranged between the insulator 20 and the conductive plate 14, and a second member 38 is airtightly connected to the inside of the first member 37. Stainless steel is an example of the material for the first member 37 and the second member 38.

[0021] The cell 31 includes an electrolyte 32, and an anode 33 and cathode 34 separated in the thickness direction by the electrolyte 32. In this embodiment, a flat-plate type cell 31 is described, but the present invention is not limited to this. The cell 31 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 system. The cell 31 may be an electrode-supported type or an electrolyte-supported type.

[0022] The electrolyte 32 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.

[0023] Examples of the material for the fuel electrode 33 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).

[0024] The material of the cathode 34 is a perovskite 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.

[0025] The anode frame 27 is a frame-shaped member that is disposed between the conductive plate 16 or the second separator 30 and the first separator 28, and surrounds the cells 31 and the current collectors 36. Second terminals 39 are connected to the anode frame 27. Stainless steel is an example of the material for the anode frame 27 and the second terminals 39. Because a second terminal 39 is provided for each cell 31 included in the stack 13, the number of second terminals 39 is equal to the number of cells 31.

[0026] The first separator 28 is a frame-shaped member, and is airtightly joined to the electrolyte 32 by brazing material or the like, avoiding the air electrode 34. The material of the first separator 28 is, for example, stainless steel.

[0027] The cathode frame 29 is a frame-shaped member that is disposed between the first separator 28 and the second separator 30 and surrounds the interconnector 35. The material of the cathode frame 29 is exemplified by an insulator such as mica.

[0028] The second separator 30 is a frame-shaped member, and is airtightly joined to the interconnector 35 by brazing material etc. The material of the second separator 30 is, for example, stainless steel.

[0029] The current collector 36 electrically connects the conductive plates 16 and the fuel electrodes 33 that are adjacent in the thickness direction, or electrically connects the interconnectors 35 and the fuel electrodes 33 that are adjacent in the thickness direction. An example of the material of the current collector 36 is a porous body made of a gas-permeable metal such as Ni.

[0030] The interconnector 35 electrically connects the current collectors 36 adjacent in the thickness direction to the air electrode 34. The material of the interconnector 35 is, for example, stainless steel.

[0031] A fuel chamber 40 is provided inside the anode frame 27, and an air chamber 41 is provided inside the cathode frame 29. The fuel chamber 40 is connected to passages 23 and 24 (see FIG. 1), and the air chamber 41 is connected to passages 25 and 26. The first separator 28 and the second separator 30 isolate the fuel chamber 40 from the air chamber 41, preventing the fuel gas in the fuel chamber 40 and the oxidizer gas in the air chamber 41 from mixing.

[0032] When stack 11 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 11 is an electrolysis device (cell 31 is an electrolysis cell), examples of the fuel gas include water vapor, carbon dioxide, and a mixed gas thereof, and examples of the oxidant gas include oxygen and air. Stack 11 also includes stacks that are capable of reversible operation as a fuel cell and an electrolysis device.

[0033] The multiple cells 31 are electrically connected in series between first terminals 15 and 17 via interconnectors 35 and current collectors 36. When the stack 11 is an electrolysis device, the positive electrode of a power source 46 (see FIG. 2) is connected to the first terminal 15, and the negative electrode of the power source 46 is connected to the first terminal 17, causing electrons to flow toward the fuel electrode 33 of the cell 31. The fuel gas that enters the fuel chamber 40 is reduced at the fuel electrode 33. Because electrons are removed at the air electrode 34, oxide ions that have migrated to the air electrode 34 via the electrolyte 32 are oxidized at the air electrode 34. As a result, energy carriers such as hydrogen and hydrocarbons are synthesized in the stack 11.

[0034] As shown in FIG. 2, the electrochemical device 10 includes a stack 11 as an electrolysis device, a voltmeter 42 that measures the potential between two second terminals 39, a control valve 43 that adjusts the flow rate of the fuel gas supplied to the stack 11, a flow meter 44 that is connected between the control valve 43 and the stack 11 and measures the flow rate of the fuel gas, a control valve (not shown) that adjusts the flow rate of the oxidant gas supplied to the stack 11, and a controller 45 to which the measurement results of the voltmeter 42 and the flow meter 44 are input.

[0035] A controller 45 detects the voltage and flow rate using a voltmeter 42 and a flow meter 44, and adjusts at least one of the power input from a power source 46 to the stack 11 and the opening of a control valve 43 so that the potential detected by the voltmeter 42 remains constant. The electrochemical device 10 in which fuel gas containing water vapor is supplied to the stack 11 is a hydrogen production device.

[0036] If the potential between the first terminals 15, 17 of the power supply 46 connected to the stack 11 is measured by a voltmeter 42 and the power supply 46 is controlled to maintain a constant potential, if the conductive plates 14, 16 or the interconnector 35 and current collector 36 connecting the conductive plate 14 to the cell 31 deteriorate and their electrical resistance increases, the voltage detected by the controller 45 will increase when the current flowing through the cell 31 is constant. As a result, the current flowing through the cell 31 from the power supply 46 during constant voltage control will change, resulting in inaccurate control of the cell 31.

[0037] In contrast, in the electrochemical device 10, second terminals 39 provided on the inner side of the first terminals 15, 17 in the thickness direction of the laminate 13 are electrically connected to the cells 31. A controller 45 detects the potential between the two second terminals 39 using a voltmeter 42, and controls a control valve 43 and a power source 46 based on the potential between the second terminals 39. Even if the conductive plates 14, 16 or the interconnector 35 and current collector 36 connecting the conductive plate 14 and the cell 31 deteriorate and the electrical resistance of these components increases, the potential between the second terminals 39 detected by the voltmeter 42 does not change, and therefore the accuracy of control of the cell 31 can be improved.

[0038] According to this embodiment, the controller 45 detects the potentials of multiple cells 31 using the voltmeter 42, so even if there is variation in the electrical characteristics of the cells 31, the cells 31 can be controlled based on the average potential of the cells 31. Therefore, even if the detected potential of a cell 31 significantly deviates from the average, the effect of that cell 31 on control can be reduced.

[0039] A second embodiment will be described with reference to Fig. 4. In the first embodiment, the stack 11 is an electrolysis device. In contrast, in the second embodiment, the stack 11 is a fuel cell. In the second embodiment, the same parts as those described in the first embodiment are designated by the same reference numerals as in the first embodiment, and the following description will be omitted.

[0040] 4 is a cross-sectional view of an electrochemical device 50 according to the second embodiment. In the electrochemical device 50, the stack 11 is a fuel cell, and a load 51 is connected to first terminals 15, 17 of the stack 11. In the fuel cell, gaseous oxygen reacts with electrons at the air electrode 34 of the cell 31 (see FIG. 3) to generate oxide ions, and the oxide ions that have moved through the electrolyte 32 react with the fuel gas at the fuel electrode 33 to generate electrons. This causes a current to flow to the load 51 via the first terminals 15, 17.

[0041] Ammeter 52 measures the current flowing through load 51 and inputs the measurement results to controller 45. Controller 45 detects the voltage, flow rate, and current using voltmeter 42, flow meter 44, and ammeter 52, and adjusts the opening of control valve 43 so that the potential of cell 31 remains constant (target value). Even if deterioration of conductive plates 14, 16 or deterioration of interconnector 35 and current collector 36 connecting conductive plate 14 and cell 31 occurs and the electrical resistance of these components increases, the potential between second terminal 39 detected by voltmeter 42 does not change, thereby improving the accuracy of control of cell 31.

[0042] According to this embodiment, the controller 45 detects the potential of one cell 31 using the voltmeter 42. Even if some of the cells 31 deviate significantly from the average, by detecting the potential of the cell 31 that is approximately in the center of the distribution of electrical characteristics among the cells 31, the outlier cells 31 do not affect the control, and the accuracy of the control of the cells 31 can be further improved.

[0043] 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.

[0044] In the embodiment, the case where the voltmeter 42 is separate from the power supply 46 has been described, but this is not necessarily limited to this. It is of course possible to employ a voltmeter in which the voltmeter 42 and the power supply 46 are integrated.

[0045] In the embodiment, the case where the anode frame 27 is conductive and the cathode frame 29 is insulating has been described, but this is not necessarily limited to this. It is of course possible to select materials such that the anode frame 27 is insulating and the cathode frame 29 is conductive. When the cathode frame 29 is conductive, the second terminal 39 is provided on the cathode frame 29.

[0046] In the embodiment, the case where the shape of the cells 31 is a rectangle has been described, but this is not necessarily limited to this. The shape of the cells 31 may be a circle or an ellipse, or may be a polygon other than a rectangle, such as a triangle or a pentagon.

[0047] In the embodiment, the gas passages 23, 24, 25, and 26 are built into the stack 11, but this is not necessarily limited to this. It is of course possible to provide manifolds serving as the gas passages 23, 24, 25, and 26 outside the cells by joining them to the cells. Examples of materials for the manifolds include ceramics with high high-temperature strength. [Explanation of symbols]

[0048] 10,50 Electrochemical equipment 13 Laminate 15,17 First terminal 31 cells 32 Electrolytes 33 Fuel electrode 34 Air electrode 39 Second terminal 42 Voltmeter

Claims

1. a stack of cells arranged in a thickness direction and connected in series to each other, the cells including an electrolyte separating an anode and an cathode in the thickness direction; two first terminals having different polarities that are disposed on outer sides of the laminate in the thickness direction and electrically connected to the cells, two second terminals provided on the inner side of the first terminals in the thickness direction of the stack and electrically connected to the cells; a voltmeter that detects the potential between the second terminals.

2. 2. The electrochemical device according to claim 1, wherein the voltmeter detects the potentials of a plurality of the cells.

3. 2. The electrochemical device according to claim 1, wherein the voltmeter detects the potential of one of the cells.

4. 4. The electrochemical device according to claim 1, wherein the cell has a function of electrolyzing a fuel gas.

5. A hydrogen production device comprising the electrochemical device according to claim 4.

6. a stack of cells arranged in a thickness direction and connected in series to each other, the cells including an electrolyte separating an anode and an cathode in the thickness direction; two first terminals having different polarities that are disposed on outer sides of the laminate in the thickness direction and electrically connected to the cells, A control method in which the potential between two second terminals of the stack, which are provided inside the first terminal in the thickness direction and electrically connected to the cell, is detected using a voltmeter, and at least one of the amount of gas supplied to the cell and the power input from the first terminal is adjusted so that the potential remains constant.

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