Methane Production System

Abstract

This methane production system (1) comprises a co-electrolysis device (30), and a reforming device (40) connected to the co-electrolysis device (30). The co-electrolysis device (30) has a co-electrolysis cell (32) including: a hydrogen electrode (2) that generates H2, CO, and O2- from CO2 and H2O; an electrolyte (3) that can convey O2-; and an oxygen electrode (4) that generates O2 from O2- transferred from the hydrogen electrode (2) through the electrolyte (3). The reforming device (40) generates CH4 from CO and H2 generated at the hydrogen electrode (2).

Description

[Technical field]

[0001] The present invention relates to a methane production system. [Background technology]

[0002] Patent Document 1 describes a hydrogen electrode that electrolyzes HO and an O 2- The electrolyte is capable of conducting oxygen, and the oxygen is transferred from the hydrogen electrode through the electrolyte. 2- and an oxygen electrode that produces O2 from the oxygen.

[0003] Patent Document 2 discloses that H2 and CO can be produced by co-electrolyzing CO2 and H2O at the hydrogen electrode of an SOEC. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2018-154864 A [Patent Document 2] JP 2019-175636 A Summary of the Invention [Problem to be solved by the invention]

[0005] By the way, in order to utilize the H2 and CO generated from CO2 and H2O by co-electrolysis using SOEC as fuel, it is effective to generate CH4 from H2 and CO using a reformer.

[0006] However, in order to transport H2 and CO from a plant where an SOEC is installed to a plant where a reformer is installed, it is necessary to separate H2 and CO and liquefy or compress them into gas.

[0007] Therefore, there is a demand to perform the production of H2 and CO and the production of CH4 on-site (i.e., within one facility).

[0008] The present invention has been made in consideration of the above-mentioned circumstances, and an object of the present invention is to provide a methane production system capable of producing H2 and CO and producing CH4 on-site. [Means for solving the problem]

[0009] The methane production system according to the present invention includes a co-electrolysis device and a reformer connected to the co-electrolysis device. The co-electrolysis device converts CO and H0 into H, CO, and O 2- a first electrode generating O 2- and an electrolyte capable of conducting O transmitted from the first electrode through the electrolyte. 2- The reformer has a co-electrolysis cell including a first electrode for producing O2 from H2 and a second electrode for producing CH4 from CO. The reformer has a reforming cell for producing CH4 from H2 and CO produced at the first electrode. Effect of the Invention

[0010] According to the present invention, it is possible to provide a methane production system capable of producing H2 and CO, and producing CH4 on-site. [Brief description of the drawings]

[0011] [Figure 1] FIG. 1 is a block diagram showing the configuration of a methane production system. [Diagram 2] FIG. 2 is a perspective view of the co-electrolysis device. [Diagram 3] FIG. 3 is a cross-sectional view of a co-electrolysis device. [Figure 4] FIG. 4 is a perspective view of a co-electrolysis cell. [Diagram 5] FIG. 5 is a cross-sectional view of a co-electrolysis cell. [Figure 6] FIG. 6 is a perspective view of the reformer. [Figure 7] FIG. 7 is a cross-sectional view of the reformer. [Figure 8]FIG. 8 is a perspective view of the reforming cell. [Figure 9] FIG. 9 is a cross-sectional view of the reforming cell. [Figure 10] FIG. 10 is a block diagram showing another configuration of the methane production system. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] (Methane production system) FIG. 1 is a block diagram showing the configuration of a methane production system 1 according to this embodiment.

[0013] The methane production system 1 includes a CO 2 supplying device 10, an H 2 O supplying device 20, a co-electrolysis device 30, a reforming device 40, a voltage detector 50, and a control unit 60.

[0014] The CO2 supplying device 10 is connected to the co-electrolysis device 30 via a first pipe L1. The CO2 supplying device 10 supplies CO2 (carbon dioxide) to the co-electrolysis device 30. During operation of the co-electrolysis device 30, it is preferable that the amount of CO2 supplied from the CO2 supplying device 10 to the co-electrolysis device 30 is constant. This can prevent the generation of C (solid carbon) and CO2 due to a disproportionation reaction of CO (carbon monoxide) generated in each co-electrolysis cell 32 of the co-electrolysis device 30. As a result, a decrease in the electrode activity of the hydrogen electrode 2 of each co-electrolysis cell 32, which will be described later, can be prevented.

[0015] The H2O supply device 20 is connected to the co-electrolysis device 30 via a first pipe L1. The H2O supply device 20 supplies H2O (moisture) to the co-electrolysis device 30. The H2O supplied from the H2O supply device 20 to the co-electrolysis device 30 is entirely or mostly gaseous (water vapor), but may be partially liquid (water). The H2O supplied from the H2O supply device 20 to the co-electrolysis device 30 may be vaporized using heat of a methane (CH4)-containing gas flowing through a third pipe L3 described later. During the operation of the co-electrolysis device 30, the amount of H2O supplied from the H2O supply device 20 to the co-electrolysis device 30 is controlled by the control unit 60. This allows the CH4 production efficiency in the reformer 40 to be optimized.

[0016] The co-electrolysis device 30 includes a manifold 31 and a plurality of co-electrolysis cells 32 .

[0017] The manifold 31 is configured to distribute CO2 and H2O to each co-electrolysis cell 32 and recover H2 and CO from each co-electrolysis device 30. The manifold 31 has a gas supply chamber 31a and a gas recovery chamber 31b therein. The gas supply chamber 31a and the gas recovery chamber 31b are airtightly separated from each other. A first pipe L1 is connected to the gas supply chamber 31a. CO2 and H2O are supplied to the gas supply chamber 31a from the first pipe L1. The gas recovery chamber 31b recovers H2 and CO generated in each co-electrolysis cell 32. A second pipe L2 is connected to the gas recovery chamber 31b. H2 and CO are discharged from the gas recovery chamber 31b to the second pipe L2.

[0018] The base end of each co-electrolysis cell 32 is supported by the manifold 31. The tip end of each co-electrolysis cell 32 is a free end. CO2 and H2O are supplied to each co-electrolysis cell 32 from the gas supply chamber 31a. In each co-electrolysis cell 32, CO2 and H2O are converted into H2, CO, and O at the hydrogen electrode 2 described later. 2- (oxygen ions) are generated, and O 2- O2 is generated from the co-electrolysis cells 32. The generated H2 and CO are collected in the gas collection chamber 31b and then discharged from the second pipe L2. The number of the co-electrolysis cells 32 is not particularly limited as long as it is one or more.

[0019] Each co-electrolysis cell 32 produces H2 (hydrogen), CO, and O2 (oxygen) by co-electrolyzing CO2 and H2O. In this specification, co-electrolysis means producing H2, CO, and O2 by electrolyzing CO2 and H2O together. H2 and CO are collected inside the co-electrolysis device 30, and O2 is discharged to the outside of the co-electrolysis device 30. Each co-electrolysis cell 32 operates at a high temperature (for example, 600°C to 850°C). The operating temperature of each co-electrolysis cell 32 is determined in consideration of the performance of the electrolyte 3 and the durability of each co-electrolysis cell 32. In this specification, the operating temperature of the co-electrolysis cell 32 means the temperature at the center of the co-electrolysis cell 32 in the longitudinal direction (x-axis direction).

[0020] An example of the configuration of the co-electrolysis device 30 will be described later.

[0021] The reformer 40 is connected to the co-electrolysis device 30. In this embodiment, the reformer 40 is directly connected to the co-electrolysis device 30 by the second pipe L2. Therefore, the H2 and CO generated in the co-electrolysis device 30 are supplied to the reformer 40 as is without changing the composition.

[0022] The reformer 40 includes a manifold 41 and a plurality of reforming cells 42 .

[0023] The manifold 41 has a configuration capable of distributing gas to each reforming cell 42 and recovering gas from each reforming cell 42. The manifold 41 has a gas supply chamber 41a and a gas recovery chamber 41b therein. The gas supply chamber 41a and the gas recovery chamber 41b are airtightly separated from each other. The gas supply chamber 41a is connected to the second pipe L2. H2 and CO are supplied to the gas supply chamber 41a from the second pipe L2. The gas recovery chamber 41b recovers CH4 and H2O generated in each reforming cell 42. The gas recovery chamber 41b is connected to the third pipe L3. A reforming catalyst may be disposed in the gas recovery chamber 41b. The reforming catalyst may be in the form of pellets. The reforming catalyst may be filled in the gas recovery chamber 41b. For example, Ru / Al2O3, Ni / Al2O3, etc. may be used as the reforming catalyst.

[0024] A base end of each reforming cell 42 is supported by the manifold 41. A tip end of each reforming cell 42 is a free end. H2 and CO are supplied to each reforming cell 42 from a gas supply chamber 41a. In each reforming cell 42, CH4 and H2O are produced from H2 and CO by a reforming catalyst described below. The produced CH4 and H2O are recovered in a gas recovery chamber 41b and then discharged to the outside of the methane production system 1 from a third pipe L3. The number of reforming cells 42 is not particularly limited as long as it is one or more.

[0025] Each reforming cell 42 produces CH4 (methane) and H2O from H2 and CO produced in the co-electrolysis device 30. In this specification, reforming means producing CH4 and H2O from H2 and CO. Each reforming cell 42 operates at a temperature lower than the operating temperature of the co-electrolysis cell 32 (for example, 200°C to 500°C). In this specification, the operating temperature of the reforming cell 42 means the temperature at the center in the longitudinal direction (x-axis direction) of the reforming cell 42. When the support substrate 45 of the reforming cell 42 described later contains MgO (magnesium oxide), MgCO3 (magnesium carbonate) is precipitated in the support substrate 45 if the operating temperature is lower than 300°C, so the operating temperature of the reforming cell 42 is preferably 350°C or higher.

[0026] The volume of the space in which the reforming cells 42 are installed in the reformer 40 (hereinafter referred to as the "reforming cell installation volume") is preferably smaller than the volume of the space in which the co-electrolysis cells 32 are installed in the co-electrolysis device 30 (hereinafter referred to as the "co-electrolysis cell installation volume"). This makes it possible to increase the heat generation density of the reforming cells 42 that cause the methane production reaction, which is an exothermic reaction, and therefore makes it easier to control the temperature of the reforming cells 42.

[0027] The reforming cell installation volume is the sum of the volume of the gap between the opposing reforming cells 42 and the volume of each reforming cell 42. Similarly, the co-electrolytic cell installation volume is the sum of the volume of the gap between the opposing co-electrolytic cells 32 and the volume of each co-electrolytic cell 32 itself.

[0028] An example of the configuration of the reformer 40 will be described later.

[0029] The voltage detector 50 detects the electromotive voltage of at least one of the multiple reforming cells 42. In this embodiment, the voltage detector 50 detects the electromotive voltage of the most downstream reforming cell 42 (hereinafter referred to as the "most downstream reforming cell 42") that is closest to the inlet of the third pipe L3 (the opening in the gas recovery chamber 41b) among the multiple reforming cells 42. The electromotive voltage of the most downstream reforming cell 42 is an index indicating the CH4 production efficiency in the reformer 40. The electromotive voltage of the most downstream reforming cell 42 being smaller than a predetermined value means that the CH4 production efficiency in the reformer 40 is not sufficient. However, the voltage detector 50 may detect the electromotive voltage of a reforming cell 42 other than the most downstream reforming cell 42.

[0030] The control unit 60 controls the amount of H2O supplied from the H2O supply device 20 to the co-electrolysis device 30. The control unit 60 changes the amount of H2O supplied depending on the electromotive voltage of the most downstream reforming cell 42 detected by the voltage detector 50. Specifically, when the electromotive voltage of the most downstream reforming cell 42 is smaller than a predetermined value, the control unit 60 determines that the CH4 production efficiency in the reformer 40 is insufficient, and reduces the amount of H2O supplied from the H2O supply device 20 to the co-electrolysis device 30. This improves the CH4 production efficiency in the reformer 40, and the electromotive voltage of the most downstream reforming cell 42 increases. As a result, the CH4 production efficiency in the reformer 40 is maintained within a desired appropriate range.

[0031] (Configuration of the co-electrolysis device 30) Fig. 2 is a perspective view of the co-electrolysis device 30. Fig. 3 is a cross-sectional view of the co-electrolysis device 30. Fig. 4 is a perspective view of the co-electrolysis cells 32. Some of the co-electrolysis cells 32 are omitted in Fig. 2.

[0032] [Manifold 31] As shown in FIGS. 2 and 3, the manifold 31 has a manifold body 33 and a partition plate .

[0033] The manifold body 33 is formed to be hollow. The partition plate 34 is disposed inside the manifold body 33. The partition plate 34 airtightly separates the gas supply chamber 31a and the gas recovery chamber 31b.

[0034] The manifold body 33 has a top plate 33a. As shown in Fig. 3, a plurality of through holes 33b are formed in the top plate 33a. The through holes 33b are arranged at predetermined intervals in the longitudinal direction (z-axis direction) of the manifold body 33. The through holes 33b extend in the width direction (y-axis direction) of the manifold body 33. In this embodiment, each through hole 33b is an elongated hole communicating with both the gas supply chamber 31a and the gas recovery chamber 31b, but may be divided into a hole communicating with the gas supply chamber 31a and a hole communicating with the gas recovery chamber 31b.

[0035] [Co-electrolysis cell 32] 2 and 3, each co-electrolysis cell 32 extends in a direction away from the manifold 31. A base end of each co-electrolysis cell 32 is fixed to a through-hole 33b of the top plate portion 33a by a bonding material (not shown) or the like. The base end of each co-electrolysis cell 32 may be inserted into the through-hole 33b or may protrude outside the through-hole 33b.

[0036] The co-electrolytic cells 32 are arranged with their principal surfaces facing each other. The co-electrolytic cells 32 are arranged at predetermined intervals along the longitudinal direction (z-axis direction) of the manifold 31. That is, the arrangement direction of the co-electrolytic cells 32 is along the longitudinal direction of the manifold 31. The co-electrolytic cells 32 are electrically connected in series or in a combination of series and parallel by current collecting members (not shown).

[0037] 3 and 4, the co-electrolysis cell 32 includes a support substrate 35, a communication member 36, a covering layer 37, and a plurality of element units 38. The co-electrolysis cell 32 according to this embodiment is a so-called horizontal stripe type solid oxide electrolysis cell (SOEC).

[0038] 3 is the longitudinal direction of the support substrate 35, and the left-right direction in FIG.

[0039] A plurality of first gas flow paths 35a and a plurality of second gas flow paths 35b are formed inside the support substrate 35. Each of the first gas flow paths 35a and each of the second gas flow paths 35b extends from the base end of the co-electrolysis cell 32 to the tip end thereof within the support substrate 35. Each of the first gas flow paths 35a and each of the second gas flow paths 35b penetrates the support substrate 35. Each of the first gas flow paths 35a is disposed at intervals from each other in the width direction of the support substrate 35. Each of the second gas flow paths 35b is disposed at intervals from each other in the width direction of the support substrate 35. In this embodiment, the inner diameter of each of the first gas flow paths 35a is larger than the inner diameter of each of the second gas flow paths 35b, but the inner diameters of each of the first gas flow paths 35a and each of the second gas flow paths 35b are not particularly limited.

[0040] Each of the first gas flow paths 35a opens to the gas supply chamber 31a. CO2 and H2O flow from the gas supply chamber 31a into each of the first gas flow paths 35a. Each of the second gas flow paths 35b opens to the gas recovery chamber 31b. H2 and CO flow out from each of the second gas flow paths 35b to the gas recovery chamber 31b.

[0041] The support substrate 35 is made of a porous material that does not have electronic conductivity so as to allow gas to pass through while preventing short circuits between the element portions 38. The support substrate 35 can be made of, for example, CSZ (calcia stabilized zirconia), 8YSZ (yttria stabilized zirconia), Y2O3 (yttria), MgO (magnesium oxide), MgAl2O4 (magnesia alumina spinel), or a composite of these. The porosity of the support substrate 35 can be 20 to 60%. The porosity described in this specification is a value measured by the Archimedes method.

[0042] The communication member 36 is attached to the tip of the support substrate 35. The communication member 36 can be made of, for example, the same porous material as the support substrate 35. The communication member 36 has a communication flow path 36a therein. The communication flow path 36a communicates with each of the first gas flow paths 35a and each of the second gas flow paths 35b.

[0043] The covering layer 37 covers the outer surfaces of the support substrate 35 and the communicating member 36. The covering layer 37 is denser than the support substrate 35 and the communicating member 36. The porosity of the covering layer 37 may be about 0 to 7%. The covering layer 37 may be made of a material used for the electrolyte 3 described later, crystallized glass, or the like.

[0044] Each element portion 38 is supported by the support substrate 35. The element portions 38 may be disposed on both main surfaces of the support substrate 35, or may be disposed on only one of the main surfaces.

[0045] [Element part 38] FIG. 5 is a cross-sectional view of the co-electrolysis cell 32 taken along the first gas flow path 35a.

[0046] Each element portion 38 has a hydrogen electrode 2, an electrolyte 3, an oxygen electrode 4, a reaction prevention film 5, and an interconnector 6. The hydrogen electrode 2 is an example of a "first electrode" according to the present invention. The electrolyte 3 is an example of an "electrolyte" according to the present invention. The oxygen electrode 4 is an example of a "second electrode" according to the present invention.

[0047] The hydrogen electrode 2 converts CO2 and HO into H2, CO, and O according to the co-electrolytic chemical reaction shown in the following formula (1). 2- Generate. Hydrogen electrode 2: CO2+H2O+4e - →CO+H2+2O 2- (1)

[0048] The hydrogen electrode 2 has a hydrogen electrode substrate 21 and a hydrogen electrode active portion 22 .

[0049] The hydrogen electrode substrate 21 is disposed on a support substrate 35. In this embodiment, the hydrogen electrode substrate 21 is embedded in a recess formed in the surface of the support substrate 35, but it may be placed on the surface of the support substrate 35. The thickness of the hydrogen electrode substrate 21 may be 50 to 500 μm.

[0050] The hydrogen electrode substrate 21 is made of a porous material having electronic conductivity. It is preferable that the hydrogen electrode substrate 21 has higher electronic conductivity than the hydrogen electrode active portion 22. The hydrogen electrode substrate 21 may or may not have oxygen ion conductivity. The hydrogen electrode substrate 21 can be made of, for example, a composite of NiO and 8YSZ, a composite of NiO and Y2O3, or a composite of NiO and CSZ.

[0051] The hydrogen electrode active part 22 is disposed on the hydrogen electrode substrate 21. The thickness of the hydrogen electrode active part 22 may be 5 to 100 μm. The hydrogen electrode active part 22 has oxygen ion conductivity and electronic conductivity. The hydrogen electrode active part 22 preferably has higher oxygen ion conductivity than the hydrogen electrode substrate 21. The hydrogen electrode active part 22 may be formed of, for example, a composite of NiO and 8YSZ, or a composite of NiO and GDC(Ce,Gd)O2 (gadolinium-doped ceria).

[0052] The electrolyte 3 is disposed between the hydrogen electrode 2 and the oxygen electrode 4. The electrolyte 3 is arranged to absorb the O 2- to the oxygen electrode 4. The electrolyte 3 is disposed on the hydrogen electrode 2. In this embodiment, the electrolyte 3 extends in the longitudinal direction of the support substrate 35 between the two interconnectors 6. The thickness of the electrolyte 3 may be, for example, 3 to 50 μm.

[0053] The electrolyte 3 is made of a dense material that has oxygen ion conductivity and does not have electronic conductivity. The electrolyte 3 is denser than the support substrate 35. The porosity of the electrolyte 3 can be, for example, 0 to 7%. The electrolyte 3 can be made of, for example, 8YSZ, LSGM (lanthanum gallate), etc.

[0054] The oxygen electrode 4 converts the oxygen transferred from the hydrogen electrode 2 through the electrolyte 3 into oxygen according to the chemical reaction shown in the following formula (2): 2- produces O2 from Oxygen electrode 4:2O 2- →O2+4e - (2)

[0055] The oxygen electrode 4 has an oxygen electrode active portion 41 and an oxygen electrode substrate 42 .

[0056] The oxygen electrode active part 41 is disposed on the reaction preventive film 5. The thickness of the oxygen electrode active part 41 can be set to, for example, 10 to 100 μm.

[0057] The oxygen electrode active part 41 is made of a porous material having oxygen ion conductivity and electron conductivity. The oxygen electrode active part 41 preferably has higher oxygen ion conductivity than the oxygen electrode substrate 42. The oxygen electrode active part 41 can be made of, for example, LSCF=(La,Sr)(Co,Fe)O3 (lanthanum strontium cobalt ferrite), LSF=(La,Sr)FeO3 (lanthanum strontium ferrite), LNF=La(Ni,Fe)O3 (lanthanum nickel ferrite), LSC=(La,Sr)CoO3 (lanthanum strontium cobaltite), SSC=(Sm,Sr)CoO3 (samarium strontium cobaltite), or the like.

[0058] The oxygen electrode substrate 42 is disposed on the oxygen electrode active portion 41. The oxygen electrode substrate 42 is electrically connected to the hydrogen electrode substrate 21 of the adjacent element portion 38 via the interconnector 6. The thickness of the oxygen electrode substrate 42 may be, for example, 50 to 500 μm.

[0059] The oxygen electrode substrate 42 is made of a porous material having electronic conductivity. The oxygen electrode substrate 42 preferably has higher electronic conductivity than the oxygen electrode active part 41. The oxygen electrode substrate 42 may or may not have oxygen ion conductivity. The oxygen electrode substrate 42 can be made of, for example, LSCF, LSC, Ag (silver), Ag-Pd (silver-palladium alloy), etc.

[0060] The reaction prevention film 5 is disposed between the electrolyte 3 and the oxygen electrode active portion 41. The reaction prevention film 5 prevents the substances contained in the electrolyte 3 and the oxygen electrode active portion 41 from reacting with each other to form a reaction layer having a large electric resistance. The reaction prevention film 5 may have a thickness of, for example, 3 to 50 μm. The reaction prevention film 5 is made of a dense material. The reaction prevention film 5 may be made of, for example, GDC.

[0061] The interconnector 6 is connected to the oxygen electrode substrate 42 and also to the hydrogen electrode substrate 21 of the adjacent element portion 38. The thickness of the interconnector 6 may be, for example, 10 to 100 μm. The interconnector 6 is made of a dense material having electronic conductivity. The interconnector 6 is denser than the support substrate 35. The porosity of the interconnector 6 may be 0 to 7%. The interconnector 6 may be made of, for example, LaCrO3 (lanthanum chromite), (Sr,La)TiO3 (strontium titanate), or the like.

[0062] (Configuration of reformer 40) Fig. 6 is a perspective view of the reformer 40. Fig. 7 is a cross-sectional view of the reformer 40. Fig. 8 is a perspective view of the reforming cells 42. In Fig. 6, some of the reforming cells 42 are omitted.

[0063] [Manifold 41] As shown in FIGS. 6 and 7, the manifold 41 has a manifold main body 43 and a partition plate 44.

[0064] The manifold body 43 is formed to be hollow. The partition plate 44 is disposed inside the manifold body 43. The partition plate 44 air-tightly separates the gas supply chamber 41a and the gas recovery chamber 41b.

[0065] The manifold body 43 has a top plate 43a. As shown in Fig. 7, a plurality of through holes 43b are formed in the top plate 43a. The through holes 43b are arranged at predetermined intervals in the longitudinal direction (z-axis direction) of the manifold body 43. The through holes 43b extend in the width direction (y-axis direction) of the manifold body 43. In this embodiment, each through hole 43b is an elongated hole communicating with both the gas supply chamber 41a and the gas recovery chamber 41b, but may be divided into a hole communicating with the gas supply chamber 41a and a hole communicating with the gas recovery chamber 41b.

[0066] [Modified Cell 42] 6 and 7, each reforming cell 42 extends in a direction away from the manifold 41. The base end of each reforming cell 42 is fixed to the through hole 43b of the top plate portion 43a via a bonding material (not shown) or the like. The base end of each reforming cell 42 may be inserted into the through hole 43b or may protrude outside the through hole 43b.

[0067] The reforming cells 42 are arranged such that their main surfaces face each other. The reforming cells 42 are arranged at predetermined intervals along the longitudinal direction (z-axis direction) of the manifold 41. That is, the arrangement direction of the reforming cells 42 is the same as the longitudinal direction of the manifold 41. The reforming cells 42 are electrically connected in series by a current collecting member (not shown). In this embodiment, a voltage detector 50 is connected to the downstreammost reforming cell 42 among the multiple reforming cells 42.

[0068] 7 and 8, the reforming cell 42 includes a support substrate 45, a communication member 46, a covering layer 47, and a plurality of reforming element portions 48. The reforming cell 42 according to this embodiment has the same configuration as the above-described co-electrolysis cell 32. In this specification, the term "same configuration" means that the shapes of the respective components are substantially the same, and that the respective components are made of substantially the same materials, regardless of the presence or absence of defects or damage that may occur during or after the preparation of the cells.

[0069] 7 (x-axis direction) is the longitudinal direction of the support substrate 45, and the left-right direction in FIG.

[0070] A plurality of first gas flow paths 45a and a plurality of second gas flow paths 45b are formed inside the support substrate 45. Each of the first gas flow paths 45a and each of the second gas flow paths 45b extends from the base end of the reforming cell 42 toward the tip end thereof through the support substrate 45. Each of the first gas flow paths 45a and each of the second gas flow paths 45b penetrates the support substrate 45. Each of the first gas flow paths 45a is disposed at intervals from each other in the width direction of the support substrate 45. Each of the second gas flow paths 45b is disposed at intervals from each other in the width direction of the support substrate 45. In this embodiment, the inner diameter of each of the first gas flow paths 45a is larger than the inner diameter of each of the second gas flow paths 45b, but the inner diameters of each of the first gas flow paths 45a and each of the second gas flow paths 45b are not particularly limited.

[0071] Each of the first gas flow paths 45a opens to the gas supply chamber 41a. CO2 and H2O flow from the gas supply chamber 41a into each of the first gas flow paths 45a. Each of the second gas flow paths 45b opens to the gas recovery chamber 41b. H2 and CO flow out from each of the second gas flow paths 45b to the gas recovery chamber 41b.

[0072] The support substrate 45 is made of a porous material that does not have electronic conductivity so as to allow gas to pass through while preventing short circuits between the reforming element sections 48. The support substrate 45 can be made of, for example, CSZ, a composite of NiO and 8YSZ, a composite of NiO and Y2O3, or a composite of MgO and MgAl2O4. The porosity of the support substrate 45 can be 20 to 60%.

[0073] The communication member 46 is attached to the tip of the support substrate 45. The communication member 46 can be made of, for example, the same porous material as the support substrate 45. The communication member 46 has a communication flow path 46a therein. The communication flow path 46a communicates with each of the first gas flow paths 45a and each of the second gas flow paths 45b.

[0074] The covering layer 47 covers the outer surfaces of the support substrate 45 and the communicating member 46. The covering layer 47 is denser than the support substrate 45 and the communicating member 46. The porosity of the covering layer 47 may be about 0 to 7%. The covering layer 47 may be made of a material used for the dense film 3a described later, crystallized glass, or the like.

[0075] Each of the modifying element sections 48 is supported by a supporting substrate 45. The modifying element sections 48 may be disposed on both main surfaces of the supporting substrate 45, or may be disposed on only one of the main surfaces.

[0076] [Modification element part 48] FIG. 9 is a cross-sectional view of the reforming cell 42 taken along the first gas flow passage 45a.

[0077] Each reforming element 48 includes a first electrode 2a, a dense membrane 3a, a second electrode 4a, a reaction-preventing membrane 5a, and an interconnector 6a. The reforming element 48 according to this embodiment has the same configuration as the element 38 of the co-electrolytic cell 32 described above.

[0078] The first electrode 2a produces CH4 and H2O from H2 and CO produced at the hydrogen electrode 2 of the co-electrolysis cell 32 in accordance with the chemical reaction shown in formula (3) below. ·First electrode 2a: 3H2+CO→CH4+H2O...(3)

[0079] The first electrode 2a has a first electrode substrate 21a and a first electrode catalyst portion 22a.

[0080] The first electrode substrate 21a is disposed on a supporting substrate 45. In this embodiment, the first electrode substrate 21a is embedded in a recess formed in the surface of the supporting substrate 45, but may be placed on the surface of the supporting substrate 45. The thickness of the first electrode substrate 21a may be 50 to 500 μm.

[0081] The first electrode substrate 21a is made of a porous material having electronic conductivity. The first electrode substrate 21a does not need to have oxygen ion conductivity. The first electrode substrate 21a can be made of, for example, a compound of NiO and 8YSZ, a compound of NiO and Y2O3, or a compound of NiO and CSZ.

[0082] The first electrode catalyst section 22a is disposed on the first electrode substrate 21a. The thickness of the first electrode catalyst section 22a may be 5 to 30 μm. The first electrode catalyst section 22a contains a reforming catalyst for producing CH4 and H2O from H2 and CO. The first electrode catalyst section 22a has electronic conductivity. The first electrode catalyst section 22a does not need to have oxygen ion conductivity. The first electrode catalyst section 22a may be composed of, for example, a compound of NiO and 8YSZ, or a compound of NiO and GDC. In this case, Ni functions as a reforming catalyst for producing CH4 and H2O from H2 and CO.

[0083] The dense film 3a is disposed on the first electrode 2a. In this embodiment, the dense film 3a extends between the two interconnectors 6a in the longitudinal direction of the support substrate 45. The dense film 3a may have a thickness of, for example, 3 to 50 μm.

[0084] The dense film 3a is made of a dense material. The dense film 3a is denser than the support substrate 45. The porosity of the dense film 3a can be, for example, 0 to 7%. The dense film 3a does not need to have oxygen ion conductivity and electronic conductivity. The dense film 3a can be made of, for example, 8YSZ, LSGM (lanthanum gallate), or the like.

[0085] The second electrode 4a has a second electrode active portion 41a and a second electrode substrate 42a.

[0086] The second electrode active portion 41a is disposed on the reaction prevention film 5a. The second electrode active portion 41a may have a thickness of, for example, 10 to 100 μm.

[0087] The second electrode active part 41a is made of a porous material having electronic conductivity. The second electrode active part 41a does not have to have oxygen ion conductivity. The second electrode active part 41a can be made of, for example, LSCF, LSF, LNF, LSC, SSC, etc.

[0088] The second electrode substrate 42a is disposed on the second electrode active portion 41a. The second electrode substrate 42a is electrically connected to the first electrode substrate 21a of the adjacent reforming element portion 48 via the interconnector 6a. The thickness of the second electrode substrate 42a may be, for example, 50 to 500 μm.

[0089] The second electrode substrate 42a is made of a porous material having electronic conductivity. The second electrode substrate 42a does not need to have oxygen ion conductivity. The second electrode substrate 42a can be made of, for example, LSCF, LSC, Ag (silver), Ag-Pd (silver-palladium alloy), etc.

[0090] The reaction prevention film 5a is disposed between the dense film 3a and the second electrode active portion 41a. The reaction prevention film 5a prevents the substances contained in the dense film 3a and the second electrode active portion 41a from reacting with each other to form a reaction layer having a large electrical resistance. The thickness of the reaction prevention film 5a can be, for example, 3 to 50 μm. The reaction prevention film 5a is made of a dense material. The reaction prevention film 5a can be made of, for example, GDC.

[0091] The interconnector 6a is connected to the second electrode substrate 42a and to the first electrode substrate 21a of the adjacent reforming element section 48. The thickness of the interconnector 6a may be, for example, 10 to 100 μm. The interconnector 6a is made of a dense material having electronic conductivity. The interconnector 6a is denser than the support substrate 45. The porosity of the interconnector 6a may be 0 to 7%. The interconnector 6a may be made of, for example, LaCrO3 (lanthanum chromite), (Sr,La)TiO3 (strontium titanate), or the like.

[0092] (Features) (1) The methane production system 1 includes a co-electrolysis device 30 and a reformer 40 connected to the co-electrolysis device 30. The co-electrolysis device 30 converts CO and H0 into H, CO, and O 2- Hydrogen electrode 2, which produces O 2- The electrolyte 3 is capable of conducting oxygen, and the oxygen is transferred from the hydrogen electrode 2 through the electrolyte 3. 2- The reformer 40 has a reforming cell 42 that produces CH4 from H2 and CO produced at the hydrogen electrode 2.

[0093] Therefore, H2 and CO produced in the co-electrolysis device 30 can be used to produce CH4 on-site. Therefore, there is no need to transport H2 and CO from the plant where the SOEC is installed to the plant where the reformer is installed.

[0094] (2) The most downstream reforming cell 42 includes a first electrode 2a containing a reforming catalyst, a second electrode 4a, and a dense membrane 3a disposed between the first electrode 2a and the second electrode 4a. The control unit 60 changes the H2O supply amount according to the electromotive voltage of the most downstream reforming cell 42 detected by the voltage detector 50. This makes it possible to maintain the CH4 production efficiency in the reformer 40 within a desired appropriate range.

[0095] (3) The reforming cell 40 has the same configuration as the co-electrolysis cell 32. This eliminates the need to separately manufacture the co-electrolysis cell 32 and the reforming cell 40, thereby reducing manufacturing costs.

[0096] (Modification of the embodiment) Although the embodiments of the present invention have been described above, the present invention is not limited to these, and various modifications are possible without departing from the spirit of the present invention.

[0097] [Variation 1] In the above embodiment, the co-electrolysis cell 32 is a horizontal stripe type SOEC, but is not limited thereto. The co-electrolysis cell 32 may be a vertical stripe type (hollow flat plate type), flat plate type, cylindrical type, or other SOEC. The configuration of the vertical stripe type SOEC is described, for example, in JP 2015-125897 A. The configuration of the flat plate type SOEC is described, for example, in JP 2020-177839 A. The configuration of the cylindrical SOEC is described, for example, in JP 2008-270203 A. However, the horizontal stripe type SOEC is particularly preferred because it has a higher H2O utilization efficiency than other SOFCs.

[0098] [Variation 2] In the above embodiment, the element section 38 has the hydrogen electrode 2, the electrolyte 3, the oxygen electrode 4, the reaction prevention film 5 and the interconnector 6, but it is sufficient that the element section 38 has at least the hydrogen electrode 2, the electrolyte 3 and the oxygen electrode 4.

[0099] [Variation 3] In the above embodiment, the reforming cell 42 has the same configuration as the co-electrolytic cell 32, but may have a different configuration from the co-electrolytic cell 32.

[0100] [Variation 4] In the above embodiment, the voltage detector 50 detects the electromotive voltage of the most downstream reforming cell 42, but it may also detect the electromotive voltage of a reforming cell 42 other than the most downstream reforming cell 42, or it may detect the average electromotive voltage of multiple reforming cells 42.

[0101] [Variation 5] In the above embodiment, the control unit 60 changes the H2O supply amount according to the electromotive voltage of the most downstream reforming cell 42 detected by the voltage detector 50, but the H2O supply amount may be fixed to a constant value. In this case, the reforming cell 42 does not need to have the first and second electrodes 2a, 4a, but only needs to have a reforming catalyst that contacts H2 and CO. The reforming catalyst may be disposed inside the dense membrane 3a.

[0102] [Variation 6] In the above embodiment, all of the exhaust gas from the reformer 40 (CH4 and H2O generated in each reforming cell 42) is discharged from the third pipe L3 to the outside of the methane production system 1, but this is not limited to the above.

[0103] For example, as shown in Fig. 10, the methane production system 1 may further include a reflux unit 70 that refluxes a portion of the exhaust gas from the reformer 40 to the co-electrolysis device 30. The reflux unit 70 is a pipe that communicates with the first pipe L1 and the third pipe L3. By refluxing a portion of the exhaust gas from the reformer 40 to the co-electrolysis device 30 in this manner, a portion of CO or H2 contained in the exhaust gas can be supplied to the hydrogen electrode 2 of the co-electrolysis device 30, and thus the vaporization of water at the hydrogen electrode 2 can be promoted, thereby increasing the electrolysis efficiency. Furthermore, when Ni is contained in the hydrogen electrode active portion 22 of the hydrogen electrode 2 of the co-electrolysis device 30, the oxidation of Ni due to the reduction action of CO or H2 can be suppressed.

[0104] The amount of exhaust gas recirculated can be easily controlled by adjusting the inner diameter of the pipe that constitutes the recirculation section 70. [Explanation of symbols]

[0105] 1. Methane production system 10 CO2 supply device 20 H2O supply device 30 Co-electrolyzer 31 Manifold 32 Co-electrolysis cell 38 Element section 2 Hydrogen electrode 3 Electrolytes 4 Oxygen electrode 40 Reformer 41 Manifold 42 Reforming Cell 48 Modification element section 2a 1st electrode 3a Dense membrane 4a 2nd electrode 50 Voltage detector 60 Control section 70 Reflux section L1 First pipe L2 Second piping L3 3rd piping

Claims

1. A co-electrolysis device; a reformer connected to the co-electrolysis device; The co-electrolysis device is charged with H ２ H supplying O ２ An O supply device; The H ２ H from the O supply to the co-electrolysis device ２ A control unit for controlling an amount of O supplied; A voltage detector; Equipped with The co-electrolysis device is ２ and H ２ O to H ２ , CO and O ２－ a first electrode generating O ２－ an electrolyte capable of conducting oxygen; and O transmitted from the first electrode through the electrolyte. ２－ From O ２ and a second electrode that produces The reformer is configured to convert the H generated at the first electrode into ２ and CO to CH ４ a reforming cell for producing The reforming cell is configured to convert the H generated at the first electrode into ２ and CO to CH ４ a first electrode containing a reforming catalyst that produces a catalytic reaction of 100% by mass spectrometry; a second electrode; and a dense membrane disposed between the first electrode and the second electrode; The voltage detector detects an electromotive voltage of the reforming cell, The control unit controls the H ２ Change the O supply amount. Methane production system.

2. The reforming cell has the same configuration as the co-electrolysis cell; The methane production system according to claim 1 .

3. the operating temperature of the reforming cell is lower than the operating temperature of the co-electrolysis cell; The methane production system according to claim 1 or 2.

4. Further, a reflux unit is provided for refluxing a portion of the exhaust gas from the reformer to the co-electrolysis device. The methane production system according to any one of claims 1 to 3.

5. A co-electrolysis device; a reformer connected to the co-electrolysis device; A reflux section; a H2O supply device; A control unit; A voltage detector; Equipped with The co-electrolysis device is ２ and H ２ O to H ２ , CO and O ２－ a first electrode generating O ２－ an electrolyte capable of conducting oxygen; and O transmitted from the first electrode through the electrolyte. ２－ From O ２ and a second electrode that produces The reformer is configured to convert the H generated at the first electrode into ２ and CO to CH ４ a reforming cell for producing The first electrode contains Ni, The reflux section is configured to reflux CO or H contained in the exhaust gas from the reformer. ２ A portion of the above is returned to the co-electrolysis device, The reforming cell includes a first electrode containing a reforming catalyst for producing CH 4 from H 2 and CO produced at the first electrode, a second electrode, and a dense membrane disposed between the first electrode and the second electrode; the H2O supplying device supplies H2O to the co-electrolysis device; The voltage detector detects an electromotive voltage of the reforming cell, The control unit changes the amount of H 2 O supplied from the H 2 O supply device to the co-electrolysis device in response to the electromotive voltage of the reforming cell detected by the voltage detector. Methane production system.

6. The reforming cell has the same configuration as the co-electrolysis cell; The methane production system according to claim 5 .

7. the operating temperature of the reforming cell is lower than the operating temperature of the co-electrolysis cell; The methane production system according to claim 5 or 6.

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