Electrolysis system

Abstract

To provide an electrolysis system in which the ratio of a carbon monoxide gas to a hydrogen gas in a syngas can be improved.SOLUTION: An electrolysis system generates a second mixed gas including carbon monoxide and hydrogen from a first mixed gas including a first steam and a first carbon dioxide gas. The electrolysis system comprises: an electrolysis unit including an electrolysis cell that generates a first carbon monoxide gas and a first hydrogen gas by performing a co-electrolytic reaction using at least part of the first steam and part of the first carbon dioxide gas; and a reverse shift reaction unit including a catalyst for accelerating a reverse shift reaction, in which a second carbon monoxide gas and a second steam are generated from part of the first hydrogen gas and other part of or the remainder of the first carbon dioxide gas. The second mixed gas includes the first carbon monoxide gas, the second carbon monoxide gas, and other part of or the remainder of the first hydrogen gas.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] FIELD OF THE INVENTION An embodiment of the present invention relates to an electrolysis system. [Background technology]

[0002] Hydrogen is one of the new energy sources. One application of hydrogen is fuel cells, which convert chemical energy into electrical energy by electrochemically reacting hydrogen and oxygen. Fuel cells have high energy utilization efficiency, and development is underway for use as large-scale distributed power sources, home power sources, and mobile power sources.

[0003] Fuel cells are classified into solid polymer, phosphoric acid, molten carbonate, solid oxide, and other types depending on the temperature range and the type of material and fuel used. From the perspective of efficiency, solid oxide fuel cells (SOFCs), which generate electrical energy through an electrochemical reaction using an electrolyte made of solid oxide, are attracting attention. Hydrogen production involves the electrolysis of water, but research is underway into solid oxide electrolysis cells (SOECs), which electrolyze water in a vapor state at high temperatures. The operating principle of SOECs is the reverse reaction of the electrochemical reaction of SOFCs, and like SOFCs, SOECs use an electrolyte made of solid oxide.

[0004] Electrolytic cells such as SOECs have a laminated structure that includes at least an oxygen electrode, an electrolyte, and a fuel electrode. These components are formed using materials with different properties. The oxygen electrode and the fuel electrode are porous, and different gases are supplied to the oxygen electrode and the fuel electrode, with a dense electrolyte separating them. The oxygen electrode and the fuel electrode are electrical conductors, and the electrolyte is an ion conductor that does not conduct electricity. Electrolytic cells come in various shapes, such as flat, cylindrical, and cylindrical-flat. For example, a flat-plate electrolytic cell has a shape in which the oxygen electrode, electrolyte, fuel electrode, etc. are laminated in a flat plate shape.

[0005] A stack formed by integrating multiple electrolysis cells is generally called a cell stack. For example, in the case of flat-plate electrolysis cells, a cell stack is formed by stacking multiple flat-plate electrolysis cells, supplying different gases to the oxygen electrode and fuel electrode of each cell, and having a structure that allows the cells to be electrically connected in series. Cells are separated by separators, which separate the gases in each cell and, because the separators are conductive, also serve to provide electrical conductivity between the cells. In addition, gas supply and discharge channels for each cell are generally formed within the separators.

[0006] In recent years, co-electrolysis, which uses SOECs to simultaneously electrolyze carbon dioxide (CO2) in addition to water vapor, has attracted attention because of its potential for reducing carbon dioxide emissions and generating fuel. In co-electrolysis using SOECs, simultaneous electrolysis of carbon dioxide and water vapor makes it possible to highly efficiently generate a mixed gas (syngas) containing carbon monoxide (CO) and hydrogen (H2). Syngas is a useful gas that can be used as a raw material for various fuels, including methane. In co-electrolysis using SOECs, a mixed gas containing water vapor and carbon dioxide is supplied to the fuel electrode side of the SOEC, and hydrogen and carbon monoxide are produced at the fuel electrode by electrolysis using the water vapor and carbon dioxide, while oxygen is produced at the oxygen electrode.

[0007] One of the challenges of syngas production by co-electrolysis is that carbon dioxide gas is more stable than water vapor, making it more difficult to electrolyze than water vapor when electrolyzing water vapor and carbon dioxide gas. The difficulty of electrolyzing carbon dioxide gas increases the energy required for electrolysis, making it difficult to improve electrolysis efficiency. Another drawback is that the difficulty of electrolyzing carbon dioxide gas makes it difficult to increase the ratio of carbon monoxide gas to hydrogen gas in syngas. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Patent No. 6818132 Summary of the Invention [Problem to be solved by the invention]

[0009] The problem to be solved by the present invention is to provide an electrolysis system capable of increasing the ratio of carbon monoxide gas to hydrogen gas in syngas. [Means for solving the problem]

[0010] An electrolysis system according to an embodiment produces a second mixed gas containing carbon monoxide and hydrogen from a first mixed gas containing first water vapor and first carbon dioxide gas. The electrolysis system includes an electrolysis unit having an electrolysis cell that produces the first carbon monoxide gas and the first hydrogen gas by a co-electrolysis reaction using at least a portion of the first water vapor and a portion of the first carbon dioxide gas, and a reverse shift reaction unit having a catalyst that promotes a reverse shift reaction that produces a second carbon monoxide gas and second water vapor from a portion of the first hydrogen gas and another portion or the remainder of the first carbon dioxide gas. The second mixed gas contains the first carbon monoxide gas, the second carbon monoxide gas, and another portion or the remainder of the first hydrogen gas. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a schematic diagram illustrating an example of a reaction mechanism of an electrolysis system. [Figure 2] FIG. 1 is a schematic diagram showing a first configuration example of an electrolysis system. [Figure 3] 2 is a schematic diagram showing an example of the configuration of a gas supply unit 10. FIG. [Figure 4] 10 is a schematic diagram showing another example of the configuration of the gas supply unit 10. FIG. [Figure 5] 2 is a cross-sectional view showing a configuration example of an electrolysis unit 20. FIG. [Figure 6] 2 is a cross-sectional view showing a structural example of a separator 22. FIG. [Figure 7] 2 is a cross-sectional view showing a structural example of a separator 22. FIG. [Figure 8] FIG. 10 is a schematic diagram showing a fourth configuration example of the electrolysis system. [Figure 9] 2 is a cross-sectional view showing a first example of the configuration of the reverse shift reaction section 30. FIG. [Figure 10] 10 is a cross-sectional view showing a second example of the configuration of the reverse shift reaction section 30. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, embodiments will be described with reference to the drawings. In each embodiment shown below, substantially identical components are denoted by the same reference numerals, and some of their descriptions may be omitted. The drawings are schematic, and the relationship between thickness and planar dimensions, the thickness ratio of each part, etc. may differ from the actual ones.

[0013] In this specification, unless otherwise specified, "connect" may include not only direct connection but also indirect connection.

[0014] 1 is a schematic diagram showing an example of the reaction mechanism of the electrolysis system of the embodiment. As shown in FIG. 1, the electrolysis system of the embodiment can generate syngas by carrying out an electrolysis reaction and a reverse shift reaction.

[0015] Examples of electrolysis reactions include co-electrolysis reactions, which can produce carbon monoxide and hydrogen from water vapor and carbon dioxide. The electrolysis reaction of water vapor can be represented, for example, by reaction formula (1). The electrolysis reaction of carbon dioxide can be represented, for example, by reaction formula (2). H2O + 2e - → H2+ O 2- ···(1) CO2+ 2e - → CO + O 2- ···(2)

[0016] Carbon monoxide and water vapor can be produced from carbon dioxide and hydrogen through the reverse shift reaction. This reaction can be represented, for example, by reaction formula (3). CO2 + H2 → CO + H2O (3)

[0017] The electrolysis system of the embodiment can generate carbon monoxide not only through the co-electrolysis reaction but also through the reverse shift reaction. Furthermore, by effectively promoting the generation of carbon monoxide through the reverse shift reaction, the amount of carbon monoxide generated through the electrolysis reaction can be reduced, the energy required for the electrolysis reaction can be reduced, and the ratio of carbon monoxide to hydrogen gas in the syngas can be increased. The reverse shift reaction can be promoted, for example, by placing a catalyst for the reverse shift reaction (also referred to as a reverse shift reaction catalyst) in a position where it can come into contact with an atmosphere containing hydrogen and carbon dioxide generated by reaction formula (1).

[0018] The reverse shift reaction is more promoted in a higher temperature environment. Therefore, by carrying out the reverse shift reaction in a high temperature environment used in the co-electrolysis reaction, for example, the reverse shift reaction can be promoted effectively.

[0019] Furthermore, the electrolysis system of the embodiment can use hydrogen gas generated by the electrolysis reaction for the reverse shift reaction, thereby enabling the reverse shift reaction to be carried out effectively.

[0020] An example of the configuration of an electrolysis system according to an embodiment will be described below.

[0021] (First configuration example of electrolysis system) Fig. 2 is a schematic diagram showing a first configuration example of an electrolysis system. Fig. 2 shows an electrolysis system 1. The electrolysis system 1 has a gas supply unit 10, an electrolysis unit 20, and a reverse shift reaction unit 30.

[0022] The electrolysis system 1 can generate a product mixed gas from, for example, a supply mixed gas. The supply mixed gas contains water vapor, carbon dioxide gas, and hydrogen gas. The supply mixed gas does not necessarily contain hydrogen gas. The product mixed gas contains at least carbon monoxide and hydrogen. The product mixed gas may contain unreacted water vapor and unreacted carbon dioxide gas.

[0023] The gas supply unit 10 has a function of supplying a supply mixed gas. The gas supply unit 10 is provided upstream of the electrolysis unit 20 and is connected to a pipe P1.

[0024] The supply mixed gas contains, for example, X% water vapor, Y% carbon dioxide gas, and Z% hydrogen gas. X, Y, and Z are numbers representing the respective ratios of water vapor, carbon dioxide gas, and hydrogen gas when the entire supply mixed gas is taken as 100%. That is, the composition of the supply mixed gas is expressed as water vapor:carbon dioxide gas:hydrogen gas = X%:Y%:Z%. X, Y, and Z are each any number equal to or greater than 0. X% is, for example, 10% to 80%. Y% is, for example, 10% to 80%. Z% is, for example, 5% to 20%. The sum of X%, Y%, and Z% is 100%. The values ​​of X, Y, and Z can be adjusted appropriately, for example, by changing the mixing ratio of water vapor, carbon dioxide gas, and hydrogen gas using the gas supply unit 10.

[0025] 3 is a schematic diagram showing an example of the configuration of the gas supply unit 10. The gas supply unit 10 includes, for example, a water vapor supply source 101, a carbon dioxide gas supply source 102, and a hydrogen gas supply source 103.

[0026] The water vapor supply source 101 has a function of supplying water vapor. The water vapor supply source 101 includes, for example, a tank for storing water (liquid), a mass flow controller for adjusting the flow rate of water supplied from the tank, and a heater for generating water vapor by heating water having a controlled flow rate. The water vapor generated by the heater flows through a pipe PA. The mass flow controller may be controlled by a controller (not shown).

[0027] The carbon dioxide gas supply source 102 has a function of supplying carbon dioxide gas. The carbon dioxide gas supply source 102 includes, for example, a cylinder cabinet that stores carbon dioxide and a mass flow controller that adjusts the flow rate of the carbon dioxide gas that flows through a pipe PB connected to the cylinder cabinet. The mass flow controller may be controlled by a controller (not shown).

[0028] The hydrogen gas supply source 103 has a function of supplying hydrogen gas. The hydrogen gas supply source 103 includes, for example, a cylinder cabinet that supplies hydrogen gas and a mass flow controller that adjusts the flow rate of the hydrogen gas that flows through a pipe PC connected to the cylinder cabinet. The mass flow controller may be controlled by a controller (not shown).

[0029] The pipes PA, PB, and PC are connected to one another at a connection point NA and to a pipe P1. The gas supply unit 10 mixes water vapor from the pipe PA, carbon dioxide gas from the pipe PB, and hydrogen gas from the pipe PC at the connection point NA to generate a supply mixed gas, and supplies the supply mixed gas to the electrolysis unit 20 via the pipe P1.

[0030] The configuration example of the gas supply unit 10 is not limited to the configuration example shown in FIG. 3. FIG. 4 is a schematic diagram showing another configuration example of the gas supply unit 10. The gas supply unit 10 shown in FIG. 4 mixes carbon dioxide gas flowing through a pipe PB from a carbon dioxide gas supply source 102 and hydrogen gas flowing through a pipe PC from a hydrogen gas supply source 103 at a connection point NB. The gas supply unit 10 also generates a supply mixed gas by heating water in a tank in a water vapor supply source 101 using a heater and humidifying the mixed gas by passing a mixed gas of carbon dioxide gas and hydrogen gas through the generated water vapor. The degree of humidification can be controlled by the temperature of the water. The supply mixed gas is supplied to the electrolysis unit 20 via a pipe P1 connected to a pipe PA. The description of the gas supply unit 10 shown in FIG. 3 can be used as appropriate for other explanations of the gas supply unit 10.

[0031] The electrolysis unit 20 has a function of performing a co-electrolysis reaction using water vapor and carbon dioxide gas. The electrolysis unit 20 is connected to a pipe P1. The pipe P1 can connect, for example, the gas supply unit 10 and the electrolysis unit 20. A supply mixed gas can flow through the pipe P1. The supply mixed gas is supplied to the electrolysis unit 20 from, for example, the gas supply unit 10 via the pipe P1. Therefore, the electrolysis unit 20 can receive the supply mixed gas from, for example, the gas supply unit 10 via the pipe P1. A pump or a flow regulator for controlling the supply and flow rate of each gas may be provided along the pipe P1. The electrolysis unit 20 can generate carbon monoxide gas and hydrogen gas by performing a co-electrolysis reaction using at least a portion of the water vapor and a portion of the carbon dioxide gas in the supply mixed gas.

[0032] The electrolysis unit 20 is connected to a pipe P2. The pipe P2 can connect the electrolysis unit 20 to a downstream device of the electrolysis unit 20, for example. Examples of the downstream device include a gas-liquid separator and a carbon dioxide separator. The gas-liquid separator can remove water vapor from the resulting mixed gas, for example. The carbon dioxide separator can produce a mixed gas of carbon monoxide gas and hydrogen gas by removing carbon dioxide from the resulting mixed gas from which water vapor has been removed. The pipe P2 does not necessarily have to be connected to the downstream device. The resulting mixed gas can flow through the pipe P2. The resulting mixed gas is, for example, discharged from the electrolysis unit 20 via the pipe P2. Therefore, the electrolysis unit 20 can discharge the resulting mixed gas or supply it to a downstream device via the pipe P2, for example. A pump or flow regulator for controlling the supply and flow rate of each gas may be provided along the pipe P2.

[0033] Fig. 5 is a cross-sectional schematic diagram showing an example configuration of the electrolysis unit 20. The electrolysis unit 20 has an electrolysis cell 21. Fig. 5 also shows an X-axis, a Y-axis, and a Z-axis, which are perpendicular to one another. The Z-axis includes, for example, the thickness direction of the electrolysis cell 21.

[0034] Examples of the electrolysis cell 21 include solid oxide electrolysis cells (SOECs). FIG. 5 shows an example in which the electrolysis cell 21 is a planar electrolysis cell and an anode-supported cell. The electrolysis cell 21 is preferably operated at high temperatures, and the electrolysis reaction in the electrolysis unit 20 is preferably carried out at a temperature of, for example, 600°C or higher and 1000°C or lower. FIG. 5 shows an example in which the electrolysis unit 20 has a cell stack CS formed by stacking three electrolysis cells 21 in the Z-axis direction, but the number of electrolysis cells 21 is not limited to the number shown in FIG. 5. Furthermore, while FIG. 5 shows a planar cell stack as the cell stack CS, it is not limited to a planar cell stack and may be, for example, a cylindrical cell stack.

[0035] The electrolysis cell 21 includes an oxygen electrode 201, an anode 202, a solid electrolyte 203, an anode support 204, an oxygen electrode current collector 205, and an anode current collector 206. These members may be stacked to form a laminate.

[0036] The oxygen electrode 201 is provided, for example, in a position where it can come into contact with air. Air flows through the space provided in the oxygen electrode 201. The oxygen electrode 201 is, for example, a porous electrical conductor. Examples of porous electrical conductors include perovskite oxides.

[0037] The anode 202 is disposed in a position where it can come into contact with, for example, water vapor, carbon dioxide gas, carbon monoxide gas, and hydrogen gas. A supply mixed gas flows through the space provided in the anode 202. The anode 202 is, for example, a porous electrical conductor. Examples of porous electrical conductors include mixed sintered bodies (cermets) of metals and solid oxides. Examples of mixed sintered bodies include yttria-stabilized zirconia and scandia-stabilized zirconia.

[0038] The solid electrolyte 203 is disposed between the oxygen electrode 201 and the anode 202 to separate them. The solid electrolyte 203 is, for example, in contact with the oxygen electrode 201 and the anode 202. The solid electrolyte 203 is, for example, an ion conductor that does not conduct electricity. Examples of ion conductors include solid oxides. Examples of solid oxides include molded bodies of stabilized zirconia, perovskite-type oxides, and ceria-based solid solutions. Because the solid electrolyte 203 is a dense electrolyte, it can separate the atmosphere in which the oxygen electrode 201 is disposed from the atmosphere in which the anode 202 is disposed.

[0039] The anode support 204 supports the anode 202. The anode support 204 may be electrically connected to the anode 202. The anode support 204 may be disposed, for example, below the anode 202. The anode support 204 may be disposed, for example, between the anode 202 and the anode current collector 206. The anode support 204 may be in contact with at least one of the anode 202 and the anode current collector 206. The anode support 204 may be, for example, a porous member made of a material such as a metal material or a ceramic material.

[0040] The oxygen electrode current collector 205 is provided to electrically connect the oxygen electrode 201 and the separator 22. The oxygen electrode current collector 205 is provided on the side of the oxygen electrode 201 opposite the solid electrolyte 203. The oxygen electrode current collector 205 can be electrically connected to the oxygen electrode 201. The oxygen electrode current collector 205 may be in contact with the oxygen electrode 201, for example.

[0041] The anode current collector 206 is provided to electrically connect the anode 202 and the separator 22. The anode current collector 206 is provided on the side of the anode 202 opposite the solid electrolyte 203. The anode current collector 206 can be electrically connected to the anode 202. The anode current collector 206 may be in contact with the anode 202, for example.

[0042] The oxygen electrode current collector 205 and the anode current collector 206 preferably have cushioning properties to enable electrical connection between the electrolysis cell 21 and the separator 22, and are preferably porous to allow the flow of air and the feed mixed gas. The oxygen electrode current collector 205 is preferably formed using a platinum or silver mesh material, for example. The anode current collector 206 is preferably formed using a nickel mesh material, for example.

[0043] In the region of the electrolysis unit 20 where no electrolysis cells 21 are disposed, it is preferable to provide some kind of dense member to separate the atmosphere in which the oxygen electrode 201 is disposed from the atmosphere in which the fuel electrode 202 is disposed. In contrast, the electrolysis unit 20 further includes a separator 22. Because the separator 22 is dense, it can, for example, separate one of the multiple electrolysis cells 21 from another of the multiple electrolysis cells 21, thereby isolating the atmospheres of adjacent electrolysis cells 21. The separator 22 is disposed between one of the multiple electrolysis cells 21 and another of the multiple electrolysis cells 21. While FIG. 5 shows multiple separators 22 disposed in the cell stack CS, the number of separators 22 is not limited to the number shown in FIG. 5.

[0044] The separator 22 includes a separator component 207 and a separator component 208. The separator component 207 and the separator component 208 are bonded together via a sealant 209 therebetween. The sealant 209 can suppress gas leakage. The sealant 209 is formed using, for example, a cured glass paste, a glass sheet, or a compressive seal.

[0045] The separator component 207 is disposed between the oxygen electrode current collector 205 of one of the plurality of electrolysis cells 21 and the anode current collector 206 of another of the plurality of electrolysis cells 21. The separator component 207 extends, for example, along a plane including the X-axis and the Y-axis.

[0046] The separator component 208 is disposed, for example, so as to surround the electrolysis cell 21 .

[0047] Examples of separator constituent material 207 and separator constituent material 208 include metal materials such as stainless steel containing metal elements such as chromium.

[0048] The electrolysis unit 20 further includes a partition plate 210 , a seal material 211 , a seal material 212 , a seal material 213 , a support plate 214 , and a penetrator 215 .

[0049] The partition plate 210 is provided to surround the oxygen electrode 201. The partition plate 210 is disposed between a separator component 207 of one of the plurality of separators 22 and a separator component 208 of another of the plurality of separators 22. The partition plate 210 can separate the atmosphere of the oxygen electrode 201 from the atmosphere of the fuel electrode 202 of one electrolysis cell 21. Although FIG. 5 shows a plurality of partition plates 210 provided in the cell stack CS, the number of partition plates 210 is not limited to the number shown in FIG. 5.

[0050] The separator 210 is disposed on the solid electrolyte 203 and separates the oxygen electrode 201 from the fuel electrode 202. The separator 210 is bonded to the separator component 208 or the solid electrolyte 203 via a sealant 211. Examples of the separator 210 include metal materials such as stainless steel. The sealant 211 is disposed between one of the separators 210 and one of the separator components 208 of the separators 22. The sealant 211 provides insulation by forming a certain thickness or more between the separators 22, thereby preventing electrical shorts between the separators 22 during electrolysis and creating a space for gas to flow to the oxygen electrode 201. The sealant 211 is formed using, for example, a compressive seal.

[0051] The partition plate 210 is bonded to the separator 22 via a sealant 212. The sealant 212 is disposed between the partition plate 210 and the separator 22.

[0052] The partition plate 210 is bonded to the electrolysis cell 21 via a sealant 213. A sealant 212 is disposed between the partition plate 210 and the electrolysis cell 21.

[0053] The sealing materials 212 and 213 can suppress gas leakage. The sealing materials 212 and 213 are formed using, for example, a hardened glass paste, a glass sheet, or a compressive seal.

[0054] The support plates 214 can support the cell stack CS. Fig. 5 shows a pair of support plates 214. The pair of support plates 214 are arranged to sandwich the cell stack CS and are fixed by penetrators 215. The penetrators 215 may penetrate the pair of support plates 214. Examples of the support plates 214 include metal materials such as stainless steel. Examples of the penetrators 215 include bolts.

[0055] Gas flow paths are provided around the periphery of the electrolytic cell 21. These gas flow paths serve as a supply flow path for the feed mixed gas and a discharge flow path for the produced mixed gas. These gas flow paths are provided, for example, in the separator 22 and connected, for example, to the pipe P1 and the pipe P2.

[0056] The cell stack CS can generate a mixed gas (syngas) containing carbon monoxide gas and hydrogen gas, for example, by carrying out a co-electrolytic reaction of water vapor and carbon dioxide gas at the anode 202.

[0057] The reverse shift reactor 30 can perform a reverse shift reaction to produce carbon monoxide gas and water vapor from a portion of the hydrogen gas produced by the co-electrolysis reaction and a portion or remainder of the carbon dioxide gas in the feed mixture. The reverse shift reactor 30 has a reverse shift catalyst that promotes the reverse shift reaction. When the feed mixture contains hydrogen gas, the reverse shift catalyst can promote the reverse shift reaction to produce carbon monoxide gas and water vapor from a portion of the hydrogen gas produced by the reverse shift reaction, at least a portion of the second hydrogen gas contained in the feed mixture, and another portion or remainder of the carbon dioxide gas contained in the feed mixture. The product mixture produced through the electrolysis unit 20 and the reverse shift reactor 30 contains carbon monoxide gas produced by the co-electrolysis reaction, carbon monoxide gas produced by the reverse shift reaction, and another portion or remainder of the hydrogen gas produced by the co-electrolysis reaction. When the feed mixture contains hydrogen gas, the product mixture may further contain hydrogen gas contained in the feed mixture.

[0058] The reverse shift reaction catalyst is disposed, for example, in a space to which the feed gas mixture is supplied. The reverse shift reaction catalyst contains at least one element selected from platinum (Pt), ruthenium (Ru), cerium (Ce), lanthanum (La), cobalt (Co), nickel (Ni), aluminum (Al), and copper (Cu). The reverse shift reaction catalyst may be formed from a metal material containing at least one of the above elements. The reverse shift reaction catalyst may be formed from an alloy material containing two or more elements selected from the above elements. An example of the alloy material is a Ni-Co alloy containing nickel and cobalt.

[0059] In a first configuration example of the electrolysis system, the reverse shift reaction unit 30 is formed by incorporating a reverse shift reaction catalyst into the anode current collector 206. The anode current collector 206 may be formed, for example, by supporting the reverse shift reaction catalyst on a current collecting substrate made of an alloy material such as SUS, or may be formed from a porous member made of the reverse shift reaction catalyst. The reverse shift reaction catalyst can be supported, for example, by forming a plating film of the reverse shift reaction catalyst on the surface of the current collecting substrate, or by dispersing a powder of the reverse shift reaction catalyst on the surface of the current collecting substrate. The anode current collector 206 may have a porous structure and may be formed using a porous material such as a mesh material, expanded metal, or foam.

[0060] By configuring the anode current collector 206 using a reverse shift reaction catalyst, a co-electrolysis reaction can be performed in the electrolysis unit 20, and a reverse shift reaction can be performed to generate carbon monoxide gas and water vapor from hydrogen gas and carbon dioxide gas that come into contact with the anode current collector 206. This effectively promotes carbon monoxide production, reduces the amount of carbon monoxide produced by the electrolysis reaction, reduces the energy required for the electrolysis reaction, and increases the ratio of carbon monoxide to hydrogen gas in the syngas. Furthermore, because the anode current collector 206 is provided in the cell stack CS, the reverse shift reaction can be performed in a high-temperature environment of 600°C to 1000°C, which is the operating temperature of the cell stack CS. This effectively promotes the reverse shift reaction without the need for a separate heating mechanism. Furthermore, by making the anode current collector 206 porous, the contact area with carbon dioxide gas and hydrogen gas can be increased, effectively promoting the reverse shift reaction. Furthermore, the hydrogen gas produced by the co-electrolysis reaction in the electrolysis unit 20 can be used for the reverse shift reaction, thereby effectively promoting the reverse shift reaction.

[0061] (Second configuration example of electrolysis system) The second configuration example of the electrolysis system differs from the first configuration example of the electrolysis system in that the anode 202 or the anode support 204 contains a reverse shift reaction catalyst to form the reverse shift reaction unit 30. In the second configuration example, the anode current collector 206 does not need to contain a reverse shift reaction catalyst. The following describes the differences between the second configuration example and the first configuration example, and the description of the first configuration example can be used for other parts as appropriate.

[0062] The anode 202 or the anode support 204 may be formed, for example, by supporting a reverse shift reaction catalyst on the surface of a porous substrate, or may be formed from a porous member containing a reverse shift reaction catalyst. The reverse shift reaction catalyst can be supported by, for example, manufacturing the anode 202 or the anode support 204 by mixing a powder of the reverse shift reaction catalyst with a raw material powder of the anode 202 or the anode support 204. Furthermore, when the anode support 204 contains a reverse shift reaction catalyst, the anode 202 is preferably porous and allows water vapor, carbon dioxide gas, hydrogen gas, and carbon monoxide gas to pass through. Note that the anode 202 and the anode support 204 may each contain a reverse shift reaction catalyst to form the reverse shift reaction unit 30.

[0063] By configuring the anode 202 or the anode support 204 using a reverse shift reaction catalyst, a co-electrolysis reaction can be performed in the electrolysis unit 20, and a reverse shift reaction can be performed to generate carbon monoxide gas and water vapor from hydrogen gas and carbon dioxide gas that come into contact with the anode 202 or the anode support 204. This effectively promotes the generation of carbon monoxide, reduces the amount of carbon monoxide produced by the electrolysis reaction, reduces the energy required for the electrolysis reaction, and increases the ratio of carbon monoxide to hydrogen gas in syngas. Furthermore, because the anode 202 or the anode support 204 is provided in the cell stack CS, the reverse shift reaction can be performed in a high-temperature environment of 600°C to 1000°C, which is the operating temperature of the cell stack CS. This effectively promotes the reverse shift reaction without the need for a separate heating mechanism. Furthermore, by making the anode 202 or the anode support 204 porous, the contact area with carbon dioxide gas and hydrogen gas can be increased, effectively promoting the reverse shift reaction. Furthermore, since the hydrogen gas produced by the co-electrolysis reaction in the electrolysis section 20 can be used for the reverse shift reaction, the reverse shift reaction can be carried out effectively.

[0064] The second exemplary configuration of the electrolysis system can be combined with other exemplary configurations as appropriate. For example, by combining the first and second exemplary configurations of the electrolysis system, the reverse shift reaction unit 30 may be configured such that at least one of the anode 202 and the anode support 204, and the anode current collector 206 each contain a reverse shift reaction catalyst.

[0065] (Third configuration example of electrolysis system) The third configuration example of the electrolysis system differs from the first configuration example of the electrolysis system in that the separator 22 contains a reverse shift reaction catalyst to form the reverse shift reaction unit 30. In the third configuration example, the anode current collector 206 does not need to contain a reverse shift reaction catalyst. The following describes the differences between the third configuration example and the first configuration example, and the description of the first configuration example can be used as appropriate for the other parts.

[0066] 6 and 7 are cross-sectional schematic diagrams showing structural examples of the separator 22. Fig. 6 and Fig. 7 show part of the XZ cross section of the separator component 207.

[0067] The separator component 207 has a substrate 271 , a surface layer 272 , and a surface layer 273 or a surface layer 274 .

[0068] The substrate 271 has a first surface and a second surface. An example of the substrate 271 includes a plate of a material containing a metal element such as chromium.

[0069] The surface layer 272 is provided on the anode 202 side of the substrate 271. The surface layer 272 is provided in contact with a first surface of the substrate 271. The surface layer 272 contains a reverse shift reaction catalyst. The surface layer 272 can be formed, for example, by forming a plating film of the reverse shift reaction catalyst on the surface of the substrate 271.

[0070] The surface layer 273 is provided on the oxygen electrode 201 side of the substrate 271. The surface layer 273 is provided in contact with the second surface of the substrate 271. The surface layer 273 contains a reverse shift reaction catalyst. The surface layer 273 can be formed, for example, by forming a plating film of the reverse shift reaction catalyst on the surface of the substrate 271. The surface layer 273 may be formed from the same material as or a different material from the reverse shift reaction catalyst of the surface layer 272.

[0071] The surface layer 274 is provided on the cathode 201 side of the substrate 271 in place of the surface layer 273. The surface layer 274 contains cobalt oxide. When a cell stack CS using a separator 22 having a metal coating (e.g., cobalt) on both sides is operated, the cell stack CS is heated in a high-temperature environment of 600°C to 1000°C, and the cathode 201 side of the separator 22 is exposed to air, and the anode 202 side is exposed to a mixed gas of carbon dioxide gas, water vapor, and hydrogen gas. Since the anode 202 side of the separator 22 is in a reducing atmosphere, the surface layer 272 remains metallic, while the cathode 201 side is oxidized and converted to a metal oxide (e.g., cobalt oxide), forming the surface layer 274. The surface layer 273 contains a reverse shift reaction catalyst to promote the reverse shift reaction. On the other hand, since there is no carbon dioxide gas or hydrogen gas near the surface layer 274, a reverse shift reaction catalyst is not required, but the spinel oxide such as cobalt oxide formed as the surface layer 274 functions as a coating to prevent chromium poisoning. In other words, it can prevent poisoning of the oxygen electrode 201 caused by evaporation of chromium from the separator 22.

[0072] By configuring the separator 22 using a reverse shift reaction catalyst, a co-electrolysis reaction can be performed in the electrolysis unit 20, and a reverse shift reaction can be performed to generate carbon monoxide gas and water vapor from hydrogen gas and carbon dioxide gas that come into contact with the separator 22. This effectively promotes the generation of carbon monoxide, reduces the amount of carbon monoxide produced by the electrolysis reaction, reduces the energy required for the electrolysis reaction, and increases the ratio of carbon monoxide to hydrogen gas in the syngas. Furthermore, because the separator 22 is installed in the cell stack CS, the reverse shift reaction can be performed in a high-temperature environment of 600°C to 1000°C, which is the operating temperature of the cell stack CS, thereby effectively promoting the reverse shift reaction without the need for a separate heating mechanism. Furthermore, by making the separator 22 porous, the contact area with carbon dioxide gas and hydrogen gas can be increased, effectively promoting the reverse shift reaction. Furthermore, the hydrogen gas produced by the co-electrolysis reaction in the electrolysis unit 20 can be used for the reverse shift reaction, thereby effectively promoting the reverse shift reaction.

[0073] The third exemplary configuration of the electrolysis system can be appropriately combined with other exemplary configurations of the electrolysis system. For example, by combining the first to third exemplary configurations of the electrolysis system, the reverse shift reaction unit 30 may be configured in which at least one of the anode 202 and the anode support 204, the anode current collector 206, and at least one of the surface layer 273 and the surface layer 274 contain a reverse shift reaction catalyst.

[0074] (Fourth configuration example of electrolysis system) The fourth configuration example of the electrolysis system differs from the first configuration example at least in that a reverse shift reaction unit 30 is provided downstream of the electrolysis unit 20. In the fourth configuration example, the anode 202, the anode support 204, the anode current collector 206, and the separator 22 may not contain a reverse shift reaction catalyst. The following describes the differences between the fourth configuration example and the first configuration example, and the description of the first configuration example can be used as appropriate for the other parts.

[0075] Fig. 8 is a schematic diagram showing a fourth configuration example of an electrolysis system. Fig. 8 shows an electrolysis system 1. The electrolysis system 1 includes a gas supply unit 10, an electrolysis unit 20, a reverse shift reaction unit 30, and an electric furnace 40. The electrolysis system 1 shown in Fig. 8 differs from the electrolysis system 1 shown in Fig. 2 in that the electrolysis unit 20 and the reverse shift reaction unit 30 are provided in the electric furnace 40, and the reverse shift reaction unit 30 is provided downstream of the electrolysis unit 20. Here, only the parts that differ from the electrolysis system shown in Fig. 1 will be described, and for the other parts, the description of the electrolysis system shown in Fig. 1 can be used as appropriate.

[0076] The electric furnace 40 can control the temperatures of the electrolysis section 20 and the reverse shift reaction section 30. The electric furnace 40 can reduce the temperature difference between the electrolysis section 20 and the reverse shift reaction section 30. The electric furnace 40 may include a part of the pipe P2.

[0077] By using the electric furnace 40 as a common heating mechanism for the electrolysis unit 20 and the reverse shift reaction unit 30, the temperature difference between the electrolysis unit 20 and the reverse shift reaction unit 30 can be easily reduced, and the electrolysis system 1 can also be made more compact.

[0078] (First Configuration Example of Reverse Shift Reaction Unit 30) 9 is a cross-sectional schematic diagram showing a first configuration example of the reverse shift reaction section 30. The reverse shift reaction section 30 shown in FIG. 9 includes a tank 31, an inlet 32 ​​connected to the tank 31, an outlet 33 connected to the tank 31, and a reverse shift reaction catalyst 34 disposed inside the tank 31.

[0079] The tank 31 has a function of performing the reverse shift reaction. The tank 31 has a space S. The feed mixed gas is introduced into the space S from an inlet 32 ​​via a part of the pipe P2. The reverse shift reaction catalyst 34 is provided, for example, inside (e.g., on the inner surface) of the tank 31 that is in contact with the space S. The reverse shift reaction catalyst 34 may be provided in a layered form. In the reverse shift reaction unit 30, a reverse shift reaction of a mixed gas containing at least hydrogen gas and carbon dioxide gas from the electrolysis unit 20 introduced into the space S proceeds via the reverse shift reaction catalyst 34 to generate a product feed gas. The product feed gas passes through another part of the pipe P2 via the outlet 33 and is supplied to a device connected downstream of the electrolysis unit 20. For other descriptions of the reverse shift reaction catalyst 34, the description of the reverse shift reaction catalyst in the first configuration example can be used as appropriate.

[0080] The tank 31 may be connected to an electric furnace 40. The electric furnace 40 can control the temperature of the reverse shift reaction section 30, for example, by cooling and / or heating the tank 31 to control the external temperature of the tank 31. This can reduce the difference in temperature between the electrolysis section 20 and the reverse shift reaction section 30.

[0081] (Second Configuration Example of Reverse Shift Reaction Unit 30) FIG. 10 is a diagram showing a second configuration example of the reverse shift reaction unit 30. The reverse shift reaction unit 30 shown in FIG. 10 has a reverse shift reaction catalyst 34 provided in a layer on at least a part of the inside (e.g., the inner surface) of a pipe P2 having a space S. In the reverse shift reaction unit 30, a reverse shift reaction of a mixed gas containing at least hydrogen gas and carbon dioxide gas from the electrolysis unit 20 introduced into the space S proceeds with the reverse shift reaction catalyst 34 to generate a product supply gas. The product supply gas passes through another part of the pipe P2 and is supplied to a device connected downstream of the electrolysis unit 20. The description of the reverse shift reaction catalyst in the first configuration example can be used for other explanations of the reverse shift reaction catalyst 34, as appropriate.

[0082] The pipe P2 may be connected to an electric furnace 40. The electric furnace 40 can control the temperature of the reverse shift reaction section 30 by, for example, heating and / or cooling the pipe P2 to control the apparent temperature of the pipe P2. This can reduce the difference in temperature between the electrolysis section 20 and the reverse shift reaction section 30.

[0083] By providing the reverse shift reaction unit 30 downstream of the electrolysis unit 20 using a reverse shift reaction catalyst, a reverse shift reaction can be performed to produce carbon monoxide gas and water vapor from hydrogen gas and carbon dioxide gas from the electrolysis unit 20. This effectively promotes carbon monoxide production, reduces the amount of carbon monoxide produced by the electrolysis reaction, reduces the energy required for the electrolysis reaction, and increases the ratio of carbon monoxide to hydrogen gas in the syngas. Furthermore, because the reverse shift reaction unit 30 is provided inside the electric furnace 40 together with the electrolysis unit 20, the reverse shift reaction can be performed in a high-temperature environment of 600°C to 1000°C, which is the operating temperature of the cell stack CS. This effectively promotes the reverse shift reaction without the need for a separate heating mechanism. Furthermore, the hydrogen gas produced by the co-electrolysis reaction in the electrolysis unit 20 can be used for the reverse shift reaction, allowing the reverse shift reaction to be performed effectively.

[0084] The fourth exemplary configuration of the electrolysis system can be combined with other exemplary configurations of the electrolysis system as appropriate. For example, by combining the first to fourth exemplary configurations of the electrolysis system, at least one of the anode 202 and the anode support 204, the anode current collector 206, and at least one of the surface layer 273 and the surface layer 274 may contain a reverse shift reaction catalyst, and a reverse shift reaction catalyst 34 may be provided downstream of the electrolysis unit 20 as shown in Figure 9 or 10 to form a reverse shift reaction unit 30.

[0085] Although several embodiments of the present invention have been described above, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be embodied in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are included within the scope and spirit of the invention, and are also included in the scope of the invention and its equivalents as defined in the claims. [Explanation of symbols]

[0086] 1...electrolysis system, 10...gas supply section, 20...electrolysis section, 21...electrolysis cell, 22...separator, 30...reverse shift reaction section, 31...tank, 32...inlet, 33...outlet, 34...reverse shift reaction catalyst, 40...electric furnace, 101...water vapor supply source, 102...carbon dioxide gas supply source, 103...hydrogen gas supply source, 201...oxygen electrode, 202...fuel electrode, 203...solid electrolyte, 204...fuel electrode support, 205...oxygen electrode current collector, 206...fuel Electrode current collector, 207...separator component, 208...separator component, 209...sealing material, 210...partition plate, 211...sealing material, 212...sealing material, 213...sealing material, 214...support plate, 215...penetrating object, 271...substrate, 272...surface layer, 273...surface layer, 274...surface layer, CS...cell stack, NA...connection point, NB...connection point, P1...piping, P2...piping, PA...piping, PB...piping, PC...piping, S...space.

Claims

1. 1. An electrolysis system for producing a second mixed gas containing carbon monoxide and hydrogen from a first mixed gas containing first water vapor and first carbon dioxide gas, comprising: an electrolysis unit having an electrolysis cell that generates a first carbon monoxide gas and a first hydrogen gas by performing a co-electrolysis reaction using at least a portion of the first water vapor and a portion of the first carbon dioxide gas; a reverse shift reaction section having a catalyst that promotes a reverse shift reaction that produces a second carbon monoxide gas and a second water vapor from a portion of the first hydrogen gas and another portion or the remainder of the first carbon dioxide gas; Equipped with the second mixed gas contains the first carbon monoxide gas, the second carbon monoxide gas, and another part or remainder of the first hydrogen gas; Electrolysis system.

2. The electrolysis cell includes a fuel electrode, an oxygen electrode, and a solid electrolyte between the fuel electrode and the oxygen electrode. The electrolysis system of claim 1 .

3. The electrolysis system according to claim 2 , wherein the anode includes the catalyst.

4. The electrolysis cell comprises: an anode current collector disposed on the anode opposite the solid electrolyte; an oxygen electrode current collector provided on the opposite side of the oxygen electrode from the solid electrolyte; and the anode is porous, the anode current collector contains the catalyst, The electrolysis system according to claim 2 .

5. The electrolysis cell comprises: The fuel electrode further includes an anode support for supporting the anode, the anode is porous, The anode support includes the catalyst. The electrolysis system according to claim 2 .

6. The electrolysis unit includes: a plurality of said electrolysis cells; a separator separating one of the plurality of electrolytic cells from another of the plurality of electrolytic cells; and the separator has a first surface facing the fuel electrode of one of the plurality of electrolytic cells and a second surface facing the oxygen electrode of another of the plurality of electrolytic cells; At least one surface selected from the group consisting of the first surface and the second surface comprises the catalyst; The electrolysis system according to claim 2 .

7. The catalyst contains at least one element selected from the group consisting of platinum, ruthenium, cerium, lanthanum, cobalt, nickel, aluminum, and copper.

7. The electrolysis system according to claim 1.

8. The catalyst comprises nickel and cobalt.

7. The electrolysis system according to claim 1.

9. the first mixed gas further contains a second hydrogen gas; the catalyst promotes a reverse shift reaction of producing the second carbon monoxide gas and the second water vapor from a portion of the first hydrogen gas, at least a portion of the second hydrogen gas, and another portion or the remainder of the first carbon dioxide gas; The electrolysis system of claim 1 .

10. The electrolysis unit further includes a gas supply unit that generates the first mixed gas and is provided upstream of the electrolysis unit. The electrolysis system of claim 1 .

11. Further, a pipe is provided to connect the electrolysis unit with a device provided downstream of the electrolysis unit, The reverse shift reaction unit is provided in the middle of the piping and has the catalyst provided inside the piping. The electrolysis system of claim 1 .

12. The reverse shift reaction section is a tank provided downstream of the electrolysis unit; The catalyst provided in the tank; having The electrolysis system of claim 1 .

13. The reverse shift reaction is carried out at a temperature of 600°C or higher and 1000°C or lower.

12. The electrolysis system according to any one of claims 1 to 6 and claims 9 to 11.

14. An electric furnace including the reverse shift reaction section and the electrolysis section is provided.

12. The electrolysis system according to any one of claims 1 to 6 and claims 9 to 11.

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