WO2023233499A1

WO2023233499A1 - Methane production system

Info

Publication number: WO2023233499A1
Application number: PCT/JP2022/022036
Authority: WO
Inventors: 洋次尾中; 誠谷島; 俊雄篠木; 誠川本; 誠治中島
Original assignee: 三菱電機株式会社
Priority date: 2022-05-31
Filing date: 2022-05-31
Publication date: 2023-12-07
Also published as: JPWO2023233499A1

Abstract

A methane production system according to the present disclosure is provided with: a supply pathway for supplying carbon dioxide and water; an electrolytic apparatus for obtaining carbon monoxide and hydrogen from the carbon dioxide and the water through electrolysis; a methane reactor for obtaining a product gas containing methane from a gas mixture containing the carbon monoxide and the hydrogen; a first separator for separating, from a returned fluid that is one portion of the product gas, a first separated fluid containing water and a second separated fluid containing hydrogen; and a first circulation pathway. The first circulation pathway includes a first return path for guiding the first separated fluid to the electrolytic apparatus, and a second return path for guiding the second separated fluid to the methane reactor.

Description

Methane generation system

The present disclosure relates to methane production systems.

Patent Document 1 discloses an apparatus for producing methane using carbon dioxide and water. This device reduces water and carbon dioxide to obtain synthesis gas containing hydrogen and carbon monoxide. This device produces methane from synthesis gas.

JP2022-22978A

With the above technology, there was a possibility that the methane production efficiency would be low.

In view of the above circumstances, the present disclosure aims to provide a methane generation system that can increase methane generation efficiency.

One aspect of the methane generation system according to the present disclosure includes a supply path for supplying carbon dioxide and water, an electrolysis device for obtaining carbon monoxide and hydrogen from the carbon dioxide and the water by electrolysis, and a supply path for supplying carbon monoxide and water. a methane reactor for obtaining a product gas containing methane from the mixed gas containing hydrogen; and a first separation fluid containing water and a second separation fluid containing hydrogen from a return fluid that is a part of the product gas. a first circulation path having a first separator for separating, a first return path that leads the first separated fluid to the electrolyzer, and a second return path that leads the second separated fluid to the methane reactor; , is provided.

According to the present disclosure, it is possible to provide a methane production system that can increase methane production efficiency.

1 is a schematic diagram of a methane generation system according to Embodiment 1. FIG. FIG. 2 is a schematic diagram of a methane generation system according to a second embodiment. FIG. 3 is a schematic diagram of a methane generation system according to Embodiment 3. FIG. 3 is a schematic diagram of a methane generation system according to a fourth embodiment. FIG. 3 is a schematic diagram of a methane generation system according to a fifth embodiment. FIG. 3 is a schematic diagram of a methane generation system according to a sixth embodiment. FIG. 7 is a schematic diagram of a methane generation system according to Embodiment 7. It is a schematic diagram of the methane production system concerning Embodiment 8.

Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. Note that the scope of the present disclosure is not limited to the following embodiments, and can be arbitrarily modified within the scope of the technical idea of the present disclosure.

Embodiment 1.
FIG. 1 is a schematic diagram showing a methane generation system in Embodiment 1.
As shown in FIG. 1, the methane generation system 1 includes a supply route 10, a co-electrolyzer 20, a methane reactor 30, a first separator 40, and a first circulation route 50.

The supply path 10 guides carbon dioxide and water supplied from a supply source (not shown) to the co-electrolysis device 20. The supply path 10 leads, for example, a mixed fluid of carbon dioxide and water to the co-electrolyzer 20 . The supply route 10 may include a first supply route for introducing carbon dioxide and a second supply route for introducing water. The supply path 10 may be provided with an evaporator (steam generator) that vaporizes water.

The co-electrolyzer 20 includes, for example, a solid oxide electrolytic cell having a cathode electrode and an anode electrode. For example, a solid oxide having oxygen ion conductivity is used in the solid oxide electrolytic cell. As the electrolyte, zirconia-based oxide or the like is used. The co-electrolyzer 20 is an example of an electrolyzer.

The co-electrolyzer 20 supplies carbon dioxide and water supplied from the supply path 10 to the cathode electrode of the solid oxide electrolytic cell. The water used for co-electrolysis in the solid oxide electrolytic cell is desirably water vapor.

The co-electrolyzer 20 may include a heating device that heats the solid oxide electrolytic cell. The heating device can adjust the temperature within the solid oxide electrolytic cell to a temperature suitable for the co-electrolytic reaction.
The ratio of carbon dioxide and water supplied to the solid oxide electrolysis cell can be determined depending on the ratio of the components (carbon monoxide, hydrogen) of the target mixed gas.

The co-electrolyzer 20 obtains a mixed gas containing carbon monoxide (CO) and hydrogen (H ₂ ) from carbon dioxide (CO ₂ ) and water (H ₂ O) by co-electrolysis. Co-electrolysis proceeds, for example, according to formula (I) shown below. This reaction is endothermic.
_CO2 + _H2O →CO+ _H2 + _O2 ...(I)

In the co-electrolysis device 20, for example, co-electrolysis can be performed using electric power generated using renewable energy (for example, solar power generation, wind power generation, etc.). Methane obtained using renewable energy can be considered a carbon-neutral fuel that does not contribute to global warming, as no additional carbon dioxide is generated when it is combusted.

In this embodiment, a co-electrolyzer 20 that obtains carbon monoxide and hydrogen from carbon dioxide and water by co-electrolysis is used, but the device for obtaining carbon monoxide and hydrogen (H ₂ ) is limited to the co-electrolyzer. do not have. For example, it is also possible to use an electrolyzer that performs independently the step of electrolyzing carbon dioxide to obtain carbon monoxide and the step of electrolyzing water to obtain hydrogen (H ₂ ).

The mixed gas obtained in the co-electrolyzer 20 contains not only carbon monoxide and hydrogen (H ₂ ) but also unreacted carbon dioxide and water.
The inlet of the co-electrolyzer 20 is a location to which the supply path 10 is connected. The outlet of the co-electrolyzer 20 is where the mixed gas is led out.

The methane reactor 30 obtains a product gas containing methane (CH ₄ ) and water (H ₂ O) from carbon monoxide (CO) and hydrogen (H ₂ ) through a methanation reaction. The methanation reaction proceeds, for example, according to formula (II) shown below. This reaction is exothermic.
CO+ _3H2 → _CH4 + _H2O ...(II)

Preferably, the methane reactor 30 includes a methanation catalyst with which the mixed gas contacts. Examples of methanation catalysts include Ni catalysts and Ru catalysts. Methanation catalysts promote methanation reactions.
The methane reactor 30 may generate methanol from a mixed gas, and may generate methane from methanol.

The product gas obtained in the methane reactor 30 includes not only methane and water, but also unreacted carbon monoxide, hydrogen (H ₂ ), carbon dioxide, and the like.
The product gas is discharged out of the system through the discharge path 60. The discharged product gas is sent to a gas production facility, for example, as a raw material for city gas or the like.
The inlet of the methane reactor 30 is where the mixed gas is introduced from the co-electrolyzer 20. The outlet of the methane reactor 30 is where the discharge path 60 is connected.

The first separator 40 separates a first separated fluid F2 containing water and a second separated fluid F3 containing hydrogen (H ₂ ) from the return fluid F1, which is a part of the product gas.
The first separator 40 employs a separation method such as adsorption separation, membrane separation, cooling separation, centrifugal separation, gravity separation, gas-liquid separation, or the like. The first separator 40 may employ one of these separation methods, or may use a combination of two or more.

The first separator 40 using adsorption separation, for example, separates a specific component by adsorbing it onto an adsorbent, an adsorption liquid, or the like. Examples of the adsorbent include silica gel, zeolite, and activated carbon. Specifically, by adsorbing a component containing water onto an adsorbent, this component can be separated from other components containing hydrogen (H ₂ ). The adsorbent may be granular, powdered, etc. The granules are, for example, bead-like (spherical), pellet-like (cylindrical), and the like. When using a powdered adsorbent, the adsorbent may be supported on the surface of the base material. The base material may have a honeycomb shape, for example.

The first separator 40 using adsorption separation has a function of separating the adsorbed material from the adsorbent. The first separator 40 includes, for example, a heating device. The heating device separates the adsorbed material from the adsorbent by heating the adsorbent. The first separator 40 may include a pressure reduction device such as a pressure reduction pump. The pressure reducing device separates the adsorbed material from the adsorbent by placing the adsorbent under reduced pressure.

The first separator 40 using membrane separation separates a specific component from other components using, for example, a permeable membrane through which low-molecular components can pass. Specifically, for example, a component containing hydrogen (H ₂ ) can be separated from a component containing water using a palladium permeable membrane.
The first separator 40 using cooling separation, for example, liquefies a specific component by cooling and separates it from other components (gas). Specifically, for example, a component containing water can be liquefied and separated from a gas containing hydrogen (H ₂ ).

The first separator 40 using centrifugation, for example, liquefies a specific component (component containing water) by cooling, and separates this component from other components (gas containing hydrogen (H ₂ )) by centrifugal force. do. The first separator 40 using gravity separation, for example, liquefies a specific component (component containing water) by cooling, and separates this component from other components (gas containing hydrogen (H ₂ )) by gravity. . The first separator 40 using gas-liquid separation, for example, liquefies a specific component (component containing water) by cooling, and converts this component into other components (hydrogen ( _H2 )) by gravity, centrifugal force, surface tension, etc. ).

The first circulation path 50 includes a lead-out path 51, a first return path 52, and a second return path 53.
The outlet path 51 connects the methane reactor 30 and the first separator 40. A starting end (first end) of the outlet path 51 is connected to a position close to the outlet of the methane reactor 30. A terminal end (second end) of the lead-out path 51 is connected to the first separator 40 . The outlet path 51 takes out a part of the product gas from the methane reactor 30 as a return fluid F1. The outlet path 51 leads the return fluid F1 to the first separator 40.

The first return path 52 connects the first separator 40 and the supply path 10. A starting end (first end) of the first return path 52 is connected to the first separator 40 . The terminal end (second end) of the third return path 552 is connected to the supply path 10. The first return path 52 can lead the first separated fluid F2 to the co-electrolyzer 20 through the supply path 10. Note that the first return path 52 may connect the first separator 40 and the co-electrolyzer 20.

The second return path 53 connects the first separator 40 and the methane reactor 30. A starting end (first end) of the second return path 53 is connected to the first separator 40 . The terminal end (second end) of the second return path 53 is connected to a position close to the inlet of the methane reactor 30. The terminal end (second end) of the second return path 53 is located closer to the inlet of the methane reactor 30 than the starting end (first end) of the outlet path 51 . The second return path 53 leads the second separation fluid F3 to the methane reactor 30.

The exhaust path 60 may be provided with a separator for removing impurities from the product gas. Impurities are, for example, components other than methane (carbon dioxide, water, hydrogen (H ₂ ), etc.). Separation methods such as adsorption separation, membrane separation, cooling separation, centrifugal separation, gravity separation, and gas-liquid separation are employed in the separator. The separator may employ one of these separation techniques, or may use a combination of two or more.

A separator using adsorption separation, for example, separates carbon dioxide, water, etc. by adsorbing it on an adsorbent, an adsorption liquid, or the like. Examples of the adsorbent include silica gel, zeolite, and activated carbon.
A separator using membrane separation uses, for example, a permeable membrane through which low-molecular components can pass through to separate specific components from other components. Specifically, low molecular weight components such as hydrogen (H ₂ ) can be separated using a palladium permeable membrane.
A separator using cooling separation, for example, liquefies a specific component by cooling and separates it from other components (gas).

A separator using centrifugation, for example, liquefies a specific component by cooling and separates this component from other components (gas) by centrifugal force. A separator using gravity separation, for example, liquefies a specific component by cooling and separates this component from other components (gases) by gravity. A separator using gas-liquid separation, for example, liquefies a specific component by cooling and separates this component from other components (gas) by gravity, centrifugal force, surface tension, or the like.

Next, an example of a methane production method using the methane production system 1 will be described.
The methane production method according to this embodiment includes a supply step, an electrolysis step, a methanation step, and a circulation step.

In the supply process, carbon dioxide (CO ₂ ) and water (H ₂ O) are introduced to the co-electrolyzer 20 through the supply path 10 .
In the electrolysis process, a mixed gas containing carbon monoxide (CO) and hydrogen (H ₂ ) is obtained from carbon dioxide and water by co-electrolysis in the co-electrolyzer 20 .

In the methanation step, a product gas containing methane (CH ₄ ) and water is obtained from carbon monoxide and hydrogen through a methanation reaction in the methane reactor 30 . The product gas includes methane and water as well as unreacted carbon monoxide, hydrogen (H ₂ ), carbon dioxide, and the like. The product gas is discharged out of the system through the discharge path 60.

In the circulation process, a part of the product gas is taken out of the methane reactor 30 through the outlet 51 and led to the first separator 40 as a return fluid F1. The first separator 40 separates the return fluid F1 into a first separated fluid F2 containing water (for example, water vapor) and a second separated fluid F3 containing hydrogen (H ₂ ). The concentration of water (eg, water vapor) in the first separation fluid F2 is higher than the concentration of water (eg, water vapor) in the return fluid F1. The concentration of hydrogen (H ₂ ) in the second separation fluid F3 is higher than the concentration of hydrogen (H ₂ ) in the return fluid F1.

The first separation fluid F2 is led to the co-electrolyzer 20 through the first return path 52 and the supply path 10. The second separation fluid F3 is led to the methane reactor 30 through the second return path 53.

The methane generation system 1 includes a first return path 52 that leads the first separated fluid F2 to the co-electrolyzer 20, and a second return path 53 that leads the second separated fluid F3 to the methane reactor 30.
According to the methane generation system 1, the second separation fluid F3 containing hydrogen (H ₂ ), which is an unreacted product, is returned to the methane reactor 30, so that the efficiency of the methanation reaction in the methane reactor 30 can be increased. can. Therefore, methane production efficiency can be increased.
According to the methane generation system 1, the first separation fluid F2 containing unreacted water (for example, water vapor) is returned to the co-electrolyzer 20. Therefore, the efficiency of the electrolytic reaction in the co-electrolyzer 20 can be increased. Since the first separation fluid F2 is returned to the co-electrolyzer 20, the heat generated in the methane reactor 30 can be used in the co-electrolyzer 20. Therefore, energy efficiency can be improved.
In the methane generation system 1, since water (for example, water vapor) is discharged from the methane reactor 30, the efficiency of the methanation reaction in the methane reactor 30 can be increased.

Embodiment 2.
Next, a methane generation system according to Embodiment 2 will be explained. Since the basic configuration of the methane generation system according to this embodiment is the same as that of Embodiment 1, the differences from Embodiment 1 will mainly be explained. Components that are the same as those in other embodiments are designated by the same reference numerals and description thereof will be omitted.

FIG. 2 is a schematic diagram of a methane generation system according to a second embodiment.
As shown in FIG. 2, the methane generation system 101 includes a cooler 70 in the second return path 53. Cooler 70 may be a heat exchanger. The cooler 70 may be a water-cooled type, an air-cooled type, or the like. The cooler 70 cools the second separation fluid F3 flowing through the second return path 53.

Since the methane generation system 101 cools the second separation fluid F3 using the cooler 70, the temperature in the methane reactor 30 can be set to a temperature suitable for the methanation reaction. Therefore, the methane production efficiency in the methane reactor 30 can be increased.

Embodiment 3.
Next, a methane generation system according to Embodiment 3 will be explained. Components that are the same as those in other embodiments are designated by the same reference numerals and description thereof will be omitted.

FIG. 3 is a schematic diagram of a methane generation system according to Embodiment 3.
As shown in FIG. 3, the methane generation system 201 includes a supply route 210 instead of the supply route 10 (see FIG. 1). The supply route 210 includes a first supply route 211 and a second supply route 212. The first supply path 211 leads carbon dioxide to the co-electrolyzer 20 . The second supply path 212 leads water to the first supply path 211 . Therefore, the second supply path 212 can lead water to the co-electrolysis device 20 via the first supply path 211.

The methane generation system 201 includes a heat exchanger 270. The heat exchanger 270 is provided across the second supply path 212 and the outlet path 51. The heat exchanger 270 can cool the return fluid F1 by exchanging heat with the water flowing through the second supply path 212. When the return fluid F1 is cooled, specific components (components containing water) are liquefied.

The methane generation system 201 includes a gas-liquid separator 240 instead of the first separator 40 (see FIG. 1). The gas-liquid separator 240 separates liquid and gas by, for example, gravity, centrifugal force, surface tension, or the like. Gas-liquid separator 240 is an example of a first separator.
The liquid obtained by the gas-liquid separator 240 becomes a first separated fluid F2 containing water. The first separated fluid F2 is guided to the co-electrolyzer 20 through the first return path 52 and the first supply path 211. The gas obtained by the gas-liquid separator 240 becomes a second separated fluid F3 containing hydrogen (H ₂ ). The second separation fluid F3 is led to the methane reactor 30 through the second return path 53.

Since the methane generation system 201 includes the heat exchanger 270, the return fluid F1 can be cooled using the water supplied by the second supply path 212. Therefore, the energy efficiency in the gas-liquid separator 240 can be improved. In the methane generation system 201, the temperature-adjusted second separated fluid F3 is obtained by the heat exchanger 270, so that the temperature in the methane reactor 30 can be set to a temperature suitable for the methanation reaction. Therefore, the methane production efficiency in the methane reactor 30 can be increased.

Embodiment 4.
Next, a methane generation system according to Embodiment 4 will be explained. Components that are the same as those in other embodiments are designated by the same reference numerals and description thereof will be omitted.

FIG. 4 is a schematic diagram of a methane generation system according to Embodiment 4.
As shown in FIG. 4, the methane generation system 301 includes a supply path 310 instead of the supply path 10 (see FIG. 1). The supply path 310 leads the mixed fluid of carbon dioxide and water to the co-electrolyzer 20 . Most carbon dioxide is a gas. Most water is liquid. Therefore, the mixed fluid flowing through the supply path 310 is a gas-liquid two-phase fluid.

The methane generation system 301 includes a heat exchanger 370. The heat exchanger 370 is provided across the supply path 310 and the outlet path 51. The heat exchanger 370 can cool the return fluid F1 by exchanging heat with the mixed fluid flowing through the supply path 310. When the return fluid F1 is cooled, specific components (components containing water) are liquefied.

Since the methane generation system 301 includes the heat exchanger 370, the return fluid F1 can be cooled using the mixed fluid supplied from the supply path 310. Therefore, the energy efficiency in the gas-liquid separator 240 can be improved. In the methane generation system 301, the temperature-adjusted second separated fluid F3 is obtained by the heat exchanger 370, so that the temperature in the methane reactor 30 can be set to a temperature suitable for the methanation reaction. Therefore, the methane production efficiency in the methane reactor 30 can be increased.

The methane generation system 301 uses a mixed fluid, which is a gas-liquid two-phase fluid, as a heat medium, so heat transfer performance is improved. Therefore, the return fluid F1 can be efficiently cooled in the heat exchanger 370.

Embodiment 5.
Next, a methane generation system according to Embodiment 5 will be described. Components that are the same as those in other embodiments are designated by the same reference numerals and description thereof will be omitted.

FIG. 5 is a schematic diagram of a methane generation system according to Embodiment 5.
As shown in FIG. 5, the methane generation system 401 includes a supply path 410 instead of the supply path 10 (see FIG. 1). The supply path 410 includes a first supply path 411 , a second supply path 412 , and a merging channel 413 . The first supply path 411 introduces carbon dioxide. The second supply path 412 introduces water. The merging channel 413 merges carbon dioxide from the first supply channel 411 and water from the second supply channel 412 and guides them to the co-electrolyzer 20 .

The methane generation system 401 includes a heat exchanger 470. The heat exchanger 470 is provided across the first supply path 411 , the second supply path 412 , and the outlet path 51 . The heat exchanger 470 can cool the return fluid F1 by heat exchange with carbon dioxide and water flowing through the

supply paths

411 and 412. When the return fluid F1 is cooled, specific components (components containing water) are liquefied.

Since the methane generation system 401 includes the heat exchanger 470, the return fluid F1 can be cooled using carbon dioxide and water supplied from the

supply paths

411 and 412. Therefore, the energy efficiency in the gas-liquid separator 240 can be improved. In the methane generation system 401, the temperature-adjusted second separated fluid F3 is obtained by the heat exchanger 470, so that the temperature in the methane reactor 30 can be set to a temperature suitable for the methanation reaction. Therefore, the methane production efficiency in the methane reactor 30 can be increased.

The supply path 410 includes a first supply path 411 that leads to carbon dioxide, and a second supply path 412 that leads to water. Carbon dioxide and water may have different pressures, etc., but in the methane generation system 401, appropriate conditions can be set for each fluid.

Embodiment 6.
Next, a methane generation system according to Embodiment 6 will be described. Components that are the same as those in other embodiments are designated by the same reference numerals and description thereof will be omitted.

FIG. 6 is a schematic diagram of a methane generation system according to Embodiment 6.
As shown in FIG. 6, the methane generation system 501 includes a supply route 10, a co-electrolyzer 20, a methane reactor 530, a first separator 40, a first circulation route 50, and a second separator 540. , a second circulation path 550.

The methane reactor 530 includes a first methane reaction section 531 and a second methane reaction section 532.
The first methane reaction section 531 generates methane from the mixed gas from the co-electrolyzer 20 through a methanation reaction to obtain an intermediate gas. The second methane reaction section 532 generates methane from the intermediate gas through a methanation reaction to obtain a product gas. Thus, the methane reactor 530 obtains product gas through a two-step methanation reaction.

The first circulation path 50 includes a lead-out path 51, a first return path 52, and a second return path 53.
The outlet path 51 connects the second methane reaction section 532 and the first separator 40. A starting end (first end) of the outlet path 51 is connected to a position close to the outlet of the second methane reaction section 532. A terminal end (second end) of the lead-out path 51 is connected to the first separator 40 . The outlet path 51 takes out a part of the product gas from the second methane reaction section 532 as a return fluid F1. The outlet path 51 leads the return fluid F1 to the first separator 40.

The first return path 52 connects the first separator 40 and the supply path 10. The first return path 52 can lead the first separated fluid F2 to the co-electrolyzer 20 through the supply path 10. Note that the first return path 52 may connect the first separator 40 and the co-electrolyzer 20.

The second return path 53 connects the first separator 40 and the second methane reaction section 532. A starting end (first end) of the second return path 53 is connected to the first separator 40 . The terminal end (second end) of the second return path 53 is connected to a position close to the inlet of the second methane reaction section 532. The terminal end (second end) of the second return path 53 is located closer to the inlet of the second methane reaction section 532 than the starting end (first end) of the outlet path 51 . The second return path 53 guides the second separation fluid F3 to the second methane reaction section 532.

Similarly to the first separator 40, the second separator 540 employs separation techniques such as adsorption separation, membrane separation, cooling separation, centrifugal separation, gravity separation, and gas-liquid separation.

The second circulation path 550 includes a lead-out path 551, a third return path 552, and a fourth return path 553.
The outlet path 551 connects the first methane reaction section 531 and the second separator 540. A starting end (first end) of the outlet path 551 is connected to a position close to the outlet of the first methane reaction section 531. A terminal end (second end) of the lead-out path 551 is connected to the second separator 540. The outlet path 551 takes out a part of the intermediate gas from the first methane reaction section 531 as a return fluid F4. The outlet path 551 leads the return fluid F4 to the second separator 540.

The third return path 552 connects the second separator 540 and the supply path 10. A starting end (first end) of the third return path 552 is connected to the second separator 540. The terminal end (second end) of the third return path 552 is connected to the supply path 10. The third return path 552 can lead the third separated fluid F5 to the co-electrolyzer 20 through the supply path 10. Note that the third return path 552 may connect the second separator 540 and the co-electrolyzer 20.

The fourth return path 553 connects the second separator 540 and the first methane reaction section 531. A starting end (first end) of the fourth return path 553 is connected to the second separator 540. The terminal end (second end) of the fourth return path 553 is connected to a position close to the inlet of the first methane reaction section 531. The terminal end (second end) of the fourth return path 553 is located closer to the inlet of the first methane reaction section 531 than the starting end (first end) of the outlet path 551. The fourth return path 553 guides the fourth separation fluid F6 to the first methane reaction section 531.

In the methane generation system 501, a portion of the intermediate gas is taken out from the first methane reaction section 531 through the outlet path 551 and guided to the second separator 540 as a return fluid F4. The second separator 540 separates the return fluid F4 into a third separated fluid F5 containing water (for example, water vapor) and a fourth separated fluid F6 containing hydrogen (H ₂ ). The concentration of water (eg, water vapor) in the third separation fluid F5 is higher than the concentration of water (eg, water vapor) in the return fluid F4. The concentration of hydrogen (H ₂ ) in the fourth separation fluid F6 is higher than the concentration of hydrogen (H ₂ ) in the return fluid F4.

In the methane generation system 501, a part of the product gas is taken out from the second methane reaction section 532 through the outlet path 51 and guided to the first separator 40 as a return fluid F1. The first separator 40 separates the return fluid F1 into a first separated fluid F2 containing water (for example, water vapor) and a second separated fluid F3 containing hydrogen (H ₂ ). The concentration of water (eg, water vapor) in the first separation fluid F2 is higher than the concentration of water (eg, water vapor) in the return fluid F1. The concentration of hydrogen (H ₂ ) in the second separation fluid F3 is higher than the concentration of hydrogen (H ₂ ) in the return fluid F1.

In the methane generation system 501, not only the first separated fluid F2 containing water is returned to the co-electrolyzer 20 through the first circulation path 50, but also the third separated fluid F5 containing water is returned through the second circulation path 550. It is returned to the co-electrolyzer 20. In the methane generation system 501, water is discharged from the methane reactor 530 at multiple locations, so water can be effectively removed. Therefore, the efficiency of the methanation reaction in the methane reactor 530 can be increased.

Embodiment 7.
Next, a methane generation system according to Embodiment 7 will be described. Components that are the same as those in other embodiments are designated by the same reference numerals and description thereof will be omitted.

FIG. 7 is a schematic diagram of a methane generation system according to Embodiment 7.
As shown in FIG. 7, the methane generation system 601 includes a supply route 10, a co-electrolyzer 20, a methane reactor 530, a first separator 40, a first circulation route 50, and a second separator 540. , a second circulation path 550, and an ejector 680. Methane generation system 601 differs from methane generation system 501 (see FIG. 6) in that it includes an ejector 680.

The ejector 680 has an inflow port 681, a first suction port 682, a second suction port 683, and an outflow port 684. Ejector 680 is provided in supply path 10 . Carbon dioxide and water flowing through the supply path 10 flow into the ejector 680 from an inlet 681 and exit from an outlet 684. Carbon dioxide and water become the driving fluids. The water serving as the driving fluid may be gas (steam) or liquid.

The first suction port 682 is connected to the terminal end (second end) of the first return path 52. The first separation fluid F2 flows into the ejector 680 from the first suction port 682 as a suction fluid. The second suction port 683 is connected to the terminal end (second end) of the third return path 552. The second suction port 683 is located downstream of the first suction port 682 in the flow direction. “Flow direction” is the direction of carbon dioxide and water flowing from inlet 681 to outlet 684. The third separation fluid F5 flows into the ejector 680 from the second suction port 683 as a suction fluid. A nozzle for ejecting driving fluid is provided inside the ejector 680.

The ejector 680 sucks the first separated fluid F2 and the third separated fluid F5 into the ejector 680 using carbon dioxide and water that have flowed in from the inlet 681 as driving fluids. The first separation fluid F2 and the third separation fluid F5 flow out of the ejector 680 through the outlet 684 together with the driving fluids carbon dioxide and water, and are supplied to the co-electrolyzer 20 through the supply path 10.

The first return path 52 and the third return path 552 may be provided with a pump or the like for sending the first separated fluid F2 and the third separated fluid F5 to the supply path 10.

Since the methane generation system 601 includes the ejector 680, the first separation fluid F2 and the third separation fluid F5 can be guided to the supply path 10 by the ejector 680. Therefore, compared to, for example, the case where the first separated fluid F2 and the third separated fluid F5 are guided to the supply path 10 using only a pump, energy saving is possible.

Since the methane generation system 601 uses the ejector 680 having multiple suction ports, the number of ejectors can be reduced. Therefore, it is advantageous in terms of downsizing and cost reduction of the device.

Embodiment 8.
Next, a methane generation system according to Embodiment 8 will be described. Components that are the same as those in other embodiments are designated by the same reference numerals and description thereof will be omitted.

FIG. 8 is a schematic diagram of a methane generation system according to Embodiment 8.
As shown in FIG. 8, the methane generation system 701 includes a supply route 10, a co-electrolyzer 20, a methane reactor 530, a first separator 40, a first circulation route 50, and a second separator 540. , a second circulation path 550, and an ejector 780. The methane generation system 701 differs from the methane generation system 601 (see FIG. 7) in that it includes an ejector 780 instead of the ejector 680.

Ejector 780 includes a first ejector section 781 and a second ejector section 782.
The first ejector section 781 has an inlet 783, a suction port 784, and an outlet 785. The first ejector section 781 is provided in the supply path 10. Carbon dioxide and water flowing through the supply path 10 flow into the first ejector section 781 from the inlet 783 and exit from the outlet 785. Carbon dioxide and water become the driving fluids. The water serving as the driving fluid may be gas (steam) or liquid. A nozzle for ejecting driving fluid is provided inside the first ejector section 781.

The suction port 784 is connected to the terminal end (second end) of the first return path 52. The first separation fluid F2 flows into the first ejector section 781 from the suction port 784 as a suction fluid.

The first ejector section 781 sucks the first separation fluid F2 using carbon dioxide and water that have flowed in from the inlet 783 as driving fluids. The first separation fluid F2 flows out from the first ejector section 781 through the outlet 785 together with carbon dioxide and water, which are driving fluids.

The second ejector section 782 has an inlet 786, a suction port 787, and an outlet 788. The second ejector section 782 is provided in the supply path 10. The second ejector section 782 is provided on the downstream side of the first ejector section 781 in the flow direction of carbon dioxide and water in the supply path 10 . Carbon dioxide and water flowing through the supply path 10 flow into the second ejector section 782 from the inlet 786 and exit from the outlet 788. Carbon dioxide and water become the driving fluids. The water serving as the driving fluid may be gas (steam) or liquid. A nozzle for ejecting driving fluid is provided inside the second ejector section 782. The second ejector section 782 is separate from the first ejector section 781.

The suction port 787 is connected to the terminal end (second end) of the third return path 552. The third separation fluid F5 flows into the second ejector section 782 from the suction port 787 as a suction fluid.

The second ejector section 782 sucks the third separated fluid F5 using the carbon dioxide, water, and the first separated fluid F2 that have flowed in from the inlet 786 as driving fluids. The third separation fluid F5 flows out from the second ejector section 782 through the outlet 788 together with the driving fluids carbon dioxide, water, and the first separation fluid F2. Carbon dioxide, water, the first separated fluid F2, and the third separated fluid F5 are supplied to the co-electrolyzer 20 through the supply path 10.

Since the methane generation system 701 includes the ejector 780, the first separation fluid F2 and the third separation fluid F5 can be guided to the supply path 10 by the ejector 780. Therefore, compared to, for example, the case where the separation fluids F2 and F5 are guided to the supply path 10 using only pumps, energy saving is possible.

In the methane generation system 701, an ejector 780 includes a first ejector section 781 that sucks the first separated fluid F2, and a second ejector section 782 that sucks the third separated fluid F5. Operating conditions for the first ejector section 781 and the second ejector section 782 can be set independently of each other. Therefore, even if conditions such as flow rates differ between the first separated fluid F2 and the third separated fluid F5, the first ejector section 781 and the second ejector section 782 can be operated appropriately.

Note that the technical scope of the present disclosure is not limited to the embodiments described above, and various changes can be made without departing from the spirit of the present disclosure.
For example, in the sixth embodiment, the methane reactor 530 includes two

methane reaction sections

531 and 532, but the number of methane reaction sections is not particularly limited. The number of methane reaction parts may be any number greater than or equal to 2. The methane generation system 501 includes two

circulation paths

50 and 550 because the number of methane reaction sections is two, but the number of circulation paths may be any number greater than or equal to two.

In Embodiment 7, the methane generation system 601 sucks the first separation fluid F2 and the third separation fluid F5 using carbon dioxide and water flowing through the supply path 10 as driving fluids, but the driving fluids are carbon dioxide and water. It may be at least one of them.
In the eighth embodiment, the ejector 780 includes two

first ejector sections

781 and 782, but the number of ejector sections may be any number greater than or equal to two.

1,101,201,301,401,501,601,701... Methane generation system 10,210,310,410... Supply route 20... Co-electrolyzer (electrolyzer) 30,530... Methane reactor 40... First separation Container 50... First circulation path 51... Outlet path 52... First return path 53... Second return path 70... Cooler 240... Gas-

liquid separator

270, 370... Heat exchanger 411... First supply path 412... Second Supply path 531...First methane reaction section 532...Second methane reaction section 540...Second separator 550...Second circulation path 551...Outlet path 552...Third return path 553...

Fourth return path

680, 780...Ejector 781 ...First ejector part 782...Second ejector part F1...Return fluid F2...First separated fluid F3...Second separated fluid F5...Third separated fluid F6...Fourth separated fluid

Claims

a supply route for supplying carbon dioxide and water;
an electrolysis device for obtaining carbon monoxide and hydrogen from the carbon dioxide and the water by electrolysis;
a methane reactor for obtaining a product gas containing methane from the mixed gas containing the carbon monoxide and the hydrogen;
a first separator that separates a first separated fluid containing water and a second separated fluid containing hydrogen from a return fluid that is a part of the product gas;
a first circulation path having a first return path that leads the first separation fluid to the electrolyzer, and a second return path that leads the second separation fluid to the methane reactor;
Methane production system.
The second return path is provided with a cooler that cools the second separation fluid.
The methane production system of claim 1.
Further comprising a heat exchanger that cools the return fluid by heat exchange with the water supplied by the supply route,
the first separator is a gas-liquid separator;
The methane production system of claim 1.
further comprising a heat exchanger that cools the return fluid by heat exchange with the mixed fluid of the carbon dioxide and the water supplied by the supply route,
the first separator is a gas-liquid separator;
The methane production system of claim 1.
The supply route includes a first supply route that supplies the carbon dioxide and a second supply route that supplies the water,
Further comprising a heat exchanger that cools the return fluid by heat exchange with the carbon dioxide and the water supplied by the first supply path and the second supply path,
the first separator is a gas-liquid separator;
The methane production system of claim 1.
The methane reactor is
a first methane reaction section that generates methane from the mixed gas to obtain an intermediate gas;
a second methane reaction section that generates methane from the intermediate gas to obtain the product gas;
a second separator that separates a third separation fluid containing water and a fourth separation fluid containing hydrogen from a portion of the intermediate gas;
Further comprising a second circulation path having a third return path that leads the third separated fluid to the electrolyzer, and a fourth return path that leads the fourth separated fluid to the first methane reaction section.
The methane production system of claim 1.
The supply path is provided with an ejector that sucks the first separation fluid and the third separation fluid using at least one of the carbon dioxide and the water as a driving fluid.
The methane production system according to claim 6.
The ejector includes a first ejector section that sucks the first separation fluid, and a second ejector section that sucks the third separation fluid.
The methane production system according to claim 7.