Methane synthesis system

Abstract

This methane synthesis system is provided with: a supply path for supplying carbon dioxide and water; a carbon dioxide consumption reaction unit for obtaining a product using at least the carbon dioxide and the water; a methane generation reaction unit which is thermally connected to the carbon dioxide consumption reaction unit and which generates methane from a reactant and hydrogen; and a first heat recovery unit that recovers heat by heat exchange with the carbon dioxide consumption reaction unit.

Description

Technical Field

[0001] The present disclosure relates to methane synthesis systems. Background Art

[0002] Patent Document 1 discloses a methane production apparatus that produces methane using bicarbonate and hydrogen.

[0003] Prior Art Literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent Application Publication No. 2021-17409 Summary of the invention

[0006] Problems to be solved by the invention

[0007] In the above-mentioned technology, the energy efficiency of the entire device may be reduced.

[0008] In view of the above circumstances, an object of the present disclosure is to provide a methane synthesis system capable of improving energy efficiency.

[0009] Solutions to Solve Problems

[0010] One mode of the methane synthesis system disclosed in the present invention comprises: a supply path for supplying carbon dioxide and water; a carbon dioxide consumption reaction unit for obtaining a product using at least the carbon dioxide and the water; a methane generation reaction unit thermally connected to the carbon dioxide consumption reaction unit for generating methane from the reactants and hydrogen; and a first heat recovery unit for recovering heat by heat exchange with the carbon dioxide consumption reaction unit.

[0011] Effects of the Invention

[0012] According to the present disclosure, it is possible to provide a methane synthesis system capable of improving energy efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 is a schematic diagram of a methane synthesis system according to an embodiment. DETAILED DESCRIPTION

[0014] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. In addition, the scope of the present disclosure is not limited to the following embodiments, and can be arbitrarily changed within the scope of the technical concept of the present disclosure.

[0015] Figure 1 It is a schematic diagram showing a methane synthesis system in an embodiment.

[0016] like Figure 1As shown, the methane synthesis system 1 includes a raw material supply path 2, a carbon dioxide consumption reaction unit 3, a methane production reaction unit 4, a first heat recovery unit 5, a hydrogen production unit 6, a separator 7, a second heat recovery unit 8, an ejector 9, an outlet path 11, a water recovery path 12, a hydrogen supply path 13, a circulation path 14, a return path 15 and a water supply path 16.

[0017] The raw material supply path 2 introduces water (e.g., water vapor) and carbon dioxide to the carbon dioxide consumption reaction unit 3. Carbon dioxide is supplied from the introduction path 21. The raw material supply path 2 introduces, for example, a mixed fluid of water and carbon dioxide to the carbon dioxide consumption reaction unit 3. The raw material supply path 2 is an example of a "supply path".

[0018] The carbon dioxide supplied from the introduction path 21 may also be carbon dioxide recovered from the atmosphere by DAC (Direct Air Capture). The carbon dioxide supplied from the introduction path 21 may also be carbon dioxide exhausted from a solid oxide fuel cell (SOFC). The carbon dioxide supplied from the introduction path 21 may also be carbon dioxide exhausted from a gas water heater, a boiler, or the like.

[0019] Carbon dioxide consumption reaction part 3, for example, holds carbonate in the reactor. In carbon dioxide consumption reaction part 3, bicarbonate is generated as a product by the reaction of water and carbon dioxide from raw material supply path 2 with carbonate. This reaction is a reaction that consumes carbon dioxide. The reaction is carried out, for example, according to formula (I) shown below. The reaction is an exothermic reaction.

[0020] K 2 CO 3 +CO 2 +H 2 O→2KHCO 3 …(I)

[0021] The carbonate is not limited to potassium carbonate, and may also be sodium carbonate, lithium carbonate, ammonium carbonate, etc. The bicarbonate is not limited to potassium bicarbonate, and may also be sodium bicarbonate, lithium bicarbonate, ammonium bicarbonate, etc.

[0022] The carbon dioxide consumption reaction unit 3 is thermally connected to the methane generation reaction unit 4. Therefore, the temperature of the carbon dioxide consumption reaction unit 3 can be adjusted by heat exchange with the methane generation reaction unit 4. Therefore, the temperature in the carbon dioxide consumption reaction unit 3 can be adjusted to a temperature suitable for the reaction represented by formula (I).

[0023] The bicarbonate (KHCO 3) is mainly solid and is held in the reactor of the carbon dioxide consumption reaction unit 3. In the carbon dioxide consumption reaction unit 3, a fluid F2 (unreacted fluid, such as unreacted gas) containing unreacted substances such as water (such as water vapor) is generated.

[0024] Formula (I) is a reaction for absorbing carbon dioxide. The carbon dioxide consumption reaction section is also referred to as a "carbon dioxide absorption reaction section".

[0025] The methane generation reaction unit 4 holds bicarbonate in a reactor, for example. In the methane generation reaction unit 4, hydrogen (H 2 ) reacts with bicarbonate (reactant) to produce carbonate, methane and water. This reaction is a methane generation reaction. The methane generation reaction is carried out, for example, according to the formula (II) shown below. This reaction is an endothermic reaction.

[0026] 2KHCO 3 +4H 2 →K 2 CO 3 +CH 4 +3H 2 O…(II)

[0027] The bicarbonate is not limited to potassium bicarbonate, and may be sodium bicarbonate, lithium bicarbonate, ammonium bicarbonate, etc. The carbonate is not limited to potassium carbonate, and may be sodium carbonate, lithium carbonate, ammonium carbonate, etc.

[0028] In the methane generation reaction section 4, a reactant fluid F3 (eg, reactant gas) containing methane and water is generated. 2 CO 3 ) is mainly solid and is maintained in the reactor of the methane generation reaction unit 4.

[0029] The methane generation reaction unit 4 is thermally connected to the carbon dioxide consumption reaction unit 3. Therefore, the methane generation reaction unit 4 can provide thermal energy by heat exchange with the carbon dioxide consumption reaction unit 3. Therefore, the temperature in the methane generation reaction unit 4 can be adjusted to a temperature suitable for the methane generation reaction.

[0030] The carbon dioxide consuming reaction section 3 and the methane generating reaction section 4 preferably have the same shape.

[0031] The first heat recovery unit 5 recovers heat from the carbon dioxide consumption reaction unit 3 by heat exchange with the carbon dioxide consumption reaction unit 3. In detail, the first heat recovery unit 5 heats the heat medium fluid by heat exchange with the carbon dioxide consumption reaction unit 3. As the heat medium fluid, water is preferably used. The water as the heat medium fluid is supplied from the water recovery path 12, for example.

[0032] A known heat exchanger can be used as the first heat recovery unit 5. As the heat exchanger, for example, a multi-tube heat exchanger, a plate heat exchanger, a coil heat exchanger, a double-tube heat exchanger, a spiral heat exchanger, etc. can be used.

[0033] The first heat recovery unit 5 may be configured to recover the heat of the methane generation reaction unit 4 by exchanging heat with the methane generation reaction unit 4 .

[0034] The carbon dioxide consumption reaction unit 3 and the methane generation reaction unit 4 constitute a composite reaction unit 100. The composite reaction unit 100 includes a first reaction unit 101 and a second reaction unit 102. Figure 1 In the example shown, the first reaction unit 101 ( Figure 1 The left part in the figure is the carbon dioxide consumption reaction part 3. The second reaction part 102 ( Figure 1 The right part in the figure is the methane generation reaction section 4.

[0035] The reactant fluid F3 (reactant gas) containing methane and water obtained in the methane generation reaction unit 4 is introduced into the separator 7 through the outlet path 11. The separator 7 separates the reactant fluid F3 into a fluid F4 containing methane and a fluid F1 containing water.

[0036] The separator 7 adopts a separation method such as liquefaction separation, membrane separation, adsorption separation, etc. For the separator 7, one of these separation methods may be adopted, or two or more of them may be combined.

[0037] The separator 7 using liquefaction separation liquefies a specific component and separates it from other components (gases), for example. Specifically, for example, a component containing water is liquefied by temperature adjustment and separated from other components (gases) containing methane.

[0038] The separator 7 using membrane separation uses, for example, a separation membrane through which components with small molecular sizes can pass, to separate specific components from other components. Specifically, for example, a separation membrane that selectively allows water to pass is used. The separation membrane separates components containing water from other components containing methane from the mixed gas.

[0039] The separator 7 using adsorption separation, for example, separates a specific component by adsorbing it on an adsorbent. Examples of the adsorbent include silica gel, zeolite, activated carbon, etc. Specifically, by adsorbing a component containing water on the adsorbent, the component can be separated from other components containing methane.

[0040] The separator 7 using adsorption separation has the function of separating the adsorbate from the adsorbent. The separator 7 is provided with a heating device, for example. The heating device separates the adsorbate from the adsorbent by heating the adsorbent. The separator 7 may also be provided with a decompression device such as a decompression pump. The decompression device promotes the separation of the adsorbate from the adsorbent by placing the adsorbent in a decompressed state.

[0041] The component containing methane (fluid F4) is discharged from the separator 7 through the discharge path 22. The component containing methane is sent to a gas production facility or the like as a raw material such as city gas.

[0042] The water recovery path 12 connects the separator 7 and the first heat recovery unit 5. The water-containing component (the water-containing fluid F1) is led out from the separator 7 through the water recovery path 12 and introduced into the first heat recovery unit 5. A pump 121 for conveying the fluid F1 to the first heat recovery unit 5 is provided on the water recovery path 12. The main component of the fluid F1 is water. The fluid F1 functions as a heat medium fluid for recovering heat from the carbon dioxide consumption reaction unit 3.

[0043] The water supply path 23 is connected to the water recovery path 12. The water recovery path 12 is supplied with water from the outside through the water supply path 23 as needed.

[0044] The second heat recovery unit 8 is provided on the outlet path 11. The second heat recovery unit 8 recovers heat of the reactant fluid F3 introduced into the separator 7 through the outlet path 11. Specifically, the fluid F1 flowing through the water recovery path 12 is heated by heat exchange with the reactant fluid F3.

[0045] A known heat exchanger can be used as the second heat recovery unit 8. For example, a multi-tube heat exchanger, a plate heat exchanger, a coil heat exchanger, a double-tube heat exchanger, a spiral heat exchanger, etc. can be used as the second heat recovery unit 8.

[0046] The hydrogen production unit 6 electrolyzes water (e.g., water vapor) supplied from the water supply path 16 to produce hydrogen (H 2 ) and oxygen (O 2 ).

[0047] In the hydrogen production unit 6, for example, electricity generated by renewable energy (such as solar power generation, wind power generation, etc.) can be used for electrolysis. Methane obtained by using renewable energy does not produce additional carbon dioxide even if it is burned and used, so it can be considered as a carbon-neutral fuel that does not affect global warming.

[0048] The hydrogen supply path 13 supplies hydrogen (H) obtained from the hydrogen production unit 6. 2 ) is introduced into the methane generation reaction unit 4.

[0049] The circulation path 14 introduces the fluid F1 (heat medium fluid) led out from the first heat recovery unit 5 into the raw material supply path 2 .

[0050] The return path 15 returns the unreacted fluid F2 discharged from the carbon dioxide consuming reaction unit 3 to the raw material supply path 2 via the ejector 9 .

[0051] The water supply path 16 introduces a portion of the fluid F1 (fluid F5 ) flowing through the circulation path 14 to the hydrogen production unit 6 .

[0052] The ejector 9 is provided on the raw material supply path 2. The ejector 9 has an inlet 9a, a first suction port 9b, a second suction port 9c, and an outlet 9d. The fluid F1 flowing through the raw material supply path 2 flows into the ejector 9 from the inlet 9a and flows out from the outlet 9d. The fluid F1 becomes a driving fluid. A nozzle for ejecting the driving fluid is provided inside the ejector 9. The first suction port 9b is connected to an introduction path 21. Carbon dioxide flows into the ejector 9 from the first suction port 9b as a suction fluid through the introduction path 21.

[0053] The second suction port 9c is connected to a return path 15. The unreacted fluid F2 discharged from the carbon dioxide consuming reaction unit 3 flows into the ejector 9 from the second suction port 9c as a suction fluid through the return path 15.

[0054] Next, an example of a methane synthesis method using the methane synthesis system 1 will be described.

[0055] The methane synthesis method of the present embodiment includes a supply step, a carbon dioxide consumption reaction step, a methane generation reaction step, a separation step, and a hydrogen production step.

[0056] In the supply process, water (H 2 O) and carbon dioxide (CO 2 ) is introduced into the carbon dioxide consumption reaction unit 3.

[0057] In the carbon dioxide consumption reaction step, bicarbonate is obtained as a product by the reaction of water and carbon dioxide from the raw material supply path 2 with carbonate in the carbon dioxide consumption reaction section 3. In the carbon dioxide consumption reaction step, a fluid F2 (unreacted fluid, such as unreacted gas) containing unreacted substances such as water (such as water vapor) is generated.

[0058] In the methane generation reaction step, in the methane generation reaction unit 4, hydrogen (H 2) reacts with bicarbonate (reactant) to generate carbonate, methane and water. In the methane generation reaction step, a reactant fluid F3 (e.g., reactant gas) containing methane and water is generated. The reactant fluid F3 (reactant gas) is introduced into the separator 7 through the outlet path 11.

[0059] In the separation step, in the separator 7 , the fluid F4 containing methane and the fluid F1 containing water are separated from the reactant fluid F3 .

[0060] The fluid F1 is led out from the separator 7 through the water recovery path 12 and introduced as a heat medium fluid into the first heat recovery unit 5. The first heat recovery unit 5 heats the fluid F1 by heat exchange with the carbon dioxide consuming reaction unit 3.

[0061] The fluid F1 led out from the first heat recovery unit 5 is introduced into the raw material supply path 2 through the circulation path 14. The fluid F1 is introduced into the carbon dioxide consumption reaction unit 3 together with the carbon dioxide introduced by the ejector 9.

[0062] A part of the fluid F1 (fluid F5) flowing through the circulation path 14 is introduced into the hydrogen production unit 6 through the water supply path 16. In the hydrogen production unit 6, a part of the water contained in the fluid F1 is electrolyzed.

[0063] The hydrogen (H) obtained in the hydrogen production unit 6 2 ) is introduced into the methane generation reaction unit 4 through the hydrogen supply path 13. The oxygen (O 2 ) is exported out of the system through export path 24.

[0064] The switching between the carbon dioxide consuming reaction section 3 and the methane generating reaction section 4 will be described.

[0065] After the carbon dioxide consumption reaction step and the methane generation reaction step, bicarbonate (KHCO 3 ) and carbonate (K 2 CO 3 ).

[0066] For example, the bicarbonate (KHCO 3 ) together with the reactor to the methane generation reaction unit 4. The carbonate (K2CO 3 ) together with the reactor moves to the carbon dioxide consumption reaction unit 3. By this method, the carbon dioxide consumption reaction unit 3 and the methane generation reaction unit 4 can be switched with each other.

[0067] In order to switch between the carbon dioxide consumption reaction unit 3 and the methane generation reaction unit 4, bicarbonate (KHCO 3), so that it moves to the methane generation reaction unit 4, and the carbonate (K 2 CO 3 ) to move it to the carbon dioxide consumption reaction section 3.

[0068] exist Figure 1 In the manner shown, the first reaction part 101 ( Figure 1 The left part in the figure is the carbon dioxide consumption reaction part 3. The second reaction part 102 ( Figure 1 The right part in the figure is the methane generation reaction section 4.

[0069] The carbon dioxide consumption reaction section 3 and the methane generation reaction section 4 may be arranged in a reverse manner. That is, the first reaction section 101 may be used as the methane generation reaction section 4 and the second reaction section 102 may be used as the carbon dioxide consumption reaction section 3.

[0070] The carbon dioxide consuming reaction unit 3 and the methane generating reaction unit 4 can also be switched by changing the route.

[0071] The raw material supply path 2 and the return path 15 are connected to the first reaction section 101 (carbon dioxide consumption reaction section 3). The hydrogen supply path 13 and the outlet path 11 are connected to the second reaction section 102 (methane generation reaction section 4).

[0072] The second raw material supply path 2A is branched from the raw material supply path 2 and connected to the second reaction unit 102. A valve V1 is provided on the raw material supply path 2. A valve V2 is provided on the second raw material supply path 2A. Figure 1 In the illustrated embodiment, valve V1 is open and valve V2 is closed.

[0073] The second return path 15A branches off from the return path 15 and is connected to the second reaction unit 102 .

[0074] The second hydrogen supply path 13A is branched from the hydrogen supply path 13 and connected to the first reaction unit 101. A valve V3 is provided on the hydrogen supply path 13. A valve V4 is provided on the second hydrogen supply path 13A. Figure 1 In the illustrated manner, valve V3 is open and valve V4 is closed.

[0075] The second lead-out path 11A branches off from the lead-out path 11 and is connected to the first reaction unit 101 .

[0076] At the end of the carbon dioxide consumption reaction step, the first reaction section 101 (carbon dioxide consumption reaction section 3) retains bicarbonate (KHCO 3 At the end of the methane generation reaction step, the carbonate (K 2 CO 3 ).

[0077] When the valve V1 is closed and the valve V2 is opened, water and carbon dioxide can be introduced into the second reactor 102 through the second raw material supply path 2A. Thus, the second reaction unit 102 can be used as a carbon dioxide consumption reaction unit. The unreacted fluid F2 is discharged through the second return path 15A and introduced into the raw material supply path 2 through the return path 15.

[0078] When the valve V3 is closed and the valve V4 is opened, hydrogen (H) can be supplied through the second hydrogen supply path 13A. 2 ) is introduced into the first reaction section 101. Thus, the first reaction section 101 can be used as a methane generation reaction section. The reactant fluid F3 is led out through the second lead-out path 11A and introduced into the separator 7 through the lead-out path 11.

[0079] By performing valve operations opposite to the above, the first reaction unit 101 can be returned to the carbon dioxide consumption reaction unit. The second reaction unit 102 can also be returned to the methane generation reaction unit 4.

[0080] In this way, the carbon dioxide consumption reaction section and the methane generation reaction section can be switched mutually.

[0081] In the methane synthesis system 1, since the carbon dioxide consumption reaction unit 3 and the methane generation reaction unit 4 are thermally connected, the heat generated in the carbon dioxide consumption reaction unit 3 can be used in the methane generation reaction unit 4. The methane synthesis system 1 recovers the heat of the carbon dioxide consumption reaction unit 3 through the first heat recovery unit 5. The fluid F1 is introduced into the carbon dioxide consumption reaction unit 3 through the raw material supply path 2, thereby, the recovered heat can be used in the carbon dioxide consumption reaction unit 3. Therefore, the energy efficiency of the entire system can be improved.

[0082] The methane synthesis system 1 can switch between the carbon dioxide consumption reaction unit 3 and the methane generation reaction unit 4 by the above method. By appropriately switching according to the progress of the reaction, the methane synthesis system 1 can be operated for a long time.

[0083] The methane synthesis system 1 can effectively utilize heat between the carbon dioxide consumption reaction section 3 and the methane production reaction section 4 by switching the carbon dioxide consumption reaction section 3 and the methane production reaction section 4 mutually.

[0084] The methane synthesis system 1 includes a return path 15 for returning the unreacted fluid F2 (unreacted gas) obtained in the carbon dioxide consuming reaction unit 3 to the carbon dioxide consuming reaction unit 3 through the raw material supply path 2 , thereby improving the reaction efficiency in the carbon dioxide consuming reaction unit 3 .

[0085] The heat medium fluid used in the first heat recovery unit 5 is the fluid F1 containing water. Therefore, the fluid F1 can be supplied as a raw material to the carbon dioxide consumption reaction unit 3. Therefore, the reaction heat in the carbon dioxide consumption reaction unit 3 can be effectively utilized. Therefore, the energy efficiency can be improved.

[0086] Since the methane synthesis system 1 includes the second heat recovery unit 8, the fluid F1 flowing through the water recovery path 12 can be heated by heat exchange with the reactant fluid F3 introduced into the separator 7 through the outlet path 11. Therefore, the heat of the methane generation reaction unit 4 can be effectively utilized. Therefore, the energy efficiency can be improved.

[0087] Since the methane synthesis system 1 includes the ejector 9 , energy saving can be achieved compared with the case where carbon dioxide is introduced into the raw material supply path 2 using only a blower, for example.

[0088] In addition, the technical scope of the present disclosure is not limited to the above-mentioned embodiment, and various changes can be made without departing from the gist of the present disclosure.

[0089] For example, in the methane synthesis system 1, when the first reaction unit 101 and the second reaction unit 102 are used alternately as the carbon dioxide consumption reaction unit and the methane generation reaction unit, the first heat recovery unit 5 is preferably configured to be able to recover heat from both the first reaction unit 101 and the second reaction unit 102. For example, the first heat recovery unit 5 can adopt a structure that is thermally connected to both the first reaction unit 101 and the second reaction unit 102. According to this structure, even if either of the first reaction unit 101 and the second reaction unit 102 is a carbon dioxide consumption reaction unit, heat can be efficiently recovered by the first heat recovery unit 5.

[0090] Description of Reference Numerals

[0091] 1 ...methane synthesis system 2 ...raw material supply path (supply path) 3 ...carbon dioxide consumption reaction section 4 ...methane generation reaction section 5 ...first heat recovery section 8 ...second heat recovery section 9 ...ejector 15 ...return path F1 ...fluid.

Claims

1. A methane synthesis system, wherein: The methane synthesis system comprises: A supply path for supplying carbon dioxide and water; A carbon dioxide consumption reaction unit, which uses at least the carbon dioxide and the water to obtain a product; a methane generating reaction section, thermally connected to the carbon dioxide consuming reaction section, for generating methane from reactants and hydrogen; and The first heat recovery unit recovers heat by exchanging heat with the carbon dioxide consuming reaction unit.

2. The methane synthesis system according to claim 1, wherein: The carbon dioxide consumption reaction section and the methane generation reaction section are switchable with each other.

3. The methane synthesis system according to claim 1 or 2, wherein: The methane synthesis system includes a return path for returning an unreacted product obtained in the carbon dioxide consuming reaction section to the carbon dioxide consuming reaction section.

4. The methane synthesis system according to any one of claims 1 to 3, wherein: The first heat recovery unit heats the heat medium fluid by heat exchange with the carbon dioxide consumption reaction unit. The thermal medium fluid is a fluid containing water.

5. The methane synthesis system according to claim 4, wherein: The methane synthesis system further includes a second heat recovery unit configured to heat the heat medium fluid by heat exchange with a fluid containing methane obtained in the methane generation reaction unit.

6. The methane synthesis system according to any one of claims 1 to 5, wherein: The supply path is provided with an ejector for sucking the carbon dioxide using the water as a driving fluid.

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