Methanation equipment and methanation method

Abstract

To provide a methanation system which has good efficiency of conversion of carbon dioxide to methane even when gas containing a low concentration of carbon dioxide is used as a carbon dioxide source, and which enables simplification of equipment and reduction of installation area thereof.SOLUTION: Methanation equipment is provided, comprising: a dissolution tank exposing carbon dioxide-containing gas to an aqueous phase, thereby producing carbon dioxide-containing solution; a culture tank for culturing methane in culture solution, thereby producing methane; a carbon dioxide gas supply flow passage for introducing carbon dioxide-containing gas into the dissolution tank; solution transfer means transferring the carbon dioxide-containing solution produced in the dissolution tank from the dissolution tank to the culture tank; a hydrogen supply flow passage for supplying hydrogen to the dissolution tank or the culture tank; and a methane discharge flow passage for discharging the produced methane from the culture tank.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a methane generator and a method for producing methane. [Background technology]

[0002] Methanation is a technology for producing methane from carbon dioxide and hydrogen, and is considered a promising technology that will contribute to achieving carbon neutrality, which means reducing the overall emission of greenhouse gases such as carbon dioxide to zero. For example, Patent Documents 1 to 3 propose methanation technologies for producing methane from carbon dioxide in exhaust gases from thermal power plants, factories, etc.

[0003] These methanation technologies require an increase in the carbon dioxide concentration of the feed gas in order to increase the concentration of methane produced by methanation. Because the carbon dioxide concentration in exhaust gas from thermal power plants and factories is low at around 10%, it is necessary to concentrate the carbon dioxide to a high concentration of over 90% using a carbon dioxide separation and capture device. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2021-151196 [Patent Document 2] Japanese Patent Application Laid-Open No. 2004-321857 [Patent Document 3] Japanese Patent Application Laid-Open No. 2014-148934 Summary of the Invention [Problem to be solved by the invention]

[0005] Changing the carbon dioxide concentration from low to high using a carbon dioxide capture device is technically difficult, and there are issues such as the need for a large equipment area and a large amount of cost. Therefore, there is thought to be demand for a methanation system that does not require carbon dioxide concentration and uses gas with low carbon dioxide concentration as a carbon dioxide supply source.

[0006] The present disclosure aims to provide a methanation system that has good conversion efficiency from carbon dioxide to methane even when a gas with a low concentration of carbon dioxide is used as a carbon dioxide supply source, and that allows for simplification of the device and a reduction in installation area. [Means for solving the problem]

[0007] [1] a dissolution tank for exposing the aqueous phase to a carbon dioxide-containing gas to produce a carbon dioxide-containing solution; a culture tank for cultivating methanogens in a culture solution to produce methane; a carbon dioxide gas supply passage for introducing a carbon dioxide-containing gas into the dissolution tank; A solution transfer means for transferring the carbon dioxide-containing solution produced in the dissolution tank from the dissolution tank to the culture tank; a hydrogen supply channel for supplying hydrogen to the dissolution tank or the culture tank; a methane discharge flow path for discharging the produced methane from the culture tank; A methane generating device comprising: [2] The dissolution tank and the culture tank are separate tanks, The solution transfer means is a solution transfer flow path connecting the dissolution tank and the culture tank. The methane generator described in [1] above. [3] The methane generation apparatus according to [2] above, wherein the solution transfer flow path is a flow path that supplies the carbon dioxide-containing solution in the dissolution tank to the culture tank without oxygen removal treatment. [4] The methane generator includes a single tank that serves as both the dissolution tank and the culture tank, The methane generator further includes a gas phase discharge flow path for discharging excess gas when the single tank functions as the culture tank; the aqueous phase is a culture medium, The solution transfer means is a switching means for switching between a dissolution tank and a culture tank, the switching means includes valves that open and close the carbon dioxide gas supply flow path, the hydrogen supply flow path, the gas phase discharge flow path, and the methane discharge flow path, and a control unit that controls the opening and closing of the valves, The control unit (i) a dissolution tank mode in which the carbon dioxide gas supply channel and the gas phase discharge channel are opened and the hydrogen supply channel and the methane discharge channel are closed, so that the single tank functions as a dissolution tank; (ii) a culture tank mode in which the single tank functions as a culture tank by closing the carbon dioxide gas supply flow path and the gas phase discharge flow path and opening the hydrogen supply flow path and the methane discharge flow path; Controlling the switching of The methane generator described in [1] above. [5] The methane generation apparatus according to [4] above, further comprising a reuse flow path for joining the excess gas phase discharged from the gas phase discharge flow path to the carbon dioxide-containing gas introduction section. [6] The methane generator comprises a single tank having a partition therein through which liquid can pass; Each tank compartment separated by the partition functions as the dissolution tank and the culture tank, The solution transfer means is the partition. The methane generator described in [1] above. [7] The methane generation apparatus described in [6] above, wherein the partition has an opening that can be opened and closed. [8] The methane generation apparatus according to [6] above, wherein the partition is a membrane that allows liquid to pass through but not microorganisms. [9] The methane generation apparatus according to any one of [1] to [3], [6] and [7] above, wherein the dissolution tank further comprises a gas phase discharge flow path for discharging excess gas phase in the dissolution tank.

[10] The methane generation apparatus according to [9] above, further comprising a reuse flow path for joining the excess gas phase discharged from the gas phase discharge flow path to the carbon dioxide-containing gas introduction section.

[11] a culture solution discharge flow path for discharging the culture solution from the culture tank; a microorganism removal device for removing microorganisms, excess water, or both from the culture solution discharged from the culture solution discharge channel; a reused culture solution supply flow path for supplying the culture solution from which microorganisms have been removed by the microorganism removal device to the dissolution tank for reuse; The methane generator according to any one of [1] to

[10] above, further comprising:

[12] The methane generator according to any one of the above [1] to

[11] , wherein the carbon dioxide-containing gas is a combustion exhaust gas.

[13] The methane generation apparatus according to [2] or [3] above, further comprising an adjustment unit that adjusts the amount of carbon dioxide-containing solution in the dissolution tank supplied from the carbon dioxide-containing solution supply flow path to the culture tank and the amount of hydrogen supplied from the hydrogen supply flow path, based on the carbon dioxide concentration of the culture solution in the culture tank or the outflow rate of the culture solution, and the carbon dioxide concentration of the liquid phase in the dissolution tank or the inflow rate of the liquid phase.

[14] exposing the aqueous phase to a carbon dioxide-containing gas in a dissolution tank; A solution transfer means for transferring the carbon dioxide-containing solution from the dissolution tank to the culture tank; Supplying hydrogen to the culture tank; Cultivating methanogens in a culture medium in the culture tank to produce methane; Discharging the produced methane from the culture tank; A method for producing methane, comprising: [Effects of the Invention]

[0008] According to the present disclosure, it is possible to provide a methanation system that has good conversion efficiency from carbon dioxide to methane even when a gas with a low concentration of carbon dioxide is used as a carbon dioxide supply source, and that allows for simplification of the device and a reduction in installation area. [Brief explanation of the drawings]

[0009] [Figure 1] 1 shows the configuration of a methane generation device according to a first embodiment of the present disclosure. [Figure 2] 1 shows the configuration of a methane generation apparatus according to a second embodiment of the present disclosure. [Figure 3] 10 shows the configuration of a methane generation apparatus according to a third embodiment of the present disclosure. [Figure 4] 10 shows the configuration of a methane generation apparatus according to a fourth embodiment of the present disclosure. [Figure 5] 10 shows the configuration of a methane generation apparatus according to a fifth embodiment of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0010] The present invention will be described in detail below, with reference to the drawings as necessary. However, the drawings are merely examples for explaining the present invention, and the technical scope of the present invention is not limited by the examples shown in the drawings.

[0011] (methane generator) The methane generation device of the present disclosure comprises: a dissolution tank for exposing the aqueous phase to a carbon dioxide-containing gas to produce a carbon dioxide-containing solution; a culture tank for cultivating methanogens in a culture solution to produce methane; a carbon dioxide gas supply passage for introducing a carbon dioxide-containing gas into the dissolution tank; A solution transfer means for transferring the carbon dioxide-containing solution from the dissolution tank to the culture tank; a hydrogen supply channel for supplying hydrogen to the dissolution tank or the culture tank; a methane discharge flow path for discharging the produced methane from the culture tank; Equipped with.

[0012] In the methane generation apparatus disclosed herein, carbon dioxide is supplied to a methanogen culture solution not by supplying the carbon dioxide-containing gas to the culture solution in gaseous form, but by exposing the carbon dioxide-containing gas to an aqueous phase. By supplying carbon dioxide in the form of a carbon dioxide-containing solution, even if the carbon dioxide concentration of the carbon dioxide-containing gas serving as the carbon dioxide supply source is low, the carbon dioxide concentration of the carbon dioxide-containing solution can be increased, thereby improving the efficiency of methane production by methanogens (e.g., the efficiency of methane conversion from carbon dioxide, etc.) and improving methanation efficiency. Furthermore, since only a small amount of gas components other than carbon dioxide (e.g., poorly water-soluble gases such as nitrogen gas and oxygen gas) in the carbon dioxide-containing gas serving as the carbon dioxide supply source are dissolved in the carbon dioxide-containing solution, removal of these gas components other than carbon dioxide is not required. This eliminates the need for equipment for removing gas components other than carbon dioxide, thereby reducing the space required for the apparatus.

[0013] <Configuration of methane generation device> Examples of the form of the methane generator of the present disclosure include a two-tank type, a single-tank type, and a single-tank type with a partition. A two-tank type methane generator has a configuration in which the dissolution tank and the culture tank are separate tanks. A single-tank type methane generator has a configuration in which the dissolution tank and the culture tank are the same tank, and is used by switching between a dissolution tank mode in which the tank functions as a dissolution tank and a culture tank mode in which the tank functions as a culture tank. A single-tank type methane generator with a partition has a single tank with a partition within the tank through which liquid can pass, and each compartment within the tank separated by the partition functions as the dissolution tank and the culture tank, respectively.

[0014] <Dissolution tank> The dissolution tank is a tank for dissolving carbon dioxide in the aqueous phase and producing a carbon dioxide-containing solution by exposing the aqueous phase held in the dissolution tank to a carbon dioxide-containing gas introduced from a carbon dioxide-containing gas inlet. The carbon dioxide-containing gas is usually introduced into the aqueous phase by bubbling. The carbon dioxide-containing solution is supplied to the culture tank. In the methane generation apparatus disclosed herein, the dissolution tank and the culture tank are configured as separate tanks, so that the carbon dioxide used for methanation is supplied to the culture tank in the form of a carbon dioxide-containing solution. Therefore, even if the carbon dioxide concentration in the carbon dioxide-containing gas serving as the carbon dioxide supply source is low, it can be supplied to the culture tank as a carbon dioxide-containing solution with a sufficiently high concentration, allowing methanation to proceed sufficiently. Therefore, even gases with a relatively low carbon dioxide gas concentration can be used as a carbon dioxide supply source.

[0015] <<Carbon dioxide>> In methanation, it is usually preferable to use a gas with a relatively high carbon dioxide concentration as the carbon dioxide-containing gas that serves as the carbon dioxide supply source. However, in the methane generation apparatus of the present disclosure, as described above, not only gases with a relatively high carbon dioxide concentration but also gases with a relatively low carbon dioxide concentration can be used as the carbon dioxide supply source. Carbon dioxide-containing gases with low carbon dioxide concentrations, such as those with a carbon dioxide concentration of 15% vol or less, 12% vol or less, or 10% vol or less, can also be used. Examples of such gases include industrial exhaust gases such as combustion exhaust. Furthermore, the carbon dioxide-containing gas inlet can be used as an intake for taking in exhaust gas after methane combustion, and the exhaust gas after methane combustion can be used as the carbon dioxide-containing gas.

[0016] <<Aqueous phase>> The aqueous phase is not particularly limited, and examples thereof include a culture solution, a nutrient-containing solution, physiological saline, and water. From the viewpoint of suppressing stress on methanogens, the aqueous phase is preferably a culture solution or a nutrient-containing solution, and from the viewpoint of simplifying the apparatus, the aqueous phase is preferably a culture solution. Examples of nutritional components contained in the nutrient-containing solution include sugars, nucleic acids, proteins, and protein hydrolysates (e.g., amino acids, peptides, etc.). Indicators of the concentration of nutrient components include direct measurements of the concentrations of these components, and the total content of one or more atoms of carbon atoms, nitrogen atoms, sulfur atoms, and phosphorus atoms.

[0017] << Carbon dioxide-containing solution >> The carbon dioxide-containing solution obtained in the dissolution tank serves as a carbon dioxide source for methane production by methanogen cultivation. Because carbon dioxide is dissolved in the aqueous phase in the dissolution tank, the carbon dioxide concentration of the carbon dioxide-containing solution can be increased. A high carbon dioxide concentration in the carbon dioxide-containing solution improves the efficiency of methane production by methanogens (e.g., the efficiency of converting carbon dioxide to methane), and thus improves methanation efficiency.

[0018] <Culture tank> The culture tank is a tank for culturing methanogens in a culture solution to produce methane from carbon dioxide and hydrogen. Carbon dioxide is supplied from a dissolution tank in the form of a carbon dioxide-containing solution. Hydrogen is supplied from a hydrogen supply channel, usually in the form of hydrogen gas, and is introduced into the culture solution by, for example, bubbling. Methane produced by the methanogens is discharged from a produced gas discharge section.

[0019] <<Methane-producing bacteria>> Methanogens include Methanobacterium alcaliphilum, Methanobacterium bryantii, Methanobacterium congolense, Methanobacterium defluvii, Methanobacterium espanolae, Methanobacterium formicicum, Methanobacterium ivanovii, Methanobacterium palustre, Methanobacterium thermaggregans, and Methanobacterium uliginosum. uliginosum, Methanobrevibacter acididurans, Methanobrevibacter arboriphilicus, Methanobrevibacter gottschalkii, Methanobrevibacter olleyae, Methanobrevibacter ruminantium, Methanobrevibacter smithii, Methanobrevibacter woesei, Methanobrevibacter wolinii, Methanothermobacter marburgensis marburgensis, Methanothermobacter thermoautotrophicusMethanothermobacter thermoautotrophicus, Methanobacterium thermoautotrophicus, Methanothermobacter thermoflexus, Methanothermobacter thermophilics, Methanothermobacter wolfeii, Methanothermus sociabilis, Methanocorpusculum bavaricum, Methanocorpusculum parvum, Methanoculleus chikuoensis, Methanoculleus submarinus, Methanogenium frigidum Examples of such bacteria include Methanogenium frigidum, Methanogenium liminatans, Methanogenium marinum, Methanomicrobium mobile, Methanocaldococcus jannaschii, Methanococcus aeolicus, Methanococcus maripaludis, Methanococcus vannielii, Methanococcus voltaei, and Methanothermococcus thermolithotrophicus.

[0020] <<Culture solution>> The culture medium may be, for example, a conventional medium used for culturing methanogens. Examples of medium components include sugars, nucleic acids, proteins, protein hydrolysates (e.g., amino acids, peptides, etc.), ocean water, lake water, marine sediments, lake sediments, salts, pH adjusters, etc. These medium components may be contained in the form of, for example, milk or meat juice, or hydrolysates thereof, yeast, or yeast extract.

[0021] <<Culture temperature>> The culture temperature may be, for example, 35° C. or higher, preferably 40° C. or higher, more preferably 45° C. or higher, or may be, for example, 65° C. or lower, preferably 60° C. or lower, more preferably 55° C. or lower. However, the optimal culture temperature may vary depending on the type of methanogen.

[0022] <Solution transfer means> The methane generation apparatus of the present disclosure includes, as a solution transfer means for transferring a carbon dioxide-containing solution from a dissolution tank to a culture tank, (a) A solution transfer channel connecting the dissolution tank and the culture tank; (b) a switching means for switching between the dissolution tank and the culture tank; or (c) Liquid-permeable partition Equipped with.

[0023] When the methane generation apparatus of the present disclosure is a two-tank type, the solution transfer means is the above-mentioned (a) solution transfer flow path. The solution transfer flow path serves as a flow path for supplying the aqueous phase (carbon dioxide-containing solution) exposed to the carbon dioxide-containing gas in the dissolution tank to the culture tank. In addition, instead of the solution transfer flow path, a container or the like for temporarily holding the aqueous phase to be pumped from the dissolution tank and introduced into the culture tank may be used. Furthermore, from the viewpoint of simplifying the equipment and reducing the equipment space, it is preferable that the solution transfer flow path is a flow path that supplies the solution to the culture tank without oxygen removal treatment.

[0024] When the methane generation apparatus of the present disclosure is a single-tank type, the solution transfer means is the above-mentioned (b) switching means. Examples of the switching means include means including valves that open and close the carbon dioxide gas supply flow path, the hydrogen supply flow path, the gas phase discharge flow path, and the methane discharge flow path, and a control unit that controls the opening and closing of the valves. Such a control unit includes: (i) a dissolution tank mode in which the carbon dioxide gas supply channel and the gas phase discharge channel are opened and the hydrogen supply channel and the methane discharge channel are closed, so that the single tank functions as a dissolution tank; (ii) a culture tank mode in which the single tank functions as a culture tank by closing the carbon dioxide gas supply flow path and the gas phase discharge flow path and opening the hydrogen supply flow path and the methane discharge flow path; The switching of the above may be controlled.

[0025] When the methane generation apparatus of the present disclosure is a single-tank type with a partition, the solution transfer means is (c) a partition that allows liquid to pass through. Examples of such a partition include a partition with an openable opening, and a membrane that allows liquid to pass through but not microorganisms. When the partition is a partition with an openable opening, the methane generation apparatus of the present disclosure may further include a means for applying pressure to the aqueous phase in the dissolution tank when the partition is opened, or a means for applying negative pressure to the culture solution in the culture tank. Examples of membranes that allow liquid to pass through but not microorganisms include resin filtration membranes with pore sizes of approximately 0.1 to 1 μm.

[0026] <Gas phase exhaust flow path, reuse flow path> The methane generator of the present disclosure may further include a gas phase discharge flow path for discharging the gas phase from the dissolution tank. Furthermore, when the methane generator includes a gas phase discharge flow path, the methane generator of the present disclosure may further include a reuse flow path for merging the gas phase discharged from the gas phase discharge flow path into the carbon dioxide gas supply flow path. By including a reuse flow path in the methane generator of the present disclosure, the dissolution rate of carbon dioxide in the carbon dioxide-containing gas can be improved, and the carbon dioxide concentration in the carbon dioxide-containing solution can be increased, thereby improving the methane conversion efficiency and suppressing the emission of undissolved carbon dioxide from the methane generator, thereby achieving the purpose of methanation. Furthermore, when the methane generator of the present disclosure is a single-tank type and includes a gas phase discharge flow path from the dissolution tank, the gas phase is further discharged from the gas phase discharge flow path in the dissolution tank mode, and the discharge of the gas phase from the gas phase discharge flow path is further stopped in the culture tank mode.

[0027] <Culture solution reuse means> The methane generator of the present disclosure may further include, as a culture solution recycling means, a culture solution discharge channel for discharging the culture solution from the culture tank, and a recycled culture solution supply channel connecting the branching point of the culture solution discharge channel to the confluence point of the aqueous phase supply channel. The recycled culture solution supply channel may also include a microorganism removal device. These devices allow the culture solution used for cultivation to be recycled as a microorganism-free culture solution that can be used for carbon dioxide dissolution. Furthermore, excess water generated as a by-product of methane production can be removed to stabilize the culture solution composition. Examples of the microorganism removal device include a membrane separation device. Examples of the membrane separation device include a device that removes microorganisms, excess water, or both using a resin filtration membrane with a pore size of approximately 0.1 to 1 μm.

[0028] <Measuring equipment, adjustment section> The methane generation device of the present disclosure comprises: (a) Carbon dioxide concentration or pH of the liquid phase in the dissolver; (b) the inflow of the liquid phase in the dissolver; (c) the flow rate of the liquid phase from the dissolver to the culture vessel; (d) the carbon dioxide concentration or pH of the culture medium in the culture tank; (e) the amount of fermentation fluid flowing out of the fermentation tank; and / or (f) the liquid level of the culture medium in the culture vessel; The methane generation device of the present disclosure may further include a measuring device for measuring the carbon dioxide concentration. The carbon dioxide concentration may be measured using pH as an index. (c) the flow rate of the liquid phase from the dissolution tank to the fermentation tank; and / or (g) Amount of hydrogen supplied from the hydrogen supply unit to the culture tank The methane generation apparatus of the present disclosure may further include an adjusting unit that adjusts the amount of carbon dioxide-containing solution supplied to the culture tank from the carbon dioxide-containing solution supply unit and the amount of hydrogen supplied from the hydrogen supply unit, based on the carbon dioxide concentration of the culture solution in the culture tank or the outflow rate of the culture solution, and the carbon dioxide concentration of the liquid phase in the dissolution tank or the inflow rate of the liquid phase. Each of the above parameters may be controlled within the above-mentioned preferred range.

[0029] <Configuration example of methane generation device> The methane generator (1) of the present disclosure may have the following configuration, for example.

[0030] In the first embodiment (FIG. 1), the methane generator (1) of the present disclosure is a two-chamber methane generator 1. The two-chamber methane generator 1 includes two separate chambers, a dissolution chamber (100) and a culture chamber (200), as well as a carbon dioxide gas supply unit (carbon dioxide gas supply flow path (101), a carbon dioxide gas supply port (102)), a solution transfer flow path (103), a hydrogen supply unit (hydrogen supply flow path (301), a hydrogen supply port (302)), and a methane discharge unit (methane discharge port (201), a methane discharge flow path (202)). FIG. 1 also shows an optional configuration in which the two-chamber methane generator (1) further includes a gas phase discharge section (gas phase outlet (104), gas phase discharge channel (107)), an aqueous phase supply channel (401), a culture solution discharge channel (402), and a recycled culture solution supply channel for transporting used culture solution from a branching point (404) of the culture solution discharge channel (402) to a joining point (403) of the aqueous phase supply channel (401).

[0031] In the second embodiment (FIG. 2), the methane generator (1) of the present disclosure is a single-tank type methane generator (1) and further includes a gas phase discharge section (gas phase discharge flow path (107)). The left figure shows the dissolution tank mode, and the right figure shows the culture tank mode. In both figures, the carbon dioxide gas supply flow path (101) and the hydrogen supply flow path (301) join via a switching valve and are connected to the single tank (100", 200") at the gas supply port (102"). The flow path connected from the single tank (100", 200") at the gas phase discharge port (104") branches into the gas phase discharge flow path (107) and the gas phase (methane) discharge flow path (202) via a switching valve. In the dissolution tank mode (left diagram), the carbon dioxide gas supply channel (101) and the gas phase discharge channel (107) are open, and the hydrogen supply channel (301) and the gas phase (methane) discharge channel (202) are closed, and the single tank functions as a single tank (100'') in the dissolution tank mode. In the fermentation tank mode (right diagram), the hydrogen supply channel (301) and the gas phase (methane) discharge channel (202) are open, and the carbon dioxide gas supply channel (101) and the gas phase discharge channel (107) are closed, and the single tank functions as a single tank (200'') in the fermentation tank mode.

[0032] In the third embodiment (FIG. 3), the methane generator (1) of the present disclosure is a partitioned single-tank methane generator (1) having a partition (501) that allows liquid to pass through the single tank (500). The interior of the tank is divided by the partition (501) into a dissolution compartment (100a) that functions as a dissolution tank and a culture compartment (200a) that functions as a culture tank. The partitioned single-tank methane generator (1) further includes a gas phase discharge unit (gas phase discharge port (104), a gas phase discharge flow path (107)) and a recycled culture solution supply unit (aqueous phase (culture solution) supply flow path (401), an aqueous phase (culture solution) discharge flow path (402), a branching portion (403), and a confluence portion (404)).

[0033] In the fourth embodiment (FIG. 4), the methane generation apparatus (1) of the present disclosure has a configuration in which the two-tank methane generation apparatus (1) of the first embodiment further includes a microorganism removal device (membrane separation device (405)) in the reuse culture solution supply flow path.

[0034] In a fifth embodiment (FIG. 5), a methane generator (1) according to the present disclosure is configured by adding a flow meter (406) for measuring the liquid flow rate in the aqueous phase (culture solution) supply channel (401), the solution transfer channel (103), and the culture solution discharge channel (402) to the two-chamber methane generator (1) of the fourth embodiment, a pH meter (407) for measuring the pH of the aqueous phase (111) in the dissolution tank (100) and the culture solution (211) in the culture tank (200), and a level meter (408) for measuring the liquid levels of the aqueous phase (111) in the dissolution tank (100) and the culture solution (211) in the culture tank (200). For example, pH is an indicator of the carbon dioxide concentration in the aqueous phase and the suitability of the culture solution for methanogen cultivation. Based on these measurements, the supply amounts of carbon dioxide-containing gas, hydrogen, and aqueous phase, the amount of aqueous phase transferred through the solution transfer channel (103), and the like may be controlled.

[0035] (Method of generating methane) The methane production method of the present disclosure includes: exposing the aqueous phase to a carbon dioxide-containing gas in a dissolution tank; Transferring the carbon dioxide-containing solution from the dissolution tank to a culture tank; Supplying hydrogen to the culture tank; Cultivating methanogens in a culture medium in the culture tank to produce methane; Discharging methane from the culture tank; Includes.

[0036] The methane production method of the present disclosure can be carried out using the methane production apparatus of the present disclosure described above. Examples of the form of the apparatus for carrying out the methane production method of the present disclosure include the two-tank type, single-tank type, and partitioned single-tank type described above.

[0037] When a two-tank methanogen is used as the apparatus for performing the methane generation method of the present disclosure, the step of transferring the carbon dioxide-containing solution from the dissolution tank to the culture tank is performed by supplying the carbon dioxide-containing solution in the dissolution tank to the culture tank. This step is not particularly limited, but may be performed, for example, by transferring the carbon dioxide-containing solution through an aqueous flow path connecting the dissolution tank and the culture tank, or by pumping the carbon dioxide-containing solution from the dissolution tank and introducing it into the culture tank. This step may also be performed by supplying the carbon dioxide-containing solution in the dissolution tank to the culture tank without oxygen removal treatment, or by directly supplying the carbon dioxide-containing solution in the dissolution tank to the culture tank.

[0038] When a partitioned single-tank type apparatus is used as the apparatus for performing the methane production method of the present disclosure, the step of transferring the carbon dioxide-containing solution from the dissolution tank to the culture tank may be performed by opening the partition, using, for example, a partition with an openable opening, a membrane that allows liquid to pass but not microorganisms to pass, etc. When the partition has an openable opening, the step may be performed by applying pressure to the aqueous phase in the dissolution tank or applying negative pressure to the culture solution in the culture tank when the partition is opened.

[0039] When a single-tank type apparatus is used as the apparatus for performing the methane production method of the present disclosure, the step of transferring the carbon dioxide-containing solution from the dissolution tank to the culture tank is (i) a dissolution tank mode in which the tank functions as a dissolution tank by supplying a carbon dioxide-containing gas from the carbon dioxide-containing gas inlet to the tank and stopping the supply of hydrogen from the hydrogen supply unit to the single tank and the discharge of methane from the product gas discharge unit; (ii) A culture tank mode in which the tank functions as a culture tank by stopping the supply of carbon dioxide-containing gas from the carbon dioxide-containing gas inlet to the tank, and supplying hydrogen from the hydrogen supply unit to the single tank and discharging methane from the produced gas discharge unit. This may be achieved by controlling the switching of the

[0040] The methane production method of the present disclosure may further include a step of discharging the gas phase in the dissolution tank, a step of merging the gas phase discharged from the gas phase discharge part with the carbon dioxide-containing gas introduction part, a step of discharging the culture solution from the culture tank, a step of removing microorganisms, excess water, or both from the culture solution discharged from the discharge part, and a step of supplying the culture solution from which microorganisms have been removed using a microorganism removal device to the dissolution tank.

[0041] The methane production method of the present disclosure also includes: (a) Carbon dioxide concentration or pH of the liquid phase in the dissolver; (b) the inflow of the liquid phase in the dissolver; (c) the flow rate of the liquid phase from the dissolver to the culture vessel; (d) the carbon dioxide concentration or pH of the culture medium in the culture tank; (e) the amount of fermentation fluid flowing out of the fermentation tank; and / or (f) the liquid level of the culture medium in the culture vessel; The carbon dioxide concentration may be measured using pH as an index. The methane production method of the present disclosure may further include a step of measuring the carbon dioxide concentration. (c) the flow rate of the liquid phase from the dissolution tank to the fermentation tank; and / or (g) Amount of hydrogen supplied from the hydrogen supply unit to the culture tank The step of adjusting the

[0042] The conditions for the methane generation method of the present disclosure can be the same as those described for the methane generation apparatus of the present disclosure. [Industrial Applicability]

[0043] According to the present disclosure, it is possible to provide a methanation system that has good conversion efficiency from carbon dioxide to methane even when a gas with a low concentration of carbon dioxide is used as a carbon dioxide supply source, and that allows for simplification of the device and a reduction in installation area. [Explanation of symbols]

[0044] 1. Methane production system 100 Dissolution tank 100'' Single Tank in Dissolver Mode 100a Dissolution Section 101 carbon dioxide gas supply channel 102 Carbon dioxide gas supply port 102'' gas supply port 103 Solution transport channel 104 Gas phase outlet 104'' Gas phase outlet 107 Gas phase exhaust flow path 111 Water phase 112 Gas Phase 200 culture tank 200'' Single tank in fermentor mode 200a culture compartment 201 Gas phase (methane) outlet 202 Gas phase (methane) exhaust flow path 211 Aqueous phase (culture solution) 212 Gas Phase 301 Hydrogen supply channel 302 Hydrogen supply port 401 Aqueous phase (culture solution) supply channel 402 Aqueous phase (culture solution) discharge channel 403 Junction 404 Branch 405 Membrane separation equipment 406 Flowmeter 407 pH meter 408 Level Gauge 500 Single tank with partition 501 Divider

Claims

1. a dissolution tank for exposing the aqueous phase to a carbon dioxide-containing gas to produce a carbon dioxide-containing solution; a culture tank for cultivating methanogens in a culture solution to produce methane; a carbon dioxide gas supply passage for introducing a carbon dioxide-containing gas into the dissolution tank; A solution transfer means for transferring the carbon dioxide-containing solution produced in the dissolution tank from the dissolution tank to the culture tank; a hydrogen supply channel for supplying hydrogen to the dissolution tank or the culture tank; a methane discharge flow path for discharging the produced methane from the culture tank; A methane generating device comprising:

2. The dissolution tank and the culture tank are separate tanks, The solution transfer means is a solution transfer flow path connecting the dissolution tank and the culture tank. The methane generator according to claim 1 .

3. The methane generation apparatus according to claim 2 , wherein the solution transfer flow path is a flow path that supplies the carbon dioxide-containing solution in the dissolution tank to the culture tank without oxygen removal treatment.

4. The methane generator includes a single tank that serves as both the dissolution tank and the culture tank, The methane generator further includes a gas phase discharge flow path for discharging excess gas when the single tank functions as the culture tank; the aqueous phase is a culture medium, The solution transfer means is a switching means for switching between a dissolution tank and a culture tank, the switching means includes valves that open and close the carbon dioxide gas supply flow path, the hydrogen supply flow path, the gas phase discharge flow path, and the methane discharge flow path, and a control unit that controls the opening and closing of the valves, The control unit (i) a dissolution tank mode in which the carbon dioxide gas supply passage and the gas phase discharge passage are opened and the hydrogen supply passage and the methane discharge passage are closed, so that the single tank functions as a dissolution tank; (ii) a culture tank mode in which the single tank functions as a culture tank by closing the carbon dioxide gas supply flow path and the gas phase discharge flow path and opening the hydrogen supply flow path and the methane discharge flow path; Controlling the switching of The methane generator according to claim 1 .

5. The methane generator according to claim 4 , further comprising a reuse flow path for allowing the excess gas phase discharged from the gas phase discharge flow path to join the carbon dioxide-containing gas introduction part.

6. The methane generator comprises a single tank having a partition therein through which liquid can pass; Each tank compartment separated by the partition functions as the dissolution tank and the culture tank, The solution transfer means is the partition. The methane generator according to claim 1 .

7. The methane generator according to claim 6 , wherein the partition has an opening that can be opened and closed.

8. 7. The methanogen according to claim 6, wherein the partition is a membrane that allows liquid to pass through but not microorganisms.

9. The methane generator according to any one of claims 1 to 3, 6 and 7, wherein the dissolution tank further comprises a gas phase discharge flow path for discharging excess gas phase in the dissolution tank.

10. The methane generator according to claim 9 , further comprising a reuse flow path for allowing the excess gas phase discharged from the gas phase discharge flow path to join the carbon dioxide-containing gas introduction part.

11. a culture solution discharge flow path for discharging the culture solution from the culture tank; a microorganism removal device for removing microorganisms, excess water, or both from the culture solution discharged from the culture solution discharge channel; a reused culture solution supply flow path for supplying the culture solution from which microorganisms have been removed by the microorganism removal device to the dissolution tank for reuse; The methane generator according to any one of claims 1 to 7, further comprising:

12. The methane generator according to any one of claims 1 to 8, wherein the carbon dioxide-containing gas is a combustion exhaust gas.

13. 4. The methane generation apparatus according to claim 2 or 3, further comprising an adjustment unit that adjusts the amount of carbon dioxide-containing solution in the dissolution tank supplied from the carbon dioxide-containing solution supply flow path to the culture tank and the amount of hydrogen supplied from the hydrogen supply flow path, based on the carbon dioxide concentration of the culture solution in the culture tank or the outflow rate of the culture solution, and the carbon dioxide concentration of the liquid phase in the dissolution tank or the inflow rate of the liquid phase.

14. exposing the aqueous phase to a carbon dioxide-containing gas in a dissolution tank; A solution transfer means for transferring the carbon dioxide-containing solution from the dissolution tank to the culture tank; Supplying hydrogen to the culture tank; Cultivating methanogens in a culture medium in the culture tank to produce methane; Discharging the produced methane from the culture tank; A method for producing methane, comprising:

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