Carbon circulation system, carbon circulation method, and mobile body

Abstract

Provided is a carbon circulation system by a novel approach. This carbon circulation system (1A) is provided with a first mobile body (2A) and a power source regeneration device (3). The first moving body is provided with a recovery device (232) in which carbon dioxide generated when methanol is used by a prime mover (24) is reacted with calcium oxide to recover the carbon dioxide in the form of calcium carbonate. The power source regeneration device (3) is provided with: a decomposer (31) that decomposes the calcium carbonate recovered by the recovery device into calcium oxide and carbon dioxide; and a generator (32) that generates methanol by reacting the carbon dioxide generated in the decomposer with green hydrogen.

Description

Carbon circulation system, carbon circulation method, and mobile body

[0001] One aspect of the present disclosure relates to a carbon cycle system.

[0002] US Patent No. 5,949,999 discloses a solid oxide electrolysis cell for use in an active carbon recycling energy system.

[0003] Japanese Patent No. 7133171

[0004] One aspect of the present disclosure aims to realize a carbon circulation system using a new method not disclosed in Patent Document 1.

[0005] A carbon circulation system according to one aspect of the present disclosure is a carbon circulation system comprising a mobile body and a power source regeneration device, wherein the mobile body comprises a tank for storing synthetic fuel produced from carbon dioxide and hydrogen, a prime mover that generates mechanical power using the synthetic fuel, and a recovery device that comprises an oxide as an absorbent for absorbing carbon dioxide and recovers carbon dioxide generated when the prime mover uses the synthetic fuel as carbonate by reacting it with the absorbent, and the power source regeneration device comprises a decomposer that decomposes the carbonate recovered by the recovery device into oxide and carbon dioxide, and a generator that produces the synthetic fuel by reacting the carbon dioxide generated in the decomposer with hydrogen.

[0006] A carbon circulation system according to one aspect of the present disclosure is a carbon circulation system comprising a mobile body and a power source regeneration device, wherein the mobile body comprises a tank that stores synthetic fuel produced from carbon dioxide and hydrogen as a power source, a prime mover that generates mechanical power using the synthetic fuel, a recovery device that has an oxide as an absorbent that absorbs carbon dioxide and recovers carbon dioxide generated when the prime mover uses the synthetic fuel by reacting it with the absorbent, and a heat-generating element that generates heat in the recovery device and decomposes the carbonate recovered by the recovery device into oxide and carbon dioxide, and the power source regeneration device comprises a generator that produces the synthetic fuel by reacting the carbon dioxide obtained by decomposition of the carbonate recovered by the recovery device in the mobile body with hydrogen.

[0007] A carbon circulation method according to one aspect of the present disclosure is a carbon circulation method realized by a carbon circulation system including a mobile body and a power source recycling device, and includes: a recovery process in which carbon dioxide generated when the mobile body uses a synthetic fuel produced from carbon dioxide and hydrogen to generate mechanical power is recovered as carbonate by reacting the carbon dioxide with an oxide that acts as an absorbent that absorbs carbon dioxide; a decomposition process in which the power source recycling device decomposes the carbonate recovered in the recovery process into an oxide and carbon dioxide; a production process in which the power source recycling device reacts the carbon dioxide generated in the decomposition process with hydrogen to produce the synthetic fuel; and a supply process in which the oxide obtained in the decomposition process and the synthetic fuel obtained in the production process are supplied from the power source recycling device to the mobile body.

[0008] A carbon circulation method according to one aspect of the present disclosure is a carbon circulation method realized by a carbon circulation system including a mobile body and a power source recycling device, and includes: a recovery process in which the mobile body recovers carbon dioxide generated when using a synthetic fuel produced from carbon dioxide and hydrogen to generate mechanical power by reacting the carbon dioxide with an oxide that acts as an absorbent that absorbs carbon dioxide, as carbonates; a decomposition process in which the mobile body generates heat and decomposes the carbonates recovered in the recovery process into oxides and carbon dioxide; a production process in which the power source recycling device reacts the carbon dioxide generated in the decomposition process with hydrogen to produce the synthetic fuel; and a supply process in which the power source recycling device supplies the synthetic fuel obtained in the production process to the mobile body.

[0009] A mobile body according to one aspect of the present disclosure includes a tank that stores synthetic fuel produced from carbon dioxide and hydrogen, a hydrogen generator that generates hydrogen from the synthetic fuel supplied from the tank, a recovery device that includes an oxide as an absorbent material for absorbing carbon dioxide and recovers carbon dioxide generated when the hydrogen generator generates hydrogen as carbonate by reacting the carbon dioxide with the absorbent material, and a prime mover that includes a fuel cell that generates electric current by reacting the hydrogen generated by the hydrogen generator with oxygen and converts the electric current generated by the fuel cell into mechanical power.

[0010] According to a carbon circulation system, a carbon circulation method, and a mobile body according to an embodiment of the present disclosure, carbon dioxide emissions into the atmosphere can be reduced to almost zero. Furthermore, the absorbent that absorbed carbon dioxide can be reused in the mobile body. Furthermore, synthetic fuel can be supplied to the mobile body in a stable manner in accordance with carbon neutrality.

[0011] 1 is a block diagram schematically showing an example of a carbon circulation system according to Embodiment 1. FIG. 2 is a schematic cross-sectional view showing an example of the structure of a hydrogen supply device. FIG. 3 is a flowchart showing an example of a carbon circulation method implemented by the carbon circulation system shown in FIG. 1. FIG. 4 is a flowchart showing an example of a carbon circulation method implemented by the carbon circulation system shown in FIG. 4. FIG. 5 is a block diagram schematically showing an example of a carbon circulation system according to Embodiment 2. FIG. 6 is a schematic cross-sectional view showing an example of the structure of a collector. FIG. 7 is a flowchart showing an example of a carbon circulation method implemented by the carbon circulation system shown in FIG. 9. FIG. 9 is a perspective view showing an example of a silicon-impregnated silicon carbide porous carrier foam and an example of an absorption block. FIG. 10 is a schematic cross-sectional view showing an example of an assembly of absorption blocks attached to an experimental apparatus. FIG. 11 is a schematic view showing an example of an experimental apparatus. FIG. 12 is a graph showing an example of experimental results. FIG. 13 is a table showing the relative ratios of the mass and volume of various objects to the mass and volume of a hydrogen cylinder assumed for hydrogen storage in a fuel cell vehicle.

[0012] [Embodiment 1] <Carbon Circulation System> Fig. 1 is a block diagram that schematically illustrates an example of a carbon circulation system 1A. As shown in Fig. 1, the carbon circulation system 1A includes a first mobile object 2A and a power source regeneration device 3. The carbon circulation system 1A is a carbon-neutral system for mobile objects that can reduce carbon dioxide emissions into the atmosphere to almost zero by circulating carbon between the first mobile object 2A and the power source regeneration device 3. The carbon circulation system 1A can also be referred to as a carbon circulation mobility system.

[0013] The first moving body 2A is a moving body that is driven by mechanical power generated using synthetic fuel. The first moving body 2A is driven by converting an electric current generated using hydrogen obtained from the synthetic fuel into mechanical power. Various moving bodies can be used as the first moving body 2A, such as industrial vehicles, agricultural vehicles, aircraft, and ships. Various vehicles can be used as the vehicle, such as passenger cars, buses, trucks, tractors, and heavy machinery. Details of the first moving body 2A will be described later.

[0014] Synthetic fuel is a liquid fuel produced from carbon dioxide and hydrogen. The hydrogen used in synthetic fuel is called green hydrogen. Green hydrogen is hydrogen that is not derived from fossil fuels and is produced without emitting carbon dioxide during the production process. Green hydrogen is produced by electrolyzing water using electricity generated from renewable or nuclear energy. Synthetic fuel produced from carbon dioxide and green hydrogen is also called e-fuel.

[0015] Synthetic fuels include alcohol-based hydrocarbons, alkenes, alkanes, aromatics, etc. Examples of synthetic fuels include methane, methanol, ethanol, propane, light oils (e.g., diesel oil), and gasoline.

[0016] The power source regeneration device 3 is a device that regenerates synthetic fuel, which serves as a power source for the first moving body 2A. The power source regeneration device 3 is also a device that regenerates the absorbent material of a recovery device 232 (described below) provided in the first moving body 2A. The power source regeneration device 3 is disposed at a power source regeneration station that regenerates synthetic fuel. Considering convenience, the power source regeneration device 3 may be disposed at a location where the first moving body 2A can stop. In this case, examples of the power source regeneration station include a gas station for gasoline or diesel vehicles, a charging point for electric vehicles, a parking lot at a home or commercial facility, a bus stop, or an airport. Details of the power source regeneration device 3 will be described later.

[0017] In the following description, an example will be given in which the synthetic fuel is methanol.

[0018] <First Moving Body> As shown in FIG. 1, the first moving body 2A includes, for example, a fuel tank 21, a water tank 22, a hydrogen supply device 23, a motor 24, and a hydrogen purification device 25.

[0019] The fuel tank 21 is a tank that contains a power source for the first moving body 2 A. In this embodiment, the fuel tank 21 contains methanol as an example of synthetic fuel.

[0020] The fuel tank 21 stores methanol supplied from the power source recovery device 3. As will be described later, the methanol produced in the power source recovery device 3 is produced from green hydrogen. Furthermore, prior to receiving methanol from the power source recovery device 3 (during initial use of the first mobile body 2A), the fuel tank 21 is supplied with methanol produced from carbon dioxide and green hydrogen. The water tank 22 is a tank for storing water.

[0021] The hydrogen supply device 23 generates hydrogen by reacting the methanol stored in the fuel tank 21 with the water stored in the water tank 22, and supplies the generated hydrogen to the fuel cell 241 of the motor 24. The hydrogen supply device 23 includes, for example, a hydrogen generation pipe 231, a recovery device 232, a heater 233, and a porous catalyst block 261.

[0022] The hydrogen generation pipe 231 and the porous catalyst block 261 function as a hydrogen generator that generates hydrogen using methanol supplied from the fuel tank 21. The hydrogen generation pipe 231 and the porous catalyst block 261 generate hydrogen by causing a reaction between the methanol contained in the fuel tank 21 and the water contained in the water tank 22.

[0023] The collector 232 is provided with an absorbent material that absorbs carbon dioxide. The absorbent material is a solid oxide. The collector 232 reacts the carbon dioxide generated when the engine 24 uses synthetic fuel with the absorbent material, thereby capturing the carbon dioxide as carbonates.

[0024] In this embodiment, the recovery device 232 recovers carbon dioxide as carbonate by reacting the carbon dioxide generated when the hydrogen generation pipe 231 and the porous catalyst block 261 generate hydrogen with an absorbent. This allows the first mobile body 2A to generate hydrogen to power the fuel cell 241 and recover the carbon dioxide generated during hydrogen generation. In this embodiment, the recovery device 232 also includes an absorption block 262, which is a porous block supporting an absorbent.

[0025] The absorbent may be any material capable of absorbing carbon dioxide. Examples of the absorbent include metal oxides, calcium oxide, nickel oxide, cobalt oxide, magnesium oxide, strontium oxide, barium oxide, and mixtures thereof. When a mixture of these materials is used as the absorbent, the absorbent may contain an additive to promote the reaction of the mixture. Zeolite may also be used as the absorbent. The absorbent may be selected depending on the type of synthetic fuel used in the first moving body 2A.

[0026] In the following description, the absorbent is calcium oxide, and the recovery device 232 recovers carbon dioxide as calcium carbonate by reacting carbon dioxide with calcium oxide as the absorbent.

[0027] 2 is a schematic cross-sectional view showing an example of the structure of the hydrogen supply device 23. In this embodiment, the hydrogen supply device 23 includes a housing 235 in which a hydrogen generation tube 231, a recovery vessel 232, and a porous catalyst block 261 are disposed. In this embodiment, the housing 235 is a reaction tube in which a fuel reforming reaction and a carbonation reaction occur. The material of the housing 235 may be, for example, a metal.

[0028] An exhaust port 234 is provided at the top of the housing 235. In this embodiment, the exhaust port 234 discharges a mixed gas containing hydrogen generated in the hydrogen generation pipe 231 and the porous catalyst block 261. The exhaust port 234 is in communication with the fuel cell 241 via, for example, a pipe. The mixed gas contains carbon monoxide, water, and carbon dioxide in addition to hydrogen.

[0029] 1 and 2 , the first mobile body 2A is equipped with a hydrogen purifier 25. The hydrogen purifier 25 purifies (separates) hydrogen from the mixed gas discharged from the outlet 234. The hydrogen purifier 25 may be equipped with, for example, a filter that selectively allows hydrogen to pass through. This allows impurities other than hydrogen to be removed from the mixed gas discharged from the outlet 234, and highly purified hydrogen can be supplied to the fuel cell 241.

[0030] The hydrogen generation pipe 231 is a pipe that introduces the methanol contained in the fuel tank 21 and the water contained in the water tank 22 from the outside to the inside of the housing 235. The material of the hydrogen generation pipe 231 may be, for example, metal. In this embodiment, the hydrogen generation pipe 231 extends from the top to the bottom of the housing 235. As a result, the methanol and water flow to the bottom of the housing 235 due to their own weight. As the methanol and water flow inside the hydrogen generation pipe 231, they react with each other, and the hydrogen generation pipe 231 emits carbon dioxide and hydrogen. That is, in the hydrogen generation pipe 231, the fuel reforming reaction shown in the following formula (1) occurs: CHOH(l) + HO(l) = CO + 3H, ΔHref = +131 kJ mol -1 ...(1) is generated. The hydrogen generation pipe 231 may contain a fuel reforming catalyst therein that promotes the fuel reforming reaction.

[0031] As described above, the collector 232 includes the absorber block 262. The absorber block 262 is a porous block having calcium oxide on its surface. The absorber block 262 may be produced, for example, by applying calcium oxide powder to the surface of a porous carrier foam of silicon carbide.

[0032] The carbon dioxide discharged from the hydrogen generation pipe 231 is introduced into the absorption block 262 and is absorbed by the calcium oxide supported by the absorption block 262. At this time, in the absorption block 262, a carbonation reaction shown in the following formula (2) occurs: CaO(S) + CO2 = CaCO3(S), ΔHref = -178 kJ mol -1 ...(2) In other words, in the absorption block 262, carbon dioxide is recovered as calcium carbonate.

[0033] In this embodiment, the recovery unit 232 includes a plurality of absorption blocks 262. As shown in Fig. 2, the absorption blocks 262 are arranged in the housing 235 so that the carbon dioxide discharged from the hydrogen generation pipe 231 passes through the absorption blocks 262. Specifically, the absorption blocks 262 are arranged in the housing 235 so that no gaps are formed between the hydrogen generation pipe 231 and the absorption blocks 262, and between the housing 235 and the absorption blocks 262.

[0034] A porous catalyst block 261 is disposed between each absorption block 262. The porous catalyst block 261 is a porous block that supports a fuel reforming catalyst. The porous catalyst block 261 is a porous block that has a fuel reforming catalyst on its surface. The porous catalyst block 261 may be produced, for example, by immersing a silicon carbide porous carrier foam in a platinum aqueous solution and then drying the silicon carbide porous carrier foam. In this way, the porous catalyst block 261 in which the fuel reforming catalyst is supported on the silicon carbide porous carrier foam may be produced.

[0035] In addition to hydrogen and carbon dioxide, unreacted methanol and water that did not completely react in the hydrogen generation tube 231 are also discharged from the hydrogen generation tube 231. Even when unreacted methanol and water are discharged from the hydrogen generation tube 231, the porous catalyst block 261 can cause a fuel reforming reaction of the unreacted methanol and water. Therefore, even when unreacted methanol and water are discharged, hydrogen can be produced from the unreacted methanol and water. Therefore, the purity of the hydrogen discharged from the outlet 234 can be increased.

[0036] By appropriately adjusting the number and size of the porous catalyst blocks 261, it is possible to cause a fuel reforming reaction for almost all of the methanol supplied to the hydrogen generation pipe 231. Therefore, the hydrogen supply device 23 can supply hydrogen obtained from almost all of the methanol supplied to the hydrogen generation pipe 231 to the fuel cell 241. Furthermore, by appropriately adjusting the number and size of the absorption blocks 262, it is possible to have the absorption blocks 262 absorb almost all of the carbon dioxide generated during hydrogen generation.

[0037] In this embodiment, the porous catalyst block 261 is disposed inside the housing 235 so that no gaps are formed between the hydrogen generation tube 231 and the porous catalyst block 261, and between the housing 235 and the porous catalyst block 261. This allows the fuel reforming reaction of unreacted methanol to occur efficiently.

[0038] As shown in the above formula (1), the fuel reforming reaction is an endothermic reaction. Therefore, in order to cause the fuel reforming reaction, it is necessary to apply heat to the inside of the hydrogen generation tube 231 and the porous catalyst block 261. Therefore, as shown in FIGS. 1 and 2 , the hydrogen supply device 23 is equipped with a resistance heating type heater 233. In other words, the resistance heating type heater 233 is equipped in the recovery device 232.

[0039] In this embodiment, the heater 233 is wrapped around the inner or outer wall of the housing 235 along the extension direction of the hydrogen generation tube 231. This allows a fuel reforming reaction to occur using the methanol and water supplied to the hydrogen generation tube 231 and the porous catalyst block 261. The heater 233 may be disposed on the hydrogen generation tube 231 along the extension direction of the hydrogen generation tube 231.

[0040] On the other hand, as shown in the above formula (2), the carbonation reaction is an exothermic reaction. Therefore, after the carbonation reaction occurs, the heat generated in the carbonation reaction can be used in the fuel reforming reaction. That is, the hydrogen generation tube 231 and the porous catalyst block 261 can generate hydrogen from methanol using the heat generated by the reaction between carbon dioxide and calcium oxide in the recovery device 232. Therefore, the heat generated in the recovery device 232 can be used to promote the fuel reforming reaction in the hydrogen generation tube 231 and the porous catalyst block 261.

[0041] In this embodiment, as described above, the absorption block 262 is disposed adjacent to the periphery of the hydrogen generation pipe 231. That is, the hydrogen generation pipe 231 and the recovery device 232 are disposed adjacent to each other. In addition, in this embodiment, the absorption block 262 is also disposed adjacent to the porous catalyst block 261. That is, the porous catalyst block 261 and the recovery device 232 are disposed adjacent to each other. Therefore, with a simple configuration, the heat generated in the recovery device 232 can be utilized for the fuel reforming reaction in the hydrogen generation pipe 231 and the porous catalyst block 261.

[0042] When the hydrogen supply device 23 of this embodiment is used, the power generation efficiency of the fuel cell 241 exceeds 50%. This value is significantly higher than the 25% energy efficiency of an internal combustion engine, and is presumably due to the fact that the heat generated by the carbonation reaction can be effectively utilized in the fuel reforming reaction. Therefore, by utilizing the heat of the carbonation reaction in the fuel reforming reaction, it can be said that the fuel efficiency and driving distance of the first mobile object 2A can be improved.

[0043] Thus, in the hydrogen supply device 23, after the carbonation reaction occurs in the recovery device 232 (absorption block 262), the heat generated in the carbonation reaction can promote the fuel reforming reaction in the hydrogen generation pipe 231. At this time, the above formulas (1) and (2) are used to calculate the carbon dioxide capture type fuel reforming reaction shown in the following formula (3): CHOH(l) + HO(l) + CaO(S) = CaCO(S) + 3H↑, ΔHref = -47 kJ mol -1 ...(3) occurs.

[0044] As shown in formula (3) above, the carbon dioxide capture type fuel reforming reaction is an exothermic reaction. Therefore, after the carbonation reaction occurs, the fuel reforming reaction proceeds self-heating. Therefore, by arranging the hydrogen generation tube 231, the porous catalyst block 261, and the recovery device 232 adjacent to each other, the fuel reforming reaction can proceed after the carbonation reaction occurs without heating the hydrogen generation tube 231 with the heater 233.

[0045] The silicon carbide porous carrier foam described above is thermally and chemically stable, has high mechanical strength, and can reduce the occurrence of agglomerate growth. Furthermore, the silicon carbide porous carrier foam has high thermal conductivity. Therefore, by using the silicon carbide porous carrier foam in the absorption block 262, the heat generated in the heater 233 and the absorption block 262 can be quickly supplied to the hydrogen generation tube 231 and the porous catalyst block 261. Furthermore, by using the silicon carbide porous carrier foam in the porous catalyst block 261, the heat can be quickly supplied to the hydrogen generation tube 231 and circulated within the porous catalyst block 261.

[0046] Furthermore, silicon carbide is a resistor. Therefore, by supplying power to the absorbing block 262, the absorbing block 262 can be made to generate heat. In this case, the first moving body 2A may be provided with a power supply mechanism that supplies power to the absorbing block 262. The power supply mechanism may be controlled together with the heater 233. Furthermore, when the first moving body 2A is provided with a power supply mechanism, it is not necessary to provide the heater 233.

[0047] The material of the porous carrier foam may be, in addition to silicon carbide, for example, nickel, aluminum, copper, silicon nitride, alumina, stainless steel, or the like.

[0048] The hydrogen supply device 23 is detachably provided on the first mobile body 2A and can be attached to a decomposer 31 provided in the power source recovery device 3, which will be described later. By removing the hydrogen supply device 23 from the first mobile body 2A and attaching it to the decomposer 31, it is possible to increase the calcium oxide that has been reduced by recovering carbon dioxide in the recovery device 232. Then, the hydrogen supply device 23 equipped with the recovery device 232 in which the calcium oxide has been increased can be attached to the first mobile body 2A. Therefore, simply by attaching and detaching the hydrogen supply device 23 to and from the first mobile body 2A and the power source recovery device 3, it becomes possible to repeatedly recover carbon dioxide in the first mobile body 2A.

[0049] Of the hydrogen supply device 23, only the recovery device 232 (absorption block 262) may be provided so as to be detachable from the first moving body 2A, and may be attachable to the decomposer 31 provided in the power source recovery device 3. In this case, simply by attaching and detaching the recovery device 232 to and from the first moving body 2A and the power source recovery device 3, it becomes possible to repeatedly recover carbon dioxide in the first moving body 2A.

[0050] Furthermore, as described above, the hydrogen supply device 23 or recovery device 232 that is detachable from the first mobile body 2A and the power source regeneration device 3 is equipped with a resistance heating type heater 233 that has a relatively simple configuration. Therefore, even when the heater 233 is provided, the total volume and weight of the hydrogen supply device 23 or recovery device 232 can be reduced.

[0051] As shown in FIG. 1 , the prime mover 24 generates mechanical power using methanol. In this embodiment, the prime mover 24 includes a fuel cell 241 that generates current using hydrogen generated by the hydrogen generation tube 231 and the porous catalyst block 261. Specifically, the fuel cell 241 generates current by reacting the hydrogen generated by the hydrogen generation tube 231 and the porous catalyst block 261 with oxygen. The prime mover 24 converts the current generated by the fuel cell 241 into mechanical power, thereby driving the first moving body 2A. Various fuel cells can be used as the fuel cell 241, including, for example, a polymer electrolyte fuel cell (PEFC) and a solid oxide fuel cell (SOFC).

[0052] A solid polymer fuel cell requires hydrogen of higher purity than a solid oxide fuel cell. Therefore, when a solid polymer fuel cell is used as the fuel cell 241, it is preferable to provide a hydrogen purifier 25 in the first moving body 2A. When a solid oxide fuel cell is used as the fuel cell 241, it is also preferable to provide a hydrogen purifier 25 in the first moving body 2A, but it is not necessarily required. Furthermore, when high-purity hydrogen (hydrogen of a purity usable in the fuel cell 241) is discharged from the hydrogen supply device 23, it is not necessary to provide a hydrogen purifier 25 in the first moving body 2A.

[0053] (Reaction Flow in the Hydrogen Supply Device) An example of the reaction flow occurring in the hydrogen supply device 23 of this embodiment will be described. First, the heater 233 heats the hydrogen generation tube 231 to preheat it. If the first moving body 2A is equipped with a power supply mechanism, the power supply mechanism may supply power to the absorption block 262 to preheat the hydrogen generation tube 231. Thereafter, a pump (not shown) is driven to supply methanol from the fuel tank 21 and water from the water tank 22 to the hydrogen generation tube 231. As a result, a fuel reforming reaction occurs in the hydrogen generation tube 231, and unreacted methanol and water are discharged from the lower outlet of the hydrogen generation tube 231 along with hydrogen and carbon dioxide.

[0054] The hydrogen, carbon dioxide, unreacted methanol, and water discharged from the hydrogen generation tube 231 flow upward inside the lowest absorption block 262. During this process, a carbonation reaction occurs in the absorption block 262, resulting in the recovery of carbon dioxide and the generation of heat. This heat is supplied to the hydrogen generation tube 231, thereby further promoting the fuel reforming reaction in the hydrogen generation tube 231. In this state, the heater 233 may stop heating the hydrogen generation tube 231. The heating time may be set in advance.

[0055] Hydrogen, unrecovered carbon dioxide, unreacted methanol, and water flow from the lowest absorption block 262 to the adjacent porous catalyst block 261 above, and then flow upward inside the porous catalyst block 261. Because carbon dioxide is absorbed in the lowest absorption block 262, the carbon dioxide concentration in the porous catalyst block 261 is lower than the carbon dioxide concentration in the lowest absorption block 262. Therefore, the fuel reforming reaction (the forward reaction of the above formula (1)) progresses in the porous catalyst block 261.

[0056] The heat generated in the lowest absorption block 262 is also supplied to the adjacent porous catalyst block 261. Therefore, the porous catalyst block 261 can utilize this heat to advance the fuel reforming reaction.

[0057] The hydrogen, unrecovered carbon dioxide, unreacted methanol, and water flow from the porous catalyst block 261 to the adjacent absorption block 262 above, and then flow upward inside the absorption block 262. A carbonation reaction also occurs in the absorption block 262, where carbon dioxide is recovered and heat is generated. This heat is supplied to the hydrogen generation pipe 231 and the adjacent porous catalyst blocks 261 above and below. Therefore, the hydrogen generation pipe 231 and these porous catalyst blocks 261 can use this heat to promote a fuel reforming reaction.

[0058] The hydrogen, unrecovered carbon dioxide, unreacted methanol, and water flow to the adjacent porous catalyst block 261 above the second-lowest absorption block 262 and then flow upward through the porous catalyst block 261. In this manner, the hydrogen, carbon dioxide, methanol, and water alternately flow between the absorption block 262 and the porous catalyst block 261. During this process, each of the multiple absorption blocks 262 absorbs carbon dioxide, and each of the multiple porous catalyst blocks 261 produces hydrogen from methanol. Therefore, the hydrogen supply device 23 can achieve a conversion rate of methanol to hydrogen as close to 100% as possible, thereby supplying hydrogen to the fuel cell 241 with high purity. Furthermore, the hydrogen supply device 23 can reduce carbon dioxide emissions into the atmosphere to almost zero. Furthermore, the first mobile unit 2A includes a hydrogen purification device 25, enabling the supply of higher-purity hydrogen to the fuel cell 241.

[0059] In this embodiment, an example has been described in which the hydrogen supply device 23 includes a plurality of porous catalyst blocks 261 and absorption blocks 262, but the present invention is not limited to this, and the hydrogen supply device 23 may include one porous catalyst block 261 and one absorption block 262. Furthermore, if the combustion reforming reaction is sufficiently carried out in the hydrogen generation tube 231 and unreacted methanol and water are not discharged from the hydrogen generation tube 231, the hydrogen supply device 23 may include only the absorption block 262.

[0060] <Power Source Regeneration Device> As shown in FIG. 1, the power source regeneration device 3 includes, for example, a decomposer 31, a generator 32, a supply mechanism 33, and a hydrogen tank .

[0061] The decomposer 31 decomposes the calcium carbonate recovered by the recovery device 232 into calcium oxide and carbon dioxide. The decomposer 31 has a mounting section 311 to which the hydrogen supply device 23 or the recovery device 232 detached from the first mobile body 2A can be attached. With the recovery device 232 attached to the mounting section 311, the decomposer 31 supplies heat to the absorption block 262 that supports calcium carbonate by absorbing carbon dioxide. As a result, the decomposer 31 causes a decomposition reaction in the absorption block 262, as shown in the following formula (4): CaCO3(S) → CaO(S) + CO2 ... (4). As a result, the decomposer 31 can convert the calcium carbonate supported by the absorption block 262 into calcium oxide. In other words, the absorption block 262 can be restored to a state where it can absorb carbon dioxide.

[0062] The collector 232 is provided with a heater 233. Therefore, in the decomposer 31, with the collector 232 attached to the attachment part 311, the heater 233 heats the absorption block 262, thereby decomposing calcium carbonate into calcium oxide and carbon dioxide in the absorption block 262.

[0063] The power source regeneration device 3 may include a power supply mechanism that supplies power to the absorption block 262. In this case, the power supply mechanism supplies power to the absorption block 262, causing the absorption block 262 to self-heat, thereby decomposing calcium carbonate into calcium oxide and carbon dioxide. When the absorption block 262 is made to self-heat, the absorption block 262 can be heated more uniformly than when the absorption block 262 is heated by the heater 233. Therefore, when the absorption block 262 is made to self-heat, the decomposition reaction can be promoted more efficiently.

[0064] The generator 32 produces methanol by reacting the carbon dioxide generated in the decomposer 31 with hydrogen. The generator 32 is connected to the decomposer 31 via, for example, a pipe, so that the carbon dioxide generated in the decomposer 31 is supplied to the generator 32. Hydrogen is supplied to the generator 32 from the hydrogen tank 34 by driving a pump (not shown). As a result, the production reaction shown in the following equation (5) occurs in the generator 32: 3H + CO → CHOH(l) + H O(l) ... (5). At this time, green hydrogen is supplied to the generator 32 from the hydrogen tank 34. The hydrogen tank 34 is a tank that stores green hydrogen.

[0065] When connected to the fuel tank 21, the supply mechanism 33 supplies the methanol produced by the generator 32 to the fuel tank 21. This allows the first moving body 2A to use the methanol produced from the carbon dioxide collected by the first moving body 2A. Therefore, the first moving body 2A can reuse the collected carbon dioxide as a power source.

[0066] The supply mechanism 33 may include, for example, a hose with a nozzle and a tank that stores the methanol generated by the generator 32. The first movable body 2A may also include a supply port that communicates with the fuel tank 21 via, for example, a pipe. In this case, the supply mechanism 33 supplies the methanol generated by the generator 32 to the fuel tank 21 by sending the methanol stored in the tank to the hose with the nozzle inserted into the supply port.

[0067] 3 is a flowchart showing an example of a carbon circulation method implemented by the carbon circulation system 1 A. In this section, the hydrogen supply device 23 is assumed to be attached to and detached from the first mobile object 2 A and the power source regeneration device 3.

[0068] When the first moving body 2A is driven, it supplies methanol and water from the fuel tank 21 and water tank 22, respectively, to the hydrogen supply device 23. The hydrogen supply device 23 supplies hydrogen generated by the fuel reforming reaction to the fuel cell 241. This enables the prime mover 24 to generate mechanical power, which in turn drives the first moving body 2A. In the hydrogen supply device 23, the carbon dioxide generated together with the hydrogen by the fuel reforming reaction is reacted with calcium oxide as an absorbent (by a carbonation reaction) in the recovery device 232, and recovered as calcium carbonate (S1; recovery step).

[0069] When the first moving body 2A is driven for a first predetermined time, most of the calcium oxide carried by the absorption block 262 of the recovery device 232 is converted to calcium carbonate through a carbonation reaction, thereby reducing the carbon dioxide recovery capacity of the absorption block 262. Therefore, the user moves the first moving body 2A to a drive source regeneration station.

[0070] The first predetermined time may be determined based on the amount of calcium oxide carried by the absorption block 262. The first predetermined time may be, for example, about half a day. The first moving body 2A may have a function of notifying the user when the driving time of the first moving body 2A reaches the first predetermined time. This allows the user to attach the collector 232 to the attachment portion 311 of the power source regeneration device 3 before the collector 232 can no longer capture carbon dioxide.

[0071] After the first predetermined time has elapsed, the user parks the first mobile unit 2A at a power source regeneration station and removes the hydrogen supply device 23 from the first mobile unit 2A. Then, the user attaches the hydrogen supply device 23, which has been removed from the first mobile unit 2A, to the attachment section 311 (S2).

[0072] In the power source regeneration device 3, the decomposer 31 heats the recovery device 232 of the hydrogen supply device 23 attached to the attachment portion 311, thereby decomposing the calcium carbonate recovered in S1 into calcium oxide and carbon dioxide (S3; decomposition step). The decomposer 31 heats the recovery device 232 using the heater 233 provided in the hydrogen supply device 23, thereby causing a decomposition reaction. This converts the calcium carbonate in the absorption block 262 into calcium oxide capable of absorbing carbon dioxide (capable of causing a carbonation reaction). The carbon dioxide decomposed in the decomposer 31 is supplied to the generator 32.

[0073] The generator 32 reacts the carbon dioxide generated in S3 with green hydrogen supplied from the hydrogen tank 34 (by a production reaction) to produce methanol used to drive the first moving body 2A (S4; production process).

[0074] After the calcium carbonate in the absorption block 262 is converted to calcium oxide in S3, the user removes the hydrogen supply device 23 from the mounting section 311 and mounts it on the first moving body 2A (S5). This allows the hydrogen supply device 23, which includes the absorption block 262 that has been returned to its original state by the decomposition reaction in S3, to be mounted on the first moving body 2A. In this way, the step of S5 is part of the supply step in which the calcium oxide obtained in S3 is supplied from the power source regeneration device 3 to the first moving body 2A.

[0075] When the collector 232 is heated for a second predetermined time by the heater 233 or the power supply mechanism, the calcium carbonate in the absorption block 262 returns to calcium oxide through a decomposition reaction. As a result, the carbon dioxide recovery capacity of the absorption block 262 returns to its original state (a state in which carbon dioxide can be recovered). Therefore, the user may remove the hydrogen supply device 23 from the attachment part 311, for example, after the second predetermined time has elapsed since the collector 232 was heated.

[0076] The second predetermined time may be set to a time long enough to return the absorption block 262 to its original state. The second predetermined time may be, for example, about half a day. The power source regeneration device 3 may have a function to notify the user when the heating time of the recovery device 232 reaches the second predetermined time. This allows the user to remove the hydrogen supply device 23 from the attachment part 311 after the absorption block 262 has returned to its original state.

[0077] Furthermore, with the user inserting the nozzle of the hose provided on the supply mechanism 33 into the supply port of the first moving body 2A, the supply mechanism 33 supplies the methanol produced in S4 to the fuel tank 21 (S6). That is, the step of S6 is part of a supply step in which the methanol produced in S4 is supplied from the power source regeneration device 3 to the first moving body 2A.

[0078] <Major Effects of the Carbon Circulation System of the Present Embodiment> As described above, in the carbon circulation system 1A, the first moving body 2A can recover calcium carbonate by reacting carbon dioxide, which is generated when the prime mover 24 uses methanol, with calcium oxide. The power source regeneration device 3 then decomposes the calcium carbonate recovered in the first moving body 2A into calcium oxide and carbon dioxide. Therefore, the calcium oxide obtained by this decomposition can be used to react with carbon dioxide in the first moving body 2A. Furthermore, methanol, which is synthesized from the carbon dioxide obtained by this decomposition and green hydrogen, can be used as a power source in the first moving body 2A.

[0079] In this way, the carbon circulation system 1A can reduce carbon dioxide emissions into the atmosphere to almost zero. Furthermore, the absorbent that absorbed the carbon dioxide can be reused in the first moving body 2A. Furthermore, by using green hydrogen to reuse the carbon dioxide captured by the first moving body 2A as a power source for the first moving body 2A, the power source for the first moving body 2A can be supplied stably and in a carbon-neutral manner. Therefore, the carbon circulation system 1A also contributes to achieving, for example, Goal 7 "Affordable and clean energy" and Goal 13 "Take urgent action to combat climate change" of the Sustainable Development Goals (SDGs) advocated by the United Nations.

[0080] In particular, the first moving body 2A generates hydrogen to power the fuel cell 241, and also recovers carbon dioxide generated during hydrogen generation as calcium carbonate by reacting it with calcium oxide. This reduces carbon dioxide emissions to the atmosphere to almost zero. Furthermore, by using the first moving body 2A together with a power source regeneration device 3 that decomposes the recovered calcium carbonate into calcium oxide and carbon dioxide, the calcium oxide obtained by this decomposition can be used to react with carbon dioxide in the first moving body 2A. Furthermore, by using the first moving body 2A together with a power source regeneration device 3 that produces methanol from the carbon dioxide obtained by this decomposition, the produced methanol can be used as a power source in the first moving body 2A. Therefore, the first moving body 2A can achieve the same effects as the carbon circulation system 1A described above.

[0081] Hydrogen has traditionally been used as a carbon-neutral fuel in vehicles, such as fuel cell vehicles (FCVs) equipped with a fuel cell and a tank for storing hydrogen.

[0082] However, because hydrogen has a low energy density, it is necessary to load hydrogen at a high density onto a mobile vehicle. Therefore, when loading hydrogen onto a mobile vehicle, processes for pressurizing (compressing) and cooling the hydrogen are required. These processes cost several times more than the cost of hydrogen production. Furthermore, pressurizing hydrogen to approximately 700 atmospheres consumes a large amount of energy. Furthermore, the mobile vehicle must be equipped with a special tank for storing hydrogen pressurized to approximately 700 atmospheres. Such a tank is heavy, weighing over 100 kg, and expensive. Furthermore, hydrogen stations that store pressurized hydrogen in this way pose a risk of explosion, and it is difficult to store large quantities of hydrogen like gasoline.

[0083] Furthermore, the larger the vehicle that uses hydrogen as fuel, the greater the amount of hydrogen that is used in a given period of time, and therefore the smaller the energy density of hydrogen, the greater the impact on its use as a fuel.

[0084] The carbon circulation system 1A eliminates the need to densely load hydrogen onto a mobile vehicle. This eliminates the various problems described above caused by the low energy density of hydrogen. Furthermore, by using synthetic fuels such as alcohol-based hydrocarbons, alkenes, alkanes, or aromatics as hydrogen carriers, the first mobile vehicle 2A can use hydrogen at normal pressure and temperature without using high-pressure hydrogen or cryogenic liquid hydrogen, and can transport hydrogen in a compact manner.

[0085] It is also possible to use SAF (Sustainable Aviation Fuel) as a synthetic fuel for vehicles. Currently, SAF is produced from biomass materials such as plants. However, due to a shortage of biomass materials, it is not possible to secure a sufficient amount of SAF for practical use. The carbon circulation system 1A can achieve carbon neutrality without using biomass materials.

[0086] Electric vehicles have also been developed as a form of transportation that can achieve carbon neutrality. However, there are limitations on the materials used to store electricity. For example, lithium-ion batteries are used as batteries for electric vehicles. Because the materials for these lithium-ion batteries are imported from abroad, there is a risk that the supply of lithium-ion batteries will be unstable. Furthermore, lithium-ion batteries have a low energy density, are expensive, and are heavy, making them disadvantageous for installation in mobile vehicles. Furthermore, in order to put electric vehicles into practical use, it will be necessary to increase the number of charging points and strengthen the power supply infrastructure for power supply. Therefore, it will be very costly to put electric vehicles into practical use.

[0087] The carbon circulation system 1A eliminates these problems by not using batteries. Furthermore, the materials used in the carbon circulation system 1A are synthetic fuels such as methanol, water, and green hydrogen, which can be sourced from Japanese-made and general-purpose materials. Therefore, the carbon circulation system 1A can easily expand the carbon-neutral market.

[0088] There is also a technology called DAC (Direct Air Capture) that captures carbon dioxide from the atmosphere. However, the use of this technology requires carbon dioxide emissions from mobile vehicles, which carries the risk of accelerating global warming due to carbon dioxide emissions. Furthermore, using this technology to selectively separate and capture carbon dioxide at a concentration of 400 ppm from the atmosphere is costly. The carbon circulation system 1A can reduce carbon dioxide emissions to almost zero, eliminating the need for technologies like DAC.

[0089] In this way, the carbon circulation system 1A realizes a new method for supplying hydrogen to mobile objects. The carbon circulation system 1A uses synthetic fuel, a liquid fuel, as a hydrogen carrier, allowing for easy storage and transport of hydrogen in mobile objects and enabling the use of conventionally used fuel tanks for mobile objects. While the mobile object must additionally be equipped with a collector 232 containing calcium oxide as an absorbent, the collector 232 may have a volume similar to that of a conventional hydrogen storage tank. Furthermore, the collector 232 is inexpensive and safe due to its function and mechanism.

[0090] 4 is a block diagram showing an example of a carbon circulation system 1Aa according to a modification of the carbon circulation system 1A. The carbon circulation system 1Aa differs from the carbon circulation system 1A in that it includes a power source recycling device 3A instead of the power source recycling device 3. The power source recycling device 3A differs from the power source recycling device 3 in that it does not include a decomposer 31.

[0091] The heater 233 is a heat-generating member that generates heat in the recovery device 232. Furthermore, when the first moving body 2A or the power source regeneration device 3A is equipped with a power supply mechanism, the absorption block 262 to which power is supplied by the power supply mechanism is a heat-generating member that generates heat in the recovery device 232. In the recovery device 232 (absorption block 262), the generated heat decomposes the recovered calcium carbonate into calcium oxide and carbon dioxide.

[0092] The generator 32 produces methanol, which is the power source for the first moving body 2A, by reacting carbon dioxide obtained by the decomposition of calcium carbonate recovered by the recovery device 232 in the first moving body 2A with green hydrogen.

[0093] The generator 32 may include, for example, a hose with a nozzle. The first moving body 2A may also have an outlet that communicates with the collector 232 (the housing 235 of the hydrogen supply device 23) via, for example, a pipe. After the first moving body 2A has been moved to a power source regeneration station, the user inserts the nozzle into the outlet. Heat is then generated in the collector 232, causing a decomposition reaction in the absorption block 262, thereby restoring the absorption block 262 to its original state of carrying calcium oxide. Carbon dioxide generated by the decomposition reaction is supplied to the generator 32 via the hose, allowing methanol to be produced in the generator 32. Therefore, the carbon dioxide collected by the first moving body 2A can be reused as a power source for the first moving body 2A.

[0094] That is, in the carbon circulation system 1Aa, the absorption block 262 can be regenerated and the carbon dioxide can be reused as a power source for the first moving body 2A simply by generating heat in the recovery device 232 without removing the hydrogen supply device 23 from the first moving body 2A. This eliminates the need to move the hydrogen supply device 23 between the first moving body 2A and the power source regeneration device 3A. This reduces the amount of work required by the user.

[0095] FIG. 5 is a flowchart showing an example of a carbon circulation method implemented by the carbon circulation system 1Aa.

[0096] As in S1 of FIG. 3, when the first moving body 2A is driven, carbon dioxide generated together with hydrogen by the fuel reforming reaction is reacted with calcium oxide as an absorbent in the recovery device 232, and recovered as calcium carbonate (S11; recovery step).

[0097] After driving the first moving body 2A for a first predetermined time, the user moves the first moving body 2A to a drive source regeneration station. The user then connects the hydrogen supply device 23 to the generator 32 without removing the hydrogen supply device 23 from the first moving body 2A. Thereafter, the calcium carbonate recovered in S11 is decomposed into calcium oxide and carbon dioxide by generating heat in the recovery device 232 using the heater 233 or a power supply mechanism (S12: decomposition step). The carbon dioxide generated in the hydrogen supply device 23 is supplied to the generator 32.

[0098] The generator 32 reacts the carbon dioxide generated in S12 with green hydrogen supplied from the hydrogen tank 34 to produce methanol used to drive the first moving body 2A (S13; production step).

[0099] The user also connects the fuel tank 21 to the supply mechanism 33. Thereafter, the supply mechanism 33 supplies the methanol generated in S13 to the fuel tank 21 (S14). That is, the step of S14 is a supply step in which the methanol obtained in S13 is supplied from the power source regeneration device 3A to the first moving body 2A.

[0100] [Embodiment 2] Another embodiment of the present disclosure will be described below. For ease of explanation, components having the same functions as those described in the above embodiment will be denoted by the same reference numerals, and their description will not be repeated. In this embodiment, too, the synthetic fuel will be methanol and the absorbent will be calcium oxide.

[0101] Fig. 6 is a block diagram that schematically illustrates an example of a carbon circulation system 1B. As shown in Fig. 6, the carbon circulation system 1B includes a second mobile object 2B and a power source regeneration device 3. The carbon circulation system 1B is a carbon-neutral system for mobile objects that can reduce carbon dioxide emissions to almost zero by circulating carbon between the second mobile object 2B and the power source regeneration device 3. The carbon circulation system 1B can also be referred to as a carbon circulation mobility system.

[0102] The second moving body 2B is a moving body driven by mechanical power generated by using methanol. The second moving body 2B is driven by mechanical power generated by burning methanol. Examples of the second moving body 2B include the various moving bodies exemplified as the first moving body 2A in the first embodiment.

[0103] The power source regeneration device 3 is a device that regenerates methanol, which serves as a power source for the second moving body 2B, and also regenerates an absorbent material provided in a recovery device 28 (described later) provided in the second moving body 2B.

[0104] 6, the second moving body 2B includes, for example, a fuel tank 21, an internal combustion engine (ICE) 27, and a collector 28. The second moving body 2B differs from the first moving body 2A in that the second moving body 2B includes the internal combustion engine 27 instead of the prime mover 24 including the fuel cell 241. The second moving body 2B also differs from the first moving body 2A in that the second moving body 2B includes the collector 28 instead of the hydrogen supply device 23. The second moving body 2B does not include the hydrogen supply device 23, and therefore does not include the water tank 22.

[0105] The fuel tank 21 is a tank that stores methanol in this embodiment as a synthetic fuel that serves as a power source for the second moving body 2 B. As described in the first embodiment, the fuel tank 21 stores methanol produced from carbon dioxide and green hydrogen.

[0106] The internal combustion engine 27 is a prime mover that generates mechanical power by burning methanol supplied from the fuel tank 21. This can drive the second moving body 2B.

[0107] The recovery device 28 includes calcium oxide that absorbs carbon dioxide, similar to the recovery device 232 of the first embodiment. The recovery device 28 recovers carbon dioxide as calcium carbonate by reacting carbon dioxide generated when the internal combustion engine 27 uses methanol with calcium oxide.

[0108] In this embodiment, the recovery device 28 recovers carbon dioxide as calcium carbonate by reacting carbon dioxide generated when the internal combustion engine 27 burns methanol with calcium oxide. This allows the second moving body 2B to recover carbon dioxide generated when the internal combustion engine 27 is driven.

[0109] 7 is a schematic cross-sectional view showing an example of the structure of the recovery device 28. In this embodiment, the recovery device 28 includes a housing 235 in which an absorption block 262 and a heater 233 are disposed. In this embodiment, the housing 235 is a reaction tube in which a carbonation reaction occurs. An exhaust port 234 is provided at the top of the housing 235. The exhaust port 234 discharges water vapor generated in the internal combustion engine 27.

[0110] The collector 28 includes the absorption block 262 described in the first embodiment. Like the collector 232, the collector 28 includes a plurality of absorption blocks 262. As shown in Fig. 7 , the absorption block 262 is arranged inside the housing 235 so that the carbon dioxide and water vapor emitted from the internal combustion engine 27 pass through the absorption block 262. Specifically, the absorption block 262 is arranged inside the housing 235 so that no gap is formed between the housing 235 and the absorption block 262.

[0111] In this embodiment, the combustion reaction shown in the following formula (6) occurs in the internal combustion engine 27: CHOH(l) + 3 / 2O → CO + 2H O ... (6) The internal combustion engine 27 and the recovery device 28 are connected by, for example, a pipe. Therefore, the carbon dioxide and water vapor emitted from the internal combustion engine 27 by the combustion reaction are supplied to the recovery device 28.

[0112] In the recovery unit 28, the carbon dioxide and water vapor supplied from the internal combustion engine 27 are supplied from below the lowest absorption block 262 so that they pass through all of the plurality of absorption blocks 262. This allows the carbon dioxide to be recovered as calcium carbonate in each absorption block 262. By appropriately adjusting the number and size of the absorption blocks 262, it is possible to have the absorption blocks 262 absorb almost all of the carbon dioxide produced by the combustion reaction.

[0113] In this embodiment, the heater 233 is disposed on the inner wall or outer wall of the housing 235 along the extension direction of the collector 28. Heating the collector 28 with the heater 233 can prevent water vapor from liquefying and reacting with carbon dioxide. The second moving body 2B may be provided with a power supply mechanism that supplies power to the absorption block 262. In this case, the absorption block 262 can be heated together with or instead of the heater 233.

[0114] The collector 28 is detachably provided on the second moving body 2B and can be attached to the decomposer 31 provided in the power source regeneration device 3. By removing the collector 28 from the second moving body 2B and attaching it to the decomposer 31, it is possible to increase the calcium oxide that has been reduced by capturing carbon dioxide in the collector 28. Then, the collector 28 with increased calcium oxide can be attached to the second moving body 2B. Therefore, it is possible to repeatedly capture carbon dioxide in the second moving body 2B simply by attaching and detaching the collector 28 to and from the second moving body 2B and the power source regeneration device 3. Furthermore, because the heater 233 is a resistance heating type heater, the total volume and weight of the collector 28 can be reduced.

[0115] (Reaction Flow in Recovery Vessel 28) An example of the reaction flow occurring in the recovery vessel 28 of this embodiment will be described. First, methanol is supplied from the fuel tank 21 to the internal combustion engine 27 by driving a pump (not shown). As a result, a combustion reaction occurs in the internal combustion engine 27, and carbon dioxide and water vapor are discharged from the internal combustion engine 27 and supplied to the lower part of the recovery vessel 28. In addition, the recovery vessel 28 is heated by the heater 233 or a power supply mechanism to preheat the recovery vessel 28. This makes it possible to prevent the water vapor from liquefying in the recovery vessel 28.

[0116] The carbon dioxide and water vapor supplied to the bottom of the collector 28 flow upward inside the lowest absorption block 262. During this process, a carbonation reaction occurs in the absorption block 262, whereby carbon dioxide is collected and heat is generated. This heat also prevents the water vapor from liquefying. If the inside of the collector 28 can be kept warm enough by the carbonation reaction to prevent the water vapor from liquefying, the heater 233 or the power supply mechanism may stop heating the collector 28. The heating time may be set in advance.

[0117] The uncaptured carbon dioxide and water vapor flow to the adjacent absorption block 262 above the lowest absorption block 262, and flow upward inside that absorption block 262. Carbon dioxide is also absorbed in that absorption block 262. In this way, the carbon dioxide and water vapor flow across the multiple absorption blocks 262. In the process, each of the multiple absorption blocks 262 absorbs carbon dioxide. Therefore, the amount of carbon dioxide emitted into the atmosphere can be reduced to almost zero, and only the water vapor that has flowed through the multiple absorption blocks 262 can be discharged from the outlet 234.

[0118] In this embodiment, an example has been described in which the collector 28 includes a plurality of absorption blocks 262 , but the collector 28 is not limited to this, and may include a single absorption block 262 .

[0119] <Power Source Regeneration Device> The power source regeneration device 3 has been described in the first embodiment. In this section, only the differences from the first embodiment will be described.

[0120] The decomposer 31 decomposes the calcium carbonate recovered by the collector 28 into calcium oxide and carbon dioxide. In the decomposer 31, the attachment section 311 is a location where the collector 28 detached from the second movable body 2B can be attached. With the collector 28 attached to the attachment section 311, the decomposer 31 supplies heat to the absorption block 262 that supports calcium carbonate by absorbing carbon dioxide, thereby causing a decomposition reaction. This allows the absorption block 262 to return to a state where it can absorb carbon dioxide.

[0121] When connected to the fuel tank 21, the supply mechanism 33 supplies the methanol generated by the generator 32 to the fuel tank 21. This allows the second moving body 2B to use the methanol generated from the carbon dioxide collected by the second moving body 2B. Therefore, the second moving body 2B can reuse the collected carbon dioxide as a power source. For example, the supply mechanism 33 may supply the methanol generated by the generator 32 to the fuel tank 21 by sending the methanol stored in the tank to a hose with a nozzle inserted into the supply port of the second moving body 2B.

[0122] <Carbon Circulation Method> FIG. 8 is a flowchart showing an example of a carbon circulation method implemented by the carbon circulation system 1B.

[0123] When the second moving body 2B is driven, methanol is supplied from the fuel tank 21 to the internal combustion engine 27. As a result, the internal combustion engine 27 generates mechanical power to drive the second moving body 2B. In the recovery device 28, carbon dioxide generated by the combustion reaction is recovered as calcium carbonate by reacting it with calcium oxide as an absorbent (S21; recovery step).

[0124] When the second moving body 2B is driven for the first predetermined time, most of the calcium oxide carried by the absorption block 262 of the collector 28 is converted to calcium carbonate through a carbonation reaction, thereby reducing the carbon dioxide recovery capacity of the absorption block 262. Therefore, the user moves the second moving body 2B to a drive source regeneration station. The second moving body 2B may have a function to notify the user when the drive time of the second moving body 2B reaches the first predetermined time.

[0125] After the first predetermined time has elapsed, the user stops the second moving body 2B at the power source regeneration station and removes the collector 28 from the second moving body 2B. Then, the user attaches the collector 28 removed from the second moving body 2B to the attachment unit 311 (S22).

[0126] In the power source regeneration device 3, the decomposer 31 heats the recovery device 28 attached to the attachment part 311, for example, by the heater 233 or a power supply mechanism. As a result, the calcium carbonate recovered in S21 is decomposed into calcium oxide and carbon dioxide (S23: decomposition step).

[0127] The generator 32 reacts the carbon dioxide generated in S23 with green hydrogen supplied from the hydrogen tank 34 to produce methanol used to drive the second moving body 2B (S24; production step).

[0128] After the calcium carbonate in the absorption block 262 is converted into calcium oxide in S23, the user removes the collector 28 from the mounting unit 311 and mounts it on the second moving body 2B (S25). As a result, the collector 28 including the absorption block 262, which has been returned to its original state by the decomposition reaction in S23, can be mounted on the second moving body 2B. In this way, the step of S25 is part of a supply step in which the calcium oxide obtained in S23 is supplied from the power source regeneration device 3 to the second moving body 2B. The user may remove the collector 28 from the mounting unit 311, for example, after a second predetermined time has elapsed since the heater 233 heated the collector 28.

[0129] Furthermore, with the user inserting the nozzle of the hose provided on the supply mechanism 33 into the supply port of the second moving body 2B, the supply mechanism 33 supplies the methanol produced in S24 to the fuel tank 21 (S26). That is, the step of S26 is part of the supply step of supplying the methanol produced in S24 from the power source regeneration device 3 to the second moving body 2B.

[0130] <Major Effects of the Carbon Circulation System of the Present Embodiment> The carbon circulation system 1B can reduce carbon dioxide emissions into the atmosphere to almost zero. In addition, the absorbent that absorbs carbon dioxide can be reused in the second moving body 2B. Furthermore, by making it possible to reuse the carbon dioxide captured by the second moving body 2B as a power source for the second moving body 2B using green hydrogen, the power source for the second moving body 2B can be supplied to the second moving body 2B in a stable manner that complies with carbon neutrality. Therefore, the carbon circulation system 1B also contributes to achieving Goal 7 and Goal 13 of the Sustainable Development Goals advocated by the United Nations.

[0131] Furthermore, like carbon circulation system 1A, carbon circulation system 1B can solve various problems that have arisen in mobile vehicles equipped with tanks and batteries for storing hydrogen, and does not require the use of technology such as DAC.

[0132] Furthermore, synthetic fuels such as methane, methanol, ethanol, propane, light oil (e.g., diesel oil), and gasoline can be used in conventionally used internal combustion engines 27. The carbon circulation system 1B is a new system that can achieve carbon neutrality by utilizing such existing internal combustion engines 27 as they are. In other words, the carbon circulation system 1B can be constructed using the existing fuel supply infrastructure, namely, the second mobile body 2B equipped with the internal combustion engine 27 and the gasoline stations used by the second mobile body 2B. Therefore, the introduction of the carbon circulation system 1B imposes little burden on users, and the carbon circulation system 1B can be easily disseminated. Therefore, the carbon circulation system 1B is easy to use both domestically and internationally, and its market is wide.

[0133] 9 is a block diagram showing an example of a carbon circulation system 1Ba according to a modification of the carbon circulation system 1B. The carbon circulation system 1Ba differs from the carbon circulation system 1B in that it includes a power source regeneration device 3A instead of the power source regeneration device 3.

[0134] As with the carbon circulation system 1Aa described above, after the collector 28 and generator 32 are connected, heat is generated in the collector 28 using the heater 233 or a power supply mechanism. In this modification, the power supply mechanism is provided in the second moving body 2B or the power source regeneration device 3A. This heat generation causes a decomposition reaction, which allows the absorption block 262 to be regenerated back to its original state of supporting calcium oxide. Furthermore, by supplying the carbon dioxide generated by the decomposition reaction to the generator 32, methanol can be generated in the generator 32. Therefore, the carbon dioxide collected by the second moving body 2B can be reused as a power source for the second moving body 2B.

[0135] That is, in the carbon circulation system 1Ba, the absorption block 262 can be regenerated and the carbon dioxide can be reused as a driving source for the second moving body 2B simply by generating heat in the recovery device 28 without removing the recovery device 28 from the second moving body 2B. This eliminates the need to move the recovery device 28 between the second moving body 2B and the power source regeneration device 3A. This reduces the amount of work required by the user.

[0136] FIG. 10 is a flowchart showing an example of a carbon circulation method implemented by the carbon circulation system 1Ba.

[0137] As in S11 of FIG. 5, when the second moving body 2B is driven, carbon dioxide generated together with hydrogen by the fuel reforming reaction in the recovery device 28 is recovered as calcium carbonate by reacting it with calcium oxide as an absorbent (S31; recovery step).

[0138] After driving the second moving body 2B for a first predetermined time, the user moves the second moving body 2B to the drive source regeneration station. Then, the user connects the recovery device 28 to the generator 32 without removing the recovery device 28 from the second moving body 2B. Thereafter, the calcium carbonate recovered in S31 is decomposed into calcium oxide and carbon dioxide by generating heat in the recovery device 28 using the heater 233 or a power supply mechanism (S32). The carbon dioxide generated in the recovery device 28 is supplied to the generator 32.

[0139] The generator 32 reacts the carbon dioxide generated in S32 with green hydrogen supplied from the hydrogen tank 34 to produce methanol used to drive the second moving body 2B (S33; production step).

[0140] The user also connects the fuel tank 21 to the supply mechanism 33. Thereafter, the supply mechanism 33 supplies the methanol generated in S33 to the fuel tank 21 (S34). That is, the step of S34 is a supply step in which the methanol obtained in S33 is supplied from the power source regeneration device 3A to the second moving body 2B.

[0141] [Embodiment 3] In this embodiment, the absorption block 262 will be described in detail. As described above, the absorption block 262 is a component that includes an oxide as an absorbent that absorbs carbon dioxide, and recovers the carbon dioxide as carbonate by reacting the carbon dioxide with the absorbent. In the following description, as in the other embodiments, the oxide is calcium oxide and the carbonate is calcium carbonate.

[0142] The absorber block 262 is a porous block formed as a composite material in which a porous material and calcium oxide as an absorbent are mixed. Specifically, the absorber block 262 is a porous block having calcium oxide supported within a porous carrier foam. The porous carrier foam may be, for example, a porous carrier foam of silicon carbide, and in particular a porous carrier foam of silicon-impregnated silicon carbide (SiSiC). As described above, the absorber block 262 may be produced by supporting calcium oxide powder within a porous carrier foam of silicon carbide.

[0143] Reference numeral 501 in Fig. 11 is a perspective view showing an example of a silicon-impregnated silicon carbide porous carrier foam 260. Reference numeral 502 in Fig. 11 is a perspective view showing an example of an absorption block 262 in which calcium oxide is supported on the silicon-impregnated silicon carbide porous carrier foam 260 shown by reference numeral 501 (a composite of silicon-impregnated silicon carbide and calcium oxide).

[0144] 11 , the absorption block 262 is a cylindrical block having through-holes 262a through which the hydrogen generation tube 231 passes. Therefore, the silicon-impregnated silicon carbide porous carrier foam 260 before calcium oxide is supported thereon has through-holes 260a along its central axis. The position, size, and number of the through-holes 260a can be selected depending on the required performance of the device having the through-holes 260a.

[0145] However, the shape of the absorber block 262 may be any shape. That is, because the absorber block 262 is made by supporting calcium oxide on a porous carrier foam of silicon carbide, the shape of the absorber block 262 can be freely formed to suit the application of the absorber block 262. Therefore, by forming a plurality of absorber blocks 262 of the same shape, such as a block shape or a cylindrical shape, it is possible to easily form an assembly that absorbs carbon dioxide, which is composed of a plurality of absorber blocks 262. Therefore, the absorber block 262 can be easily made larger.

[0146] When an absorption block is composed of calcium carbonate alone, resistance occurs due to the movement of the reactive gas (carbon dioxide). If the reactive layer that absorbs carbon dioxide is enlarged to reduce this resistance, it becomes difficult to ensure a flow path for the reactive gas within the absorption block. This makes it difficult to increase the size of the absorption block. Furthermore, because it is difficult to uniformly apply pressure or pressure to the absorption block, it is also difficult to increase the reaction rate between carbon dioxide and calcium oxide and to ensure that the reaction proceeds uniformly throughout the entire absorption block.

[0147] The absorption block 262 has a space between the foam skeleton material of the porous carrier foam and the calcium oxide, which serves as a flow path for the reaction gas within the porous carrier foam. Therefore, even when the absorption block 262 is enlarged, a flow path for the reaction gas can be secured. In other words, the high heat transfer rate enables high-speed heat transport while reducing the possibility of a decrease in reaction efficiency, allowing the absorption block 262 to be enlarged without impairing the reaction performance of the absorption block 262. Furthermore, because the absorption block 262 is constructed as the above-described composite material, pressure application or depressurization of the absorption block 262 can be performed relatively uniformly. This allows the reaction to occur uniformly throughout the entire absorption block 262. Therefore, pressurizing the absorption block 262 can promote the carbonation reaction, and depressurizing the absorption block 262 can promote the decarbonation reaction (the decomposition reaction described above, also known as the CO2 desorption reaction).

[0148] Furthermore, by using a silicon carbide porous carrier block, the absorption block 262 can be made to self-heat by supplying power to the absorption block 262, as described above. Therefore, in order to return calcium oxide that has been converted to calcium carbonate by absorbing carbon dioxide to its original state, it is no longer necessary to remove the absorption block 262 from the reactor (the hydrogen supply device 23 or the recovery device 28 in the above example) and transfer it to another device (a heating device that heats the absorption block 262) to heat the absorption block 262. This eliminates the need to perform such an operation and also the need to prepare a separate device. Furthermore, by not using a separate device for heating, the life of the absorption block 262 can be extended.

[0149] Furthermore, calcium oxide as the absorbent can be converted into calcium hydroxide by absorbing water vapor around the absorption block 262. In this case, calcium hydroxide can be converted back into calcium oxide by heating the absorption block 262. As described above, by causing the absorption block 262 to self-heat, the effort of moving the absorption block 262 can be eliminated even when converting calcium hydroxide back into calcium oxide.

[0150] Experimental Example The reactivity of the absorption and desorption of carbon dioxide in the absorption block 262 and the stability of the carbon dioxide absorption and desorption reaction with the number of uses of the absorption block 262 (hereinafter referred to as cycle stability) were examined.

[0151] The absorption block 262 was fabricated by supporting calcium oxide on a silicon-impregnated silicon carbide porous carrier foam. The initial loading amount was 97 g based on calcium hydroxide, and 74 g based on calcium oxide, for a total weight of 112 g for the absorption block 262. The appearance of the absorption block 262 is as shown by reference numeral 502 in Figure 11. In this experimental example, the fabricated absorption block 262 had a diameter of approximately 35 mm, a height of approximately 60 mm, and a capacity of approximately 58 mL.

[0152] Figure 12 is a schematic cross-sectional view showing an example of an assembly of absorption blocks 262 to be attached to the experimental apparatus (see Figure 13) for the above verification. As shown in Figure 12, a two-tiered assembly (diameter: approximately 35 mm, height: approximately 120 mm, capacity: approximately 116 mL) with the bottom surfaces adjacent to each other was prepared as an assembly 263 of absorption blocks 262 to be filled into the experimental apparatus. In other words, an assembly 263 of absorption blocks 262 with a capacity (scale) of approximately 100 mL was prepared. Of the two absorption blocks 262 included in the assembly 263, the upper absorption block 262 is referred to as the first absorption block 262A, and the lower absorption block 262 is referred to as the second absorption block 262B.

[0153] As shown in FIG. 12 , thermocouples TC1 to TC4 were provided on a two-tiered assembly 263 of absorption blocks 262. In this experimental example, thermocouples TC1 to TC3 were provided in a row along the central axis, approximately 9 mm from the central axis of the first absorption block 262A and the second absorption block 262B. Thermocouple TC1 was provided on the bottom surface of the first absorption block 262A, on the side not adjacent to the second absorption block 262B. Thermocouple TC2 was provided between the two bottom surfaces of the first absorption block 262A and the second absorption block 262B. Thermocouple TC3 was provided on the bottom surface of the second absorption block 262B, on the side not adjacent to the first absorption block 262A. Thermocouple TC4 was provided on the surface at the position where the first absorption block 262A and the second absorption block 262B are adjacent.

[0154] Fig. 13 is a schematic diagram showing an example of an experimental apparatus 100. As shown in Fig. 13, the experimental apparatus 100 includes, for example, mass flow controllers 103 and 104, a reactor 106, a temperature regulator 107, a vacuum pump 108, a gas chromatograph (GC) 109, valves V1 to V6, and pressure gauges P1 and P2. These components are connected by a pipe 120. The shaded area around the pipe 120 (the area marked "Trace heating" in the figure) is heat trace controlled.

[0155] The mass flow controllers 103 and 104, together with the valves V4 and V5, are devices for adjusting the amount of gas supplied into the experimental apparatus 100. In this experimental example, carbon dioxide and nitrogen are supplied into the experimental apparatus 100.

[0156] The reactor 106 is a container in which a reaction occurs in the material of the absorption block 262 placed inside. In this experimental example, a carbonation reaction and a decarbonation reaction occur in the absorption block 262 placed in the reactor 106. The temperature regulator 107 is a device for heating the reactor 106.

[0157] In this experimental example, a prepared assembly 263 of absorption blocks 262 was placed inside the reactor 106. During the CO2 desorption reaction (decarbonation reaction), valves V4, V5, V1, and V3 were closed, and valves V2 and V6 were opened, and the reactor 106 was depressurized by the vacuum pump 108. During the CO2 capture reaction (carbonation reaction), valves V4, V5, V1, V3, and V2 were opened, and V6 was closed, and a mixture of carbon dioxide and nitrogen was supplied to the reactor 106 as a reaction gas. The mass flow controllers 103 and 104 adjusted the carbon dioxide and nitrogen supply rates so that the carbon dioxide and nitrogen were each supplied into the experimental apparatus 100 at a rate of 100 mL / min. The outlet gas concentration (carbon dioxide concentration) of the reactor 106 was measured by a gas chromatograph 109.

[0158] In this experimental example, during the decarboxylation reaction operation, the pressure inside the reactor 106 was reduced by the vacuum pump 108, and the temperature inside the reactor 106 was heated to 920°C by the temperature regulator 107, as described above. Thereafter, during the carbonation reaction operation, carbon dioxide and nitrogen were supplied to the reactor 106 at 100 mL / min each, and the reactor 106 was cooled to 650°C at a rate of approximately 10°C / min, as described above. The change in the carbon dioxide concentration inside the reactor 106 during this cooling was measured. In this example, this temperature was controlled using the temperature of the thermocouple TC4. Furthermore, as for the carbon dioxide concentration inside the reactor 106 during the carbonation operation, the carbon dioxide concentration (mol%) at the outlet (valve V2 side) of the reactor 106 was measured by the gas chromatograph 109, as described above.

[0159] As a result, it was found that the carbon dioxide concentration at the outlet of the reactor 106 decreased when the temperature inside the reactor 106 was around 750°C (approximately 700°C to 800°C). This confirmed that carbon dioxide was absorbed by the absorption block 262, demonstrating that the absorption block 262 had the necessary function. It was then found that the carbon dioxide absorption reaction (carbonation reaction) in the absorption block 262 was completed when the temperature inside the reactor 106 was lower than approximately 700°C (approximately 650°C to 700°C), and the carbon dioxide concentration at the outlet of the reactor 106 increased. Therefore, a decarboxylation reaction was performed a predetermined time (e.g., 20 to 30 minutes) after the carbon dioxide concentration began to increase after decreasing. Specifically, the pressure inside the reactor 106 was reduced using the vacuum pump 108, and the temperature inside the reactor 106 was raised again to 920°C using the temperature regulator 107, causing carbon dioxide to be desorbed from the absorption block 262. The carbonation reaction was then performed again. That is, a mixed gas of carbon dioxide and nitrogen was circulated through the reactor 106, the temperature inside the reactor 106 was lowered again to 650°C, and the carbonation reaction was allowed to proceed in the absorption block 262. The above operations were repeated while maintaining the same measurement conditions for the decarboxylation reaction operation and the carbonation reaction operation.

[0160] FIG. 14 is a graph showing an example of experimental results of the carbonation reaction operation of the absorption block 262. Reference numeral 511 in FIG. 14 indicates the change in temperature over time (upper graph) and the change in carbon dioxide concentration [mol%] over time (lower graph) in the ninth cycle. Reference numeral 512 in FIG. 14 indicates the change in temperature over time (upper graph) and the change in carbon dioxide concentration [mol%] over time (lower graph) in the tenth cycle. The first cycle is defined as the time when the temperature in the reactor 106 was initially lowered from 920°C to 650°C and a carbonation reaction operation was performed. The ninth cycle shows the state in which the temperature in the reactor 106 was lowered from 920°C to 650°C for the ninth time and a carbonation reaction operation was performed. The tenth cycle shows the state in which the temperature in the reactor 106 was lowered from 920°C to 650°C for the tenth time and a carbonation reaction operation was performed.

[0161] In both the upper and lower graphs, the horizontal axis represents the reaction time, with 0 minute representing the time when the decarbonation reaction has been completed in the absorption block 262 and no carbonization reaction is occurring (including the time when calcium carbonate has been decarbonized and returned to calcium oxide). 0 minute may be the time when the assembly 263 of the absorption blocks 262 is introduced into the reactor 106 filled with the reaction gas. 0 minute may also be the time when a predetermined time (e.g., 5 minutes) has elapsed since the temperature inside the reactor 106 was returned to 920°C.

[0162] In the upper graph, the vertical axis represents the temperatures (°C) measured by the thermocouples TC1 to TC4. That is, the upper graph represents the change over time in the temperature distribution in the assembly 263 of the absorption block 262. The lower graph represents the carbon dioxide concentration [mol %] at the outlet of the reactor 106.

[0163] As shown in FIG. 14 , even in the ninth and tenth cycles of the carbonation reaction operation, the carbon dioxide concentration in the reactor 106 decreased when the temperature inside the reactor 106 was around 750°C (approximately 700°C to 800°C). Furthermore, the carbon dioxide concentration in the reactor 106, which had initially decreased, increased approximately 15 minutes after the temperature inside the reactor 106 dropped below approximately 700°C (approximately 650°C to 700°C). This indicates that the absorption block 262 absorbs carbon dioxide through a carbonation reaction when the temperature inside the reactor 106 is approximately 700°C to 800°C. Furthermore, approximately 15 to 20 minutes after the start of each cycle, calcium oxide converted to calcium carbonate, indicating that the carbonation reaction was complete. Furthermore, by performing a subsequent decarbonation reaction, comparable experimental results were obtained in each cycle. That is, it can be seen that calcium carbonate is converted to calcium oxide by the decarbonation reaction, and the absorption block 262 returns to its original state at the start of each cycle of the experiment.

[0164] 14 demonstrates that the absorption block 262 can absorb carbon dioxide and desorb the absorbed carbon dioxide. It also demonstrates that the reactivity of carbon dioxide absorption and desorption is constant in successive cycles, i.e., high cycle stability.

[0165] [Embodiment 4] <Mass and Volume Comparison> Figure 15 is a table showing the relative ratios [%] of the mass and volume of various objects to the mass and volume of a hydrogen cylinder assuming hydrogen storage for a fuel cell vehicle (500 km driving range, 3.3 kg of hydrogen storage). Specifically, Figure 15 is a table showing the relative ratios of the mass and volume of various objects to the mass and volume of a hydrogen cylinder installed in Toyota Motor Corporation's fuel cell vehicle MIRAI. This hydrogen cylinder stores 3.3 kg of hydrogen pressurized to approximately 70 MPa. Hereinafter, this cylinder will be referred to as the comparison hydrogen cylinder.

[0166] The objects compared with the hydrogen cylinder used as the comparison were as follows: - A general-purpose hydrogen cylinder that stores hydrogen pressurized to approximately 15 MPa (Koatsu Showa Bombe Co., Ltd., general-purpose container cylinder for hydrogen, made of manganese steel, filling pressure 14.7 MPa, internal volume 46.7 L, filling amount 7000 L) - The amount of methanol, water, and calcium oxide filled into the first moving body 2A to supply 3.3 kg of hydrogen by fuel reforming (the mass of the container is not taken into account). The amount of methanol, water, and calcium oxide filled is the amount that would supply the same amount of hydrogen as if 3.3 kg of hydrogen were stored in a vehicle of the same type as the MIRAI, assuming that the above equations (1) and (2) react stoichiometrically. - A lithium-ion battery. In this example, the mass and volume of the lithium-ion battery were calculated based on Table 4-1 of "Storage Battery Systems (Vol. 10)" (Low Carbon Society Strategy Center, Japan Science and Technology Agency, February 2023) to determine the mass and volume required to store 71.5 kWh of electricity required for driving 500 km.

[0167] As shown in Figure 15, the general-purpose hydrogen cylinder is larger in both mass and volume than the hydrogen cylinder used for comparison. The mass of the lithium-ion battery installed in the vehicle is also larger than the mass of the hydrogen cylinder used for comparison. The mass of both the general-purpose hydrogen cylinder and the lithium-ion battery is more than four times that of the hydrogen cylinder used for comparison. Meanwhile, the mass of the methanol, water, and calcium oxide filled in the first moving body 2A was approximately the same as that of the hydrogen cylinder used for comparison. Furthermore, the volume of the methanol, water, and calcium oxide filled in the first moving body 2A was approximately half the volume of the hydrogen cylinder used for comparison. Therefore, even when the first moving body 2A is equipped with synthetic fuel and a hydrogen supply device 23, the mass is approximately the same as that of the hydrogen cylinder of a conventional fuel cell vehicle, but the volume is smaller than that of the hydrogen cylinder, demonstrating the high practicality of the first moving body 2A.

[0168] <Safety of the Carbon Cycle System> Methanol, an example of a synthetic fuel, is a Class 4 hazardous alcohol, the same as gasoline. Therefore, when implementing the carbon cycle system 1A described in this specification, consideration must be given to its dangers. Gasoline is also synthesized as a synthetic fuel, and this method can also be used for gasoline. In this regard, the carbon cycle system 1A can be implemented by modifying existing fuel supply infrastructure, such as conventional gasoline stations, and it has been confirmed that the system is highly safe for hydrogen fuel filling facilities.

[0169] [Summary] A carbon circulation system according to aspect 1 of the present disclosure is a carbon circulation system comprising a mobile body and a power source regeneration device, wherein the mobile body comprises a tank for storing synthetic fuel produced from carbon dioxide and hydrogen, a prime mover that generates mechanical power using the synthetic fuel, and a recovery device that comprises an oxide as an absorbent for absorbing carbon dioxide and recovers carbon dioxide generated when the prime mover uses the synthetic fuel as carbonates by reacting the carbon dioxide with the absorbent, and the power source regeneration device comprises a decomposer that decomposes the carbonates recovered by the recovery device into oxides and carbon dioxide, and a generator that produces the synthetic fuel by reacting the carbon dioxide generated in the decomposer with hydrogen.

[0170] A carbon circulation system according to a second aspect of the present disclosure is the carbon circulation system of the first aspect, wherein the collector is detachably provided to the moving body and is attachable to the decomposer.

[0171] A carbon circulation system according to a third aspect of the present disclosure is the carbon circulation system of the first or second aspect, wherein the collector is equipped with a resistance heating type heater.

[0172] A carbon circulation system according to aspect 4 of the present disclosure is a carbon circulation system according to any one of aspects 1 to 3, wherein the power source regeneration device includes a supply mechanism that supplies the synthetic fuel to the moving body, and the supply mechanism, when connected to the tank, supplies the synthetic fuel generated by the generator to the tank.

[0173] A carbon circulation system according to aspect 5 of the present disclosure is a carbon circulation system according to any one of aspects 1 to 5, wherein the mobile body further comprises a hydrogen generator that generates hydrogen using the synthetic fuel supplied from the tank, the prime mover comprises a fuel cell that generates an electric current using the hydrogen generated by the hydrogen generator and converts the electric current generated by the fuel cell into mechanical power, and the collector reacts carbon dioxide generated when the hydrogen generator generates hydrogen with the absorbent.

[0174] A carbon circulation system according to a sixth aspect of the present disclosure is the carbon circulation system of the fifth aspect, wherein the hydrogen generator generates hydrogen from the synthetic fuel using heat generated by the reaction of carbon dioxide with the absorbent in the recovery vessel.

[0175] A carbon circulation system according to a seventh aspect of the present disclosure is the carbon circulation system of the sixth aspect, wherein the hydrogen generator and the recovery device are disposed adjacent to each other.

[0176] A carbon circulation system according to aspect 8 of the present disclosure is the carbon circulation system of any one of aspects 1 to 3, wherein the prime mover is an internal combustion engine that generates mechanical power by combusting the synthetic fuel supplied from the tank, and the collector reacts carbon dioxide generated by the prime mover combusting the synthetic fuel with the absorbent.

[0177] A carbon circulation system according to a ninth aspect of the present disclosure is a carbon circulation system comprising a mobile body and a power source regeneration device, wherein the mobile body comprises a tank that stores synthetic fuel produced from carbon dioxide and hydrogen as a power source, a prime mover that generates mechanical power using the synthetic fuel, a recovery device that has an oxide as an absorbent that absorbs carbon dioxide and recovers carbon dioxide generated when the prime mover uses the synthetic fuel by reacting it with the absorbent, and a heat-generating element that generates heat in the recovery device and decomposes the carbonate recovered by the recovery device into oxide and carbon dioxide, and the power source regeneration device comprises a generator that produces the synthetic fuel by reacting the carbon dioxide obtained by decomposition of the carbonate recovered by the recovery device in the mobile body with hydrogen.

[0178] A carbon circulation method according to aspect 10 of the present disclosure is a carbon circulation method realized by a carbon circulation system including a mobile body and a power source recycling device, and includes: a recovery process in which carbon dioxide generated when the mobile body uses a synthetic fuel produced from carbon dioxide and hydrogen to generate mechanical power is recovered as carbonate by reacting the carbon dioxide with an oxide that acts as an absorbent that absorbs carbon dioxide; a decomposition process in which the power source recycling device decomposes the carbonate recovered in the recovery process into an oxide and carbon dioxide; a production process in which the power source recycling device reacts the carbon dioxide generated in the decomposition process with hydrogen to produce the synthetic fuel; and a supply process in which the oxide obtained in the decomposition process and the synthetic fuel obtained in the production process are supplied from the power source recycling device to the mobile body.

[0179] A carbon circulation method according to aspect 11 of the present disclosure is a carbon circulation method realized by a carbon circulation system including a mobile body and a power source recycling device, and includes: a recovery process in which the mobile body recovers carbon dioxide generated when it uses a synthetic fuel produced from carbon dioxide and hydrogen to generate mechanical power by reacting the carbon dioxide with an oxide that acts as an absorbent that absorbs carbon dioxide, as carbonates; a decomposition process in which the mobile body generates heat and thereby decomposes the carbonates recovered in the recovery process into oxides and carbon dioxide; a production process in which the power source recycling device reacts the carbon dioxide generated in the decomposition process with hydrogen to produce the synthetic fuel; and a supply process in which the power source recycling device supplies the synthetic fuel obtained in the production process to the mobile body.

[0180] A mobile body according to aspect 12 of the present disclosure includes a tank that stores synthetic fuel produced from carbon dioxide and hydrogen, a hydrogen generator that generates hydrogen from the synthetic fuel supplied from the tank, a recovery device that includes an oxide as an absorbent material for absorbing carbon dioxide and recovers carbon dioxide generated when the hydrogen generator generates hydrogen as carbonate by reacting the carbon dioxide with the absorbent material, and a prime mover that includes a fuel cell that generates electric current by reacting the hydrogen generated by the hydrogen generator with oxygen and converts the electric current generated by the fuel cell into mechanical power.

[0181] [Additional Notes] The present disclosure is not limited to the above-described embodiments, and various modifications are possible within the scope of the claims. Embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included in the technical scope of the present disclosure.

[0182] 1A, 1B Carbon circulation system 2A First mobile body (mobile body) 2B Second mobile body (mobile body) 3 Power source regeneration device 21 Fuel tank (tank) 24 Prime mover 27 Internal combustion engine (prime mover) 28 Recovery device 31 Decomposer 32 Generator 33 Supply mechanism 231 Hydrogen generation tube (hydrogen generator) 232 Recovery device 233 Heater (heat generating member) 241 Fuel cell 261 Porous catalyst block (hydrogen generator)

Claims

1. A carbon recycling system comprising a mobile unit and a power source regeneration device, The aforementioned moving body is A tank that houses synthetic fuel produced from carbon dioxide and hydrogen as a power source, A prime mover that generates mechanical power using the aforementioned synthetic fuel, The system includes an oxide as an absorbent material for absorbing carbon dioxide, and a recovery unit that recovers carbon dioxide generated when the prime mover uses the synthetic fuel by reacting it with the absorbent material to recover it as carbon oxide, The aforementioned power source regeneration device is The recovery unit includes a decomposer that decomposes the carbon oxides recovered by the recovery unit into oxides and carbon dioxide, A carbon recycling system comprising: a generator that produces the synthetic fuel by reacting the carbon dioxide generated in the decomposer with hydrogen.

2. The aforementioned recovery device is It is detachably attached to the aforementioned movable body, The carbon recycling system according to claim 1, which can be attached to the aforementioned decomposer.

3. The carbon recycling system according to claim 1, wherein the recovery device is equipped with a resistance heating type heater.

4. The power source regeneration device includes a supply mechanism for supplying the synthetic fuel to the mobile body. The carbon recycling system according to claim 1, wherein the supply mechanism, while connected to the tank, supplies the synthetic fuel produced by the generator to the tank.

5. The mobile unit further comprises a hydrogen generator that produces hydrogen using the synthetic fuel supplied from the tank, The prime mover includes a fuel cell that generates an electric current using the hydrogen produced by the hydrogen generator, and converts the electric current generated by the fuel cell into mechanical power. The carbon recycling system according to claim 1, wherein the recovery device reacts carbon dioxide generated when the hydrogen generator produces hydrogen with the absorbent material.

6. The carbon recycling system according to claim 5, wherein the hydrogen generator produces hydrogen from the synthetic fuel using the heat generated by the reaction between carbon dioxide and the absorbent in the recovery unit.

7. The carbon recycling system according to claim 6, wherein the hydrogen generator and the recovery unit are arranged adjacent to each other.

8. The prime mover is an internal combustion engine that generates mechanical power by burning the synthetic fuel supplied from the tank. The carbon recycling system according to claim 1, wherein the recovery device reacts carbon dioxide generated by the combustion of the synthetic fuel by the prime mover with the absorbent.

9. A carbon recycling system comprising a mobile unit and a power source regeneration device, The aforementioned moving body is A tank that houses synthetic fuel produced from carbon dioxide and hydrogen as a power source, A prime mover that generates mechanical power using the aforementioned synthetic fuel, A recovery device equipped with an oxide as an absorbent material for absorbing carbon dioxide, which recovers carbon dioxide generated when the prime mover uses the synthetic fuel by reacting it with the absorbent material to recover it as carbon oxide, The recovery device includes a heat generating member that generates heat to decompose the carbon oxides recovered by the recovery device into oxides and carbon dioxide, The aforementioned power source regeneration device is A carbon recycling system comprising a generator that produces the synthetic fuel by reacting carbon dioxide obtained by the decomposition of carbon oxides recovered by the recovery device in the mobile body with hydrogen.

10. A carbon recycling method realized by a carbon recycling system comprising a mobile unit and a power source regeneration device, The aforementioned mobile body includes a recovery process in which carbon dioxide generated when it uses a synthetic fuel produced from carbon dioxide and hydrogen to generate mechanical power is recovered as carbon oxide by reacting it with an oxide that acts as an absorbent material for absorbing carbon dioxide, The power source regeneration device includes a decomposition step in which the carbon oxide recovered in the recovery step is decomposed into oxides and carbon dioxide, The power source regeneration device includes a production step in which the carbon dioxide generated in the decomposition step is reacted with hydrogen to produce the synthetic fuel, A carbon recycling method comprising a supply step of supplying the oxide obtained in the decomposition step and the synthetic fuel obtained in the generation step from the power source regeneration device to the mobile body.

11. A carbon recycling method realized by a carbon recycling system comprising a mobile unit and a power source regeneration device, The aforementioned mobile body includes a recovery process in which carbon dioxide generated when it uses a synthetic fuel produced from carbon dioxide and hydrogen to generate mechanical power is recovered as carbon oxide by reacting it with an oxide that acts as an absorbent material for absorbing carbon dioxide, The mobile body generates heat, thereby performing a decomposition step in which the mobile body decomposes the carbon oxides recovered in the recovery step into oxides and carbon dioxide. The power source regeneration device includes a production step in which the carbon dioxide generated in the decomposition step is reacted with hydrogen to produce the synthetic fuel, A carbon recycling method comprising a supply step of supplying the synthetic fuel obtained in the production step to the mobile body from the power source regeneration device.

12. A tank that houses synthetic fuel produced from carbon dioxide and hydrogen as a power source, A hydrogen generator that produces hydrogen from the synthetic fuel supplied from the tank, A recovery device equipped with an oxide as an absorbent material for absorbing carbon dioxide, which recovers carbon dioxide generated when the hydrogen generator produces hydrogen by reacting it with the absorbent material to recover it as carbon oxide, A mobile body comprising a fuel cell that generates an electric current by reacting hydrogen produced by the hydrogen generator with oxygen, and a prime mover that converts the electric current generated by the fuel cell into mechanical power.

13. The carbon recycling system according to claim 1 or 9, wherein the recovery device comprises a porous block made of a composite material obtained by mixing a porous material and calcium oxide as the absorbent.

14. The carbon recycling system according to claim 13, wherein the porous block has calcium oxide powder supported inside a porous carrier foam as the porous material.

15. The carbon recycling system according to claim 14, wherein the porous carrier foam is a porous carrier foam of silicon carbide.

16. The carbon recycling system according to claim 15, wherein the porous carrier foam of silicon carbide is a porous carrier foam of silicon-impregnated silicon carbide.