Carbon production system and carbon production method

Abstract

To provide a carbon generation system and a carbon generation method that can generate carbon from carbon dioxide by performing a reaction to generate methane from a raw material containing hydrogen and carbon dioxide and a reaction to generate carbon from a raw material containing methane in the same reactor.SOLUTION: A carbon generation system 1 includes a reactor 10, a raw material supply section 20, a circulation channel 30 and a water removal section 40. The reactor 10 generates methane and water from a raw material containing hydrogen and carbon dioxide. The raw material supply section 20 supplies hydrogen and carbon dioxide to the reactor 10. The circulation channel 30 returns the methane produced in the reactor 10 to the reactor 10. The water removal section 40 is provided in the circulation channel 30 to remove water generated in the reactor 10 and generate dry gas containing methane generated in the reactor 10. The raw material further contains dry gas and the reactor 10 generates carbon by contacting the raw material to a catalyst.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to carbon production systems and methods. [Background technology]

[0002] Carbon dioxide is seen as a problematic cause of global warming, and there has been a worldwide movement to curb carbon dioxide emissions. One method for reducing carbon dioxide emissions into the atmosphere and effectively utilizing carbon dioxide is to convert hydrogen and carbon dioxide into solid carbon.

[0003] Patent Document 1 discloses a carbon dioxide fixation system including a first reactor, a condenser, a second reactor, and a heat exchanger. The first reactor reacts hydrogen and carbon dioxide in the presence of a catalyst to generate a mixed gas containing methane and water vapor. The condenser condenses the moisture in the mixed gas generated in the first reactor. The second reactor produces carbon products such as carbon from methane gas. The heat exchanger exchanges heat between the mixed gas generated in the first reactor and methane gas supplied to the second reactor. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2005-60137 A Summary of the Invention [Problem to be solved by the invention]

[0005] The reaction in the first reactor is an exothermic reaction, and the reaction in the second reactor is an endothermic reaction. In the conventional technology, the heat energy generated in the first reactor is recovered by exchanging heat between the mixed gas generated in the first reactor and the methane gas supplied to the second reactor, thereby improving the energy efficiency of the system.

[0006] However, conventional systems include two high-temperature reactors, and the heat exchange between the mixed gas produced in the first reactor and the methane gas fed to the second reactor is complicated. If carbon could be produced more simply from carbon dioxide, it could contribute to reducing carbon dioxide emissions.

[0007] The present disclosure aims to provide a carbon production system and a carbon production method capable of producing carbon from carbon dioxide by carrying out a reaction to produce methane from a raw material containing hydrogen and carbon dioxide, and a reaction to produce carbon from a raw material containing methane, in the same reactor. [Means for solving the problem]

[0008] The carbon production system according to the present disclosure includes a reactor that produces methane and water from a feedstock containing hydrogen and carbon dioxide. The carbon production system includes a feedstock supply section that supplies hydrogen and carbon dioxide to the reactor. The carbon production system includes a circulation flow path that returns methane produced in the reactor to the reactor. The carbon production system includes a water removal section that is provided in the circulation flow path and removes water produced in the reactor and produces a dry gas containing the methane produced in the reactor. The feedstock further includes the dry gas, and the reactor produces carbon by contacting the feedstock with a catalyst.

[0009] The carbon production system may further include a temperature measurement unit that measures the temperature inside the reactor, and a control unit that controls the temperature so that the temperature measured by the temperature measurement unit is within a range of 500°C or more and 650°C or less.

[0010] The carbon production system may further include a dry gas flow rate adjusting unit provided in the circulation flow path and adjusting the flow rate of the dry gas supplied to the reactor. The carbon production system may further include a control unit that controls the dry gas flow rate adjusting unit so that the dry gas supplied to the reactor is 2 to 20 times in molar ratio to the total of hydrogen and carbon dioxide supplied by the raw material supply unit.

[0011] The carbon production system may further include a cooler that is provided downstream of the water removal section and upstream of the reactor in the circulation flow path, and that cools the dry gas supplied to the reactor.

[0012] The reactor may be configured such that the temperature of the catalyst located downstream of the reactor is lower than the temperature of the catalyst located upstream of the reactor.

[0013] The carbon production system may further include a catalyst supplying section that supplies a catalyst to the reactor, and a catalyst discharging section that discharges the catalyst to which carbon has been produced and adhered by contact with the raw material from the reactor without passing through the circulation flow path.

[0014] Carbon dioxide may be supplied from an outlet that discharges the catalyst of the catalyst discharge unit.

[0015] The carbon production system may further include a catalyst supplying section that supplies the catalyst to the reactor. The carbon production system may further include a carbon recovery section that is provided downstream of the reactor and upstream of the water removing section in the circulation flow path, and that recovers the catalyst that is discharged from the reactor and that has been contacted with the raw material to generate carbon and adhere to the catalyst.

[0016] The carbon production system may be supplied with carbon dioxide from an outlet that discharges the catalyst of the carbon capture section.

[0017] The raw material supplying unit may supply carbon dioxide to the catalyst supplying unit, and the catalyst supplying unit may supply the catalyst to the reactor in a state in which the catalyst has been purged with the carbon dioxide supplied by the raw material supplying unit.

[0018] The carbon production system may include a gas discharge section provided in the circulation flow path and configured to discharge at least a portion of the dry gas from which water has been removed in the water removal section.

[0019] The carbon production method according to the present disclosure includes a step of supplying hydrogen and carbon dioxide to a reactor. The carbon production method includes a step of producing methane and water in the reactor from a feedstock containing hydrogen and carbon dioxide supplied. The carbon production method includes a step of removing water produced in the reactor and producing a dry gas containing methane produced in the reactor. The carbon production method includes a step of supplying the dry gas to the reactor. The carbon production method includes a step of producing carbon in the reactor by contacting a feedstock containing the dry gas with a catalyst. Effect of the Invention

[0020] According to the present disclosure, it is possible to provide a carbon production system and a carbon production method capable of producing carbon from carbon dioxide by carrying out a reaction to produce methane from a raw material containing hydrogen and carbon dioxide, and a reaction to produce carbon from a raw material containing methane in the same reactor. [Brief description of the drawings]

[0021] [Figure 1] FIG. 1 is a schematic diagram illustrating a carbon production system according to some embodiments. [Diagram 2] 1 is a graph showing the relationship between the catalyst inlet temperature and the amount of carbon produced per unit weight of the catalyst. [Diagram 3] FIG. 1 is a schematic diagram showing a configuration of a reactor and its surroundings according to some embodiments. [Figure 4] FIG. 1 is a schematic diagram illustrating a carbon production system according to some embodiments. [Diagram 5] FIG. 1 is a schematic diagram illustrating a carbon production system according to some embodiments. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0022] Hereinafter, some exemplary embodiments will be described with reference to the drawings. Note that the dimensional ratios of the drawings are exaggerated for the convenience of explanation and may differ from the actual ratios.

[0023] [First embodiment] First, a carbon production system 1 according to the first embodiment will be described with reference to FIG. 1. As shown in FIG. 1, the carbon production system 1 according to the present embodiment includes a reactor 10, a raw material supply unit 20, a circulation flow path 30, and a water removal unit 40. The reactor 10 produces methane and water from raw materials containing hydrogen and carbon dioxide. The raw material supply unit 20 supplies hydrogen and carbon dioxide to the reactor 10. The circulation flow path 30 returns methane produced in the reactor 10 to the reactor 10. The water removal unit 40 is provided in the circulation flow path 30, and removes water produced in the reactor 10 to produce a dry gas containing methane produced in the reactor 10. The raw material further includes a dry gas. The reactor 10 produces carbon by contacting the raw material with a catalyst.

[0024] In this manner, the reactor 10 produces methane and water from the feedstock containing hydrogen and carbon dioxide. This reaction is typically an exothermic reaction and is represented by the following reaction formula (1). 4H 2 +CO 2 →CH 4 +2H 2 O+165kJ (1)

[0025] The reactor 10 also produces carbon from the raw material, which includes dry gas containing methane. This reaction is generally an endothermic reaction and is represented by the following reaction formula (2). CH 4 →C+2H 2 -75kJ (2)

[0026] Combining reaction equation (1) and reaction equation (2), we obtain the following reaction equation (3). 2H 2 +CO 2 →C+2H 2 O+90kJ (3)

[0027] As shown in the above reaction formulas (1) to (3), in the reactor 10, a reaction for producing methane from a raw material containing hydrogen and carbon dioxide, and a reaction for producing carbon from a raw material containing methane are carried out. As a result, carbon is produced from hydrogen and carbon dioxide in the reactor 10. In addition, by carrying out the reactions of the above reaction formulas (1) and (2) in the reactor 10, a part of the heat produced in the reaction shown in the above reaction formula (1) can be used for the reaction shown in the above reaction formula (2). Therefore, even without a complex heat exchange mechanism as in the case where the above two reactions are carried out in different reactors, thermal energy can be effectively used. Below, each component of the carbon production system 1 according to this embodiment will be described.

[0028] As described above, the reactor 10 produces methane and water from a raw material containing hydrogen and carbon dioxide. Note that, in the reactor 10, carbon monoxide may be produced from carbon dioxide, and methane may be produced from carbon monoxide. The reaction of producing methane from a raw material containing hydrogen and carbon dioxide is also called a methanation reaction, and can produce methane with high efficiency.

[0029] The feedstock further includes a dry gas that is supplied to the reactor 10 via the circulation flow path 30. The dry gas includes methane produced in the reactor 10. The reactor 10 then produces carbon from the feedstock.

[0030] The carbon produced in the reactor 10 may include at least one selected from the group consisting of graphite, carbon black, and carbon nanotubes. These carbon materials are used in various fields as useful functional materials.

[0031] The reactor 10 is not particularly limited, and may be a fluidized bed reactor, a kiln reactor, a fixed bed reactor, or a stirred reactor in which the mixture is forcibly stirred by an agitator or the like.

[0032] The catalyst produces carbon by contacting with the raw material. Carbon can be produced in the reactor 10 without using a catalyst, but the reaction temperature may be 1000°C or higher. The temperature in the reactor 10 is not particularly limited as long as carbon can be produced, but carbon can be produced at a low temperature, for example, 500°C to 800°C, by using an appropriate catalyst. The catalyst may be disposed in a flow path through which the raw material in the reactor 10 passes.

[0033] The catalyst may be a single type of catalyst or a mixture of multiple types of catalysts. That is, the catalyst may be a single type of catalyst that produces methane and water upon contact with hydrogen and carbon dioxide, and produces carbon upon contact with methane. The catalyst may also be a mixture of a catalyst that produces methane and water upon contact with hydrogen and carbon dioxide, and a catalyst that produces carbon upon contact with methane.

[0034] The catalyst may contain at least one selected from the group consisting of a metal, a supported catalyst in which a metal is supported on a carrier, and a carbon-based catalyst. The metal contained in the catalyst may contain at least one selected from the group consisting of nickel, iron, and cobalt. The carrier supporting the metal may contain at least one inorganic oxide of alumina and silica. The carbon-based catalyst may contain at least one of activated carbon and carbon black. Among these, it is preferable that the catalyst contains at least one of a supported catalyst in which nickel is supported on an alumina carrier and a supported catalyst in which nickel is supported on silica. This is because these supported catalysts are available at low cost and have high reactivity at low temperatures.

[0035] The carbon production system 1 may be equipped with a temperature measuring unit 11 that measures the temperature inside the reactor 10. By providing the carbon production system 1 with the temperature measuring unit 11, the reaction temperature can be grasped and the temperature inside the reactor 10 can be controlled.

[0036] The reactor 10 may be configured so that the temperature of the catalyst arranged downstream of the reactor 10 is lower than the temperature of the catalyst arranged upstream of the reactor 10. This increases the moisture ratio in the gas flowing through the circulation flow path 30. Therefore, water is easily removed in the water removing section 40, and the methane concentration in the dry gas can be increased. In addition, by lowering the catalyst temperature downstream of the reactor 10, it is expected that the methanation reaction will be promoted. The carbon production system 1 may include a cooler that cools the catalyst arranged downstream of the reactor 10. The cooler may include a cooling pipe that contacts the catalyst arranged downstream of the reactor 10. In order to lower the catalyst temperature downstream of the reactor 10, at least a part of the raw material may be supplied to the catalyst downstream of the reactor 10. The raw material supplied to the catalyst downstream of the reactor 10 may include at least one selected from the group consisting of hydrogen, carbon dioxide, and dry gas. The temperature of the catalyst arranged downstream of the reactor 10 is preferably adjusted to 200°C to 500°C.

[0037] The exhaust gas generated in the reactor 10 and containing methane is discharged from the reactor 10 through the outlet of the reactor 10. The exhaust gas discharged from the reactor 10 may contain not only methane but also unreacted hydrogen and carbon dioxide, by-product carbon monoxide and water, and impurities such as nitrogen and argon contained in the raw material. The gas discharged from the reactor 10 is supplied to the water removal section 40 via the circulation flow path 30.

[0038] The pressure in the reactor 10 is preferably near normal pressure. The pressure in the reactor 10 may be, for example, from −0.05 MPaG to 0.1 MPaG. The pressure in the reactor 10 can be controlled by adjusting the amount of raw material supplied by the raw material supply unit 20, the amount of dry gas supplied via the circulation flow path 30, the amount of exhaust gas discharged from the reactor 10, or the temperature in the reactor 10.

[0039] The raw material supply unit 20 supplies hydrogen and carbon dioxide to the reactor 10. The raw material supply unit 20 may include a hydrogen supply unit 21 and a carbon dioxide supply unit 25.

[0040] The hydrogen supply unit 21 supplies hydrogen to the reactor 10. The hydrogen supply unit 21 may include a hydrogen flow path 22, a hydrogen source 23, and a hydrogen flow rate adjustment unit 24. The hydrogen flow path 22 is provided with the hydrogen source 23 and the hydrogen flow rate adjustment unit 24, and hydrogen may be supplied from the hydrogen source 23 to the reactor 10 via the hydrogen flow path 22.

[0041] The hydrogen source 23 may be, for example, a tank containing hydrogen. The hydrogen may be obtained by electrolyzing water using renewable energy such as solar, wind, and hydraulic power. By using such hydrogen, the carbon production system 1 as a whole can reduce carbon dioxide emissions. The hydrogen flow rate regulator 24 may include a regulator valve, and the amount of hydrogen supplied from the hydrogen source 23 to the reactor 10 may be adjusted by adjusting the opening of the regulator valve with instrument air.

[0042] The carbon dioxide supplying unit 25 supplies carbon dioxide to the reactor 10. The carbon dioxide supplying unit 25 may include a carbon dioxide flow path 26, a carbon dioxide source 27, and a carbon dioxide flow rate adjusting unit 28. The carbon dioxide flow path 26 is provided with the carbon dioxide source 27 and the carbon dioxide flow rate adjusting unit 28, and carbon dioxide may be supplied from the carbon dioxide source 27 to the reactor 10 via the carbon dioxide flow path 26.

[0043] The carbon dioxide source 27 may include a carbon dioxide capture unit that captures carbon dioxide discharged from a carbon dioxide generation source such as a power plant or a factory. By using carbon dioxide captured from the carbon dioxide generation source as a raw material, the amount of carbon dioxide released into the atmosphere can be reduced. The carbon dioxide capture unit may capture carbon dioxide by, for example, a chemical absorption method, a pressure swing adsorption method, a temperature swing adsorption method, a membrane separation concentration method, or a combination of these. Note that the carbon dioxide source 27 is not limited to the above-mentioned form, and may be, for example, a tank containing carbon dioxide. The carbon dioxide flow rate adjustment unit 28 may include an adjustment valve, and the supply amount of carbon dioxide supplied to the reactor 10 from the carbon dioxide supply unit 25 may be adjusted by adjusting the opening degree of the adjustment valve with instrument air.

[0044] In the above embodiment, hydrogen and carbon dioxide are supplied to the reactor 10 by the hydrogen supply unit 21 and the carbon dioxide supply unit 25, but a mixed raw material in which carbon dioxide and hydrogen are mixed may be stored in a tank, and the mixed raw material may be supplied from the tank to the reactor 10.

[0045] The ratio of the flow rate of hydrogen to carbon dioxide supplied by the raw material supply unit 20 can be set appropriately, and may be 1.8 or more, or 1.9 or more in molar ratio. The ratio of the flow rate of hydrogen to carbon dioxide may be less than 2.2, or may be less than 2.1 in molar ratio.

[0046] The circulation flow path 30 returns the methane produced in the reactor 10 to the reactor 10. Specifically, the circulation flow path 30 connects the exhaust port of the reactor 10 to the supply port of the reactor 10. The circulation flow path 30 is provided so that the methane discharged from the exhaust port of the reactor 10 is supplied to the supply port of the reactor 10. The circulation flow path 30 is provided with a water removal unit 40.

[0047] The water removal section 40 removes the water produced in the reactor 10 and generates a dry gas containing methane produced in the reactor 10. When water is removed from the exhaust gas containing methane produced in the reactor 10, the equilibrium of the reaction shown in the above reaction formulas (1) to (3) shifts to the right. Therefore, by removing water in the water removal section 40, the carbon yield is improved.

[0048] The water removal section 40 is not particularly limited as long as it can remove water. As shown in FIG. 1, the water removal section 40 may include a heat exchanger 41 and a gas-liquid separator 42. The heat exchanger 41 cools the exhaust gas to a temperature equal to or lower than the dew point, and liquefies the water. The gas-liquid separator 42 separates the exhaust gas discharged from the reactor 10 into water liquefied by the heat exchanger 41 and dry gas containing methane. The gas-liquid separator 42 includes a cooling tank 42a, a water flow path 42b, a pump 42c, and a water cooler 42d. The water flow path 42b is connected to the cooling tank 42a. The pump 42c and the water cooler 42d are provided in the water flow path 42b. The water in the cooling tank 42a is circulated through the water flow path 42b by the pump 42c, and the water cooled by the water cooler 42d is supplied to the cooling tank 42a. The dry gas separated by the gas-liquid separator 42 is sent to the heat exchanger 41 by a fan 43 provided in the circulation flow path 30. In this embodiment, the fan 43 is provided downstream of the gas-liquid separator 42 and upstream of the reactor 10. Specifically, the fan 43 is provided upstream of the heat exchanger 41. The heat exchanger 41 exchanges heat of the exhaust gas supplied to the gas-liquid separator 42 with heat of the dry gas separated in the gas-liquid separator 42. The dry gas heated in the heat exchanger 41 is supplied to the reactor 10. Although the heat exchanger 41 is used to cool the exhaust gas, a cooler may be used instead of the heat exchanger 41. The cooler may be provided downstream of the reactor 10 and upstream of the gas-liquid separator 42 in the circulation flow path 30.

[0049] Moreover, the water removal section 40 may include an adsorbent that adsorbs moisture instead of or in addition to the gas-liquid separator 42. The adsorbent may include at least one inorganic substance selected from the group consisting of zeolite, silica, and alumina. The shape of the adsorbent is not particularly limited, and may be in the form of powder, particles, tablets, or lumps.

[0050] The dry gas from which water has been removed in the water removal section 40 is supplied to the reactor 10 as part of the raw material. As described above, the reactor 10 produces carbon by contacting the raw material containing the dry gas with the catalyst. Since the produced carbon adheres to the catalyst, the carbon adhered to the catalyst can be recovered by recovering the catalyst from the reactor 10.

[0051] The carbon production system 1 may further include a dry gas flow rate adjusting unit 31 provided in the circulation flow path 30. The dry gas flow rate adjusting unit 31 may adjust the flow rate of the dry gas supplied to the reactor 10. This adjusts the amount of methane in the reactor 10 and can lower the temperature in the reactor 10. The dry gas flow rate adjusting unit 31 may include a regulating valve, and the flow rate of the dry gas supplied to the reactor 10 may be adjusted by adjusting the opening degree of the regulating valve with instrument air.

[0052] The carbon production system 1 may include a control unit 50. The control unit 50 may control the temperature in the reactor 10 so that the temperature in the reactor 10 measured by the temperature measurement unit 11 is within a range of 500°C or more and 650°C or less. By controlling the temperature in the reactor 10 to be within the above range, the yield of carbon produced in the reactor 10 can be improved. The control unit 50 may control at least one selected from the group consisting of the hydrogen flow rate adjustment unit 24, the carbon dioxide flow rate adjustment unit 28, and the dry gas flow rate adjustment unit 31, based on the temperature in the reactor 10 measured by the temperature measurement unit 11.

[0053] The control unit 50 may include a CPU (Central Processing Unit), a ROM (Read Only Memory), and a RAM (Random Access Memory). The CPU can read a program recorded in the ROM and execute instructions such as calculations and control according to the program. The program may be stored in advance in a recording medium other than the ROM, or may be supplied to the recording medium via a wide area communication network including the Internet. The RAM records information acquired from the temperature measurement unit 11 and the like, and the CPU can read the information recorded in the RAM and use it for processing such as calculations.

[0054] FIG. 2 is a graph showing the relationship between the catalyst inlet temperature in the reactor 10 and the amount of carbon generated per unit weight of the catalyst. In this example, the above relationship is examined using a carbon generation system 1 as shown in FIG. 1. A fixed-bed reactor in which a magnetic dish is placed in a quartz tube and a catalyst is placed on the magnetic dish is used as the reactor 10. The reactor 10 is heated from the outside by an electric furnace. The catalyst contains, as a main component, a supported catalyst in which nickel is supported on silica. The supply amount of hydrogen to the reactor 10 is 40 mL / min, the supply amount of carbon dioxide is 20 mL / min, the supply amount of dry gas is 600 mL / min, and the pressure inside the reactor 10 is normal pressure.

[0055] As shown in FIG. 2, in this example, it can be seen that the amount of carbon generated increases within the range of 500°C to 650°C. In this example, since a small reactor was used, the amount of heat dissipation is large, and it is considered that the catalyst inlet temperature and the catalyst outlet temperature are almost the same. However, when a large reactor is used, the catalyst inlet temperature and the catalyst outlet temperature may differ due to the heat generated by the exothermic reaction. However, for example, when raw materials are supplied in a state where the catalyst inlet temperature in the reactor 10 is 500°C, even if the catalyst outlet temperature becomes 650°C due to the reaction heat, a sufficient amount of carbon can be generated. Therefore, the reaction can proceed even if a cooling mechanism for cooling the reactor 10 is not provided.

[0056] The temperature inside the reactor 10 may be adjusted by cooling with a cooling pipe in contact with the catalyst contained in the reactor 10, adjusting the flow rates and temperatures of the hydrogen, carbon dioxide and dry gas supplied to the reactor 10, the position at which the hydrogen, carbon dioxide and dry gas supplied to the reactor 10 are supplied to the reactor 10, supplying a cooled catalyst to the reactor 10, or the like.

[0057] The control unit 50 may control the dry gas flow rate adjustment unit 31 so that the dry gas is supplied to the reactor 10 at a molar ratio of 2 to 20 times the total amount of hydrogen and carbon dioxide supplied by the raw material supply unit 20. The higher the temperature in the reactor 10, the lower the proportion of moisture contained in the circulation flow path 30, and the more difficult it is to remove water in the water removal unit 40. Therefore, by setting the flow rate of the dry gas supplied to the reactor 10 within the above range, methane as a raw material can be supplied to the reactor 10 and the temperature in the reactor 10 can be appropriately lowered. This improves the efficiency of removing water by the water removal unit 40, thereby improving the carbon yield. The control unit 50 may control the amount of dry gas supplied by the dry gas flow rate adjustment unit 31 based on the amount of hydrogen and carbon dioxide supplied by the raw material supply unit 20. The flow rate of the dry gas supplied to the reactor 10 is preferably 5 times or more the total amount of hydrogen and carbon dioxide supplied by the raw material supply unit 20 in molar ratio. In addition, the flow rate of the dry gas supplied to the reactor 10 is preferably 15 times or less in molar ratio to the total amount of hydrogen and carbon dioxide supplied by the raw material supply unit 20 .

[0058] The carbon production system 1 may further include a cooler 32 that is provided downstream of the water removal section 40 and upstream of the reactor 10 in the circulation flow path 30 and cools the dry gas supplied to the reactor 10. As described above, even if the carbon production system 1 does not include the cooler 32, the temperature inside the reactor 10 can be lowered. However, such a cooler 32 allows fine adjustment of the temperature of the dry gas supplied into the reactor 10.

[0059] As described above, the carbon production system 1 according to this embodiment includes the reactor 10, the raw material supply unit 20, the circulation flow path 30, and the water removal unit 40. The reactor 10 produces methane and water from raw materials containing hydrogen and carbon dioxide. The raw material supply unit 20 supplies hydrogen and carbon dioxide to the reactor 10. The circulation flow path 30 returns methane produced in the reactor 10 to the reactor 10. The water removal unit 40 is provided in the circulation flow path 30, and removes water produced in the reactor 10 to produce dry gas containing methane produced in the reactor 10. The raw material further includes dry gas, and the reactor 10 produces carbon by contacting the raw material with a catalyst.

[0060] The carbon production method according to the present embodiment also includes a step of supplying hydrogen and carbon dioxide to the reactor 10. The method includes a step of producing methane and water in the reactor 10 from the supplied raw material containing hydrogen and carbon dioxide. The method includes a step of removing the water produced in the reactor 10 and producing a dry gas containing methane produced in the reactor 10. The method includes a step of supplying the dry gas to the reactor 10. The method includes a step of producing carbon in the reactor 10 by contacting the raw material containing the dry gas with a catalyst.

[0061] According to the carbon production system 1 and the carbon production method, a reaction for producing methane from a raw material containing hydrogen and carbon dioxide and a reaction for producing carbon from a raw material containing methane are carried out in the same reactor, thereby producing carbon from carbon dioxide. Therefore, the carbon production system 1 does not need to be equipped with a heat exchanger for exchanging the reaction heat for producing methane from a raw material containing hydrogen and carbon dioxide and the reaction heat for producing carbon from a raw material containing methane.

[0062] [Second embodiment] Next, a carbon generation system 1 according to a second embodiment will be described with reference to Fig. 3. As shown in Fig. 3, the carbon generation system 1 according to this embodiment further includes a catalyst supplying unit 60 and a catalyst discharging unit 70 in addition to the carbon generation system 1 according to the above embodiment. The other parts are similar to those of the carbon generation system 1 according to the above embodiment, and therefore description thereof will be omitted.

[0063] The catalyst supplying unit 60 supplies a catalyst to the reactor 10. The catalyst supplying unit 60 may include a first hopper 61, a second hopper 62, a first catalyst flow path 63, a first catalyst supply amount adjustment unit 64, a second catalyst flow path 65, and a second catalyst supply amount adjustment unit 66.

[0064] The first hopper 61 and the second hopper 62 are connected via a first catalyst passage 63. A first catalyst supply amount adjustment unit 64 is provided in the first catalyst passage 63. The first catalyst supply amount adjustment unit 64 adjusts the amount of catalyst supplied from the first hopper 61 to the second hopper 62.

[0065] The second hopper 62 and the reactor 10 are connected via a second catalyst passage 65. A second catalyst supply amount adjustment unit 66 is provided in the second catalyst passage 65. The second catalyst supply amount adjustment unit 66 adjusts the supply amount of catalyst supplied from the second hopper 62 to the reactor 10.

[0066] The raw material supply unit 20 may supply carbon dioxide to the catalyst supply unit 60. Specifically, the carbon dioxide supply unit 25 may supply carbon dioxide to the catalyst supply unit 60. The carbon dioxide supply unit 25 that supplies carbon dioxide to the reactor 10 and the carbon dioxide supply unit 25 that supplies carbon dioxide to the catalyst supply unit 60 may be the same or different. The catalyst supply unit 60 may supply the catalyst to the reactor 10 in a state in which the catalyst is purged with the carbon dioxide supplied by the raw material supply unit 20. Carbon dioxide is supplied from the carbon dioxide supply unit 25 to the first hopper 61. The carbon dioxide supplied to the first hopper 61 is supplied to the reactor 10 via the first catalyst flow path 63, the second hopper 62, and the second catalyst flow path 65.

[0067] The reactor 10 includes a reaction vessel 12, an agitator shaft 13, an agitator blade 14, and a motor 15. The reaction vessel 12 contains the agitator shaft 13 and the agitator blade 14 attached to the agitator shaft 13. The agitator shaft 13 is connected to the motor 15. The reaction vessel 12 contains a catalyst 16, which forms a catalyst layer. The motor 15 rotates the agitator shaft 13, so that the catalyst 16 in the reaction vessel 12 is agitated by the agitator blade 14, and adhesion of the powdered catalyst 16 is suppressed. An outlet is provided at the bottom of the reactor 10, and the catalyst is discharged by a catalyst discharge unit 70.

[0068] The reactor 10 is connected to a circulation flow path 30, and a dry gas containing methane is supplied to the reactor 10 via the circulation flow path 30. Hydrogen is also supplied to the reactor 10 from a hydrogen supply unit 21. Carbon dioxide is also supplied to the reactor 10 from a carbon dioxide supply unit 25 via a catalyst supply unit 60. As described above, methane and carbon are produced in the reactor 10, and the methane is discharged from the reactor 10 and returned to the reactor 10 via the circulation flow path 30.

[0069] The catalyst discharge section 70 discharges the catalyst 16, on which carbon is generated and adhered due to contact with the raw material, from the reactor 10 without passing through the circulation flow path 30. The flow path of the catalyst 16 discharged by the circulation flow path 30 and the catalyst discharge section 70 is different. The catalyst discharge section 70 includes a cylinder 71, a screw 72, and a motor 73. The screw 72 is disposed within the cylinder 71. The motor 73 is connected to the screw 72. The screw 72 rotates in conjunction with the rotation of the motor 73. The catalyst 16 supplied from the reactor 10 to the catalyst discharge section 70 is pushed out from the discharge port of the catalyst discharge section 70 by the rotation of the screw 72.

[0070] Carbon dioxide may be supplied from the outlet of the catalyst discharger 70 that discharges the catalyst 16. This allows the catalyst 16 to be cooled, to which carbon is attached and discharged from the catalyst discharger 70. Also, it is possible to suppress the intrusion of air into the reactor 10. The carbon production system 1 may further include a storage tank 74 that is connected to the catalyst discharger 70 and stores the catalyst 16 discharged from the catalyst discharger 70. Carbon dioxide may be supplied to the storage tank 74 from the raw material supply unit 20. Specifically, the carbon dioxide supply unit 25 may supply carbon dioxide to the storage tank 74. The carbon dioxide supply unit 25 that supplies carbon dioxide to the reactor 10 and the carbon dioxide supply unit 25 that supplies carbon dioxide to the storage tank 74 may be the same or different. Also, carbon dioxide may be supplied from the storage tank 74 to the outlet of the catalyst discharger 70, or may be supplied directly to the outlet of the catalyst discharger 70 without passing through the storage tank 74.

[0071] Also, an example has been described in which the catalyst supplying unit 60 includes two hoppers, the first hopper 61 and the second hopper 62. However, the catalyst supplying unit 60 may include only one hopper, or may include three or more hoppers.

[0072] Also, an example has been described in which the reactor 10 is a stirred reactor including the stirring shaft 13, the stirring blade 14, and the motor 15. However, the catalyst 16 is supplied to the reactor 10 by the catalyst supply unit 60, and the catalyst 16 in the reactor 10 is discharged by the catalyst discharge unit 70. Therefore, the catalyst 16 in the reactor 10 is flowed by the catalyst supply unit 60 and the catalyst discharge unit 70. Therefore, the reactor 10 does not need to include the stirring shaft 13, the stirring blade 14, and the motor 15.

[0073] Also, an example has been described in which the catalyst discharging unit 70 is an extruder including the cylinder 71, the screw 72, and the motor 73. However, the catalyst discharging unit 70 only needs to be able to discharge the catalyst 16 from the reactor 10, and may be a flow rate control valve provided at the discharge port of the reactor 10, or the like.

[0074] As described above, the carbon production system 1 according to this embodiment includes a catalyst supplying section 60 that supplies the catalyst 16 to the reactor 10, and a catalyst discharging section 70 that discharges the catalyst 16, to which carbon is generated and attached by contact with the raw material, from the reactor 10 without passing through the circulation flow path 30. This allows the catalyst 16 to be continuously supplied to and discharged from the reactor 10. Therefore, carbon can be continuously produced in the reactor 10 without stopping the reaction in the reactor 10 to take out the carbon.

[0075] [Third embodiment] Next, a carbon generation system 1 according to a third embodiment will be described with reference to Fig. 4. As shown in Fig. 3, the carbon generation system 1 according to this embodiment further includes a catalyst supply unit 60 and a carbon recovery unit 80 in addition to the carbon generation system 1 according to the above embodiment. The other parts are similar to those of the carbon generation system 1 according to the above embodiment, and therefore descriptions thereof will be omitted.

[0076] The catalyst supplying section 60 supplies a catalyst to the reactor 10. As the catalyst supplying section 60, the one described in the second embodiment can be used.

[0077] The carbon recovery section 80 is provided downstream of the reactor 10 and upstream of the water removal section 40 in the circulation flow path 30. The carbon recovery section 80 recovers the catalyst discharged from the reactor 10, which has been produced and adhered to the catalyst by contact with the raw material. The carbon recovery section 80 only needs to be able to recover the catalyst from the exhaust gas discharged from the reactor 10. The carbon recovery section 80 may include a cyclone or a filter, and may recover the catalyst by using these.

[0078] Carbon dioxide may be supplied from the outlet of the carbon recovery unit 80 that discharges the catalyst. This allows the catalyst to which carbon discharged from the carbon recovery unit 80 is attached to be cooled. Also, it is possible to suppress the intrusion of air into the reactor 10. The carbon production system 1 may further include a storage tank that is connected to the carbon recovery unit 80 and stores the catalyst recovered by the carbon recovery unit 80, as in the embodiment shown in FIG. 3. Carbon dioxide may be supplied to the storage tank from the raw material supply unit 20. Specifically, the carbon dioxide supply unit 25 may supply carbon dioxide to the storage tank. The carbon dioxide supply unit 25 that supplies carbon dioxide to the reactor 10 and the carbon dioxide supply unit 25 that supplies carbon dioxide to the storage tank may be the same or different. Also, carbon dioxide may be supplied from the storage tank to the outlet of the carbon recovery unit 80, but may be supplied directly to the outlet of the carbon recovery unit 80 without passing through the storage tank.

[0079] As described above, the carbon production system 1 according to this embodiment includes the catalyst supplying section 60 and the carbon recovery section 80. The catalyst supplying section 60 supplies the catalyst to the reactor 10. The carbon recovery section 80 is provided downstream of the reactor 10 and upstream of the water removing section 40 in the circulation flow path 30, and recovers the catalyst discharged from the reactor 10 and adhering to the catalyst when carbon is generated on the catalyst by contact with the raw material. This allows the catalyst to be continuously supplied to and discharged from the reactor 10. Therefore, carbon can be continuously produced in the reactor 10 without stopping the reaction in the reactor 10 to take out the carbon.

[0080] [Fourth embodiment] Next, the carbon generation system 1 according to the fourth embodiment will be described with reference to Fig. 5. As shown in Fig. 5, the carbon generation system 1 according to this embodiment includes a gas discharge section 90 that is provided in the circulation flow path 30 and discharges at least a part of the dry gas from which water has been removed in the water removal section 40. The other parts are similar to those of the carbon generation system 1 according to the above embodiment, and therefore description thereof will be omitted.

[0081] The carbon production system 1 according to the embodiment produces solid carbon and liquid water from hydrogen and carbon dioxide as shown in the reaction formula (3). Therefore, in theory, the carbon production system 1 does not produce exhaust gas. However, the raw material contains impurities such as nitrogen and argon. As the reaction proceeds, the impurities may accumulate in the reactor 10 and the circulation flow path 30. Therefore, by exhausting the dry gas by the gas exhaust unit 90, the risk of impurities accumulating can be reduced. The total flow rate of methane, carbon dioxide, and carbon monoxide in the discharged dry gas is preferably 20% or less, more preferably 10% or less, in molar ratio, relative to the flow rate of carbon dioxide supplied by the raw material supply unit 20. The content of methane, carbon dioxide, and carbon monoxide in the dry gas may be 95% or more in molar ratio.

[0082] Since the temperature of the dry gas is low, the gas exhaust section 90 is preferably provided downstream of the gas-liquid separator 42 and upstream of the heat exchanger 41 in the circulation flow path 30. Since the pressure of the dry gas is high, the gas exhaust section 90 is preferably provided downstream of the fan 43 in the circulation flow path 30.

[0083] As described above, the carbon production system 1 according to this embodiment includes the gas discharge unit 90 that is provided in the circulation flow path 30 and discharges at least a portion of the dry gas from which water has been removed in the water removal unit 40. This makes it possible to suppress the accumulation of impurities such as nitrogen and argon in the circulation flow path 30.

[0084] Although several embodiments have been described, the embodiments can be modified or modified based on the above disclosure. All components of the above embodiments and all features described in the claims may be individually extracted and combined as long as they are not mutually inconsistent.

[0085] This disclosure can contribute, for example, to Goal 13 of the United Nations-led Sustainable Development Goals (SDGs), "Take urgent action to combat climate change and its impacts." [Explanation of symbols]

[0086] 1 Carbon Generation System 10. Reactor 11 Temperature measurement part 16 Catalyst 20 Raw material supply department 30 Circulation flow path 31 Drying gas flow rate adjustment section 32 Cooler 40 Water removal section 50 Control section 60 Catalyst supply section 70 Catalyst discharge section 74 Storage Tank 80 Carbon Recovery Department 90 Gas exhaust section

Claims

1. A reactor for producing methane and water from a feedstock comprising hydrogen and carbon dioxide; A raw material supply unit that supplies hydrogen and carbon dioxide to the reactor; a circulation flow path for returning methane produced in the reactor to the reactor; a water removal unit provided in the circulation flow path, removing water produced in the reactor and generating a dry gas containing methane produced in the reactor; Equipped with The feedstock further comprises the dry gas; The reactor produces methane, water and carbon by contacting the feedstock, which includes hydrogen, carbon dioxide and the dry gas, with a catalyst.

2. A temperature measuring unit for measuring a temperature inside the reactor; A control unit controls the temperature measured by the temperature measuring unit so that the temperature is within a range of 500° C. or more and 650° C. or less; The carbon production system of claim 1 further comprising:

3. a dry gas flow rate adjusting unit provided in the circulation flow path and adjusting a flow rate of the dry gas supplied to the reactor; a control unit that controls the dry gas flow rate adjusting unit so that the dry gas is supplied to the reactor at a molar ratio of 2 to 20 times the total amount of hydrogen and carbon dioxide supplied by the raw material supply unit; 3. The carbon production system of claim 1 or 2, further comprising:

4. The carbon production system according to any one of claims 1 to 3, further comprising a cooler provided in the circulation flow path downstream of the water removal section and upstream of the reactor, for cooling the dry gas supplied to the reactor.

5. 5. The carbon production system of any one of claims 1 to 4, wherein the reactor is configured such that the temperature of the catalyst located downstream of the reactor is lower than the temperature of the catalyst located upstream of the reactor.

6. A catalyst supply unit that supplies the catalyst to the reactor; a catalyst discharge section that discharges the catalyst to which carbon is generated and adhered due to contact with the raw material from the reactor without passing through the circulation flow path; 6. The carbon production system of claim 1, further comprising:

7. The carbon production system according to claim 6 , wherein carbon dioxide is supplied from an outlet of the catalyst exhaust section that exhausts the catalyst.

8. A catalyst supply unit that supplies the catalyst to the reactor; a carbon recovery section that is provided downstream of the reactor and upstream of the water removal section in the circulation flow path, and that recovers the catalyst that is discharged from the reactor and that has been contacted with the raw material to generate carbon and that has adhered to the catalyst; 6. The carbon production system of claim 1, further comprising:

9. The carbon production system according to claim 8 , wherein carbon dioxide is supplied from an outlet that discharges the catalyst in the carbon recovery section.

10. The raw material supply unit supplies carbon dioxide to the catalyst supply unit, The carbon production system according to any one of claims 6 to 9, wherein the catalyst supply unit supplies the catalyst to the reactor in a state in which the catalyst is purged with carbon dioxide supplied by the raw material supply unit.

11. The carbon production system according to any one of claims 1 to 10, further comprising a gas exhaust section provided in the circulation flow path for exhausting at least a portion of the dry gas from which water has been removed in the water removal section.

12. supplying hydrogen and carbon dioxide to a reactor; Producing methane and water in the reactor from a feedstock containing hydrogen and carbon dioxide; removing water produced in the reactor and producing a dry gas comprising methane produced in the reactor; supplying the dry gas to the reactor; producing carbon in the reactor by contacting the feedstock, including the dry gas, with a catalyst; 16. A method for producing carbon comprising:

Images