Hydrocarbon production system and hydrocarbon production method

Abstract

A hydrocarbon generation system (1) includes a first generation device (60) for generating hydrocarbons having a carbon count of two or more from a first raw material containing hydrogen and at least one of carbon monoxide and carbon dioxide. The hydrocarbon generation system (1) includes a second generation device (70) for generating methane from a second raw material containing hydrogen and at least one of the carbon monoxide and carbon dioxide in the first raw material discharged from the first generation device (60).

Description

[Technical Field]

[0001] FIELD OF THE DISCLOSURE The present disclosure relates to hydrocarbon production systems and methods. [Background technology]

[0002] Methane is a main component of natural gas and city gas, and is used as a fuel in existing combustion facilities and power generation facilities. Methane can be produced, for example, from a feed gas containing hydrogen and carbon dioxide. Patent Document 1 discloses a method for producing methane from a feed gas containing hydrogen and carbon dioxide using at least two reactors. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Special Publication No. 2013-515684 Summary of the Invention [Problem to be solved by the invention]

[0004] Carbon dioxide is considered a problematic cause of global warming, and there has been a growing global movement to curb carbon dioxide emissions. By producing methane from carbon dioxide contained in factory exhaust gases, it is possible to curb carbon dioxide emissions and produce valuable methane. Methane can also be produced from raw materials containing carbon dioxide, as well as raw materials containing carbon monoxide. Carbon monoxide is contained in factory exhaust gases and in the combustion gases of hydrocarbons contained in biomass and waste.

[0005] On the other hand, hydrocarbons such as ethylene and propylene, which are used as raw materials for plastics or resins, are traded at higher prices than methane and can be produced from raw materials containing carbon monoxide or carbon dioxide. Furthermore, producing plastics or resins from carbon dioxide reduces carbon dioxide emissions into the atmosphere and provides carbon-neutral plastics or resins. However, the rate at which such hydrocarbons are produced from raw materials containing carbon monoxide or carbon dioxide is lower than the rate at which methane is produced, resulting in the emission of a large amount of unreacted carbon monoxide or carbon dioxide.

[0006] Therefore, an object of the present disclosure is to provide a hydrocarbon production system, a first production device, a second production device, and a hydrocarbon production method that can efficiently produce methane and hydrocarbons other than methane from at least one of carbon monoxide and carbon dioxide. [Means for solving the problem]

[0007] A hydrocarbon production system according to the present disclosure includes a first production device that produces hydrocarbons having two or more carbon atoms from a first feedstock containing at least one of carbon monoxide and carbon dioxide and hydrogen, and a second production device that produces methane from a second feedstock containing hydrogen and at least one of carbon monoxide and carbon dioxide in the first feedstock discharged from the first production device.

[0008] In the first generator, hydrocarbons having a carbon number of 2 or more may be produced from 20% by mass or more but less than 85% by mass of carbon dioxide contained in the first feedstock. In the second generator, methane may be produced from 85% by mass or more of carbon dioxide contained in the second feedstock. The first generator may be provided with an iron catalyst for producing hydrocarbons having a carbon number of 2 or more from the first feedstock, and the second generator may be provided with a nickel catalyst for producing methane from the second feedstock. The hydrocarbon production system may further include a carbon dioxide capture unit that captures carbon dioxide from a gas containing carbon dioxide, and the carbon dioxide contained in the first feedstock may include carbon dioxide separated from the carbon dioxide capture unit. The carbon dioxide capture unit may include an absorption unit that produces an alkaline solution containing carbon dioxide by gas-liquid contact between the gas containing carbon dioxide and an alkaline solution, and a separation unit that separates carbon dioxide from the alkaline solution containing carbon dioxide, and the carbon dioxide contained in the first feedstock may include carbon dioxide separated from the separation unit. At least a portion of at least one of the reaction heats generated when hydrocarbons having a carbon number of 2 or more are produced in the first generator and when methane is produced in the second generator may be recovered. The separation device may separate carbon dioxide from the alkaline solution containing carbon dioxide using at least a portion of the heat of reaction generated when hydrocarbons having a carbon number of 2 or more are produced in the first production device and at least one of the heat of reaction generated when methane is produced in the second production device. The hydrocarbons having a carbon number of 2 or more may include olefins having a carbon number of 2 or more and 4 or less. The gas discharged from the first production device may be supplied to the second production device while maintaining the pressure.

[0009] The first generator according to the present disclosure produces hydrocarbons having two or more carbon atoms from a first feedstock containing at least one of carbon monoxide and carbon dioxide and hydrogen, and is connected to a second generator. The second generator produces methane from a second feedstock containing hydrogen and at least one of carbon monoxide and carbon dioxide in the first feedstock discharged from the first generator.

[0010] The second generator according to the present disclosure produces methane from a second feedstock containing hydrogen and at least one of carbon monoxide and carbon dioxide in the first feedstock discharged from the first generator. The first generator produces hydrocarbons with a carbon number of two or more from the first feedstock containing at least one of carbon monoxide and carbon dioxide and hydrogen.

[0011] The hydrocarbon production method according to the present disclosure includes a first production step of producing hydrocarbons having two or more carbon atoms from a first feedstock containing at least one of carbon monoxide and carbon dioxide and hydrogen, and a second production step of producing methane from a second feedstock containing hydrogen and at least one of carbon monoxide and carbon dioxide in the first feedstock discharged in the first production step. [Effects of the Invention]

[0012] According to the present disclosure, it is possible to provide a hydrocarbon production system, a first production device, a second production device, and a hydrocarbon production method that can efficiently produce methane and hydrocarbons other than methane from at least one of carbon monoxide and carbon dioxide. [Brief explanation of the drawings]

[0013] [Figure 1] FIG. 1 is a schematic diagram illustrating a hydrocarbon production system according to some embodiments. DETAILED DESCRIPTION OF THE INVENTION

[0014] Hereinafter, several exemplary embodiments will be described with reference to the drawings. Note that the dimensional proportions of the drawings are exaggerated for the convenience of explanation and may differ from the actual proportions.

[0015] [Hydrocarbon Generation System] As shown in FIG. 1, the hydrocarbon production system 1 includes a pretreatment device 10, a carbon dioxide capture device 20, a first production device 60, and a second production device 70.

[0016] The pretreatment device 10 cools the carbon dioxide-containing gas G1. The gas G1 may be, for example, a combustion exhaust gas generated by burning fuel in a thermal power plant or a steel mill, or a process exhaust gas from a chemical plant. The gas G1 may also be a carbon dioxide-containing gas contained in an oil refining or petrochemical process. As described below, in the absorption device 21 of the carbon dioxide capture device 20, carbon dioxide is absorbed by the alkaline solution A. A low temperature of the alkaline solution A increases the absorption rate of carbon dioxide into the alkaline solution A, thereby improving the carbon dioxide capture efficiency of the carbon dioxide capture device 20. Therefore, by cooling the carbon dioxide-containing gas G1 in the pretreatment device 10, a temperature rise in the absorption device 21 due to the gas G1 is suppressed. However, the pretreatment device 10 is not necessarily required when the gas G1 is not hot or when it does not significantly affect the carbon dioxide capture efficiency of the carbon dioxide capture device 20. The pretreatment device 10 is, for example, a countercurrent gas-liquid contact device, and includes a cooling tank 11, a packing material 12, a cooling pipe 13, a pump 14, a cooler 15, a demister 16, an air pipe 17, and a pump 18.

[0017] A filler 12 is disposed inside the cooling tank 11. The filler 12 is provided to increase the contact area between the supplied gas G1 and the cooling water W, and brings the gas G1 supplied to the pretreatment device 10 into gas-liquid contact with the cooling water W. The filler 12 is made of an iron-based metal material such as stainless steel or carbon steel, but is not particularly limited, and any material that is durable and corrosion-resistant at the treatment temperature and has a shape that provides the desired contact area can be appropriately selected and used.

[0018] Cooling pipes 13, a pump 14, and a cooler 15 are arranged outside the cooling tank 11. The cooling pipes 13 connect the top of the cooling tank 11 above the filler 12 to the bottom of the cooling tank 11 below the filler 12. The cooling pipes 13 are provided with the pump 14 and the cooler 15. The cooling water W remaining at the bottom of the cooling tank 11 is sucked up from the bottom of the cooling tank 11 by the pump 14, cooled by the cooler 15, and then sent to the top of the cooling tank 11.

[0019] Gas G1 is supplied from a gas supply port provided in cooling tank 11 below packing material 12. Gas G1 supplied from the gas supply port rises within cooling tank 11, and gas-liquid contact with cooling water W supplied from the top of cooling tank 11 is promoted in packing material 12, resulting in cooling to an appropriate temperature. The cooled gas G1 passes through a demister 16 that removes minute droplets and is discharged from a gas outlet provided at the top of cooling tank 11. The gas outlet of pretreatment device 10 and the bottom of absorption tank 22 of carbon dioxide capture device 20 are connected by an air pipe 17, and air pipe 17 is provided with a pump 18. Gas G1 discharged from the gas outlet of pretreatment device 10 is supplied to absorption device 21 through air pipe 17 by pump 18.

[0020] On the other hand, the cooling water W, whose temperature has risen by coming into contact with the gas G1 in the filler 12, flows down to the bottom of the cooling tank 11, passes through the cooling pipe 13 again, is cooled in the cooler 15, and is then supplied from the top of the cooling tank 11.

[0021] If the gas G1 contains catalyst poisons, the pretreatment device 10 may be configured to remove the catalyst poisons from the gas G1. The pretreatment device 10 can be used, for example, to remove impurities contained in the gas G1 that poison the catalysts used in the alkaline solution A, the first generation device 60, and the second generation device 70. Examples of impurities include sulfur compounds such as sulfur dioxide, hydrogen sulfide, and carbonyl sulfide. In this case, the cooling tank 11 is also referred to as an absorption tank.

[0022] The carbon dioxide capture device 20 captures carbon dioxide from a carbon dioxide-containing gas G1. Specifically, the carbon dioxide capture device 20 generates, from the carbon dioxide-containing gas G1 to be captured, a gas having a higher carbon dioxide concentration than the gas G1 to be captured. The carbon dioxide capture device 20 can capture carbon dioxide using, for example, chemical absorption, pressure swing adsorption, temperature swing adsorption, or membrane separation concentration, but this embodiment will be described using a carbon dioxide capture device 20 that uses chemical absorption as an example. The chemical absorption method makes it possible to capture a large amount of carbon dioxide from gas at normal pressure. The carbon dioxide capture device 20 includes an absorber 21, a separator 25, a supply pipe 31, a reflux pipe 32, a pump 33, a pump 34, a heat exchanger 35, a cooler 36, an air supply pipe 37, a cleaning device 38, and a gas-liquid separator 45.

[0023] The absorber 21 produces an alkaline solution A containing carbon dioxide through gas-liquid contact between a gas containing carbon dioxide and the alkaline solution A. The separator 25 separates carbon dioxide from the alkaline solution A containing carbon dioxide. The alkaline solution A may contain an absorbent selected from the group consisting of, for example, an alkanolamine and a hindered amine having an alcoholic hydroxyl group. The alkanolamine may be, for example, at least one amine selected from the group consisting of monoethanolamine, diethanolamine, triethanolamine, methyldiethanolamine, diisopropanolamine, and diglycolamine. The hindered amine having an alcoholic hydroxyl group may be, for example, at least one amine selected from the group consisting of 2-amino-2-methyl-1-propanol (AMP), 2-(ethylamino)ethanol (EAE), and 2-(methylamino)ethanol (MAE). The alkaline solution A preferably contains monoethanolamine (MEA). The concentration of the absorbent in the alkaline solution A can be set appropriately depending on the amount of carbon dioxide contained in the gas to be treated, the treatment speed, etc., and is, for example, 10% by mass to 50% by mass, taking into consideration the fluidity of the alkaline solution A and the suppression of consumption loss.

[0024] The absorber 21, the separator 25, and the scrubber 38 are, for example, countercurrent gas-liquid contactors. The absorber 21 includes an absorption tank 22, a packing material 23, and a demister 24. The separator 25 includes a separation tank 26, a packing material 27, a demister 28, a circulation pipe 29, and a heater 30.

[0025] The supply pipe 31 connects the bottom of the absorption tank 22 below the packing material 23 of the absorption device 21 with the top of the separation tank 26 above the packing material 27 of the separation device 25. The reflux pipe 32 connects the bottom of the separation tank 26 below the packing material 27 of the separation device 25 with the top of the absorption tank 22 above the packing material 23 of the absorption device 21. A pump 33 is provided in the supply pipe 31, and a pump 34 and a cooler 36 are provided in the reflux pipe 32. A heat exchanger 35 is also provided in the supply pipe 31 and the reflux pipe 32.

[0026] The type of heat exchanger 35 is not particularly limited, and for example, a spiral type, a plate type, a double pipe type, a multi-cylinder type, a multi-circular pipe type, a volute type, a volute plate type, a tank coil type, a tank jacket type, and a direct contact liquid type can be used.

[0027] Gas G1, supplied to the absorber 21 below the packing material 23, rises within the absorption tank 22 while coming into gas-liquid contact with alkaline solution A, supplied from the top of the absorption tank 22, and carbon dioxide contained in the gas G1 is absorbed by the alkaline solution A. As the gas G1 rises within the absorption tank 22, it passes through the packing material 23, thereby promoting gas-liquid contact with the alkaline solution A. The alkaline solution A that has absorbed the carbon dioxide drips from the packing material 23 to the bottom of the absorption tank 22 and accumulates there. The alkaline solution A that accumulates at the bottom of the absorption tank 22 is pumped up by the pump 33, passed through the supply piping 31, heated by the heat exchanger 35, and then sent above the packing material 27 of the separation device 25.

[0028] The alkaline solution A heated by the heat exchanger 35 drips from above the packing material 27 while releasing carbon dioxide, and accumulates at the bottom of the separation tank 26. During this process, the alkaline solution A passes through the packing material 27, and gas-liquid contact at the packing material 27 promotes the release of carbon dioxide from the alkaline solution A. A circulation pipe 29 is provided at the bottom of the separation tank 26, and a steam heater 30 is attached to the circulation pipe 29. A portion of the alkaline solution A retained at the bottom of the separation tank 26 is diverted to the heater 30 through the circulation pipe 29, where it is heated by heat exchange with high-temperature steam, for example, to near the boiling point of the alkaline solution A, and then returned to the separation tank 26. This heating causes carbon dioxide to be released from the alkaline solution A at the bottom of the separation tank 26. Furthermore, this heating indirectly heats the packing material 27, and gas-liquid contact at the packing material 27 promotes the release of carbon dioxide from the alkaline solution A. The released gas containing carbon dioxide passes through a demister 28 that removes minute droplets, and is discharged from a gas outlet provided at the top of the separation tank 26.

[0029] Meanwhile, a portion of the alkaline solution A remaining at the bottom of the separation tank 26 is pumped up by a pump 34, passed through a reflux pipe 32, cooled in a heat exchanger 35, and then sent from the bottom of the separation tank 26 to a position above the packing material 23 of the absorber 21. During this process, heat is exchanged between the alkaline solution A passing through the supply pipe 31 and the alkaline solution A passing through the reflux pipe 32, heating the alkaline solution A passing through the supply pipe 31 and cooling the alkaline solution A passing through the reflux pipe 32. The alkaline solution A passing through the reflux pipe 32 is further cooled by a cooler 36 provided downstream of the heat exchanger 35. The alkaline solution A supplied from above the packing material 23 of the absorber 21 comes into gas-liquid contact with the gas G1 supplied from the pretreatment device 10, and carbon dioxide is again absorbed by the alkaline solution A.

[0030] The gas from which carbon dioxide has been removed in absorption tank 22 passes through demister 24, which removes minute droplets, and is discharged from a gas outlet provided at the top of absorption tank 22. The gas outlet of absorption tank 22 and the bottom of cleaning tank 39 in cleaning device 38 are connected by air pipe 37, and the gas discharged from absorption device 21 is supplied to cleaning device 38 through air pipe 37.

[0031] The cleaning device 38 removes the alkaline solution A from the gas discharged from the top of the absorption tank 22. The cleaning device 38 includes a cleaning tank 39, a filler 40, a cooling pipe 41, a pump 42, a cooler 43, and a demister 44. The filler 40 is disposed inside the cleaning tank 39. The cooling pipe 41, the pump 42, and the cooler 43 are disposed outside the cleaning tank 39. The cooling pipe 41 connects the top of the cleaning tank 39 above the filler 40 to the bottom of the cleaning tank 39 below the filler 40. The cooling pipe 41 is provided with the pump 42 and the cooler 43. Cooling water W remaining at the bottom of the cleaning tank 39 is sucked up from the bottom of the cleaning tank 39 by the pump 42, cooled by the cooler 43, and then sent to the top of the cleaning tank 39.

[0032] The gas sent from the absorption device 21 is supplied from a gas supply port provided in the cleaning tank 39 below the packing material 40. The gas supplied from the gas supply port rises within the cleaning tank 39, and gas-liquid contact is promoted between the cooling water W supplied from the top of the cleaning tank 39 and the packing material 40, thereby removing the alkaline solution A contained in the gas. The gas from which the alkaline solution A has been removed passes through a demister 44, which removes minute droplets, and is discharged as gas G2 from a gas outlet provided at the top of the cleaning tank 39. Meanwhile, the cooling water W, whose temperature has increased upon contact with the gas in the packing material 40, flows down to the bottom of the cleaning tank 39, passes through cooling piping 41, is cooled in a cooler 43, and is then supplied again from the top of the cleaning tank 39.

[0033] Similar to the filler 12 of the pretreatment device 10, the fillers 23, 27, and 40 of the carbon dioxide capture device 20 are provided to increase the contact area between the supplied gas and liquid. The fillers 23, 27, and 40 are made of an iron-based metal material such as stainless steel or carbon steel, but are not particularly limited, and any material having durability and corrosion resistance at the treatment temperature and a shape that can provide the desired contact area can be appropriately selected and used.

[0034] Gas-liquid separation section 45 separates moisture from the gas discharged from separation device 25. Gas-liquid separation section 45 includes an exhaust pipe 46, a liquid feed pipe 47, a cooler 48, a gas-liquid separator 49, and a pump 50. Exhaust pipe 46 connects the gas outlet of separation tank 26 to the upper part of gas-liquid separator 49, and cooler 48 is provided on exhaust pipe 46. Liquid feed pipe 47 connects the bottom of gas-liquid separator 49 to separation tank 26, and pump 50 is provided on liquid feed pipe 47.

[0035] The gas containing a high concentration of carbon dioxide discharged from the gas outlet of separation device 25 passes through exhaust pipe 46 and is cooled by cooler 48, and the moisture and alkaline solution A contained in the gas are condensed. The condensed water and the like are separated in gas-liquid separator 49 and supplied to separation device 25 through liquid supply pipe 47 by pump 50, and returned to alkaline solution A at the bottom of separation tank 26.

[0036] The gas separated by the gas-liquid separator 45 contains, for example, 90% or more carbon dioxide by mass and is supplied to the first generator 60 through the connecting pipe 51. Hydrogen, the flow rate of which is adjusted by the flow control valve 52, is supplied to the gas containing a high concentration of carbon dioxide passing through the connecting pipe 51. The hydrogen is not particularly limited, but may be hydrogen obtained by electrolyzing water using renewable energy such as solar, wind, or hydropower. The mixed gas containing carbon dioxide and hydrogen is compressed by the compressor 53 and supplied to the first generator 60. The ratio of the amount of hydrogen to the amount of carbon dioxide supplied to the first generator 60 can be set as appropriate, and may be, for example, a molar ratio of 2 or more, or 2.5 or more. The ratio of the amount of hydrogen to the amount of carbon dioxide supplied to the first generator 60 may be, for example, a molar ratio of less than 4 or less than 3.5.

[0037] The first production device 60 produces hydrocarbons with a carbon number of two or more from a first feedstock containing carbon dioxide and hydrogen. In this embodiment, the carbon dioxide contained in the first feedstock includes carbon dioxide separated from the carbon dioxide capture device 20. Specifically, the carbon dioxide contained in the first feedstock includes carbon dioxide separated from the separation device 25. This makes it possible to use high-concentration carbon dioxide as the first feedstock, and improves the production efficiency of hydrocarbons with a carbon number of two or more. However, as long as hydrocarbons with a carbon number of two or more can be produced, the carbon dioxide separated from the carbon dioxide capture device 20 does not need to be used as the carbon dioxide contained in the first feedstock.

[0038] In recent years, carbon dioxide has become a problem as a cause of global warming, and there has been a growing global movement to curb carbon dioxide emissions. By producing hydrocarbons with two or more carbon atoms from the carbon dioxide contained in factory exhaust gases, the amount of carbon dioxide released into the atmosphere can be reduced, and these hydrocarbons with two or more carbon atoms can be used as highly marketable hydrocarbons. Furthermore, if carbon dioxide can be used as a raw material to produce hydrocarbons such as ethylene, which is a raw material for plastics, the use of petroleum, a finite resource, can be reduced, and carbon dioxide emissions can be reduced.

[0039] The first generation device 60 can be a known reaction device, for example, a shell-and-tube type or a flat plate type reactor. Shell-and-tube type reactors are inexpensive because of their simple structure. On the other hand, flat plate type reactors have high heat exchange efficiency and are therefore excellent in removing reaction heat and improving reaction efficiency. In this embodiment, the first generation device 60 includes a reactor 61, a cooling pipe 62, a pump 63, and a cooler 64. The cooling pipe 62 connects the upstream side and downstream side of the reactor 61, and the pump 63 and the cooler 64 are connected to the cooling pipe 62.

[0040] A catalyst is disposed in the reactor 61 within the flow path through which the first feedstock passes, and hydrocarbons having two or more carbon atoms are produced by contacting the first feedstock with the catalyst. The catalyst provided in the first production device 60 is not particularly limited as long as it can produce hydrocarbons having two or more carbon atoms from the first feedstock. The catalyst is selected based on the type of hydrocarbons to be produced, and known catalysts such as iron catalysts or cobalt catalysts can be used. The iron catalyst can mainly produce light hydrocarbons, while the cobalt catalyst can mainly produce heavy hydrocarbons containing wax. The iron catalyst can mainly produce olefins and paraffins, while the cobalt catalyst can mainly produce paraffins. The iron catalyst contains iron as an active component, and the cobalt catalyst contains cobalt as an active component. The content of the active component is preferably 20 mass% or more of the total catalyst. The first production device 60 is preferably provided with an iron catalyst that produces hydrocarbons having two or more carbon atoms from the first feedstock. This allows the production of light olefins (lower olefins), which can also be used as raw materials for plastics. In the first production device 60, the reaction conditions are not particularly limited as long as hydrocarbons having two or more carbon atoms are produced, but for example, the reaction temperature is 200°C to 400°C and the pressure is 0.1 MPa to 2 MPa.

[0041] The products produced in the first production device 60 may include various compounds in addition to hydrocarbons having two or more carbon atoms. Hydrocarbons having two or more carbon atoms include, for example, olefins and paraffins, and preferably include light olefins having two or more carbon atoms and four or less. Olefins having two or more carbon atoms and four or less are useful because they can also be used as raw materials for plastics. Olefins having two or more carbon atoms and four or less are, for example, at least one olefin selected from the group consisting of ethylene, propylene, 1-butene, 2-butene, isobutene, and 1,3-butadiene.

[0042] For example, ethylene can be produced from carbon dioxide and hydrogen as shown in reaction equation (1) below. 2CO2+6H2→C2H4+4H2O (1) The standard reaction enthalpy of the above reaction at 298 K is ΔH = -128 kJ / mol. Since the above reaction is an exothermic reaction, it is preferable to cool the reaction zone to an appropriate temperature to improve the efficiency of ethylene production. In this embodiment, a known refrigerant is circulated between the reactor 61 and the cooling pipe 62 by a pump 63 to lower the temperature of the reaction zone. At this time, at least a portion of the reaction heat generated when hydrocarbons having a carbon number of 2 or more are produced in the first production device 60 may be recovered. This allows the surplus reaction heat to be effectively utilized. For example, at least a portion of the reaction heat may be heat exchanged with a known refrigerant used to cool the cooler 64, and the obtained thermal energy may be reused within the hydrocarbon production system 1.

[0043] The separator 25 of the carbon dioxide recovery unit 20 may separate carbon dioxide from the alkaline solution A containing carbon dioxide using at least a portion of the reaction heat generated when hydrocarbons having two or more carbon atoms are produced in the first production unit 60. The energy required to separate carbon dioxide from the alkaline solution A in the separator 25 is, for example, 250 GJ / t- CO 2, and the reaction heat recovered in the first generation device 60 is, for example, 40.8 GJ / t- CO2. Therefore, by exchanging heat between the heat of the steam for heating the heater 30 of the separation device 25 and the heat of the refrigerant for cooling the cooler 64 of the first generation device 60, the excess reaction heat generated in the first generation device 60 can be effectively utilized.

[0044] As described above, the first production device 60 produces valuable hydrocarbons with a carbon number of two or more from carbon dioxide, which causes global warming. In the first production device 60, although it depends on the reaction conditions, for example, hydrocarbons with a carbon number of two or more are produced from 20% by mass or more but less than 85% by mass of the carbon dioxide contained in the first feedstock. The proportion of hydrocarbons with a carbon number of two or more produced depends on the reaction conditions and may be 35% by mass or more or 50% by mass or more. In addition, the proportion of hydrocarbons with a carbon number of two or more produced may be 65% by mass or less or 55% by mass or less.

[0045] Furthermore, some of the carbon dioxide supplied to the first generator 60 is not produced as hydrocarbons and is discharged from the first generator 60 as unreacted carbon dioxide. The proportion of the carbon dioxide discharged from the first generator 60 out of the carbon dioxide supplied to the first generator 60 may be 15% by mass or more, or 45% by mass or more. Furthermore, the proportion of the carbon dioxide discharged from the first generator 60 out of the carbon dioxide supplied to the first generator 60 may be less than 80% by mass, or less than 50% by mass.

[0046] The product P1 containing hydrocarbons with a carbon number of 2 or more produced in the first generator 60 may be separated on the connecting pipe 65 connecting the outlet of the first generator 60 to the inlet of the second generator 70, or may be separated downstream of the second generator 70. Meanwhile, the gas containing carbon dioxide discharged from the first generator 60 is supplied to the second generator 70 through the connecting pipe 65. Hydrogen, the flow rate of which is adjusted by a flow control valve 66, is supplied to the gas containing carbon dioxide passing through the connecting pipe 65. Hydrogen obtained using renewable energy as described above may be used. A mixed gas containing carbon dioxide and hydrogen is compressed by a compressor 67 and supplied to the second generator 70. The ratio of the amount of hydrogen to carbon dioxide supplied to the second generator 70 can be set as appropriate, but may be, for example, a molar ratio of 3 or more, or 3.5 or more. The ratio of the amount of hydrogen to carbon dioxide supplied to the second generator 70 may be less than 5 or less than 4.5.

[0047] In this embodiment, a mixed gas containing hydrogen and carbon dioxide, which serves as the second feedstock, is supplied to the second generator 70 using a compressor 67. However, the gas discharged from the first generator 60 may be supplied to the second generator 70 while maintaining its pressure. Specifically, the compressor 67 may not be provided between the first generator 60 and the second generator 70, and the gas discharged from the outlet of the first generator 60 may be supplied directly from the supply port of the second generator 70 without adjusting its pressure. This makes it possible to maintain the pressure inside the reactor 71 at a pressure suitable for producing methane and reduce the energy required for the compressor 67.

[0048] The second generator 70 mainly produces methane from hydrogen and the second feedstock containing carbon dioxide in the first feedstock discharged from the first generator 60. That is, the first generator 60 and the second generator 70 are arranged in series, with the second generator 70 being arranged downstream of the first generator 60. The second generator 70 can produce methane from carbon dioxide and hydrogen, as shown in the following reaction formula (2). CO2+4H2→CH4+2H2O (2)

[0049] The above reaction formula (2) is called methanation (or Sabatier reaction), and can produce methane with high selectivity. That is, the mass ratio of methane produced from the carbon dioxide supplied to the second producer 70 is greater than the mass ratio of hydrocarbons with a carbon number of two or more produced from the carbon dioxide supplied to the first producer 60. In the second producer 70, although depending on the reaction conditions, for example, methane is produced from 85 mass% or more of the carbon dioxide contained in the second feedstock. The proportion of methane produced depends on the reaction conditions and may be 90 mass% or more, or may be 95 mass% or more. As described above, in the first producer 60, hydrocarbons with a carbon number of two or more are produced from, for example, 20 mass% or more but less than 85 mass% of the carbon dioxide contained in the first feedstock. However, by arranging the second producer 70 in series downstream of the first producer 60, the unreacted carbon dioxide discharged from the first producer 60 can be effectively utilized in the second producer 70.

[0050] For example, of the carbon dioxide supplied to the first producer 60, 45 mass% of the carbon dioxide is produced as hydrocarbons having two or more carbon atoms, and 55 mass% of the carbon dioxide is discharged from the first producer 60 as unreacted. However, 90 mass% of the carbon dioxide is produced as methane in the second producer 70. That is, of the carbon dioxide discharged as unreacted from the first producer 60, only 10 mass% of the carbon dioxide is discharged as unreacted from the second producer 70. Therefore, in the first producer 60 and the second producer 70 as a whole, 94.5 mass% of the carbon dioxide input as a feedstock is used to produce methane and hydrocarbons other than methane, and only the remaining approximately 5.5 mass% of the carbon dioxide is discharged. That is, the hydrocarbon production system 1 can produce hydrocarbons having two or more carbon atoms and methane from 90 mass% or more of the carbon dioxide contained in the first feedstock. Therefore, according to the hydrocarbon production system 1 of this embodiment, carbon dioxide, which is a cause of global warming, can be efficiently recovered, and valuable materials such as methane and hydrocarbons with a carbon number of 2 or more can be produced with a high yield throughout the hydrocarbon production system 1 as a whole.

[0051] It is also possible to improve the yield of hydrocarbons in the entire system by feeding the carbon dioxide discharged from the first producer 60 back into the first producer 60 as a raw material. However, in order to produce a large amount of hydrocarbons with a carbon number of two or more from carbon dioxide in the first producer 60, it is necessary to repeat the operation of supplying the carbon dioxide discharged from the first producer 60 back to the first producer 60 multiple times. For example, assuming that 55 mass % of the carbon dioxide supplied to the first producer 60 is discharged from the first producer 60, even if the reaction in the first producer 60 is repeated four times, only 92 mass % of the carbon dioxide will react.

[0052] As with the first generation apparatus 60, a known reaction apparatus can be used for the second generation apparatus 70, and a shell-and-tube type or flat plate type reactor can be used. In this embodiment, the second generation apparatus 70 includes a reactor 71, a cooling pipe 72, a pump 73, and a cooler 74. The upstream side and downstream side of the reactor 71 are connected by the cooling pipe 72, and the cooling pipe 72 is provided with the pump 73 and the cooler 74.

[0053] In the reactor 71, a catalyst is disposed in a flow path through which the second feedstock passes, and methane is produced by contacting the second feedstock with the catalyst. The catalyst disposed in the reactor 71 is not particularly limited as long as it can produce methane from the second feedstock, and known catalysts used in methanation, such as nickel catalysts or ruthenium catalysts, can be used. The nickel catalyst is a catalyst containing nickel as an active component, and the ruthenium catalyst is a catalyst containing ruthenium as an active component. The content of the active component is preferably 20 mass% or more of the entire catalyst. From the viewpoints of cost and high methane selectivity, it is preferable that the second production unit 70 be provided with a nickel catalyst that produces methane from the second feedstock. In the second production unit 70, the reaction conditions are not particularly limited as long as methane is produced, but for example, the reaction temperature is 200°C to 400°C and the pressure is 0.1 MPa to 2 MPa.

[0054] The standard reaction enthalpy of reaction in the above reaction formula (2) at 298 K is ΔH = -165 kJ / mol. Since the above reaction is an exothermic reaction, it is preferable to cool the reaction region to an appropriate temperature to improve the methane production efficiency. In this embodiment, a known coolant is circulated between the reactor 71 and the cooling pipe 72 by a pump 73 to lower the temperature of the reaction region. As with the first production unit 60, in the hydrocarbon production system 1, at least a portion of the reaction heat generated when methane is produced in the second production unit 70 may be recovered. This allows the surplus reaction heat to be effectively utilized. For example, at least a portion of the reaction heat may be heat exchanged with a known coolant used to cool the cooler 74, and the obtained thermal energy may be reused in the hydrocarbon production system 1.

[0055] The separator 25 of the carbon dioxide capture unit 20 is a second generator 70. methane Carbon dioxide may be separated from the alkaline solution A containing carbon dioxide by at least a part of the reaction heat generated when carbon dioxide is produced. The energy required to separate carbon dioxide from the alkaline solution A in the separator 25 is, for example, 250 GJ / t- CO 2, and the reaction heat recovered in the second generation device 70 is, for example, 152.6 GJ / t- CO 2. By exchanging heat between the heat of the steam used to heat the heater 30 of the separation device 25 and the heat of the refrigerant used to cool the cooler 74 of the second generation device 70, the excess reaction heat generated in the second generation device 70 can be effectively utilized.

[0056] A product P2 containing methane and a mixed gas containing carbon dioxide are discharged from the second generation device 70. Then, the product P2 containing methane is separated from the mixed gas, and a gas G3 containing carbon dioxide is discharged.

[0057] In the above embodiment, hydrocarbons having a carbon number of two or more were produced in the first generator 60 using a feedstock containing carbon dioxide as the first feedstock. Furthermore, hydrocarbons were produced in the second generator 70 using a feedstock containing carbon dioxide as the second feedstock. However, a feedstock containing carbon monoxide may be used as the first feedstock instead of or together with carbon dioxide. Similarly, a feedstock containing carbon monoxide may be used as the second feedstock instead of or together with carbon dioxide. When carbon monoxide and hydrogen are reacted in the first generator 60, depending on the reaction conditions, 20% by mass or more but less than 85% by mass of the supplied carbon monoxide becomes hydrocarbons having a carbon number of two or more, and at least one of the carbon monoxide and the carbon dioxide is discharged as an unreacted portion. Therefore, this unreacted feedstock containing carbon monoxide and carbon dioxide can be used as the second feedstock to produce methane in the second generator 70. Furthermore, when methane is generated in second generator 70 using a raw material containing carbon monoxide and hydrogen as the second feedstock, 85 mass % or more of the supplied carbon monoxide becomes methane, just as in the case where a raw material containing carbon dioxide is used as the second feedstock. Therefore, even if the first feedstock contains at least one of carbon monoxide and carbon dioxide, methane is generated from the second feedstock containing carbon monoxide and carbon dioxide discharged from first generator 60.

[0058] When the first raw material contains carbon monoxide, the first producer 60 can produce ethylene from carbon monoxide and hydrogen as shown in the following reaction formula (3). 2CO+4H2→C2H4+2H2O (3) The standard reaction enthalpy of the above reaction at 298 K is ΔH=−210 kJ / mol, and the above reaction is exothermic. Therefore, at least a portion of the reaction heat may be recovered and reused in the hydrocarbon production system 1, similar to when carbon dioxide is used as the raw material.

[0059] Similarly, when the second feedstock contains carbon monoxide, the second generator 70 can produce methane from carbon monoxide and hydrogen, as shown in the following reaction formula (4). CO+3H2→CH4+H2O (4) The standard reaction enthalpy of the above reaction at 298 K is ΔH=−206 kJ / mol, and the above reaction is exothermic. Therefore, at least a portion of the reaction heat may be recovered and reused in the hydrocarbon production system 1, similar to when carbon dioxide is used as the raw material.

[0060] Therefore, at least a portion of at least one of the reaction heats generated when hydrocarbons having a carbon number of 2 or more are produced in the first production unit 60 and the reaction heat generated when methane is produced in the second production unit 70 may be recovered. Furthermore, the separation unit 25 may separate carbon dioxide from the carbon dioxide-containing alkaline solution A using at least a portion of at least one of the reaction heats generated when hydrocarbons having a carbon number of 2 or more are produced in the first production unit 60 and the reaction heat generated when methane is produced in the second production unit 70. This can improve the energy efficiency of the entire process.

[0061] Next, the effects of the hydrocarbon production system 1 will be described.

[0062] The hydrocarbon production system 1 according to this embodiment includes a first production device 60 that produces hydrocarbons having two or more carbon atoms from a first feedstock containing hydrogen and at least one of carbon monoxide and carbon dioxide. The hydrocarbon production system 1 also includes a second production device 70 that produces methane from a second feedstock containing hydrogen and at least one of carbon monoxide and carbon dioxide contained in the first feedstock discharged from the first production device 60.

[0063] Furthermore, the first generator 60 according to this embodiment produces hydrocarbons with a carbon number of two or more from a first feedstock containing at least one of carbon monoxide and carbon dioxide and hydrogen, and is connected to the second generator 70. The second generator 70 produces methane from a second feedstock containing hydrogen and at least one of carbon monoxide and carbon dioxide in the first feedstock discharged from the first generator 60.

[0064] Furthermore, the second production device 70 according to this embodiment produces methane from a second feedstock containing hydrogen and at least one of carbon monoxide and carbon dioxide in the first feedstock discharged from the first production device 60. The first production device 60 produces hydrocarbons with a carbon number of two or more from the first feedstock containing at least one of carbon monoxide and carbon dioxide and hydrogen.

[0065] The hydrocarbon production system 1, first production device 60, and second production device 70 according to this embodiment provide the following effects. That is, of the carbon monoxide and carbon dioxide supplied to the first production device 60, unreacted carbon monoxide and carbon dioxide that have not been produced as hydrocarbons with a carbon number of two or more are used in the second production device 70 as raw materials for producing methane. Therefore, even if the first production device 60 does not provide a sufficient yield of hydrocarbons with a carbon number of two or more, methane is produced with high efficiency in the second production device 70. Therefore, the hydrocarbon production system 1 can produce not only methane but also hydrocarbons other than methane that have high added value.

[0066] Furthermore, since the first generation device 60 and the second generation device 70 consume most of the carbon monoxide and carbon dioxide contained in the first feedstock, the amount of carbon monoxide and carbon dioxide emitted from the hydrocarbon generation system 1 can be reduced.

[0067] In this way, the hydrocarbon production system 1, the first production device 60, and the second production device 70 according to this embodiment can efficiently produce methane and hydrocarbons other than methane from at least one of carbon monoxide and carbon dioxide.

[0068] [Hydrocarbon production method] Next, a hydrocarbon production method according to this embodiment will be described. The hydrocarbon production method includes a first production step and a second production step. As described above, the first production step is a step of producing hydrocarbons having two or more carbon atoms from a first feedstock containing at least one of carbon monoxide and carbon dioxide and hydrogen in the first production device 60. Furthermore, as described above, the second production step is a step of producing methane from a second feedstock containing hydrogen and at least one of carbon monoxide and carbon dioxide in the first feedstock discharged in the first production step in the second production device 70.

[0069] For the same reasons as those described above, the hydrocarbon production method according to this embodiment makes it possible to efficiently produce methane and hydrocarbons other than methane from at least one of carbon monoxide and carbon dioxide.

[0070] The entire contents of Patent Application No. 2020-051245 (filing date: March 23, 2020) are incorporated herein by reference.

[0071] Although several embodiments have been described, the embodiments can be modified or varied based on the above disclosure. All components of the above embodiments and all features described in the claims may be individually extracted and combined, unless they contradict each other.

[0072] 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]

[0073] 1. Hydrocarbon Production System 20 Carbon dioxide capture equipment 21 Absorber 25 Separation device 60 1st generation device 70 Second generation device

Claims

1. a first production device that produces hydrocarbons having a carbon number of two or more from a first feedstock containing at least one of carbon monoxide and carbon dioxide, and hydrogen; a second generator that generates methane from a second feedstock containing hydrogen and at least one of carbon monoxide and carbon dioxide in the first feedstock discharged from the first generator; Equipped with a hydrocarbon production system, wherein the second production device produces the methane from at least one of carbon monoxide and carbon dioxide contained in the second feedstock, the at least one of carbon monoxide and carbon dioxide being 85 mass% or more.

2. 2. The hydrocarbon production system according to claim 1, wherein the first production device produces the hydrocarbons having a carbon number of 2 or more from at least one of carbon monoxide and carbon dioxide contained in the first feedstock, the at least one of carbon monoxide and carbon dioxide being 20 mass% or more but less than 85 mass%.

3. 3. The hydrocarbon production system according to claim 1, wherein the first production device is provided with an iron catalyst that produces the hydrocarbons having two or more carbon atoms from the first feedstock, and the second production device is provided with a nickel catalyst that produces methane from the second feedstock.

4. Further provided is a carbon dioxide recovery device that recovers carbon dioxide from a gas containing carbon dioxide, The hydrocarbon production system according to any one of claims 1 to 3, wherein the carbon dioxide contained in the first feedstock comprises carbon dioxide separated from the carbon dioxide capture unit.

5. The carbon dioxide capture device an absorption device that produces an alkaline solution containing carbon dioxide by gas-liquid contact between a gas containing carbon dioxide and an alkaline solution; a separation device that separates carbon dioxide from the carbon dioxide-containing alkaline solution; Including, The hydrocarbon production system of claim 4 , wherein the carbon dioxide contained in the first feedstock comprises carbon dioxide separated from the separation device.

6. The hydrocarbon production system according to any one of claims 1 to 5, wherein at least a portion of at least one of reaction heats generated when the hydrocarbons having a carbon number of 2 or more are produced in the first production device and reaction heat generated when methane is produced in the second production device is recovered.

7. 6. The hydrocarbon production system according to claim 5, wherein the separation device separates the carbon dioxide from the alkaline solution containing carbon dioxide using at least a portion of at least one of reaction heats generated when the hydrocarbons having two or more carbon atoms are produced in the first production device and reaction heat generated when methane is produced in the second production device.

8. The hydrocarbon production system according to any one of claims 1 to 7, wherein the hydrocarbons having two or more carbon atoms include olefins having two or more carbon atoms and four or less carbon atoms.

9. The hydrocarbon production system according to any one of claims 1 to 8, wherein the gas discharged from the first production unit is supplied to the second production unit while maintaining pressure.

10. a first production step of producing hydrocarbons having a carbon number of two or more from a first feedstock containing at least one of carbon monoxide and carbon dioxide and hydrogen; a second production step of producing methane from a second feedstock containing hydrogen and at least one of carbon monoxide and carbon dioxide in the first feedstock discharged in the first production step; Including, a hydrocarbon production method, wherein in the second production step, the methane is produced from 85 mass% or more of the carbon monoxide and / or the carbon dioxide contained in the second feedstock.

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