Reaction System

Abstract

A reaction system (1) comprises: a carbon dioxide collection unit (20) which collects carbon dioxide by an absorption process or an adsorption process; a reaction unit (40) which generates hydrocarbon from a raw material that contains hydrogen and carbon dioxide; and a distillation unit (50) which distills the hydrocarbon, wherein the hydrocarbon is distilled in the distillation unit (50) with reaction heat which has been generated in generation of the hydrocarbon in the reaction unit (40), and carbon dioxide having been absorbed or adsorbed in the carbon dioxide collection unit (20) is separated by a low-temperature heat medium, the temperature of which, as a result of consuming part of the reaction heat in the distillation unit (50), has become lower than that of a high-temperature heat medium that is a heat medium introduced to the distillation unit (50).

Description

[Technical Field]

[0001] The present disclosure relates to reaction systems. [Background technology]

[0002] Carbon dioxide is seen as a problematic cause of global warming, and there has been a growing movement worldwide to curb carbon dioxide emissions. Known methods for reducing carbon dioxide emissions into the atmosphere and effectively utilizing carbon dioxide include methanation technology, which produces methane from carbon dioxide in exhaust gases, and Fischer-Tropsch (FT) synthesis technology, which synthesizes various hydrocarbons. Methanation and FT synthesis reactions are exothermic reactions. Therefore, there is a growing movement to effectively utilize the heat generated by methanation reactions.

[0003] Patent Document 1 discloses a heat-utilizing gas purification system including a methane gas synthesis apparatus that uses hydrogen and carbon dioxide as raw material gases, and a temperature swing adsorption gas purification apparatus provided in the raw material gas inlet and product gas outlet of the methane gas synthesis apparatus. In this system, reaction heat from the methane gas synthesis apparatus is imparted to high-temperature regeneration gas introduced into the temperature swing adsorption gas purification apparatus. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2019-052224 Summary of the Invention [Problem to be solved by the invention]

[0005] According to the conventional technology, the reaction heat of the methane gas synthesis unit is used to generate the high-temperature regeneration gas introduced into the temperature swing adsorption gas purification unit, which can improve energy efficiency. However, further improvement in energy efficiency is expected.

[0006] Therefore, an object of the present disclosure is to provide a reaction system with high energy efficiency. [Means for solving the problem]

[0007] The reaction system according to the present disclosure includes a carbon dioxide recovery unit that recovers carbon dioxide by an absorption method or an adsorption method, a reaction unit that produces hydrocarbons from a raw material containing hydrogen and carbon dioxide, and a distillation unit that distills the hydrocarbons. In the reaction system, the hydrocarbons are distilled in the distillation unit using reaction heat generated by the production of hydrocarbons in the reaction unit, and the carbon dioxide absorbed or adsorbed in the carbon dioxide recovery unit is separated by a low-temperature heat medium that has consumed part of the reaction heat in the distillation unit and has a lower temperature than the high-temperature heat medium that is introduced into the distillation unit.

[0008] The distillation section may distill the hydrocarbons produced in the reaction section.

[0009] The carbon dioxide contained in the raw material may include carbon dioxide recovered in the carbon dioxide recovery section.

[0010] The carbon dioxide recovery unit may include an absorption unit that absorbs carbon dioxide into an absorption liquid, and a separation unit that separates the carbon dioxide absorbed in the absorption liquid from the absorption liquid, and the separation unit may separate the carbon dioxide using a low-temperature heat medium.

[0011] The reaction section may comprise a fixed bed reactor.

[0012] The distillation section may include at least one of an atmospheric distillation section and a vacuum distillation section, and hydrocarbons introduced into at least one of the atmospheric distillation section and the vacuum distillation section may be distilled by the reaction heat. [Effects of the Invention]

[0013] According to the present disclosure, a highly energy-efficient reaction system can be provided. [Brief explanation of the drawings]

[0014] [Figure 1]FIG. 1 is a schematic diagram showing a reaction system according to one embodiment. [Figure 2] FIG. 2 is a schematic diagram showing a heat transfer medium flow path of a reaction system according to one embodiment. [Figure 3] FIG. 3 is a schematic diagram showing a heat transfer medium flow path of a reaction system according to one embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0015] 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.

[0016] As shown in FIG. 1, the reaction system 1 according to this embodiment includes a carbon dioxide generation source 10, a carbon dioxide recovery section 20, a carbon dioxide supply section 30, a hydrogen supply section 35, a reaction section 40, and a distillation section 50.

[0017] The carbon dioxide generation source 10 is, for example, a power plant or factory that emits carbon dioxide by burning fuel, etc. The carbon dioxide generation source 10 may include a boiler.

[0018] The carbon dioxide capture unit 20 captures the carbon dioxide generated from the carbon dioxide generation source 10. By capturing the carbon dioxide generated from the carbon dioxide generation source 10, the carbon dioxide capture unit 20 can reduce the amount of carbon dioxide released into the atmosphere.

[0019] The carbon dioxide recovery section 20 may recover carbon dioxide by a chemical absorption method. As shown in Fig. 1 , the carbon dioxide recovery section 20 may include an absorption section 21, a separation section 22, a supply pipe 23, a reflux pipe 24, a heat exchanger 25, a reboiler 26, a cooling section 28, and a gas-liquid separation section 29. The supply pipe 23 connects the lower part of the absorption section 21 to the upper part of the separation section 22. The reflux pipe 24 connects the lower part of the separation section 22 to the upper part of the absorption section 21. The supply pipe 23 and the reflux pipe 24 are provided with a heat exchanger 25.

[0020] The absorption unit 21 absorbs carbon dioxide into the absorption liquid. Specifically, the absorption unit 21 absorbs carbon dioxide through gas-liquid contact between a gas containing carbon dioxide and the absorption liquid. In this embodiment, the absorption unit 21 is an absorption tower. The separation unit 22 separates the carbon dioxide absorbed in the absorption liquid from the absorption liquid. In this embodiment, the separation unit 22 is a stripper tower. The absorption liquid may be an alkaline solution. Specifically, the absorption liquid may contain at least one of an alkanolamine and a hindered amine having an alcoholic hydroxyl group. More specifically, the absorption liquid may contain monoethanolamine (MEA).

[0021] The gas containing carbon dioxide supplied from below the absorption section 21 comes into gas-liquid contact with the absorption liquid, and the carbon dioxide contained in the gas is absorbed by the absorption liquid. The absorption liquid that has absorbed the carbon dioxide passes through the supply pipe 23, is heated by the heat exchanger 25, and is then sent to the upper part of the separation section 22. The absorption liquid heated by the heat exchanger 25 drips from the upper part of the separation section 22 while emitting carbon dioxide, and accumulates at the bottom of the separation section 22. The absorption liquid that accumulates at the bottom of the separation section 22 is heated by the reboiler 26, and the carbon dioxide is emitted from the absorption liquid. The gas containing the emitted carbon dioxide is discharged from a gas outlet provided at the top of the separation section 22.

[0022] Meanwhile, the absorption liquid remaining at the bottom of the separation section 22 is cooled in a heat exchanger 25 through the reflux piping 24 and then sent to the upper part of the absorption section 21. At this time, heat is exchanged between the absorption liquid passing through the supply piping 23 and the absorption liquid passing through the reflux piping 24, so that the absorption liquid passing through the supply piping 23 is heated and the absorption liquid passing through the reflux piping 24 is cooled. The absorption liquid supplied from above the packing material of the absorption section 21 comes into gas-liquid contact with the gas containing carbon dioxide supplied from the carbon dioxide generation source 10, and the carbon dioxide is again absorbed by the absorption liquid. The gas from which carbon dioxide has been removed in the absorption section 21 is discharged from a gas outlet provided at the top of the absorption section 21.

[0023] The gas outlet of the separation unit 22 and the reaction unit 40 are connected via a pipe 27. The pipe 27 is provided with a cooling unit 28, a gas-liquid separation unit 29, and a carbon dioxide supply unit 30. The gas containing carbon dioxide discharged from the gas outlet of the separation unit 22 passes through the pipe 27 and is cooled by the cooling unit 28, and the moisture and absorption liquid contained in the gas are condensed. The condensed water and the like are separated in the gas-liquid separation unit 29 and returned to the separation unit 22 through a pipe not shown. The gas separated from the carbon dioxide capture unit 20 contains, for example, 90% or more, 95% or more, or 99% or more carbon dioxide by mass. The carbon dioxide supply unit 30 includes a flow rate adjuster 31, a compressor 32, and a flow rate adjuster 33.

[0024] The flow rate adjuster 31 is provided in the pipe 27 downstream of the cooling unit 28 and the gas-liquid separator 29. The flow rate adjuster 31 adjusts the flow rate of the gas flowing through the pipe 27.

[0025] The compressor 32 compresses the gas. The gas compressed by the compressor 32 contains the carbon dioxide separated from the carbon dioxide capture section 20. The compressor 32 has an inlet and a discharge port, and the gas sucked in through the inlet is compressed and discharged from the discharge port.

[0026] The flow rate adjuster 33 adjusts the flow rate of the gas compressed by the compressor 32. The flow rate adjuster 33 adjusts the flow rate of the gas compressed by the compressor 32 and supplied to the reaction section 40. The flow rate adjuster 33 may include a mass flow controller.

[0027] The hydrogen supply unit 35 supplies hydrogen to the reaction unit 40. The hydrogen supply unit 35 is not particularly limited as long as it can supply hydrogen to the reaction unit 40, but hydrogen obtained by electrolyzing water using renewable energy such as solar, wind, or hydraulic power may be used. By using such hydrogen, the reaction system 1 as a whole can reduce carbon dioxide emissions.

[0028] A raw material containing hydrogen and carbon dioxide is supplied to the reaction section 40. In this embodiment, the carbon dioxide contained in the raw material includes carbon dioxide recovered by the carbon dioxide recovery section 20. This makes it possible to provide a reaction system 1 in which the carbon dioxide recovery section 20 and the reaction section 40 are integrated. However, the reaction section 40 may be independent of the carbon dioxide recovery section 20, and carbon dioxide not passing through the carbon dioxide recovery section 20 may be used as a raw material. The raw material supplied to the reaction section 40 may be heated by a heating section (not shown). The ratio of the amount of hydrogen to the amount of carbon dioxide supplied to the reaction section 40 can be set as appropriate, and may be, for example, a molar ratio of 1 or more, 2 or more, 3 or more, 3.5 or more, or 4 or more. Furthermore, the ratio of the amount of hydrogen to the amount of carbon dioxide supplied to the reaction section 40 may be, for example, a molar ratio of less than 8, less than 6, less than 5, or less than 4.5. In the case of a methanation reaction, the ratio of the amount of hydrogen to the amount of carbon dioxide supplied to the reaction section 40 may be 4, which is a stoichiometric ratio.

[0029] The reaction section 40 produces hydrocarbons from raw materials containing hydrogen and carbon dioxide. By producing hydrocarbons in the reaction section 40, not only can carbon dioxide emissions be suppressed but also carbon dioxide can be effectively utilized.

[0030] The hydrocarbons may include at least one of an alkane and an alkene. These hydrocarbons can be produced by a methanation reaction or a Fischer-Tropsch (FT) reaction. At least one of the alkanes and alkenes may include hydrocarbons having 1 to 100 carbon atoms. For example, at least one of the alkanes and alkenes may include hydrocarbons having 1 to 4 carbon atoms. Examples of alkanes having 1 to 4 carbon atoms include methane, ethane, propane, and butane. Examples of alkenes having 1 to 4 carbon atoms include ethylene, propylene, 1-butene, 2-butene, isobutene, and 1,3-butadiene. Among these, methane, ethane, and propane can be used as fuels for city gas. Furthermore, alkenes having 2 to 4 carbon atoms are useful as raw materials for plastics. The reaction product may also include compounds other than those listed above.

[0031] The reaction section 40 may include a fixed-bed reactor. The fixed-bed reactor has a relatively simple structure, making it possible to provide a reaction system 1 with a simple configuration. The fixed-bed reactor may be a single-tube reactor or a multi-tube reactor such as a shell-and-tube reactor. The fixed-bed reactor may include reaction tubes and a shell that houses the reaction tubes. By passing a heat transfer medium as a cooling medium around the outside of the reaction tubes in the shell, the reaction heat generated by the production of hydrocarbons in the reaction section 40 can be removed. A catalyst may be disposed in the reaction tube. As a result, the raw material passes through the reaction tube and comes into contact with the catalyst, causing the carbon dioxide and hydrogen contained in the raw material to react and produce hydrocarbons.

[0032] The catalyst is selected from the viewpoint of 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 alkenes and alkanes, while the cobalt catalyst can mainly produce alkanes. The iron catalyst contains iron as an active component, while the cobalt catalyst contains cobalt as an active component. The reaction conditions in the reaction section 40 are not particularly limited, but examples include a reaction temperature of 200°C to 500°C and a pressure of 0.3 MPaG to 3 MPaG.

[0033] The reaction section 40 and the atmospheric distillation column 53 of the distillation section 50 are connected via a pipe 41. The pipe 41 is provided with a cooling section 42, a gas-liquid separation section 43, and a heating section 52. The cooling section 42 cools the reaction product produced in the reaction section 40. This allows a portion of the reaction product produced in the reaction section 40 to be condensed. The gas-liquid separation section 43 separates the low-boiling-point reaction product that remains gaseous without being condensed by the cooling section 42 from the high-boiling-point reaction product that is condensed by the cooling section 42 and has a boiling point higher than that of the low-boiling-point reaction product. The low-boiling-point reaction product may contain, for example, methane. The low-boiling-point reaction product may contain ethane, propane, butane, etc. The high-boiling-point reaction product may contain multiple reaction products with different boiling points. The high-boiling-point reaction product may contain two or more hydrocarbons of C5 to C100. For example, the high-boiling-point reaction product may contain hydrocarbons of C5 to C15. The C5-15 liquid hydrocarbons can be used as aviation fuel. The high boiling point reaction product may be supplied to the distillation section 50.

[0034] The distillation section 50 distills the hydrocarbons produced in the reaction section 40. This makes it possible to provide a reaction system 1 in which the reaction section 40 and the distillation section 50 are integrated. However, the distillation section 50 may be independent of the reaction section 40 and distill hydrocarbons not produced in the reaction section 40. The distillation section 50 separates a mixture of hydrocarbons with different boiling points by utilizing the difference in boiling points. The reactants produced in the reaction section 40 may be processed by hydrotreating, such as hydrotreating, hydroisomerization, and hydrocracking. The distillation section 50 includes an atmospheric distillation section 51 and a vacuum distillation section 54.

[0035] Atmospheric distillation section 51 includes a heating section 52 and an atmospheric distillation column 53. Heating section 52 is provided in pipe 41 and heats the hydrocarbon mixture introduced into atmospheric distillation column 53. The temperature of the mixture after heating may be, for example, 300°C to 400°C. Atmospheric distillation column 53 distills the hydrocarbon mixture heated in heating section 52. Atmospheric distillation column 53 includes a plurality of plates, and by withdrawing liquid components from each plate, hydrocarbons can be separated according to their carbon numbers.

[0036] The atmospheric distillation section 51 distills a mixture of hydrocarbons with different boiling points under atmospheric pressure, for example, about 0.5 atm to 2 atm. In the atmospheric distillation section 51, the mixture can be separated into various fractions such as naphtha, kerosene, diesel, and residual oil by distillation. Naphtha may contain, for example, C4 to C12 hydrocarbons. The boiling point of C4 to C12 hydrocarbons is, for example, 35°C to 180°C. Kerosene may contain, for example, C12 to C18 hydrocarbons. The boiling point of C12 to C18 hydrocarbons is, for example, 170°C to 250°C. Diesel may contain, for example, C14 to C23 hydrocarbons. The boiling point of C14 to C23 hydrocarbons is, for example, 240°C to 350°C. Residue is hydrocarbons that remain without being fractionated and may contain, for example, hydrocarbons of C17 or higher. The boiling point of C17 or higher hydrocarbons is, for example, 350°C or higher.

[0037] The vacuum distillation unit 54 includes a heating unit 55, a vacuum distillation tower 56, and a vacuum unit (not shown). The atmospheric distillation tower 53 and the vacuum distillation tower 56 are connected via a pipe 57. The residual oil (atmospheric residual oil) distilled in the atmospheric distillation tower 53 is introduced into the vacuum distillation tower 56 via the pipe 57. The pipe 57 is provided with a heating unit 55. The heating unit 55 heats the atmospheric residual oil. The temperature of the mixture after heating may be, for example, 300°C to 400°C. The vacuum distillation tower 56 distills the atmospheric residual oil heated in the heating unit 55 under reduced pressure. The vacuum distillation tower 56 includes multiple plates, and by extracting liquid components from each plate, hydrocarbons can be separated according to their carbon numbers. The vacuum unit (not shown) discharges gas from the vacuum distillation tower 56 and reduces the pressure inside the vacuum distillation tower 56. The vacuum unit may include, for example, a vacuum pump.

[0038] The vacuum distillation section 54 distills the atmospheric residue under reduced pressure, for example, about 0.01 atm to 0.2 atm. In the vacuum distillation section 54, the atmospheric residue can be separated into fractions such as vacuum gas oil and vacuum residue by distillation. The vacuum gas oil may contain hydrocarbons with a boiling point of 350°C to 550°C, for example. The vacuum residue is the hydrocarbons that remain without being fractionated, and may contain hydrocarbons with a boiling point above 550°C, for example.

[0039] In this embodiment, hydrocarbons are distilled in the distillation section 50 using the reaction heat generated by producing hydrocarbons in the reaction section 40. Then, part of the reaction heat is consumed in the distillation section 50, and the low-temperature heat medium has a lower temperature than the high-temperature heat medium that is the heat medium introduced into the distillation section 50, and the carbon dioxide absorbed in the carbon dioxide recovery section 20 is separated by the low-temperature heat medium.

[0040] The reaction heat is exchanged via a heat medium passing through a heat medium passage 60. The heat medium passage 60 connects the carbon dioxide recovery section 20, the reaction section 40, and the distillation section 50. Specifically, the heat medium passage 60 connects the reboiler 26 of the carbon dioxide recovery section 20, the reaction section 40, the heating section 52 of the distillation section 50, and the heating section 55 of the distillation section 50.

[0041] In the reaction section 40, the heat of reaction generated by producing hydrocarbons is exchanged with the heat of the heat transfer medium. As a result, the heat transfer medium absorbs the heat of reaction and heats up, while the raw materials or products in the reaction section 40 are cooled. The reaction of producing hydrocarbons from raw materials containing hydrogen and carbon dioxide is an exothermic reaction. Therefore, by using the heat transfer medium to absorb the heat of reaction generated by producing hydrocarbons, the hydrocarbon reaction can be promoted advantageously.

[0042] The heating of the heat transfer medium with the heat of reaction may be carried out in the reaction section 40. For example, when the reaction section 40 includes a shell-and-tube reactor, the heat transfer medium may be heated by passing the heat transfer medium on the outside of the reaction tubes in the shell. Furthermore, since the reaction product having the heat of reaction passes through the cooling section 42, the heat transfer medium may be heated by passing the heat transfer medium through the cooling section 42. The high-temperature heat transfer medium heated by the heat of reaction is introduced into the distillation section 50.

[0043] In the distillation section 50, heat from the high-temperature heat transfer medium is exchanged with heat from the hydrocarbons introduced into the distillation section 50. Then, the hydrocarbons are distilled in the distillation section 50 using the high-temperature heat transfer medium. This allows the reaction heat to be used for distillation, thereby reducing the energy required for distillation. The heat transfer medium may be supplied to at least one of the atmospheric distillation section 51 and the vacuum distillation section 54. That is, the heat transfer medium may be supplied to either the atmospheric distillation section 51 or the vacuum distillation section 54, or may be supplied to both the atmospheric distillation section 51 and the vacuum distillation section 54. In this embodiment, the heating section 52 and the heating section 55 are arranged in parallel in the heat transfer medium flow path 60. The heat transfer medium transferred from the reaction section 40 is branched and supplied to the heating section 52 and the heating section 55. The low-temperature heat transfer medium, from which part of the reaction heat has been consumed in the heating section 52 and the heating section 55, is joined and introduced into the reboiler 26 of the carbon dioxide recovery section 20.

[0044] In the carbon dioxide recovery section 20, heat is exchanged between the low-temperature heat medium and the absorption liquid. As a result, the absorption liquid is heated in the reboiler 26. This promotes separation of the carbon dioxide absorbed in the absorption liquid. In addition, the low-temperature heat medium is cooled and introduced into the reaction section 40.

[0045] The heat medium may be a known heat medium such as steam or oil. When oil is used as the heat medium, it is relatively easy to handle and the device configuration can be simplified. Furthermore, when steam is used as the heat medium, the steam is less likely to deteriorate due to heat or oxidation, and costs can be reduced.

[0046] 2, in this embodiment, an example has been described in which the heat medium passage 60 connects the carbon dioxide capture section 20, the reaction section 40, and the distillation section 50, and a common heat medium circulates through the carbon dioxide capture section 20, the reaction section 40, and the distillation section 50. However, the heat medium passage 60 is not limited to this example, and different heat mediums may be passed through the heat medium passage 60.

[0047] For example, as shown in FIG. 3 , the heat medium flow path 60 may include a first circulation flow path 61, a second circulation flow path 62, and a third circulation flow path 63. The reaction system 1 may also include a first heat exchanger 64 and a second heat exchanger 65. The first circulation flow path 61 connects the reaction section 40 and the first heat exchanger 64. A first heat medium flows through the first circulation flow path 61, and circulates between the reaction section 40 and the first heat exchanger 64. The second circulation flow path 62 connects the distillation section 50, the first heat exchanger 64, and the second heat exchanger 65. A second heat medium flows through the second circulation flow path 62, and the second heat exchanger 64 circulates between the distillation section 50, the second heat exchanger 65, and the first heat exchanger 64 in this order. The third circulation flow path 63 connects the reboiler 26 of the carbon dioxide recovery section 20 and the second heat exchanger 65. A third heat medium flows through the third circulation flow path 63, and the third heat medium circulates between the reboiler 26 of the carbon dioxide recovery section 20 and the second heat exchanger 65.

[0048] The first heat medium is heated by the heat of reaction generated by producing hydrocarbons in the reaction section 40. The first heat medium and the second heat medium are heat exchanged in the first heat exchanger 64, and the second heat medium is heated. The second heat medium heated in the first heat exchanger 64 is supplied to the distillation section 50 as a high-temperature heat medium, and hydrocarbons are distilled in the distillation section 50. The second heat medium is transferred from the distillation section 50 to the second heat exchanger 65, and heat is exchanged between the heat medium in which part of the reaction heat has been consumed in the distillation section 50 and the third heat medium. The third heat medium (low-temperature heat medium) heated in the second heat exchanger 65 is introduced into the reboiler 26 of the carbon dioxide recovery section 20, and the carbon dioxide absorbed in the carbon dioxide recovery section 20 is separated. Meanwhile, the second heat medium cooled in the second heat exchanger 65 is supplied to the first heat exchanger 64, and is heated by the first heat medium in the first heat exchanger 64 as described above.

[0049] The first heat medium, the second heat medium, and the third heat medium may be the same or different heat media. Furthermore, instead of the first circulation flow path 61 and the second circulation flow path 62, a fourth circulation flow path connecting the reaction section 40 and the distillation section 50 may be used. In this case, the second heat exchanger 65 exchanges heat between the heat medium in the third circulation flow path 63 and the heat medium in the fourth circulation flow path. Similarly, instead of the second circulation flow path 62 and the third circulation flow path 63, a fifth circulation flow path connecting the distillation section 50 and the carbon dioxide recovery section 20 may be used. In this case, the first heat exchanger 64 exchanges heat between the heat medium in the first circulation flow path 61 and the heat medium in the fifth circulation flow path.

[0050] Even with the above configuration, hydrocarbons are distilled in the distillation section 50 using the reaction heat generated by producing hydrocarbons in the reaction section 40, and part of the reaction heat is consumed in the distillation section 50. Then, part of the reaction heat is consumed in the distillation section 50, and the low-temperature heat medium has a lower temperature than the high-temperature heat medium that is the heat medium introduced into the distillation section 50, and the carbon dioxide absorbed or adsorbed in the carbon dioxide recovery section 20 is separated by the low-temperature heat medium.

[0051] In this embodiment, an example has been described in which the carbon dioxide capture unit 20 captures carbon dioxide by chemical absorption. Specifically, the carbon dioxide capture unit 20 includes an absorption unit 21 that absorbs carbon dioxide into an absorption liquid, and a separation unit 22 that separates the carbon dioxide absorbed in the absorption liquid from the absorption liquid, and the separation unit 22 separates the carbon dioxide using a low-temperature heat medium. This makes it possible to capture large amounts of carbon dioxide. However, the carbon dioxide capture unit 20 may also capture carbon dioxide by solid absorption or physical adsorption. In solid absorption, carbon dioxide is captured using a solid absorbent material. In physical adsorption, carbon dioxide is captured using a solid adsorbent material.

[0052] When capturing carbon dioxide using the solid absorption method, the carbon dioxide capture unit 20 may include an absorption unit and a separation unit. Carbon dioxide is supplied to the absorption unit from the carbon dioxide generation source 10. Then, the inside of the absorption unit is kept at a low temperature and the carbon dioxide is brought into contact with a solid absorbent material, thereby allowing the carbon dioxide to be absorbed into the solid absorbent material. The solid absorbent material with the absorbed carbon dioxide is transferred to the separation unit, and the carbon dioxide absorbed into the solid absorbent material is separated by bringing the separation unit to a high temperature. Note that the carbon dioxide capture unit 20 may include an absorption / separation unit that absorbs and separates carbon dioxide, rather than having separate absorption and separation units. The inside of the absorption / separation unit is kept at a low temperature and the carbon dioxide is brought into contact with the solid absorbent material, allowing the carbon dioxide to be absorbed into the solid absorbent material. Furthermore, the carbon dioxide absorbed into the solid absorbent material can be separated by bringing the inside of the absorption / separation unit to a high temperature.

[0053] The solid absorbent may include at least one of a porous body having a basic substance supported on its surface and a porous body having a surface modified with a base. Such materials have a large specific surface area and high reactivity of the base with carbon dioxide, enabling them to absorb a large amount of carbon dioxide. The porous body may include at least one selected from the group consisting of zeolite, alumina, silica, resin, clay, and activated carbon. The basic substance may also include at least one amine compound selected from the group consisting of primary amine compounds, secondary amine compounds, and tertiary amine compounds. The base modifying the surface of the porous body may also be an amino group. These materials can be obtained by immersing a porous body in the above-mentioned amine compound, drying it, and then supporting or modifying the surface of the porous body with a basic substance. Alternatively, these materials can be obtained by modifying the porous body with a basic substance using a chemical reaction, such as a dealcoholization reaction, between the surface of the porous body and an amine compound.

[0054] The solid absorbent may contain at least one selected from the group consisting of alkali metals and alkaline earth metals. These materials can efficiently absorb carbon dioxide. The absorbent containing an alkali metal may contain at least one of an alkali metal carbonate and a lithium transition metal composite oxide. The absorbent containing an alkaline earth metal may contain an alkaline earth metal oxide, etc.

[0055] When capturing carbon dioxide using a physical adsorption method, the carbon dioxide capture unit 20 may include an adsorption unit and a desorption unit. Carbon dioxide is supplied to the adsorption unit. Then, the adsorption unit is kept at a low temperature and the carbon dioxide is brought into contact with a solid adsorbent material, thereby allowing the carbon dioxide to be adsorbed onto the solid adsorbent material. The solid adsorbent material with adsorbed carbon dioxide is transferred to the desorption unit, and the carbon dioxide adsorbed onto the solid adsorbent material can be desorbed by bringing the desorption unit to a high temperature. Note that the carbon dioxide capture unit 20 may include an adsorption / desorption unit that adsorbs and desorbs carbon dioxide, rather than having separate adsorption and desorption units. The adsorption / desorption unit is kept at a low temperature and the carbon dioxide is brought into contact with the solid adsorbent material, allowing the carbon dioxide to be adsorbed onto the solid adsorbent material. Furthermore, the carbon dioxide adsorbed onto the solid adsorbent material can be separated by bringing the adsorption / desorption unit to a high temperature.

[0056] The solid adsorbent may include a porous body, which may include at least one selected from the group consisting of zeolite, alumina, silica, resin, clay, and activated carbon.

[0057] In addition, in this embodiment, an example has been described in which the reaction section 40 includes a fixed bed reactor. However, the reaction section 40 may include a reactor other than a fixed bed reactor in addition to or instead of the fixed bed reactor. For example, the reaction section 40 may include at least one reactor selected from the group consisting of a fixed bed reactor, a slurry bed reactor, and a fluidized bed reactor.

[0058] The slurry bed reactor contains a slurry. The slurry contains liquid hydrocarbons and FT synthesis catalyst particles dispersed in the liquid hydrocarbons. A feedstock containing carbon dioxide and hydrogen is then passed through the slurry to produce hydrocarbons. The slurry bed reactor can produce hydrocarbons with a high carbon number. Therefore, components such as diesel and kerosene can be efficiently produced by distillation.

[0059] Furthermore, in this embodiment, an example has been described in which the carbon dioxide recovered by the carbon dioxide recovery unit 20 is used as the raw material for the reaction unit 40. However, the reaction unit 40 may be independent of the carbon dioxide recovery unit 20, and may use carbon dioxide that has not passed through the carbon dioxide recovery unit 20 as the raw material.

[0060] In addition, in this embodiment, an example has been described in which hydrocarbons produced in the reaction section 40 are distilled in the distillation section 50. However, the distillation section 50 may be independent of the reaction section 40 and may distill hydrocarbons that are not produced in the reaction section 40. In other words, the mixture introduced into the distillation section 50 may be crude oil, a reaction product obtained by FT synthesis, or a mixture thereof.

[0061] In addition, in this embodiment, an example has been described in which the distillation section 50 includes the atmospheric distillation section 51 and the vacuum distillation section 54. However, the distillation section 50 may include at least one of the atmospheric distillation section 51 and the vacuum distillation section 54. In this case, hydrocarbons introduced into at least one of the atmospheric distillation section 51 and the vacuum distillation section 54 by the heat of reaction may be distilled. This can promote the distillation of hydrocarbons in the atmospheric distillation section 51 or the vacuum distillation section 54. Furthermore, the distillation section 50 may include multiple distillation columns, and hydrocarbons may be distilled in each of the distillation columns. For example, naphtha may be distilled in a first distillation column, and kerosene may be distilled in a second distillation column.

[0062] If the heat required for distillation is insufficient, the heat medium may be heated by burning part of the hydrocarbons, such as methane, produced in the reaction section 40. The produced hydrocarbons are carbon dioxide-free fuel, and operation can be performed without increasing the apparent amount of carbon dioxide in the atmosphere.

[0063] As described above, the reaction system 1 according to this embodiment includes the carbon dioxide capture section 20 that captures carbon dioxide by an absorption method or an adsorption method, the reaction section 40 that produces hydrocarbons from a raw material containing hydrogen and carbon dioxide, and the distillation section 50 that distills the hydrocarbons. In this embodiment, the hydrocarbons are distilled in the distillation section 50 using the reaction heat generated when the hydrocarbons are produced in the reaction section 40. Then, the carbon dioxide absorbed or adsorbed in the carbon dioxide capture section 20 is separated by a low-temperature heat medium that has a temperature lower than that of the high-temperature heat medium that is the heat medium introduced into the distillation section 50 after part of the reaction heat is consumed in the distillation section 50.

[0064] The dissipation temperature required in separation section 22 is, for example, 100°C to 120°C, which is lower than the 350°C to 450°C temperature required for distillation in distillation section 50. Since the reaction heat can be used at a temperature suitable for carbon dioxide recovery section 20 and distillation section 50, energy efficiency can be improved compared to when the reaction heat is used separately.

[0065] The entire contents of Patent Application No. 2022-064383 (filing date: April 8, 2022) are incorporated herein by reference.

[0066] 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.

[0067] 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]

[0068] 1. Reaction System 20 Carbon Dioxide Capture Section 21 Absorption section 22 Separation part 40 Reaction section 50 Distillation Section

Claims

1. a carbon dioxide recovery unit that recovers carbon dioxide by an absorption method or an adsorption method; a reaction section for producing hydrocarbons from a feedstock containing hydrogen and carbon dioxide; a distillation section for distilling hydrocarbons; Equipped with a reaction system in which hydrocarbons are distilled in the distillation section by using reaction heat generated by producing hydrocarbons in the reaction section, and carbon dioxide absorbed or adsorbed in the carbon dioxide recovery section is separated by a low-temperature heat medium that has consumed a portion of the reaction heat in the distillation section and has a lower temperature than the high-temperature heat medium that is the heat medium introduced into the distillation section.

2. The reaction system according to claim 1 , wherein the distillation section distills hydrocarbons produced in the reaction section.

3. The reaction system according to claim 1 or 2, wherein the carbon dioxide contained in the raw material includes carbon dioxide recovered in the carbon dioxide recovery section.

4. the carbon dioxide recovery unit includes an absorption unit that absorbs carbon dioxide into an absorption liquid, and a separation unit that separates the carbon dioxide absorbed by the absorption liquid from the absorption liquid, The reaction system according to claim 1 or 2, wherein the separation unit separates carbon dioxide using the low-temperature heat medium.

5. 3. The reaction system according to claim 1, wherein the reaction section comprises a fixed-bed reactor.

6. The distillation section includes at least one of an atmospheric distillation section and a vacuum distillation section, and the hydrocarbons introduced into at least one of the atmospheric distillation section and the vacuum distillation section are distilled using the reaction heat. The reaction system according to claim 1 or 2.

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