Carbon recycle system

Abstract

To reduce input energy from the outside of the system during operation in a carbon recycle system.SOLUTION: A carbon recycle system includes: an absorption tower which has a gas introduction port for introducing a carbon dioxide containing gas and a first liquid introduction port for introducing an absorbent and which causes the absorbent to absorb CO2 contained in the carbon dioxide containing gas to separate CO2 from the carbon dioxide containing gas; a regeneration tower which has a second liquid introduction port for introducing the absorbent absorbing CO2 and a heater for heating the absorbent and which recovers CO2 discharged from the absorbent by heating the absorbent; a transfer line which has a heat exchanger for cooling the absorbent and a booster pump for rising a pressure of the absorbent and which sends the absorbent absorbing CO2 from the absorption tower to the regeneration tower; a carbon dioxide utilization facility which utilizes CO2; and a carbon dioxide line which sends CO2 from the regeneration tower to the carbon dioxide utilization facility. A pressure in the regeneration tower is higher than a pressure in the absorption tower.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a carbon recycling system that captures and reuses carbon dioxide. [Background technology]

[0002] In order to reduce carbon dioxide emissions associated with the use of fossil fuels, carbon dioxide is considered a carbon resource, and "carbon recycling" is being promoted, in which carbon dioxide is captured and reused as a variety of carbon compounds such as materials and fuels.

[0003] In order to capture carbon dioxide, carbon dioxide separation is performed to selectively separate carbon dioxide from a carbon dioxide-containing gas. Carbon dioxide separation techniques are broadly divided into two basic methods: physical absorption and chemical absorption. For example, Patent Document 1 discloses a system that uses chemical absorption to separate carbon dioxide from a carbon dioxide-containing gas and captures the separated carbon dioxide.

[0004] The carbon dioxide separation and capture system described in Patent Document 1 has an internal pressure of 2×10 5 The absorber has an internal pressure of 5×10 Pa or more, and absorbs carbon dioxide into an absorbing solution by contacting an absorbing solution containing an alkaline compound with a carbon dioxide-containing gas; a transfer line for sending out the absorbing solution that has absorbed carbon dioxide from the absorber; and 5 The system is equipped with a regeneration tower that is set to a pressure of at least Pa and that releases carbon dioxide from the absorption liquid supplied from the transfer line to regenerate the absorption liquid, and a reflux path that refluxes the regenerated absorption liquid to the absorption tower. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 2018-134604 Summary of the Invention [Problem to be solved by the invention]

[0006] In a carbon recycling system, carbon dioxide is separated and captured in a carbon dioxide separation and capture facility, and this carbon dioxide is regenerated as a carbon compound in a carbon dioxide utilization facility. As in Patent Document 1, an absorption solution that absorbs carbon dioxide using a chemical absorption method releases carbon dioxide when heated, but heating the absorption solution consumes a large amount of energy. Furthermore, the carbon dioxide captured in the carbon dioxide separation and capture facility is sent to a carbon dioxide utilization facility, and energy is consumed to pump the carbon dioxide. In this way, the operation of a carbon recycling system consumes energy, but from the perspective of suppressing carbon dioxide emissions associated with the generation of the consumed energy, it is preferable to suppress the energy input from outside the system.

[0007] The present disclosure has been made in view of the above circumstances, and aims to reduce the energy input from outside the system in a carbon recycling system that recovers and reuses carbon dioxide from a carbon dioxide-containing gas. [Means for solving the problem]

[0008] In order to solve the above problems, a carbon recycling system according to one embodiment of the present disclosure includes: an absorption tower having a gas inlet for introducing a carbon dioxide-containing gas and a first liquid inlet for introducing an absorption liquid, and separating carbon dioxide from the carbon dioxide-containing gas by causing the carbon dioxide contained in the carbon dioxide-containing gas to be absorbed by the absorption liquid; a regeneration tower having a second liquid inlet for introducing the absorption liquid that has absorbed carbon dioxide and a heater for heating the absorption liquid, and for recovering carbon dioxide released from the absorption liquid by heating the absorption liquid; a transfer line that includes a heat exchanger that cools the absorption liquid and a pressure pump that pressurizes the absorption liquid, and that sends the absorption liquid that has absorbed carbon dioxide from the absorption tower to the regeneration tower; a carbon dioxide utilization facility that utilizes carbon dioxide; a carbon dioxide line for transmitting carbon dioxide from the regeneration tower to the carbon dioxide utilization facility, The internal pressure of the regeneration tower is higher than the internal pressure of the absorption tower.

[0009] In addition, a carbon recycling system according to another embodiment of the present disclosure includes: a reverse water gas shift reactor for producing carbon monoxide and water from carbon dioxide and hydrogen by a reverse water gas shift reaction; an absorption tower having a gas inlet for introducing a carbon dioxide-containing gas and a first liquid inlet for introducing an absorption liquid, and separating carbon dioxide from the carbon dioxide-containing gas by causing the carbon dioxide contained in the carbon dioxide-containing gas to be absorbed by the absorption liquid; a carbon dioxide-containing gas line for transmitting the carbon dioxide-containing gas containing carbon monoxide, hydrogen, and carbon dioxide from the reverse shift reactor to the absorption tower; a regeneration tower having a second liquid inlet for introducing the absorption liquid that has absorbed carbon dioxide and a heater for heating the absorption liquid, and for recovering carbon dioxide released from the absorption liquid by heating the absorption liquid; a transfer line that includes a heat exchanger that cools the absorption liquid and a pressure pump that pressurizes the absorption liquid, and that sends the absorption liquid that has absorbed carbon dioxide from the absorption tower to the regeneration tower; a carbon dioxide line for transmitting carbon dioxide from the regeneration tower to the reverse shift reactor; an FT synthesis reactor that synthesizes synthetic fuel from synthesis gas containing hydrogen and carbon monoxide by an FT synthesis reaction; a synthesis gas line through which the gas containing hydrogen and carbon monoxide obtained by removing carbon dioxide from the carbon dioxide-containing gas in the absorption tower is sent to the FT synthesis reaction tank; the pressure inside the regeneration tower is higher than the pressure inside the absorption tower, The heater is configured to heat the absorption liquid with thermal energy recovered from the synthetic fuel synthesized in the FT synthesis reaction vessel. [Effects of the Invention]

[0010] According to the present disclosure, in a carbon recycling system that recovers and reuses carbon dioxide from a carbon dioxide-containing gas, it is possible to reduce the energy input from outside the system. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a schematic system diagram of a carbon recycling system according to one embodiment of the present disclosure. [Figure 2] FIG. 2 is a schematic diagram of a carbon recycling system according to a modified example. [Figure 3] FIG. 3 is a schematic diagram of a synthetic fuel production system. [Figure 4] FIG. 4 is a schematic diagram of a xylene production system. [Figure 5] Figure 5 is a schematic diagram of a CCS system. DETAILED DESCRIPTION OF THE INVENTION

[0012] Next, an embodiment of the present disclosure will be described with reference to the drawings. Fig. 1 is a schematic system diagram of a carbon recycling system 1 according to one embodiment of the present disclosure. The carbon recycling system 1 shown in Fig. 1 includes a carbon dioxide separation and capture facility 3 that separates and captures carbon dioxide from a carbon dioxide-containing gas 2, and a carbon dioxide utilization facility 4 that utilizes the carbon dioxide captured by the carbon dioxide separation and capture facility 3.

[0013] The carbon dioxide-containing gas 2 is a mixed gas of carbon dioxide and at least one gas other than carbon dioxide, and contains a larger amount of carbon dioxide than air. Examples of the carbon dioxide-containing gas 2 include coal gasification gas, natural gas containing impurities such as carbon dioxide extracted from natural gas fields, and gas emitted from thermal power plants fueled by coal, heavy oil, natural gas, etc., boilers in steel mills, kilns in cement factories, etc.

[0014] Carbon dioxide capture facility 3 The carbon dioxide separation and capture equipment 3 includes an absorption tower 5, a transfer line 7, a regeneration tower 6, and a reflux line 8. The carbon dioxide separation and capture equipment 3 according to this embodiment employs a chemical absorption method, in which carbon dioxide is chemically absorbed into an absorption liquid 51 to separate carbon dioxide from the carbon dioxide-containing gas 2.

[0015] The absorption tower 5 has an internal space extending in the vertical direction, and an absorption liquid 51 is stored in the lower part of the tower. In the absorption tower 5, the carbon dioxide-containing gas 2 introduced into the absorption tower 5 through the carbon dioxide-containing gas line 12 comes into contact with the absorption liquid 51 refluxed to the absorption tower 5 from the regeneration tower 6 through the reflux line 8. The absorption liquid 51 contains an alkaline compound, and the alkaline compound in the absorption liquid 51 reacts with the carbon dioxide in the carbon dioxide-containing gas 2, causing the carbon dioxide to be absorbed by the absorption liquid 51.

[0016] The alkaline compound in the absorbing liquid 51 is, for example, an amine compound. Examples of the amine compound include primary alkanolamines such as monoethanolamine (MEA), diglycolamine (DGA), and 2-amino-2-methyl-1-propanol (AMP), secondary alkanolamines such as 2-methylaminoethanol (MAE), 2-ethylaminoethanol (EAE), and 2-isopropylaminoethanol (IPAE), diethanolamine (DEA), and diisopropanolamine (DIPA), tertiary alkanolamines such as N-methyldiethanolamine (MDEA) and triethanolamine (TEA), and tertiary alkylamines such as N,N,N',N'-tetramethyl-1,6-diaminohexane (TMDAH), N,N,N',N'-tetramethyl-1,3-diaminobutane (TMDAB), and bis(2-dimethylaminoethyl)ether (BDER).

[0017] The absorbing liquid 51 used in this embodiment uses water in the reaction to absorb carbon dioxide. Furthermore, among the absorbing liquids 51 that use water to absorb carbon dioxide, the absorbing liquid 51 used in this embodiment has the property of separating into an alkaline solution mainly composed of alkaline compounds and a solution mainly composed of a product generated by the reaction to absorb carbon dioxide by absorbing carbon dioxide. Therefore, the absorbing liquid 51 is stored at the bottom of the absorption tower 5 in a state where it is separated into an upper layer L1 consisting of an alkaline solution mainly composed of alkaline compounds and a lower layer L2 containing a solution mainly composed of a product of the carbon dioxide absorption reaction. However, the boundary between the upper layer L1 and the lower layer L2 does not need to be clear.

[0018] The absorption tower 5 is disposed in the lower part of the tower and has at least one gas inlet 53 for blowing the carbon dioxide-containing gas 2 into the absorption liquid 51. The gas inlet 53 is preferably disposed in the upper layer L1 of the absorption liquid 51. A carbon dioxide-containing gas line 12 is connected to the gas inlet 53. The carbon dioxide-containing gas 2 is supplied from the gas inlet 53 through the carbon dioxide-containing gas line 12 into the absorption liquid 51. The temperature of the carbon dioxide-containing gas 2 supplied to the absorption tower 5 is T1, which is a temperature suitable for the absorption of carbon dioxide into the absorption liquid 51. The internal pressure of the absorption tower 5 is set to P1. The internal pressure P1 of the absorption tower 5 is atmospheric pressure, i.e., about 0.1 MPa or more, and is a pressure suitable for the absorption of carbon dioxide into the absorption liquid 51. In order to adjust the internal pressure P1 of the absorption tower 5, a gas that does not react with the absorption liquid 51, such as nitrogen gas, may be supplied to the absorption tower 5 in addition to the carbon dioxide-containing gas 2.

[0019] The absorption tower 5 is disposed in the upper part of the tower and has at least one liquid inlet 55 for spraying the absorption liquid 51 into the gas phase. A reflux line 8 is connected to the liquid inlet 55. The absorption liquid 51 is supplied into the absorption tower 5 from the liquid inlet 55 through the reflux line 8.

[0020] The absorption tower 5 is disposed between the liquid inlet 55 and the gas inlet 53 in the vertical direction inside the tower, and has a packed bed 57 filled with a packing material. The packed bed 57 serves to increase the contact area between the absorbing liquid 51 descending inside the absorption tower 5 and the carbon dioxide-containing gas 2 ascending inside the tower, and to ensure a contact time sufficient for the absorbing liquid 51 to absorb carbon dioxide. However, the packed bed 57 may be omitted.

[0021] An exhaust pipe 58 is connected to the top of the absorption tower 5. Carbon dioxide-removed gas 22 obtained by removing carbon dioxide from the carbon dioxide-containing gas 2 in the absorption tower 5 is discharged outside the tower through the exhaust pipe 58.

[0022] The starting end of a transfer line 7 is connected to the bottom of the absorption tower 5. The terminal end of the transfer line 7 is connected to the top of the regeneration tower 6. The transfer line 7 is a flow path that transfers the absorption solution 51 that has absorbed carbon dioxide from the absorption tower 5 to the regeneration tower 6, and is composed of piping or the like. The transfer line 7 is provided with a heat exchanger 71 that heats the absorption solution 51 flowing through the transfer line 7. The heat exchanger 71 exchanges heat between the low-temperature absorption solution 51 flowing through the transfer line 7 and the high-temperature absorption solution 51 flowing through the reflux line 8. The transfer line 7 is also provided with a pressure booster pump 72 that pressurizes the absorption solution 51 flowing through the transfer line 7. The pressure of the absorption solution 51 is increased to an internal pressure P2 of the regeneration tower 6 by the pressure booster pump 72.

[0023] The regeneration tower 6 has an internal space extending in the vertical direction. The internal pressure of the regeneration tower 6 is set to P2. The internal pressure P2 of the regeneration tower 6 is higher than the internal pressure P1 of the absorption tower 5 (P1 < P2). The differential pressure between the internal pressure P1 of the absorption tower 5 and the internal pressure P2 of the regeneration tower 6 is 0.1 MPa or more. Conventionally, the internal pressure P2 of the regeneration tower 6 was lower than the internal pressure P1 of the absorption tower 5, and many types of absorption liquids that release carbon dioxide by depressurizing the absorption liquid 51 that has absorbed carbon dioxide were used. In this embodiment, since the internal pressure P2 of the regeneration tower 6 is higher than the internal pressure P1 of the absorption tower 5, an absorption liquid 51 of a type that can release carbon dioxide under pressure conditions higher than the carbon dioxide partial pressure of the carbon dioxide-containing gas 2 is used. The internal pressure P2 of the regeneration tower 6 is preferably set so that the carbon dioxide partial pressure of the regeneration tower 6 corresponds to the carbon dioxide release pressure of the absorption liquid 51. The suitable carbon dioxide release pressure varies for each absorption liquid 51. Although the upper limit of the internal pressure P2 of the regeneration tower 6 is not particularly set, when the internal pressure P2 of the regeneration tower 6 increases, the equipment cost of the regeneration tower 6 that can withstand that pressure increases, so about 6 MPa is reasonable. From the above viewpoints, the internal pressure P2 of the regeneration tower 6 is, for example, 0.2 MPa or more and 6 MPa or less.

[0024] The regeneration tower 6 is arranged at the upper part inside the tower and has at least one liquid inlet 61 for ejecting the absorption liquid 51. A transfer line 7 is connected to the liquid inlet 61. The absorption liquid 51 that has absorbed carbon dioxide is supplied into the regeneration tower 6 from the liquid inlet 61 through the transfer line 7. The absorption liquid 51 ejected from the liquid inlet 61 descends inside the regeneration tower 6 and accumulates at the lower part inside the tower.

[0025] The regeneration tower has a heater 65 and at least one steam outlet 62 for ejecting the steam generated by the heater 65. The steam outlet 62 is arranged at the lower part inside the tower, and preferably, it is arranged above the liquid level of the absorption liquid 51. The absorption liquid 51 descending inside the regeneration tower 6 is heated by contacting the steam rising inside the tower, and the heated absorption liquid 51 releases the absorbed carbon dioxide.

[0026] The heater 65 has a heating container 651 that temporarily stores the absorbing solution 51 and a heating tube 652 that heats the absorbing solution 51 stored in the heating container 651. The absorbing solution 51 stored in the lower part of the regenerator 6 flows into the heating container 651 through a water intake line 66 connected to the bottom of the regenerator 6. A heat transfer medium 43 flows through the heating tube 652, to which thermal energy has been imparted by exhaust heat in the carbon recycling system 1, such as exhaust heat from the carbon dioxide utilization equipment 4 and exhaust heat from processes upstream of the carbon dioxide separation and capture equipment 3. The absorbing solution 51 in the heating container 651 is indirectly heated by the heat transfer medium 43 flowing through the heating tube 652. As the absorbing solution 51 is heated, carbon dioxide remaining in the absorbing solution 51 is released, and water in the absorbing solution 51 evaporates to generate steam. The steam generated in the heater 65, together with carbon dioxide released from the absorbing solution 51, is introduced into the regenerator 6 from a steam port 62 via a steam line 64. The inside of the regeneration tower 6 is pressurized by the steam introduced into the tower. In this way, the heater 65 can pressurize the inside of the tower of the heater 65 by using thermal energy.

[0027] The regeneration tower 6 has a packed bed 67 filled with packing material, which is disposed between the liquid inlet 61 and the steam outlet 62 in the tower in the vertical direction. The packed bed 67 serves to increase the contact area between the absorption liquid 51 descending inside the regeneration tower 6 and the high-temperature steam ejected from the steam outlet 62, and to ensure a contact time sufficient for the absorption liquid 51 to release carbon dioxide. However, the packed bed 67 may be omitted.

[0028] The start end of a reflux line 8 is connected to the bottom of the regeneration tower 6. The reflux line 8 is a flow path for refluxing the absorption liquid 51 from the regeneration tower 6 to the absorption tower 5, and is composed of piping or the like. The reflux line 8 is provided with a reflux pump 81 that sends the absorption liquid 51 to the absorption tower 5. The reflux line 8 is also provided with a heat exchanger 71 that cools the absorption liquid 51 flowing through the reflux line 8. The heat exchanger 71 exchanges heat between the low-temperature absorption liquid 51 flowing through the transfer line 7 and the high-temperature absorption liquid 51 flowing through the reflux line 8. The reflux line 8 may further be provided with a cooler that cools the absorption liquid 51 flowing through the reflux line 8.

[0029] The start end of a carbon dioxide line 9 is connected to the top of the regeneration tower 6. Carbon dioxide recovered from the absorption liquid 51 in the regeneration tower 6 flows out from the top of the tower into the carbon dioxide line 9. A cooler 91 and a separator 92 are provided in the carbon dioxide line 9. The cooler 91 condenses the water vapor discharged from the regeneration tower 6 into the carbon dioxide line 9 together with the carbon dioxide by cooling. The separator 92 separates the condensed water condensed in the cooler 91 from the carbon dioxide into gas and liquid. The condensed water separated in the separator 92 is returned to the regeneration tower 6. In addition, the carbon dioxide separated in the separator 92 is supplied to the carbon dioxide utilization facility 4 through the carbon dioxide line 9.

[0030] Carbon dioxide utilization facility 4 The carbon dioxide utilization facility 4 is, for example, a facility that uses carbon dioxide to produce carbon compounds. Examples of carbon compounds that can be produced in the carbon dioxide utilization facility 4 include carbon dioxide-derived chemical products such as paraxylene, and carbon dioxide-derived fuels known as synthetic fuels. However, the carbon dioxide utilization facility 4 is not limited to a facility that produces carbon compounds, and may also be a facility for storing carbon dioxide.

[0031] The supply pressure of carbon dioxide to the carbon dioxide utilization equipment 4 is P3. The supply pressure P3 is equal to or lower than the internal pressure P2 of the regeneration tower 6. Therefore, no compressor for compressing carbon dioxide is provided in the carbon dioxide line 9, and the carbon dioxide moves from the regeneration tower 6 to the carbon dioxide utilization equipment 4 by pressure difference without external energy being applied. The carbon dioxide line 9 may be provided with a pressure reducing valve for reducing the pressure of the carbon dioxide to the carbon dioxide supply pressure P3 to the carbon dioxide utilization equipment 4, or a flow control valve for adjusting the flow rate of carbon dioxide supplied to the carbon dioxide utilization equipment 4. However, the supply pressure P3 of carbon dioxide to the carbon dioxide utilization equipment 4 may be higher than the internal pressure P2 of the regeneration tower 6. In this case, as shown in FIG. 2, a compressor 99 for increasing the pressure of the carbon dioxide by compression is provided in the carbon dioxide line 9.

[0032] Returning to Fig. 1, the carbon dioxide utilization facility 4 may include at least one reaction tank 40 that produces carbon compounds using carbon dioxide as part of the raw material. Examples of reactions that produce carbon compounds using carbon dioxide include the reverse water gas shift reaction that produces carbon monoxide and water from carbon dioxide and hydrogen, and the methanol synthesis reaction that synthesizes methanol from carbon dioxide.

[0033] When an exothermic reaction occurs in the reaction tank 40, the thermal energy of the reaction product 41 produced in the reaction tank 40 may be used to heat the absorption liquid 51 in the heater 65 of the regeneration tower 6. For example, a heat recovery unit 42 that recovers thermal energy from the reaction product 41 flowing out of the reaction tank 40 may be provided, and the heat medium 43 from which the thermal energy has been recovered in the heat recovery unit 42 may be caused to flow into a heating tube 652 of the heater 65. However, the source of thermal energy supplied to the heater 65 is not limited to the carbon dioxide utilization facility 4.

[0034] Here, the flow of carbon dioxide and the absorbing liquid 51 in the carbon recycling system 1 configured as described above will be described. In the carbon dioxide separation and capture equipment 3, the carbon dioxide-containing gas 2 rising from the lower part of the absorption tower 5 comes into contact with the absorbing liquid 51 falling from the upper part of the absorption tower 5, and the carbon dioxide in the carbon dioxide-containing gas 2 is absorbed by the absorbing liquid 51. The absorbing liquid 51 that has absorbed the carbon dioxide falls to the lower part of the absorption tower 5, and the carbon dioxide-removed gas 22, in which carbon dioxide has been removed from the carbon dioxide-containing gas 2, rises through the absorption tower 5 and is discharged to the outside through the exhaust pipe 58. The absorbing liquid 51 that remains in the lower part of the absorption tower 5 is transferred to the regeneration tower 6 through the transfer line 7. While passing through the transfer line 7, the absorbing liquid 51 is heated by a heat exchanger 71 and pressurized by a pressure pump 72. The absorbing liquid 51 falling from the upper part of the regeneration tower 6 comes into contact with steam rising from the lower part of the regeneration tower 6, and the absorbing liquid 51 is heated, whereby carbon dioxide is released from the absorbing liquid 51. The absorption liquid 51 is regenerated by releasing carbon dioxide. The regenerated absorption liquid 51 is returned to the absorption tower 5 through the reflux line 8. The absorption liquid 51 is cooled in a heat exchanger 71 while passing through the reflux line 8. The carbon dioxide released from the absorption liquid 51 rises inside the regeneration tower 6 and is sent to the carbon dioxide utilization equipment 4 through a carbon dioxide line 9. Here, the supply pressure P3 of the carbon dioxide to the carbon dioxide utilization equipment 4 is lower than the internal pressure P2 of the regeneration tower 6, so that the carbon dioxide is sent from the carbon dioxide separation and capture equipment 3 to the carbon dioxide utilization equipment 4 by the pressure difference without inputting external energy. In the carbon dioxide utilization equipment 4, carbon compounds are produced using the carbon dioxide supplied from the carbon dioxide separation and capture equipment 3.

[0035] In the carbon recycling system 1 described above, the power required to send carbon dioxide from the carbon dioxide separation and capture equipment 3 to the carbon dioxide utilization equipment 4 is eliminated, and further, the thermal energy consumed by the heater 65 is supplied from within the system, thereby realizing a reduction in the amount of energy input from outside the system during operation. When raising the pressure of a unit amount of carbon dioxide by a unit pressure, compressing gaseous carbon dioxide with the compressor 99 requires more power to raise the pressure than pressurizing the carbon dioxide absorbed in the absorption liquid 51 with the pressure pump 72. In this way, even when the compressor 99 is provided in the carbon dioxide line 9, the reduction in the power required to raise the pressure of the carbon dioxide allows a reduction in the amount of energy input from outside the system during operation.

[0036] An application example of the carbon recycling system 1 will be described below.

[0037] [Application example 1] The carbon recycling system 1 according to the above embodiment can be applied to a synthetic fuel production system 100 that produces synthetic fuel derived from carbon dioxide. Fig. 3 is a schematic system diagram of the synthetic fuel production system 100. The synthetic fuel production system 100 shown in Fig. 3 includes a reverse shift reactor 110, a carbon dioxide separation and capture facility 3, and an FT (Fischer Tropsch) synthesis reactor 111. The reverse shift reactor 110 corresponds to the carbon dioxide utilization facility 4.

[0038] In the reverse shift reactor 110, carbon monoxide and water are produced from hydrogen and carbon dioxide by a reverse water gas shift reaction, which reduces carbon dioxide to carbon monoxide. The reverse shift reaction product sent from the reverse shift reactor 110 to the next process contains unreacted carbon dioxide and hydrogen in addition to carbon monoxide and water. The reverse shift reaction product is separated and removed by a separator 112, and then sent to a carbon dioxide separation and capture facility 3. The reverse shift reaction product from which water has been removed is a carbon dioxide-containing gas 2 containing carbon monoxide, hydrogen, and carbon dioxide. Carbon dioxide is separated from this carbon dioxide-containing gas 2 in the carbon dioxide separation and capture facility 3. The carbon dioxide separated from the carbon dioxide-containing gas 2 in the carbon dioxide separation and capture facility 3 is supplied as part of the raw material to the reverse shift reactor 110 from the regenerator 6 via a carbon dioxide line 9. Meanwhile, the carbon dioxide-removed gas 22, obtained by removing carbon dioxide from the carbon dioxide-containing gas 2, is a mixed gas of carbon monoxide and hydrogen, i.e., synthesis gas. The synthesis gas is sent from the absorption tower 5 to the FT synthesis reactor 111 via a synthesis gas line 114. In the FT synthesis reaction vessel 111, synthetic fuel is synthesized from the synthesis gas by the FT synthesis reaction. The FT synthesis reaction is an exothermic reaction, and the heat generated by the FT synthesis reaction is utilized in the heater 65 of the carbon dioxide separation and capture equipment 3. For example, a heat recovery vessel 42 that recovers thermal energy from the reaction product flowing out of the FT synthesis reaction vessel 111 may be provided, and the heat medium 43 from which thermal energy has been recovered in the heat recovery vessel 42 may be caused to flow into a heating tube 652 of the heater 65. In this way, in the synthetic fuel production system 100, surplus thermal energy within the system is utilized to heat the absorption liquid 51 in the heater 65, thereby reducing the energy input from outside the system for pressurizing the carbon dioxide discharged from the regeneration tower 6 to the carbon dioxide line 9 and for recovering carbon dioxide from the absorption liquid 51.

[0039] [Application example 2] The carbon recycling system 1 according to the above embodiment can be applied to a xylene production system 120 that produces aromatic hydrocarbons such as paraxylene from carbon dioxide. FIG. 4 is a schematic system diagram of the xylene production system 120. The xylene production system 120 shown in FIG. 4 includes a carbon dioxide separation and capture facility 3 and a carbon dioxide utilization facility 4 that produces aromatic hydrocarbons using carbon dioxide. The carbon dioxide utilization facility 4 includes two reaction tanks: a methanol synthesis reaction tank 121 and a xylene synthesis reaction tank 122.

[0040] In a xylene production system 120, a carbon dioxide separation and capture system 3 separates and captures carbon dioxide from a carbon dioxide-containing gas 2, such as combustion exhaust gas. The carbon dioxide separated from the carbon dioxide-containing gas 2 by the carbon dioxide separation and capture system 3 is supplied as a raw material to a methanol synthesis reaction tank 121 via a carbon dioxide line 9. The carbon dioxide-containing gas 2 introduced into the carbon dioxide separation and capture system 3 is at approximately atmospheric pressure, and the carbon dioxide supplied as a raw material to the methanol synthesis reaction tank 121 is at 5 MPa to 10 MPa. The carbon dioxide line 9 is provided with a compressor 99 that pressurizes gaseous carbon dioxide. In the carbon dioxide separation and capture system 3, the internal pressure P2 of the regeneration tower 6 is set higher than the internal pressure P1 of the absorption tower 5, thereby reducing the power required to compress the carbon dioxide with the compressor 99. In the methanol synthesis reaction tank 121, methanol and water are synthesized from carbon dioxide and hydrogen through a methanol synthesis reaction. The methanol synthesis reaction product sent from the methanol synthesis reaction tank 121 to the next process contains unreacted carbon dioxide and hydrogen in addition to methanol and water. The methanol synthesis reaction product is separated into gas and liquid in separator 123, and hydrogen and carbon dioxide are returned to the methanol synthesis reaction tank 121, while water and methanol are sent to the xylene synthesis reaction tank 122. In the xylene synthesis reaction tank 122, aromatic hydrocarbons including para-xylene and lower hydrocarbons are synthesized from methanol and water through a xylene synthesis reaction. The xylene synthesis reaction product sent from the xylene synthesis reaction tank 122 to the next process contains water in addition to aromatic hydrocarbons and lower hydrocarbons. The xylene synthesis reaction product is separated into gas and liquid in separator 124, and is further separated into aromatic hydrocarbons and lower hydrocarbons. The xylene synthesis reaction is an exothermic reaction, and the heat generated by the xylene synthesis reaction is utilized in heater 65 of the carbon dioxide separation and capture facility 3. For example, a heat recovery device 42 is provided to recover thermal energy from the reaction product flowing out of the xylene synthesis reaction tank 122, and the heat medium 43 from which thermal energy has been recovered by the heat recovery device 42 is caused to flow into the heating tube 652 of the heater 65.In this way, in the xylene production system 120, excess thermal energy within the system is used to heat the absorption liquid 51 in the heater 65, thereby reducing the energy input from outside the system for pressurizing the carbon dioxide discharged from the regeneration tower 6 to the carbon dioxide line 9 and for recovering carbon dioxide from the absorption liquid 51.

[0041] [Application example 3] The carbon recycling system 1 according to the above embodiment can be applied to a CCS (Carbon dioxide Capture and Storage) system 130 that stores carbon dioxide contained in exhaust gas from an integrated coal gasification combined cycle (IGCC) plant. FIG. 5 is a schematic system diagram of the CCS system 130. The CCS system 130 shown in FIG. 5 includes a cooler 131, carbon dioxide separation and capture equipment 3, and carbon dioxide injection equipment 132. The carbon dioxide injection equipment 132 corresponds to the carbon dioxide utilization equipment 4.

[0042] The temperature of the IGCC flue gas is 180°C-250°C, and the pressure is approximately 3 MPa. The IGCC flue gas is a carbon dioxide-containing gas 2 that contains a large amount of carbon dioxide. The cooler 131 cools the ICGG flue gas to a temperature suitable for carbon dioxide separation in the carbon dioxide separation and capture facility 3. The temperature suitable for carbon dioxide separation is approximately 40°C, although it depends on the type of absorption liquid 51. The IGCC flue gas cooled in the cooler 131 is introduced into the carbon dioxide separation and capture facility 3 as a carbon dioxide-containing gas 2. In the carbon dioxide separation and capture facility 3, carbon dioxide is separated from the carbon dioxide-containing gas 2. The thermal energy recovered from the IGCC flue gas by the cooler 131 is used as the thermal energy for heating the absorption liquid 51 in the carbon dioxide separation and capture facility 3. For example, the cooler 131 functions as a heat recovery device 42 that recovers thermal energy from the IGCC flue gas, and is configured to flow the heat medium 43 from which thermal energy has been recovered in the cooler 131 into the heating tubes 652 of the heater 65. In this way, in the CCS system 130, the thermal energy recovered within the system is used to heat the absorption liquid 51 in the heater 65, thereby reducing the energy input from outside the system to pressurize the carbon dioxide discharged from the regeneration tower 6 to the carbon dioxide line 9 and to recover carbon dioxide from the absorption liquid 51.

[0043] The carbon dioxide separated from the carbon dioxide-containing gas 2 in the carbon dioxide separation and capture facility 3 is sent to the carbon dioxide injection facility 132 through the carbon dioxide line 9. The carbon dioxide injection facility 132 pressurizes the carbon dioxide to about 15 MPa to 30 MPa and injects it deep underground. Here, in the carbon dioxide separation and capture facility 3, by making the internal pressure P2 of the regeneration tower 6 higher than the internal pressure P1 of the absorption tower 5, the power required to compress the carbon dioxide in the carbon dioxide injection facility 132 can be reduced.

[0044] [Summary] The carbon recycling system 1 according to the first aspect of the present disclosure includes: an absorption tower 5 having a gas inlet 53 for introducing a carbon dioxide-containing gas 2 and a first liquid inlet 55 for introducing an absorption liquid 51, and separating carbon dioxide from the carbon dioxide-containing gas 2 by causing the absorption liquid 51 to absorb the carbon dioxide contained in the carbon dioxide-containing gas 2; a regeneration tower 6 having a second liquid inlet 61 for introducing an absorption liquid 51 that has absorbed carbon dioxide and a heater 65 for heating the absorption liquid 51, and for recovering carbon dioxide released from the absorption liquid 51 by heating the absorption liquid 51; a transfer line 7 that has a heat exchanger 71 that cools the absorbing solution 51 and a pressure pump 72 that pressurizes the absorbing solution 51, and that sends the absorbing solution 51 that has absorbed carbon dioxide from the absorption tower 5 to the regeneration tower 6; a carbon dioxide utilization facility 4 that utilizes carbon dioxide; a carbon dioxide line 9 for sending carbon dioxide from the regeneration tower 6 to the carbon dioxide utilization facility 4; The pressure P2 inside the regenerator 6 is higher than the pressure P1 inside the absorber 5.

[0045] In the carbon recycling system 1 configured as described above, by increasing the internal pressure P2 of the regeneration tower 6, the carbon dioxide recovered from the absorption liquid 51 in the regeneration tower 6 is pressurized. This makes it possible to reduce the energy required to pump the carbon dioxide from the regeneration tower 6 to the carbon dioxide utilization facility 4. In other words, it is possible to reduce the energy input from outside the system when operating the carbon recycling system 1. This in turn makes it possible to reduce the operating costs of the carbon recycling system 1.

[0046] The carbon recycling system 1 according to the second item of the present disclosure is the carbon recycling system 1 according to the first item, in which the internal pressure P2 of the regeneration tower 6 is higher than the supply pressure P3 of carbon dioxide to the carbon dioxide utilization equipment 4.

[0047] According to the carbon recycling system 1 configured as described above, carbon dioxide moves from the regeneration tower 6 to the carbon dioxide utilization equipment 4 due to a pressure difference, so that a compressor or the like for pressurizing the carbon dioxide can be omitted, and the operating energy of the compressor or the like can be reduced.

[0048] The carbon recycling system 1 according to the third item of the present disclosure is the carbon recycling system 1 according to the first or second item, wherein the carbon dioxide utilization equipment 4 has a reaction tank 40 that produces a reaction product by an exothermic reaction, and the heater 65 is configured to heat the absorption liquid 51 with thermal energy recovered from the reaction product 41 produced in the reaction tank 40.

[0049] The carbon recycling system 1 configured as described above heats the absorption solution 51 by utilizing thermal energy generated within the system, and therefore can reduce the amount of energy input from outside the system for pressurizing the carbon dioxide discharged from the regeneration tower 6 to the carbon dioxide line 9 and for recovering carbon dioxide from the absorption solution 51. Consequently, the operating costs of the carbon recycling system 1 can be reduced.

[0050] The carbon recycling system 1 according to the fourth item of the present disclosure is the carbon recycling system 1 according to any one of the first to third items, and is provided with a cooler 91 that cools the carbon dioxide-containing gas 2 supplied to the absorption tower 5, and the heater 65 is configured to heat the absorption liquid 51 with thermal energy recovered from the carbon dioxide-containing gas 2 by the cooler 91.

[0051] The carbon recycling system 1 configured as described above heats the absorption solution 51 using thermal energy recovered within the system, and therefore can reduce the energy input from outside the system for pressurizing the carbon dioxide discharged from the regeneration tower 6 to the carbon dioxide line 9 and for recovering carbon dioxide from the absorption solution 51. Consequently, the operating costs of the carbon recycling system 1 can be reduced.

[0052] The carbon recycling system 1 (i.e., the synthetic fuel production system 100) according to the fifth aspect of the present disclosure includes: a reverse water gas shift reactor 110 for producing carbon monoxide and water from carbon dioxide and hydrogen by a reverse water gas shift reaction; an absorption tower 5 having a gas inlet 53 for introducing a carbon dioxide-containing gas 2 and a first liquid inlet 55 for introducing an absorption liquid 51, and separating carbon dioxide from the carbon dioxide-containing gas 2 by causing the absorption liquid 51 to absorb the carbon dioxide contained in the carbon dioxide-containing gas 2; a carbon dioxide-containing gas line 12 for sending a carbon dioxide-containing gas 2 containing carbon monoxide, hydrogen, and carbon dioxide from the reverse shift reactor 110 to the absorption tower 5; a regeneration tower 6 having a second liquid inlet 61 for introducing an absorption liquid 51 that has absorbed carbon dioxide and a heater 65 for heating the absorption liquid 51, and for recovering carbon dioxide released from the absorption liquid 51 by heating the absorption liquid 51; a transfer line 7 that has a heat exchanger 71 that cools the absorbing solution 51 and a pressure pump 72 that pressurizes the absorbing solution 51, and that sends the absorbing solution 51 that has absorbed carbon dioxide from the absorption tower 5 to the regeneration tower 6; a carbon dioxide line 9 for sending carbon dioxide from the regeneration tower 6 to the reverse shift reactor 110; an FT synthesis reactor 111 for synthesizing synthetic fuel from synthesis gas containing hydrogen and carbon monoxide by an FT synthesis reaction; a synthesis gas line 114 for sending the gas containing hydrogen and carbon monoxide obtained by removing carbon dioxide from the carbon dioxide-containing gas 2 in the absorption tower 5 to the FT synthesis reaction tank 111; The pressure P2 inside the regeneration tower 6 is higher than the pressure P1 inside the absorption tower 5, The heater 65 is configured to heat the absorbing liquid 51 with thermal energy recovered from the synthetic fuel synthesized in the FT synthesis reaction vessel 111 .

[0053] According to the carbon recycling system 1 having the above configuration, by increasing the internal pressure P2 of the regenerator 6, the carbon dioxide recovered from the absorption liquid 51 in the regenerator 6 is pressurized. Therefore, it is possible to reduce the energy required to pump the carbon dioxide from the regenerator 6 to the reverse shift reaction tank 110. Furthermore, according to the carbon recycling system 1 having the above configuration, the absorption liquid 51 is heated using the thermal energy generated by the FT synthesis reaction, thereby reducing energy loss due to heat release and reducing the energy input from outside the system for pressurizing the carbon dioxide discharged from the regenerator 6 to the carbon dioxide line 9 and recovering carbon dioxide from the absorption liquid 51. Consequently, the operating costs of the carbon recycling system 1 can be reduced.

[0054] The foregoing disclosure has been presented for purposes of illustration and description and is not intended to limit the disclosure to the form disclosed herein. For example, in the foregoing detailed description, various features of the disclosure are grouped together in a single embodiment for the purpose of streamlining the disclosure, but some of the features may also be combined. Furthermore, the features included in the disclosure may be combined into alternative embodiments, configurations, or aspects other than those discussed above. [Explanation of symbols]

[0055] 1: Carbon recycling system 2: Carbon dioxide-containing gas 3: Carbon dioxide separation and capture equipment 4: Carbon dioxide utilization equipment 5: Absorption tower 6: Regeneration Tower 7: Transfer line 9: Carbon dioxide line 12: Carbon dioxide-containing gas line 51: Absorbent 53: Gas inlet 55: Liquid inlet 55: 1st liquid inlet 61:Second liquid inlet 61: Liquid inlet 65: Heater 71:Heat exchanger 72: Pressure pump 91:Cooler 100: Synthetic fuel production system 110: Reverse shift reactor 111: Synthesis reactor 111:FT synthesis reactor 114: Syngas line 120: Xylene production system 130:CCS system 131: Cooler

Claims

1. an absorption tower having a gas inlet for introducing a carbon dioxide-containing gas and a first liquid inlet for introducing an absorption liquid, and separating carbon dioxide from the carbon dioxide-containing gas by causing the carbon dioxide contained in the carbon dioxide-containing gas to be absorbed by the absorption liquid; a regeneration tower having a second liquid inlet for introducing the absorption liquid that has absorbed carbon dioxide and a heater for heating the absorption liquid, and for recovering carbon dioxide released from the absorption liquid by heating the absorption liquid; a transfer line that includes a heat exchanger that cools the absorption liquid and a pressure pump that pressurizes the absorption liquid, and that sends the absorption liquid that has absorbed carbon dioxide from the absorption tower to the regeneration tower; a carbon dioxide utilization facility that utilizes carbon dioxide; a carbon dioxide line for transmitting carbon dioxide from the regeneration tower to the carbon dioxide utilization facility, The pressure inside the regeneration tower is higher than the pressure inside the absorption tower. Carbon recycling system.

2. The internal pressure of the regeneration tower is higher than the supply pressure of carbon dioxide to the carbon dioxide utilization facility. The carbon recycling system according to claim 1 .

3. The carbon dioxide utilization facility has a reaction tank for generating a reaction product by an exothermic reaction, The heater is configured to heat the absorption liquid with thermal energy recovered from the reaction product produced in the reaction tank. The carbon recycling system according to claim 1 .

4. a cooler that cools the carbon dioxide-containing gas to be supplied to the absorption tower, The heater is configured to heat the absorption liquid with thermal energy recovered from the carbon dioxide-containing gas by the cooler. The carbon recycling system according to claim 1 .

5. a reverse water gas shift reactor for producing carbon monoxide and water from carbon dioxide and hydrogen by a reverse water gas shift reaction; an absorption tower having a gas inlet for introducing a carbon dioxide-containing gas and a first liquid inlet for introducing an absorption liquid, and separating carbon dioxide from the carbon dioxide-containing gas by causing the carbon dioxide contained in the carbon dioxide-containing gas to be absorbed by the absorption liquid; a carbon dioxide-containing gas line for transmitting the carbon dioxide-containing gas containing carbon monoxide, hydrogen, and carbon dioxide from the reverse shift reactor to the absorption tower; a regeneration tower having a second liquid inlet for introducing the absorption liquid that has absorbed carbon dioxide and a heater for heating the absorption liquid, and for recovering carbon dioxide released from the absorption liquid by heating the absorption liquid; a transfer line that includes a heat exchanger that cools the absorption liquid and a pressure pump that pressurizes the absorption liquid, and that sends the absorption liquid that has absorbed carbon dioxide from the absorption tower to the regeneration tower; a carbon dioxide line for transmitting carbon dioxide from the regeneration tower to the reverse shift reactor; an FT synthesis reactor for synthesizing a synthetic fuel from a synthesis gas containing hydrogen and carbon monoxide by an FT synthesis reaction; a synthesis gas line through which the gas containing hydrogen and carbon monoxide obtained by removing carbon dioxide from the carbon dioxide-containing gas in the absorption tower is sent to the FT synthesis reaction tank; the pressure inside the regeneration tower is higher than the pressure inside the absorption tower, the heater is configured to heat the absorption liquid with thermal energy recovered from the synthetic fuel synthesized in the FT synthesis reactor. Carbon recycling system.

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