Carbon dioxide capture system and carbon dioxide capture method

Abstract

Disclosed in one embodiment of the present invention is a carbon dioxide capture system comprising an absorption tower and a regeneration tower. The absorption tower comprises: an exhaust gas inlet region formed to allow exhaust gas to be introduced; an absorbent inlet region disposed in a region separate from the exhaust gas inlet region and formed to allow an absorbent containing methanol to be introduced; a treatment space which is a region in which carbon dioxide in the exhaust gas is absorbed by the absorbent while the exhaust gas moves; and an absorbent discharge region through which the absorbent having absorbed the carbon dioxide is discharged from the treatment space. The regeneration tower comprises: an inlet region into which the absorbent having absorbed the carbon dioxide is introduced; a hydrogen inlet region disposed in a region separate from the inlet region and into which hydrogen gas is introduced; a mixing space in which the carbon dioxide desorbed from the absorbent having absorbed the carbon dioxide is mixed with the hydrogen gas; and a mixed gas discharge region through which the carbon dioxide mixed with the hydrogen gas in the mixing space is discharged.

Description

Carbon dioxide capture system and carbon dioxide capture method

[0001] Embodiments of the present invention relate to a carbon dioxide capture system and a carbon dioxide capture method.

[0002] Many technologies, including chemical absorption, adsorption, membrane separation, and cryogenic methods, are being developed to reduce carbon dioxide, an acidic gas in exhaust gases. Among these, the chemical absorption method, which uses an absorbent solution to absorb and capture carbon dioxide, is widely applied due to its relatively high efficiency and stable process.

[0003] In this chemical absorption method, carbon dioxide is dissolved in a solvent or solution (absorbent) in a first zone to combine with the carbon dioxide and the absorbent, then the solvent or solution containing the dissolved carbon dioxide is transferred to a second zone, where the carbon dioxide and the solvent or solution are separated. This method, which uses an absorbent liquid to absorb and capture carbon dioxide, is widely applied due to its relatively high efficiency and stable process.

[0004] However, conventional chemical absorption methods fail to achieve sufficient capture efficiency due to factors such as the inability to adequately dissolve carbon dioxide in solvents or solutions, and have limitations for use in confined spaces like ships, as they require larger carbon dioxide capture devices.

[0005] Embodiments of the present invention provide a carbon dioxide capture system and a carbon dioxide capture method that can improve carbon dioxide capture efficiency by reducing the thermal energy required for carbon dioxide capture and simplify the equipment for the carbon dioxide capture process.

[0006] The technical problems that the present invention aims to solve are not limited to those mentioned above, and other unmentioned technical problems will be clearly understood by those skilled in the art to which the present invention belongs from the description below.

[0007] One embodiment of the present invention discloses a carbon dioxide capture system comprising an absorption tower and a regeneration tower, wherein the absorption tower comprises a flue gas inlet area formed to receive flue gas, an absorbent inlet area disposed in a separate area from the flue gas inlet area and formed to receive an absorbent containing methanol, a treatment space in which carbon dioxide from the flue gas is absorbed by the absorbent as the flue gas moves, and an absorbent discharge area in which the absorbent from which carbon dioxide has been absorbed in the treatment space is discharged, and the regeneration tower comprises an inlet area into which the absorbent from which carbon dioxide has been absorbed is received, a hydrogen inlet area disposed in a separate area from the inlet area into which hydrogen gas is received, a mixing space in which the carbon dioxide desorbed from the absorbent from which carbon dioxide has been absorbed is mixed with the hydrogen gas, and a mixed gas discharge area in which the carbon dioxide mixed with the hydrogen gas in the mixing space is discharged.

[0008] According to the carbon dioxide capture system and carbon dioxide capture method of the present invention, the amount of thermal energy required to capture carbon dioxide from flue gas is significantly reduced, thereby enabling a carbon dioxide capture process that is highly energy-efficient and environmentally friendly.

[0009] In this case, since the thermal energy requirement for carbon dioxide absorption and desorption reactions is reduced, the absorption tower and regeneration tower may not include separate condensers and reboilers, which allows for the simplification of the process equipment and further ensures economic efficiency in terms of space and cost.

[0010] Furthermore, the carbon dioxide separated from flue gas through the carbon dioxide capture system and method of the present invention is discharged as a mixed gas mixed with hydrogen, which can be utilized in methanol synthesis to be reused as an absorbent or to create separate added value, making it highly economical.

[0011] The effects of the present invention are not limited to the effects described above, and should be understood to include all effects that can be inferred from the configuration of the invention described in the detailed description of the invention or the claims.

[0012] FIG. 1 is a conceptual diagram schematically showing a carbon dioxide capture system provided by one embodiment of the present invention.

[0013] FIG. 2 is a conceptual diagram schematically showing a carbon dioxide capture system provided by another embodiment of the present invention.

[0014] FIG. 3 is a conceptual diagram schematically showing a carbon dioxide capture system in another embodiment of the present invention.

[0015] FIG. 4 is a schematic diagram showing a carbon dioxide capture system according to another embodiment of the present invention.

[0016] FIG. 5 is a flowchart schematically illustrating a carbon dioxide capture method provided by one embodiment of the present invention.

[0017] One embodiment of the present invention discloses a carbon dioxide capture system comprising an absorption tower and a regeneration tower, wherein the absorption tower comprises a flue gas inlet area formed to receive flue gas, an absorbent inlet area disposed in a separate area from the flue gas inlet area and formed to receive an absorbent containing methanol, a treatment space in which carbon dioxide from the flue gas is absorbed by the absorbent as the flue gas moves, and an absorbent discharge area in which the absorbent from which carbon dioxide has been absorbed in the treatment space is discharged, and the regeneration tower comprises an inlet area into which the absorbent from which carbon dioxide has been absorbed is received, a hydrogen inlet area disposed in a separate area from the inlet area into which hydrogen gas is received, a mixing space in which the carbon dioxide desorbed from the absorbent from which carbon dioxide has been absorbed is mixed with the hydrogen gas, and a mixed gas discharge area in which the carbon dioxide mixed with the hydrogen gas in the mixing space is discharged.

[0018] In this embodiment, a drying area connected to the flue gas inlet area of ​​the absorption tower and formed to reduce the moisture of the flue gas may be further included.

[0019] In this embodiment, the regeneration tower may further include an absorbent recovery area in which the absorbent from which the carbon dioxide has been desorbed is discharged.

[0020] In this embodiment, the absorption tower may further include a circulation area into which the absorbent discharged to the absorbent recovery area is reintroduced.

[0021] In this embodiment, a methanol synthesis reactor may be further included to synthesize the carbon dioxide mixed with the hydrogen gas discharged from the mixed gas discharge area into methanol.

[0022] Another embodiment of the present invention discloses a carbon dioxide capture method comprising the steps of: introducing flue gas into a carbon dioxide capture system; introducing an absorbent into the carbon dioxide capture system; absorbing carbon dioxide from the flue gas into the absorbent; introducing hydrogen gas into the carbon dioxide capture system; mixing carbon dioxide desorbed from the absorbent in which the carbon dioxide was absorbed with the hydrogen gas; and discharging the carbon dioxide mixed with the hydrogen gas.

[0023] In the present embodiment, the method may further include the step of recovering the absorbent from which the carbon dioxide has been desorbed and the step of the recovered absorbent being introduced back into the carbon dioxide capture system.

[0024] In this embodiment, the step of synthesizing methanol from the carbon dioxide mixed with the hydrogen gas may be further included.

[0025] Other aspects, features, and advantages other than those described above will become clear from the following drawings, claims, and detailed description of the invention.

[0026] The present invention is capable of various modifications and may have various embodiments; specific embodiments are illustrated in the drawings and described in detail in the detailed description. The effects and features of the present invention, and the methods for achieving them, will become clear by referring to the embodiments described below in detail together with the drawings. However, the present invention is not limited to the embodiments disclosed below but can be implemented in various forms.

[0027] Hereinafter, embodiments of the present invention will be described in detail with reference to the attached drawings. When describing with reference to the drawings, identical or corresponding components are given the same reference numerals, and redundant descriptions thereof will be omitted.

[0028] In the following embodiments, terms such as first, second, etc. are used not in a limiting sense, but for the purpose of distinguishing one component from another component.

[0029] In the following examples, singular expressions include plural expressions unless the context clearly indicates otherwise.

[0030] In the following embodiments, terms such as "include" or "have" mean that the features or components described in the specification are present, and do not preclude the possibility that one or more other features or components may be added.

[0031] In the drawings, the size of components may be exaggerated or reduced for convenience of explanation. For example, the size and thickness of each component shown in the drawings are depicted arbitrarily for convenience of explanation, so the present invention is not necessarily limited to what is illustrated.

[0032] In the following embodiments, the x-axis, y-axis, and z-axis are not limited to three axes in an orthogonal coordinate system and can be interpreted in a broader sense that includes them. For example, the x-axis, y-axis, and z-axis may be orthogonal to each other, but they may also refer to different directions that are not orthogonal to each other.

[0033] Where an embodiment can be implemented differently, a specific process sequence may be performed differently from the order described. For example, two processes described consecutively may be performed substantially simultaneously or proceed in the reverse order of the description.

[0034] FIG. 1 is a conceptual diagram schematically showing a carbon dioxide capture system provided by one embodiment of the present invention.

[0035] Referring to FIG. 1, carbon dioxide (CO2) in exhaust gas can be discharged through a carbon dioxide capture system (100) provided by one embodiment of the present invention.

[0036] In this context, flue gas (also referred to as "exhaust gas") refers to gases emitted from power generation facilities, steel mills, chemical plants, etc., and primarily refers to gases containing carbon dioxide and moisture generated by the combustion reaction of fossil fuels (hydrocarbons). Additionally, gas components originating from impurities in the raw materials of the combustion process, such as hydrogen sulfide, sulfur oxides, nitrogen oxides, hydrochloric acid, and mercury, may also be present; however, these impurities may exist in trace amounts, or some may not be substantially present at all.

[0037] In one embodiment, the carbon dioxide capture system (100) may include an absorption tower (110) and a regeneration tower (120).

[0038] The absorption tower (110) may include a flue gas inlet area (111) formed to allow flue gas to be introduced. Additionally, the absorption tower (110) may include an absorbent inlet area (112) formed to allow an absorbent (MeOH) for capturing carbon dioxide (CO2) to be introduced.

[0039] In one embodiment, the absorbent (MeOH) may be a mixed solution containing methanol and having a structure in which carbon dioxide (CO2) is physically absorbed. For example, the absorbent (MeOH) may include a mixed form of methanol and water.

[0040] In other words, the absorbent (MeOH) can form a weak physical bond with carbon dioxide (CO2) molecules. Therefore, the absorbent (MeOH) can trigger a reversible reaction in which it captures and absorbs carbon dioxide (CO2) from the flue gas, and then desorbs and separates the CO2, with relatively low energy consumption.

[0041] As an optional example, the absorbent (MeOH) may be a mixed solution in which methanol and water are mixed in a molar ratio of 1:0.5 to 1:1.5.

[0042] At this time, the water may be a small amount contained in the exhaust gas within the carbon dioxide capture system (100) of the present invention, accumulated while passing through the absorption tower (110) and the regeneration tower (120).

[0043] In the case of an absorbent (MeOH) which is an aqueous methanol solution, if the molar ratio of water is 1.5 times or more than the molar ratio of methanol, water can hinder the physical absorption of carbon dioxide by methanol by forming hydrogen bonds with the non-covalent electron pairs of oxygen atoms present in the terminal hydroxyl groups (-OH) of methanol.

[0044] In other words, if the methanol content of the absorbent (MeOH) is lowered, the carbon dioxide (CO2) capture efficiency decreases, making it difficult to achieve the target carbon dioxide (CO2) capture rate. Accordingly, if the amount of absorbent (MeOH) is increased to increase the capture rate, the size of the carbon dioxide capture system (100) facility or the amount of energy consumed by the carbon dioxide capture system (100) may increase.

[0045] Meanwhile, when the molar ratio of water in the absorbent (MeOH), which is an aqueous methanol solution, is 0.5 times or less than the molar ratio of methanol, the carbon dioxide capture efficiency may increase as the molar ratio of methanol increases, but it may not be economical because the size of the carbon dioxide capture system (100) equipment increases and the amount of energy consumed in the carbon dioxide capture system (100) increases in order to input a large amount of methanol. In addition, if the water content of the absorbent (MeOH) decreases, there may be a problem in controlling temperature conditions, etc.

[0046] The carbon dioxide capture system (100) of the present invention aims to capture more than 90% of the carbon dioxide (CO2) contained in flue gas, and considering the carbon dioxide (CO2) capture efficiency and economic feasibility for this purpose, it is preferable that the methanol and water of the absorbent (MeOH) form a molar ratio of 1:0.5 to 1:1.5.

[0047] In addition, this absorbent (MeOH) can physically absorb carbon dioxide (CO2) at high pressure (e.g., about 35 to 55 bar). Through this, the efficiency of carbon dioxide absorption can be improved.

[0048] For example, the absorbent (MeOH) of this embodiment physically absorbs carbon dioxide at high pressure, so the absorption process may proceed with low thermal energy or without thermal energy. As a specific comparative example, it can have a higher carbon dioxide efficiency than using an absorbent that absorbs carbon dioxide through chemical bonding (e.g., MEA).

[0049] Consequently, the absorption tower (110) and regeneration tower (120) of the carbon dioxide capture system (100) of the present embodiment may not include a separate condenser and reboiler, and in this case, the equipment can be simplified, which has an economic advantage.

[0050] The absorbent inlet area (112) may be placed in a separate area from the exhaust gas inlet area (111). As an example, the exhaust gas inlet area (111) and the absorbent inlet area (112) may be placed in the upper and lower spaces of the absorption tower (110), and specifically, for example, the absorbent inlet area (112) may be placed above the exhaust gas inlet area (111). Here, the references for the upper and lower parts may be defined as references toward the ground or the direction in which gravity acts. That is, with respect to the ground, the exhaust gas inlet area (111) may be placed closer to the ground than the absorbent inlet area (112).

[0051] Since the absorbent (MeOH) absorbs carbon dioxide (CO2) under high pressure conditions, as in one embodiment, the exhaust gas injected into the exhaust gas inlet area (111) and the absorbent (MeOH) introduced into the absorbent inlet area (112) can be transported in a state where high pressure is formed. Specifically, the exhaust gas and the absorbent (MeOH) can be transported at a pressure and temperature of about 35 to 55 bar and about 10 to 15°C.

[0052] As the absorbent (MeOH) introduced into the absorption tower (110) in a liquid state moves toward the exhaust gas inlet area (111) along the direction of gravity, the exhaust gas (gas) introduced into the absorption tower (110) in a high-pressure gaseous state moves upward away from the ground, and as they mix with each other, a reaction can easily occur.

[0053] Additionally, the absorption tower (110) may include a treatment space (113) in which carbon dioxide (CO2) of the flue gas is absorbed by an absorbent, an absorbent discharge area (114) in which the absorbent that has completed the reaction in the treatment space (113) can be discharged, and a flue gas discharge area (115) in which the flue gas from which carbon dioxide (CO2) has been removed can be discharged.

[0054] The treatment space (113) may be arranged to include an area connecting the exhaust gas inlet area (111) and the absorbent inlet area (112) within the absorption tower (110). Additionally, the mixing space (123) may be arranged to include an area overlapping the inlet area (121) and the hydrogen inlet area (122). Specifically, as described above, when the absorbent (MeOH) moving in the direction of gravity and the exhaust gas (gas) moving upward away from the ground meet and mix, this space may be called the treatment space (113).

[0055] In the treatment space (113), the exhaust gas and the absorbent (MeOH) are mixed and reacted, allowing carbon dioxide (CO2) to be physically absorbed by the absorbent (MeOH). Through this, carbon dioxide (CO2) mixed in the exhaust gas can be removed.

[0056] As an optional embodiment, the absorption tower (110) may be designed to include a structure that forms a larger surface area for the exhaust gas to come into contact with the absorbent (MeOH). This allows the rate at which the absorbent (MeOH) absorbs carbon dioxide (CO2) to be increased. For example, the absorption tower (110) may be composed of a tank that forms a space that is long in the vertical direction.

[0057] As another optional embodiment, the exhaust gas inlet area (111) and the absorbent inlet area (112) of the absorption tower (110) may further include a compressor and a pump for forming high pressure. This allows for the exhaust gas and the absorbent (MeOH) to be injected at high pressure, thereby creating an operating environment that promotes physical absorption between the exhaust gas and the absorbent (MeOH).

[0058] As another optional embodiment, the absorption tower (110) may further include a mixing device (not shown) including a power source to increase the mixing rate of the exhaust gas (gas) with the absorbent (MeOH), thereby increasing the rate at which carbon dioxide (CO2) is absorbed by the absorbent (MeOH).

[0059] Meanwhile, the absorbent discharge area (114) may be positioned at the bottom of the absorption tower (110). Here, the bottom of the absorption tower (110) can be defined as an area positioned adjacent to the ground. As a specific example, the absorbent discharge area (114) may include an area closer to the ground than the exhaust gas inlet area (111).

[0060] The absorbent (MeOH) that has absorbed carbon dioxide (CO2) in the absorption tower (110) can be discharged through the absorbent discharge area (114). This is because the absorbent (MeOH) is a mixed solution containing water and methanol and is in a liquid state, so it is advantageous to discharge it through the absorbent discharge area (114) which is positioned adjacent to the ground along the direction of gravity.

[0061] On the other hand, the exhaust gas discharge area (115) may be positioned at the top of the absorption tower (110). Here, the top of the absorption tower (110) can be defined as an area positioned so as to be spaced far from the ground in the absorption tower (110).

[0062] After carbon dioxide (CO2) present in the exhaust gas introduced into the absorption tower (110) is absorbed by the absorbent (MeOH), the exhaust gas from which carbon dioxide (CO2) has been removed rises in a gaseous state in a direction opposite to the direction of gravity and can be discharged through the exhaust gas discharge area (115).

[0063] The regeneration tower (120) may include an inlet area (121) into which an absorbent (MeOH) in which carbon dioxide (CO2) has been absorbed is introduced, and a hydrogen inlet area (122) into which hydrogen gas is introduced.

[0064] The inlet area (121) of the regeneration tower (120) may further include a structure connected to the absorbent discharge area (114) of the absorption tower (110). At this time, it may further include a pressure control unit (not shown) for controlling the pressure of the absorbent (MeOH) in which carbon dioxide (CO2) is absorbed and discharged at high pressure from the absorbent discharge area (114) of the absorption tower (110). For example, the pressure control unit may include a valve.

[0065] The hydrogen inlet area (122) may be placed in a separate area from the inlet area (121) within the regeneration tower (120). Specifically, the hydrogen inlet area (122) may be placed at the bottom of the regeneration tower (120), and the inlet area (121) may be placed at the top of the hydrogen inlet area (122). Hydrogen gas (H2) may be injected through the hydrogen inlet area (122). Here, the reference for the top and bottom can be defined as a reference facing the ground or the direction in which gravity acts. That is, the hydrogen inlet area (122) may be placed closer to the ground than the inlet area (121) relative to the ground. This is to facilitate mixing for desorption due to gas movement, as the relatively lighter hydrogen gas tends to move toward the top.

[0066] Additionally, the regeneration tower (120) may include a mixing space (123) and a mixed gas discharge area (124).

[0067] The mixing space (123) may be arranged to include a space connecting the inlet area (121) and the hydrogen inlet area (122). Additionally, the mixing space (123) may be arranged to include a region overlapping the inlet area (121) and the hydrogen inlet area (122). Through the mixing space (123), the absorbent (MeOH) in which carbon dioxide (CO2) introduced into the inlet area (121) is absorbed and the hydrogen gas (H2) injected into the hydrogen inlet area (122) may be mixed with each other.

[0068] In the mixing space (123), carbon dioxide (CO2) absorbed by the absorbent (MeOH) can be desorbed by hydrogen gas (H2). At this time, by desorbing the carbon dioxide (CO2) absorbed by the methanol by the gas flow of hydrogen gas (H2) at a low pressure (e.g., atmospheric pressure level), there is no need to control the regeneration tower (120) to a high pressure for carbon dioxide desorption, thus simplifying the carbon dioxide capture process and making it economically advantageous.

[0069] Table 1 below shows the total system heat requirement relative to the unit carbon dioxide capture amount of a carbon dioxide capture system utilizing monoethanolamine, and Table 2 shows the total system heat requirement relative to the unit carbon dioxide capture amount according to the carbon dioxide capture system (100) of the present invention.

[0070] Carbon Dioxide Capture System Utilizing Monoethanolamine Reboiler 12,130,000 MJ / hr Pump 0.145 MJ / hr Total Energy 12,130,150 MJ / hr Produced CO2 760.1 kg / hr Total duty 15.959 MJ / kg CO2

[0071] Methanol Absorbent-based Carbon Dioxide Capture System Compressor 4,890.674 MJ / hr --- Total Energy 4,890.674 MJ / hr Produced CO2 772,329 kg / hr Total duty 6,332 MJ / kg CO2

[0072] Referring to Table 1, the total energy required for a conventional carbon dioxide capture system is 12,130.150 MJ / hr, and the amount of captured carbon dioxide is 760.1 kg / hr. Therefore, the energy required to capture 1 kg of carbon dioxide is 15.959 MJ. Meanwhile, referring to Table 2, the total energy required for the hydrogen-based carbon dioxide capture system of the present invention is 4,890.674 MJ / hr, and the amount of captured carbon dioxide is 772,329 kg / hr. Therefore, it can be confirmed that the energy required to capture 1 kg of carbon dioxide is 6.332 MJ, which is a significantly lower energy value compared to a conventional carbon dioxide capture system.

[0073] Meanwhile, the mixed gas discharge area (124) may be positioned in a portion of the upper part of the regeneration tower (120). Through the mixed gas discharge area (124), carbon dioxide (CO2) mixed with hydrogen gas (H2) and desorbed from the absorbent (MeOH) in the mixing space (123) may be discharged. At this time, the discharged carbon dioxide (CO2) and hydrogen (H2) mixed gas may be discharged in a molar ratio of 1:1 to 1:1.5.

[0074] A carbon dioxide capture system (100) according to one embodiment of the present invention includes an absorbent (MeOH) capable of forming a physical bond with carbon dioxide (CO2) by means of attractive force. This absorbent (MeOH) has the characteristic of being easy to desorb carbon dioxide (CO2) again through a reversible reaction.

[0075] Therefore, carbon dioxide (CO2) can be removed from the exhaust gas by reacting the exhaust gas (gas) with an absorbent (MeOH) in the absorption tower (110), and the carbon dioxide (CO2) removed from the exhaust gas can be captured by reacting the absorbent (MeOH) with the adsorbed carbon dioxide (CO2) with hydrogen gas (H2) in the regeneration tower (120).

[0076] In addition, by utilizing hydrogen gas (H2) in the process of desorbing carbon dioxide (CO2) from the absorbent (MeOH), it is possible to desorb the absorbent (MeOH) and carbon dioxide (CO2) under atmospheric pressure conditions. This simplifies the carbon dioxide capture process equipment, thereby enabling the performance of an economical and environmentally friendly carbon dioxide capture process.

[0077]

[0078] FIG. 2 is a conceptual diagram schematically showing a carbon dioxide capture system (200) provided by another embodiment of the present invention.

[0079] Referring to FIG. 2, carbon dioxide (CO2) within the exhaust gas can be discharged through a carbon dioxide capture system (200) provided by one embodiment of the present invention.

[0080] In this context, flue gas (also referred to as "exhaust gas") refers to gases emitted from power generation facilities, steel mills, chemical plants, etc., and primarily refers to gases produced by the combustion reaction of fossil fuels (hydrocarbons) that contain carbon dioxide and moisture. Additionally, gas components originating from impurities in the raw materials of the combustion process, such as hydrogen sulfide, sulfur oxides, nitrogen oxides, hydrochloric acid, and mercury, may also be present; however, these impurities may exist in trace amounts, or some may not be substantially present at all.

[0081] In one embodiment, the carbon dioxide capture system (200) may include a drying area (230), an absorption tower (210), and a regeneration tower (220).

[0082] The drying area (230) may include an area where a process of removing moisture present in the exhaust gas is performed by compressing the gas to a high pressure and cooling it to a low temperature.

[0083] The exhaust gas that has passed through the drying area (230) can be injected into the exhaust gas inlet area (211) of the absorption tower (210). As a specific example, the exhaust gas that has passed through the drying area (230) can be dried to a state containing water with a mole fraction of 0.05 mol% or less.

[0084] Through this, the exhaust gas can be introduced in a state suitable for the operating environment of the carbon dioxide capture system (200). In addition, when the absorbent (MeOH) removes carbon dioxide (CO2) in the exhaust gas through the carbon dioxide capture system, the purity of the methanol component contained in the absorbent (MeOH) is diluted due to water vapor in the exhaust gas, thereby preventing the weakening of the absorbent's function.

[0085] The absorption tower (210) may include a flue gas inlet area (211) formed to allow flue gas to be introduced. Additionally, the absorption tower (210) may include an absorbent inlet area (212) formed to allow an absorbent (MeOH) for capturing carbon dioxide (CO2) to be introduced.

[0086] In one embodiment, the absorbent (MeOH) may be a mixed solution containing methanol and having a structure that physically absorbs carbon dioxide (CO2).

[0087] In other words, the absorbent (MeOH) can form a weak physical bond with carbon dioxide (CO2) molecules. Therefore, the absorbent (MeOH) can trigger a reversible reaction in which it captures and absorbs carbon dioxide (CO2) from the flue gas, and then desorbs and separates the CO2, with relatively low energy consumption.

[0088] As an optional example, the absorbent (MeOH) may be a mixed solution in which methanol and water are mixed in a molar ratio of 1:0.5 to 1:1.5.

[0089] At this time, the water may be a small amount contained in the exhaust gas within the carbon dioxide capture system (200) of the present invention, accumulated while passing through the absorption tower (210) and the regeneration tower (220).

[0090] In the case of an absorbent (MeOH) which is an aqueous methanol solution, if the molar ratio of water is 1.5 times or more than the molar ratio of methanol, water can hinder the physical absorption of carbon dioxide by methanol by forming hydrogen bonds with the non-covalent electron pairs of oxygen atoms present in the terminal hydroxyl groups (-OH) of methanol.

[0091] In other words, if the methanol content of the absorbent (MeOH) is lowered, the carbon dioxide (CO2) capture efficiency decreases, making it difficult to achieve the target carbon dioxide (CO2) capture rate. Accordingly, if the amount of absorbent (MeOH) is increased to increase the capture rate, the size of the carbon dioxide capture system (200) facility or the amount of energy consumed by the carbon dioxide capture system (200) may increase.

[0092] Meanwhile, when the molar ratio of water in the absorbent (MeOH), which is an aqueous methanol solution, is 0.5 times or less than the molar ratio of methanol, the carbon dioxide capture efficiency may increase as the molar ratio of methanol increases, but it may not be economical because the size of the carbon dioxide capture system (200) equipment increases and the amount of energy consumed in the carbon dioxide capture system (200) increases in order to input a large amount of methanol. In addition, if the water content of the absorbent (MeOH) decreases, there may be a problem in controlling temperature conditions, etc.

[0093] The carbon dioxide capture system (200) of the present invention aims to capture more than 90% of the carbon dioxide (CO2) contained in the flue gas, and considering the carbon dioxide (CO2) capture efficiency and economic feasibility for this purpose, it is preferable that the methanol and water of the absorbent (MeOH) form a molar ratio of 1:0.5 to 1:1.5.

[0094] In addition, this absorbent (MeOH) can physically absorb carbon dioxide (CO2) at high pressure (e.g., about 35 to 55 bar). Through this, the efficiency of carbon dioxide absorption can be improved.

[0095] For example, the absorbent (MeOH) of this embodiment physically absorbs carbon dioxide at high pressure, so the absorption process may proceed with low thermal energy or without thermal energy. As a specific comparative example, it can have a higher carbon dioxide efficiency than using an absorbent that absorbs carbon dioxide through chemical bonding (e.g., MEA).

[0096] Consequently, the absorption tower (210) and regeneration tower (220) of the carbon dioxide capture system (200) of the present embodiment may not include a separate condenser and reboiler, and in this case, the equipment can be simplified, which has an economic advantage.

[0097] The absorbent inlet area (212) may be placed in a separate area from the exhaust gas inlet area (211). As an example, the exhaust gas inlet area (211) and the absorbent inlet area (212) may be placed in the upper and lower spaces of the absorption tower (210), and specifically, for example, the absorbent inlet area (212) may be placed above the exhaust gas inlet area (211). Here, the reference for the upper and lower parts may be defined as a reference facing the ground or the direction in which gravity acts. That is, with respect to the ground, the exhaust gas inlet area (211) may be placed closer to the ground than the absorbent inlet area (212).

[0098] Since the absorbent (MeOH) absorbs carbon dioxide (CO2) under high pressure conditions, as in one embodiment, the exhaust gas injected into the exhaust gas inlet area (211) and the absorbent (MeOH) introduced into the absorbent inlet area (212) can be transported in a state where high pressure is formed. Specifically, the exhaust gas and the absorbent (MeOH) can be transported at a pressure and temperature of about 35 to 55 bar and about 10 to 15°C.

[0099] As the absorbent (MeOH) introduced into the absorption tower (210) in a liquid state moves toward the exhaust gas inlet area (211) along the direction of gravity, the exhaust gas (gas) introduced into the absorption tower (210) in a high-pressure gaseous state moves upward away from the ground, and as they mix with each other, a reaction can easily occur.

[0100] Additionally, the absorption tower (210) may include a treatment space (213) in which carbon dioxide (CO2) of the exhaust gas is absorbed by an absorbent, an absorbent discharge area (214) in which the absorbent that has completed the reaction in the treatment space (213) can be discharged, and an exhaust gas discharge area (215) in which the exhaust gas from which carbon dioxide (CO2) has been removed can be discharged.

[0101] The processing space (213) may be arranged to include an area connecting the exhaust gas inlet area (211) and the absorbent inlet area (212) within the absorption tower (210). Additionally, the mixing space (223) may be arranged to include an area overlapping the inlet area (221) and the hydrogen inlet area (222). Specifically, as described above, when the absorbent (MeOH) moving in the direction of gravity and the exhaust gas (gas) moving upward away from the ground meet and mix, this space may be called the processing space (213).

[0102] In the treatment space (213), the exhaust gas and the absorbent (MeOH) are mixed and reacted, allowing carbon dioxide (CO2) to be physically absorbed by the absorbent (MeOH). Through this, carbon dioxide (CO2) mixed in the exhaust gas can be removed.

[0103] As an optional embodiment, the absorption tower (210) may be designed to include a structure that forms a larger surface area for the exhaust gas to come into contact with the absorbent (MeOH). This allows the rate at which the absorbent (MeOH) absorbs carbon dioxide (CO2) to be increased. For example, the absorption tower (210) may be composed of a tank that forms a space that is long in the vertical direction.

[0104] As another optional embodiment, the exhaust gas inlet area (211) and the absorbent inlet area (212) of the absorption tower (210) may further include a compressor and a pump for forming high pressure.

[0105] Through this, an operating environment can be created that promotes physical absorption between the flue gas and the absorbent (MeOH) by injecting the flue gas and the absorbent (MeOH) at high pressure.

[0106] As another optional embodiment, the absorption tower (210) may further include a mixing device (not shown) including a power source to increase the mixing rate of the exhaust gas (gas) with the absorbent (MeOH), thereby increasing the reaction rate at which carbon dioxide (CO2) is absorbed by the absorbent (MeOH).

[0107] Meanwhile, the absorbent discharge area (214) may be positioned at the bottom of the absorption tower (210). Here, the bottom of the absorption tower (110) can be defined as an area positioned adjacent to the ground. As a specific example, the absorbent discharge area (214) may include an area closer to the ground than the exhaust gas inlet area (211).

[0108] The absorbent (MeOH) that has absorbed carbon dioxide (CO2) in the absorption tower (210) can be discharged through the absorbent discharge area (214). This is because the absorbent (MeOH) is a mixed solution containing water and methanol and is in a liquid state, so it is advantageous to discharge it through the absorbent discharge area (214) which is positioned adjacent to the ground along the direction of gravity.

[0109] On the other hand, the exhaust gas discharge area (215) may be positioned at the top of the absorption tower (210). Here, the top of the absorption tower (210) can be defined as an area positioned so as to be spaced far from the ground in the absorption tower (210).

[0110] After carbon dioxide (CO2) present in the exhaust gas introduced into the absorption tower (210) is absorbed by the absorbent (MeOH), the exhaust gas from which carbon dioxide (CO2) has been removed rises in a gaseous state in a direction opposite to the direction of gravity and can be discharged through the exhaust gas discharge area (215).

[0111] The regeneration tower (220) may include an inlet area (221) into which an absorbent (MeOH) in which carbon dioxide (CO2) has been absorbed is introduced, and a hydrogen inlet area (222) into which hydrogen gas is introduced.

[0112] The inlet area (221) of the regeneration tower (220) may further include a structure connected to the absorbent discharge area (214) of the absorption tower (210). At this time, it may further include a pressure control unit (not shown) for controlling the pressure of the absorbent (MeOH) in which carbon dioxide (CO2) is absorbed and discharged at high pressure from the absorbent discharge area (214) of the absorption tower (210). For example, the pressure control unit may include a valve.

[0113] The hydrogen inlet area (222) may be placed in a separate area from the inlet area (221) within the regeneration tower (220). Specifically, the hydrogen inlet area (222) may be placed at the bottom of the regeneration tower (220), and the inlet area (221) may be placed at the top of the hydrogen inlet area (222). Hydrogen gas (H2) may be injected through the hydrogen inlet area (222). Here, the reference for the top and bottom can be defined as a reference facing the ground or the direction in which gravity acts. That is, the hydrogen inlet area (222) may be placed closer to the ground than the inlet area (221) relative to the ground. This is to facilitate mixing for desorption by gas movement, as the relatively lighter hydrogen gas tends to move toward the top.

[0114] Additionally, the regeneration tower (220) may include a mixing space (223) and a mixed gas discharge area (224).

[0115] The mixing space (223) may be arranged to include a space connecting the inlet area (221) and the hydrogen inlet area (222). Additionally, the mixing space (223) may be arranged to include a region overlapping the inlet area (221) and the hydrogen inlet area (222). Through the mixing space (223), the absorbent (MeOH) into which carbon dioxide (CO2) introduced into the inlet area (221) has been absorbed and the hydrogen gas (H2) injected into the hydrogen inlet area (222) may be mixed with each other.

[0116] In the mixing space (223), carbon dioxide (CO2) absorbed by the absorbent (MeOH) can be desorbed by hydrogen gas (H2). At this time, by desorbing the carbon dioxide (CO2) absorbed by the methanol by the gas flow of hydrogen gas (H2) at a low pressure (e.g., atmospheric pressure level), there is no need to control the regeneration tower (220) to a high pressure for carbon dioxide desorption, thus simplifying the carbon dioxide capture process and making it economically advantageous.

[0117] The mixed gas discharge area (224) may be located in a portion of the upper part of the regeneration tower (220). Through the mixed gas discharge area (224), carbon dioxide (CO2) mixed with hydrogen gas (H2) and desorbed from the absorbent (MeOH) in the mixing space (223) may be discharged. At this time, the discharged carbon dioxide (CO2) and hydrogen (H2) mixed gas may be discharged in a molar ratio of 1:1 to 1:1.5.

[0118] A carbon dioxide capture system (200) according to one embodiment of the present invention further includes a drying area (230) in which a process of removing moisture present in the exhaust gas is performed, thereby forming conditions more favorable for the exhaust gas to react with the absorbent (MeOH).

[0119]

[0120] FIG. 3 is a conceptual diagram schematically showing a carbon dioxide capture system (300) in another embodiment of the present invention.

[0121] Referring to FIG. 3, carbon dioxide (CO2) in the exhaust gas can be discharged through a carbon dioxide capture system (300) provided by one embodiment of the present invention.

[0122] In this context, flue gas (also referred to as "exhaust gas") refers to gases emitted from power generation facilities, steel mills, chemical plants, etc., and primarily refers to gases produced by the combustion reaction of fossil fuels (hydrocarbons) that contain carbon dioxide and moisture. Additionally, gas components originating from impurities in the raw materials of the combustion process, such as hydrogen sulfide, sulfur oxides, nitrogen oxides, hydrochloric acid, and mercury, may also be present; however, these impurities may exist in trace amounts, or some may not be substantially present at all.

[0123] In one embodiment, the carbon dioxide capture system (300) may include a drying area (330), an absorption tower (310), and a regeneration tower (320).

[0124] The drying area (330) may include an area where a process of removing moisture present in the exhaust gas is performed by compressing the gas to a high pressure and cooling it to a low temperature.

[0125] The exhaust gas that has passed through the drying area (330) can be injected into the exhaust gas inlet area (311) of the absorption tower (310). As a specific example, the exhaust gas that has passed through the drying area (330) can be dried to a state containing water with a mole fraction of 0.05 mol% or less.

[0126] Through this, the exhaust gas can be introduced in a state suitable for the operating environment of the carbon dioxide capture system (300). In addition, when the absorbent (MeOH) removes carbon dioxide (CO2) in the exhaust gas through the carbon dioxide capture system, the purity of the methanol component contained in the absorbent (MeOH) is diluted due to water vapor in the exhaust gas, thereby preventing the function of the absorbent from being weakened.

[0127] The absorption tower (310) may include a flue gas inlet area (311) formed to allow flue gas to be introduced. Additionally, the absorption tower (310) may include an absorbent inlet area (312) formed to allow an absorbent (MeOH) for capturing carbon dioxide (CO2) to be introduced.

[0128] In one embodiment, the absorbent (MeOH) may be a mixed solution containing methanol and having a structure that physically absorbs carbon dioxide (CO2).

[0129] As an optional example, the absorbent (MeOH) may be a mixed solution in which methanol and water are mixed in a molar ratio of 1:0.5 to 1:1.5.

[0130] At this time, the water may be a small amount contained in the exhaust gas within the carbon dioxide capture system (300) of the present invention, accumulated while passing through the absorption tower (310) and the regeneration tower (320).

[0131] In the case of an absorbent (MeOH) which is an aqueous methanol solution, if the molar ratio of water is 1.5 times or more than the molar ratio of methanol, water can hinder the physical absorption of carbon dioxide by methanol by forming hydrogen bonds with the non-covalent electron pairs of oxygen atoms present in the terminal hydroxyl groups (-OH) of methanol.

[0132] In other words, if the methanol content of the absorbent (MeOH) is lowered, the carbon dioxide (CO2) capture efficiency decreases, making it difficult to achieve the target carbon dioxide (CO2) capture rate. Accordingly, if the amount of absorbent (MeOH) is increased to increase the capture rate, the size of the carbon dioxide capture system (300) facility or the amount of energy consumed by the carbon dioxide capture system (300) may increase.

[0133] Meanwhile, when the molar ratio of water in the absorbent (MeOH), which is a methanol aqueous solution, is 0.5 times or less than the molar ratio of methanol, the carbon dioxide capture efficiency may increase as the molar ratio of methanol increases, but it may not be economical because the size of the carbon dioxide capture system (300) equipment increases and the amount of energy consumed in the carbon dioxide capture system (300) increases in order to input a large amount of methanol. In addition, if the water content of the absorbent (MeOH) decreases, there may be a problem in controlling temperature conditions, etc.

[0134] The carbon dioxide capture system (300) of the present invention aims to capture more than 90% of the carbon dioxide (CO2) contained in the flue gas, and considering the carbon dioxide (CO2) capture efficiency and economic feasibility for this purpose, it is preferable that the methanol and water of the absorbent (MeOH) form a molar ratio of 1:0.5 to 1:1.5.

[0135] This absorbent (MeOH) can physically absorb carbon dioxide (CO2) at high pressure (e.g., about 35 to 55 bar). This can improve the efficiency of carbon dioxide absorption. For example, since the absorbent (MeOH) of this embodiment physically absorbs carbon dioxide at high pressure, the absorption process may require low thermal energy or proceed without thermal energy. As a specific comparative example, it can have higher carbon dioxide efficiency than using an absorbent that absorbs carbon dioxide through chemical bonding (e.g., MEA).

[0136] Consequently, the absorption tower (310) and regeneration tower (320) of the carbon dioxide capture system (300) of this embodiment may not include a separate condenser and reboiler, and in this case, the equipment can be simplified, which has an economic advantage.

[0137] The absorbent inlet area (312) may be placed in a separate area from the exhaust gas inlet area (311). As an example, the exhaust gas inlet area (311) and the absorbent inlet area (312) may be placed in the upper and lower spaces of the absorption tower (310), and specifically, for example, the absorbent inlet area (312) may be placed above the exhaust gas inlet area (311). Here, the references for the upper and lower parts may be defined as references facing the ground or the direction in which gravity acts. That is, with respect to the ground, the exhaust gas inlet area (311) may be placed closer to the ground than the absorbent inlet area (312).

[0138] Since the absorbent (MeOH) absorbs carbon dioxide (CO2) under high pressure conditions, as in one embodiment, the exhaust gas injected into the exhaust gas inlet area (311) and the absorbent (MeOH) introduced into the absorbent inlet area (312) can be transported in a state where high pressure is formed. Specifically, the exhaust gas and the absorbent (MeOH) can be transported at a pressure and temperature of about 35 to 55 bar and about 10 to 15°C.

[0139] As the absorbent (MeOH) introduced into the absorption tower (310) in a liquid state moves toward the exhaust gas inlet area (311) along the direction of gravity, the exhaust gas (gas) introduced into the absorption tower (310) in a high-pressure gaseous state moves upward in a direction away from the ground, and as they mix with each other, a reaction can easily occur.

[0140] Additionally, the absorption tower (310) may include a treatment space (313) in which carbon dioxide (CO2) of the exhaust gas is absorbed by an absorbent, an absorbent discharge area (314) in which the absorbent that has completed the reaction in the treatment space (313) can be discharged, and an exhaust gas discharge area (315) in which the exhaust gas from which carbon dioxide (CO2) has been removed can be discharged.

[0141] The processing space (313) may be arranged to include an area connecting the exhaust gas inlet area (311) and the absorbent inlet area (312) within the absorption tower (310). Additionally, the mixing space (323) may be arranged to include an area overlapping the inlet area (321) and the hydrogen inlet area (322). Specifically, as described above, when the absorbent (MeOH) moving in the direction of gravity and the exhaust gas (gas) moving upward away from the ground meet and mix, this space may be called the processing space (313).

[0142] In the treatment space (313), the exhaust gas and the absorbent (MeOH) are mixed and reacted, allowing carbon dioxide (CO2) to be physically absorbed by the absorbent (MeOH). Through this, carbon dioxide (CO2) mixed in the exhaust gas can be removed.

[0143] As an optional embodiment, the absorption tower (310) may be designed to include a structure to form a larger surface area where the exhaust gas comes into contact with the absorbent (MeOH). This increases the rate at which carbon dioxide (CO2) is absorbed by the absorbent (MeOH). For example, the absorption tower (310) may be composed of a tank that forms a space that is long in the vertical direction.

[0144] As another optional embodiment, the exhaust gas inlet area (311) and the absorbent inlet area (312) of the absorption tower (310) may further include a compressor and a pump for forming high pressure.

[0145] Through this, an operating environment can be created that promotes physical absorption between the flue gas and the absorbent (MeOH) by injecting the flue gas and the absorbent (MeOH) at high pressure.

[0146] As another optional embodiment, the absorption tower (310) may further include a mixing device (not shown) including a power source to increase the mixing rate of the exhaust gas (gas) with the absorbent (MeOH), thereby increasing the reaction rate at which carbon dioxide (CO2) is absorbed by the absorbent (MeOH).

[0147] Meanwhile, the absorbent discharge area (314) may be positioned at the bottom of the absorption tower (310). Here, the bottom of the absorption tower (310) can be defined as an area positioned adjacent to the ground. As a specific example, the absorbent discharge area (314) may include an area closer to the ground than the exhaust gas inlet area (311).

[0148] The absorbent (MeOH) that has absorbed carbon dioxide (CO2) in the absorption tower (310) can be discharged through the absorbent discharge area (314). This is because the absorbent (MeOH) is a mixed solution containing water and methanol and is in a liquid state, so it is advantageous to discharge it through the absorbent discharge area (314) which is positioned adjacent to the ground along the direction of gravity.

[0149] On the other hand, the exhaust gas discharge area (315) may be positioned at the top of the absorption tower (310). Here, the top of the absorption tower (310) can be defined as an area positioned so as to be spaced far from the ground in the absorption tower (310).

[0150] After carbon dioxide (CO2) present in the exhaust gas introduced into the absorption tower (310) is absorbed by the absorbent (MeOH), the exhaust gas from which carbon dioxide (CO2) has been removed rises in a gaseous state in a direction opposite to the direction of gravity and can be discharged through the exhaust gas discharge area (315).

[0151] The regeneration tower (320) may include an inlet area (321) into which an absorbent (MeOH) in which carbon dioxide (CO2) has been absorbed is introduced, and a hydrogen inlet area (322) into which hydrogen gas is introduced.

[0152] The inlet area (321) of the regeneration tower (320) may further include a structure connected to the absorbent discharge area (314) of the absorption tower (310). At this time, it may further include a pressure control unit (not shown) for controlling the pressure of the absorbent (MeOH) in which carbon dioxide (CO2) is discharged at high pressure from the absorbent discharge area (314) of the absorption tower (310). For example, the pressure control unit may include a valve.

[0153] The hydrogen inlet area (322) may be placed in a separate area from the inlet area (321) within the regeneration tower (320). Specifically, the hydrogen inlet area (322) may be placed at the bottom of the regeneration tower (320), and the inlet area (321) may be placed at the top of the hydrogen inlet area (322). Hydrogen gas (H2) may be injected through the hydrogen inlet area (322). Here, the reference for the top and bottom can be defined as a reference facing the ground or the direction in which gravity acts. That is, the hydrogen inlet area (322) may be placed closer to the ground than the inlet area (321) relative to the ground. This is to facilitate mixing for desorption due to gas movement, as the relatively lighter hydrogen gas tends to move toward the top.

[0154] Additionally, the regeneration tower (320) may include a mixing space (323) and a mixed gas discharge area (324).

[0155] The mixing space (323) may be arranged to include a space connecting the inlet area (321) and the hydrogen inlet area (322). Additionally, the mixing space (323) may be arranged to include a region overlapping with the inlet area (321) and the hydrogen inlet area (322). Through the mixing space (323), the absorbent (MeOH) into which carbon dioxide (CO2) introduced into the inlet area (321) has been absorbed and the hydrogen gas (H2) injected into the hydrogen inlet area (322) may be mixed with each other.

[0156] In the mixing space (323), carbon dioxide (CO2) absorbed by the absorbent (MeOH) can be desorbed by hydrogen gas (H2). At this time, by desorbing the carbon dioxide (CO2) absorbed by the methanol by the gas flow of hydrogen gas (H2) at a low pressure (e.g., atmospheric pressure level), there is no need to control the regeneration tower (320) to a high pressure for carbon dioxide desorption, thus simplifying the carbon dioxide capture process and making it economically advantageous.

[0157] The mixed gas discharge area (324) may be located in a portion of the upper part of the regeneration tower (320). Through the mixed gas discharge area (324), carbon dioxide (CO2) mixed with hydrogen gas (H2) and desorbed from the absorbent (MeOH) in the mixing space (323) may be discharged. At this time, the discharged carbon dioxide (CO2) and hydrogen (H2) mixed gas may be discharged in a molar ratio of 1:1 to 1:1.5.

[0158] In one embodiment, the regeneration tower (320) may further include an absorbent recovery area (325).

[0159] The absorbent recovery area (325) may be placed in one area of ​​the regeneration tower (320) to recover the absorbent (MeOH) from which carbon dioxide (CO2) has been desorbed by hydrogen gas (H2) in the mixing space (323) of the regeneration tower (320).

[0160] For example, the absorbent recovery area (325) may be positioned at the bottom of the regeneration tower (320). Here, the reference point for the bottom can be defined as a reference point facing the ground or the direction in which gravity acts. That is, the absorbent recovery area (325) may be positioned adjacent to the ground. Through this, when the relatively light hydrogen gas (H2) and carbon dioxide (CO2) rise toward the top away from the ground, the liquid absorbent (MeOH) descending along the direction of gravity can be easily separated and discharged.

[0161] The absorbent (MeOH) of the carbon dioxide capture system (300) according to one embodiment of the present invention has the characteristic of being able to form a physical bond with carbon dioxide (CO2) by means of attractive force and easily desorbing carbon dioxide (CO2) through a reversible reaction.

[0162] Therefore, by further including a structure that can absorb carbon dioxide (CO2) from flue gas and then recover the absorbent (MeOH) from which carbon dioxide (CO2) has been desorbed in a regeneration tower (320), the absorbent (MeOH) can be reused, thereby providing a more economical and environmentally friendly carbon dioxide capture system (300).

[0163]

[0164] In addition, FIG. 4 is a schematic diagram showing a carbon dioxide capture system (400) according to another embodiment of the present invention.

[0165] Referring to FIG. 4, carbon dioxide (CO2) in the exhaust gas can be discharged through a carbon dioxide capture system (400) provided by one embodiment of the present invention.

[0166] In this context, flue gas (also referred to as "exhaust gas") refers to gases emitted from power generation facilities, steel mills, chemical plants, etc., and primarily refers to gases containing carbon dioxide and moisture generated by the combustion reaction of fossil fuels (hydrocarbons). Additionally, gas components originating from impurities in the raw materials of the combustion process, such as hydrogen sulfide, sulfur oxides, nitrogen oxides, hydrochloric acid, and mercury, may also be present; however, these impurities may exist in trace amounts, or some may not be substantially present at all.

[0167] In one embodiment, the carbon dioxide capture system (400) may include a drying area (430), an absorption tower (410), and a regeneration tower (420).

[0168] The drying area (430) may include an area where a process of removing moisture present in the exhaust gas is performed by compressing the gas to a high pressure and cooling it to a low temperature.

[0169] As a specific embodiment, the drying area (430) may include one or more compressors (431), one or more heat exchangers (432), and a gas-liquid separator (433). The gas-liquid separator (433) may include one of various types, for example, a knock-out drum.

[0170] The exhaust gas that has passed through the drying area (430) can be injected into the exhaust gas inlet area (411) of the absorption tower (410). As a specific example, the exhaust gas that has passed through the drying area (430) can be dried to a state containing water with a mole fraction of 0.05 mol% or less.

[0171] Through this, the exhaust gas can be introduced in a state suitable for the operating environment of the carbon dioxide capture system (400). In addition, when the absorbent (MeOH) removes carbon dioxide (CO2) in the exhaust gas through the carbon dioxide capture system, the purity of the methanol component contained in the absorbent (MeOH) is diluted due to water vapor in the exhaust gas, thereby preventing the weakening of the absorbent's function.

[0172] The absorption tower (410) may include a flue gas inlet area (411) formed to allow flue gas to be introduced. Additionally, the absorption tower (410) may include an absorbent inlet area (412) formed to allow an absorbent (MeOH) for capturing carbon dioxide (CO2) to be introduced.

[0173] In one embodiment, the absorbent (MeOH) may be a mixed solution containing methanol and having a structure that physically absorbs carbon dioxide (CO2).

[0174] As an optional example, the absorbent (MeOH) may be a mixed solution in which methanol and water are mixed in a molar ratio of 1:0.5 to 1:1.5.

[0175] At this time, the water may be a small amount contained in the exhaust gas within the carbon dioxide capture system (400) of the present invention, accumulated while passing through the absorption tower (410) and the regeneration tower (420).

[0176] In the case of an absorbent (MeOH) which is an aqueous methanol solution, if the molar ratio of water is 1.5 times or more than the molar ratio of methanol, water can hinder the physical absorption of carbon dioxide by methanol by forming hydrogen bonds with the non-covalent electron pairs of oxygen atoms present in the terminal hydroxyl groups (-OH) of methanol.

[0177] In other words, if the methanol content of the absorbent (MeOH) is lowered, the carbon dioxide (CO2) capture efficiency decreases, making it difficult to achieve the target carbon dioxide (CO2) capture rate. Accordingly, if the amount of absorbent (MeOH) is increased to increase the capture rate, the size of the carbon dioxide capture system (400) facility or the amount of energy consumed by the carbon dioxide capture system (400) may increase.

[0178] Meanwhile, when the molar ratio of water in the absorbent (MeOH), which is an aqueous methanol solution, is 0.5 times or less than the molar ratio of methanol, the carbon dioxide capture efficiency may increase as the molar ratio of methanol increases, but it may not be economical because the size of the carbon dioxide capture system (400) equipment increases and the amount of energy consumed in the carbon dioxide capture system (400) increases in order to input a large amount of methanol. In addition, if the water content of the absorbent (MeOH) decreases, there may be a problem in controlling temperature conditions, etc.

[0179] The carbon dioxide capture system (400) of the present invention aims to capture more than 90% of the carbon dioxide (CO2) contained in the flue gas, and considering the carbon dioxide (CO2) capture efficiency and economic feasibility for this purpose, it is preferable that the methanol and water of the absorbent (MeOH) have a molar ratio of 1:0.5 to 1:1.5.

[0180] This absorbent (MeOH) can physically absorb carbon dioxide (CO2) at high pressure (e.g., about 35 to 55 bar). This can improve the efficiency of carbon dioxide absorption. For example, since the absorbent (MeOH) of this embodiment physically absorbs carbon dioxide at high pressure, the absorption process may require low thermal energy or proceed without thermal energy. As a specific comparative example, it can have higher carbon dioxide efficiency than using an absorbent that absorbs carbon dioxide through chemical bonding (e.g., MEA).

[0181] Consequently, the absorption tower (410) and regeneration tower (420) of the carbon dioxide capture system (400) of this embodiment may not include a separate condenser and reboiler, and in this case, the equipment can be simplified, which has an economic advantage.

[0182] The absorbent inlet area (412) may be placed in a separate area from the exhaust gas inlet area (411). As an example, the exhaust gas inlet area (411) and the absorbent inlet area (412) may be placed in the upper and lower spaces of the absorption tower (410), and specifically, for example, the absorbent inlet area (412) may be placed above the exhaust gas inlet area (411). Here, the reference for the upper and lower parts may be defined as a reference facing the ground or the direction in which gravity acts. That is, with respect to the ground, the exhaust gas inlet area (411) may be placed closer to the ground than the absorbent inlet area (412).

[0183] Since the absorbent (MeOH) absorbs carbon dioxide (CO2) under high pressure conditions, as in one embodiment, the exhaust gas injected into the exhaust gas inlet area (411) and the absorbent (MeOH) introduced into the absorbent inlet area (412) can be transported in a state where high pressure is formed. Specifically, the exhaust gas and the absorbent (MeOH) can be transported at a pressure and temperature of about 35 to 50 bar and about 10 to 15°C.

[0184] As the absorbent (MeOH) introduced into the absorption tower (410) in a liquid state moves toward the exhaust gas inlet area (411) along the direction of gravity, the exhaust gas (gas) introduced into the absorption tower (410) in a high-pressure gaseous state moves upward away from the ground, and as they mix with each other, a reaction can easily occur.

[0185] Additionally, the absorption tower (410) may include a treatment space (413) in which carbon dioxide (CO2) of the exhaust gas is absorbed by an absorbent, an absorbent discharge area (414) in which the absorbent that has completed the reaction in the treatment space (413) can be discharged, and an exhaust gas discharge area (415) in which the exhaust gas from which carbon dioxide (CO2) has been removed can be discharged.

[0186] The processing space (413) may be arranged to include an area connecting the exhaust gas inlet area (411) and the absorbent inlet area (412) within the absorption tower (410). Additionally, the mixing space (323) may be arranged to include an area overlapping the inlet area (321) and the hydrogen inlet area (322). Specifically, as described above, when the absorbent (MeOH) moving in the direction of gravity and the exhaust gas (gas) moving upward away from the ground meet and mix, this space may be called the processing space (413).

[0187] In the treatment space (413), the exhaust gas and the absorbent (MeOH) are mixed and reacted, allowing carbon dioxide (CO2) to be physically absorbed by the absorbent (MeOH). Through this, carbon dioxide (CO2) mixed in the exhaust gas can be removed.

[0188] As an optional embodiment, the absorption tower (410) may be designed to include a structure that forms a larger surface area for the exhaust gas to come into contact with the absorbent (MeOH). This allows the absorption rate of carbon dioxide (CO2) into the absorbent (MeOH) to be increased. For example, the absorption tower (410) may be composed of a tank that forms a long space in the vertical direction.

[0189] As another optional embodiment, the flue gas inlet area (411) and the absorbent inlet area (412) of the absorption tower (410) may further include a compressor and a pump for forming high pressure. This allows for the creation of an operating environment that promotes physical absorption between the flue gas and the absorbent by injecting the flue gas and the absorbent (MeOH) at high pressure.

[0190] As another optional embodiment, the absorption tower (410) may further include a mixing device (not shown) including a power source to increase the mixing rate of the exhaust gas (gas) with the absorbent (MeOH), thereby increasing the reaction rate at which carbon dioxide (CO2) is absorbed by the absorbent (MeOH).

[0191] Meanwhile, the absorbent discharge area (414) may be positioned at the bottom of the absorption tower (410). Here, the bottom of the absorption tower (410) can be defined as an area positioned adjacent to the ground. As a specific example, the absorbent discharge area (414) may include an area closer to the ground than the exhaust gas inlet area (411).

[0192] The absorbent (MeOH) that has absorbed carbon dioxide (CO2) in the absorption tower (410) can be discharged through the absorbent discharge area (414). Since the absorbent (MeOH) is a mixed solution containing water and methanol and is in a liquid state, it is advantageous to discharge it through the absorbent discharge area (414) which is positioned adjacent to the ground along the direction of gravity. To facilitate the smooth discharge of the absorbent (MeOH), the absorbent discharge area (414) may further include a structure connected to a pump (P1).

[0193] On the other hand, the exhaust gas discharge area (415) may be positioned at the top of the absorption tower (410). Here, the top of the absorption tower (410) can be defined as an area positioned so as to be spaced far from the ground in the absorption tower (410).

[0194] After carbon dioxide (CO2) present in the exhaust gas introduced into the absorption tower (410) is absorbed by the absorbent (MeOH), the exhaust gas from which carbon dioxide (CO2) has been removed rises in a gaseous state in a direction opposite to the direction of gravity and can be discharged through the exhaust gas discharge area (415). To ensure smooth discharge of the remaining exhaust gas, the exhaust gas discharge area (415) may further include a structure connected to a compressor (c2).

[0195] The regeneration tower (420) may include an inlet area (421) into which an absorbent (MeOH) in which carbon dioxide (CO2) has been absorbed is introduced, and a hydrogen inlet area (422) into which hydrogen gas is introduced.

[0196] The inlet area (421) of the regeneration tower (420) may further include a structure connected to the absorbent discharge area (414) of the absorption tower (410). At this time, the pressure control unit may further include a pressure control unit for controlling the pressure of the absorbent (MeOH) in which carbon dioxide (CO2) is absorbed and discharged at high pressure from the absorbent discharge area (414) of the absorption tower (410). As a specific example, the pressure control unit may include a valve (v).

[0197] The hydrogen inlet area (422) may be placed in a separate area from the inlet area (421) within the regeneration tower (420). Specifically, the hydrogen inlet area (422) may be placed at the bottom of the regeneration tower (420), and the inlet area (421) may be placed at the top of the hydrogen inlet area (422). Hydrogen gas (H2) may be injected through the hydrogen inlet area (422). Here, the reference for the top and bottom can be defined as a reference facing the ground or the direction in which gravity acts. That is, the hydrogen inlet area (422) may be placed closer to the ground than the inlet area (421) relative to the ground. This is to facilitate mixing for desorption by gas movement, as the relatively lighter hydrogen gas tends to move toward the top.

[0198] Additionally, the regeneration tower (420) may include a mixing space (423) and a mixed gas discharge area (424).

[0199] The mixing space (423) may be arranged to include a space connecting the inlet area (421) and the hydrogen inlet area (422). Through the mixing space (423), the carbon dioxide (CO2) introduced into the inlet area (421) can be mixed with the absorbent (MeOH) that has absorbed the carbon dioxide (CO2) and the hydrogen gas (H2) injected into the hydrogen inlet area (422).

[0200] In the mixing space (423), carbon dioxide (CO2) absorbed by the absorbent (MeOH) can be desorbed by hydrogen gas (H2). At this time, by desorbing the carbon dioxide (CO2) absorbed by the methanol by the gas flow of hydrogen gas (H2) at a low pressure (e.g., atmospheric pressure level), there is no need to control the regeneration tower (420) to a high pressure for carbon dioxide desorption, thus simplifying the carbon dioxide capture process and making it economically advantageous.

[0201] The mixed gas discharge area (424) may be positioned in a portion of the upper part of the regeneration tower (420). Through the mixed gas discharge area (424), carbon dioxide (CO2) mixed with hydrogen gas (H2) and desorbed from the absorbent (MeOH) in the mixing space (423) may be discharged. At this time, the discharged carbon dioxide (CO2) and hydrogen (H2) mixed gas may be discharged in a molar ratio of 1:1 to 1:1.5. At this time, a structure connected to a compressor (c3) may be further included to facilitate the discharge of the carbon dioxide (CO2) and hydrogen (H2) mixed gas.

[0202] As an optional embodiment, a methanol synthesis reactor (not shown) for synthesizing carbon dioxide (CO2) mixed with hydrogen gas (H2) emitted from a mixed gas emission area (424) into methanol may be further included.

[0203] Methanol can be synthesized from hydrogen gas (H2) and carbon dioxide (CO2) according to the following chemical formula 1.

[0204] [Chemical Formula 1]

[0205] CO2 + 3H2 → CH3OH + H2O

[0206]

[0207] Accordingly, the carbon dioxide capture system (400) of the present invention can further enhance economic efficiency by using carbon dioxide (CO2) emitted from exhaust gas for methanol synthesis, thereby recycling it as an absorbent (MeOH) for the carbon dioxide capture system (400) of the present invention or creating separate added value.

[0208] In one embodiment, the regeneration tower (420) may further include an absorbent recovery area (425).

[0209] The absorbent recovery area (425) may be placed in one area of ​​the regeneration tower (420) to recover the absorbent (MeOH) from which carbon dioxide (CO2) has been desorbed by hydrogen gas (H2) in the mixing space (423) of the regeneration tower (420).

[0210] For example, the absorbent recovery area (425) may be positioned at the bottom of the regeneration tower (420). Here, the reference point for the bottom can be defined as a reference point facing the ground or the direction in which gravity acts. That is, the absorbent recovery area (425) may be positioned adjacent to the ground. Through this, when the relatively light hydrogen gas (H2) and carbon dioxide (CO2) rise toward the top away from the ground, the liquid absorbent (MeOH) descending along the direction of gravity can be easily separated and discharged.

[0211] As an optional embodiment, to facilitate the discharge of the absorbent (MeOH), the absorbent recovery area (425) may further include a structure connected to a pump (P2).

[0212] In one embodiment, the carbon dioxide capture system (400) may further include a circulation area (not shown) having a structure in which carbon dioxide (CO2) discharged through the absorbent recovery area (425) is desorbed from the absorbent (MeOH) and then transported back to the absorption tower (410).

[0213] As a specific example, the absorbent (MeOH) recovered in the absorbent recovery area (425) can be injected again into the absorbent inlet area (412) of the absorption tower (410) through the pump (P2). At this time, a structure passing through a heat exchanger or cooler (e) may be further included to control the temperature of the absorbent (MeOH) to be suitable for the reaction.

[0214] The absorbent (MeOH) of the carbon dioxide capture system (400) according to one embodiment of the present invention has the characteristic of being able to form a physical bond with carbon dioxide (CO2) by means of attractive force and easily desorbing carbon dioxide (CO2) through a reversible reaction.

[0215] Therefore, by further including a structure that adsorbs carbon dioxide (CO2) from the flue gas and then recovers the absorbent (MeOH) from which the carbon dioxide (CO2) has been desorbed from the regeneration tower (420) and supplies it back to the absorption tower (410), the absorbent (MeOH) can be reused, thereby enabling a more economical and environmentally friendly carbon dioxide capture process. In this case, the carbon dioxide capture process can be performed again through the carbon dioxide capture system (400) of the present invention by replenishing only the amount of absorbent (MeOH) that was not partially recovered during the carbon dioxide capture process.

[0216]

[0217] FIG. 5 is a flowchart schematically illustrating a carbon dioxide capture method provided by one embodiment of the present invention.

[0218] As an embodiment, the carbon dioxide capture method may include the steps of: introducing flue gas into a carbon dioxide capture system (S10); introducing an absorbent into a carbon dioxide capture system (S20); absorbing carbon dioxide from the flue gas into the absorbent (S30); introducing hydrogen gas into the carbon dioxide capture system (S40); desorbing carbon dioxide from the absorbent in which carbon dioxide was absorbed, and then mixing the carbon dioxide desorbed from the absorbent with the hydrogen gas (S50); discharging the carbon dioxide mixed with the hydrogen gas (S60); and discharging the flue gas from which carbon dioxide has been removed.

[0219] In the step (S10) where the flue gas is introduced into the carbon dioxide capture system, the flue gas can be supplied to the absorption tower of the carbon dioxide capture system. Specifically, the absorption tower includes a space formed vertically to accommodate gas, and the flue gas can be injected into the lower part of the absorption tower.

[0220] As an optional embodiment, the step (S10) of introducing flue gas into a carbon dioxide capture system may further include a drying step (S11) for removing water vapor from the flue gas. This can improve the reactivity of the carbon dioxide desorption reaction in the flue gas.

[0221] Additionally, the step (S10) in which the exhaust gas is introduced into the carbon dioxide capture system may further include a step (S12) in which the exhaust gas is compressed to high pressure. This allows reaction conditions to be formed so that the exhaust gas can react with an absorbent that physically combines with carbon dioxide under high pressure conditions.

[0222] In the step (S20) where the absorbent is introduced into the carbon dioxide capture system, the step (S22) in which the absorbent is compressed under high pressure may be further included. This creates reaction conditions that allow the absorbent to physically combine with the carbon dioxide present in the flue gas when mixed with the flue gas.

[0223] In the step (S30) where carbon dioxide from the flue gas is absorbed by the absorbent, a reaction may occur in which the carbon dioxide present in the flue gas is absorbed by the absorbent as the absorbent and the flue gas are mixed with each other. At this time, the absorbent may be a mixed solution containing methanol and may provide a structure that allows carbon dioxide to be physically bound.

[0224] In the step (S40) where hydrogen gas is introduced into the carbon dioxide capture system, hydrogen gas can be injected into the regeneration tower of the carbon dioxide capture system. Additionally, at this time, the absorbent with absorbed carbon dioxide can be injected into the regeneration tower. The absorbent with absorbed carbon dioxide injected into the regeneration tower may further undergo a pressure control step in which the pressure is lowered to atmospheric pressure.

[0225] In the step (S50) where carbon dioxide is desorbed from the absorbent that absorbed the carbon dioxide and then the carbon dioxide desorbed from the absorbent is mixed with hydrogen gas, a process can be performed in which the absorbent and hydrogen gas injected into the regeneration tower of the carbon dioxide capture system are mixed with each other. At this time, the carbon dioxide absorbed by the absorbent can be desorbed by the flow of hydrogen gas and mixed with hydrogen gas.

[0226] In the step (S60) where the carbon dioxide mixed with hydrogen gas is discharged, the carbon dioxide-hydrogen mixed gas generated in the regeneration tower of the carbon dioxide capture system may be discharged. The carbon dioxide and hydrogen gases discharged in this way can be separately captured, processed, or utilized.

[0227] Meanwhile, by discharging the remaining flue gas from which the carbon dioxide mixed in the flue gas has been removed according to the carbon dioxide capture method of the present invention, the harmfulness of the flue gas can be reduced and treated in an environmentally friendly manner.

[0228] As an optional embodiment, the carbon dioxide capture method may further include a step (S70) of recovering an absorbent from which carbon dioxide has been desorbed and a step (S80) of the recovered absorbent being introduced back into a carbon dioxide capture system.

[0229] In this case, the step (S80) in which the absorbed material recovered in the step (S20) in which the absorbed material is introduced into the carbon dioxide capture system is introduced again into the carbon dioxide capture system can be performed simultaneously.

[0230] By circulating and reusing the absorbent through this process, the amount of absorbent required for the carbon dioxide capture system can be reduced, making the carbon dioxide capture method more economical.

[0231] As another optional embodiment, the carbon dioxide capture method may further include the step of synthesizing carbon dioxide mixed with hydrogen gas into methanol.

[0232] Methanol can be synthesized from hydrogen gas (H2) and carbon dioxide (CO2) according to the following chemical formula 2.

[0233] [Chemical Formula 2]

[0234] CO2 + 3H2 → CH3OH + H2O

[0235]

[0236] Accordingly, the carbon dioxide capture method of the present invention can further enhance economic efficiency by using carbon dioxide (CO2) emitted from flue gas in methanol synthesis, thereby recycling it as an absorbent (MeOH) for the carbon dioxide capture system according to the embodiments of the present invention described above, or by creating separate added value.

[0237]

[0238] It goes without saying that the embodiments described above can be applied in combination with one another.

[0239] As such, the present invention has been described with reference to the embodiments illustrated in the drawings, but this is merely illustrative, and those skilled in the art will understand that various modifications and equivalent alternative embodiments are possible therefrom. Accordingly, the true technical scope of protection of the present invention should be determined by the technical spirit of the appended claims.

[0240] The specific practices described in the embodiments are examples and do not limit the scope of the embodiments in any way. Furthermore, unless specifically stated as “essential,” “importantly,” etc., a component may not be strictly necessary for the application of the present invention.

[0241] In the specification of the embodiments (particularly in the claims), the use of the term “above” and similar descriptive terms may be in both singular and plural. Furthermore, where a range is described in the embodiments, it is considered to include the invention to which individual values ​​belonging to said range are applied (unless otherwise stated), and is equivalent to describing each individual value constituting said range in the detailed description.

[0242] Finally, regarding the steps constituting the method according to the embodiment, unless the order is explicitly stated or contradicted, said steps may be performed in a suitable order. The embodiments are not necessarily limited to the order in which said steps are described.

[0243] In the embodiments, the use of all examples or exemplary terms (e.g., etc.) is merely for the purpose of describing the embodiments in detail, and the scope of the embodiments is not limited by said examples or exemplary terms unless limited by the claims. Furthermore, a person skilled in the art will understand that various modifications, combinations, and changes may be configured according to design conditions and factors within the scope of the claims or equivalents to which they are added.

[0244]

[0245] [Explanation of the symbol]

[0246] 100, 200, 300, 400: Carbon dioxide capture system

[0247] 110, 210, 310, 410: Absorption towers

[0248] 120, 220, 320, 420 : Regeneration Tower

Claims

1. Includes an absorption tower and a regeneration tower, and The above absorption tower is, A flue gas inlet area formed to allow flue gas to be introduced; An absorbent inlet area disposed in a separate area from the above-mentioned flue gas inlet area and formed to allow the introduction of an absorbent containing methanol; A treatment space, which is an area where carbon dioxide from the exhaust gas is absorbed by the absorbent as the exhaust gas moves; The above processing space includes an absorbent discharge area in which the absorbent that has absorbed the carbon dioxide is discharged, and The above-mentioned recycling tower is, An inlet area into which the absorbent that has absorbed the carbon dioxide is introduced; A hydrogen inlet area disposed in a separate area from the above-mentioned inlet area and into which hydrogen gas is introduced; A mixing space in which the carbon dioxide desorbed from the absorbent in which the carbon dioxide was absorbed is mixed with the hydrogen gas; A carbon dioxide capture system comprising a mixed gas discharge area in which the carbon dioxide mixed with the hydrogen gas is discharged in the mixed space.

2. In Paragraph 1, A carbon dioxide capture system further comprising: a drying area connected to the flue gas inlet area of ​​the absorption tower and formed to reduce the moisture of the flue gas.

3. In Paragraph 1, The above-mentioned recycling tower is, A carbon dioxide capture system further comprising an absorbent recovery area in which the absorbent from which the carbon dioxide has been desorbed is discharged.

4. In Paragraph 3, The above absorption tower is, A carbon dioxide capture system further comprising a circulation area into which the absorbent discharged to the absorbent recovery area is reintroduced.

5. In Paragraph 1, A carbon dioxide capture system further comprising a methanol synthesis reactor for synthesizing the carbon dioxide mixed with the hydrogen gas discharged from the above mixed gas discharge area into methanol.

6. Step in which flue gas is introduced into a carbon dioxide capture system; A step in which an absorbent is introduced into the carbon dioxide capture system; A step in which carbon dioxide from the exhaust gas is absorbed by the absorbent; A step in which hydrogen gas is introduced into the carbon dioxide capture system; A step in which the carbon dioxide desorbed from the absorbent in which the carbon dioxide was absorbed is mixed with the hydrogen gas; and A carbon dioxide capture method comprising the step of discharging the carbon dioxide mixed with the hydrogen gas.

7. In Paragraph 6, A step of recovering the absorbent from which the carbon dioxide has been desorbed; and A carbon dioxide capture method further comprising the step of the recovered absorbent being introduced back into the carbon dioxide capture system.

8. In Paragraph 6, A carbon dioxide capture method further comprising the step of synthesizing methanol from the carbon dioxide mixed with the hydrogen gas.

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