Carbon dioxide separation and collection system

Abstract

The present invention relates to a carbon dioxide separation and collection system. A carbon dioxide separation and collection system according to an embodiment of the present invention comprises: a compression unit which receives and compresses exhaust gas to generate compressed gas; a first cooling unit which is connected to the compression unit and receives and cools the compressed gas discharged from the compression unit to generate moisture-removed compressed gas from which moisture contained in the compressed gas is removed; a second cooling unit which is connected to the first cooling unit and cools the moisture-removed compressed gas to a temperature at which carbon dioxide in a gas state contained in the moisture-removed compressed gas having passed through the first cooling unit can be liquefied; a separation unit which is connected to the second cooling unit and separates carbon dioxide in a liquid state and the remaining gas from the moisture-removed compressed gas cooled in the second cooling unit; and a third cooling unit which receives the remaining gas from the separation unit, cools the remaining gas to generate cooled remaining gas, and supplies the cooled remaining gas to the second cooling unit.

Description

Carbon dioxide separation and capture system

[0001] The present invention relates to a carbon dioxide separation and capture system.

[0002] As global warming accelerates, problems such as abnormal temperatures and rising sea levels are occurring worldwide. The primary cause of this worsening global warming is the increase in greenhouse gas emissions, with carbon dioxide accounting for the largest proportion of all greenhouse gases. Consequently, the need to reduce carbon dioxide emissions is growing.

[0003] However, given that industrial energy efficiency is currently at its peak, excessive reductions in carbon dioxide emissions could weaken industrial competitiveness. Therefore, in addition to efforts to reduce carbon dioxide emissions, direct reductions through carbon capture, utilization, and storage (CCUS, hereinafter referred to as "CCUS") are increasingly sought as a technological alternative.

[0004] Carbon dioxide capture / storage / utilization technology includes technologies for capturing carbon dioxide generated from industrial facilities, storing the captured carbon dioxide underground, and converting carbon dioxide into useful resources with high added value.

[0005] Among these, carbon dioxide capture technology is broadly divided into post-combustion technology, pre-combustion technology, and oxy-fuel combustion technology.

[0006] Specifically, post-combustion capture technology is a method of separating carbon dioxide from exhaust gases emitted when burning fossil fuels with air, pre-combustion capture technology is a method of separating carbon dioxide in the process of producing hydrogen from fossil fuels, converting the synthesis gas generated after gasifying fossil fuels into carbon dioxide and hydrogen through the water gas shift reaction, and then separating only carbon dioxide, and oxy-combustion technology is a method of separating only carbon dioxide after combustion by separating oxygen in the air instead of air and combusting fossil fuels.

[0007] Among these, post-combustion capture technologies are classified into wet absorption methods using amine-based wet absorbents, dry absorption methods using solid absorbents, membrane separation methods using membranes, and phase separation methods using phase change.

[0008] However, in the case of the wet absorption method, there is a problem that the compression work required to liquefy the carbon dioxide separated from the wet absorbent after separating carbon dioxide from the wet absorbent is large, and a high energy is required to regenerate the wet absorbent to its initial state. The dry absorption method also has a problem that the compression work required to liquefy the carbon dioxide separated from the solid absorbent after separating carbon dioxide from the solid absorbent is large, and a high energy is required to regenerate the solid absorbent to its initial state. In addition, in the case of the membrane separation method, there is a problem that it is difficult to increase the capacity, and the durability is weak due to deterioration of the separation membrane. In addition, in the case of the phase separation method, there is a disadvantage that it shows low energy efficiency because a pressure higher than the triple point is required to separate carbon dioxide from the exhaust gas into a liquid.

[0009] Meanwhile, to improve these issues, cryogenic carbon capture processes have been proposed. Cryogenic carbon capture processes can be categorized into direct cooling, which freezes carbon dioxide in exhaust gas through a process of compressing, cooling, and expanding the exhaust gas, and indirect cooling, which freezes carbon dioxide in the exhaust gas using the cold energy of liquefied natural gas or a refrigerator.

[0010] However, in the case of conventional direct cooling methods, the compressed / cooled exhaust gas is expanded using a Joule-Thomson valve or an expander. However, in the case of a Joule-Thomson valve, since the temperature reduction according to the expansion ratio is not large, a high compression ratio is required, which causes a problem in that a relatively large amount of energy is consumed. In addition, in the case of an expander, there is a problem that the technical implementation is difficult because the separated carbon dioxide in a solid form impacts the high-speed rotating impeller.

[0011] In addition, in the case of conventional indirect cooling methods, cold energy is essential, and if external cold energy is not supplied stably, a refrigerator must be used, which causes a problem of rapid increase in energy consumption.

[0012] Therefore, there is a need for the development of a technology that can efficiently separate and capture carbon dioxide in exhaust gas while improving the problems of conventional direct cooling and indirect cooling methods.

[0013] Embodiments of the present invention have been devised to solve the above-described conventional problems, and provide a carbon dioxide separation and capture system that can be miniaturized by separating liquid carbon dioxide and the remaining gas from the exhaust gas by cooling the exhaust gas to a temperature at which carbon dioxide contained in the exhaust gas can be liquefied, rather than expanding the exhaust gas that has gone through a compression / cooling process.

[0014] In addition, the present invention aims to provide a carbon dioxide separation and capture system that not only enables economical carbon dioxide separation and capture with a miniaturized system, but also has improved energy efficiency by generating cold energy from the remaining gas and utilizing the generated cold energy to cool exhaust gas that has undergone a compression / cooling process.

[0015] In addition, the present invention seeks to provide a carbon dioxide separation and capture system capable of increasing carbon dioxide separation efficiency by converting expansion energy, which expands the remaining gas to generate cold heat from the remaining gas, into compression energy and using the converted compression energy to lower the boiling point of carbon dioxide contained in the exhaust gas.

[0016] According to one aspect of the present invention, a carbon dioxide separation and capture system may be provided, including: a compression unit that receives exhaust gas and compresses it to generate compressed gas; a first cooling unit that is connected to the compression unit and receives the compressed gas discharged from the compression unit and cools it to generate a moisture-removed compressed gas from which moisture contained in the compressed gas is removed; a second cooling unit that is connected to the first cooling unit and cools the moisture-removed compressed gas to a temperature at which gaseous carbon dioxide contained in the moisture-removed compressed gas passing through the first cooling unit can be liquefied; a separation unit that is connected to the second cooling unit and separates liquid carbon dioxide and a remaining gas from the moisture-removed compressed gas cooled in the second cooling unit; and a third cooling unit that receives the remaining gas from the separation unit, cools the remaining gas to generate a cooled remaining gas, and supplies the cooled remaining gas to the second cooling unit.

[0017] In addition, the third cooling unit may include a compander expander connected to the separation unit, which receives the remaining gas from the separation unit and expands and cools the remaining gas; and a compander compressor connected to the compander expander by a shaft, which converts expansion energy of the compander expander into compression energy to compress the moisture-removed compressed gas, thereby lowering the boiling point of carbon dioxide in the moisture-removed compressed gas.

[0018] In addition, the moisture removal compressed gas that has passed through the first cooling unit may be recompressed using the shaft power of the compander expander and then supplied to the second cooling unit, provided between the first cooling unit and the second cooling unit.

[0019] Additionally, the third cooling unit may include an expander connected to the separation unit, which receives the remaining gas from the separation unit, and expands and cools the remaining gas.

[0020] In addition, the second cooling unit includes a moisture removal compressed gas passage that provides a flow path of the moisture removal compressed gas that has passed through the first cooling unit; and a cooling residual gas passage that provides a flow path of the cooling residual gas discharged from the third cooling unit, and the moisture removal compressed gas flowing in the moisture removal compressed gas passage can be cooled by receiving cooling heat from the cooling residual gas flowing in the cooling residual gas passage and then supplied to the separation unit.

[0021] Additionally, the compression unit may include a compressor that receives energy generated from the expander and compresses the exhaust gas.

[0022] In addition, the present invention further includes a phase change induction unit provided between the separation unit and the third cooling unit, and the phase change induction unit may include an isentropic nozzle that receives the remaining gas from the separation unit, expands it isentropically, and separates carbon dioxide remaining in the remaining gas.

[0023] In addition, during the isentropic expansion process of the remaining gas supplied to the isentropic nozzle, the gaseous carbon dioxide remaining in the remaining gas is phase-changed into a solid state and supplied to the separation unit, and the remaining gas supplied to the isentropic nozzle from which the solid carbon dioxide is separated can be supplied to the third cooling unit.

[0024] In addition, the separation unit may further include a purity separation unit that is connected to the separation unit and increases the purity of the liquid carbon dioxide supplied from the separation unit.

[0025] In addition, the method may further include a recirculation unit connected to the purity separation unit and recirculating the remaining gas discharged from the purity separation unit.

[0026] According to embodiments of the present invention, rather than expanding exhaust gas that has gone through a compression / cooling process, the exhaust gas is cooled to a temperature at which carbon dioxide contained in the exhaust gas can be liquefied, thereby separating the liquid carbon dioxide and the remaining gas from the exhaust gas, thereby enabling miniaturization.

[0027] In addition, it not only enables economical carbon dioxide separation and capture with a miniaturized system, but also has the effect of improved energy efficiency by generating cold energy from the remaining gas and utilizing the generated cold energy to cool the exhaust gas that has gone through the compression / cooling process.

[0028] In addition, there is an effect that the carbon dioxide separation efficiency can be increased by converting the expansion energy that expands the remaining gas to generate cold heat from the remaining gas into compression energy and using the converted compression energy to lower the boiling point of carbon dioxide contained in the exhaust gas.

[0029] Figure 1 is a process diagram illustrating a carbon dioxide separation and capture system according to one embodiment of the present invention.

[0030] Figure 2 is a process diagram illustrating a carbon dioxide separation and capture system according to another embodiment of the present invention.

[0031] Figure 3 is a process diagram illustrating a carbon dioxide separation and capture system according to another embodiment of the present invention.

[0032] Figure 4 is a process diagram illustrating a carbon dioxide separation and capture system according to another embodiment of the present invention.

[0033] Figure 5 is a process diagram illustrating a carbon dioxide separation and capture system according to another embodiment of the present invention.

[0034] Hereinafter, specific embodiments for implementing the idea of ​​the present invention will be described in detail with reference to the drawings.

[0035] In addition, when explaining the present invention, if it is determined that a detailed description of a related known configuration or function may obscure the gist of the present invention, the detailed description is omitted.

[0036] Additionally, when it is said that a component is 'connected' to another component, it should be understood that while it may be directly connected to that other component, there may also be other components in between.

[0037] The terminology used herein is intended solely to describe specific embodiments and is not intended to limit the invention. Singular expressions include plural expressions unless the context clearly dictates otherwise.

[0038] Furthermore, the expressions "one side," "the other side," "upper side," and "lower side" in this specification are based on the drawings and may be expressed differently if the orientation of the object changes. For the same reason, some components in the attached drawings are exaggerated, omitted, or schematically depicted, and the size of each component does not fully reflect the actual size.

[0039] Additionally, terms that include ordinal numbers, such as "first," "second," etc., may be used to describe various components, but these components are not limited by such terms. These terms are used solely to distinguish one component from another.

[0040] The term "comprising" as used in the specification means specifying a particular characteristic, region, integer, step, operation, element and / or component, but does not exclude the presence or addition of other particular characteristics, regions, integers, steps, operations, elements, components and / or groups.

[0041] Hereinafter, a specific configuration of a carbon dioxide separation and capture system according to one embodiment of the present invention will be described with reference to the drawings.

[0042] Referring to FIG. 1, a carbon dioxide separation and capture system (1) according to one embodiment of the present invention may include a compression unit (10), a first cooling unit (20), a second cooling unit (30), a separation unit (40), and a third cooling unit (50).

[0043] The compression unit (10) can receive exhaust gas from an exhaust gas source (not shown) and compress it. For example, the exhaust gas may be flue gas composed of nitrogen, oxygen, carbon dioxide, and water vapor emitted from an exhaust gas source such as an engine. However, this is merely an example for convenience of explanation, and the composition of the exhaust gas may vary to include various compositions containing at least carbon dioxide.

[0044] The compression unit (10) can, for example, receive exhaust gas cooled to room temperature and compress it to generate compressed gas. For example, the compression unit (10) can include a compressor (11) that can compress exhaust gas cooled to room temperature to a predetermined pressure, for example, about 3.5 bar to about 6 bar. When exhaust gas cooled to room temperature is compressed to a predetermined pressure in the compressor (11), the vapor pressure can increase, and moisture in the compressed gas due to the increased vapor pressure can be supplied to the first cooling unit (20) and removed.

[0045] The first cooling unit (20) receives the compressed gas discharged from the compression unit (10) and cools it, thereby removing moisture contained in the compressed gas. To this end, the first cooling unit (20) may be connected to the rear end of the compression unit (10), and for convenience of explanation, the compressed gas cooled through the first cooling unit (20) and from which moisture has been removed will be referred to as moisture-removed compressed gas in the following description.

[0046] The moisture-removed compressed gas discharged from the first cooling unit (20) can be supplied to the compander compressor (52) of the third cooling unit (50) to be described later. The moisture-removed compressed gas supplied to the compander compressor (52) of the third cooling unit (50) to be described later can be recompressed, and thereby the pressure of the moisture-removed compressed gas can be increased by, for example, about 2 bar to about 3 bar. Due to this increased pressure, the vapor pressure of carbon dioxide can be further increased, and further, the boiling point of carbon dioxide can be lowered. When the boiling point of carbon dioxide is lowered, excessive cooling heat for cooling the moisture-removed compressed gas in the second cooling unit (30) provided at the rear end of the first cooling unit (20) may not be required. This will be described later.

[0047] The second cooling unit (30) can cool the moisture-removed compressed gas to a temperature at which the gaseous carbon dioxide contained in the moisture-removed compressed gas that has passed through the first cooling unit (20) can be liquefied. In other words, the gas compressed in the compression unit (10) and then cooled in the first cooling unit (20), for example, the moisture-removed compressed gas, is not cooled by expansion as in the conventional manner, but is cooled to the liquefaction temperature of the carbon dioxide through heat exchange with the remaining cooled gas in the second cooling unit (30), so that the carbon dioxide contained in the moisture-removed compressed gas can be condensed in advance in the second cooling unit (30). In other words, since the moisture-removed compressed gas is cooled to the liquefaction temperature of the carbon dioxide through heat exchange with the remaining cooled gas in the second cooling unit (30), liquefaction and capture of the carbon dioxide can be achieved simultaneously.

[0048] Meanwhile, if gas compressed in the compression unit (10) and then cooled in the first cooling unit (20), for example, a moisture-removed compressed gas, is expanded and cooled as in the past, it is difficult to miniaturize the carbon dioxide separation and capture system (1) due to the pressure lowered during the expansion process of the moisture-removed compressed gas. However, in this embodiment, since the expansion process of the moisture-removed compressed gas is omitted, the carbon dioxide separation and capture process can be performed at a relatively high pressure, thereby making miniaturization of the carbon dioxide separation and capture system (1) possible.

[0049] To this end, the second cooling unit (30) is provided at the rear end of the first cooling unit (20) and can receive the moisture-removed compressed gas that has passed through the first cooling unit (20). In the present embodiment, the moisture-removed compressed gas supplied to the second cooling unit (30) may be a moisture-removed compressed gas that has passed through the first cooling unit (20) and then been recompressed to a predetermined pressure through the compander compressor (52) of the third cooling unit (50) described later.

[0050] The second cooling unit (30) may be connected to the separation unit (40) and the third cooling unit (50). In addition, the second cooling unit (30) may include a moisture removal compressed gas passage (31) that provides a flow path for the moisture removal compressed gas that has passed through the first cooling unit (20) and a cooled residual gas passage (32) that provides a flow path for the cooled residual gas discharged from the third cooling unit (50).

[0051] At this time, the moisture-removed compressed gas flowing in the moisture-removed compressed gas path (31) can be cooled by receiving the cold heat of the cooled remaining gas flowing in the cooled remaining gas path (32) and then supplied to the separation unit (40). In other words, the cooled remaining gas generated by cooling the remaining gas separated in the separation unit (40) can be utilized as a refrigerant capable of absorbing the heat source of the moisture-removed compressed gas.

[0052] The separation unit (40) can separate liquid carbon dioxide and the remaining gas from the moisture-removed compressed gas cooled in the second cooling unit (30). To this end, the separation unit (40) can be connected to the second cooling unit (30) and the third cooling unit (50), and can be provided as a gas-liquid separator, for example.

[0053] The liquid carbon dioxide separated in the separation unit (40) can be discharged to the outside and captured, and the remaining gas separated in the separation unit (40) can be supplied to the compander expander (51) of the third cooling unit (50) to be described later. The remaining gas supplied to the compander expander (51) of the third cooling unit (50) to be described later can still be expanded to a high pressure and cooled. The cooled remaining gas expanded to a high pressure and cooled in this way can be supplied to the second cooling unit (30) and serve as a refrigerant to lower the liquefaction temperature of the carbon dioxide. Therefore, since the carbon dioxide separation and capture process can proceed smoothly at a relatively high pressure even without a separate refrigerator, the carbon dioxide separation and capture system (1) can be miniaturized.

[0054] The third cooling unit (50) can cool the remaining gas supplied from the separation unit (40) to generate cooled remaining gas, and can supply the generated cooled remaining gas to the second cooling unit (30).

[0055] To this end, the third cooling unit (50) may include a compander expander (51) connected to the separation unit (40) to receive the remaining gas from the separation unit (40), expand the remaining gas, and cool it, and a compander compressor (52) axially connected to the compander expander (51).

[0056] The compander expander (51) expands the remaining gas supplied from the separation unit (40) so that the remaining gas can be cooled. The cooled remaining gas thus cooled can be supplied to the cooled remaining gas path (32) of the second cooling unit (30). The cold heat of the cooled remaining gas flowing in the cooled remaining gas path (32) can be used to absorb the heat source of the moisture-removed compressed gas flowing in the moisture-removed compressed gas path (31).

[0057] The compander compressor (52) can be axially connected to the compander expander (51), and can convert the expansion energy generated in the compander expander (51) into compression energy. According to the present embodiment, since the compression energy converted in the compander compressor (52) enables liquefaction and separation of carbon dioxide, higher energy efficiency can be achieved compared to the conventional liquefaction and separation of carbon dioxide through a refrigeration system using a refrigerant. In addition, since construction of a miniaturized system is possible, economic feasibility can be secured.

[0058] The moisture-removed compressed gas compressed through the compander compressor (52) can be supplied to the second cooling unit (30). At this time, the compander compressor (52) can be provided between the first cooling unit (20) and the second cooling unit (30). The compander compressor (52) can recompress the moisture-removed compressed gas that has passed through the first cooling unit (20) using the shaft power of the compander expander (51) and then supply it to the second cooling unit (30).

[0059] When the moisture-removed compressed gas is recompressed by the compander compressor (52), the boiling point of the carbon dioxide contained in the moisture-removed compressed gas increases, so that the cooling required for liquefaction separation of carbon dioxide at the rear end of the compander compressor (52), for example, in the second cooling unit (30), can be reduced compared to the past.

[0060] The carbon dioxide separation and capture system (1) having the configuration described above separates liquid carbon dioxide and the remaining gas from the exhaust gas by cooling the exhaust gas to a temperature at which the carbon dioxide contained in the exhaust gas can be liquefied rather than expanding the exhaust gas that has gone through the compression / cooling process. Therefore, the carbon dioxide separation and capture process can be performed at a higher pressure than before, and thus, it has the effect of enabling economical carbon dioxide separation and capture with a compact system.

[0061] In addition, there is an effect of increasing energy efficiency by generating cold heat from the separated remaining gas and utilizing the generated cold heat to cool the exhaust gas that has gone through the compression / cooling process.

[0062] In addition, there is an effect that the carbon dioxide separation efficiency can be increased by converting the expansion energy that expands the remaining gas to generate cold heat from the remaining gas into compression energy and using the converted compression energy to lower the boiling point of carbon dioxide contained in the exhaust gas.

[0063] Hereinafter, a carbon dioxide separation and capture system according to another embodiment of the present invention will be described with reference to FIG. 2.

[0064] Referring to FIG. 2, a carbon dioxide separation and capture system (1a) according to another embodiment of the present invention may include a compression unit (10), a first cooling unit (20), a second cooling unit (30), a separation unit (40), a third cooling unit (50), and a phase change induction unit (60). However, since the carbon dioxide separation and capture system (1a) illustrated in FIG. 2 is substantially the same as the carbon dioxide separation and capture system (1) described with reference to FIG. 1 except for the phase change induction unit (60), the phase change induction unit (60), which corresponds to the difference, will be described below.

[0065] The phase change induction unit (60) can receive the remaining gas from the separation unit (40) and isentropically expand it to separate the carbon dioxide remaining in the remaining gas. To this end, the phase change induction unit (60) can be provided between the separation unit (40) and the third cooling unit (50).

[0066] The phase change induction unit (60) may include an isentropic nozzle (61) that receives the remaining gas from the separation unit (40) and expands it isentropically to induce the gaseous carbon dioxide remaining in the remaining gas to change into a solid state.

[0067] The isentropic nozzle (61) can induce the gaseous carbon dioxide contained in the remaining gas to be separated by changing the flow of the remaining gas into an isentropic flow and causing the remaining gas to expand isentropically, thereby separating the gaseous carbon dioxide contained in the remaining gas by changing its phase into a solid state. The isentropic nozzle (61) can be divided into a constriction section, an expansion section, and a throat section. The constriction section can be formed so that the flow cross-sectional area of ​​the remaining gas can be gradually reduced, and the expansion section can be formed so that the flow cross-sectional area of ​​the remaining gas can be gradually increased. The constriction section and the expansion section can be connected by a throat section, and the degree of isentropic expansion of the fluid can be controlled according to the area ratio of the expansion section and the throat section.

[0068] Meanwhile, according to the law of conservation of energy in the flow of the isentropic nozzle (61), potential energy, heat loss, and work do not occur under adiabatic conditions, and the internal energy, that is, the sum of heat energy and kinetic energy, can always be constant. In an isolated system, internal energy and kinetic energy can be expressed as enthalpy, and the pressure and temperature can be extremely low through the isentropic nozzle (61) that can isentropically expand the fluid. Accordingly, the remaining gas that has been isentropically expanded while passing through the isentropic nozzle (61) can exceed the supersonic speed, and the temperature can be lowered to -110 to -160 degrees, which is an amount that allows the gaseous carbon dioxide concentrated in the remaining gas to phase change into a solid state. The carbon dioxide that has started to solidify can be accompanied by an exothermic reaction that releases heat to the surroundings, and releases heat within the system. On the other hand, gaseous nitrogen / oxygen, excluding the carbon dioxide within the remaining gas, do not change phases during the expansion process and their temperatures decrease, so that the exothermic reaction of the carbon dioxide and thermal equilibrium can be achieved.

[0069] The isentropic nozzle (61) receives the remaining gas from the separation unit (40) and discharges it, but can induce the remaining gas to be discharged at an increased speed by decreasing the pressure thereof compared to that of the remaining gas. Inside the isentropic nozzle (61), the remaining gas expands, and during the expansion process of the remaining gas, the gaseous carbon dioxide contained in the remaining gas may undergo a phase change into a solid state. In summary, during the process in which the remaining gas passes through the isentropic nozzle (61), the carbon dioxide contained in the remaining gas undergoes a phase change into a solid state, and other gases in the remaining gas, for example, nitrogen / oxygen, expand into a gaseous state. When the remaining gas expands in this way, the internal energy, that is, the thermal energy, is converted into kinetic energy, so that the expanded gas is cooled, and the gaseous carbon dioxide contained in the expanded gas may be frozen. Here, the expanded gas isentropically expanded in the isentropic nozzle (61) may be a mixture in which solid carbon dioxide and gaseous nitrogen / oxygen coexist. Carbon dioxide separated by the isentropic nozzle (61) in this way can be supplied to the separation unit (40), and nitrogen / oxygen from which carbon dioxide has been removed can be supplied to the compander expander (51) and cooled by expansion.

[0070] Hereinafter, a carbon dioxide separation and capture system according to another embodiment of the present invention will be described with reference to FIG. 3.

[0071] Referring to FIG. 3, a carbon dioxide separation and capture system (1b) according to another embodiment of the present invention may include a compression unit (10), a first cooling unit (20), a second cooling unit (30), a separation unit (40), and a third cooling unit (50'). However, since the carbon dioxide separation and capture system (1b) illustrated in FIG. 3 is substantially the same as the carbon dioxide separation and capture system (1) described with reference to FIG. 1 except for the third cooling unit (50'), the third cooling unit (50'), which corresponds to the difference, will be described below.

[0072] The third cooling unit (50') may include an expander (53) connected to the separation unit (40) to expand and cool the remaining gas separated by the separation unit (40). This expander (53) may expand and cool the remaining gas to an ultra-low temperature. For example, the remaining gas (hereinafter referred to as the cooled remaining gas) expanded by the expander (53) and lowered in temperature may have a temperature of, for example, about -160 degrees to -180 degrees. Since sufficient cold heat can be generated in the expander (53) in this way, even if the moisture-removed compressed gas discharged from the first cooling unit (20) is supplied directly to the second cooling unit (30) without going through a process of being compressed once again, it can be effectively cooled by the sufficient cold heat of the cooled remaining gas discharged from the expander (53).

[0073] Meanwhile, the remaining cooled gas discharged from the expander (53) can be supplied to the second cooling unit (30) and can be heat-exchanged with the moisture-removed compressed gas in the second cooling unit (30). In other words, the remaining gas cooled to an ultra-low temperature through the expander (53) can be utilized as a cold heat source for cooling the moisture-removed compressed gas in the second cooling unit (30).

[0074] In addition, electric power energy can be generated in the process of the expander (53) cooling the remaining gas to an ultra-low temperature, and the electric power energy generated in this way can be supplied to the compression unit (10) and used as energy for driving the compression unit (10).

[0075] Hereinafter, a carbon dioxide separation and capture system according to another embodiment of the present invention will be described with reference to FIG. 4.

[0076] Referring to FIG. 4, a carbon dioxide separation and capture system (1c) according to another embodiment of the present invention may include a compression unit (10), a first cooling unit (20), a second cooling unit (30), a separation unit (40), a third cooling unit (50'), and a phase change induction unit (60). However, the carbon dioxide separation and capture system (1c) illustrated in FIG. 4 is substantially the same as the carbon dioxide separation and capture system (1b) described with reference to FIG. 3 except for the phase change induction unit (60), and therefore, the phase change induction unit (60), which corresponds to the difference, will be described below.

[0077] The phase change induction unit (60) can receive the remaining gas from the separation unit (40) and isentropically expand it to separate the carbon dioxide remaining in the remaining gas. To this end, the phase change induction unit (60) can be provided between the separation unit (40) and the third cooling unit (50').

[0078] The phase change induction unit (60) may include an isentropic nozzle (61) that receives the remaining gas from the separation unit (40) and expands it isentropically to induce the gaseous carbon dioxide remaining in the remaining gas to change into a solid state.

[0079] The isentropic nozzle (61) can induce the gaseous carbon dioxide contained in the remaining gas to be separated by changing the flow of the remaining gas into an isentropic flow and causing the remaining gas to expand isentropically, thereby separating the gaseous carbon dioxide contained in the remaining gas by changing its phase into a solid state. The isentropic nozzle (61) can be divided into a constriction section, an expansion section, and a throat section. The constriction section can be formed so that the flow cross-sectional area of ​​the remaining gas can be gradually reduced, and the expansion section can be formed so that the flow cross-sectional area of ​​the remaining gas can be gradually increased. The constriction section and the expansion section can be connected by a throat section, and the degree of isentropic expansion of the fluid can be controlled according to the area ratio of the expansion section and the throat section.

[0080] Meanwhile, according to the law of conservation of energy in the flow of the isentropic nozzle (61), potential energy, heat loss, and work do not occur under adiabatic conditions, and the internal energy, that is, the sum of heat energy and kinetic energy, can always be constant. In an isolated system, internal energy and kinetic energy can be expressed as enthalpy, and the pressure and temperature can be extremely low through the isentropic nozzle (61) that can isentropically expand the fluid. Accordingly, the remaining gas that has been isentropically expanded while passing through the isentropic nozzle (61) can exceed the supersonic speed, and the temperature can be lowered to -110 to -160 degrees, which is an amount that allows the gaseous carbon dioxide concentrated in the remaining gas to phase change into a solid state. The carbon dioxide that has started to solidify can be accompanied by an exothermic reaction that releases heat to the surroundings, and releases heat within the system. On the other hand, gaseous nitrogen / oxygen, excluding the carbon dioxide within the remaining gas, do not change phases during the expansion process and their temperatures decrease, so that the exothermic reaction of the carbon dioxide and thermal equilibrium can be achieved.

[0081] The isentropic nozzle (61) receives the remaining gas from the separation unit (40) and discharges it, but can induce the remaining gas to be discharged at an increased speed by decreasing the pressure thereof compared to that of the remaining gas. Inside the isentropic nozzle (61), the remaining gas expands, and during the expansion process of the remaining gas, the gaseous carbon dioxide contained in the remaining gas may undergo a phase change into a solid state. In summary, during the process in which the remaining gas passes through the isentropic nozzle (61), the carbon dioxide contained in the remaining gas undergoes a phase change into a solid state, and other gases in the remaining gas, for example, nitrogen / oxygen, expand into a gaseous state. When the remaining gas expands in this way, the internal energy, that is, the thermal energy, is converted into kinetic energy, so that the expanded gas is cooled, and the gaseous carbon dioxide contained in the expanded gas may be frozen. Here, the expanded gas isentropically expanded in the isentropic nozzle (61) may be a mixture in which solid carbon dioxide and gaseous nitrogen / oxygen coexist. Carbon dioxide separated by the isentropic nozzle (61) in this way can be supplied to the separation unit (40), and nitrogen / oxygen from which carbon dioxide has been removed can be supplied to the expander (53) and cooled by expansion.

[0082] Hereinafter, a carbon dioxide separation and capture system according to another embodiment of the present invention will be described with reference to FIG. 5.

[0083] Referring to FIG. 5, a carbon dioxide separation and capture system (1d) according to another embodiment of the present invention may include a compression unit (10), a first cooling unit (20), a second cooling unit (30), a separation unit (40), a third cooling unit (50), a purity separation unit (70), and a recirculation unit (80). However, since the carbon dioxide separation and capture system (1d) illustrated in FIG. 5 is substantially the same as the carbon dioxide separation and capture system (1) described with reference to FIG. 1 except for the purity separation unit (70) and the recirculation unit (80), the following will describe the purity separation unit (70) and the recirculation unit (80) corresponding to the differences.

[0084] The purity separation unit (70) can increase the purity of the liquid carbon dioxide supplied from the separation unit (40). To this end, the purity separation unit (70) can be connected to the separation unit (40). The liquid carbon dioxide (hereinafter referred to as “high-purity liquid carbon dioxide”) whose purity is increased through the purity separation unit (70) can be discharged to the outside and captured, and the remaining gas in a gaseous state excluding the high-purity liquid carbon dioxide, for example, nitrogen / oxygen, can be supplied to the recirculation unit (80).

[0085] The recirculation unit (80) can recirculate the remaining gas discharged from the purity separation unit (70). For this purpose, the recirculation unit (80) can be connected to the purity separation unit (70) and can be equipped with a recirculation blower, for example. The remaining gas can be supplied to the front end of the compressor (11) through the recirculation unit (80).

[0086] Although the embodiments of the present invention have been described as specific embodiments, these are merely examples, and the present invention is not limited thereto, but should be construed as having the broadest scope in accordance with the basic idea disclosed in this specification. Those skilled in the art may implement patterns of shapes not specified by combining / substituting the disclosed embodiments, but this also does not depart from the scope of the present invention. In addition, those skilled in the art may easily modify or alter the disclosed embodiments based on this specification, and it is clear that such modifications or alterations also fall within the scope of the present invention.

Claims

1. A compression unit that receives exhaust gas, compresses it, and creates compressed gas; A first cooling unit connected to the compression unit and receiving and cooling the compressed gas discharged from the compression unit, thereby generating a moisture-removed compressed gas from which moisture contained in the compressed gas is removed; A second cooling unit connected to the first cooling unit and cooling the moisture-removed compressed gas to a temperature at which gaseous carbon dioxide contained in the moisture-removed compressed gas passing through the first cooling unit can be liquefied; A separation unit connected to the second cooling unit and separating liquid carbon dioxide and the remaining gas from the moisture-removed compressed gas cooled in the second cooling unit; and A third cooling unit that receives the remaining gas from the separation unit, cools the remaining gas to generate cooled remaining gas, and supplies the cooled remaining gas to the second cooling unit. Carbon dioxide separation and capture system.

2. In paragraph 1, The third cooling unit is, A compander expander connected to the separating unit, receiving the remaining gas from the separating unit, and expanding and cooling the remaining gas; and A compander compressor connected to the compander expander by a shaft and converting the expansion energy of the compander expander into compression energy to compress the moisture-removed compressed gas, thereby lowering the boiling point of carbon dioxide in the moisture-removed compressed gas. Carbon dioxide separation and capture system.

3. In paragraph 2, The above compander compressor, It is provided between the first cooling unit and the second cooling unit, and the moisture-removed compressed gas that has passed through the first cooling unit is recompressed using the shaft power of the compander expander and then supplied to the second cooling unit. Carbon dioxide separation and capture system.

4. In paragraph 1, The third cooling unit is, An expander connected to the separating unit, receiving the remaining gas from the separating unit, and expanding and cooling the remaining gas, Carbon dioxide separation and capture system.

5. In paragraph 2 or paragraph 4, The above second cooling unit, A moisture removal compressed gas path providing a flow path of the moisture removal compressed gas passing through the first cooling unit; and Including a cooling residual gas path that provides a flow path for the cooling residual gas discharged from the third cooling unit; The moisture removal compressed gas flowing in the moisture removal compressed gas path is cooled by receiving the cooling heat of the cooled remaining gas flowing in the cooled remaining gas path and then supplied to the separation unit. Carbon dioxide separation and capture system.

6. In paragraph 2, The above compression part, Including a compressor that compresses the exhaust gas by receiving energy generated from the expander. Carbon dioxide separation and capture system.

7. In paragraph 2 or paragraph 4, Further comprising a phase change induction unit provided between the above separation unit and the third cooling unit, The above phase change inducing part is, Including an isentropic nozzle that receives the remaining gas from the separation unit, expands it isentropically, and separates carbon dioxide remaining in the remaining gas. Carbon dioxide separation and capture system.

8. In paragraph 7, In the isentropic expansion process of the remaining gas supplied to the isentropic nozzle, the gaseous carbon dioxide remaining in the remaining gas is phase-changed into a solid state and supplied to the separation unit. The remaining gas supplied to the isentropic nozzle, from which the solid carbon dioxide is separated, is supplied to the third cooling unit. Carbon dioxide separation and capture system.

9. In paragraph 4, Further comprising a purity separation unit connected to the above separation unit and increasing the purity of the liquid carbon dioxide supplied from the separation unit. Carbon dioxide separation and capture system.

10. In paragraph 9, Further comprising a recirculation unit connected to the above purity separation unit and recirculating the remaining gas discharged from the purity separation unit. Carbon dioxide separation and capture system.

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