Carbon dioxide liquefaction system for ship

Abstract

The present invention relates to a carbon dioxide liquefaction system for a ship and, more specifically, to a carbon dioxide liquefaction system for a ship, comprising: a capture cycle in which carbon dioxide is captured from exhaust gas; and a liquefaction cycle in which the carbon dioxide captured in the capture cycle is liquefied. The liquefaction cycle comprises: an evaporator which evaporates a refrigerant; a compressor which compresses the refrigerant; a condenser which condenses the refrigerant in a gas state; and an expansion valve for expanding the refrigerant in a liquid state. The carbon dioxide liquefaction system for a ship enables the carbon dioxide captured by the evaporator to be liquefied, thereby storing the carbon dioxide captured from exhaust gas of a ship with a minimized volume, while as much carbon dioxide as possible is liquefied and stored by using the same amount of refrigerant.

Description

Marine carbon dioxide liquefaction system

[0001] The present invention relates to a carbon dioxide liquefaction system for ships, and more specifically, to a carbon dioxide liquefaction system for ships that includes a capture cycle for capturing carbon dioxide from exhaust gas and a liquefaction cycle for liquefying the carbon dioxide captured in the capture cycle, wherein the liquefaction cycle includes an evaporator for evaporating a refrigerant, a compressor for compressing a refrigerant, a condenser for condensing a refrigerant in a gaseous state, and an expansion valve for expanding a refrigerant in a liquid state, and wherein the carbon dioxide captured by the evaporator is liquefied, thereby minimizing the volume of carbon dioxide captured from the ship's exhaust gas and enabling the liquefaction and storage of as much carbon dioxide as possible with the same amount of refrigerant.

[0002] Based on the IMO’s initial strategy to reduce ship greenhouse gas emissions by more than 50% compared to 2008 levels by 2050, the timing of EEDI Phase 3 regulations for certain ship types is likely to be brought forward, and as discussions on EEDI Phase 4 regulations gradually progress, stricter regulations on ship greenhouse gas emissions are becoming visible.

[0003] Onboard carbon capture systems are a highly effective technology when considering both fuel carbon neutrality and technological maturity. An onboard carbon capture system refers to a technology that selectively captures and stores carbon dioxide from exhaust gases emitted by engines during ship operations. In terms of fuel carbon neutrality, the system intuitively reduces greenhouse gas emissions into the atmosphere because it captures and stores carbon dioxide, a greenhouse gas generated from hydrocarbon fuels. Furthermore, by processing the captured carbon dioxide through underground storage or methanation using renewable energy, it can reduce greenhouse gas emissions throughout the entire lifecycle of hydrocarbon fuels. Additionally, regarding technological maturity, carbon capture technology has already been widely used in the petrochemical and power generation sectors and has recently been applied to Floating LNG (FLNG) in the offshore plant sector; therefore, the potential for applying this technology to ships is considered higher compared to other alternative fuel technologies.

[0004] The conventional carbon dioxide capture system of FIG. 1 includes an absorption tower (91) for removing carbon dioxide from exhaust gas by combining it with an absorbent, a heat exchanger (93) for receiving the absorbent that has absorbed carbon dioxide through a pump (P) and performing heat exchange, and a regeneration tower (92) for removing carbon dioxide chemically bonded to the heat-exchanged absorbent. It further includes a reboiler (94) connected to the regeneration tower (92) for heating the absorbent and a condenser (95) for processing the removed carbon so that it can be condensed and stored. Accordingly, the carbon dioxide absorption and removal device performs a carbon dioxide absorption process and an absorbent regeneration process (removal process) using the above components, and the regenerated absorbent is supplied back to the absorption tower (91). However, the synthesis of carbon dioxide and the absorbent performed in the absorption tower (91) is an exothermic reaction, so an additional cooling method is required in the absorption tower for a continuous reaction, and if foreign substances such as dust, salt, and plankton are included in the exhaust gas and mixed into the absorbent, it causes a decrease in the efficiency of the overall system.

[0005] Existing technologies have focused on capturing carbon dioxide and storing it in a gaseous state or releasing it externally, and technical approaches to liquefying carbon dioxide have been limited. In particular, in confined spaces such as ships, the size and efficiency of liquefaction facilities are critical, but existing methods have limitations in overcoming these spatial constraints.

[0006] Therefore, a carbon dioxide liquefaction system capable of operating efficiently even in the confined spaces of a ship is required.

[0007] The present invention aims to solve the problems of the aforementioned prior art and provides a carbon dioxide liquefaction system for ships that can store carbon dioxide in a liquid state in a confined space on a ship by liquefying the carbon dioxide captured by the evaporator, wherein the liquefaction cycle comprises a capture cycle for capturing carbon dioxide from exhaust gas and a liquefaction cycle for liquefying the carbon dioxide captured by the capture cycle, wherein the liquefaction cycle comprises an evaporator for evaporating a refrigerant, a compressor for compressing the refrigerant, a condenser for condensing the refrigerant in a gaseous state, and an expansion valve for expanding the refrigerant in a liquid state.

[0008] In addition, the present invention aims to provide a carbon dioxide liquefaction system for ships capable of liquefying and storing as much carbon dioxide as possible with the same amount of refrigerant by the liquefaction cycle further including a recovery unit that further cools the refrigerant condensed into a liquid state in the condenser, and the recovery unit maintaining the refrigerant in a supercooled state by heat-exchanging the condensed refrigerant with the refrigerant converted into a gaseous state through the evaporator.

[0009] In addition, the present invention aims to provide a marine carbon dioxide liquefaction system that does not require additional energy to subcool the refrigerant, wherein a portion of the refrigerant line from the condenser to the expansion valve and another portion of the refrigerant line from the evaporator to the compressor are provided at a location where they intersect, and the recovery unit is provided to exchange heat between the refrigerant transferred from the condenser to the expansion valve and the refrigerant transferred from the evaporator to the compressor so that the refrigerant passes through the expansion valve in a subcooled state.

[0010] In addition, the present invention aims to provide a carbon dioxide liquefaction system for ships in which the refrigerant flow path from the recovery unit through the expansion valve to the evaporator is supported by an anti-vibration device to maintain the supercooling of the refrigerant, thereby maintaining the supercooling of the refrigerant in a shipboard environment with high vibration.

[0011] However, the technical problems that the embodiments of the present invention aim to solve are not limited to the technical problems described above, and other technical problems may exist.

[0012] As a technical means for achieving the above-mentioned technical problem, a carbon dioxide liquefaction system for a ship according to one embodiment of the present invention comprises a capture cycle for capturing carbon dioxide from exhaust gas and a liquefaction cycle for liquefying the carbon dioxide captured in the capture cycle, wherein the liquefaction cycle comprises an evaporator for evaporating a refrigerant, a compressor for compressing the refrigerant, a condenser for condensing the refrigerant in a gaseous state, and an expansion valve for expanding the refrigerant in a liquid state, wherein the carbon dioxide captured by the evaporator can be liquefied.

[0013] In addition, according to one embodiment of the present invention, the liquefaction cycle further includes a recovery unit that further cools the refrigerant condensed into a liquid state in the condenser, and the recovery unit can maintain the refrigerant in a supercooled state by heat-exchanging the condensed refrigerant with the refrigerant converted into a gaseous state through the evaporator.

[0014] In addition, according to one embodiment of the present invention, the recovery device can heat exchange the refrigerant transferred from the condenser to the expansion valve and the refrigerant transferred from the evaporator to the compressor so that the refrigerant passes through the expansion valve in a supercooled state.

[0015] In addition, according to one embodiment of the present invention, the recovery device may be provided at a location where a part of the refrigerant line from the condenser to the expansion valve and another part of the refrigerant line from the evaporator to the compressor intersect.

[0016] In addition, according to one embodiment of the present invention, the refrigerant flow path from the recovery unit through the expansion valve to the evaporator may be supported by an anti-shake device to maintain the supercooling of the refrigerant.

[0017] In addition, according to one embodiment of the present invention, the capture cycle comprises an absorption tower that removes carbon dioxide from the exhaust gas by reacting the exhaust gas with an absorbent, a regeneration tower that receives the absorbent that has absorbed carbon dioxide from the absorption tower, removes carbon dioxide from the absorbent, and transfers the absorbent from which carbon dioxide has been removed to the absorption tower, and a reboiler that heats the absorbent by supplying thermal energy to the regeneration tower, and the carbon dioxide discharged from the regeneration tower can be liquefied through the liquefaction cycle.

[0018] In addition, according to one embodiment of the present invention, the capture cycle further comprises a condenser configured to condense a mixed gas of carbon dioxide and water vapor discharged from the regeneration tower, and the condenser may include a cooler for cooling the mixed gas of carbon dioxide and water vapor, a separation drum for separating the cooled mixed gas of carbon dioxide and water vapor into gaseous carbon dioxide and liquid water, and a return pump connected to the separation drum for separating the condensate and supplying it to the regeneration tower.

[0019] In addition, according to one embodiment of the present invention, the capture cycle may further include a cooling tower provided upstream of the absorption tower to cool the exhaust gas.

[0020] The above-described means for solving the problem are merely exemplary and should not be interpreted as intended to limit the invention. In addition to the exemplary embodiments described above, additional embodiments may exist in the drawings and the detailed description of the invention.

[0021] According to the means for solving the problem of the present invention described above, the system comprises a capture cycle for capturing carbon dioxide from exhaust gas and a liquefaction cycle for liquefying the carbon dioxide captured in the capture cycle, wherein the liquefaction cycle comprises an evaporator for evaporating a refrigerant, a compressor for compressing a refrigerant, a condenser for condensing a refrigerant in a gaseous state, and an expansion valve for expanding a refrigerant in a liquid state, thereby enabling the carbon dioxide captured by the evaporator to be liquefied, and thus providing a carbon dioxide liquefaction system for ships that can store carbon dioxide in a liquid state in a ship with limited space.

[0022] In addition, the present invention further comprises a recovery unit that further cools the refrigerant condensed into a liquid state in the condenser, and the recovery unit maintains the refrigerant in a supercooled state by heat-exchanging the condensed refrigerant with the refrigerant converted into a gaseous state through the evaporator, thereby enabling the liquefaction and storage of as much carbon dioxide as possible with the same amount of refrigerant.

[0023] In addition, the present invention is configured such that a portion of the refrigerant line from the condenser to the expansion valve and another portion of the refrigerant line from the evaporator to the compressor intersect, and the recovery unit is configured to exchange heat between the refrigerant transferred from the condenser to the expansion valve and the refrigerant transferred from the evaporator to the compressor so that the refrigerant passes through the expansion valve in a supercooled state, thereby having the effect of not requiring additional energy to supercool the refrigerant.

[0024] In addition, the present invention can provide a carbon dioxide liquefaction system for ships in which the refrigerant flow path from the recovery unit through the expansion valve to the evaporator is supported by an anti-vibration device to maintain the supercooling of the refrigerant, thereby maintaining the supercooling of the refrigerant in a shipboard environment with a lot of vibration.

[0025] However, the effects obtainable from the present invention are not limited to those described above, and other effects may exist.

[0026] FIG. 1 is a drawing illustrating a conventional carbon capture system.

[0027] FIG. 2 is a schematic diagram illustrating a carbon dioxide liquefaction system for a ship according to an embodiment of the present invention.

[0028] FIG. 3 is a schematic diagram of a liquefaction cycle according to an embodiment of the present invention.

[0029] FIG. 4 is a schematic diagram illustrating that a refrigerant is supercooled by a recovery device (206) according to an embodiment of the present invention.

[0030] FIG. 5 is a schematic diagram illustrating a liquefaction cycle according to an embodiment of the present invention being arranged inside a ship.

[0031] Embodiments of the present invention are described below with reference to the attached drawings so that those skilled in the art can easily implement the invention. However, the present invention may be embodied in various different forms and is not limited to the embodiments described herein. Furthermore, in order to clearly explain the present invention in the drawings, parts unrelated to the explanation have been omitted, and similar parts throughout the specification are denoted by similar reference numerals.

[0032] Throughout the specification of this invention, when a part is described as being "connected" to another part, this includes not only cases where they are "directly connected," but also cases where they are "electrically connected" or "indirectly connected" with other elements interposed between them.

[0033] Throughout the entire specification of the present invention, when a member is described as being located "on," "on the upper," "on the top," "under," "on the lower," or "on the bottom" of another member, this includes not only cases where the member is in contact with the other member, but also cases where another member exists between the two members.

[0034] Throughout the specification of the present invention, when a part is described as "comprising" a certain component, this means that, unless specifically stated otherwise, it does not exclude other components but may include additional components.

[0035] In addition, terms related to direction or position (upper side, upper surface, lower side, etc.) in the description of the embodiments of the present invention are established based on the arrangement state of each component shown in the drawings.

[0036] Referring to FIG. 2, a carbon dioxide liquefaction system (1) for a ship according to one embodiment of the present invention captures carbon dioxide from exhaust gas generated from an engine and liquefies and stores the captured carbon dioxide, thereby minimizing the volume of carbon dioxide captured from exhaust gas and storing it within a ship with limited space, while liquefying and storing as much carbon dioxide as possible with the same amount of refrigerant. The carbon dioxide liquefaction system (1) for a ship may include a capture cycle (100) and a liquefaction cycle (200).

[0037] The capture cycle (100) can capture carbon dioxide in exhaust gas through a chemical reaction between an absorbent and carbon dioxide in an absorption tower, and then remove carbon dioxide from the absorbent in a regeneration tower and recirculate it to the absorption tower to capture carbon dioxide in exhaust gas. The carbon dioxide captured in the capture cycle (100) can be liquefied and stored through a liquefaction cycle (200). The capture cycle (100) may include a cooling tower (101), an absorption tower (102), a regeneration tower (103), a heat exchanger (104), a reboiler (105), a condenser (106), and a carbon dioxide storage tank (107).

[0038] A cooling tower (101) may be provided to lower the temperature of exhaust gas discharged from an engine. The exhaust gas is usually discharged at a high temperature, and it is cooled to an appropriate temperature to satisfy conditions suitable for carbon dioxide capture and liquefaction. The cooling process can be carried out mainly by using water to directly contact the exhaust gas and absorb heat. In this process, as moisture in the exhaust gas condenses, impurities such as dust or fine particles can be removed together. The cooling tower (101) may be provided upstream of the absorption tower (102) to cool the exhaust gas, and in the case of a shipboard carbon dioxide liquefaction system (1), a wet scrubber may be used as the cooling tower. It is preferable that the scrubber be a wet scrubber, and as the exhaust gas passes through packing, dispersion means, etc. inside the scrubber, contaminants such as sulfur oxides may be removed by the cleaning water sprayed or supplied inside the scrubber. The sprayed cleaning water may be seawater.

[0039] The absorption tower (102) is configured to remove carbon dioxide from the exhaust gas by reacting the carbon dioxide in the exhaust gas with an absorbent, and the exhaust gas, which has been cooled to an appropriate temperature through the cooling tower (101), can have carbon dioxide absorbed by the absorbent in the absorption tower (102). The absorbent may be an amine-based, amino acid salt, inorganic salt solution, ammonia water, etc.

[0040] The regeneration tower (103) receives the absorbent that has absorbed carbon dioxide from the absorption tower (102) and can regenerate the absorbent by removing the carbon dioxide that is chemically bonded within the absorbent. The absorbent regenerated in the regeneration tower (103) can be recirculated to the absorption tower after heat exchange through the heat exchanger (104). As the absorbent that has absorbed carbon dioxide is transferred from the absorption tower (102) to the regeneration tower (103), and then the carbon dioxide is removed and transferred back to the absorption tower (102), a circulation line for the absorbent used to absorb carbon dioxide from exhaust gas can be formed. Additionally, the carbon dioxide discharged from the regeneration tower can be liquefied through the liquefaction cycle (200).

[0041] A heat exchanger (104) may be provided to perform heat exchange between an absorbent that has absorbed carbon dioxide supplied from the absorption tower (102) and an absorbent that has removed carbon dioxide supplied from the regeneration tower (103). In a preferred embodiment of the present invention, heat exchange may be performed between an absorbent that has absorbed carbon dioxide transferred from the absorption tower (102) to the regeneration tower (103) and an absorbent that has removed carbon dioxide transferred from the regeneration tower (103) to the absorption tower (102), thereby enabling the carbon dioxide absorption process within the absorption tower (102) and the carbon dioxide removal process within the regeneration tower (103) to be performed smoothly. Since the chemical bonding between carbon dioxide and the absorbent performed within the absorption tower (102) corresponds to an exothermic reaction and the removal of carbon dioxide performed within the regeneration tower (103) corresponds to an endothermic reaction, it is advantageous to keep the temperature within the absorption tower (102) low and to keep the temperature of the absorbent sprayed from the absorption tower (102) low, and conversely, it is advantageous to keep the environment within the regeneration tower (103) at a high temperature. Accordingly, the heat exchanger (104) can facilitate the carbon dioxide absorption and removal reactions performed in the absorption tower and the regeneration tower by exchanging heat between the high-temperature absorbent absorbed from the regeneration tower (103) and the low-temperature absorbent supplied from the absorption tower (102) to the regeneration tower (120).

[0042] The reboiler (105) can supply thermal energy to the regeneration tower (103) to vaporize the carbon dioxide captured in the absorbent. That is, the regeneration tower (103) receives thermal energy from the reboiler (105) and performs the absorbent regeneration process. At this time, the carbon dioxide that is vaporized and separated is discharged to the top of the regeneration tower (103), and the absorbent from which the carbon dioxide has been separated can be transferred to the absorption tower (102) for regeneration.

[0043] A condenser (106) is provided to condense a mixture of carbon dioxide and water vapor discharged from a regeneration tower (120). The condenser (106) may include a cooler that cools the mixture of carbon dioxide and water vapor by exchanging heat with cooling water, a separation drum that separates the cooled mixture of carbon dioxide and water vapor into gaseous carbon dioxide and liquid water, and a return pump connected to the separation drum that separates the condensed water and supplies it back to the regeneration tower (103).

[0044] A carbon dioxide storage tank (107) is provided to store separated carbon dioxide. In one embodiment, the carbon dioxide storage tank (107) may store carbon dioxide in a liquid state. The carbon dioxide storage tank (107) may not receive carbon dioxide separated from the condenser (106) directly, but may receive carbon dioxide that has been liquefied through the liquefaction cycle (200) described later.

[0045] A liquefaction cycle (200) may be provided to liquefy carbon dioxide collected in a capture cycle (100). The liquefaction cycle (200) may be understood as a cooling cycle that liquefies carbon dioxide transferred from a condenser (106) to a carbon dioxide storage tank (107) via a refrigerant. By liquefying the carbon dioxide separated in the liquefaction cycle (200), a large amount of carbon dioxide can be stored within a vessel in a confined space. Referring to FIG. 3, the liquefaction cycle (200) may include a refrigerant line (201), a condenser (202), an expansion valve (203), an evaporator (204), a compressor (205), and a recovery unit (206).

[0046] The refrigerant line (201) is configured to have refrigerant flowing through it and can form a closed curve to allow the refrigerant to circulate. As the refrigerant flowing along the refrigerant line (201) passes through the configuration from the condenser (202) to the compressor (205), carbon dioxide can be liquefied and cooled by cooling water. A pump may also be additionally provided on the refrigerant line (201) to pressurize and transport the liquefied refrigerant.

[0047] The refrigerant flows through the refrigerant line (201), and depending on the flow of the refrigerant, the area from the condenser (202) to the recovery unit (206) can be defined as the first line section (201a), and the area from the recovery unit (206) to the expansion valve (203) can be defined as the second line section (201b). Additionally, the area from the expansion valve (203) to the evaporator (204) can be defined as the third line section (201c), the area from the evaporator (204) to the compressor (205) can be defined as the fourth line section (201d), and the area from the compressor (205) to the condenser (202) can be defined as the fifth line section (201e). That is, within the refrigerant line (201), the refrigerant can be understood to flow sequentially from the first line section (201a) to the fifth line section (201e).

[0048] Since the critical temperature of carbon dioxide is 31.0°C and the critical pressure is 72.80 atm, the liquefaction of carbon dioxide can be carried out in a liquefaction tank controlled to have an internal pressure below the critical pressure. For the liquefaction of carbon dioxide, a refrigerant such as R134a (tetrafluoroethane) or a mixture of hydrofluorocarbons such as R410a can be used.

[0049] The condenser (202) can be understood as a configuration that condenses the vaporized refrigerant moving through the compressor (205). The cooling source used for cooling in the condenser (202) may be fresh water or seawater, but the vaporized refrigerant may also be condensed using the boil-off gas (BOG) of LNG.

[0050] An expansion valve (203) may be provided to reduce the pressure of the liquid refrigerant from a high-pressure state to a low-pressure state. The expansion valve (203) lowers the pressure of the refrigerant and simultaneously lowers the temperature so that the refrigerant can absorb heat in the evaporator. The expansion valve (203) operates before sending the liquid refrigerant coming out of the high-pressure condenser (202) to the low-pressure evaporator (204), and as a portion of the refrigerant flash evaporates and is converted into a gas, the temperature of the remaining liquid refrigerant is rapidly lowered. The refrigerant at the lowered temperature flows into the evaporator (204) and can vaporize while absorbing an external heat source.

[0051] The evaporator (204) can be understood as a component that evaporates the refrigerant. The refrigerant, which enters at low pressure and temperature after passing through the expansion valve (203), circulates inside the evaporator and exchanges heat with carbon dioxide captured from the exhaust gas. During this process, the refrigerant changes state from liquid to gas and absorbs heat from the carbon dioxide. As a result, the temperature of the carbon dioxide is lowered and liquefied, and the refrigerant is completely converted into a gaseous state.

[0052] The compressor (205) can be understood as a component that compresses the refrigerant, which has been converted to a gaseous state in the evaporator, to a high pressure and temperature. The refrigerant compressed through the compressor (205) is transferred to the condenser (202), where it releases heat and condenses into a liquid state. During the compression process of the compressor (205), the temperature and pressure of the refrigerant increase, which subsequently helps to release heat in the condenser.

[0053] The recovery unit (206) may be provided to further cool the refrigerant condensed in a liquid state in the condenser. The refrigerant may be subcooled in the recovery unit (206). For example, the recovery unit (206) may maintain the refrigerant in a subcooled state by heat-exchanging the refrigerant condensed in the condenser (202) with the refrigerant converted into a gaseous state through the evaporator (204).

[0054] To this end, the recovery unit (206) may be provided at a location where the other part of the refrigerant line of the fourth line (201d) from the evaporator (204) to the compressor (205) intersects the first line portion (201a) and the second line portion (201b) of the refrigerant line corresponding to the condenser (202) to the expansion valve (203). Accordingly, the recovery unit (206) may be provided to heat exchange the refrigerant transferred from the condenser (202) to the expansion valve (203) and the refrigerant transferred from the evaporator (204) to the compressor (205). In the recovery unit (206), when the refrigerant is supercooled in the recovery unit (206), the refrigerant may pass through the expansion valve (203) in a supercooled state.

[0055] In one embodiment, the recovery unit (206) may be equipped with a heat exchanger. Multiple flow paths may be provided inside the recovery unit to maximize the contact area between the refrigerant transferred from the condenser (202) to the expansion valve (203) and the refrigerant transferred from the evaporator (204) to the compressor (205). Additionally, the refrigerants entering the recovery unit (206) may flow in a countercurrent within the recovery unit.

[0056] Referring to FIG. 4, even if the same amount of thermal energy is supplied to the refrigerant, the temperature change is small in the latent heat section, but the temperature changes rapidly in the sensible heat section. Therefore, in a liquefaction cycle, the higher the ratio of the liquid phase in the latent heat section of the refrigerant, the more advantageous it is for the liquefaction of carbon dioxide. When the refrigerant passes through the expansion valve (203) without the recovery unit (206), some flash evaporation occurs, and as it passes through the evaporator (204), it can absorb thermal energy equivalent to the RE1 section of FIG. 4. In contrast, if the refrigerant is subcooled through the recovery unit (206), the subcooled refrigerant can absorb thermal energy equivalent to the RE2 section as it passes through the evaporator (204). That is, the latent heat available for use in the evaporator (204) increases, thereby reducing the refrigerant flow rate required for carbon dioxide liquefaction and reducing the power consumed.

[0057] When the refrigerant passes through the expansion valve (203), the temperature of the refrigerant is lower than before it enters the expansion valve. During this process, the refrigerant undergoes a flash evaporation phenomenon in which the temperature decreases without absorbing heat from the surroundings as a portion of the refrigerant vaporizes. This phenomenon occurs because enthalpy is conserved, and the temperature decreases as the pressure of the refrigerant decreases. The refrigerant that has passed through the expansion valve (203) enters the evaporator in a low-temperature and low-pressure state. The refrigerant that enters the evaporator (204) evaporates while absorbing heat from a surrounding heat source, such as carbon dioxide captured from exhaust gas. During this process, the refrigerant is completely converted into a gaseous state and performs the role of liquefying carbon dioxide in the liquefaction cycle.

[0058] Subcooling of the refrigerant in the recovery unit (206) induces the refrigerant to lose more heat while maintaining a liquid state, thereby maximizing the latent heat portion in the refrigeration cycle. As described above, through heat exchange in the recovery unit (206), the refrigerant can reach a subcooled state.

[0059] In the case where the recovery unit (206) is not provided in the liquefaction cycle (200), the refrigerant can be converted to a vaporized state immediately after exiting the condenser (202). However, by subcooling the refrigerant through the recovery unit (206), the latent heat range in which the refrigerant can absorb more thermal energy in the evaporator can be expanded. This increases the amount of carbon dioxide that can be processed in the same system and contributes to reducing the refrigerant flow rate and the system size. Accordingly, as the thermal energy that the refrigerant can absorb in the evaporator increases, the refrigerant flow rate is reduced, and more carbon dioxide can be liquefied with the same refrigerant flow rate, thereby maximizing the performance of the liquefaction cycle (200).

[0060] Referring to FIG. 5, when the liquefaction cycle (200) is provided inside a ship, a vibration prevention device (220) may be provided to maintain the supercooling of the refrigerant. The ship has environmental conditions that may affect the supercooling state of the refrigerant due to high vibration. Since the supercooling state of the refrigerant may be hindered in an environment with high vibration, the vibration prevention device (220) of the present invention may support at least a portion of the refrigerant line (201) so that the refrigerant passes through the expansion valve (203) in a supercooled state and heads toward the evaporator (204).

[0061] In one embodiment, a portion of the refrigerant flow path (201) leading from the recovery unit (206) through the expansion valve (203) to the evaporator (204) may be supported by an anti-shake device (220) to maintain the supercooling of the refrigerant.

[0062] The captured carbon dioxide can be liquefied within a liquefaction tank (210). An evaporator (204) may be provided inside the liquefaction tank (210), and supercooled refrigerant may be transferred from a recovery unit (206) through an expansion valve (203) to the evaporator (204). A portion of the refrigerant line (201b), for example, a second line portion (201b) and a third line portion (201c), may be supported indirectly or directly by an anti-shake device (220).

[0063] FIG. 5 schematically illustrates that the liquefaction tank (210), expansion valve (203), and recovery unit (206) are supported by a vibration prevention device (220). With reference to this, it can be understood that as the expansion valve (203) and recovery unit (206) are supported, the refrigerant path (201) leading from the recovery unit (206) through the expansion valve (203) to the evaporator (204) is indirectly supported by the vibration prevention device (220).

[0064] Although not shown in FIG. 5, the refrigerant passage (201), specifically the second line portion (201b) and the third line portion (201c), may be directly supported by the anti-shake device (220). Additionally, an anti-shake device (220) that supports the evaporator (204) within the liquefaction tank (210) may be additionally provided.

[0065] The anti-vibration device (220) may be configured such that one end is connected to a part of the hull and the other end is connected to a refrigerant flow path (201), an expansion valve (203), or a recovery device (206), and may be equipped with a damper that dampens vibrations so that vibrations of the hull are not transmitted to the refrigerant flow path (201).

[0066] By supporting a part or all of the refrigerant passage (201) by the anti-vibration device (220), it is possible to prevent the supercooled refrigerant inside the refrigerant passage from condensing due to vibration or moving out of the supercooled state.

[0067] In this way, the carbon dioxide liquefied in the liquefaction cycle (200) can be transferred to a carbon dioxide storage tank (107) and stored in a liquid state.

[0068] The foregoing description of the present invention is for illustrative purposes only, and those skilled in the art will understand that other specific forms can be easily modified without altering the technical spirit or essential features of the present invention. Therefore, the embodiments described above should be understood as illustrative in all respects and not restrictive. For example, each component described as a single unit may be implemented in a distributed manner, and components described as distributed may likewise be implemented in a combined form.

[0069] The scope of the present invention is defined by the claims set forth below rather than by the detailed description above, and all modifications or variations derived from the meaning and scope of the claims and equivalent concepts thereof should be interpreted as being included within the scope of the present invention.

Claims

1. A capture cycle for capturing carbon dioxide from exhaust gas, and It includes a liquefaction cycle for liquefying carbon dioxide captured in the above-mentioned capture cycle, wherein The above liquefaction cycle is, Evaporator that evaporates refrigerant, A compressor that compresses refrigerant, A condenser for condensing a refrigerant in a gaseous state, and It includes an expansion valve that expands a refrigerant in a liquid state, A shipboard carbon dioxide liquefaction system characterized by carbon dioxide captured by the above-mentioned evaporator being liquefied.

2. In Paragraph 1, The above liquefaction cycle is, It further includes a recovery unit that further cools the refrigerant condensed into a liquid state in the condenser above, and A shipboard carbon dioxide liquefaction system characterized by the above recovery device maintaining the refrigerant in a supercooled state by heat-exchanging the condensed refrigerant with the refrigerant converted into a gaseous state through the evaporator.

3. In Paragraph 2, A carbon dioxide liquefaction system for ships, characterized in that the above recovery unit is equipped with a heat exchanger that exchanges heat between the refrigerant transferred from the condenser to the expansion valve and the refrigerant transferred from the evaporator to the compressor, so that the refrigerant passes through the expansion valve in a supercooled state.

4. In Paragraph 3, A carbon dioxide liquefaction system for ships, characterized in that the above recovery unit is provided at a location where a part of the refrigerant line from the condenser to the expansion valve and another part of the refrigerant line from the evaporator to the compressor intersect.

5. In Paragraph 3, A carbon dioxide liquefaction system for ships, characterized in that the refrigerant path from the recovery unit through the expansion valve to the evaporator is supported by an anti-shake device to maintain the supercooling of the refrigerant.

6. In Paragraph 1, The above capture cycle is, Absorption tower that removes carbon dioxide from exhaust gas by reacting exhaust gas with an absorbent A regeneration tower that receives an absorbent that has absorbed carbon dioxide from the absorption tower, removes carbon dioxide from the absorbent, and transfers the absorbent from which carbon dioxide has been removed to the absorption tower, and It includes a reboiler that heats the absorbent by supplying thermal energy to the regeneration tower, and A carbon dioxide liquefaction system for ships characterized by carbon dioxide discharged from the above-mentioned regeneration tower being liquefied through the above-mentioned liquefaction cycle.

7. In Paragraph 6, The above capture cycle is, It further includes a condenser configured to condense a mixture of carbon dioxide and water vapor discharged from the above-mentioned regeneration tower, and The above capacitor is, A cooler that cools a mixture of carbon dioxide and water vapor, A separation drum for separating a mixture of cooled carbon dioxide and water vapor into gaseous carbon dioxide and liquid water, and A carbon dioxide liquefaction system for ships characterized by including a return pump connected to the separation drum to separate condensate and supply it to the regeneration tower.

8. In Paragraph 7, The above capture cycle is, A carbon dioxide liquefaction system for ships, characterized by further including a cooling tower provided upstream of the absorption tower to cool the exhaust gas.

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