Carbon dioxide capture system using cool thermal energy

Abstract

The present invention can improve heat transfer energy efficiency by significantly reducing the volume of gas cooled by the pretreatment process, thereby reducing the amount of heat required for cooling through the high concentration of carbon dioxide in the incoming gas. In addition, the present invention is a multi-stage cooling process using LNG (liquefied natural gas) and liquid nitrogen, which allows carbon dioxide to be separated and captured by sublimating (solidifying) it using cold energy with only a relatively simple process without high pressure conditions.

Description

Technology Field

[0001] The present invention relates to a carbon dioxide capture system using cold energy, and more specifically, it can improve carbon dioxide capture efficiency through a pretreatment process and at the same time efficiently sublimate (solidify) carbon dioxide using cold energy without high pressure conditions. Background Technology

[0002] Currently, many industrial machines use fossil fuels such as coal, oil, and liquefied natural gas (LNG) as energy sources, and large amounts of carbon dioxide are emitted during the process of converting fossil fuel energy into other forms of energy. As such, the problem of global warming arises from greenhouse gases generated by the excessive use of fossil fuels resulting from industrialization.

[0003] According to scenarios developed by the Intergovernmental Panel on Climate Change (IPCC), temperature increases were estimated as follows, based on the assumptions of no reduction in the rate of increase of greenhouse gas emissions versus a gradual reduction. If greenhouse gas emissions are not reduced, temperatures are estimated to rise by 1.5–4.5°C by the mid-21st century, increasing at a rate of 0.2–0.5°C every decade. If greenhouse gas emissions are gradually reduced, the temperature increase is estimated to be 0.1–0.2°C every decade. As carbon dioxide is identified as a factor in various environmental changes, including climate change, numerous studies are being conducted to reduce emissions or to capture, store, and utilize it as a useful resource. The use of fossil fuels has acted as the most significant factor in causing carbon dioxide, which has long been stored within the Earth in the form of coal, oil, and natural gas, to be released back into the atmosphere.

[0004] Apart from reducing carbon dioxide emissions through the application of various policies, the development of technologies, and the diversification of energy sources, the development of technologies to capture carbon dioxide inevitably generated in each process and to utilize or store it through appropriate methods also plays an important role in reducing carbon dioxide emissions.

[0005] In particular, the storage of carbon dioxide requires a carbon sequestration technology process to transport it to a storage location, such as a seabed. For this transportation, not only are storage devices capable of storing large quantities of carbon dioxide and storage vessels equipped with such devices required, but large-scale onshore storage facilities capable of storing carbon dioxide are also necessary before the transportation stage.

[0006] Due to economic considerations, carbon dioxide storage devices typically store carbon dioxide in a liquid state; however, this presented a limitation in that a pressure tank was essential to maintain the carbon dioxide at high pressure and low temperature.

[0007] Accordingly, various attempts have been made to separate and capture carbon dioxide into solid dry ice, but the process remains complex, and wet and dry capture and detachment methods require a large amount of energy. Furthermore, using membrane separation methods made it difficult to process large volumes of gas. In addition, to convert 10 to 20 percent of carbon dioxide into dry ice by cooling the entire exhaust gas from which moisture has been removed, it is necessary to cool the exhaust gas containing 80 to 90 percent of unnecessary nitrogen and oxygen together, which requires additional cooling energy. Consequently, there were limitations in that the process efficiency was significantly low, making it difficult to realize. Prior art literature

[0008] Republic of Korea Registered Patent 10-1546360 The problem to be solved

[0009] The problem that the present invention aims to solve is to provide a carbon dioxide capture system using cold energy that can improve carbon dioxide capture efficiency through a pretreatment process and simultaneously capture carbon dioxide by sublimating (solidifying) it using cold energy without high-pressure conditions. means of solving the problem

[0010] To solve the above-mentioned problem, the present invention provides a carbon dioxide capture system using cold energy comprising: a step of condensing and removing moisture contained in a gas generated during a fossil fuel combustion process; a step of adsorbing carbon dioxide contained in the gas from which moisture has been removed using an adsorbent; a step of desorbing the carbon dioxide adsorbed on the adsorbent through a vacuum pump; a step of first cooling a high-concentration carbon dioxide gas using cold energy by passing the gas, whose volume has been reduced through the adsorption and desorption of carbon dioxide, through a heat exchanger to exchange heat with LNG; and a step of separating and capturing the carbon dioxide contained in the gas whose temperature has been lowered through the first cooling by sublimating it using a cold energy system utilizing liquid nitrogen to form solid dry ice.

[0011] According to a preferred embodiment of the present invention, the step of condensing and removing moisture can be performed using a condenser or by using the coldness of a low-temperature gas discharged from a coldness system using liquid nitrogen.

[0012] According to a preferred embodiment of the present invention, in the adsorption step, the adsorbent may be a porous support.

[0013] According to a preferred embodiment of the present invention, the adsorption step may result in the carbon dioxide being physically dry-adsorbed onto the adsorbent, and nitrogen and oxygen being discharged, thereby reducing the total volume of the gas from which moisture has been removed and increasing the concentration of carbon dioxide contained in the gas from which moisture has been removed.

[0014] According to a preferred embodiment of the present invention, in the step of adsorbing, the adsorption is performed in an adsorption system comprising at least one porous bed packed with the adsorbent, and may be performed in a vacuum swing absorption (VSA) or pressure swing absorption (PSA) manner.

[0015] According to a preferred embodiment of the present invention, the adsorption step may be performed through multiple continuous processes by connecting two or more adsorption systems in parallel.

[0016] According to a preferred embodiment of the present invention, in the first cooling step, the LNG used in the heat exchange is discharged as NG from the heat exchanger, and the NG is transferred to the flue gas cooling heat exchanger (100) to lower the temperature of the flue gas cooling heat exchanger, thereby lowering the temperature of the gas generated in the fossil fuel combustion process.

[0017] According to a preferred embodiment of the present invention, in the step of separating and collecting dry ice, the cold energy system using liquid nitrogen comprises: a high-pressure chamber; liquid nitrogen contained within the high-pressure chamber; and an atmospheric pressure chamber arranged so as to contain at least a portion of the liquid nitrogen, into which gas whose temperature has been lowered through primary cooling is introduced; wherein heat exchange occurs between the high-concentration carbon dioxide gas contained within the gas whose temperature has been lowered through primary cooling introduced into the atmospheric pressure chamber and the liquid nitrogen, and the carbon dioxide is sublimated through cold energy utilizing the phase change energy required for the liquid nitrogen to vaporize during the heat exchange, thereby obtaining dry ice in a solid state.

[0018] According to a preferred embodiment of the present invention, the atmospheric pressure chambers may be included to be connected and arranged in two or more places within the cold and heat system.

[0019] According to a preferred embodiment of the present invention, the cold-heat system using liquid nitrogen is connected to a liquid nitrogen generator, and the liquid nitrogen contained inside the high-pressure chamber is transferred to the liquid nitrogen generator after being vaporized through the heat exchange, and can be circulated by being transferred back into the high-pressure chamber after being liquefied into liquid nitrogen through the liquid nitrogen generator.

[0020] According to a preferred embodiment of the present invention, after the step of separating and collecting dry ice, the method may further include the step of separating and collecting liquid carbon dioxide from the dry ice through a heating and depressurization process. Effects of the invention

[0021] The present invention can improve heat transfer energy efficiency by significantly reducing the volume of gas cooled by the pretreatment process, thereby reducing the amount of heat required for cooling through the high concentration of carbon dioxide in the incoming gas.

[0022] In addition, the present invention is a multi-stage cooling process using LNG (liquefied natural gas) and liquid nitrogen, which allows carbon dioxide to be separated and captured by sublimating (solidifying) it using cold energy with only a relatively simple process without high pressure conditions. Brief explanation of the drawing

[0023] FIG. 1 is a process diagram of a carbon dioxide capture system using cold heat according to a preferred embodiment of the present invention. FIG. 2 is a process diagram of a carbon dioxide capture system using cold heat according to a preferred embodiment of the present invention. Specific details for implementing the invention

[0024] Hereinafter, with reference to the attached drawings, embodiments of the present invention will be described in detail so that those skilled in the art can easily implement the present invention.

[0025] As described above, the existing method of separating and capturing carbon dioxide into solid dry ice has limitations in that it requires additional cooling energy because it must cool the entire exhaust gas from which moisture has been removed to convert 10 to 20 percent of carbon dioxide into dry ice, while also cooling the exhaust gas containing 80 to 90 percent of unnecessary nitrogen and oxygen. Consequently, the process efficiency is significantly low, making it difficult to realize.

[0026] Accordingly, the present invention seeks a solution to the aforementioned limitations by providing a carbon dioxide capture system using cold energy, comprising the steps of: condensing and removing moisture contained in the gas generated during the combustion of fossil fuels (S10); adsorbing carbon dioxide contained in the gas from which moisture has been removed using an adsorbent (S20); desorbing the carbon dioxide adsorbed on the adsorbent using a vacuum pump (S30); passing the gas with reduced volume through the adsorption and desorption of carbon dioxide through a heat exchanger to exchange heat with LNG and first cooling the high-concentration carbon dioxide gas using cold energy (S40); and sublimating the carbon dioxide contained in the gas whose temperature has been lowered through the first cooling using a cold energy system utilizing liquid nitrogen to separate and capture it as solid dry ice (S50).

[0027] Accordingly, the present invention can improve heat transfer energy efficiency by significantly reducing the volume of the gas being cooled through a pretreatment process using an adsorbent, thereby reducing the amount of heat required for cooling by increasing the concentration of the incoming gas. In addition, the present invention can separate and capture carbon dioxide by sublimating (solidifying) it using cold energy through a relatively simple process without high-pressure conditions by performing a multi-stage cooling process using LNG (liquefied natural gas) and liquid nitrogen. Through this, the present invention can improve the efficiency of carbon dioxide separation and capture.

[0028] First, FIG. 1 is a process diagram of a carbon dioxide capture system using cold energy according to a preferred embodiment of the present invention. Referring to FIG. 1, the present invention allows gas generated during the combustion of fossil fuels to be discharged from a chimney, pass through an exhaust gas cooling heat exchanger (100), and flow into a condenser (200). Through this, a step (S10) is performed to condense and remove moisture contained in the gas generated during the combustion of fossil fuels. The gas from which moisture has been removed through the condenser (200) is transferred to an adsorption system (300), and a step (S20) is performed to adsorb carbon dioxide from the gas from which moisture has been removed using an adsorbent. At this time, a large amount of nitrogen, oxygen, etc. contained in the exhaust gas is discharged through the upper part of the adsorption system (300). Subsequently, a step (S30) is performed to desorb the carbon dioxide adsorbed on the adsorbent using a vacuum pump (310). At this time, the gas whose volume has been reduced through the adsorption and desorption of carbon dioxide may be transferred to a carbon dioxide storage tank (320) at a rapid speed via a vacuum pump (310) and then transferred to a heat exchanger (400). The desorbed high-concentration carbon dioxide gas is transferred to a heat exchanger (400) where primary cooling is performed, and a step (S40) of primary cooling using cold energy is performed by passing it through the heat exchanger (400) to exchange heat with LNG. The gas whose temperature has been lowered through primary cooling is transferred to a cold energy system (500) using liquid nitrogen. Through this, a step (S50) is performed in which the carbon dioxide contained in the gas whose temperature has been lowered through primary cooling is sublimated using the cold energy system (500) using liquid nitrogen to separate and collect it as solid dry ice. Through the above-described process, the present invention can efficiently separate and collect carbon dioxide contained in the gas generated during the combustion of fossil fuels as solid dry ice.

[0029] The step (S10) of condensing and removing moisture contained in the gas generated during the fossil fuel combustion process removes the moisture contained in the gas by cooling the gas. This can be performed using a condenser (200) or by using the coldness of the low-temperature gas discharged from a coldness system (500) using liquid nitrogen.

[0030] Typically, most adsorbents are hydrophilic, so moisture tends to be adsorbed onto them. Consequently, moisture is preferentially adsorbed onto the adsorbent or is competitively adsorbed and does not easily desorb, which reduces the specific surface area of ​​the porous support and can significantly lower the adsorption efficiency of carbon dioxide.

[0031] Accordingly, the present invention has the effect of improving the adsorption efficiency of carbon dioxide using an adsorbent by preferentially condensing and removing moisture contained in the gas prior to the adsorption process.

[0032] In addition, if the gas temperature is high, difficulties may arise where the gas is not firmly adsorbed to the adsorbent, or even if adsorbed, it may easily detach. Accordingly, the present invention has the effect of improving process efficiency by lowering the gas temperature through cooling the gas prior to the adsorption process, thereby increasing the adsorption rate to the adsorbent.

[0033] The step (S20) of adsorbing carbon dioxide contained in the moisture-removed gas using an adsorbent adsorbs carbon dioxide (CO2) contained in the moisture-removed gas.

[0034] At this time, a significant amount of excess gas, such as nitrogen (N2) and oxygen (O2), can be discharged through the upper part of the adsorption system (300).

[0035] Specifically, the gas from which moisture has been removed contains more excess gases such as nitrogen and oxygen in addition to carbon dioxide. Referring to Fig. 1, the gas typically inlet to a carbon dioxide capture system may consist of 80 to 90 volume% nitrogen, 0 to 5 volume% oxygen, and 5 to 20 volume% carbon dioxide. As such, it is common for the gas generated during the combustion of fossil fuels to contain 10 to 20 volume% carbon dioxide.

[0036] For this reason, when attempting to obtain solid dry ice by sublimating (solidifying) carbon dioxide by cooling the entire gas containing nitrogen or oxygen using cold energy, a significantly large amount of energy is required, and consequently, the heat transfer energy efficiency becomes significantly lower, which leads to a limitation in that the process becomes complex and process efficiency decreases.

[0037] Accordingly, the present invention first performs a pretreatment process in which, prior to cooling using cold heat, carbon dioxide contained in the gas from which moisture has been removed is adsorbed by an adsorbent, and excess gases such as nitrogen or oxygen are discharged through the upper part of the adsorption system (300). Through this, most of the excess gases such as nitrogen or oxygen can be discharged. Specifically, the present invention causes an excess amount of carbon dioxide to adhere to the surface and internal pores of the adsorbent, and then, when the adhesion performance of the adsorbent deteriorates at a specific point in time, the inflow of gas is blocked, and carbon dioxide is desorbed through a vacuum pump (310) as described below, thereby performing high concentration of carbon dioxide.

[0038] The carbon dioxide volume concentration of the gas whose volume is reduced by passing through the adsorption system (300) can be 50 volume% or more, and preferably 60 volume% or more.

[0039] Thus, the present invention can improve heat transfer energy efficiency by significantly reducing the volume of the gas to be cooled using cold energy and increasing the carbon dioxide concentration of the incoming gas, thereby reducing the amount of heat required for cooling. In other words, by increasing the concentration of carbon dioxide, the energy loss required for cooling unnecessary gases such as nitrogen and oxygen can be minimized, and thereby the cooling effect using cold energy can be significantly enhanced.

[0040] As a specific example, assuming that the volume composition ratio of the incoming gas entering the adsorption system (300) is 90 volume% nitrogen and 10 volume% carbon dioxide, if the carbon dioxide is cooled to -80°C, which is the temperature range for sublimation under atmospheric pressure conditions, the amount of heat required to cool the nitrogen is 160 kcal / min. On the other hand, as described above, if the carbon dioxide volume concentration is increased to 60 volume% through the adsorption system (300), the amount of heat required to cool 40 volume% nitrogen within the same temperature range would be only 12 kcal / min. Therefore, the present invention can reduce the amount of cooling required to cool the gas containing carbon dioxide to about 1 / 13, and accordingly, the heat transfer energy efficiency can be significantly improved.

[0041] According to a preferred embodiment of the present invention, the adsorption step (S20) can be performed by physically dry adsorbing carbon dioxide onto an adsorbent.

[0042] Through this, carbon dioxide among the gases from which moisture has been removed is adsorbed onto the adsorbent, and most excess gases such as nitrogen and oxygen are discharged, thereby reducing the total volume and increasing the concentration of carbon dioxide to be separated and captured, which reduces the amount of heat required for cooling through the high concentration of carbon dioxide, thereby improving the heat transfer energy efficiency.

[0043] In this case, a porous support can be used as the adsorbent. Preferably, zeolite, activated carbon, silica, metal-organic frameworks, etc., can be used. In this case, carbon dioxide can be purified by penetrating and adsorbing within the porous space with a large surface area.

[0044] Meanwhile, the adsorption step (S20) may be performed in an adsorption system (300) comprising at least one porous bed packed with an adsorbent. That is, the adsorption described above may be performed through an adsorption system (300) comprising one or more beds (packing beds) filled with a porous support that is an adsorbent. Preferably, a plurality of porous beds packed with an adsorbent may be included within a single adsorption system (300) to form a multilayer structure. At this time, the number of porous beds packed with an adsorbent may be increased or decreased considering the amount of flue gas, pressure loss, carbon dioxide capture efficiency, etc. That is, a fixed-bed adsorption reaction device having a multilayer packed structure may be used as the adsorption system (300).

[0045] Forming a multilayer structure in this way has the advantage of improving the amount and efficiency of carbon dioxide captured.

[0046] In addition, the above adsorption can be performed using a vacuum swing absorption (VSA) or pressure swing absorption (PSA) method.

[0047] According to a preferred embodiment of the present invention, the adsorption step (S20) can be performed through multiple continuous processes by connecting two or more adsorption systems (300) in parallel. More preferably, 2 to 5 adsorption systems (300) can be connected in parallel.

[0048] In addition, the above multiple continuous processes are preferably performed within minutes, and more preferably within 1 to 3 minutes assuming that 6 to 10 tons of carbon dioxide are processed per day.

[0049] As described above, the present invention can perform carbon dioxide adsorption through physical dry adsorption based on van der Waals forces; however, in this case, the adsorption performance may deteriorate over time. Accordingly, by performing multiple continuous processes within a short period, it is possible to more easily achieve a high concentration of carbon dioxide.

[0050] The step (S30) of desorbing carbon dioxide adsorbed on the adsorbent through the vacuum pump (310) separates the carbon dioxide by desorbing it due to the pressure difference by passing the gas with adsorbed carbon dioxide through the vacuum pump (310) as described above.

[0051] In this way, the volume of the gas can be reduced through the adsorption and desorption of carbon dioxide, and the concentration of carbon dioxide can be increased.

[0052] The gas, with its volume reduced through the adsorption and desorption of carbon dioxide, can be transferred to a carbon dioxide storage tank (320) at a high speed via a vacuum pump (310) and then transferred to a heat exchanger (400) as described below.

[0053] The step (S40) of primary cooling using cold energy by passing the gas with reduced volume through the adsorption and desorption of carbon dioxide through a heat exchanger (400) to exchange heat with LNG can lower the temperature of the gas with reduced volume through the adsorption and desorption of carbon dioxide to a predetermined temperature range.

[0054] Referring to FIG. 1, the gas with reduced volume through the adsorption system (300) is transferred to a heat exchanger (400) and its temperature is lowered through primary cooling using the cold energy of the LNG. As described above, it may also be transferred to the heat exchanger (400) after being transferred at a rapid speed to the carbon dioxide storage tank (320) through the vacuum pump (310).

[0055] In the heat exchanger (400), the temperature of the gas can be lowered from a high temperature to a low temperature within a predetermined range through cold energy utilizing the phase change energy required for the LNG to vaporize. Specifically, in order to use LNG, it must be vaporized from a liquid state of -162°C into a gas within a range of 0°C or higher, and the gas of the present invention is first cooled using cold energy utilizing the phase change energy required at this time. After performing the first cooling, the temperature of the gas may be -50 to -30°C. Since carbon dioxide still exists as a gas under the above temperature range and atmospheric pressure conditions, an additional cooling process is required to obtain dry ice in a solid state, as described below.

[0056] According to a preferred embodiment of the present invention, in the first cooling step (S30), the LNG used for heat exchange is discharged as NG (natural gas) from the heat exchanger (400), and the NG is transferred to the flue gas cooling heat exchanger (100) to lower the temperature of the flue gas cooling heat exchanger (100), thereby lowering the temperature of the gas generated during the fossil fuel combustion process.

[0057] Specifically, referring to FIG. 1, LNG is introduced (X) into a heat exchanger (400), and the gas containing carbon dioxide is cooled first using the cold energy of the LNG. The LNG used for heat exchange can be vaporized into NG and transferred (Y) from the heat exchanger (400) to the flue gas cooling heat exchanger (100). Through this, the flue gas cooling heat exchanger (100) can be cooled first using NG containing a significant amount of cold energy, thereby lowering the temperature of the flue gas to a predetermined range. In this case, the process efficiency can be further improved by lowering the temperature of the high-temperature gas discharged from the flue gas cooling heat exchanger (100) to a predetermined range before performing the process (S10, S20, S30, S40, etc.) of the present invention. Afterwards, the NG can be transferred (Z2) to various places such as an LNG thermal power plant, an LNG reforming hydrogen refueling station, an LNG vessel, various other factories using LNG as fuel, district heating facilities, and waste incineration plants, and can be utilized effectively.

[0058] The step (S50) of separating and collecting carbon dioxide contained in the gas whose temperature has been lowered through primary cooling by sublimating it using a cold system (500) using liquid nitrogen to separate and collect it as solid dry ice is performed by sublimating (solidifying) the carbon dioxide into solid dry ice using a cold system (500) using liquid nitrogen without a separate pressurization process.

[0059] That is, the present invention can separate and collect carbon dioxide by sublimating it into solid dry ice through a nitrogen-based cooling system (500) without creating a low-temperature, high-pressure environment.

[0060] Referring to FIG. 1, a cold-heat system (500) using liquid nitrogen may include a high-pressure chamber (510); liquid nitrogen (520) contained within the high-pressure chamber (510); and an atmospheric pressure chamber (530) arranged so that at least a portion is contained in the liquid nitrogen (520), into which gas with a lowered temperature through primary cooling is introduced.

[0061] First, the high-pressure chamber (510) may be in an insulated state that blocks heat exchange with the outside. This can be formed through conventional methods used in the relevant technical field, for example, by injecting an insulating material, or by forming a vacuum insulated state in which the entire outer surface is surrounded by a vacuum insulating layer.

[0062] By blocking heat exchange with the outside, the temperature of liquid nitrogen, which is typically an ultra-low temperature of -200℃, can be maintained, thereby minimizing cold heat loss of liquid nitrogen and enabling the process to be performed stably even if the internal pressure temporarily increases due to phase changes of the liquid nitrogen.

[0063] Next, liquid nitrogen (520) can be contained inside the high-pressure chamber (510). At this time, the liquid nitrogen (520) can be contained at a level such that at least a portion of the atmospheric pressure chamber (530) is submerged. Preferably, it can be contained at a level such that at least 60% of the volume of the atmospheric pressure chamber (530) is submerged.

[0064] Next, the atmospheric pressure chamber (530) may be positioned so that at least a portion of it is contained in liquid nitrogen (520), and the gas whose temperature has been lowered through the primary cooling may be introduced into the atmospheric pressure chamber (530). In this case, heat exchange occurs between the carbon dioxide contained in the gas introduced into the atmospheric pressure chamber (530) and the liquid nitrogen (520), and the carbon dioxide can be sublimated (solidified) through cold heat utilizing the phase change energy required for the liquid nitrogen (520) to vaporize during the heat exchange, thereby obtaining dry ice in a solid state.

[0065] At this time, two or more atmospheric pressure chambers (530) may be included to be connected within the cold / heat system (500). The number of connected atmospheric pressure chambers (530) may be determined according to the amount of carbon dioxide to be processed per unit time. For example, if the amount of carbon dioxide to be processed is large, the number of atmospheric pressure chambers (530) may be increased.

[0066] Preferably, 2 to 5 may be included in a connected arrangement. In this case, there is an advantage that heat exchange between the liquid nitrogen (520) and the atmospheric pressure chamber (530) can be performed smoothly.

[0067] Additionally, referring to FIG. 1, a cold energy system (500) using liquid nitrogen is connected to a liquid nitrogen generator (600), and liquid nitrogen (520) transferred (A) and received from the liquid nitrogen generator (600) into a high-pressure chamber (510) can be transferred (B) to the liquid nitrogen generator (600) after being vaporized through the heat exchange. Afterward, it can be liquefied back into liquid nitrogen (520) through the liquid nitrogen generator (600) and transferred (A) into the high-pressure chamber (510) to be used for heat exchange. In this way, the present invention allows liquid nitrogen (520) to circulate between the cold energy system (500) using liquid nitrogen and the liquid nitrogen generator (600), thereby efficiently cooling carbon dioxide using the cold energy of the liquid nitrogen (520) to obtain dry ice in a solid state.

[0068] Meanwhile, about 60% of the gas flowing into the cold energy system (500) using liquid nitrogen may be carbon dioxide, and about 40% may be excess gases such as nitrogen and oxygen. As described above, carbon dioxide is separated and captured as dry ice, but the remaining nitrogen and oxygen can be discharged in a gaseous state because their liquefaction points are low, at -209°C and -218°C respectively at atmospheric pressure. The gas discharged in this way is a low-temperature gas of -90 to -70°C, and the cold energy of the low-temperature gas may be used to lower the temperature of the exhaust gas or to condense and remove moisture from the exhaust gas. Specifically, referring to FIG. 1, it can be seen that the low-temperature gas discharged from the cold energy system (500) using liquid nitrogen may be transferred (C) to the exhaust gas cooling heat exchanger (100) to cool the exhaust gas or transferred (C) to condense and remove moisture from the exhaust gas. In addition, the low-temperature gas used to cool the exhaust gas may be discharged into the atmosphere (Z1). Through this, the present invention can utilize waste cold sources, thereby reducing the energy required for cooling exhaust gas or removing moisture condensation from exhaust gas.

[0069] According to a preferred embodiment of the present invention, after the step (S50) of separating and collecting dry ice, the present invention may further include a step (S60) of separating and collecting liquid carbon dioxide from dry ice through a pressurization process.

[0070] In this regard, FIG. 2 is a process diagram of a carbon dioxide capture system using cold heat according to a preferred embodiment of the present invention. Referring to FIG. 2, the present invention can perform a step (S50) of separating and capturing carbon dioxide into solid dry ice by sublimating it, and then moving the dry ice to a depressurization system (700) to perform a step (S50) of separating and capturing liquid carbon dioxide from the dry ice through a depressurization and heating process.

[0071] Typically, obtaining liquid carbon dioxide requires compressing and cooling carbon at room temperature, a process that consumes a significant amount of electricity. Accordingly, the present invention enables the efficient production of liquid carbon dioxide by utilizing dry ice and performing a relatively simple additional process, thereby liquefying dry ice without separate temperature control, solely through a process of depressurizing or increasing the temperature.

[0072] Ultimately, the present invention can improve heat transfer energy efficiency by significantly reducing the volume of gas cooled in the pretreatment process, thereby reducing the amount of heat required for cooling through the high concentration of carbon dioxide in the incoming gas. Furthermore, through a multi-stage cooling process using LNG (liquefied natural gas) and liquid nitrogen, carbon dioxide can be separated and captured by sublimating (solidifying) it using cold energy through a relatively simple process without high-pressure conditions. In addition, energy saving is possible by effectively recycling or circulating LNG and liquid nitrogen. Explanation of the symbols

[0074] 100 chimneys 200 capacitor 300 adsorption system 400 heat exchanger 500 Liquid Nitrogen Cooling System 600 Liquid Nitrogen Generator

Claims

Claim 1 A step of condensing and removing moisture contained in the gas generated during the combustion of fossil fuels; a step of adsorbing carbon dioxide contained in the moisture-removed gas using an adsorbent; a step of desorbing the carbon dioxide adsorbed on the adsorbent through a vacuum pump; a step of primary cooling of the high-concentration carbon dioxide gas using cold energy by passing the gas, whose volume has been reduced through the adsorption and desorption of carbon dioxide, through a heat exchanger to exchange heat with LNG; and a step of separating and collecting solid dry ice by sublimating carbon dioxide contained in the gas whose temperature has been lowered through the first cooling without a pressurization process using a cold energy system utilizing liquid nitrogen; wherein the step of condensing and removing moisture is performed using the cold energy of the low-temperature gas discharged from the cold energy system utilizing liquid nitrogen, and in the first cooling step, the LNG used in the heat exchange is discharged as NG from the heat exchanger, and the NG is moved to an exhaust gas cooling heat exchanger to lower the temperature of the exhaust gas cooling heat exchanger, thereby lowering the temperature of the gas generated in the fossil fuel combustion process, and in the step of separating and collecting dry ice, the cold energy system utilizing liquid nitrogen comprises: a high-pressure chamber; and liquid nitrogen contained inside the high-pressure chamber; A carbon dioxide capture system utilizing cold energy, comprising: an atmospheric pressure chamber arranged so as to be contained in at least a portion of the liquid nitrogen, into which a gas whose temperature has been lowered through primary cooling is introduced; wherein heat exchange occurs between the high-concentration carbon dioxide gas contained in the gas whose temperature has been lowered through primary cooling introduced into the atmospheric pressure chamber and the liquid nitrogen, and wherein carbon dioxide is sublimated through cold energy utilizing the phase change energy required for the liquid nitrogen to vaporize during the heat exchange to obtain dry ice in a solid state. Claim 2 delete Claim 3 In claim 1, in the adsorption step, the adsorbent is a porous support, a carbon dioxide capture system using cold heat. Claim 4 A carbon dioxide capture system using cold heat according to claim 1, wherein the adsorption step is such that the carbon dioxide is physically dry-adsorbed onto the adsorbent, and nitrogen and oxygen are discharged, thereby reducing the total volume of the gas from which moisture has been removed and increasing the concentration of carbon dioxide contained in the gas from which moisture has been removed. Claim 5 A carbon dioxide capture system using cold energy according to claim 1, wherein in the adsorption step, the adsorption is performed in an adsorption system comprising at least one porous bed packed with the adsorbent, and is performed by a vacuum swing absorption (VSA) or pressure swing absorption (PSA) method. Claim 6 In claim 5, the adsorption step is a carbon dioxide capture system utilizing cold heat in which carbon dioxide adsorption is performed through multiple continuous processes by connecting two or more of the adsorption systems in parallel. Claim 7 delete Claim 8 delete Claim 9 A carbon dioxide capture system utilizing cold energy according to claim 1, wherein the atmospheric pressure chambers are included to be connected and arranged in two or more places within the cold energy system. Claim 10 A carbon dioxide capture system using cold energy according to claim 1, wherein the cold energy system using liquid nitrogen is connected to a liquid nitrogen generator, and the liquid nitrogen contained inside the high-pressure chamber is transferred to the liquid nitrogen generator after being vaporized through the heat exchange, and then circulated by being transferred back into the high-pressure chamber after being liquefied into liquid nitrogen through the liquid nitrogen generator. Claim 11 A carbon dioxide capture system using cold heat according to claim 1, further comprising the step of separating and capturing liquid carbon dioxide from the dry ice through a depressurization and heating process after the step of separating and capturing with the dry ice.

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