Marine carbon dioxide capture system

Abstract

The marine carbon dioxide collection system according to the present invention includes a carbon dioxide collection device that removes carbon dioxide contained in the exhaust gas of the main engine, a low-temperature steam generation unit that generates steam by heat exchange with the exhaust gas of the auxiliary engine, and a low-temperature steam supply line that supplies the steam generated in the low-temperature steam generation unit to the carbon dioxide collection device.

Description

Technical Field

[0001] This application claims the benefit of priority based on Korean Patent Application No. 10-2023-0030726 filed on March 8, 2023, Korean Patent Application No. 10-2023-0093363 filed on July 18, 2023, Korean Patent Application No. 10-2024-0032863 filed on March 7, 2024, and Korean Patent Application No. 10-2024-0032864 filed on March 7, 2024, and all the contents disclosed in the documents of the corresponding Korean patent applications are incorporated herein by reference in their entirety.

[0002] The present invention relates to a carbon dioxide capture system for ships, and more particularly, to a carbon dioxide capture system for ships that generates low-temperature steam using the waste heat of exhaust gas, raises the temperature of an absorbent to the regeneration temperature, and separates carbon dioxide.

Background Art

[0003] Maritime transportation is responsible for approximately 80% of the world's trade volume and is the most economical and common means of long-distance cargo transportation. The engines of large cargo ships and cruise ships generally use heavy oil with a high sulfur content. When heavy oil with a high sulfur content as described above is used as fuel, the exhaust gas contains a large amount of carbon dioxide (hereinafter referred to as CO2) and sulfur dioxide (hereinafter referred to as SO2). These pollutants are not only harmful to the human body but also cause environmental pollution when directly discharged into the atmosphere without filtration.

[0004] Therefore, the United Nations has entrusted the International Maritime Organization (hereinafter referred to as IMO) with the issue of exhaust gas emission regulations for ships navigating all seas around the world. IMO is promoting various exhaust gas reduction methods with the goal of reducing the emissions of environmental pollutants in exhaust gas discharged from ships by 40% compared to 2008 by 2030 and 50% by 2050.

[0005] In South Korea, a medium- to long-term roadmap has been established and research projects are underway to achieve the greenhouse gas reduction target set by the IMO for 2030. Accordingly, as part of proactive technological development to reduce greenhouse gas emissions from ships, the shipping and shipbuilding industries are being called upon to develop solutions for reducing emissions of carbon dioxide and sulfur dioxide, representative pollutants found in exhaust gases, in order to develop environmentally friendly ships.

[0006] To remove carbon dioxide, exhaust gases are passed through a carbon dioxide absorbent to remove the carbon dioxide from the exhaust gases. Since using a new carbon dioxide absorbent each time would increase costs, including disposal and shipping costs, it can be recycled and reused.

[0007] However, when reusing the absorbent, there is a problem in that the difference between the absorbent's regeneration temperature and the carbon dioxide absorption temperature is large, resulting in the generation of even more carbon dioxide during heating for regeneration, and thus increasing the cost of heating the absorbent. [Overview of the project] [Problems that the invention aims to solve]

[0008] The present invention aims to provide a marine carbon dioxide capture system that generates low-temperature steam using exhaust gas waste heat to raise the temperature of the carbon dioxide absorbent to the regeneration temperature of the absorbent, thereby saving fuel consumed for the regeneration of the absorbent.

[0009] Another objective of this invention is to improve the efficiency of the carbon dioxide absorption process by lowering the temperature of the exhaust gas used in the carbon dioxide absorption process.

[0010] The present invention also aims to provide a marine carbon dioxide capture system that can supply low-temperature steam to a reboiler, prevents the performance of amine-based absorbents from degrading at high temperatures, and is suitable for amine-based absorbents.

[0011] The present invention also aims to provide a marine carbon dioxide capture system that can generate low-temperature steam using the waste heat of high-temperature exhaust gas generated in a methane oxidation catalytic reactor, thereby saving fuel consumed for the regeneration of the absorbent. [Means for solving the problem]

[0012] According to one embodiment of the present invention, a marine carbon dioxide collection system includes a carbon dioxide collection device that removes carbon dioxide contained in the exhaust gas of the main engine, a low-temperature steam generation unit that generates steam by heat exchange with the exhaust gas of the auxiliary engine, and a low-temperature steam supply line that supplies the steam generated in the low-temperature steam generation unit to the carbon dioxide collection device.

[0013] According to one embodiment of the present invention, the system further includes a methane oxidation catalyst reactor provided between the auxiliary engine and the low-temperature steam generating unit, which removes methane contained in the exhaust gas of the auxiliary engine, and the low-temperature steam generating unit can generate steam by exchanging heat with the exhaust gas that has passed through the methane oxidation catalyst reactor.

[0014] According to one embodiment of the present invention, the low-temperature steam supply line may be provided with a steam tank for separating the liquid phase water in the steam.

[0015] According to one embodiment of the present invention, the low-temperature steam generating unit is a sub-economizer, and the steam may be low-temperature steam having a temperature condition of 100°C or more and less than 165°C under pressure conditions of less than 6 barg.

[0016] According to one embodiment of the present invention, a first steam valve provided on the low-temperature steam supply line may be included for adjusting the amount of steam supplied to the carbon dioxide collection device.

[0017] According to one embodiment of the present invention, the present invention may include a main economizer that generates main steam by heat exchange with the exhaust gas of the main engine, a boiler that generates high-temperature boiler steam by receiving the main steam preheated by the main economizer, and a second steam valve provided on an additional supply line that supplies the high-temperature boiler steam generated by the boiler to the carbon dioxide capture device, which converts the high-temperature boiler steam to low-temperature steam.

[0018] According to one embodiment of the present invention, the present invention may further include: a main economizer provided on the main engine exhaust line connecting the main engine and the carbon dioxide collection device, which generates main steam by exchanging heat with the exhaust gas of the main engine; a second low-temperature steam generating unit provided on the main engine exhaust line at the rear end of the main economizer, which generates second steam by exchanging heat with the main engine exhaust gas that has passed through the main economizer; and a second low-temperature steam supply line that supplies the second steam generated in the second low-temperature steam generating unit to the carbon dioxide collection device.

[0019] According to one embodiment of the present invention, the main engine or the auxiliary engine can use dual fuel.

[0020] According to one embodiment of the present invention, the present invention includes a carbon dioxide collection device that removes carbon dioxide contained in the exhaust gas of the main engine, a main economizer that generates main steam by heat exchange with the exhaust gas of the main engine, a combined low-temperature steam generation unit that generates steam by receiving both the exhaust gas of the main engine and the exhaust gas of the auxiliary engine that have passed through the main economizer, and a low-temperature steam supply line that supplies the steam generated in the combined low-temperature steam generation unit to the carbon dioxide collection device.

[0021] According to one embodiment of the present invention, the present invention further includes a boiler that receives main steam preheated by the main economizer to generate high-temperature boiler steam, and at least a portion of the boiler exhaust gas generated by the boiler can be supplied to the combined low-temperature steam generating unit.

[0022] According to one embodiment of the present invention, a marine carbon dioxide collection system includes a carbon dioxide collection device that removes carbon dioxide contained in the exhaust gas of the main engine, a low-temperature steam generation unit that generates steam by heat exchange with the exhaust gas of an auxiliary engine, and a low-temperature steam supply line that supplies the steam generated in the low-temperature steam generation unit to the carbon dioxide collection device, wherein at least a portion of the auxiliary engine exhaust gas that has passed through the low-temperature steam generation unit merges into a main engine exhaust line connecting the main engine and the carbon dioxide collection device.

[0023] According to one embodiment of the present invention, the system further includes a main economizer provided in the main engine exhaust line, which generates main steam by exchanging heat with the exhaust gas of the main engine, and at least a portion of the auxiliary engine exhaust gas that has passed through the low-temperature steam generation section can merge with the main engine exhaust line at the rear end of the main economizer.

[0024] According to one embodiment of the present invention, the present invention further includes a boiler that receives a supply of main steam preheated by the main economizer to generate high-temperature boiler steam, wherein at least a portion of the boiler exhaust gas generated by the boiler can be joined to the main engine exhaust line at the rear end of the main economizer.

[0025] According to an embodiment of the present invention, a main economizer provided on the main engine exhaust line that exchanges heat with the exhaust gas of the main engine to generate main steam, and a branch line branched from the main engine exhaust line at the rear end of the main economizer and connected to an auxiliary engine exhaust line that connects the auxiliary engine and the low-temperature steam generation unit, and at least a part of the main engine exhaust gas that has passed through the main economizer can be supplied to the low-temperature steam generation unit through the branch line.

[0026] According to an embodiment of the present invention, the main engine or the auxiliary engine can use liquid fuel.

Effects of the Invention

[0027] According to the present invention, in order to raise the temperature of the absorbent to the regeneration temperature of the carbon dioxide absorbent, low-temperature steam is generated using the exhaust gas waste heat, and the fuel consumed for the regeneration of the absorbent can be saved.

[0028] In addition, the carbon dioxide further generated for carbon dioxide capture can be reduced.

[0029] In addition, the temperature of the exhaust gas used in the carbon dioxide absorption process can be lowered, and the efficiency of the carbon dioxide absorption process can be improved.

[0030] In addition, low-pressure steam can be supplied to the reboiler, and it is possible to prevent the performance of the absorbent from deteriorating due to high temperature.

[0031] In addition, in order to raise the temperature of the absorbent to the regeneration temperature of the carbon dioxide absorbent, low-temperature steam is generated using the waste heat of the high-temperature exhaust gas generated in the methane oxidation catalytic reactor, and the fuel consumed for the regeneration of the absorbent can be saved.

Brief Description of the Drawings

[0032] [Figure 1]This figure illustrates a shipboard carbon dioxide collection system according to a first embodiment of the present invention. [Figure 2] This is a diagram illustrating a shipborne carbon dioxide collection device according to the first embodiment of the present invention. [Figure 3] This table illustrates the temperature-dependent loss rate of amine-based absorbers. [Figure 4] This table shows the conditions for saturated steam. [Figure 5] This diagram illustrates the steam-water circulation path of a marine carbon dioxide collection system according to a first embodiment of the present invention. [Figure 6] This figure illustrates a shipboard carbon dioxide collection system according to a second embodiment of the present invention. [Figure 7] This figure illustrates a shipboard carbon dioxide collection system according to a third embodiment of the present invention. [Figure 8] This figure illustrates a shipboard carbon dioxide collection system according to a fourth embodiment of the present invention. [Figure 9] This figure illustrates a shipboard carbon dioxide collection system according to a fifth embodiment of the present invention. [Figure 10] This figure illustrates a shipboard carbon dioxide collection system according to a sixth embodiment of the present invention. [Figure 11] This figure illustrates a shipboard carbon dioxide collection system according to one of the optimal embodiments of the present invention. [Figure 12] This figure illustrates a shipboard carbon dioxide collection system according to another optimal embodiment of the present invention. [Modes for carrying out the invention]

[0033] Hereinafter, some embodiments of the present invention will be described in detail with reference to illustrative drawings. When assigning reference numerals to the components in each drawing, it should be noted that, as far as possible, the same component will have the same reference numeral even if it is shown in other drawings. Furthermore, when describing embodiments of the present invention, if it is determined that a specific description of a related known configuration or function would hinder understanding of the embodiments of the present invention, such a detailed description will be omitted.

[0034] Furthermore, in describing the components of embodiments of the present invention, terms such as first, second, A, B, (a), (b), etc., may be used. Such terms are used to distinguish a component from other components, and the terms do not limit the nature, order, or sequence of the component. When it is stated that a component is “connected,” “joined,” or “connected” to another component, it should be understood that the component may be directly connected to or connected to other components, but that other components may also be “connected,” “joined,” or “connected” between each component.

[0035] In this specification, the front-back, left-right, and up-down directions are terms used for convenience of explanation and may be directions perpendicular to each other.

[0036] <First Embodiment> Figure 1 is a diagram illustrating an exhaust gas treatment procedure including a marine carbon dioxide collection system according to a first embodiment of the present invention. The marine carbon dioxide collection system includes a carbon dioxide collection device 140 that removes carbon dioxide contained in the exhaust gas of the main engine 111, a low-temperature steam generation unit 150 that generates steam by heat exchange with the exhaust gas of the auxiliary engine 121, and a low-temperature steam supply line 155 that supplies the steam generated in the low-temperature steam generation unit 150 to the carbon dioxide collection device 140.

[0037] The exhaust gases emitted from marine engines 111 and 121 contain air pollutants and greenhouse gases such as nitrogen oxides (NOx), sulfur oxides (SOx), and carbon dioxide (CO2). To reduce pollutants in the exhaust gases, pretreatment methods include reducing the sulfur content in the fuel by using alternative fuels such as methanol, liquefied natural gas (LNG), or emulsion fuel instead of diesel, thereby reducing emissions of nitrogen oxides, sulfur oxides, and particulate matter (PM).

[0038] As a post-treatment method, the pollutants can be removed through a process to remove each individual contaminant. This may include a nitrogen oxide absorption unit (not shown) for removing nitrogen oxides, a sulfur oxide removal unit (not shown) for removing sulfur oxides (SOx), and a carbon dioxide capture device 140 for removing carbon dioxide.

[0039] Depending on the type of fuel supplied to the ship engines 111 and 121, the pollutants generated may differ, and the nitrogen oxide absorber, sulfur oxide absorber, and carbon dioxide capture device 140 may all be included or some may be omitted.

[0040] The nitrogen oxide absorption section can remove nitrogen oxides from the exhaust gas by supplying an absorbent liquid, such as ammonia (NH3), into the chamber. Although the nitrogen oxide absorption section is not shown in Figure 1, the exhaust gas that has passed through the nitrogen oxide removal section can be supplied to the sulfur oxide removal section.

[0041] Sulfur oxide removal units, used to reduce industrially emitted sulfur oxides (SOx), have been used on land for about 100 years, but their installation on ships has only been in the last 30 years. Ships differ from land-based scrubbers due to spatial constraints.

[0042] Sulfur oxides (SOx) in exhaust gases are acidic substances. To neutralize them, alkaline substances may be used as sulfur oxide absorbents, or seawater, a naturally alkaline substance, may be used as a sulfur oxide absorbent. Seawater exhibits weak alkalinity due to the bicarbonates it contains, and the solubility of sulfur oxides (SOx) in seawater containing bicarbonates is approximately 2 to 3 times higher than in fresh water.

[0043] Seawater (SW) is introduced into the ship and injected into the chamber of the sulfur oxide removal unit, which is supplied with exhaust gases. It reacts with sulfur oxides (SOx) such as sulfur dioxide (SO2) and sulfur trioxide (SO3) in the exhaust gases, converting them into sulfurous acid (H2SO3) or sulfuric acid (H2SO4) aqueous solutions.

[0044] The wastewater discharged from the sulfur oxide removal unit contains sulfuric acid or trioxidant, has high acidity, and contains pollutants other than sulfuric acid and trioxidant. A water treatment system may be further provided to adjust the acidity and remove pollutants before discharging this wastewater into the sea.

[0045] On the other hand, carbon dioxide (CO2) does not dissolve in seawater as much as sulfuric acid and passes through the sulfur oxide removal section, but the exhaust gas still has a high carbon dioxide (CO2) content and requires further removal using a carbon dioxide absorbent.

[0046] To remove carbon dioxide, a carbon dioxide absorbent that reacts with carbon dioxide is required. Examples of carbon dioxide absorbents include amino acids containing amine groups, amino acid pseudo-molecules containing amines and carboxyl groups, or their alkali metal salts. When such substances are dissolved in water along with a catalyst and carbon dioxide is passed through, they can combine with carbon dioxide to produce byproducts.

[0047] However, storing or processing absorbents that have collected carbon dioxide requires separate storage space and processing costs. While it is possible to regenerate and reuse the absorbents, there is a large difference between the regeneration temperature of the absorbents and the carbon dioxide absorption temperature, requiring heat for regeneration. If boiler fuel is used for this heat generation of absorbents, it generates even more carbon dioxide, increasing the cost of regenerating the absorbents.

[0048] Referring to Figure 2, the carbon dioxide collection device 140 of the present invention will be described. The carbon dioxide collection device 140 may include a supply gas cooler 148 for cooling exhaust gas to the absorption temperature required for carbon dioxide absorption, a carbon dioxide absorption chamber 146 to which a carbon dioxide absorbent supplied from an absorbent tank 149 and exhaust gas whose temperature has been regulated via the supply gas cooler 148 are supplied, an absorbent regeneration chamber 141 for regenerating the absorbent, a reboiler 142 for supplying heat for regenerating the absorbent, and an exhaust gas cleaning unit 147 for cleaning the exhaust gas discharged from the carbon dioxide absorption chamber 146.

[0049] In addition to the precooler 115 shown in Figure 1, a supply gas cooler 148 may be further provided within the carbon dioxide capture device 140. Alternatively, only one of the two, the precooler 115 or the supply gas cooler 148, may be provided. To increase carbon dioxide absorption efficiency, exhaust gas supplied along the main engine exhaust line ML connecting the main engine 111 and the carbon dioxide capture device 140 flows into the supply gas cooler 148 and can be adjusted to the required absorption temperature (for example, amine-based absorbents are approximately 30-40°C) depending on the type of carbon dioxide absorbent. However, in some cases, only one of the two, the precooler 115 or the supply gas cooler 148, may be present, so the number of coolers is not limited.

[0050] The carbon dioxide absorption chamber 146 includes an exhaust gas inlet into which exhaust gas containing carbon dioxide flows, an absorbent supply section into which recycled carbon dioxide absorbent is supplied, a drain outlet into which waste absorbent that has absorbed carbon dioxide is discharged and flows into the absorbent regeneration chamber 141, and an exhaust gas outlet into which exhaust gas from which carbon dioxide has been removed is discharged.

[0051] The exhaust gas inlet is located at the lower end of the side of the carbon dioxide absorption chamber 146, and the exhaust gas outlet is located on the upper side, allowing the exhaust gas to move from the bottom to the top of the carbon dioxide absorption chamber 146.

[0052] The system may include an injection unit that injects an absorbent into the carbon dioxide absorption chamber 146. The injection unit includes a nozzle that injects the absorbent in the form of fine particles and supplies it to the exhaust gas in the carbon dioxide absorption chamber 146.

[0053] The absorbent can be an amine-based absorbent, and may include at least one of MEA (Mono Ethanol Amine), MDEA (Methyl Diethanol Amine), DEA (Diethanol Amine), or DGA (Diglycol Amine). Only representative amine-based absorbents are mentioned; other forms of amine-based absorbents may also be used.

[0054] Amine-based absorbents have excellent carbon dioxide absorption rates in a temperature range of approximately 30-40°C. Therefore, it is preferable to maintain the temperature (absorption temperature) inside the carbon dioxide absorption chamber 146 of the carbon dioxide collection device 140 at approximately 30-40°C. For this purpose, the aforementioned supply gas cooler 148 can be used.

[0055] The injection unit can be positioned above the carbon dioxide absorption chamber 146. By injecting the absorbent from above the carbon dioxide absorption chamber 146, the contact area with the exhaust gas can be maximized.

[0056] After carbon dioxide is removed from the absorbent regeneration chamber 141, the exhaust gas from which carbon dioxide has been removed can be discharged into the air after being washed again with water in the exhaust gas cleaning unit 147 to remove pollutants.

[0057] Furthermore, carbon dioxide in the exhaust gas, dissolved by the absorbent, can be supplied to the absorbent regeneration chamber 141 via a drain port located at the bottom of the carbon dioxide absorption chamber 146.

[0058] In the absorbent regeneration chamber 141, carbon dioxide contained in the absorbent is separated by heating it to a high temperature and vaporizing it. The regeneration temperature at which carbon dioxide is separated in the absorbent regeneration chamber 141 is approximately 100-120°C, which is more than 60°C higher than the absorption temperature (30-40°C). Therefore, external heat supply is necessary for the regeneration of the absorbent, and the absorbent can be heated by the reboiler 142. However, further carbon dioxide may be generated during the combustion process of the reboiler 142, and the efficiency of the entire system may decrease depending on the amount of reboiler 142 used.

[0059] To compensate for the difference between the absorption temperature and the regeneration temperature, an absorbent heat exchanger 145 is provided that exchanges heat between an absorbent recovery line 143, which absorbs carbon dioxide from the carbon dioxide absorption chamber 146 and supplies it to the absorbent regeneration chamber 141, and an absorbent supply line 144, which supplies the absorbent regenerated in the absorbent regeneration chamber 141 to the carbon dioxide absorption chamber 146. This allows for compensation of the temperature difference between the two chambers 146 and 141.

[0060] In other words, the temperature can be compensated for by heat exchange between the low-temperature absorbent passing through the absorbent recovery line 143 and the high-temperature absorbent passing through the absorbent supply line 144, and the temperature of the absorbent supplied to the absorbent regeneration chamber 141 can be raised to a level of 70-90°C.

[0061] However, even with heat exchange in the absorbent heat exchanger 145, it is difficult to meet the required regeneration temperature in the absorbent regeneration chamber 141. Therefore, a reboiler 142 can be used in the absorbent regeneration chamber 141 to raise the absorbent to the regeneration temperature. The reboiler 142 uses steam to heat the absorbent to the regeneration temperature. A saturated steam state is used to maximize the energy of the steam. The steam supplied to the reboiler 142 can be at or above the regeneration temperature to raise the absorbent supplied to the absorbent regeneration chamber 141 from 70-90°C to the regeneration temperature of 100-120°C. Considering the heating efficiency, the higher the steam temperature, the faster the temperature of the absorbent can be raised.

[0062] However, amine-based absorbents denature at high temperatures, and after a certain period, they become difficult to reuse and require replacement. Therefore, if the steam heated by the reboiler 142 is excessively hot, the denature of the absorbent may be accelerated. Figure 3 is a graph illustrating the rate at which amine-based absorbents denature and are lost due to temperature. The absorbent can contain components such as MEA (Mono Ethanol Amine), MDEA (Methyl Diethanol Amine), DEA (Diethanol Amine), and DGA (Diglycol Amine), and can exhibit different properties depending on the ratio.

[0063] While the loss rate varies depending on the type and mixing ratio of the absorbent, loss begins at approximately 120-150°C, and the loss of most absorbents increases significantly above 150-175°C.

[0064] Therefore, it is preferable to use low-temperature steam of 100°C to less than 165°C for the temperature of the absorbent supplied to the reboiler 142 in order to improve absorbent heating efficiency and protect against absorbent loss.

[0065] Figure 4 is a table showing saturated steam conditions, where the temperature required to form saturated steam at a specific pressure can be confirmed. To form saturated steam within the regeneration temperature range described above, low-temperature steam with a temperature range of 100°C to less than 165°C can be generated under pressure conditions of less than 6 barg. Preferably, saturated steam L with a temperature range of 134 to 152°C can be used under a pressure of 2 to 4 barg.

[0066] The higher the steam temperature, the greater the energy storage capacity, allowing for the transfer of large amounts of energy with a small amount of steam, and thus reducing the size of the piping. Therefore, the steam supplied by onboard boilers is generally 165°C or higher and 6 barg or higher. This is relatively high temperature compared to the steam required for absorbent regeneration and is referred to as high-temperature steam. Conversely, the steam required for absorbent regeneration is generally relatively lower temperature than the steam supplied by the onboard boilers and is referred to as low-temperature steam.

[0067] However, when the high-temperature steam generated by existing boilers is used directly for the regeneration of the absorbent, the absorbent is exposed to temperatures above 165°C, which can lead to a high rate of absorbent loss. The present invention utilizes waste heat from exhaust gas to generate low-temperature steam, thereby reducing the absorbent loss rate and extending the lifespan of the absorbent. This low-temperature steam is then supplied to the reboiler 142 of the carbon dioxide capture device 140 via a low-temperature steam supply line 155. The low-temperature steam supply line 155 is defined as a piping line connecting the low-temperature steam generation unit 150 to the reboiler 142 of the carbon dioxide capture device 140.

[0068] To improve efficiency in the absorbent regeneration chamber 141, at least a portion of the carbon dioxide-containing absorbent flowing in from the top of the absorbent regeneration chamber 141 can be branched via the regeneration branch line 131, heat-exchanged with the relatively high-temperature regenerated absorbent in the absorbent supply line 144 in the regeneration heat exchanger 132, and then resupplied to the absorbent regeneration chamber 141 via the resupply line 133.

[0069] The carbon dioxide gas separated from the absorbent regeneration chamber 141 can then be stored after undergoing a carbon dioxide liquefaction process or used where needed.

[0070] Referring to Figure 1, the low-temperature steam generation unit 150 generates steam by exchanging heat with the exhaust gas of the auxiliary engine 121, and the steam generated in the low-temperature steam generation unit 150 is supplied to the reboiler 142 of the carbon dioxide capture device 140 via the low-temperature steam supply line 155. The temperature of the exhaust gas from the main engine 111 is about 250 degrees Celsius, and the temperature of the exhaust gas from the auxiliary engine 121 is 300 to 400 degrees Celsius, so utilizing the waste heat from the exhaust gas of the auxiliary engine 121 is most preferable in terms of energy efficiency. Therefore, the low-temperature steam generation unit 150 utilizes the exhaust gas from the auxiliary engine 121.

[0071] The low-temperature steam generation unit 150 may also be a sub-economizer 152 that generates low-temperature steam using the waste heat from the exhaust gas of the auxiliary engine 121.

[0072] The main engine 111 is the primary power source for the operation of the ship, while the auxiliary engine 121 operates independently of the main engine 111 and is a power generation engine that supplies electricity to other parts of the ship. The auxiliary engine 121 does not produce as much exhaust gas as the main engine 111, and depending on the type of fuel, the exhaust gas treatment process to remove substances such as carbon dioxide and sulfur dioxide from the exhaust gas may be omitted. For example, in the case of a ship that uses LNG as fuel or a dual-fuel (gas / diesel) ship, the exhaust gas from the auxiliary engine 121 can be released into the atmosphere independently of the exhaust gas from the main engine 111.

[0073] The waste heat from the exhaust gas of the auxiliary engine 121 can be utilized to generate low-temperature steam in the sub-economizer 152. The low-temperature steam generated in the sub-economizer 152 can have a temperature range of 100°C to less than 165°C under a pressure of less than 6 barg. Figure 1 illustrates that the exhaust gas generated by the auxiliary engine 121 branches off from the exhaust gas discharge pipe 123 and is supplied to the sub-economizer 152 via the exhaust gas supply pipe 124, but the sub-economizer 152 may be provided on the exhaust gas discharge pipe 123, and is not limited to what is shown in Figure 1.

[0074] The low-temperature steam generated by the sub-economizer 152 can pass through the steam tank 153. If water is mixed into the steam, efficiency will decrease, so the liquid phase water can be removed in the steam tank 153, and after the water is removed, only saturated steam can be supplied to the reboiler 142. The steam tank 153 can be located on the low-temperature steam supply line 155.

[0075] The waste heat from the exhaust gas generated when the main engine 111 is running can be used to generate high-temperature steam in the main economizer 112 and boiler 154. The main economizer 112 utilizes the waste heat from the main engine 111 to raise the temperature of the water, and the boiler 154 can generate high-temperature steam using the steam / water preheated in the main economizer 112. The high-temperature steam generated in boiler 154 can be supplied to other demand points within the ship. In addition, the high-temperature steam from boiler 154 can be converted to low-temperature steam by lowering its temperature and supplied to reboiler 142. This will be explained further later, with reference to the second steam valve V2.

[0076] After generating high-temperature steam in the main economizer 112, the exhaust gas discharged into the exhaust gas discharge pipe 114 is still at a high temperature. Therefore, it can be cooled to the absorption temperature in the precooler 115 before being supplied to the carbon dioxide capture device 140. The higher the temperature of the exhaust gas supplied to the precooler 115, the more heat is wasted, requiring a larger volume of seawater to be supplied, which also causes energy loss. Methods for reusing this energy will be explained again later.

[0077] Figure 1 illustrates that exhaust gas generated by the main engine 111 branches off from the exhaust gas discharge pipe 114 and is supplied to the carbon dioxide capture device 140 via the exhaust gas supply pipe 119. However, the carbon dioxide capture device 140 may be installed on the exhaust gas discharge pipe 114, and the model is not limited to what is shown in Figure 1.

[0078] The first embodiment can be applied when the main engine 111 or the auxiliary engine 121 uses dual fuel (gas / diesel). In the first embodiment, low-temperature steam can be generated using the waste heat of the exhaust gas from the auxiliary engine 121 and used for regenerating the absorbent. In the first embodiment, at least a portion of the exhaust gas from the main engine 111 can be supplied to the carbon dioxide capture device 140.

[0079] Figure 5 illustrates the steam-water circulation path of a marine carbon dioxide capture system according to the first embodiment of the present invention. The steam-water circulation path is similarly applicable to all of the remaining embodiments.

[0080] The amount of heat in the exhaust gas produced by the auxiliary engine 121 may vary depending on the ambient temperature, fuel characteristics, and the amount of electricity used under the ship's operating conditions. The amount of steam produced by the sub-economizer 152 may be greater than the amount of steam required by the reboiler 142. To prevent excessive steam supply, a first steam valve V1 may be included to divert and discharge excess steam supplied from the steam tank 153 to the reboiler 142. The first steam valve V1 is located on the low-temperature steam supply line 155 and can adjust the amount of steam supplied from the carbon dioxide capture device 140 to the reboiler 142. The first steam valve V1 may be in the form of a 3-way valve. The first steam valve V1 can be located in the position shown in Figure 1, and its location is not limited. The excess steam generated by the sub-economizer 152 is supplied to the drain cooler 157 via the first steam valve V1 for liquefaction, stored in the feedback water tank 158, and then supplied to the boiler 154 or steam tank 153 if necessary. Alternatively, the excess steam generated by the sub-economizer 152 may be supplied to other users for use.

[0081] On the other hand, if the amount of steam generated by the sub-economizer 152 is less than the amount of heat required by the reboiler 142, a boiler 154 can be used to supply additional steam. Boiler 154 may be a dedicated boiler 154 for the reboiler 142, or it may be a boiler 154 that supplies high-temperature steam to other equipment on board the ship. Boiler 154 can burn additional fuel and generate steam independently of the engine. Boiler 154 can also generate high-temperature boiler steam by receiving the supply of main steam preheated by the main economizer 112. However, as mentioned above, when high-temperature steam above 165°C is used directly for the regeneration of the absorbent, the absorbent loss rate may be high, so a second steam valve V2 that converts the high-temperature boiler steam to low-temperature steam may be included.

[0082] The high-temperature boiler steam generated in boiler 154 at 165°C or higher is converted to low-temperature steam having a temperature range of 100°C to less than 165°C under pressure conditions of less than 6 barg as it passes through the second steam valve V2. Preferably, it is converted to low-temperature steam with a temperature range of 134 to 152°C under pressure of 2 to 4 barg.

[0083] Figure 5 shows the second steam valve V2 located on an additional supply line 159 connecting the boiler 154 and the low-temperature steam supply line 155, but is not limited to this. For example, the additional supply line 159 may be defined as a piping line directly connecting the boiler 154 and the reboiler 142 of the carbon dioxide capture device 140. That is, the low-temperature steam supply line 155 via the sub-economizer 152 and the additional supply line 159 via the boiler 154 may each be connected to the reboiler 142, or they may be integrated and connected to a single line.

[0084] Furthermore, if the amount of steam generated in boiler 154 and converted to low-temperature steam is greater than the amount of steam required by reboiler 142, the excess steam generated in boiler 154 can be discharged to drain cooler 157 via third steam valve V3. Alternatively, the excess steam generated in boiler 154 may be supplied to and used by other users.

[0085] In the reboiler 142, the low-temperature steam that has been heated by the absorbent can be liquefied into water, and a water recovery line 156 can be included to recover the liquefied water. Referring to the steam-water circulation path in Figure 5, excess steam generated in the sub-economizer 152 can be supplied to the drain cooler 157 via the first steam valve V1 for liquefaction, and excess steam generated in the boiler 154 can be supplied to the drain cooler 157 via the third steam valve V3 for liquefaction. Water stored in the feedback water tank 158 can be supplied to the boiler 154 or the steam tank 153 if necessary.

[0086] In the feedback water tank 158, the amount of water supplied to the steam tank 153 and the boiler 154 via feed water pumps P1 and P2 can be adjusted, respectively. Water can be supplied via circulation pumps P3 and P4 to ensure a stable water supply to the main economizer 112 and the sub-economizer 152. Water supplied to the steam tank 153, or water separated from the steam, can be supplied to the sub-economizer 152 via the first circulation pump P3. Water from the boiler 154 can be supplied to the main economizer 112 via the second circulation pump P4.

[0087] Instead of supplying water directly from the feedback water tank 158 to the sub-economizer 152 or main economizer 112, the water is supplied to the steam tank 153 or boiler 154, thereby maintaining a constant water level in the steam tank 153 and boiler 154 and ensuring stable steam generation. Furthermore, the amount of water supplied can be adjusted according to fluctuations in the amount of heat available from the exhaust gas to generate maximum steam.

[0088] However, if necessary, the system may be configured to supply water directly from the feedback water tank 158 to the sub-economizer 152 or the main economizer 112.

[0089] A water supply valve V4 may be included to adjust the amount of water supplied to the respective steam tanks 153 or boiler 154, depending on the available heat from the exhaust gas of the auxiliary engine 121. The water supply valve V4 can supply recovered water to the steam tanks 153 or boiler 154, depending on the available heat from the main economizer 112 and sub-economizer 152. Some losses may occur in the steam-water circulation path, and a water make-up valve may be included to supply additional water from an external feedback water tank to maintain a stable water level.

[0090] <Second Embodiment> Figure 6 illustrates a shipborne carbon dioxide collection system according to a second embodiment of the present invention. A marine carbon dioxide collection system may include a carbon dioxide collection device 140 that removes carbon dioxide contained in the exhaust gas of the main engine 111, a low-temperature steam generation unit 150 that generates steam by heat exchange with the exhaust gas of the auxiliary engine 121, a low-temperature steam supply line 155 that supplies the steam generated in the low-temperature steam generation unit 150 to the carbon dioxide collection device 140, a main economizer 112 provided on the main engine exhaust line ML connecting the main engine 111 and the carbon dioxide collection device 140 and generating main steam by heat exchange with the exhaust gas of the main engine 111, a second low-temperature steam generation unit 160 provided on the main engine exhaust line ML at the rear end of the main economizer 112 and generating second steam by heat exchange with the main engine exhaust gas that has passed through the main economizer 112, and a second low-temperature steam supply line 161 that supplies the second steam generated in the second low-temperature steam generation unit to the carbon dioxide collection device 140.

[0091] After generating high-temperature steam in the main economizer 112, the exhaust gas discharged into the exhaust gas discharge pipe 114 is still at a high temperature. Therefore, it can be cooled in the precooler 115 to the required absorption temperature for the carbon dioxide capture device 140 before being supplied to the carbon dioxide capture device 140. The higher the temperature of the exhaust gas supplied to the precooler 115, the more heat needs to be wasted, requiring a larger volume of seawater to be supplied, which also contributes to energy loss.

[0092] In the carbon dioxide capture system according to the second embodiment, a second low-temperature steam generation unit 160 is provided at the rear end of the main economizer 112 to further lower the temperature of the exhaust gas supplied to the precooler 115. This allows the waste heat of the main engine exhaust gas that has passed through the main economizer 112 to be reused in the second low-temperature steam generation unit 160. Therefore, the amount of low-temperature steam produced can be increased, and the temperature of the main engine exhaust gas supplied to the precooler 115 can be lowered. As the temperature of the main engine exhaust gas flowing into the precooler 115 is lower, the amount of cooling water (seawater) supplied to the precooler 115 can be reduced, thereby improving system efficiency.

[0093] The second low-temperature steam generation unit 160 may also be a second economizer, and the low-temperature steam generated in the second low-temperature steam generation unit 160 can be supplied to the reboiler 142 of the carbon dioxide capture device 140 via the second low-temperature steam supply line 161. Similar to Figure 6, the second low-temperature steam supply line 161 may merge with the low-temperature steam supply line 155, or it may be supplied individually to the reboiler 142 of the carbon dioxide capture device 140.

[0094] Furthermore, the carbon dioxide capture system according to the second embodiment may further include a third low-temperature steam generation unit 162 that generates third steam by heat exchange with boiler exhaust gas generated in the boiler 154, and a third low-temperature steam supply line 163 that supplies the third steam generated in the third low-temperature steam generation unit 162 to the carbon dioxide capture device 140. In the second embodiment, by providing another third low-temperature steam generation unit 162, the waste heat of the boiler exhaust gas generated in the boiler 154 can also be utilized to further increase the amount of low-temperature steam produced. The third low-temperature steam generation unit 162 may also be a third sub-economizer, and the low-temperature steam generated in the third low-temperature steam generation unit 162 can be supplied to the reboiler 142 of the carbon dioxide capture device 140 via the third low-temperature steam supply line 163. Similar to Figure 6, the third low-temperature steam supply line 163 may merge with the low-temperature steam supply line 155, or it may be supplied separately to the reboiler 142 of the carbon dioxide capture device 140.

[0095] The second embodiment is applicable to, but is not limited to, cases where the main engine 111 and auxiliary engine 121 use dual fuel (gas / diesel). In the second embodiment, in addition to the exhaust gas of the auxiliary engine 121, waste heat from the exhaust gases of the main engine 111 and boiler 154 is used, and low-temperature steam is generated by the respective low-temperature steam generating units and can be used for the regeneration of the absorbent. In the second embodiment, at least a portion of the exhaust gas of the main engine 111 can be supplied to the carbon dioxide capture device 140.

[0096] <Third Embodiment> Figure 7 illustrates a marine carbon dioxide collection system according to a third embodiment of the present invention. The marine carbon dioxide collection system may include a carbon dioxide collection device 140 that removes carbon dioxide contained in the exhaust gas of the main engine 111, a methane oxidation catalytic reactor 180 that removes methane contained in the exhaust gas of the auxiliary engine 121, a low-temperature steam generation unit 150 provided at the rear end of the methane oxidation catalytic reactor 180 that generates steam by heat exchange with the exhaust gas that has passed through the methane oxidation catalytic reactor 180, and a low-temperature steam supply line 155 that supplies the steam generated in the low-temperature steam generation unit 150 to the carbon dioxide collection device 140.

[0097] In the third embodiment, as shown in Figure 7, a methane oxidation catalyst reactor 180 is added between the auxiliary engine 121 and the low-temperature steam generation unit 150 in the first embodiment. Similarly, in Figure 6 (second embodiment), a methane oxidation catalyst reactor 180 may also be added between the auxiliary engine 121 and the low-temperature steam generation unit 150. In the third embodiment, the waste heat of the high-temperature exhaust gas generated as it passes through the methane oxidation catalyst reactor 180 can be utilized to generate low-temperature steam in the low-temperature steam generation unit 150.

[0098] Furthermore, in the third embodiment, the methane oxidation catalyst reactor 180 can be installed on the exhaust gas line of the auxiliary engine 121, and the carbon dioxide capture device 140 can be installed on the exhaust gas line of the main engine 111. Since the methane oxidation catalyst is expensive, it is used only in the low-pressure auxiliary engine (power generation engine) and not in the high-pressure main engine (propulsion engine), thereby reducing the cost of the methane oxidation catalyst.

[0099] The third embodiment is applicable to, but is not limited to, cases where the main engine 111 and auxiliary engine 121 use dual fuel (gas / diesel). The third embodiment uses the waste heat of the exhaust gas from the auxiliary engine 121, but the waste heat of the high-temperature exhaust gas that has passed through the methane oxidation catalytic reactor 180 can be used to provide a sufficient heat source for low-temperature steam generation. In the third embodiment, at least a portion of the exhaust gas from the main engine 111 can be supplied to the carbon dioxide capture device 140.

[0100] <Fourth Embodiment> Figure 8 illustrates a marine carbon dioxide collection system according to a fourth embodiment of the present invention. The marine carbon dioxide collection system may include a carbon dioxide collection device 140 that removes carbon dioxide contained in the exhaust gas of the main engine 111, a main economizer 112 that generates main steam by heat exchange with the exhaust gas of the main engine 111, a combined low-temperature steam generation unit 170 that generates steam by receiving both the exhaust gas of the main engine and the exhaust gas of the auxiliary engine 121 that have passed through the main economizer 112, and a low-temperature steam supply line 155 that supplies the steam generated in the combined low-temperature steam generation unit 170 to the carbon dioxide collection device 140.

[0101] In the fourth embodiment, the combined low-temperature steam generation unit 170 is supplied with both the main engine exhaust gas that has passed through the main economizer 112 and the exhaust gas from the auxiliary engine 121, thereby generating low-temperature steam. The combined low-temperature steam generation unit 170 may also be a combined sub-econominer. The waste heat from the main engine exhaust gas discharged from the main economizer 112 is reused in the combined low-temperature steam generation unit 170, and together with the exhaust gas from the auxiliary engine 121, low-temperature steam can be generated. Therefore, the amount of low-temperature steam generated can be increased compared to generating low-temperature steam using only the exhaust gas from the auxiliary engine 121.

[0102] Furthermore, in the fourth embodiment, at least a portion of the boiler exhaust gas generated in the boiler 154 can be supplied to the combined low-temperature steam generation unit 170. Therefore, the waste heat of the boiler exhaust gas discharged from the boiler 154 can also be utilized to generate low-temperature steam in the combined low-temperature steam generation unit 170.

[0103] The fourth embodiment is applicable to, but is not limited to, cases where the main engine 111 and auxiliary engine 121 use dual fuel (gas / diesel). In the fourth embodiment, in addition to the exhaust gas from the auxiliary engine 121, the waste heat from the exhaust gases of the main engine 111 and boiler 154 can be used to generate low-temperature steam via a single combined low-temperature steam generation unit 170, which can then be used for regenerating the absorbent. In the fourth embodiment, at least a portion of the exhaust gas from the main engine 111 can be supplied to the carbon dioxide capture device 140.

[0104] <Fifth Embodiment> Figure 9 illustrates a marine carbon dioxide collection system according to a fifth embodiment of the present invention. The marine carbon dioxide collection system includes a carbon dioxide collection device 140 that removes carbon dioxide contained in the exhaust gas of the main engine 111, a low-temperature steam generation unit 150 that generates steam by heat exchange with the exhaust gas of the auxiliary engine 121, and a low-temperature steam supply line 155 that supplies the steam generated in the low-temperature steam generation unit 150 to the carbon dioxide collection device 140. At least a portion of the auxiliary engine exhaust gas that has passed through the low-temperature steam generation unit 150 can be joined to the main engine exhaust line ML that connects the main engine 111 and the carbon dioxide collection device 140.

[0105] Furthermore, the system includes a main economizer 112 located in the main engine exhaust line ML, which generates main steam by exchanging heat with the exhaust gas of the main engine. At least a portion of the auxiliary engine exhaust gas that has passed through the low-temperature steam generation unit 150 can merge into the main engine exhaust line ML at the rear end of the main economizer 112. The merging point of the auxiliary engine exhaust gas that has passed through the low-temperature steam generation unit 150 is determined.

[0106] In the fifth embodiment, the exhaust gas from the auxiliary engine 121 contains more harmful substances than LNG, and can be combined with the exhaust gas from the main engine 111, carbon dioxide removed, and then discharged. The exhaust gas that has passed through the low-temperature steam generation unit 150 has different SOx and other content depending on the type of fuel, and if it does not meet the emission standards, it can be supplied to the precooler 115 so that it is merged into the main engine exhaust line ML and discharged into the atmosphere after passing through the sulfuric acid removal unit and carbon dioxide removal unit.

[0107] In this case, the exhaust gas that has passed through the low-temperature steam generation unit 150 can be integrated with the exhaust gas that has passed through the main economizer 112 and supplied to the carbon dioxide capture device 140. That is, at least a portion of the auxiliary engine exhaust gas that has passed through the low-temperature steam generation unit 150 can be merged into the main engine exhaust line ML and supplied to the carbon dioxide capture device 140. Therefore, in the fifth embodiment, at least a portion of the carbon dioxide contained in the exhaust gas of not only the main engine 111 but also the auxiliary engine 121 can be removed, and the required carbon dioxide emission standards can be met.

[0108] Furthermore, at least a portion of the boiler exhaust gas generated in the boiler 154 can be joined to the main engine exhaust line ML at the rear end of the main economizer 112. As mentioned in the first embodiment, the boiler 154 can burn additional fuel independently of the engine to generate steam, and at least a portion of the boiler exhaust gas generated in this process can be joined to the main engine exhaust line ML and supplied to the carbon dioxide capture device 140. Therefore, in the fifth embodiment, at least a portion of the carbon dioxide contained in the exhaust gas emitted not only from the main engine 111 and the auxiliary engine 121 but also from the boiler 154 can be removed to meet the required carbon dioxide emission standards.

[0109] Furthermore, the second low-temperature steam generation unit 160 of the second embodiment can be provided on the main engine exhaust line ML at the rear end of the main economizer 112 and configured to generate second steam by exchanging heat with the main engine exhaust gas that has passed through the main economizer 112. In addition, the third low-temperature steam generation unit 162 of the second embodiment can be configured to generate third steam by exchanging heat with the boiler exhaust gas generated in the boiler 154.

[0110] The fifth embodiment is applicable when the main engine 111 and auxiliary engine 121 use liquid fuels, but is not limited thereto. Examples of liquid fuels include, but are not limited to, diesel fuel (e.g., heavy fuel oil (HFO), very low sulfur marine oil (VLSFO), marine gas oil (MGO)), methanol, etc. In the fifth embodiment, the waste heat from the exhaust gas of the auxiliary engine 121 can be used to generate low-temperature steam, which can then be used to regenerate the absorbent. In the fifth embodiment, not only at least a portion of the exhaust gas from the main engine 111, but also at least a portion of the exhaust gas from the auxiliary engine 121 and the boiler 154 can be supplied to the carbon dioxide capture device 140.

[0111] <Sixth Embodiment> Figure 10 illustrates a marine carbon dioxide collection system according to a sixth embodiment of the present invention. The marine carbon dioxide collection system includes a carbon dioxide collection device 140 that removes carbon dioxide contained in the exhaust gas of the main engine 111, a low-temperature steam generation unit 150 that generates steam by heat exchange with the exhaust gas of the auxiliary engine 121, a low-temperature steam supply line 155 that supplies the steam generated in the low-temperature steam generation unit 150 to the carbon dioxide collection device 140, a main economizer 112 provided on the main engine exhaust line ML connecting the main engine 111 and the carbon dioxide collection device 140, which generates main steam by heat exchange with the exhaust gas of the main engine 111, and a branch line BL that branches off from the main engine exhaust line ML at the rear end of the main economizer 112 and is connected to the exhaust line SL that connects the auxiliary engine 121 and the low-temperature steam generation unit 150, so that at least a portion of the main engine exhaust gas that has passed through the main economizer 112 can be supplied to the low-temperature steam generation unit 150 via the branch line BL.

[0112] After generating high-temperature steam in the main economizer 112, the exhaust gas discharged into the exhaust gas discharge pipe 114 is still at a high temperature. Therefore, it can be cooled in the precooler 115 to the required absorption temperature for the carbon dioxide capture device 140 before being supplied to the carbon dioxide capture device 140. The higher the temperature of the exhaust gas supplied to the precooler 115, the more heat needs to be wasted, and the larger the amount of seawater that needs to be supplied, which also contributes to energy loss.

[0113] The carbon dioxide capture system according to the sixth embodiment may include a branch line BL that supplies at least a portion of the exhaust gas that has passed through the main economizer 112 to the low-temperature steam generation unit 150 in order to further lower the temperature of the exhaust gas supplied to the precooler 115. That is, the waste heat of the exhaust gas discharged from the main economizer 112 can be reused in the low-temperature steam generation unit 150, increasing the production of low-temperature steam in the low-temperature steam generation unit 150 and lowering the temperature of the exhaust gas supplied to the carbon dioxide capture device 140.

[0114] Depending on the amount of low-temperature steam generated in the low-temperature steam generation unit 150, the exhaust gas discharged from the main economizer 112 can be selectively supplied to the low-temperature steam generation unit 150 or immediately supplied to the precooler 115.

[0115] Furthermore, at least a portion of the boiler exhaust gas generated in boiler 154 can be joined to the auxiliary engine exhaust line SL and supplied to the low-temperature steam generation unit 150. Therefore, the waste heat from the boiler exhaust gas generated in boiler 154 can also be utilized to generate low-temperature steam in the low-temperature steam generation unit 150.

[0116] Furthermore, as in the fifth embodiment, at least a portion of the integrated exhaust gas that has passed through the low-temperature steam generation unit 150 can be joined to the main engine exhaust line ML at the rear end of the main economizer 112. Here, the integrated exhaust gas can be a mixture of the main engine exhaust gas from the main engine 111, the auxiliary engine exhaust gas from the auxiliary engine 121, and the boiler exhaust gas from the boiler 154. At least a portion of the integrated exhaust gas is supplied to the carbon dioxide capture device 140, which can meet the required carbon dioxide emission standards.

[0117] The sixth embodiment is applicable when the main engine 111 and auxiliary engine 121 use liquid fuels, but is not limited thereto. Examples of liquid fuels include, but are not limited to, diesel fuel (e.g., heavy fuel oil (HFO), very low sulfur marine oil (VLSFO), marine gas oil (MGO)), methanol, etc. In the sixth embodiment, in addition to the exhaust gas of the auxiliary engine 121, waste heat from the exhaust gases of the main engine 111 and boiler 154 can also be used to generate low-temperature steam, which can then be used to regenerate the absorbent. In the sixth embodiment, at least a portion of the exhaust gases of the auxiliary engine 121 and boiler 154, as well as at least a portion of the exhaust gases of the main engine 111, can be supplied to the carbon dioxide capture device 140.

[0118] The first to fourth embodiments differ in that they use dual fuels, while the fifth and sixth embodiments use liquid fuels (examples of liquid fuels include, but are not limited to, diesel fuel (e.g., heavy fuel oil (HFO), very low sulfur marine oil (VLSFO), marine gas oil (MGO)), methanol, etc.). However, they all share the features of using the exhaust gas of the auxiliary engine 121 as the base heat source for low-temperature steam generation, and the carbon dioxide capture device 140 is located in the exhaust gas line of the main engine 111. The configurations of each embodiment are not mutually exclusive and can be combined.

[0119] Figure 11 shows one of the optimal embodiments of the present invention, with reference to Figure 7 of the third embodiment, wherein an SCR (Selective Catalytic Reduction) 190 is added between the main engine 111 and the main economizer 112, and an SCR 190 or preheating 200 may be added between the auxiliary engine 121 and the methane oxidation catalytic reactor 180. The SCR 190 may be installed at the rear end of the methane oxidation catalytic reactor 180, or it may be installed in parallel. A damper 210 may also be provided at the point where the exhaust gas from the main engine 111 branches off to the carbon dioxide capture device 140. This embodiment is applicable when the main engine 111 and auxiliary engine 121 use dual fuel (gas / diesel), but is not limited thereto.

[0120] Figure 12 shows another optimal embodiment of the present invention, in which, based on Figure 9 of the fifth embodiment, an SCR 190 may be added between the main engine 111 and the main economizer 112, and an SCR 190 may be added between the auxiliary engine 121 and the low-temperature steam generation unit 150. Furthermore, a damper 210 may be provided at the point where the exhaust gas from the main engine 111 branches off to the carbon dioxide capture device 140. This embodiment is applicable when the main engine 111 and auxiliary engine 121 use liquid fuel, but is not limited thereto.

[0121] The above description is merely illustrative of the technical concept of the present invention, and any person with ordinary skill in the art to which the present invention pertains can make various modifications and variations without departing from the essential characteristics of the present invention. Therefore, the embodiments disclosed herein are for illustrative purposes only, not to limit the technical concept of the present invention, and the scope of the technical concept of the present invention is not limited by such embodiments. The scope of protection of the present invention should be interpreted in accordance with the following claims, and all technical concepts within an equivalent scope should be interpreted as being included within the scope of the rights of the present invention.

Claims

1. A carbon dioxide capture device that removes carbon dioxide contained in the exhaust gas of the main engine, A low-temperature steam generating unit that generates steam by exchanging heat with the exhaust gas of the auxiliary engine, A marine carbon dioxide collection system, comprising a low-temperature steam supply line for supplying the steam generated in the low-temperature steam generation unit to the carbon dioxide collection device.

2. The system further includes a methane oxidation catalyst reactor provided between the auxiliary engine and the low-temperature steam generating unit, which removes methane contained in the exhaust gas of the auxiliary engine. The marine carbon dioxide collection system according to claim 1, wherein the low-temperature steam generation unit generates steam by exchanging heat with the exhaust gas that has passed through the methane oxidation catalyst reactor.

3. The marine carbon dioxide collection system according to claim 1, wherein the low-temperature steam supply line is provided with a steam tank for separating the liquid phase water in the steam.

4. The low-temperature steam generation unit is a sub-economizer, The marine carbon dioxide collection system according to claim 1, wherein the steam is low-temperature steam having a temperature condition of 100°C or higher and less than 165°C under pressure conditions of less than 6 barg.

5. The marine carbon dioxide collection system according to claim 1, further comprising a first steam valve provided on the low-temperature steam supply line for adjusting the amount of steam supplied to the carbon dioxide collection device.

6. A main economizer that generates main steam by exchanging heat with the exhaust gas of the main engine, A boiler that receives main steam preheated by the main economizer and generates high-temperature boiler steam, A marine carbon dioxide collection system according to claim 1, comprising a second steam valve provided on an additional supply line that supplies high-temperature boiler steam generated in the boiler to the carbon dioxide collection device, for converting the high-temperature boiler steam to low-temperature steam.

7. A main economizer is provided on the main engine exhaust line connecting the main engine and the carbon dioxide collection device, and generates main steam by heat exchange with the exhaust gas of the main engine, A second low-temperature steam generating unit is provided on the main engine exhaust line at the rear end of the main economizer and generates second steam by exchanging heat with the main engine exhaust gas that has passed through the main economizer, The marine carbon dioxide collection system according to claim 1, further comprising a second low-temperature steam supply line for supplying the second steam generated in the second low-temperature steam generation unit to the carbon dioxide collection device.

8. The marine carbon dioxide capture system according to any one of claims 1 to 7, wherein the main engine or the auxiliary engine uses dual fuel.

9. A carbon dioxide capture device that removes carbon dioxide contained in the exhaust gas of the main engine, A main economizer that generates main steam by exchanging heat with the exhaust gas of the main engine, A combined low-temperature steam generating unit is provided, which generates steam by receiving both the main engine exhaust gas and the auxiliary engine exhaust gas that have passed through the main economizer, A marine carbon dioxide collection system, comprising a low-temperature steam supply line for supplying the steam generated in the composite low-temperature steam generation unit to the carbon dioxide collection device.

10. The system further includes a boiler that receives main steam preheated by the main economizer and generates high-temperature boiler steam, The marine carbon dioxide collection system according to claim 9, wherein at least a portion of the boiler exhaust gas generated in the boiler is supplied to the composite low-temperature steam generating unit.

11. A carbon dioxide capture device that removes carbon dioxide contained in the exhaust gas of the main engine, A low-temperature steam generating unit that generates steam by exchanging heat with the exhaust gas of the auxiliary engine, The system includes a low-temperature steam supply line that supplies the steam generated in the low-temperature steam generation unit to the carbon dioxide collection device, A marine carbon dioxide collection system wherein at least a portion of the auxiliary engine exhaust gas that has passed through the low-temperature steam generation unit merges into the main engine exhaust line connecting the main engine and the carbon dioxide collection device.

12. The system further includes a main economizer provided in the main engine exhaust line, which generates main steam by exchanging heat with the exhaust gas of the main engine, The marine carbon dioxide collection system according to claim 11, wherein at least a portion of the auxiliary engine exhaust gas that has passed through the low-temperature steam generating section merges with the main engine exhaust line at the rear end of the main economizer.

13. The system further includes a boiler that receives main steam preheated by the main economizer and generates high-temperature boiler steam, The marine carbon dioxide collection system according to claim 12, wherein at least a portion of the boiler exhaust gas generated in the boiler is joined to the main engine exhaust line at the rear end of the main economizer.

14. A main economizer is provided on the main engine exhaust line and generates main steam by exchanging heat with the exhaust gas of the main engine, The branch line includes a branch line that branches off from the main engine exhaust line at the rear end of the main economizer and is connected to an auxiliary engine exhaust line that connects the auxiliary engine and the low-temperature steam generating unit, The marine carbon dioxide collection system according to claim 11, wherein at least a portion of the main engine exhaust gas that has passed through the main economizer is supplied to the low-temperature steam generating unit via the branch line.

15. The marine carbon dioxide capture system according to any one of claims 11 to 14, wherein the main engine or the auxiliary engine uses liquid fuel.

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